ANALYSIS of ALTERNATIVES Non-Confidential Report

ANALYSIS OF ALTERNATIVES Non-confidential report

Legal name of applicant(s): Veco B.V.

Submitted by: Veco B.V.

Substance: Ammonium dichromate (EC No: 232-143-1, CAS No: 7789-09-5)

Use title: Use of ammonium dichromate as photosensitive component in a polyvinyl alcohol photolithographic lacquer system for the manufacturing of mandrels which are used in nickel electroforming processes.

Use number: 1 ANALYSIS OF ALTERNATIVES II

CONTENTS

DECLARATION ...... VII

1. SUMMARY ...... 1

2. ANALYSIS OF SUBSTANCE FUNCTION...... 3

2.1. Substance ...... 3

2.2. Use of ammonium dichromate ...... 3

2.3. Purpose and benefits of ammonium dichromate for photolithographic applications ...... 3

2.4. Usage and product examples ...... 4

2.5. Mode of action ...... 6

2.6. Process descriptions ...... 7

2.7. Characteristics and Properties of Ammonium Dichromate ...... 9

2.8. Key functionalities of Cr(VI)-based photolithographic process ...... 10

3. ANNUAL TONNAGE...... 11

4. IDENTIFICATION OF POSSIBLE ALTERNATIVES ...... 12

4.1. Description of efforts made to identify possible alternatives ...... 12

4.2. List of possible alternatives ...... 18

5. SUITABILITY AND AVAILABILITY OF POSSIBLE ALTERNATIVES ...... 19

5.1. Alternative 1: Diazo-based polymers with formaldehyde ...... 19

5.1.1. Substance ID and properties ...... 19

5.1.2. Technical feasibility ...... 20

5.1.3. Economic feasibility ...... 21

5.1.4. Reduction of overall risk due to transition to the alternative ...... 22

5.1.5. Availability ...... 22

5.1.6. Conclusion on suitability and availability for Alternative 1 ...... 22

5.2 Category 2 Alternatives ...... 23

6. OVERALL CONCLUSIONS ON SUITABILITY AND AVAILABILITY OF POSSIBLE ALTERNATIVES .. 27

7. REFERENCES...... 29

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES III

List of Tables: Table 1: Substance included in this analysis of alternatives...... 3 Table 2: Overview on product categories, exemplarily applications and number of product types for electroformed nickel products...... 4 Table 3: Ammonium dichromate typical chemical and physical properties ...... 9 Table 4: Harmonized classification of ammonium dichromate ...... 9 Table 5: Number of customers and different products...... 14 Table 6. List of alternatives with categorisation, category 1 and category 2 alternatives evaluated in chapter 5...... 18

ANALYSIS OF ALTERNATIVES IV

List of Figures Figure 1: Overview on development progress on alternatives to ammonium dichromate. 2 Figure 2: Laser foil (left) and coffee filter (right) produced using a PVA/ammonium dichromate mandrel. 4 Figure 3: Left: (Blackened) Precision parts (~5 mm) electroformed using a PVA/ammonium dichromate mandrel. Right: Detailed picture of the PVA/ammonium lacquer pattern on a mandrel for encoder disks. 5 Figure 4: Sugar sieves electroformed using a PVA/ammonium dichromate mandrel. 5 Figure 5: Cross-linking reaction involving ammonium dichromate and PVA (Kapp-Schwoerer et al., 2004) 6 Figure 6: Left: Coating machine in which the PVA-ammonium dichromate lacquer is applied to the stainless steel plate; Right: Coating machine opened (Veco, 2015). 7 Figure 7: UV exposure unit in which plate (with PVA + ammonium dichromate) is exposed to UV light (Veco, 2015). 8 Figure 8: Left: coated substrate, middle: UV-exposure through a mask pattern, the non-exposed areas remain soluble in appropriate solvents, left: development by immersion in a solvent (e.g. water) (Schauberger et al., 2013). 8 Figure 9: Part of segregated, automated process where the plates are developed with water and dried (Veco, 2015). 8 Figure 10: Overview on current development process of diazo compounds for photolithographic applications. 13 Figure 11: A single Razor Foil. 15 Figure 12: Scanning electron Micrograph of the cutting side of the Razor Foil. The so called “Raised Land” around the holes in the foil are necessary for the functioning of the foil in its final application. 15 Figure 13: Coffee filter produced on a PVA/ammonium dichromate mandrel. 16 Figure 14: SEM micrograph of the coffee filter. For the coffee brewing process the uniformity of slit sizes is important. 16 Figure 15: Expresso coffee filter element produced on PVA/ammonium dichromate mandrels. 16 Figure 16: SEM micrograph showing pores in the filter. The shape and dimensions of these filter holes are critical for the foam formation during the coffee brewing process. 16 Figure 17: Overview on development progress on alternatives to ammonium dichromate. 27

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES V

ABBREVIATIONS Acute Tox. Acute Toxicity AfA Application for authorisation AoA Analysis of Alternatives Carc. Carcinogenicity Cr(III) Trivalent chromium Cr(VI) Hexavalent chromium CSR Chemical Safety Report Eye irrit. Eye irritation PVA Polyvinyl alcohol SEA Socio-economic analysis Skin irrit. Skin irritation SVHC Substance of very high concern TPA Terephthalic aldehyde UV Ultraviolet WWTP Wastewater treatment plant

ANALYSIS OF ALTERNATIVES VI

GLOSSARY

Term Definition Electroforming Electrodeposition process (here nickel) on a model (mandrel) to form processes metal products.

Compatibility (to The capability of two or more things to exist or perform together in PVA) combination without problems or conflict. In this document compatibility refers to the capability of the cross-linking agent to support the polymerization of the PVA. Have been identified during the consultation phase for all parts of the Key Functionalities process chain and are used for the evaluation of alternatives. The negative model used in the electroforming process to produce the Mandrel final positive product, which is subsequently separated from the mandrel, by deposition of the nickel metal. Resolution and Minimum obtainable product feature size (resolution) of the definition of photo- produced image and achievable degree of reproduction of details images (definition) of the corresponding photo-image. Photosensitizing Activity of the photo sensitizer in photo induced cross-linking of the capacity PVA lacquer. Light-sensitive compound that is used as cross-linking agent to establish a selectively hardened and water insoluble PVA lacquer. Photo resist (positive Positive photo resists become soluble in the respective solvent when and negative) exposed to light of specific wavelength, while negative photo resists harden. Lacquer consisting of polyvinyl alcohol monomers selectively Photolithographic polymerized in a light induced process, supported by a cross-linking polyvinyl alcohol agent and used to establish a lacquered mandrel for the (PVA) lacquer electroforming process.

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES VII

DECLARATION We, Veco B.V., request that the information blanked out in the “public version” of the Analysis of Alternatives is not disclosed. We hereby declare that, to the best of our knowledge as of today (11 February 2016) the information is not publicly available, and in accordance with the due measures of protection that we have implemented, a member of the public should not be able to obtain access to this information without our consent or that of the third party whose commercial interests are at stake.

Use number: 1 Legal name of the applicant(s): Veco B.V.

ANALYSIS OF ALTERNATIVES 1

1. SUMMARY This Analysis of Alternatives (AoA) forms part of the Application for Authorisation (AfA) for the use of ammonium dichromate in photolithographic applications. Within this application, ammonium dichromate is used as a photosensitizer in a light-sensitive, isolating, photolithographic polyvinyl alcohol (PVA) lacquer. After exposure to light with an appropriate wavelength, those lacquers undergo crosslinking reactions, leading to an altered solubility in water and make the mandrels on which the lacquer is applied a valuable tool in nickel electroforming processes. Ammonium dichromate containing products are used as mandrels in this electroforming process and are for internal use only. This summary aims to shortly explain why the use of ammonium dichromate is essential in this specific photolithographic application. It describes the steps and effort involved in finding and approving a replacement for ammonium dichromate in this application and evaluates potential alternatives in detail (see chapter 4 and 5). The following key functionalities for the use of ammonium dichromate in the given photolithographic application are as follows and discussed in more detail in chapter 2.8.: - Photosensitizing capacity - Adhesion to substrate - Compatible to PVA - High-resolution and high definition of photo-images - Life-time of non-exposed lacquer - Temperature resistance of the resulting mandrel - Chemical resistance of the resulting mandrel - XXXXXXXXXXXXXXXXXXXXXXXXXXXX - Three-dimensional shape of the lacquer on the resulting mandrel As a result of the R&D efforts, 4 different 4-diazodiphenylamine formaldehyde (1:1) salts, as only reasonable alternative, are reported and evaluated concerning its technical and economic feasibility, as well as the reduction of the overall risk in case of transition. Besides these diazo compounds, only preliminary testing with a few other alternatives was performed. In terms of technical feasibility, 4-diazodiphenylamine formaldehyde (1:1) showed promising results during ongoing testing, but currently does not represent a viable alternative for ammonium dichromate. For the current alternative under development, development steps were initiated in 2013 and are still ongoing. As of today, this alternative has not proven to be suitable, which is discussed in more detail in chapter 5. A wide-ranging assessment concerning the influence of the alternative on the properties of the final product needs to be conducted. Furthermore, process parameters and equipment need to be adjusted and the approval on the customers' side has to be obtained. The robustness and stability of the products have to be checked and monitored in the long term. Finally, the process has to be repeated for each of the various products and customers (Chapter 4.1.1). At present, the alternative is in the initial phase of the development process where testing of specific process parameters e.g. concentration, development process, and lacquer adhesion is carried out including first preliminary scaled up experiments (Phases I and II). As not all parameters of the current setting turned out to be suitable, it is not yet clear when these phases of the development process will be accomplished. According to the current stage of research in 2016, another 2-3 years are estimated if no major drawbacks occur. Based on experiences on previous approval processes and the multitude of customers and products involved, the following steps including production tests, assessment of the long-term behaviour of the alternative in the electroforming chemistry, production

Use number: 1 Legal name of the applicant(s): Veco B.V. 2 ANALYSIS OF ALTERNATIVES tests for the full-range of PVA-based products, quality assessment at customers, and implementation of the alternative (Phases III-VII) are estimated to take at least an additional 5 to 6 years.

Figure 1: Overview on development progress on alternatives to ammonium dichromate. In conclusion, a review period of at least 7 years is needed because it coincides with realistic estimates by the applicant of the schedule required to industrialise an alternative to ammonium dichromate in this specific photolithographic application (Figure 1).

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES 3

2. ANALYSIS OF SUBSTANCE FUNCTION

2.1. Substance The following substance is the subject of this analysis of alternatives:

Table 1: Substance included in this analysis of alternatives.

Substance Intrinsic property(ies)1 Latest application date² Sunset date³ Carcinogenic (category 1B) Ammonium dichromate Mutagenic EC No: 232-143-1 21.03.2016 21.09.2017 (category 1B) CAS No: 7789-09-5 Toxic for reproduction (category 1B)

1 Referred to in Article 57 of Regulation (EC) No. 1907/2006 ² Date referred to in Article 58(1)(c)(ii) of Regulation (EC) No. 1907/2006 3 Date referred to in Article 58(1)(c)(i) of Regulation (EC) No. 1907/2006

This substance is categorised as a substance of very high concern (SVHC) and is listed on Annex XIV of Regulation (EC) No 1907/2006. Adverse effects are discussed in the CSR.

2.2. Use of ammonium dichromate Ammonium dichromate as chromium (VI) containing substance has been widely used since the middle of the 20th century. This application focuses only on the use of ammonium dichromate in photolithographic applications for the manufacturing of mandrels which are used in nickel electroforming processes.

2.3. Purpose and benefits of ammonium dichromate for photolithographic applications Ammonium dichromate offers a broad range of functions, mainly based on the characteristics of the Cr(VI) compound, and is well established in the photolithographic industry. The multifunctionality of ammonium dichromate thereby grants unique chemical and electrochemical properties. The following key functionalities for the use of ammonium dichromate in the given photolithographic applications are discussed in more detail in chapter 2.8. - Photosensitizing capacity - Adhesion to substrate - Compatible to PVA - High-resolution and high definition of photo-images - Life-time of non-exposed lacquer - Temperature resistance of the resulting mandrel - Chemical resistance of the resulting mandrel - XXXXXXXXXXXXXXXXXXXXXXXXXXXX - Three-dimensional shape of the lacquer on the resulting mandrel Several alternatives are being tested to replace ammonium dichromate. It is a challenge to find an available substitute which meets all requirements of the application while being technically and economically feasible. In addition, and specific for the current use, the substitute should also meet

Use number: 1 Legal name of the applicant(s): Veco B.V. 4 ANALYSIS OF ALTERNATIVES the requirements of the subsequent process steps regarding the use of the finished mandrel in nickel electroforming processes.

2.4. Usage and product examples Importantly, the products formed by this process – the mandrels – are for internal use only. Ammonium dichromate is used as cross-linking agent in PVA lacquers. Stainless steel plates containing a hardened layer of this lacquer (according to the specifications of the customer) are used as mandrels in nickel electroforming processes. The finished mandrel does not contain any bioavailable ammonium dichromate anymore. With these mandrels hundreds of different products are produced. For each specific product type, a different mandrel is needed. These electroformed nickel products (also no ammonium dichromate present) are used in miscellaneous industry sectors as outlined in Table 2 below. Some example products are illustrated in Figure 2-Figure 4.

Table 2: Overview on product categories, exemplarily applications and number of product types for electroformed nickel products. Number of Number of Product Category Typical Applications product types customers worldwide Sugar Sieves Industrial refining of sugar XXXX XXXX

Razor Foils Blades for electrical foil shavers XXXX XXXX Filter medium for industrial filtration and Filtration/microfiltration separation processes XXXX XXXX products Espresso coffee filters Encoders for servo systems, automotive industry Blackened products for optical application, Other precision parts XXXX XXXX photography, microscopy and endoscopy Nickel blanks/sheets for the electronics industry, SMT stencils

As shown in Table 2, Veco B.V. (Veco) delivers products from its electroforming process to m XXXX customers worldwide with XXXX XXXX product types.

Figure 2: Laser foil (left) and coffee filter (right) produced using a PVA/ammonium dichromate mandrel.

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES 5

Figure 3: Left: (Blackened) Precision parts (~5 mm) electroformed using a PVA/ammonium dichromate mandrel. Right: Detailed picture of the PVA/ammonium lacquer pattern on a mandrel for encoder disks.

Figure 4: Sugar sieves electroformed using a PVA/ammonium dichromate mandrel.

Use number: 1 Legal name of the applicant(s): Veco B.V. 6 ANALYSIS OF ALTERNATIVES

2.5. Mode of action Ammonium dichromate is used as cross-linking agent in light sensitive, isolating, photolithographic PVA lacquers (negative photo resist). Exposing ammonium dichromate containing, light-sensitive PVA lacquers to light of an appropriate wavelength (Ultraviolet (UV) light between 100nm - 380nm) a photo-induced cross-linking reaction takes place.

(NH4)2Cr2O7

Figure 5: Cross-linking reaction involving ammonium dichromate and PVA (Kapp-Schwoerer et al., 2004)

Ammonium dichromate serves as oxidizing agent and the underlying photoreaction can be described as follows: ammonium dichromate absorbs light, which then leads to a subsequent electron-transfer from the PVA polymer matrix to Cr(VI). Cr(VI) is then reduced to Cr(III). The resulting polymer radicals are now able to undergo intermolecular reactions leading to cross-linked PVA (see Figure 5). The photochemical reaction of ammonium dichromate with PVA is based on the following half reaction: 2- - + 3+ (1) Cr2O7 + 6e + 14H  2Cr + 7H2O

While PVA is converted into a ketone derivative:

+ - (2) (R1)(R2)HCOH  (R1)(R2)C=O + 2H + 2e

The crosslinking/complexation then takes place via reaction between Cr(III) and the oxidized PVA. Photo crosslinking polymers have become a major class of recording material, which are used since decades. Historically, those polymers were of biologic origin, such as gelatine, proteins from eggs (egg albumin), milk (casein) or starch (gum arabic). Since the 1930s, the sensitization of PVA has been studied and different dyes and metal ions were employed as sensitizer in polymer chemistry. Since then, ammonium dichromate mediated cross-linking reactions of PVA are used in many industrial applications such as printing plates or stencils. Cross-linking of PVA changes its solubility in water. While unbranched PVA is comparatively well soluble in water, cross-linked parts are less soluble. Therefore, parts of photosensitive lacquer are irradiated with light of a certain wavelength, leading to material hardening and alteration of the water

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES 7 solubility. The variable solubility in water and light induced polymerization is highly beneficial in photolithographic processes used for manufacturing mandrels of various geometries.

2.6. Process descriptions In the defined application, ammonium dichromate is used as photo-sensitizer (negative photo-resist or cross-linking agent) in a light-sensitive, isolating PVA lacquer. The final product is for internal use only: stainless steel plates containing a hardened layer of lacquer (according to the specifications of the customer) without any remaining Cr(VI), which are used as mandrels. For this purpose, an aqueous solution of ammonium dichromate is mixed to PVA lacquer in different ratios. Depending on the ammonium dichromate/PVA ratio several types of PVA lacquers are available:  Regular PVA lacquer: This PVA lacquer is used for large plates (>1 m2). The concentration of ammonium dichromate in this lacquer is 0.1 - 0.5 wt%.  1:1 PVA lacquer: This PVA lacquer type is used for small plates (<0.3 m2). Before addition of ammonium dichromate to the PVA, the PVA is 1:1 diluted with water. The concentration of ammonium dichromate is 0.1 – 0.5 wt%.  Diluted PVA lacquer: Used for pre-coating in order to get a better distribution of the lacquer over large substrates (> 1m2). The concentration of ammonium dichromate in this lacquer is 0.01 – 0.1 wt%. Using a closed coating machine (Figure 6), the substrate, which is usually a stainless steel plate, is first rinsed with water, before a sulphuric acid solution is applied, followed by the pre-coating (diluted photo-sensitive PVA lacquer) and the final photo-sensitive PVA lacquer.

Figure 6: Left: Coating machine in which the PVA-ammonium dichromate lacquer is applied to the stainless steel plate; Right: Coating machine opened (Veco, 2015). For the following photolithographic process, a photo-mask with product specifications (geometric pattern according to the customer’s demands) is put on top of the plate and exposed to UV light (Figure 7). The process of masking is illustrated in more detail in Figure 8. Exposed parts of the photosensitive layer will become water-insoluble due to cross-linking of the PVA molecules, while non-exposed parts will be washed off during developing with water. No ammonium dichromate is used in the development step. After drying in an oven (Figure 9), the matrix plate is used as a mandrel in nickel electroforming processes.

Use number: 1 Legal name of the applicant(s): Veco B.V. 8 ANALYSIS OF ALTERNATIVES

Figure 7: UV exposure unit in which plate (with PVA + ammonium dichromate) is exposed to UV light (Veco, 2015).

UV Stainless Steel Plate Mask Photoresist

(I) Coating (II) UV-exposure (III) Developing Figure 8: Left: coated substrate, middle: UV-exposure through a mask pattern, the non-exposed areas remain soluble in appropriate solvents, left: development by immersion in a solvent (e.g. water) (Schauberger et al.,

2013).

Figure 9: Part of segregated, automated process where the plates are developed with water and dried (Veco, 2015).

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES 9

To guarantee a constant quality of the resulting product, side reactions like “dark reactions” (crosslinking without light) that diminish the solubility difference must be avoided. Therefore a very precise knowledge of the used photosensitive lacquer is crucial. For ammonium dichromate based, photosensitive PVA lacquers, the ongoing cross-linking processes are very well controlled, making them an ideal candidate for applications in electroforming processes.

2.7. Characteristics and Properties of Ammonium Dichromate The substance is an odourless solid and appears as bright orange red crystal solids at room temperature. It is freely soluble in water. The solution of ammonium dichromate is acidic and a strong oxidizing agent, it is reactive with any reducing agent. Physical and chemical characteristics of ammonium dichromate are summarized in Table 3.

Table 3: Ammonium dichromate typical chemical and physical properties

Parameter Value

Water solubility at 20 [°C] 360 g/L

Specific gravity at 20 [°C] 2.15 g/cm³

Molecular weight 252.07 g/mol

pH value at 20 [°C] and with a concentration of 100 g/l 3.5

Melting Point > 180 °C

A search for harmonized hazard classifications and labelling for the substance ammonium dichromate was conducted and following data was obtained from the ECHA C&L inventory:

Table 4: Harmonized classification of ammonium dichromate Hazard Class and Hazard Statement Code(s) Pictograms Category Code(s) Ox. Sol. 2 H272 (May intensify fire; oxidizer)

Acute Tox. 3 H301 (Toxic if swallowed)

Acute Tox. 4 H302 (Harmful if swallowed)

Skin Corr. 1B H314 (Causes severe skin burns and eye damage)

Skin Sens. 1 H317 (May cause an allergic skin reaction)

Acute Tox. 2 H300 (Fatal if swallowed) H334 (May cause allergy or asthma symptoms or Resp. Sens. 1 breathing difficulties if inhaled) Muta. 1B H340 (May cause genetic effects)

Carc. 1B H350 (May cause cancer) H360FD (May damage fertility. May damage the Repr. 1B unborn child) STOT RE 1 H372 (causes damage to organs)

Aquatic Acute 1 H400 (Very toxic to aquatic life) H410 (Very toxic to aquatic life with long lasting Signal word: Danger Aquatic Chronic 1 effects)

Use number: 1 Legal name of the applicant(s): Veco B.V. 10 ANALYSIS OF ALTERNATIVES

2.8. Key functionalities of Cr(VI)-based photolithographic process Alternative photoresist systems for the use applied for, need to match the requirements of specific photolithographic production processes and product specifications, such as mandrel lifetimes, photolithographic process sequence and tooling, product resolution and feature definitions of the final nickel product. It is much more complex, time consuming and not economically feasible to develop and implement an entire alternative photoresist system that fulfils the needs of this specific process. Consequently, the aim of this AoA is to identify an alternative sensitizer for the current PVA photoresist system, fitting in the overall production process. Possible alternatives for ammonium dichromate photolithographic processes have to address all of the following key functionalities.  Photosensitizing capacity: Since the solubility of the cross-linked lacquer and therefore the quality of the resulting mandrel, respectively the final nickel product, is directly linked to the degree of cross linkages within the PVA lacquer, dedicated photo-sensitising capacity is needed. No testing methods are available to quantify the activity of the photosensitizer during the process. Ammonium dichromate offers excellent photosensitizing capacities with the advantage that ammonia disappears from the process. Consequently, the influence of other ions potentially influencing the reaction is diminished.  Adhesion to substrate: The intrinsic crosslinking efficiency of ammonium dichromate is very high which is critical for a sufficient adhesion of the entire lacquer to the substrate. From a mechanistic point of view, the in-situ generation of Cr(III) from Cr(VI), located next to the oxidized PVA, is expected to be crucial. This cannot be achieved by simply mixing PVA with a Cr(III) salt. Alternatives must demonstrate similar adhesion to the substrate. Therefore, mandrels are visually inspected with respect to lacquer damage, after the lithographic process and during the application of the mandrel in electroforming.  Compatible to PVA: PVA based photosensitive lacquers show highly beneficial features for their use in photolithographic processes (e.g. superior adhesion on steel after baking, low procedural costs using PVA in combination with ammonium dichromate). Therefore, possible alternatives must be compatible to PVA. This is especially important for process sequences, tooling, and mandrel lifetimes, which are directly linked to the use of PVA based system.  High-resolution and high definition of photo-images: Applying an ammonium dichromate- PVA lacquer system ensures high resolution (minimum obtainable product feature size down to a line width of XXXXXX) and high definition (reproduction of the photo-image) of the produced image. The combination of both properties is an important requirement that possible alternatives have to meet.  Life-time of non-exposed lacquer: The acceptable life-time of the pre-mixed PVA lacquer with ammonium dichromate is one day. The photosensitivity of the lacquer needs to stay stable to obtain process stability and robustness over the whole period. In addition, increased life-time of the non-exposed lacquer allows preparing the pre-mix only once a day and therefore, avoiding unnecessary additional production steps. The adequate life-time of the non-exposed lacquer represents a minimum requirement for possible alternatives.  Temperature resistance of the resulting mandrel: Current mandrels lacquered with the PVA/ammonium dichromate system, are used in electroforming processes at temperatures of 40 °C up to 65 °C. Possible alternatives must not show any limitations at the given operating temperatures.

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES 11

 Chemical resistance of the resulting mandrel: Mandrels lacquered with the PVA/ ammonium dichromate system are used in electroforming processes. Therefore, possible alternatives must be resistant to other chemicals used in such processes. No events of dissolution, degradation or wear shall occur. In addition, the mandrel shall not be a source of contamination for the electroforming process and the final product.  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX  Three-dimensional shape of the lacquer on the resulting mandrel: Slope and definition of the edges of the lacquer, define the quality of the resulting electroformed product. The shape also determines the behaviour of the electroformed product in subsequent process steps. Both aspects are important for the final customer application. Possible alternatives must fulfil the above stated criteria to be considered as reasonable alternatives to ammonium dichromate in photolithographic processes.

3. ANNUAL TONNAGE The average tonnage for the use of ammonium dichromate as photosensitive component in the PVA lacquer is < 40 kg per year.

Use number: 1 Legal name of the applicant(s): Veco B.V. 12 ANALYSIS OF ALTERNATIVES

4. IDENTIFICATION OF POSSIBLE ALTERNATIVES

4.1. Description of efforts made to identify possible alternatives To prepare the authorization of eight Cr(VI) compounds, the industry consortium CCST (Miscellaneous Chromium VI Compounds for Surface Treatment REACH Authorization Consortium) of 28 members was launched in 2012. The aim of CCST was to efficiently gather and analyse all necessary information for the three pillars of the authorization dossier (CSR, AoA, SEA). While the majority of the CCST applications are associated with the aerospace sector, the ammonium dichromate based application of this AoA has been separated from the other CCST applications.

4.1.1. Research and development in the photolithographic industry Extensive research efforts have been deployed over the last decades to identify and develop viable alternatives to the different Cr(VI) compounds in its various usages. The unique functionalities of Cr(VI), explained in detail in section 2.8, make it an ideal and not easy to replace substance in these photolithographic applications where superior requirements have to be fulfilled to ensure the quality of the final product. Steps towards the substitution of ammonium dichromate in these photolithographic applications entails the identification, evaluation and implementation of possible alternatives, which in turn is time intensive and bound to capacities available. Figure 10 illustrates the necessary steps to be taken in order to find a suitable alternative to ammonium dichromate for the use applied for. The time line is based on current R&D at Veco, and experiences with diazo compounds as the most promising alternatives, which are discussed in detail in the following chapter. R&D efforts to identify possible alternatives to ammonium dichromate, steps I and II respectively, have already been initialized in the beginning of 2013 and are still ongoing to date. In early 2013, an extensive internet search was conducted to find potential alternatives, and based on information from the PVA supplier and from an affiliate company working with the same diazo alternative, R&D was started assessing the diazo compounds. It is estimated that after successfully accomplishing these steps, meaning that a suitable alternative has finally been identified and tested on the laboratory scale, the following development steps III to VI and the iteration of the steps for each of the different applications, respectively products (step VII) will take 5 to 6 years, beneficially. A more detailed overview on the task and goal for the different phases of the alternative development is given in the following paragraph.

4.1.2. Overview on alternative development for Ammonium dichromate The whole development process comprises of several phases which are outlined in detail below. Step I: The review concerning the technical feasibility of an alternative in the first place is carried out on the laboratory scale. This includes the setup of experimental designs for testing process parameters, such as concentration, exposure energy, development process, effect on lacquer thickness, lacquer adhesion and performance in the (small-scale) electroforming system. Step II: Results from step I feed into step II including the testing of the performance under scaled- up production conditions using the by then available equipment. Already conducted testing that has not proven its suitability results in rerun of step I for further refinements.

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES 13

Figure 10: Overview on current development process of diazo compounds for photolithographic applications.

Use number: 1 Legal name of the applicant(s): Veco B.V. 14 ANALYSIS OF ALTERNATIVES

In case of a positive decision for any alternative, the following subsequent development steps (Step III-VII) and quality safety procedures need to be carried out: - Production tests (mandrel production and electroforming performance at 65°C); - Assessment of the long-term behaviour of the alternative in the electroforming chemistry; - Production tests for the full-range of PVA-based products; - Quality assessment at customers; - Implementation of the alternative. It is estimated that this will take at least 5-6 years. This time span holds for all potential alternatives actually, after a ‘go decision’ has been made in step II. Step III: In the subsequent evaluation step III, results from step II will have to be reviewed concerning influences of the alternative on properties or internal specifications of the final electroformed product. In fact, the alternative needs to comply with all requirements mentioned in section 2.8. Step IV: In the adjustment step IV, process parameters and equipment will be adjusted to fulfil demanded specifications of the final product. Step V: In the following development step, the amended process parameters, the equipment, and therefore the resulting overall process conditions, will have to be aligned with the individual customer demands. Each customer has own specific demands with regard to key functionalities of the specific product. Customer acceptance and approvals have to be reviewed individually. As shown in Table 5, products from Veco´s electroforming process are delivered to XXXXX customers worldwide with XXXXX product types. Accordingly, time needed until approval and release is extensive and varies significantly.

Table 5: Number of customers and different products. Product Number of Number of Information on customer approval process Category product types customers Tests can be performed once a year during the sugar Sugar Sieves XXXXX XXXXX campaign from September to end December. Customers have to perform field tests with fully Razor Foils XXXXX XXXXX functional electric shavers. Filtration/ XXXXX microfiltration XXXXX No reliable estimate possible products Other precision XXXXX No reliable estimate possible parts XXXXX

Step VI: Monitoring of robustness and stability of the product manufactured by using the alternate process takes place as last step. The monitoring will have to be conducted over a long time period since various articles are not produced continuously. As clearly indicated above, the multitude of applications shows the need for individual development of customized processes for each of the various electroformed products. The evaluation, implementation and monitoring therefore entails multiple iterations of the different steps (step VII). The duration of the initial steps I and II, the development of a suitable alternative at the laboratory scale including first upscaling tests is hard to predict. For the current alternative under development, these steps were initiated in 2013 and are still ongoing. As of today, this alternative has not proven to be suitable which is discussed in more detail in chapter 5. It is not yet clear when step I and II will be

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES 15 accomplished, according to the current stage of research in 2016, another 2-3 years are estimated if no major drawbacks occur. The following steps (III-VII) are estimated to take additional 5 to 6 years. Consequently, a review period of at least 7 years is necessary to conduct further R&D and finally substitute ammonium dichromate for the various products. It should be noted again that the present time line is mainly based on experiences with Alternative 1 (Diazo compounds) of this AoA. However, the time span following step I and II holds for all potential alternatives, after a ‘go decision’ based on prior R&D conducted in step I and II has been made. The multitude of products electroformed for various customers as mentioned above is a decisive issue concerning the time needed for approval and release in case of alternate processes to be developed. Articles electroformed are very diverse and each of the products require customized specifications. The Figure 11-Figure 16 outlined below provide examples of different electroformed products. Indeed, specifications vary according to individual demands. For all these products, there are XXXXX customers worldwide, most of them with specific requirements. Those detailed differentiations across a multitude of customers and products are the main reasons for multiple iterations of the approval and release steps as stated above leading to long-lasting approval and release periods.

Figure 12: Scanning electron Micrograph of the cutting Figure 11: A single Razor Foil. side of the Razor Foil. The so called “Raised Land” around the holes in the foil are necessary for the functioning of the foil in its final application.

Use number: 1 Legal name of the applicant(s): Veco B.V. 16 ANALYSIS OF ALTERNATIVES

Figure 13: Coffee filter produced on a Figure 14: SEM micrograph of the coffee filter. For PVA/ammonium dichromate mandrel. the coffee brewing process the uniformity of slit sizes is important.

Figure 15: Expresso coffee filter element produced Figure 16: SEM micrograph showing pores in the filter. on PVA/ammonium dichromate mandrels. The shape and dimensions of these filter holes are critical for the foam formation during the coffee brewing process.

4.1.3. Data searches For the analysis of alternatives, an extensive internet search and literature review was performed and technical information on the alternatives were provided by the technical experts of Veco. Furthermore, searches for publically available documents were conducted to ensure that all potential alternatives and alternative processes to ammonium dichromate in the photolithographic application were considered in the data analysis.

4.1.4. Consultations A questionnaire was provided to all consortia members to get an overview of the experiences with the alternatives, completeness and prioritization of critical parameters for their specific processes and the minimum technical requirements.

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES 17

During this survey, additional alternatives and key functionalities have been identified specifically for the photolithography sector, which were subsequently added. At this stage of the data analysis, several alternatives had been screened out after bilateral discussions with Veco. Discussions with technical experts followed by a final data analysis led to the formation of a list of alternatives divided into 2 categories, according to their potential to be suitable for the specific use and/or the maturity of the alternative within the R&D process. The most promising alternatives within this use (category 1 and 2) are assessed in detail in the following chapter.

Use number: 1 Legal name of the applicant(s): Veco B.V. 18 ANALYSIS OF ALTERNATIVES

4.2. List of possible alternatives The alternatives are classified according to their relevance; as Category 1 (R&D currently ongoing at Veco) or Category 2 (discussed mainly in literature, clear technical limitations, may only be suitable for other applications but not as general alternative, preliminary or no R&D initiated so far by Veco). An overview of the potential alternatives in each category is provided in the following table.

Table 6. List of alternatives with categorisation, category 1 and category 2 alternatives evaluated in chapter 5.

Category Alternative Diazo compounds (summarized as 4-diazodiphenylamine formaldehyde (1:1)) : • Benzenediazonium, 4-(phenylamino)-, sulfate (1:1), polymer with formaldehyde (CAS 41432-19-3) (Name on SDS: 4-Anilinobenzenediazonium hydrogen sulphate polymer with formaldehyde (1:1)) • Benzenediazonium, 4-(phenylamino)-, sulfate (1:1), polymer with formaldehyde, zinc chloride complexes (CAS 68988-17-0) (Name on SDS: 4- 1 diazodiphenylamine/formaldehyde condensate with hydrogen sulfate zinc chloride complex-low zinc) • Benzenediazonium, 4-(phenylamino)-, chloride (1:1), polymer with formaldehyde, compd. with zinc chloride (ZnCl2) (CAS 53710-65-9) • Benzenediazonium, 4-(phenylamino)-, phosphate (1:1), polymer with formaldehyde (CAS 71550-45-3)

Tungsten polyoxometalate

Iron(III) chloride

Terephthalic aldehyde

2 Non-PVA lacquer systems

Digital inkjet printing

4,4′-diazidostilbene-2,2′-sodium disulfonate (DAS)

2,5-bis(4′-azido-2′-sulfobenzyliden) cyclopentanon disodium salt (DAP)

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES 19

5. SUITABILITY AND AVAILABILITY OF POSSIBLE ALTERNATIVES Category 1 Alternatives The following assessment of the feasibility of the presented alternatives contains summarizing tables with a colour code. The colours are as follows:

Colour Explanation Not sufficient – the parameters/assessment criteria do not fulfil the requirements The parameters/assessment criteria fulfilment are not yet clear Sufficient – the parameters/assessment criteria do fulfil the requirements

5.1. Alternative 1: Diazo-based polymers with formaldehyde Alternative 1 encompasses four diazo-based compounds as given in Table 6. Diazo compounds differ - according to the respective counter-ion and stabilizing agent. The counter-anion can be HSO4 , - - H2PO4 or Cl . The stabilizing agent can be ZnCl2, ZnSO4, or CoCl2. The following compounds are currently being tested:

- Benzenediazonium, 4-(phenylamino)-, chloride (1:1), polymer with formaldehyde (ZnCl2), - Benzenediazonium, 4-(phenylamino)-, sulfate (1:1), polymer with formaldehyde (no stabilizing agent), - Benzenediazonium, 4-(phenylamino)-, sulfate (1:1), polymer with formaldehyde, (ZnCl2), - Benzenediazonium, 4-(phenylamino)-, phosphate (1:1), polymer with formaldehyde (no stabilizing agent).

In literature, the different diazo compounds are not distinguished. Until now, Veco has found that there are no significant differences between the different diazo compounds.

5.1.1. Substance ID and properties Photo reactive groups are chemically inert compounds that become reactive when exposed to ultraviolet or visible light. Practically all varieties of photo reactive groups used in reagents for crosslinking applications require exposure to UV light for molecular activation. Photo-activatable reactive chemicals in solvents for crosslinking of proteins are not limited to dichromates, but also include the group of azo-components. In general, crosslinking with diazo components leads to an increased molecular weight of the PVA materials by crosslinking their chains. After exposure to UV- light, the exposed parts are water insoluble, while the non-exposed parts remain water-soluble and will wash out by developing in water. Benzenediazonium, 4-(phenylamino)-, sulfate (1:1), polymer with formaldehyde, as well as different other diazo-compounds are generally available as photoactivatable reactive chemicals on the photolithography market. An overview of general information on the substances used within this alternative and the risk to human health and the environment is provided in Appendix 2. The main differences between the tested diazo compounds are the anion, the absence/presence of stabilizing agents (such as ZnCl2 or ZnSO4), and most importantly the degree and linearity of polymerization of the diazo polymer. Due to these differences, variations in the performance of the

Use number: 1 Legal name of the applicant(s): Veco B.V. 20 ANALYSIS OF ALTERNATIVES

PVA-diazo system in the mandrel application can be expected. Testing conducted with these different diazo compounds, confirmed the varying performance.

5.1.2. Technical feasibility General assessment: During the consultation phase, it was stated that extensive R&D efforts are ongoing on the aforementioned Benzenediazonium compound as a substitute to PVA-ammonium dichromate lacquers. Importantly, this substance does not necessarily constitute a standalone alternative but has also been tested in combination with Cr(III) chloride. The Cr(III) compound was added to improve the diazo-system, respectively to enhance the crosslinking efficiency and subsequently the adhesion of the lacquer to the substrate. Photo-sensitizing capacity: It is possible with this alternative, to produce a lithographic pattern, based on PVA lacquer. Hence, the photo-sensitizing capacity of the alternative is technically sufficient. However, the photo-sensitizing capacity as such is not the only requirement for the production of a mandrel (see following key functionalities). Adhesion to substrate: As mentioned above, the intrinsic crosslinking efficiency of ammonium dichromate is very high which is crucial for a sufficient adhesion of the entire lacquer to the substrate. These particular adhesion properties cannot be reached by diazo-components alone (insufficient adhesion). Therefore, tests series on the laboratory scale have been performed adding Cr(III) chloride to the lacquer system to enhance the crosslinking efficiency and subsequently the adhesion to the substrate. First characterisation tests showed improved adhesion properties, compared to diazo components alone. However, the adhesion was still insufficient and could not be reproduced in the current testing process (no adhesion of certain parts in some of the mandrels). As adhesion to the substrate is a crucial property for the subsequent electroforming process, further assessment and refinement is essential and accordingly, more time is needed. Pre-treatment of the stainless steel plate may provide a better lacquer adhesion. Currently, tests are going on to find a suitable pre-treatment method. Temperature resistance: Another crucial functionality is the temperature sensitivity of the lacquer- coated mandrel in the subsequent electroforming process. At a temperature of 40°C, promising electroforming results could be obtained in tests applying a mandrel coated with a diazo-containing lacquer. Both, with and without the addition of Cr(III). However, at higher electroforming process temperatures of 65°C, which are applied for most products, the PVA-diazo system with and without Cr(III) showed insufficient adhesion. For refinement and retesting diazo-solutions for this parameter, it is estimated that approximately 1 to 2 years is needed. XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXXXX Compatibility to PVA: The diazo based alternative, with and without Cr(III) chloride added, is compatible to PVA, however this is one of several key functionalities which have to be sufficiently fulfilled to guarantee the quality of the mandrel.

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES 21

Chemical resistance: The chemical resistance of the PVA-diazo lacquer, with and without addition of Cr(III) chloride, has been tested on laboratory and production scale. The PVA-diazo lacquer alternative seems to be chemically resistant to the electroforming bath chemistry. However, it will take a long time until any potential contamination of the bath caused by the mandrel can be seen. This must be further assessed during future production runs. High resolution and high definition of photo-images: Testing on laboratory scale indicate that the diazo lacquer system is comparable to the ammonium dichromate lacquer system in terms of resolution and definition of photo images. Nevertheless, high resolution and high definition is not only a result of the used aqueous solution of ammonium dichromate in combination with PVA. The specific lacquer development is partly determining the resolution and definition of the photo-image. Further research in production scale has to be carried out before a final assessment of this property can be done. Life time of non-exposed lacquer: The alternative was found to be sufficient in this regard. Conclusion: At the current stage of development, the tested diazo components, neither independently nor in combination with Cr(III) chloride, are not a feasible drop-in alternative to the aqueous solution of ammonium dichromate with PVA lacquers from the technical point of view. Several of the key functionalities stated below are not met.

Photo- High Life-time on Adhesion to Temperature Compatibility Chemical sensitizing XXXXX resolution non-exposed substrate resistance to PVA resistance capacity /definition lacquer Tested in lab Tested in lab scale only. scale only. Further Further

assessment in assessment in production production necessary. necessary.

5.1.3. Economic feasibility Implementation of a diazo based process comes with important process changes that influence the economic feasibility: - Costs for R&D: In order to further improve technically feasibility and for further development or adaptation of the process additional R&D investments are necessary in the coming years. These cost are estimated to exceed 135,000€ for 5 years. - Higher chemical costs – The annual tonnage of ammonium dichromate (40 kg) accounts for 3400€ (85€ per kg). When using diazo components, 50 kg per year would be needed, accounting for 10,000€ annually. - New equipment - An additional pre-treatment bath including air extraction must be implemented resulting in one-time costs of 70,000€. In addition to that, a nickel galvanic bath needs to be built specifically for razor foils to get the required surface quality. One-time costs for engineering, assembling and implementation are estimated as of 225,000€. - Production capacities – Based on the current performance of the alternative (XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX XXXXXXXXXX), extra production capacities would be needed to keep the production level of the nickel products on the same level. To handle this issue, the following extra costs are anticipated (based on estimate that the production has to be XXXX): o Coating machines 80,000€

Use number: 1 Legal name of the applicant(s): Veco B.V. 22 ANALYSIS OF ALTERNATIVES

o UV-exposure units 70,000€ o Development lines 350,000€ o Extra building capacities 200,000€ / year o Adapt building 250,000€ o Labour costs 6 x 60,000€ / year Taken together, one-time costs for the implementation of the alternative (including R&D costs) at same production level as current process would be 1,180,000€. Additionally, variable annual costs (building capacities, labour) per year account for 560,000€. Taking all these costs into account it can be stated that the alternative process based on diazo- compounds is clearly more expensive than Cr(VI)-based process. In combination with the currently insufficient technical performance, this cannot be considered a viable option.

5.1.4. Reduction of overall risk due to transition to the alternative As the alternative is not yet proven technically feasible, only classification and labelling information of substances and products reported during the consultation were reviewed for comparison of the hazard profile. Based on the available information on the substances used within this alternative (see Appendix 3.1.1), Cr(III) chloride would constitute the worst case scenario with a classification as Acute Tox. 4 (oral), Skin irrit. 2, Eye irrit. 2 and Acute Tox. 1 (inhalation). As such, transition from ammonium dichromate - which is a non-threshold carcinogen - to one of these substances would constitute a shift to less hazardous substances. According to the safety data sheets of the suppliers, the diazo compounds do not contain any free formaldehyde, which would not result in classification of the compounds with Carc. 1B, in view of the amended harmonized classification of formaldehyde from 1 January 2016. Any Zn-based or Co-based stabilizing agents will end up in the filtercake of the onsite WWTP.

5.1.5. Availability Extensive R&D on diazo compounds has been conducted since 2013 and progress has been achieved on the laboratory scale. Nevertheless, a comprehensive elaboration of the technical functionality of the alternative – both, on the laboratory and on the production scale – needs to be done – with and without the addition of Cr(III) chloride. First Step II tests have already been performed, but were not successful. Therefore, R&D had to step back to Step I for refinement of the process and conditions. A final decision on the overall performance in the initial tests (step I and II, chapter 4.1.1.) and the possible future use cannot be expected before 2016. In case the alternative is considered potentially suitable, the following developmental steps III to VII, as depicted in chapter 4.1.1., have to be passed, including: - Production tests (mandrel production and electroforming performance at 65° C) - Quality assessment and customer approval - Production tests full-range of PVA-based products - Implementation of alternative - Assessment of long-term behaviour of diazo in electroforming chemistry As stated, steps III to VII are estimated to take at least 5 to 6 years.

5.1.6. Conclusion on suitability and availability for Alternative 1 In summary, the tested ammonium dichromate free photo sensitizer system based on diazo-based compounds is no standalone alternative as it has not yet proven to be technically equivalent to

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES 23 ammonium dichromate. Ongoing testing of this substance showed promising results, although key functionalities such as temperature resistance and adhesion to substrate showed insufficient performance at laboratory scale. Since this system is in early research stage (Step I-II), a positive decision for the alternative (in case of) is not expected before the end of 2016 and in addition, 5 to 6 years for further development of the alternative for all product types including its implementation into the supply chain is anticipated. Consequently, the whole development and implementation process including multiple and time consuming customer approval will take at least 8 years if no major drawbacks occur.

5.2 Category 2 Alternatives Research and development currently focusses on category 1 diazo-compounds as most promising alternatives to ammonium dichromate-based photolithographic lacquer systems. The following represents a compendium of category 2 alternatives encompassing state-of-the-art information on the overall feasibility and limitations. During the consultation it was clearly stated that these alternatives are of very low maturity, with few preliminary laboratory tests performed so far. Based on the current state of knowledge, the tested substances show technical limitations for the use in photolithographic applications. In summary, Veco. has already decided to focus on further development of diazo- components. It is questionable if there will be more R&D on the Category 2 alternatives, as it is very likely that they will not be implemented.

Use number: 1 Legal name of the applicant(s): Veco B.V. 24 ANALYSIS OF ALTERNATIVES

Alternative Substance properties Overall Feasibility

• Initial testing at Veco based on literature showed thick layers with insufficient resolution and definition of patterns. Additional testing of thin layers (0.5 µm) coated with polyoxometalates lacquer indicated insufficient electrical resistance during the electroforming process causing nickel to be electroformed on top of the lacquer. The electrical A mixture of tungsten polyoxometalates and PVA as organic resistance is an intrinsic property of mandrels applied and the polymer create a deep UV photoresist, which forms a film of a electroforming process directly depends on it. water-soluble heteropolytungstic acid and a water-soluble organic • According to Carls et al. (1992) tungsten polyoxometalate creates a very polymer with a thickness of up to 1,100 Å. The film consists of stable chemical bonding, in turn not showing any degrading of the about 60 weight% tungsten with a density of 3.7 g/cm³ (Carls et resolution, even if the post-base step is delayed up to one day after al., 1992). The photoresist is hydrophilic and thus, able to wet exposure bake. However, no detailed quantitative information on relevant oxide surfaces. resolution and definition is available. The photochemical reaction of the above described film evolves Tungsten • The alternative may cause problems concerning the on-site wastewater in a way, that the heteropolytungstate exposed to UV radiation polyoxometalates treatment plant (WWTP), as it forms complexes with Ni-ions resulting absorbs the light and oxidizes the organic polymer. As a result, in Ni-release into the environment requiring adaptation of the WWTP or the polymer cross-links during a chemical amplification upon post separate disposal of the substance. exposure bake (Carls et al., 1992). The photoresist can be applied for example by spinning onto the respective layer. • For the proper application of the alternative, deep UV light (< 288 nm) is needed for sensitation entailing very high investments, as well as in The components of the resist are not toxic and because it is a very new photo tooling and exposure equipment. stable chemical bonding, the resolution does not show degrading, even if the post-base step is delayed up to one day after exposure • Additional costs arise from purchasing large amounts of the substance at bake (Carls et al., 1992). a price of € 800 per kg. As only preliminary testing was conducted with this alternative at Veco, this substance would have to pass the whole development process which would take even longer than for the alternative 1 discussed in the previous chapter. The chance of successful implementation of an alternative based on tungsten compounds is very low given the insufficient electrical resistance. Iron(III) chloride works as a cross-linking and oxidizing agent to • The Fe(III) doped PVA shows a good swelling behaviour and provides PVA during UV radiation. The resulting Iron(III) chloride doped the feasibility to cure thicker samples and can be considered for the use PVA is a convenient UV curable organometallic polymer as water-soluble and water-developable photoresist for rapid curing (Schauberger et al., 2013), used for optical data processing applications using high UV irradiation intensities (Schauberger et al., Iron (III) as iron(III) technologies and real time holographic recording. 2013). chloride or ammonium Two different UV initiated cross-linking mechanisms of Iron(III) iron(III) citrate • As stated in literature, the absorption of Fe(III) doped PVA is strongly chloride doped PVA are referenced in literature: While one increased compared to non-treated PVA for the wavelength range 250- literature reference (Manivannan et al., 1994) proposed the cross- 500 nm. This effect is caused by the Fe3+ cations (Schauberger et al., linking to be caused by charge transfer from Fe3+ to the polymer 2013) and three absorbance maxima (at 250 nm, 320 nm and 360 nm) and radical generation, another reference (Kowalonek et al., are observed. 2010) claims the generation of chlorine radicals during irradiation

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES 25

Alternative Substance properties Overall Feasibility

of FeCl3 and reaction with PVA to macro radicals followed by • Initial laboratory tests at Veco indicated that the FeCl3 + PVA system is subsequent recombination and formation of cross-links. a positive resist (in contrast to the current PVA + ammonium dichromate negative resist). Furthermore, both, the exposed and the unexposed lacquer, are removed at development, but at different speeds, making it a crucial process parameter to be controlled. When using ammonium dichromate, the exposed lacquer is not removed at all. As such, application of the alternative would entail the adaptation of the entire equipment, including the renewal of the phototooling (e.g. masks). • Ammonium iron(III) citrate may be another potential alternative (“Chiba system”), but has not yet been tested at Veco Until now, only ferric chloride has been tested in initial laboratory scale experiments. No detailed experience and testing was conducted with this alternative at Veco so far. Accordingly, this substance would have to pass the whole development process which would take even longer than for the alternative 1 discussed in the previous chapter. Furthermore, high investments are needed for renewal of the equipment and photo tooling. Terephthalic aldehyde (TPA) is an aldehyde of the aromatic dicarbonic acid terephthalic acid (or benzenedicarboxylic acid) and has been found to work as a cross-linking agent as well as a • Deep UV radiation (< 250 nm) is needed for the sensitization of TPA. probable sensitizer with PVA during ultraviolet exposure. Due to very high capital investments needed for the respective The detailed photochemical transformation of PVA has been equipment, TPA is considered economically unfeasible. Terephthalic aldehyde studied in literature (Polavka et al., 1980) by exposing PVA films No detailed experience and testing was conducted with this alternative at - in the presence as well as in the absence of TPA – to ultraviolet Veco so far. Accordingly, this substance would have to pass the whole radiation. As shown in Polavka et al. (1980), by adding TPA into development process which would take even longer than for the alternative 1 PVA, the intensity of the ultraviolet spectrum shifted to longer discussed in the previous chapter. wavelength and decreased with the duration of exposure.

In addition to PVA based lacquer systems, non-PVA lacquer systems are available and include, but are not limited to (Kapp- • Such non-PVA systems are mainly used in electronics. Since they are Schwoerer et al., 2004): dedicated to single run applications, they are not suitable to replace the Non-PVA lacquer - Cyclic poly-Isopren based resists (cyclized rubber), existing system, XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX systems - Diazo naptho quinone based resists, XXXXXXXXXXXXXXXXX. In addition, those systems are known to - Polyvinyl cinnamate type resists, be deficient in terms of robustness. - Epoxy based resists

Use number: 1 Legal name of the applicant(s): Veco B.V. 26 ANALYSIS OF ALTERNATIVES

Alternative Substance properties Overall Feasibility

• Following the consultations, the adhesion of the digitally inkjet printed lacquer to the substrate is low, as the strength of the lacquer is insufficient. • According to Singh et al. (2010), inkjet printing offers resolutions in the Following Singh et al. (2010), inkjet printing is a deposition micrometer range, and hence it is a potential technique for dispensing technique used for liquid phase materials, such as inks. These etching species, in applications like flat-panel displays, etc. As stated materials consist of a solute dissolved or otherwise dispersed in a during the consultation, the current resolution obtained by digital inkjet solvent. The process essentially involves the ejection of a fixed printing is inadequate XXXXXXXXXXXXXXXXX). quantity of ink in a chamber. A chamber filled with liquid is • The inkjet printing technique is used for applying etch resists, mainly on Digital inkjet printing contracted in response to application of an external voltage. This copper surfaces. Adhesion of the ink to the substrate as well as the sudden reduction sets up a shockwave in the liquid, which causes quality of the image are of less importance for etch resists compared to a liquid drop to eject from the nozzle. The ejected drop falls under the use in electroforming. In addition, the printed image is used only action of gravity and air resistance until it impinges on the once in etch applications. substrate. The drop then dries through solvent evaporation. Preliminary experiments at Veco have been carried out with inkjet printing, applying hotmelt and UV-curable inks. The chemical resistance in the electroforming bath as well as the adhesion of the available inks to the substrate turned out to be not sufficient. Besides, the quality of the image, i.e. contour definition of the resist spot, tolerance and resolution, would have to be improved considerably. 4,4′-diazidostilbene- 2,2′-sodium disulfonate (DAS) aqueous These monomer components are not suitable for sensitizing PVA (i.e. solution; 2,5-bis(4′- negative photoresist system). They have been used for curing positive resist azido-2′- systems only. This would lead to high investment costs for equipment and sulfobenzyliden) photo tooling in addition to the R&D costs. cyclopentanon disodium salt (DAP) aqueous solution

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES 27

6. OVERALL CONCLUSIONS ON SUITABILITY AND AVAILABILITY OF POSSIBLE ALTERNATIVES Extensive research efforts have been deployed over the last decades to identify and develop viable alternatives to ammonium dichromate-based photolithographic applications. The unique functionalities of ammonium dichromate make it an ideal and not easy to replace substance in these photolithographic applications where superior requirements have to be fulfilled to ensure the quality of the final product. As a result of the R&D efforts, the Benzenediazonium compound / formaldehyde (1:1) (or diazo compound) was identified as only potential alternative, which is the current focus of Veco´s development process. As of today, this substance does not currently support the necessary combination of key functionalities to be considered a technically feasible alternative. Current issues are temperature resistance, adhesion to substrate XXXXXXXXXXXXXXXXXXX. However, it is believed that this alternative can be turned into a suitable alternative after the necessary R&D has taken place. For the current alternative under development, development steps were initiated in 2013 and are still ongoing. As of today, this alternative has not proven to be technically suitable, which is discussed in more detail in chapter 5. It is not yet clear when step I and II of the development process will be accomplished. According to the current stage of research in 2016, another 2-3 years are estimated if no major drawbacks occur. The following steps (III-VII) are estimated to take at least an additional 5 to 6 years. Figure 17 summarizes the development stages for the substances tested. Besides the diazo compounds, only preliminary testing with a few other substances was performed, confirming that the diazo compounds are the most promising chemicals leading to a suitable alternative for ammonium dichromate.

Figure 17: Overview on development progress on alternatives to ammonium dichromate.

The multitude of products electroformed for various customers as mentioned earlier, is a decisive factor concerning the time needed for approval and release in case of alternate processes to be developed. Articles electroformed are very diverse and each of the products require customized specifications (and thus a customized mandrel). Indeed, specifications vary according to individual demands. For all of these products produced by electroforming, there are XXXXXXXXXX customers worldwide, most of them with specific requirements. Those detailed differentiations across a multitude of customers and products are the main reasons for multiple iterations of the approval and release steps as stated above leading to long-lasting approval and release periods.

Use number: 1 Legal name of the applicant(s): Veco B.V. 28 ANALYSIS OF ALTERNATIVES

Consequently, a review period of at least 7 years is necessary to conduct and intensify further R&D on the currently focused diazo compounds and finally substitute ammonium dichromate for the various products.

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES 29

7. REFERENCES Carls, J.C, Argitis, P. & Heller, A. (1992): Deep Ultraviolet Photoresist Based on Tungsten Polyoxometalates and Poly(Vinyl Alcohol) for Bilayer Photolithography, J. Electrochem. Soc., Volume 139, Issue 3, pages 786-793. Kapp-Schwoerer, D., Meier, K. & Gantner, C. (2004): Liquid Resists for Photo Chemical Machining, published at the HTP HiTech Photopolymere AG, Basel, Switzerland, 18 pages. Kowalonek, J., Kaczmarek, H. & Bajer, D. (2010): Surface Properties of Poly(vinyl alcohol) with Iron(III)chloride Before and After UV-Irradiation, Macromolecular Symposia, Special Issues: New Frontiers in Macromolecular Sciences, Volume 295, Issue 1, pages 114-118. Manivannan, G., Nikolov, O., Kardinahl, T., Keune, W. & Franke, H. (1994): Charge transfer phenomenon in optical storage material: Fe3+ doped poly(vinyl alcohol), Proc. SPIE. 2042, Photopolymers and Applications in Holography, Optical Data Storage, Optical Sensors, and Interconnects, 98. Polavka, J., Uher, M., Lapčik, L., Čeppan, M., Valašek, J. & Havlínová, B. (1980): Crosslinking of polymers by the effect of ultraviolet radiation – crosslinking of poly(vinyl alcohol) in the presence of terephtalic aldehyde, Chemické Zvesti, Volume 34, Issue 6, pages 780-787. Schauberger, J.G., Riess, G. & Kern, W. (2013): UV Crosslinking of Fe3+-doped Poly (vinyl alcohol) – Characterization of Optical Properties and Swelling Behaviour, Journal of Applied Polymer Sciences, Volume 129, Issue 6, pages 3623-3628. Singh, M., Haverinen, H.M., Dhagat, P. & Jabbour, G.E. (2010): Inkjet Printing – Process and its Applications, Advances Materials, Volume 22, pages 673-685.

Use number: 1 Legal name of the applicant(s): Veco B.V. 30 ANALYSIS OF ALTERNATIVES

APPENDIX 1 – INFORMATION ON RELEVANT SUBSTANCES FOR IDENTIFIED ALTERNATIVES

APPENDIX 2.1: ALTERNATIVE 1: 4-Anilinobenzenediazonium hydrogen sulphate polymer with formaldehyde (1:1) Table 1: Substance IDs and properties for relevant substances.

Physicochemical Parameter Value Value properties Benzenediazonium, 4- Chemical name and Physical state at 20 °C and (phenylamino)-, sulfate (1:1), composition 101.3 kPa polymer with formaldehyde EC Number 609-923-9 Melting point

CAS Number 41432-19-3 Density 4-anilinobenzenediazonium IUPAC name hydrogen sulphate polymer with Vapour pressure formaldehyde (1:1)

Molecular formula C13H13N3O5S Water solubility

Molecular weight 323.32 g Flammability Physico-chemical Parameter Value Value properties Chemical name and Physical state at 20°C and Chromium(III) chloride solid composition 101.3 kPa EC number 233-038-3 Melting point ca. 1150 °C

CAS number 10025-73-7 Density 2.87 g/cm³ (25 °C)

IUPAC name Chromium(III) chloride Vapour pressure -

Molecular formula CrCl3 Water solubility 0.585 g/cm³ Flammability Non-flammable Molecular weight 158.36 g/mol Flash Point -

Table 2: Hazard classification and labelling. No. of Additional Hazard Class Hazard Statement Notifiers classification Regulatory and Substance Name and Category Code(s) (CLP and labelling CLP status Code(s) (labelling) inventory) comments H302 (harmful if Acute tox. 4 swallowed) H315 (causes skin Notified Skin irrit. 2 25 State : Solid 4-anilinobenzene- irritation) classification diazonium hydrogen sulphate H319 (causes serious Eye irrit. 2 polymer with eye irritation) formaldehyde H242 (heating may (1:1) Self-react. D cause a fire) Notified 1 State : Powder H302 (harmful if classification Acute tox. 4 swallowed)

Use number: 1 Legal name of the applicant(s): Veco B.V. ANALYSIS OF ALTERNATIVES 31

No. of Additional Hazard Class Hazard Statement Notifiers classification Regulatory and Substance Name and Category Code(s) (CLP and labelling CLP status Code(s) (labelling) inventory) comments H319 (causes serious Eye irrit. 2 eye irritation) Aquatic acute H400 (Very toxic to 1 aquatic life) H410 (Very toxic to Aquatic aquatic life with long chronic 1 lasting effects) H319 (causes serious Notified Eye irrit. 2 1 State : Powder eye irritation) classification Not classified 7 H302 (Harmful if Additional 6 Acute Tox. 4 swallowed) parties notified Currently not the substance as REACH H315 (Causes skin Skin Irrit. 2 Acute Tox 4 registered; irritation) (H302) only. Not included in Chromium H319 (Causes 41 the CLP chloride Eye Irrit. 2 Further 6 notifiers serious eye irritation) submitted the Regulation,

classification as Annex VI; as Acute Tox 4 Included in C&L H330 (Fatal if Acute Tox. 1 (H302) and inventory inhaled) Aquatic Chronic 3 (H412).

As none of the Category 2 alternatives can be considered suitable at present and no significant research is carried out today, it is not considered relevant to present and discuss the physico-chemical properties and hazard data at this point.

Use number: 1 Legal name of the applicant(s): Veco B.V.