Shrinking Devices, Growing Demand Meeting the Electronics Gas Challenge by Dr
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Meeting the Electronics Gas Challenge Shrinking Devices, Growing Demand Meeting the Electronics Gas Challenge By Dr. Anish Tolia Demand for consumer electronics devic- cleaning of CVD (chemical vapor depo- terial. In lithography, gases are used to es is still strong. Smartphone sales will sition) reactors. There are two categories support high-precision excimer laser pro- approach 1.5 billion units in 2015. These of deposition gases: silicon precursors, cesses and patterning. The circuit design smart devices require an increasing num- which are used in CVD of silicon contain- layouts are transferred to the photoresist ber of ever more complex and smaller ing layers, and reactant gases, which are on the wafer surface. And in purging, at- semiconductors. Manufacturing fabs are used in the deposition of silicon nitride mospheric gases are used to purge process challenged to meet more complex technol- and metal nitride layers. Some gases are systems to prevent back contamination. ogy nodes. That impacts the entire supply used for doping, which introduces an im- chain, in which gases play a critical role. purity into a semiconductor to improve its Electronic Bulk Gases This article discusses the impact of cus- conductivity. In etching (removal), gases The major bulk gases used in the manu- tomer demand for smart and small devices are used to strip away undesired layers. facture of semiconductors are nitrogen on the requirements for gases needed to This includes wet or dry and blanketed (N2), hydrogen (H2), argon (Ar), oxygen produce these products. or patterned etch and CMP (chemical me- (O2 ), and helium (He). chanical polishing). Gases also are used Semiconductor Market in heating to elevate the temperature of Nitrogen is by far the most used gas in As the semiconductor market matures, the wafer and drive chemical reactions to semiconductor manufacturing. It is used its growth depends on global GDP per- modify the properties of deposited ma- for purging vacuum pumps, in abatement formance. Last year was a strong year with nine percent growth; 2015 started out strong, but analysts expect a slowing in the second half. However, long term drivers remain robust. The main drivers are still mobile and PCs, but other smaller segments such as automotive, game con- soles, medical, digital TVs, set-top boxes, wireless networks, wearable devices, and the Internet of Things (IoT) are showing high growth. The year 2014 saw an up- surge worldwide of 10 percent in integrat- ed circuits and semiconductor companies are increasing capacity to meet this de- mand. Gases Used in the Semiconductor Industry According to analysts, the 2014 electronic specialty gas market was over $2.1 billion and the 2014 electronic bulk gas market was an additional $1.9 billion, which to- gether comprised a total electronic gas market of $4.1 billion. Due to the complexity of semiconduc- tor manufacturing, there are hundreds of gases and chemicals used in several hun- dred process steps in the manufacturing of semiconductors. Gases are used in a variety of ways in semiconductor manufacturing. For ex- ample, gases are used in plasma chamber 30 November 2015 – CryoGas International Meeting the Electronics Gas Challenge systems, and as a process gas. At more ad- Number of Layers By Node vanced process nodes, nitrogen consump- tion has increased substantially. Single non immersion Single non immersion In large, advanced fabs, consumption LELE EUV of nitrogen can reach 50,000 cubic me- 50 ters per hour, which makes the case for SADP SAQP cost-effective, low-energy, on-site nitro- gen generators. Ultra-pure gaseous and 40 liquid nitrogen can be provided on-site with less than one part per billion (ppb) 30 impurities without the need for an external purifier. 20 Hydrogen is also increasing in usage due to larger fabs and enlarged capacity. It is 10 used during epitaxial deposition of silicon and silicon germanium and for surface 0 preparation. With the move to EUV (Ex- DPT treme Ultra Violet) in the future, hydrogen EUV 65mm 45mm 32mm 10nm- 10nm- use will see an even bigger spike. Hydro- 20/16 /14mm gen can be delivered as compressed gas or in liquid form (only in US and Europe), Figure 1 Source: Linde Electronics but due to the growing need, more fabs are installing on-site production through Silane (SiH4) is the primary Si source for High-purity carbon dioxide (CO2) is be- steam reforming or electrolysis. deposition of Si-based thin films such as ing increasingly used to replace air in the SiO2 and SiN. liquid immersion systems of high-end li- Argon is used in various applications in- thography systems. cluding the deep UV lithography lasers Nitrogen trifluoride (NF3) is used in the used to pattern the smallest features in cleaning of silicon wafers and is also an New Semiconductor semiconductor chips and plasma deposi- etchant. Technologies tion and etching processes. In the manu- Mobile devices are now the primary facture of silicon wafers, large amounts Tungsten hexafluoride (WF6) is used in drivers of Moore’s Law and the move to of argon are used to protect the silicon low pressure or plasma-enhanced CVD more advanced technology nodes to meet crystal from reactions with oxygen and of tungsten or tungsten silicides. consumer wants. These wants and drivers nitrogen while it is being grown at tem- of new technology include lower power, peratures change to greater than 1400ºC. Hydrogen chloride (HCl) is used to clean longer battery life, increased storage ca- And increasingly, tools using small drop- and to etch semiconductor crystals. pacity, and higher performance. What are lets of liquid argon are employed to clean some of the new semiconductor technol- debris from the smallest, most fragile chip Ammonia (NH3) is used as nitrogen ogies and their implications for gases? structures. source in the chemical vapor deposition process of nitride films. Multi-patterning Oxygen is used for purging, growing ox- Due to ever smaller devices, the feature ide layers, and in etching polymer materi- Disilane (Si2H6) is increasing in semi- size is now smaller than the wavelength als. Ultra-pure liquid oxygen (LOX) can conductor memory (DRAM and NAND of light. Multi-patterning is a way to get be provided on-site with less than 10 ppb flash) for lower-temperature silicon dep- around that. impurities without the need for an external osition for making high-quality ultra-thin Multi-patterning requires significantly purifier. epitaxial films in advanced technology more process steps and more deposition nodes and is a preferred alternative to and etch tools and thereby drives in- Helium is used in electronics manufac- silane. creased consumption of both bulk gases turing at hundreds of points in the fab for and ESGs. For example, multiple lithog- cooling, plasma processing, and leak de- Germane (GeH4) is a silicon precursor raphy steps means more laser gases and tection. used to form and deposit the SiGe (sili- deposition and etch materials, especially con-germanium) layer on silicon wafers. low-temperature deposition and high- Electronic Specialty Gases The use of germane in the semiconductor ly selective etch materials. At the same There are hundreds of electronic specialty industry is increasing due to the move to time, an increased number of process gases used in the manufacture of semicon- smaller transistors with higher switching chambers drives larger nitrogen con- ductors. Some of the most common are: speeds. sumption. November 2015 – CryoGas International 31 Meeting the Electronics Gas Challenge 3D Devices have seen many delays, it is now predict- Because of the need for lower power and ed to be in production at 7 nm in logic higher performance in more complex and (around 2018). miniscule devices, which 2D devices can- Immersion lithography creates a strong not handle, there is a move in the industry demand for precise laser gas mixes of in- to 3D devices such as 3D FinFET and 3D ert gases (Kr/Ne/Ar) mixed with N2 or H2 NAND and the resulting increase in circuit and additional bumps of ultra-high purity density. (UHP) CO2 for immersion lithography. The 3D structured semiconductor devic- While EUV tools use different gases es era started when Intel produced Trigate, from traditional and immersion lithogra- a FinFET transistor, in 2011 as its 22 nm phy, EUV is expected to be used for only logic chip. Si FinFET transistors become the most critical layers; less critical layers the mainstream logic transistor of choice will still use ArFi (immersion) and mul- at 16/14 nm. ti-patterning. With FinFET 3D CMOS transistors, For EUV, CO2 is used as a laser gas. The the industry should continue the scaling 3D FinFET new source architecture is changing the roadmap for performance, power, and area light generation concept, switching from a (PPA) into 7 nm technology nodes. direct light source (excimer lasers) to an NAND flash memory has the highest indirect light generation (a CO2 laser beam transistor density of all semiconductor hitting a tin droplet, leading to the genera- products and is moving to the 3D era to tion of EUV light). increase gate density and to reduce cost These tin droplets can cause tin deposi- per bit of storage. Another motivation of tions on the reflecting optics, leading to a 3D NAND is scaling challenges in lithog- reduction in light power. To prevent this, raphy. hydrogen is used to form volatile tin com- With FinFET technology, there is an in- pounds, which can be pumped away, pre- crease in transistor processing such as ep- venting a reduction in the amount of pho- itaxy and ALD (atomic layer deposition). tons available for illumination. Compared This drives the need for more epitaxial to other gases like nitrogen, hydrogen has materials such as trichlorosilane, HCl, and a low absorbance for EUV light, making germane as well as ALD precursors.