UCTEA Chamber of Metallurgical & Materials Engineers’s Training Center Proceedings Book

Historical Development of Czochralski Process and Single Growth

Ayberk Yenice, Necip Ünlü Istanbul Technical University, Metallurgical and Materials Engineering Department, Maslak, Istanbul, Turkey

Abstract is about 250.000 t/year [1, 2]. Since the technological developments, single with growth that invented by Jan Czochralski, diameters up to 450 mm and weights of more than 300 kg was essentially used in AEG laboratory in 1916. Further can be industrially manufactured by the Czochralski development was about obtaining bulk crystals according process today [1]. Aim of this study is to emphasize the to matching of the velocity and pulling importance of the Czochralski process via presenting a rate. Gomperz improved the Czochralski process by comprehensive overview. changing die, crucible, and cooling system in 1922. One year later, Goens and Gruneisen applied different method 2. Historical Development of Czochralski Process to obtain crystal having certain orientation. Henry Walter In the 19th and 20th centuries, the developments in from Bells Laboratory designed a new furnace and thermodynamics, nucleation and growth theories provided succeeded about crystal rotation, producing non-metallic the basic aspects of technology [2]. and enhancing dimensions. After the WWII with Although it has been accepted that the first inventor of invention of contact-transistors, importance of the crystal growth is J. Czochralski, according to Scheel [2], significantly increased. Using the founder of industrial crystal growth is A. Verneuil microprocessors provided automatic control of crystal [2,4]. Czochralski discovered his process through a growing process. In the end of 1960s, the process of creative mistake [5, 6]. While he was working on the rate single crystal technique became similar to today’s of crystallization of metals, he terminated an unsuccessful process. Research and development activities on single trial with a melt. He placed the full, hot crucible on the crystal processes have been continued due to necessity of edge of the desk to cool. Then, while taking notes, he improving technology. In this study, accidentally dipped his pen not into the ink well, but into manufacturing of single crystal, Czochralski method, its the crucible with molten tin. When he lifted his arm parameters, and historical developments have been quickly, a long and thin thread was hanging onto the pen. discussed in detail. By etching with acid, the first single crystal was drawn out 1. Introduction of the crucible by Czochralski [6]. The first drawing of Czochralski’s setup is given in Figure 1. The Czochralski process that has been invented by Jan Czochralski is a single crystal growth method by pulling poly-crystal feed from the melt [1]. Czochralski process pioneered the industry of microelectronics, , power electronics and many other technological applications. Products of crystal growth process are approximately used 60% in , 20% in optical process, and the rest is shared upon other applications like , jewelry, and watch industries [2]. It is well-known that a single crystal (mono-crystalline) is a matter in which the structure presents a strict order atomic arrangement, i.e., nearly perfect crystal [3]. Most common usage of the Czochralski process is the growth of semiconductors, especially of mono-. This technique has a significant importance for hundred years, because the demands on the required materials for Figure 1. Czochralski setup from 1916 [5]. The industries like semiconductor, photovoltaic and clockwork microprocessor have been increased significantly. motor (U) draws the single crystal (E) out of the melt (S) Although the manufacturing of bulk crystal was about which sits in the crucible (T). The resides in 20.000 t/year in 1999, today manufacturing only for a capillary (K), which is attached to a thread (F). The

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capillary (K) is shown on the right-hand side of the semiconductor crystals. Perfect single crystals of oxides apparatus, magnified six times. have a significant importance for laser applications. Czochralski measured crystallization velocities of several CaWO4 was the first Czochralski oxide crystal, grown by elements, i.e., Sn, Pb, and Zn, 90, 140, and 100 mm/min., Kurt Nassau in 1960 (Table 3). In 1961, Kurt Nassau respectively [4]. E. von Gomprez changed the obtained several divalent metal fluorides (CaF2) by using Czochralski setup by introducing a die to control crystal Czochralski method, included the common materials i.e., diameter and using a N2 stream in 1922 [4]. The NaCl, KCl, and LaF3 [4]. Czochralski process has been introduced in the USA in 1922. In 1929, the most important research was to Table 2. Manufacturing Centers of Compound Crystals determine the crystal orientation by changing of dipping [4] orientation of seed material. In 1934 and 1935, diameter Year Company Institute Crystals of crystals reached from 1-3 mm to 11 mm. Until this 1954 , Murray Hill/NJ InSb, time, only low melting temperature materials obtained as GaSb a single crystal. Henry Walter was the first to introduce 1958 1958 MIT, Lexington/MA GaAs crystal rotation to the Czochralski process, also he was 1958 Batelle Institute, Columbus/OH AlSb the first to control the crystal shape and diameter during 1959 Chicago Midway Lab., Chicago/IL InSb InSb Czochralski growth. Henry Walter obtained straight rods Strauss with 2 cm diameters and 30 cm lengths, and <110>, 1959 RCA Laboratories, Princeton/NJ GaAs <100>, and <111> orientations [4]. After the WWII, the 1960 Philips, Aachen/Germany Bi Te first Ge crystal was manufactured in the USA in 1948 by 2 3 Cd As , G.K. Teal and J. Little. In 1949, bulk silicon single 3 2 CdAs , crystals by Czochralski process were manufactured in 2 1961 IBM Corp., Poughkeepsiee/NY CdSb, Bell Laboratory, thus, the first Si-based transistor built by Zn As , Pietenpol and Ohl at Bell Labs [7]. Dash [8], from the 3 2 ZnAs , General Electric Research Laboratory, in 1959, exhibited 2 ZnSb that crystals free from can be grown by the 1961 Ampex, Culver City/CA GaAs proper selection and preparation of the seed crystal. 1961 General Electric Research Laboratory, GaSb Davies [9] from Honeywell obtained the first tellurium Schenectady/NY single crystals in 1957, and Keezer [10] from Xerox achieved the first selenium single crystal in 1967. In 1962 US Naval Ordnance Lab, White PbTe Table 1, the extendibility of the Czochralski process for Oak/MD the growth of elemental semiconductors in the USA is GaAs presented [4]. 1963 Texas Instruments Inc., Dallas/TX InAs PbTe Table 1. Manufacturing Centers of Silicon [4]. GaAs Year Company/Institute Note 1964 Stanford University, Stanford/CA GaP 1949 Bell Telephone Laboratories, First Si 1968 Hughes Res. Lab., Malibu/CA Ag3AsS3 Murray Hill/NJ crystal Ag3SbS3 1952 1952 Technische Hochschule, GeTe Stuttgart/Germany 1969 Sandia Nat. Labs. Albuquerque/NM SnTe 1954 Texas Instruments Inc. , 1959: PbTe Dallas/TX 15.24cm 1954 Raytheon Corp. , Table 3. Manufacturing Centers of Oxides [4]. Waltham/MA Year Company/Institute Crystals 1956 Associated Electrical 1960 Bell Labs, Murray Hill/NJ CaWO4 Industries Ltd., Aldermaston 1961 General Electric Research (AEI)/United Kıngdom Laboratory, Schenectady/NY Fe3O4 1956 Shockley Semiconductor Lab., Silicon 1962 Raytheon Corp., Waltham/MA Y3Fe5O12 Mountain View/CA Valley 1963 Sperry Rand Res. Center, 1957 Fairchild Semiconductor, San Silicon Sudbury/MA CaWO4 Jose/CA Valley 1963 US Army Electronics R & D Lab., CaWO4 1958 Knapic Electrophysics Silicon Fort Monmouth/NJ Inc.,Palo Alto/CA Valley 1964 Bendix Corp., Southfield/MI CaWO4 1959 General Electric Research 1965 Aerojet-General Corp., Azusa/CA Laboratory, Schenedady/NY Dash neck Cu2O 1965 Westinghouse Res. Lab., Also in 1954, the fırst compound semiconductor such as Pittsburgh/PA ZnWO4 InSb and GaSb was manufactured in 1954 at Bell 1966 IBM Corp., Poughkeepsiee/NY LiNbO3 Laboratory (Table 2). Afterwards, many institutions 1967 Union Carbide Corp., manufactured same or different type of compound Indianapolis/IN Cr:Al2O3

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1967 Air Force Cambridge Res. Lab. rotation of the crystal. The crystal diameter and the hot Bedford/MA Li2Ge7O15 zone geometry are directly related to the pulling rate. 1 1968 Sandia Nat. Labs, Albuquerque/NM LiGaO2 mm/min and 20 rpm are the typical rates for pulling, and 1970 Stanford University, Stanford/CA LiNbO3 crystal rotation, respectively. The main heater (6a) and  the bottom heater (6b) are the main parts of hot zone In Japan, Hitachi University and the Nagoya University which is the key part in controlling the growth process. presented growth in 1961 [11], and 1969 gas flow prevents the contamination of the Si melt [12], respectively. Nozaki [13] at Komatsu achieved the by residual gases such as CO and H2O, also, removes the first silicon crystal in 1970. In 1983, vapor pressure evaporating SiO from the melt surface. In the Czochralski controlled Czochralski method presented by Azuma [14] pullers, an external magnet is used to control the from Furukawa Electric Co. Ltd., for the growth of transport [15]. compound semiconductor crystals. In Figure 3, the steps of the Czochralski process is given 3. Czochralski Process detailed.

The basics of the Czochralski process is shown in Figure 2 that presents the setup of an industrial type Si Czochralski puller [15].

Figure 3. The Steps of The Czochralski Process [15]. (a–j) of the Czochralski process for growing a silicon crystal (5). (a) The polycrystalline feedstock (2) is melted Figure 2. Setup of An Industrial Type Silicon (b) in a silica crucible (1). (c, d) Seeding procedure: The Czochralski Puller [15]. Si seed crystal (4) is dipped into the melt (3), followed by the Dash procedure (e) of growing a neck (5) (e), After loading the feed material into shouldering (f), cylindrical growth (g), growth of end the bowl-shaped silica crucible, in an inert gas (argon) cone (f), lift off (i), and cooling down and removing of atmosphere, the melting is performed. By dipping a the crystal (j). silicon seed crystal into the surface of the silicon melt, crystal growth begins. Then, the seed is drawn from the Figure 4 shows a cooled silicon single crystal with a melt slowly. The vacuum-proof cylindrical main vessel diameter of 300 mm, about 2 m in length, and weighing (1) has water cooled steel walls. The upper chamber is approximately 265 kg that was produced by the directly connected with the main vessel. A major source Czochralski Process [5]. of impurity contamination to the Si crystal is the crucible material, thus, the required purity, mechanical stability, and chemical inertness are provided by using fused silica crucibles. Temperature, flow rate in the melt, argon pressure, and flow rate in the gas above the melt surface, have significant effects on the dissolution rate of the silica crucible. Additionally, high silicon melt temperature causes increasing the crucible corrosion, and decreases its mechanical stability. The purity of the growing crystal directly is related to the purity of the melt. The seed holder (5b) is typically made from molybdenum, and connected to either a pulling shaft (5c) or a pulling wire. The pulling unit (5d) provides the

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[12] T.Arizumi, N.Kobayashi,The Solid-Liquid Interface Shape During Crystal Growth by The Czochralski Method, Jpn. J. Appl. Phys. 8 (1969) 1091-1097. [13] T.Nozaki, Y.Yatsurugi, N.Akiyama, Concentration and Behavior of in Semiconductor Silicon, J. Electrochem. Soc. 117 (1970) 1566-1568. [14] K.Azuma, Method and Device for Producing Compound Single Crystal with High Dissociation, Jap. Patent, 60-11299, 1983. [15] T. Nishinga, Czochralski Growth of Silicon Crystals, Ed. By P. Rudolph, Handbook of Crystal Growth, Elsevier B.V., 2015,Amsterdam, The Netherlands.

Figure 4. A Single Crystal of Silicon, 300 mm in diameter, 2 m long, and weighing 265 kg, obtained by the Czochralski Process [5]. 4. Conclusions

Life without single crystals is barely conceivable due to the fact that microelectronics and information technology cannot be survived without single crystals. It is obvious that the evolutions begun with Jan Czochralski’s creative mistake will continue progressively.

References [1] J.Friedrich, W.Ammon, G.Müller, Handbook of Crystal Growth Chapter 2, Czochralski Growth of Silicon Crystals, Elsevier, 2015. [2] H.J.Scheel, Historical Aspects of Crystal Growth Technology, Journal of Crystal Growth, 211 (2000) 1-12. [3] P.Rahmanpour, S.Saelid, M.Hovd, Run to Run Control of The Czochralski Process, Computers and Chemical Engineering, 104 (2017), 353-365. [4] R.Uecher, The Historical Development of The Czochralski Method, Journal of Crystal Growth, 401 (2014), 7–24. [5] J.Evers, P. Klüfers, R. Staudigl, P. Stallhofer, Czochralski’s Creative Mistake: A Milestone on the Way to the Gigabit Era, Agnew. Chem. Inst., 42 (2003), 5684- 5698. [6] P. E. Tomaszewski, Jan Czochralski-Father of the Czochralski method, J. Cryst. Growth, 236, (2002), 1-4. [7] W.J.Pietenpol, R.S.Ohl, Characteristics of Silicon Transistors, Conference on Electronic Devices, 22 June 1950, U. Michigan, Ann Arbor, USA. [8] W.C.Dash, Growth of Silicon Crystals Free from Dislocations, J. Appl. Phys., 30 (1959), 459-474. [9] T.J.Davies, Growth of Tellurium Single Crystals by the Czochralski Method, J. Appl. Phys., 28 (1957), 1217- 1218. [10] R.C.Keezer, C.Wood, J.W. Moody, Crystal Growth, in: H.S. Peiser (Ed.), Pergamon, Oxford, (1967), 119-123. [11] H. Ueda,Resistivity Striations in Germanium Single Crystals, J. Phys. Soc. Jpn. 16 (1961) 61-66.

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