Jan Czochralski and His Method of Pulling Crystals

www.mrs.org/publications/bulletin HISTORICAL NOTE Jan Czochralski and His Method of Pulling Crystals The most advanced factories, or “fabs,” Main (which in due course became the in which integrated circuits are made use leading German metallurgical firm), and circular slices of silicon 300 mm in diame- 1939, when his research came to an end. ter. They are sliced from huge single crys- He worked in Frankfurt until 1929, and tals that are drawn from a molten silicon among other achievements, he played a bath; these massive crystal ingots are major role in creating the Zeitschrift für rotated as they are slowly raised in syn- Metallkunde and later, the scientific society chrony with their growth rate, and the Deutsche Gesellschaft für Metallkunde. process has been perfected to the point Throughout his years as a researcher and where the dislocation population is about research director, Czochralski mixed a million times lower than in a normal crystal. This procedure was initially devel- oped by Gordon Teal and his colleagues at Bell Laboratories and then at Texas Instruments, from 1948 to 1952. However, the process was by no means entirely new. The scientist who discovered the process on which this modern procedure was based was Jan Czochralski (1885– Jan Czochralski 1953). According to one of his nephews, Czochralski (pronounced cho-HRAL- skee) based his experiment upon an acci- dental incident. One day, after melting Physical chemist and philosopher some tin in a small dish with the intention Michael Polanyi, in 1921–1922, also in of performing an experiment with it, Berlin, improved the method by floating Czochralski interrupted his work to write on the melt a sheet of mica with a small some notes. Absent-mindedly, he dipped hole in it, as a means of assuring a neat his steel pen nib into the tin instead of the circular cross section for the crystal, and adjacent inkwell, then drew it out and used this variant as a means of making found a thin filament of solid metal hang- monocrystals (e.g., of zinc) with the aim ing from it; the slit in the nib had acted as of examining plastic deformation (see a nucleating site for the solid. Instead of Figure 2). But this did not alter the essen- cursing, he perceived the significance of tial nature of Czochralski’s discovery. the accident and exploited it. Twenty-six years later, Teal (1908–2003) In the middle of the First World War struggled with colleagues and managers (1916), in Berlin, Czochralski designed a at Bell Laboratories to force through his Figure 1. Schematic illustration of Czochralski’s method, published in simple apparatus for measuring the crys- conviction that a Czochralski-type proce- Zeitschrift für physikalische Chemie 92 tal growth rate from the melt for a number dure for Ge and Si was the correct method (1918) p. 220. of metals and submitted it in that year to for making high-quality transistors; until the Zeitschrift für physikalische Chemie, he finally had his way, the pioneers at Bell which—slowed by the desperate circum- Labs were erroneously convinced that stances of the time—delayed publication polycrystalline germanium or silicon was of the short paper until 1918. The appara- adequate. Teal did not cite Czochralski tus (see Figure 1) consisted of a simple explicitly, but it is clear from citations in mechanism for dipping a fine glass tube his patents that he was familiar with (with a hook at the upper end, attached to Czochralski’s method. In Europe, at least, a silk thread) into a bath of molten Czochralski was famous in his heyday. metal—starting with tin and going on to His method was described in some detail lead and zinc—and raising the tube, with and attributed to him in a 1949 survey of a thin rod of solid metal hanging from it, methods for growing metal crystals by at a steady (adjustable) rate using a clock- A.N. Holden, published by ASM. work mechanism. When the rate of ascent Born in Poland, Czochralski worked in matched the natural rate of crystal growth a drugstore near his hometown just before near the melting temperature, a long sin- moving to Berlin in his late teens, where gle crystal of uniform diameter resulted. If he again worked in a drugstore. At that the rate of raising was too small or too time, he studied part-time at a technical great, the solid rod either became thick- university in Berlin-Charlottenburg and ened and short or attenuated and broke subsequently worked in the laboratories off. The single-crystal nature of the rod of several technical enterprises. He had an Figure 2. Schematic illustration of under ideal conditions was verified by impressive career between 1917, when he Czochralski’s method as modified by etching. In later years, Czochralski applied was engaged to create a research laborato- Mark, Polanyi, and Schmid; published in the same method to several other metals. ry for Metallgesellschaft in Frankfurt am Zeitschrift für Physik 12 (1923) p. 58. 348 MRS BULLETIN/MAY 2004 HISTORICAL NOTE applied metallurgy with purely curiosity- industry and in scholarships for the arts, Recently, however, a monument in his driven investigations. According to a his- set up a consulting laboratory for metal- memory has been erected in his hometown. tory of the Frankfurt laboratory privately lurgy, and did much work for the Polish published in 1981, he ran a “severe and military. During World War II, he con- FOR FURTHER READING: P. Tomaszewski, hard regime” and was feared as chief trived to aid the clandestine National “Professor Jan Czochralski and His Con- engineer. In 1929, he was invited by the Army and help the persecuted individu- tribution to the Art and Science of Crystal president of Poland to return to his native als in Warsaw, while cautiously keeping Growth,” AACG [American Association land, which he duly did, and there he was on the right side of the Germans by for Crystal Growth] 27 (2) (1998) p. 12; J. put in charge of the chemistry department undertaking some manufacturing tasks Czochralski, Zeitschrift für physikalische of the Warsaw University of Technology. for them. After the war, Czochralski was Chemie 92 (1918) p. 219; and A.N. Holden, In 1939, upon the invasion by Germany, accused as a collaborator and traitor and “Preparation of Metal Single Crystals,” all Polish universities were closed, and relieved of his university post. He retired Preprint, No. 35, American Society for thereafter Czochralski worked full-time in with great bitterness to his hometown Metals (1949) p. 29. manufacturing. The German metallurgical Kcynia and founded a drugs and cosmet- community may possibly have taken his ics firm to keep himself occupied. After PAWEL E. TOMASZEWSKI departure to Poland badly; when he died his death, he was forgotten for many Polish Academy of Sciences in 1953, he received no obituary in the years; indeed, it is possible that his erst- E-mail [email protected] Zeitschrift für Metallkunde, which he had while German colleagues did not know had a major part in founding in 1911. of his death and that was why he was not ROBERT W. CAHN In Poland, Czochralski invested the commemorated in the Zeitschrift für University of Cambridge fortune he brought from Germany in Metallkunde. E-mail [email protected] MRS BULLETIN/MAY 2004 www.mrs.org/publications/bulletin 349.

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