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A method developed by the Polish scientist Jan Czochralski for producing a large single crystalline boule. This is one of the dominant techniques for the preparation of silicon boules, which are used to make wafers, the substrates for semiconductor circuitry.

Key Principles

A slowly rotating seed crystal is placed into a bath of ultra-pure molten silicon that has been heated in a special furnace to about 1500°C. It is then slowly withdrawn from the melt. The entire process takes place under a blanket of inert gas, usually argon.

Recent Changes

New microfabrication facilities use modified methods of this method to produce wider boules. They can be as large as 200mm in diameter and 2 meters long. The wider wafers that can be cut from these larger boules are less expensive to process. The process can also be used to produce aluminum oxide "ruby" wafers.

Single Crystals

In theory the surface of a single crystal can be extremely smooth. The surface that supports microelectronics must be very smooth and additionally it must have perfectly homogeneous electrical properties. A grain boundary that runs between two lines on a circuit could produce a short, or act as the dielectric layer in an unwanted capacitor.

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