Otherwise known by CZ
The Czochralski Method is a commonly used method of crystallization in the semiconductor and optics industries. It is often used to produce single crystal ingots of materials like silicon, germanium, gallium arsenide, palladium, platinum, silver, gold, and many others. The method involves a simple apparatus with a crucible, magnetic rotation motor, and a pulling motor. The machine itself typically cannot be effectively operated unless it is within a cleanroom-grade setting. Resulting materials require this level of purity to avoid failures and defects in resulting crystals.
The process starts by filling a crucible with refined solid ingredients. The crucible itself is often made of temperature-resistant, durable, and chemically stable or inert materials. The most common materials for crucibles are quartz, platinum, and boron nitride, among others. After the crucible has been filled, heating elements bring the solid ingredients to their melting point. From there, the pulling system slowly drops a rod with a seed crystal into the melt while spinning. The magnetic motor will precisely control the speed of the seed crystal as it pulls back upwards slowly. As this pulling occurs, a cone of crystal forms until the optimal diameter is reached. The speed is then adjusted to pull a consistent cylindrical crystal of the desired size until the melt runs out. Near the end, the size of the melt will shrink, and an opposite cone will form on the crystal. This double-coned cylindrical crystal is often referred to as a “boule”. The top of the crystal, with the seed crystal and cone attached, is called the “head” or “neck” of the crystal. The central cylindrical crystal is cut from the head when processing. This precise cylindrical monocrystal is called the “body” of the boule, and it is what is used for dies and optics. The bottom cone is also cut off. That piece is referred to as the “tail” of the crystal. The head and tail can often be remelted in future uses if their impurity concentrations aren’t high.
After all the processing is completed, the finished cylindrical boule can either be sliced into thin cylindrical dies (Often called wafers) for semiconductor production or it can used as a substrate for various other material science applications. It can also be cut into large pieces for use in specialty optics, such as in optical assemblies, laser crystals, and sensor arrays, among other use cases.
The process itself was named after and developed by the Polish scientist Jan Czochralski sometime in 1915. He discovered the process by accident during an investigation into crystallization rates of metals. While writing down information, he mistakenly placed his pen into molten tin instead of his inkwell. When he pulled the pen away, a single filament of tin was produced. When he later studied the filament, it appeared to be a single monocrystalline fiber. This method was then researched and developed into the method we currently use. In the modern age, it is still used in around 90% of electronics in the form of semiconductors.
Jan Czochralski, Zeitschrift für physikalische Chemie Bd.92 1918, Link / Source
Stuart Dowell, Scientist who laid the foundations for Silicon Valley honoured at long last, Link / Source
Mindat.org
Gemdat.org