Hello,

I was enjoying looking at your periodic table today when i read you comments about the square silicon boule you have. This crystal was not pulled using the Czochralski method like many of the other boules you own. I believe that it was made using the Stephanov process. In this process, a graphite shaper is inserted into the pool of liquid Si, and almost any shape can be produced. It is also possible that another technique called the edge-defined film-fed growth(EFG) process could have been used. The process is similar to the Stephanov method, however capillary feeding through the shaper is used to feed material to the growing crystal. Also, you mentioned that you believed that all boules start square. In the Czochralski process, a single crystal seed is introduced into a liquid silicon pool, and is the slowly lifted and rotated while the pool is counter-rotated. This rotation is what causes the resulting crystal to be round. In the other two methods the shaper defines the dimensions of the boule and no rotation occurs. I hope that this information is useful to you.