|MadSci Network: Computer Science|
The ultra-pure silicon for wafers is grown in huge round rods that are then sliced into wafers. The round shape comes naturally with the growth process. Making the slices square-shaped would be more work and waste material. The yield is lower near the edge of the wafer, because it is more difficult to control processes there. A circle has the lowest edge- to-area-ratio of all shapes and thus offers the highest possible yield. Some of the processes in a wafer fab, e.g. coating with photoresist by dripping on a spinning wafer, even make use of the round shape for process uniformity and would not work well with square wafers. Greetings from Singapore, Frank Berauer
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