3 ms·
They are still going to have to cut the edges off of round waffers to make them square. The process of drawing the ingots leads to inherently round waffers. Th
by johnea 2y ago
They are still going to have to cut the edges off of round waffers to make them square.
The process of drawing the ingots leads to inherently round waffers. This is something that is not done by the foundary, but by a vendor.
- throwup238 2y agoThe spin coating process that applies etch resist also favors round wafers but if they've figured that part out, it's a win because their precision positioning equipment is limited to a square X/Y stage. With round wafers, they lose quite a bit of that space and the wafers are so cheap that wasting some edges isn't a big deal compared to the reduced overhead per chip.
- adolph 2y agoBy squaring the circle, they gain by holding less non-addressable space in the etching step?
- LeifCarrotson 2y agoWhy is the precision positioning equipment limited to a square stage? Or is it actually a rectangular stage? Couldn't they use an r-theta circular positioning system instead of linear? Their optics are fundamentally circular constraints, seems like that should drive everything else to a circle.
- deleted 2y ago[deleted]
- jjk166 2y agoSure but cutting down larger ingots only affects the vendor, and these rectangular wafers could be handled by the same (or at least similarly sized) equipment for all the other downstream processes. It's way easier than retooling everything to a larger circular diameter in one go.
- dist-epoch 2y agoCutting those edges is much much cheaper than throwing away incomplete chips at the edges.