I am noticing a phenomena that looks like the reverse of microtrenching. I am dry etching using the Bosch process with SF6. For the step in question we are etching down the wide pillar with the red line, while the bottom trench is covered in resist. We observe that at the edges of our large pillar squares there are some peaks, which looks like the reverse of micro trenching. Does anyone know what causes this and how it may be avoided?
A related question is that for our squares at the center of the wafer the etch appears to be uniform, but towards the wafer edge there seems to be a ~15um difference in etch depth across square length. I know the etch is not completely uniform across the entire wafer but is there a way to improve this?
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