| 主权项 |
1. A method of forming a device comprising:
providing a substrate having top and bottom pad stacks, wherein each pad stack comprises at least first and second pad layers, and the second pad layers of the top and bottom pad stacks comprise an initial thickness TT1 and TB1 respectively; forming shallow trench isolation (STI) regions in the substrate, wherein forming the STI regions comprises
patterning the top pad stack to form openings corresponding to the STI regions,etching the substrate to form isolation trenches of the STI regions through the top pad stack openings, wherein etching the substrate removes exposed portions of the substrate and also reduces the thickness TT1 to a second thickness TT2, andafter etching the substrate, performing a pull-back process to simultaneously reduce the thickness TT2 of the second pad layer of the top pad stack to a third thickness TT3 and the thickness of TB1 of the second pad layer of the bottom pad stack to a second thickness TB2, wherein the pull-back process is a batch wet etch process and TT3 is different than TB2; and performing a removal process to completely and simultaneously remove the second pad layers of the top and bottom pad stacks having reduced thickness from the substrate after forming the STI regions. |
