NSF/SRC Engineering Research Center for Environmentally Benign Semiconductor Manufacturing
Solutions of nitric acid and HF
The higher the nitric:HF ratio, the slower and more selective the etch
Typical use - 300:1 ratio for removal of poly on product wafers and 5:1 ratio for removal of poly on dummy wafers
With the more dilute and selective etches, it is important that no oxide be present on top of the poly since that will inhibit the etch of the polysilicon.