Inventors:
Tinghao F. Wang - Fremont CA, US
Usha Raghuram - San Jose CA, US
James E. Nulty - San Jose CA, US
Assignee:
Cypress Semiconductor Corporation - San Jose CA
International Classification:
H01L021/302
H01L021/461
US Classification:
438706, 438716, 438719, 438723, 438745, 438753, 438756, 134 11, 134 12, 134 13
Abstract:
Prior to etching a poly-II layer during fabrication of an integrated circuit, a hydrofluoric acid (HF) dip is used to remove surface oxides from the poly-silicon layer and an anisotropic descumming operation is used to remove any resist material left over from a patterning operation. Following patterning, a long breakthrough etch (e. g. , sufficient to remove 300-1500 Å of oxide) using an anisotropic breakthrough etchant (e. g. , a fluorocarbon-based etchant) is performed before the poly-silicon layer is etched. The HF dip may be repeated if a predetermined time between the first dip and the etch is exceeded. The anisotropic descumming operation may be performed using an anisotropic anti-reflective coating (ARC) etch, e. g. , a Cl/O, HBr/O, CF/Oor another etch having an etch rate of approximately 3000 Å/min for approximately 10-20 seconds. The poly-silicon layer may be annealed following (but not prior to) the etch thereof.