Spaceetch, first grow a layer of 150 by thermal oxidation at 700℃? The left and right lining TEOS is used as a stop layer for etching nitride and also as a buffer layer for nitride to reduce the stress of nitride on Si. Then a layer of SIN(300? ), this is the main, but not too thick, too thick will cause damage to the lower lining structure of TEOS, that is, the lining TEOS will not be able to support.
However, the gasket requires a certain thickness, so a layer of TEOS( 1000? 100? ), thus forming an O-N-O structure.
During spacer etching, dry etching stops on the liner TEOS, and then wet etching is used to etch the liner TEOS, but it is not completely removed. After oxide stripping, the lining oxide still has 50? As the mask layer of IMP of SN+ and SP+.