The effects of STI process parameters on the integrity of dual gate oxides

The reliability of dual gate oxide has been investigated in terms of dual gate oxide and shallow trench isolation (STI) process parameters. The thick oxide constructed by the dual gate oxide process shows intrinsic inferior quality to single-step grown thin oxide due to differences in its fabrication process, mainly the double-growth scheme. A larger susceptibility to STI process parameters is also reported. In particular, the local stress developed on the curved Si surface at the STI boundary during the densification of trench-filling HDP CVD oxide causes Q/sub bd/ degradation. It has been found that the optimum D/S ratio and the densification temperature of trench-filling HDP oxide could be key parameters for obtaining reliable dual gate oxides.