Advantage of Shallow Trench Isolation over Local Oxidation of Silicon on Alignment Tolerance

Abstract

We investigate the differences between the breakdown characteristics against contact hole etching for shallow trench isolation (STI) and the local oxidation of silicon (LOCOS). Although the breakdown voltage of STI varied negligibly despite the large contact overlap, the isolation characteristics of the LOCOS were drastically degraded due to the slight overlapping with the contact hole. The cross-sectional scanning electron microscope observations revealed that the considerable difference between STI and the LOCOS is closely related to the field oxide shapes modified by contact hole etching. We concluded that STI, in which the original field oxide abruptly projects above the substrate surface, has an advantage over the LOCOS not only against isolation space reduction but also alignment tolerance reduction.