Advantage of shallow trench isolation over local oxidation of silicon an alignment tolerance

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