A New Dummy‐Free Shallow Trench Isolation Concept for Mixed‐Signal Applications

Shallow trench isolation (STI) is becoming the mainstream lateral isolation module for deep submicrometer technologies. It is generally accepted that dummy active areas need to he implemented due to the limited within-chip uniformity associated with the chemical mechanical polishing step. Dummy active areas, however, are problematic when used in mixed-signal technologies due to the increased capacitive coupling and noise associated with them. To solve this problem, we developed an STI module that ensures minimum oxide dishing and nitride erosion without the need for dummy active areas. This paper presents and discusses the fabrication process for this STI module and the results obtained with it. We have successfully implemented the new dummy-free STI process in a 0. 18 μm technology.