CONTROLLED FILLING OF SILICON TRENCHES WITH DOPED OXIDE FOR MEMS

摘要

In the fabrication of MEMS, anisotropically etched trenches are often used. These trenches are made using deep reactive ion etching and then refilled with either silicon oxide or the combination of silicon oxide and polysilicon using LPCVD process. The oxide serves either as isolation layer between electrically active areas or as sacrificial layer. This paper presents a new method of refilling the trenches by doped silicon oxide in the controlled fashion and its advantages. Using this method, a hole can be trapped inside the trench whose length can be varied from 80 to <10 percent of that of trench depth, by depositing doped oxide at low pressure in SACVD reactor, followed by furnace heat treatment. The advantage in the usage of such oxide contours lies in the selection of alternative silicon oxide etchant, ECE metal, protection layer, and their easy removal techniques. The process details are elaborated in the following sections.