Sequential deposition of SiO2 and poly-Si in isolation trenches

Abstract

Low pressure chemical vapor deposition (LPCVD) of SiO2 from tetraethoxysilane followed by LPCVD of polycrystalline silicon (poly-Si) from silane is used to refill isolation trenches. Two important characteristics of the refilled trenches which can adversely affect subsequent processing are the position of the void in the poly-Si and the depth of the groove along the top of the trench. We use evolve, a physically based, low pressure deposition simulator, to study the effects of trench width and the details of the trench profile before refill on void position and groove depth. Simulated SiO2 and poly-Si profiles in trenches with aspect ratios which range from near 4 to 20 are in good agreement with experimental profiles. In particular, evolve’s predictions of (1) the void position as a function of the position of the edge of the nitride film on the wafer’s surface, and (2) the depth of the groove as a function of the trench aspect ratio agree well with available experimental information. The reaction rate expressions used in evolve were developed in independent experiments. We do not adjust any parameters, and our simulations are entirely physically based.