US 6,440,819 B1 · Method for differential trenching in conjunction with differential fieldox growth

Abstract

A local oxidation of silicon (LOCOS) process directed to forming differential field oxide thickness on a single wafer with minimized process steps and optimized planarity. When patterning the masking layer, at least two window widths are formed in the masking layer, exposing the underlying substrate and pad oxide. When one of the window widths is sufficiently small, oxidation of the substrate will be inhibited causing reduced growth and thus a reduced field oxide thickness in that window as compared to other larger windows formed in the same masking layer, creating differential field oxide thicknesses in one growth step. To optimize planarity, prior to oxidation variable depth trenches are formed in alignment with the windows so that the resulting field oxide regions are substantially planar with the substantial surface.

Claims9

Dependent claims

A method of forming isolation regions on a substrate having a surface and having a masking layer formed over said substrate with a first window of a first width and a second window of a second width formed therein, wherein said first width is greater than said second width, comprising the steps of:

forming a first trench of a first depth in said substrate under said first window, said first trench having a width that corresponds approximately to said first width, and forming a second trench of a second depth in said substrate under said second window, said second trench having a width that corresponds approximately to said second width, wherein said first depth is greater than said second depth;
after the step of forming a first trench and a second trench, growing, in said first trench, a first isolation region of a first thickness and growing, in said second trench, a second isolation region of a second thickness;
wherein said step of growing said first isolation region and said second isolation region includes exposing said substrate to an oxidizing ambient;
and
wherein said first isolation region and said second isolation region are formed substantially planar with said substrate surface as a result of said step of growing.

2 more elements

Dependencies are inferred from the claim text.

Method for differential trenching in conjunction with differential fieldox growth

Life of this patent

Method for differential trenching in conjunction with differential fieldox growth

Life of this patent

Abstract

Claims9