A SELF-ALIGNED METHOD FOR FORMING DEEP TRENCHES IN SHALLOW TRENCHES FOR ISOLATION OF SEMICONDUCTOR DEVICES

摘要

In the fabrication of an integrated circuit, particularly an integrated circuit for radio frequency applications, a method for forming shallow and deep trenches for isolation of semiconductor devices comprised in said circuit, comprising providing a semiconductor substrate (10); optionally forming a first dielectric layer (14) on said substrate; forming at least one shallow trench (18) by using a first mask (16), said shallow trench extending into said substrate; forming a second dielectric layer (20) of a predetermined thickness (2x) on the structure obtained subsequent to the step of forming at least one shallow trench; forming at least one opening (33) in said second dielectric layer by using a second mask (22) with an edge (30) of said second mask aligned to an edge (26) of said shallow trench with a maximum misalignment (+/- x) of half the predetermined thickness (2x), said opening extending with the shallow trench to the bottom (18a) thereof, whereby a spacer (32) of a width equal to the predetermined thickness (2x) is formed in said shallow trench and along said edge thereof; and forming a deep trench (34) in said opening by using said second dielectric layer as a hard mask, said deep trench extending further into said substrate and being self-aligned to said shallow trench.