Multiple Depth Dielectric Isolation From A Single Mask
Original Publication Date: 1979-Sep-01
Included in the Prior Art Database: 2005-Feb-20
During the fabrication of various device structures it is often necessary to produce deep dielectric isolation areas which reach into the surface to different depths. The process utilizes one masking operation with the multiple depths being accomplished through control of the trench widths. The requirements for the mask can be defined by the equations: Wd = Tox(s) + Wd/1/ Tox(s) = 1/2W(s) + .3 Mum where Wd = Deep Trench Width Tox(s) = Oxide Thickness Necessary to Refill the Shallow Trench Wd/1/ = Final Deep Trench Width Ws = Shallow Trench Width The processing sequence is as follows: 1) The deposition of sufficient silicon dioxide layer 5 on the silicon surface 6 to act as a mask for a deep trench reactive ion etching (RIE) method.