Process for forming silicon oxide material
A thin layer of silicon oxide is formed by cyclic introduction of a silicon-containing precursor gas and an oxidizing gas separated by an intervening purge step. The resulting thin oxide layer enables subsequent conventional CVD of oxide to produce a more uniform deposited oxide layer over nonhomogenous surfaces, for example the silicon nitride mask/thermal oxide liner surfaces created during fabrication of shallow trench isolation structures.
1. A method of forming a shallow trench isolation structure on a silicon substrate having a plurality of trenches etched therein to define isolation regions and a plurality of masked regions on an upper surface of said substrate positioned between said isolation regions, said method comprising:
exposing the substrate to an oxidizing ambient to create a thermal oxide layer within the trench;
forming a layer of silicon oxide over the thermal oxide layer by alternating
(i) introducing to the chamber a first gas consisting of one of a silicon-containing precursor gas and an oxidant,
(ii) purging the first gas from the chamber,
(iii) introducing to the chamber a second gas consisting of the other of the silicon-containing precursor gas and the oxidant,
(iv) purging the second gas from the chamber, and
(v) repeating steps (i)-(iv) until a desired thickness of the silicon oxide layer is achieved; and
filling the trenches with chemical vapor deposited silicon oxide material.
2. The method of claim 1 wherein the silicon-containing precursor gas comprises tetraethylorthosilane (TEOS) and the oxidant comprises ozone.
3. The method of claim 1 wherein the silicon-containing precursor gas comprises SiCl 4 and the oxidant comprises steam (H 2 O).
4. The method of claim 1 wherein the silicon-containing precursor gas comprises Si(NCO) 4 and the oxidant comprises steam (H 2 O).
5. The method of claim 1 wherein the silicon-containing precursor gas comprises CH 3 OSi(NCO) 4 and the oxidant comprises hydrogen peroxide (H 2 O 2 ).