Self limiting lateral atomic layer etch
Methods of and apparatuses for laterally etching semiconductor substrates using an atomic layer etch process involving exposing an oxidized surface of a semiconductor substrate to a fluorine-containing etch gas and heating the substrate to remove non-volatile etch byproducts by a sublimation mechanism are provided herein. Methods also including additionally pulsing a hydrogen-containing gas when pulsing the fluorine-containing etch gas. Apparatuses also include an ammonia mixing manifold suitable for separately preparing and mixing ammonia for use in various tools.
1. A method of etching a substrate comprising a semiconductor material, the method comprising:
providing a patterned semiconductor substrate having a feature in a semiconductor material defined by a patterned hard mask of the substrate surface;
exposing the substrate to an oxidant to conformally oxidize a surface of the feature in the semiconductor material to form an oxidized surface;
exposing the substrate to a fluorine-containing gas to isotropically etch the oxidized surface of the substrate in a self-limiting reaction selective to non-oxidized semiconductor material; and
heating the substrate to remove non-volatile solid etch byproducts by sublimation;
such that the profile of the etched portion of the feature is maintained.
2. The method of claim 1 , wherein the substrate is etched laterally.
3. The method of claim 1 , wherein the substrate is heated to a temperature between about 60° C. and about 300° C. to remove the non-volatile solid etch byproducts.
4. The method of claim 1 , wherein the starting and ending profile of the etched portion of the feature has linear edges.
5. The method of claim 4 , wherein the oxidation, reaction and sublimation operations are cycled to remove semiconductor material in monolayer increments.
6. The method of claim 1 , wherein the oxidant is a gas selected from the group consisting of oxygen, ozone, silicon oxide, carbon monoxide, carbon dioxide, and nitrous oxide.
7. The method of claim 1 , wherein the oxidant is a plasma generated from a gas selected from the group consisting of oxygen, ozone, silicon oxide, carbon monoxide, carbon dioxide, and nitrous oxide.
8. The method of claim 1 , further comprising exposing the oxidized layer to a hydrogen-containing gas during the exposing of the substrate to a fluorine-containing gas.
9. The method of claim 1 , wherein the semiconductor layer is exposed to the oxidant at a temperature between about −60° C. and about 250° C.
10. The method of claim 5 , wherein the semiconductor material is laterally etched under the hard mask.
11. The method of claim 1 , wherein the semiconductor layer is exposed to the oxidant at a chamber pressure between about 5 mTorr and about 400 mTorr.
12. The method of claim 1 , wherein the fluorine-containing gas is selected from the group consisting of nitrogen trifluoride and sulfur trifluoride.
13. The method of claim 1 , wherein the oxidized layer is selectively etched when a chuck holding the substrate is set at a temperature between about −60° C. and about 100° C.
14. The method of claim 8 , wherein the flow rate ratio of the fluorine-containing gas to the hydrogen-containing gas is between about 1:1 and 10:1.
15. The method of claim 5 , wherein the substrate is processed without breaking vacuum.
16. The method of claim 4 , wherein the hard mask comprises nitride.