Method to increase the compressive stress of PECVD silicon nitride films
Compressive stress in a film of a semiconductor device may be controlled utilizing one or more techniques, employed alone or in combination. A first set of embodiments increase silicon nitride compressive stress by adding hydrogen to the deposition chemistry, and reduce defects in a device fabricated with a high compressive stress silicon nitride film formed in the presence of hydrogen gas. A silicon nitride film may comprise an initiation layer formed in the absence of a hydrogen gas flow, underlying a high stress nitride layer formed in the presence of a hydrogen gas flow. A silicon nitride film formed in accordance with an embodiment of the present invention may exhibit a compressive stress of 2.8 GPa or higher.
1. A method of forming silicon nitride, the method comprising:
disposing a substrate including a surface in a processing chamber;
exposing the surface to a pre-treatment plasma in the absence of deposition conditions to remove contamination, wherein the pre-treatment plasma is formed in the absence of a hydrogen gas flow; and
depositing silicon nitride layer over the plasma-treated surface by a chemical reaction in a deposition plasma between a silicon-containing precursor and a nitrogen-containing precursor in the presence of a hydrogen gas flow.
2. The method of claim 1 wherein the pre-treatment plasma is formed from an ambient comprising at least one component selected from ammonia, oxygen, and N 2 O.
3. The method of claim 1 wherein the silicon nitride is deposited in the presence of the deposition plasma.
4. The method of claim 1 wherein the silicon nitride exhibits a compressive stress of 2.8 GPa or higher.
5. The method of claim 1 further comprising forming a buffer layer over the treated surface prior to deposition of the silicon nitride.
6. The method of claim 5 wherein the silicon nitride is deposited as a film stack comprising an initiation layer formed in the absence of the hydrogen gas flow, followed by a high compressive stress layer formed in the presence of the hydrogen gas flow.
7. A method of forming silicon nitride, the method comprising:
disposing a substrate including a surface in a processing chamber;
forming a silicon oxide buffer layer over the surface; and
depositing silicon nitride over the buffer layer by a chemical reaction in a plasma between a silicon-containing precursor and a nitrogen-containing precursor in the presence of a hydrogen gas flow, wherein the silicon nitride is deposited as a film stack comprising an initiation layer formed in the absence of the hydrogen gas flow, followed by a high compressive stress layer formed in the presence of the hydrogen gas flow.
8. The method of claim 7 wherein forming the buffer layer comprises depositing the silicon oxide layer.
9. The method of claim 7 wherein the silicon nitride exhibits a compressive stress of 2.8 GPa or higher.
10. A method of preventing defects in a device, the method comprising:
depositing a silicon nitride initiation layer on a surface in the absence of a flow of hydrogen gas;
depositing a high compressive stress silicon nitride layer on the silicon nitride initiation layer by reaction between a silicon-containing precursor and a nitrogen-containing precursor in a plasma in a presence of a flow of hydrogen gas; and
etching back the high compressive stress silicon nitride layer with a diluted NF 3 plasma.
11. The method of claim 10 wherein the etch back process is performed in the same chamber as the high compressive stress deposition process.
12. The method of claim 10 wherein the etch back process is modulated so that a higher etch rate occurs on isolated areas.
13. The method of claim 10 wherein the high compressive stress silicon nitride layer exhibits a compressive stress of 2.8 GPa or higher.