Method to increase silicon nitride tensile stress using nitrogen plasma in-situ treatment and ex-situ UV cure
Stress of a silicon nitride layer may be enhanced by deposition at higher temperatures. Employing an apparatus that allows heating of a substrate to substantially greater than 400° C. (for example a heater made from ceramic rather than aluminum), the silicon nitride film as-deposited may exhibit enhanced stress allowing for improved performance of the underlying MOS transistor device. In accordance with alternative embodiments, a deposited silicon nitride film is exposed to curing with ultraviolet (UV) radiation at an elevated temperature, thereby helping remove hydrogen from the film and increasing film stress. In accordance with still other embodiments, a silicon nitride film is formed utilizing an integrated process employing a number of deposition/curing cycles to preserve integrity of the film at the sharp corner of the underlying raised feature. Adhesion between successive layers may be promoted by inclusion of a post-UV cure plasma treatment in each cycle.
1. A method of forming silicon nitride, the method comprising:
(i) disposing a substrate including a surface on a ceramic support in a processing chamber;
(ii) depositing a silicon nitride layer on a surface of the substrate with plasma-enhanced chemical vapor deposition by exposing the surface to a silicon-containing precursor gas at a temperature of greater than 400° C.;
(iii) after depositing the silicon nitride layer, treating the silicon nitride layer with a first nitrogen plasma; thereafter
(iv) exposing the silicon nitride layer to ultraviolet radiation while the temperature of the substrate is maintained at a temperature greater than 400° C.;
(v) treating the silicon nitride layer with a second nitrogen plasma after exposing the silicon nitride layer to the ultraviolet radiation; and
repeating steps (ii) through (v) one or more times to increase a thickness of the silicon nitride layer.
2. The method of claim 1 wherein the substrate is disposed on a ceramic support comprising aluminum nitride, graphite, silicon carbide, alumina, or Ytria.
3. The method of claim 1 wherein the surface is exposed to the silicon-containing precursor gas at a temperature of 480° C. or greater.
4. The method of claim 1 wherein deposition at a temperature of greater than 400° C. creates a higher stress in the silicon nitride as compared with deposition at a lower temperature.
5. The method of claim 1 wherein the silicon nitride film is deposited over a raised gate of a transistor structure present in the substrate.
6. The method of claim 1 wherein the silicon nitride layer comprises silicon oxynitride or doped silicon nitride.
7. A method of forming silicon nitride, the method comprising:
(i) disposing a substrate including a surface in a processing chamber;
(ii) forming a silicon nitride layer on the surface with plasma-enhanced chemical vapor deposition;
(iii) after forming the silicon nitride laver, treating the silicon nitride layer with a first plasma; thereafter
(iv) exposing the silicon nitride layer to ultraviolet radiation; thereafter
(v) treating the silicon nitride layer with a second plasma; and repeating steps (ii)-(v) to increase a thickness of the silicon nitride layer.
8. The method of claim 7 wherein the silicon nitride film is deposited over a raised gate of a transistor structure present in the substrate.
9. The method of claim 7 wherein the silicon nitride layers have thicknesses of 1000 Å or less.
10. The method of claim 7 further comprising heating the silicon nitride layers during and/or following exposure to the ultraviolet radiation.
11. The method of claim 7 wherein the deposition and UV exposure steps are performed in different chambers of an integrated deposition and ultraviolet system.
12. The method of claim 7 wherein the first plasma and the second plasma comprise nitrogen.
13. A method of forming silicon nitride, the method comprising:
(i) disposing a substrate including a surface on a ceramic support in a processing chamber;
(ii) depositing a silicon nitride layer on the surface with plasma-enhance chemical vapor deposition by exposing the surface to a silicon-containing precursor gas at a temperature of 480° C. or greater;
(iii) after depositing the silicon nitride layer, treating the silicon nitride layer with a first plasma;
(iv) treating the silicon nitride layer with UV radiation after being treated by the first plasma; and
(v) treating the silicon nitride layer with a second plasma after being treated by the UV process
repeating steps (ii)-(v) to increase a thickness of the silicon nitride layer.
14. The method of claim 13 wherein the treating the silicon nitride layer with UV radiation occurs while the temperature of the substrate is maintained at 480° C. or greater.
15. The method of 13 wherein the method further comprises:
depositing a second silicon nitride layer over the silicon nitride layer; and
exposing the second silicon nitride layer to ultraviolet radiation.
16. The method of claim 15 wherein the silicon nitride layer and the second silicon nitride layer have thicknesses of 1000 Å or less.
17. The method of claim 13 wherein the silicon nitride layer comprises silicon oxynitride or doped silicon nitride.
18. The method of claim 13 wherein the first plasma and the second plasma comprise nitrogen.