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The present invention pertains to methods of depositing low wet etch rate silicon nitride films on substrates using high-density plasma chemical vapor deposition techniques at substrate temperatures below 600° C. The method additionally involves the maintenance of a relatively high ratio of nit

The present invention pertains to methods of depositing low wet etch rate silicon nitride films on substrates using high-density plasma chemical vapor deposition techniques at substrate temperatures below 600° C. The method additionally involves the maintenance of a relatively high ratio of nitrogen to silicon in the plasma and a low process pressure.

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What is claimed is: 1. A method of depositing a silicon nitride film on a substrate disposed in a processing chamber using a HDP-CVD process comprising: flowing a process gas mixture comprising nitrogen and silicon into the processing chamber while maintaining a mean ratio of the atomic-nitrogen fl

What is claimed is: 1. A method of depositing a silicon nitride film on a substrate disposed in a processing chamber using a HDP-CVD process comprising: flowing a process gas mixture comprising nitrogen and silicon into the processing chamber while maintaining a mean ratio of the atomic-nitrogen flow to the atomic-silicon flow of about 50:1 or greater, maintaining a mean pressure in the processing chamber of about 40 mTorr or less and maintaining a mean substrate temperature of 600° C. or lower; and forming a high density plasma from the process gas to deposit the silicon nitride film over the substrate wherein the high density plasma has an ion density on the order of 1011 ions/cm3 or greater and an ionization fraction on the order of 10−4 or greater. 2. The method of claim 1 wherein the mean ratio of the atomic-nitrogen flow to the atomic-silicon flow is about 60:1 or greater. 3. The method of claim 1 wherein the mean ratio of the atomic-nitrogen flow to the atomic-silicon flow is about 90:1 or greater. 4. The method of claim 1 wherein the mean substrate temperature is maintained at 500° C. or below. 5. The method of claim 1 wherein the mean pressure in the processing chamber is about 15 mTorr or less. 6. The method of claim 1 wherein the wet etch rate of the deposited silicon nitride film using a hydrofluoric acid solution (1% HF in water) is less than 5 Å/min. 7. The method of claim 1 wherein the growth rate of the deposited silicon nitride film is greater than about 500 Å/min. 8. The method of claim 1 further comprising flowing argon gas into the processing chamber and maintaining a ratio of atomic-nitrogen flow to the atomic-argon flow of between 15:1 and 15:2. 9. The method of claim 1 wherein the high density plasma RF power is between 5 and 15 watts per square centimeter of substrate surface. 10. The method of claim 1 wherein the high density plasma RF power is between 5.5 and 10 watts per square centimeter of substrate surface. 11. The method of claim 1 wherein the step of forming the high density plasma does not bias the plasma towards the substrate during deposition of the silicon nitride film. 12. The method of claim 1 wherein the HDP-CVD process has a deposition to sputter ratio of greater than about 50:1. 13. The method of claim 1 wherein the process gas mixture is comprised of diatomic nitrogen (N2) and at least one gas from the group consisting of silane (SiH4), disilane (Si2H6), and TSA (N(SiH3)3). 14. A method of depositing a silicon nitride film on a substrate disposed in a processing chamber using a HDP-CVD process comprising: flowing diatomic nitrogen (N2) with a first gas flow rate and silane (SiH4) with a second gas flow rate into the processing chamber while maintaining a mean ratio of the first gas flow rate to the second gas flow rate of about 25:1 or greater maintaining a mean pressure in the processing chamber is about 40 mTorr or less and maintaining a mean substrate temperature of 600° C. or lower; and forming a high density plasma from the process gas to deposit the silicon nitride film over the substrate wherein the high density plasma has an ion density on the order of 1011 ions/cm3 or greater and an ionization fraction on the order of 10−4 or greater. 15. The method of claim 14 wherein the mean ratio of the first gas flow rate to the second gas flow rate is about 30 or greater. 16. The method of claim 14 wherein the mean ratio of the first gas flow rate to the second gas flow rate is about 40 or greater. 17. The method of claim 14 wherein the mean substrate temperature is maintained at 500° C. or below. 18. The method of claim 17 wherein the mean pressure in the processing chamber is about 15 mTorr or less. 19. The method of claim 18 wherein the wet etch rate of the deposited silicon nitride film using a hydrofluoric acid solution (1% HF in water) is less than 5 Å/min. 20. The method of claim 18 wherein the growth rate of the deposited silicon nitride film is greater than about 500 Å/min. 21. The method of claim 18 further comprising flowing argon with a third gas flow rate into the processing chamber while maintaining a ratio of the first gas flow rate to the third gas flow rate of between 15:2 and 15:4. 22. The method of claim 18 wherein the high density plasma RF power is between 5 and 15 watts per square centimeter of substrate surface. 23. The method of claim 18 wherein the high density plasma RF power is between 5.5 and 10 watts per square centimeter of substrate surface. 24. The method of claim 18 wherein the step of forming the high density plasma does not bias the plasma towards the substrate during deposition of the silicon nitride film. 25. The method of claim 18 wherein the HDP-CVD process has a deposition to sputter ratio of greater than about 50.