Specific Process Knowledge/Thin film deposition/Deposition of Silicon Nitride

Deposition of Silicon Nitride can be done with either LPCVD, PECVD or sputter deposition.

Using LPCVD

LPCVD nitride can be made in the LPCVD nitride furnace. It is a batch process meaning you can run a batch of 25 wafers at a time. The deposition takes place at temperatures of 800-850 degrees Celcius. The LPCVD nitride has a good step coverage and the film thickness is very uniform over the wafer. We have two standard LPCVD nitride processes: One for depositing stoichiometric nitride (Si₃N₄) and one for deposition low stress nitride (SNR).

Using PECVD

PECVD nitride can be deposited in one of the PECVD systems. You can run 1-3 wafers at a time depending on which one of the PECVD's you use. The deposition takes place at 300 degrees Celcius. This can be off importance for some applications but it gives a less dense film and the stoichiometry is on the following form: Si_xN_yH_z. The step coverage and thickness uniformity of the film is not as good as for the LPCVD nitride. In one of our PECVD systems (PECVD3) we allow small amounts of metal on the wafers entering the system, this is not allowed in the LPCVD and in the other PECVD (PECVD1).