Characteristics of the NO dielectric film with low pressure chemical vapor deposition in-situ nitridation

We investigated the formation of the thin NO dielectric films by in-situ nitridation of native oxide, and subsequent deposition of silicon nitride in the low pressure chemical vapor deposition systems for the application to the capacitors in high density dynamic random access memory. The native oxide was nitrided at elevated temperatures of 690 or 780°C in the flowing ammonia gas atmosphere, and nitride was deposited by flowing silane gas additionally immediately after the nitridation process. By in-situ nitridation process, we could obtaine 5 and 4.5 nm thick (equivalent oxide thickness) nitride/oxide (NO) dielectric films. These films were characterized to be electrically more reliable than the conventional oxide/nitride/oxide (ONO) films of the same equivalent oxide thickness. The nitrided NO films also showed lower leakage current and higher breakdown voltage than conventional ONO films. We obtained electrically most reliable NO films by loading the wafer at 400°C and nitriding the native oxide at 780°C.