Carbonized surface curing for etch-back process

For flash memory below the 63nm node, two step Undoped Silicon Glass (USG) deposition and one step etch-back processes are applied in manufacturing processes to get good gap fill properties for Shallow Trench Isolation (STI) structures. The characteristics of the silicon surface after an etch-back process influences the following second USG deposition thickness and variation because the USG deposition process has high under-layer dependency and surface sensitivity. It can be reduced by changing some parameters during the deposition process like O₃-TEOS ratio or temperature or pressure, but these methods also change the gap fill property and deposition rate [1]. So, we should find another method. This paper presents the detail studies of surface characteristics during processes that have been carried out to optimize the USG etch-back process.