The application of gas plasma to the fabrication of MOS-LSI

The gas plasma technique was applied to the etching of Si3N4, poly-Si, SiO2and the multi-layer films in fabrication of MOS-LSI. For Si3N4film in the selective oxidation process, the so-called side-etching can be controlled from negative, zero to positive, by varying the plasma conditions. The Al-gate MOS-LSI´s fabricated by this process work well and havegood reliability, and their wafer yield was better than that of devices fabricated by the process using the wet-chemical etching. The gas plasma technique could give the tapered etching of poly-Si film in the Si-gate process and also smooth edges without under-cutting in the multi-layer structures including the MNOS and SNOS. SiO2films could be etched successfully by the gas plasma technique, but the processing time may be too long depending on processes.