NITRIDED SiO2 FILM AS A NEW OXIDATION MASK MATERIAL
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-01
In the conventional local oxidation of silicon (LOCOS) process, a stacked structure consisting of 500 o Si3N4/100 o SiO2 is used as an oxidation mask. The Si3N4 film acts as the mask and the SiO2 film as a pad layer to minimize stress induced on silicon substrates. The stress results in defect formation in Si substrates. However, the presence of a pad oxide leads to the formation of a "bird's beak" due to lateral diffusion of oxidant through the pad oxide. During a typical field oxidation step only 20 - 30 o of the Si3N4 top layer is oxidized. So only 80 - 100 o dense, pinhole-free Si3N4 film should be enough as an oxidation mask. The thinner the Si3N4 film, less would be the stress induced on the silicon substrates.