Re-Oxidation of Thermally Nitrided Silicon Dioxide Thin Films

Abstract

Re-oxidation of thermally nitrided SiO2 thin films was studied. The SiO2 growth rate at re-oxidation is reduced until a certain time (the “oxidation delay time” or “ODT”) has passed. During the ODT, thermally nitrided SiO2 at the Si-SiO2 interface is re-oxidized. the ODT is the time required for complete oxidation of nitrided SiO2. Re-oxidation of thermally nitrided SiO2 thin films is limited not by diffusion of oxidizing species, but by oxidation of nitrided SiO2. The ODT is proportional to the nitrided SiO2 thickness. Nitrided SiO2 formation at the Si-SiO2 interface is mass-transfer controlled by nitriding species through nitrided SiO2 to Si substrate. As an application of thermal nitridation of SiO2, thermal nitridation of the local oxidation of silicon (LOCOS) pad oxide can shorten the bird's beak of LOCOS.