Process for Making Uniform, Very Thin Silicon Dioxide on Large-Area Silicon Wafers
Original Publication Date: 1985-May-01
Included in the Prior Art Database: 2005-Feb-18
By accounting for the different molecular weights of the reaction and purge gases used in an oxidation reactor, the entire surface of a wafer is exposed to reactant gases for the same amount of time and thus oxidizes uniformly. In one approach, the different gravitational forces on gases of different molecular weight are used to assure uniform motion of gas toward top or bottom vents. In a second approach, gravitational forces are minimized by premixing inert gases with reactant or purge gas to achieve an average molecular weight match between resident and replacement gas. In this case, applied forces (e.g., inlet gas pressure) can be relied upon to uniformly move resident gas toward a vent.