Thermal processing of silicon wafers

Abstract

Apparatus and methods that minimize surface defect development in silicon wafers during thermal processing at relatively high temperatures at which silicon wafers are annealed and at less extreme temperature, or for other purposes. The apparatus and methods have utility to horizontally-disposed furnaces for silicon wafers and to vertically-oriented furnaces in which larger wafers can be thermally processed. A selectively-sealable process tube encloses silicon wafers during heating of the silicon wafers to a predetermined temperature, and a heating atmosphere supply system induces through the process tube a positive flow of a process gas, such as hydrogen or argon, that is non-reactive with solid silicon at the predetermined temperature. A process tube outlet vents gas from the process tube, and an impurity sensor in the process tube outlet detects oxygen and moisture in the vented gas to verify the purity of the atmosphere surrounding the wafers during thermal processing.