Protection of silicon wafers from alkali contamination during high-temperature processing using electric field

A novel method for reducing metallic contamination of silicon wafer surface s and oxide layers during high temperature processing is described. It invo lves the application of an electric field across wafers exposed to oxidizin g and inert annealing ambients. Secondary ion mass spectrometry, capacitanc e-voltage, and vapor-phase decomposition/total reflection X-ray fluorescenc e techniques were used to measure metallic contamination levels in the sili con oxide layers. Results: indicate that a positive bins. applied to the si licon at high temperature, provides a significant reduction of Li, Na, and K content in the oxides, compared with conventional wafer processing involv ing both oxidation and annealing treatments. The results were interpreted w ithin the framework of a developed model that takes into account migration of alkali ions in the presence of an electric field, A thermodynamic approa ch to alkali metal oxidation was used to explain the similarity of the resu lts in oxygen and argon ambients. (C) 2000 The Electrochemical Society. S00 13-4651(00)01-047-8. All rights reserved.