Characterization of oxide etching and wafer cleaning using vapor phase anhydrous hydrofluoric acid and ozone

摘要

A cleaning process using anhydrous hydrofluoric acid/methanol (AHF) adn ozone was carried out in a vapor phase cleaning module (VPC).The dependence of the AHF vapor phase etch rate of thermally grown silicon dioxide on different process parameters, such as etch time,, AHF0flow and temperature was studied. The optimized etch process is attained at a temperautre of 40degC adn a pressure of 50 mbar. To demonstrate the feasibitity of this cluster tool for advanced gate dielectric formation, investigattions on surface properties after AHF vapor cleaning, such as contact angle measuremetn and atomic force microscopy (FM) were carried out. Using XPS, the surface binding states of HF-vapor treated silicon surfaces were studied. Traces of fluorine and low oxygen coverage were monitored. An ozone tratment immediately after AHF cleaning increases significantly the fluorine concentration on the silicon surface. A beneficial impact of AHF and ozone on the electricla characteristics of 4nm oxide films grown in oxygen by RTP in a cluster tool immediately after cleaning without breaking the vacuum was found.