Characterization and removal of trace heavy metal contamination on Si-surface resulted from CHF3/C2F6 reactive ion etching

Abstract

The characteristics of removal of trace heavy metal contamination on the silicon surface resulted from CHF3/C2F6 reactive ion etching (RIE) was studied using total reflection X-ray fluorescence spectroscopy (TRXRF). In order to investigate the depth profile of metallic contaminants near the surface, TRXRF measurements containing glancing angle scans were performed after slightly etching of silicon surface by repeating the cleaning procedures that diluted HF (DHF) removed the oxide grown by the mixture of H2SO4 and H2O2 (SPM) or O-2 plasma ashing treatment. RIE and O-2 plasma ashing processes resulted in metal contamination such as Fe, Ni, Zn, etc. They were present as both of plate-type and bulk-type, and the large part of plate-type contamination was removed easily. Especially, Fe resulted from RIE was the most abundant contaminant and its concentration was similar to 10(11) atoms/cm(2). Fe was mainly ditributed within similar to s nm from silicon surface and could be effectively reduced below similar to 2x10(10) atoms/cm(2) by etching of similar to 2.5 mm depth of the silicon substrate.