MICROVOLUME-SECONDARY ION MASS-SPECTROMETRY ANALYSIS OF NONVOLATILE SULFUR RESIDUES IN SEMICONDUCTOR PROCESS SOLUTIONS

The capability to detect and quantify sulfur at the part-per-billion (ppb) concentration level in ultrapure hydrochloric acid rinse solutions used in GaAs wafer fabrication is described. Nonvolatile residues formed from the deposition of nanoliter aliquots of solution onto high purity silicon wafers are analyzed using a high performance CAMECA IMS 4f ion microanalyzer. The dynamic SIMS analysis of microdroplet residues is referred to as Microvolume-SIMS (MV-SIMS). The Microvolume-SIMS analyses of two acid solutions are presented. The concentration of total sulfur detected in these solutions was 98 and 650 ppb; both values are below the SEMI specification standard of less than 1300 ppb total sulfur concentration. Despite this, the acid solution containing 650 ppb of total sulfur was responsible for causing an isolation failure halting wafer production. This finding corroborated electrical failure analyses using these same acids.