SURFACE DEPOSITION AND ADSORPTION BEHAVIOR OF HIGHBOILING-POINT ORGANIC COMPOUNDS ON SIO2 AND SI3N4 WAFERS

摘要

The deposition and adsorption behavior of airborne diethyl phthalate (DEP) on the silicon wafers coated with tworndifferent types of thin films (SiO2 and Si3N4) was investigated in this study. The airborne concentration of DEP, whichrnrepresents the major group of high boiling-point organic contaminants in the cleanroom environment, was evidentlyrncorrelated with the quantity of DEP adsorbed on both types of wafer surfaces. The deposition velocities (Vdep) of DEP on thernSiO2-film and Si3N4-film wafer after exposure period of 4 hour were estimated to be in the vicinity of 5×10 -3 and 2×10 -3rncm/sec, respectively. The "sticking coefficients", a parameter used to measure the surface adherence of organic compounds,rnwere approximately 1.2×10 -6 and 4.8×10 -7 for wafers with SiO2-film and Si3N4-film. These results demonstrated that the highrnboiling-point organic molecular contaminants such as DEP tended to deposit and remain on the SiO2-film wafer than on thernSi3N4-film wafer surface. Furthermore, an analytical procedure involving a thermal desorption - gas chromatography/massrnspectrometry (ATD-GC/MS) preceded by a self-designed heat-desorption chamber was developed. This analytical procedurernoffers an inexpensive and rapid method for trace concentrations of high boiling-point organic compounds on wafer surfaces.