EVAPORATION RATES OF OXIDES FROM UNDOPED AND SB-DOPED SI MELTS UNDER ATMOSPHERES OF PURE NE, AR, AND KR

The effect of gaseous Ne, Ar, and Kr on the evaporation rates of oxide s from undoped and Sb-doped Si melts was investigated. By measuring th e weight loss of a melt using a thermogravimetric method, we determine d the evaporation rate of different species from the melts. The measur ements were done at a melt temperature of 1442-degrees-C and a backgro und gas pressure of 1.02 atm. Because Ar is predominantly used as the background gas in the semiconductor industry, we report evaporation ra tes relative to the rates under an atmosphere of pure Ar. For the evap oration of SiO from an undoped Si melt, Ne enhanced the evaporation ra te by 37% and Kr suppressed the evaporation rate by 13%. For the evapo ration of antimony from an Sb-doped Si melt, Ne enhanced the evaporati on rate by 18% and Kr suppressed the evaporation rate by 24%. For the evaporation of antimony oxide from an Sb-doped melt, Ne enhanced the e vaporation rate by 4% and Kr suppressed the evaporation rate by 63%. W e therefore conclude that, compared with Ar, Ne enhances and Kr suppre sses the evaporation of oxides from undoped and Sb-doped Si melts. We show that the background gas affects evaporation through gas-phase dif fusion; the diffusion coefficient of the evaporating species is the hi ghest in Ne and the lowest in Kr. In addition, we show that the transp ort of the evaporating species in the melt to the surface also influen ces the overall evaporation rates.