High concentration antimony diffusion into silicon using auxiliary wafers

Abstract

The behavior of auxiliary wafers used for Sb diffusion has been studied, with the auxiliary wafers set face to face with diffusion wafers. A high Sb concentration, as high as the solid solubility of Sb into silicon, was attained by auxiliary wafers lapped with alumina powder but not attained by those lapped with carborundum powder. Sapphire substrates, chemical vapor deposition-Al2O3 film deposited on silicon wafers, and Al+ -implanted silicon wafers were used for the auxiliary wafers, and they brought desirable results. Chemical analysis showed that the glass layer grown on the diffusion wafer contained aluminum oxide, which was estimated to give a high Sb concentration in the diffusion wafer.

High Concentration Sb Diffusion into Silicon Using Auxiliary Wafers and Optimum Conditions

“…Results described above are too complex to discuss briefly. A similar phenomenon is not seen anywhere but in oar reports (6,9).…”

“…A previous paper (9) reported that comparison of the Sb concentration at the silicon surface Co with the Sb concentration at glass-silicon interface Cr for elemental Sb produced good results. Therefore, it was concluded that carrier concentration in silicon depended on the concentration of elemental Sb at the glass-silicon interface.…”

“…However, although the thickness obtained by the new process is proportionate to source concentration, this may be because the (Sb) 2 term of Eq. [2] is close to constant in the p,rese~ce of A1203 in the glass layer on the diffusion wafer (9).…”

“…Di~usion wafers in this method are set face to face with auxiliary wafers in an opentube system using Sb208. The behavior of the new diffusion process has already been investigated, and it has been confirmed that the effect of the auxiliary wafer on Sb diffusion was due to the presence of the A120~ on its w'afer surface (9).…”

“…With the decrease of ~s obtained by sequential use of the AI.~:O8 lapped wafer, it is assumed that the A1203 on the surface of the auxiliary wafer is diffused out during the diffusion procedure (9). Hence, the A1203 concentration reached on the diffusion wafer is lOwer than that which could contribute to higher concentra- Di~usion in the auxiliary wafer itself:--The dependence of as on the four different types of auxiliary wafers is shown in Table I.…”