EFFECT OF SIO2 PRECIPITATION IN SI ON GENERATION CURRENTS IN MOS CAPACITORS

Silicon substrates of various oxygen contents were heat treated to cause SiO2 precipitation. Generation currents in pulse-depleted MOS capacitors made on these substrates were measured. In substrates from the seed section of the crystal, SiO2 precipitation began during growth of the MOS oxide, and the generation currents were very low for all the anneal cycles used. In substrates from the tail section of the crystal, where the SiO 2 precipitated more slowly, the generation currents decreased with anneal time and finally leveled off at a very low value. MOS capacitors were also formed on substrates in which the precipitates extended to the surface. Such MOS capacitors all showed extremely high generation currents. The conclusion that internal gettering" by SiO2 precipitates in the bulk reduces generation currents was cross-checked with intentional copper decoration."