Monitor for molecular nitrogen during silicon implant

Abstract

Measurement of contaminating nitrogen during silicon ion implantation has been achieved by including a silicon wafer as a monitor in the implantation chamber. After silicon ion implantation, the monitor is subjected to a rapid thermal oxidation (about 1,100.degree. C. for one minute) and the thickness of the resulting grown oxide layer is measured. The thinner the oxide layer (relative to an oxide layer grown on pure silicon) the greater the degree of nitrogen contamination. For example, a reduction in oxide thickness of about 30 Angstroms corresponds to a nitrogen dosage of about 10.sup.13 atoms/sq. cm. By measuring total ion dosage during implantation and then subtracting the measured nitrogen dosage, the corrected silicon dosage may also be computed.