Sputter rate change and surface roughening during oblique and normal incidence O/sub 2//sup +/ bombardment of silicon, with and without oxygen flooding

Abstract

A sample of low-temperature epitaxial Si grown with five B delta-doped layers 5.4 nm apart has been profiled using secondary ion mass spectrometry under a variety of O/sub 2/ bombardment conditions. Energies from 400 eV to 15 keV were used with angles of incidence from 0/spl deg/ to 70/spl deg/. Analyses were performed using oxygen flooding of the sample surface during analysis, as well as without using oxygen flooding. The apparent spacing between the B delta layers was used to determine the magnitude and extent of increased sputtering rate at the beginning of an analysis. The width of the B peaks was used to evaluate depth resolution and to measure the effect of surface roughening of the profiles. It was found that sputtering with 500 eV O/sub 2/ at an angle of 50/spl deg/ while flooding with oxygen gave no measurable error in sputtering rate and resulted in no unexpected shift towards the surface of the B delta layers. These analysis conditions also resulted in depth resolution which was as good as that obtained using 400 ev O/sub 2/ bombardment at 0/spl deg/ incidence. This 0/spl deg/ method of analysis, however, resulted in a 1.1 nm shift of the topmost B delta layer towards the surface, and the 0/spl deg/ method had a sputter rate only 1/5 that of the 50/spl deg/ method of analysis.