Tapered windows in SiO2by ion implantation

The enhanced etch rate of ion damaged SiO
2
has been used to controllably taper steps in thermally grown SiO
2
. A 50-keV Ar
⁺
implantation with a dose of 3 × 10
¹³
/cm
²
produces a uniform taper of 35-45° with no vertical step at the top edge of the window. These results are observed by viewing the sample on edge with a scanning electron microscope (SEM). The taper angle of the oxide varies from near vertical (90°) at a dose of 4 × 10
¹²
/cm
²
to very small angles at large dosages.