Trench sidewall implantation with a parallel scanned ion beam

The sidewalls of trenches on 100-mm wafers were doped by implantation with an implanter whose beam scan is accurately parallel over the whole wafer surface. The doping was characterized with a staining technique and transmission electron microscopy. All the trenches exhibited symmetrical doping, with the main differences between trenches from the center and edge of a wafer being due to nonuniformity of the trench etching rather than the implant step. Although the measurements were made on 100-mm wafers, symmetrical doping should be achievable for all trenches on wafers up to 200 nm in diameter