Implant Angle Repeatability on Optima MD

Abstract

A very sensitive channeling implant has been used to quantify the repeatability of implant angles for the Optima MD over a period exceeding one month. Sensitivity of sheet resistance to variation in vertical and horizontal beam angles was measured for 500 keV P++ at a dose of 5E13 /cm2 near orientations tilt/twist of 0°/0° and 35.26°/0° for (100) wafers. Sensitivity to tilt in the vertical plane at both conditions was at least a 10% change in Rs for a 0.5° change in tilt at a tilt of 0.75° away from the channel (i.e. at 0.75°/0° and 34.5°/0°), where the variation in Rs was linear with tilt. Horizontal angle sensitivity resulted in a 7.5% change in Rs for a 0.5° change in angle, but was less sensitive to smaller angle variation, since Rs varied roughly as a second order function near the channel. Sensitivity to tilt is reduced by about a factor of 3 for implants at 0°/0° compared to 0.75°/0° with a similar response at 35.26°/0° compared to 34.5°/0°. Implants were carried out using wafers from a single boule over a period exceeding one month at the orientation of 0.75°/0°. Angle control was enabled by in‐situ measurement and correction of the beam angles in both the vertical and horizontal planes prior to implant. The repeatability of sheet resistance was used to infer the variation in angle. Attributing all Rs variation to be the result of beam angle variation showed that the standard deviation of beam angles for over 30 wafers is 0.03°.