Poly silicon resistance uniformity improvement by implant tuning

The Viista80 High Current Series Ion Implanter improved the production throughput by a high power beam density Implant. However, the high dose rate implant created an undesirable variation in Poly Resistance within the wafers. The un-uniform poly resistor will lead to a bad device matching and particularly sensitive in analog circuit design. This paper introduces a Design of Experiments (DOE) tuning method on three Implant process parameters during the Poly Silicon Implant. Three process parameters that under study are Rotations, Beam Density and Drift Expand mode (DEX). The end result of this tuning shows a significant improvement in uniformity without affecting the overall average resistance value. A best combination tuning is developed base on three parameters settings on the DOE lot and result is verified by actual production lot.