Batch Wafer Implanter: Quad Mode Ion Dose Uniformity Improvement

Quad mode implantation with a low tilt angle is a common method on gyroscopic disc batch implanter to reduce shadow effects on high aspect ratio implants. Such an approach however causes unacceptable ion dose uniformity on wafer levels that impact electrical functions and product yield. Several methodologies to improve uniformity of quad mode implantation, proposed by different researchers are discussed in this literature. Concurrently, a novel method of combining quad mode implantation with twin steps, a multi-notch implant was introduced. The newly introduced method was empirically compared against published methods to gauge effectiveness in improving ion dose uniformity on the bare silicon level. Ultimately, an improvement of within wafer uniformity of Thermawave up to 0.98% and sheet resistance up to 0.40% were found to support the claim.