Stabilization and stripping of high current implanted photoresists

The scope of this investigation was to increase the throughput of high current implantation and study the impact on the supporting tool set, photostabilization and photoresist strip. In this paper, the effects of various pre-treatments on stripping of photoresist after high current implants are reported. The surface of positive photoresist can be carbonized (hardened) by the ion implantation process and cause residues and particles during ashing. In the case of high current implants typically used for source and drain formation, a hydrogen-depleted polymer layer is formed that requires advanced stripping methods for effective wafer cleaning. An advantage to effective photoresist removal is how the photoresist is cured prior to implantation. Patterned Novalak-based positive photoresist wafers were pre-treated prior to implant with hard bake and UV photostabilization in order to quantify the effects on subsequent ion implantation and ashing. Outgassing, uniformity, and particles were measured during As⁺ and BF₂⁺ high current, high dose implants. The photoresist stripping process window was then investigated using a downstream plasma asher