James David Bernstein

Plasma immersion ion implantation as an alternative deep trench buried-plate doping technology

Plasma immersion ion implantation (PIII) has been developed as an alternative deep trench capacitor buried-plate doping technology and compared to a conventional solid-state diffusion technique using arsenosilicate glass (ASG). Novel top-down (or vertical) SIMS measurements demonstrated the conformal doping capability of PIII along the trench sidewall. The doping level by PIII was almost one order of magnitude higher than that by a conventional technique. As a consequence, PIII provided better depletion characteristics than conventional technique. Furthermore, PIII processing did not degrade node-to-buried plate leakage current characteristics. From these results, it was demonstrated that PIII is a promising technology as an alternative deep trench capacitor buried-plate doping technique for future deep trench-based DRAM processing development.

Shallow n/sup +//p/sup +/ junction formation using plasma immersion ion implantation for CMOS technology

We present CMOS transistors with n/sup +//p/sup +/ source/drain extensions doped by AsH/sub 3/ and BF/sub 3/ plasma immersion ion implantation (PIII) for the first time. We successfully demonstrate n/sup +//p/sup +/ shallow junctions with R/sub s/<1 k/spl Omega//sq for CMOS devices. No degradation in gate oxide integrity is observed for either AsH/sub 3/ or BF/sub 3/ PIII. Compared to conventional ion implantation, PIII provides much better short-channel effects and approximately 50% I/sub off/ reduction for both nMOS and pMOS devices. In particular, the flat threshold voltage roll-off and good performance in buried-channel pMOS devices is the best-reported PIII data to date.

Photoresist integrity and outgassing effects during plasma immersion ion implantation

Plasma immersion ion implantation (PIII) has been evaluated for process compatibility with photoresists. The effects of non-mass-separated ion implantation into bare Si, soft-baked (SE), hardbaked (HE), and UV/baked (UVB) patterned photoresist wafers are discussed. Outgassing of the photoresist can cause co-implantation of unintended species since the plasma will ionize these by-products. SIMS analysis was used to characterize dopant profiles and implanted C, O, and N from outgassed photoresist species. Acceptable levels of carbon are shown for a range of implants. Correlation between RGA and SIMS data shows that UVB photoresist outgasses increased amounts of CO and CO/sub 2/ during PIII implantation compared to the SB and HB photoresist. The PIII implants showed no damage to photoresist features or dimensions, as quantified with SEM cross-sectional analysis.