Abstract: For high-end or low-power CMOS devices, accurate control of the threshold voltage (V$-th$/) is crucial because V$-th$/ deviation from the target value decreases the performance and yield of devices. In the conventional process, V$-th$/ is determined by channel doping performed early in the fabrication process, and cannot be corrected afterwards even if the variation in the gate length and gate oxide thickness resulting from the fabrication process is large. With the scaling down of devices, accurate control of V$-th$/ becomes even more difficult because the effect of the process variation becomes more pronounced. We propose a new feed- forward adjustment scheme for V$-th$/ by using post- metallization hydrogen ion implantation. The implanted hydrogen deactivates channel impurities and decreases V$-th$/ for both NMOS and PMOSFETs, and this effect remains stable after standard back-end process including post-metallization annealing (400 degrees Celsius). Th V$-th$/ change obtained was about 0.1 V at a hydrogen dosage of 1 x 10$+13$/ cm$+$MIN@2$/ for NMOS and PMOS FETs. The impact of this technique on oxide reliability is small and acceptable for practical usage. Using this technique, we can adjust V$-th$/ after we measure its actual value and compensate for the V$- th$/ variation caused by processing. Hydrogen ion implantation is thus a useful technique for feed-forward yield management. !5
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