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Proceedings Paper

Yield management by threshold voltage adjustment in back-end process
Author(s): Shinya Ito; Ko Noguchi; Tadahiko Horiuchi
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Paper Abstract

For high-end or low-power CMOS devices, accurate control of the threshold voltage (Vth) is crucial because Vth deviation from the target value decreases the performance and yield of devices. In the conventional process, Vth 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 Vth becomes even more difficult because the effect of the process variation becomes more pronounced. We propose a new feed- forward adjustment scheme for Vth by using post- metallization hydrogen ion implantation. The implanted hydrogen deactivates channel impurities and decreases Vth for both NMOS and PMOSFETs, and this effect remains stable after standard back-end process including post-metallization annealing (400 degrees Celsius). Th Vth change obtained was about 0.1 V at a hydrogen dosage of 1 x 1013 cm-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 Vth after we measure its actual value and compensate for the Vth variation caused by processing. Hydrogen ion implantation is thus a useful technique for feed-forward yield management.

Paper Details

Date Published: 4 September 1998
PDF: 8 pages
Proc. SPIE 3506, Microelectronic Device Technology II, (4 September 1998); doi: 10.1117/12.323965
Show Author Affiliations
Shinya Ito, NEC Corp. (Japan)
Ko Noguchi, NEC Corp. (Japan)
Tadahiko Horiuchi, NEC Corp. (Japan)

Published in SPIE Proceedings Vol. 3506:
Microelectronic Device Technology II
David Burnett; Dirk Wristers; Toshiaki Tsuchiya, Editor(s)

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