Low-Temperature Deuterium Annealing for High-Performance and Reliable Poly-Si Channel Thin-Film Transistors

Post-metallization annealing (PMA) is used indevice fabrication to improve MOSFET performance andreliability and is typically carried out at 400 degrees C or higher.However, high-temperature PMA can result in unexpectedjunction modifications and dopant deactivation. As an alter-native, low-temperature deuterium annealing (LTDA), whichis performed at an annealing temperature 100(degrees)C lower thanthe conventional PMA, is introduced. The LTDA effectivelyreduces the traps in the silicon channel and SiO(2 )dielectric[e.g., gate dielectric and buried oxide (BOX)] with a low-thermal budget. Poly-Si channel thin-film transistors (TFTs)are fabricated as test vehicles (TVs) to verify the impactof LTDA. The electrical characterization of subthresholdswing (SS), threshold voltage (V-TH),ON-state current (ION),OFF-state current (I-OFF), and gate leakage (IG) is com-paratively studied with and without LTDA. The long-termreliability of the device following LTDA under hot-carrierinjection (HCI) stress condition is confirmed. Finally, further investigation was carried out on the reduced sheetresistance (R-sheet) and surface roughness of the poly-Sigate. The improvement of poly-Si roughness under diluteddeuterium ambient is investigated for the first time.