Characterization of Polymetal Gate Transistors With Low-Temperature Atomic-Layer-Deposition-Grown Oxide Spacer

In this letter, W/WNx/poly-Si gate DRAM transistors with oxide spacers grown by low-temperature atomic layer deposition (ALD) have been fabricated, and the electrical characteristics are analyzed. The low-temperature ALD oxide effectively prevents the oxidation of exposed tungsten, and the fabricated devices show superior electrical properties to those with nitride/oxide spacer. The data retention time is improved by 30%, and the hot-carrier degradation characteristics are also enhanced. The threshold voltage of the fabricated W/WNx/poly-Si gate n-channel transistors with ALD oxide spacer is increased due to the suppression of boron deactivation by hydrogen. In particular, the transconductance of n-channel transistors in core/peripheral circuits was found to be enhanced by less-compressive stress in ALD oxide spacers.