Tungsten Gate Replacement Process Optimization in 3D NAND Memory

Abstract

The impact of fluorine [F] amount generated from conventional WCVD process and ALD WCVD process on SONOS charge-trapping 3D NAND memory are investigated. The damage degree of blocking oxide is an index for fluorine penetration through TiN/Al2O3 then further impacts the voltage break down (VBD) of ONO device characteristics. As compared to conventional WCVD process, ALD WCVD process with laminar 2D sequential growth can provide much better fill-in performance at word line, less fluorine trap at grain boundaries, damage-free of blocking oxide, minimal stress, and low resistance replacement gate to 3D NAND Flash.