Tungsten Gate Replacement Process Optimization in 3D NAND Memory

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/Al
₂
O
₃
then further impacts the voltage break down (V
_BD
) 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.