Effects of CVD-W process on electrical properties in sub 2× nm flash devices

The physical and electrical properties of chemical vapor deposition (CVD) tungsten (W) are evaluated in terms of W nucleation layer (SiH₄ and B₂H₆ reduction). Moreover effects of W nucleation layer on contact resistance (Rc) for sub 2× nm device are also studied. The results show that electrical properties of W thin films are varied with nucleation layers. Our results reveal that W reductions gases determine the grain sizes of W films which influence both electrical and surface properties of W films. It also has been investigated that effect of boron (B) atoms in B₂H₆ reduction W layer on P⁺ Rc. Out-diffused B atoms from P⁺ junction into silicide layer during post thermal process are compensated by B of B₂H₆ reduction W layer, which result in no degradation of P⁺ Rc despite of dopants loss at the contact interfaces. We reveal that tungsten nucleation layers are correlated with physical and electrical properties of W films and device performance.