Step coverage is poor in evaporation(ballistic)-Shadow effects Heat substrate to increase surface diffusion D=D E E°<<E kT By contrast, metal CVD and sputtering=> better step coverage e.g. WF+3H2eW+ 6HF △G≈70mo(073eV) Can do below400°C 6.152J3.155J6.152J/3.155J 13 Step coverage is poor in evaporation (ballistic) - Shadow effects Heat substrate to increase surface diffusion. DS = D0S exp − EaSurf kT      EaS << Eabulk e.g. WF6 + 3H2←→ W + 6HF ∆G ≈ 70kJmole(0.73eV) Can do below 400°C By contrast, metal CVD and sputtering => better step coverage W