Influence of external bias on the surface morphology of a-C:H films grown by electron cyclotron resonance chemical vapor deposition

We have studied the influence of an external bias on the surface morphology of a-C:H films grown by electron cyclotron resonance chemical vapor deposition (ECR-CVD) on silicon substrates. We have deposited films for 1 h at different bias from + 100 V down to − 250 V and analyzed their surface morphology by atomic force microscopy (AFM). For biases equal or higher than − 80 V the film morphology is cauliflower-like, which is due to the shadowing geometry effects inherent to the deposition process. In contrast, for highly negative biases the films become ultrasmooth. Here, the film morphology is consistent with an Edwards–Wilkinson scaling behavior, which starts to operate at shorter length distances as the external bias becomes more negative. This morphology is likely due to the interplay of ion induced physical sputtering and enhanced downhill surface mobility.