The efficiency of silicon heterojunction solar cells is limited by the parasitic absorption within the intrinsic and doped hydrogenated amorphous silicon (a-Si:H) layers, hence minimizing their thickness by simultaneously preserving the high-level passivation quality is crucial. The a-Si:H must withstand subsequent processing steps, in particular the deposition of a transparent electrode. Here sputter deposition of transparent conducting oxides (TCOs) is commonly the method of choice, since this well established technique can yield uniform TCO layers with suitable electrical and optical properties. This paper aims at the design of a soft sputter deposition process, which allows utilizing well established DC magnetron sputtering on top of ultrathin a-Si:H layers, without a significant degradation of passivation quality. For this purpose, the influence of the a-Si:H thickness, the chamber pressure and the applied power are reviewed for In2O3:Sn (ITO) deposition. As a simple approach to combine excellent surface passivation, acceptable electrical TCO bulk properties and high throughput, an ITO double layer stack, featuring a few nanometers thin softly deposited intermediate ITO layer below a high rate deposited thicker ITO layer, is presented. Hereby the implied open-circuit voltage of test structures could be improved by almost 30 mV.