Novel Methode for Preparation of Interdigitated Back Contacted a-Si:H/c-Si Heterojunction Solar Cells

We present a novel method for structuring Emitter and BSF areas of interdigitated back contacted silicon heterojunction solar cells (IBC-HJ). The method combines the benefits of in-line capability with vacuum processes only, reusable masks, self alignment and furthermore an easy and extreme safe wafer handling. It is based on plasma etching of passivation layers and a following layer deposition procedure via openings in a mechanical masking. The exceptional way how the reusable masks are attached to the sample provides accurate masking over large area. By overlaying two masks the wafer can remain underneath the lower masking, which also works as a sample holder during all the structuring steps while, if necessary, the upper mask is exchanged for each particular process step. This provides an extreme safe wafer handling along all the IBC-HJ specific process steps, highly recommended for very thin wafers. This allows processing the different layers (e.g. emitter, BSF, TCO, metal) structures without the need to touch the wafer after each step. Furthermore a mechanical self aligning of the mask-stacks can be applied in mass production. First test structures are shown and cost estimation for IBC-HJ solar cells is presented.