The manufacturing process for amorphous silicon photovoltaic modules is a third-generation technology based upon a highly successful and field-proven large batch approach to amorphous silicon deposition. In this approach, a large number of tin oxide coated glass plates are coated simultaneously with amorphous silicon in a single vacuum chamber. The method allows a high plate throughput with the advantages of relatively low capital costs, straightforward maintenance, and minimal downtime. Specific features of this design for the chambers and fixturing result in low atmospheric and other impurities, low dopant cross-contamination, low particulates, and good gas utilization. Proprietary designs are employed to obtain amorphous silicon deposits with unusually good thickness uniformity. The overall manufacturing sequence is:
- glass preparation (seam and wash)
- deposition of tin oxide & laser scribing of tin oxide
- deposition of a-Si & laser scribing of a-Si
- sputter deposition of Al & laser scribing of Al
- encapsulation and testing
In the proprietary STF a-Si deposition process the source of the silicon and hydrogen atoms in a-Si:H is the gas silane (SiH4). The silane is decomposed in a vacuum chamber by electron impact in a glow discharge. The discharge is excited by radio-frequency (RF) power applied to a set of planar electrodes. The decomposition fragments are highly reactive and represent the precursor for deposition. The precursor specifies bond to the surface of the growing film. The versatility of a-Si:H results from the nature of the deposition process wherein the materials is laid down, from convenient gaseous sources, layer by layer. This allows sequential deposition of any number of layers of different materials, which each layer having any desired compositional or dopant profile. | 
