PECVD SHADOW MASK DEPOSITION OF AMORPHOUS SILICON - A SHORTCUT TO LOCAL PASSIVATING CONTACTS

摘要

We develop and investigate shadow masks for the local PECVD deposition of amorphous Si (a-Si) fingers to be applied as local poly-crystalline Si (poly-Si) passivating contacts in the industrial fabrication of novel solar cell concepts such as TOPCon, PERC+POLO and POLO-IBC. We first apply a nickel-based test mask with varying mask opening widths and demonstrate narrow poly-Si fingers down to 70 μm width suitable for application on the front side of solar cells. However, the aspect ratio of the finger opening width and the mask thickness is limiting the deposition rate of as-deposited a-Si fingers. Using a glass-based mask, we verify that the a-Si finger position is identical to the mask layout over the size of a M2 silicon wafer. The passivation quality of the n-type poly-Si is demonstrated on symmetrical lifetime samples using n-type Cz wafers, a thermal oxide interface, PECVD n-a-Si and a subsequent high-temperature anneal. We measure carrier lifetimes up to 7.78 ms corresponding to an implied Voc up to 738 mV.