Specific details on the mechanical scribing process are illustrated in Figure 3.1. The inverted pyramid structures on the silicon wafers with front texturing are shown in Figure 3.2. A homogeneous n+ emitter diffusion process is carried out at the front surface. Thermal oxidation is involved for metallization masking, passivation layers, and antireflection coatings. Rear contact is patterned using the MS process, while the front metal contact can be patterned with a photolithographic technique. Deposition of front metal contact and rear metal contact can be done with an electronic-beam evaporation technique. Silver plating of the contact layer should
be done to reduce contact loss. Structural details on conventional PERC solar cell and MS-PERC solar cell are shown on Figure 3.2. In a conventional PERC device, a selective emitter must be formed at the front side and the rear silicon oxide layers, and patterning can be done using photolithography. For an MS-PERC device, patterning must be accomplished using a mechanical scriber.