**3.4. Anti-reflection coating (ARC) patterning**

The conventional Ag metal contacts are usually formed by screen-printing and firing the Ag pastes through SiNx passivation layers. However, Ni/Cu-based metallization requires a separate step to open the ARC/passivation layer in order to form the contact grid. A simple example could be a mask and etch sequence [42]. Under this method, the passivated front surface of the cell is patterned with a photolithography process and the unprotected passivated layer is etched away using wet etching. Later on, the photoresist (PR) material is stripped away in an organic solvent solution (the process sequence is described in Fig. 6). For patterning the front contact grids, various approaches have been adopted. These approaches can be catego‐ rized as wet etching, direct etching, mechanical scribing and laser-assisted etching. All these etching methods will be discussed in this section of the chapter.

**Figure 6.** Mask and etch process sequence: (a) solar cell with a passivation layer, (b) front-electrode patterning with a photolithography process, (c) exposed ARC etching, and (d) PR removal.
