High‐precision alignment procedures for patterning processes in solar cell production

摘要： We present two approaches for high-accuracy aligning of patterning processes with each other when fabricating solar cells. We introduce the approaches on the example of two different patterning processes of which one is adjustable (laser process) and one is not adjustable (screen-printing process). The basic idea is to measure the coordinates of the applied structures of each involved patterning process at discrete grid points with respect to a reference coordinate system. We chose the grid points such that they completely define the final cell pattern. Then, we adjust the grid point coordinates of one of the patterning processes (the laser process) according to the pattern of the other process (the screen-printing process). The laser then performs the patterning by connecting the corrected grid points with each other in the desired direction. We perform the associated high-precision measurement of the patterns' coordinates by using either a high-precision offline coordinate measuring machine or a high-resolution inline camera system with subsequent computer-based data processing. The latter inline method enables high throughput and is, in turn, of great interest for mass production of solar cells. In this paper, we demonstrate the alignment procedure approaches on “pPassDop” solar cells by adjusting a locally applied laser process to the directly following screen-printing step. This proof of principle includes both above-mentioned methods for coordinate determination in separate cell batches. Our innovative alignment procedures so far demonstrated the successful matching of 40-μm-wide screen-printed contact fingers to 70-μm-wide laser-processed lines over the entire area of 6-inch solar cells.