A high-quality cross-sectioning method: Examples of applications in optimizing solar cell contact firing

A damage-free polishing method is developed to prepare a high-quality cross-section of a large length of a solar cell. A 1-inch-long sample is diced from the solar cell and embedded in wax using a specially designed chuck. The sample edge is sequentially polished by progressively reducing the grit sizes. The final polishing is done by Chemical Mechanical Polishing (CMP). This polishing procedure produces a highly flat edge, with excellent interfaces between metal contacts and the Si cell. The planarity of the wafer edge makes it possible to perform a variety of analyses of various regions and the interfaces of the cell, using optical microscopy, EDX, scanning electron microscopy (SEM), and conductive AFM (C-AFM). Here, we will discuss some details of the chuck and the polishing procedure, and present some applications for optimizing the contact firing process. This method has an added advantage of delineating the back surface field for optical observation.