A Theoretical and Experimental Analysis of Macrodecoration of Defects in Monocrystalline Silicon

Microdefect distribution in a monocrystalline silicon wafer is identified by saturating the wafer with copper at a high temperature followed by copper precipitate growth through rapid cooling followed by surface polishing and subsequent microdefect-decorating etching. The decorated microdefect field consists of etch pits that are formed by the difference in the etching rates of the precipitate influenced region around microdefects, and the etching rate of the surrounding defect-free silicon. Interplay between liquid-phase mass-transport effects and surface kinetics plays a key role in the microdefect decoration. It is shown that the macrodecoration of microdefects is typically realized in the absence of significant effects of the liquid-phase diffusion. The developed phenomenological model leads to classification of etchants as either polishing or potentially decorating and to identification of conditions necessary for an efficient microdefect decoration. The competing effects of kinetics toward microdefect decoration and liquidphase transport toward surface polishing are quantified by theoretically derived solutions for the decorating efficiency and the polishing efficiency. Autoerosion of the microdefects by mildly polishing etchants is also quantified. Analytical expressions for the microdefect-decorating and microdefect-polishing conditions are presented. Finally, decorating and polishing etchants are experimentally identified from a group of etchants and the proposed theory is verified by experimental data.