Wire-bow in situ measurements for powerful control of wire-wear during diamond-wire crystalline silicon sawing.

Abstract

Original instrumental setups embedded in industrial-type multi-diamond-wire sawing equipment are presented for in situ measurements of the apparent wire diameter, the vertical force applied to the wire web, and the wire-web bow during the cutting of crystalline silicon bricks into wafers. The proportionality relationship between the vertical force and the wire bow during the cut of a Czochralski silicon brick is, for the first time, experimentally observed as expected by the theoretical calculations. As a result, the in situ bow measurement is shown to provide a direct control of the cutting efficiency, which is inversely proportional to the vertical force. In addition, the wire-wear evolution during successive cuts is analyzed using the in situ measurement of the apparent wire diameter together with the in situ bow measurements for equivalent cutting conditions using several bow sensors distributed above the wire web. The three-dimensional plot of the cutting efficiency resulting from the bow measurement processing gives access to the distribution of the cutting efficiency along the wire web during the progress of the cut. Given the homogeneous properties of the silicon material used, the cutting efficiency proves to be a representative of the wire-wear. Moreover, the unique capability of the in situ bow measurement to provide a distribution of the measurements on the wire web during the cut allows studying the wire web behavior and the wire cutting efficiency distribution for different cutting conditions. Thanks to the innovative design of the instrumentation coupled with a data analysis based on a deep understanding of the involved physical phenomena, the in situ bow measurement is demonstrated to be a powerful tool to optimize the cutting process in terms of wafer quality and cost efficiency. Moreover, it can provide real-time information opening the door for tuning the parameters during the cutting process.