On the Optimization of Prime Silicon Wafer Geometry in Final Chemical Mechanical Polishing

For the advanced Ultra-large Scale Integrated Circuits (ULSI) manufacturing, two key geometry parameters of the 300 mm prime silicon wafers: SFQR and GBIR are of major interest to the manufacturers. During the acceptance tests of the first China-made final-touch chemical-mechanical machine (CMP). We find that to enhance the geometry parameters, we have to know the geometry of incoming wafers and to modify the polishing head pressure accordingly. After investigation of the geometry of the incoming wafers, we find wafers with concave thickness profile would be deteriorated seriously after final-touch CMP. According to the shape of every wafer, we vary the backing pressure distribution of our special designed polishing head. Eventually, the wafer thickness geometry after modification could fulfill our demand, which demonstrates that our own-made machine could be used in mass production.