Fabrication of a Novel Mechanism to Find Height Diamond Grits on Diamond Conditioner

Abstract

Diamond conditioners are indispensable for dressing CMP pads, however, due to a leveling requirement, only a small percent of the diamond grits can penetrate a pad. As these few crystals are worn out, the plastic deformation of the pad becomes great relative to the amount of the pad that is cut. Consequently, the pad becomes highly deformed and loaded with dirt. The polishing rate will then decrease and the scratch rate will increase. A novel technique has been developed to identify the cutting tips and their dulling process. The cutting paths become wider and shallower as the pad material becomes more and more deformed. Eventually, fewer and fewer scratch lines are present with most touching the diamond pushing the deformed pad around. Because there are only a handful of diamond grits that are engaged in the cutting pad, the number of working crystals can be increased substantially by improving the leveling of the diamond tips. This study constructed a scratch lines test mechanism, using the transfer method to find the height of the tips of the diamond grits, and to mark the height of the diamond grits coordinates before dressing and polishing. A digital microscope was used to confirm the location of the tips of the diamond grits. Then, the diamond grinding tool was used to decrease the high tips of the diamond grits. This study explored the relationships between the height of the diamond grits and effective working diamond grits, in order to increase the diamond conditioner's performance. The experimental results showed that the scratch lines test mechanism can quickly find the height of the diamond grits and confirm the number of effective working diamond grits. This improvement can increase the longevity of a diamond conditioner that paves the way for a future CMP of 18 inch wafers scheduled to make the debut in 2016.