The Synergetic Role of Pores and Grooves of the Pad on the Scratch Formation during STI CMP

Abstract

The polishing pad plays a vital role in achieving the desired removal rates and level of surface planarity during the chemical mechanical planarization (CMP) process. Generally the pad containing both pores and grooves is used for the shallow trench isolation (STI) CMP process. After polishing the wafer, many scratches would be produced on the surface, especially chatter mark scratches on the oxide surface. In this work, the role of pores and grooves of the pad on scratch formation was studied with STI-patterned wafers with three types of pads: pad with only pores, pad with only grooves, and pad with both grooves and pores. The pad with only grooves produced more irregular-shaped scratches when compared to the pad with only pores, but the length of the scratch was smaller. A regular chatter mark type scratch would be formed only when the pad contained both pores and grooves. The most likely occurring phenomenon might be the stick-slip motion during the process. The removal rates with three different pads were compared and they were inversely correlated to each other. The presence of pores would be essential to decrease the scratch number. However the scratch number could be greatly reduced with the combination of both pores and grooves. Overall, the number of scratches would be greater with the absence of pores, and the scratch number and intensity substantially reduced with the combination of both pores and grooves. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3447743] All rights reserved.