Study on the Grit Angle of Single Diamond Dressing on CMP Pads

Inhalt:
In chemical mechanical planarization (CMP) process, diamond dresser plays an important role in maintaining the pad surface capability. The diamond dresser bonded diamond grits condition on the polishing pad to eliminate used pad surface with debris for recovering pad surface topography and function. There are many kinds of diamond grits with different grit or rake angles, which can cause a difference of pad topography for different kind of pads. This study aims to investigate the scratches on the pad surfaces by single diamond tools having different grit angles of 90deg and 120deg on three kinds of pads including solid, porous, and composite. This research aims to analyze effects of dressing speed and down force on the characteristic of scratches. Experimental results show that the depth and width of scratches can increase as the down force becomes larger. Diamond grit with 90deg grit angle creates more chips on the pad surface because it can transform down force into more portion of shearing force as obtained from higher pad cutting rate. As diamond grit angle 120deg, some plowing phenomenon and fewer chips are observed and discussed. Results of this study can be applied on diamond dresser design and for control of optimal pad dressing parameters in advanced node of CMP process. Keywords: Diamond grit angle, Diamond dressing, Polyurethane pad, Pad cutting rate, CMP