Abstract
Based on a previous work where we investigated the effect of conditioner type and downforce on the evolution of pad surface micro-texture during break-in, we have chosen certain break-in conditions to carry out subsequent blanket SiO2 wafer polishing studies. Two different conditioner discs were used in conjunction with up to two different conditioning downforces. For each disc-downforce combination, mini-marathons were run using SiO2 wafers. Prior to polishing, each pad was broken-in for 30 min with one of the conditioner-downforce combinations. The goal of this study was to polish wafers after this break-in to see how the polishing process behaved immediately after break-in. One of the discs used in this study produced similar micro-texture results at both downforces, which echoed the results seen in the mini-marathon. When comparing the different polishing results obtained from breaking-in the pad with the different discs used in this study, the coefficient of friction (COF) and SiO2 removal rate (RR) were uncorrelated in all cases. However, the use of different discs resulted in different COF and RR trends. The uncorrelated COF and RR, as well as the differing trends, were explained by pad micro-texture results (i.e. the differing amount of fractured, poorly supported pad asperity summits).
Highlights
Chemical mechanical planarization (CMP) is the only economically-viable means of achieving global and local planarization across the wafer surface in integrated circuit manufacturing
Extensive research has shown that pad surface micro-texture plays an important role in CMP and is affected by several factors such as conditioner type, conditioning downforce, and pad break-in time [2,3,4,5,6,7,8,9,10]
Sun et al studied the effect of conditioner type and conditioning downforce on pad topography and found that the surface becomes more abrupt and copper removal rates decrease with increasing conditioning downforce [2]
Summary
Chemical mechanical planarization (CMP) is the only economically-viable means of achieving global and local planarization across the wafer surface in integrated circuit manufacturing. Extensive research has shown that pad surface micro-texture plays an important role in CMP and is affected by several factors such as conditioner type, conditioning downforce, and pad break-in time [2,3,4,5,6,7,8,9,10]. Confocal microscopy was used by Elmufdi et al to determine the effect of conditioner type and downforce on pad-wafer contact area during break-in [5].
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