Nonuniformity of Wafer and Pad in CMP: Kinematic Aspects of View

Abstract

In this paper, we analyze the nonuniformity of sliding distance on both the wafer and polishing pad from a kinematic point of view. Using the Fourier series expansion, it can be shown that in steady state the nonuniformity caused by contact relative velocity is determined by rotational speed ratio between platen and wafer carrier ( ) and the ratio of wafer radius to the distance between the platen center and wafer center ( ). In general, the nonuniformity of wafer increases with and (). An important observation for the polishing pad is that in two particular ranges of the ratio , larger ( ) on the contrary yields smaller nonuniformity. Then, a ring-type polishing pad is proposed for the purpose of improving the nonuniformity of both wafer and pad. However, it turns out the result for the pad of large size is worse than the traditional shape, unless the rotational speed of the pad is much slower than that of the wafer.

Run-to-Run Control Utilizing Virtual Metrology With Reliance Index

“…The well-known Preston equation, empirically found from the experiment of the glass polishing in 1927, has been proposed to predict the material removal rate of CMP [17], [18]. According to the Preston equation, the material removal rate is affected by the contact pressure (also denoted as tool stress) distribution at contact point, magnitude of the relative velocity (also denoted as tool rotation speed) at contact point between wafer and polishing pad, and constant representing the effect of the other remaining parameters including the slurry fluid speed, pad property, and so on.…”

“…The reason of adopting Stress, Rotspd, Sfuspd, PU, PU 2 , and PU 3 as the process parameters is based on the Preston equation, (18), and (19). The setting values of the simulated process parameters are tabulated in Table I. 3) Based on (3), the (k + 1)th run control action is derived by…”

Y2O3 nanosheets as slurry abrasives for chemical-mechanical planarization of copper

“…The planarization is characterized by the within-wafernon-uniformity (WIWNU) [5,6]. Previous studies in this regard have been focused on optimization of polishing parameters and utilization of corrosion inhibitors [7][8][9][10]. It is always desirable to develop a slurry that improves the slurry transport and contact between the polishing pad and the wafer surface.…”

Computational analysis and chemical mechanical polishing for manufacturing of optical components

“…There are many researchers have focused on the effects of the speeds on MRR and non-uniformity [8,14,27,46,51,53,[63][64][65][66][67][68][69][70][71][72][73][74][75]. Kinematic analysis is used to investigate the non-uniformity [51,70,74]. When the wafer and pad speeds increased, the non-uniformity increased.…”

“…Modifying the pad is another way to improve the uniformity. Feng [74] has proposed a ring-type polishing pad to improve the non-uniformity of both the pad and the wafer. However, the method only gives the expecting results when the pad speed is much slower than the wafer speed.…”