4 September 1998 Novel two-step AI CMP process for overcoming pattern geometry effects
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It is important and critical to obtain reasonable removal rate, low polish non-uniformity, scratchless polished surface and no metal dishing and ILD erosion for aluminum damascene process with CMP. It is difficult to meet these requirements in a single-step polishing process because lower removal rate of titanium, known as polish-inert metal, results in significant over-polish of the aluminum features and severe metal dishing and ILD erosion should be obtained. Here we evaluate a novel 2-step polishing process to accomplish the damascene process more efficiently. First, the overburden aluminum was removed fast and uniformly. In our study, more than 3,000 nm/min removal rate, less than 10% polish non- uniformity and scratchless finished surface could be obtained. Next, by adjusting slurry pH, the removal rate of Al could be about as the same as that of Ti and that of SiO2 unchanged in the meantime. By this way, it relaxes the process window to overcome the problems of the pattern geometry effects.
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Ming-Shih Tsai, Jias-Sheng Lin, Bau-Tong Dai, "Novel two-step AI CMP process for overcoming pattern geometry effects", Proc. SPIE 3508, Multilevel Interconnect Technology II, (4 September 1998); doi: 10.1117/12.324029; https://doi.org/10.1117/12.324029

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