The Role of Pad Topography in Chemical-Mechanical Polishing

Abstract

In this paper, the role of pad topography on material removal rate (MRR) in chemical-mechanical polishing (CMP) is investigated. First, based on the mechanics of pad/particle and particle/wafer sliding contacts at an asperity of the polishing pad a new MRR model is developed. The model is then extended to multi-asperity contacts, taking into account the statistics of the asperity heights. The single-asperity model reveals that the removal rate at relatively low pressure strongly depends on the pressure and the area at a sliding asperity contact. However, removal rate per asperity becomes independent of the contact pressure once it exceeds a critical value, which is determined by the asperity hardness and the particle concentration. Material removal by multi-asperity sliding contacts increases due to the increase in real contact area, provided a large number of asperity contacts at pressures greater than the critical. The plasticity index is identified as a key parameter that determines the contact area ratio and proportion of asperities in contact at pressures greater than the critical, thus the overall MRR. The model suggests that MRR in CMP can be greatly increased by controlling the surface topography of the pads. Results of polishing experiments on Cu thin films validate the model. Index Terms-CMP, material removal mechanism, modeling.

Evaluation of Chemical Mechanical Polishing-Based Surface Modification on 3D Dental Implants Compared to Alternative Methods

“…The developed lab-scale technique proposed in this study consisted of equipment that was deliberately grouped to meet the purpose for which it was combined. The most important component in CMP is the polishing pad, and its characteristics must be provided in detail in terms of the structure and materials [21]. The design of the polishing pad utilized in this work consisted of a surface layer of flexible brush-like microfibers with the ability to efficiently carry the nanoscale abrasives in the slurry independent of the sample down pressure.…”

Analysis of Correlation between Pad Temperature and Asperity Angle in Chemical Mechanical Planarization

“…At 80 degrees, it was found that the surface became blunt due to the excessive elevation and the formation of large asperities via the fusion of multiple asperities, as described above. Generally, the contact state of the asperities is closely related to the removal rate in the CMP process [20,21]. is believed to be affected by changes in the asperities' contact states due to the asperity angles, as described in this section, and the experiment was performed to examine this effect.…”

Investigation on nanoscale material removal process of BK7 and fused silica glass during chemical‐mechanical polishing

“…In the CMP process, the contact among pad asperities, glass substrates, and abrasive particles is rather complicated. Numerous abrasive particles are captured by the micro contact spots that formed between polishing pad asperities and glass substrate 12 . These trapped abrasive particles can be considered as part of the pad asperity itself and provide the “chemical tooth” that bonds with glass surface 13,14 .…”

“…Numerous abrasive particles are captured by the micro contact spots that formed between polishing pad asperities and glass substrate. 12 These trapped abrasive particles can be considered as part of the pad asperity itself and provide the "chemical tooth" that bonds with glass surface. 13,14 Therefore, the material removal for a given site on the glass surface is a superposed renewal process, which combines the successive scraping action of entrapped abrasive particles and the transient chemical activation of surface atoms by the polishing slurry.…”