Pad surface

Conditioning, an important technology in the CMP process, is to maintain the asperity structures on the pad surface, which force the abrasive particles against the wafer. A... 

In 1999, Luo and Domfeld [110] proposed that there are two typical contact modes in the CMP process, i.e., the hydro-dynamical contact mode and the solid-solid contact mode [110]. When the down pressure applied on the wafer surface is small and the relative velocity of the wafer is large, a thin fluid film with micro-scale thickness will be formed between the wafer and pad surface. The size of the abrasive particles is much smaller than the thickness of the slurry film, and therefore a lot of abrasive particles are inactive. Almost all material removals are due to three-body abrasion. When the down pressure applied on the wafer surface is large and the relative velocity of the wafer is small, the wafer and pad asperity contact each other and both two-body and three-body abrasion occurs, as is described as solid-solid contact mode in Fig. 44 [110]. In the two-body abrasion, the abrasive particles embedded in the pad asperities move to remove materials. Almost all effective material removals happen due to these abrasions. However, the abrasives not embedded in the pad are either inactive or act in three-body abrasion. Compared with the two-body abrasion happening in the wafer-pad contact area, the material removed by three-body abrasion is negligible. 

Philipossian, A. and Olsen, S., Effect of Pad Surface Texture and Slurry Abrasive Concentration on Tribological and Kinetic Attributes of ILD CMP," Materials Research Society Symposium Proceedings, Vol. 161,2003, F2.8. 

FIG. 21 Micro structure of the attachment pads, (a) Complete leg section containing the attachment pads, (b) Fracture of a shock-frozen pad. (c) Top view of the pad surface. (From Ref. 100. lOP Publishing Limited.)... 

In this example, the team examined the pad surface and the employees shoes and found hoth acceptable for the working conditions. Therefore, they decided Employee lost footing was a boundary event. The team decided to pursue the Recognized Hazard but Walked Through it Anyway further. Each of these items could also be pursued further. 

During the course of the experiment, pad surface roughness was measured by contact profilometry. Removal rate was found to be directly proportional to pad roughness (Fig. 11). Microscopic examination of the pad surface clearly showed the progressive smoothing away of the upper pad asperities (Figs. 12a-12d). No evidence of shear deformation of the asperities was... 

Fig. 10. Illustration of the polish pad surface profile created by the wafer carrier due to the polish (wear) rate being higher at the wafer edge than at the wafer center. An end effector can be used to compensate the profile if the duration vs position profile is set up correctly.

Tyres, footwear, moulded goods, paints Foam padding, surfaces, elastomers Barrier, extrusion, moulded goods Surface coatings, adhesives, composites Personal care products... 

FIGURE 2.7 ICIOOO pad surface temperature profiles during the polishing of 200-mm and 300-mm blanket oxide wafers using silica-based slurry under 6 psi downforce and 200 ml/min slurry flow rate and with two different table/carrier speeds (Strasbaugh n-Hance Polisher). 

Gitis et al. [21] demonstrated the effectiveness of a novel noninvasive instrument called PadProbe , developed by CETR Inc., in monitoring pad surface quality and pad life. PadProbe can be installed on rotational, orbital, and linear type CMP polishers (refer to Fig. 4.10). This sensor can monitor pad surface friction and wear in situ during the conditioning process. The only requirement is that the sensor should be in direct contact with the pad surface. 

Gitis N, Vinogradov M, Meyman A, Xiao J. PadProbe for quantitative control of pad surface conditions and wear. CMP User Group Conference 2002. 

The physical and mechanical properties of a polishing pad are determined not only by the chemical composition of the pad materials but also by its microstructures. As described in Table 5.1, each type of pad has its unique microstructure that ranges from large open pores to nonporous solids. Some representative microstructures of pad surfaces are shown in Fig. 5.1. 

FIGURE 5.10 (a) Pad surface temperature profiles during the polishing time (s) of 200 mm blanket oxide wafers using a commercially available silica-based slurry, (b) Pad surface temperature profiles during the polishing time (s) of 300 mm blanket oxide wafers using a commercially available silica-based slurry. 

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