Mathematical modeling of CMP conditioning process

Chang, O.M.; Kim, Hyoungjae; Park, Ki-Hyun; Park, Boumyoung; Seo, Heondeok; Jeong, Haedo

doi:10.1016/j.mee.2006.11.011

Cited by 37 publications

(21 citation statements)

References 5 publications

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“…Figure 1 schematically illustrates each of these phenomena and its relationship to the material removal rate equation. 14 Chang et al 16 modeled the typical kinematics of the conditioner and showed that the conditioner will wear the pad non-uniformly resulting in a concave pad surface. [15][16][17][18] Here the workpiece and/or conditioner (typically a fixed diamond abrasive to treat the pad for CMP or a sacrificial workpiece used during pad optical polishing) is loaded against the pad surface and, as a result, spatial and temporal changes in the pad properties (thickness profile, roughness, slurry charging level, etc.)…”

Section: Introductionmentioning

confidence: 99%

“…The influences of pad wear and changes in pad properties during polishing have been previously investigated. [15][16][17][18] Here the workpiece and/or conditioner (typically a fixed diamond abrasive to treat the pad for CMP or a sacrificial workpiece used during pad optical polishing) is loaded against the pad surface and, as a result, spatial and temporal changes in the pad properties (thickness profile, roughness, slurry charging level, etc.) can occur.…”

Section: Introductionmentioning

confidence: 99%

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Convergent Pad Polishing of Amorphous Silica

Suratwala

Steele

Feit

et al. 2012

Int J of Appl Glass Sci

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A new method of optical polishing termed “Convergent Polishing” is demonstrated where a workpiece, regardless of its initial surface figure, will converge to the lap shape in a single iteration. This method of polishing is accomplished by identifying the phenomena that contribute to non‐uniform spatial material removal, and mitigating the non‐uniformity for each phenomenon (except for the workpiece‐lap mismatch due to the workpiece surface shape). The surface mismatch at the interface between the workpiece and lap causes a spatial and time varying pressure differential which decreases with removal, thus allowing the workpiece to converge to the shape of the lap. In this study, fused (amorphous) silica workpieces are polished using ceria slurry on various polyurethane pads. Polishing parameters were systematically controlled to prevent various sources of non‐uniform material removal which include: (i) moment force, (ii) viscoelastic lap relaxation, (iii) kinematics, (iv) pad wear, and (v) workpiece bending. The last two are described herein. With these mitigations, removal uniformity has been demonstrated to within 1.0 μm over the surface after 83 μm of material removal corresponding to a within workpiece non‐uniformity (WIWNU) of <1.2%. Also, convergence has been demonstrated down to 0.18 ± 0.04 μm peak‐to‐valley flatness on 100 mm‐sized workpieces.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Convergent Pad Polishing of Amorphous Silica

Suratwala

Steele

Feit

et al. 2012

Int J of Appl Glass Sci

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“…Various researches revealed concavity of the pad shape by the conditioner disc oscillating on the pad [20,21]. In summary, the disadvantages of these methods lie in: (1) There is no method for measuring the pad shape, which is usually speculated based on the surface figure of the polished optics; (2) The planarization of the polyurethane pad by conditioner disc oscillating on the pad is difficult to achieve by the large diamond conditioner disc.…”

Section: Introductionmentioning

confidence: 99%

Deterministic measurement and correction of the pad shape in full-aperture polishing processes

Liao¹,

Zhang²,

Xie³

et al. 2015

J. Eur. Opt. Soc.-Rapid Publ.

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Full-aperture polishing is a significant process in fabricating large optical flats because it restrains Mid-Spatial Frequency errors and removes material quickly on the whole optic surface. Nevertheless, optical flats fabricated by full-aperture polishing generally fail to meet the stringent requirement of surface figure, which has to be corrected by sub-aperture polishing processes. Surface figure of optical flats in full-aperture polishing processes is primarily dependent on the pressure distribution uniformity which correlates intensively with the lap shape. At present, practical and precise means are urgently desired for measuring and correcting the lap shape, especially the polyurethane pad lap. In the study, we present a novel method for deterministic measurement of the pad shape. The method obtains the height of the pad at spirally distributed locations implemented by the revolution of the pad and translation of the laser displacement sensor. The pad shape in terms of matrixes whose elements representing the heights at the corresponding locations is then calculated by interpolation algorithm based on the obtained data. Further, we propose a method for deterministic correction of the pad shape utilizing a small conditioning tool. The dwell time algorithm and implementation strategy for the dwell time are provided for common full-aperture polishers. These solutions for the deterministic measurement and correction of the pad shape have been validated on a full-aperture polisher with polyurethane pad. The polishing experiments revealed that the optic surface figure was obviously improved.

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“…Hooper et al (2002) revealed a correlation between the conditioning density and both the wear geometry and the surface properties of the polishing pad. Chang et al (2007) proposed a conditioning process and mathematical modelling of pad wear using kinematics analysis. They demonstrated that the thickness variation in the polishing pad can be predicted with their conditioning model.…”

Section: Introductionmentioning

confidence: 99%