Pad Surface Roughness and Slurry Particle Size Distribution Effects on Material Removal Rate in Chemical Mechanical Planarization

Wang, C.; Sherman, Peter; Chandra, Abhijit; Dornfeld, David

doi:10.1016/s0007-8506(07)60110-3

Cited by 50 publications

(28 citation statements)

References 14 publications

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“…Wang et al [29] extended the model to include inelastic contact between pad asperity and wafer surface. They also incorporated the effect of abrasive particles on the material removal rate decay [30]. The model correctly predicted the MRR decay trend that matches the experimental results.…”

Section: Pad Conditioning and Its Effect On Cmp Performancementioning

confidence: 61%

“…They showed that with this modification and careful selection of pad surface roughness parameters (asperity height distribution PDF), the time-varying (dynamic) MRR model can have significant potential in the prediction of MRR and MRR decay. They further presented another model incorporating the abrasive particle effects and considered that material removal comes from the interaction of the wafer and the active particles entrapped in the pad asperity-wafer contact areas [30]. This model reflects not only the effects of pad properties such as Young's modulus, hardness, asperity density, tip curvature, and height distribution but also the effects of abrasive particle (mean) size and size distribution on the polishing removal rate at a given polishing time.…”

Section: Review Of Modeling Of Pad Effects On Polishing Performancementioning

confidence: 99%

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Pads for IC CMP

Wang

Paul

Kobayashi

et al. 2007

Microelectronic Applications of Chemical Mechanical Planarization

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The chemical-mechanical polishing or planarization (CMP) process is a complex interplay between the wafer and the consumables involved. The consumables include slurry, pad, conditioner, and so on. During polishing, the pad carries the slurry and delivers it to the wafer surface. It also transmits the normal and shear forces from the polisher to the wafer. Therefore, polishing pad plays a critical role in the CMP process and influences the outcomes such as material removal rate (MRR), within-wafer nonuniformity (WIWNU), wafer-to-wafer nonuniformity (WTWNU), step height reduction efficiency (SHRE), and defect counts.As the CMP process is a combination of mechanical and chemical processes, the polishing pad has to endure repeated mechanical stress and constant chemical attacks. The applied downforce and polishing-induced friction force cause various levels of compression and abrasion. Slurry components such as oxidizers and acids can react with different components of the pads. Thus the polishing pad must have sufficient mechanical integrity and chemical resistance to survive the rigors of polishing. Polishing pads must balance the needs of hardness, modulus for planarity, and strength to resist wear and tear during polishing. Pads must also be able to survive the aggressive slurry chemistry used in CMP polishing without degrading, delaminating, blistering, or warping, since CMP slurries for the polishing of interlevel dielectric (ILD) oxide layers are usually highly alkaline with pH as high as 11, and CMP slurries for the polishing of metal films are highly acidic Microelectronic Applications of Chemical Mechanical Planarization, Edited by Yuzhuo Li

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Section: Pad Conditioning and Its Effect On Cmp Performancementioning

confidence: 61%

Section: Review Of Modeling Of Pad Effects On Polishing Performancementioning

confidence: 99%

Pads for IC CMP

Wang

Paul

Kobayashi

et al. 2007

Microelectronic Applications of Chemical Mechanical Planarization

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show abstract

“…Similarly, from (19), (20), and (25), the relation between the nominal pressure, p, and the separation distance, d, can be estimated by…”

Section: A Contact Area Ratiomentioning

confidence: 99%

The Role of Pad Topography in Chemical-Mechanical Polishing

Kim

Saka

Chun

2014

IEEE Trans. Semicond. Manufact.

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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.

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“…Some researchers [20], [21] have investigated the number of active particles, whereas others [22], [23] have conducted some experimental studies on the contact ratio of the pad asperities. Based on these studies, it can be predicted that the effective particle number is more than 1,000,000.…”

Section: Kinematic Optimization Based On Trajectorymentioning

confidence: 99%

Kinematic Optimization for Chemical Mechanical Polishing Based On Statistical Analysis of Particle Trajectories

Zhao

Wang

et al. 2013

IEEE Trans. Semicond. Manufact.

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The abrasive effect of particles is one of the basic mechanical actions in chemical mechanical polishing (CMP). In this paper, numerical simulations of particle sliding trajectories are performed to examine the influence of the kinematic parameters on the polishing uniformity of typical rotary-type CMP equipment. The trajectory simulations are carried out based on the kinematic analysis. The results reveal that the speed ratio α and the period ratio k T 0 , which represent the coupling relationships among the three basic motions of CMP, are the two major factors affecting the trajectory distribution. Further, a trajectory density parameter is proposed to quantitatively evaluate the global uniformity of the trajectory distributions and to optimize the kinematic parameters for better uniformity. The statistical results of the trajectory density analysis reveal that the trajectory of the wafer edge is denser than that of the wafer central area. To obtain better trajectory uniformity, some particular values of α and k T 0 , that is, α = 1 and k T 0 = 1, which imply that the basic motions have a special coupling relationship, should be excluded; the preferred kinematic parameter values for CMP are α = 0.91∼0.93 and k T 0 = 5∼7. This paper provides a basic guide to the kinematic parameter settings of CMP.

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Pad Surface Roughness and Slurry Particle Size Distribution Effects on Material Removal Rate in Chemical Mechanical Planarization

Cited by 50 publications

References 14 publications

Pads for IC CMP

Pads for IC CMP

The Role of Pad Topography in Chemical-Mechanical Polishing

Kinematic Optimization for Chemical Mechanical Polishing Based On Statistical Analysis of Particle Trajectories

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