Modeling of Chemical Mechanical Polishing Processes Using a Discretized Geometry Approach

Yao, C.H.; Feke, Donald L.; Robinson, K.M.; Meikle, Scott

doi:10.1149/1.1393386

Cited by 22 publications

(14 citation statements)

References 18 publications

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“…Based on the understanding of the CMP process, researchers have modeled the feature scale surface evolution in different ways: some of the researchers (e.g., Runnels [11] and Yao et al [18]) assume that there is a fluid layer between the wafer and the pad while the others group assumes solid-to-solid contact. For the latter, there are also two kinds of models: one implies only high areas on the wafer feature have direct contact with pad and low areas are free of any loading and is not polished (e.g., Chekina [1], Elbel et al [3], and Saka et al [12]); the other assumes both high and low areas contact with the pad (e.g., Chen and Lee [2] and Vlassak [16]).…”

mentioning

confidence: 99%

An analytical dishing and step height reduction model for chemical mechanical planarization (CMP)

Chandra

2003

IEEE Trans. Semicond. Manufact.

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An analytical model for dishing and step height reduction in chemical mechanical planarization (CMP) is presented. The model is based on the assumption that at the feature scale, high areas on the wafer experience higher pressure than low areas. A Prestonian material removal model is assumed. The model delineates how dishing and step height reduction depend on slurry properties (selectivity and Preston's constants), pad characteristics (stiffness and bending ability), polishing conditions (pressure, relative velocity and overpolishing) and wafer surface geometry (linewidth, pitch and pattern density). Model predictions are in good agreement with existing experimental observations. The present model facilitates understanding of the CMP process at the feature scale. Based on the proposed model, design avenues for decreasing dishing and increasing the speed of step height reduction may be explored through modification of appropriate parameters for slurry, pad and polishing conditions. The proposed model may also be used as a design tool for pattern layout to optimize the performance of the CMP process.

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mentioning

confidence: 99%

An analytical dishing and step height reduction model for chemical mechanical planarization (CMP)

Chandra

2003

IEEE Trans. Semicond. Manufact.

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“…Fluid mechanics: The effect of flowfield and hydrodynamic pressure of the slurry was not taken into account in this model. Past models have suggested that the slurry shear rate directly affects the wear of the wafer sample [1,26,27], while other studies have shown that the sample contact stress is affected by the slurry hydrodynamic pressure [35,36]. Neither of such assumptions are taken into account in the current model.…”

Section: Modeling Assumptionsmentioning

confidence: 97%

“…3. Pad roughness: Following the pattern of past featurescale CMP models [21,25,26], the authors chose to omit pad roughness effects from the model in this study. In addition to making this assumption for simplicity purposes, it must be noted that the scale of the feature of interest (L = 70 lm) could be considered to be small enough to minimize large-scale pad roughness effects, since the asperity density of polishing pads is typically around g = 10 -5 asperities/lm 2 [12,39].…”

Section: Modeling Assumptionsmentioning

confidence: 99%

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Analysis of Feature-Scale Wear in Chemical Mechanical Polishing: Modeling and Experiments

2009

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An asperity-scale wear model was developed to predict feature-scale wear in chemical-mechanical polishing (CMP), and was compared to the measured evolution of a lithographically patterned feature during full-scale CMP tests. To conduct this study, a lithographic technique was used to pattern a set of raised square features into a Cu-coated silicon wafer. Two-dimensional contact profilometry was used to measure the topography of an isolated feature on each wafer both before polishing and at various intervals throughout the polishing process. In the wear modeling formulation, a pad deflection-based contact mechanics model was developed and combined with a particle-based wear model to predict the wear evolution of the sample during CMP. The predicted wear of the sample feature was found to agree well to experimental results.

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“…Based on the understanding of the CMP process, researchers have modeled the feature scale surface evolution in two different ways: one group (e.g., Runnels 1996 andYao et al 2000) assumes there is a fluid layer between wafer and pad while the other group assumes direct wafer-pad contact. For the latter, there are also two kinds of models: one implies only high areas on the wafer feature have direct contact with pad and low areas are free of any loading and is not polished (e.g., Elbel et al 1998, Chekina 1998and Saka et al 2001; the other assumes both high and low areas contact with pad (e.g., Gotkis et al 1998, Chen and Lee 1999, Vlassak 2001and Saka et al 2001.…”

Section: Literature Reviewmentioning

confidence: 99%

Modeling of chemical mechanical polishing at multiple scales

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Chemical Mechanical Polishing (CMP) has grown rapidly during the past decade as part of mainstream processing method in submicron integrated circuit manufacturing because of its global or near-global planarization ability. However, CMP process is influenced by many factors and is poorly understood. It makes process control and optimization very diffi cult. This study focuses on the modeling and simulation to facilitate better understanding and better control of the CMP process. The thesis outlines the modeling of CMP process in three scales: particle scale for material removal mechanism, wafer scale for within wafer nonuniformity issues and feature scale for dishing and erosion in metal CMP. At the particle scale, material removal mechanism is assumed to be due to local plastic deformation of wafer surface at the abrasive-wafer interface. Pad is assumed to deform like a beam to obtain an approximate force partition between abrasives and direct wafer-pad contact. A mechanistic material removal model is derived that delineates the influence of abrasive (shape, size and concentration), pad (rigidity) and process parameters (pressure and relative velocity) on the material removal rate (MRR). Wafer scale model is based on the solution of indentation of elastic half space by a rigid fhctionless polynomial punch. The elastic solution is derived through potential theory and complex analysis method. It is valid for any polynomial punch with integer power or noninteger power. The load-displacement relationship is also derived and the conditions for unbonded or bonded contact are obtained from the boundary condition at punch edge. The corresponding viscoelastic solution is obtained through Laplace transform and elastic-viscoelastic analogy. The elastic solution is used to explain the edge effect. The elastic analytical vi solution is first verified against numerical results from Finite Element Method (FEM) simula tion. It shows wafer curvature, indentation depth and load will influence the interface pressure distribution throughout the wafer surface and it introduces parameters control as a potential avenue for completely eliminating the within wafer nonumifonnity. Viscoelastic solution is used to explain within wafer nonuniformity, i.e., edge effect and wafer to wafer nonuniformity, i.e., removal rate decay for unconditioned pad. The relationships among wafer-pad interface pressure, wafer shape and wafer loading condition are also investigated. Feature scale model for dishing and erosion is based on Preston's relationship for material removal and constant downforce. It shows dishing will reach a limit and is governed by polishing conditions (overpolishing, pressure, velocity), slurry (selectivity), pad character istics (pad stiffness and bending ability), as well as wafer surface feature topography (pattern density, linewidth and pitch). This model is also valid for step height reduction when the same surface material is polished. Due to process complexity and coupling of various parameters, more fundamental research needs...

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Modeling of Chemical Mechanical Polishing Processes Using a Discretized Geometry Approach

Cited by 22 publications

References 18 publications

An analytical dishing and step height reduction model for chemical mechanical planarization (CMP)

An analytical dishing and step height reduction model for chemical mechanical planarization (CMP)

Analysis of Feature-Scale Wear in Chemical Mechanical Polishing: Modeling and Experiments

Modeling of chemical mechanical polishing at multiple scales

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