Analysis of Contact Deformation and Stiction Between Textured Disk and Textured Slider

Bai, Mingwu; Kato, Koji

doi:10.1115/1.1308006

Cited by 14 publications

(4 citation statements)

References 26 publications

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“…28 The model assumes that ͑i͒ the nominally flat rough surface is covered with hemispherically tipped asperities, ͑ii͒ the asperity summits have a constant radius, ͑iii͒ the heights of the asperities vary randomly, (iv) the asperities do not interact with one another, and (v) there is no deformation of the bulk. 29 If the pad is modeled as a nominally flat surface covered with hemispherical asperities and the wafer is modeled as a flat plane, a GW analysis of surface contact enables the calculation of the pad-wafer separation distance and the area of padwafer contact. The contact pressure may be described according to…”

Section: Resultsmentioning

confidence: 99%

The Effect of Interactions Between Water and Polishing Pads on Chemical Mechanical Polishing Removal Rates

Castillo-Mejia

Gold

Burrows

et al. 2003

J. Electrochem. Soc.

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The elastic properties of polishing pads critically affect polishing results during chemical mechanical polishing ͑CMP͒ of integrated circuit substrates. The ability of water to plasticize polishing pads and the resulting effects on pad performance were investigated. Water is hypothesized to penetrate the surface of the polishing pads, disrupting hydrogen bonds between adjacent polymer molecules within the pads and altering the pad elastic modulus. Infrared spectra obtained using an attenuated total reflection technique were used to confirm the effect of water on the polishing pad structure. Contact with deionized water reduced the pad elastic modulus due to the formation of a hypothesized soft layer on the pad surface. Removal of the soft layer from the pad, as occurs during conditioning, increased observed CMP removal rates. Experiments on a commercial dual-axis polisher using a noncommercial process showed decreased oxide removal rates as the duration of the pad exposure to water increased. A pad asperity-wafer contact model was developed. This model indicates that if the surface of the pad asperities is softened by the penetration of water compared to the bulk pad, then the asperities will deform to a greater degree under the applied load than in the absence of the softening. As a result, the effective pad-wafer contact area for a given applied load will increase and the average pad-wafer separation will decrease, causing the applied load to be carried by a larger number of asperity-wafer contacts and reducing the local load on the wafer surface. The reduced local loads will contribute to reduced polishing rates, consistent with experimental observation. The maximum depth of penetration of water into the pad surface was estimated to be ϳ20 m.Chemical mechanical polishing ͑CMP͒ has become an essential step in the manufacturing of advanced integrated circuits ͑ICs͒. During CMP, material is removed from the surface of a wafer when the wafer is rubbed against a polymeric polishing pad coated with aqueous slurry. Although this technology has developed rapidly in recent years, understanding of the fundamental chemical and mechanical processes involved in polishing is still developing. In this work, the effects of water penetration into the pad are considered, including effects on the pad physical properties and the resulting polishing performance.A combination of mechanical and chemical processes during polishing results in material removal from the surface of both the wafer and pad. It has been observed that as the number of wafers polished by a pad increases, pad morphology is altered by wear and glazing. 1,2 Pad glazing occurs as debris from the pad and wafer accumulates in the pad pores and as the pad surface is smoothed by the polishing. 3 In the absence of steps to counteract wear and glazing, material removal rates decrease compared to the original removal rate with increases in the number of wafers polished by a pad. 4 To maintain stable removal rates over the life of the pad, pad conditioning is widely uti...

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Section: Resultsmentioning

confidence: 99%

The Effect of Interactions Between Water and Polishing Pads on Chemical Mechanical Polishing Removal Rates

Castillo-Mejia

Gold

Burrows

et al. 2003

J. Electrochem. Soc.

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“…The GW model assumes: ͑i͒ the nominally flat rough surface is covered with hemispherically tipped asperities, (ii) the asperity summits have a common radius, (iii) the heights of the asperities vary randomly, (iv) the asperities do not interact with one another, (v) there is no deformation of the bulk of either material, and (vi) Hertzian contact/deformation occurs at the interface. 10 Numerical comparisons between the GW model and other microcontact models have led to the conclusion that for a given nominal pressure ( P nominal ) the GW gives acceptable order-of-magnitude approximations for the number of contacts (N contact ) and the real contact area between a rough surface and a smooth flat plane. 11 The GW model has also been applied by others to describe various aspects of CMP, including, for example, descriptions of pad asperity-wafer contact and hydrodynamic pressure, 12 and local asperity pressures for asperities of constant height.…”

Section: Pressures On Pad Asperitiesmentioning

confidence: 99%

Polishing Pad Surface Morphology and Chemical Mechanical Planarization

Castillo-Mejia

Kelchner

Beaudoin

2004

J. Electrochem. Soc.

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Polishing pad surface morphology has been demonstrated to be an important parameter in the optimization of chemical mechanical planarization ͑CMP͒ processes. In this work, the mechanical behavior of the asperity layer of a polishing pad and its effect on CMP is modeled. A Greenwood-Williamson microcontact model describes the asperity contact with the wafer. The local strain fields on individual asperities are calculated and then averaged, and an average elastic modulus is extracted to describe the asperity layer. The asperities are assumed to behave as an effective layer subject to this average strain field. The model is implemented on a previously developed locally relevant removal rate model for CMP. Comparison of the modeling results with polishing results obtained using a commercial CMP system shows important improvements in removal rate and uniformity prediction on the wafer-scale.

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“…The meniscus concept has recently been applied to the tribology of lubricated magnetic recording head and disk interfaces, e.g., [24,25]. We find that: (a) The meniscus volume is less than the volume of one Ztetraol 2000 lubricant chain; (b) The wetted perimeter is the length of about 8 lubricant chains stretched end to end; and (c) The wetted length is about 24 lubricant chain lengths.…”

Section: Introductionmentioning

confidence: 94%

Dynamics in the Bridged State of a Magnetic Recording Slider

2008

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A novel region of tribological interaction is explored by inducing near contact between the magnetic recording slider and disk. In this study, we performed frictional measurements over a wide range of subambient air pressure and disk rotation rate. Since the slider is supported over the disk by an air bearing, it has been found that cycling from ambient to subambient and then back up to ambient pressure over several minutes of time forms a frictional hysteresis loop. The high-friction branch of the loop, referred to as the bridged state, is characterized by an average frictional displacement and resonant vibration of the suspension mount assembly. The bridged state is currently employed for accelerated wear testing of magnetic slider/disk/lubricant systems. Future magnetic recording systems designed to operate at increasingly lower physical spacing will need to take into account these frictional forces which accompany the incipient contact between the lubricated disk and slider with finite surface roughness. A single degree of freedom model is solved to determine the equivalent dynamic friction force on the slider as an impulse series with random impulse frequency and amplitude from the measured frictional displacement in the bridged state. The mean slider-disk spacing in the bridged state is derived from the experimental friction force, the spacing probability density function, and the adhesion stress from the Lifshitz model for dispersion interaction energy.

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Analysis of Contact Deformation and Stiction Between Textured Disk and Textured Slider

Cited by 14 publications

References 26 publications

The Effect of Interactions Between Water and Polishing Pads on Chemical Mechanical Polishing Removal Rates

The Effect of Interactions Between Water and Polishing Pads on Chemical Mechanical Polishing Removal Rates

Polishing Pad Surface Morphology and Chemical Mechanical Planarization

Dynamics in the Bridged State of a Magnetic Recording Slider

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