Vertical differential displacements at a pad/sapphire interface during polishing

Mess, Francis McCarthy; Levert, Joseph A.; Danyluk, S.

doi:10.1016/s0043-1648(97)00113-0

Cited by 7 publications

(9 citation statements)

References 3 publications

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“…Slurry film thickness during polishing is largely determined by how the hydrodynamic pressure and pad aesperity contact pressure equilibrate with the downforce applied. Some researchers have found that during polishing there is a vacuum created underneath the wafer and a negative vertical pad [4,5,6]. Others have found positive fluid pressure developing in the gap between the wafer and polishing pad [7].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Wafer Shape on Slurry Film Thickness and Friction Coefficients in Chemical Mechanical Planarization

Coppeta

Rogers

et al. 2000

MRS Proc.

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The fluid film thickness and drag during chemical-mechanical polishing are largely dependent on the shape of the wafer polished. In this study we use dual emission laser induced fluorescence to measure the film thickness and a strain gage, mounted on the polishing table, to measure the friction force between the wafer and the pad. All measurements are taken during real polishing processes. The trends indicate that with a convex wafer in contact with the polishing pad, the slurry layer increases with increasing platen speed and decreases with increasing downforce. The drag force decreases with increasing platen speed and increases with increasing downforce. These similarities are observed for both in-situ and ex-situ conditioning. However, these trends are significantly different for the case of a concave wafer in contact with the polishing pad. During ex-situ conditioning the trends are similar as with a convex wafer. However, in-situ conditioning decreases the slurry film layer with increasing platen speed, and increases it with increasing downforce in the case of the concave wafer. The drag force increases with increasing platen speed as well as increasing downforce. Since we are continually polishing, the wafer shape does change over the course of each experiment causing a larger error in repeatability than the measurement error itself. Different wafers are used throughout the experiment and the results are consistent with the variance of the wafer shape. Local pressure measurements on the rotating wafer help explain the variances in fluid film thickness and friction during polishing.

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Section: Introductionmentioning

confidence: 99%

The Effect of Wafer Shape on Slurry Film Thickness and Friction Coefficients in Chemical Mechanical Planarization

Coppeta

Rogers

et al. 2000

MRS Proc.

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“…He was the first to suggest the influence of hydrodynamic lubrication, mixed-solid-liquid contact (boundary lubrication), and solid-solid contact. Since that work, a number of researchers have developed measurement techniques, such as fluorescence of the slurry, for determining the fluid film thickness (Coppeta et al 1996), , who measured vertical differential displacement and subambient pressures, and Mess et al (1997), Shan et al (1998), andNg et al (2005), who measured the subambient interfacial pressures and modeled the polishing rates by the soft-hydrodynamic approach. The negative vertical differential wafer displacement as discovered by Levert can be explained by the subambient fluid pressures that have developed between the wafer and the pad.…”

Section: Fluid Filmmentioning

confidence: 99%

Coatings for Biomedical Applications

Hauert¹,

Falub²,

Thorwarth³

et al. 2013

Encyclopedia of Tribology

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DefinitionCapillary force and surface wettability are related phenomena happening at the interfaces of solid, liquid, and air phases, and are highly dependent upon the interaction between liquids and solid surfaces. Scientific Fundamental Surface WettabilityWhen a liquid is in contact with a solid surface in air, in general, a droplet of the liquid will be formed. The shape of the droplet depends upon the interaction between the liquid and the solid surface. If the interaction is strong, i.e., the liquid "likes" the surface, the liquid drop will be "flat." On the contrary, if the interaction is weak, i.e., the liquid "hates" the surface, it will "bead up." Scientifically, such a property is described quantitatively by the concept of contact angle, which demonstrates the angle (y) at which the air-liquid and solid-liquid interfaces meet (see Fig. 1). Such a situation is the result of the force balance at the location where air, liquid, and solid phase meet, the socalled "three phase contact line." The interfacial tension of air-liquid, air-solid, and liquid-solid interface is denoted by g al , g as , and g ls , respectively. The force balance is described by the well-known Young's equation (Blake 1993; Butt et al. 2003; Isrealachvili 2003):This is a clear description of the interaction between the solid and liquid, as a smaller value of contact angle exhibits a larger difference between g as and g ls and, therefore, a much lower interfacial tension between the solid and liquid.The contact angle measurement is also an informative way to show the surface wettability of a liquid on a solid surface. If the interaction between the liquid and the solid surface is strong, a much lower interfacial energy results, and, as a result, the surface will be covered more by the liquid so that more area with higher air-solid interfacial energy is replaced by much lower interfacial energy of the liquid and solid. The result is that the liquid droplet is more spread out and has a lower value of contact angle. On the other hand, an unfavorable interaction between the liquid and solid surface generates a higher interfacial energy and, therefore, the system will maximize the area of the solid-air interface and minimize that of the interface between the liquid and solid surface. Consequently, the liquid forms a droplet with a small footprint on the surface and has a higher value of contact angle.

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“…The ideal volumetric fraction, i , can be expressed as [8] where V a is the volume of fluid A and V t is the total volume. This ideal volumetric fraction i will be a function of a number of paramters i (bow wave composition, pore composition, conditioning, pad fluid storage...) [9] Each of these independent variables may also be a function of time.…”

Section: Modelingmentioning

confidence: 99%

Investigating Slurry Transport Beneath a Wafer during Chemical Mechanical Polishing Processes

Coppeta

Rogers

Racz

et al. 2000

J. Electrochem. Soc.

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Since its introduction into integrated circuit (IC) manufacturing by IBM Corporation in the mid-1980s, chemical mechanical planarization (CMP) has become a key enabling technology in the semiconductor industry. All of the major IC manufacturers including Intel, Motorola, and IBM now incorporate CMP in the production of their chips. In addition to IC production, CMP applications have spread into other manufacturing processes including dynamic random access memory (DRAM) chips, hard drives, and modem chips.Given the magnitude of capital invested in this technology, there is a large impetus to develop a fundamental understanding of the process. Research with this goal in mind is being performed; however, an overall understanding of the process remains elusive because of the multidisciplinary nature of CMP. Researchers have focused on individual aspects of the process, such as slurry chemistry, 1-5 wafer-pad dynamics, 6-8 mechanisms, [9][10][11][12][13][14] and numerical simulations of the slurry fluid mechanics. [15][16][17] There has been, however, little experimental research regarding slurry fluid mechanics.Several researchers have commented on the importance of slurry flow and slurry distribution beneath the wafer although the importance of slurry flow has not been experimentally demonstrated. Stavreva et al. 18 discussed how the pad's ability to transport slurry could affect the polishing rate and uniformity during copper CMP. Parikh found that slurry flow rate had a large effect on the polishing uniformity on an orbital polisher. 19 Ali et al. 20 stated that the slurry composition, flow rate, and direction of slurry impingement onto the polishing pad all play important roles in interdielectric removal rates. Singer 21 reported that the manner in which slurry is transported from the outside of the wafer to its center is critically important. Sugimoto et al. 22 showed that slurry transport in grooved pads is important in reducing thermal gradients across a wafer. Since polishing rates are temperature dependent, a reduction in thermal gradients across the wafer is believed to reduce the within-wafer-nonuniformity. Ali et al. 23 postulated that the degradation in the removal rates of pads without conditioning is due to the decrease in the pad's slurry holding capacity. Liang et al. 24 postulated that Cabot's new open cell pads do not need macroscopic surface topography because of the pad's efficiency in channeling the slurry. Despite the fact that slurry flow generally is considered to be an important factor in the CMP process, there has not been an experimental study of the slurry flow or a numerical simulation sophisticated enough to examine the slurry behavior under realistic conditions. Slurry transport and mixing could influence the polishing performance in two ways: (i) transport of polished material and (ii) nonuniform slurry transport. The first mechanism was postulated by Cook in his research on glass polishing. 4 Cook suggested that polishing removal rate is influenced by the transport of polished materi...

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Vertical differential displacements at a pad/sapphire interface during polishing

Cited by 7 publications

References 3 publications

The Effect of Wafer Shape on Slurry Film Thickness and Friction Coefficients in Chemical Mechanical Planarization

The Effect of Wafer Shape on Slurry Film Thickness and Friction Coefficients in Chemical Mechanical Planarization

Coatings for Biomedical Applications

Investigating Slurry Transport Beneath a Wafer during Chemical Mechanical Polishing Processes

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