Spectral Analysis of Frictional Forces in ILD CMP

Philipossian, Ara; Rosales-Yeomans, D.; Charns, Leslie; Rogers, Chris; Doy, Toshiroh Karaki; Kinoshita, Masaharu

doi:10.1557/proc-767-f1.11

Cited by 5 publications

(3 citation statements)

References 2 publications

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“…A Fourier transform of the drag force data yields a power spectrum with features at signature frequencies. 3,18,19 The mean friction does not capture the fluctuations in drag forces arising from stick-slip phenomena or polishing vibrations. It is believed that additional information regarding the viscoelastic properties of the interface may be obtained from analysis of such power spectrum data.…”

Section: So = U P␦ ͓2͔mentioning

confidence: 99%

A Method for Measuring Frictional Forces and Shaft Vibrations during Chemical Mechanical Polishing

Carter

Werts

2007

J. Electrochem. Soc.

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A technique for determining friction forces during chemical mechanical polishing has been developed using a noncontact displacement sensor to measure polishing shaft deflections. Shaft deflections were calibrated to the shear forces acting on the substrate surface allowing in situ measurement of drag force and coefficient of friction ͑COF͒. Power spectrum data of the shaft displacements revealed a broad feature near 70 Hz. The drag force, COF, and shaft vibration intensity vary as a function of slurry, substrate, pad, and process downforce. The shaft vibration response was found to be largely decoupled from the mean drag force and COF measurements. The vibration intensity was correlated to blanket silicon dioxide removal rate for a variety of ceria-based slurries in cases where the drag force and COF values did not differentiate between conditions. In addition, a high intensity vibration response observed on blanket oxide substrates was associated with unusual pattern wafer behavior where high-density features were planarized at a higher rate compared to low-density features.

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Section: So = U P␦ ͓2͔mentioning

confidence: 99%

A Method for Measuring Frictional Forces and Shaft Vibrations during Chemical Mechanical Polishing

Carter

Werts

2007

J. Electrochem. Soc.

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“…Moreover, integration of FFT shear force data represents the total energy attributed to the various stick-slip phenomena. [11][12][13][14][15][16] From a process standpoint, such analysis exposes signatures that emerge as a direct result of variation of relevant parameters or equipment, such as rotational speed of the platen or the type of conditioning disc.…”

mentioning

confidence: 99%

Real-Time Shear and Normal Force Trends in Copper Chemical Mechanical Planarization with Different Conditioning Discs

Peckler

Han

Sampurno

et al. 2018

ECS J. Solid State Sci. Technol.

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The effect of two different commercially-available CVD-coated diamond conditioning discs on copper CMP was investigated tribologically and kinetically with the intent of correlating pad surface micro-texture to polish performance. Data analyses were particularly focused on in-situ shear and normal force measurements taken during polishing at several pressures (P) and sliding velocities (V), including Fast Fourier Transform (FFT) analysis of the data. One of the two discs consistently resulted in greater variances of shear force with increasing P and V indicative of increased pad-slurry-wafer stick-slip events. This trend correlated to higher values of coefficient of friction (COF) and removal rate (RR). By dividing the shear force variance by the normal force variance, a new parameter, termed directivity, was used to further emphasize the improved performance of the above-mentioned disc. Lastly, the tribological and kinetic data, combined with data regarding the pad's micro-texture and its extent of contact with the wafer, showed that at all values of P and V, higher values of directivity correlated to more contacting pad asperities, a greater asperity density and a thinner micro hydrodynamic lubrication layer, thus highlighting the potential importance of directivity in future studies.

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“…6 Alternatively, polymer additives have been used to improve selectivity, however, the overall material removal rate ͑MRR͒ decreased significantly upon polymer addition. 7 In this study, a different approach to increase STI CMP selectivity by introducing a selective passivation ͑lubrication͒ layer using surfactants is investigated.…”

mentioning

confidence: 99%

Selective Chemical Mechanical Polishing Using Surfactants

Moudgil

2007

J. Electrochem. Soc.

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Device fabrication using high density, small pattern size shallow trench isolation ͑STI͒ processes requires material removal selectivity during chemical mechanical polishing ͑CMP͒ steps for optimum product processing and quality control. To improve the selectivity of STI CMP processes, surfactants were applied to selectively polish silica as opposed to silicon nitrides surfaces. A ten-fold increase in selectivity over conventional colloidal silica slurry was achieved by the addition of sodium dodecyl sulfate ͑SDS͒ and pH adjustment. Adsorption characteristics of SDS on silica and silicon nitride were measured as a function of slurry pH and concentration of SDS. As indicated by streaming potential measurements and solution depletion adsorption experiments under acidic pH conditions, SDS adsorption on silicon nitride was significantly higher than silica primarily due to the electrostatic interactions. It was concluded that the preferential adsorption of SDS on silicon nitride results in the formation of a materialselective self-assembled passivation ͑lubrication͒ layer leading to selective polishing. Effects of different alkyl chain length of surfactants were tested. Various mixed surfactant systems were tested and it is believed that the addition of second surfactants promotes the adsorption on silica diminishing selectivity. The material-targeted boundary layer lubrication concept may be used to develop selective CMP polishing slurries.The fabrication of next-generation devices will require advances in shallow trench isolation ͑STI͒ technology. 1-3 STI chemical mechanical polishing ͑CMP͒ is particularly challenging due to the highly integrated and variable pattern density as well as smaller pattern sizes. Less than optimal CMP system can cause several defects such as dishing, nitride erosion, and failure to clear oxide that are detrimental to global planarization. To minimize such defects, current STI CMP processes comprised multistep or raw structure modification such as reverse mask, dummy active area, and additional active area. 1 For better productivity and process simplicity, a minimum number of processing steps is highly desirable. Accordingly, "high selectivity single-step" slurry designs are being widely investigated. 4,5 The term "selectivity" in this paper is defined as the ratio of material removal rate ͑MRR͒ of silica to that of silicon nitride as described below. It is the slurry property as to how much more it can polish silica than silicon nitride Selectivity = Material Removal Rate of Silica Material Removal Rate of Silicon Nitride ͓1͔In general, conventional silica-abrasive-based STI CMP slurries exhibit selectivity in the range of 3-4. 5 Besides its influence on planarization, high selectivity slurries are known to provide more reliable endpoint detection capability. Generally, if the oxide to nitride selectivity is greater than 15, monitoring wafer carrier motor current can be utilized for efficient endpoint detection. 6 In recent years, ceria-based abrasives have shown potential for high selec...

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Spectral Analysis of Frictional Forces in ILD CMP

Cited by 5 publications

References 2 publications

A Method for Measuring Frictional Forces and Shaft Vibrations during Chemical Mechanical Polishing

A Method for Measuring Frictional Forces and Shaft Vibrations during Chemical Mechanical Polishing

Real-Time Shear and Normal Force Trends in Copper Chemical Mechanical Planarization with Different Conditioning Discs

Selective Chemical Mechanical Polishing Using Surfactants

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