Effect of pad groove width on slurry mean residence time and slurry utilization efficiency in CMP

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A method using high-speed videography is developed for visualizing and quantifying the width of the slurry bow wave formed at the leading edge of a retaining ring during polishing. This new method overcomes many limitations of previous techniques as it employs an inert dye thereby bypassing any photobleaching issues encountered in the past. This allows the use of pads of all types and colors in a normally-lit environment. Image analysis is used to quantify and classify pixel brightness in regions of interest on the CMP pad. By employing suitable baselines, evolution of the slurry bow wave (specifically its width) as a function of polish time was calculated and analyzed. This new method was then applied to retaining ring polishing experiments at two different flow rates and in two different regions where the bow wave was formed. Results consistently show that the bow wave fluctuated with time and its width grew wider at higher flow rates, especially in region closer to the slurry injection point. Fast Fourier Transformation (FFT) was employed to convert the fluctuating component of the bow wave width from time domain to frequency domain. When looking at the spectral signature of the slurry bow wave width, major peaks were observed at 1, 2, 4, 8-9 and 12-14 Hz all of which could be theoretically explained by taking into account ring geometry and polisher kinematics.

mentioning

confidence: 99%

Visualizing Slurry Flow in Chemical Mechanical Planarization via High-Speed Videography

Bengochea

Sampurno

Stuffle

et al. 2018

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“…A broader scope of pad types and similar measurements of oxide removal rates (RR) and associated changes in particle number concentrations should be able to experimentally measure the fraction of slurry actively participating in the CMP process and help validate models that can optimize slurry utilization efficiency in CMP. 18…”

Section: Resultsmentioning

confidence: 99%

Single Particle Inductively Coupled Plasma Mass Spectrometry Study of Ceria Nanoparticle Size Distribution from Oxide CMP with Microreplicated Pads

Zazzera¹,

Chan²,

Stomberg³

et al. 2021

This work describes the use of Single Particle Inductively Coupled Plasma Mass Spectrometry (spICP-MS) to measure ceria particle number concentrations and compare changes in size distributions to silicon dioxide wafer removal rates from different chemical mechanical planarization (CMP) processes. Particle number concentrations were measured for the 21 to 559 nm size range at 1 nm size resolution. Changes in the ceria particle size distribution after CMP included a decrease in large (>130 nm) particles, an increase in small (<40 nm) particles, an increase in the total number of particles, and a decrease in median particle size. The decrease in median size was as high as 7% and influenced by flow rate, pressure and pad type. A novel microreplicated CMP pad was used which requires no pad conditioning to ensure consistent pad surface features, and the effect of different pad types on removal rate and particle size was isolated. A decrease in the median particle size correlated with higher silicon dioxide removal rates (R2 = 0.96) for a series of pad types with unique combinations of chemistry and surface features. This new combination of nano particle metrology and control of pad surface features is an innovative tool set for modeling advanced CMP processes.

“…All of these features affect surface fluid transport. [5][6][7][8][9][10] • Pad and wafer both co-rotate during the entire process (either clockwise, or counter-clockwise). This causes advective transport in the radial direction along with centrifugal forces that grow stronger near the edge of the pad.…”

mentioning

confidence: 99%

Effect of Various CVD-Coated Conditioning Disc Designs and Polisher Kinematics on Fluid Flow Characteristics during CMP

Mariscal

Sampurno

Slutz

et al. 2020

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A novel experimental technique utilizing UV-enhanced fluorescence was developed and used to measure fluid film thicknesses and general flow patterns during conditioning on a polishing pad. The method was successfully applied to several case studies for analyses of how conditioners with different working face designs (i.e. complex vane, full-face and partial-face), in conjunction with different platen angular velocities, affected fluid transport. In general, for all discs types, fluid across the pad followed similar trends where films were thickest near the wafer track center and thinnest near the pad edge (measurements showed a thickness range of appx. 0.5 to 1.1 mm). For all discs, the time for the film thicknesses to reach steady-state increased in proportion to the distance away from the pad center (times ranged between 12 and 62 s). The full-face conditioner consistently produced the thinnest films and reached steady-state the fastest. In contrast, the complex vane conditioner created the thickest films and took longest to reach steady-state. The work demonstrated the significance of understanding and visualizing the mechanisms that can contribute to fluid transport during CMP and how our novel technique could contribute, in the near future, to a greater understanding of fluid transport during in-situ conditioning.