Feasibility of a Real-Time Method in Determine the Extent of Pad Break-In During Copper Chemical Mechanical Planarization

Stuffle

et al. 2018

Self Cite

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.

Section: Bottom)mentioning

confidence: 99%

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

Bengochea

Stuffle

et al. 2018

Self Cite

“…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

et al. 2018

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.

“…We do not believe this to be due to any differences in pad micro-texture because, in previous studies, we had always obtained consistent values for COF and variance of shear force indicating a stable pad surface micro-texture. 22 Besides, it has been shown previously that stable pad micro-texture should have no, or very limited, impact on changes in removal rates. 19 However, the removal rate results in Table I are inconsistent with the typical understanding (i.e.…”

Section: Resultsmentioning

confidence: 96%

Effect of Conditioning and Slurry Application Method on Silicon Dioxide Removal Rates Using a Ceria-Based Chemical Mechanical Planarization Slurry

Han

Bahr

et al. 2017

Self Cite

In this study, the silicon dioxide removal rate using a "reverse" ceria-based slurry was investigated under four different combinations of conditioning modes and slurry application methods. In a "reverse" slurry, addition of water acts to promote material removal. Overall, the process using ex-situ conditioning with the slurry injection system (SIS) resulted the highest removal rate, while the process using in-situ conditioning with the conventional point application (PA) generated lowest removal rate. This study is aimed to explain the differences in silicon dioxide removal rate based on the variations of the actual slurry dilution ratio on top of the pad associated with conditioning and slurry application methods. The frictional analysis and Stribeck+ curves were employed to elucidate the tribological characteristics. The results showed that the conditioning modes and the slurry application methods varied the extent of the polishing vibrations. The silicon dioxide removal rate was found to linearly correlate with the extent of COF fluctuation. This work also underscored the importance of optimum slurry flow dynamics and injection geometry for obtaining a more cost-effective and environmentally benign chemical mechanical planarization process.