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Physics of the Coefficient of Friction in CMP
Borucki, Len,Philipossian, Ara,Zhuang, Yun The Korean Institute of Electrical and Electronic 2007 Transactions on Electrical and Electronic Material Vol.8 No.2
The implications of a theory of lubricated pad asperity wafer contact are traced through several fundamental areas of chemical-mechanical polishing. The hypothesized existence of a nanolubrication layer underlies a high accuracy model of polish rates. It also provides a quantitative explanation of a power law relationship between the coefficient of friction and a measure of pad surface flattening. The theory may further be useful for interpreting friction changes during polishing, and may explain why the coefficient of friction is sometimes observed to have a temperature or velocity dependence.
Physics of the Coefficient of Friction in CMP
Len Borucki,Ara Philipossian,Yun Zhuang 한국전기전자재료학회 2007 Transactions on Electrical and Electronic Material Vol.8 No.2
The implications of a theory of lubricated pad asperity wafer contact are traced through several fundamental areas of chemical-mechanical polishing. The hypothesized existence of a nanolubrication layer underlies a high accuracy model of polish rates. It also provides a quantitative explanation of a power law relationship between the coefficient of friction and a measure of pad surface flattening. The theory may further be useful for interpreting friction changes during polishing, and may explain why the coefficient of friction is sometimes observed to have a temperature or velocity dependence.
Diamond Conditioner Wear Characterizationfor a Copper CMP Process
L. Borucki,Y. Zhuang,R. Kikuma,N. Rikita,T. Yamashita,K. Nagasawa,H. Lee,T. Sun,D. Rosales-Yeomans,A. Philipossian,T. Stout 한국전기전자재료학회 2007 Transactions on Electrical and Electronic Material Vol.8 No.1
Conditioner wear, copper polish rates, pad temperature and coefficient of friction (COF) are measured for two novel Mitsubishi Materials Corporation designs during an extended wear and polishing test. Both designs are coated with a TeflonTM film to reduce substrate wear and chemical attack. Using optical interferometry, changes in the coating that result in gradual changes in diamond exposure are measured. Theories of the COF, conditioning, and polishing are applied to explain the observed performance differences between the designs.
Zhuanga, Yun,Borucki, Leonard,Philipossian, Ara,Dien, Eric,Ennahali, Mohamed,Michel, George,Laborie, Bernard,Zhuang, Yun,Keswani, Manish,Rosales-Yeomans, Daniel,Lee, Hyo-Sang,Philipossian, Ara The Korean Institute of Electrical and Electronic 2007 Transactions on Electrical and Electronic Material Vol.8 No.2
In this study, a novel slurry containing ceria as the abrasive particles was analyzed in terms of its frictional, thermal and kinetic attributes for interlayer dielectric (ILD) CMP application. The novel slurry was used to polish 200-mm blanket ILD wafers on an $IC1000_{TM}$ K-groove pad with in-situ conditioning. Polishing pressures ranged from 1 to 5 PSI and the sliding velocity ranged from 0.5 to 1.5 m/s. Shear force and pad temperature were measured in real time during the polishing process. The frictional analysis indicated that boundary lubrication was the dominant tribological mechanism. The measured average pad leading edge temperature increased from 26.4 to $38.4\;^{\circ}C$ with the increase in polishing power. The ILD removal rate also increased with the polishing power, ranging from 400 to 4000 A/min. The ILD removal rate deviated from Prestonian behavior at the highest $p{\times}V$ polishing condition and exhibited a strong correlation with the measured average pad leading edge temperature. A modified two-step Langmuir-Hinshelwood kinetic model was used to simulate the ILD removal rate. In this model, transient flash heating temperature is assumed to dominate the chemical reaction temperature. The model successfully captured the variable removal rate behavior at the highest $p{\times}V$ polishing condition and indicates that the polishing process was mechanical limited in the low $p{\times}V$ polishing region and became chemically and mechanically balanced with increasing polishing power.
Yun Zhuang,Leonard Borucki,Ara Philipossian,Eric Dien,Mohamed Ennahali,George Michel,Bernard Laborie,Yun Zhuang,Manish Keswani,Daniel Rosales-Yeomans,Hyosang Lee,Ara Philipossian 한국전기전자재료학회 2007 Transactions on Electrical and Electronic Material Vol.8 No.2
In this study, a novel slurry containing ceria as the abrasive particles was analyzed in terms of its frictional, thermal and kinetic attributes for interlayer dielectric (ILD) CMP application. The novel slurry was used to polish 200-mm blanket ILD wafers on an IC1000TM K-groove pad with in-situ conditioning. Polishing pressures ranged from 1 to 5 PSI and the sliding velocity ranged from 0.5 to 1.5 m/s. Shear force and pad temperature were measured in real time during the polishing process. The frictional analysis indicated that boundary lubrication was the dominant tribological mechanism. The measured average pad leading edge temperature increased from 26.4 to 38.4 °C with the increase in polishing power. The ILD removal rate also increased with the polishing power, ranging from 400 to 4000 A/min. The ILD removal rate deviated from Prestonian behavior at the highest p´V polishing condition and exhibited a strong correlation with the measured average pad leading edge temperature. A modified two-step Langmuir-Hinshelwood kinetic model was used to simulate the ILD removal rate. In this model, transient flash heating temperature is assumed to dominate the chemical reaction temperature. The model successfully captured the variable removal rate behavior at the highest p´V polishing condition and indicates that the polishing process was mechanical limited in the low p´V polishing region and became chemically and mechanically balanced with increasing polishing power.
Thermal, Tribological, and Removal Rate Characteristics of Pad Conditioning in Copper CMP
Lee, Hyo-Sang,DeNardis, Darren,Philipossian, Ara,Seike, Yoshiyuki,Takaoka, Mineo,Miyachi, Keiji,Furukawa, Shoichi,Terada, Akio,Zhuang, Yun,Borucki, Len The Korean Institute of Electrical and Electronic 2007 Transactions on Electrical and Electronic Material Vol.8 No.2
High Pressure Micro Jet (HPMJ) pad conditioning system was investigated as an alternative to diamond disc conditioning in copper CMP. A series of comparative 50-wafer marathon runs were conducted at constant wafer pressure and sliding velocity using Rohm & Haas IC1000 and Asahi-Kasei EMD Corporation (UNIPAD) concentrically grooved pads under ex-situ diamond conditioning or HPMJ conditioning. SEM images indicated that fibrous surface was restored using UNIPAD pads under both diamond and HPMJ conditioning. With IC1000 pads, asperities on the surface were significantly collapsed. This was believed to be due to differences in pad wear rates for the two conditioning methods. COF and removal rate were stable from wafer to wafer using both diamond and HPMJ conditioning when UNIPAD pads were used. Also, HPMJ conditioning showed higher COF and removal rate when compared to diamond conditioning for UNIPAD. On the other hand, COF and removal rates for IC1000 pads decreased significantly under HPMJ conditioning. Regardless of pad conditioning method adopted and the type of pad used, linear correlation was observed between temperature and COF, and removal rate and COF.
Thermal, Tribological, and Removal Rate Characteristics of Pad Conditioning in Copper CMP
Hyosang Lee,Darren DeNardis,Ara Philipossian,Yoshiyuki Seike,Mineo Takaoka,Keiji Miyachi,Shoichi Furukawa,Akio Terada,Yun Zhuang,Len Borucki 한국전기전자재료학회 2007 Transactions on Electrical and Electronic Material Vol.8 No.2
High Pressure Micro Jet (HPMJ) pad conditioning system was investigated as an alternative to diamond disc conditioning in copper CMP. A series of comparative 50-wafer marathon runs were conducted at constant wafer pressure and sliding velocity using Rohm & Haas IC1000 and Asahi-Kasei EMD Corporation (UNIPAD) concentrically grooved pads under ex-situ diamond conditioning or HPMJ conditioning. SEM images indicated that fibrous surface was restored using UNIPAD pads under both diamond and HPMJ conditioning. With IC1000 pads, asperities on the surface were significantly collapsed. This was believed to be due to differences in pad wear rates for the two conditioning methods. COF and removal rate were stable from wafer to wafer using both diamond and HPMJ conditioning when UNIPAD pads were used. Also, HPMJ conditioning showed higher COF and removal rate when compared to diamond conditioning for UNIPAD. On the other hand, COF and removal rates for IC1000 pads decreased significantly under HPMJ conditioning. Regardless of pad conditioning method adopted and the type of pad used, linear correlation was observed between temperature and COF, and removal rate and COF.
Szabó,, R.,Kollá,th, Z.,Molná,r, L.,Kolenberg, K.,Kurtz, D. W.,Bryson, S. T.,Benkő,, J. M.,Christensen‐,Dalsgaard, J.,Kjeldsen, H.,Borucki, W. J.,Koch, D.,Twicken, J. D.,C Blackwell Publishing Ltd 2010 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.409 No.3
<P><B>ABSTRACT</B></P><P>The first detection of the period doubling phenomenon is reported in the <I>Kepler</I> RR Lyrae stars RR Lyr, V808 Cyg and V355 Lyr. Interestingly, all these pulsating stars show Blazhko modulation. The period doubling manifests itself as alternating maxima and minima of the pulsational cycles in the light curve, as well as through the appearance of half‐integer frequencies located halfway between the main pulsation period and its harmonics in the frequency spectrum. The effect was found to be stronger during certain phases of the modulation cycle. We were able to reproduce the period‐doubling bifurcation in our non‐linear RR Lyrae models computed by the Florida–Budapest hydrocode. This enabled us to trace the origin of this instability in RR Lyrae stars to a resonance, namely a 9:2 resonance between the fundamental mode and a high‐order (ninth) radial overtone showing strange‐mode characteristics. We discuss the connection of this new type of variation to the mysterious Blazhko effect and argue that it may give us fresh insights into solving this century‐old enigma.</P>