Feature Scale DELIF Investigations in Chemical Mechanical PlanarizationA Three Year ProposalV. P. Manno and C.B. Rogers, Tufts University

Abstract:Over the past 8 years we have developed a number of techniques to measure slurry properties and model slurry behavior during the polishing process. These properties included slurry age, thickness, temperature, pressure and pH. The more recent work has focused on better spatial and temporal resolution and including pad behavior. The present proposal is to start a new program that will extend these measurements to include how the pad deforms around features on the wafer by measuring instantaneous slurry film thickness using a Nd-YAG laser. Preliminary results have shown that the method successfully measures a 1 micron increase in the pad roughness as it decompresses under a 14 micron well etched on the wafer and then re-compresses as it leaves the well. The goal of this work will be to better characterize this behavior, looking at variable downforce, variable well shapes, variable rotation rates, and variable pad grooving.

Dual Emission Laser Induced Fluorescence

Dual Emission Laser Induced Fluorescence (DELIF) is a relatively non-intrusive optical technique for measurement of a passive scalar. Fluorescence is the emission of electromagnetic radiation by a substance whose molecules are excited into higher energy states through the absorption of a certain wavelength of radiation. In DELIF, light in the visible spectrum is emitted by the molecules of dyes excited by ultraviolet light. The fluorescence intensity emitted by a dye is the function of excitation intensity and amount of absorbed light. Quantitatively, it may be estimated using

(1)

where If is the measured fluorescence intensity, is the quantum efficiency of the dye in solution, Ie is the intensity of the excitation energy source, and Abs is the amount of light absorbed by the dye. In one dimension, the fluorescence intensity of a point of dyed solution excited by a single beam of light may be represented by

(2)

where b is the distance traveled by the laser beam through the dye solution, If is the measured fluorescence intensity at the distance b through the solution, Ie is the intensity of the excitation energy source at the same distance b through the solution, Af is the fraction of the fluoresced light collected, ε is the molar absorptivity as a function of wavelength¸ or pH in the case of pH dependent dyes, C is the molar concentration of the dye, and dl is the length of the sampling volume along the path of excitation1.

1 G G Guilbault. Practical Fluorescence: Theory and Practice. Marcel Dekker, 1976.

Single dye techniques for absolute measurements tend to be less reliable because they are strongly dependent on excitation light intensities. Shadows, light variations in time, and non-uniform light sources all influence the resulting florescence intensity. DELIF is a much simpler alternative to developing complex calibrations to limit some of the factors. In DELIF, two fluorophors are present in the system. Normalization of one fluorophor to the other eliminates many of the issues that would otherwise require calibration. Fluorescence intensities of a passive scalar dependent dye are normalized by a non-passive scalar dependent fluorophor. With respect to CMP, passive scalars include fluid film thickness and temperature so equation 3 becomes,

Fluorescence Ratio . (3)

As a result of normalization, the effect of the excitation energy source variations, light reflections, and other non-uniformities along the path of light dl on fluorescence measurements are minimized. Figure 1 depicts the four principle steps in the DELIF measurement technique.

Figure 1. Dual Emission Laser Induced Fluorescence Ratio Calculation.

Although equations 3 and 4 physically quantify dye fluorescence, they do not account for other dye fluorophor behavior such as photoquenching or photodegradation. Photoquenching occurs when dye fluorescence responds nonlinearly to linear changes of excitation energy, a result of too much light. Photodegradation is decomposition of dye fluorophor by the excitation energy and is due to prolonged exposure to light. All dyes have some degree of photodegradation and can be typically characterized by a time dependence due to decomposition.

In addition to photoquenching and photodegradation, many other factors complicate qualitative measurements with dye fluorescence. Chemical changes such as pH, temperature, or excitation energy variations directly impact dye fluorescence spectra behavior. Several complications also arise with excitation energy fluctuations, physical light reflections, and environmental noise such as ambient light. Coppeta and Rogers2 2 J. Copetta, C. Rogers, Experiments in Fluids, 25, 1, (1998).

divide these effects into three different types of errors. Type I conflicts arise when dye A and dye B have emission spectra that overlap, so discerning the source of the fluorescence intensities is impossible. Type II conflicts arise when the fluorescence spectra of dye A overlaps with absorption spectra of dye B while the absorption spectra of dye B remains unaffected by changes in the passive scalar being measured. As a result, dye B absorbs the emission of dye A with a dependent being the path length traveled by the emission of dye A through dye B. The longer the distance, the greater the opportunity for absorption by dye B. Due to this attenuation of dye A and none so for dye B, their ratio is path length dependent. Finally, type III conflicts are similar to type II except for a second variable: the absorption spectra of dye B also varies with a passive scalar, such as temperature. All dyes used in these measurements are chosen to minimize these three errors.

Experimental Setup

A Struers RotoPol-31 table top polisher unit serves as a scaled version of an industrial rotary polisher such as the SpeedFam-IPEC 472. The polisher was fitted with a Mitsubishi Freqrol frequency modulator that allowed a working range from 20 rpm to 300 rpm 1 rpm. The polisher has a 12 inch rotating platen that carries the polishing pad (half of the diameter of the 24 inch commercially employed pads). To ensure the scaled setup closely replicates industrial planarization efforts, the wafer size is scaled to match the table top polisher. The ratio of the polishing pad area, Ap, to the wafer area, Aw, is held constant, resulting in a 3 inch wafer simulating a 300 mm industrial wafer.

The relative velocity of the wafer to the pad is scaled such that the rotational velocities of the wafer, w, and pad, p, are matched so that the velocity under the wafer is comparable to commercial polishing. Most runs are at polishing pad speeds of 60 rpm, the corresponding relative velocity across the wafer is approximately 0.50 m/s. This is typical of older polishers, with more recent polishes operating closer to 1 m/s. Measured removal rates and operating temperatures are typical of commercial CMP as well.

For experimental procedures, an array of control and measurement systems is integrated into table top polisher. Independently controlled parameters include wafer applied pressure, wafer rotational velocity, slurry flow rate, and pad conditioner oscillation and rotational speeds. Throughout the experimental runs, measurement systems characterize friction, fluid film thickness, and temperature at the wafer-slurry-polishing pad interface.

Figure 2. Polishing Setup.

Until recently, a Sears 20 inch drill press replaces the standard wafer carrier head mechanism of the RotoPol-31. A Dayton 1/2 HP DC motor controller allows drill press rotational velocities to range from 0 rpm to 160 rpm. Manual velocity adjustments are made by adjusting the motor’s amplifier. Absolute rotational velocity is calibrated with a tachometer.

Addition of an AMTI Force table beneath the polisher has revealed that this system applies variable down-forces to the platen with the rotation of the drill shaft and the wafer. In the new system pictured in figure 2, the drill press has been replaced by a simple aluminum shaft driven by the same Dayton ½ HP DC motor. The shaft system is support by 10 series 80/20 aluminum 2”X4” beams. A weighted lever arm is mounted on the top of the shaft to achieve variable applied wafer pressures. Weight can be applied at various points along the arm. Now, we are capable of more constant down-forces that range from 0.4 -10 0.05 psi.

During CMP, not only do polishing pad asperities compress, but also slurry debris fills and clogs pores. The result is a “glazed” surface, which adversely affects planarization performance. To prevent glazing, the polishing pad surface is conditioned by a 100 grit diamond disc to remove slurry particles while simultaneously reopening pores. The diamond disk is mounted on a rotating gimbal type PPS (polyphenylene sulfide) carrier, and rotates as it is swept radially across the polishing pad surface (see figure 3). Sweep and rotational rates are also controlled through a software interface. Conditioning may be either conducted ex situ, between wafer polishes, or in situ, during the polishing process. In this work, all conditioning is done in situ. The oscillation due to the sweeping motion

Motor

Platen

RotoPol-31

Wafer

Force Table

Steel Table

of the conditioning arm periodically starves or overloads the wafer with slurry. These periodic fluctuations in the fluid lubrication can affect planarization and are clearly seen in the friction measurements.

Figure 3. Pad Conditioning Setup.

Optical Setup

The DELIF optical measurement technique requires transparent BK-7 glass wafers as a replacement for traditional opaque silicon wafers. BK-7 glass was chosen because it is structurally similar to silicon, widely available, relatively inexpensive, and disposable. These wafers have a diameter of 75 mm (3 inch) and thickness of 12.5 mm (1/2 inch), scaled down from 300 mm wafers. The wafer is rotated by the shaft using the coupling system depicted in figure 4. The bottom of the shaft has a horizontal pin parallel to the wafer. Two more pins are inserted perpendicular to the wafer’s polishing surface such that the shaft can provide a rotational force to the wafer.

Figure 4. Shaft/Wafer coupling system.

The slurry used is Cabot Microelectronic’s Cab-O-Sperse SC-1 in a 3.1 wt% solution with small concentrations of dye added to obtain fluorescence measurements. Concentrations of 1.0 g/l of Calcein, are used for thickness measurements. The slurry consists of 100 nm fumed silica particles suspended in potassium hydroxide (KOH). In these experiments, a .3 wt% solution was used to minimize the polish. These runs behaved similarly to the 3.1 wt% cases and did not have the wafer changing shape over the course of the run. The 3.1 wt% solution has a viscosity of 1.13 cp1 and a shear rate of 8200 Hz. The slurry is delivered to the CMP system by a Masterflex peristaltic pump. Its non-intrusive nature is critical for preventing contamination, corrosion, and clogging. With 14 gauge Norprene Masterflex tubing, the pump is capable of flow rates of up to 250 mL/min. The delivery tubing and all other slurry solution containers are opaque to prevent photobleaching of the added dyes, a condition where a dye loses its sensitivity to light after being exposed for a period of time. Although the actual flow rate is manually dialed in, an optical encoder on the pump enables real time flow rate monitoring in the LabVIEW interface. The flow rates are precise to within 0.5 ml/min.

Figure 5 depicts the optical setup. A Nd/YAG laser emits a UV pulse at a wavelength of 355 nm which causes the polishing pads to fluoresce. The Calcein in the slurry absorbs the emitted pad fluorescence and in turn fluoresces at a lower energy wavelength. The fluorescence of the pad and the dye are optically separated into two cameras; one observes the pad fluorescence (camera A) while the other detects the Calcein fluorescence (camera B). The ratio of the emitted fluorescence is measured by cameral B/camera A, eliminating any lighting variations due to non-uniformities in the excitation source, ambient light contributions, and light scattering of the slurry particles. The resulting ratio value at each pixel is therefore proportional to the amount of Calcein (and the amount of slurry) along a specific column of fluid.

Figure 5. Optical Setup

The fluorescence of the pad and the Calcein is individually captured by two independently filtered digital cameras. A dichroic beam splitter and band pass filters are used to ensure that the cameras image the pad and Calcein fluorescence specific spectral bands. Each image must also be aligned both orthogonally and rotationally to ensure ratioing of the same fluorescence area in post-processing after capture. Prior to the experiment, orthogonal alignment is achieved through hardware and software

manipulation. After the Region of Interest (ROI) is selected, both identical images, are cropped and shifted horizontally and vertically until the are perfectly on top of each other. Figure 6 shows the observed filter regions for the pad and the Calcein.

Figure 6. Spectral Filter Regions.

Overview of new friction table etc (Dan’s writing something for this)

Recent Results

All images presented in Figures 6-9 are processed images of the ratio obtained by dividing the Calcein fluorescence intensity by the pad fluorescence intensity. All images were taken while the platen and the wafer were both in rotation, and those presented here were picked from thousands of available images. The dark areas in the image correspond to low values of the ratio of intensities and indicate where the pad and the wafer are close to each other, or the tops of the pad asperities. Conversely, the lighter sections of the image indicate high values of the ratio and slurry filled valleys between pad asperities.

Figure 6a is an image of the slurry layer between a Freudenberg FX9 polishing pad and a flat BK-7 wafer. Intimate contact of the pad and wafer would imply a boundary lubrication regime. Profilometer measurements of the Freudenberg FX9 pad indicate a surface roughness, Ra = 4.30.3m, suggesting that the asperity peak-to-valley height averages around 8.6m. The image in figure 6a shows these peaks and valleys clearly, and one can estimate Ra = 3.10.3 m from roughly calibrating the images. This

observation implies that the asperities are compressed 2-3 m during polishing. In the future we plan to measure the percentage of the pad in contact with the wafer. Contact measurements require the absolute calibration mentioned earlier.

In addition to detecting slurry flow over pad asperities, most images show patterns in the asperities as indicated by the dashed lines in figure 7. The striation lines in Figure 7a run from the top left to bottom right at almost 45 degrees. In figure 7b the striation lines are just off the horizontal with a slightly positive slope. These lines are most likely gouges in the pad caused by the diamond grit conditioner.

Figure 7b shows a slurry layer beneath a 14.5m deep, 1000m square well etched into the BK7 wafer over a Freudenberg FX9 polishing pad. The overall average intensity underneath the square well is significantly higher than that of the surrounding region. These high intensity regions have no black areas indicating that the asperities are not in contact with the bottom of the well. Preliminary analysis of surface roughness based upon intensity measurements on this and similar images show that the average roughness beneath the contact regions is less than the roughness beneath the wells (difference of approximately 1m). These data suggest asperity compression outside the well as in figure 7a, and the asperities have time to expand under the wells as both surfaces rotate.

Figure 7. The gray arrow indicates the slurry flow direction and the dashed white line indicates the conditioner striation direction. (a) The fluid layer during CMP of a flat wafer over a Freudenberg FX9 polishing pad. (b) Slurry film thickness between a wafer with etched 14.5m deep square well over the Freudenberg FX9 pad.

Figure 8 contains images from a polishing run with 27m deep, square wells etched into a BK7 wafer over a Freudenberg FX9 pad. The arrows in figure 8 show the direction of slurry flow. The slurry does not always fill this deeper well completely leading to air pockets within the well. The majority of the images showed air bubbles of different sizes moving across the wells. Figure 8a shows an air pocket in the center of a well. The irregular shape can probably be attributed to slurry flowing around different size asperities. The majority of the images from the runs with a 27m well are similar to figure 8b, showing air pockets in the upper left corner of the wells, which is the trailing edge of the slurry flow. Figure 8c shows one of the larger air pockets as it is dissipating through the contact region just behind the trailing edge of the well. The behavior of the air in these images implies that there is air entrapment, not cavitation, during the polishing process. One can also see the slurry in the pad below the air pocket, implying that one can estimate the dimensions and volume of the air bubble by comparing the fluorescence under the well outside of the air bubble as compared to inside the air bubble.

Figure 8. The fluid layer between a BK7 wafer with etched 27m deep square wells and a Freudenberg FX9 polishing pad. Arrows denote slurry flow direction. (a) An irregularly shaped air pocket. (b) An air pocket at the trailing corner of the well. (c) An air pocket dissipating into the pad-wafer contact region.

Figure 9 shows images of a BK7 wafer with 27m wells over a Rodel IC1000 k-grooved pad. Figures 9a and 9b are the two extreme cases observed during this run where the grooves in the pad are completely filled (9a) and have almost no slurry present (9b). Most images indicated that the grooves were partially filled as in figure 9c. In these images, air pockets beneath the wells were confined to the grooves in the pad and did not accumulate at the trailing edge of the well as observed on the flat pad figure 8. Note that it is difficult to see the well in figure 9b because the amount of slurry in the groove is significantly greater than outside the groove. This same pad was used to observe the slurry layer beneath a wafer with 14 m wells. The shallower wells were difficult to observe because the intensity contrast between the inside and outside of the wells was too low due to the dominance of the grooved regions.

Figure 9. Slurry beneath a BK7 wafer with 27m deep well on a Rodel IC100 k-grooved pad. Arrows denote slurry flow direction. (a) The grooves are completely filled with slurry. (b) The grooves have no slurry even under the square well. (c) Small air pockets are trapped in the grooves.

Figure 10 includes images from experimental polishing pads produced by Cabot Microelectronics Corporation. Figure 10a show the slurry layer between a flat BK7 wafer and the M2 thin grooved pad. Figure 10b shows fluid over an M3 xy-grooved pad. The M3 pad is slightly smoother than the M2 pad. Besides the obvious groove, the dominant features in image 10a are cross-hatched regions of high intensity indicating a pattern of valleys in the pad. This pattern was imprinted onto the pad with a woven material and tests the ability of the DELIF technique to observe larger scale features. It will not be present in the final version of this experimental pad. The surface roughness of these pads is an order of magnitude larger than the Fruedenberg FX-9 and Rodel IC1000 pads. Therefore, the intensity contrast between asperities in the Cabot pads overshadows even a 27m deep well. These large asperities limit our ability to study pad rebound and surface roughness under a patterned wafer in a similar manner as discussed in figures 7 and 8 .

Figure 10. Experimental polishing pads from Cabot Microelectronics. (a) The slurry layer between a flat BK7 wafer and an M2 thin grooved pad. (b) The slurry layer between a BK7 wafer with 27mm deep wells over an M3 x-y grooved pad.

Proposed Experiments

Over the next three years we propose to run a set of experiments to investigate better how the pad behaves under the wafer. Some critical questions we would like to answer are:

1. How does downforce affect asperity rebound under the well?2. How does well depth change the pad rebound? What is the critical well depth,

after which the pad completely relaxes under the well?3. How do sub-pads affect pad rebound?4. How quickly does the pad rebound? This would be a spatial measurement – that

is how far from the edge of the well is the pad asperities completely rebounded?5. How does grooving affect pad rebound?6. How do different feature shapes affect the slurry and pad behavior?

We propose to combine experimental measurements with a theoretical analysis to build a better model for estimating the pad and fluid behavior under the wafer during polish. This will be the doctoral work of two graduate students, working together. Cappy will work primarily on the experimental setup and Jim will be in charge of the theoretical analysis. Both students, however, will work closely together, with Jim taking measurements and Cappy undertaking some of the theoretical investigation.

Proposed Execution

We will spend the first six months of year one to completely rebuild the experiment. Much of the polisher setup is 8 years old and needs to be updated. The camera and

DELIF portion was recently updated (along with the friction table) so this will bring the whole system into a shape that will allow us to take data more efficiently over the next three years. At the same time, we will apply for complementary research funding from the NSF to better understand the frictional measurements and to correlate them to what we are seeing in the images.

The second half of year one will be dedicated to a complete re-qualification of the experimental setup, looking at minimizing (and clearly measuring) the measurement uncertainty. We will also use this time to build an initial gallery of images, looking at extremes within a predefined parameter space. At the same we will start the mathematical modeling and data analysis development.

Over the course of year two, we will gather most of the data to answer the questions laid out previously. Much of the preliminary analysis will happen at the same time to ensure the quality of the data. At the same time we will hone the theoretical analysis, with the help of two faculty members – one at MIT and one at Harvard – that both specialize in lubrication flows. The ultimate goal of the theoretical analysis will be to develop models that can be used to characterize the wafer-slurry-pad interactions during CMP.

Finally, year three will be dedicated to completion of the work. This will include the write-up of the two doctoral theses and journal articles. By the end of year three, we should have been able to fully characterize the pad and slurry behavior around feature scale topography in CMP.

Figure 11: Approximate Timeline

Fall 2005 Spring 2006 Fall Spring 2008Spring 2007 FallRig Rebuild

Re-qualificationTheoretical groundwork

Data acquisitionModel development

Thesis writingJournal articles

Budget

Yr 1 Yr 2 Yr 3 TotalSalariesManno $5,000 $5,000 $5,000 $15,000Rogers $5,000 $5,000 $5,000 $15,000McKinley $3,000 $3,000 $3,000 $9,000Stone $3,000 $3,000 $3,000 $9,000

Cappy $24,000 $24,000 $24,000 $72,000Jim $24,000 $24,000 $24,000 $72,000

Benefits $1,760 $1,760 $1,760 $5,280

Equipment

Tuition $8,800 $8,800 $8,800 $26,400Materials $5,500 $5,500 $5,500 $16,500Waste $1,100 $1,100 $1,100 $3,300

Direct Costs $81,160 $81,160 $81,160 $243,480IDR (26%) $18,814 $18,814 $18,814 $56,441Total Cost $99,974 $99,974 $99,974 $299,921

List of Publications

Mixing Measurements Using Laser Induced Fluorescence. J. Coppeta and C. Rogers. AIAA Paper Number 95-0167,1995.

A Quantitative Mixing Analysis Using Fluorescent Dyes. J. Coppeta and C. Rogers. AIAA Paper Number 96-0539, 1996.

A Technique for Measuring Slurry Flow Dynamics During Chemical Mechanical Polishing. J. Coppeta, C. Rogers, A. Philipossian, and F. B. Kaufman. Materials Research Society Proceedings, Symposium L, Fall 1996.

Characterizing Slurry Flow During CMP Using Laser Induced Fluorescence. J. Coppeta, C. Rogers, A. Philipossian, and F. B. Kaufman. CMP-MIC, pages307-314, Feb. 13-14, 1997.

Numerical Flow-Visualization of Slurry in a Chemical Mechanical Planarization Process. D. Bramono and L. M. Racz. CMP MIC, 1998.

Analysis of Flow Between a Wafer and Pad During CMP Processes. C. Rogers, J. Coppeta, L. Racz, A. Philipossian, F. Kauffman, and D. Bramono. Journal of Electronic Materials, 27(10):1082-1087, 1998.

Pad Effects on Slurry Transport Beneath a Wafer During Polishing. J. Coppeta, L. Racz, A. Philipossian, F. B. Kaufman, and C. Rogers. CMP-MIC, pages 35-43, Feb. 19-20, 1998.

Dual Emission Laser Induced Fluorescence for Direct Planar Scalar Behavior Measurements. J. Coppeta and C. Rogers. Experiments in Fluids, 25(1):1-15, 1998.

Pad effects on slurry transport beneath a wafer during polishing. J. Coppeta, C. Rogers, A. Philipossian, F. Kaufman, and L. Racz. Third International Chemical Mechanical Polish Planarization for ULSI Multilevel Interconnection Conference, Santa Clara, CA, February 1998.

Analysis of Flow Between Wafer and Pad During CMP Processes. C. Rogers, L. Racz, J. Coppeta, A. Philipossian, F. Kaufman, and D. Bramano. Journal of Electronic Materials, 27:1082-1087, 1998.

The Influence of CMP Process Parameters on Slurry Transport. J. Coppeta, C. Rogers, L. Racz, A. Philipossian, and F. B. Kaufman. CMP-MIC, pages 37-44, Feb. 11-12, 1999.

Investigating Fluid Behavior Beneath a Wafer During Chemical Mechanical Polishing Process. J. R. Coppeta. PhD. Thesis, 1999.

A Statistical Analysis of Key Parameters in Slurry Transport beneath a Wafer during Chemical-Mechanical Polishing. J. Coppeta, L. Racz, C. Rogers, A. Philipossian, and F. Kaufman. Journal on CMP for ULSI Multilevel Interconnection, 1(1):47-60, 2000.

The Effect of Wafer Shape on Slurry Film Thickness and Friction Coefficients in CMP. J. Lu, J. Coppeta, C. Rogers, V. Manno, L. Racz, A. Philipossian, M. Moinpour, and F. Kaufman. Materials Research Society Symposium, 613:E1.2.1-E1.2.6, 2000.

Using Friction Measurements to Characterize Chemical Mechanical Polishing Lubrication Regime. J. Coppeta, C. Rogers, L. Racz, A. Philipossian, and F. Kaufman. Journal of the Electrochemical Society.

Investigating Slurry Transport Beneath a Wafer During Chemical Mechanical Polishing Processes. J. R. Coppeta, C. Rogers, L. Racz, A. Philipossian, F. B. Kaufman. Journal of the Electrochemical Society, 147(5):1903-1909, 2000.

In Situ Technique for Dynamic Fluid Film Pressure Measurement during Chemical Mechanical Polishing. D. Bullen, A. Scarfo, A. Koch, D. Bramono, J. Coppeta, and L. Racz. Journal of the Electrochemical Society, 147:2741, 2000.

Fluid Film Lubrication in Chemical Mechanical Planarization. J. C. Lu. Master's Thesis, Tufts University, 2001.

Fluid Flow Analysis of the Chemical Mechanical Planarization Process. A. Scarfo. Master's Thesis, Tufts University, 2002.

Thermal Characteristics of Chemical Mechanical Planarization. J. Cornely. Master's Thesis, Tufts University, 2003.

Measurements of Slurry Film Thickness and Wafer Drag during CMP. J. Lu, C. Rogers, V. P. Manno, A. Philipossian, S. Anjur, M. Moinpour. Journal of the Electrochemical Society, 151, (4), G241-G247, 2004.

In-situ Pad Topography Measurements During CMP. C. Gray, D. Apone, C. Barns, M. Moinpour, S. Anjur, V. Manno, C. Rogers. MRS Conference Proceedings, Symposium K, Advances in Chemical Mechanical Polishing, Paper #K5.4, Spring 2004.

Pending Publications

Viewing Asperity Behavior Under the Wafer During Chemical Mechanical Polishing. C. Gray, D. Apone, C. Rogers, V. P. Manno, C. Barns, M. Moinpour, S. Anjur, M. Moinpour. Accepted for Publication in Electrochemical and Solid-State Letters, 1/2005.

Instantaneous, High Resolution, In-situ Imaging of Slurry Film Thickness During CMP. C. Gray, D. Apone, C. Rogers, V. P. Manno, C. Barns, M. Moinpour, S. Anjur, A. Philipossian. CMP-MIC, February 22-25, 2005.

Instantaneous Fluid Film Imaging in Chemical Mechanical Planarization. D. Apone, C. Rogers, C. Gray, V. Manno, C. Barns, S. Anjur, M. Moinpour. MRS Conference Proceedings, Symposium W, Recent Advances in Chemical Mechanical Planarization, Paper #W2.3, Spring 2005.

Quantitative In-situ Measurements of Asperity Bending Under the Wafer During CMP.C. Gray, D. Apone, V. Manno, C. Barns, M. Moinpour, S. Anjur, C. Rogers. MRS Conference Proceedings, Symposium W, Recent Advances in Chemical Mechanical Planarization, Paper #W5.4, Spring 2005.

Instantaneous High Resolutions Fluid Film Thickness Measurements during Chemical Mechanical Polishing. C. Gray, D. Apone, C. Rogers, V. Manno, C. Barns, M. Moinpour, S. Anjur, A. Philipossian. World Tribology Congress III, September 12-16, 2005.