Pad Characterization Update Caprice Gray Nov. 9, 2006 Cabot Microelectronics Aurora, IL

Outline Review where we were last time Non-DELIF imaging DELIF Contact detection feasibility and preliminary results Thesis Outline DELIF Modeling Experimental Outline Questions/Issue that should be resolved before proceeding forward

Last Meeting Accomplishments Set up beam splitter aligner Replace poor quality optical filters with high quality filters Determined the source of ratio drift by modeling intensity sources for each camera

Source of Ratio Drift Calibration for all previous data sets that show ratio drift. All Components the cameras actually measure Primary Source of ratio drift Experimentally Determined Constants New Ratio Calculation Determined by drift

Imaging Benchmarks: SEM Imaged in 3 regions of a used pad 1.Edge of wafer track (most glazed region) 2.Outside Wafer track (no glazing) 3.Center of wafer track (less glazing)

Imaging Benchmarks: SEM Outside of wafer track Edge of wafer track Center of wafer track In a groove Center of wafer track

Imaging Benchmarks: SEM SEM Image Highest Quality DELIF –depth

Imaging Benchmarks: Confocal Microscopy Similar to DELIF Resolution (scale bar = 160  m) Zoomed image of a pore, a cross section near the pad surface (scale bar = 40  m)

Imaging Benchmarks: Confocal Microscopy 24 images are taken every 2 mm Video start at the deepest layer and progresses to the surface

Rohm and Haas Pad-Wafer Contact Study Confocal Reflectance Interference Contrast Microscopy Images are taken through sapphire. –No slurry –Static Imaging region < 1 mm 2 –Asperity Contact ~ 50  m 2 Pads studied: –IC1000 –VP3000 –Politex –Experimental Tested 0-6 psi, contact 0-6%, experimental contact ~ 20%

DELIF for Contact 360,000+ pixels  2% ~ 7200 pixels 50  m 2 ~ 7-8 pixels (6.7  m 2 /pixel) –Focus must be really good –We are at the resolution limit for our system At this resolution, we are seeing contact region intensity smoothing Data for static DELIF on CMC D100

CMC D100 Imaging Issues Experiment: 50 consecutive static images Image drift correction was nearly 100% of signal Focus is difficult because R a >DOF –Must carefully focus at tops of pixels –Out of focus light bleeds into pixels that are in focus

CMC D100 Imaging Issues D100 Emission FX9 Emission

Thesis Outline Introduction –Why are we looking for pad-wafer contact in CMP –Literature review of experimental pad-wafer contact measurements –Project Goal = detect in-situ pad-wafer contact Methods –What is DELIF, and why use it –System model and calibration techniques –Hardware description –System limitations –Image Acquisition and Processing In-Situ Detection of Pad/Wafer Contact with DELIF during CMP

Thesis Outline Experimental Outline –Description of variables and responses –Post acquisition image interpretation (histogram analysis, etc.) Results and Discussion –Comparison on contact on hard vs. soft pads –Static measurements vs. dynamic measurements –Pressure variation effect on contact % –Relate results to previously studied pad-wafer contact measurements Conclusions –Summary of Experimental results –Contribution of results to current understanding of CMP –Could this technique be expanded to study multiple polishing pad types?

DELIF Modeling Goals –Examine how comparable our actual system is to current DELIF models –Verify our linear calibration technique (Ratio Intensity  Fluid layer thickness) Results –slurry particles  quadratic calibration –As slurry particle concentration  0, calibration  linear Old Model Current System

Experimental Outline Finish Tweaking Optics to get repeatable static data Identify 2 types of polishing pads that will work optically with our system. –Similar R a ~ 4-6  m –High and Low bulk modulus Proceed to DOE –Possible Variables: pressure, pad/wafer velocity, pad type, slurry dilution, pH –Responses: Contact area %, Contact area size, friction signature?

Open Questions Which 2 pads should I focus my study on and will I have a steady supply of them? Does slurry dilution matter? –Accurate depth measurements or minimize chatter? Should I continue to search for a static contact measurement benchmarking technique, or just use (the limited) data from literature? Which experimental variables should I concentrate on? –My variable preferences: pad modulus, pad-wafer speed, down-force