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CMP

CMP. C hemical M echanical P lanarization Carried out by Eran Cantrell, Bobby O’Ryan, And Maximus (CMP). OBJECTIVES. I ncrease removal rate I nvent a way to roughen pad surface M easure effect of roughening on removal rate and uniformity

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CMP

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  1. CMP Chemical Mechanical Planarization Carried out by Eran Cantrell, Bobby O’Ryan, And Maximus (CMP)

  2. OBJECTIVES Increase removal rate Invent a way to roughen pad surface Measure effect of roughening on removal rate and uniformity Measure effect of slurry flow rate on removal rate and uniformity Reach conclusion of how to better maintain machine efficiency

  3. Background -The CMP (Chemical Mechanical Planarization) process polishes silicon wafers, using slurry (liquid sandpaper) and a platen (polishing pad) to prepare the wafers for lithography. This requires the wafers to be as smooth and uniform as possible. This process is affected by the slurry flow rate, the pad roughness, pressure on the wafer, the platen spin rate, and the length of time the wafer is polished.

  4. Final Slurry Pump Control Box Control Me Primary Slurry Pump Carrier Slurry Delivery Arm Final Polish Platen Primary Polish Platen Polishing Arm Cleaning Station Wafer Boat Wafer Boat Unload Station Load Station Equipment Description • Load  Polish  Unload  Clean  Load • Uses Air, N2, DIW, Slurry, Water, Electricity

  5. Experimental Conditions • Five conditions were set up. This was to test the impact of two variables, while keeping all else constant: the slurry flow rate, and the pad roughening. • Conditions were set up from low SFR (75 ml/min) and low PR (30 sec), increasing to high SFR (225 ml/min) and high PR (2 min). The standard was 150 ml/min of flow rate, and 1 min of roughening. • The CRPM (carrier rotations per min) rate stayed 50 rpm constant. • The platen stayed at 30 rpm when polishing, 60 rpm when roughening. • Polishing time was 30 sec constant. The mass and thickness of the wafers were measured before and after to determine which method was removing the most material.

  6. Data

  7. Data • Each colored line represents the average of the closest three data points surrounding it. While you can see an up-down variation between averages, if you look at the individual data it is impossible to tell the groups apart.

  8. Data

  9. Recommendations for Future Work • Roughening technique should be more mechanical, and methodical. • Develop a technique to measure pad roughness.

  10. Conclusion • Pad roughening appears to increase the removal rate of the silicon dioxide film, and improves wafer uniformity. • Due to confidence interval overlap, an optimal roughening time cannot be selected. • Similar conclusions can be made about slurry flow rate.

  11. Acknowledgements • We would like to thank Jason Hower, for his tutoring throughout this process; • Dr. Milo Koretsky, for his helpful advice; • Maximus, who endured our unorthodox methods; • All the companies who have donated materials (Intel and Sumco); • And the rest of the SESEY staff, for all the support and funding (and effort) they have provided for the students.

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