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U of M Materials Science Seagate Design Group

U of M Materials Science Seagate Design Group. Alan Bagwell Tony Lindert Loc Nguyen Greg Rayner. Industrial Mentor: Dr. Vince Engelkes. Faculty Advisor: Prof. C. Daniel Frisbie. Outline. Project Goal Project Solution: CMP Overview Detailed Solution Other Considerations Summary.

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U of M Materials Science Seagate Design Group

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  1. U of M Materials Science Seagate Design Group Alan Bagwell Tony Lindert Loc Nguyen Greg Rayner Industrial Mentor: Dr. Vince Engelkes Faculty Advisor: Prof. C. Daniel Frisbie

  2. Outline • Project Goal • Project Solution: CMP Overview • Detailed Solution • Other Considerations • Summary

  3. Project Goal and Solution Main Goal: Reduce transducer RMS roughness from 10 Å to 2 Å Project Solution: Chemical Mechanical Processing / Nanogrinding

  4. Chemical Mechanical Planarization Overview • Culmination of several smoothing processes • Key components: • CMP Pad • Slurry • Process control: speed, pressure, etc. http://www.icknowledge.com/misc_technology/CMP.pdf

  5. Material Science and Engineering, Zantye, 2004

  6. Rough Lapping • Goal: Bulk removal • Multi-step process • Free Abrasive • Single crystal diamond (0.25+ micron particle size) • Zinc lapping plate • High speed and pressure for maximum removal rate • High speed leads to a reduction in planarization. Further lapping is required.

  7. Material Science and Engineering, Zantye, 2004

  8. Fine LappingFixed versus Free Abrasive Ultraprecision Polishing GMR Harddisk Magnetic Head, Zhong, 2006

  9. Material Science and Engineering, Zantye, 2004

  10. Nanogrinding • Plate Preparation • Tin-bismuth alloy (42% Sn, 58% Bi, 1.5-2 Mohs) • Surface roughness • Spiral groove • Plate is “charged” by embedding diamonds

  11. Plate Charging • 50nm polycrystalline diamond spherical particles • 6-hour+ charging times result in better planarity Ultra precision Polishing GMR Hard-disk Magnetic Head, Zhong, 2006

  12. Slurry Composition • Ethylene glycol with 6% silica colloid (30% SiO2, 10 nm) to increase plate life and removal rate • Chelating agent (Methionine) to dissolve metal ions • Corrosion inhibitors: BTA, Standapol, or Triton • Polyoxyethylene ether as a surfactant to increase wetting

  13. Slurry pH • Slider consists of softer metals and harder AlTiC ceramic • Picking the correct pH will increase the solubility of the ceramic and soften it • This will allow both materials to abrade at similar rates • At pH 11, copper in the GMR stack will corrode

  14. Slurry pH (10) On the advanced lapping process in the precision finishing of thin-film magnetic recording heads for rigid disc drives, Jiang, 2003

  15. Other Considerations • Plate Speed: 25 rpm • Nominal Pressure: 112 kPa • Slurry Flow: 1 mL every 30 seconds • Viscosity: 2.5 cP • The viscosity can be increased by partially replacingethylene glycol with diethylene glycol

  16. Summary • Fixed Abrasive Lapping • 50 nm polycrystalline spherical diamond particles embedded in tin-bismuth grooved plate • Plate charging time of 8 hours • Slurry Composition • Ethylene glycol with 6% colloidal silica (30% SiO2, 10 nm) • Standapol corrosion inhibitor • Polyoxyethylene ether surfactant • Diethylene glycol to raise viscosity to 2.5 cP • Chelating agent (Methionine) to dissolve metal ions • Organic pH regulators such as NH4OH to achieve a pH of 10

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