U of M Materials Science Seagate Design Group

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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

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Outline

• Project Overview

• Possible Solutions

• Idea Selection

• Detailed Solution

Overview

Dr. Marcus Mooney, Materials for Electronics, Seagate

Project Goals

Main Goal:• Reduce transducer RMS roughness from 10 Å to 2 Å

Other Considerations:• Materials should not undergo phase changes up to

250 ºC or react with neighboring materials• Must have a product life of at least 5 years• Ease of production and fabrication• Cost

Possible Solutions

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Solution #1: Chemical Mechanical Planarization/Polishing (CMP)

A process that uses an abrasive, corrosive slurry to physically grind flat and chemically remove the microscopic topographic features on a wafer so that subsequent processes can begin from a flat surface*.

Advantages:• Ease of implementation• Low cost

Disadvantages:• Roughness control

*www.appliedmaterials.com/products/cmp_4.html**http://www.scsolutions.com

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Solution #2: Spin-on Glass (SOG)

A process that uses an liquid form of glass to fill small gaps between metal layers*.

Advantages:• Ease of implementation• Low cost

Disadvantages:• Possible materials contamination• Magnetic and electrical property

*Optimization of Spin-On-Glass Process for Multilevel Metal Interconnects. Aric C. Madayag and Zhiping Zhou. Georgia Institute of Technology

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Solution #3 Focused Ion Beam (FIB)

FIB can be used to mill and polish sample using a focused beam of gallium ions*.

Advantages:• Superior polishing

Disadvantages:• Cost • Time• Redeposit/Contamination

* http://www.fei.com/uploadedFiles/Documents/Content/2006_06_FIBCapabilities_td.pdf

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Solution #4 Materials Change

Changing current materials for reader/writer elements with similar materials with comparable magnetic and modulus properties.

Advantages:• Better polished potential

Disadvantages:• Magnetic and electrical property

Idea Selection

Idea Selection Criteria

• Final Roughness- How well the process will achieve the 2 Å target goal.

• Ease of Implementation- Time and cost to put the process into practice

• Cost- Increase to the current production cost

• Time- Increase to the current production time

40%

30%

10%

20%

3 1 2 4

3 1 4 2

3 4 3 2

4 2 1 3

•Cost (10%)

•Time (20%)

•Final Roughness (40%)

•Ease of implementation (30%)

•Total

Idea Selection Process

CMP FIB Material Change

SOG

3.3 2.5 2.5 2.5

Detailed Solution

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

Process Control Options

http://www.icknowledge.com/misc_technology/CMP.pdf

Slurry

• Critical to achieving low roughness values• Different slurry options:

– Slurry material choice (chemical interactions)– Solution concentration– Particle size:

http://www.iop.org/EJ/abstract/0953-8984/20/22/225011

Summary

• CMP is the final process currently used in smoothing transducer elements

• CMP is the best solution for our target 2 Å roughness

• Many options for improving CMP – slurry is especially important