Searching for a Sustainable Manufacturing Process: Rapid Pad Conditioning in ULSI Fabrication

Jung-Hoon Chun

Laboratory for Manufacturing and Productivity Massachusetts Institute of Technology

Cambridge, MA 02139

April 22, 2010

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ULSI Fabrication A Typical 300-mm Fab (2008)

  Cost: $3-4 billion

  Wafers: 360,000 per year

  Chemicals/gases: $225 per wafer, $81 million per year

  Water: 1 billion gallons per year

  Waste water: 400 million gallons per year

  Energy consumption: 1.25 kWh/cm2, $25 million per year

  Total materials costs: $162 million per year

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Cleanwafer

Photoresistcoating

Exposure

Development

Etching

Cleanwafer

Plating

CMP

Cu Interconnect Fabrication

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Scratching in Cu CMP

100 µm 100 nm 10 µm 1 µm

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Pad Scratching in Cu CMP Water Slurry

100 µm 100 µm

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Current Typical Pad Conditioning Procedure

CMP Tool (Source: Applied Materials)

  Uses 50 Cu wafers

  Uses over 30 l of slurry

  Duration is 4 hours

  Must be repeated every 24 hours

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SEM Micrographs of Pad Surface New Pad Conditioned Pad

100 μm 100 μm

20 μm 20 μm

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Pad Mechanical Properties Modulus/Hardness

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Pad Asperity Radius of Curvature

  Increases by a factor of 6

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Coefficient of Friction

Sliding Friction Apparatus

  Normal Load = 200 g   Pad Diameter = 2 cm   Pressure = 5 kPa (0.73 psi)   Velocity = 0.005 m/s

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Pad Scratching Models: Contact Pressure Distributions

Elastic Deformation: Onset of Pad Yielding

Fully-Plastic Deformation

Elastic-Plastic Deformation

Frictionless With Friction

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Pad Scratching Models: Results

  Elastic Deformation

  Fully-Plastic Deformation

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Pad Scratching Regimes

Hertzian Case

Plastic Case

A

B

C

For the case of ECu = 128 GPa, = 0.3

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Asperity Control by Pad Conditioning

  New Pad   Current Conditioning   Proper Conditioning

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Summary

  Model-based understanding of scratching by pad during CMP −  Mechanistic

−  Statistical

−  Quantitative relationships between the pad mechanical properties, surface geometry, slurry, and wafer surface mechanical properties

  More environmentally-benign CMP process −  Improved yield

−  Rapid pad conditioning

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Thank You!