EE 330 Lect 9 Spring 2011

EE 330 Lect 9 Spring 2011 - EE 330 Lecture 9 IC Fabrication...

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EE 330 Lecture 9 IC Fabrication Technology Part 2
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Quiz 8 A 2m silicon crystal is cut into wafers using a wire saw. If the wire diameter is 220um and the wafer thickness is 350um, how many wafers will this 2m crystal provide? In solving this problem you may neglect any wire vibration or abrasive particles used during cutting that would increase the width of the kerf.
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And the number is …. 6 3 1 2 4 5 7 8 9
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And the number is …. 6 3 1 2 4 5 7 8 9 4
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Quiz 8 A 2m silicon crystal is cut into wafers using a wire saw. If the wire diameter is 220um and the wafer thickness is 350um, how many wafers will this 2m crystal provide? In solving this problem you may neglect any wire vibration or abrasive particles used during cutting that would increase the width of the kerf. Solution: 2 220 350 w CUT wafer Pull height m n t t um um   2 3509 220 350 w m n um um
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Crystal Preparation Source: WEB Review from Last Time
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Masking Use masks or reticles to define features on a wafer – Masks same size as wafer – Reticles used for projection – Reticle much smaller (but often termed mask) – Reticles often of quartz with chrome – Quality of reticle throughout life of use is critical – Single IC may require 20 or more reticles – Cost of “mask set” now exceeds $1million for state of the art processes – Average usage 500 to 1500 times – Mask costs exceeding 50% of total fabrication costs in sub 100nm processes – Serve same purpose as a negative (or positive) in a photographic process Review from Last Time
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Photolithographic Process Photoresist Viscous Liquid Uniform Application Critical (spinner) Baked to harden Approx 1u thick Non-Selective Types Negative – unexposed material removed when developed Positive-exposed material removed when developed Thickness about 450nm in 90nm process (ITRS 2007 Litho) Exposure Projection through reticle with stepper Alignment is critical !! E-Bean Exposures Eliminate need fro reticle Capacity very small Review from Last Time
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Deposition • Application of something to the surface of the silicon wafer or substrate – Layers 15A to 20u thick • Methods – Physical Vapor Deposition (nonselective) • Evaporation/Condensation • Sputtering (better host integrity) – Chemical Vapor Deposition (nonselective) • Reaction of 2 or more gases with solid precipitate • Reduction by heating creates solid precipitate (pyrolytic) – Screening (selective) • For thick films • Low Tech, not widely used today Review from Last Time
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IC Fabrication Technology Crystal Preparation Masking Photolithographic Process Deposition Implantation Etching Diffusion Oxidation Epitaxy Polysilicon Contacts, Interconnect and Metalization Planarization
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Implantation Application of impurities into
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This document was uploaded on 01/31/2012.

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EE 330 Lect 9 Spring 2011 - EE 330 Lecture 9 IC Fabrication...

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