3-Clean-W10 - EECS 528 Lecture Notes Winter 2010 Clean Room...

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The University of Michigan p. 1 S. W. Pang EECS 528 Lecture Notes Winter 2010 Clean Room and Wafer Clean by Stella W. Pang The University of Michigan The University of Michigan p. 2 S. W. Pang Si VLSI Technology – Fundamentals, Practice and Modeling by Plummer, Deal, and GrifFn Prentice Hall Ch. 4 – Semiconductor Manufacturing – Clean Rooms, Wafer Cleaning, and Gettering Also from MICROCHIP MANU±ACTURING by S. Wolf
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The University of Michigan p. 3 S. W. Pang Industry Requirements of Defect Control The University of Michigan p. 4 S. W. Pang Particulates Organic Films Metallic or Ionic Elements Contamination Sources - Process Equipment or Containers - Chemicals - People - Air Contamination
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The University of Michigan p. 5 S. W. Pang Example #1: MOS V TH is given by V TH = V FB + 2 φ f + 2 ε S qN A (2 φ f ) C O + qQ M C O (1) If t ox = 10 nm, then a 0.1 volt V th shift can be caused by Q M = 6.5 x 10 11 cm -2 (< 0.1% monolayer or 10 ppm in the oxide). Example #2: MOS DRAM • Refresh time of several msec requires a generation lifetime of τ = 1 σ v th N t 100 μ sec (2) • This requires N t 10 12 cm -3 or 0.02 ppb (see text). Electrical Degradation due to Contamination The University of Michigan p. 6 S. W. Pang Modeling Particle Contamination and Yield 75% of yield loss in modern VLSI fabs is due to particle contamination. • Yield models depend on information about the distribution of particles. • Particles on the order of 0.1 - 0.3 μm are the most troublesome: larger particles precipitate easily • smaller ones coagulate into larger particles Particle Diameter Particle Density 0.1 - 0.3 μm Probability of Particle Causing Yield Loss 0.2 0.4 0.6 0.8 1 • Yields are described by Poisson statistics in the simplest case. Y = exp A C D O (3) where A C is the critical area and D O the defect density . • This model assumes independent randomly distributed defects and often underpredicts yields.
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The University of Michigan p. 7 S. W. Pang MICROCHIP MANUFACTURING © 2004 by LATTICE PRESS Sunset Beach CA SOURCES OF CONTAMINATION IN CHIP-MANUFACTURING Examples of Particle-Types on IC-Wafers The University of Michigan p. 8 S. W. Pang MICROCHIP MANUFACTURING © 2004 by LATTICE PRESS Sunset Beach CA EFFECTS OF CONTAMINATION ON ULSI DEVICES Films Trace-Metals Particles Ionic Contaminants
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3-Clean-W10 - EECS 528 Lecture Notes Winter 2010 Clean Room...

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