EE 330 Lect 4 Spring 2011

EE 330 Lect 4 Spring 2011 - EE 330 Lecture 4 Statistical...

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EE 330 Lecture 4 Statistical Concepts Historical Background, Feature Sizes and Yield Digital Systems – A preview
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Quiz 3 The defect density is often considered as proprietary information. Assume, however, that a process engineer had a lapse of thought and disclosed that they were obtaining a 95% hard yield on a circuit. The competitor bought the circuit and measured the die and found the area to be 0.2cm 2 . What was the defect density in the process? A=0.2cm 2
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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 7
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Quiz 3 The defect density is often considered as proprietary information. Assume, however, that a process engineer had a lapse of thought and disclosed that they were obtaining a 95% hard yield on a circuit. The competitor bought the circuit and measured the die and found the area to be 0.2cm 2 . What was the defect density in the process? A=0.2cm 2 Solution: -Ad Y=e lnY d= - A 95 02 2 lnY ln. d= - 0.26/cm A.  
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Review from Last Time Sophisticated Integrated CAD Toolsets are extensively used in the industry to design integrated circuits Minimize the chances of an error Real asset to (and not a competitor of) the engineer Critical to pay attention to what tools tell you Feature size good metric for characterizing capabilities of a process State of the art at about 65nm Pitch sometimes used instead of feature size Drawn and actual features may differ Bragging rights focus on actual rather than drawn features Yield often determined by statistically independent events Cost of Wafers in $800 to $3000 range depending on size and process n P Y 2 / 5 . 2 $ cm C area unit per
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MOS Transistor Gate Source Drain W eff L eff Effective Width and Length Generally Smaller than Drawn Width and Length Review from Last Time
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Size of Atoms and Molecules in Semiconductor Processes o A 7 . 2 o A 4 . 5 o A 5 . 3 Silicon: Average Atom Spacing Lattice Constant S i O 2 Average Atom Spacing Breakdown Voltage 20KV/cm Air 0 A 10mV/ to 5 10MV/cm 5 Physical size of atoms and molecules place fundamental limit on conventional scaling approaches Review from Last Time
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Defects in a Wafer Defect Dust particles and other undesirable processes cause defects Defects in manufacturing cause yield loss Review from Last Time
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Hard Fault Model Ad H e Y Y H is the probability that the die does not have a hard fault A is the die area d is the defect density (typically 1cm -2 < d < 2cm -2 ) Industry often closely guards the value of d for their process Other models, which may be better, have the same general functional form Review from Last Time
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Soft Fault Model Soft fault models often dependent upon design and application k A ρ σ Often the standard deviation of a parameter is dependent upon the reciprocal of the square root of the parameter sensitive area ρ is a constant dependent upon the architecture and the process A k is the area of the parameter sensitive area Review from Last Time
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Soft Fault Model   MAX MIN X X SOFT dx x f P P SOFT
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EE 330 Lect 4 Spring 2011 - EE 330 Lecture 4 Statistical...

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