EEL 5225 F09 L05 Fab I-3

EEL 5225 F09 L05 Fab I-3 - Fabrication Technology, Part I...

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1 Lecture 5 EEL 5225, Fall 2009, H. Xie Fabrication Technology, Part I b Senturia, Ch. 3, pp. 38-42, Ch. 4, pp. 79-91 f h Agenda B Impurity Doping B Heat Treatment B Example process flows
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2 Lecture 5 EEL 5225, Fall 2009, H. Xie Impurity Doping s Overview s Ion Implantation s Example Impurity Doping
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3 Lecture 5 EEL 5225, Fall 2009, H. Xie Impurity Doping – Overview s Typical Process s Predeposition s Introduction of impurities via ion implantation s Drive-in (optional) s Redistribution of impurities via heat treatment s Applications s Doping of p- and n- semiconductors s **Ion implant used almost exclusively compared to solid- gas-source diffusion s Precise dose/depth control impurity impurity impurity P-type impurity diffusion
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4 Lecture 5 EEL 5225, Fall 2009, H. Xie Ion Implantation s Kinetic bombardment of impurities into semiconductor. +n A Ion current, I +n Projected range, R P Energy, E (keV) = T o dt nqA I Q Ref: S. A. Campbell, Science and Eng. of Micro. Fab. , 2001. Typical Implanter
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5 Lecture 5 EEL 5225, Fall 2009, H. Xie s The total implant is the superposition of many of these individual stopping events Ion Implantation Distribution Ref: A. Doolittle Notes, Georgia Tech. p R p R Δ Δ R Wafer Surface Projected Range Vertical Straggle Lateral Straggle
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6 Lecture 5 EEL 5225, Fall 2009, H. Xie Ion Implantation Distribution s Key parameters s Dose, Q (#/cm 2 ), sets: s Doping concentration levels s Ion energy, E (keV), sets: s Projected range , R P , the average distance ion travels into wafer surface s Straggle, the variation in projected range, both normal ( Δ R P ) and transverse ( ) s Model for impurity distribution p : peak concentration (#/cm 3 ) Gaussian distribution: μ = R p , σ = Δ R p Δ = 2 2 ) ( 2 ) ( exp ) ( p p P R R x x Δ = 0 2 ) ( p P R π dx x Q Δ R
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7 Lecture 5 EEL 5225, Fall 2009, H. Xie Ion Implantation Depth s Projected range ( R p ) and straggle (sigma) (∆ R p ) for Si Ref. Campbell, p. 108. Note: 1000 Å = 100 nm = 0.1 μm
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