ECE_5360_Diffusion_and_Ion_Implantation_mod

ECE_5360_Diffusion_and_Ion_Implantation_mod - Doping...

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Doping Diffusion, Implantation and Annealing
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Harvard_Fabrication_7-8.ppt – 2006 2 Introduction Dopant atoms move through Si at significant rates at high temperatures diffusion Useful for moving dopants from surface to desired depth Diffusion is a limitation in design of shallow junction processes We will discuss this through basic diffusion theory, explore concentration dependent diffusion and oxidation enhanced/retarded diffusion effects
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Harvard_Fabrication_7-8.ppt – 2006 3 Lab plans (weekly) Monday Wednesday Friday Week LAB 1 Wafer Prep & Substrate 9/15 Modern CMOS 9/17 Crystal Growth Basic 9/19 Crystal Defects 3 LAB2 Field Oxide: 9/22 Crystal Defects 9/24 wafer preparation 9/26 Lithography/Pattern transfer II 4 LAB3 Pattern Source Drain 9/29 Lithography/Pattern 10/1 Lithography/Pattern 10/3 Oxidation 5 LAB4 Pattern Source/Drain 10/6 Oxidation 10/8 Diffusion 10/10 Diffusion 6 LAB 5 Contact Deposition and 10/13 Fall Break 10/15 Diffusion 10/17 Ion implantation 7 LAB 6 Device measurements 10/20 Ion implantaion 10/22 Etching I Wet 10/24 Etching II Dry 8 LAB 7 Device Measurements 10/27 Etching I 10/29 Prelim1 10/31 PVD 9 LAB 8 Open 11/3 CVD II 11/5 Prelim 2 11/7 CVD III 10 Additional time if 11/10 CVD I 11/12 Characterization II 11/14 Characterization III 11 Additional time if 11/17 Characterization I 11/19 Ohmic contacts 11/21 Schottky barriers 12 11/24 CMP and wafer bonding 11/26 Thanksgiving break 11/28 Thanksgiving break 13 11/31 Prelim 2 12/3 Open 12/5 Open 14
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Phase Diagram for As-Si
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Harvard_Fabrication_7-8.ppt – 2006 6 Basic Mathematics of Diffusion: Fick’s 1 st Law Random Thermal Motion Yields 1 Dimension: F DC C FD x = −∇  = −   
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Harvard_Fabrication_7-8.ppt – 2006 7 Fick’s 2 nd Law 2 2 Fick's 2nd Law The Diffusion Equation if constant in CF tx C D xx C D CC DD x ∂∂ = −  = −−   = = ) ( ) ( C D C D F t C = −∇ = −∇ = C D t C 2 = In 3D If D constant in (x,y,z)
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Harvard_Fabrication_7-8.ppt – 2006 8 Classic Examples: Constant D in Space and Time Limited Source/Gaussian Diffusion Infinite Source/Constant Surface Concentration Diffusion Fixed Number/Area of Dopants at Surface ( ) 2 0 /2 Objective, find ( , ) Boundary conditions (0,0) ( ) (,) Solution: x Dt Cxt C Qx C x t dx Q t Q e Dt δ π = = = 10 10 10 12 10 14 10 16 10 18 10 20 10 22 0 0.5 1 1.5 Gaussian Diffusion Example t=1 s t=10 s t=100 s t=1000 s t=10,000 s Concentration (cm -3 ) x (um) Q=1x10 15 cm -2 D=2.59x10 -14 cm 2 /s Gaussian Diffusion
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Harvard_Fabrication_7-8.ppt – 2006 9 Gaussian Diffusion 10 10 10 12 10 14 10 16 10 18 10 20 10 22 0 0.5 1 1.5 Gaussian Diffusion Example t=1 s t=10 s t=100 s t=1000 s t=10,000 s Concentration (cm -3 ) x (um) Q=1x10 15 cm -2 D=2.59x10 -14 cm 2 /s 10 10 10 12 10 14 10 16 10 18 10 20 10 22 0 0.1 0.2 0.3 0.4 0.5 Gaussian Diffusion Example t=1 s t=10 s t=100 s t=1000 s t=10,000 s x (um) Q=1x10 15 cm -2 D=2.59x10 -14 cm 2 /s
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Harvard_Fabrication_7-8.ppt – 2006 10 Infinite Source/Constant Surface Concentration Diffusion ( ) ( ) ( ) 2 0 0 0 (,) Boundary Conditions (0, ) ( ,0) 0 0 Solution 2 1 z Cxt Ct Cx x x C x t C erfc Dt erfc z erf z erf z e d η = = ∀>  =   ≡−
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Harvard_Fabrication_7-8.ppt – 2006
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This note was uploaded on 04/04/2009 for the course ECE 5360 taught by Professor Shealy during the Fall '07 term at Cornell University (Engineering School).

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ECE_5360_Diffusion_and_Ion_Implantation_mod - Doping...

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