# 143f2010-05 - 1 N.CHEUNG EE143, Fall 2010 Homework...

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1 N.CHEUNG EE143, Fall 2010 Homework Assignment #5 (Due Oct 8, Fri 9am) Note: Different textbooks use either C(x) or N(x) to represent the concentration, and Q or to represent the dopant dose. Reading Assignment 1) Jaeger , Chapter 4 on diffusion [ Van der pauw’s Method (section 4.7.4) for sheet resistance and junction profile measurement (section 4.8) are optional. ] 2) Reprint in Bpsace : Selected sections of Chapter 9 of Wolf and Tauber. Qualitative understanding only: Section 9.2 Defects and Dopant Diffusion Section 9.7 Anomalous Diffusion Effects 3) Handout : Notes on Doping Diffusion [ 2D Diffusion math and high concentration diffusion math for refernce only] Problem 1 Simple predep calculation (how to use the erfc function) A boron predeposition step is performed into an n-type Si substrate with a background concentration C B of 1 10 16 /cm 3 . The predeposition thermal cycle is 975 o C for 15 minutes. Given: Boron solid solubility at 975 o C = 3.5 10 20 /cm 3 Boron diffusion constant at 975 o C = 1.5 10 -14 cm 2 /sec (a) Calculate the junction depth x j . (b) Calculate the incorporated boron dose Q. Problem 2 Predep followed by Drive-in A pn junction is to be formed 1 m from the surface in n-type Si substrate, which has a doping concentration of 10 17 phosphorus atoms per cm 3 . The junction is formed by a two-step diffusion of boron: The predep is solid-solubility limited at 1000ｰC and the drive-in is at 1100ｰC.

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## This note was uploaded on 03/03/2012 for the course EECS 142 taught by Professor Ee142 during the Spring '04 term at University of California, Berkeley.

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143f2010-05 - 1 N.CHEUNG EE143, Fall 2010 Homework...

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