143f2010-03 - 1 N.CHEUNG EE143, Fall 2010 Homework...

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1 N.CHEUNG EE143, Fall 2010 Homework Assignment # 3 (Due 9/24, Friday, 9am) Reading Assignments 1) Chapter 3 of Jaeger on Thermal Oxidation 2) Reprint – Chapter 9 of Mayer and Lau on Thermal Oxidation. Problem 1 Si consumed during thermal oxidation (a) A very deep vertical groove 1 m wide is etched in Si . The Si surface is covered by Si 3 N 4 which serves as an oxidation mask. The structure is then oxidized in steam at 1100ーC. 1 um Si (100) surface Si3N4 What is the width of the SiO 2 (x in mm) after the groove is completely filled with oxide (idealized schematic of cross-section shown below)? oxidation Si Si Si Si N 3 4 (b) Pure Si contains 5 ラ10 22 Si atoms per cm 3 and SiO 2 contains 2.3 ラ10 22 SiO 2 molecules per cm 3 . A long cylindrical Si rod of radius 100nm is oxidized and a 100nm-thick SiO 2 sheath is formed. What is the radius of Si region in the middle? Assume cylindrical symmetry is maintained during thermal oxidation and ignore any effects caused by stress. (This Si consumption technique is one method to fabricate silicon nanowires down to 10nm in diameter. In reality, large stress produced in the silicon rod oxidation changes the oxidation rate and volume) *There will be discrepancy in x ox , B, and B/A values due to curve reading errors. As long as your
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143f2010-03 - 1 N.CHEUNG EE143, Fall 2010 Homework...

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