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143f2010-12

143f2010-12 - N.CHEUNG EE143 F2010 Homework Assignment...

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1 N.CHEUNG EE143, F2010 Homework Assignment # 12 (Due Dec 3 ,Fri 9am) THIS IS THE LAST HW ASSIGNMENT FOR THE SEMESTER Reading Assignment 1) Jaeger Textbook, Chapter 11 on MEMS 2) Reprint in Bspace : “Stress in Thin Films” Reprint. 3) Reprint Bspace , Sections of Kov ac “Mechanical Transducers” -qualitative understanding of MEMS principles 4) EE143 Lecture Notes Problem 1 Thermal Stress in thin films A 1 m thick Al film is deposited without thermal stress on a 50 m thick Si wafer at a temperature 100°C above ambient temperature. The wafer and film are allowed to cool to the ambient. Using the values provided in the table and assuming a Poisson ratio = 0.272 for Si Thermal Expansion coefficient ( 10 -6 / o C) Youngs Modulus ( 10 11 N/m 2 ) Al 24.6 0.7 Sl 2.6 1.9 (a) Calculate thermal strain and stress for T = 100°C. (b) Calculate the radius of curvature of the substrate Problem 2 Stress of dual films A 500 m -thick bare Si wafer is originally has a radius of curvature of +300 m. After a 300nm-thick

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143f2010-12 - N.CHEUNG EE143 F2010 Homework Assignment...

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