143f2010-12-soln - EE143, F2010 N.CHEUNG Homework...

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Unformatted text preview: EE143, F2010 N.CHEUNG Homework Assignment # 12 Solutions Problem 1 (a) f = ( f- s ) T = (24.6-2.6) 10 -6 100 = 2.2 10 -3 f =E f f = 2.2 10-3 0.7 10 11 N/m 2 = 1.54 10 8 N/m 2 (b) t f =1 m = 10-6 m t s = 50 m = 5 10-5 m r = E s t s 2 ( 1- ) s 6 f t f = 0.7 meters Problem 2 f = E s t s 2 ( 1- ) s 6 r t f (a) With the oxide deposited, the oxide stress is compressive since r changes from 300m to 200m (Si wafer more curved) t f = 3 10-7 m t s = 5 10 -4 m f (oxide) = 1.9 10 11 5 10-8 ( 1- ) 6 ( 1 300 1 200 ) = - 6.05 10 7 N/m 2 (b) With both the nitride and the oxide deposited, the wafer is less curved than with oxide alone . Therefore, the nitride film has a tensile stress. However, the total stress of the dual films is still compressive since r = 240 m and is still smaller than the original curvature of 300 m....
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143f2010-12-soln - EE143, F2010 N.CHEUNG Homework...

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