Midterm 1 Oct 4 commented PS_1_. 4 2006

Midterm 1 Oct 4 commented PS_1_. 4 2006 - UCB ID:_ By...

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By signing my name below, I affirm that I have not received assistance in completing this examination paper nor have I given assistance to another student. Name:______________________________________ Chemical Engineering 150B Midterm Exam 1 October 4 th , 2006 8:10 - 9 am 100 Points Total Three Problems 1. (25 points) Copper is often used in semiconductor devices to connect one element to another. Unfortunately, though, Cu can diffuse rapidly into the silicon comprising the device, causing defects that ruin the chip. In order to prevent this, a barrier metal is deposited between the copper and the silicon. When a computer is turned on, the temperature of the chips rises rapidly to a steady value and the copper begins to diffuse through the barrier metal. At L the barrier is in contact with a much thicker piece of silicon containing virtually no copper. The maximum solubility copper in the barrier metal is C Ao and the effective diffusivity of copper in the barrier metal of D AB . a) (5 points) Assuming the total concentration of metal in the barrier region is roughly constant, the barrier metal is at an average temperature, and copper is very dilute in the barrier metal, write down an overall mole balance on copper (C A ) in the barrier. 0 L
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This note was uploaded on 07/08/2008 for the course CHEM 150b taught by Professor Bell during the Fall '08 term at University of California, Berkeley.

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Midterm 1 Oct 4 commented PS_1_. 4 2006 - UCB ID:_ By...

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