143f2010-07 - N.CHEUNG EE143, Fall 2010 Homework Assignment...

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N.CHEUNG EE143, Fall 2010 Homework Assignment # 7 (Due Oct 22, Friday 9am) Reading Assignment 1) Bspace Reprint : Chapter 10 on Etching by G. Anner, from “ Planar Processing Primer 2) EE143 Lecture Notes Problem 1 Etching Profile (a) Poly-Si of the following structure is to be etched using a completely anisotropic dry-etch process, to remove poly-Si at a rate of 0.1 m /min. However, this etch process has poor selectivities: selectivity to SiO 2 is 5; selectivity to photoresist is 2. (a) Sketch the cross-section after 5 minutes of etching. (b) Calculate the angle of the SiO 2 sidewalls after 5 minutes of etching. Problem 2 Poly-Si cross-section if mask is also etched The structure shown below is subjected to an etching process to form a poly-Si line with the following etching characteristics Vertical mask etching rate = 0.01 m/min Vertical poly-Si etching rate = 0.1 m/min Degree of anisotropy for mask etching , A m = 1 Degree of anisotropy for poly-Si etching , A f = 0 = 60ー * The mask and poly-Si have absolute uniform thicknesses.
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143f2010-07 - N.CHEUNG EE143, Fall 2010 Homework Assignment...

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