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Week-12-etching

Week-12-etching - EE 438L:Spring 2009 Microelectronic...

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10/04/09 Dr. Kian Kaviani - Spring 2009 EE 1 EE- 438L :Spring 2009 Microelectronic Processing Dr. Kian Kaviani Hsieh Ming Electrical Engineering Dept. University of Southern California Viterbi School Of Engineering
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10/04/09 Dr. Kian Kaviani - Spring 2009 EE 2 Etching of Semiconductors
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10/04/09 Dr. Kian Kaviani - Spring 2009 EE 3 Introduction What is Etching? All techniques by which material can be uniformly removed from a wafer and results in a delineation of a pattern of microcircuit How many types of etching modes exist? There are two types of etching modes: 1. Wet Etching 2. Dry Etching
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10/04/09 Dr. Kian Kaviani - Spring 2009 EE 4 Terminology of Etching 1. Etch Rate 2. Etch Rate Uniformity 3. Etch Profile (Isotropic vs. anisotropic) 4. Selectivity 5. Etch Bias
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10/04/09 Dr. Kian Kaviani - Spring 2009 EE 5 Etch Rate The rate at which the material is removed from the film by an etch process.
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10/04/09 Dr. Kian Kaviani - Spring 2009 EE 6 Etch Rate Uniformity A measure of the ability of an etch process to etch evenly. The uniformity of the etch process is expressed for three conditions: 1. Within a Wafer 2. Wafer – to – Wafer 3. Run – to – Run
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10/04/09 Dr. Kian Kaviani - Spring 2009 EE 7 Etch Profile In the process of transferring the mask pattern precisely to the film being etched, a also create a vertical edge profile. There are two possible scenario for this vertical profile
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10/04/09 Dr. Kian Kaviani - Spring 2009 EE 8 Selectivity Three kinds of materials are involved in an etch – process: 1. The photoresist mask 2. The film being etched 3. The material under the film being etched During an etch process,all three will be attacked. The difference in the etch rate of these materials characterizes the selectivity . Selectivity indicates how much faster one material etches than another under the same etch condition.
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10/04/09 Dr. Kian Kaviani - Spring 2009 EE 9 Selectivity Two selectivity – parameters are of importance in IC etching processes: Selectivity with respect to the substrate (S s ) Selectivity with respect to the masking material (S m )
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