EE 438 HW 2

EE 438 HW 2 - Jonathan Yuen EE 348 Lecture Mon. 5:00PM-7:50...

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Jonathan Yuen EE 348 Lecture Mon. 5:00PM-7:50 PM 03/11/2009 Homework #2: Basics of Lithography 1. The purpose of the hard bake (aka. development bake) process is to remove the residual solvent in the resist and improve adhesion to the increasing resistance to the etching environment. In summary, this process is used to harden the final resist image so that it will withstand the harsh environments of pattern transfer. 2. If the hard bake (aka. development bake) temperature is too low, air bubbles would form due to an evaporation of residual solvent. This would create an inaccurate structural image, chamfered resist profiles, and an unacceptable level of high dark field loss. 3. If the hard bake (aka. development bake) temperature is too high, it would cause the resist to flow and degrade the image. The temperature of flow is related to the glass transition temperature and is a measure of the thermal stability of the resist. 4. Problems for resolving sub micron patterns are pattern generation capabilities, dimensional control and throughput. To duplicate submicron patterns to match the pattern previously printed was not consistent. The method that was used during this process was called Contact Printing. Defects would easily occur on the mask, thus having a high level of inconsistency of generating patterns on a consistent basis. The solution to this problem was the Optical Projection System. Instead of the mask coming in constant contact with the wafer, a mirror image of the mask was projected onto the wafer with the
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image imprinted on using Hg lamps with the range of 350-400 nm. The throughput of
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This note was uploaded on 04/11/2009 for the course EE 438L taught by Professor Kaviani during the Spring '09 term at USC.

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EE 438 HW 2 - Jonathan Yuen EE 348 Lecture Mon. 5:00PM-7:50...

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