Interference lithography has been widely utilized as a tool for the evaluation of photoresist materials, as well as emerging resolution enhancement techniques such as immersion lithography. The interferometric approach is both simple and inexpensive to implement, however it is limited in its ability to examine the impact of defocus due to the inherently large DOF (Depth-of-Focus) in two-beam interference. Alternatively, the demodulation of the aerial image that occurs as a result of defocus in a projection system may be synthesized using a two pass exposure with the interferometric method. The simulated aerial image modulation for defocused projection systems has been used to calculate the single beam exposure required to reproduce the same level of modulation in an interferometric system through the use of a “Modulation Transfer Curve”. The two methods have been theoretically correlated, by way of modulation for projection illumination configurations, including quadrupole and annular. An interferometric exposure system was used to experimentally synthesize defocus for modulations of 0.3, 0.5, 0.7 and 1.0. Feature sizes of 90nm were evaluated across dose and synthetic focus.

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Copyright 2004 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

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Document Type

Conference Paper

Department, Program, or Center

Microelectronic Engineering (KGCOE)


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