RELAX: resolution enhancement by laser-spectrum adjusted exposure

Ivan Lalovic; Nigel Farrar; Kazuhiro Takahashi; Eric Kent; Daniel Colon; German Rylov; Alden Acheta; Koji Toyoda; Harry Levinson

doi:10.1117/12.601002

12 May 2005 RELAX: resolution enhancement by laser-spectrum adjusted exposure

Ivan Lalovic, Nigel Farrar, Kazuhiro Takahashi, Eric Kent, Daniel Colon, German Rylov, Alden Acheta, Koji Toyoda, Harry Levinson

Author Affiliations +

Proceedings Volume 5754, Optical Microlithography XVIII; (2005) https://doi.org/10.1117/12.601002
Event: Microlithography 2005, 2005, San Jose, California, United States

Abstract

In this work, we demonstrate a resolution enhancement technique for DUV lithography in which the light source spectrum is modified in order to improve the imaging performance of given device patterns. With this technique, termed RELAX, the imaging depth of focus (DOF) can be improved significantly for contact holes, and potentially line-space patterns. The improvement in the DOF comes at the expense of modest deterioration of other process performance metrics, such as exposure latitude and exposure bias, due to reduced image contrast at best focus. Compared to the FLEX-based techniques, RELAX allows a continuum of tunable spectral conditions without the drawback of multiple exposure passes, which is especially critical for step-and-scan lithography. Spectrum modification is accomplished by replacing the line narrowing and wavemeter modules of the excimer laser light source with RELAX-enabled modules. Direct wavefront modification of the laser output has been demonstrated to provide the optimum method for producing a double peak spectrum, which simulation has shown to produce the maximum DOF benefit. Results from imaging experiments of attenuated-PSM contact structures exposed using 248nm dipole illumination showed DOF improvements of up to 70% with a double peak separation of about 2pm. Lateral chromatic effects at this separation were negligible. These results agreed well with previous double exposure experiments1 and simulations of some of the design structures. The process improvements were obtained without a need for re-biasing of the mask structures, although a dose adjustment was required.

Citation Download Citation

Ivan Lalovic, Nigel Farrar, Kazuhiro Takahashi, Eric Kent, Daniel Colon, German Rylov, Alden Acheta, Koji Toyoda, and Harry Levinson "RELAX: resolution enhancement by laser-spectrum adjusted exposure", Proc. SPIE 5754, Optical Microlithography XVIII, (12 May 2005); https://doi.org/10.1117/12.601002

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