Nonlinear processes to extend interferometric lithography

Saleem H. Zaidi, S. R J Brueck

Research output: Chapter in Book/Report/Conference proceedingChapter

14 Citations (Scopus)

Abstract

The linear-systems spatial frequency limit of diffraction-limited optical lithography is approximately NA/λ, where NA is the optical system numerical aperture, and λ is the exposure wavelength. Optical resolution enhancement techniques (RETs) such as optical proximity correction, phase-shifts masks and off-axis illumination extend this resolution towards 2NA/λ. Interferometric lithography (IL) for periodic patterns and imaging interferometric lithography (IIL) for arbitrary patterns extends the frequency space coverage out towards the free-space linear systems transmission limit of 2/λ. By taking advantage of inherent processing nonlinearities, higher spatial frequencies beyond these linear systems limits can be realized. Two nonlinear processes aimed at extending the spatial frequencies available by IL are reported. The first process is a variant of spatial frequency doubling in which two maskless IL processes combined with a moire alignment scheme are used to form a spatial frequency doubled grating at a period of d/2, where d is the original grating period. A first grating is written at period d, and linewidth approximately d/4, and transferred to a thin nitride film. A second IL grating, at the same period but shifted in phase by π, is then interpolated to divide the period by two. A moire interference scheme is used to ensure proper alignment over large areas. This process has been used to frequency double a 360-nm period at I-line exposure to 180-nm period that was transferred into (110) Si using KOH etching with the nitride film as the etch mask. A second example, using photoresist nonlinearities, is the formation of nanoscale square vias (approximately 80-nm at I-line wavelengths) in a single photoresist level. This structure is formed by sequence including exposure of a grating, partial development of the resist, exposure of a second grating at right angles, and final development.

Original languageEnglish
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
PublisherSociety of Photo-Optical Instrumentation Engineers
Pages371-378
Number of pages8
Volume3676
EditionI
Publication statusPublished - 1999
Externally publishedYes
EventProceedings of the 1999 Emerging Lithographic Technologies III - Santa Clara, CA, USA
Duration: 15 Mar 199917 Mar 1999

Other

OtherProceedings of the 1999 Emerging Lithographic Technologies III
CitySanta Clara, CA, USA
Period15/3/9917/3/99

Fingerprint

Lithography
lithography
gratings
Linear systems
linear systems
Photoresists
Nitrides
Masks
photoresists
nitrides
Wavelength
masks
Photolithography
nonlinearity
alignment
Phase shift
Optical systems
Linewidth
Etching
Diffraction

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Condensed Matter Physics

Cite this

Zaidi, S. H., & Brueck, S. R. J. (1999). Nonlinear processes to extend interferometric lithography. In Proceedings of SPIE - The International Society for Optical Engineering (I ed., Vol. 3676, pp. 371-378). Society of Photo-Optical Instrumentation Engineers.

Nonlinear processes to extend interferometric lithography. / Zaidi, Saleem H.; Brueck, S. R J.

Proceedings of SPIE - The International Society for Optical Engineering. Vol. 3676 I. ed. Society of Photo-Optical Instrumentation Engineers, 1999. p. 371-378.

Research output: Chapter in Book/Report/Conference proceedingChapter

Zaidi, SH & Brueck, SRJ 1999, Nonlinear processes to extend interferometric lithography. in Proceedings of SPIE - The International Society for Optical Engineering. I edn, vol. 3676, Society of Photo-Optical Instrumentation Engineers, pp. 371-378, Proceedings of the 1999 Emerging Lithographic Technologies III, Santa Clara, CA, USA, 15/3/99.
Zaidi SH, Brueck SRJ. Nonlinear processes to extend interferometric lithography. In Proceedings of SPIE - The International Society for Optical Engineering. I ed. Vol. 3676. Society of Photo-Optical Instrumentation Engineers. 1999. p. 371-378
Zaidi, Saleem H. ; Brueck, S. R J. / Nonlinear processes to extend interferometric lithography. Proceedings of SPIE - The International Society for Optical Engineering. Vol. 3676 I. ed. Society of Photo-Optical Instrumentation Engineers, 1999. pp. 371-378
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