听
The integrated circuits in your computer or car听require manufacturing processes capable of patterning billions of nanometer-scale听features every second听with near perfect accuracy. 听, the 50-year trend of听continually smaller structures resulting in continually more powerful electronics, is possibly nearing its end. 听The challenge faced by the semiconductor industry is that current photolithography tools are constrained to transfer patterns with feature sizes larger than the "" which is roughly one half of the wavelength of the light used to project the pattern. 听 听 听 Although the industry is exploring a new generation of tools using extreme ultra-violet light to further reduce wavelength and feature size, it is widely expected that no further reductions听are possible. 听Inspired by a super-resolution microscopy technique known as听, we are showing that it is indeed possible to write features whose dimensions are substantially smaller than the diffraction limit. 听Critically, our technique uses the materials and large-area听exposures currently employed by existing semiconductor manufacturing.
The goal of is to rapidly transfer听a two-dimensional pattern onto a surface听that will then be further processed using etch or deposition tools.听First, the surface is coated in a thin film of light-sensitive resin, called photoresist.听听Next, this photoresist is exposed to a pattern of ultraviolet light created by a photomask. 听The听UV exposure initiates a chemical reaction within the resist, resulting in regions of different solubility.听听Submerging the exposed resist in a chemical developer, the undesired, high solubility regions are removed, leaving behind the projected pattern. 听Critically, the removal of photoresist is a nonlinear function of the applied UV energy dose. 听We have shown that this nonlinearity can be exploited to break the diffraction limit on feature size in single exposures covering large areas. 听听听Working at i-line (位=364nm), with standard novolak resists, we have demonstrated features as small as 50 nm. 听The processing has been developed and demonstrated听with an听interferometric lithography tool.听听Ongoing work focuses on adapting this to projection tools though the use of new mask technologies.
The team
Learn more
- D. B. Miller, A. M. Jones, R. R. McLeod, 鈥�,鈥� Journal of Micro/Nanolithography, MEMS and MOEMs 18,听013505, 2019.
- Miller, D. B, Jones, A. M, McLeod, R. R, "Super-resolution critical dimension limits of positive tone i-line photoresists," Advanced Fabrication Technologies for Micro/Nano Optics and Photonics XI, pp. 105440N, 2018
- Miller, D., Jones, A., McLeod, R. R, "," Frontiers in Optics, pp. FTh3D. 5, 2017. 听Emil Wolf Oustanding Paper Award winner.
- T. F. Scott, B. A. Kowalski, A. C. Sullivan, C.N. Bowman, R. R. McLeod,听, Science 324, 913-917, 2009.
- T.F. Scott, C. Kloxin, D. Forman, R. R. McLeod, C. Bowman,听, J. Mater. Chem 21, 14150-14155, 2011.
- Darren Forman, Doctor of Philosophy in Electrical Engineering,听, University of Colorado, 2014.
This work has been generously funded by
听 听
Sample results
Demonstration of super-resolution lithography using 364 nm to expose commercial photoresist. 听The 50 nm linewidth is significantly below the traditional diffraction limit.
An array of interference lithography exposures testing response versus exposure time. 听The color is due to diffraction. 听
Layout of the interference lithography tool including a refractive beam shaper and holographic grating used as as beam splitter.
align="none"
Our original material function. A diffraction-limited spot (a) at 473 nm creates initiating radicals via absorption by CQ. 听A Gauss-Laguerre "donut mode" (b) at 365 nm creates inhibiting radicals via absorption by TED. The resist polymerizes (c) only in the "donut hole" where initiation is not inhibited.