Line edge roughness (LER) is becoming an increasing issue as the feature size for lithographic features decreases. For chemically amplified resists (CARs) a number of causes have been attributed, but diffusion of photogenerated acids has been reported to be one of the most significant contributing factors. Our strategy has been to remove acid diffusion from the equation by investigating non-chemically amplified resists (non-CARs) for 193nm and EUV lithography.

The mechanism by which these resists function is through a molecular weight solubility switch, i.e. light interacts with the polymer resulting in chain scission of the backbone, which reduces the molecular weight of the polymer, making it more soluble in developer. Reports of poly(methylmethacrylate) (PMMA) as a non-CAR have shown that it can be patterned using EUV lithography to feature sizes as low as 22 nm with low LER. However, PMMA lacks the required sensitivity and etch resistance for use in manufacture. The low sensitivity of PMMA is inherent to its chemical structure. We have screened a range of chemical structures for their propensity to degrade at 13.5 nm / 92 eV and generated a predictive model that is able to screen structures in silico. One promising target that was identified using this model was substituted carbonates.

Figure 1. Comparison of experimentally and calculated (from structure property relationship model) determined stability indicies
Figure 2. Top down SEM images of EUVL patterned polycarbonates, showing (left) elbow features patterned to a resolution of 80 nm, and (right) line spaces at a half pitch of 50 nm and a critican dimension of 28.6 nm.

This program is supported by Intel Corp.


  • Intel – Dr Michael Leeson, Dr Todd Younkin and Dr Wang Yeuh and Dr Heidi Cao
  • IMEC – Dr Roel Gronheid; University at Albany – Prof Greg Denbeaux and Justin Waterman


  1. Jack, K.; Liu, H.; Blakey, I.; Hill, D.; Wang, Y.; Cao, H.; Leeson, M.; Denbeaux, G.; Waterman, J.; Whittaker, A. The Rational Design of Polymeric Euv Resist Materials by Qspr Modelling. Proceedings of SPIE-The International Society for Optical Engineering 2007, 6519, 65193Z.

  2. Whittaker, A. K.; Blakey, I.; Blinco, J.; Jack, K. S.; Lawrie, K.; Liu, H.; Yu, A.; Leeson, M.; Yeuh, W.; Younkin, T. Development of Polymers for Non-Car Resists for Euv Lithography. Proc. SPIE 2009, 7273, 727321.

  3. Blakey, I.; Yu, A.; Blinco, J.; Jack, K. S.; Liu, H.; Leeson, M.; Yeuh, W.; Younkin, T.; Whittaker, A. K. Polycarbonate Based Non-Chemically Amplified Photoresists for Extreme Ultraviolet Lithography. Proceedings of SPIE 2010, 7636, 763635.

  4. Yu, A.; Liu, H.; Blinco, J. P.; Jack, K. S.; Leeson, M.; Younkin, T. R.; Whittaker, A. K.; Blakey, I. Patterning of Tailored Polycarbonate Based Non-Chemically-Amplified Resists Using Extreme Ultraviolet Lithography. Macromolecular Rapid Communications 2010, accepted 9/4/2010.

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