A New Class Of Resins For Deep Ultraviolet Photoresists

C. E. Osuch; K. Brahim; F. R. Hopf; M. J. McFarland; A. Mooring; C. J. Wu

doi:10.1117/12.963627

9 July 1986 A New Class Of Resins For Deep Ultraviolet Photoresists

C. E. Osuch, K. Brahim, F. R. Hopf, M. J. McFarland, A. Mooring, C. J. Wu

Proceedings Volume 0631, Advances in Resist Technology and Processing III; (1986) https://doi.org/10.1117/12.963627
Event: 1986 Microlithography Conferences, 1986, Santa Clara, United States

Abstract

As Bowden has pointed out in his recent discussion on high resolution lithography, conventional photoresists are not particularly suitable for use in the deep ultraviolet (DUV) regime.' The reasons for this are: (1) the novolac resin is a strong absorber at wavelengths shorter than 300 nm;2 and (2) the products produced upon irradiation of the photoactive compound (PAC) absorb in this region (which prevents the phenomenon known as "photobleaching" from occurring). Of these two difficulties the first appeared, to us, to be the more restrictive. Therefore we chose to investigate alternate resins, more transparent in the DUV region, to substitute for novolac. We initially sought to remain within the realm of the dissolution inhibition mechanism and to utilize conventional PAC's. Although it was possible to prepare resins having improved UV absorbtion characteristics (a maleimidestyrene copolymer will be discussed here) and to formulate positive acting resists from them, we found that the resists were not able to adequately form high resolution images with vertical wall profiles. Examples of this behavior are presented. Because of the apparent inability to obtain satisfactory wall profiles, we abandoned the methods based on the dissolution inhibition mechanism. We then elected to explore the so-called "chemical amplification" approach pioneered by Wilson, Ito, Frechet, and their coworkers. To this end, maleimide styrene copolymer was substituted on the nitrogen atom with the tertbutyloxy carbonyl group. This resin, upon application of heat, reverts to maleimide styrene via a process which is apparently catalyzed in the presence of acid. These observations led us to develop a photoresist based on a mixture of a photoacid and the N-blocked maleimide/styrene resin. Details of the performance of this resist are presented.

Citation Download Citation

C. E. Osuch, K. Brahim, F. R. Hopf, M. J. McFarland, A. Mooring, and C. J. Wu "A New Class Of Resins For Deep Ultraviolet Photoresists", Proc. SPIE 0631, Advances in Resist Technology and Processing III, (9 July 1986); https://doi.org/10.1117/12.963627

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