Dry developed resists

The latest addition to this list of dry developing resist materials is a contribution from IBM s San Jose Research Laboratory (66-67) that evolved from efforts to design positive-tone resist materials that incorporate chemical amplification. These efforts were stimulated by the fact that the quantum yield of typical diazoquinones of the sort used in the formulation of positive photoresists is 0.2 to 0.3 thus, three or four photons are required to transform a single molecule of sensitizer. This places a fundamental limit on the photo-sensitivity of such systems. 

Ito, H. Willson, G., "Chemical Amplification in the Design of Dry Developing Resist Materials," SPE Regional Technical Conference, Ellenville, New York, Nov. 1982. 

Methods 1 and 3 have been utilized in dry developed resist systems. To our knowledge, there are no resist systems commercially available that depend on post-exposure treatment other than the post-curing effect in negative electron beam resists mentioned earlier. Since such systems are still largely in the research phase we will not discuss them here but rather refer the reader to the literature for more detailed descriptions (44-50). 

A different approach has been used by Tsuda, Nakane and their collaborators (138,139) who showed that mixtures of poly(methylisopropenyl ketone) (PMIPK) containing a bisazide sensitizer such as 4,4 -diazodiphenyl sulfide or 4-methyl-2,6-di(4-azidobenzylidene) cyclohexanone function as negative dry-developable resists. It is claimed that the bisazide... 

Acid-Catalyzed Thermolytic Depolymerization of Polycarbonates A New Approach to Dry-Developing Resist Materials... 

These experiments confirm the potential advantage of combining low energy e-beam exposure with a dry develop resist scheme proposed in 1984 by G. N. Taylor, L. E. Stillwagon, and T. Venkatesan (5). At that time lack of a high resolution, low voltage e-beam exposure system prevented these workers from experimentally verifying the concept. 

The third class of dry-developable resists involves heating the exposed resist films in a development step. This development method does not require expensive etching tools, is therefore economical, and could alleviate the potential problem of exposure tool contamination associated with the self-developing resist systems. Many of the plasma-developable resist systems involving a relief-bake step, as discussed in Section 3.2.4.1, have the thermal development characteristics to a certain extent. In the thermally developable resist scheme, development is minimal during irradiation but completed to the substrate upon postbaking. 

Coopmans, F. Ronald, B. DESIRE a novel dry developed resist system. Proc. SPIE 1986, 631, 34-39. 

H. Ito and C.G. Willson, Chemical amplification in the design of dry developing resist materials, Technical Papers of SPE Regional Technical Conference on Photopolymers, p. 331, Society of Plastics Engineers, Brookfield, CT (1982). 

F. M. Houlihan and C. G. Willson, Acid Catalyzed Thermolytic Depolymerization of Polycarbonates A New Approach to Dry-Development Resist Materials, Chap. 11, in Polymers for High Technology, ACS Symposium Series 346, M. J. Bowden and S. R. Turner, Eds., Amer. Chem. Soc., Washington D.C. (1987)... 

With respect to single layer systems (conventional, ImRe, Promote and dry developable resists), we expect that computer programs that can simulate latent image formation and development processes will become of great importance in the near future. A better understanding of the mechanism which underlies the dissolution or etching of resist layers in a developer or plasma respectively is also crucial in order to achieve the ultimate resolution of single layer photoresists. In this respect, well chosen and perfectly defined polymers are required. 

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