Wet-etch PCM

Subsequently, other RIE PCM materials were used. They were selected either for their RIE characteristics or the feasibility of the deposition process. A list of these systems is shown in Table I. During this period, Hatzakis (79) developed a two-layer wet etch PCM system for e-beam exposure. Basically, a PMMA copolymer is spun on PMMA, or vice... 

Figure 14. Resist images of the two-layer copolymer wet-etch PCM system. A 0.4-jjLm thick copolymer layer was spun on 1.4 pm of PMMA. (Reproduced with permission from Ref. 19.)...

The interfacial behavior of the copolymer/PMMA two-layer wet etch PCM system is similar to the AZ/PMMA system because of an identical bottom layer and a similar solvent for the top layer. In this case, consideration of the interfacial layer leads one to avoid using completely mutually exclusive developers. The developer for the bottom planarizing layer should be chosen such that it also develops the top layer at an low dissolution rate so that the interfacial layer can be broken through during the second... 

Figure 41. Unsensitized and unexposed Ge-Se image that was anisotropi-cally wet etched using PMMA as the wet-etch PCM.

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