Negative photomasks

Figure 4.11 Example of rewritable optical memory written image (left) and negative photomask used to record this image (right) [10], Reproduced from V. Chigrinov, H.-S. Kwok, H. Takada, and H. Takatsu, Photoaligning by azo-dyes physics and applications. Liquid Crystals Today 4, 1 (2005), International Liquid Crystal Society...

C The Epoxy Resists. The first negative tone electron beam resist materials with useful sensitivity were based on utilizing the radiation chemistry of the oxirane or epoxy moiety. The most widely used of these materials, COP (Figure 32) is a copolymer of glycidyl methacrylate and ethyl acrylate and was developed at Bell Laboratories (43,44). COP has found wide applicability in the manufacturing of photomasks. The active element... 

The surface characteristics of a microfluidic channel are very important in determining the flow in electrokinetically driven systems. In electrokinetically driven systems, the bulk flow is created by movement of the mobile diffuse layer near the channel wall/solution interface that is termed electroosmotic flow (EOF). The EOF is dependent on the surface of the microchannel walls. Roberts et al. demonstrated the generation of EOF on laser-ablated polymer substrates for the first time, using the parallel processing mode with a photomask and an ArF excimer laser at 193 nm [17]. A variety of polymer substrates such as polystyrene, polycarbonate, cellulose acetate, and poly(ethylene terephthalate) (PET) were ablated to fabricate microfluidic channels. The laser ablation process alters the surface chemistry of the machined regions and produced negatively charged. 

Negative mould fabricated by exposure to UV light through a photomask and developed in a developer solution... 

In panels (b) and (c) of fig. 3, the assumption has been made that a positive photoresist is used, i. e. a photoresist whose exposed portions are removed during development. As we will see, negative resists can be used as well. In this case, the transparent and opaque structures on the photomask have to be reversed. 

Fig. 13.1 a Chrome on quartz hard photomask, b Schematic illustration of photoresist (purple layer) exposure to UV light through a quartz-chrome hard mask. Exposure of positive resist (fe ) and negative resist (right) followed by resist removal and subsequent silicon dioxide (white layer) etching to selectively expose the silicon substrate (blue layer)... 

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