Resist contrast

Contrast curves were obtained for each resist by measuring the thickness after development of a series of 1 mm by 5 mm exposed areas the exposure dose typically varied from approximately 1 mJ/ cm2 to several J/cm2 for the slowest resists. The majority of the resists were developed in ethyl acetate for 30 to 60 sec followed by a 20-sec rinse in 2-propanol. Initially, THF or a THF/2-propanol mixture was used as the developer they were replaced by ethyl acetate because it provided superior contrast. Resist sensitivity was taken to be the incident dose which resulted in 50% exposed thickness remaining after development, Dg 5. This is the standard convention for a negative resist. 

In contrast, resistance to attack by alkali hydroxide solutions is low, probably because the hydrous alumina is dissolved. Attack is accentuated if CO2 is also present, as can occur if the calcium aluminate concrete is in contact with Portland cement concrete and exposed to atmospheric CO2 (R48). For CAHjq, the following reactions occur ... 

In addition to S. pneumoniae, the viridans group of streptococci is also developing resistance to penicillin through the same mechanism, altered penicillin-binding proteins. In contrast, resistance has not developed in Streptococcus pyogenes, and both penicillins G and V are antibiotics of choice for systemic infections caused by this organism. 

Figure 3a. The effect of VBAiHS copolymer ratio on the resist contrast Resist composition VBAiHS copolymer (Mn = 12388), N-hydroxyimide-triflate, PGMEA.

Prevention of smface sidn formation. The results of DRM and DSC studies suggest that lowering the silylation ratio can be an effective approach to solve the surface skin problem, because lowering the ratio makes the induction period shorter probably due to reduction of the depletion effect and decrease in softened segments as shown in Figure 4. However, since it is necessary to keep the silylation ratio above a certain level in order to achieve a high contrast resist, there should exist some limitation for this approach. 

Figure 5 The contrast of a photoresist strongly affects the shape of the relief image formed from a given aerial image. Resists with high contrast will produce a more digital looking relief pattern from a degraded aerial image than will a low-contrast resist.

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