Portable conformable mask bilayer process

Deep-UV resists are used in two principal modes as surface resist in single layer mode, or as the thick planarizing layer in portable conformable mask (PCM) bilayer mode. In the single layer mode, the use of deep-UV resists provides improved resolution, while in the PCM mode, a deep-UV resist is used in combination with a conventional resist to make use of the wavelength selectivity of the two types of resists. The PCM process (Figure 5.47) first exposes and develops the conventional novolac-based thin top resist using a 436 nm masked exposure. A second full exposure is then made in the deep-UV, which is... 

FIGURE 5.47 Schematic of portable conformable mask (PCM) bilayer process. (PR, photoresist dUV, deep-UV). 

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