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Positive photoresists with actinic dyes are used rather commonly on highly reflective topographies. Non-actinic dyes either by themselves or in combination with actinic dyes are recently becoming available in positive photoresist systems for level-to-level alignment purposes. It is known that actinic dyes decrease the photospeed of a given positive photoresist system, however their effect on the dissolution rate of the exposed/unexposed resist is more complicated. For example, it has been shown that hydrophobic dyes may, through surface effects, decrease the ability of the developer to wet the surface of the exposed resist, thereby decreasing the apparent photospeed of the resist. The above effects, caused by the presence of the dye in the resist, can make establishing a given process for these dyed resists extremely difficult. However, it can be shown that by using Development Rate Monitor (DRM) techniques, a process for dyed photoresists, with acceptable process latitude, can be more easily established. In this study, viable techniques are investigated via DRM methods. Some of the process parameters that have been considered in this study are: 1. Unexposed film thickness loss, contrast (gamma), critical dimensions (CD) and photospeed fluctuation(s) as a function of developer type/concentration. 2. Using the PROSIM©1 approach, relevant values from the above are used to consider their impact on the contrast of a given dyed resist system. 3. The effect of both actinic and non-actinic dyes, together and separately, in the same resist, is considered using the approaches described above. Any apparent synergism is compared and its effect on overall process latitude is reviewed. The results obtained for the DRM modeling of dyed resist processes in this study demonstrate the validity of the DRM procedure(s) and its relevance to day-to-day production requirements.
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