During development, a positive tone resist film is patterned by a removal of exposed areas, while unexposed areas are removed when negative resists are used. To achieve reproducible results, temperatures between 21 and 23 °C 0,5 °C for organic solvent developers (AR 600-50, -50, -56) and 0,5 °C for aqueous-alkaline developers (AR 300-26, -35, -40) are highly recommended.
Developer AR 600-50 is a solvent-based developer which was especially designed for copolymer films (AR-P 617). With this developer, the sensitivity of the e-beam resist is further enhanced.
Developer AR 600-55 is, just like the next AR 600-56 resist, also solvent-based. As high speed developer, AR 600-55 is preferably used for PMMA films (AR-P 630-670), if short development times for a high process throughput are desired. Copolymer films (AR-P 617), e.g. also as two-layer system PMMA/copolymer, can likewise be developed with this developer.
Developer AR 600-56 is slower than 600-55 and preferably used for PMMA films (AR-P 630-670), if high resolutions and a high contrast are desired despite prolonged development times. This developer is also suitable for copolymer films.
In contrast to novolac-based resists, the development of PMMA layers may be interrupted at any time and continued later without problems. To achieve a particularly high resolution, isopropanol or isopropanol/water developers may be used. In this case however, a higher dose is required for exposure.
For the development of exposed CSAR resist films, developers AR 600-546, 600-548, and 600-549 are suitable. As the weakest developer, AR 600-546 provides a broad process window with the highest contrast values > 15. If the stronger developer AR 600-548 is used, the sensitivity can be increased by a factor of 6 to 10 μC/cm² (30 kV). Developer AR 600-549 with intermediate strength renders CSAR 62 twice as sensitive as compared to AR 600-546, shows likewise no dark erosion, and the contrast is about 4. Especially for CSAR 62, the temperature of the developer plays a major role. Lower temperatures reduce the dark field loss, but also the sensitivity. Own tests may be necessary to determine the optimal conditions.
The aqueous-alkaline developer AR 300-40 product line comprises metal ion free developers of various concentrations. Usage of these developers minimises the possibility of metal ion contamination on the substrate surface as compared to the metal ion-containing developers (AR 300-46, AR 300-35). They exhibit excellent netting features and work, as aqueous-based solutions, without leaving any residues. Especially developer AR 300-46 and 300-47 are recommended (some also in dilutions) for the novolac-based e-beam resists AR-P 7000. Metal ion free developers are more sensitive to dilution variations. These developers should thus be diluted very carefully, if possible with scales and immediately prior to use in order to assure reproducible results.
Higher developer concentrations of AR 300-40 formally lead to a higher photosensitivity for positive resist developer systems, resulting in a minimum exposure intensity required, reduced development times, and a high process throughput. Possible disadvantages are however a higher dark field loss and also, in some cases, a low process stability (too fast). Negative coatings demand higher exposure doses for crosslinking at higher developer concentrations.
Low developer concentrations of AR 300-40 result in a higher contrast for positive resist films and reduce the resist removal in unexposed or only partly exposed areas even at longer development times. Mandatorily, however, the exposure intensity has to be increased. Negative resists require a lower exposure dose at lower developer concentrations (for cross-linking). The time needed for complete development is extended.
The service time of the developing bath of aqueous-alkaline developers for immersion development is limited by factors such as the process throughput and CO2 absorption from air. The throughput is dependent on the fraction of exposed areas. CO2 absorption is also caused by frequent opening of developer containers and results in a reduced development rate. CO2 does not play a role in the case of solvent developers, but a solvent mixture (e.g. AR 600-55, 600-56 AR) may nevertheless change due to the different evaporation numbers of the respective solvents. It is thus also recommended to rather replace the developer in doubt.
Overview E-beam FAQs