ZEP520A, fabricated and distributed by ZEON Corporation, is one of the most widely used positive-tone resists for electron-beam lithography (EBL), probably second only to PMMA. Compared to PMMA, it exhibits a higher sensitivity, making it more suitable for patterning large areas and/or high density designs. It also has high resolution (~20 nm), high contrast, and good dry-etch resistance, making it a preferred choice for those fabricating fine structures that require low edge roughness, such as Si photonic devices.
However, ZEP520A is also one of the most expensive EBL resist in the market. In order to reduce the cost of fabrication for nanoFAB users, CSAR 60 (AR-P 6200), fabricated and distributed by Allresist GmbH, was tested and validated. As can be seen in the side-by-side comparison below, CSAR 62 behaves almost exactly like ZEP520A, but at a lower material cost.
ZEP520A (left) CSAR 62 (right). Both were exposed at 30 kV with 150 μC/cm², and developed with ZED-N50 at room temperature for 20 s. Scale bars are both 5 μm.
More in-depth comparisons, including exposures at different acceleration voltages and development at different temperatures, can be found here. Essentially, CSAR 62 performed nearly identically to ZEP520A for the same process parameters. Another striking result during the tests was that the CSAR 62 film thickness was precisely measured via spectroscopic reflectometry (Filmetrics F50-UV), using the ZEP520A optical constants (n,k)—this is a strong indicator that both films are virtually the same, both physically and chemically.
Once the current stock of ZEP520A is depleted, users will no longer be able to purchase it from the nanoFAB. Instead, CSAR 62 (AR-P 6200.13) will be offered it its place. However, users still wishing to purchase their own ZEP520A from ZEON for use in the nanoFAB may continue to do so.
For more information about this resist and its usage, please contact Gustavo de Oliveira.
Documentation
