We present the characterization of dyed doped/modified Epocore resist (Microresist Technology, Germany) with three commercially-available dyes (Proquimac Color, Spain). After being doped with lilac, red and yellow dyes in a 1:2500 ratio (dye:Epocore, w:w), an exposure dose test was performed. The obtaining lithographic performance is similar to the non-doped Epocore. Hence, the inclusion of the dye does not affect either the absorbance in the UV range or the structurability of the polymer. In a second step, this polymer is used to define integrated absorbance filters, by using standard soft lithography techniques. Concretely, four different filter lengths have been fabricated. The highest absorbance value was found with filter length of 500 μm, with stop-bands at concrete regions of the visible spectra: -5.17 dB@592.0 nm for lilac dye, -3.30 dB@531.0 nm for red dye, and -4.40 dB@496.8 nm for yellow dye. Additionally, a non-zero passband penalty (-0.75 dB) in the red filter is observed. Moreover, bleaching of the filters was also tested by a continuous exposure to UV light. The doped polymer retains 96% of its filtering properties after a dose close to 40.000 J/cm2.
- Resist and resist processing
- Absorbance filters