Protective Coating Novolac Electra 92 (AR-PC 5091)
Conductive protective coating for novolac-based e-beam resists
Top layer for the dissipation of e-beam charges on insulating substrates
Characterisation
- as protective coating， this resist is not sensitive to light / radiation
- thin， conductive layers for the dissipation of charges during electron exposure
- coating of novolac-based e-beam resist AR-N 7000
- longterm-stable and cost-efficient alternative to Espacer
- easy removal with water after exposure
- polyaniline-derivative dissolved in water and IPA
Conductivity
Resistance measurements of AR-PC 5091.02 layers obtained after spin deposition. For thinner films， the resistance increases and the conductivity decreases.
Note: Novolac-based e-beam resists possess other surface properties than CSAR 62 or PMMA. AR-PC5091 was thus developed with a different solvent mixture. In all other respects however， the polymer composition of AR-PC 5090 and AR-PC 5091 is identical so that both resists are referred to as “Electra 92“.
Process parameters
REM dissipation of charges
50 nm lines written on glass at a pitch of 150 nm with AR-N 7520.07 and AR-PC 5091.02
Protective Coating Novolac Electra 92 (AR-PC 5091)
Process conditions
This diagram shows exemplary process steps for resist Electra 92 (AR-PC 5091.02) and e-beam resist AR-N 7520.07neu. All specifications are guideline values which have to be adapted to own specific conditions.
Processing instructions
The conductivity may be varied by adjusting the thickness with different rotational speeds. Thicker layers of 90 nm thus have a 2.5 times higher conductivity as compared to 60 nm thick layers. In the case that crack formation is observed after tempering of the protective coating， the tempering step can be omitted.
For the build-up of an even conductive layer， the substrate should be wetted with the resist solution before the
spin process is started.
Protective Coating Electra 92
Application examples for PMMA-Electra 92
Shelf live of Electra 92
Conductivity properties of differently aged Electra 92 batches
The conductivity was determined as a function of the measured temperature. At temperatures < 100 °C， both resists show a virtually identical conductivity. Electra 92 is thus characterised by a very long shelf life. Conductivity measurements up to a temperature of 160°C which were performed directly on a hotplate showed a large increase of the conductivity by a factor of 10 (see diagram). This fact is due to the complete removal of water from the layer. After a few hours of air humidity absorption under room conditions， the conductivity decreases again to
the initial value. In the high vacuum of e-beam devices， the water is also completely removed and the conductivity thus increases accordingly. This effect has been demonstrated in direct conductivity measurements under mediate vacuum conditions. Temperatures above 165 °C destroy the polyaniline irreversibly and no conductivity is observed any more
CSAR 62 on glass with Electra 92 for deriving
30 – 150 nm squares of CSAR 62 on glass
The combination of CSAR 62 with Electra 92 - AR-PC5090.02 offers the best options to realise complex ebeam structuring processes on glass or semi-insulating substrates like e.g. gallium arsenide. The excellent sensitivity and highest resolution of the CSAR are complemented harmoniously by the conductivity of Electra 92.
At a CSAR 62 film thickness of 200 nm， squares with an edge length of 30 nm could reliably be resolved on glass.
PMMA Lift-off on glass with Electra 92
200 nm squares produced with 2-layer PMMA lift-off
Initially， the PMMA resist AR-P 669.04 (200 nm thickness) was coated on a quartz substrate and tempered. The se cond PMMA resist AR-P 679.03 was then applied (150nm thickness) and tempered， followed by coating with Electra 92. After exposure， Electra 92 was removed with
water， the PMMA structures were developed (AR 600-56) and the substrate vaporised with titanium/gold. After a liftoff with acetone， the desired squares remained on the glass with high precision.
PMMA-Lift-off auf Glas mit Electra 92
Protective Coating Electra 92
Application examples for PMMA Electra 92
Electra 92 with HSQ on quartz
20 nm bars of HSQ， prepared on quartz AR-PC 5090.02
After a coating of Electra 92 on an HSQ resist， even this resist can be patterned on a quartz substrate with very high quality. The HSQ resist (20 nm thickness) was irradiated with the required area dose of 4300 μC/cm2.
SX AR-PC 5000/90.2 was subsequently completely removed within 2 minutes with warm water and no residues could be detected. After development of the HSQ resist， the structures with high-precision 20 nm bars remained.
Lift-off struktures on garnet
Lift-off structures on garnet (University of California， Riverside，Department of Physics and Astronomy)
Plasmonic structures on quartz
Silver nanoparticles on quartz， generated with AR-P 672.11 and ARPC 5090.02 (Aarhus University， Denmark)
Application examples for Novolac Electra 92
