1. Are there resists for other film thicknesses available?
In general we offer ready–to-use resists for the film thicknesses given in the spin curves. Thinner film thicknesses can be obtained by diluting the resists with the recommended thinner (solvent mixture).
We guarantee unchanged resist properties of the ready-to-use resists before the expiration date and by storage of the resists at the recommended conditions.
2. Can the resists be used for film preparation by spray coating?
In general the resists were designed for film preparation by spin coating. Film preparation by spray coating should also be possible, but up to now we are not able to give guidelines for this method.
3. For which applications do you recommend ma-N 400 or ma-N 1400?
Both resist series differ in their available film thickness regions, their sensitivity, in the thermal stability of the resist patterns and in the profile of the undercutted patterns. For pattern transfer processes via PVD (physical vapour deposition) and lift-off the ma-N 400 is recommended for pattern transfer by evaporation or by sputtering with low thermal impact. ma-N 1400 is recommend for sputtering processes at higher temperatures.
4. What is the difference between the single layer negative resist systems ma-N 400 or ma-N 1400 and a bilayer system, e.g. LOR and a positive tone photoresist, for a pattern transfer process via lift-off, and what is the possible resolution of both systems?
For the lithographic processing of the single layer resist systems ma-N 400 and ma-N 1400 less processing steps are necessary than for the bilayer system. The thermal stability of the ma-N 1400 is higher than that of the ma-N 400 series and of the bilayer system. In general, the resolution of both systems, the single layer and the bilayer system is comparable, but the resolution of the bilayer system can be slightly better.
For clean lift-off processing, the resist film thickness should be 1.5 to 2 times that of the metal layer to be deposited.
5. What is the difference between the material systems Epocore/ Epoclad and Ormocore/ Ormoclad for the manufacture of polymer based waveguides?
Both material systems are composed of different chemical components. For a detailed comparison of both material systems, of the lithographic processing and the properties of the manufactured waveguides see the attached pdf document.
6. Which adhesion promoter is suitable for which substrate (silicon Si, silicondioxide SiO2, glass, copper Cu or gold Au) and resist material?
In any case the substrates have to be free of impurities and moisture. They should be baked at 200 °C and cooled down to room temperature immediately before coating. Alternatively, oxygen or ozone plasma cleaning is recommended.
For improving the resist film adhesion to semiconductor substrates, e.g. FR 4, or for applying multiple coating and patterning of resist films, e.g. with Epoclad/ Epocore/ Epoclad, a short oxygen plasma activation step is recommended.
7. How can strongly crosslinked ma-N 2400, ma-N 400 and ma-N 1400 resist films be removed?
The ready-to-use removers mr-Rem 660 (NMP based), mr-Rem 400/ 500 (NMP free), mr-Rem 700 (NMP and NEP free), ma-R 404/ S (strongly alkaline) and aceton are recommended for the remove of the resists. Using mr-Rem 660 or mr-Rem 400 the remove can be done ultrasonic-assisted and at higher temperatures between 40 and 60 °C.
For the residue-free remove of during the pattern transfer process strongly crosslinked ma-N 2400, ma-N 400 or ma-N 1400 films an oxygen plasma step is highly recommended.
8. Are there data available for the high etch resistance of the ma-N 2400, ma-N 400 and ma-N 1400 series?
In general the resists exhibit a good etch resistance.
The series gave good results in dry etching (e.g. with CF4 or high dry density SF6/ O2 plasma). The etch rates of the resists strongly depend on the etching conditions. The etching equipment has an influence, the amount of open wafer surface to be etched, the etch gas composition and all other parameters such as pressure, temperature or voltage.
If required, the etch resistance and thermal stability of the resist can be increased by applying a higher prebake temperature or a longer prebake time. The developing time will increase in this case. Hardbaking of the developed resist patterns is also recommended for an increase of the etch resistance and the thermals stability.
In general the etch selectivity can be assume for the most etch applications as 1 to 1.
We cannot deliver any more detailed data. This is nearly impossible since etching conditions can differ very much from lab to lab.
9. Is there a resist available which is suitable for pattern transfer via HF-etch?
HF etching is a bit demanding. HF doesn´t attack the resist. But it can diffuse through and under the photoresist and lift it from below causing bad adhesion of the resist on the substrate. This is why a film thickness as high as possible should be chosen, and the resist should be hardened (stronger prebake + hardbake). Nevertheless it depends strongly on the HF concentration and the etch time how acceptably the photoresist sustains the etching.
10. Is there a developer that doesn´t corrode Al and Al containing substrates, respectively?
We recommend to apply metasilicate based developers for processing of the ma-N series resists on Al and Al containing substrates. You can purchase the developers from our company. Metasilicate practically doesn´t corrode Al.
11. How can be avoided the electrostatic charging effect during e-beam lithography when resist layers are exposed on insulating substrates?
There are some recommendations to avoid or reduce the electrostatic charging during e-beam exposure on insulating substrates.
1: Deposition of a thin metal layer as top coat layer:
Coat a thin metal layer (e.g. Al or Cr, ~ 10 – 20 nm) on top of the resist layer. The thin metal layer has to be removed after exposure and prior development.
In the case when using ma-N 2400 resist, the developer is aqueous alkaline based and the thin Al layer (which is soluble in weak alkaline solutions) is dissolved or removed during development step.
Thin Cr layer can be removed using e.g. Chrome Etch 18 solution.
2: Coat of a thin conductive layer.
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[Mohamed_1] K. Mohamed et al “Surface charging suppression using PEDOT/PSS in the fabrication of three dimensional structures on a quartz substrate” Microelectronic Engineering Vol. 86 (2009) 535 - 538”
12. Is there any literature available about the use/ processing or application of the resists ma-N 400, ma-N 1400, ma-N 2400, mr-EBL 6000, Epocore/ Epoclad or mr-DWL?
[Bilenberg] B. Bilenberg, M. Schøler, P. Shi, M. S. Schmidt, P. Bøggild, M. Fink, C. Schuster, F. Reuther, C. Gruetzner, A. Kristensen „Comparison of high resolution negative electron beam resists” J. Vac. Sci. Technol. B 24(4) (2006) 1776
[Blideran] M.M. Blideran, M. Häffner, B.-E. Schuster, C. Raisch, H. Weigand, M. Fleischer, H. Peisert, T. Chassé, D.P. Kern „Improving etch selectivity and stability of novolak based negative resists by fluorine plasma treatment” Microelectronic Engineering 86 (2009) 769–772
[Cardenas] J. Cardenas, C. B. Poitras, J. T. Robinson, K. Preston, L. Chen, M. Lipson “Low loss etchless silicon photonic waveguides” Optics Express Vol. 17, No 6 (2009) 4752
[Chen] S. C. Chen, Y. C. Lin, J. C. Wu, L. Horng, C. H. Cheng „Parameter optimization for an ICP deep silicon etching system” Microsyst Technol (2007) 13: 465–474
[Elsner_1] H. Elsner, H.-G. Meyer, A. Voigt, G. Gruetzner “Evaluation of the ma-N 2400 series DUV photoresists for the electron beam exposure“ Microelectron. Eng. 46 (1999), 389–392
[Elsner_2] H. Elsner, H.-G. Meyer “Nanometer and high aspect ratio patterning by electron beam lithography using simply DUV negative tone resists” Microelectronic Engineering Vol. 57-58 (2001), 291 - 296
[Gondarenko] A. Gondarenko, J. S. Levy, M. Lipson “High confinement micron-scale silicon nitride high Q ring resonator” Optics Express Vol. 17, No. 14 (2009) 11366
[Konijn] M. Konijn, M.M. Alkaisi , R.J. Blaikie “Nanoimprint lithography of sub-100 nm 3D structures” Microelectronic Engineering 78–79 (2005) 653–658
[Mohamed_2] K. Mohamed, M. M. Alkaisi, R. J. Blaikie “A Three-Dimensional Ultraviolet Curable Nanoimprint Lithography (3D UV-NIL)” American Institute of Physics (AIP) Conf. Proc. 1151, (2009) 114
[Verhagen] E. Verhagen, A. Polman, L. (Kobus) Kuipers "Nanofocusing in laterally tapered plasmonic waveguides” Optics Express Vol. 16, No. 1 (2008) 45
[Voigt_1] A. Voigt, H. Elsner, H.-G. Meyer, G. Gruetzner “Nanometer patterning using ma-N 2400 series DUV negative photoresist and electron beam lithography“ Proc. SPIE 3676 (1999) 485–491
[Yu] Q. Yu, S. Braswell, B. Christin, J. Xu, P. M. Wallace, H. Gong, D. Kaminsky “Surface-enhanced Raman scattering on gold quasi-3D nanostructure and 2D nanohole arrays” Nanotechnology 21 (2010) 355301 (9pp)
ma-N 400/ ma-N 1400:
[Voigt_2] A. Voigt, G. Gruetzner, E. Sauer, S. Helm, T. Harder, S. Fehlberg, J. Bendig „A series of AZ-compatible negative photoresists“ Proc. SPIE 2348 (1995) 413–420
[Voigt_3] A. Voigt, M. Heinrich, K. Hauck, R. Mientus, G. Gruetzner, M. Töpper, O. Ehrmann „A Single Layer Negative Tone Lift-Off Photo Resist for Patterning a Magnetron Sputtered Ti/Pt/Au Contact System and for Solder Bumps“ Microelectron. Eng. 78 – 79 (2005) 503 - 508
[Goeppl] M. Goeppl, A. Fragner, M. Baur, R. Bianchetti, S. Filipp, J. M. Fink, P. J. Leek, G. Puebla, L. Steffen, A. Wallraff „Coplanar Waveguide Resonators for Circuit Quantum Electrodynamics” J. Appl. Phys. 104, 113904 (2008)
[Lysko] J. M. Lysko, B. Latecki, M. Nikodem „Gas micro-fow-metering with the in-channel Pt resistors” J. of Telecommunications & Information Technology (2005) 98
[Figi] H. Figi, M. Jazbinsek, C. Hunziker, M. Koechlin, P. Guenter „Electro-optic single-crystalline organic waveguides and nanowires grown from the melt” Optics Express Vol. 16, No. 15 (2008) 11310
[Guo] H.C. Guo, D. Nau, A. Radke, X.P. Zhang, J. Stodolka, X.L. Yang, S.G. Tikhodeev, N.A. Gippius, H. Giessen “Large-area metallic photonic crystal fabrication with interference lithography and dry etching” Appl. Phys. B 81 (2005) 271–275
[Ceyssens] F. Ceyssens, M. Driesen, K. Wouters, R. Puers, K.U. Leuven „A low-cost and highly integrated fiber optical pressure sensor system” Sensors and Actuators A 145–146 (2008) 81–86
[DeDockera] H.W.J.A. De Doncker, T. Guan, M. Driesen, R. Puers "Biaxial and Uniaxial Epoxy Accelerometers” Procedia Chemistry 1 (2009) 572–575
[Driesen] M. Driesen, K. Wouters, R. Puers „Etch rate optimization in reactive ion etching of epoxy photoresists” Procedia Chemistry 1 (2009) 796–799
[Gijsenbergh] P. Gijsenbergh, K. Wouters, K. Vanstreels, R. Puers “Determining the physical properties of EpoClad negative photoresist for use in MEMS applications” J. Micromech. Microeng. 21 (2011) 074001 (6pp)
[Himmelhuber] R. Himmelhuber, M. Fink, K. Pfeiffer, U. Ostrzinski, A. Klukowska, G. Gruetzner, R. Houbertz, H. Wolter „Innovative materials tailored for advanced microoptic applications“ Proc- SPIE Vol. 6487 (2007)
[Wouters_1] K. Wouters, R. Puers "Determining the Young’s modulus and creep effects in three different photo definable epoxies for MEMS applications” Sensors and Actuators A 156 (2009) 196–200
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[Cadarso] V. J. Cadarso, K. Pfeiffer, U Ostrzinski, J. B. Bureau, G. A. Racine, A. Voigt, G. Gruetzner, J. Brugger “Direct writing laser of high aspect ratio epoxy microstructures” J. Micromech. Microeng. 21 (2011) 017003 (6pp)