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micro resist technology GmbH

The most frequently asked questions about our products:

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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 during the expiration date and by storage the resists at the recommended storage 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 via evaporation and 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 slightly be better.

For clean lift-off processing, the film thickness should be 1.5 to 2 times that of the metal deposition layer.

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.

Summary in PDF »

6) Which adhesion promoter is suitable for which substrate (silicon Si, silicondioxide SiO₂, glass, copper Cu or gold Au) and resist material?

Product	Si	SiO2, glass	Au	Cu
ma-N 2400	HMDS	HMDS	-	-
ma-N 400	HMDS	HMDS	-	-
ma-N 1400	HMDS	HMDS	-	-
mr-UVL 6000	-	-	-	Omnicoat (optional)
mr-EBL 6000	-	-	-	Omnicoat (optional)
Epocore/ Epoclad	-	-	-	Omnicoat (optional)
XP mr-P 15 AV	-	-	-	-

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 (solvent based) and ma-R 404/ S (strongly alkaline) are recommended for the remove of the resists. Using mr-Rem 660 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.

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 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-P 15AV?
ma-N 2400:
a) 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
b) 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
c) H. Elsner, H.-G. Meyer: Microelectronic Engineering Vol.57-58 (2001), 291 - 296

ma-N 400/ ma-N 1400:
a) 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
b) 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. 69 (2004)

EpoCore/ EpoClad:
a) R. Himmelhuber, M. Fink, K. Pfeiffer, U. Ostrzinski, A. Klukowska, G. Gruetzner, R. Houbertz, H. Wolter „Innovative materials tailored for advanced microoptic applications“ SPIE Photonics West 20 -25 Januar 2007 San Josa California USA

XP mr-P 15 AV:
a) Anja Voigt, Marina Heinrich, Gabi Gruetzner “Characterization of new ultra thick chemically amplified positive tone photoresists suitable for electroplating application“ Proc. SPIE 5376 (2004), 915

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