The resists Atlas 46 S = AR-N 4600-10 and Atlas 46 R = AR-N 4650-10 are photoresists with negative effect and high layer thickness with extremely stable resist structures. In addition, AR-N 4650-10 is removable easily and thus very well suited for photolithographic and electro-plating applications. The characteristics of AR-N 4600-10 are comparable to those of SU-8.

The resists consist of poly[(o-cresyl glycidyl ether)-co-formaldehyde] in an organic solvent mixture with the main ingredient 1-methoxy-2-propyl-acetate (PGMEA) and various acid generators. Both resists are developed within a few seconds with the solvent mixtures AR 300–12 or AR 600-70. For a slower and higher-contrast development, AR 600-07 is suitable.

The layer thicknesses of both resists are adjusted to 10 µm at 1000 rpm, further layer thicknesses in the range of 100 nm up to 100  µm are available upon request. It is recommended to softbake on the hot plate at 65° 5 min over 3min ramp at 95 °C for 5 min.

Both resists can be structured by i-line or UV exposure. Prior to exposure, the substrates should be cooled down to room temperature. It is recommended to temper subsequently on the hot plate at 105°C – 110°C for about 2 min, to achieve cross-linking.

For a quick development of a few seconds (5 – 10 s), AR 300-12 or AR 600-70 is recommended. Developing for too long may cause an increase of dark erosion in the case of AR-N 4650-10. A suitable stopper is AR 600-60. The resist layers must be rinsed with DI-water and dried immediately after developing.

The sensitivity for a layer thickness of 10 µm is approximately 120 – 140 mJ/cm2 in broadband UV.

Fig. 1 and 2: Atlas 46S and Atlas 46R are very well suited for the generation of defined structures with vertical walls.

Atlas 46S can be structured at a wavelength of 365nm (i-line), but it is significantly more sensitive in the wavelength range of 250 – 320nm and nearly transparent at 405nm or respectively 436nm (h- or respectively g-line). By use of optimized PAG’s, the photosensitivity of the resist version SX AR-N 4610-10/1 can be significantly increased at 365nm:

Fig. 3: Overlap spectrum of a mercury vapor discharge lamp (blue line) and the absorption curve of SX AR-N 4610-10/1

The new special resist SX AR-N 4620-10/1 can even be structured in the wavelength range of 405 nm up to 436 nm.

The different absorption characteristics can be used to generate well-defined 3d structures:

Fig. 4: Process overview for the generation of three-dimensional architectures in the two-layer process with AR-N 4600-10 as bottom resist and SX AR-N 4610-10/1 or respectively SX AR-N 4620-10/1 as top resist

The process was applied successfully for the generation of bridged resist structures:

Fig. 5: 3d structures generated in two-layer process