i-line grayscale exposure using ma-P 1200G resist series for industry applications

Introduction i-line grayscale exposure using ma-P 1200G resist series for industry applications — Sebastian Schermera, Andrew Zanzalc, Patrick Reynoldsc, Stephen DeMoorc, Christian Helkea,b, Jeremy Bielingb, Anja Voigtdand Danny Reutera,b aFraunhofer Institute for Electronic Nano Systems, Chemnitz, GERMANY bUniversity of Technology Chemnitz, Center for Micro and Nano Technologies (ZfM), Chemnitz, GERMANY cBenchmark Technologies, Massachusetts, USA dMicro Resist Technology (MRT) GmbH, Berlin, GERMANY ACKNOWLEDGEMENT This project has received funding from the European Union’s Horizon Europe research and innovation programme under grant agreement no 101137624. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor UKRI can be held responsible for them. The authors also would like to thank all involved colleagues of Fraunhofer ENAS and ZfM of Technical University of Chemnitz for their support. M.Sc. Sebastian Schermer — Group Lithography and Photonic Micro-/ Nanostructures Department Nano Device Technologies Tel. +49 371 45001-459 [email protected] Fraunhofer ENAS Technologie-Campus 3 / 09126 Chemnitz / Germany Characterization 2.5D structures can be achieved by using grayscale lithography, which can be done with maskless patterning technologies like electron beam (e-beam) or direct laser writing1,2. These technologies offer a high design flexibility, but the downside of these sequential exposures / direct writing tools are low writing speeds, which hampers scalability to high volume. To overcome those limitations and enable higher volume manufacturing,i-line wafer stepper with specialized grayscale (Benchmark Technologies) reticles is used within this work. ◼High throughput grayscale process with i-line wafer Stepper for different applications and specific customers needs ◼SEM-images (stage 45°) of fabricated structures in different resist thicknesses (Lenses, Pyramids, Slanted Gratings, Pixel Array, Needles) 5 µm 5 µm 5 µm 5 µm 10 µm 20 µm 5 µm 10 µm 10 µm 20 µm 10 µm 2 µm 2 µm 10 µm 5 µm 5 µm 10 µm 2 µm 100 µm 100 µm Project Partner - Process Development: Fraunhofer ENAS, Germany - Resist Development: Micro Resist Technology, Germany - Reticle Design: Benchmark Technologies, USA Experimental Processing Parameter Substrate preparation Dehydration bake: Oven, 30 min at 200 °C Spin -coating, resist 3.5 ml ma-P 1215G at 3000 rpm, 60 s, 1.8 µm film thickness 4.5 ml ma-P 1275G at 3000 rpm, 60 s, 8.1 µm film thickness Softbake ma-P 1215G:Hotplate, 90 s at 105 °C ma-P 1275G: Hotplate, 600 s at 105 °C Exposure NIKON NSR2205i11D i-line Stepper, various doses Development ma-P 1215G: No PEB; mr-D 526/S: 65 s, DI-W rinsing ma-P 1275G: No PEB; ma-D 532/S: 240 s, DI-W rinsing Mask Fabrication ◼6”X 6”X 0.25”Reticle designed on a 1 nm grid at 5x for writing on a variable shaped e-beam tool; gray level are modulated using half-toning technique3,4 ◼Writer grid and resolution capability allow for ~ 1900 gray levels for a 64 µm diameter lens design (at wafer scale) ◼Adapted reticle used contrast data from a previous grayscale reticle ◼Structure fidelity relies on known contrast curves; for structure transfer via etching also the contrast curve after etching is necessary Grayscale in Industry Applications i-line grayscale reticle based exposure has the advantage to offer high throughput and can be used in existing i-line tools in the industry: ◼Tuning the slope of sidewalls ◼Implementing different height level −Reducing Lithography/Etching Steps →Cost Reduction and New Design Possibilities References [1] Grushina, A. "Direct-write grayscale lithography." Advanced Optical Technologies 8.3-4, 163-169 (2019). [2] McKenna, C., et al. "Maskless direct write grayscale lithography for MEMS applications." 2010 18th Biennial University/Government/Industry Micro/Nano Symposium. IEEE, (2010). [3] Gan, O., et al. "Programmed resist sidewall profiles using subresolution binary grayscale masks for Si-photonics applications." Advanced Fabrication Technologies for Micro/Nano Optics and Photonics V. Vol. 8249. SPIE, (2012). [4] Heller, M., et al. "Grayscale lithography: 3D structuring and thickness control." Optical Microlithography XXVI. Vol. 8683. SPIE, (2013). Contrast Curves Fig. 1: Contrast Curves of a) ma-P 1215G with a resist thickness of 1.8 µm and b) ma-P 1275G with a resist thickness of 8.1 µm. Fig. 4: Tuned sidewalls in 8.1 µm ma-P 1275G. Fig. 2: SEM images of different structures in ma-P 1275G with 8.1 µm thickness. Fig. 3: SEM images of different structures in ma-P 1215G with 1.8 µm thickness. a) b) Fig. 5: a) Schematic view and SEM image of waveguide with out-of-plane mirror at both ends in 8.1 µm ma-P 1275G; b) Detail view of out-of-plane mirror. a) b) Photonic Applications Usable grayscale transition area Usable grayscale transition area Dose to clear Dose to clear