Development and Characterization of an Integrated Thick Resist Film Processing Tool D. 1 Goustouridis , 1 Raptis , 2 Valamontes , I. E. I. 1 1,4 N. Tsikrikas , M. Chatzichrisitidi 3 Karanikas , 1Institute 4 of Microelectronics, NCSR ‘Demokritos’, Athens, 15310 Greece 2 Department of Electronics, TEI of Athens, 12210 Aegaleo, Greece 3 Datec Electronics S.A. Dorieon 28, Athens 11852, Greece Chemistry Department, University of Athens, Zografou 15771, Greece E-mail: [email protected] Introduction: In micromachining – microsystems applications the patterning of resist films with thickness of several tens of microns is common. The processing conditions of such thick resist films are quite different from the ones used in mainstream microelectronics. For example in the case of SU-8 the Post Apply Bake (PAB) should be done in two different temperatures. In this direction several processing tools have been developed, e.g. . In addition, for the preparation of thick films, more than one spin coating steps are required. In the present work a thick resist film processing tool capable to resist application, PAB and PEB is presented and applied in case of the UV-patterning of thick epoxy based resist films. Spreader set-up Results Wafer Uniformity Spreader Computer software 24.5μm 24.9μm 99.7μm 100.6μm 99.3μm 100.1μm 102.3μm 101.8μm 102.8μm 24.6 μm Photo of the spreader set-up a) Casting Solvent Evaporation Int. Signal (a.u) 1200 Two epoxy based CARs capable to form high viscosity solutions were investigated. A) TADEP resist [2,3] with Propylene Glycol Methyl Ether Acetate (PGMEA) as casting solvent and B) SU-8 2015 with Gamma Butyrolactone (GBL). TADEP was used for 25μm thick films and SU-8 for 100 μm thick films (this SU-8 formulation is used for max. 40μm thick films with spin coating). Processing Conditions Micrometers Adjustment Exposure (365nm) PEB Development Final Thickness TADEP 60°C/30min + 100°C/60min SU-8 65°C/5min + 95°C/20min 100 μm 200 μm 1100 mJ/cm2 95°C/8min 250 mJ/cm2 65°C/2min + 95°C/10min PGMEA/12min 99.4 μm TMAH/10min 25.6 μm 140 1000 800 120 600 400 40 60 80 100 Time (s) 1000 Experimental procedure PAB 1200 80 60 800 SU-8 2015 1200 1000 90 800 600 60 1300 100 400 1200 40 20 600 0 1000 2000 3000 4000 5000 0 6000 120 Temperature (oC) TADEP 1400 160 1400 200 80 1100 60 1000 300 0 450 Temperature (oC) Blade Inside the spreader c) Wafer uniformity for a) TADEP resist b, c) SU-8 resist. The wafer uniformity maximum deviation is 1.4% and the spreader repeatability is 1.9% Interferometer module Wafer holder and hot plate 101.9 μm b) Temperature (oC) Leveling mechanism 100.6 μm Int. Signal (a.u) Computer communication port 24.6μm 97.9μm Int. Signal (a.u.) Temperature controller 24.3μm Int. Signal (a.u.) Leveling mechanism 30 600 Time (sec) 0 200 400 Time (s) 600 800 1000 1200 1400 1600 1800 2000 Time (sec) TADEP resist has PGMEA (b.p. 146°C) as casting solvent whereas SU-8 has GBL (b.p. 205°C). TADEP shows a high evaporation in the first 5min (~100nm/sec), then the evaporation rate decreases and when the temperature reaches 100°C the rate initially increases and then is very low. SU-8 has a slower evaporation rate in the beginning (~30nm/sec) at 65°C that decreases with time (~12nm/sec) and then it increases again with temperature elevation (~35nm/sec) and after 3min at 95°C it is very low. Lithographic Results TADEP resist. Top-down optical micrograph. Line-width is 5 μm and the resist thickness is 25 μm. SU-8 resist. Top-down optical micrograph. 10 μm squares and circle diameter. The resist thickness is 100 μm. Conclusions: In the present work, a thick resist film processing tool capable of resist application and PAB was presented and applied in case of the UV-patterning of thick resist films. This particular tool could be equipped with UV-exposure capability in the future allowing the complete processing of the thick resist films except the development-drying steps that allowing the penetration of micromachining technology in research labs without easy access in conventional lithography equipment. References 1. G. Bleidiessel, G. Gruetzner, F. Reuther, S. Fehlberg, B. Loechel, A. Maciossek Microelectron. Eng. 41-42 433(1998) 2. M. Chatzichristidi, I. Raptis, P. Argitis J. Everett, J. Vac. Sci. Technol. B 20, 2968 (2002) 3. M. Chatzichristidi, E. Valamontes, P. Argitis, I. Raptis, J.A. van Kan, F. Zhang, F. Watt Microelectron. Eng. 85 945 (2008) Acknowledgments: This work was partially financially supported by Greek Secretariat for Research & Technology through the 05-NONEU467 (Greece-Singapore project).