A COMPARATIVE STUDY ON THE PHOTORESIST PATTERNING OF GLASS AND SILICON WITH MICROHOLES VIA MASKLESS PHOTOLITHOGRAPHY

Year 2022, Volume: 3 Issue: 2, 84 - 90, 15.12.2022

Furkan Güçlüer , Filiz Keleş

https://doi.org/10.55696/ejset.1150239

Abstract

Maskless photolithography, a useful tool used in patterning the photoresist which acts as a mask prior to the actual etching process of substrate, has attracted attention mainly due to the taking advantage of reducing cost because of not requiring a preprepared mask and freedom in creating the desired pattern on any kind of substrate. In this study, we performed the positive photoresist patterning with microstructures on both glass and silicon substrates via maskless photolithography. Specifically, we examined the discrepancies between the transparent (glass) and reflective (silicon) substrates even though the photolithographic process has been carried out under the same conditions. Since the positive photoresist patterning was the subject of this study, we could successfully produce the microholes with almost circular shapes and properly placed in squarely packed on both substrates as confirmed by optical microscopy and profilometer mapping measurements. We observed additional rings around the holes when silicon was used as substrate while very clear microholes were obtained for glass. Besides, the number of the rings increased when the writing speed of laser (velocity) reduced. We claim that these important findings can be attributed to the standing wave effect phenomenon which results from the multiple reflections through the semi-transparent photoresist coated on the reflective surface of the polished silicon. In brief, we reveal an important conclusion, in this study, based on the differences in formation of the microholes only due to the substate preference while all the photolithographic process parameters are kept the same.

Keywords

Maskless photolithography, positive photoresist, microholes, glass, silicon, standing wave effect

References

• M. Sun et al., "Broad-band three dimensional nanocave ZnO thin film photodetectors enhanced by Au surface plasmon resonance," Nanoscale, vol. 8, no. 16, pp. 8924-8930, 2016.
• H. N. Pham et al., "The enhancement of visible photodetector performance based on Mn doped ZnO nanorods by substrate architecting," Sensors and Actuators A: Physical, vol. 311, p. 112085, 2020.
• K.-S. Han, J.-H. Shin, W.-Y. Yoon, and H. Lee, "Enhanced performance of solar cells with anti-reflection layer fabricated by nano-imprint lithography," Solar Energy Materials and Solar Cells, vol. 95, no. 1, pp. 288-291, 2011.
• C. López‐López et al., "Multidirectional light‐harvesting enhancement in dye solar cells by surface patterning," Advanced Optical Materials, vol. 2, no. 9, pp. 879-884, 2014.
• Y. Wang et al., "Maskless inverted pyramid texturization of silicon," Scientific Reports, vol. 5, no. 1, pp. 1-6, 2015.
• J. Sheu, H. Chou, W. Cheng, C. Wu, and L. Yeou, "Silicon Nanomachining by Scanning Probe Lithography and Anisotropic Wet Etching," in Materials & Process Integration for MEMS: Springer, 2002, pp. 157-174.
• S. H. Zaidi, D. S. Ruby, and J. M. Gee, "Characterization of random reactive ion etched-textured silicon solar cells," IEEE Transactions on Electron Devices, vol. 48, no. 6, pp. 1200-1206, 2001.
• A. Baram and M. Naftali, "Dry etching of deep cavities in Pyrex for MEMS applications using standard lithography," Journal of Micromechanics and Microengineering, vol. 16, no. 11, p. 2287, 2006.
• J. A. Corno, "Chemical and structural modification of porous silicon for energy storage and conversion," Georgia Institute of Technology, 2008.
• M. Z. Mohammed, A.-H. I. Mourad, and S. A. Khashan, "Maskless lithography using negative photoresist material: impact of UV laser intensity on the cured line width," Lasers in Manufacturing and Materials Processing, vol. 5, no. 2, pp. 133-142, 2018.
• J. Schober, J. Berger, C. Eulenkamp, K. Nicolaus, and G. Feiertag, "Thick film photoresist process for copper pillar bumps on surface acoustic wave-wafer level packages," in 2020 IEEE 8th Electronics System-Integration Technology Conference (ESTC), 2020: IEEE, pp. 1-7.
• I. Khandaker, D. Macintyre, and S. Thoms, "Fabrication of microlens arrays by direct electron beam exposure of photoresist," Pure and Applied Optics: Journal of the European Optical Society Part A, vol. 6, no. 6, p. 637, 1997.
• J. Koch et al., "Maskless nonlinear lithography with femtosecond laser pulses," Applied Physics A, vol. 82, no. 1, pp. 23-26, 2006.
• V. Starkov, E. Y. Gavrilin, J. Konle, H. Presting, A. Vyatkin, and U. König, "SU8 photoresist as an etch mask for local deep anodic etching of silicon," Physica Status Solidi (a), vol. 197, no. 1, pp. 150-157, 2003.
• M. Han, W. Lee, S.-K. Lee, and S. S. Lee, "3D microfabrication with inclined/rotated UV lithography," Sensors and Actuators A: Physical, vol. 111, no. 1, pp. 14-20, 2004.
• M.-C. Chou, C. Pan, T. Wu, and C. Wu, "Study of deep X-ray lithography behaviour for microstructures," Sensors and Actuators A: Physical, vol. 141, no. 2, pp. 703-711, 2008.
• C. A. Mack. "Semiconductor Lithography (Photolithography) - The Basic Process." http://www.lithoguru.com/scientist/lithobasics.html (accessed July 24, 2022).
• S. M. Karazi, I. U. Ahad, and K. Benyounis, "Laser Micromachining for Transparent Materials," 2017.
• S. Hava, J. Ivri, and M. Auslender, "Wavenumber-modulated patterns of transmission through one-and two-dimensional gratings on a silicon substrate," Journal of Optics A: Pure and Applied Optics, vol. 3, no. 6, p. S190, 2001.
• C. A. Mack, "Analytical expression for the standing wave intensity in photoresist," Applied Optics, vol. 25, no. 12, pp. 1958-1961, 1986.