A Design of Anisotropic Wet Etching System to Reduce Hillocks on Etched Surface of Silicon Substrate

Authors: Alonggot Limcharoen Kaeochotchuangkul, Pathomporn Sawatchai

Abstract:

This research aims to design and build a wet etching system, which is suitable for anisotropic wet etching, in order to reduce etching time, to reduce hillocks on the etched surface (to reduce roughness), and to create a 45-degree wall angle (micro-mirror). This study would start by designing a wet etching system. There are four main components in this system: an ultrasonic cleaning, a condenser, a motor and a substrate holder. After that, an ultrasonic machine was modified by applying a condenser to maintain the consistency of the solution concentration during the etching process and installing a motor for improving the roughness. This effect on the etch rate and the roughness showed that the etch rate increased and the roughness was reduced.

Keywords: Anisotropic wet etching, wet etching system, Hillocks, ultrasonic cleaning.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.3566383

References:

[1] K. P. Rola and I. Zubel, "45° micromirrors fabricated by silicon anisotropic etching in KOH solutions saturated with alcohols," 2011 International Students and Young Scientists Workshop "Photonics and Microsystems", pp. 110-114, 2011.
[2] K. P. Rola, "Anisotropic etching of silicon in KOH + Triton X-100 for 45° micromirror applications," Microsystem Technologies, vol. 23, no. 5, pp. 1463-1473, 2017.
[3] Tang B., Pal, P., Gosalvez M. A., Shikida M., Sato K., Amakawa H. & Itoh S. (2009). Ellipsometry study of the adsorbed surfactant thickness on Si {1 1 0} and Si {1 0 0} and the effect of pre-adsorbed surfactant layer on etching characteristics in TMAH. Sensors and Actuators A: Physical, 156(2), 334-341.
[4] Marc J. Madou, Manufacturing Techniques for Microfabrication and Nanotechnology, Taylor & Fracis Group, 2011.
[5] Yang C.-R., Chen P.-Y., Chiou Y.-C. & Lee R.-T. (2005). Effects of mechanical agitation and surfactant additive on silicon anisotropic etching in alkaline KOH solution. Sensors and Actuators A: Physical, 119(1), 263-270.
[6] Xu Y. W., Michael A., & Kwok C. Y. (2011). Formation of ultra-smooth 45° micromirror on (100) silicon with low concentration TMAH and surfactant: Techniques for enlarging the truly 45° portion. Sensors and Actuators A: Physical, 166(1), 164-171.
[7] Limcharoen A., Pakpum C., Witit-anun N., Chaiyakun S., & Limsuwan P. (2012). An Alternative Design of Light Delivery System for Heat-Assisted Magnetic Recording Applied Mechanics and Materials, 117-119, 712-716.
[8] Qingbin Jiao, Xin Tan, Jiwei Zhu, Shulong Feng & Jianxiang Gao. (2016). Effects of ultrasonic agitation and surfactant additive on surface roughness of Si (1 1 1) crystal plane in alkaline KOH solution. Ultrasonics Sonochemistry, 31, 222-226.
[9] Pakpum C., & Pussadee N. (2015). Design of Experiments for (100) Si Vertical Wall Wet Etching Using Sonicated NaOH Solution Applied Mechanics and Materials, 804, 12-15
[10] Pakpum C. (2015). Wet Etching Technique to Reduce Pyramidal Hillocks for Anisotropic Silicon Etching in NaOH/IPA Solution Key Engineering Materials, 659, 681-685.
[11] Oliver Powell & Barry Harrison. (2001). Anisotropic etching of {100} and {110} planes in (100) silicon. Journal of Micromechanics and Microengineering, 11(3), 217-220.
[12] Shinmo An, Seung Gol Lee, Se-Guen Park, El-Hang Lee & Beom-Hoan O. (2014). Efficacy of low etch rate in achieving nanometer-scale smoothness of Si (1 0 0) and (1 1 0) plane surfaces using KOH and KOH/IPA solutions for optical mold applications. Sensors and Actuators A: Physical, 209, 124-132.
[13] Krzysztof P. Rola & Irena Zubel. (2011). 45° micromirrors fabricated by silicon anisotropic etching in KOH solutions saturated with alcohols 2011 International Students and Young Scientists Workshop "Photonics and Microsystems" 110-114.
[14] Krzysztof P. Rola, Konrad Ptasiński, Adrian Zakrzewski & Irena Zubel. (2014). Silicon 45° micromirrors fabricated by etching in alkaline solutions with organic additives. Microsystem Technologies, 20(2), 221-226.
[15] Theo Baum & David J Schiffrin. (1997). AFM study of surface finish improvement by ultrasound in the anisotropic etching of Si in KOH for micromachining applications. Journal of Micromechanics and Microengineering, 7(4), 338-342
[16] Jing Chen, Litian Liu, Zhijian Li, Zhimin Tan, Qianshao Jiang, Huajun Fang, Yang Xu & Yanxiang Liu. (2002). Study of anisotropic etching of (1 0 0) Si with ultrasonic agitation. Sensors and Actuators A: Physical, 96(2–3), 152-156.
[17] Guo Dung John Su, Chen Wei Chiu & Fukang Jiang. (2005). Vertical Micromirrors Integrated With Electromagnetic Microactuators for Two-Dimensional Optical Matrix Switches, IEEE Photonics Technology Letters, 17(9), 1860-1862.
[18] Bin Tang, Miguel A Gosalvez, Prem Pal, Shitaro Itoh, Hirotaka Hida, Mitsuhiro Shikida, Kazuo Sato. (2009). Adsorbed Surfactant Thickness on A Si Wafer Dominating Etching Properties of TMAH Solution. 2009 International Symposium on Micro-NanoMechatronics and Human Science, Nagoya, Japan.
[19] Wei Xu Y., Michael A., Yee Kwok C. & Ding Peng G. (2009). A novel technique of fabricating rear 45° micromirror for stacked die optical interconnect. Procedia Chemistry, 1(1), 1167-1170.
[20] Shankar Dutta, Md Imran, P. Kumar, R. Pal, P. Datta & R. Chatterjee (2011). Comparison of etch characteristics of KOH, TMAH and EDP for bulk micromachining of silicon (110). Microsystem Technologies 17(10-11):1621–1628.
[21] Irena Zubel, Malgozata Kramkowska & Krzysztof Rola. (2012). Silicon anisotropic etching in TMAH solutions containing alcohol and surfactant additives, Sensor and Actuator A: Physical, 178, 126-135.
[22] Anoop Prakash A B, J. Grace Jency &Manu C Mathew (2013). A Review of various Wet Etching Techniques used in Micro Fabrication for Real Estate Consumption. International Conference on Innovations In Intelligent Instrumentation, Optimization And Signal Processing “ICIIIOSP-2013”. International Journal of Computer Applications (0975 – 8887).
[23] Pakpum C., & Pussadee N. (2014). Fabrication of 90° Wall of {100} Plane on (100) Si by NaOH Solution Via Design of Experiments Advanced Materials Research, 909, 27-31.
[24] Krzysztof P. Rola, Konrad Ptasiński, Adrian Zakrzewski & Irena Zubel. (2014). Silicon 45° micromirrors fabricated by etching in alkaline solutions with organic additives. Microsystem Technologies, 20(2), 221-226.
[25] Ravinder Chutani, Nicolas Passilly, Jorge Albero, Maciej Baranski & Christophe Goreck. (2014). Deep Wet-Etched Silicon Cavities for Micro-Optical Sensors: Influence of Masking on {111} Sidewalls Surface Quality. Journal Of Microelectromechanical Systems, 23, (3), 585-590.
[26] Shinmo An, Seung Gol Lee, Se-Guen Park, El-Hang Lee & Beom-Hoan O. (2014). Efficacy of low etch rate in achieving nanometer-scale smoothness of Si (1 0 0) and (1 1 0) plane surfaces using KOH and KOH/IPA solutions for optical mold applications. Sensors and Actuators A: Physical, 209, 124-132.
[27] Pakpum C., & Pussadee N. (2015). Design of Experiments for (100) Si Vertical Wall Wet Etching Using Sonicated NaOH Solution Applied Mechanics and Materials, 804, 12-15
[28] Jianyu Fu, Junjie Li, Jiahan Yu, Ruiwen Liu, Junfeng Li, Weibing Wang, Wenwu Wang & Dapeng Chen (2018). Improving sidewall roughness by combined RIE-Bosch process, Materials Science in Semiconductor Processing, 83, 186-191
[29] R. K. Savkina, A. B. Smirnov, A. I. Gudymenko, V. A. Morozhenko, A. S. Nikolenko, M. I. Smoliy & T. G. Kryshtab. (2018). Silicon surface functionalization based on cavitation processing. Surface & Coatings Technolog, 343, 17-23.