Batch furnace CVD of pure boron layers on Si and GaN substrates for low-leakage-current diode fabrication
Main Article Content
Abstract
Boron deposition on both n-Si and n-GaN in the temperature range 250 – 500 °C has been shown to form diodes with low saturation currents, i.e., electron injection from the n-substrate into the B-layer was efficiently suppressed. Moreover, down to 3-nm-thick B-layers on Si were shown to form a material barrier to Al, opening the possibility of fabricating Au-free gates for GaN HEMTs. Several different chemical- and physical-vapor deposition (CVD/PVD) methods for depositing B have been studied for fabricating p⁺n-like Si diodes, called PureB diodes, all with comparable results. In this paper, the deposition of B-layers from diborane in a CVD batch furnace system is evaluated, particularly for use as a barrier material to enable Al-contacting of GaN diodes. These Al-B diodes could provide an option for fabricating CMOS-compatible, low-leakage current diodes at industrially attractive high throughput. The bulk B has high resistivity, which, combined with the fact that non-uniformities in the nm range are typical due to gas depletion along the furnace tube, gives uncontrollable, often high diode series resistance. A simulation study shows that Al-B could, nevertheless, be used as a gate stack in HEMTs for low-frequency power applications.
Keywords
boron, gallium-nitride, silicon, chemical vapor deposition, diodes, HEMTs, gate resistance
Article Details
References
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[2] X. Liu, L. K. Nanver, and T. L. M. Scholtes, Nanometer-thin pure boron layers as mask for silicon micromachining, J. Microelectromech. Syst., vol. 26, no. 6, pp. 1428-1434, Dec. 2017. https://doi.org/10.1109/JMEMS.2017.2764322;
[3] V. Mohammadi, L. Qi, N. Golshani, C. K. R. Mok, W. de Boer, A. Sammak, J. Derakhshandeh, J. van der Cingel, and L. K. Nanver, VUV/Low-Energy electron Si photodiodes with postmetal 400 °C PureB deposition, IEEE Electron Device Lett., vol. 34, no. 12, pp. 1545-1547, Dec. 2013. https://doi.org/10.1109/LED.2013.2287221;
[4] A. Šakic, L. K. Nanver, G. van Veen, K. Kooijman, P. Vogelsang, T. L. M. Scholtes, W. de Boer, W. H. A. Wien, S. Milosavljevic, C. T. H. Heerkens, T. Kneževic, and I. Spee, Versatile silicon photodiode detector technology for scanning electron microscopy with high-efficiency sub-5 keV electron detection, in IEDM Tech. Dig., pp. 31-4, Dec. 2010. https://doi.org/10.1109/IEDM.2010.5703458;
[5] F. Sarubbi, L. K. Nanver and T. L. M. Scholtes, High effective gummel number of CVD boron layers in ultrashallow p⁺n diode configurations, IEEE Trans. on Electron Devices., vol. 57, no. 6, pp. 1269-1278, Jun. 2010. https://doi.org/10.1109/TED.2010.2045672;
[6] T. Kneževic, X. Liu, E. Hardeveld, T. Suligoj, and L. K. Nanver, Limits on thinning of boron layers with/without metal contacting in PureB Si (Photo)diodes, IEEE Electron Device Lett., vol. 40, no. 6, pp. 858-861, Jun. 2019. https://doi.org/10.1109/LED.2019.2910465;
[7] S. D. Thammaiah, X. Liu, T. Knezevic, K. M. Batenburg, A. A. I. Aarnink, L. K. Nanver, PureB diode fabrication using physical or chemical vapor deposition methods for increased back-end-of-line accessibility, Solid-State Electronics., vol. 177, p. 107938, Mar. 2021. https://doi.org/10.1016/j.sse.2020.107938;
[8] V. Mohammadi, S. Ramesh, and L. K. Nanver, Thickness evaluation of deposited pureB layers in micro-/millimeter-sized windows to Si, in Proc. Int. Conf. Microelectronic Test Struct. (ICMTS)., pp. 194-199, Jun. 2014. https://doi.org/10.1109/ICMTS.2014.6841492;
[9] K. Kamimura, M. Ohkubo, T. Shinomiya, M. Nakao, and Y. Onuma, Preparation and properties of boron thin films, J. Solid State Chem., vol. 133, no. 1, pp. 100-103, Oct. 1997. https://doi.org/10.1006/jssc.1997.7323;
[10] O. A. Golikova, Amorphous boron films with enhanced electrical conductivity, Semiconductors., vol. 34, no. 3, pp. 363-366, Mar. 2000. https://doi.org/10.1134/1.1187987;
[11] S. D. Thammaiah, T. Knezevic, and L. K. Nanver, Nanometer-thin pure boron CVD layers as material barrier to Au or Cu metallization of Si, J. Material Science, Materials in Electronics., vol. 32, pp. 7123-7135, Feb. 2021. https://doi.org/10.1007/s10854-021-05422-7;
[12] H. Sun, M. Liu, P. Liu, X. Lin, J. Chen, M. Wang, and D. Chen, Optimization of Au-free ohmic contact based on the gate-first double-metal AlGaN/GaN MISHEMTs and SBDs Process, IEEE Trans. Electron Devices., vol. 65, no. 2, pp. 622-628, Feb. 2018. https://doi.org/10.1109/TED.2017.2778072;
[13] B. Ofuonye, J. Lee, M. Yan, C. Sun, J.-M. Zuo, and I. Adesida, Electrical and microstructural properties of thermally annealed Ni/Au and Ni/Pt/Au Schottky contacts on AlGaN/GaN heterostructures, Semiconductor Science and Technology., vol. 29, no. 9, p. 095005, Jul. 2014. https://doi.org/10.1088/0268-1242/29/9/095005;
[14] T. Hashizumea, K. Nishiguchia, S. Kanekia, J. Kuzmikb, and Z. Yatabec, State of the art on gate insulation and surface passivation for GaN-based power HEMTs, Materials Science in Semiconductor Processing., vol. 78, pp. 85-95, May 2018. https://doi.org/10.1016/j.mssp.2017.09.028;
[15] J. T. Asubar, Z. Yatabe, D. Gregusova, and T. Hashizume, Controlling surface/interface states in GaN based transistors: Surface model, insulated gate, and surface passivation, J. Appl. Phys., vol. 129, p. 121102, Mar. 2021. https://doi.org/10.1063/5.0039564;
[16] D. R. Schuette, R. C. Westhoff, J. S. Ciampi, G. E. Perlin, D. J. Young, B. F. Aull, R. K. Reich, and D. C. Shaver, MBE back-illuminated silicon Geigermode avalanche photodiodes for enhanced ultraviolet response, in Proc. SPIE 8033, Advanced Photon Counting Techniques V., p. 80330D, May 2011. https://doi.org/10.1117/12.887736;
[17] S. D. Thammaiah, J. Lundsgaard Hansen, and L. K. Nanver, Nanometer-thin pure B layers grown by MBE as metal diffusion barrier on GaN diodes, 2019 China Semiconductor Technology International Conference (CSTIC), Shanghai, China, 2019, pp. 1-3. https://doi.org/10.1109/CSTIC.2019.8755633;
[18] X. Liu, Low temperature pure boron layer deposition for silicon diode and micromachining applications, Ph.D. dissertation, University of Twente, Enschede, The Netherlands, 2021;
[19] V. Mohammadi, N. Golshani, K. R. C. Mok, W. B. de Boer, J. Derakhshandeh, and L. K. Nanver, Temperature dependency of the kinetics of PureB CVD deposition over patterned Si/SiO2 surfaces, Microelectronic Engineering., vol. 125, pp. 45-50, Aug. 2014. https://doi.org/10.1016/j.mee.2014.03.015;
[20] A. Persano, I. Pio, V. Tasco, M. Cuscunà, A. Passaseo, and A. Cola, Electrical properties of planar AlGaN/GaN Schottky diodes: Role of 2DEG and analysis of non-idealities, J. Appl. Phys., vol. 121, no. 13, p. 135701, Apr. 2017. https://doi.org/10.1063/1.4979530;
[21] T. Zine-Eddine, H. Zahra, and M. Zitouni, Design and analysis of 10 nm T-gate enhancement-mode MOSHEMT for high power microwave applications, Journal of Science Advanced Materials and Devices., vol. 4, no. 1, pp. 180-187, Mar. 2019. https://doi.org/10.1016/j.jsamd.2019.01.001;
[22] Sentaurus Device User Guide Version N-2017.09, Synopsys, Mountain View, CA, USA, 2017.