Gas-phase chemistry and etching mechanism of SiNx thin films in C4F8 + Ar inductively coupled plasma

Significance 

Silicon nitride films are preferred for finishing works in micro- and nano-electronic technology. These applications, however, require precision pattering on the field surface that has remained a challenge to achieve. Previously, researchers have identified the dry etching process as an effective solution for the precision problem. Even though the plasma parameters, etching characteristics and treated surface states of plasma-enhanced chemical vapor deposition-formed SiNx films have been previously investigated, it was evident that no comprehensive results could be obtained due to the lack of detailed data on the plasma chemistry.

To this note, Nomin Lim (PhD candidate) and Professor Kwang-Ho Kwon from Korea University together with Professor Alexander Efremov from the State University of Chemistry and Technology explored the etching characteristics and mechanisms of nonstoichiometric plasma-enhanced chemical vapor deposition-formed SiNx thin films in C4F8 + Ar coupled plasma to determine appropriate matching of the gas-phase and heterogenous chemistries. Their main objectives were to determine the influence of the changes in the operating conditions on the SiNx etching kinetics through gas-phase plasma characteristics as well as to identify the gas-phase related parameters for characterizing of the etching process. The work is published in the journal, Thin Solid Films.

Briefly, the SiNx etching rates and the etching selectivity i.e. SiNx/Si and SiNx/SiO2 were all measured as functions of gas pressure, bias power, input power, and C4F8/Ar mixing ratio. Consequently, the plasma diagnostics based on Langmuir probes and zero-dimensional plasma modeling was used to determine the steady-state composition, plasma parameters, and chemistry. Furthermore, the relationship between the measured etching rate and model predicted fluxes of the active species were examined to analyze the etching mechanism of the SiNx.

The authors observed that within the given input process conditions operation range, the SiNx etching kinetics did not only appear similar to Si and SiO2 in the steady-state etching regime but also exhibited the features of the ion-assisted chemical reactions in the neutral-flux-limited mode. Besides, the SiNx etching process was influenced by the fluorocarbon polymer film thickness. Additionally, it was worth noting that the differences in the effective reaction probabilities for SiNx, Si and SiO2 agreed well with the corresponding differences in the fluorocarbon film thickness and reaction thresholds.

According to the authors, changes in the input process parameters of the effective probability including the deposition and etching kinetics of the fluorocarbon polymer films could be characterized by the behavior of the ratio of the fluorocarbon radicals, fluorine atoms and ion energy flux that ideally reflected the fluorocarbon film thickness. The authors believe the importance of the paper in that the developed model adequately described the plasma chemistry by reflecting the relationships between input process parameters and gas-phase composition. This would lead to advancement in silicon-based materials used in micro- and nanotechnology.

About the author

Alexander Efremov

Professor
Full Doctor (Physical Chemistry), Ph.D. (Physical Chemistry),
Dept. of Microelectronic Devices & Materials Technology
Ivanovo State University of Chemistry & Technology
F. Engels. st., 7, Ivanovo 153000, Russia
e-mail: [email protected]

Alexander M. Efremov received the ME, Ph.D, and the DSc (full doctor) degrees from Ivanovo State University of Chemistry and Technology (Ivanovo, Russia) in 1989, 1995 and 2005, respectively. From 1989 and up to now he was with the Department of Electronic Devices and Materials Technology, Ivanovo State University of Chemistry and Technology, where he worked as research engineer, professor assistant, associate professor and, since 2005, as the full professor. During his teaching experience which was started at 1992, Alexander Efremov conducted tutorial and practical classes, supervised scientific work of students and post-graduate students, delivered lectures on such courses as “Plasma chemistry and plasma technology”, “Solid state physical chemistry”, “Physical methods in chemical researches”, “Solid state electronics and microelectronic devices”, “Scientific basis of nanotechnologies”. Also, from 2002 to 2004 and in 2006 he worked as an invited researcher and visiting professor for the Plasma Application Laboratory, School of Electrical and Electronic Engineering, Chung-Ang University (Seoul, Korea). In 2003, he was joined as a lecturer in the School of Electrical and Electronic Engineering, Chung-Ang University where he delivered lecture course on “Plasma chemistry and plasma modelling”.

His scientific major is physics and chemistry of low-temperature low-pressure halogen-containing plasmas, including such fields as kinetics and mechanisms of volume and heterogeneous plasma processes, plasma etching mechanisms for inorganic materials and plasma modeling. During last years, the dominant attention was attracted to the development of the original modelling algorithms which allow one the prediction and optimization of plasma etch processes through the critical and comparative analysis for various plasma etching gases, gas mixtures and process conditions. Alexander Efremov have published more than 200 papers, including about 100 papers in SCI journals.

About the author

Kwang-Ho Kwon

Professor
Ph.D (Electrical engineering)
Dept. of Control & Instrumentation engineering
Korea University
Sejong-ro 2511, Sejong 30019, South Korea
e-mail: [email protected]
Home page : http://plasmaappl.tistory.com

Kwang-Ho Kwon received the Ph.D degree from Korea University in 1993. From 2005 and up to now he was with the Department of Control and Instrumentation engineering, Korea University as the full professor. From 1987 to 1995, he researched and developed semiconductor processes as a senior researcher at ETRI, the government research institute of Korea.  From 1995 to 2005, he was an associate professor in the Department of Electronic Engineering, Hanseo University. From 2012 to 2014, he served as the Dean of academic and student affairs at Korea University.

In Korea University, he served as Dean of the College of Science and Technology from 2014 to 2016. In 2013, He was an Associate Editor for SCIE-level journal “Journal of Semiconductor Technology and Science (JSTS).” He was a guest editor for the journal “Proceeding of higher School. Ser. Chemistry and Chemical Technology (Russian journal)” from 2014 to 2017. In 2016, he was a visiting professor at the university of Taxas at Arlington. In 2017, he worked as a inviting researcher and visiting professor at the KIST’s Nanophotonic Research Center, the government research institute of Korea. His scientific major includes plasma processing, etching technology, and sensor materials and devices. To date, he have published more than 163 papers at the international SCI journals

About the author

Nomin Lim

Student
Ph.D. course (Control & Instrumentation)
Dept. of Control & Instrumentation engineering
Korea University
Sejong-ro 2511, Sejong 30019, South Korea
e-mail: [email protected]

Nomin Lim is in the Department of Control and Instrumentation Engineering, Korea University, and is conducting plasma process research under the guidance of Prof. Kwang-ho Kwon.After etching various materials (Mo, SiO2, Si, HfO2, etc.) necessary for the fabrication of highly integrated circuits by using plasma of various gas chemistry, it is analyze the characteristics of plasma by using optical spectroscopy and double Langmuir probe. He is conducting research to systematically identify the mechanism of etching through analysis. In addition, He conducted research to increase the performance of triboelectric generators by applying plasma etching technology to triboelectric generators. By analyzing the surface of the plasma-treated material and examining the characteristics of the plasma used, the cause of the increase in the performance of the friction generator was analyzed. The current research interest is the drive of humidity sensors in dew point.

Reference

Lim, N., Efremov, A., & Kwon, K.-H. (2019). Gas-phase chemistry and etching mechanism of SiNx thin films in C4F8 + Ar inductively coupled plasma. Thin Solid Films, 685, 97-107.

Go To Thin Solid Films

Check Also

An exact microgrid formation model for load restoration in resilient distribution system - Advances in Engineering

An exact microgrid formation model for load restoration in resilient distribution system