Surface cleaning process for plasma-etched SiC wafer
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Surface cleaning process for plasma‑etched SiC wafer Lihuan Zhao1 · Haiping Shang1,2 · Dahai Wang1 · Yang Liu1 · Miao Xue1 · Jiahan Yu1 · Weibing Wang1 Received: 11 February 2020 / Accepted: 30 June 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In this paper, we explored a method to remove the contamination and impurities left on SiC surface after plasma-etched process. The stubborn contamination is resulting from fluorochemical caused by plasma-etched process, residue left after stripping Ni metal mask, Ni–O compounds formed by the metal mask with SiC Si surface oxide film and carbon-containing contamination introduced by the process environment. By adding a layer of S iO2 mask between SiC and the original metal mask together with ultrasonic cleaning and oxygen plasma cleaning process, the sample surface roughness was effectively reduced from 1.090 to 0.055 nm. Moreover, this method supplies a valuable reference for solving the problem of surface contamination caused by plasma etched. Keywords Plasma etched · Surface roughness · Surface cleanliness
1 Introduction As a newly emerging semiconductor material, SiC has attracted extensive attention in the field of high-power and harsh environment applications [1–5] due to its high hardness, high melting point, and strong thermal conductivity [6]. In order to apply SiC to semiconductor devices, such as pressure sensors, power devices, and transistors, [7–9] plasma-etched process is often used, but it is worth noting that some contamination generated in the etching process is easy to adhere to the sample surface. What is more, the existence of contamination and impurities directly increase the surface roughness and then hinder the next processes and weaken the performance of devices [10–13]. A clean, flat surface is extremely important for many processes, such as bonding and metal contact [14–16]. Some contaminant can be removed by conventional wet cleaning or plasma cleaning, but some remains stubborn after treatment with strong acids, strong bases, organic solutions, or plasma. For example, plasma etching of SiC wafer would result in stubborn fluorocarbon contamination, * Haiping Shang [email protected] 1
Institute of Microelectronics of the Chinese Academy of Science, Beijing 100029, China
Kunshan Branch, Institute of Microelectronics of Chinese Academy of Sciences, Suzhou 215347, China
2
whereas the contamination cannot be removed off by a series of treatments, including simple UV–ozone and solvent cleans, oxygen plasma, deposited oxide, and thermal oxidation [15]. Previous studies have reported two effective removal methods for the contamination: one is thermal oxidation and the other is oxygen plasma bombardment at high RF power [15, 16]. For the former, after stripping thermal oxide layer, the characteristic size of sample will be changed and the roughness of the sample surface can hardly be guaranteed. For the second method, the surface of SiC sample will form an oxide film under the condition of oxygen plasma bomb
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