Fabrication of high quality, thin Ge-on-insulator layers by direct wafer-bonding for nanostructured thermoelectric devices. (21st February 2017)

• Record Type: Journal Article
• Authors: Veerappan, Manimuthu; Mukannan, Arivanandhan; Salleh, Faiz; Shimura, Yosuke; Hayakawa, Yasuhiro; Ikeda, Hiroya
• Is Part Of: Semiconductor science and technology. Volume 32:Number 3(2017:Mar.)
• Publication Date: 2017-02-21
• Subjects: Ge on insulator -- direct wafer bonding -- multistep cooling -- surface treatment -- bonding mechanism; Semiconductors -- Periodicals; 621.38152
• DOI: 10.1088/1361-6641/aa5391
• Languages: English
• ISSNs: 0268-1242

Abstract

Abstract: A simple means of fabricating thin Ge-on-insulator (GOI) layers with a strong bond at the Ge/SiO2 interface through direct wafer-bonding is described. In this work, high quality Ge/SiO2 bonding was achieved under ambient air and at room temperature as a result of the extremely hydrophilic bonding surfaces obtained by chemical treatment prior to direct bonding. Based on the results of this work, the first-ever bonding mechanism between ammonium hydroxide treated Ge and SiO2 /Si wafer surfaces is proposed. In addition, strain generated during post-annealing as a consequence of the significant thermal-expansion mismatch between Ge and SiO2 was gradually relieved by applying a multistep-cooling process. Structural characteristics of the thin GOI layer were analyzed by cross-sectional scanning electron microscopy, Raman spectroscopy, x-ray diffraction and transmission electron microscopy. It was determined that direct wafer-bonding followed by polishing could produce a GOI layer as thin as 156 nm, with sub-nm surface roughness.