High-density-plasma (HDP)-CVD oxide to thermal oxide wafer bonding for strained silicon layer transfer applications

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• 作者：R. Singh ; I. Radu ; M. Reiche ; C. Himcinschi ; B. Kuck ; B. Tillack ; U. Gö ; sele ; S.H. Christiansen
• 关键词：Direct wafer bonding ; High-density-plasma-CVD oxide ; Atomic force microscopy ; Infra-red transmission imaging ; Strained silicon on insulator ; Bonded interface ; Transmission electron microscopy
• 刊名：Applied Surface Science
• 出版年：2007
• 期刊代码：6_01694332
• 类别：ms
• 出版时间：30 January 2007
• 卷：253
• 期：7
• 页码：3595-3599
• 文件大小：588 K

摘要

Direct wafer bonding between high-density-plasma chemical vapour deposited (HDP-CVD) oxide and thermal oxide (TO) has been investigated. HDP-CVD oxides, about 230 nm in thickness, were deposited on Si(0 0 1) control wafers and the wafers of interest that contain a thin strained silicon (sSi) layer on a so-called virtual substrate that is composed of relaxed SiGe (4 μm thick) on Si(0 0 1) wafers. The surfaces of the as-deposited HDP-CVD oxides on the Si control wafers were smooth with a root-mean-square (RMS) roughness of <1 nm, which is sufficiently smooth for direct wafer bonding. The surfaces of the sSi/SiGe/Si(0 0 1) substrates show an RMS roughness of >2 nm. After HDP-CVD oxide deposition on the sSi/SiGe/Si substrates, the RMS roughness of the oxide surfaces was also found to be the same, i.e., >2 nm. To use these wafers for direct bonding the RMS roughness had to be reduced below 1 nm, which was carried out using a chemo-mechanical polishing (CMP) step. After bonding the HDP-CVD oxides to thermally oxidized handle wafers, the bonded interfaces were mostly bubble- and void-free for the silicon control and the sSi/SiGe/Si(0 0 1) wafers. The bonded wafer pairs were then annealed at higher temperatures up to 800 °C and the bonded interfaces were still found to be almost bubble- and void-free. Thus, HDP-CVD oxide is quite suitable for direct wafer bonding and layer transfer of ultrathin sSi layers on oxidized Si wafers for the fabrication of novel sSOI substrates.