Silicon-On-Insulator Structure by Wafer Bonding

• Main Authors: Hung； Mong Chi, 洪盟琪
• Other Authors: Wan Chi Meen；Yew Tri Rung
• Format: Others
• Language: en_US
• Published: 1994
• Online Access: http://ndltd.ncl.edu.tw/handle/92177686740946934699

碩士 === 國立清華大學 === 材料科學(工程)研究所 === 82 === Wafer bonding is an attractive technique for silicon-on- insulator (SOI) structure. To apply this method to SOI structure, it is very important to obtain void-free interface. Two sufficiently flat, smooth, particle-free, and high hydrophilic surfaces are contacted for silicon wafer bonding at room temperature without using any external force. Then the bonded wafers are loaded into a furance at temperature 1050 ℃ in a nitrogen atmo- sphere and stayed them for 1.5-2 hours to prompt the bonding strengh. Basically, The SOI wafer is fabricated by four basic process steps. The first step is to achieve a sufficiently flat, smooth, particle-free, and hydrophilic surface by a number of wet chemical cleaning processes. The second step is the mating of two wafers together at room temperature without using any external force. The third step consists of the annealing over 800 ℃ (usually 1000-1100 ℃ used) to increase the bond strengh. The four step is to thin down one of the two wafers to an appro- priate thickness by grinding, lapping, polishing, and etching. Our experiments focus on the first three steps. The local bonded structure was characterized by cross-sectional transmission electron micro- scopy (XTEM). Surface chemical conditions of silicon and silicon dioxide after wet cleaning were investigated by Fourier tranformation in- frared ray (FT-IR) spectroscopy, including trans- mission and attenuated total reflection methods. Surface micro-roughness of silicon and silicon dioxide after wet cleaning was observed by atomic force microscopy (AFM). The distribution of dust particles on wafer surfaces after cleaned by the solutions was studied by surface scan microscopy (SSM). The presence of voids at bonded interfaces prepared after hydrophilizing surface treatment have previously been demonstrated by using a transmission infrared ray image system.