Effect of various interfacial SiO2 layer on the properties of wafer direct bonding

• Main Authors: Huang, Li-Yang, 黃立陽
• Other Authors: Hu, Chen-Ti
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/30069515584580804129

碩士 === 國立清華大學 === 材料科學工程學系 === 97 === 　　The technology of wafer direct bonding has been employed in present study to bond several types of silicon bonded wafer pairs with various interfacial SiO2 layers, such as: a silicon wafer with a surface native oxide layer bonded to another silicon wafer with a native oxide layer, a silicon wafer with a native oxide bonded to a thermally oxidized silicon wafer, or a thermally oxidized silicon wafer bonded to another thermally oxidized silicon wafer. Those wafers were cleaned by chemical solution with/without activation process by oxygen plasma treatment prior to wafer direct bonding. 　　The bonding qualities and the cross-sectional microstructures of those bonded wafer pairs were examined with the infrared (IR) photography, optical microscope (OM), field emission scanning electron microscope (FESEM), and the crack opening method for bonding surface energy evaluation. From these results, the bonded wafer pairs with plasma surface activation demonstrated better bonding qualities than those with chemical solution cleaning process only. Moreover, the boned wafer pairs with thicker interfacial SiO2 layer have greater bonding strengths. It is suggested that the increase of hydroxyl groups (-OH) with plasma activation process induces higher van der Waals attraction forces or hydrogen bond between the surfaces of two bonded wafers. 　　The second aim of this study is to examine the relationship of thermal healing properties for recovering the surface energy of previously de-bonded wafer pairs by crack opening method versus various thicknesses of interfacial SiO2 layers. An optimal process option for the bonded wafer pairs with thickness of interfacial SiO2 layers is suggested from this study. 　　The temperature and the time for effectively thermal healing process in a bonded wafer pairs with a thin interfacial SiO2 layer (~36Å) have to be higher (~1273K) and longer (~90min). On the other hand, the temperature and time for effectively thermal healing process in a bonded wafer pairs with a relatively thick interfacial SiO2 layer (~1000Å) were found to be lower (~973K) and shorter (~45min), respectively. 　　From the present investigation, the significant of interfacial SiO2 layer in the wafer bonding process as well as the thermal healing behavior was observed. Furthermore, the bonded wafer pairs with an appropriate interfacial SiO2 layer demonstrate a great potential on the constructions and applications in MEMS, micro-sensors and micro-pumps, etc.