Influence of microwave annealing on direct bonded silicon wafers

• Published in: Thin solid films 2008-02, Vol.516 (8), p.2158-2161
• Main Authors: Alford, T.L., Tang, T., Thompson, D.C., Bhagat, S., Mayer, J.W.
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Defects and impurities in crystals; microstructure; Design. Technologies. Operation analysis. Testing; Direct bonding; Electronics; Exact sciences and technology; Integrated circuits; Microelectronic fabrication (materials and surfaces technology); Microscopic defects (voids, inclusions, etc.); Microwave annealing; Molecular electronics, nanoelectronics; Physics; Rapid thermal annealing; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Silicon; Silicon on insulator; Structure of solids and liquids; crystallography
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2007.06.118

Strong and nearly void free bonding was achieved using direct bonding followed by microwave annealing. Silicon wafers were cleaned, O 2 plasma surface activated, and bonded at room temperature. After microwave annealing at 400 °C, the bond strength of hydrophilic wafers was found to be in the range between 0.2 and 1.6 J/m 2. Additional heating of bonded wafers was done at elevated temperatures and for prolonged times using either rapid thermal annealing or microwave annealing. In either case, additional annealing showed no impact on wafer separation area, void, or bond strength. Thus, the initial microwave anneal dictated the ultimate bond strength regardless of subsequent annealing method. The mechanism for wafers bonded in this work involved dipole–dipole bonding and, hydrogen bonding. The initial microwave anneals typically required times less than 60 min. As a result, microwave annealing was shown to be a promising low temperature alternative for wafer bonding when compared to the currently used mechanical furnace anneals.