J. Fan,^1,a L. C. Tu,¹ and C. S. Tan^2
1 MOE Key Laboratory of Fundamental Physical Quantities Measurement, School of Physics, Huazhong University of Science and Technology, Wuhan 430074, People’s Republic of China
² School of Electrical and Electronics Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798
(Received 28 November 2013; accepted 17 February 2014; published online 25 February 2014)

    This work systematically investigated a high-κ Al2O3 material for low temperature wafer-level bonding for potential applications in 3D microsystems. A clean Si wafer with an Al2O3 layer thickness of 50 nm was applied as our experimental approach. Bonding was initiated in a clean room ambient after surface activation, followed by annealing under inert ambient conditions at 300 ◦C for 3 h. The investigation consisted of three parts: a mechanical support study using the four-point bending method, hermeticity measurements using the helium bomb test, and thermal conductivity analysis for potential heterogeneous bonding. Compared with samples bonded using a conventional oxide bonding material (SiO2), a higher interfacial adhesion energy (∼11.93 J/m2) and a lower helium leak rate (∼6.84 × 10−10 atm.cm3/sec) were detected for samples bonded using Al2O3. More importantly, due to the excellent thermal conductivity performance of Al2O3, this technology can be used in heterogeneous direct bonding, which has potential applications for enhancing the performance of Si photonic integrated devices.