Hydrogen implantation was carried out on (001) germanium samples with doses of 3 × 1016 cm−2, 5 × 1016 cm−2 and 1 × 1017 cm−2 with 60 KeV, and germanium surface blistering phenomenon, raised by subsequent annealing in air in the temperature regions (200–250°C for 1 × 1017 cm−2 and 250–350°C for 3 × 1016 cm−2 and 5 × 1016 cm−2) for distinct durations, was studied. In Arrhenius plots that reflects the onset blistering time of annealing as a function of annealing temperature, there is a break point separated the each plot into two parts with distinct activation energies (∼2.1 eV and ∼0.6 eV) for 3 × 1016 cm−2 and 5 × 1016 cm−2 doses. The break point seems to be similar to other known materials but the opposite turning direction of the straight-line is completely different from other known materials because it is possible to derive from the diversity of defect-hydrogen complexes in germanium. On the other hand, the simple straight-line in Arrhenius plot is generated in the temperature range from 200–250°C with 1.57 eV activation energy as increasing H-implanted dose up to 1 × 1017 cm−2. The phenomenon of modifying blistering activation energy with H-implanted dose may be due to the mergence through the low and high activation energy because of competitive desorption of the defect-hydrogen complexes. The critical size of blisters to be exploded into craters increases with the enhancement of H-implanted dose and the rectangle-like periphery of the craters is obviously formed.
Using an original and dynamic crack-opening method the distribution of surface energy values is analyzed and compared for various surface pretreatment methods in a low-temperature silicon direct-bonding technique. Warm nitric acid and O 2 plasmasurface pretreatments were used prior to bonding. In the case of O 2 plasma-enhanced wafer bonding, a great number of bubbles is observed at the bonding interface after a long annealing time, although the annealing temperature is as low as 120°C. For the first time, large fluctuations of surface energy values have been presented in the case of O 2 plasma-enhanced wafer bonding even if trenches are etched at the bonding interface to avoid the formation of annealing voids. Contrastingly, wet surface treatment such as warm nitric acid prior to bonding results in a relatively low but uniform surface energy value over the whole bonded wafer interface.Wafer bonding technology is an important approach in the microelectromechanical system ͑MEMS͒ domain and for the fabrication of three-dimensional integrated devices and circuits. It is an effective extension toward the third direction for planar processes. Fusion wafer direct bonding 1 is more attractive than the use of an adhesive layer at the interface to avoid possible postprocess complications or even the degradation of the integrated device and circuit performance. Reaching a high and uniform bonding surface energy as well as a void-free interface at low temperature is a challenge for the device fabrication process compatibility. Low temperature wafer bonding is often required in material integration, 2 especially for the bonding of materials which present different thermal expansion coefficients, to avoid diffusion of doped profile broadening or melting of metal interconnections, etc. Research articles 3-5 have shown that bonding strength in low-temperature wafer bonding was drastically improved in response to O 2 plasma-assisted surface treatment prior to bonding. However, a large number of voids were raised by subsequent annealing steps without any exception for Si-Si bonding. These bubbles severely affect the efficient mass production and reliability of integrated systems. Therefore, particular care has to be taken to reduce as much as possible the formation of interface voids. Wafer bonding quality is also defined by the uniformity of the surface energy value over the entire bonded area. The fusion wafer bonding is usually associated with an interfacial reaction and diffusion procedure 5,6 along the bonding interface. In this work, the surface energy of hydrophilic bonded samples is measured at several locations along the bonding interface in order to quantify the bonding homogeneity. To our knowledge few articles in the literature talk about the homogeneous bonding energy of bonded wafers. 7,8 In Ref. 8 the authors mention that surface energy is higher at the rim of bonded hydrophilic silicon wafer than in the central area, but no characterization was presented. Here, we present for the first time the great variation of ...
The annealing blistering after hydrogen implantation is a fundamental to achieve GeOI (germanium-on-insulator) by the well-known Smart-cut process. The impacts of H implantation dose and energy on the annealing kinetic plots are studied. The experimental results indicated: (1) the implantation with low dose or energy results in Arrhenius plot with a break point that separate the plot into two regions due to different activation energy; (2) the situation of the kinked kinetic plot, high and low temperature corresponding to high and low activation energy, is against that for other known materials; (3) the unitary activation energy occurs as either implantation dose or energy is enhanced. Moreover, the critical size to form craters increases with the rise of either dose or energy in H-implanted Ge. The variation of the kinetic plot may be related to the different desorption energy from the diverse types of H-platelets with distinct bind energy in germanium.
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