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Vertically stacking and bonding individual processed wafers with through-Si vias (TSV) to form three dimensional integrated circuits (3DIC) introduces the possibility of reducing signal propagation delay, a reduction in power consumption and heterogeneous device integration. Cu thermocompression bonding is seen as a general route to realize 3DIC, with bonded metals providing both mechanical adhesion as well as electrical interconnection. Mechanical testing to assess the bond quality of bonded processed wafers can be very costly, particularly on production wafers which have multilayer devices designed in the chips. A new non-destructive characterization method based on measured resonance frequency is proposed. Capacitive and resistive characteristics of the contact interface are amplified and utilized with a designed external circuit that consists of an inductor and a resistor. This new measurement technique shows an improvement in sensitivity as compared to contact resistance measurement, as well as eliminates stray resistance effect from line resistance and probing contact resistance. A 3D bonded Cu-Cu test structure that enables three methods of bond interface characterization, i.e. electrical contact resistance measurement, resonance-frequency characterization method and die shear test was designed and fabricated. DOCTOR OF PHILOSOPHY (MSE)

We describe the results produced from our research on integrating GaN devices with Si CMOS integrated circuits. High quality, low bow and robust 200 mm GaN on SEMI-spec epitaxial Si (725 μm) wafers are achieved by using a unique shaped susceptor and careful control of buffer design. High brightness InGaN/GaN MQW LEDs emitting at 450 nm with total III-N stack thickness of 3.6 μm have also been demonstrated. The growth technology of GaN on SEMI-spec 200 mm leads to new wafer/device platforms such as GaN-OI and CMOS + GaN that will open new avenues in device performance and integration of III-N devices with Si CMOS.

Epoxy type encapsulation does not suffice in High Pressure High Temperature (HPHT) environment and hence is not suitable for harsh environment applications. In this work, alternative encapsulation methods exploring the use of thickened lid/base and a novel dome shaped cavity design would be discussed. Results show that such methods are viable and are possible alternatives for similar harsh environment applications.

As deep earth oil exploration transits into deeper earth, it faces challenges in producing reliable microelectronics devices and sensors that will not degrade under a higher temperature and pressure environment. Numerous physical issues limit the manufacturing of this type of reliable microelectronics devices, especially those related to packaging materials and assembly of the microelectronics devices. One of the key requirements in reliability will be a continuous operating time of more than 500 h at 300°C. It is reported that the mechanical performance of a high temperature Au-Ge eutectic alloy is able to fulfill the minimum interconnection properties specified by the oil and gas exploration industry. However, the impact of thermal aging to Au-Ge eutectic alloy electrical property is not clear. The electrical resistivity of thermally aged Au-Ge eutectic alloys has been evaluated in this study. It is observed that the electrical resistivity decreases with thermal aging time until saturation. This effect is mainly contributed by the grain growth of Au, which results in a reduction in grain boundaries, thus causing a decrease in electrical resistivity. It has been determined that Au-Ge eutectic alloy is a suitable interconnection material in term of its electrical property to be used for high temperature electronics packaging.

The concept of Multichip module (MCM) packaging is popularized for evaluating prototypes of novel devices and materials in extreme environmental conditions. The packaging for these types of electronics must be mechanically well-built and the metallization must be low in thermal conductivity in order to prevent the heat transfer from the external environment to the protected device. Strong bonding between metal and ceramic has been an issue of concern for many years due to delamination tendencies at the interfaces. This paper evaluates the adhesion characteristics of sputtered Copper (Cu) thin films to alumina (Al 2 O 3 ) substrates. The relationship between the surface roughness of the Al 2 O 3 substrate with appropriate surface treatment and the adhesion with Cu thin film is established experimentally. An adhesion layer with lower thermal conductivity and smaller coefficient of thermal expansion (CTE) mismatch such as Titanium (Ti) or Chromium (Cr) was also inserted in between to investigate the adhesion improvement of the metal-substrate. We have seen that Ti is essentially used as an adhesion layer between the bonding of Cu and Al 2 O 3 for electronic applications. With higher adhesion strength, and smaller CTE mismatch with Cu and Al 2 O 3 , insertion of Ti adhesion layer with optimum substrate surface roughness could lead to a more reliable packaging solution.

High temperature electronics for the exploration and monitoring of down-hole activities in geothermal wells and other oil and gas industry applications must operate reliably at a minimum temperature of 300°C for as long as 500 hours continuously. This study investigates if ceramic to ceramic bonding, using glass frit as the intermediate layer, is able to tolerate a high temperature environment of 300°C for 500 hours. Since glasses have the potential to join to ceramic due to chemical compatibility between the two materials, the use of glass frit for ceramic to ceramic bonding is considered a simple and yet robust method that is often used for hermetic sealing of microelectronic packages. The materials used in this study were alumina substrate and bismuth-based glass frit paste 4115DS-1Ha from Asahi Glass Company (AGC). The study includes an initial characterisation of the glass frit and evaluation of the shear strength of the bonding. The average hot shear strength (shear test performed at 250°C) for samples after thermal aging at 300°C for 500 hours was found to be 28.72 MPa. This value is approximately 3.6 times above the minimally required shear strength of 7.9 MPa according to the MIL-STD-883G specification. Further aging till 1000 hours showed only a 30% drop in shear strength to 19.72 MPa. Based on this study, the use of glass frit as a joining layer for ceramic to ceramic bonding for use in a high temperature environment was concluded to be qualified, at least from the perspective of shear strength retention.