Simulation of mass flux divergence distributions for an evaluation of commercial test structures with tungsten-plugs
The evaluation of via structures, metallisations as well as a miniaturisation of the layout dimensions lead to the determination of new test structures. The time for prediction of the reliability of such structures should be very short but also effective. For instance for fast reliability prediction, constant power or constant current tests can be used. Due to a change in fault mechanisms an extrapolation to working conditions is sometimes difficult. Simulations can help in prediction of the failure mechanism as well as the determination of the weakest link in the structures. In this study the void location as well as the mass flux divergence distribution of a conventional tungsten-plugged metallisation structure was investigated by finite element simulation (using ANSYS/spl reg/). A calculation routine is used for the determination of the mass flux divergences and the void formation in the model. The suitability of the simulation in test structure design will be shown. Based on the default models the overlap of the metallisation, the metallisation length, and width and the applied current density was varied. The stress free temperature was set to 450/spl deg/C. This temperature was taken from the last process step. The substrate temperature was set to 150/spl deg/C like the temperature in the reliability stress test. The mechanical stress and temperature and current density distribution as well as the influence of the different migration mechanism was determined. Using these results the void formation and its localisation was calculated and compared with the measurement.
Electromigration Characteristic of SnAg
1 Ph.D. Candidate 2 Corresponding Author, Professor Abstract Electromigration is a reliability concern of microelectronic interconnections, especially for flip chip solder bump with high current density applied. This study shows that with the line-to-bump geometry in a flip chip solder joint, the current density changes significantly between the Al trace and the bump, while the current crowding effect generates more heat between them. This large Joule heating under high current density can enhance the migration of Sn atoms at the current entrance of the solder bump, and cause the void formation at the entrance point. The present study finds two kinds of electromigration failure modes at the cathode/chip side of the solder bump: the pancake-like and the cotton-like void. The experimental finding shows that the effects of polarity and tilting are key factors to observe in the electromigration behavior of SnAg3.0Cu0.5 solder bumps. Consequently, this study has designed a three-dimensional numerical model and a corresponding test vehicle to verify the numerical finding. The maximum current density is simulated through the finite element method (FEM) to provide a better understanding of local heat and current crowding. This study finds that the current crowding ratio is reduced linearly while the void formation is increased. Furthermore, it is concluded that there is a linear relationship between the growth of the intermetallic compound (IMC) layer and the applied current density at the anode/substrate side.
Techno-economic analysis of chemical looping combustion with humid air turbine power cycle
Abstract Power generation from fossil fuel-fired power plant is the largest single source of CO2 emission. CO2 emission contributes to climate change. On the other hand, renewable energy is hindered by complex constraints in dealing with large scale application and high price. Power generation from fossil fuels with CO2 capture is therefore necessary to meet the increasing energy demand, and reduce the emission of CO2. This paper presents a process simulation and economic analysis of the chemical looping combustion (CLC) integrated with humid air turbine (HAT) cycle for natural gas-fired power plant with CO2 capture. The study shows that the CLC–HAT including CO2 capture has a thermal efficiency of 57% at oxidizing temperature of 1200 °C and reducer inlet temperature of 530 °C. The economic evaluation shows that the 50 MWth plant with a projected lifetime of 30 years will have a payback period of 7 years and 6 years for conventional HAT and CLC–HAT cycles respectively. The analysis indicates that CLC–HAT process has a high potential to be commercialised.