Bias Stress Induced Conduction Mechanism Evolution in Silica Based Inter-Metal Dielectrics
The real-time conduction mechanism evolution during bias stress of three silica based inter-metal dielectrics in Cu damascene structures was investigated. Capacitance measurements at 1 MHz and I-V measurements were intermittently inserted into the process of bias stress to monitor the conduction mechanism evolution with time. All experiments show that the capacitance is constant and the I-V curve slope decreases with bias stress and converges to the half of the initial value. Based on these findings, we conclude that the conduction mechanism changes from a normal Frenkel-Poole emission to an "abnormal" Frenkel-Poole emission with bias stress
Enhanced dielectric-constant reliability of low-k porous organosilicate glass (k = 2.3) for 45-nm-generation Cu interconnects
The mechanism of the dielectric-constant increase in porous organosilicate glasses (OSGs) under electric-field stress has been revealed for the first time, where the dielectric-constant increase is caused by the oxidation of methyl groups in porous OSGs. By optimizing the methyl content, the authors developed a highly reliable, novel low-k porous OSG (k =2.3) with a dielectric-constant lifetime of 10/sup 3/ years for 45-nm-generation copper interconnects. The newly developed porous OSG was successfully integrated into 240-nm-pitch copper interconnects, where the line-to-line capacitance shows a much longer lifetime than the case of conventional porous OSGs.
Reduction of gas flow nonuniformity in gas turbine engines by means of gas-dynamic methods
Gas flow nonuniformity is one of the main sources of rotor blade vibrations in the gas turbine engines. Usually, the flow circumferential nonuniformity occurs near the annular frames, located in the flow channel of the engine. This leads to the increased dynamic stresses in blades and as a consequence to the blade damage. The goal of the research was to find an acceptable method of reducing the level of gas flow nonuniformity as the source of dynamic stresses in the rotor blades. Two different methods were investigated during this research. Thus, this study gives the ideas about methods of improving the flow structure in gas turbine engine. On the basis of existing conditions (under development or existing engine) it allows the selection of the most suitable method for reducing gas flow nonuniformity.