Studies On The Microstructure And Its Impact On Electrical And Thermal Properties Of Porous Low-k Materials

With increasing requirements for electrical performance of on-chip wiring, resistance-capacitance (RC) delay, electric power consumption and cross talk become dominant factors restricting the develop of Ultra-large-scale integrated circuits when the dimension of the device is further scaled down. Low dielectric constant materials which are found to be promising materials for meeting these requirements are crucial for the development of ultra-large-scale integrated circuits. Recently, nanoporous organic silicon composite materials were prepared by taking advantage of low dielectric constant as porous low dielectric constant materials. Some of promising materials have many merits, such as porous MSQ films, zeolite films, silica xerogel films, and so on. MSQ films have a very low dielectri constant of low to 2.3 and are shown to have good thermal stability (up to 850℃), stable network structure, low leakage current and so on. Since these materials have received extensive attentions, researcher established many experimental strategies to prepare the low-k materials and test the performance, and tried to construct a theoretical model to predice properties of materials. Finding materials with some excellent properties to meet the requirements of microelectrics technology, and establishing theoretical model can quantitatively predict and further guide the experiments are necessary. In this paper, on the base of the fractal theory and effective medium theory, we established a analytical model to study the relationship between the microstructure and properties of materials, and further study the performance of the material.Based on the structural characteristics of porous media, we used the typically fractal model to simulate the geometry structure of porous dilectrics. Then, we studied the diffusion, penetration, annihilation and other processes of positrons in porous thin films, in order to provide the theoretical basis of simulating the movement of the Cu ions in low dielectric constant thin films and predict the leakage current and other important information of materials. Which are help to characterize the information of pore structure, such as pore size and pore connectivity. In this study, we firstly introduced the knowledge of fluid dynamics to simulate the diffusion of the positronium in conneted pores. Combining fractal structure, a more suitable medium approximation is developed to study the effective thermal conductivity of porous low dielectric constant materials. Cubic spline interpolation for fitting discrete predictions from the fractal model is used to obatain the continous function of the effective thermal conductivity versus porosity.A new design method based on fractal theory has been developed and implemented in low-dielectric constant and high thermal conductivity materials. According to this method, low-k and high thermal conductivity samples made of AIN/BN/SiOC, with different component fractions have been prepared. Measurements for determining the dielectric and thermal properties have also been performed. The results show that we successfully synthesized ceramic samples with low dielectric constant (<3.5) and high thermal conductivity (≥2W/(mK)). This proves that the proposed material component design method is a valid one.