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|Title:||Void formation and vacancy injection in Silicon and Silicon Germanium|
|Advisor:||Haddara, Y. M.|
Knights, A. P.
|Keywords:||Void formation;vacancy injection;Silicon;Silicon Germanium|
|Abstract:||<p> Substantial development of silicon-based technology is required to continue to improve product reliability and production yield of silicon-based IC devices. Defects play a key role in process technology and research is required into their properties and interactions with host and impurity atoms. Cavities formed by ion implantation of helium into a silicon substrate are known to be efficient gettering sites for mobile interstitials and metallic impurities. In addition, the existence of a buried void layer drastically reduces the unintentional parasitic transistor gain in power devices by introducing mid-gap energy levels in the substrate. Utilizing slow positron annihilation spectroscopy (PAS), void formation by implanted He+ at a dose of lxl016/cm2 and energy of 60 keV subsequently subjected to various annealing conditions, i.e. different temperatures, times, ramp rate and ambients, is reported. Quantitative measurement of cavity sizes shows that the annealing temperature largely influences helium out-diffusion from the implanted region. Consequently, different void evolution processes associated with specific annealing temperatures are found. Furthermore, larger voids are formed in oxygen ambient leading us to suggest that the supersaturation of interstitials enhances bubble migration and coalescence during the stage when a large fraction of He atoms remains in the cavities. </p> <p> In recent years, SiGe pseudomorphic alloys have become attractive for heterostructure devices due to their higher mobility, lower noise and lower power consumption, as compared with traditional Si devices. More importantly, SiGe is highly compatible with Si processing technologies. With the continuous improvement of SiGe technology, it has been coupled with complementary metal oxide semiconductor (CMOS) technology and has the potential to replace III-V compound semiconductor devices in the near future. However, many unknowns remain in this material system. The study of point defect injection during various thermal treatments is important in itself, and would also allow additional tools for the study of dopant diffusion in the material under different conditions. With preexistent voids in the buried substrate, we performed furnace wet oxidation on a Si0.98Geo.08 sample at 900 °C for half an hour. A small shrinkage of the voids, as compared to complete annihilation in the case of inert annealing, signifies vacancy injection during the oxidation process. Possible defect generation mechanisms and difference in growth rate enhancement in dry and wet oxidation are discussed. Based on a literature review of Si and SiGe oxidation, we suggest that stress relaxation and the Si replacement mechanism are responsible for the catalytic effect of the oxide growth and the change of point defect generation. </p>|
|Appears in Collections:||Digitized Open Access Dissertations and Theses|
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|Su_Han_Z_2006Feb_Masters.pdf||3.86 MB||Adobe PDF||View/Open|
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