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Study Of The Buried Oxide Stress Impact Mechanism On The Micro Cantilever Fabrication Breakage

Posted on:2017-01-08Degree:MasterType:Thesis
Country:ChinaCandidate:R ZhongFull Text:PDF
GTID:2308330485451019Subject:Measuring and Testing Technology and Instruments
Abstract/Summary:PDF Full Text Request
In recent years, the micro-nano processing technology based on SOI wafers, especially in the field of high sensitivity micro cantilever sensor fabrication, has been payed more and more concern. In order to get longer and thinner cantilever beam structure with SOI wafers, bulk silicon etching process during the back releasing in the fabrication of cantilever beam becomes extremely important. But due to the existence of internal compressed stress in the buried oxide layer (BOX), the floppy cantilever beam with high aspect ratio of vertical section is very fragile, which causes the cantilever beams’breakage during the back releasing technique. This research focused on the key device in the MRFM, micro cantilever, which have a great sensitivity performance owing to its ability in single electron spin force detection. The length of micro cantilever is required to be longer than 300μm,and the thickness should be less than 1 μm,when the width is designed to be 10μm.To quantitatively analyze the impact that the oxidation stress in BOX layer effecting in fabrication process of the floppy cantilevers, the author verified the pattern method process’effect contributed to the release of internal stress firstly. By studying the source of BOX internal stress, the author dug into regulations of its damage and how the pattern BOX method releases the stress. According to the technic’s regulations in the study, the author managed to improve the micro cantilever beam fabrication process based on SOI, and finally explored the influence of internal stress in buried oxide layer on other sensors’production.This research mainly adopts the way of theoretical analysis, FEM simulation and experimental verification with the combination of research results methods. Moreover, there is a lot of work on the research in the following paragraphs:(1) The author analyzed the mechanism of BOX layer breakage in the fabrication process of cantilever, including the analysis of failure process in the original previously method, buried oxide layer internal stress and tensile failure mechanism of brittle material, which are applied to the research background of this paper. We also summarized the thought of patterning the buried oxide layer technology and the analysis of the whole fabrication process, discussed the influence of the way that internal stress changes, in order to solve the stress effect of processing technology.(2) We studied the source in which the buried oxide layer stress generated. Considering different kinds of SOI silicon wafer manufacturing methods and their internal stress factors, based on heterogeneous oxidation of silicon material theory. We also analyzed the influence factors that affect the internal stress, so as to get the expression of internal stress and numerical model under different conditions.(3) By the discussions of the internal stress in different conditions and under the influence factors, we established the numerical theory model. At different annealing temperature, the top of the silicon strip speed and the influence factors of SOI wafer size, SOI material and the final size of the internal stress of the cantilever model get along with the change condition of the theory.(4) By the FEM simulation method, a buried oxide layer simulation model of internal stress is established. We designed the cantilever model in view of the wet etching residual thickness of bulk silicon in modeling process, to confirm the BOX internal stress’s breaking mechanism in the process of the cantilever production. According to the theory of brittle material fracture and the simulation data, technological parameters like the bulk silicon thickness is redesigned and the buried oxide layer patterning process got redesigned. With the buried oxide stress model and the simulation results, We reconsidered the micro cantilever fabrication process based on SOI, and design the verification experiment to verify the results.The research studied the internal stress in the buried oxide layer of the SOI wafer, and the mechanism of the cantilever structure breakage in its own fabrication, which plays an important role in the field of micro sensor production based on SOI wafer. The internal stress’s impact mechanism and the way it analyzed described in this paper will also help to put forward some new methods, in order to reduce the side effects of internal stress in the production of various kinds of micro/nano components in MEMS.
Keywords/Search Tags:micro-nano fabrication technology, micro-cantilever, BOX internal stress, oxidation stress analysis, ANSYS simulation
PDF Full Text Request
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