| Based on the extensive research literature, the formation of 3D PN junction and the application in the fabrication of isotope batteries and X-ray detectors is explained, and the fabrication technology is also studied, specially the formation principle of porous structure fabricated by Electrochemical etching is discussed in the paper. At the same time, the fabrication experiment of 3D PN junction by the use of SiO2 and Si3N4 mask.The formation, application and the research status of 3D PN junction based on macroporous silicon and the work in this thesis are firstly introduced in Chapter 1.The fabrication technology of 3D PN junction, focus on the Electrochemical etching on porous silicon and its impact factors, are described in Chapter 2.The fabrications of macroporous silicon structure on the p-type silicon by the use of SiO2 mask and 3D PN junction by further diffusion are discussed in Chapter 3. The electrical properties are measured including IV and CV test. The impact of the hole depth is simulated and the impact of the wall thickness is specially analyzed. It was found that the increasing depth has little impact on the effective junction area when the wall thickness is so thin that the diffusion layers is close to converge.The fabrications of macroporous silicon structure on the p-type silicon by the use of Si3N4 mask with low stress and 3D PN junction by further diffusion are discussed in Chapter 4. It is important to increase the wall thickness to enhance the effective junction area. It was found that the wall thickness can not increase the wall thickness by the use of Si3N4 mask with strong corrosion resistance and low stress, indicating that wet etching may not be able to achieve increasing of wall thickness. To solve the problem, DRIE dry etching is employed to fabricate macroporous silicon. And this work is still in progress.Summary is present in Chapter 5, and prospect on the development of energy conversion chips based on 3D PN junction structure is portrayed. |
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