【作者】 刘健敏；

【导师】 夏义本；

【作者基本信息】 上海大学 ， 材料学， 2007， 博士

【摘要】 CVD金刚石薄膜具有优异的电学、光学、热学、机械性能和化学稳定性，能够耐高温、耐腐蚀和抗强辐射，成为当前微电子器件在苛刻环境下工作的首选材料。CVD金刚石薄膜的制备及其应用已经成为国际前沿课题。本文主要研究了HFCVD金刚石薄膜的制备及其在光电器件方面的应用。首先，采用热丝辅助化学气相沉积(HFCVD)法，通过改变生长参数，获得了不同晶粒尺寸以及晶粒尺寸相近的不同取向的金刚石薄膜。通过微电子光刻工艺成功制备了不同晶粒取向、不同晶粒尺寸的金刚石薄膜紫外光探测器。研究表明，探测器性能与金刚石薄膜晶粒大小密切相关，随着晶粒尺寸的增加，光电流／暗电流之比以及净光电流均提高。在晶粒尺寸相近的情况下，(100)取向的金刚石薄膜探测器的光谱响应特性优于其它取向的金刚石薄膜探测器。同时，提出对器件采用甲烷和空气后处理工艺，明显提高了紫外光探测器的光谱响应特性。薄膜的取向性、晶粒尺寸和后处理工艺对金刚石薄膜紫外光探测器的性能有显著的影响。认为采用大晶粒、高度(100)取向的薄膜以及合适的后处理工艺有利于提高金刚石薄膜紫外光探测器的性能。其次，制备了自支撑金刚石薄膜，研制出ZnO／金刚石薄膜结构紫外光探测器。研究了金刚石薄膜成核面的表面粗糙度，Au电极与ZnO压电薄膜的接触特性以及ZnO压电薄膜的晶粒尺寸对紫外光探测器电学性能的影响。主要得到以下结果：自支撑金刚石薄膜的成核面表面极其光洁，粗糙度达到1．5nm(1μm×1μm)：采用金原子轰击，结合退火处理工艺，使Au／ZnO薄膜形成很好的低阻欧姆接触；ZnO／金刚石薄膜结构紫外光探测器暗电流和光电流的大小与ZnO薄膜的晶粒尺寸有关，晶粒尺寸越大，暗电流越小，而光电流越大；多晶ZnO薄膜晶界密度较高，由于晶界富含陷阱，探测器的光响应呈现出较长的光电流上升以及衰减时间(分别为10 min与3 min)。光电流的上升以及衰减过程证实了载流子的陷阱效应。最后，在不同的工艺参数条件(沉积温度和气压)下沉积纳米晶金刚石薄膜作为X射线掩膜材料。结果表明，在沉积温度为640℃、沉积气压为2．5kPa条件下，可实现高透过率的、光滑的纳米金刚石薄膜。采用氢刻蚀的方法进一步优化了纳米金刚石薄膜的生长工艺。通过显微结构和光学性能的表征和分析表明，在反应气压、衬底温度等沉积参数保持一定的情况下，随着刻蚀时间的增加，晶粒尺寸逐步减小，薄膜的表面平整度、折射率以及光学透过率得到明显改善，X射线透过率明显提高，光学透过率在632．8nm处达到51％，X射线透过率在258eV处达到52．8％，符合X射线光刻掩模材料的要求。研究结果表明，纳米金刚石薄膜X射线掩膜材料的光学性能主要是由薄膜中的sp~2键含量以及薄膜的表面粗糙度共同决定的。更多还原

【Abstract】 The unique optical, electrical, thermal, mechanical properties and outstanding chemical stability of diamond film make it an ideal material for micro-electronics devices in future especially at high temperature, high radiation and corrosion environments. It has been the international interesting subjects that the fabrication of CVD diamond films and their applications. In this thesis, the fabrication of HFCVD diamond films and their applications in photoelectron devices are studied.Firstly, diamond films with different orientation and grain size were achieved by changing the deposition condition in hot filament chemical vapor deposition (HFCVD) system. The UV detectors were fabricated successfully from diamond thin films with different orientation and grain size by the microelectronic processing. Results show that the performance of the detector was related to the grain size of the diamond film. With increasing the grain size, the photocurrent, the ratio of photocurrent to dark current and the net photocurrent increased. In the case of the diamond films with similar grain size, the detector fabricated from (100)-oriented diamond film had a better characteristic of spectral response than the ones from other orientation. In addition, a successive post treatment of the detector in CH4 gas followed by air atmosphere can enhance obviously the spectral responsivity of the UV detector. The orientation, the grain size of the diamond thin film and the post treatment can affect the performance of UV detector significantly. It’s important to achieve the diamond film with big grain size and highly (100)-oriented and use the proper post treatment, which is in favor of fabricating the UV detector with good performance.Secondly, freestanding diamond films were prepared, and ultraviolet photodetectors with ZnO/diamond film structure were fabricated. The surface roughness of nucleation side of freestanding diamond film, the properties of Au contacts on ZnO films and effects of grain sizes on the electrical characteristics of photodetectors were discussed. The results indicated that the surfaces of nucleation sides were very smoother, and the surface roughness of nucleation side reached 1.5nm(1μm×1μm); Due to the bombardment with Au atoms and the annealing process, fine ohmic contacts were formed between Au electrodes and ZnO films; Dark currents and photocurrents of photodetectors were related to the grain size of ZnO films, For the photodetector with a bigger grain size, a lower dark current and a higher photocurrent were obtained; The photocurrent increases swiftly and then saturate gradually with the irradiation time process. Due to using the polycrystalline ZnO films with high densities of grain boundaries which are full of traps, the photoconductor shows the transient UV-response with a long photocurrent rise and decay time of around 10 min and 3 min, respectively. The photocurrent rise and decay process confirmed the carrier trapping effect.Thirdly, the fabrication of NCD films on different conditions for X-ray mask matetrial has been studied. The result shows that the nano-crystalline diamond film has a higher transmission and a smoother surface at deposition temperature of 640℃and gas pressure of 2.5kPa. Hydrogen etching method is applied to the experiments to optimize the parameters. From the charactristic of the structure and optical property, the grain size and surface roughness decrease while the refractive index and optical transmission increase obviously under certain deposit parameters (gas pressure and substrate tempreture) and longer etching time. Optical transmission reaches 51% at the wavelength of 632.8nm. Soft X-ray transmission measurements by synchrotron radiation are also carried out on the NCD films. The result shows that the X-ray transmission has an obvious improvement when the NCD film is fabricated from the hydrogen etching method. And the transmission reaches 52.8% at an X-ray photon energy of 258eV, which has meet the requirement for X-ray mask matetrial. The optical performance of the NCD films is mainly co-determined by the two factors of surface roughness and the content of sp~2 phase更多还原