4H-SiC PIN型日盲紫外探测器的研究及制备

发布时间：2018-03-19 08:50

  本文选题：紫外探测器　切入点：4H-SiC　出处：《西安电子科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：紫外探测器是一类军民两用的探测器,在导弹预警、水质检测和灾害天气预报等方面均有重要的用途。4H-SiC具有禁带宽度宽、击穿电场高、热导率高以及载流子饱和漂移速率快等特点,使其成为制备紫外探测器的理想材料之一。相对于早期的硅基紫外光探测器,4H-SiC紫外探测器具有良好的可见日盲特性,不需要昂贵的滤光系统、能在室温下工作以及较低的暗电流等优点。国内外对4H-SiC PIN型紫外探测器的研究在近几十年均有相关的报道,PIN型结构的紫外探测器具有较低的噪声、较高的量子效率和较快的响应速度等特点。本文主要基于所设计的器件结构和材料参数用器件仿真软件Sentaurus模拟了PIN型紫外探测器的电响应特性和光谱响应特性。通过仿真研究发现:(1)p层掺杂浓度或厚度改变时其对器件的暗电流影响很小,当p层的掺杂浓度或厚度减小时器件的光电流和光谱响应会有相应的提高且器件光谱响应的峰值波长会往短波方向移动;(2)本征i层的掺杂浓度或厚度在一定范围内变化时其对器件暗电流和光电流的影响很小,当i层的掺杂浓度减小或厚度增加时器件的光谱响应会有相应的提高且器件光谱响应的峰值波长会往长波方向移动。通过仿真观察发现,相对于本征i层,当p层材料参数改变时,其对器件光电流和光谱响应的影响更为显著。同时还提出了三种有利于减小器件表面反射率,提高器件外量子效率的方法,并用仿真验证了这三种方法的可行性。这三种方法分别是减小器件正面电极的面积、在器件表面添加一层减反射薄膜和增加器件表面的粗糙度。其中前两种方法比较容易实现,因此在实际器件制备过程中这两种方法的设计实现应着重考虑。对于第三种方法,在实际工艺中我们一般采用图形化表面来提高器件表面的粗糙度,该方法对器件制备工艺的要求比较高。最后进行了器件制备的相关实验,主要关键的工艺包括外延片的标准清洗、光刻和金属剥离、ICP干法刻蚀、高温热氧化和欧姆接触电极的制备等。其中对光刻和金属剥离、4H-SiC的ICP刻蚀以及4H-SiC的P型欧姆接触实验做了主要的研究:(1)在光刻和金属剥离实验中,采用了正胶进行剥离,磁控溅射的方式淀积金属,最后在丙酮溶液中进行剥离,金属剥离后的效果满足实验的要求;(2)在对4H-SiC进行ICP刻蚀时,采用了SF6和O2的混合气体,气体的流量分别为50sccm和10sccm,刻蚀后得到的侧面轮廓较为陡直;(3)在4H-SiC P型欧姆接触实验中,采用了Ti/Al金属,金属层的厚度分别为30nm/120nm,在1000℃通N2的氛围下退火1min,经测量计算后得到的比接触电阻率大小约为5.37×10-4Ω?cm2。在制备器件的实验过程中根据每一道工艺的结果和可重复性研究并确定了合适的工艺方案。
[Abstract]:Ultraviolet detector is a kind of dual-purpose detector. It has important applications in missile early warning, water quality detection and disaster weather forecast. 4H-SiC has wide forbidden band width and high breakdown electric field. Due to its high thermal conductivity and high carrier saturation drift rate, it has become one of the ideal materials for preparing UV detectors. Compared with the early silicon-based UV detectors, 4H-SiC UV detectors have good visible and solar blindness. There is no need for expensive filter system, which can work at room temperature and has the advantages of low dark current. The research on 4H-SiC PIN UV detector has been reported in recent decades. In this paper, based on the designed device structure and material parameters, the electrical and spectral response characteristics of the PIN type UV detector are simulated by using the device simulation software Sentaurus. The simulation results show that the influence of the doping concentration or thickness on the dark current of the device is very small. When the doping concentration or thickness of the p-layer decreases, the photocurrent and spectral response of the device will be improved accordingly, and the peak wavelength of the spectral response of the device will shift to the shortwave direction.) the doping concentration or thickness of the intrinsic I layer is in a certain range. The effect of internal variation on the dark current and photocurrent of the device is very small. When the doping concentration of I layer decreases or the thickness increases, the spectral response of the device will increase and the peak wavelength of the spectral response of the device will move towards the direction of long wave. When the p-layer material parameters are changed, the photocurrent and spectral response of the device are more significantly affected. Three methods are also proposed to reduce the surface reflectivity of the device and improve the quantum efficiency outside the device. The feasibility of the three methods is verified by simulation. The three methods are to reduce the area of the front electrode of the device, to add an antireflection film on the surface of the device and to increase the roughness of the surface of the device. The first two methods are easy to implement. Therefore, the design and realization of these two methods should be considered in the process of practical device fabrication. For the third method, we generally use graphical surface to improve the roughness of device surface in the practical process. This method has a high requirement for the fabrication process of the device. Finally, the relevant experiments of device fabrication are carried out. The main key processes include standard cleaning of the epitaxial plate, lithography and dry etching of the metal strip ICP. High temperature thermal oxidation and preparation of ohmic contact electrode. The ICP etching of lithography and exfoliation of 4H-SiC and the P-type ohmic contact experiment of 4H-SiC were mainly studied. The metal was deposited by magnetron sputtering, and finally peeled off in acetone solution. The effect of metal stripping met the requirements of the experiment. (2) in the ICP etching of 4H-SiC, the mixed gas of SF6 and O2 was used. The flow rate of the gas is 50sccm and 10sccm, respectively. The side profile obtained by etching is steeper and steeper. In the experiments of 4H-SiC P ohmic contact, Ti/Al metal is used. The thickness of metal layer is 30nm / 120nm, annealed at 1000 鈩，

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