發(fā)布時間：2018-03-19 08:50

  本文選題：紫外探測器　切入點：4H-SiC　出處：《西安電子科技大學》2015年碩士論文　論文類型：學位論文

【摘要】：紫外探測器是一類軍民兩用的探測器,在導彈預警、水質檢測和災害天氣預報等方面均有重要的用途。4H-SiC具有禁帶寬度寬、擊穿電場高、熱導率高以及載流子飽和漂移速率快等特點,使其成為制備紫外探測器的理想材料之一。相對于早期的硅基紫外光探測器,4H-SiC紫外探測器具有良好的可見日盲特性,不需要昂貴的濾光系統(tǒng)、能在室溫下工作以及較低的暗電流等優(yōu)點。國內外對4H-SiC PIN型紫外探測器的研究在近幾十年均有相關的報道,PIN型結構的紫外探測器具有較低的噪聲、較高的量子效率和較快的響應速度等特點。本文主要基于所設計的器件結構和材料參數用器件仿真軟件Sentaurus模擬了PIN型紫外探測器的電響應特性和光譜響應特性。通過仿真研究發(fā)現(xiàn):(1)p層摻雜濃度或厚度改變時其對器件的暗電流影響很小,當p層的摻雜濃度或厚度減小時器件的光電流和光譜響應會有相應的提高且器件光譜響應的峰值波長會往短波方向移動;(2)本征i層的摻雜濃度或厚度在一定范圍內變化時其對器件暗電流和光電流的影響很小,當i層的摻雜濃度減小或厚度增加時器件的光譜響應會有相應的提高且器件光譜響應的峰值波長會往長波方向移動。通過仿真觀察發(fā)現(xiàn),相對于本征i層,當p層材料參數改變時,其對器件光電流和光譜響應的影響更為顯著。同時還提出了三種有利于減小器件表面反射率,提高器件外量子效率的方法,并用仿真驗證了這三種方法的可行性。這三種方法分別是減小器件正面電極的面積、在器件表面添加一層減反射薄膜和增加器件表面的粗糙度。其中前兩種方法比較容易實現(xiàn),因此在實際器件制備過程中這兩種方法的設計實現(xiàn)應著重考慮。對于第三種方法,在實際工藝中我們一般采用圖形化表面來提高器件表面的粗糙度,該方法對器件制備工藝的要求比較高。最后進行了器件制備的相關實驗,主要關鍵的工藝包括外延片的標準清洗、光刻和金屬剝離、ICP干法刻蝕、高溫熱氧化和歐姆接觸電極的制備等。其中對光刻和金屬剝離、4H-SiC的ICP刻蝕以及4H-SiC的P型歐姆接觸實驗做了主要的研究:(1)在光刻和金屬剝離實驗中,采用了正膠進行剝離,磁控濺射的方式淀積金屬,最后在丙酮溶液中進行剝離,金屬剝離后的效果滿足實驗的要求;(2)在對4H-SiC進行ICP刻蝕時,采用了SF6和O2的混合氣體,氣體的流量分別為50sccm和10sccm,刻蝕后得到的側面輪廓較為陡直;(3)在4H-SiC P型歐姆接觸實驗中,采用了Ti/Al金屬,金屬層的厚度分別為30nm/120nm,在1000℃通N2的氛圍下退火1min,經測量計算后得到的比接觸電阻率大小約為5.37×10-4Ω?cm2。在制備器件的實驗過程中根據每一道工藝的結果和可重復性研究并確定了合適的工藝方案。
[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，

本文編號：1633537