發(fā)布時間：2018-01-17 14:08

  本文關鍵詞：帶偏角4H-SiC同質外延生長和拉曼散射研究　出處：《西北大學》2015年碩士論文　論文類型：學位論文

  更多相關文章： 4H-SiC 拉曼光譜 載流子濃度 LOPC模

【摘要】：碳化硅(SiC)屬于第三代寬禁帶半導體材料,是重要的間接帶隙半導體之一,具有優(yōu)異的物理特性和電學特性。因而,SiC電子器件非常適合在高溫、高頻和大功率等特殊情況下工作,在許多領域都具有很重要的應用價值。制造SiC功率器件的關鍵之一,是在4H-SiC上生長一層同質外延層,其物理、電學特性,都與其摻雜的載流子濃度密切相關。因此,需要一種有效可靠的方法對4H-SiC外延層的載流子濃度進行研究。拉曼散射是一種對實驗樣品沒有損害的測試方法,不用對樣品進行專門的處理,并可以方便快捷的對樣品結構進行分析。本文使用水平熱壁低壓化學氣相沉積技術,進行了有偏角4H-SiC襯底上同質外延生長工藝的實驗,對三個影響載流子濃度的實驗參數(shù)進行對比實驗,得出最適合拉曼散射載流子分析的碳硅比、生長溫度和生長氣壓。經過對比分析后,我們使用最佳的實驗方案：在偏離(0001)面8。的2寸n型4H-SiC單晶上生長不同摻雜濃度的外延層。制備過程中SiH4、C3H8作為Si源和C源；高純N2與TMA作為摻雜的N和Al源,氫氣為載氣。外延樣品生長溫度在1580℃,壓力為100mbar。通過調節(jié)N2與TMA來改變摻雜N和A1的濃度。在室溫下對不同摻雜濃度的4H-SiC外延層進行拉曼光譜測試,通過使用MATLAB擬合等離子聲子耦合模的線型,并通過擴展的經典介電函數(shù)計算出載流子的濃度。通過對比發(fā)現(xiàn)經過拉曼測量后計算出來的載流子濃度的理論計算值,與SIMS測量的結果符合的很好。即可與通過拉曼測試來給出材料的載流子濃度。對LOPC峰進行分析,發(fā)現(xiàn)隨著摻雜濃度的變大,載流子濃度變大,LOPC峰藍移,頻移變大,散射強度變小,峰寬變寬。LOPC峰發(fā)生藍移主要和壓縮應力有關。隨著摻雜濃度的增加,其LOPC峰的半高寬會變寬,這與晶體內缺陷的變化有密切關系。隨著摻雜濃度的增大,使得自由載流子濃度增加,自由載流子數(shù)量的增加就會使得勢能降低,從而引起散射強度降低,隨之引起峰強的變化。
[Abstract]:Silicon carbide (sic) is one of the third generation wide band gap semiconductor materials and is one of the important indirect band gap semiconductors with excellent physical and electrical properties. Therefore sic electronic devices are very suitable for high temperature. High frequency and high power are very important applications in many fields. One of the keys to fabricate SiC power devices is to grow a homogeneous epitaxial layer on 4H-SiC. The electrical properties are closely related to the carrier concentration. An effective and reliable method is needed to study the carrier concentration of 4H-SiC epitaxial layer. Raman scattering is a kind of testing method without any damage to the experimental sample. The structure of the sample can be analyzed conveniently and quickly. In this paper, the experiment of homoepitaxial growth on 4H-SiC substrate with deflection angle was carried out by using horizontal hot wall and low pressure chemical vapor deposition technology. The three experimental parameters affecting carrier concentration were compared, and the C / Si ratio, growth temperature and growth pressure which were most suitable for Raman scattering carrier analysis were obtained. We use the best experimental scheme: the epitaxial layer with different doping concentration is grown on the 2-inch n-type 4H-SiC single crystal deviated from the plane 80.The SiH4 is used in the preparation process. C _ 3H _ 8 is used as Si source and C source. High purity N2 and TMA were used as doped N and Al sources and hydrogen as carrier gas. The growth temperature of epitaxial samples was 1580 鈩，

本文編號：1436564