本文選題：氮化鎵外延生長 + 大尺寸硅襯底　； 參考：《華中科技大學(xué)》2016年博士論文

【摘要】：自1993年第一支GaN基電子器件發(fā)明以來,以AlGaN/GaN異質(zhì)結(jié)為核心的高電子遷移率晶體管在近二十年內(nèi)得到了快速發(fā)展。然而,目前GaN基電子器件成本高昂,市場(chǎng)空間較小,相比于GaN基LED器件,還遠(yuǎn)談不上成功,而基于大尺寸硅襯底外延GaN基HEMT是降低器件成本擴(kuò)大市場(chǎng)應(yīng)用的重要途徑之一。硅襯底成本低廉,大尺寸制備容易,熱導(dǎo)率良好以及可與傳統(tǒng)硅工藝相兼容,使其成為HEMT外延生長的首選襯底。但是GaN與Si(111)襯底之間巨大的晶格失配和熱失配會(huì)導(dǎo)致GaN薄膜位錯(cuò)密度高、翹曲大以及容易龜裂,使得GaN電子器件制備困難,限制了GaN基HEMT器件的廣泛應(yīng)用。為了提高硅襯底上HEMT材料質(zhì)量,使其滿足高性能器件制備的要求,本論文主要圍繞HEMT外延生長中緩沖層設(shè)計(jì)、應(yīng)力控制層設(shè)計(jì)、翹曲控制、高阻層設(shè)計(jì)和AlGaN/GaN/Ga(Al)N源區(qū)設(shè)計(jì)等方面開展研究工作,取得的主要成果如下：對(duì)于A1N緩沖層外延生長,分別研究了硅襯底熱處理時(shí)間、預(yù)鋪TMA1時(shí)間、同溫/雙溫生長以及A1N厚度對(duì)薄膜形貌和晶體質(zhì)量的影響,發(fā)現(xiàn)襯底熱處理最佳時(shí)長約為5 min,并且熱處理過程中通入SiH4可以改善A1N表面形貌,最佳預(yù)鋪鋁時(shí)間為12-15s,單溫生長更適合A1N薄膜生長,最優(yōu)A1N緩沖層厚度為-250 nm,對(duì)應(yīng)的薄膜(0002)面雙晶搖擺曲線半高寬為1014"。對(duì)于應(yīng)力控制層設(shè)計(jì),提出了兩層AlGaN應(yīng)力控制層結(jié)構(gòu),通過預(yù)先引入壓應(yīng)力,成功實(shí)現(xiàn)了高質(zhì)量無裂紋的GaN薄膜外延生長�；赥EM表征和Williamson-Hall測(cè)試方法,系統(tǒng)研究了外延層的馬賽克結(jié)構(gòu)演變過程,發(fā)現(xiàn)AlGaN應(yīng)力控制層不僅過濾大量位錯(cuò),而且引入的壓應(yīng)力使得部分位錯(cuò)轉(zhuǎn)彎湮滅,最終才得以實(shí)現(xiàn)鏡面光滑無裂紋低位錯(cuò)密度的GaN薄膜,5μm×5 μm區(qū)域RMS=0.31nm, (0002)面和(1012)面雙晶搖擺曲線半高寬分別為305"和336"。對(duì)于翹曲控制,詳細(xì)分析了硅上GaN外延生長過程中應(yīng)變的演化機(jī)制,硅上A1N生長時(shí)受到輕微張應(yīng)力(0.66 GPa),而AlGaN 1和AlGaN2由于晶格失配分別受到較大的壓應(yīng)力(-3.57 GPa和-2.41 GPa)。由于GaN生長初期存在3D轉(zhuǎn)2D的過程,在此過程中,“裂紋轉(zhuǎn)彎湮滅”會(huì)釋放部分壓應(yīng)力,“晶粒合并”會(huì)引入一定張應(yīng)力,最終降低了GaN薄膜所受的壓應(yīng)力(-0.75 GPa)。為降低GaN-on-Si翹曲高度,提出了兩種有效降低外延片翹曲的方案：增加硅襯底厚度以及減薄AlGaN/AIN層厚度。對(duì)于高阻層設(shè)計(jì),首先建立了MOCVD生長條件與碳濃度的量化函數(shù)關(guān)系,然后基于建立的生長條件與碳濃度的函數(shù)關(guān)系,對(duì)比了Ga(Al)N層中不同碳濃度(從-1016cm-3分布到1019 cm-3)、不同鋁組分(0和7%)、不同厚度(從1.7μm到3.1 μm)和不同類型硅襯底(n型和p型)對(duì)HEMT器件擊穿電壓的影響。實(shí)驗(yàn)發(fā)現(xiàn),采用p型硅襯底以及在Alo.07Gao.93N層中摻碳,可以獲得更高的關(guān)態(tài)擊穿電壓,最終成功制備了擊穿電壓為1000 V @ 1μA/mm的器件。對(duì)于AlGaN/GaN/Ga(Al)N異質(zhì)結(jié)設(shè)計(jì),首先研究了AlGaN背勢(shì)壘層和GaN溝道層對(duì)材料電學(xué)性能的影響,然后理論計(jì)算結(jié)合實(shí)驗(yàn)設(shè)計(jì)分析了AlGaN/GaN中GaN溝道層、A1N插入層、AlGaN勢(shì)壘層和GaN帽層與HEMT電學(xué)性能的關(guān)系,提出采用Al0.07Ga0.93N背勢(shì)壘層和較厚的GaN溝道層(150 nm),并通過降低溝道層中碳雜質(zhì)濃度1017cm-3、改善界面形貌、減少合金散射和提高勢(shì)壘層質(zhì)量,可以大幅度改善HEMT電學(xué)性能,最終實(shí)現(xiàn)了遷移率μ=2094 cm2/Vs,二維電子氣密度ns=1.23×1013cm-2,方塊電阻R□=243Ω的硅上GaN基HEMT材料外延生長�；趦�(yōu)化的硅上HEMT外延生長條件,分別在四英寸和六英寸硅襯底上外延生長了高質(zhì)量AlGaN/GaN/Alo.o7Gao.93N HEMT外延結(jié)構(gòu),外延片鏡面光滑無裂紋翹曲低,電學(xué)性能優(yōu)異(遷移率大于2000 cm2/Vs,方塊電阻低于280Ω)。基于生長的6英寸HEMT外延片,制作出有源區(qū)面積為1.7×2.8 mm2的GaN器件,輸出電流達(dá)19 A,比導(dǎo)通電阻為11.9mΩ·cm2。
[Abstract]:Since the invention of the first GaN based electronic device in 1993, the high electron mobility transistor with AlGaN/GaN heterojunction as the core has developed rapidly in the past twenty years. However, the GaN based electronic devices are at a high cost and the market space is small. Compared to the GaN based LED devices, it is far from successful, and based on the epitaxial GaN base of large size silicon substrate. HEMT is one of the important ways to reduce the cost of the device to expand the market. Silicon substrate is low cost, large size preparation, good thermal conductivity and compatible with traditional silicon technology, making it the preferred substrate for HEMT epitaxial growth. But the large lattice mismatch and thermal mismatch between GaN and Si (111) will lead to the dislocation density of GaN film High, warped and easy to crack, making GaN electronic devices difficult to prepare, limiting the wide application of GaN based HEMT devices. In order to improve the quality of HEMT materials on the silicon substrate, to meet the requirements of high performance device preparation, this paper focuses on the design of buffer layer, stress control layer design, warpage control, and high resistance layer design in HEMT epitaxial growth. The main achievements of AlGaN/GaN/Ga (Al) N source area design are as follows: for the epitaxial growth of A1N buffer layer, the influence of the heat treatment time of the silicon substrate, the pre spread of the TMA1 time, the same temperature / double temperature growth and the thickness of the A1N on the morphology and crystal quality of the thin film are studied. It is found that the optimum length of the substrate heat treatment is about 5 min. In the process of heat treatment, SiH4 can improve the surface morphology of A1N, the optimum pre laying aluminum time is 12-15s, the single temperature growth is more suitable for A1N film growth, the optimum A1N buffer thickness is -250 nm, and the corresponding film (0002) surface double crystal swing curve is half width and half width is 1014 ". For the stress control layer design, the two layer AlGaN stress control layer structure is put forward. The epitaxial growth of high quality GaN film without crack was successfully realized by pre introduction of compressive stress. Based on TEM characterization and Williamson-Hall testing, the evolution process of the mosaic structure of epitaxial layer was studied systematically. It was found that the AlGaN stress control layer not only filtered a large number of dislocation, but also the introduction of pressure stress made some dislocation turn annihilation, finally, only GaN thin film with smooth mirror smooth and no crack low dislocation density, 5 mu m x 5 mu m region RMS=0.31nm, (0002) and (1012) surface double crystal swing curve half width and width are 305 "and 336" respectively. For warpage control, the evolution mechanism of the strain in the growth of GaN on silicon is analyzed in detail. The A1N growth of silicon on silicon is slightly Zhang Yingli (0.66 GPa), and A LGaN 1 and AlGaN2 are subjected to larger compressive stresses (-3.57 GPa and -2.41 GPa) due to the lattice mismatch. Due to the existence of 3D to 2D at the initial stage of GaN growth, the "crack turn annihilation" will release partial pressure stress in this process. The "grain merger" will introduce a certain tensile stress and at the end reduce the compressive stress (-0.75 GPa) of the GaN film. At low GaN-on-Si warpage height, two schemes to effectively reduce the warpage of epitaxial film are proposed: increasing the thickness of silicon substrate and thinning the thickness of the AlGaN/AIN layer. For the design of high resistance layer, the relationship between the growth condition of MOCVD and the quantitative function of carbon concentration is first established, and then the Ga (Al) N layer is compared based on the relationship between the established growth strip and the carbon concentration. The effects of different carbon concentrations (from -1016cm-3 distribution to 1019 cm-3), different aluminum components (0 and 7%), different thickness (from 1.7 to 3.1 u m) and different types of silicon substrates (N and P) on the breakdown voltage of HEMT devices. It is found that the use of P silicon substrate and the doping of carbon in the Alo.07Gao.93N layer can achieve a higher breakdown voltage, and the final success is successful. The devices with a breakdown voltage of 1000 V @ 1 A/mm are prepared. For the design of AlGaN/GaN/Ga (Al) N heterojunction, the influence of the AlGaN back barrier layer and the GaN channel layer on the electrical properties of the material is first studied. Then the theoretical calculation and experimental design are used to analyze the GaN channel layer, the A1N intercalation layer, the AlGaN barrier layer and the GaN cap layer and the electrical properties of the AlGaN/GaN. By using the Al0.07Ga0.93N back barrier layer and the thicker GaN channel layer (150 nm), and by reducing the carbon impurity concentration in the channel layer, improving the interface morphology, reducing the alloy scattering and improving the barrier layer quality, the HEMT electrical properties can be greatly improved, and the mobility of the =2094 cm2/Vs and the two-dimensional electron gas density ns=1.23 x 10 are finally realized. 13cm-2, the epitaxial growth of GaN based HEMT material on silicon on the block resistance R / =243 Omega. Based on the optimized HEMT epitaxial growth conditions on silicon, the epitaxial growth of high quality AlGaN/GaN/Alo.o7Gao.93N HEMT epitaxial structure on four inch and six inch silicon substrates, with smooth surface without crack and low warpage, and excellent electrical properties (mobility greater than 2000 cm) 2/Vs, the block resistance is less than 280 omega). Based on the growth of 6 inch HEMT epitaxial film, a GaN device with an area of 1.7 * 2.8 mm2 active area is produced with an output current of 19 A and a specific resistance of 11.9m Omega cm2..
【學(xué)位授予單位】：華中科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TN386

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本文編號(hào)：1973023