大尺寸硅衬底GaN基HEMT外延生长研究

发布时间：2018-06-03 13:53

  本文选题：氮化镓外延生长 + 大尺寸硅衬底　； 参考：《华中科技大学》2016年博士论文

【摘要】：自1993年第一支GaN基电子器件发明以来,以AlGaN/GaN异质结为核心的高电子迁移率晶体管在近二十年内得到了快速发展。然而,目前GaN基电子器件成本高昂,市场空间较小,相比于GaN基LED器件,还远谈不上成功,而基于大尺寸硅衬底外延GaN基HEMT是降低器件成本扩大市场应用的重要途径之一。硅衬底成本低廉,大尺寸制备容易,热导率良好以及可与传统硅工艺相兼容,使其成为HEMT外延生长的首选衬底。但是GaN与Si(111)衬底之间巨大的晶格失配和热失配会导致GaN薄膜位错密度高、翘曲大以及容易龟裂,使得GaN电子器件制备困难,限制了GaN基HEMT器件的广泛应用。为了提高硅衬底上HEMT材料质量,使其满足高性能器件制备的要求,本论文主要围绕HEMT外延生长中缓冲层设计、应力控制层设计、翘曲控制、高阻层设计和AlGaN/GaN/Ga(Al)N源区设计等方面开展研究工作,取得的主要成果如下：对于A1N缓冲层外延生长,分别研究了硅衬底热处理时间、预铺TMA1时间、同温/双温生长以及A1N厚度对薄膜形貌和晶体质量的影响,发现衬底热处理最佳时长约为5 min,并且热处理过程中通入SiH4可以改善A1N表面形貌,最佳预铺铝时间为12-15s,单温生长更适合A1N薄膜生长,最优A1N缓冲层厚度为-250 nm,对应的薄膜(0002)面双晶摇摆曲线半高宽为1014"。对于应力控制层设计,提出了两层AlGaN应力控制层结构,通过预先引入压应力,成功实现了高质量无裂纹的GaN薄膜外延生长。基于TEM表征和Williamson-Hall测试方法,系统研究了外延层的马赛克结构演变过程,发现AlGaN应力控制层不仅过滤大量位错,而且引入的压应力使得部分位错转弯湮灭,最终才得以实现镜面光滑无裂纹低位错密度的GaN薄膜,5μm×5 μm区域RMS=0.31nm, (0002)面和(1012)面双晶摇摆曲线半高宽分别为305"和336"。对于翘曲控制,详细分析了硅上GaN外延生长过程中应变的演化机制,硅上A1N生长时受到轻微张应力(0.66 GPa),而AlGaN 1和AlGaN2由于晶格失配分别受到较大的压应力(-3.57 GPa和-2.41 GPa)。由于GaN生长初期存在3D转2D的过程,在此过程中,“裂纹转弯湮灭”会释放部分压应力,“晶粒合并”会引入一定张应力,最终降低了GaN薄膜所受的压应力(-0.75 GPa)。为降低GaN-on-Si翘曲高度,提出了两种有效降低外延片翘曲的方案：增加硅衬底厚度以及减薄AlGaN/AIN层厚度。对于高阻层设计,首先建立了MOCVD生长条件与碳浓度的量化函数关系,然后基于建立的生长条件与碳浓度的函数关系,对比了Ga(Al)N层中不同碳浓度(从-1016cm-3分布到1019 cm-3)、不同铝组分(0和7%)、不同厚度(从1.7μm到3.1 μm)和不同类型硅衬底(n型和p型)对HEMT器件击穿电压的影响。实验发现,采用p型硅衬底以及在Alo.07Gao.93N层中掺碳,可以获得更高的关态击穿电压,最终成功制备了击穿电压为1000 V @ 1μA/mm的器件。对于AlGaN/GaN/Ga(Al)N异质结设计,首先研究了AlGaN背势垒层和GaN沟道层对材料电学性能的影响,然后理论计算结合实验设计分析了AlGaN/GaN中GaN沟道层、A1N插入层、AlGaN势垒层和GaN帽层与HEMT电学性能的关系,提出采用Al0.07Ga0.93N背势垒层和较厚的GaN沟道层(150 nm),并通过降低沟道层中碳杂质浓度1017cm-3、改善界面形貌、减少合金散射和提高势垒层质量,可以大幅度改善HEMT电学性能,最终实现了迁移率μ=2094 cm2/Vs,二维电子气密度ns=1.23×1013cm-2,方块电阻R□=243Ω的硅上GaN基HEMT材料外延生长。基于优化的硅上HEMT外延生长条件,分别在四英寸和六英寸硅衬底上外延生长了高质量AlGaN/GaN/Alo.o7Gao.93N HEMT外延结构,外延片镜面光滑无裂纹翘曲低,电学性能优异(迁移率大于2000 cm2/Vs,方块电阻低于280Ω)。基于生长的6英寸HEMT外延片,制作出有源区面积为1.7×2.8 mm2的GaN器件,输出电流达19 A,比导通电阻为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..
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN386

【相似文献】

相关期刊论文 前10条

1 汤广平,刘明登,全宝富,赵慕愚;SiCl_4-SiH_4-H_2混合源的硅外延生长[J];半导体学报;1986年06期

2 高桥健二;潼l⒚，

本文编号：1973023