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一、引言 GaAs集成电路的发展与在半绝缘衬底上进行外延的外延层或进行出子注入形成导电沟道的质量和接触区的常规工艺有关。由于在器件和电路制造过程中,存在外延材料成本高以及难以制成浅结等问题,所以,近年来,国际上广泛开展了离子注入高纯半绝缘GaAs来制造砷化镓场效应晶体管和进行GaAs单片集成电路的研究。离子注入具有掺杂浓度可控,均匀性和重复性好的特点,以及与其它工艺组合灵活等优点。但注入样品必须在高温(≥800℃)下退火,以消除注入损伤和电激活掺杂剂。在通常的炉子退火(850℃,30′)条件下,由于GaAs表面的As原子易挥发,使得GaAs的化学计量比失配,造成器件特性变坏。使用包封层,虽然解决了As原子的挥发问题,但由于包封层与样品之间的热膨胀系数不匹配,在高温下存在热应力,进而引起膜皱曲甚至脱落,样品表面层中该热应力引入缺陷杂质对材料特性产生影响。目前,国外研究较多的是快速热退火(RTA)。这种方法由于退火时间短,退火温度高,更有利于复杂缺陷的消除,激活层电特性好,注入杂质和衬底杂质的互扩散小,不需包封层,因此消除了包封层和衬底界面处的应力和组分互扩散,而且退火时不涉及AsH_3这样的有毒气体。
I. INTRODUCTION The development of GaAs integrated circuits has something to do with the conventional process of epitaxy of epitaxial layers on semi-insulating substrates or of sub-implanting to create the quality and contact area of the conducting channel. Due to the high cost of epitaxial materials and the difficulty in making shallow junctions in the device and circuit manufacturing processes, in recent years, ion implantation of high purity semi-insulating GaAs has been widely carried out in the world to make gallium arsenide field effect transistors GaAs Monolithic Integrated Circuit. Ion implantation with doping concentration controllable, uniform and good reproducibility characteristics, and combined with other flexible process advantages. However, the injected sample must be annealed at high temperatures (≥800 ° C) to eliminate implant damage and electrically activated dopants. Under the condition of normal furnace annealing (850 ℃, 30 ’), the stoichiometric ratio of GaAs is mismatched due to the volatility of As atoms on the surface of GaAs, resulting in deterioration of device characteristics. The use of an encapsulant solves the problem of volatilization of As atoms but due to the mismatch of the thermal expansion coefficient between the encapsulant and the sample, there is thermal stress at high temperature, which in turn causes the film to buckle or even come off, and the heat in the sample surface layer Impacts of stress on the introduction of defects affect the material properties. At present, more research abroad is rapid thermal annealing (RTA). Due to the short annealing time and high annealing temperature, this method is more conducive to the elimination of complex defects. The active layer has good electrical properties. The interdiffusion of impurities and impurities is small, and no encapsulation layer is needed. Therefore, the encapsulation layer and The stress and composition at the substrate interface diffuse into each other and the annealing does not involve toxic gases like AsH 3.