High Speed Field Programmable LSI Using Current-Drive Silicidation

采用钽/非晶硅/钽结构研制了反熔丝器件，大大缩短了大规模集成电路的开发周期。我们已经证明，通常只在高于70 0ﾟC的温度下发生的硅化反应，可以在室温下通过“电流驱动硅化”进行，从而允许对反熔丝进行非常快速的编程。用超净等离子体工艺制造的反熔丝器件，可以在短时间内用“电流驱动硅化”方法编程，相当于5000m/s的反应速度，这在通常的热反应中是不可想象的。硅化后的接触电阻小于30omega，在硅化之前，非晶硅在200250ﾟC的温度范围内沉积时，将漏电流限制在足够低的水平上，以分离开和关状态。我们已经证明，通过在多室De…中顺序地在Ta膜上沉积非晶态硅在多位置系统中，在不将钽表面暴露在洁净室空气中的情况下，反熔丝在高达400ﾟC的温度下不会退化。为了表征操作偏置下泄漏电流的来源和电流驱动硅化的机理，我们研究了以钽、钛和铝为金属的反熔丝结构。此外，我们使用n型和p型硅衬底，形成了Ta/非晶硅/晶硅类型的肖特基二极管，目的是表征势垒高度和二极管特性。我们还通过研究接触电阻随编程参数的变化，以及通过分析接触区横截面的扫描电子显微镜和透射电子显微镜照片，阐明了许多固化机理。最后，为了建立实用LSI电路的设计规则，采用NMOS技术对TEG进行了精心设计，使寄生电容和寄生电阻最小化。根据本研究的结果，建立了Ta/非晶硅/Ta的反熔丝结构的制造工艺的基本原理，该结构允许高速编程和非常低的状态电阻。较少

The antifuse device, that enables to drastically shorten the development cycle time of LSI circuits, was developed using tantalum/amorphous silicon/tantalum structure. We have shown that the silicidation reaction, that usually occurs only at temperatures higher than 700ﾟC,can be carried out at room temperature by the "current-drive silicidation" allowing a very fast programming of the antifuse. Antifuse devices made by ultraclean plasma process can be programd by "current drive silicidation" in the short time of less than 1 nsec, that is equivalent to a reaction speed of 5000m/sec, unimaginable in usual thermal reaction. The contact resistance after the silicidation is less than 30 OMEGA, and before the silicidation, the amorphous silicon, when deposited at temperature in the range of 200-250ﾟC,limits the leakage current at a level low enough to separate the on and off states. We have shown that by depositing the amorpous silicon over the tantalum film in sequence in a multi chamber de … More position system, without exposing the tantalum surface to the clean room air, there is no degradation of the antifuse up to a temperature as high as 400ﾟC.In order to characterize the origin of the leakage current under the operation bias and the mechanism of the current drive silicidation, we have studied antifuse structures using tantalum, titanium, and aluminum as the metal. In addition, we have formed Schottky diodes of the type tantalum/amorphous silicon/crystalline silicon, using silicon substrates of both, n and p type, with the purpose of characterizing the barrier height and the diode characteristics. We have also clarified many of the cilicidation mechanism by studying the contact resistance as a function of the programming parameter, as well as by analyzing SEM and TEM pictures of the cross sections at the contact region. Finally, in order to establish design rules of practical LSI circuits, TEG's were carefully designed to minimize the parasitic capacitances and resistances, using nMOS technology. From the results obtained in this research, the fundamentals of the fabrication process of antifuse structures of the type tantalum/amorphous silicon/tantalum, which allows high speed programming and very low on state resistance, were established. Less