【作者】 习毓；

【导师】 李德昌；

【作者基本信息】 西安电子科技大学 ， 材料物理与化学， 2008， 硕士

【摘要】 横向高压功率器件LDMOS(Lateral Diffused Metal Oxide Semiconductor Field Effect Transistor)以其高耐压、高增益、高跨导、宽动态范围、低失真和易于与低压电路工艺兼容等优点,广泛应用于射频功率集成电路中。射频大功率LDMOS由于具有P、L波段以上的工作频率和高的性价比而成为3G手机基站射频放大器的首选器件。如今LDMOS已经发展到了第五代,设计者们都在努力的通过改变器件的结构或者工艺来提高器件的整体性能。因此,本文在频率特性和电学特性满足使用要求的情况下,主要集中在可靠性的研究方面。本文利用二维器件模拟软件ISE,建立了射频LDMOS器件的模型,比较了射频LDMOS器件的击穿电压和衬底浓度、漂移区浓度、沟道区浓度的关系,分析了RESURF技术原理,验证了RESURF技术对提高LDMOS击穿电压的作用。最后,通过对各个参数的模拟比较,得到了优化的射频LDMOS结构,在大量模拟实验的基础上,最终为射频LDMOS的设计奠定了数据基础。射频LDMOS可靠性的研究主要从两个方面进行。一方面是从击穿电压方面研究,击穿电压是射频LDMOS一个重要的电学参数,同时也是器件可靠性的一个重要方面,我们主要从结构上进行调整,使器件的击穿电压满足使用要求,同时分析了RESURF技术原理,讨论了击穿电压和衬底浓度、漂移区浓度、沟道区浓度的关系。另一方面是从ESD方面进行研究,由于静电放电引起的局部电热击穿也是LDMOS可靠性关键的一个方面,在论文中主要讨论了电热击穿的基本机理和在不增加器件尺寸的情况下不同的LDMOS结构在提高二次电流方面的作用。我们在二维器件模拟软件ISE平台下,采用RESURF技术,提出了在器件内部嵌入一个寄生晶闸管的横向双扩散MOSFET(ESCR-LDMOS)结构。模拟了基于RESURF技术的RF-LDMOS的频率参数(ft、gm)、电学参数(Vt、Idss、BVds)和反应可靠性的雪崩击穿电压(BVds)和二次电流(It2)。文中重点讨论了ESCR-LDMOS器件的击穿电压、电热击穿机理和由于ESD引起的二次电流It2和频率特性,最后给出器件的各个电学参数的模拟结果。在工作频率为1GHZ、阈值电压为3.8V且在不增加器件尺寸、并保持相同的漂移长度(2.7um)和击穿电压(40V)的情况下,与传统的LDMOS器件结构相比,ESCR-LDMOS新结构的二次电流It2是普通LDMOS的7.5倍,并表现出优异的频率特性。更多还原

【Abstract】 Lateral high-voltage power device LDMOS has advantages of high voltage, large gain, high transconductance, wide dynamic range, low distortion and compatibility with low-voltage circuit process. LDMOS is more and more widely used in power radio frequency integrated circuits. LDMOS is the preferred device used in the RF amplifier of 3G base stations because of its high operating frequency up to P or L band and attractive ratio of performance and price. Nowadays, LDMOS has developed to the fifth generation, designers try their best to improve the whole performances through altering device structure and changing process. Therefore, the hot spot of this article concentrate on reliability of LDMOS when frequency behavior and electrical behavior meet application requirement.In the paper, the structure and model of RF-LDMOS had been established; the relations of the breakdown voltage to the substrate concentration,drift doses and channel concentration had been discussed in detail with the software ISE. The theory of the FRESUF technology had been analyzed, the effect of the RESURF to the LDMOS had been proved. At last, the optimal structure of RF-LDMOS has been received after the simulations on the parameters of the RF-LDMOS. Lots of data have been received for the final design of RF-LDMOS.We research the reliability of RF-LDMOS from two aspects. Firstly, breakdown voltage. Breakdown voltage is an important electrical parameter, and is also an important reliability parameter of RF-LDMOS. We mainly improve device structure and make breakdown voltage meet application requirement, analyse the theory of the FRESUF technology, and discuss the relationship the breakdown voltage to the substrate concentration, drift doses and channel concentration. Secondly, ESD protection. Local electro-thermal breakdown caused by ESD is also an important reliability parameter of RF-LDMOS. We mainly study the basic local electro-thermal breakdown mechanism and the function which all kinds of structures of LDMOS can increase maximum second breakdown current, if device measure is not increased.Under 2D-device simulation software ISE, we propose a new lateral double diffused MOSFET with embedded SCR which based on RESURF technology, what we called is ESCR-LDMOS. we simulate frequency parameter RF-LDMOS (ft, gm), electrical parameter(Vt, Idss, BVds), avalanche breakdown voltage (BVds) and maximum second breakdown current(It2) which can reflect reliability. We mainly disscuss avalanche breakdown voltage, local electro-thermal breakdown mechanism, maximum second breakdown current by ESD and frequency characteristic of ESCR-LDMOS, at last we give the simulation results of every electrical parameter. Under 1GHZ operation frequency, 3.8V threshold voltage, the second current of the new structure with the same length of the device measure, drift region and 40V breakdown voltage is 7.5 times than convenional LDMOS, and with excellent RF character.更多还原