CAREER: Fundamental Reliability Physics of MOS Devices Based on Deuterium Isotope Effects

拟议的职业发展计划是在MOS晶体管可靠性物理方面的综合研究和教学努力。这份职业建议书的研究部分侧重于MOS器件退化机理及其同位素效应的基础研究。MOS晶体管的退化是由于高能超热电子导致SiO_2-Si界面的Si-H(氢)键断裂所致。目前的理论和实验表明，Si-H键的断裂是由两个相互竞争的过程引起的：由高能超热电子引起的激发和由Si-H键的振动模和Si晶格的声子模之间的能量耦合引起的去激发。Si-D键与Si晶格(到声子)之间的能量耦合比Si-H键与Si晶格之间的能量耦合要有效得多。因此，Si-D键比Si-H键更强健，这就是所谓的同位素效应。基于这一原理，经过氘处理的MOS晶体管表现出比传统的氢处理更长的热载流子寿命(超过50倍)。有证据表明，如果了解退化的机制及其同位素效应，MOS晶体管的寿命有可能进一步提高100倍以上。这两个振动模之间的有效能量耦合的特征是它们的频率相同或非常接近。能量耦合的研究对于理解降解的机理及其同位素效应是至关重要的。该研究计划将集中在两个方面：1)从基本角度研究深亚微米MOS晶体管的退化机理；2)研究CMOS型反相器中MOS器件的动态热载流子退化。在第一个推力中，我将使用拉曼光谱和红外光谱来研究Si-H键和Si-D键的振动模式。研究计划的最终目标是开发预测原理，根据这些原理可以设计工艺以实现MOS晶体管的最大寿命改进。在第二个推力中，我将研究动态应力或交流应力下晶体管的氚同位素效应，因为晶体管在实际电路中是在交流条件下工作的。这一职业计划的教育部分寻求支持开发新的实验课程、集成电路器件制造，并在阿巴拉契亚社区(代表性不足的群体)开展有重点的教育推广活动。在肯塔基州通过研究挑战信托基金(RCTF)的支持下，英国正在建设一个设备制造设施。将开发一门专注于集成电路器件制造的新实验课程，相当于美国其他大学的类似课程。这门课程是一门动手实验课程，学生有机会为集成电路制造半导体器件。本课程将于2001年秋季开课，面向高年级本科生和研究生。该项目的多学科性质将为学生提供一个独特的研究和学习环境。其目标是通过综合方法开展研究和教学，在物理、材料科学和电气工程等传统学科之间架起桥梁。教育目标的另一个组成部分涉及针对肯塔基州东部和南部包括阿巴拉契亚社区的高中生的教育推广活动。其中一个目标是通过举办一系列微电子领域的研讨会来鼓励这些高中生追求高科技职业。另一个是提供一个实验项目，教他们建造一些有用的数字电路。高中生将从已经建立的项目中招募，该项目由农村发展中心组织，PI已经参与了罗杰斯学者项目。

The proposed CAREER development program is an integrated research and teaching effort in MOStransistor reliability physics. The research component of this CAREER proposal focuses on fundamental study of mechanisms for the MOS device degradation and its isotope effect. The MOS transistor degradation is caused by Si-H (hydrogen) bond breaking at the SiO2-Si interface due to the energetic hot electrons. The current theory and experiments suggest that the Si-H bond breaking is caused by two competing processes: the excitation due to the energetic hot electrons and the de-excitation by energy coupling between the vibrational modes of the Si-H bonds and the phonon modes of the Si lattice. The energy coupling between the Si-D (deuterium) bonds and the Si lattice (TO phonon) is much more efficient than that between the Si-H bonds and the Si lattice. Therefore the Si-D bonds are more robust than Si-H bonds, which is the so-called isotope effect. Based on this principle, the deuterium-treated MOS transistors exhibit much longer hot-carrier lifetime (over 50 times) than the traditional hydrogen treatment. Evidence shows that there is a potential for further improvement of MOS transistor lifetime by over 100 times, if the mechanisms for degradation and its isotope effect are understood. The characterization of the efficient energy coupling between the two vibrational modes is that their frequencies are the same or very close. The study of the energy coupling is vital to understand the mechanisms for degradation and its isotope effect. The proposed research program will focus on two thrusts: 1) Degradation mechanisms for deep-submicron MOS transistors from fundamental point of view and 2) Study of dynamic hot-carrierdegradation of MOS devices in CMOS inverters. In the first thrust, I will use Raman and Infrared (IR)spectroscopy to study the vibrational modes of the Si-H and Si-D bonds. The ultimate goal of theresearch program is to develop predictive principles from which the processing can be designed toachieve the maximum lifetime improvement for MOS transistors. In the second thrust, I will study thedeuterium isotope effect for transistors under the dynamic stress or AC stress, because the transistors areoperating in AC conditions in the real circuits. The proposed research builds upon and expands theresearch work that the PI is already undertaking.The educational component of this CAREER program seeks support for development of a newexperimental course, integrated circuit device fabrication, and focused educational outreach activitiesin Appalachian communities (underrepresented groups). With the support from the State of Kentuckythrough the Research Challenge Trust Fund (RCTF), a Device Fabrication Facility is under constructionat UK. A new experimental course focused on fabrication of integrated circuit devices will be developed,which is equivalent to similar courses in other universities in the US. The class is a hands-on lab coursewhere students have the opportunity to build semiconductor devices for integrated circuits. This class willfirst be taught in the Fall 2001 for senior undergraduate students and graduate students. Themultidisciplinary nature of this program will provide students with a unique environment for researchand learning. The goal is to build bridges between these traditional disciplines such as physics, materialsscience, and electrical engineering by conducting research and teaching through an integrated approach.The other component of the educational objectives involves the educational outreach activities targetedfor high school students from Eastern and Southern Kentucky including Appalachian communities. Oneof the objectives is to encourage those high school students to pursue high-tech career by presenting aseries of seminars in microelectronics. Another one is to offer an experimental project to teach them tobuild some useful digital circuits. The high school students will be recruited from the already establishedprogram, the Rogers Scholar Program organized by the Center for Rural Development, which the PIalready participates.