Semiconductor Manufacturing Research Area
Professors Chang, Christofides, Hicks, Manousiouthakis, Orkoulas, and Nobe
The microelectronics industry is the largest manufacturing employer in the United States, generating revenues in excess of one trillion dollars in 2001. The microelectronics industry has been growing faster than the national average because of the development of revolutionary new products for communication, information storage, and computing. The world is now ringed with satellites providing worldwide voice, video (DirecTVTM), and data transmission. Many of these new technologies were developed by companies located in California and the Southwestern United States, including Intel, AMD, LSI Logic, Hewlett-Packard, Motorola, Lucent Technologies, Cirrus Logic, Silicon Graphics, Hughes Electronics, Cisco Systems, Vitesse Semiconductor, Netscape Communications, Broadcom Corp., and 3Com Corp, to name a few.
The heart of this industry is the computer chip and the tiny solid-state transistors and capacitors that comprise them. By constantly shrinking the device dimensions, integrated circuits have become more and more powerful, while the cost per function has continued to drop. At dimensions below 0.13 micrometer, microprocessors can operate at GHz and DRAM chips can store gigabits of information. All these advances hinge on developing sophisticated chemical processes for depositing, patterning, and etching thin-film circuits onto semiconductor surfaces. The semiconductor equipment industry, which provides these process tools, generated close to $70 billion in revenues annually. This industry is also a California success story, and is represented by highly profitable companies such as Applied Materials, Novellus Systems, Lam Research, Silicon Valley Group, KLA-Tencor, and many others.
Chemical engineers have an important role to play in microelectronics technology. They are needed to operate and control the sophisticated chemical processes that fabricate the chips. Even more importantly, Ph.D. chemical engineers are needed to continuously research and develop new processes capable of fabricating the next generation of denser and denser integrated circuits. These individuals have the requisite knowledge of mathematics, physics and chemistry that is essential to define features in semiconductor materials with dimensions ranging from 10 to 1000 angstroms.
At UCLA, we have an exciting program for training graduate chemical engineers in microelectronics research. We offer students a sequence of graduate courses designed to provide in-depth knowledge of the field: Surface and Interface Engineering, Electrochemical Processing, Plasma Processing of Materials, and Physical and Chemical Vapor Deposition. In addition, students may pursue a minor field of study in Electrical Engineering, taking the three-course sequence of Solid-State Physics, Semiconductor Electronics and Semiconductor Devices. In addition, students may take the semiconductor processing laboratory course where in ten weeks they fabricate and test their own complementary metal-oxide-semiconductor (CMOS) devices. The UCLA School of Engineering is world renowned for its scholarship in semiconductor physics, chemistry, materials, and engineering.
UHV Surface analytical System.
Chemical engineering research in microelectronics at UCLA is at the cutting edge of semiconductor process technology. Professor Chang's research focuses on the deposition and etching of ultra-thin novel dielectrics for more reliable solid-state electronic devices such as transistors and capacitors. These materials are essential in increasing the silicon-based transistor's switching speed, and in accommodating the increasing complexity of ultra-large scale integrated circuits. Professor Chang's research is a balance between material synthesizing and processing, with an emphasis on understanding the highly sophisticated gas-phase and surface reactions, the deposition and etching kinetics, and material characteristics.
High Density Plasma Etcher and Diagnostics.
Students working with Professor Chang also learn to study systematically and monitor accurately surface reaction kinetics by using well-defined reactive beams of radicals, ions, and molecules, as well as in-situ diagnostics and analytical techniques.
Professor Chang is also interested in developing environmentally benign vapor-phase cleaning processes to enhance the performance of integrated circuits and replace hazardous liquid cleaning techniques now in use. By integrating in-situ vapor phase cleaning processes with thin film deposition and etching processes, surfaces and interfaces can be preserved at atomically smooth and clean conditions for giga-scale integration of the microelectronics.
Professor Chang is also interested in density functional theory calculations that allows an accurate calculation of the physical and chemical properties of various surfaces and interfaces and enables predictive modeling of these technologically important structures.
Surface and Interface structure.
More recently, mature semiconductor manufacturing techniques have been applied to fabricate chemical sensors on silicon in Professor Chang's lab, in collaboration with the Sandia National Laboratory. A chemical analysis device is being realized using micro-analytical systems that combine a calibration cell, a gas chromatography column, a thermal conductivity detector, and a miniature mass analyzer.
Chemical Thermal Conductivity Detector Fabricated at UCLA.
Students working with Professor Hicks can learn all about the new developments in chemical vapor deposition for the fabrication of space photovoltaics, solid-state lasers and high-speed transistors. During MOCVD, a series of surface reactions occur, including adsorption and desorption of the precursor molecules, surface diffusion, nucleation and growth, and desorption of reaction products. In our laboratory, we characterize these surface reactions, and in particular, identify the sites on the semiconductor surface that mediate them. By understanding the atomic-scale processes that govern thin film growth, we make it possible to build new and more powerful devices. At UCLA, the surface chemistry of MOCVD is revealed with state-of-the-art instruments and techniques, including reflectance difference spectroscopy, infrared spectroscopy, scanning tunneling microscopy, electron diffraction, x-ray photoemission, and ab initio molecular cluster calculations.
Atomic resolution scanning tunneling micrograph of a gallium indium arsenide surface.
Professor Hicks' group has developed an atmospheric pressure plasma process for cleaning, etching and deposition of materials. A picture of a plasma jet operating at atmospheric conditions is shown below. The "cold flame" (T~75oC) is impinging on the hand of a student. The plasma jet produces a large flux of atoms and/or radicals, depending on the gas fed to the device. This flux of reactive species is well suited for high-tech materials applications. Unlike previous low-temperature plasmas, this device does not need to be operated in a vacuum.
Atmospheric Plasma Source
Research under the direction of Professors Christofides and Manousiouthakis focuses on two issues a) the development of first-principles numerical models for rapid thermal processing, chemical vapor deposition and plasma processes, and b) the derivation of simplified models that can be readily used for reactor design and controller synthesis. The theoretical description of plasma processes is augmented by the experimental work of Professors Chang and Hicks. They have undertaken several projects to characterize the reactions of metastable, radical and ionized species on metal and oxide surfaces during etching. Of particular interest are atmospheric-pressure plasmas that show promise for a variety of new applications.
Professor Nobe's research interests are in materials electrochemistry, including the kinetics and mechanisms of electrodeposition (electroplating) and electrodissolution (corrosion) of semiconductors, metals, and conducting polymers, oscillatory behavior in electrochemical systems, electroorganic processes, fuel cells and batteries. Students working with Professor Nobe acquire exceptional training in electrochemical processing for various industries including nano and microelectronics and micro-electromechanical devices. Currently, Prof. Nobe is collaborating with Profs. Judy and Yang from the UCLA electrical engineering department to develop a shock-resistive low-power MEMS-magnetometer, which can be incorporated with other MEMS-based inertial microsensors, to create wireless miniaturized micro-power sensor networks. The UCLA MEMS magnetometer detects the deflection of the microcompass capacitively, just as the motion of a mass is detected in inertial microsensors. Based on this concept, MEMS magnetometers with electrodeposited hard magnetic materials can covertly detect ferrous objects (small arms, jeeps, tanks, submarines, etc) at significant distance (>100 m) in adverse conditions (rain, fog, snow, etc.). Since the sensitivity of the magnetometer is dependent on the shape and magnetic properties of materials, different magnetic materials and configurations are currently investigated.
UCLA Shock-Resistant Low-Power MEMS Magnetometer. (Left) first generation, and (Right) third generation with enhanced dissolution rate of sacrificial oxide.
State-of-the-art facilities are available for conducting research in microelectronics manufacturing. Numerous computer workstations are used for process modeling research. A full range of surface science equipment is available for characterizing the atomic composition and structure of semiconductor, metal, and dielectric materials. Students also learn first hand how to fabricate semiconductor devices in a class 1000/100 cleanroom with a full complement of tools for manufacturing integrated circuits. UCLA Chemical Engineering offers students an exceptional opportunity for launching a career in microelectronics.