PEER Project Descriptions: Summer 2001
1.
Design
and Development of Advanced Metallizations in Wide Band-Gap Semiconductor
Devices
Prof. Agis A. Iliadis
Wide band gap semiconductors like SiC, GaN, AlN, ZnO and others, are rapidly becoming of critical importance to the development of new and emerging device technologies, especially for high power, high temperature, and opto-electronic applications. The performance of such devices critically depends, among other things, upon the quality and integrity of the ohmic metallizations of the devices. The development of such metallizations requires both theoretical and practical foundation currently not available for these semiconductors.
The project involves clean-room processing and fabrication of ohmic metallizations on SiC and other wide band-gap semiconductors and the theoretical and experimental evaluation of the contacts prior to and after thermal treatments in moderate (1000 C) and high (1500 C) temperatures. The processing of the contacts consists of semiconductor surface preparation and deposition of metals like Pt, Mo and Ti, and the experimental evaluation includes a host of advanced analytical techniques such as Secondary Ion Mass Spectroscopy (SIMS), Atomic Force Microscopy (AFM), and Transmission Electron Microscopy (TEM). Electrical evaluation of the contacts will be done using a transmission line method (TLM) to measure the contact resistance of the contacts. The deposition of the metals will be done by focused ion beam (FIB), and electron beam deposition. Design for improved TLM structures will be done with MEDICI and other design software.
The study will provide the student with valuable experience sought after by Semiconductor Industry today and will help develop an understanding of the metallurgy of the metal-semiconductor interfaces, the current transport mechanisms through the contacts, and the parameters that are critical to the development of high temperature low contact resistance ohmic contacts.
2.
Development
of MEMS-based Microphone and Speaker for Biomedical Applications
Prof.
Reza Ghodssi
Micro-Electro-Mechanical Systems (MEMS) are sensors and actuators constructed using microlithography-based manufacturing processes. MEMS technology is currently employed in a wide range of devices, including microaccelerometers for crash detection in vehicles, pressure sensors for implantable medical devices, miniature mirror arrays for projection displays, and chemical assay systems. The benefits of MEMS devices include small size, low power consumption, ease of integration into arrays, potential for monolithic integration with electronics, and low cost in high volume. This project involves the development of a MEMS-based microphone and speaker for biomedical application. The MEMS components are integrated modules of a Microsystem on a Chip that also includes optoelectronics components and VLSI circuit. In this project the tasks are divided into three areas of design, fabrication and testing of microstructures and microdevices. The preliminary design requires the use of standard software such as Matlab and MatCAD as well as state-of-the-art simulation software, MEMCAD. The MEMS Sensors and Actuators Lab (MSAL) in the Department of Electrical and Computer Engineering at the University of Maryland and the new cleanroom facility at the Army Research Lab (ARL) are used for the development of the new process technologies and fabrication of these devices. It is expected that the team members would interact closely with both graduate students and senior researchers in all three areas. The final goal is to examine and characterize the fabricated MEMS device and evaluate its performance based on required design criteria.
3.
High
Temperature Aluminum Nitride dielectrics for Wide Bandgap Power Devices
Dr. R.D. Vispute
and Prof. T. Venkatesan
The ultimate goal is to provide passivation and gate dielectric films that provide for stable and reliable WBG power device operation at junction temperatures up to 350°C under operating fields of at least 2 MV/cm. In this research area we will focus strictly on developing thin film dielectric layers with a high quality interface between the film and SiC. We will study pulsed laser deposition (PLD) system for the fabrication of the dielectric layers and then scale-up the large-area PLD process. We will then provide thinner films (as thin as 500 Å) with the same interface and bulk dielectric quality. We plan to extend this investigation to various dielectric materials. Student working on this project will focus on growth and atomic-scale structure and properties of the SiC-AlN, fabrication of multilayer dielectric stacks on SiC, and post-depositon processing of materials.
4.
Development
of P-type SiC Technology
Prof. T. Venkatesan,
Dr. R.D. Vispute,
and R. P. Sharma
Silicon Carbide (SiC) is the most promising wide band gap semiconductor material for high temperature-high power, and high-speed electronic devices. The development of SiC electronic materials and device technologies is rapidly maturing. Exploiting this material and novel process technologies, the Army is interested in developing its future combat systems, which require a variety of electronic devices operating at high-temperature and high-power conditions. In this area we will focus on the development of critical technologies, processes, and characterization techniques to fabricate smooth and device quality p-type SiC for high temperature and high-power thyristor switch that is necessary for power electronics in future combat systems. The students involved in this project will focus on: 1) fabrication of cap layers for p-type SiC which can withstand temperatures above 1600C (that include large area pulsed laser deposition of AlN, Al2O3/AlN, and other compatible high temperature ceramic materials), 2) laser annealing approach for selective area annealing as well as controlled thermal budgeting for obtaining doped material with smooth surface morphology, 3) characterization of ion-implanted and annealed SiC by Rutherford backscattering spectrometry and ion channeling, and atomic force microscopy.