Material Science and Engineering

Material science and engineering program has affiliation with various state-of-the-art laboratories and center for graduate students to do research with world class faculty.

A UHV wafer bonding unit, specially designed to use surface characterization and thin-film deposition techniques to measure and control substrate and interface chemistry within limits necessary to make heterojunction devices, is available to produce integrated heterostructures with well controlled chemistry that are tractable for quantitative nanostructural and property measurements. This unit is capable of synthesizing interfaces by direct wafer bonding and/or in-situ thin film deposition methods, and offers greater flexibility for producing advanced integrated artificial structures. It consists of five interconnected ultra high vacuum (UHV) chambers for in-situ surface preparation and analysis, addition of interface interlayers by e-beam or UHV sputter deposition, a bonding chamber, and a sample entry and preparation chamber. The base pressure is 2x10-10 Torr. Orientation of the bonded pairs can be controlled to ~ 0.1 degree prior to bonding. Ex-situ surface preparations using etching and low energy reactive plasma cleaning is done in a cleanroom to protect substrates prior to insertion in the bonding instrument. An atomic force microscope (AFM) is also available to provide direct measurements of these effects, to supplement the indirect information of RHEED.

The existing cleanroom facility located in the Jonsson School of Electrical Engineering and Computer Science is utilized for initial unit process development. The total area of this facility is 10,000 sq. ft., with 5,000 sq. ft. of class 1,000 space. This facility contains semiconductor processing equipment including optical and e-beam lithography, chemical processing hoods, evaporation and sputter deposition systems, as well as a wide variety of material and processing diagnostics. The lithography component in the cleanroom facility consists of a Quintel contact printer, an HTG contact printer, and an e-beam lithography system. The Quintel aligner is a G-line contact printer with ~ 1 micron resolution and backside alignment capability (~1 micron). It will accept up 150 mm wafers. Exposed resist is developed in 3 versatile “APT” 914 and 915 developers using spray and spin wet processes. The thin-film deposition component of the lab includes a Uniaxis Plasma Enhanced CVD (up to 150 mm wafer), three E-beam evaporators (each fitting up to 150 mm wafers) and an AJA four-gun sputter deposition system (designed for 100 mm wafers). A “Tystar” Low Pressure Chemical Vapor Deposition reactor is designed for either 100-150 mm wafers and has 4 tubes. It will allow deposition of low stress silicon nitride, polysilicon and silicon dioxide. Films can be etched in any of 3 reactive ion etchers. These include: a “Technics” RIE setup for 100-105 mm wafers, a “Plasma Technologies” RIE accommodating up to 150 mm wafers and a “Drytech” Deep-RIE for 100 mm wafers. There are several anneal and oxidation furnaces available including 5 Minibrute tube furnaces (100mm) and a new Rapid Thermal Anneal (RTA) system (up to 200 mm wafers). The clean room diagnostics include a SEM, a spectroscopic ellipsometer, optical microscope, profilometer, ALESSI 4 point probe, a new Cascade Summit series electrical probe station (200 mm capability) with a chuck heating (to 150?C) and cooling stage (to -65?C) as well as associated electrical characterization instrumentation (parameter analyzers, CV meters, etc.), and a high resolution AFM. The SEM is a Phillips XL-30 tool with a 4 nm resolution and a EDAX material analysis system capable of handling a 100mm wafer with offset positioning. The AFM is a Park Scientific International model LS with two deflection stages, one with 10 micron travel and the other, 100 micron travel.

The University of Texas at Dallas has recently undergone a substantial growth in materials characterization and synthesis capabilities. This capability will provide graduate students with tools uniquely suited to engage in research areas of modern materials science and engineering.

A new, unique multi-module cluster tool is now available at UTD for the fabrication and characterization of thin films. The system is capable of thin film deposition using PVD methods including electron beam evaporation, molecular beam deposition, sputter deposition and thermal evaporation methods. Additionally, in-situ characterization techniques include angle-resolved monochromatic x-ray and ultraviolet photoelectron spectroscopy, Auger electron spectroscopy, atomic force and scanning tunneling microscopy/spectroscopy. The system utilizes 100mm diameter wafers (for cleanroom process compatibility), and modified sample plates for the various deposition and characterization techniques. Wafers are transported throughout the system in a UHV transfer tube. Each deposition module has heating and rotational capability for the study of film uniformity and growth kinetics. The laboratory housing the tool is also equipped with wet chemical preparation facilities for wafer surface preparation.

The focused ion beam system is a FEI Nova 200 NanoLab which is a dual column SEM/FIB. It combines ultra-high resolution field emission scanning electron microscopy (SEM) and focused ion beam (FIB) etch and deposition for nanoscale prototyping, machining, 2-D and 3-D characterization, and analysis. Five gas injection systems are available for deposition (e.g. Pt, C, SiO2) and etching (e.g. Iodine for metals, and a dielectric etch). Nanoscale chemical analysis is done with energy dispersive X-ray spectroscopy (EDS). A high resolution digital patterning system controlled from the User Interface is also available. Predefined device structures in Bitmap format can be directly imported to the patterning system for nanoscale fabrication. The FEI Nova 200 is also equipped with a Zyvex F100 nano-manipulation stage, which includes four manipulators with 10 nm positioning resolution. The four manipulators can be fitted with either sharp whisker probes for electrically probing samples or microgrippers for manipulating nanostructures as small as 10 nanometers. This is the first instrument of its kind in the world that combines a dual beam FIB with the F100 nanomanipulator, providing unparalleled nanofabrication and nanomanipulation.

The facility operates and maintains two state-of-the-art transmission electron microscopes (TEM), and a host of sample preparation equipment. It also provides microscopy computing and visualization capabilities. Techniques and equipment available include the following: (i) High Resolution Structural Analysis - The high-resolution imaging TEM is a JEOL 2100 F which is a 200kV field emission TEM. Its capability includes atomic scale structural imaging with a resolution of better than 0.19 nm, and in-situ STM/TEM. (ii) High Resolution Chemical and Electronic Structure Analysis - High resolution analytical TEM is a second JEOL 2100F field emission TEM/STEM equipped with an energy dispersive x-ray spectrometer (EDS), an electron energy loss spectrometer (EELS), and a high angle Z-contrast imaging detector. This instrument performs chemical and electronic structure analysis with a spatial resolution of better than 0.5 nm in EELS mode and is also capable of spectrum imaging and mapping. The image resolution in the chemically sensitive Z-contrast scanning TEM (STEM) mode is approximately 0.14 nm. Capabilities also include in-situ cryogenic cooling and heating, and a computer control system for remote microscopy operation.

A Rigaku Ultima III X-ray Diffractometer system is available for thin film diffraction characterization. The system is equipped with a cross beam optics system to permit either High-resolution parallel beam with a motor controlled multilayer mirror, or a Bragg-Brentano Para-Focusing beam (without the multilayer mirror) which are permanently mounted, pre-aligned and user selectable with no need for any interchange between components. Curved graphite crystal or Ge monochrometers are also available. An integrated annealing attachment permits the in-situ examination of film structure up to 1500?C. The instrument enables a variety of applications including in-plane and normal geometry phase identification, quantitative analysis, lattice parameter refinement, crystallite size, structure refinement, residual stress, density, roughness (from reflectivity geometries), and depth-controlled phase identification. Detection consists of a computer controlled scintillation counter. Sample sizes up to 100 mm in diameter can be accommodated on this system. A new Rigaku Rapid Image Plate Diffractometer system is also available for small spot (30?m – 300?m) XRD work. The digital image plate system enables the acquisition of diffraction data over a 204? angle with a rapid laser scanning readout system. An integrated annealing attachment permits the in-situ examination of film structure up to 900?C on this system. A complete set of control, database and analysis workstations and software are associated with these new systems.

In addition to the facilities on campus, cooperative arrangements have been established with many local industries to make their facilities available to U.T. Dallas graduate engineering students.