Semiconductor technology program. Progress briefs

The current status of NBS work on measurement technology for semiconductor materials, process control, and devices is reported. Results of both in-house and contract research are covered. Highlighted activities include modeling of diffusion processes, analysis of model spreading resistance data, and studies of resonance ionization spectroscopy, resistivity-dopant density relationships in p-type silicon, deep level measurements, photoresist sensitometry, random fault measurements, power MOSFET thermal characteristics, power transistor switching characteristics, and gross leak testing. New and selected on-going projects are described. Compilations of recent publications and publications in press are included

Semiconductor technology program. Progress briefs

Measurement technology for semiconductor materials, process control, and devices is reviewed. Activities include: optical linewidth and thermal resistance measurements; device modeling; dopant density profiles; resonance ionization spectroscopy; and deep level measurements. Standardized oxide charge terminology is also described

Methods of measurement for semiconductor materials, process control, and devices Quarterly report, 1 Jul. - 30 Sep. 1970

NBS activities in developing methods of measurement for semiconductor materials, process control, and device

Methods of measurement for semiconductor materials, process control, and devices Quarterly report, 1 Oct. - 31 Dec. 1969

Methods of measurement for semiconductor material, process control, and device

Methods of measurement for semiconductor materials, process control, and devices

Activities directed toward the development of methods of measurement for semiconductor materials, process control, and devices are described. Accomplishments include the determination of the reasons for differences in measurements of transistor delay time, identification of an energy level model for gold-doped silicon, and the finding of evidence that it does not appear to be necessary for an ultrasonic bonding tool to grip the wire and move it across the substrate metallization to make the bond. Work is continuing on measurement of resistivity of semiconductor crystals; study of gold-doped silicon; development of the infrared response technique; evaluation of wire bonds and die attachment; measurement of thermal properties of semiconductor devices, delay time, and related carrier transport properties in junction devices, and noise properties of microwave diodes; and characterization of silicon nuclear radiation detectors

Standard measurements of the resistivity of silicon by the four probe method Final report, 3 Apr. - 30 Nov. 1967

Point measuring method for precise resistance analyses on silicon slice

Investigating the role of N-deacetylase/N-sulfotransferase 2 in heparin biosynthesis

Heparan sulfate (HS) is a highly sulfated polysaccharide, produced ubiquitously in the human body, which plays a key role in signaling and regulatory events. Heparin (HP), a structural analog of HS produced in mast cells, maintains a higher density of sulfation. HP is widely regarded for its anticoagulant properties. However, its mode of production, by extraction from animal tissues, has been recently compromised. This presents an opportunity to develop a new approach to synthesize HP and improve its safety and efficacy. The overall goal of our research is to develop an enzymatic-based approach to the design of HP-like compounds. A key component of this goal is to understand the biosynthetic pathway of HP. The biosynthesis of HS has long been thought of as a stepwise process, consisting of: initiation of polysaccharide synthesis on a core protein, elongation, and modification. Recent research has shown that this process is a more dynamic event involving cooperation between the glycosyltransferase enzymes, epimerase, and sulfotransferases. Because the process is nontemplate driven, interactions among enzymes are key components. N-deacetylase/N-sulfotransferase (NDST) is the initial sulfotransferase to modify the polysaccharide. Most of the subsequent reactions rely on the GlcNS residue for substrate binding. NDST-2 is responsible for synthesizing HP in vivo, while NDST-1 is involved with HS synthesis. We aim to characterize the substrate specificity and modification patterns of NDST-2 to gain a thorough understanding of HP biosynthesis. We present a study of NDST-2 modification using a structurally-defined oligosaccharide library. We identified a pentasaccharide as the smallest oligosaccharide modified by NDST-2. We determined that NDST-2 does not have a directional mode of action, and is unaffected by pre-existing N-sulfation on the oligosaccharide. We demonstrated by one pot reaction that NDST-2 can cooperate with C5-epimerase, and 2-O-sulfotransferase to form an IdoUA2S-GlcNS domain in vitro. The domain was formed in both short and long oligosaccharides already carrying GlcNS and IdoUA2S. This was a key discovery in uncovering the biosynthetic pathway of HP, as this repeating domain comprises up to 90% of the overall structure of HP. The result uncovers a new mechanism for control of the biosynthesis of HP.Doctor of Philosoph

Physical Electronics

Contains reports on two research projects

The study of the epitaxial parameters on reliability of silicon planar devices technical summary report, 25 jun. 1964 - 25 jun. 1965

Effect of varying epitaxial deposition parameters on reliability of silicon planar solid state device