John E. Parmeter

The thermal stability of diamond-like carbon

Abstract Diamond-like carbon (DLC) is a potential, low-cost substitute for diamond in certain applications, but little is known of the temperature range over which its desirable properties are retained. We have investigated the stability of DLC films at elevated temperature and high humidity using Raman spectroscopy, Auger electron spectroscopy and thermal desorption analysis. Exposure to boiling water and a hot (225 °C), humid environment does not appear to affect the DLC structure. Thermal desorption analysis detected the onset of hydrogen evolution from DLC in vacuum at 260 °C. Raman spectra show the conversion from DLC to nano-crystalline graphite (“glassy” carbon) beginning at 300 °C in ambient air. Auger spectroscopy confirms the conversion of sp 3 -bonded carbon to sp 2 -bonded carbon above 300 °C. Conversion to nano-crystalline graphite is complete by 450–600 °C in air. The structure and properties of DLC films are expected to be retained up to temperatures of at least 260 °C.

Chemical additives for improved copper chemical vapour deposition processing

Abstract Techniques for improved copper chemical vapour deposition (CVD) processing by the addition of trimethylvinylsilane (tmvs) and hexafluoroacetylacetone (Hhfac) during copper deposition from the volatile liquid precursor Cu(hfac)(tmvs) are described. The tmvs enables stable high vaporization rates of precursor by direct liquid injection and the Hhfac permits higher deposition rates of smoother copper films. The resistivity of the copper films averages approximately 1.8 μΩcm as deposited. Combined together, these results mark an important advance toward a manufacturable copper CVD process.

Metal CVD for microelectronic applications: An examination of surface chemistry and kinetics

Abstract We review the surface chemistry and kinetics relevant to the chemical vapor deposition (CVD) of metals used for microelectronic applications. Our efforts focus on the surface chemistry of aluminum, tungsten, and copper CVD, which have received the most recent interest for metallization. We first briefly review a variety of topics concerning the applications and the chemistry and kinetics of metal CVD. We also give a brief overview of the application of surface science techniques to the study of CVD-related surface chemistry.

High density plasma etching of III–V nitrides

Two broad classes of plasma chemistry were examined for dry etching of GaN, AlN, and InN. The etch rates for CH4/H2‐based plasmas are low (∼ 400 A/min) even under high microwave power (1000 W) electron cyclotron resonance conditions. Halogen‐based plasmas (Cl2, I2, Br2) produce rates up to ∼3000 A/min with smooth stoichiometric surfaces. Preferential sputtering of N occurs for high ion energies, leading to rough GaN surfaces at rf power above ∼200 W. Etch rates for high ion density discharges are typically an order of magnitude faster than for conventional reactive ion etching.

Enhanced Chemical Vapor Deposition of Copper from ( hfac ) Cu ( TMVS ) Using Liquid Coinjection of TMVS

A direct liquid connection system has been applied to the chemical vapor deposition of copper using the commercially available Cu(I) precursor (hfac)Cu(TMVS), where hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate and TMVS = trimethylvinyl-silane. Precursor delivery was enhanced through the use of a coinjection system wherein additional TMVS was mixed with tire copper precursor before injection into the vaporization chamber. The results reported here demonstrate the capability of depositing blanket cooper for high purity (on the order of 99.99% copper) and low resistivity (1.85 {+-} 0.1 {mu}{Omega}-cm). These copper films have been deposited at rates up to and exceeding 1,500 {angstrom}/min. The effects of temperature and carrier gas on deposition rate and resistivity are examined. The as-deposited films demonstrate and dependence of grain size with thickness and little structural or morphological change with annealing. This study suggests that liquid coinjection is an effective method for enhancing deposition rates and for producing high quality copper films from copper(I) precursors.

The challenge of standoff explosives detection

While there currently are a number of effective technologies and methodologies for explosive screening when close proximity to the person, package, or vehicle being screened is feasible, the problem of detecting explosives at significant standoff distances remains one of the most difficult - and most important - challenges confronting physical security specialists. Among the major detection techniques, trace detection suffers from the fact that available vapor plumes are normally too dilute for detection at appreciable standoff under all but the most favorable conditions, and probing bulk techniques suffer from an intrinsic 1/r/sup 4/ fall-off of the signal intensity with distance. Research into potential means of standoff detection is necessary to try to address this important problem. This paper presents an overview of detection technologies that could prove useful in certain standoff detection applications, along with comments on future research needs. A distinction is made between remote detection, in which the personnel searching for explosives maintain a safe standoff distance from the object being screened but where a sampling and/or detection unit may approach the object closely, and true standoff detection, where both the personnel and the sampling/detection equipment maintain a large standoff distance.

Characterization of thin copper films grown via chemical vapor deposition using liquid coinjection of trimethylvinylsilane and (hexafluoroacetylacetonate) Cu (trimethylvinylsilane)

We have developed a technique recently for copper chemical vapor deposition utilizing direct liquid coinjection of trimethylvinylsilane (TMVS) and the copper (I) precursor (hexafluoroacetylacetonate) Cu (TMVS). We present here an investigation of the properties of copper films deposited using this technique. The films were grown on Si3N4 substrates at temperatures in the range of 220–250 °C and characterized using several experimental techniques, with an emphasis placed on factors influencing copper film resistivity. The average as‐deposited film resistivity is 1.86 μΩ cm; this value is reduced to 1.82 μΩ cm when the effects of surface scattering are taken into account. The resistivity is essentially independent of film thickness for thicknesses between 0.2 and 3.5 μm, and is reduced by less than 0.05 μΩ cm by annealing at 400–600 °C in vacuum. The total impurity content of the films is approximately 100 parts per million. The film density is 97±2% of the bulk copper value. The average grain size increase...

Explosives detection portal for high-volume personnel screening

We discuss a trace explosive detection portal for high-volume personnel screening, which has been developed recently at Sandia National Laboratories (SNL), using funding provided by the Federal Aviation Administration (FAA) and the Department of Energy (DOE) Office of Safeguards and Security (OSS). This portal screens individuals for explosives using noninvasive means to collect explosive residue in the forms of vapor and particulate contamination. The portal combines a commercially available ion mobility spectrometer (IMS) with a preconcentrator developed at SNL to perform detection of explosives. The prototype portal has undergone one series of tests at the Albuquerque International Airport, and we are now proceeding to develop an improved, second-generation portal, and to find a company to market the portal.

Treatment of InP surfaces in radio frequency H2 and H2/CH4/Ar plasmas: In situ compositional analysis, etch rates, and surface roughness

The surface composition, etch rates, and surface roughness of indium phosphide (InP) surfaces treated in radio frequency (rf) hydrogen and hydrogen/argon/methane plasmas have been investigated using in situ Auger spectroscopy and ex situ scanning electron microscopy and atomic force microscopy. In agreement with most previous studies, hydrogen plasmas are found to completely remove surface carbon and oxygen impurities, but at the expense of some degree of surface phosphorus depletion. This depletion can be minimized by utilizing brief plasma exposure times and low rf power settings. Oxygen removal is found to be rate limiting in the production of a clean surface. InP etching in hydrogen/argon/methane can be performed either in a low density, capacitively coupled plasma mode, or in a high density, inductively coupled plasma mode. For operation in the low density regime, the etched surfaces have a constant and nearly stoichiometric composition, independent of plasma parameters. Etch rates vary from ∼20–400 ...

Surface reactions of tetraneopentyl zirconium on zirconium carbide thin films

Interest has arisen recently in the use of metal alkyl compounds as precursors in the chemical vapor deposition of metal carbides. This paper presents results of a study of the surface chemistry of one such precursor, tetraneopentyl zirconium (ZrNp4), on zirconium carbide thin films. Decomposition of the precursor leads to the desorption of both methane and a larger hydrocarbon species that is tentatively identified as neopentane. The desorption of large amounts of methane may help to explain the fact that ZrC films grown to date with this precursor are not stoichiometric but rather contain excess carbon.