Kwang Hwa Chung

Size determination of nanoparticles in low-pressure plasma with laser-induced incandescence technique

We derive analytic formulas describing the temporal behavior of the laser-induced incandescence (LII) signal in both case of the heat transfer governed by radiation and collision. Using these formulas, we can describe the temporal behavior of the LII signal and determine the dimension of nanosize particles in low-pressure plasma. Simple calibration procedure is introduced for quantitative measurement of the particle size with the LII technique.

Measurement uncertainties for vacuum standards at Korea Research Institute of Standards and Science

The Korea Research Institute of Standards and Science has three major vacuum systems: an ultrasonic interferometer manometer (UIM) (Sec. II, Figs. 1 and 2) for low vacuum, a static expansion system (SES) (Sec. III, Figs. 3 and 4) for medium vacuum, and an orifice-type dynamic expansion system (DES) (Sec. IV, Figs. 5 and 6) for high and ultrahigh vacuum. For each system explicit measurement model equations with multiple variables are, respectively, given. According to ISO standards, all these system variable errors were used to calculate the expanded uncertainty (U). For each system the expanded uncertainties (k=1, confidence level=95%) and relative expanded uncertainty (expanded uncertainty/generated pressure) are summarized in Table IV and are estimated to be as follows. For UIM, at 2.5–300Pa generated pressure, the expanded uncertainty is <4.17×10−2Pa and the relative expanded uncertainty is <1.18×10−2; at 1–100kPa generated pressure, the expanded uncertainty is <7.87Pa and the relative expanded uncerta...

Hot cathode ionization gauge calibration with the KRISS ultra-high vacuum standards

The calibration system for ultra-high vacuum standards at the Korea Research Institute of Standards and Science (KRISS) uses a restriction in the range 5 × 10-7 Pa to 2 × 10-3 Pa. Using this system, we have calibrated for argon two commercially available gauges, an extractor gauge and a stabil-ion gauge. The correction factor of the extractor gauge in the lower pressure range was about 1.07 but it rose by 4%, reaching 1.11 at 2 × 10-5 Pa, while that of the stabil-ion gauge slowly decreased from 1.04 to 1.02 over four decades of the pressure range.

The static expansion system as a new medium vacuum primary standard in KRISS

A new medium vacuum primary standard using the static expansion method was developed in Korea Research Institute of Standards and Technology. We compared the system with an ultrasonic interferometer manometer using two capacitance diaphragm gauges with full-scale ranges of 133 Pa and 1333 Pa. The results showed that the two standards are coincident with each other within the range of uncertainty at calibrated pressures 3 Pa to 100 Pa.

Size Monitoring of Nanoparticles Growing in Low-Pressure Plasma using Laser-Induced Incandescence Technique

To describe the temporal behavior of laser-induced incandescence (LII) signals emitted from nanoparticles in atmospheric flames or low-pressure processing plasmas, we derive two analytic formulae in detail from the energy balance equation of nanoparticles heated by laser pulses. We demonstrate quantitative size monitoring by observing Si nanoparticles growing in an argon plasma diluted with 5% SiH4 at a pressure of 20 mTorr, using the LII technique. In this experiment, it is found that the signal-to-noise ratio of the LII signal is sufficient to allow the identification of particles larger than 10 nm in diameter with a measurement uncertainty that is estimated to be less than 5%.

The outgassing from TiN and BN films grown on stainless steel by IBAD

Abstract In search of low-outgassing vacuum material, TiN and h-BN thin films were grown on stainless steel by ion beam assisted deposition (IBAD). The film structures and surface chemistries were studied by XRD, FT-IR, XPS, and Auger depth profile. The outgassing rates of bare, TiN coated, and two h-BN coated AISI 304 samples were compared by using thermal desorption spectroscopy. XPS showed that some Ti–Ti bonds remained in as-deposited TiN, and these excess Ti seemed to cause a sharp increase in H 2 peak at 360°C. All coatings reduced the outgassing, but the h-BN sample grown at a substrate temperature of 200°C had the lowest outgassing rate.

Low Vacuum Generation and Control on BIEN Technology: Mass Flow and Dry Pumping Characteristics

Since a clean environment and finite mass flow control on the molecular level are continuously required in current R&D fields and actual process lines, technologies on vacuum generation and control have been playing a significant role in merging a variety of technologies like Bio, Information, Environment, Energy, Space and Nano. Currently, the drive towards dry vacuum pumping has broadly occurred across a spectrum of vacuum applications, from semiconductor manufacture to industrial processing, due to its most visible advantages: it is contamination free. The integrated characteristics evaluation system for dry vacuum pumps has been established in KRISS in collaboration with several branch dry pump suppliers in Korea. The evaluation system exploits a constant volume flow meter to measure mass flow rates real-timely in standard level, and facilitates the evaluation of spatially averaged sound power levels using a semi-anechoic chamber. New and overhauled roots, claw, classical screw, and scroll type pumps supplied from the manufacturers have been evaluated using the evaluation system in terms of ultimate pressure, pumping speed, vibration, and sound power. We selected the mass flow measuring method with a constant chamber volume of 875 L because of its direct monitoring capability which does not allow blind mass flow rate measurements, and proved that the method allows us to measure five decades of mass flow rates from 1×10-2 to 1×103 mbar-l/s with a measurement uncertainty of ±3%, which is within the internationally accepted standards limit. In this work, we demonstrate how the integrated pump characteristics evaluation and mass flow control method have been significant in the low vacuum range of 10-4 to 103 mbar.

Non-Destructive Characteristics Evaluation for Low Vacuum Dry Pumps in the Semi-Conductor Manufacturing Process Line

Since positive-displacement dry vacuum pumps were first launched into the semiconductor industry in 1984, issues concerning about characteristics evaluation on consistent bases have been continuously arisen from the mass production lines. The non-destructive, in-situ purposed characteristics evaluation system for dry vacuum pumps has been established collaborating with a semi-conductor manufacturer and branch dry pump manufacturers in Korea. The evaluation method exploits the constant volume flow meter to measure the mass flow rate in standards level, and facilitates the evaluation of spatially averaged sound power levels using a semi-anechoic chamber. New and overhauled roots and claw type pumps have been evaluated in terms of ultimate pressure, pumping speed, vibration, and sound power. The correlation analyzed among those results shows clear signs of pump degradation related each other. Recent results are applicable to the semiconductor process line to warn early symptoms of pump degradation and malfunction. Introduction Currently the drive towards dry vacuum pumping has very broadly occurred across the spectrum of vacuum applications from semiconductor manufacture to industrial processing due to the most noticeable merit of contamination free [1]. Besides this remarkable milestone of the dry pumping, the issues concerning about characteristics evaluation on consistent bases have been continuously arisen from the semiconductor mass production lines which generate copious quantities of particulate, condensate, or corrosive material as reaction by-products. On behalf of these issues the integrated characteristics evaluation system for dry vacuum pumps has been developed collaborating with several branch dry pump suppliers in Korea. The evaluation system facilitates the evaluation of spatially averaged sound power levels using a semi-anechoic chamber, and exploits the constant volume flow-meter to measure the mass flow rate in standards level. Using the evaluation system, we expect to trace the symptoms of devastating malfunctions or characteristic degradations during the manufacturing processes, reported in the Korea semiconductor industry. In this recent work we demonstrate the systematic, comprehensive approach for evaluating a dry pump, which is not yet attempted in the vacuum community. Integrated Evaluation System for Low Vacuum Dry Pumps The international standards codes for the evaluation recommended by ISO/CD 1607, 5607, and PNEUROP 6602 [2, 3, 4] are, unfortunately, far from being identical. Pursuing the consolidated domestic evaluation standards, the integrated evaluation system for low vacuum dry pumps has been established at the Center for Vacuum Technology in the Korea Research Institute of Standards and Science through careful review of the international standards by concentrated evaluation experiments. Fig. 1 illustrates the schematic diagram of the integrated evaluation system for the pumps, which consists of four main parties: a test dome, a mass flow injection/measurement system, a data Key Engineering Materials Online: 2004-08-15 ISSN: 1662-9795, Vols. 270-273, pp 2345-2350 doi:10.4028/www.scientific.net/KEM.270-273.2345

Fabrication of an electron-stimulated desorption apparatus and a study on desorbed hydrogen on the cold surface of Cu and rare-gas solid

An electron-stimulated desorption (ESD) system was assembled in order to study ESD ions desorbed from the cold surface of materials. We have investigated electronically stimulated ions desorbed from physisorbed hydrogen on Cu and rare-gas solid. The desorption yield showed a dependence on incident electron energy. Desorbed H+ and H+2 ions of exposed H2 on the surface of rare-gas solid were much higher than H2 exposed directly to the surface of Cu. The kinetic energy of desorbed H+ and H+2 ions depends on incident electron energy. When the incident electron energy was 200 eV, the kinetic energies of H+ and H+2 were 5.0044 eV and 0.8405 eV, respectively.

Leak Rate Calibration System

The leak rate calibration system down to 10 -8 Pa m 3 /s (10 -7 mbar L/s, 10 -7 std. cc/s) is built at the Korea Research Institute of Standards and Science (KRISS) and its characteristics are elaborated in this paper. The calibration system consists of a constant-pressure type flowmeter, an orifice-flow-type ultra high vacuum system and a leak-mounting manifold. A known amount of gas flows measured by the flowmeter can be used to calibrate ‘standard leak’ by passing flows alternately from the leak and the flowmeter through a constant conductance. The flowmeter is designed to keep the pressure in a variable-volume chamber of the flowmeter constant by changing the volume with a moving piston. The piston is attached to a step motor by a micrometer screw and is fully automated by a computer. The flow rate is calculated from the pressure and the speed of the piston. The flowmeter and the ultra high vacuum system are evacuated by turbo molecular pumps to the base pressure below 10 -8 Pa. This system has been used in leak rate calibration by comparison with the reference leak and by the direct measurement method using the flowmeter. The calibration results of commercial standard leaks, which require calibration by users, show significant difference with nominal values.