Y.H. Shin

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.

Plasma density measurements by phase resolved cutoff

A method for precise measurement of absolute electron density in the plasma using plasma frequency is proposed. The phase difference between two antennas (radiating and detecting antennas) and its slow time modulation was used, instead of the transmittance used in previous cutoff probe, and a remarkable result is observed. This method can determine the absolute electron density precisely: It is not only in a good agreement with the previous method very closely but also is able to find the cutoff point clearly even in difficult conditions where there are ambiguities to determine the cutoff point with previous method.

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.

Study of outgassing of stainless steel with various surface treatments

Abstract The desorption of gases from stainless steel surfaces treated by several different methods was measured by thermal desorption spectroscopy (TDS) and compared. The adsorption of contaminants on sample surfaces was also investigated by Auger electron spectroscopy (AES). It was shown that the electrochemical polishing and dissociated hydrogen gas treatment reduce the desorption of water and CO N 2 substantially. Mirror polishing or fine polishing processes were used to reduce outgassing rather than pool controlled electrochemical polishing. From AES, it was found that on the fresh metal surface a few layers of oxides were formed, and on that layer carbon compound contaminants accumulate, then N2 gas is adsorbed very loosely. The adsorption state of carbon on a H treated sample was different from that on an untreated sample.

Study on self-bias voltage induced on the substrate by r.f. bias power in a high density plasma

Characteristics of the self-bias voltage induced on the substrate by a r.f. bias power in a high density helicon wave plasma were studied. The self-bias voltage induced on the wafer by r.f. bias of 300 kHz (less than the ion plasma frequency value) was directly measured with a Pt wafer using a high voltage probe. The self-bias voltage and the peak-to-peak voltage were influenced by both bias and source RF power in the high-density plasma. A new probe system was designed to trace these phenomena. It was found that these phenomena were related to the charging time of the blocking capacitor by the ion current. The role and effect of the negative ions on the etching process at low RF frequency are discussed. A method to apply the RF bias effectively without the influence of the source power was suggested for application in a real etching system.

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.

Density measurement of particles in rf silane plasmas by the multipass laser extinction method

Measurement of the time evolution of the particle number density was investigated in rf silane plasmas by using the multipass laser extinction method. A He–Ne laser beam underwent multiple reflections on one horizontal plane of the plasma. The extinction signal increased in proportion to the beam pass numbers. A 1011cm−3 density of 8nm radius particles was measured at 10s in a 32mTorr and 50W discharge using nine passes. The primary particle density was obtained by comparing the measured particle sizes with the calculated sizes from the light extinction signals and the Brownian free molecule coagulation model.

Measurement of electron density with the phase-resolved cut-off probe method

The phase resolved cut-off probe method, a precise measurement method for the electron density, was recently proposed [J. H. Kwon et al., Appl. Phys. Lett. 96, 081502 (2010)]. This paper presents the measurements of electron density using the method under various experimental conditions (different pressures, powers, chamber volumes, and discharge sources). The result shows that the method is not only in good agreement with the previous method using wave transmittance under various experimental conditions but it is also able to find the cut-off point clearly even under difficult conditions such as high pressure (∼ 1 Torr), high discharge power, and small plasma volume. The details of the experimental setup, the operating mechanism of the probe method, and the data processing procedure (algorithm) are also addressed. Furthermore, the reliability of the measurement method is investigated by using an electromagnetic field simulation with cold plasma model (CST-Drude model, Computer Simulation Technology).

A hybrid solution of non-uniform planar-type inductively coupled plasma-heating problem

Previous solution of RF (radio frequency) heating problem in ICP (inductively coupled plasma) production was obtained by an analytic mode of analysis for the entire region of source chamber. In this work, antenna region is treated by an analytic technique and a numerical solution for plasma region is obtained. Since antenna region is not fully solved, computing time is significantly saved and non-uniform plasma parameters can be easily considered by adopting the numerical method in the plasma region. In this calculation, some results for solenoidal-type ICP are obtained and compared with the previous fully analytic results (Yoon et al., Phy. Rev. E55(6) (1997) 7536). Also, calculations of local field profiles and plasma impedance for non-uniform plasma are compared with each other. These results are somewhat different trend from planar case (Yoon et al., Thin Solid Films, 2002).