A wafer-like apparatus for two-dimensional measurement of plasma parameters and temperature distribution in low-temperature plasmas.

A wafer-type monitoring apparatus that can simultaneously measure the two-dimensional (2D) distributions of substrate temperature and plasma parameters is developed. To measure the temperature of the substrate, a platinum resistance temperature detector is used. The plasma density and electron temperature are obtained using the floating harmonics method, and incoming heat fluxes from the plasma to the substrate are obtained from the plasma density and electron temperature. In this paper, 2D distributions of the substrate temperature, plasma density, and electron temperature are obtained simultaneously for the first time in inductively coupled plasma. The shapes of the 2D distributions of the substrate temperature and incoming heat flux are similar to each other, but some differences are found. To understand that, an energy balance equation for the substrate is established, which shows good agreement with the experimental results. This apparatus will promote the understanding of surface reactions, which are very sensitive to the temperatures and plasma densities in plasma processing.

A monitoring device made of an anodic aluminum oxide template for plasma-induced charging potential measurements in the high-aspect-ratio trench structure.

A monitoring device is proposed to investigate the charge accumulation effects in a high-aspect-ratio trench structure. This monitoring device is made of an anodic aluminum oxide (AAO) template, which is a self-organized material with parallel pores, to demonstrate a high aspect ratio trench structure. A top electrode and bottom electrode were formed in the AAO contact structure for measuring electric potentials. These electrodes can be assumed to be electrically floating due to the very high input resistance of the measurement circuit. Therefore, the electric potentials resulting from the charge accumulation can be measured. In this paper, the fabrication process of the proposed device and experimental demonstrations are presented.

The New Approach for Establishing the Cellular Response Guideline for Medical Applications of Polydiacetylene as Innovative Parameters.

Argon plasma jet (Ar-PJ) has been widely used in clinical medicine; however, the cellular effects of Ar-PJ therapy applying to living tissues have not been clarified yet. It is necessary to investigate cellular responses to Ar-PJ in establishing guidelines on the therapeutic use of Ar-PJ. Interestingly, in the Ar-PJ-treated cells, the fragmented mitochondria, a typical cellular stress indicator, were discovered even in the cells located in the live zones (1∼3 zones). Using microscopic measurements of the mitochondrial length, we found that the fragmented mitochondria were mainly in the zones 1 and 2, the closest to the direct exposure point of Ar-PJ. Whereas, the mitochondria in the zone 4 retained their lengths to normal. This quantitative measurement of mitochondrial morphology was combined with the color scores of the polymerizable supramolecular (PS) sensor in diagnostic categories. The results demonstrate that the mitochondrial length (0.98∼3.94 µm) is inversely proportional to the PS sensor color scores (87∼0) in the zones 1∼4. On the combination of these three diagnostic parameters, the effective range of Ar-PJ for cellular responses was determined: the zones 1∼3, the color scores 87∼12 and the mitochondrial lengths 0.98∼2.57 µm. Our study is the first demonstration of mitochondrial fragmentation in response to Ar-PJ and the first attempt to establish the diagnostic guideline for Ar-PJ therapies by combinations with biological, physical and chemical aspects. Thus, this study will make great advances in the field of bioplasma applications.

Effect of Electron Energy Distribution on the Hysteresis of Plasma Discharge: Theory, Experiment, and Modeling.

Hysteresis, which is the history dependence of physical systems, is one of the most important topics in physics. Interestingly, bi-stability of plasma with a huge hysteresis loop has been observed in inductive plasma discharges. Despite long plasma research, how this plasma hysteresis occurs remains an unresolved question in plasma physics. Here, we report theory, experiment, and modeling of the hysteresis. It was found experimentally and theoretically that evolution of the electron energy distribution (EED) makes a strong plasma hysteresis. In Ramsauer and non-Ramsauer gas experiments, it was revealed that the plasma hysteresis is observed only at high pressure Ramsauer gas where the EED deviates considerably from a Maxwellian shape. This hysteresis was presented in the plasma balance model where the EED is considered. Because electrons in plasmas are usually not in a thermal equilibrium, this EED-effect can be regarded as a universal phenomenon in plasma physics.

Control of Size Uniformity of Cu Nanoparticle Array Produced by Plasma-Induced Dewetting.

The effects of plasma parameters such as plasma density, electron temperature, and sheath voltage on the uniformity of Cu nanoparticle arrays were investigated. These parameters were controlled by varying the pressure, RF power, and substrate bias voltage. A floating harmonic method was used to monitor the plasma parameters. Uniform nanoparticle arrays were produced when hole generation was increased by using a high ion.bombardment energy. As oppose to a low energy flux condition, where small and large nanoparticles coexisted due to a small number of holes, a larger number of holes was generated and distributed more uniformly during a high energy flux condition.

Real-time dielectric-film thickness measurement system for plasma processing chamber wall monitoring.

An in-situ real-time processing chamber wall monitoring system was developed. In order to measure the thickness of the dielectric film, two frequencies of small sinusoidal voltage (∼1 V) signals were applied to an electrically floated planar type probe, which is positioned at chamber wall surface, and the amplitudes of the currents and the phase differences between the voltage and current were measured. By using an equivalent sheath circuit model including a sheath capacitance, the dielectric thickness can be obtained. Experiments were performed in various plasma condition, and reliable dielectric film thickness was obtained regardless of the plasma properties. In addition, availability in commercial chamber for plasma enhanced chemical vapor deposition was verified. This study is expected to contribute to the control of etching and deposition processes and optimization of periodic maintenance in semiconductor manufacturing process.

Probe diagnostics in the far scrape-off layer plasma of Korea Superconducting Tokamak Advanced Research tokamak using a sideband harmonic method.

Plasma characteristics in the far scrape-off layer region of tokamak play a crucial role in the stable plasma operation and its sustainability. Due to the huge facility, electrical diagnostic systems to measure plasma properties have extremely long cable length resulting in large stray current. To overcome this problem, a sideband harmonic method was applied to the Korea Superconducting Tokamak Advanced Research tokamak plasma. The sideband method allows the measurement of the electron temperature and the plasma density without the effect of the stray current. The measured plasma densities are compared with those from the interferometer, and the results show reliability of the method.

Thermal compression chip interconnection using organic solderability preservative etched substrate by plasma processing.

The solderability of copper organic solderbility preservative (CuOSP) finished substrate was enhanced by the plasma etching. To improve the solderability of TC interconnection with the CuOSP finished substrate, the plasma etching process is used. An Oxygen-Hydrogen plasma treatment process is performed to remove OSP material. To prevent the oxidation by oxygen plasma treatment, hydrogen reducing process is also performed before TC interconnection process. The thickness of OSP material after plasma etching is measured by optical reflection method and the component analysis by Auger Electron Spectroscopy is performed. From the lowered thickness, the bonding force of TC interconnection after OSP etching process is lowered. Also the electrical open/short test was performed after assembling the completed semiconductor packaging. The improved yield due to the plasma etching process is achieved.

Mechanism of solid-state plasma-induced dewetting for formation of copper and gold nanoparticles.

Cu and Au nanoparticles were fabricated by plasma treatment on Cu and Au films at 653 K. The nanoparticles were formed by dewetting the metallic films using plasma. Scanning electron microscopy and transmission electron microscopy investigations showed that the plasma-induced dewetting of the Cu and Au films proceeded through heterogeneous hole nucleation and growth along the grain boundaries to lower the surface energy. The amount of energy transferred to surface atoms by one Ar ion was calculated to be 16.1 eV, which was sufficient for displacing Cu and Au atoms. Compared to thermally activated dewetting, more uniform particles could be obtained by plasma-induced dewetting because a much larger number of holes with smaller sizes was generated. The plasma dewetting process is less sensitive to the oxidation of metallic films compared to the annealing process. As a result, Cu nanoparticles could be fabricated at 653 K, whereas the thermally activated dewetting was not possible.

Vernet syndrome by varicella-zoster virus.

Vernet syndrome involves the IX, X, and XI cranial nerves and is most often attributable to malignancy, aneurysm or skull base fracture. Although there have been several reports on Vernet's syndrome caused by fracture and inflammation, cases related to varicella-zoster virus are rare and have not yet been reported in South Korea. A 32-year-old man, who complained of left ear pain, hoarse voice and swallowing difficulty for 5 days, presented at the emergency room. He showed vesicular skin lesions on the left auricle. On neurologic examination, his uvula was deviated to the right side, and weakness was detected in his left shoulder. Left vocal cord palsy was noted on laryngoscopy. Antibody levels to varicella-zoster virus were elevated in the serum. Electrodiagnostic studies showed findings compatible with left spinal accessory neuropathy. Based on these findings, he was diagnosed with Vernet syndrome, involving left cranial nerves, attributable to varicella-zoster virus.

Two-dimensional-spatial distribution measurement of electron temperature and plasma density in low temperature plasmas.

A real-time measurement method for two-dimensional (2D) spatial distribution of the electron temperature and plasma density was developed. The method is based on the floating harmonic method and the real time measurement is achieved with little plasma perturbation. 2D arrays of the sensors on a 300 mm diameter wafer-shaped printed circuit board with a high speed multiplexer circuit were used. Experiments were performed in an inductive discharge under various external conditions, such as powers, gas pressures, and different gas mixing ratios. The results are consistent with theoretical prediction. Our method can measure the 2D spatial distribution of plasma parameters on a wafer-level in real-time. This method can be applied to plasma diagnostics to improve the plasma uniformity of plasma reactors for plasma processing.

Electrical test method using high density plasmas for high-end printed circuit boards.

A novel electrical test method that uses high-density plasmas, such as inductively coupled discharges, is proposed to detect open/short failures of high-end printed circuit boards (PCBs). The PCB is inserted into the plasma chamber with the top side facing the plasma sheath, and the bottom of the PCB is connected to the probe pin for the dc voltage bias and current measurements. A failure, including a latent open, can be precisely detected by biasing the dc voltage near the plasma potential due to the specific characteristics of the sheath formed on the PCB surface.

Note: Interpolation for evaluation of a two-dimensional spatial profile of plasma densities at low gas pressures.

An interpolation algorithm for the evaluation of the spatial profile of plasma densities in a cylindrical reactor was developed for low gas pressures. The algorithm is based on a collisionless two-dimensional fluid model. Contrary to the collisional case, i.e., diffusion fluid model, the fitting algorithm depends on the aspect ratio of the cylindrical reactor. The spatial density profile of the collisionless fitting algorithm is presented in two-dimensional images and compared with the results of the diffusion fluid model.

Radio frequency-compensated Langmuir probe with auxiliary double probes.

A radio frequency (rf) compensation design using auxiliary double probes connected in parallel with a main measurement probe was developed for Langmuir probe diagnostics. This probe structure can reduce the sheath impedance of the main probe. In our probe design, the sheath capacitance of the probe can be increased and its sheath resistance can be decreased with increasing dc bias differential voltage between the auxiliary double probes. The I-V characteristic curve and electron energy distribution functions measured by our probe system had sufficient rf compensation performance in inductively coupled plasmas.

New interpolation algorithm for evaluation a spatial profile of plasma densities in radio frequency discharges.

A new interpolation to estimate a spatial profile of plasma densities of unmeasured regions for two-dimensional probe diagnostics is proposed. Our algorithm is based on the plasma diffusion characteristics. From a comparison with a well known interpolation, Modified Shepard, it has been found that our method gives more accurate plasma density profile, especially at the edge region of the measurement substrate, and improves computational efficiency.

Comparison of pressure dependence of electron energy distributions in oxygen capacitively and inductively coupled plasmas.

Electron energy distribution functions (EEDFs) were measured with increasing gas pressure in oxygen capacitively and inductively coupled plasmas. It was found that, in the capacitive discharge, abnormally low-energy electrons became highly populated and the EEDF evolved to a more distinct bi-Maxwellian distribution as the gas pressure was increased. This pressure dependence of the EEDF in the oxygen capacitive discharge is contrary to argon capacitively coupled plasma, where--at high gas pressure--low-energy electrons are significantly reduced due to collisional heating and the EEDF evolves to the Maxwellian. The highly populated low-energy electrons at high gas pressure, which was not observed in inductively coupled oxygen plasma, show that collisional heating is very inefficient in terms of the oxygen capacitive discharge. It appears that this inefficient collisional heating seems to be attributed to a low electric field strength at the center of the oxygen capacitive plasma.