Development of Virtual Metrology Using Plasma Information Variables to Predict Si Etch Profile Processed by SF6/O2/Ar Capacitively Coupled Plasma.

In the semiconductor etch process, as the critical dimension (CD) decreases and the difficulty of the process control increases, in-situ and real-time etch profile monitoring becomes important. It leads to the development of virtual metrology (VM) technology, one of the measurement and inspection (MI) technology that predicts the etch profile during the process. Recently, VM to predict the etch depth using plasma information (PI) variables and the etch process data based on the statistical regression method had been developed and demonstrated high performance. In this study, VM using PI variables, named PI-VM, was extended to monitor the etch profile and investigated the role of PI variables and features of PI-VM. PI variables are obtained through analysis on optical emission spectrum data. The features in PI-VM are investigated in terms of plasma physics and etch kinetics. The PI-VM is developed to monitor the etch depth, bowing CD, etch depth times bowing CD (rectangular model), and etch area model (non-rectangular model). PI-VM for etch depth and bowing CD showed high prediction accuracy of R-square value (R2) 0.8 or higher. The rectangular and non-rectangular etch area model PI-VM showed prediction accuracy R2 of 0.78 and 0.49, respectively. The first trial of virtual metrology to monitor the etch profile will contribute to the development of the etch profile control technology.

Safety evaluation of atmospheric pressure plasma jets in in vitro and in vivo experiments.

PURPOSE: The atmospheric pressure plasma jet (APPJ) has been introduced as an effective disinfection method for titanium surfaces due to their massive radical generation at low temperatures. Helium (He) has been widely applied as a discharge gas in APPJ due to its bactericidal effects and was proven to be effective in our previous study. This study aimed to evaluate the safety and effects of He-APPJ application at both the cell and tissue levels. METHODS: Cellular-level responses were examined using human gingival fibroblasts and osteoblasts (MC3T3-E1 cells). He-APPJ was administered to the cells in the experimental group, while the control group received only He-gas treatment. Immediate cell responses and recovery after He-APPJ treatment were examined in both cell groups. The effect of He-APPJ on osteogenic differentiation was evaluated via an alkaline phosphatase activity assay. In vivo, He-APPJ treatment was administered to rat calvarial bone and the adjacent periosteum, and samples were harvested for histological examination. RESULTS: He-APPJ treatment for 5 minutes induced irreversible effects in both human gingival fibroblasts and osteoblasts in vitro. Immediate cell detachment of human gingival fibroblasts and osteoblasts was shown regardless of treatment time. However, the detached areas in the groups treated for 1 or 3 minutes were completely repopulated within 7 days. Alkaline phosphatase activity was not influenced by 1 or 3 minutes of plasma treatment, but was significantly lower in the 5 minute-treated group (P=0.002). In vivo, He-APPJ treatment was administered to rat calvaria and periosteum for 1 or 3 minutes. No pathogenic changes occurred at 7 days after He-APPJ treatment in the He-APPJ-treated group compared to the control group (He gas only). CONCLUSIONS: Direct He-APPJ treatment for up to 3 minutes showed no harmful effects at either the cell or tissue level.

Quantitation of the ROS production in plasma and radiation treatments of biotargets.

Medical treatment utilizing non-thermal plasma is based on the production of reactive oxygen species (ROS) and their interactions with biomatters. On the basis of empirical data from practices, plasma treatment has been planned with regard to the setup of a plasma generator's parameters, including gas combination, gas-flow rate, and applied voltage. In this study, we quantitated plasma treatment in terms of the plasma dose on the target matter, which can be contrasted with the radiation dose to targets under radiation exposure. We measured the OH radical production in cell culture medium and intracellular ROS production from plasma treatment in comparison with those from X-ray exposure. The clonogenic cell deaths from plasma and X-ray exposures were also compared. In plasma treatment, the clonogenic cell death was better predicted by intracellular ROS production rather than by medium OH production.

The bactericidal effect of an atmospheric-pressure plasma jet on Porphyromonas gingivalis biofilms on sandblasted and acid-etched titanium discs.

PURPOSE: Direct application of atmospheric-pressure plasma jets (APPJs) has been established as an effective method of microbial decontamination. This study aimed to investigate the bactericidal effect of direct application of an APPJ using helium gas (He-APPJ) on Porphyromonas gingivalis biofilms on sandblasted and acid-etched (SLA) titanium discs. METHODS: On the SLA discs covered by P. gingivalis biofilms, an APPJ with helium (He) as a discharge gas was applied at 3 different time intervals (0, 3, and 5 minutes). To evaluate the effect of the plasma itself, the He gas-only group was used as the control group. The bactericidal effect of the He-APPJ was determined by the number of colony-forming units. Bacterial viability was observed by confocal laser scanning microscopy (CLSM), and bacterial morphology was examined by scanning electron microscopy (SEM). RESULTS: As the plasma treatment time increased, the amount of P. gingivalis decreased, and the difference was statistically significant. In the SEM images, compared to the control group, the bacterial biofilm structure on SLA discs treated by the He-APPJ for more than 3 minutes was destroyed. In addition, the CLSM images showed consistent results. Even in sites distant from the area of direct He-APPJ exposure, decontamination effects were observed in both SEM and CLSM images. CONCLUSIONS: He-APPJ application was effective in removing P. gingivalis biofilm on SLA titanium discs in an in vitro experiment.

Optimal Parameters for Intervertebral Disk Resection Using Aqua-Plasma Beams.

OBJECTIVE: A minimally invasive procedure for intervertebral disk resection using plasma beams has been developed. Conventional parameters for the plasma procedure such as voltage and tip speed mainly rely on the surgeon's personal experience, without adequate evidence from experiments. Our objective was to determine the optimal parameters for plasma disk resection. METHODS: Rate of ablation was measured at different procedural tip speeds and voltages using porcine nucleus pulposi. The amount of heat formation during experimental conditions was also measured to evaluate the thermal safety of the plasma procedure. RESULTS: The ablation rate increased at slower procedural speeds and higher voltages. However, for thermal safety, the optimal parameters for plasma procedures with minimal tissue damage were an electrical output of 280 volts root-mean-square (Vrms) and a procedural tip speed of 2.5 mm/s. CONCLUSION: Our findings provide useful information for an effective and safe plasma procedure for disk resection in a clinical setting.

Efficacy of a new navigable percutaneous disc decompression device (L'DISQ) in patients with herniated nucleus pulposus related to radicular pain.

STUDY DESIGN: An institutional, prospective clinical data analysis. OBJECTIVE: To evaluate the safety and efficacy of a new navigable percutaneous disc decompression device (L'DISQ) in patients with lumbar disc herniation with radicular pain. METHODS AND OUTCOME MEASURES: We performed disc decompressions using L'DISQ on 27 patients with persistent disabling back and leg pain for 1 month or longer (average 6.48 months) due to a herniated lumbar intervertebral disc. Baseline data were prospectively gathered before the index procedure and at 1, 4, 12, and 24 weeks post-procedure. Data included pain intensity (visual analog scale [VAS]), measure of disability (Oswestry Disability Index [ODI] and Rolando-Morris Questionnaire [RM]), health-related quality of life (Bodily Pain Scale of Short Form-36 version 2 [SF-36 BP]), and passive straight leg raising test (SLR). RESULTS: The VAS fell from 7.08±1.22 to 1.84±0.99 scores at 24 weeks post-procedure. At 24 weeks, the ODI had fallen from 41.88±10.61 to 16.66±8.55% and the RM from 11.52±3.91 to 2.68±1.97 points. The SF-36 BP dropped significant improvement from 32.89±5.83 to 49.57±4.96 scales. In the SLR test, the angular change of 24 weeks showed considerable improvement from 60.20±20.02 to 83.00±14.29 degrees. No major complication occurred, although two cases developed a disc reherniation 1 month post-procedure. CONCLUSIONS: The L'DISQ device is specifically designed to remove herniated disc using a wand that can be navigated into a disc protrusion or extrusion. Following decompression, we measured clinically significant pain improvement and decreased disability for patients with both radicular and axial pain caused by protruded and extruded discs.

Self-consistent circuit model for plasma source ion implantation.

A self-consistent circuit model which can describe the dynamic behavior of the entire pulsed system for plasma source ion implantation has been developed and verified with experiments. In the circuit model, one-dimensional fluid equations of plasma sheath have been numerically solved with self-consistent boundary conditions from the external circuit model including the pulsed power system. Experiments have been conducted by applying negative, high-voltage pulses up to -10 kV with a capacitor-based pulse modulator to the planar target in contact with low-pressure argon plasma produced by radio-frequency power at 13.56 MHz. The measured pulse voltage and current waveforms as well as the sheath motion have shown good agreements with the simulation results.