• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.346-349
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• 2002

High Power and high dose ion implantation is essentially needed to make power MOSFET devices based on SiC wafers, because the diffusivities of the impurities such as Al, N, p, B in SiC crystal are very low. In addition, it is needed high temperature annealing for electrical activation of the implanted species. Due to the very high annealing temperature, the surface morphology after electrical activation annealing becomes very rough. We have found the different surface morphologies between implanted and unimplanted region. The unimplanted region showed smoother surface morphology It implies that the damage induced by high energy ion implantation affects the roughening mechanism. Some parts of Si-C bonding are broken in the damaged layer, s\ulcorner the surface migration and sublimation become easy. Therefore the macrostep formation will be promoted. N-type 4H-SiC wafers, which were Al ion implanted at acceleration energy ranged from 30kev to 360kev, were activated at 1600$^{\circ}C$ for 30min. The pre-activation annealing for damage relaxation was performed at 1100-1500$^{\circ}C$ for 30min. The surface morphologies of pre-activation annealed and activation annealed were characterized by atomic force microscopy(AFM).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.403-403
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• 2008

This article reports changes in the mechanical properties of chromium steel after nitrogen implantation at high temperature. The samples are implanted with 120keV N-ion at doses ranging from $1\times1080$ to $4\times1080ions/cm^2$ and at substrate temperature ranging from 25 to $400^{\circ}C$. Nano-hardness and AES(Auger electrons spectroscopy) were measured from nitrogen ion implanted layer. The sliding wear and impact wear properties of the implanted samples were also measured. The results revealed that the hardness and mechanical properties of ion implanted samples depend strongly on the ion doses and implantation temperature. The hardness of the nitrogen implanted sample with 120keV, $4\times10^{18}ions/cm^2$, $335^{\circ}C$ was measured to be approximately 20 GPa, which is approximately 5 times higher than that of un-implanted sample (H=3.8 GPa). Also, the sliding wear and impact wear properties of nitrogen implanted samples were greatly improved. Detailed experiment results will be presented.

• Korean Journal of Materials Research
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• v.14 no.7
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• pp.494-499
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• 2004

The structural, electrical and optical properties of GaN epilayers grown on various ion-implanted sapphire(0001) substrates by MOCVD were investigated. Sapphire substrates have been widely adopted to grow high quality GaN epilayer despite the large differences of lattice constant and thermal expansion coefficient between them. So, GaN or AlN buffer layer and pre-treatment was indispensably introduced before the GaN epilayer growth. The ion-implanted substrate's surface had decreased internal free energies during the growth of the ions implanted sapphire(0001) substrates. The crystal and optical properties of GaN epilayers grown in ions implanted sapphire(0001) substrate were improved. Also, excessively roughened and modified surface by ions degraded the GaN epilyers. Not only the ionic radius but also the chemical species of implanted sapphire(0001) substrates could improve the properties of GaN epilayers grown by MOCVD. This result implies that higher quality of GaN epilayers was achieved by using ion-implanted sapphire(0001) substrate with various ions.

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.11a
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• pp.106-106
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• 1996

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.4
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• pp.712-718
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• 2003

The effects of nitrogen ion implantation on vacuum evaporated cadmium sulphide (CdS) thin films were investigated by X-ray diffraction, optical transmittance spectra, and Raman scattering studies. The as-deposited CdS films have a hexagonal structure with preferential (0 0 2) orientation. Formation of Cd metallic clusters was observed in ion implanted films from the XRD patterns. The band gap of N+ implanted films decreased, whereas the optical absorption coefficient values increased with the increase of implantation dose. The Raman peak position appeared at 299 cm-1 and the FWHM increased with the ion dose. A decrease in the area of Raman peak of CdS Al(LO) mode is seen on implantation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.12
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• pp.750-758
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• 2016

For the channel doping of shallow junction and retrograde well formation in CMOS, indium can be implanted in silicon. The retrograde doping profiles can serve the needs of channel engineering in deep MOS devices for punch-through suppression and threshold voltage control. Indium is heavier element than B, $BF_2$ and Ga ions. It also has low coefficient of diffusion at high temperatures. Indium ions can be cause the erode of wafer surface during the implantation process due to sputtering. For the ultra shallow junction, indium ions can be implanted for p-doping in silicon. UT-MARLOWE and SRIM as Monte carlo ion-implant models have been developed for indium implantation into single crystal and amorphous silicon, respectively. An analytical tool was used to carry out for the annealing process from the extracted simulation data. For the 1D (one-dimensional) and 2D (two-dimensional) diffused profiles, the analytical model is also developed a simulation program with $C^{{+}{+}}$ code. It is very useful to simulate the indium profiles in implanted and annealed silicon autonomously. The fundamental ion-solid interactions and sputtering effects of ion implantation are discussed and explained using SRIM and T-dyn programs. The exact control of indium doping profiles can be suggested as a future technology for the extreme shallow junction in the fabrication process of integrated circuits.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.3
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• pp.251-263
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• 2008

In this paper, we report an analytical modeling and 2-D Synopsys Sentaurus TCAD simulation of ion implanted silicon carbide MESFETs. The model has been developed to obtain the threshold voltage, drain-source current, intrinsic parameters such as, gate capacitance, drain-source resistance and transconductance considering different fabrication parameters such as ion dose, ion energy, ion range and annealing effect parameters. The model is useful in determining the ion implantation fabrication parameters from the optimization of the active implanted channel thickness for different ion doses resulting in the desired pinch off voltage needed for high drain current and high breakdown voltage. The drain current of approximately 10 A obtained from the analytical model agrees well with that of the Synopsys Sentaurus TCAD simulation and the breakdown voltage approximately 85 V obtained from the TCAD simulation agrees well with published experimental results. The gate-to-source capacitance and gate-to-drain capacitance, drain-source resistance and trans-conductance were studied to understand the device frequency response. Cut off and maximum frequencies of approximately 10 GHz and 29 GHz respectively were obtained from Sentaurus TCAD and verified by the Smith's chart.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.33 no.4
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• pp.439-446
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• 2023

Objectives: The aims of this study are to investigate how X-rays are emitted to surrounding parts during the ion implantation process, to analyze these emissions in relation to the properties of the ion implanter equipment, and to estimate the resulting exposure dose. Eight ion implanters equipped with high-voltage electrical systems were selected for this study. Methods: We monitored X-ray emissions at three locations outside of the ion implanters: the accelerator equipped with a high-voltage energy generator, the impurity ion source, and the beam line. We used a Personal Portable Dose Rate and Survey Meter to monitor real-time X-ray levels. The SX-2R probe, an X-ray Features probe designed for use with the Radiagem^TM meter, was also utilized to monitor lower ranges of X-ray emissions. The counts per second (CPS) measured by the meter were estimated and then converted to a radiation dose (𝜇Sv/hr) based on a validated calibration graph between CPS and μGy/hr. Results: X-rays from seven ion implanters were consistently detected in high-voltage accelerator gaps, regardless of their proximity. X-rays specifically emanated from three ion implanters situated in the ion box gap and were also found in the beam lines of two ion implanters. The intensity of these X-rays did not show a clear pattern relative to the devices' age and electric properties, and notably, it decreased as the distance from the device increased. Conclusions: In conclusion, every gap, in which three components of the ion implanter devices were divided, was found to be insufficiently shielded against X-ray emissions, even though the exposure levels were not estimated to be higher than the threshold.

• Journal of Microbiology and Biotechnology
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• v.14 no.2
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• pp.363-366
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• 2004

In order to obtain an industrial strain with higher L(+)-lactic acid yield, the wild type strain Rhizopus oryzae PW352 was mutated by means of Nitrogen ions implantation (l5 Kev, $7.8 \times 10^{14} - 2.08 \times 10^{15} ions/Cm^2$ and two mutants RE3303 and RF9052 were isolated. After 36 h shake-flask cultivation, the concentration of L(+)-lactic acid reached 131-136 g/l, the conversion rate of glucose was as high as 86%-90% and the productivity was 3.61 g/l.h. It was almost a 75% increase in lactic acid production compared with the wild type strain. Maximum fermentation temperature of RF9052 was increased to $45^{\circ}C$ from original $36^{\circ}C$. At the same time, the preferred range of fermentation temperature of RF9052 was broadened compared with PW352.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.111-111
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• 2007

Further scaling the semiconductor devices down to low dozens of nanometer needs the extremely shallow depth in junction and the intentional counter-doping in the silicon gate. Conventional ion beam ion implantation has some disadvantages and limitations for the future applications. In order to solve them, therefore, plasma source ion implantation technique has been considered as a promising new method for the high throughputs at low energy and the fabrication of the ultra-shallow junctions. In this paper, we study about the effects of DC bias and base pressure as a process parameter. The diluted mixture gas (5% $PH_3/H_2$) was used as a precursor source and chamber is used for vacuum pressure conditions. After ion doping into the Si wafer(100), the samples were annealed via rapid thermal annealing, of which annealed temperature ranges above the $950^{\circ}C$. The junction depth, calculated at dose level of $1{\times}10^{18}/cm^3$, was measured by secondary ion mass spectroscopy(SIMS) and sheet resistance by contact and non-contact mode. Surface morphology of samples was analyzed by scanning electron microscopy. As a result, we could accomplish the process conditions better than in advance.