• Journal of Korean Vacuum Science & Technology
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• v.5 no.1
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• pp.19-24
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• 2001

The paper represents the results of the development and the test of "cold cathode" ion source model with 5 cm aperture where the glow discharge is utilized for generation of electrons in the cathode of the ion source. The results of probe measurements of the ion source are represented. The integral parameters such as electron energy distribution function(EEDF), electron density and mean electron energy, discharge voltage-current characteristics, and distribution of ion beam were studied.

• Korean Journal of Materials Research
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• v.12 no.1
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• pp.44-47
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• 2002

DV(Discrete Variation)-X${\alpha}$ cluster calculation was employed to calculate the electronic states of ${\gamma}'- Fe_4N$ which was one of iron nitride phases synthesized from plasma ion nitriding to improve surface hardness and wear resistance. The result of calculated electron density of states for Fe was similar to the result of band calculation. The cluster used for calculation of electronic states of ${\gamma}'-Fe_4N$ was based on $Fe_{14}N$ cluster which comprises 15 atoms. Finally the electronic states of ${\gamma}'- Fe_4N$ such as net-charge, band order, energy level, electron wave-function, and contour map for electron density were derived by the calculation.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.5
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• pp.416-422
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• 2015

Lithium Ion capacitor (LIC) is a new storage device which combines high power density and high energy density compared to conventional supercapacitors. LIC is capable of storing approximately 5.10 times more energy than conventional EDLCs and also have the benefits of high power and long cycle-life. In this study, LICs are assembled with activated carbon (AC) cathode and pre-doped graphite anode. Cathode material of natural graphite and artificial graphite kinds of MAGE-E3 was selected as the experiment proceeds. Super-P as a conductive agent and PTFE was used as binder, with the graphite: conductive agent: binder of 85: 10: 5 ratio of the negative electrode was prepared. Lithium doping condition of current density of $2mA/cm^2$ to $1mA/cm^2$, and was conducted by varying the doping. Results Analysis of Inductively Coupled Plasma Spectrometer (ICP) was used and a $1mA/cm^2$ current density, $2mA/cm^2$, when more than 1.5% of lithium ions was confirmed that contained. In addition, lithium ion doping to 0.005 V at 10, 20 and $30^{\circ}C$ temperature varying the voltage variation was confirmed, $20^{\circ}C$ cell from the low internal resistance of $4.9{\Omega}$ was confirmed.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.233-233
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• 2010

Magnetic random access memory (MRAM), based on magnetic tunnel junction (MTJ) and CMOS, is a prominent candidate among prospective semiconductor memories because it can provide nonvolatility, fast access time, unlimited read/write endurance, low operating voltage and high storage density. The etching of MTJ stack with good properties is one of a key process for the realization of high density MRAM. In order to achieve high quality MTJ stack, the use of CoFeB and IrMn magnetic films as free layers was proposed. In this study, inductively coupled plasma reactive ion etching of CoFeB and IrMn thin films masked with Ti hard mask was investigated in a $Cl_2$/Ar gas mix. The etch rate of CoFeB and IrMn films were examined on varying $Cl_2$ gas concentration. As the $Cl_2$ gas increased, the etch rate monotonously decreased. The effective of etch parameters including coil rf power, dc-bais voltage, and gas pressure on the etch profile of CoFeB and IrMn thin film was explored, At high coil rf power, high dc-bais voltage, low gas pressure, the etching of CoFeB and IrMn displayed better etch profiles. Finally, the clean and vertical etch sidewall of CoFeB and IrMn free layers can be achieved by means of thin Ti hard mask in a $Cl_2$/Ar plasma at the optimized condition.

• Journal of the Semiconductor & Display Technology
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• v.18 no.4
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• pp.35-39
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• 2019

Effect of Ge₂Sb₂Te₅ (GST) chalcogen composition on plasma induced damage was investigated by using Ar ions and F radicals. Experiments were carried out with three different modes; the physical etching, the chemical etching, and the ion-enhanced chemical etching mode. For the physical etching by Ar ions, the sputtering yield was obtained according to ion bombarding energy and there was no change in GST composition ratio. In the plasma mode, the lowest etch rate was measured at the same applied power and there was also no plasma induced damage. In the ion-enhanced chemical etching conditions irradiated with high energy ions and F halogen radicals, the GST composition ratio was changed according to the density of F radicals, resulting in higher roughness of the etched surface. The change of GST composition ratio in halogen plasma is caused by the volatility difference of GST-halogen compounds with high energy ions over than the activation energy of surface reactions.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.287-287
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• 2011

ITRS(international technology roadmap for semiconductors)에 따르면 MOS (metal-oxide-semiconductor)의 CD(critical dimension)가 45 nm node이하로 줄어들면서 poly-Si/SiO2를 대체할 수 있는 poly-Si/metal gate/high-k dielectric이 대두되고 있다. 일반적으로 metal gate를 식각시 정확한 CD를 형성시키기 위해서 plasma를 이용한 RIE(reactive ion etching)를 사용하고 있지만 PIDs(plasma induced damages)의 하나인 PICD(plasma induced charging damage)의 발생이 문제가 되고 있다. PICD의 원인으로 plasma의 non-uniform으로 locally imbalanced한 ion과 electron이 PICC(plasma induced charging current)를 gate oxide에 발생시켜 gate oxide의 interface에 trap을 형성시키므로 그 결과 소자 특성 저하가 보고되고 있다. 그러므로 본 연구에서는 이에 차세대 MOS의 metal gate의 식각공정에 HDP(high density plasma)의 ICP(inductively coupled plasma) source를 이용한 중성빔 시스템을 사용하여 PICD를 줄일 수 있는 새로운 식각 공정에 대한 연구를 하였다. 식각공정조건으로 gas는 HBr 12 sccm (80%)와 Cl2 3 sccm (20%)와 power는 300 w를 사용하였고 200 eV의 에너지로 식각공정시 TEM(transmission electron microscopy)으로 TiN의 anisotropic한 형상을 볼 수 있었고 100 eV 이하의 에너지로 식각공정시 하부층인 HfO2와 높은 etch selectivity로 etch stop을 시킬 수 있었다. 실제 공정을 MOS의 metal gate에 적용시켜 metal gate/high-k dielectric CMOSFETs의 NCSU(North Carolina State University) CVC model로 effective electric field electron mobility를 구한 결과 electorn mobility의 증가를 볼 수 있었고 또한 mos parameter인 transconductance (Gm)의 증가를 볼 수 있었다. 그 원인으로 CP(Charge pumping) 1MHz로 gate oxide의 inteface의 분석 결과 이러한 결과가 gate oxide의 interface trap양의 감소로 개선으로 기인함을 확인할 수 있었다.

• Corrosion Science and Technology
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• v.20 no.3
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• pp.112-117
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• 2021

Inductively coupled plasma magnetron sputtering (ICPMS) has the advantage of being able to dramatically improve coating properties by increasing the plasma ionization rate and the ion bombardment effect during deposition. Thus, this paper presents the comparative results of CrN films deposited by direct current magnetron sputtering (dcMS) and ICPMS systems. The structure, microstructure, and mechanical and corrosive properties of the CrN coatings were investigated by X-ray diffractometry, scanning electron microscopy, nanoindentation, and corrosion-resistance measurements. The as-deposited CrN films by ICPMS grew preferentially on a 200 plane compared to dcMS on a 111 plane. As a result, the films deposited by ICPMS had a very compact microstructure with high hardness. The nanoindentation hardness reached 19.8 GPa, and 13.5 GPa by dcMS. The corrosion current density of CrN film prepared by ICPMS was about 9.8 × 10^-6 mA/cm², which was 1/470 of 4.6 × 10^-3 mA/cm², the corrosion current density of CrN film prepared by dcMS.

• Journal of the Korean Ceramic Society
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• v.40 no.10
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• pp.967-972
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• 2003

The inner-diameter 5 cm cold hollow cathode ion source was designed for the high current density and the homogeneous beam profile of ion beam. The ion source consisted of a cylindrical cathode, a generation part of magnetic field, a plasma chamber, convex type ion optic system with two grid electrode, and DC power supply system. The cold hollow cathode ion sources were classified into standard type (I), electron output electrode modified type (II). The operation of the ion source was done with discharge current, ion beam potential and argon gas flow rate. The modification of electron output electrode resulted in uniform plasma generation and uniform area of ion beam was extended from 5 cm to 20 cm. Improved ion source was evaluated with beam uniformity, ion current, team extraction efficiency, and ionization efficiency.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.155.2-155.2
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• 2013

Strain-relaxed SiGe layer on Si substrate has numerous potential applications for electronic and opto- electronic devices. SiGe layer must have a high degree of strain relaxation and a low dislocation density. Conventionally, strain-relaxed SiGe on Si has been manufactured using compositionally graded buffers, in which very thick SiGe buffers of several micrometers are grown on a Si substrate with Ge composition increasing from the Si substrate to the surface. In this study, a new plasma process, i.e., the combination of PIII&D and HiPIMS, was adopted to implant Ge ions into Si wafer for direct formation of SiGe layer on Si substrate. Due to the high peak power density applied the Ge sputtering target during HiPIMS operation, a large fraction of sputtered Ge atoms is ionized. If the negative high voltage pulse applied to the sample stage in PIII&D system is synchronized with the pulsed Ge plasma, the ion implantation of Ge ions can be successfully accomplished. The PIII&D system for Ge ion implantation on Si (100) substrate was equipped with 3'-magnetron sputtering guns with Ge and Si target, which were operated with a HiPIMS pulsed-DC power supply. The sample stage with Si substrate was pulse-biased using a separate hard-tube pulser. During the implantation operation, HiPIMS pulse and substrate's negative bias pulse were synchronized at the same frequency of 50 Hz. The pulse voltage applied to the Ge sputtering target was -1200 V and the pulse width was 80 usec. While operating the Ge sputtering gun in HiPIMS mode, a pulse bias of -50 kV was applied to the Si substrate. The pulse width was 50 usec with a 30 usec delay time with respect to the HiPIMS pulse. Ge ion implantation process was performed for 30 min. to achieve approximately 20 % of Ge concentration in Si substrate. Right after Ge ion implantation, ~50 nm thick Si capping layer was deposited to prevent oxidation during subsequent RTA process at $1000^{\circ}C$ in N2 environment. The Ge-implanted Si samples were analyzed using Auger electron spectroscopy, High-resolution X-ray diffractometer, Raman spectroscopy, and Transmission electron microscopy to investigate the depth distribution, the degree of strain relaxation, and the crystalline structure, respectively. The analysis results showed that a strain-relaxed SiGe layer of ~100 nm thickness could be effectively formed on Si substrate by direct Ge ion implantation using the newly-developed PIII&D process for non-gaseous elements.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.4
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• pp.387-394
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• 2013

As the feature size of integrated circuits continues to decrease, the challenge of achieving an oxidation-free exposed layer after photoresist (PR) stripping is becoming a critical issue for semiconductor device fabrication. In this article, the hydrogen plasma characteristics in direct plasma and the PR stripping rate in remote plasma were studied using a $120{\Phi}$ cylindrical inductively coupled plasma source. E mode, H mode and E-H mode transitions were observed, which were defined by matching the $V_{rms}$ and total impedance. In addition, the dependence of the E-H mode transition on pressure was examined and the corresponding plasma instability regions were identified. The plasma density and electron temperature increased gradually under the same process conditions. In contrast, the PR stripping rate decreased with increasing proportion of $H_2$ gas in mixed $H_2/N_2$ plasma. The decrease in concentration of reactive radicals for the removal of PR with increasing $H_2$ gas flow rate suggests that NH radicals have a dominant effect as the main volatile product.