• Proceedings of the Materials Research Society of Korea Conference
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• 1993.11a
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• pp.98.2-99
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• 1993

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.179-180
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• 2007

반도체의 최소 회로 선폭이 감소함에 따라 Contact 저항이 크게 증가하게 된다. Contact 저항을 낮추기 위하여 Tungsten Metal Contact을 일반적으로 사용하며, Si 기판과의 Ohmic 접촉 및 WF6의 Fluorine과 Si 반응을 억제하기 위한 Barrier Metal로 Ti/TiN 이중막을 사용한다. 본 논문에서는 90nm급 이하 제품의 CVD Ti/TiN Barrier Metal이 유발하는 불량 현상과 원인 규명에 대하여 연구하였으며, Ohmic Contact형성을 위해 TiSix형성 최적화 방안에 대해 정리하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.33-36
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• 2004

탄소 도핑$(5{\times}10^{19}\;cm^{-3})$된 p-type GaAsSb 에피층 위에, Ti/Pt/Au, Pd/Au, Pd/Ir/Au를 이용한 다층 오믹 접촉을 제작하였다. MOCVD(metal-organic chemical vapor deposition)를 이용하여 성장시킨 이 p-GaAsSb의 정공 이동도는 탄소의 도핑 농도가 매우 높음에도 불구하고, $50\;cm^2/Vs$로 측정되었다. 오믹 접촉의 전기적 특성을 측정하기 위하여 TLM(Transfer length method)를 이용하였다. Pd/Ir/Au을 이용한 오믹접촉의 specific contact resistivity는 $10^{-8}\;ohm-cm^2$ 보다 작은 수치를, transfer length는 100 nm보다 작은 수치를 보였으며, Ti/Pt/Au을 이용한 ohmic contact의 specific contact resistivity는 $10^{-7|\;ohm-cm^2$ 보다 작은 수치를, transfer length는 400 nm보다 작은 수치를 나타내었다.

• Korean Journal of Materials Research
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• v.25 no.7
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• pp.352-357
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• 2015

To research the characteristics of ITO film depending on a polarity of SiOC, specimens of ITO/SiOC/glass with metal-insulator-substrates (MIS) were prepared using a sputtering system. SiOC film with 17 sccm of oxygen flow rate became a non-polarity with low surface energy. The PL spectra of the ITO films deposited with various argon flow rates on SiOC film as non-polarity were found to lead to similar formations. However, the PL spectra of ITO deposited with various argon flow rates on SiOC with polarity were seen to have various features owing to the chemical reaction between ITO and the polar sites of SiOC. Most ITO/SiOC films non-linearly showed the Schottky contacts and current increased. But the ITO/SiOC film with a low current demonstrated an Ohmic contact.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.8
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• pp.438-444
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• 2000

We report the effects of etch process parameters on the ohmic contact formation in the plasma etching of GaN. Planar inductively coupled plasma system with $CH_4/H_2/Ar$gas chemistry has been used as etch reactor. The contact resistance and the specific contact resistance have been investigated using transfer length method as a function of RF bias power and %Ar gas concentration in total flow rate. AES(Auger electron spectroscopy) analysis revealed that the etched GaN has nonstoichiometric Ga rich surface and was contaminated by carbon and oxygen. Especially large amount of carbon was detected at the sample etched for high bias power (or voltage) condition, where severe degradation of contact resistance was occurred. We achieved the low ohmic contact of $2.4{\times}10^{-3} {\Omega}cm^2$ specific contact resistance at the input power 400 W, RF bias power 150 W, and working pressure 10mTorr with 10 sccm $CH_4$, 15 sccm H2, 5 sccm Ar gas composition.

• Korean Journal of Materials Research
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• v.12 no.12
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• pp.918-923
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• 2002

In this work, CdTe films were deposited on CdS/ITO/glass substrate by a close spaced sublimation (CSS) method. A $Cu_2$Te layer was deposited on the CdTe film by evaporating $Cu_2$Te powder. Then the samples were annealed for p+ ohmic contact. TEM and XRD analysis showed that $CdTe/Cu_2$Te interface exhibited different forms with various annealing temperature. A good p+ ohmic contact was achieved when the annealing temperature was between $180^{\circ}C$ to $200^{\circ}C$. Best cell efficiency of 12.34% was obtained when post annealing temperature was $200^{\circ}C$ for 5 min. Thermal stress test of the CdS/CdTe cells with carbon back contact showed that the $Cu_2$Te contact was stable at $50^{\circ}C$ in $N_2$ and was slowly degraded at $100^{\circ}C$ in $N_2$. In comparison to the conventional carbon contact, the $Cu_2$Te contact showed a better thermal stability.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1509_1510
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• 2009

This paper presents the design and simulation results of ohmic contact RF MEMS silicon switch with a high isolation at high frequencies along with the position of a contact part, initial off-state and intermediate off-state including the state where a contact part is placed right over a signal line of coplanar waveguide (CPW). The ohmic contact part is connected with comb drives made of high resistivity single crystalline silicon. The released contact part is $30{\mu}m$ apart from the edge of signal line on the glass substrate along the lateral direction (x-direction) at initial off-state. The electrostatic force of the comb electrode creates the x-directional movement thus initial state is converted to the intermediate off-state. The initial off-state of the switch results in isolations of -31 dB, -24 dB and reflections of -0.45 dB, -0.67 dB at 50 GHz and 110 GHz, respectively. It shows the isolation degradation when the contact part moves right over the signal line of CPW like an initial off-state of a conventional MEMS switch. The isolations and reflections are -31 dB, -24 dB and -0.50 dB, -1.31 dB at 50 GHz and 110 GHz, respectively at the intermediate off-state.

• Korean Journal of Materials Research
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• v.19 no.8
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• pp.443-446
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• 2009

This study develops a highly transparent ohmic contact scheme using indium oxide doped ZnO (IZO) as a current spreading layer for p-GaN in order to increase the optical output power of nitride-based lightemitting diodes (LEDs). IZO based contact layers of IZO, Ni/IZO, and NiO/IZO were prepared by e-beam evaporation, followed by a post-deposition annealing. The transmittances of the IZO based contact layers were in excess of 80% throughout the visible region of the spectrum. Specific contact resistances of $3.4\times10^{-4}$, $1.2\times10^{-4}$, $9.2\times0^{-5}$, and $3.6\times10^{-5}{\Omega}{\cdot}cm^2$ for IZO, Ni/Au, Ni/IZO, and NiO/IZO, respectively were obtained. The forward voltage and the optical output power of GaN LED with a NiO/IZO ohmic contact was 0.15 V lower and was increased by 38.9%, respectively, at a forward current of 20 mA compared to that of a standard GaN LED with an Ni/Au ohmic contact due to its high transparency, low contact resistance, and uniform current spreading.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.6
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• pp.231-238
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• 2015

In this paper, we have studied a sheet resistance property of N- and P-type thin films deposited on ITO glass by use of RF magnetron sputtering. The N-type samples which has the deposition condition of 150W RF power, shows the highest current value, and the samples deposited for 15 minutes shows a better Ohmic contact property. As the substrate temperature, RF power and deposition time are increased, the sheet resistance of the samples is increased, and the low sheet resistance sample shows a better I-V property. The P-type samples shows the highest current value by 150W RF power condition as similar as N-type samples. and the samples deposited for 20 minutes shows a better ohmic contact property. The sheet resistance of the both types samples is increased as increasing RF power and deposition time.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.120-120
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• 1999

III-nitride계 물질들은 blue와 UV 영역의 LED, LD와 같은 광소자뿐만 아니라 HBT, FET와 같은 전자소자로도 널리 응용되고 있다. 이와 같은 물질을 이용한 소자를 제작할 수 있는 낮은 저항의 ohmic contact은 필수적이다. Al이나 Ti와 같은 물질을 기초로 한 n-GaN의 경우는 이미 많은 연구결과가 발표되어 전기적 광학적 소자를 동작하는데 충분히 낮은 ohmic contact저항( )을 었다. 그러나 p-GaN의 ohmic contact은 아직까지 많은 문제점을 내포하고 있다. 그 중의 하나는 높은 doping 농도( )의 p-GaN 박막을 성장하기가 어렵다는 것이며, 또 하나는 낮은 접촉 비저항을 얻기 위해선 7.5eV이상의 큰 재가 function을 지닌 금속을 선택해야 한다. 그러나 5.5eV 이상의 재가 function을 갖는 금속은 존재하지 않는다. 위와 같은 문제점들은 p-GaN의 접촉 비저항이 이상의 높은 값을 갖게 만들고 있으며, 이에 대한 해경방안으로는 고온의 열처리를 통하여 p-GaN와 금속 사이에서 화학적 반응을 일으킴으로써 표면 근처에서 캐리어농도를 증가시키고, 캐리어 수송의 형태가 tunneling 형태로 일어날 수 있도록 하는 tunneling current mechanism을 이용하는 것이다. 이로 인해 결국 낮은 접촉 비저항을 얻을 수 있게되며, 일반적으로 p-GaN에서는 Nidl 좋은 물질로 알려져 있다. 그러나 Ni은 50$0^{\circ}C$이상의 열처리에서 쉽게 산화되는 특성 때문에 높은 캐리어를 얻는데 어려운 문제점이 있다. 이에 본 연구에서는 MBE로 성장된 p-GaN박막을 Mg의 activation을 더욱 증가시키기 위해 N2 분위기에서 15분간 90$0^{\circ}C$에서 annealing을 하였으며, ohmic 접촉을 위한 금속으로 높은 재가 function과 좋은 adhesion 그리고 낮은 자체저항을 가지고 있는 Ni/Au를 ohmic metal로 하여 contact한 후에 90$0^{\circ}C$에서 10초간 rapid thermal annealing (RTA)처리를 했다. 성장된 박막의 광학적 성질은 PL로써 측정하였으며, photoconductivity 실험을 통해 impurity의 life time을 분석하였고, persistent photoconductivity를 통해 dark current를 측정하였다. 또한 contact resistance를 계산하기 위해 circular-TLM method을 이용하여 I-V 특성을 조사하였다.