• KIEE International Transactions on Electrophysics and Applications
• /
• v.12C no.4
• /
• pp.208-213
• /
• 2002

The present study describe the electrical performance of amorphous T $a_2$ $O_{5-X}$ fabricated on the buffer layers Ti and Ti $O_2$. T $a_2$ $O_{5-X}$ thin films were grown on the Ti and Ti $O_2$ layers as a capacitor layer using reactive sputtering method. The X-ray pattern analysis indicated that the two as-deposited films were amorphous and the amorphous state was kept stable on the RTA(rapid thermal annealing) at even $700^{\circ}C$. Measurements of dielectric properties of the reactive sputtered T $a_2$ $O_{5-X}$ thin films fabricated in two simple MIS(metal insulator semiconductor), structures, (Cu/T $a_2$ $O_{5}$ Ti/Si and CuT $a_2$ $O_{5}$ Ti $O_2$Si) show that the amorphous T $a_2$ $O_{5}$ grown on Ti showed high dielectric constant (23～39) and high leakage current density(10$^{-3}$ ～10$^{-4}$ (A/$\textrm{cm}^2$)), whereas relatively low dielectric constant (～15) and tow leakage current density(10$^{-9}$ ～10$^{-10}$ (A/$\textrm{cm}^2$)) were observed in the amorphous T $a_2$ $O_{5}$ deposited on the Ti $O_2$ layer. The electrical behaviors of the T $a_2$ $O^{5}$ thin films were attributed to the contribution of Ti- $O_2$ and the compositionally gradient Ta-Ti-0, being the low dielectric layer and high leakage current barrier. In additional, The T $a_2$ $O_{5}$ Ti $O_2$ thin films exhibited dominant conduction mechanism contributed by the Poole-Frenkel emission at high electric field. In the case of T $a_2$ $O_{5}$ Ti $O_2$ thin films were related to the diffusion of Ta, Ti and O, followed by the creation of vacancies, in the rapid thermal treated thin films.films.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.1 no.4
• /
• pp.202-208
• /
• 2001

In Recent results suggested that doping $Ta_2O_5$ with a small amount of $TiO_2$ using standard ceramic processing techniques can increase the dielectric constant of $Ta_2O_5$ significantly. In this paper, this concept is studied using RTCVD (Rapid Thermal Chemical Vapor Deposition). Ti-doped $Ta_2O_5$ films are deposited using $TaC_{12}H_{30}O_5N$, $C_8H_{24}N_4Ti$, and $O_2$ on both Si and $NH_3$-nitrided Si substrates. An $NH_3$-based interface layer at the Si surface is used to prevent interfacial oxidation during the CVD process and post deposition annealing is performed in $H_2/O_2$ ambient to improve film quality and reduce leakage current. A sputtered TiN layer is used as a diffusion barrier between the Al gate electrode and the $TaTi_xO_y$ dielectric. XPS analyses confirm the formation of a ($Ta_2O_5)_{1-x}(TiO_2)_x$ composite oxide. A high quality $TaTi_xO_y$ gate stack with EOT (Equivalent Oxide Thickness) of $7{\AA}$ and leakage current $Jg=O.5A/textrm{cm}^2$ @ Vg=-1.0V has been achieved. We have also succeeded in forming a $TaTi_x/O_y$ composite oxide by rapid thermal oxidation of the as-deposited CVD TaTi films. The electrical properties and Jg-EOT characteristics of these composite oxides are remarkably similar to that of RTCVD $Ta_2O_5, suggesting that the dielectric constant of $Ta_2O_5$ is not affected by the addition of $TiO_2$.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.71-71
• /
• 2011

Dye-sensitized solar cells (DSCs) have drawn great academic attention due to their potential as low-cost renewable energy sources. DSCs contain a nanostructured TiO2 photoanode, which is a key-component for high conversion efficiency. Particularly, one-dimensional (1-D) nanostructured photoanodes can enhance the electron transport for the efficient collection to the conducting substrate in competition with the recombination processes. This is because photoelectron colletion is determined by trapping/detrapping events along the site of the electron traps (defects, surface states, grain boundaries, and self-trapping). Therefore, 1-D nanostructured photoanodes are advantageous for the fast electron transport due to their desirable features of greatly reduced intercrystalline contacts with specified directionality. In particular, anodic TiO2 nanotube (NT) electrodes recently have been intensively explored owing to their ideal structure for application in DSCs. Besides the enhanced electron transport properties resulted from the 1-D structure, highly ordered and vertically oriented nanostructure of anodic TiO2 NT can contribute additional merits, such as enhanced electrolyte diffusion, better interfacial contact with viscous electrolytes. First, to confirm the advantages of 1-D nanostructured material for the photoelectron collection, we compared the electron transport and charge recombination characteristics between nanoparticle (NP)- and nanorod (NR)-based photoanodes in DSCs by the stepped light-induced transient measurements of photocurrent and voltage (SLIM-PCV). We confirmed that the electron lifetime of the NR-based photoanode was much longer than that of the NP-based photoanode. In addition, highly ordered and vertically oriented TiO2 NT photoanodes were prepared by electrochemical anodization method. We compared the photovoltaic properties of DSCs utilizing TiO2 NT photoanodes prepared by one-step anodization and two-step anodization. And, to reduce the charge recombination rate, energy barrier layer (ZnO, Al2O3)-coated TiO2 NTs also applied in DSC. Furthermore, we applied the TiO2 NT photoanode in DSCs using a viscous electrolyte, i.e., cobalt bipyridyl redox electrolyte, and confirmed that the pore structure of NT array can enhance the performances of this viscous electrolyte.

• Journal of the Microelectronics and Packaging Society
• /
• v.30 no.2
• /
• pp.52-59
• /
• 2023

The effects of dielectric curing temperature and temperature/humidity treatment conditions on the interfacial adhesion energies between Ti diffusion barrier/polybenzoxazole (PBO) dielectric layers were systematically investigated for Cu redistribution layer applications of fan-out wafer level package. The initial interfacial adhesion energies were 16.63, 25.95, 16.58 J/m² for PBO curing temperatures at 175, 200, and 225 ℃, respectively. X-ray photoelectron spectroscopy analysis showed that there exists a good correlation between the interfacial adhesion energy and the C-O peak area fractions at PBO delaminated surfaces. And the interfacial adhesion energies of samples cured at 200 ℃ decreased to 3.99 J/m² after 500 h at 85 ℃/85 % relative humidity, possibly due to the weak boundary layer formation inside PBO near Ti/PBO interface.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.16 no.2
• /
• pp.179-184
• /
• 2016

In recent years, the on-resistance, power loss and cell density of Si power devices have not exhibited significant improvements, and performance is approaching the material limits. GaN is considered an attractive material for future high-power applications because of the wide band-gap, large breakdown field, high electron mobility, high switching speed and low on-resistance. Here we report on the Ohmic contact resistance and reverse-bias characteristics of AlGaN/GaN Schottky barrier diodes with and without annealing. Annealing in oxygen at $500^{\circ}C$ resulted in an increase in the breakdown voltage from 641 to 1,172 V for devices with an anode-cathode separation of $20{\mu}m$. However, these annealing conditions also resulted in an increase in the contact resistance of $0.183{\Omega}-mm$, which is attributed to oxidation of the metal contacts. Auger electron spectroscopy revealed diffusion of oxygen and Au into the AlGaN and GaN layers following annealing. The improved reverse-bias characteristics following annealing in oxygen are attributed to passivation of dangling bonds and plasma damage due to interactions between oxygen and GaN/AlGaN. Thermal annealing is therefore useful during the fabrication of high-voltage GaN devices, but the effects on the Ohmic contact resistance should be considered.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.444-445
• /
• 2009

The metallic contact system of silicon solar cell must have several properties, such as low contact resistance, easy application and good adhesion. Ni is shown to be a suitable barrier to Cu diffusion as well as desirable contact metal to silicon. Nickel monosilicide(NiSi) has been suggested as a suitable silicide due to its lower resistivity, lower sintering temperature and lower layer stress than $TiSi_2$. Copper and Silver can be plated by electro & light-induced plating method. Light-induced plating makes use the photovoltaic effect of solar cell to deposit the metal on the front contact. The cell is immersed into the electrolytic plating bath and irradiated at the front side by light source, which leads to a current density in the front side grid. Electroless plated Ni/ Electro&light-induced plated Cu/ Light-induced plated Ag contact solar cells result in an energy conversion efficiency of 16.446 % on $0.2\sim0.6\;{\Omega}{\cdot}cm$, $20\;\times\;20\;mm^2$, CZ(Czochralski) wafer.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.172-172
• /
• 2011

현대 반도체 금속배선 연구에서는 기존에 쓰이던 Al (Aluminium) 금속배선 대신에 Cu(Copper) 금속배선 연구가 진행 되고 있다. Cu는 Al 보다 비저항이 낮고, 녹는점도 Al보다 높다는 장점이 있지만 저온에서 기판인 Si (Silicon) 과 반응하고 접착력이 우수하지 못 하다는 단점이 있다. 이런 문제를 해결하기 위하여 확산방지막을 기판과 금속배선 사이에 삽입하는 방법이 제시 되었다. 확산방지막으로는 기존에 쓰이던 Ti (Titanium) 계열의 확산방지막과 W (Tungsten) 계열의 확산방지막이 있다. 이번 연구에서는 W 계열의 확산방지막에 불순물 C (Carbon), N(Nitrogen)을 첨가한 W-C-N 확산방지막 시편을 제조하였고, N2의 비율을 변화시키며 $600^{\circ}C$ 열처리를 하였다. 실험 결과 질소의 포함 농도에 따라 확산방지막의 안정도가 변화한다는 결과를 얻었으며, 질소 첨가량에 따라 시편의 표면 보다는 시편의 중간층의 물성 변화율이 큰데 이는 시편 표면의 질소는 열처리 중 확산에 의한 시편과의 분리 현상이 일어나지만 시편의 중간층은 trap현상에 의하여 시편에 남아있어 질소의 영향을 받아 시편의 중간층이 더욱 질소 유량에 따른 영향이 큰 것을 확인하였다. 이 결과로부터 W-C-N 박막은 첨가된 질소의 유량에 따라 박막의 안정도가 결정된 다는 것을 알았다. 본 연구에서 시편은 rf magnetron sputtering 방법으로 제작하였고 연속압입 실험은 Hysitron사의 Triboindenter를 이용하였다. Indenting에 사용된 압입팁은 Berkovich tip을 사용하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.2
• /
• pp.162-172
• /
• 2008

We studied the effect of an Al underlayer on the growth of carbon nanotubes (CNTs) and their field emission characteristics, First of all, CNTs were grown on the Invar catalyst layers with different thickness of 1 to 10 nm, showing that the CNT length was saturated for the catalyst 5 nm or thicker. The CNTs grown on the 5-nm-thick catalyst were ${\sim}10{\mu}m$ long and ${\sim}30nm$ in diameter. Second, an Al underlayer was applied between the catalyst layer and the Ti diffusion barrier to reduce the diameters of CNTs for better field emission properties by forming spherical Al oxide particles on which smaller catalyst nanoparticles would occur. The optimal thickness of an Al underlayer underneath the 5-nm-thick catalyst was ${\sim}15nm$, producing the CNTs with the length of ${\sim}15{\mu}m$ and the diameter of ${\sim}15nm$. The field emission measurements, following the tape activation, showed that the thinner and longer CNTs gave rise to better field emission performance with the lower turn-on and threshold electric fields.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2001.06a
• /
• pp.73-73
• /
• 2001

Boron-containing materials have several excellent properties, such as superlnardness, insulation and non-Rinear optical property. Recently, oxynitride compounds, such as Si(ON), Ti(ON), became the promising materials applied in diffusion barrier layer and solar cell. With the expectation of obtaining the hybrid property, we have firstly grown the BON thin film by radio frequency (R.F.) plasma enhanced metalorganic chemical vapm deposition (PEMOCVD) with 100 kHz frequency and trimethyl borate precursor. The plasma source gases used in this study were Ar and $H_2$, and two kinds of nhmgen source gases, $N_2$ and <$NH_3$, were also employed. The as-grown films were characterized by XPS, IR, SEM and Knoop microlhardness tester. The relationship between the films hardness and the growth rate indicated that the hardness of the film was dependent on several factors such as nitrogen source gas, substrate temperature and film thickness due to the variation of the composition and the structure of the film. Both nitrogen and carbon content could raise the film hardness, on which nitrogen content did stronger effect than carbon. The smooth morphology and continuous structure was benefit of obtaining high hardness. The maximum hardness of BON film was about 10 GPa.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.338-338
• /
• 2013

Monolithic three-dimensional integrated circuits (3D-ICs) 구현 시 bonding 과정에서 발생되는 aluminum (Al) 이나 copper (Cu) 등의 interconnect metal의 확산, 열적 스트레스, 결함의 발생, 도펀트 재분포와 같은 문제들을 피하기 위해서는 저온 공정이 필수적이다. 지금까지는 polymer 기반의 bonding이나 Cu/Cu와 같은 metal 기반의 bonding 등과 같은 저온 bonding 방법이 연구되어 왔다. 그러나 이와 같은 bonding 공정들은 공정 시 void와 같은 문제가 발생하거나 공정을 위한 특수한 장비가 필수적이다. 반면, 두 물질의 합금을 이용해 녹는점을 낮추는 eutectic bonding 공정은 저온에서 공정이 가능할 뿐만 아니라 void의 발생 없이 강한 bonding 강도를 얻을 수 있다. Aluminum-germanium (Al-Ge) 및 aluminum-indium (Al-In) 등의 조합이 eutectic bonding에 이용되어 각각 $424^{\circ}C$ 및 $454^{\circ}C$의 저온 공정을 성취하였으나 여전히 $400^{\circ}C$이상의 eutectic 온도로 인해 3D-ICs의 구현 시에는 적용이 불가능하다. 이러한 metal 조합들에 비해 indium (In)과 tin (Sn)은 각각 $156^{\circ}C$ 및 $232^{\circ}C$로 굉장히 낮은 녹는점을 가지고 있기 때문에 In-Sn 조합은 약 $120^{\circ}C$ 정도의 상당히 낮은eutectic 온도를 갖는다. 따라서 본 연구팀은 In-Sn 조합을 이용하여 $200^{\circ}C$ 이하에서monolithic 3D-IC 구현 시 사용될 eutectic bonding 공정을 개발하였다. 100 nm SiO2가 증착된 Si wafer 위에 50 nm Ti 및 410 nm In을 증착하고, 다른Si wafer 위에 50 nm Ti 및 500 nm Sn을 증착하였다. Ti는 adhesion 향상 및 diffusion barrier 역할을 위해 증착되었다. In과 Sn의 두께는 binary phase diagram을 통해 In-Sn의 eutectic 온도인 $120^{\circ}C$ 지점의 조성 비율인 48 at% Sn과 52 at% In에 해당되는 410 nm (In) 그리고 500 nm (Sn)로 결정되었다. Bonding은 Tbon-100 장비를 이용하여 $140^{\circ}C$, $170^{\circ}C$ 그리고 $200^{\circ}C$에서 2,000 N의 압력으로 진행되었으며 각각의 샘플들은 scanning electron microscope (SEM)을 통해 확인된 후, 접합 강도 테스트를 진행하였다. 추가로 bonding 층의 In 및 Sn 분포를 확인하기 위하여 Si wafer 위에 Ti/In/Sn/Ti를 차례로 증착시킨 뒤 bonding 조건과 같은 온도에서 열처리하고secondary ion mass spectrometry (SIMS) profile 분석을 시행하였다. 결론적으로 본 연구를 통하여 충분히 높은 접합 강도를 갖는 In-Sn eutectic bonding 공정을 $140^{\circ}C$의 낮은 공정온도에서 성공적으로 개발하였다.