Young-Soon Kim

Direct Copper Electroless Deposition on a Tungsten Barrier Layer for Ultralarge Scale Integration

In the present study, copper is deposited directly on tungsten using an electroless solution. Typically, Cu is deposited on a noble metal seed layer by an electroless process. The seed layers are platinum, palladium (Pd),silver, gold, rhodium, or iridium, while Pd is preferred. It has been proposed that copper (Cu) is deposited on tungsten (W) by a different mechanism. This work has implications for the direct plating of Cu/low k barrier layers. The best deposition conditions were found to be a CuSO 4 concentration of 0.0305 mol/L, a solution pH of 11.8, and glyoxylic acid concentration of 0.09 mol/L at 60°C. Under the best conditions for 10 min, the grain shape is spherical, and the surface roughness is ∼11 nm. It is demonstrated that fine-grained, uniform copper film can be obtained for ultralarge scale integrated devices. The thickness of the film was 134 nm for 12 min. The deposition rate was 11.2 nm/min. According to increasing the pH, Cu film is of the Cu 2 O phase and the grain shape of Cu is changed. Adjusting the pH resulted in oriented Cu and without impurity peaks during electroless deposition. The roughness of the Cu films depends greatly on the concentration of glyoxylic acid unlike pH changes. The resulting deposited copper concentration was 97 atom % as measured by Rotherford backscattering. The film of Cu/W has good adhesive strength, because a Cu/W alloy forms during electroless deposition.

Atomic Layer Deposition of Pd on TaN for Cu Electroless Plating

The essential points of this technique are the use of an ultrathin Pd catalyst on TaN by atomic layer deposition (ALD) and ultrasonic vibration in the electroless plating bath. We demonstrated Cu electroless deposition (ELD) on an ALD-Pd passivated TaN barrier layer. The Pd film deposited by ALD was 3 nm thickness on the TaN substrate and had good coverage with low surface roughness. For the Cu ELD process, we used ethylenediamine-tetraacetic acid (EDTA), glyoxylic acid, and additional chemicals such as polyethylene glycol, Re-610 and 2,2dipyridine. The Cu ELD was performed at a temperature of 60-65°C for 30 min. The success of ELD Cu in gap filling a patterned TaN substrate with 130 nm openings and an aspect ratio of three is attributed to the removal of hydrogen gas from the surface by ultrasonic vibration for 1 s after 15 min of deposition in the bath. In this work, we suggest the use of ultrasonic vibration in the Cu electroless plating bath without a chemical inhibitor.

Preparation of Y1−xYbxBa2Cu3O7−y superconducting films by chemical vapor deposition

High Tc Y1−xYbxBa2Cu3O7−y films were prepared on SrTiO3(100) substrates by chemical vapor deposition method. Yb1Ba2Cu3O7−y films were obtained at higher oxygen partial pressure compared with Y1Ba2Cu3O7−y films at the same deposition temperature. Tc,o (R=0) decreased about 1.5 K when Y was fully substituted with Yb. The caxis lattice parameter of Y1−xYbxBa2Cu3O7−y films also decreased as the amount of Yb(x) increased.

Comparative study of diamond films grown on silicon substrate using microwave plasma chemical vapor deposition and hot-filament chemical vapor deposition technique

Diamond films on the p-type Si(111) and p-type(100) substrates were prepared by microwave plasma chemical vapor deposition (MWCVD) and hot-filament chemical vapor deposition (HFCVD) by using a mixture of methane CH4 and hydrogen H2 as gas feed. The structure and composition of the films have been investigated by X-ray Diffraction, Raman Spectroscopy and Scanning Electron Microscopy methods. A high quality diamond crystalline structure of the obtained films by using HFCVD method was confirmed by clear XRD-pattern. SEM images show that the prepared films are poly crystalline diamond films consisting of diamond single crystallites (111)-orientation perpendicular to the substrate. Diamond films grown on silicon substrates by using HFCVD show good quality diamond and fewer non-diamond components.

Preparation and Characterization of Magnesium Diboride Superconductor by Melting Process

The recent discovery of the binary metallic magnesium diboride (MgB2) superconductor having a remarkably high transition temperature (Tc) of 39 K has generated excitement among the scientist worldwide and gained great scientific interest. Various methods (viz. PLD, solid state reaction etc.) are reported for the preparation of this material in different forms (bulk, wire, thin film) which require a high processing temperature (750 to 950 °C). In this paper, we report a new method of processing MgB2 superconductor that meets all the properties when compared with other processes. In this work, polycrystalline MgB2 was prepared by using melting process at low temperature (660 °C). The stoichiometric mixture of Mg-rich and B-rich was pressed into pellets and piled to form Mg-rich/B-rich/Mg-rich system. The piled specimen was then heated up to 800 °C for four hrs with a heating rate of 5 °C/min. The sample was then kept at 660 °C for 12 hrs after cooling from 800 to 660 °C in 30 min. For comparison, the sample was also sintered at 660 °C for 24 hrs. The samples were characterized by using XRD, EDX, SEM, four probe AC methods and magnetization measurements using SQUID magnetometer. The critical temperature was found to be 39 K which shifts towards lower temperature with increasing applied field (0 to 9T). The critical current density, according to Bean’s critical state model was estimated and found to be ∼105 A/cm2, which is comparable to the reported data.