Studies on formation of carborane film prepared by using a deuterium glow discharge method.

Carborane powders (C2B10H12) were deposited on silicon substrates and the physical properties of the films were investigated as functions of the distance of the sample from the electrode, the carborane mass, and the plasma-pulse. To obtain the optimum thickness of the films, three silicon substrates were positioned at 6.5, 16.5, and 36.5 cm from the electrode, and the thickness of the samples was analyzed by using XRD, TEM, and SEM. For the deposition, the carborane powder was warmed to 80 degrees C in 10 minutes and was applied a DC-power pulse of 900 W (150 volts, 6 amps) for 2 hours. The mass of carborane and the on-time sequence were varied during the deposition. The combined results of XRD and TEM studies revealed that the structure of the deposited film is an amorphous phase. A careful analysis of the SEM images show that the thickness of the carborane films increased as increasing the mass of the flown carborane while it remained constant when a plasma-pulse time was varied. The thickest film of 353 A was achieved from the samples placed closest to the carborane inlet and the thickness became thinner as farther from the source suggesting that the density of the evaporated carborane powder in a chamber decreased as increasing the distance of the sample from the carborane inlet.

The effect of thermal annealing on pentacene thin film transistor with micro contact printing.

We used micro contact printing (micro-CP) to fabricate inverted coplanar pentacene thin film transistors (TFTs) with 1-microm channels. The patterning of micro-scale source/drain electrodes without etch process was successfully achieved using Polydimethylsiloxane (PDMS) elastomer stamp. We used the Ag nano particle ink as an electrode material, and the sheet resistance and surface roughness of the Ag electrodes were effectively reduced with the 2-step thermal annealing on a hotplate, which improved the mobility, the on-off ratio, and the subthreshold slope (SS) of the pentacene TFTs. In addition, the device annealing on a hotplate in a N2 atmosphere for 30 sec can enhance the off-current and the mobility properties of OTFTs without damaging the pentacene thin films and increase the adhesion between pentacene and dielectric layer (SiO2), which was investigated with the pentacene films phase change of the XRD spectrum after device annealing.

Novel palladium germanide schottky contact for high performance schottky barrier ge MOSFETs and characterization of its leakage current mechanism.

The leakage current mechanism of Palladium (Pd) germanide Schottky contact on n-type Ge-on-Si substrate is analyzed in depth. The electric field dependent analysis shows that the dominant leakage current mechanism is the Poole-Frenkel emission due to the existence of deep level traps in the depletion region of the Pd germanide/n-type Ge Schottky diode. The analysis of the dependence of leakage current on temperature also shows that the Poole-Frenkel emission and generation current are the dominant components below 100 degrees C and that the Schottky emission related to thermionic emission of majority carriers over a potential barrier is the main cause of this dominance at high temperature region.

Formation of metal and dielectric liners using a solution process for deep trench capacitors.

We demonstrated the feasibility of metal and dielectric liners using a solution process for deep trench capacitor application. The deep Si trench via with size of 10.3 microm and depth of 71 microm were fabricated by Bosch process in deep reactive ion etch (DRIE) system. The aspect ratio was about 7. Then, nano-Ag ink and poly(4-vinylphenol) (PVPh) were used to form metal and dielectric liners, respectively. The thicknesses of the Ag and PVPh liners were about 144 and 830 nm, respectively. When the curing temperature of Ag film increased from 120 to 150 degrees C, the sheet resistance decreased rapidly from 2.47 to 0.72 Omega/sq and then slightly decreased to 0.6 Omega/sq with further increasing the curing temperature beyond 150 degrees C. The proposed liner formation method using solution process is a simple and cost effective process for the high capacity of deep trench capacitor.

Magnetic properties of hydrogen-included TiZrNiPd quasicrystals.

Quasicrystals prepared by rapid quenching of Pd-added TiZrNi ingots were hydrogenated, and effects of hydrogen for magnetic properties were compared with the unhydrogenated ones under magnetic fields from -10000 to 10000 Oe. The magnetization values obtained from vibrating sample magnetometer (VSM) were analyzed with the combination of powder X-ray diffraction (XRD) data. While its contribution is larger than that of Pd, hydrogen decreases the magnetic moments of both Pd-doped and undoped quasicrystals. As increasing the amount of absorbed hydrogen which is represented by H/M (hydrogen to host metal atom ratio) values from 0 to 1.19, the magnetization values of Ti53Zr27Ni20 quasicrystals measured at 10000 Oe significantly decreased from 0.301 to 0.212 emu/g. A careful analysis of XRD data demonstrated that the reduced interactions of magnetic dipole moments between Ni atoms, as the product of the expansion of the quasilattice constants after hydrogenation, are responsible for the decreased magnetization values in hydrogenated TiZrNiPd quasicrystal samples.

Thermal endurance and microstructural evolution of PtGe for high-performance nano-scale Ge-on-Si MOSFETS.

The thermal endurance and microstructural evolution of Ni-germanide (NiGe) and Pt-germanide (PtGe) on a Ge-on-Si substrate were compared in this paper. In case of the Ni/TiN structure, the sheet resistance exhibited a stable RTP window of 350 to 600 degrees C, while that of the Pt/TiN structure showed more stable characteristics up to 700 degrees C. Furthermore, after post-germanidation annealing, NiGe exhibited the formation of islands due to the severe agglomeration as well as a prominent grain boundary grooving, which accounts for the sharp increase of the sheet resistance from 550 degrees C, whereas PtGe showed a smooth and continuous surface morphological stability without signs of agglomeration even up to 600 degrees C. Although about two times higher resistivity (31.5 micro ohms-cm) and greater Ge consumption (3.27 nm) were shown, PtGe showed more stable sheet resistance, better surface and interface morphological stability and a wider thermal processing window above 100 degrees C than NiGe. Therefore, PtGe is more suitable for the germanided shallow source/drain for nano-scale Ge MOSFETs than NiGe.

Improvement of heavy dopant doped Ni-silicide using ytterbium interlayer for nano-scale MOSFETS with an ultra shallow junction.

In this paper, a novel Ni silicide with Yb interlayer (Yb/Ni/TiN) on a boron cluster (B18H22) implanted source/drain junction is proposed for the first time, and its thermal stability characteristics are analyzed in depth. The proposed Ni-silicide exhibits a wider RTP temperature window for uniform sheet resistance, surface roughness and better thermal stability than the conventional structure (Ni/TiN). In addition, the cross-sectional profile of the proposed Ni-silicide showed less agglomeration despite the high temperature post-silicidation annealing, and it can be said that the proposed structure was little dependence on the temperature post-silicidation annealing. The improvement of Ni silicide properties is analyzed and found to be due to the formation of the rare earth metal--NiSi (YbNi2Si2), whose peaks were confirmed by XRD. The junction leakage current of the p + -n junction with Yb/Ni/TiN and B18H22 implantation is smaller than that with Ni/TiN by almost one order of magnitude as well as improving the thermal stability of ultra shallow junction.

Study of surface-modified PVP gate dielectric in organic thin film transistors with the nano-particle silver ink source/drain electrode.

We have fabricated the flexible pentacene based organic thin film transistors (OTFTs) with formulated poly[4-vinylphenol] (PVP) gate dielectrics treated by CF4/O2 plasma on poly[ethersulfones] (PES) substrate. The solution of gate dielectrics is made by adding methylated poly[melamine-co-formaldehyde] (MMF) to PVP. The PVP gate dielectric layer was cross linked at 90 degrees under UV ozone exposure. Source/drain electrodes are formed by micro contact printing (MCP) method using nano particle silver ink for the purposes of low cost and high throughput. The optimized OTFT shows the device performance with field effect mobility of the 0.88 cm2/V s, subthreshold slope of 2.2 V/decade, and on/off current ratios of 1.8 x 10(-6) at -40 V gate bias. We found that hydrophobic PVP gate dielectric surface can influence on the initial film morphologies of pentacene making dense, which is more important for high performance OTFTs than large grain size. Moreover, hydrophobic gate dielelctric surface reduces voids and -OH groups that interrupt the carrier transport in OTFTs.

Maskless laser direct patterning of PEDOT/PSS layer for soluble process organic thin film transistor.

In this work, we have fabricated TIPS-pentacene TFTs with conductive polymer (3,4-ethylenedioxythiophene):poly(4-stylenesulfonate) (PEDOT:PSS) source/drain electrodes which is patterned by maskless laser direct patterning (LDP). The 5-microm resolution of source and drain patterns with PEDOT:PSS were clearly defined. Furthermore, the OTFTs with 10-microm channel length were successfully achieved by exposing the focused Neodymium:Yttrium Aluminum Garnet (Nd:YAG) laser beam onto the spin-coated PEDOT:PSS films and developing with deionized water. The electrical performance of the TIPS-pentacene TFTs with PEDOT:PSS source/drain electrodes were improved with decrease of the sheet resistance of PEDOT:PSS films when the PEDOT:PSS films were annealed at the temperature above 200 degrees C.

Sub-50 nm template fabrications for nanoimprint lithography using hydrogen silsesquioxane and silicon nitride.

The sub-50 nm templates are successfully fabricated using hydrogen silsesquioxane (HSQ) and silicon nitride on silicon substrate. The HSQ template is directly patterned by e-beam direct writing. The cured HSQ pattern is used for the template of nanoimprint process. The silicon nitride template is reactively ion etched by ZEP resist mask pattern which is prepared by e-beam direct writing using ZEP resist. The line widths of HSQ templates and ZEP patterns after developments are between 22-30 nm and 24-30 nm, respectively. The line width of silicon nitride templates without performing descum is same as that of the ZEP pattern but shows a rough surface. When plasma descum was performed before RIE, the line width of silicon nitride templates increased from 27 nm to 35 nm and has a clean surface. The HSQ template fabrication results in this study will be promise for sub-nm imprint process.