Mitsuo Koike

Analysis of resistance behavior in Ti- and Ni-salicided polysilicon films

The sheet resistance of TiSi/sub 2/-polycide (TiSi/sub 2/-polysilicon) lines increases as they are made narrower. This phenomenon has been investigated in detail. It is found that the relationship between sheet resistance and line width (W) is characterized by three distinct regions according to the value of W. The abrupt increase in sheet resistance observed in the region W/spl les/0.2 /spl mu/m cannot be explained in terms of the phase transition from C54 to C49, which we show to be the cause of the rising resistance at larger W. By adopting a new test pattern for sheet resistance measurements and using it in combination with TEM and EDX analysis we conclude that the cause of this abrupt increase is the presence of large inter-grain layers where silicide is very sparse. On the contrary, NiSi films have no such inter-grain layers, and good resistance values can be obtained even with 0.1 /spl mu/m lines. The NiSi process appears to be a suitable candidate to replace TiSi/sub 2/ in future deep-sub-micron high-speed CMOS devices. >

Effects of nitrogen in HfSiON gate dielectric on the electrical and thermal characteristics

The effects of the nitrogen in the HfSiON gate dielectric on the electrical and thermal properties of the dielectric were investigated. It is clearly demonstrated that nitrogen enhances the dielectric constant of silicates. High dielectric constants of the HfSiON are maintained and boron penetration is substantially suppressed in the HfSiON during high temperature annealing. These properties are ascribed to the homogeneity of the bond structure in the film containing nitrogen through high temperature annealing.

Electrical properties and microstructures of Pt/Ba0.5Sr0.5TiO3/SrRuO3 capacitors

Thin film polycrystalline Ba0.5Sr0.5TiO3 capacitors employing conductive perovskite oxide SrRuO3 as a bottom electrode were fabricated on Si substrates by rf-magnetron sputtering. Dielectric constants of these capacitors were observed to be 206, 214, and 146 for 60, 40, and 20 nm Ba0.5Sr0.5TiO3 (BSTO) thicknesses, respectively. The lowest SiO2 equivalent thickness of 0.54 nm was obtained for 20-nm-thick BSTO capacitors; their leakage current density was less than 1×10−7 A/cm2 for ±1.8 V bias. The cross-sectional transmission electron microscope observation revealed that BSTO and SrRuO3 (SRO) formed continuous columnar grains and showed epitaxial growth at the interface of BSTO/SRO within each column; this microstructure of the capacitors was tentatively designated “local epitaxial film.”

Depth resolution improvement in secondary ion mass spectrometry analysis using metal cluster complex ion bombardment

Secondary ion mass spectrometry analyses were carried out using a metal cluster complex ion of Ir4(CO)7+ as a primary ion beam. Depth resolution was evaluated as a function of primary ion species, energy, and incident angle. The depth resolution obtained using cluster ion bombardment was considerably better than that obtained by oxygen ion bombardment under the same experimental condition due to reduction of atomic mixing in the depth. The authors obtained a depth resolution of ∼1nm under 5keV, 45° condition. Depth resolution was degraded by ion-bombardment-induced surface roughness at 5keV with higher incident angles.

Thermally stable ultra-thin nitrogen incorporated ZrO/sub 2/ gate dielectric prepared by low temperature oxidation of ZrN

Ultra-thin nitrogen incorporated ZrO/sub 2/ (ZrON) film is successfully prepared by low temperature oxidation of ZrN. Capacitance equivalent thickness (CET) of 15 /spl Aring/ with Jg=1 mA/cm/sup 2/@ Vg=-1 V is demonstrated. There is no increase in CET up to 1000/spl deg/C. Silicide formation at poly-Si/ZrO/sub 2//Si stack at high temperature annealing is also inhibited. In addition, the boron penetration from p+ poly-Si to Si substrate is substantially suppressed.

Effect of Hf-N bond on properties of thermally stable amorphous HfSiON and applicability of this material to sub-50nm technology node LSIs

The electric and structural properties of hafnium silicon oxynitride (HfSiON) with high Hf/(Hf+Si) (35/spl sim/100%) were investigated, focusing on the role of Hf-N bonds inside the material. The results show that the existence of Hf-N bonds in the films result in a high dielectric constant and high thermal stability. Using ultra-thin HfSiON with high Hf and high N concentrations, thermally stable amorphous high-k stacks with EOT of 0.6 nm and with 10/sup -5/ times Jg reduction, relative to that in SiO/sub 2/ was obtained.

Effect of Film Composition of Nitrogen Incorporated Hafnium Aluminate (HfAlON) Gate Dielectric on Structural Transformation and Electrical Properties through High-Temperature Annealing

We investigated the effect of nitrogen on the structural and electrical properties of nitrogen incorporated hafnium aluminate (HfAlON) gate dielectrics through high-temperature annealing. It was found that 30 at.% nitrogen substantially suppresses HfO2 segregation after the annealing. An amorphous HfAlON film with a k-value of 17 after 1000°C appeared at the composition of Hf ratio = 35% and N = 32 at.%, accompanied by improved boron blocking from the p+poly-Si gate. At an Hf ratio higher than 47%, however, cubic-HfN crystals emerged from HfAlON after the annealing. The cubic-HfN significantly increased gate leakage current through the film. We conclude that the applicability of HfAlON gate dielectric to the further scaling down of LSIs is inherently limited by metallic HfN formation at high process temperatures.

Degradation mechanism of HfSiON gate insulator and effect of nitrogen composition on the statistical distribution of the breakdown

We intensively investigate the degradation mechanism of HfSiON during constant voltage stress. It is found that unstable trap-sites in the HfSiON play a significant role in the conduction path creation. We also find Weibull slopes increase and the statistical fluctuation of post-breakdown conductance is suppressed with increasing nitrogen concentration of the film, probably due to the improved homogeneity of the HfSiON microstructure.

Precipitation of Boron in Highly Boron-Doped Silicon

The clustering of boron in highly boron-doped silicon and its influence on electrical deactivation are reported. Highly boron-doped crystalline silicon was fabricated as a starting material by solid phase epitaxy of boron-doped amorphous silicon films. Boron can be supersaturated in the crystallized samples annealed at a low temperature of about 600°C. A lot of precipitates, containing clustered boron, were observed in the samples annealed at high temperatures of about 1000°C. The chemical states and the atomic configuration of boron in samples annealed at various temperatures corresponded to the electrical deactivation of boron.

Insight into the S/D engineering by high-resolution imaging and precise probing of 2D-carrier profiles with scanning spreading resistance microscopy

For the first time, high-resolution carrier imaging has been carried out on (110)/(100) pFETs and nFETs with scanning spreading resistance microscopy (SSRM). The S/D of (110) pFETs shows less lateral distribution than that of (100), strongly indicating 2D-channeling effect of boron I/I. Direct evidence has been shown that As out-diffusion under NiSi made conductive paths that degrade junction leakage on (110) nFETs. The Si:C influences on S/D profiles are also directly observed. We also succeeded in a full-FIB sample-making for the first time, showing the high potential of SSRM technology for further scaled devices.