Effect of molybdenum electrode annealing on the interface properties between metal and pentacene

Contact resistance between molybdenum (Mo) electrode and pentacene was studied with transmission line method (TLM). The Mo electrodes were annealed at 200 °C, 400 °C, 600 °C and 800 °C for 1 h and pentacene layer of 300 Å thickness was vacuum deposited on patterned Mo to form Mo–pentacene contact. Current–voltage measurement for Mo–pentacene contact showed linear relationship and it was confirmed that ohmic contact was formed. XRD and AFM measurements showed that Mo could be crystallized at annealing temperatures above 600 °C. 800 °C annealed Mo showed larger grains and work function was increased from 4.60 eV to 4.80 eV due to the decrease in defect density. The contact resistance was reduced down to 11.2 MΩ cm from 37.8 MΩ cm of as-deposited Mo. Also the pentacene film deposited on annealed Mo was denser with better crystallinity. Bottom contact organic field-effect transistor made with 800 °C annealed Mo showed better performance than as deposited Mo.     

Oxide precipitates in annealed nitrogen-doped 300 mm CZ-SI

The lateral distribution of oxide precipitates as well as the denuded zone were investigated in a set of 300 mm CZ silicon wafers containing different amounts of nitrogen. Two light scattering methods, infrared light scattering tomography (IR-LST) as well as scanning infrared microscopy (SIRM) were used to characterize the precipitation density and the spatial distribution. The obtained results show that under certain heat treatments a high density of oxide precipitates, more than 1×10⁹ cm⁻³, can be achieved in the depth of 300 mm wafers. With increasing nitrogen content the radial distribution of precipitates becomes more uniform. A 10–60 μm wide precipitation-free denuded zone was observed. A comparison between IR-LST and SIRM results was performed indicating the dominance of relatively small precipitates.     

Temperature dependent resistivity study on zinc oxide and the role of defects

The temperature dependent (30–550 °C) resistivity of zinc oxide (ZnO) has been studied by the standard four probe resistivity method. The room-temperature resistivity of the sample is measured as 0.75 M Ωm. Resistivity versus temperature plot of the sample shows normal NTCR (negative temperature coefficient of resistance) behavior up to 300 °C. However, a crossover from NTCR to a PTCR (positive temperature coefficient of resistance) behavior is observed at ～300 °C. The origin of the PTCR behavior is explained with the defects present in the ZnO annealed up to 550 °C. Temperature dependent S-parameter (positron annihilation line-shape parameter) indicates the formation of oxygen vacancy like defects in this temperature region. At the PTCR region, the activation energy for the electron conduction is calculated ～2.6 eV. This value is very close to the theoretically predicted defect level energy of 2.0 eV for oxygen vacancies present in ZnO.     

New challenges for 300 mm Si technology: 3D interconnects at wafer scale by aligned wafer bonding

A new alignment technique is proposed for wafer level 3D interconnects fabrication: the SmartView^®. This original procedure is using alignment keys located in the bonding interface and enables an alignment precision of 1 μm. The method uses two top–bottom microscope pairs for observing the alignment keys and a minimal Z-axis travel during wafer alignment procedure. After the alignment procedure, the wafers are secured for subsequent wafer bonding procedures. The alignment process is presented in detail, as well as the integration of such an equipment in high production systems able to run wafers up to 300 mm diameter.     

A MEMS-based pneumatic micro-conveyor for planar micromanipulation

This paper present a two dimensional pneumatic actuator based on silicon MEMS technology for objects micro-manipulation using tilted air jets. The device is composed of three layers stacked together, two micro-machined silicon wafers and a Pyrex glass wafer. The system is composed of a set of micro-conveyors in about 9 mm × 9 mm area. Each micro-conveyor has four nozzles and can generate tilted air-jets which allow four conveyance directions. An experiment of the conveyance of a silicon chip of 3 mm diameter and weighing approximately 2 mg was performed with pulsed air flow.     

CMOS temperature sensor with ring oscillator for mobile DRAM self-refresh control

This paper presents novel low-cost CMOS temperature sensor for controlling the self-refresh period of a mobile DRAM. In the proposed temperature sensor, the temperature dependency of poly resistance is used to generate a temperature-dependent bias current, and a ring oscillator driven by this bias current is employed to obtain the digital code pertaining to on-chip temperature. This method is highly area-efficient, simple and easy for IC implementation as compared to traditional temperature sensors based on bandgap reference. The proposed CMOS temperature sensor was fabricated with an 80 nm 3-metal DRAM process, which occupies extremely small silicon area of only about 0.016 mm² with under 1 μW power consumption for providing 0.7 °C effective resolution at 1 sample/s processing rate. This result indicates that as much as 73% area reduction was obtained with improved resolution as compared to the conventional temperature sensor in mobile DRAM.     

Thermal stability of back side metallization multilayer for power device application

Metallization multilayers on the back side of a power device were focused in this study. Si wafers coated with high melting point metals were exposed at 300 °C for 300 h to investigate diffusion condition of the metallization layer. We developed and examined the thermal stability of die bonding material (Au paste) including sub–micrometer–sized Au particles. Auger electron spectroscopy was applied to observe the atomic composition of the multilayers in depth direction after the high temperature aging. Surface morphology was observed using optical microscope and scanning electron microscope. While atomic composition on Ti/Au changed drastically after the high temperature aging, other multilayers maintained their metallization composition. However, the surface morphology was slightly changed on Ti/Ru/Au, W/Au, and Ta/Au. Bond strength on the Ti/Pt/Au kept over 40 MPa with unified bonding layer after exposing at 300 °C for 1000 h.     

Structural characterization of ultra-thin (0 0 1) silicon films bonded onto (0 0 1) silicon wafers:: a transmission electron microscopy study

Ultra-thin (0 0 1) silicon films (thickness less than 25 nm) directly bonded onto (0 0 1) silicon wafers have been investigated by transmission electron microscopy. Twist interfacial dislocations accommodate the twist between the two crystals, whereas tilt interfacial dislocations accommodate the tilt resulting from the residual vicinality of the initial surfaces. In low-twist angle grain boundaries, twist interfacial dislocations are dissociated and no precipitates are detected. In high-twist angle grain boundaries, there is no dissociation and a high density of silicon oxide precipitates is observed at the interface. Tilt interfacial dislocations are pinned by these precipitates, they are more mobile than precipitates. Without precipitates, their lines are straighter than those with precipitates, and this is especially when the bonded wafers are annealed at a high temperature. When no precipitates are present, tilt interfacial dislocations are associated by pairs, and we demonstrate that each tilt interfacial dislocations introduce a diatomic interfacial step at the interface.     

Behavior of chemically deposited PbS thin films subjected to two different routes of post deposition annealing

Lead sulfide (PbS) thin films were prepared on soda lime glass substrates at room temperature by Chemical Bath Deposition (CBD) technique. This paper reports a comparative study of characteristic properties of as-prepared PbS thin films after thermal treatment through two different routes. Studies were carried out for as-prepared as well as rapidly and gradually annealed samples at 100, 200 and 300 °C. The characterizations of the films were carried out using X-ray diffraction, scanning electron microscopy and optical measurement techniques. The structural studies confirmed the polycrystalline nature and the cubic structure of the films. As-deposited films partly transformed to Pb₂O₃ when gradually annealed to 300 °C. The presence of nano crystallites was revealed by structural and optical absorption measurements. The values of average crystallite size were found to be in the range 18–20 nm. The variation in the microstructure, thickness, grain size, micro strain and optical band gap on two types of annealing were compared and analyzed. Data showed that post deposition parameters and thermal treatment strongly influence the optical properties of PbS films. Optical band gap of the film gets modified remarkably on annealing. Direct band gap energy values for rapidly and gradually annealed samples varied in the range of 1.68–2.01 eV and 1.68–2.12 eV respectively. Thus we were succeeded in tailoring direct band gap energies by post deposition annealing method.     

Mechanical properties of nitrogen-doped CZ silicon crystals

We investigated the effect of the nitrogen doping level on plastic properties of 300 mm silicon material in the temperature range between 650°C and 1000°C. Undoped, low N-doped, and high N-doped materials were examined. The dependence of the upper and lower yield point and the size dependence of indentation related dislocation rosettes on temperature were obtained.An increase in the nitrogen concentration leads to enhanced upper and lower yield points. Possible mechanisms of interaction of dislocations with impurities resulting in hardening of silicon single crystals are discussed. Finite element method (FEM) calculated data of bearing stress observed in 300 mm Si wafers annealed in a vertical furnace are compared with measured upper yield point values. At high nitrogen concentration the tolerable process temperatures, where plastic flow of Si wafers under load can be avoided, are significantly increased.     

Influence of thermal annealing on electrical and optical properties of indium tin oxide thin films

Transparent conducting indium tin oxide (ITO) thin films with the thickness of 300 nm were deposited on quartz substrates via electron beam evaporation, and five of them post-annealed in air atmosphere for 10 min at five selected temperature points from 200 °C to 600 °C, respectively. An UV–vis spectrophotometer and Hall measurement system were adopted to characterize the ITO thin films. Influence of thermal annealing in air atmosphere on electrical and optical properties was investigated in detail. The sheet resistance reached the minimum of 6.67 Ω/sq after annealed at 300 °C. It increased dramatically at even higher annealing temperature. The mean transmittance over the range from 400 nm to 800 nm reached the maximum of 89.03% after annealed at 400 °C, and the figure of merit reached the maximum of 17.79 (Unit: 10⁻³ Ω⁻¹) under the same annealing condition. With the annealing temperature increased from 400 °C to 600 °C, the variations of transmittance were negligible, but the figure of merit decreased significantly due to the deterioration of electrical conductivity. With increasing the annealing temperature, the absorption edge shifted towards longer wavelength. It could be explained on the basis of Burstein–Moss shift. The values of optical band gap varied in the range of 3.866–4.392 eV.     

105 nm Gate length pMOSFETs with high-K and metal gate fabricated in a Si process line on 200 mm GeOI wafers

We report on the fabrication and electrical characterization of deep sub-micron (gate length down to 105 nm) GeOI pMOSFETs. The Ge layer obtained by hetero-epitaxy on Si wafers has been transferred using the Smart Cut^TM process to fabricate 200 mm GeOI wafers with Ge thickness down to 60–80 nm. A full Si MOS compatible pMOSFET process was implemented with HfO₂/TiN gate stack. The electrical characterization of the fabricated devices and the systematic analysis of the measured performances (I_ON, I_OFF, transconductance, low field mobility, S, DIBL) demonstrate the potential of pMOSFET on GeOI for advanced technological nodes. The dependence of these parameters have been analyzed with respect to the gate length, showing very good transport properties (μ_h ～ 250 cm²/V/s, I_ON = 436 μA/μm for L_G = 105 nm), and OFF current densities comparable or better than those reported in the literature.     

Low temperature molten salt synthesis of YAG: Ce spherical powder and its thermally stable luminescent properties after post-annealing treatment

Spherical YAG: Ce particles were successfully synthesized at 350 °C by the molten-salt method. The effect of temperature and amount of salt on the crystallization and particle size of YAG: Ce were investigated thoroughly. The results demonstrated that the powders prepared at 350 °C in salt to reactant ratio 2:1 were pure YAG: Ce phase with 200–300 nm in particle size. The as-synthesized phosphors were later post annealed at 1200 °C in O₂, air and N₂, respectively. The results showed that the emission intensity of YAG: Ce sensitively depended on the post-treated atmosphere and the phosphor annealed in N₂ showed the highest emission intensities and a good thermal stability.     

Effect of annealing on photoluminescence of passivated porous silicon

Photoluminescence (PL) of annealed porous silicon (PS) without and with nitrogen passivation has been investigated. The un-nitridated PS emits intense blue and green light, while that with passivation, emits only blue light and its intensity increases obviously. It is found that the PL intensity of the nitrified PS decreases with increasing temperature from 300 °C to 700 °C, but increases drastically after annealing at 800 °C and 900 °C, which might be due to the formation of Si–N bonds that passivates the non-radiative centers (Si dangling bonds) on the surface of PS samples. However, the intensity of the un-nitridated PS decreases continuously with increasing temperature from 300 °C to 900 °C, which might be due to desorption of hydrogen.     

Effect of thermal annealing on the structural,morphological and super capacitor behavior of MnO2 nanocrystals

Precursors of nanosized manganese dioxide were prepared through a chemical precipitation method. The synthesized precursors of MnO₂ were subjected to thermo gravimetric analysis. The thermal analysis results showed the MnO₂ formation at 500 °C. To study the effect of thermal treatments on the capacitive behavior of MnO₂, the precursors were annealed at different temperatures (300, 400 and 500 °C). The annealed products were characterized by X-ray diffraction (XRD), Fourier transforms infra-red spectroscopy (FT-IR) and cyclic Voltammetry (CV) analysis. Among the annealed products, MnO₂ annealed at 400 °C exhibits high specific capacitance. The morphologies of the products annealed at 400 and 500 °C were analyzed by a scanning electron microscope (SEM) and atomic force microscopy (AFM). The sample annealed at 500 °C shows spherical morphology with the inclusion of nanorods. To confirm the morphology of the annealed products, field emission transmission electron microscope (FE-TEM) measurements were carried out.     

Ultraviolet-assisted annealing for low-temperature solution-processed p-type gallium tin oxide (GTO) transparent semiconductor thin films

Solution-processed p-type gallium tin oxide (GTO) transparent semiconductor thin films were prepared at a low temperature of 300 °C using ultraviolet (UV)-assisted annealing instead of conventional high-temperature annealing (> 500 °C). We report the effects of UV irradiation time on the structural, optical, and electrical properties of sol-gel derived GTO thin films and a comparison study of the physical properties of UV-assisted annealed (UVA) and conventional thermally annealed (CTA) GTO thin films. The Ga doping content was fixed at 15 at% in the precursor solution ([Ga]/[Sn]+[Ga] = 15%). After a spin-coating and preheating procedure was performed two times, the dried sol-gel films were heated on a hotplate at 300 °C under UV light irradiation for 1–4 h. Each UVA GTO thin film had a dense microstructure and flat free surface and exhibited an average optical transmittance approaching 85.0%. The level of crystallinity, crystallite size, and hole concentration density of the GTO thin films increased with increasing UV irradiation time. In this study, the UVA 4 h thin film samples exhibited the highest hole concentration (9.87 × 10¹⁷ cm⁻³) and the lowest resistivity (1.8 Ω cm) and had a hole mobility of 5.1 cm²/Vs.     

The correlation of γ-irradiation,particle size and their effects on physical properties of AgInSe2 nanostructure thin films

In this work the effect of γ-irradiation on the optical and electrical properties of near stoichiometric AgInSe₂ nanostructure thin films have been characterized. The XRD pattern of ingot AgInSe₂ powder prepared by solid state reaction showed tetragonal polycrystalline single-phase structure. The thin films of thickness 75 nm were prepared by inert gas condensation (IGC) technique at using constant Ar flow and substrate temperature of 300 K.Thin films were exposed to annealing process at 473 K for 2 h in vacuum of 10⁻² Torr. The amorphous and tetragonal nanocrystalline structures were detected for as-deposited and annealed films respectively by grazing incident in-plane X-ray diffraction (GIIXD) technique. The structure and average particle size of annealed irradiated films by different γ-doses from 0 to 4 Mrad were determined using high resolution transmission electron microscope (HRTEM). Optical transmission, reflection and absorption spectra were studied for both annealed unirradiated and irradiated films. Two optical transitions for each annealed unirradiated and film exposed to γ-irradiation doses from 0 to 4 Mrad were observed. The evaluated E_g1 due to 1^st transition have decreased from 1.52 to 1.44 eV and E_g2 due to 2^nd transition have decreased from 2.83 to 2.30 eV as the particle size increased from 7.3 to 9.5 nm by raising the irradiation dose up to 1 Mrad. The behavior of d.c. electrical conductivity with temperature that measured under vacuum was examined for all films under investigation. The evaluated activation energies due to irradiation doses are ranging from 0.58 to 0.68 eV.     

Study on critical dimension of printable phase defects using an EUV microscope

We constructed an extreme ultraviolet microscopy (EUVM) system for actinic mask inspection that consists of Schwarzschild optics and an X-ray zooming tube. This system was used to inspect finished extreme ultraviolet lithography (EUVL) masks and Mo/Si glass substrates. A clear EUVM image of a 300-nm-wide pattern on a 6025 glass mask was obtained. The resolution was estimated to be 50 nm or less from this pattern. Programmed phase defects on the glass substrate were also used for inspection. The EUV microscope was able to resolve a programmed pit defect with a width of 40 nm and a depth of 10 nm and also one with a width of 70 nm and a depth of 2 nm. However, a 75-nm-wide 1.5-nm-deep pit defect was not resolved. Thus, in this study, one critical dimension of a pit defect was estimated to be a depth of 2 nm.     

Annealing temperature dependent structural and optical properties of electrodeposited CdSe thin films

Cadmium selenide films were synthesized using simple electrodeposition method on indium tin oxide coated glass substrates. The synthesized films were post annealed at 200 °C, 300 °C and 400 °C. X-ray diffraction of the films showed the hexagonal structure with crystallite size <3 nm for as deposited films and 3–25 nm for annealed films. The surface morphology of films using field emission scanning electron microscopy showed granular surface. The high resolution transmission electron microscopy of a crystallite of the film revealed lattice fringes which measured lattice spacing of 3.13 Å corresponding to (002) plane, indicating the lattice contraction effect, due to small size of CdSe nanocrystallite. The calculation of optical band gap using UV–visible absorption spectrum showed strong red-shift with increase in crystallite size, indicating to the charge confinement in CdSe nanocrystallite.     

Systematic study of the influence of the Czochralski hot zone design on the point defect distribution with respect to a “perfect” crystal

In the present paper the influence of the hot zone design on the quality and yield of silicon crystals with 100 mm and 300 mm diameters is numerically studied using the software package CrysVUn. Based on the numerical results solutions for the design of the heat shields are identified which allow nominally to grow the crystals at higher growth velocities, and at the same time with improved quality in terms of smaller point defect concentrations and improved radial uniformity, compared to conventional hot zones.