An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

Semiconductor device, and manufacturing method thereof

When mirror-polished, flat, and clean wafers of almost any material are brought into contact at room temperature, they are locally attracted to each other by van der Waals forces and adhere or bond. This phenomenon is referred to as wafer bonding. The most prominent applications of wafer bonding are silicon-on-insulator (SOI) devices, silicon-based sensors and actuators, as well as optical devices. The basics of wafer-bonding technology are described, including microcleanroom approaches, prevention of interface bubbles, bonding of III-V compounds, low-temperature bonding, ultra-high vacuum bonding, thinning methods such as smart-cut procedures, and twist wafer bonding for compliant substrates. Wafer bonding allows a new degree of freedom in design and fabrication of material combinations that previously would have been excluded because these material combinations cannot be realized by the conventional approach of epitaxial growth.

Semiconductor wafer bonding

This article presents measurements of piezoelectric coefficients of lead zirconate titanate (PZT) thin films. The normal load method is used to measure the coefficients for PZT films with various compositions prepared by the sol‐gel technique or by organometallic chemical vapor deposition (OMCVD). The as‐deposited OMCVD films have a piezoelectric coefficient of 20–40×10−12 m/V, whereas the unpoled sol‐gel films are not piezoelectric. After poling the thin films having a composition near the morphotropic phase boundary; these values increase to 200×10−12 m/V for OMCVD films and 400×10−12 m/V for sol‐gel films. The difference may arise from an incomplete poling of the OMCVD films.

Measurement of piezoelectric coefficients of ferroelectric thin films

Recent advances in flexible and stretchable electronics (FSE), a technology diverging from the conventional rigid silicon technology, have stimulated fundamental scientific and technological research efforts. FSE aims at enabling disruptive applications such as flexible displays, wearable sensors, printed RFID tags on packaging, electronics on skin/organs, and Internet-of-things as well as possibly reducing the cost of electronic device fabrication. Thus, the key materials components of electronics, the semiconductor, the dielectric, and the conductor as well as the passive (substrate, planarization, passivation, and encapsulation layers) must exhibit electrical performance and mechanical properties compatible with FSE components and products. In this review, we summarize and analyze recent advances in materials concepts as well as in thin-film fabrication techniques for high-k (or high-capacitance) gate dielectrics when integrated with FSE-compatible semiconductors such as organics, metal oxides, quantum...

High- k Gate Dielectrics for Emerging Flexible and Stretchable Electronics

The development of a method for integrating highly efficient energy conversion materials onto stretchable, biocompatible rubbers could yield breakthroughs in implantable or wearable energy harvesting systems. Being electromechanically coupled, piezoelectric crystals represent a particularly interesting subset of smart materials that function as sensors/actuators, bioMEMS devices, and energy converters. Yet, the crystallization of these materials generally requires high temperatures for maximally efficient performance, rendering them incompatible with temperature-sensitive plastics and rubbers. Here, we overcome these limitations by presenting a scalable and parallel process for transferring crystalline piezoelectric nanothick ribbons of lead zirconate titanate from host substrates onto flexible rubbers over macroscopic areas. Fundamental characterization of the ribbons by piezo-force microscopy indicates that their electromechanical energy conversion metrics are among the highest reported on a flexible medium. The excellent performance of the piezo-ribbon assemblies coupled with stretchable, biocompatible rubber may enable a host of exciting avenues in fundamental research and novel applications.

Piezoelectric Ribbons Printed onto Rubber for Flexible Energy Conversion

Highly c‐axis oriented and epitaxial PbTiO3 thin films were grown on MgO single crystals and epitaxial Pt film substrates by the rf‐magnetron sputtering method. The films with a 98% c‐axis orientation rate were obtained under low deposition rate (<20 A/min) and low gas pressure (∼1 Pa) using a PbO‐rich target. Phase transition of the PbTiO3 thin film was studied by high‐temperature x‐ray diffraction. It was found that the c‐axis of the tetragonal phase was parallel to the substrate just below Tc and the c‐axis becomes perpendicular to the substrate with lowering of temperature. These films show high resistivity (∼1010/Ω cm). It was found that significant pyroelectric currents are detected on all specimens without poling treatment. The polarization directions of the films are the same in all specimens. One of these films had a low relative dielectric constant of 97 and a high pyroelectric coefficient of 2.5×10−8 C/cm2 K without poling treatment. These films will be suitable for applications such as pyroelectric infrared detector and piezoelectric transducer.

Preparation of c‐axis oriented PbTiO3 thin films and their crystallographic, dielectric, and pyroelectric properties

Lead zirconate‐titanate (PZT) thin films with tetragonal and rhombohedral structures have been successfully grown with good epitaxy on MgO single crystals and on [100]‐oriented platinum thin films by rf‐magnetron sputtering. The PZT films were obtained by using sputtering targets with compositions of Pb(ZrxTi1−x)O3, where x=0.2–0.8. The tetragonal PZT thin films have a strong [001] orientation, and the rhombohedral ones are (100) oriented. Asymmetric D‐E hysteresis loops were observed on the tetragonal films. Nearly symmetric loops were observed on the rhombohedral films and the rhombohedral loops around the morphotropic phase boundary had slim loops. The tetragonal thin films of x=0.45 have a spontaneous polarization of 45 μC/cm2, a remanent polarization of 40 μC/cm2, and a coercive field of 150 kV/cm. It was found that significant pyroelectric currents are detected on both [001]‐oriented tetragonal and (100)‐oriented rhombohedral PZT films even without a poling treatment, and the direction is the same i...

Preparation of epitaxial Pb(ZrxTi1−x)O3 thin films and their crystallographic, pyroelectric, and ferroelectric properties

Using an rf‐magnetron sputtering method, highly c‐axis‐oriented La‐modified PbTiO3 (PLT) thin films with compositions of Pb1−xLaxTi1−x/4O3, where x=0.05, 0.10, and 0.15, have been obtained on MgO single‐crystal and epitaxial Pt thin‐film substrates under conditions of low gas pressure and low deposition rate. The degree of c‐axis orientation of the PLT films decreases, and the tetragonality of PLT becomes smaller with increasing La content. The Curie point of the films decreases at a rate of 18 °C/at. % of La with an increase of La content. D‐E hysteresis loops were observed, and these became slim and symmetric with increasing La. It was found that significant pyroelectric currents are detected on all as‐grown specimens even without a poling treatment, and the directions are the same in all specimens. Relative dielectric constant er decreases, and pyroelectric coefficient γ increases with increasing degree of c‐axis orientation. er and γ became large with increase of La content in the films. Considering the figure of merit for pyroelectric infrared detection and the temperature coefficient of γ, it was concluded that PLT films with x=0.10 were good material for pyroelectric infrared detectors.

Epitaxial growth and the crystallographic, dielectric, and pyroelectric properties of lanthanum-modified lead titanate thin films

The national project of "Ultra High-Density Electronic System Integration" was initiated in 1999. This is the first project to focus on a niche area between electronic devices and systems. It aims to develop technologies for overcoming the problems in terms of performance of electronic systems. Three-dimensional (3D) LSI chip stacking, optoelectronics hybrid integration, and optimum circuit design are the technology categories. For the 3D stacking technology, a chip-based stacking technology is under extensive development that includes wafer preparation for chip stacking, wafer thinning, chip stacking, and inspection and testing. In this paper, the current development status of the 3D stacking technology, called V-STACK technology, is introduced.

https://iopscience.iop.org/article/10.1143/JJAP.40.3032/pdf

Current Status of Research and Development for Three-Dimensional Chip Stack Technology

Highly c‐axis oriented La‐modified PbTiO3 (PLT) thin films were deposited on (100) oriented Pt thin film or (100) cleaved MgO single crystals by rf‐magnetron sputtering. Figures of merit for infrared detector were studied on the PLT thin films. It was found that a composition Pb1−xLaxTi1−x/4O3 where x=0.10 (PL10) was the most suitable for the infrared detector. The films have the advantage of having pyroelectric effect and polarization with the same direction even without a poling treatment. The films have high figures of merit Fv(=γ/cver) of 0.83×10−10 (C cm/J) and Fm(=γ/cv(er tan δ)1/2) of 1.2×10−8 (C cm/J) because of relative low‐dielectric constant er of 200 and high‐pyroelectric coefficient γ of 5.3×10−8 C/cm2 K. Both the Fv and the Fm of the films are 3 times as large as those of PbTiO3 ceramics. High sensitive pyroelectric infrared sensors were fabricated by using the PL10 films. The thickness of the films is 2 μm, and the electrodes were vacuum evaporated Ni‐Cr of approximate area 7×10−4 cm2. The ...

Yoshihiro Tomita

Papers

Preparation of c‐axis oriented PbTiO3 thin films and their crystallographic, dielectric, and pyroelectric properties

Preparation of epitaxial Pb(ZrxTi1−x)O3 thin films and their crystallographic, pyroelectric, and ferroelectric properties

Epitaxial growth and the crystallographic, dielectric, and pyroelectric properties of lanthanum-modified lead titanate thin films

Current Status of Research and Development for Three-Dimensional Chip Stack Technology

Preparation and characteristics of pyroelectric infrared sensors made of c‐axis oriented La‐modified PbTi03 thin films