Taeko Ando

Tensile testing of silicon film having different crystallographic orientations carried out on a silicon chip

Abstract Uniaxial tensile testing of single-crystal silicon film was carried out on a silicon chip. A tensile testing system was integrated on a silicon chip. A process for fabricating a test chip containing a specimen whose tensile axis has an arbitrary orientation was developed. The mechanical properties, such as elastic modulus and fracture strain, of silicon films having different orientations of 〈100〉, (110), and 〈111〉, are measured. The results are compared with those of bulk materials.

Cross comparison of thin-film tensile-testing methods examined using single-crystal silicon, polysilicon, nickel, and titanium films

This paper reports on the results of comparing different types of tensile testing methods that are used to evaluate thin-film properties. We tested the same material fabricated on a single wafer using different testing techniques at five different research institutions. The testing methods were different in the way the specimen was gripped. Materials tested were single-crystal silicon (SCS), polysilicon, nickel, and titanium films. Specimens with three different shapes were processed through the same fabrication steps. The tensile strength, fracture strain, and Youngs modulus of the films were measured and compared. The measured values of the mechanical properties of all the testing methods were in good agreement with each other, thus demonstrating their accuracy.

Effect of temperature on fracture toughness in a single-crystal-silicon film and transition in its fracture mode

A change in the fracture mode of a micrometer-sized single-crystal-silicon (SCS) film was observed at a temperature slightly higher than room temperature (RT). Silicon films with a notch on one side were tested under tensile stress at temperatures ranging from RT to 500 °C. The mean fracture toughness was 1.28 MPa at RT and the value remained similar up to 60 °C. However, it drastically increased to nearly twice this value above 70 °C. Differences in the fracture mode and dislocation activity were found by scanning and transmission electron microscopy (SEM and TEM). These results show that the fracture mode changed even at a low temperature near 70 °C due to the activation of dislocations at the notch tip.

Non-photolithographic pattern transfer for fabricating pen-shaped microneedle structures

We developed a new fabrication process for pen-shaped microneedle structures by using non-photolithographic pattern transfer. The process is a combination of anisotropic wet etching and a dicing technology that uses a saw. The process has an advantage, in which the needle diameter is easily changed by altering the groove profile formed in the dicing-saw process. We fabricated pen-shaped needle structures in a dense array for medical applications. The needle height was larger than 200 µm, and the pitch distance was about 200 µm in the experiments. The width of the needle ranged from 10 to 30 µm. The radius at the needle tip was less than 100 nm.

Tensile testing of SiO2 and Si3N4 films carried out on a silicon chip

Abstract The tensile testing of SiO 2 and Si 3 N 4 films was carried out on a silicon chip. The silicon chip has an integrated tensile testing system containing a thin-film specimen and a loading mechanism. We developed fabrication processes of the testing chips for SiO 2 and Si 3 N 4 films. The SiO 2 specimen was fabricated by thermally oxidizing a single-crystal silicon specimen made from a silicon-on-insulator (SOI) wafer. The Si 3 N 4 specimen was fabricated from an LPCVD film deposited on a silicon wafer. The measured Youngs moduli of SiO 2 and Si 3 N 4 were 74 and 370 GPa, respectively.

Effect of crystal orientation on fracture strength and fracture toughness of single crystal silicon

This paper presents the dependence of fracture toughness, fracture strength, and fracture behavior, such as crack propagation, on the crystal orientation of single-crystal silicon. We conducted on-chip tensile testing to measure fracture strength and fracture toughness of single-crystal silicon films with [100] and [110] surface in the <100> and <110> loading direction. The loading direction had a significant effect on fracture toughness, which was 2.17 MPa/spl radic/m in the <100> direction and 1.27 MPa/spl radic/m in <110>. However, the fracture stress varies with both loading direction and surface orientation. We observed a fracture specimen on which a [111] cleavage plane eventually appeared on any crystal types of the specimen.

Micro tensile-test of silicon film having different crystallographic orientations

Uniaxial tensile testing of a single-crystal silicon film was carried out on a silicon chip. A tensile testing system was integrated on a silicon chip. A process for fabricating a test chip containing a specimen whose tensile axis has an arbitrary orientation was developed. The mechanical properties, such as elastic modulus and fracture strain, of silicon films having different orientations of <100>, <110>, and <111>, are tested and compared.

Cross comparison of thin film tensile-testing methods examined with single-crystal silicon, polysilicon, nickel, and titanium films

This paper reports on the results of comparing different types of tensile testing methods that are used to evaluate thin-film properties. We tested the same material fabricated on a single wafer using different testing techniques at five different research institutions. The testing methods were different in the way the specimen was gripped. Materials tested were single-crystal silicon (SCS), polysilicon, nickel, and titanium films. Specimens with three different shapes were processed through the same fabrication steps. The tensile strength, fracture strain, and Youngs modulus of the films were measured and compared. The measured values of the mechanical properties of all the testing methods were in good agreement with each other, thus demonstrating their accuracy.This paper reports the results of a comparison of the different types of tensile testing methods used to evaluate thin films properties. We tested the same material fabricated on a single wafer using different testing techniques at five different research institutions. The testing methods are different in the way of gripping the specimen. Materials tested were single-crystal silicon, polysilicon, nickel, and titanium films. Specimens of three different shapes were processed through the same fabrication steps. The tensile strength, fracture strain, and Youngs modulus of the films were measured and compared. The measured values of the mechanical properties were in good agreement with each other among the testing methods, thus demonstrating the accuracy of these testing methods.

Orientation-dependent fracture strain in single-crystal silicon beams under uniaxial tensile conditions

The proposed method for testing the uniaxial tensile characteristics of thin film materials is integrated onto a silicon chip. The developed process for fabricating the test chips starts with SOI wafers whose top silicon layer is prepared for the test materials. The results of testing single-crystal silicon films having orientations of <100>, <110>, and <111> were compared with those from bending tests of bulk silicon. The measured Youngs moduli and fracture strains clearly showed orientation dependence, and the measured values were reasonable compared with those of the bulk materials. The fracture strains varied from 0.4 to 2.2% depending on the orientation and were the lowest in the <111> direction.

A method for measuring the fracture toughness of micrometer-sized single crystal silicon by tensile test

We developed a method of measuring the fracture toughness,-which is a material constant in the macroscopic domain, of single crystal silicon on a micrometer-scale. We notched the thin film specimen on a single edge and then conducted uniaxial tensile test to failure. The average value of measured fracture toughness of specimens on the (100) plane was 1.58 MPa/spl middot/m/sup 1/2/ with scatter. This is slightly higher than, but comparable to, the value for bulk silicon. Scanning electron microscope (SEM) observation of the failed specimens revealed that the fracture developed mainly along the [110] cleavage plane.