Shin-Etsu Chemical Co., Ltd.

Koji Kato

Masayuki Tanno

Shoji Akiyama

Waichi Yamamura

Jun Abe

Yoshinori Kuwabara

Shoji Kano

Kazutoshi Nagata

Provided is a method for producing a lithium tantalate single crystal substrate capable of suppressing increase in volume resistivity of the lithium tantalate single crystal substrate owing to reduction failure even when a lithium carbonate power is repeatedly used in heat treatment for the lithium tantalate single crystal substrate. The invention is a method for producing a lithium tantalate single crystal substrate having a volume resistivity of 1&#xd7;10&#x3a9;&#xb7;cm or more and less than 1&#xd7;10&#x3a9;&#xb7;cm, including a step of heat-treating a lithium tantalate single crystal substrate having a volume resistivity of 1&#xd7;10&#x3a9;&#xb7;cm or more and having a single-domain structure, under normal pressure and at a temperature of 350&#xb0; C. or higher but not higher than the Curie temperature thereof while burying it in a lithium carbonate powder having a BET specific surface area of 0.13 m/g or more, wherein the lithium carbonate powder is a used lithium carbonate powder that has been used in burying a lithium tantalate single crystal substrate in heat treatment for the lithium tantalate single crystal structure under normal pressure and at a temperature of 350&#xb0; C. or higher but not higher than the Curie temperature thereof, and in the heat treatment step, the heat treatment is carried out in a mixed gas atmosphere of an inert gas and a reducing gas at the start of the heat treatment, and after the heat treatment in the mixed gas atmosphere, the heat treatment is carried out in a single gas atmosphere of an inert gas.

Method for producing lithium tantalate single crystal substrate

To provide a method for producing a composite wafer capable of reducing a spurious arising by reflection of an incident signal on a joint interface between a lithium tantalate film and a supporting substrate, in the composite wafer including a supporting substrate having a low coefficient of thermal expansion, and a lithium tantalate film having a high coefficient of thermal expansion stacked on the supporting substrate. The method for producing a composite wafer is a method for producing a composite wafer that produces a composite wafer by bonding a lithium tantalate wafer having a high coefficient of thermal expansion to a supporting wafer having a low coefficient of thermal expansion, wherein prior to bonding together, ions are implanted from a bonding surface of the lithium tantalate wafer and/or the supporting wafer, to disturb crystallinity near the respective bonding surfaces.

Method for producing composite wafer

An object of the present invention is to provide a bonded substrate which is excellent in temperature characteristics and suppresses unnecessary response due to reflection of an elastic wave at a bonding interface. [Means to Solve the Problems] The present invention is unique in that a bonded substrate is constructed by bonding a LiTaOsubstrate and a base plate wherein a Li concentration at a base plate-bonding face of the LiTaOsubstrate is higher than that at a LiTaOsubstrate-side end face of the bonded substrate, that the difference between the Li concentration at the base plate-bonding face of the LiTaOsubstrate and the Li concentration at the LiTaOsubstrate-side end face of the bonded substrate is 0.1 mol % or greater, that the Li concentration at the base plate-bonding face of the LiTaOsubstrate satisfies an equation Li/(Li+Ta)&#xd7;100=(50+&#x3b1;) mol %, where &#x3b1; is in the range of &#x2212;1.2&#x3c;&#x3b1;&#x3c;0.5, that the Li concentration at the LiTaOsubstrate-side end face of the bonded substrate satisfies an equation Li/(Li+Ta)&#xd7;100=(48.5+&#x3b2;) mol %, where &#x3b2; is in the range of &#x2212;0.5&#x3c;&#x3b2;&#x3c;0.5, and that the thickness measured from the base plate-bonding face of the LiTaOsubstrate to the LiTaOsubstrate-side end face of the finished bonded substrate becomes greater than 5 times but less than 20 times the wavelength of the surface acoustic wave or that of the leaky surface acoustic wave.

Bonded substrate and a manufacturing method thereof, and a surface acoustic wave device using the said bonded substrate

[Object] It is an object of the present invention to provide a lithium tantalate single crystal substrate which undergoes only small warpage, is free from cracks and scratches, has better temperature non-dependence characteristics and a larger electromechanical coupling coefficient than a conventional Y-cut LiTaOsubstrate. [Means to solve the Problems] The lithium tantalate single crystal substrate of the present invention is a rotated Y-cut LiTaOsingle crystal substrate having a crystal orientation of 36&#xb0; Y-49&#xb0; Y cut characterized in that: the substrate is diffused with Li from its surface into its depth such that it has a Li concentration profile showing a difference in the Li concentration between the substrate surface and the depth of the substrate; and the substrate is treated with single polarization treatment so that the Li concentration is substantially uniform from the substrate surface to a depth which is equivalent to 5-15 times the wavelength of either a surface acoustic wave or a leaky surface acoustic wave propagating in the LiTaOsubstrate surface.

Lithium tantalate single crystal substrate, bonded substrate, manufacturing method of the bonded substrate, and surface acoustic wave device using the bonded substrate

An object of the present invention is to provide a method of manufacturing a composite substrate including a piezoelectric layer with less Li amount variation and a support substrate. A method of manufacturing a composite substrate of the present invention includes a step of performing ion implantation into a piezoelectric substrate, a step of bonding the piezoelectric substrate and the support substrate, a step of separating the bonded substrate, at an ion-implanted portion of the piezoelectric substrate, into the piezoelectric layer bonded to the support substrate and the remaining piezoelectric substrate after the step of bonding the piezoelectric substrate and the support substrate, and a step of diffusing Li into the piezoelectric layer after the separating step.

Composite substrate and method of manufacturing composite substrate

A PBN-coated carbon heater is disclosed in which the carbon base body is anisotropic with respect to thermal expansion coefficient such that the maximum-to-minimum coefficient ratio is 1.02 through 1.50 for temperatures between 50 and 800 degree C.; preferably the carbon base body is also anisotropic with respect to electric resistivity such that the maximum-to-minimum resistivity ratio is greater than 1.04 but not greater than 1.51, and the direction in which the resistivity is maximum coincides the direction of the heater pattern in which the electricity runs the longest distance.

Carbon body coated with pyrolytic boron nitride, and a carbon heater including this carbon body

The method is adapted for forming an aluminum nitride thin film having a high density and a high resistance to thermal shock by a chemical vapor deposition process and includes steps of mixing a gas containing aluminum atoms (Al) and a gas containing nitrogen atoms (N) with a gas containing oxygen atoms (O) and feeding the mixture to a member to be covered by an aluminum nitride thin film.

Growing community of inventors

Gunma, Japan

Koji Kato