Abstract: A composite substrate production method of the invention includes (a) a step of mirror polishing a substrate stack having a diameter of 4 inch or more, the substrate stack including a piezoelectric substrate and a support substrate bonded to each other, the mirror polishing being performed on the piezoelectric substrate side until the thickness of the piezoelectric substrate reaches 3 ?m or less; (b) a step of creating data of the distribution of the thickness of the mirror-polished piezoelectric substrate; and (c) a step of performing machining with an ion beam machine based on the data of the thickness distribution so as to produce a composite substrate have some special technical features.

Abstract: A metal film is formed on at least a surface of a second substrate composed of ceramic (step c), and a first substrate composed of a group nitride is bonded to the second substrate through the metal film (step d). Since the metal film generally has higher thermal conductivity than oxide films, a composite substrate having high heat dissipation can be produced as compared with a case where the first substrate is bonded to the second substrate through an oxide film. In addition, a step of out diffusion is not required because of nonuse of an oxide film, thereby simplifying the process.

Abstract: A composite substrate 10 includes a supporting substrate 12 and a piezoelectric substrate 14 which are bonded to each other. In this embodiment, the supporting substrate 12 and the piezoelectric substrate 14 are bonded to each other by an adhesive layer 16. In the composite substrate 10, since the supporting substrate 12 is composed of a translucent alumina ceramic, alignment is easily performed during FCB compared with the case where the supporting substrate is composed of an opaque ceramic. Furthermore, preferably, the linear transmittance and the total light transmittance from the front of the supporting substrate 12 in the visible light range (360 to 750 nm) are 10% or more and 70% or more, respectively.

Abstract: A composite substrate 10 includes a piezoelectric substrate 12 and a support layer 14 bonded to the piezoelectric substrate 12. The support layer 14 is made of a material having no crystalline anisotropy in a bonded surface thereof and has a smaller thickness than the piezoelectric substrate 12. The piezoelectric substrate 12 and the support layer 14 are bonded together with an adhesive layer 16 therebetween. The composite substrate 10 has a total thickness of 180 ?m or less. The base thickness ratio Tr=t2/(t1+t2) is 0.1 to 0.4, where t1 is the thickness of the piezoelectric substrate 12, and t2 is the thickness of the support layer 14. The thickness t1 is 100 ?m or less. The thickness t2 is 50 ?m or less.

Abstract: A composite wafer 10 includes a supporting substrate 12 and a semiconductor substrate 14 which are bonded to each other by direct bonding. The supporting substrate 12 is a translucent alumina substrate with an alumina purity of 99% or more. The linear transmittance of the supporting substrate 12 at the visible light range is 40% or less. Furthermore, the total light transmittance from the front at a wavelength of 200 to 250 nm of the supporting substrate 12 is 60% or more. The average crystal grain size of the supporting substrate 12 is 10 to 35 ?m. The semiconductor substrate 14 is a single crystal silicon substrate. Such a composite wafer 10 has insulation performance and thermal conduction comparable to those of a SOS wafer, can be manufactured at low cost, and can be easily made to have a large diameter.

Abstract: A composite substrate 10 is a substrate formed by bonding a piezoelectric substrate 12 and a support substrate 14 having a coefficient of thermal expansion lower than that of the piezoelectric substrate 12. The support substrate 14 has a first surface 14a bonded to the piezoelectric substrate 12 and a second surface 14b opposite to the first surface 14a. The coefficient of thermal expansion of the support substrate 14 is decreased along a thickness direction from the second surface 14b to an intermediate position 14c located between the first surface 14a and the second surface 14b.

Abstract: A composite substrate according to the present invention includes a piezoelectric substrate that is a single-crystal lithium tantalate or lithium niobate substrate, a support substrate that is a single-crystal silicon substrate, and an amorphous layer joining together the piezoelectric substrate and the support substrate. The amorphous layer contains 3 to 14 atomic percent of argon. The amorphous layer includes, in order from the piezoelectric substrate toward the composite substrate, a first layer, a second layer, and a third layer. The first layer contains a larger amount of a constituent element (such as tantalum) of the piezoelectric substrate than the second and third layers. The third layer contains a larger amount of a constituent element (silicon) of the support substrate than the first and second layers. The second layer contains a larger amount of argon than the first and third layers.

Abstract: The present invention provides a composite substrate comprising a piezoelectric substrate that is a single-crystal lithium tantalate or lithium niobate substrate, a support substrate that is a single-crystal silicon substrate, and an amorphous layer containing argon and joining together the piezoelectric substrate and the support substrate. The amorphous layer includes, in order from the piezoelectric substrate toward the composite substrate, a first layer, a second layer, and a third layer. The first layer contains a larger amount of a constituent element of the piezoelectric substrate than the second and third layers, the third layer contains a larger amount of a constituent element of the support substrate than the first and second layers, and the second layer contains a larger amount of argon than the first and third layers.

Abstract: In a composite substrate 10, a bonding surface 21 of a piezoelectric substrate 20 is an irregular surface which is partially planarized. The irregular surface which is partially planarized includes a plurality of protrusions 23, each having a flat portion 25 on the tip thereof. The piezoelectric substrate 20 and the supporting substrate 30 are directly bonded to each other at the flat portions 25. By forming the bonding surface 21 into an irregular surface (rough surface) and providing flat portions 25 at the same time, it is possible to secure a sufficient contact area between the piezoelectric substrate 20 and the supporting substrate 30. Accordingly, in the composite substrate in which the piezoelectric substrate 20 and the supporting substrate 30 are bonded to each other, the bonding surface 21 can be roughened and direct bonding can be performed.

Abstract: The present invention provides a composite substrate comprising a piezoelectric substrate that is a single-crystal lithium tantalate or lithium niobate substrate, a support substrate that is a single-crystal silicon substrate, and an amorphous layer containing argon and joining together the piezoelectric substrate and the support substrate. The amorphous layer includes, in order from the piezoelectric substrate toward the composite substrate, a first layer, a second layer, and a third layer. The first layer contains a larger amount of a constituent element of the piezoelectric substrate than the second and third layers, the third layer contains a larger amount of a constituent element of the support substrate than the first and second layers, and the second layer contains a larger amount of argon than the first and third layers.

Abstract: A composite substrate according to the present invention includes a piezoelectric substrate that is a single-crystal lithium tantalate or lithium niobate substrate, a support substrate that is a single-crystal silicon substrate, and an amorphous layer joining together the piezoelectric substrate and the support substrate. The amorphous layer contains 3 to 14 atomic percent of argon. The amorphous layer includes, in order from the piezoelectric substrate toward the composite substrate, a first layer, a second layer, and a third layer. The first layer contains a larger amount of a constituent element (such as tantalum) of the piezoelectric substrate than the second and third layers. The third layer contains a larger amount of a constituent element (silicon) of the support substrate than the first and second layers. The second layer contains a larger amount of argon than the first and third layers.

Abstract: A composite wafer 10 includes a supporting substrate 12 and a semiconductor substrate 14 which are bonded to each other by direct bonding. The supporting substrate 12 is a translucent alumina substrate with an alumina purity of 99% or more. The linear transmittance of the supporting substrate 12 at the visible light range is 40% or less. Furthermore, the total light transmittance from the front at a wavelength of 200 to 250 nm of the supporting substrate 12 is 60% or more. The average crystal grain size of the supporting substrate 12 is 10 to ?m. The semiconductor substrate 14 is a single crystal silicon substrate. Such a composite wafer 10 has insulation performance and thermal conduction comparable to those of a SOS wafer, can be manufactured at low cost, and can be easily made to have a large diameter.

Abstract: A pyroelectric element includes a pyroelectric substrate; a light-receiving section composed of a front-side electrode, a back-side electrode, and a light-receiving portion; and a light-receiving section composed of a front-side electrode, a back-side electrode, and a light-receiving portion. Since the pyroelectric substrate warps in a cavity-facing region opposite a cavity, the light-receiving area of the light-receiving sections is greater than that in the case where there is no warp. It is thus possible to improve detection sensitivity of the pyroelectric element without making the size of the pyroelectric element larger than that in the case where there is no warp.

Abstract: In a composite substrate 10, a bonding surface 21 of a piezoelectric substrate 20 is an irregular surface which is partially planarized. The irregular surface which is partially planarized includes a plurality of protrusions 23, each having a flat portion 25 on the tip thereof. The piezoelectric substrate 20 and the supporting substrate 30 are directly bonded to each other at the flat portions 25. By forming the bonding surface 21 into an irregular surface (rough surface) and providing flat portions 25 at the same time, it is possible to secure a sufficient contact area between the piezoelectric substrate 20 and the supporting substrate 30. Accordingly, in the composite substrate in which the piezoelectric substrate 20 and the supporting substrate 30 are bonded to each other, the bonding surface 21 can be roughened and direct bonding can be performed.

Abstract: A pyroelectric element includes a pyroelectric substrate being a substrate of lithium tantalate single crystal having an X-axis, a Y-axis, and a Z-axis as crystal axes; front-side electrodes disposed on a front side of the pyroelectric substrate; and back-side electrodes paired with the front-side electrodes, respectively. The pyroelectric substrate is a Y-offcut plate obtained by cutting the lithium tantalate single crystal at an angle turned by a cut angle ? from the Y-axis toward the Z-axis about the X-axis that coincides with a direction along the electrode plane, and the cut angle ? is 30° to 60° or 120° to 150°. The pyroelectric substrate is preferably 10 ?m or less in thickness, and is more preferably 5 ?m to 10 ?m in thickness.

Abstract: A pyroelectric element includes a pyroelectric substrate being a substrate of lithium tantalate single crystal having an X-axis, a Y-axis, and a Z-axis as crystal axes; front-side electrodes disposed on a front side of the pyroelectric substrate; and back-side electrodes paired with the front-side electrodes, respectively. The pyroelectric substrate is a Y-offcut plate obtained by cutting the lithium tantalate single crystal at an angle turned by a cut angle ? from the Y-axis toward the Z-axis about the X-axis that coincides with a direction along the electrode plane, and the cut angle ? is 30° to 60° or 120° to 150°. The pyroelectric substrate is preferably 10 ?m or less in thickness, and is more preferably 5 ?m to 10 ?m in thickness.

Abstract: A pyroelectric element includes a pyroelectric substrate; a light-receiving section composed of a front-side electrode, a back-side electrode, and a light-receiving portion; and a light-receiving section composed of a front-side electrode, a back-side electrode, and a light-receiving portion. Since the pyroelectric substrate warps in a cavity-facing region opposite a cavity, the light-receiving area of the light-receiving sections is greater than that in the case where there is no warp. It is thus possible to improve detection sensitivity of the pyroelectric element without making the size of the pyroelectric element larger than that in the case where there is no warp.

Abstract: A metal film 23 is formed on at least a surface 12a of a second substrate 12 composed of ceramic (step c), and a first substrate 21 composed of a group 13 nitride is bonded to the second substrate 12 through the metal film 23 (step d). Since the metal film 23 generally has higher thermal conductivity than oxide films, a composite substrate 10 having high heat dissipation can be produced as compared with a case where the first substrate 21 is bonded to the second substrate 12 through an oxide film. In addition, a step of out diffusion is not required because of nonuse of an oxide film, thereby simplifying the process.

Abstract: There is provided a lamb wave device with small variations in frequency, the device including: a piezoelectric thin film; an IDT electrode which is provided on a main surface of the piezoelectric thin film; and a support structure which supports a laminate of the IDT electrode and the piezoelectric thin film, and is formed with a cavity that isolates the laminate, wherein a film thickness h of the piezoelectric thin film and a pitch p of a finger of the IDT electrode are selected such that a lamb wave is excited at a target frequency, the lamb wave making dispersibility of a sonic velocity v with respect to the film thickness h of the piezoelectric thin film small.

Abstract: There is provided a lamb wave device with small variations in frequency, the device including: a piezoelectric thin film; an IDT electrode which is provided on a main surface of the piezoelectric thin film; and a support structure which supports a laminate of the IDT electrode and the piezoelectric thin film, and is formed with a cavity that isolates the laminate, wherein a film thickness h of the piezoelectric thin film and a pitch p of a finger of the IDT electrode are selected such that a lamb wave is excited at a target frequency, the lamb wave making dispersibility of a sonic velocity v with respect to the film thickness h of the piezoelectric thin film small.