Patent Description:
Conventionally, there has been disclosed a piezoelectric element in which two piezoelectric films are stacked together via an adhesion layer. See <CIT> (Patent Reference <NUM>), for example.

However, a high-performance piezoelectric film integrated device cannot be obtained when a plurality of piezoelectric films are arranged in superimposition in a conventional device.

The document from<NPL> discloses piezoelectric bimorph cantilever microactuators based on single-crystal A1<NUM>Ga<NUM>As. Fabricated devices are characterized for their quasistatic and resonant behavior when driven in both unimorph and bimorph configurations. Quasistatic actuator behavior is compared with a simple analytic model. Measured unimorph and bimorph tip deflections match well with the model, with deviations resulting from imperfections in device geometry and electrical resistivity of the electrodes. The•effects of bimorph actuation on linearity and structural damping at resonance are also evaluated.

As further prior art, reference is made to <CIT> and to <CIT> Al.

An object of the present disclosure is to provide a high-performance piezoelectric film integrated device in which two or more types of piezoelectric elements each including a monocrystalline piezoelectric film are provided in superimposition, a manufacturing method thereof, and an acoustic oscillation sensor including the piezoelectric film integrated device.

A piezoelectric film integrated device according to the present invention is defined in claim <NUM>.

According to the present disclosure, by providing two or more types of piezoelectric elements each including a monocrystalline piezoelectric film in superimposition, the performance of the piezoelectric film integrated device and the acoustic oscillation sensor can be increased.

The present disclosure will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and wherein:.

A piezoelectric film integrated device, a manufacturing method thereof, and an acoustic oscillation sensor according to each embodiment will be described below with reference to the drawings. The following embodiments are just examples and a variety of modifications are possible within the scope of the present disclosure. In the present application, the piezoelectric film integrated device is a device in which two or more monocrystalline piezoelectric films are provided on the same substrate. Further, in the present application, the acoustic oscillation sensor is a sensor that detects status (e.g., distance, shape, movement or the like) of a detection target object by outputting an acoustic oscillatory wave and detecting reflected waves of the acoustic oscillatory wave. The acoustic oscillation sensor is referred to also as an "ultrasonic sensor". In general, and in the present application, the acoustic oscillatory wave is made up of at least one of a sonic wave and an ultrasonic wave. Namely, the acoustic oscillatory wave includes a sonic wave, an ultrasonic wave, or both of a sonic wave and an ultrasonic wave.

<FIG> is a side view schematically showing the structure of a piezoelectric film integrated device <NUM> according to a first embodiment. <FIG> is a top view schematically showing the structure of the piezoelectric film integrated device <NUM>. <FIG> is a cross-sectional view of the piezoelectric film integrated device <NUM> in <FIG> taken along the line S3-S3. <FIG> is a bottom view schematically showing the structure of the piezoelectric film integrated device <NUM>.

The piezoelectric film integrated device <NUM> includes an SOI substrate <NUM> as a substrate and a platinum (Pt) film <NUM> as an electrode provided on the SOI substrate <NUM>. As shown in <FIG>, the Pt film <NUM> is connected to a connector <NUM> via a wiring layer formed on the SOI substrate <NUM>. The SOI stands for Silicon On Insulator. Further, in the SOI substrate <NUM>, there may be formed a drive circuit for driving the piezoelectric film integrated device <NUM> and thereby generating the acoustic oscillatory wave, a processing circuit that executes a process by using an acoustic oscillatory wave detection signal, and so forth.

The piezoelectric film integrated device <NUM> includes a first piezoelectric element (<NUM>, <NUM>) as a lower-side piezoelectric element provided on the Pt film <NUM> and a second piezoelectric element (<NUM>, <NUM>) as an upper-side piezoelectric element provided on the first piezoelectric element. A Pt film <NUM> has a function as a common electrode for the first piezoelectric element (<NUM>, <NUM>) and the second piezoelectric element (<NUM>, <NUM>). However, the second piezoelectric element (<NUM>, <NUM>) may have an electrode film other than the Pt film <NUM>. The first piezoelectric element includes a monocrystalline AlN film <NUM> as a first monocrystalline piezoelectric film and the Pt film <NUM> as a first electrode film superimposed on the monocrystalline AlN film <NUM>. The second piezoelectric element includes a monocrystalline PZT film <NUM> as a second monocrystalline piezoelectric film and a Pt film <NUM> as a second electrode film superimposed on the monocrystalline PZT film <NUM>. The AlN represents aluminum nitride. The PZT represents piezoelectric zirconate titanate (lead zirconate titanate). As the first monocrystalline piezoelectric film, instead of the monocrystalline AlN film <NUM>, a piezoelectric film made of a different monocrystalline material such as a monocrystalline lithium tantalate (monocrystalline LiTaO<NUM>) film or a monocrystalline lithium niobate (monocrystalline LiNbO<NUM>) film may be used. As the second monocrystalline piezoelectric film, instead of the monocrystalline PZT film <NUM>, a piezoelectric film made of a different monocrystalline material such as a monocrystalline potassium sodium niobate (monocrystalline KNN) film or a monocrystalline barium titanate (monocrystalline BaTiO<NUM>) film may be used. In the illustrated example, the first monocrystalline piezoelectric film is a piezoelectric body that detects the acoustic oscillatory wave (or its reflected waves), and is desired to be a piezoelectric body having lower specific inductive capacity and higher detection sensitivity compared to the second monocrystalline piezoelectric film. The second monocrystalline piezoelectric film is a piezoelectric body that generates the acoustic oscillatory wave, and is desired to be a piezoelectric body having a higher piezoelectric constant and capable of obtaining greater oscillation amplitude compared to the first monocrystalline piezoelectric film.

Incidentally, it is permissible even if the first piezoelectric element as the lower-side piezoelectric element includes a monocrystalline PZT film as the first monocrystalline piezoelectric film and a Pt film and the second piezoelectric element as the upper-side piezoelectric element includes a monocrystalline AlN film and a Pt film superimposed on the monocrystalline AlN film.

Further, the piezoelectric film integrated device <NUM> includes an insulation film 35a, a wiring film 36a formed on the insulation film 35a, an insulation film 35b, and a wiring film 36b formed on the insulation film 35b.

The SOI substrate <NUM> includes a Si substrate <NUM>, a silicon dioxide (SiO<NUM>) part <NUM> as an insulation film, and a monocrystalline silicon (monocrystalline Si) part <NUM>. A cavity <NUM> is formed by etching the Si substrate <NUM> in a region of the monocrystalline silicon (monocrystalline Si) part <NUM> under the monocrystalline PZT film <NUM> and the monocrystalline AlN film <NUM> (i.e., a region overlapping with the piezoelectric films), and the SiO<NUM> part <NUM> and the monocrystalline silicon (monocrystalline Si) part <NUM> situated in the region where the cavity <NUM> is formed have a function as a vibrating plate. Further, variations in the thickness of the vibrating plate due to influence of the etching can be prevented by forming the silicon dioxide (SiO<NUM>) part <NUM> made of a material different from the Si substrate <NUM> and giving the silicon dioxide (SiO<NUM>) part <NUM> a function as an etching stop layer. Furthermore, as the substrate, a substrate made of a different material such as a glass substrate or an organic film substrate may also be used instead of the SOI substrate <NUM>. In the Si substrate <NUM> of the SOI substrate <NUM>, the cavity <NUM> that exposes the SiO<NUM> part <NUM> is formed. The cavity <NUM> is formed in a circular shape as an opening shape corresponding to the shape of the monocrystalline PZT film <NUM> or the monocrystalline AlN film <NUM>. The acoustic oscillatory wave generated by the monocrystalline PZT film <NUM> is outputted through the cavity <NUM>, and the monocrystalline AlN film <NUM> detects reflected waves of the acoustic oscillatory wave through the cavity <NUM>.

The monocrystalline AlN film <NUM> of the first piezoelectric element is an epitaxial growth film having a (<NUM>)-surface as a crystal face parallel to a surface of the Pt film <NUM> and being stuck (or bonded) on the surface of the Pt film <NUM>. The monocrystalline PZT film <NUM> of the second piezoelectric element is an epitaxial growth film having a (<NUM>)-surface as a crystal face parallel to the surface of the Pt film <NUM> and being stuck (or bonded) on the surface of the Pt film <NUM> of the first piezoelectric element. The thickness of the monocrystalline PZT film <NUM> is generally in a range of <NUM> to <NUM>, and preferably in a range of <NUM> to <NUM>. The thickness of the monocrystalline AlN film <NUM> is generally in a range of <NUM> to <NUM>, and preferably in a range of <NUM> to <NUM>. The Pt film <NUM> is formed on an upper surface of the SOI substrate <NUM>. The surface (upper surface) of the Pt film <NUM> and the (<NUM>)-surface as the crystal face of the monocrystalline AlN film <NUM> are joined together by intermolecular force. The surface of the Pt film <NUM> of the first piezoelectric element and the (<NUM>)-surface as the crystal face of the monocrystalline PZT film <NUM> are joined together by intermolecular force. For these joints, the use of an adhesive agent is unnecessary. For excellently joining these surfaces by intermolecular force, the surface roughness of the Pt film <NUM> and the Pt film <NUM> is desired to be less than or equal to <NUM>. For this purpose, a process for smoothing the surfaces of the Pt film <NUM> and the Pt film <NUM> may be executed.

Further, a crystal c-axis direction of the monocrystalline PZT film <NUM> and a crystal c-axis direction of the monocrystalline AlN film <NUM> are in the parallel relationship. This feature will be described later by using <FIG>.

<FIG> is a cross-sectional view schematically showing the structure of the epitaxial growth film including the monocrystalline PZT film <NUM>. <FIG> is a diagram showing the crystal structure of the monocrystalline PZT film <NUM> in <FIG>. <FIG> is a diagram schematically showing the crystal structure of the epitaxial growth film in <FIG>. Incidentally, in <FIG>, the dimension in a vertical direction is reduced greatly compared to the dimension in a horizontal direction.

The epitaxial growth film in <FIG> is formed on a growth substrate <NUM> that is a monocrystalline Si substrate. The epitaxial growth film in <FIG> has a structure in which a monocrystalline zirconium dioxide (ZrO<NUM>) film <NUM>, a monocrystalline Pt film <NUM>, a monocrystalline SRO film <NUM>, a monocrystalline PZT film <NUM> and a monocrystalline Pt film <NUM> are stacked in this order. The growth substrate <NUM> is an example of a substrate whose upper surface is a (<NUM>)-surface. The ZrO<NUM> film <NUM> is an example of an orientation film having a cubic crystal structure and whose upper surface is a (<NUM>)-surface. The Pt film <NUM> is an example of a conductive film having a cubic crystal structure and whose upper surface is a (<NUM>)-surface. The SRO film <NUM> is a SrRuO<NUM> film (strontium ruthenate film) and is an example of an orientation film. The monocrystalline PZT film <NUM> is an example of a monocrystalline piezoelectric film for outputting oscillation. In cases where the monocrystalline PZT film <NUM> includes complex oxide having perovskite structure, the monocrystalline PZT film <NUM> can be grown epitaxially in the (<NUM>)-orientation in the cubic crystal representation on the growth substrate <NUM>. On the monocrystalline PZT film <NUM>, the Pt film <NUM> having a cubic crystal structure and being (<NUM>)-oriented is further grown epitaxially.

"The ZrO<NUM> film <NUM> is (<NUM>)-oriented" means that the (<NUM>)-surface of the ZrO<NUM> film <NUM> having a cubic crystal structure is formed along the (<NUM>)-surface of the growth substrate <NUM>, namely, is parallel to the (<NUM>)-surface of the growth substrate <NUM>. Further, "is parallel to" also means a state in which an angle formed by the upper surface of the growth substrate <NUM> and the (<NUM>)-surface of the ZrO<NUM> film <NUM> is less than or equal to <NUM>°. Furthermore, the meaning of "orientation" is the same also for relationship between other films.

Table <NUM> shows the lattice constant of monocrystalline Si of the growth substrate <NUM>, the lattice constant of ZrO<NUM> of the ZrO<NUM> film <NUM>, the lattice constant of Pt of the Pt film <NUM>, the lattice constant of SRO of the SRO film <NUM>, and the lattice constant of monocrystalline PZT of the monocrystalline PZT film <NUM>.

The lattice constant of Si is <NUM>, the lattice constant of ZrO<NUM> is <NUM>, and inconsistency of the lattice constant of ZrO<NUM> with the lattice constant of Si is as small as <NUM>%, and thus the consistency of the lattice constant of ZrO<NUM> with the lattice constant of Si is high. Therefore, as shown in the schematic diagram of <FIG>, the ZrO<NUM> film <NUM> as an orientation film can be grown epitaxially on a principal surface formed by the (<NUM>)-surface of the growth substrate <NUM>. Accordingly, the ZrO<NUM> film <NUM> can be (<NUM>)-oriented in a cubic crystal structure on the (<NUM>)-surface of the growth substrate <NUM>, and crystallinity of the ZrO<NUM> film <NUM> can be improved.

In cases where the ZrO<NUM> film <NUM> is a zirconium dioxide film having a cubic crystal structure and (<NUM>)-oriented, the ZrO<NUM> film <NUM> is oriented so that the ZrO<NUM> film <NUM>'s <<NUM>> direction along the upper surface of the growth substrate <NUM> as the principal surface is parallel to the <<NUM>> direction along the upper surface of the growth substrate <NUM>.

Incidentally, "the ZrO<NUM> film <NUM>'s <<NUM>> direction along the upper surface of the growth substrate <NUM> is parallel to the <<NUM>> direction along the upper surface of the growth substrate <NUM>" means not only that the ZrO<NUM> film <NUM>'s <<NUM>> direction is perfectly parallel to the <<NUM>> direction along the upper surface of the growth substrate <NUM> but also a state in which an angle formed by the ZrO<NUM> film <NUM>'s <<NUM>> direction and the <<NUM>> direction along the upper surface of the growth substrate <NUM> is less than or equal to <NUM>°. The same goes not only for the ZrO<NUM> film <NUM> but also for in-plane orientation of a film in a different layer.

Meanwhile, although the lattice constant of ZrO<NUM> is <NUM> and the lattice constant of Pt is <NUM> as shown in Table <NUM>, if Pt is rotated in a plane by <NUM>°, the length of a diagonal line is <NUM> and the inconsistency of the length of the diagonal line with the lattice constant of ZrO<NUM> is as small as <NUM>%. Thus, the Pt film <NUM> can be grown epitaxially on the (<NUM>)-surface of the ZrO<NUM> film <NUM>.

Further, as shown in Table <NUM>, the lattice constant of Pt is <NUM>, the lattice constant of SRO is <NUM> - <NUM>, and the inconsistency of the lattice constant of SRO with the lattice constant of Pt is as small as <NUM>% or less. Thus, the consistency of the lattice constant of SRO with the lattice constant of Pt is high, and the SRO film <NUM> can be grown epitaxially on the (<NUM>)-surface of the Pt film <NUM> as shown in <FIG>. Accordingly, the SRO film <NUM> can be (<NUM>)-oriented in the pseudo-cubic crystal representation on the (<NUM>)-surface of the Pt film <NUM>, and the crystallinity of the SRO film <NUM> can be improved.

In cases where the monocrystalline PZT film <NUM> has a cubic crystal structure and includes a (<NUM>)-oriented PZT film, the piezoelectric zirconate titanate (lead zirconate titanate) film is oriented so that its <<NUM>> direction along the upper surface of the growth substrate <NUM> is parallel to the <<NUM>> direction along the upper surface of the growth substrate <NUM>.

On the (<NUM>)-oriented monocrystalline PZT film <NUM>, the Pt film <NUM> is grown epitaxially in the (<NUM>)-orientation and thereby formed as an electrode. The electrode film on the monocrystalline PZT film <NUM> is the uppermost layer, and thus may also be formed by a different manufacturing method.

<FIG> is a cross-sectional view schematically showing the structure of the epitaxial growth film including the monocrystalline AlN film <NUM> as a monocrystalline piezoelectric film. <FIG> is a diagram schematically showing a (<NUM>)-surface of the crystal of each of the monocrystalline SRO film, the monocrystalline Pt film and the monocrystalline ZrO<NUM> film, and <FIG> is a diagram showing the lattice constant of the crystal of monocrystalline SRO. <FIG> is a diagram schematically showing the crystal structure of the monocrystalline AlN film <NUM>, and <FIG> is a diagram showing the lattice constant of the crystal of the monocrystalline AlN film <NUM>.

The epitaxial growth film in <FIG> is formed on a growth substrate <NUM> that is a monocrystalline Si substrate, for example. The epitaxial growth film has a structure in which a ZrO<NUM> film <NUM>, a Pt film <NUM>, an SRO film <NUM>, a monocrystalline AlN film <NUM> and a Pt film <NUM> are stacked in this order. The growth substrate <NUM> is an example of a substrate whose upper surface is a (<NUM>)-surface. The ZrO<NUM> film <NUM> is an example of an orientation film having a cubic crystal structure and whose upper surface is a (<NUM>)-surface. The Pt film <NUM> is an example of a conductive film having a cubic crystal structure and whose upper surface is a (<NUM>)-surface. The SRO film <NUM> is a SrRuO<NUM> film. The monocrystalline AlN film <NUM> is an example of a monocrystalline piezoelectric film for detecting oscillation (i.e., for input). The Pt film <NUM> is an example of an upper electrode. In <FIG>, the shape of the (<NUM>)-surface of the SRO cubic crystal as bird's-eye viewed from above is shown. In <FIG>, the shape of the (<NUM>)-surface as a crystal face of the AlN hexagonal crystal as bird's-eye viewed from above is shown.

In cases where the monocrystalline AlN film <NUM> is formed of a hexagonal crystal of aluminum nitride, the monocrystalline AlN film <NUM> can be grown epitaxially in the (<NUM>)-orientation in the hexagonal crystal representation on the growth substrate <NUM>. On the monocrystalline AlN film <NUM>, the Pt film <NUM> having a cubic crystal structure and (<NUM>)-oriented can be further grown epitaxially.

"The ZrO<NUM> film <NUM> is (<NUM>)-oriented" means that the (<NUM>)-surface of the ZrO<NUM> film <NUM> having a cubic crystal structure is along the (<NUM>)-surface of the growth substrate <NUM>, namely, is parallel to the (<NUM>)-surface of the growth substrate <NUM>. Further, "parallel" also means a state in which an angle formed by the (<NUM>)-surface of the ZrO<NUM> film <NUM> and the principal surface of the growth substrate <NUM> is less than or equal to <NUM>°. The same goes for orientation between other layers.

Table <NUM> shows the lattice constant of Si, the lattice constant of ZrO<NUM>, the lattice constant of Pt, the lattice constant of SRO, and the lattice constant of monocrystalline AlN.

The lattice constant of Si is <NUM>, the lattice constant of ZrO<NUM> is <NUM>, and the inconsistency of the lattice constant of ZrO<NUM> with the lattice constant of Si is as small as <NUM>%, and thus the consistency of the lattice constant of ZrO<NUM> with the lattice constant of Si is high. Thus, the ZrO<NUM> film <NUM> can be grown epitaxially on a principal surface formed by the (<NUM>)-surface of the growth substrate <NUM>. Accordingly, the ZrO<NUM> film <NUM> can be (<NUM>)-oriented in a cubic crystal structure on the (<NUM>)-surface of the growth substrate <NUM>, and the crystallinity of the ZrO<NUM> film <NUM> can be improved. The (<NUM>)-surface of the cubic crystal is shown in <FIG>.

In cases where the ZrO<NUM> film <NUM> as an orientation film is a zirconium dioxide film having a cubic crystal structure and (<NUM>)-oriented, the ZrO<NUM> film <NUM> is oriented so that the ZrO<NUM> film <NUM>'s <<NUM>> direction along the upper surface of the growth substrate <NUM> as the principal surface is parallel to the <<NUM>> direction along the upper surface of the growth substrate <NUM>.

Incidentally, "the ZrO<NUM> film <NUM>'s <<NUM>> direction along the upper surface of the growth substrate <NUM> is parallel to the <<NUM>> direction along the upper surface of the growth substrate <NUM>" means not only that the ZrO<NUM> film <NUM>'s <<NUM>> direction is perfectly parallel to the <<NUM>> direction along the upper surface of the growth substrate <NUM> but also a state in which an angle formed by the ZrO<NUM> film <NUM>'s <<NUM>> direction and the <<NUM>> direction along the upper surface of the growth substrate <NUM> is less than or equal to <NUM>°. The same goes for orientation between films in different layers.

Meanwhile, although the lattice constant of ZrO<NUM> is <NUM> and the lattice constant of Pt is <NUM>, if Pt is rotated in a plane by <NUM>°, the length of a diagonal line is <NUM> and the inconsistency of the length of the diagonal line with the lattice constant of ZrO<NUM> is as small as <NUM>%, and thus the Pt film <NUM> can be grown epitaxially on the (<NUM>)-surface of the ZrO<NUM> film <NUM>.

Further, the lattice constant of Pt is <NUM>, the lattice constant of SRO is <NUM> - <NUM>, and the consistency of the lattice constant of SRO with the lattice constant of Pt is high. Thus, the SRO film <NUM> can be grown epitaxially on the (<NUM>)-surface of the Pt film <NUM> as shown in <FIG>. Accordingly, the SRO film <NUM> can be (<NUM>)-oriented in the pseudo-cubic crystal representation on the (<NUM>)-surface of the Pt film <NUM>, and the crystallinity of the SRO film <NUM> can be improved. The length of the diagonal line of the (<NUM>)-surface of the SRO film is <NUM> - <NUM> and the inconsistency with the width <NUM> of the AlN hexagonal crystal is as small as <NUM>% as shown in <FIG>, and thus the monocrystalline AlN film <NUM> can be grown epitaxially in the (<NUM>)-orientation on the (<NUM>)-surface of the SRO film <NUM>.

In cases where the monocrystalline AlN film <NUM> has a hexagonal crystal structure and includes a (<NUM>)-oriented aluminum nitride film, the monocrystalline AlN film <NUM> is oriented so that its <<NUM>> direction along the upper surface of the growth substrate <NUM> is parallel to the <<NUM>> direction of the upper surface of the growth substrate <NUM>. The (<NUM>)-surface of the hexagonal crystal is shown in <FIG>. On the (<NUM>)-oriented monocrystalline AlN film <NUM>, the Pt film <NUM> is further grown epitaxially in the (<NUM>)-orientation and thereby formed as an electrode. The electrode film on the monocrystalline AlN film <NUM> is the uppermost layer, and thus may also be formed by a different manufacturing method.

A method for manufacturing the piezoelectric film integrated device <NUM> by using the PZT epitaxial growth film (including the monocrystalline PZT film <NUM> and the Pt film <NUM>) as a piezoelectric element deposited on the growth substrate <NUM> of monocrystalline Si whose upper surface is a (<NUM>)-surface and the AlN epitaxial growth film (including the monocrystalline AlN film <NUM> and the Pt film <NUM>) as a piezoelectric element deposited on the growth substrate <NUM> of monocrystalline Si whose upper surface is a (<NUM>)-surface will be described below.

<FIG> is a flowchart showing a method of manufacturing the piezoelectric film integrated device <NUM>. <FIG> show step ST102 in <FIG>. <FIG> show step ST103 in <FIG>, and <FIG> show step ST104 in <FIG>. <FIG> show step ST109 in <FIG>. <FIG> show step ST105 in <FIG>, and <FIG>show step ST106 in <FIG>. <FIG> and <FIG> show step ST107 in <FIG>. <FIG> shows step ST108 in <FIG>, and <FIG> shows step ST110 in <FIG>.

First, a wiring layer is formed on the SOI substrate <NUM> being a device substrate (step ST101). Subsequently, as shown in <FIG>, the Pt film <NUM> as the electrode is formed on the principal surface of the SOI substrate <NUM>.

Further, the SRO film <NUM>, the monocrystalline PZT film <NUM> and the Pt film <NUM> are grown epitaxially on the growth substrate <NUM> as a first growth substrate as shown in <FIG> (step ST103), and the monocrystalline PZT film <NUM> and the Pt film <NUM> are formed into a circular shape by means of etching as shown in <FIG> (step ST104).

Furthermore, the SRO film <NUM>, the monocrystalline AlN film <NUM> and the Pt film <NUM> are grown epitaxially on the growth substrate <NUM> as a second growth substrate as shown in <FIG> (step ST105), and the monocrystalline AlN film <NUM> and the Pt film <NUM> are formed into a circular shape by means of etching (step ST106) as shown in <FIG>.

Subsequently, an individual piece (i.e., a piezoelectric element as the AlN epitaxial growth film) formed with the monocrystalline AlN film <NUM> and the Pt film <NUM> is held by a stamp <NUM> as a holding member as shown in <FIG>, the individual piece is peeled off by etching the SRO film <NUM> as a sacrificial layer as shown in <FIG> and is moved onto the SOI substrate <NUM> (step ST107), and the individual piece (i.e., the piezoelectric element as the epitaxial growth film) formed with the monocrystalline AlN film <NUM> and the Pt film <NUM> is stuck (or bonded) on the Pt film <NUM> as shown in <FIG>.

Subsequently, an individual piece (i.e., the second piezoelectric element in the first embodiment) formed with the monocrystalline PZT film <NUM> and the Pt film <NUM> is held by the stamp <NUM> as the holding member as shown in <FIG>, and the individual piece is peeled off by etching the SRO film <NUM> as a sacrificial layer as shown in <FIG> and is moved onto the SOI substrate <NUM> being the device substrate as shown in <FIG> (step ST109).

Subsequently, as shown in <FIG>, the individual piece (i.e., the piezoelectric element as the epitaxial growth film) formed with the monocrystalline PZT film <NUM> and the Pt film <NUM> is stuck (or bonded) on the Pt film <NUM> (step ST110). Subsequently, the insulation film 35a and the wiring film 36a are formed on the monocrystalline PZT film <NUM> and the Pt film <NUM>, and the insulation film 35b and the wiring film 36b are formed on the monocrystalline AlN film <NUM> and the Pt film <NUM>.

<FIG> is a diagram showing crystal c-axes of the monocrystalline PZT film <NUM> as the first monocrystalline piezoelectric film and the monocrystalline AlN film <NUM> as the second monocrystalline piezoelectric film. As shown in <FIG>, at the time of the sticking, the hexagonal crystal of AlN and the cubic crystal of PZT are arranged in a phase relationship so that their c-axes are parallel to each other as illustrated, by which efficiency of the piezoelectric oscillation driving of the monocrystalline PZT film <NUM> and the piezoelectric oscillation reception of the monocrystalline AlN film <NUM> is maximized.

As shown in <FIG>, the SOI substrate <NUM> is etched up to the SiO<NUM> part <NUM>, thereby thinning down a back side of the piezoelectric element and forming the vibrating plate. The thickness of the vibrating plate can be set at a desired thickness by controlling the thickness of each layer of the SOI substrate <NUM>.

<FIG> schematically shows the configuration of the acoustic oscillation sensor <NUM> employing a semiconductor integrated device according to the first embodiment. <FIG> shows a principle of operation of the acoustic oscillation sensor. Upper and lower electrodes of the monocrystalline PZT film <NUM> are connected to a drive-reception circuit <NUM> and an AC bias at a frequency in the audible range or a frequency higher than the audible range is applied to the electrodes of the monocrystalline PZT film <NUM>, by which the monocrystalline PZT film <NUM> oscillates in its thickness direction and the SiO<NUM> part <NUM> also oscillates in a similar manner. Due to the oscillation, the acoustic oscillatory wave is radiated and reflected waves bounced off a detection target object <NUM> oscillate the vibrating plate of the SOI substrate <NUM> having the monocrystalline AlN film <NUM> stuck thereon. Electric charge excited in the monocrystalline AlN film <NUM> due to the oscillation is amplified by the drive-reception circuit <NUM>, and a control circuit <NUM> computes a distance to the detection target object <NUM> based on a time difference Δt regarding the reception of the reflected waves. The control circuit <NUM> and the drive-reception circuit <NUM> are formed by an electric circuit or an information processing device.

<FIG> is a side view schematically showing the structure of a piezoelectric film integrated device 100a according to a modification of the first embodiment. <FIG> is a top view schematically showing the structure of the piezoelectric film integrated device 100a. <FIG> is a cross-sectional view of the piezoelectric film integrated device 100a in <FIG> taken along the line S28-S28. <FIG> is a bottom view schematically showing the structure of the piezoelectric film integrated device 100a. When the SOI substrate <NUM> is etched up to the SiO<NUM> part <NUM>, a cavity <NUM> may also be formed into a shape other than the circular shape, such as a quadrangular shape. The shape of the cavity <NUM> is desired to be a shape corresponding to a two-dimensional shape of the piezoelectric element.

As described above, the monocrystalline PZT film <NUM> and the monocrystalline AlN film <NUM>, which are unlikely to grow epitaxially on the same SOI substrate <NUM> because of the difference in the lattice constant and the crystal structure, are respectively grown in monocrystalline epitaxial growth on separate growth substrates, peeled off from the growth substrates, and stuck (or bonded) on a common SOI substrate <NUM> in superimposition with each other, by which a high-performance piezoelectric film integrated device <NUM> can be manufactured.

Further, since the monocrystalline PZT film <NUM> has a higher piezoelectric constant compared to a polycrystalline PZT film, amplitude of the oscillation can be increased with ease.

Furthermore, since the monocrystalline AlN film <NUM> has lower specific inductive capacity compared to a polycrystalline AlN film, the oscillation reception sensitivity can be increased.

Moreover, conventionally, in order to form piezoelectric films of different types, a process like temporarily covering one piezoelectric film with a protective layer, forming the other piezoelectric film, and thereafter removing the protective layer used to be a complicated process, and application of heat in processing in each step used to leave residual stress distortion in the piezoelectric films and cause deterioration in the efficiency of the sensor. In the manufacturing method in the first embodiment, the sticking of the epitaxial growth films as the piezoelectric elements is employed, and thus the piezoelectric film integrated device and the acoustic oscillation sensor can be formed in a state with no residual stress distortion.

<FIG> is a side view schematically showing the structure of a piezoelectric film integrated device <NUM>. <FIG> is a top view schematically showing the structure of the piezoelectric film integrated device <NUM>. <FIG> is a cross-sectional view of the piezoelectric film integrated device <NUM> in <FIG> taken along the line S32-S32.

In the first embodiment, the AlN epitaxial growth film including the monocrystalline AlN film <NUM> and the Pt film <NUM> is grown on the growth substrate <NUM> and is stuck (or bonded) on the Pt film <NUM> on the SOI substrate <NUM>, and the PZT epitaxial growth film including the monocrystalline PZT film <NUM> and the Pt film <NUM> is grown on the growth substrate <NUM> and is stuck (or bonded) on the AlN epitaxial growth film that has been stuck (or bonded) on the Pt film <NUM> on the SOI substrate <NUM>. Alternatively, in the first embodiment, the AlN epitaxial growth film is stuck (or bonded) on the PZT epitaxial growth film that has been stuck (or bonded) on the Pt film <NUM> on the SOI substrate <NUM>. In contrast, in a second embodiment, the PZT epitaxial growth film is grown on an SOI substrate <NUM>. The upper surface of the SOI substrate <NUM> is formed by a (<NUM>) -surface. Therefore, the PZT epitaxial growth film can be grown epitaxially on the SOI substrate <NUM> by a process similar to the process in the first embodiment.

<FIG> is a flowchart showing a method of manufacturing the piezoelectric film integrated device <NUM>. <FIG> shows step ST201 in <FIG>, and <FIG> shows step ST202 in <FIG>. <FIG> shows step ST207 in <FIG>.

First, as shown in <FIG>, the ZrO<NUM> film <NUM> and the Pt film <NUM> as an electrode layer are formed on the principal surface of the SOI substrate <NUM> being the device substrate (step ST201). Further, an epitaxial growth film made up of the SRO film <NUM>, the monocrystalline PZT film <NUM> and the Pt film <NUM> is formed by epitaxially growing the SRO film <NUM>, the monocrystalline PZT film <NUM> and the Pt film <NUM> on the Pt film <NUM> (step ST201). Subsequently, as shown in <FIG>, the epitaxial growth film including the monocrystalline PZT film <NUM> is formed into a desired shape (e.g., circular shape) by means of etching (step ST202). Subsequently, the Pt film <NUM> as an electrode is formed by etching the Pt film <NUM> as the electrode layer, and a wiring layer is formed on the SOI substrate <NUM> (step ST203).

Subsequently, the individual piece of the AlN epitaxial growth film (upper-side piezoelectric element) made up of the monocrystalline AlN film <NUM> and the Pt film <NUM> is held by the stamp <NUM> as the holding member, and the individual piece of the AlN epitaxial growth film is peeled off by etching the SRO film <NUM> as the sacrificial layer and is moved onto and stuck (or bonded) on the PZT epitaxial growth film on the SOI substrate <NUM> being the device substrate as shown in <FIG> (steps ST204 to ST207). Namely, the piezoelectric element including the monocrystalline AlN film <NUM> and the Pt film <NUM> described in the first embodiment is stuck (or bonded) on the Pt film <NUM>. At the time of the sticking, the crystal orientation of the monocrystalline PZT film <NUM> is checked by an inspection or the like, and the crystal orientation of the monocrystalline PZT film <NUM> and the crystal orientation of the monocrystalline AlN film <NUM> are aligned with each other as shown in <FIG>. Since the orientation of the monocrystalline PZT film <NUM> is fixed on the SOI substrate <NUM>, the angle of the sticking of the monocrystalline AlN film <NUM> is adjusted. It is also possible to check the crystal orientation at the time of the etching process shown in <FIG> and thereafter form the piezoelectric film to be in the same orientation as in the first embodiment by using a mask. As shown in <FIG>, the insulation film 35a and the wiring film (lead wiring) 36a are formed on the monocrystalline PZT film <NUM> and the Pt film <NUM>, and the insulation film 35b and the wiring film (lead wiring) 36b are formed on the monocrystalline AlN film <NUM> and the Pt film <NUM>.

Thereafter, the manufacture of the piezoelectric film integrated device <NUM> shown in <FIG> is completed by etching the SOI substrate <NUM> similarly to the first embodiment.

In the second embodiment, the epitaxial growth film including the monocrystalline AlN film <NUM> is stuck on the Pt film <NUM> on the SOI substrate <NUM> having the epitaxially grown monocrystalline PZT film <NUM> thereon, by which a monocrystalline and high-performances piezoelectric film integrated device can be obtained similarly to the first embodiment.

In the second embodiment, alignment accuracy of the monocrystalline PZT film <NUM> increases compared to the first embodiment. Therefore, in the second embodiment, the acoustic oscillatory wave output performances increases compared to the first and third embodiments.

Except for the above-described features, the second embodiment is the same as the first embodiment.

<FIG> is a side view schematically showing the structure of a piezoelectric film integrated device <NUM>. <FIG> is a top view schematically showing the structure of the piezoelectric film integrated device <NUM>. <FIG> is a cross-sectional view of the piezoelectric film integrated device in <FIG> taken along the line S39-S39.

In the first embodiment, the AlN epitaxial growth film is grown on the growth substrate <NUM>, the PZT epitaxial growth film is grown on the growth substrate <NUM>, and the PZT epitaxial growth film is stuck (or bonded) on the AlN epitaxial growth film that has been stuck (or bonded) on the Pt film <NUM> on the SOI substrate <NUM>. Alternatively, in the first embodiment, the AlN epitaxial growth film is stuck (or bonded) on the PZT epitaxial growth film that has been stuck (or bonded) on the Pt film <NUM> on the SOI substrate <NUM>. In contrast, in a third embodiment, the PZT epitaxial growth film is grown on an SOI substrate <NUM>. The upper surface of the SOI substrate <NUM> is formed by a (<NUM>)-surface. Therefore, the AlN epitaxial growth film can be grown epitaxially on the SOI substrate <NUM> by a process similar to the process in the first embodiment.

<FIG> is a flowchart showing a method of manufacturing the piezoelectric film integrated device <NUM>. <FIG> shows step ST301 in <FIG>, and <FIG> shows step ST302 in <FIG>. <FIG> shows step ST307 in <FIG>.

First, as shown in <FIG>, the ZrO<NUM> film <NUM> and the Pt film <NUM> as an electrode layer are formed on the principal surface of the SOI substrate <NUM> being the device substrate. Further, an epitaxial growth film made up of the SRO film <NUM>, the monocrystalline AlN film <NUM> and the Pt film <NUM> is formed by epitaxially growing the SRO film <NUM>, the monocrystalline AlN film <NUM> and the Pt film <NUM> on the Pt film <NUM> (step ST301). Subsequently, as shown in <FIG>, the epitaxial growth film including the monocrystalline AlN film <NUM> is formed into a desired shape (e.g., circular shape) by means of etching (step ST302). Subsequently, the Pt film <NUM> as the first electrode is formed by etching the Pt film <NUM> as the electrode layer, and a wiring layer is formed on the SOI substrate <NUM> (step ST303).

Subsequently, the individual piece of the PZT epitaxial growth film (upper-side piezoelectric element) made up of the monocrystalline PZT film <NUM> and the Pt film <NUM> is held by the stamp <NUM> as the holding member, and the individual piece of the PZT epitaxial growth film is peeled off by etching the SRO film <NUM> as the sacrificial layer and is moved onto and stuck (or bonded) on the AlN epitaxial growth film on the SOI substrate <NUM> being the device substrate as shown in <FIG> (steps ST304 to ST307). Namely, the piezoelectric element including the monocrystalline PZT film <NUM> and the Pt film <NUM> described in the first embodiment is stuck (or bonded) on the Pt film <NUM>. At the time of the sticking, the crystal orientation of the monocrystalline PZT film <NUM> is checked by an inspection or the like, and the crystal orientation of the monocrystalline PZT film <NUM> and the crystal orientation of the monocrystalline AlN film <NUM> are aligned with each other as shown in <FIG>. Since the orientation of the monocrystalline AlN film <NUM> is fixed on the SOI substrate <NUM>, the angle of the sticking of the monocrystalline PZT film <NUM> is adjusted. It is also possible to check the crystal orientation at the time of the etching process shown in <FIG> and thereafter form the piezoelectric film to be in the same orientation as in the first embodiment by using a mask. As shown in <FIG>, the insulation film 35a and the wiring film (lead wiring) 36a are formed on the monocrystalline PZT film <NUM> and the Pt film <NUM>, and the insulation film 35b and the wiring film (lead wiring) 36b are formed on the monocrystalline AlN film <NUM> and the Pt film <NUM>.

In the third embodiment, the epitaxial growth film including the monocrystalline PZT film <NUM> is stuck (or bonded) on the AlN epitaxial growth film including the epitaxially grown monocrystalline AlN film <NUM> and the Pt film <NUM>, by which a high-performances piezoelectric film integrated device <NUM> can be obtained by use of a plurality of monocrystalline piezoelectric films similarly to the first embodiment.

In the third embodiment, the alignment accuracy of the monocrystalline AlN film <NUM> increases compared to the first embodiment. Therefore, in the third embodiment, the acoustic oscillatory wave detection sensitivity and the S/N ratio increase compared to the first and second embodiments.

Except for the above-described features, the third embodiment is the same as the first or second embodiment.

A piezoelectric film integrated device <NUM> according to a first modification differs from the piezoelectric film integrated device <NUM> according to the first embodiment in which the epitaxial growth film stuck (or bonded) on the Pt film <NUM> is formed with the monocrystalline AlN film <NUM> and the Pt film <NUM> and the epitaxial growth film stuck (or bonded) on the Pt film <NUM> is formed with the monocrystalline PZT film <NUM> and the Pt film <NUM>, in that the epitaxial growth film stuck (or bonded) on the Pt film <NUM> on the SOI substrate <NUM> is formed with a Pt film <NUM>, the monocrystalline AlN film <NUM> and the Pt film <NUM> and the epitaxial growth film stuck (or bonded) on the Pt film <NUM> is formed with a Pt film <NUM>, the monocrystalline PZT film <NUM> and the Pt film <NUM>. Except for these features, the piezoelectric film integrated device <NUM> according to the first modification is the same as the piezoelectric film integrated device <NUM> according to the first embodiment.

<FIG> is a cross-sectional view showing a state in which the Pt film <NUM>, the SRO film <NUM>, the Pt film <NUM>, the monocrystalline PZT film <NUM> and the Pt film <NUM> have successively been grown epitaxially on the ZrO<NUM> film <NUM> on the Si substrate <NUM>. <FIG> is a cross-sectional view showing a state in which the Pt film <NUM>, the SRO film <NUM>, the Pt film <NUM>, the monocrystalline AlN film <NUM> and the Pt film <NUM> have successively been grown epitaxially on the ZrO<NUM> film <NUM> on the Si substrate <NUM>.

<FIG> is a cross-sectional view schematically showing the structure of the piezoelectric film integrated device <NUM> according to the first modification. <FIG> is a top view schematically showing the structure of the piezoelectric film integrated device <NUM> in <FIG>. In <FIG>, each component identical or corresponding to a component shown in <FIG> (first embodiment) is assigned the same reference character as in <FIG>. In the piezoelectric film integrated device <NUM> according to the first modification, the epitaxial growth film formed with the Pt film <NUM>, the monocrystalline AlN film <NUM> and the Pt film <NUM> (shown in <FIG>) is stuck (or bonded) on the Pt film <NUM>, and the epitaxial growth film formed with the Pt film <NUM>, the monocrystalline PZT film <NUM> and the Pt film <NUM> (shown in <FIG>) is stuck (or bonded) on the Pt film <NUM>. Except for these features, the piezoelectric film integrated device <NUM> according to the first modification is the same as the piezoelectric film integrated device <NUM> according to the first embodiment.

Incidentally, it is also possible to use the epitaxial growth film formed with the Pt film <NUM>, the monocrystalline PZT film <NUM> and the Pt film <NUM> (shown in <FIG>) instead of the epitaxial growth film formed with the monocrystalline PZT film <NUM> and the Pt film <NUM> in the piezoelectric film integrated device <NUM> or <NUM> according to the second or third embodiment (shown in <FIG> or <FIG>). Further, it is also possible to use the epitaxial growth film formed with the Pt film <NUM>, the monocrystalline AlN film <NUM> and the Pt film <NUM> (shown in <FIG>) instead of the epitaxial growth film formed with the monocrystalline AlN film <NUM> and the Pt film <NUM> in the piezoelectric film integrated device <NUM> or <NUM> according to the second or third embodiment (shown in <FIG> or <FIG>).

The piezoelectric film integrated devices <NUM>, <NUM> and <NUM> and the acoustic oscillation sensors <NUM> according to the embodiments are usable not only for a distance sensor but also for other types of sensors such as a fingerprint sensor and a vein (pulse wave) sensor.

Further, with a piezoelectric film integrated device in which pairs of the monocrystalline PZT film <NUM> and the monocrystalline AlN film <NUM> are arranged in a matrix, a surface shape of the detection target object can be detected.

Claim 1:
A piezoelectric film integrated device (<NUM>, 100a, <NUM>, <NUM>, <NUM>) comprising:
a substrate (<NUM>, <NUM>, <NUM>);
an electrode (<NUM>) provided on the substrate (<NUM>, <NUM>, <NUM>);
a first piezoelectric element that is provided on the electrode (<NUM>) and includes a first monocrystalline piezoelectric film (<NUM> or <NUM>) and a first electrode film (<NUM> or <NUM>) superimposed on the first monocrystalline piezoelectric film (<NUM> or <NUM>); and
a second piezoelectric element that is provided on the first piezoelectric element and includes a second monocrystalline piezoelectric film (<NUM> or <NUM>) and a second electrode film (<NUM> or <NUM>) superimposed on the second monocrystalline piezoelectric film (<NUM> or <NUM>),
characterised in that
the second monocrystalline piezoelectric film (<NUM> or <NUM>) has a crystal structure different from a crystal structure of the first monocrystalline piezoelectric film (<NUM> or <NUM>).