JP6488657B2 - Actuator - Google Patents

Description

  The present invention relates to an actuator having a cantilever structure.

  A cantilever structure in which a cantilever including a piezoelectric element is fixed on a substrate such as silicon using a micro-electromechanical system (MEMS) microfabrication technology that combines an electric circuit element and a fine mechanical element. The actuator (displacement element) is already known.

  For example, Patent Document 1 discloses a cantilever actuator in which a substrate is protruded or retracted with respect to a length direction of the cantilever in a fixing portion of the cantilever.

  However, in the actuator of the above-mentioned Cited Document 1, in the fixing portion of the cantilever to the substrate, film peeling occurs at each interface of the piezoelectric element itself, the electrode film sandwiching the piezoelectric element, and the protective film due to the stress due to the displacement of the piezoelectric element. There was a problem that occurred.

  An object of the present invention is to solve the above-described problems and provide an actuator that can suppress film peeling at the fixing portion by reducing the stress at the fixing portion of the cantilever to the substrate.

The actuator according to one aspect of the present invention is
An actuator comprising a piezoelectric vibration member including an upper electrode and a lower electrode formed so as to sandwich a piezoelectric element, and a vibration plate that vibrates by the piezoelectric vibration member,
The diaphragm is formed so that the thickness of the diaphragm changes in a step shape at a predetermined boundary in the longitudinal direction of the diaphragm,
The upper electrode and the lower electrode have overlapping regions that overlap in the thickness direction of the diaphragm,
The overlapping region is formed at a position deviating from the boundary in the longitudinal direction of the diaphragm.

  According to the present invention, it is possible to reduce the stress at the adhesion interface of each layer, so that film peeling of each layer from the adhesion interface can be suppressed.

It is a top view of the actuator which concerns on embodiment of this invention. It is a longitudinal cross-sectional view of an actuator when it cuts along the A-A 'line of FIG. 1A. FIG. 1B is a top view illustrating a first step in the method for manufacturing the actuator of FIG. 1A. It is a longitudinal cross-sectional view of an actuator when it cuts along the B-B 'line of FIG. 2A. FIG. 1B is a top view illustrating a second step in the method for manufacturing the actuator of FIG. 1A. It is a longitudinal cross-sectional view of an actuator when it cuts along the C-C 'line of FIG. 3A. FIG. 3 is a top view illustrating a third step in the method for manufacturing the actuator of FIG. 1A. FIG. 4B is a longitudinal sectional view of the actuator when cut along the line D-D ′ in FIG. 4A. FIG. 3A is a top view illustrating a fourth step in the method for manufacturing the actuator in FIG. 1A. It is a longitudinal cross-sectional view of an actuator when it cuts along the E-E 'line of FIG. 5A. It is a top view of the actuator which concerns on the modification 1 of embodiment of this invention. FIG. 6B is a longitudinal sectional view of the actuator when cut along the line F-F ′ of FIG. 6A. It is a top view of an actuator concerning modification 2 of an embodiment of the present invention. It is a longitudinal cross-sectional view of an actuator when it cuts along the G-G 'line | wire of FIG. 7A. It is a top view of the actuator which concerns on the modification 3 of embodiment of this invention. It is a longitudinal cross-sectional view of an actuator when it cuts along the H-H 'line | wire of FIG. 8A.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In addition, in each following embodiment, the same code | symbol is attached | subjected about the same component.

Embodiment.
FIG. 1A is a top view of an actuator according to an embodiment of the present invention, and FIG. 1B is a longitudinal sectional view of the actuator when cut along the line AA ′ of FIG. 1A. In FIG. 1A and FIG. 1B, the actuator includes a piezoelectric vibrating body 6 and a silicon substrate 1 that is a vibrating plate that vibrates by the piezoelectric vibrating body 6. The piezoelectric vibrator 6 includes, for example, a piezoelectric element 3 such as lead zirconate titanate (PZT), an upper electrode 4 and a lower electrode 2 formed of a metal such as platinum, rhodium, ruthenium, and iridium. And a protective film (passivation film) 5 such as a film. Here, each layer constituting the piezoelectric vibrating body 6 has a rectangular shape.

  1A and 1B, the piezoelectric element 3 is formed between the upper electrode 4 and the lower electrode 2, and the piezoelectric element 3 expands and contracts in the length direction by applying a predetermined voltage between the upper electrode 4 and the lower electrode 2. Then, bending displacement is generated in the cantilever part 10 described later. The silicon substrate 1 is formed such that the thickness of the silicon substrate 1 changes in a stepped manner in the longitudinal direction of the silicon substrate 1 with the cantilever fixed end B as a boundary. Here, the lower electrode 2 and the piezoelectric element 3 are formed across the cantilever fixed end B, and the upper electrode 4 is not formed across the cantilever fixed end B. That is, an overlapping region OA where the upper electrode 4 and the lower electrode 2 overlap in the thickness direction of the silicon substrate 1 is formed at a position deviated from the boundary in the longitudinal direction of the silicon substrate 1.

  As described above, the actuator shown in FIGS. 1A and 1B includes the fixed portion 20 including the first film thickness portion 1a and the second film thickness portion 1b having a smaller film thickness than the first film thickness portion 1a. And a cantilever portion 10. That is, in the longitudinal direction of the silicon substrate 1, the fixing portion 20 is located on one side of the boundary and the cantilever portion 10 is located on the other side of the boundary, and the overlapping region OA is formed in the cantilever portion 10. To position. With this configuration, only the stress due to the displacement of the piezoelectric element 3 at the cantilever portion 10 is generated at the cantilever fixed end B. Accordingly, excessive stress is not generated at the adhesion interface of each layer of the lower electrode 2, the piezoelectric element 3, the upper electrode 4, and the protective film 5 formed across the cantilever fixed end B. It becomes possible to suppress film peeling.

  2A to 5A are top views illustrating steps of the manufacturing method of the actuator of FIG. 1A, and FIGS. 2B to 5B are BB ′, CC ′, and DD of FIGS. 2A to 5A. , EE ′ is a longitudinal sectional view of the actuator when cut along each line. Next, the manufacturing method of the actuator of FIG. 1A will be described below with reference to these drawings.

  2A and 2B, a metal such as platinum, rhodium, ruthenium, and iridium is deposited on the silicon substrate 1 using a sputtering method, a vacuum evaporation method, or the like. Next, the lower electrode 2 is formed on the silicon substrate 1 by patterning using a photolithography process and a dry etching method.

  In FIGS. 3A and 3B, for example, lead zirconate titanate (PZT) is deposited using, for example, sputtering, ion plating, air sol, sol-gel, or the like. Next, the piezoelectric element 3 is formed on the lower electrode 2 by patterning using a photolithography process and a dry etching method.

  4A and 4B, a piezoelectric element 3 is formed by depositing a metal such as platinum, rhodium, ruthenium, or iridium using a sputtering method or a vacuum evaporation method, and patterning the metal using a photolithography process, a dry etching method, or the like. An upper electrode 4 is formed thereon. Here, the upper electrode 4 is patterned so as to be formed on a thinned silicon substrate 1 to be described later, thereby forming an overlapping region OA in which the upper electrode 4 and the lower electrode 2 overlap in the thickness direction of the silicon substrate 1. Is done.

  5A and 5B, a protective film (passivation film) 5 such as an oxide film is deposited using, for example, LPCVD. Next, the silicon substrate 1 is partially (selectively) etched from the back side using a silicon deepening technique such as a wet etching technique or an ICP dry etching technique. That is, the silicon substrate 1 is thinned so that the thickness of the silicon substrate 1 changes stepwise in the longitudinal direction of the silicon substrate 1 with the cantilever fixed end B as a boundary. Accordingly, the silicon substrate 1 has the first film thickness portion 1a and the second film thickness portion 1b having a film thickness smaller than that of the first film thickness portion 1a. Further, the actuator includes a fixed portion 20 made of the first film thickness portion 1a and a cantilever portion 10 made of the second film thickness portion 1b.

  According to the actuator according to the above embodiment, since the upper electrode 4 is not formed on the cantilever fixed end B, even if a voltage is applied between the upper electrode 4 and the lower electrode 2, only the cantilever portion 10 has a piezoelectric element. 3 contraction due to the inverse piezoelectric effect occurs. Accordingly, excessive stress is not generated at the adhesion interface of each layer of the lower electrode 2, the piezoelectric element 3, and the protective film 5 formed across the cantilever fixed end B, so that delamination of each layer from the adhesion interface is suppressed. It becomes possible to do.

Modification 1
6A is a top view of an actuator according to Modification 1 of the embodiment of the present invention, and FIG. 6B is a longitudinal sectional view of the actuator when cut along the line FF ′ of FIG. 6A. The actuator shown in FIGS. 6A and 6B is different from the actuator shown in FIGS. 1A and 1B in the following points. 1A and 1B, the lower electrode 2 and the piezoelectric element 3 are formed over the cantilever fixed end B, and the upper electrode 4 is not formed over the cantilever fixed end B. On the other hand, in this modification, the upper electrode 4 and the piezoelectric element 3 are formed over the cantilever fixed end B, and the lower electrode 2 is not formed over the cantilever fixed end B. . The actuator according to the first modification of the embodiment of the present invention performs the same operation as that of the actuator according to the above-described embodiment, and can obtain the same effects.

Modification 2
7A is a top view of an actuator according to Modification 2 of the embodiment of the present invention, and FIG. 7B is a longitudinal sectional view of the actuator when cut along the line GG ′ of FIG. 7A. 7A and 7B is characterized in that, compared with the actuator of FIGS. 1A and 1B, both ends of the piezoelectric element 3 are formed in a ladder shape instead of being formed in a linear shape at both ends. And 7A and 7B, one end of the piezoelectric element 3 on the fixed portion 20 side has a ladder shape. The actuator according to the second modification of the embodiment of the present invention can perform the same operation as the actuator according to the above-described embodiment, and can obtain the same effects. Furthermore, compared with the actuator according to the above-described embodiment, the stress at the adhesion interface of each layer of the lower electrode 2, the piezoelectric element 3, and the protective film 5 can be further reduced. Further suppression is possible.

Modification 3
FIG. 8A is a top view of an actuator according to Modification 2 of the embodiment of the present invention, and FIG. 8B is a longitudinal sectional view of the actuator when cut along the line HH ′ of FIG. 8A. The actuator shown in FIGS. 8A and 8B includes a piezoelectric element 3 in which an opening 7 is provided in a part on the fixed portion 20 side instead of the linear piezoelectric element 3 as compared with the actuator shown in FIGS. 1A and 1B. It is characterized by that. The actuator according to the third modification of the embodiment of the present invention can perform the same operation as the actuator according to the above-described embodiment, and can obtain the same effects. Furthermore, compared with the actuator according to the above-described embodiment, the stress at the adhesion interface of each layer of the lower electrode 2, the piezoelectric element 3, and the protective film 5 can be further reduced. Further suppression is possible.

  In the modification described above, only the piezoelectric element 3 is patterned to relieve stress at the adhesion interface of each layer, but the present invention is not limited to this. For example, the stress at the adhesion interface of each layer may be relieved by patterning the lower electrode 2 and the upper electrode 4 formed so as to sandwich the piezoelectric element 3. Even in this case, the same effect as the above-described modification can be obtained.

Summary of Embodiment The actuator according to the first aspect is:
An actuator comprising a piezoelectric vibration member including an upper electrode and a lower electrode formed so as to sandwich a piezoelectric element, and a vibration plate that vibrates by the piezoelectric vibration member,
The diaphragm is formed so that the thickness of the diaphragm changes in a step shape at a predetermined boundary in the longitudinal direction of the diaphragm,
The upper electrode and the lower electrode have overlapping regions that overlap in the thickness direction of the diaphragm,
The overlapping region is formed at a position deviating from the boundary in the longitudinal direction of the diaphragm.

The actuator according to the second aspect is the actuator according to the first aspect,
The diaphragm has a first film thickness part and a second film thickness part having a film thickness smaller than the first film thickness part,
The overlapping region is formed in the second film thickness portion.

The actuator according to the third aspect is the actuator according to the first or second aspect,
In the longitudinal direction, it has a fixed part located on one of the boundaries, and a cantilever part located on the other of the boundaries,
The overlapping region is located in the cantilever part.

The actuator according to the fourth aspect is the actuator according to any one of the first to third aspects,
One end of the piezoelectric element has a rectangular shape.

The actuator according to the fifth aspect is the actuator according to any one of the first to third aspects,
One end of the piezoelectric element has a ladder shape.

1 ... silicon substrate,
2 ... lower electrode,
3 ... piezoelectric element,
4 ... Upper electrode,
5 ... protective layer,
6 ... piezoelectric vibrator,
7 ... opening,
10 ... cantilever part,
20: Fixed part.

JP-A-6-273160

Claims (6)

A piezoelectric vibrator including an upper electrode and a lower electrode is formed to the piezoelectric element for clamping, an actuator and a diaphragm that vibrates by the piezoelectric vibrator,
The diaphragm is formed in the predetermined boundary in the longitudinal direction of the vibrating plate so that the thickness of the diaphragm is changed stepwise,
It said upper electrode and said lower electrode has an overlapping area that overlaps in the thickness direction of the diaphragm,
The overlapping region is formed in a position deviated from the boundary in the longitudinal direction of the diaphragm,
In the longitudinal direction, it has a fixed part located on one side of the boundary, and a cantilever part located on the other side of the boundary,
The overlapping region is located in the cantilever part,
Any one of the upper electrode and the lower electrode, and the piezoelectric element are extended to the fixed portion across the boundary . The actuator according to claim 1, wherein any one of the upper electrode and the lower electrode and the piezoelectric element are formed in a stepped shape. The actuator according to claim 2, wherein any one of the upper electrode and the lower electrode and the piezoelectric element include a protective layer to be deposited. The diaphragm includes a first film thickness portion, and a second thickness portion having a smaller thickness than the first film thickness portion,
The overlap region, the actuator according to any one of claims 1-3, characterized in that formed on the second film thickness portion. The activator Interview error over data according to any one of claims 1-4, characterized in that one end of the piezoelectric element has a rectangular shape. The activator Interview error over data according to any one of claims 1-4, characterized in that one end of the piezoelectric element is a ladder shape.

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