JP5227566B2 - Actuator - Google Patents

Description

  The present invention relates to a micro-electro-mechanical system (MEMS) actuator such as an electrostatic drive type or piezoelectric drive type micro switch or a variable capacitor.

2. Description of the Related Art MEMS (Micro-electro-mechanical System) actuators are applied to various optical switches, communication circuits, micro switches used in electronic devices, variable capacitance capacitors, and the like.
A MEMS actuator driven by an electrostatic force (Patent Document 1) includes, for example, a movable electrode formed on a movable beam, a fixed electrode fixed on a substrate, and a dielectric film provided between the movable electrode and the fixed electrode. It has an electrostatic drive mechanism consisting of As this dielectric film, various films can be used in addition to silicon nitride and silicon oxide frequently used in a normal semiconductor process, but the orientation of the film is not considered.
By applying a driving voltage between the movable electrode and the fixed electrode, both electrodes are attracted by an electrostatic force to move the movable beam and drive it. At the time of driving, a driving voltage of several tens of volts is applied to the dielectric film having a thickness of about 0.1 μm to 1 μm or less, so that the dielectric film is exposed to a high electric field. Due to this high electric field, charges are injected and trapped at the interface and inside of the dielectric film according to the driving time.
The injected charge exerts the same action on the electrostatic drive mechanism as the drive voltage applied from the outside. Therefore, a threshold voltage (pull-in voltage) for attracting the movable electrode to the fixed electrode, and a threshold voltage ( (Pullout voltage) is significantly shifted. In a more remarkable case, a so-called sticking phenomenon occurs, in which even if the drive voltage is set to 0, the electrode does not operate while the electrodes are fixed. These drive voltage shifts and sticking phenomena are serious practical problems.

On the other hand, a MEMS actuator driven by piezoelectric power (Patent Document 2) uses a piezoelectric film sandwiched between electrode layers as a movable beam, and has a feature that it can be driven at a relatively low voltage. In this piezoelectric drive type MEMS actuator, the movable beam has a piezoelectric drive mechanism made of a piezoelectric film sandwiched between piezoelectric drive electrode layers. In this piezoelectric drive type MEMS actuator, it is known to use, for example, an AlN film as the piezoelectric film constituting the movable beam. Since the driving DC voltage is applied between the piezoelectric driving electrode layers sandwiching the piezoelectric film, even if charge injection / trapping occurs in the piezoelectric film, there is almost no influence on driving.
However, even in a variable capacitor element using a piezoelectric actuator of a MEMS drive type, an RF signal fixed electrode formed on a substrate and a movable electrode provided on a movable beam (sometimes also used as a piezoelectric drive electrode) A dielectric film for forming the capacitance of the variable capacitor is formed between them, and silicon nitride or silicon oxide frequently used in a normal semiconductor process is used. When the RF signal fixed electrode and the movable electrode are in contact with each other through a dielectric film, if a large amplitude RF voltage is applied between these electrodes, charge injection / trapping to the dielectric film occurs, which is a significant case. However, even if the piezoelectric driving voltage is set to 0, a sticking phenomenon occurs in which the electrodes do not operate while the electrodes are fixed, which is a serious problem in practical use.

On the other hand, in a thin film piezoelectric resonator, a technique for improving the performance of a piezoelectric film by providing an Al—Ta amorphous alloy layer on the base of the piezoelectric film has been reported (Patent Document 3).
JP 2004-172504 A JP 2006-346830 A JP 2006-19935 A

  The present invention is based on the above-mentioned problems, and its purpose is to eliminate charge injection and charge trapping in the dielectric film in an electrostatic drive type or piezoelectric drive type actuator, and drive voltage shift or electrode fixation. It is an object of the present invention to provide an actuator having stable driving characteristics.

According to one aspect of the present invention, a substrate, a fixed electrode provided on the main surface of the substrate, a movable beam facing the main surface and held above the substrate with a gap therebetween, Provided between the fixed electrode and the movable beam, and provided with a dielectric film made of aluminum nitride having c-axis orientation with a full width at half maximum of 4.6 degrees or less, and on the main surface, below the fixed electrode. There is provided an actuator comprising: a base film made of an aluminum compound .

According to another aspect of the present invention, the substrate, the RF signal fixed electrode provided on the main surface of the substrate, the counter electrode facing the main surface, and held above the substrate with a space therebetween. , A movable beam including a DC driving lower electrode, a piezoelectric film, and a DC driving upper electrode, and the RF signal fixed electrode and the movable beam. The full width at half maximum of the orientation is 4.6 degrees. Provided below is an actuator comprising: a dielectric film made of aluminum nitride with c-axis orientation; and a base film made of an aluminum compound provided below the RF signal fixed electrode on the main surface. Is done.

  According to the present invention, in an electrostatic drive type or piezoelectric drive type actuator, charge injection into a dielectric film or charge trap is eliminated, and problems of drive voltage shift and electrode sticking are solved, thereby enabling stable drive. An actuator having the characteristics is provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a schematic cross-sectional view illustrating the configuration of an actuator according to the first embodiment of the invention.
As shown in FIG. 1, the actuator 101 according to the first embodiment of the present invention has a substrate 110. A base film 130 is provided on the main surface of the substrate 110, a fixed electrode 140 is provided on the base film 130, and a dielectric film 150 is further provided on the fixed electrode 140. As the base film 130, for example, a film made of an amorphous alloy of aluminum / tantalum (Al / Ta) or aluminum nitride (AlN) can be used. As the fixed electrode 140, a film made of aluminum can be used. The dielectric film 150 can be made of an aluminum nitride film and has a small full width at half maximum and a c-axis orientation.

A movable beam 170 is disposed opposite the main surface of the substrate 110 with a gap from the substrate 110. A part of the movable beam 170 is joined by the anchor part 120 provided on the substrate 110, whereby the movable beam 170 is held with a gap from the substrate 110.
The actuator shown in FIG. 1 uses a film made of an aluminum / tantalum amorphous alloy or aluminum nitride as the base film 130, and the orientation of the fixed electrode 140 provided thereon can be increased. . Specifically, a c-axis orientation having an orientation full width at half maximum of 5 degrees or less is obtained. In addition, the dielectric film 150 provided on the fixed electrode 140 also has high orientation, and a c-axis orientation with a full width at half maximum of 5 degrees or less is obtained.

  When the full width at half maximum of the alignment of the dielectric film 150 is reduced and the orientation is increased, the density of charge traps in the dielectric film 150 decreases, and as a result, charge injection and charge trapping into the dielectric film 150 can be suppressed. This mechanism will be described with reference to FIG.

FIG. 2 is an explanatory diagram illustrating the relationship between the orientation of the dielectric film and the amount of charge injected into the dielectric film.
As shown in FIG. 2A, the amorphous silicon nitride (α-SiN) film 330 has a large number of dangling bonds serving as traps. When this α-SiN film is sandwiched between the upper electrode 310 and the lower electrode 320 and a voltage is applied, a large amount of charge 360 is injected and trapped. On the other hand, as shown in FIG. 2B, in the polycrystalline (poly) aluminum nitride (polyAlN) film 340, the crystal size is relatively large, the grain boundaries are reduced, and the injection amount of the charge 360 is reduced. To do. Furthermore, as shown in FIG. 2C, in the case of the highly oriented aluminum nitride film 350, the grain boundaries are further reduced, and the amount of charge 360 to be injected can be extremely reduced. Thus, in order to reduce the injection of electric charges into the dielectric film, it is effective to reduce the grain boundaries in the dielectric film and reduce the traps. That is, charge injection can be suppressed by reducing the full width at half maximum of the dielectric film.

The actuator illustrated in FIG. 1 can improve the orientation of the dielectric film 150 by using a film made of an aluminum / tantalum amorphous alloy or aluminum nitride as the base film 130, and charges are injected when a voltage is applied. It is difficult to suppress the formation of charge traps, and as a result, an actuator having excellent operational stability can be realized.
At this time, in order to ensure practical operational stability, the full width at half maximum of the orientation of the dielectric film 150 made of AlN is desirably 5 degrees or less.

  An example of a method for highly aligning the AlN film is a method using an amorphous metal base. Further, it is possible to use a method in which the orientation of a single crystal substrate such as a silicon (111) substrate or a silicon (100) substrate is taken over and epitaxially grown thereon. Furthermore, there is also a method in which a highly oriented AlN film is grown by taking the orientation film as a highly oriented film and taking over the orientation, and various metals or insulating films can be used as the underlying film in this case. For example, a method using a (111) plane of an fcc type crystal structure such as Al or Au, a method using a (110) plane of a bcc type crystal structure such as Mo, W, or Ta, a hexagonal type such as Ti or AlN Examples include a method using the (0001) plane of the crystal structure. In these methods, the orientation of the AlN film is affected by the crystal orientation of the underlying material, and the orientation of the AlN film improves as the thickness of the underlying material increases. Moreover, the method which combined said each method can be utilized.

  Note that the movable electrode 171 can be provided on the portion of the movable beam 170 facing the fixed electrode 140, but if the movable beam 170 is conductive, the movable beam 170 itself can be used as the movable electrode 171. The actuator illustrated in FIG. 1 is an example, and in this case, the movable electrode 171 is the same as the movable beam 170. Note that the movable electrode 171 may be provided separately on the movable beam 170.

  The dielectric film 150 is not necessarily provided on the substrate 110, and may be provided between the fixed electrode 140 and the movable electrode 171 (movable beam 170). For example, the dielectric film 150 may be provided on a portion of the movable beam 170 facing the fixed electrode 140. Further, in the case of a piezoelectric drive type actuator in which the movable beam 170 has a piezoelectric laminated structure, AlN may be used as the piezoelectric film and the AlN may be used as the dielectric film 150.

The actuator illustrated in FIG. 1 can be used as a microswitch or a capacitor. In addition to the movable electrode 171 (movable beam 170) and the fixed electrode (130), various electrodes can be further provided, and a switch or a capacitor using the electrodes can be configured.
In the present specification, the “actuator” includes not only the movable portion but also various switches and various capacitors configured to include the movable portion.

Example 1
Hereinafter, the first embodiment will be described in detail.
The actuator of Example 1 of the present invention has the structure shown in FIG. That is, the base film 130, the fixed electrode 140, and the dielectric film 150 are stacked on the main surface of the substrate 110, and the movable beam 170 is opposed to the main surface of the substrate 110 with a gap from the substrate 110. Are held by the anchor part 120.

FIG. 3 is a schematic cross-sectional view of each step showing the manufacturing method of the actuator of the first embodiment of the present invention.
First, as shown in FIG. 3A, a silicon nitride film was formed by LP-CVD (Low Pressure Chemical Vapor Deposition) on the main surface of a substrate 110 having an insulating surface, thereby forming an anchor portion 120. .
A base film 130, a fixed electrode 140, and a dielectric film 150 were formed in this order on the other part of the main surface of the substrate 110. That is, an amorphous alloy film made of Al / Ta having a thickness of 30 nm is formed as a base film 130 by a sputtering method, and then an Al film having a thickness of 500 nm is formed as a fixed electrode 140 by a sputtering method. Thereafter, an AlN film having a thickness of 500 nm was formed as the dielectric film 150 by sputtering. Lithography and reactive ion etching (RIE) were used for forming the anchor portion 120, the base film 130, the fixed electrode 140, and the dielectric film 150 into predetermined shapes. In addition, as a method of said film-forming and shaping | molding, not only the method demonstrated above but various methods can be used.

  Next, as shown in FIG. 3B, after the sacrificial layer 160 is formed on the main surface of the substrate 110, the anchor portion 120, and the dielectric film 150, the anchor portion 120 is formed by CMP (Chemical Mechanical Polishing) technology. Surface polishing and planarization were performed until exposed. As the sacrificial layer 160, polycrystalline silicon was used. However, the sacrificial layer 160 is not limited to this, and various inorganic materials, various metal materials, and various organic materials that can be selectively etched with respect to other film materials such as the base film 130, the fixed electrode 140, and the dielectric film 150 described above. Material can be used.

  Next, as shown in FIG. 3C, the movable beam 170 was formed on the anchor portion 120 and the sacrificial layer 160. Specifically, an Al layer having a thickness of 500 nm was formed by sputtering, and patterned by lithography and etching to form a movable beam 170 having a predetermined shape.

Next, as shown in FIG. 3D, the sacrificial layer 160 was removed by selective etching using XeF ₂ as an etching gas.
In this way, an actuator having the structure shown in FIG. 1 was produced.

  In the actuator of Example 1 having such a structure, by using an Al / Ta amorphous alloy as the base film, the fixed electrode 140 can be highly oriented in the (111) direction. When the orientation of the fixed electrode 140 was measured by the ω mode rocking curve method, the full width at half maximum (FWHM) was as small as 0.9 degrees, and a high orientation was confirmed. Further, by heteroepitaxially growing an AlN layer to be the dielectric film 150 on the fixed electrode 140, the AlN layer is highly oriented in the c-axis direction, and the full width at half maximum measured by the ω-mode rocking curve method is 1. It was 6 degrees. Thus, by using an Al / Ta amorphous alloy as a base film, a dielectric film 150 made of an AlN film having high orientation was obtained.

(Examples 2 to 4)
Next, Examples 2 to 4 will be described.
The second to fourth embodiments are different from the first embodiment in that AlN is used as the base film 130, and other conditions are the same as those of the first embodiment. And the thickness of the base film 130 of Examples 2-4 was 1000 nm, 500 nm, and 200 nm, respectively. These actuators of Examples 2 to 4 can provide the fixed electrode 140 and the dielectric film 150 having high orientation by using an AlN film having a thickness of 200 to 1000 nm as the base film 130.

Table 1 shows the relationship between the type and thickness of the base film 130 and the full width at half maximum of the alignment of the fixed electrode 140 and the dielectric film 150 in Examples 1 to 4 described above.

  As shown in Table 1, in the actuators of Examples 1 to 4, the dielectric film 150 had a full width at half maximum of 1.6 degrees to 4.6 degrees, and exhibited very high orientation. In addition, the fixed electrode 140 had a full width at half maximum of 0.9 to 3.8 degrees, and this also showed very high orientation.

Next, an operation test of the actuators of Examples 1 to 4 manufactured as described above was performed.
FIG. 4 is an explanatory diagram illustrating the operation test conditions of the actuator according to the embodiment of the invention.
As shown in FIG. 4, the operation test method is as follows.
(1) First, a voltage is gradually applied between the fixed electrode 140 and the movable electrode 171 (movable beam 170) to measure capacitance-applied voltage characteristics (CV measurement). The initial value of the pull-in voltage that contacts 150 is measured.
(2) Thereafter, a drive voltage of 15 V is applied as a load for 1000 seconds, and the drive voltage is removed.
(3) Then, voltage is gradually applied again, CV measurement is performed, and the pull-in voltage after the load test is measured.
In this way, the change in the pull-in voltage (shift amount ΔV) before and after the load test was obtained.

The relationship between the full width at half maximum of the dielectric film 150 of Examples 1 to 4 and the shift amount ΔV of the pull-in voltage before and after the load test will be described.
FIG. 5 is a graph showing the operation test results of the actuators of Examples 1 to 4 of the present invention.
As shown in FIG. 5, in each of the actuators of Examples 1 to 4, the full width at half maximum of the dielectric film 150 was 5 degrees or less, and the shift amount ΔV of the pull-in voltage was 0.5 V or less. Thus, it was confirmed that the actuators of Examples 1 to 4 were excellent in operational stability.

Next, a comparative example will be described.
(Comparative Examples 1-2)
The actuator of Comparative Example 1 uses AlN having a thickness of 100 nm as the base film 130 in the actuator shown in FIG. Comparative Example 2 has a structure in which no base film is provided.
Table 2 shows the types and thicknesses of the base film 130 of the actuators of Comparative Examples 1 and 2 and the values of the full width at half maximum of the alignment of the fixed electrode 140 and the dielectric film 150.

  As shown in Table 2, in the actuator of Comparative Example 1, the base film 130 is thin, and the full width at half maximum of the alignment of the fixed electrode 140 and the dielectric film 150 thereon is 5.1 degrees and 5.8, respectively. A large value was shown with the degree. Further, the actuator of Comparative Example 2 did not have the base film 130, and the full widths at half maximum of the fixed electrode 140 and the dielectric film 150 showed larger values of 6.2 degrees and 7.0 degrees, respectively. Thus, when there is no base film or when the film thickness of the base film is thin, the full width at half maximum of the orientation of the dielectric film 150 becomes large, and the orientation of the dielectric film 150 becomes low.

  Moreover, the shift amount ΔV of the pull-in voltage before and after the load test was obtained for Comparative Examples 1 and 2 under the same test conditions as in Examples 1 to 4 (however, the load voltage application time was shortened to 100 seconds). The result is shown in FIG. Although the load voltage application time is reduced to 1/10 and the load is reduced as compared with Examples 1 to 4, in Comparative Example 1, the shift amount ΔV of the pull-in voltage is as large as 1.5 V, and the reliability of the actuator I found that there was a problem with sex. In Comparative Example 2, it was found that the shift amount ΔV of the pull-in voltage is further large as 3.1 V, and similarly there is a problem in the reliability of the actuator.

  As shown in FIG. 5, when the full width at half maximum of the dielectric film 150 is greater than 5 degrees, the shift amount ΔV of the pull-in voltage is rapidly increased. Therefore, it is desirable that the full width at half maximum of the dielectric film 150 is 4.6 degrees or less. Further, as shown in Table 1, the full width at half maximum of the orientation of the fixed electrode 140 at this time is desirably 3.8 degrees or less. Further, when AlN is used as the base film 130, the thickness of the AlN film needs to be greater than a certain level, and specifically, the thickness is desirably 200 nm or more.

(Comparative Example 3)
The actuator of Comparative Example 3 is the same as that of Example 1 except that the silicon nitride film formed by the LP-CVD method is used as the dielectric film 150 in the actuator of Example 1.

  Under the same test conditions as in Examples 1 to 4 (however, the load voltage application time was reduced to 100 seconds), the shift amount ΔV of the pull-in voltage in Comparative Example 3 was determined. As a result, although the load voltage application time was shortened to 1/10 and the load was reduced as compared with Examples 1-4, the shift amount ΔV of the actuator of Comparative Example 3 was as large as 6.7 V, which was large. It has been found that charge injection occurs and there is a problem in the stability of operation. This is because many traps for charges are formed in the silicon nitride film, so that a large amount of charges are injected and trapped in the silicon nitride dielectric film. Therefore, it is desirable to use an AlN material for the dielectric film 150.

(Example 5)
Next, an actuator according to a fifth embodiment of the present invention will be described. The actuator of the fifth embodiment is an example of an electrostatic drive MEMS switch, and is an example in which a switch contact electrode is separately provided.
FIG. 6 is a schematic cross-sectional view illustrating the structure of the actuator of the fifth example of the invention. In the actuator 102 of this embodiment, a movable contact electrode 190 is provided at the tip of the movable beam 170. A fixed contact electrode 180 facing the movable contact electrode 190 is provided on the substrate 110. The movable contact electrode 190 and the fixed contact electrode 180 constitute a switch contact. Other configurations are the same as those in the first embodiment, and the same components are denoted by the same reference numerals. The movable contact electrode 190 and the fixed contact electrode 180 are, for example, Au layers produced by sputtering, and are formed by patterning using a well-known lithography method and lift-off method.

  The actuator is driven by applying a voltage between the movable electrode 171 (movable beam 170) facing the fixed electrode 140. At this time, the movable contact electrode 190 and the fixed contact electrode 180 are in ohmic contact, and can be used as a radio frequency (RF) switch.

  When the shift amount ΔV of the pull-in voltage was measured under the same test conditions as in Examples 1 to 4, the shift amount ΔV was as small as 0.3 V, and stable operation could be confirmed.

(Example 6)
Next, an actuator according to a sixth embodiment of the present invention will be described. The actuator of the present embodiment is an example of a piezoelectric drive MEMS variable capacitor.
FIG. 7 is a schematic cross-sectional view illustrating the structure of the actuator of the sixth example of the invention.
As illustrated in FIG. 7, the actuator 103 according to the sixth embodiment uses a movable beam 200 including a bimorph piezoelectric drive actuator instead of the movable beam 170 according to the first embodiment. That is, the bimorph type piezoelectric movable beam 200 is provided on the substrate 110 so as to face each other. The bimorph movable beam 200 has a structure in which a lower electrode 210, a lower piezoelectric film 220, an intermediate electrode 230, an upper piezoelectric film 240, and an upper electrode 250 are laminated. The bimorph movable beam 200 is held by the anchor portion 120 with a gap from the substrate 110. The lower electrode 210, the intermediate electrode 230, and the upper electrode 250 are made of Al, and the lower piezoelectric film 220 and the upper piezoelectric film 240 are made of AlN, and are formed in a predetermined shape by lithography and etching techniques. The configuration other than the bimorph movable beam 200 is the same as that of the first embodiment, and the fixed electrode 140 and the dielectric film 150 are a highly oriented Al film and an AlN film.

In the actuator 103 of this embodiment, the piezoelectric movable beam 200 can be bent up and down by grounding the intermediate electrode 230 and applying a drive voltage to the lower electrode 210 and the upper electrode 250. By this bending, the distance between the fixed electrode 140 and the lower electrode 210 provided on the substrate 110 changes, and functions as a capacitance variable capacitor.
Note that the lower electrode 210 functions as the movable electrode 171 facing the fixed electrode 140.

In this embodiment, the voltage (contact voltage) when the piezoelectric movable beam 200 is bent downward and the lower electrode 210 is in contact with the dielectric film 150 is 2.8V. While the lower electrode 210 is in contact with the dielectric film 150, an AC voltage with an amplitude of 10 V is applied between the fixed electrode 140 and the lower electrode 210 for 100 seconds to remove the AC voltage, and then the piezoelectric driving voltage is swept to obtain a contact voltage. Was 2.9 V, and there was almost no shift from the initial value of the contact voltage, and stable operation could be confirmed.
In this embodiment, the movable beam has a structure in which two piezoelectric films are stacked by three electrodes. However, the present invention is not limited to this, and a structure in which one piezoelectric film is sandwiched between two electrodes or A movable beam having various structures such as a structure in which three or more piezoelectric films are sandwiched between electrodes can be used.

  In this embodiment, the lower electrode 210, the intermediate electrode 230, and the lower piezoelectric film 220 function as a DC driving lower electrode, a DC driving upper electrode, and a piezoelectric film, respectively. Further, the intermediate electrode 230, the upper electrode 250, and the upper piezoelectric film 240 function as another DC driving lower electrode, another DC driving upper electrode, and another piezoelectric film, respectively. The fixed electrode 150 functions as an RF signal fixed electrode.

(Example 7)
Next, an actuator according to a seventh embodiment of the present invention will be described.
FIG. 8 is a schematic cross-sectional view illustrating the structure of the actuator of the seventh example of the invention.
As shown in FIG. 8, the actuator 104 according to the seventh embodiment includes a DC driving lower electrode 410, a piezoelectric film 420, and a DC driving upper electrode instead of the movable beam 170 according to the first embodiment shown in FIG. 430 and the movable beam 400 having a configuration in which 430 and 430 are stacked. An RF signal fixed electrode 141 is provided on the main surface of the substrate 110 via an underlayer 130, and a dielectric film 150 is provided between the RF signal fixed electrode 141 and the movable beam 400. As the base layer 130, the RF signal fixed electrode 141, and the dielectric film 150, the same materials as the base layer 130, the fixed electrode 140, and the dielectric film 150 illustrated in FIG. 1 can be used.
In the actuator 104, the driving beam 400 is bent by applying a driving voltage between the DC driving lower electrode 410 and the DC driving upper electrode 430 and applying a voltage to the piezoelectric film 420. Thus, the DC driving lower electrode 410 and the dielectric film 150 are in contact with each other, and a capacitor is formed between the DC driving lower electrode 410 and the RF signal fixed electrode 141 through the dielectric film 150.
In this embodiment, since the highly oriented AlN film (the c-axis orientation with the full width at half maximum of 4.6 degrees or less) is used as the dielectric film 150, charge injection and trapping to the dielectric film 150 are suppressed, An actuator having stable driving characteristics can be realized.

(Example 8)
Next, an actuator according to an eighth embodiment of the present invention will be described.
FIG. 9 is a schematic cross-sectional view illustrating the structure of the actuator of the eighth example of the invention. As shown in FIG. 9, the actuator 105 of the eighth embodiment is provided with the base film 130 and the dielectric film 150 which are respectively provided below and above the fixed electrode 140 in the actuator of the sixth embodiment shown in FIG. 7. In addition, the difference is that the lower electrode 210 is formed except for the portion facing the fixed electrode 140. In this configuration, the lower piezoelectric film 220 facing the fixed electrode 140 functions as a dielectric film in the first to seventh embodiments. Further, the intermediate electrode 230 becomes the movable electrode 231.
The lower piezoelectric film 220 can be formed by a highly oriented AlN film (c-axis oriented with a full width at half maximum of 4.6 degrees or less). The actuator illustrated in FIG. 9 has a dielectric film made of a highly oriented AlN film provided between the fixed electrode 140 and the movable electrode 231, thereby suppressing injection and trapping of charges into the dielectric film and stable driving. An actuator having characteristics can be realized.

By using the actuators of the embodiments and examples of the present invention described above, microswitches and capacitance variable capacitors can be formed, and various electronic circuits can be manufactured using them.
FIG. 10 is a schematic view illustrating an electronic circuit and an electronic device using the actuator of the embodiment of the invention.
As shown in FIG. 10, an electronic circuit 500 including a filter with a variable frequency can be manufactured by incorporating the variable capacitor manufactured by the actuator 105 according to the embodiment of the present invention. The electronic circuit 500 can be used in various electronic devices 600 such as a mobile phone.

The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. For example, regarding the specific configuration of each element constituting the actuator, the scope of the present invention is within the scope of the present invention as long as a person skilled in the art can implement the present invention in the same manner by appropriately selecting from the well-known ranges and obtain the same effect. Is included.
Moreover, what combined any two or more elements of each specific example in the technically possible range is also included in the scope of the present invention as long as the gist of the present invention is included.

  In addition, all actuators that can be implemented by those skilled in the art based on the actuators described above as embodiments of the present invention are also within the scope of the present invention as long as they include the gist of the present invention.

  In addition, in the category of the idea of the present invention, those skilled in the art can conceive of various changes and modifications, and it is understood that these changes and modifications also belong to the scope of the present invention. .

FIG. 3 is a schematic cross-sectional view illustrating the configuration of the actuator according to the first embodiment of the invention. It is explanatory drawing which illustrates the relationship between the orientation of a dielectric film, and the amount of electric charge injection to a dielectric film. It is a schematic cross section of each process showing the manufacturing method of the actuator of the 1st example of the present invention. It is explanatory drawing which illustrates the operation | movement test condition of an actuator. It is a graph which shows the operation test result of the actuator of Examples 1-4 of this invention. It is a schematic cross section which illustrates the structure of the actuator of the 5th Example of this invention. It is a schematic cross section which illustrates the structure of the actuator of the 6th Example of this invention. It is a schematic cross section which illustrates the structure of the actuator of the 7th Example of this invention. It is a schematic cross section which illustrates the structure of the actuator of the 8th Example of this invention. It is a schematic diagram which illustrates the electronic circuit and electronic device using the actuator of embodiment of this invention.

Explanation of symbols

101, 102, 103, 104, 105 Actuator 110 Substrate 120 Anchor part 130 Base film 140 Fixed electrode 141 Fixed electrode for RF signal 150 Dielectric film 160 Sacrificial layer 170, 200, 400 Movable beam 171, 231 Movable electrode 210 Lower electrode 220 Lower part Piezoelectric film 230 Intermediate electrode 240 Upper piezoelectric film 250 Upper electrode 310 Upper electrode 320 Lower electrode 410 DC driving lower electrode 420 Piezoelectric film 430 DC driving upper electrode 500 Electronic circuit 600 Electronic device

Claims (6)

A substrate,
A fixed electrode provided on the main surface of the substrate;
A movable beam facing the main surface and held above the substrate with a gap;
A dielectric film made of aluminum nitride provided between the fixed electrode and the movable beam and having a full width at half maximum of 4.6 degrees or less and c-axis orientation;
A base film made of an aluminum compound provided on the main surface under the fixed electrode;
An actuator comprising: The fixed electrode, according to claim 1 Symbol mounting of the actuator orientation FWHM is characterized in that it consists of an aluminum film having c-axis oriented below 3.8 degrees. A substrate,
An RF signal fixed electrode provided on the main surface of the substrate;
A movable beam facing the main surface and held above the substrate with a gap, and including a DC driving lower electrode, a piezoelectric film, and a DC driving upper electrode;
A dielectric film made of aluminum nitride provided between the RF signal fixed electrode and the movable beam and having an orientation full width at half maximum of 4.6 degrees or less and c-axis orientation;
A base film made of an aluminum compound provided on the main surface under the RF signal fixed electrode;
An actuator comprising: 4. The actuator according to claim 3, wherein the RF signal fixed electrode is made of a c-axis oriented aluminum film having a full width at half maximum of 3.8 degrees or less. The actuator according to any one of claims 1 to 4, wherein the aluminum compound is any one selected from AlN, an Al-Ta amorphous alloy, and a mixture thereof. The actuator according to any one of claims 1 to 4, wherein the base film is a film made of AlN having a thickness of 200 nm or more.

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