Patent Application
20180076381
The present invention relates to a method for producing a piezoelectric element, a piezoelectric element, a piezoelectric drive device, a robot, and a pump.
A piezoelectric actuator (piezoelectric drive device) which drives a driven body by vibrating a piezoelectric body does not need a magnet or a coil, and therefore is utilized in various fields (see, for example, JP-A-2004-320979). In such a piezoelectric drive device, a piezoelectric element (bulk piezoelectric element) including a bulky piezoelectric body is generally utilized (see, for example, 2008-227123).
On the other hand, as the piezoelectric element, a piezoelectric element including a piezoelectric body in the form of a thin film (thin-film piezoelectric element) is known. The thin-film piezoelectric element is mainly utilized for performing ink injection in an inkjet printer head.
When a thin-film piezoelectric element as described above is used in a piezoelectric drive device, there is a high possibility that the piezoelectric drive device or an apparatus driven by the device can be miniaturized. In the case where a thin-film piezoelectric element is used in a piezoelectric drive device, for example, in order to prevent a short circuit between an upper electrode and a lower electrode of the piezoelectric element, or the like, it is desirable to cover a side surface of the piezoelectric body with an insulating layer. However, such an insulating layer may be peeled off in a production step after a step of forming the insulating layer, at the time of driving the piezoelectric drive device, or the like.
One object according to some embodiments of the invention is to provide a method for producing a piezoelectric element capable of suppressing peeling off of the insulating layer. Further, one object according to some embodiments of the invention is to provide a piezoelectric element capable of suppressing peeling off of the insulating layer. Further, one object according to some embodiments of the invention is to provide a piezoelectric drive device including the piezoelectric element. Further, one object according to some embodiments of the invention is to provide a robot or a pump including the piezoelectric drive device.
Further, the working accuracy of a thin-film piezoelectric element to be used in an inkjet printer head as described above or the like is high, and therefore, when such a thin-film piezoelectric element is used in a piezoelectric drive device, the cost becomes high.
One object according to some embodiments of the invention is to provide a method for producing a piezoelectric element capable of achieving cost reduction.
Further, the output of a thin-film piezoelectric element is generally significantly smaller than that of a bulk piezoelectric element. Therefore, a currently existing thin-film piezoelectric element cannot obtain a sufficient output for utilizing the element as, for example, a drive source of a motor for driving a joint of a robot in some cases.
One object according to some embodiments of the invention is to provide a piezoelectric element for an ultrasonic motor capable of achieving a high output, and a method for producing the element. Further, one object according to some embodiments of the invention is to provide an ultrasonic motor including the piezoelectric element for an ultrasonic motor. Further, one object according to some embodiments of the invention is to provide a robot or a pump including the ultrasonic motor.
The invention has been made to solve at least part of the above-mentioned problems and can be realized as the following embodiments or application examples.
One embodiment of a method for producing a piezoelectric element according to the invention includes:
a step of forming a first electrode layer;
a step of forming a piezoelectric body layer on the first electrode layer;
a step of forming a second electrode layer on the piezoelectric body layer;
a step of patterning the second electrode layer;
a step of patterning the piezoelectric body layer by wet etching; and
a step of forming an organic insulating layer on a side surface of the patterned piezoelectric body layer.
According to such a method for producing a piezoelectric element, a side surface of the piezoelectric body layer can be formed into a concave and convex shape. According to this, the area of a contact surface between the piezoelectric body layer and the organic insulating layer can be increased. Therefore, according to such a method for producing a piezoelectric element, adhesion between the piezoelectric body layer and the organic insulating layer can be improved, and peeling off of the organic insulating layer can be suppressed.
Incidentally, in the description according to the invention, when the term ““on” is used in, for example, a sentence such as “on” a specific object (hereinafter referred to as “A”), another specific object (hereinafter referred to as “B”) is formed”, the term “on” is used while assuming that the term includes a case where B is formed directly on A, and a case where B is formed on A through another object.
In Application Example 1, the piezoelectric body layer may be formed by repeating formation of a precursor layer by a liquid-phase method and crystallization of the precursor layer.
According to such a method for producing a piezoelectric element, a groove portion can be formed on a side surface of a piezoelectric body layer, and the side surface of the piezoelectric body layer can be formed into a concave and convex shape.
In Application Example 1 or 2, the material of the organic insulating layer may be a photosensitive material.
According to such a method for producing a piezoelectric element, the organic insulating layer can be patterned by light exposure, development, and baking (a heat treatment) without performing etching. Therefore, according to such a method for producing a piezoelectric element, the step can be shortened, and thus, cost reduction can be achieved.
In Application Example 3, the Young's modulus of the organic insulating layer may be 1 GPa or more.
According to such a method for producing a piezoelectric element, a force (deformation) generated in a piezoelectric body layer 40 by applying a voltage can be efficiently transmitted to the below-mentioned vibrating plate through the organic insulating layer.
In any one of Application Examples 1 to 4, the thickness of the organic insulating layer may be 1.5 times or more and 3 times or less the thickness of the piezoelectric body layer.
According to such a method for producing a piezoelectric element, the organic insulating layer can suppress an increase in the opening area of a contact hole provided in the organic insulating layer while reliably covering the side surface of the piezoelectric body layer.
In any one of Application Examples 1 to 5, the thickness of the piezoelectric body layer may be 1 μm or more and 10 μm or less.
According to such a method for producing a piezoelectric element, in the case where the piezoelectric element is used in an ultrasonic motor, the occurrence of a crack in the piezoelectric body layer can be suppressed while ensuring an output of the ultrasonic motor.
One embodiment of a piezoelectric element according to the invention includes:
a first electrode layer;
a piezoelectric body layer provided on the first electrode layer;
a second electrode layer provided on the piezoelectric body layer; and
an organic insulating layer provided on a side surface of the piezoelectric body layer, wherein
the piezoelectric body layer is formed by repeating formation of a precursor layer by a liquid-phase method and crystallization of the precursor layer to form a stacked body, and patterning the stacked body by wet etching.
According to such a piezoelectric element, peeling off of the organic insulating layer can be suppressed.
One embodiment of a piezoelectric drive device according to the invention includes:
a vibrating plate; and
the piezoelectric element according to Application Example 7 provided on a surface of the vibrating plate.
According to such a piezoelectric drive device, the device includes the piezoelectric element according to the invention, and therefore, has high reliability.
One embodiment of a robot according to the invention includes:
a plurality of link portions;
a joint portion for connecting the plurality of link portions; and
the piezoelectric drive device according to Application Example 8 which rotates the plurality of link portions at the joint portion.
According to such a robot, the robot can include the piezoelectric drive device according to the invention.
One embodiment of a pump according to the invention includes:
the piezoelectric drive device according to Application Example 8;
a tube for transporting a liquid; and
a plurality of fingers for blocking the tube by driving the piezoelectric drive device.
According to such a pump, the pump can include the piezoelectric drive device according to the invention.
One embodiment of a method for producing a piezoelectric element according to the invention includes:
a step of forming a first electrode layer;
a step of forming a piezoelectric body layer on the first electrode layer;
a step of forming a second electrode layer on the piezoelectric body layer;
a step of forming a resist layer on the second electrode layer;
a step of patterning the second electrode layer by wet etching;
a step of patterning the piezoelectric body layer by wet etching; and
a step of removing an eaves portion of the second electrode layer generated by side etching in the step of patterning the piezoelectric body layer by wet etching.
According to such a method for producing a piezoelectric element, the piezoelectric body layer and the second electrode layer are patterned by wet etching. Therefore, according to such a method for producing a piezoelectric element, as compared with the case where the piezoelectric body layer and the second electrode layer are patterned by dry etching, cost reduction can be achieved. For example, when the piezoelectric body layer or the second electrode layer of 1 μm is etched, it takes about 10 minutes in the case of dry etching, but etching can be achieved in about 2 minutes in the case of wet etching. Further, in the case of wet etching, a resist layer used as a mask for etching can be easily peeled off with a solution of acetone or the like, and peeling off of the resist layer and cleaning of a wafer (a substrate with the piezoelectric body layer and the like formed thereon) can be performed simultaneously. On the other hand, in the case of dry etching, the resist layer is denatured, and therefore, necessity to perform asking or the like occurs, and the resist layer cannot be peeled off by a simple step. Further, the price of an etching device for wet etching is lower than the price of an etching device for dry etching. Therefore, according to the method for producing a piezoelectric element in which the piezoelectric body layer and the second electrode layer are patterned by wet etching, cost reduction can be achieved.
In Application Example 11,
the step of forming the second electrode layer may include
in the step of removing the eaves portion,
According to such a method for producing a piezoelectric element, the electrically conductive layer in the eaves portion can be removed in a short time. For example, when the electrically conductive layer is tried to be removed before removing the adhesion layer, an area coming into contact with an etching liquid is small, and it takes time to remove the electrically conductive layer in some cases.
In Application Example 11 or 12, the second electrode layer may contain at least one of copper and gold.
According to such a method for producing a piezoelectric element, the resistance of the second electrode layer can be decreased as compared with the second electrode layer composed of, for example, iridium.
In any one of Application Examples 11 to 13, the thickness of the second electrode layer may be 50 nm or more and 10 μm or less.
According to such a method for producing a piezoelectric element, an increase in the size of the piezoelectric element can be suppressed while decreasing the resistance of the second electrode layer.
In any one of Application Examples 1 to 14, the thickness of the piezoelectric body layer may be 1 μm or more and 10 μm or less.
According to such a method for producing a piezoelectric element, in the case where the piezoelectric element is used in an ultrasonic motor, the occurrence of a crack in the piezoelectric body layer can be suppressed while ensuring an output of the ultrasonic motor.
One embodiment of a piezoelectric element for an ultrasonic motor according to the invention includes:
a first electrode layer;
a piezoelectric body layer provided on the first electrode layer; and
a second electrode layer provided on the piezoelectric body layer, wherein
the second electrode layer contains copper, and
the thickness of the second electrode layer is 50 nm or more and 10 μm or less.
According to such a piezoelectric element for an ultrasonic motor, an increase in the size of the piezoelectric element can be suppressed while decreasing the resistance of the second electrode layer. According to such a piezoelectric element for an ultrasonic motor, by decreasing the resistance of the second electrode layer, in the case where the element is used in an ultrasonic motor, a high output can be achieved.
In Application Example 16, the second electrode layer may include
an adhesion layer,
an electrically conductive layer provided on the adhesion layer and containing the copper, and
an antioxidation layer provided on the electrically conductive layer.
According to such a piezoelectric element for an ultrasonic motor, oxidation of the electrically conductive layer can be prevented by the antioxidation layer.
In Application Example 16 or 17, the material of the antioxidation layer may be the same as the material of the adhesion layer.
According to such a piezoelectric element for an ultrasonic motor, the antioxidation layer can be formed using the same sputtering device as the sputtering device used for forming the adhesion layer (using the same sputtering target), and therefore, cost reduction can be achieved.
In Application Example 16 or 17, the material of the antioxidation layer may be a polymer.
According to such a piezoelectric element for an ultrasonic motor, the antioxidation layer can be formed by dipping the electrically conductive layer in, for example, a chemical liquid containing a polymer, and the antioxidation layer can be formed by a simple method.
One embodiment of a method for producing a piezoelectric element for an ultrasonic motor according to the invention includes:
a step of forming a first electrode layer;
a step of forming a piezoelectric body layer on the first electrode layer; and
a step of forming a second electrode layer on the piezoelectric body layer, wherein
the second electrode layer contains copper, and
the thickness of the second electrode layer is 50 nm or more and 10 μm or less.
According to such a method for producing a piezoelectric element for an ultrasonic motor, an increase in the size of the piezoelectric element can be suppressed while decreasing the resistance of the second electrode layer. According to such a piezoelectric element for an ultrasonic motor, by decreasing the resistance of the second electrode layer, in the case where the element is used in an ultrasonic motor, a high output can be achieved.
In Application Example 20,
the step of forming the second electrode layer may include
According to such a method for producing a piezoelectric element for an ultrasonic motor, oxidation of the electrically conductive layer can be prevented by the antioxidation layer.
In Application Example 20 or 21, the material of the adhesion layer and the material of the antioxidation layer may be the same.
According to such a method for producing a piezoelectric element for an ultrasonic motor, the antioxidation layer can be formed using the same sputtering device as the sputtering device used for forming the adhesion layer, and therefore, cost reduction can be achieved.
In Application Example 20 or 21, the material of the antioxidation layer may be a polymer.
According to such a piezoelectric element for an ultrasonic motor, the antioxidation layer can be formed by dipping the electrically conductive layer in, for example, a chemical liquid containing a polymer, and the antioxidation layer can be formed by a simple method.
One embodiment of an ultrasonic motor according to the invention includes:
a vibrating plate; and
the piezoelectric element for an ultrasonic motor according to any one of Application Examples 16 to 19 provided on a surface of the vibrating plate.
According to such an ultrasonic motor, the ultrasonic motor includes the piezoelectric element for an ultrasonic motor according to the invention, and therefore, a high output can be achieved.
One embodiment of a robot according to the invention includes:
a plurality of link portions;
a joint portion for connecting the plurality of link portions; and
the ultrasonic motor according to Application Example 24 which rotates the plurality of link portions at the joint portion.
According to such a robot, the robot can include the ultrasonic motor according to the invention.
One embodiment of a pump according to the invention includes:
the ultrasonic motor according to Application Example 24;
a tube for transporting a liquid; and
a plurality of fingers for blocking the tube by driving the ultrasonic motor.
According to such a pump, the pump can include the ultrasonic motor according to the invention.
Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings. Note that the embodiments described below are not intended to unduly limit the content of the invention described in the claims. Further, not all the configurations described below are necessarily essential components of the invention.
First, a piezoelectric element according to this embodiment will be described with reference to the drawings.
As shown in
The shape of the substrate 10 is a flat plate shape. The substrate 10 is, for example, a semiconductor substrate (specifically, a silicon substrate). The substrate 10 can be deformed according to the deformation of the piezoelectric body layer 40.
The foundation layer 20 is provided on the substrate 10. The foundation layer 20 may be constituted by an oxide silicon layer provided on the substrate 10 and a zirconium oxide layer provided on the silicon oxide layer. The foundation layer 20 can function as an etching stopper layer when etching the first organic insulating layer 60. The foundation layer 20 can be deformed according to the deformation of the piezoelectric body layer 40.
The first electrode layer 30 is provided on the foundation layer 20. The first electrode layer 30 may be constituted by an iridium layer provided on the foundation layer 20 and a platinum layer provided on the iridium layer. The thickness of the iridium layer is, for example, 5 nm or more and 100 nm or less, preferably about 20 nm. The thickness of the platinum layer is, for example, 50 nm or more and 300 nm or less, preferably about 130 nm. The first electrode layer 30 is one electrode for applying a voltage to the piezoelectric body layer 40. Incidentally, the material of the first electrode layer 30 may be only one type of metal material such as Ti, Pt, Ta, Ir, Sr, In, Sn, Au, Al, Fe, Cr, Ni, or Cu, or a mixed material or a stacked material of two or more types of these metal materials.
The piezoelectric body layer 40 is provided on the first electrode layer 30. The piezoelectric body layer 40 is constituted by, for example, a plurality of layers. In the example shown in the drawing, the piezoelectric body layer 40 is constituted by a first layer 42 provided on the first electrode layer 30, a second layer 44 provided on the first layer 42, and a third layer 46 provided on the second layer 44.
Incidentally, for convenience sake, in
The width of the lower surface of the first layer 42 of the piezoelectric body layer 40 is larger than the width of the lower surface of the second layer 44. The width of the lower surface of the second layer 44 is larger than the width of the lower surface of the third layer 46. In the example shown in the drawing, the widths of the layers 42, 44, and 46 decrease toward the second electrode layer 50 side from the first electrode layer 30 side. The side surface of each of the layers 42, 44, and 46 is inclined with respect to the upper surface 12 of the substrate 10. In the example shown in the drawing, the angles of inclination with respect to the upper surface 12 of the side surfaces of the respective layers 42, 44, and 46 are the same.
On the side surface 4 of the piezoelectric body layer 40, a groove portion 5 is provided. The groove portion 5 is constituted by the end portion of each of the layers 42, 44, and 46. A plurality of groove portions 5 are provided according to the number of layers constituting the piezoelectric body layer 40. It can also be said that the side surface 4 of the piezoelectric body layer 40 has a concave and convex shape due to the end portions of the layers 42, 44, and 46.
The thickness T1 of the piezoelectric body layer 40 is, for example, 1 μm or more and 10 μm or less, preferably 1.5 μm or more and 7 μm or less, more preferably about 3 μm. When the thickness of the piezoelectric body layer 40 is less than 1 μm, in the case where the piezoelectric body layer 40 is used in an ultrasonic motor, the output of the ultrasonic motor may be insufficient in some cases. Specifically, when the application voltage to the piezoelectric body layer 40 is increased for trying to increase the output, the piezoelectric body layer 40 may cause electrical breakdown in some cases. When the thickness of the piezoelectric body layer 40 is 1 μm, a voltage of 20 V to 40 V can be applied to the piezoelectric body layer 40. When the thickness of the piezoelectric body layer 40 is more than 10 μm, a crack may occur in the piezoelectric body layer 40 in some cases.
As the piezoelectric body layer 40, a perovskite-type oxide piezoelectric material is used. Specifically, the material of the piezoelectric body layer 40 is lead zirconate titanate (Pb(Zr,Ti)O3:PZT) or lead zirconate titanate niobate (Pb(Zr,Ti,Nb)O3:PZTN).
The second electrode layer 50 is provided on the piezoelectric body layer 40. The thickness T2 of the second electrode layer 50 is, for example, 50 nm or more and 10 μm or less, preferably 1 μm or more and 7 μm or less, more preferably about 1.0 μm. When the thickness of the second electrode layer 50 is less than 50 nm, the resistance of the second electrode layer 50 may be high in some cases. For example, the resistance of the entire piezoelectric element 100 is in a saturated state when the thickness of the second electrode layer 50 is 10 μm, and even if the thickness of the second electrode layer 50 is increased to more than 10 μm, the resistance of the entire piezoelectric element 100 cannot be decreased, but the thickness of the second electrode layer 50 becomes large. The second electrode layer 50 is the other electrode for applying a voltage to the piezoelectric body layer 40. In the example shown in the drawing, the second electrode layer 50 includes an adhesion layer 52 provided on the piezoelectric body layer 40 and an electrically conductive layer 54 provided on the adhesion layer 52.
The thickness of the adhesion layer 52 of the second electrode layer 50 is, for example, 10 nm or more and 100 nm or less, preferably about 50 nm. The adhesion layer 52 is, for example, a TiW layer, a Ti layer, a Cr layer, an NiCr layer, or a stacked body thereof. The adhesion layer 52 can improve the adhesion property between the piezoelectric body layer 40 and the electrically conductive layer 54. Incidentally, in the case where the material of the piezoelectric body layer 40 is PZT, the adhesion layer 52 is preferably a TiW layer. According to this, the suppression of deformation of the piezoelectric body layer 40 can be prevented by the adhesion layer 52.
The thickness of the electrically conductive layer 54 of the second electrode layer 50 is, for example, 1 μm or more and 10 μm or less. When the thickness of the electrically conductive layer 54 is less than 1 μm, the resistance of the second electrode layer 50 may be high in some cases. When the thickness of the electrically conductive layer 54 is more than 10 μm, the size of the piezoelectric element 100 may be large in some cases. The electrically conductive layer 54 is, for example, a Cu layer, an Au layer, an Al layer, or a stacked body thereof. That is, the electrically conductive layer 54 contains at least one of copper and gold. By the electrically conductive layer 54, the resistance of the second electrode layer 50 can be decreased.
The first organic insulating layer 60 is provided on the side surface 4 of the piezoelectric body layer 40. Specifically, the first organic insulating layer 60 is provided so as to cover the side surface 4 of the piezoelectric body layer 40. The groove portion 5 is filled with the first organic insulating layer 60. In the example shown in the drawing, the first organic insulating layer 60 is also provided on the electrode layers 30 and 50. The thickness T3 of the first organic insulating layer 60 (the thickness of the first organic insulating layer 60 located on the first electrode layer 30) is, for example, 1.5 times or more and 3 times or less the thickness T1 of the piezoelectric body layer 40. When the thickness of the first organic insulating layer 60 is smaller than 1.5 times the thickness of the piezoelectric body layer 40, the side surface 4 of the piezoelectric body layer 40 cannot be covered therewith in some cases. When the thickness of the first organic insulating layer 60 is larger than 3 times the thickness of the piezoelectric body layer 40, the opening areas of contact holes 60a and 60b provided in the first organic insulating layer 60 may be large in some cases. Specifically, the thickness of the first organic insulating layer 60 is 1.5 μm or more and 30 μm or less, preferably 2 μm or more and 10 μm or less, more preferably about 3 μm.
The material of the first organic insulating layer 60 is an organic material. Specifically, the material of the first organic insulating layer 60 is an epoxy-based resin, an acrylic resin, a polyimide-based resin, a silicone-based resin, or the like. The material of the first organic insulating layer 60 is a photosensitive material. The “photosensitive” refers to a property that a substance causes a chemical reaction by light. Specifically, the first organic insulating layer 60 can be patterned by light exposure, development, and baking (a heat treatment) without using etching. The Young's modulus of the first organic insulating layer 60 is, for example, 1 GPa or more. The Young's modulus of the first organic insulating layer 60 may be determined based on JIS K7161. The heat resistance of the first organic insulating layer 60 is preferably high, and the deflection temperature under load (thermal deformation temperature) of the first organic insulating layer 60 is preferably, for example, 200° C. or higher.
The first wiring layer 70 is connected to the second electrode layer 50. The first wiring layer 70 is provided in the first contact hole 60a provided on the second electrode layer 50 of the first organic insulating layer 60. A plurality of first contact holes 60a are provided, and the number of first contact holes is not particularly limited. The first wiring layer 70 is provided on the first organic insulating layer 60.
The second wiring layer 72 is connected to the first electrode layer 30. The second wiring layer 72 is provided in the second contact hole 60b provided on the first electrode layer 30 of the first organic insulating layer 60. A plurality of second contact holes 60b are provided, and the number of second contact holes is not particularly limited. The second wiring layer 72 is provided on the first organic insulating layer 60. The second wiring layer 72 is provided so as to sandwich the piezoelectric body layer 40 (on both lateral sides of the piezoelectric body layer 40).
The first wiring layer 70 and the second wiring layer 72 each include, for example, a seed layer 6 and an electrically conductive layer 7 provided on the seed layer 6. The thickness of the seed layer 6 is, for example, 50 nm or more and 100 nm or less. The seed layer 6 is, for example, a TiW layer, a Ti layer, a Cr layer, an NiCr layer, or a stacked body thereof. In particular, when considering electric corrosion (electrochemical corrosion), the seed layer 6 is preferably a TiW layer. The thickness of the electrically conductive layer 7 is, for example, 1 μm or more and 10 μm or less. The electrically conductive layer 7 is, for example, a Cu layer, an Ni layer, an Au layer, an Al layer, or a stacked body thereof.
The second organic insulating layer 62 is provided on the first organic insulating layer 60 so as to cover the wiring layers 70 and 72. The thickness and the material of the second organic insulating layer 62 may be the same as the thickness and the material of the first organic insulating layer 60.
The third wiring layer 74 is connected to the first wiring layer 70. The third wiring layer 74 is provided in a third contact hole 62a provided on the first wiring layer 70 of the second organic insulating layer 62. The third wiring layer 74 is further provided on the second organic insulating layer 62.
The fourth wiring layer 76 is connected to the second wiring layer 72. The fourth wiring layer 76 is provided in a fourth contact hole 62b provided on the second wiring layer 72 of the second organic insulating layer 62. The fourth wiring layer 76 is further provided on the second organic insulating layer 62.
The third wiring layer 74 and the fourth wiring layer 76 each include, for example, a seed layer 8 and an electrically conductive layer 9 provided on the seed layer 8. The thickness and the material of the seed layer 8 may be the same as the thickness and the material of the seed layer 6. The thickness of the electrically conductive layer 9 is, for example, 1 μm or more and 10 μm or less. The electrically conductive layer 9 is, for example, a stacked body obtained by stacking a Cu layer, an Ni layer, and an Au layer in this order, and the thickness of the Ni layer is about 2 μm, and the thickness of the Au layer is 300 nm or less. By the Ni layer, a reaction between the Cu layer and the Au layer can be suppressed. Further, by the Au layer, when bonding to a wiring of the below-mentioned ultrasonic motor, the wiring and the wiring layers 74 and 76 can be bonded by the Au layers (gold-gold bonding).
Incidentally, in the above description, an example in which two organic insulating layers are provided is described, however, the number of organic insulating layers is not particularly limited. In addition, also the number of wiring layers is not particularly limited.
Next, a method for producing the piezoelectric element 100 according to this embodiment will be described with reference to the drawings.
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Incidentally, the liquid-phase method is a method of depositing a thin film material using a raw material liquid containing a constituent material of a thin film (piezoelectric body layer), and specifically, a sol-gel method, an MOD (Metal Organic Deposition) method, or the like.
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By the above-mentioned steps, the piezoelectric element 100 can be produced.
The piezoelectric element 100 and the method for producing the same have, for example, the following characteristics.
In the method for producing the piezoelectric element 100, the piezoelectric body layer 40 is patterned by wet etching, and on the side surface 4 of the patterned piezoelectric body layer 40, the first organic insulating layer 60 is formed. Therefore, on the side surface 4 of the piezoelectric body layer 40, for example, the groove portion 5 can be formed, and thus, the side surface 4 can be formed into a concave and convex shape. Due to this, the area of the contact surface between the piezoelectric body layer 40 and the first organic insulating layer 60 can be increased. Therefore, according to the method for producing the piezoelectric element 100, the adhesion property between the piezoelectric body layer 40 and the first organic insulating layer 60 can be improved, and peeling off of the first organic insulating layer 60 can be suppressed.
In the method for producing the piezoelectric element 100, the piezoelectric body layer 40 is formed by repeating formation of a precursor layer by a liquid-phase method and crystallization of the precursor layer. Therefore, in the method for producing the piezoelectric element 100, the groove portion 5 can be formed on the side surface 4 of the patterned piezoelectric body layer 40, and thus, the side surface 4 can be formed into a concave and convex shape.
In the method for producing the piezoelectric element 100, the material of the organic insulating layers 60 and 62 is a photosensitive material. Therefore, the organic insulating layers can be patterned by light exposure, development, and baking without performing etching. Therefore, in the method for producing the piezoelectric element 100, the step can be shortened, and thus, cost reduction can be achieved.
In the method for producing the piezoelectric element 100, the Young's modulus of the organic insulating layers 60 and 62 is 1 GPa or more. Therefore, a force (deformation) generated in the piezoelectric body layer 40 by applying a voltage can be efficiently transmitted to the below-mentioned vibrating plate 510 (see
In the method for producing the piezoelectric element 100, the thickness T3 of the first organic insulating layer 60 is 1.5 times or more and 3 times or less the thickness T1 of the piezoelectric body layer 40. Therefore, in the method for producing the piezoelectric element 100, the first organic insulating layer 60 can suppress an increase in the opening areas of the contact holes 60a and 60b while reliably covering the side surface 4 of the piezoelectric body layer 40.
In the method for producing the piezoelectric element 100, the thickness T1 of the piezoelectric body layer 40 is 1 μm or more and 10 μm or less. According to this, in the case where the piezoelectric element 100 is used in an ultrasonic motor, the occurrence of a crack in the piezoelectric body layer 40 can be suppressed while ensuring an output of the ultrasonic motor.
In the method for producing the piezoelectric element 100, the piezoelectric body layer 40 and the second electrode layer 50 are patterned by wet etching. Therefore, in the method for producing the piezoelectric element 100, as compared with the case where the piezoelectric body layer and the second electrode layer are patterned by dry etching, cost reduction can be achieved. For example, when the piezoelectric body layer or the second electrode layer of 1 μm is etched, it takes about 10 minutes in the case of dry etching, but etching can be achieved in about 2 minutes in the case of wet etching. Further, in the case of wet etching, a resist layer used as a mask for etching can be easily peeled off with a solution of acetone or the like, and peeling off of the resist layer and cleaning of a wafer (a substrate with the piezoelectric body layer and the like formed thereon) can be performed simultaneously. On the other hand, in the case of dry etching, the resist layer is denatured, and therefore, necessity to perform asking or the like occurs, and the resist layer cannot be peeled off by a simple step. Further, the price of an etching device for wet etching is lower than the price of an etching device for dry etching. Therefore, in the method for producing the piezoelectric element 100 in which the piezoelectric body layer and the second electrode layer are patterned by wet etching, cost reduction can be achieved. Further, when a layer composed of gold or copper is etched by dry etching, the inside of an etching device may be contaminated in some cases. Further, when a piezoelectric body layer is etched by dry etching, etching damage to the first electrode layer may be caused in some cases. In the method for producing the piezoelectric element 100, such a problem of device contamination or etching damage can be avoided.
In the method for producing the piezoelectric element 100, the eaves portion 56 is removed by wet etching. Therefore, a short circuit between the first electrode layer 30 and the second electrode layer 50 can be prevented. For example, if the eaves portion 56 remains, the eaves portion 56 may break through the first organic insulating layer 60 to cause a short circuit between the first electrode layer 30 and the second electrode layer 50 in some cases.
In the method for producing the piezoelectric element 100, in the step of removing the eaves portion 56 (S114), after the adhesion layer 52 is removed, the electrically conductive layer 54 is removed. Therefore, the electrically conductive layer 54 of the eaves portion 56 can be removed in a short time. For example, when the electrically conductive layer is tried to be removed before removing the adhesion layer, an area of the electrically conductive layer coming into contact with an etching liquid is small, and therefore, it may take time to remove the electrically conductive layer in some cases.
In the method for producing the piezoelectric element 100, the thickness T2 of the second electrode layer 50 is 50 nm or more and 10 μm or less. According to this, an increase in the size of the piezoelectric element 100 can be suppressed while decreasing the resistance of the second electrode layer 50. By decreasing the resistance of the second electrode layer 50, the efficiency of the applied voltage can be improved, and further, the amount of heat generated by the resistance of the second electrode layer 50 can be reduced. Further, a thin-film piezoelectric element has a larger capacitance than a bulk piezoelectric element, and therefore, the impedance of the piezoelectric body layer is decreased. Therefore, by decreasing the resistance of the second electrode layer 50, the impedance of the piezoelectric body layer can be increased, and a voltage to be applied to the piezoelectric body layer can be increased. As a result, in the case where the piezoelectric element 100 is used in an ultrasonic motor, a high output can be achieved.
In the method for producing the piezoelectric element 100, the second electrode layer 50 contains at least one of copper and gold. Therefore, the resistance of the second electrode layer 50 can be decreased as compared with the second electrode layer 50 composed of, for example, iridium. Incidentally, copper has a higher binding property (is more likely to bind to another material) than gold, and therefore has a high adhesion property to the first organic insulating layer 60. Due to this, the outermost surface of the second electrode layer 50 is preferably copper.
In the piezoelectric element 100, the second electrode layer 50 contains copper, and the thickness T2 of the second electrode layer 50 is 50 nm or more and 10 μm or less. According to this, an increase in the size of the piezoelectric element 100 can be suppressed while decreasing the resistance of the second electrode layer 50. By decreasing the resistance of the second electrode layer 50, the efficiency of the applied voltage can be improved, and further, the amount of heat generated by the resistance of the second electrode layer 50 can be reduced. Further, a thin-film piezoelectric element has a larger capacitance than a bulk piezoelectric element, and therefore, the impedance of the piezoelectric body layer is decreased. Therefore, by decreasing the resistance of the second electrode layer 50, the impedance of the piezoelectric body layer can be increased, and the voltage to be applied to the piezoelectric body layer can be increased. As a result, in the case where the piezoelectric element 100 is used in an ultrasonic motor, a high output can be achieved.
Incidentally, in the above description, an example in which the piezoelectric body layer 40 is formed by a liquid-phase method is described, however, the method for forming the piezoelectric body layer 40 is not particularly limited, and may be a PVD (Physical Vapor Deposition) method such as a sputtering or a laser abrasion method. For example, when the piezoelectric body layer 40 is formed by a sputtering method, on the side surface 4 formed by wet etching, a plurality of convex portions 45 having an upward convex domed shape are formed as shown in
Further, in the above-mentioned example, the wiring layers 70, 72, 74, and 76 are formed by a so-called semi-additive method, however, the wiring layers 70, 72, 74, and 76 may be formed by a so-called subtractive method. That is, the wiring layers 70, 72, 74, and 76 may be formed by forming a seed layer and an electrically conductive layer by a sputtering method or the like, forming a resist layer on the electrically conductive layer, and etching the electrically conductive layer and the seed layer using the resist layer as a mask.
Hereinafter, the invention will be more specifically described by showing experimental examples. Incidentally, the invention is by no means limited to the following experimental examples.
From
Next, a piezoelectric element according to a first variation of this embodiment will be described with reference to the drawing.
Hereinafter, with respect to the piezoelectric element 200 according to the first variation of this embodiment, members having the same function as the constituent members of the piezoelectric element 100 according to this embodiment are denoted by the same reference numerals, and a detailed description thereof is omitted. This also applies to a piezoelectric element according to a second variation of this embodiment described later.
As shown in
The antioxidation layer 55 is, for example, a TiW layer, a Ti layer, a Cr layer, an NiCr layer, or a stacked body thereof. The material of the antioxidation layer 55 may be the same as the material of the adhesion layer 52. The antioxidation layer 55 is formed by, for example, a sputtering method or a CVD method. By using the same material as the material of the antioxidation layer 52 for the material of the adhesion layer 55, the antioxidation layer 55 can be formed using, for example, the same sputtering device as the sputtering device used for forming the adhesion layer 52 (using the same sputtering target), and therefore, cost reduction can be achieved.
The material of the antioxidation layer 55 may be a polymer. Specifically, the material of the antioxidation layer 55 may be a thiazole-based or imidazole-based mixed polymer. The thickness of the antioxidation layer 55 composed of a polymer is, for example, several nanometers or less. The antioxidation layer 55 composed of a polymer is formed by, for example, dipping the electrically conductive layer 54 in a chemical liquid containing a polymer. In this manner, the antioxidation layer 55 composed of a polymer can be formed by a simple method. A treatment for forming the antioxidation layer 55 composed of a polymer is performed after forming the electrically conductive layer 54, and further, may also be performed after removing the eaves portion 56 and removing the first resist layer 80. In addition, a treatment for forming the antioxidation layer composed of a polymer may be performed after forming the electrically conductive layer 7 of the wiring layers 70 and 72, and the electrically conductive layer 9 of the wiring layers 74 and 76. That is, the wiring layers 70 and 72 may include the antioxidation layer provided on the electrically conductive layer 7. Further, the wiring layers 74 and 76 may include the antioxidation layer provided on the electrically conductive layer 9. According to this, oxidation of the electrically conductive layers 7 and 9 can be prevented.
Next, a piezoelectric element according to a second variation of this embodiment will be described with reference to the drawing.
In the above-mentioned piezoelectric element 100, one piezoelectric body layer 40 is included as shown in
In the piezoelectric element 300, the first electrode layer 30 is used as a common electrode, and a plurality of piezoelectric body layers 40 are provided on the first electrode layer 30. The number of piezoelectric body layers 40 is not particularly limited, however, in the example shown in the drawing, five piezoelectric body layers 40 are provided. The five piezoelectric body layers 40a, 40b, 40c, 40d, and 40e are separated from each other. In the example shown in the drawing, the areas of the piezoelectric body layers 40a, 40b, 40c, and 40d are the same, and the piezoelectric body layer 40e has a larger area than the piezoelectric body layers 40a, 40b, 40c, and 40d. The piezoelectric body layers 40a and 40b are provided side by side in the longitudinal direction of the piezoelectric body layers, the piezoelectric body layers 40c and 40d are provided side by side in the longitudinal direction of the piezoelectric body layers, and the piezoelectric body layer 40e is provided between the piezoelectric body layers 40a and 40b and the piezoelectric body layers 40c and 40d. The planar shape of each piezoelectric body layer 40 is, for example, a rectangle.
A plurality of second electrode layers 50 are provided according to the number of piezoelectric body layers 40. In the example shown in the drawing, five second electrode layers 50 are provided, and the second electrode layers 50a, 50b, 50c, 50d, and 50e are provided on the piezoelectric body layers 40a, 40b, 40c, 40d, and 40e, respectively. The planar shape of each second electrode layer 50 is, for example, a rectangle.
Incidentally, the first electrode layer 30 may not be one common electrode, but five first electrode layers 30 having the same planar shape as the second electrode layers 50 may be provided. Further, the piezoelectric body layers 40a, 40b, 40c, 40d, and 40e may not be separated from each other and may be one continuous piezoelectric body layer.
Next, a piezoelectric drive device (ultrasonic motor) 500 according to this embodiment will be described with reference to the drawings.
As shown in
Two piezoelectric elements 300 are provided interposing the vibrating plate 510 therebetween. The two piezoelectric elements 300 may be provided symmetrically with respect to the vibrating plate 510. In the example shown in the drawing, the piezoelectric elements 300 are provided on a first surface 510a and a second surface 510b of the vibrating plate 510. The piezoelectric elements 300 are provided so that the wiring layers 74 and 76 face toward the vibrating plate 510. Although not shown in the drawings, on the first surface 510a and the second surface 510b, a gold wiring is provided, and the piezoelectric elements 300 may be provided on the vibrating plate 510 by gold-gold bonding between the gold wiring and the gold layer of the wiring layers 74 and 76. Incidentally, the piezoelectric elements 300 may be adhered to the vibrating plate 510 with an electrically conductive adhesive.
The vibrating plate 510 is provided between the two piezoelectric elements 300. Here,
On the upper surface (first surface 510a) and the lower surface (second surface 510b) of the vibrating body portion 512, the piezoelectric element 100 is provided. The ratio of the length L to the width W of the vibrating body portion 512 is preferably set as follows: L:W=about 7:2. This ratio is a preferred value for the vibrating body portion 512 to perform ultrasonic vibrations (described later) such that it bends right and left along its plane. The length L of the vibrating body portion 512 is, for example, 3.5 mm or more and 30 mm or less, and the width W thereof is, for example, 1 mm or more and 8 mm or less. Incidentally, in order for the vibrating body portion 512 to perform ultrasonic vibrations, the length L is preferably, 50 mm or less. The thickness of the vibrating body portion 512 (the thickness of the vibrating plate 510) is, for example, 50 μm or more and 700 μm or less. When the thickness of the vibrating body portion 512 is 50 μm or more, the vibrating body portion has sufficient rigidity for supporting the piezoelectric element 300. Further, when the thickness of the vibrating body portion 512 is 700 μm or less, a sufficiently large deformation can be caused in response to deformation of the piezoelectric element 100.
On one short side of the vibrating plate 510, a protrusion portion 520 (also referred to as “contact portion” or “operation portion”) is provided. The protrusion portion 520 is a member for applying a force to a driven body by coming into contact with the driven body. The protrusion portion 520 is preferably formed from a material having durability such as a ceramic (for example, Al2O3).
The drive circuit 600 can rotate a rotor (driven body) coming into contact with the protrusion portion 520 in a predetermined rotation direction by applying a cyclically varying AC voltage or pulsating voltage between the pair of second electrode layers 50a and 50d and the first electrode layer 30 to cause the piezoelectric drive device 500 to perform ultrasonic vibrations. Here, the “pulsating voltage” refers to a voltage obtained by adding a DC offset to the AC voltage, and the direction of the voltage (electric field) is one direction from one electrode toward the other electrode. Further, the drive circuit 600 can rotate the rotor coming into contact with the protrusion portion 520 in the opposite direction by applying an AC voltage or a pulsating voltage between the other pair of second electrode layers 50b and 50c and the first electrode layer 30. The application of such a voltage is performed simultaneously in the two piezoelectric elements 300 provided on both surfaces of the vibrating plate 510. In the example shown in
Incidentally, in the case where the drive circuit 600 applies an AC voltage or a pulsating voltage between the other pair of second electrode layers 50b and 50c and the first electrode layer 30, the rotor 700 rotates in the opposite direction. Further, when the same voltage as applied to the pair of second electrode layers 50a and 50d (or the other pair of second electrode layers 50b and 50c) is applied to the second electrode layer 50e in the center, the piezoelectric drive device 500 expands and contracts in the longitudinal direction, and therefore, a force to be applied to the rotor 700 from the protrusion portion 520 can be further increased.
The above-mentioned piezoelectric drive device 500 can apply a large force to a driven body by utilizing resonance, and can be applied to various devices. For example, the piezoelectric drive device 500 can be used as a drive device in various apparatuses such as a robot (also including an electronic component conveying device (IC handler)), a dosing pump, a timepiece calendar feeding device, and a printing device (for example, a sheet feeding mechanism, however, not applicable to a head since the vibrating plate is not caused to resonate in the piezoelectric drive device used for the head). Hereinafter, a representative embodiment will be described.
In each of the joint portions 2020, the above-mentioned piezoelectric drive device 500 is incorporated, and the joint portions 2020 can be rotated or bent at a given angle using the piezoelectric drive device 500. To the tip of the arm 2010, a robot hand 2000 is connected. The robot hand 2000 includes a pair of gripping portions 2003. Also in the robot hand 2000, the piezoelectric drive device 500 is incorporated, and it is possible to grip an object by opening and closing the gripping portions 2003 using the piezoelectric drive device 500. Further, the piezoelectric drive device 500 is also provided between the robot hand 2000 and the arm 2010, and it is also possible to rotate the robot hand 2000 with respect to the arm 2010 using the piezoelectric drive device 500.
Here, in the inside of the joint portion 2020 of the wrist or the robot hand 2000, in addition to the piezoelectric drive device 500, an electric power line for supplying electric power to various devices such as a force sensor or a gyro sensor, a signal line for transmitting a signal, or the like is included, and thus a large number of wirings are necessary. Therefore, it was very difficult to dispose wirings inside the joint portion 2020 or the robot hand 2000. However, in the piezoelectric drive device 500 of the embodiment described above, a drive current can be made smaller than that of a general electric motor or a piezoelectric drive device in the related art, and therefore, wirings can be disposed even in a small space such as the joint portion 2020 (particularly a joint portion at the tip of the arm 2010) or the robot hand 2000.
The reservoir 2211 is a storage portion for storing a liquid to be transported. The tube 2212 is a tube for transporting the liquid to be sent from the reservoir 2211. The protrusion portion 520 of the piezoelectric drive device 500 is provided in a state of being pressed against the side surface of the rotor 2222, and the piezoelectric drive device 500 rotationally drives the rotor 2222. The rotational force of the rotor 2222 is transmitted to the cam 2202 through the deceleration transmission mechanism 2223. The fingers 2213 to 2219 are members for blocking the tube 2212. When the cam 2202 rotates, the fingers 2213 to 2219 are sequentially pressed outward in the radial direction by a projection portion 2202A of the cam 2202. The fingers 2213 to 2219 sequentially block the tube 2212 from the upstream side (the reservoir 2211 side) in the transportation direction. Due to this, the liquid in the tube 2212 is sequentially transported to the downstream side. By doing this, it is possible to realize the liquid feed pump 2200 capable of accurately feeding an extremely small amount of a liquid and also having a small size.
The arrangement of each member is not limited to one shown in the drawing. Further, a configuration in which a member such as a finger is not included and a ball or the like provided on the rotor 2222 blocks the tube 2212 may be adopted. The liquid feed pump 2200 as described above can be used for a dosing device or the like which administers a medicinal solution such as insulin to the human body. Here, by using the piezoelectric drive device 500 of the embodiment described above, a drive current becomes smaller than that of a piezoelectric drive device in the related art, and therefore, power consumption of the dosing device can be suppressed. Therefore, in the case where the dosing device is driven with a battery, the use of the piezoelectric drive device 500 is particularly effective.
The above-mentioned embodiments and variations are examples, and the invention is not limited thereto. For example, the respective embodiments and the respective variations can also be appropriately combined.
The invention includes substantially the same configurations (for example, configurations having the same functions, methods and results, or configurations having the same objects and effects) as the configurations described in the embodiments. Further, the invention includes configurations in which a part that is not essential in the configurations described in the embodiments is substituted. Further, the invention includes configurations having the same effects as in the configurations described in the embodiments, or configurations capable of achieving the same objects as in the configurations described in the embodiments. In addition, the invention includes configurations in which known techniques are added to the configurations described in the embodiments.
The entire disclosures of Japanese Patent Application Nos. 2015-052219, filed Mar. 16, 2015, No. 2015-052220, filed Mar. 16, 2015, and No. 2015-052221 filed Mar. 16, 2015 are expressly incorporated by reference herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-052219 | Mar 2015 | JP | national |
| 2015-052220 | Mar 2015 | JP | national |
| 2015-052221 | Mar 2015 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/000650 | 2/9/2016 | WO | 00 |
