WO2015076135A1

WO2015076135A1 - Thin film piezoelectric actuator and method for manufacturing same

Info

Publication number: WO2015076135A1
Application number: PCT/JP2014/079724
Authority: WO
Inventors: 陽介中野
Original assignee: コニカミノルタ株式会社
Priority date: 2013-11-20
Filing date: 2014-11-10
Publication date: 2015-05-28
Also published as: JPWO2015076135A1

Abstract

This method for manufacturing a thin film piezoelectric actuator has: a step for pattern-forming a piezoelectric element (7) on one surface of a substrate (2); a step for pattern-forming a first dividing trench (11) on the one surface side of the substrate (2) by means of dry etching; a step for forming a first resist (12) on the one surface of the substrate (2), said first resist planarizing a surface by covering the piezoelectric element (7) and the first dividing trench (11); a step for bonding a film base material on the first resist (12); a step for forming a second resist on the other surface of the substrate (2); and a step for forming, at one time, a diaphragm and a second dividing trench by dry-etching the substrate (2) from the other surface side using the second resist as a mask, said second dividing trench penetrating the substrate by being connected to the first dividing trench (11).

Description

Thin film piezoelectric actuator and manufacturing method thereof

The present invention relates to a method of manufacturing a thin film piezoelectric actuator in which a substrate is divided to manufacture individual thin film piezoelectric actuators, and a thin film piezoelectric actuator manufactured by the manufacturing method.

Conventionally, an ink jet printer having an ink jet head having a plurality of channels for discharging liquid ink is known. By controlling the ejection of ink while moving the inkjet head relative to a recording medium such as paper or cloth, a two-dimensional image can be output to the recording medium. Ink can be ejected using a pressure actuator (piezoelectric, electrostatic, thermal deformation, etc.) or by generating bubbles in the ink in the tube by heat. Among them, the piezoelectric actuator has advantages such as high output, modulation, high responsiveness, and choice of ink, and has been frequently used in recent years.

Piezoelectric actuators include those using bulk piezoelectric materials and those using thin film piezoelectric materials (piezoelectric thin films). Since the former has a large output, large droplets can be discharged, but it is large and expensive. On the other hand, since the latter has a small output, the amount of droplets cannot be increased, but is small and low in cost. In order to realize a small, low-cost printer with high resolution (small droplets may be sufficient), it can be said that it is suitable to configure an actuator using a piezoelectric thin film.

In an inkjet head using a piezoelectric thin film as an actuator, a piezoelectric element having a structure in which a piezoelectric thin film is sandwiched between an upper electrode and a lower electrode is formed on a thin silicon (vibration plate) having a thickness of several microns. A high frequency electric field of the order of kHz is applied to the piezoelectric element, and the piezoelectric thin film expands and contracts in the in-plane direction of the diaphragm due to the inverse piezoelectric effect, thereby displacing the diaphragm. As a result, the volume of the pressure chamber in contact with the diaphragm changes, and ink in the pressure chamber can be ejected.

The above-mentioned piezoelectric thin film is formed on a silicon substrate by chemical film-forming methods such as CVD (Chemical Vapor Deposition), physical methods such as sputtering and ion plating, and liquid phase growth such as sol-gel methods. It is formed using a film process. As a material of the piezoelectric thin film, a crystal having a perovskite structure made of lead (Pb), zirconium (Zr), titanium (Ti), and oxygen (O) called PZT (lead zirconate titanate) is often used.

A piezoelectric thin film and electrodes (upper electrode and lower electrode) are formed on one surface side of the silicon substrate in the actuator, and functional parts such as an ink flow path and a pressure chamber are formed on the other surface side. These are formed by a highly accurate processing process using a semiconductor process technology such as photolithography. The portion of the silicon substrate that forms the upper wall of the pressure chamber constitutes the diaphragm described above.

At this time, a plurality of piezoelectric elements are arranged at a high density on a relatively large silicon wafer having a diameter of 6 inches or a diameter of 8 inches, a plurality of actuators are collectively formed, and then the silicon wafer is divided into pieces. For example, the cost can be significantly reduced as compared with single wafer manufacturing in which actuators are manufactured individually.

For example,

Patent Documents

1 and 2 disclose a technique for dividing a wafer having a thin portion. In Patent Document 1, a protective film is attached to a thin portion of a wafer via a resist, and then the wafer is cut and cut and divided by a dicing apparatus. In Patent Document 2, a wafer and a hard substrate are bonded together with a resist, and a thin portion and a divided groove are simultaneously formed by dry etching, and then a wafer portion remaining in the divided groove, that is, a lower portion of the divided groove is sharpened. It is ruptured with a blade (for example, razor), and then dipped in acetone to remove the resist and collect the hard substrate and each chip.

Japanese Patent Laying-Open No. 2005-197436 (refer to claim 1, paragraphs [0010] to [0018], FIG. 1, etc.) Japanese Patent Laid-Open No. 2006-32716 (see

claims

1, 2, 4, paragraphs [0020] to [0023], FIGS. 5 to 8 etc.)

However, in the inkjet head actuator, the mechanical strength of the diaphragm made of thin silicon having a thickness of only a few microns is very weak. For this reason, if the above-described method of

Patent Document

1 or 2 is used as it is for manufacturing an actuator, there arises a problem that when the wafer is divided into individual pieces, the diaphragm is damaged and the yield is lowered. More specifically, when the method disclosed in Patent Document 1 is used, when the wafer is cut using a dicing apparatus, the vibration plate, which is a thin-walled portion, is damaged by vibration from the blade and the hydraulic pressure of the cutting water. Further, when the method of Patent Document 2 is used, the diaphragm is damaged by vibration when the wafer portion remaining in the dividing groove is mechanically cut with a sharp blade.

Further, Patent Document 2 discloses that the resist for bonding the wafer and the hard substrate is desirably thin in consideration of heat dissipation. However, in the actuator of the ink jet head, a step corresponding to the thickness of the piezoelectric element occurs on one surface side of the substrate, that is, the side where the piezoelectric element is formed. For this reason, when the thickness of the resist is reduced, a step corresponding to the thickness of the piezoelectric element is generated on the surface of the resist. In this case, air (bubbles) is involved when the hard substrate is bonded to the resist, and heat distribution occurs in the wafer during dry etching when forming the thin portion. As a result, the accuracy of dry etching is reduced, and it is difficult to accurately form the thin portion.

The present invention has been made to solve the above-described problems, and its purpose is to reduce the breakage of the diaphragm and improve the yield in manufacturing individual thin film piezoelectric actuators by dividing the substrate. Another object of the present invention is to provide a method for manufacturing a thin film piezoelectric actuator capable of accurately forming a diaphragm and a thin film piezoelectric actuator manufactured by the manufacturing method.

A manufacturing method of a thin film piezoelectric actuator according to one aspect of the present invention is a manufacturing method of a thin film piezoelectric actuator in which a substrate is divided to manufacture individual thin film piezoelectric actuators, and an electrode and a piezoelectric are formed on one surface of the substrate. Patterning and forming a piezoelectric element including a thin film, patterning and forming a first dividing groove for dividing the substrate on one surface side of the substrate by dry etching, and on one surface of the substrate A step of forming a first resist that covers the piezoelectric element and the first dividing groove and flattens the surface; a step of attaching a film base material on the first resist; and On the other surface opposite to the one surface, a diaphragm positioned corresponding to the piezoelectric element and a second divided groove positioned corresponding to the first divided groove are patterned. A step of forming a second resist for annealing, and the substrate is dry-etched from the other surface side using the second resist as a mask, thereby connecting the diaphragm and the first dividing groove. And simultaneously forming the second dividing groove penetrating therethrough.

Since the substrate is divided by forming the first and second dividing grooves in the substrate by dry etching, the substrate can be divided without damaging the diaphragm due to mechanical processing such as dicing. Thereby, the breakage of the diaphragm at the time of dividing the substrate can be reduced and the yield can be improved. Moreover, since the surface of the 1st resist is flat when affixing a film base material on a 1st resist, it can affix without entraining a bubble. Thereby, in dry etching at the time of forming the diaphragm, it is possible to suppress the heat distribution from being generated in the substrate due to the bubbles and to reduce the accuracy of the dry etching, and the diaphragm can be formed with high accuracy.

1 is a plan view showing a schematic configuration of a thin film piezoelectric actuator according to an embodiment of the present invention, and a cross-sectional view taken along line A-A ′ in the plan view. It is sectional drawing which shows the manufacturing process of the said thin film piezoelectric actuator. It is sectional drawing which shows the manufacturing process of the said thin film piezoelectric actuator. FIG. 10 is a cross-sectional view showing another configuration of the film base used, which is a part of the manufacturing process of the thin film piezoelectric actuator.

An embodiment of the present invention will be described below with reference to the drawings. In this specification, when the numerical range is expressed as A to B, the numerical value range includes the values of the lower limit A and the upper limit B.

[Configuration of thin film piezoelectric actuator]
FIG. 1 is a plan view showing a schematic configuration of a thin film piezoelectric actuator (hereinafter also simply referred to as an actuator or a chip) of the present embodiment, and a sectional view taken along the line AA ′ in the plan view. Is. The thin film piezoelectric actuator 1 of this embodiment is configured by laminating a thermal oxide film 3, a lower electrode 4, a piezoelectric thin film 5, and an upper electrode 6 in this order on a substrate 2.

The substrate 2 has a pressure chamber 2a for containing ink. And the part which makes the upper wall of the pressure chamber 2a in the board | substrate 2 comprises the diaphragm 2b. The thermal oxide film 3 is formed for the purpose of protecting and insulating the substrate 2. The lower electrode 4, the piezoelectric thin film 5 and the upper electrode 6 constitute a piezoelectric element 7.

When a driving signal (driving voltage) is supplied to the lower electrode 4 and the upper electrode 6 from a driving circuit (not shown), the piezoelectric thin film 5 is perpendicular to the thickness direction according to the potential difference between the lower electrode 4 and the upper electrode 6. Expands and contracts in one direction (direction parallel to the surface of the substrate 2). Then, due to the difference in length between the piezoelectric thin film 5 and the diaphragm 2b, a curvature is generated in the diaphragm 2b, and the diaphragm 2b is displaced (curved or vibrated) in the thickness direction.

Therefore, if the ink is stored in the pressure chamber 2a, a pressure wave is propagated to the ink in the pressure chamber 2a due to the vibration of the vibration plate 2b described above, and the ink in the pressure chamber 2a is ejected (not shown). ) To the outside as ink droplets.

[Manufacturing method of thin film piezoelectric actuator]
Next, a method for manufacturing the thin film piezoelectric actuator 1 will be described. 2 and 3 are cross-sectional views showing the manufacturing process of the thin film piezoelectric actuator 1. The thin film piezoelectric actuator 1 is roughly manufactured through the following steps (1) to (16). The steps (2) to (7) correspond to the step of patterning the piezoelectric element 7. Further, the steps (2) to (10) are performed on one surface side with respect to the substrate 2, and the steps (11) to (14) are performed on the other surface side with respect to the substrate 2.

(1) Substrate preparation step (2) Lower electrode layer formation step (3) Piezoelectric thin film layer formation step (4) Upper electrode layer formation step (5) Upper electrode patterning step (6) Piezoelectric thin film patterning step (7) Lower electrode patterning Step (8) First division groove forming step (9) First resist forming step (10) Film substrate pasting step (11) Second resist forming step (12) Dry etching step 1
(13) Dry etching process 2
(14) Second resist removal step (15) Film substrate peeling step (16) First resist removal step

Hereinafter, the details of the steps (1) to (16) will be described.

(1) Substrate preparation process First, the substrate 2 is prepared. The material of the substrate 2 is crystalline silicon (Si) that is widely used in MEMS (Micro Electro Mechanical Systems). Here, two

Si substrates

2c and 2e are bonded via an oxide film 2d made of SiO _2. An SOI (Silicon on Insulator) structure is used. The Si substrate 2c is also called a supporting silicon substrate, the oxide film 2d is also called an intermediate oxide film, and the Si substrate 2e is also called a silicon device layer.

The thickness of each of the Si substrate 2c, the oxide film 2d, and the Si substrate 2e can be changed depending on the design of the actuator. In the present embodiment, the thickness of the Si substrate 2c is, for example, 600 μm, the thickness of the oxide film 2d is, for example, 0.5 μm, and the thickness of the Si substrate 2e is, for example, 5 μm. The substrate 2 may be a semiconductor substrate made of single crystal silicon.

On the Si substrate 2e of the substrate 2, a thermal oxide film 3 made of SiO ₂ is further formed. The thermal oxide film 3 is formed by thermally oxidizing the surface of the substrate 2. The thickness of the thermal oxide film 3 is, for example, 0.1 μm.

(2) Lower electrode layer forming step A lower electrode layer 4 a serving as a base of the lower electrode 4 is formed on the surface of the thermal oxide film 3. The lower electrode layer 4a is formed by sequentially forming a titanium (Ti) layer and a platinum (Pt) layer from the thermal oxide film 3 side by sputtering. The Ti layer is an adhesion layer provided in order to improve the adhesion between the Pt layer and the thermal oxide film 3, and has a thickness of about 10 nm, for example. The adhesion layer may be composed of a titanium oxide (TiOx) layer. The Pt layer has self-orientation and is oriented in the (111) direction with respect to the substrate 2. The thickness of the Pt layer is, for example, about 100 nm. The lower electrode layer 4a may be composed of three layers of Ti (for example, thickness 20 nm), Pt (for example, thickness 100 nm), and Ti (for example, thickness 10 nm).

(3) Piezoelectric thin film layer forming step A piezoelectric thin film layer 5a made of lead zirconate titanate (PZT) is formed on the lower electrode layer 4a at a temperature of 600 ° C. by sputtering. The thickness of the piezoelectric thin film layer 5a is, for example, 4 to 5 μm. At this time, it is desirable that the ratio of Zr and Ti constituting PZT is around 52:48 constituting the MPB (Morphotropic Phase Boundary) composition. In addition, the PZT film constituting the piezoelectric thin film layer 5a is preferably oriented at (100) of the perovskite layer that provides high piezoelectric characteristics.

A buffer layer for controlling the crystal orientation of the piezoelectric thin film layer 5a may be formed between the piezoelectric thin film layer 5a and the lower electrode layer 4a. As the buffer layer, there are perovskite-type lead lanthanum titanate (PLT), strontium ruthenium oxide (SRO), strontium titanium oxide (STO), etc., and the (100) direction parallel to the substrate surface (laminated surface). It is desirable that it be oriented. Thereby, the growth of the (100) -oriented PZT film can be facilitated, and the (100) -oriented PZT film can be obtained more stably. The piezoelectric thin film layer 5a formed in this way has a very high value of −180 pm / V in the piezoelectric constant d ₃₁ .

(4) Upper electrode layer forming step The upper electrode layer 6a is formed on the piezoelectric thin film layer 5a by sputtering. The upper electrode layer 6a is formed by laminating a Ti layer and a gold (Au) layer. The Ti layer is formed in order to improve the adhesion between the piezoelectric thin film layer 5a and the Au layer. The thickness of the Ti layer is, for example, 0.01 μm, and the thickness of the Au layer is, for example, 0.2 μm.

(5) Upper electrode patterning step A resist is applied on the upper electrode layer 6a by a spin coat method, a spray method, or the like, exposed and developed to form a mask pattern of the upper electrode 6, and then the upper electrode layer 6a. Is wet etched to form a pattern of the upper electrode 6.

(6) Piezoelectric thin film patterning step A resist pattern is formed on the piezoelectric thin film layer 5a, and the piezoelectric thin film layer 5a is wet etched with a mixed etching solution such as hydrofluoric acid, hydrogen peroxide, hydrofluoric acid, etc. A pattern of the thin film 5 is formed. The resist pattern has a circular portion having a diameter of 180 to 250 μm at a position corresponding to the pressure chamber, and the piezoelectric thin film 5 having a size corresponding to the circular portion is formed by patterning.

(7) Lower electrode patterning step A resist is applied on the lower electrode layer 4a by a spin coat method, a spray method, or the like, exposed and developed to form a mask pattern of the lower electrode 4, and then the lower electrode layer 4a is formed. The pattern of the lower electrode 4 is formed by wet etching or dry etching. Thereby, a piezoelectric element 7 composed of the lower electrode 4, the piezoelectric thin film 5 and the upper electrode 6 is formed.

(8) First Divided Groove Forming Step A resist is applied on the substrate 2 by a spin coat method, a spray method, or the like, and exposure and development are performed to form a mask pattern of chip divided grooves. Thereafter, the outermost thermal oxide film 3 is etched using a gas such as trifluoromethane (CHF ₃ ) by reactive ion etching which is a kind of dry etching, and then a gas such as sulfur hexafluoride (SF ₆ ) is used. Then, the Si substrate 2e is etched. Thereby, the first division grooves 11 are formed at predetermined division positions of the substrate 2. The depth of the first dividing groove 11 is a depth corresponding to the thickness of the thermal oxide film 3 and the Si substrate 2e, and is, for example, 4 to 7 μm.

(9) First Resist Forming Step A first resist 12 is formed on the substrate 2 so as to cover the piezoelectric element 7 and the first dividing groove 11 and to flatten the surface. The first resist 12 can be applied on the substrate 2 by a spin coating method, a spray method, or the like. Concavities and convexities (steps) are formed on the surface of the substrate 2 by the formation of the piezoelectric elements 7 and the first dividing grooves 11, but the first resist 12 has a certain degree of flatness to cover the concavities and convexities. It is desirable to have a thickness (for example, 20 μm or more). For example, Shipley S1830 is suitable as the first resist 12.

(10) Film substrate pasting step The film substrate 13 is pasted on the first resist 12. As the film substrate 13, a film substrate with an adhesive layer (adhesive film) having an adhesive layer 13b on one side of the substrate 13a can be used. For example, a dicing tape or a back grind tape is suitable. What is necessary is just to cut the excess part (part protruded from the board | substrate 2) of the film base material 13 with a cutter. Further, the film base 13 may be cut in advance according to the size of the substrate 2.

Here, when the adhesion between the first resist 12 and the adhesive layer 13b of the film base 13 is good, the film base 13 is difficult to peel off thereafter. It is desirable to use one having an adhesive layer 13b that is less adhesive than before peeling by heating or irradiation with light such as ultraviolet rays (UV). As such a film substrate 13, for example, UDT-1005M3 manufactured by Denka Adtex can be used.

In addition, as a method for attaching the film base material 13 on the first resist 12, for example, as described in Japanese Patent Application Laid-Open No. 2004-266183, the film base material is pressed with a roller or the like from the edge of the substrate. A method of adhering or a method of adhering a film substrate in a vacuum atmosphere as described in JP-A No. 2001-210701 is suitable. By these methods, it is possible to reduce entrainment of air (bubbles) between the first resist 12 and the film substrate 13.

(11) Second resist formation step On the surface of the substrate 2 opposite to the side on which the piezoelectric element 7 is formed, the diaphragm 2b positioned corresponding to the piezoelectric element 7 and the first dividing groove 11 are provided. A second resist 22 is formed for patterning the second dividing groove 21 positioned at the same position. That is, a resist for patterning the diaphragm 2b and the second dividing groove 21 by applying the second resist 22 on the surface by a spin coat method, a spray method or the like, and performing exposure and development. Form a pattern. At this time, the second resist 22 may include an ink flow path pattern.

The phrase “the diaphragm 2 b is positioned corresponding to the piezoelectric element 7” means that the diaphragm 2 b is positioned below the piezoelectric element 7 (particularly the piezoelectric thin film 5), and corresponds to the first dividing groove 11. The position of the second dividing groove 21 means that the second dividing groove 21 is located below the first dividing groove 11 (almost the same position in the in-plane direction of the substrate 2).

Next, the substrate 2 is dry-etched from the above surface side, so that the diaphragm 2b and the second divided groove 21 that is connected to and penetrates the first divided groove 11 are formed at the same time. This step is performed in the following two steps (12) and (13).

(12) Dry etching process 1
Using the second resist 22 as a mask, the Si substrate 2c is dry etched. That is, using the intermediate oxide film (oxide film 2d) as an etching stopper layer, the Si substrate 2c is deeply etched by a Bosch process (using SF ₆ or C ₄ F ₈ as an etching gas) such as an ICP (Inductively Coupled Plasma) apparatus. Etching process.

(13) Dry etching process 2
The exposed intermediate oxide film (oxide film 2d) is removed by dry etching such as RIE (Reactive Ion Etching) using a gas such as CHF ₃ . Thereby, the pressure chamber 2a having a diameter of about 200 μm is formed. At this time, the Si substrate 2e constituting the upper wall of the pressure chamber 2a becomes the vibration plate 2b (movable part).

In addition, the pressure chamber 2a and the diaphragm 2b are formed by etching, and at the same time, the second divided groove 21 is also formed. At this time, the first dividing groove 11 is formed by etching the Si substrate 2e, and the first resist 12 is buried in the removed portion of the Si substrate 2e. When the oxide film 2d is removed by etching at the time of forming the first resist 12, the first resist 12 filling the first dividing groove 11 is exposed. That is, when the second divided groove 21 is formed by etching the Si substrate 2c and the oxide film 2d, the second divided groove 21 is connected to the first divided groove 11 and penetrates in the substrate thickness direction. Thereby, the board | substrate 2 is separated into pieces. At this point, each of the separated substrates 2 is supported by the film base material 13 via the first resist 12 and therefore does not come apart.

(14) Second resist removal step While the divided individual substrates 2 are attached to the film base 13 via the first resist 12, the second resist 22 is used with a gas such as O ₂ . Remove by dry etching.

(15) Film substrate peeling step The film substrate 13 attached to the first resist 12 is peeled off. As described above, if a film substrate 13 that is made low in adhesiveness by UV irradiation or the like is used, the film substrate 13 can be easily peeled off by such UV irradiation. Even if the film substrate 13 is peeled off, the piezoelectric element 7 is protected by the first resist 12, so that the piezoelectric element 7 is scratched at the time of peeling, or the adhesive of the adhesive layer 13 b of the film substrate 13 is piezoelectric. It adheres to the element 7 and does not remain.

(16) First resist removing step The first resist 12 is removed by dry etching using a gas such as O ₂ . Thereby, the thin film piezoelectric actuator 1 corresponding to each substrate 2 is completed. At this time, the first resist 12 is dry-etched in a state where the divided individual substrates 2 are supported by the base of the dry etching apparatus (for example, ICP apparatus). The corresponding thin film piezoelectric actuator 1 is not scattered and does not interfere.

As described above, in the present embodiment, the first divided groove 11 and the second divided groove 21 are formed in the substrate 2 by dry etching to divide the substrate 2, so that the substrate is mechanically processed by dicing or the like. Compared with the case of dividing 2, the substrate 2 can be divided without damaging the diaphragm 2 b such as vibration. As a result, it is possible to improve the yield by reducing the breakage of the diaphragm 2b at the time of dividing the substrate, and to reduce the manufacturing cost.

Further, when the film base material 13 is stuck on the first resist 12, the surface of the first resist 12 is flat, so that the film base material 13 can be stuck without entraining bubbles. In the state where air bubbles are interposed between the first resist and the film base material 13, heat distribution is generated in the substrate 2 during the subsequent dry etching in the steps (12) and (13), so that the etching accuracy is deteriorated. Resulting in. However, in this embodiment, since the surface of the first resist 12 is flat and there is no bubble entrainment when the film base material 13 is attached, the etching accuracy is good and stable, and the diaphragm 2b is accurately formed. can do.

Further, since the first resist 12 is removed by dry etching after the film base material 13 is peeled off from the first resist 12, as described above, the individual substrates 2 are supported by the base of the dry etching apparatus. The first resist 12 can be removed. Therefore, it is possible to reduce the damage of the diaphragm 2b due to the chips corresponding to the divided individual substrates 2 being scattered and interfering with each other when or after the first resist 12 is removed. Moreover, since each chip cannot be separated, handling of each chip is also facilitated. Furthermore, by removing the first resist 12 after the film substrate 13 is peeled off by a dry process, the diaphragm 2b is not stressed, and the diaphragm 2b is damaged when the first resist 12 is removed. Nor.

Moreover, since the adhesive film 13b which has the adhesion layer 13b which becomes lower adhesion than before peeling by heating or light irradiation is used as the film substrate 13, the film substrate 13 is peeled from the first resist 12. It becomes easy and the workability | operativity at the time of manufacture can be improved.

[Other examples of film substrate]
FIG. 4 is a cross-sectional view showing another configuration of the film substrate 13 to be used, which is a part of the manufacturing process of the thin film piezoelectric actuator 1. In the film substrate 13, the adhesive layer 13b attached to one side of the substrate 13a contains the thermal foam 31. At the time of peeling, the thermal foam 31 is foamed by heating, so that the adhesive layer 13b is lower than before peeling. It may be a heat-foamed sheet that becomes sticky. As such a film base 13 (thermal foam sheet), for example, TG-0330-6 and TG-0330-4 manufactured by Sumilon can be used.

The adhesive layer 13b has a two-layer structure. Thermal foam 31 is scattered in the first layer (first layer counted from the base 13a side) of the adhesive layer 13b, and in the second layer (second layer counted from the base 13a side), Non-adhesive layers 32 (olefin resin layers containing a surfactant) that are sufficiently thin with respect to the entire thickness of the adhesive layer 13b are dotted at a mixing rate of 10 to 75 wt%. The blending ratio of the non-adhesive layer 32 may be larger than the blending ratio in the above-mentioned TG-0330-6 or TG-0330-4 manufactured by Sumilon.

When the film base 13 shown in FIG. 4 is peeled from the first resist 12, the heat-foamed body 31 is foamed by heating, whereby the pressure-sensitive adhesive layer 13b is lowered and the pressure-sensitive adhesive force becomes almost zero. It becomes easy to peel the material 13, and workability | operativity at the time of manufacture can be improved. In particular, since the thermal foam 31 is foamed, the film base 13 is relatively pushed up with respect to the substrate 2, so that the film base 13 can be easily peeled without applying a load to the substrate 2. Become. Moreover, since the non-adhesive layer 32 is scattered on the contact side of the adhesive layer 13b with the first resist 12, it is possible to prevent the first resist 12 and the adhesive layer 13b from being firmly fixed, Peeling of the film base 13 can be further facilitated.

Thus, by using the film base material 13 in which the thermal foam 31 is present in the adhesive layer 13b and the non-adhesive layer 32 is scattered on the surface layer portion of the adhesive layer 13b, the film base material 13 is stress-free. Can be peeled off (without stressing the chip).

In the above, the manufacturing method of the thin film piezoelectric actuator applicable to the ink jet head has been described. However, the manufacturing method of the present embodiment can be variously applied to the manufacture of a device using a piezoelectric element, for example, a thermal sensor or an ultrasonic wave. It can also be applied to the manufacture of devices such as sensors.

The manufacturing method of the thin film piezoelectric actuator of the present embodiment described above can be expressed as follows, and the following effects are obtained.

The manufacturing method of the thin film piezoelectric actuator of the present embodiment is a manufacturing method of a thin film piezoelectric actuator in which a substrate is divided to manufacture individual thin film piezoelectric actuators, and includes an electrode and a piezoelectric thin film on one surface of the substrate. Patterning the piezoelectric element, forming a first dividing groove for dividing the substrate on one surface side of the substrate by dry etching, forming the first dividing groove on one surface of the substrate, Forming a first resist for flattening the surface covering the piezoelectric element and the first dividing groove, a step of attaching a film base material on the first resist, and one surface of the substrate And patterning a diaphragm located corresponding to the piezoelectric element and a second divided groove located corresponding to the first divided groove on the other surface opposite to A second resist for forming the substrate, and dry etching the substrate from the other surface side using the second resist as a mask, thereby connecting the diaphragm and the first dividing groove. Forming the second dividing groove penetrating therethrough at the same time.

According to the above manufacturing method, the piezoelectric element is formed on one surface side of the substrate, and the first division groove is formed by dry etching. Then, the diaphragm and the second divided groove are formed simultaneously by dry etching the substrate from the other surface side. At this time, since the second dividing groove is connected to the first dividing groove and penetrates the substrate, eventually, the substrate is along the first and second dividing grooves simultaneously with the formation of the diaphragm and the second dividing groove. And divided into individual thin film piezoelectric actuators (chips).

In this way, the substrate is not mechanically divided using a dicing device or a blade as in the past, but the substrate is divided by dry etching, so that damage caused by mechanical processing (vibration or water pressure of cutting water) ) Is not applied to the diaphragm. Thereby, the breakage of the diaphragm at the time of dividing the substrate can be reduced, and the yield at the time of chip manufacture can be improved.

Further, a first resist is formed on one surface of the substrate so as to cover the piezoelectric element and the first dividing groove. Since the surface of this 1st resist is flat, when a film base material is affixed on this 1st resist, it can affix without enclosing a bubble. As a result, it is possible to suppress a decrease in the accuracy of dry etching caused by heat distribution in the substrate during dry etching when the diaphragm is formed, and the diaphragm can be formed with high accuracy.

In the above manufacturing method, after the diaphragm and the second divided groove are simultaneously formed by dry etching, the film base material is peeled off, and then the first resist is removed by dry etching. May further be included.

After forming the diaphragm and the second dividing groove on the substrate, the film base material is peeled off, and the first resist is removed to obtain individual chips. At this time, since the first resist is removed by dry etching, it is possible to remove the first resist while supporting each chip on the base of the dry etching apparatus. Thereby, since the individual chips are not separated, the breakage of the diaphragm due to the interference (contact) between the chips can be reduced, and the handling of each chip is facilitated.

As the film base material, an adhesive film having an adhesive layer that becomes less adhesive at the time of peeling than before peeling by heating or light irradiation may be used. In this case, since the pressure-sensitive adhesive layer is lowered by heating or light irradiation, the film base material (pressure-sensitive adhesive film) can be easily peeled off, and the workability is improved.

As the film substrate, a heat-foamed sheet having an adhesive layer that becomes less sticky than before peeling due to foaming of the heat-foamed material by heating at the time of peeling may be used. In this case, since the pressure-sensitive adhesive layer is lowered by heating, the film substrate (thermally foamed sheet) is easily peeled off, and workability is improved. In particular, since the thermal foam is foamed, the film base material is relatively pushed up with respect to the substrate. Therefore, the film base material can be easily peeled without applying a load to the substrate.

The thin film piezoelectric actuator of the present embodiment described above is manufactured by the manufacturing method described above.

The present invention can be used for manufacturing devices such as an actuator of an inkjet head, a thermal sensor, and an ultrasonic sensor.

DESCRIPTION OF SYMBOLS 1 Thin film piezoelectric actuator 2 Board | substrate 2b Diaphragm 4 Lower electrode 5 Piezoelectric thin film 6 Upper electrode 7 Piezoelectric element 11 1st division groove 12 1st resist 13 Film base material (adhesive film, thermal foam sheet)
13b Adhesive layer 21 Second dividing groove 22 Second resist 31 Thermal foam

Claims

A thin film piezoelectric actuator manufacturing method for manufacturing individual thin film piezoelectric actuators by dividing a substrate,
Patterning a piezoelectric element including an electrode and a piezoelectric thin film on one surface of the substrate;
Patterning a first dividing groove for dividing the substrate on one surface side of the substrate by dry etching;
Forming a first resist on one surface of the substrate to flatten the surface so as to cover the piezoelectric element and the first dividing groove;
A step of affixing a film substrate on the first resist;
On the other surface of the substrate opposite to the one surface, a vibration plate positioned corresponding to the piezoelectric element and a second divided groove positioned corresponding to the first divided groove are patterned. Forming a second resist for performing,
Using the second resist as a mask, the substrate is dry-etched from the other surface side, thereby simultaneously forming the diaphragm and the second divided groove penetrating through the first divided groove. A method of manufacturing a thin film piezoelectric actuator.
A step of peeling the film substrate after simultaneously forming the diaphragm and the second divided groove by dry etching;
The method of manufacturing a thin film piezoelectric actuator according to claim 1, further comprising a step of removing the first resist by dry etching.
3. The method for producing a thin film piezoelectric actuator according to claim 2, wherein an adhesive film having an adhesive layer that becomes less adhesive at the time of peeling by heating or light irradiation than before peeling is used as the film substrate.
3. The method of manufacturing a thin film piezoelectric actuator according to claim 2, wherein a thermal foam sheet having an adhesive layer that becomes less adhesive than before peeling when the thermal foam is foamed by heating at the time of peeling is used as the film base.
A thin film piezoelectric actuator manufactured by the manufacturing method according to claim 1.