JP2013016738A - Ferroelectric element, ink jet recording head, and ink jet image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferroelectric element that is reliable enough to sufficiently remove etching residue, and suppresses leak current.SOLUTION: A ferroelectric element comprises a diaphragm 11, a lower electrode 20, a ferroelectric layer 30, and an upper electrode 40 formed in this order on a silicon substrate 10. The angle of inclination of the side face of the ferroelectric layer 30 is made θ2=30°, and the angle of inclination of the side face of the upper electrode 40 is made θ1=30°. Accordingly, the collision angle of etching gas or plasma particles is close to a plain surface, which improves the removal rate of etching residue.

Description

  The present invention relates to a ferroelectric element, an ink jet recording head having the ferroelectric element, and an ink jet image forming apparatus (including a multifunction peripheral) including the ink jet recording head.

Since a piezoelectric element as a ferroelectric element including a ferroelectric layer can function as an actuator, it can be widely applied to a liquid ejecting head of an ink jet printer, a gyro sensor, and the like.
For example, when a piezoelectric element is used as the liquid ejecting head, increasing the displacement amount of the ferroelectric film leads to an increase in the liquid ejecting amount.
The piezoelectric element has a capacitor structure in which a ferroelectric layer is sandwiched between a lower electrode and an upper electrode. By arranging such capacitor structures at a high density, a high-quality image can be printed.
On the other hand, when manufacturing a piezoelectric element with a large displacement and a high density, a highly accurate film forming process and patterning process are indispensable. In these processes, the ferroelectric layer is damaged and leakage current is reduced. There was an increase.

  In order to suppress such a leakage current, for example, in Patent Document 1, a lower electrode formed above the base and a lower electrode above the partial region of the base are formed. Including an ferroelectric layer and an upper electrode formed above the ferroelectric layer, and an angle θ formed between the side surface of the ferroelectric layer and the upper surface of the base is set to 45 ° to 75 °, A piezoelectric element, an ink jet recording head, and an ink jet printer that have good displacement and can suppress leakage current are disclosed.

However, although it is described in Patent Document 1 that the displacement amount is good, the improvement value of the displacement amount is only 2.5%, as is apparent from FIG.
According to the test conducted by the present inventors at a similar angle, when the angle is set to 45 ° to 75 °, the residue at the time of etching the ferroelectric and the upper electrode appears in the inclined portion, and the protective layer is a subsequent process. It was found that this was an obstacle during film formation.
Further, it has been found that when the wiring process for applying the driving voltage is performed after the protective layer is coated, the peeling of the wiring film and the increase of the leakage current of the ferroelectric are affected. That is, it has been found that when the tilt angle of Patent Document 1 is implemented, a new problem that degrades reliability occurs.
Furthermore, in the case of a conductive oxide electrode, it has been found that the above residue is remarkably generated, and the influence of the residue after etching affects the next step, which greatly deteriorates the reliability of the device.
In other words, after applying an interlayer insulating layer in a later step, when forming a wiring pattern or forming a moisture-resistant protective layer to ensure reliability, the coverage is degraded due to residues formed during electrode etching. It is expected to cause leaks and short circuits.

  The present invention has been made in view of the present situation as described above. The main object of the present invention is to provide a ferroelectric element that has good reliability and can suppress a leakage current because there are few etching residues. Objective.

In order to achieve the above object, the present invention comprises a substrate and a diaphragm made of an insulator disposed on the substrate, and a lower electrode made of a conductive oxide and a ferroelectric on the diaphragm in order. In a ferroelectric element formed by laminating a body layer, an upper electrode made of a metal and a conductive oxide, an angle θ1 formed between the upper electrode arranged in parallel to the substrate and a side surface of the upper electrode, the lower electrode And the side surface of the ferroelectric layer, and the angle θ3 formed between the lower electrode arranged in parallel with the substrate and the side surface of the lower electrode are each less than 45 °.
The present invention also includes a substrate and a diaphragm made of an insulator disposed on the substrate, and a lower electrode made of a conductive oxide, a ferroelectric layer, a metal, and a conductive material in order on the diaphragm. In the ferroelectric element formed by laminating an upper electrode made of a conductive oxide, the side surface of the upper electrode is formed inside the extended line of the side surface of the ferroelectric layer.
Here, the “side surface of the upper electrode” means an outer peripheral surface having a vertical height.

  According to the present invention, since there are few etching residues, reliability is favorable and leakage current can be suppressed.

1 is a partial cross-sectional view of a ferroelectric element according to an embodiment of the present invention. It is sectional drawing of the ferroelectric element containing the inclination-angle of a lower electrode. It is sectional drawing of the ferroelectric element of the example in which the side surface (outer peripheral surface) of an upper electrode is located inside the upper surface end of a ferroelectric layer. It is sectional drawing of the ferroelectric element in which the protective layer was formed. It is a schematic diagram which shows the principle of the presence or absence of an etching residue, (a) is sectional drawing for demonstrating the reason for the residue with the inclination angle in a prior art example, (b) is the top view, (c) is the top view of this invention It is sectional drawing for demonstrating the reason that the residue in an inclination angle does not remain. FIG. 2 is an exploded perspective view of a single inkjet recording head. It is a flowchart which shows the manufacturing process of a ferroelectric element. 1 is a schematic perspective view of an ink jet image forming apparatus. FIG.

Embodiments of the present invention will be described below with reference to the drawings.
An outline of a method for manufacturing a thin film ferroelectric actuator formed with a normal film thickness of several μm or less will be described.
A piezoelectric actuator is formed by laminating a diaphragm layer, an electrode layer (lower part), a ferroelectric film layer, an electrode layer (upper part), a protective layer, an interlayer insulating layer, and an electrode wiring layer on a Si substrate.
In order to form the shape of the ferroelectric element, after forming the ferroelectric film or the upper electrode layer, the shape of the ferroelectric element and the shape of the upper electrode are formed into desired shapes by an etching technique. Further, since the protective layer and the interlayer insulating layer need only be formed in a desired portion, in order to obtain a desired shape, the protective layer and the interlayer insulating layer are formed by the same etching technique as the piezoelectric film or the upper electrode layer.
The outline is such a configuration, but a more detailed description will be given regarding the materials and processes used.

The substrate is a material that can be easily processed with the required mechanical strength and chemical resistance, and is required to have thermal resistance because it passes through many thermal processes when forming the ferroelectric film. From such a background, a Si (silicon) substrate is suitable, and a Si substrate is mainly used.
The vibration plate layer is formed on the Si substrate by plasma CVD, sputter film formation, thermal oxidation, or the like using an oxide or nitride single layer film or laminated film. In simple terms, it is often formed by thermal oxidation of Si. However, when used as a piezoelectric actuator, particularly an inkjet head, it is formed in consideration of required strength and vibration characteristics.
Specifically, a SiO ₂ thermal oxide film, a laminated film of SiO ₂ film and SiN film, a ZrO ₂ film, a laminated film of SiO ₂ film and ZrO ₂ film, etc. are used. The total film thickness is about several μm.

Conventionally, metal materials such as Pt, Ir, Ru, Ti, Ta, Rh, and Pd have been used as the electrode material. Traditionally, Pt is mainly used, but the background of Pt being used frequently is a face-centered cubic lattice (FCC) structure, which is a close-packed structure, and has high self-orientation, and SiO ₂ that is a material of the diaphragm. This is because, even if a film is formed on such an amorphous film, it is strongly oriented to (111), and the ferroelectric film thereon is also well oriented.
However, since the orientation is strong, columnar crystals grow and there is a problem that Pb and the like are easily diffused into the base electrode along the grain boundary. There was also a problem with the adhesion between Pt and SiO _2, and the Pt film was peeled off.
Therefore, in order to improve the adhesion between Pt and SiO ₂ , a metal film such as Ti, Zr, Ta, an oxide film such as TiO ₂ , Ta ₂ O ₅ , ZrO ₂ , or a nitride film such as TiN is used. ing.

Finally, as an electrode material, interdiffusion of materials due to a repeated thermal process, influence on crystallinity of a ferroelectric layer to be laminated next, and electrical characteristics when formed as an element, that is, PE It is selected comprehensively in view of characteristics such as hysteresis characteristics, leakage current characteristics, and fatigue characteristics.
In recent years, conductive oxide electrode materials having the same perovskite structure as ferroelectrics have been studied as electrodes with ferroelectrics. _{Specifically, IrO 2, LaNiO 3, RuOx} , SrO, etc. SrRuO _3, CaRuO ₃ are known.
The range of conductive oxide electrodes that can be selected are BaRuO ₃ , SrRuO ₃ , (Ba, Sr) RuO ₃ , BaPbO ₃ , LaCuO ₃ , LaNiO ₃ , LaCoO ₃ , LaTiO ₃ , (La, Sr) CoO ₃ , (La , Sr) VO ₃ , (La, Sr) MnO ₃ , LuNiO ₃ , CaVO ₃ , CaIrO ₃ , CaRuO ₃ , CaFeO ₃ , SrVO ₃ , SrCrO ₃ , SrIrO ₃ , SrFeO ₃ , ReO ₃ , etc. Among these constituent materials, ruthenium oxides (for example, RuO ₃ , BaRuO ₃ , SrRuO ₃ , (Ba, Sr) RuO ₃ ) are particularly preferable from the viewpoint of low electrical conductivity, easy handling, and high stability of characteristics. It is.

In the present embodiment to be described later, the form applied as the lower electrode and the upper electrode has been described with SrRuO ₃ , but is not limited thereto.
Further, as an electrode forming process to be used, a sputter film forming method is mainly used. In addition, it can carry out by well-known methods, such as a vacuum evaporation method and CVD (Chemical Vapor Deposition) method.
The characteristics required as an electrode material can be summarized as follows.
(1) The electric resistance is sufficiently low.
(2) The mismatch between the ferroelectric material and the lattice constant is small.
(3) High heat resistance.
(4) Low reactivity.
(5) High diffusion barrier property.
(6) Good adhesion to the substrate, adhesion layer material, and ferroelectric.
(7) The electrical characteristics as an element are good.
As a film thickness, it can form in the range of about 50-400 nm by the sum total of adhesion layer-electrode layer-oxide electrode layer.

As a ferroelectric, lead zirconate titanate (hereinafter referred to as PZT) having a Zr: Ti ratio of 52:48 is usually used, and it is used as a mainstream because of its good piezoelectric performance and stable characteristics. It has been. Regardless of the above composition, lead zirconate titanate is used as an oxide containing lead, zirconium, and titanium as constituent elements at various ratios, and with additives mixed or substituted.
As another material system, a perovskite oxide represented by the general formula ABO ₃ (A includes Pb, B includes Zr and Ti) is preferably used, and niobate titanate using Nb. Lead zirconate (PZTN) is known.
Furthermore, BaTiO ₃ (barium titanate, BT), barium, strontium, titanium composite oxide (BST), strontium, bismuth, tantalum composite oxide (SBT), etc. that do not use Pb are used from the viewpoint of environmental friendliness. Can do.

As the process, a liquid phase method such as a sol-gel method or a metal organic thermal coating decomposition method (MOD method), a gas phase method such as a sputtering method, an ablation method, or a CVD method is used.
For example, when using the sol-gel method, a solution in which an organometallic compound containing Pb, Zr, and Ti is dissolved in a solvent is applied on the lower electrode film, and then a drying step and a degreasing step, and By passing through a crystallization heat treatment step, a ferroelectric layer can be formed. The drying step and the crystallization heat treatment step may be performed for each coating layer, or several layers may be performed together. When one layer or several layers are combined, a series of steps can be repeated to obtain a ferroelectric layer having a desired film thickness. The temperature of the drying step is 350 to 550 ° C., and the temperature of the crystallization heat treatment step is about 600 to 750 ° C. The heating time is about several tens of seconds to several minutes.

The film thickness of the ferroelectric layer can be, for example, several tens of nm to several μm.
Next, a ferroelectric layer element portion is formed. For forming the element portion, a mask layer at the time of etching is usually formed by patterning a photosensitive resist, and the element portion is formed by dry or wet etching. The patterning of the photosensitive resist can be performed by a known photolithography technique.
That is, a photosensitive resist is applied to a sample substrate to be etched by a spin coater or a roll coater, and then exposed to ultraviolet rays with a glass photomask on which a desired pattern has been formed in advance, followed by pattern development, washing with water and drying to form a photosensitive resist mask layer. Form.
In the formed photosensitive resist mask layer, the inclination of the edge of the pattern affects the inclined cross section during etching.Therefore, depending on the desired inclination angle, the resist selectivity (ratio of the etching rate of the material to be etched and the mask material). ) Should be selected. The photosensitive resist remaining on the film after etching can be removed by a dedicated stripping solution or oxygen plasma ashing.

Etching is selected from dry etching using a reactive gas because of the stability of the shape. Etching gas is a halogen gas such as chlorine or fluorine, or a gas obtained by mixing Ar or oxygen with a halogen gas. Can be implemented.
By changing the etching gas or the etching conditions, the etching can be performed continuously with the upper electrode and the ferroelectric material, or the resist pattern can be redone once and divided into several times.
When using a conductive oxide electrode, it is important to pay attention to the angle at the time of pattern etching so that no residue is generated at the time of etching. The angle should always be such that the surface and side surfaces are treated with the etching gas, and the angle should be less than 45 °.

An upper electrode layer is formed on the ferroelectric layer. The material of the upper electrode layer can be the same material as that of the lower electrode layer. Unlike the lower electrode material layer, the material of the upper electrode is not a high-temperature process, such as forming a ferroelectric layer, and it does not require lattice constant matching with the ferroelectric material. Wider than the lower width electrode.
However, since it has been shown in the prior art that oxygen deficiency in the ferroelectric increases over time during ferroelectric operation, a conductive oxide electrode is used as a supply source for the deficient oxygen component. Has been done. That is, the oxide electrode layer described in the section of the lower electrode material has been used at the contact interface with the dielectric material.
Therefore, the material system specifically used is the same as that of the lower electrode, and as the oxide electrode layer, IrO2, LaNiO ₃ , RuO2, SrO, SrRuO ₃ , CaRuO _{3 and the} like are used, and as the metal electrode layer, Pt, Ir, Ru, Ti, Ta, Rh, Pd, etc. are used.

As a process for forming the upper electrode, a sputter film formation method is mainly employed. In addition, it can carry out by well-known methods, such as a vacuum evaporation method and CVD (Chemical Vapor Deposition) method.
The film thickness of the upper electrode can be formed in the range of about 50 to 300 nm as the sum of the oxide electrode layer and the electrode layer.
In addition, this step may be a process sequence in which the upper electrode layer is formed and the upper electrode shape ferroelectric layer shape is continuously formed after forming the electrode before forming the element portion of the ferroelectric layer.
The protective layer is disposed for the purpose of shielding the ferroelectric element portion sandwiched between the electrodes and the cross-sectional portion where the element shape is formed from the influence of the driving environment such as humidity. Since an oxide is used as the material of the protective layer and denseness is required, an ALD (Atomic Layer Deposition) method is used in particular. Specifically, an Al ₂ O ₃ ALD film is used. The film thickness is about 30 to 100 nm.

Next, the interlayer insulating layer is used as an insulating layer for contact between the wiring electrode and the upper and lower electrodes of the ferroelectric element which are stacked in the next step. The material is formed of oxide, nitride, or a mixture thereof.
The film thickness is 300 to 700 nm. After the formation of the interlayer insulating layer, a through hole for contact between the wiring electrode and the upper and lower electrodes is formed by etching using photolithography. The remaining resist is removed by ashing or the like using oxygen plasma.
The wiring electrode layer is used for taking out individual electrodes and common electrodes of the ferroelectric element, and is formed by selecting a material that can make ohmic contact with the upper and lower electrode materials. Specifically, it is possible to use a wiring material in which pure Al or Al contains a heat-lock formation-inhibiting component such as several atomic% of Si. Alternatively, from the viewpoint of conductivity, a wiring material for semiconductors mainly composed of Cu may be used.

The film thickness is set so that the wiring resistance does not hinder the ferroelectric drive considering the resistance due to the routing distance. Specifically, the film thickness is about 1 μm for Al wiring. The wiring electrode layer formed in this way forms a desired shape using a photolithography technique. The remaining resist is removed by ashing or the like using oxygen plasma.
The wiring material layer is covered with an oxide or nitride protective layer in order to ensure environmental resistance except for portions necessary for electrical connection.
Finally, the substrate in which the ferroelectric actuator element is formed by deepening the Si substrate by ICP (Inductively Coupled Plasma) etching is completed in the liquid chamber portion up to the vibration plate portion using photolithography technology.

Here, it describes about the ferroelectric element which is the objective of this invention, is reliable, and can suppress a leakage current.
As described above, after forming the film up to the upper electrode, an etching process for forming the shape of the element is performed. In this etching process, redeposition (deposition of residues) of an object to be etched accompanying the etching becomes a problem.
The reason why redeposition is a problem is that the material to be etched, such as ferroelectrics and electrode materials, is difficult to etch, so the residue deposited by redeposition also becomes difficult to etch, and it is difficult to etch as the process continues. When it adheres to the film, it becomes a cause that a leak current is generated through a residue as a residue, a coating defect in a later process, and a residue.
However, when the inclination angle is less than 45 °, as will be described later, since the residue portion is effectively contacted by reactive etching and plasma treatment, insufficient etching and redeposition are unlikely to occur. Therefore, the ferroelectric element structure that works effectively even when the interlayer insulating layer is coated and has less leakage can be realized.

The reason why the angle is less than 45 ° was obtained experimentally.
As shown in FIGS. 5 (a) and 5 (b), a residue R was generated on the inclined portion in the vicinity of 55 ° (55.2 °). Further, even at 45 °, generation of residue was observed in the inclined portion.
The reason is that when the inclination angle θ is 45 ° or more, the collision angle α of the etching gas or the plasma particles P with respect to the inclined surface (the side surface of the ferroelectric layer and the upper electrode) is small, so that the residue R exists on the inclined surface. It is because it is easy to do or the removal rate falls.
On the other hand, in the configuration in which the angle was less than 45 °, no residue was observed in the inclined portion, the leakage current in the case of the element was small, and there was no short circuit.
At the angle of the present invention (less than 45 °), as shown in FIG. 5C, the collision angle α of the etching gas and the plasma particles P with respect to the inclined surface is increased, and the generation of the residue R is suppressed, or the removal rate thereof. Because it becomes higher.

[Example 1]
(Example of forming a piezo head by the SG process)
An example in which a thin film ferroelectric actuator is fabricated in the configuration shown in FIG. In this embodiment, θ = 30 °.
First, the diaphragm 11 was formed on the surface of the Si (100) substrate material 10 by CVD. As a detailed laminated structure, a SiO ₂ film was formed with a film thickness of 600 nm. Next, after forming a polysilicon film of 250 nm, four layers of a SiO ₂ film of 100 nm and a SiN film of 150 nm were sequentially laminated, and a SiO ₂ film of 100 nm was further formed. A polysilicon film having a thickness of 250 nm was formed again, and then a SiO ₂ film having a thickness of 600 nm was formed, whereby the diaphragm 11 having a laminated structure was obtained.
These laminated structures are for improving the durability of the diaphragm, and may be a film in which only a SiO ₂ film is formed in a thickness of 1 to 3 μm.
Next, the lower electrode layer 20 is formed on the substrate on which the vibration plate 11 is formed. As the adhesion layer material 21, a Ti film having a thickness of 50 nm was formed by sputtering, and then the electrode films 22 and 23 were formed as a Pt film 250 nm and an SrRuO ₃ film was formed as 60 nm to form the lower electrode layer 20.
The sputtering conditions for Ti and Pt at this time were as follows: the degree of vacuum was 0.5 Pa, the sputtering gas was Ar 30 sccm, the input power was 500 w, and the substrate temperature was 300 ° C. The SrRuO ₃ film was annealed for 5 minutes under the condition of 550 ° C. using an RTA apparatus (Rapid Thermal Annealing, Accu Thermo AW410 manufactured by Hysol) because sufficient crystallization was not obtained at a substrate temperature of 300 ° C.

The lower electrode 20 formed in this way was oriented in the (111) plane, and the half width of the (111) plane was 2.34 °.
Next, a lead titanate-based piezoelectric thin film to be a ferroelectric film (ferroelectric layer) 30 was formed on the lower electrode film 20 by a sol-gel method. Specifically, lead acetate trihydrate, titanium isopropoxide, and zirconium propoxide were used as starting materials, and 2 methoxyethanol was used as a solvent.
First, lead acetate trihydrate is dissolved in 2 methoxyethanol and distilled at 137 ° C. to discharge crystal water. Next, the hydrated Zr and Ti alkoxides weighed so as to obtain the most generally easy to obtain properties (in this case Pb / Ti / Zr = 100/47/53), the dehydrated lead acetate solution In addition, a composite alkoxide solution was prepared in Pb, Ti, and Zr by refluxing at 127 ° C.

Using this solution, a thin film was formed on a SrRuO ₃ / Pt / Ti / diaphragm 11 / Si substrate with the (111) plane oriented in the film thickness direction by spin coating at 3000 rpm.
Next, after drying this, the organic material pyrolysis was repeated 10 to 25 times at a temperature condition of 350 to 500 ° C. and holding time: 3 to 5 minutes, respectively, and then 700 ° C. at a heating rate of 30 ° C./sec. C. Firing for 5 minutes was performed in an O ₂ atmosphere to form a Pb (Ti _0.47 Zr _0.53 ) O ₃ thin film 30 having a thickness of 300 nm to 1 μm.
After forming the ferroelectric film 30, a RIE dry etching apparatus is used to form a photoresist pattern by using a photolithographic technique using a photoresist, and after patterning the photoresist, using a fluorine-based etching gas. A ferroelectric element portion was formed by
At this time, the shape of the photoresist was adapted so that the inclination angle of the ferroelectric portion was θ2 = 30 °, and the cross-sectional inclination angle measurement of the ferroelectric element portion was performed by cross-sectional measurement of SEM.

Further, the upper electrode film 40 was formed. The production conditions were the same as for the lower electrode, SrRuO ₃ being 40 nm as the conductive oxide electrode layer 41, and then a Pt film electrode as the metal electrode layer 42 at a substrate temperature of 300 ° C. and a film thickness of 100 to 150 nm. Formed. The process conditions are an RF input power of 500 W and an Ar gas pressure of 0.5 Pa.
As in the case of the ferroelectric material, the upper electrode 40 is also formed by using a photolithographic technique to form a photosensitive resist pattern, and this time, the upper electrode layer 40 is etched with a chlorine-based etching gas to form the upper electrode. . At this time, the shape of the photoresist was adapted so that the inclination angle of the upper electrode portion was θ1 = 30 °, and the cross-sectional inclination angle measurement of the ferroelectric element portion was performed by cross-sectional measurement of SEM.

Further, the lower electrode is subjected to photolithographic patterning with a photosensitive resist as a pattern portion wider than the ferroelectric pattern and the upper electrode pattern, and the lower electrode 20 is formed in the same manner as the ferroelectric element formation and the upper electrode formation. Went.
The lower electrode 20 was formed by etching the upper electrode layer 40 with a chlorine-based etching gas in the same manner as the upper electrode. As shown in FIG. 2, the shape of the photoresist is adapted so that the inclination angle of the upper electrode portion at this time is θ2 = 30 °, and the cross-sectional inclination angle measurement of the ferroelectric element portion is performed by the cross-sectional measurement of the SEM. Carried out.
Further, using the photosensitive resist in the state of the laminated film thus formed, first, the Si substrate side is patterned and etched so as to have a shape as shown in FIG. A cavity was formed.
At this time, the SiO ₂ film to be the vibration plate 11 becomes an etching stop layer. Next, a holding substrate was bonded to the processed Si substrate side, and a mask layer was similarly formed on the ferroelectric film 30 side using a photosensitive resist, and then processed by ICP. After the ICP processing, the mask layer formed with the photosensitive resist was removed. Thus, a piezoelectric element composed of the lower electrode film 20 / ferroelectric film 30 / upper electrode film 40 is obtained.

Thereafter, a nozzle plate 80 in which nozzle holes 79 corresponding to the pressurized liquid chamber 70 are formed in SUS316 (plate thickness 50 μm) on the opposite side of the pressurized liquid chamber 70 from the piezoelectric element is joined with an epoxy resin. The piezoelectric actuator structure (droplet discharge head 1) was completed.
Here, the dimensional parameters used are a ferroelectric pitch of 85 μm, a ferroelectric width of 46 μm, a length of 750 μm, and a ferroelectric thickness of 2 μm.
The liquid chamber width was 60 μm, the liquid chamber length was 800 μm, and the liquid chamber depth was 55 μm.
Electrical measurements were performed on the ferroelectric element thus formed. The measured items were leakage current and mechanical ferroelectric fluctuation. The measurement environment was set to 34-37% RH with the humidity cut off, and was carried out in a desiccator. Electrically, there was no leakage and short circuit, and the fluctuation amount was 0.15-0.2 μm when 30-50 V was applied.

[Example 2]
(Example when upper electrode is narrower than PZT (ferroelectric film 30))
In order to eliminate leakage of the upper electrode side surface (peripheral surface having a height in the vertical direction) and the ferroelectric side surface, the upper electrode width can be made narrower than the PZT width. In FIG. 3, the size is made smaller than the dimension PZT corresponding to the range of one side X. Specifically, X = 2 μm. As a result of measuring the electrical characteristics, there was no leakage or short circuit. The specific determination of the leak was that there was a leak when μA flowed when 50 V was applied.
Normally, when a voltage of the same condition is applied by a strip type pattern having a width of 60 μm and a length of 800 μm in an 85 μpitch pattern equivalent to 300 dpi, the amount of electricity flowing through the element is about pA.

[Example 3]
(Example of further including a protective layer)
In Example 1, the protective layer 50 was formed on the upper electrode. Although it was a normal indoor condition of 25 ° C. and 60% RH, leakage and electrode discharge were swept from 0 to 200 VDC, and the current detected by several μA usually increased by an order of magnitude or more. In this case, it was determined that there was a leakage current.
In the case of a short circuit (short), the determination was made in a completely conductive state or a completely open state. In the case of the protective layer, leakage and short circuit did not occur.

[Comparative example]
(Comparative example 1) When θ = 45 ° or more An oblique SEM image when θ is 55.2 ° that is 45 ° or more is shown in FIG. The redeposited material etched on the inclined portion is deposited as a residue R. If such a deposit exists, the interlayer insulating layer cannot be sufficiently covered, which causes a leak.
(Comparative example 2) When there is no protective layer on an upper electrode The electrical property was measured in the state which does not form a protective layer on an upper electrode. As a result, discharge occurred between the electrodes, and dissolution of the upper electrode and discharge traces were observed.

An embodiment of a single ink jet recording head is shown in FIG. The common flow path plate 72 is joined to the piezoelectric actuator substrate 71 to which the nozzle plate 80 is joined, and the piezoelectric actuator 73 as a ferroelectric element is driven by a flexible printed board on which a drive circuit for driving the piezoelectric body is mounted. .
By using this heat-resistant adhesion layer, peeling of the electrode layer does not occur, so that a drive failure due to disconnection does not occur and a stable inkjet head can be obtained.
In FIG. 6, reference numeral 31 denotes a pressurized liquid chamber, 32 denotes a fluid resistance portion, 33 denotes a common liquid chamber, 33a denotes an ink supply portion, and 74 denotes a piezoelectric element protection space.
FIG. 7 is a flowchart showing the manufacturing process of the ferroelectric element.

Next, an example of an ink jet image forming apparatus (ink jet recording apparatus) equipped with the ink jet recording head according to the present invention will be described with reference to FIGS. 8 is an explanatory perspective view of the recording apparatus, and FIG. 9 is an explanatory side view of a mechanism portion of the recording apparatus.
The ink jet recording apparatus includes a carriage that is movable in the main scanning direction inside the recording apparatus main body 81, a recording head that includes the ink jet recording head mounted on the carriage, an ink cartridge that supplies ink to the recording head, and the like. The mechanism portion 82 and the like are accommodated, and a sheet feeding cassette (sheet feeding tray) 84 on which a large number of sheets 83 can be stacked from the front side is detachably attached to the lower portion of the apparatus main body 81.
Further, the manual feed tray 85 for manually feeding the paper 83 can be opened, the paper 83 fed from the paper feed cassette 84 or the manual feed tray 85 is taken in, and a required image is displayed by the printing mechanism unit 82. After recording, the paper is discharged to a paper discharge tray 86 mounted on the rear side.

The printing mechanism 82 holds a carriage 93 slidably in the main scanning direction by a main guide rod 91 and a sub guide rod 92 which are guide members horizontally mounted on left and right side plates (not shown). A head 94 composed of the ink jet recording head that ejects ink droplets of each color (Y), cyan (C), magenta (M), and black (Bk) crosses a plurality of ink ejection ports (nozzles) with the main scanning direction. And are mounted with the ink droplet ejection direction facing downward.
Each ink cartridge 95 for supplying ink of each color to the head 94 is replaceably mounted on the carriage 93.
The ink cartridge 95 has an air port that communicates with the atmosphere upward, a supply port that supplies ink to the ink jet recording head below, and a porous body filled with ink inside. The ink supplied to the ink jet recording head is maintained at a slight negative pressure by the capillary force.
Here, the heads 94 of the respective colors are used as the recording heads, but one head having nozzles for ejecting ink droplets of the respective colors may be used.

The carriage 93 is slidably fitted to the main guide rod 91 on the rear side (downstream side in the paper conveyance direction) and is slidably mounted on the sub guide rod 92 on the front side (upstream side in the paper conveyance direction). Yes.
In order to move and scan the carriage 93 in the main scanning direction, a timing belt 100 is wound around a driving pulley 98 and a driven pulley 99 that are rotationally driven by a main scanning motor 97, and the timing belt 100 is fixed to the carriage 93. . The carriage 93 is reciprocated by forward and reverse rotation of the main scanning motor 97.
On the other hand, in order to convey the paper 83 set in the paper feed cassette 84 to the lower side of the head 94, the paper 83 is guided to the paper feed roller 101 and the friction pad 102 for separating and feeding the paper 83 from the paper feed cassette 84. A guide member 103, a conveyance roller 104 that reverses and conveys the fed paper 83, a conveyance roller 105 that is pressed against the circumferential surface of the conveyance roller 104, and a leading roller that defines a feeding angle of the sheet 83 from the conveyance roller 104. 106. The transport roller 104 is rotationally driven by a sub-scanning motor 107 through a gear train.

Corresponding to the range of movement of the carriage 93 in the main scanning direction, there is provided a printing receiving member 109 which is a sheet guide member for guiding the sheet 83 fed from the conveying roller 104 below the recording head 94. A conveyance roller 111 and a spur 112 that are rotationally driven to send the paper 83 in the paper discharge direction are provided downstream of the printing receiving member 109 in the paper conveyance direction, and a paper discharge roller that sends the paper 83 to the paper discharge tray 86. 113 and a spur 114, and guide members 115 and 116 that form a paper discharge path are disposed.
At the time of recording, the recording head 94 is driven according to the image signal while moving the carriage 93, thereby ejecting ink onto the stopped sheet 83 to record one line. Record the line.
Upon receiving a recording end signal or a signal that the trailing edge of the paper 83 has reached the recording area, the recording operation is terminated and the paper 83 is discharged.

A recovery device 117 for recovering defective ejection of the head 94 is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 93. The recovery device 117 includes a cap unit, a suction unit, and a cleaning unit. The carriage 93 is moved to the recovery device 117 side during printing standby and the head 94 is capped by the capping means, and the ejection port portion is kept in a wet state to prevent ejection failure due to ink drying.
Further, by ejecting ink that is not related to recording during recording or the like, the ink viscosity of all the ejection ports is made constant and stable ejection performance is maintained.
When a discharge failure occurs, the discharge port (nozzle) of the head 94 is sealed with a capping unit, and bubbles and the like are sucked out from the discharge port with the suction unit through the tube. Is removed by the cleaning means to recover the ejection failure.
Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body and absorbed and held by an ink absorber inside the waste ink reservoir.
As described above, in the ink jet recording apparatus, since the electrode layer is not peeled off by using the heat-resistant adhesive layer, there is no ink droplet ejection failure due to driving failure, and stable ink droplet ejection characteristics can be obtained. The image quality is improved without any omission.

DESCRIPTION OF SYMBOLS 10 Substrate 11 Diaphragm 20 Lower electrode 30 Ferroelectric layer 40 Upper electrode 50 Protective film

JP 2008-235569 A

Claims (9)

A substrate and a diaphragm made of an insulator disposed on the substrate, and a lower electrode made of a conductive oxide, a ferroelectric layer, a metal and a conductive oxide in that order on the diaphragm In a ferroelectric element formed by laminating electrodes,
An angle θ1 formed between the upper electrode disposed in parallel with the substrate and the side surface of the upper electrode, an angle θ2 formed between the lower electrode and the side surface of the ferroelectric layer, and a lower electrode disposed in parallel with the substrate And a side surface of the lower electrode, each of which has an angle θ3 of less than 45 °. The ferroelectric element according to claim 1,
The ferroelectric element, wherein a side surface of the upper electrode is formed inside an extension line of a side surface of the ferroelectric layer. A substrate and a diaphragm made of an insulator disposed on the substrate, and a lower electrode made of a conductive oxide, a ferroelectric layer, a metal and a conductive oxide in that order on the diaphragm In a ferroelectric element formed by laminating electrodes,
The ferroelectric element, wherein a side surface of the upper electrode is formed inside an extension line of a side surface of the ferroelectric layer. The ferroelectric element according to claim 3, wherein
An angle θ formed by the upper surface of the lower electrode and the side surface of the ferroelectric layer is less than 45 °. In the ferroelectric element according to any one of claims 1 to 4,
A ferroelectric element comprising a protective film covering at least a side surface of the ferroelectric layer. The ferroelectric element according to claim 5, wherein
The ferroelectric element, wherein the protective film is made of silicon oxide or aluminum oxide. In the ferroelectric element as described in any one of Claims 1-6,
The ferroelectric element, wherein the ferroelectric layer contains lead zirconate titanate.   An ink jet recording head comprising the ferroelectric element according to claim 1.   An ink jet image forming apparatus comprising the ink jet recording head according to claim 8.

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