JP2013184313A - Method of manufacturing liquid droplet ejection head, liquid droplet ejection head, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid droplet ejection head which can maintain ink ejection characteristics excellently, and obtain stable ink ejection characteristics even after continuously ejecting.SOLUTION: When a liquid droplet ejection head 300 is made, after a vibrating membrane 202 that contains at least one of a silicon oxide film and a silicon nitride film is formed by LPCVD (low pressure chemical vapor deposition) accumulation on a substrate 201, and a surface of the vibrating membrane 202 is polished by CMP (chemical mechanical polishing) using at least cerium oxide particles for abrasive particles so that a period of projections with the depth of 5 nm or more exceeds 150 nm. Then, after a lower electrode film 203 that contains a Pt group metal is formed, an electromechanical conversion film 204 such as PZT (lead titanate zirconate) and an upper electrode film 205 such as Pt are formed.

Description

  The present invention relates to a method for manufacturing a droplet discharge head, a droplet discharge head manufactured by the manufacturing method, and an image forming apparatus including the droplet discharge head.

  Some image forming apparatuses such as printers, facsimiles, and copying machines are equipped with a droplet discharge head that discharges ink droplets for image formation. The droplet discharge head includes a nozzle that discharges ink droplets, a pressurizing chamber that stores ink that becomes droplets, and energy generation means that serves as a driving source that pressurizes the ink in the pressurizing chamber. The pressurizing chamber is also referred to as an ink flow path, a pressurized liquid chamber, a pressure chamber, a discharge chamber, a liquid chamber, and the like. The ink in the pressurizing chamber is pressurized by the energy generating means and ejected as ink droplets from the nozzle. As this energy generating means, an electromechanical conversion element such as a piezoelectric element, an electrothermal conversion element such as a heater, or a vibration plate that forms the wall surface of an ink flow path, and an element that includes an electrode facing the vibration plate are employed. .

Two types of electromechanical transducers have been put into practical use, one using a longitudinal vibration mode that extends and contracts in the axial direction of the electromechanical transducer and one using a flexural vibration mode. As an electromechanical conversion element using the flexural vibration mode, an element in which a uniform electromechanical conversion element layer (piezoelectric material layer: piezoelectric material film) is formed over the entire surface of the diaphragm by a film forming technique is known. In order to fabricate the electromechanical transducer, the piezoelectric material film is cut into a shape corresponding to the pressure generation chamber by a lithography method and disposed independently in each pressure generation chamber.
In an electromechanical conversion element using such a flexure mode, when the vector component of the spontaneous polarization axis of the piezoelectric material layer matches the electric field application direction, the expansion and contraction accompanying the increase / decrease in the electric field application intensity occurs effectively, A piezoelectric constant is obtained. Therefore, it is most preferable that the spontaneous polarization axis of the piezoelectric material layer completely coincides with the electric field application direction. In addition, in order to suppress variations in the ink discharge amount, it is preferable that the in-plane variation in the piezoelectric performance of the piezoelectric material layer is small. Considering these points, the piezoelectric material layer needs to have excellent crystal orientation.

Patent Document 1 describes that a piezoelectric film having excellent crystal orientation can be formed by forming a piezoelectric film on a Ti-containing noble metal electrode on which Ti is deposited in an island shape.
Patent Document 2 describes that a piezoelectric film having excellent crystal orientation can be formed by using an MgO substrate as a substrate.
Patent Document 3 describes a method of manufacturing a ferroelectric film in which an amorphous ferroelectric film is formed and then the film is crystallized by a rapid heating method.
Further, Patent Document 4 discloses that in the film forming step, a perovskite complex oxide (including inevitable impurities) having any crystal structure of tetragonal, orthorhombic, and rhombohedral. Of the piezoelectric film which is preferentially oriented to any one of the (100) plane, the (001) plane, and the (111) plane, and the degree of orientation is 95% or more. A manufacturing method is described.
Various studies have been made on the above-described diaphragm to improve performance. A metal oxide film (see, for example, Patent Document 5), a polysilicon film, a silicon oxide film, and a silicon nitride film (see, for example, Patent Document 6). Attempts have been made to form such as.

  The present invention has been made in view of the above problems, and a method for manufacturing a droplet discharge head capable of maintaining good ink discharge characteristics and obtaining stable ink discharge characteristics even when continuously discharged. An object is to provide an ejection head and an image forming apparatus.

  The method of manufacturing a droplet discharge head according to the present invention includes at least an oscillation layer formed by CVD, a pair of electrode layers containing a Pt group metal formed on the oscillation film, and an electric machine formed by sandwiching the electrode film In a method for manufacturing a droplet discharge head including a conversion layer, the surface of the vibration film is subjected to CMP polishing after the vibration layer is formed and before the electrode layer is formed.

  According to the present invention, an electrode layer having excellent crystal orientation and an electromechanical conversion layer can be produced, and a droplet discharge head having good ink discharge characteristics and stable ink continuous discharge characteristics can be obtained.

2 is a cross-sectional view of a droplet discharge head according to Embodiment 1. FIG. It is an expanded sectional view of the A section in FIG. FIG. 3 is an X-ray diffraction result of Pt on a CVD laminated film and a thermal oxide film of the droplet discharge head according to Embodiment 1, and (a) is a graph comparing Pt (111) peaks when θ-2θ is swung. (B) is a graph showing a rocking curve of Pt (111). 6 is a graph showing a cross-sectional profile of a CVD laminated film after CMP processing in the method for manufacturing a droplet discharge head according to Embodiment 1. It is a graph which similarly shows the CVD laminated film cross-sectional profile without CMP process. It is a figure which shows the cross section of Pt electrode film on a CVD laminated film, (a) is a SEM image when CMP processing is not carried out on a CVD laminated film, (b) is SEM when CMP treatment is carried out on a CVD laminated film. It is a statue. 3 is a cross-sectional view of a droplet discharge head array according to Embodiment 1. FIG. 5 is a perspective view of an image forming apparatus according to Embodiment 2. FIG. It is sectional drawing of the image forming apparatus.

The present inventor has found that in a piezoelectric element having a diaphragm composed of layers formed by LPCVD, the surface roughness of the diaphragm greatly affects the crystal orientation of the lower electrode film and the electromechanical conversion film. It has been found that it has an influence on the superiority and inferiority of the droplet discharge characteristics, and that control of the surface roughness of the diaphragm is therefore important. In addition, by reducing the surface roughness of the diaphragm, it is possible to obtain an electromechanical vibration film that is less likely to cause electric field concentration, can increase the pressure resistance, and can suppress deterioration of the electromechanical conversion film. Got.
Specifically, it has been found that the surface roughness of the CVD laminated film is not merely small, but there is another factor other than the roughness. That is, when the inventors observed paying attention to the period of the convex part of roughness, the period of the convex part of the CVD laminated film was found to be close to the grain size when Pt was crystallized, and the period of the convex part was found. It has been found that there is a cause of deterioration of Pt crystallinity.
The difference in crystallinity depending on the surface roughness between the thermally oxidized SiO ₂ film and the CVD laminated film is shown in Reference Example 1 described later. According to Table 1 of the reference example, the surface roughness is not significantly different between the thermally oxidized SiO ₂ film and the CVD laminated film, and a difference larger than the difference in surface roughness of the same thermally oxidized SiO ₂ film appears as a difference in crystallinity. I understand that. In addition, about the roughness of such a vibration layer, sufficient examination is not made | formed by the prior art mentioned above.

Based on these findings, by reducing the surface roughness of the diaphragm, it is possible to improve the processing accuracy of the post-process, good uniformity within the wafer surface, and uniform ink ejection characteristics of each liquid ejecting head I found what I could do.
In addition, the diaphragm composed of a film formed by the LPCVD method is a film that has been conventionally applied to semiconductors and MEMS devices. For this reason, since it is easy to process, a stable diaphragm can be obtained without introducing new process problems and without using an expensive substrate such as SOI, and a liquid droplet ejection head with high accuracy and little variation can be realized.

  In the diaphragm including the polysilicon film, the surface roughness is increased by the crystal grains of the polysilicon, and the roughness of the diaphragm is increased. In addition, it is possible to reduce the surface roughness of an amorphous silicon film. However, the process of forming a piezoelectric film with excellent crystal orientation requires heat treatment at a high temperature such as a firing step, and therefore the roughness and stress of the silicon film fluctuate, and highly reliable droplets. It is difficult to realize a discharge head. In addition, the process of forming the piezoelectric element is limited, and in some cases, the yield and cost may be affected. Thus, the film thickness of the silicon layer affects the surface roughness. If the silicon layer is made thinner, the surface roughness can be reduced, but the rigidity of the diaphragm is significantly reduced.

On the other hand, CMP (Chemical Mechanical Polishing), which is a technique for flattening the surface of a material surface, is generally used in a planarization process of a substrate surface, which is a semiconductor element manufacturing technique. CMP has been performed not only on a single substrate but also on a substrate on which unevenness has already occurred due to different materials, such as a step of planarizing an interlayer insulating film after forming a pattern. For this reason, improvements in abrasives and polishing methods have been made (see Patent Document 7 and Patent Document 8).
Further, the present invention is not limited to the manufacture of semiconductor elements, and there is an attempt to convert the substrate to a magnetic recording medium and flatten the substrate (see Patent Document 9).

Hereinafter, a method for manufacturing a droplet discharge head, a droplet discharge head, and an image forming apparatus according to embodiments for carrying out the present invention will be described.
A method for manufacturing a droplet discharge head according to Embodiment 1 will be described. First, the structure of the droplet discharge head will be described. 1 is a cross-sectional view of a droplet discharge head according to Embodiment 1, and FIG. 2 is an enlarged cross-sectional view of a portion A in FIG.
The droplet discharge head 300 according to the embodiment includes a substrate 201 on which a pressurizing chamber 301 for storing ink is formed, a vibration film 202 that is a vibration layer that pressurizes the pressure chamber 301, and an electric that drives the vibration film 202. A mechanical conversion element 210. The pressurizing chamber 301 is formed so as to have openings on both sides of the substrate 201, a nozzle plate 303 having a nozzle 302 is disposed on one (lower side in the drawing), and the vibration film 202 is disposed on the other opening side. It arrange | positions and it is comprised so that ink can be accommodated in an inside.
The electromechanical conversion element 210 includes a lower electrode film 203 that is one of a pair of electrode layers formed on the upper surface of the vibration film 202, an electromechanical conversion film 204 that is disposed with the adhesion layer 206 sandwiched between the lower electrode film 203, The upper electrode film 205 which is the other of the pair of electrode layers is disposed on the upper surface of the mechanical conversion film 204. The electromechanical conversion film 204 is a ferroelectric layer having piezoelectric characteristics.

The droplet discharge head 300 is manufactured as follows. As the substrate 201, a silicon single crystal substrate is preferably used, and it is usually preferable to have a thickness of 100 to 600 μm. There are three types of plane orientation of the silicon single crystal: (100), (110), and (111). In the semiconductor industry, (100) and (111) are generally widely used. In the first embodiment, a single crystal substrate mainly having a (100) plane orientation is mainly used.
The pressurizing chamber 301 processes a silicon single crystal substrate by etching. As an etching method, anisotropic etching is generally used. Anisotropic etching utilizes the property that the etching rate differs with respect to the plane orientation of the crystal structure. For example, in anisotropic etching immersed in an alkaline solution such as KOH, the (111) plane has an etching rate of about 1/400 compared to the (100) plane. Accordingly, a structure having an inclination of about 54.74 ° can be produced in the plane orientation (100), whereas a deep groove can be formed in the plane orientation (110). For this reason, it is possible to increase the arrangement density while maintaining rigidity.
In the first embodiment, a single crystal substrate having a (110) plane orientation can be used. However, it should be noted that in this case, SiO ₂ that is a mask material may also be etched.

The vibration film 202 receives a force generated by the electromechanical conversion film 204 and deforms and displaces the ink so that the ink in the pressurizing chamber 301 is ejected from the nozzle 302 as an ink droplet. Therefore, the vibration film 202 is required to have a predetermined strength. In the first embodiment, the vibration film 202 is formed by LPCVD (Low Pressure Chemical Vapor Deposition) laminating method which is a kind of CVD (Chemical Vapor Deposition) laminating method. The surface roughness of the vibration film 202 is 4 nm or less in terms of arithmetic average roughness. If this range is exceeded, the dielectric breakdown voltage of PZT (Lead Titanate Zirconate) as the electromechanical conversion film 204 formed after that becomes very poor and leaks easily. As the material, polysilicon, silicon oxide film, silicon nitride film or a combination thereof can be used.
The vibration film 202 formed by the LPCVD method has been generally applied to semiconductors and MEMS devices in the past, and is easy to process. Therefore, it does not introduce new process problems and does not use an expensive substrate such as SOI. A stable vibration film can be obtained.
In the first embodiment, the vibration film 202 is formed by forming a silicon oxide film (for example, a thickness of 200 nm) on the substrate 201 having a (100) plane orientation by the LPCVD method (or heat treatment film forming method), and then forming a polysilicon film. (For example, a thickness of 500 nm) is formed. The thickness of the polysilicon layer is preferably 0.1 to 3 μm, and the surface roughness is preferably an arithmetic average roughness of 5 nm or less. Further, a silicon nitride film is formed by LPCVD. Thereafter, the vibration film 202 is polished by CMP to form the lower electrode film 203.

The lower electrode film 203 is at least selected from elements having a (111) orientation, for example, Pt, Ir, IrO ₂ , RuO ₂ , LaNiO ₃ and SrRuO ₃ via the adhesion layer 206 on the vibration film 202. It is formed of a metal whose main component is a metal, a metal oxide, or a combination thereof. As metal materials, platinum with high heat resistance and low reactivity has been used for some time, but it may not be enough barrier for lead, and platinum such as iridium and platinum-rhodium is sometimes used. Group elements and these alloy films can be used.
In addition, when platinum is used, the adhesiveness with the diaphragm is poor, so that Ti, TiO ₂ , Ta, Ta ₂ O ₅ , Ta ₃ N _{5 and the} like are preferably laminated first. As a manufacturing method, vacuum film formation such as sputtering or vacuum deposition is generally used. As a film thickness, 0.05-1 micrometer is preferable and 0.1-0.5 micrometer is further more preferable. At this time, when PZT is selected as the electromechanical conversion film 204, the crystallinity thereof preferably has (111) orientation. Therefore, it is preferable that the material of the lower electrode film 203 contains Pt having a high (111) orientation.
The material of the upper electrode film 205 is not particularly limited, and materials exemplified for the lower electrode film, materials generally used in semiconductor processes such as Al and Cu, and combinations thereof can be used.

The electromechanical conversion film 204 is composed of a ferroelectric material having piezoelectric characteristics. In the first embodiment, PZT is mainly used. PZT is a solid solution of lead zirconate (PbTiO ₃ ) and lead titanate (PbTiO ₃ ), and the characteristics differ depending on the ratio. In general, the composition exhibiting excellent piezoelectric properties has a ratio of PbZrO ₃ and PbTiO ₃ of 53:47, and expressed by chemical formula as Pb (Zr0.53Ti0.47) O ₃ : general PZT (53/47). It is.
Examples of composite oxides other than PZT include barium titanate. In this case, a barium titanate precursor solution can be prepared by using barium alkoxide and a titanium alkoxide compound as starting materials and dissolving them in a common solvent.
These materials are described by the general formula ABO ₃ and correspond to composite oxides whose main components are A = Pb, Ba, SrB = Ti, Zr, Sn, Ni, Zn, Mg, and Nb. Specific descriptions thereof include (Pb1-X, Ba) (Zr, Ti) O ₃ , (Pb1-X, Sr) (Zr, Ti) O ₃ , which partially replaces Pb at the A site with Ba or Sr. This is the case. Such substitution is possible with a divalent element, and the effect thereof has an effect of reducing characteristic deterioration due to evaporation of lead during heat treatment.

As a manufacturing method, it can be manufactured by a spin coater using a sputtering method or a Sol-gel method. In that case, since patterning is required, a desired pattern is obtained by photolithography etching or the like.
When PZT is produced by the Sol-gel method, PZT precursor solution can be produced by using lead acetate, zirconium alkoxide, and titanium alkoxide compound as starting materials and dissolving them in methoxyethanol as a common solvent to obtain a uniform solution. . Since the metal alkoxide compound is easily hydrolyzed by moisture in the atmosphere, an appropriate amount of a stabilizer such as acetylacetone, acetic acid or diethanolamine may be added to the precursor solution as a stabilizer.
When a PZT film is formed on the entire surface of the substrate 201, a coating film is formed by a solution coating method such as spin coating, and heat treatments such as solvent drying, thermal decomposition, and crystallization are performed. Since the transformation from the coating film to the crystallized film involves volume shrinkage, it is necessary to adjust the precursor concentration so that a film thickness of 100 nm or less can be obtained in one step in order to obtain a crack-free film.

Moreover, when producing by the inkjet construction method, a patterned film can be obtained. As for the surface modifying material, although it varies depending on the material of the base, the silane compound is mainly selected when the oxide is used as the base, and the alkanethiol is mainly selected when the metal is the base.
The thickness of the electromechanical conversion film 204 is preferably 0.5 to 5 μm, and more preferably 1 μm to 2 μm. If it is smaller than this range, sufficient displacement cannot be generated. If it is larger than this range, many layers must be laminated, and the number of steps increases and the process time increases.

FIG. 3 shows the result of X-ray diffraction (XRD) of PZT formed into a 1 μm film by spin coating using a solution prepared by the Sol-gel method. From this, it can be seen that PZT has a film in which the (111) plane is highly preferentially oriented. In addition, depending on the heat treatment conditions of PZT, it is an orientation film other than (111). When the following formula is used, the (111) orientation degree is 0.95 or more and the (110) orientation degree is 0.05. The following is preferable.
The calculation method expressing the ratio of each orientation when the sum of the peaks of each orientation obtained by XRD is 1 is as follows. This represents the average degree of orientation.
ρ = I (hkl) / ΣI (hkl)
Denominator: Sum of peak intensities Numerator: Peak intensity in any orientation If this range is exceeded, sufficient characteristics cannot be obtained for displacement degradation after continuous driving.

Examples will be described below.
<Example 1: A thermal oxide film is formed on the surface of a Si substrate material, and then a vibration film is formed by a CVD lamination method>
A thermal oxide film (film thickness: 1 micron) was formed on a silicon wafer as the substrate 201, and the vibration film 202 was produced by LPCVD. A silicon oxide film was formed to a thickness of 200 nm, and then a polysilicon film was formed to a thickness of 500 nm. Next, a 200 nm silicon nitride film was formed by LPCVD. Further, a silicon oxide film was formed to a thickness of 700 nm, a silicon nitride film was formed to 200 nm, and a silicon oxide film 800 was formed. This was thermally oxidized to form a SiO ₂ insulating film. This SiO ₂ film becomes the vibration film 202. The SiO ₂ film thickness at this time was 2 μm.

Next, CMP polishing (Chemical Mechanical Polishing) was performed, and the uppermost silicon oxide film was polished by 100 nm. Cerium oxide was used as the abrasive. A cerium oxide having an average particle size of 20 nm was used, and the treatment was performed with a slurry in which cerium oxide was dispersed by mixing with a dispersant and water at a concentration in the range of 5 to 20% by weight. As the additive, ammonium polyacrylate (solid content: 2.4% by weight) is appropriately mixed as a polymer additive, and the oxide film is polished by CMP treatment for 30 to 40 seconds while dropping at a rate of 200 ml / min. It was.
The polished wafer was washed with pure water and then dried to finish the CMP process. Here, when the roughness of the surface after the CMP treatment was measured, it was Ra 3 nm, and Ra was smaller in numerical value than on the CVD laminated film. FIG. 4 shows a cross-sectional profile of the surface roughness. FIG. 5 shows what was not processed. Although these are not profiles at the same position, it can be seen that the depth of the short period convex portion is small.

Next, a Ti metal film was formed as an electrode film adhesion layer serving as an adhesion layer 206 with the lower electrode film 203 on the CVD laminated film serving as the vibration plate. The film forming apparatus is an automatic sputtering apparatus E-401S manufactured by Canon Anelva. The formation conditions of the adhesion layer 206 are a substrate temperature of 300 ° C., an RF input power of 500 W, an Ar gas pressure of 1.3 Pa, and a formed film thickness of 50 nm. Next, a Pt electrode film as the lower electrode film 203 was formed with a thickness of 200 nm. The process conditions were a substrate temperature of 300 ° C., RF input power of 500 W, and Ar gas pressure of 1.3 Pa. Thereby, the lower electrode film 203 has the (111) plane oriented in the film thickness direction.
Next, an SrRuO ₃ film (SrRuO ₃ ) having a thickness of 60 nm was formed as an oxide electrode film on the lower electrode film 203. The formation conditions were a substrate temperature of 550 ° C., an RF input power of 500 W, an Ar gas containing 30% O 2 gas as a sputtering gas, and a gas pressure of 6 Pa.
Next, an electromechanical conversion film 204 was formed. As the material of the electromechanical conversion film 204, the most common raw material of PZT (composition that gives Zr / Ti = 52/48 after firing, Pb excess is 15 atomic%) was selected. A certain alkoxide containing the metal elements Pb, Zr and Ti constituting PZT as a starting material was formed. As the solidification baking of the piezoelectric film after the single-layer spin coating, an RTA apparatus was used, and the baking was performed in an oxygen atmosphere under a temperature condition of 490 ° C. × 5 min. Subsequently, the second and third layers were solidified and fired in the same manner, and were fired in an atmosphere in dry air under conditions of 750 ° C. × 3 min as firing for crystallization. The film thickness when these three layers (M = 3) were laminated was 250 nm.

This three-layer lamination was repeated 6 times in the same procedure, and an electromechanical conversion film 204 having a total film thickness of 1.5 μm was formed. Next, after laminating the electromechanical conversion film 204 by 1.5 μm, the upper electrode film 205 was formed to form an element and evaluated as a device. That is, SrRuO ₃ having a thickness of 40 nm was formed on the electromechanical conversion film 204 as an oxide electrode film. The formation conditions were a substrate temperature of 550 ° C., an RF input power of 300 W, an Ar gas containing 30% O 2 gas as a sputtering gas, and a gas pressure of 6 Pa. Further, a Pt electrode film to be the upper electrode film 205 was formed with a film thickness of 100 nm. The process conditions are a substrate temperature of 300 ° C., RF input power of 500 W, and Ar gas pressure of 1.3 Pa. If only the characteristics are to be measured, it is sufficient to stack only the Pt electrode film. The upper electrode film 205 has a structure of a single Pt layer or a Pt electrode film / oxide electrode film.
Then, after forming a resist pattern using a photolithography technique, the cross section was etched and resist ashed into the shape shown in FIG. At this time, the upper electrode film 205 was formed in a strip shape having a size of 45 μm × 1 mm.
Further, a device was formed by forming a passivation film for protecting the element, forming an interlayer insulating layer (not shown), forming a connection between the wiring electrode film and the element, forming a passivation film for protecting the wiring, and the like.

After forming to this state, a driving voltage was repeatedly applied under the following conditions for a fatigue test after polarization treatment. The upper electrode film side was set to a positive potential, and the lower electrode film side was set to a negative potential (ground potential).
[Polarization processing conditions]
Applied voltage: 40V (Slowly increase the voltage from 0V in 3min, hold for 1min. Slowly decrease the voltage to 0V in 3min.)
Evaluation after polarization: The capacitance measured with a rectangular wave of 1 kHz of the applied voltage of the repeated driving voltage test between the upper electrode film and the lower electrode film was measured as an initial value.
[Test conditions for repeated application of drive voltage]
Applied voltage: DC 0-30V rectangular wave (upper electrode film is positive potential)
Application period: 100 kHz
Duty: 50% (plus electric potential application time ratio)
Evaluation during the test: The initial value of capacitance after polarization was normalized to 1, and the same evaluation as the evaluation after polarization was performed at each point for each number of times of application, and the attenuation rate was observed. The point at which the initial value was attenuated by 10% after normalization was taken as the fatigue evaluation point.

As a result, it was found that up to 1012 times can be secured with attenuation within 10% of the initial value under the above conditions.
Furthermore, the crystallinity evaluation of these electrode films and the cross-sectional appearance evaluation of the electrode films were performed by the following means. Evaluation was made by measuring the crystallinity of PZT and Pt by X-ray diffraction. Specifically, the measurement of θ-2θ was scanned at an angle of 20 to 60 ° with an X-ray diffractometer manufactured by Philips: model X′Pert-PRO, and the peak of Pt (111) (peak position: 39.98 at 2θ). The vicinity was evaluated based on the strength and the half-value width of the rocking curve (shown as FWHM in the figure and the table). As for SRO (SrRuO ₃ ), since it overlaps with the peak of Pt (111) at θ-2θ, MRD measurement is performed by swinging the Psi angle at the position of 2θ corresponding to Pt (111), and SRO (111 The crystallinity was evaluated by the peak intensity at the Psi angle corresponding to) and the full width at half maximum when Psi was shaken. For MRD, the MRD apparatus model X'Pert MRD manufactured by Philips was used.
The results are shown in Table 1.

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In addition, the FIB cross section was formed and SEM observation was performed (SEM apparatus is model NVision 40 manufactured by Carl Zeiss), and knowledge from the cross section was obtained. The SEM image is shown in FIG.

(Example 2)
The result of observing the cross-sectional structure of the film after the formation of the piezoelectric film by the same process as in Example 1 is shown in FIG. In the cross-sectional structure, the lower side of the drawing is a surface subjected to the CMP process, but a large convex portion is not observed but undulates and represents a relatively flat surface. The Pt cavities formed during the heat treatment of the piezoelectric film are also aligned substantially vertically.

(Example 3)
A droplet discharge head row 320 in which a plurality of droplet discharge heads 300 are arranged side by side was created. FIG. 7 is a cross-sectional view of a droplet discharge head array according to the embodiment. Ink ejection evaluation was performed by the droplet ejection head row 320. Using an ink whose viscosity was adjusted to 5 cp, the discharge state when an applied voltage of −10 to −30 V was applied with a simple Push waveform was confirmed, and it was confirmed that discharge was possible from any nozzle hole.

(Comparative Example 1)
In the procedure of Example 1, Ti 50 nm, Pt 250 nm, and then SRO 60 nm were laminated without CMP polishing the CVD laminated film, and the crystallinity was evaluated by X-ray diffraction. The peak intensity of Pt (111) on the CVD laminated film was about 1 digit lower (about 12%) than that on the thermal oxide film. Moreover, the rocking curve half-width of Pt (111) was as wide as about 2.5 times that of Pt on the thermally oxidized SiO ₂ film, and it was found that the crystallinity was very poor. FIG. 2 shows the comparison. The crystallinity of the electrode film laminated on the CVD laminated film is higher than that of the electrode film formed on the structure subjected to the CMD treatment of Example 1, and the crystallinity of Pt (111) is the peak intensity and the half width of the rocking curve. It turns out that it is remarkably inferior in the point.
Further, when this sample was subjected to cross-sectional observation of the Pt portion after the PZT was formed, the CVD laminated film was not a flat film but was roughened, and the laminated Pt film cavity (occurred after PZT firing) was in various directions. It turned out to be inclined. FIG. 6A shows the cross-sectional SEM image. From observation of a cross-sectional SEM processed by FIB (Focused Ion Beam), it is confirmed that the film itself is not a flat surface but a rough surface as a cross-sectional structure of the CVD laminated film. Furthermore, the Pt cavity structure does not necessarily stand vertically. On the other hand, the film subjected to the CMD process, that is, the film shown in FIG. 6B is flat.

(Comparative Example 2)
FIG. 6A shows the result of observing the cross-sectional structure of the film after forming the piezoelectric film by the same process as in Example 1 except that the CMP process was not performed. In the cross-sectional structure, the lower side of the figure represents the surface of the CVD laminated film, but Pt is greatly influenced by the heat treatment of the piezoelectric film. The concave portion of Pt corresponds to the convex portion of the CVD laminated film, but has an enhanced shape for heat treatment of the piezoelectric film. The surface is not flat, and the Pt cavities formed during the heat treatment of the piezoelectric film are changed to inclined cavities accordingly. Here, when the measurement was performed on the concave portion of Pt, the average period was 95 nm (50 to 137 nm in width), and the average depth was 17.5 μm (7 to 18.5 nm in width).
On the other hand, since the particle diameter of Pt used as the electrode film is approximately 100 nm on average (80 to 120 nm in width), it is considered that the periodic pattern of the recesses affects the crystallization and grain growth of Pt.

As described above, according to the manufacturing method of the droplet discharge head according to the first embodiment, the surface of the vibration film 202 is planarized and formed in contact with the vibration film 202 by polishing the vibration film 202 with CMP. The crystallinity of the lower electrode film 203 can be ensured. Since the lower electrode film 203 also has an effect as a crystallinity control film that governs the crystallinity of the electromechanical conversion film 204 laminated thereon, if the crystallinity of the electromechanical conversion film 204 is ensured, the electromechanical device as a device Good characteristics can be obtained.
Further, the CMP polished surface does not simply flatten the surface, but improves the crystallinity of the lower electrode film 203 formed on the vibration film 202 formed by CVD lamination. For this purpose, even if the surface roughness of the vibration film 202 is rough, it is only necessary to remove convex portions having a depth of 100 nm or less and a period of less than 150 nm. This is because the crystal grain size of the lower electrode film 203 formed in contact with the CVD laminated vibration film 202 is 80 to 130 nm, and irregularities of less than 150 nm influence the crystallinity.
The reason why at least cerium oxide particles are used as the abrasive particles is that cerium oxide has a lower hardness than the silica particles and alumina particles as an abrasive, and scratches are less likely to occur on the polished surface. As a result, deterioration of the crystallinity of the lower electrode film 203 due to scratches generated as a side effect of the polishing process is prevented.
In addition, since the lower electrode film 203 is mainly composed of at least one selected from Pt, Ir, IrO ₂ , RuO ₂ , LaNiO ₃ and SrRuO _{3, the} electromechanical conversion film 204 laminated on the lower electrode film 203 is used. The crystallinity can be controlled well.
Further, since the vibration film 202 includes at least one of a silicon oxide film and a silicon nitride film, it is possible to grasp the film stress when the droplet discharge head is configured, and to easily form a discharge waveform to be applied electrically. Become.

(Reference Example 1)
In Example 1, instead of using a sample obtained by polishing the CVD laminated film with CMP, a thermally oxidized SiO ₂ film was formed on the roughened surface, and then Ti 50 nm, Pt 250 nm, and then SRO 60 nm were laminated as electrode films, and X-ray diffraction was performed. Was used to evaluate crystallinity. As a result, a Pt (111) XRD peak comparable to that of a non-roughened thermally oxidized SiO ₂ film was obtained. Therefore, it can be seen that in order to obtain good electrode film crystallinity as an underlayer of the electrode film, ordinary mere surface roughness is not effective.

<Embodiment 2>
Next, an image forming apparatus equipped with a droplet discharge head manufactured by the method for manufacturing a droplet discharge head according to Embodiment 1 will be described. FIG. 8 is a perspective view of the image forming apparatus according to the embodiment, and FIG. 9 is a cross-sectional view of the image forming apparatus.
The image forming apparatus 10 includes a carriage 93 that can move in the main scanning direction inside the apparatus main body 81, a recording head 94 that includes the droplet discharge head row 320 according to Embodiment 1 mounted on the carriage 93, and a recording head 94. And a printing mechanism 82 composed of an ink cartridge or the like for supplying ink to the printer. In the image forming apparatus 10, a sheet feeding cassette (or sheet feeding tray) 84 on which a large number of sheets 83 can be stacked from the front side can be detachably attached to the lower part of the apparatus main body 81. Further, the image forming apparatus 10 has a configuration capable of opening and tilting a manual feed tray 85 for manually feeding the paper 83. The image forming apparatus 10 takes in the paper 83 fed from the paper feed cassette 84 or the manual feed tray 85, records a required image by the printing mechanism unit 82, and then discharges the paper to a paper discharge tray 86 mounted on the rear side. To do.

The printing mechanism unit 82 holds the carriage 93 slidably in the main scanning direction with a main guide rod 91 and a sub guide rod 92 that are horizontally mounted on left and right side plates (not shown). The carriage 93 includes a recording head 94 including a droplet discharge head array 320 that discharges ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk), and a plurality of ink discharge ports. (Nozzles) are arranged in a direction crossing the main scanning direction, and are mounted with the ink droplet ejection direction facing downward. Further, each ink cartridge 95 for supplying ink of each color to the recording 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 inkjet head below, and a porous body filled with ink inside. Accordingly, the ink supplied to the ink jet head is maintained at a slight negative pressure by the capillary force of the porous body. Further, although the recording head 94 of each color is used here as the recording head, a single head having nozzles for ejecting ink droplets of each color may be used.

  Here, the carriage 93 is slidably disposed on the main guide rod 91 on the rear side (downstream side in the sheet conveyance direction), and is slidably disposed on the sub guide rod 92 on the front side (upstream side in the sheet conveyance direction). Yes. In order to move and scan the carriage 93 in the main scanning direction, a timing belt 100 is stretched between a driving pulley 98 and a driven pulley 99 that are rotationally driven by a main scanning motor 97. 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 recording head 94, the paper feed roller 101 and the friction pad 102 for separating and feeding the paper 83 from the paper feed cassette 84 and the paper 83 are guided. The guide member 103 is provided. Furthermore, a conveying roller 104 that reverses and conveys the fed paper 83, a conveying roller 105 that is pressed against the peripheral surface of the conveying roller 104, and a leading end roller 106 that defines a feeding angle of the sheet 83 from the conveying roller 104; Is provided. The transport roller 104 is rotationally driven through a gear train by a sub-scanning motor (not shown).
A printing receiving member 109 is provided as a paper guide member that guides the paper 83 sent from the transport roller 104 below the recording head 94 in accordance with the movement range of the carriage 93 in the main scanning direction. A conveyance roller 111 and a spur 112 that are rotationally driven to send the paper 83 in the paper discharge direction are provided on the downstream side of the printing receiving member 109 in the paper conveyance direction, and the paper 83 is further delivered to the paper discharge tray 86. A roller 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.

Further, a recovery device 107 for recovering defective ejection of the recording 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 107 includes a cap unit, a suction unit, and a cleaning unit. The carriage 93 is moved to the recovery device 107 side during printing standby, and the recording 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 recording head 94 is sealed by the capping unit, and bubbles and the like are sucked out together with the ink from the discharge port by the suction unit through the tube. Etc. are removed by the cleaning means, and the ejection failure is recovered. 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, since the ink jet recording apparatus includes the liquid droplet ejection head array 320 manufactured in the first embodiment of the present invention, there is no ink droplet ejection failure due to vibration plate drive failure, and stable ink droplet ejection characteristics. Is obtained, and the image quality is improved.

  201 substrate, 202 vibration film (vibration layer), 203 lower electrode film, 204 electromechanical conversion film, 205 upper electrode film, 206 adhesion layer, 210 electromechanical conversion element, 300 droplet ejection head, 301 pressurization chamber, 302 nozzle , 303 Nozzle plate

JP 2004-186646 A JP 2004-262253 A JP 2003-218325 A JP 2007-258389 A JP-A-2005-144918 JP 2004-262253 A JP 2002-203819 A JP 2004-134751 A JP 2009-301630 A

Claims (7)

A method of manufacturing a droplet discharge head comprising at least a vibration layer formed by CVD, a pair of electrode layers containing a Pt group metal formed on the vibration layer, and an electromechanical conversion layer formed between the electrode layers In
A method of manufacturing a droplet discharge head, comprising: forming a vibrating layer and subjecting the surface of the vibrating layer to CMP polishing before forming the electrode layer.   3. The method for manufacturing a droplet discharge head according to claim 1, wherein when performing CMP polishing, a polishing particle containing at least cerium oxide particles is used.   A droplet discharge head manufactured by the method for manufacturing a droplet discharge head according to claim 1.   4. The droplet discharge head according to claim 3, wherein in a state after the surface of the vibration layer is subjected to CMP polishing, a period of convex portions having a depth of 5 nm or more from the surface of the vibration layer exceeds 150 nm. 5. The droplet discharge head according to claim 3, wherein the electrode layer is mainly composed of at least one selected from Pt, Ir, IrO ₂ , RuO ₂ , LaNiO ₃ and SrRuO ₃ .   6. The droplet discharge head according to claim 3, wherein the vibration layer includes at least one of a silicon oxide film and a silicon nitride film.   A droplet discharge head according to any one of claims 3 to 6, and a transport unit that transports a recording medium that forms an image with ink discharged from the droplet discharge head. Image forming apparatus.

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