JP2008296417A - Liquid droplet ejecting head, its manufacturing method, and liquid droplet ejector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid droplet ejecting head which can secure a stable displacement characteristic by preventing the occurrence of defects to a piezoelectric element, and to provide its manufacturing method and a liquid droplet ejector. <P>SOLUTION: The liquid droplet ejecting head 10 is equipped with an ink chamber substrate 12 with cavities 12a which communicate with nozzles 11a to eject liquid and are surrounded by diaphragms 12A, an elastic film 13 formed contacting with the cavities 12a and the diaphragms 12A, and the piezoelectric elements 14 comprised of a lower electrode 4 prepared on the elastic film 13, a piezoelectric film 5 and an upper electrode 6. The elastic film 13 is formed into a projecting shape toward the cavity 12a side in a region where the film contacts with the cavity 12a. The projecting shape has a slope at a side surface. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a droplet discharge head, a manufacturing method thereof, and a droplet discharge apparatus.

  It has been proposed to use a droplet discharge method (inkjet method) when forming an image or manufacturing a microdevice. As this droplet discharge method, for example, there is a method in which a functional liquid containing a wiring material in a semiconductor device is formed into droplets and discharged from a droplet discharge head to form a desired wiring pattern on a substrate.

  Such a droplet discharge head includes a nozzle that discharges ink droplets, a cavity (pressure generation chamber) that communicates with the nozzle, a partition that forms a side wall surface of the cavity, and an elastic film that forms a top surface of the cavity. And a piezoelectric element formed on the elastic film. By driving the piezoelectric element, the elastic film is displaced and ink droplets are ejected from the nozzles. The piezoelectric element has a structure in which a piezoelectric film made of a ferroelectric material such as lead zirconate titanate (PZT) is sandwiched between a pair of electrodes, a lower electrode and an upper electrode.

When the piezoelectric active part in which the upper electrode is formed on the piezoelectric film is driven, cracks are particularly likely to occur at the end of the piezoelectric active part, which may cause fatal damage to the piezoelectric active part. Here, the piezoelectric active portion is a portion where piezoelectric strain is generated by applying a voltage to both electrodes. From the above, a floating electrode that is electrically independent from the upper electrode is formed around the upper electrode, and cracks in the upper electrode are generated by not directly adjoining the portion where displacement occurs and the portion where displacement does not occur at all. (See Patent Document 1), or by providing a clearance between the end of the piezoelectric active part and the peripheral wall of the cavity, it is possible to suppress the occurrence of cracks at the end of the piezoelectric active part during vibration. (Refer to Patent Document 2) A flow path forming layer is provided between the flow path forming substrate and the elastic film, and the opening of the cavity is defined by the opening of the flow path forming layer, thereby preventing the elastic film from being broken. (See Patent Document 3) has been proposed.
Japanese Patent Laid-Open No. 11-115184 Japanese Patent Laid-Open No. 11-179992 JP 2002-59555 A

According to Patent Documents 1 to 3 described above, it is possible to suppress damage to the piezoelectric active portion during driving as compared with the related art. However, the droplet discharge head described in the above document has the following problems to be improved.
In the case of the above configuration, the elastic film formed on the flow path forming substrate may be cracked due to repeated vibration of the piezoelectric active part. That is, since the elastic film deforms the region (movable part) corresponding to the cavity by vibration, stress concentration is likely to occur at the boundary with the region (fixed part) fixed by the partition wall of the cavity. For this reason, a crack or the like is generated in the elastic film at the boundary between the movable part and the fixed part, and this may affect the vibration reliability and the displacement amount and cause a printing defect.
Therefore, there is a demand for a technique for suppressing the occurrence of cracks by relaxing the stress concentration in the vicinity of the cavity partition wall of the elastic film.

  The present invention has been made in view of the above-mentioned problems of the prior art, and is a droplet discharge head capable of preventing a failure in a piezoelectric element and ensuring stable displacement characteristics, and its It is an object to provide a manufacturing method and a droplet discharge device.

  In order to solve the above problems, a droplet discharge head according to the present invention includes a flow path forming portion having a pressure generation chamber that is in communication with a nozzle opening for discharging a liquid and surrounded by a partition, and the pressure generation chamber and the partition A droplet discharge head comprising: an elastic film formed in contact with the piezoelectric film; and a piezoelectric element including a lower electrode, a piezoelectric film, and an upper electrode provided on the elastic film, wherein the elastic film has a pressure A convex shape is formed on the pressure generating chamber side in a region in contact with the generating chamber, and the convex surface has a sloped side surface.

According to the droplet discharge head of the present embodiment, the elastic film is formed by providing an elastic film having a convex shape on the side of the pressure generation chamber that is in contact with the pressure generation chamber, and the convex shape having a sloped side surface. The stress applied to the boundary (near part) between the region vibrating by the piezoelectric element and the region fixed by the partition wall can be relaxed.
Thus, by forming the film thickness of the region corresponding to the partition wall to be thinner than the region corresponding to the pressure generating chamber of the elastic film, the elastic film is easily bent while maintaining its mechanical strength. Further, since the Young's modulus in the vicinity decreases and the amount of displacement of the elastic film increases, it becomes possible to suppress the occurrence of cracks in the elastic film during driving, and to increase the amount of displacement of the elastic film. Accordingly, the amount of ink discharged can be increased.
Accordingly, it is possible to improve printing defects caused by cracks in the elastic film and improve the reliability of the droplet discharge head. In addition, it is possible to improve the vibration reliability and displacement of the piezoelectric element and to maintain them for a long period of time.

The flow path forming portion is preferably formed on a silicon substrate, and the elastic film preferably has a silicon oxide film formed by thermally oxidizing the surface of the silicon substrate.
According to such a configuration, an elastic film having excellent vibration characteristics can be obtained.

  The method for manufacturing a droplet discharge head according to the present invention includes a flow path forming portion having a pressure generation chamber that is in communication with a nozzle opening for discharging a liquid and surrounded by a partition, and is formed in contact with the pressure generation chamber and the partition. And a piezoelectric element including a lower electrode, a piezoelectric film, and an upper electrode provided on the elastic film, wherein the flow path forming portion is provided on the substrate. It has a flow path forming part forming step to be formed, an elastic film forming step of forming an elastic film on the substrate, and a piezoelectric element forming step of forming the piezoelectric element on the elastic film.

According to the manufacturing method of the droplet discharge head of the present invention, the region corresponding to the partition wall of the pressure generation chamber is thinner than the region corresponding to the pressure generation chamber, and the region corresponding to the pressure generation chamber and the pressure generation chamber By forming an elastic film whose boundary part with the region corresponding to the partition wall is an inclined surface, the stress applied to the boundary between the region vibrating by the piezoelectric element and the region fixed by the partition wall is relieved. be able to.
As described above, the elastic film is formed so that the region corresponding to the partition wall of the pressure generation chamber is thinner than the region corresponding to the pressure generation chamber of the elastic film and the boundary portion is an inclined surface. It becomes easy to bend, maintaining mechanical strength. At the same time, the Young's modulus at the boundary portion decreases and the amount of displacement of the elastic film increases, so that it is possible to suppress the occurrence of cracks in the elastic film during driving, and the amount of displacement of the elastic film increases. As a result, the ink discharge amount can be increased.
Accordingly, it is possible to improve printing defects caused by cracks in the elastic film and improve the reliability of the droplet discharge head. In addition, it is possible to improve the vibration reliability and displacement of the piezoelectric element and to maintain them for a long period of time.

  Further, the substrate is made of silicon, and the elastic film forming step includes a step of forming a silicon nitride film in a region corresponding to the partition of the pressure generation chamber on the surface opposite to the pressure generation chamber of the substrate, and a thermal process using the silicon nitride film as a mask. Performing an oxidation process to form a first oxide film in a region corresponding to the pressure generating chamber; removing the silicon nitride film and the first oxide film; removing the silicon nitride film and the first oxide film; It is preferable to include a step of thermally oxidizing the surface of the substrate thus formed to form a second oxide film and a step of flattening the surface of the second oxide film.

  According to such a manufacturing method, on the substrate made of silicon, the elastic film having different film thicknesses in the region corresponding to the partition of the pressure generation chamber and the region corresponding to the pressure generation chamber is reliably and easily formed. be able to. Moreover, the vicinity part can be made into the desired slope.

An electronic apparatus according to the present invention includes the droplet discharge head described above.
As described above, since the liquid droplet ejection head having excellent reliability is provided, the liquid droplet ejection apparatus itself has good ejection performance, high performance and high reliability.

  Embodiments of the present invention will be described below with reference to the drawings. In each drawing used for the following description, the scale of each member is appropriately changed to make each member a recognizable size.

(Configuration of droplet discharge head)
1 is an exploded perspective view of a droplet discharge head, FIG. 2 is a side sectional view showing a schematic configuration of the droplet discharge head, and FIG. 3 is an enlarged view showing a configuration of a piezoelectric element in the droplet discharge head. FIG. Note that FIG. 1 is shown upside down from a normally used state.
In these drawings, reference numeral 10 denotes a droplet discharge head. As shown in FIG. 1, the droplet discharge head 10 includes a head body and a piezoelectric element 14 provided on the head body. The droplet discharge head 10 is used as a so-called ink jet recording head, and is used in an ink jet printer which is an embodiment of a droplet discharge device described later.

  That is, the droplet discharge head 10 includes a nozzle plate 11, an ink chamber substrate 12, an elastic film 13, and a piezoelectric element 14 bonded to the elastic film 13, as shown in FIG. 15 is housed. The base body 15 is formed of, for example, various resin materials, various metal materials, etc., and the ink chamber substrate 12 is fixed and supported on the base body 15 as shown in FIG.

  As shown in FIGS. 1 and 2, a plurality of cavities (pressure generating chambers) 12a and ink cartridges are formed by partition walls 12A, nozzle plates 11, and elastic films 13 formed by patterning the ink chamber substrate 12. A reservoir 12b that temporarily stores ink supplied from (not shown) and an ink supply port 12c that supplies ink from the reservoir 12b to each cavity 12a are partitioned.

  The nozzle plate 11 is composed of, for example, a stainless steel rolling plate or the like, and a large number of nozzles 11a for discharging ink droplets are formed in a line. The pitch between the nozzles 11a can be appropriately set according to the printing accuracy.

  Further, as a base material (substrate) constituting the ink chamber substrate 12, a silicon single crystal substrate having a plane orientation (110) is used as will be described later. Such a plane orientation enables easy and reliable anisotropic etching, so that the processability and reliability of the flow path forming portions such as the reservoir 12b and the cavities 12a are high.

  Each cavity 12a is disposed corresponding to each nozzle 11a as shown in FIG. 1, and its volume is variable by the vibration of the elastic film 13, and the nozzle 11a is changed by this volume change. Ink droplets are discharged from the nozzle.

  The average thickness of the ink chamber substrate 12, that is, the thickness including the cavity 12a is not particularly limited, but is preferably about 10 to 1000 μm, and more preferably about 100 to 500 μm. The volume of the cavity 12a is not particularly limited, but is preferably about 0.1 to 100 nL, more preferably about 0.1 to 10 nL.

  Here, as shown in FIG. 2, on the inner wall surfaces of the cavity 12a, the reservoir 12b, and the ink supply port 12c of the ink chamber substrate 12, a protective film 16 made of an ink-resistant material, for example, tantalum oxide (TaOx). Is provided with a thickness of about 50 nm. The ink resistance referred to here is etching resistance against alkaline ink. In the present embodiment, the protective film 16 is also provided on the surface of the ink chamber substrate 12 on the side where the cavities 12a and the like are opened, that is, the bonding surface to which the nozzle plate 11 is bonded. Of course, since the ink is not substantially in contact with such a region, the protective film 16 may not be provided.

The elastic film 13 has a configuration in which a thermal oxide film layer and a metal oxide layer are laminated on at least one surface. Specifically, the elastic film 13 is formed by laminating an elastic layer 13a made of silicon dioxide (SiO ₂ ) and a metal oxide layer 13b made of zirconium oxide (ZrO ₂ ) provided on the elastic layer 13a. It will be.

The elastic film 13 of the present embodiment has a different film thickness depending on the region. Specifically, as shown in FIG. 4A, a recess is formed on the cavity 12a side of the elastic layer 13a, whereby the cavity 12a side of the elastic layer 13a corresponds to the partition wall 12A of the cavity 12a. The film thickness of the area 130A in contact with the cavity 12a is relatively thin relative to the film thickness of the area 130B that forms the top surface of the cavity 12a. In addition, the vicinity 130C of the region 130A in the region 130B has a slope distribution in which the film thickness gradually decreases toward the region 130A, and has a gentle slope 20 as shown in FIG. Yes. Here, the slope 20 may be formed by a curved surface as well as a flat surface. And as shown in FIG.4 (b), the slope 20 is formed in the peripheral part of the area | region 130B. The film thickness of each region 130A, 130B of the elastic layer 13a is appropriately set in consideration of the size of the cavity 12a, etc. In this embodiment, the film thickness of the region 130A is 0.5 μm, and the film thickness is in the center of the region 130B. The film thickness is 1.0 μm.
Such an elastic film 13 is disposed on the surface of the ink chamber substrate 12 opposite to the nozzle plate 11, and a plurality of piezoelectric elements 14 are provided on the surface.

In FIG. 2, the elastic film 13 has a uniform film thickness, but this is shown in a simplified manner. Actually, the film thickness varies depending on the region as described above. The metal oxide layer 13b described above may be composed of titanium oxide (TiO _2).

  Further, at a predetermined position of the elastic film 13, a communication hole 13 c that penetrates in the thickness direction of the elastic film 13 is formed as shown in FIG. 1. The communication hole 13c supplies ink to the reservoir 12b from an ink cartridge 631 (see FIG. 8), which will be described later.

  As shown in FIG. 2, each piezoelectric element 14 is disposed corresponding to the substantially central portion of each cavity 12a. Each of these piezoelectric elements 14 is electrically connected to a piezoelectric element driving circuit described later, and is configured to operate (vibrate, deform) based on a signal from the piezoelectric element driving circuit. That is, each piezoelectric element 14 functions as a vibration source (head actuator), and the elastic film 13 vibrates (deflects) due to the vibration (deflection) of the piezoelectric element 14 and instantaneously changes the internal pressure of the cavity 12a. It is intended to function to enhance.

Hereinafter, the piezoelectric element 14 will be described in detail.
As shown in FIG. 3, the piezoelectric element 14 has a structure in which a piezoelectric film 5 made of lead zirconate titanate (PZT) is sandwiched between a lower electrode 4 and an upper electrode 6. In general, one of the electrodes of the piezoelectric element 14 is used as a common electrode, and the other electrode and the piezoelectric film 5 are patterned for each cavity 12a. In this embodiment, the lower electrode 4 is a common electrode of the piezoelectric element 14 and the upper electrode 6 is an individual electrode of the piezoelectric element 14, but there is no problem even if this is reversed for the convenience of the drive circuit and wiring. In any case, a laminated body 14a composed of the lower electrode 4, the piezoelectric film 5 and the upper electrode 6 is formed for each cavity 12a.

  The lower electrode 4 is configured by sequentially stacking a Pt layer and an Ir layer, and has a film thickness of about 0.2 μm. Further, the upper electrode 6 can employ a conductive material, such as platinum (Pt), iridium (Ir), aluminum (Al), etc. In this embodiment, iridium is used, and the thickness is about 0.1 μm. It is formed in a film thickness.

The lower electrode 4 is made of zirconium oxide (ZrO ₂ ), is patterned in the vicinity of both ends in the longitudinal direction of the cavity 12a, and is continuously provided along the parallel direction of the cavities 12a.

  The piezoelectric film 5 is composed of a crystalline ferroelectric film and is provided on the lower electrode 4 independently for each cavity 12a. The piezoelectric film 5 has an inclined surface whose side end face 51a is inclined at a predetermined angle with respect to the elastic film 13, and has a so-called taper shape in a side sectional view.

  Similar to the piezoelectric film 5, the upper electrode 6 is provided independently for each cavity 12 a. The upper electrode 6 of the present embodiment has an inclined surface whose side end surface 61 a is continuous with the side end surface 51 a (inclined surface) of the piezoelectric film 5, and is patterned simultaneously with the piezoelectric film 5. That is, like the piezoelectric film 5, the taper shape is formed in a side sectional view.

  In the present embodiment, the inclination angle θ of the side end face 51a of the piezoelectric film 5 and the side end face 61a of the upper electrode 6 with respect to the surface of the lower electrode 4 is in the range of about 10 ° to 50 °, more preferably 40 ° or less. Here, the side end surfaces 51a and 61a are formed so that the inclination angle θ is 30 °.

  An insulating hydrogen barrier film 17 is provided on the elastic film 13 to cover the exposed surfaces of the upper electrode 6, the piezoelectric film 5, and the lower electrode 4. In the present embodiment, the insulating hydrogen barrier film 17 is formed using, for example, aluminum oxide (alumina: AlOx), and the film thickness is set to 0.2 μm.

The insulating hydrogen barrier film 17 prevents deterioration of the piezoelectric film 5 due to a reducing substance such as hydrogen (H ₂ ), water (H ₂ O), etc., and this changes the electrical characteristics of the capacitor. Thus, a high-quality liquid droplet ejection head 10 can be obtained.

  Each upper electrode 6 has a lead electrode 18 made of, for example, gold (Au) or the like and extending to the elastic film 13 through a through hole 17 a provided in the insulating hydrogen barrier film 17. Each is connected. In this way, the piezoelectric element 14 is configured.

(Droplet discharge)
Next, a case where ink droplets are ejected from the droplet ejection head 10 having such a configuration will be described.
The droplet discharge head 10 is in a state where a predetermined discharge signal is not input via a piezoelectric element driving circuit (not shown), that is, between the lower electrode 4 and the upper electrode 6 of the piezoelectric element 14 shown in FIG. In a state where no voltage is applied, the piezoelectric film 5 is not deformed. For this reason, the elastic membrane 13 is not deformed, and the volume of the cavity 12a is not changed. Therefore, ink droplets are not ejected from the nozzle 11a when in this state.

  On the other hand, in a state where a predetermined ejection signal is input via the piezoelectric element driving circuit, that is, in a state where a constant voltage (for example, about 30 V) is applied between the lower electrode 4 and the upper electrode 6 of the piezoelectric element 14, In the piezoelectric film 5, bending deformation occurs in the minor axis direction. As a result, the elastic film 13 is bent by, for example, about 500 nm, and the volume of the cavity 12a changes. At this time, the pressure in the cavity 12a instantaneously increases, and ink droplets can be ejected from the nozzle 11a.

  That is, when a voltage is applied, the crystal lattice of the piezoelectric film 5 is stretched in a direction perpendicular to the surface, but is simultaneously compressed in a direction parallel to the surface. In this state, a tensile stress is applied to the piezoelectric film 5 in the plane. Accordingly, the elastic film 13 is deflected and bent by this stress. The greater the displacement amount (absolute value) of the piezoelectric film 5 in the minor axis direction of the cavity 12a, the greater the deflection amount of the elastic film 13, and more efficiently eject ink droplets. Here, “efficient” means that the same amount of ink droplets can be ejected with a smaller voltage.

When the ejection of one ink is completed in this way, the piezoelectric element driving circuit stops applying the voltage between the lower electrode 4 and the upper electrode 6. As a result, the piezoelectric element 14 returns to its original shape, and the volume of the cavity 12a increases. At this time, pressure (pressure in the positive direction) from the ink cartridge 631 (see FIG. 8), which will be described later, toward the nozzles 11a acts on the ink. Therefore, air is prevented from entering the ink chamber 521 from the nozzle 11a, and an amount of ink commensurate with the amount of ink discharged is supplied from the ink cartridge 631 to the cavity 12a via the reservoir 12b. According to the droplet discharge head 10, since the adhesiveness between the piezoelectric element 14 and the elastic film 13 is high and it is difficult to peel off, the above-described ink discharge can be performed over a long period of time.
In this way, arbitrary (desired) characters and figures are printed by sequentially inputting ejection signals to the piezoelectric element 14 at the position where ink droplet ejection is desired via the piezoelectric element drive circuit. be able to.

  In the present embodiment, when the piezoelectric element 14 is driven, the inclined surface 20 in the vicinity 130C of the region 130B extends in the surface direction, and the entire region 130B is deformed into a convex shape in the cavity 12a to discharge ink. . That is, the elastic film 13 is likely to cause stress concentration at the boundary between the region 130A fixed by the partition wall A of the cavity 12a and the region 130B deformed by the vibration of the piezoelectric element 14, but in the present embodiment as described above. With this configuration, the Young's modulus in the boundary portion, that is, the vicinity portion 130C is reduced, and the deformation amount of the region 130B is improved, so that a desired ink discharge amount can be obtained.

(Method for manufacturing droplet discharge head)
Subsequently, as an embodiment of the method for manufacturing a droplet discharge head according to the present invention, a process for manufacturing the droplet discharge head 10 will be described with reference to the drawings. 5 to 7 are process diagrams for explaining a manufacturing process of the droplet discharge head.
First, the base material to be the ink chamber substrate 12, that is, the substrate 2 made of the above-described (110) -oriented silicon single crystal substrate (Si substrate) is prepared. Then, an elastic film 13 is formed on the substrate 2. As described above, the elastic film 13 is formed by laminating the elastic layer 13a made of silicon dioxide and the metal oxide layer 13b made of zirconium oxide (ZrO ₂ ). Therefore, first, a silicon dioxide (SiO ₂ ) layer functioning as the elastic layer 13a is formed on the substrate 2 by thermally oxidizing the substrate 2, and zirconium oxide is formed as a metal oxide layer 13b on the silicon dioxide layer. A (ZrO ₂ ) layer is formed. In this way, the elastic film 13 is formed integrally with the substrate 2.

Below, the formation method of the elastic film 13 is explained in full detail.
(LOCOS oxidation)
First, in order to obtain the elastic film 13 having a desired shape, the substrate 2 is subjected to a thermal oxidation process using the LOCOS method.
As shown in FIG. 5A, after the SiN film 31 is formed on the substrate 2 by the CVD method or the sputtering method, the photolithography technique and the etching technique are used as shown in FIG. The SiN film 31 in the region 120B other than the region corresponding to the partition wall 12A of the cavity 12a, that is, the region 120B corresponding to the cavity 12a is removed, and a mask M1 covering the region 120A corresponding to the partition wall 12A of the cavity 12a is patterned.

  Next, as shown in FIG. 5C, the substrate 2 is thermally oxidized using the mask M1 as an antioxidant film to form a first oxide film 32 in a region 120B corresponding to the cavity 12a. At this time, the temperature and time of the thermal oxidation treatment are adjusted to form the first oxide film 32 with a predetermined thickness. Thereafter, as shown in FIG. 5D, the first oxide film 32 and the mask M1 on the substrate 2 are removed by etching. Then, the convex part 33 appears in the area | region 120A corresponding to the partition 12A, and the surface of the board | substrate 2 becomes uneven | corrugated shape. Further, by performing LOCOS oxidation, the side wall of the convex portion 33 becomes a gentle slope, and the region 120A and the region 120B can be connected by a gentle curve.

(Formation of elastic film)
Next, as shown in FIG. 5E, the substrate 2 from which the first oxide film 32 and the mask M1 have been removed is thermally oxidized to form a second oxide film 34 on the entire surface thereof. The second oxide film 34 is formed along the surface shape of the substrate 2 and reflects the outer shape of the convex portion 33.

  Subsequently, as shown in FIG. 5 (f), the surface of the uneven oxide film 34 is planarized by CMP or etchback, and then silicon dioxide is formed on the substrate 2 as shown in FIG. 6 (a). The elastic layer 13a is formed. The thickness of the elastic layer 13a is relatively different between the region 130A corresponding to the partition wall 12A of the cavity 12a and the region 130B corresponding to the cavity 12a due to the convex portion 33 formed on the substrate 2. In addition, the vicinity 130C of the region 130A in the region 130B is a gentle inclined surface 20.

  In the elastic layer 13a, the thickness of the region 130A is preferably 20% to 70% of the thickness of the region 130B. In this embodiment, the thickness of the region 130A is 0.5 μm. The film thickness of the region 130B is 1.0 μm. Here, when the film thickness of the region 130A is less than 20% with respect to the film thickness of the region 130B, the mechanical strength as the elastic film 13 becomes low, and the repeated action of vibration cannot be obtained well during driving. End up. Further, when the film thickness of the region 130A exceeds 70% with respect to the film thickness of the region 130B, the effect of preventing the occurrence of cracks at the boundary portion between the region 130A and the region 130B becomes low. Therefore, by setting the thickness of the region 130A of the elastic film 13 to 20% or more and 70% or less with respect to the thickness of the region 130B, the occurrence of cracks and the like is suppressed, and the durability is reduced due to elastic fatigue. Can be prevented.

Next, a metal film made of zirconia (Zr) is formed on the second oxide film 34 by CVD or sputtering. Then, by thermally oxidizing the metal film, the metal film is converted into zirconium oxide (ZrO ₂ ) to form the metal oxide layer 13b.
In this way, the elastic layer 13a and the metal oxide layer 13b are formed on the substrate 2, and the elastic film 13 integrated with the substrate 2 is obtained.

  Subsequently, the surface of the elastic film 13 opposite to the substrate 2 side, that is, the surface of the metal oxide layer 13b is subjected to surface treatment. Specifically, in the present embodiment, as the surface treatment, plasma treatment is performed on the elastic film 13 in an atmosphere using argon (Ar) added with hydrogen (H 2) as a treatment gas.

Next, the piezoelectric element 14 is formed on the elastic film 13.
First, as shown in FIG. 6B, the lower electrode 4 is formed on the treated surface 55a of the elastic film 13 (metal oxide layer 13b) metallized by the plasma treatment by a known method such as sputtering. To do. Since the lower electrode 4 is formed by laminating the Pt layer 4a and the Ir layer 4b, the Pt layer 4a and the Ir layer 4b are sequentially laminated on the processing surface 55a.

  The step of forming the lower electrode 4 is preferably performed continuously in an inert atmosphere in a chamber (processing chamber) in which the above-described plasma processing (surface processing) is performed. In this way, it is possible to prevent the processing surface 55a from being exposed to the atmosphere, and thus it is possible to prevent the adhesion with the Pt layer 4a from being deteriorated due to contamination, oxidation, adhesion of impurities, or the like of the processing surface 55a.

  As shown in FIG. 6C, a precursor layer 5 </ b> A of the piezoelectric film 5 made of lead zirconate titanate (PZT) is formed on the lower electrode 4. Here, in this embodiment, a sol formed by dissolving and dispersing a metal organic substance in a solvent (dispersibility) is applied and dried to form a precursor layer 5A, and this precursor layer 5A is further degreased to remove organic components. After the separation, each piezoelectric film 5 is obtained by firing and crystallizing. Note that Ti may be provided as an adhesion layer between the lower electrode 4 and the piezoelectric film 5. Moreover, the manufacturing method of the piezoelectric film 5 is not limited to the sol-gel method described above, and for example, a MOD (Metal-Organic Decomposition) method or the like may be used.

  The piezoelectric film 5 is made of a ferroelectric material such as lead zirconate titanate, or a relaxor ferroelectric material to which a metal such as niobium, nickel, magnesium, bismuth or ytterbium is added. Also good.

Subsequently, the precursor layer 6A of the upper electrode 6 is formed on the precursor layer 5A of the piezoelectric film 5 by a known method such as a sputtering method in the same manner as the precursor layer 5A.
As the precursor layer 6A, a conductive material such as platinum (Pt), iridium (Ir), aluminum (Al), or the like can be used. Note that when aluminum is used, iridium or the like is laminated thereon to prevent electric corrosion.

  Thus, after forming the precursor layer 5A of the piezoelectric film 5 and the precursor layer 6A of the upper electrode 6 on the lower electrode 4, as shown in FIG. 6D, the precursor layer 5A and the precursor layer 6A are simultaneously formed. Patterning is performed to form the piezoelectric film 5 and the upper electrode 6. At this time, the inclination angle θ of the side end face 51a of the piezoelectric film 5 and the side end face 61a of the upper electrode 6 formed by patterning with respect to the lower electrode 4 is in the range of about 10 ° to 50 °, in this embodiment, about Patterning is performed to be 30 °.

Specifically, patterning is performed using a resist having a predetermined opening pattern provided on the precursor layer 6A as a mask M2. At this time, the angle θ1 of the end face of the mask M2 with respect to the precursor layer 6A is an angle of about 30 °. It has become. When the precursor layer 5A and the precursor layer 6A are etched using the mask M2, the mask M2 is etched together with the precursor layer 5A and the precursor layer 6A, and the side end surface 61a of the upper electrode 6 becomes an inclined surface, and the surface of the precursor layer 5A. As a result of the etching, the side end surface 51a of the piezoelectric film 5 becomes an inclined surface continuous to the side end surface 61a of the upper electrode 6. Thus, the side end face 51a of the piezoelectric film 5 and the side end face 61a of the upper electrode 6 are inclined at the same angle.
Through the above steps, the laminated body 14 a constituting the piezoelectric element 14 is formed on the elastic film 13.

  In forming the piezoelectric film 5 and the upper electrode 6 as described above, the side end surfaces 51a and 61a can be formed by using, for example, an ion milling method.

  Thereafter, as shown in FIG. 6E, the insulating hydrogen is formed by sputtering using aluminum oxide (AlOx) so as to cover the laminated body 14a composed of the lower electrode 4, the piezoelectric film 5, and the upper electrode 6. After the barrier film 17 is formed, as shown in FIG. 7A, the insulating hydrogen barrier film 17 is patterned for each stacked body 14a to expose the upper electrode 6 located in the lower layer. 17a is formed. Then, a metal layer (not shown) made of gold (Au) is formed over the entire surface of the substrate 2 so as to fill each through-hole 17a, and then this metal layer is patterned for each stacked body 14a. A lead electrode 18 is formed. In this way, the piezoelectric element 14 is formed in a region facing each cavity 12a.

  After the piezoelectric element 14 is formed, as shown in FIG. 7B, the substrate 2 serving as the base material that becomes the ink chamber substrate 12 is patterned using the mask M3, and as shown in FIG. By forming recesses 22A serving as cavities 12a at positions corresponding to the piezoelectric elements 14, and recesses (not shown) serving as reservoirs 12b and ink supply ports 12c at predetermined positions, partition walls 12A are formed. In this embodiment, the substrate 2 constituting the ink chamber substrate 12 is made of, for example, a silicon single crystal having a plane orientation (110). Since the substrate 2 having such a plane orientation (110) is suitable for anisotropic etching, the ink chamber substrate 12 can be formed easily and reliably.

Specifically, a mask M3 is formed on the surface of the substrate 2 opposite to the elastic film 13 in accordance with the positions where the cavities 12a, the reservoirs 12b, and the ink supply ports 12c are to be formed. Wet etching is performed with a high-concentration alkaline aqueous solution such as potassium hydroxide and tetramethylammonium hydroxide.
At this time, the mask M3 is formed so that the center of the projection 33 formed by LOCOS oxidation is the center of the partition wall 12A.

  Thus, the ink chamber substrate 12 can be formed by removing the substrate 2 by etching until the elastic film 13 is exposed in the thickness direction. Further, at this time, the portion that remains without being etched becomes the partition wall 12A. The method for patterning the substrate 2 is not limited to the wet etching described above. For example, parallel plate type reactive ion etching, inductive coupling type, electron cyclotron resonance type, helicon wave excitation type, magnetron type Also, dry etching such as a plasma etching method or an ion beam etching method can be employed.

Next, the nozzle plate 11 on which the plurality of nozzles 11a are formed is joined in a state where the nozzles 11a are aligned so as to correspond to the recesses 22A that become the cavities 12a. Thereby, a plurality of cavities 12a, a reservoir 12b, and a plurality of ink supply ports 12c are formed. For joining the nozzle plate 11, for example, an adhesive method using an adhesive, a fusion method, or the like can be used.
Thereafter, the ink chamber substrate 12 is attached to the substrate 15, whereby the droplet discharge head 10 is manufactured.

As described above, in the present invention, the thickness of the elastic film 13 provided on the ink chamber substrate 12 is thinner in the region 130A corresponding to the partition wall 12A of the cavity 12a than in the region 130B corresponding to the cavity 12a. Further, since the boundary (neighboring portion 130C) between the region 130A and the region 130B is the inclined surface 20, the boundary (boundary portion 130C) between the region 130B vibrating by the piezoelectric element 14 and the region 130A fixed by the partition wall 12A. It is possible to effectively relieve the stress applied to. As described above, the elastic film 13 has an inclined distribution in which the film thickness gradually decreases from the region 130B to the region 130A, so that the elastic film 13 is easily bent while maintaining its mechanical strength. Thereby, it becomes possible to suppress the generation of cracks or the like in the elastic film 13 during driving, and it is possible to suppress a decrease in durability due to elastic fatigue. At the same time, the Young's modulus in the vicinity 130C of the elastic film 13 decreases, so that the displacement of the piezoelectric element 14 increases and the ink discharge amount can be increased. Thus, the vibration reliability and displacement amount of the piezoelectric element 14 can be improved and maintained for a long period of time.
As described above, it is possible to improve printing defects due to cracks in the elastic film 13 and improve the reliability of the droplet discharge head 10.

  In addition, in order to obtain the elastic film 13 having a desired shape as described above, the surface of the substrate 2 is subjected to a thermal oxidation process by the LOCOS method so that the surface thereof is made uneven. By using the LOCOS method, a gentle slope without a step can be formed at the boundary between the region 120B corresponding to the cavity 12a of the substrate 2 and the region 120A corresponding to the partition wall 12A of the cavity 12a. This slope reflects the shape of the slope 20 in the vicinity 130 </ b> C of the elastic film 13. Although the substrate 2 can be processed by ion milling or etching, it is preferable to use the LOCOS method in order to suitably obtain the gentle slope 20 having no step.

  In the present invention, since the insulating hydrogen barrier film 17 prevents the deterioration of the piezoelectric film 5 due to hydrogen or water, long-term reliability as the piezoelectric element 14 is ensured.

  The preferred embodiments according to the present invention have been described above with reference to the accompanying drawings. However, it goes without saying that the present invention is not limited to such examples, and the above embodiments may be combined. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

  In the above embodiment, the elastic film 13 is formed integrally with the substrate 2. However, for example, a separately prepared elastic film 13 may be bonded to the substrate 2. In this case, similarly to the above embodiment, etching is performed so as to expose the elastic film 13 from the back surface (surface on which the silicon dioxide layer is not formed) side of the substrate 2 to form the cavity 12a and the reservoir 12b. Can be formed integrally with the substrate 2.

(Droplet discharge device)
Next, an ink jet printer as an embodiment of a droplet discharge apparatus including the droplet discharge head 10 will be described. The ink jet printer includes not only a printer that prints on paper or the like but also an industrially used droplet discharge device.

FIG. 8 is a schematic configuration diagram of the ink jet printer. Reference numeral 60 in FIG. 8 denotes an ink jet printer. In the following description, the upper side in FIG. 8 is referred to as “upper part” and the lower side is referred to as “lower part”.
The ink jet printer 60 includes an apparatus main body 620. The ink jet printer 60 has a tray 621 for placing the recording paper P on the upper rear side, a discharge port 622 for discharging the recording paper P on the lower front side, and an operation panel on the upper surface. 670.

  The operation panel 670 is composed of, for example, a liquid crystal display, an organic EL display, an LED lamp, and the like. A display unit (not shown) for displaying an error message and the like, and an operation unit (not shown) including various switches and the like. Z)).

  Inside the apparatus main body 620, there are mainly a printing apparatus 640 provided with a reciprocating head unit 630, a paper feeding apparatus 650 for feeding the recording paper P one by one to the printing apparatus 640, the printing apparatus 640 and the paper feeding apparatus. A control unit 660 for controlling the 650 is provided.

  Under the control of the control unit 660, the paper feeding device 650 intermittently feeds the recording paper P one by one. The recording paper P that is intermittently fed passes near the lower portion of the head unit 630. At this time, the head unit 630 reciprocates in a direction substantially perpendicular to the feeding direction of the recording paper P, and printing on the recording paper P is performed. That is, the reciprocation of the head unit 630 and the intermittent feeding of the recording paper P are the main scanning and the sub-scanning in printing, and ink jet printing is performed.

  The printing apparatus 640 includes a head unit 630, a carriage motor 641 serving as a drive source for the head unit 630, and a reciprocating mechanism 642 that reciprocates the head unit 630 in response to the rotation of the carriage motor 641. .

  In the lower part of the head unit 630, a droplet discharge head 10 having a large number of nozzles 11a, an ink cartridge 631 that supplies ink to the droplet discharge head 10, and the droplet discharge head 10 and the ink cartridge 631 are mounted. And a carriage 632.

  Note that full-color printing can be performed by using an ink cartridge 631 filled with ink of four colors of yellow, cyan, magenta, and black (black). In this case, the head unit 630 is provided with the droplet discharge heads 10 corresponding to the respective colors.

The reciprocating mechanism 642 includes a carriage guide shaft 643 whose both ends are supported by a frame (not shown), and a timing belt 644 extending in parallel with the carriage guide shaft 643.
The carriage 632 is supported by the carriage guide shaft 643 so as to be able to reciprocate and is fixed to a part of the timing belt 644.
When the timing belt 644 travels forward and backward through a pulley by the operation of the carriage motor 641, the head unit 630 reciprocates while being guided by the carriage guide shaft 643. During this reciprocation, ink is appropriately ejected from the droplet ejection head 10 and printing on the recording paper P is performed.

The sheet feeding device 650 includes a sheet feeding motor 651 as a driving source and a sheet feeding roller 652 that rotates by the operation of the sheet feeding motor 651.
The paper feed roller 652 is composed of a driven roller 652a and a drive roller 652b that are vertically opposed to each other with a feeding path (recording paper P) of the recording paper P interposed therebetween. The drive roller 652b is a paper feed motor 651. It is connected to. With such a configuration, the paper feed roller 652 can feed a large number of recording sheets P installed on the tray 621 one by one toward the printing apparatus 640. Instead of the tray 621, a configuration in which a paper feed cassette that stores the recording paper P can be detachably mounted may be employed.

The control unit 660 performs printing by controlling the printing device 640, the paper feeding device 650, and the like based on print data input from a host computer such as a personal computer or a digital camera.
Although not shown in the figure, the control unit 660 mainly stores a memory that stores a control program for controlling each unit, a piezoelectric element drive circuit that drives the piezoelectric element (vibration source) 14 to control ink ejection timing, A driving circuit for driving the printing device 640 (carriage motor 641), a driving circuit for driving the paper feeding device 650 (paper feeding motor 651), and a communication circuit for obtaining print data from the host computer, and electrically connected thereto And a CPU for performing various controls in each unit.

In addition, for example, various sensors that can detect the printing environment such as the remaining amount of ink in the ink cartridge 631, the position of the head unit 630, temperature, and humidity are electrically connected to the CPU.
The control unit 660 obtains print data via the communication circuit and stores it in the memory. The CPU processes the print data and outputs a drive signal to each drive circuit based on the process data and input data from various sensors. The piezoelectric element 14, the printing device 640, and the paper feeding device 650 are operated by this drive signal. Thus, desired printing is performed on the recording paper P.

In such an ink jet printer 60, as described above, since the elastic film 13 and the piezoelectric element 14 have high adhesiveness and a highly reliable liquid droplet ejection head 10, the ink jet printer itself is also ejected. High performance and high reliability with good performance.
Note that the ink jet printer of the present invention can also be a droplet discharge device used industrially as described above. In this case, as the ink (liquid material) to be ejected, various functional materials are adjusted to an appropriate viscosity with a solvent or a dispersion medium and used.

It is a disassembled perspective view of a droplet discharge head. It is a sectional side view showing a schematic structure of a droplet discharge head. It is an enlarged view showing a configuration of a piezoelectric element in a droplet discharge head. It is an enlarged view which shows the structure of the elastic film in a droplet discharge head, (a) is a sectional side view, (b) is a top view. It is a manufacturing process figure which shows the manufacturing method of a droplet discharge head. FIG. 6 is a manufacturing process diagram following FIG. 5; FIG. 7 is a manufacturing process diagram following FIG. 6; It is a schematic block diagram of an inkjet printer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Droplet discharge head, 11a ... Nozzle, 12a ... Cavity (pressure generation chamber), 12 ... Ink chamber substrate (channel formation part), 13 ... Elastic film, 4 ... Lower electrode, 5 ... Piezoelectric film, 6 ... Upper electrode, 14 ... piezoelectric element, 51a ... side end face, 61a ... side end face, 17 ... insulating hydrogen barrier film, 60 ... ink jet printer

Claims (5)

A flow path forming portion having a pressure generating chamber that is in communication with a nozzle opening for discharging liquid and surrounded by a partition;
An elastic film formed in contact with the pressure generating chamber and the partition;
A piezoelectric element comprising a lower electrode, a piezoelectric film, and an upper electrode provided on the elastic film;
A droplet discharge head comprising:
The droplet discharge head according to claim 1, wherein the elastic film has a convex shape toward the pressure generation chamber in a region in contact with the pressure generation chamber, and the convex shape has an inclined side surface. The flow path forming part is formed on a silicon substrate,
2. The droplet discharge head according to claim 1, wherein the elastic film has a silicon oxide film formed by thermally oxidizing the surface of the silicon substrate. A flow path forming portion having a pressure generating chamber that is in communication with a nozzle opening for discharging liquid and surrounded by a partition;
An elastic film formed in contact with the pressure generating chamber and the partition;
A piezoelectric element comprising a lower electrode, a piezoelectric film, and an upper electrode provided on the elastic film;
A method of manufacturing a droplet discharge head comprising:
A flow path forming part forming step of forming the flow path forming part on a substrate;
An elastic film forming step of forming the elastic film on the substrate;
And a piezoelectric element forming step of forming the piezoelectric element on the elastic film. The substrate is made of silicon;
The elastic film forming step includes
Forming a silicon nitride film in a region corresponding to the partition wall of the pressure generation chamber on the surface of the substrate opposite to the pressure generation chamber;
Forming a first oxide film by performing a thermal oxidation process using the silicon nitride film as a mask;
Removing the silicon nitride film and the first oxide film;
Thermally oxidizing the surface of the substrate to form a second oxide film;
The method of manufacturing a droplet discharge head according to claim 3, further comprising a step of planarizing a surface of the second oxide film.   A droplet discharge apparatus comprising the droplet discharge head according to claim 1.

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