JP2005349714A - Method for manufacturing liquid discharge head and liquid discharge head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture an inexpensive, high performance piezoelectric element by crystallizing a piezoelectric substance through laser annealing. <P>SOLUTION: A vibrating plate 5 made of heat-resistant glass is anodic bonded to a Si substrate 1 in which a groove is formed to be formed as a liquid flow channel comprising a pressure chamber 2, a liquid inlet 3, a nozzle 4, or the like. After forming a lower electrode 11 on the vibrating plate 5, an amorphous piezoelectric substance film is formed. A part of the amorphous piezoelectric substance film corresponding to the pressure chamber 2 is irradiated with laser light to be crystallized, thereby forming a piezoelectric film 12. Between the piezoelectric film 12 and an amorphous part 12b, which is not irradiated with the laser light, an intermediate layer 12c is provided in which an amorphous substance and a crystal coexist. On these areas, a pad 14 for wire bonding which connects an upper electrode 13 to the outside is formed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing an on-demand type liquid discharge head that discharges a liquid such as ink by a driving force of a piezoelectric element, and a liquid discharge head.

  In recent years, liquid discharge recording apparatuses such as inkjet printers have become widespread as printers that perform high-quality color printing at low cost. The liquid discharge recording apparatus is expected to be applied not only to printing on paper but also to a very wide range of fields such as textile printing, coating of industrial chemicals and pattern materials. As a typical liquid discharge recording apparatus, there are a piezoelectric system using a piezoelectric element and a thermal system using heater heating, both of which have advanced performance.

As for the piezoelectric type liquid discharge recording apparatus, what is currently commercialized is generally a bulk piezoelectric material such as Pb (Zr _x Ti _(1-x) ) O ₃ (hereinafter referred to as “PZT”). Therefore, it can be said that there is a limit to increasing the density and length of the head. In order to solve this technical problem, an attempt has been made to produce a liquid discharge head using a thin film as a piezoelectric body. As one method for manufacturing a liquid discharge head using a thin film as a piezoelectric body, there is a method disclosed in Patent Document 1 or the like. In this method, first, a Si substrate is heated to form a SiO ₂ thermal oxide film on the surface, which is used as a diaphragm. Further, a lower electrode, a piezoelectric film, and an upper electrode are formed on the diaphragm. Thereafter, a liquid channel is formed by etching the Si substrate from the back side, and finally, the pressure channel is formed by covering this liquid channel with a nozzle plate. This method is characterized in that the piezoelectric element is performed before forming the liquid flow path.

  As another manufacturing method, first, a liquid flow path is formed on the Si substrate by anisotropic etching, and a diaphragm made of glass having a thermal expansion coefficient substantially equal to that of the Si substrate is anodic bonded on the Si substrate. There is a method in which a pressure chamber is formed by the method and a piezoelectric element is formed on a vibration plate.

  FIG. 5 shows a liquid discharge head according to a conventional example. A groove serving as a liquid flow path such as a pressure chamber 102, a liquid supply port 103, and a nozzle 104 is formed in an Si substrate 101 by anisotropic etching. The diaphragm 105 is anodically bonded, and a piezoelectric element 106 having a lower electrode 106 a, a piezoelectric film 106 b, and an upper electrode 106 c is provided on a portion of the diaphragm 105 corresponding to the pressure chamber 102.

There are the following piezoelectric bodies used in such a liquid discharge head. First, as a method using a bulk body, a method of attaching bulk ceramics to a diaphragm bonded on a Si substrate (see Patent Document 2), or as a method using a piezoelectric thin film, a thin film on another substrate is used. A piezoelectric element made of an electrode and a piezoelectric body, and a method of bonding (transferring) the piezoelectric element to a vibration plate on a Si substrate (see Patent Document 3), or a thin film piezoelectric element on a vibration plate by screen printing There is a method of directly forming (see Patent Document 4 and Patent Document 5).
Japanese Patent Laid-Open No. 11-179904 Japanese Patent Laid-Open No. 9-94965 Japanese Patent Laid-Open No. 10-286953 Japanese Patent Laid-Open No. 5-286131 Japanese Patent Laid-Open No. 5-286132

  In a manufacturing method that processes a liquid flow path before forming a piezoelectric element, it is essential to use a piezoelectric film, which is a thin film piezoelectric body, in consideration of high density, high definition, and lengthening of the liquid discharge head. In particular, it is considered that a method of directly forming a piezoelectric film on a vibration plate will become a necessary technique in the future.

  However, when a piezoelectric element is manufactured by a film formation technique, if a piezoelectric thin film corresponding to the liquid flow path is formed into a strip pattern on the diaphragm, the piezoelectric film is peeled or cracked by the driving vibration of the piezoelectric element. In particular, this phenomenon occurs remarkably at the film edge.

  In order to improve ejection stability, it is necessary to apply vibration only to the pressure chamber when ejecting liquid such as ink and not to displace on the liquid supply port. Therefore, a configuration in which the piezoelectric element is formed only on the pressure chamber is desirable, but in this case, the probability of peeling of the piezoelectric element is increased as described above.

  Even when wiring is connected to the upper electrode of the piezoelectric element by wire bonding, it is not desirable on the piezoelectric film that is displaced.

  Furthermore, in a manufacturing method in which a thin film piezoelectric body is directly formed on a vibration plate, if glass is used as the vibration plate, it is necessary to produce the piezoelectric film at a temperature below the softening point of the glass. However, when producing a PZT piezoelectric film having excellent characteristics, a temperature of at least 600 ° C. is required. Further, since the pressure chamber is formed by anodic bonding of the Si substrate and the glass, it is necessary to make the thermal expansion coefficients of the Si substrate and the glass equal. For these reasons, the diaphragm has heat resistance. In addition, the condition that the thermal expansion coefficient is equal to that of Si is required, and the selection range of the diaphragm material is limited. Therefore, a technique for forming a high-quality piezoelectric film without being affected by the softening point of glass is desired in order to expand the selection range of the diaphragm material.

  The present invention has been made in view of the above-mentioned unsolved problems of the prior art, and enables an amorphous piezoelectric body to be efficiently crystallized at a low temperature, thereby improving the discharge performance and reducing the price. An object of the present invention is to provide a method of manufacturing a liquid discharge head and a liquid discharge head that can greatly contribute.

  In order to achieve the above object, a method for manufacturing a liquid discharge head according to the present invention is a method for manufacturing a liquid discharge head in which a pressure chamber is pressurized by a piezoelectric element and liquid is discharged from a discharge port. The method includes a step of forming a piezoelectric film and a step of forming the piezoelectric element by crystallizing the amorphous piezoelectric film by irradiating a laser beam.

  By using laser annealing to crystallize the amorphous piezoelectric film, only the piezoelectric film on the pressure chamber is selectively crystallized, and the region near the liquid supply port includes an intermediate layer containing amorphous and crystals. It can be left as a movable area.

  Since the vibration plate is not displaced by the piezoelectric element on the liquid supply port, it is possible to manufacture a liquid discharge head having excellent liquid discharge characteristics such as ink. Further, by configuring the end portion of the piezoelectric element so as not to be displaced, peeling of the piezoelectric film or the like can be effectively prevented. Further, by connecting an external wiring to the end portion that is not displaced, a strong wiring can be achieved.

  In order to avoid stress concentration near the boundary between the crystal portion and the portion remaining in the amorphous state due to laser annealing, the laser intensity is continuously changed near the boundary to provide an intermediate layer in which amorphous and crystals are mixed.

  In the process of crystallizing an amorphous piezoelectric film, laser annealing, which allows partial and selective heating, can be used to raise the temperature of a vibrating plate such as glass compared to annealing by heating the entire substrate. In addition to avoiding deformation and softening caused by the above, there is an advantage that the range of selection of the diaphragm material is widened because the influence of the difference in thermal expansion coefficient between the substrate and the diaphragm is reduced.

  FIG. 1 shows a liquid discharge head according to an embodiment. In this liquid discharge head, first, a groove serving as a liquid flow path such as a pressure chamber 2, a liquid supply port 3, and a nozzle 4 is processed in a Si substrate 1 as a substrate, and a vibrating plate 5 such as glass is anodic bonded thereon. A piezoelectric element 10 including a lower electrode 11 and a piezoelectric film 12 such as PZT is formed thereon, and a wiring 15 by wire bonding is connected to the upper electrode 13 via a pad 14.

  The piezoelectric film 12 is a laser annealing film obtained by partially and selectively crystallizing an amorphous piezoelectric film corresponding to the shape of the pressure chamber 2 by laser annealing. The crystallized piezoelectric film 12 causes a piezoelectric phenomenon when a voltage is applied to the upper electrode 13 and the lower electrode 11, but no piezoelectric phenomenon occurs in the remaining amorphous portion 12 b corresponding to the liquid supply port 3. Further, in order to reduce the occurrence of cracks or the like at the boundary between the piezoelectric film 12 where the piezoelectric phenomenon occurs and the amorphous part 12b where the piezoelectric phenomenon does not occur, an intermediate layer 12c in which crystals and amorphous are mixed is formed between the two. .

  As described above, the piezoelectric film 12 is provided only on the pressure chamber 2, and the amorphous portion 12 b and the intermediate layer 12 c which are non-movable regions are provided on the connected portions such as the liquid supply port 3 and the pad 14. A liquid discharge head having excellent durability can be manufactured. Further, since PZT or the like formed on the diaphragm 5 is locally crystallized by laser annealing, the influence of heat on the diaphragm 5 such as glass is reduced as compared with the case where the entire substrate is heated. This increases the range of diaphragm material selection.

  FIG. 2 is a process diagram showing a manufacturing method of the liquid discharge head according to the first embodiment. First, as shown in FIG. 2A, the pressure of FIG. 1 is applied to a Si (100) substrate 1 by anisotropic etching. A groove serving as a liquid flow path including the chamber 2, the liquid supply port 3, the nozzle 4 and the like is formed. In this method, it is possible to increase the density and length of the nozzles using a semiconductor processing process, and it is possible to obtain high resolution as a liquid discharge head.

  Next, as shown in FIG. 2 (b), a glass plate to be the vibration plate 5 is anodically bonded onto the Si substrate 1. The anodic bonding method is performed by heating the Si substrate 1 and the glass plate so as to press each other and applying an electric field between them. As the glass material, it is necessary to be a material capable of anodic bonding with Si, and since amorphous PZT formed thereon is crystallized by laser annealing, the closer the thermal expansion coefficient to the Si substrate, A higher softening point temperature is preferable. In this example, heat-resistant glass was used. After anodically bonding the glass, it was polished until the thickness became 1 to 10 μm, and this was used as the diaphragm 5.

Next, as shown in FIG. 2C, a Ti film and a Pt film to be the lower electrode 11 were formed on the diaphragm 5 by sputtering at room temperature. Here, the Ti film was an adhesion layer and was formed to a thickness of about 20 nm. The Pt film was formed to a thickness of about 100 to 300 nm as the lower electrode 11 of the piezoelectric element. Here, the electrode material is not limited to Pt, and a metal material such as Au, Al, Ni, or Pt, or an oxide electrode material such as SrRuO ₃ or LaNiO ₃ may be used.

  Next, as shown in FIG. 2D, a piezoelectric film 12a, which is amorphous PZT, was formed to a thickness of about 1 to 10 μm at room temperature by sputtering. The PZT film forming method is not limited to the sputtering method, and a vacuum film forming method such as an MOCVD method or a sol-gel method may be used. Further, it is necessary to select a film thickness with the largest displacement amount in relation to the thickness of the diaphragm 5.

  In the laser annealing step shown in FIG. 2 (e), the piezoelectric film 12a at the site on the pressure chamber 2 is selectively crystallized using the laser beam P. Here, it is known that the transmittance T of amorphous PZT varies depending on the wavelength of the laser beam as shown in the graph of FIG. 4, and it is necessary to select a laser having a wavelength of 360 nm or less. For this reason, ArF (λ = 193 nm), KrF (λ = 248 nm), XeCl (λ = 308 nm), XeF (λ = 351 nm) can be used as the laser light P.

  In the laser annealing step, in order to improve productivity, the laser beam P may be one that can widen the irradiation area to the extent that the diaphragm 5 of heat-resistant glass is not deformed, or a plurality of lasers may be used at the same time. Good. As shown in FIG. 1, the boundary portion between the amorphous and the crystal is formed by gradually changing the laser intensity or changing the laser irradiation time in order to avoid stress concentration caused by driving of the piezoelectric element. Then, the intermediate layer 12c in which amorphous and crystals are mixed is formed. The intermediate layer 12c is configured to have a large proportion of crystallized PZT on the pressure chamber 2 side and a large proportion of amorphous PZT on the liquid supply port 3 side.

Next, as shown in FIG. 2F, a Pt film was formed as the upper electrode 13 to a thickness of about 100 to 300 nm. Also in this case, the film was formed at room temperature using the sputtering method. Here, the electrode material is not limited to Pt, and a metal material such as Au, Al, Ni, and Pt, or an oxide electrode material such as SrRuO ₃ and LaNiO ₃ may be used. Further, a vacuum film forming method such as MOCVD method or a sol-gel method may be used for forming the electrode.

  After the piezoelectric element layers 11 to 13 are formed in this way, patterning is performed to etch and remove the upper electrode 13 and the piezoelectric film 12 in portions other than the portion corresponding to the liquid flow path, as shown in FIG. Do. Finally, wiring is performed by wire bonding in the non-movable region as described above.

  FIG. 3 is a process diagram showing a method of manufacturing a liquid discharge head according to the second embodiment. As shown in FIG. 3A, first, the pressure of FIG. 1 is applied to a Si (100) substrate 1 by anisotropic etching. A liquid flow path including the chamber 2, the liquid supply port 3, the nozzle 4 and the like is formed. The steps (a) to (d) in FIG. 3 are the same as the steps (a) to (d) in FIG. Further, since the components other than the upper electrode 23 are the same as those in the first embodiment, the same reference numerals are used.

  Next, as shown in FIG. 3B, a glass plate to be the vibration plate 5 is anodically bonded onto the Si substrate 1. The anodic bonding method is performed by heating the Si substrate 1 and the glass plate so as to press each other and applying an electric field between them. The glass material needs to be a material that can be anodically bonded to Si, and since amorphous PZT formed thereon is crystallized by laser annealing, the closer the thermal expansion coefficient to the Si substrate, A higher softening point temperature is preferable. In this example, heat-resistant glass was used. After anodically bonding the glass plate, the glass plate was polished until the thickness became 1 to 10 μm, and this was used as the diaphragm 5.

Next, as shown in FIG. 3C, a Ti / Pt film was formed on the vibration plate 5 by sputtering at room temperature. Here, the Ti film was an adhesion layer and was formed to a thickness of about 20 nm. The Pt film was formed to a thickness of about 100 to 300 nm as the lower electrode 11 of the piezoelectric element. Here, the electrode material is not limited to Pt, and a metal material such as Au, Al, Ni, or Pt, or an oxide electrode material such as SrRuO ₃ or LaNiO ₃ may be used.

  Next, as shown in FIG. 3D, a PZT piezoelectric film 12a, which is an amorphous piezoelectric body, was formed by sputtering to a thickness of about 1 to 10 μm at room temperature. The PZT film forming method is not limited to the sputtering method, and a vacuum film forming method such as an MOCVD method or a sol-gel method may be used. Further, it is necessary to select a film thickness with the largest displacement amount in relation to the thickness of the diaphragm 5.

  Further, as shown in FIG. 3E, an electrode film that transmits the laser beam P was formed as an upper electrode 23 to a thickness of about 100 to 300 nm. Also in this case, the film is formed at room temperature using the sputtering method, but a vacuum film forming method such as MOCVD method or a sol-gel method may be used. Here, the material of the electrode film may be any material that transmits laser light and has conductivity. In this example, ITO was used.

  Next, as shown in FIG. 3F, PZT on the pressure chamber 2 was selectively crystallized using the laser beam P. Here, since the transmittance of amorphous PZT changes as shown in FIG. 4, it is necessary to select a laser having a wavelength of 360 nm or less as in the first embodiment. In addition, the transmittance of ITO decreases near 300 nm. For these reasons, it is necessary to use a laser having a wavelength between 300 nm and 360 nm, and an XeF laser (λ = 351 nm) is appropriate.

  Even when the upper electrode 23 absorbs laser, when the thickness of the electrode film is much thinner than that of the piezoelectric body, the heat generated in the electrode is conducted. For example, ArF laser (λ = 193 nm), KrF laser (Λ = 248 nm) can also be used.

  In the laser annealing process, in order to improve the productivity, it is preferable that the irradiation area of the laser beam P is increased so that the diaphragm 5 made of heat-resistant glass is not deformed. Alternatively, a plurality of lasers can be used simultaneously. As shown in FIG. 1, the boundary between the amorphous and the crystal is formed by gradually changing the laser intensity or changing the laser irradiation time in order to avoid stress concentration caused by driving of the piezoelectric element. An intermediate layer 12c made of amorphous and crystal is formed. The intermediate layer 12c is configured to have a large proportion of crystallized PZT on the pressure chamber 2 side and a large proportion of amorphous PZT on the liquid supply port 3 side.

  After the PZT on the pressure chamber 2 is crystallized, as shown in FIG. 3G, patterning is performed to etch and remove the electrode and PZT in portions other than the portion corresponding to the liquid flow path. Finally, wiring by wire bonding is performed in the non-movable area.

1 shows a liquid discharge head according to an embodiment, in which (a) is a cross-sectional view taken along a liquid flow path, and (b) is a cross-sectional view taken along line AA of (a). 6 is a process diagram illustrating a method of manufacturing a liquid ejection head according to Embodiment 1. FIG. 6 is a process diagram illustrating a method for manufacturing a liquid discharge head according to Embodiment 2. FIG. It is a graph which shows the transmittance | permeability of amorphous PZT. 1 shows a liquid ejection head according to a conventional example, in which (a) is a cross-sectional view taken along a liquid flow path, and (b) is a cross-sectional view taken along line AA of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Si substrate 2 Pressure chamber 3 Liquid supply port 4 Nozzle 5 Diaphragm 11 Lower electrode 12 Piezoelectric film 12a Amorphous piezoelectric film 12b Amorphous part 12c Intermediate layer 13, 23 Upper electrode 14 Pad 15 Wiring

Claims (8)

In a method of manufacturing a liquid ejection head that pressurizes a pressure chamber with a piezoelectric element and ejects liquid from an ejection port,
Forming an amorphous piezoelectric film as a material of the piezoelectric element;
Forming the piezoelectric element by crystallizing the amorphous piezoelectric film by irradiating a laser beam;
A method of manufacturing a liquid discharge head, comprising:   2. The method of manufacturing a liquid discharge head according to claim 1, wherein in the step of forming the piezoelectric element, laser light is selectively irradiated to a portion of the amorphous piezoelectric film corresponding to the pressure chamber.   3. The method of manufacturing a liquid discharge head according to claim 1, wherein an upper electrode is formed on the piezoelectric element after the step of forming the piezoelectric element.   3. The liquid discharge head according to claim 1, wherein, in the step of forming the piezoelectric element, an upper electrode having laser permeability is formed on the amorphous piezoelectric film before irradiating the laser beam. Manufacturing method.   A liquid discharge head manufactured by the method for manufacturing a liquid discharge head according to claim 1.   6. The liquid ejection head according to claim 5, wherein a region where amorphous and crystal are mixed is provided integrally with the piezoelectric element.   The liquid discharge head according to claim 6, wherein an upper electrode made of an oxide is formed on the piezoelectric element.   8. The liquid discharge head according to claim 7, wherein a wiring portion for connecting the upper electrode to an external wiring is provided on the region.

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