JP2008302588A - Ink jet head and method of manufacturing ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film piezoelectric ink jet head having a high performance actuator.
An Si channel substrate and a nozzle plate are Au-Au bonded, and a thermal oxide film is provided between the Si substrate and Au.
[Selection] Figure 1

Description

  The present invention relates to an ink jet head configured by joining a plurality of flow path substrates and a method for manufacturing the same, and more particularly to an ink jet head using a thin film piezoelectric actuator suitable for industrial use and a method for manufacturing the same.

  Ink-jet heads for ejecting minute droplets are being developed not only for consumer use such as printers, but also for industrial uses such as wiring pattern direct drawing devices and liquid crystal color filter manufacturing. Various types of ink-jet heads have been put into practical use, but in industrial applications, development of types using piezoelectric elements is progressing due to the large tolerance for ink. For example, in Japanese Patent Application Laid-Open No. 5-286131, a uniform piezoelectric thin film is formed by a film forming technique over the entire surface of the diaphragm, and this piezoelectric thin film is divided into shapes corresponding to individual liquid chambers by a lithography method. In other words, an actuator is formed so as to be independent for each individual liquid chamber. This eliminates the need for attaching the actuator to the diaphragm, and allows the actuator to be formed on the thin film diaphragm by a precise and simple technique called a lithography method. There is an advantage that the thickness can be reduced and high-speed driving becomes possible. In the above publication, a discharge port is formed so that droplets are discharged in a direction parallel to the substrate surface. This is a so-called edge shooter type, but from the viewpoint of increasing the density, it is approximately perpendicular to the laminating direction of the diaphragm and piezoelectric film. A so-called side shooter type that discharges droplets from a smooth surface is preferable. A side shooter type ink jet head is generally configured by joining a flow path substrate having an actuator and a nozzle plate having fine discharge ports.

There are two methods for bonding the flow path substrate and the nozzle plate: one using an adhesive and the other using a solid phase bonding using Au or the like. The ink jet head has excellent characteristics as a method for joining an inkjet head, such as no inflow of ink. Solid-phase bonding methods include a method of bonding silicon substrates having clean and smooth surfaces at a high temperature of about 1000 ° C, a method of activating and bonding substrates having a smooth surface in a high vacuum, etc. There is. In particular, Au-Au bonding bonded via Au does not require special equipment or high temperature, and is more tolerant of dust on the bonding surface than other solid-phase bonding methods, making it an excellent technique for industrial applications. It is. JP-A-2006-76180 is disclosed as an example of forming an inkjet head using Au-Au bonding.
Japanese Patent Laid-Open No. 5-286131 JP 2006-76180 A

  Since a thin film piezoelectric material is processed by a lithography method and a head for forming an actuator uses a precise processing method called a lithography method, it is possible to manufacture an actuator with extremely high accuracy as compared with the conventional method. In order to take full advantage of this advantage, it is required to form individual liquid chambers with high accuracy. As a technique for forming a fine structure having a high aspect ratio such as an individual liquid chamber with high accuracy, there is a MEMS technique, and a silicon substrate is generally used as a substrate material using the MEMS technique. In particular, the nozzle plate needs to be formed with high accuracy because the shape of the discharge port has a great influence on the discharge performance, and is preferably formed on a silicon substrate using MEMS technology. In general, in solid phase bonding, the smoothness of the bonding surface is extremely important, and a surface roughness of preferably 1 nm or less is required. The silicon substrate is a suitable material also from the viewpoint of the required bonding surface smoothness.

  However, the present inventor has found that there are the following problems when attempting to form a thin film piezoelectric ink jet head by bonding members processed on a silicon substrate using Au-Au bonding.

  Dry etching is used to process the flow path and the piezoelectric body with high precision. However, since the thickness of the piezoelectric body is as thin as several μm, it is easily damaged by the dry etching process and its characteristics are likely to deteriorate. Accordingly, in order to avoid characteristic deterioration due to process damage such as when a flow path is formed, it is preferable to form the piezoelectric body as much as possible at the end of the head manufacturing process. However, it has been found that when a piezoelectric body is formed on a head in which a silicon member is bonded to Au—Au, a large number of unbonded portions (voids) are generated at the bonded portion. This void not only causes a decrease in bonding strength, but if the void is present in a flow path such as an individual liquid chamber, it tends to become a bubble pool, making the discharge unstable. Will also cause problems. As a result of intensive studies on the generation of voids, it was found that the heat treatment performed in the piezoelectric body formation process is the cause. In general, heat treatment at about 700 ° C. is necessary to obtain a high-performance piezoelectric body. In the above-mentioned Japanese Patent Application Laid-Open No. 5-286131, the piezoelectric body is fired at 500 ° C., but according to the study of the present inventor, voids are formed when heat treatment at 500 ° C. or higher is performed on the Au-Au bonded head. Many have been found to occur. Therefore, in a head using Au-Au bonding, formation of a thin film piezoelectric body could not be brought to the end of the head manufacturing process. Therefore, in the head using Au-Au bonding, an actuator whose characteristics are deteriorated due to process damage has to be used.

  As described above, a silicon substrate is suitable as the flow path material. However, since silicon has a low resistance to an alkaline solution and a highly alkaline ink cannot be used, development in industrial applications is limited. Furthermore, as described above, the surface roughness of the bonding surface is extremely important in the solid phase bonding, and preferably a surface roughness of 1 nm or less is required. As far as the present inventor knows, there are no examples that disclose the structure, manufacturing method, and the like.

  A so-called bump bonding method using Au bumps is known as a method for bonding structures, but in general, an ultrasonic wave is applied in bump bonding, and a thin film diaphragm of several μm is provided. It is not suitable for the type of inkjet head. Further, in the case of bump bonding, the bump thickness is several μm or more, and since it is formed using a plating method, the surface roughness is several tens of nm or more, which is far from the region where good solid phase bonding can be performed. Further, when bump bonding is performed, the bumps are crushed and bonded by applying a high pressure of 100 MPa or more, but such high pressure is unsuitable as a method for manufacturing an ink jet head having a thin film diaphragm. In order to apply such a high pressure, generally, the area of the bumps must be very small, which is not suitable for the purpose of sealing the flow path of the inkjet head. For the above reasons, even bonding using the same Au is completely different from the present invention in bump bonding, and it is inappropriate to discuss in comparison.

  Accordingly, an object of the present invention is to provide a thin film piezoelectric ink jet head having a high performance actuator using Au—Au bonding for bonding. It is another object of the present invention to provide a thin film piezoelectric ink jet head in which there are few limitations on the ink that can be used even when a silicon substrate is used. Still another object of the present invention is to provide a method of manufacturing a thin film piezoelectric ink jet head having a high performance actuator using Au-Au bonding. Another object of the present invention is to provide a method of manufacturing a thin film piezoelectric ink jet head with a limited number of inks that can be used even when a silicon substrate capable of high precision processing is used.

  The present invention has been made in view of the above problems, and an inkjet head according to the present invention is formed by bonding a silicon substrate having an ink flow path formed on a silicon substrate, and the substrate and another member via Au. The inkjet head is characterized in that a member for preventing diffusion of silicon and Au is provided at least between the bonding Au provided at the bonding portion and the silicon member. . Further, the inside of the flow path formed in the silicon member is covered with a member made of the same material as the member for preventing diffusion of the silicon and Au. Further, a member made of the same material as the member for preventing diffusion of silicon and Au provided in the flow path formed in the silicon member is formed by joining Au and silicon member provided in the joint portion. It is characterized in that it is formed thinner than a member for preventing diffusion of Au and silicon provided between them. Further, the member provided to prevent the diffusion of Au and silicon is a thermal oxide film of silicon. In addition, a method for manufacturing an inkjet head according to the present invention includes a substrate having a channel formed on a silicon substrate, and the silicon substrate on which the channel is formed and another member are bonded via Au. In the manufacturing method, a step of forming a channel on the silicon substrate, a step of providing a member for preventing diffusion of Au and silicon on the substrate after the channel is formed on the silicon substrate, And a step of forming Au for bonding after the step of providing a member for preventing diffusion of Au and silicon. Further, in a method of manufacturing an inkjet head, which includes a substrate having a flow path formed on a silicon substrate, and the silicon substrate on which the flow path is formed and another member are bonded via Au. A step of providing a member for preventing diffusion of Au and silicon, a step of providing a member for preventing diffusion of Au and silicon on the silicon substrate, a step of forming a flow path in the silicon substrate, and a silicon substrate And forming a bonding Au after forming the flow path in the step. Furthermore, after the flow path is formed in the silicon substrate, there is a step of providing a member for preventing diffusion of Au and silicon in the flow path.

  According to the ink jet head and the manufacturing method thereof of the present invention, a thin film piezoelectric ink jet head having a thin film piezoelectric actuator that uses an excellent Au-Au joint as a method of joining the ink jet head and has little characteristic deterioration due to damage to the manufacturing process such as a flow path Can be obtained.

  As described above, according to the present invention, a thin film piezoelectric ink jet head having a high-performance actuator using Au—Au bonding for bonding can be obtained. In addition, a thin film piezoelectric ink jet head with a limited number of inks that can be used even when a silicon substrate is used can be obtained. In particular, by providing a thermal oxide film as a barrier layer under the bonding layer, it is possible to obtain an inkjet head with improved bonding reliability and excellent durability.

  The present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of an inkjet head according to the present invention.

  The flow path substrate 15 in which the individual liquid chamber 9 is formed in the silicon substrate 2 and the nozzle plate 16 in which the ink discharge port 11 and the communication path 10 to the individual liquid chamber 9 are formed in the silicon substrate 1 are bonded by Au-Au bonding. The ink jet head is formed by bonding. The flow path substrate 15 includes a thin film diaphragm 3, an insulating film 4, a thin film piezoelectric actuator 8 including a common electrode 5, a piezoelectric thin film 6, and individual electrodes 7. Between the Au-Au bonding layer 12 and the silicon substrate 2 of the flow path substrate 15 and the silicon substrate 1 of the nozzle plate, silicon thermal oxide films 13a and 13b are provided as a diffusion preventing layer for Au and silicon. . The present inventor has found that a void generated when heat-treating a head having an Au-Au bonded silicon substrate is diffusion due to the heat of Au and silicon, and a layer for preventing the diffusion of Au and silicon is formed between Au and the silicon substrate. This is because it has been found that this problem can be solved by providing it in between. It has also been found that a silicon thermal oxide film has a high anti-diffusion ability, a good surface smoothness, and a preferable material in consideration of process suitability and the like as a material for the diffusion prevention layer. Although silicon oxide films formed by sputtering or CVD were also examined, the surface smoothness was not sufficient compared to silicon oxide films formed by thermal oxidation, and the ability to prevent diffusion of silicon and Au during heat treatment It was inferior to the thermally oxidized silicon film. However, even a silicon oxide film formed by a CVD method, a sputtering method, or the like can be used by optimizing the film formation conditions and performing smoothing such as surface polishing after the film formation. Surface polishing methods include CMP, smoothing by applying a cluster ion beam at an angle close to the surface of the bonding surface, and methods of making ions or plasma incident at a shallow angle on the surface of the bonding surface. Can be used. Since Au and the silicon thermal oxide film have poor adhesion, a titanium layer is provided as an adhesion layer (not shown) between the Au-Au bonding layer 12 and the silicon oxide films 13a and 13b.

  As described above, the silicon thermal oxide films 13a and 13b are provided as the diffusion preventing layer between the silicon substrates 1 and 2 and the Au bonding layer 12, so that the heat resistance is higher than that of the conventional head using the Au-Au bonding. Improved. Further, the joining portion is limited to the periphery of the flow path, and can be joined with a small force by forming a convex shape with respect to the non-joining region. FIG. 3 shows an example in which the bonding state was evaluated by an ultrasonic microscope after the head of this example was heat-treated at 700 ° C., which is the same as the firing condition of the piezoelectric body. In FIG. 3, a white part is a place with a space | gap and is a flow path or an unjoined part. It can be seen from FIG. 3 that there are no noticeable unjoined parts other than the flow path. As a comparative example, FIG. 4 shows an example in which a head without a diffusion prevention layer was prepared and the joining condition was evaluated after heat treatment at 700 ° C. in the same manner. Compared to FIG. 3, it can be seen that a large number of unjoined portions are generated in portions other than the flow path. Next, a method for manufacturing the ink jet head according to the present invention will be described. FIG. 5 is a view showing a method of producing the individual liquid chamber substrate portion of the ink jet head according to the present invention. As shown in FIG. 5A, a silicon substrate 2 having a thin film diaphragm 3 is prepared. Here, the thin film diaphragm is made of single crystal silicon having a thickness of 5 μm, the insulating film 4 is made of thermally oxidized silicon having a thickness of 1 μm, and the single crystal silicon substrate 2 is made of SOI (Silicon On Insulator) having a thickness of 200 μm. A silicon thermal oxide film having a thickness of 1 μm is provided between the single crystal thin film diaphragm 3 and the single crystal silicon substrate 2 (not shown). Here, as the substrate to be used, a substrate having a sufficiently smooth surface (preferably having a surface roughness Ra of 1 nm or less) is used as the surface to be bonded (the lower surface in the figure). A carefully polished silicon substrate surface can usually be used without problems. Next, as shown in FIG. 5B, a diffusion preventing layer 13a is provided. Here, 1 μm thick thermally oxidized silicon was used as the diffusion preventing layer. Since the silicon substrate 2 is thermally oxidized to provide the diffusion preventing layer 13a, the surface of the diffusion preventing layer 13a reflects the smoothness of the smooth surface of the silicon substrate 2, and has the same smoothness. Yes. Simultaneously with the step of providing the diffusion prevention layer 13a, the insulating film 4 made of thermally oxidized silicon having a thickness of 1 μm is provided on the thin film diaphragm 3. Here, the SOI substrate is thermally oxidized to form the diffusion prevention layer 13a and the insulating film 4. However, an SOI substrate having a thermal oxide film with an appropriate thickness on both surfaces of the substrate may be used. Next, an etching mask 15 for etching the individual liquid chamber is provided as shown in the figure. Here, a positive type photoresist mainly composed of novolak resin was used as the etching mask 15. Using this etching mask 15, the diffusion prevention layer 13a is etched as shown in FIG. As an etching method, dry etching using a fluorine-based gas was performed. Next, as shown in FIG. 5D, the individual liquid chamber was etched. Here, it is necessary to etch the silicon vertically over a depth of 200 μm. In this example, an inductively coupled plasma (ICP) etching apparatus capable of generating high-density plasma was used as an etching apparatus, and etching was performed using a fluorine-based gas and a fluorocarbon-based gas to form individual liquid chambers. At this time, etching is performed using an unillustrated 1 μm thick thermal oxide film between the thin film diaphragm 3 and the single crystal silicon substrate 2 as an etching stop layer, so that the individual liquid chamber 9 having a uniform depth and a uniform thickness are obtained. A thin film diaphragm 3 is formed. Next, the etching mask 15 for the individual liquid chamber is removed, and the diffusion preventing layer 13a is exposed (FIG. 5E). As a method for removing the etching mask 15, ashing using oxygen plasma or ozone, wet stripping using an organic solvent, or a combination thereof may be used. As described above, the exposed surface of the diffusion prevention layer 13a is smooth reflecting the smooth surface of the silicon substrate 2, and has a surface suitable for solid phase bonding. After removing the etching mask 15 and exposing the diffusion preventing layer 13a, it is also preferable from the viewpoint of removing dust and process damage to remove the surface layer of the diffusion preventing layer 13a by etching or the like. In this case, it is important that etching does not impair the smoothness of the surface of the diffusion preventing layer 13a. Light wet etching using hydrofluoric acid can be suitably used. Next, as shown in FIG. 5F, titanium and Au are formed by sputtering as the bonding layer 12 on the exposed surface of the diffusion preventing layer 13a. Since the surface roughness of Au depends on the film thickness, it is necessary to select the Au film thickness carefully. FIG. 12 shows the relationship between the Au film thickness and the surface roughness. Both have a surface roughness of 1 nm or less, but according to the study of the present inventors, if the surface is smooth, less pressure is required for bonding. 100 nm was selected. Further, although the sputtering method is used as a method for forming the bonding layer, other methods such as a vacuum deposition method can be used as long as adhesion and smoothness are good. Next, the manufacturing process of the nozzle plate will be described. As shown in FIG. 7A, thermally oxidized silicon having a thickness of 1 μm is formed as a diffusion prevention layer 13b on a single crystal silicon substrate 1 having a thickness of 200 μm. Next, as shown in FIG. 7B, an etching mask 16 for the communication path 10 between the individual liquid chamber and the nozzle and an etching mask 17 for the nozzle 11 are formed on both surfaces of the substrate. In this embodiment, a positive type photoresist mainly composed of novolak resin is used as an etching mask. Next, the diffusion prevention layer 13b is etched using the etching mask 16 formed as shown in FIG. As an etching method, dry etching using a fluorine-based gas was performed. Next, as shown in FIG. 7D, silicon is etched from both sides using the etching mask 16 and the etching mask 17 to form the communication path 10 and the nozzle 11 between the individual liquid chamber and the nozzle. In this embodiment, the depth of the communication path 10 is 150 μm, and the depth of the nozzle 11 is 50 μm. Etching was performed using a fluorine-based gas and a fluorocarbon-based gas, using an inductively coupled plasma (ICP) etching apparatus capable of generating a high-density plasma, similar to the etching of the individual liquid chamber. After etching the silicon, the etching masks 16 and 17 are removed to expose the surface of the diffusion prevention layer 13b (FIG. 7E), and 30 nm of titanium and 100 nm of Au are sputtered on the exposed surface of the diffusion prevention layer 13b. To form a nozzle plate as shown in FIG. The nozzle plate thus prepared and the individual liquid chamber substrate were aligned, and Au-Au bonding was performed in vacuum under the conditions of a temperature of 300 ° C. and a pressure of 2 Mpa to produce a flow path substrate. Next, a thin film piezoelectric actuator was produced. FIG. 8 is a diagram for explaining a manufacturing process of the thin film piezoelectric actuator. For simplification, the portion below the thin film diaphragm 3 in FIG. 1 is omitted. As shown in FIG. 8A, titanium 30 nm and Pt 300 nm were sequentially formed on the insulating film 4 on the thin film diaphragm 3 by the sputtering method to form the lower electrode 5. Next, lead zirconate (PZT) was formed by sputtering to a thickness of 3 μm, and heat treatment was performed at 700 ° C. in an oxygen atmosphere to form a thin film piezoelectric body 6. Further, titanium 30 nm and Pt 300 nm were formed on the thin film piezoelectric body 6 by the sputtering method to form the upper electrode 7. After the upper electrode 7 is formed, an upper electrode etching mask 18 is formed as shown in FIG. The upper electrode 7 is formed by dry etching of Pt and titanium using the etching mask 18. (FIG. 8C) Next, the etching mask 18 is removed as shown in FIG. 8D, and an etching mask 19 for PZT is formed as shown in FIG. 8E. Using this etching mask 19, PZT is etched (FIG. 8F). Finally, the etching mask 19 is removed to complete the thin film piezoelectric actuator 8 (FIG. 8G). The thin film piezoelectric inkjet head manufactured in this example passes through 700 ° C of the thermal process of the thin film piezoelectric after joining the individual liquid chamber substrate and the nozzle plate, but no deterioration is seen at the joint. Stable ejection characteristics were obtained. Further, the bonding layer 12 may be formed subsequently to the diffusion preventing layer 13, and a silicon etching mask may be formed thereon to proceed to the subsequent process. In this case, it is necessary to pay sufficient attention to the material and thickness of the silicon etching mask and the removal method so that the surface of the bonding layer is not damaged by the manufacturing process.

  Next, a thin film piezoelectric ink jet head which is another embodiment is shown in FIG. The same numbers as those in FIG. 1 have already been described with reference to FIG. By forming the flow path such as the individual liquid chamber 9, the communication path 10, and the nozzle 11 and then thermally oxidizing the entire substrate, a diffusion barrier layer 13 is formed and a thermal oxide film 14 is also formed in the flow path. . Since the thermal oxide film formed in the flow path is chemically stable to alkaline ink, it is possible to use alkaline ink that attacks silicon. Next, a manufacturing method of the individual liquid chamber substrate portion of the thin film piezoelectric inkjet head shown in FIG. 2 will be described. As shown in FIG. 6A, a silicon substrate 2 having a thin film diaphragm 3 is prepared. Here, the thin film diaphragm uses a single crystal silicon having a thickness of 5 μm, and an SOI substrate having a thickness of 200 μm of the single crystal silicon substrate 2, and between the thin film diaphragm 3, which is a silicon single crystal, and the single crystal silicon substrate 2. Is provided with a 1 μm thick silicon thermal oxide film (not shown). Here, as the substrate to be used, a substrate having a sufficiently smooth surface (preferably having a surface roughness Ra of 1 nm or less) is used as the surface to be bonded (the lower surface in the figure). A carefully polished silicon substrate surface can usually be used without problems. An etching mask 15 for forming an individual liquid chamber is formed on the surface of the SOI substrate opposite to the surface on which the actuator is formed by photolithography. As the material of the etching mask 15, it is sufficient that the etching rate is sufficiently slower than the etching rate of silicon. In this example, a positive photoresist mainly composed of 6 μm thick novolak resin was used. A silicon thermal oxide film, a silicon oxide film formed by another method, aluminum, or the like can also be used as an etching mask. Next, as shown in FIG. 6B, the silicon substrate 2 is etched to form individual liquid chambers 9. After the formation of the individual liquid chamber 9, thermal oxidation is performed to form the insulating film 4, the diffusion prevention layer 13a, and the thermal oxide film 14a in the flow path at the same time. At this time, thermal oxidation was performed so that the thickness of the diffusion preventing layer 13a was 0.5 μm (FIG. 6C). In this embodiment, since the photoresist is used as the etching mask for forming the individual liquid chamber, the etching is performed after the etching mask is completely removed before the thermal oxidation treatment. However, when a silicon thermal oxide film is formed and used as an etching mask in advance, only a part of the surface may be removed, or all may be removed in the sense of removing dust generated in the process. . From the viewpoint of dust removal, a thermal oxide film is formed in advance, a pressure chamber forming etching mask is formed thereon with a photoresist or the like, and after etching the pressure chamber, the etching mask and the thermal oxide film are formed. It is preferable to remove all of them. Finally, as shown in FIG. 6 (D), titanium 30 nm and Au 100 nm were formed as a bonding layer by sputtering. Similarly, the nozzle plate was also thermally oxidized after forming the communication path 10 and the nozzle 11 by etching to form the diffusion prevention layer 13b and the thermal oxide film 14b in the flow path at the same time. Thereafter, 30 nm of titanium and 100 nm of Au were sequentially formed as the bonding layer 12 on the diffusion preventing layer 13b by a sputtering method. The nozzle plate thus prepared and the individual liquid chamber substrate were aligned, and Au-Au bonding was performed in vacuum under the conditions of a temperature of 300 ° C. and a pressure of 2 Mpa to produce a flow path substrate. The thin film piezoelectric actuator was produced in the same manner as in the example.

  In this example, the SOI substrate shown in FIG. 9 was used. An ink jet head element is formed using this substrate. Hereinafter, a specific forming method will be described in order.

  As shown in FIG. 10A, a silicon substrate 2 having a thin film diaphragm 3 is prepared. Here, the thin film diaphragm uses a single crystal silicon having a thickness of 5 μm, and an SOI substrate having a thickness of 200 μm of the single crystal silicon substrate 2, and between the thin film diaphragm 3, which is a silicon single crystal, and the single crystal silicon substrate 2. Is provided with a silicon thermal oxide film having a thickness of 1 μm (FIG. 10 (A) 4). An etching mask 15 for forming an individual liquid chamber is formed on the surface of the SOI substrate opposite to the surface on which the actuator is formed by photolithography. Photoresist OFPR (registered trademark) 800 (Tokyo Ohka Kogyo Co., Ltd.) was used as an etching mask material, and was applied by spin coating so as to have a film thickness of 4.5 μm. Thereafter, drying, exposure and development were performed to obtain an etching mask pattern. CDS630 (Canon Marketing Japan product) was used for resist application, drying and development, and proximity UX3000 (USHIO Inc. product) was used for exposure. Then, the insulating layer was dry etched using this resist mask. The insulating layer was a thermal oxide film, and dry etching was performed using Rainbow 4500 (product of Ram Research). Thereafter, a dry etching process using a Bosch process was performed to form an individual liquid chamber as shown in FIG. Using AMS2000 (Alcatel product), dry etching was performed to a depth of 200 μm over about 30 minutes. Etching is controlled by time management, but the thermal oxide film located under the thin film diaphragm plays a role as a substantial etching stop layer.

  Thereafter, the etching mask made of photoresist was dry peeled off. For the peeling, MAS8220 (Canon Marketing Japan product) was used as in the previous time, and the treatment was performed at 250 ° C. for 60 seconds. Then, a thermal oxide film is provided by heat-treating Si exposed by the etching process (FIG. 10C). For the formation of the thermal oxide film, VF5100 (manufactured by Koyo Thermo System Co., Ltd.) was used, and heat treatment was performed at 700 ° C. for 2 hours under O 2 gas. A thermal oxide film of 0.2 μm could be provided on the Si surface etched by this heat treatment. This thermal oxide film makes it possible to use ink that cannot be used in the channel where Si is exposed.

  Next, a process for forming a thin film piezoelectric actuator will be described. A piezoelectric film is formed on the upper surface side of the substrate finished up to the formation of the thermal oxide film shown in FIG. Hereinafter, a description will be given with reference to FIG.

  In FIG. 8, for simplification, the description below the diaphragm (individual liquid chamber side) is omitted.

  FIG. 8 is a diagram for explaining a manufacturing process of the thin film piezoelectric actuator. As shown in FIG. 8A, titanium 30 nm and Pt 300 nm were successively formed on the insulating film 4 on the thin film diaphragm 3 by the sputtering method to form the lower electrode 5. The thin film diaphragm is a part of the SOI substrate and is the same as that shown in FIG. 9-3. The insulating film 4 is a thermal oxide film of the SOI substrate and has a film thickness of 1 μm. Titanium of the lower electrode film was used as an adhesion layer with the thermal oxide film. Sputtering equipment! Using a mirror (product of Shibaura Mechatronics), film formation was performed by DC discharge. Next, lead zirconate titanate (PZT) was formed to a thickness of 3 μm by sputtering, and heat treatment was performed at 700 ° C. in an oxygen atmosphere to form a thin film piezoelectric body 6. MPS6000 (ULVAC product) was used for the film formation of PZT. Further, titanium 30 nm and Pt 300 nm were formed on the thin film piezoelectric body 6 by a sputtering method to form the upper electrode 7. Similar to the lower electrode, titanium was used as the adhesion layer for the upper electrode. After the upper electrode 7 is formed, an upper electrode etching mask 18 is formed as shown in FIG. As the etching mask, a desired etching mask pattern was obtained by spin coating a photoresist (OFPR (registered trademark) 800 Tokyo Ohka Kogyo Co., Ltd.) with a thickness of 2 μm, followed by drying, exposure and development. Using this etching mask 18, dry etching of Pt and titanium was performed to form the upper electrode 7. (FIG. 8C) NE550 (ULVAC product) was used as the dry etching apparatus. Then, the etching mask 18 was removed as shown in FIG. The etching mask is removed using a dry etching method, and the apparatus used is MAS8220 (Canon Marketing Japan product). Next, an etching mask 19 for PZT is formed as shown in FIG. A photoresist was used for this etching mask as in the case of the upper electrode. A photoresist (OFPR (registered trademark) 800 Tokyo Ohka Kogyo Co., Ltd.) was spin-coated to a thickness of 4.5 μm, dried, exposed and developed to obtain a desired etching mask pattern. Using this etching mask 19, PZT is etched (FIG. 8F). Etching of PZT was performed by a dry etching method similar to the upper electrode, and NE550 (ULVAC product) was also used as the apparatus. By controlling the etching amount to the PZT film thickness by this etching, the lower electrode becomes a piezoelectric element unit having a solid film. It is also possible to form the lower electrode pattern by etching the lower electrode film simultaneously with the etching of PZT. In this case, the thermal oxide film under the lower electrode also serves as an etching stop layer. Finally, the etching mask 19 is removed to complete the thin film piezoelectric actuator 8 (FIG. 8G). This etching mask was removed by the dry etching method as described above, and the apparatus used was MAS8220 (Canon Marketing Japan product). Thus, the thin film piezoelectric actuator provided on the upper side of the SOI substrate shown in FIG. 9 was formed.

  Next, the formation of the nozzle plate will be described. As shown in FIG. 7A, thermally oxidized silicon having a thickness of 1 μm is formed as a diffusion prevention layer 13b on a single crystal silicon substrate 1 having a thickness of 200 μm. For the formation of the oxide film, a thermal oxidation furnace VF5100 (product of Koyo Thermo System Co., Ltd.) was used, and the treatment was performed at 1000 ° C. for 4 hours. Thereafter, the thermal oxide film was removed on one side by dry etching. Rainbow 4500 (a product of Rams Research) was used to remove the film. Next, as shown in FIG. 7B, an etching mask 16 for the communication path 10 between the individual liquid chamber and the nozzle and an etching mask 17 for the nozzle 11 are formed on both surfaces of the substrate. Photoresist OFPR (registered trademark) 800 (Tokyo Ohka Kogyo Co., Ltd.) was used as an etching mask, and coating and development were performed with CDS630 (Canon Marketing Japan). The resist film thickness was 4.5 μm, and a desired pattern was printed using UX3000 (USHIO INC.).

  Next, the diffusion prevention layer 13b is etched using the etching mask 16 formed as shown in FIG. Etching was dry etching using a fluorine-based gas, and Rainbow 4500 (a product of Rams Research) was used. Next, as shown in FIG. 7D, silicon is etched from both sides using the etching mask 16 and the etching mask 17 to form the communication path 10 and the nozzle 11 between the individual liquid chamber and the nozzle. In this embodiment, the depth of the communication path 10 is 150 μm, and the depth of the nozzle 11 is 50 μm. For etching, an inductively coupled plasma (ICP) etching apparatus (AMS200 Alcatel product) that generates high-density plasma was used, and etching was performed by a Bosch process using fluorine-based gas and fluorocarbon-based gas alternately. After the silicon etching, the etching masks 16 and 17 were removed. For the etching mask peeling treatment, wet peeling was performed using a peeling solution 106 (Tokyo Ohka Kogyo Co., Ltd.). Then, in order to form a thermal oxide film in the nozzle, heat treatment was performed using VF5100 (product of Koyo Thermo System Co., Ltd.). A thin thermal oxide film of 0.2 μm was obtained by treatment at 700 ° C. for 2 hours (not shown in the figure). Then, 30 nm of titanium and 100 nm of Au were formed by sputtering on the surface of the exposed diffusion prevention layer 13b (FIG. 7E), and a nozzle plate shown in FIG. 7F was manufactured. Shibaura Mechatronics products for the deposition of titanium and Au! I used a mirror.

Next, using the substrate formed up to FIG. 10C, a photoresist is applied as shown in FIG. 10D. The resist used was OFPR (registered trademark) 800 (Tokyo Ohka Kogyo Co., Ltd.), CDS630 (Canon Marketing Japan) was used for coating and development, and UX3000 (Ushio Electric product) was used for exposure. Since this process is a resist coating for lift-off, the coating was thick to a thickness of 6 μm. Thereafter, as shown in FIG. 10E, a desired pattern was obtained by exposure and development processing. Then, titanium 30 nm and Au 100 nm were continuously formed by sputtering (FIG. 10F). Shibaura Mechatronics Co., Ltd. also forms this film! A mirror was used. Then, the substrate was immersed in acetone to remove the resist. FIG. 10 (G). This removal of the resist also removes the titanium and Au films on the resist at the same time, leaving the titanium and Au films only in the regions necessary for bonding. The bonding area is designed to surround the individual liquid chamber and the common liquid chamber, and in order to effectively use the pressure during bonding, the bonding area is minimized. (Fig. 11)
The nozzle plate (FIG. 7 (F)) prepared as described above and the individual liquid chamber substrate (FIG. 10 (G) + FIG. 8 (G)) are aligned, and the temperature is 300 ° C. and the pressure is 2 MPa in vacuum. Au-Au bonding was performed under a pressure time of 60 min to obtain an ink jet head. A sectional view of the obtained inkjet head is shown in FIG. A bond aligner (BA6 SUSS Microtech Co., Ltd. product) was used for alignment during bonding, and a wafer bonding apparatus (SB6 SUSS Microtech Co., Ltd. product) was used for bonding.

  The ink jet head thus obtained was free from bonding failure and excellent in durability.

1 is a schematic diagram of an inkjet head according to the present invention. FIG. 6 is a schematic diagram showing another example of an ink jet head according to the present invention. The ultrasonic microscope image which shows generation | occurrence | production of the unjoined part by heat processing. The ultrasonic microscope image which shows the junction part after the heat processing in this invention. The manufacturing process figure of the separate liquid chamber board | substrate by this invention. FIG. 6 is another manufacturing process diagram of the individual liquid chamber substrate according to the present invention. The manufacturing process figure of the nozzle plate by this invention. Manufacturing process drawing of a thin film piezoelectric actuator. Sectional drawing of an SOI substrate. The manufacturing process figure of the separate liquid chamber board | substrate accompanying a heat processing process. The figure which shows a joining area | region. The table | surface which shows the relationship between the film thickness of Au, and surface roughness.

Explanation of symbols

1 Silicon substrate
2 Silicon substrate
3 Thin film diaphragm
4 Insulating layer
5 Lower electrode
6 Thin film piezoelectric
7 Upper electrode
8 Thin film piezoelectric actuator
9 Individual liquid chamber
10 communication path
11 nozzles
12 Bonding layer
13 Diffusion prevention layer
14 Thermal oxide film in channel
15 Etching mask for forming individual liquid chamber
16 Etching mask for communication path formation
17 Nozzle forming etching mask
18 Etching mask for upper electrode formation
19 Etching mask for forming thin film piezoelectric part

Claims (9)

  In a silicon substrate in which an ink flow path is formed on a silicon substrate, and an inkjet head in which the substrate and another member are bonded via Au, at least a bonding Au provided in a bonding portion; An ink-jet head characterized in that a member for preventing diffusion of silicon and Au is provided between the silicon member.   2. The ink jet head according to claim 1, wherein the inside of the flow path formed in the silicon member is covered with a member made of the same material as the member for preventing diffusion of silicon and Au. Inkjet head.   2. The ink jet head according to claim 1, wherein the joining portion has a step with respect to the non-joining portion and has a convex shape.   3. The inkjet head according to claim 1, wherein a member made of the same material as the member for preventing diffusion of silicon and Au provided in a flow path formed in the silicon member is formed in the joint portion. An inkjet head characterized in that it is formed thinner than a member for preventing diffusion of Au and silicon provided between a bonding Au and a silicon member provided.   5. The ink jet head according to claim 1, wherein the bonding Au is formed so as to surround the flow path.   6. The ink jet head according to claim 1, wherein the member provided for preventing diffusion of Au and silicon is a thermal oxide film of silicon.   In a manufacturing method of an ink jet head, which includes a substrate in which a flow path is formed on a silicon substrate, and the silicon substrate on which the flow path is formed and another member are bonded via Au, the flow path to the silicon substrate Forming a flow path in the silicon substrate, providing a member for preventing diffusion of Au and silicon on the substrate, and preventing diffusion of Au and silicon on the silicon substrate. And a step of forming Au for bonding after the step of providing the member.   In a method of manufacturing an ink jet head, which includes a substrate having a flow path formed on a silicon substrate, and the silicon substrate on which the flow path is formed and another member are bonded via Au. A step of providing a member for preventing diffusion with silicon, a step of providing a member for preventing diffusion of Au and silicon on the silicon substrate, a step of forming a flow path in the silicon substrate, Forming a bonding Au after forming the path, and a method of manufacturing an ink jet head.   In a method of manufacturing an ink jet head, which includes a substrate having a flow path formed on a silicon substrate, and the silicon substrate on which the flow path is formed and another member are bonded via Au. Including a step of providing a member for preventing diffusion with silicon, a step of providing Au for bonding, and a step of forming a channel in the silicon substrate after the Au for bonding is provided. A method for manufacturing an inkjet head.

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