JP2012126070A - Silicon nozzle substrate and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a silicon nozzle substrate preventing the occurrence of cavities due to corrosion, even if deficiencies are caused in an edge.SOLUTION: The silicon nozzle substrate 1 includes: a nozzle hole 21 that penetrates a silicon substrate 44; a first liquid droplet protective film 41 consisting of a thermal silicon oxide that is formed by heating the surface of the silicon substrate 44 for covering an inner wall surface 14 of the nozzle hole 21; and a second liquid droplet protective film 42 formed on the liquid droplet protective film 41 in the inner wall surface 14 and a discharging surface 15 that is a surface at the side of discharging a liquid droplet. In the silicon nozzle substrate 1, the thickness of the first liquid droplet protective film 41 is equal to or more than that of the second liquid droplet protective film 42 in the inner wall surface 14.

Description

  The present invention relates to a silicon nozzle substrate having nozzle holes for discharging droplets and a method for manufacturing the same.

  In recent years, a droplet discharge device has attracted attention as a device for forming an image or the like by discharging droplets of ink (liquid material) onto a medium. In general, a droplet discharge device forms an image or the like by discharging droplets from nozzles while relatively moving a droplet discharge head including a plurality of nozzles and a medium. The droplet discharge head generally includes a nozzle substrate in which a plurality of nozzle holes for discharging droplets are formed, a pressure chamber bonded to the nozzle substrate and communicating with the nozzle hole, a reservoir And a cavity substrate having an ink flow path formed thereon. And it is comprised so that a droplet may be discharged from the selected nozzle hole by applying a pressure to a pressure chamber with a drive part.

In such a droplet discharge head, particularly a droplet discharge head using a silicon nozzle substrate formed by processing a silicon substrate on a nozzle substrate, generally the surface on the side where the nozzle holes of the silicon nozzle substrate are formed A droplet protective film made of silicon oxide (SiO ₂ ) is formed on the surface (hereinafter referred to as “ejection surface”) (see, for example, Patent Document 1). The reason is to protect the ejection surface from ink droplets when droplets are ejected. This is because the ink is generally alkaline and can erode (etch) the silicon material if it stays on the ejection surface.

  Such a droplet protective film is generally formed by a vapor deposition method. The reason is in the method of forming the silicon nozzle substrate. Generally, in a silicon nozzle substrate, a recess (hole) is formed on the silicon substrate as a base material from the bonding surface side that is the surface opposite to the discharge surface, and then the silicon substrate is formed to a thickness of several tens of μm from the discharge surface side. It is formed through a process of thinning it into a nozzle hole penetrating the above-mentioned recess into the silicon substrate. Since such a thinned silicon substrate may be deformed such as warpage when heated, it is difficult to form a thermally oxidized silicon film on the surface. Therefore, the above-described droplet protective film is formed by a vapor phase growth method (particularly, a plasma polymerization method) that can be formed at a relatively low temperature.

JP 2006-159661 A

  However, the droplet protective film formed by the above-described vapor phase growth method has a problem that defects (chips) are likely to occur. Such defects can expose the silicon substrate and cause erosion, which can degrade the ejection quality and reliability of the droplet ejection head. FIGS. 11A to 11C show the drop of the droplet protective film in the conventional droplet discharge head and its influence. FIG. 11 is an enlarged cross-sectional view showing an enlarged edge portion of a nozzle hole (not shown in the figure). In this figure, the water-repellent film 43 (see FIG. 3 and the like described later) and the hydrophilic film 45 (see FIG. 3 and the like described later) are not shown. In addition, each element to which a reference numeral is given in the figure will be described in the embodiments described later.

FIG. 11A shows a state in which a plasma polymerization film 42 as a second droplet protective film is formed (deposited) on the ejection surface 15 and the inner wall surface 14 of the nozzle hole. The plasma polymerization film 42 is a film corresponding to the above-described droplet protective film, and is a film made of a silicon compound formed by a plasma polymerization method. On the inner wall surface 14, a thermal silicon oxide film 41 as a first droplet protective film is also formed below the plasma polymerization film 42. The film thickness is approximately 0.1 μm. As described above, since the ejection surface 15 has undergone a grinding process, the thermal silicon oxide film 41 is removed, and the plasma polymerization film 42 is formed directly on the single crystal silicon substrate 44.
The film thickness of the plasma polymerized film 42 is approximately 1.3 μm on the discharge surface 15 and approximately 0.5 μm on the inner wall surface 14. Since the nozzle hole is a hole having a fine diameter, silicon particles (that is, the precursor) are less likely to enter the discharge surface 15 that is an open surface during film formation by the plasma polymerization method. Therefore, it is formed so that the ratio of the film thickness on the ejection surface 15 to the film thickness on the inner wall surface 14 is approximately 2.5 to 1.

  FIG. 11B is a diagram illustrating a state in which the defect 11 is generated at the edge portion of the nozzle hole and the exposed portion 17 is generated due to the defect. FIG. 11C is a diagram showing a state in which a part of the single crystal silicon substrate 44 has been eroded by the ink that has entered from the exposed portion 17. Since the film formed by the vapor deposition method has lower adhesion to the single crystal silicon substrate 44 than the thermally oxidized silicon film 41, a defect 11 as shown may occur when an impact is applied.

  The defect 11 is likely to occur so that the ratio of the dimension (a and illustration) perpendicular to the inner wall surface 14 to the dimension (b and illustration) perpendicular to the discharge surface 15 is approximately 1: 1. . In the following description, the dimension perpendicular to the inner wall surface 14 indicated by “a” is the dimension of the defect 11. As described above, the ratio of the film thickness on the discharge surface 15 side and the film thickness on the inner wall surface 14 side of the plasma polymerization film 42 is approximately 2.5 to 1. Therefore, when a defect 11 having a dimension close to the film thickness on the discharge surface 15 side of the plasma polymerization film 42 occurs, the exposed portion 17 is formed on the discharge surface 15 side of the single crystal silicon substrate 44. If the ejection of ink droplets is repeated in such a state, there is a problem that the ink enters from the exposed portion 17 to generate the cavity portion 18 in the single crystal silicon substrate 44. Such a cavity 18 reduces the discharge quality and reliability of a droplet discharge head using the silicon nozzle substrate.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A silicon nozzle substrate according to this application example includes a nozzle hole penetrating the silicon substrate and a thermally oxidized silicon formed by heating the surface of the silicon substrate covering the inner wall surface of the nozzle hole. And a second droplet protective film formed on the first droplet protective film on the inner wall surface and on a discharge surface which is a surface on the droplet discharge side. In the nozzle substrate, the thickness of the first droplet protective film is one or more times that of the second droplet protective film on the inner wall surface.

  According to the experimental results (described later), the size of the defect of the second droplet protective film generated at the edge portion of the nozzle hole is almost twice the thickness of the second droplet protective film on the inner wall surface. Fits within. Therefore, with such a configuration, it is possible to reduce a phenomenon in which the silicon substrate is exposed when a defect occurs in the second droplet protective film at the edge portion (on the ejection surface side) of the nozzle hole. Therefore, the reliability of the silicon nozzle substrate and the droplet discharge head including the silicon nozzle substrate can be improved.

  Application Example 2 In the silicon nozzle substrate described above, the film thickness of the first droplet protective film is 1 to 2 times the film thickness of the second droplet protective film on the inner wall surface. A silicon nozzle substrate characterized by that.

  According to experimental results (described later), the size of the above-mentioned defect hardly exceeds twice the thickness of the second droplet protective film on the inner wall surface. Therefore, the sum of the thickness of the second droplet protective film on the inner wall surface and the thickness of the first droplet protective film on the inner wall surface is the sum of the thickness of the second droplet protective film on the inner wall surface. If it is the structure which becomes 2 times-3 times, the phenomenon in which the above-mentioned silicon substrate is exposed can be reduced further.

  Application Example 3 In the above-described silicon nozzle substrate, the thickness of the second droplet protective film on the ejection surface is 2.5 times the thickness of the second droplet protective film on the inner wall surface. A silicon nozzle substrate characterized by being at least twice as large.

  In the above-mentioned defect, the dimension in the direction perpendicular to the substrate surface of the silicon substrate and the dimension in the horizontal direction are often close to each other at the edge portion of the nozzle hole. Therefore, with such a configuration, the above-described phenomenon that the silicon substrate is exposed can be further reduced.

  Application Example 4 The silicon nozzle substrate according to the above-described silicon nozzle substrate, wherein the thickness of the second droplet protective film on the inner wall surface is 0.5 μm or more.

  According to the experimental results, the size of the defect described above rarely exceeds 1.0 μm. Accordingly, with such a configuration, a protective film of 1.0 μm or more can be formed on the inner wall surface of the nozzle hole together with the first droplet protective film formed with a thickness of at least 0.5 μm or more, and the edge portion The phenomenon in which the silicon substrate is exposed due to defects occurring in the substrate can be further reduced.

  Application Example 5 A method for manufacturing a silicon nozzle substrate according to this application example includes a first step of forming a recess on a first surface of a silicon substrate, and heating the silicon substrate to at least an inner wall surface of the recess. A second step of forming a thermally oxidized silicon film as a first droplet protective film, and the second surface of the silicon substrate from the second surface side opposite to the first surface; Is thinned until reaching the recess, and a second droplet protective film is formed on the second surface and the inner wall surface in a third step in which the recess becomes a nozzle hole penetrating the silicon substrate. A silicon nozzle substrate having a fourth step, wherein the second step has a thickness of the second droplet protective film formed on the inner wall surface in the fourth step. It is a step of forming the thermal silicon oxide film having a film thickness of 1 or more times And features.

  With such a manufacturing method, it is possible to form a silicon nozzle substrate with a low possibility of exposing the silicon substrate even when a defect occurs in the second droplet protective film. Therefore, a silicon nozzle substrate with improved reliability and a droplet discharge head including the silicon nozzle substrate can be obtained.

  Application Example 6 In the method for manufacturing the silicon nozzle substrate described above, the second step is 1 in thickness of the second droplet protective film formed on the inner wall surface in the fourth step. A method for producing a silicon nozzle substrate, which is a step of forming the thermally oxidized silicon film having a film thickness of 2 to 2 times.

  With such a manufacturing method, it is possible to form a silicon nozzle substrate that is even less likely to expose the silicon substrate even when a defect occurs in the second droplet protective film. Therefore, it is possible to obtain a silicon nozzle substrate with further improved reliability and a droplet discharge head including the silicon nozzle substrate.

  Application Example 7 In the above silicon nozzle substrate manufacturing method, the fourth step is a step of forming the second droplet protective film using a plasma polymerization method. A method for manufacturing a nozzle substrate.

  With such a manufacturing method, the second droplet protective film having a dense structure can be formed at a suitable film thickness ratio between the second surface and the inner wall surface. Therefore, it is possible to form a silicon nozzle substrate in which the possibility of exposing the silicon substrate is further reduced even when a defect occurs in the second droplet protective film.

  Application Example 8 In the above silicon nozzle substrate manufacturing method, the fourth step is a step of forming the second droplet protective film having a thickness of 0.5 μm or more on the inner wall surface. A method of manufacturing a silicon nozzle substrate.

  According to the plasma polymerization method, the second droplet protective film can be formed on the second surface with a film thickness approximately 2.5 times or more that of the second droplet protective film on the inner wall surface. Therefore, according to such a manufacturing method, the second droplet protective film having a sufficient thickness can be formed on the second surface, and the silicon nozzle substrate having further improved reliability and the droplet including the silicon nozzle substrate. A discharge head can be obtained.

FIG. 3 is a perspective development view of a droplet discharge head including the silicon nozzle substrate according to the first embodiment as a constituent element. FIG. 3 is a longitudinal sectional view of a main part of a droplet discharge head including a silicon nozzle substrate according to the first embodiment as a constituent element. The expanded sectional view of the edge part of the silicon nozzle substrate of a 1st embodiment. The expanded sectional view of the edge part of the silicon nozzle substrate of 2nd Embodiment. The figure which shows distribution of the dimension of a defect | deletion. Process sectional drawing which shows the manufacturing method of the silicon nozzle substrate concerning 3rd Embodiment. Process sectional drawing which shows the manufacturing method of the silicon nozzle substrate concerning 3rd Embodiment. Process sectional drawing which shows the manufacturing method of the silicon nozzle substrate concerning 3rd Embodiment. Process sectional drawing which shows the manufacturing method of the silicon nozzle substrate concerning 3rd Embodiment. Process sectional drawing which shows the manufacturing method of the silicon nozzle substrate concerning 3rd Embodiment. The figure which shows the defect | deletion of the droplet protective film in the conventional droplet discharge head, and its influence.

  Hereinafter, a silicon nozzle substrate and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to the drawings. As described above, since the silicon nozzle substrate is an element constituting a droplet discharge head (inkjet head) as shown in FIG. 1 described later, the configuration including the configuration of the droplet discharge head will be described. The present invention is not limited to the structure and shape shown in the following figures. In each of the following drawings, the scale of each layer and each part is different from the actual scale so that each layer and each part can be recognized in the drawing. Unless otherwise specified, the following description will be made with the upper side of the figure as the upper side and the lower side as the lower side.

(First embodiment)
FIG. 1 is an exploded perspective view of a droplet discharge head 8 including the silicon nozzle substrate 1 according to the first embodiment of the present invention as a constituent element. FIG. 2 is a longitudinal sectional view of a main part of the droplet discharge head 8. As shown in FIG. 1, the droplet discharge head 8 includes nozzle holes 21 formed in the discharge surface 15 so as to be arranged in two rows in the longitudinal direction. FIG. 2 is a cross-sectional view taken along a line perpendicular to the longitudinal direction, and is a cross-sectional view showing a schematic configuration of the right half of FIG.

  As shown in FIG. 1, the droplet discharge head 8 according to the present embodiment includes a silicon nozzle substrate 1, a cavity substrate 3 in which an ink flow path is provided independently for each nozzle hole 21, and a cavity substrate 3. The electrode substrate 4 on which the individual electrode 31 corresponding to the diaphragm 22 is formed is bonded.

  The silicon nozzle substrate 1 is a plate-like member formed by subjecting a single crystal silicon substrate 44 to predetermined processing, and nozzle holes 21 for ejecting ink droplets are formed in two rows at a predetermined pitch. . The nozzle hole 21 is a hole that penetrates the single crystal silicon substrate 44, and includes a first nozzle hole 21a that discharges droplets and a second nozzle hole 21b that introduces droplets. The first nozzle hole 21a opens to the discharge surface 15 side, and the second nozzle hole 21b opens to the bonding surface 16 side. The constituent material of the silicon nozzle substrate 1 is not limited to a single crystal silicon substrate, and a polycrystalline silicon (polysilicon) substrate can also be used.

  Of the two front and back surfaces of the silicon nozzle substrate 1, the surface facing the outside of the droplet discharge head 8, that is, the surface on the droplet discharge side is the discharge surface 15. On the other hand, the surface to be bonded to the cavity substrate 3 is the bonding surface 16. The surface in the thickness direction of the silicon nozzle substrate 1, that is, the surface orthogonal to the two front and back surfaces is the end surface 13. A surface generated by forming the nozzle hole 21 through the single crystal silicon substrate 44, that is, the hole surface of the nozzle hole 21 is the inner wall surface 14.

  The four types of surfaces described above include a silicon oxide film 41 as a first droplet protective film and a silicon oxide surface as a second droplet protective film in order to protect the single crystal silicon substrate 44 from ink. At least one of the plasma polymerized film 42 having a layer is formed. In general, ink is alkaline and may erode (etch) the single crystal silicon substrate 44. The two-layer films (41, 42) described above are thin films having at least a surface made of silicon oxide, and can protect the single crystal silicon substrate 44 from ink erosion.

  As shown in FIG. 2, a thermal silicon oxide film 41 is formed on three surfaces of the silicon nozzle substrate 1 excluding the discharge surface 15. A plasma polymerization film 42 is formed on three surfaces excluding the adhesive surface 16. As described above, the thermally oxidized silicon film 41 is a film formed by thermally oxidizing the surface of the single crystal silicon substrate 44. The plasma polymerized film 42 is a film made of silicon oxide formed on the above-described three surfaces by the plasma polymerization method after finishing the process of forming the thermal silicon oxide film 41 and the process of thinning the single crystal silicon substrate 44. The present invention relates to the film thickness of the thermally oxidized silicon film 41 and the plasma polymerized film 42 and the ratio (ratio) thereof.

  Note that a film formed by the plasma polymerization method tends to be thin in a fine region. As will be described later, since the plasma polymerized film 42 is formed by mounting a support substrate 51 (see FIG. 8 described later) on the adhesive surface 16 side, the inner wall surface 14 is formed thinner than the discharge surface 15. Also on the inner wall surface 14, the plasma polymerization film 42 is formed thick in the vicinity of the ejection surface 15, and has a tendency to become thinner as it approaches the bonding surface 16 side. Accordingly, there may be a slight difference between the film thickness of the plasma polymerization film 42 on the inner wall surface 14 of the first nozzle hole 21a and the film thickness of the plasma polymerization film 42 on the inner wall surface 14 of the second nozzle hole 21b. In the present specification, the film thickness of the plasma polymerization film 42 on the inner wall surface 14 is defined as the film thickness on the inner wall surface 14 of the first nozzle hole 21 a in the inner wall surface 14. When simply described as “inner wall surface 14”, the inner wall surface 14 of the first nozzle hole 21 a is indicated.

  The cavity substrate 3 is also made of a single crystal silicon substrate like the silicon nozzle substrate 1 and is bonded to the bonding surface 16 side of the silicon nozzle substrate 1. In the cavity substrate 3, ink flow paths communicating with the nozzle holes 21 of the silicon nozzle substrate 1 are formed by anisotropic wet etching. The ink flow path includes a discharge recess 250 serving as the discharge chamber 25 with the bottom wall serving as the diaphragm 22, a reservoir recess 230 serving as the reservoir 23 serving as a common ink chamber, and an orifice communicating the reservoir recess 230 and each discharge recess 250. 24 and an orifice recess 240. The reservoir 23 constitutes a common ink chamber in each discharge chamber 25 and communicates with each discharge chamber 25 via an orifice 24.

  An insulating film 29 made of silicon oxide, which is an insulating material, is formed on the entire surface of the cavity substrate 3 or at least a region facing the electrode substrate 4. The insulating film 29 functions to prevent dielectric breakdown and occurrence of short circuit when the droplet discharge head 8 is driven.

  The electrode substrate 4 is made of a glass base material, and concave portions 310 are formed at positions facing the respective vibration plates 22 of the cavity substrate 3. In each recess 310, individual electrodes 31 made of ITO (Indium Tin Oxide) are formed by sputtering.

  The individual electrode 31 includes a lead portion 31a and a terminal portion 31b connected to a flexible wiring board (not shown). The terminal portion 31b has an end portion of the cavity substrate 3 opened for wiring. It is exposed in the electrode extraction part 36. And the terminal part 31b of each individual electrode 31 and the common electrode 27 on the cavity substrate 3 are connected via the drive circuit 5 such as an IC driver. The electrode substrate 4 is formed with an ink supply port 35 that communicates with the reservoir 23 for supplying ink. The ink supply port is connected to an ink tank (not shown). The open end portion of the gap 34 formed between the diaphragm 22 and the individual electrode 31 is sealed with a sealing material 33 made of resin such as epoxy so that moisture and dust do not enter inside.

  The electrode substrate 4 and the above-described cavity substrate 3 are anodically bonded so that the individual electrode 31 and the diaphragm 22 face each other with a predetermined (for example, 0.1 μm) gap 34 therebetween. Thus, an electrostatic actuator that can apply a required pressure to the discharge chamber 25 is configured by the individual electrode 31 facing the gap 34 and the diaphragm 22 having the insulating film 29.

  The droplet discharge head 8 discharges ink as droplets by the operation described below. First, when the drive circuit 5 is driven and charges are supplied to the individual electrodes 31 to charge them positively, the diaphragm 22 is charged negatively, and an electrostatic attractive force is generated between the individual electrodes 31 and the diaphragm 22. To do. Due to the electrostatic attractive force, the diaphragm 22 is attracted to the individual electrode 31 and bent. As a result, the volume of the discharge chamber 25 increases. When the supply of electric charges to the individual electrode 31 is stopped, the electrostatic attractive force disappears, and the diaphragm 22 returns to its original state due to its elastic force. At this time, the volume of the discharge chamber 25 decreases rapidly, and the pressure at that time causes Part of the ink in the ejection chamber 25 is ejected from the nozzle hole 21 toward the ejection surface 15 as ink droplets.

FIG. 3 is an enlarged cross-sectional view of the vicinity of the edge portion 19 (see FIG. 2) of the nozzle hole 21 in the silicon nozzle substrate 1 of the present embodiment, and shows a portion similar to the portion shown in FIG. .
FIG. 3A is a diagram showing a normal state, that is, a state where no defect 11 has occurred. The silicon nozzle substrate 1 of the present embodiment has a plasma polymerization film 42 as a second droplet protective film having a film thickness of 0.5 μm or more on the inner wall surface 14 and 1 to 2 times the film thickness of the plasma polymerization film. A thermal silicon oxide film 41 is formed as a first droplet protective film having a thickness of. On the discharge surface 15, a plasma polymerization film 42 having a thickness of 2.5 times or more the film thickness of the plasma polymerization film 42 on the inner wall surface 14 is formed.

  Specifically, the thickness of the thermally oxidized silicon film 41 is 0.8 μm. The film thickness of the plasma polymerized film 42 is approximately 1.3 μm on the discharge surface 15 and approximately 0.5 μm on the inner wall surface 14, as in the above-described conventional silicon nozzle substrate. Therefore, the silicon nozzle substrate 1 of the present embodiment has the thermally oxidized silicon film 41 having a thickness 1.6 times the film thickness of the plasma polymerization film 42 on the inner wall surface 14. On the discharge surface 15, the plasma polymerization film 42 having a thickness 2.6 times that of the plasma polymerization film 42 on the inner wall surface 14 is provided.

  A hydrophilic film 45 formed by oxidizing the plasma polymerized film 42 is formed on the plasma polymerized film 42 on the inner wall surface 14, and a water repellent film 43 is formed on the plasma polymerized film 42 on the discharge surface 15. ing. The hydrophilic film 45 improves the fluidity of the ink in the nozzle hole 21 to improve the ejection performance, and the water repellent film 43 suppresses the ejected ink droplets from staying on the ejection surface 15.

  FIG. 3B is a diagram showing a state in which a defect 11 having a dimension (a length indicated as “a”) of approximately 1.2 μm is generated. As described above, in the silicon nozzle substrate 1, the film thickness of the plasma polymerization film 42 on the inner wall surface 14 is 0.5 μm. Therefore, when the defect 11 having such a dimension occurs, an exposed portion 17 (see FIG. 11) is generated in the case of a conventional silicon nozzle substrate.

  However, the silicon nozzle substrate 1 of the present embodiment has the thermally oxidized silicon film 41 having a thickness of 0.8 μm on the inner wall surface 14. That is, on the inner wall surface 14, a droplet protective film having a total thickness of 1.3 μm is formed by combining (overlapping) the plasma polymerization film 42 and the thermal silicon oxide film 41. Therefore, even if a defect 11 having a dimension, that is, a length of 1.2 μm in a direction perpendicular to the inner wall surface 14 is generated, a droplet protective film (a laminated body of a thermally oxidized silicon film 41 and a plasma polymerized film 42) having a thickness larger than that. ) Can prevent the exposed portion 17 (see FIG. 11) from occurring. Therefore, the possibility of forming the exposed portion 17 and the cavity portion 18 (see FIG. 11) resulting from the exposed portion is reduced, and the discharge quality and reliability are improved.

  Here, the dimension of 1.2 μm is a sufficiently large value as an expected value of the dimension of the defect 11. FIG. 5 is a diagram showing a distribution of dimensions of the defect 11 (length indicated by “a” in FIG. 3). As shown in the figure, most of the dimensions of the defect 11 (approximately 94%) are within 1.1 μm. Therefore, like the silicon nozzle substrate 1 of the present embodiment, the silicon nozzle substrate that can prevent the exposed portion 17 from being generated even if the defect 11 having a dimension of 1.2 μm occurs is sufficiently reliable under normal use conditions. It has sex.

  In addition, the thermally oxidized silicon film 41 itself, which is thicker than the conventional example, included in the silicon nozzle substrate 1 of the present embodiment effectively suppresses the occurrence of the exposed portion 17. The thermal silicon oxide film 41 formed by oxidizing the surface of the single crystal silicon substrate 44 is superior in adhesion and the like as compared with a film separately laminated on the surface. Therefore, even when the irregularly shaped defect 11 is generated, the thermally oxidized silicon film 41 is rarely lost, and the exposure of the single crystal silicon substrate 44 under the thermally oxidized silicon film can be effectively suppressed.

  Furthermore, the silicon nozzle substrate 1 of the present embodiment is effective in generating the exposed portion 17 by making the thickness of the thermally oxidized silicon film 41 1.6 times the thickness of the plasma polymerization film 42 on the inner wall surface 14. Is suppressed. The film thickness of the plasma polymerized film 42 is greatly different between the discharge surface 15 and the inner wall surface 14. As described above, that is, it is difficult for silicon particles as a film forming material to enter the surface of the fine structure such as the inner wall surface 14. Therefore, the film thickness of the plasma polymerization film 42 is formed so that the ratio of the film thickness on the discharge surface 15 to the film thickness on the inner wall surface 14 is approximately 2.5 to 1.

  On the other hand, as described in paragraph (0009), the defect 11 has a ratio between a dimension (a and illustration) perpendicular to the inner wall surface 14 and a dimension (b and illustration) perpendicular to the discharge surface 15. It tends to occur so as to be approximately 1: 1. Therefore, it is preferable that the film thickness of the droplet protective film is substantially the same between the ejection surface 15 and the inner wall surface 14. For this purpose, the thickness of the thermally oxidized silicon film 41 needs to be 1 to 2 times the thickness of the plasma polymerized film 42 on the inner wall surface 14. In the silicon nozzle substrate 1 of this embodiment, the thickness of the thermally oxidized silicon film 41 is 1.6 times the thickness of the plasma polymerization film 42 on the inner wall surface 14. As a result, the occurrence of the exposed portion 17 due to the defect 11 is effectively suppressed, and the reliability is improved.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. FIG. 4 is an enlarged cross-sectional view of the vicinity of the edge portion 19 (see FIG. 2) of the nozzle hole 21 in the silicon nozzle substrate 2 of the second embodiment, and shows a portion similar to the portion shown in FIG. It is. Similar to the silicon nozzle substrate 1 according to the first embodiment described above, the silicon nozzle substrate 2 of the present embodiment is combined with the cavity substrate 3 and the electrode substrate 4 to form the droplet discharge head 8. . The configuration is similar to that of the silicon nozzle substrate 1, and the only difference is the film thickness of the droplet protective film. Therefore, the drawings corresponding to FIGS. 1 and 2 are omitted.

  FIG. 4A is a diagram showing a normal state, that is, a state where no defect 11 has occurred. The silicon nozzle substrate 2 of the present embodiment has a plasma polymerized film 42 having a film thickness of 0.5 μm or more on the inner wall surface 14 and a thermally oxidized silicon film 41 having a film thickness of 1 to 2 times the film thickness of the plasma polymerized film. Are common to the silicon nozzle substrate 1 of the first embodiment described above. In addition, the plasma polymerization film 42 having a film thickness of 2.5 times or more the film thickness of the plasma polymerization film 42 on the inner wall surface 14 is formed on the discharge surface 15. The silicon nozzle substrate 1 is common. However, each droplet protective film (41, 42) is formed thicker than the droplet protective film of the silicon nozzle substrate 1 of the first embodiment.

  Specifically, the thickness of the thermally oxidized silicon film 41 as the first droplet protective film is 1.2 μm. The film thickness of the plasma polymerization film 42 as the second droplet protective film is approximately 2.0 μm on the ejection surface 15 and approximately 0.8 μm on the inner wall surface 14. Therefore, the silicon nozzle substrate 2 of the present embodiment has the thermally oxidized silicon film 41 having a thickness 1.5 times the film thickness of the plasma polymerization film 42 on the inner wall surface 14. A plasma polymerization film 42 having a thickness 2.5 times as large as the plasma polymerization film 42 on the inner wall surface 14 is provided on the discharge surface 15. The mode of the water repellent film 43 and the hydrophilic film 45 is the same as that of the silicon nozzle substrate 1 described above.

  FIG. 4B is a view showing a state in which a defect 11 having a dimension (shown as “a”) of approximately 1.8 μm is generated. As described above, the inner wall surface 14 is formed with a thermal silicon oxide film 41 having a thickness of 1.2 μm and a plasma polymerization film 42 having a thickness of 0.8 μm, that is, a droplet protective film having a total thickness of 2.0 μm. Has been. Therefore, even when the defect 11 having such a size occurs, the occurrence of the exposed portion 17 (see FIG. 11) can be suppressed.

  Here, the dimension of 1.8 μm is a value slightly exceeding the maximum value of the dimension of the defect 11 that can be predicted. As shown in FIG. 5, the size of the defect 11 is almost within 1.7 μm. Therefore, in the silicon nozzle substrate 2 of the present embodiment, the occurrence of the exposed portion 17 is suppressed even when the largest possible defect 11 occurs, and the reliability is further improved. Further, since the thickness of the thermally oxidized silicon film 41 is 1.5 times the thickness of the plasma polymerized film 42 on the inner wall surface 14, the droplet protective film on the inner wall surface 14 is the same as the silicon nozzle substrate 1 described above. The film thickness is equivalent to the film thickness of the droplet protective film on the ejection surface 15. Therefore, the occurrence of the exposed portion 17 due to the defect 11 is effectively suppressed, and the reliability is improved.

(Third embodiment)
Next, as a third embodiment of the present invention, a method for manufacturing the above-described silicon nozzle substrate 1 will be described with reference to process cross-sectional views of FIGS. Each of the above drawings is an enlarged cross-sectional view showing a portion of the single crystal silicon substrate 44 in the vicinity of the nozzle hole 21 shown in FIG. The silicon nozzle substrate 1 of the first embodiment and the silicon nozzle substrate 2 of the second embodiment are substantially the same except for the film thickness of the thermally oxidized silicon film 41 and the like. Therefore, the manufacturing method of the silicon nozzle substrate 2 is substantially the same as the manufacturing method shown in the present embodiment except for the formation conditions of the thermally oxidized silicon film 41 and the like. In addition, the code | symbol described in the parenthesis in each process sectional drawing mentioned above has shown the area | region etc. in which the component shown in above-mentioned FIG. 1 etc. will be formed in the future. Hereinafter, it demonstrates in order of a process.

First, as shown in FIG. 6A, the single crystal silicon substrate 44 is heated in an oxygen-containing atmosphere to form a second thermally oxidized silicon film 46 on the entire surface. As the oxygen-containing atmosphere, a mixed atmosphere of oxygen (O ₂ ) and water vapor (H ₂ O) is used. The heating condition is 1075 ° C. for 4 hours. By the thermal oxidation treatment under such conditions, the second thermal silicon oxide film 46 having a film thickness of approximately 1.0 μm can be formed.

  Next, as shown in FIG. 6B, a first resist film 47 is formed on the bonding surface 16 side through a second thermal silicon oxide film 46. Then, the first resist film 47 is patterned by exposure and development processing, and the first resist film 47 is removed from a region where the second nozzle hole 21b is to be formed in the future.

  Next, as shown in FIG. 6C, the second thermally oxidized silicon film 46 in a region not covered with the first resist film 47 is made to a predetermined thickness by using a hydrofluoric acid-based etching solution. Thin film. Here, the “region not covered with the first resist film 47” means the entire area of the surface that will become the ejection surface 15 in the future and the second nozzle hole in the future on the adhesive surface 16 side. This is a region where 21b is formed.

Next, as shown in FIG. 6D, the first resist film 47 is removed from the single crystal silicon substrate 44 and removed. Peeling is preferably performed using an etching (peeling) solution containing sulfuric acid (H ₂ SO ₄ ). An organic etching (stripping) solution can also be used.
Next, as shown in FIG. 7E, a second resist film 48 is formed on the adhesive surface 16 via a second thermal silicon oxide film 46. Then, the second resist film 48 is patterned by exposure and development processing, and the second resist film 48 is removed from a region where the first nozzle holes 21a will be formed in the future.

Next, as shown in FIG. 7F, the second thermal silicon oxide film 46 is removed from a region where the first nozzle hole 21a is to be formed in the future by using a hydrofluoric acid-based etching solution. The single crystal silicon substrate 44 is exposed. At the same time, the second thermal silicon oxide film 46 is removed from the surface that will become the ejection surface 15 in the future, and the single crystal silicon substrate 44 is exposed.
Next, as shown in FIG. 7G, the second resist film 48 is peeled off from the single crystal silicon substrate 44 and removed. Stripping conditions and the like are the same as the stripping conditions for the first resist film 47 described above.

Next, as shown in FIG. 7H, the region not covered with the second thermal silicon oxide film 46 on the bonding surface 16, that is, the region that will become the first nozzle hole 21a in the future is anisotropically etched. Then, it is dug down to a depth of about 25 μm. The etching apparatus is preferably an ICP (inductively coupled plasma) dry etching apparatus. As an etching gas, it is preferable to use C ₄ F ₈ and SF ₆ alternately. Under such conditions, the single crystal silicon substrate 44 can be etched in the vertical direction by SF ₆ while suppressing the etching from proceeding in the side surface direction (direction parallel to the bonding surface 16) by C ₄ F ₈ .

  Next, as shown in FIG. 8I, the second thermally oxidized silicon film 46 is removed from the region where the second nozzle hole 21b will be formed in the future by using a hydrofluoric acid-based etching solution. The single crystal silicon substrate 44 is exposed. At the same time, the second thermally oxidized silicon film 46 in the region other than the above region is thinned.

  Next, as shown in FIG. 8 (j), using an ICP (inductively coupled plasma) dry etching apparatus again, a region not covered with the second thermally oxidized silicon film 46 on the bonding surface 16 side is vertically aligned. Dig down to a depth of approximately 40 μm in the direction. The etching conditions are the same. As a result, a concave portion (that is, a hole) having a convex section is formed, which includes a portion that will become the first nozzle hole 21a in the future and a portion that will become the second nozzle hole 21b in the future. The process up to here is the first process.

Next, the second thermal silicon oxide film 46 is entirely removed using a hydrofluoric acid-based etching solution. Next, the single crystal silicon substrate 44 is heated again in an oxygen-containing atmosphere, and as shown in FIG. 8 (k), the first crystal silicon substrate 44 including the inner wall surface 14 of the above-described recess is formed on the entire surface. A thermally oxidized silicon film 41 is formed as a droplet protective film.
The step of forming the thermal silicon oxide film 41 is the second step. In this step, the thickness of the plasma polymerization film 42 as the second droplet protective film formed on the inner wall surface 14 of the first nozzle hole 21a (see FIG. 9 described later) in the fourth step described later is 1 This is a step of forming a thermal silicon oxide film 41 having a film thickness twice or more. This step is more preferably a step of forming a thermal silicon oxide film 41 having a thickness of 1 to 2 times the thickness of the plasma polymerized film 42.

In the manufacturing method of this embodiment, the film thickness of the plasma polymerized film 42 formed on the inner wall surface 14 in the fourth step described later is 0.5 μm. The film thickness of the thermally oxidized silicon film 41 formed in this step is 0.8 μm. That is, in the manufacturing method of this embodiment, the thermally oxidized silicon film 41 having a film thickness 1.6 times the film thickness of the plasma polymerization film 42 is formed.
As the above oxygen-containing atmosphere, a mixed atmosphere of oxygen (O ₂ ) and water vapor (H ₂ O) is used. The heating (oxidation) condition is 2.75 hours at 1000 ° C. By the oxidation treatment under such conditions, a thermally oxidized silicon film 41 having a thickness of about 0.8 μm can be formed.

  Next, as shown in FIG. 8L, a support substrate 51 made of a transparent material such as glass is attached to the bonding surface 16 side. 8 (l) to FIG. 9 (o), which will be described later, are shown upside down. The above-mentioned support substrate 51 is attached by using a double-sided tape 53 having a self-peeling layer (not shown) whose adhesive strength is easily reduced by ultraviolet rays or heat on at least one surface. Do so as to face each other. Such a pasting operation is performed in a vacuum. By performing the pasting operation in a vacuum, it is possible to suppress the generation of bubbles or the like on the pasting surface.

Next, as shown in FIG. 9 (m), the single crystal silicon substrate 44 is thinned from the surface that will become the ejection surface 15 in the future. The discharge surface 15 is formed by such processing. The above-described cross section (convex concave portion) is a hole penetrating the single crystal silicon substrate 44. As a result, the nozzle hole 21 composed of the first nozzle hole 21a and the second nozzle hole 21b is formed. The step of forming the nozzle hole 21 is a third step.
Note that the above-described thinning is performed by combining the process of grinding the single crystal silicon substrate 44 to a thickness of 71 μm with a back grinder and the process of polishing to a thickness of 65 μm with a CMP apparatus or the like.

  Next, as shown in FIG. 9 (n), as a fourth step, a plasma polymerization film 42 as a second droplet protective film is formed on the discharge surface 15 and the inner wall surface 14. The plasma polymerized film 42 is formed by forming a silicon polymer film by a plasma polymerization method using siloxane as a raw material, and then irradiating the silicon polymer film with UV (ultraviolet rays) for dehydration condensation and oxidizing the surface. In addition, according to the plasma polymerization method, a thin film can be formed at a temperature at which the above-described self-peeling layer does not deteriorate, specifically at a low temperature of 100 ° C. or less.

In this step, the film thickness on the inner wall surface 14 of the first nozzle hole 21a is 0.5 μm or more, and the film thickness on the discharge surface 15 is 2.5 times or more of the film thickness on the inner wall surface 14 described above. This is a step of forming a plasma polymerized film 42. As described above, since the nozzle hole 21 is a hole having a small diameter, when the film is formed under the condition (time, etc.) that the film thickness on the inner wall surface 14 is 0.5 μm, approximately 1.3 μm is formed on the discharge surface 15. A plasma polymerized film 42 having a film thickness of 2.6 times the film thickness on the inner wall surface 14 is formed.
A thermal silicon oxide film 41 has already been formed on the inner wall surface 14. Therefore, a two-layer structure of the thermally oxidized silicon film 41 and the plasma polymerized film 42 is formed on the inner wall surface 14 by the above processing. The plasma polymerized film 42 is also formed on the inner wall surface 14 of the second nozzle hole 21b, but is not shown in the figure.

Next, as shown in FIG. 9 (o), a thin film of a material containing fluorine atoms is formed on the discharge surface 15 and the inner wall surface 14 by vapor deposition or dipping, thereby forming a water repellent film 43.
Next, as shown in FIG. 9 (p), a protective film 52 is attached to the discharge surface 15 side. Then, ultraviolet rays are irradiated from the support substrate 51 side. As described above, since the support substrate 51 is formed of a transparent material, the above-described ultraviolet rays pass through the support substrate and irradiate the double-sided tape 53. As a result, the above self-peeling layer is deteriorated and the adhesive force of the double-sided tape 53 is reduced. Thereafter, the support substrate 51 and the double-sided tape 53 are peeled off from the single crystal silicon substrate 44 as shown in FIG.

Next, as shown in FIG. 10 (r), argon (Ar) plasma or oxygen (O ₂ ) plasma is irradiated from the bonding surface 16 side. Then, as shown in FIG. 10S, the water repellent film 43 is removed from the adhesive surface 16 and the inner wall surface 14 of the nozzle hole 21. Then, after immersing in the primer treatment solution for 1 hour, it is rinsed purely. Then, baking is performed at 80 ° C. for 1 hour. At this time, a silane coupling agent is used as the primer treatment liquid. By this treatment, a hydrophilic film (not shown) is formed on the thermally oxidized silicon film 41 on the bonding surface 16 side, and adhesion to the cavity substrate 3 (see FIG. 1) is improved. And finally, as shown in FIG.10 (t), the protective film 52 is removed.

  Through the above steps, the inner wall surface 14 has a laminate of a thermal silicon oxide film 41 having a film thickness of 0.8 μm and a plasma polymerization film 42 having a film thickness of 0.5 μm, and a film thickness of 1.3 μm on the discharge surface 15. The silicon nozzle substrate 1 having the plasma polymerized film 42 can be obtained. As described above, the silicon nozzle substrate 1 has an exposed portion 17 (see FIG. 11) and a cavity portion 18 (see FIG. 11) when a defect 11 (see FIG. 3) having a size within 1.1 μm, which can normally occur, occurs. Occurrence) can be effectively suppressed. Therefore, according to the manufacturing method of this embodiment, the silicon nozzle substrate 1 with improved reliability can be obtained. Further, by using the silicon nozzle substrate 1 obtained by the manufacturing method of this embodiment as a constituent element, it is possible to obtain a droplet discharge head 8 (see FIG. 1) with improved reliability.

  DESCRIPTION OF SYMBOLS 1 ... Silicon nozzle substrate of 1st Embodiment, 2 ... Silicon nozzle substrate of 2nd Embodiment, 3 ... Cavity substrate, 4 ... Electrode substrate, 5 ... Drive circuit, 8 ... Droplet discharge head, 11 ... Defect, DESCRIPTION OF SYMBOLS 13 ... End surface, 14 ... Inner wall surface, 15 ... Discharge surface, 16 ... Adhesion surface, 17 ... Exposed part, 18 ... Hollow part, 19 ... Edge part, 21 ... Nozzle hole, 21a ... First nozzle hole, 21b ... First 2 nozzle holes, 22 ... diaphragm, 23 ... reservoir, 24 ... orifice, 25 ... discharge chamber, 27 ... common electrode, 29 ... insulating film, 31 ... individual electrode, 31a ... lead part, 31b ... terminal part, 33 ... Sealing material 34... Gap 35. Ink supply port 36. Electrode extracting portion 41. Thermal silicon oxide film as first droplet protective film 42. Plasma polymerized film as second droplet protective film 43 ... water repellent film, 44 ... single crystal silicon Plate 46... Second thermal silicon oxide film 47. First resist film 48. Second resist film 51. Support substrate 52. Protective film 53 Double-sided tape 230 Reservoir recess 240. Orifice recess, 250 ... discharge recess, 310 ... recess.

Claims (8)

A nozzle hole penetrating the silicon substrate, a first droplet protective film made of thermally oxidized silicon formed by heating the surface of the silicon substrate covering the inner wall surface of the nozzle hole,
A silicon nozzle substrate comprising: a second droplet protective film formed on a discharge surface which is a surface on the first droplet protective film on the inner wall surface and on a droplet discharge side;
The silicon nozzle substrate, wherein the film thickness of the first droplet protective film is one or more times the film thickness of the second droplet protective film on the inner wall surface. The silicon nozzle substrate according to claim 1,
2. The silicon nozzle substrate according to claim 1, wherein a thickness of the first droplet protective film is 1 to 2 times a thickness of the second droplet protective film on the inner wall surface. The silicon nozzle substrate according to claim 2,
The silicon nozzle substrate, wherein a film thickness of the second droplet protective film on the ejection surface is 2.5 times or more of a film thickness of the second droplet protective film on the inner wall surface. The silicon nozzle substrate according to claim 3,
The silicon nozzle substrate, wherein the second droplet protective film on the inner wall surface has a thickness of 0.5 μm or more. A first step of forming a recess in the first surface of the silicon substrate;
A second step of heating the silicon substrate to form a thermal silicon oxide film as a first droplet protective film on at least the inner wall surface of the recess;
The silicon substrate is thinned from a second surface side opposite to the first surface until the second surface reaches the recess, and the recess is formed with a nozzle hole penetrating the silicon substrate. A third step of
A fourth step of forming a second droplet protective film on the second surface and the inner wall surface;
A method of manufacturing a silicon nozzle substrate having
The second step is a step of forming the thermal silicon oxide film having a thickness of 1 or more times the thickness of the second droplet protective film formed on the inner wall surface in the fourth step. A method of manufacturing a silicon nozzle substrate. A method for producing a silicon nozzle substrate according to claim 5,
The second step is a step of forming the thermally oxidized silicon film having a thickness that is 1 to 2 times the thickness of the second droplet protective film formed on the inner wall surface in the fourth step. A method for producing a silicon nozzle substrate, characterized in that: A method for producing a silicon nozzle substrate according to claim 6,
The method of manufacturing a silicon nozzle substrate, wherein the fourth step is a step of forming the second droplet protective film using a plasma polymerization method. A method for producing a silicon nozzle substrate according to claim 7,
The method of manufacturing a silicon nozzle substrate, wherein the fourth step is a step of forming the second droplet protective film having a thickness of 0.5 μm or more on the inner wall surface.

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