Single crystal silicon substrate, liquid discharge head, and method for manufacturing single crystal silicon substrate

Abstract

To manufacture a liquid discharge head which has a small size and high resolution.SOLUTION: A single crystal silicon substrate 20 at least a part of which constitutes a liquid channel includes a first through hole 21 having an inclined side wall 21a inclined with respect to substrate surfaces 20a and 20b of the single crystal silicon substrate 20, and a second through hole 22 which constitutes a channel 51 and where the side wall is constituted of a vertical side wall 22a closer to vertical than the inclined side wall 21a with respect to the substrate surfaces 20a and 20b, wherein the first through hole 21 is formed by crystal anisotropic etching, and the second through hole 22 is formed by metal assist chemical etching.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a single crystal silicon substrate, a liquid ejection head, and a method for manufacturing a single crystal silicon substrate. [Background technology]

[0002] Various silicon substrates have been used in the past. Such silicon substrates are preferably used in various liquid ejection heads, such as inkjet heads that eject ink as a liquid. As a liquid ejection head equipped with such a silicon substrate, for example, Patent Document 1 discloses a droplet ejection head equipped with a flow path substrate and a sealing substrate that can be formed from silicon or the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-62035 Summary of the Invention [Problem to be solved by the invention]

[0004] A liquid ejection head that is small and high-resolution is preferable. The droplet ejection head of Patent Document 1 has a reservoir-forming substrate, which serves as a sealing substrate, and a first opening serving as a through-hole for arranging wiring connected to a piezoelectric element, and a through-hole serving as an ink reservoir. Both the first opening and the ink reservoir are formed by anisotropic etching using potassium hydroxide as an etchant. When the through-hole is formed in this manner, the side of the through-hole forms a slope relative to the substrate surface. Therefore, as shown in the figure, the side of the first opening serving as the first through-hole clearly forms a slope relative to the substrate surface of the reservoir-forming substrate, and the side of the ink reservoir serving as the second through-hole also forms a slope relative to the substrate surface of the reservoir-forming substrate. However, if both the first through-hole and the second through-hole have sloped sides, the substrate surface must be made wider, which could result in an increased size of the liquid ejection head and a wider nozzle pitch, resulting in lower resolution. [Means for solving the problem]

[0005] Therefore, in order to solve the above problem, the single crystal silicon substrate of the present invention is a single crystal silicon substrate, at least a portion of which forms a liquid flow path, and is equipped with a first through hole having an inclined sidewall that is inclined with respect to the substrate surface of the single crystal silicon substrate, and a second through hole that forms the flow path and has a sidewall that is closer to perpendicular to the substrate surface than the inclined sidewall, and is characterized in that the first through hole is formed by crystalline anisotropic etching and the second through hole is formed by metal-assisted chemical etching.

[0006] Furthermore, a method for manufacturing a single crystal silicon substrate according to the present invention for solving the above-mentioned problems is characterized by comprising the steps of: forming a first through hole having an inclined sidewall inclined with respect to a substrate surface by crystal anisotropically etching a first etching target region on a first surface of a substrate surface of the single crystal silicon substrate; forming a catalyst film in a second etching target region on a second surface of the substrate surface of the single crystal silicon substrate opposite to the first surface; and contacting the single crystalline silicon substrate with the catalyst film formed thereon with an etching solution to etch the second etching target region, thereby forming a second through hole having a sidewall constituted by a vertical sidewall that is closer to perpendicular to the second surface than the inclined sidewall. [Brief explanation of the drawings]

[0007] [Figure 1] 2A and 2B are bottom views of a liquid ejection head according to a first embodiment of the present invention and an enlarged view of a partial region X thereof. [Figure 2] FIG. 2 is a side cross-sectional view of the liquid ejection head of FIG. [Figure 3] FIG. 2 is a perspective view of the liquid ejection head of FIG. 1. [Figure 4] 2A to 2C are diagrams illustrating a manufacturing process of the sealing plate of the liquid ejection head of FIG. 1. [Figure 5] 4 is a flowchart showing a method for manufacturing the sealing plate of the liquid ejection head of FIG. [Figure 6] 3 is a flowchart showing a manufacturing method for the entire liquid ejection head of FIG. [Figure 7] 5A to 5C are diagrams illustrating a manufacturing process of a sealing plate of a liquid ejection head according to a second embodiment of the present invention. [Figure 8] 8A to 8C are diagrams illustrating a manufacturing process of a sealing plate of a liquid ejection head according to a third embodiment of the present invention. [Figure 9] 10A to 10C are diagrams illustrating a manufacturing process of a sealing plate of a liquid ejection head according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] First, the present invention will be briefly described. A first aspect of the present invention for solving the above problem provides a single crystal silicon substrate, at least a portion of which forms a flow path for a liquid, comprising: a first through hole having an inclined sidewall that is inclined with respect to a substrate surface of the single crystal silicon substrate; and a second through hole that forms the flow path and has a sidewall that is vertical with respect to the substrate surface and is closer to vertical than the inclined sidewall, wherein the first through hole is formed by crystal anisotropic etching and the second through hole is formed by metal-assisted chemical etching.

[0009] According to this aspect, the first through hole is formed by crystal anisotropic etching, and the second through hole is formed by metal-assisted chemical etching. By forming the through hole by metal-assisted chemical etching, the sidewall of the through hole can be made more vertical than when the through hole is formed by crystal anisotropic etching. Therefore, the sidewall of the second through hole can be configured as a vertical sidewall that is approximately perpendicular to the substrate surface. This allows the manufacture of a single-crystal silicon substrate with a dense structure, and a small, high-resolution liquid ejection head.

[0010] A second aspect of the single crystal silicon substrate according to the present invention is characterized in that, in the first aspect, the substrate surface has a first surface on which the inclined sidewall is exposed and a second surface opposite the first surface, the first through hole and the second through hole penetrate from the first surface to the second surface, and the opening of the second through hole on the first surface side has an inclined surface with respect to the first surface that widens as it approaches the first surface.

[0011] According to this aspect, the opening of the second through hole on the first surface side has an inclined surface with respect to the first surface that widens as it approaches the first surface. This makes it possible to prevent burrs and the like from remaining in the opening. Furthermore, by providing such an opening, for example, when liquid flows into the second through hole from the opening, the liquid can flow in favorably.

[0012] A third aspect of the liquid ejection head of the present invention comprises a cavity substrate having the first or second single crystal silicon substrate, a third surface on which a piezoelectric element and a conductive portion connected to the piezoelectric element are formed, and a fourth surface opposite the third surface, at least a portion of which forms the flow path, and wherein the third surface is bonded to the substrate surface so that a portion of the conductive portion is exposed through the first through hole, and the flow path on the fourth surface is connected to the second through hole.

[0013] According to this aspect, by bonding the third surface to the substrate surface using the single crystal silicon substrate and the cavity substrate, a portion of the conductive portion is exposed through the first through-hole, and the flow path of the fourth surface is connected to the second through-hole, a small, high-resolution liquid ejection head can be manufactured.

[0014] A fourth aspect of the present invention provides a method for manufacturing a single crystal silicon substrate, comprising the steps of: forming a first through hole having an inclined sidewall inclined with respect to the substrate surface by anisotropically etching a first etching target region on a first surface of the substrate surface of the single crystal silicon substrate; forming a catalyst film in a second etching target region on a second surface of the substrate surface opposite to the first surface; and contacting the single crystal silicon substrate with the catalyst film formed thereon with an etching solution to etch the second etching target region, thereby forming a second through hole having a sidewall constituted by a vertical sidewall that is closer to perpendicular to the second surface than the inclined sidewall.

[0015] According to this aspect, a first through-hole with an inclined sidewall is formed by crystal anisotropic etching of a first etching target region, and a second through-hole with a vertical sidewall is formed by etching a second etching target region on which a catalyst film is formed. Forming a through-hole using a catalyst film, such as metal-assisted chemical etching, allows for a through-hole with a sidewall that is closer to vertical than through-holes formed by crystal anisotropic etching. This allows for the sidewall of the second through-hole to be formed with a vertical sidewall that is approximately perpendicular to the substrate surface. This allows for the manufacture of a single-crystal silicon substrate with a dense structure, and a small, high-resolution liquid ejection head.

[0016] A fifth aspect of the present invention is a method for manufacturing a single crystal silicon substrate according to the fourth aspect, characterized in that in the step of forming the first through hole, an alkaline aqueous solution is used as an etching solution, and in the step of forming the second through hole, the second through hole is formed by metal-assisted chemical etching.

[0017] According to this aspect, the step of forming the first through hole uses an alkaline aqueous solution as an etching solution, and the step of forming the second through hole uses metal-assisted chemical etching to form the second through hole. By manufacturing the single crystal silicon substrate in this manner, it is possible to manufacture the single crystal silicon substrate simply and with high precision.

[0018] A sixth aspect of the present invention is a method for manufacturing a single crystal silicon substrate according to the fifth aspect, characterized in that in the step of forming the catalyst film, the catalyst film is formed by electroless plating or vapor deposition.

[0019] According to this aspect, the catalyst film is formed by electroless plating or vapor deposition. By manufacturing the single crystal silicon substrate in this manner, the single crystal silicon substrate can be manufactured particularly simply and with high precision.

[0020] A seventh aspect of the method for manufacturing a single crystal silicon substrate according to the present invention is characterized in that, in any one of the fourth to sixth aspects, the step of forming the second through hole includes a step of passing the second through hole from the second surface to the first surface, and providing an inclined surface with respect to the first surface at an opening of the second through hole on the first surface side, the inclined surface widening toward the first surface.

[0021] According to this aspect, the second through hole penetrates from the second surface to the first surface, and the opening of the second through hole on the first surface side has an inclined surface with respect to the first surface that widens as it approaches the first surface. This makes it possible to prevent burrs and the like from remaining at the opening. Furthermore, by providing such an opening, for example, when liquid flows into the second through hole from the opening, the liquid can flow in favorably.

[0022] [Example 1] Next, a liquid ejection head 1 according to a first embodiment of the present invention will be described in detail with reference to Figures 1 to 4. In the following figures, in order to make the structure of the liquid ejection head 1 easier to understand, some components have been simplified, some components have been omitted, and the aspect ratio of some components has been changed.

[0023] 1 is a bottom view of an inkjet head that can form an image by conveying a medium in a movement direction A, or by moving the liquid ejection head 1 itself in the movement direction A relative to a stationary medium, and ejecting ink as a liquid onto the medium from nozzles N. The liquid ejection head 1 of this embodiment is a so-called line head in which nozzles N are provided corresponding to the entire medium in a width direction B that intersects with the movement direction A.

[0024] When arranging multiple nozzles N on the nozzle forming surface 11, which is the bottom surface of the line head, the simplest way to arrange the nozzles N is to line up the nozzles N in the width direction B. However, when the nozzles N are arranged in this manner, the pitch between adjacent nozzles N in the width direction B becomes wider. When the pitch between adjacent nozzles N becomes wider, the resolution decreases. Therefore, in the liquid ejection head 1 of this embodiment, multiple nozzle rows 12, in which the nozzles N are lined up in a straight line, are arranged so as to be oblique to the movement direction A.

[0025] As shown in the enlarged view of region X in Figure 1, in the liquid ejection head 1 of this embodiment, the nozzles N in each nozzle row 12 are spaced apart in the width direction B at a pitch P1. Furthermore, adjacent nozzle rows 12 are configured to eject the same ink, and the positions of the nozzles N in adjacent nozzle rows 12 in the width direction B are shifted by half the pitch P1 for each nozzle row 12, so that the spacing between the nozzles N in the width direction B of the liquid ejection head 1 is a pitch P0, which is half the pitch P1. By arranging the nozzle rows 12 in this way, the liquid ejection head 1 of this embodiment achieves a high resolution of 1200 dpi (dots per inch) at a pitch P0.

[0026] In addition to arranging the nozzle rows 12 so that they are oblique to the movement direction A, further improvement in resolution can be achieved by narrowing the gap between adjacent nozzles N. The liquid ejection head 1 of this embodiment has the configuration shown in FIG. 2, which narrows the gap between adjacent nozzles N. FIG. 2 is a cross-sectional view taken along a direction roughly along the movement direction A. In the liquid ejection head 1 of this embodiment, the same ink is supplied to both nozzle rows 12A and 12B of the nozzle rows 12 from an ink cartridge (not shown), and the nozzles N of nozzle row 12A and the nozzles N of nozzle row 12B can eject the same ink. Furthermore, the liquid ejection head 1 of this embodiment is configured to be usable by circulating ink, and ink flows in a flow direction F inside the liquid ejection head 1. More specifically, in both nozzle row 12A and nozzle row 12B, ink flowing from the ink cartridges in flow direction F returns to circulation flow path 51D via flow path 51A corresponding to second through-hole 22 in sealing plate 20 (described later), flow path 51B corresponding to a through-hole in cavity substrate 30 (described later), and flow path 51C formed by cavity substrate 30 and flow path substrate 40 (described later), all of which form part of flow path 51. In this way, by sharing circulation flow path 51D between the two nozzle rows 12, the distance between adjacent nozzle rows 12 is narrowed. Note that the ink that returns to circulation flow path 51D flows again in flow direction F through flow path 51 and is reused.

[0027] The detailed configuration of the liquid ejection head 1 of this embodiment will be described below with reference to Figures 2 and 3. Figure 3 shows a portion of the nozzle row 12A side of the liquid ejection head 1 of this embodiment. The liquid ejection head 1 of this embodiment includes a sealing plate 20, a cavity substrate 30, and a flow path substrate 40.

[0028] The sealing plate 20 is a single-crystal silicon substrate, at least a portion of which constitutes a liquid flow path 51. The sealing plate 20 has a first surface 20a and a second surface 20b opposite the first surface 20a as substrate surfaces, and is provided with a first through-hole 21 having an inclined sidewall 21a inclined with respect to the first surface 20a and the second surface 20b. The sealing plate 20 also constitutes the flow path 51 and is provided with a second through-hole 22 having a sidewall formed by a vertical sidewall 22a that is closer to perpendicular to the first surface 20a and the second surface 20b than the inclined sidewall 21a. The second through-hole 22 is part of the flow path 51 and serves as an ink reservoir. By using the second through-hole 22 having a sidewall formed by a nearly vertical sidewall 22a as an ink reservoir, it is possible to prevent the sealing plate 20 from becoming larger in the surface direction of the substrate surface, thereby enabling the liquid ejection head 1 to be made smaller.

[0029] The cavity substrate 30 has a third surface 30a and a fourth surface 30b opposite the third surface 30a as substrate surfaces. The third surface 30a is bonded to the second surface 20b, thereby bonding the cavity substrate 30 to the sealing plate 20. Like the sealing plate 20, the cavity substrate 30 of this embodiment is a single-crystal silicon substrate, but is not limited to a single-crystal silicon substrate. The third surface 30a is formed with a piezoelectric element 32 as an electrode portion 31, and electrode films 33 and 34 as conductive portions electrically connected to the piezoelectric element 32. At least a portion of the fourth surface 30b forms a flow path 51. A piezoelectric element accommodating chamber 23 is provided in the region of the sealing plate 20 corresponding to the position where the electrode portion 31 is formed. The electrode film 33 extends from the piezoelectric element accommodating chamber 23 to the first through-hole 21. From another perspective, a tape carrier package (TCP) is mounted in the first through-hole 21 using COF (chip-on-flex) technology. In COF mounting, a special tool is used to heat and press the TCP, but by making the first surface 20a side wider and the second surface 20b side narrower during COF mounting, it is possible to prevent the sealing plate 20 and cavity substrate 30 from becoming larger in the surface direction, making it possible to miniaturize the liquid ejection head 1.

[0030] The flow path substrate 40 has a pressure chamber 41 provided at a position facing the electrode section 31 via the cavity substrate 30, and the pressure chamber 41 has a nozzle N that ejects ink in an ejection direction D. The pressure chamber 41 forms part of the flow path 51 and is connected to the circulation flow path 51D, so that ink that cannot be ejected from the nozzle N can flow into the circulation flow path 51D. When the electrode section 31 is energized, the piezoelectric element 32 deforms and the cavity substrate 30 vibrates, applying pressure to the pressure chamber 41, and the ink in the pressure chamber 41 is ejected from the nozzle N in the ejection direction D.

[0031] In the sealing plate 20 of this embodiment, the first through-hole 21 is formed by crystal anisotropic etching, and the second through-hole 22 is formed by metal-assisted chemical etching (MACE). Forming the through-holes by MACE allows for sidewalls that are closer to vertical than through-holes formed by crystal anisotropic etching. Therefore, the sidewalls of the second through-hole 22 can be configured as vertical sidewalls 22a that are substantially perpendicular to the first and second substrate surfaces 20a and 20b. By configuring the sealing plate 20 in this manner, a single-crystal silicon substrate with a dense structure can be manufactured, allowing for the manufacture of a compact, high-resolution liquid ejection head 1. Furthermore, by forming the first through-hole 21 by crystal anisotropic etching and the second through-hole 22 by metal-assisted chemical etching, etching can be performed in an all-wet state without using dry etching, which uses a large amount of greenhouse gases. Therefore, configuring the sealing plate 20 in this manner improves productivity and reduces the amount of electricity and greenhouse gases used in manufacturing.

[0032] Here, the angle of the vertical sidewall 22a with respect to the substrate surface is preferably 90° ±2° or less. This is because by using a single crystal silicon wafer with a Miller index (plane index) of (100) for the substrate surface of the sealing plate 20 and by optimizing the composition of the etching solution, it is possible to control the thickness of the sealing plate 20 within a range of, for example, about 400 μm during vertical etching by MACE, thereby ensuring perpendicularity.

[0033] The angle of the inclined sidewall 21a relative to the substrate surface is preferably 45.0° or more and 54.7° or less. 54.7° is the angle between the surface portion of the first surface 20a of the sealing plate 20, which has a Miller index (plane index) of (100), and the crystal plane, which has a Miller index (plane index) of (111) and where etching progresses most slowly. -1 (1 / 3 1 / 2 ) value. Also, 45° is the COS angle where the next stable Miller index (plane index) forms with the (110) crystal plane. -1 (1 / 2 1 / 2 ) is the value. Compared to when the angle is 45°, when the angle is 54.7°, the etching surface is more stable and the overall size of the sealing plate 20 can be made smaller.

[0034] The liquid ejection head 1 of this embodiment includes the sealing plate 20, which is a single-crystal silicon substrate as described above, and the cavity substrate 30, which has the third surface 30a and the fourth surface 30b as described above. The liquid ejection head 1 of this embodiment is configured such that the third surface 30a is bonded to the second surface 20b, which is the substrate surface of the sealing plate 20, thereby exposing a portion of the conductive portion through the first through-hole 21, and the flow path 51, of which the fourth surface 30b is a part, communicates with the second through-hole 22. In this way, the liquid ejection head 1 of this embodiment is configured such that the third surface 30a is bonded to the substrate surface of the sealing plate 20 by the sealing plate 20 and the cavity substrate 30, thereby exposing a portion of the conductive portion through the first through-hole 21, and the flow path 51 in the fourth surface 30b communicates with the second through-hole 22, thereby achieving a small size and high resolution.

[0035] Next, a manufacturing method of the sealing plate 20 of this embodiment will be described with reference to FIGS. 4 and 5. As shown in FIG. 5, the manufacturing method of the sealing plate 20 of this embodiment begins with an etching preparation process in step S10. In the etching preparation process in step S10, an oxide film 202 (SiO2) is first formed on a single-crystal silicon substrate 201 (top diagram in FIG. 4) as shown in the second diagram from the top of FIG. 4. Then, as shown in the third diagram from the top of FIG. 4, a resist 203 is patterned by photolithography. As shown in the fourth diagram from the top of FIG. 4, an Au film 204, which is a gold film that serves as a catalyst film for MACE, is formed. Then, as shown in the fifth diagram from the top of FIG. 4, lift-off is performed. Note that in this embodiment, the Au film 204 was formed by evaporating Au over the entire bottom surface in the figure; however, the formation of the Au film 204 is not limited to this method. Here, in the state shown in the fifth diagram from the top of FIG. 4, the Au film 204 has a disk shape when viewed from below. Thereafter, as shown in the sixth diagram from the top of Fig. 4, an oxide film 202 represented by SiO2 is formed over the entire lower surface in the drawing, and after patterning with resist by photolithography, the resist is removed by etching as shown in the seventh diagram from the top of Fig. 4. This corresponds to the etching preparation step of step S10.

[0036] Next, the first through-hole forming process of step S20 in FIG. 5 is performed. Specifically, as shown in the eighth diagram from the top of FIG. 4, a through-hole corresponding to first through-hole 21 is formed by crystal anisotropic etching, which is wet etching using potassium hydroxide (KOH). At this time, a recess corresponding to piezoelectric element accommodating chamber 23 is also formed. Note that the recess corresponding to piezoelectric element accommodating chamber 23 is shallower than the through-hole corresponding to first through-hole 21. Therefore, for example, in the state shown in the seventh diagram from the top of FIG. 4, a thin oxide film 202 represented by SiO may be left in the region corresponding to the recess corresponding to piezoelectric element accommodating chamber 23. Then, a through-hole corresponding to first through-hole 21 may be formed by crystal anisotropic etching, and then the oxide film 202 in the region of the lower surface of single-crystal silicon substrate 201 corresponding to piezoelectric element accommodating chamber 23 in the figure may be etched, and then the recess corresponding to piezoelectric element accommodating chamber 23 may be formed by crystal anisotropic etching.

[0037] Next, the second through-hole forming process of step S30 in FIG. 5 is performed. Specifically, a through-hole corresponding to the second through-hole 22 is formed by MACE using a hydrogen fluoride aqueous solution obtained by mixing hydrogen fluoride and hydrogen peroxide, as shown in the ninth diagram from the top of FIG. 4. Then, when the Au film 204 is etched, the sealing plate 20 of this embodiment is completed, as shown in the bottom diagram of FIG. 4. Note that in this embodiment, the second through-hole forming process of step S30 is performed after the first through-hole forming process of step S20. However, the first through-hole forming process of step S20 may be performed after the second through-hole forming process of step S30 by changing the content of the etching preparation process of step S10, for example.

[0038] As described above, the method for manufacturing sealing plate 20 of this embodiment as a method for manufacturing a single-crystal silicon substrate includes a first through-hole forming step S20 in which first through-holes 21 having inclined sidewalls 21a inclined with respect to the substrate surface are formed by crystal anisotropically etching a first etching target region on first surface 20a of the substrate surface of sealing plate 20, which is a single-crystal silicon substrate, where the first through-holes 21 are to be formed. It also includes an etching preparation step S10 in which, corresponding to the fourth and fifth views from the top in FIG. 4 , an Au film 204, which is an Au catalyst film, is formed in a second etching target region on second surface 20b of the substrate surface, where the second through-holes 22 are to be formed. The method also includes a second through-hole formation process in step S30 in which the single-crystal silicon substrate 201 on which the Au film 204 has been formed is brought into contact with an aqueous hydrogen fluoride solution as an etching solution to etch a second etching target region corresponding to the formation region of the second through-hole 22, thereby forming the second through-hole 22 whose sidewall is composed of a vertical sidewall 22a that is closer to perpendicular to the second surface 20b than the inclined sidewall 21a.

[0039] As described above, the method for manufacturing the sealing plate 20 of this embodiment involves forming a first through hole 21 with an inclined sidewall 21a by anisotropically etching the first etching target region, and then etching the second etching target region, on which a catalyst film is formed, to form a second through hole 22 with a sidewall composed of a vertical sidewall 22a. Forming a through hole using a catalyst film such as MACE allows for a through hole with a sidewall that is closer to vertical than through holes formed by anisotropically etching. Therefore, the sidewall of the second through hole 22 can be composed of a vertical sidewall 22a that is approximately perpendicular to the substrate surface. Therefore, by performing the method for manufacturing the sealing plate 20 of this embodiment, a sealing plate 20 with a dense structure can be manufactured, and a small, high-resolution liquid ejection head 1 can be manufactured.

[0040] Here, in the first through-hole forming process of step S20, an alkaline aqueous solution of potassium hydroxide is used as the etching solution, and in the second through-hole forming process of step S30, the second through-hole 22 is formed by MACE. By manufacturing the sealing plate 20 in this manner, the sealing plate 20 can be manufactured easily and with high precision. As the alkaline aqueous solution used as the etching solution, for example, in addition to the potassium hydroxide aqueous solution used in this embodiment, a tetramethylammonium hydroxide (THAM) aqueous solution or the like can be preferably used, but there is no particular limitation. Because the potassium hydroxide aqueous solution is inexpensive, it can be used, for example, in silicon substrate processing that does not involve semiconductors. On the other hand, because the THAM aqueous solution does not contain mobile ions such as Na or K, it can be used, for example, in crystal anisotropic etching of silicon substrate processing that involves semiconductors.

[0041] In the step of forming a catalyst film in the etching preparation step of step S10, the method is not particularly limited, but the catalyst film is preferably formed by electroless plating or vapor deposition, because by forming the catalyst film by electroless plating or vapor deposition to manufacture the sealing plate 20, the sealing plate 20 can be manufactured particularly easily and with high precision.

[0042] Next, a method for manufacturing the entire liquid ejection head 1 using the sealing plate 20 formed as described above will be described with reference to the flowchart in Fig. 6. First, in step S110, the sealing plate 20 is formed. The formation of the sealing plate 20 is as described above. Next, in step S120, the cavity substrate 30 is formed using a conventional manufacturing method, and in step S130, the sealing plate 20 and the cavity substrate 30 are bonded together. Note that the order of steps S110 and S120 may be reversed, or they may be performed simultaneously.

[0043] Thereafter, in step S140, an ink protective film made of titanium oxide (TiOx), hafnium oxide (HfOx), or the like is formed by chemical vapor deposition (CVD) or the like. In step S150, a flow path substrate 40 is formed using a conventional manufacturing method, but step S150 may be performed before step S140. In step S160, the flow path substrate 40 is bonded to the substrate on which the sealing plate 20 and the cavity substrate 30 are bonded. In step S170, the substrate is cut into chips by laser scribing or the like, and in step S180, TCP constituting the conductive portion is mounted by COF mounting. Finally, in step S190, a case component is attached, completing the manufacture of the liquid ejection head 1. This method allows the liquid ejection head 1 chips to be assembled in wafer form, stabilizing quality and facilitating mass production.

[0044] [Example 2] The liquid ejection head of Example 2 will be described below with reference to FIG. 7. FIG. 7 is a diagram corresponding to FIG. 4 showing the liquid ejection head 1 of Example 1. The liquid ejection head of this example is similar to the liquid ejection head 1 of Example 1 except for the configuration described below. Therefore, the liquid ejection head of this example has the same features as the liquid ejection head 1 of Example 1 except for the points described below. Therefore, in FIG. 7, components that are common to Example 1 above are indicated by the same reference numerals, and detailed descriptions thereof will be omitted.

[0045] Here, the top diagram in FIG. 7 corresponds to the fifth diagram from the top in FIG. 4. The steps of this embodiment corresponding to the top to fourth diagrams in FIG. 4 are the same as those in Example 1, and therefore will be omitted. However, in this embodiment, the Au film 204 has a circular ring shape when viewed from below. When MACE is performed from the state of the top diagram in FIG. 7 in the same manner as in Example 1, the state shown in the second diagram from the top in FIG. 7 is obtained. The second diagram from the top in FIG. 7 shows a state in which a cylindrical hole has been formed in the single-crystal silicon substrate 201 by MACE. Thereafter, when the Au film 204 is etched, the state shown in the third diagram from the top in FIG. 7 is obtained.

[0046] Subsequently, an oxide film 202 represented by SiO2 is formed over the entire single-crystal silicon substrate 201, resulting in the state shown in the fourth diagram from the top in FIG. 7. Subsequently, resist is patterned by photolithography, and the resist is removed by etching, resulting in the state shown in the fifth diagram from the top in FIG. 7. Here, the oxide film 202 is also absent on the first surface 20a side corresponding to the second through-hole 22. Subsequently, anisotropic etching of silicon (Si) forming the single-crystal silicon substrate 201 results in the state shown in the sixth diagram from the top in FIG. 7. Here, a recess is also formed on the first surface 20a side corresponding to the second through-hole 22. Finally, the oxide film 202 is removed, resulting in the state shown in the bottom diagram in FIG. 7. Note that in the above, etching by MACE is stopped by the oxide film 202, and removal of the oxide film 202 opens the first through-hole 21 and the second through-hole 22. The anisotropic etching stops on the crystal plane of the single-crystal silicon substrate 201 with Miller indices (plane indices) of (111).

[0047] As shown in the bottom diagram of FIG. 7 , in the sealing plate 20 of this embodiment formed in this manner, the opening 24 on the first surface 20a side of the second through hole 22 widens toward the first surface 20a. Specifically, the sealing plate 20 of this embodiment has a first surface 20a and a second surface 20b as substrate surfaces, and the first surface 20a is the surface on which the inclined sidewall 21a is exposed. The first through hole 21 and the second through hole 22 penetrate from the first surface 20a to the second surface 20b, and the opening 24 on the first surface 20a side of the second through hole 22 has an inclined surface 24a relative to the first surface 20a that widens toward the first surface 20a. This configuration of the sealing plate 20 of this embodiment prevents burrs and other defects from remaining in the opening 24. Furthermore, by forming such openings 24, for example, when a liquid such as ink flows into the second through hole 22 from the opening 24, the liquid can flow favorably. The "side on which the inclined sidewall 21a is exposed" can also be expressed as "the side on which the inclined sidewall 21a is visible when viewed from a direction perpendicular to the substrate surface."

[0048] Furthermore, when manufacturing the sealing plate 20 of this embodiment, the manufacturing flow is similar to that of FIG. 5 , but in FIG. 5 , the second through hole forming process of step S30 includes a process of penetrating the second through hole 22 from the second surface 20b to the first surface 20a and providing an inclined surface 24a with respect to the first surface 20a that widens toward the first surface 20a at the opening 24 of the second through hole 22 on the first surface 20a side. By performing the second through hole forming process of step S30 in this manner, it is possible to prevent burrs and the like from remaining at the opening 24. Furthermore, by forming the opening 24 in this manner, for example, when a liquid is to flow from the opening 24 into the second through hole 22, the liquid can flow in an appropriate manner.

[0049] [Example 3] The liquid ejection head of Example 3 will be described below with reference to FIG. 8. FIG. 8 is a diagram corresponding to FIG. 4 showing the liquid ejection head 1 of Example 1. The liquid ejection head of this example is similar to the liquid ejection head 1 of Example 1 except for the configuration described below. Therefore, the liquid ejection head of this example has the same features as the liquid ejection head 1 of Example 1 except for the points described below. Therefore, in FIG. 8, components common to Example 1 above are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0050] The top diagram in Fig. 8 shows a state in which an oxide film 202 represented by SiO2 is formed over the entire single crystal silicon substrate 201, and the oxide film 202 is patterned with resist by photolithography and then the resist is removed by etching, repeatedly completing the etching preparation step of step S10 in Fig. 5. The second diagram from the top in Fig. 8 shows a state in which the first through-hole formation step of step S20 in Fig. 5 has been performed on the single crystal silicon substrate 201 in the state shown in the top diagram in Fig. 8. The third diagram from the top in Fig. 8 shows a state in which an oxide film 202 has been further formed on the single crystal silicon substrate 201 in the state shown in the second diagram from the top in Fig. 8.

[0051] The fourth diagram from the top in FIG. 8 shows a state in which the single crystal silicon substrate 201 in the state shown in the third diagram from the top in FIG. 8 is patterned with a resist by photolithography, the resist is removed by etching, and an Au film 204 is formed by electroless plating. The fifth diagram from the top in FIG. 8 shows a state in which the second through-hole formation process of step S30 in FIG. 5 has been performed on the single crystal silicon substrate 201 in the state shown in the fourth diagram from the top in FIG. 8. The bottom diagram in FIG. 8 shows a state in which the Au film 204 has been etched on the single crystal silicon substrate 201 in the state shown in the fifth diagram from the top in FIG. 8. By forming the sealing plate 20 of this embodiment through the steps shown in FIG. 8, a sealing plate 20 having a shape similar to that of the sealing plate 20 of Example 2 formed through the steps shown in FIG. 7 can be manufactured.

[0052] [Example 4] The liquid ejection head of Example 4 will be described below with reference to FIG. 9. FIG. 9 is a diagram corresponding to FIG. 4 showing the liquid ejection head 1 of Example 1. The liquid ejection head of this example is similar to the liquid ejection head 1 of Example 1 except for the configuration described below. Therefore, the liquid ejection head of this example has the same features as the liquid ejection head 1 of Example 1 except for the points described below. Therefore, in FIG. 9, components common to Example 1 above are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0053] The sealing plates 20 of Examples 1 to 3 were formed by performing MACE only from the second surface 20b side in the second through-hole forming process of step S30. The sealing plate 20 of the present examples is formed by performing MACE not only from the second surface 20b side but also from the first surface 20a side in the second through-hole forming process of step S30, and has a shape similar to that of the sealing plate 20 of Example 1 formed through the steps shown in FIG.

[0054] The top diagram in Fig. 9 shows a state after the etching preparation step of step S10 in Fig. 5 is completed, in which an Au film 204 is formed not only on the second surface 20b side but also on the first surface 20a side in the region corresponding to the second through-hole 22, and an oxide film 202 represented by SiO2 is formed in the remaining region. The second diagram from the top in Fig. 9 shows a state in which an oxide film 202 is further formed on both the first surface 20a side and the second surface 20b side of the single-crystal silicon substrate 201 in the state shown in the top diagram in Fig. 9. The third diagram from the top in Fig. 9 shows a state in which the oxide film 202 in the region corresponding to the first through-hole 21 on the first surface 20a is removed by patterning a resist by photolithography and then removing the resist by etching the single-crystal silicon substrate 201 in the state shown in the second diagram from the top in Fig. 9.

[0055] The fourth diagram from the top in FIG. 9 illustrates a state in which the single-crystal silicon substrate 201 in the state illustrated in the third diagram from the top in FIG. 9 has been subjected to the first through-hole forming process of step S20 in FIG. 5. The fifth diagram from the top in FIG. 9 illustrates a state in which the single-crystal silicon substrate 201 in the state illustrated in the fourth diagram from the top in FIG. 9 has been subjected to photolithography to form a resist pattern, and the resist has been removed by etching to remove the oxide film 202 from the region of the second surface 20b corresponding to the piezoelectric element accommodating chamber 23. The sixth diagram from the top in FIG. 9 illustrates a state in which the single-crystal silicon substrate 201 in the state illustrated in the fifth diagram from the top in FIG. 9 has been subjected to silicon etching, and the first through-hole forming process of step S20 in FIG. 5 has also been performed. At this time, the region corresponding to the piezoelectric element accommodating chamber 23 is also etched.

[0056] The seventh diagram from the top in FIG. 9 illustrates a state in which the oxide film 202 of the single-crystal silicon substrate 201 in the state illustrated in the sixth diagram from the top in FIG. 9 has been etched, followed by the second through-hole formation process of step S30 in FIG. 5 . Here, MACE is performed from the top to bottom in the diagram. The bottom diagram in FIG. 9 illustrates a state in which the Au film 204 of the single-crystal silicon substrate 201 in the state illustrated in the seventh diagram from the top in FIG. 9 has been etched. By forming the sealing plate 20 of this embodiment through the steps illustrated in FIG. 9 , it is possible to manufacture a sealing plate 20 having a shape similar to that of the sealing plate 20 of Example 1 formed through the steps illustrated in FIG. 4 .

[0057] The present invention is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit of the present invention. For example, a single-crystal silicon substrate such as the sealing plate 20 described above can be used for devices other than liquid ejection heads, such as micropumps. Furthermore, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate. [Explanation of symbols]

[0058] 1...liquid ejection head, 11...nozzle formation surface, 12...nozzle row, 12A...nozzle row, 12B...nozzle row, 20...sealing plate (single crystal silicon substrate), 20a...first surface (substrate surface), 20b...second surface (substrate surface), 21...first through hole, 21a...inclined side wall, 22...second through hole, 22a...vertical side wall, 23...piezoelectric element accommodating chamber, 24...opening, 24a...inclined surface, 30...cavity substrate, 30 a...third surface, 30b...fourth surface, 31...electrode portion, 32...piezoelectric element, 33...electrode film (conductive portion), 34...electrode film (conductive portion), 40...flow path substrate, 41...pressure chamber, 51...flow path, 51A...flow path, 51B...flow path, 51C...flow path, 51D...circulation flow path, 201...single crystal silicon substrate, 202...oxide film, 203...resist, 204...Au film (catalyst film), N...nozzle, P0...pitch, P1...pitch

Claims

1. A single crystal silicon substrate, at least a portion of which constitutes a liquid flow path, a first through hole having an inclined sidewall inclined with respect to a substrate surface of the single crystal silicon substrate; The flow path is formed by a vertical wall that is closer to a vertical plane than the inclined side wall. A second through hole having a side wall formed therein; Equipped with The first through hole is formed by crystal anisotropic etching, and the second through hole is formed by metal-assisted etching. A single crystal silicon substrate formed by chemical etching.

2. 2. The single crystal silicon substrate according to claim 1, The substrate surface includes a first surface on the side where the inclined sidewall is exposed and a second surface on the opposite side to the first surface. and the first through hole and the second through hole extend from the first surface to the second surface, The opening of the second through hole on the first surface side widens as it approaches the first surface. A single crystal silicon substrate having an inclined surface with respect to one surface.

3. The single crystal silicon substrate according to claim 1 or 2, a third surface on which a piezoelectric element and a conductive portion that is conductive to the piezoelectric element are formed; a cavity substrate having a fourth surface opposite to the third surface that configures the flow path; Equipped with When the third surface is bonded to the substrate surface, a part of the conductive portion is and the flow path is in communication with the second through hole. head.

4. A first etching target area on a first surface of a substrate surface of a single crystal silicon substrate is subjected to crystal anisotropic etching. By etching, a first through hole having an inclined sidewall inclined with respect to the substrate surface is formed. and A catalyst film is formed on a second etching target region on a second surface of the substrate opposite to the first surface. forming a The single crystal silicon substrate having the catalyst film formed thereon is brought into contact with an etching solution. The second etching target area is etched to form a vertical portion with respect to the second surface that is larger than the inclined sidewall. forming a second through hole having a sidewall with a nearly vertical sidewall; 1. A method for producing a single crystal silicon substrate, comprising:

5. 5. The method for producing a single crystal silicon substrate according to claim 4, In the step of forming the first through hole, an alkaline aqueous solution is used as an etching solution, In the step of forming the second through hole, the second through hole is formed by metal-assisted chemical etching.

4. A method for manufacturing a single crystal silicon substrate, comprising:

6. 6. The method for producing a single crystal silicon substrate according to claim 5, In the step of forming the catalyst film, the catalyst film is formed by electroless plating or vapor deposition.

4. A method for producing a single crystal silicon substrate, comprising:

7. 7. The method for producing a single crystal silicon substrate according to claim 4, In the step of forming the second through hole, the second through hole is formed from the second surface to the first surface. Penetrate, The second through hole has an opening on the first surface side, the opening being wider as it approaches the first surface. A method for manufacturing a single crystal silicon substrate, comprising the step of providing an inclined surface with respect to one surface. Law.

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