The present disclosure relates to a single crystal silicon substrate, a liquid discharge head, and a method for manufacturing a single crystal silicon substrate.
In the past, various silicon substrates have been used. Such silicon substrates are desirably used in various liquid discharge heads such as an ink-jet head that discharges ink as liquid. As a liquid discharge head including such a silicon substrate, for example, JP-A-2007-62035 discloses a liquid droplet discharge head including a flow path substrate and a sealing substrate that can be formed of silicon or the like.
The liquid discharge head is desirably small and has a high resolution. Here, in the liquid droplet discharge head of JP-A-2007-62035, a reservoir forming substrate that is the sealing substrate is provided with a first opening portion as a through-hole at which a wiring line electrically coupled to a piezoelectric element is arranged, and a through-hole that is an ink reservoir. Here, both the first opening portion and the ink reservoir are formed by anisotropic etching using potassium hydroxide as an etching solution. When a through-hole is formed by such a method, a side surface of the through-hole forms an inclined surface with respect to a substrate surface. Therefore, it can be said that a side surface of the first opening portion as a first through-hole clearly forms an inclined surface with respect to a substrate surface of the reservoir forming substrate as illustrated in a drawing, and a side surface of the ink reservoir as a second through-hole also forms an inclined surface with respect to the substrate surface of the reservoir forming substrate. However, when both the first through-hole and the second through-hole are configured such that the side surfaces form the inclined surfaces, the substrate surface needs to be widely configured, and there is a possibility that the liquid discharge head becomes large and a pitch between nozzles is increased to lower a resolution.
Thus, a single crystal silicon substrate according to the present disclosure for resolving the above problem is a single crystal silicon substrate at least a part of which constitutes a flow path for liquid, the single crystal silicon substrate including a first through-hole including an inclined side wall inclined with respect to a substrate surface of the single crystal silicon substrate, and a second through-hole constituting the flow path and including a side wall constituted by a vertical side wall more nearly vertical to the substrate surface than the inclined side wall is, wherein the first through-hole is formed by crystal anisotropic etching, and the second through-hole is formed by metal-assisted chemical etching.
Additionally, a method for manufacturing a single crystal silicon substrate according to the present disclosure for resolving the above problem includes subjecting a first etching target region of a first surface of a substrate surface of a single crystal silicon substrate to crystal anisotropic etching to form a first through-hole including an inclined side wall inclined with respect to the substrate surface, forming a catalyst film in a second etching target region of a second surface of the substrate surface of the single crystal silicon substrate, the second surface being opposite to the first surface, and bringing the single crystal silicon substrate with the catalyst film formed into contact with an etching solution to etch the second etching target region to form a second through-hole, the second through-hole including a side wall constituted by a vertical side wall more nearly vertical to the second surface than the inclined side wall is.
First, the present disclosure will be schematically described.
A single crystal silicon substrate according to a first aspect of the present disclosure for resolving the above problem is a single crystal silicon substrate at least a part of which constitutes a flow path for liquid, the single crystal silicon substrate including a first through-hole including an inclined side wall inclined with respect to a substrate surface of the single crystal silicon substrate, and a second through-hole constituting the flow path and including a side wall constituted by a vertical side wall more nearly vertical to the substrate surface than the inclined side wall is, wherein the first through-hole is formed by crystal anisotropic etching, and the second through-hole is formed by metal-assisted chemical etching.
According to the present 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 a through-hole by metal-assisted chemical etching, the through-hole can include a side wall more nearly vertical than in a case of forming a through-hole by crystal anisotropic etching. Therefore, the side wall of the second through-hole can be constituted by the vertical side wall substantially vertical to the substrate surface. Therefore, a single crystal silicon substrate having elaborate structure can be manufactured, and a liquid discharge head that is small and has a high resolution can be manufactured.
A single crystal silicon substrate according to a second aspect of the present disclosure is the single crystal silicon substrate according to the first aspect, further including, as the substrate surfaces, a first surface on a side where the inclined side wall is exposed, and a second surface opposite to the first surface, wherein the first through-hole and the second through-hole extend from the first surface to the second surface, and an opening portion of the second through-hole on the first surface side is provided with an inclined surface with respect to the first surface, the inclined surface widening toward the first surface.
According to the present aspect, the opening portion of the second through-hole on the first surface side is provided with the inclined surface with respect to the first surface that widens toward the first surface. Thus, it is possible to prevent or restrict burrs and the like from remaining in the opening portion. In addition, with such an opening portion, for example, when liquid is poured into the second through-hole from the opening portion, the liquid can be suitably poured.
A liquid discharge head according to a third aspect of the present disclosure includes the first or second single crystal silicon substrate, and a cavity substrate including a third surface at which a piezoelectric element and a conductive portion electrically coupled to the piezoelectric element are formed, and a fourth surface at least a part of which constitutes the flow path and that is opposite to the third surface, wherein the third surface is bonded to the substrate surface with a part of the conductive portion exposed through the first through-hole, and the flow path of the fourth surface communicates with the second through-hole.
According to the present aspect, the third surface is bonded to the substrate surface by the above single crystal silicon substrate and the cavity substrate with a part of the conductive portion exposed through the first through-hole, and the flow path of the fourth surface communicates with the second through-hole. Thus, it is possible to manufacture a liquid discharge head that is small and has a high resolution.
A method for manufacturing a single crystal silicon substrate according to a fourth aspect of the present disclosure includes subjecting a first etching target region of a first surface of a substrate surface of a single crystal silicon substrate to crystal anisotropic etching to form a first through-hole including an inclined side wall inclined with respect to the substrate surface, forming a catalyst film in a second etching target region of a second surface of the substrate surface, the second surface being opposite to the first surface, and bringing the single crystal silicon substrate with the catalyst film formed into contact with an etching solution to etch the second etching target region to form a second through-hole, the second through-hole including a side wall constituted by a vertical side wall more nearly vertical to the second surface than the inclined side wall is.
According to the present aspect, the first etching target region is subjected to crystal anisotropic etching to form the first through-hole including the inclined side wall, and the second etching target region with the catalyst film formed is etched to form the second through-hole including the side wall constituted by the vertical side wall. By forming a through-hole using a catalyst film as in metal-assisted chemical etching, it is possible to form a through-hole including a side wall more nearly vertical than when a through-hole is formed by crystal anisotropic etching. Therefore, the side wall of the second through-hole can be constituted by the vertical side wall substantially vertical to the substrate surface. Therefore, a single crystal silicon substrate having elaborate structure can be manufactured, and a liquid discharge head that is small and has a high resolution can be manufactured.
A method for manufacturing a single crystal silicon substrate according to a fifth aspect of the present disclosure is the method according to the fourth aspect, wherein while forming the first through-hole, an alkaline aqueous solution is used as the etching solution, and while forming the second through-hole, the second through-hole is formed by metal-assisted chemical etching.
According to the present aspect, while forming the first through-hole, an alkaline aqueous solution is used as an etching solution, and while forming the second through-hole, the second through-hole is formed by metal-assisted chemical etching. By manufacturing a single crystal silicon substrate in this manner, the single crystal silicon substrate can be manufactured easily and with high accuracy.
A method for manufacturing a single crystal silicon substrate according to a sixth aspect of the present disclosure is the method according to the fifth aspect, wherein while forming the catalyst film, the catalyst film is formed by an electroless plating method or a vapor deposition method.
According to the present aspect, the catalyst film is formed by an electroless plating method or a vapor deposition method. By manufacturing a single crystal silicon substrate in this manner, the single crystal silicon substrate can be manufactured particularly easily and with high accuracy.
A method for manufacturing a single crystal silicon substrate according to a seventh aspect of the present disclosure is the method according to any one of the fourth to sixth aspects, wherein while forming the second through-hole, the second through-hole is caused to extend from the second surface to the first surface, and forming the second through-hole includes providing an opening portion of the second through-hole on the first surface side with an inclined surface with respect to the first surface, the inclined surface widening toward the first surface.
According to the present aspect, the second through-hole is caused to extend from the second surface to the first surface, and the opening portion of the second through-hole on the first surface side is provided with the inclined surface with respect to the first surface that widens toward the first surface. Thus, it is possible to prevent or restrict burrs and the like from remaining in the opening portion. In addition, with such an opening portion, for example, when liquid is poured into the second through-hole from the opening portion, the liquid can be suitably poured.
Next, a liquid discharge head 1 of Example 1 of the present disclosure will be described in detail with reference to
When the plurality of nozzles N are arranged at a nozzle forming surface 11 that is a bottom surface of the line head, the nozzles N can be arranged most simply by arranging the nozzles N in the width direction B. However, when the nozzles N are arranged in such a manner, a pitch between the nozzles N adjacent in the width direction B is widened. When the pitch between the adjacent nozzles N is widened, a resolution is lowered. Therefore, in the liquid discharge head 1 of the present example, a plurality of nozzle rows 12 in which the nozzles N are aligned in straight lines are arranged so as to be inclined with respect to the moving direction A.
As illustrated in an enlarged view of the region X in
Note that, in addition to arranging the nozzle rows 12 so as to be inclined with respect to the moving direction A as described above, the interval between the adjacent nozzles N is narrowed, and thus it is possible to further increase the resolution. The liquid discharge head 1 of the present example is configured as illustrated in
The detailed configuration of the liquid discharge head 1 of the present example will be further described with reference to
The sealing plate 20 is a single crystal silicon substrate at least a part of which constitutes the flow path 51 of liquid. In addition, the sealing plate 20 includes a first surface 20a and a second surface 20b that is a surface opposite to the first surface 20a as substrate surfaces, and includes a first through-hole 21 including an inclined side wall 21a inclined with respect to the first surface 20a and the second surface 20b. In addition, the sealing plate 20 includes the second through-hole 22 that constitutes the flow path 51 and that includes a side wall constituted by a vertical side wall 22a more nearly vertical to the first surface 20a and the second surface 20b than the inclined side wall 21a is. Then, the second through-hole 22 is a part of the flow path 51, and serves as an ink reservoir. As described above, since the second through-hole 22 including the side wall constituted by the vertical side wall 22a that is nearly vertical serve as the ink reservoir, it is possible to prevent or restrict the sealing plate 20 from becoming large in a planar direction in which the substrate surface expands, and it is possible to reduce a size of the liquid discharge head 1.
The cavity substrate 30 includes a third surface 30a and a fourth surface 30b that is a surface opposite to the third surface 30a as substrate surfaces, and is bonded to the sealing plate 20 by the third surface 30a being bonded to the second surface 20b. Similar to the sealing plate 20, the cavity substrate 30 of the present example is also a single crystal silicon substrate, but is not limited to be the single crystal silicon substrate. Further, a piezoelectric element 32 and electrode films 33 and 34 as conductive portions electrically coupled to the piezoelectric element 32 are formed as an electrode portion 31 at the third surface 30a, and at least a part of the fourth surface 30b constitutes the flow path 51. Note that, a piezoelectric element accommodation chamber 23 is provided in a region of the sealing plate 20 corresponding to a formation position of the electrode portion 31. The electrode film 33 extends from the piezoelectric element accommodation chamber 23 to the first through-hole 21. From another viewpoint, a tape carrier package (TCP) is chip-on-flex (COF) mounted at the first through-hole 21. In the COF mounting, a dedicated tool is used for thermal compression bonding of the TCP, but by widening the first surface 20a side and narrowing the second surface 20b side at the time of the COF mounting, it is possible to prevent or restrict the sealing plate 20 or the cavity substrate 30 from becoming large in the planar direction, and it is possible to reduce the size of the liquid discharge head 1.
The flow path substrate 40 is provided with a pressure chamber 41 at a position facing the electrode portion 31 via the cavity substrate 30, and the pressure chamber 41 is provided with the nozzle N that discharges ink in a discharge direction D. The pressure chamber 41 forms a part of the flow path 51 and is coupled to the circulating flow path 51D, so that the ink which cannot be fully discharged from the nozzle N can be caused to flow to the circulating flow path 51D. When the electrode portion 31 is energized, the piezoelectric element 32 is deformed and the cavity substrate 30 vibrates, so that pressure is applied to the pressure chamber 41, and the ink in the pressure chamber 41 is discharged from the nozzle N in the discharge direction D.
Here, in the sealing plate 20 of the present example, 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). By forming a through-hole by MACE, it is possible to form a through-hole including a side wall more nearly vertical than when a through-hole is formed by crystal anisotropic etching. Therefore, the side wall of the second through-hole 22 can be constituted by the vertical side wall 22a substantially vertical to the first surface 20a and the second surface 20b that are the substrate surfaces. By forming the sealing plate 20 as described above, a single crystal silicon substrate having elaborate structure can be manufactured, and the liquid discharge head 1 that is small and has a high resolution can be manufactured. Further, by forming the first through-hole 21 by crystal anisotropic etching and forming the second through-hole 22 by metal-assisted chemical etching, etching can be performed in an all-wet state, without using dry etching that uses a large amount of greenhouse gases. For this reason, by forming the sealing plate 20 as described above, it is possible to improve productivity, and reduce an amount of electric power and use of greenhouse gases accompanying manufacturing.
Here, an angle formed by the vertical side wall 22a with respect to the substrate surface may be 90° plus or minus 2°. This is because by using a single crystal silicon wafer in which Miller indices (indices of crystal plane) of the substrate surface that is a front surface are (100) for the sealing plate 20, and devising composition of an etching solution, it is possible to manage vertical etching by MACE, for example, a thickness of the sealing plate 20 in a range of about 400 μm, and to secure verticality.
Further, an angle formed by the inclined side wall 21a with respect to the substrate surface may be from 45.0° to 54.7°. 54.7° is an angle formed by a front surface portion of the first surface 20a of the sealing plate 20 having the Miller indices (indices of crystal plane) of (100) and a crystal plane having Miller indices (indices of crystal plane) of (111) where etching progresses the slowest, and is a value of COS−1 (⅓1/2) in calculation. In addition, 45° is an angle formed by a crystal plane that is stable next and has Miller indices (indices of crystal plane) of (110), and is a value of COS−1 (½1/2). Note that, as compared with the case where the angle is 45°, an etching surface is more stable when the angle is 54.7°, and an entire size of the sealing plate 20 can be reduced.
In addition, the liquid discharge head 1 of the present example includes the sealing plate 20 that is the single crystal silicon substrate as described above, and the cavity substrate 30 that includes the third surface 30a and the fourth surface 30b as described above. Then, in the liquid discharge head 1 of the present example, the third surface 30a is bonded to the second surface 20b that is the substrate surface of the sealing plate 20 with a part of the conductive portion exposed via the first through-hole 21, and the flow path 51 partially constituted by the fourth surface 30b communicates with the second through-hole 22. As described above, the liquid discharge head 1 of the present example has the configuration in which 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 described above to expose a part of the conductive portion via the first through-hole 21, and the configuration in which the flow path 51 of the fourth surface 30b communicates with the second through-hole 22, and thus has a small size and a high resolution.
Next, a method for manufacturing the sealing plate 20 of the present example will be described with reference to
Next, a first through-hole forming step in step S20 of
Next, a second through-hole forming step in step S30 of
As described above, the method for manufacturing the sealing plate 20 of the present example as the method for manufacturing the single crystal silicon substrate includes the first through-hole forming step of step S20 for forming the first through-hole 21 including the inclined side wall 21a inclined with respect to the substrate surface, by performing crystal anisotropic etching on the first etching target region corresponding to the formation region of the first through-hole 21 of the first surface 20a of the substrate surface of the sealing plate 20 that is the single crystal silicon substrate. In addition, corresponding to the fourth and fifth diagrams from the top of
As described above, in the method for manufacturing the sealing plate 20 of the present example, the first etching target region is subjected to crystal anisotropic etching to form the first through-hole 21 including the inclined side wall 21a, and the second etching target region with the catalyst film formed is etched to form the second through-hole 22 including the side wall constituted by the vertical side wall 22a. By forming a through-hole by using a catalyst film as in MACE, it is possible to form a through-hole including a side wall more nearly vertical than when a through-hole is formed by crystal anisotropic etching. Therefore, the side wall of the second through-hole 22 can be constituted by the vertical side wall 22a substantially vertical to the substrate surface. Therefore, by performing the method for manufacturing the sealing plate 20 of the present example, it is possible to manufacture the sealing plate 20 having elaborate structure, and it is possible to manufacture the liquid discharge head 1 having a small size and a high resolution.
Here, in the first through-hole forming step of Step S20, a potassium hydroxide aqueous solution that is an alkaline aqueous solution is used as an etching solution, and in the second through-hole forming step of Step S30, the second through-hole 22 is formed by MACE. By manufacturing the sealing plate 20 in this manner, it is possible to manufacture the sealing plate 20 easily and with high accuracy. Note that, as the alkaline aqueous solution as the etching solution, for example, in addition to the potassium hydroxide aqueous solution used in the present example, a tetramethyl ammonium hydroxide (THAM) aqueous solution or the like can be suitably used, but no particular limitation is imposed thereon. The potassium hydroxide aqueous solution is inexpensive, and thus can be used, for example, for silicon substrate processing that does not involve a semiconductor. On the other hand, the THAM aqueous solution does not contain mobile ions such as Na and K, and thus can be used, for example, in crystal anisotropic etching processing for silicon substrate processing involving a semiconductor.
Note that, while forming the catalyst film in the etching preparation step of step S10, the method thereof is not particularly limited, but the catalyst film may be formed by an electroless plating method or a vapor deposition method. This is because the sealing plate 20 can be manufactured particularly easily and with high accuracy, by forming the catalyst film by the electroless plating method or the vapor deposition method to manufacture the sealing plate 20.
Next, a method for manufacturing the entire liquid discharge head 1 using the sealing plate 20 formed as described above will be described with reference to a flowchart of
Thereafter, in step S140, an ink protective film made of titanium oxide (TiOx), hafnium oxide (HfOx), or the like is formed as film by a chemical vapor deposition (CVD) method or the like to form the ink protective film. In addition, although the flow path substrate 40 is formed using an existing manufacturing method or the like in step S150, step S150 may be performed before step S140. Then, in step S160, the flow path substrate 40 is bonded to the substrate in which the sealing plate 20 and the cavity substrate 30 are bonded. Then, in step S170, this is divided into chips by laser scribing or the like, and in step S180, the TCP constituting the conductive portion is COF-mounted. Finally, in step S190, a case component is mounted to complete the manufacture of the liquid discharge head 1. In such a method, since a chip of the liquid discharge head 1 can be assembled in a wafer state, quality can be stabilized, and mass production becomes easy.
Hereinafter, a liquid discharge head of Example 2 will be described with reference to
Here, a top diagram of
Thereafter, when the oxide film 202 represented by SiO2 is formed at the entire single crystal silicon substrate 201, a state illustrated in a fourth diagram from the top of
As illustrated in the bottom diagram of
In addition, when the sealing plate 20 of the present example is manufactured, a manufacturing flow is the same as that of
Hereinafter, a liquid discharge head of Example 3 will be described with reference to
A top diagram of
A fourth diagram from the top of
Hereinafter, a liquid discharge head of Example 4 will be described with reference to
The sealing plate 20 of Example 1 to Example 3 is formed by performing MACE only from the second surface 20b side in the second through-hole forming step of Step S30. The sealing plate 20 of the present example 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 step of Step S30, and is the sealing plate 20 having the same shape as that of the sealing plate 20 of Example 1 formed through the stages illustrated in
A top diagram of
A fourth diagram from the top of
A seventh diagram from the top of
the present disclosure is not limited to the present examples described above, and can be realized in various configurations without departing from the gist of the present disclosure. For example, a single crystal silicon substrate such as the sealing plate 20 described above can be used in a micropump or the like, other than the liquid discharge head. Further, appropriate replacements or combinations may be made to the technical features in the present examples which correspond to the technical features in the aspects described in the SUMMARY section to solve some or all of the problems described above or to achieve some or all of the advantageous effects described above. Additionally, when the technical features are not described herein as essential technical features, such technical features may be deleted appropriately.
Number | Date | Country | Kind |
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2022-078679 | May 2022 | JP | national |