Laminate substrate and manufacturing method thereof, and liquid discharge head

Abstract

To suppress variation in hole width of a silicon substrate at a boundary between the silicon substrate and a silicon oxide film.SOLUTION: A laminate substrate 8 includes a silicon substrate 9, and a silicon oxide film 10 laminated on the silicon substrate 9. The silicon oxide film 10 has an open hole 12 penetrating in a thickness direction X, and the silicon substrate 9 has an open hole 13 communicating with the open hole 12. The open hole 13 has a first portion 17 adjacent to the open hole 12, and a second portion 18 adjacent to the first portion 17 on an opposite side of the open hole 12. The first portion 17 has a plurality of first recesses 14A of which the width varies periodically in the thickness direction X. The second portion 18 has a plurality of second recesses 14B of which the width varies periodically in the thickness direction X. A maximal value W1 of the width of the first recesses 14A is smaller than a maximal value W2 of the width of the second recesses 14B.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a laminated substrate, a manufacturing method thereof, and a liquid ejection head. [Background technology]

[0002] Patent Document 1 describes a liquid ejection head used in inkjet printers, etc., in which a liquid ejection flow path is formed in a laminated substrate of a silicon substrate and a silicon oxide film. Patent Document 2 describes the formation of a liquid ejection flow path in a silicon substrate by dry etching, which is a so-called Bosch process, in which isotropic etching, formation of a sidewall protection film, and anisotropic etching are repeated. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7119943 specification [Patent Document 2] International Publication No. 2016 / 158917 Summary of the Invention [Problem to be solved by the invention]

[0004] When forming a through hole penetrating the silicon oxide film in the laminated substrate described in Patent Document 1 and further forming a hole communicating with the through hole in the silicon substrate, it is possible to apply the Bosch process described in Patent Document 2. In this case, reaction products generated by etching the silicon oxide film are deposited at the bottom of the through hole in the silicon oxide film. The deposited reaction products are removed by the Bosch process, but the thickness of the reaction products varies within the wafer surface. For this reason, the width of the hole in the silicon substrate may vary within the wafer surface at the boundary between the silicon substrate and the silicon oxide film.

[0005] An object of the present invention is to provide a laminated substrate capable of suppressing variations in width of a hole in a silicon substrate at the boundary between the silicon substrate and a silicon oxide film. [Means for solving the problem]

[0006] The laminated substrate of the present invention has a silicon substrate and a silicon oxide film laminated on the silicon substrate. The silicon oxide film has a through hole penetrating in the thickness direction, and the silicon substrate has a hole communicating with the through hole. The hole has a first portion adjacent to the through hole and a second portion adjacent to the first portion on the opposite side of the through hole. The first portion has a plurality of first recesses whose widths change periodically in the thickness direction, and the second portion has a plurality of second recesses whose widths change periodically in the thickness direction. The maximum width of the first recesses is smaller than the maximum width of the second recesses. Effect of the Invention

[0007] According to the present invention, it is possible to provide a laminated substrate capable of suppressing variations in width of a hole in a silicon substrate at the boundary between the silicon substrate and a silicon oxide film. [Brief description of the drawings]

[0008] [Figure 1] 1 is a partial cross-sectional view of a liquid ejection head according to an embodiment of the present invention. [Diagram 2] 2 is a partial cross-sectional view of a laminated substrate of the liquid ejection head shown in FIG. [Diagram 3] 1A to 1C are diagrams illustrating an outline of a manufacturing process for a laminated substrate according to a comparative example. [Figure 4] FIG. 1 is a schematic diagram of an apparatus used for etching. [Diagram 5] FIG. 4 is a partial cross-sectional view of a laminated substrate of a comparative example. [Figure 6] 2A to 2C are diagrams illustrating an outline of a manufacturing process for a laminated substrate of the liquid ejection head shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a laminated substrate according to an embodiment of the present invention will be described with reference to the drawings. The embodiment described below is one example of a technically preferred form of the present invention, and the present invention is not limited to this embodiment. Each figure is a schematic diagram, and the shape, size, number, etc. of each part are merely examples. The laminated substrate of the embodiment shown below is applied to a liquid ejection head using a piezoelectric element, but can also be applied to a liquid ejection head using a heating resistor element or an electrothermal conversion element. The ejected liquid is not limited to ink as long as it can be ejected from the liquid ejection head.

[0010] In the following explanation and drawings, the thickness direction X means the direction in which the silicon substrate and the silicon oxide film are stacked. Thickness and depth mean the dimension in the thickness direction X or the thickness direction of the wafer. Any direction perpendicular to the thickness direction X is called the radial direction R. Width means the dimension in the radial direction R, and is equal to the diameter in the case of a hole or through hole with a circular cross section.

[0011] 1 shows a partial cross-sectional view of a liquid ejection head 1. The liquid ejection head 1 has an actuator substrate 2 and an ejection port forming substrate 3 bonded to the actuator substrate 2. The actuator substrate 2 has a piezoelectric element 4, a vibration membrane 5 laminated on the piezoelectric element 4, and a liquid supply path 6 penetrating the actuator substrate 2 in the thickness direction X. The piezoelectric element 4 is an energy generating element that imparts energy to ink for ejection. A pressure chamber 7 is formed between the vibration membrane 5 and the ejection port forming substrate 3, and ink is filled into the pressure chamber 7 through the liquid supply path 6.

[0012] The ejection port forming substrate 3 has a laminated substrate 8 in which a silicon substrate 9 and a silicon oxide film 10 are laminated. The laminated substrate 8 is created in a wafer process. The laminated substrate 8 has a liquid ejection flow path 11 penetrating the ejection port forming substrate 3 in the thickness direction X. An ejection port 12 from which ink is ejected is formed on the most downstream side in the ejection direction of the liquid ejection flow path 11. By applying a drive voltage with a pull-push-pull waveform to the piezoelectric element 4, the vibration membrane 5 vibrates, and the pressure chamber 7 repeatedly expands and contracts. By pressurizing the ink in the pressure chamber 7, the ink is ejected through the liquid ejection flow path 11.

[0013] FIG. 2 is an enlarged view of part A in FIG. 1, showing a partial cross-sectional view of the laminated substrate 8. FIG. 2(a) shows a cross-sectional view of the laminated substrate 8 formed on the outer periphery of the wafer, and FIG. 2(b) shows a cross-sectional view of the laminated substrate 8 formed on the inner periphery of the wafer. The configurations of the laminated substrate 8 formed on the outer periphery of the wafer and the laminated substrate 8 formed on the inner periphery of the wafer are slightly different, the reason for which will be described later. The silicon oxide film 10 has a back surface (hereinafter referred to as a first surface S1) of the surface in contact with the silicon substrate 9, and a contact surface (hereinafter referred to as a second surface S2) with the silicon substrate 9. The silicon substrate 9 has a contact surface (hereinafter referred to as a third surface S3) with the silicon oxide film 10. The first to third surfaces S1 to S3 are parallel to each other.

[0014] The silicon oxide film 10 has a first through hole 12 penetrating in the thickness direction X, and the silicon substrate 9 has a second through hole 13 penetrating in the thickness direction X and communicating with the first through hole 12. The first through hole 12 and the second through hole 13 form a liquid discharge flow path 11. The central axes of the first through hole 12 and the second through hole 13 are generally aligned. Depending on the application of the laminated substrate 8, the silicon substrate 9 may be provided with a hole, instead of the second through hole 13, that communicates with the first through hole 12 and terminates midway in the thickness direction X.

[0015] The first through hole 12 can be formed by dry etching such as reactive ion etching (RIE). The combination of silicon oxide film 10 and RIE allows highly anisotropic etching in the thickness direction X, so that large irregularities are not formed on the side wall of the first through hole 12. The second through hole 13 is formed by dry etching (Bosch process) in which isotropic etching, formation of a side wall protective film, and anisotropic etching are repeated, so that the amount of side etching, i.e., the amount of etching in the radial direction R, is greater than that of the first through hole 12. As a result, a periodic recessed structure in which a plurality of recesses 14 called scallops are continuous in the thickness direction X is formed on the side of the second through hole 13. The recesses 14 are annular grooves extending circumferentially on the side of the second through hole 13, and have a cross-sectional shape that is approximately semicircular.

[0016] The width W of the first through hole 12 decreases monotonically from the first surface S1 to the second surface S2. Since the silicon oxide film 10 is located outside the silicon substrate 9, that is, downstream in the ink ejection direction, at least the downstream side of the liquid ejection flow path 11 has a relatively smooth tapered side. Since the first through hole 12 is formed in almost the same shape in any region of the wafer, it is possible to suppress the variation in the diameter of the ejection port 12 within the wafer. In addition, when the pressure chamber 7 expands, the ink is drawn in and a meniscus is stretched in the first through hole 12 of the silicon oxide film 10. Since the first through hole 12 has a tapered shape, the meniscus is stably formed near the boundary between the first through hole 12 and the second through hole 13, compared to when the first through hole 12 has a constant cross section. In order to stably form the meniscus, it is preferable that the average inclination angle θ of the side surface 15 of the first through hole 12 with respect to the second surface S2 is 60° or more and less than 90°.

[0017] (Comparative Example) In order to explain the effect of this embodiment, the configuration and manufacturing method of a laminated substrate 108 of a comparative example will be described with reference to FIGS. 3 to 5. FIG. 3 shows an outline of the manufacturing process of the laminated substrate 108 of the comparative example. First, as shown in FIG. 3(a), a laminated substrate 108 in which a silicon substrate 9 and a silicon oxide film 10 are laminated is prepared. Next, in order to form a first through hole 12 in the silicon oxide film 10, a photoresist 16 is applied as shown in FIG. 3(b), and a pattern of the first through hole 12 is formed by photolithography. Next, as shown in FIG. 3(c), the silicon oxide film 10 is etched through the photoresist 16 to form the first through hole 12. FIG. 4 shows an outline of an etching apparatus 31 used in the comparative example. A wafer WA is carried into a chamber 32 and is adsorbed and held on a sample stage 33. Microwaves are supplied to the chamber 32, and the gas inside the chamber 32 is excited by the microwaves and a magnetic field generated by a coil 34, and plasma is formed in the space above the wafer WA. A high frequency bias power is applied to the sample stage 33, and ions in the plasma are incident on the wafer WA, thereby etching the wafer WA.

[0018] When the silicon oxide film 10 is etched, reaction by-products 41 and 42 are generated. The reaction by-products 41 and 42 penetrate into the first through-holes 12 and are deposited at the bottoms of the first through-holes 12, i.e., on the upper surface of the silicon substrate 9. The reaction by-products 41 on the outer periphery side of the wafer and the reaction by-products 42 on the inner periphery side of the wafer have the same components, but the reaction by-products 42 on the inner periphery side of the wafer have a thicker film thickness than the reaction by-products 41 on the outer periphery side of the wafer. This difference in film thickness occurs because the gas distribution in the chamber 32 is different between the inner and outer periphery parts of the wafer.

[0019] Next, as shown in FIG. 3(d), the silicon substrate 9 is etched through the photoresist 16 and the first through hole 12 to form holes 43 and 44 that will become the second through hole 13. The etching is performed by the Bosch process. Since the reaction by-products 41 and 42 are deposited in the first through hole 12, the first few cycles of the Bosch process are used to remove the reaction by-products 41 and 42, which are etching inhibitors, and do not contribute to the etching of the silicon substrate 9. Etching of the silicon substrate 9 starts from the first through hole 12 from which the reaction by-products 41 and 42 have been removed. Since the reaction by-products 41 are removed from the first through hole 12 on the outer periphery side of the wafer before the reaction by-products 41 are removed from the first through hole 12 on the inner periphery side of the wafer, the formation of the hole 43 on the outer periphery side of the wafer starts at a stage where the reaction by-products 42 on the inner periphery side of the wafer remain.

[0020] As shown in FIG. 3(e), the reaction by-products 42 on the inner circumference side of the wafer are removed, and the formation of the hole 44 on the inner circumference side of the wafer to become the second through hole 13 is started. Since the formation of the hole 44 on the inner circumference side of the wafer starts halfway through the first cycle that contributes to etching the silicon substrate 9, the recess 14 near the boundary with the silicon oxide film 10 is smaller than the hole 43 on the outer circumference side of the wafer (see FIG. 5). Thereafter, as shown in FIG. 3(f), the Bosch process is continued, and the holes 43, 44 in the silicon substrate 9 become deeper. However, since a protective film is formed on the sidewall in the Bosch process, the shape of the holes 43, 44 formed in the first cycle, i.e., the holes 43, 44 near the boundary with the silicon oxide film 10, hardly changes. Although not shown, the Bosch process is further continued to form the second through hole 13 in the silicon substrate 9.

[0021] Fig. 5 shows cross-sectional views of the first through hole 12 and the second through hole 13 of a laminated substrate 108 of a comparative example. Fig. 5(a) shows a cross-sectional view of the first through hole 12 and the second through hole 13 on the outer peripheral side of the wafer, and Fig. 5(b) shows a cross-sectional view of the first through hole 12 and the second through hole 13 on the inner peripheral side of the wafer. As described above, a recess 14 is formed on the side of the second through hole 13 due to the Bosch process. The dimensions are defined as follows. D1: width of the recess 14 on the outer periphery of the wafer at the boundary with the silicon oxide film 10 D2: Width of the recess 14 on the inner periphery of the wafer at the boundary with the silicon oxide film 10 D3: Width of the first through hole 12 at the boundary with the silicon substrate 9 on the outer periphery of the wafer D4: Width of the first through hole 12 at the boundary with the silicon substrate 9 on the inner periphery side of the wafer In the comparative example, D1 > D2. This is because the size of the recess 14 adjacent to the silicon oxide film 10 is different between the inner peripheral side and the outer peripheral side of the wafer. On the other hand, since the etching of the silicon oxide film 10 proceeds in the same manner on the inner peripheral side and the outer peripheral side of the wafer, D3 and D4 are approximately equal. There is almost no difference between D2 and D4 on the inner peripheral side of the wafer, and a difference between D1 and D3 occurs on the outer peripheral side of the wafer. In an actual Bosch process, the difference between D1 and D3 reaches about several micrometers, so a flow resistance occurs in the liquid discharge flow path 11 during discharge. Also, the flow resistance of the liquid discharge flow path 11 varies between the inner peripheral side and the outer peripheral side of the wafer.

[0022] In the comparative example, a new cycle of the Bosch process was started at the timing when the reaction by-products 41 on the outer peripheral side of the wafer were just removed, so D1 > D2. However, the timing at which the formation of the second through-hole 13 in the silicon substrate 9 is started depends on the relationship between the thickness of the reaction by-products 41 and 42 and the removal amount per unit time. For example, depending on the thickness of the reaction by-products 41 and 42, a new cycle of the Bosch process may be started at the timing when the reaction by-products 42 on the inner peripheral side of the wafer are just removed, and in this case, D1 < D2 may occur. For this reason, the magnitude relationship of D1 to D4 is not limited to the relationship shown in FIG. 5, but since the thickness of the reaction by-products 41 and 42 is different between the inner peripheral side and the outer peripheral side of the wafer, the difference between D1 - D3 and D2 - D4 is the same in that it is different between the inner peripheral side and the outer peripheral side of the wafer.

[0023] (Schematic manufacturing process of the laminated substrate 8 of the present embodiment) Referring to FIGS. 2 and 6, the schematic manufacturing process of the laminated substrate 8 of the present embodiment will be described. The etching apparatus 31 used in the present embodiment is the same as that in FIG. 4. The processes shown in FIGS. 6(a) to 6(c) are the same as the processes shown in FIGS. 3(a) to 3(c) of the comparative example, so the description thereof will be omitted. Similar to the comparative example, the reaction by-products 42 on the inner peripheral side of the wafer have a thicker film thickness than the reaction by-products 41 on the outer peripheral side.

[0024] In the steps shown in Figs. 6(d) to 6(f), the second through-hole 13 is formed penetrating the silicon substrate 9 in the thickness direction X. First, as shown in Fig. 6(d), the silicon substrate 9 is etched through the photoresist 16 and the first through-hole 12 to form the hole 43 to become the second through-hole 13. The etching is performed by the Bosch process. Since the reaction by-products 41 and 42 are deposited in the first through-hole 12, the first few cycles of the Bosch process are used to remove the reaction by-products 41 and 42, which are etching inhibitors, and do not contribute to the etching of the silicon substrate 9. Since the reaction by-products 41 are removed from the first through-hole 12 on the outer periphery side of the wafer before the reaction by-products 41 are removed from the first through-hole 12 on the inner periphery side of the wafer, the formation of the hole 43 on the outer periphery side of the wafer is started at the stage where the reaction by-products 42 on the inner periphery side of the wafer remain. The above points are the same as those of the comparative example.

[0025] In this embodiment, the etching conditions are changed between the first few cycles (hereinafter referred to as the initial cycles) of the Bosch process for forming the second through hole 13 and the remaining cycles thereafter (hereinafter referred to as the final cycle). Figures 6(d) and 6(e) show the initial cycles, and Figure 6(f) shows the final cycle. The portion of the holes 43, 44 formed in the initial cycle is referred to as the first portion 17, and the portion of the holes 43, 44 formed in the final cycle is referred to as the second portion 18 (see Figure 2). That is, the process of forming the holes 43, 44 includes a process of forming the first portion 17 adjacent to the first through hole 12, and a process of forming the second portion 18 adjacent to the first portion 17 on the opposite side of the first through hole 12 after forming the first portion 17.

[0026] In the initial cycle, the amount of silicon etched per unit time is reduced compared to the final cycle. In order to reduce the amount of silicon etched per unit time, at least one of the following measures may be changed: shortening the dry etching time per cycle, reducing the output of the coil 34, or reducing the pressure of the chamber 32 compared to the final cycle. As shown in Figs. 6(d) and 6(e), the initial cycle continues until the reaction by-products 42 on the inner circumference side of the wafer are removed and the formation of the holes 44 on the inner circumference side of the wafer is started. The formation of the holes 43, 44 starts first on the outer circumference side of the wafer, and a small recess 14 is formed on the side of the hole 43. On the inner circumference side of the wafer, the formation of the holes 44 starts later than on the outer circumference side of the wafer, and a small recess 14 is similarly formed on the side of the hole 44. The timing of transition from the initial cycle to the final cycle can be calculated in advance from the initial thickness of the reaction by-products 42 on the inner circumference side of the wafer and the amount of the reaction by-products 42 removed per cycle in the initial cycle. The initial thickness of the reaction by-products 42 can be obtained by testing.

[0027] 6(f), the Bosch process is continued in a final cycle in which the amount of silicon etched per unit time is increased, and second through-holes 13 are formed in the silicon substrate 9. After the reaction by-products 41 and 42 are removed from the entire wafer, the final cycle in which the amount of silicon etched per unit time is increased is performed, thereby shortening the time required to form the second through-holes 13. When the second through-holes 13 are formed over the entire wafer, the final cycle is completed.

[0028] FIG. 2 shows cross sections of the first through hole 12 and the second through hole 13 formed by the above process. As described above, the second through hole 13 has a first portion 17 adjacent to the first through hole 12 and a second portion 18 adjacent to the first portion 17 on the opposite side of the first through hole 12. The first portion 17 has a plurality of first recesses 14A whose widths change periodically in the thickness direction X. The second portion 18 has a plurality of second recesses 14B whose widths change periodically in the thickness direction X. The maximum width W1 of the first recesses 14A is smaller than the maximum width W2 of the second recesses 14B. According to this embodiment, even if reaction by-products 41 and 42 are present, D1 and D2 have approximately the same value over the entire wafer, so that the difference between D1-D3 and D2-D4 is also approximately constant over the entire wafer, and the variation in flow resistance of the liquid discharge flow path 11 can be suppressed. In addition, since the period during which the initial cycle is performed is limited, the overall processing time does not increase significantly from the comparative example.

[0029] (Example) The present invention will be described in more detail with reference to an embodiment. In the embodiment, the ejection port forming substrate 3 shown in FIG. 2 was produced. The manufacturing process was the same as that shown in FIG. 6. First, as shown in FIG. 6(a), a wafer was prepared in which a silicon oxide film 10 having a thickness of 0.5 μm was laminated on the surface of a silicon substrate 9 having a thickness of 20 μm. In order to ensure strength during the process, the thickness of the wafer was set to 625 μm except for the portion to be processed. Next, as shown in FIG. 6(b), a photoresist 16 was applied to the silicon oxide film 10 to a thickness of 15 μm, and an opening was formed in the photoresist 16 by irradiating it with ultraviolet light and developing it. The opening was a circle having a diameter of 30 μm as viewed from the thickness direction X.

[0030] Next, as shown in FIG. 6(c), the silicon oxide film 10 was etched by RIE to form the first through-hole 12. A mixed gas of C4F8 gas, CF4 gas, and Ar gas was used as the gas used for etching. The gas pressure was 0.3 Pa, the gas flow rate was 500 sccm, the output of the coil 34 was 1500 W, and the platen output was 400 W. The angle θ between the side surface 15 of the first through-hole 12 and the contact surface (second surface S2) of the silicon oxide film 10 with the silicon substrate 9 was about 80°. At the bottom of the first through-hole 12, a reaction by-product 41 with a thickness of 50 nm was deposited on the outer periphery of the wafer, and a reaction by-product 42 with a thickness of 60 nm was deposited on the inner periphery of the wafer.

[0031] Next, as shown in FIG. 6(d), the silicon substrate 9 was etched through the openings in the photoresist 16 and the first through-holes 12 by a Bosch process using SF6, and the first portion 17 of the second through-hole 13 was formed in the silicon substrate 9 on the outer periphery of the wafer. The etching conditions were a coil 34 output of 2000 W and an etching time of 0.6 seconds. The Bosch process was performed multiple times, and the reaction by-products 41 on the outer periphery of the wafer were removed. Thereafter, etching of the silicon substrate 9 was started on the outer periphery of the wafer, and the first portion 17 having the first recess 14A with a dimension T1 of 0.4 μm in the thickness direction X was formed. Before the formation of the first portion 17 on the outer periphery of the wafer was started, a processing time equivalent to a depth of 2.4 μm of the silicon substrate 9 was consumed to remove the reaction by-products 41 on the outer periphery of the wafer with a thickness of 50 nm. During this time, the reaction by-products 42 on the inner periphery of the wafer were also removed, but not completely.

[0032] Next, as shown in Fig. 6(e), a first portion 17 of the second through hole 13 was formed on the inner circumference side of the wafer by a Bosch process under the same etching conditions as in Fig. 6(d). Before the formation of the first portion 17 on the inner circumference side of the wafer was started, a processing time equivalent to a depth of 3.2 µm of the silicon substrate 9 was consumed. As the etching of the silicon substrate 9 continued on the outer circumference side of the wafer, the depth of the first portion 17 on the outer circumference side of the wafer reached 1.6 µm.

[0033] In order to form the first portion 17 over the entire wafer, it is necessary to secure a certain depth of the first portion 17 on the outer periphery of the wafer. For example, in the case of the Bosch process in which the silicon substrate 9 is etched by 0.8 μm per cycle, if the thickness of the silicon oxide film 10 is 0.5 μm, four cycles are required on the inner periphery of the wafer and three cycles are required on the outer periphery of the wafer to remove the reaction by-products 41 and 42. In other words, the silicon substrate 9 is etched by 0.8 μm on the outer periphery of the wafer until the reaction by-products 42 on the inner periphery of the wafer are completely removed. Therefore, in order to form the first portion 17 over the entire wafer, it is necessary to form the first portion 17 to a depth of at least 0.8 μm on the outer periphery of the wafer. In other words, it is preferable that the first portion 17 includes a portion that is 0.8 μm or more away from the contact surface between the silicon oxide film 10 and the silicon substrate 9.

[0034] The dimension T1 in the thickness direction X of the recess 14 in the first portion 17 can be determined based on the formation accuracy in the in-plane direction of the liquid ejection flow path 11. For example, if the formation accuracy in the in-plane direction of the liquid ejection flow path 11 is to be within 0.2 μm, the dimension T2 in the radial direction R of the recess 14 on one side may be set to within 0.1 μm. Since the ratio of T1 to T2 is about 3, the dimension T1 of the recess 14 in the first portion 17 may be set to about 0.3 μm or less, or to 0.25 μm or less with a margin of error.

[0035] Next, as shown in FIG. 6(f), the output of the coil 34 was increased from 2000 W to 2500 W, and the etching time was increased from 0.6 seconds to 2.5 seconds (final cycle), and the Bosch process was continued. A second portion 18 having a second recess 14B was formed over the entire area of ​​the wafer. After that, although not shown in the figure, the Bosch process was continued under the same conditions to form a second through hole 13 having a depth of 20 μm. Thereafter, the photoresist 16 was peeled off, and the ejection port formation substrate 3 shown in FIG. 2 was obtained.

[0036] (Additional Note) This specification includes the following disclosure. [Configuration 1] A silicon substrate and a silicon oxide film laminated on the silicon substrate, the silicon oxide film has a through hole penetrating in a thickness direction, the silicon substrate has a hole communicating with the through hole, The hole has a first portion adjacent to the through hole and a second portion adjacent to the first portion on an opposite side of the through hole, the first portion has a plurality of first recesses whose widths change periodically in the thickness direction, the second portion has a plurality of second recesses whose widths change periodically in the thickness direction, A laminated substrate, wherein the maximum width of the first recess is smaller than the maximum width of the second recess. [Configuration 2] The laminated substrate according to configuration 1, wherein the silicon oxide film has a contact surface with the silicon substrate and a back surface of the contact surface, and the width of the through hole monotonically decreases from the back surface to the contact surface. [Configuration 3] 3. The laminated substrate according to configuration 2, wherein an average inclination angle of the side surface of the through hole with respect to the contact surface is 60° or more and less than 90°. [Configuration 4] 4. The laminated substrate of any one of configurations 1 to 3, wherein the first portion includes a portion that is 0.8 μm or more away from a contact surface between the silicon oxide film and the silicon substrate, and the length of each recess in the first portion in the thickness direction is 0.25 μm or less. [Configuration 5] 5. The laminated substrate of any one of configurations 1 to 4, wherein the hole is a through hole. [Configuration 6] A laminated substrate according to configuration 5 and an energy generating element, the through hole and the hole form a liquid ejection flow path through which liquid is ejected; The energy generating element applies energy to the liquid for ejection. [Method 1] forming a through hole penetrating in a thickness direction in a silicon oxide film laminated on a silicon substrate; forming a hole in the silicon substrate that communicates with the through hole; forming the hole includes forming a first portion adjacent to the through hole, and forming a second portion adjacent to the first portion on the opposite side of the through hole after forming the first portion; the first portion has a plurality of first recesses whose widths change periodically in the thickness direction, the second portion has a plurality of second recesses whose widths change periodically in the thickness direction, A method for manufacturing a laminated substrate, wherein the maximum width of the first recess is smaller than the maximum width of the second recess. [Method 2] The method for manufacturing a laminated substrate according to method 1, wherein the hole is formed by dry etching that repeats isotropic etching, formation of a sidewall protective film, and anisotropic etching, and the step of forming the first portion etches the silicon substrate by a smaller amount per unit time than the step of forming the second portion. [Method 3] The method for manufacturing a laminated substrate according to method 2, wherein reducing the amount of etching of the silicon substrate per unit time is achieved by at least one of shortening the dry etching time per cycle, reducing the coil output of an etching apparatus, and reducing the chamber pressure. [Explanation of symbols]

[0037] 8. Laminated Board 9 Silicon Substrate 10 Silicon oxide film 12 First through hole 13 Second through hole

Claims

1. A silicon substrate and a silicon oxide film laminated on the silicon substrate, the silicon oxide film has a through hole penetrating in a thickness direction, the silicon substrate has a hole communicating with the through hole, the hole has a first portion adjacent to the through hole and a second portion adjacent to the first portion on an opposite side of the through hole; the first portion has a plurality of first recesses whose widths change periodically in the thickness direction, the second portion has a plurality of second recesses whose widths change periodically in the thickness direction, A laminated substrate, wherein the maximum width of the first recess is smaller than the maximum width of the second recess.

2. 2. The laminated substrate according to claim 1, wherein the silicon oxide film has a contact surface with the silicon substrate and a back surface of the contact surface, and the width of the through hole monotonically decreases from the back surface to the contact surface.

3. The laminated substrate according to claim 2 , wherein an average inclination angle of the side surface of the through hole with respect to the contact surface is equal to or greater than 60° and less than 90°.

4. 4. The laminated substrate according to claim 1, wherein the first portion includes a portion that is 0.8 μm or more away from a contact surface between the silicon oxide film and the silicon substrate, and a length in the thickness direction of each recess of the first portion is 0.25 μm or less.

5. The laminated substrate according to claim 1 , wherein the hole is a through hole.

6. A laminated substrate according to claim 5 and an energy generating element, the through hole and the hole form a liquid ejection flow path through which liquid is ejected; The energy generating element applies energy to the liquid for ejection.

7. forming a through hole penetrating in a thickness direction in a silicon oxide film laminated on a silicon substrate; forming a hole in the silicon substrate that communicates with the through hole; forming the hole includes forming a first portion adjacent to the through hole, and forming a second portion adjacent to the first portion on an opposite side of the through hole after forming the first portion; the first portion has a plurality of first recesses whose widths change periodically in the thickness direction, the second portion has a plurality of second recesses whose widths change periodically in the thickness direction, A method for manufacturing a laminated substrate, wherein the maximum width of the first recess is smaller than the maximum width of the second recess.

8. 8. The method for manufacturing a laminated substrate according to claim 7, wherein the hole is formed by dry etching that repeats isotropic etching, formation of a sidewall protective film, and anisotropic etching, and the step of forming the first portion etches the silicon substrate by a smaller amount per unit time than the step of forming the second portion.

9. 9. The method for manufacturing a laminated substrate according to claim 8, wherein the etching amount of the silicon substrate per unit time is reduced by at least one of shortening a dry etching time per cycle, reducing a coil output of an etching apparatus, and reducing a chamber pressure.

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