Method for manufacturing a substrate and method for manufacturing a substrate for a liquid discharge head

Abstract

To provide a method for forming a deposit film containing HFO dissolved in a peeling liquid, in silicon etching using the deposit film.SOLUTION: A method for processing a silicon substrate alternately and repeatedly performs an etching step of forming an etching pattern on a silicon substrate, and a protective film formation step of forming a protective film on a wall surface of the silicon substrate exposed in the etching step, wherein the protective film formation step includes a protective film removal step of removing the protective film formed in the protective film formation step using a peeling liquid, and the protective film formation step forms the protective film using mixed gas of 2,3,3,3-tetrafluoropropene and perfluorocyclobutane.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for processing a silicon substrate, and more particularly to a method for processing a silicon substrate used for a liquid ejection head. [Background technology]

[0002] In general MEMS (Micro Electro Mechanical Systems) processing and some semiconductor device processing, there are many examples of processing structures that penetrate silicon substrates or have a similar depth. Currently, the silicon substrates used in liquid ejection heads are processed by applying the microfabrication technology of semiconductor devices. In general liquid ejection heads used in liquid ejection printing methods, a flow path forming member is formed on a silicon substrate.

[0003] The flow path forming member is composed of an ejection port for ejecting droplets and a liquid flow path connected to the ejection port. Generally, a plurality of liquid flow paths are arranged in a row. An ejection energy generating element is provided on the silicon substrate in a portion of the liquid flow path, and droplets are ejected from the ejection port by energy generated by the ejection energy generating element. The silicon substrate is also formed with a plurality of liquid supply ports connected to each liquid flow path, and a common liquid chamber communicating with these liquid supply ports.

[0004] In such a configuration, for example, the liquid is heated and bubbled using thermal energy from an ejection energy generating element such as an ejection heater, and droplets are ejected from the ejection orifice. At that time, the liquid is supplied from the supply port to the liquid flow path, and the liquid is supplied from the common liquid chamber to the supply port.

[0005] When forming such a supply port, an opening in the silicon substrate is required, and vertical processing by dry etching is sometimes used from the viewpoint of improving density, etc. For etching of the silicon substrate, plasma etching is preferably used, which alternately repeats an etching step and a deposition film formation step. Specifically, it is a technology consisting of a cycle in which the following three steps are continuously repeated in order. (1) Silicon etching step using fluorine radicals (2) Fluorocarbon-based deposition film formation step (3) Removal of the deposition film at the bottom of the pattern using ions

[0006] By protecting the sidewalls of the etching pattern formed in step (1) with the deposition film (hereinafter referred to as the deposition film) formed in step (2), a vertical etching shape can be achieved. This enables high-speed processing of silicon. The process gas used in step (2) is perfluorocyclobutane (C 4 F 8 ), and steps (1) and (3) are sulfur hexafluoride (SF 6 ) is usually used. The gas used in step (2) is hereafter referred to as depogas.

[0007] In the above-mentioned step (2), as shown in Patent Document 1, 2,3,3,3-tetrafluoropropene may be used as the deposition gas. This gas has the rational formula C 3 H 2 F 4 It is written as "HFO" and is sometimes abbreviated as HFO. The deposition film formed with HFO is C 4 F 8 It is known that the protective film functions at a thinner thickness than the conventional method. Therefore, the deposition time is shorter, and the etching time to remove the bottom deposition film is shorter. This is synonymous with an improved etching rate, and as a result, there is an advantage in that the process time is shorter. In addition, fluorocarbon gases have a problem with their global warming potential, but C 4 F 8 is 10300 On the other hand, the HFO is very low at 4, which is also attractive.

[0008] The fluorocarbon-based deposit film formed in the above etching method is characterized by being formed on the sidewalls of the etched pattern and other locations in the substrate that are less susceptible to impacts from ions supplied from the plasma. If these are left as they are, they may become detached from the substrate and become foreign matter in the subsequent manufacturing process, so they must be removed. Methods for removal include ashing with oxygen plasma and cleaning with chemicals.

[0009] Ashing with oxygen plasma is highly reliable for removing fluorocarbon-based deposit films. However, its use may be limited when an organic film exists as a structure on the surface, or when oxidation of the surface is desired. In such cases, cleaning with a chemical solution is effective for removing the deposit film. Chemical solutions used for cleaning the deposit film include swelling peeling type, dissolving type, and a combination of swelling peeling and dissolving type. One example of a swelling peeling type chemical solution is hydrofluoroether (HFE). This chemical solution has a very high permeability and can penetrate into the deposit film, causing it to swell and peel off from the substrate. However, hydrofluoroether (HFE) chemical solution does not have the ability to dissolve the deposit film. Therefore, the deposit film floats in the liquid, and there is a concern that it may reattach to the substrate and generate foreign matter.

[0010] On the other hand, an example of a dissolving type or a combined type of swelling stripping and dissolving chemical solution is a stripping solution containing hydroxylamine. Hydroxylamine has a high ability to dissolve metal oxide residues (dry etching residues) due to its reducing action, so a stripping solution containing this component is preferably used in the insulating film etching process of semiconductors. In semiconductor processes, resist and fluorocarbon-based deposit films are generally removed by ashing, and then metal oxide residues are removed, but it has been found that such stripping solutions can also dissolve fluorocarbon-based deposit films. Although the details of the reaction have not been clarified, it is believed that the film itself is dissolved after penetrating into the deposit film and causing swelling stripping, and it has also come to be used for deposit film removal. In a broader sense, it has been found that a stripping solution containing an amine and an organic polar solvent has the function of dissolving the deposit film. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2014-138122 A Summary of the Invention [Problem to be solved by the invention]

[0012] However, the conventional C 4 F 8 It was found that the deposition film formed by the deposition gas from HFO dissolves in the above-mentioned stripping solution, whereas the deposition film formed by the deposition gas from HFO hardly dissolves at all. As a result, the deposition film formed by HFO could not be dissolved and removed by the stripping solution.

[0013] In order to solve the above problems, an object of the present invention is to provide a method for forming a deposition film that dissolves in a stripping solution in silicon etching using a deposition film containing HFO. [Means for solving the problem]

[0014] In order to achieve the above object, a method for processing a silicon substrate according to the present invention includes the steps of: an etching step of forming an etching pattern on a silicon substrate; a protective film forming step of forming a protective film on the wall surface of the silicon substrate exposed in the etching step; In a method for processing a silicon substrate, The protective film formed in the protective film forming step is removed using a stripping solution. A removal step; Including, In the protective film forming step, the protective film is formed using a mixed gas containing 2,3,3,3-tetrafluoropropene and perfluorocyclobutane. In order to achieve the above object, a method for processing a substrate for a liquid ejection head according to the present invention comprises the steps of: an etching process for forming an etching pattern on a substrate for a liquid ejection head; a protective film forming step of forming a protective film on the side wall of the liquid ejection head substrate exposed in the etching step; a liquid supply port for supplying liquid and a flow path communicating with the liquid supply port, a protective film removing step of removing the protective film formed in the protective film forming step by using a stripping solution; Including, In the protective film forming step, the protective film is formed using a mixed gas containing 2,3,3,3-tetrafluoropropene and perfluorocyclobutane. Effect of the Invention

[0015] According to the present invention, it becomes possible to dissolve a deposited film containing an HFO in a stripping solution. [Brief description of the drawings]

[0016] [Figure 1] Schematic diagram of the process of deposition film formation by C4F8 [Diagram 2] An explanatory diagram showing how the formed deposition film is dissolved in a stripping solution. [Diagram 3] A diagram showing the time required for the deposition film to dissolve in the stripping solution. [Figure 4] Illustrative diagram of passivation breakdown in which silicon is eroded [Diagram 5] A diagram showing the decrease in the components forming the deposition film in the depth direction. [Figure 6] FIG. 11 is an explanatory diagram of a manufacturing method of a liquid ejection head in the third embodiment. [Figure 7] FIG. 11 is an explanatory diagram of a manufacturing method of a liquid ejection head in the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, with reference to the drawings, the mode for carrying out the present invention will be described in detail by way of example. The dimensions, materials, shapes, and relative positions of the components described in the embodiments should be appropriately changed depending on the configuration of the device to which the invention is applied and various conditions. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the present invention. The components described in the embodiments are merely examples, and are not intended to limit the scope of the present invention to only those.

[0018] Here, the deposition film formed with 2,3,3,3-tetrafluoropropene (hereafter referred to as HFO) was 4 F 8 It has been found that it functions as a protective film with a thickness thinner than that of SF 6 This means that the resistance to etching by etching agents is high, but at the same time, the resistance to dissolution by stripping agents may also be high.

[0019] The deposition film formed by HFO is C 4 F 8 The reason why the etching resistance is higher than that of the The C / F ratio is C4 F 8 The deposition film produced by HFO is higher than that produced by . -Many carbon-carbon bonds (CC bonds). -A three-dimensional carbon-carbon network is formed. Inferences such as the following have been made.

[0020] Another possibility is that the average molecular length of the deposited membrane may be different. 4 F 8 It has been found that the solubility of the deposition film formed by the plasma deposition method varies depending on the plasma conditions. Generally, the higher the plasma density, the easier the deposition film is to dissolve.

[0021] C 4 F 8 The process by which a deposition film is formed is as follows: (1) Dissociation of the parent gas (breaking down of molecules) produces C x F y is formed. (2) C x F y is polymerized to form the long-chain molecule -(CF 2 ) n - Formation. (3) Attachment of long-chain molecules to the substrate and further polymerization on the substrate. The conceptual diagram is shown in Figure 1. When the plasma density is high, the dissociation of (1) becomes active, and the molecular length of (2) becomes relatively short during the polymerization process, which may make it more likely to dissolve.

[0022] Deposition film and C by HFO 4 F 8 The difference in the deposition film due to HFO cannot be explained from the viewpoint of plasma density. However, for some reason, the molecular length of the deposition film formed by HFO is C 4 F 8 If the length of the deposition film is significantly longer than that of the deposition film formed by the method described above, this would not be inconsistent with the fact that the deposition film does not dissolve in the stripping solution.

[0023] This time, C for HFO 4 F8 The inventors discovered that by adding HFO to the HFO deposit film, which is difficult to dissolve in the stripping solution, a mixed gas is formed, and the deposited film formed by this mixed gas is dissolved in the stripping solution. 4 F 8 It is speculated that the reason for this is that the incorporation of components derived from the HFO created a starting point for a reaction with the stripping solution. Below, the process from forming the etching pattern, to forming the deposit film that functions as a protective film, and then removing the deposit film using a stripping solution will be explained with reference to FIG. 2. As shown in FIG. 2(a), in the process of forming the etching pattern (etching process), the surface of the substrate 1 is masked with a mask 2, and an etching pattern (pattern 3) is formed by etching (etching step). Then, in the process of forming the protective film (protective film forming process), the surface of the mask 2 and the side walls (wall surfaces) inside the substrate exposed by etching are coated with the above-mentioned HFO and C. 4 F 8 A deposition film 4 is formed by a mixed gas of the above gases (deposition film formation step). 4 F 8 Assuming that the component 5 derived from the C is dispersed in the C-type polymer, the C-type polymer is removed by the step of removing the deposition film 4 that functions as a protective film (protective film removing step), as shown in FIG. 4 F 8 The deposited film 4 containing the component 5 derived from the C-type cellulose membrane is swelled and peeled off by immersion in a peeling solution 6, and is then removed from the wall surface (deposited film removal step). As shown in FIG. 2(c), the peeling solution 6 is 4 F 8 The resulting component 5 is introduced into the ion exchange membrane. Ultimately, as shown in Fig. 2(d), the entire deposition membrane is split from the inside and dissolved in the stripping solution 6. This is believed to be true regardless of which of the above mechanisms is assumed.

[0024] HFO flow rate and C 4 F 8 By changing the flow rate of 4 F 8Figure 3 shows the time required for the deposited film to dissolve in the stripping solution when the mixing ratio of the two is varied. The deposited film used was a film formed to a thickness of 200 to 300 nm only in the process of forming the deposited film as a protective film described above (deposited film formation step). The stripping solution contains an amine and an organic polar solvent. Incidentally, the resist and deposited film dissolve as the stripping solution penetrates into the film and decomposes it, so the dissolution time is not simply proportional to the film thickness. Therefore, since it is difficult to specify it as a dissolution rate (nm / min, etc.), it is expressed here as a dissolution time. In this verification, it was found that the dissolution time was at least C 4 F 8 The solubility improved when the mixing ratio was 16.7% or more, and at mixing ratios above that, the solubility was almost saturated, and the dissolution time remained constant. With this assumed mechanism, it is expected that the effect will be achieved even with a small mixing ratio, and it is assumed that dissolution will occur even at around 5%.

[0025] There is no particular upper limit on the mixing ratio, but C 4 F 8 The higher the mixing ratio of HFO, the easier it is to dissolve in the stripping solution, but the etching resistance decreases. It is necessary to select an appropriate value while balancing productivity. In practice, if the mixing ratio exceeds 80%, it is not possible to use HFO for the deposition film. Therefore, the advantage of HFO in the deposition film is almost lost. 4 F 8 The mixing ratio must be between 16.7% and 80%.

[0026] On the other hand, etching using a deposition film containing HFO has another aspect. In vertical etching of a silicon substrate, a phenomenon called passivation breakdown occurs when the etched wall is not sufficiently protected, and silicon is eroded. As shown in Figure 4(a), this phenomenon usually occurs when the SF is applied for a long time during etching pattern formation. 6 This often occurs near openings exposed to etching gases containing HFO or C. 4 F 8In the case of a pattern with a high aspect ratio (etching depth / etching opening width) using a deposition film containing HFO, the etching gas penetrates through the path 8, causing a passivation breakdown 9. However, in the case of a pattern with a high aspect ratio (etching depth / etching opening width) using a deposition film containing HFO, the etching gas penetrates through the path 8, causing a passivation breakdown 9. As shown in FIG. 1, the sidewall may break at mid-depth, resulting in passivation breakdown 9.

[0027] Generally, in etching patterns with a high aspect ratio, a phenomenon called microloading occurs, making it difficult for the ions and radicals that cause etching and deposition to penetrate deep inside. The occurrence of passivation breakdown 9 halfway along the sidewall suggests that the components that form the CF-based deposit film decrease in the depth direction faster than the decrease in the depth direction of F radicals, which are the etchant required for etching, and that the balance is lost and unprotected areas appear along the way. In other words, as shown in Figure 5, if the decrease in etchant decreases linearly with depth, for example, C 4 F 8 If we assume that the deposition film from C decreases linearly in almost the same way, whereas the deposition film from HFO adheres in large quantities near the front and decreases slowly toward the back, we can get the results shown in Figure 4(b). In other words, it is inferred that the deposition film formed by HFO has a high probability of adhering to the surface and does not penetrate deep into the wall. For example, as mentioned above, 4 F 8 This phenomenon can occur if we assume that the difference between the deposited film and HFO is that the average molecular length of HFO is longer.

[0028] In such cases, in order to improve the protection of the sidewalls by the deposition film, it is necessary to make changes such as increasing the thickness of the deposition film or reducing the etching time, which may result in reducing the process time, which is an advantage of HFO.

[0029] In contrast, in this embodiment, the C 4 F 8 Applying the mixing process, gradually C 4 F8 As shown in Figure 5, the mixing ratio of C 4 F 8 Since it is expected that the coverage of the deposition film at high aspect ratios will be higher in the case of C 4 F 8 By increasing the mixing ratio of C, the protection under high aspect ratios, which HFO is weak at, is improved. 4 F 8 It can be supplemented by ingredients derived from

[0030] The mixture ratio ramp process described above is 4 F 8 The mixing ratio of may be increased continuously, or C 4 F 8 The mixing ratio of C was fixed at a constant value in the initial stage of deposition film formation, and then it was divided into several stages. 4 F 8 The mixing ratio of C may be increased stepwise. 4 F 8 The mixing ratio may be 0%. The initial deposition film is attached near the opening, so it is easy to remove with the stripping solution, and it may be acceptable even if it does not dissolve completely. The essential condition of this case is that at least a part of the deposition film formed during the process is a film that dissolves in the stripping solution. Conversely, if the deposition gas in the final stage is C 4 F 8 Only C may be 100%. 4 F 8 If the dissolution time when a mixed gas with a mixing ratio of 16.7% to 80% is used to form a deposited film is shorter than the dissolution time when only HFO is used to form a deposited film, this falls within the configuration of the invention that solves the problem of this case, and even if the mixing ratio before and after that is outside that range, the process as a whole meets the requirements for solving the problem of this case.

[0031] In this way, HFO was used for the depogas 4 F 8 The mixed gas containing the above was used for deposition film formation. This makes it possible to improve the solubility of the deposition film without reducing the effects of shortening the process time and reducing the global warming potential, which are the advantages of silicon etching using HFO.

[0032] Example 1 In Example 1 of the present invention, a silicon substrate (hereinafter simply referred to as substrate) was etched to form a pattern with a width of 200 μm, a length of 20,000 μm, a depth of 500 μm, and an aspect ratio of 2.5. As described in the Background Art section, the etching process in this example is a cycle in which the following three steps are continuously repeated in order. (1) Silicon etching step using fluorine radicals (etching process) (2) Fluorocarbon-based deposition film formation step (protective film formation process) (3) Removal of the deposition film at the bottom of the pattern using ions These steps may start with (1) or with (2). (2) is called the deposition film formation step, and (3) → (1) is called the etching step.

[0033] A mask of the pattern to be etched is formed on a substrate, and the recesses are etched (1). A deposition film (hereafter referred to as "depot film") is formed on the newly exposed silicon surface (2). Next, ions are used to selectively remove the deposit film at the bottom of the pattern. This exposes silicon at the bottom of the pattern, and etching proceeds as described in the next step (1). From the second cycle onwards, the deposit film is deposited not only on the newly exposed surface, but also on the already exposed surface.

[0034] The conditions for the deposition film formation step were HFO flow rate of 200 sccm and C 4 F 8 Flow rate 40sccm, C 4 F 8 The mixture ratio was 16.7%, and a deposition film was formed on the exposed wall of the substrate by forming an etching pattern. The deposition film formation step was performed under the conditions of HFO flow rate of 240 sccm and C 4 F 8Flow rate 0sccm, C 4 F 8 Compared to when a deposition film was formed with a mixture ratio of 0%, an etching shape with no significant difference was achieved.

[0035] C 4 F 8 The etching rate when only HFO was used as the deposition gas was 7.8 μm / min, whereas the etching rate when the HFO flow rate was 200 sccm and C 4 F 8 Flow rate 40sccm, C 4 F 8 At a mixture ratio of 16.7%, an etching rate of 9.5μm / min was achieved, improving productivity by approximately 1.3 times.

[0036] It was confirmed that the deposition film formed in the above-mentioned deposition film formation step dissolves in the stripping solution containing amine and organic polar solvent in the above-mentioned protective film removal process. The processing conditions were 60°C for 30 minutes. This enabled both improved productivity and dissolution of the deposition film in the stripping solution.

[0037] Example 2 In Example 2 of this embodiment, a silicon substrate was etched to have a pattern with a width of 20 μm, a length of 40 μm, a depth of 250 μm, and an aspect ratio of 12.5. This corresponds to a high aspect ratio pattern. Note that the etching process in this embodiment is omitted because it is the same as that in Example 1.

[0038] C 4 F 8 When only HFO was used as the deposition gas, the etching rate was 12.3 μm / min, whereas when HFO was also used as the deposition gas and the HFO flow rate was 240 sccm, the etching rate was 17.6 μm / min. However, under the same conditions, the sidewall broke and passivation breakdown occurred at a depth of about 100 μm.

[0039] In order to suppress this, we optimized the conditions by increasing the time of the deposition film formation step and decreasing the time of the etching step, and the etching rate was reduced to 11.7 μm / min. 4 F 8 The rate was actually lower than when chisel was used as the depot gas.

[0040] So, HFO and C 4 F 8 The total flow rate of C was fixed at 240 sccm in the initial stage of deposition film formation. 4 F 8 Flow rate 40sccm, C for deposit gas 4 F 8 The mixture ratio was set at 16.7%. From there, the C 4 F 8 The mixture ratio is continuously increased, and finally reaches C 4 F 8 Flow rate 120sccm, C 4 F 8 The mixture ratio was set to 50.0%. This enabled us to suppress the passivation breakdown at a depth of about 100 μm. However, the C 4 F 8 By increasing the mixing ratio of C, the amount of the deposited film at the bottom increases, so it takes time to remove the deposited film at the bottom, and the etching rate decreases accordingly. As a result, the etching rate became 13.5 μm / min, but 4 F 8 The results were better than those obtained when only SiO2 was used as the deposition gas. With further detailed optimization, it is possible to improve the rate a little more without causing passivation breakdown.

[0041] In addition, it was confirmed that the deposition film formed in the deposition film formation step dissolves in the stripping solution containing amine and organic polar solvent in the protective film removal process. The processing conditions were 60°C for 30 minutes. This enabled both improved productivity and dissolution of the deposition film in the stripping solution.

[0042] Example 3 As Example 3 of the present invention, a method for manufacturing a liquid ejection head having a structure as shown in Figs. 6 and 7 will be described. Residual deposit film may become foreign matter and cause ejection abnormality, so in a pattern processed by plasma etching of silicon, it is necessary to dissolve and remove the deposit film. On a silicon substrate 101 for a liquid ejection head (hereinafter simply referred to as substrate 101), an ejection energy generating element 106 is formed, and a wiring formation layer 102 including the ejection energy generating element 106 and wiring 103 is formed. The wiring 103 is formed of Al with Cu added, and in order to take out an electrode from the Al wiring, TiW is formed as an adhesion layer 104 and Au is formed as an electrode 105 (Fig. 6(a)).

[0043] In order to finally form a liquid supply port 110 for supplying liquid to a discharge port 113 of a liquid discharge head in the substrate 101, dry etching of silicon or a silicon-based insulating film is performed. In this embodiment, first, a novolac-based positive resist 108 is used as a mask to mask the surface opposite to the surface having the wiring formation layer 102, except for the surface on which the common flow path 107 is to be formed, and then dry etching is performed to form a recess (etching pattern) required for forming the common flow path 107 communicating with the liquid supply port 110 (FIG. 6(b)). Then, the silicon etching is performed under the conditions for a low aspect ratio used in embodiment 1 of this invention, that is, HFO flow rate of 200 sccm, C 4 F 8 Flow rate 40sccm, C 4 F 8Using a deposition gas with a mixture ratio of 16.7%, a fluorocarbon deposition film 109 is formed on the surface of the resist 108 and in the recess of the substrate 101 where the common flow path 107 is to be formed. Next, the deposition film 109 formed on the bottom surface of the recess is selectively removed. After that, dry etching is performed again on the bottom surface of the recess from which the deposition film has been removed. Then, the sidewall inside the substrate 101 where the deposition film 109 is not formed is exposed, so the deposition film 109 is formed again on the surface of the resist 108 and the above-mentioned recess, including the sidewall inside the substrate 101 that has already been etched. Then, the deposition film 109 formed on the bottom surface of the recess is selectively removed again, and dry etching is performed. This series of steps is repeated to perform vertical processing by dry etching, thereby forming the common flow path 107 (FIG. 6(c)). The common flow path 107 has an opening width of about 200 μm, a depth of about 450 μm, and an aspect ratio of 2.25.

[0044] Next, a part of the resist surface that had been altered by dry etching was removed by ashing, and then the remaining resist 108 that had been masking the surface of the substrate 101 and the deposition film 109 that covered the side walls inside the substrate were removed with a stripping solution (FIG. 6(d)). When stripping the deposition film 109, a stripping solution containing an amine and an organic polar solvent was used, and the processing conditions were 60°C and 30 minutes. It was confirmed that the deposition film 109 dissolved in the stripping solution without any problems.

[0045] Next, a novolac-based positive resist 111 was used as a mask to mask the surface on the side having the wiring formation layer 102, except for the area where the liquid supply port 110 was to be formed, and dry etching was performed to form a recess (etching pattern) required for forming the liquid supply port 110 (FIG. 7(a)). Next, the silicon-based interlayer insulating film of the wiring formation layer 102 was opened by dry etching mainly using a fluorocarbon-based material, and then the etching was performed under the conditions for a high aspect ratio used in Example 2 of the silicon etching of this case, that is, HFO and C 4 F 8 The total flow rate of the deposition film was 240 sccm. 4 F 8 Flow rate 40sccm, C4 F 8 A fluorocarbon-based deposition film 112 is formed on the surface of the resist 111 and in the recess where the liquid supply port 110 is to be formed, using a deposition film with a mixing ratio of 16.7%. Next, the deposition film 112 formed on the bottom surface of the recess is selectively removed. Thereafter, dry etching is again performed on the bottom surface of the recess from which the deposition film has been removed. Then, the sidewall inside the substrate 101 on which the deposition film 112 is not formed is exposed, so the deposition film 112 is again formed on the surface of the resist 111 and the above-mentioned recess, including the sidewall inside the substrate 101 that has already been etched. Then, the deposition film 112 formed on the bottom surface of the recess is selectively removed again, and dry etching is performed. By repeating this series of steps, the C in the deposition film formation is gradually improved. 4 F 8 The mixture ratio is continuously increased, and finally reaches C 4 F 8 Flow rate 120sccm, C 4 F 8 The deposition film 112 was formed using a deposition gas with a mixture ratio of 50.0%. Then, similar to the formation of the common flow path 107, vertical processing was performed by dry etching to form a liquid supply port 110 that communicates with the common flow path 107 (FIG. 7(b)). The liquid supply port 110 has an opening width of about 20 μm, a depth of about 170 μm, and an aspect ratio of 8.5. When etching a pattern with such a high aspect ratio, a deposition film using HFO gas is likely to cause passivation breakdown on the side wall, and therefore bubbles may accumulate in the recessed portion caused by etching. However, as described above, the C contained in the deposition gas that forms the deposition film may cause the deposition film to be damaged. 4 F 8 The stepwise increase in the mixing ratio of is effective in suppressing the occurrence of passivation breakdown and the occurrence of bubble accumulation, etc.

[0046] Next, a part of the resist surface that had been altered by the dry etching was removed by ashing, and then the remaining resist 111 that had been masking the surface of the wiring formation layer 102 and the deposition film 112 covering the side walls inside the substrate were removed with a stripping solution (FIG. 7(c)). The stripping solution used contained an amine and an organic polar solvent, and the processing conditions were 60°C and 30 minutes. It was confirmed that the deposition film 112 dissolved in the stripping solution without any problems. The above-described steps constitute the processing method for the liquid ejection head substrate 101 in this embodiment.

[0047] In this embodiment, the amount of C contained in the deposition gas is determined by the aspect ratio of the pattern to be fabricated. 4 F 8 By changing the mixing ratio pattern to a fixed value or to increase it stepwise and change it to a gradient, the shape and the time required for etching can be optimized. Moreover, the deposited film can be dissolved in the stripping solution.

[0048] In this embodiment, thereafter, ejection ports 113 for ejecting droplets and liquid flow paths 114 connected to the ejection ports were formed by organic structure 115 (FIG. 7(d)). Through the above steps, a liquid ejection head could be manufactured.

[0049] The disclosure of this embodiment includes the following method. (Method 1) an etching step of forming an etching pattern on a silicon substrate; a protective film forming step of forming a protective film on the wall surface of the silicon substrate exposed in the etching step; In a method for processing a silicon substrate, a protective film removing step of removing the protective film formed in the protective film forming step by using a stripping solution; Including, A method for processing a substrate, wherein in the protective film forming step, the protective film is formed using a mixed gas containing 2,3,3,3-tetrafluoropropene and perfluorocyclobutane. (Method 2) The method for processing a substrate according to Method 1, wherein a mixing ratio of the perfluorocyclobutane in the mixed gas is 16.7% or more and 80% or less. (Method 3) The method for processing a substrate according to Method 2, wherein in the protective film forming step, the mixture ratio is constant. (Method 4) 3. The method for processing a substrate according to method 2, wherein in the protective film forming step, the mixture ratio is gradually increased. (Method 5) 5. The method for processing a substrate according to any one of Methods 1 to 4, wherein in the protective film removing step, the protective film is removed using a stripping solution containing an amine and an organic polar solvent. (Method 6) an etching process for forming an etching pattern on a substrate for a liquid ejection head; a protective film forming step of forming a protective film on the side wall of the liquid ejection head substrate exposed in the etching step; a liquid supply port for supplying liquid and a flow path communicating with the liquid supply port, a protective film removing step of removing the protective film formed in the protective film forming step by using a stripping solution; Including, The method for processing a substrate for a liquid ejection head, wherein in the protective film forming step, the protective film is formed using a mixed gas of 2,3,3,3-tetrafluoropropene and perfluorocyclobutane. (Method 7) The method for processing a substrate for a liquid ejection head according to Method 6, wherein a mixing ratio of the perfluorocyclobutane in the mixed gas is 16.7% or more and 80% or less. (Method 8) 8. The method for processing a substrate for a liquid ejection head according to Method 7, wherein in the protective film forming step, the mixture ratio is constant. (Method 9) 8. The method for processing a substrate for a liquid ejection head according to Method 7, wherein in the protective film forming step, the mixture ratio is gradually increased. (Method 10) 10. The method for processing a substrate for a liquid ejection head according to any one of Methods 6 to 9, wherein in the protective film removing step, the protective film is removed using a stripping liquid containing an amine and an organic polar solvent. [Explanation of symbols]

[0050] 1...silicon substrate, 2...mask, 3...pattern, 4...deposition film made by HFO, 5...C contained in the deposition film 4 F 8 6...Removal solution

Claims

1. Etching process to form an etching pattern on a silicon substrate, A protective film formation step is performed to form a protective film on the wall surface of the silicon substrate exposed in the etching step, In a method for manufacturing a substrate in which the following is repeated alternately, The protective film formed in the protective film formation step is removed using a stripping solution in a protective film removal step, Includes, A method for manufacturing a substrate, characterized in that, in the protective film formation step, the protective film is formed using a mixed gas containing 2,3,3,3-tetrafluoropropene and perfluorocyclobutane.

2. The method for manufacturing a substrate according to claim 1, characterized in that the mixing ratio of perfluorocyclobutane in the mixed gas is 16.7% or more and 80% or less.

3. The method for manufacturing a substrate according to claim 2, characterized in that the mixing ratio is constant in the protective film formation step.

4. The method for manufacturing a substrate according to claim 2, characterized in that the mixing ratio is gradually increased in the protective film formation step.

5. The method for manufacturing a substrate according to claim 1 or 2, characterized in that the protective film is removed using a stripping solution containing an amine and an organic polar solvent in the protective film removal step.

6. An etching step of forming an etching pattern on a silicon substrate, A protective film formation step is to form a protective film on the side wall of the silicon substrate that was exposed in the etching step, In a method for manufacturing a substrate for a liquid discharge head, in which the process is repeated alternately to form at least one of a liquid supply port for supplying liquid and a flow path communicating with the liquid supply port, The protective film formed in the protective film formation step is removed using a stripping solution in a protective film removal step, Includes, A method for manufacturing a substrate for a liquid dispensing head, characterized in that, in the protective film formation step, the protective film is formed using a mixed gas of 2,3,3,3-tetrafluoropropene and perfluorocyclobutane.

7. The method for manufacturing a substrate for a liquid discharge head according to claim 6, characterized in that the mixing ratio of perfluorocyclobutane in the mixed gas is 16.7% or more and 80% or less.

8. The method for manufacturing a substrate for a liquid discharge head according to claim 7, characterized in that the mixing ratio is constant in the protective film formation step.

9. The method for manufacturing a substrate for a liquid discharge head according to claim 7, characterized in that the mixing ratio is gradually increased in the protective film formation step.

10. The method for manufacturing a substrate for a liquid discharge head according to claim 6 or 7, characterized in that the protective film is removed using a stripping solution containing an amine and an organic polar solvent in the protective film removal step.

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