JP2010240970A - Groove forming method for glass substrate, method for manufacturing electrostatic actuator, and method for manufacturing liquid droplet ejection head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a groove forming method for a glass substrate, capable of precisely forming a groove having multiple steps on a glass substrate at low cost. <P>SOLUTION: An etching protection film B having stepwise opening holes 21a to 23a is formed on a surface of a glass substrate 2. The etching protection film B and the glass substrate 2 are simultaneously etched so as to form grooves 9a to 9c having multiple steps corresponding to the stepwise opening holes 21a to 23a on the glass substrate 2. At that time, the etching protection film B having the stepwise opening holes 21a to 23a is an oxide film such as a TEOS oxide film or a nitride film. In the etching, an etching rate of the glass substrate 2 and an etching rate of the etching protection film B are differentiated, thereby determining the film thickness of each of the steps of the etching protection film B. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a glass substrate groove forming method, an electrostatic actuator manufacturing method, and a droplet discharge head manufacturing method.

In an electrostatically driven inkjet head, there is a need for improved ejection power and lower drive voltage. To achieve this, a method for forming individual electrodes in multiple stages by providing multistage grooves in a glass substrate There is.
Some conventional electrostatic actuators are provided with multi-steps in the short side direction of the individual electrodes, and the steps are formed by providing multi-step grooves in a substrate made of silicon or borosilicate glass. And the multistage groove | channel is formed by repeating etching and patterning (for example, refer patent document 1).

JP 2000-318155 A (Page 5, FIG. 7)

In the technique of Patent Document 1, if a multi-stage groove is formed in a substrate made of silicon, the unit price of the silicon substrate is high, which increases the cost, and anodic bonding cannot be performed when the silicon substrate is bonded to the cavity substrate. Furthermore, since the silicon substrate is not transparent, there is a problem that the inside of the actuator cannot be observed.
On the other hand, when borosilicate glass is used, the above-mentioned problems are solved, but there remains a problem that etching and patterning must be repeated when forming a multi-stage groove. The number of processes for forming the substrate increases, the cost increases, and the etching amount varies from stage to stage, so that etching variations are likely to occur, and the gap accuracy also decreases.

  The present invention has been made in order to solve the above-described problems. A multi-step groove is formed on a glass substrate by one etching without repeating etching and patterning many times, thereby reducing processes and costs. Another object of the present invention is to provide a glass substrate groove forming method, an electrostatic actuator manufacturing method, and a droplet discharge head manufacturing method having high etching accuracy and no variation in etching.

A glass substrate groove forming method according to the present invention is a glass substrate groove forming method for forming a recess having a multi-step groove on a glass substrate, and an etching protective film having a stepped opening hole on the surface of the glass substrate. Then, the etching protective film and the glass substrate are simultaneously etched to form a multistage groove corresponding to the stepped opening hole in the glass substrate.
An etching protective film having a stepped opening is formed in advance on the glass substrate, and the etching protective film and the glass substrate are etched at the same time in one step, so that multi-step grooves are accurately formed on the glass substrate. can do. Further, since the steps are formed without using a photo process, the process can be simplified and the cost can be reduced.

In the method for forming a groove of a glass substrate according to the present invention, the thickness of the step portion of the etching protective film is determined based on the difference between the etching rate of the glass substrate and the etching rate of the etching protective film.
Since the thickness of the step portion of the etching protective film is determined by the difference in the etching rate, multi-step grooves can be formed with high accuracy even for members having different etching rates.

Further, the glass substrate groove forming method according to the present invention includes a step of forming an etching protective film having an opening hole by covering the surface of the glass substrate with a mask, and an upper portion of the opening hole of the etching protective film from the opening hole. A step of further forming an etching protective film having an opening hole wider than the opening hole by covering with a wide mask, and forming an etching protective film in which the opening hole diameter is increased in a stepped shape by repeating the above steps. And etching the etching protective film having the opening and the glass substrate at the same time to form a multistage groove in the glass substrate.
By forming an etching protective film with stepped opening holes on the glass substrate and etching it simultaneously in one step, it is possible to form an extremely shallow step on the glass substrate with high accuracy, and etching variation for each step. The gap accuracy is improved. In addition, since the multi-stage groove is formed without using a photo process, the number of etchings can be reduced, and the process and cost can be reduced.

The method for forming a groove in a glass substrate according to the present invention includes a step of forming a first-stage etching protective film having a first opening hole by covering the surface of the glass substrate with a first mask; A second-stage etching having a second opening hole wider than the first opening hole by covering an upper portion of the first opening hole of the eye etching protection film with a second mask wider than the first opening hole. Forming a protective film; and covering the upper part of the second opening hole of the second stage etching protective film with a third mask wider than the second opening hole, and forming a third wider than the second opening hole. Forming a third-stage etching protective film having a plurality of opening holes, and simultaneously etching the etching protective film in which the first to third opening holes have a stepped diameter and the glass substrate to form a glass substrate And a step of forming a three-stage groove.
By forming an etching protective film with three openings on the glass substrate and etching it simultaneously in one step, it is possible to form ultra-shallow steps on the glass substrate with high precision, and etching variations for each step. The gap accuracy is improved. In addition, since the three-stage groove is formed without using a photo process, the number of etchings can be reduced, and the process and cost can be reduced. Further, the step formation of the etching protective film by the mask can be performed only by changing the mask three times, and the tact time can be shortened as compared with the photoetching process.

In the glass substrate groove forming method according to the present invention, the alignment mark is simultaneously formed when the first opening hole is formed in the first-stage etching protective film, and the second mask is formed on the alignment mark. The alignment hole and the alignment hole of the third mask are aligned to perform pattern alignment.
The first to third opening holes formed in the step-shaped etching protective film can be accurately aligned.

In the method for forming a groove in a glass substrate according to the present invention, an etching protective film having a stepped opening is used as an oxide film.
Since the etching protective film is formed of an oxide film, it can be formed on the glass substrate at a low temperature, and the accuracy of the film pattern is improved.

In the glass substrate groove forming method according to the present invention, the oxide film is a TEOS oxide film.
Since the oxide film is formed of the TEOS oxide film, the oxide film can be formed on the glass substrate at a low temperature of 450 ° C. or lower, and the accuracy of the oxide film pattern is improved.

In the glass substrate groove forming method according to the present invention, the oxide film and the glass substrate are etched with a hydrofluoric acid-based etchant.
The oxide film and the glass substrate can be reliably etched with a hydrofluoric acid-based liquid.

In the glass substrate groove forming method according to the present invention, oxygen plasma treatment is performed after the growth of an oxide film having stepped openings.
Since the oxygen plasma treatment is performed after the growth of the oxide film, the oxide film can be stabilized in a desired shape.

In the glass substrate groove forming method according to the present invention, a nitride film is used as the etching protective film having stepped openings.
Since the etching protective film is a nitride film, the accuracy as the etching protective film is high.

The manufacturing method of the electrostatic actuator according to the present invention includes forming a recess having a multi-stage groove on a glass substrate by the above-described glass substrate groove forming method, providing an electrode in the recess, and providing the diaphragm on the glass substrate provided with the electrode. An electrostatic actuator including a silicon substrate having the electrode and a diaphragm facing the electrode with a gap is manufactured.
An electrostatic actuator having excellent discharge power and a low drive voltage can be manufactured with high accuracy and at low cost.

A manufacturing method of a droplet discharge head according to the present invention includes joining a nozzle substrate having a plurality of nozzle holes to a silicon substrate of an electrostatic actuator manufactured by the above-described electrostatic actuator manufacturing method, and the nozzle substrate and the silicon substrate. In this case, a discharge chamber communicating with each of the nozzles is formed between the two and a droplet discharge head for discharging droplets from the nozzles by deformation of the vibration plate.
A droplet discharge head having excellent discharge power and a low drive voltage can be manufactured with high accuracy and at low cost.

1 is an exploded perspective view of a droplet discharge head according to Embodiment 1 of the present invention. FIG. 2 is a longitudinal sectional view of a main part in a state where the droplet discharge head of FIG. 1 is assembled. Sectional drawing which shows the manufacturing process of the glass substrate of the droplet discharge head of FIG. Sectional drawing which shows the manufacturing process of the glass substrate following FIG. Sectional drawing which shows the manufacturing process of the glass substrate following FIG. Sectional drawing which shows the manufacturing process of the glass substrate following FIG. Sectional drawing which shows the manufacturing process of the glass substrate following FIG. The perspective view of the droplet discharge device which concerns on Embodiment 2 of this invention.

Embodiment 1 FIG.
1 is an exploded perspective view of a droplet discharge head according to Embodiment 1 of the present invention, and FIG. 2 is a longitudinal sectional view of the assembled droplet discharge head of FIG.
1 and 2, the droplet discharge head includes a cavity substrate 1 as a first substrate having a vibration plate, a glass substrate 2 as a second substrate having an electrode 8, and a third having a nozzle hole 12. It has a three-layer structure in which a nozzle substrate 3 as a substrate is laminated.
A cavity substrate 1 as an intermediate first substrate is a silicon substrate, a plurality of discharge chambers 5 having a bottom wall as a diaphragm 4, and a common reservoir for supplying liquid (ink) to each discharge chamber 5 7 Then, a TEOS film of 0.1 μm is formed on the entire surface of the cavity substrate 1 by plasma CVD to form an insulating film 15. This is to prevent dielectric breakdown or short-circuit during driving of the droplet discharge head and to prevent the cavity substrate 1 from being etched by the liquid.

The glass substrate 2 as the second substrate to be bonded to the lower surface of the cavity substrate 1 uses borosilicate glass, and the cavity substrate 1 and the glass substrate 2 are bonded by anodic bonding.
The concave portion 9 for providing the electrode 8 on the glass substrate 2 is formed by a multi-stage groove A, and the facing distance between the diaphragm 4 and the electrode 8 disposed to face the diaphragm 4, that is, the gap (gap) G is 3 It is formed in steps. The concave portion 9 has a deepest portion of 190 nm and a shallowest portion of 150 nm. The concave portion 9 is patterned in a slightly larger shape similar to the shape of the electrode portion so that the electrode 8, the lead portion 10, and the terminal portion 11 are provided therein. The electrode 8 is produced by forming an electrode pattern by sputtering an electrode member (ITO member in this embodiment) in the recess 9 by sputtering to a thickness of 70 nm. Therefore, the gap G after the anodic bonding of the cavity substrate 1 and the glass substrate 2 in the present embodiment is 120 nm at the deepest portion.

The nozzle substrate 3 as a third substrate bonded and bonded to the upper surface of the cavity substrate 1 uses a silicon substrate having a thickness of 180 μm, and the nozzle holes 12 communicating with the discharge chambers 5 are formed on the surface of the nozzle substrate 3, respectively. In addition, an orifice 6 that communicates the discharge chamber 5 and the reservoir 7 is provided. The nozzle hole 12 is a two-stage nozzle, and improves the straightness of the liquid by the rectifying action of the liquid flow.
In addition, diaphragms 13 are formed at both ends of the nozzle substrate 3 so as to face the reservoir 7 formed on the cavity substrate 1 and suppress the pressure fluctuation in the reservoir 7. The diaphragm 13 is formed by processing a part of the nozzle substrate 3 thinly, for example, by etching. Each of the above numerical values shows an example.

The operation of the droplet discharge head configured as described above will be described.
An oscillation circuit 18 is connected between the terminal portion 11 of the electrode 8 provided on the glass substrate 2 and the common electrode 19 provided on the cavity substrate 1. When a pulse voltage of 0 V to 30 V is applied to the electrode 8 by the oscillation circuit 18 and the surface of the electrode 8 is positively charged, the corresponding vibration plate 4 is charged to a negative potential, and the vibration plate 4 acts to attract static electricity. To bend down.
Next, when the pulse voltage is turned off, the diaphragm 4 is restored. Therefore, the pressure in the discharge chamber 5 rises rapidly, and the droplets 16 are discharged from the nozzle holes 12 toward the recording paper 17.
Next, when the diaphragm 4 is bent downward again, the liquid is supplied from the reservoir 7 through the orifice 6 into the discharge chamber 5.
The cavity substrate 1 and the oscillation circuit 18 are connected to each other through a common electrode 19 opened in a part of the cavity substrate 1 by dry etching. The liquid is supplied to the droplet discharge head through a liquid supply port 14 formed on the electrode substrate 2.

The diaphragm 4 in the droplet discharge head of Embodiment 1 is a high-concentration boron-doped layer, and the boron-doped layer has the same thickness as the desired diaphragm 4.
The etch rate of silicon etching by alkali, when the dopant is boron, in the region of high concentration (about 5 × 10 ¹⁹ atoms / cc or more), very small.
In the first embodiment, utilizing this, the region where the diaphragm 4 is formed is a high-concentration boron-doped layer, and etching is performed when the boron-doped layer is exposed when forming the discharge chamber 5 by alkali anisotropic etching. The diaphragm 4 is manufactured to a desired plate thickness by a so-called etching stop technique in which the rate becomes extremely small.

A manufacturing method of the glass substrate 2 as the second substrate of the droplet discharge head in the first embodiment will be described in detail with reference to manufacturing process diagrams of FIGS. In addition, the numerical value shown below shows the example, It does not limit to this.
First, as shown in FIG. 3A, a glass substrate 2 made of borosilicate glass having a thickness of 1 mm and having both surfaces polished is prepared.

  Next, as shown in FIG. 3B, a first silicon mask 31 is placed on one side of the glass substrate 2 cleaned with RCA or the like. At this time, the first silicon mask 31 and the glass substrate 2 are fixed with a heat resistant tape (not shown).

  Next, as shown in FIG. 3C, a first stage TEOS oxide film 21 which is an etching protective film is formed on a portion where the glass substrate 2 is exposed. For example, when the first-stage groove 9a (see FIG. 2) of the glass substrate 2 is formed with a depth of 20 nm, the glass etching rate of the glass substrate 2 is 15 Å / sec, and the TEOS oxide film that is an etching protective film Since the rate is 30 Å / sec, the first stage TEOS oxide film 21 is formed so as to have a thickness of 40 nm. At this time, alignment marks for a second silicon mask 32 and a third silicon mask 33 (see FIGS. 4 and 5) described later are also formed at the same time.

  Next, as shown in FIG. 3D, the heat-resistant tape is peeled off, and the first silicon mask 31 is removed from the glass substrate 2. As a result, a first opening hole 21 a is formed in the first stage TEOS oxide film 21. The first opening 21a is formed in the first step of the glass substrate 2 when the glass substrate 2 is etched using a step-shaped oxide film (etching protective film) B (see FIG. 5J) described later. This corresponds to the portion where the groove 9a is formed.

  As shown in FIG. 4E, the first silicon mask 31 is formed on the first opening hole 21a of the first stage TEOS oxide film 21 of the glass substrate 2 so as to cover the opening hole 21a. A wider second silicon mask 32 is placed. At this time, the alignment holes of the second silicon mask 32 are aligned with the alignment marks formed in FIG. 3C to align the pattern, and the second silicon mask 32 and the glass substrate 2 are bonded with heat resistant tape. Fix it.

  Next, as shown in FIG. 4F, a second-stage TEOS oxide film 22 as an etching protective film is formed in a portion where the first TEOS oxide film 21 is exposed. For example, when the second-stage groove 9b (see FIG. 2) of the glass substrate 2 is formed at 20 nm, the glass etching rate of the glass substrate 2 is 15 Å / sec, and the TEOS oxide film rate as an etching protective film is 30 Å. / Sec, the second stage TEOS oxide film 22 is formed to have a thickness of 40 nm.

  Next, as shown in FIG. 4G, the heat-resistant tape is peeled off, and the second silicon mask 32 is removed from the glass substrate 2. Thus, a second opening hole 22a is formed in the second stage TEOS oxide film 22. The second opening hole 22a forms a second-stage groove 9b of the glass substrate 2 when the glass substrate 2 is etched using a stepped oxide film B (see FIG. 5J) described later. It corresponds to the part to be.

  As shown in FIG. 5 (h), the second silicon mask 32 is formed on the second opening hole 22a of the second stage TEOS oxide film 22 of the glass substrate 2 so as to cover the opening hole 22a. A third silicon mask 33 having a wider width is placed thereon. At this time, the alignment holes of the third silicon mask 32 are aligned with the alignment marks formed in FIG. 3C to align the pattern, and the third silicon mask 32 and the glass substrate 2 are bonded with heat-resistant tape. Fix it.

  Next, as shown in FIG. 5I, a third-stage TEOS oxide film 23, which is an etching protection film, is formed on the portion where the second TEOS oxide film 22 is exposed. For example, when the third-stage groove 9c (see FIG. 2) of the glass substrate 2 is formed at 150 nm, the glass etching rate of the glass substrate 2 is 15 Å / sec, and the TEOS oxide film rate as an etching protective film is 30 Å. / Sec, so that the film thickness of the third stage TEOS oxide film 23 is 300 nm.

Next, as shown in FIG. 5 (j), the heat-resistant tape is peeled off, and the third silicon mask 33 is removed from the glass substrate 2. In this way, the third opening hole 23a is formed in the third stage TEOS oxide film 23, and the stepped shape is formed together with the opening holes 21a and 22a of the first and second stage TEOS oxide films 21 and 22. An oxide film (an oxide film having a stepped opening, that is, an etching protective film) B is formed. The third opening hole 23a corresponds to a portion where the third groove 9c of the glass substrate 2 is formed when the glass substrate 2 is etched using the stepped oxide film B.
In the above process, after the growth of the first, second, and third stage TEOS oxide films 21, 22, and 23, oxygen plasma treatment is performed, and the first, second, and third stage TEOS oxide films 21, 22 and 23 are stabilized in a desired shape.

Next, as shown in FIG. 6K, the stepped oxide film B and the glass substrate 2 are simultaneously etched with a hydrofluoric acid-based glass etching solution for a desired time. At this time, since the glass etching rate is 15 Å / sec and the TEOS oxide film rate is 30 Å / sec, the stepped oxide film B is etched at twice the rate of the glass substrate 2.
When the stepped oxide film B is etched by 40 nm, a portion of the glass substrate 2 corresponding to the first opening hole 21a is etched by 20 nm to form the first step groove 9a. The first opening hole 21a has a thickness of zero.

  Next, as shown in FIG. 6L, when the stepped oxide film B is further etched by 40 nm, the portion of the glass substrate 2 corresponding to the second opening hole 22a of the stepped oxide film B is 20 nm. The second stage groove 9b is formed by etching. At this time, the first-stage groove 9a is further etched by 20 nm. Thus, when the stepped oxide film B is etched by 40 nm, the thickness of the second opening 22a becomes zero.

  Next, as shown in FIG. 6M, when the stepped oxide film B is further etched by 300 nm, the portion of the glass substrate 2 corresponding to the third opening hole 23a of the stepped oxide film B is 150 nm. The third stage groove 9c is formed by etching. At this time, the first and second stage grooves 9a and 9b are further etched by 150 nm. Thus, when the stepped oxide film B is etched by 150 nm, the third opening hole 23a has a thickness of 0, and the stepped oxide film B is all etched.

  In this way, the etching of the glass substrate 2 proceeds further from the portion where the stepped oxide film B is not etched, and finally, as shown in FIG. A recess 9 having a three-step groove A) is formed. In the recess 9, the first-stage groove 9a has a depth of 20 nm, the second-stage groove 9b has a depth of 20 nm, and the third-stage groove 9c has a depth of 150 nm.

  As shown in FIG. 7 (n), after the glass substrate 2 is washed with sulfuric acid, an ITO film is formed on the entire surface of the concave portion 9 where the pattern is formed by sputtering. For example, when the gap G is formed with a thickness of 120 nm, the deepest portion of the recess 9 is 190 nm, so that the ITO film is formed with a thickness of 70 nm. Next, scrub cleaning is performed, a resist pattern is formed so that the ITO pattern remains in the recess 9 having the multi-step groove A of the glass substrate 2, and the ITO film, ie, the electrode 8 is formed by etching the ITO film.

  Finally, as shown in FIG. 7 (o), a hole 14a to be the liquid supply port 14 is formed by sandblasting or drilling.

In the above description, the case where the concave portion 9 having the three-step groove A is formed in the glass substrate 2 has been described. However, the multi-step groove A is not limited to three steps, for example, two steps or four or more steps. You may form in.
In the above description, the case where an oxide film is used as an etching protective film has been described. However, the present invention is not limited to this. For example, a nitride film may be used. In the case of a nitride film, the etching rate is slower than in the case of an oxide film, but the accuracy as an etching protective film is higher than in the case of an oxide film. Even when a nitride film is used as the etching protective film, the method of forming the groove of the glass substrate 2 is substantially the same as that of the oxide film.

Conventionally, when the multi-step groove A is formed, the photoetching process is used. However, when this is done, variations occur in etching when each step is formed, and the variations are accumulated to form steps in the surface. Although accuracy could not be obtained, according to the present invention, since there is no photoetching step and etching can be performed once, there is no variation in level difference and gap accuracy can be improved.
In addition, according to the present invention, since a photo etching process is not performed many times as in the prior art, no resist is used. Furthermore, since the etching process is performed once, the number of times the etching solution is used can be reduced. Thus, steps can be reduced and costs can be reduced.

Furthermore, according to the present invention, when the etching protective film is formed of the TEOS oxide film, the film can be formed at a low temperature of 450 ° C. or lower, and the first to third silicon masks 31 to 33 are not bent. Since the film can be formed, the film does not wrap around from the floating portions of the first to third silicon masks 31 to 33, and the pattern accuracy can be improved.
Moreover, since it is only necessary to replace the first to third silicon masks 31 to 33 and repeat the film formation, the tact time can be shortened compared to the photoetching process.

After manufacturing the glass substrate 2 provided with the recesses 9 having the multi-stage grooves A as described above (see FIGS. 3 to 7), a silicon substrate having a vibration plate is bonded to the glass substrate 2, and the glass substrate 2 An electrostatic actuator including the electrode 8 and a diaphragm facing the electrode 8 with a gap (gap) G is manufactured (not shown).
Furthermore, the nozzle substrate 3 having a plurality of nozzle holes 12 is joined to the silicon substrate (cavity substrate) 1 of the electrostatic actuator manufactured as described above, and the nozzle substrate 3 and the silicon substrate (cavity substrate) 1 are connected. A discharge chamber 5 communicating with each of the nozzles 12 is formed therebetween, and a droplet discharge head for discharging the droplets 16 from the nozzles 12 is manufactured by deformation of the diaphragm 4 (see FIG. 2).

Embodiment 2. FIG.
FIG. 8 is a perspective view of a droplet discharge apparatus including the droplet discharge head according to the first embodiment.
A droplet discharge device 100 shown in FIG. 8 is a general inkjet printer.
The droplet discharge head according to Embodiment 1 has a plurality of ultra-shallow steps formed on the glass substrate 2 with high accuracy, and has excellent gap accuracy without variation in etching for each step. The droplet discharge device 100 can be obtained.
In addition to the ink jet printer shown in FIG. 8, the droplet discharge head shown in Embodiment 1 can be used for variously changing droplets to produce a color filter for a liquid crystal display, to form a light emitting portion of an organic EL display device, It can also be applied to the discharge of biological liquids.

  1 cavity substrate, 2 glass substrate, 3 nozzle substrate, 4 vibration plate, 5 discharge chamber, 6 orifice, 7 reservoir, 8 electrode, 9 recess, 9a first step groove, 9b second step groove, 9c second 3rd stage groove, 12 nozzle holes, 21 1st stage TEOS oxide film (first stage etching protection film), 21a 1st opening hole, 22 2nd stage TEOS oxide film (2nd stage) Etching protection film), 22a second opening hole, 23 third stage TEOS oxide film (third etching protection film), 23a third opening hole, 31 first silicon mask (first , 32 Second silicon mask (second mask), 33 Third silicon mask (third mask), A Multi-stage groove, B Step-shaped oxide film (oxide having step-shaped opening holes) film).

Claims (12)

A glass substrate groove forming method for forming a recess having a multistage groove on a glass substrate,
Forming an etching protective film having a stepped opening hole on the surface of the glass substrate, and simultaneously etching the etching protective film and the glass substrate to form a multi-stage corresponding to the stepped opening hole in the glass substrate; A method for forming a groove in a glass substrate, comprising forming a groove.   2. The method for forming a groove in a glass substrate according to claim 1, wherein the thickness of the step portion of the etching protection film is determined based on a difference between the etching rate of the glass substrate and the etching rate of the etching protection film. Forming an etching protective film having an opening hole by covering the surface of the glass substrate with a mask;
Forming an etching protective film having an opening hole wider than the opening hole by covering an upper portion of the opening hole of the etching protective film with a mask wider than the opening hole;
The above-described steps are repeated to form an etching protective film in which the opening hole has a stepped diameter, and the etching protective film having the stepped opening hole and the glass substrate are simultaneously etched to form a multi-stage on the glass substrate. Forming a groove of
The method for forming a groove in a glass substrate according to claim 1, wherein: Forming a first-stage etching protective film having a first opening hole by covering the surface of the glass substrate with a first mask;
An upper portion of the first opening hole of the first-stage etching protective film is covered with a second mask wider than the first opening hole, and a second opening hole wider than the first opening hole is formed. Forming a second-stage etching protective film comprising:
An upper portion of the second opening hole of the second-stage etching protective film is covered with a third mask wider than the second opening hole, and a third opening hole wider than the second opening hole is formed. Forming a third-stage etching protective film having:
Etching the etching protective film in which the first to third opening holes have a stepped diameter and the glass substrate simultaneously to form a three-stage groove in the glass substrate;
The method for forming a groove in a glass substrate according to claim 3, wherein:   An alignment mark is simultaneously formed when forming the first opening hole in the first-stage etching protective film, and the alignment hole of the second mask and the alignment hole of the third mask are formed in the alignment mark. 5. The method for forming a groove in a glass substrate according to claim 4, wherein the alignment of the pattern is performed by combining the two.   6. The method for forming a groove in a glass substrate according to claim 1, wherein the etching protective film having the step-shaped opening holes is an oxide film.   7. The method for forming a groove in a glass substrate according to claim 6, wherein the oxide film is a TEOS oxide film.   8. The method for forming a groove in a glass substrate according to claim 6, wherein the oxide film and the glass substrate are etched with a hydrofluoric acid-based etchant.   The method for forming a groove in a glass substrate according to any one of claims 6 to 8, wherein an oxygen plasma treatment is performed after the growth of the oxide film.   6. The method for forming a groove in a glass substrate according to claim 1, wherein the etching protective film having the stepped opening is a nitride film.   A recess having a multistage groove is formed in the glass substrate by the glass substrate groove forming method according to claim 1, an electrode is provided in the recess, and the diaphragm is provided on the glass substrate provided with the electrode. A method of manufacturing an electrostatic actuator, comprising: bonding a silicon substrate having an electrode; and manufacturing the electrostatic actuator including the electrode and a diaphragm facing the electrode with a gap.   A nozzle substrate having a plurality of nozzle holes is bonded to the silicon substrate of the electrostatic actuator manufactured by the method for manufacturing an electrostatic actuator according to claim 11, and each of the nozzles is interposed between the nozzle substrate and the silicon substrate. A method of manufacturing a droplet discharge head, comprising: forming a discharge chamber communicating with the nozzle and discharging a droplet from the nozzle by deformation of the vibration plate.

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