JP4660683B2 - Nozzle plate manufacturing method and droplet discharge head manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a nozzle plate having nozzle holes for discharging droplets, a method for manufacturing a droplet discharge head, a nozzle plate, and a droplet discharge head .

As a droplet discharge head for discharging droplets, for example, an inkjet head mounted on an inkjet recording apparatus is known. Ink jet heads generally include a nozzle plate in which a plurality of nozzle holes for discharging ink droplets are formed, and an ink in a discharge chamber, a reservoir, or the like that is joined to the nozzle plate and communicates with the nozzle holes. And a cavity plate in which a flow path is formed, and an ink droplet is ejected from a selected nozzle hole by applying pressure to the ejection chamber by a driving unit. As a driving means, there are a method using an electrostatic force, a piezoelectric method using a piezoelectric element, a bubble jet (registered trademark) method using a heating element, and the like.
In recent years, there has been an increasing demand for high quality printing, image quality, and the like for inkjet heads, and thus there is a strong demand for higher density and improved ejection performance. Against this background, various devices and proposals have been made for the nozzle portion of an inkjet head.

  In order to improve ink ejection characteristics in an inkjet head, the nozzle has a cross-sectional shape in which a nozzle hole part having a narrow cross section at the tip side and a nozzle hole part spreading in a cone shape or a pyramid shape are formed on the rear side. It is desirable to use something. For example, as shown in Patent Document 1, when the nozzle shape is a cylindrical shape on the front end side and the inner peripheral surface of the rear side portion is a quadrangular pyramid shape, when using a nozzle having a cylindrical shape as a whole, In comparison, the direction of the ink pressure applied to the nozzle from the ink cavity side can be aligned in the nozzle axis direction, and stable ejection characteristics can be obtained. Further, as shown in Patent Document 2, if the nozzle is formed into a cylindrical shape by anisotropic dry etching at the tip side and the nozzle portion at the rear side is tapered by anisotropic wet etching, In addition, there is less risk of the occurrence of ink stagnation, and more stable ejection characteristics can be obtained.

JP 56-1335075 (FIG. 2) Japanese Patent Laid-Open No. 10-315461 (FIGS. 1 and 2)

  However, as in Patent Documents 1 and 2, when the tapered nozzle portion serving as the ink inlet is formed on the silicon single crystal substrate by anisotropic wet etching, it depends on the plane orientation of the silicon single crystal substrate. The taper angle is determined, and there is a problem that there is a limit to increasing the nozzle density. That is, in order to increase the nozzle density, it is necessary to reduce the thickness of the nozzle plate. However, if this is done, the nozzle plate will be cracked or chipped, making handling difficult.

Accordingly, the present invention provides a method for manufacturing a nozzle plate for droplet discharge, a method for manufacturing a droplet discharge head, a nozzle plate, and a droplet discharge head that have stable discharge characteristics and can achieve a high nozzle density, that is, a high density. The purpose is to provide.

Further, in the method for manufacturing a nozzle plate according to the present invention, the nozzle holes for discharging droplets are formed in a cylindrical shape perpendicular to the substrate surface and on the tip side in the discharge direction, and from the injection port part A nozzle plate having a tapered cross-sectional area gradually increasing toward a rear end side in a discharge direction, and forming a nozzle hole by etching a silicon substrate, A step of performing dry etching on one surface to form an injection port portion; a step of forming an etching protective film on at least one surface and a side surface and a bottom surface of the injection port portion; and an injection port portion of the etching protective film The peripheral portion of the substrate is removed larger than the hole diameter of the injection port portion to form an opening, and the silicon substrate having the etching protective film in which the opening is formed is dry-etched, Forming a Jo moiety, a silicon substrate, but the one surface and a step of thinning to the tip of the injection port portion from the side opposite to the opening.
As described above, since the tapered portion of the nozzle hole is formed by dry etching without depending on anisotropic wet etching, the nozzle density can be increased. In addition, since the entire nozzle hole is formed by dry etching, the boundary portion between the jet port portion and the tapered portion can be formed into a smooth and continuous shape, with good bubble discharge and stable ejection characteristics. Can be formed. Further, in the etching step when forming the tapered portion, since the side surface and the bottom surface of the injection port portion are protected with an etching protective film, the influence of the etching gas on the hole diameter of the injection port portion can be prevented, The hole diameter accuracy of the injection port portion can be maintained.

In the method for manufacturing a nozzle plate according to the present invention, the dry etching for forming the tapered portion is the first for forming the protective film for protecting the side surface by suppressing the etching in the side surface direction of the tapered portion. Gas, a second gas for accelerating the etching of the tapered portion in the depth direction, and a third gas for adjusting the taper angle by etching the protective film. is there.
Thereby, the taper angle of the tapered portion can be freely controlled with high accuracy.

As the pre Kido dry etching, is suitable dry etching with ICP (Inductively Coupled Plasma) discharge.

A method for manufacturing a droplet discharge head according to the present invention is a method for manufacturing a droplet discharge head using any one of the above-described nozzle plate manufacturing methods.
If a droplet discharge head is manufactured using any one of the above-described nozzle plate manufacturing methods, a droplet discharge head having stable droplet discharge characteristics and a high density can be obtained.

The nozzle plate according to the present invention is manufactured using any one of the above-described nozzle plate manufacturing methods.
A droplet discharge head according to the present invention has the nozzle plate described above . Thereby, it is possible to provide a high-density droplet discharge head having stable droplet discharge characteristics.

Embodiment 1 FIG.
Hereinafter, an embodiment of a droplet discharge head provided with a nozzle plate of the present invention will be described with reference to the drawings. Here, an electrostatic drive type inkjet head will be described with reference to FIGS. 1 to 3 as an example of a droplet discharge head. Note that the present invention is not limited to the structure and shape shown in the following drawings, and also for a droplet discharge head and a droplet discharge device that discharge droplets by other different drive methods. Applicable.

  FIG. 1 is an exploded perspective view showing an exploded schematic configuration of the ink jet head according to the first embodiment, and a part thereof is shown in cross section. FIG. 2 is a cross-sectional view of the ink jet head showing a schematic configuration of the right half of FIG. 1, in which the nozzle portion is further enlarged. FIG. 3 is a top view of the inkjet head of FIG. 1 and 2 are shown upside down from a state in which they are normally used.

  As shown in FIGS. 1 and 2, an inkjet head (an example of a droplet discharge head) 10 according to the first embodiment includes a nozzle plate 1 in which a plurality of nozzle holes 11 are provided at a predetermined pitch, and each nozzle hole. 11, the cavity plate 2 provided with an ink supply path independently of the electrode plate 11 and the electrode substrate 3 provided with the individual electrodes 31 facing the diaphragm 22 of the cavity plate 2 are bonded together. .

  The nozzle plate 1 is made of, for example, a silicon single crystal substrate (hereinafter also simply referred to as a silicon substrate) having a thickness of 180 μm. In the nozzle plate 1, a recess 12 is formed in a region where a plurality of nozzle holes 11 are provided, and a nozzle hole 11 for ejecting ink droplets is opened on the bottom surface of the recess 12. That is, the flow path resistance of each nozzle hole 11 is adjusted by thinning the length of the nozzle portion (substrate thickness) by the recess 12. This ensures uniform ejection performance and prevents other objects such as recording paper from coming into direct contact with the ejection surface (bottom surface of the recess 12), so that the recording paper is soiled or the tip of the nozzle hole 11 is damaged. Can be prevented.

  As shown in FIG. 2, each nozzle hole 11 is provided on the same axis as the cylindrical injection port portion 11a perpendicular to the surface of the nozzle plate 1 (the bottom surface of the recess 12 on the substrate surface) and the injection port portion 11a. The injection port portion 11a has a larger diameter (or cross-sectional area) than the introduction port portion 11b, and the boundary portion 11c between the injection port portion 11a and the introduction port portion 11b includes a trumpet shape (including a taper shape and a round shape). The same shall apply hereinafter.) As a result, no ink stagnation occurs at the boundary portion 11c, so that the flow path resistance of the nozzle hole 11 can be reduced, and the ink droplet ejection direction can be aligned with the central axis direction of the nozzle hole 11. The discharge characteristics can be exhibited. That is, there is no variation in the flying direction of ink droplets, there is no scattering of ink droplets, and variations in the ejection amount of ink droplets can be suppressed.

  Further, in FIG. 2 of the nozzle plate 1, an orifice (narrow groove) 13 that forms a part of the ink flow path is provided on the lower surface (the surface on the joint side with the cavity plate 2). Further, a diaphragm portion 14 that is thinned by a concave portion is provided at a position corresponding to a reservoir 23 of the cavity plate 2 described later. The diaphragm portion 14 is provided to suppress pressure fluctuation in the reservoir 23.

  The cavity plate 2 is made of, for example, a (110) plane silicon single crystal substrate having a thickness of about 140 μm (this substrate is also simply referred to as a silicon substrate hereinafter). The silicon substrate is subjected to anisotropic wet etching to form recesses 24 and 25 for constituting the discharge chamber 21 and the reservoir 23 of the ink flow path. A plurality of recesses 24 are independently formed at positions corresponding to the nozzle holes 11. Therefore, as shown in FIG. 2, when the nozzle plate 1 and the cavity plate 2 are joined, each recess 24 constitutes a discharge chamber 21 and communicates with each nozzle hole 11 and the orifice 13 serving as an ink supply port. Both communicate with each other. The bottom wall of the discharge chamber 21 (recessed portion 24) is a diaphragm 22.

  The other recess 25 is for storing liquid material ink, and constitutes a common reservoir (common ink chamber) 23 for each discharge chamber 21. The reservoirs 23 (recesses 25) communicate with all the discharge chambers 21 through the orifices 13, respectively. Further, a hole penetrating the electrode substrate 3 described later is provided in the bottom of the reservoir 23, and ink is supplied from an ink cartridge (not shown) through the ink supply hole 34 of the hole.

  In addition, as described above, a silicon single crystal substrate having a (110) orientation is used for the cavity plate 2 by performing anisotropic wet etching on the silicon substrate so that the side surfaces of the recesses and the grooves are formed on the upper surface of the silicon substrate. This is because the etching can be performed perpendicularly to the lower surface, whereby the density of the inkjet head can be increased.

An insulating film made of SiO ₂ or TEOS (Tetraethylorthosilicate Tetraethoxysilane) is formed on the entire surface of the cavity plate 2 or at least the surface facing the electrode substrate 3 by thermal oxidation or plasma CVD (Chemical Vapor Deposition). 26 is applied with a film thickness of 0.1 μm. This insulating film 26 is provided for the purpose of preventing dielectric breakdown and short circuit when the ink jet head is driven.

  The electrode substrate 3 is made from a glass substrate having a thickness of about 1 mm, for example. Among them, it is suitable to use a borosilicate heat-resistant hard glass having a thermal expansion coefficient close to that of the silicon substrate of the cavity plate 2. This is because when the electrode substrate 3 and the cavity plate 2 are anodically bonded, the thermal expansion coefficients of the two substrates are close to each other, so that the stress generated between the electrode substrate 3 and the cavity plate 2 can be reduced, and as a result, peeling, etc. This is because the electrode substrate 3 and the cavity plate 2 can be firmly bonded without causing the above problem.

  The electrode substrate 3 is provided with a recess 32 at a position on the surface of the cavity plate 2 facing each diaphragm 22. The recess 32 is formed with a depth of about 0.3 μm by etching. And in each recessed part 32, the individual electrode 31 which generally consists of ITO (Indium Tin Oxide: Indium tin oxide) is formed by the thickness of 0.1 micrometer, for example. Therefore, the gap (gap) formed between the diaphragm 22 and the individual electrode 31 is determined by the depth of the recess 32 and the thickness of the insulating film 26 covering the individual electrode 31 and the diaphragm 22. This gap greatly affects the ejection characteristics of the inkjet head. Here, the material of the individual electrode 31 is not limited to ITO, and a metal such as chromium may be used. However, since ITO is transparent, it is generally easy to confirm whether or not a discharge has occurred. ITO is used.

  The individual electrode 31 has a lead part 31a and a terminal part 31b connected to a flexible wiring board (not shown). As shown in FIGS. 1 to 3, these terminal portions 31 b are exposed in the electrode extraction portion 29 in which the end portion of the cavity plate 2 is opened for wiring.

  As described above, the nozzle plate 1, the cavity plate 2, and the electrode substrate 3 are generally manufactured individually, and the main body of the inkjet head 10 is manufactured by bonding them together as shown in FIG. 2. That is, the cavity plate 2 and the electrode substrate 3 are joined by anodic bonding, and the nozzle plate 1 is joined to the upper surface (the upper surface in FIG. 2) of the cavity plate 2 by adhesion or the like. Furthermore, the open end portion of the interelectrode gap formed between the diaphragm 22 and the individual electrode 31 is sealed with a sealing material 27 made of resin such as epoxy. Thereby, moisture and dust can be prevented from entering the gap between the electrodes, and the reliability of the inkjet head 10 can be kept high.

Finally, as shown in a simplified manner in FIGS. 2 and 3, a drive control circuit 4 such as an IC driver is connected to the terminal portion 31 b of each individual electrode 31 and the common electrode 28 provided on the cavity plate 2. They are connected via a wiring board (not shown).
Thus, the ink jet head 10 is completed.

Next, the operation of the inkjet head 10 configured as described above will be described.
The drive control circuit 4 is an oscillation circuit that controls the supply and stop of charges to the individual electrodes 31. This oscillation circuit oscillates at, for example, 24 kHz, and supplies electric charges by applying pulse potentials of, for example, 0 V and 30 V to the individual electrodes 31. When the oscillation circuit is driven and charges are supplied to the individual electrode 31 to be positively charged, the diaphragm 22 is negatively charged and an electrostatic force (Coulomb force) is generated between the individual electrode 31 and the diaphragm 22. Therefore, the diaphragm 22 is attracted to the individual electrode 31 by this electrostatic force and bends (displaces). As a result, the volume of the discharge chamber 21 increases. When the supply of electric charges to the individual electrode 31 is stopped, the diaphragm 22 returns to its original state due to its elastic force, and at this time, the volume of the discharge chamber 21 decreases rapidly. Part of the ink is ejected from the nozzle hole 11 as an ink droplet. Next, when the vibration plate 22 is similarly displaced, ink is supplied from the reservoir 23 to the discharge chamber 21 through the orifice 13.

As described above, the inkjet head 10 according to the first embodiment includes the cylindrical injection port portion 11a in which the nozzle holes 11 are perpendicular to the surface (discharge surface) of the nozzle plate 1, and the coaxial with the injection port portion 11a. The nozzle hole 11 has an inlet port portion 11b that is provided on the top and has a larger diameter than the jet port portion 11a, and a boundary portion 11c between the jet port portion 11a and the inlet port portion 11b is formed in a trumpet shape. The flow resistance of the nozzle hole 11 can be reduced without generating vortices or the like. Therefore, ink droplets can be ejected straight in the direction of the central axis of the nozzle hole 11 and have extremely stable ejection characteristics. Moreover, the discharge property of bubbles is also good.
Furthermore, since the cross-sectional shape of the inlet port portion 11b can be formed in a circular shape or a quadrangular shape, the density of the inkjet head 10 can be increased without reducing the thickness of the nozzle plate 1.

  In addition, the cross-sectional shape of the injection port portion 11a and the introduction port portion 11b of the nozzle hole 11 is not particularly limited, and is formed in a square shape or a circular shape. However, a circular shape is preferable because it is advantageous in terms of discharge characteristics and workability.

Next, a method for manufacturing the inkjet head 10 will be described with reference to FIGS.
4 to 7 are cross-sectional views of the manufacturing process showing the manufacturing method of the nozzle plate. FIGS. 8 and 9 are cross-sectional views of the manufacturing process showing the manufacturing method of the cavity plate 2 and the electrode substrate 3. Here, FIG. Now, a method for manufacturing the cavity plate 2 after bonding the silicon substrate 200 to the electrode substrate 3 will be mainly described.
First, a method for manufacturing the nozzle plate 1 will be described.

(1) Manufacturing Method of Nozzle Plate 1 First, a silicon substrate 100 having a thickness of 180 μm is prepared, and a SiO ₂ film 101 having a thickness of 1 μm is uniformly formed on the entire surface of the silicon substrate 100 (FIG. 4A). ). The SiO ₂ film 101 is formed, for example, by setting the silicon substrate 100 in a thermal oxidation apparatus and performing thermal oxidation for 4 hours in an oxygen and water vapor mixed atmosphere at an oxidation temperature of 1075 ° C. The SiO ₂ film 101 is used as an etching resistant material for silicon.

Next, a resist 102 is coated on both surfaces of the silicon substrate 100, and a portion 105b to be the inlet portion 11b of the nozzle hole 11 is patterned on the joint surface 100b on the side to be joined to the cavity plate 2, thereby introducing the inlet portion 11b. Then, the resist 102 in the portion 105b is removed (FIG. 4B).
Then, for example, half-etching the SiO ₂ film 101 with a buffered hydrofluoric acid aqueous solution prepared by mixing an aqueous solution with an ammonium fluoride aqueous solution of hydrofluoric acid in a one-to-6, to reduce the SiO ₂ film 101 of the portion 105b of the inlet port portion 11b (FIG. 4 (C)).
After that, the resist 102 is peeled off (FIG. 4D).

  Next, after removing the resist 102, the resist 106 is coated again on both surfaces of the silicon substrate 100, and the portion 105a that becomes the injection port portion 11a of the nozzle hole 11 is patterned on the bonding surface 100b to form the injection port portion 11a. The resist 106a 105a is removed (FIG. 5E).

Then, for example, the SiO ₂ film 101 is half-etched with a buffered hydrofluoric acid aqueous solution in which a hydrofluoric acid aqueous solution and an ammonium fluoride aqueous solution are mixed 1: 6 to open the SiO ₂ film 101 of the portion 105a to be the injection port portion 11a ( FIG. 5 (F)). When the opening of the SiO ₂ film 101 is finished, the resists 106 on both sides are peeled off (FIG. 5G).

Next, as shown in FIG. 6H, the opening of the SiO ₂ film 101 is anisotropically dry-etched at a depth of 25 μm, for example, by dry etching using ICP (Inductively Coupled Plasma) discharge, so that the nozzle hole 11 A concave portion 107 to be the injection port portion 11a is formed. In this case, for example, C ₄ F ₈ (fluorocarbon: first etching gas) and SF ₆ (sulfur fluoride: second etching gas) are used as etching gases, and these etching gases are used alternately. And the etching gas introduction time is changed stepwise. Here, C ₄ F ₈ is used to protect the side surface of the recess 107 so that etching does not proceed in the side direction of the recess 107, and SF ₆ is used to promote the etching of the recess 107 in the vertical direction.

In the first embodiment, for example, the introduction times of C ₄ F ₈ and SF ₆ are started from 3 seconds and 4.5 seconds, respectively, and only the introduction time of SF ₆ is increased stepwise by 0.2 seconds. To 3 seconds and 6 seconds at the end. That is, the introduction time of C ₄ F ₈ is constant at 3 seconds each time, and only the introduction time of SF ₆ is increased stepwise by 0.02 seconds each time. This was alternately introduced 76 times for each etching gas, and anisotropic dry etching was performed so as to be 3 seconds and 6 seconds, respectively, at the end.

Next, half etching is performed with, for example, a buffered hydrofluoric acid aqueous solution in which a hydrofluoric acid aqueous solution and an ammonium fluoride aqueous solution are mixed 1: 6 so that only the SiO ₂ film 101 of the portion 105a to be the introduction port portion 11b is eliminated (FIG. 6 ( I)). Then, the opening of the SiO ₂ film 101 is again anisotropically dry etched at a depth of, for example, 40 μm by dry etching using ICP discharge, so that a recess 108 having a diameter larger than the recess 107, that is, the inlet portion 11b is obtained. A recess 108 is formed. As a result, the longitudinal cross-sectional shape of the recess 107 is changed from a bowl-shaped middle thick shape as shown in FIG. 6 (I) to the flange 109 being gradually etched as shown in FIGS. 6 (J) and 6 (K), and the inlet is tapered. Further, as shown in FIG. 6 (L), the inlet portion (boundary portion 11c of the injection port portion 11a and the inlet portion 11b of the nozzle hole 11) finally has a trumpet shape. Formed.

Next, after the SiO ₂ film 101 remaining on the surface of the silicon substrate 100 is removed with an aqueous hydrofluoric acid solution, the silicon substrate 100 is set in a thermal oxidation apparatus, an oxidation temperature of 1075 ° C., an oxidation time of 4 hours, and a mixed atmosphere of water vapor and oxygen. The SiO ₂ film 110 having a thickness of 1 μm is uniformly formed on the side surface and the bottom surface of the concave portion 107 to be the injection port portion 11a and the concave portion 108 to be the inlet portion 11b processed by the ICP dry etching apparatus. (FIG. 7M).

Next, a resist (not shown) is coated on both surfaces of the silicon substrate 100, and the portion 111 to be the ink ejection surface is patterned. For example, buffered hydrofluoric acid in which a hydrofluoric acid aqueous solution and an ammonium fluoride aqueous solution are mixed 1: 6. Etching with an aqueous solution opens the SiO ₂ film 110 and strips the resist (FIG. 7N).

  Next, the silicon substrate 100 is immersed in an aqueous potassium hydroxide solution having a concentration of 25 wt%, and the portion 111 that becomes the ink discharge surface is etched to form the ink discharge surface 112 (the bottom surface of the recess 12 in FIGS. 1 and 2). . At this time, the silicon substrate thickness of the etching part (substrate thickness of the nozzle part) is set to 60 μm (FIG. 7O). At this time, although not shown, the orifice 13 and the diaphragm portion 14 shown in FIGS. 1 and 2 are also formed by etching.

Finally, if the SiO ₂ film 110 on the surface of the silicon substrate 100 is removed with a hydrofluoric acid aqueous solution or the like, the nozzle plate 1 is completed (FIG. 7 (P)).

In the method of manufacturing a nozzle plate 1 of the first embodiment, first, the introduction time of the second C ₄ F _8, SF ₆ as an etching gas, respectively 3 seconds, starting from 3 seconds, SF ₆ As shown in FIG. 6 (K), even if only the introduction time of the nozzle is changed stepwise and becomes 3 seconds and 6 seconds at the end, the injection port portion 11a and the introduction port portion 11b of the nozzle hole 11 are The boundary portion 11c could be formed in a trumpet shape with a rounded shape.
In addition, the introduction time of C ₄ F ₈ is constant or monotonously decreased, and the introduction time of SF ₆ is constant or monotonously increased (except when the introduction times of C ₄ F ₈ and SF ₆ are both constant). Even if it makes it, the same nozzle shape (vertical cross-sectional shape) is obtained.
In dry etching, oxygen (O ₂ ), argon (Ar), hydrogen (H ₂ ), trifluoromethane (CHF ₃ ), or the like may be added to SF ₆ .
Further, in the manufacturing method of the nozzle plate 1 of the first embodiment, a borosilicate glass substrate can be used instead of the single crystal silicon substrate.

As described above, according to the manufacturing method of the nozzle plate 1 of the first embodiment, the anisotropy of the nozzle hole 11 is obtained by using two or more kinds of etching gas and changing the introduction time of the etching gas. By performing dry etching, the boundary portion 11c between the injection port portion 11a and the introduction port portion 11b of the nozzle hole 11 can be formed in a trumpet shape with high dimensional accuracy.
Moreover, since the nozzle hole 11 is produced only by anisotropic dry etching, the nozzle plate 1 can be produced at a lower cost compared to a production method combining anisotropic dry etching and anisotropic wet etching.

(2) Manufacturing Method of Cavity Plate 2 and Electrode Substrate 3 Here, a method for manufacturing the cavity plate 2 from the silicon substrate 200 after bonding the silicon substrate 200 to the electrode substrate 3 will be described with reference to FIGS. Briefly described.

The electrode substrate 3 is manufactured as follows.
First, a concave portion 32 is formed by etching a glass substrate 300 made of borosilicate glass or the like with a plate thickness of about 1 mm with hydrofluoric acid using, for example, a gold / chromium etching mask. Note that the recess 32 has a groove shape slightly larger than the shape of the individual electrode 31, and a plurality of the recesses 32 are formed for each individual electrode 31.
Then, an individual electrode 31 made of ITO (Indium Tin Oxide) is formed inside the recess 32 by sputtering, for example.
Thereafter, the hole 34a to be the ink supply hole 34 is formed by a drill or the like, whereby the electrode substrate 3 is manufactured (FIG. 8A).

  Next, after both surfaces of the silicon substrate 200 having a thickness of, for example, 525 μm are mirror-polished, a silicon oxide film made of TEOS (TetraEthylorthosilicate) having a thickness of 0.1 μm is formed on one surface of the silicon substrate 200 by plasma CVD (Chemical Vapor Deposition). An insulating film 26 is formed (FIG. 8B). Note that before the silicon substrate 200 is formed, a boron doped layer for forming the thickness of the diaphragm 22 with high accuracy may be formed using an etching stop technique. Etching stop is defined as a state in which bubbles generated from the etching surface are stopped, and in actual wet etching, it is determined that the etching is stopped when the generation of bubbles is stopped.

Then, the silicon substrate 200 and the electrode substrate 3 manufactured as shown in FIG. 8A are heated to, for example, 360 ° C., and the anode is connected to the silicon substrate 200 and the electrode substrate 3 is connected to the cathode, and the voltage is about 800V. A voltage is applied to join by anodic bonding (FIG. 8C).
After anodic bonding of the silicon substrate 200 and the electrode substrate 3, the bonded silicon substrate 200 is etched with an aqueous potassium hydroxide solution or the like, thereby reducing the thickness of the silicon substrate 200 to, for example, 140 μm (FIG. 8 ( D)).

Next, a TEOS film having a thickness of, for example, 1.5 μm is formed on the entire upper surface of the silicon substrate 200 (the surface opposite to the surface to which the electrode substrate 3 is bonded) by plasma CVD.
Then, a resist for forming the recess 24 to be the discharge chamber 21 and the recess 25 to be the reservoir 23 is patterned on the TEOS film, and the TEOS film in these portions is removed by etching.
Thereafter, the silicon substrate 200 is etched with a potassium hydroxide aqueous solution or the like, thereby forming a recess 24 to be the discharge chamber 21 and a recess 25 to be the reservoir 23 (FIG. 9E). At this time, the portion that becomes the electrode extraction portion 29 for wiring is also etched and thinned. In the wet etching step of FIG. 9E, for example, a 35% by weight potassium hydroxide aqueous solution can be used first, and then a 3% by weight potassium hydroxide aqueous solution can be used. Thereby, surface roughness of the diaphragm 22 can be suppressed.

After the etching of the silicon substrate 200 is completed, the TEOS film formed on the upper surface of the silicon substrate 200 is removed by etching with a hydrofluoric acid aqueous solution (FIG. 9F).
Next, a TEOS film (insulating film 26) is formed to a thickness of, for example, 0.1 μm by plasma CVD on the surface of the silicon substrate 200 where the recesses 24 to be the discharge chambers 21 are formed (FIG. 9G).
Thereafter, the electrode lead-out portion 29 is opened by RIE (Reactive Ion Etching) or the like. Further, laser processing is performed from the hole portion that becomes the ink supply hole 34 of the electrode substrate 3 to penetrate the bottom portion of the concave portion 25 that becomes the reservoir 23 of the silicon substrate 200, thereby forming the ink supply hole 34 (FIG. 9H). . Further, the open end portion of the interelectrode gap between the diaphragm 22 and the individual electrode 31 is sealed by filling a sealing material (not shown) such as an epoxy resin. Further, as shown in FIGS. 1 and 2, the common electrode 28 is formed on the end portion of the upper surface of the silicon substrate 200 (the surface on the bonding side with the nozzle plate 1) by sputtering.

As described above, the cavity plate 2 is manufactured from the silicon substrate 200 bonded to the electrode substrate 3.
Finally, the main body of the inkjet head 10 shown in FIG. 2 is manufactured by joining the nozzle plate 1 manufactured as described above to the cavity plate 2 by bonding or the like.

  According to the method of manufacturing the ink jet head 10 of the first embodiment, the cavity plate 2 is manufactured from the silicon substrate 200 in a state of being bonded to the electrode substrate 3 manufactured in advance. Since the plate 2 is supported, even if the cavity plate 2 is thinned, it is not cracked or chipped, and handling is easy. Therefore, the yield is improved as compared with the case where the cavity plate 2 is manufactured alone.

Embodiment 2. FIG.
FIG. 10 is a cross-sectional view of the ink jet head according to the second embodiment, in which the nozzle portion is further enlarged. In FIG. 10, the same parts as those in FIG.
In the second embodiment, a nozzle plate 400 is used instead of the nozzle plate 1 of the first embodiment, and the other configuration is the same as that of the first embodiment. In the following, the differences between the second embodiment and the first embodiment will be described, and overlapping descriptions will be omitted.

  The nozzle hole 41 of the nozzle plate 400 includes a cylindrical injection port portion 41a on the front end side in the discharge direction, and a tapered portion in which the nozzle cross-sectional area gradually increases from the injection port portion 41a toward the rear end side in the discharge direction. 41b. The injection port portion 41a is provided perpendicular to the surface of the nozzle plate 400 (the bottom surface of the recess 12 on the substrate surface), and the injection port portion 41a and the tapered portion 41b are provided coaxially. With this configuration, the ink droplet ejection direction can be aligned with the central axis direction of the nozzle hole 41, and stable ink ejection characteristics can be exhibited. That is, there is no variation in the flying direction of ink droplets, there is no scattering of ink droplets, and variations in the ejection amount of ink droplets can be suppressed.

  Here, in the second embodiment, when the nozzle density is increased, the manufacturing process of the nozzle plate 400 is characterized, and the manufacturing process will be described in detail below.

11 to 16 are cross-sectional views of the manufacturing process showing the method for manufacturing the nozzle plate 400.
First, a silicon substrate 411 having a substrate thickness of 280 μm is prepared, set in a thermal oxidation apparatus, and subjected to thermal oxidation treatment under conditions of an oxidation temperature of 1075 ° C., an oxidation time of 4 hours, and a mixed atmosphere of oxygen and water vapor. A SiO ₂ film 412 having a thickness of 1 μm, which serves as an etching protection film, is uniformly formed on both surfaces 411a and 411b (FIG. 11A).

Next, a resist 413 is coated on the bonding surface 411a on the silicon substrate 411 on the side to be bonded to the cavity plate 2, and a portion 413a corresponding to the spray port portion 41a is removed from the resist 413 to form a resist pattern (FIG. 11 (B)).
Then, using the resist pattern as a mask, etching is performed with, for example, a buffered hydrofluoric acid aqueous solution (hydrofluoric acid aqueous solution: ammonium fluoride aqueous solution = 1: 6), and a portion 412a corresponding to the injection port portion 41a is opened from the SiO ₂ film 412. . At this time, the SiO ₂ film 412 on the back surface 411b is etched and completely removed (FIG. 11C).
Thereafter, the resist pattern is peeled off by sulfuric acid cleaning or the like (FIG. 11D).

Next, anisotropic dry etching is performed vertically at a depth of 50 μm, for example, through the opening 412a of the SiO ₂ film 412 by an ICP dry etching apparatus to form the injection port portion 41a (FIG. 11E). As an etching gas in this case, for example, C ₄ F ₈ and SF ₆ are used, and these etching gases may be used alternately. Here, C ₄ F ₈ is used to protect the side surface of the groove so that the etching does not proceed to the side surface of the groove to be formed, and SF ₆ is used to promote the vertical etching of the Si substrate.
Thereafter, the SiO ₂ film 412 remaining on the surface of the silicon substrate 411 is removed with a hydrofluoric acid aqueous solution (FIG. 12F).
Then, the silicon substrate 411 is set in a thermal oxidation apparatus, and is subjected to thermal oxidation treatment under conditions of an oxidation temperature of 1075 ° C., an oxidation time of 4 hours, and a mixed atmosphere of oxygen and water vapor. A SiO ₂ film 414 having a thickness of 1 μm is uniformly formed (FIG. 12G). At this time, the SiO ₂ film 414 is also formed on the entire inner surface (side surface and bottom surface) of the injection port portion 41a.

Next, a resist 415 is coated on the bonding surface 411a of the silicon substrate 411 that is bonded to the cavity plate 2, and a portion 415a that serves as a gas introduction path when dry-etching the tapered portion 41b is formed from the resist 415. After removing, the resist 415 is patterned (FIG. 12H).
Then, using the resist pattern as a mask, the SiO ₂ film 414 is dry-etched with an RIE dry etching apparatus to form an opening 414a in the SiO ₂ film 414 (FIG. 12 (I)).
Thereafter, the resist pattern is removed by washing with sulfuric acid or the like (FIG. 12J).

FIG. 13 is a diagram showing step (J) in FIG. 12 and subsequent steps, and shows only the nozzle hole portion in an enlarged manner.
An ICP dry etching apparatus is used to dry-etch in a tapered shape using the SiO ₂ film 414 as an etching mask to form a tapered portion 41b (FIG. 13K). As an etching gas in this case, for example, a gas (first gas) that forms a protective film for protecting the side surface such that etching of the side surface such as C ₄ F ₈ does not proceed, and etching of the silicon substrate 411 such as SF ₆ are performed. A gas (second gas) that promotes gas and a gas (third gas) such as O ₂ that removes organic substances (here, a protective film) are mixed and introduced. As a result, tapered dry etching starting from the opening 414a of the SiO ₂ film 414 becomes possible. In this example, SF ₆ , C ₄ F ₈ and O ₂ are introduced at 20, 40 and 50 cc per minute, respectively, to form a tapered portion 41b having a taper angle of 75 degrees and a depth of 14 μm. Here, since the SiO ₂ film 414 as an etching protective film is formed on the side surface and the bottom surface of the injection port portion 41a, the etching port portion 41a is affected by the etching gas during the etching step (K). There is no such thing, and it is possible to maintain the shape of the injection port portion 41a.
Thereafter, the SiO ₂ film 414 remaining on the side surface and bottom surface of the injection port portion 41a and the surface of the silicon substrate 411 is removed with a hydrofluoric acid aqueous solution (FIG. 13L).

Then, the silicon substrate 411 is set in a thermal oxidation apparatus, an oxidation temperature of 1000 ° C., an oxidation time of 2 hours, thermal oxidation treatment is performed under conditions in an oxygen atmosphere, and an injection port portion 41a and a tapered portion processed by an ICP dry etching apparatus A SiO ₂ film 416 having a thickness of 0.1 μm is uniformly formed on the entire surface of the silicon substrate 411 including the side surface and the bottom surface of 41b (FIG. 14M).
Next, a double-sided tape 600 having a self-peeling layer 601 whose adhesion is easily reduced by stimulation with ultraviolet rays or heat is attached to a support substrate 500 made of a transparent material (glass or the like) (FIG. 14N). Specifically, the surface of the self-peeling layer 601 of the double-sided tape 600 bonded to the support substrate 500 and the bonding surface 411a of the silicon substrate 411 face each other and are bonded in a vacuum. As a result, clean adhesion without bubbles remaining at the bonding interface becomes possible. If bubbles remain at the bonding interface during the bonding, the thickness of the silicon substrate 411 to be thinned by the next grinding process (O) may cause variations.

Then, grinding is performed with a back grinder from the discharge surface side of the silicon substrate 411, and the silicon substrate 411 is thinned until the tip end portion 41c of the injection port portion 41a is opened (FIG. 14 (O)). Other thinning methods include a method using a polisher and a CMP apparatus. When these processing methods are used, abrasive residue or the like remains in the nozzle hole 41, so that the inner walls of the injection port portion 41a and the tapered portion 41b are washed in the water removal removal process of the abrasive in the nozzle hole 41. The In addition to these methods, the silicon substrate 411 may be thinned by dry etching. That is, for example, by dry etching using SF ₆ as an etching gas, the silicon substrate 411 is thinned until the SiO ₂ film 416 at the tip portion 41c of the injection port portion 41a is exposed, and the SiO ₂ film 416 at the tip portion 41c is then thinned. It may be removed by dry etching using an etching gas such as CF ₄ or CHF ₃ .

Next, the silicon substrate 411 is immersed in cleaning water in which ozone is dissolved for 10 minutes to form an oxide film 417 having a thickness of 2 nm on the discharge surface 411a (FIG. 14P). At this time, a part of the self-peeling layer 601 that has entered the nozzle hole 41 is also removed. In addition, the surface of the silicon substrate 411 is cleaned, and foreign matter and dirt are not attached. This makes it possible to uniformly coat the ink repellent film formed in the next step.
Subsequently, an ink repellent process is performed on the ejection surface 411a of the silicon substrate 411 (FIG. 14 (Q)). That is, an ink repellent material containing F atoms is formed by vapor deposition or dipping to form the ink repellent layer 418. At this time, the inner walls of the ejection port portion 41a and the tapered portion 41b are also subjected to ink repellent treatment.
Next, the support substrate 500 is peeled off. That is, first, the dicing tape 700 is attached as a support tape to the discharge surface 411a (FIG. 15R).

Then, UV light is irradiated from the support substrate 500 side, and the self-peeling layer 601 of the double-sided tape 600 is peeled from the silicon substrate 411 (FIG. 15S).
Then removed Ar sputtering or 0 ₂ plasma treatment ink-repellent layer 418 extra formed on the inner wall of the injection port portion 41a and a tapered portion 41b of the silicon substrate 411 (Fig. 15 (T)).
A surface 411b of the silicon substrate 411 opposite to the surface to which the dicing tape 700 is attached is adsorbed and fixed to an adsorbing jig 800 connected to a vacuum pump, and the dicing tape 700 is peeled in this state (FIG. 16U). ).
Finally, the suction fixing of the suction jig 800 is released, and the nozzle plate 400 is completed (FIG. 16 (V)). Although not shown, a through groove is formed in the silicon substrate 411 at the same time as the nozzle hole 41 is formed in the nozzle plate outer ring, and the nozzle plate 400 is removed when the suction jig 800 is removed. It is designed to be divided into pieces.

As another example, when the gas introduction amount in the step (K) is such that SF ₆ , C ₄ F ₈ , and O ₂ are 20, 40, and 70 cc per minute, respectively, the taper angle is 65 degrees. A tapered portion 41b having a depth of 13 μm could be formed.

As described above, according to the manufacturing method of the nozzle plate 400 of the second embodiment, since the tapered portion 41b is formed by dry etching without depending on anisotropic wet etching, the nozzle density can be increased. It is. In addition, since the entire nozzle hole is formed by dry etching, the boundary portion between the injection port portion 41a and the tapered portion 41b can be formed into a smooth and continuous shape, has good bubble discharge properties, and has stable discharge characteristics. An ink jet head can be formed. Further, in the etching process when forming the tapered portion 41b, the side surface and the bottom surface of the injection port portion 41a are protected by the SiO ₂ film 414 as an etching protection film, and therefore the influence of the etching gas on the hole diameter of the injection port portion 41a. It is possible to prevent this, and the hole diameter accuracy of the injection port portion 41a can be maintained.

  Further, since the hole shape on the tip side of the nozzle hole 41 is a cylindrical shape, when the silicon substrate 411 serving as the nozzle plate 400 is ground to open the tip portion 41c of the nozzle hole 41, the grinding amount is larger than a predetermined amount. Even if there is a slight deviation, the nozzle hole diameter, which is very much related to the discharge performance, does not change, so that it is possible to manufacture with a high yield, that is, it is possible to manufacture at a low cost.

  Further, by forming the nozzle hole 41 by dry etching using ICP (Inductively Coupled Plasma) discharge, it can be formed with high accuracy in a short time.

  In each of the above embodiments, the ink jet head, the nozzle plate thereof, and the manufacturing method thereof have been described. However, the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the idea of the present invention. Can be changed. For example, by changing the liquid material ejected from the nozzle holes, in addition to inkjet printers, the production of color filters for liquid crystal displays, the formation of light-emitting portions of organic EL display devices, the microarray of biomolecule solutions used for genetic testing, etc. It can be used as a droplet discharge device for various uses such as manufacture of

FIG. 2 is an exploded perspective view illustrating a schematic configuration of the inkjet head according to the first embodiment. FIG. 2 is a cross-sectional view of the inkjet head showing a schematic configuration of the right half of FIG. 1. FIG. 3 is a top view of the inkjet head of FIG. 2. Sectional drawing of the manufacturing process which shows the manufacturing method of a nozzle plate. Sectional drawing which shows the manufacturing process following FIG. Sectional drawing which shows the manufacturing process following FIG. Sectional drawing which shows the manufacturing process following FIG. Sectional drawing of the manufacturing process which shows the manufacturing method of a cavity plate and an electrode substrate. Sectional drawing which shows the manufacturing process following FIG. FIG. 4 is a cross-sectional view of an inkjet head according to a second embodiment. Sectional drawing of the manufacturing process which shows the manufacturing method of the nozzle plate of FIG. Sectional drawing of the manufacturing process of the nozzle plate following FIG. Sectional drawing of the manufacturing process of the nozzle plate following FIG. Sectional drawing of the manufacturing process of the nozzle plate following FIG. Sectional drawing of the manufacturing process of the nozzle plate following FIG. FIG. 16 is a cross-sectional view of the nozzle plate manufacturing process following FIG. 15.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nozzle plate, 2 Cavity plate, 3 Electrode board | substrate, 4 Drive control circuit, 10 Inkjet head, 11 Nozzle hole, 11a Ejection port part, 11b Introduction port part, 11c Boundary part, 12 Recessed part, 13 Orifice, 14 Diaphragm part, 21 Discharge chamber, 22 Diaphragm, 23 Reservoir, 24 Recessed part, 25 Recessed part, 26 Insulating film, 27 Sealing material, 28 Common electrode, 29 Electrode extracting part, 31 Individual electrode, 31a Lead part, 31b Terminal part, 32 Recessed part, 34 Ink supply hole, 100 silicon substrate, 101 SiO ₂ film, 102 resist, 106 resist, 107 recess, 108 recess, 109 collar, 110 SiO ₂ film, 112 ink ejection surface, 200 silicon substrate, 300 glass substrate, 411 silicon substrate 412 SiO ₂ film, 414 SiO ₂ film, 414a opening .

Claims (4)

The nozzle hole for discharging the droplet is a cylindrical portion perpendicular to the substrate surface and is the tip side in the discharge direction, and the cross-sectional area of the nozzle from the nozzle portion toward the rear end side in the discharge direction Wherein the nozzle hole is formed by etching a silicon substrate, and the nozzle hole is formed by etching a silicon substrate,
Applying dry etching to one surface of the silicon substrate to form the injection port portion;
Forming an etching protective film on at least the one surface and the side surface and bottom surface of the injection port portion;
Of the etching protective film, the step of forming the opening by removing the peripheral portion of the spray port portion larger than the hole diameter of the spray port portion;
Performing dry etching on the silicon substrate having the etching protective film in which the opening is formed, and forming the tapered portion;
And a step of thinning the silicon substrate from the surface opposite to the one surface until the tip of the injection port portion is opened.   In the dry etching for forming the tapered portion, the first gas for forming a protective film for protecting the side surface by suppressing the etching in the side surface direction of the tapered portion, and the depth of the tapered portion. 2. The method according to claim 1, wherein the second gas for promoting lateral etching and the third gas for adjusting the taper angle by etching the protective film are introduced. Manufacturing method of nozzle plate.   3. The method for manufacturing a nozzle plate according to claim 1, wherein the dry etching is dry etching by ICP discharge.   A method for manufacturing a droplet discharge head, wherein the droplet discharge head is manufactured using the method for manufacturing a nozzle plate according to claim 1.

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