Substrate having a hole, method for manufacturing the substrate, infrared sensor, and method for manufacturing the infrared sensor

A resist mask 40, having penetrating holes 41, is formed on a rear surface of a silicon substrate 2. A planar shape of each penetrating hole 41 is formed to a shape with which its respective sides are curved to inwardly convex arcuate shapes with respect to a regular quadrilateral that is a target shape of a transverse section at a processing ending end side of a corresponding cavity 3. Next, dry etching is applied to the silicon substrate 2. The cavities 3 are thereby formed in the silicon substrate 2. As the etching progresses, a transverse sectional shape of each cavity 3 decreases in inward projection amounts of the respective arcuate shaped sides in the transverse sectional shape of the corresponding penetrating hole 41 of the resist mask 40. At a processing ending end side of the cavity 3, its planar shape is substantially the same shape as the regular quadrilateral that is the target shape.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a substrate having a hole, a method for manufacturing the substrate, an infrared sensor, and a method for manufacturing the infrared sensor.

2. Description of the Related Art

As a method for forming a hole, with which a transverse sectional shape is a polygonal shape, in a substrate, there is known a method where dry etching using a mask having a penetrating hole with a transverse section that is a polygon is applied to the substrate.

SUMMARY OF THE INVENTION

The inventor of preferred embodiments of the present invention described and claimed in the present application conducted an extensive study and research regarding a substrate having a hole and a method for manufacturing the substrate, such as the one described above, and in doing so, discovered and first recognized new unique challenges and previously unrecognized possibilities for improvements as described in greater detail below.

When a hole is formed in a substrate by dry etching using a mask having a penetrating hole with which a transverse sectional shape is a polygon, a transverse sectional shape at a processing ending end side is blunted in comparison to the transverse sectional shape of the penetrating hole of the mask. There is thus a problem that the transverse sectional shape at the processing ending end side cannot be formed to a predetermined polygon.

A conventional method for forming a hole, with which a transverse sectional shape is, for example, a regular quadrilateral shape (square), in a substrate shall now be described with reference toFIG. 19A,FIG. 19B, andFIG. 19C.FIG. 19Ais a plan view,FIG. 19Bis a vertical sectional view, andFIG. 19Cis a bottom view.

A mask110has a penetrating hole111with which a transverse sectional shape is a regular tetragon. Dry etching is applied to a substrate100in a state where the mask110is disposed at a surface side of the substrate100(upper surface side of the substrate100in the present example). A hole101is thereby formed in the substrate100. As shown inFIG. 19C, a bottom surface shape (transverse sectional shape) at a processing ending end side of the hole101is a shape that is not a regular tetragon but is close to being a circle.

An object of the present invention is to provide a substrate having a hole, with which a transverse sectional shape at a processing ending end side is a shape close to being a predetermined polygon, and a method for manufacturing the substrate.

An object of the present invention is to provide an infrared sensor that includes a substrate having a hole, with which a transverse sectional shape at a processing ending end side is a shape close to being a predetermined polygon, and a method for manufacturing the infrared sensor.

In order to overcome the previously unrecognized and unsolved challenges described above, a preferred embodiment of the present invention provides a substrate having a hole. With the substrate having the hole, a transverse sectional shape of a processing starting end side of the hole is a shape with which respective sides of a predetermined polygon are formed to inwardly convex arcuate shapes and a transverse sectional shape of a processing ending end side of the hole is a shape closer to the predetermined polygon in comparison to the transverse sectional shape of the processing starting end side of the hole. With the present arrangement, a substrate with which a transverse sectional shape of a processing ending end side of a hole is a shape close to a predetermined polygonal shape is obtained.

In the preferred embodiment of the present invention, the predetermined polygon is a quadrilateral.

In the preferred embodiment of the present invention, the predetermined polygon is a triangle.

An infrared sensor according to the present invention includes the substrate having the hole, a heat insulating film held by the substrate so as to face the hole, and a pyroelectric element formed above the heat insulating film.

With the present arrangement, an infrared sensor that includes a substrate with which a transverse sectional shape of a processing ending end side of a hole is a shape close to a predetermined polygon is obtained. Also with the present arrangement, the hole of the substrate can be used as a cavity for thermally separating the pyroelectric element from the substrate.

With the preferred embodiment of the present invention, the pyroelectric element includes a lower electrode formed at a surface of the heat insulating film at an opposite side from the hole, an upper electrode disposed at an opposite side from the heat insulating film with respect to the lower electrode, and a pyroelectric film provided between the lower electrode and the upper electrode.

The present invention is a method for manufacturing a substrate having a hole and includes a step of disposing, on one surface side of the substrate, a mask having a penetrating hole with a shape with respective sides thereof being curved to inwardly convex arcuate shapes with respect to a predetermined polygon and a step of applying dry etching to the substrate via the mask to forma hole in the substrate.

With the present manufacturing method, a substrate having a hole, with which a transverse sectional shape of a processing ending end side is a shape close to a predetermined polygon, can be manufactured.

In the preferred embodiment of the present invention, the predetermined polygon is a quadrilateral.

In the preferred embodiment of the present invention, the predetermined polygon is a triangle.

A method for manufacturing an infrared sensor according to the present invention includes a step of forming a heat insulating film above one surface of the substrate, a step of forming a pyroelectric element above the heat insulating film, a step of forming a covering film covering surfaces of the heat insulating film and the pyroelectric element, a step of forming, above the pyroelectric element, a contact hole, exposing a portion of the upper electrode, in the covering film, a step of forming, above the covering film, a wiring with one end portion contacting the upper electrode via the contact hole and another end portion being led to an outer side of the pyroelectric element, and a step of forming a cavity, penetrating through the substrate in a thickness direction, at a position of the substrate facing the pyroelectric element. The step of forming the cavity includes a step of disposing, on a surface of the substrate at an opposite side from the surface at which the heat insulating film has been formed, a mask having a penetrating hole with a shape with respective sides thereof being curved to inwardly convex arcuate shapes with respect to a predetermined polygon and a step of applying dry etching to the substrate via the mask to form the cavity in the substrate.

With the present manufacturing method, an infrared sensor can be manufactured that includes a substrate having a hole, with which a transverse sectional shape of a processing ending end side is a shape close to a predetermined polygon.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention shall now be descried in detail with reference to the attached drawings.

FIG. 1is a schematic plan view of an infrared sensor to which a substrate having a hole according to a first preferred embodiment of the present invention is applied.FIG. 2is a schematic enlarged plan view showing a vicinity of an A portion ofFIG. 1in enlarged manner.FIG. 3is a schematic sectional view taken along line III-III inFIG. 2. InFIG. 2, a filter layer indicated by the symbol16inFIG. 3is omitted.

The infrared sensor1includes a silicon substrate2. A plurality of cavities3, penetrating through the silicon substrate2in a thickness direction, are formed in the silicon substrate2. The cavities3are formed by digging in from a rear surface of the silicon substrate2. The cavities3are formed to thermally separate pyroelectric elements10, to be described below, from the silicon substrate2. Each cavity3is formed to a regular quadrilateral (square) shape in plan view. The plurality of cavities3are disposed in an array in plan view. The cavity3is an example of a hole according to the present invention.

A heat insulating film4is formed above the silicon substrate2to close the cavities3. The heat insulating film4is constituted of silicon oxide (SiO2) in the present preferred embodiment. Above the heat insulating film4, pyroelectric elements10are disposed at positions facing the respective cavities3. Each pyroelectric element10is formed to a regular quadrilateral shape in plan view. The plurality of pyroelectric elements10are disposed in an array in plan view.

The pyroelectric elements10include lower electrodes5, formed at a front surface of the heat insulating film4at an opposite side from the cavities3, pyroelectric films6, formed above the lower electrode5, and upper electrodes7, formed above the pyroelectric films6.

Each lower electrode5is constituted of main electrode portions5A, each of regular quadrilateral shape in plan view that constitutes the corresponding pyroelectric element10, lead-out portions5B, each extending outside the corresponding cavity3from a center of length of one side of the corresponding main electrode portion5A, and a wiring portion5C, connected to corresponding lead-out portions5B and extending in parallel to the one side of corresponding main electrode portions5A. The lower electrode5has, for example, a two-layer structure with which a layer constituted of titanium (Ti) and a layer constituted of platinum (Pt) are laminated in that order from the heat insulating film4side.

Each pyroelectric film6is formed to a regular quadrilateral shape slightly smaller than the corresponding main electrode portion5A of the lower electrode5in plan view. The four sides of the pyroelectric film6are, in plan view, respectively parallel to the four sides of the main electrode portion5A of the lower electrode5and disposed at inner sides across predetermined intervals with respect to the corresponding sides of the main electrode portion5A. In the present preferred embodiment, the pyroelectric film6is constituted of lead zirconate titanate (PZT:Pb(Zr,Ti)O3) and is formed, for example, by a sol-gel method.

Each upper electrode7is formed to a regular quadrilateral shape slightly smaller than the corresponding pyroelectric film6in plan view. The four sides of the upper electrode7are, in plan view, respectively parallel to the four sides of the pyroelectric film6and disposed at inner sides across predetermined intervals with respect to the corresponding sides of the pyroelectric film6. In the present preferred embodiment, the upper electrode7has a two-layer structure with which a layer constituted of iridium (Ir) and a layer constituted of iridium oxide (IrO2) are laminated in that order from the pyroelectric film6side.

Also, a covering film11is formed above the heat insulating film4. Portions of an upper surface of the heat insulating film4exposed from the lower electrodes5, portions of upper surfaces of the main electrode portions5A of the lower electrodes5exposed from the pyroelectric films6, the lead-out portions5B and the wiring portions5C of the lower electrodes5, portions of upper surfaces of the pyroelectric films6exposed from the upper electrodes7, side surfaces of the pyroelectric films6, and the upper electrodes7are covered all together by the covering film6. The cover film11includes a hydrogen barrier film12, constituted of alumina (Al2O3), and an insulating film13, formed above the hydrogen barrier film12and constituted of silicon oxide (SiO2).

Wirings14are formed in a predetermined pattern above the covering film11. The wirings14are constituted of a metal material that contains aluminum (Al) as a main component. The wirings14are provided at positions facing the upper electrodes7across the cover film11. Between the wirings14and the upper electrodes7, penetrating holes (contact holes)15are formed to penetrate through in a thickness direction in the cover film11. One end portions of the wirings14enter into the penetrating holes15and are connected to the upper electrodes7inside the penetrating holes15. Each wiring14is constituted of electrode connection portions14A, each of regular quadrilateral shape in plan view having a central portion connected to the corresponding upper electrode7, lead-out portions14B, each extending outside the corresponding cavity3from a center of length of one side of the corresponding electrode connection portion14A, and a main wiring portion14C, connected to the lead-out portions14B and extending in parallel to the one side of the electrode connection portions14A. In plan view, the main wiring portions14C of the wiring14and the wiring portions5C of the lower electrode5are disposed so as to be orthogonal to each other.

Also, optical filter layers16, which transmit near infrared rays, are formed on surfaces of the covering film11and the wirings14at regions facing the cavities3in plan view. The optical filter layers16are constituted of titanium (Ti) in the present preferred embodiment.

When a temperature of the pyroelectric film6inside a pyroelectric element10increases due to incidence of infrared rays, a pyroelectric current due to spontaneous polarization of the pyroelectric film6is output from the pyroelectric element10. The infrared rays can thus be detected based on the pyroelectric current.

FIG. 4AtoFIG. 4Kare sectional views of an example of a manufacturing process of the infrared sensor1and show a section corresponding toFIG. 3.

First, as shown inFIG. 4A, the heat insulating film4is formed on a front surface of the silicon substrate2. However, as the silicon substrate2, that which is thicker in thickness than the silicon substrate2at a final stage is used. Specifically, the heat insulating film4constituted of a silicon oxide film is formed on the front surface of the silicon substrate2.

Next, as shown inFIG. 4B, a lower electrode film31, which is a material layer of the lower electrodes5, is formed above the heat insulating film4. The lower electrode film31is constituted, for example, of a Pt/Ti laminated film having a Ti film as a lower layer and a Pt film as an upper layer. Such a lower electrode film31may be formed by a sputtering method.

Next, a material film (pyroelectric material film)32of the pyroelectric films6is formed on an entire surface above the lower electrode film31. Specifically, the pyroelectric material film32is formed, for example, by the sol-gel method. Such a pyroelectric material film32is constituted of a sintered body of metal oxide crystal grains.

Next, an upper electrode film33, which is a material of the upper electrodes7, is formed on an entire surface of the pyroelectric material film32. The upper electrode film33is constituted, for example, of an IrO2/Ir laminated film having an IrO2film as a lower layer and an Ir layer as an upper layer. Such an upper electrode film33may be formed by the sputtering method.

Next, as shown inFIG. 4CtoFIG. 4E, patterning of the upper electrode film33, the pyroelectric material film32, and the lower electrode film31is performed. First, a resist mask with a pattern of the upper electrodes7is formed by photolithography. Then, as shown inFIG. 4C, the upper electrode film33is etched using the resist mask as a mask to form the upper electrodes7of the predetermined pattern.

Next, after peeling off the resist mask, a resist mask with a pattern of the pyroelectric films6is formed by photolithography. Then, as shown inFIG. 4D, the pyroelectric material film32is etched using the resist mask as a mask to form the pyroelectric films6of the predetermined pattern.

Next, after peeling off the resist mask, a resist mask with a pattern of the lower electrodes5is formed by photolithography. Then, as shown inFIG. 4E, the lower electrode film31is etched using the resist mask as a mask to form the lower electrodes5of the predetermined pattern. The lower electrodes5, each constituted of the main electrode portions5A, the lead-out portions5B, and the wiring portion5C, are thereby formed. The pyroelectric elements10, each constituted of the main electrode portion5A of the lower electrode5, the pyroelectric film6, and the upper electrode7, are thereby formed.

Next, after peeling off the resist mask, the hydrogen barrier film12covering the entire surface is formed as shown inFIG. 4F. The hydrogen barrier film12is, for example, an Al2O3film formed by the sputtering method. The insulating film13is thereafter formed on an entire surface above the hydrogen barrier film12. The insulating film13is, for example, an SiO2film. The covering film11, constituted of the hydrogen barrier film12and the insulating film13, is thereby formed. Subsequently, the penetrating holes (contact holes)15are formed by successively etching the insulating film13and the hydrogen barrier film12.

Next, as shown inFIG. 4G, a wiring film constituting the wirings14is formed by the sputtering method above the insulating film13(covering film11), including interiors of the penetrating holes15. Thereafter, the wiring film is patterned by photolithography and etching to form the wirings14.

Next, a titanium layer, which is a material of the optical filter layers16, is formed on surfaces of the insulating film13(covering film11) and the wirings14. Thereafter, the titanium layer is patterned by photolithography and etching to form the filter layers16as shown inFIG. 4H. Next, as shown inFIG. 4I, the silicon substrate2is made thin by the silicon substrate2being ground from the rear surface.

Next, as shown inFIG. 4JandFIG. 4K, the cavities3are formed in the silicon substrate2. In the present preferred embodiment, each cavity3is formed so that a transverse sectional shape of a processing ending end side (heat insulating film side) of the cavity3will be a quadrilateral shape. In other words, a target shape of a transverse section of the processing ending end side (heat insulating film side) of the cavity3is a regular quadrilateral. First, as shown inFIG. 4J, a resist mask40, having penetrating holes41, is formed by photolithography on a rear surface of the silicon substrate2.FIG. 5is a plan view of a portion of the resist mask40. A planar shape (transverse sectional shape) of each penetrating hole41is formed to a shape with which its respective sides are curved to inwardly convex arcuate shapes with respect to the target shape (the regular quadrilateral indicated by alternate long and two short dashes lines T inFIG. 5) of the transverse section at the processing ending end side of the corresponding cavity3.

Next, in the state where the resist mask40is formed on the rear surface of the silicon substrate2, dry etching is applied to the silicon substrate2. For example, plasma etching is used as the dry etching. The cavities3are thereby formed in the silicon substrate2as shown inFIG. 4K.

FIG. 6Ais a bottom view of a bottom surface shape at a processing starting end side (the substrate2rear surface side) of a cavity3.FIG. 6Bis a sectional view taken along VIB-VIB inFIG. 4K. That is,FIG. 6Bis a sectional view of a transverse sectional shape at a center-of-length portion (center-of-depth portion) of the cavity3.FIG. 6Cis a plan view of a planar shape at a processing ending end side (the substrate2front surface side) of the cavity3.

As shown inFIG. 5, the transverse sectional shape of each penetrating hole41formed in the resist mask40is formed to the shape with which its respective sides are curved to inwardly convex arcuate shapes with respect to the target shape T of the transverse section at the processing ending end side of the corresponding cavity3. Therefore, as shown inFIG. 6A, the bottom surface shape at the processing starting end side (the substrate2rear surface side) of the cavity3is substantially the same shape as the transverse sectional shape of the penetrating hole41. As the etching progresses, inward projection amounts of the respective arcuate shaped sides of the transverse sectional shape of the cavity3decrease as shown, for example, inFIG. 6B. That is, as the etching progresses, the transverse sectional shape of the cavity3approaches the regular quadrilateral that is the target shape T. At the processing ending end side (the substrate2front surface side) of the cavity3, the planar shape is substantially the same shape as the regular quadrilateral that is the target shape T as shown inFIG. 6C.

In other words, in comparison to the transverse sectional shape at the processing starting end side (the substrate2rear surface side) of the cavity3, the transverse sectional shape at the processing ending end side of the cavity3is a shape that is closer to the regular quadrilateral that is the target shape T. In the present preferred embodiment, the inward projection amounts of the respective arcuate shaped sides of the transverse sectional shape of the penetrating hole41are determined so that the transverse sectional shape at the processing ending end side (the substrate2front surface side) of the cavity3will be a shape that is substantially the same as the regular quadrilateral that is the target shape T.

With the preferred embodiment described above, the transverse sectional shape at the processing ending end side of each cavity3can be made a shape close to a target shape (a predetermined polygon).

Although with the preferred embodiment described above, the target shape of the transverse section at the processing ending end side of each cavity3is a regular quadrilateral, the target shape may be a polygon other than a regular quadrilateral, such as a triangle, a quadrilateral other than a regular quadrilateral, a pentagon, or a hexagonal shape. When the target shape of the transverse section at the processing ending end side of each cavity3is a polygon, each penetrating hole formed in the resist mask for forming the cavities is formed to a shape with which respective sides thereof are curved to inwardly convex arcuate shapes with respect to the polygon that is the target shape.

For example, if the target shape of the transverse section at the processing ending end side of each cavity3is a regular triangle, a resist mask40A having a penetrating hole41A such as shown inFIG. 7Ais used. The penetrating hole41A is formed to a shape with which respective sides thereof are curved to inwardly convex arcuate shapes with respect to the regular triangle that is the target shape. When dry etching is applied to the substrate2using the resist mask40A shown inFIG. 7A, the planar shape at the processing ending end side of the cavity3becomes a shape such as shown inFIG. 7B.

FIG. 8Ais an illustrative plan view for describing the arrangement of a main portion of an inkjet printing head to which a substrate having a hole according to a second preferred embodiment of the present invention is applied.FIG. 8Bis an illustrative plan view of the main portion of the inkjet printing head and is a plan view with a protective substrate omitted.FIG. 9is an illustrative sectional view taken along line IX-IX inFIG. 8A.FIG. 10is an illustrative enlarged sectional view of a portion of a section taken along line X-X inFIG. 8A.FIG. 11is an illustrative plan view of a pattern example of a lower electrode of the inkjet printing head.

The arrangement of an inkjet printing head201shall now be described in outline with reference toFIG. 9.

The inkjet printing head201includes an actuator substrate202, a nozzle substrate203, and a protective substrate204. A movable film formation layer210is laminated on a front surface202aof the actuator substrate202. In the actuator substrate202, ink flow passages (ink reservoirs)205are formed. In the present preferred embodiment, the ink flow passages205are formed to penetrate through the actuator substrate202. Each ink flow passage205is formed to be elongate along an ink flow direction241, which is indicated by an arrow inFIG. 9. Each ink flow passage205is constituted of an ink inflow portion206at an upstream side end portion (left end portion inFIG. 9) in the ink flow direction241and a pressure chamber207in communication with the ink inflow portion206. InFIG. 9, a boundary between the ink inflow portion206and the pressure chamber207is indicated by an alternate long and two short dashes line.

The nozzle substrate203is constituted, for example, of a silicon substrate. The nozzle substrate203is adhered to a rear surface202bof the actuator substrate202. The nozzle substrate203, together with the actuator substrate202and the movable film formation layer210, defines the ink flow passages205. More specifically, the nozzle substrate203defines bottom surface portions of the ink flow passages205. The nozzle substrate203has ink discharge holes203aeach facing a pressure chamber207. Each ink discharge hole203apenetrates through the nozzle substrate203and has a discharge port203bat an opposite side from the pressure chamber207. Therefore, when a volume change occurs in a pressure chamber207, the ink retained in the pressure chamber207passes through the ink discharge hole203aand is discharged from the discharge port203b. The ink discharge hole203ais an example of the hole of the present invention.

Each portion of the movable film formation layer210that is a top roof portion of a pressure chamber207constitutes a movable film210A. The movable film210A (movable film formation layer210) is constituted, for example, of a silicon oxide (SiO2) film formed above the actuator substrate202. The movable film210A (movable film formation layer210) may be constituted of a laminated film, for example, of a silicon (Si) film formed above the actuator substrate202, a silicon oxide (SiO2) film formed above the silicon film, and a silicon nitride (SiN) film formed above the silicon oxide film. In the present specification, the movable film210A refers to a top roof portion of the movable film formation layer210that defines the top surface portion of the pressure chamber207. Therefore, portions of the movable film formation layer210besides the top roof portions of the pressure chambers207do not constitute the movable film210A.

Each movable film210A has a thickness of, for example, 0.4 μm to 2 μm. If the movable film210A is constituted of a silicon oxide film, the thickness of the silicon oxide film may be approximately 1.2 μm. If the movable film210A is constituted of a laminated film of a silicon film, a silicon oxide film, and a silicon nitride film, the thickness of each of the silicon film, the silicon oxide film, and the silicon nitride film may be approximately 0.4 μm.

Each pressure chamber207is defined by a movable film210A, the actuator substrate202, and the nozzle substrate203and is formed to a substantially rectangular parallelepiped shape in the present preferred embodiment. The pressure chamber207may, for example, have a length of approximately 800 μm and a width of approximately 55 μm. Each ink inflow portion206is in communication with one end portion in a long direction of a pressure chamber207.

A piezoelectric element209is disposed on a front surface of each movable film210A. Each piezoelectric element209includes a lower electrode211formed above the movable film formation layer210, a piezoelectric film212formed above the lower electrode211, and an upper electrode213formed above the piezoelectric film212. In other words, the piezoelectric element209is arranged by sandwiching the piezoelectric film212from above and below by the upper electrode213and the lower electrode211.

The upper electrode213may be a single film of platinum (Pt) or may have a laminated structure, for example, in which a conductive oxide film (for example, an IrO2(iridium oxide) film) and a metal film (for example, an Ir (iridium) film) are laminated. The upper electrode213may have a thickness, for example, of approximately 0.2 μm.

As each piezoelectric film212, for example, a PZT (PbZrxTi1-xO3:lead zirconate titanate) film formed by a sol-gel method or a sputtering method may be applied. Such a piezoelectric film212is constituted of a sintered body of a metal oxide crystal. The piezoelectric film212is formed to be of the same shape as the upper electrode213in plan view. The piezoelectric film212has a thickness of approximately 1 μm. The overall thickness of each movable film210A is preferably approximately the same as the thickness of the piezoelectric film212or approximately ⅔ the thickness of the piezoelectric film212.

The lower electrode211has, for example, a two-layer structure with a Ti (titanium) film and a Pt (platinum) film being laminated successively from the movable film formation layer210side. Besides this, the lower electrode211may be formed of a single film that is an Au (gold) film, a Cr (chromium) layer, or an Ni (nickel) layer, etc. The lower electrode211has main electrode portions211A, in contact with lower surfaces of the piezoelectric films212, and an extension portion211B extending to a region outside the piezoelectric films212. The lower electrode211may have a thickness, for example, of approximately 0.2 μm.

A hydrogen barrier film214is formed above the extension portion211B of the lower electrode211and above the piezoelectric elements209. The hydrogen barrier film214is constituted, for example, of Al2O3(alumina). The hydrogen barrier film214has a thickness of approximately 50 nm to 100 nm. The hydrogen barrier film214is provided to prevent degradation of characteristics of the piezoelectric film212due to hydrogen reduction.

An insulating film215is laminated on the hydrogen barrier film214. The insulating film215is constituted, for example, of SiO2or low-hydrogen SiN, etc. The insulating film215has a thickness of approximately 500 nm. Upper wirings217, a lower wiring218, and dummy wirings219are formed above the insulating film215. These wirings217,218, and219may be constituted of a metal material that includes Al (aluminum). These wirings217,218, and219have a thickness, for example, of approximately 1000 nm (1 μm).

One end portion of each upper wiring217is disposed above one end portion (downstream side end portion in the ink flow direction241) of an upper electrode213. A contact hole233, penetrating continuously through the hydrogen barrier film214and the insulating film215, is formed between the upper wiring217and the upper electrode213. The one end portion of the upper wiring217enters into the contact hole233and is connected to the upper electrode213inside the contact hole233. From above the upper electrode213, the upper wiring217crosses an outer edge of the pressure chamber207and extends outside the pressure chamber207.

The lower wiring218is disposed above the extension portion211B of the lower electrode211at an opposite side from the pressure chambers207with respect to the ink inflow portions206of the ink flow passages205. A plurality of contact holes234, penetrating continuously through the hydrogen barrier film214and the insulating film215, are formed between the lower wiring218and the extension portion211B of the lower electrode211. The lower wiring218enters into the contact holes234and is connected to the extension portion211B of the lower electrode211inside the contact holes234.

The dummy wirings219are not electrically connected to either of the upper wirings217and the lower wiring218and are electrically insulated wirings. The dummy wirings219are formed in the same process as a process in which the upper wirings217and the lower wiring218are formed.

A passivation film221, covering the wirings217,218, and219and the insulating film215is formed above the insulating film215. The passivation film221is constituted, for example, of SiN (silicon nitride). The passivation film221may have a thickness, for example, of approximately 800 nm.

Pad openings235that expose portions of the upper wirings217are formed in the passivation film221. The pad openings235are formed in a region outside the pressure chambers207and are formed, for example, at tip portions (end portions at opposite sides from the portions of contact with the upper electrodes213) of the upper wirings217. Pads242that cover the pad openings235are formed above the passivation film221. The pads242enter into the pad openings235and are connected to the upper wirings217inside the pad openings235.

Ink supply penetrating holes222, penetrating through the passivation film221, the insulating film215, the hydrogen barrier film214, the lower electrode211, and the movable film formation layer210are formed at positions corresponding to end portions of the ink flow passages205at the ink inflow portion206sides. Penetrating holes223, each including an ink supply penetrating hole222and being larger than the ink supply penetrating hole222, are formed in the lower electrode211. The hydrogen barrier film214enters into gaps between the penetrating holes223in the lower electrode211and the ink supply penetrating holes222. The ink supply penetrating holes222are in communication with the ink inflow portions206.

The protective substrate204is constituted, for example, of a silicon substrate. The protective substrate204is disposed above the actuator substrate202so as to cover the piezoelectric elements209. The protective substrate204is bonded to the passivation film221via an adhesive250. The protective substrate204has housing recesses252in a facing surface251that faces a front surface202aof the actuator substrate202. The piezoelectric elements209are housed inside the housing recesses252. Further, the protective substrate204has formed therein ink supply passages253that are in communication with the ink supply penetrating holes222. The ink supply passages253penetrate through the protective substrate204. An ink tank (not shown) storing ink is disposed above the protective substrate204.

Each piezoelectric element209is formed at a position facing a pressure chamber207across a movable film210A. That is, the piezoelectric element209is formed to contact a front surface of the movable film210A at an opposite side from the pressure chamber207. Each pressure chamber207is filled with ink by the ink being supplied from the ink tank to the pressure chamber207through an ink supply passage253, an ink supply penetrating hole222, and an ink inflow portion206. The movable film210A defines a top surface portion of the pressure chamber207and faces the pressure chamber207. The movable film210A is supported by portions of the actuator substrate202at a periphery of the pressure chamber207and has flexibility enabling deformation in a direction facing the pressure chamber207(in other words, in the thickness direction of the movable film210A).

The upper wirings217and the lower wiring218are connected to a drive circuit (not shown). Specifically, the pads242of the upper wirings217and the drive circuit are connected via a connecting metal member (not shown). As shall be described later, a pad243(seeFIG. 8A) is connected to the lower wiring218. The pad243of the lower wiring218and the drive circuit are connected via a connecting metal member (not shown). When a drive voltage is applied from the drive circuit to a piezoelectric element209, the piezoelectric film212deforms due to an inverse piezoelectric effect. The movable film210A is thereby made to deform together with the piezoelectric element209to bring about a volume change of the pressure chamber207and the ink inside the pressure chamber207is pressurized. The pressurized ink passes through the ink discharge hole203aand is discharged as microdroplets from the discharge port203b.

The arrangement of the inkjet printing head201shall now be described in more detail with reference toFIG. 8AtoFIG. 11.

A plurality of the ink flow passages205(pressure chambers207) are formed as stripes extending parallel to each other in the actuator substrate202. The piezoelectric element209is disposed respectively in each of the plurality of ink flow passages205. The ink supply penetrating holes222are provided respectively for each of the plurality of ink flow passages205. The housing recesses252and the ink supply passages253in the protective substrate204are provided respectively for each of the plurality of ink flow passages205.

The plurality of ink flow passages205are formed at equal intervals that are minute intervals (for example, of approximately 30 μm to 350 μm) in a width direction thereof. Each ink flow passage205is elongate along the ink flow direction241. Each ink flow passage205is constituted of an ink inflow portion206in communication with an ink supply penetrating hole222and the pressure chamber207in communication with the ink inflow portion206. In plan view, the pressure chamber207has an oblong shape that is elongate along the ink flow direction241. That is, the top surface portion of the pressure chamber207has two side edges along the ink flow direction241and two end edges along a direction orthogonal to the ink flow direction241. In plan view, the ink inflow portion206has substantially the same width as the pressure chamber207. An inner surface of an end portion of the ink inflow portion206at an opposite side from the pressure chamber207is formed to a semicircle in plan view. The ink supply penetrating hole222is circular in plan view (see especiallyFIG. 8B).

Each piezoelectric element209has, in plan view, a rectangular shape that is long in a long direction of a pressure chamber207(movable film210A). A length in a long direction of the piezoelectric element209is shorter than a length in the long direction of the pressure chamber207(movable film210A). As shown inFIG. 8B, respective end edges along a short direction of the piezoelectric element209are disposed at inner sides at predetermined intervals respectively from respective corresponding end edges of the movable film210A. Also, a width in the short direction of the piezoelectric element209is narrower than a width in a short direction of the movable film210A. Respective side edges along the long direction of the piezoelectric element209are disposed at inner sides at predetermined intervals from respective corresponding side edges of the movable film210A.

The lower electrode211is formed on substantially an entirety of the front surface of the movable film formation layer210(see especiallyFIG. 11). The lower electrode211is a common electrode used in common for the plurality of piezoelectric elements209. The lower electrode211includes the main electrode portions211A of rectangular shape in plan view that constitute the piezoelectric elements209and the extension portion211B led out from the main electrode portions211A in directions along the front surface of the movable film formation layer210to extend outside the peripheral edges of the top surface portions of the pressure chambers207.

A length in a long direction of each main electrode portion211A is shorter than the length in the long direction of each movable film210A. Respective end edges of the main electrode portion211A are disposed at inner sides at predetermined intervals respectively from the respective corresponding end edges of the movable film210A. Also, a width in a short direction of the main electrode portion211A is narrower than the width of the movable film210A in the short direction. Respective side edges of the main electrode portion211A are disposed at inner sides at predetermined intervals from the respective corresponding side edges of the movable film210A. The extension portion211B is a region among the entire region of the lower electrode211that excludes the main electrode portions211A.

In plan view, the upper electrodes213are formed to rectangular shapes of the same pattern as the main electrode portions211A of the lower electrode211. That is, a length in a long direction of each upper electrode213is shorter than the length in the long direction of each movable film210A. Respective end edges of the upper electrode213are disposed at inner sides at predetermined intervals respectively from the respective corresponding end edges of the movable film210A. Also, a width in a short direction of the upper electrode213is narrower than the width in the short direction of the movable film210A. Respective side edges of the upper electrode213are disposed at inner sides at predetermined intervals from the respective corresponding side edges of the movable film210A.

In plan view, the piezoelectric films212are formed to rectangular shapes of the same pattern as the upper electrodes213. That is, a length in a long direction of each piezoelectric film212is shorter than the length in the long direction of each movable film210A. Respective end edges of the piezoelectric film212are disposed at inner sides at predetermined intervals respectively from the respective corresponding end edges of the movable film210A. Also, a width in a short direction of the piezoelectric film212is narrower than the width in the short direction of the movable film210A. Respective side edges of the piezoelectric film212are disposed at inner sides at predetermined intervals from the respective corresponding side edges of the movable film210A. A lower surface of the piezoelectric film212contacts an upper surface of the main electrode portion211A of the lower electrode211and an upper surface of the piezoelectric film212contacts a lower surface of the upper electrode213.

Each upper wiring217extends from an upper surface of one end portion of a piezoelectric element209and along an end surface of the piezoelectric element209continuous to the upper surface and extends further along the front surface of the extension portion211B of the lower electrode211in a direction along the ink flow direction241. The tip portion of the upper wiring217is disposed further downstream in the ink flow direction241than a downstream side end of the protective substrate204. The pad openings235that expose central portions of tip portion front surfaces of the upper wirings217are formed in the passivation film221. The pads242are provided on the passivation film221so as to cover the pad openings235. The pads242are connected to the upper wirings217inside the pad openings235.

In plan view, the lower wiring218has a rectangular main wiring portion218A that is long in a direction orthogonal to the ink flow direction241and a lead portion218B extending along the ink flow direction241from one end portion of the main wiring portion218A. A tip portion of the lead portion218B is disposed further downstream in the ink flow direction241than the downstream side end of the protective substrate204. The lower wiring218enters into the plurality of contact holes234and is connected to the extension portion211B of the lower electrode211inside the contact holes234. A pad opening236that exposes a central portion of a tip portion front surface of the lead portion218B is formed in the passivation film221. The pad243is provided above the passivation film221so as to cover the pad opening236. The pad243is connected to the lead portion218B inside the pad opening236.

FIG. 14is a bottom view of a main portion of the protective substrate as viewed from the actuator substrate side of the inkjet printing head.

As shown inFIG. 8A,FIG. 10, andFIG. 14, in the facing surface251of the protective substrate204, the plurality of housing recesses252are formed in parallel at intervals in a direction orthogonal to the ink flow direction241. In plan view, the plurality of housing recesses252are disposed at positions facing the plurality of pressure chambers207. With respect to the respective housing recesses252, the ink supply passages253are disposed at upstream sides in the ink flow direction241. In plan view, each housing recess252is formed to a rectangular shape slightly larger than the pattern of the upper electrode213of the corresponding piezoelectric element209. The corresponding piezoelectric element209is housed in each housing recess252.

In plan view, the ink supply passages253of the protective substrate204have circular shapes of the same pattern as the ink supply penetrating holes222at the actuator substrate202side. In plan view, the ink supply passages253are matched with the ink supply penetrating holes222.

In plan view, the dummy wirings219include first dummy wirings219A of circular annular shapes that surround the ink supply passages253(ink supply penetrating holes222). Above the actuator substrate202, the first dummy wirings219A are disposed in regions facing regions of the facing surface251of the protective substrate204peripheral to the ink supply passages253. A width of each first dummy wiring219A (difference between an inner diameter and an outer diameter of each first dummy wiring219A) is preferably not less than ⅓ a diameter of each ink supply passage253. Upper surfaces of the first dummy wirings219A are flat. Each first dummy wiring219A constitutes a base220that supports the protective substrate204and increases adhesion with the facing surface of the protective substrate204.

The dummy wirings219further include second dummy wirings219B of elongate rectangular shapes that are formed at width central portions of regions between adjacent pressure chambers207and at outward sides of the pressure chambers207at respective outer sides of the set of plurality of pressure chambers and extend in the direction along the ink flow direction241. Upper surfaces of the second dummy wirings219B are flat. Each second dummy wiring219B constitutes a base that supports the protective substrate204and increases adhesion with the facing surface of the protective substrate204.

In bonding the protective substrate204to the actuator substrate202, the protective substrate204is pressed against the actuator substrate202in a state where the adhesive250is coated on a portion of bonding of the actuator substrate202and the protective substrate204. In this process, the facing surface251of the protective substrate204is pressed via the passivation film221against the first dummy wirings219A and the second dummy wirings219B that are the bases with flat upper surfaces. The facing surface251of the protective substrate204is thus bonded firmly via the passivation film221and the adhesive250to the upper surfaces of the first dummy wirings219A and the second dummy wirings219B. Defective adhesion is thus made unlikely to occur at the portion of bonding of the facing surface251of the protective substrate204and the actuator substrate202.

In the present second preferred embodiment, by the first dummy wirings219A (bases220) of circular annular shapes surrounding the ink supply passages253(ink supply penetrating holes222) being provided at the actuator substrate202side, occurrence of defective bonding between the actuator substrate202and lower surfaces of wall portions of the protective substrate204between the housing recesses252and the ink supply passages253can be suppressed. Leakage of ink into a housing recess252from an ink supply passage253can thereby be suppressed.

FIG. 12is an illustrative plan view of a pattern example of the insulating film of the inkjet printing head.FIG. 13is an illustrative plan view of a pattern example of the passivation film of the inkjet printing head.

In the present second preferred embodiment, above the actuator substrate202, the insulating film215and the passivation film221are formed on substantially an entirety of a region of the protective substrate204outside the housing recesses252in plan view. However, in this region, the ink supply penetrating holes222and the contact holes234are formed in the insulating film215. In this region, the ink supply penetrating holes222and the pad openings235and236are formed in the passivation film221.

In the regions of the protective substrate204inside the housing recesses252, the insulating film215and the passivation film221are formed just in one end portions (upper wiring regions) in which the upper wirings217are present. In each of these regions, the passivation film221is formed to cover an upper surface and a side surface of an upper wiring217above the insulating film215. In other words, in the insulating film215and the passivation film221, openings237are formed in regions, within the inner side regions of the housing recesses252in plan view, that exclude the upper wiring regions. The contact holes233are further formed in the insulating film215.

In the present preferred embodiment, in a region at the inner side of the peripheral edge of each pressure chamber207in plan view, the insulating film215and the passivation film221are formed just in the upper wiring region in which an upper wiring217is present. Therefore, most of the side surface and the upper surface of each piezoelectric element209are not covered by the insulating film215and the passivation film221. Displacement of each movable film210A can thereby be increased in comparison to a case where entireties of the side surface and the upper surface of the piezoelectric element209are covered by the insulating film and the passivation film.

FIG. 15AtoFIG. 15Mare sectional views of an example of a manufacturing process of the inkjet printing head201and show a section corresponding toFIG. 9.

First, as shown inFIG. 15A, the movable film formation layer210is formed on the front surface202aof the actuator substrate202. However, as the actuator substrate202, that which is thicker than the thickness of the actuator substrate202at the final stage is used. Specifically, a silicon oxide film (for example, of 1.2 μm thickness) is formed on the front surface of the actuator substrate202. If the movable film formation layer210is constituted of a laminated film of a silicon film, a silicon oxide film, and a silicon nitride film, the silicon film (for example, of 0.4 μm thickness) is formed on the front surface of the actuator substrate202, the silicon oxide film (for example, of 0.4 μm thickness) is formed above the silicon film, and the silicon nitride film (for example, of 0.4 μm thickness) is formed above the silicon oxide film.

A base oxide film, for example, of Al2O3, MgO, or ZrO2, etc., may be formed on the front surface of the movable film formation layer210. Such base oxide films prevent metal atoms from escaping from the piezoelectric film212to be formed later. When metal electrons escape, the piezoelectric film212may degrade in piezoelectric characteristics. Also, when metal atoms that have escaped become mixed in the silicon layer constituting each movable film210A, the movable film210A may degrade in durability.

Next, a lower electrode film271, which is a material layer of the lower electrode211, is formed above the movable film formation layer210(above the base oxide film in the case where the base oxide film is formed) as shown inFIG. 15B. The lower electrode film271is constituted, for example, of a Pt/Ti laminated film having a Ti film (for example, of 10 nm to 40 nm thickness) as a lower layer and a Pt film (for example, of 10 nm to 400 nm thickness) as an upper layer. Such a lower electrode film271may be formed by the sputtering method.

Next, a material film (piezoelectric material film)272of the piezoelectric films212is formed on an entire surface above the lower electrode film271. Specifically, for example, the piezoelectric material film272of 1 μm to 3 μm thickness is formed by a sol-gel method. Such a piezoelectric material film272is constituted of a sintered body of metal oxide crystal grains.

Next, an upper electrode film273, which is a material of the upper electrodes213, is formed on the entire surface of the piezoelectric material film272. The upper electrode film273may, for example, be a single film of platinum (Pt). The upper electrode film273may, for example, be an IrO2/Ir laminated film having an IrO2film (for example, of 40 nm to 160 nm thickness) as a lower layer and an Ir film (for example, of 40 nm to 160 nm thickness) as an upper layer. Such an upper electrode film273may be formed by the sputtering method.

Next, as shown inFIG. 15CandFIG. 15D, patterning of the upper electrode film273, the piezoelectric material film272, and the lower electrode film271is performed. First, a resist mask with a pattern of the upper electrodes213is formed by photolithography. Then, as shown inFIG. 15C, the upper electrode film273and the piezoelectric material film272are etched successively using the resist mask as a mask to form the upper electrodes213and the piezoelectric films212of the predetermined patterns.

Next, after peeling off the resist mask, a resist mask with a pattern of the lower electrode211is formed by photolithography. Then, as shown inFIG. 15D, the lower electrode film271is etched using the resist mask as a mask to form the lower electrode211of the predetermined pattern. The lower electrode211, constituted of the main electrode portions211A and the extension portion211B having the penetrating holes223, is thereby formed. The piezoelectric elements209, each constituted of a main electrode portion211A of the lower electrode211, a piezoelectric film212, and an upper electrode213, are thereby formed.

Next, after peeling off the resist mask, the hydrogen barrier film214covering the entire surface is formed as shown inFIG. 15E. The hydrogen barrier film214may be an Al2O3film formed by the sputtering method and may have a film thickness of 50 nm to 100 nm. Thereafter, the insulating film215is formed above the entire surface of the hydrogen barrier film214. The insulating film215may be an SiO2film and may have a film thickness of 200 nm to 300 nm. Next, the contact holes233and234are formed by successively etching the insulating film215and the hydrogen barrier film214.

Next, as shown inFIG. 15F, a wiring film that constitutes the upper wirings217, the lower wiring218, and the dummy wirings219(219A and219B) is formed by the sputtering method above the insulating film215as well as inside the contact holes233and234. Thereafter, the wiring film is patterned by photolithography and etching to form the upper wirings217, the lower wiring218, and the dummy wirings219(219A and219B) at the same time.

Next, as shown inFIG. 15G, the passivation film221that covers the wirings217,218, and219is formed on the front surface of the insulating film215. The passivation film221is constituted, for example, of SiN. The passivation film221is formed, for example, by plasma CVD.

Next, a resist mask, having openings corresponding to the pad openings235and236, is formed by photolithography, and the passivation film221is etched using the resist mask as a mask. The pad openings235and236are thereby formed in the passivation film221as shown inFIG. 15H. After the resist mask is peeled off, the pads242and243, respectively connected to the upper wirings217and the lower wiring218via the pad openings235and the pad opening236, are formed above the passivation film221.

A resist mask having openings corresponding to the openings237and the ink supply penetrating holes222is then formed by photolithography, and using the resist mask as a mask, the passivation film221and the insulating film215are etched successively. The openings237and the ink supply penetrating holes222are thereby formed in the passivation film221and the insulating film215as shown inFIG. 15I.

Next, the resist mask is peeled off. A resist mask having openings corresponding to the ink supply penetrating holes222is then formed by photolithography, and the hydrogen barrier film214and the movable film formation layer210are etched using the resist mask as a mask. The ink supply penetrating holes222are thereby formed in the hydrogen barrier film214and the movable film formation layer210as shown inFIG. 15J.

Next, as shown inFIG. 15K, the adhesive250is coated onto the facing surface251of the protective substrate204and the protective substrate204is fixed onto the actuator substrate202so that the ink supply passages253and the ink supply penetrating holes222are matched. In this process, the facing surface251of the protective substrate204is pressed via the passivation film221against the first dummy wirings219A and the second dummy wirings219B that are the bases with flat upper surfaces. The facing surface251of the protective substrate204is thus bonded firmly via the passivation film221and the adhesive250to the upper surfaces of the first dummy wirings219A and the second dummy wirings219B.

Next, as shown inFIG. 15L, rear surface grinding for thinning the actuator substrate202is performed. The actuator substrate202is made thin by the actuator substrate202being ground from the rear surface202b. For example, the actuator substrate202with a thickness of approximately 670 μm in the initial state may be thinned to a thickness of approximately 300 μm. Next, etching (dry etching or wet etching) from the rear surface of the actuator substrate202is performed on the actuator substrate202to form the ink flow passages205(the ink inflow portions206and the pressure chambers207).

In the etching process, the base oxide film formed on the front surface of the movable film formation layer210prevents the escaping of metal elements (Pb, Zr, and Ti in the case of PZT) from the piezoelectric film212and keeps the piezoelectric characteristics of the piezoelectric film212in a satisfactory state. Also as mentioned above, the base oxide film formed on the front surface of the movable film formation layer210contributes to maintaining the durability of the silicon layer that forms each movable film210A.

Thereafter, as shown inFIG. 15M, the nozzle substrate203is adhered onto the rear surface of the actuator substrate202and the inkjet printing head201is thereby obtained.

FIG. 16AandFIG. 16Bare partially enlarged sectional views of steps of forming an ink discharge hole203ain the nozzle substrate203and show a section corresponding toFIG. 9. In the present preferred embodiment, each ink discharge hole203ais formed so that a transverse sectional shape of a processing ending end side (actuator substrate202side) of the ink discharge hole203awill be a quadrilateral shape. In other words, a target shape of a transverse section of the processing ending end side of the ink discharge hole203ais a regular quadrilateral.

First, a resist mask290, having penetrating holes291, is formed by photolithography on surface (rear surface) of the nozzle substrate203at an opposite side from the surface bonded to the rear surface of the actuator substrate202.FIG. 17is an enlarged bottom view of a portion of the resist mask290. A bottom surface shape (transverse sectional shape) of each penetrating hole291is formed to a shape with which its respective sides are curved to inwardly convex arcuate shapes with respect to the target shape (the regular quadrilateral indicated by alternate long and two short dashes lines T inFIG. 17) of the transverse section at the processing ending end side of the corresponding ink discharge hole203a.

Next, in the state where the resist mask290is formed on the rear surface of the nozzle substrate203, dry etching is applied to the nozzle substrate203. The ink discharge holes203aare thereby formed in the nozzle substrate203as shown inFIG. 16B.

FIG. 18Ais an enlarged bottom view of a bottom surface shape at a processing starting end side (the nozzle substrate203rear surface side) of an ink discharge hole203.FIG. 18Bis an enlarged sectional view taken along XVIIIB-XVIIIB inFIG. 16B. That is,FIG. 18Bis an enlarged sectional view of a transverse sectional shape at a center-of-length portion (center-of-depth portion) of the ink discharge hole203a.FIG. 18Cis an enlarged plan view of a planar shape at a processing ending end side (the nozzle substrate203front surface side) of the ink discharge hole203a.

As shown inFIG. 17, the transverse sectional shape of each penetrating hole291formed in the resist mask290is formed to the shape with which its respective sides are curved to inwardly convex arcuate shapes with respect to the target shape T of the transverse section at the processing ending end side of the corresponding ink discharge hole203a. Therefore, as shown inFIG. 18A, the bottom surface shape at the processing starting end side (the nozzle substrate203rear surface side) of the ink discharge hole203ais substantially the same shape as the transverse sectional shape of the penetrating hole291. As the etching progresses, inward projection amounts of the respective arcuate shaped sides of the transverse sectional shape of the ink discharge hole203adecrease as shown, for example, inFIG. 18B. That is, as the etching progresses, the transverse sectional shape of the ink discharge hole203aapproaches the regular quadrilateral that is the target shape T. At the processing ending end side (the nozzle substrate203front surface side) of the ink discharge hole203a, the planar shape is substantially the same shape as the regular quadrilateral that is the target shape T as shown inFIG. 18C.

In other words, in comparison to the transverse sectional shape at the processing starting end side (the nozzle substrate203rear surface side) of the ink discharge hole203a, the transverse sectional shape at the processing ending end side of the ink discharge hole203ais a shape that is closer to the regular quadrilateral that is the target shape T. In the present preferred embodiment, the inward projection amounts of the respective arcuate shaped sides of the transverse sectional shape of the penetrating hole291are determined so that the transverse sectional shape at the processing ending end side (nozzle substrate203front surface side) of the ink discharge hole203awill be a shape that is substantially the same as the regular quadrilateral that is the target shape T.

Thereafter, the resist mask290is peeled off. The nozzle substrate203having the ink discharge holes203asuch as shown inFIG. 9is thereby obtained.

Although with the second preferred embodiment described above, the target shape of the transverse section at the processing ending end side of each ink discharge hole203ais a regular quadrilateral, the target shape may be a polygon other than a regular quadrilateral, such as a triangle, a quadrilateral other than a regular quadrilateral, a pentagon, or a hexagonal shape.

Although with the first and second preferred embodiments described above, cases where the present invention is applied to an infrared sensor and an inkjet printing head were described, the present invention may also be applied to a device other than an infrared sensor or an inkjet printing head as long as it is a device that includes a substrate having a hole with a transverse section having a polygonal shape.

The present application corresponds to Japanese Patent Application No. 2016-1219 filed on Jan. 6, 2016 in the Japan Patent Office, and the entire disclosure of this application is incorporated herein by reference.