U.S. patent application number 15/352196 was filed with the patent office on 2017-07-06 for substrate having a hole, method for manufacturing the substrate, infrared sensor, and method for manufacturing the infrared sensor.
This patent application is currently assigned to ROHM CO., LTD.. The applicant listed for this patent is ROHM CO., LTD.. Invention is credited to Yoshikazu FUJIMORI, Tatsuya SUZUKI.
Application Number | 20170191874 15/352196 |
Document ID | / |
Family ID | 59226231 |
Filed Date | 2017-07-06 |
United States Patent
Application |
20170191874 |
Kind Code |
A1 |
SUZUKI; Tatsuya ; et
al. |
July 6, 2017 |
SUBSTRATE HAVING A HOLE, METHOD FOR MANUFACTURING THE SUBSTRATE,
INFRARED SENSOR, AND METHOD FOR MANUFACTURING THE INFRARED
SENSOR
Abstract
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.
Inventors: |
SUZUKI; Tatsuya; (Kyoto,
JP) ; FUJIMORI; Yoshikazu; (Kyoto, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ROHM CO., LTD. |
Kyoto |
|
JP |
|
|
Assignee: |
ROHM CO., LTD.
Kyoto
JP
|
Family ID: |
59226231 |
Appl. No.: |
15/352196 |
Filed: |
November 15, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01J 5/34 20130101; C23C
14/34 20130101; C23C 14/083 20130101; C23C 14/081 20130101; H01L
37/02 20130101; C23C 14/185 20130101; G01J 5/0235 20130101; G01J
5/024 20130101 |
International
Class: |
G01J 5/02 20060101
G01J005/02; C23C 14/08 20060101 C23C014/08; C23C 14/34 20060101
C23C014/34; C23C 14/18 20060101 C23C014/18 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 6, 2016 |
JP |
2016-001219 |
Claims
1. A substrate having a hole, the substrate having the hole being
such that 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.
2. The substrate having the hole according to claim 1, wherein the
predetermined polygon is a quadrilateral.
3. The substrate having the hole according to claim 1, wherein the
predetermined polygon is a triangle.
4. An infrared sensor comprising: the substrate having the hole
according to claim 1; a heat insulating film held by the substrate
so as to face the hole; and a pyroelectric element formed above the
heat insulating film.
5. The infrared sensor according to claim 4, wherein 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.
6. A method for manufacturing a substrate having a hole, the method
for manufacturing the substrate having the hole comprising: 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 form a hole in the substrate.
7. The method for manufacturing the substrate having the hole
according to claim 6, wherein the predetermined polygon is a
quadrilateral.
8. The method for manufacturing the substrate having the hole
according to claim 6, wherein the predetermined polygon is a
triangle.
9. A method for manufacturing an infrared sensor, the method for
manufacturing the infrared sensor comprising: 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; and wherein 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.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the invention
[0002] 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
[0003] 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
[0004] 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.
[0005] 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.
[0006] 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 to FIG. 19A, FIG. 19B, and FIG. 19C. FIG. 19A is a plan
view, FIG. 19B is a vertical sectional view, and FIG. 19C is a
bottom view.
[0007] A mask 110 has a penetrating hole 111 with which a
transverse sectional shape is a regular tetragon. Dry etching is
applied to a substrate 100 in a state where the mask 110 is
disposed at a surface side of the substrate 100 (upper surface side
of the substrate 100 in the present example). A hole 101 is thereby
formed in the substrate 100. As shown in FIG. 19C, a bottom surface
shape (transverse sectional shape) at a processing ending end side
of the hole 101 is a shape that is not a regular tetragon but is
close to being a circle.
[0008] 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.
[0009] 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.
[0010] 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.
[0011] In the preferred embodiment of the present invention, the
predetermined polygon is a quadrilateral.
[0012] In the preferred embodiment of the present invention, the
predetermined polygon is a triangle.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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 form
a hole in the substrate.
[0017] 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.
[0018] In the preferred embodiment of the present invention, the
predetermined polygon is a quadrilateral.
[0019] In the preferred embodiment of the present invention, the
predetermined polygon is a triangle.
[0020] 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.
[0021] 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.
[0022] The above and other elements, features, steps,
characteristics and advantages of the present invention will become
more apparent from the following detailed description of the
preferred embodiments with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is 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.
[0024] FIG. 2 is a partially enlarged plan view showing an A
portion of FIG. 1 in enlarged manner.
[0025] FIG. 3 is a schematic enlarged sectional view taken along
line III-III in FIG. 2.
[0026] FIG. 4A is a sectional view of an example of a manufacturing
process of the infrared sensor.
[0027] FIG. 4B is a sectional view of a step subsequent to that of
FIG. 4A.
[0028] FIG. 4C is a sectional view of a step subsequent to that of
FIG. 4B.
[0029] FIG. 4D is a sectional view of a step subsequent to that of
FIG. 4C.
[0030] FIG. 4E is a sectional view of a step subsequent to that of
FIG. 4D.
[0031] FIG. 4F is a sectional view of a step subsequent to that of
FIG. 4E.
[0032] FIG. 4G is a sectional view of a step subsequent to that of
FIG. 4F.
[0033] FIG. 4H is a sectional view of a step subsequent to that of
FIG. 4G.
[0034] FIG. 4I is a sectional view of a step subsequent to that of
FIG. 4H.
[0035] FIG. 4J is a sectional view of a step subsequent to that of
FIG. 4I.
[0036] FIG. 4K is a sectional view of a step subsequent to that of
FIG. 4J.
[0037] FIG. 5 is a bottom view of a portion of a resist mask used
in the steps of FIG. 4J and FIG. 4K.
[0038] FIG. 6A is a bottom view of a bottom surface shape at a
processing starting end side of a cavity.
[0039] FIG. 6B is a sectional view taken along VIB-VIB in FIG.
4K.
[0040] FIG. 6C is a plan view of a planar shape at a processing
ending end side of the cavity.
[0041] FIG. 7A is a bottom view of a portion of a resist mask used
in a case where a target planar shape at a processing ending end
side of a cavity is a regular triangle.
[0042] FIG. 7B is a plan view of a planar shape at a processing
ending end side of a cavity obtained by applying dry etching to a
substrate using the resist mask shown in FIG. 7A.
[0043] FIG. 8A is 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.
[0044] FIG. 8B is an illustrative plan view of the main portion of
the inkjet printing head and is a plan view with a protective
substrate omitted.
[0045] FIG. 9 is an illustrative sectional view taken along line
IX-IX in FIG. 8A.
[0046] FIG. 10 is an illustrative enlarged sectional view of a
portion of a section taken along line X-X in FIG. 8A.
[0047] FIG. 11 is an illustrative plan view of a pattern example of
a lower electrode of the inkjet printing head.
[0048] FIG. 12 is an illustrative plan view of a pattern example of
an insulating film of the inkjet printing head.
[0049] FIG. 13 is an illustrative plan view of a pattern example of
a passivation film of the inkjet printing head.
[0050] FIG. 14 is a bottom view of a main portion of the protective
substrate as viewed from an actuator substrate side of the inkjet
printing head.
[0051] FIG. 15A is a sectional view of an example of a
manufacturing process of the inkjet printing head.
[0052] FIG. 15B is a sectional view of a step subsequent to that of
FIG. 15A.
[0053] FIG. 15C is a sectional view of a step subsequent to that of
FIG. 15B.
[0054] FIG. 15D is a sectional view of a step subsequent to that of
FIG. 15C.
[0055] FIG. 15E is a sectional view of a step subsequent to that of
FIG. 15D.
[0056] FIG. 15F is a sectional view of a step subsequent to that of
FIG. 15E.
[0057] FIG. 15G is a sectional view of a step subsequent to that of
FIG. 15F.
[0058] FIG. 15H is a sectional view of a step subsequent to that of
FIG. 15G.
[0059] FIG. 15I is a sectional view of a step subsequent to that of
FIG. 15H.
[0060] FIG. 15J is a sectional view of a step subsequent to that of
FIG. 15I.
[0061] FIG. 15K is a sectional view of a step subsequent to that of
FIG. 15J.
[0062] FIG. 15L is a sectional view of a step subsequent to that of
FIG. 15K.
[0063] FIG. 15M is a sectional view of a step subsequent to that of
FIG. 15L.
[0064] FIG. 16A is a partially enlarged sectional view of a step of
forming an ink discharge hole in a nozzle substrate.
[0065] FIG. 16B is a partially enlarged sectional view of a step
subsequent to that of FIG. 16A.
[0066] FIG. 17 is an enlarged bottom view of a portion of a resist
mask used in the step of FIG. 16A.
[0067] FIG. 18A is an enlarged bottom view of a bottom surface
shape at a processing starting end side of an ink discharge
hole.
[0068] FIG. 18B is an enlarged sectional view taken along
XVIIIB-XVIIIB in FIG. 16B.
[0069] FIG. 18C is an enlarged plan view of a planar shape at a
processing ending end side of the ink discharge hole.
[0070] FIG. 19A, FIG. 19B, and FIG. 19C show a conventional method
for forming a hole, with which a transverse sectional shape is, for
example, a regular quadrilateral shape, in a substrate, with FIG.
19A being a plan view, FIG. 19B being a vertical sectional view,
and FIG. 19C being a bottom view.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0071] Preferred embodiments of the present invention shall now be
described in detail with reference to the attached drawings.
[0072] FIG. 1 is 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. 2 is a
schematic enlarged plan view showing a vicinity of an A portion of
FIG. 1 in enlarged manner. FIG. 3 is a schematic sectional view
taken along line in FIG. 2. In FIG. 2, a filter layer indicated by
the symbol 16 in FIG. 3 is omitted.
[0073] The infrared sensor 1 includes a silicon substrate 2. A
plurality of cavities 3, penetrating through the silicon substrate
2 in a thickness direction, are formed in the silicon substrate 2.
The cavities 3 are formed by digging in from a rear surface of the
silicon substrate 2. The cavities 3 are formed to thermally
separate pyroelectric elements 10, to be described below, from the
silicon substrate 2. Each cavity 3 is formed to a regular
quadrilateral (square) shape in plan view. The plurality of
cavities 3 are disposed in an array in plan view. The cavity 3 is
an example of a hole according to the present invention.
[0074] A heat insulating film 4 is formed above the silicon
substrate 2 to close the cavities 3. The heat insulating film 4 is
constituted of silicon oxide (SiO.sub.2) in the present preferred
embodiment. Above the heat insulating film 4, pyroelectric elements
10 are disposed at positions facing the respective cavities 3. Each
pyroelectric element 10 is formed to a regular quadrilateral shape
in plan view. The plurality of pyroelectric elements 10 are
disposed in an array in plan view.
[0075] The pyroelectric elements 10 include lower electrodes 5,
formed at a front surface of the heat insulating film 4 at an
opposite side from the cavities 3, pyroelectric films 6, formed
above the lower electrode 5, and upper electrodes 7, formed above
the pyroelectric films 6.
[0076] Each lower electrode 5 is constituted of main electrode
portions 5A, each of regular quadrilateral shape in plan view that
constitutes the corresponding pyroelectric element 10, lead-out
portions 5B, each extending outside the corresponding cavity 3 from
a center of length of one side of the corresponding main electrode
portion 5A, and a wiring portion 5C, connected to corresponding
lead-out portions 5B and extending in parallel to the one side of
corresponding main electrode portions 5A. The lower electrode 5
has, 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 film 4
side.
[0077] Each pyroelectric film 6 is formed to a regular
quadrilateral shape slightly smaller than the corresponding main
electrode portion 5A of the lower electrode 5 in plan view. The
four sides of the pyroelectric film 6 are, in plan view,
respectively parallel to the four sides of the main electrode
portion 5A of the lower electrode 5 and disposed at inner sides
across predetermined intervals with respect to the corresponding
sides of the main electrode portion 5A. In the present preferred
embodiment, the pyroelectric film 6 is constituted of lead
zirconate titanate (PZT: Pb(Zr,Ti)O.sub.3) and is formed, for
example, by a sol-gel method.
[0078] Each upper electrode 7 is formed to a regular quadrilateral
shape slightly smaller than the corresponding pyroelectric film 6
in plan view. The four sides of the upper electrode 7 are, in plan
view, respectively parallel to the four sides of the pyroelectric
film 6 and disposed at inner sides across predetermined intervals
with respect to the corresponding sides of the pyroelectric film 6.
In the present preferred embodiment, the upper electrode 7 has a
two-layer structure with which a layer constituted of iridium (Ir)
and a layer constituted of iridium oxide (IrO.sub.2) are laminated
in that order from the pyroelectric film 6 side.
[0079] Also, a covering film 11 is formed above the heat insulating
film 4. Portions of an upper surface of the heat insulating film 4
exposed from the lower electrodes 5, portions of upper surfaces of
the main electrode portions 5A of the lower electrodes 5 exposed
from the pyroelectric films 6, the lead-out portions 5B and the
wiring portions 5C of the lower electrodes 5, portions of upper
surfaces of the pyroelectric films 6 exposed from the upper
electrodes 7, side surfaces of the pyroelectric films 6, and the
upper electrodes 7 are covered all together by the covering film 6.
The cover film 11 includes a hydrogen barrier film 12, constituted
of alumina (Al.sub.2O.sub.3), and an insulating film 13, formed
above the hydrogen barrier film 12 and constituted of silicon oxide
(SiO.sub.2).
[0080] Wirings 14 are formed in a predetermined pattern above the
covering film 11. The wirings 14 are constituted of a metal
material that contains aluminum (Al) as a main component. The
wirings 14 are provided at positions facing the upper electrodes 7
across the cover film 11. Between the wirings 14 and the upper
electrodes 7, penetrating holes (contact holes) 15 are formed to
penetrate through in a thickness direction in the cover film 11.
One end portions of the wirings 14 enter into the penetrating holes
15 and are connected to the upper electrodes 7 inside the
penetrating holes 15. Each wiring 14 is constituted of electrode
connection portions 14A, each of regular quadrilateral shape in
plan view having a central portion connected to the corresponding
upper electrode 7, lead-out portions 14B, each extending outside
the corresponding cavity 3 from a center of length of one side of
the corresponding electrode connection portion 14A, and a main
wiring portion 14C, connected to the lead-out portions 14B and
extending in parallel to the one side of the electrode connection
portions 14A. In plan view, the main wiring portions 14C of the
wiring 14 and the wiring portions 5C of the lower electrode 5 are
disposed so as to be orthogonal to each other.
[0081] Also, optical filter layers 16, which transmit near infrared
rays, are formed on surfaces of the covering film 11 and the
wirings 14 at regions facing the cavities 3 in plan view. The
optical filter layers 16 are constituted of titanium (Ti) in the
present preferred embodiment.
[0082] When a temperature of the pyroelectric film 6 inside a
pyroelectric element 10 increases due to incidence of infrared
rays, a pyroelectric current due to spontaneous polarization of the
pyroelectric film 6 is output from the pyroelectric element 10. The
infrared rays can thus be detected based on the pyroelectric
current.
[0083] FIG. 4A to FIG. 4K are sectional views of an example of a
manufacturing process of the infrared sensor 1 and show a section
corresponding to FIG. 3.
[0084] First, as shown in FIG. 4A, the heat insulating film 4 is
formed on a front surface of the silicon substrate 2. However, as
the silicon substrate 2, that which is thicker in thickness than
the silicon substrate 2 at a final stage is used. Specifically, the
heat insulating film 4 constituted of a silicon oxide film is
formed on the front surface of the silicon substrate 2.
[0085] Next, as shown in FIG. 4B, a lower electrode film 31, which
is a material layer of the lower electrodes 5, is formed above the
heat insulating film 4. The lower electrode film 31 is 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 film
31 may be formed by a sputtering method.
[0086] Next, a material film (pyroelectric material film) 32 of the
pyroelectric films 6 is formed on an entire surface above the lower
electrode film 31. Specifically, the pyroelectric material film 32
is formed, for example, by the sol-gel method. Such a pyroelectric
material film 32 is constituted of a sintered body of metal oxide
crystal grains.
[0087] Next, an upper electrode film 33, which is a material of the
upper electrodes 7, is formed on an entire surface of the
pyroelectric material film 32. The upper electrode film 33 is
constituted, for example, of an IrO.sub.2/Ir laminated film having
an IrO.sub.2 film as a lower layer and an Ir layer as an upper
layer. Such an upper electrode film 33 may be formed by the
sputtering method.
[0088] Next, as shown in FIG. 4C to FIG. 4E, patterning of the
upper electrode film 33, the pyroelectric material film 32, and the
lower electrode film 31 is performed. First, a resist mask with a
pattern of the upper electrodes 7 is formed by photolithography.
Then, as shown in FIG. 4C, the upper electrode film 33 is etched
using the resist mask as a mask to form the upper electrodes 7 of
the predetermined pattern.
[0089] Next, after peeling off the resist mask, a resist mask with
a pattern of the pyroelectric films 6 is formed by
photolithography. Then, as shown in FIG. 4D, the pyroelectric
material film 32 is etched using the resist mask as a mask to form
the pyroelectric films 6 of the predetermined pattern.
[0090] Next, after peeling off the resist mask, a resist mask with
a pattern of the lower electrodes 5 is formed by photolithography.
Then, as shown in FIG. 4E, the lower electrode film 31 is etched
using the resist mask as a mask to form the lower electrodes 5 of
the predetermined pattern. The lower electrodes 5, each constituted
of the main electrode portions 5A, the lead-out portions 5B, and
the wiring portion 5C, are thereby formed. The pyroelectric
elements 10, each constituted of the main electrode portion 5A of
the lower electrode 5, the pyroelectric film 6, and the upper
electrode 7, are thereby formed.
[0091] Next, after peeling off the resist mask, the hydrogen
barrier film 12 covering the entire surface is formed as shown in
FIG. 4F. The hydrogen barrier film 12 is, for example, an
Al.sub.2O.sub.3 film formed by the sputtering method. The
insulating film 13 is thereafter formed on an entire surface above
the hydrogen barrier film 12. The insulating film 13 is, for
example, an SiO.sub.2 film. The covering film 11, constituted of
the hydrogen barrier film 12 and the insulating film 13, is thereby
formed. Subsequently, the penetrating holes (contact holes) 15 are
formed by successively etching the insulating film 13 and the
hydrogen barrier film 12.
[0092] Next, as shown in FIG. 4G, a wiring film constituting the
wirings 14 is formed by the sputtering method above the insulating
film 13 (covering film 11), including interiors of the penetrating
holes 15. Thereafter, the wiring film is patterned by
photolithography and etching to form the wirings 14.
[0093] Next, a titanium layer, which is a material of the optical
filter layers 16, is formed on surfaces of the insulating film 13
(covering film 11) and the wirings 14. Thereafter, the titanium
layer is patterned by photolithography and etching to form the
filter layers 16 as shown in FIG. 4H. Next, as shown in FIG. 4I,
the silicon substrate 2 is made thin by the silicon substrate 2
being ground from the rear surface.
[0094] Next, as shown in FIG. 4J and FIG. 4K, the cavities 3 are
formed in the silicon substrate 2. In the present preferred
embodiment, each cavity 3 is formed so that a transverse sectional
shape of a processing ending end side (heat insulating film side)
of the cavity 3 will 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 cavity 3 is a regular
quadrilateral. First, as shown in FIG. 4J, a resist mask 40, having
penetrating holes 41, is formed by photolithography on a rear
surface of the silicon substrate 2. FIG. 5 is a plan view of a
portion of the resist mask 40. A planar shape (transverse sectional
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 the target shape (the regular quadrilateral
indicated by alternate long and two short dashes lines T in FIG. 5)
of the transverse section at the processing ending end side of the
corresponding cavity 3.
[0095] Next, in the state where the resist mask 40 is formed on the
rear surface of the silicon substrate 2, dry etching is applied to
the silicon substrate 2. For example, plasma etching is used as the
dry etching. The cavities 3 are thereby formed in the silicon
substrate 2 as shown in FIG. 4K.
[0096] FIG. 6A is a bottom view of a bottom surface shape at a
processing starting end side (the substrate 2 rear surface side) of
a cavity 3. FIG. 6B is a sectional view taken along VIB-VIB in FIG.
4K. That is, FIG. 6B is a sectional view of a transverse sectional
shape at a center-of-length portion (center-of-depth portion) of
the cavity 3. FIG. 6C is a plan view of a planar shape at a
processing ending end side (the substrate 2 front surface side) of
the cavity 3.
[0097] As shown in FIG. 5, the transverse sectional shape of each
penetrating hole 41 formed in the resist mask 40 is 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
cavity 3. Therefore, as shown in FIG. 6A, the bottom surface shape
at the processing starting end side (the substrate 2 rear surface
side) of the cavity 3 is substantially the same shape as the
transverse sectional shape of the penetrating hole 41. As the
etching progresses, inward projection amounts of the respective
arcuate shaped sides of the transverse sectional shape of the
cavity 3 decrease as shown, for example, in FIG. 6B. That is, as
the etching progresses, the transverse sectional shape of the
cavity 3 approaches the regular quadrilateral that is the target
shape T. At the processing ending end side (the substrate 2 front
surface side) of the cavity 3, the planar shape is substantially
the same shape as the regular quadrilateral that is the target
shape T as shown in FIG. 6C.
[0098] In other words, in comparison to the transverse sectional
shape at the processing starting end side (the substrate 2 rear
surface side) of the cavity 3, the transverse sectional shape at
the processing ending end side of the cavity 3 is 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 hole 41 are determined so that the
transverse sectional shape at the processing ending end side (the
substrate 2 front surface side) of the cavity 3 will be a shape
that is substantially the same as the regular quadrilateral that is
the target shape T.
[0099] Lastly, the resist mask 40 is peeled off. The infrared
sensor 1 shown in FIG. 3 is thereby obtained.
[0100] With the preferred embodiment described above, the
transverse sectional shape at the processing ending end side of
each cavity 3 can be made a shape close to a target shape (a
predetermined polygon).
[0101] Although with the preferred embodiment described above, the
target shape of the transverse section at the processing ending end
side of each cavity 3 is 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 cavity
3 is 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.
[0102] For example, if the target shape of the transverse section
at the processing ending end side of each cavity 3 is a regular
triangle, a resist mask 40A having a penetrating hole 41A such as
shown in FIG. 7A is used. The penetrating hole 41A 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 substrate 2
using the resist mask 40A shown in FIG. 7A, the planar shape at the
processing ending end side of the cavity 3 becomes a shape such as
shown in FIG. 7B.
[0103] FIG. 8A is 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. 8B is an illustrative
plan view of the main portion of the inkjet printing head and is a
plan view with a protective substrate omitted. FIG. 9 is an
illustrative sectional view taken along line IX-IX in FIG. 8A. FIG.
10 is an illustrative enlarged sectional view of a portion of a
section taken along line X-X in FIG. 8A. FIG. 11 is an illustrative
plan view of a pattern example of a lower electrode of the inkjet
printing head.
[0104] The arrangement of an inkjet printing head 201 shall now be
described in outline with reference to FIG. 9.
[0105] The inkjet printing head 201 includes an actuator substrate
202, a nozzle substrate 203, and a protective substrate 204. A
movable film formation layer 210 is laminated on a front surface
202a of the actuator substrate 202. In the actuator substrate 202,
ink flow passages (ink reservoirs) 205 are formed. In the present
preferred embodiment, the ink flow passages 205 are formed to
penetrate through the actuator substrate 202. Each ink flow passage
205 is formed to be elongate along an ink flow direction 241, which
is indicated by an arrow in FIG. 9. Each ink flow passage 205 is
constituted of an ink inflow portion 206 at an upstream side end
portion (left end portion in FIG. 9) in the ink flow direction 241
and a pressure chamber 207 in communication with the ink inflow
portion 206. In FIG. 9, a boundary between the ink inflow portion
206 and the pressure chamber 207 is indicated by an alternate long
and two short dashes line.
[0106] The nozzle substrate 203 is constituted, for example, of a
silicon substrate. The nozzle substrate 203 is adhered to a rear
surface 202b of the actuator substrate 202. The nozzle substrate
203, together with the actuator substrate 202 and the movable film
formation layer 210, defines the ink flow passages 205. More
specifically, the nozzle substrate 203 defines bottom surface
portions of the ink flow passages 205. The nozzle substrate 203 has
ink discharge holes 203a each facing a pressure chamber 207. Each
ink discharge hole 203a penetrates through the nozzle substrate 203
and has a discharge port 203b at an opposite side from the pressure
chamber 207. Therefore, when a volume change occurs in a pressure
chamber 207, the ink retained in the pressure chamber 207 passes
through the ink discharge hole 203a and is discharged from the
discharge port 203b. The ink discharge hole 203a is an example of
the hole of the present invention.
[0107] Each portion of the movable film formation layer 210 that is
a top roof portion of a pressure chamber 207 constitutes a movable
film 210A. The movable film 210A (movable film formation layer 210)
is constituted, for example, of a silicon oxide (SiO.sub.2) film
formed above the actuator substrate 202. The movable film 210A
(movable film formation layer 210) may be constituted of a
laminated film, for example, of a silicon (Si) film formed above
the actuator substrate 202, a silicon oxide (SiO.sub.2) film formed
above the silicon film, and a silicon nitride (SiN) film formed
above the silicon oxide film. In the present specification, the
movable film 210A refers to a top roof portion of the movable film
formation layer 210 that defines the top surface portion of the
pressure chamber 207. Therefore, portions of the movable film
formation layer 210 besides the top roof portions of the pressure
chambers 207 do not constitute the movable film 210A.
[0108] Each movable film 210A has a thickness of, for example, 0.4
.mu.m to 2 .mu.m. If the movable film 210A is constituted of a
silicon oxide film, the thickness of the silicon oxide film may be
approximately 1.2 .mu.m. If the movable film 210A 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 .mu.m.
[0109] Each pressure chamber 207 is defined by a movable film 210A,
the actuator substrate 202, and the nozzle substrate 203 and is
formed to a substantially rectangular parallelepiped shape in the
present preferred embodiment. The pressure chamber 207 may, for
example, have a length of approximately 800 .mu.m and a width of
approximately 55 .mu.m. Each ink inflow portion 206 is in
communication with one end portion in a long direction of a
pressure chamber 207.
[0110] A piezoelectric element 209 is disposed on a front surface
of each movable film 210A. Each piezoelectric element 209 includes
a lower electrode 211 formed above the movable film formation layer
210, a piezoelectric film 212 formed above the lower electrode 211,
and an upper electrode 213 formed above the piezoelectric film 212.
In other words, the piezoelectric element 209 is arranged by
sandwiching the piezoelectric film 212 from above and below by the
upper electrode 213 and the lower electrode 211.
[0111] The upper electrode 213 may be a single film of platinum
(Pt) or may have a laminated structure, for example, in which a
conductive oxide film (for example, an IrO.sub.2 (iridium oxide)
film) and a metal film (for example, an Ir (iridium) film) are
laminated. The upper electrode 213 may have a thickness, for
example, of approximately 0.2 .mu.m.
[0112] As each piezoelectric film 212, for example, a PZT
(PbZr.sub.xTi.sub.1-xO.sub.3: lead zirconate titanate) film formed
by a sol-gel method or a sputtering method may be applied. Such a
piezoelectric film 212 is constituted of a sintered body of a metal
oxide crystal. The piezoelectric film 212 is formed to be of the
same shape as the upper electrode 213 in plan view. The
piezoelectric film 212 has a thickness of approximately 1 .mu.m.
The overall thickness of each movable film 210A is preferably
approximately the same as the thickness of the piezoelectric film
212 or approximately 2/3 the thickness of the piezoelectric film
212.
[0113] The lower electrode 211 has, for example, a two-layer
structure with a Ti (titanium) film and a Pt (platinum) film being
laminated successively from the movable film formation layer 210
side. Besides this, the lower electrode 211 may be formed of a
single film that is an Au (gold) film, a Cr (chromium) layer, or an
Ni (nickel) layer, etc. The lower electrode 211 has main electrode
portions 211A, in contact with lower surfaces of the piezoelectric
films 212, and an extension portion 211B extending to a region
outside the piezoelectric films 212. The lower electrode 211 may
have a thickness, for example, of approximately 0.2 .mu.m.
[0114] A hydrogen barrier film 214 is formed above the extension
portion 211B of the lower electrode 211 and above the piezoelectric
elements 209. The hydrogen barrier film 214 is constituted, for
example, of Al.sub.2O.sub.3 (alumina). The hydrogen barrier film
214 has a thickness of approximately 50 nm to 100 nm. The hydrogen
barrier film 214 is provided to prevent degradation of
characteristics of the piezoelectric film 212 due to hydrogen
reduction.
[0115] An insulating film 215 is laminated on the hydrogen barrier
film 214. The insulating film 215 is constituted, for example, of
SiO.sub.2or low-hydrogen SiN, etc. The insulating film 215 has a
thickness of approximately 500 nm. Upper wirings 217, a lower
wiring 218, and dummy wirings 219 are formed above the insulating
film 215. These wirings 217, 218, and 219 may be constituted of a
metal material that includes Al (aluminum). These wirings 217, 218,
and 219 have a thickness, for example, of approximately 1000 nm (1
.mu.m).
[0116] One end portion of each upper wiring 217 is disposed above
one end portion (downstream side end portion in the ink flow
direction 241) of an upper electrode 213. A contact hole 233,
penetrating continuously through the hydrogen barrier film 214 and
the insulating film 215, is formed between the upper wiring 217 and
the upper electrode 213. The one end portion of the upper wiring
217 enters into the contact hole 233 and is connected to the upper
electrode 213 inside the contact hole 233. From above the upper
electrode 213, the upper wiring 217 crosses an outer edge of the
pressure chamber 207 and extends outside the pressure chamber
207.
[0117] The lower wiring 218 is disposed above the extension portion
211B of the lower electrode 211 at an opposite side from the
pressure chambers 207 with respect to the ink inflow portions 206
of the ink flow passages 205. A plurality of contact holes 234,
penetrating continuously through the hydrogen barrier film 214 and
the insulating film 215, are formed between the lower wiring 218
and the extension portion 211B of the lower electrode 211. The
lower wiring 218 enters into the contact holes 234 and is connected
to the extension portion 211B of the lower electrode 211 inside the
contact holes 234.
[0118] The dummy wirings 219 are not electrically connected to
either of the upper wirings 217 and the lower wiring 218 and are
electrically insulated wirings. The dummy wirings 219 are formed in
the same process as a process in which the upper wirings 217 and
the lower wiring 218 are formed.
[0119] A passivation film 221, covering the wirings 217, 218, and
219 and the insulating film 215 is formed above the insulating film
215. The passivation film 221 is constituted, for example, of SiN
(silicon nitride). The passivation film 221 may have a thickness,
for example, of approximately 800 nm.
[0120] Pad openings 235 that expose portions of the upper wirings
217 are formed in the passivation film 221. The pad openings 235
are formed in a region outside the pressure chambers 207 and are
formed, for example, at tip portions (end portions at opposite
sides from the portions of contact with the upper electrodes 213)
of the upper wirings 217. Pads 242 that cover the pad openings 235
are formed above the passivation film 221. The pads 242 enter into
the pad openings 235 and are connected to the upper wirings 217
inside the pad openings 235.
[0121] Ink supply penetrating holes 222, penetrating through the
passivation film 221, the insulating film 215, the hydrogen barrier
film 214, the lower electrode 211, and the movable film formation
layer 210 are formed at positions corresponding to end portions of
the ink flow passages 205 at the ink inflow portion 206 sides.
Penetrating holes 223, each including an ink supply penetrating
hole 222 and being larger than the ink supply penetrating hole 222,
are formed in the lower electrode 211. The hydrogen barrier film
214 enters into gaps between the penetrating holes 223 in the lower
electrode 211 and the ink supply penetrating holes 222. The ink
supply penetrating holes 222 are in communication with the ink
inflow portions 206.
[0122] The protective substrate 204 is constituted, for example, of
a silicon substrate. The protective substrate 204 is disposed above
the actuator substrate 202 so as to cover the piezoelectric
elements 209. The protective substrate 204 is bonded to the
passivation film 221 via an adhesive 250. The protective substrate
204 has housing recesses 252 in a facing surface 251 that faces a
front surface 202a of the actuator substrate 202. The piezoelectric
elements 209 are housed inside the housing recesses 252. Further,
the protective substrate 204 has formed therein ink supply passages
253 that are in communication with the ink supply penetrating holes
222. The ink supply passages 253 penetrate through the protective
substrate 204. An ink tank (not shown) storing ink is disposed
above the protective substrate 204.
[0123] Each piezoelectric element 209 is formed at a position
facing a pressure chamber 207 across a movable film 210A. That is,
the piezoelectric element 209 is formed to contact a front surface
of the movable film 210A at an opposite side from the pressure
chamber 207. Each pressure chamber 207 is filled with ink by the
ink being supplied from the ink tank to the pressure chamber 207
through an ink supply passage 253, an ink supply penetrating hole
222, and an ink inflow portion 206. The movable film 210A defines a
top surface portion of the pressure chamber 207 and faces the
pressure chamber 207. The movable film 210A is supported by
portions of the actuator substrate 202 at a periphery of the
pressure chamber 207 and has flexibility enabling deformation in a
direction facing the pressure chamber 207 (in other words, in the
thickness direction of the movable film 210A).
[0124] The upper wirings 217 and the lower wiring 218 are connected
to a drive circuit (not shown). Specifically, the pads 242 of the
upper wirings 217 and the drive circuit are connected via a
connecting metal member (not shown). As shall be described later, a
pad 243 (see FIG. 8A) is connected to the lower wiring 218. The pad
243 of the lower wiring 218 and 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 element 209, the
piezoelectric film 212 deforms due to an inverse piezoelectric
effect. The movable film 210A is thereby made to deform together
with the piezoelectric element 209 to bring about a volume change
of the pressure chamber 207 and the ink inside the pressure chamber
207 is pressurized. The pressurized ink passes through the ink
discharge hole 203a and is discharged as microdroplets from the
discharge port 203b.
[0125] The arrangement of the inkjet printing head 201 shall now be
described in more detail with reference to FIG. 8A to FIG. 11.
[0126] A plurality of the ink flow passages 205 (pressure chambers
207) are formed as stripes extending parallel to each other in the
actuator substrate 202. The piezoelectric element 209 is disposed
respectively in each of the plurality of ink flow passages 205. The
ink supply penetrating holes 222 are provided respectively for each
of the plurality of ink flow passages 205. The housing recesses 252
and the ink supply passages 253 in the protective substrate 204 are
provided respectively for each of the plurality of ink flow
passages 205.
[0127] The plurality of ink flow passages 205 are formed at equal
intervals that are minute intervals (for example, of approximately
30 .mu.m to 350 .mu.m) in a width direction thereof. Each ink flow
passage 205 is elongate along the ink flow direction 241. Each ink
flow passage 205 is constituted of an ink inflow portion 206 in
communication with an ink supply penetrating hole 222 and the
pressure chamber 207 in communication with the ink inflow portion
206. In plan view, the pressure chamber 207 has an oblong shape
that is elongate along the ink flow direction 241. That is, the top
surface portion of the pressure chamber 207 has two side edges
along the ink flow direction 241 and two end edges along a
direction orthogonal to the ink flow direction 241. In plan view,
the ink inflow portion 206 has substantially the same width as the
pressure chamber 207. An inner surface of an end portion of the ink
inflow portion 206 at an opposite side from the pressure chamber
207 is formed to a semicircle in plan view. The ink supply
penetrating hole 222 is circular in plan view (see especially FIG.
8B).
[0128] Each piezoelectric element 209 has, in plan view, a
rectangular shape that is long in a long direction of a pressure
chamber 207 (movable film 210A). A length in a long direction of
the piezoelectric element 209 is shorter than a length in the long
direction of the pressure chamber 207 (movable film 210A). As shown
in FIG. 8B, respective end edges along a short direction of the
piezoelectric element 209 are disposed at inner sides at
predetermined intervals respectively from respective corresponding
end edges of the movable film 210A. Also, a width in the short
direction of the piezoelectric element 209 is narrower than a width
in a short direction of the movable film 210A. Respective side
edges along the long direction of the piezoelectric element 209 are
disposed at inner sides at predetermined intervals from respective
corresponding side edges of the movable film 210A.
[0129] The lower electrode 211 is formed on substantially an
entirety of the front surface of the movable film formation layer
210 (see especially FIG. 11). The lower electrode 211 is a common
electrode used in common for the plurality of piezoelectric
elements 209. The lower electrode 211 includes the main electrode
portions 211A of rectangular shape in plan view that constitute the
piezoelectric elements 209 and the extension portion 211B led out
from the main electrode portions 211A in directions along the front
surface of the movable film formation layer 210 to extend outside
the peripheral edges of the top surface portions of the pressure
chambers 207.
[0130] A length in a long direction of each main electrode portion
211A is shorter than the length in the long direction of each
movable film 210A. Respective end edges of the main electrode
portion 211A are disposed at inner sides at predetermined intervals
respectively from the respective corresponding end edges of the
movable film 210A. Also, a width in a short direction of the main
electrode portion 211A is narrower than the width of the movable
film 210A in the short direction. Respective side edges of the main
electrode portion 211A are disposed at inner sides at predetermined
intervals from the respective corresponding side edges of the
movable film 210A. The extension portion 211B is a region among the
entire region of the lower electrode 211 that excludes the main
electrode portions 211A.
[0131] In plan view, the upper electrodes 213 are formed to
rectangular shapes of the same pattern as the main electrode
portions 211A of the lower electrode 211. That is, a length in a
long direction of each upper electrode 213 is shorter than the
length in the long direction of each movable film 210A. Respective
end edges of the upper electrode 213 are disposed at inner sides at
predetermined intervals respectively from the respective
corresponding end edges of the movable film 210A. Also, a width in
a short direction of the upper electrode 213 is narrower than the
width in the short direction of the movable film 210A. Respective
side edges of the upper electrode 213 are disposed at inner sides
at predetermined intervals from the respective corresponding side
edges of the movable film 210A.
[0132] In plan view, the piezoelectric films 212 are formed to
rectangular shapes of the same pattern as the upper electrodes 213.
That is, a length in a long direction of each piezoelectric film
212 is shorter than the length in the long direction of each
movable film 210A. Respective end edges of the piezoelectric film
212 are disposed at inner sides at predetermined intervals
respectively from the respective corresponding end edges of the
movable film 210A. Also, a width in a short direction of the
piezoelectric film 212 is narrower than the width in the short
direction of the movable film 210A. Respective side edges of the
piezoelectric film 212 are disposed at inner sides at predetermined
intervals from the respective corresponding side edges of the
movable film 210A. A lower surface of the piezoelectric film 212
contacts an upper surface of the main electrode portion 211A of the
lower electrode 211 and an upper surface of the piezoelectric film
212 contacts a lower surface of the upper electrode 213.
[0133] Each upper wiring 217 extends from an upper surface of one
end portion of a piezoelectric element 209 and along an end surface
of the piezoelectric element 209 continuous to the upper surface
and extends further along the front surface of the extension
portion 211B of the lower electrode 211 in a direction along the
ink flow direction 241. The tip portion of the upper wiring 217 is
disposed further downstream in the ink flow direction 241 than a
downstream side end of the protective substrate 204. The pad
openings 235 that expose central portions of tip portion front
surfaces of the upper wirings 217 are formed in the passivation
film 221. The pads 242 are provided on the passivation film 221 so
as to cover the pad openings 235. The pads 242 are connected to the
upper wirings 217 inside the pad openings 235.
[0134] In plan view, the lower wiring 218 has a rectangular main
wiring portion 218A that is long in a direction orthogonal to the
ink flow direction 241 and a lead portion 218B extending along the
ink flow direction 241 from one end portion of the main wiring
portion 218A. A tip portion of the lead portion 218B is disposed
further downstream in the ink flow direction 241 than the
downstream side end of the protective substrate 204. The lower
wiring 218 enters into the plurality of contact holes 234 and is
connected to the extension portion 211B of the lower electrode 211
inside the contact holes 234. A pad opening 236 that exposes a
central portion of a tip portion front surface of the lead portion
218B is formed in the passivation film 221. The pad 243 is provided
above the passivation film 221 so as to cover the pad opening 236.
The pad 243 is connected to the lead portion 218B inside the pad
opening 236.
[0135] FIG. 14 is a bottom view of a main portion of the protective
substrate as viewed from the actuator substrate side of the inkjet
printing head.
[0136] As shown in FIG. 8A, FIG. 10, and FIG. 14, in the facing
surface 251 of the protective substrate 204, the plurality of
housing recesses 252 are formed in parallel at intervals in a
direction orthogonal to the ink flow direction 241. In plan view,
the plurality of housing recesses 252 are disposed at positions
facing the plurality of pressure chambers 207. With respect to the
respective housing recesses 252, the ink supply passages 253 are
disposed at upstream sides in the ink flow direction 241. In plan
view, each housing recess 252 is formed to a rectangular shape
slightly larger than the pattern of the upper electrode 213 of the
corresponding piezoelectric element 209. The corresponding
piezoelectric element 209 is housed in each housing recess 252.
[0137] In plan view, the ink supply passages 253 of the protective
substrate 204 have circular shapes of the same pattern as the ink
supply penetrating holes 222 at the actuator substrate 202 side. In
plan view, the ink supply passages 253 are matched with the ink
supply penetrating holes 222.
[0138] In plan view, the dummy wirings 219 include first dummy
wirings 219A of circular annular shapes that surround the ink
supply passages 253 (ink supply penetrating holes 222). Above the
actuator substrate 202, the first dummy wirings 219A are disposed
in regions facing regions of the facing surface 251 of the
protective substrate 204 peripheral to the ink supply passages 253.
A width of each first dummy wiring 219A (difference between an
inner diameter and an outer diameter of each first dummy wiring
219A) is preferably not less than 1/3 a diameter of each ink supply
passage 253. Upper surfaces of the first dummy wirings 219A are
flat. Each first dummy wiring 219A constitutes a base 220 that
supports the protective substrate 204 and increases adhesion with
the facing surface of the protective substrate 204.
[0139] The dummy wirings 219 further include second dummy wirings
219B of elongate rectangular shapes that are formed at width
central portions of regions between adjacent pressure chambers 207
and at outward sides of the pressure chambers 207 at respective
outer sides of the set of plurality of pressure chambers and extend
in the direction along the ink flow direction 241. Upper surfaces
of the second dummy wirings 219B are flat. Each second dummy wiring
219B constitutes a base that supports the protective substrate 204
and increases adhesion with the facing surface of the protective
substrate 204.
[0140] In bonding the protective substrate 204 to the actuator
substrate 202, the protective substrate 204 is pressed against the
actuator substrate 202 in a state where the adhesive 250 is coated
on a portion of bonding of the actuator substrate 202 and the
protective substrate 204. In this process, the facing surface 251
of the protective substrate 204 is pressed via the passivation film
221 against the first dummy wirings 219A and the second dummy
wirings 219B that are the bases with flat upper surfaces. The
facing surface 251 of the protective substrate 204 is thus bonded
firmly via the passivation film 221 and the adhesive 250 to the
upper surfaces of the first dummy wirings 219A and the second dummy
wirings 219B. Defective adhesion is thus made unlikely to occur at
the portion of bonding of the facing surface 251 of the protective
substrate 204 and the actuator substrate 202.
[0141] In the present second preferred embodiment, by the first
dummy wirings 219A (bases 220) of circular annular shapes
surrounding the ink supply passages 253 (ink supply penetrating
holes 222) being provided at the actuator substrate 202 side,
occurrence of defective bonding between the actuator substrate 202
and lower surfaces of wall portions of the protective substrate 204
between the housing recesses 252 and the ink supply passages 253
can be suppressed. Leakage of ink into a housing recess 252 from an
ink supply passage 253 can thereby be suppressed.
[0142] FIG. 12 is an illustrative plan view of a pattern example of
the insulating film of the inkjet printing head. FIG. 13 is an
illustrative plan view of a pattern example of the passivation film
of the inkjet printing head.
[0143] In the present second preferred embodiment, above the
actuator substrate 202, the insulating film 215 and the passivation
film 221 are formed on substantially an entirety of a region of the
protective substrate 204 outside the housing recesses 252 in plan
view. However, in this region, the ink supply penetrating holes 222
and the contact holes 234 are formed in the insulating film 215. In
this region, the ink supply penetrating holes 222 and the pad
openings 235 and 236 are formed in the passivation film 221.
[0144] In the regions of the protective substrate 204 inside the
housing recesses 252, the insulating film 215 and the passivation
film 221 are formed just in one end portions (upper wiring regions)
in which the upper wirings 217 are present. In each of these
regions, the passivation film 221 is formed to cover an upper
surface and a side surface of an upper wiring 217 above the
insulating film 215. In other words, in the insulating film 215 and
the passivation film 221, openings 237 are formed in regions,
within the inner side regions of the housing recesses 252 in plan
view, that exclude the upper wiring regions. The contact holes 233
are further formed in the insulating film 215.
[0145] In the present preferred embodiment, in a region at the
inner side of the peripheral edge of each pressure chamber 207 in
plan view, the insulating film 215 and the passivation film 221 are
formed just in the upper wiring region in which an upper wiring 217
is present. Therefore, most of the side surface and the upper
surface of each piezoelectric element 209 are not covered by the
insulating film 215 and the passivation film 221. Displacement of
each movable film 210A can thereby be increased in comparison to a
case where entireties of the side surface and the upper surface of
the piezoelectric element 209 are covered by the insulating film
and the passivation film.
[0146] FIG. 15A to FIG. 15M are sectional views of an example of a
manufacturing process of the inkjet printing head 201 and show a
section corresponding to FIG. 9.
[0147] First, as shown in FIG. 15A, the movable film formation
layer 210 is formed on the front surface 202a of the actuator
substrate 202. However, as the actuator substrate 202, that which
is thicker than the thickness of the actuator substrate 202 at the
final stage is used. Specifically, a silicon oxide film (for
example, of 1.2 .mu.m thickness) is formed on the front surface of
the actuator substrate 202. If the movable film formation layer 210
is 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 .mu.m thickness) is formed on the front surface of
the actuator substrate 202, the silicon oxide film (for example, of
0.4 .mu.m thickness) is formed above the silicon film, and the
silicon nitride film (for example, of 0.4 .mu.m thickness) is
formed above the silicon oxide film.
[0148] A base oxide film, for example, of Al.sub.2O.sub.3, MgO, or
ZrO.sub.2, etc., may be formed on the front surface of the movable
film formation layer 210. Such base oxide films prevent metal atoms
from escaping from the piezoelectric film 212 to be formed later.
When metal electrons escape, the piezoelectric film 212 may degrade
in piezoelectric characteristics. Also, when metal atoms that have
escaped become mixed in the silicon layer constituting each movable
film 210A, the movable film 210A may degrade in durability.
[0149] Next, a lower electrode film 271, which is a material layer
of the lower electrode 211, is formed above the movable film
formation layer 210 (above the base oxide film in the case where
the base oxide film is formed) as shown in FIG. 15B. The lower
electrode film 271 is 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 film
271 may be formed by the sputtering method.
[0150] Next, a material film (piezoelectric material film) 272 of
the piezoelectric films 212 is formed on an entire surface above
the lower electrode film 271. Specifically, for example, the
piezoelectric material film 272 of 1 .mu.m to 3 .mu.m thickness is
formed by a sol-gel method. Such a piezoelectric material film 272
is constituted of a sintered body of metal oxide crystal
grains.
[0151] Next, an upper electrode film 273, which is a material of
the upper electrodes 213, is formed on the entire surface of the
piezoelectric material film 272. The upper electrode film 273 may,
for example, be a single film of platinum (Pt). The upper electrode
film 273 may, for example, be an IrO.sub.2/Ir laminated film having
an IrO.sub.2 film (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 film 273 may
be formed by the sputtering method.
[0152] Next, as shown in FIG. 15C and FIG. 15D, patterning of the
upper electrode film 273, the piezoelectric material film 272, and
the lower electrode film 271 is performed. First, a resist mask
with a pattern of the upper electrodes 213 is formed by
photolithography. Then, as shown in FIG. 15C, the upper electrode
film 273 and the piezoelectric material film 272 are etched
successively using the resist mask as a mask to form the upper
electrodes 213 and the piezoelectric films 212 of the predetermined
patterns.
[0153] Next, after peeling off the resist mask, a resist mask with
a pattern of the lower electrode 211 is formed by photolithography.
Then, as shown in FIG. 15D, the lower electrode film 271 is etched
using the resist mask as a mask to form the lower electrode 211 of
the predetermined pattern. The lower electrode 211, constituted of
the main electrode portions 211A and the extension portion 211B
having the penetrating holes 223, is thereby formed. The
piezoelectric elements 209, each constituted of a main electrode
portion 211A of the lower electrode 211, a piezoelectric film 212,
and an upper electrode 213, are thereby formed.
[0154] Next, after peeling off the resist mask, the hydrogen
barrier film 214 covering the entire surface is formed as shown in
FIG. 15E. The hydrogen barrier film 214 may be an Al.sub.2O.sub.3
film formed by the sputtering method and may have a film thickness
of 50 nm to 100 nm. Thereafter, the insulating film 215 is formed
above the entire surface of the hydrogen barrier film 214. The
insulating film 215 may be an SiO.sub.2 film and may have a film
thickness of 200 nm to 300 nm. Next, the contact holes 233 and 234
are formed by successively etching the insulating film 215 and the
hydrogen barrier film 214.
[0155] Next, as shown in FIG. 15F, a wiring film that constitutes
the upper wirings 217, the lower wiring 218, and the dummy wirings
219 (219A and 219B) is formed by the sputtering method above the
insulating film 215 as well as inside the contact holes 233 and
234. Thereafter, the wiring film is patterned by photolithography
and etching to form the upper wirings 217, the lower wiring 218,
and the dummy wirings 219 (219A and 219B) at the same time.
[0156] Next, as shown in FIG. 15G, the passivation film 221 that
covers the wirings 217, 218, and 219 is formed on the front surface
of the insulating film 215. The passivation film 221 is
constituted, for example, of SiN. The passivation film 221 is
formed, for example, by plasma CVD.
[0157] Next, a resist mask, having openings corresponding to the
pad openings 235 and 236, is formed by photolithography, and the
passivation film 221 is etched using the resist mask as a mask. The
pad openings 235 and 236 are thereby formed in the passivation film
221 as shown in FIG. 15H. After the resist mask is peeled off, the
pads 242 and 243, respectively connected to the upper wirings 217
and the lower wiring 218 via the pad openings 235 and the pad
opening 236, are formed above the passivation film 221.
[0158] A resist mask having openings corresponding to the openings
237 and the ink supply penetrating holes 222 is then formed by
photolithography, and using the resist mask as a mask, the
passivation film 221 and the insulating film 215 are etched
successively. The openings 237 and the ink supply penetrating holes
222 are thereby formed in the passivation film 221 and the
insulating film 215 as shown in FIG. 15I.
[0159] Next, the resist mask is peeled off. A resist mask having
openings corresponding to the ink supply penetrating holes 222 is
then formed by photolithography, and the hydrogen barrier film 214
and the movable film formation layer 210 are etched using the
resist mask as a mask. The ink supply penetrating holes 222 are
thereby formed in the hydrogen barrier film 214 and the movable
film formation layer 210 as shown in FIG. 15J.
[0160] Next, as shown in FIG. 15K, the adhesive 250 is coated onto
the facing surface 251 of the protective substrate 204 and the
protective substrate 204 is fixed onto the actuator substrate 202
so that the ink supply passages 253 and the ink supply penetrating
holes 222 are matched. In this process, the facing surface 251 of
the protective substrate 204 is pressed via the passivation film
221 against the first dummy wirings 219A and the second dummy
wirings 219B that are the bases with flat upper surfaces. The
facing surface 251 of the protective substrate 204 is thus bonded
firmly via the passivation film 221 and the adhesive 250 to the
upper surfaces of the first dummy wirings 219A and the second dummy
wirings 219B.
[0161] Next, as shown in FIG. 15L, rear surface grinding for
thinning the actuator substrate 202 is performed. The actuator
substrate 202 is made thin by the actuator substrate 202 being
ground from the rear surface 202b. For example, the actuator
substrate 202 with a thickness of approximately 670 .mu.m in the
initial state may be thinned to a thickness of approximately 300
.mu.m. Next, etching (dry etching or wet etching) from the rear
surface of the actuator substrate 202 is performed on the actuator
substrate 202 to form the ink flow passages 205 (the ink inflow
portions 206 and the pressure chambers 207).
[0162] In the etching process, the base oxide film formed on the
front surface of the movable film formation layer 210 prevents the
escaping of metal elements (Pb, Zr, and Ti in the case of PZT) from
the piezoelectric film 212 and keeps the piezoelectric
characteristics of the piezoelectric film 212 in a satisfactory
state. Also as mentioned above, the base oxide film formed on the
front surface of the movable film formation layer 210 contributes
to maintaining the durability of the silicon layer that forms each
movable film 210A.
[0163] Thereafter, as shown in FIG. 15M, the nozzle substrate 203
is adhered onto the rear surface of the actuator substrate 202 and
the inkjet printing head 201 is thereby obtained.
[0164] FIG. 16A and FIG. 16B are partially enlarged sectional views
of steps of forming an ink discharge hole 203a in the nozzle
substrate 203 and show a section corresponding to FIG. 9. In the
present preferred embodiment, each ink discharge hole 203a is
formed so that a transverse sectional shape of a processing ending
end side (actuator substrate 202 side) of the ink discharge hole
203a will be a quadrilateral shape. In other words, a target shape
of a transverse section of the processing ending end side of the
ink discharge hole 203a is a regular quadrilateral.
[0165] First, a resist mask 290, having penetrating holes 291, is
formed by photolithography on surface (rear surface) of the nozzle
substrate 203 at an opposite side from the surface bonded to the
rear surface of the actuator substrate 202. FIG. 17 is an enlarged
bottom view of a portion of the resist mask 290. A bottom surface
shape (transverse sectional shape) of each penetrating hole 291 is
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 in FIG. 17) of the transverse section at the
processing ending end side of the corresponding ink discharge hole
203a.
[0166] Next, in the state where the resist mask 290 is formed on
the rear surface of the nozzle substrate 203, dry etching is
applied to the nozzle substrate 203. The ink discharge holes 203a
are thereby formed in the nozzle substrate 203 as shown in FIG.
16B.
[0167] FIG. 18A is an enlarged bottom view of a bottom surface
shape at a processing starting end side (the nozzle substrate 203
rear surface side) of an ink discharge hole 203. FIG. 18B is an
enlarged sectional view taken along XVIIIB-XVIIIB in FIG. 16B. That
is, FIG. 18B is an enlarged sectional view of a transverse
sectional shape at a center-of-length portion (center-of-depth
portion) of the ink discharge hole 203a. FIG. 18C is an enlarged
plan view of a planar shape at a processing ending end side (the
nozzle substrate 203 front surface side) of the ink discharge hole
203a.
[0168] As shown in FIG. 17, the transverse sectional shape of each
penetrating hole 291 formed in the resist mask 290 is 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 hole 203a. Therefore, as shown in FIG. 18A, the bottom
surface shape at the processing starting end side (the nozzle
substrate 203 rear surface side) of the ink discharge hole 203a is
substantially the same shape as the transverse sectional shape of
the penetrating hole 291. As the etching progresses, inward
projection amounts of the respective arcuate shaped sides of the
transverse sectional shape of the ink discharge hole 203a decrease
as shown, for example, in FIG. 18B. That is, as the etching
progresses, the transverse sectional shape of the ink discharge
hole 203a approaches the regular quadrilateral that is the target
shape T. At the processing ending end side (the nozzle substrate
203 front surface side) of the ink discharge hole 203a, the planar
shape is substantially the same shape as the regular quadrilateral
that is the target shape T as shown in FIG. 18C.
[0169] In other words, in comparison to the transverse sectional
shape at the processing starting end side (the nozzle substrate 203
rear surface side) of the ink discharge hole 203a, the transverse
sectional shape at the processing ending end side of the ink
discharge hole 203a is 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
hole 291 are determined so that the transverse sectional shape at
the processing ending end side (nozzle substrate 203 front surface
side) of the ink discharge hole 203a will be a shape that is
substantially the same as the regular quadrilateral that is the
target shape T.
[0170] Thereafter, the resist mask 290 is peeled off. The nozzle
substrate 203 having the ink discharge holes 203a such as shown in
FIG. 9 is thereby obtained.
[0171] 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 hole 203a is 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.
[0172] 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.
[0173] 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.
[0174] While preferred embodiments of the present invention have
been described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing the scope and spirit of the present invention. The scope
of the present invention, therefore, is to be determined solely by
the following claims.
* * * * *