U.S. patent application number 13/014647 was filed with the patent office on 2011-07-28 for liquid composition, method of producing silicon substrate, and method of producing liquid discharge head substrate.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Hiroyuki Abo, Kenta Furusawa, Keisuke Kishimoto, Shuji Koyama, Taichi Yonemoto.
Application Number | 20110183448 13/014647 |
Document ID | / |
Family ID | 43884864 |
Filed Date | 2011-07-28 |
United States Patent
Application |
20110183448 |
Kind Code |
A1 |
Abo; Hiroyuki ; et
al. |
July 28, 2011 |
LIQUID COMPOSITION, METHOD OF PRODUCING SILICON SUBSTRATE, AND
METHOD OF PRODUCING LIQUID DISCHARGE HEAD SUBSTRATE
Abstract
A liquid composition used to carry out crystal anisotropic
etching of a silicon substrate provided with an etching mask formed
of a silicon oxide film with the silicon oxide film used as a mask
includes cesium hydroxide, an alkaline organic compound, and
water.
Inventors: |
Abo; Hiroyuki; (Tokyo,
JP) ; Yonemoto; Taichi; (Isehara-shi, JP) ;
Koyama; Shuji; (Kawasaki-shi, JP) ; Furusawa;
Kenta; (Yokohama-shi, JP) ; Kishimoto; Keisuke;
(Yokohama-shi, JP) |
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
43884864 |
Appl. No.: |
13/014647 |
Filed: |
January 26, 2011 |
Current U.S.
Class: |
438/21 ;
252/79.5; 257/E21.219; 438/753 |
Current CPC
Class: |
C09K 13/02 20130101;
B41J 2/1603 20130101; B41J 2/1635 20130101; B41J 2/1629 20130101;
H01L 21/30608 20130101; B41J 2/1628 20130101; B41J 2/1639 20130101;
B41J 2/1645 20130101 |
Class at
Publication: |
438/21 ;
252/79.5; 438/753; 257/E21.219 |
International
Class: |
H01L 21/306 20060101
H01L021/306; C09K 13/02 20060101 C09K013/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 28, 2010 |
JP |
2010-017006 |
Claims
1. A liquid composition used to carry out crystal anisotropic
etching of a silicon substrate provided with an etching mask formed
of a silicon oxide film with the silicon oxide film used as a mask,
the liquid composition comprising: cesium hydroxide; an alkaline
organic compound; and water.
2. The liquid composition according to claim 1, wherein the
alkaline organic compound includes tetramethylammonium
hydroxide.
3. The liquid composition according to claim 1, wherein a ratio by
weight of the cesium hydroxide to the weight of the liquid
composition is 1% by weight to 40% by weight inclusive.
4. The liquid composition according to claim 2, wherein a ratio by
weight of the tetramethylammonium hydroxide to the weight of the
liquid composition is 5% by weight to 25% by weight inclusive.
5. A method of producing a silicon substrate, the method
comprising: preparing a silicon substrate on which a silicon oxide
film formed with an opening is formed on at least one surface of
the substrate; and etching the substrate from the opening by using
a liquid composition containing cesium hydroxide, an alkaline
organic compound, and water as an etching solution and using the
oxide film as a mask to form a through-port penetrating through the
substrate.
6. The method according to claim 5, wherein the alkaline organic
compound includes tetramethylammonium hydroxide.
7. A method of producing a liquid discharge head substrate
including a silicon substrate provided with an energy generation
element generating energy used to discharge ink above a first
surface of the silicon substrate, the liquid discharge head
substrate being provided with a supply port penetrating through the
liquid discharge head substrate to supply a liquid to the energy
generation element, the method comprising: preparing a silicon
substrate including the energy generation element disposed above
the first surface and a silicon oxide film with an opening on at
least a second surface which is a back surface of the silicon
substrate; etching the silicon substrate from the opening by using
a liquid composition containing cesium hydroxide, an alkaline
organic compound, and water as an etching solution and using the
oxide film as a mask to form a through-port penetrating through the
silicon substrate; and forming the supply port by using the
through-port.
8. The method according to claim 7, wherein the alkaline organic
compound includes tetramethylammonium hydroxide.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a liquid composition, a
method of producing a silicon substrate, and a method of producing
a liquid discharge head substrate.
[0003] 2. Description of the Related Art
[0004] In recent years, various silicon devices have been applied
to a variety of devices such as liquid discharge heads,
thermosensors, pressure sensors, and acceleration sensors with
developments of micromachining technologies. These various silicon
devices are desired to satisfy various demands on production cost
reduction, miniaturization, and higher functions. For satisfying
these demands, fine processing technologies which are
micromachining technologies are used in the production of these
silicon devices. In these micromachining technologies, anisotropic
silicon wet etching technologies are used to form a desired
structure and, for example, a method is used in which silicon is
etched by using an alkaline etching solution which is an aqueous
solution of potassium hydroxide or tetramethylammonium
hydroxide.
[0005] However, because a long time is required for anisotropic
silicon wet etching, it is desired to shorten the time required for
silicon etching to improve productivity from the reason that
production time is determined by the etching time. Japanese Patent
Application Laid-Open No. 2009-206335 discusses that an etching
solution containing an alkaline organic compound, sodium hydroxide,
and a silicon-containing compound is used to improve silicon
etching rate.
[0006] However, there is a possibility that the liquid composition
discussed in Japanese Patent Application Laid-Open No. 2009-206335
fails to facilitate the formation of a desired shape when it is
applied to a method of producing a silicon device using a silicon
oxide film as an etching mask because a difference in etching rate
between silicon oxide and silicon is insufficient.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to an etching liquid
composition which has a high etching rate, is reduced in the
corrosion of a silicon oxide film, and enables anisotropic
selective etching of silicon in anisotropic silicon etching.
[0008] According to an aspect of the present invention, a liquid
composition used to carry out crystal anisotropic etching of a
silicon substrate provided with an etching mask formed of a silicon
oxide film with the silicon oxide film used as a mask includes
cesium hydroxide, an alkaline organic compound, and water.
[0009] According to an exemplary embodiment of the present
invention, an isotropic silicon etching liquid composition can be
provided which has a high silicon etching rate and is reduced in
the ability to etch a silicon oxide film used as an etching mask.
This etching liquid composition can contribute to the productivity
of a production process using silicon fine processing
technologies.
[0010] Further features and aspects of the present invention will
become apparent from the following detailed description of
exemplary embodiments with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate exemplary
embodiments, features, and aspects of the invention and, together
with the description, serve to describe the principles of the
invention.
[0012] FIGS. 1A to 1E are sectional views illustrating a method of
producing a silicon substrate according to an exemplary embodiment
of the present invention.
[0013] FIGS. 2A to 2E are sectional views illustrating a method of
producing a liquid discharge head according to an exemplary
embodiment of the present invention.
[0014] FIG. 3 is a perspective view illustrating an example of a
silicon substrate according to an exemplary embodiment of the
present invention.
[0015] FIG. 4 is a perspective view illustrating an example of a
liquid discharge head according to an exemplary embodiment of the
present invention.
DESCRIPTION OF THE EMBODIMENTS
[0016] Various exemplary embodiments, features, and aspects of the
invention will be described in detail below with reference to the
drawings.
[0017] A liquid composition used to carry out crystal anisotropic
etching of silicon according to an exemplary embodiment of the
present invention includes cesium hydroxide, an alkaline organic
compound, and water.
[0018] Though the liquid composition mainly includes an aqueous
solution containing cesium hydroxide, an alkaline organic compound,
and water, mixing of other liquid components is not excluded. Any
material may be used as an additional component to be added to the
liquid composition insofar as it does not impair the etching
characteristics of each of the above cesium hydroxide and alkaline
organic compound.
[0019] Any material may be used as the alkaline organic compound
according to the present exemplary embodiment insofar as it is a
compound exhibiting desired alkalinity allowing the etching of
silicon, and an alkali compound giving desired etching
characteristics may be used. Examples of these alkali compounds
include tetramethylammonium hydroxide (TMAH) and tetraethylammonium
hydroxide hydride (TEAH). Tetramethylammonium hydroxide is given as
a preferable example. With regard to the concentration of the
alkaline organic compound in the liquid composition, the alkaline
organic compound is preferably used in such a manner that its
concentration is 4% by weight to 25% by weight inclusive based on
the total weight of the liquid composition. The concentration of
the alkaline organic compound is preferably 5% by weight or more in
view of, particularly, maintaining necessary etching ability for a
long period of time and is preferably 25% by weight or less in view
of particularly increasing necessary etching rate.
[0020] Further, cesium hydroxide is used as the inorganic alkali
compound to be mixed with the alkaline organic compound.
[0021] Further, the ratio by weight of cesium oxide to the liquid
composition is preferably 1% by weight to 60% by weight inclusive.
The ratio by weight of cesium oxide is preferably 1% by weight or
more with the view of sufficiently improving the silicon etching
rate and is preferably 40% by weight or less in consideration of,
for example, cost performance.
[0022] The ratio of the amount of cesium hydroxide and alkaline
organic compound to the amount of water in the liquid composition
is preferably 80 percent or more, more preferably 95 percent or
more and even more preferably 98 percent or more, to allow cesium
hydroxide and alkaline organic compound to function
efficiently.
[0023] The etching liquid composition according to the present
exemplary embodiment may be preferably used as the etching
solutions in the productions of various silicon devices, such as
liquid discharge heads, pressure sensors, and acceleration sensors,
in the fields of microelectromechanical system (MEMS) involving a
silicon wet etching process.
[0024] FIG. 3 is a perspective view illustrating a monocrystal
silicon substrate 1 having a {100} plane azimuth with a
through-port 6 formed thereon by anisotropic etching using a
silicon oxide film 4 as a mask. The through-port 6 is formed in
such a manner as to be narrower toward the front surface from the
back surface of the silicon substrate 1. An oxide film 4 and a
resin layer 7 are formed on the back surface of the silicon
substrate 1.
[0025] A method of forming a through-port on a monocrystal silicon
substrate will be described with reference to FIGS. 1A to 1E.
[0026] FIGS. 1A to 1E are sectional views each illustrating a
section perpendicular to the substrate 1 taken along line A-A' in
FIG. 3 and are typical sectional views illustrating a fundamental
process of producing a silicon substrate with a through-port formed
using an etching liquid composition according to the present
exemplary embodiment.
[0027] A mother material 1a of silicon is prepared as illustrated
in FIG. 1A. In this case, the mother material 1a has a {100}
principal plane.
[0028] Then, as illustrated in FIG. 1B, the silicon oxide film 4 is
formed on the back surface 101, which is another surface of the
silicon mother material 1a illustrated in FIG. 1A. The silicon
oxide film 4 may be formed as a deposition film by the chemical
vacuum deposition (CVD) method or may be formed on the surface
layer by thermal oxidation of the silicon mother material 1a. The
substrate 1 of silicon (referred to also as a silicon substrate 1)
with the oxide film 4 formed on its back surface 101 is thus
obtained. As to the condition of the mother material 1, an oxide
film 5 is formed also on the front surface 102 when the mother
material 1 is thermally oxidized.
[0029] At this time, the resin layer 7 patterned to etch the
silicon oxide film 4, which is to be a mask in the formation of the
through-port 6, is formed in advance on the back surface 101 of the
silicon substrate 1. This resin layer 7 may be formed of, for
example, a polyether amide.
[0030] Then, as illustrated in FIG. 1C, the silicon oxide film 4 is
etched by using the resin layer 7 as a mask to form an opening
portion 11 in the oxide film 4.
[0031] Then, as illustrated in FIG. 1D, silicon of the substrate 1
is etched by using the etching liquid composition of the present
exemplary embodiment from the opening portion 11. The {100} plane
of silicon is etched preferentially and the etching advances
towards the front surface 102 of the substrate 1. The oxide film 5
on the front surface 102 is etched by a liquid composition at a low
rate and the etching is finished just before the oxide film 5 is
exposed as a region to be etched. A {111} plane S appears on the
side surface and the through-port 6 penetrating through the
substrate 1 is formed.
[0032] Then, as illustrated in FIG. 1E, the silicon oxide film 5 on
the front surface of the silicon substrate 1 is removed to obtain
the substrate 1 put into the state illustrated in FIG. 3.
[0033] After that, the resin layer 7 and the oxide film 4 may be
removed by, for example, etching.
[0034] FIG. 4 is a typical perspective view illustrating an example
of a liquid discharge head according to an exemplary embodiment of
the present invention and is also a partly broken view illustrating
the inside structure. As illustrated in FIG. 4, the liquid
discharge head is provided with a silicon substrate 1 as the liquid
discharge head substrate with energy generation elements 3 formed
in two rows at fixed pitches. A flow path 12 and liquid discharge
ports 10 opened above the energy generation element 3 are formed on
the substrate 1 by using a coating resin layer 9 constituting a
flow path forming member, thereby forming the upper liquid flow
path communicating with each discharge port 10 from a liquid supply
port 60, which is formed by anisotropic silicon etching and opened
from a space between the two rows of energy generation elements 3.
This liquid discharge head discharges liquid droplets from the
discharge ports 10 when pressure enough to energize the energy
generation elements 3 is applied to the liquid filled in the flow
path through the supply port 60. Further, the oxide film 4 is
formed on the back surface of the silicon substrate 1. The liquid
discharge head may be applied to inkjet recording heads configured
to perform recording by sticking ink to a recording medium or
inkjet heads for producing color filters.
[0035] A method of producing the liquid discharge head substrate
will be described with reference to FIGS. 2A to 2E.
[0036] FIGS. 2A to 2E are sectional views each illustrating a
section perpendicular to the substrate taken along line B-B' in
FIG. 4 and typical sectional views illustrating a fundamental step
for producing a liquid discharge head according to an exemplary
embodiment of the present invention. Though the formations of the
flow path and discharge port, which will be described below, are
inessential processes, explanations will be made taking, as an
example, a production method in which the flow path and discharge
port are formed according to the production of the liquid discharge
head substrate in the present exemplary embodiment.
[0037] A sacrifice layer 2 and a plurality of energy generation
elements 3, such as thermal resistances that generate the energy
utilized to discharge liquid, are arranged on the front surface,
which is the first surface, of the monocrystal silicon substrate 1
having a {100} plane azimuth as illustrated in FIG. 2A. An
insulating film (not illustrated), such as a thermal oxidation
film, is formed between the energy generation element 3 and the
silicon part of the silicon substrate 1. Further, a silicon oxide
film 4, which is to be a mask used to form the ink supply port 60,
is formed on the back surface, which is the second surface, of the
substrate 1. Wiring of the energy generation element 3 and a
semiconductor device used to drive the energy generation element 3
are not illustrated. The sacrifice layer 2 and other elements and
wirings are covered with the protective film 5. The energy
generation element 3 may be covered. The sacrifice layer 2 is
formed of, for example, aluminum or polysilicon and the protective
film 5 is formed of, for example, an oxide, nitride, or carbide of
silicon. The resin layer 7 used to etch the silicon oxide film 4 is
formed on the back surface of the substrate 1 in advance by
patterning.
[0038] Then, as illustrated in FIG. 2B, a positive resist 8, which
is to be a patterning material of the flow path 12, is applied to
the substrate 1 illustrated in FIG. 1A and then exposed to light
and developed. Next, a coating resin layer 9 is applied by, for
example, spin coating, exposed to, for example, ultraviolet light
or Deep UV and developed to form the discharge port 10. This step
is not necessarily carried out in this stage.
[0039] Then, as illustrated in FIG. 2C, the opening portion 11 is
formed by wet etching using the resin layer 7 as a mask.
[0040] Then, as illustrated in FIG. 2D, silicon of the substrate 1
is etched by using the etching liquid composition according to an
exemplary embodiment of the present invention. The region to be
etched spreads towards the front surface of the substrate 1 and
reaches the sacrifice layer 2. If the sacrifice layer 2 can be
rapidly dissolved in the liquid composition of the present
exemplary embodiment, the etching is allowed to continue. The
supply port 60 penetrating through the substrate 1 is formed in the
above-described manner.
[0041] Thereafter, the resin layer 7 is removed. However, this step
may be performed according to the need.
[0042] Then, the positive resist 8, which is the patterning
material, is removed after the protective film 5 is etched as
illustrated in FIG. 2E, and the coating resin layer 9, which is the
material covering the patterning material, is thermally cured.
[0043] The silicon substrate 1 with nozzle portions formed by the
above steps is cut/separated into chips by a dicing saw and the
like to obtain a liquid discharge head. After that, electrical
connection is made for driving the energy generation elements 3 and
then, a support member (tank case) is connected to supply ink. The
oxide film may be removed according to the need before the back
surface is connected to the support member.
[0044] Hereinafter, exemplary embodiments of the present invention
will be described in more detail by way of Examples 1 to 6.
However, the present invention is not limited to those
examples.
[0045] The etching liquid compositions of Examples 1 to 6 in Table
1 were prepared as anisotropic silicon etching liquid compositions
to examine their properties.
Example 1
[0046] In Example 1, an aqueous solution (anisotropic silicon
etching liquid composition) containing 5% by weight of
tetramethylammonium hydroxide (hereinafter abbreviated as TMAH),
which is an alkaline organic compound, and 10% by weight of cesium
hydroxide (hereinafter abbreviated as CsOH) as an inorganic alkali
compound was prepared. Then, a silicon wafer sample used to measure
an etching rate was dipped at 80.degree. C. for one hour in the
etching liquid composition of Example 1. The wafer sample was
rinsed with ultra-pure water, then dried, and the etching amounts
of the wafer sample in the directions of the 100 and 111 planes of
silicon were measured to determine an etching rate. A wafer on
which a silicon oxide film was formed by using an etching liquid
composition having the same composition was used to determine the
etching rate of the silicon oxide film in the same manner as
above.
Example 2
[0047] In Example 2, an aqueous solution containing 5% by weight of
TMAH and 1% by weight of CsOH was prepared as an etching liquid
composition. Then, a silicon wafer sample and a wafer on which a
silicon oxide film was formed were used to carry out etching in the
same condition as in Example 1 to examine a silicon etching rate
and also to measure the etching rate of the silicon oxide film.
Example 3
[0048] In Example 3, an aqueous solution containing 25% by weight
of TMAH and 40% by weight of CsOH was prepared as an etching liquid
composition. Then, each etching rate was measured in the same
manner as in Example 1.
Example 4
[0049] In Example 4, an aqueous solution containing 5% by weight of
TMAH and 40% by weight of CsOH was prepared as an etching liquid
composition. Then, each etching rate was measured in the same
manner as in Example 1.
Example 5
[0050] In Example 5, an aqueous solution containing 25% by weight
of TMAH and 1% by weight of CsOH was prepared as an etching liquid
composition. Then, each etching rate was measured in the same
manner as in Example 1.
Example 6
[0051] In Example 6, an aqueous solution containing 2% by weight of
TMAH and 1% by weight of CsOH was prepared as an etching liquid
composition. Then, each etching rate was measured in the same
manner as in Example 1.
[0052] The results of the measurement of etching rate of the
etching liquid compositions of Examples 1 to 6 are illustrated in
Table 1.
Comparative Example 1
[0053] For comparison, potassium hydroxide (hereinafter abbreviated
as KOH) was used as the inorganic alkali compound, which was to be
added to the alkaline organic compound, as illustrated in Table 2
to prepare an anisotropic silicon etching liquid composition,
thereby examining properties of the composition.
[0054] An aqueous solution containing 25% by weight of TMAH and 40%
by weight of KOH was prepared as an etching liquid composition.
Then, a silicon wafer sample and a wafer on which a silicon oxide
film was formed were used to carry out etching using this etching
liquid composition in the same condition as in Example 1 to examine
a silicon etching rate and silicon oxide film etching rate. The
results are illustrated in Table 2.
Comparative Example 2
[0055] For comparison, potassium hydroxide (hereinafter abbreviated
as KOH) was used as the inorganic alkali compound, which was to be
added to the alkaline organic compound, as illustrated in Table 2
to prepare an anisotropic silicon etching liquid composition,
thereby examining properties of the composition. Specifically, an
aqueous solution containing 5% by weight of TMAH and 10% by weight
of KOH was prepared as an etching liquid composition. Then, a
silicon wafer sample and a wafer on which a silicon oxide film was
formed were used to carry out etching using this etching liquid
composition in the same condition as in Example 1 to examine a
silicon etching rate and silicon oxide film etching rate. The
results are illustrated in Table 2.
[0056] As illustrated in Table 1, it was confirmed that when the
etching liquid compositions of Examples of the present exemplary
embodiment were used, silicon could be selectively etched at a
higher etching rate than a silicon oxide film.
[0057] The compositions of the Examples each have a significantly
lower silicon oxide film etching rate than the compositions of
Comparative Examples. Therefore, the liquid compositions of the
Examples ensure that silicon can be more selectively etched than a
silicon oxide film.
[0058] This reason is that the liquid compositions of the Examples
each contain cesium ions, which have a large ion radius and a low
diffusing speed in a silicon oxide film as compared with the liquid
compositions of the Comparative Examples containing potassium ions
having a high diffusing speed in a silicon oxide film.
[0059] According to the exemplary embodiments of the present
invention, as mentioned above, an isotropic silicon etching liquid
composition can be provided, which has a high etching rate and
small capability of etching a silicon oxide film which is
frequently used for an etching mask. Further, the use of the
etching liquid composition according to the exemplary embodiment of
the present invention can improve silicon fine processing
efficiency.
[0060] Accordingly, the present invention can be widely applied to
technical fields relating to fine processing of silicon wafers and
the like.
TABLE-US-00001 TABLE 1 Silicon etching liquid composition Organic
Inorganic Silicon etching alkali alkali rate compound compound
Etching 100 111 Silicon oxide film TMAH CsOH temperature plane
plane etching rate (wt %) (wt %) (.degree. C.) (.mu.m/h) (.mu.m/h)
(.mu.m/h) Example 1 5 10 80 80.4 9.1 0.025 Example 2 5 1 80 64.1
7.1 0.028 Example 3 25 40 80 33.2 3.9 0.034 Example 4 5 40 80 83.9
11.8 0.030 Example 5 25 1 80 24.1 3.0 0.010 Example 6 2 1 80 37.1
5.4 0.022
TABLE-US-00002 TABLE 2 Silicon etching liquid composition Organic
Silicon etching alkali Inorganic rate Silicon compound alkali
Etching 100 111 oxide film TMAH compound temperature plane plane
etching rate (wt %) KOH (wt %) (.degree. C.) (.mu.m/h) (.mu.m/h)
(.mu.m/h) Comparative 25 40 80 32.4 5.3 2.1 Example 1 Comparative 5
10 80 78.5 12.3 0.305 Example 2
[0061] Next, a method of producing a silicon device by using the
etching liquid composition according to an exemplary embodiment of
the present invention will be described in detail, though the
present invention is not limited to the following Examples at
all.
(Example in which a Through-Port is Formed in a Silicon
Substrate)
[0062] An example relating to a method of forming a through-port in
a silicon substrate by using an etching liquid composition
according to an exemplary embodiment of the present invention will
be described in detail with reference to FIGS. 1A to 1E.
[0063] FIGS. 1A to 1E are typical sectional views illustrating a
fundamental process of producing a silicon substrate provided with
a through-port formed using an etching liquid composition according
to an exemplary embodiment of the present invention.
[0064] A silicon mother material 1a was prepared as illustrated in
FIG. 1A.
[0065] Next, as illustrated in FIG. 1B, a silicon oxide film 4 or 5
was formed on each side of the silicon mother material 1a
illustrated in FIG. 1A by the thermal oxide formation method. As to
the condition of the formation, thermal treating temperature was
1000.degree. C., treating time was 60 minutes and H.sub.2/O.sub.2
mixture gas was used. Thereafter, a resin layer 7 was formed on the
back surface of the silicon substrate 1 by patterning. A polyether
amide was used for the resin layer 7.
[0066] Then, as illustrated in FIG. 1C, the silicon oxide film 4
formed on the back surface of the silicon substrate 1 was etched by
Buffered Hydrofluoric Etch (BHF) by using the resin layer 7 as a
mask to form an opening portion 11. In this case, the opening
portion 11 can be formed using a dry etching apparatus utilizing
reactive ion etching technologies.
[0067] Next, as illustrated in FIG. 1D, etching was carried out by
using the etching liquid composition of the present exemplary
embodiment to form a through-port 6. As the etching liquid
composition, an anisotropic silicon etching liquid composition
containing 5% by weight of alkaline organic compound TMAH and 10%
by weight of CsOH as an inorganic alkali compound was prepared. The
temperature of the etching solution was set to 80.degree. C. to
carry out etching. In this case, the addition of CsOH resulted in
that the silicone etching rate of this anisotropic silicone etching
liquid composition became 1.4 times to 1.9 times that of the
anisotropic silicon etching liquid composition which singly
contained TMAH but no CsOH to be added.
[0068] Next, as illustrated in FIG. 1E, the silicon oxide film 5 on
the front surface of the silicon substrate 1 was removed to form a
silicon substrate formed with the through-port 6.
[0069] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all modifications, equivalent
structures, and functions.
[0070] This application claims priority from Japanese Patent
Application No. 2010-017006 filed Jan. 28, 2010, which is hereby
incorporated by reference herein in its entirety.
* * * * *