U.S. patent application number 11/245912 was filed with the patent office on 2006-04-06 for electrochemical processing apparatus and method.
Invention is credited to Kazutaka Momoi, Nobuhiko Sato, Kazutaka Yanaqita.
Application Number | 20060070884 11/245912 |
Document ID | / |
Family ID | 36124465 |
Filed Date | 2006-04-06 |
United States Patent
Application |
20060070884 |
Kind Code |
A1 |
Momoi; Kazutaka ; et
al. |
April 6, 2006 |
Electrochemical processing apparatus and method
Abstract
A processing apparatus electrochemically processes part of a
first surface of a member having the first surface and a second
surface. The processing apparatus includes a support which supports
the member to expose the first surface, a first electrode which is
arranged to oppose a first portion of the first surface, a second
electrode which is arranged to oppose a second portion of the first
surface, a third electrode which applies a potential to the member
from a second surface side, and a processing bath to fill a space
defined by the first and second electrodes and the member with a
processing liquid.
Inventors: |
Momoi; Kazutaka;
(Hiratsuka-shi, JP) ; Yanaqita; Kazutaka;
(Yokohama-shi, JP) ; Sato; Nobuhiko;
(Sagamihara-shi, JP) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
3 WORLD FINANCIAL CENTER
NEW YORK
NY
10281-2101
US
|
Family ID: |
36124465 |
Appl. No.: |
11/245912 |
Filed: |
October 6, 2005 |
Current U.S.
Class: |
205/118 |
Current CPC
Class: |
C25D 11/02 20130101;
C25D 17/10 20130101; C25D 5/02 20130101; C25D 11/005 20130101 |
Class at
Publication: |
205/118 |
International
Class: |
C25D 5/02 20060101
C25D005/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 6, 2004 |
JP |
2004-294272 |
Claims
1. A processing apparatus for electrochemically partially
processing a first surface of a member having the first surface and
a second surface, the apparatus comprising: a support which
supports the member to expose the first surface; a first electrode
which is arranged to oppose a first portion of the first surface; a
second electrode which is arranged to oppose a second portion of
the first surface; a third electrode which applies a potential to
the member from a second surface side; and a processing bath to
fill a space defined by said first and second electrodes and the
member with a processing liquid.
2. The apparatus according to claim 1, wherein said first and
second electrodes are arranged such that a distance between said
second electrode and the second portion of the first surface is
smaller than that between said first electrode and the first
portion of the first surface.
3. The apparatus according to claim 1, further comprising a power
supply which provides a potential to said first, second, and third
electrodes, wherein said power supply is configured to decrease an
electric field intensity between said second and third electrodes
to be lower than that between said first and third electrodes.
4. The apparatus according to claim 1, wherein the first portion
comprises a region to be electrochemically processed, and the
second portion comprises a region not to be electrochemically
processed.
5. The apparatus according to claim 1, wherein said first and
second electrodes are arranged at such positions not to be in
contact with the member.
6. The apparatus according to claim 1, wherein the member is
supported to expose the first surface entirely.
7. A processing method of electrochemically processing part of a
first surface of a member having the first surface and a second
surface, the method comprising: a step of arranging the member such
that a first electrode opposes a first portion of the first
surface, that a second electrode opposes a second portion of the
first surface, and that a third electrode applies a potential to
the member from a second surface side; and a step of processing the
member while applying a potential to the first, second, and third
electrodes.
8. The method according to claim 7, wherein the first and second
surfaces are processed with different chemical liquids.
9. A method of manufacturing a member having first and second
surfaces, the method comprising: a step of arranging the member
such that a first electrode opposes a first portion of the first
surface, that a second electrode opposes a second portion of the
first surface, and that a third electrode applies a potential to
the member from a second surface side; and a step of
electrochemically processing the member while applying a potential
to the first, second, and third electrodes.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a processing apparatus for
a member and a processing method and, more particularly, to a
processing apparatus and processing method which electrochemically
process part of the first surface of a member having the first and
second surfaces.
BACKGROUND OF THE INVENTION
[0002] Methods for obtaining a substrate which has been subjected
to a target process in only the processing-target region of its
entire surface can be roughly divided into two methods. According
to the first method, the entire surface of the substrate is
subjected to a target process, and after that the
non-processing-target region of the entire surface is removed by
etching or cutting. According to the second method, only the
processing-target region of the entire surface is subjected to a
target process, while the non-processing-target region is not
processed.
[0003] More specifically, according to the first method, the entire
surface of the substrate is subjected to an electrochemical process
such as plating or a chemical process. After that, part of the
processed region is removed by etching or cutting to leave an
unprocessed region. For example, after the entire surface of the
substrate is plated, a protective film is formed to cover only a
region on which a plated layer should be left. The substrate is
then immersed in a solution that dissolves the plating material, so
that a processed region and unprocessed region can be formed on the
substrate surface. This method has a drawback in that a removing
process such as etching or cutting is indispensable, so that the
number of steps increases to increase the cost. If the process for
the processing-target region progresses in the direction of depth
of the substrate as in a chemical process, the removing step for
forming an unprocessed region undesirably forms a step on the
substrate surface.
[0004] According to the second method, a protective film is formed
in advance to cover the non-processing-target region of the
substrate surface, or a member is brought into contact with the
substrate surface, to divide a processing-target region and the
non-processing-target region, and after that a process is
performed. Regarding the chemical process, "Volker Lehmann,
Electrochemistry of Silicon, WILEY-VCH, Germany, 2002, pp.
107-108." describes a method of forming an oxide film or nitride
film on the substrate surface in advance and a method of applying a
resist to the substrate surface in advance.
[0005] With the method of forming a protective film, how to remove
the protective film after the process becomes an issue. In the
method of applying a resist film, the residual resist can be
removed by a stripping liquid such as acetone or a heated
sulfuric-acid-based solution. The resist or stripping liquid,
however, remains in the pores of a porous layer formed by the
chemical process, and may be burned or evaporate in a later
annealing process. Then, an evaporated substance may corrode the
chamber or attach to the substrate surface to increase the number
of foreign substances, or cause impurity contamination in the later
step.
[0006] To bring the member into contact with the substrate surface,
the processing-target region and non-processing-target region may
be divided by using seal member such as an O-ring. With this
method, when the seal member comes into contact with the substrate,
foreign substances can undesirably attach to the substrate. In
particular, a powerful cleaning method to remove the foreign
substances cannot be applied to a porous layer or plated layer that
can be formed by anodizing. This is because cleaning can damage the
porous layer or plated layer. Thus, the foreign substances which
have attached as the seal member comes into contact are undesirably
carried to the next process. Also, as the seal member comes into
contact with the substrate, it can damage the substrate.
[0007] When a seal member is used, if the seal is insufficient,
sometimes a processing liquid can enter the non-processing-target
region by capillarity. As the size of the semiconductor substrate
or liquid crystal panel increases, the region to be sealed also
becomes large, and the problem of defective sealing becomes more
conspicuous. As the process is repeated, the function of the seal
member such as an O-ring degrades due to wear or a chemical
change.
[0008] According to the method disclosed in Japanese Patent
Laid-Open No. 2002-246364, a mask is arranged to oppose the
processing-target region of a wafer. A processing liquid is
supplied to the gap between the processing-target region and mask
by the capillary action to process the processing-target region.
This method provides one solution for the problem of foreign
substances attaching to the substrate and the problem of damage to
the substrate.
[0009] According to the method described in Japanese Patent
Laid-Open No. 2002-246364, since the processing liquid is supplied
to the gap between the processing-target region and mask by using
the capillary action, the gap must be inevitably sufficiently
small. Therefore, the supply amount of the processing liquid is
limited, and sometimes the processing liquid accordingly degrades
during the process. Such a small gap makes it difficult to
circulate the processing liquid and is thus inappropriate for
uniformly processing the processing-target region. When this method
is applied to cleaning, the foreign substances removed by cleaning
attach to the substrate again at a high possibility. Therefore, the
actual application of the method described in Japanese Patent
Laid-Open No. 2002-246364 is supposed to be limited to simple ones
such as coating removal.
SUMMARY OF THE INVENTION
[0010] The present invention has been made on the basis of the
above situation, and has as its object to provide a novel technique
which electrochemically processes part of a member to form a
processed region and unprocessed region.
[0011] More specifically, it is an object of the present invention
to provide a technique to form a member having a processed region
which is processed more uniformly.
[0012] According to the first aspect of the present invention,
there is provided a processing apparatus for electrochemically
partially processing a first surface of a member having the first
surface and a second surface, comprising a support which supports
the member to expose the first surface, a first electrode which is
arranged to oppose a first portion of the first surface, a second
electrode which is arranged to oppose a second portion of the first
surface, a third electrode which applies a potential to the member
from a second surface side, and a processing bath to fill a space
defined by the first and second electrodes and member with a
processing liquid.
[0013] According to a preferred embodiment of the present
invention, preferably, the first and second electrodes are arranged
such that a distance between the second electrode and the second
portion of the first surface is smaller than that between the first
electrode and the first portion of the first surface.
[0014] According to another preferred embodiment of the present
invention, the processing apparatus can further comprise a power
supply which provides a potential to the first, second, and third
electrodes. The power supply is preferably configured to decrease
an electric field intensity between the second and third electrodes
to be lower than that between the first and third electrodes.
[0015] According to still another preferred embodiment of the
present invention, the first portion comprises a region to be
electrochemically processed, and the second portion comprises a
region not to be electrochemically processed.
[0016] According to still another preferred embodiment of the
present invention, preferably, the first and second electrodes are
arranged at such positions not to be in contact with the
member.
[0017] According to the second aspect of the present invention,
there is provided a processing method of electrochemically
processing part of a first surface of a member having the first
surface and a second surface, comprising a step of arranging the
member such that a first electrode opposes a first portion of the
first surface, that a second electrode opposes a second portion of
the first surface, and that a third electrode applies a potential
to the member from a second surface side, and a step of processing
the member while applying a potential to the first, second, and
third electrodes.
[0018] According to the present invention, there is provided a
novel technique for electrochemically processing part of a member
to form a processed region and unprocessed region and, more
particularly, a technique to form a member having a processed
region which is processed more uniformly.
[0019] According to the third aspect of the present invention,
there is provided a method of manufacturing a member having first
and second surfaces, comprising a step of arranging the member such
that a first electrode opposes a first portion of the first
surface, that a second electrode opposes a second portion of the
first surface, and that a third electrode applies a potential to
the member from a second surface side, and a step of
electrochemically processing the member while applying a potential
to the first, second, and third electrodes.
[0020] Other features and advantages of the present invention will
be apparent from the following description taken in conjunction
with the accompanying drawings, in which like reference characters
designate the same or similar parts throughout the figures
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate embodiments of
the invention and, together with the description, serve to explain
the principles of the invention.
[0022] FIG. 1 is a view showing the structure of a processing
apparatus according to the first embodiment of the present
invention; and
[0023] FIG. 2 is a view showing the structure of a processing
apparatus according to the second embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] The preferred embodiments of the present invention will be
described with reference to the accompanying drawings.
First Embodiment
[0025] FIG. 1 is a view showing the structure of a processing
apparatus according to the first embodiment of the present
invention. A processing apparatus 100 shown in FIG. 1 is configured
to electrochemically process part of a first surface 10a of a
substrate (e.g., a silicon substrate) 10 which serves as a member
having the first surface 10a and a second surface 10b. An example
of the electrochemical process can include a chemical process,
plating, and electrolytic oxidation.
[0026] The processing apparatus 100 has a support 140 which
supports the member 10 to expose its first surface 10a, a first
electrode (main electrode) 115 which is arranged to oppose a first
portion 10a1 of the first surface 10a, a second electrode
(auxiliary electrode) 125 which is arranged to oppose a second
portion 10a2 of the first surface 10a, a third electrode 150 which
applies a potential to the member 10 from the second surface 10b
side, and a processing bath 160 which serves to fill the space
defined by the first electrode 115, second electrode 125, and
member 10 with a processing liquid 135.
[0027] The above structure preferably has such a layout that the
support 140 supports the member 10 by coming into contact with a
portion of the member 10 other than the first surface 10a, and that
the first surface 10a is entirely in contact with the processing
liquid 135.
[0028] For example, the support 140 can be formed as a chucking pad
which chucks the second surface 10b of the member 10 with a
negative pressure. The support 140 can have a ring-like shape and
be arranged to oppose the second electrode 125.
[0029] The first portion 10a1 is a processing-target portion or
region to be processed with the processing liquid 135, and the
second portion 10a2 is a non-processing-target portion or region
not to be processed with the liquid 135. Desirably, the
non-processing-target region is not processed at all. However,
sometimes it will do as far as the non-processing-target region is
processed with a lower degree than the processing-target region
is.
[0030] In the example shown in FIG. 1, the first portion 10a1 has a
circular shape while the second portion 10a2 has a ring-like
shape.
[0031] The distance between the second electrode 125 and member 10
(or third electrode 150) is smaller than that between the first
electrode 115 and member 10 (or third electrode 150). In order to
improve the controllability of separation of the region to be
processed and the region not to be processed, the distance between
the second electrode 125 and the first surface 10a of the member 10
is preferably 1 mm or less, and more preferably 0.2 mm or less.
[0032] The distance between the first electrode 115 and member 10
can be determined within a range where the above conditions are
satisfied, and is preferably 5 mm or more. When the first electrode
115 and member 10 are spaced apart from each other by a certain
distance in this manner, the degrees of freedom of movement of the
processing liquid 135, and a reaction gas if it is generated by the
process, on the first portion 10a1 can be increased. To increase
the degrees of freedom of the processing liquid 135 or reaction gas
on the first portion 10a1 contributes to the uniform process of the
first portion 10a1. In order to process the first portion 10a1 more
uniformly, preferably, a circulation system is formed to circulate
the processing liquid, so that a fresh processing liquid 135 is
constantly supplied to the first portion 10a. Circulation of the
processing liquid is also effective in removing the reaction gas
from the first portion 10a1.
[0033] In the structure in which the second electrode 125 is in
contact with the processing liquid 135, the second electrode 125 is
preferably made of a material inactive to the processing liquid
135. When the processing apparatus 100 is to be applied to a
chemical process, the second electrode 125 is preferably made of a
material, e.g., a diamond electrode, graphite, or SiC, which is
inactive to a chemical processing liquid (e.g., a liquid containing
hydrogen fluoride). The second electrode 125 may be covered with a
protective member made of a material inactive to the processing
liquid 135.
[0034] Typically, the boundary between the first and second
portions 10a1 and 10a2 can be located near the intermediate portion
between the end (outer end in FIG. 1) of the first electrode 115
and the end (inner end in FIG. 1) of the second electrode 125.
[0035] The third electrode 150 can be arranged to oppose the first
electrode 115 through the member 10 as a processing target. The
third electrode 150 may be arranged to be in direct contact with
the second surface lob of the member 10 (in this case, the third
electrode 150 can also serve as a support which supports the member
10), or to provide a potential to the member 10 from the second
surface 10b side through a conductive liquid (electrolytic
liquid).
[0036] The processing bath 160 can be formed of, e.g., a bottom
member 105 which supports the third electrode 150 and support 140;
an intermediate wall 106, and a top wall 110. The intermediate wall
106 and top wall 110 may be connected with an adhesive or the like,
or separably connected by connecting elements such as bolts. The
bottom member 105 and intermediate wall 106 can be separably
connected by connecting elements such as bolts through a seal
member such as an O-ring 145.
[0037] When the member 10 as the processing target is to be
arranged on the support 140 of the processing apparatus 100 or be
unloaded from the processing apparatus 100, typically, the bottom
member 105 is removed from the intermediate wall 106. If a high
throughput is required, for example, an openable/closeable access
port is preferably formed in the side portion of the processing
bath 160, so that the member 10 can be loaded in and unloaded from
the processing apparatus 100 through the access port.
[0038] The processing apparatus 100 can further include a power
supply 170 which provides a potential to the first, second, and
third electrodes 115, 125, and 150. The power supply 170 is
configured or adjusted to decrease the electric field intensity
between the second and third electrodes 125 and 150 to be lower
than that between the first and third electrodes 115 and 150. The
power supply 170 can include a DC power supply 120 which provides a
potential difference between the first and second electrodes 115
and 150 and a circuit 130 which provides a potential to the second
electrode 125. The circuit 130 can be a circuit that makes the
second and third electrodes 125 and 150 equipotential, a circuit
that provides a potential difference between the second and third
electrodes 125 and 150, or a resistor. When a resistor is arranged
between the second and third electrodes 125 and 150, the current
flowing between the first and second electrodes 115 and 125 can be
limited.
[0039] As described above, when the second electrode 125 is
arranged to oppose the second portion 10a2, the electric field
intensity between the second and third electrodes 125 and 150 can
be controlled to be lower than that between the first and third
electrodes 115 and 150 by using the second electrode 125. When the
distance between the second electrode 125 and member 10 is
decreased to be smaller than that between the first electrode 115
and member 10, supply of the reaction species to the second portion
10a2 is limited. More specifically, the current flowing through the
second portion 10a2 can be controlled to be smaller than that
flowing through the first portion 10a1. As the supply of the
reaction species to the second portion 10a2 is limited,
electrochemical reaction in the second portion 10a2 is more
suppressed than in the first portion 10a1. As a result, the first
portion 10a1 can be processed with a higher degree than the second
portion 10a2 is to provide a difference between the first and
second portions 10a1 and 10a2.
[0040] As compared to a case wherein the second electrode 125 is
not provided, with the presence of the second electrode 125, the
electric line of force which passes through the first portion 10a1
as the processing-target region can be uniformed, so that the
process in the first portion 10a1 is uniformed.
[0041] A method of processing the member 10 such as a substrate by
using the processing apparatus 100 will be described. First, the
member 10 is supported by the support 140. In this case, in the
processing apparatus 100 having the structure shown in FIG. 1, with
the bottom member 105 being removed from the intermediate wall 106,
the member 10 is aligned with a predetermined position on the
bottom member 105, and is supported by the support 140 with
negative pressure chucking or the like. Subsequently, the bottom
member 105 is connected to the lower portion of the intermediate
wall 106 by a connecting element (not shown). Thus, the processing
bath 160 including the bottom member 105, intermediate wall 106,
and top wall 110 is formed. Then, the processing liquid 135 is
injected in the processing bath 160 to fill the space defined by
the first electrode 115, second electrode 125, and member 10 with
the processing liquid 135.
[0042] Then, the power supply 170 provides a potential to the
first, second, and third electrodes 115, 125, and 150 to
electrochemically process the member 10. The power supply 170 is
configured or adjusted to decrease the electric field intensity
between the second and third electrodes 125 and 150 to be lower
than that between the first and third electrodes 115 and 150. An
example of the electrochemical process can include a chemical
process, plating, and anodizing.
[0043] After a prescribed period of time elapses, the power supply
170 is stopped to end the electrochemical process. The processing
liquid 135 is discharged from the processing bath 160, and the
member 10 is unloaded from the processing bath 160. In the
processing apparatus 100 having the structure shown in FIG. 1, with
the third electrode 150 being removed from the intermediate wall
106, the member 10 may be unloaded from the support 140.
[0044] A member with an electrochemically processed surface can be
manufactured in this manner.
[0045] An example in which the surface (first surface) of a
semiconductor substrate is to be anodized by using the processing
apparatus 100 will be described.
[0046] The processing apparatus 100 was prepared. The semiconductor
substrate as the processing-target member 10 was supported by the
support 140 in accordance with the procedure described above, and
part (the first portion) of the surface (first surface) of the
semiconductor substrate was anodized.
[0047] The conditions for anodize were as follows: [0048]
Semiconductor substrate; p.sup.+ silicon substrate with a
resistivity of 16 m.OMEGA..cndot.cm [0049] Chemical processing
liquid; HF:IPA=42.5:9.2 (wt. %) (prepared by mixing hydrofluoric
acid and IPA) [0050] Depth of chemical processing liquid; 20 mm
from the surface of the semiconductor substrate [0051] Current
Conditions (cathode=first electrode 115, anode=third electrode
150); 5.12 A, 210 sec
[0052] The distance between the semiconductor substrate and first
electrode, the distance between the semiconductor substrate and
second electrode, and the potential difference between the
semiconductor substrate and second electrode were set as follows:
[0053] Distance between semiconductor substrate (region within the
radius of 90 mm from the center) and first electrode; 20 mm [0054]
Distance between semiconductor substrate (region outside the radius
of 90 mm to the outermost circumference); 1 mm [0055] Potential
difference between semiconductor substrate and second electrode; 0
(equipotential)
[0056] The semiconductor substrate was processed under the above
conditions, and the result was compared to a case wherein the
second electrode (auxiliary electrode) was not provided. In the
case wherein the second electrode (auxiliary electrode) was
provided, variations in current density in the second portion (the
region opposed to the second electrode) 10a2 of the semiconductor
substrate could be decreased by one order of magnitude. Thus, the
thickness of the anodized layer (porous layer) could be decreased
to 1/10 or less when compared to the case wherein the second
electrode (auxiliary electrode) was not provided.
[0057] The electric field intensity distribution was analyzed by
numerical simulation. It was confirmed that when the second
electrode (auxiliary electrode) was provided, variations in current
density in the region where the second electrode (auxiliary
electrode) was provided could be suppressed to 1/10 or less when
compared to the case wherein the second electrode was not
provided.
Second Embodiment
[0058] FIG. 2 is a view showing the structure of a processing
apparatus according to the second embodiment of the present
invention. A processing apparatus 200 shown in FIG. 2 is configured
to electrochemically process part of a first surface 10a of a
substrate (e.g., a silicon substrate) 10 which serves as a member
having the first surface 10a and a second surface 10b. An example
of the electrochemical process can include a chemical process,
plating, and electrolytic oxidation.
[0059] The processing apparatus 200 has a support 205 which
supports the member 10 to expose its first surface 10a, a first
electrode (main electrode) 215 which is arranged to oppose a first
portion 10a1 of the first surface 10a, a second electrode
(auxiliary electrode) 240 which is arranged to oppose a second
portion 10a2 of the first surface 10a, a third electrode 220 which
is arranged to oppose the second surface 10b so as to apply a
potential to the member 10 from the second surface 10b side, and a
processing bath 260 to fill the space defined by the first
electrode 215, second electrode 240, and member 10 with a
processing liquid 230 and to fill the space between the member 10
and third electrode 220 with an electrolytic liquid 235.
[0060] In this manner, when necessary, the chemical liquid
(processing liquid, electrolytic liquid, and the like) can be
changed between the first surface 10a side and second portion 10a2
side of the member 10.
[0061] The second electrode 240 is supported by an electrode
support member 245. Typically, the electrode support member 245 can
have a ring-like shape.
[0062] For example, the support 205 is formed as a chucking pad
having a chucking groove 206, and supports the member 10 by
negative pressure suction. The support 205 typically has a
ring-like shape. The region (opening) inside the ring-like shape
preferably has an area equal to or smaller than that of the first
portion 10a1 of the member 10. Then, the electric line of force
which should pass through the first portion 10a1 can be prevented
from spreading to the outer second portion 10a2 side.
[0063] The first portion 10a1 is a portion to be processed with the
processing liquid 230 (processing-target region), and the second
portion 10a2 is a portion not to be processed with the processing
liquid 230 (non-processing-target region). Desirably, the
non-processing-target region is not processed at all. However,
sometimes it will do as far as the non-processing-target region is
processed with a lower degree than the processing-target region is.
In the example shown in FIG. 2, the first portion 10a1 has a
circular shape while the second portion 10a2 has a ring-like
shape.
[0064] The distance between the second electrode 240 (electrode
support member 245) and member 10 is smaller than that between the
first electrode 215 and member 10. In order to improve the
controllability of separation of the processing-target region
(processed region) and non-processing-target region (unprocessed
region), the distance between the second electrode 240 and the
first surface 10a of the member 10 is preferably 1 mm or less, and
more preferably 0.2 mm or less. The second electrode 240 is
preferably made of a material inactive to the processing
liquid.
[0065] The distance between the first electrode 215 and member 10
can be determined within a range where the above conditions are
satisfied, and is preferably 5 mm or more. When the first electrode
215 and member 10 are spaced apart from each other by a certain
distance in this manner, the degrees of freedom of movement of the
processing liquid 230 on the first portion 10a1 can be increased.
If a reaction gas is generated by the process, the degrees of
freedom of movement of the reaction gas can be increased. To
increase the degrees of freedom of the processing liquid 230 or
reaction gas on the first portion 10a1 contributes to the uniform
process of the first portion 10a1. In order to process the first
portion 10a1 more uniformly, preferably, a circulation system is
formed to circulate the processing liquid, so that a fresh
processing liquid 230 is constantly supplied to the first portion
10a. Circulation of the processing liquid is also effective in
removing the reaction gas from the first portion 10a1.
[0066] The processing apparatus 200 can further include a power
supply 270 which provides a potential to the first, second, and
third electrodes 215, 240, and 220. The power supply 270 is
configured or adjusted to decrease the electric field intensity
between the second and third electrodes 240 and 220 to be lower
than that between the first and third electrodes 215 and 220. The
power supply 270 can include a DC power supply 225 which provides a
potential difference between the first and second electrodes 215
and 220 and a circuit 250 which provides a potential to the second
electrode 240. The circuit 250 can be a circuit that makes the
second and third electrodes 240 and 220 equipotential, a circuit
that provides a potential difference between the second and third
electrodes 240 and 220, or a resistor. When a resistor is arranged
between the second and third electrodes 240 and 220, the current
flowing between the first and second electrodes 215 and 240 can be
limited.
[0067] A case will be described hereinafter wherein a silicon
substrate as the member 10 is to be anodized by using the
processing apparatus 200. When the first surface side of the
silicon substrate is to be anodized, the first electrode 215 serves
as the cathode and the third electrode 220 serves as the anode.
Regarding the materials of the electrodes, particularly of the
anode, a material is preferable that has a lower ionization
tendency than silicon and makes an electrode which is not dissolved
by electrode reaction. For example, platinum is preferably used to
form the cathode, and platinum or low-resistivity silicon is
preferably used to form the anode.
[0068] The processing liquid 230 is injected between the member 10
and first electrode (cathode) 215, and the electrolytic liquid
(conductive solution) 235 is injected between the silicon substrate
10 and third electrode (anode) 220.
[0069] As the processing liquid 230, for example, one which is
identical to that (HF:IPA=42.5:9.2 (wt. %)) of the example of the
first embodiment can be used, and selected freely in accordance
with a chemically processed target layer (porous layer). The
electrolytic liquid 235 may be identical to the chemical processing
liquid 230, or selected arbitrarily from conductive materials. For
example, when a low-resistivity silicon substrate is to be employed
as the third electrode (anode) 220, if a chemical processing liquid
is used as the electrolytic liquid 235, the surface of the third
electrode 220 is also undesirably processed chemically. To prevent
this, preferably, the concentration of the hydrofluoric acid (HF)
is decreased, and the process is performed under such conditions
that no porous layer is formed on the surface of the third
electrode 220.
[0070] The electrode support member 245 which supports the second
electrode 240 can have a ring-like shape. The inner edge of the
ring-shaped electrode support member 245 substantially coincides
with the boundary between the region to be processed (processed
region) and region not to be processed (unprocessed region). The
second electrode 240 is preferably made of a material, e.g., a
diamond electrode, graphite, or SiC, which is inactive to the
chemical processing liquid 230. The second electrode 240 may be
covered with a protective member made of a material inactive to the
processing liquid 240. The distance between the second electrode
240 (electrode support member 245) and the first surface 10a of the
member 10 is preferably 1 mm or less, and more preferably 0.2 mm or
less.
[0071] As described above, when the second electrode 240 is
arranged to oppose the second portion 10a2, the electric field
intensity between the second and third electrodes 240 and 220 can
be controlled to be lower than that between the first and third
electrodes 215 and 220. When the distance between the second
electrode 240 and member 10 is decreased to be smaller than that
between the first electrode 215 and member 10, supply of the
reaction species to the second portion 10a2 is limited. More
specifically, the current flowing through the second portion 10a2
can be controlled to be smaller than that flowing through the first
portion 10a1. As the supply of the reaction species to the second
portion 10a2 is limited, electrochemical reaction in the second
portion 10a2 is more suppressed than in the first portion 10a1. As
a result, the first portion 10a1 can be processed with a higher
degree than the second portion 10a2 is to provide a difference
between the first and second portions 10a1 and 10a2.
[0072] As compared to a case wherein the second electrode 240 is
not provided, with the presence of the second electrode 240, the
electric line of force which passes through the first portion 10a1
as the processing-target region can be uniformed, so that the
process in the first portion 10a1 is uniformed.
[0073] As many apparently widely different embodiments of the
present invention can be made without departing from the spirit and
scope thereof, it is to be understood that the invention is not
limited to the specific embodiments thereof except as defined in
the claims.
CLAIM OF PRIORITY
[0074] This application claims priority from Japanese Patent
Application No. 2004-294272 filed on Oct. 6, 2004, the entire
contents of which are hereby incorporated by reference herein.
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