U.S. patent application number 11/709141 was filed with the patent office on 2007-06-28 for method of etching semiconductor device.
This patent application is currently assigned to MITSUBISHI CHEMICAL CORPORATION. Invention is credited to Makoto Ishikawa, Masaru Miyoshi, Noriyuki Saitou, Keiichi Sawai, Yoshihide Suzuki.
Application Number | 20070145003 11/709141 |
Document ID | / |
Family ID | 26624743 |
Filed Date | 2007-06-28 |
United States Patent
Application |
20070145003 |
Kind Code |
A1 |
Suzuki; Yoshihide ; et
al. |
June 28, 2007 |
Method of etching semiconductor device
Abstract
In a method of etching a semiconductor device or a liquid
crystal device, an etching liquid is prepared to include a solvent,
and a solute containing at least iodine, at least one iodine
compound and alcohol. The etching liquid is applied to a substrate
of the semiconductor device or the liquid crystal device having
plural gold columns on a gold layer or gold alloy columns on a gold
alloy layer.
Inventors: |
Suzuki; Yoshihide;
(Osaka-shi, JP) ; Sawai; Keiichi; (Osaka-shi,
JP) ; Saitou; Noriyuki; (Kitakyushu-shi, JP) ;
Miyoshi; Masaru; (Kitakyushu-shi, JP) ; Ishikawa;
Makoto; (Kitakyushu-shi, JP) |
Correspondence
Address: |
KANESAKA BERNER & PARTNERS
Suite 310
1700 Diagonal Road
Alexandria
VA
22314
US
|
Assignee: |
MITSUBISHI CHEMICAL
CORPORATION
Tokyo
JP
SHARP KABUSHIKI KAISHA
Osaka-shi
JP
|
Family ID: |
26624743 |
Appl. No.: |
11/709141 |
Filed: |
February 22, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10301653 |
Nov 22, 2002 |
|
|
|
11709141 |
Feb 22, 2007 |
|
|
|
Current U.S.
Class: |
216/23 ;
257/E21.309 |
Current CPC
Class: |
H01L 21/32134 20130101;
C23F 1/14 20130101; C11D 7/261 20130101; C11D 7/10 20130101; C11D
11/0047 20130101; C11D 1/523 20130101 |
Class at
Publication: |
216/023 |
International
Class: |
C30B 33/00 20060101
C30B033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 28, 2001 |
JP |
2001-362899 |
Oct 21, 2002 |
JP |
2002-306001 |
Claims
1. A method of etching a semiconductor device or a liquid crystal
device, comprising: preparing an etching liquid including a
solvent, and a solute containing at least iodine, at least one
iodine compound and alcohol, and applying said etching liquid to a
substrate of the semiconductor device or the liquid crystal device
having plural gold columns on a gold layer or gold alloy columns on
a gold alloy layer.
2. A method as claimed in claim 1, wherein said alcohol is primary
alcohol.
3. A method as claimed in claim 2, wherein said alcohol is primary
alcohol and has a number of carbon atoms of at least 2.
4. A method as claimed in claim 1, wherein said iodine is contained
in an amount of 0.5 to 10% by weight.
5. A method as claimed in claim 1, wherein said columns have a
square shape, and a height H of the columns perpendicular to the
substrate to a least distance d between adjacent columns (H/d) is
more than 1.
6. A method as claimed in claim 5, wherein the least distance d
between the adjacent columns is 10 .mu.m or less.
7. A method as claimed in claim 6, wherein said etching liquid has
a surface tension of 45 mN/m or lower.
8. A method as claimed in claim 1, wherein said etching liquid
further includes a surfactant.
9. A method as claimed in claim 8, wherein the surfactant has a
main chain and at least one side chain, said main chain having at
least one member selected from the group consisting of at least one
nitrogen atom and at least one oxygen atom, and said side chain
having at least one hydroxyl group of an alcohol
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The application is a divisional application of Ser. No.
10/301,653 filed on Nov. 22, 2002.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a method of etching a
semiconductor device, in particular etching gold or gold alloy
deposited on a substrate for a semiconductor device or a liquid
crystal device.
[0003] (I) Gold and gold alloy are widely used as electrode wiring
materials for semiconductor devices and liquid crystal display
devices. The electrode wiring materials of gold or gold alloy can
be processed finely by a wet etching method using an etching
liquid.
[0004] Gold and gold alloy are conventionally wet-etched with an
etching liquid such as an iodine etching liquid consisting of
iodine, a salt of iodide and water; a bromine etching liquid
consisting of bromine, a salt of bromide and water; and aqua regia
(a mixture of nitric acid and hydrochloric acid). The iodine
etching liquid is well reactable to gold and gold alloy, resulting
in higher etching speed, and is easy to be handled.
[0005] A substrate having bump electrodes on which a semiconductor
devices and other devices are installed consists of a base
substrate of silicon, a primary metal layer formed on the silicon
substrate, and a bump electrode(s) (a projecting electrode(s)) of
gold or gold alloy formed on the primary metal layer. The primary
metal layer has a base layer of Ti/W, Ti/N, Ti/Pt, etc. and a
surface layer of gold or gold alloy formed on the base layer. The
surface layer is formed so as to improve adhesion of the bump
electrode to the base layer.
[0006] The substrate with the bump electrodes is produced as
follows: firstly a 0.1 to 0.3 .mu.m thick base layer is formed on
the silicon substrate; a 0.1 to 1 .mu.m thick surface layer of gold
or gold alloy is formed thereon; a resist layer is plated by
lithographic technique on the surface of an area of the surface
layer other than that on which the bump electrode is to be formed;
after that the bump electrodes are formed by depositing a gold or
gold alloy layer having a predetermined thickness by a plating
method on the surface of the surface layer on which the bump
electrodes are to be formed. The bump electrodes project vertically
toward the surface of the substrate.
[0007] Secondly, the resist layer is removed, so that the surface
of the surface layer which has been covered with the resist layer
is exposed to the air. The exposed surface layer is removed by wet
etching, and the base layer which had been covered with the surface
layer is further removed by wet etching. The above process produces
the substrate having the silicone base substrate having thereon the
fine bump electrodes which project in the vertical direction toward
the surface of the base substrate.
[0008] The finished substrate further has the above-described metal
base layer and the surface layer of gold or gold alloy between the
silicon substrate and the bump electrode.
[0009] The surface layer should be equally removed by etching it
and the bump electrodes should be etched as little as possible
during etching the surface layer in order to form the bump
electrodes with high precision in size.
[0010] However, the metal surface layer may not be removed fully
when the surface layer is produced by a sputtering method according
to the above-described conventional etching method. This is because
as follows.
[0011] A rate of etching a sputtered gold or gold alloy layer is
generally lower than that of a plated gold or gold alloy layer,
which is probably due to the difference in the crystal structure of
the layers. Since the surface layer of sputtered gold or gold alloy
is etched at a lower etching rate than the bump electrodes of
plated gold or gold alloy, the sputtered surface layer may not be
removed completely and remain on the substrate as residues when the
etching process is conducted such that the bump electrode is etched
as little as possible.
[0012] The surface layer is especially apt to remain as residues in
a portion between column-shaped bump electrodes which are arranged
closed to each other, because the portion is in a valley-like shape
and the etching liquid is difficult to be diffused to the bottom of
the valley-like portion.
[0013] When much time is spent in etching the surface layer, the
residues will disappear in the entire surface of the substrate
including the valley-shaped portion. However, the etching process
for a long time etches the bump electrodes in a large amount so
that the bump electrodes lack the precision of the form, because
the plated bump electrodes are etched at a higher rate than the
sputtered surface layers.
[0014] Thus the bump electrode is not easy to be formed with high
precision by the conventional etching liquid.
[0015] (II) Japanese patent publications S51-20976B, S49-123132A,
S63-176483A and H6-333911A disclose an etching liquid for etching a
minute electrode wiring pattern for semiconductor devices and
liquid crystal display devices formed by using photolithographic
technique on a substrate, which is added with an alcohol,
surfactant and glycerin in order to weaken the surface tension of
the etching liquid, whereby its affinity for both the gold and gold
alloy and a photoresist film made of a synthetic resin can be
improved, resulting in high etching accuracy.
[0016] However, none of the Japanese patent publications discloses
an etching liquid added with additives such as an alcohol for
etching the gold or gold alloy layer from which the photoresist has
been removed.
[0017] The etching process of etching the gold or gold alloy layer
with a mask of the photoresist differs from an etching process of
finely processing the same type of metals on the substrate without
using the mask wherein a bump electrode and a primary metal layer
are etched. It should be noted that teaching of the etching liquid
for the former process has not been applied to that for the latter
one and no person skilled in the art would have thought to apply it
to the latter.
SUMMARY OF THE INVENTION
[0018] An object of the present invention is to provide a method of
etching a semiconductor device in a process of fining a wiring of a
substrate for a semiconductor device or a liquid crystal
device.
[0019] More particularly, the object of the present invention is to
provide a method of etching a semiconductor device, wherein a gold
or gold alloy layer on a substrate for a semiconductor or a liquid
crystal can be etched equally, gold or gold alloy columns are
formed on the layer, and etching of the gold or gold alloy columns
is suppressed.
[0020] The etching liquid of the invention comprises as solute at
least iodine, at least one iodine compound and alcohol. The etching
liquid is for etching a gold or gold alloy layer formed on a
substrate for a semiconductor or a liquid crystal. Plural gold or
gold alloy columns are formed on the layer.
[0021] The etching liquid etches the layer equally while the liquid
etches scarcely the columns. The etching liquid etches the layers
equally and rapidly even at the bottom-like area between the
columns close to each other.
DETAILED DESCRIPTION
[0022] The etching liquid of the invention is preferable for
etching the layer formed thereon the gold or gold alloy columns
having a square shape and having (I): an aspect ratio H/d of more
than 1 wherein "H" is the height of the columns perpendicular to
the surface of the substrate and "d" is the least distance between
the adjacent columns, or (II): the least distance d of not more
than 10 .mu.m.
[0023] The etching liquid of the invention consists of solvent and
solute. Water is preferably employed as the solvent. The solute
includes at least iodine, at least one iodine compound and
alcohol.
[0024] The content of iodine in the etching liquid is preferable to
be 0.1 to 20% by weight, particularly 0.5 to 10% by weight, more
particularly 1 to 8% by weight, most particularly 1.5 to 4% by
weight but not limitative thereto.
[0025] The rate of etching gold or gold alloy increases as the
content of iodine in the etching liquid becomes higher. Too high
content of iodine in the etching liquid expands the difference
between the etching rate of the gold or gold alloy layer among the
columns and the etching rate of the columns. In this case, the
evenness of the etched metal layers of gold or gold alloy, etc. can
decrease. The etching rate decreases as the content of iodine
becomes too low, so that too much time may be required in the
etching process.
[0026] Iodine is difficult to dissolve in water but is relatively
easy to dissolve in solutions of an iodide salt(s) such as
potassium iodide, ammonium iodide, etc. The solution of an iodide
salt(s) for use in desolution of iodine is preferable to contain at
least one iodide salt in an amount as much as two to ten times
moles of iodine to be dissolved into the solution. The solution of
the iodide salt(s) for use in dissolution of iodine may contain one
kind of iodide salt or two or more kinds of iodide salts.
[0027] The alcohol contained in the etching liquid is soluble in
the solvent, and is preferably primary alcohol, more preferably
primary alcohol having a number of carbon of 2 or more,
particularly of 2 to 4, more particularly of 2 to 3. Examples of
the primary alcohol are methanol, ethanol, 1-propanol, 1-butanol,
etc. The etching liquid may contain one kind of alcohol or two or
more kinds of alcohol.
[0028] A temperature of the etching liquid during the etching
process is a room temperature or higher than it, preferably 20 to
50.degree. C. The composition of the etching liquid may change
during the etching process due to evaporation of the solvent and
the solute. An alcohol having a low vapor pressure such as ethanol,
1-propanol, specifically 1-propanol is preferably employed in order
to make less the change of the composition of the etching
liquid.
[0029] Secondary alcohol and tertiary alcohol having a number of
carbon atoms of 3 or more may decrease stability of the etching
liquid due to a reaction of their hydroxyl groups with the iodide
compounds to liberate iodine into the etching liquid.
[0030] The content of the alcohol in the etching liquid affects a
surface tension of the etching liquid or diffusion characteristics
of the etching liquid. The content also influences the etching
liquid in depression of etching the gold or gold alloy columns. The
content of the alcohol in the etching liquid is therefore
determined preferably with reference to the size of the pattern of
the gold or gold alloy columns on the substrate to be etched.
[0031] When the substrate fulfills at least one of the following
conditions A and B, the etching liquid is preferable to have a
surface tension of 50 mN/m or lower and the alcohol concentration
thereof is preferably determined such that the etching liquid has
such a value of the surface tension. The surface tension of the
etching liquid is measured by a surface tension meter. [0032]
Condition A: The aspect ratio H/d is equal to or more than 1,
specifically the gold or gold alloy columns have a square shape and
the aspect ratio H/d is higher than 1; [0033] Condition B: The
distance between the columns d is 10 .mu.m or smaller.
[0034] The etching liquid is improved in its diffusion
characteristics and depression thereof in etching the gold or gold
alloy columns, as its surface tension decreases. However, when the
surface tension of the etching liquid is too low, the etching rate
decreases to lower a through put. Thus, the surface tension is
preferable to be 20 to 50 mN/m, particularly 25 to 45 mN/m.
[0035] The effect of depression of etching the gold or gold alloy
columns due to the addition of the alcohol is thought to be
affected by the form of iodine (or I.sub.2 and I.sub.3.sup.-)
existing in the etching liquid. The etching rate increases as the
concentration of iodine increases provided that the alcohol
concentration is constant. The iodine concentration is preferably
determined after the alcohol concentration is determined such that
the etching liquid has a predetermined surface tension in order to
prepare the etching liquid having a desired etching rate.
[0036] The etching liquid may further contain a surfactant. The
etching liquid added with the surfactant gives a surprising effect
of depressing side etching. The side etching means a phenomenon in
which the side surface of the gold or gold alloy layer under the
columns is etched. The gold or gold alloy columns free from the
side etching have such a high strength that damage to the columns
is prevented when the columns are stressed perpendicularly to the
surface of the substrate. In applications where the substrate
having the columns free from the side etching is joined with
another substrate such as a substrate for a liquid crystal display,
the columns are prevented from being damaged, so that production
yield increases.
[0037] The surfactant should not make the etching effect of the
etching liquid worse and is preferable to be hardly oxidized by
iodine in the etching liquid. The surfactant specified by the
following general formula (1) is preferable because it is hard to
be oxidized and destructured by iodine: R-A-B-R' (1); in which:
[0038] R represents a hydrocarbon group which may have one or more
substituents;
[0039] A represents a carbonyl group, a hydrocarbon group which may
have at least one substituent, or at least one oxygen atom;
[0040] B represents NR'' (wherein R'' represents a hydrocarbon
group which has at least one hydroxyl group), NH or an oxygen
atom;
[0041] R' represents a hydrocarbon group which has at least one
hydroxyl group; and
[0042] R'' may be either same as or different from R'.
[0043] The hydrocarbon group represented as R can be an alkyl
group, an alkenyl group, an alkynyl group, or an aryl group, etc.
The number of carbon atoms of the hydrocarbon group is preferably 3
to 20, more preferably 6 to 14 but not limitative thereto. The
hydrocarbon group may be either in a saturated form or in an
unsaturated form and may be either straight-chain or cyclic. The
hydrocarbon group is preferably straight-chain, more preferably
straight-chain and saturated.
[0044] The above hydrocarbon group represented as R may have a
substituent group. Examples of the substituent group are a hydroxyl
group, an ether group, an ammonium group, a halogen atom, a nitro
group, a cyano group, a carbonyl group, an alkoxycarbonyl group, a
carboxyl group, an aldehyde group, and a sulfonyl group, etc, but
not limitative thereto.
[0045] In the above general formula (1), A represents a carbonyl
group, a hydrocarbon group which may have a substituent, or an
oxygen atom. Examples of the hydrocarbon group A are an alkylene
group, and alkylidene group, etc. The hydrocarbon group can have
the number of carbon atoms of 3 to 20, preferably 6 to 14, but not
limitative thereto. The hydrocarbon group may be either saturated
or unsaturated. The hydrocarbon group may be either straight-chain
or cyclic. The hydrocarbon group is preferably straight-chain, more
preferably straight-chain and saturated. The carbonyl group is
preferably employed as A.
[0046] In the above general formula (1), R' represents a
hydrocarbon group having at least one hydroxyl group which is
bonded preferably to the end of the hydrocarbon group. The number
of carbon atoms of the hydrocarbon group is preferably 1 to 5, more
preferably 1 to 3, but not limitative thereto. The hydrocarbon
group may be either saturated or unsaturated. The hydrocarbon group
may be either straight-chain or cyclic. The hydrocarbon group is
preferably straight-chain, more preferably straight-chain and
saturated. The R' is preferably an alkanol group which is
straight-chain and saturated and has a hydroxyl group at the end
thereof.
[0047] In the above general formura (1), B represents NR'' wherein
the R'' represents a hydrocarbon group having at least one hydroxyl
group, NH or an oxygen atm. R'' may be the same as R' or may differ
from R'. The B is preferably NR'' or NH, and more preferably NR''
in which R'' is the same as R'.
[0048] The surfactant specified by the above formula (1) is
preferably an alkanolamide type wherein the A is a carbonyl group
and the B is NR''. The alkanolamide type is stable in the etching
liquid and give a very good effect of inhibiting side etching on
the gold or gold alloy layer. The alkanolamide type is difficult to
be absorbed by the substrate and remains little on the etched
surface of the substrate. The etching liquid contains the
surfactant preferably in an amount of 5 wt. % or less, preferably
0.001 wt. % (10 ppm) to 5 wt. %, more preferably 0.01 wt. %
(100ppm) to 1 wt. %, yet more preferably 0.05 wt. % (500 ppm) to 1
wt. %, while the invention is not limited thereto. The surfactant
of too low concentration may not give sufficient effects, while the
surfactant of too high concentration may saturate the effects. The
etching liquid may be bubbled when the content of the surfactant is
too high.
[0049] The etching liquid is used for etching a substrate for a
semiconductor device or a liquid crystal device which has a gold or
gold alloy layer thereon and a plurality of fine gold or gold alloy
columns (bump electrodes) on the gold or gold alloy layer. The
substrate includes a silicon wafer used for production of a
semiconductor device, a silicon wafer in a process of producing a
semiconductor device, and a substrate on which a semiconductor
device or a liquid crystal displaying device is installed, and the
like.
[0050] The etching liquid of the invention etches a fine electrode
wiring pattern on a substrate including above with high
precision.
[0051] Since the etching liquid of the invention etches a substrate
for a semiconductor device or liquid crystal, it should have a high
purity and is preferably prepared from high-purity chemicals which
contain metal impurity of less than 1 ppm by weight. The lower the
content of each impurity is, the more preferable the chemicals
are.
[0052] Fine particles existing in the etching liquid is preferably
removed such that the number of the fine particles having a
diameter of 0.5 .mu.m or more becomes 1000 or less per 1 ml of the
etching liquid since the particles may disturb the etching liquid
to etch evenly the substrate having a fine pattern. The particles
can be removed by filtering the prepared etching liquid with a
microfilter. The etching liquid can be filtered either in a
one-pass system or in a circulation system. The circular system is
preferable to the one-pass system because the former is superior in
efficiency of removing particles to the latter.
[0053] The microfilter preferably has pores having a diameter of
0.2 .mu.m or less and may consist of high-density polyethylene,
fluororesin such as polytetrafluoroethylene, and the like.
[0054] The etching liquid of the invention is employed in various
kinds of wet etching processes. An immersion etching process and a
spray etching process are well known and the etching liquid can be
employed in either process. The immersion etching process is
preferably employed because the composition of the etching liquid
hardly changes due to the evaporation thereof during the process.
In case of the immersion etching process, a substrate to be etched
is immersed in the etching liquid within a batch wherein the
etching liquid is circulated. The substrate is preferably swung in
the etching liquid, so that the etching liquid is applied to the
finely formed portion of the pattern on the substrate evenly. In
stead thereof the substrate may be left at rest during the etching
process.
[0055] The etching liquid is etched in the etching liquid
preferably at a room temperature or a raised temperature, more
preferably 25.degree. C. to 70.degree. C., yet more preferably
25.degree. C. to 50.degree. C., so that the etching rate increases
and the etching liquid evaporates little while the invention is not
limitative thereto.
[0056] The shape and arrangement of the fine projections and
depressions of gold or gold alloy on the surface of a substrate to
be etched such as for a semiconductor etc. are not limited and may
be adapted to various configurations for various applications. The
substrate may be a silicon wafer which has thereon a semiconductor
device, etc. and which has a base layer consisting of a metal or
alloy such as Ti/W, Ti/N, Ti/Pt of a thickness of about 0.1 to 0.3
.mu.m and a surface layer of gold or gold alloy of a thickness of
about 0.1 to 1 .mu.m formed thereon by sputtering, and gold or gold
alloy columns having a height H of 5 to 25 .mu.m, perpendicularly
to the substrate arranged on the upper layer such that the distance
d between the columns is 2 to 20 .mu.m, and thus the aspect ratio
H/d is 0.25 to 12.5. But the substrate is not limited to the
above.
[0057] The etching liquid of the invention is very effective in
etching the substrate having gold or gold alloy columns having a
square shape and an aspect ratio H/d higher than 1. Specifically,
it is effective in etching the substrate having fine projections in
which the least distance d between the adjacent gold or gold alloy
columns is 10 .mu.m or smaller. That is, the etching liquid of the
invention etches the gold or gold alloy layer on the substrate
effectively while it etches scarcely gold or gold alloy columns on
the layer without changing the shape of columns, whereby the
pattern with high precision is produced.
EXAMPLES AND COMPARATIVE EXAMPLES
[0058] Without further elaboration, it is believed that one skilled
in the art, using the preceding description, can utilize the
present invention to its fullest extent. The following embodiments
are, therefore, to be construed as merely illustrative, and not
limitative in any way whatsoever, of the remainder of the
disclosure.
[0059] The present invention is further illustrated by the
following Examples.
[0060] A mother substrate for etching tests was prepared by forming
on a silicon wafer a titanium/tungsten thin layer having a
thickness of about 0.2 .mu.m by sputtering, forming on the layer a
gold thin layer having a thickness of about 0.4 .mu.m by
sputtering, and forming a plurality of gold columns (bump
electrodes) by plating on the gold layer. The gold columns had a
square shape and a height H of 10 .mu.m perpendicular to the
substrate, and were arranged such that the distance d therebetween
is 7.7 .mu.m and the aspect ratio is about 1.3.
[0061] The mother substrate was cut into pieces having a width of
about 15 mm and a length of about 50 mm to prepare a sample
substrate to be etched.
Examples 1-5, Comparative Examples 1 and 2
[0062] Etching liquids having a composition and a surface tension
shown in Table 1 in which the other part of each composition was
water were prepared, respectively. The surface tension of each
etching liquid was measured by a surface tension meter (A-3 Type of
Kyowa CBVP System Surface Tension Meter, commercially available
from Kyowa Science Ltd.) at a room temperature.
[0063] Each of the chemicals used for preparing the etching liquids
had a purity as high as 99.9% or higher and contained metal
impurities of 0.1 to 2.0 ppm by weight. The number of particles
having a diameter of 0.5 .mu.m or larger contained in each etching
liquid was less than 100 per 1 ml. TABLE-US-00001 TABLE 1 potassium
surface iodine iodide 1-propanol ethanol tension [wt. %] [wt. %]
[wt. %] [wt. %] [m/Nm] Examples 1 1.9 7.3 33.2 0 27.7 2 2.85 11.0
33.2 0 27.9 3 1.9 7.3 0 33.2 32.2 4 2.85 11.0 0 33.2 32.9 5 1.9 7.3
0 10.0 47.7 Comparative 1 1.9 7.3 0 0 65.0 Examples 2 2.85 11.0 0 0
66.0
[0064] Each etching liquid of 150 g was poured into a beaker having
a capacity of 200 ml and kept at 30.degree. C. The above sample
substrate was immersed in each etching liquid for a predetermined
time during which it is swung sideways and up and down. After that
the substrate was taken out of the etching liquid and was rinsed
with ultrapure water (Milli Q-SP, commercially available from
Nippon Millipolya Ltd.) for one minute. And then the substrate was
dried with clean air.
[0065] The surface of the substrate was observed at its condition
and configuration of the surface of each substrate were observed by
a laser microscope (VK-8500, available from Keyence Ltd.). The
etching rate of the portion of the gold layer between the gold
columns, the etching rate of the other portion of the gold layer,
and the etching rate of the gold columns were detected from changes
with time of residues of the gold layer and the height of the gold
columns.
[0066] The ratio of the etching rate of the gold column to the
etching rate of the portion of the gold layer between the columns
was also detected.
[0067] The results are shown in Table 2. TABLE-US-00002 TABLE 2
etching rate of etching rate of etching rate of gold layer gold
layer golod column formed by sputtering formed by formed by between
gold columns sputtering plating formed by plating ratio of
[.ANG./min.] [.ANG./min.] [.ANG./min.] etching rates Examples 1
1000 1980 667 2.97 2 1000 3025 1000 3.03 3 1333 4725 1000 4.73 4
2000 9000 2000 4.50 5 4000 8000 1000 8.00 Comparative 1 4000 14500
1600 9.06 Examples 2 4000 9800 500 19.60
[0068] Table 2 shows that the etching liquids of Examples 1 through
5 etch the substrate evenly such that the gold columns were etched
to the objective form. Particularly, the etching liquids of
Examples 1 through 4 to each of which the primary alcohol was added
such that the surface tension thereof became 45 mN/m or lower were
improved in ability to get into the narrow portions between the
columns, and reduced the difference in etching rate between the
rate of etching the plated gold columns reactively and the rate of
etching the sputtered gold layer between the gold columns by the
diffusion of the etching liquid.
[0069] On the contrary, in Comparative Examples 1 and 2, all the
gold layer between the gold columns was observed to be etched
unevenly. After the gold layer between the gold columns was etched
out, all the columns were found to be deformed through the
observation of their shapes. This means that the etching liquids of
the Comparative Examples 1 and 2 did not etch the substrates
evenly.
[0070] In Example 2 and Comparative Example 2, the condition of
side etching occurred in the gold layer directly under the gold
columns was observed, respectively, after the etching process. The
substrates etched were cut across the surface and the gold layer in
which the side etching occurred was observed by a scanning electron
microscope (SEM: JSM-6320F, available from Nippon Electron Ltd.).
The thickness of the gold layer and the length of progress of side
etching were detected from SEM photographs, and the ratio of the
length of side etching to the thickness of the gold layer was
calculated. The ratio was employed as barometer of the side
etching. The side etching progresses more slowly as the ratio
becomes smaller. The results are shown in Table 3.
Example 6
[0071] An etching process was conducted in the same manner as that
in Example 2 except that a surfactant of a type of fatty
alkanolamide (N-diethanolamide having saturated alkyl chain in
which the number of carbon atoms is 9;
C.sub.9H.sub.19CO--N(OC.sub.2H.sub.5).sub.2) was added such that
the concentration thereof became 500 ppm. The condition of side
etching was observed to evaluate the etching liquid in the same
manner as that in Example 2. The results are shown in Table 3.
TABLE-US-00003 TABLE 3 estimation composition of etching liquid
barometer of side etching potassium (ratio of length of side
etching iodine iodide 1-propanol surfactant to thickness of gold
layer [wt. %] [wt. %] [wt. %] [wt. ppm] formed by sputtering)
Example 2 2.85 11 33.2 0 1.8 Example 6 2.85 11 33.2 500 0.6
Comparative 2.85 11 0 0 7 Example 2
[0072] Table 3 shows that the side etching progressed slower in
Examples 2 and 6 than in Comparative Example 2, and the etching
liquid of Example 6 in which the surfactant was added produced
scarcely the side etching.
[0073] As described above, the etching liquid of the invention
etches evenly the gold or gold alloy layer on the substrate for a
semiconductor device or a liquid crystal device having the gold or
gold alloy layer and the gold or gold alloy columns on the layer,
and the gold or gold alloy columns are etched scarcely.
[0074] The etching liquid of the invention etches scarcely the gold
or gold alloy column to be left as an electrode or a wiring and
etches the gold or gold alloy layer on the substrate evenly, so
that it realizes fine process of the gold or gold alloy wiring and
the gold or gold alloy electrode layer on the substrate for a
semiconductor or a liquid crystal with high precision.
[0075] The foregoing is considered illustrative only of the
principles of the invention. Further, since numerous modifications
and changes will readily occur to those skilled in the art, it is
not desired to limit the invention to the exact construction and
operation shown and described. Accordingly, all suitable
modifications and equivalents may be resorted to that fall within
the scope of the invention and the appended claims.
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