U.S. patent application number 11/678912 was filed with the patent office on 2007-06-14 for substrate surface cleaning liquid medium and cleaning method.
This patent application is currently assigned to MITSUBISHI CHEMICAL CORPORATION. Invention is credited to Atsushi Itou, Hideaki Mochizuki, Hitoshi MORINAGA.
Application Number | 20070135322 11/678912 |
Document ID | / |
Family ID | 19163340 |
Filed Date | 2007-06-14 |
United States Patent
Application |
20070135322 |
Kind Code |
A1 |
MORINAGA; Hitoshi ; et
al. |
June 14, 2007 |
SUBSTRATE SURFACE CLEANING LIQUID MEDIUM AND CLEANING METHOD
Abstract
A substrate surface cleaning liquid medium and a cleaning method
using the cleaning liquid medium are capable of removing finely
particulate contaminants more efficiently than conventional
techniques from substrates for devices in the production of
semiconductor devices, display devices, etc., which cleaning liquid
medium contains the following ingredients (A), (B), (C), and (D),
has a pH of 9 or higher, and a content of ingredient (C) of 0.01 to
4% by weight: (A) an ethylene oxide addition type surfactant which
has an optionally substituted hydrocarbon group and a
polyoxyethylene group in the same molecular structure and in which
the ratio of the number of carbon atoms contained in the
hydrocarbon group (m) to the number of oxyethylene groups in the
polyoxyethylene group (n), m/n, is m/n.ltoreq.1.5, (B) an alkali
ingredient, (C) hydrogen peroxide, and (D) water.
Inventors: |
MORINAGA; Hitoshi; (Fukuoka,
JP) ; Mochizuki; Hideaki; (Fukuoka, JP) ;
Itou; Atsushi; (Fukuoka, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
MITSUBISHI CHEMICAL
CORPORATION
Tokyo
JP
|
Family ID: |
19163340 |
Appl. No.: |
11/678912 |
Filed: |
February 26, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10294658 |
Nov 15, 2002 |
|
|
|
11678912 |
Feb 26, 2007 |
|
|
|
Current U.S.
Class: |
510/175 ;
257/E21.228 |
Current CPC
Class: |
C11D 3/3947 20130101;
C23G 1/18 20130101; C11D 11/007 20130101; C11D 3/044 20130101; H01L
21/02052 20130101; C11D 1/72 20130101; C11D 11/0047 20130101 |
Class at
Publication: |
510/175 |
International
Class: |
C11D 7/32 20060101
C11D007/32 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 16, 2001 |
JP |
2001-350947 |
Claims
1-15. (canceled)
16. A semiconductor substrate surface cleaning liquid medium
consisting essentially of the ingredients (A), (B), (C), and (D),
wherein (A) is an ethylene oxide addition type surfactant which has
an optionally substituted hydrocarbon group and a polyoxyethylene
group in the same molecular structure and in which the ratio of the
number of carbon atoms contained in the hydrocarbon group (m) to
the number of oxyethylene groups in the polyoxyethylene group (n)
is 1.5 or less, wherein ethylene oxide addition type surfactant is
selected from the group consisting of at least one polyoxyalkylene
alkyl ether, at least one polyoxalkylene fatty acid ester, at least
one polyoxyalkylene alkyl amine, at least one polyoxylalkylene
alkly ether sulfate, and combinations thereof; (B) is an alkali
ingredient; (C) is hydrogen peroxide; and (D) is water; wherein the
substrate surface cleaning liquid medium has a pH of from about
10.5 to 11.5, an ingredient (A) content ranging from 0.0001% to
0.01% by weight, and an ingredient (C) content ranging from 0.01 to
4% by weight.
17. The semiconductor substrate surface cleaning liquid medium of
claim 16, wherein m/n is 0.5.ltoreq.m/n.ltoreq.1.5.
18. The semiconductor substrate surface cleaning liquid medium of
claim 16, wherein ingredient (B) is represented by the following
general formula: (R.sup.1).sub.4N.sup.+OH.sup.- (1) wherein R.sup.1
represents a hydrogen atom or an alkyl group which may have one or
more substituents selected from the group consisting of a hydroxy
group, an alkoxy group and a halogen atom, provided that the four
R.sup.1s may be the same or different.
19. The semiconductor substrate surface cleaning liquid medium of
claim 18, wherein ingredient (B) is ammonium hydroxide.
20. The semiconductor substrate surface cleaning liquid medium of
claim 16, wherein the number of moles of oxyethylene groups added
(n) in ingredient (A) is 10.ltoreq.n.ltoreq.50.
21. The semiconductor substrate surface cleaning liquid medium of
claim 16, wherein ingredient (A) is a polyoxyethylene alkyl
ether.
22. The semiconductor substrate surface cleaning liquid medium of
claim 16, wherein the ratio of the content of ingredient (A), a, to
the content of ingredient (C), c, is
1/3000.ltoreq.a/c.ltoreq.1/20.
23. The semiconductor substrate surface cleaning liquid medium of
claim 18, further comprising a complexing agent.
24. The semiconductor substrate surface cleaning liquid medium of
claim 16 which, when used for cleaning a semiconductor substrate
surface, attains a percentage removal of particles of 94% or higher
after the cleaning with respect to the removal of particles having
a particle diameter of 0.06 .mu.m or larger present on the
semiconductor substrate surface, and which, when used for cleaning
a semiconductor substrate surface having a silicon thermal oxide
film thereon, etches the silicon thermal oxide film to a depth of 1
nm or less.
25. The semiconductor substrate surface cleaning liquid medium of
claim 24, wherein the percentage removal of particles is 94% or
higher when the semiconductor substrate surface cleaning liquid
medium in contact with the semiconductor substrate surface has a
temperature of 60.degree. C. or lower.
26. A semiconductor substrate surface cleaning liquid medium
consisting essentially of the ingredients (A), (B), (C), (D), and
(E) wherein: (A) is an ethylene oxide addition type surfactant
which has an optionally substituted hydrocarbon group and a
polyoxyethylene group in the same molecular structure and in which
the ratio of the number of carbon atoms contained in the
hydrocarbon group (m) to the number of oxyethylene groups in the
polyoxyethylene group (n) is 1.5 or less, wherein ethylene oxide
addition type surfactant is selected from the group consisting of
at least one polyoxyalkylene alkyl ether, at least one
polyoxalkylene fatty acid ester, at least one polyoxyalkylene alkyl
amine, at least one polyoxylalkylene alkly ether sulfate, and
combinations thereof; (B) is an alkali ingredient; (C) is hydrogen
peroxide; (D) is water; and (E) is a complexing agent; wherein the
substrate surface cleaning liquid medium has a pH ranging from
about 10.5 to 11.5 and an ingredient (C) content ranging from 0.01
to 4% by weight.
27. The semiconductor substrate surface cleaning liquid medium of
claim 26, wherein m/n is 0.5.ltoreq.m/n.ltoreq.1.5.
28. The semiconductor substrate surface cleaning liquid medium of
claim 26, wherein ingredient (B) is represented by the following
general formula: (R.sup.1).sub.4N.sup.=OH.sup.- (1) wherein R.sup.1
represents a hydrogen atom or an alkyl group which may have one or
more substituents selected from the group consisting of a hydroxy
group, an alkoxy group and a halogen atom, provided that the four
R.sup.1s may be the same or different, provided that
(R.sup.1).sub.4N.sup.+OH.sup.- is not ammonium hydroxide.
29. The semiconductor substrate surface cleaning liquid medium of
claim 26, wherein the number of moles of oxyethylene groups added
(n) in ingredient (A) is 10.ltoreq.n.ltoreq.50.
30. The semiconductor substrate surface cleaning liquid medium of
claim 26, wherein ingredient (A) is a polyoxyethylene alkyl
ether.
31. The semiconductor substrate surface cleaning liquid medium of
claim 26, wherein the content of ingredient (A) ranges from 0.0001
to 0.5% by weight.
32. The semiconductor-substrate surface cleaning liquid medium of
claim 26, wherein the ratio of the content of ingredient (A), a, to
the content of ingredient (C), c, is
1/3000.ltoreq.a/c.ltoreq.1/20.
33. The semiconductor substrate surface cleaning liquid medium as
claimed in claim 16, wherein the content of ingredient (A) is from
0.0003 to 0.1% by weight.
34. The semiconductor substrate surface cleaning liquid medium of
claim 26, wherein the complexing agent is
ethylenediaminedi-o-hydroxyphenylacetic acid.
35. The semiconductor substrate surface cleaning liquid medium of
claim 16, wherein the pH is about 10.5.
36. The semiconductor substrate surface cleaning liquid medium of
claim 26, wherein the pH is about 10.5
Description
FIELD OF THE INVENTION
[0001] The present invention relates to cleaning liquid mediums for
cleaning the surfaces of substrates for devices in steps in the
production of semiconductor devices, display devices, or the like
and to a method of cleaning with the same. More particularly, the
invention relates to substrate surface cleaning liquid mediums and
a cleaning method which are effective in efficiently removing
contaminant particles (fine particles) present on a substrate in a
certain time period to highly clean the substrate surface.
BACKGROUND OF THE INVENTION
[0002] In steps in the production of semiconductor devices such as
microprocessors, memories, and CCDs or of flat panel display
devices such as TFT liquid-crystal displays, a circuit pattern or
thin film of submicron size is formed on surfaces of substrates
made of silicon (Si), silicon oxide (SiO.sub.2), glass, or another
material. It is extremely important to reduce the contaminants
present in a slight amount on the substrate surface in each step in
the production.
[0003] Among such contaminants, fine particles such as, e.g.,
silica particles, alumina particles and particles of organic
substances especially reduce the yield of devices. It is therefore
necessary to reduce these fine particles as much as possible before
the substrate is sent to the subsequent step. The technique
generally employed for the removal of such contaminants is to clean
the substrate surface with a cleaning liquid medium.
[0004] It is generally known that alkaline solutions are effective
in the removal of particulate contaminants. Alkaline aqueous
solutions such as aqueous solutions of ammonia, potassium
hydroxide, tetramethylammonium hydroxide, or the like are used for
the surface cleaning of silicon or SiO.sub.2 substrates for
semiconductor devices or glass substrates for display devices.
Cleaning with a cleaning liquid medium comprising ammonia, hydrogen
peroxide, and water (referred to as "SC-1 cleaning liquid medium"
or "APM cleaning liquid medium") is also used extensively (this
cleaning is referred to as "SC-1 cleaning" or "APM cleaning") (see,
for example, W. Kern and D. A. Puotinen, RCA Review, p. 187, June
(1970)). The cleaning generally requires from 1 to 15 minutes.
[0005] Typical apparatus for the cleaning are of two kinds. One of
these is a batch cleaning apparatus in which two or more substrates
placed in a cassette are cleaned usually by immersion in a cleaning
liquid medium placed in a cleaning tank. The other is a
sheet-by-sheet (so-called single wafer) cleaning apparatus in which
one substrate is attached to a holder and a cleaning liquid medium
is sprinkled over the substrate surface usually while revolving the
substrate (e.g., when the substrate has a disk form, it is revolved
in the circumferential direction) The batch cleaning apparatus can
treat a large number of substrates per unit time (has a high
throughput). However, this apparatus not only has a large size but
also has problems, for example, that the contaminants which have
been released from the device formation-side surface of a substrate
or from the back side thereof may readhere to the device
formation-side surface of another substrate to cause the so-called
cross contamination and that it is necessary to use the cleaning
liquid medium in a large amount even when only one substrate is
cleaned.
[0006] On the other hand, the sheet-by-sheet cleaning apparatus has
a small size and is free from cross contamination. However, it has
a problem that the throughput is low because substrates are cleaned
one by one.
[0007] Recently, as a result of the trend toward higher fineness in
circuit patterns, particles smaller than those which have been
regarded as contaminants have become problematic. Particles have
the property of becoming difficult to remove as the particle
diameter thereof decreases. It has been pointed out that the APM
cleaning is insufficient in the ability to remove fine particles
having a particle diameter on a 0.1 .mu.m level (see H. Morinaga,
T. Futatsuki, and T. Ohmi, J. Electrochem. Soc., Vol. 142, p. 966
(1995)). In device production, a further improvement in throughput
and a further increase in production efficiency are desired and to
reduce the cleaning time also is an important subject.
[0008] APM cleaning has been used for more than 30 years in order
to remove particulate contaminants. At present, however, the
particle diameters of the particles which should be removed are far
smaller and the production efficiency required is far stricter as
compared with those at that time when this cleaning method was
developed. There is a desire for a cleaning method which can more
efficiently remove fine particles to highly clean the substrate
surface in a shorter time period.
[0009] On the other hand, addition of various surfactants to an
alkaline cleaning liquid medium has been proposed for the purpose
of, e.g., inhibiting the substrate surface from being roughened or
etched, improving wetting properties, or improving the ability to
remove oily contaminants or particulate contaminants.
[0010] For example, Japanese Patent Laid-Open No. 335294/1993
proposes a technique for inhibiting a substrate surface from being
roughened. This technique comprises adding a surfactant to an
alkaline solution of hydrogen peroxide and thereby regulating the
solution so as to have a contact angle of 10.degree. or smaller
with semiconductor substrates.
[0011] Japanese Patent No. 3,169,024 proposes a technique for
improving the substrate surface-wetting properties of a cleaning
liquid medium. This technique comprises adding an ethylene oxide
addition type nonionic surfactant which has a polyoxyethylene group
and the number of ethylene oxide(oxyethylene) groups in the
polyoxyethylene group is from 3 to 10 to an alkaline cleaning
liquid medium containing hydrogen peroxide.
[0012] Japanese Patent Laid-Open No. 2001-40389 proposes to add
various surfactants to an alkaline aqueous solution in order to
inhibit the silicon substrate from being etched.
[0013] Japanese Patent Laid-Open No. 121418/1999 proposes a
cleaning liquid medium for semiconductor substrates which contains
a specific surfactant so as to have the improved ability to remove,
in particular, oily contaminants.
[0014] Japanese Patent Laid-Open No. 245281/1995 proposes to add an
alkylbenzenesulfonic acid to an alkaline cleaning liquid medium
containing hydrogen peroxide in order to improve the ability to
remove contaminants. Furthermore, Japanese Patent Laid-Open No.
251416/1993 proposes to add a fluorochemical surfactant comprising
a fluoroalkyl-sulfonamide compound to an APM cleaning liquid medium
in order to improve the ability to remove particles.
[0015] However, even when those known surfactants are actually
added to an APM cleaning liquid medium for the purpose of more
efficiently removing fine particles on a 0.1 .mu.m level in a
shorter time period, which is the recent subject as stated above,
then no improvement is obtained in the ability to remove particles
on a 0.1 .mu.m level or use of the cleaning liquid medium thus
obtained poses problems because it produces the following side
effects (1) to (4). [0016] (1) The surfactants in the cleaning
liquid mediums separate out as oil droplets at room temperature or
elevated temperatures. The cleaning liquid mediums thus become
milk-white. They have reduced cleaning performance and use of these
cleaning liquid mediums results, for example, in residual oil
droplets on the substrate surface. [0017] (2) The cleaning liquid
mediums froth considerably and adversely influence the operation of
the cleaning apparatus. [0018] (3) The surfactants themselves
remain on the substrate surface. [0019] (4) The surfactants are
substances which may adversely influence the natural environment
and there is no appropriate method of treatment for waste liquids
resulting from the cleaning.
SUMMARY OF THE INVENTION
[0020] The invention has been achieved in order to eliminate the
problems described above. An aim of the invention is to provide
cleaning liquid mediums capable of removing finely particulate
contaminants more efficiently than conventional techniques from
substrates for devices in the production of semiconductor devices,
display devices, or the like. Another aim of the invention is to
provide a cleaning method which enables the cleaning.
[0021] In order to accomplish those aims, the present inventors
directed attention to the technique in which a surfactant is added
to an APM cleaning liquid medium as a base.
[0022] The present inventors made intensive investigations in order
to overcome the problems described above. As a result, they have
found that when a specific surfactant is incorporated into a liquid
mixture comprising water, an alkali, and hydrogen peroxide and
having a pH of 9 or higher, then the ability to remove finely
particulate contaminants is greatly improved and this cleaning
liquid medium produces almost no side effects. It has also been
found that this cleaning effect is improved by optimizing the
concentration of hydrogen peroxide. The inventors have further
found that this surface cleaning liquid medium for device
substrates simultaneously satisfies the ability to remove particles
from a substrate surface and the property of inhibiting the
substrate surface from being etched. In addition, this cleaning
liquid medium is almost free from the decrease in percentage
removal of particles which accompanies a decrease in cleaning
liquid medium temperature during cleaning and has been a problem
for cleaning liquid mediums heretofore in use. Namely, the cleaning
liquid medium was found to have an unexpected effect that even when
it is used at temperatures around 50.degree. C., which are regarded
as low for substrate cleaning, the cleaning liquid medium shows the
high ability to remove particles (under such conditions, etching
is, of course, inhibited). The invention has been thus
completed.
[0023] The invention provides a substrate surface cleaning liquid
medium which comprises the following ingredients (A), (B), (C), and
(D), has a pH of 9 or higher, and a content of ingredient (C) of
from 0.01 to 4% by weight: [0024] (A) an ethylene oxide addition
type surfactant which has an optionally substituted hydrocarbon
group and a polyoxyethylene group in the same molecular structure
and in which the ratio of the number of carbon atoms contained in
the hydrocarbon group (m) to the number of oxyethylene groups in
the polyoxyethylene group, i.e., m/n, is 1.5 or less, [0025] (B) an
alkali ingredient, [0026] (C) hydrogen peroxide, and [0027] (D)
water.
[0028] The invention further provides a substrate surface cleaning
liquid medium which, when used for cleaning a substrate surface,
attains a percentage removal of particles of 94% or higher after
the cleaning with respect to the removal of particles having a
particle diameter of 0.06 .mu.m or larger present on the surface,
and which, when used for cleaning a substrate surface having a
silicon thermal oxide film thereon, etches the silicon thermal
oxide film to a depth of 1 nm or less.
DETAILED DESCRIPTION OF THE INVENTION
[0029] Ingredient (A) in the invention is an ethylene oxide
addition type surfactant which has an optionally substituted
hydrocarbon group and a polyoxyethylene group in the same molecular
structure, and is characterized in that the ratio of the number of
carbon atoms contained in the hydrocarbon group (m) to the number
of oxyethylene groups in the polyoxyethylene group (n) is 1.5 or
less.
[0030] Examples of this surfactant include polyoxyalkylene alkyl
ethers such as polyoxyethylene alkyl ethers, polyoxyalkylene
alkylphenyl ethers, polyoxyalkylene fatty acid esters,
polyoxyalkylene alkylamines, and polyoxyalkylene alkyl ether
sulfates. Preferred of these are those which have as the optionally
substituted hydrocarbon group an alkyl group having no phenyl
group. Specific examples of such preferred surfactants include
polyoxyethylene alkyl ethers, polyoxyalkylene alkyl ethers,
polyoxyethylene fatty acid esters, polyoxyethylene alkylamines, and
polyoxyethylene alkyl ether sulfates. Especially preferred from the
standpoints of the ability to remove particles, etc. are
polyoxyethylene alkyl ethers represented by formula (2) and
polyoxyalkylene alkyl ethers represented by formula (3):
R.sup.2O--(CH.sub.2CH.sub.2O).sub.nH (2)
R.sup.2O--(CH.sub.2CH.sub.2O).sub.n(C.sub.3H.sub.6O).sub.n'H (3)
wherein R.sup.2 represents an alkyl group which may have one or
more substituents selected from the group consisting of a hydroxy
group, an amino group, an alkoxy group and a halogen atom;
C.sub.3H.sub.6O represents an oxypropylene group; n is a natural
number of 50 or less; and n' is a natural number of 20 or less.
[0031] The ratio of the number of carbon atoms contained in the
optionally substituted hydrocarbon group (m) to the number of
oxyethylene groups in the polyoxyethylene group (n), m/n, is not
particularly limited as long as it is 1.5 or lower. However, the
ratio is preferably 0.5.ltoreq.m/n.ltoreq.1.5, more preferably
0.7.ltoreq.m/n.ltoreq.1.5, most preferably
1.0.ltoreq.m/n.ltoreq.1.4. When m/n is too low, there are cases
where the ability to remove particles is reduced and the increased
length of the oxyethylene chain not only makes the surfactant have
reduced solubility in water but also poses problems, for example,
that the burden of waste liquid treatment increases. On the other
hand, values of m/n exceeding 1.5 are undesirable in that the
surfactant in the alkaline liquid medium separates out as fine oil
droplets to make the liquid medium milk-white and pose problems,
for example, that the cleaning performance is reduced and oil
droplets remain. In the case where the main chain has one or more
hydrocarbon groups as substituents, the total number of carbon
atoms in the hydrocarbon group as the main chain and in the
hydrocarbon groups as substituents is referred to as m.
[0032] The number of oxyethylene groups in the polyoxyethylene
group (n) is preferably 10.ltoreq.n.ltoreq.50, more preferably
11.ltoreq.n.ltoreq.25, most preferably 11.ltoreq.n.ltoreq.15. When
n is less than 10, there are cases where the ability to remove
particles is reduced even when the ratio m/n is within the optimal
range shown above. On the other hand, too large values of n are
undesirable in that there are problems, for example, that the
burden of waste liquid treatment increases and the surfactant is
apt to decompose in the cleaning liquid medium.
[0033] Specific examples of such surfactants include
polyoxyethylene (n=11) lauryl ether, polyoxyethylene (n=15) cetyl
ether, polyoxyethylene (n=20) oleyl ether, and polyoxyethylene
(n=14) oleylcetyl ether.
[0034] Those surfactants may be used alone or in combination of two
or more thereof in any desired ratio. In the case where two or more
surfactants (compounds) differing in m and n are used
simultaneously, one of these may be a compound in which m/n exceeds
1.5 as long as the effects of the invention are not lessened
thereby. In this case, the value of m/n in which m and n each are
the average of the m's or n's for all the surfactant compounds used
is preferably m/n.ltoreq.1.5, more preferably
0.5m/n.ltoreq.1.5.
[0035] The content of ingredient (A) in the cleaning liquid medium
is generally from 0.0001 to 0.5% by weight, preferably from 0.0003
to 0.1% by weight, more preferably from 0.001 to 0.01% by weight,
based on the cleaning liquid medium. When the concentration of the
surfactant (A) is too low, the ability of the surfactant to remove
particulate contaminants is insufficient. When the concentration
thereof is increased too high, not only the ability to remove
particulate contaminants remains unchanged but also there are cases
where the cleaning liquid medium froths considerably, is unsuitable
for use in cleaning steps, and increases the burden of waste liquid
treatment with biodegradation.
[0036] The surfactant (A) in the ordinary form on the market may
contain metal impurities, e.g., Na, K, and Fe, in an amount of
about from 1 ppm to several thousand ppm by weight. Consequently,
there is the possibility that the surfactant (A) to be used in the
invention might be a metal contamination source. Because of this,
the content of each metal impurity contained in the surfactant (A)
to be used in the invention is reduced beforehand to preferably 3
ppm by weight or less, more preferably 1 ppm by weight or less. For
obtaining a surfactant purified to such a degree, purification may
be conducted, for example, by dissolving a surfactant in water and
passing the resultant solution through an ion-exchange resin to
catch the metal impurities with the resin.
[0037] The alkali ingredient to be used as ingredient (B) in the
invention is a general term for alkaline ingredients which upon
dissolution in water give solutions whose pH values are in the
alkaline region. The alkali ingredient (B) is not particularly
limited. However, typical examples thereof include ammonium
hydroxide(aqueous ammonia solution) and organic alkalis.
[0038] Examples of the organic alkalis include amine compounds such
as quaternary ammonium hydroxides, amines, and amino alcohols.
Preferred quaternary ammonium hydroxides are ones having alkyl
groups which have 1 to 4 carbon atoms and may be substituted with a
hydroxy group, an alkoxy group or a halogen atom. These
substituents may be the same or different. Examples of such alkyl
groups include methyl, ethyl, propyl, butyl, hydroxymethyl,
hydroxyethyl, hydroxypropyl, and hydroxybutyl.
[0039] Specific examples of such quaternary ammonium hydroxides
include tetramethylammonium hydroxide (TMAH), tetraethylammonium
hydroxide, trimethyl(hydroxyethyl)-ammonium hydroxide (common name:
choline), and triethyl(hydroxyethyl)ammonium hydroxide. Examples of
the amine compounds other than these include ethylenediamine,
monoethanolamine, and triethanolamine.
[0040] Also usable are the hydroxides of alkali metals or alkaline
earth metals, such as sodium hydroxide, potassium hydroxide, and
calcium hydroxide, and alkaline salts such as sodium hydrogen
carbonate and ammonium hydrogen carbonate.
[0041] Preferred of those alkali ingredients enumerated above are
ammonium hydroxide, tetramethylammonium hydroxide (TMAH), and
trimethyl(hydroxyethyl)ammonium hydroxide (common name: choline)
from the standpoints of cleaning effect, reduced residual metal
amount, profitability, cleaning liquid medium stability, etc.
Especially preferred is ammonium hydroxide.
[0042] Those alkali ingredients may be used alone or in combination
of two or more thereof in any desired ratio. The concentration of
the alkali ingredient in the cleaning liquid medium of the
invention may be suitably selected. However, it is generally
preferably from 0.001 to 5% by weight, more preferably from 0.002
to 1% by weight. In case where the concentration thereof is too
low, the contaminant-removing effect which is to be attained by the
invention cannot be obtained. On the other hand, too high
concentrations thereof are undesirable in that not only the effect
is not enhanced any more and such high concentrations are
uneconomical, but also there is a stronger possibility that the
substrate surface might be damaged by etching.
[0043] Ingredient (C) in the invention is hydrogen peroxide. The
presence of hydrogen peroxide in a given concentration is important
especially in the cleaning of substrates in which silicon is
exposed on the surface. Silicon has the property of readily
dissolving in alkaline solutions. Hydrogen peroxide oxidizes the
silicon surface to form an extremely thin SiO.sub.2 film. Since
this SiO.sub.2 film has a far lower rate of dissolution under
alkaline conditions than silicon, it can inhibit etching and
surface roughening. In conventional techniques, the concentration
of hydrogen peroxide in the alkaline cleaning liquid mediums is 1%
by weight or more, preferably 3% by weight or more, and too low
concentrations of hydrogen peroxide lead to problems that the
silicon is excessively etched and the surface is roughened.
[0044] The present inventors made investigations on the optimal
hydrogen peroxide concentration in substrate surface cleaning
liquid mediums on the premise that the specific surfactant (A)
described above is added. As a result, it has been found that even
when the hydrogen peroxide concentration is lower than in the
conventional techniques, the problem of substrate surface
roughening can be overcome while maintaining sufficient cleaning
performance. The concentration of hydrogen peroxide in the cleaning
liquid medium of the invention is generally from 0.01 to 4% by
weight, preferably from 0.05 to less than 3% by weight, more
preferably from 0.1 to less than 2% by weight, most preferably from
0.2 to less than 1% by weight. When the concentration of hydrogen
peroxide is too low, there are cases where problems such as the
following (1) to (3) arise. [0045] 1) The silicon is excessively
etched or the surface is roughened. [0046] 2) The ability of
hydrogen peroxide to remove organic contaminants is reduced. [0047]
3) An SiO.sub.2 film is not sufficiently formed, so that the
hydrophobic bare silicon (uncovered with an oxide film) remains
exposed on the surface. Since this bare silicon repels the cleaning
liquid medium or the ultrapure water to be used for rinsing, the
cleaning performance decreases.
[0048] On the other hand, when the concentration of hydrogen
peroxide is too high, not only a higher cleaning effect cannot be
expected, but also there are cases where the following and other
problems arise: 1) the hydrogen peroxide oxidatively decomposes the
surfactant and other organic additives; 2) the cleaning cost
increases; and 3) the burden of waste liquid treatment
increases.
[0049] In the cleaning liquid medium of the invention, the ratio of
the content of the specific surfactant (A), a, to the content of
hydrogen peroxide (C), c, i.e., the ratio a/c, is generally
1/3000.ltoreq.a/c.ltoreq.1/20, preferably
1/1500.ltoreq.a/c.ltoreq.1/30, more preferably
1/1000.ltoreq.a/c.ltoreq.1/50, most preferably
1/1000.ltoreq.a/c.ltoreq.1/100. In case where a/c is too small, not
only the ability to remove particulate contaminants decreases but
also the surfactant is apt to be decomposed by the hydrogen
peroxide. When a/c is too large, there are cases where such large
surfactant ratios pose problems, for example, that the surfactant
remains on the substrate surface and the cleaning liquid medium
froths during cleaning.
[0050] Ingredient (D) in the invention is water. In the case where
a highly clean substrate surface is desired, the water to be used
generally is deionized water, preferably ultrapure water. It is
also possible to use electrolytic ionic water obtained by water
electrolysis or hydrogenated water obtained by dissolving hydrogen
gas in water.
[0051] Besides the ingredients (A), (B), (C), and (D) described
above, a complexing agent may be incorporated into the cleaning
liquid medium of the invention. The incorporation of a complexing
agent is preferred in that it is effective in obtaining an
extremely highly clean substrate surface on which metallic
contaminants have been further diminished. The complexing agent to
be used in the invention may be any of known complexing agents. In
selecting a complexing agent, all of the level of contamination of
the substrate surface, kind of the metal, level of cleanness
required of the substrate surface, complexing agent cost, chemical
stability, and other factors may be taken into account. Examples of
the complexing agent include the compounds enumerated under the
following (1) to (4).
(1) Compounds Having Nitrogen as Donor Atom and Carboxyl and/or
Phosphono Group
[0052] Examples thereof include amino acids such as glycine;
nitrogen-containing carboxylic acids such as iminodiacetic acid,
nitrilotriacetic acid, ethylenediaminetetraacetic acid [EDTA],
trans-1,2-diaminocyclohexanetetraacetic acid [CyDTA],
diethylenetriaminepentaacetic acid [DTPA], and
triethylenetetraminehexaacetic acid [TTHA]; and nitrogen-containing
phosphonic acids such as
ethylenediaminetetrakis(methylenephosphonic acid) [EDTPO],
nitrilotris(methylenephosphonic acid) [NTPO], and
propylenediaminetetra(methylenephosphonic acid) [PDTMP].
(2) Compounds Having Aromatic Hydrocarbon Ring and Two or More OH
and/or O.sup.- Groups Directly Bonded to Constituent Carbon Atoms
of the Ring
[0053] Examples thereof include phenols and derivatives thereof,
such as catechol, resorcinol, and Tiron.
(3) Compounds Having Both the Structures (1) and (2)
(3-1) Ethylenediaminedi-o-hydroxyphenylacetic Acid [EDDHA] and
Derivatives Thereof
[0054] Examples thereof include nitrogen-containing aromatic
carboxylic acids such as ethylenediaminedi-o-hydroxyphenylacetic
acid [EDDHA],
ethylenediamine-N,N'-bis[(2-hydroxy-5-methylphenyl)acetic acid]
[EDDHMA], ethylenediamine-N,N'-bis[(2-hydroxy-5-chlorophenyl)acetic
acid] [EDDHCA], and
ethylenediamine-N,N'-bis[(2-hydroxy-5-sulfophenyl)acetic acid]
[EDDHSA]; and nitrogen-containing aromatic phosphonic acids such as
ethylenediamine-N,N'-bis[(2-hydroxy-5-methylphenyl)phosphonic acid]
and ethylenediamine-N,N'-bis[(2-hydroxy-5-phosphophenyl)-phosphonic
acid].
(3-2) N,N'-Bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic Acid
[HBED] and Derivatives Thereof
[0055] Examples thereof include
N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid [HBED],
N,N'-bis(2-hydroxy-5-methylbenzyl)ethylenediamine-N,N'-diacetic
acid [HMBED], and
N,N'-bis(2-hydroxy-5-chlorobenzyl)ethylenediamine-N,N'-diacetic
acid.
(4) Others
[0056] Other examples include amines such as ethylenediamine,
8-quinolinol, and o-phenanthroline; carboxylic acids such as formic
acid, acetic acid, oxalic acid, and tartaric acid; hydrogen halides
or salts thereof, such as hydrofluoric acid, hydrochloric acid,
hydrogen bromide, and hydrogen iodide; and oxoacids and salts
thereof, such as phosphoric acid and condensed phosphoric
acids.
[0057] Those complexing agents may be used in the form of an acid
or a salt, e.g., ammonium salt.
[0058] Preferred of those complexing agents from the standpoints of
cleaning effect, chemical stability, etc. are nitrogen-containing
carboxylic acids such as ethylenediaminetetraacetic acid [EDTA] and
diethylenetriaminepentaacetic acid [DTPA]; nitrogen-containing
phosphonic acids such as
ethylenediaminetetrakis(methylenephosphonic acid) [EDTPO] and
propylenediaminetetra(methylenephosphonic acid) [PDTMP];
ethylenediaminedi-o-hydroxyphenylacetic acid [EDDHA] and
derivatives thereof; and
N,N'-bis(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid
[HBED].
[0059] Especially preferred of those from the standpoint of
cleaning effect are ethylenediaminedi-o-hydroxyphenylacetic acid
[EDDHA], ethylenediamine-N,N'-bis[(2-hydroxy-5-methylphenyl)acetic
acid] [EDDHMA], diethylenetriaminepentaacetic acid [DTPA],
ethylenediaminetetraacetic acid [EDTA], and
propylenediaminetetra(methylenephosphonic acid) [PDTMP].
[0060] Those completing agents may be used alone or in combination
of two or more thereof in any desired ratio. The concentration of
the complexing agent in the cleaning liquid medium of the invention
may be selected at will according to the kind and amount of the
contaminant metal impurity and the level of cleanness required of
the substrate surface. However, it is generally preferably from 1
to 10,000 ppm by weight, more preferably from 5 to 1,000 ppm by
weight, most preferably from 10 to 200 ppm by weight. In case where
the concentration thereof is too low, the contaminant-removing
effect and adhesion-preventing effect of the complexing agent
cannot be obtained. On the other hand, too high concentrations
thereof are undesirable in that not only the effects are not
enhanced any more and such high concentrations are uneconomical,
but also there is a stronger possibility that the complexing agent
might remain adherent to the substrate surface after the surface
treatment.
[0061] Complexing agents of the ordinary reagent grades on the
market may contain metal impurities, e.g., Fe, in an amount of
about from 1 ppm to several thousand ppm. Consequently, there is
the possibility that the complexing agent to be used in the
invention might be a metal contamination source. In an initial
stage, such metal impurities are present in the form of a stable
complex with the complexing agent. However, while the complexing
agent is used as a surface-treating agent over a prolonged period
of time, it decomposes to release the metals, which adhere to the
substrate surface. Because of this, the content of each of the
metal impurities, e.g., Fe, Al, and Cu, contained in the complexing
agent to be used in the invention is reduced beforehand to
preferably 5 ppm or less, more preferably 2 ppm or less. For
obtaining a complexing agent purified to such a degree,
purification may be conducted, for example, by dissolving a
complexing agent in an acidic or alkaline solution, filtering the
resultant solution to remove any insoluble impurities, neutralizing
the filtrate to precipitate crystals again, and separating the
crystals from the liquid.
[0062] In the cleaning liquid medium of the invention, any desired
alkali ingredient can be used even when the cleaning liquid medium
contains a complexing agent. However, preferred alkali ingredients
for use in the cleaning liquid medium containing a complexing agent
are ammonium hydroxide, tetramethylammonium hydroxide (TMAH),
trimethyl-(hydroxyethyl)ammonium hydroxide (common name: choline),
and the like from the standpoints of reduced residual metal amount,
profitability, cleaning liquid medium stability, etc. Especially
preferred is ammonium hydroxide.
[0063] The cleaning liquid medium of the invention is characterized
by having a pH of 9 or higher. The pH thereof is not particularly
limited as long as it is 9 or higher. However, from the standpoints
of particle removal and adhesion prevention, the pH of the cleaning
liquid medium is generally preferably from 9 to 12, more preferably
from 10 to 11.5. A known pH regulator may be used as long as the
effects of the invention are not lessened thereby. In case where
the pH of the cleaning liquid medium is too low, the ability to
remove particles and the ability to prevent particle adhesion are
insufficient. Even when the pH thereof is too high, not only the
effects are not enhanced any more and the necessity of a large
amount of an alkali is uneconomical, but also there is a stronger
possibility that the substrate surface might be damaged by
etching.
[0064] The cleaning liquid medium of the invention may further
contain other ingredients. Examples of such ingredients include
organic sulfur-containing compounds (e.g., 2-mercaptothiazoline,
2-mercaptoimidazoline, 2-mercaptoethanol, and thioglycerol),
organic nitrogen-containing compounds (e.g., benzotriazole,
3-aminotriazole, N(R).sub.3 (wherein R is an alkyl group having 1
to 4 carbon atoms), N(ROH).sub.3 (wherein R is an alkyl group
having 1 to 4 carbon atoms), urea, and thiourea), water-soluble
polymers (e.g., polyethylene glycol and poly(vinyl alcohol)),
anticorrosive agents such as alkyl alcohol compounds (ROH (wherein
R is an alkyl group having 1 to 4 carbon atoms)), acids such as
sulfuric acid, hydrochloric acid, and hydrofluoric acid, pH buffers
such as ammonium fluoride and ammonium phosphate, reducing agents
such as hydrazine, dissolved gases such as hydrogen, argon,
nitrogen, and ozone, and known surfactants/organic solvents.
[0065] When the cleaning liquid medium of the invention is used to
clean a substrate, an exceedingly high particle-removing effect is
obtained only through one-step cleaning. However, cleaning may be
conducted in two or more steps using the cleaning liquid medium of
the invention in combination with one or more other cleaning liquid
mediums according to the kinds of contaminants desired to be
further removed. Examples of such optional cleaning liquid mediums
include a cleaning liquid medium containing hydrofluoric acid, a
hydrochloric acid/hydrogen peroxide/water mixture ("SC-2 cleaning
liquid medium" or "APM cleaning liquid medium"), a sulfuric
acid/hydrogen peroxide mixture ("SPM cleaning liquid medium" or
"piranha cleaning liquid medium"), ozonized ultrapure water, and
hydrogenated ultrapure water. In particular, a combination of
cleaning with a cleaning liquid medium containing hydrofluoric acid
and cleaning with the cleaning liquid medium of the invention is
preferred in that the metallic contaminants, particulate
contaminants, and organic contaminants present on the substrate
surface can be efficiently removed in a short time period. Cleaning
with a cleaning liquid medium containing hydrofluoric acid is
preferably conducted under the conditions of a hydrofluoric acid
concentration of from 0.03 to 3% by weight and a cleaning time of
from 1 second to 5 minutes. It is especially preferred to conduct
this cleaning under such conditions that the cleaning time is 45
seconds or shorter and the hydrofluoric acid concentration (C), %
by weight, and the cleaning time (t), second, satisfy the
relationship 0.25.ltoreq.tC.sup.1.29.ltoreq.5. This is because use
of such cleaning conditions has the following excellent effects:
metallic contaminants can be sufficiently removed in an extremely
short time period and almost no side effects are produced such as
water marks, particle readhesion, and dimensional change through
the treatment due to etching.
[0066] For the cleaning liquid medium of the invention and the
cleaning method using the same, the substrate to be cleaned may be
any of various substrates. Of these, the substrates which are made
of semiconductors, glasses, metals, ceramics, resins, magnetic
materials, superconductors, or the like and in which particulate
contaminants are problematic are suitable for the surface cleaning.
In particular, the cleaning liquid medium and cleaning method of
the invention are suitable for the cleaning of substrates for
semiconductor devices and substrates for display devices, which are
required to have exceedingly high surface cleanness. Examples of
the materials of such substrates and of the materials of wirings,
electrodes, and the like present on the surface thereof include
semiconductor materials such as Si, Ge (germanium), and GaAs
(gallium-arsenic); insulating materials such as SiO.sub.2, silicon
nitride, hydrogen silsesquioxane (HSQ), glasses, aluminum oxide,
transition metal oxides (e.g., titanium oxide, tantalum oxide,
hafnium oxide, and zirconium oxide), (Ba, Sr)TiO.sub.3(BST),
polyimides, and organic thermoset resins; and metals such as W
(tungsten), Cu (copper), Cr (chromium), Co (cobalt), Mo
(molybdenum), Ru (ruthenium), Au (gold), Pt (platinum), Ag
(silver), and Al (aluminum) and alloys of these metals, silicides,
and nitrides.
[0067] In particular, semiconductor device substrates having a
semiconductor material such as silicon or an insulating material
such as silicon nitride, silicon oxide, or a glass on part or all
of the surface are highly strongly desired to be reduced in
contamination with fine particles. The cleaning method of the
invention is hence suitable for application to these
substrates.
[0068] For preparing the cleaning liquid medium of the invention,
known techniques may be used. The cleaning liquid medium may be
prepared by mixing beforehand two or more of constituent
ingredients for the cleaning liquid medium (e.g., a surfactant,
ammonium hydroxide, hydrogen peroxide, water, and optional
ingredients including a complexing agent) and then mixing the
resultant mixture with the remaining ingredients. Alternatively,
all the ingredients may be mixed at a time.
[0069] In the cleaning method of the invention, the cleaning liquid
medium is brought into direct contact with a substrate. Examples of
techniques for contacting the cleaning liquid medium with the
substrate include: a dipping method in which a cleaning tank is
filled with the cleaning liquid medium and the substrate is
immersed therein; a spinning method in which the substrate is
rotated at a high speed while allowing the cleaning liquid medium
fed through a nozzle to flow over the substrate; and a spraying
method in which the cleaning liquid medium is sprayed over the
substrate to clean it. Examples of apparatus usable for conducting
such cleaning operations include a batch cleaning apparatus in
which two or more substrates placed in a cassette are
simultaneously cleaned and a sheet-by-sheet cleaning apparatus in
which one substrate attached to a holder is cleaned. The cleaning
method of the invention is applicable to any of the techniques
described above. It is, however, preferred to apply the cleaning
method of the invention to, in particular, the sheet-by-sheet
cleaning apparatus, in which a reduction in cleaning period and a
reduction in cleaning liquid medium amount are desired. The
cleaning method of the invention satisfies these desires. It is
also preferred to apply the cleaning method of the invention to the
batch cleaning apparatus because a higher particle-removing effect
is obtained.
[0070] Although the cleaning may be conducted at room temperature,
it may be performed with heating for the purpose of improving the
cleaning effect. The cleaning is conducted at a temperature in the
range of generally from room temperature to 90.degree. C.,
preferably from 40 to 80.degree. C.
[0071] The time period of this cleaning is generally from 30
seconds to 30 minutes, preferably from 1 to 15 minutes, in the case
of batch cleaning, and is generally from 1 second to 5 minutes,
preferably from 15 seconds to 1 minute, in the case of
sheet-by-sheet cleaning. Too short time periods result in an
insufficient cleaning effect. In case where the cleaning period is
prolonged excessively, this results only in a reduced throughput
and no effect compensating for the prolongation of cleaning period
is expected.
[0072] The cleaning with the cleaning liquid medium may be
conducted in combination with cleaning with a physical force, e.g.,
mechanical cleaning by scrubbing with a cleaning brush or
ultrasonic cleaning. In particular, use of ultrasonic irradiation
or brush scrubbing in combination with the cleaning with the
cleaning liquid medium is preferred in that the ability to remove
particulate contaminants is further improved, leading to a
reduction in cleaning time period. It is especially preferred to
irradiate the substrate with an ultrasonic having a frequency of
0.5 MHz or higher because this irradiation and the surfactant
produce a synergistic effect to greatly improve the ability to
remove particles on a 0.1 .mu.m level.
[0073] The other substrate surface cleaning liquid medium of the
invention will be explained next.
[0074] The other substrate surface cleaning liquid medium of the
invention is a cleaning liquid medium which, when used for cleaning
a substrate surface, attains a percentage removal of particles of
94% or higher after the cleaning with respect to the removal of
particles having a particle diameter of 0.06 .mu.m or larger, i.e.,
fine particles such as, e.g., silica particles, alumina particles
present on the surface, and which, when used for cleaning a
substrate surface having a silicon thermal oxide film thereon,
etches the silicon thermal oxide film to a depth of 1 nm or
less.
[0075] The term "after the cleaning" as used for specifying this
substrate surface cleaning liquid medium of the invention means
that the substrate surface has been contacted with this substrate
surface cleaning liquid medium. More specifically, that term means
that the substrate surface has been in contact with the cleaning
liquid medium for at least 1 minute. In this contact, the substrate
surface cleaning liquid medium may be stationary or flowing. Any
desired method may be used for the contact, and examples thereof
include the dipping method, spinning method, and spraying method
described above.
[0076] This substrate surface cleaning liquid medium of the
invention is also characterized in that when the cleaning liquid
medium is used for cleaning a substrate surface having a silicon
thermal oxide film thereon, it etches the silicon thermal oxide
film to a depth of 1 nm or less.
[0077] This substrate surface cleaning liquid medium of the
invention produces an excellent effect with respect to each of the
ability to remove particles from the substrate surface even in
cleaning at a relatively low temperature of about from room
temperature to 50.degree. C. and the property of inhibiting the
silicon thermal oxide film from being etched.
[0078] In particular, this cleaning liquid medium preferably is one
which after the cleaning attains a percentage removal of particles
of 94% or higher when the temperature thereof during contact with
the substrate surface was 60.degree. C. or lower, desirably
50.degree. C. or lower. In this cleaning, too low cleaning liquid
medium temperatures may result in reduced cleaning performance.
Consequently, the temperature thereof is preferably not lower than
room temperature, more preferably 40.degree. C. or higher.
[0079] This substrate surface cleaning liquid medium of the
invention may suitably be acidic, neutral, or alkaline according to
the substrate to be cleaned. However, the cleaning liquid medium
preferably is alkaline because the alkaline cleaning liquid medium
has the excellent ability to remove particles.
[0080] This substrate surface cleaning liquid medium of the
invention can have any desired composition. However, this cleaning
liquid medium preferably has the substrate surface cleaning liquid
medium composition according to the invention described above.
Namely, it preferably comprises the following ingredients (A), (B),
(C), and (D), has a pH of 9 or higher, and has a content of
ingredient (C) of from 0.01 to 4% by weight. [0081] (A) An ethylene
oxide addition type surfactant which has an optionally substituted
hydrocarbon group and a polyoxyethylene group in the same molecular
structure and in which the ratio of the number of carbon atoms
contained in the hydrocarbon group (m) to the number of oxyethylene
groups in the polyoxyethylene group (n), i.e., m/n, is 1.5 or less,
[0082] (B) An alkali ingredient, [0083] (C) Hydrogen peroxide, and
[0084] (D) Water.
[0085] Specific embodiments of the invention will be explained
below by reference to Examples. However, the invention should not
be construed as being limited to the following Examples in any way
unless the invention departs from the spirit thereof.
(Preparation of Contaminated Silicon Wafer)
[0086] A 4-inch silicon wafer was immersed in an acidic aqueous
solution having a pH of about 3 containing dispersed therein
Si.sub.3N.sub.4 particles having particle diameters of about from
0.05 to 3 .mu.m and an average particle diameter of about 0.3 .mu.m
in a concentration of 0.05 mg/l.
[0087] After the immersion, the silicon wafer was rinsed with
ultrapure water for 10 minutes and dried with nitrogen blowing or a
spin-drier. Thus, a silicon wafer contaminated with Si.sub.3N.sub.4
particles was obtained.
[0088] Silicon wafer analysis for Si.sub.3N.sub.4 particles present
thereon was conducted in the following manner. The contaminated
silicon wafer and silicon wafers which had been cleaned were
analyzed by the same method. A laser surface analyzer (LS-5000,
manufactured by Hitachi Engineering Co., Ltd.) was used to count
the Si.sub.3N.sub.4 particles. In preparing the contaminated
silicon wafer, the number of the Si.sub.3N.sub.4 particles present
on the silicon wafer was regulated so as to be in the range of from
2,000 to 10,000 per 4-inch silicon wafer.
EXAMPLE 1 AND COMPARATIVE EXAMPLE 1
[0089] The silicon wafer contaminated with Si.sub.3N.sub.4
particles was cleaned for particle removal with an APM 1 cleaning
liquid medium (cleaning liquid medium consisting of an aqueous
solution prepared by mixing 29% by weight ammonia water, 31% by
weight aqueous hydrogen peroxide solution, and water in a ratio of
1/2/40 by volume) or with a cleaning liquid medium prepared by
adding the surfactant shown in Table 1 to the APM 1. These two
cleaning liquid mediums had a pH of about 10.5. The liquid medium
temperature and the cleaning time were regulated to 70.degree. C.
and 10 minutes, respectively, and ultrasonic irradiation was not
conducted. The cleaning was conducted by the dip cleaning
method.
[0090] The number of the Si.sub.3N.sub.4 particles remaining on the
surface of the cleaned silicon wafer obtained was counted, and the
contaminant particle-removing ability of the cleaning liquid medium
was evaluated in the following five grades based on the degree of
removal determined from that number. The degrees of removal of 90%
and higher are indicated by removing ability AAA, those of from 70%
to less than 90% are indicated by AA, those of from 50% to less
than 70% are indicated by A, those of from 30% to less than 50% are
indicated by B, and those less than 30% are indicated by C. The
results obtained are shown in Table 1.
[0091] The solubility of ingredient (A) in each cleaning liquid
medium was evaluated based on the following criteria. When a
cleaning liquid medium placed in a rectangular quartz vessel with a
capacity of about 4 l to a depth of about 10 cm had the same
clarity as the cleaning liquid medium containing no ingredient (A),
the solubility of the ingredient (A) in this cleaning liquid medium
was rated as good. When a cleaning liquid medium thus placed in the
vessel had no clarity, i.e., was turbid, e.g., milk-white, then the
solubility of the ingredient (A) in this cleaning liquid medium was
rated as poor. The results obtained are shown in Table 1.
TABLE-US-00001 TABLE 1 Cleaning agent ingredients Hydrogen Alkali
peroxide pH of Surfactant (A) ingredient (C) cleaning Particle
Structural Concentration (B) Concentration liquid Ultrasonic
removing formula m n m/n (wt ppm) Kind (wt %) medium irradiation
Solubility ability Example 1
C.sub.12H.sub.25O--(C.sub.2H.sub.4O).sub.11H 12 11 1.1 33 ammonium
1.4 about not good A hydroxide 10.5 conducted Comparative nil -- --
-- 0 ammonium 1.4 about not good C Example 1 hydroxide 10.5
conducted Cleaning method, dip cleaning; Kind of APM, APM 1;
Cleaning liquid medium temperature, 70.degree. C.; Cleaning time,
10 min
[0092] Table 1 shows that the surfactant according to the invention
had distinctly good solubility and the cleaning liquid medium
containing this surfactant had a satisfactory
particulate-contaminant-removing ability.
EXAMPLE 2 AND COMPARATIVE EXAMPLE 2
[0093] Cleaning was conducted in the same manner as in Example 1,
except that use was made of the same APM 1 cleaning liquid medium
as in Example 1 or a cleaning liquid medium prepared by adding the
surfactant shown in Table 2 to the APM 1, and that ultrasonic
irradiation was conducted For the ultrasonic irradiation was used
HI MEGA SONIC (600 W, 950 kHz), manufactured by Kaijo Corp. Those
two cleaning liquid mediums had a pH of about 10.5. The results
obtained are shown in Table 2. TABLE-US-00002 TABLE 2 Cleaning
agent ingredients Hydrogen Alkali peroxide pH of Surfactant (A)
ingredient (C) cleaning Particle Structural Concentration (B)
Concentration liquid Ultrasonic removing formula m n m/n (wt ppm)
Kind (wt %) medium irradiation Solubility ability Example 2
C.sub.12H.sub.25O--(C.sub.2H.sub.4O).sub.11H 12 11 1.1 33 ammonium
1.4 about conducted good AAA hydroxide 10.5 Comparative nil -- --
-- 0 ammonium 1.4 about conducted good A Example 2 hydroxide 10.5
Cleaning method, dip cleaning; Kind of APM, APM 1; Cleaning liquid
medium temperature, 70.degree. C.; Cleaning time, 10 min
[0094] Table 2 shows that the surfactant according to the invention
had distinctly good solubility and the cleaning liquid medium
containing this surfactant had a satisfactory particle-removing
ability.
EXAMPLE 3 AND COMPARATIVE EXAMPLE 2
[0095] Cleaning was conducted in the same manner as in Example 2,
except that use was made of the same APM 1 cleaning liquid medium
as in Example 2 or a cleaning liquid medium prepared by adding the
surfactant and complexing agent shown in Table 2 to the APM 1.
Cleaning for removing metallic contaminants was further conducted
in the following manner.
(Preparation of Contaminated Silicon Wafer)
[0096] A 4-inch silicon wafer was immersed in an APM cleaning
liquid medium containing ions of metals (Fe and Cu). The APM
cleaning liquid medium was prepared by mixing 29% by weight ammonia
water, 31% by weight aqueous hydrogen peroxide solution, and water
in a ratio of 1/1/5 by volume. The metal ion-containing APM
cleaning liquid medium was prepared by adding metal ion-containing
aqueous solutions to that APM cleaning liquid medium in such
amounts as to result in an Fe content of 20 ppb and a Cu content of
1 ppm.
[0097] After the immersion, the silicon wafer was rinsed with
ultrapure water for 10 minutes and dried with nitrogen blowing.
Thus, a silicon wafer contaminated with metals was obtained.
[0098] Silicon wafer analysis for metals (Fe and Cu) present
thereon was conducted in the following manner. The contaminated
silicon wafer and silicon wafers which had been cleaned were
analyzed by the same method. The metals present on the surface of
each wafer were recovered with an aqueous solution containing 0.1%
by weight hydrofluoric acid and 1% by weight hydrogen peroxide.
This solution was then analyzed with an inductively-coupled-plasma
mass spectrometer (ICP-MS) to determine the amount of each metal,
which was converted to concentration on the substrate surface
(atoms/cm.sup.2). The thus-obtained results of the analysis of the
contaminated silicon wafer are shown in Table 3.
[0099] The silicon wafer contaminated with metals was cleaned for
metal removal with an APM 2 cleaning liquid medium (cleaning liquid
medium consisting of an aqueous solution prepared by mixing 29% by
weight ammonia water, 31% by weight aqueous hydrogen peroxide
solution, and water in a ratio of 1/1/30 by volume) or with a
cleaning liquid medium prepared by adding the surfactant and
complexing agent shown in Table 3 to the APM 2. These two cleaning
liquid mediums had a pH of about 10.5. The liquid medium
temperature and the cleaning time were regulated to 60.degree. C.
and 10 minutes, respectively, and the cleaning was conducted by the
dip cleaning method. The amounts of the metals (Fe and Cu)
remaining on the cleaned silicon wafer surface are shown in Table
3. TABLE-US-00003 TABLE 3 Cleaning agent ingredients Hydrogen
Surfactant (A) Alkali peroxide Concentration ingredient (C)
Structural (wt (B) Concentration formula m n m/n ppm) Kind (wt %)
Example 3 C.sub.12H.sub.25O--(C.sub.2H.sub.4O).sub.11H 12 11 1.1 33
ammonium 1.4 hydroxide Comparative nil -- -- -- 0 ammonium 1.4
Example 2 hydroxide Before cleaning (silicon wafer contaminated
with metals) Cleaning agent Metal- ingredients removing Complexing
ability agent pH of Concentration Concentration cleaning Particle-
(.times.10.sup.10 (wt liquid removing atoms/cm.sup.2) Kind ppm)
medium Solubility ability Fe Cu Example 3 EDDHA 28 about good AAA
<0.1 <0.1 10.5 Comparative -- 0 about good A 500 3 Example 2
10.5 Before cleaning (silicon wafer 1000 3000 contaminated with
metals) to to 3000 5000 Cleaning method, dip cleaning; Cleaning
time, 10 min "Particle removal" 1/2/40; cleaning liquid medium
temperature, 70.degree. C. "Metal removal" 1/1/30; cleaning liquid
medium temperature, 60.degree. C.
[0100] Table 3 shows that the surfactant according to the invention
had distinctly good solubility and the cleaning liquid medium
containing this surfactant in combination with the complexing agent
had a satisfactory particulate-contaminant-removing ability and
satisfactory contaminant-metal-removing ability.
EXAMPLES 4 TO 10 AND COMPARATIVE EXAMPLES 3 TO 5
[0101] Cleaning was conducted in the same manner as in Example 1,
except that use was made of an APM 3 cleaning liquid medium
(cleaning liquid medium consisting of an aqueous solution prepared
by mixing 29% by weight ammonia water, 31% by weight aqueous
hydrogen peroxide solution, and water in a ratio of 1/2/60 by
volume) or cleaning liquid mediums prepared by adding each of the
surfactants shown in Table 4 to the APM 3, that the cleaning was
conducted with a sheet-by-sheet cleaning apparatus at a liquid
medium temperature of room temperature for a cleaning time of 30
seconds, and that ultrasonic irradiation was used in combination
with the cleaning.
[0102] This cleaning with a sheet-by-sheet cleaning apparatus was
conducted by the general method. The specific procedure is as
follows. While the contaminated silicon wafer was kept being
revolved in the circumferential direction, each cleaning liquid
medium was continuously applied to the wafer surface at a constant
flow rate for a given period (cleaning time) to clean the surface.
Immediately after the cleaning, the silicon wafer was rinsed with
ultrapure water and spin-dried to obtain a cleaned silicon wafer.
The rotational speed of the silicon wafer was 600 rpm, and the flow
rate of the cleaning liquid medium was 1 l/min. The cleaning liquid
mediums each had a pH of about 10.5. The results obtained are shown
in Table 4.
[0103] The cleaning liquid mediums in which the solubility of the
surfactant was "poor" had the high possibility that the insoluble
ingredient might contaminate the substrate for devices and thus
reduce device performance or yield. Because of this, these cleaning
liquid mediums were not evaluated for
particulate-contaminant-removing ability. The same applies also to
Comparative Example 6. TABLE-US-00004 TABLE 4 Cleaning agent
ingredients Alkali Hydrogen pH of Surfactant (A) ingredient
peroxide (c) cleaning Particle Structural Concentration (B)
Concentration liquid removing formula m n m/n (wt ppm) Kind (wt %)
medium Solubility ability Example 4
C.sub.12H.sub.25O(C.sub.2H.sub.4O).sub.11H 12 11 1.1 100 ammonium 1
about good AA hydroxide 10.5 Example 5
C.sub.12H.sub.25O(C.sub.2H.sub.4O).sub.11H 12 11 1.1 30 ammonium 1
about good AA hydroxide 10.5 Example 6
C.sub.12H.sub.25O(C.sub.2H.sub.4O).sub.11H 12 11 1.1 20 ammonium 1
about good AA hydroxide 10.5 Example 7
C.sub.12H.sub.25O(C.sub.2H.sub.4O).sub.11H 12 11 1.1 10 ammonium 1
about good A hydroxide 10.5 Example 8
C.sub.12H.sub.25O(C.sub.2H.sub.4O).sub.13H 12 13 0.9 100 ammonium 1
about good AA hydroxide 10.5 Example 9
C.sub.8H.sub.17O(C.sub.2H.sub.4O).sub.8H 8 8 1.0 100 ammonium 1
about good A hydroxide 10.5 Example
C.sub.18H.sub.35O(C.sub.2H.sub.4O).sub.30H 18 30 0.6 100 ammonium 1
about good A 10 hydroxide 10.5 Comparative nil -- -- -- 0 ammonium
1 about good B Example 3 hydroxide 10.5 Comparative
C.sub.12H.sub.25O(C.sub.2H.sub.4O).sub.4H 12 4 3 100 ammonium 1
about poor not Example 4 hydroxide 10.5 conducted Comparative
C.sub.12H.sub.25O(C.sub.2H.sub.4O).sub.5H 12 5 2.4 100 ammonium 1
about poor not Example 5 hydroxide 10.5 conducted Cleaning method,
sheet-by-sheet cleaning; Kind of APM, APM 3; Cleaning temperature,
room temperature; Cleaning time, 30 sec
[0104] Table 4 shows that the surfactants according to the
invention had distinctly good solubility and the cleaning liquid
mediums containing these surfactants had a satisfactory
particulate-contaminant-removing ability.
EXAMPLE 11 AND COMPARATIVE EXAMPLE 3
[0105] Cleaning for particulate-contaminant removal was conducted
in the same manner as in Example 4, except that use was made of the
same APM 3 cleaning liquid medium as in Example 4 or a cleaning
liquid medium prepared by adding the surfactant and complexing
agent shown in Table 5 to the APM 3. Furthermore, cleaning for
metallic-contaminant removal was conducted in the same manner as in
Example 3, except that use was made of the same APM 1 cleaning
liquid medium as in Example 1 or a cleaning liquid medium prepared
by adding the surfactant and complexing agent shown in Table 5 to
the APM 1. The cleaning time and cleaning liquid medium temperature
were regulated to 60 seconds and 80.degree. C., respectively. Those
cleaning liquid mediums each had a pH of about 10.5. TABLE-US-00005
TABLE 5 Cleaning agent ingredients Hydrogen Surfactant (A) Alkali
peroxide Concentration ingredient (C) Structural (wt (B)
Concentration formula m n m/n ppm) Kind (wt %) Example 11
C.sub.12H.sub.25O--(C.sub.2H.sub.4O).sub.11H 12 11 1.1 100 ammonium
1 hydroxide Comparative nil -- -- -- 0 ammonium 1 Example 3
hydroxide Before cleaning (silicon wafer contaminated with metals)
Cleaning agent Metal- ingredients removing Complexing ability agent
pH of Concentration Concentration cleaning Particle-
(.times.10.sup.10 (wt liquid removing atoms/cm.sup.2) Kind ppm)
medium Solubility ability Fe Cu Example 11 EDDHA 70 about good AA
9.5 <0.1 10.5 Comparative -- -- about good B >1000 3 Example
3 10.5 Before cleaning (silicon wafer 1000 3000 contaminated with
metals) to to 3000 5000 Cleaning method, sheet-by-sheet cleaning
"Particle removal" 1/2/60; cleaning time, 30 sec; cleaning liquid
medium temperature, room temperature "Metal removal" 1/2/40;
cleaning time, 60 sec; cleaning liquid medium temperature,
80.degree. C.
[0106] Table 5 shows that the surfactant according to the invention
had distinctly good solubility and the cleaning liquid mediums
containing this surfactant in combination with the complexing agent
had a satisfactory particulate-contaminant-removing ability and
satisfactory metallic-contaminant-removing ability.
EXAMPLES 12 AND 13 COMPARATIVE EXAMPLE 6
[0107] Cleaning was conducted in the same manner as in Example 4,
except that use was made of the same APM 3 cleaning liquid medium
as in Example 4 or cleaning liquid mediums prepared by adding each
of the compounds shown in Table 6 to the APM 3, and that the
cleaning liquid medium temperature and cleaning time were regulated
to 50.degree. C. and 60 seconds, respectively. Those cleaning
liquid mediums each had a pH of about 10.5. The results obtained
are shown in Table 6. TABLE-US-00006 TABLE 6 Cleaning agent
ingredients Alkali Hydrogen pH of Surfactant (A) ingredient
peroxide (C) cleaning Particle- Structural Concentration (B)
Concentration liquid removing formula m n m/n (wt ppm) Kind (wt %)
medium Solubility ability Example
C.sub.12H.sub.25O--(C.sub.2H.sub.4O).sub.11H 12 11 1.1 100 ammonium
1 about good AAA 12 hydroxide 10.5 Example
C.sub.8H.sub.17O--(C.sub.2H.sub.4O).sub.8H 8 8 1.0 100 ammonium 1
about good AA 13 hydroxide 10.5 Comparative
C.sub.12H.sub.25O--(C.sub.2H.sub.4O).sub.7H 12 7 1.7 100 ammonium 1
about poor not Example hydroxide 10.5 conducted Cleaning method,
sheet-by-sheet cleaning; Kind of APM, APM 3; Cleaning temperature,
50.degree. C.; Cleaning time, 60 sec
[0108] Table 6 shows that the surfactants according to the
invention had distinctly good solubility and the cleaning liquid
mediums containing these surfactants had a satisfactory
particulate-contaminant-removing ability.
EXAMPLES 14 TO 24 AND COMPARATIVE EXAMPLES 7 TO 11
[0109] "Evaluation of Ability to Remove Fine Contaminant Particles
(.gtoreq.0.06 .mu.m)"
[0110] A 4-inch silicon wafer to which from 7,000 to 12,000
Si.sub.3N.sub.4 particles having a diameter of 0.06 .mu.m or larger
were adhered as a substrate was cleaned with the APM 1 cleaning
liquid medium or cleaning liquid mediums prepared by adding each of
the surfactants shown in Table 7 to the APM 1 by means of a
sheet-by-sheet cleaning apparatus to remove particles. This
cleaning was conducted under the conditions of a silicon wafer
rotational speed of 1,000 rpm, cleaning liquid medium feed rate of
1 l/min, cleaning time of 60 seconds, and liquid medium temperature
of 50.degree. C. Ultrasonic irradiation was used in combination
with the cleaning. Those cleaning liquid mediums each had a pH of
about 10.5.
[0111] With respect to silicon wafer analysis for particles present
thereon, a laser surface analyzer (LS-6600, manufactured by Hitachi
Engineering Co., Ltd.) was used to count the particles.
[0112] The number of the particles remaining on the surface of each
cleaned silicon wafer obtained through the cleaning was counted,
and the degree of contaminant-particle removal was determined
therefrom and evaluated in the following five grades.
[0113] Namely, the degrees of removal of 90% and higher are
indicated by removing ability AAA, those of from 70% to less than
90% are indicated by AA, those of from 50% to less than 70% are
indicated by A, those of from 30% to less than 50% are indicated by
B, and those less than 30% are indicated by C. The results obtained
are shown in Table 7.
[0114] "Evaluation of Solubility"
[0115] The solubility of the surfactant (A) in each cleaning liquid
medium was evaluated based on the following criteria. When a
cleaning liquid medium placed in a rectangular quartz vessel with a
capacity of about 4 l to a depth of about 10 cm had the same
clarity as the cleaning liquid medium to which the surfactant (A)
had not been added, then the solubility of the surfactant (A) in
this cleaning liquid medium was rated as good. When a cleaning
liquid medium thus placed in the vessel had no clarity, i.e., was
turbid, e.g., milk-white, then the solubility of the surfactant (A)
in this cleaning liquid medium was rated as poor. Also with respect
to the cleaning liquid mediums in which the surfactant (A) was in
an incompletely dissolved state, the solubility of the surfactant
(A) was rated as poor. The results obtained are shown in Table 7.
As stated under "Examples 4 to 10 and Comparative Examples 3 to 5",
the cleaning liquid mediums in which the solubility of the
surfactant was "poor" were not subjected to the evaluation of
particulate-contaminant-removing ability. TABLE-US-00007 TABLE 7
Cleaning agent ingredients Alkali Hydrogen pH of Surfactant (A)
ingredient peroxide (C) cleaning Particle- Structural Concentration
(B) Concentration liquid removing formula m n m/n (wt ppm) Kind (wt
%) medium Solubility ability Example
C.sub.8H.sub.17O(C.sub.2H.sub.4O).sub.20H 8 20 0.4 70 ammonium 1.4
about good A 14 hydroxide 10.5 Example
C.sub.12H.sub.25O(C.sub.2H.sub.4O).sub.11H 12 11 1.1 70 ammonium
1.4 about good AA 15 hydroxide 10.5 Example
C.sub.12H.sub.25O(C.sub.2H.sub.4O).sub.20H 12 20 0.6 70 ammonium
1.4 about good A 16 hydroxide 10.5 Example
C.sub.12H.sub.25O(C.sub.2H.sub.4O).sub.23H 12 23 0.5 70 ammonium
1.4 about good A 17 hydroxide 10.5 Example
C.sub.12H.sub.25O(C.sub.2H.sub.4O).sub.30H 12 30 0.4 70 ammonium
1.4 about good A 18 hydroxide 10.5 Example
C.sub.13H.sub.27O(C.sub.2H.sub.4O).sub.8.5H 13 8.5 1.5 70 ammonium
1.4 about good AA 19 hydroxide 10.5 Example
C.sub.16H.sub.33O(C.sub.2H.sub.4O).sub.15H 16 15 1.1 70 ammonium
1.4 about good AA 20 hydroxide 10.5 Example
C.sub.16H.sub.33O(C.sub.2H.sub.4O).sub.23H 16 23 0.7 70 ammonium
1.4 about good A 21 hydroxide 10.5 Example
C.sub.18H.sub.37O(C.sub.2H.sub.4O).sub.15H 18 15 1.2 70 ammonium
1.4 about good A 22 hydroxide 10.5 Example
C.sub.18H.sub.37O(C.sub.2H.sub.4O).sub.30H 18 30 0.6 70 ammonium
1.4 about good B 23 hydroxide 10.5 Example
C.sub.18H.sub.37O(C.sub.2H.sub.4O).sub.50H 18 50 0.4 70 ammonium
1.4 about good A 24 hydroxide 10.5 Comparative nil -- -- -- 0
ammonium 1.4 about -- C Example 7 hydroxide 10.5 Comparative
C.sub.8H.sub.17O(C.sub.2H.sub.4O).sub.4H 8 4 2.0 70 ammonium 1.4
about poor not Example 8 hydroxide 10.5 conducted Comparative
C.sub.13H.sub.27O(C.sub.2H.sub.4O).sub.5H 13 5 2.6 70 ammonium 1.4
about poor not Example 9 hydroxide 10.5 conducted Comparative
C.sub.16H.sub.33O(C.sub.2H.sub.4O).sub.8H 16 8 2.0 70 ammonium 1.4
about poor not Example hydroxide 10.5 conducted 10 Comparative
C.sub.18H.sub.37O(C.sub.2H.sub.4O).sub.11H 18 11 1.6 70 ammonium
1.4 about poor not Example hydroxide 10.5 conducted 11 Cleaning
method, sheet-by-sheet cleaning; Kind of APM, APM 1; Cleaning
temperature, 50.degree. C.; Cleaning time, 60 sec
[0116] Table 7 shows that the surfactants (A) according to a
constituent requirement of the invention had good solubility, and
the cleaning liquid mediums of the invention had a satisfactory
particulate-contaminant-removing ability.
EXAMPLES 25 AND 26 AND COMPARATIVE EXAMPLES 12 AND 13
[0117] A 6-inch silicon wafer to which from 4,000 to 5,000
SiO.sub.2 particles having a diameter of 0.06 .mu.m or larger were
adhered as a substrate was cleaned with the APM 1 cleaning liquid
medium or a cleaning liquid medium prepared by adding the
surfactant shown in Table 8 to the APM 1 by the dip cleaning method
to remove particles. The cleaning time and temperatures used are
shown in Table 8. Ultrasonic irradiation was used in combination
with the cleaning. For the ultrasonic irradiation was used HI MEGA
SONIC (600 W, 950 kHz), manufactured by Kaijo Corp. Those two
cleaning liquid mediums had a pH of about 10.5.
[0118] With respect to silicon wafer analysis for particles present
thereon, a laser surface analyzer (LS-6600, manufactured by Hitachi
Engineering Co., Ltd.) was used to count the particles. The degree
of particle removal (%) determined therefrom is shown in Table
8.
[0119] "Measurement of Etching Depth"
[0120] A silicon wafer piece having a thermal oxide film having a
thickness of 1,000 .ANG. was immersed in a cleaning liquid medium,
subsequently rinsed with running pure water for 5 minutes, and then
dried with N.sub.2 blowing. The thickness of the film of the test
piece was measured before and after the cleaning, and the etching
depth was calculated using the following equation. Etching depth
(nm)=[film thickness before cleaning (nm)]-[(film thickness after
cleaning (nm)]
[0121] For the film thickness measurement for the test piece, a
light interference type film thickness meter (NanoSpec L-6100,
manufactured by Nanometrics, Inc.) was used. The results obtained
are shown in Table 8. TABLE-US-00008 TABLE 8 Cleaning agent
ingredients Hydrogen Cleaning peroxide liquid Degree Kind
Surfactant (A) Alkali (C) pH of medium Clean- Etch- of of Concen-
ingredient Concen- cleaning temper- ing ing particle cleaning
Structural tration (B) tration liquid ature time depth removal
agent formula m n m/n (wt ppm) Kind (wt %) medium (.degree. C.)
(min) (nm) (%) Example APM 1
C.sub.12H.sub.25O--(C.sub.2H.sub.4O).sub.11H 12 11 1.1 33 ammonium
1.4 about 40 10 0.4 96 25 hydroxide 10.5 Example APM 1
C.sub.12H.sub.25O--(C.sub.2H.sub.4O).sub.11H 12 11 1.1 33 ammonium
1.4 about 50 10 0.7 97 26 hydroxide 10.5 Compar- APM 1 nil -- -- --
0 ammonium 1.4 about 50 10 0.7 91 ative hydroxide 10.5 Example 12
Compar APM 1 nil -- -- -- 0 ammonium 1.4 about 80 10 2.8 94 ative
hydroxide 10.5 Example 13 Cleaning method, sheet-by-sheet cleaning;
Kind of APM, APM 1
[0122] Table 8 shows that the cleaning liquid mediums of the
invention attained distinctly high degrees of removal of particles
having a diameter of 0.06 .mu.m or larger, which were not lower
than 94%, and the depths of etching caused by these were not larger
than 1 nm.
EXAMPLE 27 AND COMPARATIVE EXAMPLE 14
[0123] Cleaning was conducted in the same manner as in Example 12,
except that use was made of the APM 3 cleaning liquid medium or a
cleaning liquid medium prepared by adding the surfactant shown in
Table 9 to the APM 3. An etching depth measurement was made in the
same manner as in Example 25. The results obtained are shown in
Table 9. TABLE-US-00009 TABLE 9 Cleaning agent ingredients Hydrogen
Cleaning peroxide liquid Degree Kind Surfactant (A) Alkali (C) pH
of medium Clean- Etch of of Concen- ingredient Concen- cleaning
tempera- ing ing particle cleaning Structural tration (B) tration
liquid ture time depth removal agent formula m n m/n (wt ppm) Kind
(wt %) medium (.degree. C.) (min) (nm) (%) Example APM 3
C.sub.12H.sub.25O--(C.sub.2H.sub.4O).sub.11H 12 11 1.1 100 ammonium
1 about 50 1 0.07 94 27 hydroxide 10.5 Compar- APM 3 nil -- -- -- 0
ammonium 1 about 50 1 0.07 86 ative hydroxide 10.5 Example 14
Cleaning method, sheet-by-sheet cleaning; Kind of APM, APM 3
[0124] Table 9 shows that the cleaning liquid medium of the
invention attained a distinctly high degree of particle removal,
which was not lower than 94%.
[0125] As apparent from the results given above, the cleaning
liquid mediums of the invention are superior in surfactant
solubility and in the ability to remove particulate contaminants to
the conventional cleaning liquid mediums (Comparative Examples). Of
these cleaning liquid mediums, those containing a complexing agent
in combination with the surfactant are more preferred in that they
have the improved ability to remove metallic contaminants while
having the intact surfactant solubility and particle-removing
ability. Furthermore, the cleaning liquid mediums of the invention
are excellent cleaning liquid mediums which attain an etching depth
of 1 nm or smaller and a degree of particle removal of 94% or
higher with respect to the removal of fine particles having a
diameter of 0.06 .mu.m or larger.
[0126] With the cleaning liquid mediums of the invention,
particulate contaminants present on substrates to be cleaned, such
as silicon wafers, can be efficiently removed to a high degree in a
short time period. Consequently, these cleaning liquid mediums are
exceedingly useful when industrially used in methods of contaminant
removal in steps in the production of semiconductor devices,
display devices, or the like.
[0127] While the invention has been described in detail and with
reference to specific embodiments thereof, it will be apparent to
one skilled in the art that various changes and modifications can
be made therein without departing from the spirit and scope
thereof.
[0128] This application is based on Japanese patent application No.
2001-350947 filed on Nov. 16, 2001, the entire contents thereof
being hereby incorporated by reference.
* * * * *