U.S. patent application number 09/816340 was filed with the patent office on 2001-10-25 for aqueous hydroxylamine solution.
Invention is credited to Imai, Naoshi, Toguro, Kouzou.
Application Number | 20010034312 09/816340 |
Document ID | / |
Family ID | 18600146 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010034312 |
Kind Code |
A1 |
Imai, Naoshi ; et
al. |
October 25, 2001 |
Aqueous hydroxylamine solution
Abstract
An aqueous hydroxylamine solution containing hydroxylamine in an
amount of 30 wt. % or more, which contains iron in an amount of not
more than 10 ppb, metal components other than iron in an amount of
not more than 5 ppb for each metal component and
trans-1,2-diaminocyclohexane-N,N,N',N'-tetra- acetic acid in an
amount of 0.0005 to 0.5 wt. % is obtained by distillation of a
concentrated aqueous crude hydroxylamine solution using a
specifically surface treated distilling apparatus.
Inventors: |
Imai, Naoshi; (Gumma,
JP) ; Toguro, Kouzou; (Gumma, JP) |
Correspondence
Address: |
NIXON PEABODY, LLP
8180 GREENSBORO DRIVE
SUITE 800
MCLEAN
VA
22102
US
|
Family ID: |
18600146 |
Appl. No.: |
09/816340 |
Filed: |
March 26, 2001 |
Current U.S.
Class: |
510/175 |
Current CPC
Class: |
C01B 21/14 20130101;
C01B 21/1481 20130101; C23C 22/68 20130101; C01P 2006/80
20130101 |
Class at
Publication: |
510/175 |
International
Class: |
C11D 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 24, 2000 |
JP |
2000-083528 |
Claims
What is claimed is:
1. An aqueous hydroxylamine solution containing hydroxylamine in an
amount of not less than 30 weight %, which contains iron in an
amount of not more than 10 ppb, metal components other than iron in
an amount of not more than 5 ppb for each metal component and
trans-1,2-diaminocyclohexane- -N,N,N',N'-tetraacetic acid in an
amount of 0.0005 to 0.5 weight %.
2. The aqueous hydroxylamine solution of claim 1, wherein the
amount of iron is not more than 5 ppb.
3. The aqueous hydroxylamine solution of claim 2 claim 1, wherein
the amount of iron is not more than 3 ppb.
4. The aqueous hydroxylamine solution of claim 1, wherein each
amount for sodium and potassium is not more than 2 ppb.
5. The aqueous hydroxylamine solution of claim 1, wherein each
amount for sodium and potassium is not more than 1 ppb.
6. The aqueous hydroxylamine solution of claim 1, wherein the
amounts of metal components other than iron are not more than 2 ppb
for each.
7. A process for the preparation of the aqueous hydroxylamine
solution of claim 1, comprising the steps of: heating in a vessel
an aqueous crude hydroxylamine solution containing 40 to 60 weight
% of hydroxylamine and 15 to 200 ppb of iron, in the presence of
trans-1,2-diaminocyclohexane-N,- N,N',N'-tetraacetic acid in an
amount of 0.0005 to 0.5 weight % based on the weight of the crude
solution, to distill water off and to give a concentrated aqueous
hydroxylamine solution containing hydroxylamine in an amount of 70
to 95 weight %; and distilling the concentrated aqueous
hydroxylamine solution to give an aqueous hydroxylamine distillate
by means of a stainless steel-made distilling apparatus of which
inner surface has been previously treated with an aqueous
hydroxylamine salt solution.
8. The process of claim 7, wherein the distilling apparatus is
equipped with a device for keeping a distilled aqueous
hydroxylamine solution from contamination with the concentrated
solution which spatters in the vessel.
9. The process of claim 7, wherein the concentrated aqueous
hydroxylamine solution is distilled, while a portion of the
concentrated aqueous hydroxylamine solution is taken out from the
vessel.
10. The process of claim 9, wherein the concentrated aqueous
hydroxylamine solution taken out from the vessel is mixed with a
freshly supplied aqueous crude hydroxylamine solution to give an
aqueous mixture which is then supplied into the vessel.
11. The process of claim 10, wherein a portion of the concentrated
aqueous hydroxylamine solution taken out from the vessel is wasted
before the mixing.
12. The process of claim 7, wherein
trans-1,2-diaminocyclohexane-N,N,N',N'- -tetraacetic acid is
supplemented to the aqueous hydroxylamine distillate.
Description
FIELD OF THE INVENTION
[0001] This invention relates to a highly-concentrated and
highly-purified aqueous solution of free hydroxylamine (which is
not in the form of a salt). The invention particularly relates to a
highly-concentrated aqueous hydroxylamine solution containing
almost no metal components and having such high stability that the
solution is advantageously used for processing or washing
electronic devices.
BACKGROUND OF THE INVENTION
[0002] An aqueous hydroxylamine solution has been hitherto used,
for instance, as a processing solution or detergent for producing
electronic devices. In particular, a highly-concentrated and
highly-purified aqueous hydroxylamine solution containing almost no
impurities (particularly, metal components) has been recently
required, for example, for washing very small and highly-integrated
electronic devices such as semiconductor IC chips.
[0003] Hydroxylamine (NH.sub.2OH) is generally synthesized by a
known method. In the method, sodium bisulfite and sodium nitrite
are reacted in an aqueous phase to prepare an aqueous solution of
sodium hydroxylamine sulfonate, which is then hydrolyzed to obtain
an aqueous hydroxylamine sulfate solution. The obtained solution is
neutralized with sodium hydroxide to give an aqueous free
hydroxylamine solution.
[0004] Hydroxylamine normally takes the form of crystals at room
temperature, and its melting and boiling points are 33.degree. C.
and 57.degree. C. (at 20 mmHg), respectively. The crystals of
hydroxylamine are known to be explosive when heated, and an aqueous
hydroxylamine solution is also known to be so unstable that it is
liable to rapidly decompose. For this reason, an aqueous solution
of stable hydroxylamine salt is beforehand prepared, and the free
hydroxylamine is produced when it is used in industry. Since this
process is troublesome and inconvenient, it has been desired to
find out a stabilizing agent specifically effective for free
hydroxylamine. Examples of the stabilizing agents hitherto having
been proposed include 8-hydroxyquinoline (Japanese Patent
Provisional Publication No. 57-100908), 1,10-phenanthroline
(Japanese Patent Provisional Publication No. 58-69841), bipyridine
(Japanese Patent Provisional Publication No. 58-69842),
thiocarboxylic acids (Japanese Patent Provisional Publication No.
58-69843) and quinoline (Japanese Patent Provisional Publication
No. 58-69844). Further, WO 97/22549 and U.S. Pat. No. 5,783,161
teach that trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid
effectively stabilizes free hydroxylamine.
[0005] The already proposed stabilizing agents, however, are not
fully effective when used in a normal manner. In addition, a
prepared aqueous hydroxylamine solution generally contains
impurities such as metal components (e.g., iron, aluminum, alkali
metals such as sodium and potassium), which are originally
contained in the starting materials or introduced in the
preparation process.
[0006] In order to prepare a highly-purified aqueous free
hydroxylamine solution suitable for processing or washing
semiconductor devices, concentration and distillation by heating
are indispensable. However, these treatments are liable to cause
explosion, and hence it is very difficult to safely distill the
aqueous hydroxylamine solution (which is unstable and corrosive)
keeping its distillate from contamination with impurities.
SUMMARY OF THE INVENTION
[0007] The present invention provides a highly-concentrated and
highly-purified aqueous (free) hydroxylamine solution which
contains, in particular, almost no metal components such as iron.
The invention also provides a process for safely and easily
preparing the aqueous hydroxylamine solution.
[0008] The inventors already found a stabilizing agent by which an
aqueous free hydroxylamine solution is stabilized effectively
enough to safely concentrate and distill by heating, which is
trans-1,2-diaminocyclohexane- -N,N,N',N'-tetraacetic acid (CDTA).
The CDTA makes it easy to store and transport an aqueous free
hydroxylamine solution. Further, the CDTA makes it possible to
safely produce and supply a purified aqueous hydroxylamine solution
containing sodium and potassium in an amount of 30 to 100 ppb for
each and iron in an amount of 50 to 100 ppb. However, the purity of
this level is still not advantageous for treating electronic
devices. In order to further purify the aqueous hydroxylamine
solution, the solution must be further concentrated and distilled
by heating. Such severe distillation procedure is not easy, because
a distilling apparatus is easily corroded by hydroxylamine to
release new impurities.
[0009] The present inventors have further studied and finally
discovered that a highly-purified aqueous hydroxylamine solution
can be obtained by distilling an aqueous crude hydroxylamine
solution (hereinafter, referred to as "crude solution") in the
presence of the specific stabilizing agent
(trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid) using a
stainless steel-made distilling apparatus which preferably has
equipment (e.g., spatter separator) for keeping spatters of the
concentrated solution from contaminating the resulting solution and
which has an inside surface treated with an aqueous hydroxylamine
salt so that the surface may not be corroded to release impurities.
Thus prepared aqueous hydroxylamine solution is much more pure than
the crude solution, and therefore is suitable for the use in
washing semiconductor devices.
[0010] The invention resides in an aqueous hydroxylamine solution
containing hydroxylamine in an amount of not less than 30 weight %,
which contains iron in an amount of not more than 10 ppb, metal
components other than iron in an amount of not more than 5 ppb for
each metal component and
trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid in an
amount of 0.0005 to 0.5 weight %.
[0011] The invention further resides in a process for the
preparation of a highly purified aqueous hydroxylamine solution,
comprising the steps of:
[0012] heating in a vessel an aqueous crude hydroxylamine solution
containing 40 to 60 weight % of hydroxylamine and 15 to 200 ppb of
iron, in the presence of
trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid in an
amount of 0.0005 to 0.5 weight % based on the weight of the crude
solution, to distill water off and to give a concentrated aqueous
hydroxylamine solution containing hydroxylamine in an amount of 70
to 95 weight %; and
[0013] distilling the concentrated aqueous hydroxylamine solution
to give an aqueous hydroxylamine distillate by means of a stainless
steel-made distilling apparatus of which inner surface has been
previously treated with an aqueous hydroxylamine salt solution.
[0014] The preferred embodiments of the invention are as
follows.
[0015] (1) The aqueous hydroxylamine solution, wherein the amount
of iron is not more than 5 ppb (more preferably, not more than 3
ppb).
[0016] (2) The aqueous hydroxylamine solution, wherein the amounts
of sodium and potassium are not more than 2 ppb (more preferably,
not more than 1 ppb) for each.
[0017] (3) The aqueous hydroxylamine solution, wherein the amounts
of metal components other than iron are not more than 2 ppb (more
preferably, not more than 1 ppb) for each.
[0018] (4) The distilling apparatus is equipped with a device for
keeping a distilled aqueous hydroxylamine solution from
contamination with the concentrated solution which spatters in the
vessel.
[0019] (5) The concentrated aqueous hydroxylamine solution is
distilled, while a portion of the concentrated aqueous
hydroxylamine solution is taken out from the vessel.
[0020] (6) The concentrated aqueous hydroxylamine solution taken
out from the vessel is mixed with a freshly supplied aqueous crude
hydroxylamine solution to give an aqueous mixture which is then
supplied into the vessel.
[0021] (7) A portion of the concentrated aqueous hydroxylamine
solution taken out from the vessel is wasted before the mixing.
[0022] (8) Trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid
is supplemented to the aqueous hydroxylamine distillate.
BRIEF DESCRIPTION OF THE DRAWING
[0023] FIGURE is a flow sheet of a distilling apparatus
advantageously used for preparing a purified aqueous hydroxylamine
solution of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The process for preparing an aqueous hydroxylamine solution
of the invention is described below by referring to the attached
drawing.
[0025] The distilling apparatus shown in FIGURE is composed of a
material tank A for storing the starting material (i.e., crude
aqueous hydroxylamine solution), a circulating pump B which
continuously leads the starting material from the tank A to a
heater C and then to an evaporating can D through a transferring
line 1, a condenser E for cooling a purified hydroxylamine gas
separated from spatters of the material and led through a
gas-transferring line 3 connecting to the upper part of the
evaporating can D, a pressure-reducing line (vacuum pump) 5
connecting to the outlet line of the condenser E, and a product
tank F for storing the resultant purified aqueous hydroxylamine
solution which is condensed from the vapor containing hydroxylamine
gas and which is led through a condensed liquid-transferring line 4
connecting to the condenser E. The pressure-reducing line (vacuum
pump) 5 keeps the internal pressure of the apparatus (evaporating
can D, gas-transferring line 3, condenser E) at a predetermined
level. A circulating line 2 is connected to the lower part of the
evaporating can D, and a distillation residue of the concentrated
solution in the evaporating can D is sent back to the starting
material by the pump B through the line 2. A blow line 6 is
provided between the pump B and the heater C, and a portion of the
distillation residue is removed through the blow line 6 so as to
keep the content of impurities at an allowed level.
[0026] The evaporating can D (the main part of the distilling
apparatus) is equipped with a spatter separator (not shown) for
keeping spatters of the concentrated solution from entering the
resulting solution. The evaporating can D is made of stainless
steel, and its inside surface is beforehand treated with an aqueous
solution of hydroxylamine salt (e.g., hydroxylamine sulfate,
hydroxylamine phosphate, hydroxylamine chloride) so as not to be
corroded when it is kept into contact with corrosive hydroxylamine.
The anticorrosive treatment can be performed by heating the inside
surface at an atmospheric pressure in the presence of an aqueous
hydroxylamine solution salt (approx. 0.2 to 20 wt. %) at approx. 50
to 200.degree. C. for more than approx. 3 minutes.
[0027] The aqueous hydroxylamine solution of the invention can be
prepared using the distilling apparatus of FIGURE in the following
manner.
[0028] First, the aqueous crude hydroxylamine solution (starting
material) is supplied into the material tank A. The crude solution
can be prepared by the aforementioned known method. Generally, the
crude solution contains not small amounts of impurities of
non-volatile metal components such as iron, aluminum, sodium,
potassium and calcium. The contents of hydroxylamine and iron in
the starting material of the crude solution are in the ranges of 40
to 60 wt. % and 15 to 200 ppb, respectively. Prior to distillation,
trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (CDTA) is
added to the crude solution in an amount of 0.0005 to 0.5 wt. %
based on the weight of the solution. CDTA stabilizes the crude
solution to keep hydroxylamine from decomposing.
[0029] The circulating pump B continuously sends the starting
material (crude aqueous hydroxylamine solution) to the heater C
through the transferring line 1, and the solution is heated by the
heater C. The heated solution is then transferred to the
evaporating can D, in which the pressure is beforehand reduced by
the pressure-reducing line (vacuum pump) 5 and the transferred
hydroxylamine solution is concentrated and distill by heating. When
the solution is distilled under a reduced pressure, the liquid
temperature is preferably kept as low as possible. The distilling
conditions usually are in the range of 45 to 50.degree. C./12 to 17
mmHg. By the distillation under that conditions, the solution is
concentrated so that the content of hydroxylamine can become in the
range of 70 to 90 wt. % (particularly 78 to 90 wt. %). Spatters of
the solution splashing during the concentration are separated by
equipment such as a spatter separator.
[0030] The concentrated solution gives vapor containing
highly-purified hydroxylamine gas, in which impurities are
decreased by separating the spatters. The aqueous hydroxylamine gas
(distillate gas) is sent to the condenser E through the
gas-transferring line 3 connecting to the upper part of the
evaporating can D. Preferably, the inside surface of the apparatus
including the gas-transferring line 3, where the distillate runs,
is beforehand treated for making anticorrosive as described above
or covered with anticorrosive material (e.g., polypropylene,
polyethylene, polytetrafluoroethylene).
[0031] While the distillation is continuously performed, a residue
of the concentrated solution accumulates in the evaporating can D.
The residue contains impurities (metal components) in high
contents, but it also contains the stabilizing agent. During the
distillation, the concentrated solution is preferably controlled so
that the contents of the stabilizing agent and impurities
(particularly, iron) may be kept in the ranges of 0.0005 to 0.5 wt.
% and less than approx. 5 ppm, respectively, based on the amount of
the solution. For controlling the concentration of the solution,
the distillation is preferably carried out while the residue is
taken out. A portion of the residue is properly taken out through
the circulating line 2 (which connects to the lower part of the
evaporating can D) and the blow line 6, so as to keep hydroxylamine
from decomposing and further to keep the amount of accumulated
impurities at an allowed level. In order to effectively perform the
distillation, the residue is mixed with a freshly supplied aqueous
crude hydroxylamine solution, and the obtained mixture is again
concentrated by heating. A portion of the residue may be removed
before or after the residue is mixed with the freshly supplied
crude solution, and then the remaining mixture may be concentrated
by heating.
[0032] The highly-purified hydroxylamine gas is cooled and
condensed in the condenser E, and the produced aqueous solution is
introduced through the condensed liquid-transferring line 4 into
the product tank F, in which the resulting solution is stored. The
stabilizing agent,
trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (CDTA) is
preferably supplemented to thus obtained solution.
[0033] The prepared highly-concentrated and highly-purified aqueous
hydroxylamine solution of the invention contains hydroxylamine in
an amount of not less than 30 wt. %. The content of iron is not
more than 10 ppb, preferably not more than 5 ppb, and more
preferably not more than 3 ppb. The contents of metal components
other than iron are not more than 5 ppb, preferably not more than 2
ppb, and more preferably not more than 1 ppb, for each component.
In particular, each content of sodium and potassium is preferably
not more than 2 ppb, and more preferably not more than 1 ppb. The
resulting purified aqueous hydroxylamine solution of the invention
contains the stabilizing agent of trans-1,2-diaminocyclohexane--
N,N,N',N'-tetraacetic acid in an amount of 0.0005 to 0.5 wt. %.
[0034] The present invention is further described with the
following non-restrictive working examples.
[EXAMPLE 1]
[0035] An aqueous hydroxylamine solution according to the invention
was prepared from the crude solution by means of the distilling
apparatus shown in FIGURE. The conditions for the preparation
process were as follows.
[0036] (1) A spatter separator was provided to the evaporating can
to separate spatters of the solution splashing during the
concentration. The evaporating can and the gas-transferring line
(through which the distillate gas runs) were made of stainless
steel, and their inside surfaces were beforehand treated with a
hydroxylamine salt. For the anticorrosive treatment, the inside
surfaces were heated at approx. 100.degree. C. at atmospheric
pressure for 8 hours in the presence of an aqueous
hydroxylamine-sulfate solution (20 wt. %).
[0037] (2) The starting material was an aqueous crude hydroxylamine
solution of approx. 50 wt. % containing
trans-1,2-diaminocyclohexane-N,N,- N',N'-tetraacetic acid
(stabilizing agent) in an amount of 0.005 wt. % based on the weight
of the solution.
[0038] (3) Into the distilling apparatus, the starting material was
continuously supplied from the material tank A at a rate of 250
L/hour. The resulting highly-purified aqueous hydroxylamine
solution was produced at a rate of 230 L/hour, while the
hydroxylamine solution containing a relatively high amount of
impurities was taken out through the blow line at a rate of 20
L/hour.
[0039] (4) The conditions for distillation were controlled so that
the liquid temperature in the evaporating can would be kept in the
range of 45 to 50.degree. C./12-17 mmHg.
[0040] Thus, an aqueous hydroxylamine solution of the invention
containing hydroxylamine in the amount of approx. 50 wt. % was
prepared. The contents of metal components in the prepared solution
are set forth in Table 1. In Table 2, the contents of metal
components in the starting material (i.e., aqueous crude
hydroxylamine solution) are also shown.
1TABLE 1 (1) aqueous hydroxylamine solution of the invention Metal
components in the solution (ppb) Al Ca Cr Cu Fe Pb Mg Mn Ni K Na Zn
0.6 0.2 0.9 0.2 1-3.1 <0.3 0.05 0.03 0.2 <0.3 <0.1 0.6
[0041] (2) crude aqueous hydroxylamine solution (starting
material)
2TABLE 2 Metal components in the solution (ppb) Al Ca Cr Cu Fe Pb
Mg Mn Ni K Na Zn 65 5 8 <1 42 <1 3 <1 4 32 23 <1
[0042] The results in Table 1 indicate that the highly-purified
aqueous hydroxylamine solution of the invention contains metal
components (particularly iron, aluminum, and alkali metals such as
sodium and potassium) in remarkably reduced amounts, as compared
with the starting aqueous crude hydroxylamine solution.
* * * * *