U.S. patent application number 10/497158 was filed with the patent office on 2005-01-13 for apparatus for generating f2 gas method for generating f2 gas and f2 gas.
This patent application is currently assigned to Toyo Tanso Co., Ltd.. Invention is credited to Hiraiwa, Jiro, Tada, Yoshitomi, Takebayashi, Hitoshi, Tojo, Tetsuro.
Application Number | 20050006248 10/497158 |
Document ID | / |
Family ID | 19187509 |
Filed Date | 2005-01-13 |
United States Patent
Application |
20050006248 |
Kind Code |
A1 |
Tojo, Tetsuro ; et
al. |
January 13, 2005 |
Apparatus for generating f2 gas method for generating f2 gas and f2
gas
Abstract
An F.sub.2 gas generating apparatus for generating a high purity
F.sub.2 gas by subjecting an electrolytic bath made of KF.2HF to
electrolysis is characterized by comprising a preparing system for
preparing KF.2HF from KF or KF.HF, an HF supplying system for
supplying HF into the electrolytic bath and the preparing system,
and an F.sub.2 gas generating system for generating the F.sub.2 gas
by subjecting KF.2HF prepared by the preparing system to
electrolysis.
Inventors: |
Tojo, Tetsuro; (Kagawa,
JP) ; Hiraiwa, Jiro; (Kagawa, JP) ;
Takebayashi, Hitoshi; (Kagawa, JP) ; Tada,
Yoshitomi; (Kagawa, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Toyo Tanso Co., Ltd.
Osaka
JP
555-0011
|
Family ID: |
19187509 |
Appl. No.: |
10/497158 |
Filed: |
June 7, 2004 |
PCT Filed: |
December 9, 2002 |
PCT NO: |
PCT/JP02/12868 |
Current U.S.
Class: |
205/619 |
Current CPC
Class: |
C25B 15/00 20130101;
C25B 1/245 20130101 |
Class at
Publication: |
205/619 |
International
Class: |
C25B 001/24 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 2001 |
JP |
2001-382722 |
Claims
1. An F.sub.2 gas generating apparatus for generating an F.sub.2
gas by subjecting an electrolytic bath comprising KF.2HF to
electrolysis, being characterized by comprising: a preparing system
for preparing KF.2HF from KF or KF.HF; an HF supplying system for
supplying HF into the electrolytic bath and the preparing system;
and an F.sub.2 gas generating system for generating the F.sub.2 gas
by subjecting KF.2HF prepared by the preparing system to
electrolysis.
2. The F.sub.2 gas generating apparatus as set forth in claim 1,
being characterized in that a moisture removing device for removing
moisture in said KF or KF.HF is attached to the preparing
system.
3. The F.sub.2 gas generating apparatus as set forth in claim 1,
wherein an oxygen concentration in the thus-generated F.sub.2 gas
is 2% or less.
4. An F.sub.2 generating apparatus for generating an F.sub.2 gas by
subjecting an electrolytic bath comprising KF.2HF to electrolysis,
comprising: a preparing system for preparing KF.2HF from KF or
KF.HF; an HF supplying system for supplying HF into the
electrolytic bath and the preparing system; and an F.sub.2 gas
generating system for generating the F.sub.2 gas by subjecting
KF.2HF prepared by the preparing system to electrolysis, being
characterized by being provided with a moisture controlling device
for adjusting moisture in an atmosphere outside each of the
preparing system, the HF supplying system, and the F.sub.2 gas
generating system or all the systems as a whole.
5. The F.sub.2 gas generating apparatus as set forth in claim 4,
wherein the moisture controlling device is a box which contains
each of the systems or all the systems as a whole and is capable of
controlling an atmosphere inside the box.
6. An F.sub.2 gas generating method for generating an F.sub.2 gas
by subjecting an electrolytic bath comprising KF.2HF to
electrolysis, comprising the steps of: heat-deaerating KF or KF.HF
for a predetermined period of time in an atmosphere of vacuum or an
inert gas in a preparing system, for preparing KF.2HF from said KF
or KF.HF, which is attached with a moisture removing device for
removing moisture in said KF or KF.HF; cooling said KF or KF.HF to
room temperature in an atmosphere of vacuum or the inert gas in the
preparing system; supplying HF changed into a vapor phase from an
HF supplying system into said preparing system; allowing said KF or
KF.HF, and said HF to react with each other in the preparing system
to generate KF.2HF; supplying the thus-generated KF.2HF into an
electrolytic cell in an F.sub.2 gas generating system; and
Subjecting said KF.2HF to electrolysis to generate an F.sub.2 gas
having a low oxygen concentration.
7. The F.sub.2 gas generating method as set forth in claim 6,
wherein, in the preparing system, said KF or KF.HF is heated at
from 200.degree. C. to 300.degree. C. to remove adsorbed water or
crystallization water of said KF or KF.HF therefrom.
8. An F.sub.2 gas generated by a method comprising the steps of:
heat-deaerating KF or KF.HF for a predetermined period of time in
an atmosphere of vacuum or an inert gas in a preparing system, for
preparing KF.2HF from KF or KF.HF, which is attached with a
moisture removing device for removing moisture in said KF or KF.HF;
cooling said KF or KF.HF to room temperature in an atmosphere of
vacuum or the inert gas in the preparing system; supplying HF
changed into a vapor phase from an HF supplying system into said
preparing system; allowing said KF or KF-HF, and said HF to react
with each other in the preparing system to generate KF.2HF;
supplying the thus-generated KF.2HF into an electrolytic cell in an
F.sub.2 gas generating system; and Subjecting said KF.2HF to
electrolysis.
9. The F.sub.2 gas as set forth in claim 8, wherein an oxygen
concentration is 2% or less.
Description
TECHNICAL FIELD
[0001] The present invention relates to an apparatus for generating
F.sub.2 gas, a method for generating the F.sub.2 gas, and F.sub.2
gas. Particularly, the present invention relates to an F.sub.2 gas
generating apparatus for generating high purity F.sub.2 gas, in
which a quantity of an impurity is extremely small, for use in a
manufacturing process of semiconductor or the like, method for
generating F.sub.2 gas, and F.sub.2 gas.
BACKGROUND ART
[0002] F.sub.2 gas has been used as a primary gas indispensably,
for example, in a field of semiconductor manufacturing. Although
the F.sub.2 gas may sometimes be used alone, nitrogen trifluoride
gas (hereinafter also referred to as "NF.sub.3 gas") which has been
synthesized based on the F.sub.2 gas has been recently used as a
cleaning gas or a dry etching gas for semiconductor. Further, neon
fluoride gas (hereinafter also referred to as "NeF gas"), argon
fluoride gas (hereinafter also referred to as "ArF gas"), krypton
fluoride gas (hereinafter also referred to as "KrF gas") and the
like are excimer laser oscillation gases used for patterning of a
semiconductor integrated circuit. Mixed gas of rare gas and the
F.sub.2 gas is in many cases used as a raw material of the excimer
laser oscillation gas.
[0003] The F.sub.2 gas is generated by performing electrolysis by
using carbon as an anode and nickel as a cathode in an electrolytic
cell containing a bath comprising a predetermined quantity of
KF.HF. Ordinarily, the KF.HF contained in the electrolytic cell is
used in a form of KF.2HF to be prepared by further appropriately
supplying HF into a predetermined quantity of an initially loaded
HF. In a case in which KF.2HF is insufficient, KF.HF is loaded and,
then, HF is once again added thereto to prepare a predetermined
quantity of the bath.
[0004] KF, as a component of the bath, is high in hygroscopicity
and ordinarily comes to contain moisture at the time of
constructing the bath. We have previously made an application (WO
01/77412A1) having a content regarding an apparatus for generating
a high purity fluorine gas having a small quantity of
impurities.
[0005] However, an F.sub.2 gas to be generated in a manner as
described above is such a type of F.sub.2 gas as an initially
generated F.sub.2 gas contains oxygen by from 45% to 55% therein.
The F.sub.2 gas to be generated and water in an electrolytic bath
are reacted with each other in accordance with the formula (1)
described below, thereby ordinarily reducing a quantity of oxygen
contained in the F.sub.2 gas. Nevertheless, it is difficult to
bring the quantity thereof to 3000 ppm or less.
2F.sub.2+H.sub.2O.fwdarw.F.sub.2O+2HF (1)
[0006] The high purity F.sub.2 gas is required as the
above-described excimer laser oscillation gas or for performing a
surface treatment on a stepper lens (CaF.sub.2 single crystal) of
the excimer laser. An oxygen concentration to be contained in the
F.sub.2 gas is required to be 1000 ppm or less as the excimer laser
oscillation gas in the former case and 500 ppm or less as a gas for
such surface processing of the stepper lens (CaF.sub.2 single
crystal) of the excimer laser in the latter case.
[0007] An object according to the invention is to provide an
F.sub.2 gas generating apparatus which can consistently generates a
high purity F.sub.2 gas in which a quantity of oxygen to be
contained is extremely small amount, an F.sub.2 gas generating
method and the high purity F.sub.2 gas.
DISCLOSURE OF THE INVENTION
[0008] To solve the above-described problems, the present invention
provides an F.sub.2 gas generating apparatus for generating an
F.sub.2 gas by subjecting an electrolytic bath comprising KF.2HF to
electrolysis, being characterized by comprising:
[0009] a preparing system for preparing KF.2HF from KF or
KF.HF;
[0010] an HF supplying system for supplying HF into the
electrolytic bath and the preparing system; and
[0011] an F.sub.2 gas generating system for generating the F.sub.2
gas by subjecting KF.2HF prepared by the preparing system to
electrolysis.
[0012] After KF.2HF is prepared from KF or KF.HF in a closed
preparing system, the thus-prepared KF.2HF is loaded in an
electrolytic cell connected with the preparing system in a closed
space. Accordingly, KF.2HF loaded in the electrolytic cell is
allowed to be an electrolytic bath without absorbing moisture,
namely, having a small oxygen content. By this, a quantity of
oxygen to be contained in the F.sub.2 gas to be obtained by
subjecting this electrolytic bath to electrolysis is allowed to be
small from an initial stage of generation.
[0013] Further, the F.sub.2 gas generating apparatus according to
the invention is characterized in that a moisture removing device
for removing moisture in the KF or KF-HF is attached to the
preparing system.
[0014] At the time of preparing KF.2HF from KF or KF.HF, a quantity
of oxygen can surely be reduced.
[0015] Further, the F.sub.2 gas generating apparatus according to
the invention is an F.sub.2 gas generating apparatus in which an
oxygen concentration in the thus-generated F.sub.2 gas is 2% or
less.
[0016] The quantity of oxygen in the F.sub.2 gas is reduced to be
2% or less, preferably 0.2% or less (2000 ppm or less) and more
preferably 0.02% or less (200 ppm or less). Accordingly, the
F.sub.2 gas can be used as an excimer laser oscillating gas or as a
gas for surface treatment of a stepper lens (CaF.sub.2 single
crystal) of an excimer laser.
[0017] Further, the F.sub.2 gas generating apparatus according to
the invention is an F.sub.2 gas generating apparatus for generating
an F.sub.2 gas by subjecting an electrolytic bath comprising KF.2HF
to electrolysis, comprising:
[0018] a preparing system for preparing KF.2HF from KF or
KF.HF;
[0019] an HF supplying system for supplying HF into the
electrolytic bath and the preparing system; and
[0020] an F.sub.2 gas generating system for generating the F.sub.2
gas by subjecting KF.2HF prepared by the preparing system to
electrolysis, being characterized by being provided with a moisture
controlling device for adjusting moisture in an atmosphere outside
each of the preparing system, the HF supplying system, and the
F.sub.2 gas generating system or all the systems as a whole.
[0021] Since the moisture controlling device controlling the
moisture in the atmosphere outside each of the preparing system,
the HF supplying system and the F.sub.2 gas generating systems or
all the systems as a whole is provided, contamination of oxygen can
surely be controlled.
[0022] Further, the F.sub.2 gas generating apparatus according to
the invention is an F.sub.2 gas generating apparatus in which the
moisture controlling device is a box which contains each of the
systems or all the systems as a whole and is capable of controlling
an atmosphere inside the box.
[0023] Since the moisture controlling device is a box capable of
controlling the atmosphere, adjustment of atmosphere moisture of
each of the systems or all the systems as a whole can easily be
performed. Accordingly, contamination of oxygen can surely be
controlled.
[0024] Further, an F.sub.2 gas generating method according to the
invention is an F.sub.2 gas generating method for generating an
F.sub.2 gas by subjecting an electrolytic bath comprising KF.2HF to
electrolysis, comprising the steps of:
[0025] heat-deaerating KF or KF.HF for a predetermined period of
time in an atmosphere of vacuum or an inert gas in a preparing
system, for preparing KF.2HF from the KF or KF.HF, which is
attached with a moisture removing device for removing moisture in
the KF or KF-HF;
[0026] cooling the KF or KF.HF to room temperature in an atmosphere
of vacuum or the inert gas in the preparing system;
[0027] supplying HF changed into a vapor phase from an HF supplying
system into the preparing system;
[0028] allowing the KF or KF.HF, and the HF to react with each
other in the preparing system to generate KF.2HF; supplying the
thus-generated KF.2HF into an electrolytic cell in an F.sub.2 gas
generating system; and
[0029] subjecting the KF.2HF to electrolysis to generate an F.sub.2
gas having a low oxygen concentration.
[0030] By providing such arrangement, it becomes possible to allow
the quantity of oxygen in the F.sub.2 gas generated to be small
amount. As a result, the F.sub.2 gas is allowed to be used as the
excimer laser oscillating gas or as a gas for surface processing of
the stepper lens (CaF.sub.2 single crystal) of the excimer
laser.
[0031] Further, the F.sub.2 gas generating method according to the
invention is an F.sub.2 gas generating method in which, in the
preparing system, the KF or KF.HF is heated at from 200.degree. C.
to 300.degree. C. to remove adsorbed water or crystallization water
of the KF or KF.HF therefrom.
[0032] Accordingly, the moisture in KF or KF.HF can surely be
removed. To this end, it becomes possible to remove oxygen in the
moisture whereupon the oxygen concentration in the F.sub.2 gas to
be generated can surely be reduced from an initial stage of F.sub.2
gas generation.
[0033] Further, an F.sub.2 gas according to the invention is an
F.sub.2 gas generated by a method comprising the steps of:
[0034] heat-deaerating KF or KF-HF for a predetermined period of
time in an atmosphere of vacuum or an inert gas in a preparing
system, for preparing KF.2HF from KF or KF.HF, which is attached
with a moisture removing device for removing moisture in the KF or
KF.HF;
[0035] cooling the KF or KF.HF to room temperature in an atmosphere
of vacuum or the inert gas in the preparing system;
[0036] supplying HF changed into a vapor phase from an HF supplying
system into the preparing system;
[0037] allowing the KF or KF.HF, and the HF to react with each
other in the preparing system to generate KF.2HF;
[0038] supplying the thus-generated KF.2HF into an electrolytic
cell in an F.sub.2 gas generating system; and
[0039] subjecting the KF.2HF to electrolysis. Therefore, since the
F.sub.2 gas is a high purity F.sub.2 gas which is extremely low in
the oxygen concentration, it can be used as various types of
primary gases for a semiconductor manufacture.
[0040] Further, the F.sub.2 gas according to the invention is an
F.sub.2 gas in which an oxygen concentration is 2% or less.
[0041] The oxygen concentration is reduced to be preferably 0.2% or
less (2000 ppm or less) and more preferably 0.02% or less (200 ppm
or less). To this end, The F.sub.2 gas can be-used as the excimer
laser oscillating gas or as the gas for the surface processing of
the stepper lens (CaF.sub.2 single crystal) of the excimer
laser.
BRIEF DESCRIPTION OF THE DRAWINGS
[0042] FIG. 1 is a schematic view of a fluorine gas generating
apparatus according to the present invention.
[0043] FIG. 2 is a chart showing a relationship among quantities of
electricity in cases of Example 1, Comparative Examples 1 and 3,
and a quantity of O.sub.2 in F.sub.2 gas.
BEST MODE FOR CARRYING OUT THE INVENTION
[0044] Hereinafter, an example of embodiments according to the
present invention will be described with reference to FIG. 1.
[0045] An F.sub.2 gas generating apparatus G according to the
present embodiment, which generates a high purity F.sub.2 gas by
subjecting an electrolytic bath 24 comprising KF.2HF to
electrolysis, comprises a preparing system A which prepares KF.2HF
from KF or KF.HF, an HF supplying system B which supplies HF to the
electrolytic bath 24 and the preparing system A, and an F.sub.2 gas
generating system C which generates an F.sub.2 gas by subjecting
KF.2HF which has been prepared by the preparing system A to
electrolysis.
[0046] In FIG. 1, the preparing system A which prepares KF.2HF from
KF or KF.HF comprises a KF.2HF preparing device 7 comprising a
vessel 7a made of Ni which contains KF 10, and an upper cover 7b
which hermetically seals the vessel 7a, a heater 9 which covers the
vessel 7a of the KF.2HF preparing device 7 and heats KF 10 inside
the vessel 7a, a cooling water pipe 8 for use in cooling, a vacuum
piping 2, provided in the upper cover 7b, which is connected with a
vacuum-exhausting system D, an inert gas purging piping 3, and an
HF supplying and a KF.2HF sending-out piping 1 which is inserted in
KF 10 and connected to both the HF supplying system B and the
F.sub.2 gas generating system C.
[0047] In the HF supplying system B which supplies HF to the
preparing system A, an HF cylinder 11 placed on a load cell 12 is
arranged in a box 13, which is connected to an acrylic scrubber
(not shown). A surface of the HF cylinder 11 is covered by a heater
14 to maintain an interior of the HF cylinder 11 at a predetermined
temperature. Further, a quantity of gas inside the HF cylinder 11
is measured by a load cell 12 to measure a quantity of an HF gas to
be supplied to both the preparing system A and the F.sub.2 gas
generating system C. The HF cylinder 11 is connected with the
preparing system A via the HF sending-out piping 5.
[0048] The F.sub.2 gas generating system C comprises, as primary
members, an electrolytic bath 24 comprising a KF.2HF mixed molten
salt, an electrolytic cell 20 which contains the electrolytic bath
24, both an anode 22 and a cathode 23 which electrolyze the
electrolytic bath 24.
[0049] The electrolytic cell 20 is integrally formed of a metal,
such as Ni, MONEL.RTM., pure iron, and stainless steel. The
electrolytic cell 20 is separated into an anode chamber 28 and a
cathode chamber 29 by a partition wall 27 comprising Ni or
MONEL.RTM.. The anode 22 comprising a low polarized carbon, and the
cathode 23 comprising Ni, or Fe are disposed in the anode chamber
28 and the cathode chamber 29, respectively. A discharge port 25
for the F.sub.2 gas to be generated from the anode chamber 28 and
the cathode chamber 29 and a discharge port 26 for an H.sub.2 gas
to be generated from the cathode chamber 7 are disposed in the
upper cover 30 of the electrolytic cell 20. Further, the
electrolytic cell 20 is provided with a heater 31 for heating an
interior of the electrolytic cell 20 whereupon a heat insulating
material (not shown) is provided around the heater 12. The heater
12 is not limited to any particular form but any forms, including a
ribbon-type heater, a nichrome wire and the like are permissible.
Preferably, the heater 12 is allowed to be in form such that it
covers a whole circumference of the electrolytic cell 2.
[0050] The vacuum-exhausting system D is constructed by molecular
sieves 16 and a vacuum pump 17 and sucks moisture which is desorbed
from KF 10 when KF 10 contained in the preparing system A is heated
by a heater 9.
[0051] Next, an operation of the F.sub.2 gas generating apparatus G
will be explained.
[0052] After the preparing system A is subjected to thermal
processing at from 250.degree. C. to 300.degree. C. by the heater
9, a predetermined quantity of KF 10 is loaded in the vessel 7a.
The preparing system A thus loaded with KF is once again heated at
from 250.degree. C. to 300.degree. C. either in vacuum or while
being purged with an ultra-high purity inert gas and left to stand
for from 24 hours to 48 hours to allow KF 10 therein to be dried.
On this occasion, an interior of the vessel 7b is exhausted by the
vacuum-exhausting system D in a state in which a vacuum piping
valve 2a is opened and a valve 3a and a valve 4b are closed. By
subjecting KF 10 to such heating processing for from 24 hours to 48
hours at from 250.degree. C. to 300.degree. C. while being purged
by the ultra-high purity inert gas in a manner as described above,
adsorbed water and crystallization water in KF 10 can be desorbed
therefrom.
[0053] When thermogravimetry (hereinafter also referred to as "TG"
in short) and differential thermal analysis (hereinafter also
referred to as "DTA" in short) were performed, endothermic peaks
were observed at 43.4.degree. C., 64.4.degree. C., 90.8.degree. C.
and 151.6.degree. C. The endothermic peaks at 43.4.degree. C.,
64.4.degree. C., and 90.8.degree. C. thereamong are attributable to
desorption of adsorbed water while the endothermic peak at
151.6.degree. C. is attributable to desorption of crystallization
water. It is considered that the adsorbed water of KF as a starting
material can easily be decomposed by a reaction represented by the
formula (1). On the other hand, since not only the crystallization
water corresponding to the endothermic peak which appears at
151.6.degree. C. of the DTA is strong in an interaction with KF,
but also HF contained in the electrolytic bath as a major component
forms a network by hydrogen bonds, it is considered that, when the
crystallization water becomes extremely small in quantity, it
becomes hardly diffused, thereby allowing it difficult to be
removed. Therefore, as described above, by subjecting KF to thermal
processing such that it is once again heated at from 250.degree. C.
to 300.degree. C. while being purged by the ultra-high purity inert
gas for from 24 hours to 48 hours and preferably for from 10 hours
to 30 hours, the crystallization water became capable of being
desorbed.
[0054] Thereafter, the resultant KF is cooled to room temperature,
the valve 2a is closed, and the valve 4b and the valve 3a are
opened. On this occasion, an ultra-purity inert gas piping 4 is
previously heated by a line heater 15 to be at from 30.degree. C.
to 35.degree. C. Then, the HF gas cylinder 11 is heated by a heater
14 to gasify HF and, when a valve 5 is opened, HF is gradually
introduced into KF 10 in the preparing system A. At such
introduction, KF 10 and HF are vigorously reacted with each other
to generate heat whereupon water is allowed to flow in a pipe 8 for
cooling water in order to cool the KF.2HF adjusting device 7 and
prevent the temperature thereof from being 100.degree. C. or more.
This is performed because, when the temperature exceeds 100.degree.
C. and reaches 200.degree. C., a vigorous bumping of HF is
generated to exhibit a state like an explosion.
[0055] In a manner as described above, HF is introduced into the
preparing system A and, when a molar ratio of HF against KF 10
becomes higher than that of KF.HF, a supply speed of HF can be
elevated. Then, after it is confirmed by a load cell 12 in the HF
supplying system B that a predetermined quantity of HF was supplied
into the preparing system A, a valve 5a is closed and, at the same
time, the valve 4a is opened to allow the high purity inert gas to
be introduced through a piping 1 and exhausted through the inert
gas purging piping 3. This is performed to prevent possible
flow-back into the piping 1 and solidification therein of KF.2HF
which has been prepared from KF 10 to be caused by allowing HF in
the piping 1 to be rapidly absorbed in KF.2HF 10.
[0056] Then, after an interior of the preparing system A is purged
by the inert gas for an appropriate duration of time, the valve 4b
is closed. Subsequently, the inert gas is supplied through the
inert gas purging piping 3. At the same time, a valve 18 and valve
19 are opened. The preparing system A sends out KF.2HF thus
prepared therein into the electrolytic cell 20 in the F.sub.2 gas
generating system C through the piping 1 by a gas pressure of the
inert gas to be introduced through the inert gas purging piping 3.
On this occasion, the electrolytic cell 20 has previously been
subjected to thermal processing at from 250.degree. C. to
300.degree. C. to allow the adsorbed water and the like to be
desorbed.
[0057] In such a manner as described above, the F.sub.2 gas
generating apparatus according to the invention can supply high
purity KF.2HF which is small amount in a moisture adsorption
quantity into the electrolytic cell in the F.sub.2 gas generating
apparatus without allowing high purity KF.2HF to contact with air
to construct a high purity electrolytic bath, that is, KF.2HF bath
inside the electrolytic cell. In such a manner as described above,
an oxygen concentration in the electrolytic bath is extremely
reduced.
[0058] Further, the preparing system A, the HF supplying system B,
and the F.sub.2 gas generating system C can be contained in boxes
respectively in which atmospheres thereof can be controlled. In
this manner, moistures in the atmospheres outside respective
systems can be adjusted, and thereby oxygen to be incorporated in
respective systems can be controlled. Alternatively, all of the
systems, that is, the F.sub.2 gas generating apparatus G, can be
contained in one box. Furthermore, by placing all of the systems in
a clean room, same effect as that to be obtained by placing the
system in the box in which the atmosphere can be controlled can be
obtained. As mentioned above, by controlling such contamination of
oxygen, it becomes possible to more surely reduce the oxygen
concentration in the F.sub.2 gas to be generated.
[0059] Still further, the F.sub.2 gas generating apparatus and the
F.sub.2 gas generating method according to the invention are not
limited to the aforementioned embodiments.
EXAMPLES
[0060] Hereinafter, the F.sub.2 gas generating apparatus according
to the invention will specifically be explained with reference to
Examples.
Example 1
[0061] In an F.sub.2 gas generating apparatus G as shown in FIG. 1,
after a preparing system A was previously subjected to thermal
processing at from 250.degree. C. to 300.degree. C. by a heater 9,
KF 10 was loaded in a vessel 7a. Then, the preparing system A was
once again subjected to thermal processing at from 250.degree. C.
to 300.degree. C., while being purged by a high purity N.sub.2 gas
having a purity of 99.9999%, and left to stand for from 24 hours to
48 hours to allow KF 10 to be dried. Thereafter, the system A is
cooled to room temperature and, then, HF was introduced into KF 10
in the preparing system A. On this occasion, water was allowed to
flow in a cooling water pipe 8 for cooling a KF.2HF adjusting
device 7 to be 100.degree. C. or less. Next, after it was confirmed
by a load cell 12 in an HF supplying system B that a predetermined
quantity of HF was supplied in the preparing system A, an interior
of the preparing system A was purged by a high purity N.sub.2 gas
for an appropriate duration of time and, then, a high purity
N.sub.2 gas was supplied therein and, thereafter, such KF.2HF
prepared was sent out into an electrolytic cell 20 in a F.sub.2 gas
generating system C through piping 1 to construct an electrolytic
bath having a bath volume of 7 1. Subsequently, in the F.sub.2 gas
generating system C, a constant current electrolysis was performed
at an applied current density of 10 A/dm.sup.2 while using a carbon
electrode and a Ni electrode as an anode and a cathode,
respectively. Then, when a quantity of electricity reached about
100 Ahr, a quantity of O.sub.2 in such F.sub.2 gas generated was
measured by gas chromatography, thereby finding it to be about 650
ppm.
Example 2
[0062] A constant current electrolysis was performed at an applied
current density of 15 A/dm.sup.2 using KF.2HF similar to that in
Example 1 as an electrolytic bath while using a carbon electrode as
an anode and a Ni electrode as a cathode in an F.sub.2 gas
generating system C. Then, when a quantity of electricity reached
about 100 Ahr, a quantity of O.sub.2 in such F.sub.2 gas generated
was measured by gas chromatography, thereby finding it to be about
450 ppm.
Example 3
[0063] A constant current electrolysis was performed at an applied
current density of 2 A/dm using KF.2HF similar to that in Example 1
as an electrolytic bath, while using a carbon electrode as an anode
and a Ni electrode as a cathode in an F.sub.2 gas generating system
C. Then, when a quantity of electricity reached about 100 Ahr, a
quantity of O.sub.2 in such F.sub.2 gas generated was measured by
gas chromatography, thereby finding it to be about 950 ppm.
Example 4
[0064] A constant current electrolysis was performed at an applied
current density of 20 A/dm.sup.2 using KF.2HF similar to that in
Example 1 as an electrolytic bath, while using a carbon electrode
as an anode and a Ni electrode as a cathode in an F.sub.2 gas
generating system C which was contained in a box (not shown),
namely, a moisture controlling device, to control moisture inside
the box to be 40%. Then, when a quantity of electricity reached
about 100 Ahr, a quantity of O.sub.2 in such F.sub.2 gas generated
was measured by gas chromatography, thereby finding it to be about
70 ppm.
Comparative Example 1
[0065] A constant current electrolysis was performed at an applied
current density of 10 A/dm.sup.2 using KF.2HF prepared in a
conventional method as an electrolytic bath, while using a carbon
electrode as an anode and a Ni electrode as a cathode in an F.sub.2
gas generating system C. Then, when a quantity of electricity
reached about 100 Ahr, a quantity of O.sub.2 in such F.sub.2 gas
generated was measured by gas chromatography, thereby finding it to
be about 30000 ppm.
Comparative Example 2
[0066] A constant current electrolysis was performed at an applied
current density of 15 A/dm.sup.2 using KF.2HF prepared in a
conventional method as an electrolytic bath, while using a carbon
electrode as an anode and a Ni electrode as a cathode in an F.sub.2
gas generating system C. Then, when a quantity of electricity
reached about 100 Ahr, a quantity of O.sub.2 in such F.sub.2 gas
generated was measured by gas chromatography, thereby finding it to
be about 25000 ppm.
Comparative Example 3
[0067] A constant current electrolysis was performed at an applied
current density of 1 A/dm.sup.2 using KF.2HF similar to that in
Example 1 as an electrolytic bath, while using a carbon electrode
as an anode and a Ni electrode as a cathode in an F.sub.2 gas
generating system C. Then, when a quantity of electricity reached
about 100 Ahr, a quantity of O.sub.2 in such F.sub.2 gas generated
was measured by gas chromatography, thereby finding it to be about
21000 ppm.
[0068] In FIG. 2, shown is a relationship among quantities of
electricity in cases of Example 1, Comparative Examples 1 and 3,
and a quantity of O.sub.2 in the F.sub.2 gas.
[0069] As shown in FIG. 2, it is found that, in Example 1 in which
KF.2HF which was prepared after moisture was desorbed from KF by
drying it was used as an electrolytic bath, a quantity of O.sub.2
in the F.sub.2 gas was small from an initial stage of F.sub.2 gas
generation.
INDUSTRIAL APPLICABILITY
[0070] The present invention is constituted as described above
whereupon, by using KF.2HF after KF is dried allowing adsorbed
water or crystallization water to be desorbed therefrom, it becomes
possible to stably generate an F.sub.2 gas in which an oxygen
concentration to be contained is extremely low from an initial
stage of the F.sub.2 gas generation.
* * * * *