U.S. patent application number 11/211748 was filed with the patent office on 2006-03-02 for semiconductor manufacturing apparatus and chemical exchanging method.
Invention is credited to Takashi Higuchi, Kunihiro Miyazaki, Toshiki Nakajima.
Application Number | 20060042756 11/211748 |
Document ID | / |
Family ID | 35941389 |
Filed Date | 2006-03-02 |
United States Patent
Application |
20060042756 |
Kind Code |
A1 |
Miyazaki; Kunihiro ; et
al. |
March 2, 2006 |
Semiconductor manufacturing apparatus and chemical exchanging
method
Abstract
A semiconductor manufacturing apparatus for cleaning a
semiconductor substrate comprises a high-temperature circulation
type chemical bath which is filled with a chemical to be used for
cleaning of a semiconductor substrate and in which the chemical is
circulated and reused, a draining mechanism which drains the
chemical in the chemical bath therefrom, an auxiliary fluid
supplying mechanism which adds to the drained chemical regarded as
a waste chemical an auxiliary fluid, and thereby heats the waste
chemical, a heat exchanger in which the heated waste chemical is
stored temporarily and a new chemical is allowed to flow, and which
cools the waste chemical and raises temperature of the new chemical
by heat exchange, and a pipe in which the new chemical having the
temperature raised in the heat exchanger is supplied to the
chemical bath.
Inventors: |
Miyazaki; Kunihiro;
(Yokohama-shi, JP) ; Higuchi; Takashi; (Kyoto-shi,
JP) ; Nakajima; Toshiki; (Suwa-shi, JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
35941389 |
Appl. No.: |
11/211748 |
Filed: |
August 26, 2005 |
Current U.S.
Class: |
156/345.18 ;
216/93 |
Current CPC
Class: |
B08B 3/08 20130101; B08B
3/14 20130101; B08B 3/00 20130101 |
Class at
Publication: |
156/345.18 ;
216/093 |
International
Class: |
C23F 1/00 20060101
C23F001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 27, 2004 |
JP |
2004-248970 |
Claims
1. A semiconductor manufacturing apparatus comprising: a
high-temperature circulation type chemical bath which is filled
with a chemical to be used for cleaning of a semiconductor
substrate in a state that a temperature of the chemical is raised
to a predetermined temperature, and in which the chemical is
circulated and reused; a draining mechanism which drains the
chemical in the chemical bath therefrom; an auxiliary fluid
supplying mechanism which adds to the drained chemical regarded as
a waste chemical an auxiliary fluid to generate heat by mixture
with the waste chemical, and thereby heats the waste chemical; a
heat exchanger in which the heated waste chemical is stored
temporarily and a new chemical is allowed to flow, and which cools
the waste chemical and raises temperature of the new chemical by
heat exchange between the waste chemical and the new chemical; and
a supply mechanism which supplies the new chemical having the
temperature raised in the heat exchanger to the chemical bath.
2. The apparatus according to claim 1, wherein volume of a pipe of
the heat exchanger to the waste chemical is equivalent to or more
than volume of the chemical supplied to the chemical bath.
3. The apparatus according to claim 1, wherein the auxiliary fluid
generates heat of dilution, reaction or neutralization by mixture
with the waste chemical.
4. The apparatus according to claim 1, wherein the chemical
contains sulfuric acid, the auxiliary fluid is water and the
chemical is heated with heat of dilution generated by mixture with
the auxiliary fluid.
5. The apparatus according to claim 1, wherein the chemical
contains hydrochloric acid, the auxiliary fluid is an organic
alkali and the chemical is heated with heat of neutralization
generated by mixture with the auxiliary fluid.
6. The apparatus according to claim 1, wherein the chemical
contains at least ammonia, the auxiliary fluid is an organic acid
and the chemical is heated with heat of reaction generated by
mixture with the auxiliary fluid.
7. The apparatus according to claim 1, wherein an addition volume
of the auxiliary fluid is set in accordance with temperature of the
waste chemical required to raise temperature of the new chemical to
a predetermined temperature in the heat exchanger.
8. The apparatus according to claim 1, further comprising a
concentration gauge which measures concentration of at least one
chemical in the chemical bath, wherein an addition volume of the
auxiliary fluid is determined in accordance with measurement result
of the concentration gauge.
9. The apparatus according to claim 8, wherein the addition volume
of the auxiliary fluid is determined in accordance with
concentration measured by the concentration gauge such that
temperature of the waste chemical is temperature required to raise
the temperature of the new chemical to the predetermined
temperature.
10. The apparatus according to claim 1, further comprising: a
chemical circuit which supplies a chemical overflowing from a top
portion of the chemical bath, from a bottom portion of the chemical
bath; and a heater which is provided in a middle portion of the
chemical circuit to raise temperature of a chemical to a
predetermined temperature.
11. The apparatus according to claim 1, further comprising a pipe
which allows the new chemical to bypass the heat exchanger.
12. The apparatus according to claim 1, further comprising another
draining mechanism which allows a small quantity of waste chemical
drained from the chemical bath not to be supplied to the heat
exchange, but to be drained directly to outside.
13. A semiconductor manufacturing apparatus comprising: a
high-temperature circulation type chemical bath which is filled
with a chemical to be used for cleaning of a semiconductor
substrate in a state that a temperature of the chemical is raised
to a first temperature, and in which the chemical is circulated and
reused; a draining mechanism which drains the chemical in the
chemical bath therefrom; an auxiliary fluid supplying mechanism
which adds to the drained chemical regarded as a waste chemical of
second temperature lower than the first temperature an auxiliary
fluid to generate heat by mixture with the waste chemical, and
thereby heats the waste chemical at third temperature higher than
the first temperature; a heat exchanger in which the heated waste
chemical is stored temporarily and a new chemical is allowed to
flow, and which cools the waste chemical and raises temperature of
the new chemical to the first temperature by heat exchange between
the waste chemical and the new chemical; and a supply mechanism
which supplies the new chemical having the temperature raised in
the heat exchanger to the chemical bath.
14. A method of exchanging a chemical in a high-temperature
circulation type chemical bath, comprising: preparing a
semiconductor manufacturing apparatus comprising the
high-temperature circulation type chemical bath which is filled
with a chemical to be used for cleaning of a semiconductor
substrate, and in which the chemical is circulated and reused after
the cleaning; draining the chemical in the chemical bath therefrom;
adding to the drained chemical regarded as a waste chemical an
auxiliary fluid to generate heat by mixture with the waste
chemical, and thereby heating the waste chemical; temporarily
storing the heated waste chemical in a heat exchanger; allowing a
new chemical to flow in the heat exchanger, and cooling the waste
chemical and raising temperature of the new chemical by heat
exchange between the waste chemical and the new chemical in the
heat exchanger; and supplying the new chemical having the
temperature raised to the chemical bath.
15. The method according to claim 14, wherein a fluid which
generates heat of dilution, reaction or neutralization by mixture
with the waste chemical is used as the auxiliary fluid mixed with
the waste chemical.
16. The method according to claim 14, wherein an addition volume of
the auxiliary fluid is set in accordance with temperature of the
waste chemical required to raise temperature of the new chemical to
a predetermined temperature in the heat exchanger.
17. The method according to claim 14, wherein concentration of at
least one chemical in the chemical bath is measured and an addition
volume of the auxiliary fluid is set in accordance with the
measurement result.
18. The method according to claim 17, wherein the addition volume
of the auxiliary fluid is set in accordance with the measured
concentration of the chemical such that temperature of the waste
chemical is temperature required to raise the temperature of the
new chemical to the predetermined temperature.
19. The method according to claim 14, wherein a small quantity of
the waste chemical drained from the chemical bath is drained
directly to outside.
20. A method of manufacturing a semiconductor apparatus configured
to house a semiconductor substrate in a high-temperature
circulation type chemical bath which is filled with a chemical to
be used for cleaning of a semiconductor substrate and in which the
chemical is circulated and reused after the cleaning, and to clean
the semiconductor substrate, the method comprising: draining the
chemical in the chemical bath therefrom; adding to the drained
chemical regarded as a waste chemical an auxiliary fluid to
generate heat by mixture with the waste chemical, and thereby
heating the waste chemical; temporarily storing the heated waste
chemical in a heat exchanger; allowing a new chemical to flow in
the heat exchanger, and cooling the waste chemical and raising
temperature of the new chemical by heat exchange between the waste
chemical and the new chemical in the heat exchanger; supplying the
new chemical having the temperature raised to the chemical bath;
and housing the substrate in the chemical bath in which chemicals
are exchanged by draining the waste chemical and supplying the new
chemical, and thereby cleaning the substrate.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. 2004-248970,
filed Aug. 27, 2004, the entire contents of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a semiconductor manufacturing
apparatus in which a semiconductor substrate is cleaned by use of a
high-temperature circulation type chemical bath and a chemical
exchanging method for exchanging chemicals in the high-temperature
circulation type chemical bath.
[0004] 2. Description of the Related Art
[0005] Various types of method for cleaning a semiconductor
substrate have been proposed. When a high-concentration g chemical
is used, a system of repeatedly circulating and using chemicals for
cleaning of a semiconductor substrate is adopted. In this
circulation system, chemicals particularly heated for use are
generally a mixture of sulfuric acid and hydrogen peroxide
solution, a phosphoric acid solution, a mixture of hydrochloric
acid and hydrogen peroxide solution, and a mixture of ammonia and
hydrogen peroxide solution.
[0006] If chemicals are well used in a circulation system in which
a semiconductor substrate are repeatedly cleaned with the same
chemicals, impurities are dissolved in the chemicals or a reaction
among the chemicals proceeds relative to initial concentration and,
as a result, concentration of the chemicals is varied. For this
reason, the chemicals need to be changed regularly or irregularly.
When a high-temperature chemical is exchanged with a new chemical,
a waste chemical valve provided at a pipe of a lowermost portion of
a processing bath to drain the chemical therefrom. When cooling is
necessary, an entire amount of chemical in the processing bath is
temporarily stored in a cooling tank and then drained. When cooling
is unnecessary, the chemical is drained as it is.
[0007] When draining an entire amount of chemical is ended, the
waste chemical valve is closed and a new chemical is supplied to
the processing bath. After the amount of chemical in the processing
bath reaches the amount for circulation, a pump is operated and
temperature of the chemical is raised by a heater. After the
temperature is raised to a predetermined processing temperature, it
is controlled at a constant temperature. Then, the temperature of
the new chemical becomes the processing temperature and cleaning
the semiconductor substrate is conducted again. In this case, the
electric energy is required until the temperature of the new
chemical is raised to the processing temperature at which the
semiconductor substrate can be cleaned, and the processing needs to
be waited during the temperature rise.
[0008] To solve these problems, a method of effectively using
energy by raising the temperature of the new chemical by use of the
chemical (waste chemical) to be drained from the processing bath
has been proposed (Jpn. Pat. Appln. KOKAI Publication No.
2000-266496). In this method, the temperature of the new chemical
to be supplied to the processing bath can be raised by conducting
heat exchange between the high-temperature waste chemical and the
new chemical by a heat exchanger. Thus, electric energy can be
reduced and the time to raise the temperature of the new chemical
to the processing temperature can be shortened.
[0009] However, this kind of method has a problem. The method of
Jpn. Pat. Appln. KOKAI Publication No. 2000-266496 is heat exchange
in a case where the fluid flow exists at any time. Specifically,
this method relates to heat exchange in a system in which the
inflow fluid (new chemical) to be supplied to the processing bath
and the outflow fluid (waste chemical) to be drained from the
processing bath flow simultaneously. Therefore, this method cannot
be applied to a system of supplying the new chemical to the
processing bath after making the processing bath completely empty.
Moreover, there is another problem that the new chemical and the
waste chemical may be mixed inside the processing bath.
[0010] In a general heat exchange system, the temperature of the
new chemical is lower than that of the waste chemical
(substantially equal to the temperature of the processing
temperature). For this reason, the temperature of the new chemical
cannot be raised to the processing temperature by conducting heat
exchange alone. To further raise the temperature of the new
chemical raised by heat exchange up to the processing temperature,
electric energy is required.
[0011] As explained above, in the conventional semiconductor
manufacturing apparatus in which a semiconductor substrate is
cleaned by use of a high-temperature circulation type chemical
bath, electric energy is required to raise the temperature of the
new chemical to the processing temperature and the processing must
be waited during the temperature rise of the new chemical. In
addition, a method using heat exchange between the waste chemical
and the new chemical has been proposed. In this method, however,
the new chemical and the waste chemical may be mixed inside the
processing bath. Moreover, the temperature of the new chemical
cannot be raised to the processing temperature by heat exchange,
and needs to be raised by the other means.
BRIEF SUMMARY OF THE INVENTION
[0012] An aspect of the present invention is a semiconductor
manufacturing apparatus comprising: a high-temperature circulation
type chemical bath which is filled with a chemical to be used for
cleaning of a semiconductor substrate in a state that a temperature
of the chemical is raised to a predetermined temperature, and in
which the chemical is circulated and reused, a draining mechanism
which drains the chemical in the chemical bath therefrom, an
auxiliary fluid supplying mechanism which adds to the drained
chemical regarded as a waste chemical an auxiliary fluid to
generate heat by mixture with the waste chemical, and thereby heats
the waste chemical, a heat exchanger in which the heated waste
chemical is stored temporarily and a new chemical is allowed to
flow, and which cools the waste chemical and raises temperature of
the new chemical by heat exchange between the waste chemical and
the new chemical, and a supply mechanism which supplies the new
chemical having the temperature raised in the heat exchanger to the
chemical bath.
[0013] Another aspect of the present invention is a semiconductor
manufacturing apparatus comprising: a high-temperature circulation
type chemical bath which is filled with a chemical to be used for
cleaning of a semiconductor substrate in a state that a temperature
of the chemical is raised to a first temperature, and in which the
chemical is circulated and reused, a draining mechanism which
drains the chemical in the chemical bath therefrom, an auxiliary
fluid supplying mechanism which adds to waste chemical of second
temperature lower than the first temperature of the drained
chemical an auxiliary fluid to generate heat by mixture with the
waste chemical, and thereby heats the waste chemical at third
temperature higher than the first temperature, a heat exchanger in
which the heated waste chemical is stored temporarily and a new
chemical is allowed to flow, and which cools the waste chemical and
raises temperature of the new chemical to the first temperature by
heat exchange between the waste chemical and the new chemical, and
a supply mechanism which supplies the new chemical having the
temperature raised in the heat exchanger to the chemical bath.
[0014] Still another aspect of the present invention is, in a
semiconductor manufacturing apparatus comprising: a
high-temperature circulation type chemical bath which is filled
with a chemical to be used for cleaning of a semiconductor
substrate, and in which the chemical is circulated and reused after
the cleaning, a method of exchanging the chemical in the
high-temperature circulation type chemical bath, comprising
draining the chemical in the chemical bath therefrom, adding to the
drained chemical regarded as a waste chemical an auxiliary fluid to
generate heat by mixture with the waste chemical, and thereby
heating the waste chemical, temporarily storing the heated waste
chemical in a heat exchanger, allowing a new chemical to flow in
the heat exchanger, and cooling the waste chemical and raising
temperature of the new chemical by heat exchange between the waste
chemical and the new chemical in the heat exchanger, and supplying
the new chemical having the temperature raised to the chemical
bath.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0015] FIG. 1 is a schematic diagram showing a semiconductor
manufacturing apparatus according to a first embodiment of the
present invention;
[0016] FIG. 2 is a cross-sectional view showing an inner structure
of a heat exchanger used in the first embodiment shown in FIG.
1;
[0017] FIG. 3 is an illustration showing heat exchange in the heat
exchanger of FIG. 2;
[0018] FIG. 4 is a schematic diagram showing a semiconductor
manufacturing apparatus according to a second embodiment of the
present invention; and
[0019] FIG. 5 is a graph showing variation in temperature of a
diluted waste chemical in a case where water is added to sulfuric
acid waste.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Embodiments of the present invention will be explained below
with reference to the accompanying drawings.
First Embodiment
[0021] FIG. 1 is a schematic diagram showing a semiconductor
manufacturing apparatus according to a first embodiment of the
present invention.
[0022] Reference numeral 11 denotes a processing bath
(high-temperature circulation type chemical bath) employed for
cleaning of a semiconductor substrate such as a Si wafer or the
like. The processing bath 11 is filled with, for example, a
sulfuric acid based high-temperature chemical 12. A semiconductor
substrate 13 is dipped into the chemical 12 in the processing bath
11 and then cleaned.
[0023] The chemical 12 in the processing bath 11 is circulated by a
pump (P) 14. In other words, the chemical is supplied from a bottom
portion of the processing bath 11 by the pump 14, and the chemical
spilling from a top portion of the processing bath 11 is supplied
again from the bottom portion of the processing bath 11 through a
chemical circuit. A heater (H) 15 which controls a temperature of
the chemical and a filter (F) 16 through which particles are
removed as impurities, are inserted into the chemical circuit. A
small quantity of the chemical 12 in the processing bath 11 is
circulated by the pump 14 and the temperature control and removal
of particles are conducted by the heater 15 and the filter 16,
during cleaning of the semiconductor substrate 13 or standby. A
concentration monitor 17 is provided outside the processing bath 11
to measure concentration of the chemical 12.
[0024] A waste chemical valve 21 is provided between the pump 14
and heater 15 of the pipe at the lower most portion of the
processing bath 11, for example, the chemical circuit. The chemical
12 in the processing bath 11 is drained by the valve 21.
Furthermore, a new chemical is supplied to the processing bath 11
from a topside of the processing bath 11.
[0025] Specifically, when a time to exchange the chemical has come,
operations of the pump 14 and heater 15 are stopped, the waste
chemical valve 21 is opened, and the chemical is drained from the
pipe at the lowermost portion of the processing bath 11. When an
entire amount of chemical is drained, the waste chemical valve 21
is closed and a new chemical is supplied to the processing bath 11.
After the amount of the chemical 12 in the processing bath 11
reaches the amount for circulation, the pump 14 is operated, and
the temperature of the chemical 12 is raised by the heater 15.
After the temperature is raised up to the predetermined
temperature, the temperature is controlled at a constant
temperature. When the temperature becomes a predetermined
processing temperature (processing temperature), cleaning the
semiconductor substrate 13 is conducted again.
[0026] The basic structure explained above is the same as the prior
art. Besides this, a heat exchanger 31 which conducts heat exchange
between the waste chemical drained from the processing bath 11 and
the new chemical supplied to the processing bath 11, and a water
adding mechanism 32 which adds water to the waste chemical as an
auxiliary fluid to raise the temperature of the waste chemical, are
provided in the present embodiment.
[0027] In other words, the heat exchanger 31 is provided in the
waste chemical system of the high-temperature circulation type
chemical bath such that the chemical (waste chemical) drained from
the processing bath 11 via the valve 21 is supplied to the heat
exchanger 31. The waste chemical supplied to the heat exchanger 31
is temporarily stored in the heat exchanger 31 and finally
discharged to outside from a valve 23. On the other hand, the new
chemical is supplied to the heat exchanger 31 via a valve 24 and
heated by the heat exchanger 31. The new chemical having
temperature raised by the heat exchanger 31 is supplied to the
processing bath 11. The water adding mechanism 32 adds water to the
waste chemical which is to be supplied to the heat exchanger 31, by
opening a valve 22, such that the temperature of the waste chemical
is raised by heat of dilution. Therefore, the waste chemical reacts
with water and the temperature of the waste chemical is thereby
raised. Thus, the waste chemical having temperature raised is
supplied to the heat exchanger 31.
[0028] The heat exchanger 31 comprises a pipe 35 in which the waste
chemical is temporarily stored and a new chemical pipe 36 provided
in the pipe 35 as shown in FIG. 2 which illustrates an internal
structure of the heat exchanger 31. Volume of the waste chemical
side pipe 35 of the heat exchanger 31 is equal to or more than the
volume of chemical in the processing bath 11. An outer wall of the
pipe 35 is subjected to heat resistance. In other words, the
chemical in the processing bath 11 can be entirely drained to the
heat exchanger 31. When the processing bath 11 is made empty and
the new chemical is supplied thereto, the waste chemical and the
new chemical are not mixed inside the processing bath 11. The pipe
of the new chemical supplying side does not need to have the same
volume as the processing bath 11. A necessary amount of new
chemical may be supplied to the processing bath 11 by opening or
closing the supply-side valve 24 under on-off control as occasion
requires, while monitoring the new chemical temperature inside the
heat exchanger 31. To improve heat exchanger effectiveness, an
agitator (not shown) may be provided at the pipe of the waste
chemical side.
[0029] A waste chemical temperature monitor 37 is provided at a
waste chemical outlet side of the heat exchanger 31. A new chemical
temperature monitor 38 is provided at a new chemical outlet side of
the heat exchanger 31.
[0030] The volume of water added to the waste chemical before heat
exchange may be determined in accordance with a detected value of
the concentration monitor 17.
[0031] Specifically, concentration of sulfuric acid in the chemical
12 may be detected by the concentration monitor 17 before draining
the chemical in the processing bath 11 and the addition volume of
water which can be diluted may be preliminarily considered on the
basis of the detection result and set within this range.
[0032] When the chemical in the processing bath 11 is exchanged
with the new chemical, in the above-described structure, operations
of the pump 14 and heater 15 are first stopped, the valve 21 is
opened, and an entire volume of chemical 12 in the processing bath
11 is drained and temporarily stored in the heat exchanger 31. At
this time, to heat the waste chemical, the valve 22 is opened and a
predetermined volume of water is added to the waste chemical. Thus,
the temperature of the heat exchanger 31 to be supplied to the heat
exchanger 31 is raised to be higher than the processing
temperature. The volume of water added to the waste chemical can be
adjusted by the monitors 37 and 38 shown in FIG. 2 while checking
the temperatures of the waste chemical and new chemical. When an
entire volume of chemical 12 is drained, the waste chemical valve
21 is closed.
[0033] Next, the valve 24 is opened and the new chemical is
supplied to the processing bath 11 through the heat exchanger 31.
The temperature of the new chemical supplied to the heat exchanger
31 is raised by heat exchange with the waste chemical, and the new
chemical of raised temperature is supplied to the processing bath
11. Therefore, to raise the temperature of the new chemical to the
processing temperature, electric energy consumption can be reduced
or no electric energy needs to be consumed.
[0034] FIG. 3 illustrates heat exchange between the waste chemical
and the new chemical in the heat exchanger 31. The temperature of
the waste chemical supplied to the heat exchanger 31 is represented
by T1, the temperature of the waste chemical discharged from the
heat exchanger 31 is represented by T2, the temperature of the new
chemical supplied to the heat exchanger 31 is represented by T2',
and the temperature of the new chemical discharged from the heat
exchanger 31 is represented by T1'. On the principle of heat
exchange, temperature T1' cannot be higher than temperature T1. For
this reason, if the waste chemical of lower temperature than the
processing temperature is supplied to the heat exchanger 31 as it
is, temperature T1' becomes lower than the processing temperature
and great temperature raising energy is required for the new
chemical. In the present embodiment, temperature T1 is made higher
than the processing temperature by preliminarily raising the
temperature of the waste chemical with heat of dilution by addition
of water. For this reason, temperature T1' can be made higher up to
the processing temperature.
[0035] Variation in the temperature of the diluted waste chemical
in a case where water is added to the sulfuric acid waste, is shown
in FIG. 5. A horizontal axis represents the concentration of
sulfuric acid waste diluted after addition of water and a vertical
axis represents the temperature of the waste chemical. This figure
shows an example of variation in the temperature of diluted waste
chemical in a case where water is arbitrarily added to 93% and 78%
sulfuric acid wastes both having temperature of 100.degree. C. In
general, the concentration of the sulfuric acid waste used for
semiconductor cleaning is approximately 80%. If water is added such
that the concentration of the waste chemical becomes 75%, the
temperature of the waste chemical can be raised by approximately
10.degree. C. and heat exchange loss in the fluid heat exchanger
can be compensated.
[0036] After the volume of the chemical in the processing bath 11
reaches the circulation volume by supply of the new chemical, the
pump 14 is operated and the temperature of the chemical 12 is
raised by the heater 15. After the temperature of the chemical 12
is raised to a predetermined temperature, it is controlled as a
constant temperature. Thus, the temperature of the chemical 12
becomes the predetermined temperature and cleaning the
semiconductor substrate 13 is conducted again.
[0037] As explained above, since high-concentration sulfuric acid
solution is drained in the semiconductor cleaning step using
high-temperature sulfuric acid, the temperature of the waste
chemical to be supplied to the heat exchanger 31 can be made higher
than the processing temperature used in circulation, by heat of
dilution caused by water. For this reason, even if the heat
exchanger effectiveness is poor, the temperature of the new
chemical can be sufficiently raised up to, for example, circulation
temperature (processing temperature). Therefore, new temperature
raising energy for the new chemical can be reduced or no electric
energy needs to be consumed. In this case, the heater 15 in the
chemical circuit may be employed to keep the circulation
temperature (processing temperature).
[0038] The waste chemical in the heat exchanger 31 is discharged to
outside by opening the valve 23. Since this waste chemical is
cooled by heat exchange with the new chemical, a cooling mechanism
for cooling the waste chemical is unnecessary. Therefore, even if
there is no heat resistance of the waste chemical pipe in a clean
room, the waste chemical can be discharged without a cooling tank
or the like.
[0039] After the cleaned semiconductor substrate 13 is taken out of
the processing bath 11, the chemical deposited on the semiconductor
substrate is sufficiently removed therefrom by use of ultrapure
water, in a cleaning bath (not shown). Then, the semiconductor
substrate 13 is dried and transferred to a next semiconductor
manufacturing step. If impurities deposited on the semiconductor
substrate 13 can hardly be removed therefrom with one chemical, the
semiconductor substrate 13 is successively cleaned by conducting
ultrapure water rinsing between cleaning steps using the chemical.
Finally, after ultrapure water rinsing is conducted to sufficiently
remove the chemical deposited on the semiconductor substrate
therefrom, the semiconductor substrate is dried.
[0040] Moreover, when the waste chemical is exchanged for a new
chemical, the substrate 13 is taken out of the processing bath 11,
and after the exchange ends, it accommodates the substrate 13 in
the processing bath 11.
[0041] According to the present embodiment, as described above,
when the chemical in the processing bath 11 employed as the
high-temperature circulation type chemical bath is exchanged, an
entire volume of chemical 12 in the processing bath 11 is drained
and stored in the heat exchanger 31, and the heat of the
high-temperature waste chemical is supplied to the new chemical by
the heat exchanger 31. Thus, electric energy to raise the
temperature of the new chemical can be reduced and the circulation
heating time for the temperature rise can be reduced.
[0042] Moreover, the temperature of the waste chemical to be used
for heat exchange can be made further higher by adding water in the
heat exchanger 31 and heating the waste chemical with heat of
dilution. Particularly, since the concentration of sulfuric acid is
high in the high-temperature circulation type chemical bath using
sulfuric acid, heat of dilution caused by addition of water is
great, which is very effective for the temperature rise. By raising
the temperature of the waste chemical up to a sufficiently high
temperature, new electric energy is not required when the new
chemical is supplied. In addition, at the chemical exchange, an
entire volume of chemical in the processing bath 11 is drained from
the processing bath 11 and then the new chemical is supplied
thereto. Thus, mixture of the new chemical and waste chemical in
the processing bath 11 can be preliminarily prevented.
[0043] In other words, the temperature of the new chemical can be
raised by heat exchange between the new chemical and waste chemical
without mixing the new chemical and waste chemical in the
processing bath 11, and further reduction of electric energy and
reduction of the chemical exchange time can be achieved.
Second Embodiment
[0044] FIG. 4 is a schematic diagram showing a semiconductor
manufacturing apparatus according to a second embodiment of the
present invention. Elements like or similar to those disclosed in
the first embodiment are denoted by similar reference numbers and
are not described in detail here.
[0045] The present embodiment is different from the first
embodiment in view of setting an addition amount of water by the
water adding mechanism 32 on the basis of the measurement result of
the concentration monitor 17. In addition, a valve 25 which does
not allow the waste chemical to partially pass through the heat
exchanger 31, but allows the waste chemical to be directly
discharged, is provided between the waste chemical valve 21 and the
heat exchanger 31. A valve 26 which does not allow the new chemical
to partially pass through the heat exchanger 31, but allows the new
chemical to be directly supplied to the processing bath 11, is
provided at a new chemical side pipe of the heat exchanger 31.
[0046] In the present embodiment, too, the new chemical having
temperature raised by the heat exchanger 31 can be supplied without
mixture of the new chemical and waste chemical in the processing
bath 11, similarly to the first embodiment.
[0047] In addition to this, the addition volume of water can be set
in the following manners on the basis of the measurement result of
the concentration monitor 17, in the present embodiment:
[0048] (1) The concentration of sulfuric acid is monitored in a
system using high-temperature sulfuric acid, a desired temperature
of the waste chemical is obtained empirically or experimentally
such that the temperature of the new chemical to be raised in the
heat exchanger 31 becomes the processing temperature, and the
addition volume of water is determined such that the temperature of
the new chemical can be raised to the temperature of the waste
chemical. In this case, electric energy to raise the temperature of
the new chemical is unnecessary. In other words, the temperature of
the new chemical can be raised to the processing temperature by
heat exchange alone.
[0049] (2) The concentration of sulfuric acid is monitored in a
system using high-temperature sulfuric acid, and a necessary volume
of water is determined on the basis of the relationship between the
concentration of the waste chemical to be drained from the
processing bath 11 and the predetermined concentration of the waste
chemical. Recently, reducing as much discharge of the waste
chemical out of factories as possible has been desired from the
viewpoint of reduction of load on environment. For example,
sulfuric acid is often recovered from a semiconductor manufacturing
apparatus after discharging and used in other industrial fields as
dilute sulfuric acid. In this case, sulfuric acid needs to be
recovered in accordance with a certain degree of concentration.
[0050] In other words, generally, the sulfuric acid based waste
chemical is not disposed of as industrial waste, but is often used
for other industrial purposes. The concentration of sulfuric acid
is desired to be constant. Thus, the addition volume of water is
determined such that the concentration of sulfuric acid in the
waste chemical becomes 75% on the basis of the measurement result
of the concentration monitor 17. The waste chemical discharged by
opening the valve 23 after heat exchange thereby contains sulfuric
acid having concentration of 75%, and can be used for other
purposes as it is.
[0051] If the concentration of the waste chemical is set at the
above value, the temperature of the new chemical may not be raised
to the processing temperature by the heat exchanger 31. The
temperature of dilute waste chemical in case where water is added
to 93% or 78% sulfuric acid waste having temperature of 100.degree.
C. is shown in FIG. 5. A vertical axis represents the temperature
of the waste chemical and a horizontal axis represents the
concentration of sulfuric acid waste diluted after addition of
water. In general, the concentration of the sulfuric acid waste
used for semiconductor cleaning is approximately 80%. The
temperature of the waste chemical can be raised by approximately
10.degree. C. by adding water such that the concentration of the
waste chemical of approximately 100.degree. C. becomes 75%. Heat
exchange loss in the fluid heat exchanger can be thereby
compensated. If the temperature of the new chemical does not reach
the processing temperature, the new chemical may be heated by the
heater 15 or other means. In this case, too, since the temperature
of the new chemical has been raised to some extent by heat
exchange, a small quantity of electric energy is only needed to
raise the temperature up to the processing temperature.
[0052] If the temperature of the new chemical raised by the heat
exchanger 31 is equal to or higher than the processing temperature,
the temperature of a total volume of new chemical may become the
processing temperature in the processing bath 11 by bypassing a
small quantity of new chemical by the valve 26. Moreover, a small
quantity of waste chemical may be preliminarily drained through the
valve 21 and then the temperature of the new chemical may be raised
to the processing temperature by the waste chemical which is heated
by heat of dilution generated by mixture of remaining waste
chemical and water.
Modified Embodiment
[0053] The present invention is not limited to the above-described
embodiments. In the embodiments, water is used as an auxiliary
fluid for the sulfuric acid based chemical used as a cleaning fluid
and the waste chemical is heated by heat of dilution. However,
combination of the chemical and the auxiliary fluid can be
arbitrarily changed. For example, a chloric acid based chemical can
be heated with heat of neutralization generated by adding an
organic alkali thereto. An ammonium based chemical can be heated
with heat of reaction generated by adding an organic acid thereto.
However, a substance which is not deposited or precipitated inside
the heat exchanger when the temperature is lowered, needs to be
selected.
[0054] A position where the auxiliary fluid is added may be the
pipe to enter the heat exchanger or in the heat exchanger. A relief
valve (not shown) may be provided at the waste chemical side of the
processing bath as a safety device. FIG. 2 shows only one chemical.
However, if a mixture chemical containing two or more chemicals
including pure water is used, the new chemical supply pipe may be
arranged parallel to the heat exchanger 31 and temperatures of two
or more chemicals may be simultaneously raised by heat exchange. A
fluid such as hydrogen peroxide which is decomposed at high
temperature may be supplied, at necessary amount, directly to the
processing bath, without heat exchange.
[0055] As the semiconductor substrate cleaning, there are batch
cleaning of dipping some semiconductor substrates into the
processing bath containing the chemical and simultaneously cleaning
them, and single wafer cleaning of blowing the chemical onto the
semiconductor substrates while rotating them one by one. The
present invention can be applied to any chemical circulation system
using a high-concentration chemical even if the system is batch
cleaning or single wafer cleaning.
[0056] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *