The present invention provides a wet-processing apparatus comprising a chamber having a working space, means for wet processing in the working space, means for supplying nitrogen gas in fluid communication with the chamber, a nitrogen gas outlet located in a wall of the chamber, means for cleaning nitrogen gas by removing contaminants mixed therewith located in an area of the chamber downstream of the working space and upstream of the nitrogen gas outlet and having a contaminated gas inlet and a treated gas outlet in fluid communication with the chamber, means for diverting gas in the chamber located downstream of the treated gas outlet and upstream of the nitrogen gas supplying means, the means for diverting gas having a first position providing egress of treated gas from the chamber through the nitrogen gas outlet while inhibiting fluid communication to other parts of the chamber and a second position permitting fluid communication and recirculation of the treated gas to other parts of the chamber while preventing egress of the treated gas through the nitrogen gas outlet, and means for circulating nitrogen gas in the chamber.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a wet-process apparatus and a control method for 
the same and, in particular, to a wet-process apparatus which is equipped 
with a function of quickly creating a highly clean space as needed when 
using chemicals in a clean room, and to a control method for such an 
apparatus. 
2. Description of the Related Art 
FIG. 4 is a schematic sectional view of a conventional wet-process 
apparatus. In the drawing, a wet-process apparatus 1 includes a chamber 2 
isolated from the atmospheric air. Provided in the upper section of the 
chamber 2 is a nitrogen-gas supply pipe 3 for supplying nitrogen gas 4 
into the wet-process apparatus 1. The nitrogen gas 4 introduced into the 
wet-process apparatus 1 through the nitrogen-gas supply pipe 3 is fed to a 
fine cleaning filter 6 by means of a nitrogen-gas supply fan 5 to become 
highly clean nitrogen gas 7, which is introduced into a working space 9 
separated from atmospheric air by an opening/closing means 8, such as a 
window or a door that can be opened and closed. 
Arranged in the working space 9 is a chemical vessel 11 containing a 
chemical 10, and, lodged in the chemical vessel 11 are a plurality of 
semiconductor wafers 13 held by a cassette 12, which can be immersed in 
and taken out of the chemical vessel 11, and further, transferred to other 
places, by means of an automatic transfer handle 14. The chemical vessel 
11 is supported by a draining board 15 having a large number of holes to 
allow waste liquid 16 of the chemical 10 to drop therethrough. The waste 
liquid 16 is discharged through a drain port 17 provided at the bottom of 
the apparatus. 
When the highly clean nitrogen gas 7 is contaminated with mist of the 
chemical 10, it becomes contaminated nitrogen gas 18, which is discharged 
to the outside through a gas outlet 19. 
An example of such a wet-process clean apparatus for creating a highly 
clean space as needed when using chemicals in a clean room, is disclosed, 
for example, in Japanese Patent Laid-Open No. 2-211216. 
In the conventional wet-process apparatus 1, constructed as described 
above, the nitrogen gas 4 supplied through the nitrogen-gas supply pipe 3 
is conveyed to the fine cleaning filter 6 by the nitrogen-gas supply fan 
5, supplying the working space 9 with highly clean nitrogen gas 7. In the 
working space 9, the highly clean nitrogen gas 7 flows downwards from 
above, creating a highly clean nitrogen-gas atmosphere in the space. 
Further, in this space, the automatic transfer handle 4 carries out the 
operations of immersing or extracting the cassette 12, containing 
semiconductor wafers 13, in or out of the chemical 10 and transferring it 
to some other place. 
Insofar as they are transferred through the nitrogen-gas atmosphere, the 
semiconductor wafers 13 which have been processed with the chemical 10 are 
free from the formation of a natural oxide film thereon; however, if 
transferred through air which contains oxygen and water, the wafers cannot 
avoid the formation of a natural oxide film thereon, adversely affecting 
the characteristics of the semiconductor devices to be made of these 
wafers. Accordingly, it is desirable that the wet-process operation be 
performed in a highly clean nitrogen-gas atmosphere. 
On the downstream side of the working space 9, the highly clean nitrogen 
gas 7 is contaminated with mist of the chemical 10, and is discharged 
through the gas outlet 19 to the exterior of the system as contaminated 
nitrogen gas 18. Further, that portion of the chemical 10 which has flowed 
downwards through the draining board 15, accumulates in the lower section 
of the wet-process apparatus as waste liquid 16, which is discharged 
through the drain port 17 to the exterior of the system. 
A problem with the conventional wet-process apparatus 1, described above, 
is that all the nitrogen gas 3 supplied thereto is discharged to the 
exterior of the system, which means a large quantity of nitrogen gas is 
required to maintain a nitrogen-gas atmosphere in the working space 9 for 
a long period of time, resulting in an enormous running cost for the 
apparatus. 
SUMMARY OF THE INVENTION 
This invention has been made with a view to solving the above problem; it 
is accordingly an object of this invention to provide a wet-process 
apparatus and a control method for the same which help to attain a 
reduction in running cost and which make it possible to maintain a 
nitrogen-gas atmosphere of stable nitrogen density for a long period of 
time. 
In order to achieve the above object, according to one aspect of the 
present invention, there is provided a wet-process apparatus comprising: 
a chamber; 
a wet processing means arranged in this chamber and adapted to perform wet 
processing; 
a working space in which wet processing is performed by the wet processing 
means; 
a nitrogen-gas supply means for introducing nitrogen gas into the 
above-mentioned chamber; 
a nitrogen-gas circulation means for causing the introduced nitrogen gas to 
circulate in the chamber; and 
a nitrogen-gas cleaning means for cleaning the nitrogen gas by eliminating 
any contaminant in the nitrogen gas circulating in the chamber. 
According to another aspect of the present invention, there is provided a 
method of controlling a wet-process apparatus, the method comprising the 
steps of: 
closing an exhaust gas processing section by means of a damper when 
starting the apparatus so that the gas in this exhaust gas processing 
section does not circulate in the apparatus and, at the same time, 
discharging the gas in the apparatus through a gas outlet so as to create 
a nitrogen-gas atmosphere therein; 
closing both the damper and the gas outlet when the nitrogen-gas density in 
the apparatus has reached a predetermined value so that nitrogen gas can 
circulate in the exhaust gas processing section; and 
causing the nitrogen gas in an apparatus chamber to circulate in the 
exhaust gas processing section to clean this nitrogen gas.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is a schematic sectional view of a wet-process apparatus in 
accordance with an embodiment of this invention. In the four accompanying 
drawings, the same or equivalent components are referred to by the same 
reference numerals. In FIG. 1, a wet-process apparatus 1A includes a 
chamber 2, in which is provided an exhaust gas processing section 20 for 
eliminating the contaminant in contaminated nitrogen gas 18 resulting from 
contamination from mist of the chemical 10. This exhaust gas processing 
section 20 is equipped with a gas inlet 19, in which is provided a filler 
21 for enlarging gas/liquid contact area. Assuming that the contaminant in 
the contaminated nitrogen gas 18 is an acid mist, the exhaust gas 
processing section 20 is robe equipped with: pH-controlling--agent supply 
nozzles 22 for supplying the contaminated nitrogen gas 18 with a 
pH-controlling agent to control its pH; demisters 23 and 24, which are 
gas/liquid contact devices; alkali-aqueous-solution supply nozzles 25 for 
supplying an alkali-aqueous solution such as NaOH aqueous solution; and an 
alkali-aqueous reception pan 26 for receiving NaOH aqueous solution or the 
like in the middle stage of the exhaust gas processing section 20. 
In the wet-process apparatus 1A, constructed as described above, a 
circulation fan 27 serving as the circulation means is provided, which 
sucks in contaminated nitrogen gas 18 at the gas inlet 19 and conveys the 
same to the exhaust gas processing section 20. The construction of this 
exhaust gas processing section 20 varies depending upon the type of 
contaminant in the contaminated nitrogen gas 18; when, for example, the 
contaminant is an acid mist, the filler 21 and the NaOH-aqueous-solution 
reception pan 26, described above, constitute the exhaust gas processing 
section 20, which then eliminates the acid mist in the contaminated 
nitrogen gas 18, whereby a clean nitrogen gas 28 is obtained. This clean 
nitrogen gas 28 is then mixed with the nitrogen gas 4 supplied through the 
nitrogen-gas supply pipe 3, and is supplied to a fine cleaning filter 6 by 
the circulation fan 27; by means of the fine cleaning filter, a highly 
clean nitrogen gas 7 is obtained, which is supplied to a working space 9. 
Thus, insofar as there is no intrusion of air or the like from the 
outside, it is possible to create a clean nitrogen-gas atmosphere without 
continuously feeding nitrogen gas to the apparatus, and it can be 
maintained in a stable manner if the supply of nitrogen-gas from the 
outside is stopped. 
The changes with time in the nitrogen density of the clean nitrogen gas 
supplied to the working space 9 of the wet-process apparatus 1A of the 
above embodiment of this invention were compared with those in the 
conventional wet processing device 1. In both cases, the area of the fine 
cleaning filter 6 through which the cleaned nitrogen gas was blown out was 
1 m(width).times.0.8 m(depth); and the blowing velocity of the nitrogen 
gas was 0.5 m/min. Further, in the case of this embodiment, in which 
nitrogen gas 4 is caused to circulate in the wet-process apparatus by 
means of the circulation fan 27, the volume of the apparatus portion in 
which the nitrogen gas 4 circulated was 1 m(width).times.1 
m(depth).times.1 m(height)=1 m.sup.3. The purity of the nitrogen gas 4 
supplied was 99.999% or more; and the target purity of the cleaned 
nitrogen gas was 99% or more. 
In the case of the conventional apparatus, the clean nitrogen gas supplied 
to the working space 9 attained a purity of 99% or more almost immediately 
after the supply of nitrogen gas 4 was started, creating a highly clean 
atmosphere in the space. The nitrogen gas 4, however, had to be supplied 
continuously at a rate of not less than 24 m.sup.3 /min. 
Regarding the apparatus of the above embodiment of this invention, the 
nitrogen gas 4 was supplied at a rate of 0.5 m.sup.3 /min. and then, at a 
rate of 1 m.sup.3 /min., and an examination was carried out on both cases. 
The chart of FIG. 2 shows the changes with time in the nitrogen-gas 
density (purity) in the working space in these two cases. In the drawing, 
the curve A represents the case where the nitrogen gas 4 was supplied at 
the rate of 0.5 m.sup.3 /min., and the curve B represents the case where 
it was supplied at the rate of 1 m.sup.3 /min. As shown in FIG. 2, it took 
approx. 35 minutes at the nitrogen-gas supply rate of 0.5 m.sup.3 /min,. 
and approx. 18 minutes at the rate of 1 m.sup.3 /min., for the cleaned 
nitrogen gas to attain a purity of 99% or more. The amount of nitrogen gas 
4 consumed to create a nitrogen-gas atmosphere in the working space 9 at 
the same cleanliness level as that of the conventional apparatus was 
approx. 1/50 at the nitrogen-gas supply rate of 0.5 m.sup.3 /min., and 
approx. 1/25 at the rate of 1 m.sup.3 /min., as compared to that of the 
conventional apparatus. 
FIG. 3 is a schematic sectional view of a wet-process apparatus 1B in 
accordance with another embodiment of this invention . In the drawing, the 
wet-process apparatus 1B is equipped with a switching damper 30 and a gas 
outlet 31. 
When starting the wet-process apparatus 1B, the damper 30 is first closed 
as indicated at A in the drawing so as to prevent the gas in the exhaust 
gas processing section 20 from circulating in the apparatus, and the 
nitrogen gas 4 supplied by the circulation fan 27 is allowed to circulate 
in the apparatus; the gas which has been in the apparatus is discharged 
through the gas outlet 31. This arrangement makes it possible to create a 
nitrogen-gas atmosphere quickly in the wet-process apparatus 1B. When the 
density of the nitrogen gas 4 in the apparatus has reached a predetermined 
value, the gas outlet 31 is closed by an opening/closing or closure means 
(not shown) and, at the same time, the damper 30 is opened, i.e., switched 
to the position B, so that the gas in the exhaust gas processing section 
20 can circulate in the apparatus. In this condition, the same operation 
as that described above is performed to cause nitrogen gas 4 to circulate 
in the apparatus, whereby it is possible to maintain a nitrogen-gas 
atmosphere in the apparatus with a small amount of nitrogen gas. Further, 
with this control method, it is possible, for example, to create a 
nitrogen-gas atmosphere of a desired density in several tens of seconds 
after the wet-process apparatus 1B is started. 
While in the above-described embodiments a means for supplying high-purity 
nitrogen gas was employed for the purpose of creating a nitrogen-gas 
atmosphere in the working space 9, the same effect can be obtained by 
extracting exclusively nitrogen from circulating air by means of a 
nitrogen-film separation device or an adsorption separation device and 
supplying the nitrogen thus obtained to the apparatus again. Also in that 
case, the same effect in terms of running cost can be expected when the 
amount of nitrogen gas extracted and supplied to the apparatus is the same 
as in the above embodiments. 
Further, while the above embodiments were described with reference to the 
case where the contaminant in the contaminated nitrogen gas 18 was an acid 
mist, the present invention is also applicable to other types of 
contaminant. 
As described above, it is possible, with the present invention, to 
drastically reduce the consumption of nitrogen gas, so that a substantial 
reduction in running cost can be attained; further, a nitrogen-atmosphere 
of stable density can be maintained in the apparatus for a long period of 
time. Further, when starting the apparatus, the gas in the apparatus can 
be quickly replaced by nitrogen gas to create a nitrogen gas atmosphere of 
a predetermined density in a short time, and, subsequently, the nitrogen 
gas in the apparatus is processed in the exhaust gas processing section to 
become clean nitrogen gas.