Cleaning and liquid contact with solids – Apparatus – Automatic controls
Reexamination Certificate
1999-12-10
2002-10-15
Stinson, Frankie L. (Department: 1746)
Cleaning and liquid contact with solids
Apparatus
Automatic controls
C134S0580DL, C134S113000, C134S100100, C134S902000
Reexamination Certificate
active
06463941
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a concentration control apparatus and more particularly, to a concentration control apparatus of a liquid chemical that is capable of real-time measurement and management of the concentration and/or composition of a liquid chemical used for various treatments, such as wafer etching, wafer cleaning, and so on, in semiconductor device fabrication.
2. Description of the Prior Art
Conventionally, various cleaning apparatuses for cleaning a semiconductor wafer have been known, an example of which is disclosed in the Japanese Non-Examined Patent Publication No. 5-121388 published in May 1993. This prior-art cleaning apparatus is comprised of a wafer heating means for heating a semiconductor wafer, a wafer holding means for holding the wafer, and a cleaning liquid diffusing means for diffusing a cleaning liquid over the wafer held by the wafer holding means.
FIG. 1
schematically shows the configuration of this prior-art cleaning apparatus.
As seen from
FIG. 1
, this apparatus has a halogen lamp
161
for heating an underlying semiconductor wafer
160
, a wafer holder
162
for holding the wafer
160
, an arm
163
for operating the holder
162
, a motor
164
for rotating the wafer
160
in the horizontal plane, a rotational shaft
165
for transmitting the rotation motion of the motor
164
to the wafer
160
through the arm
163
, a nozzle
166
for spraying a liquid cleaning chemical toward the wafer
60
held by the holder
162
, the two nozzles for spraying pure water toward the wafer
60
to rinse the same. The lamp
161
, the wafer holder
162
, the arm
163
, and the nozzles
166
and
167
are provided in a chamber
170
. The motor
164
is located outside the chamber
170
. The rotational shaft
165
penetrates the bottom wall of the chamber
170
.
On operation, the wafer
160
held by the holder
162
is heated by the halogen lamp
161
in the chamber
170
while supplying a nitrogen (N
2
) gas through a gas port
171
of the chamber
170
and rotating the wafer
160
by the motor
164
in the horizontal plane. Then, a specific cleaning liquid is sprayed from the nozzle
166
toward the wafer
160
, thereby cleaning the wafer
160
. The drain generated in the chamber
170
is flown out of the chamber
170
through a drain port
172
. After the cleaning process is completed, pure water is sprayed from the nozzles
167
toward the wafer
160
, thereby rinsing the wafer
160
.
With the prior-art cleaning apparatus shown in
FIG. 1
, since the halogen lamp
161
is provided in the chamber
170
, the wafer
160
can be heated to a specific temperature in a short time during the cleaning process. Also, the N
2
gas is introduced into the chamber
170
during the cleaning process and therefore, the cleaning atmosphere is stabilized, resulting in highly-reproducible cleaning operation.
On the other hand, various concentration control apparatuses for controlling the concentration of liquid chemicals been known. An example of the apparatuses of this sort is disclosed in the Japanese Non-Examined Patent Publication No. 60-223131 published in Nov. 1985. In this apparatus, the concentration of a cleaning liquid stored in a container is detected or monitored. Based on the detection result of the concentration thus obtained, the supply of source liquids to the container is controlled to stabilize the concentration of the liquid in the container. Taking the fact that the concentration detection operation necessitates a little time (i.e., a little time lag) into consideration and it is performed intermittently, the concentration control includes prediction of the concentration change to occur in the container after the detection of the liquid concentration (i.e., at the concentration detection operation next time).
FIG. 2
schematically shows the configuration of this prior-art concentration control apparatus.
As seen from
FIG. 2
, this prior-art apparatus has a storage container
270
in which a specific cleaning liquid CO having a specific concentration is stored. A source liquid supplying section
271
is provided over the container
270
for supplying two source liquids C
1
and C
2
to the container
270
. The section
271
includes two storage tanks
272
a
and
272
b
in which the source liquids C
1
and C
2
are respectively stored, two valves
273
a
and
273
b
located respectively in the flow paths communicating with the tanks
272
a
and
272
b
, and two valves
274
a
and
274
b
located respectively in these flow paths. The section
271
supplies the source liquids C
1
and C
2
to the container
270
while controlling the flow rates of the liquids C
1
and C
2
by using the pumps
273
a
and
273
b
and the valves
274
a
and
274
b.
The storage container
270
is equipped with a concentration monitoring section
275
for monitoring or detecting the concentration of the cleaning liquid CO in the container
270
. The section
275
includes a pump
276
for pumping up the solution CO from the container
270
for sampling the same, and a monitoring device
277
for monitoring the concentration of the liquid CO thus pumped up.
A control section
278
is provided between the supplying section
271
and the monitoring section
275
. The control section
278
controls the operation of the supplying section
271
according to the output of the monitoring section
275
. Specifically, the control section
278
has a feedback control system
279
a
and a predictive control system
279
b
. The section
278
controls the concentration of the cleaning liquid CO in the container
270
under the cooperation of these systems
279
a
and
279
b.
In the monitoring operation of the monitoring section
275
, the pump
276
is activated to deliver the liquid CO in the container
270
to the monitoring device
277
for the purpose of sampling the same. Then, after a little time period passes required for detecting the concentration, the value of the concentration is read out.
The concentration data thus obtained in the monitoring section
275
is sent to the control section
278
. Then, the control section
278
predicts the concentration change that will occur in the container
270
at the next-time monitoring operation, and controls the valves
274
a
and
274
b
and the pumps
273
a
and
273
b
so as to increase or decrease the supply rates of the source liquids C
1
and C
2
according to the result of the prediction operation.
With the above-described prior-art apparatuses shown in
FIGS. 1 and 2
, however, the following problems occur.
In single-wafer treating apparatuses such as single-wafer etchers designed for treating a single semiconductor wafer in each step, an advantage that the treatment condition can be easily controlled as desired arises. However, if an easily-decomposable liquid chemical or a mixture of several liquid chemicals is used as a treating agent, the prior-art apparatus shown in
FIG. 1
has a problem that it is unable to find the deterioration and/or abnormal initial concentration of the agent in early stages. This is because the apparatus has no means for detecting or monitoring the concentration change of the agent during the ongoing treatment step for each wafer.
On the other hand, the prior-art apparatus shown in
FIG. 2
has the monitoring section
275
for monitoring the concentration of the cleaning liquid CO stored in the container
270
. Therefore, the above-described problem of the prior-art apparatus of
FIG. 1
does not occur. However, the sampling of the liquid CO from the container
270
by the monitoring section
275
causes some pressure loss in the supply lines (not shown) of the liquid CO to a specific cleaning chamber. As a result, not only the liquid CO is required in surplus but also the required amount of the liquid CO for each cleaning step tends to fluctuate.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a concentration control apparatus of a liquid chemical that is capable of real-time concentration/composition co
Katten Muchin Zavis & Rosenman
NEC Corporation
Stinson Frankie L.
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