U.S. patent application number 09/783956 was filed with the patent office on 2001-07-26 for cleaning method and apparatus.
Invention is credited to Hyakutake, Hironobu, Kitahara, Shigenori, Shindo, Naoki.
Application Number | 20010009156 09/783956 |
Document ID | / |
Family ID | 26446485 |
Filed Date | 2001-07-26 |
United States Patent
Application |
20010009156 |
Kind Code |
A1 |
Shindo, Naoki ; et
al. |
July 26, 2001 |
Cleaning method and apparatus
Abstract
Cleaning liquid supply nozzles 32 are provided within a
processing tank 30 for cleaning semiconductor wafers W. A distilled
water source 31 and the cleaning liquid supply nozzles 32 are
connected via a distilled water supply pipeline 33 and a chemical
supply tank 36 and the cleaning liquid supply nozzles 32 are
connected via a chemical supply pipeline 35. A flow-rate adjustment
valve 37 is provided in the distilled water supply pipeline 33, and
the supply of distilled water from the distilled water supply
pipeline 33 to the processing tank 30 and the supply of a chemical
from the chemical supply pipeline 35 to the processing tank 30 are
switched by a switching valve 34. A temperature sensor 39 is
disposed within the processing tank 30 for detecting the
temperature of a processing liquid (the chemical or rinse liquid)
therein and a CPU 40 controls the flow-rate adjustment valve 37 and
the switching valve 34 on the basis of a temperature signal from
the temperature sensor 39, so that the time required for the
processing can be determined from the temperature of the cleaning
liquid, thus improving the cleaning capability and cleaning
precision.
Inventors: |
Shindo, Naoki; (Kurume-shi,
JP) ; Kitahara, Shigenori; (Chikugo-shi, JP) ;
Hyakutake, Hironobu; (Tosu-shi, JP) |
Correspondence
Address: |
Michael A. Makuch
SMITH, GAMBRELL & RUSSELL
Suite 800
1850 M Street, NW
Washington
DC
20036
US
|
Family ID: |
26446485 |
Appl. No.: |
09/783956 |
Filed: |
February 16, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09783956 |
Feb 16, 2001 |
|
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09291970 |
Apr 15, 1999 |
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6203627 |
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Current U.S.
Class: |
134/57R ;
134/100.1; 134/18; 134/36 |
Current CPC
Class: |
B08B 3/044 20130101;
H01L 21/67057 20130101; H01L 21/67248 20130101 |
Class at
Publication: |
134/57.00R ;
134/100.1; 134/18; 134/36 |
International
Class: |
B08B 003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 16, 1998 |
JP |
106374/1998 |
Dec 18, 1998 |
JP |
360429/1998 |
Claims
What is claimed is:
1. A cleaning method for immersing an object to be processed into a
cleaning liquid within a processing tank and cleaning said object
therein, wherein said cleaning method comprises the steps of:
detecting a temperature of said cleaning liquid in which said
object is immersed or to be immersed, and generating a
corresponding temperature signal; determining an immersion time for
the immersion of said object in said cleaning liquid, based on said
temperature signal; and immersing said object in said cleaning
liquid, for said immersion time.
2. The cleaning method as defined in claim 1, further comprising
the steps of: rectifying said immersion time to be shorter than a
reference immersion time if the detected temperature of said
cleaning liquid is higher than a reference temperature; rectifying
said immersion time to be longer than a reference immersion time if
the detected temperature of said cleaning liquid is lower than the
reference temperature; and immersing said object in said cleaning
liquid, for said rectified immersion time.
3. The cleaning method as defined in claim 1, wherein: said
cleaning liquid is one of a chemical, a mixture of a chemical and a
rinse liquid, and a rinse liquid.
4. The cleaning method as defined in claim 1, wherein: a cleaning
process comprises a chemical treatment on the object within the
processing tank and an immediately subsequent rinse treatment on
said object.
5. A cleaning method for immersing an object to be processed into a
cleaning liquid within a processing tank and cleaning said object
therein, said cleaning method being such as to comprise a chemical
supply timeband during which a chemical is supplied into said
processing tank to gradually increase the concentration of said
chemical in said cleaning liquid and an immediately subsequent
stabilized concentration timeband; wherein said cleaning method
comprises the steps of: detecting a temperature of said cleaning
liquid in which said object is immersed or to be immersed, and
generating a corresponding temperature signal; rectifying the
length of said chemical supply timeband, based on said temperature
signal; and immersing said object in said cleaning liquid, for an
immersion time that comprises said rectified chemical supply
timeband length.
6. The cleaning method as defined in claim 5, further comprising
the steps of: pre-determining rectification times in accordance
with the concentration ratio of a processing liquid, for each of a
temperature that is greater than a reference temperature for said
processing liquid and a temperature that is less than said
reference temperature; and rectifying the length of said chemical
supply timeband on the basis of said temperature signal by
subtracting said rectification time from a reference time for a
temperature that is greater than said reference temperature, or
adding said rectification time to said reference time for a time
that is less than said reference temperature.
7. The cleaning method as defined in claim 5, wherein: said
cleaning liquid is one of a chemical, a mixture of a chemical and a
rinse liquid, and a rinse liquid.
8. A cleaning method for immersing an object to be processed into a
cleaning liquid within a processing tank and cleaning said object
therein, said cleaning method being such as to comprise a chemical
supply timeband during which a chemical is supplied into said
processing tank to gradually increase the concentration of said
chemical in said cleaning liquid and an immediately subsequent
stabilized concentration timeband; wherein said cleaning method
comprises the steps of: detecting a temperature of said cleaning
liquid in which said object is immersed or to be immesed, and
generating a corresponding temperature signal; rectifying the
length of said stabilized concentration timeband, based on said
temperature signal; and immersing said object in said cleaning
liquid, for an immersion time that comprises said rectified
stabilized concentration timeband length.
9. The cleaning method as defined in claim 8, further comprising
the steps of: pre-determining rectification coefficients in
accordance with the concentration ratio of a processing liquid, for
each temperature of said processing liquid; and rectifying the
length of said stabilized concentration timeband by multiplying a
reference time for said stabilized concentration timeband by said
rectification coefficient.
10. The cleaning method as defined in claim 8, wherein: said
cleaning liquid is one of a chemical, a mixture of a chemical and a
rinse liquid, and a rinse liquid.
11. A cleaning method for immersing an object to be processed into
a cleaning liquid within a processing tank and cleaning said object
to be processed therein, said cleaning method being such as to
comprise a chemical supply timeband during which a chemical is
supplied into said processing tank to gradually increase the
concentration of said chemical in said cleaning liquid and an
immediately subsequent stabilized concentration timeband; wherein
said cleaning method comprises the steps of: detecting a
temperature of said cleaning liquid in which said object is
immersed or to be immersed, and generating a corresponding
temperature signal; pre-determining a rectification time in
accordance with a concentration ratio of a processing liquid, for
each of a temperature that is greater than a reference temperature
for said processing liquid and a temperature that is less than said
reference temperature; rectifying the length of said chemical
supply time band by subtracting said rectification time from a
reference time for a temperature given by said temperature signal
that is greater than said reference time, or adding said
rectification time to said reference time for a temperature given
by said temperature signal that is less than said reference
temperature; pre-determining a rectification coefficient in
accordance with the concentration ratio of said processing liquid,
for each temperature of said processing liquid; rectifying the
length of said stabilized concentration timeband by multiplying a
reference time for said stabilized concentration timeband by a
rectification coefficient corresponding to the temperature given by
said temperature signal; and immersing said object in said cleaning
liquid, for an immersion time that comprises said rectified
chemical supply timeband length and said rectified stabilized
concentration timeband length.
12. The cleaning method as defined in claim 11, wherein: said
cleaning liquid is one of a chemical, a mixture of a chemical and a
rinse liquid, and a rinse liquid.
13. A cleaning method for immersing an object to be processed into
a cleaning liquid within a processing tank and cleaning said object
to be processed therein, said cleaning method comprising the steps
of: detecting a temperature of said cleaning liquid in which said
object is immersed or to be immersed, and generating a
corresponding temperature signal; pre-determining rectification
coefficients in accordance with a concentration ratio of a
processing liquid, for each temperature of said processing liquid;
determining the value of a rectification coefficient, based on said
temperature signal; rectifying the immersion time of said object in
the processing liquid, by multiplying a reference time for
immersion with said rectification coefficient value; and immersing
said object in said cleaning liquid, for said rectified immersion
time.
14. The cleaning method as defined in claim 13, wherein: said
cleaning liquid is one of a chemical, a mixture of a chemical and a
rinse liquid, and a rinse liquid.
15. A cleaning apparatus comprising a processing tank for
accommodating an object to be processed, a chemical supply source,
a rinse liquid supply source, a chemical supply pipeline connecting
said processing tank to said chemical supply source, and a rinse
liquid supply pipeline connecting said processing tank to said
rinse liquid supply source, wherein said cleaning apparatus further
comprises: temperature detection means for detecting the
temperature of a chemical and/or a rinse liquid in which said
object is immersed or to be immersed, and generating a
corresponding temperature signal; flow-rate adjustment means
provided in said chemical supply pipeline and/or said rinse liquid
supply pipeline; and control means for controlling said flow-rate
adjustment means on the basis of said temperature signal.
16. The cleaning apparatus as defined in claim 15, further
comprising: a switching valve for connecting said chemical supply
pipeline and said rinse liquid supply pipeline to said processing
tank, and for controlling the flow-rates from said chemical supply
pipeline and said rinse liquid supply pipeline into said processing
tank.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] The present invention relates to a cleaning method and a
cleaning apparatus wherein an object to be processed, such as a
semiconductor wafer or a glass substrate for an LCD, is immersed in
a cleaning liquid and a rinse liquid and cleaned.
[0003] 2. Description of Related Art
[0004] A cleaning method that is widely used during the process of
manufacturing semiconductor devices generally involves immersing
objects to be processed, such as semiconductor wafers or glass
substrates for LCDs (hereinafter called "wafers"), sequentially
into a series of cleaning tanks, each filled with a chemical
(processing liquid) such as ammonia water (NH.sub.4OH) or
hydrofluoric acid (HF) or a rinse liquid such as distilled water or
ozone water, to clean them.
[0005] A so-called one-path type of apparatus is known in the art
as one form of this cleaning apparatus, wherein a rinse liquid
(such as distilled water or ozone water) and a dilute liquid (for
example, diluted hydrofluoric acid (DHF) including a rinse liquid
and a chemical) such as hydrofluoric acid (HF) are supplied in turn
in the same processing tank, and a wafer or the like is immersed
within this rinse liquid and diluted liquid for a predetermined
time to clean it. With this cleaning apparatus, a dilute liquid
(such as DHF) comprising a predetermined quantity of a chemical
mixed into a rinse liquid is poured into the processing tank and
the wafer or the like is immersed in this dilute liquid (DHF), or
the dilute liquid is supplied into the processing tank after the
wafer or the like has been accommodated therein, whereby an etching
type of "cleaning" can be performed to remove particles adhering to
the surfaces of the wafer or to remove metals such as Ni and Fe or
natural oxide films that have adhered physically or chemically
thereto. The wafer is subsequently immersed in rinse liquid that is
supplied to the processing tank, so that any chemical adhering to
the wafer surfaces can be removed.
[0006] In this prior-art type of cleaning apparatus, the time
during which the wafer or the like is immersed and processed in the
cleaning liquid is constant, so that if the temperature of the
cleaning liquid within the processing tank changes, the wafer
processing capability thereof will also change. With cleaning
(etching) by DHF, for example, a problem occurs in that the etching
characteristics will change, so that the cleaning capability and
the cleaning precision thereof will deteriorate.
[0007] The present invention was devised in the light of the above
situation and has as an object thereof the provision of a cleaning
method and apparatus wherein control of processing time is based on
the temperature of the cleaning liquid, thereby enabling
improvements in cleaning capability and cleaning precision.
SUMMARY OF THE INVENTION
[0008] In order to achieve the above object, the present invention
provides a cleaning method for immersing an object to be processed
into a cleaning liquid within a processing tank and cleaning the
object therein, wherein this cleaning method comprises the steps
of: detecting the temperature of the cleaning liquid in which the
object to be processed is immersed or to be immersed, and
generating a corresponding temperature signal; determining an
immersion time for the immersion of the object in the cleaning
liquid, based on the temperature signal; and immersing the object
to be processed in the cleaning liquid, for the immersion time.
[0009] The present invention also provides a cleaning method for
immersing an object to be processed into a cleaning liquid within a
processing tank and cleaning the object therein, this cleaning
method being such as to comprise a chemical supply timeband during
which a chemical is supplied into the processing tank to gradually
increase the concentration of the chemical in the cleaning liquid
and an immediately subsequent stabilized concentration timeband;
wherein the cleaning method comprises the steps of: detecting the
temperature of the cleaning liquid in which the object is immersed
or to be immersed, and generating a corresponding temperature
signal; rectifying the length of the chemical supply timeband,
based on the temperature signal; and immersing the object to be
processed in the cleaning liquid, for an immersion time that
comprises the rectified chemical supply timeband length.
[0010] The present invention further provides a cleaning method for
immersing an object to be processed into a cleaning liquid within a
processing tank and cleaning the object therein, this cleaning
method being such as to comprise a chemical supply timeband during
which a chemical is injected into the processing tank to gradually
increase the concentration of the chemical in the cleaning liquid
and an immediately subsequent stabilized concentration timeband;
wherein the cleaning method comprises the steps of: detecting the
temperature of the cleaning liquid in which the object is immersed
or to be immersed, and generating a corresponding temperature
signal; rectifying the length of the stabilized concentration
timeband, based on the temperature signal; and immersing the object
to be processed in the cleaning liquid, for an immersion time that
comprises the rectified stabilized concentration timeband
length.
[0011] Even further, the present invention provides a cleaning
method for immersing an object to be processed into a cleaning
liquid within a processing tank and cleaning the object to be
processed therein, this cleaning method being such as to comprise a
chemical supply timeband during which a chemical is supplied into
the processing tank to gradually increase the concentration of the
chemical in the cleaning liquid and an immediately subsequent
stabilized concentration timeband; wherein the cleaning method
comprises the steps of: detecting the temperature of the cleaning
liquid in which the object to be processed is immersed or to be
immersed, and generating a corresponding temperature signal;
pre-determining a rectification time in accordance with the
concentration ratio of a processing liquid, for each of a
temperature that is greater than a reference temperature for the
processing liquid and a temperature that is less than the reference
temperature; rectifying the length of the chemical supply timeband
by subtracting the rectification time from a reference time for a
temperature given by the temperature signal that is greater than
the reference temperature, or adding the rectification time to the
reference time for a temperature given by the temperature signal
that is less than the reference temperature; pre-determining a
rectification coefficient in accordance with the concentration
ratio of the processing liquid, for each temperature of the
processing liquid; rectifying the length of the stabilized
concentration timeband by multiplying a reference time for the
stabilized concentration timeband by a rectification coefficient
corresponding to the temperature given by the temperature signal;
and immersing the object in the cleaning liquid, for an immersion
time that comprises the rectified chemical supply timeband length
and the rectified stabilized concentration timeband length.
[0012] Furthermore, the present invention provides a cleaning
method for immersing an object to be processed into a cleaning
liquid within a processing tank and cleaning the object to be
processed therein, wherein this cleaning method comprises the steps
of: detecting the temperature of the cleaning liquid in which the
object is immersed or to be immersed, and generating a
corresponding temperature signal; pre-determining a rectification
coefficient in accordance with the concentration ratio of a
processing liquid, for each of a temperature that is greater than a
reference temperature for the processing liquid and a temperature
that is less than the reference temperature; determining the value
of a rectification coefficient, based on the value of the
temperature signal; rectifying by multiplying an immersion time for
the immersion of the object in the cleaning liquid by the value of
the rectification coefficient based on the value of the temperature
signal; and immersing the object in the cleaning liquid, for
precisely the rectified immersion time.
[0013] Yet further, the present invention provides a cleaning
apparatus comprising a processing tank for accommodating an object
to be processed, a chemical supply source, a rinse liquid supply
source, a chemical supply pipeline connecting the processing tank
to the chemical supply source, and a rinse liquid supply pipeline
connecting the processing tank to the rinse liquid supply source,
wherein this cleaning apparatus further comprises: temperature
detection means for detecting the temperature of a chemical and/or
a rinse liquid in which the object is immersed or to be immersed,
and generating a corresponding temperature signal; flow-rate
adjustment means provided in the chemical supply pipeline and the
rinse liquid supply pipeline; and control means for controlling the
flow-rate adjustment means on the basis of the temperature
signal.
BRIEF DESCRIPTION OF DRAWINGS
[0014] FIG. 1 is a schematic plan view of a cleaning system using
the cleaning apparatus of this invention;
[0015] FIG. 2 is a schematic sectional view of an embodiment of the
cleaning apparatus of this invention;
[0016] FIG. 3 is a graph of the relationship between processing
liquid concentration and time, to illustrate the basic concept of
rectification by the cleaning method of the present invention;
[0017] FIG. 4 is a graph of the relationship between processing
liquid concentration and time, to illustrate specific details of
the rectification method of the cleaning method of the present
invention;
[0018] FIG. 5 is a graph of the relationships between etching
amount, processing liquid concentration, and time, when no
temperature-related rectification is performed for the chemical
supply timeband;
[0019] FIG. 6 is a graph of the relationships between etching
amount, processing liquid concentration, and time, to illustrate
rectification of the chemical supply timeband;
[0020] FIG. 7 is a graph of the relationships between etching
amount, processing liquid concentration, and time, when no
temperature-related rectification is performed for the stabilized
concentration timeband;
[0021] FIG. 8 is a graph of the relationships between etching
amount, processing liquid concentration, and time, to illustrate
rectification of the stabilized concentration timeband;
[0022] FIG. 9 is a graph of the relationship between processing
liquid concentration and time when the detected temperature has
fallen below the reference temperature, illustrating the total
rectification method of the cleaning method of the present
invention; and
[0023] FIG. 10 is a graph of the relationship between processing
liquid concentration and time when the detected temperature has
risen above the reference temperature, illustrating the total
rectification method of the cleaning method of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] Embodiments of the present invention will be described
below, with reference to the accompanying drawings. This
embodiments are described as applications to a cleaning system for
semiconductor wafers, by way of example.
[0025] A schematic plan view of an example of a cleaning system for
semiconductor wafers, to which the cleaning apparatus of this
invention is applied, is shown in FIG. 1.
[0026] The above mentioned cleaning system is mainly configured of
a conveyor portion 2 for conveying containers such as carriers 1
into and out of the system, where each carrier 1 contains
substrates to be processed such as semiconductor wafers W
(hereinafter called "wafers") in a horizontal state; a processing
portion 3 for processing the wafers W with chemicals or cleaning
fluids and also drying them; and an interface portion 4 located
between the conveyor portion 2 and the processing portion 3, for
receiving the wafers W, adjusting the positions thereof, and
changing the attitudes thereof.
[0027] The conveyor portion 2 is provided with a carrier inlet
portion 5a and a carrier outlet portion 5b together with a wafer
reception portion 6, aligned along one side edge portion of the
cleaning system. In this case, the configuration is such that a
conveyor mechanism (not shown in the figure) is arranged between
the carrier inlet portion 5a and the wafer reception portion 6, and
carriers 1 are conveyed from the carrier inlet portion 5a to the
wafer reception portion 6 by this conveyor mechanism.
[0028] A carrier lifter (not shown in the figure) is disposed in
each of the carrier outlet portion 5b and the wafer reception
portion 6, with the configuration being such that empty carriers 1
can be transferred by these carrier lifters into a reception
portion of a carrier standby portion (not shown in the figure)
provided above the conveyor portion 2, and out of the carrier
standby portion. A carrier transfer robot (not shown in the figure)
that is capable of horizontal movement (in the X and Y directions)
and vertical movement (in the Z direction) is disposed in the
carrier standby portion, with the arrangement being such that empty
carriers 1 transferred out of the wafer reception portion 6 are
aligned and also transferred out to the carrier outlet portion 5b
by this carrier transfer robot. It is also possible to place not
only empty carriers but also carriers 1 containing wafers W within
this carrier standby portion.
[0029] The wafer reception portion 6 opens into the interface
portion 4, and a lid-opening mechanism 7 is disposed in the
aperture portion thereof. The configuration is such that the lid
members (not shown in the figure) of the carriers 1 are opened and
closed by this lid-opening mechanism 7. The lid member of a carrier
1 containing unprocessed wafers that has been conveyed into the
wafer reception portion 6 can therefore be removed by the
lid-opening mechanism 7 so that the wafers W can be conveyed out of
the carrier 1, and, once all of the wafers W have been transferred,
the lid member can be closed again by the lid-opening mechanism 7.
In a similar manner, the lid member of an empty carrier 1 that has
been conveyed into the wafer reception portion 6 from the carrier
standby portion can be removed by the lid-opening mechanism 7 so
that wafers W can be conveyed into the carrier 1, and, once all of
the wafers W have been transferred, the lid member can be closed
again by the lid-opening mechanism 7. Note that a mapping sensor 8
for detecting the number of wafers W accommodated within each
carrier 1 is disposed in the vicinity of the aperture portion of
the wafer reception portion 6.
[0030] Within the interface portion 4 are disposed a wafer transfer
arm 9 for holding a plurality of wafers W, such as 25 wafers W, in
a horizontal state and also transferring them in that horizontal
state to and from the carrier 1 in the wafer reception portion 6; a
pitch changer (not shown in the figure) for holding a plurality of
wafers W, such as 50 wafers W, at a predetermined spacing, but in a
vertical state; an attitude modification device 10 positioned
between the wafer transfer arm 9 and the pitch changer, for
changing the attitude of a plurality of wafers W, such as 25 wafers
W, from a horizontal state to a vertical state; and a position
detection means such as a notch aligner (not shown in the figure)
for detecting notches (not shown in the figure) provided in wafers
W that have been adjusted to a vertical state. A conveyor path 16
linked to the processing portion 3 is also provided in the
interface portion 4, and a wafer conveyor means such as a wafer
conveyor chuck 15 is disposed in a freely movable manner on this
conveyor path 16.
[0031] The processing portion 3 comprises a first processing unit
11 for removing particles and organic contaminants adhering to the
wafers W, a second processing unit 12 for removing metal
contaminants adhering to the wafers W, a cleaning/drying unit 13
for removing oxide films adhering to the wafers W and also drying
the wafers W, and a chuck cleaning/drying unit 14 for cleaning and
drying a wafer conveyor chuck 15, all of these components being
arrayed in a line. The cleaning apparatus of this invention is used
in the first and second processing units 11 and 12 and the
cleaning/drying unit 13. Note that the previously mentioned wafer
conveyor chuck 15 is disposed along the conveyor path 16 that is
provided corresponding to the units 11 to 14, in such a manner that
it is capable of movement in the X and Y directions (horizontal
directions), the Z direction (the vertical direction), and the
.theta. direction (a rotational direction). A chemical tank and a
storage portion 17 containing piping and various vessels are
constructed at each of positions corresponding to the units 11 to
14, on the side thereof opposite to the conveyor path 16.
[0032] The description now turns to the processing or cleaning
apparatus in accordance with this invention.
[0033] A schematic section through a typical embodiment of the
cleaning apparatus of this invention is shown in FIG. 2. This
cleaning apparatus 20 is provided with a processing tank 30 filled
with a cleaning liquid {such as hydrofluoric acid (HF) in diluted
form (DHF) or a rinsing liquid such as distilled water}, and an
object to be processed such as a semiconductor wafer W (hereinafter
called a "wafer W") is immersed in the dilute hydrofluoric acid
(DHF) or rinsing liquid to clean the surfaces thereof. Washing
liquid supply means such as cleaning liquid supply nozzles 32 are
provided within this processing tank 30 to supply the cleaning
liquid into the processing tank 30. The apparatus is also provided
with a rinse liquid supply pipeline such as a distilled water
supply pipeline 33, connected between the cleaning liquid supply
nozzles 32 and a rinse liquid supply source such as a distilled
water source 31; a chemical supply pipeline such as an HF supply
pipeline 35, connected by a switching valve 34 to the distilled
water supply pipeline 33; and an HF supply tank 36 acting as a
chemical supply source, connected by the HF supply pipeline 35 to
the cleaning liquid supply nozzles 32. In addition, an adjustment
valve 37 that is capable of adjusting the flow rate (hereinafter
called a "flow-rate adjustment valve") is provided on the distilled
water source 31 side of the distilled water supply pipeline 33, and
a pump 38 acting as a chemical supply means is provided in the HF
supply pipeline 35.
[0034] A temperature sensor 39 acting as a temperature detection
means is disposed within the processing tank 30, to detect the
temperature of the cleaning liquid, such as DHF, that is supplied
to the processing tank 30 to fill it. A temperature signal from
this temperature sensor 39 is sent to a central processing unit
(CPU) 40 that is a control means, and the arrangement is such that
control signals obtained by comparison with information that is
previously stored in the CPU 40 are sent to the flow-rate
adjustment valve 37 and the switching valve 34 to adjust the supply
times of the distilled water and HF.
[0035] Instead of disposing the temperature sensor 39 within the
processing tank 30 to detect the temperature of the cleaning liquid
such as DHF in the processing tank 30, the configuration could be
such that the temperatures of the chemical (such as HF) and rinse
liquid (such as distilled water) are detected before they are
supplied to the processing tank 30, or that of the distilled water
alone is detected. More specifically, a temperature sensor 39A
could be disposed in the distilled water supply pipeline 33 after
the chemical (HF) and rinse liquid (distilled water) are mixed
together (on the secondary side of the switching valve 34), or a
temperature sensor 39B or 39C could be disposed in the distilled
water supply pipeline 33 on the primary or secondary side of the
switching valve 34.
[0036] This makes it possible to adjust the supply times of the
diluted liquid which is a mixture of a chemical such as HF and a
rinse liquid such as distilled water (DHF, where the ratio of HF to
distilled water is 1:100), by detecting the temperature of the DHF
that fills the processing tank 30 and also controlling the
flow-rate adjustment valve 37 and the switching valve 34 on the
basis of the thus detected temperature.
[0037] A switching means such as a switching valve 43 is provided
in an exhaust pipeline 42 connected to an exhaust port 41 provided
in a lower portion of the processing tank 30.
[0038] The processing tank 30 is also configured of an inner tank
30a filled with the cleaning liquid and an outer tank 30b covering
the outer peripheral edge of an aperture portion of the inner tank
30a, and a drain pipeline 46 provided with a valve 45 is connected
to an exhaust port 44 provided in a base portion of the outer tank
30b.
[0039] A wafer boat 21 that is capable of raising and lowering is
disposed within the processing tank 30. This wafer boat 21 is
configured in such a manner that it takes a plurality of wafers W,
such as 50 wafers W, that have been transferred from the wafer
conveyor chuck 15 and conveys them into the processing tank 30,
then it conveys the processed wafers W upwards and once again
transfers them to the wafer conveyor chuck 15. A resistivity meter
22 that measures the resistivity of the distilled water in the
inner tank 30a of the processing tank 30 is connected by a
discharge pipeline 22b provided with a valve 22a to the inner tank
30a, on the outer side of the upper portion of the processing tank
30. The resistivity meter 22 is configured so that the valve 22a is
closed while a cleaning liquid (such as DHF) is being supplied into
the processing tank 30.
[0040] The description now turns to the sequence of cleaning
performed by the cleaning apparatus of the above configuration.
First of all, before wafers W are introduced into the processing
tank 30, the temperature of the cleaning liquid such as DHF
accumulated within the processing tank 30 or to be supplied
thereto, or that of distilled water to be supplied thereto, is
detected by the temperature sensor 39 and is also monitored by the
CPU 40.
[0041] The detected temperature is compared with prestored
information within the CPU 40 to determine the time of the cleaning
process, such as that of etching, and the flow-rate adjustment
valve 37 and the switching valve 34 are operated by control signals
from the CPU 40 so that a predetermined quantity of DHF at a
predetermined concentration is supplied into the processing tank
30. Simultaneously therewith, the wafers W are introduced into the
processing tank 30 and are set therein, and a cleaning process such
as etching is performed thereon. After a predetermined cleaning
process (etching) has been performed in this manner, the cleaning
liquid (DHF) within the processing tank 30 is exhausted and
distilled water is supplied to the processing tank 30 to perform a
rinse, after which the wafers W are pulled up out of the processing
tank 30 and the cleaning process ends.
[0042] A specific embodiment of the cleaning method of this
invention will be described below.
[0043] This embodiment is targeted at etching variations caused by
fluctuations in the temperature of the cleaning liquid, such as the
rinse liquid (distilled water), {whether the temperature of the
rinse liquid (distilled water) is greater or less than a reference
temperature}, and has the objective of keeping the etching amount
constant by controlling the processing time of the cleaning liquid,
for example. As means of solving this problem, the situation at
which the DHF concentration is constant is taken as a base point
and the subsequent processing time is rectified.
[0044] When it comes to rectifying the processing time, the
cleaning time is divided into two parts, as shown in FIG. 4. The
time during which the cleaning is performed can be divided into two
parts: a "chemical supply timeband" during which the chemical is
introduced into the processing tank and a "stabilized concentration
timeband". In this case, the chemical supply timeband means the
transitional timeband during which processing is performed, from
the supply of the chemical and from a state at which the chemical
concentration within the processing tank is substantially zero
until it reaches a predetermined concentration. The stabilized
concentration timeband means the timeband during which the
processing is performed at a concentration that is substantially
stable over the entire area (the predetermined concentration at
which the wafer W is cleaned)--it does not matter whether the
chemical is, or is not, introduced during this period. Since the
chemical supply timeband and the stabilized concentration timeband
are linked together smoothly, the chemical concentration within a
region of the stabilized concentration timeband adjacent the
chemical supply timeband is the same as the chemical concentration
within the stabilized concentration timeband. In other words, a
timeband during which the concentration is constant extends over
the entire stabilized concentration timeband to part of the
chemical supply timeband. In addition, a distilled or pure water
rinse timeband means a timeband during which distilled water is
supplied to the processing tank after the cleaning process is
complete, to rinse the wafer W while lowering the concentration
from the predetermined concentration.
[0045] The above rectification method consists of the following
blocks:
[0046] (1) Rectification of the chemical supply timeband (the
reference supply time T0 of the chemical, such as HF)
[0047] (2) Rectification of the stabilized concentration timeband
(the supply or halt time T1 of the chemical, such as HF)
[0048] (1) Rectification of Chemical Supply Timeband
[0049] If there is no such temperature rectification, variations
will occur in the etching amount, as shown by the curves E0H to E0L
in FIG. 5. In this case, if a reference temperature (such as
23.degree. C.) is taken as normal and the etching amount at this
reference temperature is assumed to be E0N, the rectification is
performed such that the etching amount is always E0N, regardless of
the actual temperature.
[0050] Therefore, if the detected temperature has fallen below the
reference temperature, the processing time is extended until the
etching amount is E0N. In other words, the processing time is
rectified as shown in FIG. 6 and by the following equation:
[0051] T0R=T0+t0L (Equation 1)
[0052]
[0053] where T0R is the post-rectification chemical supply time
(timeband) and t0L is a predetermined concentration ratio derived
by previous experimentation, which gives chemical supply timebands
for temperatures below the reference temperature (such as
23.degree. C.), with respect to ratios of HF to distilled water of
1:200, 1:300, 1:400, 1:600, and 1:800 (for specific values, see
Table 1 below).
[0054] Similarly, if the detected temperature has risen above the
reference temperature, the processing time is shortened so that the
etching amount is still E0N. In other words, the processing time is
rectified as shown in FIG. 6 and by the following equation:
T0R=T0-t0H (Equation 2)
[0055] where t0H is a predetermined concentration ratio derived by
previous experimentation, which gives chemical supply timebands for
temperatures above the reference temperature (such as 23.degree.
C.), with respect to ratios of HF to distilled water of 1:200,
1:300, 1:400, 1:600, and 1:800 (for specific values, see Table
1).
[0056] Therefore, the post-rectification chemical supply time TOR
changes depending on the processing temperature, the concentration
of DHF and the pre-rectification chemical supply time TO before
rectification.
1TABLE 1 CHEMICAL SUPPLY TIME RECTIFICATION (sec.) Temp. of
process- ing DHF concentration ratio liquid 1:200 1:300 1:400 1:600
1:800 15.0 a 15 = 70 b 15 c 15 d 15 e 15 16.0 a 16 b 16 c 16 d 16 e
16 17.0 a 17 b 17 c 17 d 17 e 17 18.0 a 18 b 18 c 18 d 18 e 18 19.0
a 19 b 19 c 19 d 19 e 19 20.0 a 20 b 20 c 20 d 20 e 20 21.0 a 21 =
18 b 21 c 21 d 21 e 21 22.0 a 22 = 9 b 22 c 22 d 22 e 22 23.0 a 23
= 0 b 23 = 0 c 23 = 0 d 23 = 0 e 23 = 0 24.0 a 24 = 9 b 24 c 24 d
24 e 24 25.0 a 25 b 25 c 25 d 25 e 25 26.0 a 26 b 26 c 26 d 26 e 26
27.0 a 27 b 27 c 27 d 27 e 27 28.0 a 28 b 28 c 28 d 28 e 28 29.0 a
29 b 29 c 29 d 29 e 29 30.0 a 30 b 30 c 30 d 30 e 30 a indicates
(1:200) b indicates (1:300) c indicates (1:400) d indicates (1:600)
e indicates (1:800)
[0057] During the chemical supply timeband, the concentration of
the processing liquid rises together with the start of supply of
the chemical into the processing tank, but this will reach a
saturation near the end of the supply time, and there is a timeband
during which the concentration is constant. One point that requires
consideration in this case is that the chemical supply time T0 must
be long enough that no problem occurs if part of the end of the
chemical supply time T0 is cut to shorten the chemical supply
timeband, if the detected temperature is higher than the reference
temperature. In other words, the concentration must be constant at
the end of the chemical supply, even if the chemical supply time T0
is cut. The condition of Equation 3 is therefore necessary:
T0.gtoreq.(time until the concentration becomes constant)+{chemical
supply time (shortened)to}(Max.) (Equation 3)
[0058] However, if the configuration is such that the reference
chemical supply time T0 can be set freely, the value given in Table
1 (rectification time t0) can become infinitely large, making data
processing impossible, so that the setting of the chemical supply
time T0 is fixed at a value such as T0 is 5 (minutes) and thus it
is not possible to input the reference chemical supply time T0 as
specified by a recipe.
[0059] In addition, the etching amount is related to the
concentration of the processing liquid, so the DHF concentration
must be determined while the etching amount of the wafer W to be
processed is compared with the etching amount with respect to the
DHF concentration, shown in Table 2.
2 TABLE 2 DHF Concentration Ratio Etching Amount (in Angstroms)
1:200 48.16 1:300 24.15 1:400 13.46 1:600 5.55 1:800 2.78
[0060] (2) Rectification of Stabilized Concentration Timeband
[0061] If there is no such temperature rectification, variations
will occur in the etching amount, as shown by E1H to E1L in FIG. 7.
Thus, if a reference temperature (such as 23.degree. C.) is taken
as normal and the etching amount at this reference temperature is
assumed to be E1N, the rectification is performed such that the
etching amount is always E1N, regardless of the actual
temperature.
[0062] Therefore, if the temperature has changed, the rectification
is perfomed such that the etching amount is E1N. In other words,
the rectification time to ensure that the concentration is constant
can be expressed by the following equation:
T1R=k.times.T1 (Equation 4)
[0063] where T1R is the post-rectification stabilized concentration
timeband, T1 is the pre-rectification processing time for the
stabilized concentration timeband (can be set as required by the
operator), and k is a rectification coefficient dependent on
predetermined concentrations and temperatures derived previously by
experimentation (see Table 3).
3TABLE 3 RECTIFICATION COEFFICIENT (k) Temp. of process- ing DHF
concentration ratio liquid 1:200 1:300 1:400 1:600 1:800 15.0 .sup.
a 15 = b 15 c 15 d 15 e 15 1.74 16.0 a 16 b 16 c 16 d 16 e 16 17.0
a 17 b 17 c 17 d 17 e 17 18.0 a 18 b 18 c 18 d 18 e 18 19.0 a 19 b
19 c 19 d 19 e 19 20.0 a 20 b 20 c 20 d 20 e 20 21.0 .sup. a 21 = b
21 c 21 d 21 e 21 1.12 22.0 .sup. a 22 = b 22 c 22 d 22 e 22 1.06
23.0 .sup. a 23 = .sup. b 23 = .sup. c 23 = .sup. d 23 = .sup. e 23
= 1.00 1.00 1.00 1.00 1.00 24.0 .sup. a 24 = b 24 c 24 d 24 e 24
0.95 25.0 a 25 b 25 c 25 d 25 e 25 26.0 a 26 b 26 c 26 d 26 e 26
27.0 a 27 b 27 c 27 d 27 e 27 28.0 a 28 b 28 c 28 d 28 e 28 29.0 a
29 b 29 c 29 d 29 e 29 30.0 a 30 b 30 c 30 d 30 e 30 a indicates
(1:200) b indicates (1:300) c indicates (1:400) d indicates (1:600)
e indicates (1:800)
[0064] Thus, if the detected temperature has fallen below the
reference temperature, T1R=kL.times.T1 (where kL is greater than 1)
is used to extend the processing time of the stabilized
concentration timeband. Similarly, if the detected temperature has
risen above the reference temperature, T1R=kH.times.T1 (where kH is
less than 1) is used to shorten the processing time of the
stabilized concentration timeband.
[0065] Performing both the rectification of the chemical supply
timeband of (1) above and the rectification of the stabilized
concentration timeband of (2) above makes it possible to clean the
wafer W within the optimum processing time. In other words, it is
possible to achieve the optimum etching amount based on the
temperatures of the cleaning liquid and the distilled water, by
rectifying the chemical supply timeband of (1) above and also
rectifying the stabilized concentration timeband of (2) above.
[0066] Therefore, if the detected temperature has fallen below the
reference temperature, the rectified time for the stabilized
concentration timeband is given by adding Equation 1 and Equation
4, as follows:
T0R+T1R=(T0+toL)+(kL.times.T1) (where kL>1) (Equation 5)
[0067] Equation 5 can be rewritten as follows:
T0R+T1R=T0+(toL+kL.times.T1) (Equation 6)
[0068] In this case, T0 is the pre-rectification supply time for
the chemical (HF) and (toL+kL.times.T1) is the processing time for
the portion wherein the concentration is constant, which can be
considered to be equivalent to the pre-rectification processing
time T1 for the stabilized concentration timeband. If the detected
temperature is lower than the reference temperature, therefore, the
processing could be performed with the pre-rectification DHF
processing time T1 (the stabilized concentration timeband) changed
to (toL+kL.times.T1), as shown in FIG. 9.
[0069] One point that requires consideration in this case is that
if the supply of the chemical into the processing tank is to
continue while the wafer W is being processed, the chemical within
the chemical tank (the HF supply tank 36) might be insufficient. It
is therefore necessary in such processing to halt the supply of the
chemical into the processing tank 30 before the chemical in the
chemical tank becomes insufficient, and perform the processing in a
state in which cleaning liquid is accumulated within the processing
tank.
[0070] If the detected temperature is higher than the reference
temperature, on the other hand, Equation 2 and Equation 4 are added
together, as follows:
T0R+T1R=(T0-toH)+(kH.times.T1) (where kH<1) (Equation 7)
[0071] Equation 7 can be rewritten as follows:
T0R+T1R=T0+(-toH+kH.times.T1) (Equation 8)
[0072] In this case, (-toH+kH.times.T1) is the processing time for
the portion wherein the concentration is constant, which can be
considered to be equivalent to the pre-rectification processing
time T1 for the stabilized concentration timeband. If the detected
temperature is higher than the reference temperature, therefore,
the processing could be performed with the pre-rectification DHF
processing time T1 (the stabilized concentration timeband) changed
to (-toH+kH.times.T1), as shown in FIG. 10. Note that the
processing time is shorter in this case, so that the processing
time is cut by the amount shown by Tcut in FIG. 10. In other words,
the following processing is omitted:
Tcut=(T0R+T1R)-(T0+T1)
[0073] Note also that, if the temperature sensor 39 detects the
temperature of the distilled water in this cleaning method, the
attachment position thereof could be either on the processing tank
30 as shown in FIG. 2 or on the distilled water supply pipeline 33.
In addition, the temperature control range for this cleaning method
is described herein as a range of 15.degree. C. to 30.degree. C.,
but this temperature control range can be set as required.
[0074] If the cleaning performed in this cleaning method is done in
the sequence of rinsing (distilled water treatment), followed by
chemical treatment (DHF treatment), and then rinsing (distilled
water treatment), the timing at which the rectification coefficient
(k) is determined (the timing of the initial temperature sampling)
is from the start of temperature monitoring to the start of
chemical (HF) supply (at the start of T0). Furthermore, the timing
of the temperature monitoring is monitoring of the temperature for
five seconds, by way of example, from a predetermined time before
the start of chemical supply to the end of the DHF treatment (at
the start of rinsing).
[0075] If the cleaning is performed in the sequence of chemical
treatment (DHF treatment) then rinsing (distilled water treatment),
the timing at which the rectification coefficient (k) is determined
(the timing of the initial temperature sampling) is from the start
of temperature monitoring until the introduction of the wafer W. In
such a case, the entire processing time is rectified by selecting
only the rectification coefficient (k) and thus rectifying the
processing time for the stabilized concentration timeband alone.
The timing of the temperature monitoring is such that the
temperature monitoring starts at the point at which the wafer W is
introduced to the end of the DHF treatment (at the start of
rinsing).
[0076] If the temperature should deviate from the temperature
control range (such as 15.degree. C. to 30.degree. C.) during the
cleaning, it is preferable that the chemical treatment (DHF
treatment) is immediately interrupted to switch to rinsing, then
the apparatus waits on standby after the rinse. In such a case, it
is also preferable that an alarm or the like is output and the
introduction of a new lot into the processing tank is prevented.
Furthermore, if the temperature should deviate from within
+0.5.degree. C. to -0.4.degree. C. of the initial sampled
temperature during the processing, it is preferable that the
chemical treatment (DHF treatment) is immediately interrupted to
switch to rinsing, then the apparatus waits on standby after the
rinse. In such a case too, it is preferable that an alarm or the
like is output, the introduction of a new lot into the processing
tank is prevented, and the current lot is assumed to be abnormally
completed (abnormal lot). Note that if the temperature of the
processing liquid falls by more than -0.5.degree. C. (if the
stipulated etching is not attained), it is preferable that the
processing continues by the current lot is assumed to be abnormally
completed (abnormal lot). In such a case too, it is preferable that
an alarm or the like is output and the introduction of a new lot
into the processing tank is prevented.
[0077] Other Embodiments
[0078] The cleaning apparatus in accordance with the present
invention was described in the above embodiment as being applied to
the second processing unit 12, but it should be obvious that the
cleaning apparatus of this invention can also be applied to the
first processing unit 11 and the cleaning/drying unit 13.
Furthermore, it is also possible to use it for another type of
etching such as etching by tetraetoxysilane (TEOS), by using
ammonia water in the processing liquid.
[0079] In addition, the cleaning apparatus and cleaning method in
accordance with the present invention were described in the above
embodiment as being applied to a cleaning system for semiconductor
wafers, but this invention can also be applied to other objects to
be processed, such as glass substrates for LCDs.
EXAMPLE 1
[0080] Favorable results were obtained when the relationship
between the temperature of the cleaning liquid and the processing
time was as shown in Table 4, during cleaning (etching) in
accordance with the above cleaning method.
4 TABLE 4 Temperature Processing time .DELTA. + 2.degree. C.
(27.degree. C.) -6 sec. (174 sec.) .DELTA. + 1.degree. C.
(26.degree. C.) -3 sec. (177 sec.) Basic temp. (For ex. 25.degree.
C.) Basic time (180 sec.) .DELTA. - 1.degree. C. (24.degree. C.) +3
sec. (183 sec.) .DELTA. - 2.degree. C. (23.degree. C.) +6 sec. (186
sec.)
EXAMPLE 2
[0081] Favorable etching was performed when processing was done by
the cleaning (etching) of the above described cleaning method, when
the cleaning liquid (DHF) was diluted 1:200, the detected
temperature of the distilled water was lower than the reference
temperature (such as 23.degree. C.) at 21.degree. C., and
processing was performed for a processing time (T0R+T1R) obtained
by substituting into Equations 5 and 6 the chemical supply
rectification time obtained from Table 1 (t0L=a21) of 18 seconds
and the rectification coefficient obtained from Table 3 (kL=a21) of
1.12.
[0082] Similarly, favorable etching was performed when processing
was done when the detected temperature of the distilled water
cleanigher than the reference temperature (such as 23.degree. C.)
at 24.degree. C., and processing was performed for a processing
time (T0R+T1R) obtained by substituting into Equations 7 and 8 the
chemical supply rectification time obtained from Table 1 (t0H=a24)
of 5 seconds and the rectification coefficient obtained from Table
3 (kH=a24) of 0.95.
[0083] Note that the values of the chemical supply rectification
time (t0) and the rectification coefficient (k) for other portions
are omitted from Tables 1 and 3, but these omitted values can be
obtained by experimentation.
[0084] It is clear from the above description that the present
invention makes it possible to achieve uniform cleaning of an
object to be processed, by detecting the temperature of the
cleaning liquid accumulated within the processing tank, setting an
immersion time for the object to be processed on the basis of a
detected temperature signal or rectifying the processing time of
the chemical supply timeband for the cleaning liquid on the basis
of the detected temperature signal, and rectifying the processing
time of the stabilized concentration timeband. It is therefore
possible to achieve uniform processing reactions (such as etching
reactions), thus improving the cleaning capability and cleaning
precision.
[0085] In addition, by using a chemical, a dilute liquid that is a
mixture of a chemical and a rinse liquid, or a rinse liquid as the
cleaning liquid, it is also possible to rinse the object to be
processed within the same processing tank immediately after the
chemical, the dilute liquid that is a mixture of the chemical and
the rinse liquid, or the rinse liquid has accumulated within the
processing tank and the object to be processed has been subjected
to a cleaning process therein.
[0086] It is also possible to simplify the piping system and also
make the entire apparatus more compact, by connecting the chemical
supply pipeline to the rinse liquid supply pipeline by a switching
means and controlling the switching means on the basis of detection
signals from a control means.
* * * * *