Cleaning and liquid contact with solids – Processes – With work or work parts movable during treatment
Reexamination Certificate
2000-09-29
2002-12-17
Stinson, Frankie L. (Department: 1746)
Cleaning and liquid contact with solids
Processes
With work or work parts movable during treatment
C134S018000, C134S05600D, C134S113000, C134S902000
Reexamination Certificate
active
06494967
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a chemical treating apparatus and a flow rate controlling method thereof, particularly to a chemical treating apparatus used in the manufacturing process of semiconductor devices, especially in the cleaning process, and a flow rate controlling method thereof.
2. Description of the Prior Art
As it will be stated below, there are two methods for treating (cleaning, etching, etc.) the face surface or the back surface of a substrate such as a semiconductor substrate, a quartz substrate, and the like.
(a) One method of chemical treatment is using an overflow type chemical treating apparatus
101
, as shown in
FIG. 1
, in which the subject of treatment (for example, semiconductor wafer, glass wafer, etc.)
131
is placed in a main bath
111
, and a liquid treating chemical
121
in (shown by an arrow) is supplied to the main bath
111
from its bottom portion while the liquid treating chemical
121
out (shown by an arrow) in the main bath
111
is discharged from the top portion of the main bath
111
into an outer bath
112
provided on the top periphery of the main bath
111
.
(b) The other method is using a down-flow type chemical treating apparatus
102
, as shown in
FIG. 2
, in which the subject of treatment (for example, a semiconductor wafer, a glass wafer, etc.)
131
is placed in a main bath
111
, and a liquid treating chemical
121
in (shown by an arrow) is supplied to the main bath
111
from an outer bath
112
formed on the top periphery of the main bath
111
while the liquid treating chemical
121
out (shown by an arrow) in the main bath
111
is discharged from the bottom portion of the main bath
111
.
In each method mentioned above, a liquid treating chemical
121
is supplied to a main bath
111
storing the subject of treatment
131
while the liquid treating chemical
121
is discharged to the outside of the main bath
111
, wherein the adopted flow rate of the liquid treating chemical supplied ranges widely from a very small quantity to several dozens dm
3
/min. Generally, the optimum flow rate is set depending on the geometric shape of the main bath
111
and an outer bath
112
, the subject of treatment
131
and the type of the liquid treating chemical
121
supplied. The set flow rate does not always have only one value; recent multi-functionalization in apparatuses has made it possible that more than one liquid treating chemicals are supplied alternately. In such a case, each time the type of liquid treating chemical is changed, the flow rate should be changed. Furthermore, even though apparatuses are designed so that the flow rate of a liquid treating chemical supplied is always constant during the supply, there are some cases where the flow rate variation during each supplying operation or the variation over a long time period exceeds a negligible level.
Further, in order to treat (for example, clean, wet-etch, etc.) the subject of treatment
131
uniformly, it is required that the liquid treating chemical
121
is sufficiently in contact with the face surface (or the back surface) of the subject of treatment
131
and that the liquid treating chemical
121
flows as laminar state as possible.
In the above-described overflow type chemical treating apparatus
101
, regardless of the amount or variation of supply from the bottom portion of the main bath
111
, the flow rate of the liquid treating chemical
121
in the main bath
111
is determined by the height of the wall of the main bath
111
. Thus, unless the liquid treating chemical
121
is discharged from the main bath
111
, the flow rate is stable irrespective of the amount of supply. Most of the conventional cleaning baths are overflow type ones which have such a structure that the liquid treating chemical
121
is supplied from the bottom portion of the main bath
111
and discharged to the outer bath
112
. Therefore, the discharging capacity should be equivalent or exceed to the expected amount of supply. In addition, various discharging methods are applicable; that is, either the method using gravitation or the method using a pump is available. Therefore, variation of supply can be managed naturally by allowing the opening of the discharging port to have some extra area, for example.
On the other hand, in the above-mentioned down-flow type chemical treating apparatus
102
, in order to keep the amount of the liquid treating chemical in the main bath
111
constant independent of the variation in the amount of supply of the liquid treating chemical
121
from the outer bath
112
, it is necessary to discharge the same amount of the liquid treating chemical
121
as the amount of supply.
OBJECT AND SUMMARY OF THE INVENTION
OBJECT OF THE INVENTION
However, the conventional method which has been applicable to discharge a liquid treating chemical from the bottom portion of a main bath is either dropping the liquid treating chemical by gravity or discharging the liquid treating chemical with a pulsation pump. Therefore, the method for discharging a liquid treating chemical from the bottom portion of a main bath has been utilized only for the purpose of reducing the amount of the liquid treating chemical in the main bath or emptying the main bath. In such a conventional method, it is hard to allow the amount of discharge to be continuously variable and to control the amount of discharge according to the amount or variation of amount of the liquid treating chemical supplied from the outer bath. Specifically, since it is hard to discharge the liquid treating chemical from the main bath according to the amount of supply of the liquid treating chemical, the flow rate (the liquid level) of the main bath is not constant.
To be concrete, when the amount of the liquid treating chemical
121
supplied from the outer bath
112
is decreased from the liquid level
121
A as shown in
FIG. 7A
, on which the liquid treating chemical
121
is held at a certain height higher than the side wall
111
s
of the main bath
111
and lower than the side wall
112
s
of the outer bath
112
, to the level shown in
FIG. 7B
for example, the amount of discharge exceeds the amount of supply, and the amount of the liquid treating chemical
121
in the main bath
111
decreases. With the decrease, the liquid level
121
A lowers, and when the level is lower than the upper end of the wall
111
s
of the main bath
111
, the flow of the liquid treating chemical
121
around the subject of treatment
131
changes from the laminar state. In such a situation, the liquid treating chemical
121
dropping down the inner wall of the main bath
111
flows only in the neighborhood of the side wall
111
s
of the main bath
111
. Furthermore, after the liquid level
121
A reaches the subject of treatment
131
, the upper portion of the subject of treatment
131
exposes from the liquid level
121
A, which makes the treatment (for example, cleaning, etching, etc.) ineffective in such a portion.
On the other hand, when the flow rate of a liquid treating chemical
121
in (shown by an arrow) supplied increases, as shown in
FIG. 7C
, the amount of discharge does not catch up with the amount of supply. Consequently, the amount of the liquid treating chemical
121
left in the outer bath
112
and the main bath
111
increases, and soon the liquid treating chemical overflows the outer bath
112
.
When attempting a solution of the above problem using the prior art, as shown in
FIGS. 8A and 8B
, the attempt must be followed by opening and closing a valve for supply
141
, a valve for discharge
142
or a pump (not shown in FIGS.). As shown in
FIG. 8A
, when the liquid level
121
A of the liquid treating chemical
121
lowers with the decreasing amount of supply, the valve for discharge
142
is in closing action while the valve for supply
141
is in opening action. On the other hand, as shown in
FIG. 8B
, when the liquid level
121
A of the liquid treating chemical
121
rises with the increasing amount of supply for the treating bath
110
, the valve for supply
Makita Masahiro
Nishizaki Mitsuhiro
Kananen, Esq. Ronald P.
Rader & Fishman & Grauer, PLLC
Sony Corporation
Stinson Frankie L.
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