Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
1999-05-28
2001-10-09
Dang, Thi (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C134S110000
Reexamination Certificate
active
06299723
ABSTRACT:
CLAIM OF FOREIGN PRIORITY UNDER 35 U.S.C. §119
This patent application claims priority under 35 U.S.C. section 119 to Japanese Patent Application No. 150093/98, filed on May 29, 1998.
FIELD OF THE INVENTION
The present invention relates to an apparatus that prevents dehydration and airlock of filters which is a significant problem in both wet processes such as wet etching, wet cleaning, wet scrubber processes, and dry processes such as Chemical Mechanical Polishing (CMP) or spin coater processes and spin developer processes during manufacturing of semiconductors or liquid crystals or the like.
BACKGROUND OF THE INVENTION
FIG. 1
is a flow diagram that illustrates filtering of a chemical solution in a conventional chemical solution circulation system. A chemical solution is circulated by suction of a pump
5
front an outer bath
3
of a chemical solution bath
1
and supplied to the primary side of a filter in a filtration unit
7
via the pump
5
. Then, the chemical solution passes through the filter in the filtration unit
7
to reach the secondary side of the filter during which rubbish and particles in the chemical solution are retained by the filter. The chemical solution, freed of rubbish and particles, reaches an inner bath
2
of the chemical solution bath
1
, where it acts on wafers (not shown) to etch or wash them.
FIG. 2
is a flow diagram that illustrates filtering in a chemical solution supply system, in which a chemical solution
4
is drawn by pump
5
from a chemical solution bottle
6
and supplied to a chemical solution bath I through a Filtration unit
7
. Since rubbish and particles are retained by a filter in the filtration unit
7
the supplied chemical solution is cleaned. Alternatively, the chemical solution
4
may be pressure-fed by N
2
gas or the like from the chemical solution bottle
6
to the filtration unit
7
.
Chemical solution circulation system or chemical solution supply system often contain bubbles, air or the like (hereinafter collectively referred to as air) which are generated by the operation of the pump, N
2
gas for pressure feeding, leakage at pipeline joints, the variation in the pipeline diameter or other factors. Thus, air in the chemical solution frequently reaches the primary side of the filter in the filtration unit
7
.
Some air does not enter the filter pores
8
in the filtration unit
7
, but rather coalesces into air particles
10
that gather at the top of the filtration unit
7
as shown in FIG.
3
. These air particles are conventionally recycled to the outer bath
3
of the chemical solution bath
1
or the chemical solution bottle
6
by opening and closing a deaeration valve
11
provided in the deaeration line
9
connected to the top of the filtration unit
7
(FIGS.
1
and
2
).
However, the remaining air is deposited on the membrane of filter
8
or is forced into the membrane of the filter
8
by the pump pressure or pressure feeding. The air forced into pores in the membrane of the filter
8
is stabilized there and gradually blocks the pores of the filter
8
. Alternatively, the filter pores may also be blocked with rubbish, particles, etc.
Such blockage of the filters with air (airlock phenomenon) decreases the filtration flow rate of the circulating chemical solutions i.e. a decrease in the amount filtered per unit time. Therefore, the ability to remove particles from a chemical solution bath by filtration is reduced. These particles then adhere to products to constitute a major cause of low product yields. In extreme situations, no circulation takes place so that the resultant pressure damages the pump.
With chemical solution supply filters, the lowered filtration flow rate may lead to a longer supply period, and accordingly a longer solution replacement period in the system. In extreme cases, no chemical solution is supplied to the system.
Japanese Patent Application No. 75012/89 and Japanese Patent Application No. 127006/89 disclose examples of chemical solution filtration systems to preventing airlock phenomenon. The chemical solution filtration system disclosed in Japanese Patent Application No. 75012/89 comprises an air reservoir
23
connected via a connecting pipeline
24
to the primary stage of a filtration unit
13
that incorporates a filter membrane
14
. The air reservoir
23
includes a deaeration line
19
and a liquid level sensor
20
, as shown in FIG.
4
.
In this system, a deaeration valve
22
provided in the deaeration line
19
is opened when the liquid level sensor
20
detects that the liquid level on the primary side of the filter has been lowered to a determined level by the air introduced from a chemical solution inlet
17
. When the liquid level sensor
20
detects a rise in liquid level, on the contrary, the deaeration valve
22
is closed.
In this system, however, chemical solutions are pumped from the chemical solution inlet
17
through the air reservoir
23
and the connecting pipeline
24
to the primary side of the filter
14
. Therefore, the air
12
that reaches the primary side of the filter
14
in the filtration Unit
13
or is generated from a bubble-forming chemical solution in the filtration unit
13
cannot not reach the air reservoir
23
through the connecting pipeline
24
because of the flow of the chemical solution.
The chemical solution filtration system, disclosed in Japanese Patent Application No. 127006/89, comprises a deaeration port
27
located at the top of a filtration unit
13
. Filtration unit
13
incorporates a filter membrane
14
, an air reservoir
23
and an air recycle line
15
connected between the deaeration port
27
and chemical solution inlet
17
of the air reservoir
23
, as shown in FIG.
5
. In this system, the air
12
that reaches filtration unit
13
or is generated in the filtration unit
13
flows in direction
18
through the air recycle line
15
to the air reservoir
23
.
In this system however, chemical solutions can reach the filtration unit either by striking the baffle
16
or going along the air recycle line
15
. Thus, it was found that the air
12
could not rise up against the flow of chemical solutions reaching the primary side of the filter membrane
14
. The flow of chemical solutions prevented air
12
from escaping through the air recycle line
15
which considerably reduced the deaeration effect.
Therefore, neither of the above two systems could effectively overcome airlock phenomenon.
SUMMARY OF THE INVENTION
In order to overcome the above problems, an anti-airlock apparatus for filters is provided that comprises a process bath for processing wafers, a filtration unit incorporating a filter for preliminarily filtering a process solution connected to a first deaeration line, and a tank body having a determined volume provided on the primary side of said filtration unit and connected to a second deaeration line. At least the filtration unit and tank body are connected to each other via a pipeline, and the first and second deaeration lines are separately operated and arc directly connected to the most upstream side of the process solution.
Preferably, said tank body has a internal process solution transfer length between about three times and about twenty times the inner diameter of the pipeline and an air transfer height between three times and about fifty times the inner diameter of the pipeline.
The anti-airlock apparatus for filters of the present invention can be used in circulation or supply systems for wet processes such as wet etching, wet cleaning, wet scrubber process, and non-wet processes such as CMP, spin coater processes, spin developer processes, or the like.
Suitable process solutions preferably include chemical solutions (NH
4
OH, H
2
O
2
, HF, HNO
3
, H
3
PO
4
, HCl, H
2
SO
4
, buffered HF, isopropyl alcohol, etc.), stripping agents, organic solvents, surfactants solutions, pure water, photoresist (cyclized polyisoprene, novolak resins, styrene, etc.), developers (organic solvents, organic alkalis, organic alkalis containing surfactants, etc.), CMP slurries (based on iron nitrate, hydrogen
Saito Kyoko
Sato Nobuyoshi
Seto Hideaki
Yamamoto Haruhiko
Dang Thi
LSI Logic Corporation
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