Container for high purity liquid chemicals

Details Container for high purity liquid chemicals Container for high purity liquid chemicals

1999-10-29

2001-05-29

Jacyna, J. Casimer (Department: 3751)

Dispensing

Collapsible wall-type container

With wall-collapsing means

C222S105000, C222S400700

Reexamination Certificate

active

06237809

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a container used for the storage or discharge of a high purity liquid chemical, which is employed in the fields of semiconductors and liquid crystals.
The rule for designing, for instance, integrated circuits have increasingly required a high degree of miniaturization thereof because of the recent rapid progress in the electronic devices. High purity liquid chemicals such as liquid photoresists used for such fine patterning techniques should not give rise to any quality deterioration, during the storage and transportation thereof, such as an increase in the amount of impure fine particles in such a liquid chemical, degeneration of components thereof, quantitative changes in the composition, an increase in the quantity of impure metal elements present therein or deterioration of light-sensitive components due to irradiation of the chemical with light rays. The increase in the quantity of impure fine particles in such a liquid photoresist and the degeneration of the components thereof are mainly caused by dissolution of some components present in the container material into the liquid photoresist. If a photoresist film is formed by applying such a contaminated liquid photoresist onto the surface of a substrate, pinholes would be formed thereon. In addition, the quantitative changes in the composition of the liquid are resulted from the permeation of an organic solvent present in the liquid into the exterior through the wall of the container. The liquid accordingly entrains a change in its viscosity and the thickness of the resulting photoresist film is correspondingly changed. The quality deterioration of these liquid photoresists has serious adverse effects on the quality of the resulting semiconductors and liquid crystal displays and yields thereof and would, in turn, shorten the lifetime of the liquid per se.
It has been known that the term “cleanness” is used as an indication for estimating the extent of the quality deterioration of a liquid photoresist in container due to any release of impure fine particles from the container into the liquid during the storage thereof over a long period of time. The cleanness is evaluated by storing ultra high pure water or a liquid photoresist in a container to be tested for a predetermined period of time and then determining the number of fine particles, whose particle size is not less than 0.2 &mgr;m, included in 1 ml of the liquid stored in the container. More specifically, the cleanness can be defined by the following equation:
Cleanness (particles/ml)=[c(particles)×a/2(ml)]/[b(ml)×a(ml)]  (1)
In the equation (1), a represents the volume of the container, and b represents the quantity of the liquid content taken from the container to be tested. First, the sample liquid for determining the initial cleanness of the liquid is taken from the container according to the following method. To a test container having a volume of a (ml), there is added ultra pure water or a liquid photoresist in an amount of a half of the volume, a/2 (ml), of the container, followed by shaking it for 15 seconds, allowing it to stand over 24 hours and then collection of a sample liquid. On the other hand, the sample liquid used for the evaluation of the cleanness after the storage of the water or the liquid photoresist is taken from the container by the following method: That is, the container used for the determination of the initial cleanness is tightly sealed with a plug, then allowed to stand for a predetermined time period and then rotated over three turns while paying an attention so as not to form any air bubble, followed by the collection of a sample liquid. In the equation (1), c represents the number of fine particles, as determined using a particle counter, which are present in the whole liquid sample and have a particle size of not less than 0.2 &mgr;m. Accordingly, the initial cleanness and that determined after the storage over a predetermined period of time can be calculated on the basis of the number of fine particles thus determined. In this regard, the lower the numerical value indicating the cleanness, the higher the quality of the liquid photoresist. More specifically, if the cleanness is less than 100 particles/ml, such a liquid chemical can stably be stored without causing any quality deterioration of semiconductors and liquid crystal displays (LCD) and any reduction of the yield thereof.
As containers for storing liquid photoresists and related liquid chemicals, there have usually been used, for instance, glass containers and metal containers. However, the glass and metal containers cannot ensure a high cleanness of the contents thereof. This is because sodium ions are released from the glass container and each metal container releases ions of the corresponding metal element constituting the container such as iron ions. In this respect, Japanese Patent Application Publication No. Hei 6-99000 proposes a method for eliminating these adverse effects, which comprises using a container consisting of a pouch made from an inert and corrosion-resistant plastic film (polytetrafluoroethylene film) and an external bottle or an overpack which surrounds the pouch and discharging a liquid chemical accommodated in the pouch using a dispenser.
However, such a polytetrafluoroethylene pouch cannot ensure an acceptable level of the cleanness. This method also suffers from a problem in that the pouch is disposable, but it is difficult to dispose the same after the practical use thereof. Moreover, polytetrafluoroethylene is very expensive.
SUMMARY OF THE INVENTION
The present invention has been developed for eliminating the foregoing drawbacks associated with the conventional containers for storing and discharging high purity liquid chemicals and thus, it is an object of the present invention to provide a container, which never deteriorates the quality of high purity liquid chemicals such as liquid photoresists during the storage and transportation thereof and which is hardly broken. It is another object of the present invention to provide a container, which permits stable and easy discharge of a high purity liquid chemical.
The following is the description of the present invention developed for accomplishing the objects described above. The present invention will be described below in detail with reference to the accompanying drawings, which correspond to specific embodiments of the present invention.
As will be seen from
FIG. 1
, the container for a high purity chemical according to the present invention comprises a flexible internal container
2
formed from a polyolefinic high purity resin and a gas-tight, self-supporting external container
3
, which accommodates the internal container
2
, wherein these internal and external containers are joined together in such a manner that the space formed between these two containers are arbitrary closed and opened so as to ensure the communication with the outside, a liquid-discharge pipe
16
provided with a check valve
19
connected to the pipe midway therein is gas-tightly inserted into the internal container down to the bottom thereof and a connector
12
connected to a pressure source
11
is fitted to the external container
3
.
It is preferred in the container for high purity chemicals, as shown in
FIG. 3
, that an airtightness-maintaining tool
17
, which holds the liquid-discharge pipe
16
at an opening
20
of the internal container is engaged with an opening
21
of the external container through screwing and the screwing member may be closed and opened so that the interior of the external container is arbitrary communicated with the outside.
Alternatively, the container for high purity chemicals may comprise, as shown in
FIGS. 3 and 4
, the liquid-discharge pipe
16
, which is divided into an upper portion
16
A provided with the check valve
19
midway therein and a lower portion
16
B inserted into the internal container
2
, and a cover
31
for opening and closing, which is engaged wit

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