Carrier box for semiconductor substrate

Details Carrier box for semiconductor substrate Carrier box for semiconductor substrate

2000-05-30

2002-05-28

Mayekar, Kishor (Department: 1741)

Chemical apparatus and process disinfecting, deodorizing, preser

Chemical reactor

With means applying electromagnetic wave energy or...

Reexamination Certificate

active

06395240

ABSTRACT:

This application is a 35 U.S.C. 371 National Stage filing of PCT/JP98/05368 filed Nov. 30, 1998.
FIELD OF THE INVENTION
The present invention relates generally to a carrier box for a semiconductor substrate, and in particular to a carrier box for receiving and carrying a substrate including a Si wafer, a glass substrate, a metal coated substrate or the like used in industries, such as the semiconductor industry, liquid crystal industry and precision machinery industry.
BACKGROUND OF THE INVENTION
Air cleaning in a conventional clean room will be described with reference to
FIG. 18
taking a case of air cleaning in a semiconductor manufacturing plant.
In
FIG. 18
, outside air
1
is passed through a pre-filter
2
to remove coarse particles, air-conditioned by an air-conditioner
3
and dedusted by a medium efficiency particulate air filter
4
. Then small particles are removed by HEPA (high efficiency particulate air) filter
6
installed on a ceiling of a clean room
5
so that cleanliness class of 100 to 1,000 may be maintained in the clean room
5
(see “Clean Design” pp. 11-24, summer of 1988). Each of reference numerals
7
-
1
,
7
-
2
respectively designates a fan and an airflow is shown by arrows.
A conventional clean room is configured as shown in
FIG. 18
since air cleaning therein purposes to remove particles. Though effective in removing particles, this configuration is of no effect in removing gaseous harmful components.
In addition, a large clean room as shown in
FIG. 18
has a disadvantage in that it is excessively expensive to accomplish super cleanliness therein (“BREAK THROUGH” vol. 5, pp. 38-41, 1993).
It is of no doubt that, in the semiconductor industries, products will be continuously and increasingly required to be of higher quality and precision, and accordingly not only particles (particulate material) but also a gaseous material will be seriously regarded as a contaminant. That is, control of gaseous material (gaseous harmful component) will gain in importance while at present, removal of only particles is required. A conventional filter for a clean room as shown in
FIG. 18
removes only particles, and a gaseous harmful component in outside air is introduced into a clean room without being removed thereby giving rise to a potential problem.
That is, in a clean room, adding to the particles (particulate material), a gaseous material such as an exhaust gas of automobile which cannot be collected and removed by a conventional dedusting filter (e.g. HEPA or ULPA filter) and is consequently introduced into the clean room, an organic gas or so-called hydro-carbon (H.C.) generated by an outgassing from a high molecular synthetic resin material which is extensive use, or a basic (alkaline) gas such as amine will become problematic as a gaseous harmful component.
Among these materials, H.C. is required to be removed since it causes contamination, even if it is of extremely low concentration in a normal atmosphere (indoor or outdoor air).
Recently, outgassing from high molecular synthetic resins of structural members of the clean room and instruments used therein (e.g. wafer storage box) has been discussed as a source of H.C. (“1994 Annual Report of Japan Machinery Federation” pp. 41-49, March of 1995).
The gaseous material generated by operation in a clean room also is problematic. That is, since a gaseous material generated in a clean room is added to that introduced thereinto from outside air (because the gaseous material cannot be removed by the filter of the clean room, gaseous material in the outside air is introduced thereinto) as a cause of origination of the gaseous material in a normal clean room, the gaseous material reaches a higher concentration in the clean room as compared with that in the outside air, and contaminates a base material of a wafer or a substrate.
That is, when the above contaminants (particles or gaseous harmful components) attach to a surface of a wafer or a partially or completely finished product, such contaminants may cause a breakage or short-cut in a circuit (pattern) on the surface of the substrate resulting in a failure. On the other hand, among gaseous materials, {circle around (1)} attaching to a surface of the wafer (substrate), H.C. increases a contact angle and affects an affinity (conformability) between the substrate and a resist. Deterioration of the affinity has a negative effect on a film thickness of the resist and on adhesion between the substrate and the resist (“Air Cleaning” vol. 33, No. 1, pp. 16-21, 1995). In addition, H.C. cause a pressure resistance deterioration (deterioration in reliability) of an oxide film of the wafer (Proceedings of the 39th Joint Lecture Meeting of Japan Society of Applied Physics, p. 686, 1992). {circle around (2)} NH
3
causes a formation of ammonium salt and resulting a blooming on the wafer (deterioration in resolution) (“The Newest Technology Course—Materials—Semiconductor Process Seminar, Oct. 29, 1996” pp. 15-25, Realise Corp., 1996).
Consequently, not only particles but also gaseous contaminants lower the productivity (yield) of the semiconductor products.
Especially, due to the causes of generation described above and further because of the promotion of air circulation in a clean room in recent years with a view to saving energy, the gaseous materials as gaseous harmful components in a clean room become condensed to a significantly higher concentration than that present in outside air, and attach to a base material or substrate and contaminate the surface thereof. A degree of contamination can be represented by the contact angle of the basic material or the substrate, that is, a greater contamination results in a larger contact angle. In a base material or substrate having a large contact angle, even if a film is formed thereon, an adhesive strength of the film is not sufficient (low conformability), and a lower yield results.
The term “contact angle” used herein means a contact angle of wettability by a water and represents a degree of contamination on the surface of a substrate. That is, when a hydrophobic (oily) contaminant is attached to the surface of a substrate, the surface repels water, making it harder for it to be wetted. This results in an increased contact angle. Accordingly, a large contact angle indicates high contamination while a low contact angle indicates low contamination.
Especially, because recently air in a clean room is circulated to save energy, an amount of the gaseous harmful components in a clean room gradually increase and contaminate a base material and substrate.
As a measure to protect a substrate from contamination by these contaminants,
(1) transportation by a robot is effective. That is, since a person is a source of dust and gas, it is important to exclude any interposition thereof in order to maintain the cleanliness (“Monthly Semiconductor World, January” pp. 112-116, 1997),
(2) From a viewpoint of cleaning, it is proposed that, in a future space cleaning, a local cleaning (mini environment) in which a clean space is limited (localized) will be effective ({circle around (1)} “Nikkei Microdevices, July”, pp. 136-141, 1995, {circle around (2)} “Proceedings of IES”, pp. 373-378, 1994).
Presently, though a system in which a Si wafer is received in a synthetic resin (plastic) box to be transported is being investigated as a mini environment, it is reported that (1) when unexpected dusting occurs within the box, particle contamination might become more serious, (2) a countermeasure for outgassing (gas generation) from the box material is required, and (3) a periodical cleaning process of the box itself is required because of (1) and (2) described above, which adds some complexity and causes some problems in practical use (“KANOMAX Aerosol Seminar”, pp. 1-10, 1996).
In the light of these problems, the inventors of the present invention have proposed a space cleaning system using a photo-electron or a photo-catalyst as a technology for local cleaning.
For example, 1) “Cleaning System by Photo-electron (removal of particulate materials)” i

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