Gas separation – With means securing or retaining separating media – Unit or cohesive sheet-like media in flow line or frame
Patent
1997-03-27
1999-12-07
Bushey, C. Scott
Gas separation
With means securing or retaining separating media
Unit or cohesive sheet-like media in flow line or frame
55524, B01D 4600
Patent
active
059975989
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention concerns an air filter for use in a clean room used, for example, in factories or research laboratories relevant to the field of semiconductors, food-stuffs and biotechnology, a method of manufacturing thereof, a local facility and a clean room equipped with the air filter.
BACKGROUND ART
In clean rooms used heretofore, for example, in factories or research laboratories in the relevant field of semiconductors, foodstuffs, medicines and biotechnology, dry air filters for trapping air-born particles are disposed to air introduction paths and air passing therethrough is introduced into the clean room.
Air filters used at present in clean rooms include ULPA (abbreviation for Ultra Low Penetration Air) using glass fibers for the filter medium and HEPA (abbreviation for High Efficiency Particle Air), and such filters are excellent filters in view of removal of dusts and, for example, ULPA filters can remove fine particles even of 0.1 .mu.m. Further, non-glass type filters using fluoro resin or quartz fibers instead of the glass fibers for the filter medium have also been developed so as not to release inorganic substances from the air filters.
Recently, with the increase of integration degree of semiconductors, diffusing of gaseous organic substances as well as dusts in the clean room air have considered to be the cause of the defective. That is, it has been pointed out that organic substances are adsorbed on the surface of semiconductor substrates (silicon wafers) in clean rooms, to deteriorate device characteristics (for example, Fujii, "Gaseous Contaminants and Current Situation for Countermeasure of Removal", Air Cleaning, Vol. 32, No. 3, p 43 (1994), published from the Foundation of Japan Air Cleaning Society).
Further, it has been well-known that an n-type semiconductor is obtained by doping P (phosphorus) and a p-type semiconductor is obtained by doping B (boron, into a silicon wafer in semiconductor manufacturing steps but, if phosphorus compounds or boron compounds are present in the clean room air, these may possibly cause unnecessary doping, so that it is necessary to remove such ingredients from the clean room air.
The present invention has been accomplished to solve the problems described above and it is an object thereof to provide an air filter for trapping air-born particles that can eliminate the presence of gaseous organic substances, for example, in clean rooms, semiconductor production apparatus or the like, a method of manufacturing an air filter therefor, a treatment agent constituting the air filter, a method of manufacturing a filter medium, a clean room and a local facility such as a semiconductor production apparatus in which gaseous organic substances are not present, as well as a clean room and a local facility in which phosphorus compounds and boron compounds are not present.
DISCLOSURE OF THE INVENTION
The present inventors have made earnest studies for attaining the foregoing object and, as a result, have accomplished the present invention based on the finding that presence of gaseous organic substances in a clean room and a local facility such as a semiconductor production apparatus is mainly caused by air filters disposed to air introduction paths and gaskets intervened for attaching the air filters to openings, for example, of a ceiling.
That is, it has been found by the study of the present inventors that gaseous organic substances such as cyclosiloxanes, carboxylic acid esters, phosphoric acid esters, hydrocarbons, and phenols are released from the existent air filters described above and that such organic substances are released from treatment agents impregnated between each of fibers upon forming the fibers into a cloth-like filter medium (including a binder for binding fibers, a water repellent for improving dust trapping effect and a plasticizer or an antioxidant), silicone oils deposited to fibers in a case where the filter medium is glass fibers (this is a reinforcing material upon spinning glass fibers which serves also as a
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Imafuku Masayuki
Kobayashi Sadao
Wakayama Yoshihide
Bushey C. Scott
Taisei Corporation
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