Gas separation: apparatus – Solid sorbent apparatus – Plural diverse separating means
Patent
1999-05-12
2000-11-14
Spitzer, Robert H.
Gas separation: apparatus
Solid sorbent apparatus
Plural diverse separating means
96154, 553852, 55524, 55DIG5, B01D 5304
Patent
active
061464511
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an air filter capable of being installed in a high efficiency air cleaning apparatus, an air cleaning device or the like such as a clean room, a clean bench, a storage means (stocker) for half-finished products, etc., for removing gaseous inorganic and/or organic impurities contained in the limited space that is defined by the high efficiency air cleaning apparatus, the device or the like. The invention also relates to a method for manufacturing the air filter and also relates to the high efficiency air cleaning apparatus, the device or the like provided with the filter manufactured according to the method.
In the following description, the expression "air cleaning apparatus," and "device" seem to be too general, so that it would be described in terms of "clean room," "clean bench," "storage means (stocker)" or others having the function similar thereto, without altering the gist and scope of the invention, for more practical and better understanding of the invention.
BACKGROUND OF THE INVENTION
Today, the clean room, the clean bench, and the like are widely used for manufacturing a large scale integrated (LSI) circuit, a liquid crystal display (LCD) panel and so forth, all of which have to be carefully protected from specific impurities or contaminants contained in the ordinary air. In case of manufacturing products like these items, however, it is not rare that they are forced to be kept inside a carrier or a stocker in the form of a half-finished product after having passed through predetermined manufacturing steps. Consequently, they come to exposed to the inside atmosphere of the carrier or stocker until they are transferred to the next manufacturing step. Furthermore, it is also not rare that this intermediate storage or waiting state is continued over a period of several to several tens hours. Consequently, should the atmosphere of the clean room or the like be insufficiently cleaned, gaseous impurities contained therein would be deposited on the semiconductor substrate surface of LSI or glass substrate surface of LCD. Acid substances, alkaline substances, organic substances, and various dopants are considered as impurities that would give an ill influence to the performance of LSI or LCD when they are deposited on the substrate surface thereof. Especially, sulfur oxides SOx among acid substances reacts with ammonia gas contained, if any, in the clean room atmosphere to unfavorably form a thin cloudy matter consisting of ammonium sulfate over the surface of a silicon wafer, a glass substrate, a lens, a mirror, a hard disk, a magnetic disk, and so forth. Thus, this would give the ill influence to the manufacture of semiconductor elements, LCD substrates, and magnetic memory parts. The most popular sulfurous acid gas representing sulfur oxides may be generated from various sources. For instance, it may be generated from sulfuric acid that is used in the rinsing process carried out inside the clean room, and also it might be contained as an atmospheric pollutant or volcanic gas in the outdoor air introduced to the clean room. Boron B also may act as a contaminant against thin film transistors (TFT), and it contaminates the channel region of TFT to make the characteristic thereof worse.
According to one example of the actual measurement of various contaminants contained in the atmosphere of the ordinary clean room that is not provided with any chemical protective measure against gaseous contaminants, it is reported that there are contained in such atmosphere acid substances of about 100 ppt-1,000 ppt, basic substances of about 1,000 ppt-10,000 ppt, organic substances of about 1,000 ppt-10,000 ppt, and dopants of about 10 ppt-100 ppt, respectively.
According to the allowable concentration (ppt) of the chemical contaminant required for 0.25.mu. process (after '98), which is disclosed in the article entitled "Forecast Of Airborne Molecular Contamination Limits For The 0.25 Micron High Performance Logic Process" of Technology Transfer #95052812A-TR
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Sakata Soichiro
Sato Katsumi
Takahashi Hideto
Spitzer Robert H.
Takasago Thermal Engineering Co.
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