Gas separation: apparatus – Solid sorbent apparatus – Plural diverse separating means
Patent
1998-09-28
2000-09-19
Spitzer, Robert H.
Gas separation: apparatus
Solid sorbent apparatus
Plural diverse separating means
96154, 55524, 55DIG5, B01D 5304
Patent
active
061205842
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention generally relates to an air cleaning apparatus such as a clean room, a clean bench and so forth, which is used in the manufacture of precision products such as semiconductor elements (e.g. LSI), liquid crystal displays (LCD) and so forth, and has the function of controlling the relative humidity of the air in the working space and also removing gaseous organic impurities and fine particulate impurities contained in air of the working space. More particularly, the invention relates to an air filter which can be installed in such apparatus for removing gaseous organic impurities contained in the air of the working space, and further relates to a method for manufacturing the same.
In the following description, the expression `air cleaning apparatus` seems to be too general, so that it will be expressed as just `clean room` or `clean room or the like` for more practical and concrete understanding of the invention.
BACKGROUND ART
It is well known that a clean room, a clean bench and so on are widely made use of in the process of manufacturing LSI's and LCD's. For instance, in case of manufacturing a DRAM of 1-megabit from a bare wafer (silicon wafer), there is required a semiconductor manufacturing line consisting of the manufacturing steps of about 200. Also, in case of manufacturing a TFT of the 9.4 type from a bare glass plate (LCD substrate), there is required a LCD panel manufacturing line consisting of the manufacturing steps of about 80. In such a manufacturing line, it is not possible in practice to continuously convey the object good e.g. silicon wafer or LCD substrate from process to process up to the goal without leaving the object good in any standby position. Consequently, it may happen that semifinished products are held in a certain place or area for hours being exposed to the air of the working space. For instance, in the manufacturing line of the TFT-LCD, the half-finished LCD substrate which has been finished up to the formation of an electric circuit through the prior steps, is left in a standby position in a proper carrier or a storage compartment or room for several to several tens hours being exposed to the ordinary clean room air.
As such, when the silicon wafer or the LCD substrate are left in the ordinary clean room air for a long time, it often happens that some organic substances are deposited on the surface of the wafer or the LCD substrate. If such deposition of organic substances occurs, it causes the following an inconvenient state. That is, if an insulating oxide film (SiO.sub.2) is formed on the silicon wafer surface on which organic substances are deposited, the carbon component of the organic substance is captured within the silicon dioxide film, which reduces the dielectric strength of the silicon dioxide film, thus a leakage current being increased to a great extent. Furthermore, adsorption of the organic substances disturbs the close contact between the silicon wafer surface and a photoresist film applied thereto, thus, causing failure in light exposure and etching in the photolithographic process, and resulting in incorrect formation of a circuit pattern. In addition, adsorption of the organic substances results in increasing the surface resistivity of the silicon dioxide film formed on the silicon wafer, which causes the silicon wafer to be easily charged, thereby electrostatically adsorbing the fine airborne particles thereon, and readily causing the dielectric breakdown thereof. Still further, if organic impurities contained in the clean room air are irradiated by the ultra-violet rays emitted from the optical instruments, an optical CVD reaction might take place in the clean room air, so that products generated through such reaction might stick to and cloud up the surfaces of the lens and the mirror constituting an optical instrument such as a light projector, thereby reducing the optical efficiency.
Organic substances contained in the air of the working space can give a similar ill influence to the glass substrate as the LCD substrat
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Okada Takao
Sakata Soichiro
Sato Katsumi
Takahashi Hideto
Spitzer Robert H.
Takasago Thermal Engineering Co., Ltd.
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