Gas separation: processes – With timing of operation
Reexamination Certificate
2000-06-02
2001-09-04
Smith, Duane (Department: 1724)
Gas separation: processes
With timing of operation
C055S385200, C055S356000, C055S467000, C055S385100, C096S424000, C096S115000, C095S090000, C095S273000
Reexamination Certificate
active
06284020
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for removing detrimental chemical impurities adhered to substrates to maintain necessary high cleanliness, and to a box for accommodating the substrates to store and transfer. The substrates include ones such as semiconductor wafers that are between processing machines in manufacturing semiconductor devices, substrates on which LCD pattern is formed, substrates for photo-masking, and magnetic discs.
2. Discussion of the Background
As semiconductor devices become finer- and denser-packed, processing becomes more complicated. As a result, adverse affects of contamination due to gaseous impurities generated in the process become conspicuous. For instance, in the dry etching process or the CVD (Chemical Vapor Deposition) process for metallic wiring, acid gases of high vapor pressure such as chlorine (Cl) and fluorine (F) compounds remain on semiconductor wafers to corrode the metallic wiring on the semiconductor wafers. Further, in the deep-UV lithography processes, basic gases such as ammonia or the like in the atmosphere or adsorbed by the semiconductor wafers cause an abnormality of pattern in machining the resist. These adverse influences due to the gaseous impurities on process performance cause problems.
In the existing manufacturing method of semiconductor devices, to secure and maintain cleanliness of the atmosphere in a clean room in which the semiconductor wafers are processed, a gaseous impurity-trapping filter such as a chemical filter or activated carbon filter is provided to an air conditioner to trap and remove efficiently these detrimental gaseous impurities. By employing such a method, the detrimental gaseous impurities in the process are prevented from causing contamination.
However, when transferring semiconductor wafers from one processing machine to another processing machine or from one room to another room in a clean room, and from one machine to another machine laid between clean rooms, as a clean space isolated from the space inside or outside the clean room, hermetically sealed boxes are in use. Accordingly, when transferring wafers from one process to another process, in the hermetically sealed box, due to out gases from the wafers, concentrations of these gaseous impurities become high. As a result, these gaseous impurities brought in by the wafers themselves contaminate the clean room.
Japanese Patent Application No. HEI 6-87964 discloses a method for cleanly isolating semiconductor wafers from contaminated space outside a clean room. In the method, semiconductor wafers are accommodated in a box of which atmosphere is the same with that of the clean room, and the box is transferred from a clean room to another clean room.
In the box constituted for the inside thereof to communicate with the outside atmosphere, a particle-trapping HEPA (High Efficiency Particle Air) filter or ULPA (Ultra Low Penetration Air) filter and a gaseous impurity-trapping chemical filter are disposed. In the box, semiconductor wafers and substrates for LCD, which are objects to be processed, are accommodated and transferred. However, in this method, the chemical filter filters the atmosphere always containing impurities to supply into the box. Accordingly, there is a problem that the chemical filter has very short life.
Further, Japanese Patent Laid-open Publication (KOKAI) No. HEI 8-148551 discloses a hermetically sealed case for accommodating substrates that is provided with filters that trap gaseous impurities at a gas inlet and outlet where the atmospheric gas goes in and out. However, the flow rate of the gas in the atmosphere, being restricted to approximately 1 1/min, is impractical. For instance, when a volume of 23 1 of a box for 8-inch wafer is replaced by the atmospheric gas to trap impurities, under such a flow rate, more than 20 min is required. Accordingly, impurities that are brought in the box from the external atmosphere during opening/closing to insert the wafers are adhered to the wafers. The impurity gas, being a base such as ammonia, is adsorbed by resist on the surface of the wafer to react to the resist, and being an acid such as sulfur oxide and chlorine, is absorbed by metallic wiring on the surface of the wafer to corrode the metallic wiring.
SUMMARY OF THE INVENTION
The present invention is carried out considering the aforementioned circumstances. An object of the present invention is to provide a method by which in a closed space such as a clean room gaseous impurities brought in by substrates such as semiconductor wafers or the like are efficiently removed to maintain an atmosphere of high cleanliness. Another object of the present invention is to provide a box for accommodating these substrates.
The present invention involves a method that in transferring substrates such as semiconductor wafers from one processing machine to another processing machine in a clean room or laid across between clean rooms and in storing these, can maintain cleanliness of the substrates such as semiconductor wafers. That is, with a box comprising a clean space, the substrates such as the semiconductor wafers are accommodated in the clean space, transferred and stored. The clean space, isolated from the space inside or outside the clean room, involves of circulating air generated by a filter and a ventilating fan.
A method of maintaining cleanliness of a substrate of the present invention comprises a first step of accommodating at least one substrate with a gaseous impurity-trapping filter disposed close thereto in a hermetically sealed box, and a second step of circulating an atmosphere in the box at a rate of two times or more per minute so that impurity in the atmosphere is adsorbed by the gaseous impurity-trapping filter.
According to the present invention, in the second step, the atmosphere in the box is preferably circulated at a rate of from two to five times per minute. In the box, to the substrate, a particles-trapping filter is disposed in the further close vicinity.
An atmosphere circulating apparatus circulates the atmosphere in the box. The atmosphere circulating apparatus is intermittently operated as the need arises.
As the substrate of the present invention, for instance semiconductor substrates or glass substrates for mask process can be cited.
The present method for maintaining cleanliness of the substrates comprises a third step of transferring the box to a prescribed position while maintaining cleanliness of the atmosphere in the box.
The box for accommodating substrates of the present invention comprises a housing in which space for accommodating the substrate is hermetically closed with a lid, and a gaseous impurity-trapping filter disposed in the housing and adsorbing impurity contained in an atmosphere of the space, and an atmosphere circulating apparatus having a circulating capacity to circulate the atmosphere through the gaseous impurity-trapping filter, a ratio of the circulating capacity to the space volume being two or more, preferably from two to five.
In the present invention, the gaseous impurity-trapping filter is formed in pleat, in honeycomb, in sponge, in particle or in plane shape. The present box for accommodating the substrates is provided with a portable power supply. The portable power supply is attached to the outside of the housing.
In the present box for accommodating the substrates, the atmosphere circulating apparatus is intermittently operated.
Inside of the present box for accommodating the substrates comprises a particles-trapping filter between the gaseous impurity-trapping filter and the substrates.
In the present invention, as the substrate, semiconductor substrate and glass substrate for mask processing can be cited.
According to the present invention, in steps requiring high cleanliness such as semiconductor wafer processing steps, the semiconductor wafer or the like can be transferred and stored in the efficiently hermetic-sealed box, in which high cleanliness of the atmosphere is maintained by use of a gaseous impurity-t
Katano Makiko
Mizuno Ayako
Okumura Katsuya
Greene Jason M.
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Smith Duane
LandOfFree
Method of maintaining cleanliness of substrates and box for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of maintaining cleanliness of substrates and box for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of maintaining cleanliness of substrates and box for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2437408