Metal working – Barrier layer or semiconductor device making
Patent
1996-09-05
1998-06-02
Breneman, R. Bruce
Metal working
Barrier layer or semiconductor device making
118715, 118719, C23C 1600
Patent
active
057592144
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a nitrogen gas supply system, more particularly to a system for supplying nitrogen gas to a wafer processing unit and to a wafer conveyor in a semiconductor producing apparatus.
BACKGROUND ART
In the field of semiconductor industry, nitrogen gas is consumed in huge amounts. Accordingly, these days, a nitrogen gas generator such as a cryogenic air separation plant is installed near the semiconductor producing apparatus so as to supply nitrogen gas generated by the nitrogen gas generator to each section.
FIG. 1 shows one example of prior art nitrogen gas supply system for supplying nitrogen gas to a wafer processing unit 11 and to a nitrogen gas tunnel type wafer conveyor (hereinafter simply referred to as conveyor) 12. A cryogenic air separation plant 13 is employed as the nitrogen gas generator. The cryogenic air separation plant 13 can relatively easily provide high-purity nitrogen gas to be suitably employed for treating semiconductors.
Feedstock air introduced through a passage 14 into the cryogenic air separation plant 13 is cooled by a heat exchanger 15, after compression and purification, and is introduced to a distillation column 16, where it is subjected to well-known condensation and fractionation treatments to generate nitrogen gas. After the thus formed nitrogen gas is allowed to resume substantially normal temperature by the heat exchanger 15, the nitrogen gas is allowed to flow through a passage 17 to be supplied through a passage 17a to the wafer processing unit 11 and through a passage 17b to the conveyor 12, respectively.
The wafer processing unit 11 is an apparatus for applying a predetermined processing to wafers so as to produce semiconductor products. Usually, a vacuum pump 18 is connected to the wafer processing unit 11 to provide a pressure lower than atmospheric pressure for wafer treatment. While consumption of nitrogen gas in this wafer processing unit 11 fluctuates depending on the operational state of the processing unit 11, the cryogenic air separation plant 13 is preferably operated such that the amount of nitrogen gas to be generated may be constant so as to ensure stable operation of the separation unit 13. Accordingly, the nitrogen gas to be fed from the cryogenic air separation plant 13 to the wafer processing unit 11 assumes an oversupply or undersupply state depending on the operational state of the wafer processing unit 11. Thus, in the oversupply state, the nitrogen gas generated by the cryogenic air separation plant 13 is partly liquefied and stored in a liquid nitrogen tank 19, whereas the liquid nitrogen in the liquid nitrogen tank 19 is gasified, in the undersupply state, to be introduced through the passage 17a to the wafer processing unit 11.
Meanwhile, the conveyor 12 Is a nitrogen gas levitating conveyor composed, for example, of a box-like tunnel and a perforated panel disposed in the tunnel to demarcate the internal space of the tunnel into an upper space and a lower space, and nitrogen gas is designed to be supplied to the space defined below the perforated panel to be jetted through openings of the panel in a predetermined direction to transport wafers placed on the perforated panel being levitated by the nitrogen gas.
The nitrogen gas supplied into the tunnel of the conveyor 12 is not only employed for the transportation of wafers but also is brought into contact with the wafers when jetted through the perforated panel to keep purity of the wafers. More specifically, the nitrogen gas brought into contact with the wafers protects the wafer surfaces from moisture and hydrocarbons. Although the tunnel constituents of the conveyor 12 may sometimes generate a gas causative of wafer contamination, such gas is carried away by the nitrogen gas.
The conveyor 12 and the wafer processing unit 11 are connected to each other via a gate valve 20 for wafer transference. This gate valve 20 is opened as necessary to pick up a wafer transported through the tunnel of the conveyor 12 using suitable pick-up means such as a va
REFERENCES:
patent: 5256204 (1993-10-01), Wu
patent: 5527390 (1996-06-01), Ono et al.
Ishihara Yoshio
Ohmi Tadahiro
Breneman R. Bruce
Lund Jeffrie R.
Nippon Sanso Corporation
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