Vacuum exhaust apparatus and drive method of vacuum apparatus

Abstract

Pairs of rotors (R1, R2, R3, R4, R5 and R6) driven rotationally by a motor (22) are disposed in the body (21) of a main pump (20) comprising a multistage Roots dry vacuum pump. A suction opening (23) communicating with the rotor chamber of the rotor R1 is provided in the upper wall portion at the left end of the body (21). A delivery section (24) communicating with the delivery side of the rotor chamber of rotor R6 on the final stage is coupled to an exhaust pipe (25) and is provided with a silencer (26) and further coupled to a check valve (28) through a pipe (27). The check valve (28) has its forward direction toward the atmospheric side. The delivery section (24), or a delivery section (24') at the side intermediate stage, is coupled to an auxiliary pump (30) having an exhaust capacity smaller than that of the main pump (20). When the motor (22) is driven, gas exhausted through rotation of the rotors (R1-R6) is carried sequentially to the downstream side from the rotor chambers and a vacuum processing chamber coupled to the suction opening (23) is exhausted. The delivery section (24) on the final stage is exhausted by driving the auxiliary pump (30), and the pressure is reduced. Consequently, the burden of the exhaust action on the rotor (R6) on the final stage or the rotor (R5) on the intermediate stage is lessened, and the power consumption of the motor (22) can be reduced significantly as compared with the prior art.

Description

[TECHNICAL FIELD][0001] This invention relates to a vacuum exhaust apparatus, for example, for semiconductor manufacturing equipment and more particularly to a vacuum exhaust apparatus of the energy conservation type and a driving method for the vacuum exhaust apparatus to reduce consumed electric power.[BACKGROUND OF THE TECHNIQUE][0002] Oil-sealed rotary vacuum pumps were used in most cases for early semiconductor manufacturing equipment. Electric power consumed by the oil-sealed rotary vacuum pump is generally little and it has a construction by which low ultimate pressure can be easily obtained. However, the following points should be noted where the oil-sealed rotary pump is used in semiconductor manufacturing equipment:[0003] (1) The gasses used in semiconductor manufacturing equipment are strongly reactant in most cases. When such gas is exhausted, it reacts with vacuum pump oil and so produces reaction materials which sometimes makes the vacuum pump impossible to rotate or t...

AI Technical Summary

Benefits of technology

0035] A further object of the invention is to provide a drive method for a vacuum exhaust

Problems solved by technology

(1) The gasses used in semiconductor manufacturing equipment are strongly reactant in most cases. When such gas is exhausted, it reacts with vacuum pump oil and so produces reaction materials which sometimes makes the vacuum pump impossible to rotate or the pump oil is caused to deteriorate in lubrication capability.

(2) Vapor of the vacuum pump oil diffuses into the vacuum treatment or processing chamber and contaminates it.

(3) Used vacuum pump oil contains arsenic compound and phosphorus compound as toxic material in most cases. Treatment of such harmful industrial waste requires considerable cost and the number of management procedures is also considerable. For the above reasons a recently developed dry vacuum pump (called also a "dry-sealed vacuum pump" according to the international standard ISO / DIS3529 / .dagger-dbl.U-1975) which does not use sealing oil, is used instead of the oil-sealed rotary vacuum pump.

However, there is a problem that the required electric power of the dry vacuum pump is larger than that of the oil-sealed vacuum pump.

However, the pitch changes of the screw grooves are limited to some extent.

However, mechanical trouble is apt to occur.

The correct angle of the rotor side surface to the axis is difficult to manufacture, and the gap between the rotor side surface and the partition wall is difficult to maintained at 0.1 mm to 0.2 mm.

However, in the vacuum exhaust apparatus 2, the energy of the whole vacuum exhaust system including the first pump 3 cannot be always effectively conserved, although the consumed electric power of the first pump 3 can be definitely reduced.

Generally, the vacuum processing chamber 1 of the semiconductor manufacturing apparatus contains fine particles which are apt to fly up, and to be attached to a semiconductor wafer placed in the vacuum processing chamber 1, resulting in a bad semiconductor.

However, the butterfly valve itself and an opening control apparatus for valve opening are expensive and raise the cost.

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