Evacuating unit with reduced diameter exhaust duct

• US 6,474,949 B1
• Filed: 11/20/2000
• Issued: 11/05/2002
• Est. Priority Date: 05/20/1998
• Status: Expired due to Fees

• Current Assignee: Ebara Corporation
• Original Assignee: Ebara Corporation
• Inventors: Isozaki, Takahiro, Arai, Satoshi, Usui, Katsuaki
• Primary Examiner(s): Freay, Charles G.
• Assistant Examiner(s): Solak, Timothy P.
• Application Number:
  US09/700,748
• Time in Patent Office: 715 Days
• Field of Search: 417/2, 417/44.2, 417/43, 417/53
• US Class Current: 417/2
• CPC Class Codes: F04B 2203/0209 Rotational speed
• CPC Class Codes: F04B 37/08 by condensing or freezing, e.g. cryogenic pumps
• CPC Class Codes: F04B 49/06 Control using electricity regulating by means of floats actuating electric switches F04B49/04
• CPC Class Codes: F04D 19/04 specially adapted to the production of a high vacuum, e.g. molecular pumps
• CPC Class Codes: F04D 27/0261 by varying driving speed
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

An apparatus for and a method of evacuating a vacuum chamber (process chamber) or the like of a semiconductor fabrication facility, for example. The evacuating apparatus has a vacuum chamber to be evacuated, a discharge pipe connecting the vacuum chamber to an atmospheric port, a vacuum pump connected to the discharge pipe and operable at a variable rotational speed, and a controller for controlling the rotational speed of the vacuum pump.

Claims

1. An apparatus for evacuating a vacuum chamber through a discharge pipe, comprising:

a vacuum pump having a variable rotational speed;

a controller for controlling the rotational speed of said vacuum pump to keep a back pressure on the vacuum pump in a predetermined target range; and

a discharge pipe competing an outlet port of the vacuum pump to an atmospheric port and having a diameter corresponding to a specific flow capability in which said diameter is less than a predetermined diameter corresponding to an evacuating flow capability of the vacuum pump,

wherein said predetermined target range is determined depending on the evacuating flow capability of the vacuum pump and a conductance of the discharge pipe.

2. An apparatus according to claim 1, further comprising:

a discharge port on said vacuum pump; and

a back pressure sensor connected to said discharge port for detecting a back pressure on the vacuum pump, wherein said controller controls the rotational speed of said vacuum pump based on a detected output from said back pressure sensor.

3. An apparatus according to claim 1, wherein said controller controls the rotational speed of said vacuum pump so as to keep said back pressure less than a predetermined target range.

4. An apparatus according to claim 3, wherein a booster pump is further provided in series with said vacuum pump.

5. An apparatus according to claim 1, wherein said controller controls the rotational speed of said vacuum pump according to a previously inputted pattern so as to keep said hack pressure in said predeternined target range.

6. An apparatus according to claim 5, wherein said previously inputted pattern comprises linearly increasing rotational speed of the vacuum pump with a gradient until a predetermined speed and then maintaining the predetermined speed.

7. An apparatus according to claim 6, wherein said gradient is determined depending on the evacuating flow capability of the vacuum pump and a conductance of the discharge pipe.

8. An apparatus according to claim 1, wherein a diameter of said discharge pipe is ¼

of a diameter corresponding to an evacuating flow capability.

9. A method of evacuating a vacuum chamber through a discharge pipe with a vacuum pump having a variable rotational speed, comprising:

connecting a discharge pipe from an outlet port of the vacuum pump to the atmospheric port, said discharge pipe having a flow capability less than an evacuating flow capability of said vacuum pump; and

controlling the rotational speed of said vacuum pump so as to keep the back pressure in a predetermined target range wherein said predetermined target range is determined depending on an evacuating flow capability of the vacuum pump and a conductance of the discharge pipe.

10. A method according to claim 9, further comprising:

detecting a back pressure of said vacuum pump by a pressure sensor; and

controlling said rotational speed of said vacuum pump based on detected back pressure thereby.

11. A method according to claim 10, wherein said controller controls the rotational speed of said vacuum pump according to a previously inputted pattern so as to keep said back pressure in said predetermined target range.

12. A method according to claim 11, further comprising:

increasing the rotational speed linearly with a gradient until a predetermined speed is reached; and

maintaining the predetermined speed according to said previously inputted pattern.

13. A method according to claim 12, wherein said gradient is determined depending on the evacuating flow capability of the vacuum pump and the conductance of the discharge pipe.

14. A method according to claim 9, wherein a booster pump is connected in series with said vacuum pump.

15. A method according to claim 9, wherein a diameter of said discharge pipe is ¼

of a diameter corresponding to an evacuating flow capability.