Method and apparatus for enhanced cleaning of a workpiece with mechanical energy

• US 5,975,094 A
• Filed: 11/26/1997
• Issued: 11/02/1999
• Est. Priority Date: 11/26/1997
• Status: Expired due to Fees

• Current Assignee: SpeedFam-Ipec Corporation
• Original Assignee: Speedfam Corporation (Lam Research Corporation)
• Inventors: Shurtliff, Eric C.
• Primary Examiner(s): Till, Terrence R.
• Application Number:
  US08/979,098
• Time in Patent Office: 706 Days
• Field of Search: 15/21.1, 15/77, 15/88.2, 15/88.3, 15/94, 15/102, 15/103.5, 134/1.3, 134/6, 134/7, 134/69 R, 134/122 R, 134/184, 134/902
• US Class Current: 134/1.3
• CPC Class Codes: H01L 21/67046 using mainly scrubbing means, e.g. brushes

Abstract

An improved cleaning apparatus for cleaning semiconductor wafers, rigid memory disks, flat panel displays, and other workpieces employs vibrational mechanical energy in addition to contact mechanical cleaning. The cleaning apparatus includes a cleaning element configured to contact and scrub a workpiece during a cleaning process. The cleaning clement is coupled to a mechanical energy emitter that generates low frequency mechanical vibrations (or ultrasonic mechanical energy) at a predetermined frequency. The mechanical energy is conducted through the cleaning element and to the workpiece to facilitate removal of particulate and debris from the surface of the workpiece. Use of ultrasonic energy also causes the cleaning solution to cavitate, thus providing ultrasonic cleaning to the workpiece via the cleaning solution.

Claims

1. An apparatus for cleaning a workpiece, said apparatus comprising:

a cleaning element configured to contact said workpiece during a cleaning process wherein said cleaning element comprises a substantially rigid core configured to conduct mechanical energy and a cleaning material coupled to said core, said cleaning material contacting said workpiece during said cleaning process; and

a mechanical energy emitter in communication with said cleaning element, said mechanical energy emitter being configured to apply mechanical energy to said cleaning element during said cleaning process, said mechanical energy emitter comprising means for transforming an excitation signal into ultrasonic mechanical energy, and means for directing said ultrasonic mechanical energy to said cleaning element.

2. An apparatus according to claim 1, wherein said cleaning material substantially surrounds said core.

3. An apparatus according to claim 1, wherein said core contacts a portion of said mechanical energy emitter such that mechanical energy is transmitted from said mechanical energy emitter to said cleaning element.

4. An apparatus according to claim 1, wherein said core is formed from material suitable for mechanical energy conduction.

5. An apparatus according to claim 1, wherein said cleaning material is coupled to said core via a mounting element, said mounting element being configured to contact said core and to substantially prevent contact between said cleaning material and said core.

6. An apparatus according to claim 5, wherein:

said core includes a nodal point located thereon, said nodal point transmitting a substantially reduced amount of mechanical energy relative to other points located on said core; and

said mounting element contacts said core approximately at said nodal point.

7. An apparatus according to claim 1, wherein said means for directing comprises an ultrasonic horn configured to couple to said cleaning element.

8. An apparatus according to claim 1, wherein said mechanical energy emitter causes said cleaning element to mechanically vibrate during said cleaning process.

9. An apparatus according to claim 1, further comprising means for applying a cleaning solution to said cleaning element during said cleaning process.

10. An apparatus for cleaning a workpiece, said apparatus comprising:

a cleaning element configured to contact and mechanically clean said workpiece during a cleaning process, said cleaning element comprising a substantially rigid core; and

means for applying mechanical energy at a predetermined frequency to said core during said cleaning process, said predetermined frequency being within a range of approximately 30 kHz to 50 kHz.;

wherein;

said core is tuned to facilitate conduction of mechanical energy at said predetermined frequency;

said cleaning element is substantially cylindrical in shape;

said cleaning element is configured to rotate about its longitudinal axis during said cleaning process; and

said means for applying mechanical energy causes said cleaning element to mechanically vibrate at approximately said predetermined frequency during said cleaning, process.

11. An apparatus according to claim 10, further comprising a solution tank in which said cleaning element is substantially immersed in a cleaning solution during said cleaning process, wherein said means for applying mechanical energy is further configured to apply mechanical energy to said cleaning solution during said cleaning process.

12. An apparatus according to claim 10, wherein said cleaning element further comprises a cleaning material coupled to said core, said cleaning material contacting said workpiece during said cleaning process.

13. An apparatus according to claim 12, wherein:

said core includes a nodal point located thereon, said nodal point transmitting a substantially reduced amount of mechanical energy relative to other points located on said core; and

said cleaning material is coupled to said core via a mounting element located approximately at said nodal point.

14. An apparatus according to claim 13, wherein the location of said nodal point upon said core is associated with at least one of said predetermined frequency, a material from which said core is formed, and the dimensions of said core.

15. An apparatus according to claim 13, wherein:

said core is substantially cylindrical in shape and comprises an annular channel formed therein at said nodal point;

said mounting element is substantially ring-shaped and is received within said annular channel; and

said mounting element is capable of rotation around said core.

16. An apparatus according to claim 12, wherein said cleaning material substantially surrounds said core.

17. An apparatus according to claim 10, wherein said means for applying mechanical energy is coupled to said core.

18. An apparatus according to claim 17, wherein said means for applying mechanical energy comprises an ultrasonic emitter.

19. A method for cleaning workpieces, said method comprising the steps of:

providing a cleaning element configured to contact a workpiece, wherein said cleaning element is substantially cylindrical in shape;

translationally moving said cleaning element relative to said workpiece to thereby perform mechanical cleaning of said workpiece by rotating said cleaning element about its longitudinal axis; and

applying vibrational energy to said cleaning element during said moving step to thereby perform vibrational mechanical cleaning of said workpiece, wherein said applying step causes said cleaning element to vibrate at an ultrasonic frequency.

20. A method according to claim 19 wherein:

said cleaning element comprises a substantially rigid core configured to conduct ultrasonic mechanical energy; and

said method further comprises the step of tuning said core to facilitate conduction of ultrasonic mechanical energy at said ultrasonic frequency.

21. A method according to claim 19, further comprising the steps of:

substantially immersing said cleaning element in a cleaning solution; and

applying vibrational energy to said cleaning solution during said moving step to thereby perform vibrational mechanical cleaning of said workpiece.

22. A method according to claim 19, wherein said applying step is performed by a mechanical energy emitter configured to communicate mechanical energy to said cleaning element.

23. A method according to claim 19, wherein said applying step comprises the steps of:

transforming an excitation signal into vibrational energy; and

directing said vibrational energy to said cleaning element.

24. A method for cleaning workpieces, said method comprising the steps of:

providing a cleaning element configured to contact a workpiece;

dispensing a cleaning solution onto said cleaning element;

translationally moving said cleaning element relative to said workpiece to thereby perform mechanical cleaning of said workpiece, said moving step being performed after said dispensing step; and

applying vibrational energy to said cleaning element during said moving step to thereby perform vibrational mechanical cleaning of said workpiece, said applying step causing said cleaning element to vibrate at an ultrasonic frequency.

25. A method according to claim 24, wherein:

said cleaning element comprises a substantially rigid core configured to conduct ultrasonic mechanical energy; and

said method further comprises the step of tuning said core to facilitate conduction of ultrasonic mechanical energy at said ultrasonic frequency.

26. A method according to claim 24, further comprising the steps of:

substantially immersing said cleaning element in a cleaning solution; and

applying vibrational energy to said cleaning solution during said moving step to thereby perform vibrational mechanical cleaning of said workpiece.

27. A method according to claim 24, wherein said applying step is performed by a mechanical energy emitter configured to communicate mechanical energy to said cleaning element.

28. A method according to claim 24, wherein said applying step comprises the steps of:

transforming an excitation signal into vibrational energy; and

directing said vibrational energy to said cleaning element.