Method of cleaning and treating a semiconductor device including a micromechanical device

• US 6,024,801 A
• Filed: 12/09/1996
• Issued: 02/15/2000
• Est. Priority Date: 05/31/1995
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Wallace, Robert M., Douglas, Monte A.
• Primary Examiner(s): Gulakowski, Randy
• Assistant Examiner(s): CHAUDHRY, SAEED T
• Application Number:
  US08/761,579
• Time in Patent Office: 1,163 Days
• Field of Search: 134/1, 134/1.3, 134/19, 134/26, 134/30, 427/299, 438/694, 438/770, 438/771
• US Class Current: 134/1
• CPC Class Codes: B08B 7/00 Cleaning by methods not provided for in a single other subclass or a single group in this subclass
• CPC Class Codes: B08B 7/0021 by liquid gases or supercritical fluids
• CPC Class Codes: B81B 3/0005 Anti-stiction coatings
• CPC Class Codes: B81C 1/00857 after manufacture, e.g. back-end of the line process
• CPC Class Codes: B81C 1/0096 For avoiding stiction when the device is in use, i.e. after manufacture has been completed
• CPC Class Codes: B81C 2201/112 Depositing an anti-stiction or passivation coating, e.g. on the elastic or moving parts
• CPC Class Codes: B81C 2201/117 Using supercritical fluid, e.g. carbon dioxide, for removing sacrificial layers
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

A method of cleaning and treating a device, including those of the micromechanical (10) and semiconductor type. The surface of a device, such as the landing electrode (22) of a digital micromirror device (10), is first cleaned with a supercritical fluid (SCF) in a chamber (50) to remove soluble chemical compounds, and then maintained in the SCF chamber until and during the subsequent passivation step. Passivants including PFDA and PFPE are suitable for the present invention. By maintaining the device in the SCF chamber, and without exposing the device to, for instance, the ambient of a clean room, organic and inorganic contaminants cannot be deposited upon the cleaned surface prior to the passivation step. The present invention derives technical advantages by providing an improved passivated surface that is suited to extend the useful operation life of devices, including those of the micromechanical type, reducing stiction forces between contacting elements such as a mirror and its landing electrode. The present invention is also suitable for cleaning and passivating other surfaces including a surface of semiconductor wafers, and the surface of a hard disk memory drive.

Claims

1. A method of cleaning and treating a device surface, comprising:

placing said device surface in an enclosed and controlled environment;

exposing said device surface to a cleaning medium rendered as a supercritical fluid;

purging said environment of substances including a soluble chemical compound liberated from said device surface by said cleaning medium; and

treating said device surface in said enclosed and controlled environment by depositing a lubrication passivant before said device surface is removed from said environment to prevent contaminants from depositing upon said device surface prior to said treatment.

2. The method of claim 1 wherein said cleaning medium comprises a cleaning additive.

3. The method of claim 1 further comprising varying a density of said cleaning medium.

4. The method of claim 1 further comprising varying a thermodynamic state of said cleaning medium.

5. The method of claim 1 further comprising irradiating said device surface to increase a reactivity between said cleaning medium and said device surface.

6. The method as specified in claim 1 wherein an inert gas is used to purge said environment.

7. A method for cleaning and treating a micro mechanical device, comprising:

placing said device in a sealed chamber;

introducing into said chamber a cleaning medium rendered as a supercritical fluid;

flushing from said chamber substances liberated from said device and said chamber by said cleaning medium; and

introducing into said chamber a treating medium forming a lubricating film on said device after said step of flushing and before said device is removed from said chamber to preserve said device until treating said device with said treating medium.

8. The method of claim 7 wherein said cleaning medium comprises a cleaning additive dissolved in said cleaning medium to enhance an effectiveness of said cleaning medium.

9. The method of claim 7 further comprising varying a temperature of said cleaning medium to vary a density of said cleaning medium to enhance a cleaning effectiveness of said cleaning medium.

10. The method of claim 7 further comprising varying a temperature of said cleaning medium to vary a thermodynamic state of said cleaning medium.

11. The method of claim 7 further comprising varying a temperature of said device to vary a density of said cleaning medium within a region surrounding said device.

12. The method of claim 7 further comprising introducing a transitioning medium into said chamber between said steps of introducing said cleaning and said treating mediums.

13. The method of claim 7 wherein said cleaning medium comprises carbon dioxide.

14. The method of claim 7 wherein said cleaning medium comprises an additive whose molecules form micelles with particles attached to said device to enhance an ability of said cleaning medium to dislodge said particles.

15. The method of claim 7 wherein said cleaning medium comprises an additive whose molecules attach to said device, further comprising irradiating said molecules to vary a temperature of said device to vary a density of said cleaning medium within a region surrounding said device.

16. The method of claim 7 wherein said film protects said device.

17. The method of claim 7 wherein said treating medium chemically modifies said devise.

18. The method as specified in claim 7 wherein an inert gas is used to flush said chamber.

19. A method of processing a wafer, comprising the steps of:

a) placing a wafer having a wafer surface in an enclosed and controlled environment;

b) exposing said wafer surface to a cleaning medium rendered as a supercritical fluid;

c) purging said environment of substances including a soluble chemical compound liberated from said wafer surface by said cleaning medium; and

d) applying a material on said wafer surface while said wafer remains in said enclosed and controlled environment to prevent contaminants from depositing upon said wafer surface prior to said material application.

20. The method as specified in claim 19 further comprising the step of depositing a layer of gate oxide as said material on said wafer surface, thereby providing an uncontaminated gate oxide-wafer surface interface.

21. The method as specified in claim 19 further comprising the step of growing a layer of gate oxide as said material on said wafer surface, thereby providing an uncontaminated gate oxide-wafer surface interface.

22. The method as specified in claim 19 comprising the step of applying a lubricating film as said material on said wafer surface.

23. The method as specified in claim 22 wherein said film is formed as a monolayer.