Method of passivating a micromechanical device within a hermetic package

• US 5,936,758 A
• Filed: 05/11/1998
• Issued: 08/10/1999
• Est. Priority Date: 04/12/1996
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Jascott, Ronald, Gale, Richard O., Fisher, Edward C.
• Primary Examiner(s): Phan, James
• Application Number:
  US09/075,809
• Time in Patent Office: 456 Days
• Field of Search: 359/224, 359/900, 257/678, 257/680, 257/687, 257/701, 257/702, 257/704
• US Class Current: 359/224.1
• CPC Class Codes: B81B 3/0005 Anti-stiction coatings
• 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 2203/0109 Bonding an individual cap on the substrate
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A method of passivating a hermetically sealed micromechanical device (14) with a passivant (100). A predetermined quantity of the passivant (100) is placed within the cavity (54) of a lid (42) after the lid and package base (46) have been activated. Thereafter, by heating the package (10) including the passivant, the passivant will sublime within the hermetically sealed package (10) to provide a monolayer of passivant across the active surfaces of the micromechanical die (14). An improved hermetic seal is achieved since the passivant is sublimed after the laser weld process. In addition, the effectiveness of the passivation process is improved since the passivation is performed after the package is sealed, without the risk of any impurities entering into the package to degrade the effectiveness of the passivation.

Claims

1. A method rendering passive a surface of a micromechanical device, comprising the steps of:

a) placing said micromechanical device in a package;

b) placing a predetermined quantity of a passivant in said package;

c) sealing said micromechanical device and said passivant from the ambient; and

d) activating said passivant to passivate said micromechanical device with said passivant to render said micromechanical device passive.

2. The method as specified in claim 1, comprising the step of attaching a lid to said package to seal said micromechanical device from the ambient.

3. The method as specified in claim 1 comprising the step of hermetically sealing said micromechanical device in said package in said step c).

4. The method as specified in claim 1 comprising the step of placing said passivant in said step b) of the type that sublimates in said package when activated.

5. The method as specified in claim 1 wherein said micromechanical device comprises a DMD having a deflectable member engaging a landing surface, said passivant passivating said landing surface.

6. The method as specified in claim 1 wherein said passivant comprises PFDA.

7. The method as specified in claim 1 wherein said passivant is in pill form when placed in said package.

8. The method as specified in claim 1 wherein said passivant comprises a granular material when placed in said package.

9. The method as specified in claim 1 wherein said passivant forms a monolayer across said micromechanical device in said step d).