Hermetically sealed microdevice with getter sheild

• US 20060063462A1
• Filed: 09/23/2004
• Published: 03/23/2006
• Est. Priority Date: 09/23/2004
• Status: Active Grant

• Current Assignee: Temic Automotive of North America, Incorporated (Continental AG)
• Original Assignee: Temic Automotive of North America, Incorporated (Continental AG)
• Inventors: Ding, Xiaoyi, Schuster, John P., Frye, Jeffrey J.
• Granted Patent: US 7,204,737 B2
• Time in Patent Office: Days
• US Class Current: 445/25
• CPC Class Codes: B81B 7/0038 using materials for controlling the level of pressure, contaminants or moisture inside of the package, e.g. getters
• CPC Class Codes: B81B 7/007 Interconnections between the MEMS and external electrical signals

Abstract

A microdevice that comprises a device microstructure (38) and vent channel (34) in a wafer (14) that is sandwiched between a substrate (10) and a cap (16). The cap (16) and substrate (10) have recesses (41, 21) around the microstructure (22) to define a cavity. A vent (25) is connected to the vent channel (34) and subsequently to the cavity. The vent (25) is used to evacuate and seal the microstructure (38) in the cavity. A getter layer (32) can be used to maintain the cavity vacuum. An electrical connection can be provided through the vent (25), vent channel (34) and cavity to the getter (32) to electrically ground the getter layer (32).

Claims

1. A method of making a hermetically sealed microdevice, the method comprising the steps of:

providing a substrate with a recess therein;

providing a cap with a recess therein;

defining a microstructure and a vent channel in a silicon layer, the vent channel configured to couple to the recesses after the bonding step;

forming a vent, the vent configured to couple to the vent channel after the bonding step;

disposing a getter layer in at least one of the recesses;

bonding the cap, silicon wafer, and substrate together such that the recesses in the cap and substrate form a cavity to enclose the microstructure, and wherein the vent, vent channel and cavity are coupled together;

evacuating the cavity through the vent and vent channel; and

sealing the vent to provide a hermetically sealed cavity enclosing the microstructure.

2. The method of claim 1, further comprising the step of providing an electrical connection through the vent and cavity to the getter layer to electrically ground the getter layer.

3. The method of claim 1, wherein the step of defining includes patterning and etching the silicon wafer to provide the microstructure and vent channel.

4. The method of claim 1, wherein the sealing step includes solder sealing the vent.

5. The method of claim 1, wherein the step of disposing the getter layer includes disposing a three layer composite getter layer consisting of a shield layer, a getter layer, and a protection layer.

6. The method of claim 1, wherein the step of bonding includes anodic bonding of the cap, silicon layer and substrate to form a microdevice assembly.

7. The method of claim 1, wherein the bonding step includes wafer level bonding of multiple microdevices.

8. The method of claim 1, wherein the forming step includes forming the vent in the substrate.

9. The method of claim 1, wherein the forming step includes forming the vent in the cap.

12. The method of claim 1, wherein the step of anodic bonding includes anodic bonding the microdevice wafer to the substrate such that the microdevice wafer is sandwiched between the cap and substrate.

10. A method of making a hermetically sealed microdevice, the method comprising the steps of:

providing a substrate with a recess therein;

providing a cap with a recess therein;

defining a microstructure and a vent channel in a silicon wafer, the vent channel configured to couple to the recesses after the bonding step;

forming a vent, the vent configured to couple to the vent channel after the bonding step;

disposing metal interconnects;

mounting the silicon wafer to the substrate;

disposing a composite thin metal film getter in the recess of the cap and providing for a ground connection thereto;

anodic bonding the cap to the silicon wafer such that the recess in the cap forms a cavity to enclose the microstructure and the vent is aligned with the vent channel, and the vent, vent channel and cavity are coupled together;

evacuating the cavity through the vent and vent channel; and

sealing the vent with solder to provide a hermetically sealed cavity enclosing the microstructure and to provide an external electrical ground connection to the getter layer.

11. The method of claim 10, wherein the composite thin metal film getter of the composing step consists of three layers:

an electrical shield and outgassing block layer facing to the cap recess, a getter layer, and an outermost anti-oxidation layer.

13. The method of claim 10, wherein the forming step includes forming the vent in the substrate.

14. The method of claim 10, wherein the forming step includes forming the vent in the cap.

15. A hermetically sealed microdevice assembly comprising:

a substrate having a recess defined therein;

a cap having a recess defined therein;

a device microstructure and a vent channel formed in a silicon wafer layer bonded to the substrate such that a portion of the microstructure floats over the substrate recess and bonded to the cap such that a portion of the microstructure floats below the cap recess, wherein the substrate and cap recesses provide a cavity to enclose the microstructure, and wherein the vent channel is coupled with the cavity;

a conductive getter layer disposed in at least one of the recesses of the cavity; and

a vent connected to the vent channel and thereby to the cavity, the vent having a seal to hermetically seal the microstructure in the cavity.

16. The microdevice assembly of claim 15, further comprising an electrical connection through the vent, vent channel and cavity to the getter layer to electrically ground the getter layer.

17. The microdevice assembly of claim 15, wherein the vent seal includes solder.

18. The microdevice assembly of claim 15, wherein the cap, microdevice wafer, and substrate are anodically bonded together.

19. The microdevice assembly of claim 15, wherein the vent is formed in the substrate.

20. The microdevice assembly of claim 15, wherein the vent is formed in the cap.