Wafer bonding material with embedded rigid particles

• US 20070238262A1
• Filed: 03/28/2006
• Published: 10/11/2007
• Est. Priority Date: 03/28/2006
• Status: Active Grant

• Current Assignee: Atomica Corporation (Answers.com Corporation)
• Original Assignee: Innovative Micro Technology Incorporated
• Inventors: Summers, Jeffery
• Granted Patent: US 7,807,547 B2
• Time in Patent Office: Days
• US Class Current: 438/455
• CPC Class Codes: B81C 1/00269 Bonding of solid lids or wafers to the substrate
• CPC Class Codes: B81C 2203/0109 Bonding an individual cap on the substrate
• CPC Class Codes: B81C 2203/019 characterised by the material or arrangement of seals between parts
• CPC Class Codes: H01L 23/10 characterised by the material or arrangement of seals between parts, e.g. between cap and base of the container or between leads and walls of the container
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/01079 Gold [Au]

Abstract

A material for bonding a lid wafer to a device wafer, which includes an adhesive substance with rigid particles embedded in the adhesive substance. The rigid particles may be particles or spheres of alumina, silica, or diamond, for example. The adhesive substance may be glass frit, epoxy, glue, cement or solder, for example. When the adhesive is applied and melted, and pressure is applied between the lid wafer and the device wafer, the lid wafer approaches the device wafer until a minimum separation is reached, which is defined by the rigid particles.

Claims

1. A bonding material which bonds a lid wafer to a device wafer, comprising:

an adhesive substance which adheres the lid wafer to the device wafer; and

at least one rigid particle in the adhesive substance, having a dimension which defines a minimum separation between the lid wafer and the device wafer.

2. The bonding material of claim 1, wherein the at least one rigid particle comprises at least one of alumina, sapphire, silica, metal and diamond.

3. The bonding material of claim 1, wherein the adhesive substance comprises at least one of glass frit, epoxy, glue, cement, solder, metal and metal alloy.

4. The bonding material of claim 1, wherein the bonding material is disposed in a layer around the perimeter of a MEMS device fabricated on the device wafer.

5. The bonding material of claim 1, wherein the volume ratio of the at least one rigid particle to the adhesive substance in the bonding material is between about 3% and about 50%.

6. The bonding material of claim 1, further comprising:

a solvent which dilutes the adhesive substance.

7. The bonding material of claim 1, wherein the at least one rigid particle is a sphere having a diameter of between about 1 μ

m and about 100 μ

m.

8. The bonding material of claim 1, wherein the at least one rigid particle is a sapphire sphere of about 10 μ

m diameter.

9. The bonding material of claim 1, wherein the bonding material material is a layer about 200 μ

m wide and about 10 μ

m thick.

10. A method for bonding a lid wafer to a device wafer, comprising:

providing an adhesive substance;

providing a plurality of rigid particles;

mixing the rigid particles into the adhesive substance to form a bonding material;

applying the bonding material to at least one of a lid wafer and a device wafer;

squeezing the lid wafer and the device wafer until a minimum separation is reached defined by the rigid particles; and

hardening the adhesive substance in the bonding material.

11. The method of claim 10, wherein squeezing the lid wafer and the device wafer comprises applying pressure between the lid wafer and the device wafer of between about 50 N and about 2000 N.

12. The method of claim 10, further comprising at least one of:

heating the bonding material and applying ultra-violet light to the bonding material.

13. The method of claim 10, further comprising:

baking the bonding material to remove solvent from the bonding material.

14. The method of claim 13, wherein baking the bonding material to remove solvent from the bonding material comprises baking the bonding material at a temperature of about 290 degrees centigrade for about 2 hours.

15. The method of claim 10, further comprising:

heating the bonding material to melt the bonding material; and

cooling the bonding material to harden the bonding material.

16. The method of claim 15, wherein heating the bonding material to melt the bonding material comprises:

heating the bonding material to at least about 450 degrees centigrade for at least about 10 minutes.

17. The method of claim 10, further comprising:

mixing a solvent into the bonding material, in an amount sufficient to maintain the viscosity of the bonding material at a level within about 50% of a viscosity of the adhesive substance.

18. The method of claim 10, further comprising:

providing an environment around the lid wafer and the device wafer including at least one of air, SF₆, He, N₂, H₂, Ne, vacuum or partial vacuum around the lid wafer and the device wafer.

19. The method of claim 18, wherein the environment is provided at a pressure of less than about 70 psi.

20. The method of claim 10, wherein applying the bonding material to at least one of the lid wafer and the device wafer comprises forcing the bonding material through at least one of a silk screen and a stencil.