Method for multi-frequency bonding

• US 6,780,759 B2
• Filed: 10/01/2001
• Issued: 08/24/2004
• Est. Priority Date: 05/09/2001
• Status: Active Grant

• Current Assignee: Silicon Genesis
• Original Assignee: Silicon Genesis
• Inventors: Farrens, Shari N., Franklin, Mark A., Franklin, William J., Liu, Wei
• Primary Examiner(s): LE, DUNG ANH
• Application Number:
  US09/969,550
• Publication Number:
  US 20030003684A1
• Time in Patent Office: 1,058 Days
• Field of Search: 438/455, 438/456, 438/457, 438/653
• US Class Current: 438/635
• CPC Class Codes: B32B 2315/02 Ceramics
• CPC Class Codes: B32B 2457/14 Semiconductor wafers
• CPC Class Codes: B32B 38/0008 Electrical discharge treatment, e.g. corona, plasma treatment; wave energy or particle radiation heat treatment B32B38/0036
• CPC Class Codes: C04B 2237/341 Silica or silicates
• CPC Class Codes: C04B 2237/525 by heating
• CPC Class Codes: C04B 37/00 Joining burned ceramic articles with other burned ceramic articles or other articles by heating soldering and welding materials B23K35/24; laminated products B32B, E04C
• CPC Class Codes: C04B 37/001 directly with other burned ceramic articles
• CPC Class Codes: H01J 37/32082 Radio frequency generated discharge H01J37/32357, H01J37/32366, H01J37/32394 and H01J37/32403 take precedence
• CPC Class Codes: H01J 37/32165 Plural frequencies
• CPC Class Codes: H01L 21/187 by direct bonding
• CPC Class Codes: H01L 2224/8319 Arrangement of the layer connectors prior to mounting
• CPC Class Codes: H01L 2224/8385 using a polymer adhesive, e.g. an adhesive based on silicone, epoxy, polyimide, polyester
• CPC Class Codes: H01L 24/26 Layer connectors, e.g. plate connectors, solder or adhesive layers; Manufacturing methods related thereto
• CPC Class Codes: H01L 24/83 using a layer connector
• CPC Class Codes: H01L 2924/01013 Aluminum [Al]
• CPC Class Codes: H01L 2924/01018 Argon [Ar]
• CPC Class Codes: H01L 2924/01033 Arsenic [As]
• CPC Class Codes: H01L 2924/01072 Hafnium [Hf]
• CPC Class Codes: H01L 2924/01074 Tungsten [W]
• CPC Class Codes: H01L 2924/01082 Lead [Pb]
• CPC Class Codes: H01L 2924/04953 : TaN
• CPC Class Codes: H01L 2924/07802 : not being an ohmic electrical conductor

Abstract

A method and technique for achieving a high strength bond between two substrates includes igniting a plasma using a source RF signal. The substrates are biased with a bias RF signal during surface treatment by the plasma. The treated surfaces are brought into contact. The resulting bonded substrates show an improvement over bonds attained using conventional bonding techniques.

Claims

1. A method for bonding substrates comprising:

providing a first substrate having a first surface to be bonded;

supplying a first gas;

igniting said first gas to produce a plasma by a first frequency signal and applying said first signal to a first electrode that applies the first frequency signal to the first gas;

producing a second frequency signal;

applying said second frequency signal to said first substrate, said first surface of said first substrate being exposed to said plasma without etching said first surface; and

contacting said first surface of said first substrate to a first surface of a second substrate to produce a bond therebetween.

2. The method of claim 1 wherein said second frequency signal is a second RF signal that is applied to said substrate subsequent to said first frequency signal reaching full power to said first electrode.

3. The method of claim 1 further including spacing said first electrode from said first surface of said first substrate by an amount sufficient to substantially avoid etching said first surface with said plasma.

4. The method of claim 1 wherein said first electrode is spaced apart from said first surface of said first substrate by a distance substantially in the range of one mm to 150 mm.

5. The method of claim 1 wherein said first frequency signal is of a higher frequency than said second frequency signal.

6. The method of claim 1 further comprising applying said second frequency signal to said second substrate, said first surface of said second substrate being exposed to said plasma without etching said first surface of said second substrate.

7. The method of claim 1 wherein said first frequency signal is of a frequency that produces a plasma which does not etch said first surface.

8. The method of claim 1 wherein a frequency of said first frequency signal is not an integral multiple of a frequency of said second frequency signal.

9. The method of claim 1 further including applying a pressure upon a second surface of said first substrate to at least enhance a bonding action between said first surface of said first substrate and said first surface of said second substrate.

10. The method of claim 1 wherein first gas is selected from the group consisting of hydrogen, argon, water vapor, nitrogen, oxygen, ammonia, helium, silane and peroxide vapor.

11. The method of claim 1 further including extinguishing said plasma, wherein said contacting is performed subsequent to said extinguishing said plasma.

12. The method of claim 1 further including extinguishing said plasma, wherein said contacting is performed prior to said extinguishing said plasma.

13. The method of claim 1 further including extinguishing said plasma and then performing a purge by introducing a second gas.

14. The method of claim 13 wherein said second gas is the same as said first gas.

15. The method of claim 13 wherein said contacting is performed during said step of performing a purge.

16. The method of claim 1 wherein interior surfaces of said vacuum chamber have a silicon coating.

17. The method of claim 1 wherein said second frequency signal is applied to a second electrode, said first substrate being in electrical contact with said second electrode.

18. The method of claim 1 further including exposing said first surface of said second substrate to said plasma prior to said contacting.

19. The method of claim 1 further including exposing said first surface of said first substrate and said first surface of said second substrate to said plasma at the same time.

20. A method for bonding substrates comprising:

providing a plasma including supplying a first gas and applying a first radio frequency (RF) signal to a first electrode, wherein said gas is ignited to form said plasma;

applying a second RF signal to a second electrode, said second RF signal having a frequency less than a frequency of said first RF signal;

disposing a first substrate in electrical contact with said second substrate, a first surface of said first substrate being exposed to said plasma;

spacing said first electrode from said first surface such that there is substantially no etching of said first substrate by said plasma; and

contacting said first surface of said first substrate to a first surface of a second substrate.

21. The method of claim 20 wherein said second RF signal is applied to said substrate subsequent to applying said first RF signal to said first electrode.

22. The method of claim 20 wherein said first electrode is spaced apart from said first surface of said first substrate by a distance substantially in the range of one quarter of an inch to two inches.

23. The method of claim 20 wherein said first RF signal is of a higher frequency than said second RF signal.

24. The method of claim 20 wherein said first RF signal is of a frequency that produces a plasma which does not etch said first surface.

25. The method of claim 20 wherein a frequency of said first RF signal is not an integral multiple of a frequency of said second RF signal.

26. The method of claim 20 further including applying a pressure upon a second surface of said first substrate to at least enhance a bonding action between said first surface of said first substrate and said first surface of said second substrate.

27. The method of claim 20 wherein first gas is selected from the group consisting of hydrogen, argon, water vapor, nitrogen, oxygen, ammonia, and peroxide vapor.

28. The method of claim 20 further including extinguishing said plasma, wherein said contacting is performed subsequent to said extinguishing said plasma.

29. The method of claim 20 further including extinguishing said plasma, wherein said contacting is performed prior to said extinguishing said plasma.

30. The method of claim 20 wherein interior surfaces of said vacuum chamber have a silicon coating.