Heterogeneous annealing method and device

1. A method of integrating a first element having a first contact structure with a second element having a second contact structure, comprising:

bonding a first element with a first metal bonding structure directly to a second element with a second metal bonding structure;

thinning said first element to a thickness that would result in distortion of said first element if heated to a temperature to facilitate direct connections between the first and second direct metal bonding structure; and

attaching a third element having a thickness to reduce said distortion to the thinned first element;

heating bonded first, second, and third elements; and

forming electrical connections between said first and second metal bonding structures.

2. The method recited in claim 1 , further comprising removing the third element.

3. The method recited in claim 1 , wherein the bonding comprises applying pressure using a clamp.

4. The method recited in claim 3 , comprising placing the first and second elements in a flexible container.

5. The method recited in claim 4 , comprising evacuating the flexible container.

6. The method recited in claim 4 , comprising applying pressure to the container.

7. A method of integrating a first element having a first surface with a first insulating material and a first contact structure with a second element having a second surface with a second insulating material and a second contact structure, comprising:

directly bonding the first insulating material to the second insulating material;

removing a portion of the second element to leave a remaining portion having a first thickness;

directly bonding a third element having a coefficient of thermal expansion (CTE) substantially the same as a CTE of the first element to the said remaining portion; and

heating the first and third elements and remaining portion to directly contact the first and second contact structures.

8. The method recited in claim 7 , further comprising removing the third element.

9. The method recited in claim 7 , wherein the first and second contact structures comprise nickel, the first element comprises a GaN/sapphire substrate, the second element comprises a silicon CMOS substrate, and the third element comprises a silicon substrate, the method comprising:

heating to a temperature in a range of 300-350° C.

10. The method recited in claim 7 , wherein the first element comprises a GaN/sapphire structure with sapphire substrate in the range of approximately 500-1000 micron thickness, the second element comprises a silicon CMOS substrate of 500-750 micron thickness, the method comprising:

heating to a temperature in a range of 75-150° C.

11. The method recited in claim 7 , wherein the first and second contact structures comprise copper, the first element comprises silicon oxide, the second element comprises silicon oxide, the method comprising:

heating to a temperature about 100° C.

12. The method recited in claim 7 , wherein the first element and the second element have a difference in coefficient of thermal expansion of less than 0.5 ppm/° C.

13. The method recited in claim 7 , wherein the first and third elements have substantially the same coefficient of thermal expansion.

14. The method recited in claim 13 , wherein the second element has a coefficient of thermal expansion different from the first and third elements.

15. The method recited in claim 7 , wherein the first thickness is in a range of 1-10 microns.

16. The method recited in claim 7 , comprising:

directly bonding the third element having a coefficient of thermal expansion different from the CTE of the first element in a range of 0.3 to 1.0 ppm/° C.

17. The method recited in claim 7 , comprising:

directly bonding the third element having a coefficient of thermal expansion different from the CTE of the first element by less than about 0.3 ppm/° C.

18. The method recited in claim 7 , comprising:

directly bonding the third element having a coefficient of thermal expansion different from the CTE of the first element by less than about 0.5 ppm/° C.

19. The method recited in claim 7 , comprising:

directly bonding the third element having a coefficient of thermal expansion different from the CTE of the first element by less than about 1.0 ppm/° C.

20. The method recited in claim 7 , wherein at least one of the first and second contact structures is copper, comprising:

heating to a temperature in a range of 150-250° C.

21. The method recited in claim 20 , comprising:

forming at least one of the first and second contact structures to have a surface 0-10 nm below a surface of the respective first and second insulating material.

22. The method recited in claim 7 , wherein at least one of the first and second contact structures is nickel, comprising:

heating to a temperature in a range of 250-350° C.

23. The method recited in claim 22 , comprising:

forming at least one of the first and second contact structures from to have a surface 0-10 nm below a surface of the respective first and second insulating material.

24. The method recited in claim 7 , comprising:

thinning the third material to a thickness in a range of about 0.1-1 nm.

25. The method recited in claim 7 , comprising:

thinning the third material to a thickness in a range of about 1-10 nm.

26. The method recited in claim 7 , comprising:

thinning the third material to a thickness in a range of about 10-100 nm.

27. The method recited in claim 7 , comprising:

thinning the third material to a thickness in a range of about 2-20 nm; and

heating to a temperature of at least 350° C.

28. The method recited in claim 7 , comprising:

forming a via filled with conductive material connected to at least one of the first and second contact structures.

29. The method recited in claim 7 , wherein at least one of said first and second contact structures comprises a direct metal bonding structure.

30. The method recited in claim 7 , wherein the bonding comprises applying pressure using a clamp.

31. The method recited in claim 30 , comprising placing the first and second elements in a flexible container.

32. The method recited in claim 31 , comprising evacuating the flexible container.

33. The method recited in claim 31 , comprising applying pressure to the container.