Method of room temperature covalent bonding
View Patent ↗A method of bonding includes using a bonding layer having a fluorinated oxide. Fluorine may be introduced into the bonding layer by exposure to a fluorine-containing solution, vapor or gas or by implantation. The bonding layer may also be formed using a method where fluorine is introduced into the layer during its formation. The surface of the bonding layer is terminated with a desired species, preferably an NH 2 species. This may be accomplished by exposing the bonding layer to an NH 4 OH solution. High bonding strength is obtained at room temperature. The method may also include bonding two bonding layers together and creating a fluorine distribution having a peak in the vicinity of the interface between the bonding layers. One of the bonding layers may include two oxide layers formed on each other. The fluorine concentration may also have a second peak at the interface between the two oxide layers.
1. A bonding method, comprising:
forming first and second bonding layers on respective first and second elements, at least one of said bonding layers comprising a fluorinated oxide layer;
heating said fluorinated oxide layer;
after said heating, bringing into contact said first and second bonding layers in ambient at room temperature; and
forming a bond between said first and second layers at room temperature.
2. A method as recited in claim 1 , comprising:
forming a bond of at least 600 mJ/m 2 at room temperature.
3. A method as recited in claim 1 , comprising:
forming a bond of at least 1000 mJ/m 2 at room temperature.
4. A method as recited in claim 1 , comprising:
forming a bond of at least 2500 mJ/m 2 at room temperature.
5. A method as recited in claim 1 , comprising:
forming each of said first and second bonding layers to have a surface roughness in a range of about 0.1 to 1.5 nm.
6. A method as recited in claim 5 , comprising:
activating said first and second bonding layers.
7. A method as recited in claim 1 , comprising:
activating said first and second bonding layers.
8. A method as recited in claim 1 , wherein forming at least one of said bonding layers comprising a fluorinated oxide layer comprises:
forming an oxide layer; and
exposing said oxide layer to a fluorine-containing solution.
9. A method as recited in claim 8 , comprising:
exposing said oxide layer to a solution containing HF.
10. A method as recited in claim 8 , comprising:
exposing said oxide layer to a solution containing about 0.025% HF.
11. A method as recited in claim 1 , comprising:
exposing said fluorinated oxide layer to an RCA solution after said heating.
12. A method as recited in claim 1 , comprising:
heating said fluorinated oxide layer at a temperature of in a range of about 100–300° C.
13. A method as recited in claim 1 , comprising:
heating said fluorinated oxide layer at a temperature of about 250° C.
14. A method as recited in claim 1 , comprising:
exposing said fluorinated oxide layer to an RCA solution after said heating.
15. A method as recited in claim 1 , wherein forming at least one of said bonding layers comprising a fluorinated oxide layer comprises:
forming an oxide layer; and
exposing said oxide layer to a fluorine-containing gas.
16. A method as recited in claim 15 , comprising:
exposing said oxide layer to HF vapor.
17. A method as recited in claim 15 , comprising:
exposing said oxide layer to a plasma containing one of SF 6 and CF 4 .
18. A method as recited in claim 1 , wherein forming at least one of said bonding layers comprising a fluorinated oxide layer comprises depositing an oxide using a gas containing F.
19. A method as recited in claim 1 , wherein forming at least one of said bonding layers comprising a fluorinated oxide layer comprises depositing a PECVD oxide using a gas containing one of SiF 4 and CF 4 .
20. A method as recited in claim 1 , wherein forming at least one of said bonding layers comprising a fluorinated oxide layer comprises:
forming an oxide layer; and
implanting a F-containing species into said oxide layer.
21. A method as recited in claim 20 , comprising:
implanting a F-containing species into said oxide layer to a dose in a range of about 1×10 15 to 1×10 16 /cm 2 .
22. A method as recited in claim 1 , comprising:
etching said first and second bonding layers by exposure to an RIE process.
23. A method as recited in claim 1 , comprising:
exposing said bonding layers to one of an NH 4 OH solution and vapor.
24. A method as recited in claim 1 , comprising:
covering first portions said first bonding layer; and
fluorinating second portions of said first bonding layer not covered in said covering step; and
bonding said second portions to said second bonding layer.
25. A method as recited in claim 1 , wherein forming said fluorinated oxide in one of said first and second bonding layers comprises:
exposing a first oxide layer to fluorine; and
forming a second oxide layer on said first oxide layer after said exposing step.
26. A method as recited in claim 25 , comprising:
forming said second oxide layer at a temperature in a range of about 100–300° C.
27. A method as recited in claim 25 , comprising:
forming said second oxide layer at a temperature of about 250° C.
28. A method as recited in claim 1 , comprising:
forming at least one of said first and second bonding layers to have a fluorine concentration of at least 10 17 /cm 3 .
29. A method as recited in claim 1 , comprising:
forming a fluorine concentration having a first peak in the vicinity of an interface between said first and second bonding layers and a second peak in at least one of said first and second layers separated from said first peak.
30. A method as recited in claim 1 , comprising:
exposing said first oxide layer to a fluorine-containing gas.
31. A method as recited in claim 30 , comprising:
exposing said first oxide layer to HF vapor.
32. A method as recited in claim 30 , comprising:
exposing said first oxide layer to a plasma containing one of SF 6 and CF 4 .
33. A method as recited in claim 1 , wherein forming said first oxide layer comprises depositing an oxide using a gas containing F.
34. A method as recited in claim 1 , wherein forming said first oxide layer comprises depositing a PECVD oxide using a gas containing one of SiF 4 and CF 4 .
35. A method as recited in claim 1 , comprising:
implanting a F-containing species into said first oxide layer.
36. A method as recited in claim 35 , comprising:
implanting a F-containing species into said first oxide layer to a dose in a range of about 1×10 15 to 1×10 16 /cm 2 .
37. A method of forming a bonded structure, comprising:
forming a first bonding layer comprising:
forming a first oxide layer,
introducing fluorine into said first oxide layer, and
forming a second oxide layer on said first oxide layer after said introducing step;
bonding said first bonding layer to a second bonding layer; and
forming a fluorine concentration having a first peak in the vicinity of an interface between said first and second bonding layers and a second peak in the vicinity of an interface between said first and second oxide layers.
38. A method as recited in claim 37 , comprising:
heating said first oxide layer at a temperature of in a range of about 100–300° C. before said bonding.
39. A method as recited in claim 37 , comprising:
diffusing fluorine from said first oxide layer into said second oxide layer.
40. A method as recited in claim 37 , comprising:
exposing said first oxide layer to one of a solution, vapor and gas each containing fluorine.
41. A method as recited in claim 37 , wherein:
forming said first oxide layer comprises depositing an oxide using a gas containing fluorine.
42. A method as recited in claim 37 , comprising:
exposing said first oxide layer to a plasma containing one of SF 6 and CF 4 .
43. A method as recited in claim 37 , wherein forming said first oxide layer comprises depositing an oxide using a gas containing F.
44. A method as recited in claim 38 , comprising:
exposing said first oxide layer to a fluorine-containing gas.
45. A bonding method, comprising:
forming a first oxide layer on a first element;
exposing said first oxide layer to fluorine;
forming a second oxide layer on said first oxide layer;
forming a third oxide layer on a second element;
bringing into contact a surface of said second oxide layer with a surface of said third oxide layer in ambient at about room temperature; and
forming a bond between said second and third oxide layers at about room temperature.
46. A method as recited in claim 45 , wherein forming said third oxide layer comprises:
forming a fourth oxide layer on said second element;
exposing said fourth oxide layer to fluorine; and
forming a fifth oxide layer on said first oxide layer;
said method further comprising:
bringing into contact a surface of said second oxide layer with a surface of said fifth oxide layer in ambient at about room temperature; and
forming a bond between said second and fifth oxide layers at about room temperature.
47. A method as recited in claim 38 , wherein forming said first oxide layer comprises depositing an oxide using a gas containing F.
48. A method as recited in claim 38 , wherein forming said first oxide layer comprises depositing a PECVD oxide using a gas containing one of SiF 4 and CF 4.
49. A method as recited in claim 38 , comprising:
implanting a F-containing species into said first oxide layer.
50. A method as recited in claim 45 , comprising:
exposing said first oxide layer to a solution containing about 0.025% HF.