Direct bonding process using a compressible porous layer

1. A method for direct bonding between a first element and a second element, including at least the following steps:

deposition of at least one first porous layer on at least one face of the first element, where the first porous layer is compressible and in which the deposition of the at least one first porous layer includes at least use of a PECVD deposition of porous SiOCH,

production of at least one first bonding layer on the first porous layer, and

rigid connection by direct bonding of the second element with the first bonding layer.

2. The method according to claim 1 , in which the first porous layer has a void volume ratio greater than or equal to approximately 10% and/or includes at least one elastically deformable material having a Young modulus of less than or equal to approximately 20 GPa, and/or at least one plastically deformable material having an elastic limit of less than or equal to approximately 350 MPa.

3. The method according to claim 1 , in which the size of the pores of the first porous layer is less than or equal to approximately one tenth the thickness of the first porous layer, and/or is less than the size of the particles likely to be present at the bonding interface between the two elements when a rigid connection by direct bonding is made.

4. The method according to claim 1 , in which the first element and/or the second element includes a substrate or an electronic chip.

5. The method according to claim 1 , also including the following steps:

production, on at least one face of the second element, of at least one second compressible porous layer,

production of at least one second bonding layer on the second porous layer,

and in which a rigid connection by direct bonding of the second element with the first bonding layer is obtained by bringing the first bonding layer directly into contact with the second bonding layer.

6. The method according to claim 5 , in which the second porous layer has a void volume ratio greater than or equal to approximately 10% and/or includes at least one elastically deformable material having a Young modulus of less than or equal to approximately 20 GPa, and/or at least one plastically deformable material having an elastic limit of less than or equal to approximately 350 MPa.

7. The method according to claim 1 , in which the first porous layer is thicker than the first bonding layer.

8. The method according to claim 5 , in which the second porous layer is thicker than the second bonding layer.

9. The method according to claim 5 , in which the production of the second porous layer includes at least use of a PECVD deposition of porous SiOCH.

10. The method according to claim 1 , in which the deposition of the first porous layer includes a deposition of a material able to be etched and intended to form the first porous layer, followed by formation of pores by chemical etching in the deposited material.

11. The method according to claim 5 , in which the production of the second porous layer includes a deposition of a material able to be etched and intended to form the second porous layer, followed by formation of pores by chemical etching in the deposited material.

12. The method according to claim 1 , in which the deposition of the first porous layer includes at least use of the following steps:

deposition of a material of the first porous layer, where pore-forming particles are added to the said deposited material, and

elimination of the said pore-forming particles, forming pores within the material of the first porous layer.

13. The method according to claim 5 , in which the production of the second porous layer includes at least use of the following steps:

deposition of a material of the second porous layer, where pore-forming particles are added to the said deposited material, and

elimination of the said pore-forming particles, forming pores within the material of the second porous layer.

14. The method according to claim 12 , in which the material of the first porous layer includes SiOCH.

15. The method according to claim 13 , in which the material of the second porous layer includes SiOCH.

16. The method according to claim 1 , in which production of the first bonding layer includes a step of deposition of a material of the first bonding layer on the first porous layer.

17. The method according to claim 5 , in which production of the second bonding layer includes a step of deposition of a material of the second bonding layer on the second porous layer.

18. The method according to claim 1 , in which production of the first bonding layer includes a step of thermal, plasma or chemical treatment of a portion of the first porous layer, where the said treated portion of the first porous layer forms the first bonding layer.

19. The method according to claim 5 , in which production of the second bonding layer includes a step of thermal, plasma or chemical treatment of a portion of the second porous layer, where the said treated portion of the second porous layer forms the second bonding layer.

20. The method according to claim 1 , also including, between the step of production of the first bonding layer and the step of rigid connection by direct bonding of the second element with the first bonding layer, implementation of the following steps:

photolithography and etching of at least one bonding pad location through the first bonding layer, the first porous layer and a portion of the first element,

deposition, at least in the said location, of at least one electrically conductive material forming the bonding pad,

chemical mechanical planarisation, stopping at the first bonding layer,

and in which, when the second element is rigidly connected by direct bonding with the first bonding layer, the bonding pad produced in the first element is rigidly connected by direct bonding with a bonding pad produced in the second element.

21. The method according to claim 1 , also including, before the step of production of the first bonding layer, implementation of the following steps:

photolithography and etching, through a portion of the first element, of at least one bonding pad location,

deposition, at least in the said location, of at least one electrically conductive material forming the bonding pad,

in which production of the first porous layer includes implementation of the following steps:

deposition of the first porous layer on the first element and the bonding pad,

chemical mechanical planarisation of the first porous layer, stopping at the bonding pad,

and in which, when the second element is rigidly connected by direct bonding with the first bonding layer, the bonding pad produced in the first element is rigidly connected by direct bonding with a bonding pad produced in the second element.

22. The method according to claim 20 , also including, prior to the deposition of the electrically conductive material in the said location, deposition of at least one layer of material forming a barrier to diffusion of the material of the bonding pad, where the electrically conductive material is subsequently deposited on this layer of barrier material.

23. The method according to claim 21 , also including, prior to the deposition of the electrically conductive material in the said location, deposition of at least one layer of material forming a barrier to diffusion of the material of the bonding pad, where the electrically conductive material is subsequently deposited on this layer of barrier material.

24. A method for direct bonding between a first element and a second element, including at least the following steps:

deposition of at least one first porous layer on at least one face of the first element, where the first porous layer is compressible, including

deposition of a material of the first porous layer, wherein the material of the first porous layer includes SiOCH,

addition of pore-forming particles to the deposited material, and

elimination of the pore-forming particles, forming pores within the material of the first porous layer;

production of at least one bonding layer on the first porous layer; and

rigid connection by direct bonding of the second element with the first bonding layer.