Device for detecting electromagnetic radiation comprising a raised electrical connection pad
A device for detecting electromagnetic radiation, including a readout circuit, which is located in a substrate, and an electrical connection pad, which is placed on the substrate, including a metal section that is raised above the substrate and electrically connected to the readout circuit. The detection device furthermore includes a protection wall that extends under the raised metal section so as to define therewith at least one portion of a cavity, and what is called a reinforcing layer section that is located in the cavity and on which the raised metal section rests.
1. A device for detecting electromagnetic radiation, including:
a readout circuit that is located in a substrate;
an electrical connection pad, which is placed on said substrate, including a metal section that is raised above said substrate and electrically connected to said readout circuit;
wherein:
a protection wall extends under said raised metal section so as to define therewith at least one portion of a cavity, having a longitudinal dimension and a thickness according to a plane parallel to said substrate, said longitudinal dimension being larger than said thickness;
a reinforcing layer section, made from a mineral material, is located in said cavity, on which said raised metal section rests.
2. The detection device according to claim 1 , wherein said reinforcing section has a surface extent that is larger than or equal to 25 of that of what is called a lower surface, which is oriented toward said substrate, of said raised metal section.
3. The detection device according to claim 1 , wherein said protection wall extends continuously so as to define a closed cavity.
4. The detection device according to claim 1 , wherein said protection wall extends continuously so as to define a cavity that is open locally.
5. The detection device according to claim 1 , including at least one thermal detector that is placed on said substrate and electrically connected to said electrical connection pad by said readout circuit, and including a membrane that is suitable for absorbing said electromagnetic radiation to be detected and that is suspended above said substrate at a distance from said latter substantially equal to that separating said raised metal section from said substrate.
6. The detection device according to claim 1 , wherein said protection wall is made from an electrically conductive material, said wall electrically connecting said electrical connection pad to said readout circuit.
7. The detection device according to claim 1 , wherein said protection wall encircles at least one electrically conductive via electrically connecting said raised metal section to a subjacent section of a metal line of said readout circuit.
8. The detection device according to claim 1 , wherein said raised metal section has a lower surface, which is oriented toward said substrate, a dimension of which parallel to said substrate is larger than or equal to 2 times said distance separating said raised metal section from said substrate along an axis that is substantially orthogonal to said substrate.
9. The detection device according to claim 1 , wherein said electrical connection pad includes substantially no reinforcing section outside of said cavity.
10. The detection device according to claim 1 , wherein said protection wall includes a plurality of rectilinear segments, each segment having a longitudinal dimension and a thickness in a plane parallel to said substrate, said longitudinal dimension being larger than said thickness.
11. A process for producing said detection device according to claim 1 , comprising:
depositing a sacrificial layer on an etch-stop layer covering said substrate containing said readout circuit;
forming a protection wall through said sacrificial layer, so as to subsequently define at least one portion of a cavity;
forming a raised metal section on said sacrificial layer, so that it rests on said protection wall and participates in said definition of said cavity;
etching at least partially said sacrificial layer, a section of said sacrificial layer, called said reinforcing section, which is located in said cavity, being unetched following this said etching step.
12. The process according to claim 11 , wherein said sacrificial layer is made of a mineral material and wherein said etching step is carried out by chemical attack in an acid medium.
13. The process according to claim 11 , wherein, concomitantly to said formation of said protection wall, anchoring pillars are formed that are intended to mechanically support absorbing membranes of thermal detectors.
14. The detection device according to claim 1 , wherein said reinforcing section has a surface extent that is larger than or equal to 50% of that of what is called a lower surface, which is oriented toward said substrate, of said raised metal section.
15. The detection device according to claim 1 , wherein said reinforcing section has a surface extent that is larger than or equal to 75% of that of what is called a lower surface, which is oriented toward said substrate, of said raised metal section.
16. The detection device according to claim 1 , wherein said raised metal section has a lower surface, which is oriented toward said substrate, a dimension of which parallel to said substrate is larger than or equal to 10 times said distance separating said raised metal section from said substrate along an axis that is substantially orthogonal to said substrate.
17. The detection device according to claim 1 , wherein said raised metal section has a lower surface, which is oriented toward said substrate, a dimension of which parallel to said substrate is larger than or equal to 25 times said distance separating said raised metal section from said substrate along an axis that is substantially orthogonal to said substrate.
18. The process according to claim 11 , wherein said sacrificial layer is made of a material based on silicon oxide, and wherein said etching step is carried out by chemical attack in vapour-phase hydrofluoric acid.