HERMETIC PACKAGE COMPRISING A GETTER, PART COMPRISING SUCH A HERMETIC PACKAGE, AND ASSOCIATED MANUFACTURING PROCESS

Abstract

The invention concerns a hermetically sealed package forming a low pressure or vacuum enclosure, and receiving at least one component of imaging bolometer type. The hermetically sealed package includes a monolithic layer of a getter material capable of capturing gases present in the enclosure, the layer of getter material having a thickness in the range from 20 nanometers to 200 nanometers.

Claims

1. A hermetically sealed package forming a low pressure or vacuum enclosure, and receiving at least one component of imaging bolometer type, said hermetically sealed package comprising a monolithic layer of a getter material capable of capturing gases present in said enclosure, wherein the layer of getter material is deposited on the walls and/or the upper portion of said enclosure and has a thickness in the range from 20 nanometers to 200 nanometers, the layer of getter material being made of zirconium (Zr), of titanium (Ti), of vanadium (V), of hafnium (Hf), of niobium (Nb), of tantalum (Ta), of cobalt (Co), of yttrium (Y), of barium (Ba), of iron (Fe), or of an alloy of these materials.

2. The hermetically sealed package according to claim 1, wherein the layer of getter material has a thickness in the range from 20 nanometers to 100 nanometers.

3. The hermetically sealed package according to claim 1, wherein the layer of getter material has a porosity smaller than 5%.

4. The hermetically sealed package according to claim 1, wherein the layer of getter material has a base topped with a structuring pattern, the thickness of said base being greater than 20 nanometers.

5. (canceled)

6. The hermetically sealed package according to claim 1, wherein the layer of getter material is further formed with rare earths or aluminum (Al).

7. A component of imaging bolometer type, wherein said component comprises the hermetically sealed package according to claim 1.

8. A method of manufacturing the component of imaging bolometer type according to claim 7, wherein said method comprises a step of physical vapor deposition (PVD) by evaporation of a monolithic layer of a getter material with a thickness in the range from 20 to 200 nanometers.

9. The method of manufacturing a component according to claim 8, wherein said method comprises a structuring of the deposition of the layer of getter material on a substrate carried out by: a first step of deposition of a resin layer on said substrate; a second step of structuring of said resin layer by photolithography; a third step of deposition of said layer of getter material by physical vapor deposition (PVD) by evaporation; and a fourth step of dissolving of said resin layer.

10. The method of manufacturing a component according to claim 8, wherein said method comprises a second step of deposition of a layer of a getter material on a previously-deposited layer of a getter material, said second deposition step being carried out by: a first step of deposition of a resin layer on said previously-deposited layer of getter material; a second step of structuring of said resin layer by photolithography; a third step of deposition of said new layer of getter material by physical vapor deposition (PVD) by evaporation; and a fourth step of dissolving of said resin layer.

11. The method of manufacturing a component according to claim 8, wherein said method comprises a step of sealing said hermetically sealed package at a temperature in the range from 180° C. to 450° C., configured to ensure an activation of said layer of getter material.

12. The method of manufacturing a component according to claim 8, wherein said method comprises an activation step carried out by Joule effect by coupling the layer of getter material to a resistive circuit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The way to implement the present embodiments, as well as the resulting advantages, will better appear from the description of the following non-limiting embodiment, given as an indication, based on the accompanying drawings, among which FIGS. 1 and 6 show:

[0063] FIG. 1: a simplified cross-section view of a component encapsulated in a package under a predetermined pressure according to an embodiment where the getter is arranged on an upper wall of the enclosure;

[0064] FIG. 2: a simplified cross-section view of a component encapsulated in a package under a predetermined pressure according to an embodiment where the getter is arranged on a substrate of the enclosure;

[0065] FIG. 3: a simplified cross-section view of the getter of FIG. 2 according to a first embodiment before the activation phase;

[0066] FIG. 4: a simplified cross-section view of the getter of FIG. 3 after the activation phase;

[0067] FIG. 5: a simplified cross-section view of the getter of FIG. 2 according to a second embodiment before the activation phase; and

[0068] FIG. 6: a simplified cross-section view of the getter of FIG. 5 after the activation phase.

DETAILED DESCRIPTION

[0069] FIG. 1 illustrates a component 11 encapsulated in an enclosure 12 under a predetermined pressure, for example, under a pressure lower than 10.sup.−3 mbar. Component 11 corresponds to an imaging bolometer.

[0070] To guarantee the pressure in enclosure 12, a getter material 15 is arranged within the latter.

[0071] In the example of FIG. 1, enclosure 12 is formed by the sealing of walls 14 to a substrate 13 by means of a metal sealing joint 20, thus forming a hermetically sealed package 10 around component 11.

[0072] As a variant, package 10 may be formed by walls 14 arranged around one or a plurality of substrates 13 or by an assembly formed by walls 14 and one or a plurality of substrates 13.

[0073] Getter 15 has to be arranged in the volume defined by enclosure 12 to capture the gases present in enclosure 12 after the activation of said getter. In the example of FIG. 1, getter 15 is arranged on the inner surface of an upper wall 14 of package 10 opposite enclosure 12. In the example of FIG. 2, getter 15 is arranged on the upper surface of substrate 13 opposite enclosure 12.

[0074] Getter 15 has a thickness e in the range from 20 nanometers to 200 nanometers, and preferably from 20 nanometers to 100 nanometers. Preferably, getter 15 also has a porosity smaller than 5%. The getter may be made of zirconium (Zr), of titanium (Ti), of vanadium (V), of hafnium (Hf), of niobium (Nb), of tantalum (Ta), of cobalt (Co), of iron (Fe), of yttrium (Y), of barium (Ba), or of an alloy of these materials.

[0075] Further, aluminum (Al) and rare earths such as chromium (Cr), cerium (Ce), cesium (Cs), or lanthanum (La) may be added to these metals to improve the characteristics of getter 15, such as the grain size, the free oxide formation enthalpy, or the catalytic activity for the cracking of the gas molecules.

[0076] FIGS. 3 and 4 illustrate the process of activation of a solid, that is, non-structured getter 15. This type of getter 15 may be obtained by physical vapor deposition by evaporation.

[0077] Before the activation, as illustrated in FIG. 3, the upper surface of getter 15 in contact with air forms an oxide layer due to the presence of oxygen molecules in the air. By heating package 10, for example, to perform a sealing by metal welding 20 at a temperature in the range from 180° C. to 450° C., oxide atoms 21 migrate across thickness e of getter 15.

[0078] After the activation, as illustrated in FIG. 4, the atoms originating from oxide layer 21 are thus stored in thickness e of getter 15, and the gas molecules 22 present in the enclosure and resulting from their desorption out of the walls forming the enclosure may be captured by getter 15, having a surface, thus activated, which is highly reactive to gases capable of desorbing into the enclosure, and typically hydrogen, nitrogen, carbon dioxide, methane.

[0079] To increase the surface area of capture of the gas molecules present in enclosure 12, it is possible to structure the upper surface of getter 15 as illustrated in FIGS. 5 and 6. For this purpose, a lithography may be carried out on the upper surface to form a base 16 topped with a structuring pattern 17. Such a structuring may be formed by a deposition of resin and then again a getter deposition or a resin deposition and then etching.

[0080] In this embodiment, it is preferable for base 16 to have a thickness e.sub.1 greater than 20 nanometers since oxide molecules 21 migrate, at least partly, into this base 16 during the activation, that is, between FIGS. 5 and 6. If the trenches extend all the way to the substrates, the diffusion of oxide molecules 21 may be performed laterally, that is, from the sides towards the inside.

[0081] In the description of FIGS. 1 to 6, getter 15 is described with an oxide layer 21 covering getter 15. As a variant, the contemplated embodiments may be carried out with a layer of noble metal protecting getter 15 before the activation. This layer of noble metal, for example, having a 20-nm thickness, would also be dissolved in the volume of getter 15 during the activation phase.

[0082] The activation phase is also described by heating during the thermal sealing of the package. As a variant, the activation may be carried out by Joule effect by coupling getter 15 to a resistive circuit without modifying the contemplated embodiments.

[0083] The disclosed embodiments thus provide using a thin getter 15, that is, with a thickness e in the range from 20 to 200 nm, and advantageously from 20 to 100 nanometers. As previously described, thin getter 15 enables to obtain a higher density of grain boundaries than getters of the state of the art, as well as a higher purity. Further, the thinness of getter 15 improves the resistance to mechanical stress, so that the lithography method may be used to structure getter 15.

[0084] The disclosed embodiments also enable to consume less material and to limit the manufacturing time of getter 15.