Process for mounting a matrix-array electroluminescent component on a carrier

Abstract

A process for mounting a light component on a carrier. The light component includes a generally planar substrate, on a first face of which submillimetre-sized electroluminescent semiconductor elements are epitaxied in the form of a matrix. The process is noteworthy in that it eliminates the need for a layer of filler material between the component and the carrier, while providing good thermal and electrical conductivity between the component and the carrier and high mechanical strength.

Claims

1. Process for mounting a light component on a carrier, comprising: providing a light component which comprises a generally planar substrate having a first face on which a matrix-array of submillimetre-sized electroluminescent semiconductor elements are epitaxied and spatially isolated from one another in the form of a matrix; forming at least one first electrically conductive track which comprises copper on a second face of the planar substrate of the light component which is opposite to the first face having the matrix array of submillimetre-sized electroluminescent semiconductor elements thereon; providing a carrier; forming at least one second electrically conductive track which comprises copper on a face of the carrier; forming an assembly composed of the carrier and the light component by positioning the second face of the light component on said face of the carrier such that each of the first electrically conductive tracks of the light component makes contact with a respective one of the second electrically conductive tracks of the carrier; annealing the assembly composed of the carrier and the light component at a temperature of between 200 C. and 400 C. to form a hybrid bonding connection which includes a copper-copper connection at each contact site of the first and second electrically conductive tracks, said copper-copper connection providing mechanical attachment and heat exchange between the light component and the carrier.

2. Process according to claim 1, wherein the first electrically conductive tracks formed on the second face of the substrate of the light component are arranged so as to allow each of the electroluminescent semiconductor elements of the light component to be supplied with electric current.

3. Process according to claim 1, wherein the substrate of the light component comprises silicon, sapphire, silicon carbide or gallium nitride.

4. Process according to claim 1, wherein the carrier comprises silicon or glass.

5. Process according to claim 1, wherein the formation of the first and second electrically conductive tracks on the light component and on the substrate comprises the use of a photolithographic process to produce voids in the substrate and in the carrier.

6. Process according to claim 5, wherein copper is deposited in each of the voids.

7. Process according to claim 1, wherein the carrier and the light component comprise alignment marks that are intended to facilitate the positioning of the component on the carrier.

8. Process according to claim 2, wherein the carrier and the light component comprise alignment marks that are intended to facilitate the positioning of the component on the carrier.

9. Process according to claim 2, wherein the substrate of the light component comprises silicon, sapphire, silicon carbide or gallium nitride.

10. Process according to claim 2, wherein the carrier comprises silicon or glass.

11. Process according to claim 1, wherein: the first electrically conductive track is a first copper track, the second electrically conductive track is a second copper track, and the first copper track directly contacts the second copper track such that the hybrid bonding connection comprises a copper-to-copper connection between the light component and the carrier.

12. Process according to claim 1, wherein the light component is a monolithic light component.

13. Process according to claim 1, wherein the forming an assembly comprises positioning the light component on said face of the carrier without providing an adhesive or filler material between the light component and the face of the carrier.

14. Process according to claim 1, wherein the hybrid bonding connection is formed without providing pressure to connect the light component and the carrier.

Description

(1) FIG. 1 schematically shows a solution known from the prior art, according to which a light component 10 is attached to a generally planar carrier 20. The component 10 is what is referred to as a monolithic component comprising a substrate 12 on which submillimetre-sized elementary electroluminescent light sources 14 are epitaxied. Electrical connections, represented by wires 30, are provided between the component 10 and its carrier 20. These connections ensure that each of the elementary sources 14 of the matrix-array component 10 is supplied with power. The empty gap between the wires 30 is filled with a heat-conducting resin 32, which holds the component 10 securely to the carrier 20 and provides heat exchange between the component 10 and the carrier 20.

(2) The main steps of a preferred embodiment of the process according to the invention are shown in FIG. 2. In a first step a), at least one electrically conductive track, comprising for example copper, is formed on the back face of the substrate of the matrix-array light component. This is the face which does not comprise the elementary light sources. Similarly, at least one electrically conductive track, comprising for example copper, is formed on a face of the carrier to which the matrix-array component is to be attached. This corresponds to step b). It goes without saying that the order of steps a) and b) may be inverted or that they may be carried out simultaneously in parallel, without however departing from the scope of the present invention. In the following step c), the light component and the carrier that have been prepared in this way are positioned such that the tracks comprising copper that were formed in the preceding steps make contact.

(3) Other electrically conductive metals or materials may be used instead of copper as long as they exhibit similar properties, without however departing from the scope of the present invention.

(4) Next, the assembly composed of the carrier and of the light component is annealed in an oven provided for this purpose at a temperature of between 200 C. and 400 C. This corresponds to the final step d). During the annealing operation, what is referred to as a hybrid-bonding connection is formed between the matrix-array component and its carrier. This component-carrier connection is electrically and thermally conductive, and at the same time provides high mechanical strength of hold between the matrix-array component and the carrier. The process requires neither the use of adhesive nor the application of pressure to the components during assembly on the carrier and forms a direct connection without producing a void between the component and the carrier.

(5) FIG. 3 provides an illustration of an electroluminescent component 100 in step a) of the process, and the carrier 120 in step b) of the process, which were described above. The component 100 comprises a first face 106 on which the electroluminescent sources 104 are epitaxied in the form of a matrix. Voids 101 are formed on a second face 108, which is located on the back side of the first face 106. The substrate 106 preferably comprises silicon, GaN, sapphire or silicon carbide. The voids are designed so as to correspond to the network of electrical connections that are required to supply each of the elementary sources 104 with power. To achieve this, photolithographic processes that are known per se in the prior art, and will not be described in detail within the context of the present invention, may be used. Once the voids have been formed, copper is deposited at the bottom of the voids, so as to fill them. An optional polishing step may be envisaged so as to provide a generally smooth interface between the voids 101 thus filled and the surface 108. A similar process is used to form the copper-containing tracks on the surface of the carrier. The electroluminescent component 100 and the carrier 120 are shown adjacent to one another prior to joining together as an assembly.

(6) FIG. 4 shows the result of the process according to the invention. The component 100 comprises a first face 106 on which the electroluminescent sources 104 are epitaxied in the form of a matrix. On a second face 108, voids form a network of ribs in the image of the required electrical connections. The ribs or voids are filled with copper 105. The carrier 128, comprising silicon or glass, has, on its face 128, copper tracks 125 which correspond to the tracks 105 on the back face 108 of the component 100. During the operation of annealing the assembly formed by the component 100 and the carrier 120, the required hybrid-bonding connection is formed at the site of the lands 105 and 125, respectively.

(7) In a preferred embodiment, the electrically conductive tracks 125 are functionally connected to means for driving the power supply of the light sources 104. Such means are known in the art and generally entail converter elements that are configured to transform a direct current of a first intensity, supplied in general by a current source internal to the motor vehicle in which the component 100 is used, into a load current of a second intensity, suitable for selectively supplying power to the light sources 104 of the component 100. A light module for a motor vehicle may advantageously also comprise control means produced in the form of a microcontroller element, which means allow the means for driving the power supply to be controlled so as to meet setpoints received from other members of the motor vehicle.