HYBRID ELECTRONIC DEVICE PROTECTED AGAINST HUMIDITY AND METHOD OF PROTECTING A HYBRID ELECTRONIC DEVICE AGAINST HUMIDITY

Abstract

This method concerns the protection against humidity of a device including a first and a second electronic components respectively having two opposite surfaces, the surfaces: being separated by a non-zero distance shorter than 10 micrometers; having an area greater than 100 mm.sup.2; being connected by an assembly of electrical interconnection elements spaced apart from one another by a space void of matter. This method includes applying a deposit of thin atomic layers onto the device to form a layer of mineral material covering at least the interconnection elements, the layer of mineral material having a permeability to water vapor smaller than or equal to 10.sup.−3 g/m.sup.2/day.

Claims

1. A method of protecting against humidity by providing a device comprising a first and a second electronic components respectively having two opposite surfaces, said surfaces: being separated by a non-zero distance shorter than 10 micrometers; having an area greater than 100 mm.sup.2; being connected by an assembly of electrical interconnection elements spaced apart from one another by a space void of matter, the method further comprising applying a deposit of thin atomic layers onto the device to form a layer of mineral material covering at least said interconnection elements, the layer of mineral material having a permeability to water vapor smaller than or equal to 10.sup.−3 g/m.sup.2/day.

2. The method of claim 1, wherein the mineral material is selected from the group consisting of the compounds of formula TiO.sub.2, ZrO.sub.2, SiO.sub.x, SiN.sub.x, SiO.sub.xN.sub.y, ZnSe, ZnO, Sb.sub.2O.sub.3, aluminum oxides, and transparent conductive oxides (TCO).

3. The method of claim 1, wherein the layer of mineral material has a thickness in the range from 10 nanometers to 100 nanometers.

4. The method of claim 1: wherein the application of the deposit of thin atomic layers comprises placing the structure in a chamber and injecting into said chamber reactant gases for the forming of the layer of mineral material; and wherein the injection of the reactant gases is carried out without pumping in the chamber.

5. The method of claim 1, comprising depositing a filling material totally filling the space void of matter separating the opposite surfaces of the two components, the deposition of the filling material being carried out after the deposition of the layer of mineral material on the interconnection elements.

6. A device comprising a first and a second electronic components respectively having two opposite surfaces, said surfaces: being separated by a non-zero distance shorter than 10 micrometers; having an area greater than 100 mm.sup.2; being connected by a set of different electrical interconnection elements, said device comprising a layer of mineral material at least covering said interconnection elements, the layer of mineral material having a permeability to water vapor smaller than or equal to 10.sup.−3 g/m.sup.2/day.

7. The device of claim 6, wherein the mineral material is selected from the group consisting of the compounds of formula TiO.sub.2, ZrO.sub.2, SiO.sub.x, SiN.sub.x, SiO.sub.xN.sub.y, ZnSe, ZnO, Sb.sub.2O.sub.3, aluminum oxides, and transparent conductive oxides (TCO).

8. The device of claim 6, wherein the layer of mineral material has a thickness in the range from 10 nanometers to 100 nanometers.

9. The device of claim 6 comprising a filling material totally filling the space separating the opposite surfaces of the two components.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention will be better understood on reading of the following description provided as an example only in relation with the accompanying drawings, where the same reference numerals designate the same or similar elements, among which:

[0042] FIGS. 1 to 5 are simplified cross-section views illustrating a method of manufacturing a hybridized device with a “flip-chip” technique according to the state of the art, such as discussed hereabove; and

[0043] FIGS. 6 to 8 are simplified cross-section views illustrating a method of manufacturing a hybridized device with a “flip-chip” technique according to the invention, comprising a step of waterproofing the electrical interconnects.

DETAILED DESCRIPTION OF THE INVENTION

[0044] Referring to FIGS. 6 to 8, a method of manufacturing a device 30 comprising two hybridized electronic components 10a, 10b, comprising electrical interconnects 16, starts similarly to the state of the art, as for example described in relation with FIGS. 1 and 2. This device comprises two electronic components, for example, separated by a distance in the range from 1 micrometer to 10 micrometers, having a mutually facing area larger than 100 mm.sup.2 (for example, two square surfaces having a 10-millimeter side length opposite each other), and having a surface density of interconnects in the range from 10.sup.10/m.sup.2 to 10.sup.12/m.sup.2.

[0045] Once the hybridization is finished and before applying an encapsulation material 18, a step of waterproofing electrical interconnects 16 with a mineral layer is implemented by means of an “ALD”.

[0046] As known per se, ALD is an atomic layer deposition technique comprising successively exposing a surface placed in a chamber, or “reaction chamber”, to different chemical precursors, to obtain ultra-thin layers. The deposition of an atomic layer usually occurs in 4 steps: [0047] a) injecting into the chamber a first gaseous precursor causing the forming on the surface of a monolayer made of chemisorbed species and of other physisorbed species; [0048] b) purging the reaction chamber, for example, by means of a sweeping with ultra pure nitrogen to remove any species which has not reacted as well as possible reaction byproducts; [0049] c) injecting into the chamber a second gaseous precursor causing the forming of the layer of desired material on the surface; [0050] d) purging the chamber to remove species which have not reacted and possible reaction byproducts. Conventionally, a pumping of the chamber is carried out during the injection of precursors to cause a flow thereof in the chamber.

[0051] Advantageously, device 30 is placed in the chamber, particularly on a support 32, and the precursor injection is performed with no pumping, so that device 30 is bathed in the precursors, which integrally diffuse in volume 20 between components 10a, 10b without causing a gas disturbance. A layer 34 deposited over the entire exposed surface of device 30, and thus on interconnects 16, is thus obtained (FIG. 6).

[0052] The layer of mineral material deposited by ALD is advantageously an electrically insulating layer, particularly a layer of a material of formula TiO.sub.2, ZrO.sub.2, SiO.sub.x, SiN.sub.x, SiO.sub.xN.sub.y, ZnSe, ZnO, Sb.sub.2O.sub.3, aluminum oxides (e.g. Al.sub.2O.sub.3), and transparent conductive oxides (or “TCO”, e.g. indium-tin oxide (“ITO”) or aluminum zinc oxide (“AZO”)), particularly having a thickness in the range from 10 nanometers to 100 nanometers. A layer having a permeability to water vapor smaller than or equal to 10.sup.−3 g/m.sup.2/day is thus obtained.

[0053] Advantageously, a layer of Al.sub.2O.sub.3, de TiO.sub.2 or of ZrO.sub.2 is deposited. These materials, in addition to their waterproofing property, have a good wettability with resins currently used for the filling, and thus help the resin progress by capillarity.

[0054] In a first variation, layer 34 is made of a single material.

[0055] In a second variation, layer 34 is a multilayer of different mineral materials, called nanolaminated, which enables to combine different permeability properties, or to obstruct gas diffusion paths in a layer by depositing a layer of different material. Advantageously, layer 34 is an Al.sub.2O.sub.3/TiO.sub.2 bilayer or an Al.sub.2O.sub.3/ZrO.sub.2 bilayer. A bilayer especially enables to passivate the layer in contact with the interconnects (e.g. Al.sub.2O.sub.3) with a humidity-stable material.

[0056] Due to the insulating character of watertight layer 34, connection areas 22 of the device are not accessible to an electric connection, particularly by wire bonding. The method thus carries on with the exposing of at least one of connection areas 22, advantageously by implementing an isotropic etching, with a direction normal to the main plane of the device, such as illustrated by the arrows of FIG. 7. Such an isotropic etching results in removing the portions of watertight layers on the upper surface of second component 10b and the portions of watertight layer 34 of first component 10a which are not opposite second component 10b, and accordingly the portions of layer 34 covering connection areas 22. The isotropic etching is for example an ion machining (bombarding with unidirectional ions), an isotropic plasma etching, etc. In case of need, the lateral edges 36 of the device are also exposed, for example, by inclining device 30 during the isotropic etching, while avoiding for the etching to reach interconnects 16.

[0057] Once interconnects 16 have been waterproofed, the manufacturing method carries on conventionally with the filling of volume 20 between components with resin 18 and the connection of areas 22, for example, as described in relation with FIGS. 3 to 5. A hybridized device having its interconnects encapsulated with a watertight layer 34 and having its volume 20 between electronic components 10a and 10b filled with resin 18 is thus obtained (FIG. 8).

[0058] As a numerical example, the waterproofing method has been tested on the display of a projector comprising an array of 1746×1000 pixels (and thus as many interconnects) with a 10-micrometer pitch, hybridized on a CMOS control array provided with microtubes coated with a gold layer and respectively inserted into the indium balls of the pixel array, the interconnects being thus formed of microtubes inserted into balls. The size of the active array thus is 17.46 mm by 10 mm and the pixel array is spaced apart from the control array by a 5-micrometer distance. Such a hybridization is for example described in documents WO 2009/115686 and U.S. 2011/0094789. Due to the invention, a 25-nanometer layer of Al.sub.2O.sub.3 has been deposited by ALD on each of the interconnects, the method ending with an underfilling by capillarity by means of a resin, for example, “Epotek 353ND”© of Epoxy Technology Inc., USA.

[0059] In light of the foregoing, it should be understood that the invention applies to any type of “flip-chip” hybridization (thermocompression of balls, insertion of male elements into female elements, insertion of solid or hollow elements into balls of lower ductility, insertion at room temperature or not, etc.).

[0060] Similarly, the invention applies to any device comprising two opposite components connected by interconnects, be they electrical or not, whether the device has been obtained by “flip-chip” hybridization or not.

[0061] Similarly, although a final underfilling step has been described, the invention also encompasses devices which are not provided with such an encapsulation.