INTEGRATED ELECTRONIC DEVICE WITH A REDISTRIBUTION REGION AND A HIGH RESILIENCE TO MECHANICAL STRESSES AND METHOD FOR ITS PREPARATION

Abstract

An integrated electronic device includes a semiconductor body and a passivation structure including a frontal dielectric layer bounded by a frontal surface. A conductive region forms a via region, extending into a hole through the frontal dielectric layer. An overlaid redistribution region extends over the frontal surface. A barrier structure includes at least a first barrier region extending into the hole and surrounding the via region. The first barrier region extends over the frontal surface. A first coating layer covers the top and the sides of the redistribution region and a second coating layer covers the first coating layer. A cavity extends between the redistribution region and the frontal surface and is bounded on one side by the first coating layer and on the other by the barrier structure.

Claims

1. An integrated electronic device, comprising: a semiconductor body; a passivation structure over the semiconductor body, the passivation structure including a frontal dielectric layer bounded by a frontal surface; a conductive region of a first metal material, the conductive region including a via region extending into a hole passing through the frontal dielectric layer, and including an overlaid redistribution region extending over the frontal surface, the overlaid redistribution region having a top and at least one side; a barrier structure including at least one first barrier region of a second metal material extending into the hole and surrounding the via region, the at least one first barrier region further extending over the frontal surface; a first coating layer of a third metal material covering the top and the at least one side of the redistribution region; and a second coating layer of a fourth metal material covering the first coating layer, the second coating layer including a cavity extending between the redistribution region and the frontal surface, the cavity bounded on one side by the first coating layer and on another side by the barrier structure.

2. The integrated electronic device according to claim 1, wherein the barrier structure comprises a multilayer structure.

3. The integrated electronic device according to claim 1, wherein the fourth material of the second coating layer protects the first coating layer and distribution region from oxidation or corrosion.

4. The integrated electronic device according to claim 1, wherein the barrier structure prevents the migration of the first material to the passivation structure.

5. The integrated electronic device according to claim 1, wherein the first material is copper.

6. The integrated electronic device according to claim 5, wherein the third material is selected from nickel and an alloy of nickel.

7. The integrated electronic device according to claim 1, wherein the fourth material is selected from palladium, gold, and palladium/gold.

8. An integrated electronic circuit, comprising: a die including an integrated electronic device, the integrated electronic device including: a semiconductor body; a passivation structure over the semiconductor body, the passivation structure including a frontal dielectric layer bounded by a frontal surface; a conductive region including a via region extending in a hole through the frontal dielectric layer, the conductive region including a redistribution region extending over the frontal surface and having a top and at least one side; a barrier structure including at least one first barrier region extending into the hole and surrounding the via region, the at least one first barrier region further extending over the frontal surface; a first coating layer covering the top and the at least one side of the redistribution region; and a second coating layer covering the first coating layer, the second coating layer including a cavity extending between the redistribution region and the frontal surface, the cavity bounded on one side by the first coating layer and on another side by the barrier structure; an encapsulation region surrounding the die; and at least one conductive terminal extending in part inside the encapsulation region and in part outside the encapsulation region, the at least one conductive terminal being electrically coupled to the redistribution region through at least one wired connection.

9. The integrated electronic circuit of claim 8 further comprising a seed layer on the at least one first barrier region and extending over the frontal surface.

10. The integrated electronic device of claim 8, wherein the barrier structure comprises a multilayer structure.

11. A fabrication process for an integrated electronic device, the fabrication process comprising: forming a hole through a frontal dielectric layer of a die including a semiconductor body and a passivation structure including the frontal dielectric layer having a frontal surface; forming a via region extending into the hole; forming a redistribution region over the via region and extending over the frontal surface of the frontal dielectric layer, the redistribution region including an upper portion including a top and sides; forming a first barrier region extending into the hole and surrounding the via region, the first barrier region including portions extending over the frontal surface and including sides; forming a first coating layer covering the top and the sides of the redistribution region; forming a first contact region between the first coating layer and the sides of the redistribution region; forming a second contact region between first coating layer and the sides of the first barrier region; forming a second coating layer covering the first coating layer; and bringing into contact by capillarity the first barrier region with an aqueous solution to selectively dissolve the barrier region at the second contact region to separate the barrier region from the first coating layer.

12. The fabrication process according to claim 11, wherein the aqueous solution comprises a solution including at least one oxidizing agent.

13. The fabrication process according to claim 12, wherein the oxidizing agent is selected from the group consisting of hydrogen peroxide, nitric acid, and ozone.

14. The fabrication process according to claim 12, wherein the aqueous solution comprises an acid.

15. The fabrication process according to claim 14, wherein the acid is selected from the group consisting of nitric acid, hydrofluoric acid, and hydrochloric acid.

16. The fabrication process according to claim 12, wherein the aqueous solution comprises a base.

17. The fabrication process according to claim 16, wherein the base is selected from the group consisting of ammonium hydroxide, tetramethylammonium hydroxide, and their derivates.

18. The fabrication process according to claim 11, wherein the aqueous solution is a mixture selected from the group consisting of NH.sub.4OH:H.sub.2O.sub.2:H.sub.2O, TMAH:H.sub.2O.sub.2:H.sub.2O, H.sub.2O.sub.2:H.sub.2O, HF:H.sub.2O.sub.2:H.sub.2O and HNO.sub.3:HF:H.sub.2O.

19. The fabrication process according to claim 18, wherein the ratio between oxidant and acid or base is in the range between 1:0.05 and 1:20.

20. The fabrication process according to claim 11, wherein the barrier region is formed from a material selected from the group consisting of Ti, Ta, TiN, TiW, TaNTa.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0046] For a better understanding of the disclosure, embodiments thereof are now described, purely by way of non-limiting example and with reference to the appended drawings, in which:

[0047] FIGS. 1A and 1B show schematically transverse cross sections (not to scale) of portions of an integrated electronic device;

[0048] FIGS. 2A-2G show schematically transverse cross sections (not to scale) of portions of the integrated electronic device shown in FIG. 1, during successive steps of a fabrication process; and

[0049] FIGS. 3A and 3B show schematically transverse cross sections (not to scale) of portions of an embodiment of the present integrated electronic device;

[0050] FIGS. 4A-4D show schematically transverse cross sections (not to scale) of portions of the integrated electronic device shown in FIG. 3, during successive steps of a fabrication process;

[0051] FIG. 5 shows schematically a transverse cross section of an integrated electronic circuit (chip) that includes the present integrated electronic device.

DETAILED DESCRIPTION

[0052] The applicant has observed how the frontal structure 8 shown in FIG. 1A gives rise, in the presence of high temperatures, to mechanical forces which are not able to be freely dispersed because of the strong adhesion present between the capping structure formed by the first and second coating layers 30, 32 and the barrier layer 22. The present integrated electronic device thus arises from the idea of creating gaps between the capping structure and the barrier layer 22.

[0053] In particular, as shown in FIG. 1B, the inventors have highlighted the presence of capillary openings 70 between the capping structure formed by the first and second coating layers 30, 32 and the first dielectric layer 11. These capillary openings 70 are spontaneously generated during the step of growing the first and the second coating layer 30, 32 because of a poor adhesion between the materials constituting these layers and the materials constituting the first dielectric layer 11. In more detail, as exemplified schematically in FIG. 1B, the capillary openings 70 are formed between the frontal surface S.sub.front of the first dielectric layer 11 and the lower portion of the capping structure formed by the first and second coating layers 30, 32 and are internally bounded by the barrier layer 22 so as to form a fluidic communication between the outside of the frontal structure 8 and the barrier layer 22.

[0054] The presence of these capillary openings 70 allows an integrated electronic device to be fabricated as described hereinbelow.

[0055] In the following, the present integrated electronic device is described, without any loss of generality, with reference to the differences compared with what is shown in FIG. 1. Elements already present in the integrated electronic device 10 shown in FIG. 1 will be indicated with the same reference symbols, unless specified otherwise.

[0056] One embodiment of the present integrated electronic device is shown in FIG. 3A, where it is indicated with 40.

[0057] In particular, FIG. 3A shows only an upper portion of the integrated electronic device 40, given that the elements disposed underneath the fourth dielectric layer 16 are not shown.

[0058] This having been said, the first coating layer, here indicated with 41, covers the top and the sides of the redistribution layer 25 and is disposed on top of the first dielectric layer 11 and separated from this by means of the capillary openings 70 which typically have a transverse cross section of less than 10 nm.

[0059] Furthermore, the first coating layer 41 is physically separated from the first patterned barrier layer 22, given that, between the first patterned barrier layer 22 and the first coating layer 41, a cavity 50 is present that extends below the patterned seed layer 24 as far as the first dielectric layer 11.

[0060] In greater detail, the cavity 50 is bounded at its base by the first dielectric layer 11, at the top by the patterned seed layer 24 and laterally on one side by the first patterned barrier layer 22 and on the other by the first coating layer 41 (FIG. 3B).

[0061] The second coating layer, here indicated with 42, entirely covers the first coating layer 41 and this is also disposed on top of the first dielectric layer 11 and separated from this by means of the capillary openings 70 which typically have a transverse cross section of less than 10 nm.

[0062] Therefore, in the frontal structure of the integrated electronic device 40, indicated with 48, the cavity 50 is present that thus reduces the intrinsic mechanical stress that the first coating layer 41 exerts on the passivation structure 21.

[0063] Similarly, the integrated electronic device 40 is lacking points at which the first patterned barrier layer 22 and the first coating layer 41 come into contact; these points represent points at which the structure formed by the redistribution layer 25 and by the first and second coating layers 41, 42 exerts the maximum mechanical stress during the processes at high temperature.

[0064] The embodiment shown in FIG. 3A may be obtained by implementing the following fabrication process.

[0065] Initially, an integrated electronic device as illustrated with reference to FIGS. 2A to 2G is fabricated.

[0066] Once the structure has been obtained, as illustrated in FIGS. 2G and 4A, subsequently, as shown in FIG. 4B, the first coating layer 41 is formed, which layer entirely covers the exposed portions of the redistribution layer 25, of the patterned seed layer 24 and of the barrier layer 22. As previously stated, the first coating layer 41 may be formed from nickel, or else, again by way of example, from a nickel-phosphorous (NiP), nickel-phosphorous-tungsten (NiPW) or nickel-phosphorous-molybdenum (NiPMo) alloy.

[0067] For example, the first coating layer 41 is formed by means of deposition on the exposed metal surfaces.

[0068] The subsequent formation of the second coating layer 42 thus leads to what is shown in FIG. 4B. For example, the second coating layer 42 is formed by means of electroless deposition and selectively grows on the exposed surfaces of the first coating layer 41.

[0069] In this step of growing the first and the second coating layers 41, 42, the capillary openings 70 are spontaneously generated due to poor adhesion between the materials that constitute these layers and the materials that constitute the first dielectric layer 11.

[0070] Subsequently, as illustrated in the detail in FIG. 4C, the first barrier layer 22 is brought into contact through the capillary openings 70 with an aqueous solution 80 for the selective dissolution of the barrier layer 22 at the location of the second contact region 61.

[0071] In more detail, the contact between the first barrier layer 22 and the aqueous solution 80 is possible by virtue of the presence of capillary openings 70 which allow the attraction through capillarity of the aqueous solution 80 towards the second contact region 61.

[0072] In this region, the aqueous solution 80 causes a dissolution of the barrier layer 22 at the location of the second contact region 61 without altering the structure of the first coating layer 41 and of the patterned seed layer 24 generating the cavity 50 (FIG. 4D).

[0073] The aqueous solution 80 comprises at least one oxidizing agent, in particular chosen from within the group composed of hydrogen peroxide, nitric acid and ozone.

[0074] The aqueous solution 80 may furthermore comprise an acid, in particular selected from within the group composed of nitric acid, hydrofluoric acid and hydrochloric acid.

[0075] Alternatively, the aqueous solution 80 may furthermore comprise a base, in particular selected from within the group composed of ammonium hydroxide, tetramethylammonium hydroxide and their derivates.

[0076] For example, the aqueous solution 80 may be a mixture chosen from within the group composed of NH.sub.4OH:H.sub.2O.sub.2:H.sub.2O, TMAH:H.sub.2O.sub.2:H.sub.2O, H.sub.2O.sub.2:H.sub.2O, HF:H.sub.2O.sub.2:H.sub.2O and HNO.sub.3:HF:H.sub.2O. The ratio between oxidant and acid or base may vary between 1:0.05 and 1:20. The aqueous solution 80 is such that it performs a selective wet etching on the barrier layer 22 in such a manner as to completely separate it from the first coating layer 41 and to form the cavity 50. This etch may take place by dissolution of the barrier layer 22 or oxidation and successive dissolution of the barrier layer 22. The dissolution of the barrier layer 22 is furthermore auto-limiting since the oxidant contained in the aqueous solution 80 tends to be subjected to decomposition reactions that generate gaseous oxygen. These decomposition reactions are catalyzed by the presence of copper, such as for example that from which the patterned seed layer 24 is formed. Therefore, it is hypothesized that, when the aqueous solution 80 encounters the patterned seed layer 24, the gaseous oxygen generated by the decomposition reaction of the aqueous solution impedes the further infiltration of fresh aqueous solution through the capillary openings 70.

[0077] The advantages that are offered by the present integrated electronic device are clearly apparent from the preceding description. In particular, the present integrated electronic device disposes of a frontal structure such that the passivation structure is subjected to lower mechanical stresses, compared with known devices.

[0078] As shown in FIG. 5, subsequent to the process of dicing of the die 4, the present integrated electronic device 40 may for example form a chip 500, which includes the individual die, indicated with 504, together with a lead frame 506. The chip 500 furthermore comprises an encapsulation or packaging region 509, which is formed for example by an epoxy resin, and one or more conducting wires 510.

[0079] In more detail, the lead frame 506 comprises a pad 507, on which the individual die 504 rests, and a plurality of terminals 512, each of which extends in part inside of the packaging region 509 and in part outside. Furthermore, the terminals 512 are electrically coupled to the individual die 504 through the conducting wires 510, which implement corresponding wire bondings and make contact with the redistribution layer 25/palladium layer (detail not visible in FIG. 5). The packaging region 509 surrounds the individual die 504, the pad 507 and the conducting wires 510.

[0080] Finally, it will be clear that modifications and variants may be applied to the present integrated electronic device and to the related fabrication process, without straying from the scope of the present disclosure.

[0081] For example, the passivation structure may be different compared with that described. Furthermore, the first and the second coating layers, the first barrier layer and, where present, the further barrier layers may have different thicknesses with respect to those described and may be formed from materials different from those described.

[0082] It is furthermore possible for the vias formed in a monolithic manner with the redistribution layer to be different from the distal vias. More generally, the level of the vias integrated with the redistribution layer is irrelevant. Even more generally, the same reference to RDL technology, intended as characteristic thicknesses and materials, is irrelevant for the purposes of the present integrated electronic device.

[0083] There are furthermore possible embodiments in which a further metal layer, formed for example from gold, extends over the second coating layer.

[0084] With regard to the fabrication process, some of the steps described may be carried out in a different order with respect to that described. Furthermore, it is possible for the fabrication process to include steps not described hereinabove.

[0085] The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.