WAFER LEVEL PACKAGING HAVING REDISTRIBUTION LAYER FORMED UTILIZING LASER DIRECT STRUCTURING

Abstract

A wafer-level package includes an integrated circuit (IC) die with pads on its front side. Surrounding the die's edge sides and front side is a resin layer containing an activatable catalyst material. A first passivation layer is positioned with its back surface contacting the front of the resin layer adjacent the die's front side, and a first solder resist layer is placed with its back surface contacting the front of the passivation layer. The redistribution layer includes first activated portions of the resin layer near the pads, forming electrical connections from the pads to the resin's back surface. Second activated portions extend along the resin's back surface toward the edge sides, while third activated portions run along the resin layer surrounding the die's edge sides. A first interconnect structure extends from the second activated portions, through the passivation and solder resist layers.

Claims

1. A wafer-level package, comprising: an integrated circuit die having a plurality of pads on its front side; a resin layer surrounding edge sides of the integrated circuit die, and surrounding the front side of the integrated circuit die; wherein the resin layer includes an activatable catalyst material; a first passivation layer having its back surface in contact with a front surface of the resin layer adjacent the front side of the integrated circuit die; a first solder resist layer having its back surface in contact with a front surface of the first passivation layer; and a redistribution layer comprising: first activated portions of the resin layer adjacent the plurality of pads to form electrical connections extending from the plurality of pads to the back surface of the resin layer; second activated portions of the resin layer extending along the back surface of the resin layer toward portions of the resin layer surrounding the edge sides of the integrated circuit die; third activated portions of the resin layer extending along the portions of the resin layer surrounding the edge sides of the integrated circuit die; and a first interconnect structure extending from the second activated portions of the resin layer, through the first passivation layer, and through the first solder resist layer.

2. The wafer-level package of claim 1, wherein the redistribution layer further comprises solder balls respectively connected to the first interconnect structure at locations thereof extending through the first solder resist layer.

3. The wafer-level package of claim 1, further comprising a molding layer in contact with the first, second, and third activated portions of the resin layer, in contact with un-activated portions of the resin layer that surround the edge sides of the integrated circuit die, and in contact with un-activated portions of the resin layer that surround the front side of the integrated circuit die.

4. The wafer-level package of claim 1, wherein the redistribution layer further comprises: a second passivation layer having its front surface in contact with a back side of the integrated circuit die; a second solder resist layer having its front surface in contact with a back side of the second passivation layer; and a second interconnect structure extending from the third activated portions of the resin layer, through the second passivation layer, and through the second solder resist layer; wherein the second solder resist layer has openings defined therein exposing portions of the second interconnect structure.

5. The wafer-level package of claim 4, further comprising: a dummy pillar spaced apart from the integrated circuit die, the first, second, and third activated portions of the resin layer, and un-activated portions of the resin layer that surround the edge sides of the integrated circuit die; an additional resin layer surrounding edge sides of the dummy pillar, and surrounding a front side of the dummy pillar; wherein the first passivation layer also has its back surface in contact with a front surface of the additional resin layer; and an additional redistribution layer comprising: first activated portions of the additional resin layer adjacent the front side of the dummy pillar; second activated portions of the additional resin layer extending along the back surface of the additional resin layer toward portions of the additional resin layer surrounding the edge sides of the dummy pillar; third activated portions of the additional resin layer extending along the portions of the additional resin layer surrounding the edge sides of the dummy pillar; and a third interconnect structure extending from the second activated portions of the additional resin layer, through the first passivation layer, and through the first solder resist layer.

6. The wafer-level package of claim 5, wherein the second passivation layer also has its front surface in contact with the back side of the dummy pillar; further comprising a fourth interconnect structure extending from the third activated portions of the additional resin layer, through the second passivation layer, and through the second solder resist layer; and wherein the second solder resist layer has openings defined therein exposing portions of the fourth interconnect structure.

7. The wafer-level package of claim 5, wherein the additional resin layer surrounding the dummy pillar includes an activatable catalyst material identical to that of the resin layer surrounding the integrated circuit die.

8. The wafer-level package of claim 5, wherein the dummy pillar is comprised of a material selected to match thermal expansion characteristics of the integrated circuit die.

9. The wafer-level package of claim 1, wherein the activatable catalyst material in the resin layer comprises copper-chromium oxide spinel, copper sulfate, copper hydroxide phosphate, or cupric rhodanate particles embedded within the resin layer.

10. An apparatus, comprising: a plurality of integrated circuit dice, each having a plurality of pads on a front side; a resin layer disposed over and surrounding edge sides of each integrated circuit die and at least partially covering the front side of each integrated circuit die, the resin layer including an activatable catalyst material; a first passivation layer disposed over the resin layer; a first solder resist layer disposed over the first passivation layer; and a redistribution layer comprising: first activated portions of the resin layer adjacent the plurality of pads to form electrical connections extending from the plurality of pads to a back surface of the resin layer; second activated portions of the resin layer extending along the back surface of the resin layer toward portions of the resin layer surrounding the edge sides of the plurality of integrated circuit dice; third activated portions of the resin layer extending along the portions of the resin layer surrounding the edge sides of the plurality of integrated circuit dice; and a first interconnect structure extending from the second activated portions of the resin layer, through the first passivation layer, and through the first solder resist layer.

11. The apparatus of claim 10, further comprising solder balls respectively connected to the first interconnect structure at locations extending through the first solder resist layer.

12. The apparatus of claim 10, further comprising a molding layer in contact with the first, second, and third activated portions of the resin layer, in contact with un-activated portions of the resin layer that surround the edge sides of the plurality of integrated circuit dice, and in contact with un-activated portions of the resin layer that surround the front side of the plurality of integrated circuit dice.

13. The apparatus of claim 10, further comprising: a second passivation layer having its front surface in contact with a back side of each integrated circuit die; a second solder resist layer having its front surface in contact with a back side of the second passivation layer; and a second interconnect structure extending from the third activated portions of the resin layer, through the second passivation layer, and through the second solder resist layer, wherein the second solder resist layer has openings defined therein exposing portions of the second interconnect structure.

14. The apparatus of claim 13, further comprising: at least one dummy pillar spaced apart from the plurality of integrated circuit dice, the first, second, and third activated portions of the resin layer, and un-activated portions of the resin layer that surround the edge sides of the plurality of integrated circuit dice; an additional resin layer surrounding edge sides of the at least one dummy pillar and surrounding a front side of the at least one dummy pillar; wherein the first passivation layer also has its back surface in contact with a front surface of the additional resin layer; and an additional redistribution layer comprising: first activated portions of the additional resin layer adjacent the front side of the at least one dummy pillar; second activated portions of the additional resin layer extending along the back surface of the additional resin layer toward portions of the additional resin layer surrounding the edge sides of the at least one dummy pillar; third activated portions of the additional resin layer extending along the portions of the additional resin layer surrounding the edge sides of the at least one dummy pillar; and a third interconnect structure extending from the second activated portions of the additional resin layer, through the first passivation layer, and through the first solder resist layer.

15. The apparatus of claim 14, wherein the second passivation layer also has its front surface in contact with the back side of the at least one dummy pillar; further comprising a fourth interconnect structure extending from the third activated portions of the additional resin layer, through the second passivation layer, and through the second solder resist layer; and wherein the second solder resist layer has openings defined therein exposing portions of the fourth interconnect structure.

16. The apparatus of claim 10, wherein the activatable catalyst material in the resin layer comprises copper-chromium oxide spinel, copper sulfate, copper hydroxide phosphate, or cupric rhodanate particles embedded within the resin layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 is cross sectional view of a wafer-level package formed using prior art techniques.

[0033] FIG. 2 is a cross sectional view of a first wafer-level package forming using techniques described herein.

[0034] FIG. 3 is a cross sectional view of a second wafer-level package forming using techniques described herein.

[0035] FIGS. 4A-4L illustrate the series of steps involved in fabricating the first wafer-level package of FIG. 2.

[0036] FIGS. 5A-5M illustrate the series of steps involved in fabricating the second wafer-level package of FIG. 3.

DETAILED DESCRIPTION

[0037] The following disclosure enables a person skilled in the art to make and use the subject matter disclosed herein. The general principles described herein may be applied to embodiments and applications other than those detailed above without departing from the spirit and scope of this disclosure. This disclosure is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed or suggested herein.

[0038] With initial reference to FIG. 2, a first wafer-level package 20 is now described. The first wafer-level package 20 is comprised of a semiconductor die 27 having pads or pins 25a and 25b on its front side. A resin encapsulation 26 surrounds the edge sides of the semiconductor die 27, and further covers the front side of the semiconductor die 27 except at the locations where holes are formed therethrough for passage of conductors 24a and 24b from a redistribution layer (RDL) to reach pads 25a, 25b at the front side of the semiconductor die 27. Portions of a molding layer 23 are in contact with the front surface and side surfaces of the resin encapsulation 26 at locations where the RDL is not present.

[0039] The RDL is formed within the resin encapsulation 26, within the portions of the molding layer 23 in contact with the front surface of the resin encapsulation 26, within a passivation layer 22 having its back surface in contact with a front surface of the resin encapsulation 26 and its front surface in contact with a back surface of a solder resist layer 21, and within the solder resist layer 21 itself. In particular, the RDL includes conductors 24a and 24b that extend through the resin encapsulation 26 at the front surface to contact the pads 25a and 25b of the wafer 27, and that extend upward (through the molding layer 23) alongside with and in contact with the portions of the resin encapsulation 26 on the sides of the semiconductor die 27 to reach vias 70a and 70b. The RDL also includes conductors 90a and 90b that extend through the passivation layer 22 and into the solder resist layer 21 to contact solder balls 31a and 31b.

[0040] The vias 70a and 70b extend through a passivation layer 28 extending on the back surface of the semiconductor die 27 and on the back surfaces of the portions of the resin encapsulation 26 and molding layer 23 which are present adjacent the side edges of the semiconductor die 27, to contact conductive pads 71a and 71b extending along the back surface of the passivation layer 28. A back solder resist layer 29 extends along a front surface of the passivation layer 28, and has holes 30a and 30b defined therein to expose the conductive pads 71a and 71b.

[0041] The RDL also includes conductors 33a and 33b that contact pads (not shown) of the semiconductor die 27 and extend through the molding layer 23 to contact conductors 91a and 91b, which in turn extend through the passivation layer 22 and the solder resist layer 21 to contact solder balls 32a and 32b. The molding layer 23 surrounds the conductors 24a and 24b on their sides, and surrounds the sides of the resin encapsulation 26 on portions of the sides thereof where the conductors 24a and 24b are not present.

[0042] Of note here is that the conductors 24a, 24b and 33a, 33b are not vias, and are not formed by drilling and filling. As will be explained below in detail, the conductors 24a, 24b and 33a, 33b are formed by activating desired areas of the resin encapsulation 26, which contains an activatable catalyst, and then plating the activated areas.

[0043] Another embodiment, showing a second wafer-level package 40, is now described with reference to FIG. 3. Here, the structure is the same as the first wafer-level package 20, except there is an additional structure. Here, a dummy pillar 36 is surrounded on its sides by a resin encapsulation 35, and is surrounded on its front side by the resin encapsulation 35. Here, the RDL includes a conductor 24c extending along the back surface of the resin encapsulation 35, and upward (through the molding layer 23) alongside with and in contact with the portions of the resin encapsulation 35 on the side edges of the dummy pillar 36 to reach via 70c. The RDL here also includes a conductor 92 extending through the passivation layer 22 into the solder resist layer 21 to contact the solder ball 37. The via 70c extends through a passivation layer 28 on the back surface of the dummy pillar 36 to contact pad 71c. As stated, the solder resist layer 29 extends along the back surface of the passivation layer 28, and moreover, has a hole 30c defined therein to expose the conductive pad 71c. The molding layer 22 surrounds the conductor 24c on its side, and surrounds the surfaces of the resin encapsulation 25 on portions thereof where the conductor 24c is not present.

[0044] In this embodiment, not only are the conductors 24a, 24b and 33a, 33b not vias, and not formed by drilling and filling, but the conductor 24c is not a via and is not formed by drilling and filling. As will be explained below in detail, the conductors 24a, 24b, 24c and 33a, 33b are formed by activating desired areas of the resin encapsulation 26, which contains an activatable catalyst, and then plating the activated areas.

[0045] Formation of the first wafer-level package 20 is now described with reference to the series of drawing FIGS. 4A-4L. Referring first to FIG. 4A, a single incoming wafer 9 is singulated using a saw blade or laser cutting tools into reconstituted die 27(1), 27(2), and 27(3) that have their back sides placed onto a tape layer 50 on a carrier 51, as shown in FIG. 4B, for example using a pick and place operation. The carrier 51 can be round or rectangular, with capacity for multiple die, and has a greater surface area than that of the die 27. The carrier 51 may be a temporary substrate containing a sacrificial base material, and the tape layer 50 acts as a temporary adhesive bonding film.

[0046] Note that while three reconstituted die 27(1), 27(2), and 27(3) are shown for brevity, in reality, there may be any number of reconstituted die, and the number of such die may be generally dependent upon the size of the wafer 9. Also note that in the descriptions below, the components and layers are the same on each die 27(1), 27(2), and 27(3), and are therefore described but once. Moreover, in the drawings, such components and layers have a parenthetical (1), (2), or (3) appended thereto indicating to which die they belong, but in the descriptions below, will be described without the parentheticals for ease of reading and because such components and layers are the same for each die.

[0047] Continuing now with the description, each reconstituted die 27 has pads or pins 25a and 25b formed on a front side of the die, and is sprayed on its front side and edge sides with a laser direct structuring (LDS) compatible resin 26, as shown in FIG. 4C. The resin encapsulation layer 26, as sprayed, is infused or implanted with a laser-activated catalyst or particles that become conductive when exposed to certain laser radiation, such as infrared (IR) laser radiation. For example, the resin encapsulation layer 26 may include particles such as copper-chromium oxide spinel, copper sulfate, copper hydroxide phosphate, or cupric rhodanate, embedded within the insulating layer.

[0048] The resin encapsulation layer 26 is then cured, ending up with a thickness of 15 to 25 microns. Thereafter, laser light is used to form a desired pattern of conductive traces in the resin encapsulation layer 26 by activating the catalyst in the desired portions of the resin encapsulation layer 26 to make those portions conductive. For, example, laser activation can be applied at the locations along the front side and edge sides of the layer 26 where portions of the RDL is desired. Then, a plating or deposition process, such as sputtering, electrolytic plating, or electroless plating, is used to form an electrically conductive layer on the resin encapsulation layer 26, comprised of the conductors 24a, 24b, 55a, and 55b as shown in FIG. 4D. The conductor 24a makes contact with pad 25a on the semiconductor die 27 and runs across the front surface of the resin encapsulation layer 26 to form the illustrated shape. Similarly, the conductor 24b makes contact with pad 25b on the semiconductor die 27 and runs across the front surface of the encapsulation layer 26 to form the illustrated shape.

[0049] The portions of the conductors 24a and 24b that extend through the resin 26 to contact the pads 25a and 25b actually vias, formed by laser drilling and LDS activation of the material in the walls of the holes formed by laser drilling, followed by plating.

[0050] A molding layer 56 is then conformally deposited over the conductors 24a, 24b, 55a, and 55b and the resin encapsulation layer 26, and polished to form a flat surface, as shown in FIG. 4E. Thereafter, a passivation layer 22 is deposited over the conductors 24a and 24b and the molding layer 56, for example, using plasma vapor deposition, chemical vapor deposition, printing, lamination, spin coating, or spray coating techniques, as shown in FIG. 4F. Holes are formed in the passivation layer 22, and conductors 57a, 57b, 58a, and 58b are formed (without using LDS techniques, but instead by conventional drilling and patterning) on the passivation layer 22 and extending through the holes to make contact with the conductors 24a, 24b, 58a, and 58b, as also shown in FIG. 4F, completing the formation of the front side redistribution layer (RDL).

[0051] Thereafter, a solder resist layer 21 is deposited over the passivation layer 22 and the conductors 57a, 57b, 58a, and 58b, also shown in FIG. 4F, and then holes 54a, 54b, 54c, and 54d are formed in the solder resist layer 21, for example by a patterning and etching process. Solder balls 31a, 31b, 32a, and 32b are then formed in the holes 54a, 54b, 54c, and 54d to make contact with the conductors 57a, 57b, 58a, and 58b, shown in FIG. 4G.

[0052] The formed wafer is then separated from the tape 50 and carrier 51, flipped over, and placed onto a new tape 61 and carrier 60, as shown in FIG. 4H. A back grinding operation is then performed, as shown in FIG. 4I, exposing the back surface of the die 27, as well as portions of the resin encapsulation layer 26 abutting the sides of the die 27, portions of the conductors 24a and 24b abutting the resin encapsulation layer 26, and portions of the molding layer 56 abutting the conductors 24a and 24b.

[0053] Next, a passivation layer 80 is deposited over the back surfaces of the die 27, the resin encapsulation layer 26, the conductors 24a and 24b, and the molding layer 56, for example, using plasma vapor deposition, chemical vapor deposition, printing, lamination, spin coating, or spray coating techniques, as shown in FIG. 4J. Holes are formed in the passivation layer 80, and conductors 70a, 70b, 71a, and 71b are formed on the passivation layer 80 and extending through the holes to make contact with the conductors 24a and 24b. Thereafter, a solder resist layer 81 is deposited over the passivation layer 80 and the conductors 71a and 71b, and then holes 30a and 30b are formed in the solder resist layer 81, for example by a patterning and etching process, to expose the conductors 71a and 71b, completing the formation of the back side redistribution layer (RDL).

[0054] The tape 61 and carrier 60 are then removed, as shown in FIG. 4K. The die 27 are then singulated through the solder resist 81, passivation layer 80, molding layer 56, passivation layer 22, and solder resist layer 21 with a saw blade or laser cutting tool into individual wafer level packages 20(1), 20(2), and 20(3), as shown in FIG. 4L.

[0055] Formation of the second embodiment of the wafer-level package 20 is now described with reference to the series of drawing FIGS. 5A-5N. Referring first to FIG. 5A, a single incoming wafer 9 is singulated using a saw blade or laser cutting tools into reconstituted die 27(1) and 27(2) as well as dummy pillars 8(1) and 8(2) that are placed onto a tape layer 50 on a carrier 51, as shown in FIG. 5B, for example using a pick and place operation. The carrier 51 can be round or rectangular, with capacity for multiple die, and has a greater surface area than that of the die 27. The carrier 51 may be a temporary substrate containing a sacrificial base material, and the tape layer 50 acts as a temporary adhesive bonding film.

[0056] Note that while two reconstituted die 27(1) and 27(2), as well as two dummy pillars 8(1) and 8(2) are shown for brevity, in reality, there may be any number of reconstituted die, and the number of such die may be generally dependent upon the size of the wafer 9. Also note that in the descriptions below, the components and layers are the same on each die 27(1) and 27(2), as well as on each dummy pillar 8(1) and 8(2), and are therefore described but once. Moreover, in the drawings, such components and layers have a parenthetical (1) or (2) appended thereto indicating to which die they belong, but in the descriptions below, will be described without the parentheticals for ease of reading and because such components and layers are the same for each die.

[0057] Continuing now with the description, each reconstituted die 27 has pads or pins 25a and 25b formed thereon. Each reconstituted die 27 and dummy pillar 8 is sprayed on its front side and edge sides with a laser direct structuring (LDS) compatible resin 26, as shown in FIG. 5C. The resin encapsulation layer 26, as sprayed, is infused or implanted with a laser-activated catalyst or particles that become conductive when exposed to certain laser radiation, such as infrared (IR) laser radiation. For example, the resin encapsulation layer 26 may include particles such as copper-chromium oxide spinel, copper sulfate, copper hydroxide phosphate, or cupric rhodanate, embedded within the insulating layer.

[0058] The resin encapsulation layer 26 is then cured, ending up with a thickness of 15 to 25 microns. Thereafter, laser light is used to form a desired pattern of conductive traces in the resin encapsulation layer 26 by activating the catalyst in the desired portions of the resin encapsulation layer 26 to make those portions conductive. For example, laser activation can be applied at the locations along the front side and edge sides of the layer 26 where portions of the RDL are desired. Then, a plating or deposition process, such as sputtering, electrolytic plating, or electroless plating, is used to form an electrically conductive layer on the resin encapsulation layer 26, comprised of the conductors 24a, 24b, 55a, 55b, and 83 as shown in FIG. 5D. The conductor 24a makes contact with pad 25a on the semiconductor die 27 and runs across the front surface of the resin encapsulation layer 26 to form the illustrated shape. Similarly, the conductor 24b makes contact with pad 25b on the semiconductor die 27 and runs across the front surface of the encapsulation layer 26 to form the illustrated shape. Likewise, conductor 83 runs across the back surface of the encapsulation layer 26 on the dummy pillar 8 to form the illustrated shape.

[0059] A molding layer 56 is then conformally deposited over the conductors 24a and 24b, 55a and 55b, 83, and the resin encapsulation layer 26, and polished to form a flat surface, as shown in FIG. 5E. Thereafter, a passivation layer 22 is deposited over the conductors 24a and 24b, 55a and 55b, and 83 and the molding layer 56, for example, using plasma vapor deposition, chemical vapor deposition, printing, lamination, spin coating, or spray coating techniques, as shown in FIG. 5F. Holes are formed in the passivation layer 22, and conductors 57a, 57b, 58a, 58b, and 84 are formed on the passivation layer 22 and extending through the holes to make contact with the conductors 24a, 24b, 58a, 58b, and 83 as also shown in FIG. 5F, completing the formation of the front side redistribution layer (RDL).

[0060] Thereafter, a solder resist layer 21 is deposited over the passivation layer 22 and the conductors 57a, 57b, 58a, 58b, and 84 also shown in FIG. 5F, and then holes 54a, 54b, 54c, 54d, and 54e are formed in the solder resist layer 21, for example by a patterning and etching process, as shown in FIG. 5G. Solder balls 31a, 31b, 32a, 32b, and 77 are then formed in the holes 54a, 54b, 54c, 54d, and 54e to make contact with the conductors 57a, 57b, 58a, 58b, and 84 shown in FIG. 5H.

[0061] The formed packages are then separated from the tape 50 and carrier 51, flipped over, and placed onto a new tape 61 and carrier 60, as shown in FIG. 5I. A back grinding operation is then performed, as shown in FIG. 5J, exposing the back surface of the die 27 and dummy pillar 8, as well as portions of the resin encapsulation layer 26 abutting the sides of the die 27 and dummy pillar 8, portions of the conductors 24a, 24b, and 83 abutting the resin encapsulation layer 26, and portions of the molding layer 56 abutting the conductors 24a, 24b, and 83 together with portions of the resin encapsulation layer 26

[0062] Next, a passivation layer 80 is deposited over the back surfaces of the die 27, the resin encapsulation layer 26, the conductors 24a, 24b, and 83, and the molding layer 56, for example, using plasma vapor deposition, chemical vapor deposition, printing, lamination, spin coating, or spray coating techniques, as shown in FIG. 5K. Holes are formed in the passivation layer 80, and conductors 70a, 70b, 71a, 71b, 7, and 6 are formed on the passivation layer 80 and extending through the holes to make contact with the conductors 24a, 24b, and 83. Thereafter, a solder resist layer 81 is deposited over the passivation layer 80 and the conductors 71a, 71b, and 6, and then holes 30a, 30b, and 30c are formed in the solder resist layer 81, for example by a patterning and etching process, to expose the conductors 71a, 71b, and 6 completing the formation of the back side redistribution layer (RDL).

[0063] The tape 61 and carrier 60 are then removed, as shown in FIG. 5L. The die 27 are then singulated through the solder resist 81, passivation layer 80, molding layer 56, passivation layer 22, and solder resist layer 21 with a saw blade or laser cutting tool into individual wafer level packages 20(1), 20(2), and 20(3), as shown in FIG. 5M.

[0064] The techniques described herein can be used to form fan-out wafer-level packages and fan-in wafer-level packages. Indeed, these techniques allow for the formation of wafer-level packages at a reduced cost and complexity due to the use of the LDS resin to form the basis of the RDL, eliminating the need for more expensive and time consuming steps.

[0065] While the disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be envisioned that do not depart from the scope of the disclosure as disclosed herein. Accordingly, the scope of the disclosure shall be limited only by the attached claims.