Through via nub reveal method and structure

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present application relates to the field of electronics, and more particularly, to methods of forming electronic component structures.

2. Description of the Related Art

To allow backside contact to an electronic component such as an integrated circuit die, electrically conductive through vias are formed in the electronic component. The through vias extend entirely through the electronic component from the active surface to the inactive surface of electronic component.

The inactive surface of the electronic component is etched to reveal through via nubs, i.e., portions, of the through vias. A chemical vapor deposition (CVD) inorganic dielectric layer such as a plasma enhanced chemical vapor deposition (PECVD) silicon oxide is deposited on the inactive surface of the electronic component and completely encloses the through via nubs. Unfortunately, formation of a CVD inorganic dielectric layer is relatively expensive thus increasing the fabrication cost.

The inorganic dielectric layer is thinned using chemical mechanical polish (CMP) to reveal the ends of the through via nubs. More particularly, the inorganic dielectric layer and a portion of the through via nubs are thinned such that the exposed ends of the through via nubs are parallel to and coplanar with the exterior surface of the inorganic dielectric layer. Unfortunately, chemical mechanical polish is relatively expensive thus increasing the fabrication cost.

SUMMARY OF THE INVENTION

In accordance with one embodiment, a method includes applying a backside passivation layer to an inactive surface of an electronic component and to enclose a through via nub protruding from the inactive surface. The method further includes laser ablating the backside passivation layer to reveal a portion of the through via nub.

In one embodiment, the backside passivation layer is formed of a low cost organic material. By forming the backside passivation layer of an organic material, the fabrication cost is reduced as compared to the formation of a relatively expensive CVD inorganic dielectric layer.

Further, by using a laser ablation process, the backside passivation layer is removed in a controlled manner to reveal the portion of the through via nub. Further, by using a laser ablation process, the resulting thickness of the backside passivation layer is set to a desired value in a controlled manner. Further, by using a laser ablation process, the fabrication cost is reduced as compared to the use of chemical mechanical polish.

These and other features of the present invention will be more readily apparent from the detailed description set forth below taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a through via nub reveal method in accordance with one embodiment;

FIG. 2 is a cross-sectional view of an array including a substrate including a plurality of electronic components in accordance with one embodiment;

FIG. 3 is a cross-sectional view of the array of FIG. 2 at a later stage during fabrication in accordance with one embodiment;

FIG. 4 is a perspective views of the region IV of the array of FIG. 3 in accordance with one embodiment;

FIG. 5 is a cross-sectional view of the array of FIG. 3 at a later stage during fabrication in accordance with one embodiment;

FIG. 6 is a cross-sectional view of the array of FIG. 5 at a later stage during fabrication in accordance with one embodiment;

FIG. 7 is a cross-sectional view of the region VII of the array of FIG. 6 at a later stage during fabrication in accordance with one embodiment;

FIG. 8 is a cross-sectional view of the array of FIG. 5 at a later stage during fabrication in accordance with another embodiment; and

FIG. 9 is a cross-sectional view of the region IX of the array of FIG. 8 at a later stage during fabrication in accordance with one embodiment.

In the following description, the same or similar elements are labeled with the same or similar reference numbers.

DETAILED DESCRIPTION

As an overview and in accordance with one embodiment, referring to FIG. 5, a backside passivation layer 550 is applied to an inactive surface 212 of an electronic component 204 and to enclose through via nubs 344 protruding from inactive surface 212. Referring to FIG. 6, backside passivation layer 550 is laser ablated to reveal top portions 656 of through via nubs 344.

In one embodiment, backside passivation layer 550 is formed of a low cost organic material. By forming backside passivation layer 550 of an organic material, the fabrication cost is reduced as compared to the formation of a relatively expensive CVD inorganic dielectric layer.

Further, by using a laser ablation process, backside passivation layer 550 is removed in a controlled manner to reveal top portions 656 of through via nubs 344. Further, by using a laser ablation process, the resulting thickness of backside passivation layer 550 is set to a desired value in a controlled manner. Further, by using a laser ablation process, the fabrication cost is reduced as compared to the use of chemical mechanical polish.

Now in more detail, FIG. 1 is a block diagram of a through via nub reveal method 100 in accordance with one embodiment. FIG. 2 is a cross-sectional view of an array 200 including a substrate 202 including a plurality of electronic components 204 in accordance with one embodiment.

In one embodiment, substrate 202 is a silicon wafer. Substrate 202 includes a frontside, e.g., first, surface 206 and an opposite backside, e.g., second, surface 208.

Substrate 202 includes electronic components 204 integrally connected to one another. For simplicity, the term substrate 202 shall be used herein and it is to be understood that this term generally includes electronic components 204.

In one embodiment, electronic components 204 are integrated circuit chips, e.g., active components. However, in other embodiments, electronic components 204 are passive components such as capacitors, resistors, or inductors.

In accordance with this embodiment, electronic components 204 include active surfaces 210 and opposite inactive surfaces 212. Active surfaces 210 and inactive surfaces 212 generally define frontside surface 206 and backside surface 208 of substrate 202, respectively. For simplicity, the terms frontside surface 206 and backside surface 208 shall be used herein and it is to be understood that these terms generally include active surfaces 210 and inactive surfaces 212, respectively. Electronic components 204 further includes bond pads 214 formed on active surfaces 210.

Electronic components 204 are delineated from one another by singulation streets 216. Substrate 202 is singulated, e.g., sawed, along singulation streets 216 to separate electronic components 204 from one another at a later stage during fabrication.

Referring now to FIGS. 1 and 2, in a form through vias operation 102, through vias 218 are formed though electronic components 104. Through vias 218 include dielectric through via passivation linings 220 and electrically conductive through via columns 222.

Illustratively, through via apertures 224 are formed, e.g., by laser drilling, into electronic components 104 from frontside surface 206. Through via passivation linings 220, e.g., silicon oxide (SiO₂), are formed on the sidewalls of through via apertures 224. In one embodiment, the silicon of substrate 202 exposed within through via apertures 224 is oxidized to form through via passivation linings 220. In another embodiment, a dielectric material is deposited within through via apertures 224 to form through via passivation linings 220. In one embodiment, through via passivation linings 220 are 0.15 μm thick although have other values in other embodiments.

Through via columns 222 are formed within through via passivation linings 220. Illustratively, an electrically conductive material, e.g., copper or tungsten, is deposited, e.g., plated, within through via passivation linings 220 to form through via columns 222. Through via passivation linings 220 electrically isolate through via columns 222 from substrate 202.

Substrate 202 is then thinned, sometimes called backgrinded, to expose through vias 218 at backside surface 208 of substrate 202. In one embodiment, the pitch of through vias 218 is in the range of 10 μm to 30 μm although the pitch has other values in other embodiments.

Through via passivation linings 220 are hollow cylinders and through via columns 222 are solid cylinders formed within through via passivation linings 220.

Through vias 218 are cylindrical in shape although may taper slightly between frontside surface 206 and backside surface 208. More particularly, referring to a first through via 218A of the plurality of through vias 218, through via 218A include a cylindrical outer surface 226, a circular active surface end 228, and a circular inactive surface end 230.

Cylindrical outer surface 226 is defined by the cylindrical outer surface of through via passivation lining 220 of through via 218A. Cylindrical outer surface 226 has a longitudinal axis L perpendicular to frontside surface 206 and backside surface 208. Cylindrical outer surface 226 extends from active surface end 228 to inactive surface end 230. Although the terms parallel, perpendicular, and similar terms are used herein to describe various features, in light of this disclosure, those of skill in the art will understand that the features may not be exactly parallel or perpendicular but only substantially parallel or perpendicular to within accepted manufacturing tolerances.

Active surface end 228 is circular in accordance with this embodiment. Active surface end 228 is coplanar with and parallel to frontside surface 206 of substrate 202.

Active surface end 228 includes a circular active surface column end 232 surrounded by an annular active surface passivation lining end 234. Active surface column end 232 is the lower end of through via column 222 and thus is electrically conductive. Active surface passivation lining end 234 is the lower end of through via passivation lining 220 and thus is a dielectric.

Similarly, inactive surface end 230 is circular in accordance with this embodiment. Inactive surface end 230 is coplanar with and parallel to backside surface 208 of substrate 202.

Inactive surface end 230 includes a circular inactive surface column end 236 surrounded by an annular inactive surface passivation lining end 238. Inactive surface column end 236 is the upper end of through via column 222 and thus is electrically conductive. Inactive surface passivation lining end 238 is the upper end of through via passivation lining 220 and thus is a dielectric.

Although only a single through via 218A is described in detail, in light of this disclosure, those of skill in the art will understand that all of the through vias 218 include cylindrical outer surfaces 226, active surface ends 228, inactive surface ends 230, active surface column ends 232, active surface passivation lining ends 234, inactive surface column ends 236, and inactive surface passivation lining ends 238 in a similar manner.

As illustrated in FIG. 2, frontside surface 206 of substrate 202 is mounted to a carrier 240, e.g., a silicon carrier, by an adhesive 242. In one embodiment, the thickness of carrier 240 is 700 μm although has other values in other embodiments.

FIG. 3 is a cross-sectional view of array 200 of FIG. 2 at a later stage during fabrication in accordance with one embodiment. FIG. 4 is a perspective views of the region IV of array 200 of FIG. 3 in accordance with one embodiment. Referring now to FIGS. 1, 2, 3, and 4 together, from form through vias operation 102, flow moves to an etch backside surface to expose nubs of through vias operation 104.

In etch backside surface to expose nubs of through vias operation 104, backside surface 208 of substrate 202 is blanket etched, i.e., removed, to expose through via nubs 344 of through vias 218. In one embodiment, backside surface 208 is removed using a selective etch that etches substrate 202, e.g., silicon, but does not etch through vias 218, e.g., silicon oxide and copper.

Generally, in etch backside surface to expose nubs of through vias operation 104, substrate 202 is thinned from backside surface 208. Stated another way, a portion of substrate 202 at backside surface 208 as illustrated in FIG. 2 is removed to form a recessed backside surface 346 as illustrated in FIG. 3.

Accordingly, after performance of etch backside surface to expose nubs of through vias operation 104, substrate 102 includes a recessed backside surface 346. Inactive surfaces 212 generally define recessed backside surface 346. For simplicity, the term recessed backside surface 346 shall be used herein and it is to be understood that this term generally include inactive surfaces 212.

The distance D2 between recessed backside surface 346 and frontside surface 206 as illustrated in FIG. 3 is less than the distance D1 between backside surface 208 and frontside surface 206 as illustrated in FIG. 2. Stated another way, substrate 202 is thinned from an initial thickness equal to distance D1 (FIG. 2) to a final thickness equal to distance D2 (FIG. 3).

In one embodiment, distance D1 is 50 μm and distance D2 is 48 μm although distances D1, D2 have other values in other embodiments.

However, through vias 218 are not thinned and thus through via nubs 344 are exposed as illustrated in FIG. 3. Through vias 218 are sometimes said to stand proud of recessed backside surface 346.

Through via nubs 344 are the upper portions of through vias 218 including the upper portions of through via passivation linings 220 and through via columns 222 exposed and uncovered by substrate 202. Through via nubs 344 are cylindrical protrusions protruding upwards from recessed backside surface 346.

Referring again to through via 218A, through via nub 344 includes a cylindrical nub outer surface 348 and inactive surface end 230. Cylindrical nub outer surface 348 is the upper, e.g., first, portion of cylindrical outer surface 226 of through via 218A exposed from substrate 202. A cylindrical enclosed, e.g., second, portion 349 of cylindrical outer surface 226 of through via 218A remains enclosed within and in contact with substrate 202.

Inactive surface end 230 is spaced above recessed backside surface 346. More particularly, a distance D3 exists between inactive surface end 230 and recessed backside surface 346. Distance D3 is equal to the difference between the initial thickness (distance D1 as illustrated in FIG. 2) of substrate 202 prior to performance of etch backside surface to expose nubs of through vias operation 104 and the final thickness (distance D2) of substrate 202 after performance of etch backside surface to expose nubs of through vias operation 104, i.e., D3=D1-D2. In one embodiment, distance D3 is 2 μm although distance D3 has other values in other embodiments.

Although only a single through via 218A is described in detail, in light of this disclosure, those of skill in the art will understand that all of the through vias 218 include through via nubs 344 including cylindrical nub outer surfaces 348 in a similar manner.

FIG. 5 is a cross-sectional view of array 200 of FIG. 3 at a later stage during fabrication in accordance with one embodiment. Referring now to FIGS. 1 and 5 together, from etch backside surface to expose nubs of through vias operation 104, flow moves to an apply backside passivation layer operation 106. In apply backside passivation layer operation 106, a backside passivation layer 550 is applied to recessed backside surface 346 of substrate 202 and through via nubs 344.

Backside passivation layer 550 includes a lower, e.g., first, passivation layer surface 552 attached to recessed backside surface 346. Backside passivation layer 550 further includes an opposite upper, e.g., second, passivation layer surface 554, which is planar. Backside passivation layer 550 is a dielectric material.

In one embodiment, backside passivation layer 550 is formed from an organic material such as polyimide (PI), polybutyloxide (PBO), benzocyclobutene (BCB), a polymer, or other carbon containing material. By forming backside passivation layer 550 of an organic material, the fabrication cost is reduced as compared to the formation of a relatively expensive CVD inorganic dielectric layer. In one embodiment, backside passivation layer 550 is formed by spinning or spraying an organic material onto recessed backside surface 346.

Backside passivation layer 550 has a thickness equal to a distance D4 between lower passivation layer surface 552 and upper passivation layer surface 554. In one embodiment, distance D4 is in the range of 3 μm to 4 μm with a thickness control of ±0.1 μm although distance D4 has other values in other embodiments.

Distance D4 is greater than the distance D3 that through via nubs 344 protrude above recessed backside surface 346. Accordingly, through via nubs 344 including cylindrical nub outer surface 348 and inactive surface ends 230 are completely enclosed within backside passivation layer 550. More particularly, backside passivation layer 550 exists between inactive surface ends 230 of through vias 218 and upper passivation layer surface 554.

FIG. 6 is a cross-sectional view of array 200 of FIG. 5 at a later stage during fabrication in accordance with one embodiment. Referring now to FIGS. 1, 5, and 6 together, from apply backside passivation layer operation 106, flow moves to a laser ablate backside passivation layer to reveal portions of through via nubs operation 108. In laser ablate backside passivation layer to reveal portions of through via nubs operation 108, backside passivation layer 550 is laser ablated to reveal top, e.g., first, portions 656 of through via nubs 344.

In accordance with this embodiment, a laser, e.g., an excimer laser, is directed at upper passivation layer surface 554 of backside passivation layer 550. This laser laser-ablates, i.e., removes, upper passivation layer surface 554 to expose top portions 656 of through via nubs 344 of through vias 218. Upper passivation layer surface 554 is laser-ablated, sometimes call global or mass ablated, while through via nubs 344 are not removed.

In one embodiment, the laser used during the laser ablation process selectively laser-ablates backside passivation layer 550 and does not laser ablate through via nubs 344 even though the laser is directed at through via nubs 344. In another embodiment, the laser used during the laser ablation process is directed only at backside passivation layer 550 to avoid laser ablation of through via nubs 344.

Generally, in laser ablate backside passivation layer to reveal portions of through via nubs operation 108, backside passivation layer 550 is thinned from upper passivation layer surface 554. Stated another way, a portion of backside passivation layer 550 at upper passivation layer surface 554 as illustrated in FIG. 5 is removed to form a recessed upper passivation layer surface 658 as illustrated in FIG. 6.

Accordingly, after performance of laser ablate backside passivation layer to reveal portions of through via nubs operation 108, backside passivation layer 550 includes a recessed upper passivation layer surface 658. The distance D4 between upper passivation layer surface 554 and lower passivation layer surface 552 as illustrated in FIG. 5 is greater than the distance D5 between recessed upper passivation layer surface 658 and lower passivation layer surface 552 as illustrated in FIG. 6. Stated another way, backside passivation layer 550 is thinned from an initial thickness equal to distance D4 (FIG. 5) to a final thickness equal to distance D5 (FIG. 6).

However, through vias 218 are not thinned and top portions 656 of through via nubs 344 are exposed. Top portions 656 of through via nubs 344 are the upper portions of through via nubs 344 including the upper portions of through via passivation linings 220 and through via columns 222 exposed and uncovered by backside passivation layer 550. Top portions 656 of through via nubs 344 are cylindrical protrusions protruding upwards from recessed upper passivation layer surface 658.

Referring again to through via 218A, top portion 656 of through via nub 344 of through via 218A includes a cylindrical top portion outer surface 660 and inactive surface end 230. Cylindrical top portion outer surface 660 is the upper, e.g., first, portion of cylindrical nub outer surface 348 of through via nub 344 of through via 218A exposed from backside passivation layer 550. A cylindrical enclosed, e.g., second, portion 662 of cylindrical nub outer surface 348 of through via nub 344 of through via 218A remains enclosed within and in contact with backside passivation layer 550.

Inactive surface end 230 is spaced above recessed upper passivation layer surface 658. More particularly, a distance D6 exists between inactive surface end 230 and recessed upper passivation layer surface 658. Distance D6 is equal to the difference between the distance D3 which through via nubs 344 protrude above lower passivation layer surface 552 and distance D5 between lower passivation layer surface 552 and recessed upper passivation layer surface 658, i.e., D6=D3−D5.

Although only a single through via 218A is described in detail, in light of this disclosure, those of skill in the art will understand that all of the through vias 218 include top portions 656, cylindrical top portion outer surfaces 660 and cylindrical enclosed portions 662 in a similar manner.

By using a laser ablation process, backside passivation layer 550 is removed in a controlled manner around top portions 656 of through via nubs 344. Further, by using a laser ablation process, the resulting thickness (equal to distance D5) of backside passivation layer 550 is set to a desired value in a controlled manner, e.g., to within +0.1 μm. Further, by using a laser ablation process, the fabrication cost is reduced as compared to the use of chemical mechanical polish.

In one embodiment, any residue on recessed upper passivation layer surface 658 and top portions 656 of through via nubs 344 is removed, e.g., using a soft etch, plasma clean, or combination of these techniques.

FIG. 7 is a cross-sectional view of the region VII of array 200 of FIG. 6 at a later stage during fabrication in accordance with one embodiment. Referring now to FIGS. 1 and 7 together, from laser ablate backside passivation layer to reveal portions of through via nubs operation 108, flow moves to a form circuit pattern on backside passivation layer operation 110.

In form circuit pattern on backside passivation layer operation 110, an electrically conductive circuit pattern 764 is formed on backside passivation layer 550. More particularly, circuit pattern 764 is formed on recessed upper passivation layer surface 658 of backside passivation layer 550. Backside passivation layer 550 electrically isolates circuit pattern 764 from substrate 202, i.e., from recessed backside surface 346.

Circuit pattern 764 is electrically connected to through vias 218. More particularly, circuit pattern 764 contacts and is electrically connected to inactive surface column ends 236 of through via columns 222 of through vias 218. As top portions 656 of through via nubs 344 protrude above recessed upper passivation layer surface 658, electrical interconnection between circuit pattern 764 and through vias 218 is facilitated.

In one embodiment, circuit pattern 764 includes terminals and/or traces. Illustratively, a terminal, sometimes called pad, provides an electrically conductive area to which other electrical conductors, e.g., solder balls, are mounted. A trace is a long yet narrow electrical conductor extending in a horizontal direction substantially parallel to recessed upper passivation layer surface 658 that electrically interconnects other electrical conductors, e.g., terminals of circuit pattern 764, with one another. Although terminals and traces are set forth as examples of features of circuit pattern 764, in light of this disclosure, those of skill in the art will understand that circuit pattern 764 is formed with other electrically conductive features in other embodiments depending upon the particular application.

FIG. 8 is a cross-sectional view of array 200 of FIG. 5 at a later stage during fabrication in accordance with another embodiment. Referring now to FIGS. 1, 5, and 8 together, from apply backside passivation layer operation 106, flow moves to laser ablate backside passivation layer to reveal portions of through via nubs operation 108. In laser ablate backside passivation layer to reveal portions of through via nubs operation 108, backside passivation layer 550 is laser ablated to reveal contact area, e.g., first, portions 866 of inactive surface ends 230 of through via nubs 344.

In accordance with this embodiment, a laser is directed at upper passivation layer surface 554 of backside passivation layer 550. This laser laser-ablates, i.e., removes, selective portions of upper passivation layer surface 554 to reveal contact area portions 866 of inactive surface ends 230 of through via nubs 344 of through vias 218. Upper passivation layer surface 554 is laser-ablated, i.e., removed, while through via nubs 344 are not removed.

Generally, in laser ablate backside passivation layer to reveal portions of through via nubs operation 108, circuit pattern apertures 868 are formed in backside passivation layer 550 to expose contact area portions 866 of inactive surface ends 230 of through via nubs 344 of through vias 218. Circuit pattern apertures 868 extend between upper passivation layer surface 554 and contact area portions 866. Circuit pattern apertures 868 have a diameter DIA1 less than a diameter DIA2 of through vias 218. In one embodiment, diameter DIA2 of through vias 218 is less than or equal to 20 μm, e.g., is in the range of 5 μm to 10 μm, although diameter DIA2 has other values in other embodiments.

Accordingly, contact area portions 866 of inactive surface ends 230 are the portions of inactive surface ends 230 exposed and uncovered by circuit pattern apertures 868. Further, enclosed area, e.g., second, portions 870 of inactive surface ends 230 of through via nubs 344 of through vias 218 remain enclosed within and covered by backside passivation layer 550.

In one embodiment, contact area portions 866 are inactive surface column ends 236 of through via columns 222 of through vias 218. In accordance with this embodiment, enclosed area portions 870 are inactive surface passivation lining ends 238 of through via passivation linings 220 of through vias 218.

In light of this disclosure, those of skill in the art will understand that in various embodiments a contact area portion 866 includes (1) a portion of inactive surface column end 236 only; (2) the entire inactive surface column end 236; (3) the entire inactive surface column end 236 and a portion of inactive surface passivation lining end 238; or (4) a portion of inactive surface column end 236 and a portion of inactive surface passivation lining end 238, depending upon the diameter of the circuit pattern aperture 868 and the tolerance in alignment of the circuit pattern aperture 868 with the through via 218.

By using a laser ablation process, circuit pattern apertures 868 are formed in backside passivation layer 550 in a controlled manner to expose contact area portions 866 of through via nubs 344. Further, by using a laser ablation process, the fabrication cost is reduced as compared to the use of chemical mechanical polish.

FIG. 9 is a cross-sectional view of the region IX of array 200 of FIG. 8 at a later stage during fabrication in accordance with one embodiment. Referring now to FIGS. 1 and 9 together, from laser ablate backside passivation layer to reveal portions of through via nubs operation 108, flow moves to form circuit pattern on backside passivation layer operation 110.

In form circuit pattern on backside passivation layer operation 110, an electrically conductive circuit pattern 964 is formed on backside passivation layer 550. More particularly, circuit pattern 964 is formed on upper passivation layer surface 554 and within circuit pattern apertures 868 of backside passivation layer 550. Backside passivation layer 550 electrically isolates circuit pattern 964 from substrate 202, i.e., from recessed backside surface 346.

Circuit pattern 964 is electrically connected to through vias 218. More particularly, circuit pattern 964 contacts and is electrically connected to contact area portions 866 of through vias 218.

In one embodiment, circuit pattern 964 includes terminals and/or traces in a manner similar to that described above regarding circuit pattern 764 of FIG. 7 and so is not repeated here.

Referring again to FIGS. 6 and 8, array 200 is singulated on singulation streets 216 to form a plurality of individual electronic component packages 600, 800, respectively. More particularly, substrate 202 and backside passivation layer 550 are cut, e.g., using a laser, mechanical sawing, or other singulation technique to form electronic component packages 600, 800. However, in other embodiments, array 200 is singulated at later stages during manufacture.

Although formation of a plurality of electronic component packages 600, 800 simultaneously in array 200 is described above, in other embodiments, electronic component 204 are processed individually (after singulation of substrate 202) using the methods as described above.

The drawings and the forgoing description gave examples of the present invention. The scope of the present invention, however, is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of the invention is at least as broad as given by the following claims.