# Patent

## Title
Bonding pad structure with dense via array

## Abstract

A bonding pad structure comprises a first dielectric layer, a first conductive island in a second dielectric layer over the first dielectric layer and a via array having a plurality of vias in a third dielectric layer over the first conductive island. The structure also comprises a plurality of second conductive islands in a fourth dielectric layer over the via array. The second conductive islands are each separated from one another by a dielectric material of the fourth dielectric layer and in contact with at least one via of the via array. The structure further comprises a substrate over the second conductive islands. The substrate has an opening defined therein that exposes at least one second conductive island. The structure additionally comprises a bonding pad over the substrate. The bonding pad is in contact with the at least one second conductive island through the opening in the substrate.

## Background
PRIORITY CLAIM
The present application is a continuation of U.S. application Ser. No. 13/435,702, filed Mar. 30, 2012, which is incorporated herein by reference in its entirety.


TECHNICAL FIELD
The present disclosure relates generally to an integrated circuit and more particularly a bonding pad with dense via array.
BACKGROUND
A bonding or bumping pad is used for electrical connections, such as wire bonding or flip-chip bumps, etc. In a slot structure with multiple vias/metal pads connected to the bonding pad, each via is connected to a respective metal pad (or metal island). The adhesion between via and metal pad is relatively weak resulting in peeling or cracking at an interface of the via and metal pad during a bonding or bumping process. With increasing bonding/bumping forces, a peeling rate at the via/metal pad interface also increases. Further, the via density is limited in the slot structure.



BRIEF DESCRIPTION OF THE DRAWINGS
Reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
FIG. 1A is a schematic diagram of an exemplary bonding pad structure according to some embodiments;
FIG. 1B is a schematic diagram of another exemplary bonding pad structure according to some embodiments;
FIG. 2 is a top view of the exemplary dense via array in the bonding pad structures in FIGS. 1A and 1B according to some embodiments;
FIGS. 3A-3K are schematic diagrams of intermediate fabrication steps of an exemplary bonding pad structure similar to FIG. 1A according to some embodiments;
FIG. 4 is a schematic diagram of yet another exemplary bonding pad structure according to some embodiments; and
FIG. 5 is a schematic diagram of yet another exemplary bonding pad structure according to some embodiments.



DETAILED DESCRIPTION
The making and using of various embodiments are discussed in detail below. It should be appreciated, however, that the present disclosure provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use, and do not limit the scope of the disclosure.
In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a feature on, connected to, and/or coupled to another feature in the present disclosure that follows may include embodiments in which the features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the features, such that the features may not be in direct contact. In addition, spatially relative terms, for example, “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “up,” “down,” “top,” “bottom,” etc. as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) are used for ease of the present disclosure of one features relationship to another feature. The spatially relative terms are intended to cover different orientations of the device including the features.
FIG. 1A is a schematic diagram of an exemplary bonding pad structure 100 according to some embodiments. The bonding pad structure 100 includes a substrate 102, a first conductive island 107 formed in a dielectric layer 104 and disposed over the substrate 102. A first via array 110 with multiple vias is formed in another dielectric layer 108 and disposed over the first conductive island 107. A second conductive island 113 is formed in the dielectric layer 108 and disposed over the first via array 110. A bonding pad 122 (e.g., a conductive metal island) is formed through and over the passivation layer 120 and disposed over the second conductive island 113.
The first conductive island 107, the first via array 110, and the second conductive island 113 are electrically connected to the bonding pad 122. The dielectric layer 108 can comprise multiple dielectric layers, e.g., second and third dielectric layers 108a, 108b (as depicted in FIGS. 3D and 3G), each having a thickness corresponding to the first via array 110 and the second conductive island 113. A passivation layer 120 is formed over the dielectric layer 108 and the bonding pad 122 is connected to the second conductive island 113 through the passivation layer 120. The first via array 110 is connected to no other conductive island in the dielectric layer 104 except the first conductive island 107 and no other conductive island in the dielectric layer 108 is connected to the via array 110 except the second conductive island 113.
The substrate 102 comprises silicon, intermetal dielectric (IMD), low-k dielectric, or any other suitable material in some embodiments. The first conductive island 107 and the second conductive island 113 comprise conductive metal such as Cu, Cu alloy, W, Au, Al, or any other suitable material and barrier metal such as Ta, Ti, TaN, TiN, or any other suitable material in some embodiments. The barrier metal prevents the conductive metal diffusion into neighboring portions of the dielectric layer 104, 108 and/or the substrate 102.
The dielectric layers 104 and 108 comprise SiO2, low-k dielectric, SiC, SiN, SiOC, TEOS, or any combination thereof in some embodiments. The first via array 110 comprises conductive metal such as Cu, W, or any other suitable material, and barrier metal such as TiN, TaN, or any other suitable material to prevent the conductive metal diffusion to neighboring dielectric layer and/or substrate. The passivation layer 120 comprises SiC, TEOS, hard black diamond (HBD), SiN, or any other suitable material in some embodiments.
Because the first conductive island 107 or the second conductive island 113 is not slotted (i.e., individually divided) but a single solid (i.e., continuous) part, the first via array 110 can be more densely populated. Thus, the via density is increased and the ratio of via area over the first or second conductive island 107, 113 area can range from 10% to 99% in some embodiments. From the increased via density, the adhesion between the first via array 110 and the first conductive island 107, the second conductive island 113, and the bonding pad 122 is stronger, thus reducing the peeling rate at the via interface.
Also, the contact resistance between the first via array 110 and the first conductive island 107, the second conductive island 113, and the bonding pad 122 is reduced. The vias in the first via array 110 are distributed in any form or shape and do not have to be uniformly distributed. The first via array 110 can be partially dense in a certain portion of the first conductive island 107 area, for example.
FIG. 1B is a schematic diagram of another exemplary bonding pad structure 101 according to some embodiments. The bonding pad structure 101 is similar to the bonding pad structure 100 in FIG. 1A but adds another level including a second via array 116 formed in a dielectric layer 114 and a third conductive island 118. The second via array 116 is disposed over the second conductive island 113.
The dielectric layer 114 can comprise multiple dielectric layers, e.g., a fourth and a fifth dielectric layer, each having a thickness corresponding to the second via array 116 and the second conductive island 118. The bonding pad 122 is disposed over the third conductive island 118 and connected to the third conductive island 118 and the second via array 116, which is in turn connected to the second conductive island 113, the first via array 110, and the first conductive island 107. The second via array 116 is connected to no other conductive island in the dielectric layer 108 except the second conductive island 113 and no other conductive island in the dielectric layer 114 is connected to the second via array 116 except the third conductive island 118 in some embodiments.
The third conductive island 118 comprises conductive metal such as Cu, Cu alloy, W, Au, Al, or any other suitable material and barrier metal such as Ta, Ti, TaN, TiN, or any other suitable material in some embodiments. The barrier metal prevents the conductive metal diffusion into neighboring dielectric layer and/or substrate. The dielectric layer 114 comprises SiO2, low-k dielectric, SiC, SiN, SiOC, TEOS, or any combination thereof in some embodiments. The second via array 116 comprises conductive metal such as Cu, W, or any other suitable material, and barrier metal such as TiN, TaN, or any other suitable material to prevent the conductive metal diffusion to neighboring portions of the dielectric layer 114 or the substrate 102.
FIG. 2 is a top view of the exemplary dense via array in the bonding pad structures in FIGS. 1A and 1B according to some embodiments. A bonding pad structure 200 including a conductive island (e.g., metal pad) 202 is shown having a dense via array 204. The conductive island 202 is, for example, the first conductive island 107, the second conductive island 113 in FIG. 1A, or the third conductive island 118 in FIG. 1B. The dense via array 204 is, for example, the first via array 110 in FIG. 1A or the second via array 116 in FIG. 1B. The via array 204 can be distributed in any form or shape and don't have to be uniformly distributed as shown in FIG. 2. The via array 204 can be partially dense in a certain portion of the conductive island 202, for example.
FIGS. 3A-3K are schematic diagrams of intermediate fabrication steps of an exemplary bonding pad structure similar to FIG. 1A according to some embodiments. In FIG. 3A, a dielectric layer 104 such as intermetal dielectric (IMD) is formed on a substrate 102 by chemical vapor deposition (CVD), for example. The dielectric layer 104 comprises SiO2, low-k dielectric, SiC, TEOS, hard black diamond (HBD), SiOC, or any other suitable material with a thickness ranging from 500 Å to 5000 Å in some embodiments.
In FIG. 3B, trenches 103 for conductive islands (i.e., solid metal pads) are formed in the dielectric layer 104 by dry etching process, for example. A trench width (length) ranges from 5 μm to 100 μm in some embodiments.
In FIG. 3C, barrier metal 105 and a conductive metal 106 are deposited to form the conductive islands 107 in the dielectric layer 104 by physical vapor deposition (PVD), CVD, and planarized by chemical-mechanical planarization (CMP), for example. The conductive metal 106 comprises Cu, Cu alloy, W, Au, Al, or any other suitable material in some embodiments. The barrier metal 105 comprises Ta, Ti, TaN, TiN, or any other suitable material in some embodiments. The barrier metal 105 prevents the conductive metal 106 diffusion into neighboring portions of the dielectric layer 104 or the substrate 102.
In FIG. 3D, a dielectric layer 108a (e.g., an IMD) is formed over the first conductive islands 107 (that include barrier metal 105 and conductive metal 106) and the dielectric layer 104 by chemical vapor deposition (CVD), for example. The dielectric layer 108a comprises SiO2, low-k dielectric, SiC, TEOS, hard black diamond (HBD), SiOC, or any other suitable material with a thickness ranging from 500 Å to 5000 Å in some embodiments.
In FIG. 3E, dense via holes 109 are formed in the dielectric layer 108a by dry etching, for example. The via hole size ranges from 0.08 μm to 5 μm in some embodiments.
In FIG. 3F, a dense via array 110 is formed in the via holes 109 by PVD, CVD, or CMP, for example. Each via in the via array 110 includes a barrier metal and a conductive metal. The conductive metal comprises Cu, Cu alloy, W, Au, Al, or any other suitable material in some embodiments. The barrier metal comprises Ta, Ti, TaN, TiN, or any other suitable material in some embodiments. The barrier metal prevents the conductive metal diffusion into neighboring portions of the dielectric layer 108a. 
In FIG. 3G, a dielectric layer 108b (e.g., an IMD) is formed over the first via array 110 by CVD, for example. The dielectric layer 108b comprises SiO2, low-k dielectric, SiC, TEOS, hard black diamond (HBD), SiOC, or any other suitable material in some embodiments.
In FIG. 3H, trenches for conductive islands (i.e., solid metal pads) are etched out by dry etching process, and then the second conductive islands 113 that include barrier metal 111 and conductive metal 112 are formed in the dielectric layer 108b by PVD, CVD, and CMP, for example. The conductive metal 112 comprises Cu, Cu alloy, W, Au, Al, or any other suitable material in some embodiments. The barrier metal 111 comprises Ta, Ti, TaN, TiN, or any other suitable material in some embodiments. The barrier metal 111 prevents the conductive metal 112 diffusion into neighboring portions of the third dielectric layer 108b. 
In FIG. 3I, a passivation layer 120 is formed by CVD, for example. The passivation layer 120 comprises SiC, TEOS, hard black diamond (HBD), SiN, or any other suitable material with a thickness ranging from 500 Å to 20000 Å in some embodiments.
In FIG. 3J, trenches 121 for bonding (or bumping) pads 122 are formed in the passivation layer 120 by dry etching, for example. The trench width (length) ranges from 5 micrometers to 100 micrometers in some embodiments.
In FIG. 3K, bonding/bumping pads 122 (e.g., metal pad) that also include barrier metal 123 are formed over the conductive islands 113 (i.e., the barrier metal 111 and conductive metal 112) by PVD and dry etching, for example. The bonding/bumping pads 122 comprise AlCu or any other suitable material with a thickness from 1000 Å-20000 Å in some embodiments. The barrier metal 123 comprises TiN, TaN, or any other suitable material in some embodiments.
FIG. 4 is a schematic diagram of yet another exemplary bonding pad structure 400 according to some embodiments. The bonding pad structure 400 is similar to the bonding pad structure 101 in FIG. 1B, except that there are multiple conductive islands 119 in FIG. 4 connected to the via array 116 in the dielectric layer 114, instead of one conductive island 118 as shown in FIG. 1B. The bonding pad structure 400 still has increased adhesion between the first and second via arrays 110 and 116, and the conductive islands 107, 113, and 119 compared to a slot structure where every via is connected to a respective metal island separately.
FIG. 5 is a schematic diagram of yet another exemplary bonding pad structure according to some embodiments. The bonding pad structure 500 is similar to the bonding pad structure 101 in FIG. 1B, except that the bonding pad 122 is formed through the substrate 102 (upside down from FIG. 1B) instead of the passivation layer 120. The substrate 102 is a base layer comprising silicon, in some embodiments.
An aspect of this description relates to a bonding pad structure that comprises a first dielectric layer, a first conductive island in a second dielectric layer over the first dielectric layer and a via array having a plurality of vias in a third dielectric layer over the first conductive island. The structure also comprises a plurality of second conductive islands in a fourth dielectric layer over the via array. The second conductive islands of the plurality of second conductive islands are each separated from one another by a dielectric material of the fourth dielectric layer and in contact with at least one via of the via array. The structure further comprises a substrate over the plurality of second conductive islands. The substrate has an opening defined therein that exposes at least one second conductive island of the plurality of second conductive islands. The structure additionally comprises a bonding pad over the substrate. The bonding pad is in contact with the at least one second conductive island of the plurality of second conductive islands through the opening in the substrate.
Another aspect of this description relates to a bonding pad structure that comprises a substrate and a first conductive island in a first dielectric layer over the substrate. The first conductive island comprises a barrier layer and a conductive material. The structure also comprises a via array having a plurality of vias in a second dielectric layer over the first conductive island. The structure further comprises a plurality of second conductive islands in a third dielectric layer over the via array. Each second conductive island of the plurality of second conductive islands is separated from other second conductive islands of the plurality of second conductive islands by a dielectric material of the third dielectric layer and in contact with at least one via of the via array. The structure additionally comprises a bonding pad over the plurality of second conductive islands. At least one second conductive island of the plurality of second conductive islands is in contact with the bonding pad.
A further aspect of this description relates to a bonding pad structure that comprises a substrate and a first conductive island in a first dielectric layer over the substrate. The first conductive island comprises a barrier layer and a conductive material. The structure also comprises a via array having a plurality of vias in a second dielectric layer over the first conductive island. The structure further comprises a plurality of second conductive islands in a third dielectric layer over the via array. Each second conductive island of the plurality of second conductive islands is separated from other second conductive islands of the plurality of second conductive islands by a dielectric material of the third dielectric layer and in contact with at least one via of the via array. The structure additionally comprises a bonding pad over the plurality of second conductive islands. At least one second conductive island of the plurality of second conductive islands is in contact with the bonding pad.
A skilled person in the art will appreciate that there can be many embodiment variations of this disclosure. Although the embodiments and their features have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, and composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosed embodiments, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure.
The above method embodiment shows exemplary steps, but they are not necessarily required to be performed in the order shown. Steps may be added, replaced, changed order, and/or eliminated as appropriate, in accordance with the spirit and scope of embodiment of the disclosure. Embodiments that combine different claims and/or different embodiments are within the scope of the disclosure and will be apparent to those skilled in the art after reviewing this disclosure.

## Claims

1. A bonding pad structure, comprising:
a first layer;
a first conductive island in a second dielectric layer over the first layer;
a via array having a plurality of vias in a third dielectric layer over the first conductive island;
a plurality of second conductive islands in a fourth dielectric layer over the via array, the second conductive islands of the plurality of second conductive islands each being separated from one another by a dielectric material of the fourth dielectric layer and in contact with at least one via of the via array;
a top layer over the plurality of second conductive islands, the top layer having an opening defined therein, wherein the opening exposes at least one second conductive island of the plurality of second conductive islands; and
a bonding pad over the top layer, the bonding pad being in contact with multiple second conductive islands of the plurality of second conductive islands through the opening in the top layer.

2. The bonding pad structure of claim 1, wherein the first layer is a dielectric layer.

3. The bonding pad structure of claim 1, wherein the first conductive island and the vias of the via array are electrically connected to the bonding pad through the at least one second conductive island of the plurality of second conductive islands.

4. The bonding pad structure of claim 1, wherein the vias of the via array are connected with the first conductive island, and the vias of the via array are free from a connection with any other conductive island in the second dielectric layer.

5. The bonding pad structure of claim 4, wherein the vias of the via array are free from a connection with any other conductive island in the fourth dielectric layer.

6. The bonding pad structure of claim 1, wherein the top layer comprises silicon, an intermetal dielectric, or a low-k dielectric.

7. The bonding pad structure of claim 1, wherein the first conductive island comprises one or more of Cu, Cu alloy, W, Au, Al, TaN, Ta, or Ti.

8. The bonding pad structure of claim 1, wherein the first layer, the second dielectric layer, and the third dielectric layer independently comprise one or more of SiO2, a low-k dielectric material, SiC, SiN, SiOC, or TEOS.

9. The bonding pad structure of claim 1, wherein the vias of the via array are disposed non-uniformly over the first conductive island and a first portion of the vias of the via array are disposed more densely than a second portion of the vias of the via array.

10. The bonding pad structure of claim 1, wherein the first conductive island comprises a continuous surface over which the vias of the via array are disposed, and the vias of the via array contact the continuous surface of the first conductive island.

11. A bonding pad structure, comprising:
a substrate;
a first conductive island in a first dielectric layer over the substrate, the first conductive island comprising a barrier layer and a conductive material;
a via array having a plurality of vias in a second dielectric layer over the first conductive island;
a plurality of second conductive islands in a third dielectric layer over the via array, each second conductive island of the plurality of second conductive islands is separated from other second conductive islands of the plurality of second conductive islands by a dielectric material of the third dielectric layer and in contact with at least one via of the via array; and
a bonding pad over the plurality of second conductive islands, at least two second conductive islands of the plurality of second conductive islands being in contact with the bonding pad.

12. The bonding pad structure of claim 11, wherein the first conductive island and the vias of the via array are electrically connected to the bonding pad.

13. The bonding pad structure of claim 11, wherein the vias of the via array are arranged non-uniformly over the first conductive island.

14. The bonding pad structure of claim 13, wherein a first portion of the vias of the via array are disposed more densely than a second portion of the vias of the via array.

15. The bonding pad structure of claim 11, wherein the first conductive island comprises a continuous surface over which the vias of the via array are positioned.

16. The bonding pad structure of claim 11, wherein the barrier layer comprises a metal material different from the conductive material of the first conductive island.

17. The bonding pad structure of claim 11, wherein the first conductive island and the second conductive islands of the plurality of second conductive islands comprise a same material.

18. A bonding pad structure, comprising:
a substrate;
a first conductive island in a first dielectric layer over the substrate;
a via array having a plurality of vias in a second dielectric layer over the first conductive island, wherein the first conductive island comprises a continuous surface, and the vias of the via array occupy an area over the continuous surface in a range of about 10% to about 99% of a surface area of the continuous surface;
a plurality of second conductive islands in a third dielectric layer over the vias of the via array, each second conductive island of the plurality of second conductive islands comprises a conductive material and a barrier layer between the conductive material and the third dielectric layer; and
a bonding pad over the second conductive islands of the plurality of second conductive islands, wherein at least one second conductive island of the plurality of second conductive islands is in contact with the bonding pad.

19. The bonding pad structure of claim 18, further comprising:
a passivation layer over the fourth dielectric layer, wherein the bonding pad is connected to the at least one second conductive island of the plurality of second conductive islands through the passivation layer.

20. The bonding pad structure of claim 18, wherein at least two second conductive island of the plurality of second conductive islands is in contact with the bonding pad.