SOLDER PAD, SEMICONDUCTOR CHIP COMPRISING SOLDER PAD, AND FORMING METHOD THEREFOR

A solder pad, a semiconductor chip including the solder pad, and a forming method therefor are provided. A solder pad includes at least two metal layers and a dielectric layer located between adjacent metal layers. The solder pad includes a laser drilling region; the dielectric layer is provided with an opening corresponding to the laser drilling region; a metal plug is provided in the opening, both ends of the metal plug being respectively in contact with the adjacent metal layers. A method for forming a solder pad improves the quality of laser drilling performed on a solder pad and reduces the difficulty of the laser drilling; laser acts on a metal substance without being in contact with a dielectric layer, so as to effectively prevent a dielectric layer from heat distortion.

The present application claims priority to Chinese Patent Application No. 201511009450.8, titled “SEMICONDUCTOR CHIP AND FORMING METHOD THEREFOR”, filed on Dec. 29, 2015 with the State Intellectual Property Office of People's Republic of China, and Chinese Patent Application No. 201521116234.9, titled “SEMICONDUCTOR CHIP”, filed on Dec. 29, 2015 with the State Intellectual Property Office of People's Republic of China, both of which are incorporated herein by reference in their entireties.

FIELD

The present disclosure relates to the technical field of semiconductor chips, and in particular to the field of semiconductor chip manufacturing

BACKGROUND

Laser drilling technology is widely used in the field of semiconductors, especially in the field of semiconductor chip packaging.

Reference is made toFIG. 1andFIG. 2, whereFIG. 1is a schematic structural diagram of a wafer-level semiconductor chip, andFIG. 2is a schematic structural diagram of a package of a semiconductor chip. Referring toFIG. 1, a wafer100includes multiple semiconductor chips201arranged in an array. A cutting trench region is provided between adjacent semiconductor chips201. After the wafer level packaging and testing are completed, the semiconductor chips201are separated from each other along the cutting trench regions. Each of the semiconductor chips201includes an integrated circuit and multiple contact pads electrically connected to the integrated circuit. The contact pad is configured to electrically connect with an external circuit.

Referring toFIG. 2, an image sensing chip is taken as an example. A protection layer203is arranged on a first surface I of the semiconductor chip201. Contact pads202are located in the protection layer203. An optical device layer207is arranged in a position in the protection layer203corresponding to a photosensitive region. A partition wall205is arranged on a protection substrate200. After the semiconductor chip201is laminated with the protection substrate200in an alignment manner, the optical device layer207is located in a cavity206formed by surrounding by the partition wall205.

In the structure shown inFIG. 2, in order to electrically connect the contact pad202and the external circuit, a laser hole209penetrating the contact pad202is formed on the contact pad202and a metal wiring layer210extending to a second surface II of the semiconductor chip201is formed in the laser hole209, then a solder ball212connected to the metal wiring layer210is formed on the second surface II. The contact pad202is electrically connected to the external circuit through the solder ball212. In addition, in order to prevent mutual interference between the metal wiring layer210and other circuits in the semiconductor chip201, an insulating layer208a and an insulating layer211are formed on the semiconductor chip201to isolate the metal wiring layer from the other circuits.

In the conventional technology, the contact pad generally has a multi-layer structure, i.e., including at least two metal layers and a dielectric layer between adjacent metal layers. The structure and the material of the contact pad directly affect the quality and difficulty of laser drilling. Therefore, a technical issue to be solved by those skilled in the art is how to improve the quality of the laser drilling for the contact pad and reduce the difficulty of the laser drilling.

SUMMARY

A contact pad with a new structure is designed according to the disclosure, which improves a quality of laser drilling for the contact pad and reduces difficulty of the laser drilling.

In an aspect of the present disclosure, a contact pad is provided, where the contact pad includes at least two metal layers and a dielectric layer located between adjacent metal layers. A laser drilling region is arranged on the contact pad, an opening is arranged in a position in the dielectric layer corresponding to the laser drilling region, a metal plug is arranged in the opening, and both ends of the metal plug are in contact with adjacent metal layers, respectively.

Optionally, the metal plug includes: a barrier layer formed on a bottom of the opening in contact with the metal layer and a sidewall of the opening; a diffusion barrier layer located on the barrier layer; and a filler metal located on the diffusion barrier layer and filling the opening.

Optionally, the filler metal is made of tungsten, the barrier layer is made of titanium, and the diffusion barrier layer is made of titanium nitride.

Optionally, at least one opening is further arranged in a region other than a position of the opening in the dielectric layer to form a conductive plug in the at least one opening, and both ends of the conductive plug are electrically connected to adjacent metal layers, respectively.

Optionally, the conductive plug and the metal plug are made of a same material and have a same structure.

Optionally, the metal layer includes a barrier layer tightly integrated with a protection layer or the dielectric layer of the contact pad, an intermediate metal layer bonded with the barrier layer, and an anti-reflection layer deposited on the intermediate metal layer.

Optionally, the barrier layer is made of titanium, the intermediate metal layer is made of aluminum-copper alloy, and the anti-reflection layer is made of titanium nitride.

Optionally, a laser hole is arranged in the laser drilling region, and the laser hole penetrates the metal layer and the metal plug sequentially.

In another aspect of the present disclosure, a semiconductor chip including the above-described contact pad is provided.

In another aspect of the present disclosure, a method for forming a contact pad of a semiconductor chip is provided, which includes: (a) forming a metal layer; (b) forming a dielectric layer on the metal layer; (c) forming a metal plug in the dielectric layer, where the metal plug is located in a laser drilling region; and (d) forming another metal layer on the dielectric layer.

Optionally, the step of forming the metal plug in the dielectric layer includes: forming an opening on the dielectric layer with an etching process; forming a barrier layer on a bottom of the opening and a sidewall of the opening with a deposition process; forming a diffusion barrier layer on the barrier layer with the deposition process; and forming a filler metal filling the opening on the diffusion barrier layer with the deposition process.

Optionally, the filler metal is made of tungsten, the barrier layer is made of titanium, and the diffusion barrier layer is made of titanium nitride.

Optionally, the method further includes: arranging at least one opening in a region other than a position of the opening to form a conductive plug in the at least one opening, where both ends of the conductive plug are electrically connected to adjacent metal layers, respectively.

Optionally, the conductive plug and the metal plug are formed with a same material and method.

Optionally, the step of forming the metal layer includes: depositing a barrier layer on a protection layer or the dielectric layer of the contact pad with a deposition process; depositing an intermediate metal layer on the barrier layer with the deposition process; depositing an anti-reflection layer on the intermediate metal layer with the deposition process; and forming a metal layer having a same shape as that of the contact pad by imprinting a silicon wafer using photoresist and performing an etching process.

Optionally, the barrier layer is made of titanium, the intermediate metal layer is made of aluminum-copper alloy, and the anti-reflection layer is made of titanium nitride.

Optionally, a laser hole sequentially penetrating the metal layer and the metal plug is formed in the laser drilling region of the contact pad.

Optionally, steps (b) to (d) are performed repeatedly to form multiple metal layers and dielectric layers. Beneficial effects of the disclosure are that: the quality of the laser drilling for the contact pad is improved and the difficulty of laser drilling is reduced. The laser acts on the metal material and is prevented from contacting with the dielectric layer, and thus thermal deformation of the dielectric layer can be effectively prevented and an inner wall of the laser hole can be prevented from cracking. In addition, since a whole sidewall of the laser hole is made of metal, electrical conductivity of the contact pad is improved.

DETAILED DESCRIPTION OF EMBODIMENTS

The specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. However, the embodiments are not intended to limit the present disclosure. Any modifications to structures, methods or functions made by those skilled in the art based on these embodiments fall within the protection scope of the present disclosure.

It should be noted that these drawings are provided for the purpose of facilitating understanding of the embodiments of the present disclosure and should not be construed as limiting the present disclosure. For the sake of clarity, the dimensions shown in the figures are not drawn to scale and may be enlarged, reduced, or altered in other manner.

Referring toFIG. 3AandFIG. 3B, a semiconductor chip301includes an integrated circuit (not shown inFIG. 3A) and multiple contact pads31electrically connected to the integrated circuit. The contact pad31is configured to electrically connect with an external circuit. A structure and a function of the integrated circuit are not limited in the present disclosure, and the integrated circuit is broadly explained herein. That is, the so-called integrated circuit is a circuit having some functions and formed by integrating a number of commonly used electronic elements such as a resistor, a capacitor, a transistor and connection lines between the electronic elements with a semiconductor process. A protection layer32is arranged on a surface of the semiconductor chip301, and the contact pad31is arranged in the protection layer32.

A laser drilling region310is arranged on the contact pad31, and in a subsequent process of the laser drilling, a laser hole320is arranged in the laser drilling region and an area of the laser drilling region is greater than an area of the laser hole. In order to simplify the laser drilling operation and facilitate positioning the laser hole to the laser drilling region, the laser drilling region is arranged at a center of the contact pad31. In this way, the laser drilling operation is performed only by aligning a laser beam with the center of the contact pad31without additionally providing a laser alignment mark.

In this embodiment, a shape of the laser drilling region310is square. The shape of the laser drilling region310is not limited in the present disclosure, and the shape of the laser drilling region310may be circular, as long as the laser hole is located in the laser drilling region and there is a spacing between a sidewall of the laser hole and a side edge of the laser drilling region310.

FIG. 4is a cross-sectional view of the contact pad31. In this embodiment, the contact pad31includes four metal layers, that is, a first metal layer311, a second metal layer312, a third metal layer313, and a fourth metal layer314. A first dielectric layer315is provided between the first metal layer311and the second metal layer312, a second dielectric layer316is provided between the second metal layer312and the third metal layer313, and a third dielectric layer317is provided between the third metal layer313and the fourth metal layer314.

An opening is arranged in a position in each of the dielectric layers corresponding to the laser drilling region310, and a metal plug is arranged in the opening. InFIG. 4, a first metal plug325, a second metal plug326and a third metal plug327are arranged in the openings of the dielectric layers. Both ends of each metal plug are in contact with adjacent metal layers respectively, that is, both ends of the first metal plug325are in contact with the first metal layer311and the second metal layer312respectively, both ends of the second metal plug326are in contact with the second metal layer312and the third metal layer313respectively, and both ends of the third metal plug327are in contact with the third metal layer313and the fourth metal layer314respectively.

In a subsequent process of the laser drilling, a laser hole320penetrating the contact pad31is formed in the laser drilling region310of the contact pad31. InFIG. 4, the laser hole320penetrates the fourth metal layer314, the third metal plug327, the third metal layer313, the second metal plug326, the second metal layer312, the first metal plug325, and the first metal layer311, sequentially.

In order to improve stability of an electrical connection between metal layers, at least one opening is further arranged in a region other than positions of the openings in the dielectric layers to provide a conductive plug330in the at least one opening. Both ends of the conductive plug330are electrically connected to adjacent metal layers, respectively.

In order to improve simplicity and convenience of the process, the metal plug and the conductive plug can be fabricated simultaneously.

The contact pad31is formed in a wafer level process.

First, a first metal layer311is formed, and a first dielectric layer315is formed on the first metal layer311. Second, a first metal plug325and at least one conductive plug330are formed in the first dielectric layer315. Then, a second metal layer312is formed on the first dielectric layer315. The above steps are performed repeatedly and finally a structure of a contact pad as shown inFIG. 4is formed.

The metal layer has a multi-layer structure. Referring toFIG. 5, the second metal layer312is taken as an example, and a process of fabricating the second metal layer312includes the following four steps:

(1) depositing a barrier layer3121on the first dielectric layer315, where the barrier layer3121is made of titanium, and the barrier layer3121is tightly integrated with the first dielectric layer315;

(2) depositing an intermediate metal layer3122on the barrier layer3121, where the intermediate metal layer3122is made of aluminum-copper alloy, and the barrier layer3121is bonded well with the intermediate metal layer;

(3) depositing an anti-reflection layer3123on the aluminum-copper alloy layer3112, where the anti-reflection layer3123is made of titanium nitride, and the anti-reflection layer3123may serve as an anti-reflection layer in the etching process; and

(4) forming the second metal layer312having the same shape as that of the contact pad by imprinting a silicon wafer by using photoresist and performing the etching process.

For the first metal layer311, a barrier layer is deposited on a protection layer32of the contact pad.

Referring toFIG. 6, the second metal plug326is taken as an example, and a process of fabricating the second metal plug326includes the following six steps:

(1) forming a second dielectric layer316on the second metal layer312after the second metal layer312is fabricated, where the second dielectric layer316may be made of silicon oxide or silicon nitride;

(2) forming an opening in the dielectric layer316by etching the second dielectric layer316, where the second metal layer312is exposed through the bottom of the opening;

(3) depositing a barrier layer3162on the bottom and a sidewall of the opening, where the barrier layer3162is made of titanium;

(4) depositing a diffusion barrier layer3163on the barrier layer3162, where the diffusion barrier layer is made of titanium nitride;

(5) depositing, in the opening, a filler metal3164filling the opening; in this embodiment, the filler metal3164is made of tungsten which can fill the opening without any void and has good grinding and polishing properties, the barrier layer3162serves as adhesive between the filler metal3164and the second dielectric layer316, and the diffusion barrier layer3163is used to block diffusion of the filler metal3164; and

(6) grinding and polishing the filler metal3164to make a height of the filler metal3164flush with the surface of the second dielectric layer316.

The process of fabricating the conductive plug330is the same as the process of fabricating the second metal plug326and is not described herein again.

Based on the special design of the structure of the laser drilling region310in the present disclosure, the quality of the laser drilling for the contact pad is improved and the difficulty of the laser drilling is reduced. The laser acts on the metal material and is prevented from contacting with the dielectric layer, thermal deformation of the dielectric layer can be effectively prevented and an inner wall of the laser hole can be prevented from cracking. In addition, since the whole sidewall of the laser hole is made of metal, the electrical conductivity of the contact pad is improved.

It should be understood that although the specification is described according to the embodiments, not each of the embodiments includes only one independent technical solution. The description of the specification is merely for the sake of clarity and those skilled in the art should take the specification as a whole, and the technical solutions in the embodiments may also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

The series of detailed descriptions set forth above only describe the feasible embodiments of the present disclosure and are not intended to limit the protection scope of the present disclosure. Any equivalent embodiment or modification made without departing from the technical spirit of the present disclosure should fall within the protection scope of the present disclosure.