KR20010036333A - Method for forming bonding pad in semiconductor device - Google Patents

Abstract

PURPOSE: A method for manufacturing a bonding pad of a semiconductor device is provided to improve reliability of the device using copper as a metal interconnection and to easily adopt a conventional wire bonding method, by preventing a copper pad from being oxidized. CONSTITUTION: An interlayer dielectric(120) is formed on an integrated circuit structure(110). The interlayer dielectric is patterned to expose an interconnection of the integrated circuit structure and prepare a space where a copper pad(130) is formed. Copper is buried in the space for forming the copper pad to form the copper pad. A cap layer(140) made of a conductive material is formed on the copper pad. A passivation layer(150) is applied on the entire surface of the structure having the cap layer and patterned to expose the cap layer. An annealing process is performed regarding the resultant structure to form an inter-metal compound(140a) in an interface between the cap layer and the copper pad and to form a surface oxide layer(140b) on the cap layer.

Description

Bonding pad formation method of semiconductor device {METHOD FOR FORMING BONDING PAD IN SEMICONDUCTOR DEVICE}

The present invention relates to a method of forming a bonding pad of a semiconductor device, and more particularly, to a method of forming a bonding pad of a semiconductor device using copper wiring as interconnect wiring.

As is well known, aluminum (Al) and its alloy thin films have been widely used as metal wirings for semiconductor devices because of their high electrical conductivity, excellent pattern formation by dry etching, good adhesion to silicon oxide films, and low cost. .

However, as the degree of integration of semiconductor devices increases, the line width of metal wirings decreases. Such reduction in line width increases the possibility of disconnection by intensifying the electromagnetization or stress migration of aluminum (Al). Increase. In such a highly integrated semiconductor device, when aluminum (Al) is used as the metal wiring, it is likely to be disconnected, making it difficult to secure the reliability of the semiconductor device.

Furthermore, as semiconductor devices become more integrated, the line width of the wiring is reduced and the spacing between the wirings is narrowed, so that the size of the via hole or the contact hole is smaller, and the aspect ratio of the hole is increased. As such, when the aspect ratio of the hole is increased, the step coverage of the interconnect wiring is lowered when embedding the metal in the hole to form the interconnect wiring, so that the interconnect wiring is thinner locally. Formed, and aluminum (Al) is very likely to be disconnected at such a thinly formed interconnection line. In addition, an increase in resistance due to a decrease in line width causes a decrease in device performance.

Therefore, a metal material is required to replace aluminum (Al), which has been widely used as a metal wiring material of a semiconductor device. Thus, copper (Copper: Cu) is a metal material to replace such aluminum (Al). Is being considered. That is, copper (Cu) has a lower specific resistance than aluminum (Al), and has excellent electrical mass transfer and stress migration characteristics. Therefore, by adopting such copper as a metal wiring of a semiconductor device, the reliability of a semiconductor device that is highly integrated can be improved. It is expected to increase.

On the other hand, when forming the interconnect wiring, in order to electrically connect the interconnect wiring with the outside (for example, a power supply), the bonding pad region is exposed to the outside at the top of the interconnect wiring, Such exposed portions will be used as interconnect wiring and bonding pads.

Conventionally, wire bonding has been performed on such copper pads using techniques such as wedge bonding or ultrasonic bonding.

However, such conventional bonding techniques require the friction of the bonding wires to the bonding pads for adhesion to each other (ie, intermetallic bonding), such as aluminum (Al) wires or gold (Au) to the aluminum pads. It may be suitable for the bonding of wires, but not for the bonding of gold or aluminum wires to copper pads.

Because, in such conventional bonding methods, copper is easily oxidized to form relatively thick copper oxides, which are used as insulators between bonding materials such as copper (Cu), aluminum (Al), gold (Au), etc. This is because the metal bond is inhibited, so that the function as the bonding pad is lost.

Therefore, in a semiconductor device using copper as interconnect wiring, in order to adopt a conventional wire bonding technique in wire bonding, a technique capable of preventing the copper pads from oxidizing during wire bonding has been required.

Accordingly, in order to prevent the copper pads from being exposed when forming the wire bonding, a technique of forming an aluminum pad on the upper portion of the copper interconnect wiring has been conventionally described. As follows.

First, as shown in FIG. 1A, a copper interconnect wiring 30 separated by an interlayer insulating film 20 is formed on top of the integrated circuit structure 10 by a damascene process.

Referring next to FIG. 1B, aluminum is formed by stacking aluminum (Al) on the upper front surface of the structure on which the copper interconnect wiring 30 is formed, and then patterning the aluminum layer by photolithography. The pad 40 is formed.

Referring back to FIG. 1C, a passivation layer 50 is formed by stacking an insulator on the upper surface of the aluminum pad 40 and the interlayer insulating film 20, and then, the protective film 50 is conventional photolithography. By patterning by technique, the aluminum pad 40 is exposed. The exposed aluminum pad 40 will have wire bonding formed thereon.

Conventionally, as described above, copper is used for the formation of the interconnect wiring, but aluminum is used for the pad, thereby solving the problem caused by the high degree of oxidation of copper.

However, in the conventional method described above, when the thickness of the aluminum pad is thin (for example, 100 kPa or less), aluminum forming the pad is diffused into the copper wiring in a subsequent thermal process, and when such diffusion is intensified, aluminum There is a problem that the copper wiring can be exposed locally through the pad, and it is certainly not possible to prevent oxidation of the copper wiring.

The present invention has been made in view of the above-described point, and an object thereof is to provide a method for forming a copper pad which can prevent the surface from being oxidized during the wire bonding process.

In order to achieve the above object, the present invention provides a method of forming a bonding pad of a semiconductor device using copper as a metal wiring, comprising the steps of: forming an interlayer insulating film on top of an integrated circuit structure; Patterning the interlayer insulating film to expose interconnect lines of the integrated circuit structure, thereby providing a space for forming a copper pad; Embedding copper in the copper pad forming space to form a copper pad; Forming a cap layer made of a conductive material on top of the copper pads; Applying a protective film to the entire upper surface of the structure on which the cap layer is formed, and patterning the protective film to expose the cap layer; Performing a thermal process on the structure completed by the above process to form an intermetallic compound at the interface between the cap layer and the copper pad, and forming a surface oxide film on the surface of the cap layer. Provide a method.

1 is a cross-sectional view sequentially illustrating a method of forming a bonding pad of a semiconductor device according to an exemplary embodiment of the present disclosure;

2 is a sequential process diagram illustrating a method of forming a bonding pad of a semiconductor device in accordance with a preferred embodiment of the present invention.

<Explanation of symbols for main parts of drawing>

10, 110: integrated circuit structure 20, 120: interlayer insulating film

30 copper interconnect wiring 40 aluminum pad

50, 150: protective film 130: copper pad

140: cap layer 140a: intermetallic compound

140b: surface oxide film

Hereinafter, a method of forming a bonding pad of a semiconductor device according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying FIG. 2.

At this time, the core technical idea of the present invention is, "In a semiconductor device using copper for interconnect wiring, after forming a cap layer of a conductive material on top of the copper interconnect wiring, between the cap layer and the copper interconnect wiring by a thermal process. The intermetallic compound is formed, the surface of the cap layer forms a surface oxide film, and the copper interconnect wiring is exposed to the outside by the triple structure of the intermetallic compound-cap layer-surface oxide film or the dual structure of the intermetallic compound-surface oxide film. By preventing the formation of the wires, it is possible to adopt conventional wire bonding techniques for forming the wire bonding of the semiconductor device using copper as interconnect wiring, and to improve the reliability of the wiring, that is, the reliability of the semiconductor device. The embodiments described later will be understood from such a core technical idea.

2 is a sequential process diagram illustrating a method of forming a bonding pad of a semiconductor device according to an exemplary embodiment of the present invention. At this time, in order to help the understanding of the present invention, in order to distinguish the reference number 10 in FIG. 1, in FIG.

Referring to FIG. 2A, an interlayer insulating film 120 is formed on top of the integrated circuit structure 110 by stacking insulators using conventional lamination techniques. In this case, a typical lamination technique may include physical vapor deposition (PVD), spin-on technique, and the like, and as an insulator, an oxide film, a nitride film, a polymer, Spin-on-glass, etc. are mentioned, for example. In addition, the interlayer insulating film 120 is not called an interlayer insulating film in the present state, but since it will be used as an interlayer insulating film with a copper wiring formed on the insulating film in a subsequent process, it is called an interlayer insulating film for convenience.

Meanwhile, the integrated circuit structure 110 may be formed of a semiconductor substrate on which integrated circuit devices are formed, and the integrated circuit devices may include a doped region in a semiconductor region separated by a field oxide film. In addition, the integrated circuit structure 110 will be formed on top of such an integrated circuit device metal wiring to form one or more layers that are mutually insulated between layers through an interlayer insulating film, the metal wiring penetrates the interlayer insulating film. Interconnection wiring between the layers.

Subsequently, the interlayer insulating film 120 is patterned by a conventional photolithography technique, thereby providing a space for forming a copper pad. In FIG. 2C, only the space in which one interconnection wire is to be formed is illustrated for convenience, but in practice, copper pad forming spaces corresponding to the number to be formed will be provided. In addition, metal wiring (eg, interconnection wiring) provided in the integrated circuit structure 110 may be exposed in the copper pad formation space formed by the patterning of the interlayer insulating layer 120.

Referring to FIG. 2B, copper is deposited on the entire upper surface of the integrated circuit structure 110 and the patterned interlayer insulating layer 120 exposed by the copper pad formation space by a technique such as blanket deposition. The copper film 130 'is formed. At this time, it is preferable that the thickness of the stacked copper film 130 ′ is formed to a thickness such that the copper pad formation space can be sufficiently filled.

Referring to FIG. 2C, by performing an etch back process using an etchant or chemical mechanical polishing (CMP), and removing the copper film 130 ′ to the surface of the interlayer insulating film 120. To form a copper pad (130).

Referring to FIG. 2D, using a conventional metal lamination technique such as sputtering, a conductive metal is deposited on the upper front surface of the interlayer insulating film 120 including the copper interconnect wiring 130 to form a cap layer ( 140).

At this time, the thickness of the cap layer 140 will be preferably formed in the thickness range of 30 ~ 500Å. That is, the thickness of the cap layer 140 because the material forming the cap layer 140 has a high probability of being diffused into the copper interconnect wiring 130 during a subsequent atmosphere control thermal process (eg, an oxidizing atmosphere thermal process). The thickness of the cap layer 140 formed on the upper portion of the copper interconnect wiring 130 may be thin when the thickness of the copper interconnect wiring 130 is formed. Therefore, the thickness of the cap layer 140 may be preferably formed at least 30 kPa or more. In addition, the thickness range is extended to 500 kW to secure the required bond strength even when the process variables do not deviate significantly from the existing conditions (power, temperature, pressure, etc.) during wire bonding.

Meanwhile, the cap layer 140 may be formed of a metal wire, which is typically used in a semiconductor process, for example, gold (Au), aluminum (Al), or the like, and more preferably, a conventional wire bonding technique. It would be more desirable to use aluminum (Al), which has been widely used and demonstrated its reliability.

The cap layer 140 is then patterned by conventional photolithography techniques, so that the cap layer 140 remains only on top of the copper pad 130. In this case, in order to prevent the edge of the copper pad 130 may be exposed, it may be more preferable to form the width of the cap layer 140 wider than the surface of the copper pad 130.

Referring to FIG. 2E, a protective film 150 is formed by stacking an insulator on an upper front surface of the interlayer insulating layer 120 including the patterned cap layer 140 by a conventional insulator deposition technique (eg, CVD or spin-on technique). After forming, the protective layer 150 is patterned by photolithography to expose the cap layer 140. At this time, the protective film 150 will prevent the structure formed by the above-described process chemically and physically damaged during the subsequent process. In addition, the range of the cap layer 140 exposed by the patterning of the passivation layer 150 may be a bonding pad region.

Referring to FIG. 2F, a thermal process is performed at a predetermined temperature (for example, a predetermined temperature within a range of 250 to 450 ° C.) to form a diffusion barrier 140a at an interface between the cap layer 140 and the copper pad 130. The surface oxide film 140b is formed on the surface of the cap layer 140.

That is, when the atmosphere control thermal process is performed in the above-described temperature range, the material (for example, aluminum) forming the cap layer 140 and copper located at the interface between the copper pad 130 react to react with each other. For example, an Al—Cu compound), such an intermetallic compound will delay diffusion of the material forming the cap layer 140 into the copper pad 130 in a subsequent thermal process.

Then, the upper portion of the cap layer 140 exposed to the outside by such an atmosphere control thermal process is thermally oxidized to form a surface oxide film (for example, alumina (Al 2 O 3) when the cap layer is formed of aluminum (Al)) 140b. ). At this time, the surface oxide film 140b may be formed of a three-layer structure including the cap layer 140, the intermetallic compound 140a, and the copper pad 130, or the bonding pad of the two-layer structure described above. Or to prevent physical contamination or damage, and can easily be broken and removed when forming wire bonding, resulting in a strong physical metal bond.

According to the present invention described above, it is possible to prevent the oxidation of the copper pad, to improve the reliability of the semiconductor device using copper as metal wiring, and to easily adopt a conventional wire bonding technique in forming the wire bonding. It works.

Claims (4)

In the method of forming the bonding pad of the semiconductor device which uses copper as a metal wiring, Forming an interlayer insulating film on top of the integrated circuit structure; Patterning the interlayer insulating film to expose interconnect lines of the integrated circuit structure, thereby providing a space for forming a copper pad; Embedding copper in the copper pad forming space to form a copper pad: Forming a cap layer made of a conductive material on top of the copper pads; Applying a protective film to the entire upper surface of the structure on which the cap layer is formed, and patterning the protective film to expose the cap layer; Performing a thermal process on the structure completed by the above process to form an intermetallic compound at an interface between the cap layer and the copper pad, and forming a surface oxide film on a surface of the cap layer; Bonding pad forming method of a semiconductor device comprising a. The method of claim 1, wherein the cap layer, Bonding pad formation method of a semiconductor device characterized by being formed in the thickness range of 30-500 kPa. The method of claim 2, wherein the cap layer, A bonding pad forming method of a semiconductor device, characterized in that formed from aluminum. The thermal process according to any one of claims 1 to 3, wherein Bonding pad forming method of a semiconductor device, characterized in that carried out in a temperature range of 250 ~ 450 ℃.