JP2002110730A - Bonding pad and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove particles stuck to the tip of a probe needle, and also to suppress electrical continuity failure. SOLUTION: A polysilicon layer 6 connected to a gate electrode is formed on a silicon substrate 7, an interlayer insulating film 5 is formed thereupon, and further the bonding pad where a metal layer 2, 3, 4, having a three-layer structure, is contacted directly and laminated, is formed thereupon. By forming an opening 22 through the third metal layer 2 and a barrier metal layer 1, 1 above and below the metal layer, the convexoconcave surface is formed on this bonding pad surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding pad which is a terminal for inputting / outputting an electric signal from / to the outside of a semiconductor device, and a semiconductor device.

[0002]

2. Description of the Related Art Electrical characteristics of a semiconductor device manufactured through a wafer process are inspected in an inspection step before being mounted. In the inspection process, a probe card of a tester is used. In the probe card, a plurality of probe needles are implanted on a substrate, and each needle is brought into contact with a bonding pad of a semiconductor device, and electrical characteristics are examined. At that time, the probe needle is pressed as shown in FIG.

FIG. 6 shows a bonding pad portion of a semiconductor device, in which 10 is a silicon substrate, 12 is a protective film, and a bonding pad 14 is exposed in an opening of the protective film 12. 16 is a probe needle of the probe card. A large number of probe needles 16 are obliquely implanted on the substrate surface of the probe card, and the tip of the probe needle 16 is pressed along the surface of the bonding pad 14 when the probe card is pressed toward the semiconductor device. At the inspection position, the probe card stops pressing at the inspection position, and returns to the final position for inspection while returning slightly by reaction.

At this time, the surface layer of the bonding pad 14 is slightly broken by frictional movement caused by sliding of the tip of the probe needle 16 on the bonding pad, and stable electric contact is obtained. When the probe needle 16 repeats such a movement, the metal of the bonding pad surface layer that has been cut off adheres to the tip of the probe needle 16. As a result, the contact resistance with the bonding pad increases, and accurate electrical characteristics cannot be measured.

Therefore, as one method of solving such inconvenience, a probe needle is rubbed against a sheet containing an abrasive to scrape off foreign matter attached to the tip of the probe needle. However, that method requires extra movement of the probe card, which complicates the inspection process.

As another method, it has been proposed to form a rhenium layer on the bonding pad so that the metal on the surface of the bonding pad hardly adheres to the probe needle (see Japanese Patent Application Laid-Open No. H11-111753). .
Although it does not relate to the problem of contact between the bonding pad and the probe needle, an interlayer insulating film is formed at the bonding pad part to prevent cracks from occurring in the underlying thermal oxide film due to the impact during the bonding operation. It has been proposed to provide a plurality of openings to form a recess (see Japanese Patent Application Laid-Open No. 6-5653).

[0007]

In the proposed method in which the material of the surface layer of the bonding pad is made different in order to make it difficult for foreign matter to adhere to the tip of the probe needle, a metal other than a normal metal is deposited on the wiring layer. In addition, the semiconductor manufacturing process has to be drastically changed.

In the method of forming unevenness on a bonding pad with an interlayer insulating film in order to soften an impact at the time of bonding, a projection of the interlayer insulating film exists below a surface metal layer of the bonding pad. The metal film is thin on the protrusion of the interlayer insulating film. For this reason, when the probe needle is pressed and slid during the inspection, the metal layer on the interlayer insulating film is peeled off, and there is a possibility that a conduction failure may occur at a subsequent portion in bonding.

According to the present invention, there is provided a bonding pad having a structure capable of removing foreign substances adhering to the tip of a probe needle without using another abrasive, and having a poor conduction failure, and a semiconductor provided with such a bonding pad. It is intended to provide a device.

[0010]

The bonding pad of the present invention comprises one or a plurality of metal layers in direct contact with each other, and has a surface with irregularities. A barrier metal layer may be formed above or below the metal layer. In the present invention, the direct contact of the metal layer includes a case where a conductive layer such as a barrier layer is interposed between the metal layers, and indicates a state where the insulating layer is not interposed. .

Even if the metal on the surface of the bonding pad is peeled off and adheres to the tip of the probe needle, the adhesion is removed from the probe needle because the bonding pad surface has irregularities. Therefore, maintenance such as polishing of the probe needle is unnecessary, and the work load and cost can be reduced. In addition, since the bonding pad is constituted by one layer or a plurality of metal layers which are in direct contact, unlike the proposed bonding pad in which the protrusion of the interlayer insulating film is embedded inside, Since there is no extremely thin portion of the film, there is no possibility that the electrical continuity is deteriorated due to the rubbing of the probe needle.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS There are several methods for forming irregularities on the surface of a bonding pad. The unevenness can be formed by providing a plurality of openings in the uppermost metal layer.
Further, the unevenness can be formed by providing a plurality of openings in a metal layer below the uppermost layer, and the uppermost metal layer can be a continuous deposited film. The opening for forming the unevenness can have a depth corresponding to the thickness of the metal layer in which the opening is formed. In this case, the opening can be formed at the same time as the formation of another wiring portion, and the number of steps does not increase. In addition, the opening for forming the unevenness may have a depth smaller than the thickness of the metal layer in which the opening is formed. In that case, friction with the probe needle can be adjusted.

[0013]

FIG. 1 is a plan view of a bonding pad according to one embodiment. A plurality of openings 2 are formed in the bonding pad 20.
2 are formed. Opening width of opening 22 and opening 22
The width of the protrusion formed by the above is smaller than the width of the tip of the probe needle 16 shown in FIG. For this reason, the probe needle 16 must cross over at least one step while sliding on the bonding pad surface when the probe card is pressed against the semiconductor device for inspection and when the probe card is separated from the semiconductor device after the inspection is completed. Accordingly, even if foreign matter is attached to the tip of the probe needle 16, it is removed at that time.

FIG. 2 shows a cross section of the bonding pad of one embodiment, and shows a cross section taken along line 8-8 'in FIG. Generally, a semiconductor device includes a plurality of wiring layers, and the bonding pad of the present invention is formed by being stacked so as to be in direct contact with each other without interposing an interlayer insulating film between the wiring layers. FIG. 2 shows an example in which bonding pads are formed by wiring having a three-layer metal structure. A polycrystalline silicon layer 6 connected to a gate electrode is formed on a silicon substrate 7 in order from the bottom, and a first metal layer 4 is formed thereon via an interlayer insulating film 5. Further, a second metal layer 3 is formed thereon via a barrier metal layer 1. Further, a third metal layer 2 is formed thereover via a barrier metal layer 1, and the barrier metal layer 1 is also formed on the third metal layer 2.

The three metal layers 2, 3, and 4 have a thickness of 500 to
The barrier metal layer 1 is made of 1200 nm of aluminum, copper or an alloy thereof, and is made of titanium or titanium nitride having a thickness of 100 nm or less. By forming openings 22 in the third metal layer 2 and the upper and lower barrier metal layers 1 and 1, irregularities are formed on the surface of the bonding pad.

In this embodiment, an opening is formed by the uppermost metal layer 2 of the three metal layers, and the remaining protrusions are directly connected to the lower metal layer 3, so that the electrical connection is formed in the bonding pad. There is no electrically isolated wiring portion. This does not hinder conduction during bonding.

The opening 22 in this embodiment can be formed by patterning the uppermost metal layer 2 at the same time as patterning the other wiring portions, so that the number of steps does not increase. In the bonding pad of the embodiment shown in FIG. 1, the openings 22 are formed in isolated rectangles, respectively.
Although the convex portions are in a mesh shape, the concave and convex portions are not limited to such a shape, and the concave and convex portions may be formed by an opening that becomes a stripe-shaped convex portion.

FIG. 3 shows a sectional shape of the second embodiment. In this embodiment, the opening 22 is formed by etching the uppermost metal layer 2 to a depth smaller than its thickness. In order to form the opening 22 which is shallower than the thickness of one metal layer, a photograph for forming the opening 22 of the bonding pad is formed separately from the photolithography and etching steps for patterning other wiring portions. Plate making and etching steps are required. However, such a shallow unevenness is advantageous for adjusting the magnitude of friction with the tip of the probe needle while removing foreign substances adhering to the tip of the probe needle.

FIG. 4 shows a third embodiment. Here, the opening 22 is not formed by patterning the uppermost metal layer 2, but by forming the lower metal layer 3.
And the uppermost metal layer 2 is formed by CVD (Chemical Vapor Deposition).
It is a continuous film deposited by the method. In this embodiment, since the uppermost metal film 2 is continuous, the friction with the tip of the probe needle can be moderately reduced while removing the foreign matter attached to the tip of the probe needle.

In the embodiment shown in FIG. 4, since the opening can be formed by patterning the metal layer 3 at the same time as patterning the other wiring portions, the number of steps does not increase. However, also in the embodiment of FIG. 4, the depth of the opening formed in the metal layer 3 may be smaller than the thickness of the metal layer 3 as in the embodiment of FIG. The metal layer forming the opening is
The metal layer is not limited to the layer shown in the embodiment, and may be another metal layer. Further, the number of layers to be stacked and the thickness of the film are not limited to those shown in the embodiments. Alternatively, the bonding pad may be formed by a single-layer metal wiring having unevenness on the surface.

FIG. 5 shows a semiconductor device chip having a bonding pad according to the present invention. That chip 3
2, a required number of bonding pads 20 as shown in FIG. 1 are arranged. By providing the bonding pad, the inspection process is facilitated, and the reliability of the bonding pad is improved without impairing the conduction of the bonding pad.

[0022]

The bonding pad of the present invention is composed of one or a plurality of metal layers in direct contact with each other.
Since the surface has irregularities, foreign substances adhering to the tip of the probe needle can be removed, and the reliability of electrical conduction of the bonding pad can be maintained. Regardless of which metal layer is used to form the opening, if the opening is formed by patterning the metal layer, the patterning can be formed simultaneously with the patterning of other wiring portions. Does not lead to an increase. Also, if the opening is made shallower than the thickness of the metal layer forming the opening,
The friction with the tip of the probe needle can be adjusted. The semiconductor device having such a bonding pad can facilitate an inspection process while maintaining electrical reliability.

[Brief description of the drawings]

FIG. 1 is a plan view showing a bonding pad of one embodiment.

FIG. 2 is a sectional view showing a part of the bonding pad of the embodiment.

FIG. 3 is a sectional view showing a part of a bonding pad according to a second embodiment.

FIG. 4 is a sectional view showing a part of a bonding pad according to a third embodiment.

FIG. 5 is a plan view showing one embodiment of a semiconductor device chip.

FIG. 6 is a schematic sectional front view showing a bonding pad portion and a probe needle of the semiconductor device.

[Explanation of symbols]

 Reference Signs List 1 barrier metal layer 2, 3, 4 metal layer 5 interlayer insulating film 7 silicon substrate 16 probe needle 20 bonding pad 22 opening 32 semiconductor device chip

Claims (6)

[Claims] 1. A bonding pad comprising one or a plurality of metal layers which are in direct contact with each other, and having irregularities on the surface. 2. The bonding pad according to claim 1, wherein the unevenness is formed by providing a plurality of openings in an uppermost metal layer. 3. The bonding pad according to claim 1, wherein the unevenness is formed by providing a plurality of openings in a metal layer below the uppermost layer, and the uppermost metal layer is a continuous deposited film. 4. The bonding pad according to claim 2, wherein the opening has a depth corresponding to the thickness of the metal layer in which the opening is formed. 5. The bonding pad according to claim 2, wherein the opening has a depth smaller than the thickness of the metal layer in which the opening is formed. 6. A semiconductor device having the bonding pad according to claim 1.