JPH05136221A - Probe and inspection method using it - Google Patents

Abstract

PURPOSE:To prevent the damage of an electrode by a probe and also, reduce the contact resistance between the probe and the electrode when inspecting the electric property of a semiconductor wafer. CONSTITUTION:The probe 1 is one where a ball 3 of Au is attached to the top of a probe body 2. The probe body 2 consists of hard metal such as W (tungsten), and the top is provided with a metallized layer 4 consisting of Ni or Sn with the view of improving the adhesion between Au and W. To attach the ball 3 to the top of the probe body 2, the top of a wire of Au is to be fused and the top of the probe body 2 is to be brought into contact with here.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique effectively applied to the inspection of electrical characteristics of an LSI or the like using a probe (probe).

[0002]

2. Description of the Related Art In an LSI inspection process, an electrical characteristic is inspected by applying a probe to an Al pad (electrode) formed on the surface of a semiconductor wafer.

However, in the above inspection method, the probe is W
Since it is made of a hard metal such as (tungsten) and its tip is sharp, the surface of the pad is easily damaged. There is also a problem that the tip of the probe becomes dirty due to the damage on the surface of the pad, the tip is worn during repeated use, and the contact resistance with the pad varies.

Some measures have already been proposed for such a problem. For example, JP-A-59-1483
Japanese Patent No. 45 discloses a substrate having the same bumps as pads,
Disclosed is a probe that prevents damage to a pad during inspection by laminating an anisotropic connector having conductivity only in the thickness direction.

Further, in Japanese Patent Laid-Open No. 60-198838, a metal projection is provided on an insulating substrate through a silicone resin or a polyimide resin to reduce the impact on the pad and obtain a low contact resistance. Disclosed are such probes.

[0006]

In recent years, with the increase in the number of pins of a logic LSI such as a gate array, a semiconductor chip is placed on a substrate or the like via a solder bump (also called a CCB bump) formed on a pad. The flip chip method of down bonding is widely used.

However, in the case of the flip chip system,
Since the probe is applied to the solder bump on the pad to perform the electrical characteristic inspection, the above-mentioned problem becomes more serious. That is, since the solder bumps are softer than the Al pads, they are easily damaged when a probe with a sharp tip is applied, causing a connection failure during face-down bonding. Further, since solder has a higher electric resistance than Al, the contact resistance with the probe is large, and the reliability of inspection is likely to decrease.

In this case, before forming solder bumps on the pad, that is, on the pad, BLM (Ball Limiting Meta) is formed.
It may be possible to perform an electrical property test at the stage of forming a metallization consisting of a three-layer film of Cr, Cu and Au, which is referred to as “lisation”, but if the surface of the BLM is damaged by the probe, bumps are formed during solder bump formation. There is a problem in that voids are generated in the interior, causing connection failure during face-down bonding.

Therefore, an object of the present invention is to provide a technique capable of preventing the electrode from being damaged by the probe.

Another object of the present invention is to provide a technique capable of reducing the contact resistance between the probe and the electrode.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0012]

Among the inventions disclosed in the present application, a brief description will be given to the outline of typical ones.
It is as follows.

(1) The present invention is a probe having at its tip a metal ball which is soft like Au and has a low electric resistance.

(2) The present invention is an inspection method in which the probe or the electrode is vibrated when the probe is brought into contact with the electrode.

[0015]

According to the above means (1), it is possible to prevent the electrode from being damaged by the probe. Moreover, the contact resistance between the probe and the electrode can be reduced.

According to the above-mentioned means (2), since the natural oxide film on the electrode surface is removed by the vibration of the probe or the electrode, the contact resistance between the probe and the electrode can be reduced.

[0017]

[Embodiment 1] FIG. 1 is a view showing a tip portion of a probe according to an embodiment of the present invention. In this probe 1, an Au ball 3 is attached to the tip of a probe body 2.

FIG. 2 is a sectional view of the vicinity of the tip of the probe 1. The probe main body 2 is made of a hard metal such as W, and a metallized layer 4 made of Ni or Sn is provided at the tip of the probe main body 2 for the purpose of improving the adhesiveness between Au and W. This metallized layer 4 is formed by plating, vapor deposition,
It can be formed using a sputtering method or the like.

To attach the ball 3 to the tip of the probe body 2, for example, the tip of a wire of Au is melted in the air and the tip of the probe body 2 is brought into contact therewith. At this time, in order to prevent the molten Au from diffusing into a portion other than the metallized layer 4, an oxide film 5 may be provided in a portion other than the metallized layer 4. The oxide film 5 can be formed by vapor deposition, sputtering, or the like.

FIG. 3 is a sectional view of a semiconductor wafer 6 showing a method for inspecting a semiconductor wafer using the probe 1.

The figure shows a flip-chip type semiconductor wafer 6, in which a BLM 8 consisting of a three-layer film of Cr, Cu and Au is formed on the uppermost Al wiring 7.

Since the probe 1 of this embodiment is composed of the Au ball 3 having a soft tip, the surface of the probe 1 is not damaged even if it is brought into direct contact with the BLM 8. Therefore, even if solder bumps are formed on the BLM 8 after the inspection is completed, voids do not occur inside the bumps.

Further, since the tip of the probe 1 of this embodiment is made of the Au ball 3 having a small electric resistance, the contact resistance with the BLM 8 can be made small, and thus the reliability is high. An inspection can be done.

Needless to say, the probe 1 of this embodiment can be used not only for the flip-chip type semiconductor wafer 6 but also for the inspection of a semiconductor wafer having an Al pad for wire bonding.

That is, by using the probe 1 of this embodiment, it is possible to prevent the surface of the Al pad from being damaged during the inspection. In addition, the probe 1
Since the wear of the tip of the probe can be suppressed, the probe 1
The variation in contact resistance between the pad and the pad can be prevented, and the reliability of the inspection is improved.

Further, when the probe 1 of this embodiment is applied to the Al pad, the thin oxide film on the surface of the Al pad can be removed by vibrating the probe 1 or the semiconductor wafer. The contact resistance with can be further reduced. Also in this case, since the tip of the probe 1 is composed of the Au ball 3,
Does not damage the surface of the pad.

Further, in the probe 1 of this embodiment, a bent portion 9 as shown in FIG. 4 may be provided in a part of the probe body 2. As a result, the impact when the probe 1 is applied to the BLM 8 or the Al pad is absorbed and alleviated by the bent portion 9, so that the surface damage of the BLM 8 or the Al pad can be prevented more reliably.

The Au ball 3 is attached to the tip of the probe 1.
As a method of attaching the, a method may be used in which the tip of the probe body 2 is melted in the air to form a W ball, and then Au is plated or vapor-deposited on the surface of the ball.
At this time, by forming a metallized layer of Ni or Sn on the surface of the ball and then plating or vapor depositing Au,
The adhesiveness between Au and W can be improved.

The material of the ball 3 is not limited to Au, but is made of a relatively soft material so as to prevent the electrode surface from being damaged as much as possible during the inspection. In order to reduce the contact resistance as much as possible, it must be made of a material with low electric resistance, and for the same reason, it must be made of a material that does not easily form an oxide film. Any metal can be used if it exists. Examples of such a metal material include Pt, Ir, and Ro.

[0030]

[Embodiment 2] FIG. 5 is a view showing a tip portion of a probe which is another embodiment of the present invention. In this probe 1, the cross-sectional shape of the tip of the probe main body 2 is processed into a square shape or a trapezoidal shape, which makes it possible to increase the contact area with the BLM8 or the Al pad, so that the surface of the BLM8 or the Al pad is damaged. Can be suppressed.

In this case as well, Au is attached to the tip of the probe main body 2.
By forming the thin film layer 10 by plating or vapor deposition, it is possible to more reliably prevent damage to the surface of the BLM 8 or the Al pad, and it is possible to reduce the contact resistance with the BLM 8 or the Al pad.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say.

In the above-mentioned embodiment, the case of applying to the electric characteristic inspection of the semiconductor wafer has been described. However, the probe of the present invention is applicable to the electric characteristic inspection using the probe such as when the probe is applied to the electrode formed on the substrate. Can be widely applied.

[0034]

The effects obtained by the typical ones of the inventions disclosed in this application will be briefly described as follows.
It is as follows.

(1) According to the present invention, it is possible to prevent the probe from damaging the electrode.

(2) According to the present invention, the contact resistance between the probe and the electrode can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a main part of a probe according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of this probe.

FIG. 3 is a cross-sectional view of essential parts of a semiconductor wafer showing an inspection method using this probe.

FIG. 4 is a diagram showing a main part of a probe which is another embodiment of the present invention.

FIG. 5 is a cross-sectional view showing the main parts of a probe that is another embodiment of the present invention.

[Explanation of symbols]

 1 probe 2 probe body 3 ball 4 metallization layer 5 oxide film 6 semiconductor wafer 7 Al wiring 8 BLM 9 bent portion 10 thin film layer

Front page continued (72) Inventor Takayuki Uda 2326 Imai, Ome City, Tokyo, Hitachi Device Development Center (72) Inventor Kanji Otsuka 2326 Imai, Ome City, Tokyo Hitachi, Ltd. Device Development Center

Claims (5)

[Claims] 1. A probe having a metal ball at its tip. 2. The probe according to claim 1, wherein at least the surface of the metal ball is made of Au. 3. The probe according to claim 1, wherein a bent portion is provided to reduce the impact on the electrode. 4. An inspection method, which comprises vibrating the probe or the electrode when the probe according to claim 1, 2 or 3 is brought into contact with the electrode. 5. A probe having a square or trapezoidal cross section at its tip.