JP2000269277A - Probe for testing wafers and method of testing wafers - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent damage to an electrode pad by forming a probe body into such a shape that the diameter with respect to the axis line becomes smaller as it reaches toward the end part and forming an end face at the end part vertical to the axis line of the probe, with the diameter of the end face set within a specified value or larger. SOLUTION: A passivation film 4 is formed on an interconnection 3 made of aluminum, etc., in the uppermost layer of a wafer. A bump forming region of the passivation film 4 is formed into an octogonal opening for external connection. At the opening and its periphery, an electrode pad 1 made of Cu/TiW is formed. On the electrode pad 1, a probe 20 for testing a wafer is installed. The probe 20 has a shape with a diameter D with respect to the axis line of the probe body becoming smaller as it reaches toward an end part. An end face 20a at the end is formed vertical to the axis line L of the probe, and the diameter of the end face 20a is set at 15 μm or above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer inspection probe and a wafer inspection method, and more particularly, to a wafer inspection probe and a wafer inspection method capable of reducing contact resistance in an LSI on which a flip-chip type semiconductor element is formed. It is about.

[0002]

2. Description of the Related Art In general, in this kind of wafer inspection, it is an important element to reduce the contact resistance between a semiconductor element and a probe to improve the inspection accuracy. For this purpose, for example, as shown in FIG. 5, a probe 5 having a flat tip or a probe 6 having a hemispherical tip is stapled to the electrode pad 1 formed on the semiconductor element. There has been proposed a method of obtaining a stable contact between the electrode pad 1 and the probes 5 and 6 by further applying a load and probing the needle so that the needle rubs on the electrode pad.

However, in this method, the tip of the probe made of a hard metal such as tungsten comes into contact with the electrode pad 1 made of aluminum or the like. There was a thing attached to the tip. Aluminum adhered to the tip of the probe was oxidized and changed into alumina (insulating material) 7 having an insulating property, thereby increasing the contact resistance between the probe 6 and the electrode pad 1 (see FIG. 6). .

For example, Japanese Patent Application Laid-Open No. Hei 8-220139 discloses a probe 8 in which the tip 8a of the probe 8 is formed so as to be substantially parallel to the upper surface of the electrode pad of the semiconductor device (see FIG. 7). This technology uses the probe tip 8
The electrode a is almost in contact with the electrode pad 1 over the entire surface a, and it is possible to prevent an insulator or the like from adhering to the contact portion between the probe 8 and the electrode pad 1. As a result, the electrical contact resistance between the probe 8 and the electrode pad 1 is reduced, which has the effect of improving the accuracy of wafer inspection.

[0005] Wafer inspection is an inspection in which the electrical characteristics and the like of a semiconductor integrated circuit device are evaluated on a wafer at the time of manufacturing and non-defective products and defective products are selected. Therefore, not damaging the wafer during inspection is also an important factor. Inspection of a wafer of a flip-chip type semiconductor element is performed by touching a metal bump, an electrode pad, or an uppermost layer wiring. Therefore, when a stylus is touched on the metal bump, a certain predetermined force is applied in order to ensure reliable conduction between the bump and the probe. As a result, the bumps may fall off or deform, and the reliability of the connection with the outside may be reduced.

When a stylus is placed on the electrode pad 1,
The stylus breaks the barrier film of the metal bump and loses the barrier function, and the aluminum wiring and the metal bump react with each other, causing a failure of the bump to fall off (see FIG. 8). Also, the uppermost layer wiring 3
When the stylus is touched upward, stylus marks 11 are formed on the uppermost wiring 3 by the stylus, and a barrier film 12 is formed thereon by a sputtering method or a vapor deposition method. The barrier film on the stitches 11 has a particularly thin portion or a defective portion, which causes a problem that the barrier effect is impaired, the aluminum wiring reacts with the metal bump, and the metal bump easily falls off (see FIG. 9). .

For example, Japanese Unexamined Patent Publication No. 1-295444 discloses a method in which a bump connecting portion 13 where a bump is formed on an uppermost layer wiring 3 and a pad portion 14 which is touched by a probe are provided. It is disclosed that after a wafer inspection is performed by touching the pad portion 14 of the above, the passivation film 4 is formed, and the bump connection portion 13 in the region where the bump is formed is opened to form the electrode pad 2 and the metal bump 15. (See FIG. 10). In this technology, a bump connection part and a pad part are provided on the top layer wiring, and the top layer wiring touched by the probe is covered with a passivation film. It does not cause any damage and has a reasonable effect in improving reliability.

[0008]

However, the above-mentioned Japanese Patent Application Laid-Open No. 8-220139 has a problem that the reliability of the probe 8 in terms of damage to the electrode pad 1 at the time of the stylus is reduced. In the flip chip method, usually the electrode pad is provided on the entire surface of the chip,
Wafer inspection is performed using a vertical needle probe card. The tip of the vertical needle is a plane that is approximately parallel to the surface of the electrode pad 1. In order to ensure reliable conduction between the probe 8 and the wafer, it is necessary to further apply a load after the probe and the wafer have been contacted. At this time, the electrode pad 1 is damaged because the tip of the probe goes deep into the electrode pad 1 or rubs the surface of the electrode pad and touches the probe with the corner of the probe tip. If the electrode pad is damaged due to the damage of the probe, the metal of the bump reacts with the aluminum of the wiring, and the metal bump is likely to fall off.

Japanese Patent Application Laid-Open No. 1-295444 has a new problem in terms of miniaturization and multifunctionality. That is, another space is required for wafer inspection and bump formation. Providing separate electrodes for probing in wafer inspection and areas for forming metal bumps increases the space required for the pad area per external output, resulting in miniaturization and multifunctionalization. This causes a problem that it is difficult to reduce the chip size.

[0010] Therefore, one of the main objects of the present invention is to provide a probe and a wafer inspection method which improve reliability without damaging an electrode pad which is a barrier film.
Another object of the present invention is to provide a probe and a wafer inspection method capable of sufficiently obtaining contact between the probe and the wafer during wafer inspection. Another object of the present invention is to provide a probe and a wafer inspection method that do not require a special space for wafer inspection.

[0011]

In order to solve the above-mentioned problems, the present invention basically employs the following configuration. That is, the first aspect according to the present invention is:
A probe for wafer inspection, wherein the tip of the probe body has a tapered shape at the tip, and the tip of the tapered shape is formed perpendicular to the axis of the probe, and the tip of the probe has a diameter of 15 μm. The second aspect of the present invention is a probe for wafer inspection as described above, and the probe body of the probe body is provided on the passivation film and in the electrode pad concave portion before the formation of the solder bump provided on the passivation film opening. Inspection of the wafer by making the diameter of the shaft tapered at the tip and making the tip of the tapered shape perpendicular to the axis of the probe, and contacting the probe with the tip having a diameter of 15 μm or more at the tip of the probe. Wafer inspection method.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A wafer inspection probe according to the present invention is a wafer inspection probe for solving the above-mentioned problems in the prior art, wherein the shaft diameter of the probe body is tapered at the tip. And the tip surface of the tapered shape is formed perpendicular to the axis of the probe, and the diameter of the tip surface of the probe tip is 15 μm or more.
A highly reliable inspection can be performed without damaging the electrode pad.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a wafer inspection probe and a wafer inspection method according to an embodiment of the present invention. That is, FIG. 1 is a perspective view showing a wafer inspection probe according to one embodiment of the present invention. Here, the wafer inspection probe 20 is configured such that the shaft diameter D of the probe main body is tapered at the distal end, and the tapered distal end surface 20a is formed perpendicular to the axis L of the probe. The diameter of the surface 20a is formed to be 15 μm or more.

FIG. 2 is a longitudinal sectional view taken along the line AA of FIG. In the present embodiment, the probe 20 has a cylindrical shape, and the tip portion 20b is formed in a frusto-conical shape. The diameter d of the distal end surface 20a of the probe 20 is formed smaller than the diameter of the concave portion of the electrode pad 1 to be inspected.
Therefore, it can be inserted into the recess of the electrode pad 1 with a margin.

As shown in FIG. 2, a passivation film 4 is formed on the uppermost wiring 3 formed of aluminum or the like of a wafer. A region of the passivation film 4 where a bump is to be formed is opened, for example, in an octagonal shape for external connection. And in the opening and its surrounding area,
An electrode pad 1 made of Cu / TiW is provided.
Further, according to the present invention, the flat tip surface 2 of the probe 20 is provided.
No. 0a touches in parallel on the electrode pad 1 forming the bump. In this embodiment, the tip of the probe 20 is flat, and the diameter of the tip surface 20a is set to 15 μm or more.

The load applied by the probe 20 to the electrode pad 1 is such that the diameter of the flat tip surface 20a at the tip of the probe is one.
Since the thickness is 5 μm or more, the load applied to the electrode pad 1 per unit area can be reduced. Therefore, damage to the electrode pad 1 due to the probe 20 can be reduced, and as a result, the bumps are prevented from falling off, and the effect of improving reliability is brought about.

Further, a probe 2 applied to the electrode pad 1
As a result, the stylus on the electrode pad 1 became possible. Therefore, no special area is required for wafer inspection, and the area required for one external output can be reduced. As a result, an effect that the chip size can be reduced is obtained.

This will be described in more detail with reference to FIGS. FIG. 3 shows the relationship between the needle tip diameter, the frequency of occurrence of damage to the barrier film, and the overdrive amount when the probe 20 having a flat tip according to the present invention is stapled on the electrode pad 1. As shown in FIG. 3, the overdrive amount is set to 1 in order to secure the conduction between the probe and the wafer.
Even if the diameter is as large as 00, 125, and 150 μm, the barrier metal film will not be damaged if the needle tip diameter is 15 μm or more.

FIG. 4 shows the relationship between the load per unit area applied to the electrode pad 1 by the probe 20 and the needle tip diameter. When conducting the test, it is necessary to perform the probe with a certain fixed force in order to ensure the electrical connection between the probe and the wafer, which is represented by the overdrive amount here. The wafer is set on the stage, and the stage is raised to perform stylus. The point where the longest probe and the electrode pad 1 touched the probe was set to 0 μm in overdrive, and the stage was further raised from there to bring the probe and the wafer closer to each other so that the probe 20 and the wafer could be reliably connected.
When the overdrive amount is large, the load applied to the wafer by the probe increases.

As shown in FIG. 4, according to the present invention, by setting the diameter of the flat portion at the tip of the needle to 15 μm or more, the load applied to the electrode pad by the probe per unit area is reduced.
It is reduced to 44% as compared with the case where the tip diameter is 10 μm. Therefore, it can be seen that the frequency of occurrence of the damage to the electrode pad 1 by the probe 20 is reduced, and the failure of dropping of the bump is prevented and the reliability is remarkably improved.

Furthermore, since the reliability of the stylus on the electrode pad 1 has been improved, a wafer inspection can be performed by touching the electrode pad 1. Therefore, no special area is required for the wafer inspection, and the chip inspection is not required. The effect that the size can be reduced is obtained.

Next, a wafer inspection method using the wafer inspection probe of the present invention will be described. First, the concave portions of the electrode pad 1 before the formation of the solder bumps, which are provided on the passivation film 4 and the passivation film opening,
The shaft diameter D of the probe body 20 is tapered at the tip,
The tapered distal end surface 20a is connected to the axis L of the probe.
And the tip surface 2 of the probe tip.
The wafer is inspected by contacting a probe having a diameter of 0a of 15 μm or more.

As described above, according to the wafer inspection method using the probe of the present invention, there is no possibility that the probe will damage the electrode pad. Further, the chip size can be reduced without requiring a special area for wafer inspection.

The present invention is not limited to the above-described embodiment, and various design changes can be made based on the technical concept of the present invention.

[0025]

According to the present invention, since the above-mentioned technical configuration is employed, even if the probe is stuck on the electrode pad, the barrier film is not damaged. As a result, it is possible to prevent the bumps from falling off, thereby improving the reliability. Further, since there is no problem in reliability even if a stylus is provided on the electrode pad, a wafer inspection on the electrode pad becomes possible, and no special area is required for the wafer inspection. As a result, the chip size can be reduced. The reason is that a probe having a flat portion at the tip of the probe having a diameter of 15 μm or more is stapled on the electrode pad to perform a wafer inspection, and the load applied to the electrode pad by the probe per unit area is reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a wafer inspection probe according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view taken along the line AA of FIG. 1;

FIG. 3 is an explanatory diagram showing a relationship among a needle tip diameter, a damage occurrence frequency of a barrier film, and an overdrive amount.

FIG. 4 is an explanatory diagram showing a relationship between a load per unit area applied by a probe to an electrode pad and a needle tip diameter.

FIG. 5 is a side view showing one embodiment of a conventional wafer inspection probe.

FIG. 6 is a side view showing another embodiment of the conventional wafer inspection probe.

FIG. 7 is a side view showing another embodiment of the conventional wafer inspection probe.

FIG. 8 is a side view showing another embodiment of the conventional wafer inspection probe.

FIG. 9 is a cross-sectional view showing a needle mark when a conventional wafer inspection probe is used.

FIG. 10 is an explanatory view showing one embodiment of a conventional wafer inspection method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrode pad 3 Top layer wiring 4 Passivation film 5, 6 Probe 7 Insulating material 8 Probe 8a Tip 9 Probe 10 Crack 11 Needle mark 12 Barrier film 13 Bump connection part 14 Pad part 15 Metal bump 20 Probe 20a Tip surface 20b Tip

Claims (6)

[Claims] 1. A probe for wafer inspection, wherein an axis diameter of a probe main body is tapered at a distal end portion, and a distal end surface of the tapered shape is formed perpendicular to an axis of the probe. A wafer inspection probe having a surface diameter of 15 μm or more. 2. The wafer inspection probe according to claim 1, wherein said probe is formed in a cylindrical shape, and a tip portion is formed in a frusto-conical shape. 3. The probe according to claim 1, wherein the probe is formed in a polygonal column shape, and a tip portion is formed in a truncated polygonal pyramid shape.
A wafer inspection probe as described in the above. 4. The wafer inspection probe according to claim 1, wherein a diameter of a tip end surface of the probe tip is formed smaller than a diameter of a concave portion of an electrode pad to be inspected. 5. The probe of claim 1, wherein the probe body has a tapered tip with a tapered tip at a tip of the electrode pad recess formed on the passivation film and at the passivation film opening before solder bump formation. A wafer inspection method comprising: forming a probe perpendicular to the axis of the probe; and contacting a probe having a tip end surface having a diameter of 15 μm or more with the probe to inspect the wafer. 6. The probe according to claim 5, wherein the tip of the probe body has a tapered shape at the tip, and the tip surface of the tapered shape is formed perpendicular to the axis of the probe, and the tip face of the probe tip has a diameter of 15 μm or more. 6. The wafer inspection method according to claim 5, wherein the wafer is inspected using a probe formed smaller than the concave portion of the electrode pad.