JPH10189671A - Probing pad structure of semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a probing pad against imperfect contact caused by an insulating film on the pad by a simple structure by a method wherein the surface of the probing pad is turned rugged. SOLUTION: A lower wiring 6 is formed on a base layer 5. An interlayer insulating film 7 is formed on the lower wiring layer 6, and a large number of openings 9 are provided to the interlayer insulating film 7 through a photolithographic process for the formation of a multi-contact hole. An upper pad 8 is formed on the multi-contact hole by patterning. In this case, the surface of the upper pad 8 is turned rugged by the openings 9 of the multi-contact hole and the projections 10 of the interlayer insulating film 7 left between the openings 9. The upper pad 8 makes an electrical continuity with the lower wiring 6 through the intermediary of the multi-contact hole. By this setup, a probe needle is protected against imperfect contact caused by an insulating film on the surface of a pad, so that a measurement of high reliability can be carried out so as to improve semiconductor device in quality, productivity, and yield.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer probing pad structure, and more particularly to a semiconductor wafer probing pad structure for preventing poor contact of probe needles.

[0002]

2. Description of the Related Art In a manufacturing process of a semiconductor integrated circuit, an electrical characteristic of each element formed on a semiconductor wafer is measured using a prober device. This prober device is shown in FIG.
As shown in (1), a test in which a large number of probe needles 4 provided on a probe card 3 are pressed against a wafer 2 fixed and held on a wafer support table made of a vacuum chuck or the like and connected to each probe needle 4 The electrical characteristics are measured by a circuit (not shown). Each probe needle 4
Of the electrode pads formed on the wafer 2 are used as probing pads and are pressed against the upper surfaces of the pads.

FIG. 4 shows a conventional probing pad structure. A lower wiring 6 made of aluminum or the like is patterned and formed on a base layer 5 made of an interlayer insulating film between the silicon substrate and a lower wiring layer. An interlayer film 7 made of an insulating film such as SiO2 is formed on the lower wiring 6, and an opening 9 is formed in the interlayer film 7 by a photolithography process using a resist mask, thereby forming a contact hole. The upper layer pad 8 is formed in this contact hole by patterning. The upper layer pad 8 is electrically connected to the lower layer wiring 6 via this contact hole. In this case, a passivation film made of an insulating film such as plasma nitride (P-SiN) is formed on the same upper wiring as the upper pad 8, and this passivation film is removed from the upper pad 8. The probe needle 4 of the prober device is pressed against the upper layer pad 8 from above. At this time, since the probe needle 4 is resiliently pressed from above by its own elasticity, the probe needle 4 comes into contact with the pad surface while slightly moving in the horizontal direction as shown by the arrow in the figure to perform the characteristic test.

FIG. 5 is an explanatory diagram of a patterning positional relationship of the above-mentioned conventional probing pad. As shown in the figure, the entire contact hole is formed by one opening 9 provided in the interlayer film 7, and the upper layer pad 8 is formed so as to cover the opening 9.

[0005] However, when the probe needle is brought into contact with such a probing pad for measurement, poor contact of the probe needle becomes a problem. That is, even if an insulating film such as a passivation film that cannot be completely removed remains on the surface of the upper layer pad 8 or an oxide film such as alumina is formed, the probe needle 4 may be pressed against the upper layer pad 8. In some cases, reliable conduction cannot be obtained due to the insulating film on the surface.

In order to address such a problem of poor contact, the following method has conventionally been adopted. (1) Overdrive the probing. That is, the probe needle is pressed against the pad with a force larger than the normal pressing force.

(2) The tip of the probe needle is thinned to make it easy to penetrate the insulating film on the pad surface.

(3) Before the test step, an insulating film processing process for removing the insulating film on the pad surface is performed.

[0009]

However, the above-mentioned conventional method for dealing with the contact failure caused by the insulating film on the surface of the probing pad has the following problems.
In the method based on the overdriving of the probing in the above (1), the amount of horizontal movement on the pad is large because the probe needle is pressed strongly, and the probe may come off the pad.
There is a limit to the amount of overdrive in order to prevent the probe needle from coming off the pad, and it is unsuitable for a fine pad having a high-density circuit pattern.

In the method of (2), in which the tip of the probe needle is made thinner and sharper, the strength of the probe needle becomes weaker, the handling property becomes worse, the wear becomes larger, the life of the needle becomes shorter, and the probe is replaced. The frequency increases, the maintenance becomes troublesome, and the cost increases.

In the method of performing the insulating film treatment process before the test (3), the method according to the type of the insulating film on the pad is
The processing method must be changed, which complicates the process and complicates management, and increases the number of processing steps, complicating the entire manufacturing process and lowering productivity.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned problems of the prior art, and has a simple structure and can easily prevent a contact failure caused by an insulating film on a pad. For the purpose of providing.

[0013]

In order to achieve the above object, according to the present invention, a contact hole is formed in an interlayer film on a lower wiring, and an upper pad which is electrically connected to the lower wiring through the contact hole is formed. In a probing pad structure for a semiconductor wafer in which a probe is brought into contact with the upper layer pad to perform a test, the contact hole includes a plurality of openings, and the upper layer pad corresponds to an interlayer film remaining between these openings and each opening. An object of the present invention is to provide a probing pad structure for a semiconductor wafer, characterized in that an uneven surface is formed on the surface.

According to this structure, the contact hole has a multi-contact hole shape having a large number of openings,
Since the surface of the upper pad has an uneven surface, the insulating film formed or remaining on the surface is easily peeled off.
Therefore, by pressing the probe needle with a normal pressing force without increasing the overdrive amount, when the probe needle moves horizontally, the insulating film on the pad surface is easily peeled off by the probe needle, and the probe needle is securely In this state, the pad contacts the pad and conducts to the internal lower wiring in a stable ohmic contact state.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a preferred embodiment,
The lower wiring is a signal line.

In this configuration, the multi-contact hole structure is not applied to the pad of the power supply line through which a large current flows, and the multi-contact hole structure can be applied only to the pad of the signal line with a relatively small current. As a result, it is possible to suppress an increase in electromigration at a large current based on the porous shape of the pad on the power supply line, maintain a stable function, and prevent a shortening of the life. Also, in this case, since a large current flows in the power supply line, even if an insulating film exists on the pad surface, due to dielectric breakdown,
The effect of the insulating film disappears, and the probe needle becomes conductive with the pad.

In a further preferred embodiment, the upper pad is the uppermost layer of a multilayer wiring structure.

According to this structure, the multi-contact hole structure is applied only to the contact hole communicating with the uppermost pad in the multi-layer wiring structure, and the contact hole in the lower layer has a normal contact hole shape with one opening. Can be. As a result, it is possible to prevent the step coverage of the upper layer wiring from being deteriorated due to the influence of the multi-contact hole on the lower wiring layer side, the positional deviation of the contact hole, and the processing margin for preventing the positional deviation from being deteriorated. In this case, it is sufficient to apply the multi-contact hole structure only to the contact holes directly communicating with the uppermost pad in order to form irregularities on the surface of the uppermost pad contacting the probe needle.

The larger the step due to the unevenness of the pad surface for probing, the more easily the insulating film is peeled off and the effect of preventing poor contact is increased. Conversely, if the step is large, the strength of wire bonding to the pad is reduced. .
Therefore, the degree of the unevenness on the pad surface is determined appropriately in consideration of the trade-off relationship with the wire bonding strength, by appropriately selecting the layout, the numerical aperture and the size of the multi-contact hole, and according to the material and size of the pad. It is desirable to form a necessary and sufficient and optimal uneven surface.

[0020]

FIG. 1 is a sectional view of a probing pad structure according to an embodiment of the present invention. A lower wiring 6 made of aluminum or the like is patterned and formed on a base layer 5 made of an interlayer insulating film between the silicon substrate and a lower wiring layer. An interlayer film 7 made of an insulating film such as SiO2 is formed on the lower wiring 6, and a large number of openings 9 are provided in the interlayer film 7 by a photolithography process using a resist mask, thereby forming a multi-contact hole. You. An upper pad 8 made of aluminum or the like is patterned and formed in the multi-contact hole.
In this case, an uneven surface is formed on the surface of the upper layer pad 8 by the openings 9 of the multi-contact hole and the projecting wall 10 of the interlayer film remaining therebetween. In a state where such an uneven surface is formed, the upper pad 8 is electrically connected to the lower wiring 6 via the multi-contact hole. In this case, as described above, a passivation film made of an insulating film such as plasma nitride (P-SiN) is formed on the same upper wiring as the upper pad 8, and the passivation film is removed from the upper pad 8. You. Such upper layer pad 8
The probe needle 4 of the prober device is pressed from above. At this time, since the probe needle 4 is resiliently pressed from above by its own elasticity, the probe needle 4 comes into contact with the pad surface while slightly moving in the horizontal direction as shown by the arrow in the figure to perform the characteristic test.

In this case, since the surface of the upper layer pad 8 is uneven, the insulating film formed or remaining on the surface is easily peeled off. Therefore, by pressing the probe needle 4 with a normal pressing force without increasing the overdrive amount, when the probe needle moves horizontally, the insulating film on the pad surface is easily peeled off by the probe needle, and the probe needle It reliably contacts the pad and conducts to the internal lower wiring in a stable ohmic contact state.

FIG. 2 is an explanatory view of the patterning positional relationship of the probing pad composed of the multi-contact holes of the above embodiment. As illustrated, a number of openings 9 are formed inside the upper layer pad 8, and the connecting portions 1 between the openings 9 are formed.
The projecting wall 10 of FIG. 1 is formed by leaving the insulating film at 0 ′. The number, size and layout of such openings 9
As described above, an appropriate selection is made in consideration of the trade-off with the wire bonding strength in a later step.

[0023]

As described above, according to the present invention, by forming irregularities on the surface of the probing pad, the poor contact of the probe needle caused by the insulating film on the surface of the pad is eliminated, and highly reliable measurement is performed. As a result, quality can be improved, and productivity and yield can be increased.

In the structure of the present invention, since the insulating film on the pad surface is mechanically removed, the present invention can be applied to any kind of insulating film. High usability.

Further, since the pad having the uneven surface of the structure of the present invention can be obtained by using a mask having an increased hole numerical aperture in the contact hole forming process, a special process for forming the uneven surface is not required. Since it can be easily formed, the process does not become complicated, the productivity does not decrease, and the cost does not increase.

The probe device used for the structure of the present invention is applied to a probe card having a structure in which a probe needle is provided in a normal oblique direction and, as described above, moves somewhat horizontally by pressing force. However, the present invention is not limited to this, and a vertical pressing type probe needle can be applied as long as it has a horizontal movement mechanism.

[Brief description of the drawings]

FIG. 1 is a sectional view of a probing pad structure according to an embodiment of the present invention.

FIG. 2 is a configuration explanatory view of a contact hole of the pad structure of FIG. 1;

FIG. 3 is a basic configuration diagram of a prober used in the present invention.

FIG. 4 is a cross-sectional view of a conventional probing pad structure.

FIG. 5 is an explanatory view of a configuration of a contact hole having a pad structure of FIG. 4;

[Explanation of symbols]

4: probe needle, 5: base layer, 6: lower wiring, 7: interlayer film, 8: upper pad, 9: opening, 10: projecting wall.

Claims (3)

[Claims] A contact hole formed in an interlayer film on the lower wiring, an upper pad electrically connected to the lower wiring through the contact hole, and a semiconductor for testing by bringing a probe needle into contact with the upper pad. In the wafer probing pad structure, the contact hole includes a plurality of openings, and an uneven surface is formed on an upper layer pad surface corresponding to the openings and an interlayer film remaining between the openings. Probing pad structure. 2. The probing pad structure for a semiconductor wafer according to claim 1, wherein said lower wiring is a signal line. 3. The probing pad structure for a semiconductor wafer according to claim 1, wherein said upper layer pad is an uppermost layer of a multilayer wiring structure.