JPH067552B2 - Method of forming bump metal and bump substrate used in the method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a bump metal forming method used for manufacturing a high-density mounting structure of a semiconductor integrated circuit such as an IC and an LSI, and a bump substrate used for the method. .

(Constitution of conventional example and its problems) Conventionally, there is a tape carrier mounting method as a high-density mounting method of semiconductor elements. As shown in FIGS. 1 (A) and 1 (B), the conductive mounting method forms bump metal 3 on the electrode pad 2 of the semiconductor chip 1,
The inner lead 5 of the tape carrier 4 is connected to the bump metal 3 by a gearing bonding method.

Generally, the disadvantage of this tape carrier mounting method is that bump metal is directly formed on the semiconductor chips in a wafer at once, so even if a part of the semiconductor chips in the wafer is defective, The problem is that bump metal is formed even on a defective semiconductor chip. This means that the bump metal is unnecessary, and in particular, when a precious metal such as Au is used as the bump metal, the total cost for mounting the semiconductor chip is increased.

In view of this problem, FIG. 2 (A) to FIG. 2 (C), FIG.
As shown in FIGS. 3A and 3B, a semiconductor element mounting method and a substrate used for the mounting have come to be used. Hereinafter, description will be given with reference to the drawings. Figure 2 (A) -Figure 2
As shown in (C), the mounting method of the semiconductor element is bump substrate 6
A first step of temporarily forming a bump metal 3 (for example, an Au-plated bump) on the upper surface by electrolytic plating, a second step of pressure-bonding the bump metal 3 on the same substrate to the inner lead 5 of the tape carrier 4, and a bump The third step of separating the bump metal 3 from the substrate 6 and transferring the bump metal 3 to the inner lead 5, and the tape carrier 4 having the bump metal 3 transferred to the inner lead 5 with respect to the electrode pad 2 of the semiconductor chip 1 that has undergone the characteristic inspection in advance. This is a mounting method having a fourth step of performing bonding. As shown in FIGS. 3 (A) and 3 (B), the bump substrate 6 used in this mounting method has a bump-plated substrate 7 having a smooth main surface and a transparent conductive film layer 8 serving as a plating electrode. And the insulating protective film layer 9, the transparent conductive film layer 8 is provided on the bump-plated substrate 7, and the insulating protective film layer 9 is provided on the transparent conductive film layer 8. This is a configuration in which an opening portion 10 is selectively provided.

The operation of the mounting method configured as above and the bump substrate 6 used for the mounting method will be described below. First, in the mounting method, the bump metal 3 is temporarily formed on the bump substrate 6 by electrolytic plating, and the temporarily formed bump metal 3 is pressure-bonded to the inner lead 5 of the tape carrier 4.
The bump metal 3 is peeled off from the bump substrate 3 and transferred to the inner lead 5. After that, the electrodes are bonded to the electrodes of the non-defective semiconductor chip 1 that has undergone the characteristic inspection. As a result, the bump metal 3 is not formed on the defective semiconductor chip 1, unnecessary use of the bump metal 3 can be prevented, and the total cost for mounting the semiconductor chip 1 can be reduced.

Further, in the bump metal 6 used for mounting, the transparent conductive film layer 8 is connected to the plating power source at the external connection electrode portion 11 at the end of the substrate and subjected to electrolytic plating treatment, whereby the insulating protective film layer 9 is formed. A plating layer is formed on the transparent conductive layer 8 as a cathode in the opening 10. Generally, in the bump substrate 6 formed by the plating method, the transparent conductive film layer 8 has a function as a cathode during plating, and
The bump metal 3 has a property of being easily separated from the transparent conductive film layer 8 when the bump metal 3 formed on the inner surface is pressure-transferred to the inner lead 5, and the bump metal 3 is removed from the bump substrate 6 when handling the bump substrate 6. Use one that has enough adhesive strength to prevent peeling. From this, the bump substrate 6
The bump metal 3 to be transferred by pressure bonding to the inner lead 5 of the tape carrier 4 can be formed thereon. However, at this time, as shown in FIG. 3 (B), the bump substrate 6 has a plating layer formed on the openings 10 of the insulating protective film layer 9 by electrolytic plating. Since the amount of protrusion of the plating decreases as the distance from the external connection electrode portion 11 increases due to the resistance, there is a problem that the dimensional uniformity of the thickness of the plating layer of the plating protruded on the bump substrate 6 is not very accurate. Was.

(Object of the Invention) In view of the above problems in the bump metal formation,
The present invention provides a bump metal forming method and a bump substrate used for the method for the purpose of achieving highly accurate and uniform thickness of a plating layer which is a bump metal formed in a bump substrate.

(Structure of the Invention) The present invention comprises a bump-plated substrate, a transparent conductive film layer, an insulating protective film layer, and a low-resistance metal layer, wherein the insulating protective film layer has an opening portion at a desired local portion, and has the low resistance. The metal layer has a mesh-like shape having openings larger than the openings, and the shortest distances between the openings and the low resistance metal layer are substantially equal to each other. A transparent conductive film layer as an upper layer, and the insulating protective film layer as an upper layer of the transparent conductive film layer, the low resistance metal layer between the bump plated substrate and the transparent conductive film layer, or With the structure provided between the transparent conductive film layer and the insulating protective film layer, the equivalent resistance of the transparent conductive film layer is reduced, and the metal protrusion speed of the plating layer in the process of forming the bump metal is made uniform, The thickness of the plating layer is made uniform and the bump metal The dimensional accuracy can be improved.

(Description of Embodiments) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a schematic plan view showing a bump substrate of the present invention, FIG. 5 is an enlarged view of the same portion, FIG. 6 is an enlarged view of the same cross section, FIG. 7 is a sectional view of a substrate of another structure, and FIG. 8 is a bump metal. FIG. 7 is a process drawing showing the method for forming the above.

As shown in FIGS. 4 to 6, in the bump substrate used in the method of the present invention, the transparent conductive film layer 18 is uniformly formed on the entire main plane of the bump plating substrate 17 made of glass or the like having a flat surface. An electrode metal wiring network 21 made of a low resistance metal material having ohmic contact with the layer 18 is formed on the layer 18 so as to surround the outer peripheral area of the opening 20 of the insulating protective film layer 19. I am doing it. Further, on the transparent conductive film layer 18 including the electrode metal wiring network 21, the SiO2 film region has a structure in which the entire surface is covered with an insulating protective film layer 19 capable of selective opening such as a photoresist film. As shown in FIGS. 5 and 6, the layer 19 has an opening 20 formed in a part thereof, and the surface of the transparent conductive film layer 18 is exposed at the same portion.

Further, the structure of the transparent conductive film layer 18 and the electrode metal wiring network 21 may be the structure shown in FIG. 7 other than the above. That is, the electrode metal wiring network 21 is previously formed on the main surface of the bump-plated substrate 17, and then the transparent conductive film layer 18 and the insulating protective film layer 19 are sequentially applied.

The operation of the bump substrate configured as described above will be described below. A cathode of a plating power source (not shown) is connected to the external connection electrode portion 22 shown in FIG. 4 formed of an electrode metal wiring network 21 provided at one end of the bump substrate 16 for electrolytic plating (eg, Au electrolytic plating). When the treatment is performed, plating is performed by stacking the transparent conductive film layer 18 exposed at the opening 20 of the bump substrate 16 as a cathode on the same portion as shown in FIG. 8 (F).
The bump metal 24 as shown in FIG. At this time,
In the bump substrate 16, a dedicated electrode metal wiring network 21 made of a low resistance metal layer is formed at equal distances in the peripheral region of the opening 20 for forming bump metal, so that the resistance of the transparent conductive film layer 18 is less likely to affect the resistance. The plating is deposited without being received. That is, the plating conditions are made uniform in all parts on the bump substrate 16, and the variation in the dimensional accuracy of the bump metal due to the difference in plating speed can be suppressed.

When a transparent material is used for all of the transparent conductive film layer, the insulating protective film layer, and the bump-plated substrate as in this embodiment, the bump substrate is a transparent substrate except for the electrode wiring network and the bump metal. Therefore, the effect that it becomes possible to carry out the alignment at the time of transfer and bonding by the transmissive method is produced in addition to the above effect.

Next, regarding the method of forming the bump metal, FIG. 8 (A) to FIG.
An explanation will be given with reference to (F). First, bump plating board 1
A low-resistance metal layer 23, for example, a thin film of copper, nickel or the like is formed on the entire surface of 7 by vapor deposition or electroless plating. Next, the low resistance metal layer 23 is selectively etched to form an electrode metal wiring network.
Form 21. Then, a transparent conductive film layer 18, for example, a film made of tin oxide and indium oxide is formed on the bump-plated substrate 17 by sputter deposition. Then, the insulating protective film layer 19 is formed of a silicon oxide film, a silicon nitride film, or a silicon resin film. Then, the insulating protection film layer 19 is selectively etched to form an opening 20. Finally, electroplating is performed to form the bump metal 24. The bump metal 24 formed by the above-described forming method has good dimensional accuracy because the electrode metal wiring network 21 made of a low resistance metal layer uniformly supplies current to the openings of the entire bump substrate.

Even if the electrode metal wiring network 21 is formed on the transparent conductive film layer 18 formed on the bump substrate 17, the same effect as described above can be obtained.

(Effect of the invention) As described above, according to the present invention, since the electrode metal wiring network which is the low resistance metal layer is arranged in a mesh in the bump substrate, even when the bump metal is temporarily formed by the plating method, The bump metal can be temporarily formed with good dimensional accuracy without variation in the bump metal formation dimension.

[Brief description of drawings]

FIGS. 1 (A) and (B) are schematic sectional views of a general tape carrier method, FIGS. 2 (A), (B) and (C) are schematic sectional views showing a transfer bump bonding method, and FIG. 3 (A). ) Is a schematic sectional view of the bump substrate, FIG. 3B is a schematic plan view of the bump substrate, FIG. 4 is a schematic plan view of the bump substrate of the present invention, and FIG.
FIG. 6 is a sectional view of the same, FIG. 7 is a sectional view of a substrate having another structure, and FIGS. 8A to 8F are partial sectional views showing respective steps of the bump metal forming method of the present invention. 1 ... Semiconductor chip, 2 ... Electrode pad, 3, 24 ... Bump metal, 4 ... Tape carrier, 5 ... Inner lead,
6,16 ... bump substrate, 7,17 ... bump plated substrate,
8, 18 ... Transparent conductive film layer, 9, 19 ... Insulating protective film layer, 1
0,20 ... Opening part, 11,22 ... External connection electrode part, 21 ... Electrode metal wiring network,
23 ... Low resistance metal layer.

Claims (3)

[Claims] 1. A first step of forming a transparent conductive film layer on a bump-plated substrate, a second step of forming an insulating protective film layer on the transparent conductive film layer, and a desired local portion of the insulating protective film layer. A third step of forming an opening in the transparent conductive film layer to form an exposed portion on a part of the transparent conductive film layer; and a fourth step of protruding an electroplated metal to the exposed portion using the exposed portion as an electrode. , Before the first step, or between the first step and the second step, or between the second step and the third step, respectively on the bump-plated substrate and the transparent conductive film layer. In addition to having a step of forming a resistance metal layer, the shape of the low resistance metal layer is formed in a mesh shape, and the shortest distance between the aperture and the low resistance metal layer is formed to be substantially equal. And method for forming bump metal. 2. A bump-plated substrate, a transparent conductive film layer, an insulating protective film layer, and a low resistance metal layer, wherein the insulating protective film layer has an opening at a desired local portion, and the low resistance metal layer is The shape is a mesh with openings larger than the openings, and the shortest distances between the openings and the low-resistance metal layer are substantially equal to each other and transparent to the upper layer of the bump-plated substrate. A conductive film layer, the insulating protective film layer on the transparent conductive film layer, and the low-resistance metal layer between the bump-plated substrate and the transparent conductive film layer, or the transparent conductive film layer. And a bump substrate provided between the insulating protective film layer and the insulating protective film layer. 3. The bump substrate according to claim 2, wherein the bump-plated substrate is transparent.