JP2000031146A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent crackings of a protecting film in inner-lead bonding due to the difference between the electrode pad on a semiconductor device and a protective film, the defective barrier-metal coverage, the lack of planarity at the surface of a bump, and the like. SOLUTION: On an electrode pad 4a, protective film 5 is formed thicker than in the electrode pad 4a. Then, by performing etch back or chemical- mechanical polishing for the electrode pad 4a and the protective film 5, a part of the protective film 5 is also removed so that the electrode pad 4a and the protecting film 5 become approximately the same hight, and the difference in the heights of the protective films is eliminated. In this way, when pressure is applied on the bump in the assembling process such as inner-lead bonding, the phenomenon of resulting crack formation in the protective film can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention particularly relates to a semiconductor device having a bump connected to an external lead and a method of manufacturing the same.

[0002]

2. Description of the Related Art A conventional method of manufacturing a semiconductor device will be described.

FIGS. 3 and 4 are sectional views showing a conventional method of manufacturing a semiconductor device. In particular, FIG. 4C is a completed cross-sectional view of the semiconductor device, in which 1 is a semiconductor substrate, 2 is a MOS transistor, and 3 is another element mounted on the semiconductor substrate 1 including the MOS transistor 2. A protective film 4 made of an insulating material formed by the above, 4 is an electrode wiring, 4a is an electrode pad, 5 is a protective film made of an insulating material for protecting the electrode wiring 4, 5a is a step portion of the protective film, 6 is a barrier metal of a bump, Reference numeral 7 denotes a photoresist, 8 denotes a bump, and 8a denotes a bump step portion.

Next, a method of manufacturing a semiconductor device will be described. First, an element such as a MOS transistor 2 is formed on a semiconductor substrate 1. Next, the surface is covered with a protective film 3. At this time, a portion of the protective film 3 corresponding to, for example, a portion on the diffusion layer formed on the semiconductor substrate 1 to be electrically contacted is opened (FIG. 3A). Next, MOS
The electrode wiring 4 and the electrode pad 4a to be joined to the type transistor 2 are simultaneously formed (FIG. 3B). Next, the entire surface of the wafer is covered with the protective film 5, and the surface is further etched to expose the surface of the electrode pad 4a (FIG. 3C).
Next, the barrier metal 6 is formed by sputtering or electron beam evaporation (FIG. 3D). Then, a photoresist 7 is formed on the barrier metal 6 (FIG. 3E), and a metal bump 8 is formed by a plating method (FIG. 4A). At that time, a bump step portion 8a is formed on the electrode pad 4a reflecting the unevenness of the lower opening.
Finally, the photoresist 7 is removed (FIG. 4B), and unnecessary portions of the barrier metal 6 are etched by a wet etching method or a dry etching method, thereby completing the manufacture of the semiconductor device (FIG. 4C). )).

[0005]

However, FIG.
In the semiconductor device manufactured by the method shown in FIG. 4, the protective film 5 forms a protective film step portion 5a on the electrode pad 4a. For this reason, when pressure is applied from above the bumps in an assembling process such as inner lead bonding (hereinafter abbreviated as ILB), which is a typical assembling method, the pressure is locally applied to the protective film step portion 5a by the electrode pad 4a. As a result, cracks in the protective film occur at this location. In addition, since there is a protection film stepped portion 5a due to the electrode pad 4a, when the barrier metal 6 is formed, the coverage of the barrier metal 6 deteriorates at the protection film stepped portion 5a, and the barrier metal disconnection occurs in a later plating step. There is a possibility that an unplated portion may be generated due to this. Also, a bump step 8a is formed on the upper portion of the bump 8 under the influence of the protective film step 5a, and the flatness of the surface of the bump 8 is lost. When connecting to the wiring, there is a possibility that the bonding between the bump 8 and the lead may be deteriorated.

SUMMARY OF THE INVENTION In view of the above problems, the present invention is directed to a semiconductor device having a flat bump surface by eliminating a step in an insulating film (protective film), eliminating cracks in the insulating film and improving barrier metal coverage. It is intended to provide a manufacturing method.

[0007]

In order to achieve the above object, a semiconductor device according to the present invention has a first electrode (electrode pad) formed on a substrate, and the electrode pad is formed of an insulating film (protective film).
And the upper surface of the electrode pad is formed at substantially the same height as the surface of the protective film. An inner lead for taking out a signal to the outside is joined to the electrode pad via a barrier metal. In this configuration, a second electrode (bump) is formed.

With such a structure, the upper surface of the electrode pad and the surface of the protective film are formed at substantially the same height.
When there is almost no step, and pressure is applied to the bump formed over the electrode pad and a part of the protective film in the assembling process of the ILB or the like, pressure is locally applied to the step part of the protective film and the protective film is This makes it possible to prevent the occurrence of cracks.

In addition, by eliminating the step of the protective film, it is possible to improve the barrier metal coverage at the time of forming the barrier metal, thereby eliminating the unplated portion due to the breakage of the barrier metal in a later bump, for example, in a gold plating process. effective.

Furthermore, by eliminating the step of the protective film and improving the barrier metal coverage, it is possible to prevent the protective film and the barrier metal step, which are the base, from appearing on the bump surface as they are in the plating step when forming the bump. The feature is that the bump surface is flattened, and thus, when the bump is connected to an external wiring such as a lead in an assembling process, an effect that a very good bonding is expected can be expected.

Further, in the method of manufacturing a semiconductor device according to the present invention, in particular, while exposing the upper surface of the electrode pad,
The step of making the upper surface of the electrode pad and the surface of the protective film have substantially the same height is performed by a chemical mechanical polishing method.
With such a configuration, the upper surface of the electrode pad and the surface of the protective film can be made substantially the same height.

[0012]

Embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 and FIG. 2 are schematic explanatory diagrams of a manufacturing process according to an embodiment of a method of manufacturing a semiconductor device of the present invention.
In particular, FIG. 2D is a completed sectional view of the semiconductor device. Note that the same members as those in the prior art shown in FIGS. 3 and 4 are denoted by the same reference numerals, and detailed description thereof will be omitted. The electrode pads 4a are connected to wirings extended from various elements formed on the semiconductor substrate. In some cases, it is formed so as to be connected to a wiring extending from the electrode of the MOS transistor 2 in the figure.

Next, the semiconductor device and its manufacturing method will be described. First, an element such as a MOS transistor 2 is formed on a silicon semiconductor substrate 1. next,
The surface is covered with a protective film 3 made of silicon nitride or the like, and a portion of the protective film 3 corresponding to a contact portion for extracting an electric signal, such as a diffusion layer formed on the semiconductor substrate 1, is opened (FIG. 1A).

Next, the electrode wiring 4 and the electrode pad 4a of the MOS transistor 2 are formed in different steps (FIG. 1).
(B)). Here, the electrode pad 4a is formed according to the height of the electrode wiring 4.
Is formed to be higher. This is because only the electrode pads 4a are brought into contact with the barrier metal 6 of the bumps 8 formed on the protective film 3 in the next step. As these materials, alloys mainly composed of aluminum, copper, and the like are used. Next, the entire surface of the substrate is covered with a protective film 5 (FIG. 1C). As a material of the protective film 5, a nitride film (SiN) or the like is used. The thickness of the protective film 5 is about 10 to 15 μm.

Next, the electrode pads 4a and the protective film 5 are uniformly removed by etching back over the entire surface (FIG. 1D). It is appropriate to use a surface polishing method called a chemical mechanical polishing method as an etch back method. At this time, it is necessary to perform the surface polishing while paying sufficient attention to various parameters such as the horizontality of the substrate and the horizontality of the polishing jig so that the electrode pads 4a and the protective film 5 have a uniform height inside the semiconductor substrate. is there. Further, it is necessary to use a fine polishing material so as not to cause cracks in the protective film 5. Then, the protective film 5 and the electrode pad 4a
Is etched back until the film thickness becomes about 1 to 2 μm.
A method of performing dry etching using an etching solution or an etching gas for etching the materials of the electrode pad 4a and the protective film 5 at the same rate is also effective.

Next, a barrier metal 6 is formed (FIG. 1).
(E)). As a forming method, sputtering, electron beam evaporation, or the like is used. As the material of the barrier metal 6, a noble metal such as Au, Pd, or Cu, or Ti or TiW is used. Further, the film thickness is about 0.1 to 1 μm.
Next, a photoresist 7 is applied on the barrier metal 6,
A portion of the photoresist 7 where the bump 8 is to be grown
Is removed (FIG. 2A). Next, bumps 8 are grown (FIG. 2B). An electrolytic plating method is used to grow the bumps 8. If an electroless plating solution is used, the bump 8 can be formed without the barrier metal 6. The material of the bump 8 is usually a noble metal such as Au, Cu, or Ag, or a solder. The growth height is 1
About 0 to 25 μm is desirable.

Next, the photoresist 7 is removed (FIG. 2).
(C)). Finally, unnecessary portions of the barrier metal 6 are etched by a wet etching method or a dry etching method, thereby completing the manufacture of the semiconductor device (FIG. 2D).

The following effects are produced by the above-described semiconductor device and the method of manufacturing the same according to the present invention. First, the step between the electrode pad 4a and the protective film 5 is eliminated by etching back the electrode pad 4a and the protective film 5. Therefore, barrier metal 6
Also, there is no step on the surface of the bump 8. This makes it possible to prevent a phenomenon that when a pressure is applied to a bump in an assembling process of the ILB or the like, a pressure is locally applied to a step portion of the protective film and a crack of the protective film is generated. In addition, by eliminating the step, the step between the electrode pad 4a and the protective film 5 does not appear on the surface of the bump 8 as it is, and the surface can be made flat. As a result, when the bump 8 is connected to an external wiring such as a lead in the assembling process, the bonding area between the bump 8 and the surface of the lead is increased, and in addition, the load of the ILB is uniformly applied to the bump 8, so that the bonding strength is extremely high. Has the effect of being improved.

Further, the step between the electrode pad 4a and the protective film 5 is eliminated to improve the barrier metal cover range when the barrier metal 6 is formed, thereby preventing unplating due to barrier metal disconnection in a later plating step. Has the effect of eliminating.

[0021]

As described above, according to the present invention, the bumps are applied to the bumps in the assembling process of the ILB and the like by eliminating the step of the insulating film by etching back the electrode pad and the insulating film. In such a case, it is possible to prevent a phenomenon in which a pressure is locally applied to a step portion of the insulating film and an insulating film crack occurs.

In addition, by eliminating the step of the insulating film, the barrier metal coverage at the time of forming the barrier metal can be improved, which has the effect of eliminating unplating due to barrier metal disconnection in the subsequent plating step.

In the plating step of forming the bump by eliminating the step of the insulating film and making the barrier metal almost flat, the step of the insulating film and the barrier metal, which are the base, does not appear on the bump surface as it is.
By enabling the bump surface to be flat, the bonding area between the bump and the lead surface increases when connecting the bump to external wiring such as leads during the assembly process.
In addition, since the load of the ILB is uniformly applied to the bump, there is an effect that the bonding becomes very good.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing steps from the start of manufacturing to the formation of a barrier metal in a method of manufacturing a semiconductor device according to the present invention.

FIG. 2 is a schematic explanatory view showing steps from the formation of a photoresist to the end of the manufacturing, following the manufacturing step shown in FIG. 1;

FIG. 3 is a schematic explanatory view showing steps from the start of manufacturing to the formation of a photoresist in a method of manufacturing a semiconductor device according to a conventional technique.

FIG. 4 is a schematic explanatory view showing the steps from the bump formation to the end of the manufacturing, following the manufacturing steps shown in FIG. 3;

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 2 transistor 3, 5 protective film 4 electrode wiring 4a electrode pad 6 barrier metal 7 photoresist 8 bump

Claims (4)

[Claims] A first electrode formed on a substrate; an insulating film formed to surround the first electrode;
A second electrode joined to the first electrode and extracting a signal to the outside, wherein the upper surface of the first electrode and the surface of the insulating film are formed at substantially the same height. 2. The semiconductor device according to claim 1, wherein a barrier metal is formed between said first electrode and said second electrode. Forming a first electrode on the substrate;
Forming an insulating film covering the first electrode, removing the surface of the insulating film to expose the upper surface of the first electrode, and removing the upper surface of the first electrode and the surface of the insulating film. And a step of forming a second electrode on the first electrode for bonding a conductor for extracting a signal to the outside. Method. 4. The method according to claim 3, wherein the step of removing the surface of the insulating film is performed by a chemical mechanical polishing method.