JPH04349630A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To simplify a bump electrode forming process to improve the manufacturing efficiency and form bump electrodes having required heights free from the height variation. CONSTITUTION:After adhesion and diffusion barrier metal layers 25 and 26 are selectively formed on a plurality of electrode pads 23 formed on the main surface of a semiconductor substrate 21, a bump metal layer 28 is applied to the whole main surface of the semiconductor substrate 21. The bump metal layer 28 is melted by a thermal treatment and approximately semi-spherical bump electrodes 29 are formed on the metal layers 25 and 26 by the surface tension of the bump metal. After that, melted metal layer 28 remnants 29a remaining on a passivation film 22 are removed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device having bump electrodes, and more particularly to a method for forming the bump electrodes.

0002

2. Description of the Related Art Conventionally, a method for manufacturing this type of semiconductor device has been described, for example, in Japanese Patent Application Laid-open No. 146452/1983. The manufacturing method will be explained below with reference to the drawings.

FIGS. 2(1) to 2(3) are manufacturing process diagrams showing a conventional method for manufacturing a semiconductor device. This semiconductor device is manufactured through the following steps (a) to (c).

(a) Process of FIG. 2(1) A field oxide film 2 is formed over the entire main surface of the semiconductor substrate 1 on which semiconductor elements are formed. After forming the electrode pad 3 at a predetermined location on the field oxide film 2, the entire main surface of the semiconductor substrate 1 is covered with a passivation film 4, and the passivation film 4 is selectively removed to expose the electrode pad 3. let

A current conducting layer 5 made of aluminum or the like is deposited over the entire main surface of the semiconductor substrate 1, and an adhesion metal layer 6 and a diffusion barrier plating layer 7 are formed on the current conducting layer 5. Thereafter, portions of the adhesion metal layer 6 and the diffusion barrier plating layer 7 other than the portions where the bump electrodes are to be formed are removed.

After covering the current conducting layer 5 near the outer edges of the adhesion metal layer 6 and the diffusion barrier plating layer 7 with a resist film 8 for plating, it is set in a bump plating apparatus. Then, by electroplating, current is applied to the current conducting layer 5 to form a diffusion barrier plating layer 9 on the diffusion barrier plating layer 7.

A pseudo electrode layer 10 is selectively formed on the diffusion barrier plating layer 9 and the resist film 8. This pseudo electrode layer 10 is formed of tin, gold, etc., and its formation area is
It is formed so that it is sufficiently large compared to the area of the diffusion barrier plating layer 9.

By an electroplating method using a bump plating device, current is applied to the current conducting layer 5 using the pseudo electrode layer 10 as an electrode for electroplating, and a lead plating layer 11 is formed on the pseudo electrode layer 10.
and a tin plating layer 32 are sequentially formed. At this time, since the area of the pseudo electrode layer 10 is sufficiently large, the formation area of the lead plating layer 11 and the tin plating layer 12 formed thereon is also sufficiently large (b). After removing the resist film 8 with a solvent such as acetone, the outer edge of the current conducting layer 5 is removed using an etching solution.

(c) Process pseudo electrode layer 1 in FIG. 2(3)
0, the lead plating layer 11 and the tin plating layer 12 at a temperature of 340
Heat to about ~350°C. Then, the lead and tin in the lead plating layer 11 and the tin plating layer 12 are melted and alloyed to become solder, and due to their surface tension, they gather on the diffusion barrier plating layer 9, forming a circle with a height of about 25 to 100 μm. Hill-like (
A hemispherical bump electrode 13 is formed. At this time, the pseudo electrode layer 10 is also melted or diffused at the same time, and the lead plating layer 1
1 and the tin plating layer 12 and disappear.

Bump electrodes 13 are formed in this way, but the lead plating layer 11 and the tin plating layer 1 are made larger enough to make the area of the pseudo electrode layer 10 larger than the diffusion barrier layer 9.
2 can be made thinner. Therefore, the plating time for forming these is significantly shortened, the working efficiency of the plating process is improved, and the overall manufacturing process of the semiconductor device can be rationalized.

[0011]

[Problems to be Solved by the Invention] However, the conventional manufacturing method has the following problems.

(1) When forming a plurality of bump electrodes 13 on a semiconductor substrate 1, a plurality of electrode pads 3 are formed on the main surface of the semiconductor substrate 1, and an adhesive metal layer 6 is formed on them.
and diffusion barrier plating layer 7 are respectively formed. Then, after forming a diffusion barrier plating layer 9, a pseudo electrode layer 10, a lead plating layer 11, and a tin plating layer 12 each having a predetermined planar area on each diffusion barrier plating layer 7, a heat treatment is performed to form a bump electrode 13. Since the bump electrodes 13 are formed respectively, there are many steps for forming the bump electrodes 13, and there is a problem that the manufacturing efficiency is low. Moreover, on each diffusion barrier plating layer 7,
A diffusion barrier plating layer 9 and a pseudo electrode layer 1 are respectively separately formed.
0, etc., there is a problem in that variations in height are likely to occur between the bump electrodes 13.

(2) On each diffusion barrier plating layer 7,
Diffusion barrier plating layer 9, pseudo electrode layer 10, lead plating layer 1
1 and the tin plating layer 12, the semiconductor substrate 1 is set on the bump plating layer, the electrical contact terminal of the device is brought into contact with the current conducting layer 5, and the current conducting layer 5 is energized to generate electricity. A diffusion barrier plating layer 9, a pseudo electrode layer 10, etc. are formed by a plating method. At this time, since the current conductive layer 5 is covered with a resist film 8 for plating, poor contact between the electrical contact terminals of the device and the current conductive layer 5 is likely to occur. It is difficult to form the bump electrodes 13.

[0014] The present invention solves the problems that the prior art had, such as low manufacturing efficiency due to the large number of steps for forming the bump electrodes, and the fact that variations in the height of the bump electrodes are likely to occur.
Another object of the present invention is to provide a method for manufacturing a semiconductor device that solves the problem of difficulty in forming bump electrodes of a predetermined height due to poor contact during electroplating.

[0015]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the first invention covers the entire main surface of the semiconductor substrate with a passivation film after forming electrode pads on the main surface of the semiconductor substrate, and In a method of manufacturing a semiconductor device in which the passivation film is selectively removed to expose the electrode pad and a bump electrode is formed on the exposed electrode pad, the following measures are taken.

That is, after selectively forming a metal layer for adhesion and a diffusion barrier on the electrode pad, a bump metal layer is deposited on the entire main surface of the semiconductor substrate. Then, the bump metal layer is melted by heat treatment to form a bump electrode on the adhesion and diffusion barrier metal layer, and then, the molten metal residue of the bump metal layer remaining on the passivation film is removed. .

[0017] In the second invention, after forming the metal layer for adhesion and diffusion barrier in the first invention, the following treatment is performed. That is, a current conductive layer is formed over the entire main surface of the semiconductor substrate, and the bump metal layer is deposited on the current conductive layer by electroplating by passing current through the current conductive layer. Then, after melting the current conducting layer and the bump metal layer by heat treatment and forming a bump electrode on the adhesion and diffusion barrier metal layer, the current conducting layer and the bump metal layer remaining on the passivation film are formed. Remove molten metal residue.

[0018]

[Operation] According to the first invention, since the method for manufacturing a semiconductor device is configured as described above, after selectively forming a metal layer for adhesion and diffusion barrier on the electrode pad, the main surface of the semiconductor substrate A bump metal layer with a predetermined thickness is formed over the entire surface. As a result, when the heat-treated bump metal layer is melted,
Due to its surface tension, a substantially hemispherical bump electrode of uniform height with no height variations is formed on the metal layer for adhesion and diffusion barrier.

Moreover, since the bump metal layer formed over the entire main surface is separated into individual electrode pads when melted by heat treatment, the manufacturing process can be simplified. Furthermore, by setting the thickness of the bump metal layer to a desired value, a bump electrode of a predetermined height can be formed.

According to the second aspect of the invention, the current conductive layer formed on the entire principal part of the main surface of the semiconductor substrate is used as an electrode for electroplating when forming a bump metal layer using an electroplating method. It has the function of relatively easily depositing a bump metal layer of a predetermined thickness on the current conducting layer. When the current conductive layer and the bump metal layer are melted by heat treatment, the current conductive layer melts and disappears in the molten bump metal layer, and their surface tension acts to form a bump electrode.

Moreover, since the current conductive layer is not covered with a plating resist film as in the conventional case, the problem of poor contact with the electrode terminal during electroplating is eliminated, and the function is to ensure proper electroplating. be. Therefore, the above problem can be solved.

[0022]

Embodiment FIGS. 1(1) to 1(3) are process diagrams for manufacturing a semiconductor device showing a first embodiment of the present invention. This semiconductor device is manufactured through, for example, the following steps (A) to (C).

(A) Process of FIG. 1(1) A field oxide film 22 is formed over the entire main surface of a semiconductor substrate 21 such as a silicon substrate on which a semiconductor element is formed. Electrode pads 23 made of aluminum or the like are selectively formed at predetermined positions on field oxide film 22 . Furthermore, after a passivation film 24 is grown by a chemical vapor deposition method (CVD method) or the like, a bump formation area is opened on the electrode pad 23 by a photolithography technique or the like.

Next, an adhesive metal layer 25 of titanium or the like and a diffusion barrier layer 2 of platinum or the like are formed over the entire main surface of the semiconductor substrate 21.
A metal layer consisting of 6 is formed. After that, the adhesive metal layer 25
Then, the portions of the diffusion barrier layer 26 other than the portions where the bump electrodes are to be formed are removed by photolithography or the like. The adhesive metal layer 25 has a function of adhering to the field oxide film 22 and the electrode pad 23.

(B) A current conductive layer 27 made of copper, gold, or the like having a thickness of about several μm is formed over the entire main surface of the semiconductor substrate 21 by a thin film forming technique such as the process vapor deposition method shown in FIG. 1(2). A hole is formed in the current conducting layer 27 at the position of the electrode pad 23 by photolithography or the like. This brings the end of the current conducting layer 27 into contact with and overlaps the end of the diffusion barrier layer 26.

The semiconductor substrate 21 is set in, for example, a bump plating apparatus, and current is applied to the current conducting layer 27 by electroplating to form a bump metal layer 28 on the entire surface. This bump metal layer 28 can be made of various materials, such as solder, indium, tin, gold, etc., depending on the desired bump electrode. However, a metal with a relatively low melting point is desirable since melting treatment is performed in a subsequent process. The plating thickness of this bump metal layer 28 is, for example, approximately 10 to 20 μm.

(C) Step of FIG. 1(3) Under a nitrogen gas atmosphere, the bump metal layer 28 is heated to a temperature of, for example, 340°C.
Heat to about ~350°C. Then, the bump metal layer 28
is melted, and due to the surface tension of the molten metal, it gathers on the diffusion barrier layer 26 to form a hemispherical bump electrode 29. At this time, the current conducting layer 27 is also melted or diffused at the same time, and is fused to the bump metal layer 28 and disappears.

That is, the bump metal layer 28 and the current conducting layer 2
7 is melted by heating, the bump metal layer 28 and the current conducting layer 27 are repelled by the passivation film 24 formed around the electrode pad 23 and gathered on the electrode pad 23 due to surface tension, forming a hemispherical bump electrode. 2
9 is formed.

At this time, the molten metal residue 29a of the bump metal layer 28 and the current conducting layer 27 that has not been absorbed by the hemispherical bump electrode 29 remains on the passivation film 24. Therefore, the molten metal residue 29a is removed as follows.

For example, after cooling and solidifying, the molten metal residue 29a is blown off and removed from the passivation film 24 using an ultrasonic cleaner or an air blower using an inert gas such as air or nitrogen gas. Other methods include blowing away the molten metal residue 29a while it is melting, or removing it by tilting the semiconductor substrate 21 and applying an impact, as appropriate in consideration of workability, removal efficiency, etc. Just choose.

By removing the molten metal residue 29a in this manner, a semiconductor device having the desired bump electrode 29 can be obtained.

In this first embodiment. It has the following advantages:

(i) A current conductive layer 27 is formed over the entire principal part of the main surface of the semiconductor substrate 21, and a bump metal layer 28 of a predetermined thickness is formed by applying current to the current conductive layer 27 using an electroplating method. Plate. At this time, the current conducting layer 2
7 is not covered with a plating resist film as in the conventional case, it is possible to prevent poor electrical contact with the bump plating apparatus, and it is possible to form the bump metal layer 28 with a predetermined thickness. Therefore, the height of the bump electrode 29 formed by melting the bump metal layer 28 can be precisely formed to a predetermined height as designed.

(ii) After forming the current conducting layer 27 and the bump metal layer 28 on the entire main surface of the semiconductor substrate 21, the bump metal layer 28 and the current conducting layer 27 are melted by heat treatment, and the surface thereof is heated. Hemispherical bump electrodes 29 are formed by tension. Therefore, the number of steps for forming the bump electrodes 29 is reduced compared to the conventional method, and manufacturing efficiency is significantly improved. Moreover, since a plurality of bump electrodes 29 are simultaneously formed by melting the current conducting layer 27 and the bump metal layer 28 formed on the entire surface of the main part, it is possible to prevent variations in the height of each bump electrode 29, thereby making it uniform. Bump electrodes 29 with a certain height can be manufactured.

(iii) After forming the bump electrode 29,
Molten metal residue 29a remains on the passivation film 24. However, since this is repelled by the passivation film 24 and remains roughly separated from each bump electrode 29, it can be easily removed. On this occasion,
Since the molten metal residue 29a of materials such as solder and tin is relatively inexpensive, the cost increase due to the removal of the molten metal residue 29a is not a big problem.

FIG. 3 shows a method of manufacturing a semiconductor device according to a second embodiment of the present invention, and is a sectional view of the semiconductor device during the manufacturing process. This FIG. 3 corresponds to a partial cross-sectional view of FIG. 1(2).

This embodiment differs from the first embodiment in the following points:
This is because the step of opening holes at 23 electrode pads in the current conducting layer 27 in the step of FIG. 1(2) is omitted.

That is, the adhesive metal layer 25 is placed on the electrode pad 23.
After selectively forming the diffusion barrier layer 26, a current conducting layer 27A is formed on the entire surface by vapor deposition or the like. Thereafter, current is applied to the current conducting layer 27A by electroplating to deposit the bump metal layer 28 on the entire surface of the current conducting layer 27A. Thereafter, by heat treatment, the bump metal layer 28 and the current conducting layer 2 are removed.
7A is melted and a hemispherical bump electrode 29 is formed by its surface tension.

In this second embodiment, the diffusion barrier layer 26
Since the current conducting layer 27A is present thereon, during the heating process, the molten bump metal layer 28 does not immediately collect on the diffusion barrier layer 26 to form a hemispherical bump electrode 29 as in the first embodiment. . In other words, by heat treatment,
When the bump metal layer 28 melts, the thin current conducting layer 27A diffuses or melts and is absorbed into the bump metal layer 28.

Then, in substantially the same manner as in the first embodiment, the molten bump metal layer 28 is repelled by the passivation film 24 and gathered on the diffusion barrier layer 26 due to surface tension, forming a hemispherical bump electrode 29. Ru.

In addition to having almost the same advantages as the first embodiment, the second embodiment does not have any holes in the current conducting layer 27A, so the hole processing step can be omitted, and thereby the bump electrodes 29 can be easily formed. The formation process can be simplified and costs can be further reduced.

FIG. 4 shows a method of manufacturing a semiconductor device according to a third embodiment of the present invention, and is a sectional view of the semiconductor device during the manufacturing process. This FIG. 4 corresponds to a partial cross-sectional view in FIG. 1(2).

This embodiment differs from the first and second embodiments in that the current conducting layer 27 or 27A is omitted.

That is, in this embodiment, after selectively forming a metal layer consisting of an adhesion metal layer 25 and a diffusion barrier layer 26 on the electrode pad 23, the entire main surface of the semiconductor substrate 21 is coated by a method other than electroplating. The bump metal layer 28 is formed by other means such as vapor deposition or sputtering. after that,
As in the first and second embodiments, the bump metal layer 28 is melted by heat treatment, and the bump electrode 29 is formed on the diffusion barrier layer 26 by its surface tension.

In addition to obtaining almost the same advantages as the first and second embodiments, the third embodiment uses a method other than electroplating to form the bump metal layer 28. , the current conducting layers 27 and 27A can be omitted, thereby simplifying the manufacturing process. In addition, since electroplating is not used, problems such as poor contact with the electrical contact terminals of bump plating equipment can be fundamentally solved, resulting in a highly reliable and low-cost semiconductor with a stable bump electrode height. A device is obtained.

[0046] Note that the present invention is not limited to the above embodiments,
Various modifications are possible.

For example, although the bump metal layer 28 is formed of a single layer, it may be formed of multiple layers of different materials such as a lead layer or a tin layer, or it may be formed of multiple layers of the same material. In this way, the semiconductor substrate 2 in the above embodiment
It is also possible to change the material, shape, structure, etc. of each layer on 1 to those other than those shown in the drawings.

[0048]

As described in detail above, according to the first invention, after selectively forming a metal layer on an electrode pad, a bump metal layer is deposited on the entire main surface of a semiconductor substrate, Since the bump metal layer is melted by heat treatment to form the bump electrode, the process of forming the bump electrode is simplified compared to the conventional method of forming a bump metal layer individually for each electrode pad. , thereby significantly improving the manufacturing efficiency of semiconductor devices.

Moreover, since the bump metal layer is formed on the entire surface and is melted by heat treatment to form individual bump electrodes, a plurality of uniform bumps with no variation in height can be formed. Electrodes can be manufactured easily. Furthermore, if a bump metal layer is formed on the entire main surface of a semiconductor substrate by a method other than electroplating, such as vapor deposition or sputtering, there will be a problem of poor electrical contact when electricity is applied when electroplating is used. can be fundamentally solved, and bump electrodes of a predetermined height can be formed easily and accurately.

According to the second aspect of the present invention, a current conducting layer is formed on the entire principal part of the main surface of the semiconductor substrate, and the bump metal layer is formed by electroplating by passing current through the current conducting layer. Almost similarly to the first invention, the number of steps for forming bump electrodes is reduced, improving manufacturing efficiency, and variations in the heights of a plurality of bump electrodes are eliminated, making it possible to form bump electrodes with uniform heights.

Furthermore, since the bump metal layer is formed on the current conducting layer using electroplating, it is possible to form the bump metal layer with a desired thickness relatively easily. At this time, since the current conductive layer is not covered with a plating resist film unlike in the past, poor contact between the electrical contact terminal of the bump plating equipment and the current conductive layer can be prevented, and the bump electrode of a predetermined height can be Can be formed with high precision.

[Brief explanation of drawings]

FIG. 1 is a manufacturing process diagram of a semiconductor device showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of a conventional semiconductor device.

FIG. 3 is a cross-sectional view showing a second embodiment of the present invention during the manufacturing process of a semiconductor device.

FIG. 4 is a cross-sectional view during the manufacturing process of a semiconductor device showing a third embodiment of the present invention.

[Explanation of symbols]

21 Semiconductor substrate 22 Field oxide film 23
Electrode pad 24 Passivation film 25
Adhesion metal layer 26 Diffusion barrier layer 27, 27A
Current conducting layer 28 Bump metal layer 29
Bump electrode 29a Molten metal residue

Claims (2)

[Claims] 1. After forming an electrode pad on the main surface of a semiconductor substrate, the entire main surface of the semiconductor substrate is covered with a passivation film, the passivation film is selectively removed to expose the electrode pad, and the exposed electrode pad is covered with a passivation film. In the method for manufacturing a semiconductor device in which a bump electrode is formed on the electrode pad, a metal layer for adhesion and a diffusion barrier is selectively formed on the electrode pad, and then a bump metal layer is formed on the entire main surface of the semiconductor substrate. deposit and melt the bump metal layer by heat treatment to form a bump electrode on the adhesion and diffusion barrier metal layer, and remove molten metal residue of the bump metal layer remaining on the passivation film. A method for manufacturing a semiconductor device, characterized in that: 2. The method of manufacturing a semiconductor device according to claim 1, wherein after forming the metal layer for adhesion and diffusion barrier, a current conducting layer is formed on the entire principal part of the main surface of the semiconductor substrate; The bump metal layer is deposited on the current conducting layer by electroplating by applying electricity to the current conducting layer, and the current conducting layer and the bump metal layer are melted by heat treatment to form the metal layer for adhesion and diffusion barrier. A method for manufacturing a semiconductor device, comprising forming a bump electrode thereon, and removing molten metal residue of the current conducting layer and the bump metal layer remaining on the passivation film.