JPH04280434A - Manufacture of semiconductor integrated circuit device - Google Patents

Abstract

PURPOSE:To suppress a variation in a Pb-Sn ratio of a bump. CONSTITUTION:Before a heat treatment for forming a bump 7, a metal layer 5d made of a Cu-Sn intermetallic compound for suppressing movement of Sn at the time of heat treating is formed between a metal layer 5c made of Cu of a base metal film 5 and a metal layer 6b made of Sn of a metal film 6 for the bump.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for manufacturing semiconductor integrated circuit devices, and more particularly to a technology for forming bump electrodes.

0002

[Prior Art] Figure 6 shows an example of a conventional method of forming bump electrodes.
This will be explained with reference to FIG.

FIG. 6 shows a semiconductor chip 49 before bump formation.
A partial cross-sectional view is shown. A wiring 52 is formed on the upper surface of an insulating film 51 formed on a semiconductor substrate 50.

The wiring 52 is made of aluminum (Al), for example.
Alternatively, it is made of an Al alloy and is connected to a base metal film 55 through a through hole 54 bored in an insulating film 53 covering it.

The base metal film 55 includes, for example, a chromium (Cr) layer 55a, a Cr-copper (Cu) layer 55b, and a Cr-copper (Cu) layer 55b in order from the bottom.
A U layer 55c and a gold (Au) layer 55d are laminated.

A bump metal film 56 for forming bumps is formed on the base metal film 55. The metal film 56 for bumps includes, for example, a Pb layer 56 for bumps in order from the bottom layer.
a and a bump Sn layer 56b are laminated.

[0007] Such a semiconductor substrate 50 is subjected to heat treatment at a predetermined temperature to melt the bump metal film 56, and as shown in FIG. 7, bumps 57 made of, for example, Pb-5% Sn are formed.

[0008] Regarding the bump electrode technology, for example, Ohmsha Co., Ltd., published November 30, 1980, "L
SI Handbook” P409-P410.

[0009]

SUMMARY OF THE INVENTION However, the present inventors have discovered that the above-mentioned conventional bump forming technology has the following problems.

In the conventional case, when the metal film for bumps is heated and melted, Sn in the Sn layer for bumps moves to the Cu layer of the underlying metal film, and an intermetallic compound consisting of Cu-Sn is formed between the Cu layer and the Au layer. A phenomenon of layer formation occurs.

[0011] As a result, the Pb-Sn ratio of the bumps formed by heat treatment fluctuates, causing problems such as fluctuations in the remelting temperature and strength of the bumps.

The present invention has been made in view of the above-mentioned problems, and its object is to provide a technique that can suppress fluctuations in the Pb--Sn ratio of bumps.

Another object of the present invention is to provide a technique capable of optimizing process control conditions for semiconductor integrated circuit devices.

The above and other objects and novel features of the present invention will become apparent from the description of the specification and the accompanying drawings.

[0015]

[Means for Solving the Problems] Among the inventions disclosed in this application, a brief overview of typical inventions will be as follows.
It is as follows.

That is, the invention according to claim 1 forms a base metal film having a Cu-based metal layer on the electrode of the lower wiring through a contact hole drilled in an insulating film on a semiconductor substrate, and A method for manufacturing a semiconductor integrated circuit device, comprising: forming a metal film for bumps made of Pb and Sn, and then heating and melting the metal film for bumps to form bumps thereon; Prior to this, a function is provided between the Cu-based metal layer and the bump metal film to suppress a phenomenon in which Sn contained therein moves to the Cu-based metal layer when the bump metal film is heated and melted. This is a method of manufacturing a semiconductor integrated circuit device in which layers are formed in advance.

[0017]

[Operation] According to the above-mentioned invention as set forth in claim 1, the functional layer suppresses the phenomenon in which Sn contained in the bump metal film moves to the Cu-based metal layer in the underlying metal film when the bump metal film is heated and melted. Can be done.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 are sectional views of essential parts during the manufacturing process of a semiconductor integrated circuit device according to an embodiment of the present invention.

FIG. 1 shows a cross-sectional view of a semiconductor integrated circuit device before bump forming heat treatment.

The semiconductor substrate 1 is made of, for example, single crystal silicon (
An insulating film 2a is deposited on its upper surface.

The insulating film 2a is made of silicon dioxide (Si), for example.
2), and wiring (lower layer wiring) 3 is formed on its upper surface.

The wiring 3 is made of Al or Al alloy, for example, and is electrically connected to the underlying metal film 5 through a through hole (connection hole) 4 formed in the insulating film 2b covering it. Note that the insulating film 2b is also made of, for example, SiO2.

The base metal film 5 includes metal layers 5a in order from the bottom layer.
~5e are laminated.

The metal layer 5a is made of, for example, Cr, the metal layer 5b is made of, for example, Cr-Cu, the metal layer (Cu-based metal layer) 5c is made of, for example, Cu, and the metal layer 5e is made of, for example,
For example, it is made of Au.

By the way, in this embodiment, between the metal layer 5c made of Cu and the metal layer 5e made of Au,
A metal layer (functional layer) 5d is formed.

The metal layer 5d is made of, for example, an intermetallic compound of Cu and Sn, and is a layer for suppressing the movement of Sn for forming the bump into the metal layer 5c made of Cu during the bump formation heat treatment described later. be. The molar ratio of Cu and Sn in the metal layer 5d is, for example, 3: at which they are stable.
The amount of Sn is set to be slightly smaller than that of 1, and the ratio is about 3:1 after the bump forming heat treatment.

However, the metal layer 5d after the bump formation heat treatment
The molar ratio of Cu to Sn is not limited to 3:1 and can be changed in various ways, for example, it may be about 4:1.

The reason why the metal layer 5d contains Cu is, for example, for the following two reasons.

First, Cu easily reacts with Sn to form an intermetallic compound. The second reason is to improve the adhesion between the metal layer 5d and the underlying metal layer 5c made of Cu by including Cu in the metal layer 5d.

A bump metal film 6 is formed on the base metal film 5. The bump metal film 6 is formed by laminating metal layers 6a and 6b in order from the bottom layer. The metal layer 6a is made of, for example, Pb, and the metal layer 6b is made of, for example, Sn.

In this embodiment, the semiconductor substrate 1 as described above is heat-treated to melt the metal film 6 for bumps, and as shown in FIG. 2, hemispherical bumps 7 made of, for example, Pb-Sn-Au form. At this time, in this embodiment, the metal layer 5d made of Cu and Sn acts to suppress the movement of Sn in the bump metal layer 6b (see FIG. 1) to the metal layer 5c.

Therefore, according to this embodiment, Sn of the bump metal layer 6b is bonded to the underlying metal film 5 during the bump forming heat treatment.
Since the phenomenon of migration to the metal layer 5c can be suppressed, it is possible to suppress fluctuations in the Pb-Sn ratio of the bumps 7.

Therefore, fluctuations in the remelting temperature and strength of the bumps 7 caused by fluctuations in the Pb-Sn ratio of the bumps 7 can be suppressed, and improvements in semiconductor integrated circuit devices such as optimization of the remelting temperature range of the bumps 7 can be achieved. It becomes possible to optimize process control conditions during the manufacturing process.

As a result, it is possible to significantly improve the yield and reliability of semiconductor integrated circuit devices.

Next, another embodiment of the present invention will be described.

FIG. 3 is a sectional view of a main part during the manufacturing process of a semiconductor integrated circuit device according to another embodiment of the present invention.

In this embodiment, the metal layer 5d, which is the functional layer in FIG. 1, is composed of, for example, only a single element of Sn. The amount of Sn in the metal layer 5d is such that it forms an intermetallic compound with Cu in the metal layer 5c, and is such that it does not dissolve into the bumps. The other structure before the bump forming heat treatment step is the same as that of the previous embodiment.

The semiconductor substrate 1 is subjected to heat treatment to melt the bump metal 6 and form bumps 7 as shown in FIG. 3.

At this time, in this embodiment, Sn in the metal layer 5d, which is a functional layer, moves to the metal layer 5c made of Cu, and an intermetallic compound of Cu and Sn is formed between the metal layers 5c and 5d. A metal layer 5f consisting of the following is formed. Therefore, it is possible to suppress the phenomenon in which Sn in the metal layer 6b (see FIG. 1) for forming the bump 7 moves to the metal layer 5c during the bump formation heat treatment.

In addition, during the heat treatment for forming the bump, Sn in the metal layer 5d shown in FIG. 1 moves to a certain extent to the metal layer 5e and reacts with Au in the metal layer 5e. A metal layer 5g made of Au-Sn is formed thereon.

As described above, in this embodiment as well, Sn for forming the bumps 7 is used in the metal layer 5c during the bump forming heat treatment.
Since the phenomenon of movement can be suppressed, it is possible to obtain the same effect as in the embodiment described above.

Next, another embodiment of the present invention will be described.

FIGS. 4 and 5 are sectional views of essential parts during the manufacturing process of a semiconductor integrated circuit device according to another embodiment of the present invention.

FIG. 4 shows a sectional view of a main part of a semiconductor integrated circuit device before bump formation. As shown in FIG. 4, in this embodiment, between the base metal film 5 and the bump metal film 6, a metal layer 8a made of Pb and a metal layer 8a made of Sn
A metal layer (functional layer) 8b is formed.

However, the amount of Sn in the metal layer 8b is set to a value that takes into consideration the amount of Sn that will migrate to the metal layer 5c during the bump forming heat treatment.

The semiconductor substrate 1 is subjected to a heat treatment to heat and melt the bump metal 6, thereby forming bumps 7 as shown in FIG.

At this time, in this embodiment, Sn in the metal layer 8b, which is a functional layer, moves to the metal layer 5c made of Cu, and a metal layer 5f made of Cu--Sn is formed on the metal layer 5c. Therefore, during the bump formation heat treatment, the bump 7
Sn of the metal layer 6b (see FIG. 4) forming the metal layer 5c
It is possible to suppress the phenomenon of movement to.

Therefore, in this embodiment as well, it is possible to obtain the same effects as in each of the embodiments described above.

[0049] Above, the invention made by the present inventor has been specifically explained based on examples, but the present invention is not limited to the above-mentioned examples, and can be modified in various ways without departing from the gist thereof. Needless to say.

For example, in the embodiment described with reference to FIG. 3, a case has been described in which a metal layer made of an intermetallic compound of Sn and Cu is formed during the bump formation heat treatment, but the invention is not limited to this. For example, after forming a base metal film having a functional layer made of Sn, heat treatment is performed at a predetermined temperature to form a metal layer made of an intermetallic compound of Cu and Sn on the base metal film. A film may also be formed.

Further, in the above embodiments, the case where the present invention is applied to bump formation has been described, but the present invention is not limited to this. For example, a semiconductor chip mounted on a package substrate via bumps may be attached to a cap. The present invention may be applied to the sealing portion of a sealed chip carrier type semiconductor integrated circuit device, and the portion where the back surface of the semiconductor chip and the inner wall surface of the cap are joined.

[0052]

[Effects of the Invention] Among the inventions disclosed in this application, the effects obtained by the typical inventions are briefly explained as follows.
It is as follows.

That is, according to the invention described in claim 1,
Since it is possible to suppress the phenomenon in which Sn in the bump metal moves to the Cu-based metal layer in the base metal film when the bump metal film is heated and melted, the Pb-Sn of the bump formed by heat treatment can be suppressed.
It becomes possible to suppress fluctuations in the ratio.

Therefore, it is possible to suppress variations in the remelting temperature and strength of the bump due to variations in the Pb-Sn ratio of the bump, so that it is possible to optimize the temperature range during bump remelting, etc. It becomes possible to optimize process control conditions during the manufacturing process of the device.

As a result, it is possible to significantly improve the yield and reliability of semiconductor integrated circuit devices.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a semiconductor integrated circuit device according to an embodiment of the present invention during a manufacturing process.

FIG. 2 is a cross-sectional view of a main part of the semiconductor integrated circuit device during the manufacturing process following FIG. 1;

FIG. 3 is a sectional view of a main part during the manufacturing process of a semiconductor integrated circuit device according to another embodiment of the present invention.

FIG. 4 is a sectional view of a main part during the manufacturing process of a semiconductor integrated circuit device according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view of a main part during the manufacturing process of the semiconductor integrated circuit device following FIG. 4;

FIG. 6 is a partial cross-sectional view of a conventional semiconductor integrated circuit device during a bump forming process.

FIG. 7 is a partial cross-sectional view of the conventional semiconductor integrated circuit device during the bump formation process following FIG. 6;

[Explanation of symbols]

1 Semiconductor substrate 2a Insulating film 2b Insulating film 3 Wiring (lower layer wiring) 4 Through hole (connection hole) 5 Base metal film 5a Metal layer 5b Metal layer 5c Metal layer (Cu-based metal layer) 5d Metal layer (functional layer) 5e Metal layer 5f Metal layer 5g metal layer 6 Metal film for bumps 6a Metal layer (lead) 6b Metal layer (tin) 7 Bump 8a Metal layer 8b Metal layer (functional layer) 49 Semiconductor chip 50 Semiconductor substrate 51 Insulating film 52 Wiring 53 Insulating film 54 Through hole 55 Base metal film 55a Cr layer 55b Cr-Cu layer 55c Cu layer 55d Au layer 56 Metal film for bumps 56a　Pb layer for bumps 56b Sn layer for bump 57 Bump

Claims (3)

[Claims] 1. A base metal film having a copper-based metal layer is formed on the electrode of the lower wiring through a connection hole drilled in an insulating film on a semiconductor substrate, and a bump made of lead and tin is formed on the base metal film. A method for manufacturing a semiconductor integrated circuit device, in which a bump is formed on a base metal film by heating and melting the metal film for bumps after forming a metal film, the method comprising: forming a bump on a base metal film; A functional layer is formed in advance between the metal layer and the bump metal film for suppressing a phenomenon in which tin in the bump metal film moves to the copper-based metal layer when the bump metal is heated and melted. 1. A method of manufacturing a semiconductor integrated circuit device, comprising: 2. The method of manufacturing a semiconductor integrated circuit device according to claim 1, wherein the functional layer is a metal layer containing tin. 3. A method for manufacturing a semiconductor integrated circuit device, wherein the metal layer according to claim 2 is made of simple tin or copper-tin.