JPH10242151A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduced the man-hour for forming bump electrodes by applying a solder past of solder grains contg. As and Zn in a bonder on connection pads and heat-treating it to directly form solder bumps contg. As and Zn on the pads. SOLUTION: On an Si substrate 11 and Al or Al alloy connection pads 12 are formed and covered with a protective film 13, except the central parts of the pads, openings 14 are formed into the exposed central parts of the pads 12, and a paste 15 contg. many solder grains in a bonder is applied on the exposed parts and protective film 13 located round these parts through the openings 14 and heat-treated to form approximately spherical bump electrodes 16, i.e., solder bumps contg. As and Zn directly formed on the pads 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art For example, in a semiconductor chip mounting technique called a flip chip method, a bump electrode made of solder formed on a connection pad of a semiconductor chip is mounted on a connection pad formed on a circuit board, and heat treatment is performed. By doing so, the solder is reflowed to perform bonding. Therefore, it is necessary to form a bump electrode made of solder on the semiconductor chip.

Next, a part of a conventional method of manufacturing such a semiconductor device, that is, a method of forming a bump electrode will be described with reference to FIG. First, as shown in FIG. 2A, a connection pad 2 made of aluminum (Al) or an aluminum alloy is formed on a silicon substrate (semiconductor substrate) 1, and the upper surface of the connection pad 2 is formed at a portion other than the center of the connection pad 2. A connection pad is prepared in which the protection film 3 is covered and the center of the connection pad 2 is exposed through the opening 4 formed in the protection film 3. Next, the protective film 3 of the connection pad 2 is formed by reverse sputter etching using argon (Ar).
The native oxide film (not shown) of aluminum formed on the exposed portion exposed through the opening 4 is removed. Next, as shown in FIG. 2B, a base metal layer 5 is formed on the entire upper surface.
To form In this case, the base metal layer 5 has a two-layer structure or a three-layer structure. Next, a plating resist layer 6 is formed on the upper surface of the base metal layer 5 except for a portion corresponding to the connection pad 2. Therefore, in this state, the plating resist layer 6 in a portion corresponding to the connection pad 2 is formed.
Is formed with a flat circular opening 7.

[0004] Next, by using the base metal layer 5 as a plating current path and performing electrolytic plating of solder, a bump electrode 8 made of solder is formed on the upper surface of the base metal layer 5 in the opening 7 of the plating resist layer 6. . In this case, solder plating is isotropically deposited on the plating resist layer 6. For this reason, the shape of the bump electrode 8 at this stage becomes a mushroom shape. The reason why the shape of the projecting electrode 8 at this stage is a mushroom shape is that the thickness of the plating resist layer 6 is limited, and even if the upper limit is, for example, about 50 μm, the final projecting electrode 9 will be described later. This is to make the height higher. Next, the plating resist layer 6 is peeled off. Next, when unnecessary portions of the underlying metal layer 5 are etched and removed using the bump electrodes 8 as a mask, the underlying metal layer 5 remains only under the bump electrodes 8 as shown in FIG. Next, FIG.
As shown in (D), when the heat treatment is performed, the mushroom-shaped protruding electrode 8 is melted and then rounded due to surface tension to become substantially spherical. By solidifying in this state, a substantially spherical protruding electrode 9 is formed. .

The reason why the base metal layer 5 is formed on the entire upper surface at the beginning of the step shown in FIG. 2B is that it is used as a plating current path when performing electrolytic plating of solder, as described above. . The reason why the base metal layer 5 is left only under the protruding electrode 8 in the step shown in FIG. 2C is that, as shown in FIG. This is for improving the adhesion to the connection pad 2 made of an alloy.

[0006]

However, in the conventional method of forming such a bump electrode, a natural oxide film on the connection pad 2 is removed, a base metal layer 5 is formed on the entire upper surface, and then an opening is formed. Then, a plating resist layer 6 having a metal layer 7 is formed, a plating process is performed, the plating resist layer 6 is peeled off, an unnecessary portion of the base metal layer 5 is removed, and a substantially spherical projection electrode 9 is formed by heat treatment. Therefore, there is a problem that the number of forming steps is considerably large and the cost is increased. An object of the present invention is to reduce the number of steps for forming a bump electrode.

[0007]

SUMMARY OF THE INVENTION The present invention provides a solder paste obtained by mixing solder particles containing antimony and zinc into a binder on a connection pad made of aluminum or an aluminum alloy provided on a semiconductor substrate. Is applied and heat-treated to directly form solder bumps containing antimony and zinc on the connection pads.

According to the present invention, since antimony and zinc improve the adhesion between the protruding electrode made of solder and the connection pad made of aluminum or aluminum alloy, the adhesion between the protruding electrode and the connection pad is improved. This eliminates the need for a base metal layer. Further, since the solder paste is applied on the connection pads, plating is not required, and a base metal layer as a plating current path is not required. As a result, the step of forming the base metal layer and the plating step including the formation and peeling of the plating resist layer become unnecessary, and the number of steps of forming the bump electrode can be reduced.

[0009]

1A to 1C show a part of a manufacturing process of a semiconductor device according to an embodiment of the present invention, that is, each forming process of a bump electrode.
Therefore, a method for forming the protruding electrode of this embodiment will be described with reference to these drawings in order.

First, as shown in FIG. 1A, a connection pad 12 made of aluminum or an aluminum alloy is formed on a silicon substrate (semiconductor substrate) 11, and the upper surface of the connection pad 12 is formed in a portion other than the center of the connection pad 12. The protective film 13 is covered, and the central portion of the connection pad 12 is
The one exposed through the opening 14 formed in the above is prepared. Next, as shown in FIG.
A large number of solder particles (not shown) in the binder (not shown) are formed on the exposed portion exposed through the opening 14 of the protective film 13 and on the protective film 14 located around the exposed portion. Is applied by screen printing. In this case, 3 to 7% by weight of antimony (Sb) and 0.1% of zinc (Zn) are contained in the solder particles.
The content is 5 to 1.5 wt%. The binder is made of an organic material containing metaethanolamine as a main component.
Then, the opening 14 of the protective film 13 in the connection pad 12 is formed.
When the solder paste 15 is applied on the exposed portion exposed through the connection pad, the connection pad 1
Out of 2, the natural oxide film (not shown) of aluminum formed on the exposed portion exposed through the opening 14 of the protective film 13 is removed. Therefore, there is no need to remove the natural oxide film of aluminum by reverse sputter etching using argon unlike the related art, and the number of steps can be reduced accordingly.

Next, as shown in FIG. 1C, when heat treatment is performed, the binder evaporates and the solder particles are melted. Then, the molten solder particles are 1
The projections 16 are gathered and rolled into a substantially spherical shape, and solidified in this state, thereby forming a substantially spherical protruding electrode 16, that is, a solder bump containing antimony and zinc.
In this case, since antimony and zinc suppress interdiffusion between tin (Sn) in the protruding electrode 16 and aluminum in the connection pad 12 and suppress dissolution of aluminum in the solder, the antimony and zinc are formed of solder. The adhesion between the protruding electrode 16 and the connection pad 12 made of aluminum or an aluminum alloy is improved.

As described above, since antimony and zinc improve the adhesion between the bump electrode 16 made of solder and the connection pad 12 made of aluminum or aluminum alloy, the adhesion between the bump electrode 16 and the connection pad 12 is improved. A base metal layer for improving the performance is not required. Further, since the solder paste 15 is applied on the connection pads 12, plating is not required, and a base metal layer as a plating current path is not required. As a result, the step of forming the base metal layer and the plating step including the formation and peeling of the plating resist layer become unnecessary, and the number of steps of forming the bump electrode 16 can be reduced. Therefore, cost can be reduced.

[0013]

As described above, according to the present invention, antimony and zinc improve the adhesiveness between the bump electrode made of solder and the connection pad made of aluminum or aluminum alloy. The need for a base metal layer for improving the adhesion to the substrate is eliminated. Further, since the solder paste is applied on the connection pads, plating is not required, and a base metal layer as a plating current path is not required. As a result, the step of forming the base metal layer and the plating step including the formation and peeling of the plating resist layer become unnecessary, and the number of steps of forming the bump electrode can be reduced. Therefore, cost can be reduced.

[Brief description of the drawings]

FIGS. 1A to 1C are cross-sectional views each showing a part of a manufacturing process of a semiconductor device according to an embodiment of the present invention, that is, each forming process of a bump electrode.

FIGS. 2A to 2D are cross-sectional views each showing a part of a manufacturing process of a conventional semiconductor device, that is, each forming process of a bump electrode.

[Explanation of symbols]

 Reference Signs List 11 silicon substrate 12 connection pad 15 solder paste 16 protruding electrode

Claims (2)

[Claims] 1. A solder paste obtained by mixing solder particles containing antimony and zinc in a binder is applied to a connection pad made of aluminum or an aluminum alloy provided on a semiconductor substrate, and heat-treated. A method of manufacturing a semiconductor device, wherein a solder bump containing antimony and zinc is directly formed on the connection pad. 2. An antimony content of 3 to 7 in the solder particles.
2. The method according to claim 1, wherein the composition contains 0.5% to 1.5% by weight of zinc.