JP2784122B2 - Semiconductor device manufacturing method - Google Patents

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. More particularly, the present invention relates to a method for manufacturing a semiconductor device capable of easily forming a bump on a bonding pad of a semiconductor chip.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of electronic devices, semiconductor devices incorporating integrated circuits (ICs) and the like have not led to lead wires by molding with resin, but have bumps on bonding pads of semiconductor chips. In the state of a semiconductor device (so-called bare chip) on which is formed, there is an increasing number of devices directly connected to wiring leads such as a printed circuit board. In such a semiconductor device, as shown in a cross-sectional view of a bump portion of the semiconductor device in FIG. 2, an external connection electrode terminal of a semiconductor circuit formed on a semiconductor substrate 21 is formed around the periphery of a semiconductor chip by aluminum wiring or the like. The bonding pad 23 is led out, a passivation film 24 is formed as a protective film on the surface of the semiconductor substrate 21 other than the bonding pad 23, and a metal bump 25 is formed on the bonding pad 23 with a barrier metal 26 interposed therebetween. It is formed by a plating method or the like. After that, the barrier metal other than the bump 25 is etched. Barrier metal 26
For example, has good adhesion to the material constituting the bonding pad, has the function of preventing the diffusion of the bump metal to the bonding pad 23 and, on the contrary, the bonding pad metal to the bump 25, and has a deteriorated surface. A metal that is difficult to be used and has good compatibility with the bump metal is selected, and is usually formed of a plurality of layers.

As shown in FIG. 2, as a method of forming a bump 25 on the bonding pad 23, a barrier metal 26 is formed on the entire surface by vapor deposition or sputtering, and a resist film 27 is formed on a portion where no bump is to be formed. Is provided, and a bump 25 is formed by an electrolytic plating method, or a barrier metal is patterned by a photolithography process and is left only on a bonding pad, and is masked with a metal mask. By laminating unnecessary metal materials together with a metal mask, or by screen printing on the above-mentioned patterned barrier metal 26, etc.
A method of attaching a paste-like metal for bumps to form the bumps 25 is employed.

[0004]

As a conventional bump forming method, the above-mentioned plating method is mainly used. However, in the plating method, when the bump metal is formed by solder, the barrier is formed without melting the solder. Since it is difficult to etch only the metal, the above-described method has been studied. However, in these methods, as described above, the barrier metal must be patterned by the photolithography process so that it remains only at the bump formation location. Therefore, steps of vapor deposition of a barrier metal, resist coating, exposure, resist development, resist baking, barrier metal etching, and resist removal must be performed. Therefore, the production takes time and the cost increases.

Further, if a material such as gold used for the barrier metal 26 enters the inside of the semiconductor substrate 21, it becomes an impurity for the silicon of the semiconductor substrate, so that it is difficult to deposit by a conventional process apparatus. There is a problem that such equipment is required.

It is an object of the present invention to provide a method of manufacturing a semiconductor device which can solve such a problem, can form a barrier metal in a small number of steps, and can easily form a bump.

[0007]

According to a method of manufacturing a semiconductor device of the present invention, a semiconductor circuit is formed on a semiconductor substrate, and an electrode film for leading out from the semiconductor circuit is led to a peripheral portion of a semiconductor chip to form a bonding pad. A method of manufacturing a semiconductor device, comprising: forming, on a bonding pad, a bump for connection to an external lead;
The main component is aluminum with a thickness of 1 μm or more
Formed from metal film, etch the bonding pad surface
To activate the aluminum and to interdiffuse with the material of the bonding pad on the bonding pad.
The first material is made of a metal having a small amount and good adhesion.
Layer, made of metal with a small amount of mutual diffusion with the first layer
A second layer and a third layer made of a metal which is hardly oxidized are sequentially formed by an electroless plating method to provide a barrier metal, and a bump is formed on the surface of the barrier metal by screen printing. It is a feature.

[0008]

[0009]

According to the present invention, since the barrier metal is formed by the electroless plating method, the barrier metal can be selectively adhered only to the surface of the bonding pad, and a photoresist step for etching is not required. In addition, since it adheres only to the bonding pad, there is no waste of the material, and since it is only necessary to immerse the material in the electroless plating solution, a large amount of batch processing can be performed at one time. Furthermore, the bumps can be formed in a short time by forming the subsequent bumps by a screen printing method or the like.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a sectional view of a bump portion for explaining one embodiment of a method for manufacturing a semiconductor device of the present invention.

A semiconductor circuit 2 is formed on a semiconductor substrate 1, and electrode terminals for connection to external leads of the semiconductor circuit are led to the periphery of the semiconductor chip by a thin metal film such as aluminum to form a bonding pad 3. Have been. On the surface of the semiconductor substrate 1 other than the bonding pads 3, a passivation film 4 is formed as a protective film. A barrier metal 5 is provided on the bonding pad 3.
Is formed, and the bump 9 is formed thereon. In forming the barrier metal 5, first, as the first layer 6, a material having a small amount of mutual diffusion with aluminum or the like as a material of the bonding pad and having good adhesion, for example,
Metals such as zinc, titanium, chromium and palladium are deposited. The outermost layer 8 of the barrier metal is preferably made of gold, platinum or the like from the viewpoint of preventing deterioration such as oxidation of the surface.
In this case, for example, in order to prevent the bump metal from diffusing into the first layer 6 or the bonding pad 3, the second metal 6 made of a metal such as nickel or copper having a small amount of mutual diffusion with the bump 9 or the first layer 6 is used. It is preferable that the two layers 7 are formed in a three-layer structure in which the two layers 7 are interposed between the first layer 6 and the outermost layer 8. However, a single layer may be used as long as a material that fulfills these functions can be used.

In order to manufacture this semiconductor device, first, a semiconductor circuit, a bonding pad 3 and, for example, about 1 μm
A passivation film 4 made of a silicon nitride film is formed by a normal semiconductor device manufacturing process in the state of a semiconductor wafer. Here, a method of forming the barrier metal 5 and the bump 9 on the bonding pad 3 will be described. Note that the bonding pad 3
Is preferably formed using a metal containing aluminum as a main component (which may contain some silicon or copper) and having a thickness of 1 μm or more.

First, a barrier metal 5 is deposited on a bonding pad by an electroless plating method. As a specific example, Al-Si is 100 μm × 100 μm and has a size of 1 μm.
The semiconductor chip on which the bonding pad was formed with the above thickness was immersed in an alkaline degreasing agent containing 5% by weight of sodium hydroxide at 25 ° C. for about 5 minutes to perform degreasing. Then, it was immersed in 10% by weight of phosphoric acid at 25 ° C. for about 5 minutes, and the surface of the bonding pad was etched and activated.
At this time, the bonding pad aluminum surface is 0.5
Etching was performed by about μm. In consideration of the loss due to the etching, the thickness of the bonding pad is set to 1 as described above.
It is preferable to form it with a thickness of at least μm. Next
A zinc film was formed on the surface of the bonding pad to a thickness of about 0.1 μm by zincate treatment at 25 ° C. In addition, 80-
Electroless nickel plating is performed with a Ni-P plating solution at 90 ° C., a nickel layer is formed as a second layer 7 to a thickness of about 1 to 1.2 μm, and then a gold film of about 0.05 μm is formed at 80 to 90 ° C. It was formed as the outermost layer. After that, at room temperature
The barrier metal 5 was formed by washing with pure water for 10 minutes.

Next, bumps are formed on the barrier metal 5. As a specific example, a metal mask having a thickness of about 0.05 mm is placed on the semiconductor wafer so that only the barrier metal is exposed, and a solder paste is applied by a printing method so as to be embedded in the opening. Then, at 200-240 ° C, about 5
By melting the solder paste for a minute, the thickness becomes 50
A bump of about 70 μm was formed.

According to the above-described manufacturing method, each layer of the barrier metal can be formed with good adhesion and uniform film only on the bonding pad by electroless plating, so that a highly reliable barrier metal 5 can be easily obtained. Can be. The obtained semiconductor device was subjected to a heating test at 175 ° C. for 100 hours. However, there was no problem in both mechanical and electrical characteristics, and the effect of the barrier metal was confirmed.

Further, according to the present invention, the formation of the gold film 8 can be performed in the same procedure as the other metal films, so that a dedicated vapor deposition device is not required.

In the above embodiment, Al-Si is used as the material of the bonding pad 3. However, the present invention is not limited to this, and any metal material such as aluminum which is preferable for an electrode film may be used. You can choose.

[0018]

According to the present invention, since the barrier metal is formed by electroless plating, the barrier metal can be formed only on each bonding pad, and the barrier metal can be easily formed without the need for a photoresist step. it can. Furthermore, a large number of semiconductor devices can be collectively subjected to electroless plating while keeping a semiconductor wafer, and a barrier metal can be formed in a short time. In addition, since the bump can be formed by screen printing or the like, the bump can be formed in a short time, and a significant reduction in manufacturing cost can be achieved.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of a bump portion for explaining one embodiment of a method for manufacturing a semiconductor device of the present invention.

FIG. 2 is an explanatory cross-sectional view of a bump portion of a conventional semiconductor device.

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 3 bonding pad 4 passivation film 5 barrier metal 6 first layer 7 second layer 8 outermost layer 9 bump

Claims (1)

(57) [Claims] 1. A semiconductor circuit is formed on a semiconductor substrate, an external electrode film is led out from the semiconductor circuit to a peripheral portion of a semiconductor chip to form a bonding pad, and a connection with an external lead is formed on the bonding pad. A method of manufacturing a semiconductor device provided with bumps for bonding , wherein said bonding pad is made of aluminum having a thickness of 1 μm or more.
Formed from a metal film containing aluminum as a main component, and etching the surface of the bonding pad to remove aluminum.
And activates the material of the bonding pad on the bonding pad.
A small amount of metal that diffuses into the material
A first layer made of a metal, and the amount of mutual diffusion with the first layer is small.
The second layer made of a hard metal and the hard metal
Forming a third layer in order by electroless plating to form a barrier metal, and forming a bump on the surface of the barrier metal by screen printing .