JPH10135213A - Method of forming electrodes of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form low-m.p. metal bump electrodes by, dipping a semiconductor element in an electroless plating liq. to form a metal deposition layer on element electrodes, and heating this layer to form the metal bump electrodes; the deposition layer is made of a third metal contg. a dispersed second metal and substituted by a first metal of the element electrodes. SOLUTION: Pb fine powder 4 is disposed in an Sn-contg. electroless plating liq. 5, an Si wafer 16 is dipped in this liq. to elute Zn 3. On the surface of Al electrodes 13 an Sn metal deposition layer 7 contg. the Pb fine powder 4 is formed instead of Zn 3. The Si wafer 16 is heat-treated to make an eutectic with the deposition layer 7 to complete a semiconductor device having bump electrodes made of a lowm.p. Pb-Sn eutectic solder. This greatly reduces the cost for completing the semiconductor device and very easily forms low-m.p. metal bump electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an electrode of a semiconductor device having a projection electrode.

[0002]

2. Description of the Related Art In recent years, demands for high-density mounting of semiconductor devices have been increasing, and in order to meet the demand, semiconductor devices mounted on a wiring board using a face-down bonding method, for example, flip-flops, have been demanded. Many semiconductor devices such as chips and tape carrier chips have been used. Such a semiconductor device has a low melting point glass or Si formed over the active surface of the semiconductor element 11 as shown in FIG.
An Al electrode 13 as an element electrode is exposed from an opening of the protective insulating film 12 made of a nitride film or the like, and a barrier metal 14 made of TiW / Au or the like as a metal for adhesion and a metal for a diffusion barrier is formed on the protective insulating film 12. The barrier metal 14 is formed over the inside and outside of the opening, and Au or C
It generally has a structure in which a protruding electrode 15 called a hemispherical bump made of u, Ni or the like is formed by an electrolytic plating method or the like.

[0003] That is, in manufacturing this type of semiconductor device, the following manufacturing method is employed.
First, as shown in FIG. 5A, after the diffusion step is completed, a silicon wafer 16 in which the semiconductor element 11 is formed is prepared, and an Al electrode which is an element electrode exposed from an opening of the protective insulating film 12 is prepared. The native oxide film 17 formed on the surface of the substrate 13 is removed by etching. And FIG.
As shown in (b), a barrier metal 14 having a two-layer structure is formed over the entire surface by employing a vapor deposition method.
The barrier metal 14 is generally made of Ti / Pd, Cr / Au or the like in addition to TiW / Au, and each has a thickness of about 0.2 to 0.5 μm.

[0005] Subsequently, as shown in FIG.
After an opening corresponding to the electrode 13 is provided, a photoresist layer 18 serving as a plating mask is formed on the barrier metal 14.
Electrolytic plating is performed after the silicon wafer 16 having the barrier metal 14 as one electrode is immersed in an electrolytic plating solution formed thereon and containing Au or the like. Then, Au or the like in the electrolytic plating solution is deposited on the photoresist layer 18.
Is deposited in the opening, so that a protruding electrode 15 made of Au or the like is formed. At this time, the photoresist layer 18 may be either a positive type or a negative type, and has a thickness of about 1 to 20 μm.

Further, the photoresist layer 18 is removed,
Further, as shown in FIG. 5D, after a photoresist layer 19 covering the protruding electrode 15 is newly formed, the unnecessary barrier metal 14 is removed by etching, and then the photoresist layer 19 is removed. The semiconductor device as shown is completed. When the barrier metal 14 is made of Pd or Au, the etchant is an aqua regia.
In the case of TiW, a hydrogen peroxide-based etchant is used.

[0006]

By the way, when a semiconductor device is manufactured by employing the above-mentioned conventional electrode forming method,
The following inconvenience was to occur. That is, if such an electrode forming method is adopted, processes such as photolithography, vapor deposition, and etching must be repeatedly performed many times, and it is necessary to use expensive equipment for each of these processes. And the semiconductor element 11
It takes a long time to form the protruding electrode 15 provided in
This leads to an increase in cost spent until completion of the semiconductor device.

In the conventional electrode forming method, since the protruding electrode 15 is formed after adopting electrolytic plating, the protruding electrode 15 is formed of a single metal such as Au, Cu, or Ni. 15 is extremely easy to form, but it is very difficult to form a bump electrode made of a practically advantageous low melting point metal, for example, a eutectic metal such as Pb / Sn solder or In / Au solder. Had become. In other words, although it is desirable that the protruding electrodes of the semiconductor element be made of a material that can be mounted on a wiring board by simultaneous reflow soldering with other electronic components or the like, it is desirable to use a conventional electrode forming method. In fact, it was difficult to form a protruding electrode made of a low melting point metal.

The present invention has been made in view of these inconveniences, and it is possible to reduce the manufacturing cost and to form a protruding electrode made of a low melting point metal very easily. The present invention provides a forming method.

[0009]

According to the present invention, there is provided a method of forming an electrode of a semiconductor device, comprising the steps of: removing a natural oxide film formed on an element electrode of a semiconductor element; Replacing the surface with a first metal, and immersing the semiconductor element in an electroless plating solution containing a third metal in which fine powder of the second metal is dispersed, and dispersing the second metal. Forming the metal deposition layer made of the third metal on the device electrode by replacing the metal deposition layer with the first metal;
Applying a heat of at least the melting point of at least one of the second metal and the third metal to the metal deposition layer to form a protruding electrode. And when this method is adopted,
It is possible to reduce the manufacturing cost of the semiconductor device as compared with the case where the conventional method is adopted, and it is possible to extremely easily form the protruding electrode made of the low melting point metal in which the second and third metals are eutectic. become.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to a first aspect of the present invention, there is provided a method for forming an electrode of a semiconductor device, comprising the steps of: removing a natural oxide film formed on an element electrode of a semiconductor element; Substituting the surface of the electrode with a first metal; immersing the semiconductor element in an electroless plating solution containing a third metal in which fine powder of the second metal is dispersed; Disposing a metal deposition layer made of a third metal dispersed on the element electrode by replacing the first metal with a first metal;
Applying a heat of at least the melting point of at least one of the second metal and the third metal to the metal deposition layer to form a protruding electrode.

According to a second aspect of the present invention, in the method for forming an electrode of a semiconductor device, the first metal in the first aspect is zinc (Zn) or palladium (Pd) and the second metal is lead (Pb). ) And the third metal is tin (S
n). According to a third aspect of the present invention, there is provided a method for forming an electrode of a semiconductor device, wherein the first metal is Zn or Pd, the second metal is indium (In), and the third metal is Is gold (Au).

An embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a side sectional view schematically showing a main part of a semiconductor device manufactured by employing an electrode forming method according to the present embodiment, and FIG. FIG. 3 is a process cross-sectional view showing a method according to a procedure, and FIG. Since the basic structure of the semiconductor device at this time is not different from that of the conventional semiconductor device, FIGS.
The same reference numerals are given to parts and portions that are identical to each other.

In the semiconductor device according to the present embodiment, as shown in FIG. 1 in a simplified manner, a protective insulating film 12 made of a low melting point glass, a Si nitride film, or the like formed by covering an active surface of a semiconductor element 1. An opening for exposing the surface of the Al electrode 13 which is an element electrode is formed, and a low-melting-point metal directly conducting with the Al electrode 13, that is, Pb / Sn solder is formed from this opening. It has a structure in which the protruding electrode 2 made of such a eutectic metal is formed. That is, in the conventional semiconductor device, the barrier metal 14 having a two-layer structure made of a metal for adhesion and a metal for diffusion barrier is used.
Although the structure in which the Al electrode 13 and the protruding electrode 15 are electrically connected after the interposition was employed, the semiconductor device according to the present embodiment has the structure in which the barrier metal 14 is not interposed and the Al electrode 13 and the protruding electrode 2 are in contact with each other and are electrically connected.

Next, a method for forming an electrode of the semiconductor device according to the first embodiment will be described with reference to FIG. In this case, the protruding electrode 2 is formed while processing is performed in a wafer state on which the semiconductor element 1 is formed.

First, as shown in FIG. 2A, a silicon wafer 16 in which the semiconductor element 1 is formed after the diffusion step is completed, and the element electrode exposed from the opening of the protective insulating film 12 is prepared. The natural oxide film 17 formed on the surface of the Al electrode 13 is removed by etching according to a procedure similar to the conventional one. Then, the Al electrode 13
In order that the natural oxide film 17 is not formed again on the upper surface and that the electroless plating in the next step can be performed stably
As shown in FIG. 2B, the surface of the Al electrode 13 from which the natural oxide film 17 has been removed is replaced with Zn3 as a first metal. That is, in this case, Zn3 is selectively replaced on the surface of the Al electrode 13 by zincate treatment. Note that, here, the substitution with Zn3 is performed after adopting the zincate processing, but the present invention is not limited to such substitution, and the substitution with Pd is performed after adopting the activation processing. Is also good.

Subsequently, as shown in FIG. 3, fine powder 4 of Pb as a second metal is dispersed, and
A glass storage tank 6 in which an acid bath type electroless plating solution 5 containing Sn as a third metal is stored is prepared, and a silicon wafer 16 in which the semiconductor element 1 is formed is electrolessly prepared. Immersion in the plating solution 5 is performed. In this case, the fine powder 4 of Pb has a size having a diameter of about 1 to 5 μm. Then, when the silicon wafer 16 is immersed in the electroless plating solution 5, Zn3 is eluted into the electroless plating solution 5 by an initial reaction of the electroless plating, and then Sn starts a deposition reaction. As shown in (c), on the surface of the Al electrode 13, a metal deposition layer 7 made of Sn containing the fine powder 4 of Pb is deposited instead of Zn3, and this metal deposition layer 7 A predetermined height from the opening of the protective insulating film 12,
For example, it grows until it reaches about 5 to 15 μm.

Further, after taking out the silicon wafer 16 from the electroless plating solution 5 and washing it sufficiently, the silicon wafer 16 is heated at a temperature not lower than the melting point of the metal deposition layer 7 made of Sn containing the fine powder 4 of Pb. For example, when the silicon wafer 16 is heat-treated by applying heat of about 200 ° C., P
The metal deposition layer 7 made of Sn containing the fine powder 4 of b is eutectic, and the low melting point eutectic metal Pb.S
The semiconductor device of FIG. 1 including the protruding electrode 2 made of n solder is completed. In this case, the heat above the melting point of both Pb and Sn is applied. However, if the heat above the melting point of only one of Pb and Sn is applied, the metal deposition layer 7 is heated.
Of the eutectic. Of course, even when such a procedure is adopted, the bump electrode 2 made of Pb / Sn solder can be obtained.

In the above description, the protruding electrode 2 is formed while the semiconductor element 1 is formed in a wafer state while processing is performed. However, the processing must be performed in the wafer state. Instead, for example, it is also possible to select only non-defective semiconductor devices from among the semiconductor devices divided and chipped in advance, and to form the protruding electrodes 2 for each of the non-defective semiconductor devices chipped. In this case, there is an advantage that unnecessary electrode formation is not required.

(Embodiment 2) Embodiment 1
In this example, the projecting electrode 2 made of Pb / Sn solder is formed.
Can be formed. In this case, the following electrode forming method is adopted. Note that the structure and electrode forming procedure of the semiconductor device according to the second embodiment are basically the same as those of the first embodiment, and the second metal that was Pb was changed to In and the third metal that was Sn was changed to Sn. Only the point that the metal is Au is different from that of the first embodiment. Therefore, the second embodiment will be described with reference to FIGS.

In the semiconductor device according to the present embodiment, as shown in FIG. 1, the surface of an Al electrode 13 serving as an element electrode is exposed on a protective insulating film 12 formed by covering an active surface of a semiconductor element 1. An opening is formed, and a projecting electrode 2 made of In.Au solder, which is a eutectic metal having a low melting point and directly connected to the Al electrode 13, is formed from the opening. I have. That is, the semiconductor device according to the second embodiment employs a structure in which the Al electrode 13 and the protruding electrode 2 are in direct contact with each other and then conductive.

Hereinafter, a method for forming an electrode of a semiconductor device according to the second embodiment will be described with reference to FIG. First, FIG.
As shown in FIG. 2A, after the natural oxide film 17 formed on the surface of the Al electrode 13 exposed from the opening of the protective insulating film 12 is removed by etching, as shown in FIG. The surface of the Al electrode 13 from which the natural oxide film 17 has been removed is replaced with Zn3 as the first metal. It is needless to say that the substitution may be performed using Pd instead of Zn3.

Next, as shown in FIG. 3, a neutral bath-type electroless electroless powder in which the fine powder 4 made of In, which is the second metal, is dispersed and contains Au, which is the third metal. After preparing a glass storage tank 6 in which the plating solution 5 is stored, the silicon wafer 16 is immersed in the electroless plating solution 5. The fine powder 4 of In has a size having a diameter of about 1 to 5 μm. Subsequently, when the silicon wafer 16 is immersed in the electroless plating solution 5, Zn3 is eluted into the electroless plating solution 5 by the initial reaction of the electroless plating, and as a result, the precipitation reaction of Au starts.
As shown in FIG.
Is deposited, and the metal deposited layer 7 grows from the opening of the protective insulating film 12 to a predetermined height, for example, about 5 to 15 μm.

Further, after the silicon wafer 16 is taken out of the electroless plating solution 5 and sufficiently washed,
When the silicon wafer 16 is heat-treated by applying heat at a temperature equal to or higher than the melting point of, for example, about 180 ° C., the fine In powder 4 melts and becomes eutectic with the metal deposition layer 7 made of Au. A semiconductor device provided with the protruding electrode 2 made of In.Au solder which is a eutectic metal having a melting point is completed. That is, when the electrode forming method according to the second embodiment is employed, the protruding electrode 2 in which In and Au are eutectically formed is formed extremely easily and at low cost by electroless plating.

[0025]

According to the method of forming an electrode of a semiconductor device according to the present invention, the number of times of various processes which require a long time after using expensive equipment is reduced as compared with the case where the conventional method is employed. As a result, it is possible to not only achieve a significant reduction in the cost spent until the completion of the semiconductor device, but also to obtain an effect that the protruding electrode made of a low melting point metal can be formed extremely easily.

[Brief description of the drawings]

FIG. 1 is a side sectional view schematically showing a main part of a semiconductor device manufactured by employing an electrode forming method according to an embodiment.

FIG. 2 is a process cross-sectional view showing a method of forming an electrode of the semiconductor device according to the present embodiment in accordance with a procedure.

FIG. 3 is an explanatory diagram showing a state in which electrodes are being formed in the semiconductor device according to the present embodiment;

FIG. 4 is a side sectional view schematically showing a main part of a semiconductor device according to a conventional technique.

FIG. 5 is a process sectional view showing a procedure for forming an electrode of a semiconductor device according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor element 2 Protruding electrode 3 Zn (first metal) 4 Fine powder of Pb (fine powder composed of second metal) 5 Electroless plating solution 7 Metal deposition layer

Claims (3)

[Claims] A step of removing a native oxide film formed on an element electrode of a semiconductor element; a step of replacing a surface of the element electrode from which the native oxide film has been removed with a first metal; A semiconductor element is immersed in an electroless plating solution containing a third metal in which fine powder of a metal is dispersed, and a metal deposition layer of the third metal in which a second metal is dispersed is formed on the first metal. Forming a step on the device electrode, and applying a heat of at least one of the melting point of at least one of the second metal and the third metal to the metal deposition layer to form a protruding electrode. A method for forming an electrode of a semiconductor device. 2. The method for forming an electrode of a semiconductor device according to claim 1, wherein the first metal is zinc or palladium, the second metal is lead, and the third metal is tin. A method for forming an electrode of a semiconductor device, comprising: 3. The method for forming an electrode of a semiconductor device according to claim 1, wherein the first metal is zinc or palladium, the second metal is indium, and the third metal is gold. A method for forming an electrode of a semiconductor device, comprising: