JPH10256180A - Method for surface-treating metal, formation of electrode, method for bonding electrode, and device for surface-treating metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a natural oxide film to be hardly formed on the surface of a metallic film, particularly, on the surface of a metallic electrode. SOLUTION: After a metallic film 12 composed of indium is formed on a substrate 11, a surface metallic layer 13 is formed on the surface of the metallic film 12 by implanting germanium ions 14 into the surface of the film 12 with energy of about 10-200keV. The surface metallic layer 13 is composed of indium containing germanium by about 1-10%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal surface treatment method and a surface treatment apparatus for preventing oxidation of a metal surface, and an electrode forming method and an electrode bonding method using the above metal surface treatment method. It is.

[0002]

2. Description of the Related Art In general, a metal reacts with oxygen or water in the air to form a natural oxide film on its surface. Since the natural oxide film is an insulator, the metal on which the natural oxide film is formed is electrically disconnected. Therefore, when a metal is used for an electrical connection, a natural oxide film must be sufficiently considered. Once a natural oxide film is formed on the surface of the metal,
It is difficult to remove the natural oxide film. As the only method for removing the natural oxide film, a method of reducing and dissolving the natural oxide film using a flux or the like is known. However, this method involves a step of cleaning the flux and a method of removing the metal resulting from the residue of the flux. It has many problems such as corrosion. Hereinafter, the adverse effects of the natural oxide film will be described by taking fine electrical connection between electrodes of an electronic component as an example.

At present, a large number of semiconductor devices are used in multimedia devices and portable communication devices, and it is desired that all of these semiconductor devices are packaged by a small and lightweight mounting method. ing. For this reason,
As a mounting method, a TAB method or a flip chip method is adopted, and it is necessary that a protruding electrode is formed on an aluminum electrode of a semiconductor element.

At present, as a method of forming a protruding electrode on an aluminum electrode, after repeatedly performing vapor deposition, photolithography, etching and the like on a wafer after a diffusion step, the protruding electrode is formed by electrolytic plating or vapor deposition. Is formed.

FIG. 12 shows a sectional structure of a protruding electrode formed by a conventional electrode forming method. As shown in FIG. 12, the protruding electrode is covered with a protective film 101 on an aluminum electrode 101 formed on a semiconductor substrate 100. A barrier metal layer 102 is formed on the unexposed portion, and a hemispherical protruding electrode 104 is formed on the barrier metal 103.

As a metal material used for the protruding electrode 104, solder (PbSn), indium (In), gold (Au), or the like is known. Among them, solder and indium are metals having high oxidizability. Therefore, oxidation starts immediately when it comes into contact with air. For this reason, the projection electrode 10
On the surface of No. 4, a natural oxide film 105 having a thickness of about several nm is formed.

Hereinafter, a method for joining an aluminum electrode formed on a substrate and a protruding electrode formed on an electronic component will be described with reference to FIGS. 13 (a) to 13 (d).

First, as shown in FIG. 13A, an aluminum electrode 111 formed on a wiring board 110 and an electronic component 11 are formed.
After aligning the protruding electrodes 113 formed in No. 2 with each other,
As shown in FIG. 13B, a flux 114 is applied on the wiring substrate 110. The flux 114 is a solvent for reducing and dissolving a natural oxide film formed on the surface of the bump electrode 113 to obtain a new metal surface.

Next, as shown in FIG. 13C, the electronic component 112 is brought close to the wiring
Is brought into contact with the aluminum electrode 111, and in a state where both are in contact with each other, heat is applied to the projecting electrode 113 at a temperature equal to or higher than the melting point of the material constituting the projecting electrode 113. When solder is used as the material of the protruding electrode 113, heat of about 230 ° C. is applied, and when indium is used, heat of about 160 ° C. or more is applied. By this heating, the applied flux 11
4 is in an active state, the natural oxide film formed on the surface of the bump electrode 113 is reduced and dissolved, and the bump electrode 113 and the aluminum electrode 111 are joined.

Next, as shown in FIG. 13D, the flux 114 is removed by washing.

[0011]

By the way, with the miniaturization of the semiconductor element and the miniaturization and the narrow pitch of the protruding electrode and the aluminum electrode, the following method is used for joining the electrodes. Problems occur.

First, there is a problem that the native oxide film formed on the surface of the bump electrode is not completely removed by the flux. That is, the problem is that most of the natural oxide film is removed, but the natural oxide film slightly remains in the minute surface region of the bump electrode. Even if a slight natural oxide film remains on the surface of the protruding electrode, there is no particular problem when the bonding area between the electrodes is relatively large, but when the electrode becomes finer and the bonding area between the electrodes becomes smaller. As a result, adverse effects such as an increase in connection resistance and occurrence of connection failure occur.

Second, since the reduction action of the flux is a chemical reaction, it is relatively easy to occur in a large area. However, when the electrode becomes finer and the area of the applied flux becomes smaller, the reduction action of the flux decreases. Is difficult to occur uniformly and stably.

Third, with the miniaturization and narrowing of the pitch of the electrodes, the gap between the electrodes is inevitably reduced and the gap between the electronic component and the substrate is also reduced. And a flux remains between the electronic component and the substrate. That is, when flux remains between the electronic component and the substrate,
Since the protruding electrode and the aluminum electrode are corroded, an electrical failure such as an increase in connection resistance or a connection failure occurs.

In view of the above, it is an object of the present invention to prevent a natural oxide film from being easily formed on the surface of a metal film, particularly an electrode made of metal.

[0016]

A first metal surface treatment method according to the present invention comprises: an oxide film removing step of removing a natural oxide film formed on a surface of a metal film made of a first metal; A metal forming a surface metal layer made of a metal in which a first metal contains a second metal having a valence one greater than that of the first metal on the surface of the metal film from which the natural oxide film has been removed And a layer forming step.

According to the second metal surface treatment method of the present invention, when the natural oxide film is not formed on the surface of the metal film, the first metal forming the metal film is formed on the surface of the metal film. A metal layer forming step of forming a surface metal layer made of a metal containing a second metal having a valence one greater than the first metal;

According to the first or second metal surface treatment method, the first metal forming the metal film is applied to the surface of the metal film from which the natural oxide film has been removed or the natural oxide film has not been formed. In order to form a surface metal layer made of a metal containing a second metal having a valence one greater than that of the first metal, the second metal is formed.
Since the metal emits charge and is ionized, many charges emitted from the second metal accumulate near the surface of the metal film. Therefore, the ions of the first metal diffused in the vicinity of the surface of the metal film obtain electric charges released from the second metal and are stabilized.

In the first or second metal surface treatment method, the first metal is preferably indium, and the second metal is preferably germanium.

In the first or second metal surface treatment method, the metal layer forming step preferably includes a step of forming a surface metal layer by implanting ions of the second metal into the surface of the metal film. .

In the first or second metal surface treatment method, the metal layer forming step preferably includes a step of irradiating the surface of the metal film with a second metal plasma to form a surface metal layer. .

The method of forming a first electrode according to the present invention is characterized in that an electronic component or a wiring board is formed by using an alloy of a first metal and a second metal having a valence one greater than the first metal. An electrode forming step of forming an electrode, and an oxide film removing step of removing a natural oxide film formed on the surface of the electrode by irradiating the surface of the electrode with argon ions or argon atoms in a vacuum. ing.

According to the method of forming the first electrode, the second electrode is formed of an alloy of the first metal and the second metal having a valence one greater than the first metal. Since the metal releases charges and is ionized, a large amount of charges released from the second metal accumulate near the surface of the metal film. Therefore, the ions of the first metal obtain the electric charge released from the second metal and are stabilized.

According to a second method of forming an electrode according to the present invention, there are provided an electrode forming step of forming an electrode made of a first metal on an electronic component or a wiring board, and argon ions or argon atoms on a surface of the electrode in a vacuum. By irradiating
An oxide film removing step of removing a natural oxide film formed on the surface of the electrode; and applying a first metal to the surface of the electrode from which the natural oxide film has been removed in vacuum in comparison with the first metal. A metal layer forming step of forming a surface metal layer made of a metal containing a second metal having a larger number by one.

According to the method of forming the second electrode, the surface of the electrode from which the natural oxide film has been removed is provided on the surface of the first metal constituting the electrode, the first metal having a valence one greater than the first metal. In order to form a surface metal layer made of a metal containing metal 2,
Since the second metal emits charges and is ionized, a large amount of charges emitted from the second metal accumulate near the surface of the electrode. For this reason, the ions of the first metal diffused in the vicinity of the surface of the electrode obtain electric charges released from the second metal and are stabilized.

In the method for forming the first or second electrode,
Preferably, the first metal is indium and the second metal is germanium.

In the method for forming the first or second electrode,
The metal layer forming step preferably includes a step of forming a surface metal layer by irradiating the surface of the electrode with plasma of the second metal.

[0028] A first electrode bonding method according to the present invention includes a first electrode forming step of forming an electrode on a first electronic component;
A second electrode forming step of forming an electrode on the second electronic component or the wiring board; and bonding the electrodes of the first electronic component and the electrodes of the second electronic component or the wiring board to each other after positioning. Assuming a method of joining electrodes with a joining step,
At least one of the first electrode forming step and the second electrode forming step is an alloy of a first metal and a second metal having a valence one greater than the first metal. An electrode forming step of forming an electrode comprising
An oxide film removing step of irradiating the surface of the electrode with argon ions or argon atoms to remove a natural oxide film formed on the surface of the electrode.

According to the first electrode bonding method, an electrode made of an alloy of the first metal and the second metal having a valence one larger than that of the first metal is formed. Since the metal releases charges and is ionized, a large amount of charges released from the second metal accumulate near the surface of the metal film. Therefore, the ions of the first metal obtain the electric charge released from the second metal and are stabilized.

[0030] A second electrode bonding method according to the present invention includes a first electrode forming step of forming an electrode on a first electronic component;
A second electrode forming step of forming an electrode on a second electronic component or a wiring board, and after aligning the electrode of the first electronic component with the electrode of the second electronic component or the wiring board,
Assuming a method of joining electrodes including a joining step of joining to each other, at least one of the first electrode forming step and the second electrode forming step forms an electrode made of a first metal. An electrode forming step to perform, in a vacuum, an oxide film removing step of removing a natural oxide film formed on the surface of the electrode by irradiating the surface of the electrode with argon ions or argon atoms, and in a vacuum,
A metal layer for forming a surface metal layer on the surface of the electrode from which the natural oxide film has been removed, the metal being made up of a first metal and a second metal having a valence larger by one than the first metal; Forming step.

According to the second electrode bonding method, the surface of the electrode from which the natural oxide film has been removed is provided on the surface of the first metal constituting the electrode with a valence one larger than that of the first metal. In order to form a surface metal layer made of a metal containing metal 2,
Since the second metal emits charges and is ionized, a large amount of charges emitted from the second metal accumulate near the surface of the electrode. For this reason, the ions of the first metal diffused in the vicinity of the surface of the electrode obtain electric charges released from the second metal and are stabilized.

In the first or second electrode joining method,
Preferably, the first metal is indium and the second metal is germanium.

In the first or second electrode bonding method,
The metal layer forming step preferably includes a step of forming a surface metal layer by irradiating the surface of the electrode with plasma of the second metal.

In the first or second electrode joining method,
One of the electrode formed on the first electronic component and the electrode formed on the second electronic component or the wiring board is preferably formed of gold.

The metal surface treatment apparatus according to the present invention is provided with a vacuum chamber whose inside is held in a vacuum, a sample table holding a substrate, and a flow rate controlled in the vacuum chamber. A gas introducing means for introducing the gas, and a plasma generating means for converting the gas introduced into the chamber into a plasma by the gas introducing means, and a vacuum generating chamber,
A beam gun for irradiating the substrate held on the sample stage with an ion beam or an atom beam while scanning the same.

According to the metal surface treatment apparatus of the present invention, the plasma generating means for converting the gas introduced into the chamber by the gas introducing means into one vacuum chamber and the substrate held on the sample stage are provided in one vacuum chamber. And a beam gun for irradiating while scanning an ion beam or an atom beam, by irradiating the surface of an electrode made of a first metal formed on an electronic component or a wiring substrate with argon ions or argon atoms, Removing a native oxide film formed on the surface of the electrode; and irradiating a beam of ions or atoms of a second metal onto the surface of the electrode from which the native oxide film has been removed, thereby forming a second metal on the first metal. The step of forming a surface metal layer made of a metal containing a metal can be performed continuously in a vacuum chamber.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) A metal surface treatment method according to a first embodiment of the present invention will be described below with reference to FIGS.

First, as shown in FIG. 1, a natural oxide film formed on the surface of a metal film 12 made of indium (In: group III) deposited on a substrate 11 is removed. On the surface, a metal having a higher valence than indium by one, such as germanium (Ge: IV)
A surface metal layer 13 made of a metal containing (group) is formed.

The amount of germanium contained in the surface metal layer 13 is preferably in the range of 1% to 10%. The reason is that if the content of germanium is less than 1%, the effect of suppressing the formation of a natural oxide film cannot be sufficiently obtained, and if the content of germanium exceeds 10%, it takes time to inject germanium. On the other hand, the effect of suppressing the formation of the natural oxide film is saturated.

In the first embodiment, the metal film 1
In the case where the surface metal layer 13 is formed immediately after the metal film 12 is deposited, that is, before the natural oxide film is formed, the natural oxide film is removed. Is unnecessary.

The metal forming the metal film 12 is not limited to indium, and the metal forming the surface metal film 13 may be a metal having a valence larger by one than the metal forming the metal film 12. For example, it is not limited to indium.

Hereinafter, a metal layer forming step of forming a surface metal layer 13 made of a metal containing indium and germanium on the surface of the metal film 12 made of indium will be described.

FIG. 2 shows a first method of forming a metal layer. The first method is a method of forming a metal film 1 made of indium.
The surface metal layer 13 made of a metal containing indium and germanium is formed on the surface of the metal film 12 by implanting germanium ions 14 into the surface of the metal film 2. When the surface metal layer 13 is formed only in the vicinity of the surface of the metal film 12, germanium is ion-implanted at an implantation energy of about 10 KeV to 200 KeV, and implanted so that the peak content of germanium becomes 1% or more. Good. The peak content is a value when the germanium content reaches a peak in a distribution diagram showing the distribution of the germanium content with respect to the depth from the surface of the metal film 12 as shown in FIG.

FIG. 3 shows a second method of the metal layer forming step. In the second method, the metal film 1 made of indium is used.
Plasma 1 containing germanium ions 14 on the surface of
By irradiating 5, a surface metal layer 13 made of a metal containing germanium in indium is formed on the surface of the metal film 12. The second method is plasma 1
Although it depends on the irradiation power of No. 5, the irradiation energy of the plasma is not so large, so the surface metal layer 13 is formed only on the very surface portion of the metal film 12.
As a gas for generating plasma containing germanium, germanium tetrafluoride (GeF ₄ ) can be used. The plasma can be generated by a method using high frequency application, but other methods can be used sufficiently.

Hereinafter, the surface of the metal film 12
The reason why it is difficult to form a natural oxide film on the surface of the metal film 12 when the surface metal layer 13 including a metal having a valence larger than that of the metal constituting the metal film 13 is formed will be described.

First, the mechanism by which a natural oxide film is formed on the surface of the metal film 12 will be described. When oxygen molecules adhere to the surface of the metal film 12, the attached oxygen molecules are ionized while trying to become chemically stable,
Emit charge inside. When the charges released in the metal film 12 accumulate near the surface of the metal film 12, indium constituting the metal film 12 ionizes in an attempt to neutralize the charges accumulated near the surface of the metal film 12, and 12 near the surface. The indium ions diffused in the vicinity of the surface of the metal film 12 are charged and neutralized in the process of obtaining charges.
2 is combined with oxygen ions adhering to the surface of the metal film 12 to form indium oxide, so that a natural oxide film is formed on the surface of the metal film 12.

However, if a metal having a valence one greater than indium, such as germanium, is present on the surface of the metal film 12, germanium releases charges and is ionized. Many charges released from germanium accumulate. For this reason, the metal film 12
Indium ions diffused in the vicinity of the surface of the surface become stable by gaining charge released from germanium, so that the bond between indium ions and oxygen ions is suppressed, and the formation of a natural oxide film composed of indium oxide is considered to be suppressed. .

An experiment performed to confirm that the above theory is correct will be described below. This experiment is an evaluation test performed to evaluate the oxidation resistance when a surface metal layer 13 made of a metal containing germanium in indium is formed on the surface of the metal film 12 made of indium. As an evaluation test, a first sample in which a surface metal layer 13 containing 1% germanium in indium was formed on a surface of a metal film 12 and a second sample in which the surface metal layer 13 was not formed were prepared. The first sample was subjected to an oxidation treatment for holding at a temperature of 130 ° C. for 2 hours (denoted after Ge-implanted oxidation), and was not subjected to the oxidation treatment (denoted before Ge-implanted oxidation). The second sample was subjected to an oxidation treatment (noted after oxidation without Ge implantation), and Auger analysis was performed on each sample.

FIG. 4 shows the oxygen dip profile of the metal film 12 when Auger analysis is performed on each of the above-mentioned samples, that is, the intensity (arbitrary unit: oxygen molecule) with respect to the depth (Å) from the surface of the metal film 12. Number) is shown. As apparent from FIG. 4, the thickness of the oxide film of the sample without Ge implantation after the oxidation treatment was 55 °, whereas the thickness of the oxide film of the sample with Ge implantation after the oxidation treatment was 32 °. Thus, it can be seen that the oxidation could be suppressed by about 42%. Note that the thickness of the oxide film is defined by a depth to a portion which is １ ／ of the peak value of the oxygen content.

From the results of the above evaluation tests, it was confirmed that the above theory was correct.

(Second Embodiment) Hereinafter, an electrode forming method according to a second embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to (b) and FIGS. 7 (a) and 7 (b). The electrode forming method according to the second embodiment uses the metal surface treatment method according to the first embodiment.

First, as shown in FIG. 6A, a barrier metal layer 2 is formed on a portion of the aluminum electrode 21 formed on the semiconductor substrate 20 which is not covered with the protective film 22.
3, a hemispherical projection electrode 24 made of indium is formed on the barrier metal 23, and a natural oxide film 25 having a thickness of about several nm is formed on the surface of the projection electrode 24.
Are formed.

Next, as shown in FIG. 6B, an argon beam 2 made of argon ions or argon atoms is applied to the protruding electrode 24 in a vacuum chamber.
Irradiation 6 is performed to physically remove the natural oxide film 25.

Next, as shown in FIG. 7A, while holding the semiconductor substrate 20 in a vacuum chamber, germanium tetrafluoride (GeF ₄ ) gas 27 is introduced into the chamber.
And applying high frequency power into the chamber to generate plasma containing germanium ions. As a result, the germanium ions 28 having obtained high energy repeatedly collide with the surface of the protruding electrode 24 made of indium, and the germanium ions 28
4 is doped on the surface of the bump electrode 24.
A surface metal layer 29 made of a metal containing indium and germanium is formed on the surface of the substrate. The applied voltage of the high frequency power applied to the chamber is 100 to 5
An appropriate value is about 00 W, and an appropriate flow rate of the gas introduced into the chamber is about 10 to 50 SCCM.

Is as follows.

As a method for introducing germanium ions to the surface of the projecting electrode 24, instead of irradiating the projecting electrode 24 with plasma containing germanium ions, FIG.
As shown in the above, germanium ions may be implanted into the surface of the bump electrode 24. The implantation conditions of germanium ions in this case are the same as in the first embodiment.

Next, the semiconductor substrate 20 is taken out of the vacuum chamber into the atmosphere. Even in this case, FIG.
Since the surface metal layer 29 is formed on the surface of the bump electrode 24, a natural oxide film is unlikely to be formed on the surface of the bump electrode 24 as shown in FIG.

In the second embodiment, the method of forming the protruding electrode 24 has been described. However, the method of forming an electrode according to the present invention can be applied to the case of forming an electrode having a flat shape. Of course.

Hereinafter, a metal surface treatment apparatus used in the electrode forming method according to the second embodiment will be described with reference to FIG.

Vacuum chamber 3 in which the inside is kept in a vacuum
At the bottom center of 0, a sample table 32 on which a substrate 31 is placed and which serves as a lower electrode is arranged, and the sample table 32 is grounded.

At the upper part of the vacuum chamber 30, a gas containing a metal to be injected into the surface of the protruding electrode 24 (see FIGS. 6 and 7) and having a controlled flow rate, for example, germanium tetrafluoride is introduced into the vacuum chamber 30. Gas introduction part 3 for introduction
3 are provided.

A spiral coil 34 is arranged on the outer peripheral portion of the peripheral wall of the vacuum chamber 30, and high-frequency power is applied to both ends of the coil 34 from a high-frequency power supply 35. As a result, the gas containing the metal introduced from the gas introduction unit 33 is turned into plasma, and the germanium ions contained in the plasma advance toward the grounded sample stage 32. Doping occurs by colliding with the protruding electrodes formed on the formed substrate 31.

At the upper center of the vacuum chamber 30, a beam gun 34 for irradiating the substrate 31 placed on the sample stage 32 with argon ions or argon atoms is provided. It has a drive unit for irradiating the argon atom while scanning over the entire surface of the substrate 31.

The metal surface treatment apparatus used in the electrode forming method according to the second embodiment includes a beam gun 34 for irradiating a substrate 31 placed on a sample table 32 with argon ions or argon atoms, and a beam gun 34 in a chamber 30. Since it is provided with a gas introduction unit 33 for introducing a gas and a coil 34 for converting the gas introduced from the gas introduction unit 33 into plasma, the projection is performed in a vacuum state by argon ions or argon atoms irradiated from the beam gun 34. After removing the native oxide film 25 of the electrode 24, germanium ions can be introduced into the surface of the bump electrode 24 while keeping the bump electrode 24 in a vacuum state.

(Third Embodiment) Hereinafter, an electrode forming method according to a third embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG.

In the electrode forming method according to the third embodiment, instead of introducing germanium to the surface of the protruding electrode 24 made of indium, germanium is added to the indium by 1 to 1.
The bump electrode 24 is formed of an indium-germanium alloy containing 10%.

First, as shown in FIG. 6A, the barrier metal layer 2 is formed on a portion of the aluminum electrode 21 formed on the semiconductor substrate 20 which is not covered with the protective film 22.
3 are formed on the barrier metal 23, and the protruding electrodes 24 are formed on the barrier metal 23 by the indium-germanium alloy.
To form As a method of forming the protruding electrode 24, a resist pattern having an opening in a protruding electrode forming region is formed on the barrier metal 23, and then the indium-germanium alloy is vapor-deposited over the entire surface to deposit a metal film. ,
Thereafter, when the resist pattern is lifted off, the protruding electrodes 24 are formed.

Next, as shown in FIG. 6B, in the vacuum chamber, the projection electrode 24 is irradiated with an argon beam 26 made of argon ions or argon atoms to physically oxidize the natural oxide film 25. After the removal, the semiconductor substrate 20 is taken out of the vacuum chamber into the atmosphere. By doing so, the natural oxide film 25 slightly formed after the formation of the bump electrode 24 is removed, and thereafter, the natural oxide film 25 is formed on the surface of the bump electrode 24 for the reason described in the first embodiment. Not formed.

(Fourth Embodiment) Hereinafter, as a method for bonding electrodes according to a fourth embodiment of the present invention, a method for bonding a protruding electrode formed on an electronic component and a wiring electrode formed on a wiring board will be described. Will be described with reference to FIGS. 9A and 9B.

First, the second or third electronic component 40 is placed on the electronic component 40.
The protruding electrode 41 is formed by the electrode forming method according to the third embodiment, and the flat wiring electrode 43 is formed on the wiring board 42 by the electrode forming method according to the second or third embodiment. In this case, when the protruding electrode 41 or the wiring electrode 43 is made of a material that is hardly oxidized such as Au or the like, a surface metal layer as shown in the second embodiment is formed on the protruding electrode 41 or the wiring electrode 43. No need to do. Therefore, in the electrode bonding method according to the fourth embodiment, at least one of the protruding electrode 41 and the wiring electrode 43 is a surface metal made of indium containing germanium formed by the electrode forming method of the second embodiment. It has a layer or is formed of an alloy of germanium and indium formed by the electrode forming method of the third embodiment.

Next, as shown in FIG. 9A, after aligning the protruding electrodes 41 of the electronic component 40 with the wiring electrodes 43 of the wiring board 42, the electronic component 40 is placed on the wiring board 42. Then, the protruding electrode 41 and the wiring electrode 43 are brought into contact.
Thereafter, heat at a temperature equal to or higher than the melting point of the metal constituting the protruding electrode 41 is applied to the contact portion between the protruding electrode 41 and the wiring electrode 43. The heating temperature in this case is lower than the melting point of indium of about 160 ° C. when the surface metal layer containing germanium having a thin film thickness of about 50 ° is formed on the surface of the bump electrode 41 made of indium. A slightly higher temperature, specifically, about 180 ° C. is preferable.

When heated as described above, the protruding electrode 41 is instantaneously melted. In this case, since there is no natural oxide film on the surface of the projecting electrode 41, the projecting electrode 41 easily wets and reacts with the wiring electrode 43 of the wiring board 42. It is bonded to the wiring electrode 43. The bonding atmosphere does not need to be controlled at all, and sufficiently fine bonding can be performed in the air and without flux.

In the fourth embodiment, the method of joining the projecting electrode of the electronic component to the wiring electrode of the wiring board is used. Instead, the projecting electrode of one electronic component is connected to another electronic component. The present invention is also applicable to bonding to a protruding electrode or a flat electrode of a component.

(Fifth Embodiment) Hereinafter, as a method for bonding electrodes according to a fifth embodiment of the present invention, a method for bonding a protruding electrode formed on an electronic component to a wiring electrode formed on a wiring board will be described. 10 (a), (b) and FIG.
This will be described with reference to (a) to (c).

First, the second or third electronic component 40 is placed on the electronic component 40.
The protruding electrode 41 is formed by the electrode forming method according to the third embodiment, and the flat wiring electrode 43 is formed on the wiring board 42 by the electrode forming method according to the second or third embodiment. As in the fourth embodiment, when the protruding electrode 41 or the wiring electrode 43 is made of a material that is extremely difficult to oxidize, such as Au, the protruding electrode 41 or the wiring electrode 4 is used.
It is not necessary to form a surface metal layer as shown in the second embodiment for No. 3. Therefore, in the electrode bonding method according to the fifth embodiment, the projection electrode 41 and the wiring electrode 43
At least one of them has a surface metal layer made of indium containing germanium formed by the electrode forming method of the second embodiment, or is formed by the electrode forming method of the third embodiment. It is formed of an alloy of germanium and indium.

Next, as shown in FIG. 10A, after the projecting electrode 41 of the electronic component 40 and the wiring electrode 43 of the wiring substrate 42 are aligned, the electronic component 4 on the wiring substrate 42 is
A suitable amount of the photocurable insulating resin 44 is applied to the mounting area of No. 0.

Next, as shown in FIG. 11A, after the electronic component 40 is placed on the wiring board 42 and the protruding electrodes 41 and the wiring electrodes 43 are brought into contact with each other, pressure is applied without heating. The electronic component 40 is pressed against the wiring board 42 by the tool 45.

Next, as shown in FIG. 11B, the insulating resin 44 is irradiated with ultraviolet rays 46 to cure the insulating resin 44. Thus, the protruding electrode 41 of the electronic component 40 and the wiring electrode 43 of the wiring board 42 are insulated from the insulating resin 44.
Are joined.

Next, as shown in FIG. 11C, the pressing tool 45 is raised to end the pressing.

As in the fifth embodiment, the projection electrode 4
1 and the wiring electrode 43, since there is no natural oxide film on the surface of the protruding electrode 41, sufficiently fine bonding can be performed in the air at room temperature and without flux.

In the fifth embodiment, the method of joining the projecting electrode of the electronic component and the wiring electrode of the wiring board is replaced with the method of joining the projecting electrode of one electronic component and the other. The present invention is also applicable to bonding to a protruding electrode or a flat electrode of a component.

[0082]

According to the method for treating the surface of the first or second metal, the ions of the first metal diffused near the surface of the metal film obtain electric charges released from the second metal and are stabilized.
Since the bond between the first metal and the oxygen ion is suppressed, a situation in which a natural oxide film of the first metal is formed on the surface of the metal film can be suppressed for a long time.

In the first or second metal surface treatment method, when the first metal is indium and the second metal is germanium, indium ions diffused near the surface of the metal film are released from germanium. Since the generated charge is obtained and stabilized, the bond between indium and oxygen ions is suppressed, so that a situation in which a natural oxide film of indium is formed on the surface of the metal film can be suppressed for a long time.

In the first or second metal surface treatment method, when the metal layer forming step includes the step of forming the surface metal layer by implanting ions of the second metal, the second metal can be treated with a large energy. Can be implanted to a deep portion of the metal film, so that a thick surface metal layer can be formed.

In the first or second metal surface treatment method, if the metal layer forming step includes the step of irradiating the second metal plasma to form the surface metal layer, the second metal can be reduced in energy. In this case, the surface metal layer can be formed without damaging the metal film.

According to the method of forming the first electrode, the ions of the first metal of the electrode are stabilized by obtaining the charge released from the second metal, so that the bonding between the first metal and the oxygen ions is suppressed. Therefore, a situation in which a natural oxide film of the first metal is formed on the surface of the electrode can be suppressed for a long time. In addition, since a step of irradiating the surface of the electrode with argon ions or argon atoms in a vacuum to remove a natural oxide film formed on the surface of the electrode is provided, in a step of forming the electrode, Even if a slight natural oxide film is formed due to the above, the natural oxide film is removed, so that the situation where the first metal natural oxide film is formed on the surface of the metal film is suppressed for a long time. can do.

According to the method of forming the second electrode, the ions of the first metal diffused in the vicinity of the surface of the electrode obtain electric charges released from the second metal and are stabilized. The formation of a natural oxide film of the first metal on the surface of the electrode can be suppressed over a long period of time because the bonding with the first metal is suppressed.

Therefore, the electrical conduction on the surface of the electrode formed by the first or second electrode forming method is improved.

In the method for forming the first or second electrode,
When the first metal is indium and the second metal is germanium, indium ions obtain charges released from germanium on the surface of the electrode and are stabilized,
A situation in which a natural oxide film of indium is formed on the surface of the electrode can be suppressed for a long time.

In the method for forming the first or second electrode,
When the metal layer forming step includes the step of forming the surface metal layer by irradiating the plasma of the second metal, the second metal can be injected with small energy, so that the surface metal layer can be formed without damaging the electrode. Since it can be formed, electrical conduction on the surface of the electrode is further improved.

According to the first electrode bonding method, the first metal ion of the electrode obtains the charge released from the second metal and is stabilized, so that the bond between the first metal and the oxygen ion is suppressed. Therefore, a situation in which a natural oxide film of the first metal is formed on the surface of the electrode can be suppressed for a long time. In addition, since a step of irradiating the surface of the electrode with argon ions or argon atoms in a vacuum to remove a natural oxide film formed on the surface of the electrode is provided, in a step of forming the electrode, Even if a slight natural oxide film is formed due to the above, the natural oxide film is removed, so that the situation where the first metal natural oxide film is formed on the surface of the metal film is suppressed for a long time. can do.

According to the second electrode bonding method, the first metal ions diffused in the vicinity of the surface of the electrode obtain electric charges released from the second metal and stabilize. The formation of a natural oxide film of the first metal on the surface of the electrode can be suppressed over a long period of time because the bonding with the first metal is suppressed.

Therefore, at the junction between the electrodes joined by the first or second electrode joining method, the electrical conduction becomes good, and the connection resistance is reduced. In addition, since a natural oxide film is not easily formed on the surface of the electrode, the wettability of the electrode with the other electrode to be bonded is improved, so that bonding can be performed in the air without flux.
Accordingly, fine bonding can be realized, and a flux cleaning step is not required, so that it is not necessary to control the atmosphere at the time of bonding, so that the load on an apparatus for bonding electrodes can be greatly reduced and flux cleaning equipment can be provided. It becomes unnecessary. Therefore, the cost of the equipment can be significantly reduced. Further, since fine bonding can be realized without using a flux, there is no problem such as corrosion of a metal material due to a residue of the flux, and thus the reliability of the bonded portion of the electrode is greatly improved.

In the first or second electrode joining method,
When the metal layer forming step includes the step of forming the surface metal layer by irradiating the plasma of the second metal, the second metal can be injected with small energy, so that the surface metal layer can be formed without damaging the electrode. Since it can be formed, the connection resistance at the junction of the electrodes is further reduced.

In the first or second electrode joining method,
If the electrode formed on the first electronic component or the electrode formed on the second electronic component or the wiring board is formed of gold, a natural oxide film is extremely difficult to be formed, and thus the connection resistance at the junction of the electrodes is reduced. Is further reduced.

According to the metal surface treatment apparatus of the present invention, the step of irradiating the surface of the electrode made of the first metal with argon ions or argon atoms to remove the natural oxide film formed on the surface of the electrode Then, the surface of the electrode from which the natural oxide film has been removed is irradiated with a beam of a second metal ion or atom to form a surface metal layer made of a metal in which the first metal contains the second metal. And the steps can be continuously performed in the vacuum chamber, so that the metal surface treatment in which a natural oxide film is not easily formed on the surface of the metal film can be easily and reliably performed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a metal surface treatment method according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a first method of a metal layer forming step in the metal surface treatment method according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing a second method of the metal layer forming step in the metal surface treatment method according to the first embodiment of the present invention.

FIG. 4 is a diagram showing the results of an evaluation test for evaluating the metal surface treatment method according to the first embodiment of the present invention, and shows the oxygen dip profile of the metal film when Auger analysis is performed on each sample. Is shown.

FIG. 5 is a diagram illustrating a peak content of germanium ions implanted into a surface portion of a metal film.

FIGS. 6A and 6B are cross-sectional views showing respective steps of an electrode forming method according to second and third embodiments of the present invention.

FIGS. 7A and 7B are cross-sectional views illustrating respective steps of an electrode forming method according to a second embodiment of the present invention.

FIG. 8 is a schematic sectional view of a metal surface treatment apparatus for performing a surface metal layer forming step in each embodiment of the present invention.

FIGS. 9A and 9B are cross-sectional views illustrating respective steps of an electrode bonding method according to a fourth embodiment of the present invention.

FIGS. 10A and 10B are cross-sectional views illustrating respective steps of an electrode bonding method according to a fifth embodiment of the present invention.

FIGS. 11A to 11C are cross-sectional views illustrating respective steps of an electrode bonding method according to a fifth embodiment of the present invention.

FIG. 12 is a cross-sectional view of a protruding electrode formed by a conventional electrode forming method.

13 (a) to 13 (d) are cross-sectional views showing respective steps of a conventional electrode bonding method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Substrate 12 Metal film 13 Surface metal layer 14 Germanium ion 15 Plasma 20 Semiconductor substrate 21 Aluminum electrode 22 Protective film 23 Barrier metal 24 Projection electrode 25 Natural oxide film 26 Argon beam 27 Germanium fluoride gas 28 Germanium ion 29 Surface metal layer 30 Vacuum chamber 31 Substrate 32 Sample table 33 Gas introduction unit 34 Coil 35 High frequency power supply 36 Beam gun 40 Electronic component 41 Protrusion electrode 42 Wiring board 43 Wiring electrode 44 Insulating resin 45 Press tool

Claims (15)

[Claims] An oxide film removing step of removing a natural oxide film formed on a surface of a metal film made of a first metal; and forming a first oxide film on the surface of the metal film from which the natural oxide film has been removed.
Forming a surface metal layer made of a metal containing a second metal having a valence one greater than the first metal in the metal of the first metal. Surface treatment method. 2. When a native oxide film is not formed on the surface of the metal film, a valence of the first metal constituting the metal film is higher than that of the first metal on the surface of the metal film. A method for treating a surface of a metal, comprising: a metal layer forming step of forming a surface metal layer made of a metal containing one larger second metal. 3. The method according to claim 1, wherein the first metal is indium, and the second metal is germanium. 4. The method according to claim 1, wherein the step of forming the metal layer includes a step of forming the surface metal layer by implanting ions of the second metal into a surface of the metal film. The method for treating a surface of a metal according to claim 1. 5. The method according to claim 1, wherein the step of forming the metal layer includes a step of irradiating the surface of the metal film with plasma of the second metal to form the surface metal layer. The method for treating a surface of a metal according to claim 1. 6. An electrode forming step of forming, on an electronic component or a wiring board, an electrode made of an alloy of a first metal and a second metal having a valence larger by one than the first metal; Irradiating the surface of the electrode with argon ions or argon atoms to remove a natural oxide film formed on the surface of the electrode. Forming method. 7. An electrode forming step of forming an electrode made of a first metal on an electronic component or a wiring board, and irradiating the surface of the electrode with argon ions or argon atoms in a vacuum to form a surface of the electrode. An oxide film removing step of removing a natural oxide film formed on the surface of the electrode from which the natural oxide film has been removed in a vacuum. Is 1
A metal layer forming step of forming a surface metal layer made of a metal containing a second metal that is larger than the second metal. 8. The method according to claim 6, wherein the first metal is indium, and the second metal is germanium. 9. The method according to claim 7, wherein the step of forming a metal layer includes a step of forming the surface metal layer by irradiating the surface of the electrode with plasma of the second metal. Method of forming electrodes. 10. A method for forming an electrode on a first electronic component, comprising:
An electrode forming step, a second electrode forming step of forming an electrode on a second electronic component or a wiring board, and an electrode of the first electronic component and an electrode of the second electronic component or the wiring board.
A method of joining electrodes, comprising: a joining step of joining together after positioning, wherein at least one electrode forming step of the first electrode forming step and the second electrode forming step includes a first metal and a first metal forming step. An electrode forming step of forming an electrode made of an alloy with a second metal having a valence one greater than that of the first metal; and irradiating the surface of the electrode with argon ions or argon atoms in a vacuum. An oxide film removing step of removing a natural oxide film formed on the surface of the electrode. 11. A method for forming an electrode on a first electronic component, comprising:
An electrode forming step, a second electrode forming step of forming an electrode on a second electronic component or a wiring board, and an electrode of the first electronic component and an electrode of the second electronic component or the wiring board.
In a method for bonding electrodes, the method further comprising: bonding the electrodes to each other after the alignment, wherein at least one of the first electrode forming step and the second electrode forming step is formed of a first metal An electrode forming step of forming an electrode, and an oxide film removing step of removing a natural oxide film formed on the surface of the electrode by irradiating the surface of the electrode with argon ions or atoms in a vacuum. In vacuum, the first metal has a valence of 1 on the surface of the electrode from which the natural oxide film has been removed, as compared with the first metal.
A metal layer forming step of forming a surface metal layer made of a metal containing a second metal that is larger than the second metal. 12. The method according to claim 12, wherein the first metal is indium,
The method according to claim 10, wherein the second metal is germanium. 13. The method according to claim 11, wherein the step of forming the metal layer includes a step of irradiating the surface of the electrode with plasma of the second metal to form the surface metal layer. How to join the electrodes. 14. An electrode formed on the first electronic component and one of the electrodes formed on the second electronic component or the wiring board are formed of gold. A method for bonding electrodes according to claim 11. 15. A vacuum chamber whose inside is held in a vacuum, a sample stage provided in the vacuum chamber and holding a substrate, and a gas introduction for introducing a gas whose flow rate is controlled into the vacuum chamber. Means, provided in the chamber, plasma generating means for converting the gas introduced into the chamber by the gas introducing means into plasma, and a substrate provided in the vacuum chamber and held on the sample stage And a beam gun for irradiating an ion beam or an atom beam while scanning toward the surface of the metal.