JPH09306871A - Method and apparatus for manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a high-connectability metal film by electroless plating while preventing a natural oxide film from being formed on Al electrodes of a semicon ductor device. SOLUTION: A natural oxide film on Al electrodes 2 is uniformly removed by dry etching and then plating is made in an inert atmosphere to perfectly prevent the natural oxide film on the electrodes 2 from being formed again. This eliminates the need of treatments such as Zn grain film forming to avoid forming the natural oxide film. Thus it is possible to form electrodes having a good adhesion property and high connectability by electroless plating.

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 a bonding electrode used for mounting a bare chip on a semiconductor element and an electrode forming apparatus.

[0002]

2. Description of the Related Art In recent years, in an electrode forming method for forming a bonding electrode on an Al electrode of a semiconductor element by an electroless plating method, all the forming steps are performed by a wet process.

An example of an electrode forming method by the above-mentioned conventional electroless plating method will be described below with reference to the drawings.

FIG. 5 shows a cross-sectional view of the semiconductor element in the vicinity of the Al electrode before the formation of the electrode by the electroless plating method, and FIG. 6 shows the semiconductor element shown in FIG. It is a sectional view showing a step of forming an electrode by an electrolytic plating method. 5 and 6, 1 is an Al electrode of a semiconductor element, 2 is a natural oxide film, 6 is a semiconductor element, 2
8 is a protective film, 33 is a silicon oxide film, 3 is a Zn particle film,
Reference numeral 4 is a Ni film, and 5 is an Au film.

A conventional method for forming electrodes on a semiconductor element by electroless plating will be described below with reference to FIG.

First, FIG. 6A shows a wet etching process of the Al electrode 1 formed on the semiconductor element 6. In this step, the natural oxide film 2 formed on the surface of the Al electrode 1 is removed by immersing it in an aqueous solution of phosphoric acid or sodium hydroxide. Next, FIG.
As shown in (b), a Zn particle film is formed on the Al electrode 1. The natural oxide film was removed by the process of FIG. 6 (a) described above, but if it is left as it is, the natural oxide film will be neglected again on the Al electrode 1. In order to prevent the formation, by immersing the semiconductor element in an alkaline (pH 13 to 14) solution containing Zn kept at room temperature for 30 seconds, the substitution reaction between Al and Zn ion in the solution is utilized to form Al. A Zn particle film 3 having a film thickness of about 300 to 500 Å is formed on the surface of the electrode 1.

Next, as shown in FIG. 6C, Ni plating is formed on the Al electrode 1 by electroless plating. The Zn particle film 3 formed in the above step of FIG. 6B is dissolved in the electroless Ni plating solution, whereby Zn and electroless N
After Ni is deposited by the substitution reaction of Ni ions in the i plating solution, Ni is deposited by the self-reduction reaction of the electroless Ni plating solution.
Ni is self-deposited on the upper surface and a Ni film 4 is formed. Further, as shown in FIG. 6D, an Au film is formed on the formed Ni film 4 by electroless plating. This is the Ni film 4
This is a process performed by itself to improve the poor electrical connectivity due to the presence of the Ni oxide film. For the purpose of enhancing the electrical connectivity, the Au film 5 and Ni in an electroless Au plating solution are used. It is formed by a substitution reaction with Au ions.

Incidentally, the electrodes are usually formed in the air in the steps of FIGS. 6 (a) to 6 (d).

[0009]

As described above, in order to form a metal film on an Al electrode of a semiconductor element by an electroless plating method utilizing a chemical reaction, a strong natural oxide film exists on the Al electrode surface. Therefore, in order to cause a reaction of electroless plating on the surface of the Al electrode, A
It is essential to remove the natural oxide film on the l-electrode surface.

However, in the electrode formation using the conventional electroless plating method as described above, since the natural oxide film is removed by wet etching, the etching state is not constant depending on the thickness and density of the natural oxide film. Further, since the natural oxide film is reformed on the Al electrode surface from which the natural oxide film has been removed due to oxygen in the air or dissolved oxygen in the solution or the cleaning water, the treatment step for forming the Zn particle film 3 is performed. It becomes indispensable. Further, the Zn particle film 3 has a problem that the adhesion between the Al electrode and the metal film formed by electroless plating is deteriorated.

[0011]

In order to solve the above problems, in the method of forming an electrode on a semiconductor device of the present invention, the natural oxide film on the Al electrode of the semiconductor device is removed by dry etching and controlled to an inert atmosphere. It is provided with the steps of transporting the semiconductor element under the environment and forming the metal film by the electroless plating method.

With the above structure, the present invention completely prevents the re-formation of the natural oxide film of the Al electrode by treating the plating step in an inert atmosphere and at the same time, prevents the formation of the natural oxide film. The processing steps such as the formation of the Zn particle film 3 can be omitted. This makes it possible to form an electrode by electroless plating having good adhesion and high connectivity.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A method for forming a bonding electrode on a semiconductor element according to an embodiment of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a sectional view of a semiconductor element having a bonding electrode according to the first embodiment of the present invention, and FIG. 2 is a schematic view of an apparatus for forming a bonding electrode according to the present embodiment. 3 is a process sectional view of forming a bonding electrode for a semiconductor element. 1 to 3, 1 is an Al electrode, 6 is a semiconductor element, and 7 is Ni.
A film, 8 is an Au film.

Therefore, first, the bonding electrodes in the semiconductor device shown in FIG. 1 will be described below. A Ni film is formed by deposition on an Al electrode 1 which is an external electrode of a semiconductor element by electroless plating, and an Au film is deposited on the Al film electrolessly to form a connecting projection electrode. When the semiconductor device shown in FIG. 1 is mounted on a bare chip, the above-mentioned bonding protruding electrodes are directly connected to the circuit board by flip-chip mounting or packaged in a TCP.

As described above, the semiconductor element usually has an external electrode for making an electrical connection to the outside.
When packaging in a resin package or the like, a metal wire is connected to this external electrode. As the external electrode, Al used for wiring of the semiconductor element is used. recent years,
Due to the demand for smaller and more sophisticated electronic equipment, TCP (Tape Carrier)
PKG), and further, a high-density mounting technology such as a flip-chip method for directly mounting a bare chip on a circuit board is required. These external electrodes of the semiconductor element used in the mounting technique require a protruding electrode for bonding as shown in FIG.

Next, with reference to FIGS. 2 and 3, a method of manufacturing a semiconductor device according to an embodiment of the present invention will be described in the order of steps.

First, FIG. 3A shows a dry etching step of the Al electrode 1 formed on the semiconductor element. The above process of FIG. 3A is performed in the dry etching apparatus 12 of FIG. The dry etching apparatus 12 has 17 vacuum pumps, 18 power supplies, 19 high-frequency generators, and 20 suction valves for sucking Ar or Freon sputtering gas 29.

Specifically, the semiconductor element 6 is installed on the electrode 27 of the dry etching apparatus 12, the inside of the dry etching apparatus 12 is evacuated by the vacuum pump 17, and the sputtering gas 29 of Ar or Freon is dried by the suction valve 20. It is filled in the etching device 12, the voltage of the power supply 18 is raised, and a high frequency is applied by the high frequency generator 19, while Ar
Etching is performed until the natural oxide film 2 on the Al electrode 1 is completely removed by a Freon sputtering gas 29 to expose the Al surface 11 having no oxide film.

Next, in the state shown in FIG.
Is carried. In this step, the inside of the conveying path 14 of FIG. 2 is conveyed. The transfer path 14 includes a vacuum pump 23 for drawing a vacuum in the transfer path 14 and the dry etching apparatus 1.
2 at the connecting portion between the transport path 14 and 2 and 24 second load locks at the connecting portion between the electroless plating apparatus 13 and the transport path 14.
It has a load lock and 26 leak valves for changing the transfer path 14 from a vacuum state to an inert atmosphere 9 of nitrogen or Ar gas.

Specifically, when the semiconductor element 6 is transferred from the dry etching apparatus 12, the inside of the transfer path 14 is kept in a vacuum state by the vacuum pump 23, the first load lock is opened, and the semiconductor element 6 is transferred from the dry etching apparatus 12 to the dry etching apparatus 12. Transport. When the semiconductor element 6 is transferred into the transfer path 14, the first load lock is closed, the leak valve 26 is opened, and the transfer path 14 is filled with nitrogen or Ar gas. With no pressure difference, the second load lock is opened and the semiconductor element 6 is transported to the electroless plating apparatus 13. That is, in this step, the semiconductor element 6 is moved to the next step without passing through the oxidizing atmosphere under the environment in which the inert atmosphere 9 is controlled to 1 atm by nitrogen or Ar gas.

Further, as shown in FIG. 3C, a Ni film is formed by electroless plating. This step is performed in the electroless plating apparatus 13 shown in FIG. And electroless plating apparatus 1
Reference numeral 3 has a management device 21 for controlling the gas pressure and temperature of nitrogen or Ar gas for making the inert atmosphere 9 constant, and a plating chamber 22.

Concretely, 2 to 5 in an electroless Ni plating bath 10 at 90 ° C. installed in an environment in which the inside of the electroless plating apparatus 13 is controlled to an inert atmosphere 9 of 1 atm by nitrogen gas.
A Ni film 8 having a thickness of 0.7 to 1.2 μm is formed on the Al surface 11 of the Al electrode 6 on the semiconductor element 6 which has no oxide film by immersion for a minute. That is, in this step, immediately after the semiconductor element was immersed in the electroless Ni plating bath 10, Al without an oxide film was formed.
There is a Ni precipitation reaction due to a substitution reaction between the surface 11 and Ni ions in the electroless Ni plating solution, and the Ni surface thus deposited is affected by the action of the reducing agent in the electroless Ni plating solution.
Causes an autodeposition reaction to grow the Ni film 7. The above steps are performed in the apparatus shown in FIG.

Next, as shown in FIG. 2D, an Au film 8 is formed by electroless plating. In this process, A
Since the Ni film 7 is formed on the 1-electrode 1, the re-formation of the natural oxide film on the Al electrode 1 is completely prevented.
Processing in the atmosphere is also possible. In addition, the Ni film 7 is electroless A for the purpose of preventing deterioration of connectivity due to oxidation in the atmosphere.
The Au film 8 is formed on the Ni film 7 in the u plating bath 34 in the range of 0.1 to 0.1.
2 μm is formed.

As described above, according to the present embodiment, the natural oxide film on the Al electrode is removed by dry etching, and the metal film is formed by electroless plating in an environment controlled to an inert atmosphere. Since it is possible to prevent the formation of Al, it is possible to extremely easily form a highly adherent metal film on the surface of the Al electrode.

(Second Embodiment) The second embodiment of the present invention will be described below.
The method of manufacturing the semiconductor element in the above will be described with reference to the drawings.

FIG. 4 is a sectional view showing the manufacturing process of the semiconductor device according to the present embodiment based on the apparatus.

First, as shown in FIG. 4A, the Al electrode formed on the semiconductor element is dry-etched.
This dry etching apparatus includes a vacuum pump 17
Power source, 19 high-frequency generators, and 20 suction valves for sucking Ar or Freon sputter gas 29.

Specifically, the electrode 2 of the dry etching apparatus
7, the semiconductor element 6 is installed, the inside of the dry etching apparatus 12 is evacuated by the vacuum pump 17, and the suction valve 20
Further, Ar or Freon gas is filled in the dry etching apparatus 12, and the natural oxide film 2 on the Al electrode 1 is completely removed by the Ar or Freon sputter gas 29 while increasing the voltage of the power supply 18 and applying a high frequency by the high frequency generator 19. Etching is performed until the Al surface 11 having no oxide film is exposed. A transport container 30 for transporting the semiconductor element is installed in this dry etching apparatus.

Next, FIG. 4B shows a step of moving the semiconductor element 6 to the transfer container 30. After the dry etching is completed, the inside of the dry etching apparatus and the transfer container 30 are brought to an inert atmosphere 9 of 1 atm with nitrogen or Ar gas, the semiconductor element 6 is moved to the transfer container 30, the first gate is closed, and the inside of the transfer container 30 is closed. Seal tightly.

Subsequently, as shown in FIG. 4 (c), electroless Ni
Perform the plating process. After the transport container 30 is transported from the dry etching apparatus to the electroless Ni plating bath 10 installed in the atmosphere, the transport container 3 is transported in the electroless Ni plating bath 10.
The first gate 31 and the second gate 32 of 0 are opened, and the transfer container 30 is filled with the electroless Ni plating solution. Since the transport container 30 is released in the electroless Ni plating bath 10, the oxide-free Al surface 11 of the semiconductor element 6 is not oxidized by oxygen in the atmosphere, and the electroless Ni plating bath 1 at 90 ° C.
By immersing the Al electrode 6 on the semiconductor element 6 in the atmosphere for 2 to 5 minutes, the N-layer of 0.7 to 1.2 μm is formed on the Al surface 11 without the oxide film.
The i film 7 is formed.

Then, as shown in FIG. 2D, electroless Au is used.
Perform the plating process. In this step, since the Ni film 7 is formed on the Al electrode 1, there is no re-formation of the natural oxide film on the Al electrode 1, and therefore the treatment in the atmosphere is possible. Therefore, in order to prevent the Ni film 7 from deteriorating the connectivity due to the oxidation in the atmosphere, the Ni film 7 is Ni in the electroless Au plating bath 34.
An Au film 8 having a thickness of 0.1 to 0.2 μm is formed on the film 7.

From the above, Al is formed by dry etching.
By removing the natural oxide film on the electrode and transporting it to the electroless plating solution in a container controlled to an inert atmosphere, and then forming a metal film by electroless plating, even in an electroless plating bath installed in the atmosphere , A metal film having high adhesiveness can be formed on the surface of the Al electrode.

Further, according to the present embodiment, since the semiconductor device which has been dry-etched is transported by using the transport container, the plating apparatus itself can be a conventionally used one. It is not necessary to create a new device in which the dry etching device and the plating device are integrated as in the case of the above-described first embodiment.

In the first and second embodiments, the Ni film 7 is formed on the Al electrode 1 in the electroless plating process.
However, the Ni film 7 may be a Cu film, a Pd film, or an Au film.

[0036]

According to the present invention, Al is formed by dry etching.
By removing the native oxide film on the electrode uniformly and treating the plating process after dry etching in an inert atmosphere,
The re-formation of the natural oxide film of the l-electrode is completely prevented, and the process for forming the Zn particle film 3 for preventing the formation of the natural oxide film becomes unnecessary. This makes it possible to form an electrode by electroless plating having good adhesion and high connectivity.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of an apparatus for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 3 is a sectional view of a semiconductor element manufacturing process in the embodiment of the present invention.

FIG. 4 is a sectional view of a semiconductor element manufacturing process in the embodiment of the present invention.

FIG. 5 is a sectional view of a conventional semiconductor device.

FIG. 6 is a sectional view of a manufacturing process of a semiconductor element by a conventional electroless plating method.

[Explanation of symbols]

 1 Al electrode 2 Natural oxide film 3 Zn particle film 4 Ni film 5 Au film 6 Semiconductor element 7 Ni film 8 Au film 9 Inert atmosphere 10 Electroless Ni plating bath 11 Al surface without oxide film 12 Dry etching device 13 Electroless Plating device 14 Transport path 17 Vacuum pump 18 Power supply 19 High frequency generator 20 Intake valve 21 Management device 22 Plating chamber 23 Vacuum pump 24 First load lock 25 Second load lock 26 Leak valve 27 Electrode 28 Protective film 29 Sputter gas 30 Transport container 31 First Gate 32 Second Gate 33 Silicon Oxide Film 34 Electroless Au Plating Bath

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/92 604D 604Z 604E

Claims (2)

[Claims] 1. A step of removing a natural oxide film existing on the surface of an Al electrode formed on a semiconductor element by dry etching, and a semiconductor element having the Al electrode from which the natural oxide film is removed, in an inert atmosphere environment. A method of manufacturing a semiconductor device, which comprises a step of transporting the semiconductor element below, and a step of depositing a metal film on the surface of the Al electrode of the semiconductor element by an electroless plating method in the inert atmosphere environment after the transport. 2. A dry etching means for removing a natural oxide film existing on the surface of an Al electrode formed on a semiconductor element, and the Al electrode from which the natural oxide film is removed in the semiconductor element under an inert atmosphere environment. An apparatus for manufacturing a semiconductor element, comprising: a means for depositing a metal film on the surface by electroless plating; and a means for transporting the semiconductor element from the dry etching means to the means for depositing the metal film in an inert atmosphere environment.