JPH0772357B2 - Electroplating method - Google Patents

Description

The present invention relates to an electroplating method for forming a plating film on a plate-shaped member to be plated.

[Conventional technology]

2. Description of the Related Art Conventionally, there is known a hybrid infrared image sensor in which bump electrodes made of a soft metal such as indium are formed on a photoelectric conversion semiconductor chip and a signal processing silicon IC semiconductor chip, and the bump electrodes are faced and thermocompression bonded.
The bump electrodes are typically made of a soft metal such as indium, and are arranged in a diameter of 25 μm, a height of 10 μm, and a pitch of 50 μm, for example, 64 × 64 pieces. In addition, the formation method is such that a resist film having an opening is formed on the plating base metal film, and then the bump electrode is plated and grown only on the opening using the plating base metal film as a cathode, and then the unnecessary resist film and the plating are used. The underlying metal film is removed.

[Problems to be Solved by the Invention]

However, in the conventional plating film formation for the bump electrode, as shown in FIG. 3, since the resist film 3 formed on the plating base metal 2 of the substrate 1 is hydrophobic, the opening thereof is exposed to the plating solution 5. It is hard to get wet sufficiently, bubbles 7 remain in the openings, and defective plating is likely to occur. As a matter of course, the defective plating portion becomes a pixel defect and impairs the performance of the image sensor. In particular, the larger the height of the bump to be formed, the larger the resist film thickness, and the finer the element, the smaller the opening diameter. Therefore, the plating failure due to poor wettability is remarkable.

Furthermore, the addition of a surface-active material improves wettability to some extent, but introduces impurities into the plated film, which deteriorates the thermocompression bonding property for reasons such as increasing the hardness of the plated bump. Not applicable to.

In this way, the occurrence of defective bump plating has been an obstacle to increasing the pixel size and miniaturization of the sensor.

An object of the present invention is to solve the above-mentioned drawbacks and to provide an electroplating method which improves wettability and eliminates the generation of defective bumps.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the present invention evacuates a plating tank in which a member to be plated and an anode plate are arranged inside to be evacuated, and subsequently, in a plating solution supplied to the inside of the plating tank. After immersing the member to be plated, electroplating is started.

[Action]

The member to be plated has a resist film formed with an opening, but in the electroplating method of the present invention, when the plating solution is supplied to the member, it is in a vacuum. No gas remains and no bubbles remain. Therefore, the plating solution sufficiently contacts the plating base metal in the opening, and the wettability can be improved without requiring any surface active material or the like, so that a good bump without defects can be formed.

〔Example〕

Next, an embodiment in which the present invention is applied to In bump plating will be described with reference to the drawings.

1 (a) to 1 (c) are views showing a process of forming In bumps to which the electroplating method of the present invention is applied, and FIG. 2 shows an example of a plating apparatus used for carrying out this. FIG. Here, the member to be plated for forming the plated film is a flat plate-shaped substrate 1 as shown in FIG.
The plating base metal 2 is formed on the resist film 3 and the resist film 3 having the openings 4 formed thereon is used as a mask.

In FIG. 2, first, the plating tank 11 and the plating solution tank 16
The valves 17a, 17b, 17c, 17d provided in the pipes that connect the two are closed, the plating solution is stored in the plating solution tank 16, and the plating target member 12 serving as the cathode and the anode plate made of indium are placed inside the plating tank 11. 13 and 13 are arranged to face each other. Next, by switching the vacuum pump 15 or the valve 17e of the pipe communicating with the atmosphere, the vacuum pump 15
The inside of the plating tank 11 is evacuated by. The plating tank 11 is a closed container that can maintain a vacuum. Subsequently, the valves 17a and 17c are opened, the plating solution 5 is introduced from the plating solution tank 16 by the solution feed pump 14, and the member 12 to be plated and the anode branch 13 are immersed in the plating solution 5. Here, as shown in FIG. 1 (b), the plating solution 5 enters the opening 4 of the resist film 3 of the member to be plated and sufficiently contacts the plating base metal. Then, by applying a current from the plating power source 18, the In plating bump 6 is formed as shown in FIG. 1 (c).

After filling the plating bath 11 with the plating solution 5, the valve is normally closed.
It suffices to switch the 17e and introduce the atmosphere, but by continuing to draw a vacuum during plating, the control of the liquid tank pump becomes complicated, but the bubbles generated during plating can be effectively removed.

After the plating is completed, the valves 17a and 17c are closed, the valves 17b and 17d are opened, and the plating solution is returned to the plating solution tank 16 by the solution sending pump 14, so that the next member to be plated may be replaced. According to the method of the present invention, as shown in FIG. 3, no air bubbles remain and no bump plating failure occurs.

It is needless to say that the above embodiment is just an example and can be similarly applied to bump plating other than indium.

〔The invention's effect〕

As described above, according to the present invention, bubbles do not remain in the openings for forming bump plating, and thus bumps having no plating defect can be formed.

[Brief description of drawings]

1 (a) to 1 (c) are enlarged views of a member to be plated for explaining the process of forming In bumps to which the electroplating method of the present invention is applied, and FIG. 2 is a plating used for carrying out this. FIG. 3 is a partial sectional view showing an example of the device, and FIG. 3 is a view showing an In bump shape by a conventional method. 1 ... Substrate, 2 ... Undercoat metal 3 ... Resist film, 4 ... Aperture 5 ... Plating liquid, 6 ... In plating bump 7 ... Bubble, 11 ... Plating tank 12 ... Plated member , 13 …… Anode plate 14 …… Liquid feeding pump, 15 …… Vacuum pump 16 …… Plating liquid tank, 17a, 17b, 17c, 17d, 17e …… Valve 18 …… Plating power supply

Claims (1)

[Claims] 1. A plating tank in which a member to be plated and an anode plate are arranged inside to face each other is evacuated to a vacuum, and then the member to be plated is immersed in a plating solution supplied to the inside of the plating tank. After that, the electroplating method is characterized in that the electroplating is started.