JP2002334896A - Method for forming bump electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of the stripping of a resin pattern by etching taking a long time, causing lowering of the throughput, when a thick resin pattern is formed and when bump electrode of larger height are formed by electroless plating. SOLUTION: A reliable method for forming bump electrodes having larger height at low cost can be provided, by forming a ring-like resin pattern on pats, forming bump electrodes through electroless plating, and then peeling off the ring-like resin pattern by etching, thereby peeling of the resin pattern from the thickness direction by etching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a bump electrode on a pad of a semiconductor chip in a semiconductor wafer.

[0002]

2. Description of the Related Art In recent years, flip chip mounting in which a semiconductor chip is directly mounted on a substrate in a face-down manner has been developed in order to reduce the size of a semiconductor package and mount the semiconductor chip on a motherboard with high density. Above all,
The market demand for inexpensively manufacturing narrow and high-pitch protruding electrodes used for ACF (Anticonductive Film) mounting is in full swing.

FIG. 5 shows a method of manufacturing a protruding electrode by a conventional electroless plating method. FIG. 6 shows a top view and a sectional view of adjacent protruding electrodes formed by a conventional electroless plating method. Shows a method for manufacturing a bump electrode by another conventional electroless plating method.

In a semiconductor wafer shown in FIG. 5A, elements are formed on a wafer 1 (not shown), a pad 3 for an external electrode is formed, and the element and the pad 3 are protected by a passivation film 2. I do.

[0005] Next, in the protruding electrode forming step shown in FIG. 5B, the surface of the pad 3 is soft-etched, the aluminum on the surface of the pad 3 is replaced with zinc by zincate treatment, and electroless nickel plating is performed. Electrolytic gold plating is performed to form the protruding electrodes 5.

FIG. 6A is a top view of adjacent protruding electrodes. The projecting electrode 5 is formed on the pad 3 by an electroless plating method.

FIG. 6B is a sectional view taken along the line AA ′ of FIG. 6A. The protruding electrode 5 is formed on the pad 3 formed on the wafer 3. In the electroless plating method, the plating is isotropically deposited.
It is deposited in the plane direction on the passivation film 2. Therefore, when the height of the protruding electrode is increased, the space between adjacent pads is reduced, so that there has been a problem that the height of the protruding electrode cannot be increased.

The semiconductor wafer shown in FIG.
Description is omitted because it is the same as (a).

Next, in a pattern forming step shown in FIG. 7B, a photosensitive polyimide which can withstand an electroless plating solution in a later step is thickly coated by a spin coating method, exposed, developed, and cured. Then, a pattern 10 having the pad 3 opened is formed.

Next, in the protruding electrode forming step shown in FIG. 7C, the surface of the pad 3 is soft-etched, the aluminum on the surface of the pad 3 is replaced with zinc by zincate treatment, and electroless nickel plating is performed. Electrolytic gold plating is performed to form the bump electrodes 5.

Next, in a peeling step shown in FIG. 7D, polyimide serving as a mask for electroless plating is peeled with hydrazine. However, when polyimide is thickly applied in order to produce a tall protruding electrode, there has been a problem that it takes a long time to peel off.

[0012]

However, the above-described method of manufacturing a protruding electrode by the electroless plating method has the following problems. That is, since the electroless plating grows isotropically, when a protruding electrode having a high height is formed, the electroless plating is deposited in the horizontal direction at the same time as the height direction. There were problems such as being unable to respond to putting. Also, in the case of the method of forming a pattern with a thick-film resist and forming a protruding electrode having a high height, it takes a long time to peel off since a photosensitive resin having chemical resistance that can withstand an electroless plating solution is applied thickly. There was a problem.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an inexpensive manufacturing method and a structure of a narrow pitch and high projection electrode used for ACF mounting and the like. It is.

[0014]

In order to achieve the above object, the present invention relates to a method of manufacturing an electrode disposed on a pad of a semiconductor wafer, the method comprising the steps of: A ring forming step of forming a ring-shaped organic insulating film, an electrode forming step of forming electrodes on the pad by electroless plating, and a step of peeling the ring-shaped organic insulating film. Things.

The ring forming step includes a resin coating step of coating a photosensitive resin on the semiconductor wafer, an exposure step of exposing a pattern of the ring-shaped organic insulating film, and a step of developing the photosensitive resin. And a developing step.

Further, the electrode forming step includes an electroless nickel step of depositing nickel and an electroless gold step of depositing gold on the nickel.

Further, in the ring forming step, the thickness of the ring-shaped organic insulating film is made smaller than its height.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method and structure for manufacturing a bump electrode according to the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram for explaining a process of manufacturing a bump electrode according to an embodiment of the present invention. FIG. 2 is an explanatory view illustrating a ring forming step in the embodiment of the present invention. FIG. 3 is an explanatory diagram for explaining a projecting electrode forming step in the embodiment of the present invention. FIG. 4 is an explanatory view showing the structure of the bump electrode according to the embodiment of the present invention. The same members as those in the prior art are denoted by the same reference numerals.

First, the semiconductor wafer shown in FIG. 1A is the same as that of the above-mentioned prior art, and the description is omitted.

In the ring forming step shown in FIG. 1B, a ring 4 made of an organic insulating film is formed so as to surround the pad 3.

In the protruding electrode forming step shown in FIG. 1C, a protruding electrode is formed on the pad 3 inside the ring 4 by an electroless plating method.

In the ring peeling step shown in FIG. 1D, the organic insulating film forming the ring is peeled. Since the organic insulating film has a ring shape, the organic insulating film is peeled off not only in the height direction but also in the thickness direction of the ring, so that the organic insulating film is quickly peeled off. For example, when an organic insulating film made of polyimide is formed under the conditions shown in FIG.
Etching peeling was possible in about 20 minutes with a hydrazine solution at 0 ° C. On the other hand, in the case of an organic insulating film made of polyimide formed by a conventional method, it took about 50 minutes to remove the 10-micron thick film by etching.

FIG. 2 illustrates the ring forming step shown in FIG. 1B of the present invention. Since the semiconductor wafer of FIG. 2A is the same as that of the above-described conventional technology, the description is omitted.

In the resin coating step shown in FIG. 2B, a photosensitive resin 6 having photosensitivity and capable of withstanding the subsequent electroless plating step is thickly applied to the surface of the wafer 1 by spin coating, printing, or the like. I do. For example, a positive type photosensitive resin CRC-8300 manufactured by Sumitomo Bakelite Co., Ltd.
By spin coating under the condition of 0 second, a thickness of about 16 microns was obtained.

In the exposure step shown in FIG. 2C, the photosensitive resin 6 is exposed so that a ring pattern 7 can be formed. In the case of the CRC-8300, the exposure amount is about 400 mJ /
Exposure in cm ² .

In the developing step shown in FIG. 2D, the photosensitive resin 6 is developed, and the remaining photosensitive resin is thermally cured to form the ring 4. In the case of the above-mentioned CRC-8300, development was carried out with an alkali developer, washed with pure water, and then spin-dried. Then 3
Cured at 20 ° C. for 30 minutes at an oxygen concentration of 10 ppm or less, a ring 4 having a height of about 10 microns and a width of about 4 microns was formed.

FIG. 3 illustrates the bump electrode forming step of the present invention shown in FIG. 1 (c). The completion of the ring in FIG. 3A is the completion of the ring forming step in FIG.

The electroless nickel process shown in FIG.
The pad 3 is soft-etched, the aluminum on the surface of the pad 3 is replaced with zinc by zincate treatment, and electroless nickel plating is performed to form nickel 8 on the inside of the ring 2.
To form For example, aluminum is soft-etched with an aluminum etching solution CleanPac manufactured by Packtech, Germany, and zinc-substituted with a zincate treatment solution ZincPac manufactured by Packtech, and the electroless nickel plating solution NicPac manufactured by Packtech is used. After use, nickel 8 was deposited. By plating at a liquid temperature of 90 ° C. for about 30 minutes, nickel 8 having a thickness of about 10 microns is formed.
Was precipitated.

In the electroless gold process shown in FIG. 3C, gold 9 is deposited on the nickel 8 with an electroless gold plating solution to form the protruding electrodes 5. For example, 0.05 μm of gold 9 was deposited by plating at 90 ° C. for about 10 minutes using the electroless plating solution IGPac manufactured by Pactech.

FIG. 4 shows the structure of adjacent protruding electrodes of the present invention. FIG. 4A is a top view of adjacent protruding electrodes.
Although the protruding electrodes formed by the electroless plating are isotropically deposited, the protruding electrodes 5 do not precipitate around the pads 3 since the deposition in the direction between the pads is prevented by the ring made of the organic insulating film at the time of plating deposition.

FIG. 4B is a sectional view taken along the line AA ′ of FIG. A pad 3 is formed on the wafer 1, and an outer peripheral portion of the pad 3 is protected by a passivation film 2. The ring formed during the formation of the protruding electrode allows the protruding electrode 5 to be formed.
Are formed in the height direction. Therefore, even if the adjacent pad 3 becomes narrow, a protruding electrode having a high height can be formed.

[0032]

As described above, according to the method for manufacturing a bump electrode of the present invention, the bump electrode can be provided by an inexpensive electroless plated bump deposited in the height direction.

The ring can be easily formed by using a photosensitive resin for forming the ring.

Also, by using electroless nickel plating and electroless gold plating as the electroless plating solution, nickel plating can be easily deposited on the pad, and gold can be deposited to prevent oxidation.

Further, since the width of the ring is smaller than the thickness, the ring can be easily peeled.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a semiconductor wafer, a ring forming step, a projecting electrode forming step, and a ring peeling step in a process of manufacturing a projecting electrode according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a semiconductor wafer, a resin application step, an exposure step, and a development step in a ring formation step according to the embodiment of the present invention.

FIG. 3 is an explanatory view showing a completed ring, an electroless nickel process, and an electroless gold process in a projecting electrode forming process according to the embodiment of the present invention.

FIG. 4 is an explanatory view showing a top view and a cross-sectional view of adjacent protruding electrodes in the structure of the protruding electrodes according to the embodiment of the present invention.

FIG. 5 shows a semiconductor wafer,
It is explanatory drawing which shows a projection electrode formation process.

FIG. 6 is an explanatory view showing a top view and a cross-sectional view of adjacent projecting electrodes in the structure of a conventional projecting electrode.

FIG. 7 shows a semiconductor wafer,
It is explanatory drawing which shows a pattern formation process, a projection electrode formation process, and a peeling process.

[Explanation of symbols]

 Reference Signs List 1 wafer 2 passivation film 3 pad 4 ring 5 protruding electrode 6 photosensitive resin 7 ring pattern 8 nickel 9 gold 10 pattern

Claims (4)

[Claims] 1. A method of manufacturing an electrode disposed on a pad of a semiconductor wafer, comprising: a ring forming step of forming a ring-shaped organic insulating film on a periphery of the pad on which the electrode is disposed; A method for manufacturing a protruding electrode, comprising: an electrode forming step of forming an electrode thereon by an electroless plating method; and a step of peeling off the ring-shaped organic insulating film. 2. The ring forming step includes a resin coating step of coating a photosensitive resin on the semiconductor wafer, an exposure step of exposing a pattern of the ring-shaped organic insulating film, and developing the photosensitive resin. The method of claim 1, further comprising a developing step. 3. The method according to claim 1, wherein the electrode forming step includes an electroless nickel step of depositing nickel and an electroless gold step of depositing gold on the nickel. A method for manufacturing a bump electrode. 4. The method according to claim 1, wherein in the ring forming step, the thickness of the ring-shaped organic insulating film is made smaller than its height.