JPH05291260A - Forming method for bump - Google Patents

Abstract

PURPOSE:To inexpensively form bumps having a fast forming time and uniform height only in many types of semiconductor integrated circuit chips of non- defective product by using a heater block vertically movable in a bonding tool. CONSTITUTION:A protrusion electrode 3 for connecting an electrode pad 4 on a semiconductor integrated circuit chip 5 to a substrate and a semiconductor device (package) is easily formed by using a heater block 2 vertically movable in a bonding tool 1. For example, the electrode 3 is formed by punching a material of Au, Sl, solder, etc., of a ribbon state having a thickness of about 10-50mum by the tool 1. Further, for example, the formed electrode 3 is formed by heating the electrode 3 moved down in the tool 1 by the vertically movable block 2.

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 projection electrode used when mounting a semiconductor integrated circuit chip on a semiconductor device and a semiconductor substrate.

[0002]

2. Description of the Related Art In recent years, in the field of semiconductor integrated circuits, large-scale integration has been promoted, and the number of pads for supplying input / output signals and power supply voltage has been increasing more and more, while operating speed has been accelerated. is there.

In mounting a semiconductor integrated circuit that is highly integrated as described above, the pad pitch is being reduced as the number of pads is increased. However, in the conventional wire bonding technique, the pitch is limited to 100 μm, and the increase in the time required for wire bonding due to the increase in the number of pads is also a serious problem.

Therefore, in order to solve such a problem, metal foil wiring is formed on a long flexible film substrate, and this is connected to a semiconductor integrated circuit chip having a protruding electrode formed on an electrode pad. TAB (Tape Autom)
The aged bonding technology has been proposed and is being developed.

However, although there are several methods of forming the bump electrodes (bumps) used for connecting the film carrier and the semiconductor integrated circuit chip, there is no method for forming the bump electrodes which is easy, low cost and compatible with a wide variety of products.
Typical examples of the bump forming method are (1) plating bump method, which is a plating bump method in which a gold (Au) bump or a solder bump by evaporation is formed on the electrode pad through a multi-layer barrier metal by plating. FIG. 6 is a process diagram showing a plating bump method process.

FIG. 6A shows a metal film deposition step. In FIG. 6B, a photolithography step for forming bumps is performed to form a plating pattern with a photoresist. Using the metal film as one electrode, bumps are formed in the pattern by the electrolytic plating method shown in FIG. 6C. And FIG.
The unnecessary photoresist in (d) is removed, and FIG.
In (e), a new photoresist is applied on the bumps,
A pattern for etching the barrier metal is formed. In this photolithography process, mask exposure is
Since it is performed via bumps, high resolution cannot be obtained. The resist pattern includes bumps and is formed so as to cover the periphery of the bumps. Using this resist pattern as a mask, all exposed barrier metal on the wafer is removed by etching, and finally the resist pattern is removed in FIG. 6 (f).

As described above, in the plating bump method, since bumps are formed during the process, it is difficult to form bumps easily, and bumps are formed regardless of whether they are non-defective products or defective products, resulting in high time and cost. .. (2) Transfer bump method

FIG. 7 is a process diagram of a bump forming method by a transfer method. When the aluminum electrode 14 of the chip 13 and the bump 15 on the bump forming substrate 16 are aligned, the chip 13 and the bump 15 are heated / pressurized to form an Au / Al alloy, and then the chip 13 is pulled up. The bumps on the bump forming substrate 16 are separated and joined to the aluminum electrodes 14 on the chip 13. However, as the number of bumps to be transferred increases, the pad pitch becomes narrower and it becomes difficult to align the bumps and pads. (3) Ball bump method

FIG. 8 is a process chart showing a method of forming bumps by wire bonding type ball bonding. A ball is formed on the Au wire 18 at the tip of the capillary 17, and this is bonded onto the aluminum electrode 19 while applying ultrasonic waves. Next, in the bonded state, the capillary 17 is slid as it is, and the Au wire is cut by the neck of the ball 18.

The problem with this method is that it takes time to form bumps for the number of electrodes and that bumps are irregular. If the chip has 300 electrodes, it takes 60 seconds. For this reason, it is suitable for processing a very small number of chips, but it is not suitable for mass production at least, and the bonding speed is always constant even after mass production, so the bump forming cost is not reduced. Further, when the bumps are formed, they may be left at a high temperature for at least several tens of seconds, so that it is possible that purple plague is generated, and wire remains are generated, which makes it difficult to form uniform bumps. (4) Mesa bump method

FIG. 9 is a sectional view of the mesa bump, 70 μ.
Etching a copper foil of m thickness, L at the tip of the lead
The protrusion 20 is formed in a region of the SI chip that is in contact with the aluminum electrode. That is, only the tips are left in the portion corresponding to the inner leads 21, and the other portions are etched by about 35 μm.

A feature of the mesa bump is that it is not necessary to process the aluminum electrode of the LSI chip in order to form the bump on the lead side. However, there are problems such as low bonding strength per unit bonding area and extremely high parallelism required.

[0013]

As described above, when bumps for film carrier connection are formed on the electrode pads on the semiconductor integrated circuit chip, bump formation is easy and stable bumps are formed only on non-defective chips. But it was impossible. The present invention is different from the above bump forming method in the forming method, and an object thereof is to easily supply stable bumps.

[0014]

According to the present invention, a bonding tool having a heater block capable of moving up and down is used in the tool, and Au, Al, solder or the like having a thickness of 10 μm to 50 μm is used.
The ribbon-shaped metal thin film is punched out by pressing the ribbon-shaped metal thin film on the electrode pad of the semiconductor integrated circuit chip with a bonding tool heated by a heater block. At this time, the positioning of the bonding tool to the electrode pad of the semiconductor integrated circuit chip is performed with high accuracy by a position recognition camera.

After the bumps are formed on the electrode pads of the semiconductor integrated circuit chip, the heater block in the tool descends to heat the bumps, thereby adjusting the shape of the bumps formed on the electrode pads.

[0016]

According to the above bump forming method, even if the type of the semiconductor integrated circuit chip on which the bump is formed is changed, only the good semiconductor integrated circuit chip after the characteristic evaluation can be inexpensively and easily provided with the bump formed uniformly. It is possible to form.

[0017]

Embodiments of the present invention will be described in detail below with reference to the drawings.

1a to 1e are sectional views of a bump forming method according to an embodiment of the present invention. The position of the electrode 4 is registered in the machine body in advance by the position recognition camera 22. In Fig. 1a, a bonding tool 1 having a heater block 2 which can be moved up and down is located above the positioned electrode 4, and at this time, the heater block should be positioned deeper than the metal thin film contact surface of the bonding tool. Is characterized by. Then, between the bonding tool 1 and the electrode 4, there is a ribbon-shaped metal thin film 3. In Fig. 1b, the bonding tool 1 heated by the internal heater block descends and contacts the metal thin film 3. Next, as shown in Fig. 1c, when the bonding tool 1 continues to descend even after the contact with the metal thin film 3, it adheres to the metal thin film 3 and the punching electrode 4. After bonding the bonding 1 to the electrode 4, the heater block 2 descends,
By pressing the metal thin film 3 adhered to the electrode 4, the adhesive strength between the electrode 4 and the metal thin film 3 is increased and the shape is shaped. Finally, the heater block 2 rises to complete bump formation, and the bonding tool 1 moves to the next electrode position to form bumps. FIG. 2 is a perspective view of an embodiment of the present invention. Next, a second embodiment of the present invention will be described.

3A to 3D are sectional views of the second embodiment. A bump is formed by plating a low melting point solder on the transparent substrate 6, for example, an alumina substrate having good thermal conductivity, at the same position as the electrode 4. Keep it.

This substrate is placed above the semiconductor integrated circuit chip 5 with the bump forming surface as the back surface. At this time, since the substrate 6 is transparent, the bumps formed on the substrate 6 and the electrodes 4 of the semiconductor integrated circuit chip 5 are aligned with each other. Easy to do,
Here, the position recognition camera 22 aligns the bumps of the substrate 6 with the electrodes 4 of the semiconductor integrated circuit chip 5, and after the alignment is completed, the bonding tool 1 heated to the position of the bump descends from above the substrate 6. The bumps are formed on the electrodes 4 by heating the positions where the bumps are formed on the substrate 6.

FIG. 4 is a perspective view of the second embodiment. FIG. 5 shows a bonding tool used in the present invention. The bonding tool A has a flat tip, and the bonding tool B has a rounded tip.

[0022]

As described above, when bumps are formed by using the present invention, it is possible to inexpensively form bumps having a high formation time and a uniform height only on non-defective products of various kinds of semiconductor integrated circuit chips. You can

[Brief description of drawings]

FIG. 1 is a sectional view of a bump forming method according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the bump forming method according to the first embodiment of the present invention.

FIG. 3 is a sectional view of a bump forming method according to a second embodiment of the present invention.

FIG. 4 is a perspective view of a bump forming method according to a second embodiment of the present invention.

FIG. 5 is an external view showing formation of a bonding tool used in the present invention.

FIG. 6 is a process diagram showing a plating bump method of Conventional Example 1.

FIG. 7 is a process diagram showing a transfer bump method of Conventional Example 2.

FIG. 8 is a process diagram showing a ball bump method of Conventional Example 3;

FIG. 9 is a partial side view showing a mesa bump method of Conventional Example 4.

[Explanation of symbols]

 1 ... Bonding tool 2 ... Heater block 3 ... Metal thin film 4 ... Electrode 5.13 ... Semiconductor integrated circuit chip 6 ... Transparent substrate 7-14.19 ... Electrode pad 8 ... Barrier metal 9 ... Protective film 10/12 ... Photoresist 11.15 ... Bump 16 ... Bump forming substrate 17 ... Capillary 18 ... Wire 20 ... Projection 21 ... Inner lead 22 ... CCD camera

Claims (3)

[Claims] 1. A bump characterized in that a bump electrode for bonding a substrate and a semiconductor device (package) can be easily formed on an electrode pad on a semiconductor integrated circuit chip by using a heater block that can move up and down in a bonding tool. Forming method. 2. The bump electrode is formed by punching with a bonding tool a ribbon-shaped material having a thickness of about 10 μm to 50 μm made of a material such as Au, Al or solder. Item 7. The bump forming method according to Item 1. 3. The bump forming method according to claim 2, wherein a heater block capable of raising and lowering the formed protruding electrode descends in a bonding tool to heat the protruding electrode for forming.