JPH07183304A - Method for manufacturing semiconductor device - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for manufacturing a semiconductor device, which has a small number of steps and can use a pad made of any metal as long as it is a plated metal. A semiconductor chip having a plurality of pads and a circuit board having a plurality of pads are aligned with a desired gap so that the pads face each other, and an adhesive or the like is used to center the semiconductor chip. Section and the circuit board are bonded and fixed, and the semiconductor chip and the circuit board that are bonded and fixed to each other are placed in a plating solution, and electroplated between the pad of the semiconductor chip and the pad of the circuit board. And a step of depositing metal to form metal bumps for electrically and mechanically joining the pads.

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 semiconductor device, and more particularly to a method for manufacturing a semiconductor device in which a semiconductor chip is mounted face down on a pad of a circuit board having required wiring via bumps.

[0002]

2. Description of the Related Art Recently, many methods using bare chips have been developed as a technology to cope with high speed and high density of electronic devices. Specific examples of these methods include a wire bonding method, a TAB method, and a flip chip method.

The wire bonding method is a method in which a semiconductor chip is placed face up and pads of the chip and pads on a circuit board are connected by wires such as gold. However, with the wire bonding method, it is currently difficult to connect between pads having a very small pitch of 50 μm, and it is not suitable for high density.

The TAB method is a method in which wiring is made of a copper foil on a polyimide film and pads of a semiconductor chip and leads of the copper foil are connected via bumps. However, the TAB method has problems that an expensive polyimide film is used and that the film is thermally shrunk with respect to a fine connection, so that high dimensional accuracy cannot be obtained.

On the other hand, in the flip chip method, metal bumps are deposited on the pads of the semiconductor chip by the vapor deposition method, the dip method,
It is a method of forming by a plating method, etc., and aligning and connecting with a pad on the surface of the circuit board. A method of manufacturing a semiconductor device by such a flip chip method will be described below with reference to FIG. A metal film such as Cu, Ni, Cr, Ti or a composite film of these is formed on the aluminum pad 33, which is partially covered with the passivation film 32 such as silicon nitride of the semiconductor chip 31, by a vapor deposition method or the like, and then patterned. To form the barrier metal 34. Subsequently, metal bumps 35 such as solder are formed on the barrier metal 34 by vapor deposition, plating or the like. Next, the pads 37 of the circuit board 36 are aligned with the bumps 35 of the semiconductor chip 31, and the bumps 35 and the pads 37 of the circuit board are aligned.
Are heated and joined to manufacture a semiconductor device.

Compared with the wire bonding method, the TAB method, etc., the flip chip method is capable of utilizing the entire surface of the semiconductor chip for connection, and because the connection is made by bumps, it is possible to perform bonding at a very fine pitch. High-density mounting is possible and electronic devices can be downsized. In addition, since the semiconductor chip and the circuit board are directly connected by the metal bumps, extra wiring such as wires and tapes is not required, and the signal transmission delay can be reduced, so that the speed of the electronic device can be increased.

However, the above-mentioned conventional flip-chip method has the following drawbacks. (1) It is necessary to form a barrier metal on the semiconductor chip, which increases the number of steps.

(2) There is a problem in reliability because heat treatment is required in the bump forming and joining steps. (3) Metals used for connection are Sn, Pb, In, Bi, A
u, Ag, Sb and their compounds are limited to soft metals.

[0009]

As described above, the conventional flip-chip method has many steps and the metal used for connection is limited, so that a simple and versatile semiconductor device has not been obtained. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method of manufacturing a semiconductor device which has a small number of steps and can use a pad made of any metal as long as it is a plated metal. .

[0010]

SUMMARY OF THE INVENTION According to the present invention, a semiconductor chip having a plurality of pads and a circuit board having a plurality of pads are aligned and bonded at desired intervals such that the pads face each other. For example, a step of adhering and fixing the central portion of the semiconductor chip and the circuit board using an agent and the like, and placing the semiconductor chip and the circuit board that are adhered and fixed to each other in a plating solution, and electroplating the semiconductor chip A step of depositing a metal between the pad and the pad of the circuit board to form a metal bump that electrically and mechanically joins the pad to each other. Is the way.

The pads of the semiconductor chip are formed of, for example, aluminum or its alloy. The pads of the circuit board are formed of, for example, copper or an alloy thereof.

As the adhesive, for example, an epoxy adhesive, an acrylic adhesive or the like can be used. Examples of the plating metal include copper, nickel, aluminum, gold, silver, tin, lead, iron, titanium, chromium, bismuth,
Indium, antimony and alloys of these can be used.

As means for depositing metal between the pads of the semiconductor chip and the pads of the circuit board by the electroplating, for example, a common wiring connecting all pads is formed on the circuit board, and the common wiring is formed. It is possible to employ a method of forming a metal bump that deposits a metal on the pad of the circuit board by applying a voltage to each pad through the pad and electrically and mechanically bonds to the pad of the semiconductor chip. However, after the plating step, the common wiring is removed by etching or the like to electrically separate the pads from each other. As another means, the conductor part is provided between the pad of the semiconductor chip and the pad of the circuit board in which a common electrode having a plurality of conductor parts having a shape similar to the pad is fixed to each other with an adhesive. Metal bumps that are arranged so as to face each other are formed by electrically energizing the common electrode to deposit metal from the front and back surfaces of the conductor portion to electrically and mechanically bond the pad of the semiconductor chip and the pad of the circuit board. The method can be adopted. in this case,
After forming the bumps, the conductors are electrically separated from the common electrode.

[0014]

According to the present invention, a semiconductor chip having a plurality of pads and a circuit board having a plurality of pads are aligned at desired intervals so that the pads face each other, and an adhesive or the like is used. Adhesively fix the central portion of the semiconductor chip and the circuit board together, place the semiconductor chip and the circuit board in a plating solution, and perform electroplating to form a pad of the semiconductor chip and a pad of the circuit board. A metal bump can be formed by depositing a metal in between to electrically and mechanically bond the pads. That is, the bump forming step and the bonding step between the semiconductor chip and the pad of the circuit board can be simultaneously performed. As a result, it becomes unnecessary to dispose the barrier metal between the pad and the bump of the semiconductor chip as in the conventional case, and the heat treatment step for melting the metal bump can be omitted. However, it is also permissible to prevent the diffusion of metal by using a barrier metal depending on the nature of the bump. Further, since the semiconductor chip and the circuit board are connected in advance with resin, the connection strength between them can be improved as compared with the case of connecting only with the bumps. Therefore, the process can be simplified and a highly reliable semiconductor device can be manufactured.

In the electroplating step, the oxide film on the surface of the pad of the semiconductor chip made of aluminum or the surface of the pad of the circuit board made of copper, for example, can be removed. Can be connected.

Further, when the applied voltage changes when the pads of the semiconductor chip and the pads of the circuit board are joined by metal bumps formed by electroplating, it can be detected that the joining is completed. it can.

Further, the metal bumps grown by the electroplating method include tin, lead, bismuth, indium, gold,
Not only relatively soft metals such as silver and antimony,
Since a hard metal such as copper, nickel, aluminum, iron, titanium, and chromium can be used, there is an advantage that the bump material can be selected according to the application and performance of the semiconductor device. In addition, if the pads of the circuit board are selectively used as cathodes for electroplating, it is possible to connect only the necessary pad portions of the circuit board and the semiconductor chip.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. First, the thickness of the desired element is 500μ
A 6-inch semiconductor wafer of m was diced to form a 10 mm square semiconductor chip 2 having an aluminum pad 1 having a 100 μm square and a pitch of 150 μm shown in FIG.
A passivation film 3 made of silicon nitride is formed on the surface of the semiconductor chip 2 so as to cover parts other than the pad 1. Subsequently, an epoxy adhesive layer 4 having a thickness of 50 μm was applied to the central 7 mm square portion of the semiconductor chip 2 other than the pad 1.

Next, as shown in FIG. 2, a circuit board 8 having copper pads 6 connected to each other by a common wiring 5 and having a surface other than the pads 6 covered with a solder resist film 7 is prepared. The aluminum pad 1 of the semiconductor chip 2 and the pad 6 of the circuit board 8 are aligned by, for example, a positioning device using a half mirror, and the adhesive layer 4 in the central portion of the semiconductor chip 2 causes the circuit board 8 and After contacting the semiconductor chip 2,
The semiconductor chip 2 and the circuit board 6 were integrated by curing the adhesive layer 4.

Next, as shown in FIG. 3, 250 g of copper sulfate
/ L, sulfuric acid 50g / l plating solution at a temperature of 25 ℃ 1
1. A circuit board 8 integrated with the semiconductor chip 2 is immersed in a plating tank 12 in which 1 is accommodated, a common wiring 5 of the circuit board 8 is used as a cathode, and high-purity copper is used as an anode 13, and a current density is 5 A. / Dm ^{2 was} applied and electrolytic copper plating was performed with gentle stirring. In FIG. 4, 14 is a DC power supply, 15 is an ammeter connected in series to the DC power supply 14, and 16 is a voltmeter connected in parallel to the power supply 14. When copper is deposited from the pads 6 of the circuit board 8 by the electrolytic copper plating process to form a plating film (copper bump) 9 having a thickness of 50 μm as shown in FIG. 4, the semiconductor chip 2 of the semiconductor chip 2 is formed. It was connected to the aluminum pad 1. At this time, the applied voltage and current were monitored by the voltmeter 16 and the ammeter 15, and the completion of the connection between the semiconductor chip 2 and the circuit board 8 could be confirmed by detecting the voltage change.

Next, the circuit board 8 on which the semiconductor chip 2 is integrated and the copper bumps 9 are formed is taken out from the plating tank 12, washed with pure water, dried by nitrogen blowing, and then the circuit board 8 is removed. A semiconductor device was manufactured by cutting a desired portion of the common wiring and electrically separating the pad 6 as a wiring 10 having a predetermined function (see FIG. 5).

A 10 mm square semiconductor chip having 200 bumps was bonded onto a resin circuit board such as a printed wiring board by the method described above. This sample is -65 ℃
(30 min) → 25 ° C (5 min) → 150 ° C (30
min) → 25 ° C. (5 min) for 5000 cycles, but no fracture was observed at the connection points. Since the resin adhesive is filled between the circuit board and the semiconductor chip, the reliability is improved as compared with the bonding using only the metal bumps. The strength of the metal bumps was 70 g / piece, and there was no problem, and no short circuit occurred between the bumps.

Although copper is used as the metal bump to be connected in the above embodiment, the present invention is not limited to this. For example, nickel, aluminum, gold, silver, iron, tin,
Lead, indium, bismuth, titanium, chromium, antimony or alloys thereof may be used.

In the above-described embodiment, the metal bumps are formed on the pads of the circuit board by electroplating. However, after forming the resist film on the bonding area of the adhesive layer and the surface of the circuit board excluding the pads, the electroplating is performed. A metal bump having a shape similar to the area may be formed on the pad of the circuit board. Although a resin circuit board such as a printed wiring board is used in the above embodiments, the base material may be a silicon-based or alumina-based aluminum nitride-based material.

[0025]

As described in detail above, according to the present invention, the semiconductor chip and the circuit board can be connected at the same time when the metal bumps are formed, and a metal such as a barrier metal is not necessary, and the conventional flip chip method is used. It is possible to provide a method of manufacturing a semiconductor device which can reduce the number of steps as compared with the conventional method and can use various metals as bumps as compared with the conventional method, and has a wide range of applications.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing the manufacturing process of the semiconductor device according to the embodiment of the invention.

FIG. 3 is a cross-sectional view showing the manufacturing process of the semiconductor device according to the embodiment of the invention.

FIG. 4 is a cross-sectional view showing the manufacturing process of the semiconductor device according to the embodiment of the invention.

FIG. 5 is a cross-sectional view showing the manufacturing process of the semiconductor device according to the embodiment of the invention.

FIG. 6 is a cross-sectional view showing a semiconductor device manufactured by a conventional method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Aluminum pad, 2 ... Semiconductor chip, 4 ... Adhesive layer, 5 ... Common wiring, 6 ... Copper pad, 8 ... Circuit board, 9
... copper bumps, 10 ... wiring, 11 ... plating solution, 12 ... plating bath, 13 ... copper anode, 14 ... DC power supply.

Claims (1)

[Claims] 1. A step of fixing a semiconductor chip and a circuit board by aligning a semiconductor chip having a plurality of pads and a circuit board having a plurality of pads so that the pads face each other, and fixing the semiconductor chip and the circuit board together. The semiconductor chip and the circuit board thus prepared are placed in a plating solution, and a metal is deposited between the pad of the semiconductor chip and the pad of the circuit board by electroplating to electrically bond the pads. And a step of forming metal bumps.