JPH0793310B2 - Semiconductor chip with electrode and mounting method thereof - Google Patents

Description

TECHNICAL FIELD The present invention is applicable to a method for directly attaching a semiconductor chip to a printed circuit board, that is, a chip-on-board (COB) or a chip-on-glass (COG). The present invention relates to a semiconductor chip with an electrode that can handle

2. Description of the Related Art In recent years, wiring circuits have become finer, and the tendency for high-density mounting has gradually increased. In particular, it is necessary to mount semiconductor chips on a printed circuit board in a bare state or in a state close to a bare state. Is coming. Especially in computers, it is very common to mount a high density of about 100 multi-terminal chips on a multilayer ceramic substrate. The method of directly mounting a semiconductor chip on a substrate directly without a wire is roughly classified into a wire bonding method and a wireless bonding method. Among them, the film carrier (TAB) method and the flip chip (CCB) method are the most well known. Has been.

The TAB method is a bare chip electrode construction method for tape carriers, as described in "IC Packaging Technology" P.84 (Industrial Research Association 1980) edited by the Japan Microelectronics Association, and its outline is shown in FIG. Shown in. Al ₃ is formed on the silicon 1 covered with the thermally oxidized SiO ₂ by a vacuum deposition method, and Al ₃ is left only at a desired position by a photolithography technique. Further, by repeating vapor deposition and photolithography, a SiO ₂ or glass protective film 4 is formed at a desired position as a passivation film, and Cr or Ti is deposited on the Al ₃ electrode pad.
Adhesion metal 5 such as Cu, Ni, W, Pt, Ag
A diffusion barrier metal 6 such as is sequentially generated. Then, by forming Au bump metal 7 by plating and connecting it to the lead frame as an external connection terminal,
So-called inner bonding is performed.

Regarding the flip chip method, the outline thereof is described in P.80 of the above-mentioned reference and JP-A-58-51511. The feature of this method is that the chip is turned upside down and the bare chip is directly connected to the printed circuit board through the electrodes formed on the surface of the chip. In FIG. 2, instead of the Au bump metal 7, a bump of solder is adhered by a solder dipping method or the like using Au plating as a base, and the structure of a well-known controlled collapse flip chip is generally known. Is. In addition to the flip chip, a ball method in which a metal ball is attached to the electrode (IBM S
LT), Al bump, and pedestal method. All the other methods are inconvenient because they have to be bonded by chip by ultrasonic pressure bonding, and the chip itself is damaged when bumps are formed. You need to be very careful not to give it.

However, all of these methods require a vacuum vapor deposition step using an expensive vapor deposition apparatus, and the problem is that Cr and Ti of the adhesion metal are extremely easily oxidized. As a result, a diffusion barrier metal such as Cu must be vapor-deposited continuously in quick succession, and when the solder bumps are formed by the solder dipping method in the flip chip method, the height uniformity of the bumps is maintained. Is extremely difficult, and complicated photolithography technology must be repeatedly used to form a vapor-deposited metal or the like at a desired position. Furthermore, a thin layer of aluminum oxide is formed on the electrode pad aluminum. Occurs as a result of air oxidation, which may result in insufficient adhesion strength between aluminum and chromium, resulting in the problem of chromium peeling. In addition, there was a defect that the visual inspection was extremely difficult.

Means for Solving the Problems The present invention is intended to provide an electrode-equipped semiconductor chip without the above-mentioned drawbacks, in which the electrode pad of the semiconductor chip is bonded with a wire,
In order to form the wire pillar and to bond the wire pillar directly to the printed circuit board, the wire pillar is reinforced with metal.

The electrode for external connection of the above-mentioned semiconductor bare chip of the present invention is an extremely reliable wire bonding technology already established as a connection technique for connecting the wire forming the core of the electrode to the Al electrode pad. Moreover, since the wire after bonding is plated and coated with plating metal to form the electrode pillar, the contact with the aluminum electrode pad becomes more reliable, and it is reinforced by plating. Since the pillar electrode is extremely robust, it is easy to handle when directly attached by soldering, and the semiconductor chip is not damaged even if external force is applied.

Example Next, an example of the present invention will be described with reference to the drawings.

Example 1 Using a photolithography technique, a bare semiconductor chip in which an electrode of aluminum 3 and a protective film 4 of SiO ₂ or the like are formed at a desired position on a substrate of silicon 1 having a film of SiO ₂ 2 is formed. prepare. 30 μm diameter Au on aluminum 3 electrode pad
The wire was bonded with a bonding device to form a 170 micron long wire pillar 8. After that, around the wire pillar 8, plating was performed for 2 hours at an operating temperature of 68 ° C. using an electroless Ni plating solution Nipposit 468 manufactured by Shipley Co., and the Au wire was coated with metallic nickel having a thickness of 18 microns. Was coated as the reinforcing material 9. The electrode terminal for external connection of the semiconductor chip obtained in this way was extremely rugged and easy to handle because it was sufficiently reinforced by hard nickel plating compared to the case of using only Au wire. . When the contact state between the pillar electrode and the Al electrode pad was examined visually and with a tester, no contact failure was found,
In addition, the chip could be mounted directly on the cream solder pre-applied to the printed circuit board, the board was heated, the cream solder was melted, and soldering was performed so that the chip could be directly attached directly. . Instead of the above Ni plating, Ag paint may be used to coat the Au wire pillar, but in this case,
Reinforcement of wire pillars is slightly inferior to that of plating. Furthermore, when soldering, Ag
There are problems such as the possibility of biting. For plating on wire pillars, instead of Ni plating,
Au, Cu, Sn, a metal suitable for plating such as solder, and any metal suitable for later bonding is within the scope of the present invention, and in some cases, it is also effective to combine some of these platings. Target.

Example 2 Similar to Example 1, wire bonding of an Au wire having a diameter of 32 μm was performed on an Al electrode pad of a bare chip to form a pillar having a height of 370 μm, and the same method as described in Example 1 was performed. Nickel plating, and then using an Au plating solution consisting of potassium cyanide potassium 15 g / and potassium pyrophosphate 30 g /, operating temperature 30 ° C., current density 1 A / dm ²
Electrolytic Au plating was performed to deposit about 1.2 μm of Au plating on the soldered part approximately 150 μm from the tip of the pillar electrode.

With the pillar electrodes thus obtained, there was no contact failure, and direct bonding was possible by bonding to a printed circuit board, immersing in a molten solder jet, and performing soldering in a flow system. Further, as a bonding method other than soldering, if a wiring circuit board plated with Sn is used, connection can be achieved by forming an Au—Sn eutectic alloy.

Example 3 Instead of the Au wire of Example 1, 35% diameter Al-Si 1%
Bonded the thin wire. This wire pillar was dipped in a treatment solution consisting of caustic soda 50 g /, zinc oxide 7 g /, ferric chloride 2 g /, Rochelle salt 50 g /, and sodium nitrate 1 g /, and treated at 25 ° C for 20 seconds. Nickel plating was performed in the same manner as in 1. The obtained results were comparable to the strength of the pillar electrode and the contact failure rate in comparison with Example 1. Further, as a wire for bonding, a Cu wire can be used instead of the Al wire, but in this case, the treatment with ZnCl ₂ becomes unnecessary.

The structure of the electrode terminal for external connection of the semiconductor chip of the present invention is
It is a highly reliable pillar-shaped electrode in which a metal wire is bonded to an Al electrode pad and plated with a metal, and the wire pillar is sufficiently reinforced by plating and is extremely durable. Therefore, it is easy to handle and it is a perfect electrode for a bare chip for COB. Further, there is an advantage that not only the vapor deposition work using an expensive vapor deposition apparatus is unnecessary but also the complicated photolithography process is reduced. Furthermore, the presence or absence of contact failure in the bonding can be easily inspected visually without using a special inspection device, which is convenient. The so-called COB method, in which the bare chips are aligned, arranged on the printed circuit board, and batch-bonded only by passing through the furnace once, is easy and suitable for high-density mounting. Also, in the conventional flip chip method,
Adjusting the electrode bumps to a certain height was quite difficult, but according to the present invention, the height adjustment is extremely easy, and its shape and size are far more freely selectable than the conventional ones. is there.

[Brief description of drawings]

FIG. 1 is a sectional view of a pillar-shaped semiconductor chip with electrodes for external connection according to the present invention, and FIG. 2 is a sectional view of a conventional bump-shaped semiconductor chip with electrodes for COB. 1 ... Silicon, 2 ... SiO ₂ , 3 ... Al, 4 ... Protective film, 5 ... Adhesion metal, 6 ... Diffusion barrier metal, 7 ...
Bump metal, 8 …… Wire pillar, 9 …… Reinforcement material.

Front page continued (72) Inventor Toshio Tsuda 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Yoshihiro Bessho, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) Reference Document JP-A-58-182248 (JP, A)

Claims (6)

[Claims] 1. An electrode-equipped semiconductor chip having a wire pillar formed by using a wire-bondable metal on an electrode pad of the semiconductor chip, wherein the wire pillar is covered with metal to be reinforced. Chips. 2. The electrode-equipped semiconductor chip according to claim 1, wherein the metal is a plated metal. 3. A semiconductor chip with an electrode according to claim 1, wherein the wire-bondable metal contains Au, Al or Cu as a main component. 4. A wire-bondable metal is used,
Wire pillars are formed on the electrode pads of the semiconductor chip,
A method of mounting a semiconductor chip, comprising: directly bonding an electrode-equipped semiconductor chip, in which the wire pillar is reinforced by covering the wire pillar with a metal, to a printed circuit board by soldering. 5. The method of mounting a semiconductor chip according to claim 4, wherein the direct bonding to the printed circuit board is amorphous bonding or thermocompression bonding. 6. The method of mounting a semiconductor chip according to claim 4, wherein the coating of the wire pillar is performed by a plating method.