JPS60195953A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To enhance the reliability and to reduce the cost of a semiconductor device by forming the first layer with materials to be heat treated of iron, nickel, cobalt or copper and noble metal, and forming the second layer with noble metal as an external electrode. CONSTITUTION:A heat treated material of nickel and gold is formed as the first layer 11 on the upper surface of a metallized layer 10 formed by coating a high melting point metal such as tungsten (buried partly in substrate 1) on the surface of a package substrate 1, and gold is coated as the second layer 12 on the upper surface of the layer 11, and inner and outer electrodes 6, 13 of two layers are formed. In other words, since a semiconductor device having the electrodes is hermetically sealed with low melting point glass, the soldability at the external electrode is maintained even if the semiconductor device is formed and heated at the softening temperature of low melting point glass such as, for example, at 450 deg.C, thereby effectively solder-mounting it.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a technique that is effective when applied to the formation of electrodes in semiconductor devices.

[Background technology]

BACKGROUND OF THE INVENTION As electronic devices become more compact, the demand for so-called chip carrier type semiconductor devices, which are leadless and suitable for high-density packaging, is expected to increase further in the future.

A chip carrier type semiconductor device consisting of a ceramic package has a pellet attached to the bottom of the cavity of the package substrate using gold-silicon eutectic or the like, and electrically connected between the bonding pad of the pellet and the internal electrode of the package using a wire made of gold or the like. After the connection is made, the package substrate and the cap are bonded together using a silver brazing material, so that the inside can be hermetically sealed.

Further, the external electrodes of the semiconductor device are formed by coating a so-called printed conductor (metallized) layer directly on the top surface of the package with nickel as the first layer and gold as the second layer so that soldering can be carried out. , it can be formed by applying it by a method such as plating (Japanese Unexamined Patent Publication No. 53-36468).
.

Incidentally, in the semiconductor device described above, since a silver brazing filler metal with a low melting point is used, it has the advantage of being able to be packaged at a relatively low temperature. The drawback is that it has to be expensive.

Therefore, it is conceivable to reduce the cost of a semiconductor device made of a chip carrier type package by using an inexpensive low-melting glass as a package sealant.

However, in order to hermetically seal a package using low melting point glass, it is necessary to place the low melting point glass between the package substrate and the cap and heat it at a high temperature for a certain period of time, e.g.
It is necessary to perform heat treatment to 50°C.

However, when performing the heat treatment as described above, the solderability of the external electrode of the package consisting of the two layers of nickel and gold decreases, especially when the metal is formed thinly, so it is difficult to attach the semiconductor device. The inventor of the present invention discovered a problem that mounting using solder is no longer possible. The main cause of this is thought to be that the nickel on the inside is oxidized through the metal because it is thin, or that the nickel that has reached the surface is oxidized as alloying between nickel and gold progresses and diffuses. It will be done.

Therefore, although the above problem can be solved by forming a thick gold layer on the surface, increasing the thickness of the gold layer inevitably brings about the problem of increased cost of the semiconductor device.

[Purpose of the invention]

An object of the present invention is to provide an effective technique that can be applied to improve the reliability of a chip carrier type semiconductor device made of a ceramic package.

Another object of the present invention is to provide an effective technique that can be applied to the highly reliable electrode formation of the semiconductor device.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, iron as the first layer on the metallized layer.

By depositing a heat-treated product of nickel, cobalt, or copper and a noble metal, and depositing a noble metal as a second layer on the first layer to form an electrode, the first layer is made of iron, nickel,
Compared to using cobalt or copper alone, it is possible to manufacture semiconductor devices by heating them to the softening temperature of glass and hermetically sealing the package. It is possible to provide a semiconductor device.

Further, the semiconductor device includes iron on the metallized layer.

After depositing nickel, cobalt or copper and depositing a noble metal on the top surface, heat treatment is performed at a predetermined temperature for a predetermined time in a reducing or inert gas atmosphere to form the first layer of heat-treated product. and then depositing a noble metal on the first layer.'

Note that the heat-treated product here refers to alloys in a broad sense, including intermetallic compounds, and is not necessarily limited to those in which the entire first layer is in a uniform state; This also includes those in which a chemically stable alloy layer is formed only near the interface.

[Embodiment 1] The figure shows a semiconductor device made of a chip carrier according to Embodiment 1 of the present invention in a cross-sectional view taken along a plane passing approximately through the center thereof.

In the semiconductor device of Example 10, a pellet 3 is attached to the bottom of a cavity 2 of a package substrate 1 made of ceramic using a brazing material 4 such as gold-silicon eutectic, and a bonding pad 5 and an internal electrode 6 of the pellet are connected with gold. After making an electrical connection with the wire 7, etc., a ceramic cap 8 is adhered to the package substrate sealing part via a low melting point glass 9, and the cavity 2 is hermetically sealed. .

Note that the semiconductor device of the first embodiment is characterized in that a metallized layer 10 formed of a high-melting point metal such as tungsten is formed on the surface of the package substrate 1 (part of which is buried within the substrate). , a heat-treated product of nickel and gold is formed as the first layer 11, and a second layer 12 is formed on the upper surface of the first layer 11.
The two-layered internal electrode 6 and external electrode 13 are formed by depositing gold as a metal layer.

In other words, since the semiconductor device equipped with the electrodes is hermetically sealed with low-melting glass, the solderability of the external electrodes is maintained even when heat-treated to, for example, 450°C. It can be mounted by soldering.

This is because the second layer of gold is relatively thin at the glass sealing temperature, and even if pinholes occur in the i-th layer, the first layer is less susceptible to oxidation. ,
Furthermore, compared to the case where the first layer is formed only of nickel, the heat-treated product of the first layer shown in this example has a second layer formed of nickel.
It is thought that this is because it forms an alloy with the gold layer and traps it. Therefore, even after the package is hermetically sealed, the initial state of electrode formation is maintained, so it is considered that solderability is maintained.

In the semiconductor device of Example 10, nickel is first deposited on a metallized layer made of tungsten or the like of a package substrate 1 manufactured by a conventional method by a method such as plating, and then gold is similarly deposited on the upper surface of the nickel. wear it. In this case, the metal deposition thickness is, for example, 2 μm for nickel and 0 μm for gold.
．． 5μ is sufficient.

Thereafter, the package substrate 1 coated with nickel and gold is heat-treated at approximately 450°C for 30 minutes in an atmosphere of reducing gas such as hydrogen or inert gas such as nitrogen or argon. A heat-treated product is formed.

Nitsuo and gold are relatively easy to form metal-containing substances, right? ,
When heating in air, the solderability deteriorates significantly, but if heat treatment is performed in an oxygen-free atmosphere as described above, then the solderability will be significantly reduced. In this case, it is thought that an oxidation-resistant alloy is formed.

It should be noted that the conditions for the stress-boosting treatment for forming the first layer are not limited to the conditions described above, and the first layer can be sufficiently formed at a temperature of about 300° C. or higher.

After forming the first layer as described above, a second layer is formed by depositing gold, for example by plating, on the first layer. The second layer is 1. For example, 1 μ of compassion is sufficient.

After completing assembly such as pellet attachment and wire bonding using the usual method using the package substrate 1 with the two-layer electrode formed as described above, a cap made of ceramic and a sealing portion of the package base are assembled. The semiconductor device of Example 1 is packaged by heating the package to, for example, about 450° C. and hermetically sealing the package with a low melting point glass interposed between the package and the package.

Since the semiconductor device of this example is equipped with the relatively chemically stable fourteenth electrode as described above, the external electrode is exposed to air at a high temperature during the glass sealing process of the package. Even when exposed, it still has good soldering properties.

Furthermore, since the first layer is chemically stable, it is possible to provide a semiconductor device with sufficient solderability even if the second noble metal layer is formed relatively thin.

[Example 2] A semiconductor device according to Example 2 of the present invention has almost the same structure as Example 1, except for the electrodes.

That is, in the semiconductor device of the second embodiment, the electrode is formed using iron instead of nickel, which is the material of the first layer 11 of the electrode shown in the first embodiment. others,
All other constituent materials including the electrode materials are the same as those in Example 1, and the manufacturing method thereof can be carried out similarly.

When the electrode is formed using iron as in Example 2,
As in the case of nickel, it is possible to manufacture semiconductor devices having electrodes with excellent solderability. this is,
This is thought to be due to the fact that iron, like nickel, forms the first layer consisting of a chemically stable heat-treated product.

[Embodiment 3] A semiconductor device according to Embodiment 3 of the present invention is almost the same as that shown in Embodiment 1 above.

In the semiconductor device of Example 30, the first layer of the electrode is formed of a heat-treated product of cobalt and gold, using cobalt instead of nickel in Example 1, and further includes the following: Gold is deposited on the first layer 11 as the second layer 12.

Even if the electrode is made up of two layers in which cobalt is deposited on the metallized layer 10 and gold is deposited on the cobalt layer, the electrode can be made to have oxidation resistance and good solderability. However, by heating cobalt and gold in a non-oxidizing atmosphere and depositing them on the first layer 11 as in Example 3, an electrode with extremely excellent oxidation resistance and solderability can be obtained. It is something that can be formed. Therefore, extremely reliable semiconductor devices can be manufactured.

Note that cobalt and gold have low reactivity, so they can be used at relatively high temperatures.
For example, a range of 600°C to 900°C is preferable, and 600°C to 900°C is preferable.
An electrode with sufficient oxidation resistance can be obtained by processing for about 30 minutes at about .degree.

[Fourth Embodiment] A semiconductor device according to a fourth embodiment of the present invention is almost the same as that of the first embodiment.

In the present Example 40 semiconductor device, the electrode is formed of a first layer 1 made of a heat-treated product of copper and silver on the metallized layer 10.
1, a second layer 12 made of silver was formed on the first layer.

In the electrode shown in Example 4, copper with a thickness of 0.5 to 1.0 μm, for example, is deposited on the metallized layer 10 by plating, and then silver with a thickness of 0.5 to 1.0 μm is deposited on the metallized layer 10. After being deposited by plating or the like, heat treatment is performed in a non-oxidizing atmosphere under predetermined conditions to form the first layer, and about 1 μm of gold is deposited on the first layer in the same manner as the second layer. Layer 12 is formed by trapping.

The first layer 11 made of steel and silver is the same as the electrode first layer 11 made of nickel and gold in Example 1.
Similar to K, the reactivity of copper and silver is high, so the temperature is relatively low.
For example, heat treatment at 300° C. or higher is preferable. By performing the heat treatment in this way, it is possible to form the first layer consisting of a chemically stable heat-treated product, so that a semiconductor device equipped with an extremely excellent electrode as in Example 3 can be manufactured. It can also be manufactured more cheaply.

〔effect〕

(1) A first layer of a heat-treated product of iron, nickel, cobalt, or copper and noble metal is formed on the metallized layer for at least the external electrode of a chip-type carrier semiconductor device consisting of a ceramic package, and the first layer By forming a second layer of noble metal on top, the first layer can be made chemically stable, so even at the glass sealing temperature, the first layer can be formed through the second layer or through pinholes in the second layer. It is possible to provide a semiconductor device including an electrode that is less susceptible to oxidation.

(2) Since the first layer is chemically stable, it is possible to suppress the reaction with the second layer, so that destruction of the second layer due to alloy formation with the second layer, etc. can be prevented.

(3) From (1) and (2) above, even if the package is hermetically sealed using low-melting glass, it is possible to provide a semiconductor device having external electrodes with good solderability.

(4) From (3) above, a highly reliable semiconductor device that can be reliably soldered mounted can be provided at a low cost.

(5) By forming the first electrode layer with a heat-treated product of iron or nickel and gold, the thickness of the second layer can be made thinner than when the first layer is formed of iron or nickel alone. This makes it possible to significantly reduce the amount of gold used, thereby reducing the cost of semiconductor devices.

(6) By forming the first electrode layer with a heat-treated product of cobalt and gold, a very chemically stable first layer can be formed, providing an extremely reliable semiconductor device. can.

(7) From (6) above, since the first layer can be formed as a very chemically stable first layer, the second layer of gold can be made even thinner, resulting in a significant cost reduction. can be achieved.

(8) By forming the first layer with a heat-treated product of copper and silver, in addition to the same effects as described in (6) and (7) above, it can be formed with inexpensive materials. Therefore, it is possible to further reduce the cost of the semiconductor device.

(9) After depositing iron, nickel, cobalt, or copper on the metallized layer and depositing a noble metal on top of that, chemical It is possible to easily and reliably form a thermally stable heat-treated product.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, the combinations of electrode materials are not necessarily limited to those shown in the examples. In particular, although only the case where the second layer is made of gold has been described, it may be made of other noble metals such as silver or palladium, and the thickness of the electrode material is not limited to that shown in the examples. Needless to say.

Furthermore, although only the plating method is used as the method for depositing the electrode material, other methods such as vapor deposition may be used, and the plating method may be either electroplating or chemical plating.

Furthermore, it goes without saying that the conditions for heat treatment of the first electrode layer can be arbitrarily changed depending on the material used, and are not limited to the temperature for 9 hours, etc. shown in the examples.

[Brief explanation of the drawing]

The figure is a cross-sectional view showing a semiconductor device that is an embodiment of the present invention. 1...Package board, 2...Cavity, 3...
・Belle, 4... Brazing metal, 5... Ponding pad, 6... Internal electrode, 7... Wire, 8...
Cap, 9... Low melting point glass, 10... Metallized layer, 11... First layer, 12... Second layer, 13...
・External electrode.

Claims (1)

[Claims] 1. A package is formed in a chip carrier type semiconductor device made of a ceramic package. At least the external electrode of the military includes a first layer formed of a heat-treated product of iron, nickel, cobalt, or copper and a noble metal on a metallized layer, and a second layer formed of a noble metal on the first layer. A semiconductor device whose main characteristic is that it consists of: 2. The semiconductor device according to claim 1, wherein the noble metal is gold or silver. 3. A method for manufacturing a chip carrier type semiconductor device comprising a ceramic package, in which at least an external electrode of the electrodes formed on the package is coated with iron, nickel, cobalt or copper on a metal layer; Furthermore, after depositing the precious metal on the first layer, heat treatment is performed in a reducing, original or inert atmosphere to form a second illumination layer, and then a noble metal is deposited on the first layer. 1. A method of manufacturing a semiconductor device, characterized in that the second layer is formed using a method of manufacturing a semiconductor device. 4. The method of manufacturing a semiconductor device according to claim 3, wherein the heat treatment is performed at a temperature range of 300°C to 900°C. 5. The method of manufacturing a semiconductor device according to claim 3, wherein iron, nickel, cobalt, copper, or a noble metal is deposited by plating.