JPH06163628A - Semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To protect a monolithic micro wave integrated circuit front the adverse effect in a resin forming process. CONSTITUTION:On a surface of a semiconductor substrate 1, a wiring 2 and an air bridge wiring 3 are formed, and, directly under the wiring 2, a through hole 4, penetrating up to the rear surface of the substrate 1, is formed. A wiring 5 and a bonding pad 6, electrically connected to the wiring 2 through the through hole 4, are provided on the rear surface. A guard ring 7 and a cap metal 8 that protect the surface of the substrate 1 are provided. The bonding pad 6 an the rear surface is, by way of a banding wire 9, connected to a lead frame 10. The entire semiconductor is resin-sealed up with a plastic package. With this, degradation of high frequency performance, AC performance, yield, characteristics fluctuation, and moisture resistance are prevented, for improved free degree in wiring design.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit, and more particularly to a semiconductor integrated circuit used in the high frequency field.

[0002]

2. Description of the Related Art In recent years, semiconductor technology has made remarkable progress, and process technology such as miniaturization technology or self-alignment technology is supporting such progress. Even in the high frequency field, Si bipolar and GaAs-based MMIC (monolithic microwave integration) devices have been developed. Circuits) are becoming faster and more sophisticated.

The market in this field is rapidly expanding with the development of mobile communication and satellite broadcasting, and there is a strong demand for cost reduction. Therefore, the MMIC envelope is switched from an expensive ceramic package to a plastic package. ing.

The following problems occur due to the resin formation by this plastic package.

First, in the MMIC of a GaAs-based device, it is common to incorporate an inductance (L),
Especially in the case of high frequency, air bridge wiring is used to maintain AC performance. However, when forming a resin in a plastic package, the inductance is easily destroyed and the dielectric constant of the resin is larger than that of air. Capacity will also increase. Due to such a cause, the AC performance and the yield decrease.

Further, due to the stress at the time of resin formation, characteristic variations of diffusion resistance, transistors (FET, bipolar transistor, etc.) occur. In particular, the fluctuation directions do not all fluctuate in the same direction but fluctuate at random, so that the pairing property deteriorates, and DC performance, AC
Performance will also deteriorate.

Further, in the case of a GaAs-based device, a good insulating film (thermal oxide film in Si bipolar) for protecting the semiconductor surface cannot be formed. Therefore, even if the top protective film is laminated, the envelope is molded. Then, moisture easily reaches the device surface. Due to such a decrease in moisture resistance, corrosion and characteristic changes occur.

[0008]

As described above, the conventional M
In the MIC, there are problems such as deterioration of AC performance and yield, deterioration of characteristic variation due to resin formation by a plastic package, and occurrence of corrosion and characteristic variation due to deterioration of moisture resistance.

Therefore, the present invention has been made in view of the above conventional circumstances, and its object is to:
It is an object of the present invention to provide a semiconductor integrated circuit, particularly a monolithic microwave integrated circuit, which can prevent deterioration of high frequency performance, characteristic variation, and moisture resistance without being adversely affected by the resin forming process.

[0010]

In order to achieve the above object, according to the present invention, a through hole is formed just below the wiring of an integrated circuit formed on the front surface of a semiconductor substrate and communicates with the back surface of the semiconductor substrate. Wirings and bonding pads electrically connected to the wirings of the integrated circuit through are provided on the back surface of the semiconductor substrate.

Further, according to the present invention, a concave cap metal for sealing the entire surface of the integrated circuit is provided on the integrated circuit formed on the surface of the semiconductor substrate.

[0012]

With the above-mentioned means, the present invention provides a wiring and a bonding pad electrically connected to the wiring on the front surface of the semiconductor substrate on the back surface, and further, a concave type for sealing the entire surface of the integrated circuit having the air bridge wiring. Since the cap metal is provided, it is effective for protection of inductance, prevention of stress during resin formation, and improvement of moisture resistance.

[0013]

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

FIG. 1 is a sectional structural view of a semiconductor integrated circuit of the present invention.

As shown in the figure, the wiring 2 and the air bridge wiring 3 are formed on the surface of the semiconductor substrate 1.
Immediately below a part of the wiring 2, a through hole 4 is formed to reach the back surface of the semiconductor substrate 1.

A wiring 5 and a bonding pad 6 which are electrically connected to the wiring 2 through the through hole 4 are provided on the back surface.

A guard ring 7 and a cap metal 8 for protecting the entire surface of the semiconductor substrate 1 including the air bridge wiring 3 are provided on the substrate 1.

Further, the bonding pad 6 provided on the back surface is connected to the lead frame 10 by the bonding wire 9.

The entire semiconductor integrated circuit thus formed is resin-sealed in the plastic package 11.

Next, a method of manufacturing a semiconductor integrated circuit according to the present invention will be described with reference to process sectional views shown in FIG.

First, the semi-insulating GaAs substrate 1 (-10 ⁷
Ωcm) on the surface of the GaAs MESFET process,
That is, the MMIC is formed using steps such as ion implantation, annealing, CVD deposition, etching, and metal formation. As a result, the Au wiring 2 and the air bridge wiring 3 having a thickness of 2 μm and a gap of 3 μm are formed (FIG. 2A).

Next, the substrate 1 immediately below a part of the Au wiring 2
Is removed by etching until it penetrates to the back surface.
After forming the through hole, the through hole 4 and the substrate 1 are formed by using a plating method.
The Au wiring 5 and the bonding pad 6 are provided on the back surface of the (FIG. 2B).

Further, a guard ring 7 made of an insulating material and having a height of about 10 μm, which is higher than the height of the air bridge wiring 3, is formed at the end of the MMIC, and a cap metal 8 is adhered onto the guard ring 7 to cover the entire surface of the MMIC. Are sealed (FIG. 2C).

Finally, after connecting the lead frame 10 and the bonding pad 6 with the bonding wire 9, the entire substrate 1 is resin-sealed with the plastic package 11 to complete the semiconductor integrated circuit shown in FIG. .

In this embodiment, as shown in FIG. 2 (c), the entire MMIC surface is protected by using the guard ring 7 and the cap metal 8. However, the present invention is not limited to this, and a concave cap metal may be used. The MMIC surface may be adhered to protect the entire surface of the MMIC.

[0026]

As described above, in the semiconductor integrated circuit of the present invention, since the concave cap metal for sealing the entire surface of the integrated circuit is provided on the integrated circuit formed on the surface of the semiconductor substrate, the resin It is possible to prevent deterioration of AC performance and yield, fluctuation of characteristics, and deterioration of humidity resistance without being adversely affected by the forming process.

At the same time, in the semiconductor integrated circuit of the present invention, a through hole is formed immediately below the wiring of the integrated circuit formed on the front surface of the semiconductor substrate and communicates with the back surface of the semiconductor substrate. Since the wiring and the bonding pad to be electrically connected are provided on the back surface of the semiconductor substrate, the degree of freedom in wiring design is increased and high frequency performance can be maintained.

[Brief description of drawings]

FIG. 1 is a structural cross-sectional view of a semiconductor integrated circuit of the present invention.

FIG. 2 is a manufacturing process diagram of a semiconductor integrated circuit of the present invention.

[Explanation of symbols]

 1 Semi-insulating GaAs substrate 2 Au wiring 3 Air bridge wiring 4 Through hole 5 Au wiring 6 Bonding pad 7 Guard ring 8 Cap metal 9 Bonding wire 10 Lead frame 11 Plastic package

Claims (2)

[Claims] 1. A wiring is formed immediately below the wiring of the integrated circuit formed on the front surface of the semiconductor substrate, and a through hole communicating with the back surface of the semiconductor substrate is formed. The wiring electrically connected to the wiring of the integrated circuit through the through hole. And a bonding pad provided on the back surface of the semiconductor substrate. 2. A semiconductor integrated circuit characterized in that a concave cap metal for sealing the entire surface of the integrated circuit is provided on the integrated circuit formed on the surface of the semiconductor substrate.