JPS62298142A - Semiconductor device - Google Patents

Abstract

PURPOSE:To improve the heat radiation from a substrate, and obtain a high frequency semiconductor device for medium or high output power, by forming a recessed part on the back side of the substrate in order to constitute the thin region of an internal circuit for microwave, and forming an air hole and a metal layer whose surface is recessed. CONSTITUTION:On the surface of a semiconductor substrate 1, an integrated internal circuit 2 for microwave is formed. From the substrate back side toward its front side, a recessed part 5 is formed to make the region of the circuit thin. Around the circuit 2, air holes 4 reaching the surface of the recessed part 5 are formed, on the surface of which a metal layer 6 is formed to increase the heat radiation. According to such a constitution, the generated heat is rapidly conducted to the metal layer 6 and rdiated, because the substrate of the internal circuit part generating heat is thin. The heated air escapes upward through the hole 4. Thereby, the heat radiation is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, and particularly to a semiconductor device incorporating a microwave integrated circuit.

[Conventional technology]

Conventionally, thermal limitations have been a problem when attempting to obtain medium or high output characteristics in semiconductor devices incorporating microwave integrated circuits.

FIG. 2 is a cross-sectional view of an example of a conventional microwave integrated circuit.

An internal circuit 2 for microwaves is formed on a semiconductor substrate 1 such as GaAs, and is drawn out to a bonding pad 3. The semiconductor substrate is polished to a thickness of about 200 to 250 μm to improve heat dissipation. Even with this method, only a small output could be obtained.

In order to increase the output, the semiconductor substrate 7 is
PH3 (Plated He) on the back side of the substrate.
Attempts were made to improve the heat dissipation effect by forming a heat sink called 100 μm thick with Au plating, etc.
It was impractical in terms of cost, reliability, etc.

[Problem that the invention seeks to solve]

In the conventional semiconductor device described above, Ga is added to the semiconductor substrate.
When As is used, GaAs has poor thermal conductivity compared to Si, and the dissipation of heat generated from transistors and the like forming the internal circuit becomes a problem. Therefore, with the structure shown in Figure 2, only a small output microwave integrated circuit can be obtained, and the PH8 structure has a chip area of 2 am'
There were problems in that the size was 411 mo, the cost was high, and the reliability was low.

[Means for solving problems]

The semiconductor device of the present invention includes a semiconductor substrate, a microwave internal circuit integrated and formed on the surface of the semiconductor substrate, and a region of the microwave internal circuit that is dug from the back surface of the semiconductor substrate toward the front surface. It is configured to include a recessed portion having a reduced thickness, an air hole provided around the microwave internal circuit and reaching the surface of the recessed portion, and a metal layer provided on the surface of the recessed portion.

〔Example〕

Next, embodiments of the present invention will be described using the drawings.

FIGS. 1A and 1B are a plan view and a sectional view taken along the line A-A' of an embodiment of the present invention.

This embodiment includes a semiconductor substrate 1, a microwave internal circuit 2 integrated and formed on the surface of the semiconductor substrate 1, and a region of the microwave internal circuit 2 that is excavated from the back surface of the semiconductor substrate 1 toward the front surface. , an air hole 4 provided around the microwave internal circuit 2 and reaching the surface of the recess 5 , and a metal layer 6 provided on the surface of the recess 5 . . The substrate thickness in the region where the internal circuit 2 is formed is 50 to 80 μm. The shape of the air hole 4 is cylindrical,
It can be any truncated cone shape.

In the present invention, the thickness of the semiconductor substrate 1 is maintained at the same thickness at the start of manufacturing, and is not made thinner as explained in FIG. 2. This is because the thicker the chip periphery, the higher the mechanical strength. The recesses may be formed by either wet etching (chemical etching) or dry etching (plasma etching, etc.). At least one air hole 4 shall be provided.

In this embodiment, four are provided, but six or eight may be provided.

The semiconductor chip made in this way is mounted in a container using a brazing material.

With the above structure, the thickness of the substrate in the internal circuit portion that generates heat is thin, so even if a substrate with poor thermal conductivity such as GaAs is used, the generated heat is quickly transferred to the metal layer 6. and is dissipated through the metal layer 6 and the brazing material. In addition, the air heated by the heat radiation from the metal layer 6 is transferred to the air hole 4.
Go through it and escape to the top. Due to these factors, heat dissipation performance is significantly improved.

〔Effect of the invention〕

As explained above, the present invention has an inverted circuit shape in which the substrate thickness of the heat generating part is thinner than that of the pond part, the inner surface of the recess is coated with a metal having good thermal conductivity, and air holes are provided around the heat generating part. Since the heated air is allowed to escape, the heat dissipation performance is greatly improved, which has the effect of providing high-frequency semiconductor devices for medium and high power outputs.The improved heat dissipation performance also improves reliability. It has the effect of improving.

[Brief explanation of the drawing]

1(a) and (b) are a plan view and a sectional view of an embodiment of the present invention, and FIG. 2 is a sectional view of an example of a conventional microwave integrated circuit. 1... Semiconductor substrate, 2 ...internal circuit, 3...ponding pad, 4...air hole, 5...recess, 6...
...Metal layer.

Claims (1)

[Claims] a semiconductor substrate, a microwave internal circuit integrated and formed on a surface of the semiconductor substrate, and a recess that is dug from the back surface of the semiconductor substrate toward the front surface to reduce the thickness of the region of the microwave internal circuit. . A semiconductor device comprising: an air hole provided around the microwave internal circuit and reaching the surface of the recess; and a metal layer provided on the surface of the recess.