JPH0823044A - Manufacture of high frequency semiconductor device - Google Patents

Abstract

PURPOSE:To alleviate the thermal strain in assembling of the high frequency semiconductor device of a ceramic casing having a copper flange, and to prevent generation of cracks by a method wherein, after the ceramic casing with a copper flange has been assembled, heat treatment is conducted at a specific temperature, and the outer casing is formed. CONSTITUTION:A ceramic casing is composed of a beryllia substrate part 1 on which a silicon transistor chip 4, formed by beryllia, is mounted, a ceramic frame part 2a where a sealing cap is mounted, a ceramic substrate 2b provided with an electrode lead-out part 5 with is used to lead out the electrode of a transistor chip, and a copper heat sink 3 having a screwing part. After assembling the abovementioned ceramic casing, heat treatment is conducted at 450 to 500 deg.C, the thermal strain generated when assembling the ceramic casing in the manufacture of the high frequency semiconductor device is alleviated, and the generation of cracks is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a high frequency semiconductor device, and more particularly to a method of manufacturing a ceramic envelope using a copper flange.

[0002]

2. Description of the Related Art High-frequency and high-power transistors have been remarkably increased in output. In addition to high-output and high-performance transistor chips, large-sized envelopes and low thermal resistance have been actively used.

Here, of the ceramic envelopes used in the semiconductor device for high frequency and high power, the structure of the ceramic envelope for the silicon transistor and the manufacturing method thereof will be described with reference to FIG.

The ceramic envelope is a beryllia substrate portion 1 formed of beryllia and mounting a silicon transistor chip 4, a frame portion 2a, both of which are made of ceramic, for mounting a sealing cap, and an electrode lead-out for leading out electrodes of the transistor chip. It is composed of a ceramic substrate portion 2b (not shown) on which the portion 5 is provided, and a heat sink 3 made of copper and provided with a screwing portion.

The point of the above structure is that a material having a high thermal conductivity is used in order to effectively dissipate the heat generated by the semiconductor element. Further, the difference in the coefficient of thermal expansion between the respective materials is made small, and cracks due to strain generated by heat treatment or the like are prevented as much as possible.

The thermal conductivity and the coefficient of thermal expansion of each material used in the following table are displayed.

[0007]

[Table 1] After forming each of the above members, use a silver brazing material to bond them at 850 ° C.
Then, Ni, Au plating is applied to complete the envelope.

The heat treatment process in the semiconductor device manufacturing process is a 400 ° C. AuSi eutectic process for mounting semiconductor elements and internal matching circuit parts, a 200 ° C. Au wire bonding process, and a 300 ° C. sealing process.

[0009]

The above-mentioned method of manufacturing an envelope using a copper flange has a drawback that cracks are generated in a ceramic or the like due to thermal strain in a heat treatment step in a semiconductor device manufacturing step.

As a method for reducing the thermal strain, a method of reducing the contact area between copper and ceramic or beryllia or a method of using a copper-tungsten alloy having a small coefficient of thermal expansion instead of copper can be considered, but in either case, the heat conduction is deteriorated. However, there is a drawback that it invites a decrease in reliability.

Further, when the envelope is made large, the contact area between the metal and the ceramic or beryllia becomes large, so that the thermal strain due to the difference in the coefficient of thermal expansion becomes more remarkable.

When an envelope using a copper flange as described above is used, cracks are likely to occur in ceramics and beryllia in the semiconductor device manufacturing process.

An object of the present invention is to alleviate thermal strain in the assembly of a ceramic envelope whose flange is made of copper in the manufacture of a high frequency semiconductor device and prevent the occurrence of cracks.

[0014]

In the method of manufacturing a high frequency semiconductor device according to the present invention, a ceramic envelope having a flange made of copper is assembled and then heat treated at 450 to 500 ° C. to form the envelope. It is characterized by doing.

[0015]

According to the present invention, the thermal distortion of the assembly in the manufacture of the high frequency semiconductor device of the ceramic envelope whose flange is made of copper can be relaxed and the occurrence of cracks can be prevented.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a ceramic envelope for a silicon bipolar transistor according to an embodiment of the present invention will be described below with reference to FIG.

The ceramic envelope is a beryllia substrate portion 1 formed of beryllia for mounting a silicon transistor chip 4, a frame portion 2a for mounting a sealing cap, and a lead portion for leading out electrodes of the transistor chip. It is composed of a ceramic substrate portion (not shown) provided with the portion 5, and a heat sink 3 made of copper and provided with a screwing portion.

Then, the manufacturing is performed as follows.

First, the beryllia substrate 1 on which the silicon transistor chip 4 is mounted, the frame portion to which the sealing cap is attached, and the ceramic substrate portion 2b on which the electrode lead-out portion 5 is provided are molded and sintered.

Next, the above-mentioned parts are made 850 by using a silver brazing material.
Bond and assemble at ℃. Further, Ni and Au plating is applied.

Next, heat treatment is performed at 450 to 500.degree.

Next, a semiconductor device and an internal matching component 400
AuSi eutectic mounting process at ℃, A at 200 ℃
A u wire bonding process and a 300 ° C. sealing process are performed.

Even in the heat treatment in each of these steps, no cracks were generated in the semiconductor element / internal matching component, the beryllia substrate / ceramic substrate.

It is considered that the cause of cracks due to thermal strain is largely influenced by the hardness of copper in addition to the coefficient of thermal expansion, and cracks can be prevented by reducing the hardness by heat treatment.
Further, it is more effective to heat-treat after assembling the envelope than to heat-treat only the copper material. Due to the heat treatment after assembling, the thermal strain at the time of assembling the envelope is also alleviated.

When the inventor made a trial confirmation, it was found that if the Vickers hardness of copper was 50 or less, no crack was generated in the ceramic or the like. To obtain this Vickers hardness, the heat treatment temperature is 450 ° C. or higher and the heat treatment time is 10
It's good for about a minute. Further, at a heat treatment temperature of 500 ° C. or higher, the Ni and Au plating layers were likely to be deteriorated and discolored.

From these facts, the heat treatment temperature is 450 to
If the temperature is set to 500 ° C and the heat treatment time is set to about 10 minutes, N
It is possible to stably obtain hardness such that cracks do not occur in the ceramic or the like without the i and Au plating layers being deteriorated or discolored.

The manufacturing method of the ceramic envelope for the silicon bipolar transistor has been described above as one embodiment of the present invention. However, the manufacturing method of the present invention can be applied to an envelope in which various ceramics and metals are in contact with each other. The same effect can be expected.

[0028]

As described above, according to the present invention, the thermal distortion of the ceramic envelope using the copper flange can be relaxed, and the yield and reliability of the semiconductor device can be improved.

[Brief description of drawings]

FIG. 1 shows an envelope for explaining a main part of an embodiment of a high-frequency semiconductor device according to the present invention, in which (a) is a top view,
(B) is a sectional view taken along the line AA of (a), and (c) is a sectional view in a direction different from that of (b).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Berrillia substrate part 2a ... Frame part 3 ... Heat sink 4 ... Silicon transistor chip 5 ... Electrode lead-out part

Claims (1)

[Claims] 1. A method of manufacturing a high-frequency semiconductor device, comprising assembling a ceramic envelope whose flange is made of copper, and then heat treating it at 450 to 500 ° C. to form the envelope.