JPS6358368B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a novel hybrid integrated circuit device.

In a high-output transistor, which is an example of a semiconductor device, a collector current of several amperes or more flows.
At this time, heat is generated inside the transistor pellet as a semiconductor element. In order to avoid instability of characteristics and accelerated deterioration of lifetime due to this heat generation, methods are used to prevent the temperature of the transistor pellet from rising beyond the permissible limit temperature.

One method to prevent temperature rise has traditionally been to attach the stem, which serves as a support for the transistor pellet, to a radiator, and to release the heat generated by the transistor pellet to the outside via the stem and the radiator. It's here.

However, for high power transistors,
As mentioned above, in order to flow a large collector current,
In order to secure the current path and to efficiently dissipate heat, the transistor pellet must be mounted so that the collector region is directly fixed to the stem. By the way, since this type of transistor is usually used with the emitter or base grounded, the collector terminal or stem cannot be directly attached to a heat sink (or chassis) etc. which is often grounded.

For this reason, usually an insulating plate such as mica or polyester terephthalate (Mylar) is sandwiched between the stem and the heatsink to provide electrical insulation, and between the stem and the insulating plate and between the insulating plate and the heatsink. Grease was interposed to fill the gaps and aid heat radiation, and the stem and heat radiator were further fixed on top of this by screwing through insulating washers.
However, even in this case, since the collector region is electrically connected to the stem (the stem cannot be grounded), it is difficult to avoid the effects of noise due to electromagnetic interference.

On the other hand, as an attempt to achieve electrical insulation, efficient heat dissipation, and prevention of electromagnetic interference, there are examples in which a semiconductor element is mounted on a metal support via beryllia porcelain or alumina porcelain. However, when using beryllia porcelain, (1) beryllium itself is highly toxic, so strict care must be taken when handling it, and it is difficult to obtain and expensive.

(2) The thermal expansion coefficient of Beryliya porcelain is 7.6×10 ^-6 /
Since there is a difference between the temperature and that of silicon (~3×10 ^-6 /°C), thermal fatigue is likely to occur at the junction between the semiconductor element and the beryllium ceramic, making it difficult to firmly integrate the two.

(3) Molybdenum (5.2×10 ^-6 /℃) and tungsten (4.3×10 ^-6 /℃) can be used to alleviate thermal fatigue at the joint.
It is necessary to interpose a spacer such as (°C) in addition to the insulating plate, but in this case, it is not only disadvantageous in terms of heat dissipation, but also economically disadvantageous in terms of the number of parts and processing steps required for integration.

Other problems remain. Also, molybdenum and tungsten are heavy metals (the specific gravity of molybdenum is
10.27, and the specific gravity of tungsten is 19.3), which means that it cannot fully comply with the direction of weight reduction that semiconductor devices are aiming for. On the other hand, even when alumina porcelain is used, problems similar to those described in (1) and (2) above arise, except for the problem of toxicity.

Although the drawbacks of conventional power hybrid integrated circuit devices using transistors have been described above, similar problems remain not only in transistors but also in other integrated circuit devices such as diodes and thyristors.

The present invention corrects the above-mentioned drawbacks and provides a hybrid integrated circuit that provides excellent electrical insulation between the semiconductor element and the support, efficient heat dissipation, noise prevention due to electromagnetic interference, strong bonding of the semiconductor element, and light weight. The purpose is to provide equipment.

The present invention provides an apparatus comprising a metal support, an insulating carrier fixed on the metal support, and at least two semiconductor circuit elements placed and fixed on the carrier by a metal layer. The insulating carrier is made of a silicon carbide sintered body, and a silicon dioxide thin film is formed on the surface of the sintered body on which the circuit element is mounted, and the silicon dioxide thin film has a dielectric strength of 2000 V between the support body and the element. A hybrid integrated circuit device is characterized in that it has a thickness equal to or greater than the above.

That is, the present invention uses silicon carbide (relative density 98~
100%) is bending strength ~100Kg/ ^mm2 (room temperature), Vickers hardness (300g) 3700~4000, coefficient of thermal expansion (room temperature ~ 900℃) 4 x 10 ^-6 /℃, thermal diffusivity (room temperature)
0.229cm ² /s, thermal conductivity (room temperature) 0.18cal/cm・
It exhibits physical properties of s・℃ and specific gravity of 3.17, and among these properties, the coefficient of thermal expansion is particularly close to that of silicon, which allows for strong integration without causing thermal fatigue at the bonded part, and the thermal conductivity is low. Heat dissipation is efficient because it is almost equivalent to alumina magnetism, and it is mechanically robust.In addition to silicon carbide itself being lightweight, there is no need to use heavy metals such as molybdenum or tungsten as spacers. Focusing on the fact that it has desirable properties as a matrix for an insulating plate between a semiconductor element and a support,
This was done after confirming its effectiveness through practical application.

In order to obtain an insulating board suitable for the aforementioned purpose,
Preferably, a silicon carbide powder molded product is sintered under pressure in a vacuum. The silicon dioxide thin film responsible for electrical insulation may be formed by thermally oxidizing a silicon carbide sintered body, but if necessary, it may be formed by direct sputtering or CVD on the silicon carbide sintered body.
(Chemical Vapor Deposition) method or the like.

The present invention will be explained in detail below using examples.

Example 1 As shown in FIG. 1, a semiconductor device in this example includes four silicon diode pellets 41, 41' as semiconductor elements, which are formed on a silicon carbide sintered body 42 by thermal oxidation. The diode pellets are integrated on a copper support 45 via an insulating carrier provided with a silicon dioxide thin film 43 of approximately 1.5 μm and an aluminum layer 44 provided thereon, and lead wires 46, 46' are attached to each diode pellet. A lead wire 47 is also provided on the layer 44, and the four diodes are electrically connected so that they each play a part of the rectifier circuit, and a resin mold is formed so that at least the silicon diode pellets 41 and 41' are isolated from the outside air. It is a hybrid integrated circuit device. The resin mold is not shown. The silicon pellets and the insulating carrier and the insulating carrier and the copper support were bonded by forming metallized layers on the bonding surfaces of the silicon pellets and the insulating carrier, and by soldering.

In the hybrid integrated circuit device of this example obtained with such a configuration, the dielectric strength voltage between the copper lead wire 46 and the copper support 45 is 2000 V or more, and the thermal resistance between the transistor pellet and the copper support is 1. C/W or less was obtained. Furthermore, the noise due to electromagnetic interference was approximately 30 dB lower than when there was no electrical insulation between the transistor pellet and the copper support. Even after the transistor pellets were subjected to thermal changes between room temperature and 125°C 1000 times, no abnormality was found in the integrated portion between the transistor pellets 41, 41' and the silicon carbide sintered body 42. Ta.

This high dielectric strength voltage was obtained because of the silicon dioxide thin film 43 with high insulation resistance and the transistor pellets 41, 41' silicon carbide sintered body 42.
This is because there is insulation between them. The low thermal resistance is due to the silicon dioxide thin film 43 being formed extremely thin and the silicon carbide sintered body 42 having good thermal conductivity helping heat radiation. Further, the noise can be reduced because the copper support 45 is electrically insulated from the transistor pellets 41, 41', so that the copper support 45 can be grounded.

The reason why we were able to create a robust integration that is resistant to thermal fatigue is that the coefficients of thermal expansion of the transistor pellets and the silicon carbide sintered body are almost the same, so residual stress changes due to temperature changes in the integrated part. This is because the silicon carbide sintered body itself has high mechanical strength and can sufficiently withstand changes in stress caused by thermal expansion of the molding resin.

Furthermore, since the present invention has a transistor mounted on a silicon dioxide film formed on a silicon carbide sintered body, a remarkable effect of reducing the high dielectric constant of the sintered body itself can be obtained, and as a result, the signal processing speed can be increased. I was able to improve it.

In addition, in the case of this example, four diode pellets could be placed on the same insulating carrier, so the spacer weight was significantly reduced, and the weight could be reduced by approximately 30% compared to the conventional equivalent semiconductor device. Ta.

As described above, it has been demonstrated that a carrier in which a silicon dioxide thin film is provided on a silicon carbide sintered body is extremely useful as an insulating carrier for a circuit device in which a plurality of semiconductor elements are integrated.

Embodiment 2 As shown in FIG. 2, a semiconductor device in this embodiment includes silicon diode pellets 511, 512, 513, 514 as semiconductor elements, and silicon dioxide films 53, 5 on silicon carbide 52, 52'.
3', are integrated via aluminum layers 54, 54', and these integrated bodies are integrated on a copper support 55, and a lead wire 56 is attached to each diode pellet.
1,562,563,564 are attached, and lead wires 57, 564 are attached to the aluminum layers 54, 54'.
57', electrically connected so that the four diodes each play a part of the rectifier circuit, and at least silicon diode pellets 511, 51
This is a hybrid integrated circuit device in which parts No. 2,513, and 514 are resin-molded so as to be isolated from the outside air. The range mold is not shown.

The insulation properties, heat dissipation properties, thermal fatigue resistance, and noise prevention effects of the semiconductor device obtained with such a configuration were equivalent to those of Example 1. In addition, in this example, as in Example 1, the dielectric constant of the silicon carbide sintered body itself is reduced by the silicon dioxide thin film, allowing for speedy processing and weight compared to conventional products of equivalent semiconductor devices. was able to be reduced by approximately 20%.

As described above, it has been confirmed that the present invention can be applied without problems even when a plurality of insulating carriers made of silicon carbide and silicon dioxide are placed on the same support.

Although the present invention has been described above using examples, the present invention is not limited thereto, and the effects and advantages of the present invention can be enjoyed even in the following cases, for example.

(1) When a silicon dioxide thin film is locally provided on the surface of the silicon carbide sintered body on which the semiconductor element is placed.

(2) When the support is made of a metal other than copper, such as aluminum.

(3) When the material of the semiconductor element has a small difference in thermal expansion coefficient from the insulating carrier such as germanium, gallium arsenide, or phosphogallium.

(4) Not limited to cases where the electrodes of a semiconductor element are on both main surfaces of the same element (when the semiconductor element generates significant heat), but cases where all electrodes are provided on one main surface.

(5) When the objects placed on the insulating carrier include other electronic circuit elements such as resistors and capacitors in addition to semiconductor elements.

(6) Semiconductor elements may be solder or metals other than aluminum, such as gold, silver, copper, gallium, tin, silicon, germanium, palladium, chromium,
When placed on an insulating carrier via a metal made of at least one element selected from nickel, molybdenum, and tungsten.

As explained above, according to the present invention, the following advantages and effects can be achieved.

(1) Since the insulating carrier base material is made of a silicon carbide sintered body with good heat dissipation and silicon dioxide is formed thinly, the thermal resistance between the semiconductor element and the support is low. As a result, overheating of the semiconductor element can be prevented, so that the characteristics of the semiconductor device can be kept stable.

(2) Since a large insulation resistance can be obtained even with a thin silicon dioxide film, the dielectric strength voltage between the semiconductor element and the support can be increased without impairing heat dissipation performance.

(3) Since the semiconductor element is electrically isolated from the support and the support can be grounded,
It is possible to prevent the characteristics of a semiconductor device from being affected by electromagnetic interference.

(4) Since the difference in thermal expansion coefficient between the semiconductor element and the insulating carrier is small, the stress generated thermally in the part where they are fixed is small, and thermal fatigue of the part due to temperature changes can be reduced. As a result, strong integration that is stable against temperature changes is possible.

(5) Since the insulating carrier has excellent mechanical strength, the semiconductor element mounted thereon can easily withstand mechanical shocks applied from the outside.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing embodiments of the power hybrid integrated circuit device of the present invention, respectively. 41, 41', 511-514...Silicon transistor pellet, 45,55...Copper support,
43, 53, 53'... silicon dioxide film, 42,
52, 52'...Silicon carbide sintered body, 44, 54,
54'...Laminated vapor deposition film.

Claims (1)

[Claims] 1. A device comprising a metal support, an insulating carrier fixed on the metal support, and at least two semiconductor circuit elements placed and fixed on the carrier by a metal layer. In this, the insulating carrier is made of a silicon carbide sintered body, and a silicon dioxide thin film is formed on the surface of the sintered body on which the circuit element is mounted, and the silicon dioxide thin film is formed between the support body and the element. A hybrid integrated circuit device characterized by having a thickness such that the dielectric strength voltage is 2000V or more. 2 In claim 1, the semiconductor circuit element is a diode, a transistor, a thyristor,
A hybrid integrated circuit device comprising at least one type of integrated circuit element.