JP2001024093A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase mechanical strength by reducing defect which causes insulation deterioration by constituting one ceramic insulation substrate by a plurality of unit substrate modules formed by dividing a ceramic substrate finely and mutually adhering edges of a plurality of unit substrate modules arranged plane. SOLUTION: An insulation substrate 100 is constituted as one large insulation substrate by arranging small regular hexazonal unit substrate modules 11 formed by dividing one ceramic insulation substrate finely on the same plane without a clearance, and adhering and setting adjacent edges of the plurality of unit substrate modules 11 mutually by resin 12. Since each unit substrate module 11 of the insulation substrate 100 is small, probability of inclusion of defect in each module is little. As a result, it is possible to extremely reduce a possibility that defect causes the insulation substrate 100 to be broken, thus lowering insulation property and raising dielectric breakdown between a semiconductor element and a heat sink.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having a semiconductor element mounted on an insulating substrate, and more particularly, to a semiconductor device in a power module having one or more power semiconductor elements. The present invention relates to a highly reliable semiconductor device that prevents cracking of an insulating substrate to be mounted.

[0002]

2. Description of the Related Art As shown in FIG. 4, a general power module which is a semiconductor device of this type includes a metal radiator plate 5 as shown in FIG.
Insulating substrate 1 made of ceramics mounted on
A copper foil 2 is provided on the insulating substrate 1, a plurality of semiconductor elements 3 are mounted on the copper foil 2, and the semiconductor elements 3 are connected by lead wires 4.

At the periphery of the heat sink 5, a plastic case 6 is set up so as to surround the entire case.
Further, a terminal holder 8 to which an external terminal lead wire 7 is attached from above is attached so as to entirely cover the upper side of the case 6 thus raised.
One end of the external terminal lead wire 7 is connected to the semiconductor element 3 and the other end extends to the outside, so that the semiconductor element 3 can be electrically connected to the outside.

In addition, a silicone gel 9 is poured into an internal space surrounded by the case 6 and the terminal holder 8 and hardened, thereby securely fixing the entire power module. The periphery between the case 6 and the terminal holder 8 is sealed with a sealing member 10 made of epoxy resin or the like.

[0005] The insulating substrate 1 is inserted between the semiconductor element 3 and the radiator plate 5, so that the radiator plate 5, which is normally mounted on a casing grounded via a control panel or the like, and operates at a high pressure. 3 is electrically insulated.

Since the semiconductor element 3 switches a large current, heat loss is large and heat generation is large.
Therefore, an excessive rise in temperature not only lowers the switching characteristics but also has a high risk of destroying the semiconductor element 3 itself. For this reason, it is necessary to radiate the heat generated in the semiconductor element to the heat radiating plate 5 as efficiently as possible, and the insulating substrate 1 provided therebetween is required to have high thermal conductivity. Therefore, as long as the insulation characteristics allow, it is necessary to make the insulating substrate as thin as possible from the viewpoint of heat dissipation. Note that ceramics such as aluminum nitride and aluminum oxide are used as the insulating material having excellent thermal conductivity applied to the insulating substrate.

As described above, an insulating substrate requires high thermal conductivity, but a ceramic insulating substrate is usually produced by molding as a powder containing a solvent, drying and sintering. In this case, for example, yttria or the like is used as a sintering aid, but it is sintered in a state where it is gathered at the grain boundary to become a defect. Further, a defect occurs when the gas generated during sintering remains as minute voids.
Then, in the production process of the controlled ceramics, there is a possibility that a defect is mixed, although the probability is low.

[0008] Ceramics, which is a brittle material, is very sensitive to defects, and the mechanical strength is drastically reduced even if there are minute defects of several tens of μm. Since the mechanical strength increases as the probability of existence of a defect increases, the larger the size of one insulating substrate, the easier it is to develop a mechanical strength lower.

[0009]

As described above, ceramics are very sensitive to defects, and the mechanical strength is significantly reduced by small defects introduced during the manufacturing process. In particular,
When the semiconductor element generates heat, a large thermal stress is generated due to a difference in coefficient of thermal expansion between the insulating substrate and the metal radiator plate 5,
Alternatively, when the heat sink is attached to the housing, the flatness between the attachment surface and the heat sink differs due to a difference in surface accuracy, and a large bending load is applied when tightening the bolts. If the insulating board is normal,
Although it has a sufficient strength, if a defect is present, the strength is reduced to less than half of the normal strength, and there is a high possibility of breakage. If the insulating substrate breaks, the insulation properties in the thickness direction will decrease, causing dielectric breakdown between the semiconductor element and the heat sink,
There is a problem that the device stops. That is, a large-capacity power unit using a semiconductor device is usually used as a power source for a large factory such as a rolling line and semiconductor manufacturing, and a power source for industrial equipment such as a vehicle and an elevator. The social consequences of doing so are enormous.

[0010] The present invention has been made in view of the above,
The aim is to provide a highly reliable semiconductor device using an insulating substrate with excellent insulation and thermal conductivity while reducing the presence of defects that cause insulation deterioration and increasing mechanical strength. Is to do.

[0011]

According to a first aspect of the present invention, there is provided a semiconductor device having a semiconductor element mounted on an insulating substrate, wherein the insulating substrate comprises a ceramic substrate. The plurality of finely divided unit substrate modules and the edges of the plurality of unit substrate modules arranged in a plane such that the plurality of finely divided unit substrate modules constitute one ceramic insulating substrate are adhered to each other. And an adhesive to be used.

According to the first aspect of the present invention, the insulating substrate is formed as a single ceramic insulating substrate by bonding edges of a plurality of unit substrate modules obtained by finely dividing the ceramic substrate to each other with an adhesive. Therefore, the probability that a defect is mixed into each unit substrate module is reduced, whereby the mechanical strength is increased, and the insulation characteristics can be improved.

[0013] The present invention described in claim 2 provides the present invention in claim 1.
In the invention described above, the plurality of unit substrate modules have the same polygonal or circular shape.

According to the second aspect of the present invention, since each unit substrate module has the same polygonal or circular shape, thermal stress does not concentrate on the interface between the unit substrate module and the adhesive. There is no danger of occurrence, and the mechanical properties can be improved.

Further, the present invention according to claim 3 provides the invention according to claim 2.
In the described invention, the polygon is a hexagon.

According to the third aspect of the present invention, since the shape of the insulating substrate is hexagonal, it is possible to provide mass productivity and a thermal stress relaxation characteristic having a circular shape.

According to a fourth aspect of the present invention, in the first aspect, the adhesive is a resin or a rubber.

According to the fourth aspect of the present invention, since the adhesive is a resin or a rubber, the elasticity is large, the elasticity is high, and the deformation to the ceramic substrate is absorbed by the adhesive made of the resin or the rubber. The insulating substrate is not cracked even when it is deformed due to a rise in temperature or when it is mounted.

According to a fifth aspect of the present invention, there is provided a semiconductor device comprising a semiconductor element mounted on an insulating substrate, wherein the insulating substrate is mounted on the insulating element so that only the semiconductor element can be mounted. The gist of the present invention is that it comprises an insulating substrate unit made of a ceramic substrate having a mounting area slightly larger than the size, and a peripheral portion formed around the insulating substrate unit by resin or rubber into a substrate shape.

According to the fifth aspect of the present invention, the insulating substrate is a small insulating substrate unit slightly larger than the semiconductor element so as to mount only the semiconductor element, and its peripheral portion is made of resin or rubber. Therefore, a substrate that is not easily broken by the resin or rubber in the peripheral portion can be configured.

Further, the present invention described in claim 6 provides the present invention according to claim 5.
In the invention described in the above, the gist is that the ceramic substrate is polygonal or circular.

According to the present invention, since the ceramic substrate is polygonal or circular, thermal stress does not concentrate on the interface between the ceramic substrate and the resin or rubber.
Therefore, there is no danger of cracking, and the mechanical properties can be improved.

According to a seventh aspect of the present invention, in the first or fifth aspect, the ceramic substrate is formed of aluminum nitride or aluminum oxide.

According to the present invention, since the ceramic substrate is made of aluminum nitride or aluminum oxide, it has excellent thermal conductivity.

The present invention according to claim 8 provides the present invention according to claim 4.
Alternatively, in the invention described in Item 5, the resin is an epoxy resin.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing a structure of an insulating substrate 100 used for a semiconductor device according to one embodiment of the present invention. The insulating substrate 100 shown in FIG. 1 has a plurality of small regular hexagonal unit substrate modules 11 formed by finely dividing a single ceramic insulating substrate and arranged on the same plane without any gap. Adjacent edges of the substrate module 11 are adhered to each other with a resin 12 and solidified to form one large insulating substrate. Note that the resin 12 constituting the adhesive may be rubber.

The insulating substrate 100 thus configured is
Since the individual unit substrate module 11 is small, the probability of inclusion of a defect included in each module is low, and therefore, the insulating substrate 100 is cracked due to the defect, the insulating characteristics are reduced, and the distance between the semiconductor element and the heat sink is reduced. Is extremely reduced to cause dielectric breakdown.

Since the resin 12 filling the gap between the plurality of unit substrate modules 11 has a larger elastic modulus than the ceramics, when a large deformation occurs, the resin 12 is almost deformed, The insulating substrate 100 exhibits excellent flexibility not found in the conventional integrated ceramic insulating substrate. As a result, the insulating substrate 100 is not cracked by deformation due to temperature rise or deformation during mounting.

When the ceramic substrate is divided into small pieces like the insulating substrate 100 of the present embodiment shown in FIG.
Partitions of resin having low thermal conductivity are formed in the plane direction of the insulating substrate 100, and the thermal conductivity of the entire insulating substrate 100 is reduced. Therefore, the layer of the resin 12 is made as thin as possible to minimize the reduction in thermal conductivity. It needs to be suppressed. Industrially, the unit substrate modules 11 having the same shape as shown in FIG. 1 are suitable for mass production and have a desirable shape. Therefore, in order to spread the plurality of unit board modules 11 without gaps, it is desirable to use a polygon such as a triangle, a square, and a hexagon as shown in FIG.

Further, thermal stress is easily generated at the interface between the resin 12 and the ceramic substrate, and there is a risk that cracks may be generated due to stress concentration in the resin layer near the corners of the ceramic. From such a viewpoint, it is desirable that the unit substrate module 11 is circular. Then, the unit substrate modules 11 having variously changed circle sizes are spread without gaps, and the edges of the adjacent unit substrate modules 11 are adhered to each other with the resin 12 and cured, so that the insulation is excellent in mechanical properties and resistant to cracking. The substrate 100 can be used.

The hexagonal unit substrate module 11 having the above-described polygonal mass productivity and circular thermal stress relaxation characteristics is the most effective shape.

The insulating substrate 100 shown in FIG. 1 is composed of a plurality of hexagonal unit substrate modules 11 each made of aluminum nitride and having a side of 8 mm and a thickness of 1 mm. 12 was impregnated and cured under vacuum to obtain about 80 mm × 80 mm
A 1 mm insulating substrate 100 was produced. For comparison, one integrated aluminum nitride substrate of the same size was manufactured as a conventional product, and the insulating substrate 100 of the present invention was manufactured.
As a result of comparison between the conventional substrate and this conventional product, the mechanical strength was almost the same, but the amount of deformation (deflection) at the time of destruction of the insulating substrate 100 of the present invention was about three times larger than that of the conventional product, and it was more flexible. Substrate was confirmed. In addition, as a result of the 30-sheet test, the conventional product has a large variation,
Although there were two points having extremely low strength, none of the insulating substrates 100 of the present invention had low strength.

FIG. 2 is a plan view showing the structure of an insulating substrate 200 used in a semiconductor device according to another embodiment of the present invention. The insulating substrate 200 shown in FIG.
An insulating substrate unit 110 made of a ceramic substrate having a mounting area slightly larger than the semiconductor element 3 so that only the semiconductor element 3 can be mounted, and a peripheral portion 120 formed of a resin or rubber around the insulating substrate unit 110 in a substrate shape. Be composed.

Generally, the only portion of the insulating substrate 200 that requires thermal conductivity is the portion on which the semiconductor element 3 is mounted and its periphery. Therefore, as in the present embodiment, only this portion is made of a ceramic substrate. By disposing the insulating substrate unit 110 and molding the peripheral portion 120 thereof with resin or rubber, it is possible to effectively produce an insulating substrate having excellent thermal conductivity as a whole and resistant to cracking. In this case, since the peripheral portion 120 does not need to be thin, a circular insulating substrate unit 110 with less stress concentration is optimal as shown in FIG.

Further, since the spread of heat when conducted through the solid is inside the range of 45 degrees, the heat generated in the semiconductor element 3 as shown in FIG. Conducted to 110 and escaped to the heat sink 5,
The spread is a portion that spreads 45 degrees from the end of the semiconductor element 3. Therefore, the insulating substrate other than the portion within the range of 45 degrees hardly contributes to heat dissipation. Therefore, an insulating substrate unit 110 composed of a ceramic substrate slightly larger than the semiconductor element 3 is disposed immediately below the semiconductor element 3 so that only the semiconductor element 3 can be mounted like the insulating substrate 200 of the present embodiment shown in FIG. This will provide sufficient heat dissipation. Since the peripheral portion 120 of the insulating substrate unit 110 is not involved in heat dissipation, the peripheral portion 120 may be formed of resin or rubber.

The resin constituting the peripheral portion 120 or the resin for the adhesive for bonding the unit substrate modules 11 in the embodiment of FIG. Are better.

In the insulating substrate 200 shown in FIG. 2, the insulating substrate unit 110 is specifically made of aluminum nitride, having a diameter of 20 mm and a thickness of 1 mm.
A peripheral portion 120 surrounding the periphery of the insulating substrate unit 110 is molded with epoxy resin filled with 60 wt% of silicon powder, and has a total size of about 50 mm × 50 mm.
A semiconductor element 3 having a side of 12 mm and a side of 12 mm was bonded onto the insulating substrate unit 110 as a 1 × 1 mm insulating substrate 200.

In order to compare the performance of the insulating substrate 200 configured as described above, one integrated aluminum nitride insulating substrate having the same shape as a conventional product was manufactured. Then, the insulating substrate 200 of the present invention and the conventional insulating substrate have a thickness of 10 mm on the surface opposite to the mounting surface of the semiconductor element 3.
The copper heat sink was connected to the insulating substrate by soldering. With the insulating substrate thus configured, the semiconductor element 3 is left standing at room temperature.
When the temperature rise was measured, the insulating substrate 200 of the present invention was almost at the same level as the conventional product, and there was no inferior heat dissipation.

[0039]

As described above, according to the present invention,
Adhesives are used to bond the edges of a plurality of unit substrate modules in which the insulating substrate is finely divided from the ceramic substrate to form a single ceramic insulating substrate, reducing the probability of defects entering each unit substrate module. Thus, the mechanical strength is increased, and the insulation properties can be improved.

Further, according to the present invention, since each unit substrate module has the same polygonal or circular shape, thermal stress does not concentrate on the interface between the unit substrate module and the adhesive, and therefore, there is a danger of cracks being generated. And mechanical properties can be improved.

Furthermore, according to the present invention, since the shape of the insulating substrate is hexagonal, it is possible to provide mass productivity and a circular thermal stress relaxation characteristic.

According to the present invention, since the adhesive is resin or rubber, it has a high elastic modulus and is flexible, and the deformation on the ceramic substrate is absorbed by the adhesive made of resin or rubber. The insulating substrate does not break even when deformed.

Further, according to the present invention, the insulating substrate is a small insulating substrate unit slightly larger than the semiconductor element so as to mount only the semiconductor element, and its peripheral portion is made of resin or rubber. In addition, a substrate that is not easily broken by the resin or rubber in the peripheral portion can be configured.

Further, according to the present invention, since the ceramic substrate is polygonal or circular, thermal stress does not concentrate on the interface between the ceramic substrate and the resin or rubber, and therefore there is no danger of cracking, and mechanical Characteristics can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing a structure of an insulating substrate used in a semiconductor device according to one embodiment of the present invention.

FIG. 2 is a plan view showing a structure of an insulating substrate used in a semiconductor device according to another embodiment of the present invention.

FIG. 3 is an explanatory diagram showing heat conduction characteristics in the insulating substrate unit in the embodiment shown in FIG.

FIG. 4 is a cross-sectional view illustrating a structure of a power module that is a general semiconductor device.

[Explanation of symbols]

 Reference Signs List 3 semiconductor element 5 heatsink 11 unit substrate module 12 resin 100, 200 insulating substrate 110 insulating substrate unit 120 peripheral part

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01L 25/18 H01L 25/04 C (72) Inventor Yuki Sekiya 1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba Fuchu Plant (72) Inventor Kenji Kijima 1 Toshiba-cho, Fuchu-shi, Tokyo F-term in the Fuchu Plant of Toshiba Corporation (reference) 5F036 AA01 BA23 BB08 BE01

Claims (8)

[Claims] In a semiconductor device configured by mounting a semiconductor element on an insulating substrate, the insulating substrate includes a plurality of unit substrate modules obtained by finely dividing a ceramic substrate, and a plurality of unit substrate modules obtained by finely dividing the ceramic substrate. A semiconductor device comprising: an adhesive for bonding edges of the plurality of unit substrate modules arranged in a plane so as to form one ceramic insulating substrate. 2. The semiconductor device according to claim 1, wherein the plurality of unit substrate modules have the same polygonal or circular shape. 3. The semiconductor device according to claim 2, wherein said polygon is a hexagon. 4. The semiconductor device according to claim 1, wherein said adhesive is resin or rubber. 5. In a semiconductor device configured by mounting a semiconductor element on an insulating substrate, the insulating substrate has a mounting area slightly larger than the size of the semiconductor element so that only the semiconductor element can be mounted. A semiconductor device comprising: an insulating substrate unit made of a ceramic substrate; and a peripheral portion formed around the insulating substrate unit with a resin or rubber into a substrate shape. 6. The semiconductor device according to claim 5, wherein said insulating substrate unit is polygonal or circular. 7. The semiconductor device according to claim 1, wherein the ceramic substrate is formed of aluminum nitride or aluminum oxide. 8. The semiconductor device according to claim 4, wherein the resin is an epoxy resin.