Semiconductor device having radiation structure Number:6,960,825 from the United States Patent and Trademark Office (PTO) owispatent

Title: Semiconductor device having radiation structure

Abstract: A semiconductor device includes two semiconductor chips that are interposed between a pair of radiation members, and thermally and electrically connected to the radiation members. One of the radiation members has two protruding portions and front ends of the protruding portions are connected to principal electrodes of the semiconductor chips. The radiation members are made of a metallic material containing Cu or Al as a main component. The semiconductor chips and the radiation members are sealed with resin with externally exposed radiation surfaces.

Patent Number: 6,960,825 Issued on 11/01/2005 to Mamitsu,   et al.

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Inventors:	Mamitsu; Kuniaki (Nukata-gun, JP); Hirai; Yasuyoshi (Gamagori, JP)
Assignee:	Denso Corporation (Kariya, JP)
Appl. No.:	699837
Filed:	November 4, 2003

Foreign Application Priority Data

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	Nov 24, 1999[JP]	11-333119
	Nov 24, 1999[JP]	11-333124
	Mar 24, 2000[JP]	2000-88579
	Mar 30, 2000[JP]	2000-97911
	Mar 30, 2000[JP]	2000-97912
	Oct 04, 2000[JP]	2000-305228

Current U.S. Class:	257/718; 257/712; 257/723
Intern'l Class:	H01L 023/34
Field of Search:	257/712,713,722,729,718,179,720,723

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References Cited [Referenced By]

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Other References

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Primary Examiner: Potter; Roy
Attorney, Agent or Firm: Posz Law Group, PLC

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Parent Case Text

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CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of application No. 09/717,227, which was filed on Nov. 22, 2000, now U.S. Pat. No. 6,703,707 and which was bases upon and claimed the benefit of Japanese Patent Applications No. 11-333119 filed on Nov. 24, 1999, No. 11-333124 filed on Nov. 24, 1999, No. 2000-88579 filed on Mar. 24, 2000, No. 2000-97911 filed on Mar. 30, 2000, No. 2000-97912 filed on Mar. 30, 2000 and No. 2000-305228 filed on Oct. 4, 2000, the contents of which are incorporated herein by reference.

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Claims

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1. A semiconductor device comprising:

a semiconductor chip;

first and second radiation members thermally and electrically connected to the semiconductor chip interposed therebetween and protruding from a resin, and having a radiation surface for radiating heat from the semiconductor chip; and

first and second bonding members respectively interposed between the first radiation member and the semiconductor chip and between the semiconductor chip and the second radiation member, wherein:

the first and second radiation members are made of a metallic material that is superior to tungsten and molybdenum in at least one of an electrical conductivity and a thermal conductivity.

2. The semiconductor device of claim 1, wherein each of the first and second radiation members includes a partially disposed metallic member having a thermal expansion coefficient approximate to that of the semiconductor chip.

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Description

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BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a semiconductor device in which heat is radiated from both sides of a semiconductor chip accommodated therein.

2. Description of the Related Art

For example, JP-A-6-291223 discloses a semiconductor device in which heat is radiated from both sides of a semiconductor chip. FIGS. 1A to 1C show this semiconductor device. As shown in the figures, a pair of radiation members J2, J3 sandwich several semiconductor chips J1, and are thermally and electrically connected to the semiconductor chips J1. The several semiconductor chips J1 arranged on a plane and the radiation members J2, J3 are sealed with resin J5.

Each of the radiation members J2, J3 serves as an electrode, and has a surface exposed from the resin J5 at an opposite side of the face contacting the semiconductor chips J1. Each of the radiation members J2, J3 performs radiation of heat by making the exposed surface contact a contact body (not shown) that can exhibit a radiation action. A control terminal J4 connected with a control electrode of the semiconductor chips J1 protrudes to an outside from the resin J5.

Used as the radiation members J2, J3 is W (tungsten) or Mo (molybdenum) having a thermal expansion coefficient approximate to that of the semiconductor chips J1. The radiation member J2 that is connected to the surfaces of the semiconductor chips J1 on which the control electrode is formed is an emitter electrode, and the radiation member J3 that is connected to the surfaces of the semiconductor chips J1 at an opposite side of the control electrode is a collector electrode.

Besides, several solder bumps J7 protrudes from an insulating plate J6 that has a through hole at a center thereof in which the radiation member J2 penetrates as the emitter electrode. The solder bumps J7 are bonded to bonding pads existing in unit patterns of the respective semiconductor chips J1 disposed on the radiation member J3 as the collector electrode.

When the radiation members J2, J3 serving also as electrodes are made of metallic material such as W or Mo having linear thermal expansion coefficient approximate to that of the semiconductor chips J1 made of Si (silicon), these metallic materials are, in electrical conductivity about one third of that of Cu (copper) or Al (aluminum), and in thermal conductivity about one third to two third thereof. Thus, in the present circumstances involving an increased requirement for flowing a large current in the semiconductor chip, using W or Mo as a member that serves as a radiation member and an electrode simultaneously causes many problems.

Also, in general, a larger chip is required to accommodate a larger current. However, there are many technological problems to increase the chip size, and it is easier to manufacture plural smaller chips and accommodate them into one package.

In the technique disclosed in the publication describe above, the several semiconductor chips J1 are formed in the semiconductor device. However, as shown in FIG. 1A, because the radiation member J2 has a simple rectangular shape, and is provided at the center of the device, disposal of different semiconductor chips in one device is limited. That is, when the semiconductor chips are different from one another in, for example, thickness, it is difficult for the one emitter electrode having a simple shape to be connected to all of the different semiconductor chips.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above problem. An object of the present invention is to improve a radiation property and an electrical conductivity of a semiconductor device including radiation members that are thermally and electrically connected to both surfaces of a semiconductor chip therein. Another object of the present invention is to provide a semiconductor device easily accommodating several different semiconductor chips therein.

For example, according to one aspect of the present invention, in a semiconductor device in which a semiconductor chip is thermally and electrically connected to first and second radiation members therebetween, the first and second radiation members are made of a metallic material that is superior to tungsten and molybdenum in at least one of an electrical conductivity and a thermal conductivity. Accordingly, the radiation property and the electrical conductivity of the semiconductor device can be improved.

According to another aspect of the present invention, in a semiconductor device in which first and second semiconductor chips are thermally and electrically connected to first and second radiation members therebetween, the first radiation member has first and second protruding portions protruding toward the first and second semiconductor chips, and first and second front end portions of the first and second protruding portions are thermally and electrically connected to the first and second semiconductor chips through a bonding member.

In this case, even when the first and second semiconductor chips are different from each other in thickness, the first and second radiation members can be provided with first and second radiation surfaces approximately parallel to each other by controlling protruding amounts of the first and second protruding portions.

According to still another aspect of the present invention, in a semiconductor device in which a semiconductor chip is disposed between, a first conductive member and a second conductive member, the first conductive member is further bonded to a third conductive member at an opposite side of the semiconductor chip so that a bonding area between the first conductive member and the third conductive member is smaller than that between the first conductive member and the semiconductor chip. Accordingly, stress concentration on the first conductive member can be suppressed to prevent occurrence of cracks. This results in improved radiation property and electrical conductivity of the semiconductor device.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiments described below with reference to the following drawings, in which;

FIG. 1A is a schematic view showing a semiconductor device according to a prior art;

FIG. 1B is a cross-sectional view showing the semiconductor device, taken along line IB—IB in FIG. 1A;

FIG. 1C is a cross-sectional view showing the semiconductor device, taken along line IC—IC in FIG. 1A;

FIG. 2A is a cross-sectional view showing a semiconductor device in a first preferred embodiment;

FIG. 2B is an enlarged cross-sectional view showing a part indicated by arrow IIB in FIG. 2A;

FIG. 3 is a table showing metals usable for a radiation member in the first embodiment;

FIG. 4A is a cross-sectional view partially showing a semiconductor device in a second preferred embodiment;

FIGS. 4B to 4D are cross-sectional views respectively showing a first side radiation member and a Si chip in the second embodiment;

FIGS. 5A to 5C are cross-sectional views respectively taken along lines VA—VA, VB—VB, and VC—VC in FIGS. 4B to 4D;

FIG. 6 is a cross-sectional view showing a semiconductor device in a third preferred embodiment;

FIG. 7 is a cross-sectional view showing a semiconductor device in a fourth preferred embodiment;

FIG. 8A is a cross-sectional view showing a semiconductor device in a fifth preferred embodiment;

FIG. 8B is a cross-sectional view taken along line VIIIB—VIIIB in FIG. 8A;

FIG. 9A is a cross-sectional view showing a semiconductor device in a sixth preferred embodiment;

FIG. 9B is an enlarged cross-sectional view showing a part indicated by arrow IXB in FIG. 9A;

FIG. 9C is a cross-sectional view showing an example in the sixth embodiment;

FIG. 10 is a cross-sectional view showing a semiconductor device in a seventh preferred embodiment;

FIG. 11 is a cross-sectional view showing a semiconductor device in an eighth preferred embodiment;

FIG. 12 is a cross-sectional view showing a semiconductor device in a ninth preferred embodiment;

FIG. 13 is a cross-sectional view showing a semiconductor device in a tenth preferred embodiment;

FIGS. 14A to 14C are cross-sectional views showing a method for manufacturing the semiconductor device shown in FIG. 13 in a stepwise manner;

FIG. 15 is a cross-sectional view schematically showing a second lead member and a soldering member as a modified example of the tenth embodiment;

FIG. 16 is a cross-sectional view schematically showing a method for manufacturing a semiconductor device in an eleventh preferred embodiment;

FIG. 17 is a cross-sectional view schematically showing a method for manufacturing a semiconductor device in a twelfth preferred embodiment;

FIG. 18 is a cross-sectional view schematically showing another method for manufacturing the semiconductor device in the twelfth embodiment;

FIG. 19 is a cross-sectional view showing a semiconductor device in a thirteenth preferred embodiment;

FIGS. 20A to 20C are cross-sectional views for explaining a method for manufacturing the semiconductor device shown in FIG. 19;

FIG. 21 is a cross-sectional view showing a semiconductor device in a fourteenth preferred embodiment;

FIG. 22 is a cross-sectional view showing a semiconductor device in a fifteenth preferred embodiment;

FIG. 23 is a cross-sectional view showing a semiconductor device as a modification of the thirteenth embodiment;

FIG. 24 is a cross-sectional view showing a semiconductor device in a sixteenth preferred embodiment;

FIG. 25 is an enlarged cross-sectional view showing a part surrounded by a broken line in FIG. 24;

FIG. 26 is a top plan view showing the semiconductor device in a direction indicated by arrow XXVI in FIG. 24;

FIG. 27 is a top plan view showing a semiconductor device in a seventeenth preferred embodiment;

FIG. 28A is a cross-sectional view showing the semiconductor device, taken along line XXVIIIA—XXVIIIA in FIG. 27;

FIG. 28B is a cross-sectional view showing the semiconductor device, taken along line XXVIIIB—XXVIIIB in FIG. 27;

FIG. 29 is a diagram showing an equivalent circuit of an IGBT chip in the semiconductor device in the seventeenth embodiment;

FIGS. 30A to 30D are schematic views showing a method for manufacturing radiation members in the seventeenth embodiment;

FIG. 31 is a schematic view showing a constitution observed in a side direction in a manufacturing process of the semiconductor device;

FIGS. 32A to 32C are schematic views showing a step for caulking fixation;

FIG. 33 is a cross-sectional view partially showing an IGBT chip as an example;

FIG. 34 is a cross-sectional view showing a semiconductor device in an eighteenth preferred embodiment;

FIGS. 35A and 35B are cross-sectional views showing a radiation member used in a modified example of the eighteenth embodiment; and

FIG. 36 is a cross-sectional view showing a semiconductor device in a modified embodiment of the seventeenth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(First Embodiment)

A first preferred embodiment is described with reference to FIGS. 2A and 2B. As shown in FIG. 2A, a pair of radiation members 2, 3 are disposed to sandwich two Si chips 1a, 1b that are disposed on a plane. The radiation members 2, 3 are thermally and electrically connected to principal electrodes of the Si chips 1a, 1b through bonding members 4. Hereinafter, connection means thermal and electrical connection except cases in which specific descriptions are presented. A control electrode of the Si chip 1a is electrically connected to a control terminal 5, which is connected to a lead frame, via a wire 8 formed by wire bonding.

Specifically, the radiation member (first side radiation member) 2, facing upper surfaces (first surfaces) 6a of the Si chips 1a, 1b to which the wire bonding is performed is formed with protruding portions 2a protruding at a step-like shape at positions facing the principal electrodes of the Si chips 1a, 1b. Front ends of the protruding portions 2a are generally flat and the flat portions are respectively connected to the principal electrodes through the bonding members 4. Being generally flat means flat at a level that does not interfere with bonding between the protruding portions 2a and the principal electrodes.

Next, the protruding portions 2a are explained in more detail. As shown in FIG. 2B, when the Si chips 1a, 2b are power devices, each withstand voltage at peripheral portions of the Si chips 1a, 1b is kept by guard rings 7 that is provided on one surface of each chip, i.e., on the surface 6a or a surface (second surface) 6b opposed to the surface 6a.

Like the present embodiment, when metallic materials as the radiation members 2, 3 are bonded to the both surfaces of each Si chip 1a, 1b, the radiation member 2 is bonded to the surface (the first surfaces in this embodiment) 6a where the guard rings 7 are provided. However, referring to FIG. 2B, a distance indicated by an arrow B at the peripheral portions of the Si chips 1a, 1b, i.e., at the regions one of which is indicated by a broken line in the figure, the first side radiation member 2 must be electrically insulated from the guard rings 7 and from the edge surfaces of the Si chips 1a, 1b. Therefore, insulated regions must be provided there.

Because of this, the radiation member 2 has the protruding portions 2a at the positions facing the principal electrodes of the Si chips 1a, 1b. In other words, the radiation member 2 has recess portions at the positions facing the guard rings 7 of the Si chips 1a, 1b to avoid the high withstand regions (insulated regions).

The radiation member (second side radiation member) 3 bonded to the other surfaces 6b of the Si chips 1a, 1b has no protruding portion, and is generally flat. That is, the second side radiation member 3 is generally so flat that it does not interfere with mountability of the Si chips 1a, 1b to the radiation member 3. In the respective radiation members 2, 3, respective surfaces opposite to the surfaces facing the Si chips 1a, 1b constitute radiation surfaces 10 that are also generally flat and are approximately parallel to each other.

Here, in this embodiment, the wire-bonded Si chip is an IGBT (Insulated Gate Bipolar Transistor) 1a, while the other Si chip is a FWD (free-wheel diode) 1b. In the IGBT 1a, the first side radiation member 2 is an emitter, the second side radiation member 3 is a collector, and the control electrode is a gate. As shown in FIG. 2A, the thickness of the FWD 1b is larger than that of the IGBT 1a. Therefore, in the first side radiation member 2, the protruding portion 2a facing the IGBT 1a has a protruding amount relatively larger than that of the other protruding portion 2a facing the FWD 1b.

As the first side and second side radiation members 2, 3, for example, a metallic material including Cu or Al as a main component can be used, which has electrical conductivity and thermal conductivity larger than those of W and Mo, and is cheaper that those. FIG. 3 is a table showing examples of metallic materials usable as the radiation members 2, 3. As shown in FIG. 3, the radiation members 2, 3 can be made of one of metal "a" to metal "l", anoxia copper, and the like. Here, for example, metal "a" is an alloy containing, in mass ratio, Fe (iron) at 2.3%, An (zinc) at 0.1%, P (phosphorous) at 0.03%, and Cu as the remainder.

The bonding members 4 are preferable to have a shear strength superior to a shear stress produced by thermal stress, and to be superior in both thermal conductivity and electrical conductivity. As such conductive members 4, for example, solder, brazing filler metal, or conductive adhesive can be used. The wire 8 for wire bonding can be made of Au (gold), Al, or the like which is used for wire bonding in general.

Also, as shown in FIG. 2A, these members 1 to 5, and 8 are sealed with resin 9 while exposing the radiation surfaces 10 of the radiation members 2, 3 at the opposite side of the Si chips 1a, 1b, and exposing simultaneously the control terminal 5 at the opposite side of the wire bonding. The radiation surfaces 10 of the respective radiation members 2, 3 serve as electrodes and perform radiation of heat simultaneously. The resin 9 preferably has a thermal expansion coefficient approximate to those of the radiation members 2, 3. For example, epoxy based mold resin can be used as such resin 9.

Further, the resin-sealed members 1 to 5 and 8 are sandwiched by a pair of outside wiring members 11 so that the radiation surfaces 10 contact the outside wiring members 11. Each of the outside wiring members 11 is a flat plate having a portion with a plate shape or a fine wire shape that is conducted to be interconnected with an outside. The outside wiring members 11 and the resin-sealed members 1 to 5, and 8 are further sandwiched by a pair of outside cooling members 13 with plate-shaped high thermal conductivity insulating substrates 12 interposed therebetween. The resin-sealed members 1 to 5 and 8, the outside wiring members 11, the high thermal conductivity insulating substrates 12, and the outside cooling members 13 are fixed by volts 4 or the like screwed from the outside cooling members 13.

The outside wiring members 11 may be made of any materials provided that they are superior in thermal conductivity and electrical conductivity. The high thermal conductivity insulating substrates 12 can be made of, for example, one of AlN (aluminum nitride), SiN (silicon nitride), Al₂O₃ (aluminum dioxide), SiC (silicon carbide), BN (boron nitride), diamond or the like. The outside cooling members 13 is constructed to include a radiation fin, or to be cooled by water.

According to the constitution described above, as to an electrical path, current flow in the order of the outside wiring member 11 contacting the first side radiation member 2, the first side radiation member 2, the Si chips 1a, 1b, the second side radiation member 3, the outside wiring member 11 contacting the second side radiation member 3 or in the inverse order. As to a thermal path, heat produced in the Si chips 1a, 1b is transferred to the first side and second side radiation members 2, 3, the outside wiring members 11, the high thermal conductivity insulating substrates 12, and the outside cooling members 13, and then is radiated.

Next, a method for manufacturing the semiconductor device shown in FIGS. 2A and 2B is explained. First, the principal electrodes on the second surfaces 6a of the Si chips 1a, 1b are bonded to the second side radiation member 3 through the bonding members 4. Next, the control electrode of the Si chip 1a and the control terminal 5 are electrically connected to each other by wire bonding. After that, the principal electrodes on the first surfaces 6a of the Si chips 1a, 1b are bonded to the front ends of the protruding portions 2a of the first side radiation member 2 by bonding members 4. Here, the protruding portions 2a of the first side radiation member 2 are formed by pressing or the like previously.

Subsequently, a die (not show) is prepared, and the integrated Si chips 1a, 1b and the first side and second side radiation members 2, 3 are disposed in the die and is sealed with resin. Accordingly, electrical insulation between the radiation members 2, 3 can be attained. Successively, as described above, with respect to the radiation surfaces 10, the outside wiring members 11, the high thermal conductivity insulating substrates 12, and the outside cooling members 13 are disposed in this order. Then, the outside cooling members 13 are fastened with volts, so that the members 11 to 13 are fixed. In consequence, the semiconductor device in the present embodiment is completed.

According to the present embodiment, because the first side and second side radiation members 2, 3 are made of metallic material containing Cu or Al as a main component that is superior in thermal conductivity and electrical conductivity, the semiconductor device can be provided with improved radiation property and improved electrical conductivity. Further, because these members can be manufactured at lower cost as compared to a conventional case using W or Mo, the semiconductor device can be provided at low cost. Furthermore, the metallic material containing Cu or Al as the main component is so soft as compared to W or Mo that workability for forming the protruding portions 2a on the first side radiation member 2 is good.

Besides, because the protruding portions 2a are provided on the first side radiation member 2 and are connected to the respective different Si chips 1a, 1b, the connection between the respective Si chips 1a, 1b and the radiation member 2 can be performed appropriately. Specifically, the protruding amounts and the shapes of the protruding portions 2 can be changed in accordance with the thicknesses of the Si chips 1a, 1b and the shapes of the principal electrodes of the Si chips 1a, 1b. Because of this, the different semiconductor chips 1a, 1b can be easily accommodated in the semiconductor device.

The radiation surfaces 10 of the radiation members 2, 3 may have irregularities thereon or may not be parallel to each other. However, in this embodiment, the radiation surfaces 10 are made flat and approximately parallel to each other. This is made possible because the surface step, i.e., the difference in thickness between the Si chips 1a, 1b can be absorbed by the protruding portions 2a by controlling the protruding amounts thereof in accordance with the respective thicknesses of the Si chips 1a, 1b.

As a result, in the present embodiment, because the radiation surfaces 10 are generally flat and approximately parallel to each other, when the volts are fastened to the radiation surfaces 10 with the outside wiring members 11, the high thermal conductivity insulating substrates 12, and the outside cooling members 13 interposed therebetween, the surfaces 10 and these members 11 to 13 can be brought in contact with each other securely and easily at the interfaces thereof.

Moreover, because the radiation surfaces 10 are approximately parallel to each other, a force produced by fastening the volts is uniformly applied to the members 1 to 5, 8, 9, and 11 to 13. Therefore, these members 1 to 5, 8, 9, and 11 to 13 are not damaged or destroyed by deviation of the force, and the assembling performance can be improved.

In general, though the IGBT 1a and the FWD 1b are used as a pair, as the distance between the IGBT 1a and the FWD 1b is decreased, an operation on a circuit becomes more ideal. According to the present embodiment, because the IGBT 1a and the FWD 1b are disposed adjacently to each other in the integrally resin-sealed semiconductor device, the operation of the IGBT 1a can approach the ideal state in the semiconductor device.

When the object of the invention is limited to provide a semiconductor device capable of accommodating the different semiconductor chips 1a, 1b easily, the materials for forming the first side and second side radiation members 2, 3 are not limited to the materials containing Cu or Al as a main component but may be other conductive materials having electrical conductivity. That is, when the prevention of breakage of the bonding members 4 caused by thermal stress is of greater importance, the first side and second side radiation members 2, 3 should be made of metallic material having a thermal expansion coefficient approximate to that of the Si chips 1a, 1b. On the other hand, when the radiation property and the electrical conductivity are of greater importance, the radiation members 2, 3 should be made of metallic material containing Cu or Al as a main component.

The resin 9 used in the present embodiment not only insulates the radiation members 2, 3 from each other but also reinforces the bonding between the radiation members 2, 3 and the Si chips 1a, 1b by connecting the radiation members 2, 3 to the Si chips 1a, 1b. Therefore, even when the radiation members 2, 3 are made of a metallic material containing Cu or Al as a main component, which has a thermal nexpansion coefficient different from that of the Si chips 1a, 1b, the breakage of the bonding members 4 caused by thermal stress can be relaxed by the resin 9.

Especially when the resin 9 has a thermal expansion coefficient approximate to that of the radiation members 2, 3, stress is applied to the Si chips 1a, 1b to promote expansion and contraction similar to those of the radiation members 2, 3 when temperature varies. Therefore, stress applied to the bonding members 4 is relaxed and generation of strain is restricted, resulting in improvement of reliability at the connection portions.

Incidentally, although the second side radiation member 3 has no protruding portion thereon in the present embodiment, it may have a protruding portion. Thermal conductive grease or the like may be applied to the contact faces between the outside wiring members 11 and the high thermal conductivity insulating substrates 12, and between the high thermal conductivity insulating substrates 12 and the outside cooling members 13 to enhance thermal bonding further.

The contact between each outside wiring member 11 and each high thermal conductivity insulating substrate 12 is preferable to be fixed by pinching as in the present embodiment in consideration of the difference in thermal expansion coefficient between the members 11 and 12. However, each radiation surface 10 and each outside wiring member 11 can be connected by solder, brazing filler metal or the like because these members can be made of materials having thermal expansion coefficient not largely different from each other.

The body of the first side radiation member 2 may be separated from the protruding portions 2a. For example, the protruding portions 2a may be bonded to a plate-shaped body of the member 2 by soldering, welding, or the like. The material forming the first side radiation member 2 is not always necessary to be identical with that forming the second side radiation member 3. In the present embodiment, although the resin-sealing is performed by a die, the sealing may be performed by potting without any die.

Although it is described that the resin 9 for sealing has a thermal expansion coefficient approximate to those of the first side and second side radiation members 2, 3, the resin 9 is not limited to that, but may be other appropriate resin when there is no need to consider bonding strength between the Si chips 1a, 1b and the radiation members 2, 3.

Although it is described in the present embodiment that the IGBT 1a and the FWD 1b are used as the Si chips, in some cases such as that only one Si chip is used, or the same kind of Si chips are used, the connecting structure between the Si chip(s) and the radiation members 2, 3 is not complicated. In these cases, the protruding portions 2a need not be formed on one of the radiation members 2, 3. As described above, the semiconductor device having improved radiation property and electrical conductivity can be provided by forming the radiation members 2, 3 from a metallic material containing Cu or Al as a main component having electrical conductivity and thermal conductivity higher than those of W or Mo.

(Second Embodiment)

A second preferred embodiment differs from the first embodiment in an inside shape of the first side radiation member 2. FIG. 4A shows a semiconductor device in the second embodiment, and FIGS. 4B to 4D are cross-sectional views partially showing various first side radiation members 2 and Si chips 1a, 1b facing the respective radiation members 2. FIGS. 5A to 5C are cross-sectional views respectively taken along lines VA—VA, VB—VB, VC—VC in FIGS. 4B to 4D.

In FIG. 4A, the first side radiation member 2 is partially omitted, and the cross-sectional shapes shown in FIGS. 4B to 4D are applicable to the omitted part. FIG. 4A also omits the outside wiring members 11, the high thermal conductivity insulating substrates 12, and the outside cooling members 13. Hereinafter, different portions from those in FIG. 2A are explained. In FIGS. 4A to 4D and 5A to 5C, the same parts as those in FIG. 2A are indicated with the same reference numerals, and those explanation is made simple.

As shown in FIGS. 4A to 4D and 5A to 5C, the first side radiation member 2 has a space 15 at a portion connected to the Si chips 1a, 1b. The space 15 can have a lattice shape as in an example shown in FIG. 5A, be composed of several concentric circles as in an example shown in FIG. 5B, and be composed of several concentric rectangles as in an example shown in FIG. 5C. The shape of the space 15 in a direction perpendicular to the connection surface between the radiation member 2 and the Si chips 1a, 1b is as shown in FIG. 4B, 4C, or 4D. That is, there are cases where the space 15 is open at the connecting portions with the Si chips 1a, 1b, is open at the radiation surface 10, and is closed both at the connecting portions with the Si chips 1a, 1b and the radiation surface 10.

The space 15 can be formed by, for example, cutting work. When the space 15 is closed both at the connecting portions with the Si chips 1a, 1b and the radiation surface 10 as shown in FIG. 4D, it can be formed by forming the radiation member with the space opened at the connecting portions with the Si chips 1a, 1b by cutting first as shown in FIG. 4B, and then by bonding a metal plate to close the opening portions by welding or the like.

According to the present embodiment, the same effects as those described in the first embodiment can be attained. In addition, the space 15 formed in the first side radiation member 2 increases the rigidity of the radiation member 2. As a result, stress applied to the Si chips 1a, 1b and to the bonding members 4 can be reduced, so that the breakage of the Si chips 1a, 1b can be prevented and the reliability in the bonding between the Si chips 1a, 1b and the radiation member 2 can be enhanced.

The other features not described in the second embodiment are substantially the same as those in the first embodiment. The space 15 is exemplified in cases it extends in the thickness direction of the Si chips 1a, 1b; however, it may extend in a surface direction of the chips 1a, 1b. Further, the space 15 may be formed in the second side radiation member 3. The space 15 needs not be formed uniformly at the portions contacting the Si chips 1a, 1b, and can be arranged appropriately at required positions.

The shape of the space 15 is not limited to the examples shown in the figures, provided that it can reduce the rigidity of the radiation member. When the radiation members 2, 3 are made of a metallic material including Cu or Al, it is easy to form the space 15 because the radiation members 2, 3 are easy to be processed.

(Third Embodiment)

FIG. 6 shows a semiconductor device in a third preferred embodiment, in which the outside wiring members 11, the high thermal conductivity insulating substrates 12, and the outside cooling members 13 shown in FIG. 2A are omitted. Hereinafter, different portions from those in the first embodiment are mainly explained, and in FIG. 6, the same parts as those in FIG. 2A are indicated with the same reference numerals.

As shown in FIG. 6, in the third embodiment, metallic members (partially disposed metallic members) 16 made of Mo, W, Cu—Mo, or the like having a thermal expansion coefficient approximate to that of Si chips are disposed at the portions of the first side and second side radiation members 2, 3 facing the Si chips 1a, 1b. The partially disposed metallic members 16 can be previously formed on the radiation members 2, 3 by soldering, brazing, shrinkage fitting, or press-fitting. To position the partially disposed metallic members 16 with respect to the Si chips 1a, 1b with high accuracy, the Si chips 1a, 1b and the partially disposed metallic members 16 should be bonded by soldering, brazing, or the like, previous to the bonding between the partially disposed. metallic members 16 and the radiation members 2, 3 by soldering, brazing, or the like.

According to the present embodiment, the same effects as those in the first embodiment can be attained. In addition, because the thermal expansion coefficient at the connecting portions between the Si chips 1a, 1b and the first side and second side radiation members 2, 3 are approximated to each other, thermal stress produced by a change in temperature can be reduced at the connecting portions and the bonding strength can be enhanced. Also, the addition of the metallic members 16 having the thermal expansion coefficient approximate to that of the Si chips 1a, 1b approaches the strain of the radiation members 2, 3 as a whole to Si, so that stress applied to the Si chips 1a, 1b can be lowered.

Accordingly, the semiconductor device can be provided with high reliability to the bonding strengths between the Si chips 1a, 1b and the radiation members 2, 3 and without breakage of the Si chips 1a, 1b while securing the same effects as those in the first embodiment. Incidentally, the other features not described in this embodiment are substantially the same as those in the first embodiment. The partially disposed metallic members 16 need not be provided at the entire region of each radiation member 2 or 3 connected to the Si chips 1a, 1b. The partially disposed metallic members 16 should be disposed at necessary positions appropriately. Also, in this embodiment, the space 15 may be formed in at least one of the first side and second side radiation members 2, 3 as in the second embodiment.

(Fourth Embodiment)

FIG. 7 shows a semiconductor device in a fourth preferred embodiment. This embodiment relates to a modification of the outside wiring members 11 describ