JP2967065B2 - Semiconductor module - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor module.

[0002]

2. Description of the Related Art In recent years, as a semiconductor module which handles relatively high power, such as a power transistor module or a switching power supply module, a metal circuit board such as a copper plate and a metal plate are joined to the front and back of a ceramic substrate to form a ceramic circuit board. Further, a semiconductor module in which a heat sink is joined to a metal plate is used.

Here, as a method of joining the ceramic substrate and the metal circuit plate or the metal plate in the process of manufacturing the ceramic circuit substrate, an active metal such as Ti, Zr, Hf, Nb, etc. is added to Ag-Cu brazing material or the like. A method using an active metal brazing material containing 10% (active metal method), a tough pitch electrolytic copper containing 100 to 1000 ppm of oxygen as a metal circuit board, or a copper plate whose surface is oxidized to a thickness of 1 to 10 μm. Direct bonding of ceramic substrate and copper plate,
A so-called direct bonding method (DBC method: direct bonding copper method) and the like are known.

For example, in the direct bonding method, first, a copper circuit board punched into a predetermined shape is made of aluminum oxide (Al).
₂ O ₃ ) A sintered body or an aluminum nitride (AlN) sintered body or the like is placed in contact with a ceramic substrate and heated.
A eutectic liquid phase of Cu-Cu ₂ O is generated at the bonding interface, and after wetting the surface of the ceramic substrate with this liquid phase, the liquid phase is cooled and solidified, whereby the ceramic substrate and the copper circuit board are directly bonded. You. A ceramic circuit board to which such a direct bonding method is applied has a strong bonding strength between the ceramic substrate and the copper circuit board, and can be miniaturized and mounted with a simple structure that does not require a metallization layer or a brazing material layer. And the manufacturing process can be shortened.

However, in a semiconductor module such as a power transistor module using a ceramic circuit board in which a metal circuit board or the like is bonded to a ceramic substrate by the direct bonding method, the active metal method, or the like, the metal plate is designed to allow a large current to flow. In many cases, the thickness is as thick as 0.3 to 0.5 mm. That is, when a ceramic substrate and a metal circuit board or the like having significantly different coefficients of thermal expansion are joined to each other, a thermal stress due to the difference in thermal expansion is generated due to a cooling process after the joining or addition of a cooling / heating cycle. This stress exists as a compressive and tensile residual stress distribution on the ceramic substrate side near the joint, and the main stress of the residual stress acts particularly on the ceramic portion close to the outer peripheral end of a metal circuit board or the like. The residual stress may cause cracks in the ceramic substrate, cause a dielectric strength failure, or cause peeling of the metal plate. Further, even if cracks do not occur in the ceramic substrate, the ceramic substrate has an adverse effect of reducing its strength.

[0006] With the recent increase in the density and integration of semiconductor elements, miniaturization of semiconductor modules and electronic components themselves has been promoted.

In particular, aluminum nitride substrates have high thermal conductivity and low thermal expansion characteristics as compared with other ceramic substrates, but have relatively low mechanical strength, so they are added in a circuit board mounting process. The circuit board may be damaged by the pressing force or the impact force.

FIG. 4 is a sectional view showing the structure of such a conventional semiconductor module 1. As shown in FIG. In the semiconductor module 1 shown in FIG. 4, a metal circuit board 3 is joined to a front surface of a ceramic substrate 2 made of an AlN sintered body having a large thickness and a high thermal conductivity, while a back copper plate is provided on the lower surface of the ceramic substrate 2. Of metal plates 4 are integrally joined. A semiconductor element 7 is mounted on a predetermined position of the metal circuit board 3 by soldering, and the semiconductor element 7 and an electrode portion of the metal circuit board 3 are electrically connected by bonding wires 8.

This ceramic circuit board is integrated with the surface of a thick heat sink plate 5 made of, for example, copper via a metal plate 4 by soldering to form a semiconductor module 1. The semiconductor module 1 is fixed on the device casing 9, the radiating fins, or the mounting board by tightening the mounting screws 6.

[0010]

However, in the conventional semiconductor module 1 described above, the back copper plate (metal plate)
In addition, a heat sink plate that improves heat dissipation and prevents cracking of the ceramic substrate is indispensable, and it is necessary to use a ceramic substrate with a large thickness to increase the resistance to cracking. In this case, the size of the case becomes large and it is difficult to reduce the size, and there is a problem that the manufacturing cost of the ceramic substrate increases. In addition, since the thickness of the substrate is increased, even when an AlN substrate having a high thermal conductivity is used, the thermal resistance is increased, and there is a problem that good heat dissipation cannot be obtained as expected.

An object of the present invention is to provide a semiconductor module which has a simple structure, can be reduced in size, and has improved heat dissipation and heat cycle resistance. .

[0012]

According to a first aspect of the present invention, there is provided a semiconductor module comprising Li, Na, K, Fe, Ca, Sr, and B as impurity cation elements.
a thermally conductive silicon nitride substrate containing a, Mn, and B in total of 1.0% by weight or less, preferably 0.3% by weight or less, and having a thermal conductivity of 60 w / mk or more; A semiconductor element mounted on a conductive silicon nitride substrate, a metal circuit board bonded to the semiconductor element mounting surface side of the high thermal conductive silicon nitride substrate, and a semiconductor element non-mounting surface of the high thermal conductive silicon nitride substrate. And a metal plate joined to the device casing or the mounting board.

Further, the semiconductor module according to the present invention comprises:
In other words, as described in claim 2, it is composed of a silicon nitride crystal phase and a grain boundary phase, and the ratio of the crystalline compound phase in the grain boundary phase to the whole grain boundary phase is 20.
% Or more, preferably 50% or more, a high thermal conductive silicon nitride substrate, a semiconductor element mounted on the high thermal conductive silicon nitride substrate, and a semiconductor element mounting surface side of the high thermal conductive silicon nitride substrate. It is characterized by comprising a bonded metal circuit board, and a metal plate bonded to the non-semiconductor element mounting surface side of the high thermal conductive silicon nitride substrate and bonded to an equipment casing or a mounting board.

That is, as shown in FIG. 1 or 3, only one metal plate including a heat sink is interposed between the high thermal conductive silicon nitride substrate non-mounting surface of the silicon nitride substrate and the equipment casing or mounting board. It is a semiconductor module.

In a preferred embodiment of the semiconductor module according to the present invention, the thickness of the metal plate joined to the equipment casing or the mounting board is less than the thickness of the metal circuit board. In another embodiment, the thickness of the metal plate joined to the equipment casing or the mounting board is twice or more the thickness of the metal circuit board.

The high thermal conductive silicon nitride substrate used in the present invention is made of Ti, Zr, Hf, V, Nb, Ta,
At least one selected from the group consisting of Cr, Mo, W
It is preferable to contain the seed in an amount of 0.1 to 3.0% by weight in terms of oxide. This Ti, Zr, Hf, V, Nb, T
At least one selected from the group consisting of a, Cr, Mo, and W can be contained as an oxide, carbide, nitride, silicide, or boride by being added to the silicon nitride powder.

Here, as an example of a method for producing a silicon nitride substrate having high thermal conductivity used in the present invention, oxygen is not more than 1.7% by weight, and Li, Na, K,
Fe, Ca, Sr, Ba, Mn, and B are 1.0% by weight or less in total, and 90% by weight or more of α-phase silicon nitride, and a rare earth element is added to silicon nitride powder having an average particle size of 1.0 μm or less. A raw material mixture containing 1.0 to 17.5% by weight or less of elements converted to oxides is molded to prepare a molded body, and the obtained molded body is degreased. It is manufactured by pressure sintering and gradually cooling the sintered body at a cooling rate of 100 ° C. or less per hour from the sintering temperature to a temperature at which a liquid phase formed during sintering by the rare earth element solidifies. be able to.

The content range of the rare earth element oxide of 1.0 to 17.5% by weight is, of course, a mathematical expression, but the lower limit of the content is 1.0% by weight.
And an upper limit of 17.5% by weight.

According to the above production method, the ratio of the crystal compound phase to the entire grain boundary phase in the grain boundary phase in the silicon nitride crystal structure is 20% or more, the porosity is 2.5% or less, and the thermal conductivity is 2.5% or less. 60W / mK or more, three-point bending strength of 650 at room temperature
A silicon nitride substrate having excellent mechanical properties and thermal conductivity properties of not less than MPa can be obtained.

The semiconductor module according to the present invention comprises a metal circuit board and a metal having conductivity on the front and back surfaces of the high thermal conductive silicon nitride substrate manufactured as described above by using the direct bonding method or the active metal method. It is manufactured by bonding the plates together.

As described above, in the semiconductor module of the present invention, in addition to the high strength and toughness characteristics inherently possessed by the silicon nitride sintered body, in particular, the high thermal conductivity nitride having significantly improved thermal conductivity is used as the ceramic substrate. Since a silicon substrate is used, the substrate is unlikely to crack due to thermal cycling or the impact force during assembly, and furthermore, a back copper plate (back metal plate) and a heat sink plate to enhance heat dissipation and structural strength Both can be a structure that is not required. Therefore, the structure of the semiconductor module is simplified, the manufacturing cost is greatly reduced, and the semiconductor module can be downsized and high-density mounting is possible.

Further, heat generated from a heat-generating component such as a semiconductor element mounted on the substrate is quickly transmitted to the outside of the system through the high thermal conductivity silicon nitride substrate, so that heat radiation is extremely good.
In addition, since a silicon nitride substrate having high strength and high toughness is used, a large maximum deflection of the module can be ensured. Therefore, no module fastening cracks occur in the assembly process, and it is possible to mass-produce semiconductor devices using the semiconductor modules at a high production yield and at low cost.

Since a silicon nitride substrate having a higher thermal conductivity is used, even when a semiconductor element for high output and high integration is mounted, deterioration of thermal resistance characteristics is small and excellent. Exhibits heat dissipation.

In particular, since the mechanical strength of the silicon nitride substrate itself having a high thermal conductivity is excellent, when the required mechanical strength characteristics are fixed, the thickness of the substrate is larger than when other ceramic substrates are used. It is possible to further reduce the size. Since the substrate thickness can be reduced, the thermal resistance value can be further reduced, and the heat radiation characteristics can be further improved.
Further, since the required mechanical characteristics can be sufficiently coped with even a thinner substrate than before, it is possible to further reduce the manufacturing cost of the substrate.

When only the conventional high thermal conductive aluminum nitride substrate is used as a component of the circuit board, it is necessary to increase the thickness of the aluminum nitride substrate in order to secure a certain level of mechanical strength. However, in the semiconductor module of the present invention, high heat dissipation is ensured at the same time as high heat dissipation is achieved by the high thermal conductivity silicon nitride substrate having a small thickness. Therefore, the whole module can be formed compactly.

[0026]

Next, an embodiment of the present invention will be described.
A specific description will be given with reference to the following embodiments and the accompanying drawings. First, a high thermal conductive silicon nitride substrate used in the present invention will be described, and then a semiconductor module using the high thermal conductive silicon nitride substrate as a ceramic substrate will be described.

First, various high thermal conductive silicon nitride substrates to be used as components of the semiconductor module of the present invention were manufactured by the following procedure.

That is, a silicon nitride raw material containing 1.3% by weight of oxygen and a total of 0.15% by weight of the impurity cation element and containing 97% of α-phase silicon nitride and having an average particle size of 0.55 μm. As shown in Tables 1 to 3, as shown in Tables 1 to ₃ , rare earth oxides such as Y ₂ O ₃ and Ho ₂ O ₃ as sintering aids, and Ti, Hf compounds, and Al ₂ O ₃ powders as needed. ,
AlN powder was added, and the mixture was wet-mixed in ethyl alcohol using a silicon nitride ball for 72 hours, and then dried to prepare raw material powder mixtures. Next, a predetermined amount of an organic binder was added to each of the obtained raw material powder mixtures and uniformly mixed, followed by press molding at a molding pressure of 1000 kg / cm ² to produce a large number of molded bodies having various compositions.

Next, each of the obtained compacts was degreased in an atmosphere gas at 700 ° C. for 2 hours.
After the densification sintering is performed under the sintering conditions shown in (1) to (3), sintering is performed until the temperature in the sintering furnace falls to 1500 ° C. by controlling the amount of electricity to a heating device attached to the sintering furnace. The sintered bodies were cooled by adjusting the cooling rates of the bodies so as to be the values shown in Tables 1 to 3, respectively, to prepare silicon nitride sintered bodies according to Samples 1 to 51, respectively. Further, the obtained sintered body was cut to obtain a high thermal conductive silicon nitride substrate having a predetermined shape and a thickness of 0.5 mm.

The average values of the porosity, the thermal conductivity (25 ° C.), and the three-point bending strength at room temperature of each of the silicon nitride substrates according to Samples 1 to 51 thus obtained were measured. Furthermore, the ratio of the crystal phase to the grain boundary phase was measured by X-ray diffraction for each silicon nitride substrate, and the results shown in Tables 1 to 3 below were obtained.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

As is clear from the results shown in Tables 1 to 3, in the silicon nitride sintered bodies according to Samples 1 to 51, the raw material composition and the amount of impurities were appropriately controlled, and the densified sintering was performed as compared with the conventional example. Since the cooling rate of the sintered compact immediately after completion is set lower than before, the crystal phase is included in the grain boundary phase, and the higher the proportion of the crystal phase, the higher the heat conductivity and the higher the strength of the silicon nitride. An elementary substrate was obtained.

On the other hand, 1.3 to 1.5% by weight of oxygen and 0.13 to 1.5%
A raw material powder having an average particle size of 0.60 μm containing 0% by weight and containing 93% of α-phase type silicon nitride was used, and Y ₂ O ₃ (yttrium oxide) powder was added to the silicon nitride powder in an amount of 3%. To 6% by weight and 1.3 to 1.6% by weight of alumina powder
After shaping and degreasing the added raw material powder, sintering is performed at 1900 ° C. for 6 hours, and after sintering, furnace cooling (cooling rate:
(400 ° C. per hour). The thermal conductivity of the obtained sintered body was as low as 25 to 28 W / m · K, which was close to the thermal conductivity of a silicon nitride sintered body manufactured by a conventional general manufacturing method.

Next, the thickness of each of the obtained samples 1 to 51 was set to 0.1.
A semiconductor module was manufactured by integrally joining a metal circuit board and a metal plate to both sides of a 5-mm high thermal conductivity silicon nitride substrate using a direct joining method or an active metal method.

FIG. 1 is a sectional view showing the structure of a semiconductor module 1a according to one embodiment of the present invention.

In FIG. 1, a copper plate 3 as a metal circuit board is integrally joined to the surface of the high thermal conductive silicon nitride substrate 10, and a metal plate is mounted on the back surface of the high thermal conductive silicon nitride substrate 10. The copper plate 4a is joined, and these constitute the semiconductor module 1a.

The copper plates 3 and 4a of the semiconductor module 1a shown in FIG.
Are directly joined by a so-called DBC method. The copper plate 3 when such a DBC method is used,
As 4a, 100 to 3 oxygen such as tough pitch copper is used.
It is preferable to use copper containing 000 ppm, but it is also possible to use oxygen-free copper whose surface is oxidized. Instead of a single plate of copper or a copper alloy, a clad plate with another metal member having at least a joining surface with the high thermal conductive silicon nitride substrate 10 made of copper can be used.

The copper plate 3 bonded to the surface of the high thermal conductive silicon nitride substrate 10 is to be a mounting portion for semiconductor components and the like, and is patterned into a desired circuit shape. A semiconductor element 7 is soldered to a predetermined position of the copper plate 3, and an electrode portion of the semiconductor element 7 is electrically connected to an electrode portion of the copper plate 3 by a bonding wire 8. The copper plate 4a bonded to the back surface of the high thermal conductive silicon nitride substrate 10 prevents warpage of the high thermal conductive silicon nitride substrate 10 at the time of bonding, and is 2 か ら from the vicinity of the center.
In the divided state, it is bonded and formed on the entire back surface of the silicon nitride substrate 10 having high thermal conductivity. As shown in FIG.
The thickness t ₁ of the rear surface side of the copper plate 4a may be used having the same thickness as the copper plate 3 as a metal circuit plate with a mounting portion such as a semiconductor component, but the thickness of the copper plate 3 t ₀ less, Further copper plate 3
It is preferable to the 70-90% of the thickness copper sheet having a thickness of t ₀ used.

On the other hand, when the metal plate 4b to be bonded to the back surface of the high thermal conductive silicon nitride substrate 10 is given a function as a heat sink plate for improving heat dissipation, as shown in FIG. Alternatively it is preferable that the thickness t ₂ of the metal plate 4b is joined to the mounting board at least twice the thickness t ₀ of the metal circuit plate. By setting the thickness t ₂ of the metal plate 4b to be bonded to the back side of the high thermal conductive silicon nitride substrate 10 to be at least twice the thickness t ₀ of the metal circuit board 3, this metal plate can serve as a heat sink. In order to fulfill the function, it is possible to further improve the heat dissipation of the semiconductor module (in this case, from a different point of view, a structure in which a heat sink is directly joined to the high thermal conductive silicon nitride substrate 10 without using a back metal plate) You can also say).

Here, the semiconductor module 1 shown in FIG.
a is obtained by bonding the copper plates 3 and 4a to the high thermal conductive silicon nitride substrate 10 by the DBC method.
The semiconductor module may be a semiconductor module in which 4a is bonded to a high thermal conductive silicon nitride substrate 10 via an active metal-containing layer. The active metal-containing layer is formed of a brazing material containing at least one active metal selected from Ti, Zr, Hf, Nb, and the like (hereinafter, referred to as a brazing material).
Active metal-containing brazing material) layer. As the composition of the active metal-containing brazing material to be used, for example, an Ag-Cu eutectic composition (72 wt% Ag-28 wt% Cu) or a Ag-Cu-based brazing material or a Cu-based brazing material having a composition in the vicinity thereof is mainly used. Examples of the composition include 1 to 10% by weight of at least one active metal selected from Ti, Zr, Hf, Nb and the like. In addition, 1 to 10 In is added to the active metal-containing brazing material.
% By weight.

As in the semiconductor module 1a shown in FIG. 1, the copper plates 3 and 4a are
The one joined by the BC method has advantages that a simple structure, high joining strength can be obtained, and the manufacturing process can be simplified. On the other hand, a semiconductor module in which the copper plates 3 and 4a are bonded to the high thermal conductive silicon nitride substrate 10 by the active metal method has high bonding strength and the active metal-containing brazing material layer also functions as a stress relaxation layer. Reliability can be further improved. For this reason, it is preferable to select a joining method according to required characteristics, applications, and the like.

When a metal circuit board and a metal plate are joined to the high thermal conductive silicon nitride substrate 10 by the active metal method, not only a copper plate but also various metal plates such as a nickel plate and a tungsten It is also possible to use a plate, a molybdenum plate, an alloy plate thereof, a clad plate (including a clad plate with a copper plate) and the like.

The semiconductor module 1a shown in FIG.
Is inserted through the mounting screw through hole 11 formed in the outer edge of the silicon nitride substrate 10 so that the mounting screw 6a is inserted into the equipment casing 9.
Etc. However, silicon nitride sintered bodies have high hardness and are not easily drilled. Therefore, in order to simplify the manufacturing process, for example, as shown in FIG. 2, a frame-shaped case 12 in which a through hole 11a for a mounting screw is formed is prepared. , And the module can be pressed and fixed to the equipment casing 9 or the like by the mounting screw 6b.

Next, specific examples of the embodiment and evaluation results thereof will be described.

Example 1 First, samples 1 to 3 were used as high thermal conductive silicon nitride substrates.
A silicon nitride substrate according to No. 51 was oxidized in the air to form a 4 μm thick oxide layer (SiO ₂ layer) on the surface.
Thermally conductive silicon nitride substrate 10 having a thickness of 0.5 mm
And a copper plate 3 as a 0.3 mm thick metal circuit board and a 0.25 mm thick metal plate made of tough pitch copper (oxygen content: 300 ppm) formed by pressing. 4a was prepared.

Then, as shown in FIG. 1, two copper plates 3 and 4a are respectively disposed in direct contact with both sides of the high thermal conductive silicon nitride substrate 10 and are placed in a nitrogen gas atmosphere at 1348K.
The semiconductor element 7 was soldered on the copper plate 3 and wire-bonded to obtain the desired semiconductor module 1a.

On the other hand, as a comparative example, a processing was performed in the same manner as in Example 1 except that an aluminum nitride substrate having a thickness of 0.6 mm was used instead of the high thermal conductive silicon nitride substrate 10. Such a semiconductor module was manufactured.

A thermal cycle test (TCT: 233 K × 30 minutes + RT ×) was performed on the semiconductor module 1 a according to Example 1 and the semiconductor module of Comparative Example thus obtained.
(10 minutes + 398K x 30 minutes is defined as one cycle)), and the rate of occurrence of cracks in the ceramic substrate was measured. As a result, the semiconductor module of Example 1
No crack occurred even after the TCT of the cycle, whereas the semiconductor module according to the comparative example had 100 cracks.
In the cycle, cracks occurred in 5 to 9% of the ceramic substrate.

Example 2 A high thermal conductive silicon nitride substrate 10 having a thickness of 0.5 mm according to samples 1 to 51 was prepared as a high thermal conductive silicon nitride substrate. A copper plate 3, 4 having a thickness of 0.3 mm and a copper plate 5 having a thickness of 0.25 mm formed by processing were prepared.

Then, on both surfaces of the high thermal conductive silicon nitride substrate 10, In: Ag: Cu: Ti = 14.0: 59.
An active metal-containing brazing material having a composition of 0: 23.0: 4.0 is applied as a paste, and the copper plate 3
After laminating 4a, bonding was performed by heating in a nitrogen gas atmosphere, and further, the semiconductor element 7 was solder-bonded to the copper plate 3 and subjected to wire bonding to obtain a target semiconductor module.

When the semiconductor module thus obtained was subjected to a thermal cycle test under the same conditions as in Example 1, the same good results as in Example 1 were obtained, and the semiconductor module was excellent in reliability against thermal cycles. It was confirmed.

Example 3 First, samples 1 to 3 were used as high thermal conductive silicon nitride substrates.
A silicon nitride substrate according to No. 51 was oxidized in the air to form a 4 μm thick oxide layer (SiO ₂ layer) on the surface.
Thermally conductive silicon nitride substrate 10 having a thickness of 0.5 mm
In addition, a 0.3 mm thick copper plate 3 and a 0.6 mm thick copper plate 4b made of tough pitch copper (oxygen content: 300 ppm) formed by press working were prepared.

Then, as shown in FIG. 3, two copper plates 3 and 4b are placed in direct contact with both surfaces of the high thermal conductive silicon nitride substrate 10 and are heated at 1348 K in a nitrogen gas atmosphere. And bonding the semiconductor element 7 to the copper plate 3
The above was solder-bonded and subjected to wire bonding to obtain a target semiconductor module.

On the other hand, as a comparative example, processing was performed in the same manner as in Example 3 except that the aluminum nitride substrates 2a and 2b having a thickness of 0.6 mm were used instead of the high thermal conductive silicon nitride substrate 10. A semiconductor module according to a comparative example was manufactured.

A thermal cycle test (TCT: 233 K × 30 minutes + RT × 10) was performed on the semiconductor module of Example 3 and the semiconductor module of Comparative Example obtained in this manner.
Min + 398K x 30 min as one cycle), and the rate of occurrence of cracks in the ceramic substrate was measured. As a result, the semiconductor module 1b of Example 3 did not crack even after 100 cycles of TCT, whereas the semiconductor module of the comparative example cracked 4 to 7% of the ceramic substrate in 100 cycles. Was.

Example 4 A high thermal conductive silicon nitride substrate 10 having a thickness of 0.5 mm according to samples 1 to 51 was prepared as a high thermal conductive silicon nitride substrate. A 0.3 mm thick copper plate 3 having a predetermined shape formed by processing and a thickness of 0.3 mm.
A 6 mm copper plate 4b was prepared.

Then, on both surfaces of the high thermal conductive silicon nitride substrate 10, In: Ag: Cu: Ti = 14.0: 59.
An active metal-containing brazing material having a composition of 0: 23.0: 4.0 is applied as a paste, and the copper plate 3
After laminating 4b, bonding was performed by heating in a nitrogen gas atmosphere, and further, the semiconductor element 7 was solder-bonded on the copper plate 3 and wire-bonded to obtain a target semiconductor module.

When a thermal cycle test was performed on the semiconductor module obtained in this manner under the same conditions as in Example 3, the same good results as in Example 3 were obtained, and the reliability of the thermal cycle was excellent. It was confirmed.

Further, according to the semiconductor module according to each of the above embodiments, in addition to the high strength and high toughness characteristics inherently possessed by the silicon nitride sintered body, the high thermal conductivity silicon nitride substrate, in particular, the thermal conductivity is greatly improved. 10 is used. Therefore,
Both the back copper plate (back metal plate) and the heat sink plate are not required, and only one of them is sufficient, and the structure of the module is simplified, and the manufacturing cost is greatly reduced. Further, heat generated from heat-generating components such as the semiconductor element 7 mounted on the substrate is quickly transmitted to the outside of the system via the silicon nitride substrate 10 having high thermal conductivity, so that heat dissipation is extremely good.

Since the silicon nitride substrate 10 having high strength and high toughness and high thermal conductivity is used, a large maximum deflection of the module can be ensured. Therefore, in the assembly process, the module is connected to the equipment casing 9.
Even when it is fixed by the mounting screw 6a, no tightening crack occurs.

Since the high thermal conductivity silicon nitride substrate 10 has a high toughness value, cracks are less likely to occur in the junction between the substrate 10 and the metal circuit board or the metal plates 4a and 4b due to thermal cycling. Is significantly improved, and a semiconductor module excellent in durability and reliability can be provided.

[0064]

As described above, according to the semiconductor module of the present invention, in addition to the high strength and high toughness characteristics inherently possessed by the silicon nitride sintered body, in particular, the high thermal conductivity significantly improved the thermal conductivity. Using a silicon nitride substrate
The substrate is less likely to crack due to thermal cycling or impact force during assembly, and does not require both a back copper plate (back metal plate) and a heat sink plate for improving heat dissipation and structural strength. Therefore, the structure of the semiconductor module is simplified, the manufacturing cost is greatly reduced, and the semiconductor module can be downsized and high-density mounting is possible.

Further, heat generated from a heat-generating component such as a semiconductor element mounted on the substrate is quickly transmitted to the outside of the system through the high thermal conductivity silicon nitride substrate, so that heat radiation is extremely good. In addition, since a silicon nitride substrate having high strength and high toughness is used, a large maximum deflection of the module can be ensured. Therefore, the module does not crack in the assembly process.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the structure of a semiconductor module according to one embodiment of the present invention.

FIG. 2 is a sectional view of a semiconductor module according to another embodiment of the present invention.

FIG. 3 is a sectional view of a semiconductor module according to another embodiment of the present invention.

FIG. 4 is a sectional view showing the structure of a conventional semiconductor module.

[Explanation of symbols]

 1, 1a, 1b, semiconductor module 2 ceramic substrate (AlN substrate) 3 metal circuit board (copper plate) 4, 4a, 4b metal plate (back copper plate) 5 heat sink plate 6, 6a, 6b mounting screw 7 semiconductor element (Si chip) Reference Signs List 8 bonding wire 9 equipment casing (mounting board, radiation fin) 10 high thermal conductive silicon nitride substrate 11, 11a, 11b, 11c mounting screw through hole 12 case 13 terminal

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsutsuyasu Komatsu 2-4, Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Inside Keihin Works, Toshiba Corporation (72) Inventor, Toshun Sato 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Address Toshiba Corporation Yokohama office (56) References JP-A-7-187793 (JP, A) JP-A-6-196584 (JP, A) JP-A 9-157054 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H01L 23/15

Claims (6)

(57) [Claims] 1. A highly thermally conductive silicon nitride substrate comprising a silicon nitride crystal phase and a grain boundary phase, wherein a ratio of a crystalline compound phase in the grain boundary phase to the whole grain boundary phase is 20% or more. A semiconductor element mounted on the high thermal conductive silicon nitride substrate, a metal circuit board bonded to the semiconductor element mounting surface side of the high thermal conductive silicon nitride substrate, and a semiconductor element mounted on the high thermal conductive silicon nitride substrate. A semiconductor module comprising: a metal plate joined to a mounting surface side and joined to an equipment casing or a mounting board. 2. The semiconductor module according to claim 1, wherein the thickness of the metal plate joined to the equipment casing or the mounting board is equal to or less than the thickness of the metal circuit board. 3. The semiconductor module according to claim 1, wherein the thickness of the metal plate joined to the equipment casing or the mounting board is at least twice the thickness of the metal circuit board. 4. The high thermal conductive silicon nitride substrate is composed of a silicon nitride crystal phase and a grain boundary phase, and the ratio of the crystalline compound phase in the grain boundary phase to the entire grain boundary phase is 50.
%. The semiconductor module according to claim 1, wherein 5. The semiconductor module according to claim 1, wherein the metal circuit board and the metal plate are joined to the high thermal conductive silicon nitride substrate by a direct joining method. 6. The semiconductor module according to claim 1, wherein said metal circuit board and said metal plate are joined to said high thermal conductive silicon nitride substrate by an active metal-containing layer.