JP3450570B2 - High thermal conductive silicon nitride circuit board - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high thermal conductivity silicon nitride circuit board used for semiconductor devices and the like, and particularly to a high thermal conductivity silicon nitride circuit which can improve mechanical strength and heat cycle characteristics and is excellent in heat dissipation characteristics. Regarding a circuit board.

[0002]

2. Description of the Related Art Conventionally, a circuit board in which a conductive metal circuit board is integrally bonded with a brazing material to the surface of a ceramic board having excellent insulating properties such as an alumina (Al ₂ O ₃ ) sintered body has been known. Widely used.

On the other hand, a ceramic sintered body containing silicon nitride as a main component generally has excellent heat resistance even in a high temperature environment of 1000 ° C. or higher, and also has excellent thermal shock resistance. As a high-temperature structural material that replaces the heat-resistant superalloy described above, it has been attempted to be applied to various high-strength heat-resistant parts such as gas turbine parts, engine parts, and steel-making machine parts. In addition, since it has excellent corrosion resistance to metals, it has been tried to apply it as a melt-resistant material of molten metal, and because it has excellent wear resistance, it can be put to practical use in sliding members such as bearings and cutting tools. ing.

Conventionally, as a composition of a silicon nitride ceramics sintered body, yttrium oxide (Y
₂ O ₃ ), cerium oxide (CeO), calcium oxide (CaO) and other rare earth elements or alkaline earth element oxides are known to be added as sintering aids. Higher sinterability and higher density and strength.

A conventional silicon nitride sintered body is formed by adding the above-mentioned sintering aid to a silicon nitride raw material powder and molding the obtained sintered body at a temperature of about 1600 to 1850 ° C. in a firing furnace. It is manufactured by a manufacturing method in which after firing for a time, the furnace is cooled, and the resulting sintered body is ground and polished.

[0006]

However, although the silicon nitride sintered body manufactured by the above-mentioned conventional method has excellent mechanical strength such as toughness, it is different from other aluminum nitrides in terms of thermal conductivity. AlN) sintered body, beryllium oxide (BeO) sintered body, silicon carbide (SiC) sintered body, etc. are significantly lower than those in electronic materials such as semiconductor circuit boards that require heat dissipation. Has not been put to practical use, and has a drawback that its application range is narrow.

On the other hand, the above-mentioned aluminum nitride sintered body has the characteristics of high thermal conductivity and low thermal expansion coefficient as compared with other ceramics sintered bodies, so that it is possible to achieve high speed, high output, and multi-functionality.
Although it is the mainstream as a circuit board component for semiconductor chips and package materials, which are becoming larger in size, a material that is sufficiently satisfactory in terms of mechanical strength has not been obtained. Therefore, there has been a demand for the development of a ceramics sintered body having high mechanical strength and high thermal conductivity.

Further, when the circuit board having the above-mentioned ceramic sintered body substrate as a main component is fixed to the mounting boat by screwing or the like in the assembly process, a slight deformation due to the pressing force of the screw or an impact at the time of handling is caused. The circuit board may be damaged, and the manufacturing yield of semiconductor devices may be significantly reduced. Therefore, the circuit board is also required to have both high strength characteristics to withstand external force and excellent heat dissipation characteristics to cope with high output and high heat generation.

Further, in a circuit board formed by integrally joining a metal circuit board and a semiconductor chip on the surface of a ceramic substrate as described above, the mechanical strength and toughness of the ceramic substrate itself are insufficient, so that the semiconductor chip Due to the repeated heat cycle, the ceramic substrate in the vicinity of the joint portion of the metal circuit board is apt to crack and the heat resistance cycle characteristic and reliability are low.

The present invention has been made in order to meet the above-mentioned demands, and utilizes the high strength characteristics originally possessed by a silicon nitride sintered body, and further has high thermal conductivity and excellent heat dissipation and heat resistance. It is an object of the present invention to provide a high thermal conductivity silicon nitride circuit board with greatly improved cycle characteristics.

[0011]

In order to achieve the above-mentioned object, the present inventor has determined the type of silicon nitride powder, the type and amount of addition of sintering aids and additives, and the sintering conditions that have been conventionally used. After further study, we have developed a silicon nitride sintered body that has high thermal conductivity, which is more than twice the thermal conductivity of conventional silicon nitride sintered bodies. Further, using this silicon nitride sintered body as a substrate material, an oxide layer having a predetermined thickness is formed on the surface thereof,
When manufacturing a circuit board by directly bonding a metal circuit board onto the board through this oxide layer, it is possible to obtain a circuit board that satisfies all of mechanical strength, toughness value, heat cycle characteristics and heat dissipation. Confirmed by experiment.

Specifically, a raw material mixture obtained by adding a predetermined amount of a rare earth element oxide or the like to fine and highly pure silicon nitride powder is molded and degreased, and the obtained molded body is heated at a predetermined temperature for a certain period of time. After carrying out densification sintering while holding, it is gradually cooled at a cooling rate not higher than a predetermined value, and when the obtained sintered body is manufactured by grinding and grinding, the thermal conductivity of the conventional silicon nitride sintered body is It has been revealed that a silicon nitride sintered body having a high strength, which is more than doubled, specifically 60 W / mK or more, can be obtained, and a new silicon nitride satisfying both heat dissipation characteristics and strength characteristics. Developed raw material. It has been found that when this silicon nitride material is applied to a substrate material for a semiconductor-mounting circuit board, excellent heat dissipation characteristics, durability, and heat cycle characteristics can be achieved at the same time.

A glass phase (amorphous phase) in the grain boundary phase is obtained by using a high-purity silicon nitride raw material powder having a reduced content of oxygen and impurity cation elements and sintering the powder under the above conditions. Can be effectively suppressed, and the crystalline compound in the grain boundary phase is 20% by volume or more (relative to the whole grain boundary phase),
It is more preferably 50% by volume or more, so that 60 W / m · K or more, even more preferably 80 W / m · K or more, and further 100 W / m · K or more even when only the rare earth element oxide is added to the raw material powder. It was found that a silicon nitride sintered body substrate having high thermal conductivity can be obtained.

Further, conventionally, when the heating power source of the firing furnace was turned off after the sintering operation was finished to cool the sintered body by the furnace, the cooling rate was as rapid as 400 to 800 ° C./hour. According to the experiments by the inventor, the cooling rate is 10
By controlling the temperature slowly to 0 ° C or lower, the grain boundary phase of the silicon nitride sintered body structure changes from an amorphous state to a phase containing a crystalline phase, and high strength characteristics and high heat transfer characteristics are simultaneously achieved. It turned out that

A part of the high thermal conductivity silicon nitride sintered body itself having a thermal conductivity of 60 W / m · K or more has already been applied for a patent by the present inventor, and further, JP-A-6-
The application has been disclosed in Japanese Patent No. 135771 and Japanese Patent Laid-Open No. 7-48174. The silicon nitride sintered bodies described in these patent applications contain the rare earth element in an amount of 2.0 to 7.5% by weight in terms of oxide. However, as a result of further improvement research conducted by the present inventor, when the contained rare earth element exceeds 7.5% by weight in terms of oxide, the sintered body has a higher thermal conductivity, and the sintered body has a higher thermal conductivity. 7.5% by weight due to good binding
It is preferable to use a material having a viscosity of more than. In particular, the effect is remarkable when the rare earth element is a lanthanoid series element. By the way, even when the ratio of the crystal compound phase in the grain boundary phase to the whole grain boundary phase is 60 to 70%, the sintered body can achieve a high thermal conductivity of 110 to 120 W / m · K or more.

However, when the above silicon nitride sintered body is used as a ceramic substrate material, even if tough pitch electrolytic copper containing 100 to 1000 ppm of oxygen is used as the metal circuit board, or copper having a surface oxide layer is used. However, it was difficult to join. In principle, as described in JP-A-52-37914, for example, heating at a predetermined temperature should produce and bond a eutectic melt, but it does not actually bond.

In order to solve this problem, the present inventor has found that the reason why the joining is impossible is a predetermined temperature at the time of direct joining (in the case of copper, 10
The eutectic melt was generated by heating at 65 ° C. to 1083 ° C.), which was considered to be due to poor wettability between the generated eutectic melt and the silicon nitride sintered body.

From this point of view, in order to improve the wettability of the eutectic melt and the silicon nitride sintered body at the time of heating, the surface of the silicon nitride sintered body (substrate) has a thickness of 0 in advance. .5
After forming an oxide layer of 10 μm, oxygen is added to 100 to 1
It was possible to directly bond tough pitch electrolytic copper containing 000 ppm or copper having an oxide layer formed on the surface by heating at a predetermined temperature.

In this case, direct bonding is possible only by forming an oxide layer on the surface of the silicon nitride substrate, but even if the metal circuit board is tough pitch electrolytic copper containing 100 to 1000 ppm of oxygen, By pre-forming a copper oxide layer of a predetermined thickness on the surface of the copper circuit board, the bonding strength between the silicon nitride substrate and the copper circuit board is further improved,
It has been found that the durability of the circuit board is further improved.

Further, the center line average roughness (R
When a) is roughened to be in the range of 5.0 to 10.0 μm, the bonding strength between the substrate and the metal circuit board is increased, and a circuit board having excellent durability can be obtained. Was also found.

The present invention has been completed based on the above findings. That is, the high-thermal-conductivity silicon nitride circuit board according to the present invention has a rare earth element converted to an oxide of 2.0 to 1.
7.5% by weight, Li and N as impurity cation elements
a, K, Fe, Ca, Mg, Sr, Ba, Mn, and B are contained in a total amount of 0.3 wt% or less, and the thermal conductivity is 60 W / m.
On the surface of the silicon nitride substrate of K or more, the thickness is 0.5 to
A 10 μm oxide layer is formed, and the metal circuit board is directly bonded to the silicon nitride substrate through the oxide layer.

In another embodiment, the grain boundary phase is composed of silicon nitride particles and a grain boundary phase, the crystal compound phase in the grain boundary phase accounts for 20% or more of the total grain boundary phase, and the thermal conductivity is 60 W / m. An oxide layer having a thickness of 0.5 to 10 μm is formed on the surface of the silicon nitride substrate of K or more, and the metal circuit board is directly bonded to the silicon nitride substrate through the oxide layer. It is characterized by being

Further, the metal circuit board may contain oxygen even if
Even tough pitch electrolytic copper containing 0 to 1000 ppm is preferably a copper circuit board having a copper oxide layer with a thickness of 1.0 μm or more on the surface in order to improve the bonding strength.

Here, when the metal circuit board is a copper circuit board, since the binder in the direct bonding method is oxygen, this copper circuit board should be bonded to the silicon nitride substrate by the Cu--O eutectic compound. become. Further, when the metal circuit board is an aluminum circuit board, aluminum is preferable as the binder in the direct joining method, so that the aluminum circuit board is A
It is preferably bonded to the silicon nitride substrate by an l-Si eutectic compound.

The high-thermal-conductivity silicon nitride substrate used in the high-thermal-conductivity silicon nitride circuit substrate according to the present invention is manufactured, for example, by the following method. That is, 1.7% by weight of oxygen
Hereinafter, Li, Na, K, F as impurity cation elements
e, Ca, Mg, Sr, Ba, Mn, B total 0.3
2.0% to 17.5% by weight in terms of oxide of a rare earth element in a silicon nitride powder having an average particle diameter of 0.8 μm or less, containing 90% by weight or less of α-phase type silicon nitride. When,
A raw material mixture to which at least one of alumina and aluminum nitride is added in an amount of 1.0% by weight or less is formed to prepare a formed body, and the obtained formed body is degreased at a temperature of 1800 to 2100 ° C. Atmospheric pressure sintering, the cooling rate of the sintered body from the above sintering temperature to the temperature at which the liquid phase formed by the above rare earth element during sintering solidifies 1
The temperature is set to 00 ° C. or lower, and the obtained sintered body is manufactured by grinding and grinding into a predetermined shape.

In the above manufacturing method, Ti, Zr, Hf, V, Nb, Ta and C are further added to the raw material mixture.
At least one selected from the group consisting of oxides, carbides, nitrides, suicides, and borides of r, Mo, W is 0.2
~ 3.0 wt% may be added.

According to the above manufacturing method, a grain boundary phase containing a rare earth element or the like is formed in the silicon nitride crystal structure, the porosity is 2.5% or less, the thermal conductivity is 60 W / m · K or more, and It is possible to obtain a silicon nitride substrate having a point bending strength of 650 MPa or more at room temperature and excellent mechanical properties and thermal conductivity.

The silicon nitride powder which is the main raw material of the high thermal conductivity silicon nitride substrate used in the present invention has sinterability,
Considering strength and thermal conductivity, oxygen content is 1.7 wt% or less, preferably 0.5 to 1.5 wt%, Li, N
α phase in which the total content of impurity cation elements such as a, K, Fe, Mg, Ca, Sr, Ba, Mn, and B is suppressed to 0.3% by weight or less, preferably 0.2% by weight or less 90% by weight or more, preferably 93% by weight or more of type silicon nitride and having an average particle size of 1.0 μm or less, preferably 0.4
A fine silicon nitride powder of about 0.8 μm is used.

By using a fine raw material powder having an average particle size of 1.0 μm or less, a dense sintered body having a porosity of 2.5% or less can be formed even with a small amount of a sintering aid. It is also possible to reduce the risk of the sintering aid impairing the heat conduction characteristics.

Li, Na, K, Fe, Ca, Mg,
Since Sr, Ba, Mn, and B act as substances that impair the thermal conductivity as impurity cation elements, 60 W / m ·
In order to secure the thermal conductivity of K or more, it is possible to achieve by setting the total content of the impurity cation elements to 0.3% by weight or less. Particularly, for the same reason, it is more preferable that the total content of the impurity cation elements is 0.2% by weight or less. Since the silicon nitride powder used to obtain a usual silicon nitride sintered body contains a relatively large amount of Fe, Ca, and Mg, the total amount of Fe, Ca, and Mg is the above. It is a measure of the total content of impurity cation elements.

Further, by using a silicon nitride raw material powder containing 90% by weight or more of α-phase type silicon nitride, which is superior in sinterability as compared with β-phase type, a high density sintered body is manufactured. can do.

The rare earth elements added to the silicon nitride raw material powder as a sintering aid include Ho, Er, Yb, Y,
Depending on the oxide such as La, Sc, Pr, Ce, Nd, Dy, Sm, Gd or the sintering operation, these oxide substances may be used alone or in combination of two or more kinds. Good, but especially holmium oxide (Ho ₂ O
₃ ) and erbium oxide (Er ₂ O ₃ ) are preferred.

Particularly, by using the lanthanoid series elements Ho, Er, and Yb as the rare earth element, the sinterability or high thermal conductivity is improved, and the firing is sufficiently dense even in the low temperature region of about 1850 ° C. A union is obtained. Therefore, the effect of reducing the equipment cost and running cost of the firing apparatus can be obtained. These sintering aids are
It reacts with the silicon nitride raw material powder to form a liquid phase and functions as a sintering accelerator. Further, in the metal circuit board bonding process described later, a part of the metal diffuses toward the oxide layer and accumulates inside the oxide layer so as to concentrate.

The amount of the above-mentioned sintering aid added is in the range of 2.0 to 17.5% by weight based on the raw material powder in terms of oxide.
If the addition amount is less than 2.0% by weight, the sintered body (silicon nitride substrate) is insufficiently densified, especially when the rare earth element is an element having a large atomic weight such as a lanthanoid element. A sintered body having a low strength and a low thermal conductivity is formed on. On the other hand, if the addition amount exceeds 17.5% by weight, an excessive amount of grain boundary phase is generated, and the thermal conductivity and the strength start to decrease, so the above range is set. Particularly, for the same reason, it is desirable that the amount is 4 to 15% by weight.

Alumina (Al ₂ O ₃ ) as another selective additive component in the above-mentioned manufacturing method plays a role of promoting the function of the sintering promoter of the rare earth element, and particularly, the pressurization. It exhibits a remarkable effect when sintering is performed.

When the amount of Al ₂ O ₃ added is less than 0.1% by weight, the densification is insufficient, while when it exceeds 1.0% by weight, an excessive amount of grain boundary phase is produced. Or begins to form a solid solution in silicon nitride and causes a decrease in thermal conductivity. Therefore, the addition amount is 1.0% by weight or less, preferably 0.
It is set in the range of 1 to 0.75% by weight. In particular, in order to secure good performances in both strength and thermal conductivity, the addition amount should be 0.
It is desirable to set in the range of 2 to 0.6% by weight.

When used in combination with AlN, which will be described later, it is desirable to set the total amount added to 1.0% by weight or less.

Further, aluminum nitride (AlN) as another additive component suppresses the evaporation of silicon nitride in the sintering process and also promotes the function of the above rare earth element as a sintering accelerator. Is.

When the amount of AlN added is less than 0.1% by weight (less than 0.05% by weight when used in combination with alumina), densification tends to be insufficient, while 1.0% by weight
When the amount exceeds the above range, an excessive amount of grain boundary phase is generated or begins to form a solid solution in silicon nitride, and thermal conductivity is deteriorated. Therefore, the addition amount is in the range of 0.1 to 1.0% by weight. And In particular, in order to secure good performances in both strength and thermal conductivity, it is desirable to set the addition amount within the range of 0.1 to 0.5% by weight. When used in combination with Al ₂ O ₃ , the addition amount of AlN is preferably in the range of 0.05 to 0.5% by weight.

Further, Ti, Zr, Hf, V, Nb and T used as other selective addition components in the above-mentioned manufacturing method.
The oxides, carbides, nitrides, suicides, and borides of a, Cr, Mo, and W promote the function of the above-mentioned rare earth element sintering promoter and, at the same time, function as a dispersion strengthener in the crystal structure of Si ₃ It is intended to improve the mechanical strength of the N ₄ substrate.
When the addition amount of these compounds is less than 0.1% by weight, the densification of the structural member is insufficient, while when it exceeds 3.0% by weight, thermal conductivity and mechanical strength and Since the electrical breakdown strength decreases, the addition amount is preferably in the range of 0.1 to 3.0% by weight. Particularly preferably, it is desirable to set to 0.2 to 2.0% by weight.

The compounds such as Ti, Zr and Hf also function as a light-shielding agent that colors the silicon nitride substrate and imparts opacity. Therefore, especially when applied to a circuit board on which an integrated circuit or the like that easily causes a malfunction due to light is applied,
It is desirable to add the above compound appropriately to form a silicon nitride substrate having excellent light-shielding properties.

While aluminum nitride (AlN) suppresses evaporation of silicon nitride in the sintering process, it further promotes the function of the above-mentioned sintering promoter, and, like alumina, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W
It serves to relatively reduce the amount of oxides added such as.
The amount of aluminum compound such as alumina or aluminum nitride added is Ti, Zr, Hf, V, Nb, Ta,
There is a close relationship with the amounts of Cr, Mo and W oxides added. That is, the addition amount of the above Ti compound is 0.2% by weight.
And an aluminum compound such as Al ₂ O ₃ and AlN is added alone or in combination, and the addition amount is less than 0.1% by weight, the densification is insufficient, while 1.0% by weight
When the amount exceeds the above range, an excessive amount of grain boundary phase is generated or begins to form a solid solution in silicon nitride, and thermal conductivity is deteriorated. Therefore, the addition amount is in the range of 0.1 to 1.0% by weight. Is set to. In particular, in order to secure good performances in both strength and thermal conductivity, it is desirable to set the addition amount within the range of 0.1 to 0.5% by weight.

The porosity of the silicon nitride substrate has a large effect on the thermal conductivity and strength, so it is set to 2.5% or less, preferably 0.5% or less. If the porosity exceeds 2.5%, it will hinder the heat conduction, and the thermal conductivity of the silicon nitride substrate will decrease, and the strength of the silicon nitride substrate will also decrease.

Although the silicon nitride substrate is structurally composed of a silicon nitride crystal and a grain boundary phase, the ratio of the crystal compound phase in the grain boundary phase has a great influence on the thermal conductivity of the silicon nitride substrate. However, in the high thermal conductivity silicon nitride substrate of the present invention, it is necessary that the volume ratio is 20% or more of the grain boundary phase, and more preferably 50% or more is occupied by the crystal phase. If the crystal phase is less than 20%, the thermal conductivity will be 60 W / mK
This is because it is not possible to obtain a silicon nitride substrate having excellent heat dissipation properties and high temperature strength as described above.

Further, as described above, the porosity of the silicon nitride substrate is set to 2.5% or less, and 20% by volume or more of the grain boundary phase formed in the silicon nitride crystal structure is occupied by the crystal phase. A silicon nitride compact at a temperature of 1800 to 21
It is important to perform pressure sintering at 00 ° C. for about 2 to 10 hours and gradually cool the sintered body immediately after the completion of the sintering operation to 100 ° C. or less per hour.

When the sintering temperature is set to less than 1800 ° C., the densification of the sintered body is insufficient, the porosity becomes 2.5 vol% or more, and both the mechanical strength and the thermal conductivity decrease. . On the other hand, if the sintering temperature exceeds 2100 ° C., the silicon nitride component itself tends to evaporate and decompose. Not especially pressure sintering,
When pressureless sintering is carried out, decomposition vaporization of silicon nitride begins at around 1800 ° C.

The cooling rate of the sintered body immediately after the completion of the above-described sintering operation is an important control factor for crystallizing the grain boundary phase, and when the cooling rate is 100 ° C./hour or more, rapid cooling is performed. Indicates that the grain boundary phase of the sintered body structure becomes amorphous (glass phase), and the liquid phase generated in the sintered body occupies less than 20% by volume as a crystal phase in the grain boundary phase, resulting in strength and thermal conductivity. Will decrease together.

The temperature range in which the cooling rate should be strictly adjusted is a temperature range from a predetermined sintering temperature (1800 to 2100 ° C.) to the solidification of the liquid phase produced by the reaction of the above-mentioned sintering aid. Is enough. By the way, the liquidus freezing point when the above-mentioned sintering aid is used is approximately 1600 to 15
It is about 00 ° C. The cooling rate of the sintered body from at least the sintering temperature to the liquidus solidification temperature is set to 10 per hour.
0 ° C or lower, preferably 50 ° C or lower, more preferably 2
By controlling the temperature to 5 ° C or lower, 20% or more, preferably 50% or more of the grain boundary phase becomes a crystal phase, and finally a highly heat conductive silicon nitride substrate excellent in both thermal conductivity and mechanical strength is obtained. To be

The high thermal conductivity silicon nitride substrate used in the present invention is manufactured, for example, through the following process. That is, with respect to the fine silicon nitride powder having a predetermined fine particle diameter and a small amount of impurities, a predetermined amount of a sintering aid, an organic binder, and other necessary additives and, if necessary, Al ₂ O. _The raw material mixture is adjusted by adding ₃ , AlN or a compound such as Ti, Zr, Hf and the like, and then the obtained raw material mixture is molded to obtain a molded product having a predetermined shape. As a forming method of the raw material mixture, a general-purpose die pressing method, a sheet forming method such as a doctor blade method, or the like can be applied.

Subsequent to the above molding operation, the molded body is heated in a non-oxidizing atmosphere at a temperature of 600 to 800 ° C. or in air at a temperature of 400 to 500 ° C. for 1 to 2 hours, and the organic binder added in advance is added. Remove components thoroughly and degrease.
Next, the degreased molded body is subjected to 1800 to 210 in an inert gas atmosphere such as nitrogen gas, hydrogen gas or argon gas.
Atmosphere pressure sintering is performed at a temperature of 0 ° C. for a predetermined time, and the obtained sintered body is ground and polished to obtain a high thermal conductivity silicon nitride substrate having a predetermined shape.

The high thermal conductivity silicon nitride substrate manufactured by the above manufacturing method has a porosity of 2.5% or less, 60 W / m · K.
(25 ° C) or higher, further 100 W / m · K or higher, high thermal conductivity, and three-point bending strength of 650 MPa at room temperature
As described above, the mechanical properties of 800 MPa or more are excellent.

A silicon nitride substrate in which the thermal conductivity of the entire substrate is 60 W / mK or more by adding SiC having a high thermal conductivity to silicon nitride having a low thermal conductivity is within the scope of the present invention. Is not included. However, in the case of a silicon nitride based substrate in which a silicon nitride sintered body having a thermal conductivity of 60 W / m · K or more is combined with high thermal conductivity SiC or the like, the thermal conductivity of the silicon nitride substrate itself is It goes without saying that as long as it is 60 W / m · K or more, it falls within the scope of the present invention.

The high thermal conductivity silicon nitride circuit board according to the present invention is formed on the surface of the silicon nitride board manufactured as described above.
It is manufactured by forming an oxide layer having a thickness of 0.5 to 10 μm and directly bonding the metal circuit board to the silicon nitride substrate through the oxide layer.

Here, the metal circuit board is directly and integrally bonded to the surface of the silicon nitride substrate without using a bonding agent such as a brazing material. That is, a eutectic compound (eutectic melt) of a component of a metal circuit board and a substrate component is generated by heating, and both members are joined using this eutectic compound as a joining agent. To be done.

First, an oxide layer is formed in advance on the surface of the silicon nitride substrate to enhance the wettability with respect to the substrate. This oxide layer is formed by heating the silicon nitride substrate at a temperature of about 1000 to 1400 ° C. for 2 to 15 hours in an oxidizing atmosphere such as air. When the thickness of the oxide layer is less than 0.5 μm, the effect of improving the wettability is small, while 10 μm
Since the improvement effect is saturated even if it is set to exceed 10 and the thermal conductivity tends to decrease rather, the thickness of the oxide layer needs to be in the range of 0.5 to 10 μm, preferably 1 to 5 μm. The range of is desirable.

Initially, the oxide layer was composed only of SiO ₂ , which is an oxide of the Si ₃ N ₄ substrate component, but during the bonding operation of the metal circuit boards by heating, the Si ₃ N ₄
The rare earth element oxide added to the substrate as a sintering aid diffuses and moves toward the oxide layer, resulting in a composition in which the rare earth oxide is diffused in the oxide layer. For example, an oxide layer after heating the joining operation if as a sintering aid was used Y ₂ O ₃ is, Y ₂ O ₃ and 1-20 wt% of SiO ₂ -Y ₂ O _3, such as yttria silicate containing It will be composed of compounds.

As the metal constituting the above-mentioned metal circuit board, a eutectic compound with a substrate component such as a simple substance of copper, aluminum, iron, nickel, chromium, silver, molybdenum, cobalt, or an alloy thereof is formed and directly contacted. There is no particular limitation as long as it is a metal to which legality can be applied, but copper, aluminum or an alloy thereof is particularly preferable from the viewpoint of conductivity and cost.

The thickness of the metal circuit board is determined in consideration of the current-carrying capacity and the like, but the thickness of the silicon nitride substrate is 0.25 to 0.25.
The range of 1.2mm, while the thickness of the metal circuit board is 0.1
When set in the range of up to 0.5 mm and combining the two, they are less likely to be affected by deformation due to the difference in thermal expansion.

Particularly when a copper circuit board is used as the metal circuit board, a copper circuit board made of tough pitch electrolytic copper containing 100 to 1000 ppm of oxygen is used, or a copper material having an oxygen content of less than 100 ppm or no copper material is used. When a copper circuit board made of oxygen copper is used, a copper oxide layer having a predetermined thickness is formed in advance on the surface of the copper circuit board, as described later, so that the copper circuit board can be bonded by direct bonding. However, in order to increase the amount of Cu-O eutectic that is generated even when using the copper circuit board made of the above-mentioned tough pitch electrolytic copper, and to improve the bonding strength between the substrate and the copper circuit board, the surface of the copper circuit board is predetermined. It is desirable to pre-form a thick copper oxide layer.

The copper oxide layer has a thickness of, for example, 20 to 12 at a temperature of 150 to 360 ° C. in the atmosphere of a metal circuit board.
It is formed by performing a surface oxidation treatment of heating for 0 seconds. Here, when the thickness of the copper oxide layer is less than 1 μm, the amount of Cu—O eutectic generated is small, so that the unbonded portion between the substrate and the copper circuit board increases, and sufficient bonding strength is obtained. Absent. On the other hand, even if the thickness of the copper oxide layer is too large to exceed 10 μm, the effect of improving the bonding strength is small and the conductive characteristics of the copper circuit board are rather impaired. Therefore, the thickness of the copper oxide layer formed on the surface of the copper circuit board is 1 to 10
The range of μm is preferred. And for the same reason 1-5
The range of μm is more desirable.

Further, the bonding strength tends to be higher when the surface of the copper circuit board is rougher than when the surface is smooth. In the surface oxidation treatment, the surface roughness of the copper circuit board can be increased by raising the heating temperature or prolonging the treatment time. The surface roughness of the copper circuit board after the surface oxidation treatment is the center line average roughness (Ra).
Is preferably in the range of 5 to 10 μm. If necessary, the surface roughness of the copper circuit board may be adjusted by sandblasting the surface of the copper circuit board.

When the metal circuit board is a copper circuit board, the joining operation is carried out as follows. That is, a copper circuit board having a copper oxide layer optionally formed thereon is placed in contact with a predetermined position on the surface of a silicon nitride substrate having a high thermal conductivity formed with an oxide layer, and the melting point of copper (10
The temperature is below 83 ° C.) and the temperature is higher than the eutectic temperature of copper-copper oxide (1065 ° C.), and the produced Cu—O eutectic compound liquid phase (eutectic melt) is used as a bonding agent to form a copper circuit board in a silicon nitride substrate Bonded directly to the surface. This direct bonding method is a so-called copper direct bonding method (DBC: Direct Bonding Copper method).

On the other hand, when the metal circuit board is an aluminum circuit board, Si is selected as the binder and Si ₃ N
₄ Al-Si produced by heating the aluminum circuit board to the surface of the substrate while heating it above the eutectic temperature of aluminum-silicon
The Al circuit board is directly bonded to the surface of the Si ₃ N ₄ substrate by using the eutectic compound liquid phase (eutectic melt) as a bonding agent to manufacture the high thermal conductive Si ₃ N ₄ circuit board of the present invention.

According to the high thermal conductive Si ₃ N ₄ circuit board according to the present invention, which is formed by directly bonding the metal circuit board to the surface of the Si ₃ N ₄ board using the direct bonding method as described above, Since there is no inclusion such as adhesive or brazing material between the Si ₃ N ₄ substrate and the Si ₃ N ₄ substrate, the thermal resistance between the two is small,
It is possible to quickly dissipate the heat generated by the semiconductor element provided on the metal circuit board outside the system.

According to the high-thermal-conductivity silicon nitride circuit board according to the present invention, in addition to the high-strength and high-toughness characteristics originally possessed by the silicon-nitride sintered body, the high-thermal-conductivity silicon nitride is significantly improved. Since an oxide film is formed on the surface of the base board and the metal circuit boards are integrally bonded by the direct bonding method, the circuit board does not suffer from tightening cracks during the assembly process, and a semiconductor device using the circuit board can be manufactured. Mass production is possible with high manufacturing yield.

Since the toughness value of the silicon nitride substrate is high,
It is possible to provide a semiconductor device in which cracks are less likely to occur in a substrate due to heat cycle, heat cycle characteristics are remarkably improved, and durability and reliability are excellent.

Since a silicon nitride substrate having a higher thermal conductivity is used, even when a semiconductor element aiming at higher output and higher integration is mounted, the thermal resistance characteristic is less deteriorated and excellent. Exhibits heat dissipation characteristics.

Particularly, since the silicon nitride substrate itself has excellent mechanical strength, it is possible to further reduce the substrate thickness as compared with other ceramic substrates when the required mechanical strength characteristics are kept constant. It will be possible. Since the substrate thickness can be reduced, the thermal resistance value can be further reduced, and the heat dissipation characteristics can be further improved. Further, since it is possible to sufficiently meet the required mechanical characteristics even with a substrate thinner than before, it is possible to mount the circuit board at a high density and further downsize the semiconductor device.

[0069]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will now be specifically described with reference to the following examples.

First, a silicon nitride substrate forming each circuit board will be described, and then a circuit board using this silicon nitride substrate will be described.

Examples 1 to 3 1.3 wt% oxygen, Li as the impurity cation element,
Containing 0.15 wt% of Na, K, Fe, Ca, Mg, Sr, Ba, Mn and B in total, and 97% of α-phase type silicon nitride
With respect to the average particle size silicon nitride material powder of 0.55μm comprising, an average particle size of 0.7μm as a sintering aid Y ₂ O
₃ (yttrium oxide) powder 5% by weight, average particle size 0.5
1.0 wt% of Al ₂ O ₃ (alumina) powder of μm was added, wet-mixed in ethyl alcohol for 24 hours, and then dried to prepare a raw material powder mixture.

Next, a predetermined amount of an organic binder was added to the obtained raw material powder mixture and the mixture was uniformly mixed.
A large number of compacts were produced by press molding with a compacting pressure of cm ² . Next, after degreasing the obtained molded body in an atmospheric gas at 700 ° C. for 2 hours, the degreased body was held at 1900 ° C. for 6 hours at 9 atm in a nitrogen gas atmosphere, and after performing densification sintering, The cooling rate of the sintered body is 100 ° C / hr until the temperature inside the sintering furnace drops to 1500 ° C by controlling the amount of electricity supplied to the heating device attached to the sintering furnace.
(For Example 1), 50 ° C / hr (for Example 2), 25 ° C /
The sintered body was cooled after adjusting to hr (for Example 3), and the obtained sintered body was subjected to polishing to prepare silicon nitride substrates for Examples 1 to 3, respectively.

Comparative Example 1 On the other hand, immediately after the completion of the densification sintering, the heating apparatus power supply was turned off, and the sintered body was cooled at the conventional cooling rate (about 500 ° C./hr) for cooling the sintered body. A silicon nitride substrate for Comparative Example 1 was prepared by performing a sintering treatment under the same condition 2 as described above.

Comparative Example 2 1.5 wt% oxygen, Li as the impurity cation element,
A silicon nitride raw material powder having an average particle size of 0.60 μm, containing Na, K, Fe, Ca, Mg, Sr, Ba, Mn and B in a total amount of 0.6% by weight and including α-phase type silicon nitride 93%. Was treated under the same conditions as in Example 1 except for using, to prepare a silicon nitride substrate for Comparative Example 2.

Comparative Example 3 1.7% by weight of oxygen, Li as an impurity cation element,
Raw material powder of silicon nitride having an average particle size of 1.1 μm, containing 0.7% by weight of Na, K, Fe, Ca, Mg, Sr, Ba, Mn, and B in total and containing 91% of α-phase type silicon nitride. Was treated under the same conditions as in Example 1 except for using, to prepare a silicon nitride substrate for Comparative Example 3.

With respect to the silicon nitride substrates thus obtained for Examples 1 to 3 and Comparative Examples 1 to 3, porosity and 25 ° C.
Was measured. Further, the ratio (volume ratio) of the crystal phase in the grain boundary phase was measured for each Si ₃ N ₄ substrate by the X-ray diffraction method, and the results shown in Table 1 below were obtained.

[0077]

[Table 1]

As is clear from the results shown in Table 1, in the silicon nitride substrates for Examples 1 to 3, as compared with Comparative Example 1, the cooling rate of the sintered body immediately after the completion of the densification sintering was higher than that of the conventional one. Since it is set low, the grain boundary phase contains a crystalline phase,
The higher the proportion of the crystal phase, the higher the strength of the heat-dissipating Si ₃ N ₄ substrate having high heat conductivity.

On the other hand, when the cooling rate of the sintered body was set high as in Comparative Example 1 and was rapidly cooled, the grain boundary phase was entirely amorphous and the thermal conductivity decreased. In addition, Comparative Example 2
When the silicon nitride powder containing a large amount of the impurity cation element as much as 0.6% by weight is used as described above, even if the cooling rate of the sintered body is the same as in Example 1, all the grain boundary phases are amorphous. It formed and the thermal conductivity fell.

Further, as in Comparative Example 3, the average particle size is 1.1.
In the case of using a silicon nitride powder having a coarseness of μm, the densification was insufficient in the sintering and both the strength and the thermal conductivity decreased.

Next, the thickness of the Si ₃ N ₄ substrate for Examples 1 to 3 adjusted as described above was changed to 0.635 mm and 0.4 mm.
While being processed into Si ₃ N ₄ for Comparative Examples 1 to 3,
By processing the substrate thickness to 0.635 mm and heating each Si ₃ N ₄ substrate at a temperature of 1300 ° C. for 12 hours in an oxidation furnace, the entire surface of the substrate is oxidized to form a 2 μm thick oxide layer. Formed.

Next, a copper circuit board made of tough pitch electrolytic copper having a thickness of 0.3 mm is placed in contact with the surface side of each Si ₃ N ₄ substrate on which an oxide layer has been formed, while a 0.25 mm thickness is provided on the back side. A copper circuit board made of tough pitch copper is placed as a backing material in contact with each other to form a laminated body, and the laminated body is inserted into a heating furnace set to a temperature of 1075 ° C. adjusted to a nitrogen gas atmosphere and heated for 1 minute, thereby Si ₃ N ₄ circuit boards were prepared by directly bonding copper circuit boards to both sides of the Si ₃ N ₄ board.

[0083] Each Si ₃ N ₄ circuit board 1, the oxide layer 3 is formed on the entire surface the Si ₃ N ₄ substrate 2 as shown in FIG. 1, metal surface the Si ₃ N ₄ substrate 2 While the copper circuit board 4 as a circuit board is directly joined, the copper circuit board 5 as a back copper board is similarly directly joined on the back side, and a solder layer (not shown) is further provided at a predetermined position on the front side copper circuit board 4. It has a structure in which the semiconductor element 6 is integrally bonded via the via. Si
_When copper circuit boards 4 and 5 are bonded to both sides of ₃ N ₄ substrate 2,
The copper circuit board 5 as the back copper plate is effective because it contributes to promotion of heat dissipation and prevention of warpage.

Comparative Example 4 On the other hand, instead of the Si ₃ N ₄ substrate in the example, an aluminum nitride (AlN) substrate having a thickness of 0.635 mm and a thermal conductivity of 170 W / m · K was used. An oxide layer was formed in the same manner as in Example, and a copper circuit board was further integrally bonded to the AlN substrate by using a direct bonding method to manufacture an AlN circuit board according to Comparative Example 4.

Comparative Example 5 Further, instead of the Si ₃ N ₄ substrate in the example, an aluminum nitride (AlN) substrate having a thickness of 0.8 mm and a thermal conductivity of 70 W / m · K was used. A comparative example 5 was prepared by forming an oxide layer in the same manner as in the example, and further integrally bonding a copper circuit board to an AlN substrate using a direct bonding method.
An IN circuit board was manufactured.

In order to evaluate the strength characteristics, toughness, and heat cycle characteristics of the circuit boards according to the examples and comparative examples prepared as described above, the three-point bending strength and the maximum deflection amount of each circuit board were measured, and A thermal cycle test (TCT) was carried out to investigate the occurrence of cracks on the circuit board.

[0087] maximum deflection amount adds a load to the central portion while supporting each circuit board support span 50 mm, Si ₃
It was measured as the maximum deflection height until the N ₄ substrate or the AlN substrate was broken.

In the heat resistance cycle test, each circuit board was heated from −45 ° C. to room temperature (RT), then from room temperature to + 125 ° C., and then again at room temperature.
A temperature rising / falling cycle was repeated by repeating one cycle until cooling to 45 ° C., and the number of cycles until cracks and the like occurred in the substrate was measured.

The results of each measurement are shown in Table 2 below.

[0090]

[Table 2]

As is clear from the results shown in Table 2 above,
According to the Si ₃ N ₄ circuit board according to each example, the bending strength and the maximum deflection amount are large as compared with the comparative example. Therefore, it has been proved that tightening cracks are less likely to occur in the assembly process of the circuit board, and the manufacturing yield of the semiconductor device using the circuit board can be significantly improved.

Further, in the heat resistance cycle test, the Si ₃ N ₄ circuit board of each example was free from cracks of the Si ₃ N ₄ board and peeling of the metal circuit board (Cu circuit board) even after 1000 cycles. It was confirmed to have excellent durability and reliability. In addition, the withstand voltage characteristics did not deteriorate even after 1000 cycles.

On the other hand, in the Si ₃ N ₄ circuit boards according to Comparative Examples 1 to ₃ , although the three-point bending strength, the amount of flexure and the heat resistance cycle characteristics are good, the thermal conductivity of the Si ₃ N ₄ board is 60 W / Since it is relatively low at less than m · K, it has been found to be unsuitable for a semiconductor device that is also aimed at high output.

Further, in the AlN circuit board according to Comparative Example 4, since the AlN board having high thermal conductivity is used,
Although it has excellent heat dissipation characteristics, it was confirmed that the strength and deflection were small, and it was difficult to withstand tightening cracks in the assembly process and impact during handling. Also, in the heat resistance cycle test, cracks occurred after 100 cycles,
It has been found that the withstand voltage characteristic is also deteriorated.

Further, the AlN circuit board according to Comparative Example 5 has a higher thermal conductivity than the conventional Si ₃ N ₄ board, and therefore has good heat dissipation, but has insufficient strength and deflection. is there. In the heat resistance cycle test, 150
It was found that cracks occurred after the cycle and the withstand voltage characteristics deteriorated.

Next, an embodiment of a circuit board using another silicon nitride substrate having various compositions and characteristic values will be specifically described with reference to Example 4 below.

Example 4 First, various silicon nitride substrates which are constituent materials of a circuit board were manufactured by the following procedure.

That is, a silicon nitride raw material powder having an average particle diameter of 0.55 μm, containing 1.3% by weight of oxygen, 0.15% by weight of the impurity cation elements in total, and 97% of α-phase type silicon nitride. On the other hand, as shown in Tables 3 to 5, rare earth oxides such as Y ₂ O ₃ and Ho ₂ O ₃ as sintering aids,
If necessary, Ti, Hf compound, Al ₂ O ₃ powder, Al
N powder was added, and the mixture was wet-mixed in ethyl alcohol for 72 hours using a silicon nitride ball 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 .
Many molded articles having various compositions were manufactured.

Next, each molded body obtained was degreased for 2 hours in an atmosphere gas at 700 ° C.
After performing the densification sintering under the sintering conditions shown in to 5, the amount of electricity supplied to the heating device attached to the sintering furnace is controlled to perform the sintering until the temperature inside the sintering furnace drops to 1500 ° C. The sintered bodies were cooled by adjusting the cooling rates of the bodies to the values shown in Tables 3 to 5, and the silicon nitride sintered bodies of Samples 1 to 51 were prepared.

With respect to each of the silicon nitride sintered bodies according to Samples 1 to 51 thus obtained, the average value of porosity, thermal conductivity (25 ° C.) and three-point bending strength at room temperature was measured. Furthermore, the ratio (area ratio) of the crystal phase in the grain boundary phase was measured for each sintered body by the X-ray diffraction method, and the results shown in Tables 3 to 5 below were obtained.

[0101]

[Table 3]

[0102]

[Table 4]

[0103]

[Table 5]

As is clear from the results shown in Tables 3 to 5, in the silicon nitride sintered bodies according to Samples 1 to 51, the raw material composition was appropriately controlled, and immediately after the densification and sintering was completed as compared with the conventional example. Since the cooling rate of the sintered body is set lower than before, the higher the ratio of the crystal phase in the grain boundary phase and the higher the proportion of the crystal phase, the higher the heat dissipation and the high strength silicon nitride sintered body with high heat dissipation. was gotten.

On the other hand, 1.3 to 1.5% by weight of oxygen and 0.13 to 0.1% by weight of the above impurity cation elements are included.
A silicon nitride raw material powder containing 6% by weight and containing 93% of α-phase type silicon nitride and having an average particle size of 0.60 μm was used, and 3% of Y ₂ O ₃ (yttrium oxide) powder was added to the silicon nitride powder. ~ 6 wt% and 1.3-1.6 wt% alumina powder
The added raw material powder is shaped and degreased, then sintered at 1900 ° C. for 6 hours, and cooled in a furnace (cooling rate: 400 ° C./hour) to obtain a sintered body having a low thermal conductivity of 25 to 28 W / m · K. The thermal conductivity was close to that of the silicon nitride sintered body manufactured by the conventional general manufacturing method.

Then, the silicon nitride sintered bodies according to Samples 1 to 51 thus obtained were polished to give silicon nitride substrates having a thickness of 0.4 mm and 0.635 mm, as in Examples 1 to 3. Were prepared respectively.

Further, each silicon nitride substrate was heated in an oxidation furnace at a temperature of 1300 ° C. for 12 hours to oxidize the entire surface of the substrate to form an oxide layer having a thickness of 2 μm.

On the other hand, the copper circuit boards with thicknesses of 0.3 mm and 0.25 mm prepared in Examples 1 to 3 were heated at a temperature of 250 ° C. for 30 seconds on a hot plate in contact with the atmosphere for surface oxidation treatment. A copper oxide layer having a thickness of 1.5 μm was integrally formed on the surface.

Next, a direct bonding method (D) was applied to the surface of each silicon nitride substrate on which the above oxide layer was formed in the same manner as in Examples 1 to 3.
A silicon nitride circuit board according to Example 4 as shown in FIG. 2 was prepared by integrally bonding the copper circuit boards and the like using the BC method).

In each Si ₃ N ₄ circuit board 1a, as shown in FIG. 2, an oxide layer 3 is formed on the entire surface of the Si ₃ N ₄ board 2a, and on the bonding surface side of the copper circuit boards 4 and 5. Copper oxide layers 7 and 7 are formed on the Si ₃ N ₄ substrate 2a.
While the copper circuit board 4 as a metal circuit board is directly joined to the front surface side, the copper circuit board 5 as a back copper plate is similarly directly joined to the back surface side, and further at a predetermined position of the copper circuit board 4 on the front surface side. It has a structure in which the semiconductor elements 6 are integrally joined via a solder layer (not shown).

The maximum deflection amount and bending strength of each Si ₃ N ₄ circuit board according to Example 4 in which the circuit layer was formed by the DBC method as described above are equal to or higher than those in Examples 1 to 3, and the heat cycle Even after 1000 cycles in the test, there was no cracking of the Si ₃ N ₄ substrate or peeling of the circuit layer, and excellent heat cycle characteristics were obtained.

In particular, since the oxide layer 3 is formed on the surface of the silicon nitride substrate 2a and the copper oxide layer 7 is further formed on the surfaces of the copper circuit boards 4 and 5, this occurs at the time of bonding by the DBC method. The amount of Cu—O eutectic compound to be used was increased, and the bonding strength between the substrate 2a and the copper circuit boards 4 and 5 could be further improved. Specifically, the copper circuit boards 4 and 5 in Example 4
The area ratios of the non-bonded portions of Nos. 1 and 2 are 5.2% and 5.6%, respectively.
Example 2: 13.8%, 11.5%, Example 3: 11.
6%, 14.6%), and the bonding strength (peel strength) of the copper circuit board was increased by 20 to 30%.

[0113]

As described above, according to the high thermal conductive silicon nitride circuit board of the present invention, the thermal conductivity is significantly increased in addition to the high strength and high toughness characteristic inherent in the silicon nitride sintered body. Since an oxide film is formed on the surface of the improved silicon nitride board and the metal circuit board is integrally bonded by the direct bonding method, the circuit board does not suffer from cracking due to tightening during the assembly process. It becomes possible to mass-produce existing semiconductor devices with a high manufacturing yield.

Furthermore, as the metal circuit board, by using a copper circuit board having a copper oxide layer having a predetermined thickness formed in advance on the surface thereof, the bonding strength between the substrate and the copper circuit board can be further increased.

Since the toughness value of the silicon nitride substrate is high,
It is possible to provide a semiconductor device in which cracks are less likely to occur in a substrate due to heat cycle, heat cycle characteristics are remarkably improved, and durability and reliability are excellent.

Since a silicon nitride substrate having a higher thermal conductivity is used, the thermal resistance characteristics are less deteriorated even when a semiconductor element for high output and high integration is mounted, which is excellent. Exhibits heat dissipation characteristics.

In particular, since the silicon nitride substrate itself has excellent mechanical strength, it is possible to further reduce the substrate thickness as compared with other ceramic substrates when the required mechanical strength characteristics are kept constant. It will be possible. Since the substrate thickness can be reduced, the thermal resistance value can be further reduced, and the heat dissipation characteristics can be further improved. Further, since it is possible to sufficiently meet the required mechanical characteristics even with a substrate thinner than before, it is possible to mount the circuit board at a high density and further downsize the semiconductor device.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a high thermal conductivity silicon nitride circuit board according to the present invention.

FIG. 2 is a cross-sectional view showing another configuration example of the high thermal conductivity silicon nitride circuit board according to the present invention.

[Explanation of symbols]

1,1a High thermal conductivity silicon nitride circuit board (Si ₃ N ₄
Circuit board) 2,2a Silicon nitride (Si ₃ N ₄ ) board 3 Oxide layer (SiO ₂ film) 4 Metal circuit board (Cu circuit board) 5 Metal circuit board (back copper plate) 6 Semiconductor element (chip) 7 Oxidation Copper layer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H05K 3/20 C04B 35/58 102Y 3/38 H01L 23/36 M (72) Inventor Nobuyuki Mizutani Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa 2-4 Stock company Toshiba Keihin Office (72) Inventor Yu Komorida Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa 2-4 Stock Company Toshiba Keihin Office (72) Inventor Satoshi Satoshi Shinsugita, Isogo-ku, Yokohama-shi, Kanagawa Town No. 8 Toshiba Corporation Yokohama Works (72) Inventor Takashi Hino 4 Keio Works, Toshiba Corporation, 2 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa (56) Reference JP-A-3-218975 (JP, A) JP-A-6-135771 (JP, A) JP-A-59-3077 (JP, A) JP-A-5-504933 (JP, A)

Claims (8)

(57) [Claims] 1. A rare earth element converted into an oxide of 2.0 to 2.0.
17.5 wt%, Li, N as impurity cation element
a, K, Fe, Ca, Mg, Sr, Ba, Mn, and B are contained in a total amount of 0.3 wt% or less, and the thermal conductivity is 60 W / m.
An oxide layer containing SiO ₂ as a main component and having a thickness of 0.5 to 10 μm is formed on the surface of a silicon nitride substrate having a thickness of K or more and a thickness of 0.25 to 1.2 mm. A metal circuit board is directly bonded to the silicon nitride substrate through a material layer, and the silicon nitride circuit substrate has a supporting span of 50 m.
With a load applied to the central part while being supported by m,
The maximum deflection until the substrate breaks is 1.0 to 1.5
mm , high thermal conductivity silicon nitride circuit board. 2. A silicon nitride particle and a grain boundary phase, wherein the crystal compound phase in the grain boundary phase accounts for 20% or more of the total grain boundary phase, and the thermal conductivity is 60 W / m.multidot.
An oxide layer containing SiO ₂ as a main component and having a thickness of 0.5 to 10 μm is formed on the surface of a silicon nitride substrate having a thickness of K or more and a thickness of 0.25 to 1.2 mm. A metal circuit board is directly bonded to the silicon nitride substrate through a material layer, and the silicon nitride circuit substrate has a supporting span of 50 m.
With a load applied to the central part while being supported by m,
The maximum deflection until the substrate breaks is 1.0 to 1.5
mm , high thermal conductivity silicon nitride circuit board. 3. The high heat conductive silicon nitride circuit board according to claim 1, wherein the metal circuit board is a copper circuit board having a copper oxide layer with a thickness of 1.0 μm or more on the surface. 4. The thermal conductivity of a silicon nitride substrate is 100 W /
The high thermal conductivity silicon nitride circuit board according to claim 1 or 2, characterized in that it is at least m · K. 5. The metal circuit board contains oxygen of 100 to 1000 p.
3. A high thermal conductivity silicon nitride circuit board according to claim 1, which is made of tough pitch electrolytic copper containing pm. 6. The high-thermal-conductivity silicon nitride circuit board according to claim 1, wherein the silicon nitride board has a roughened surface. 7. The high thermal conductivity according to claim 1, wherein the metal circuit board is a copper circuit board, and the copper circuit board is bonded to the silicon nitride substrate by a Cu—O eutectic compound. Silicon nitride circuit board. 8. The high thermal conductivity according to claim 1, wherein the metal circuit board is an aluminum circuit board, and the aluminum circuit board is bonded to the silicon nitride substrate by an Al—Si eutectic compound. Silicon nitride circuit board.