JP2546792B2 - Method for manufacturing substrate material for semiconductor device and substrate material - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention efficiently dissipates heat generated in a mounted semiconductor element, and a method and a method for manufacturing a substrate material for a semiconductor device having a thermal expansion coefficient close to that of the semiconductor element. Substrate material.

[0002]

2. Description of the Related Art As a substrate material for mounting a semiconductor element,
In order to suppress cracks and peeling due to thermal stress between the semiconductor element and the semiconductor element to be mounted, it is required to have a coefficient of thermal expansion relatively close to that of the semiconductor element. The coefficient of thermal expansion relatively close to that of the semiconductor element is close to the coefficient of thermal expansion of the envelope, and improves the durability of the packaged semiconductor device. On the other hand, in order to prevent the temperature rise of the semiconductor element, it is also required to have a good heat dissipation characteristic in order to efficiently dissipate the heat generated in the semiconductor element. Due to such requirements, metal materials such as W, Mo, Kovar, 42 alloy and ceramics such as alumina and beryllia are used as substrate materials. In some cases, various Cu alloys are used for a substrate that requires particularly high thermal conductivity.

By the way, in recent years, semiconductor integrated technology has made remarkable progress, and as a part thereof, the size and density of semiconductor elements have been rapidly increased. The amount of heat generated in semiconductor elements is also increasing with the increase in size and high density integration. Therefore, even in the substrate on which the semiconductor element is mounted, not only the coefficient of thermal expansion is close to that of the semiconductor element and the envelope material,
In order to more efficiently dissipate the amount of heat generated in a semiconductor element to the outside, development of a material having higher thermal conductivity is required. In order to meet this demand, for example, JP-A-50
In Japanese Patent Laid-Open No. 62776, Si is used as an electrode by using a sintered body containing components having excellent thermal conductivity such as Cu and Ag and W and Mo.
It is introduced to interpose between the element and the Cu terminal plate. Further, in Japanese Patent Application Laid-Open No. 59-21032, C is added in a W powder sintered body by an infiltration method which is one method of powder metallurgy.
Materials infiltrated with u have been introduced. In these sintered materials, the coefficient of thermal expansion and the thermal conductivity of the substrate can be arbitrarily set by changing the contents of Cu, Ag and the like. Therefore, C is optimally selected according to the material of the semiconductor element to be mounted and the shape and size of the package.
It is expected that when a sintered body containing u and Ag is used, a semiconductor element mounting substrate having a coefficient of thermal expansion similar to that of a semiconductor element and excellent thermal conductivity can be obtained.

[0004]

When a Cu-W type composite material is manufactured by a conventional powder metallurgy method, the infiltration method is adopted in order to make the dispersion of Cu uniform in W in the range where the Cu content is small. To be done. In the infiltration method, a W powder is filled in a mold in advance, pressure is applied to a mold punch to compact and mold the W powder, and the molten Cu is infiltrated into the product. By the infiltration method, it is generally easy to obtain a high density material.
However, it is difficult to infiltrate Cu into every corner of the entire W porous structure. As a result, it is inevitable that defects such as pinholes and closed pores due to uninfiltrated parts and holes will occur inside and on the surface of the sintered body. The defective portion has poor thermal conductivity and deteriorates the characteristics of the substrate material.

In addition, Ni or Au may be used on a substrate having a pinhole.
When the plating is applied, defects such as swelling and non-plating occur in the plating layer. The adhesion strength of the plating layer itself is also lowered, and it is easy to peel from the substrate surface. As a result, the state of adhesion of the mounted semiconductor element to the substrate deteriorates, and the contact resistance increases. In addition, a heat flow path having a sufficient heat dissipation ability is not formed between the semiconductor element and the substrate, which causes the temperature of the semiconductor element to rise during operation. The present invention has been devised in order to solve such a problem, and uses a W half-sintered body having a skeleton structure, which is contained in a state in which a conductive component Cu is coated in advance, to remove Cu. An object of the present invention is to provide a substrate material for mounting a semiconductor element, which allows Cu to uniformly permeate in the permeating step evenly by permeating, and has no defects such as a non-permeate portion and closed pores.

[0006]

In order to achieve the object, the manufacturing method of the present invention is to uniformly mix W powder containing 0.1 to 15% by volume of Cu, and to obtain a powder mixture. By phase sintering, a porous semi-sintered body in which W particles are coated with Cu is formed, and the final content of Cu is 10
A Cu permeating material is placed on the upper surface of the semi-sintered body in an amount adjusted to a range of ˜50% by volume, and the entire body is heated to allow molten Cu to permeate into the voids of the semi-sintered body. And

Cu oxide can also be used as a raw material for the powder mixture. In this case, the Cu oxide is uniformly mixed with the W powder and then reduced to a metal state. The reduction can also be performed by reduction firing that maintains the atmosphere during sintering as reducing. In the substrate material manufactured by this method, there are no voids such as pinholes and closed pores in the surface layer portion and inside, and Cu is uniformly dispersed. Therefore, it is used as a substrate material for mounting a semiconductor element, which is free from local fluctuations in thermal and electrical characteristics and has excellent quality stability.

[0008]

In order to eliminate the pinholes which adversely affect the thermal conductivity and the plating property, it is necessary that the molten Cu uniformly penetrates into the semi-sintered body obtained by sintering the W powder. Is. Therefore, in the present invention, a predetermined amount of Cu is preliminarily contained in the semi-sintered body in a coated state in order to improve the affinity for the permeated Cu. In the semi-sintered body of W, the width of the void space is large and small, and there is a path through which molten Cu easily flows and a path with a large inflow resistance depending on the dispersion state of oxides, impurities, additive elements, etc. It is a porous sintered body having. Cu was applied to this porous sintered body by the infiltration method.
Incorporation of molten Cu inevitably preferentially enters a path having a small inflow resistance and infiltrates into the inside of the sintered body.
As a result, the ratio of molten Cu entering the path having a large inflow resistance is reduced, and the path is likely to be confined as closed pores in the sintered body after infiltration.

According to the infiltration method adopted in the present invention, the W particles constituting the W sintered body are eliminated in order to eliminate the difference in difficulty of inflowing the molten Cu along the inflow path inside the W sintered body. The surface of is previously coated with Cu, which is the same material as the penetrant. Then, the permeating material is arranged on the upper surface of the W sintered body, and the molten Cu is permeated into the inside of the sintered body. As a result, the water-welding action by the coating and the downflow action by gravity work, and the molten Cu permeates the inside of the sintered body evenly without forming closed pores in the inflow path. This uniform Cu permeation is achieved by simply converting the semi-sintered body of W and Cu into C
It cannot be obtained only by infiltration with u, but rather the inflow path is closed by Cu contained in the sintered body. as a result,
A closed path remains inside the sintered body to the end, forming a closed pore. In this respect, the present invention requires a small amount of Cu
Since the W particles are coated with, the Cu contained in the semi-sintered body does not promote the formation of closed pores.

In the present invention, taking advantage of such an infiltration method, the infiltration material is heated and melted while the Cu infiltration material is placed on the upper surface of the semi-sintered body. The molten Cu spreads over the entire upper surface of the semi-sintered body and then flows down and penetrates into the semi-sintered body. At this time, since the surface of the W particles of the semi-sintered body is coated with Cu, the wettability of the semi-sintered body with respect to the molten Cu is good. Therefore, uniform penetration into the inside of the semi-sintered body is promoted. 1 and 2 show Cu in a semi-sintered body in which Cu is previously contained in a coated state and in a normal semi-sintered body.
It is a figure which compares and permeates the penetration process of. In order to manufacture a semi-sintered body containing Cu in a coated state, FIG.
As shown in (1), the W powder 1 is mixed with the Cu powder 2 and compacted, and the voids 3 which are voids are formed inside. When this green compact is heated to a temperature above the melting point of Cu and liquid phase sintered, Cu melts and the surface of the W particle 1 is coated.
Then, a semi-sintered body in which the W particles 1 are bonded to each other through the coated Cu is manufactured.

On the upper surface of the obtained semi-sintered body, a Cu permeation material 5 is arranged as shown in FIG. 1 (b). Cu penetration material is Cu
When heated and held at a temperature equal to or higher than the melting point of, the molten Cu 6 generated by melting of the Cu permeation material 5 spreads on the surface of the semi-sintered body, then flows down and permeates into the inside of the semi-sintered body. At this time, W
The Cu coating 4 on the surface of the particles 1 acts as an introduction path, and a so-called water-repellent action is developed. That is, FIG.
As shown in (c), molten Cu6 permeates the entire cross section of the porous structure. The permeation surface 7 at this time advances uniformly in the permeation direction. As a result, each hole 3 inside the semi-sintered body was completely filled with molten Cu6, and as shown in FIG.
As shown in, the Cu is uniformly dispersed throughout the porous structure,
A sintered body having no defects such as pinholes inside can be obtained. On the other hand, in the normal infiltration method, as shown in FIG. 2A, the W particles 1 are compacted and then pre-sintered to be used as the porous body. The Cu permeating material 4 is arranged so as to come into contact with the upper surface, the lower surface or the side surface of this porous body (FIG. 2B), and the heated / melted Cu is similarly impregnated into the porous body. At this time, since there is no coating of Cu on the surface of the W particles 1, the molten Cu 6 preferentially enters the inside of the porous body with a path having a small inflow resistance as shown in FIG.
Will be out of order. As a result, at the stage when the sintering is completed, the uninfiltrated portion 8 and the holes 9 remain inside the sintered body, which causes pinholes, closed pores, and the like.

As is clear from this comparison, when the semi-sintered body containing Cu in the coated state is used, the molten Cu6 is evenly distributed over the entire W semi-sintered body,
It is possible to obtain a Cu-W sintered body that does not have defects such as non-penetrating portions and voids that adversely affect the thermal conductivity and plating property. Since the sintered body obtained by the infiltration method has a uniform distribution of Cu and no pinholes, the quality of the sintered body is more stable and the properties are localized compared with the substrate material produced by the simple infiltration method. Never fluctuates. When Ni, Au, or the like is plated on the surface of the obtained sintered body, there are no defects such as non-penetrated portions and voids, so that a plating layer having excellent adhesion and no defects is formed. Therefore, when the semiconductor element is bonded via this plating layer, a bonding interface without a gap is obtained, and the contact resistance can be reduced. Also in this respect, the characteristics of the semiconductor element are stabilized, and the thermal conductivity from the semiconductor element to the substrate is improved.

In order to uniformly impregnate the molten Cu into the porous semi-sintered body of W, the W powder raw material used is subjected to pretreatment and mixing conditions in which secondary particles are completely pulverized. It is preferable to choose. For example, W secondary particles are removed and pulverized by HF treatment, a ball mill, an attritor, or the like. This suppresses the generation of the non-penetrable portion due to the W secondary particles. Further, when the W powder and the Cu powder are processed by a mechanical mixing method such as a ball mill or an attritor, or a mechanical alloying method, C is contained in the W matrix.
The u powder can be dispersed uniformly, and more favorable results can be obtained. The amount of the Cu powder pre-blended with the powder of W or the like is determined in the range of preferably 15% by volume or less in consideration of the affinity of the molten Cu for the porous semi-sintered body of W in the infiltration step. When the amount of Cu compounded exceeds 15% by volume, there is a tendency that the variation in the physical property values increases, as shown in Examples described later. This is C that connects W particles
It is speculated that this is due to the fact that the u phase increases and closed pores are easily formed in the semi-sintered body.

The lower limit of the amount of Cu compounded is not particularly limited, but is preferably 0.1% by volume or more in order to enhance the affinity of Cu for the W semi-sintered body. The semi-sintered body of W is a porous body having pores filled with molten Cu inside. In order to facilitate the formation of a semi-sintered body whose porosity is adjusted to a predetermined value, Ni, Fe, C which promotes the active sintering reaction within a range that does not significantly reduce the thermal conductivity.
It is also possible to add a small amount of a third component such as o. For example, when 0.5% by volume or less of Ni is added, the sintering reaction is promoted, and a W semi-sintered body having a porous structure containing Cu in a coated state at a relatively low temperature is obtained. Further, since the amount of shrinkage increases due to the active sintering, it becomes easy to adjust the porosity. The addition of the third component is more effective when the content of Cu is smaller.

[0015]

【Example】

Example 1: W powder having an average particle size of 3 μm was mixed with Cu powder in a ratio shown in Table 1 and mixed with a ball mill. This powder mixture was compacted and then heated at a temperature equal to or higher than the melting point of Cu for liquid phase sintering to produce a semi-sintered body having a porous structure. For comparison, a semi-sintered body obtained by sintering W powder was manufactured without compounding Cu powder. Molten Cu was added to each semi-sintered body so that the final Cu content was 35% by volume.
Were permeated or infiltrated. In the permeation method, a Cu permeation material adjusted so that the final Cu content was 35% by volume was placed on the semi-sintered body and heated and maintained at a temperature not lower than the melting point of Cu. The obtained sintered body was machined to produce 20 test pieces each having a size of 5 mm × 15 mm × 40 mm. After measuring the physical properties of each test piece, the presence or absence of pinholes was investigated by a fluorescent flaw detection method. The survey results are shown in Table 1.

[0016]

[Table 1]

As is apparent from Table 1, in the comparative examples in which the infiltration method is applied to the semi-sintered body containing no Cu, pinholes are often detected. On the other hand, in the case where Cu is infiltrated into the semi-sintered body containing Cu, the generation of pinholes is significantly suppressed even if the Cu content is as small as 0.05% by volume. Has been done. Further, when the Cu content was 0.1% by volume or more, there were no pinholes. The obtained sintered body was subjected to electroless plating with Ni plating having a thickness of 3 μm and Au plating having a thickness of 0.3 μm, and then an Si element was bonded via a plating layer. Then, when the bonding interface between the Si element and the substrate was observed, the adhesiveness of the Si element to the substrate was extremely excellent in the one manufactured according to the present invention. Therefore, the heat generated in the operating Si element was efficiently transferred to the substrate through the bonding interface and was dissipated to the outside. On the other hand, in the case where the Si element was mounted on the substrate manufactured by the infiltration method, voids were detected at the bonding interface, and the effective thermal conductivity was lower than the thermal conductivity of the substrate material itself shown in Table 1. .

Example 2 Cu powder and Ni powder were blended in the proportions shown in Table 1 to W powder having an average particle size of 3 μm, and a semi-sintered body having a porous structure was manufactured in the same manner as in Example 1. After that, a Cu permeation material was placed on the upper surface of the semi-sintered body, and the heat-melted Cu was permeated into the semi-sintered body. Table 1 also shows the results of examining the physical properties of test pieces cut out from the obtained sintered body. It can be seen from Table 1 that the addition amount of Ni is preferably 0.5% by volume or less in terms of thermal conductivity.

Example 3: A W powder having an average particle size of 3 μm was mixed with 2% by volume of Cu powder in advance to manufacture a semi-sintered body having a porous structure. After that, finally the Cu content is 10 each
Cu infiltrant adjusted to have a volume%, 30 volume%, 50 volume% and 60 volume% is arranged on the upper surface of the semi-sintered body,
The heat-melted Cu was permeated into the semi-sintered body. A test piece was cut out from the obtained sintered body, and its physical property values were measured.
Table 2 shows the measurement results.

[0020]

[Table 2]

As can be seen from Table 2, the sample No. 9 having a low Cu content has a slightly insufficient specific gravity. Sample No. 13, which has a high Cu content, has a coefficient of thermal expansion of more than 10 × 10 ⁻⁶ / ° C. The coefficient of thermal expansion of semiconductor elements is 10 ^-6 / ° C on average
Therefore, it was found that it is preferable to maintain the final Cu content within the range of 10 to 50% by volume in order to reduce the difference in thermal expansion between the substrate and the semiconductor element.

[0022]

As described above, according to the present invention, the required amount of W is added to the upper surface of the W semi-sintered body containing Cu in a coating state by liquid-phase sintering of W powder containing a part of Cu. The Cu permeation material adjusted to the above is arranged, and the permeation material is heated and melted. The melted penetrant spreads over the entire upper surface of the semi-sintered body and then flows down and permeates into the semi-sintered body. As a result, the pores were filled with Cu all over the semi-sintered body,
It is possible to obtain a sintered body with high thermal conductivity and an appropriate coefficient of thermal expansion without defects such as pinholes and closed pores. The sintered body produced in this manner is suitable for mounting a large-capacity semiconductor element with a particularly high integration density because it enables efficient dissipation of the amount of heat generated in the mounted semiconductor element to the outside. Used as a substrate material.

[Brief description of drawings]

1 is a model showing the progress of sintering according to the present invention.

FIG. 2 is a model showing the progress of sintering according to the conventional infiltration method.

[Explanation of symbols]

1: W particle 2: Cu powder 3: Void 4: Coating 5: Cu penetrant 6: Molten Cu 7: Entry surface
8: Uninfiltrated part 9: Void

Claims (3)

(57) [Claims] 1. W containing 0.1 to 15% by volume of Cu
The powders are uniformly mixed, and the obtained powder mixture is subjected to liquid phase sintering to form a porous semi-sintered body in which W particles are coated with Cu. The final content of Cu is 10 to 50% by volume. A semiconductor element mounting, characterized in that a Cu permeating material is placed on the upper surface of the semi-sintered body in an amount adjusted to a range, and Cu melted by permeating the whole is permeated into the voids of the semi-sintered body. Of manufacturing substrate material for automobile. 2. A method for producing a substrate material for mounting a semiconductor device, comprising using an oxide as a raw material of the powder mixture according to claim 1, uniformly mixing the oxide, and then reducing the oxide to a metal state. . 3. A method manufactured by the method according to claim 1 or 2,
Substrate material for mounting semiconductor devices with no voids inside.