JP3198139B2 - AlN metallized substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a co-fired AlN metallized substrate.

[0002]

2. Description of the Related Art In recent years, with the development of semiconductor devices requiring a large current, such as power ICs and high-frequency transistors, the amount of heat radiation from semiconductor devices tends to increase. Accordingly, the mounting board and the package used are required to have high thermal conductivity and excellent heat dissipation. With respect to such characteristics required for the substrate, an aluminum nitride sintered body substrate has been attracting attention. Aluminum nitride substrates have high thermal conductivity, about 5 times or more that of aluminum oxide substrates, have excellent heat dissipation, and have excellent properties such as a low coefficient of thermal expansion close to that of Si chips.

When an aluminum nitride substrate is used as a mounting board or a package for a semiconductor device, a conductive material is formed on the surface or inside of the aluminum nitride substrate for the purpose of forming a circuit or a mounting portion of an electronic component. It is indispensable to form a metallized layer (metallized layer) having properties.

As a method of forming the above-mentioned metallized layer on a ceramic substrate, for example, a method using a high melting point metal such as W, Mo, W-Mo or the like is known. In this refractory metal method, a paste is prepared by adding a resin binder or a dispersion medium to refractory metal powder, and the refractory metal paste is applied on a substrate by a printing method or the like, and then at a predetermined temperature. This is a method of forming a metallized layer by firing. However, the above-mentioned aluminum nitride is inferior in wettability and reactivity with metal as compared with oxide-based ceramics such as aluminum oxide and the like. Will be. Therefore, a metallized layer (high melting point metal layer) is formed by a so-called simultaneous firing method in which the aluminum nitride substrate and the high melting point metal layer are simultaneously fired.

[0005]

As described above, since aluminum nitride has poor wettability and reactivity with metal, a refractory metal layer is formed on an aluminum nitride substrate by a simultaneous firing method. . However, even when the above-described simultaneous firing method is applied, a satisfactory bonding strength is not always obtained. That is, in the case of manufacturing a semiconductor package or the like using an aluminum nitride substrate, multi-layered internal wiring is formed by a simultaneous firing method, but the bonding strength between each aluminum nitride layer and the high melting point metal layer (internal wiring layer) is low. Insufficiency causes problems such as poor conduction, reduced hermeticity of the package, and defective structure such as peeling. The present invention has been made to address such a problem, and has made it possible to form a high-melting-point metal layer with high bonding strength on an aluminum nitride substrate, thereby improving the reliability of AlN.
It is intended to provide a metallized substrate.

[0006]

The AlN metallized substrate of the present invention is a co-fired AlN metallized substrate comprising an aluminum nitride substrate and a high melting point metal layer provided in contact with the aluminum nitride substrate. and construction material particles before Symbol aluminum nitride substrate in a refractory metal layer is dispersed and precipitated, before Symbol from the bonding interface of the aluminum nitride substrate of a refractory metal prior SL is within 10μm particles are dispersed precipitates, further The refractory metal layer and the nitride
It is characterized in that there is no void at the interface with the luminium substrate .

As the aluminum nitride substrate in the present invention, a substrate obtained by a usual liquid phase sintering method using a sintering aid is used. As the sintering aid, CaO-based or Y ₂ O ₃
A system or the like is used. The CaO-based sintering aid is CaCO ₃
It is also possible to use as. These sintering aids are added in the range of about 0.5 to 10% by weight based on the aluminum nitride powder.

Further, as a material for forming the high melting point metal layer,
W, Mo, W-Mo, etc. are used. Such a conductive layer made of a high melting point metal may be formed as a surface wiring on the surface of an aluminum nitride substrate, or may be formed as an internal wiring inside an aluminum nitride substrate. The refractory metal layer in the present invention does not have to be formed of a refractory metal alone as described above, but may include other additives.

The AlN metallized substrate of the present invention is obtained by simultaneously firing the above-described aluminum nitride substrate and the high-melting-point metal layer and integrating them. By appropriately controlling the conditions for the simultaneous firing, the particles of the constituent material of the aluminum nitride substrate, that is, the compound particles mainly composed of aluminum nitride and the sintering aid component, are dispersed and precipitated in the high melting point metal layer. Fine particles of a high melting point metal are dispersed and deposited within 10 μm from the bonding interface of the aluminum nitride substrate. Furthermore, in the interface gap
Reprecipitating constituent particles of aluminum nitride substrate
Thereby, a continuous interface is formed by filling the interface gap.
The deposition amount of the constituent material particles of the aluminum nitride substrate in the high melting point metal layer is preferably about 1 to 10% by volume. Further, it is preferable that the deposition amount of the high melting point metal fine particles deposited in the aluminum nitride substrate is about 0.2 to 2% by volume ratio. Generally, the latter particles are smaller.

Next, a method for manufacturing an AlN metallized substrate according to the present invention will be described in detail with reference to FIG. First, an AlN green sheet containing a sintering aid such as CaO and a high melting point metal paste such as W paste are prepared. The AlN green sheet may be produced by a usual doctor blade method or the like. The high-melting-point metal paste is prepared as a paste having a desired viscosity by adding a resin binder and, if necessary, a dispersion medium or a plasticizer to the high-melting-point metal powder and uniformly dispersing the same.

Using the AlN green sheet and the high melting point metal paste as described above, as shown in FIG. 1A, a high melting point metal paste 2 is formed on the AlN green sheet 1 by, for example, a screen printing method. Apply to shape. When manufacturing an AlN multilayer wiring board, a high-melting point metal paste 2 is applied to each of a plurality of AlN green sheets 1 and then a predetermined number of them are laminated. At this time, at the stage of applying the high melting point metal paste 2, microscopically, there is a gap 3 between the AlN green sheet 1 and the applied layer of the high melting point metal paste 2, and a continuous interface is not necessarily formed. It is not formed.

Next, the AlN green sheet 1 coated with the high melting point metal paste 2 is fired at a predetermined temperature,
As shown in (b), the AlN substrate 4 and the refractory metal layer 5 are formed by simultaneous firing. Here, in order to obtain the AlN metallized substrate of the present invention, the constituent materials of the AlN substrate 4, that is, Al, N and a sintering aid component (Ca in the figure) diffuse into the high melting point metal layer 5, and High melting point metal (W in the figure)
It is important to set the firing conditions so as to diffuse into the AlN substrate 4 and form a solid solution. As specific firing conditions, the firing temperature is set to a high temperature of about 1750 to 1900 ° C. Further, the firing time is preferably about 0.5 to 10 hours. Thus, the interdiffusion is promoted by firing at a high temperature.

After this firing step, the mixture is cooled to room temperature.
In this cooling step, as shown in FIG. 1 (c), since the solid solubility limit of the interdiffused Al, N and the sintering aid component is reduced, they are recombined into AlN particles 6, and the refractory metal Conditions are set so that the fine particles 7 are sufficiently dispersed and precipitated.
In the firing step, the constituent elements are interdiffused between the AlN substrate 4 and the refractory metal layer 5, and conditions are set such that the interdiffused components are sufficiently precipitated in the cooling step to further increase the interface. AlN solid-dissolves Ca and precipitates again in the gap 3. By this re-deposition, as shown in FIG. 1D, the interfacial gap 3 is filled with AlN 8 containing Ca, and a continuous interface 9 is formed. The AlN 8 grows epitaxially with a certain crystal orientation relationship with the refractory metal layer 5.

The continuous interface 9 formed by the epitaxial growth of AlN 8 has a high bonding strength.
The reliability (mechanical strength, conductivity, airtightness, etc.) of the refractory metal layer 5 can be greatly improved. The components of the aluminum nitride substrate diffused into the high melting point metal layer 5 promote sintering of the high melting point metal.
Sintering density is increased, and the conductivity can be further improved.

[0015]

Next, an embodiment of the present invention will be described. Example 1 First, a CaCO ₃ powder having an average particle diameter of 0.5 μm was added to an AlN powder having an average particle diameter of 1.0 μm as a sintering aid in an amount of 1% by weight in terms of CaO.
It was added and mixed to prepare a substrate raw material powder. Next, an appropriate amount of PVC (polyvinyl butyral) was added as a binder to the substrate raw material powder, and after sufficiently kneading, eight AlN green sheets having a thickness of 0.4 mm were produced by a doctor blade method. On the other hand, an appropriate amount of a resin binder and a dispersion medium were mixed with W powder having an average particle size of 1.0 μm to prepare a W paste.

Next, W is added to each of the above AlN green sheets.
The pastes were respectively screen-printed, dried and then laminated and integrated. The coating thickness of W paste is about 20μm
(After drying). Next, this laminate was placed in a degreasing furnace, subjected to a degreasing treatment in a nitrogen atmosphere at 700 ° C. × 3 hours, and then heated to 1800 ° C. in a firing furnace. Hold at this temperature for 6 hours, simultaneously sinter the AlN green sheet and the W coating layer in a nitrogen atmosphere, and then up to 1500 ° C at 100 ° C / hr.
And then furnace-cooled to room temperature. Through the above steps, an AlN multilayer wiring substrate for PGA (AlN metallized substrate) in which a W layer was provided as an internal wiring layer in an AlN substrate was manufactured.

In the AlN multilayer wiring board thus obtained,
The bonding interface between the 1N substrate and the W layer was observed by SEM, and the surface was analyzed by EPMA analysis. FIG.
5 shows an SEM photograph of a bonding interface of the 1N multilayer wiring board. FIG. 3 is a schematic diagram of the SEM photograph of FIG.

As is apparent from FIG. 3, AlN particles 13 containing a composite oxide of CaO and Al ₂ O ₃ are precipitated in the W layer 12 existing between the AlN layers 11. 11
In the vicinity of the interface inside, fine particles 14 of W were precipitated. From the surface analysis by EPMA, it was confirmed that the constituent elements of the AlN particles 13 were Al, N, Ca and O, and the constituent element of the fine particles 14 was W. And AlN layer 1
It was confirmed that the bonding interface 15 between the first layer 1 and the W layer 12 was a continuous interface having no voids or the like. The amount of AlN particles 13 deposited in the W layer 12 was 5% by volume,
The precipitation amount of the W fine particles 14 in 1 was 1% by volume ratio. Further, the W fine particles 14 were precipitated in a range of 5 to 6 μm from the bonding interface 15.

The bonding interface 15 in the AlN layer 11
A high-resolution TEM observation of the cross section was performed to examine the crystal structure in the vicinity of. As a result, toward the bonding interface 15
It was confirmed that epitaxial growth of AlN occurred.

Next, the AlN in the AlN multilayer wiring board is
In order to evaluate the bonding strength between the layer and the W layer, a W layer was formed on the surface of the AlN substrate by simultaneous firing under the same conditions as in the above example. Then, the bonding strength of the W layer was measured by a four-point bending test by preparing a bending test piece by bonding bulk AlN to the AlN on both sides by an active metal method, and a good result of 160 MPa was obtained. When the conductivity (W layer) and airtightness of the AlN multilayer wiring board were evaluated by the four-terminal method and the He leak test, the conductivity was 9 to 10 μΩcm and 1 × 10 ⁻⁵ c
Good results of catm / sec were obtained.

As a comparison with the present invention, CaCO ₃ as an auxiliary agent was added at 0.5% by weight in terms of CaO, the conditions for simultaneous calcination were 1700 ° C. × 3 hours, and the subsequent cooling was 5%.
An AlN multilayer wiring board was manufactured in the same manner as in the above example except that the process was performed at a temperature of 00 ° C./hr. The interface structure of this AlN multilayer wiring board is also SEM similarly to the above embodiment.
And EPMA analysis showed that AlN particles and W
Fine particles were hardly precipitated, and a slight gap was present at the joint interface, and a continuous interface was not formed.

When the bonding strength and conductivity of the W layer of the AlN multilayer wiring board according to the comparative example and the airtightness of the multilayer board were evaluated in the same manner as in Example 1, the bonding strength of the W layer was 80 MPa. The conductivity of the W layer was 13 to 15 μΩcm, and the airtightness was 5 × 10 ⁻⁵ cc atm / sec, all of which were inferior to the examples. Example 2 To AlN powder having an average particle size of 1.0 μm, 3% by weight of Y ₂ O ₃ powder having an average particle size of 1.0 μm was added as a sintering aid and mixed to prepare a substrate raw material powder. Next, an appropriate amount of PVC was added as a binder to the substrate raw material powder, sufficiently kneaded, and eight AlN green sheets having a thickness of 0.4 mm were produced by a doctor blade method. On the other hand, an appropriate amount of a resin binder and a dispersion medium were mixed with W powder having an average particle size of 1.0 μm to prepare a W paste.

Next, W is added to each of the AlN green sheets described above.
The pastes were respectively screen-printed, dried and then laminated and integrated. The coating thickness of W paste is about 20μm
(After drying). Next, this laminate was placed in a degreasing furnace, subjected to a degreasing treatment in a nitrogen atmosphere at 700 ° C. × 3 hours, and then heated to 1800 ° C. in a firing furnace. Hold at this temperature for 6 hours, simultaneously sinter the AlN green sheet and the W coating layer in a nitrogen atmosphere, and then up to 1500 ° C at 100 ° C / hr.
And then furnace-cooled to room temperature. Through the above steps, an AlN multilayer wiring substrate (AlN metallized substrate) for PGA in which a W layer was provided as an internal wiring layer in the AlN substrate was manufactured.

A of the AlN multilayer wiring board thus obtained
The bonding interface between the 1N substrate and the W layer was observed by SEM, and the surface was analyzed by EPMA analysis. As a result, SE
The secondary electron image of M was similar to that of Example 1,
AlN particles containing a composite oxide of Y ₂ O ₃ and Al ₂ O ₃ are precipitated in the W layer existing between the layers, and fine particles of W are deposited near the interface in the AlN layer. I was Also, E
According to the surface analysis by PMA, the constituent element of the AlN particles was A
l, N, Y and O, and the constituent element of the fine particles is W
Was confirmed. Then, it was confirmed that the bonding interface between the AlN layer and the W layer was a continuous interface having no voids or the like. The amount of AlN particles deposited in the W layer was 6% by volume, and the amount of W particles deposited in the AlN layer was 1% by volume. In addition, W fine particles were deposited in a range of 5 to 6 μm from the bonding interface.

In order to examine the crystal structure of the AlN layer in the vicinity of the junction interface, high-resolution TEM observation of the cross section was performed. As a result, it was confirmed that AlN was epitaxially grown toward the junction interface.

Next, the AlN in the AlN multilayer wiring board is
In order to evaluate the bonding strength between the layer and the W layer, a W layer was formed on the surface of the AlN substrate by simultaneous firing under the same conditions as in Example 2 above. When the bonding strength of this W layer was measured by the same method as in Example 1, a good result of 200 MPa was obtained. In addition, the conductivity (W
When the layer and airtightness were evaluated by the same method as in Example 1, good results of 9 to 11 μΩcm and 1 × 10 ⁻⁵ cc atm / sec or less were obtained.

As a comparison with the present invention (Comparative Example 2), the addition amount of Y ₂ O ₃ was reduced to 2% by weight, the conditions for simultaneous firing were 1700 ° C. × 3 hours, and the subsequent cooling was performed. Was carried out under the condition of 500 ° C./hr to produce an AlN multilayer wiring board in the same manner as in Example 2 above. Regarding the interface structure of this AlN multilayer wiring board, similarly to the above-described embodiment,
When examined by SEM and EPMA analysis, AlN particles and W particles were hardly precipitated, respectively, and a slight gap was present at the joint interface, and no continuous interface was formed.

The bonding strength and conductivity of the W layer of the AlN multilayer wiring board according to Comparative Example 2 and the airtightness of the multilayer substrate were evaluated in the same manner as in Example 1. The bonding strength of the W layer was 100 MPa. The conductivity of the W layer was 13 to 15 μΩcm, and the airtightness was 5 × 10 ⁻⁵ cc atm / sec, both of which were inferior to those of Example 2.

AlN according to each of the above Examples and Comparative Examples
As can be seen from the evaluation results of the multilayer wiring board, A
lN particles are dispersed and deposited, and W
By setting the firing conditions and the subsequent cooling conditions so that the fine particles are dispersed and deposited, the bonding strength of the W layer can be greatly increased, and an AlN multilayer wiring substrate (AlN metallized substrate) with excellent reliability can be obtained. It becomes possible.

In the above embodiment, an example in which a W layer as a refractory metal layer is formed in an AlN substrate has been described.
The same effect as in the above example was obtained also in the case where the W layer was formed on the surface of the AlN substrate. In addition, A of the above embodiment
In the 1N multilayer wiring board, a similar interface structure was observed in the via holes (filled with W) connecting each W layer.

[0031]

As described above, according to the present invention, since the bonding strength between the aluminum nitride substrate and the high melting point metal layer can be greatly improved, mechanical strength, conductivity, airtightness, etc. can be improved. The present invention can provide an AlN metallized substrate excellent in reliability, thereby greatly contributing to improvement in reliability of a semiconductor package and a semiconductor mounting substrate.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of a manufacturing process of an AlN metallized substrate of the present invention.

FIG. 2 is an enlarged SEM photograph showing a bonding interface of an AlN metallized substrate manufactured in one example of the present invention.

FIG. 3 is a diagram schematically showing the SEM photograph shown in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... AlN green sheet 2 ... Coating layer of high melting point metal paste 3 ... Interface void 4 ... AlN substrate 5 ... High melting point metal layer 6 ... Precipitated particles by constituent material of AlN substrate 7 ... High melting point Precipitated metal particles 8: AlN by epitaxial growth

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 23/14 C04B 37/02 H05K 3/38

Claims (4)

(57) [Claims] And 1. A aluminum nitride substrate, the co-fired AlN metallized substrate and a refractory metal layer in contact with the aluminum nitride substrate, the refractory metal layer constituting material before Symbol aluminum nitride substrate is particles are dispersed precipitated, before Symbol from the bonding interface of the aluminum nitride substrate of a refractory metal prior SL is within 10μm particles are dispersed precipitates, further the nitride Al and the refractory metal layer
An AlN metallized substrate characterized in that there is no void at the interface with the minium substrate . 2. The method according to claim 1, wherein the aluminum nitride substrate contains a sintering aid.
The AlN metallized substrate according to claim 1, wherein the AlN metallized substrate is included. 3. The method according to claim 1, wherein the refractory metal layer has
The deposition amount of the constituent material particles of the aluminum substrate is 1 to 1 by volume ratio.
A according to claim 1 or 2, wherein the value is 0%.
1N metallized substrate. 4. The method according to claim 1, wherein the refractory metal is tungsten.
A according to any one of claims 1 to 3, wherein
1N metallized substrate.