JP3016538B2 - Surface-treated aluminum nitride 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 novel surface-treated aluminum nitride substrate. More specifically, it is a surface-treated aluminum nitride base material that achieves high bonding strength with a metallized layer.

[0002]

2. Description of the Related Art In recent years, in the development of electronic equipment, how to efficiently dissipate heat from a chip to the outside of the system in accordance with technological trends such as higher integration, smaller size, lighter weight, higher speed, and higher output of circuits. Has come to be taken up as a general problem of electronic equipment.

[0003] As a suitable base material for solving the above-mentioned problems of such electronic equipment, an aluminum nitride base material having excellent thermal conductivity has attracted attention.

That is, an aluminum nitride base material has a thermal conductivity about 10 times that of an alumina base material, and has excellent electrical insulation, a thermal expansion coefficient close to that of silicon, and a strength equal to or higher than that of an alumina base material. Therefore, it is expected as a base material for electronic devices having excellent heat dissipation.

[0005] By the way, generally, a substrate for electronic equipment is provided with a metallized layer made of a metallized component such as gold, platinum, silver-palladium, etc. on its surface to form electrodes and wiring between devices.
A pattern such as a resistor is formed.

[0006] These patterns are usually formed by a printing method. That is, it is performed by printing and firing a paste for forming a desired metallized layer by screen printing on an electronic device base material (hereinafter, referred to as a metallized layer forming paste). The above-mentioned metallized layer forming paste is obtained by adding an oxide of several weight% to a powdery metallized composition as a main component and further dispersing an organic binder and an organic solvent, or becomes the main component. Generally, a metal organic compound having a metallized composition and an additive of the metal organic compound are uniformly dissolved to be in a liquid state.

[0007] However, when the metallized layer formed by the above method is used for an alumina base material, a good bonding strength can be obtained, but a high bonding strength cannot be obtained for an aluminum nitride base material. Occurs.

As a method of solving the above problems, for example, Japanese Patent Application Laid-Open No. 01-24083 proposes a method of forming aluminum oxide by oxidizing the surface of an aluminum nitride base material. Also, Japanese Patent Application Laid-Open No. 01-19 / 1990
No. 6149 proposes a method of forming a surface layer made of silicon oxide on a surface of an aluminum nitride substrate via a bonding layer made of an aluminum oxide layer. Furthermore, Japanese Patent Application Laid-Open No. 05-85869 proposes a method in which aluminum oxide is formed on the surface of aluminum nitride by an oxidation treatment, and then a metal alkoxide is applied and baked to coat the substrate surface with an oxide.

[0009]

In any of the above methods, aluminum oxide is formed on the surface of an aluminum nitride substrate because most of the metallization layer forming pastes currently available on the market target an alumina substrate. Because it is.

[0010] However, the aluminum oxide layer formed by oxidizing the surface of aluminum nitride does not contain an auxiliary agent or the like which is firmly bonded to the paste unlike a commercially available alumina substrate, and thus has a high purity. Sufficient bonding strength with the metallized layer formed on the surface cannot be obtained.

Further, when aluminum oxide is formed, the surface of the base material loses its smoothness, and when a pattern is formed using the thin film paste, pattern distortion or disconnection may occur.

On the other hand, when an intermediate layer made of silicon oxide or metal alkoxide is provided on a layer made of aluminum oxide formed by the above-mentioned oxidation treatment, the bonding strength with the metallized layer is good, The interface between the layer and the aluminum oxide becomes brittle, and peeling is likely to occur at this portion. Also, the intermediate layer cannot restore the surface smoothness lost by the formation of the aluminum oxide layer.

Therefore, there is a need to develop a surface-treated aluminum nitride substrate having a surface treatment layer which has a high bonding strength with the metallized layer, does not lose the smoothness of the substrate surface, and does not peel off from the aluminum nitride substrate. Was a big challenge.

[0014]

Means for Solving the Problems The present inventors have conducted research to develop a surface-treated aluminum nitride base material which has solved the above-mentioned problems. As a result, the surface of the aluminum nitride substrate has a surface treatment layer having a specific amount of yttrium oxide and / or calcium oxide added to silicon oxide or silicon oxide containing a specific ratio of aluminum oxide. The surface-treated aluminum nitride substrate significantly improves the bonding strength with the metallized layer, and can extremely reliably prevent the metallized layer from peeling off from the aluminum nitride substrate. Further, forming the surface-treated layer The present inventors have found that the bonding strength can be further improved without losing the smoothness of the surface of the substrate by interposing a thin oxidized layer on the surface layer portion of the aluminum nitride substrate, and the present invention has been proposed.

That is, the present invention relates to (1) silicon oxide or aluminum oxide having a ratio of 80% by weight or less based on the total amount of silicon oxide and silicon oxide on the surface of the aluminum nitride base material; (2) 0.01 to 2 with respect to the above silicon oxide or the total amount of silicon oxide and aluminum oxide.
A surface-treated aluminum nitride substrate having a layer of yttrium oxide and / or calcium oxide in a weight%, and a thickness formed on a surface layer of the aluminum nitride substrate on the surface of the aluminum nitride substrate. 1 μm
(1) silicon oxide or 80% by weight based on the total amount of silicon oxide and silicon oxide through the following oxidation treatment layer;
Aluminum oxide in the following proportions: and (2) 0.01 to 2% by weight of yttrium oxide and / or silicon oxide or the total amount of silicon oxide and aluminum oxide.
Another object of the present invention is to provide a surface-treated aluminum nitride substrate having a layer made of calcium oxide formed thereon.

In the present invention, the shape, size, and the like of the aluminum nitride substrate are not particularly limited, and may be determined as appropriate for the application. For example, if the thickness is 0.1
mm or more, and generally, a plate-like body of 0.15 to 20 mm is used.

It is preferable that the surface roughness of the aluminum nitride substrate be 0.1 μm or less in terms of Ra in order to keep the surface of the surface treatment layer formed thereon smooth.

In the case where an oxidized layer is provided on the surface of the aluminum nitride base material as described later, the oxidized layer is sufficiently effective with a small thickness of 1 μm or less. The smoothness of the substrate surface is not lost.

Accordingly, the smooth surface has an advantage that a fine pattern can be easily formed by a thin metallized layer.

In the present invention, the surface treatment layer formed on the surface of the aluminum nitride substrate is made of silicon oxide or a specific ratio of aluminum oxide and silicon oxide, and a specific amount of yttrium oxide and / or calcium oxide. is important.

That is, the surface treatment layer having such a configuration can exhibit an extremely high bonding force to the aluminum nitride substrate or the oxidized layer formed on the surface of the aluminum nitride substrate.

In the composition of the composite oxide constituting the surface treatment layer, the silicon oxide can be metallized with the surface treatment layer without impairing the smoothness of the surface of the aluminum nitride substrate or the aluminum nitride substrate having the oxidation treatment layer. It is an important component for firmly bonding the layer. This effect is presumed to be such that silicon oxide has a function of uniformly mixing and dispersing aluminum oxide, yttrium oxide, and calcium oxide.

Aluminum oxide is effective for further improving the bonding strength by uniformly bonding the surface-treated layer and the aluminum nitride substrate or the oxidized layer of the aluminum nitride substrate. It is desirable that the amount of addition be 80% by weight or less based on the total amount of silicon oxide. That is, when the proportion of aluminum oxide in the surface treatment layer exceeds 80% by weight, not only the bonding strength with the metallized layer decreases, but also the smoothness of the surface treatment layer surface is impaired.

When aluminum oxide is used as described above, the ratio of aluminum oxide in the surface treatment layer is as follows:
Although it may be within the above range, it is particularly preferably in the range of 10 to 75% by weight from the viewpoint of ease and stability of forming the surface treatment layer.

The yttrium oxide and / or calcium oxide constituting the surface treatment layer has high reactivity with the aluminum nitride base material and the oxidation treatment layer formed on the surface of the aluminum nitride base material. It is a particularly important component for increasing the bonding strength with the aluminum nitride substrate or the oxidized layer formed on the surface of the aluminum nitride substrate. The addition amount is required to be 0.01 to 2.0% by weight based on silicon oxide or the total of silicon oxide and aluminum oxide.

That is, when the content of yttrium oxide and / or calcium oxide in the surface treatment layer is less than 0.01% by weight, the reaction with the aluminum nitride base material or aluminum nitride having the oxidation treatment layer is insufficient, and the bonding strength is reduced. On the other hand, when the proportion of yttrium oxide and / or calcium oxide exceeds 2.0% by weight, the dispersion in the surface treatment layer becomes uneven and the surface treatment layer is peeled off.

It is sufficient that only one of yttrium oxide and / or calcium oxide in the surface treatment layer is present, but both may be present simultaneously if the total amount is within the above range. The ratio of yttrium oxide and / or calcium oxide may be within the above range, but is preferably in the range of 0.05 to 1.5% by weight from the viewpoint of ease and stability of forming the surface treatment layer. Preferably, there is.

In the present invention, the thickness of the surface treatment layer is not particularly limited, but is generally adjusted to 0.01 to 0.2 μm, preferably 0.03 to 0.1 μm, in order to sufficiently exert the bonding force. .

In the present invention, the method for forming the surface treatment layer is not particularly limited as long as it is a method for forming a composite oxide having the above composition. In general, a solution of a metal organic or inorganic compound is solidified from a sol to a gel by a hydrolysis / polycondensation reaction, and a sol-gel method of producing an oxide by heating the gel, once the substance to be obtained is in the gas phase, A vacuum deposition method for returning to a solid phase on a substrate, a sputtering method, or the like is employed.

Among them, the sol-gel method is particularly preferable because yttrium oxide and calcium oxide can be more uniformly dispersed in the surface treatment layer and the bonding strength between the surface treatment layer and the aluminum nitride substrate can be improved.

The method of forming the surface treatment layer using the sol-gel method will be described in more detail. For example, metal alkoxides of silicon, aluminum, yttrium and calcium adjusted to the above specific composition can be obtained by adding ethyl lactate and After dissolving in acetylacetone at about 80 ° C, a mixed solution of ethyl lactate, acetic acid and pure water is dropped, and then uniformly applied to the surface of the aluminum nitride substrate by a spin coater, and dried at 400 to 600 ° C for about 30 minutes. To obtain a surface treatment layer.

As described above, the surface treatment layer of the present invention can be directly bonded to an aluminum nitride substrate.
Through the oxidation treatment layer formed on the surface of the aluminum nitride base material, a higher bonding force is exhibited.

In the present invention, the oxidized layer formed on the surface of the aluminum nitride substrate is obtained by oxidizing the surface layer of the aluminum nitride substrate and converting it to aluminum oxide. It is necessary to further improve the bonding strength with the layer.

That is, since the above-mentioned oxidized layer is formed by changing aluminum nitride itself, the bonding strength with the base material is high.
In addition, since it has high reactivity with the surface treatment layer, it may exhibit good bonding strength to this surface treatment layer.

The thickness of the oxidized layer needs to be 1 μm or less. If the thickness of the oxidized layer exceeds 1 μm, the smoothness of the aluminum nitride substrate surface is lost, and it becomes difficult to form a pattern using a thin metallized layer forming paste. In addition, the consistency with the aluminum nitride base material is reduced, and the aluminum nitride base material is easily separated from the base material.

The thickness of the oxidized layer may be within the above range, preferably 0.7 μm or less, more preferably
It is preferable to adjust the thickness to 0.005 to 0.6 μm in order to sufficiently exhibit the smoothness of the aluminum nitride substrate surface.

As the method of forming the oxidized layer, a known method of converting aluminum nitride to aluminum oxide, such as a method of heating an aluminum nitride substrate in air or water vapor, a method of corroding with a chemical, or a method of performing plasma irradiation, is particularly used. Adopted without restrictions.

Among them, the method of heating in the air is most suitable for achieving the object of the present invention. The heating temperature is preferably 950 to 1200 ° C., and the thickness of the oxidation treatment layer can be adjusted by adjusting the heating temperature and the heating time.

The surface-treated aluminum nitride substrate of the present invention has a high bonding strength to a metallized layer, and an aluminum nitride substrate having a metallized layer can be obtained with high reliability. As the metallization layer,
Examples include electrodes and wiring materials such as gold, platinum, silver-palladium and copper, and bonding materials such as solder and molybdenum-manganese.

[0040]

As will be understood from the above description, the surface-treated aluminum nitride substrate according to the present invention has a silicon oxide containing silicon oxide or a specific proportion of aluminum oxide on the surface of the aluminum nitride substrate. By forming a surface treatment layer containing a specific amount of yttrium oxide and / or calcium oxide in silicon directly or through an oxidation treatment layer formed on the surface of the aluminum nitride substrate, electrodes and resistors are formed. It can be firmly bonded to the metallized layer to be formed.

The surface treatment layer also has a high bonding strength to an aluminum nitride substrate and an oxidized layer formed by treating the surface of the aluminum nitride substrate. High bonding force can be exhibited.

Further, since the surface treatment layer is formed while maintaining the smoothness of the surface of the aluminum nitride base material, a fine pattern can be formed by a paste for forming a metallized layer of a thin film.

Therefore, the surface-treated aluminum nitride base material of the present invention can be widely used as a base material for electronic equipment on which resistors, electrodes and the like of any material, shape and size are mounted. In particular, since the thermal conductivity of aluminum nitride is very good, its effect is remarkable when it is used for a member such as a chip or a device in which heat generation adversely affects equipment.

[0044]

EXAMPLES The present invention will be described specifically with reference to the following examples, but the present invention is not limited to these examples.

Various tests in Examples and Comparative Examples were performed by the following methods.

(1) Bonding force measurement test A gold paste was screen-printed on the entire surface of the surface-treated aluminum nitride substrate, and then fired at 800 ° C. for 1 hour to form a gold metallized layer.

The gold paste is a thick film paste (thickness: 6)
μm) and a thin film paste (0.8 μm thick).

Next, nickel plating was applied to the surface of the gold metallized layer to obtain a test piece for measuring the bonding strength. The reason why nickel plating is applied is to prevent the solder used below from directly reacting with gold and alloying. Nickel plating was performed by an electroplating method, and a Watts bath was used as a nickel bath. The Watts bath was composed of 24 g of nickel sulfate and 4.5 g of nickel chloride in 100 cc of pure water.
It was prepared by adding 3 g of boric acid and stirring it uniformly. The plating temperature was set to 60 ° C., and plating was performed at a voltage of 1.5 V and a current of 100 mA using a nickel plate as an anode. The thickness of the nickel plating layer was 1.0 μm.

After nickel plating, a stainless steel rod having a cross-sectional area of 1 mm ² was mounted perpendicular to the nickel plating surface. The joining between the stainless steel bar and the nickel plating was performed by interposing a solder between them. After confirming that the solder has been installed correctly, fix the aluminum nitride substrate so that it does not move, pull up the stainless steel bar with a tensile tester, and instantly separate the surface-treated aluminum nitride substrate and stainless steel bar. Was defined as the bonding force between the gold and the metallized layer.

The above test was performed 10 times on the same specimen, and the average was taken as the measured value.

(2) Pattern accuracy test In the same manner as in the bonding strength measurement test described in (1) above, gold was applied to the entire surface of the surface-treated aluminum nitride substrate using a thin film paste (0.8 μm thick). Was formed to obtain a test piece.

Next, a positive type thick film resist material was applied on the surface of the gold metallized layer of the obtained specimen so as to have a uniform thickness, and a linear pattern having a line width of 5 μm and a line interval of 5 μm was formed. Exposure and development were performed to obtain 5 lines.

After the development was completed, the gold other than the pattern to be obtained was removed by ion milling. The acceleration voltage during ion milling was 600 W, and the introduced gas was argon.

The linear pattern after ion milling was observed with an optical microscope, and the presence or absence of disconnection or distortion was observed.
The pattern accuracy was evaluated as ○ when no disconnection or distortion was present, and as × when confirmed.

Examples 1 to 14 Aluminum nitride substrates having the surface treatment layers shown in Table 1 were produced by the following methods.

First, a 1-inch square, 0.635 mm thick aluminum nitride substrate was ground to finish the shape to a 1-inch square, 0.5 mm thick. The surface roughness of the aluminum nitride substrate was Ra 0.05 μm.

100 g of ethyl lactate containing tetraethoxysilane and aluminum isopropoxide weighed to the composition shown in Table 1 over the entire surface of the oxidized layer.
And 10 g of ethanol containing yttrium trichloride weighed to have the composition shown in Table 1, were uniformly mixed at room temperature, and then heated to 80 ° C.

Next, acetylacetone was added and the mixture was heated to 80 ° C.
After stirring under reflux for 2 hours, the solution was added with ethyl lactate 2
0 g, pure water 0.9 g, and acetic acid 9 g.
Stirred at reflux for 2 hours.

After the metal alkoxide solution thus obtained was gradually cooled to room temperature, 0.5 ml of the solution was applied onto a surface of an aluminum nitride substrate rotating at a predetermined speed by a spin coater, and the solution was prepared. It was applied to the entire surface of the material.

After application of the solution, it was dried at 500 ° C. for 30 minutes to obtain a surface-treated layer.

The surface-treated layer containing calcium oxide shown in Table 1 was prepared by uniformly mixing tetraethoxysilane, aluminum isopropoxide and dimethoxycalcium in a composition shown in Table 1 in 100 g of ethyl lactate. After dissolution, the temperature was raised to 80 ° C. Next, acetylacetone was added thereto, and the mixture was stirred at 80 ° C. for 2 hours under reflux. Then, a mixture of 20 g of ethyl lactate, 0.9 g of pure water and 9 g of acetic acid was appropriately added to the solution and refluxed at 80 ° C. for 2 hours. With stirring.

After the metal alkoxide solution thus obtained was gradually cooled to room temperature, the solution was spin-coated.
The solution was applied to the entire surface of the aluminum nitride substrate by applying 0.5 ml onto the surface of the aluminum nitride substrate rotating at a predetermined speed.
After applying the solution, the solution was dried at 500 ° C. for 30 minutes to form a surface treatment layer.

A bonding force measurement test and a pattern accuracy test were performed on the surface-treated aluminum nitride base material obtained as described above.

The results are shown in Table 1.

Examples 15 to 24 Aluminum nitride substrates having the surface treatment layers shown in Table 2 were produced by the following methods.

First, a 1 inch square, 0.635 mm thick aluminum nitride substrate was ground to finish the shape to 1 inch square, 0.5 mm thick. The surface roughness of the aluminum nitride substrate was Ra 0.05 μm.

Next, this aluminum nitride base material was
Heating was carried out for a predetermined time in a batch-type electric furnace kept at 0 ° C. in the air atmosphere to obtain an oxidized layer having a thickness shown in Table 2.

Further, the metal alkoxide solutions respectively prepared in the same manner as in Examples 1 to 14 were applied to the entire surface of the oxidized layer by the same method.
It was dried for a minute to form a surface-treated layer.

The bonding strength measurement test and the pattern accuracy test were performed on the surface-treated aluminum nitride base material obtained as described above.

The results are shown in Table 2.

Comparative Examples 1 to 10 Metals prepared using the same aluminum nitride substrate as in Examples 1 to 14 so that the proportion of yttrium oxide or calcium oxide contained in the surface treatment layer is outside the range of the present invention. The alkoxide solution was applied on the aluminum nitride substrate surface in the same manner as in Examples 1 to 14, and dried to form a surface treatment layer.

Table 1 also shows the results of a bonding strength measurement test and a pattern accuracy test performed on the surface-treated aluminum nitride base material obtained as described above.

Comparative Examples 11 to 18 An aluminum nitride substrate having an oxidized layer formed so that the thickness of the layer was out of the range of the present invention was prepared, and a metal alkoxide solution was applied to the surface thereof. Coating and drying were performed in the same manner as described above to form a surface treatment layer.

A bonding strength measurement test and a pattern accuracy test were performed on the surface-treated aluminum nitride base material obtained as described above.

The results are shown in Table 2.

[0076]

[Table 1]

[0077]

[Table 2]

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Claims (2)

(57) [Claims] (1) silicon oxide or aluminum oxide in a proportion of not more than 80% by weight based on the total amount of silicon oxide and silicon oxide; A surface-treated aluminum nitride substrate comprising a layer of yttrium oxide and / or calcium oxide of 0.01 to 2% by weight based on silicon oxide or the total amount of silicon oxide and aluminum oxide. 2. A method comprising the steps of: (1) forming silicon oxide or silicon oxide on the surface of an aluminum nitride base material through an oxidation treatment layer having a thickness of 1 μm or less formed on a surface portion of the aluminum nitride base material; Aluminum oxide in a proportion of 80% by weight or less based on the total amount of silicon; and (2) oxidation of 0.01 to 2% by weight based on the total amount of the silicon oxide or silicon oxide and aluminum oxide. A surface-treated aluminum nitride substrate on which a layer made of yttrium and / or calcium oxide is formed.