JPH03228874A - Production of ceramic substrate - Google Patents

Abstract

PURPOSE:To improve the adhesion between AlN and an alumina-based oxide layer by heat treating an AlN sintered body under specified conditions to form an alumina-based oxide layer on the surface. CONSTITUTION:A mixture of AlN powder having <=1mum average grain diameter and Dy oxide powder having <=0.2mum average grain diameter is press formed at 0.2-2kg/cm<2> pressure for 1-20sec and then sintered at 1750-2000 deg.C in a gaseous N2 atmosphere to obtain an AlN sintered body consisting of 90.0-99.8wt.% of an AlN crystal grain phase having 2-10mum average grain diameter and a Dy oxide phase. The sintered body is heat treated at 1050-1150 deg.C for 0.1-5hr in the atmosphere in which the partial pressure of steam is controlled to <=1.0X10<->2atm to form an alumina based oxide layer having 0.05-1.0mum thickness on the surface of the sintered body.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a ceramic substrate using a sintered aluminum nitride body.

[Prior art and problems to be solved by the invention] Alumina substrates have been widely used as ceramic substrates for mounting electronic devices including semiconductor devices in electronic devices because they are chemically stable and highly reliable. It is used. However, in recent years, it has a significantly higher thermal conductivity than alumina,
Aluminum nitride, which has excellent heat dissipation properties, is attracting attention and being used as a substrate material for semiconductor components.

As such materials, the applicant has previously proposed PCT/JP
No. 87100607 (International Publication Number WO3810125
No. 9), an alumina-based oxide layer is formed on the surface of an aluminum nitride sintered body containing dysprosium (Dy) oxide, and Ti, Cr, M0. We have proposed a substrate material in which a plating layer made of Ni or Cu is formed via a metallized layer made of W or the like.

In this material, the alumina-based oxide layer is formed by heat-treating an aluminum nitride sintered body in the atmosphere. In that case, when the alumina-based oxide layer is made relatively thick, stress is applied to the interface due to the difference in thermal expansion between the sintered body base material and the alumina-based oxide formed on its surface, and the laminated layer including the metallized layer may peel off. Conversely, even when the alumina-based oxide layer is made as thin as 11 JfIl or less, the strength of the interface between the aluminum nitride sintered body and the alumina-based oxide layer, or the strength of the alumina-based oxide layer itself, cannot be said to be sufficient. . As a result, the laminated portion including the metallized layer may peel off, and it has been found that it is necessary to improve the alumina-based oxide layer in order to improve reliability.

On the other hand, Japanese Patent Publication No. 1-208375 discloses a method for manufacturing a semiconductor circuit board with increased thermal conductivity by directly bonding a metal mainly composed of copper to an aluminum nitride substrate,
In order to improve bonding properties, the water vapor partial pressure in the atmospheric gas during heat treatment is controlled to less than 3.5 x 110-2at for the purpose of forming an oxide film on the surface of aluminum nitride. A method is disclosed.

However, the oxidation treatment of aluminum nitride is actually 130
It was found that because the process was carried out at 0°C (Example 1, etc.), the rate of formation of the alumina-based oxide layer was fast, and as a result, there was a problem in that the formed oxide was not sufficiently dense. Furthermore, it has been found that if the temperature is 1300° C., the oxide layer becomes too thick, and the stress applied to the interface between aluminum nitride and the oxide layer becomes large, making it easy for the laminated portion to peel off.

Therefore, an object of the present invention, when manufacturing a ceramic substrate made of an aluminum nitride sintered body, is to provide a sufficiently dense layer on the surface of the sintered body so that a metallized layer of Ti, Mo, etc. will firmly adhere to the surface of the sintered body. It is an object of the present invention to provide a method for forming an oxide layer in which the strength of the interface between aluminum nitride and the oxide layer is increased.

[Means to solve the problem]

As a result of intensive research in view of the above-mentioned problems, the present inventors have previously applied a sintered body to the surface of a sintered body mainly made of aluminum nitride.
Thickness of 0.05 to 1.0 IJf is achieved by heat treatment within a specific temperature range in an atmosphere with extremely low water vapor partial pressure.
We discovered that a dense and strong oxide layer with a thickness of less than rl is formed at the interface between aluminum nitride and the oxide layer, improving reliability against peeling, including the metallized layer or glass layer above it. Completed the invention.

That is, in the method for manufacturing a semiconductor substrate made of an aluminum nitride sintered body of the present invention, the aluminum nitride sintered body is
Water vapor partial pressure is 1. By heat treating at 1050 to 1150°C for 0.1 to 5 hours in an atmosphere of OX 110-2at or less, the surface of the sintered body is coated with a thickness of 0.0
It is characterized by forming an alumina-based oxide layer of 5 to 1.0 JJfIl.

The present invention will be explained in detail below.

In the present invention, the highly thermally conductive aluminum nitride sintered body is prepared by mixing aluminum nitride powder with an average particle size of 1 mm or less and Dy oxide powder with an average particle size of 0.2 mm or less, and sintering it after forming. A
It is preferable to produce a composite powder in which Dy oxide powder is uniformly adhered to the surface of 4N particles, which is then molded and sintered. Therefore, the case in which the aluminum nitride obtained in this manner is subjected to oxidation treatment will be described in detail below.

First, the molding performed after mixing the raw material powders can be performed using a normal mold. Molding pressure is generally 0.2~2
kg/c+d, and the forming time is 1-20 seconds.

The obtained molded body may be subjected to isostatic pressing. By performing hydrostatic pressing, the sintered density and mechanical strength of the sintered body can be improved.

The molded body is sintered in an N2 gas atmosphere at a temperature of 1750 to 20
This can be carried out by pressureless sintering at a temperature of 00°C.

In addition, special sintering methods such as a pressure sintering method, a hot press method, a HIP method, etc. can be used.

The aluminum nitride sintered body thus obtained has an aluminum nitride crystal grain phase 9 with an average grain size of 2 to 10 μm.
0.0 to 99.8% by weight, and the remainder substantially consists of a dysprosium oxide phase. If the proportion of the aluminum nitride crystal grain phase is more than 99.8% by weight, that is, the proportion of the dysprosium oxide phase is less than 0.2% by weight, the sinterability will be poor; .0
If the proportion of the dysprosium oxide phase exceeds 10% by weight, the thermal conductivity may decrease. The preferred ratio of aluminum nitride crystal grain phase is 95.
It is 5 to 98.5% by weight. Furthermore, if the average particle size of the aluminum nitride crystal particles is less than 2 μm, the sintered density will not improve, while if it exceeds 10 μm, the mechanical strength of the sintered body will decrease. A desirable average particle size is 3 to 7 μm.

The dysprosium oxide phase generally contains A1 in addition to Dy, DyAj203 and/or hiA12 (IV!L
) It is a glass phase represented by the composition of 4. Dy in oxide phase
The proportion of AI is about 60 to 80% by weight, and the proportion of AI is 5 to 50%.
The percentage of 0 is about 10 to 40% by weight.

Most of this oxide phase consists of 3 atoms between aluminum nitride crystal grains.
It gathers at a focal point, and the rest is dispersed on the grain boundaries. Generally, the thermal conductivity of an aluminum nitride sintered body decreases due to the precipitation of an oxide phase at grain boundaries, so the thermal conductivity can be improved by concentrating the oxide phase at triple points. However, a certain amount of it also exists at grain boundaries, and it is necessary to increase mechanical strength (flexural strength, etc.).

An aluminum nitride sintered body having such a composition and structure has a density of 95% or more of the theoretical density. If the density is less than 95%, sufficient thermal conductivity cannot be obtained even if the above compositional and structural requirements are met, and mechanical strength is also poor. A more preferable density is 98% or more.

Next, an alumina-based oxide layer is formed on the surface of the aluminum nitride sintered body. For this purpose, the water vapor pressure must be 1.
In an atmosphere of Ox 110-2at or less, 1050-1
Heat treatment at 150° C. for 0.1 to 5 hours. As a result, an alumina-based oxide layer mainly composed of α-A1203, which is dense and has high interface strength with the aluminum nitride base material, can be obtained.

Under the above oxidation treatment conditions, the water vapor partial pressure was set to 1. OX1
If it is larger than 10@-2 at, the crystals of the oxide layer will have a coarse columnar shape and the density will be low, so the strength of the interface between the sintered body base material and the oxide layer and the strength of the oxide layer itself will be weakened.

Furthermore, since the surface becomes smooth, the adhesion area with the metallized layer formed on the oxide layer becomes smaller. Therefore, the metallized layer is less likely to peel off. Furthermore, the water vapor partial pressure is set to 1. OXXl0-
When it is larger than 2at, the layer thickness becomes too large, the stress at the interface between the sintered body base material and the oxide layer becomes excessive, and the reliability against peeling decreases. A more preferable range of water vapor partial pressure is 4. OX 10 3 atm or less. Optimal adhesion strength can be obtained within this range.

When the heat treatment temperature is lower than 1050℃, α-A12
An oxide layer mainly composed of 03 is not formed, or even if it is formed, the crystallization is insufficient, and the strength of the oxide layer itself or the interface strength between the sintered body base material and the oxide layer is insufficient. On the other hand, if the temperature is higher than 1150° C., the resulting oxide layer will not be sufficiently dense and will have small pores inside, and will have an excessive thickness when a practical heat treatment pattern is used.

A more preferable heat treatment temperature is 1075 to 1125°C.

If the treatment time is shorter than 0.1 hour, the oxide layer will still not have a sufficient thickness, making metallization difficult. On the other hand, if the time is longer than 5 hours, the oxide layer becomes too thick. The preferred treatment time is 0°5 to 2 hours.

The thickness of the oxide layer obtained under the above conditions is 0.05 to 1.
The surface has an uneven striped pattern.

The thickness of the oxide layer is 1. When it is larger than OIA, the interface strength between the oxide layer and the sintered body base material becomes weak. A more preferable thickness is 0.1 to 0.7 μs, and optimal adhesion strength can be obtained within this range.

In order to obtain a semiconductor substrate, after forming the first layer made of the alumina-based oxide, Ti and Cr are deposited thereon.

M0. One or two selected from the group consisting of W and Mn
A second layer consisting of at least one species, Ni, Cu, Au,
A third layer made of one or more selected from Pt and Ag is laminated.

The second layer is a bonding layer that improves the adhesion strength between the first layer and the third layer made of alumina-based oxide. This second layer can be formed by a physical vapor deposition method such as an ion blasting method or a sputtering method.

The third layer prevents corrosion of the aluminum nitride or the second layer by the solder or brazing material and ensures wettability of the solder or brazing material.

This third layer can be formed by a physical vapor deposition method such as an ion blasting method or a sputtering method, or a chemical plating method.

The top layer above the third layer is made of 1, Au, or 3 to improve wettability with solder or brazing material used to bond electronic devices including semiconductors onto ceramic substrates. Preferably, a layer is formed.

Furthermore, instead of forming a metallized layer as a second layer on the alumina-based oxide layer, an amorphous glass layer, a partially crystallized glass layer, or a crystallized inorganic glass layer may be formed. .

The ceramic substrate thus obtained has high adhesive strength in the laminated film, as well as high airtightness and smoothness, and is therefore preferable as a package or sealing substrate for semiconductor devices such as LSIs and VLSIs.

The method for manufacturing a ceramic substrate of the present invention has been described above using a Dy-containing aluminum nitride sintered body, but the present invention is not limited to this. It can also be applied to

〔Example〕

The present invention will be explained in further detail by the following examples.

Example 1 Commercially available aluminum nitride powder with an average particle size of 0.5 μm (
Oxygen content (2.1 wt%) 97 wt% and 3 wt% of Dy2O3 powder having an average particle size of 0.2 μm were blended and mixed for 24 hours using a plastic ball in a plastic ball mill container containing 500 cc of ethyl alcohol. After mixing, it is granulated and dried by spray drying method, and 1. It was molded under a pressure of Okg/c++f. Then, 1750-1900 in N2 gas at 1 atm.
After sintering for 1 hour at a temperature of °C, 10mm x 10++
+m x 2 +nm was processed to obtain an aluminum nitride sintered body.

This sintered body was held for 1 hour while changing the water vapor partial pressure of the atmosphere and the treatment temperature to form an alumina-based oxide film.

Next, Figure 1 (a) and (b) ((b) is n- of (a)
As shown in the cross section taken along the n-line (3-3), a second layer was formed on the 8 mm x 8 + nm portion of the surface of the sintered body 1 on which the alumina-based oxide layer 2 was formed by an ion-blating method. 50
Form a layer of 00 Ti and on top of that as a third layer 1
A N1 layer of 0000 A was formed. Furthermore, by electrolytic plating, a Ni layer of 2 layers as a fourth layer and a layer of Au of 0.3 layers as a fifth layer were formed thereon. By this, T
A sample 5 having a metallized layer 3 of i-N i-N 1-Au was obtained.

In order to evaluate the adhesion between this sintered body and the metallized layer, as shown in FIG.
The edge of the sample was pulled off in a direction perpendicular to the top surface of the sample as shown by the solid line. Thereby, the rate of peeling of the metallized layer 3 was measured.

The results are shown in FIG. In addition, each curve A in Fig. 3,
Water vapor partial pressure at the time of oxide film creation for B, C, D, and E,
Table 1 shows the dew points corresponding to each water vapor partial pressure. For the dew point, −14= is also added to each measurement point in FIG. Incidentally, all cases where peeling occurred were at the interface between aluminum nitride and alumina-based oxide.

From Table 1 and Figure 3, water vapor partial pressure is 1. OX 110-2at
It can be seen that it is preferable to set the treatment temperature to 1050°C to 1150°C. Further, it can be seen that the oxide film thickness is preferably 1.0 or less.

Next, in order to investigate the cause of the peeling, the cross sections of the sintered bodies of the samples X and Y in FIG. 3 before metallization, that is, after the oxide film was formed, were observed using a scanning electron microscope.

An electron micrograph of the crystal structure of sample X at that time is shown in FIG. 4, and that of sample Y is shown in FIG.

Comparing Figures 4 and 5, sample Y, in which peeling was more likely to occur, has coarse columnar crystals in the alumina-based oxide layer 2 formed on the aluminum nitride sintered body 1. This is thought to be the cause of the metallized layer peeling off from the interface between the aggregate and the alumina-based oxide layer.

Further, an alumina-based oxide is heated to a water vapor partial pressure of 3.2 x 110-3 at/cI+! at a temperature of 1100°C. So 0.
Similar peeling tests were conducted on samples formed by holding for 1 to 5 hours, but no peeling occurred except for 4% peeling after 0.1 hours. From this, it was found that a good alumina-based oxide film can be formed with a practical and relatively short heat treatment time.

Example 2 As in Example 1, 97 wt% of aluminum nitride powder and 3 wt% of DyzO3 powder were mixed, then molded and sintered.
Furthermore, it was processed to 10mm x 10mm x 2mm,
An aluminum nitride sintered body was obtained. For this sintered body,
As in Example 1, an oxide film was formed by changing the water vapor partial pressure of the atmosphere and the treatment temperature.

In order to evaluate the adhesion between the sintered body and the metallized layer in 1.
A Ti layer of 5,000 amps was formed as a second layer on the portion m by the ion blasting method, and a Ni layer of 10,000 amps was formed thereon as a third layer. Furthermore, a Ni layer of 2JJfrI as a fourth layer and an Au layer of 0.3AIIrI as a fifth layer were formed by electrolytic plating thereon to obtain a sample.

Two samples prepared under the same conditions were joined together by solder (60%Pb-40%Sn) at the metallized portions on their side surfaces, and a three-point bending test shown in FIG. 6 was conducted. Thereby, the ratio of the area broken at the interface between aluminum nitride and alumina-based oxide to the area joined by solder was determined, and this was determined as the ratio of the fractured area of the joint. The maximum load P is 5k.
g, the distance between the fulcrums was 8 mm. In the figure, 5 is a sample and 6 is a joint.

The results are shown in FIG. From Figure 7, the water vapor partial pressure is 4.
OX 110-3at or less, processing temperature 1050℃
It can be seen that it is particularly preferable to set the temperature to 1150°C and the oxide film thickness to 0.7a++ or less.

〔Effect of the invention〕

As explained above, according to the manufacturing method of the present invention, a thin oxide layer having a dense structure can be formed on the aluminum nitride sintered body. Therefore, the thermal conductivity is high,
A ceramic substrate in which aluminum nitride and an alumina-based oxide layer are firmly bonded can be obtained.

[Brief explanation of drawings]

Figure 1 schematically shows the sample used in the peel test, (a)
Figure 2 is a front view showing the peel test method, Figure 3 is a diagram (graph) showing the results of the peel test, Figure 4 is a scanning electron micrograph showing the crystal structure of an aluminum nitride sintered body with an oxide layer formed by the method of the present invention. Figure 5 is a scanning electron micrograph showing the crystal structure of an aluminum nitride sintered body with an oxide layer formed by increasing the partial pressure of water vapor. A scanning electron micrograph showing the crystal structure of the sintered body, 8 Figure 6 is a front view showing the method of the bending test, and Figure 7 is a diagram (graph) showing the results of the bending test. 1... Aluminum nitride sintered body 2... Alumina-based oxide layer 3... Metallized layer 5... Sample 6... Joint portion 40... With mending tape

Claims (6)

[Claims] (1) In a method for manufacturing a ceramic substrate made of an aluminum nitride sintered body, the aluminum nitride sintered body is
By heat treating at 1050 to 1150°C for 0.1 to 5 hours in an atmosphere with a water vapor partial pressure of 1.0 x 10^-^2 atm or less, the surface of the sintered body is coated with a thickness of 0.0
A method characterized by forming an alumina-based oxide layer with a thickness of 5 to 1.0 μm. (2) In the method according to claim 1, the water vapor partial pressure is set to 4.0 x 10^-^3 atm or less, and the thickness of the alumina-based oxide layer is set to 0.1 to 0.7 μm. How to characterize it. (3) The method according to claim 1 or 2, further comprising a second layer of Ti, C, on the alumina-based oxide layer.
A method for manufacturing a ceramic substrate, comprising forming a metallized layer made of one or more selected from the group consisting of r, Mo, W, and Mn. (4) In the method for manufacturing a ceramic substrate according to claim 3, a metallized layer made of one or more selected from the group consisting of Ni, Cu, Au, Pt, and Ag is further formed as the third layer. A method for manufacturing a ceramic substrate, characterized in that: (5) In the method according to claim 4, Ti is formed as the second layer by a physical vapor deposition method, and the third layer is a Ni layer formed by a physical vapor deposition method, a Ni layer formed by a chemical plating method, and a Ni layer formed by a chemical plating method. A method for manufacturing a ceramic substrate, characterized in that the ceramic substrate is formed by sequentially laminating Au layers using a target plating method. (6) The method of manufacturing a ceramic substrate according to claim 1 or 2, further comprising forming a glass layer on the alumina-based oxide layer.