JPH075402B2 - Aluminum nitride sintered body and surface treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to α-Al ₂ O ₃ and dysprosium (Dy) on the outer peripheral surface of an aluminum nitride sintered body used for semiconductor substrates, IC substrates, etc. Also, the present invention relates to an aluminum nitride sintered body having a water resistance while forming an oxide layer composed of two phases of aluminum and a solid solution oxide of aluminum to facilitate metallization.

[Prior Art] Aluminum nitride has come to be used as an insulating substrate material because of its high thermal conductivity, low thermal expansion coefficient, and high mechanical strength.

When using a substrate material made of aluminum nitride as a package for semiconductors, etc., place the Si chip on the aluminum nitride substrate, cover the top surface with ceramic such as aluminum nitride hermetically, The aluminum substrate and the ceramic covering it were joined together and projected outside. The bonding surface between the aluminum nitride substrate and the ceramic covering it is metallized for close contact, and the lead frame portion is further soldered.

However, it is difficult to metallize aluminum nitride because it is chemically stable. Therefore, a method of metallizing while oxidizing the surface of the aluminum nitride sintered body is disclosed in JP-A-
It is disclosed in Japanese Patent No. 75208.

Further, Japanese Patent Application Laid-Open No. 61-84037 discloses a method of forming an alumina layer on the surface of an aluminum nitride ceramic substrate.

[Problems to be Solved by the Invention] When an aluminum nitride sintered body is used as a package for a semiconductor or the like, there is a problem that the aluminum nitride sintered body has poor water resistance and easily reacts with water to generate ammonia.

Further, since the aluminum nitride sintered body is difficult to metallize, a complicated means of metallizing while oxidizing the surface of the aluminum nitride sintered body had to be taken for the metallization.

Therefore, the present invention is a layer consisting of two phases of α-Al ₂ O ₃ and a solid solution oxide of dysprosium and aluminum in advance on the surface of the aluminum nitride sintered body by performing various heat treatment tests on the aluminum nitride sintered body. The present invention provides an aluminum nitride sinter that is formed to have water resistance and can be easily metallized, and a surface treatment method thereof.

[Means for Solving the Problems] The present invention provides α-Al ₂ O ₃ and a solid solution oxide of dysprosium and aluminum on the outer surface of an aluminum nitride sintered body using dysprosium as a sintering aid. The aluminum nitride sintered body is characterized in that an oxide layer consisting of two phases is formed.

Another invention is to heat the aluminum nitride sintered body using dysprosium as a sintering aid at 950 to 1200 ° C. for 30 minutes or less in an atmosphere containing oxygen to form α- on the outer surface of the aluminum nitride sintered body. A surface treatment method for an aluminum nitride sintered body, which comprises forming an oxide layer having two phases of Al ₂ O ₃ and a solid solution oxide of dysprosium and aluminum.

The outer surface layer is formed by performing a heat treatment at 950 to 1200 ° C. for 30 minutes or less in an oxidizing atmosphere in which oxygen is 21% or less.

This layer is preferably made of α-Al ₂ O ₃ and a solid solution oxide of dysprosium and aluminum obtained by adding dysprosium as a sintering aid for aluminum nitride. Water resistance is not always sufficient with the α-Al ₂ O ₃ layer alone, and the presence of solid solution oxides serves as a binder between α-Al ₂ O ₃ particles so that it has sufficient water resistance. Can be done.

The oxidizing atmosphere containing 21% or less of oxygen is used because it is difficult to form a water-resistant and dense layer if the oxygen content is more than 21%.

The heat treatment temperature is set to 950 to 1200 ° C. because if it is lower than 950 ° C., the α-Al ₂ O ₃ layer is not formed, and if it is higher than 1200 ° C., many small holes are formed in the outer surface layer, and the binder becomes a binder. This is because it is difficult to form a solid solution oxide of prosium and aluminum. The treatment time of 30 minutes or less means that if it is longer than that, a large number of small holes are generated in the outer surface layer and the layer becomes 5 μm or more, which makes it difficult to sufficiently utilize the high thermal conductivity inherent to aluminum nitride. This is because.

The thickness of the α-Al ₂ O ₃ layer is 0.5 to 3 μm because it is 0.5 μm.
This is because if it is smaller than this, metallization becomes difficult, and if it is larger than 3 μm, the thermal conductivity deteriorates and it becomes difficult to radiate heat from the semiconductor element.

The surface roughness of the Al ₂ O ₃ layer is preferably 6.3 μm or less in order to improve the metallization.

[Example] An aluminum nitride sintered body sintered by using dysprosium as a sintering aid was exposed to air at six temperatures of 900, 950, and 1000.
Each was heated at 1100, 1200, and 1300 ° C. for 30 minutes to form a two-phase layer of α-Al ₂ O ₃ and solid solution oxides of dysprosium and aluminum on the surface of the sintered body.

Each of the above heat treatments was taken by taking an electron microscopic structure photograph of the surface and the fracture surface of the aluminum nitride sintered body, and FIG.
It is shown in (f). In the figure, the upper side is the surface and the lower side is the fracture surface. For comparison, an electron micrograph of the surface and fracture surface of the aluminum nitride sintered body of the present invention which is not heat-treated is also shown in FIG. 1 (g). As can be seen from FIGS. 1 (a) to 1 (g), when the heating temperature is 950 to 1300 ° C.
It can be seen that a layer composed of two layers of -Al ₂ O ₃ and solid solution oxides of dysprosium and aluminum is formed in a thickness of 0.3 to 3 µm. However, if the heating temperature is 1200 ° C or higher,
Since a large number of small holes are formed in the aluminum nitride sintered particles and there is no water resistance, it is not desirable to use it in a semiconductor device package. Further, it can be seen that a layer having a heating temperature of 900 ° C. does not form a layer consisting of α-Al ₂ O ₃ and a solid solution oxide.

Next, the heating temperature is 900, 1000, 1100, 120 by X-ray analysis method.
The composition of the surface of the aluminum nitride sintered body at 0, 1300 ° C was identified,
The measurement results are shown in FIG.

From Fig. 2, it is found that α-Al ₂ O _{3 in} the sample whose sintering temperature is 950-1300 ℃
And solid solution oxides of dysprosium and aluminum [DyAl
O ₃ and DyAl ₂ (AlO ₄ ) ₃ ] are generated, and a comparative example (g)
You can see that it has not occurred. At 950 ° C., other similar surface layers are formed in the photograph of FIG. 1 (b), so α-Al ₂ O ₃ and solid solution oxides of dysprosium and aluminum are formed. I presume.

Next, in order to test the water resistance (pressure cooker test) of the aluminum nitride sintered bodies with heating temperatures of 1000, 1100, 1200, and 1300 ° C, place each under 121 ° C, 2 atm, and 100% temperature conditions, and weigh the weight due to corrosion. The increase is shown in Figure 3 over time. In FIG. 3, untreated ones are also measured and shown for comparison.

The sample at the heat treatment temperature of 950 to 1200 ° C. has a weight gain (g / m ² ) of about 0.7 g / m ² and has water resistance. Heat treatment temperature 1300 ℃
The sample of 1 has a large weight increase and does not have water resistance, but this is because even if a layer of α-Al ₂ O ₃ and another solid solution oxide is generated,
It is considered that this is because it is porous as shown in FIG. 1 (f).
This is also because the untreated sample has aluminum nitride exposed on the surface.

Next, each sample corresponding to FIGS. 1A to 1G was metallized, a Kovar jig was soldered, and a tensile load was applied to the Kovar jig to measure the adhesive strength.

As a result, in each of the samples (b) to (f) corresponding to this example, it was about 7 kg / cm ² , and 3 kg / cm ^{2 in} the case of the comparative example (g).
Turns out to be much stronger.

Further, as a result of measuring the surface roughness of the samples corresponding to FIGS. 1 (a) to (g), the results of Examples (b) to (f) are slightly rougher than those of Comparative Example (g), but still 5.4 μm or less. In terms of heat conduction, it is much smaller than the standard value of 0.8 μm and there is no problem.

[Effect of the Invention] In the present invention, α-Al ₂ O ₃ of the surface of the aluminum nitride sintered body,
An oxide layer consisting of two phases of dysprosium and a solid solution oxide of aluminum is formed. Therefore, when it is used as an insulating substrate for a semiconductor package or the like, the thermal conductivity is high, and the Al ₂ O ₃ layer on the surface facilitates metallization and has sufficient water resistance. Further, according to the method of the present invention, it is possible to reliably produce an aluminum nitride sintered body having the above effects.

[Brief description of drawings]

1 (a) to 1 (g) are electron micrographs (2000 times) of the surface (upper side in the figure) and the fracture surface (lower side in the figure) of the aluminum nitride sintered bodies of the samples of the present invention and the comparative example. , Second
Similarly, FIG. 3 is a graph showing the results of the component test of the sample of the present invention and the comparative example by the X-ray diffraction method, and FIG. 3 is a graph showing the water resistance of the sample of the present invention and the comparative example.

Claims (4)

[Claims] 1. An oxide layer comprising two phases of α-Al ₂ O ₃ and a solid solution oxide of dysprosium and aluminum on the outer surface of an aluminum nitride sintered body using dysprosium as a sintering aid. An aluminum nitride sintered body characterized by being formed. 2. An aluminum nitride sintered body using dysprosium as a sintering aid in an atmosphere containing oxygen in a range of 950 to 120.
Aluminum nitride that forms an oxide layer consisting of two phases of α-Al ₂ O ₃ and solid solution oxides of dysprosium and aluminum on the outer surface of the aluminum nitride sintered body by heating at 0 ° C for 30 minutes or less Surface treatment method of sintered body. 3. The surface treatment method for an aluminum nitride sintered body according to claim 2, wherein the oxide layer on the outer surface has a thickness of 0.5 to 3 μm. 4. The surface treatment method for an aluminum nitride sintered body according to claim 2, wherein the surface roughness of the outer surface is 6.3 μm or less.