JP2661259B2 - Manufacturing method of aluminum nitride substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method for producing an aluminum nitride substrate, which aims to provide a method for producing a substrate having excellent thermal conductivity and good adhesion to a metal. After laminating a plurality of green sheets, a green sheet mainly composed of aluminum nitride and a metallization aid comprising a single metal of tungsten or molybdenum or a carbide or oxide of the metal is added. After being placed, pressurized and integrated, it is fired in a non-oxidizing atmosphere to constitute a method for manufacturing an aluminum nitride substrate.

[Industrial applications]

The present invention relates to a method for manufacturing an aluminum nitride (hereinafter abbreviated as AlN) substrate having high thermal conductivity.

Due to the necessity of processing a large amount of information at high speed, information processing apparatuses have been reduced in size and capacity, and LSIs and VLSIs with improved integration have been put to practical use in semiconductor integrated circuits, which are the main components of the information processing apparatuses.

These integrated circuits are mounted in a chip form on a chip mounting substrate (interposer) made of ceramic.
There is a mounting type in which an LSI module is mounted on a printed circuit board and mounted on a printed wiring board or the like as a replacement unit.

As described above, the degree of integration of a semiconductor integrated circuit increases, and the amount of heat generated by the device increases at an accelerated pace as high-density mounting is performed.

In other words, the calorific value per IC was small at about 3.5 W at the beginning, but the calorific value per LSI has now increased to about 10 W, and when a large number of ICs are mounted in a matrix, Are enormous and tend to increase.

Conventionally, as a substrate on which an LSI chip or the like is mounted, an alumina (Al ₂ O ₃ ) substrate having high thermal conductivity and excellent heat resistance has been used.

However, the thermal conductivity of alumina is excellent.
It is about 20 W / mK, which is insufficient as a material for the substrate for mounting a chip.

Therefore, attention has been paid to AlN having a thermal conductivity as large as 320 W / mK (theoretical value), and the practical use of this substrate has been promoted.

Table 1 compares the properties of AlN and Al ₂ O ₃ .

In other words, AlN has a small coefficient of thermal expansion in addition to its excellent thermal conductivity, and the coefficient of thermal expansion of Si constituting the LSI (3.6 × 10
⁻⁶ / ° C.) and a low dielectric constant are also advantageous in that cross-talk can be reduced when forming a multilayer substrate. However, AlN does not fit well with metal, so a thick film paste such as tungsten (W) or molybdenum (Mo) is screen-printed on an AlN substrate and fired to form patterns for conductor lines and heat sinks as in the past. Even so, there is a problem that it is easily peeled off, and this solution has been required.

[Conventional technology]

In order to use AlN as a heat sink material for a semiconductor laser or as a substrate for high-density mounting, it is premised that adhesion to a conductor pattern formed on the AlN substrate is excellent.

Therefore, conventionally, oxides such as yttrium oxide (Y ₂ O ₃ ) and lanthanum oxide (La ₂ O ₃ ) which easily react with AlN are replaced with W or Mo.
When mixed in conductor paste and fired at high temperature
AlN is oxidized to Al ₂ O _3, and is reacted with manganese (Mn) or titanium (Ti) powder contained in the paste to form a reaction layer such as a spinel structure.
It has been proposed that a conductive layer be formed. (JP 50
-75208) Also, after forming a low melting point oxide such as SiO ₂ -Al ₂ O ₃ on the AlN substrate, it is heated to about 1800 ° C. in an oxygen-containing atmosphere to oxidize AlN, Has a thickness of 1 to 10
There has been proposed a method of forming a μm-thick SiO ₂ —Al ₂ O ₃ layer to improve the adhesion to a conductive pattern formed thereon. When forming an AlN substrate, 0.1 to 10 parts by weight of a metal powder or a carbide powder such as titanium (Ti), vanadin (V), and chrome (Cr) is added to the raw material powder. And baking to form an AlN substrate having excellent adhesion to metal. (Japanese Patent Application Laid-Open No. 61-281074,
[Problems to be Solved by the Invention] However, the AlN substrate formed by such a method has excellent adhesiveness to the conductor pattern. However, the thermal conductivity decreases and the number of steps increases. Therefore, there is a problem that the cost increases.

Therefore, it is an object to form an AlN substrate that does not lower the thermal conductivity and has excellent adhesion to metal.

[Means for solving the problem]

The above problem is that after laminating a plurality of green sheets containing AlN as a main component, a metallization aid consisting of a single metal of W or MO or a carbide or oxide of this metal is added to AlN. AlN which is placed on a green sheet mainly composed of a material, pressed and integrated, and then fired in a non-oxidizing atmosphere
The problem can be solved by adopting a method of manufacturing a substrate.

[Action]

The present invention relates to a method of manufacturing an AlN substrate by adding W
Alternatively, the AlN substrate obtained by adding a metal powder of Mo or a metallization aid consisting of such a carbide or oxide to form a green sheet, and then firing it, has excellent adhesion to the metal. From this known fact, as shown in FIG.
A green sheet 1 in which a metallization aid is added to N is placed on a conventional green sheet 2 mainly composed of AlN, and a structure is formed by pressing and integrating the green sheet.

In this way, the green sheet to which the metallization aid has been added has a thickness of about 250 μm, while the thickness of the substrate is as thick as about 2 mm. An AlN substrate with excellent adhesion can be produced.

As for the amount of the metallization aid added to the AlN powder, as a result of an experiment, when added in an amount of 10 parts by weight or more in terms of a metal element, sinterability deteriorates and the lower layer is easily peeled off.

〔Example〕

Example 1: (W Example of Use) yttrium oxide as a sintering aid (Y ₂ O ₃₎ 7 wt%
100 parts by weight of the added AlN powder, 1 to 5 parts by weight of a W powder having an average particle diameter of 0.8 μm as a metallization aid, 10 parts by weight of PVB (polyvinyl butyral) as a binder, and DBP (dibutyl phthalate) as a plasticizer Was kneaded with a ball mill for 36 hours, and a green sheet for a surface layer having a thickness of 250 μm was prepared by a doctor blade method.

Further, an AlN green sheet having a thickness of 250 μm was prepared in the same manner using a material having the above composition except for the metallization aid.

Then, a green sheet for a surface layer containing a metallization aid is placed on the AlN green sheet 14 layer, and after being integrated by pressing at a pressure of 50 MPa, at 1900 ° C. for 6 hours in a N ₂ gas stream. Firing was performed to form an AlN substrate having a thickness of 3 mm.

For such a substrate, the thermal conductivity was measured by using a disk cut into a diameter of 10 mm, spraying carbon, and using a laser flash method.

Next, to measure the adhesion strength to metal, a commercially available copper (Cu) paste was applied to the surface of the AlN substrate to a thickness of 30 μm in an area of 2 mm square and baked at 800 ° C. in an N ₂ atmosphere. A tensile wire was soldered and pulled in the vertical direction at a speed of 0.5 mm / sec. The value at which the joint peeled from the substrate was defined as the peel (Peel) strength.

Table 1 shows the results when the content of W as a metallizing aid was changed.
The thermal conductivity and peel strength of the AlN substrate are shown.

Note that, for comparison, the thermal conductivity of the substrate obtained by forming all the layers in the lower stage with a green sheet for the surface layer and firing them was also recorded.

As described above, as the W content increases, the peel strength increases, while the thermal conductivity decreases. However, even when 5% by weight is added, the value shows 151 W / mk.

Example 2: (Use example of WC) An AlN substrate was prepared in exactly the same manner as in Example 1 except that WC (tungsten carbide) was used as a metallization aid, and the thermal conductivity and peel strength were measured.

 Table 2 shows the results.

Thus, an AlN substrate using WC as a metallizing agent is as excellent as a substrate using W.

Example 3: (Mo use example) An AlN substrate was prepared in exactly the same manner as in Example 1 except that the metallization aid was changed to Mo, and the thermal conductivity and the peel strength were measured.

 Table 3 shows the results.

Example 4 except that (W ₂ N Using example) a metal aid was changed to W ₂ N (tungsten nitride) made a AlN substrate in the same manner as in Example 1, the peel strength was measured and the thermal conductivity .

 Table 4 shows the results.

Example 5: except for changing the (MoO example of using the ₂₎ metallizing aid MoO ₂ (molybdenum oxide) made a AlN substrate in the same manner as in Example 1, the peel strength was measured and the thermal conductivity.

Table 5 shows the results. The peel strength is high and the thermal conductivity is excellent.

In the above embodiment, Y ₂ O ₃ was used as a sintering aid. In the following embodiment, calcium oxide (CaO) was used as a sintering aid at 2% by weight, and similar characteristics were obtained. Is shown.

Example 6: (use of W, sintering aid CaO, 2%) An AlN substrate was prepared in exactly the same manner as in Example 1 except that CaO was used as a sintering aid, and the thermal conductivity and peel strength were measured. did.

 Table 6 shows the results.

Example 7: (Using WC, sintering aid is CaO, 2%) An AlN substrate was prepared in the same manner as in Example 1 except that CaO was used as a sintering aid and WC was used as a metallization aid. The thermal conductivity and peel strength were measured.

 Table 7 shows the results.

[Effects of the Invention] As described above, according to the present invention, it is possible to directly form a conductor pattern without performing a surface treatment on an AlN substrate, and since a high thermal conductivity of about 200 W / mk is maintained. It can be used not only as an integrated circuit substrate but also as a heat sink.

[Brief description of the drawings]

 FIG. 1 is a sectional view of an AlN substrate according to the present invention. In the figure, 1 is a green sheet obtained by adding a metallization aid to AlN, and 2 is a conventional green sheet.

Claims (2)

(57) [Claims] 1. After laminating a plurality of green sheets mainly composed of aluminum nitride, a green sheet mainly composed of aluminum nitride to which a metallization aid is added is placed and integrated by pressing. And baking in a non-oxidizing atmosphere. 2. A method for manufacturing an aluminum nitride substrate according to claim 1, wherein said metallization aid comprises a single metal of tungsten or molybdenum, or one of carbides and oxides of said metal. .