JPH0143706B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a glass-ceramic substrate using magnesia as a ceramic powder.

BACKGROUND OF THE INVENTION Electronic devices, especially electronic computers, have made remarkable progress in order to achieve higher speed and larger capacity information processing, and the electronic circuits used in these devices are becoming smaller and more dense.

This particularly applies to semiconductor devices such as ICs and LSIs; conventionally, each chip was bonded to a wiring board made of alumina ceramic using adhesive or eutectic bonding, and the chips were bonded using methods such as wire bonding. A semiconductor device is constructed by making a circuit connection between the terminals of the semiconductor device and the wiring on the ceramic substrate, and then applying a resin sheath or a hermetic seal sheath, and a mounting method has been used in which the semiconductor device is mounted on a printed wiring board.

However, in order to achieve further miniaturization and higher density, it is possible to bond multiple chips to a ceramic multilayer wiring board and connect the circuits, and then apply a hermetic or other sheathing to the chips, or to take advantage of advances in moisture-resistant treatment technology. Therefore, a mounting system is being put into practical use in which a plurality of chips are attached to a ceramic multilayer wiring board by face-down bonding and used as a replacement unit.

Since the number of terminals of the chip mounted on the ceramic wiring board used for such applications is enormous, it is necessary to increase the number of constituent layers of the multilayer wiring board and to miniaturize the wiring pattern.

Further, when a chip is mounted by face-down bonding, it is necessary to match the expansion coefficients of the substrate and the chip in order to maintain the reliability of the chip.

The present invention relates to a method for manufacturing a glass ceramic substrate developed for this purpose.

[Conventional technology]

Conventional ceramic multilayer substrates are made of alumina (α-
A green sheet is formed using Al ₂ O ₃ ) as the main constituent, and molybdenum/manganese (Mo/Mn),
It is made by screen printing a conductive paste such as tungsten/manganese (W/Mn) to create a conductive pattern, stacking these, and then firing them at a high temperature of over 1,000 degrees Celsius.

Ceramic substrates become thinner as they become more multi-layered, and pattern widths need to be reduced as circuits become more complex, but alumina porcelain substrates have a relatively high dielectric constant of 9 to 10. As a result, crosstalk and conductor resistance due to capacitance between multilayer interconnects increase, and these effects cannot be ignored.

Therefore, borosilicate glass, which has a low dielectric constant of 4 to 5 and can be fired at about 900°C, has come to be used as a substrate.

A feature of this substrate is that the firing temperature is low, so it is possible to form fine conductor patterns using low-resistance metals such as gold (Au) and copper (Cu).

However, glass substrates have problems in terms of mechanical strength.

Therefore, glass-ceramic substrates with improved mechanical strength by adding ceramic powder have been put into practical use.

Alumina is selected as a component of ceramic powder because of its low coefficient of expansion and high hardness, and is generally used as a substrate for mounting silicon semiconductor chips.

However, some semiconductor materials have large coefficients of thermal expansion and are unsuitable for use with conventional alumina substrates or glass ceramic substrates.

For example, gallium arsenide (GaAs) according to the present invention falls under this category, and when a chip formed using a GaAs substrate is bonded to a conventional ceramic substrate or glass ceramic substrate, the difference in coefficient of thermal expansion is too large, so that it is difficult to cope with temperature fluctuations. This creates mechanical stress and reduces reliability.

For this purpose, it is necessary to use a glass-ceramic substrate with an expansion coefficient compatible with GaAs, and magnesia (MgO) is suitable as a ceramic component.

Figure 1 is an explanatory diagram of this relationship, with absolute temperature plotted on the horizontal axis and thermal expansion coefficient plotted on the vertical axis, with 293 degrees being the reference point for comparison.

As is clear from the figure, the thermal expansion coefficient of alumina 2 is much smaller than that of GaAs 1.
Also, Magnesia 3 is slightly larger.

The present invention uses magnesia as a ceramic component of glass-ceramic, and FIG. 2 shows the change in thermal expansion coefficient with respect to MgO content in a system consisting of borosilicate glass and MgO.

From the figure, it can be seen that in order to match the thermal expansion coefficient of GaAs, which is 10.7×10 ^-4 , the MgO content should be set to 40% from characteristic curve 4.

Based on the above, it should be easy to create a glass-ceramic substrate suitable for GaAs, but MgO has extremely poor wettability with glass, is not uniformly dispersed, and has problems such as creating gaps at the interface with the glass after firing. There was a problem that a glass-ceramic substrate could not be produced.

[Problem that the invention seeks to solve]

As explained above, a glass ceramic containing MgO as a ceramic component is suitable as a substrate to which a GaAs chip is bonded, but the problem is that the wettability of both is poor.

[Means to solve the problem]

The above problem can be solved by adding a binder and a solvent to glass powder to which ceramic powder has been added, kneading this to make a green sheet, printing a wiring pattern on the green sheet, and firing it. This problem can be solved by a method of manufacturing a glass ceramic substrate using magnesia powder coated with an alumina film produced by thermally decomposing aluminum nitrate.

[Effect]

The present invention utilizes the very good wettability of alumina (α-Al ₂ O ₃ ) and borosilicate glass to improve the wettability by coating magnesia (MgO) powder with an alumina film. It is something to do.

That is, by repeatedly immersing MgO powder in an aluminum nitrate aqueous solution, drying it, and thermally decomposing it, an alumina film is formed on the surface.

〔Example〕

MgO powder with a particle size of about 1 μm is immersed in an aqueous aluminum nitrate solution with a concentration of about 30%, thoroughly stirred, filtered, and dried.

This is carried out in air at a temperature above the pyrolysis temperature, e.g.
When heated at 300 degrees, Al 2 O ₃ can be precipitated on the surface of MgO grains by the reaction of 2Al(NO ₃ ) ₃ → Al ₂ O ₃ + 6NO ₂ + 3/2O ₂ , and by repeating this, _{Al 2} Can be coated with O ₃ membrane.

This powder is mixed with borosilicate glass (e.g. Corning Co., Ltd.).
No. 7052) powder, using polyvinyl butyral as a binder and methyl cellosolve as a solvent, kneaded in a ball mill for 48 hours, used this to make a green sheet, and calcined at about 600 degrees. Thereafter, the substrate was baked at 900 degrees for 1 hour.

The density of the glass-ceramic substrate made in this way and the substrate made by adding an equal amount of untreated MgO was measured by a water absorption test.
While the untreated substrate shows a high water absorption rate of 9%, the substrate applied with the present invention has a low water absorption rate of 0.1%, which means that the substrate is dense and has a low wettability between MgO and borosilicate glass. I was able to prove that it was good.

〔Effect of the invention〕

As described above, by carrying out the present invention, it becomes possible to manufacture a glass ceramic substrate suitable for mounting a GaAs chip, and it becomes possible to improve the reliability of a GaAs semiconductor device.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the temperature dependence of the coefficient of thermal expansion, and FIG. 2 is an explanatory diagram showing the change in the coefficient of thermal expansion of borosilicate glass to which magnesia is added. In the figure, 4 is a thermal expansion characteristic curve.

Claims (1)

[Claims] 1. A glass-ceramic substrate made by adding a binder and a solvent to glass powder added with ceramic powder, kneading this to make a green sheet, printing a wiring pattern on the green sheet, and firing it,
A method for manufacturing a glass-ceramic substrate, characterized in that magnesia powder coated with an alumina film produced by thermally decomposing aluminum nitrate is used as ceramic powder.