JP3078415B2 - Aluminum nitride wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device such as a multilayer substrate or a semiconductor package, such as a semiconductor package, using a high thermal conductivity aluminum nitride sintered body as an insulator. The present invention relates to an aluminum wiring board.

[0002]

2. Description of the Related Art Conventionally, a ceramic insulator for a ceramic substrate on which a semiconductor element is mounted or a ceramic substrate for multilayer wiring is made of a material having high electrical insulation such as alumina ceramic, but is formed inside or on the surface thereof. With the increasing integration of wiring layers and the semiconductor elements mounted on them, it has become a major issue how to efficiently dissipate the heat generated from them, but conventional alumina ceramics have a low thermal conductivity. It was very low, about 20 W / m · k, and could not meet these requirements.
In addition, in a multilayer wiring board and a substrate for mounting a semiconductor element, the frequency of an electric signal transmitted in a wiring layer tends to increase with the demand for an increase in the amount of information and a higher processing speed.

[0003] Recently, a sintered body of aluminum nitride, which is a kind of non-oxidizing ceramics, has high electrical insulation,
In addition, since it has high thermal conductivity of 100 W / m · k or more, development of a substrate using an aluminum nitride sintered body as an insulator instead of conventional alumina ceramics is being advanced.

[0004] Usually, aluminum nitride sintered bodies are prepared by adding an element belonging to Group 3a of the periodic table or a second element of the periodic table to the aluminum nitride powder.
A sintering aid consisting of an oxide or nitride of a group a element is added, and the resultant is molded to form a sintering aid in a non-oxidizing atmosphere such as nitrogen.
It is obtained by firing at a temperature of 00 to 2000 ° C. According to this method, a sintered body having a crystal particle diameter of 1 to 20 μm is obtained.

[0005]

The present inventors have been studying the application of aluminum nitride sintered bodies to multilayer wiring boards and semiconductor element mounting boards used in the high-frequency range. It has been found that the dielectric loss tangent of the composite shows a high value at a specific frequency, which causes a problem that the signal transmitted through the wiring layer is attenuated.

[0006]

Means for Solving the Problems The present inventors have conducted research on the above-mentioned behavior, and as a result, the dielectric loss tangent of the sintered body fluctuates depending on the frequency of a signal transmitted to the wiring layer, and the specific frequency range is changed. It was found that the dielectric tangent had a maximum value and that the frequency at which the dielectric tangent exhibited a maximum value varied depending on the crystal grain size of the aluminum nitride sintered body. Therefore, by selecting the crystal grain size of the sintered body constituting the substrate according to the frequency of the electric signal to be used so as to satisfy a specific condition, the dielectric constant is always low regardless of the frequency of the transmitted electric signal. The present inventors have found that a substrate that can maintain a tangent can be provided, and have reached the present invention.

That is, according to the aluminum nitride wiring substrate of the present invention, the average crystal grain size of the aluminum nitride crystal is 0.1 mm.
An aluminum nitride wiring substrate, wherein a wiring layer is formed inside or on a surface of an insulator made of an aluminum nitride sintered body of 5 to 40 μm, and a frequency of an electric signal transmitted to the wiring layer is 100 MHz or more, When the average crystal grain size of the aluminum nitride sintered body is d (mm) and the frequency of an electric signal transmitted to the wiring layer is f (Hz),
The product of the d and the f is 3000 or less, or 3000
By setting it to 0 or more, the dielectric loss tangent of the aluminum nitride-based sintered body is made 0.01 or less.

[0008]

According to the present invention, the average crystal grain size of the aluminum nitride sintered body forming the insulator of the substrate is determined with respect to the frequency f (Hz) of the electric signal transmitted to the wiring layer formed on the wiring substrate. d (m) is d × f value of 3000 or less, or 30
By selecting the frequency of the electric signal and the sintered body constituting the substrate so as to satisfy the relationship of not less than 000, the value can always be controlled to a low value of 0.01 or less. As a result, a signal transmitted due to an increase in the dielectric loss tangent is not attenuated, and a stable state can always be maintained.
Long-term reliability as a wiring board can be provided.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The aluminum nitride sintered body used in the present invention can be manufactured by a known method. That is, 0.01 to 20% by weight of an aluminum nitride powder having an average particle diameter of 0.3 to 2.5 μm and a sintering aid composed of an oxide, nitride or the like of an element of Group 3a or Group 2a of the periodic table. %, And after molding by a known method, 1600
It can be obtained by firing in a non-oxidizing atmosphere such as nitrogen at ２０００2000 ° C. Note that the crystal grain size in the sintered body tends to increase as the grain size of the aluminum nitride raw material powder increases, and the size tends to increase as the firing time increases. By adjusting the firing temperature, the firing time, and the like, the temperature can be appropriately controlled.

In order to form a wiring layer on the surface of such a sintered body, for example, a conductor paste containing a metal such as copper can be applied to the surface of the sintered body and fired at 700 to 900 ° C. However, in such a case, in order to increase the adhesion between the conductor layer and the sintered body, the surface of the sintered body is oxidized to interpose an Al ₂ O ₃ film, or aluminum nitride powder is added to the conductor layer. Can also.

In the case of manufacturing a multilayer wiring board,
For example, a green sheet molded body was prepared by the above-described method, and a conductor paste containing a high melting point metal such as tungsten and molybdenum and, if desired, a component of a substrate such as aluminum nitride powder was applied to the sheet surface, and these were laminated and pressed. Thereafter, the molded body and the conductor can be simultaneously fired in a non-oxidizing atmosphere such as nitrogen at 1600 to 2000 ° C.

On the surface of the substrate obtained as described above, passive components, semiconductor elements, and the like are appropriately mounted to form an electric circuit.

Therefore, first, a plurality of substrates having different average crystal grain sizes of aluminum nitride were manufactured based on the above method. The average crystal grain size of the obtained sintered body was determined by drawing a straight line in an electron micrograph, measuring the crystal grain size on the line, dividing the number by the number of crystal grains, and taking 20 points.
The three-dimensional average crystal particle diameter was obtained using the correction coefficient and the three-dimensional particle diameter.

The conductor layer has a frequency of 100 MHz to 30 GH.
An electric signal having a frequency of z and an output of 1 mW was transmitted, and the dielectric loss tangent of the insulator at this time was measured. Measurement of dielectric loss tangent is 10
From 0 MHz to 1 GHz, based on the reflected wave method, from 5 GHz to
In the 30 GHz band, each was measured based on the cavity resonator method. FIG. 1 shows the relationship between the frequency and the dielectric loss tangent of a substrate using an aluminum nitride sintered body having an average particle size of 11 μm. As is clear from FIG. 1, it is understood that the dielectric loss tangent of the aluminum nitride sintered body has a maximum value in a specific frequency band at a frequency of 100 MHz or more.

Next, based on the properties shown in FIG. 1, the dielectric loss tangents of the sintered bodies having different average particle diameters were measured, and the frequency fo was plotted on the horizontal axis, and the average particle diameter d was plotted on the vertical axis. FIG. 2 shows the relationship between and the average particle size. Then, the value of the dielectric loss tangent at each coordinate point is represented by を, 25 × 10 ⁻⁴ or less.
~ 75 × 10 ^-4 for △, 75-125 for × 10 ^-4 for □, 1
25 × 10 ⁻⁴ or more was indicated as Δ. According to FIG.
It was found that the frequency showing the maximum value of the dielectric loss tangent in each sintered body tends to increase as the grain size decreases.

In FIG. 2, line X is a line of d × f = 3000, and line Y is a line of d × f = 30000. In the figure, a region B sandwiched between line X and line Y has a dielectric loss tangent of 0.0.
The region A outside the line X and the line Y is a region having a dielectric loss tangent of 0.01 or less.

Therefore, in order to always maintain the dielectric loss tangent of the insulator of the substrate at 0.01 or less, the relationship between the average crystal grain size d (m) of the sintered body and the operating frequency (Hz) is shown in FIG. It is necessary to be in the area A. That is, according to the present invention, d
Xf needs to be 3,000 or less, or 30,000 or more.

The aluminum nitride substrate on which the wiring layer of the present invention is formed is also used as a pulse transmission substrate. In this case, the pulse rise time Tr (sec) is such that fmax = 0. The product of the maximum frequency component fmax defined by 35 / Tr and the average grain size d (m) of the crystal constituting the substrate is 3000 or less, or 30.
000 or more.

[0019]

As described above in detail, according to the present invention, the frequency f (Hz) of the electric signal transmitted to the wiring layer formed on the wiring board is changed with respect to the frequency f (Hz) of the aluminum nitride forming the insulator of the substrate. By controlling the average crystal grain size d (m) of the sintered body to satisfy a specific condition, the dielectric loss tangent of the insulator made of the aluminum nitride sintered body can always be controlled to a low value. This prevents the signal from being attenuated, maintains stable substrate characteristics at all times, and provides long-term reliability as a wiring substrate.

[Brief description of the drawings]

FIG. 1 is a view showing the relationship between the frequency and the dielectric loss tangent of a substrate made of an aluminum nitride sintered body having an average particle size of 11 μm.

FIG. 2 shows the average crystal grain size d of an aluminum nitride sintered body
FIG. 3 is a diagram showing values of dielectric loss tangent at each coordinate point using (m) and frequency (Hz) as coordinate axes.

Continuing on the front page Jury President Yuko Matsuda Judge Noboru Nakazawa Judge Judge Nakajima Kiyoshi (56) References JP-A-1-189191 (JP, A)

Claims (1)

(57) [Claims] A wiring layer is formed inside or on a surface of an aluminum nitride sintered body having an average crystal grain size of 0.5 to 40 μm, and the frequency of an electric signal transmitted to the wiring layer is 100 MHz. An aluminum nitride wiring substrate as described above, wherein the average crystal grain size of the aluminum nitride sintered body is d (mm), and the frequency of an electric signal transmitted to the wiring layer is f (Hz). Said d
An aluminum nitride wiring substrate, wherein the product of f and f is 3000 or less, or 30000 or more, whereby the dielectric loss tangent of the aluminum nitride sintered body is 0.01 or less.