JP3368624B2 - Substrate for semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diamond heat dissipation board and a multi-layer wiring board having extremely high heat dissipation, which are used when mounting a semiconductor device, a compressor and the like.

[0002]

2. Description of the Related Art Regarding the heat radiation characteristics for a package or the like on which a semiconductor element is mounted, the required characteristics are becoming more and more stringent due to an increase in the amount of heat generated due to higher performance of the mounted element. On the other hand, as a method of lowering the thermal resistance of the package, for example, a material having higher thermal conductivity is adopted, and convection heat transfer is improved by forced air cooling or forced water cooling. .

[0003]

Among the methods for reducing the thermal resistance of packages and the like, regarding the method of using a high thermal conductive material, the thermal resistance can be minimized by using diamond having the highest thermal conductivity. . Since diamond having a relatively large area can be obtained by the vapor phase synthesis method, it can be used as a substrate material. But,
The high production cost of the substrate materials (alumina, polyimide, etc.) currently used is a big problem. In particular, when arranging a high-frequency wiring circuit directly on diamond, it is said that both the dielectric constant and the dielectric loss of the substrate diamond must be low, and diamond with such characteristics is of extremely high purity. However, there is a problem that the manufacturing cost thereof is further increased.

[0004]

Therefore, the present inventors have
We have conducted repeated studies to reduce the manufacturing cost of diamond substrate materials. Increasing the diamond growth rate is effective for reducing the manufacturing cost, but this causes deterioration of the crystallinity of the obtained diamond, which in turn causes deterioration of the dielectric properties. The deterioration of the crystallinity and dielectric properties of the diamond and the evaluation of the manufacturing cost and the heat dissipation properties were carried out in detail, and the properties required for the substrate were compared and examined. Even if diamond is vapor-phase synthesized under conditions of high growth rate to synthesize diamond with poor dielectric constant and dielectric loss, its thermal conductivity can be maintained at a constant level. It has been found that it is economically most advantageous to provide such a low cost as a semiconductor mounting substrate even if it is not disposed on the upper side but is disposed via a polyimide film having excellent dielectric properties.

[0005]

The concrete contents of the present invention will be described below. Appropriate synthesis conditions exist for the diamond obtained by the vapor phase synthesis method depending on the growth method and the required characteristics of the diamond. In the case of diamond having a low dielectric constant and low dielectric loss, the growth rate is 5 μm / hr. Often less than. Therefore, in order to manufacture a substrate having a thickness of several hundreds of μm for use in mounting a semiconductor element under these conditions, a synthesis time of about 100 hours or more is required. There is also a condition for further increasing the growth rate, but in that case, crystal disorder or the like becomes large in the obtained diamond, and the growth of the non-diamond component occurs. Along with this, the dielectric characteristics also deteriorate.

Regarding the dielectric characteristics, it is desirable that the relative permittivity and the dielectric loss thereof are small, because it becomes a factor that causes a delay in wiring when mounting a semiconductor element which performs high-speed processing. Pure diamond has a relative dielectric constant of 5.7 and a dielectric loss of 0.001 or less. However, for example, in the vapor phase synthesis method, diamond grown by using the hot filament CVD method under the condition that the source gas is methane 1% -hydrogen has a relative dielectric constant of 5.9 at 100 MHz and a dielectric loss of 0. 002, but the growth rate is 0.8 μm / hr
Met. On the other hand, diamond grown at a methane concentration of 5% had a relative dielectric constant of 6.6 and a dielectric loss of 0.04 at 100 MHz, but its growth rate was 10 μm / hr. Also in the latter diamond, the thermal conductivity was 12 W / cm · K, which was sufficient for practical use, and the manufacturing cost was 1/3 or less of the former. When the growth rate is increased in order to reduce the manufacturing cost, the dielectric characteristics deteriorate.Therefore, for high-frequency devices that have high signal transmission speed requirements, place the wiring on another insulator with excellent dielectric characteristics. Alternatively, it is desirable to reduce the wiring density to deal with the problem.

As described above, the crystallinity of diamond, which has relatively deteriorated dielectric properties in order to reduce the manufacturing cost, is also deteriorated. Raman spectroscopy is widely used to evaluate the crystallinity of diamond. As an index of crystallinity, the peak ratio (Y / X) of diamond carbon (X) and non-diamond carbon (Y), or The full width at half maximum of the peak of diamond carbon can be increased. The vapor phase synthetic diamond grown under the growth conditions suitable for diamond growth has a peak ratio (Y / X) of 0.10 or less and a half value width of 5 cm ^-1 or less. However, when grown under the condition that the growth rate is high, the crystallinity is disturbed, and the peak ratio (Y / X) of Raman spectroscopic analysis is 0.15 or more, or the half value width is 7 cm ^-1 or more. However, the peak ratio (Y
/ X) is 0.60 or more, or the half-value width of 15 cm ^-1 or more, the diamond has a thermal conductivity of 10 W / cm · K or less, which is not preferable.

As described above, in order to reduce the manufacturing cost, even if the dielectric property is deteriorated or the crystallinity is deteriorated, the thermal conductivity can still be large (10 W / cm · K or more), In this case, sufficient heat dissipation can be secured. It was found that even if the growth time is greatly shortened, the diamond substrate can be manufactured without impairing the superiority of heat dissipation characteristics, and the manufacturing cost can be significantly reduced. Specifically, the growth rate is 2 to 4 times or more, or 5 μm /
A speed of more than hr can be obtained, a large thermal conductivity can be secured,
Moreover, the manufacturing cost can be reduced. When manufacturing a multi-layer substrate having diamond as an insulating layer, it is possible to use a diamond layer having relatively poor dielectric properties according to the present invention for a lower layer portion having a relatively wide wiring interval or a substrate that does not require high-speed processing. .

The diamond substrate of the present invention may have a low-frequency power source and a grounding wire inside or on the surface thereof, but is also effective as a simple heat sink having no circuit inside or on the surface thereof. The diamond having the characteristics of the present invention can be produced by any known vapor phase synthesis method, but from the viewpoint of reducing the production cost, the hot filament CVD method, the arc discharge plasma jet CVD method, the microwave plasma CVD method. Is preferred.

[0010]

EXAMPLES Example 1 Diamond was grown to 300 μm on a polycrystalline Si substrate (25 × 25 × 5 mm) by the hot filament CVD method. Synthesis conditions are methane-6
% High-purity hydrogen is supplied as the source gas, and the total pressure is 7
The substrate temperature was 0 Torr and 850 ° C. The film formation time was 40 hours and the growth rate was 7.5 μm / hr (Sample A). On the other hand, as a comparative example, the synthesis conditions are methane 2% -hydrogen, total pressure 30 Torr, substrate temperature 900 ° C.
And diamond was grown to 200 μm. The film formation time is 100 hours, and the film formation rate is 2.0 μm / h.
r (Sample B).

After that, these were taken out from the reaction vessel, a KrF excimer laser was focused so as to have an output density of 5 J / cm ⁻² , and the diamond growth surface was scanned twice to perform surface flattening processing. After processing, the Si substrate was dissolved in chromium mixed acid to obtain a diamond freestanding film.
When the thermal conductivity of these films was measured, Sample A was 11.
It was 5 W / cm · K and Sample B was 16 W / cm · K.
As a result of Raman spectroscopic analysis, the ratio (Y / X) of the peak (X) of diamond carbon and the peak (Y) of non-diamond carbon was 0.35 for sample A and 0.06 for sample B. There, half width of the peak of diamond carbon for samples a 8.2 cm ^-1, for samples B was 4.6 cm ^-1 (Figure 1).

Metal W was deposited on the flattened surface by RF sputtering to a thickness of 0.3 μm. A dielectric property measurement circuit is formed by ordinary lithography technology, and the dielectric constant and dielectric loss are set to 100.
When measured at MHz, the relative permittivity is 6.4 for sample A and 5.8 for sample B, and the dielectric loss is 0.03 for sample A and 0.0 for sample B.
It was 008. Further, when the volume resistivity at direct current was measured, both A and B were 10 ⁹ Ωcm or more. As described above, the growth rate was quadrupled, and the thermal conductivity could be secured at 10 W / cmK or more even if the crystallinity (peak ratio of Raman spectroscopic analysis, full width at half maximum) and the dielectric properties were deteriorated.

Example 2 Polycrystalline Si substrate (25 × 2)
5 × 5 mm) by the hot filament CVD method.
Diamond was grown under the conditions as shown in (Sample C
~ E). These samples were subjected to the treatment as shown in Example 1, Raman spectroscopic analysis, and dielectric property measurement,
The results of thermal conductivity measurement are also shown in Table 1. As shown in the sample D, the thermal conductivity can be maintained high even when the peak ratio, the half width, or the dielectric property of Raman spectroscopic analysis is bad. Also, if the growth rate is increased too much, the thermal conductivity cannot be maintained high (Sample E).

[0014]

[Table 1]

[0015]

As described above, by using the semiconductor device substrate provided by the present invention, it is possible to obtain a substrate having a high heat dissipation property at a low manufacturing cost. Due to the cost reduction of this board, the application of the board with high heat dissipation to general-purpose equipment and electronic equipment in the field of portable equipment will be advanced, which will contribute to higher performance, smaller size and lower cost of these equipment. .

[Brief description of drawings]

FIG. 1 is a diagram showing a result of Raman spectroscopic analysis of a sample manufactured in Example 1.

[Explanation of symbols]

A: Raman spectroscopic analysis of sample A B: Raman spectroscopic analysis of sample B

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-154650 (JP, A) JP-A-63-288975 (JP, A) JP-A-2-23639 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 23/12-23/15

Claims (3)

(57) [Claims] 1. A substrate on which a semiconductor device is mounted, which has at least a vapor-phase synthetic diamond layer, and the diamond layer has a thermal conductivity of 10 W / cm · K or more and 100 M.
A semiconductor element mounting substrate having a relative permittivity of 6 or more and a dielectric loss of 0.01 or more at Hz. 2. A substrate on which a semiconductor device is mounted, which has at least a vapor phase synthetic diamond layer, and the peak ratio of diamond carbon (X) and non-diamond carbon (Y) by Raman spectroscopic analysis of the diamond layer ( Y /
The semiconductor element mounting substrate according to claim 1, wherein X) is 0.15 or more. 3. A substrate on which a semiconductor device is mounted, which has at least a vapor phase synthetic diamond layer, and a half value width of a peak of diamond carbon by Raman spectroscopic analysis of the diamond layer is 7 cm ⁻¹ or more. The semiconductor element mounting substrate according to claim 1.