JPS6224647A - Substrate for mounting semiconductor element - Google Patents

Abstract

PURPOSE:To obtain a substrate with superior electric insulation and heat- conductivity by forming a thin coating film of diamond on the surface of a metal substrate with superior heat-conductivity with PVD or CVD method. CONSTITUTION:A substrate for mounting a semiconductor element 3 is formed with a metal plate 1 with superior heat-conductivity and a diamond coating layer 2 applied on the surface of the plate with PVD or CVD method. Then, a semiconductor element 6 is mounted through a metallizing layer 4 and an Au plating layer 5. The diamond coating layer 2 obtained with PVD and CVD method has smaller roughness of the surface and is superior in closely contacting with the substrate. When a semiconductor is mounted on the substrate, no gap is produced between the element and the substrate, thereby making it possible to increase the radiation of heat from the element.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a substrate for mounting semiconductor elements that can efficiently dissipate heat generated in semiconductor elements, and can be widely applied as a component of circuit boards such as semiconductor packages and multi-chip boards. .

In recent years, with the increase in speed, density, and size of semiconductor devices,
An increase in the amount of heat generated from semiconductor elements has become a problem, and there is an increasing demand for high heat dissipation characteristics for substrates for mounting semiconductor elements. Therefore, such a substrate is required to have both high electrical insulation and high heat dissipation properties.

As such a substrate, one in which an electrically insulating inorganic coating layer is formed on the surface of a highly thermally conductive metal substrate by screen printing, brazing, thermal spraying, anodic oxidation, or the like is considered. However, no matter which method the inorganic coating layer is formed, the coating layer is porous and does not have sufficient thermal conductivity as desired. Furthermore, since it is porous, moisture in the atmosphere, conductive ions in water, etc. diffuse through the coating layer, causing deterioration of electrical insulation over time. For this reason, the coating layer needs to have a certain degree of thickness. From this point of view, there is a limit to the ability to improve thermal conductivity by making the coating layer thinner.

An object of the present invention is to solve such problems by forming a dense diamond coating layer, and to provide a substrate for mounting a semiconductor element that has excellent electrical insulation and thermal conductivity.

To achieve this objective, the diamond coating layer is PV
It is formed by D method or CVD method.

That is, in the present invention, on the surface of a metal substrate with good thermal conductivity,
A thin coating layer made of diamond is applied by PVD or CV
The present invention is characterized by a substrate for mounting a semiconductor element formed by the D method.

Since the PVD method and the CVD method are methods of forming a coating layer by colliding a coating material containing a compound with the substrate in the smallest units of substances such as ions and molecules, particles with a small particle size are precipitated. Therefore, a dense coating layer can be obtained. Therefore, it is possible to make the coating layer thinner and improve thermal conductivity without deteriorating electrical insulation.

Furthermore, in the PVD method and CVD method, when the coating material is collided with the substrate in the form of ions or molecules, it is possible to further improve the density by changing the nucleus growth rate relative to the nucleation rate. , moisture in the atmosphere, conductive ions in water, or metal fine particles and metal ions in the metallizing layer formed on the coating layer in a subsequent process, especially metal ions that are prone to electromigration such as silver, and sodium. Even in cases where ions with a small ionic radius such as chlorine or the like pose a problem, it is possible to provide a coating layer in which these ions do not diffuse into the coating layer.

Further, the coating layer obtained by the PVD method or the CVD method has low surface roughness and excellent adhesion to the substrate. Therefore, when a semiconductor element is mounted on the substrate, no air gap is created between the element and the substrate, allowing for high heat dissipation from the element, and its electrical insulation is sufficiently stable even against repeated heating. are doing.

Furthermore, the substrate of the present invention can be particularly effectively applied to high frequency devices using GaAs semiconductor elements. That is, in high-frequency devices, the dielectric properties of the semiconductor element mounting substrate are a problem, but diamond with a low dielectric constant can be easily and uniformly coated over a wide area of the substrate using the PVD method or the CVD method.

In the present invention, the metal substrate has a thermal conductivity of 0.2Ca.
It is preferable to use a metal plate of 1/am-sec. As a result, the above-mentioned PVD method and CVD method
Al2O3, which has been widely used in combination with the characteristics of the
It has become possible to support high-speed, high-output semiconductor devices, which could not be supported by semiconductor element mounting substrates made of sintered ceramics such as 2Mg0 and 5IO2.

Note that the applications of the present invention can be further expanded by using a composite metal plate whose thermal conductivity and mechanical properties can be arbitrarily changed depending on the application in place of the metal plate. Specific metal plates and composite metal plates include Sl, Cu, A1
various high thermal conductivity type Cu alloys, copper clad stainless steel clad copper, copper talad kovar clad copper or M
Examples include sintered bodies mainly composed of O or W.

Further, the diamond used for the coating layer is applied to a thickness of 1 to 10 μm in consideration of electrical insulation and thermal conductivity.

A semiconductor device assembled using the thus obtained semiconductor element mounting substrate is shown in FIG.

Reference numeral 1 denotes a metal plate, the surface of which is coated with a diamond coating layer 2 to form a substrate 3 for mounting a semiconductor element. 4
5 is a metal rising layer, and 5 is an Au plating layer, through which a semiconductor element 6 is mounted.

Examples will be described below.

31 A semiconductor element mounting substrate coated with a diamond thin film for mounting a semiconductor element was prepared by a plasma-CVD method. A CuW alloy with a thickness of 1 mm was used as the metal substrate.

In the 7'Raz7-CVD method, a gas containing ethylene is flowed into a reactor while controlling the total gas pressure to 1.0 Torr, and a high frequency electrode (13.56 M H
z) 300 W was applied to turn ethylene gas into plasma, and diamond was coated by gas phase reaction at a deposition rate of 500 to 1000 angstroms/min.

When the resulting diamond film with a thickness of 5 μm was observed using X-ray diffraction and a scanning electron microscope, it was found to be diamond or diamond-like crystals having a fine polycrystalline structure with a grain size of 1 μm or less.

In addition, Ni was coated by vacuum evaporation on the CuW alloy plate coated with the obtained diamond film, and the dielectric strength voltage between Ni and CuW was measured, and it was found to be over 500 V, indicating that the diamond film has good electrical insulation properties. I understand.

The semiconductor element mounting substrate obtained as described above has good thermal conductivity and good heat resistance, and also has good electrical insulation properties by controlling the precipitated particles of the coating layer.
Even when a paste that is prone to electromigration was used as an electrode on an insulating coating layer, high insulation properties could be obtained.

As explained above, according to the present invention, a highly dense coating layer can be obtained, and by reducing the thickness, thermal conductivity can be improved without deteriorating electrical insulation. The semiconductor element mounting substrate obtained in this way is
It can fully cope with the increase in speed, density, and size of integrated circuits.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a semiconductor device using the semiconductor element mounting substrate of the present invention. (Main reference numbers) 1...Metal plate, 2...Diamond coating layer, 3...
Substrate for mounting semiconductor elements, 4. Metal rising layer,

Claims (1)

[Claims] A substrate for mounting a semiconductor element, characterized in that a thin coating layer of diamond is formed on the surface of a metal substrate with good thermal conductivity by a PVD method or a CVD method.