JPS6120358A - Substrate for mounting semiconductor element - Google Patents

Abstract

PURPOSE:To obtain the titled substrate of high heat-dissipation excellent in electrical insulation by a method wherein the surface of the base metal is coated with a thin layer of Ti or TiO2 to a thickness of 0.5-10mum and provided with a ceramic coat layer thereon by a vapor phase method. CONSTITUTION:The surface of the base metal 1 of composite material or a sintered compact of infiltrated powder is coated with a thin layer of Ti or TiO2 2 and with a ceramic layer 3 thereon. The Ti or TiO2 layer has a large effect in preventing the diffusion of a metal such as Cu when coating the base metal; besides, a Ti oxide layer or a TiO2 layer produced in the outermost surface by spontaneous oxidation in the case of a Ti layer is very dense and prevents the oxidation of the base metal, and is excellent in wetting with ceramic materials. The Ti layer or TiO2 layer in this case is preferably 0.5-10mum. As the material of a ceramic layer is the outer layer, any of Al2O3, SiO2, MgO, etc. or their composite can be used. It is preferable that the ceramic layer is 1.0-20mum thick.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application This invention relates to a substrate for mounting semiconductor elements, particularly a substrate with high heat dissipation and excellent electrical insulation.

BACKGROUND OF THE INVENTION Conventionally, alumina-based substrates have been widely used as substrates on which semiconductor elements are mounted. However, in recent years, as the density and speed of IC devices have increased, substrates for mounting semiconductors have come to be required to have higher heat dissipation than alumina-based substrates.

The following materials other than alumina-based materials have been proposed as electrically insulating semiconductor element mounting substrates aimed at high heat dissipation.

■ A thin Al2O2 plate laminated to a Cu plate or a Cu alloy plate ■ An AI plate whose surface is treated with alumite to give it electrical insulation ■ A type using BeO However, in the type ■, the AhOa thin plate is 100 μm thick.
Therefore, the thin plate becomes a barrier to heat conduction and sufficient thermal conductivity cannot be obtained. Further, the coefficient of thermal expansion of Cu is also larger than that of the semiconductor element substrate.

■The A10 layer obtained by alumite treatment is porous, so not only does it not provide sufficient electrical insulation, but the thermal expansion coefficient of metal Al is too large compared to semiconductor elements such as Si and GaAs, so it is large. When a semiconductor device is mounted, there are drawbacks such as cracks or cracks in the device due to a mismatch (difference) in the coefficient of thermal expansion. Type (2) is expensive and has the disadvantage that BeO is toxic.

In order to eliminate these drawbacks, in recent years the coefficient of thermal expansion has been increased to 10.
A substrate has been proposed in which a thin layer of ceramic is coated on the surface of a metal plate whose temperature is below
0 μm or less, therefore, it does not act as a barrier to heat conduction, and the thermal expansion coefficient of the metal plate is 10 × 10171°C or less, which is close to that of the semiconductor element and coating ceramic, so it will not cause cracks or cracks in the semiconductor element or ceramic layer. never occurs. Thermal expansion coefficient is 10×10cTs
/α°C or less metal plate materials include W, Mo,
A composite material is used that is a combination of a metal with a small coefficient of thermal expansion such as Ta, or a powder sintered body of such metal, and a metal with high thermal conductivity, such as Cu, Ag, or an alloy thereof. For example, C made by infiltrating Cu into a W sintered body.
u-W alloy, etc.

Problems to be Solved by the Invention However, in such composite materials or infiltrated powder sintered bodies, materials with good thermal conductivity such as Cu or Cu alloys are coated with a ceramic thin layer on the exposed surface. In this case, there was a drawback that sufficient electrical insulation could not be obtained.

This invention was made in consideration of the drawbacks of the prior art, and it is possible to reliably apply a composite material or an infiltrated powder sintered body in which a material with good thermal conductivity such as Cu or Cu alloy is exposed on at least a part of the surface. This is a substrate for mounting a semiconductor element coated with a thin layer of ceramic with good electrical insulation, and has a coefficient of thermal expansion close to that of the semiconductor element, good thermal conductivity, electrical insulation on the surface, and excellent corrosion resistance. The purpose is to provide a mounting board.

20 Means for Solving the Problems The inventors of the present invention have conducted a detailed investigation into the cause of the decrease in the electrical insulation properties of the ceramic layer of the conventional substrate for mounting semiconductor elements, and have found that: ■ Composite materials or infiltrated powder sintering The surface of the body is rough.

Therefore, a ceramic layer of uniform thickness may not be formed.
The surface of a thermally conductive material such as u causes an oxidation reaction that impairs its adhesion to the ceramic layer. ■ The temperature (heating) during ceramic coating causes metal materials such as Cu to diffuse to the surface of the ceramic layer. We found that this was due to two causes.

Therefore, in order to solve this problem, the surface roughness of the composite material or infiltrated powder sintered body is alleviated and the exposed metal surfaces such as Cu are coated to prevent oxidation reaction on the metal surface and diffusion into the ceramic layer. For the purpose of electrical insulation, we consider coating a part of the base metal surface of composite materials, powder sintered bodies, etc. with other substances, and then coat them with various substances, and then apply a ceramic coating on top of them to create electrical insulation. As a result of investigating the properties, it was found that a coating coated with Ti or TiO2 not only has an effect of preventing the diffusion of metals such as Cu, but also has excellent adhesion with the upper ceramic layer, and forms a ceramic layer with satisfactory electrical insulation properties. The present invention was made based on the discovery that this can be done.

The present invention relates to a composite material of a metal with a small coefficient of thermal expansion and a metal with good thermal conductivity, or a material in which a powder sintered body of the former is infiltrated with the latter metal such as Cu or a Cu alloy, that is, a material in which the latter metal is infiltrated on the surface. Ti or T is added to the exposed metal plate.
This is a substrate for mounting a semiconductor device, characterized in that it is coated with a thin layer of iO2 to a thickness of 05 to 10 μm and further coated with a thin layer of ceramic.

The present invention will be explained below with reference to the drawings. As shown in Fig. 1, a thin Ti or TiO2 layer (2) is coated on the surface of a base metal (1) of a composite material or infiltrated powder sintered body, It has a structure in which a ceramic layer (3) is coated thereon.

It goes without saying that surface roughness is generally reduced by coating, but the reason why Ti and TiO2 are selected as coating materials is that when the Ti or TlO2 layer is coated on the underlying metal, it is effective in preventing the diffusion of metals such as Cu. This is because, in the case of a Ti layer, the Ti oxide layer or TlO2 layer formed on the outermost surface by natural oxidation is very dense, prevents oxidation of the underlying metal, and has good wettability with the ceramic material.

In this case, the Ti layer or TiO2 layer is 0.5 to 10μ
m is good. If the thickness is less than 0.05 μm, the present invention has no effect, and if the thickness is more than 10 μm, the Ti layer or Ti layer may be damaged by heating during ceramic coating due to internal stress in the Ti layer or TiO2 layer.
This is because cracks and peeling occur in the iO2 layer.

The material of the outer ceramic layer is A120a.

5i02, MgO, etc., or a complex thereof can be used. Also, the thickness of the ceramic layer is 1
．． 0 to 20 μm is good. If it is less than 1.0 μm, sufficient electrical insulation cannot be obtained, and if it is more than 20 μm, the ceramic layer tends to crack or peel due to the internal stress of the ceramic layer, and even if no cracks or peeling occur, the ceramic layer itself This is because the thickness of the coating acts as a barrier to heat conduction and increases the cost required for coating.

There are various methods for forming these coatings, such as vacuum deposition, ion plating, ion sputtering, and CvD1 plasma CVD, but the effects of the present invention remain the same no matter which method is used.

E, Example Example 1゜W powder sintered body was infiltrated with 1100
A substrate of 0011 with a thickness of 1 fin was prepared, and a thin layer of Ti was coated with a thickness of 4.0 μm by vacuum evaporation. Vacuum deposition is performed at a vacuum level of 2 x 10-5 Torr and a substrate temperature of 20
A 99.9% pure Ti raw material was irradiated with an electron beam at 0° C. to melt Tl, and the material was deposited on a substrate at a deposition rate of 1 μm/mt. The thus obtained Cu-W (copper-tungsten) composite material whose surface was coated with a 40-μm thin layer of Ti was coated with 6.0 μm of Al2O3 by plasma-CVD.
Coated to a thickness of . In the plasma-CVD method, after heating the substrate to 600°C, AICβB, CO2, and H2 are placed in a chamber controlled at a gas pressure of 1.0 Torr.
A high frequency (13,56 MHz) voltage of 300 W was applied to the parallel plate electrodes attached to the substrate to ionize a part of the gas and perform a gas phase reaction.
A120a was deposited on the surface at a rate of .

The thus obtained AJhOa-coated substrate has an insulation resistance of 2 MΩ or more, and even if it is left in a humid atmosphere at a temperature of 90°C and a humidity of 90% for 60 hours, there will be no corrosion or peeling of the film (coating layer). did not occur.

Example 2 A sample in which the same base metal as in Example 1 was coated with a Ti layer to a thickness of 4.0 μm and a sample without Ti coating were coated with Al2O8 to various thicknesses, and Aβ metal was coated on the surface. Nine points were deposited on an area of 2×2j11, a voltage of IOV was applied between the M metal and the underlying metal, and the insulation resistance value therebetween was measured.

The results of the average resistance values of the nine points were as shown in FIG.

From these results, it can be seen that the substrate in which the base metal is coated with a Ti layer and the ceramic layer is coated thereon has a significantly superior insulation resistance value.

9. Effects of the Invention As explained in detail above, the substrate for mounting a semiconductor element, which is a metal plate in which a thin layer of Ti or TiO2 is coated on a base metal and a ceramic coating is applied to the base metal, according to the present invention has electrical insulation and heat resistance. It has excellent properties such as hardness and corrosion resistance, and good heat dissipation properties, and has excellent performance when used in pancages, hybrid IC substrates, motherboards, etc. on which high-density, high-speed semiconductor elements are mounted.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a substrate for mounting a semiconductor element according to the present invention, and FIG.
The figure is a graph showing the relationship between the thickness of the ceramic layer and the insulation resistance in Example 2. (1) Base metal, (2) Thin coating layer, (3) Ceramic layer. Agent Patent Attorney 1) Rio Naka Figure 1 A/2031 no Takusaku<t7rL) Figure 2 Procedural Amendment (Voluntary)

Claims (1)

[Scope of Claims] 1. A metal composite or infiltrated powder sintered body containing a metal having a coefficient of thermal expansion of 10×10^-^6cm/cm°C or less and having good thermal conductivity, at least one part of the material surface. In a substrate for mounting a semiconductor element in which a ceramic layer is coated on the surface of a base metal plate in which a metal with good thermal conductivity is exposed, the surface of the base metal is coated with 0 Ti or TiO_2.
．． A semiconductor element mounting substrate 2 characterized in that a thin layer coating is applied to a thickness of 5 to 10 mm, and a ceramic coating layer is formed thereon by a vapor phase method, and the metal with good thermal conductivity is Cu or a Cu alloy. The substrate 3 for mounting a semiconductor element according to claim 1 is characterized in that the base metal plate is a metal plate obtained by infiltrating a powder sintered body of W, Mo, and Ta with Cu or a Cu alloy. A semiconductor element mounting substrate 4 according to claim 1, characterized in that the ceramic layer is Al_2O with a thickness of 1.0 to 20 μm.
_3, SiO_2, MgO, or a composite thereof, the semiconductor element mounting substrate 5 according to any one of claims 1 to 3, wherein the thin Ti or TiO_2 layer is in a vacuum state. The semiconductor element mounting device according to any one of claims 1 to 3, wherein the layer is formed by any one of vapor deposition, ion plating, and ion sputtering. substrate