JPH035074B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a thermally conductive insulating substrate. [Problems to be solved by conventional technology/inventions] With the development of IC, LSI, etc., electronic circuits have become smaller, more highly integrated, and have higher output, and the packaging density of semiconductor elements has also increased. There is. As semiconductor devices become more highly integrated, have higher output power, and become more dense, the number of elements per chip is increasing year by year, and the amount of heat generated per chip is also increasing. This increase in heat generation has a significant effect on the reliability of semiconductor devices, and therefore there is an increasing demand for package materials with good thermal conductivity. In addition, in hybrid ICs, heat-generating components are now housed together in the same package, and insulating substrates with good thermal conductivity are required to further promote high-density packaging. Furthermore, when considering actually mounting the device, it is preferable that the coefficient of thermal expansion is close to that of the device, other package constituent materials, and the circuit board, so that the chip can be directly bonded. As a substrate that satisfies both of the above, Al+Al ₂ O ₃
Ceramic substrates made of (alumina), crystalline SiC, BeO, etc., and enamel substrates made of metal substrates coated with ceramic are being considered, but all of them are expensive except for enamel substrates.
BeO substrates are toxic, crystalline SiC substrates use BeO as a sintering aid, and the dielectric constant at high frequencies is as high as approximately 40 at _{1MHz .} has a large linear expansion coefficient,
Since Al ₂ O ₃ lacks insulating properties, an epoxy coat is required to compensate for this, resulting in improved thermal conductivity and
There is a problem of insufficient heat resistance, and substrates made of inexpensive enamel have disadvantages such as a large coefficient of linear expansion and poor thermal conductivity of the enamel. The present invention has a coefficient of linear expansion that is close to the coefficient of thermal expansion of elements or other package constituent materials and circuit boards, has good thermal conductivity and heat resistance, can produce thick film circuits, and has a smooth surface. The object of the present invention is to provide an insulating substrate that does not have the drawbacks of the conventional substrates. [Means for Solving the Problems] The present invention has found that the above problems can be solved by using a substrate whose surface is coated with an insulating layer having high thermal conductivity on the surface of a crystalline silicon substrate that has been oxidized or oxidized. The present invention relates to a thermally conductive insulating substrate in which at least a portion of the surface of a crystalline silicon substrate that has been oxidized or oxidized is covered with an insulating layer having high thermal conductivity. [Example] The crystalline silicon substrate used in the present invention is, for example, a substrate made of single crystal silicon or polycrystalline silicon and has a thermal conductivity of about 100 W/m・℃ or more, and has a diameter of 10 to 200 mmφ or 10 to 200 mm□. in thickness
Examples include substrates having a shape of 0.1 to 5 mm. The crystalline silicon used for the substrate may be of metallic grade and may be doped p-type or n-type. Furthermore, if through holes or the like are to be formed in the substrate, it is preferable to form them before forming or oxidizing the substrate in order to improve the insulation properties of the through holes. In the present invention, a substrate obtained by oxidizing or oxidizing the above substrate is used, and at least a portion of the surface of this substrate is covered with an insulating layer having high thermal conductivity. The crystalline silicon substrate is oxidized or oxidized in order to achieve homogeneous and dense insulation and to strengthen the adhesion with the subsequently covered insulation layer.
The substrate is preferably oxidized or oxidized to a thickness of at least 0.1 μm from the surface, and preferably 0.5 μm thick.
More preferably, the thickness of the oxidized or oxidized layer is 5 μm or less to prevent internal stress distortion of the oxidized or oxidized layer and cracks caused by it. This is preferable from the point of view of As a method for oxidizing or oxidizing a crystalline silicon substrate, in the presence of nitrogen gas or oxygen gas,
It can be formed by a normal DC discharge method, such as a PF discharge method or a microwave plasma discharge method that uses a high frequency of about KHz to MHz, but it is preferable to bias the crystalline silicon substrate to a negative potential and perform plasma treatment. It is preferable because it has high properties and adhesion strength. Covering at least a portion of the surface means that at least a necessary portion is covered, and there is no particular limitation on the proportion of the surface of the substrate to be covered.
It may be the entire surface of the substrate or only a small portion. The insulating material forming the insulating substrate having a high thermal conductivity, preferably 50 W/m・℃ or more, more preferably 100 W/m・℃ or more, is, for example, at least one of silicon, germanium, and carbon. As a main component, ie, 30 atm% or more, this material may contain hydrogen or a halogen group element, preferably 0.1 to 30 atm%. Of course, other materials may also be used. Specific examples of the above-mentioned materials include hard carbon materials such as diamond, diamond-like carbon, silicon carbide, and germanium carbide (Japanese Patent Application No. 60-83137, No. 60-179025,
60-209620 (materials described in each specification etc.), silicon carbide, silicon nitride, silicon germanium, silicon germanium carbide, silicon carbide nitride, silicon oxide, silicon nitride oxide,
Non-single-crystalline materials containing silicon such as silicon carbide oxide (JP-A-60-82669, JP-A-60-119784, and Japanese Patent Application JP-A-59-187036)
Materials described in the specification etc.), c-BN, h-
Examples include BN, AlN, BP, etc. Using one or more of the above materials, preferably a film thickness of 0.5 to 10 μm,
More preferably, an insulating layer with a thickness of 1 to 10 μm is formed. When an insulating layer is formed using two or more types of materials, a composite insulating layer may be used. When the material forming the insulating layer is diamond-like carbon, a material containing one or both of silicon or germanium atoms in a range of 9 atm% or less has lower internal stress and greater adhesion, and is better suited to diamond-like carbon. It is preferable because it has physical properties close to , and it is more preferable to contain it in the range of 0.1 to 4 atm %. Note that if the amount of silicon or germanium in the film exceeds 9 atm%, the thermal conductivity tends to decrease. Regarding such effects of trace amounts of Si and Ge,
Details are currently unknown, but probably Si, Ge sp ³
It is thought that the orbit works effectively for diamond nucleation. When the material forming the insulating layer is amorphous silicon carbide, it is preferable that the material contains at least one of hydrogen atoms and halogen group elements in a range of 30 atm% or less from the viewpoint of high thermal conductivity. More preferably, the content is in the range of 0.1 to 10 atm%. The insulating layer as described above usually has an electrical resistance of 10 ^-6 (Ω cm) ^-1 or less, preferably 10 ^-8 (Ω cm) ^-1 or less, more preferably 10 ^-9 (Ω cm) ^{-1 or} less. Conductivity and 50V/
It is preferable for use in an insulating substrate to have a withstand voltage of at least μm, more preferably at least 100 V/μm. Next, a method for manufacturing the thermally conductive insulating substrate of the present invention will be explained. There is no particular limitation on the method for forming an insulating layer on the surface of a crystalline silicon substrate that has been oxidized or oxidized, and any method can be applied as long as an insulating layer made of the above-mentioned materials can be formed. or the method described in the specification can be suitably employed. Examples of such methods include diamond, diamond-like carbon, silicon carbide,
Amorphous silicon carbide, hexagonal BN, cubic crystal
DC discharge plasma CVD method, RF discharge plasma CVD method, plasma CVD method that combines both DC discharge and RF discharge, which can be applied to forming an insulating layer made of BN etc. Examples include plasma CVD methods that combine both RF discharge and RF discharge. diamond, diamond-like carbon,
When forming an insulating layer made of silicon carbide, amorphous silicon carbide, etc., applying a plasma CVD method that mixes both DC discharge and RF discharge, which has a magnetic field perpendicular to the electric field on the substrate, can improve crystallinity and thermal properties. This method is preferable because a film with excellent conductivity can be produced at high speed. DC discharge with a magnetic field orthogonal to the electric field on the substrate
A specific method for manufacturing a photothermal conductive insulating substrate by a plasma CVD method that combines both RF discharge and discharge is, for example, as shown in FIG. A negative DC voltage, preferably between -150 and -
Apply a DC voltage of 600 V, apply RF power, preferably 100-400 W (140-560 mW/cm ² ), preferably a reaction pressure of 0.1-20 Torr, 200
At a substrate temperature of ~350°C, a magnetic field B parallel to the substrate surface,
A preferred method is to form the insulating layer while applying a magnetic field B of 100 to 1000 Gauss. Note that 4 is a gas inlet. In addition to the above methods, ion plating methods, cluster beam methods, thermal CVD methods, ionization vapor deposition methods, etc. may also be employed. The substrate of the present invention manufactured in this way has a thermal conductivity almost equal to that of single crystal silicon (120 W/m・℃
degree), surface Vickers hardness is 500 or more, preferably 1500 or more, more preferably 2000 or more, and electrical conductivity is 1×10 ^-6 although it varies depending on the type of insulating layer.
(Ω・cm) ^-1 or less, preferably 1×10 ^-8 (Ω・cm) ^-1
The following characteristics include a dielectric constant of 20 or less at 1MHz (15 or less in the case of silicon carbide) and a dielectric loss of 0.02 or less at 1KHz. In addition, since a crystalline silicon substrate is used as the substrate for forming the insulating layer, the coefficient of linear expansion is almost the same as that of LSI and IC chips, and the chip can be directly bonded, and it can withstand heating up to 800°C, so high-temperature processing is not required. Suitable for IC substrates and multilayer substrate materials such as hybrid IC substrates for thick film circuits. It is also easy to plate, vapor deposit, or sputter copper for wiring. Furthermore, it is extremely stable against acids and alkalis, has good adhesion to the insulating layer, and has high through-hole reliability. Hereinafter, the substrate of the present invention will be explained based on Examples. Examples 1 to 8 and Comparative Example 1 A 0.5 mmφ through hole was drilled in a 0.5 mm thick single crystal Si substrate, and after trimming and polishing, plasma treatment was performed.
I put it in a CVD device. Attach the board to the RF electrode side,
Apply −100V DC voltage to the board and 0.1Torr O ₂
Introducing gas and 13.56MHz RF of 0.1W/ ^cm2 at room temperature
plasma oxidized. The thickness of the oxide layer was measured by SIMS. The substrate was then raised to 200℃ and the gases were changed to SiH ₄ and CH _4.
The DC voltage was changed to -50V, and a-SiC with Eg = 2.5 eV was deposited at 0.5 Torr and RF power of 0.1 W/ ^cm2 . The thermal conductivity of the obtained substrate was measured using a laser flash method. The electrical conductivity was measured in the plane direction where Al electrodes were attached parallel to the a-SiC, and in the thickness direction of the Si back surface and the a-SiC. Heat resistance was evaluated by raising the temperature to 500°C three times and observing changes in the a-SiC film. The results are shown in Table 1. Note that ○ in Table 1 indicates good, ×
indicates defective.

[Table] [Effects of the invention] The substrate of the present invention, in which an insulating layer with high thermal conductivity is provided on a crystalline silicon substrate made of silicon or oxidized, has an extremely high insulating layer and a thermal conductivity that is almost the same as that of Si. In addition, it does not cause harmful peeling even after repeated heating, and its coefficient of linear expansion is
Since it is the same as Si chips such as LSI and IC, it has the characteristic that it can be directly bonded.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a plasma CVD apparatus used to manufacture the substrate of the present invention. (Main symbols in the drawings), 1: A crystalline silicon substrate that has been oxidized or oxidized.

Claims (1)

[Scope of Claims] 1. A thermally conductive insulating substrate in which at least a portion of the surface of a crystalline silicon substrate that has been oxidized or oxidized is covered with an insulating layer having high thermal conductivity. 2. The crystalline silicon substrate that has been oxidized or oxidized is
2. The substrate according to claim 1, which is obtained by forming through holes in a crystalline silicon substrate and then forming or oxidizing the substrate. 3 Claim 1 in which the crystalline silicon substrate is a single crystal silicon substrate or a polycrystalline silicon substrate
Substrate described in section. 4. The substrate according to claim 1, wherein oxidation or oxidation occurs from the surface of the crystalline silicon substrate to a thickness of at least 0.1 μm. 5. The substrate of claim 1, wherein the oxidation or oxidation occurs from the surface of the crystalline silicon substrate to a thickness of at least 0.5 μm. 6 The thickness of the insulating layer with high thermal conductivity is 0.5 to 10 μm
A substrate according to claim 1. 7 The thickness of the insulating layer with high thermal conductivity is 1 to 10 μm
A substrate according to claim 1. 8 The electrical conductivity of the insulating layer with high thermal conductivity is 10 ^-6
(Ω·cm) ⁻¹ or less, the substrate according to claim 1. 9 The electrical conductivity of the insulating layer with high thermal conductivity is 10 ^-8
(Ω·cm) ⁻¹ or less, the substrate according to claim 1. 10. The substrate according to claim 1, wherein the insulating layer with high thermal conductivity is made of a material containing at least one of silicon, germanium, and carbon as a main component, and may also contain hydrogen or a halogen group element.