JPH0634402B2 - Heat dissipating substrate having boron compound semiconductor and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a novel heat dissipation substrate utilizing the high thermal conductivity of boron compounds such as boron phosphide (BP) and boron arsenide (BAs), a method for producing the same, and boron. The present invention relates to a compound semiconductor device.

[Prior Art] With the progress of higher integration and higher output of semiconductor elements, how to dissipate heat generated during the operation of the element has become an important issue.

Until now, as a heat dissipation substrate for semiconductor elements, Al ₂ O ₃ , SiC,
Although AlN is used, their thermal conductivity is not always sufficient. BeO and diamond have higher thermal conductivity. However, BeO is not manufactured domestically because it is toxic. Diamond is expensive and cannot be produced over a wide area, which is a major obstacle to its practical application. Therefore, there is a strong demand for higher speed, smaller size, lighter weight, higher output, and higher reliability of electronic devices, and thus it is desired to develop a high-performance, high-thermal-conductivity substrate that efficiently dissipates the heat generated by the element outside the system. .

On the other hand, a semiconductor element having excellent heat resistance and radiation resistance has been demanded along with the expansion of the usage environment of the semiconductor element, but it has not yet reached the practical range.

[Problems to be Solved by the Invention] The present invention has been made in view of such a fact, and provides a heat dissipation board having high heat conductivity and high heat dissipation efficiency, and a method for easily manufacturing such a heat dissipation board. It is an object of the present invention to provide a semiconductor element having excellent heat resistance and radiation resistance.

[Means for Solving the Problems] In order to achieve such an object, the heat dissipation substrate of the present invention comprises a substrate and one or more of boron phosphide and boron arsenide formed on the substrate as a main component. A heat dissipation substrate made of a boron-based compound semiconductor, wherein the boron-based compound semiconductor has a primary growth layer on the substrate and a second growth layer on the primary growth layer.
It is characterized by having a two-layer structure composed of a next growth layer.

The manufacturing method of the present invention is characterized in that, when the above-described boron-based compound semiconductor is grown on the substrate, the substrate temperature is rapidly raised during the growth and then the growth is continued.

[Operation] Growing boron phosphide (BP) on a Si substrate has already been performed. However, the physical properties of boron phosphide, especially thermal properties such as thermal conductivity, have not been clarified experimentally so far. The present inventors have revealed that boron-based compound semiconductors such as HP and BAs have high thermal conductivity and also have high electric insulation.

Since the heat dissipation substrate of the present invention utilizes the high thermal conductivity of the boron-based compound semiconductor, it has high heat dissipation efficiency,
Since the film directly laminated on the IC or LSI substrate can be used as a heat sink, the structure of the semiconductor device can be simplified and the number of assembling steps can be reduced. Furthermore, the boron-based compound semiconductor according to the present invention has a small coefficient of thermal expansion, and thus has high reliability.

According to the manufacturing method of the present invention, the electrical resistance of the boron-based compound semiconductor can be made extremely high, so that a heat dissipation substrate suitable for a semiconductor element can be manufactured.

The semiconductor device using the boron-based compound semiconductor according to the present invention has excellent heat resistance, radiation resistance and heat dissipation characteristics.

[Examples] Hereinafter, the present invention will be described in detail with reference to Examples.

FIG. 1 is a schematic view of a semiconductor device using a heat dissipation board according to the present invention. In the figure, 1 is a Si substrate and 2 is an element structure formed on the substrate 1. 3 is a BP heat dissipation board, which also serves as an insulating plate. The heat dissipation substrate 3 is a layer directly grown on the Si substrate 1, and the surface opposite to the Si substrate side is metallized with copper or the like. Metallization layer 4 solder 5
Thus, the fins 6 are soldered to complete the cooling structure of the semiconductor device.

FIG. 2 is a schematic view of an example of a conventional semiconductor device cooling structure shown for comparison. The SIC heat dissipation substrate 9 having the metallization layers 7 and 8 on both sides is soldered to the Si substrate 1, and the SIC heat dissipation substrate 9 is soldered to the fins 6. 10 and 11 are solder layers. As is clear from the comparison between FIG. 1 and FIG. 2, the cooling structure using the heat sink of the present invention has a simpler structure than the conventional example. Therefore, the manufacturing process can be simplified.

Next, a method of growing the BP film on the Si substrate will be described.

The boron-based III-V group compound semiconductor containing boron phosphide (BP) is generally obtained by causing a reaction gas to flow on a high-frequency-heated Si single crystal and subjecting it to a thermal decomposition method on a substrate. However, it was not possible to obtain high-purity BP by the conventional method because of Si autodoping from the Si substrate.

FIG. 3 shows a CVD apparatus for forming the BP film of the present invention. In the figure, 12 is a reaction tube, 13 is a cooling tube for passing cooling water, and 14 is a high frequency coil. A graphite susceptor 15 is installed in the reaction tube 12, and a Si substrate 16 is supported on the susceptor 15.

The susceptor 15 is an inclined frame 17 made of quartz rod or the like.
Two tilted bodies placed on top and further made of quartz in front and back
It is sandwiched by 18,19. A mixed gas of B ₂ H ₆ , PH ₃ and H ₂ is caused to flow from the gas inlet 12A of the reaction tube to form BP on the heated Si substrate 16. By improving the temperature uniformity on the Si substrate by rectifying the flow of the reaction gas by providing the inside of the reaction tube as shown in FIG. 3 and by giving the inclined body 19 an appropriate mass. I was able to.

A BP film was grown on a Si (111) substrate using B ₂ H ₆ and PH ₃ as source gases. Growth conditions are B ₂ H ₆ (5% hydrogen diluted) 50-60cc / min, PH ₃ (5% hydrogen diluted) 300-500cc / m
in, hydrogen gas (carrier) 3000 to 5000 cc / min, substrate temperature 900 to 1200 ° C.

Under the above conditions, a high thermal conductivity BP film could be grown on a Si substrate.

Next, an example of measuring the thermal properties of the BP film according to the present invention will be described.

The thermal expansion coefficient of the BP film of the present invention is extremely small at 4 × 10 ⁻⁶ / ° C.

The thermal diffusivity of BP film was obtained by the laser flash method.

A thin film / thin plate, which was impossible with the conventional laser flash method, was irradiated with a laser beam in a ring shape along the central axis of the sample, and the temperature change at the center of the back surface of the sample was measured to determine the thermal diffusivity. . As a result, a value of 1.8 cm ² / sec was obtained at room temperature.

The specific heat of the BP film was measured by Parkinson's DSC, and a value of 0.9 (J / g ° C) was obtained. BP film density is 2.97 / cm
³ , and the thermal conductivity of BP obtained from the above results is 4.8 (J / cm ° C · S) at room temperature.

Next, the thermal conductivity of BP was measured up to a high temperature. The results are shown in FIG. 4 in comparison with other materials. As shown,
The BP film has higher thermal conductivity than other materials over the entire temperature range. The high thermal conductivity of this BP film was first clarified by the present inventors.

In addition to such high thermal conductivity, a method of giving a high electrical resistance to the BP film has been found.

FIG. 5 is a diagram showing an example of heating conditions of the Si substrate for growing the BP film. Initially the substrate temperature is 1050 ℃
As shown in the figure, after growing the BP film on the Si substrate, the temperature is rapidly raised to 1080 ° C to continue the growth, and after the growth of the predetermined film thickness is completed, the temperature is lowered to 1050 ° C again and kept constant. After holding for a while, slowly cool. The sectional structure of the BP film thus grown is shown in FIG.

First, the primary growth layer 22 containing Si grows on the Si substrate 21,
When the temperature was further increased, scaly growth started as the secondary growth layer 23, and a BP film consisting of two layers was obtained.

The hole was measured by the four-terminal method for the secondarily grown BP film. The resistivity of the obtained BP film is 10 ⁶ to 10 ⁸ Ωcm
And the resistivity of the conventional BP only for primary growth 10 ¹ to 10 ² Ω
The insulation was able to be increased compared to cm. There was no change in the thermal conductivity of the BP film grown secondarily.

The substrate temperature for primary growth is not limited to 1050 ° C, and can be selected according to the type and properties of the film to be grown.
The secondary growth may be performed by rapidly raising the temperature by about 10 to 60 ° C. with respect to the primary growth temperature. The thickness required for the primary growth layer is not critical and may be several tens of μm or more,
The thickness of the secondary growth layer is set as needed. After completion of the secondary growth, it may be omitted to keep the same temperature as the primary growth temperature.

As described above, the BP film of the present invention has both high thermal conductivity and high insulating properties, and is therefore extremely useful as a heat dissipation substrate for semiconductor elements.

Finally, examples of the semiconductor device having the BP film of the present invention will be described. FIG. 7 shows an embodiment of a pn junction diode according to the present invention. In the figure, 24 is a Si substrate, 25 is an n-BP layer,
26 is a p-BP layer and 27 and 28 are Al electrode layers. This device is manufactured by stacking an n-type BP layer and a p-type BP layer on a Si substrate. The n-type layer is formed by increasing the ratio of PH _{3 in} the reaction gas and controlling the reaction temperature to be low, and forming the p-type layer by decreasing the ratio of PH ₃ or controlling the reaction temperature to be high. You can The order of stacking the n-type layer and the p-type layer may be reversed.

The diode of this embodiment is superior in heat resistance to the conventional diode, and further radiation (α-ray, neutron ray, X-ray, etc.)
In addition, it has a strong characteristic and has excellent heat dissipation characteristics.

In addition, the same can be done with the surface barrier diode.

Although the above example shows BP, the same effect can be obtained for BAs and these liquid crystals. Ie BAs
Also has a zincblende crystal structure, and its electronic structure, chemical bond, electrical and optical properties are very close to those of BP,
Since the semiconductor properties are very similar, the same effect as BP can be obtained.

Similar effects are also obtained in a multi-component system to which other elements are added. The present invention is not limited to a single crystal film, but can be applied to a boron-based compound semiconductor composed of a polycrystalline, non-crystalline, sintered body or the like.

[Effects of the Invention] As described above, the present invention utilizes a high thermal conductivity and is used for a heat sink of an IC, a laser diode, or the like. The effects obtained by the present invention are listed as follows: (1) If a film grown on Si, GaAs, etc. used for IC, laser, etc. is used as a heat sink, the material structure becomes simple and the number of parts and the number of assembling steps are increased. Can be reduced, and the effects of reducing the size and weight of the device and improving reliability are significant.

(2) High insulative property and small thermal expansion coefficient, so high reliability.

(3) Like microwave oscillation transistors and optical communication laser diodes used in space communications and car phones,
Since it operates at a high current density, it is particularly effective for those that generate a lot of heat.

Further, the semiconductor device using the boron-based compound semiconductor according to the present invention has excellent heat dissipation characteristics, heat resistance, and radiation resistance, and thus has a wide range of application.

INDUSTRIAL APPLICABILITY The present invention can be applied to a wide range of information industries such as electronic computers and optical communications.

[Brief description of drawings]

FIG. 1 is a schematic view of a semiconductor device using a heat dissipation substrate of the present invention, FIG. 2 is a schematic view of a semiconductor device using a conventional heat dissipation substrate, and FIG. 3 is a cross section of a CVD device for forming a BP film of the present invention. Fig. 4, Fig. 4 is a characteristic diagram showing the thermal conductivity of BP in comparison with other materials, Fig. 5 is a diagram showing an example of the growth method of the BP film of the present invention, and Fig. 6 is a secondary diagram of the BP film. FIG. 7 is a sectional view for explaining the growth, and FIG. 7 is a diagram showing the structure of an embodiment of a pn junction diode according to the present invention. 1 ... Si substrate, 2 ... element structure, 3 ... BP heat dissipation substrate, 4 ... metallization layer, 5 ... solder, 6 ... fin, 7,8 ... metallization layer, 9 ... heat dissipation substrate (SiC ), 10, 11 …… Solder, 12 …… Reaction tube, 14 …… High frequency coil, 15 …… Susceptor, 16 …… Si substrate, 18,19 …… Inclined body, 21 …… Si substrate. 22 …… Primary growth layer, 23 …… Secondary growth layer, 24 …… Si substrate, 25 …… n-BP layer, 26 …… p-BP layer, 27,28 …… Al electrode layer.

Front page continuation (72) Takefumi Mitsuhashi 1-chome Namiki, Tsukuba, Ibaraki Prefectural Institute of Inorganic Materials (72) Inventor Shinichi Okaya 3-9-12 Matsubara-cho, Akishima-shi, Tokyo Rikagaku Co., Ltd. (72) Inventor Fumihito Muta, 3-9-12 Matsubara-cho, Akishima-shi, Tokyo Science & Measurement Co., Ltd. (72) Inventor Takeshi Koshiro, 3-9-12, Matsubara-cho, Akishima-shi, Tokyo Examiner, Science & Technology Co., Ltd. Kawamada Hideo (56) Reference JP-A-49-53787 (JP, A) JP-A-62-8600 (JP, A)

Claims (3)

[Claims] 1. A heat dissipation substrate comprising a substrate and a boron-based compound semiconductor having a boron phosphide or boron arsenide formed on the substrate or a mixed crystal thereof as a main component, the boron-based compound semiconductor. Is the primary growth layer on the substrate and
A heat dissipation substrate having a two-layer structure comprising a secondary growth layer on a next growth layer. 2. The heat dissipation substrate according to claim 1, wherein the boron-based compound semiconductor is grown on a substrate of a semiconductor device. 3. When growing a boron-based compound semiconductor containing, as a main component, one of boron phosphide and boron arsenide or a mixed crystal thereof on a substrate, after the substrate temperature is rapidly raised during the growth, A method for manufacturing a heat dissipation substrate having a boron-based compound semiconductor layer, characterized by continuing growth.