JPH0419699B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a method for manufacturing a compound semiconductor thin film structure,
More specifically, the present invention relates to a method for manufacturing a compound semiconductor thin film structure with excellent reliability. BACKGROUND ART Conventionally, the following three methods are known as methods for manufacturing compound semiconductor thin film structures. That is, as a first method,
A known method is to form a structure by forming a compound semiconductor thin film by vapor deposition, MBE, CVD, etc. on a substrate with excellent crystallinity and good operability, such as Cr-doped semi-insulating GaAs or sapphire. However, this method often requires complicated surface treatment immediately before forming the compound semiconductor thin film, and the types of substrates that can be used are limited in order to match the lattice constants. It has drawbacks such as being expensive. Next, as a second method, a method is known in which a compound semiconductor thin film is formed on an amorphous substrate such as glass by a method such as vapor deposition or CVD to form a structure. However, this method has the disadvantage that the compound semiconductor thin film formed on the amorphous substrate generally does not have good crystallinity, and requires complicated post-processing to improve the crystallinity. be. A third method is to use evaporation, MBE, or
After forming a compound semiconductor thin film by a method such as CVD, adhering the compound semiconductor thin film to a substrate using an adhesive such as an epoxy resin, and then physically or chemically removing the crystalline substrate. A method of manufacturing a compound semiconductor thin film structure (hereinafter abbreviated as CSTS) is known (Japanese Patent Publication No. 51-45234, etc.). However, this method (so-called transfer method) has the disadvantage that the obtained structure has an organic adhesive layer such as epoxy resin or phenol resin, and therefore has poor reliability, especially heat resistance and moisture resistance. There is. The present inventors have conducted extensive research to overcome the drawbacks of the conventional methods described above and to develop a method that can obtain a highly reliable compound semiconductor thin film structure using simple means. The compound semiconductor crystal layer grown on the crystal growth substrate is transferred to an insulating substrate for permanent support, fused using low melting glass, and then the crystal growth substrate is removed. We have found that the object can be achieved, and based on this knowledge, we have completed the present invention. That is, the present invention includes a step of growing a compound semiconductor crystal on an insulating crystal growth substrate to form a first composite consisting of the substrate and a compound semiconductor crystal thin film, and a step of growing the compound semiconductor crystal on an insulating substrate for permanent support. forming a glass layer that is lower than the melting point of the compound semiconductor crystal and whose coefficient of linear expansion is in the range of ±10×10 ^-7 /°C with respect to that of the substrate to form a second composite;
a step of bringing the first composite body and the second composite body into close contact so that the compound semiconductor crystal thin film of the former is in contact with the glass layer of the latter, and then heating them to a temperature of 900° C. or less to fuse the two; The present invention provides a method for manufacturing a compound semiconductor thin film structure in which the permanently supporting insulating substrate and the compound semiconductor thin film are integrated, the method comprising selectively removing only the crystal growth substrate of the first composite. be. In the method of the present invention, it is necessary to first form a thin film of compound semiconductor crystal on a predetermined crystal growth substrate and then transfer it onto the predetermined substrate via a low melting point glass layer. and without diffusing the compound semiconductor thin film into the glass.
Unable to transfer smoothly. Next, embodiments of the present invention will be outlined with reference to the accompanying drawings. 1A to 1D are explanatory diagrams of the manufacturing process of a structure according to the method of the present invention, and the reference numeral 1 in the figures is
2 is a compound semiconductor insulating crystal growth substrate, 2 is a compound semiconductor thin film, 3 is a substrate, and 4 is a low melting glass layer. First, as the first step, as shown in Figure 1A,
Selectively removable compound semiconductor crystal growth substrate 1
A crystal of a desired compound semiconductor thin film 2 is grown thereon, and as a second step, as shown in FIG. 1B,
A low melting glass layer 4 is formed on a suitable substrate 3. Next, as the third step, as shown in Figure 1C,
After the compound semiconductor thin film 2 on the crystal growth substrate and the low melting glass layer 4 on the base are brought into close contact, the glass layer is softened and bonded, and in the fourth and final step, the crystal growth substrate 1 is selected. Upon removal, a structure as shown in FIG. 1D is obtained. The structure obtained through this process has a compound semiconductor thin film formed on the substrate via a glass layer, and unlike conventional structures, it does not have an organic layer, making it extremely reliable. It is excellent. The crystal growth substrate used in the method of the present invention is one that allows the crystals of the compound semiconductor thin film to grow well, yet does not strongly adhere to the compound semiconductor thin film, or is soluble in a solution that does not dissolve the compound semiconductor thin film, And it is preferable that it is crystalline. Examples of such materials include mica, graphite, sodium chloride, potassium chloride, potassium bromide, sodium iodide, alum, and the like. In order to form a compound semiconductor thin film on the above-mentioned crystal growth substrate, normal vapor deposition (heater heating, EB
Methods such as heating), MBE, sputtering, and CVD are used. At this time, the thickness of the thin film is 200Å to 10μ.
A range of 500 Å to 2 μ is preferable in consideration of ease of transfer and characteristics. In the method of the present invention, a so-called low-melting glass is required as the glass used to form a glass layer having a softening point lower than the melting point of the compound semiconductor on the substrate, and the softening point (Ts) of this glass is
There is no particular restriction as long as it is lower than the melting point (Tm) of the compound semiconductor, but if it is too low, the heat resistance will not improve, so the softening point is generally 300
℃ or more and 20°C or more lower than Tm, more preferably 50°C or more lower than Tm. Further, the coefficient of thermal expansion of the glass used in the present invention needs to be close to the coefficient of thermal expansion of the substrate used, and if it is significantly different from the coefficient of thermal expansion of the substrate,
Unnecessary strain may be applied to the compound semiconductor thin film or the substrate may be damaged. Therefore, the linear expansion coefficient of glass is ±15× the linear expansion coefficient of the base material.
It is desirable that the temperature is in the range of 10 ^-7 /°C, preferably ±10×10 ^-1 /°C, preferably ±5×10 ^-7 /°C. Further, the glass used in the present invention preferably has a high insulation resistance, and when used as an electrical element, it is usually necessary to have a resistivity higher than 10 ⁸ Ωcm. The material used as the insulating substrate for permanent support in the method of the present invention may be one that has a higher softening point than the glass used, but is stable in shape in the temperature range from the softening point of the glass to room temperature. Something is preferable. Examples of such materials include inorganic materials such as ceramics, and specific examples include alumina, ferrite, silicon nitride, quartz, sapphire, and borosilicate glass. In the method of the present invention, a typical method for forming a glass layer on a substrate is a method in which powdered glass is dispersed in a nitrocellulose binder or the like and then coated on the substrate and then fired. It will be done. In this case, in order to make the glass layer thickness uniform, the glass layer thickness is preferably 50 to 500 microns, more preferably 100 to 300 microns. In some cases, it is more preferable to make the glass layer thickness uniform by wrapping or the like. Another method of forming a glass layer on a substrate is
Methods include vapor deposition (heater heating, EB heating) and sputtering. In the case of vapor deposition, in order to control the composition of the deposited glass layer, several types of glass compositions are usually codeposited, and the film thickness is 1000 Å.
A range of ~10μ is preferred. Moreover, more preferable results can be obtained by forming this glass layer on both the substrate and the compound semiconductor thin film. Examples of methods for fusing the compound semiconductor thin film and the glass layer in the method of the present invention include heating in an electric furnace or high-frequency furnace. However, since it is better to keep only the glass layer under high temperature, It is preferable to carry out this process, and in some cases, it is preferable to carry out the process in an atmosphere of an inert gas such as argon or nitrogen. The temperature during bonding needs to be equal to or higher than the softening point of the glass, but if it is too close to the softening point, uneven bonding tends to occur, so it is preferably 10° C. or more higher than the softening point. However, if the heating temperature is too high or the glass is softened for too long, the compound semiconductor thin film will diffuse into the glass layer, making it impossible to achieve the original purpose. From the viewpoint of this diffusion, the upper limit of temperature and time limit vary depending on the physical properties of the compound semiconductor used. Removal of the crystal growth substrate in the method of the present invention is as follows:
This may be done by physical or chemical methods, depending on the type of substrate used. For example, when mica is used as a substrate, the substrate can be mechanically peeled off from a compound semiconductor thin film adhered to the substrate through glass, and when sodium chloride is used, water is used to dissolve only the sodium chloride. can be done. The structure manufactured by the method of the present invention has excellent reliability, and in particular has remarkable improvement in heat resistance compared to conventional structures. For example, structures using conventional epoxy adhesives lose their functionality as a structure because the adhesive burns at temperatures above 200°C, but structures using the low-volume glass of the present invention In this case, it will not lose its function as a structure even at high temperatures of around 400°C, depending on the glass used. Furthermore, an improvement in industrial productivity can be mentioned as a secondary effect of the present invention. That is, since the structure obtained by the present invention has excellent heat resistance,
Bonding using high melting point ball solder, which was impossible with conventional structures, is possible. In addition, with structures using conventional organic adhesives, ultrasonic bonding was impossible due to the presence of a soft adhesive layer, but the structure of the present invention has a hard glass layer and can be subjected to ultrasonic bonding. . Therefore, since the structure of the present invention allows the two types of bonding described above, whichever method is used, the bonding process can be automated, and industrial productivity can be greatly improved. Furthermore, the structure manufactured by the method of the present invention is
It can be processed into elements of various shapes. In other words, magnetoelectric conversion elements (Hall elements, Hall heads, magnetoresistive elements, etc.), junction transistors, field effect transistors, static induction transistors, piezoelectric elements, light emitting elements, temperature sensing elements, moisture sensing elements, and more. It is also possible to integrate it into an IC (integrated circuit). Next, the present invention will be explained in more detail with reference to Examples. In addition, in the embodiment of the present invention,
In order to mainly compare with Publication No. 45234, we will mainly discuss InSb-based compound semiconductor thin films.
Originally, the present invention is not limited to InSb-based thin films, for example, InAs, InP, GaAs, GaSb,
GaP or ternary GaxIn ₁ −xSb, GaxAl ₁ −
It can also be applied to thin films such as xAs and InSb ₁ −xAsx. Example 1 In and Sb were deposited using mica as a substrate for crystal growth and a vacuum evaporation apparatus having two boats as a compound semiconductor thin film forming apparatus.
At this time, the substrate temperature was set to 440℃, and the degree of vacuum was set to 1.5×.
10 ^-6 Torr, set to 1μ in 30 minutes,
An InSb-based composite crystal thin film was manufactured. On the other hand, manufactured by Iwaki Glass Co., Ltd., the coefficient of linear expansion is 69×10 ^-7 /
℃ T191BF with nitrocellulose (Asahi Kasei H)
-20) It was dispersed in a 2% n-butyl acetate solution, applied to a 1 mm thick ferrite plate (3000L manufactured by Tohoku Kinzoku Co., Ltd.) with a coefficient of linear expansion of 75×10 ^-7 /°C, and fired at 650°C. The InSb-based composite crystal thin film obtained as described above and the low-melting glass layer were brought into close contact with each other and placed in an electric furnace with a 100 g weight placed thereon, and the temperature of the electric furnace was raised to 460°C. The temperature was then maintained at 460°C for 2 minutes, and then lowered, and when it reached 80°C, it was taken out and the mica was mechanically peeled off. The InSb-based CSTS thus obtained was processed into the pattern shown in FIG. 2, and the hole mobility was measured to be 4400 cm ² /V·S at 20°C. Then this
When the hole mobility of CSTS was attempted to be measured at a high temperature of 280°C, it was found to be 1700 cm ² /V·S. Comparative Example 1 After producing an InSb composite crystal thin film in the same manner as in Example 1, it was adhered to a 1 mm thick ferrite plate using an epoxy resin (ME-264 manufactured by Nippon Pernox Co., Ltd.), and the mica was mechanically peeled off. , and processed into the pattern shown in Figure 2. An attempt was made to measure the hole mobility of this sample at a high temperature of 250°C, but the film became crumbly and could not be measured. Example 2 Using sodium chloride as a substrate for crystal growth,
An InSb-based composite crystal thin film was manufactured using the same method as in Example 1. The InSb-based composite crystal thin film formed on this sodium chloride was
Iwaki Glass Co., Ltd. T-
After transferring using 191BF, sodium chloride was removed using water. After processing this structure into a Hall element, we measured the sensitivity of 100 elements and found that 40
It was ~56 mV/5 mA x 1K Gauss. The moisture resistance test of this element was carried out at 65℃ and 97% humidity for 12 hours and 25 hours.
When the test was carried out under conditions of 20 repetitions of a 12-hour dry-wet cycle at 65% °C, there was no change in sensitivity in 92 of them. Comparative Example 2 A Hall element was prepared in the same manner as in Example 2, except that epoxy resin (AER331 manufactured by Asahi Kasei Corporation) was used for transfer.
When 100 units were manufactured and a similar test was conducted, 73 of them showed no change in sensitivity. Example 3 Using the same equipment as in Example 1, an InAs thin film was manufactured by a three-temperature evaporation method. At this time, potassium bromide was used as the crystal growth substrate, and the substrate temperature was set at 550℃.
The degree of vacuum was set to 2×10 ^-6 Torr. On the other hand, manufactured by Corning, the coefficient of linear expansion is 89×10 ^-7 /℃
The same 1417 glass as in Example 1 was placed on a 0.5 mm thick alumina plate with a coefficient of linear expansion of 81×10 ^-7 /°C at 780°C.
After firing, wrapping was performed. At this time, the final glass layer thickness was 138-141μ. The InAs thin film obtained as described above and the low-melting glass layer were placed in close contact with each other, placed in an electric furnace with a 100 g weight placed thereon, and the atmosphere was made into an argon atmosphere.
The temperature was raised to ℃ and immediately lowered. Then, it was taken out at 50°C, and potassium bromide was removed using water. The InAs-based thin film structure thus obtained was patterned as shown in FIG. 2, and the hole mobility was measured to be 3400 cm ² /V·S at 20°C. Also, the input resistance at 20℃ was 187Ω,
Furthermore, it can be measured even at high temperatures of 300℃.
Its value was 122Ω. Examples 4 to 6 and Comparative Examples 3 to 5 InSb-based composite crystal thin films were manufactured in the same manner as in Example 1 using mica as a substrate for crystal growth. Next, a ferrite plate with a thickness of 0.5 mm and a coefficient of linear expansion of 80 × 10 ^-7 /℃ was used as the base, and
7520, 8463, Iwaki Glass T-191BF, T-
Transfer was performed using 029 and 1200 manufactured by Asahi Glass Co., Ltd., and external evaluation (visual observation) of the obtained thin film structure was performed. The results are shown in Table 1.

[Table] Example 7 An InSb composite crystal thin film of 1 μm was grown on a mica substrate in the same manner as in Example 1, and sputtering was performed using T-191BF manufactured by Iwaki Glass Co., Ltd. as a target to form a 1 μm thin film. On the other hand, after wrapping a 0.5 mm thick ferrite plate with a coefficient of linear expansion of 75×10 ^-7 /℃ to make the surface smooth, a plate made by Iwaki Glass Co., Ltd. with a coefficient of linear expansion of 69×10 ^-7 /℃ was wrapped.
Sputtering was performed using T-191BF as a target to form a 2μ thin film. Then, the T-191BF layers formed in this way were placed in close contact with each other, a 500 g weight was placed on them, and the transfer was performed at 380°C for 1 minute in an electric furnace in a nitrogen atmosphere, and then the mica was peeled off. A thin film structure could be obtained. When this thin film structure was processed into the pattern shown in Figure 2 and the hole mobility was measured, it was found that
It had a function of 5100cm ² /V・S. Furthermore, it had a mobility of 1900 cm ² /V·S even at a high temperature of 280°C.

[Brief explanation of drawings]

1A to 1D are explanatory diagrams of the manufacturing process of a thin film structure according to the method of the present invention, in which reference numeral 1 is a compound semiconductor crystal growth substrate, 2 is a compound semiconductor thin film, 3 is a substrate, and 4 is a substrate for crystal growth of a compound semiconductor. It is a low melting glass layer. Figure 2 shows a sample produced by the method of the present invention.
This is a pattern used to measure the electrical characteristics of CSTS, and symbols a and a' in the figure are input electrodes,
b and b' are output electrodes.

Claims (1)

[Claims] 1. A step of growing a compound semiconductor crystal on an insulating substrate for crystal growth to form a first composite consisting of the substrate and a thin film of the compound semiconductor crystal, and growing the compound semiconductor crystal on an insulating substrate for permanent support at the melting point of the compound semiconductor crystal. a step of forming a second composite by forming a glass layer whose linear expansion coefficient is lower than that of the substrate within the range of ±10×10 ^-7 /°C; the first composite and the second composite; The former compound semiconductor crystal thin film was brought into close contact with the latter glass layer, and then heated at 900°C.
The permanent support insulating substrate and the compound semiconductor thin film are integrated into a A method for manufacturing a compound semiconductor thin film structure.