JPS6228568B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing an InSb thin film device with extremely low current noise. InSb, a type of compound semiconductor, exhibits a remarkable galvanomagnetic effect and is therefore often used in magnetoelectric transducers such as Hall elements and magnetoresistive elements. At this time, the thickness of InSb is required to be extremely thin, so the InSb film can be manufactured using physical vapor deposition methods such as vacuum evaporation, or chemical vapor deposition methods such as the well-known CVD method (hereinafter, these are simply referred to as vapor deposition methods). ) is used. A thin film of approximately 3 to 0.1 μm is used.
If it is less than 0.1 μm, the level of noise itself is too high and is not suitable for practical use. However, the thin films produced by these methods are polycrystalline films with a crystal grain size of 1 to 20 μmφ and contain many crystal defects. In order to coarsen the crystal grains and reduce crystal defects, a method of zone melting the InSb film is known. However, even with this method, the grain size is about 0.5 to 2 mm, and crystal defects cannot be completely removed. like this
When an element is formed using an InSb film and a current is passed through it, noise is superimposed on the output. For example, the level of the noise is as follows. Film thickness 2μm, element width 200
When a current of 4000 A/cm ² is passed through a μm Hall element, the Hall voltage between the elements is 2 to 10 μV (deposited InSb
membrane) or 0.8 to 2μV (zone melt
InSb film) noise is generated. However, this value is r. of the noise voltage observed in the frequency band 100Hz to 10KHz.
ms value. Also, the Hall coefficient R of such a film is
_H has a value of about 300 to 350 cm ³ /C, and the signal magnetic field
In the case of 10G, the output of the above element is about 2.5 to 2.8mV. Therefore, in the case of the conventional zone melt InSb film, the signal-to-noise ratio (S/N) for the above device is
It is 68 to 73 dB, and it is difficult to obtain a better S/N than this. However, the present inventors have discovered that a zone-melted InSb polycrystalline thin film containing certain impurities generates very little noise and can obtain a good S/N ratio. FIGS. 1 and 2 show evaluations of changes in S/N and noise level N when Na is doped into a 1.4 μm thick zone-melt InSb film using the above device. The S/N of a polycrystalline InSb film containing 5×10 ¹⁶ to 1×10 ¹⁸ cm ^-3 of Naa is 73 to 76 dB, which is better than that of a zone melt film that is not doped. More preferably 1×10 ¹⁷ to 6×10 ¹⁷ (cm
^-3 ). In addition to Na, impurities that have a similar effect on S/N improvement include Cu, Au, Ag, Zn, K,
It was found that they are Li, Cd, B, Fe, Ca, Mg, Ba, Al, and Pb. These elements, with the exception of Pb and Fe, were limited to elements in group 2 of the periodic table. The reason why these elements are effective in improving the S/N is unknown, but it is thought that they are connected to the defects contained in the InSb film and reduce the noise generation ability of these defects. In addition, the Hall coefficient of the film tends to increase regardless of the type of element, but
This point differs from the known behavior of impurities in single-crystal bulk InSb, and suggests that impurities in polycrystalline InSb films are closely related to crystal defects. The amount of impurity that gives the best S/N shows a similar tendency for all elements, ranging from 5×10 ¹⁶ to 1×
It was within the range of 10 ¹⁸ cm ^-3 . In addition, when two or more types of elements were mixed, the optimum amount was such that the total amount was the above value. Table 1 shows the S/N of films obtained by doping zone-melt InSb thin films with various elements.

[Table] Methods for mixing the impurities into the InSb thin film can be broadly divided into solid phase diffusion methods, in which the impurities are diffused at temperatures below the melting point of InSb, and liquid phase diffusion methods, in which the impurities are diffused at temperatures above the melting point. This can be achieved by using either diffusion method or by using both of them together. The first method is to contact the surface of an InSb polycrystalline thin film subjected to zone melting with a substance containing at least one of the above-mentioned predetermined elements (of course, it also includes a simple substance of the above-mentioned elements) to serve as a diffusion source. ,InSb
This is a method in which heat treatment is performed at a temperature below the melting point of. Here, the substance containing the predetermined element may be any substance that can decompose and release the element during heating of InSb and diffuse into the InSb film. For this purpose, each element alone, their hydroxides, oxides, or thermoset glasses containing the above elements are suitable. In the case of Cu, Cu alone, Cu
Examples include (OH) ₂ , CuO, etc., and a good example of B is spion glass containing B (thermosetting glass manufactured by Emulsiton Co., Ltd.). Note that as a method for bringing the single substances into contact, a vapor deposition method, ion implantation, or the like can be used. Furthermore, when providing a diffusion source on the back surface of the InSb polycrystalline thin film, the diffusion source may be formed by using a substrate material containing these impurity elements. The second method is to form a layer containing a predetermined impurity element as described above on the desired substrate (for example, for conductive elements such as Ag and Cu,
It must not be formed so thick that electrical continuity occurs. ) An InSb thin film is formed on this layer by vapor deposition,
This is a method of performing zone melt processing. this is
This is an example in which a diffusion source layer is provided on the back side of an InSb polycrystalline thin film. The third method is to form an InSb thin film on a desired substrate by vapor deposition, adhere a substance containing the above-mentioned elements to the surface of the InSb thin film, and then perform zone melting. At this time, the method involves performing zone melt treatment. At this time, as a method of diffusing the predetermined element, as described in the first method, there is a method of contacting a substance containing the predetermined element, or a protective film (usually InSb) to prevent the molten InSb from curling due to surface tension. ₂ O ₃ film is used) may also contain a predetermined element. These methods will be specifically described below with reference to Examples. Example 1 InSb was deposited on a well-cleaned Dow Corning #7059 glass substrate by a three-temperature evaporation method, and a protective film of In ₂ O ₃ was formed on the surface, followed by zone melting. . Thereafter, In ₂ O ₃ was removed by buffing, and the InSb surface was finished flat. At this time, the thickness of the InSb film was set to 0.5 to 3.0 μm. Thereafter, the InSb surface was etched with a dilute solution of KOH or aqua regia to remove surface contamination. A desired impurity element was brought into contact with this InSb surface. Various methods can be considered, but examples include the following method. The method of applying the compound is
Cu(OH) ₂ , NaOH, KOH, LiOH, Ca(OH) ₂ ,
Mg(OH) ₂ , Ba(OH) ₂ , Al(OH) ₃ , Zn
The InSb film was immersed in an aqueous solution of hydroxides such as (OH) ₂ and Fe(OH) ₃ or in various organic solvents such as alcohol and ether. In addition, for elements that are difficult to obtain in compounds, such as Au, Ag, Cd, and Pb, it is possible to directly coat the InSb surface with a thickness of several tens to several hundred Å by vapor deposition.
It was covered. Furthermore, in elements such as B, spin-on
We used a method of applying thermosetting glass containing impurities, which is commercially available as glass. Depending on the type of element, it is possible to apply it using two or more methods.
No difference was observed depending on the application method. InSb coated with impurities using the method described above
Heat treatment was performed in a vacuum furnace at 10 ^-1 Torr at a temperature below the melting point of InSb. To find out the optimal diffusion amount,
Heat treatments were carried out at various times and temperatures. Thereafter, a Hall element with a width of 200 μm was formed by photo-etching, and a current of 4000 Å/cm ² and 10 G was applied.
A magnetic field was applied to evaluate the output S and noise N (frequency band 100 to 10 KHz) appearing at the Hall terminal. As a result, 250~
Heat treatment at 450℃ for 1 minute or more is effective;
The most significant improvement in S/N was achieved by heat treatment at 400°C for about 1 hour. The above-mentioned Table 1 was obtained in this way for an element having a film thickness of 2 μm. In the above example, heating was carried out in a vacuum of 10 ^-1 Torr, but this was done to prevent InSb from being oxidized during heating; It may also be carried out in the atmosphere. In addition, in the examples, solid-phase diffusion was performed by bringing impurities into contact with the surface of the InSb film. An InSb film may be formed on the conductive element (which must not be deposited so thickly as to cause electrical conduction), and then subjected to heat treatment. Further, even if two or more types of elements are doped, the same effect can be obtained as long as the content is within the above range. Example 2 In Example 1, a method was described in which an impurity element was brought into contact with the front or back surface of a zone-melted InSb film and solid-phase diffused into the InSb film through appropriate heat treatment. This method has the advantage that the amount of diffusion can be controlled by temperature and time. However, in addition to the solid phase diffusion method, there is a liquid phase diffusion method in which liquid InSb is doped with impurities. This example will be described below. InSb was deposited to a thickness of 2 μm on a Dow Corning #7059 glass substrate by a three-temperature deposition method. After that, it was immersed in a 10% LiOH alcohol solution and then dried. Thereafter, a protective film of In ₃ O ₃ was formed and zone melting was performed. In zone melting, the InSb film is melted once, so the InSb film attached to the surface is
LiOH decomposes and all Li is once incorporated into InSb, resulting in a concentration of 10 ²⁰ cm ^-3 or more. However, zone melting has the effect of segregation of impurities, so by repeating zone melting, 5×10 ¹⁶ to 1×
InSb can be purified to an appropriate concentration of 10 ¹⁸ cm ^-3 . The S/N of the InSb film thus obtained was evaluated in the same manner as in Example 1 and is shown in Table 2, and the effect of improving the S/N is remarkable.

[Table] The above method describes how to control the impurity concentration by repeating zone melting.
In the case of elements such as Ag and Cu, by controlling the amount deposited on the InSb surface, a desired impurity concentration can be obtained in one zone melt. Further, as a method of controlling the amount of impurities that come into contact with the InSb surface, an ion implantation method can also be used. As stated above, the present inventors have discovered that Cu, Au, Ag,
Zn, Na, K, Cd, B, Li, Ca, Mg, Ba, Al,
It has been found that a zone melt polycrystalline InSb film containing Pb and Fe in an amount of 5×10 ¹⁶ to 10 ¹⁸ cm ⁻³ has an extremely good S/N ratio. In this example, the S/N evaluation was performed using a Hall element, but the present invention is applicable not only to Hall elements, but also to all polycrystalline InSb devices that require low noise, such as magnetoresistive elements and infrared detectors. It can be applied to thin films and has great industrial benefits.

[Brief explanation of the drawing]

FIGS. 1 and 2 are diagrams showing changes in S/N and N depending on the impurity concentration of Na in InSb, respectively.

Claims (1)

[Claims] 1. An InSb polycrystalline thin film is formed on a predetermined substrate by a vapor deposition method so that the film thickness is 0.1 to 3 μm, and
After zone melting the InSb polycrystalline thin film, the InSb
The thin film is Cu, Au, Ag, Zn, Na, K, Cd, B,
A diffusion source material containing at least one element selected from the group of Li, Ca, Fe, Mg, Ba, Al, and Pb is brought into contact with the diffusion source material, and heat treatment is performed at a temperature below the melting point of InSb. The total concentration of elements is 5
A method for manufacturing an InSb polycrystalline thin film for a magnetoelectric transducer, characterized in that the InSb polycrystalline thin film is contained in a range of ×10 ¹⁶ to 1 × 10 ¹⁸ cm ^-3 . 2 For use in the magnetoelectric transducer described in claim 1
A method for producing an InSb polycrystalline thin film for a magnetoelectric transducer, characterized in that the heat treatment is performed at 250 to 450°C for 1 minute or more. 3. In the method for manufacturing an InSb polycrystalline thin film for a magnetoelectric transducer according to claim 1 or 2, the Cu, Na, K, Li, Ca, Fe, Mg, Ba,
A method for manufacturing an InSb polycrystalline thin film for a magnetoelectric conversion element, characterized in that hydroxides of these elements are used as a diffusion source of Al. 4. In the method for manufacturing an InSb polycrystalline thin film for a magnetoelectric transducer according to claim 1 or 2, the Cu, Au, Ag, Zn, Cd, Fe, Mg, Al,
A method for producing an InSb polycrystalline thin film for a magnetoelectric transducer, characterized in that a single element of these elements is used as a Pb diffusion source. 5. A method for producing an InSb polycrystalline thin film for a magnetoelectric transducer according to claim 1 or 2, characterized in that a thermosetting glass containing B is used as the B diffusion source. for
Method for manufacturing InSb polycrystalline thin film. 6. Form an InSb polycrystalline thin film on a predetermined substrate so that the film thickness is 0.1 to 3 μm, and add the InSb polycrystalline thin film to Cu, Au, Ag, Zn, Na, K, Cd, B, Li,
Zone melting is performed by contacting with a diffusion source material containing at least one element selected from the group of Ca, Fe, Mg, Ba, Al, and Pb, and the total concentration of the at least one element is 5×10 ¹⁶ 1. A method for producing an InSb polycrystalline thin film for a magnetoelectric transducer, characterized in that the InSb polycrystalline thin film is contained within a range of 1×10 ¹⁸ cm ⁻³ . 7 For magnetoelectric transducer according to claim 6
In the method for manufacturing an InSb polycrystalline thin film, the Cu,
A method for producing an InSb polycrystalline thin film for a magnetoelectric transducer, characterized in that hydroxides of Na, K, Li, Ca, Fe, Mg, Ba, and Al are used as diffusion sources for these elements. 8 For use in the magnetoelectric transducer described in claim 6
In the method for manufacturing an InSb polycrystalline thin film, the Cu,
A method for manufacturing an InSb polycrystalline thin film for a magnetoelectric transducer, characterized in that Au, Ag, Zn, Cd, Fe, Mg, Al, and Pb are used alone as diffusion sources. 9 For magnetoelectric transducer according to claim 6
A method for producing an InSb polycrystalline thin film for a magnetoelectric transducer, characterized in that a thermosetting glass containing B is used as the B diffusion source.