JPH0115135B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing an indium-antimony mixed crystal that is used for various purposes as a semiconductor, and more specifically to a method for manufacturing an indium-antimony mixed crystal with improved electrical properties. Indium-antimony (hereinafter referred to as InSb)
The thin film has a mobility of 78000cm ² /V・sec at room temperature.
This value is much higher than that of indium-arsenic (30,000 cm ² /V・sec) and gallium-arsenide (7,000 cm ² /V・sec), making it an excellent material for Hall elements and magnetoresistive elements. It has gained attention as a non-contact potentiometer for position detection devices for direct drive motors, VTRs, audio equipment, etc. By the way, when considering the Hall effect,
The Hall coefficient R _H and the Hall mobility μ _H are important parameters. For an InSb sample patterned and electroded in the shape shown in the attached drawing, the voltage generated between output electrodes 3 and 4 when input electrodes 1 and 2 are connected to constant current power supply I is calculated.
V _Hi , and the voltage generated between output electrodes 3 and 4 when input electrodes 1 and 2 are connected to constant voltage power supply V is V _Hv
In this case, V _Hi and V _Hv are calculated by the following formulas. V _Hi = I/t・R _H・B・I・f …(1) V _Hv =ω/l・μ _H・B・V・f …(2) However, t is the sample film thickness, and l is the pattern , ω is the width of the pattern, B is the magnetic flux density of the applied external magnetic field, I is the current passed through the sample, V is the voltage applied to the sample, f is the sample form factor, _R The Hall coefficient of , μ _H is the Hall mobility. As is clear from equation (1), the output voltage is inversely proportional to the film thickness of the sample, so it is better to use a thin film when making a highly sensitive Hall element or magnetoresistive element. Furthermore, since the forbidden band width of InSb is narrow, the Hall coefficient R _H in equation (1) above changes significantly depending on the temperature, resulting in a large temperature dependence of the constant current output voltage V _Hi in practical use. appear. On the other hand, the Hall mobility μ _H given by equation (2) is
Since there are relatively few changes due to temperature, for practical purposes,
InSb Hall elements are mainly used under constant voltage, and therefore it is desired to increase the mobility rather than increase the Hall coefficient. Conventionally, a method known for producing a high-mobility InSb thin film is to cut out a bulk single crystal and polish it to make it thin. The thin film obtained in this way has excellent properties, but
Cutting out and polishing a single crystal is not necessarily suitable as an industrial method because it involves a large amount of loss and wastes expensive InSb single crystals. Another method has also been proposed in which In and Sb are deposited on a substrate to a thickness of about 10 μm by vapor deposition or other means, and then zone melted and polished to form a thin film (Japanese Patent Application Laid-Open No. 50-9373).
However, this method is complicated and has considerable limitations when implemented industrially. By the way, the simplest method for producing an InSb thin film is to deposit it on a substrate simply by vapor deposition.Many vapor deposition methods have been tried so far, but only a film with a thickness of about 1 μm and a hole mobility of 25,000 cm ² /
It was not possible to obtain a thin film of Vsec or higher. By controlling the atomic arrival velocity ratio (AIn/Asb) of In and Sb in the substrate to 1.1 to 1.7, the present inventors first created an InSb composite crystal with uniform composition and properties consisting of an InSb crystal and a single In crystal. However, as a result of further research,
It was discovered that the mobility could be further improved by treatment under specific conditions, and the present invention was completed based on this finding. That is, in the present invention, when indium and antimony are vapor-deposited on a substrate to produce an indium-antimony mixed crystal, the atomic arrival velocity ratio AIn/ASb of indium and antimony on the substrate is determined in the presence of nitrogen. The present invention provides a method characterized in that vapor deposition is performed under conditions of 1.1 to 1.7. In this case, it is preferable that nitrogen be present at least in a higher proportion than the atmospheric component ratio. The present inventors introduced a rare gas such as Ar during evaporation with the aim of achieving higher mobility based on the previously proposed manufacturing method, but this resulted in a decrease in mobility. A significant improvement in mobility was observed when nitrogen was introduced during deposition. What is important in this case is that the nitrogen content is greater than the atmospheric component ratio. The relative amount of nitrogen to other gases varies depending on the initial vacuum level and the vacuum level after introduction. For example, if the initial vacuum level is 10 ^-6 Torr,
When the degree of vacuum is lowered to ×10 ^-6 Torr by introducing nitrogen, the nitrogen content ratio becomes approximately 90 mol%. Surprisingly, a change in atmosphere of this magnitude (from 80 mol% in air to 90 mol%) has a significant effect. i.e. 80mol of nitrogen content in air
By depositing in an atmosphere of nitrogen more than %,
This resulted in a considerable improvement in mobility. On the other hand, when the nitrogen ratio is less than 80 mol %, there is no effect of improving the mobility, and depending on the quality of other component gases, the mobility may actually decrease. The method of the invention can take various embodiments.
For example, you can raise the vacuum level sufficiently, then introduce nitrogen, and then increase the vacuum level again for evaporation. Alternatively, you can install a nitrogen valve in the evaporation equipment and introduce a small amount of nitrogen while increasing the initial vacuum level to the overall vacuum level. Possible methods include vapor deposition at a lower temperature. For example, a preferred embodiment is a method in which the degree of vacuum is raised to 10 ^-7 Torr, the degree of vacuum is lowered to 10 ^-5 Torr by introducing nitrogen, and then the degree of vacuum is continued to be introduced. Component gases other than nitrogen are not specified. Also, the final vacuum degree limit is set from the mean free path of indium and antimony,
Usually the vacuum level is 10 ^-3 Torr or higher. In the method of the present invention, it is necessary to select the atomic arrival velocity ratio Aln/ASb of indium and antimony in the range of 1.1 to 1.7, thereby making it possible to obtain particularly high mobility. Although it is extremely preferable to use single In and Sb as the evaporation source at this time, there is no particular limitation. As an evaporation source for In and Sb
InSb or InSb+In (or Sb) at an appropriate mixing ratio can also be used. Also, as an evaporation source of Sb only
GaSb etc. can also be used. The substrate of the present invention is not particularly limited, and commonly used materials such as sapphire, CaF ₂ , NaCl, mica, glass Cr-doped GaAs, etc. can be used.
Particularly preferred is a crystalline substrate. More preferred is mica, which can be easily cleaved. The substrate temperature is not particularly limited. A constant temperature or a substrate temperature that is gradually or rapidly increased or decreased during the deposition can be applied. However, the upper temperature limit is
It is limited by the melting point of InSb, about 530°C. Any means for carrying out the present invention may be used as long as it does not destroy the basic concept of the present invention.
That is, ordinary vapor deposition (heater heating, EB heating,
Flash evaporation), MBE, ion beam method, etc. can be applied. Thin film formation rate has a fairly wide range of 0.1
~1000 Å/sec can be applied, but 1~100 Å/sec is particularly preferable from the viewpoint of ease of control of AIn/ASb. The present invention will be further explained below using Examples. Example 1 Mica was used as the substrate. A vacuum evaporation apparatus having a concentrically rotating substrate holder capable of holding six wafers was used. The substrate temperature was detected by a Pt-Pd thermocouple placed 10 mm above the wafer, and another thermocouple was provided for control. Both In and Sb used as raw materials were 6-N manufactured by Furuuchi Chemical Co., Ltd. First, the degree of vacuum was set to 1×10 ^-6 Torr, and the substrate temperature was set to 400°C. Next, nitrogen was introduced through a needle valve to lower the degree of vacuum to 10 ^-4 Torr, and the needle valve was fixed as it was. Next, AIn/
In and Sb were evaporated to give an ASb of 1.4, and evaporated to a thickness of 1.1 μm in 30 minutes. Substrate temperature
Vapor deposition was performed while increasing the temperature to 480℃. When we patterned six wafers as shown in the attached drawing and measured their characteristics, we found that the mobility was
It was 26,000 to 28,000 cm ² /V·sec. Comparative Example 1 In Example 1, nitrogen was not introduced and the process was carried out at a vacuum level of 10 ^-6 Torr, and the mobility of the obtained film was
It was 20,000 to 22,000 cm ² /V·sec. Example 2 Vapor deposition was carried out in the same manner as in Example 1 except that the substrate temperature was kept constant at 440° C. The mobility of the obtained film was 22,000 to 23,000 cm ² /V·sec. Comparative Example 2 In Example 2, vapor deposition was performed at a vacuum level of 10 ⁻⁶ Torr without introducing nitrogen, and the mobility of the obtained film was 15,000 to 17,000 cm ² /V·sec. Examples 3 to 5 and Reference Examples Table 1 shows the results of AIn/ASb of 0.9, 1.2, 1.3, and 1.6 under nitrogen introduction in the same manner as in Example 1.

[Table] Comparative Examples 3 to 6 Table 2 shows comparative examples for Examples 3 to 5 and Reference Examples in which nitrogen was not introduced.

[Table] Example 6 The same procedure as in Example 1 was carried out except that the initial degree of vacuum was 10 ^-6 Torr and the degree of vacuum after nitrogen introduction was 10 ^-5 TOrr, and the mobility was 25,000 to 27,000 cm ² /V・sec. A thin film was obtained. Example 7 The same procedure as in Example 1 was carried out using glass as the substrate.
A thin film of 6000 to 8000 cm ² /V·sec was obtained. Comparative Example 7 As a comparison with Example 8, a thin film of 4000 to 6000 cm ² /V·sec was obtained when nitrogen was not introduced.

[Brief explanation of drawings]

The drawing is a plan view for explaining sample patterning and electrode attachment in the present invention. In the figure, 1 and 2 are input electrodes, and 3 and 4 are output electrodes.

Claims (1)

[Claims] 1. When producing an indium-antimony mixed crystal by vapor depositing indium and antimony on a substrate, the atomic arrival velocity ratio AIn/ASb of indium and antimony on the substrate in the presence of nitrogen is
A method characterized by performing vapor deposition under conditions of 1.1 to 1.7.