JPH0359572B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an indium-antimony-arsenic (InSbAs) compound semiconductor thin film useful as a semiconductor for various uses, and more specifically,
The present invention relates to a method for manufacturing an InSbAs-based compound semiconductor thin film having extremely high mobility.

InSbAs-based compounds represented by the formula InSb _1-x As _x (where x is a number less than 1 indicating the atomic ratio of arsenic) are:
Since the temperature dependence of the resistance is smaller than that of indium-antimony (InSb) based compounds, the atoms have the advantage that the temperature compensation required for InSb atoms is not required or can be made very easy. Therefore, InSb _1-x As _x can be said to be an extremely useful substance as a semiconductor element material, but this substance has the disadvantage that it is difficult to manufacture even when obtained as a bulk crystal.

On the other hand, when using this semiconductor material to make semiconductor devices such as electromagnetic transducers and thin film field effect transistors, it is necessary to form it into a thin film, and conventional methods for forming such thin films include , a method of cutting out and polishing a bulk crystal is known. Although the thin film obtained by this method has excellent properties, cutting out and polishing such a single crystal causes a large amount of loss, and is not necessarily suitable as an industrial method.

By the way, as a simple method for manufacturing a thin film of InSb _{1-x As} West German Published Patent No. 2252197). However, according to this method,
Since it is difficult to control x, the inventors first determined the atomic arrival velocity ratio (arrival
We proposed a method in which an InSb-based composite crystal thin film was formed by evaporating A _Sb /A _Io at a rate of less than 1 on a deposition substrate, and then As and In were evaporated thereon.

This method certainly makes it easier to control the arsenic atomic ratio x, but in terms of characteristics, the value obtained is only about half of that obtained from bulk crystals.
As a result of repeated experimental studies, the inventors of the present invention found that the properties of the InSbAs-based compound semiconductor thin film could be made extremely superior by placing detailed restrictions on the deposition conditions at the stage of the InSb-based composite crystal thin film. The present invention has now been completed.

That is, in the present invention, the arrival velocity ratio of antimony atoms to indium atoms (A _Sb /A _Io ) at the initial stage of vapor deposition is 1.0 or more, and the substrate temperature (absolute temperature) T is set by the formula 1/Tc = 1.29 × 10 ^-3 −3.84 ×10 ^-5 logP [Here, Tc is the environmental substrate temperature (absolute temperature), P
is the degree of vacuum during deposition (Torr)] Indium and antimony are evaporated onto a substrate under conditions selected such that Tc ≦ T ≦ Tc + 30, where Tc is the substrate temperature in the environment given by Then, the above-mentioned attained velocity ratio (A _Sb /A _Io ) was made smaller than 1.0 to form an indium-antimony based thin film with a composition ratio of antimony to indium (F _Sb /F _Io ) of 0.65 to 0.95. InSb _1-x As _x (x in the formula is a number less than 1 indicating the atomic ratio of arsenic) is characterized in that arsenic alone or arsenic and indium are simultaneously vapor-deposited thereon. The present invention provides a method for manufacturing an indium-antimony-arsenic compound semiconductor thin film.

In the method of the present invention, indium (In) and antimony (Sb) are first vapor-deposited onto a substrate, and in the initial stage of vapor deposition, indium and antimony are deposited so that the arrival velocity ratio of both atoms, A _Sb /A _Io , is 1.0 or more. The substrate temperature (absolute temperature) given as a function of the degree of vacuum P (Torr) of the deposition system is greater than or equal to Tc.
It is important to keep the substrate temperature (absolute temperature) within a range of 30 degrees Celsius or less during deposition. this
After the formation of InSb nuclei at the initial stage of vapor deposition in the InSb-based thin film formation stage, the ratio of the speeds of the above two atoms reaching the substrate is
It is necessary to form an InSb-based thin film in which the composition ratio of antimony to indium (F _Sb /F _Io ) is within the range of 0.65 to 0.95 by controlling the vapor deposition so that A _Sb /A _Io is less than 1.0. can be,
Furthermore, arsenic (As) alone or As and In are simultaneously vapor-deposited on the high-mobility InSb-based thin film formed in this way. By depositing As so that the sum of the number of atoms in _the Sb film (F _Sb ) and the number of As atoms reached is greater than 1.0, the InSb _1-x As _xThin films can be manufactured.

The method of the present invention will be described in further technical detail below.

In the first half of the InSb-based thin film formation stage of the present invention, the substrate temperature T at the initial stage of vapor deposition is, for example, 5×
When performing vapor deposition under a vacuum of 10 ^-6 Torr, set the value within the range of 670≦T700 (〓), and at the same time set A _Sb /A _Io to 1.0 or more and start vapor deposition. and about 500 to 3000Å
At the stage where InSb nuclei are formed, A _Sb /A _Io is gradually lowered, and the deposition is performed so that the final F _Sb /F _Io is 0.65 to 0.95. formed in this way
InSb-based composite crystal thin films consist of large InSb crystals and large In crystals, and exhibit high mobility characteristics of 40,000 to 60,000 cm ² /VS.

Substrate temperature at the boundary that gives the substrate temperature at the initial stage of evaporation
Tc is closely related to the equilibrium vapor pressure of Sb particularly in the vacuum degree range of 10 ^-6 to ^{10 -3} Torr. fact
As long as the substrate temperature was set to a temperature higher than Tc, Sb could not be deposited on the substrate by vapor deposition. In this manner, in the method of the present invention, since there is Sb that does not adhere to the substrate in the initial stage, the following relationship holds: ∫ ^t _p A _Sb /A _Io dtF _Sb /F _Io (). However, ∫ ^t _p dt means integration over the entire deposition time. Equality holds within experimental error when the initial ratio A _Sb /A _Io is close to 1.0. Therefore, our InSb
The intention in the system thin film formation stage is F _Sb /
Since the objective is to form a thin film with F _Io of 0.65 to 0.95, it is not necessarily necessary to keep the integral value of A _Sb /A _Io within this range. However, when considering the control of F _Sb /F _Io , it is preferable to operate so that the equality sign in the above equation () holds.

Furthermore, in the present invention, the initial stage of vapor deposition is the time period required for the formation of nuclei for the growth of InSb crystals,
This corresponds to the time period when the film thickness reaches approximately 500 to 3000 Å from the start of deposition, but the film formed at this initial stage depends on the final desired film thickness, initial deposition conditions, overall deposition time, etc. It is difficult to clearly define the thickness and time.

It is only during this initial deposition period that it is necessary to deposit A _Sb /A _Io at 1.0 or more. If InSb
The remaining time in the system thin film formation stage is also 1.0 or more.
When vapor deposition is performed using A _Sb /A _Io , only a thin film with poor crystallinity and low mobility or a ragged film is obtained. That is, in this time period, it is necessary to deposit A _Sb /A _Io at a ratio of less than 1, especially at an ultimate velocity ratio of 0.95 or less.

In the second half of the present invention, in the InSb _1-x As _x conversion step, As alone or As and In are simultaneously deposited.
When x is 0.35 or less, As alone is deposited, and x
is more than 0.35, it is preferable to deposit As and In at the same time. Most of the crystals generated at this time are InSb _1-x As _x , and the others are trace amounts of InAs and In. In this case, x is x=1−F _Sb /F _Io () and is almost automatically determined from the composition ratio F _Sb /F _Io of the InSb-based thin film formed in the first half.
Here, x is also equal to F _As /F _Io , and since excess As does not adhere to the substrate, it is F _As A _As , so considering equation (B), F _Sb + A _As /F _Io > 1.0. As
must be vapor-deposited. Even when As and In are deposited simultaneously, the InSb-based thin film formation stage
InSb _1-x When the total number of In atoms in the film deposited at the stage of forming _x is expressed as ΣF _Io , it is necessary to deposit As to such an extent that A _As > F _As = ΣF _Io F _Sb () . As is clear from this formula (), if As is deposited in sufficient excess, the composition of InSb _1-x As _x can be easily controlled by controlling In and Sb. However, the formula () holds true when the InSb-based thin film F _Sb /F _Io formed in the first half is 0.65~
When F _Sb /F _Io is 0.95 and larger than 0.95, it is not preferable because it becomes two-phase or a large amount of InSb is formed. Moreover, when it is smaller than 0.65, the film becomes non-uniform with many pinholes, which is not preferable.

The characteristics of the InSb ¹ _{-x As} 0.95%/
The trace amount of InAs and In does not substantially affect the properties.

On the other hand, if A _Sb /A _Io is set smaller than 1.0 at the beginning of vapor deposition, there is no problem with the state of the formed film, but the high mobility InSb _1-x As _x
It is not possible to obtain thin films. Furthermore, if the substrate temperature at the initial stage of deposition is lower than the boundary substrate temperature Tc, not only will the film become blueish and dull, but the characteristics will also deteriorate significantly, and if it is too high above (Tc + 30) °C, there will be fluctuations. This is not preferable because it becomes larger and the number of pinholes increases, resulting in a lower yield, which is very disadvantageous industrially.

In the method of the present invention, there is no particular restriction on the substrate temperature during the deposition time period other than the initial stage, but it is preferable to perform the deposition while increasing the substrate temperature.

However, in the first half of the InSb-based thin film formation stage,
Needless to say, the temperature needs to be set lower than the melting point of InSb, which is 530°C, and in the second half, lower than the melting point of InSb _1-x As _x (approximately 800°C, depending on x).

The degree of vacuum during deposition is generally used
A degree of vacuum of 10 ^-3 Torr or more is used, but an appropriate degree of vacuum is selected in relation to the desired temperature of the substrate and in light of the relational expression with Tc. In that case, the temperature of the substrate at the boundary can be changed by introducing various gases into the evaporation system or by controlling the pumping speed and changing the degree of vacuum. In such a case, it is preferable to set the desired degree of vacuum using, for example, nitrogen gas.

Furthermore, in the present invention, the first half of the InSb-based thin film formation stage and the second half of the InSb _{1-x As} It's good to wear.

In the method of the present invention, a single vapor deposition source is used as the vapor deposition source.
Although it is preferable to use In, Sb and As, compounds such as InSb and GaSb may be used as the Sb, and compounds such as InSb and GaAs may also be used as the As source.

When using a compound as a vapor deposition raw material, use Sb.
In the case of As, in consideration of controlling the atomic arrival speed, it is preferable to use compounds with other metals forming the compound whose vapor pressure as a single substance is as small as possible than the vapor pressure of Sb or As.

There are no particular limitations on the deposition substrate used in the method of the present invention, and commonly used substrates can be advantageously used. Such substrates include, for example, sapphire, CaF ₂ , NaCl, mica, glass, Cr-
Examples include dove GaAs. Particularly preferred are crystalline substrates.

The vapor-deposited thin film obtained by the method of the present invention can be formed to have any thickness within a range that maintains the characteristics, depending on the intended use as a semiconductor device and its desired characteristics. Usually, a range from several 1000 Å to 10 μm is advantageously adopted industrially.

Means or devices for carrying out the method of the present invention include:
There are no limitations as long as they do not deviate from the technical concept of the present invention described above. For example, heating means such as heater heating or EB heating, or extremely ordinary means such as flash deposition may be used for vapor deposition, or
MBE, ion beam method, etc. can also be applied.

Further, the thin film deposition rate by the method of the present invention can be in a wide range of, for example, 0.1 to 1000 Å/sec, but the film thickness formation rate of about 1 to 100 Å/sec is preferable due to the ease of controlling the attained rate ratio. preferable.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 A vacuum evaporation apparatus was used that could accommodate six wafers, had a substrate holder that rotated concentrically, and two boats. The substrate temperature was controlled using three Pt-Rd thermocouples placed 10 mm above the wafer so that the difference between the maximum and minimum values of each display temperature was within 5°C. The degree of vacuum was measured using a B-A gauge in the middle of the pipe leading from the bell gear to the exhaust system, immediately after the main suction valve.

Mica was used as the substrate, and 6-N In and Sb for semiconductors manufactured by Furuuchi Chemical Co., Ltd. were used as the raw materials.
First, the degree of vacuum is set to 5×10 ^-6 Torr (substrate temperature at the boundary Tc
(390°C), and the substrate temperature was set at 420°C. Next, the power of the In and Sb boats was controlled respectively so that A _Sb /A _Io was 1.1 for the first 5 minutes and 0.63 for the remaining time, and the substrate temperature was increased until the film thickness reached 0.8 μm. Deposited for 25 minutes. The substrate temperature at this time was 500°C.

Then, while increasing the substrate temperature to 550℃
As was deposited for 5 minutes so that A _As /A _As +A _Sb was 0.35.

When the obtained thin film was examined by x-ray diffraction, As
The atomic ratio x was 0.34, and only trace amounts of In and cInAs could be detected.

When the characteristics of the six wafers were measured by the Pau method, the mobility was 30,000 to 32,000 cm ² /V·S. Furthermore, when the temperature dependence of the resistance of three of these films was investigated, it was found to be -0.95%/deg at 50°C, which was much smaller than -1.5%/deg for the InSb-based thin film.

Comparative Example 1 Vapor deposition was carried out in the same manner as in Example 1 except that in the InSb thin film formation step, the power of the board was controlled so that A _Sb /A _Io was 0.66 during the entire vapor deposition period.

The obtained thin film had an As atomic ratio x of 0.34, a hole mobility of 20,000 to 21,500 cm ² /V·S, and a temperature dependence of resistance of -0.94%/deg.

Example 2 The same substrate, raw materials, and equipment as in Example 1 were used. First, the degree of vacuum was set to 2 × 10 ^-6 Torr, and then 4-N nitrogen was introduced using a needle valve.
×10 ^-5 Torr (Tc is 414°C), and the needle valve was fixed. Next, set the substrate temperature to 430℃,
So that A _Sb /A _Io is more than 1.0 for the first 6 minutes,
For the remaining time, the power of the two boats was controlled so that the temperature was 0.84, and the substrate temperature was increased while vapor deposition was carried out for 30 minutes to a film thickness of 1.0 μm.
The substrate temperature at that point was 510°C.

Next, while depositing a large amount of As, the substrate temperature was increased.
The temperature was raised to 550°C to obtain a 1.1 μm thick InSbAs thin film.

When the obtained thin film was examined by X-ray diffraction, x=0.14, and some InAs and In were detected.

When we investigated the Hall mobility and Eoo (0〓 handgap calculated from the temperature dependence of the Paul coefficient) of this film, they were 45000cm ² /V・S, respectively.
It was 0.21eV.

Comparative Example 2 Example 2 except that the initial substrate temperature was 410°C
The same is true.

In the obtained thin film, x=0.08, and a slightly large amount of InAs was detected. In addition, it had a dull color in appearance and had a low hole mobility of 7000 cm ² /V·S.

Comparative Example 3 Vapor deposition was carried out in the same manner as in Example 2, except that in the InSb-based thin film formation step, the power of the boat was controlled so that A _Sb /A _Io was 1.0 or more during the entire deposition period.

The x of the obtained thin film was so small that it could not be detected by X-axis diffraction, and almost no As was contained in the crystal.

Comparative example 4 Example 2 except that the initial substrate temperature was 450°C
Vapor deposition was carried out under the same conditions.

The obtained thin film had many transparent parts, x
= 0.21, and the amount of As attached to the six films varied. When the hole mobility of these six sheets was measured, it was 16,300 to 32,500 cm ² /V·S.

Example 3 The substrate, raw materials, and equipment were the same as in Example 1, and 4-
The vacuum level was set to 8×10 ^-5 Torr (Tc is
418℃). Next, set the substrate temperature to 435℃,
A _Sb /A _Io is 1.0 for the first 5 minutes, and for the rest of the time
The power of the boat was controlled so that the temperature was 0.7, and the deposition was carried out for 30 minutes while raising the substrate temperature to 515°C. Next, As was evaporated for 10 minutes while raising the substrate temperature to 570° C. so that A _As /A _As +A _Sb was 0.5.

The restored thin film had x=0.30, had a blueish silvery luster, and was recognized to be a large crystal based on the way it reflected light.

When we investigated the temperature dependence of the hole mobility and resistance of this film at 50℃, we found that it was 37000cm ² /
X·S, -0.95%/deg, making it an excellent material for magnetoelectric conversion elements.

Claims (1)

[Claims] 1. The arrival velocity ratio of antimony atoms to indium atoms at the initial stage of vapor deposition is 1.0 or more, and the substrate temperature (absolute temperature) T is expressed by the formula 1/Tc=1.29×10 ^-3 −3.84×10 ^-5 logP [Here, Tc is the substrate temperature (absolute temperature) at the boundary, P
is the degree of vacuum during deposition (Torr)] Indium and antimony are evaporated onto a substrate under conditions selected so that Tc ≦ T ≦ Tc + 30, where Tc is the boundary substrate temperature given by . Then, the above attained velocity ratio is made smaller than 1.0 so that the composition ratio of antimony to indium (F _Sb /F _Io ) is 0.65.
The general formula InSb _1-x As _x (in the formula, x is arsenic A method for producing an indium-antimony-arsenic compound semiconductor thin film represented by (a number less than 1 indicating an atomic ratio).