JPH07321038A - Semiconductor thin film forming method and device - Google Patents

Abstract

PURPOSE:To provide growing means of extremely high quality hetero structural thin film developing no defects and inner diffusion, which is indispensable for super lattice such as HBT. CONSTITUTION:In order to grow a hetero structural thin film comprising multiple semiconductor thin films, a step lowering the substrate temperature at a specific lowering ratio in the growing step is included at least one time. Accordingly, the formation of the thin film, especially one wherein the growing thin film surface temperature of a heterostructural thin film comprising multiple thin films in different radiation absorption coefficient is constabtly maintained or within a specific range may be attained so that the surface defectives and the inner diffusion of thin film component element due to the abnormal raise in the surface temperature may be avoided thereby realizing a high quality hetero-structural thin film optimum for super lattice device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound semiconductor thin film crystal growth method and apparatus thereof, and is particularly useful as a compound semiconductor thin film growth technique for forming a heterostructure. The present invention relates to a growth technique for a high-quality compound semiconductor heterostructure thin film.

[0002]

2. Description of the Related Art As a conventional semiconductor thin film forming method, for example, JP-A-5-144751 or JP-A-5-213 is known.
There is one described in Japanese Patent No. 46. Further, as a conventional thin film raw material, a gas source molecular beam epitaxy method (Gas Source Molec), which is a semiconductor thin film growth technique using gas
ulal Beam Epitaxy, GSMBE
Are omitted), for example, those described in Japanese Patent Laid-Open No. 5-90160. FIG. 9 shows the commonly used G
An example of arrangement of main components of the SMBE device is shown.

A substrate 1 on which a thin film is grown, a heat source 2 for heating and holding the substrate 1 at an arbitrary temperature and a control thermocouple 5 for measuring the substrate temperature are provided at positions facing the back surface of the substrate 1. The heat source 2 and the control thermocouple 5 are respectively connected to the power source 3 and the temperature controller 4. A solid source molecular beam cell 7 and a cracking cell 6 are placed at positions facing the surface of the substrate 1.

A solid source molecular beam cell 7 is filled with a solid group III raw material 8 which is a thin group III raw material, and is heated to an arbitrary temperature and evaporated and then supplied to the substrate 1. The cracking cell 6 is connected to a cylinder (not shown) filled with a gaseous group V raw material, which is a group V thin film raw material, and the gaseous group V raw material is introduced into the cracking cell 6 from the cylinder. It is heated to an arbitrary temperature in the cracking cell 6, decomposed, and then supplied to the substrate 1. Each solid source molecular beam cell 7 and cracking cell 6 is provided with shutters 6a and 7a, respectively.

The heating of the substrate 1 or the holding of the substrate temperature are performed in the following procedure. A desired substrate temperature is set in advance in the temperature controller 4. Substrate 1 measured with control thermocouple 5
Is input to the temperature controller 4, the difference from the desired substrate temperature set in the temperature controller 4 is calculated, and the amount of electric power required to reach or hold the desired substrate temperature is supplied from the power source 3 to the heat source 2 Supply to. The heat source 2 supplied with electric power generates heat,
It emits radiant heat. The substrate 1 absorbs the radiant heat emitted from the heat source 2, and the substrate temperature rises or is maintained at a desired substrate temperature. The substrate temperature is adjusted by repeating this procedure.

By the way, the growth of a semiconductor thin film such as a III-V group compound semiconductor thin film by the conventional method has been carried out in the following steps.

First, the shutter 6a is opened to supply the group V raw material to the substrate 1, and the substrate temperature is heated to a predetermined temperature in accordance with the procedure described above to remove the oxide on the substrate surface. Next, the substrate temperature is set to a desired temperature for growing the thin film by the temperature controller 4 (hereinafter referred to as initial growth temperature), and the temperature is maintained in the above-described procedure. Generally, the growth temperature of the thin film is lower than the temperature at which the oxide is removed. After this, open the shutter 7a
The Group III raw material is supplied to the substrate, and the Group III-V thin film is grown for a predetermined time. During the growth of the III-V thin film, the initial growth temperature set in the temperature controller 4 is kept constant throughout. After that, the shutters 7a and 6a are sequentially closed to close the group III raw material and the V
The supply of the group raw material to the substrate 1 is stopped, and the growth of the III-V group thin film is completed.

[0008]

However, in the method of forming a thin film according to the conventional method, the surface temperature during thin film growth is
The surface of the thin film is heated by the radiant heat from the solid source molecular beam cell or cracking cell, causing a problem of abnormal rise.

FIG. 10 shows the I on the InP substrate according to the conventional method.
When forming a heterostructure thin film consisting of an nGaAs thin film and an InP thin film, the temperature of the growing thin film surface measured by a radiation thermometer placed at a position facing the substrate surface and the back surface of the InP substrate measured by a control thermocouple. The growth time dependence of the temperature was shown. The temperature of the backside of the substrate measured by the control thermocouple is maintained at the temperature at the start of growth even after the start of growth, but the temperature of the surface of the InGaAs thin film during growth measured by the radiation thermometer is The initial growth temperature has risen to 512 ° C., which is 52 ° C. higher than 460 ° C. It is also seen that this temperature increase almost progresses during the growth of the InGaAs thin film. InGaAs thin film is more In
The reason why the temperature of the thin film surface rises significantly with respect to the P thin film is
It is considered that the nGaAs thin film and the InP thin film have different light absorption (hereinafter referred to as radiation absorption) characteristics. That is, since the InGaAs thin film has a property of efficiently absorbing the radiant heat from the solid source molecular beam cell or the cracking cell than the InP thin film, the surface temperature of the InGaAs thin film abnormally increased.

FIG. 11 shows InG similarly grown by the conventional method.
In of a heterostructure thin film composed of an aAs thin film and an InP thin film
The sketch which observed the P thin film surface by the Nomarski differential interference microscope is shown. Many surface defects appear due to the lack of phosphorus on the surface. The density of this defect is 1
The number was about 100 to 200 per cm ² .

FIG. 12 shows InG similarly grown by the conventional method.
In of a heterostructure thin film composed of an aAs thin film and an InP thin film
The sketch which observed the InGaAs thin film surface after selectively removing only P thin film using hydrochloric acid type etchant by the Nomarski differential interference microscope is shown. InGaAs
No defects caused by arsenic deficiency appear on the surface of the thin film.

The following phenomenon can be considered as the reason why the surface defects caused by the phosphorus deficiency occur only in the InP thin film.

Phosphorus has a much higher vapor pressure than arsenic,
It is also a material with extremely low adhesion efficiency. In addition, the growth temperature range of the InP thin film that can obtain a high quality InP thin film by the GSMBE method is 450 ° C to 490 ° C. From these, the above-mentioned thin film surface temperature after the growth of the InP thin film is 512
Since the growth temperature of the InP thin film is too high, the re-evaporation of phosphorus is presumably accelerated during the growth of the InP thin film. Therefore, during growth of the InP thin film, the absolute amount of phosphorus taken in on the surface of the thin film is insufficient, or once taken in, it is evaporated again. As a result In
It is considered that the absolute amount of phosphorus required for forming the P thin film was insufficient, and many surface defects were caused by the lack of phosphorus.

FIG. 13 shows an undoped InGaAs thin film grown according to the conventional example and beryllium of 5 × 10 ¹⁹ / c.
of m ³ doped superlattice structure obtained by stacking InGaAs thin films alternately with the results of measuring the distribution in the depth direction of the element a secondary ion mass spectrometer. The solid line showing the beryllium concentration in the thin film is tailed to the undoped InGaAs thin film region. This result shows that in the thin film forming method according to the conventional method, beryllium is internally diffused from the beryllium-doped InGaAs thin film layer to the undoped InGaAs thin film layer during its growth.

From the above results, in the semiconductor thin film forming means according to the conventional method, there occurs a phenomenon in which the surface temperature of the thin film in which the growth actually progresses abnormally rises. As a result, it is clear that surface defects and internal diffusion of elements in the thin film occur on the surface of the grown semiconductor thin film.

As described above, V is formed on the surface of the thin film.
Needless to say, it is impossible to make electronic devices and optical devices if surface defects occur due to the lack of a group. Further, the internal diffusion of the element as a dopant has a great influence on the characteristics of electronic devices and optical devices. Among them, the diffusion of a dopant in a hetero-bipolar transistor (hereinafter abbreviated as HBT) is one of the causes of causing significant deterioration of device characteristics such as current gain and operating speed. Further, in this description, only the growth of a heterostructure thin film composed of an InGaAs thin film and an InP thin film is mentioned, but the same problem is caused by, for example, InGaP, G
It also occurs during the growth of thin films or heterostructure thin films of other materials such as aAs, ZnS, ZnSe.

The present invention is to eliminate the above problems,
In particular, in a method of growing a superlattice heterostructure device such as HBT, it is to provide a means for growing a high quality thin film, particularly a heterostructure thin film, without defects and diffusion.

[0018]

[Means for Solving the Problems] After removing the oxide on the substrate while irradiating the substrate with a group V source, the substrate temperature is set in a temperature controller at an initial growth temperature at which a high quality thin film can be obtained. After that, the supply of the group III raw material is started and the growth of the group III-V thin film is started. The surface temperature of the growing III-V thin film is measured by a radiation thermometer, and when the temperature reaches a predetermined temperature which is the upper limit of the growth temperature to obtain a high quality thin film, or the surface temperature of the thin film In synchronization with the change, gradually adjust the substrate temperature setting value of the temperature controller.

[0019]

[Function] By adjusting the substrate temperature setting value of the temperature controller according to the temperature change of the thin film surface during growth, even the heterostructure thin film composed of different thin films having different radiation absorption characteristics can be grown. It is possible to keep the surface temperature of the thin film within the growth temperature range where a high quality film can be obtained. Further, the predetermined temperature of the thin film surface, which is a guide for adjusting the substrate temperature set value of the temperature controller, is a temperature below the upper limit of the growth temperature at which a high quality film can be obtained. Since this suppresses an abnormal rise in the temperature of the thin film surface, the re-evaporation rate during the growth of the elements with high vapor pressure and low deposition efficiency that compose the thin film becomes appropriate, which leads to the formation of defects and diffusion. An extremely high quality thin film or heterostructure thin film can be realized.

[0020]

The method for growing a heterostructure thin film according to the present invention will be described below with reference to an embodiment of growing a heterostructure thin film composed of an InGaAs thin film and an InP thin film on an InP substrate.

FIG. 1 shows a chart for changing the substrate temperature set value of the temperature controller during the growth process of various thin films according to the method for growing a heterostructured thin film according to the present invention.

FIG. 2 is a schematic diagram of the GSMBE apparatus used in this embodiment. In FIG. 2, the same reference numerals as those of the conventional GSMBE device (FIG. 9) indicate the same parts.

As the thin film raw material, solid In12 and solid Ga10 as group III raw materials, and arsine (A) as group V raw material.
sH ₃ ) 16 and phosphine (PH ₃ ) 17 are used.

InP substrate 20 for growing a heterostructure thin film
Are placed in a growth chamber 13 maintained in a vacuum atmosphere.
Solid source In12 and solid Ga10 are solid source molecular beam cells 1
1 and 9 are filled, heated to an arbitrary temperature and evaporated, and then supplied to the InP substrate 20. Arsine 16 and phosphine 17 are filled in cylinders 18 and 19, respectively.
Arsine 16 and phosphine 17 are valve 16 respectively
a, introduced into the cracking cell 6 via the valve 17a, heated to an arbitrary temperature in the cracking cell 6 and decomposed, and then supplied to the InP substrate 20 in the form of As ₂ and P ₂ . Each solid source molecular beam cell 9, 11 and cracking cell 6 is provided with a shutter 6a, 9a, 11a, respectively.

Using the GSMBE apparatus of FIG. 2, a heterostructure thin film composed of an InGaAs thin film and an InP thin film according to the substrate temperature change chart shown in FIG. 1 is formed by the following procedure.

First, the valve 17a and the shutter 6a are opened I
While irradiating the nP substrate 20 with P ₂ ,
The oxide on the InP substrate 20 is removed by heating to 00 ° C. After that, the temperature of the InP substrate 20 is changed to 460 ° C., which is the growth temperature of the InGaAs thin film, and the temperature is maintained for a while. After this, the valve 17a is closed and the valve 16a is opened A
The InP substrate 20 is irradiated with s ₂ and then the shutters 9a,
11a is opened, In and Ga are irradiated on the InP substrate 20, and I
The growth of the nGaAs thin film is started. The temperature of the surface of the growing thin film is measured by a radiation thermometer 14 placed at a position facing the InP substrate 20 via a transmission window 15. The above 5
The values of 00 ° C. and 460 ° C. are the values of the temperature of the surface of the InP substrate 20 measured by using the radiation thermometer 14 when the shutters 6a, 9a, 11a of the respective cells are closed. The value of indicates the value measured by the radiation thermometer 14. The reason for closing the shutters 6a, 9a and 11a of each cell when measuring the temperature of the surface of the InP substrate 20 or the thin film using the radiation thermometer 14 is as follows. Generally, when measuring the temperature of an object to be measured, such as a semiconductor, using a radiation thermometer, in order to avoid malfunction of the radiation thermometer (measurement error), the back light source such as a fluorescent lamp or filament bulb that reflects on the semiconductor surface is shielded. Means are needed. GS
In the case of MBE, the cells that are heated to a high temperature and red-heated serve as the back light source. Therefore, in order to accurately measure the temperature of the thin film surface, the shutters 6a, 9a and 11a of the cells must be closed. The surface temperature of a growing InGaAs thin film absorbs radiant heat emitted from the cell more efficiently than InP because the radiant absorption coefficient of InGaAs is different from InP, and rises as the film thickness increases as the growth progresses. It is known from previous experiments. Generally GSMB
In the E method, a high quality InGaAs thin film is obtained when the growth temperature is grown in the range of 450 ° C to 510 ° C. Therefore, the temperature of the InGaAs thin film surface during growth is
By controlling the substrate temperature set value input in advance to the temperature controller 4 so that it is always within the above temperature range during the growth, high-quality InGaAs
A thin film is obtained. In this example, when the surface temperature of the InGaAs thin film reached 480 ° C., the substrate temperature set value of the temperature controller 4 was changed to a value 10 ° C. lower than the initial growth temperature.
The surface temperature of the InGaAs thin film after changing the set value is 4
The temperature decreased to 62 ° C. and increased again as the growth of the InGaAs thin film proceeded. The surface temperature of the InGaAs thin film of 480 ° C., which is a guide for changing the initial growth temperature of the temperature controller 4, is
The temperature is a temperature at which the dopant does not diffuse internally even when the InGaAs thin film is grown while being doped with an element serving as a dopant, for example, silicon or beryllium. By repeating the above procedure during the growth of the InGaAs thin film, the surface temperature of the InGaAs thin film is controlled to 460 ° C or higher and 480 ° C or lower. After growing the InGaAs thin film for a predetermined time while taking the above steps, the shutters 9a and 11a are closed to stop the growth of InGaAs. After this, the valve 16a is closed and the valve 17
A is opened and P ₂ is irradiated toward the InP substrate 20, and then the shutter 11a is opened to grow an InP thin film for a predetermined time. The surface temperature of the InP thin film also rises as the thickness of the InGaAs thin film increases as the growth proceeds, similar to the growth of the InGaAs thin film. In this embodiment, the surface temperature of the InP thin film is 473 at maximum.
It rose to ℃. Since this temperature is within the range of 450 ° C. to 490 ° C., which is the growth temperature at which the above-mentioned high quality InP thin film can be obtained, the temperature controller 4 is used during the growth of the InP thin film.
The setting value of the substrate temperature was not changed.

FIG. 3 shows a change chart of the substrate temperature set value in the growth process of the second embodiment of the present invention. InGa
The same steps as in the first embodiment are taken until the growth of the As thin film is started. The rate of increase in the surface temperature of the growing InGaAs thin film was calculated from the statistics of the experimental results obtained so far.
It has been found that the film thickness of the s thin film increases by about 1 ° C. as the film thickness increases from 20 nm to 30 nm. In other words InGaAs
By growing the InGaAs thin film while lowering the substrate temperature setting value of the temperature controller 4 by 0.1 ° C. within the time when the thin film of 2 nm or 3 nm is formed, the temperature of the thin film surface during the growth is increased. It is possible to maintain the temperature at the start. In this example, the growth rate of the InGaAs thin film was 16.8 nm per minute, and InGaA
s The rate of rise of the surface temperature of the thin film is 25 n on average
As the temperature increases by 1 ° C per m, 0.7 per minute
The substrate temperature set value of the temperature controller 4 was changed at a rate of decrease of ° C. During the growth of the InGaAs thin film, the substrate temperature set value of the temperature controller 4 was continuously changed at the above-mentioned reduction rate. The steps after the formation of the InGaAs thin film are the same as those in the first embodiment.

FIG. 4 is a set temperature change chart of the substrate temperature in the growth process of the third embodiment of the present invention. InGa
The same steps as in the first embodiment are taken until the growth of the As thin film is started. The substrate temperature is not changed during the growth of the InGaAs thin film, but is performed at the initial growth temperature for a predetermined time. I
The surface temperature of the nGaAs thin film after growth is 508 ° C.
Met. After that, the shutters 9a and 11a are closed and InGa
Stop the growth of As. At this time, the temperature of the thin film surface is 460
The substrate temperature set value of the temperature controller 4 is changed so that the temperature becomes higher than or equal to 480 ° C. During this period, the As ₂ irradiation toward the InP substrate 20 is continued. When the temperature of the thin film surface is maintained at 460 ° C. or higher and 480 ° C. or lower by repeating the above procedure, the valve 16a is closed, the valve 17a is opened, P ₂ is irradiated toward the InP substrate 20, and then the shutter 11a is opened to open the InP thin film. Growth for a predetermined time. According to the present embodiment, since the substrate temperature setting value of the temperature controller 4 is changed at the interface between the InGaAs thin film and the InP thin film during the growth interruption, a great effect can be obtained in terms of flattening the interface.

FIG. 8 shows a second embodiment of the gas source MBE device according to the present invention. 8, the same reference numerals as those of the gas source MBE device of FIG. 2 indicate the same parts.

The transmission window 15 for the radiation thermometer 14 is provided with a shutter 15a to prevent fogging due to vapor deposition of the thin film raw material on the transmission window 15. Each shutter 6a, 9a,
The shutter drive system 21 controls the opening / closing operation of the shutters 11a and 15a. The temperature control system 22 is a radiation thermometer 1
4 and the temperature controller 4. This temperature control system 2
2 stores the emissivity of a plurality of desired thin films,
It is possible to set the emissivity of any desired thin film to the radiation thermometer 14 at any time. Control of the thin film surface temperature according to the first embodiment using the GSMBE apparatus of FIG. 8 is performed by the following procedure. Incidentally, the control of the thin film surface temperature based on the other second and third embodiments is also performed by the same procedure as described below.

First, the emissivity of the InP substrate 20 is set in the radiation thermometer 14 from the temperature control system 22. After this, InG
The above steps are taken until the aAs thin film is grown. In
Simultaneously with or before the growth of the GaAs thin film, the emissivity of the radiation thermometer 14 is adjusted from the temperature control system 22 to InGaAs.
Change to the emissivity of the thin film. I during InGaAs thin film growth
The temperature of the nGaAs thin film surface is measured by the shutter control system 2
1, the shutter 15a of the transmission window 15 for the radiation thermometer 14 is opened, and at the same time, the shutters 6a, 9a of the cell,
11a is closed in the order of the cell shutters 9a and 11a of In12 and Ga10 which are group III raw materials, and then the shutter 6a of the cracking cell 6 for supplying the group V raw material, and the radiation thermometer 14 while keeping this state for an arbitrary time. InGaAs
The temperature of the thin film surface is measured. The temperature of the surface of the InGaAs thin film measured by the radiation thermometer 14 is measured by the temperature control system 22 as needed.
Sent to. After measuring the surface temperature of the InGaAs thin film for an arbitrary time, the shutter 15a of the transmission window 15 is closed again by the shutter control system 21, and V is synchronized with this.
Shutter 6a of cracking cell 6 for group materials, then
The cell shutters 9a and 11a for In12 and Ga10, which are group III raw materials, are opened in this order. As described above, the measurement time of the surface temperature of the InGaAs thin film is arbitrary, but there is no problem, but the time during which the re-evaporation of arsenic from the surface of the InGaAs thin film does not affect the quality of the InGaAs thin film sufficiently. desirable. In this embodiment,
The measurement time of the surface temperature of the InGaAs thin film is 5 seconds. The above procedure is repeated multiple times during the growth of the InGaAs thin film to measure the surface temperature of the InGaAs thin film during the growth.
When the surface temperature of the InGaAs thin film reaches 480 ° C,
The temperature control system 22 changes the substrate temperature set value of the temperature controller 4 so that the surface temperature of the InGaAs thin film is in the range of 460 ° C. or higher and 480 ° C. or lower. By repeating the above procedure, the In
The surface temperature of the GaAs thin film is exactly 460 ° C or higher and 480
Controlled within a certain range below ℃ with extremely high precision. After that, the above-mentioned steps are taken to continue the growth of the InP thin film. Simultaneously with or before the growth of the InP thin film, the emissivity of the InGaAs thin film set in the radiation thermometer 14 from the temperature control system 22 is changed to the emissivity of the InP thin film. During the growth of InP thin film, InGaA
s The InP thin film surface temperature during growth is measured by the same procedure as the thin film surface temperature measurement.

Although the thin film surface temperature is controlled by using both the radiation thermometer 14 and the control thermocouple 5 in this embodiment, the radiation thin film surface temperature is controlled by using only the radiation thermometer 14. May be controlled. In that case, the following measures are necessary. Generally, the radiation thermometer 14 has a limited temperature measurement range. The lower limit of measurement of the radiation thermometer 14 used in this example is 400 ° C. For this reason, when heating the substrate until it reaches the above-mentioned temperature, it is necessary to appropriately control the amount of electric power supplied from the power source 3 to the heat source 2 to suppress a rapid temperature rise of the substrate.

FIG. 5 shows InGaA grown on an InP substrate according to the first embodiment using the GSMBE apparatus of FIG.
In a heterostructure thin film composed of an s thin film and InP, I
It is a sketch of observing the surface of the nP thin film with a Nomarski differential interference microscope. It can be seen that the surface morphology, which has been a problem in the past, due to the phosphorus deficiency due to the abnormal increase in the surface temperature of the growing thin film does not appear at all, and the surface morphology is in an extremely good state.

FIG. 6 shows that in the same heterostructure thin film, In
Selectively remove only P thin film with hydrochloric acid etchant
It is a sketch of observing the surface of an aAs thin film with a Nomarski differential interference microscope. As with the surface of the InP thin film, no surface defects were observed on the surface of the InGaAs thin film, indicating that good morphology was obtained.

FIG. 7 shows undoped InGaAs grown according to the second embodiment by using the GSMBE apparatus shown in FIG.
It is the result of measuring the distribution state of the element in the depth direction of the superlattice structure in which the thin film and the InGaAs thin film doped with 5 × 10 ¹⁹ / cm ^{3 of} beryllium were alternately stacked by the secondary ion mass spectrometer. Beryllium-doped InG produced in the same-structure superlattice structure grown by the conventional method
No beryllium was diffused from the aAs thin film layer to the undoped InGaAs thin film layer, and an excellent doping profile was obtained.

As described above, according to the present invention, in the formation of a thin film, particularly a heterostructure thin film composed of a plurality of thin films having different radiation absorptances, the temperature of the thin film surface during the growth is always kept exactly constant. Alternatively, since it is maintained within a certain range with high accuracy, a high-quality heterostructure can be obtained without causing surface defects or internal diffusion of its constituent elements due to the deficiency of group V elements due to an abnormal rise in the surface temperature of the thin film during growth. Clearly, thin films are readily obtained, facilitating the fabrication of superlattice heterostructure devices such as HBTs.

Needless to say, the same effect can be obtained even if the set value of the substrate temperature is changed by a method combining a plurality of embodiments described in the present invention. Further, in this embodiment, only the formation of the heterostructure thin film composed of the InGaAs thin film and the InP thin film on the InP substrate is described for the sake of description, but other material systems such as GaAs and InGaP for III-V group compound semiconductors are described. , II-VI group compound semiconductors can be applied to the growth of a thin film of ZnS, ZnSe, etc., or a heterostructure thin film composed of a combination thereof, and the same effect as that of this embodiment can be obtained. Of course.

[0038]

The thin film formed by the thin film forming method according to the present invention,
In particular, if a method for forming a heterostructure thin film is adopted, it is possible to easily obtain a high quality heterostructure thin film without defects and internal diffusion.
It becomes easy to create high-performance devices such as.

[Brief description of drawings]

FIG. 1 is a chart for changing a substrate temperature set value during thin film growth showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a gas source MBE device used in an example of the present invention.

FIG. 3 is a chart of changing a substrate temperature set value during thin film growth showing a second embodiment of the present invention.

FIG. 4 is a chart for changing a substrate temperature set value during thin film growth showing a third embodiment of the present invention.

FIG. 5 is a sketch diagram of Nomarski differential interference microscope observation of the InP thin film surface of the InGaAs / InP heterostructure thin film grown according to the present invention.

FIG. 6 is a sketch drawing of Nomarski differential interference microscope observation of an InGaAs thin film of an InGaAs / InP heterostructure thin film grown according to the present invention.

FIG. 7: Beryllium-doped InG grown according to the present invention
It is a figure which shows the secondary ion mass spectrometry result of the depth direction of an aAs / InGaAs superlattice structure.

FIG. 8 is a second gas source MB used in the example of the present invention.
It is a block diagram of an E apparatus.

FIG. 9 is a layout view of a main part of a gas source MBE device.

FIG. 10: InGaAs / In grown according to the conventional method
Temperature change during growth of P heterostructure thin film

FIG. 11: InGaAs / In grown according to the conventional method
Sketch drawing of Nomarski differential interference microscope observation of InP thin film of P heterostructure thin film

FIG. 12: InGaAs / In grown according to the conventional method
It is a sketch drawing of Nomarski differential interference microscope observation of the InGaAs thin film of P heterostructure thin film.

FIG. 13: Beryllium-doped I grown according to conventional method
It is a figure which shows the secondary ion mass spectrometry result of the nGaAs / InGaAs superlattice structure of the depth direction.

[Explanation of symbols]

1 ... Substrate, 2 ... Heat source, 3 ... Power supply, 4 ... Temperature controller, 5 ...
Control thermocouple, 6 ... Cracking cell, 6a ... Shutter, 7 ... Solid source molecular beam cell, 7a ... Shutter, 8 ...
Solid III, 9 ... Solid source molecular beam cell, 9a ... Shutter, 10 ... Solid Ga, 11 ... Solid source molecular beam cell, 1
1a ... Shutter, 12 ... Solid In, 13 ... Growth chamber, 14
... radiation thermometer, 15 ... transparent window, 15a ... transparent window shutter 16 ... arsine, 16a ... valve, 17 ... phosphine,
17a ... Valve, 18 ... Cylinder, 19 ... Cylinder, 20 ...
InP substrate, 21 ... Shutter drive system, 22 ... Temperature control system.

Front page continuation (72) Inventor Kiyoshi Ouchi 1-280, Higashi Koigokubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (12)

[Claims] 1. A desired thin film comprising a group IV element, a group III-V element or a group II-VI element of the Periodic Table of Elements or a combination thereof is formed on the surface of a substrate which is kept at an arbitrary temperature in a vacuum atmosphere. In the method for forming a thin film by supplying a component of the desired thin film or a gas containing the component through a cell, in the process of forming the desired thin film, after forming the desired thin film, A method for forming a thin film, comprising a step of reducing the temperature at a predetermined reduction rate at least once. 2. A method of forming a thin film, wherein the step of reducing the temperature of the substrate according to claim 1 is performed continuously and continuously while forming the desired thin film. 3. The thin film formation according to claim 1, wherein the predetermined reduction rate is 1 ° C./20 nm or more and 1 ° C./30 nm or less with respect to a desired thin film thickness formed on the substrate. Method. 4. A method for forming a thin film, wherein the desired thin film according to claim 1 is a thin film in which the desired thin film is doped with an element functioning as a dopant. 5. A thin film forming method, wherein the desired thin film according to any one of claims 1 to 4 is a thin film containing at least arsenic as an element constituting the desired thin film. 6. The desired thin film of claim 5 is InGaAs
And a thin film forming method. 7. A heterostructure in which the desired thin film according to any one of claims 1 to 4 comprises one thin film containing at least arsenic as an element constituting the desired thin film and the other thin film containing at least phosphorus as its constituent element. A method for forming a thin film, which is a thin film. 8. The heterostructure thin film according to claim 7,
The thin film forming method according to claim 1, wherein the thin film forming method is performed only for forming one thin film containing at least arsenic as a constituent element of the heterostructure thin film. 9. The heterostructure thin film according to claim 7, wherein the heterostructure thin film is InP.
And a heterostructure thin film composed of InGaAs. 10. The heterostructure thin film according to claim 7, wherein the heterostructure thin film comprises a base and an emitter in a heterobipolar transistor,
A method for forming a thin film, which is a collector and a base. 11. A vacuum container maintained in a vacuum atmosphere,
The substrate according to claim 1, a heat source for heating the substrate to an arbitrary temperature, a heat source for supplying electric power to the heat source, a temperature controller for controlling the supply amount of the electric power, and a position facing the substrate. The cell according to claim 1, a shutter for blocking a gas containing the desired thin film component or a component supplied from the cell to the substrate, a transmission window, and the surface of the substrate through the transmission window or the transmission window. In a thin film forming apparatus equipped with a radiation thermometer for measuring the temperature of the surface of a desired thin film as described above, when forming a heterostructure thin film in which the desired thin film is composed of two or more different thin films, A thin film forming apparatus, wherein the emissivity is set to the emissivity of each thin film forming the heterostructure thin film in-situ when each thin film is formed. 12. The thin film forming apparatus according to claim 11, wherein the desired thin film is synchronized with an opening / closing operation of a shutter for blocking a component of the desired thin film or a gas containing the component supplied from the cell to the substrate. Alternatively, the thin film forming apparatus is characterized in that the surface temperature of the substrate is measured by the radiation thermometer.