JPH0669131A - Formation of semiconductor thin film - Google Patents

Abstract

PURPOSE:To obtain an Si-Ge thin film in which crystal defect and dislocation are suppressed by heating a silicon substrate at a constant rate in a group IV based hydrogen gas atmosphere containing silicon, introducing group IV based hydrogen gas containing Ge upon transition through a specific temperature, and then keeping a specific temperature range. CONSTITUTION:Group IV based hydrogen gas containing silicon is fed into a reaction tube. Surface temperature of a substrate is then risen quickly at an appropriate rate in the range of 50-200 deg.C/sec. When the surface temperature of the substrate reaches an appropriate temperature in the range of 500-600 deg.C, a valve is opened to feed group IV based hydrogen gas containing germanium into the reaction tube. Surface temperature of the substrate is then set in the range of 700-800 deg.C. Consequently, an Si-Ge thin film 204 having the same orientation as the surface of the substrate is grown by about 2000Angstrom on the silicon substrate 200.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor thin film forming method, and more particularly to a group IV semiconductor epitaxial thin film forming method.

[0002]

2. Description of the Related Art There is an epitaxial growth technique as a method for forming a silicon-germanium (Si-Ge) thin film on a silicon (Si) substrate.

As a thin film forming technique, a molecular beam epitaxial method (also called MBE method) and a chemical vapor deposition method (also called CVD method) are usually used.

The MBE method has the advantage of not disturbing the impurity distribution of the formed thin film because the crystal can be grown at a low temperature. The MBE method is a method in which a solid source is used as a raw material to generate a molecular beam and the molecular beam is applied to a substrate in a film forming chamber to grow crystals. Since the film formation chamber is maintained in an ultrahigh vacuum (10 ⁻⁹ to 10 ⁻¹⁰ Torr), molecules that cannot be captured by the substrate among the component elements that reach the substrate in the form of a beam are carried away by the vacuum system. Only fresh molecular beams reach the substrate surface at all times.
However, in the MBE method, the source capacity of the electron gun evaporator is limited and the growth rate is slow, resulting in 1000 A ° (however, A °
It has been difficult to rapidly grow a single crystal film having a thickness of about Å.

On the other hand, the CVD method using a gas source uses S
It is also used for forming a thin film of i-Ge. This method is a method of depositing thin films such as an oxide film, a nitride film, and a crystal film on a wafer by a chemical reaction at high temperature. Normal pressure C
There are two methods called the VD method and the low pressure CVD method. The latter low-pressure CVD method is also used for forming a Si-Ge thin film, and uses silane (SiH ₄ ) gas and germane (Ge).
It is a method of growing crystals on a substrate by utilizing reactions such as thermal decomposition, hydrogen (H ₂ ) reduction, and substitution by heat treatment in an atmosphere of H ₄ ) gas or in a reduced pressure atmosphere. . In the atmospheric pressure CVD method, since the growth is performed under the atmospheric pressure, the number of gas molecules is large and the crystal growth rate is high. However, there is a problem that the film thickness is not uniform as compared with the low pressure CVD.

For this reason, it is advantageous to form the semiconductor thin film by using the low pressure CVD method which is relatively easy to form a thin film.

[0007]

However, since the above-described low pressure CVD method and atmospheric pressure CVD method require the thermal decomposition of the raw material gas, the substrate is exposed to a higher temperature than the MBE method. Further, since the method of promoting the crystal growth by utilizing the chemical reaction generation between the source gas and the substrate surface, the film quality of the grown thin film greatly depends on the state of the substrate surface. Therefore, in order to remove the oxide film even after introducing the substrate into the reaction furnace after sufficiently cleaning the substrate in the pretreatment step,
For example, it was necessary to perform heat treatment in hydrogen gas at a high temperature of 1000 ° C. or higher. It is disclosed in Document I that dislocations are likely to be generated by heat treatment at such a high temperature (Document I “VLSI LSI Dictionary” Science Forum, P558-559, 1988).

Therefore, if a crystal is grown on the surface of the substrate at a relatively low heating temperature, the crystal is formed under the influence of the oxide film remaining on the surface of the substrate and the contaminants adhering to the surface. Therefore, there is a problem that crystal defects or dislocations are generated inside the crystal (see FIG. 6A).

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for forming a semiconductor thin film which does not require a high temperature heat treatment and which forms a Si-Ge thin film with few crystal defects and dislocations. To provide.

[0010]

In order to achieve this object, according to the first semiconductor thin film forming method of the present invention, heat treatment is carried out in a reaction furnace to form a group IV semiconductor crystal thin film on a silicon substrate. In the method of forming (1), (a) 50 ° C./sec to 2 in a Group IV-based hydrogen gas atmosphere containing silicon.
A step of heating and heating the silicon substrate at a heating rate determined within a range of 00 ° C./sec; and (b) heating the silicon substrate at a heating rate of 500 ° C. to 60 ° C.
After introducing a group IV hydrogen gas containing germanium when passing a temperature defined in the range of 0 ° C., the heating temperature of the silicon substrate is kept at 700 ° C. to 800 ° C.
It is characterized in that the step (a) and the step (b) are continuously performed, including a step of forming a Ge thin film.

Further, in carrying out the present invention, it is preferable to mix an inert gas containing hydrogen chloride with the group IV hydrogen gas containing silicon used in the step (a).

According to the second semiconductor thin film forming method of the present invention, in the method for forming a group IV semiconductor thin film on a silicon substrate by performing heat treatment in a reaction furnace,
(1) A step of chemically treating the substrate to form an oxide film having a film thickness of about 10 A ° (angstrom), and (2) a mixed gas atmosphere of a group IV hydrogen gas containing silicon and germanium. After switching, the silicon substrate is heated and heated at a predetermined heating rate within a range of 25 ° C / sec to 50 ° C / sec, and then the heating temperature is maintained at a predetermined temperature within a range of 700 ° C to 800 ° C. The method is characterized by including a step of forming a Si-Ge thin film.

Further, preferably, when the substrate is chemically treated in the step (1), an aqueous solution containing hydrogen peroxide (H ₂ O ₂ ) is preferably used.

[0014]

According to the first semiconductor thin film forming method of the present invention described above, the ascending temperature determined within the range of 50 ° C./sec to 200 ° C./sec in the group IV hydrogen gas atmosphere containing silicon (Si). The silicon substrate is heated and heated at a temperature rate. Since the heating and heating are performed rapidly in this manner, impurities and oxide films and the like attached to the substrate after cleaning the substrate are removed by the reducing action of the radical reaction.

Further, the heating temperature is 500 while the heating temperature is raised.
A group IV hydrogen gas containing germanium is introduced into the furnace when a predetermined temperature within the range of ℃ to 600 ℃ is passed. Since the heating temperature is a relatively low temperature, which is a suitable temperature within the range of 500 ° C. to 600 ° C., a Group IV hydrogen gas containing germanium is introduced at this temperature to grow a silicon crystal by silane (SiH ₄ ) gas. Can be suppressed.

Further, since the reducing action by the silane (SiH ₄ ) gas is promoted, the oxide film and contaminants on the substrate surface are removed.

Next, the heating temperature is set to 700 ° C. in a Group IV hydrogen gas atmosphere containing silicon and germanium.
The temperature is kept at 800 ° C. to form a Si—Ge thin film.

Si formed by the method of the present invention described above
-The Ge thin film is substantially free of impurities and oxide film,
In addition, since it is not necessary to expose the heating temperature to a high temperature of 1000 ° C. or higher as in the conventional case, it is possible to substantially form a Si—Ge thin film having a uniform film quality with few crystal dislocations and crystal defects. By mixing an inert gas containing hydrogen chloride (HCl) in the above-described Group IV hydrogen gas atmosphere containing silicon, the impurities and oxide film attached on the substrate can be removed more efficiently.

Further, according to the second semiconductor thin film forming method of the present invention, at the stage of cleaning the substrate, the substrate may be chemically treated to form an oxide film of about 10 A ° in advance. Under such a condition, it is possible to suppress the natural oxide film formed during the transfer from the cleaning process to the reaction furnace. In a mixed gas atmosphere of a group IV hydrogen gas containing silicon and germanium, heating is slowly performed at a heating rate of 25 ° C./sec to 50 ° C./sec.
The temperature is kept within the range of 00 ° C. for 60 seconds to form a Si-Ge thin film. In this temperature rising process, the oxide film, contaminants and the like formed in advance are removed by the reducing action of the radical reaction. Since the Si-Ge thin film can be formed in this manner, a Si-Ge thin film having a uniform film quality with few crystal dislocations and crystal defects can be substantially obtained.

[0020]

Embodiments of the present invention will now be described with reference to the drawings. It should be noted that each of the drawings merely schematically shows the dimensions, shapes, and positional relationships of the respective constituent components to the extent that these inventions can be understood. Further, in the following description, specific materials and conditions are used for description, but these materials and conditions are merely one preferred example, and thus the present invention is not limited thereto.

First, Si used in the embodiment of the present invention.
An apparatus for forming a Ge single crystal thin film will be described.

FIG. 3 is a diagram schematically showing the overall structure of an apparatus for explaining an embodiment of the present invention. This thin film forming apparatus includes a reaction furnace 11 (also referred to as a chamber) made of quartz, and has a structure in which a substrate 15 on a substrate support 13 in the reaction furnace 11 can be taken in and out. Further, a heating unit 12 is provided outside the reaction furnace 11 so as to surround the periphery of the reaction furnace. This heating unit 12
Is configured by using any suitable constituent means such as an infrared lamp.

The heating unit 12 at this time is preferably installed using a plurality of lamps so that the substrate 15 can be heated uniformly.

In the vicinity of the substrate 15, temperature measuring means 14 for measuring the surface temperature of the substrate, for example, a thermocouple is provided.

Exhaust means for evacuating the inside of the reaction furnace 11 will be described below.

The reaction furnace 11 is equipped with exhaust means 21 and 22 for exhausting vacuum, and the automatic opening / closing valve 2
It is connected to the reaction furnace 11 via 4, 25, 26, 27, 28, 29 and 30. This automatic open / close valve 24
To 30 by arbitrarily opening and closing the reactor 1
The pressure within 1 can be controlled in any suitable manner. Therefore, the inside of the reaction furnace 11 can be arbitrarily and suitably maintained in a low vacuum exhaust state and a high vacuum exhaust state. Further, a vacuum gauge 34 is provided to measure the degree of vacuum at this time.

Further, this device includes a relief valve 31.
Is provided. The valve 31 is automatically opened when the pressure inside the reaction furnace 11 exceeds atmospheric pressure, for example, 760 Torr. The exhaust means 22 exhausts the gas supplied from the gas supply source (described later) into the reaction furnace 11 by opening the valve 31. The exhaust means 21 described above,
22 is composed of, for example, a diffusion pump 21 and a rotary pump 22 connected to this pump 21. At this time, the gas may be exhausted through the exhaust pipe 23 as an exhaust path.
In addition, the gauges for pressure measurement and control are
Any suitable one may be selected according to the degree of vacuum, and, for example, a pressure control conductance valve or the like may be used.

Next, the gas supply system will be described.

In the first and second embodiments, the gas supply pipe 58 having the gas supply system arranged as shown in the figure and the automatic opening / closing valve 5 are provided.
1, 52, 53, 54, 55, 56 and 57, automatic gas flow controllers 46, 47, 48, 49 and 50
It is composed by. Flow controllers and reactor 1
Gas supply connection portions (hereinafter, referred to as connection portions) 41, 42, 43, 44 and 45 are provided on the side opposite to 1. Each flow rate controller and each gas supply unit are connected. Therefore, the valves 51 to 56 are arbitrarily and appropriately selected so that a desired gas can be supplied to the reaction furnace 11 independently or adjusted to an arbitrary gas mixing ratio. In the first embodiment, hydrogen gas (H ₂ ) is used for the connecting portion 41, and silane (S) is used for the connecting portion 42.
iH ₄ ) gas, the connection part 43 is a germane (GeH ₄ ) gas, and the connection part 44 is a spare gas supply part.

First, the basic steps of the semiconductor forming method of the present invention will be described by taking a Si-Ge thin film as an example.

FIGS. 1 and 2 are curve diagrams showing a heating cycle and a gas flow for explaining an embodiment of the present invention. In the figure, the horizontal axis represents time (seconds) and the vertical axis represents temperature (° C).

First, an outline of the Si-Ge thin film forming method of the first embodiment will be described with reference to FIG.

The substrate is cleaned under suitable conditions in the substrate pretreatment step, and the substrate is introduced into a vacuum-evacuated reaction furnace. Subsequently, in a Group IV hydrogen gas atmosphere containing silicon, for example, silane (SiH ₄ ) gas, 50 ° C./sec to 2
The silicon substrate is heated and heated at an appropriate heating rate determined within the range of 00 ° C./sec (I _a flow in FIG. 1).

Subsequently, when the temperature of the surface of the silicon substrate is further increased by 500 ° C. to 600 ° C. while being heated at the same heating rate, the hydrogen gas of Group IV group containing germanium is additionally added to the SiH ₄ gas flow. To introduce. This gas is, for example, germane (GeH ₄ ) gas. Therefore, this I
I _a flow - in the process, it becomes a mixed gas atmosphere of residual silane (SiH ₄₎ germane (GeH ₄₎ was introduced into the gas and new Lata gas. Such a heating temperature of the silicon substrate in a gas atmosphere and held only between proper scheduled to the appropriate temperature determined in the range of 700 ° C. to 800 ° C. to form a Si-Ge thin film (in FIG. 1 II _a furo -).

In this embodiment, it is preferable that the holding time is 60 seconds (Ha period in FIG. 1).

Next, after the group IV hydrogen gas (mixed gas) containing silicon and germanium is exhausted, hydrogen (H ₂ ) gas is supplied to quench it to 100 ° C. In this way, a Si-Ge thin film is obtained as a semiconductor thin film on the substrate. Subsequently, the supply of hydrogen gas is stopped, the gas is evacuated in a low vacuum, an inert gas is introduced, and after reaching room temperature (25 ° C.), the substrate on which the semiconductor thin film is formed is taken out from the furnace.

Next, the outline of the method of forming the Si-Ge thin film of the second embodiment will be described with reference to FIG.

In FIG. 2, the horizontal axis represents time (second) and the vertical axis represents temperature (° C.), showing the relationship between the heating cycle and the gas flow.

An oxide film of about 10 A ° is formed in advance on the surface of the substrate under suitable conditions at the stage of the pretreatment process of the substrate.

Next, the substrate is introduced into the reaction furnace and vacuum exhaust is performed. Subsequently, a group IV hydrogen gas containing silicon and germanium, for example, a mixed gas of silane (SiH ₄ ) and germane (GeH ₄ ) is supplied to the reaction furnace.

In this gas atmosphere, 25 ° C./sec to 50 ° C. /
While heating and heating the silicon substrate at a heating rate set within the range of seconds, the silicon substrate is maintained at an appropriate temperature set within the range of 700 ° C to 800 ° C. At this time, the holding time is preferably about 60 seconds (Hb period in FIG. 2). In this step, a Si-Ge thin film as a good-quality semiconductor thin film similar to that described with reference to FIG. 1 is formed on the substrate.

Next, II _b flow in Fig - For step is omitted because it is III _a same step of the first embodiment.

Specific examples of the present invention will be described.
First, the method for forming a Si-Ge single crystal thin film of the first embodiment will be described in detail with reference to FIGS.

FIGS. 4A to 4C are process drawings for explaining the method of forming the semiconductor substrate of the first embodiment. still,
4A to 4C are cross-sectional views showing the wafer cut in the thickness direction of the silicon substrate. The following description is based on FIG.
And FIG. 4 as appropriate.

In the first embodiment, silane (SiH ₄ ) and germane (GeH ₄ ) gas are used as the source gas and the silicon substrate 200 is used as the silicon base. The main surface of the silicon substrate 200 is (100),
Of the (110) and (111) planes, it is preferable to use one type of plane or a combination of a plurality of planes. It is a substrate that is widely used at present and also Si
This is because the substrate is suitable for epitaxial growth of a Ge thin film.

In the first embodiment, the substrate is previously cleaned before the semiconductor thin film is formed. The cleaning at this time is
The natural oxide film may be removed by performing a cleaning process that is usually performed at the time of epitaxial growth. In the first embodiment, the cleaning method described below is used.

First, the substrate 200 is immersed in a sulfuric acid (H ₂ SO ₄ ) / hydrogen peroxide (H ₂ O ₂ ) aqueous solution heated to 120 ° C. for about 15 minutes. In this way, the substrate 200
An oxide film 202 of about 10 A ° is formed on the top (FIG. 4A).

Immediately thereafter, 1% by weight of hydrofluoric acid (HF) was added.
After the substrate is immersed in the aqueous solution to remove the oxide film 202, the substrate 200 is taken out of the aqueous solution and washed with pure water. Then, the substrate 200 is dried. In this pretreatment process, contaminants on the surface of the substrate are removed, and the dangling bonds of silicon atoms on the outermost surface are terminated by hydrogen atoms, so that a natural oxide film is hard to attach. However, a natural oxide film or contaminant adheres during the introduction into the reactor or in the reactor (not shown).

After the chemically treated substrate 200 is inserted into the reaction furnace 11, the inside of the reaction furnace is evacuated to a high vacuum of, for example, 1 × 10 ^-6 Torr by using the evacuation means 21 and 22. Clean inside.

Next, the valve 27 is closed and the valves 28 and 5 are
5 and 52 are not opened, and a group IV hydrogen gas containing silicon, for example, silane (SiH ₄ ) gas diluted with 10% by volume of hydrogen is supplied into the reaction furnace 11. At this time, the flow rate of silane (SiH ₄ ) is adjusted in advance so that the pressure in the reaction furnace becomes about 5 Torr.

Then, the temperature of the substrate surface is rapidly raised while measuring the measuring means 14 at an appropriate heating rate set in the range of 50 ° C./sec to 200 ° C./sec. In addition, during this temperature rising process, the natural oxide film and contaminants formed on the substrate are
It is removed by the reducing action of silane (SiH ₄ ) gas ((B) of FIG. 4).

During this temperature rising process, the temperature of the substrate surface is 5
When a suitable temperature range of about 00 ° C. to 600 ° C. is reached, the valve 53 is opened and a group IV hydrogen gas containing germanium,
For example, hydrogen diluted 1% germane (GeH ₄ ) gas is supplied into the reaction furnace.

At this time, the pressure in the reactor is, for example, 6 To
It is preferable to adjust the gas flow rate of germane in advance so that the pressure is reduced to about rr.

Heating is continuously performed in such a gas atmosphere, and the temperature is set so that the heating temperature of the substrate surface becomes a value within the range of 700 ° C to 800 ° C. The holding time is
It holds about 60 seconds (II _a flow of FIG. 1 -).

By such a method, the silicon substrate 2
00, the Si-Ge thin film 204 having the same orientation as the substrate surface.
Grows to about 2000 A ° (FIG. 4 (C)).

Then immediately close valves 52 and 53,
Open the valve 51 to supply hydrogen (H ₂ ) gas into the furnace,
For example, after quenching the substrate temperature to 100 ° C., the valve 5
1 and 55 are closed to stop the supply of gas in the reaction furnace and exhaust to a low vacuum of 0.003 Torr.

After that, the pressure inside the reaction furnace was reduced to 1 atm (760 Torr).
The substrate 200 is taken out from the furnace by introducing an inert gas up to r).

Next, a method of forming the Si-Ge thin film of the second embodiment will be described with reference to FIGS.

In the second embodiment of the present invention, in order to form a single crystal of a Si-Ge thin film having the same orientation as the substrate on the substrate 300, it is particularly important to wash the substrate 300 before introducing it into the furnace. Is.

First, the step of cleaning the substrate 300 will be described.

Sulfuric acid (H ₂ SO ₄ ) heated to 120 ° C.
The substrate 300 is immersed in an aqueous solution of hydrogen peroxide (H ₂ O ₂ ) for 15 minutes to oxidize the surface of the substrate by about 10 A ° (not shown).

Immediately thereafter, 1% by weight of hydrofluoric acid (HF) was added.
After being immersed in the aqueous solution for about 30 seconds to remove the oxide film, it is washed with pure water and dried. In this process, the contaminants and oxide film on the substrate are removed.

Next, the substrate is again immersed in an aqueous solution of sulfuric acid (H ₂ SO ₄ )-hydrogen peroxide (H ₂ O ₂ ) heated to 120 ° C. for a shorter time than the first time, for example, 15 seconds. An oxide film 302 of about 10 A ° is formed on the surface of the substrate ((A) of FIG. 5).

After that, the substrate 300 is washed with pure water,
dry.

The pretreated substrate 300 is immediately introduced into the reaction furnace, and the inside of the furnace is evacuated to a high vacuum of, for example, 1 × 10 ^-6 Torr by using the exhaust means 21 and 22, and the inside of the furnace is cleaned. Turn into.

Next, the valve 27 is closed and the valves 28, 5
2, 53 and 55 are opened, and a Group IV hydrogen gas containing silicon, for example, 10% by volume hydrogen diluted silane (Si
H ₄ ), and a group IV hydrogen gas containing germanium, for example, germane (GeH ₄ ) diluted with 1% by volume of hydrogen is supplied into the reaction furnace. In this case, the reactor pressure is, for example, 6 To
It is preferable to adjust the flow rates of the silane (SiH ₄ ) gas and germane (GeH ₄ ) gas in advance so that the pressure is reduced to about rr.

Thereafter, while the surface temperature of the substrate 300 is being measured by the measuring means 14, the temperature of the substrate 300 is raised at a predetermined heating rate within the range of 25 ° C./sec to 50 ° C./sec.
The film is held at a suitable film forming temperature in the range of 0 ° C. to 800 ° C. for about 60 seconds (I _b flow in FIG. 2). The oxide film and the adhered contaminants formed on the surface of the substrate are removed during this temperature raising process ((B) of FIG. 5).

Further, the Si-Ge thin film 304 having the same substrate surface orientation grows on the surface of the silicon substrate by about 2000 A ° by the I _b flow of FIG. 2 (FIG. 5C).

Next, immediately close the valves 52 and 53 and open the valve 51 to supply hydrogen (H ₂ ) gas into the furnace (II
_b )), after quenching the substrate 300 to about 100 ° C.,
The valves 51 and 55 are closed to stop the supply of hydrogen gas into the reaction furnace, and at the same time, the inside of the furnace is evacuated to a low vacuum, such as 0.003To
Exhaust to rr. After that, 1 atm (760
Inert gas, for example, nitrogen gas is supplied up to Torr) and the substrate is taken out of the furnace after the substrate temperature reaches about room temperature (25 ° C.).

FIG. 6A is a substrate cross-sectional view showing the inside of a conventional Si-Ge thin film.

In the conventional example, after the furnace is evacuated, the heating temperature is set to the film forming temperature of the Si—Ge thin film (for example, 700 ° C. to 80 ° C.).
After rapid heating to 0 ° C.), for example, silane (SiH ₄ ) and germane (GeH ₄ ) gas are simultaneously supplied to form a film. The Si-Ge thin film thus formed is affected by the residual oxide film on the substrate surface, contaminants, etc.
Irregularities are formed on the surface of the i-Ge thin film. Further, many crystal defects (for example, interstitial defects and vacancies) and dislocations (for example, 60 ° (degree) dislocations) are generated inside the thin film.

On the other hand, in the first and second embodiments of the present invention, silane (Si
Oxides and contaminants previously attached to the surface of the substrate are removed by the reducing effect of H ₄ ) gas and the like and the annealing effect due to the temperature rising rate. Therefore, the Si—Ge thin film formed in the subsequent step becomes a uniform film with few dislocations and crystal defects (FIG. 6B). In addition, infrared tomography is used as a means for observing crystal defects, and an electron microscope or the like is used for observing dislocations.

[0073]

As is apparent from the above description, according to the first method for forming a semiconductor thin film of the present invention, the temperature is in the range of 50 ° C./sec to 200 ° C./sec in a silane (SiH ₄ ) gas atmosphere. The temperature is raised at the heating rate determined within. During this temperature rising process, contaminants and oxide film on the surface of the substrate are removed. Subsequently, when the surface temperature of the substrate has reached a temperature determined in the range of 500 ° C. to 600 ° C., a germane (GeH ₄ ) gas is introduced to grow a silicon single crystal on the surface of the substrate without growing a single crystal. The process can be shifted to
Then, in a mixed gas atmosphere of residual silane (SiH ₄ ) gas and newly introduced germane (GeH ₄ ) gas, the heating temperature of the silicon substrate is maintained within a range of 700 ° C. to 800 ° C. for about 60 seconds, A Si-Ge thin film is formed. Further, by mixing a silane (SiH ₄ ) gas with an inert gas containing hydrogen chloride (HCl), it is possible to further accelerate the removal of the oxide film and contaminants. The Si-Ge thin film thus formed can have a surface shape with few crystal defects and dislocations and less unevenness. Therefore, a high-quality Si-Ge thin film can be formed without using high-temperature heat treatment other than the temperature raising process.

According to the second semiconductor thin film forming method of the present invention, an oxide film of about 10 A ° is previously formed on the surface of the substrate by chemical treatment in the substrate cleaning step of the pretreatment.
This serves to protect the substrate surface in advance from a natural oxide film formed in the atmosphere and impurities attached during the process. Subsequently, a group IV hydrogen gas containing silicon and germanium, such as silane (SiH
₄ ) The heating temperature is raised to 700 while the temperature of the silicon substrate is raised in a mixed gas atmosphere of gas and germane (GeH ₄ ) gas.
The temperature is set within the range of ℃ to 800 ℃, and held for about 60 seconds.

The Si-Ge thin film thus obtained is similar to the Si-Ge thin film obtained in the first forming method in that it has few crystal defects and dislocations and has few surface irregularities.
It becomes a thin film.

[Brief description of drawings]

FIG. 1 is a heating cycle gas flow curve for explaining an embodiment of the first semiconductor thin film forming method of the present invention.

FIG. 2 is a heating cycle gas flow curve for explaining an embodiment of the second semiconductor thin film forming method of the present invention.

FIG. 3 is a configuration diagram for explaining the thin film forming apparatus.

4 (A) to (C) are S of the first embodiment of the present invention.
FIG. 3 is a process chart provided for manufacturing an i-Ge thin film method.

5 (A) to (C) are S of the second embodiment of the present invention.
FIG. 3 is a process chart provided for manufacturing an i-Ge thin film method.

FIG. 6A is a cross-sectional view of the inside of a crystal of a Si—Ge thin film formed by a conventional method. Further, (B) is a cross-sectional view of the inside of the crystal of the Si—Ge thin film formed in the example of the present invention.

[Explanation of symbols]

I _a: silane (SiH ₄₎ flow - II _a: silane (SiH ₄₎ + germane (GeH ₄₎ furo - III _a: hydrogen (H ₂₎ flow - I _b: Silane (SiH ₄₎ + germane (GeH ₄₎ flow - II _b: hydrogen (H ₂₎ flow - Ha, Hb: retention 200,300: silicon substrate 202: a natural oxide film 204, 304: Si-Ge film 302: oxide film

Claims (4)

[Claims] 1. A method for forming a group IV semiconductor crystal thin film on a silicon substrate by performing heat treatment in a reaction furnace, comprising: (a) 50 ° C./sec in a group IV hydrogen gas atmosphere containing silicon. Heating temperature of the silicon substrate at a predetermined heating rate in the range of 200 to 200 ° C./sec, and (b) heating temperature of the silicon substrate while heating the silicon substrate at the heating rate of 500 to 600 ° C. After introducing a group IV hydrogen gas containing germanium when the temperature passes within the range of, the heating temperature of the silicon substrate is set to 700.
℃ ~ 800 ℃ held at a specified temperature within the range of Si-G
e A method for forming a semiconductor thin film, which comprises the step of forming a thin film, wherein the steps (a) and (b) are continuously performed. 2. The method for forming a semiconductor thin film according to claim 1, wherein the group IV hydrogen gas containing silicon used in step (a) is mixed with an inert gas containing hydrogen chloride. Method for forming semiconductor thin film. 3. A method of forming a group IV semiconductor thin film on a silicon substrate by performing heat treatment in a reaction furnace, comprising: (1) chemically treating the substrate to a film thickness of about 10 angstroms. A step of forming an oxide film, and (2) after switching to a mixed gas atmosphere of a group IV hydrogen gas containing silicon and germanium, at 25 ° C. /
The heating temperature is 700 ° C to 800 ° C while heating and heating the silicon substrate at a predetermined heating rate within the range of 50 seconds to 50 ° C / second.
A method of forming a semiconductor thin film, comprising the step of forming a Si-Ge thin film while maintaining the temperature within a range defined by. 4. The method for forming a semiconductor thin film according to claim 3, wherein when the substrate is chemically treated in the step (1), an aqueous solution containing hydrogen peroxide (H ₂ O ₂ ) is used. Method for forming semiconductor thin film.