JPH05326419A - Method for forming semiconductor thin film - Google Patents

Abstract

PURPOSE:To eliminate a problem such as the directivity of a nozzle in an MBE method and to form an Si-Ge-based semiconductor thin film having a uniform film thickness on a large-diameter Si substrate by a method wherein a single- crystal Si1-XGeX thin film and a single-crystal Si1-YGeY thin film are formed by a chemical reaction. CONSTITUTION:A silicon substrate 15 is put into a reaction furnace which is filled with a hydrogen-gas atmosphere; it is heated and treated under a reduced pressure by means of an infrared lamp; a spontaneous oxide film 61 is removed; after that, a reactive-gas atmosphere inside the reaction furnace is filled with a mixed-gas atmosphere by a silicon-containing group-IV hydrogen- based gas and a by a germanium-contained group-IV hydrogen-based gas. While the substrate 15 is heated, an Si-1-XGeX single-crystal thin film 63 is grown as a buffer layer on its main surface. Then, the relative gas concentration of the germanium-containing group-IV hydrogen gas with reference to the silicon-containing group-IV hydrogen-based gas in the mixed-gas atmosphere is increased; an Si1-YGeY single-crystal thin film 65 is grown on the thin film 63. At this time, composition ratios X, Y of Ge are set to be 0<=X<=0.1 and 0.1<=Y<=1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a semiconductor thin film, and more particularly to a method for forming a Si-Ge based semiconductor single crystal thin film.

[0002]

2. Description of the Related Art In recent years, Group IV semiconductor thin film growth techniques have been rapidly developed for the purpose of application to high-speed heterobipolar devices, microwave devices, or superlattice structure devices.

Among them, a technique for epitaxially growing a silicon-germanium (Si-Ge) thin film on a silicon (Si) substrate has attracted attention. And this technique is generally performed by the molecular beam epitaxy (MBE) technique. This MBE technique is used because it is possible to form a film at a relatively low temperature, and it is possible to obtain the advantage that the impurity distribution of the formed thin film is not disturbed.

As an example of such a thin film forming technique, there is a method disclosed in, for example, Japanese Patent Laid-Open No. 64-90519. In this conventional method, when a group IV hydrogen-based gas for forming a group IV semiconductor thin film is blown from a nozzle of an MBE apparatus into a reaction furnace (growth chamber) and applied to a heated substrate, a halogen-based gas is irradiated. In this way, a group IV semiconductor thin film is deposited.

In the MBE technique using a solid source, the capacity of the source house for generating a group IV semiconductor molecular beam is limited. Therefore, when forming a thick group IV semiconductor thin film, the film formation must be interrupted by supplementing the source. As a result, it has been difficult to grow a single crystal film quickly. In the method disclosed in the above publication, the film forming gas can be continuously supplied from the gas source outside the apparatus into the reaction furnace. Therefore, I
A group V semiconductor thin film could be continuously formed with a large thickness. Further, in this method, the halogen gas acts so as to remove the hydrogen gas adsorbed by the unpaired bond on the substrate surface, so that the film-forming gas is dissociated on the substrate surface and the group IV element is adsorbed on the substrate. Was accelerated, and as a result, the growth rate of the semiconductor thin film could be increased.

[0006]

However, the MBE technique using a gas source is not limited to the above-mentioned conventional method, and a single crystal semiconductor thin film having a uniform film thickness and film quality is grown on a large diameter wafer. Is difficult, and it is difficult to implant impurities into the semiconductor thin film at a high concentration, which is a real problem. The former is considered to be due to the directivity of the gas source blowing nozzle, and the latter is considered to be due to the MBE technique itself, in which a substrate is irradiated with a molecular flow to form a film.

Further, in the MBE technique, it is usually necessary to maintain the degree of vacuum in the reaction furnace, that is, the growth chamber in an ultrahigh vacuum state of 10 ^-10 to 10 ^-11 Torr, so the growth chamber is once exposed to the atmosphere. Then, in order to return it to the original degree of vacuum, there was a problem that the entire apparatus had to be baked for about 30 hours while exhausting the growth chamber.

Further, in forming a Group IV semiconductor thin film on a silicon substrate, generally, before starting film formation, the substrate is subjected to a reduction treatment in a hydrogen gas (H ₂ ) atmosphere and a hydrogen chloride gas (HCl) atmosphere. A heat treatment is performed to remove a natural oxide film and dirt on the base. However, even if such pretreatment is carried out, the effect due to the unevenness originally present on the underlayer surface and the effect of even a small amount of carbonized materials or metal oxides remaining on the underlayer surface cannot be ignored. There is a problem that it does not grow uniformly on the lower ground.

When the surface cleaning treatment and the Si-Ge film forming treatment are performed by rapid heating, a step of rapidly cooling to room temperature is included between the surface cleaning treatment and the Si-Ge film forming treatment. There is a problem that slip dislocations 71 are generated in the Si substrate 15 and the Si—Ge single crystal film 65 due to the stress generated in the substrate ((A) of FIG. 4). Furthermore, there is a problem that misfit dislocations and stacking faults 73 and defects 75 are generated in the film or at the interface between the thin film 65 and the underlayer 15 ((A) in FIG. 4).

Since such a problem becomes a major obstacle in industrially applying the group IV semiconductor MBE method to an actual semiconductor process, improvement is desired.

The present invention has been made in view of the above circumstances. Therefore, the object of the present invention is to solve the above-mentioned problems and to form a Si-Ge based semiconductor thin film having a film quality superior to the conventional one. To provide a method.

[0012]

In order to achieve this object, according to the present invention, silicon (S
i) In the method of forming a Si-Ge (germanium) -based semiconductor thin film on the lower ground, a reactive gas atmosphere in the reaction furnace is set to a mixed gas of a silicon-containing group IV hydrogen-based gas and a germanium-containing group IV hydrogen-based gas. While maintaining the atmosphere and heat-treating the base, single crystal S
forming a i _1-X Ge _X thin film as a buffer layer;
In the mixed gas atmosphere in this reaction furnace, the relative gas concentration of the germanium-containing group IV hydrogen-based gas with respect to the silicon-containing group IV hydrogen-based gas is made higher than the relative gas concentration when the buffer layer is formed, Moreover, while heat-treating the base, a single crystal of Si _{1-Y is formed} on the buffer layer.
And a step of forming a Ge _Y thin film (where Ge composition ratios X and Y are 0 ≦ X ≦ 0.
The value satisfies 1, 0.1 ≦ Y ≦ 1. ). Further, these steps are preferably performed continuously.

The term “silicon underlayer” as used in the present invention means not only the Si substrate itself but also a Si substrate on which an Si epitaxial layer is formed, and a substrate other than the Si substrate is a Si epitaxial layer. I formed materials, and intermediates in which elements are formed,
It means various Si underlayers on which a group V single crystal film is to be grown.

In carrying out the present invention, single crystal Si
_It is preferable that the heat treatment of the base during the formation of the _1-X Ge _X thin film and the Si _1-Y Ge _Y thin film is performed by infrared heating, and the base-holding temperature before and after the film formation is about 250 to 350 ° C.

In implementing the present invention, the single crystal Si _1-x Ge _x thin film has a Ge composition ratio X of 0 ≦ X ≦ 0.
1 and the film thickness t is 0 <t
It is preferable to form it so that the value is within a range of ≦ 50 nm.

In carrying out the present invention, the group IV hydrogen-containing gas containing silicon is changed to silane (SiH ₄ ),
Disilane (Si ₂ H ₆ ), methylsilane (Si (C
H ₃₎ H _3), trisilane (Si ₃ H _8), dimethylsilane _{(Si (CH 3) 2 H} 2), trimethylsilane (S
i (CH ₃ ) ₃ H), tetramethylsilane (Si (CH
₃ ) ₄ ), hexamethyldisilane (Si ₂ (C
H ₃ ) ₆ ), fluorotrimethylsilane (Si (C
H ₃ ) ₃ F) and difluorodimethylsilane (Si
It is preferable to use one kind or two or more kinds of gases selected from the gas group consisting of (CH ₃ ) ₂ F ₂ ).

Further, in carrying out the present invention, a Group IV hydrogen-containing gas containing germanium is added to germane (GeH).
₄ ), germanium tetrafluoride (GeF ₄ ), germanium difluoride (GeF ₂ ), germanium fluoride (Ge
F) and fluorogermane (GeH ₃ F) are preferably used as one or more gases selected from a gas group.

Further, in the practice of the present invention, the cleaning of the underlayer and the heating of the silicon underlayer during the growth of each of the Si _1-X Ge _X thin film and the Si _1-Y Ge _Y thin film are performed by infrared heating. It is suitable. As the infrared light source, for example, a tungsten-halogen lamp or a xenon-arc lamp can be used.

[0019]

According to the structure of the present invention, single crystal Si _1-X G
formation of e _X film and Si _1-Y Ge _Y thin film is performed by chemical reactions. Therefore, problems such as directivity of the nozzle in the MBE method do not occur, so that it becomes possible to form a Si-Ge based semiconductor thin film having a uniform film thickness and film quality on the lower surface of Si having a large diameter.

The Si _1-X Ge _X thin film can be used as a buffer layer, and the Si _1-Y Ge _Y thin film can be used as a growth layer for forming a semiconductor device. The underlayer holding temperature before and after forming each film, that is, the minimum temperature during the heat treatment is set to a temperature sufficiently higher than room temperature. For example, it is preferable to maintain the base holding temperature at a temperature higher than room temperature of about 250 to 350 ° C. At this temperature, the rate of surface oxide film removal and Si-Ge film formation reaction is negligibly slow and does not contribute to these reactions. Therefore, the buffer layer and the growth layer for forming the semiconductor element do not give stress to the base. Further, by using the hydrogen-based gas as the source gas, the base of silicon is not formed during the formation of the first Si _1-X Ge _X thin film. It receives a strong reducing action and removes carbides and metal oxides on the surface of the underlying silicon. Desired single crystal Si _1-Y G
Prior to growing the e _Y film, a first single crystal Si _1-X Ge _X as such a buffer layer is formed on the substrate.

When the single crystal Si _1-X Ge _X buffer layer is grown so that the germanium composition ratio X is X <0.1, the buffer layer has a composition very close to that of the underlying silicon, and Since the film surface is exposed to a hydrogen-based gas containing a large amount of silicon, the film surface is in a cleaned state and, at the same time, in a surface-conditioned state. Through such a buffer layer, the second Si _1-Y G
to form a e _Y thin film, this thin film, becomes no misfit dislocations and defects. As a result, Si _1-Y Ge
The crystallinity of the _Y thin film can be improved.

Also, Si _1-X Ge _X and Si _1-Y Ge
_Since both films of _Y are preferably heated rapidly, stress generation in both films can be reduced and slip dislocation does not occur in both films.

[0023]

Embodiments of the method for forming a semiconductor thin film of the present invention will be described below with reference to the drawings. It should be noted that the drawings used for the description merely schematically show the shapes, sizes, and arrangement relationships of the respective constituent components to the extent that the present invention can be understood. Further, in the following description, specific materials and specific numerical conditions are mentioned, but these materials and conditions are merely preferable examples, and the present invention is not limited thereto.

1. Description of Thin Film Forming Apparatus First, a suitable apparatus example for carrying out the method of the present invention will be described.

FIG. 2 is a diagram schematically showing the overall structure of an apparatus for carrying out the present invention. In this figure,
A silicon substrate 1 is used as a base of silicon in the reaction furnace 11.
5 (hereinafter sometimes simply referred to as “substrate”) is arranged.

As shown in FIG. 2, this apparatus has a reaction furnace (chamber) 11 made of, for example, quartz. The reaction furnace 11 has a structure in which a substrate 15 can be freely placed on and taken out of the substrate support 13 inside.

Further, a heating unit 12 is provided outside the reaction furnace 11. The heating unit 12 is composed of an infrared irradiating means of any suitable configuration such as an infrared lamp. As the infrared lamp 12, a tungsten halogen lamp or any other suitable lamp is used. Preferably, the plurality of infrared lamps 12 are arranged so that the inside of the reaction furnace 11 can be heated uniformly. Then, at a position near the substrate 15, temperature measuring means 14 for measuring the surface temperature of the substrate 15, for example, a thermocouple is provided.

Further, this apparatus is provided with exhaust means 21 and 22 for exhausting the inside of the reaction furnace 11. Automatic opening / closing valves 24, 25, 26, 27, 28, 29, 30 are provided between the exhaust means 21, 22 and the reaction furnace 11. By appropriately opening and closing these valves, the pressure in the reaction furnace 11 can be controlled to any suitable pressure,
It is possible to form a low vacuum exhaust state and a high vacuum exhaust state in the reaction furnace 11. Their vacuum degree is vacuum gauge 3
It can be measured at 4.

Furthermore, this device has a relief valve 31.
Is provided. The valve 31 is automatically opened when the pressure inside the reaction furnace 11 exceeds a set pressure, for example, 760 Torr. The exhaust means 22 is opened from the gas supply source (described later) by opening the valve 31, and the reaction furnace 11 is opened.
The gas supplied inside is exhausted. Further, for the above-mentioned pressure measurement and pressure control, it is also possible to select a suitable gauge according to the required degree of vacuum and separately use a pressure control conductance valve. In FIG. 2, 32 and 33 are vacuum gauges (or pressure gauges) provided in communication with the exhaust pipe 23.

Next, the gas supply system will be described. In this embodiment, a supply pipe 5 having a gas supply system arranged as shown in the drawing.
8. Automatic open / close valve 5 installed in the proper place of this supply pipe 58
1, 52, 53, 54, 55, 56 and 57, and flow controllers 46, 47, 48, 49 and 50. A raw material gas source (not shown) is connected to the raw material gas source connecting portions (hereinafter, referred to as “connecting portions”) 41 to 45 on the opposite side of the reaction furnace 11 of each flow rate controller.

The desired raw material gas can be supplied to the reaction furnace 11 by appropriately opening and closing the valves 51 to 56 so that an arbitrary gas mixing ratio is set.
In this embodiment, hydrogen (H ₂ ) gas is used for the connecting portion 41, and hydrogen diluted 10 (v / v)% silane (SiH) is used for the connecting portion 42.
₄ ) Gas, 1 (v / v)% germane (GeH ₄ ) gas diluted with hydrogen to the connecting portion 43, and an inert gas such as nitrogen (N ₂ ) gas to the connecting portion 45 so that each gas can be supplied There is. The connecting portion 44 may be, for example, S
It can be used as a gas source connection for doping desired impurities into the i-Ge based semiconductor thin film.

2. Description of Embodiment of Thin Film Forming Method Next, Si-G which is one embodiment of the semiconductor thin film of the present invention.
An example of forming an e-based single crystal thin film will be described. In this example, silane (SiH ₄ ) and germane (GeH ₄ ) are used as the source gas and a silicon substrate is used as the silicon underlayer.

FIGS. 1A to 1D are process drawings for explaining the method of forming a semiconductor thin film of this embodiment. Each drawing is a cross-sectional view showing the structure obtained in the main process steps, taken along the thickness direction. FIG. 3 is an explanatory diagram of a heating cycle in the forming method of this embodiment. The heating cycle is shown by taking the temperature (unit: ° C) on the vertical axis and the time (unit: second) on the horizontal axis. The following description will be made with reference to FIGS. 1 to 3 as appropriate.

2-1. Removal of natural oxide film On the substrate 15, the Si- of the present invention having the same orientation as the substrate is formed.
Removal of the natural oxide film 61 is important in forming the Ge-based single crystal film. Hereinafter, the case where the removal of the natural oxide film is necessary will be described, but it goes without saying that this victory is not necessary when the surface of the substrate is originally clean. This removal processing is performed as follows.

First, the substrate 15 which has been pretreated by the usual method is fixed on the substrate support 13 in the reaction furnace 11. At this point, a natural oxide film 61 has been formed on the surface of the substrate 15 ((A) of FIG. 1). Therefore, for example, 1 × 10
^The interior of the reaction furnace 11 is cleaned by exhausting to a vacuum degree of ^-6 Torr. Next, a reducing gas such as hydrogen gas is introduced into the reaction furnace 11 (H ₂ flow indicated by I in FIG. 3).
This can be done by opening the automatic opening / closing valve 51 and the valve 55 via the automatic gas flow controller 46. Then, the flow controller and the opening / closing valve of the exhaust system are adjusted to adjust the pressure in the reaction furnace 11 to, for example, 100 to 1
It is maintained within the range of × 10 ^-2 Torr.

Next, the substrate 15 is heated to 1 ° C. by the heating unit 12.
/ Sec to 10 ° C / sec at a suitable rate, preferably about 5
The temperature is raised to and held at the holding set temperature To at 0 ° C./sec. This holding temperature is the reaction temperature for removing the surface oxide film (about 8
30 to 1000 ° C.) and Si—Ge film forming reaction temperature Ts
Temperature lower than that of, for example, a temperature of 250 to 300 ° C. At this temperature, the reaction temperature for removing the surface oxide film and the Si-Ge film formation is extremely slow and does not contribute to these reactions.

Next, the natural oxide film 61 is removed by the rapid heating process by the heating unit 12 (H1 period of step I in FIG. 3). By this rapid heat treatment, the substrate 15 is heated in a reducing gas atmosphere to reduce the natural oxide film 61 of the substrate 15, and the substrate 15 from which the natural oxide film 61 is removed is obtained (FIG. 1).
(B)).

Here, the rapid heating process is performed by the heating unit 12
By the infrared lamp that constitutes the. Specifically, while the surface temperature of the substrate 15 is being measured by the temperature measuring means 14, the surface temperature of the substrate 15 is, for example, 50% by an infrared lamp.
C./sec. To 200.degree. C./sec. At a suitable rate, preferably about 50 to 75.degree. C./sec.
When the temperature reaches the range of 0 to 1000 ° C., preferably about 900 ° C., the heating of the substrate 15 is controlled so as to maintain the temperature state of about 900 ° C. for about 10 to 30 seconds. In this embodiment, since the heat treatment is carried out while the inside of the reaction furnace 11 is maintained in the depressurized state as described above, the reaction product due to the reduction of the natural oxide film is exhausted to the outside of the reaction furnace main body 11. Therefore, the degree of contamination of the substrate 15 and the reaction furnace 11 by the reaction product can be reduced.

After that, the temperature in the furnace is rapidly cooled to the holding temperature To. The rapid cooling at this time is performed by the hydrogen gas being introduced. Next, the valves 55 and 51 are closed and the valve 27 is opened, and the inside of the reaction furnace 11 is evacuated to a high vacuum of, for example, 1 × 10 ⁻⁶ Torr.

2-2. Formation of Si _1-x Ge _x Thin Film Next, a mixed gas atmosphere of a group IV hydrogen gas containing Si and a group IV hydrogen gas containing Ge is used as the reactive gas atmosphere in the reaction furnace 11. In this gas atmosphere, Si _1-x Ge is deposited on the main surface of the silicon substrate 15 while performing rapid heat treatment on the silicon substrate 15.
_{An x} single crystal thin film is formed as a buffer layer.

Therefore, first, the valve 27 is closed and the valves 28, 55, 52 are opened, and first, in this case, hydrogen is diluted to 10 (v / v) as a group IV hydrogen gas containing Si.
v)% silane (SiH ₄ ) is supplied into the reaction furnace 11, and subsequently, the valve 53 is opened and hydrogen diluted 1 (v / v)% germane (GeH ₄ ) is used as a group IV hydrogen gas containing Ge. ) Is supplied into the reaction furnace 11. At this time, the relative concentration of the Ge-containing Group IV hydrogen-based gas with respect to the silicon-containing Group IV hydrogen-based gas is set so that, for example, the flow ratio of hydrogen-diluted silane and hydrogen-diluted germane is 10: 1, and the reaction furnace 11 The flow rates of both gases are adjusted in advance so that the inside is in a reduced pressure state of, for example, about 10 Torr (see FIG. 3).
II (SiH ₄ + GeH ₄ ) flow).

Next, in such a gas atmosphere, the heating portion 12 performs a rapid heat treatment on the silicon substrate 15 (H2 period of step II in FIG. 3).

This rapid heating process is performed by an infrared lamp which constitutes the heating unit 12. Specifically, while measuring the surface temperature of the substrate 15 by the temperature measuring means 14, the surface temperature of the substrate 15 is, for example, 50 ° C./sec.
At a suitable rate between 200 ° C / sec, preferably about 50-
The substrate surface temperature is increased to about 8 by increasing the temperature at 75 ° C / sec.
When the suitable film formation processing temperature Ts of 00 to 850 ° C. is reached,
The heating of the substrate 15 is controlled so as to maintain this temperature state of about 800 to 850 ° C. for about 1 to 10 seconds.

By this film forming process, the first Si _1-x Ge _x single crystal film having the same plane orientation as the substrate plane orientation (in this case, the Ge composition ratio 0 ≦ X <0.1) is formed on the substrate 15. 63 buffer layers grow to a thickness of about 10-50 nm (Fig. 1
(C)).

2-3. Formation of Si _1-Y Ge _Y Thin Film Next, following the film formation of the first Si _1-x Ge _x single crystal film 63, the Ge-containing IV group hydrogen in the reaction furnace 11 with respect to the Si-containing IV group hydrogen-based gas is formed. The relative concentration of the system gas is set higher than in the case of forming the buffer layer 63. Hydrogen dilution S mentioned above
The gas flow rate is adjusted so that the flow rate ratio of iH ₄ and hydrogen diluted GeH ₄ is 4: 1 (also step I in FIG. 3).
Indicated by I (SiH ₄ + GeH ₄₎ furo -). In addition, the inside of the reaction furnace 11 is kept in a reduced pressure state of about 10 Torr.

After the inside of the reaction furnace 11 is adjusted to such an atmosphere, the surface temperature of the substrate 15 is measured by the temperature measuring means 14 and the film formation processing temperature Ts is maintained for about 60 to 120 seconds. The substrate 15 on which the _1-X Ge _X thin film 63 has been formed is heated by the heating means 12 (step II in FIG. 3).
H3 period). After that, the temperature in the furnace is rapidly cooled to the holding temperature To, the valves 52 and 53 are closed, the hydrogen line valve 51 is then opened, and H ₂ gas is introduced to stop the film formation (step III in FIG. 3). H ₂ flow).

By this film forming process, the second Si having the same plane orientation as the substrate plane orientation is formed on the Si _1-X Ge _X thin film 63.
_1-Y Ge _Y single crystal film (in this case, Ge composition ratio Y≈0.
2) 65 grows to a film thickness of about 250 nm ((D) of FIG. 1).

The Si _1-x Ge _x single crystal film 63
Is a thin film, but preferably the film thickness t is 0 <t
Any suitable value within the range of ≦ 50 nm is preferable. Further, the Ge composition ratio of the thin film 63 is preferably set to any suitable value within the range of 0 ≦ X ≦ 0.1. Furthermore, the Si _1-Y Ge _Y single crystal film 6 formed via the buffer layer 63
In consideration of forming an element on this film, it is preferable that the film thickness 5 be any suitable value in the range of about 10 to 600 nm. The Ge composition ratio of the thin film 65 is 0.1 ≦ Y ≦ 1.
Any suitable value within the range is preferable. Thus, the Si _1-X Ge _X thin film 63 and the Si _1-Y Ge _Y thin film 65 are formed.
A Si-Ge thin film 67 composed of and is obtained.

Next, the valve 55 is closed, the supply of gas into the reaction furnace 11 is stopped, the heating of the substrate 15 by the heating unit 12 is stopped, and the substrate temperature is raised from the held temperature To to the room temperature RT. Wait for them to cool.

Then, an inert gas is introduced to the reaction furnace 11
The internal pressure is set to 1 atm (760 Torr), and the crystal-grown substrate is taken out of the reaction furnace 11 (shown as step IV in FIG. 3).

The embodiments of the method for forming a semiconductor thin film of the present invention have been described above, but the present invention is not limited to the above-mentioned embodiments.

For example, in the above-described embodiment, SiH ₄ diluted with hydrogen and Ge diluted with hydrogen are used as the semiconductor thin film forming gas.
The case of using H ₄ gas has been described. However, the gases that can be used are not limited to these. Instead of SiH ₄ gas, for example, Si ₂ H ₆ , Si (CH ₃ ) H ₃ , Si _{3
H 8, Si (CH 3)} 2 H 2, Si (CH 3) 3 H, S
_{i (CH 3) 4, Si} 2 (CH 3) 6, Si (CH 3)
One or more gases selected from the group of gases consisting of ₃ F and Si (CH ₃ ) ₂ F ₂ , or SiH
_{Even if} a mixed gas of ₄ and these gases is used, the same effect as that of the embodiment can be expected. Instead of GeH ₄ , for example, one or more gases selected from the gas group consisting of GeF ₄ , GeF ₂ , GeF and GeH ₃ F, or a mixed gas of GeH ₄ and these gases may be used. Even if it is used, the same effect as that of the embodiment can be expected.

Although the substrate is heated by using the tungsten-halogen lamp in the above-mentioned embodiments, a xenon arc lamp, a laser beam, a heater or the like may be used instead.

FIG. 4B shows the result of the method of the present invention.
The Si—Ge based semiconductor thin film 6 is formed on the main surface of the Si underlayer 15.
It is explanatory drawing of the state when 7 was created. According to the present invention, as is clear from the above-described embodiments, the surface of the Si underlayer is cleaned before film formation, and thereafter, Si is cleaned.
A thin buffer layer 63 of Si _1-X Ge _X and a Si _1-Y Ge _Y thin film 65 are sequentially formed on the lower surface of the lower layer at a temperature sufficiently higher than room temperature. During the formation of the buffer layer 63, since the Si-containing group IV hydrogen-based gas has a much higher concentration than the Ge-containing group IV hydrogen-based gas, a large amount of Si is contained.
The H ₄ can remove contaminants on the underlying surface.

Further, the buffer layer 63 is formed of Si _1-X Ge.
_{Since X} (0 ≦ X <0.1), the lattice constant of the buffer layer 63 is close to the lattice constant of Si. Therefore, the buffer layer 63 is strained due to the mismatch of lattice constants. There are few films. Further, a thin film 65 of Si _1-Y Ge _Y (0.1 ≦ Y ≦ 1) having a substantially uniform lattice constant is formed on the buffer layer 63 whose surface is cleaned. The thin film 65 is also a single-crystal Si _1-Y G that does not generate defects or misfit dislocations.
It is an e _Y film.

Since both films 63 and 65 are preferably formed by rapid heating, stress generation in both films can be reduced. Therefore, there is no risk of slip dislocations occurring in both films 63 and 65.

[0057]

According to the above-described method of the present invention, in the process of forming the single crystal Si-Ge buffer layer, the underlying Si surface is exposed to a hydrogen-containing gas containing a large amount of silicon, for example, silane gas. The base surface is subjected to a strong reducing action peculiar to silane gas, so that the carbide and metal oxides on the base surface are removed and the surface is cleaned.

Further, since the single crystal Si _1-x Ge _x buffer layer (Ge composition ratio X is X <0.1) has a composition close to that of the underlying silicon, lattice relaxation occurs and a film with less strain is formed. Can be formed. Through such a buffer layer, a Si _1-Y Ge _Y film (G
The e composition ratio Y of 0.1 ≦ Y ≦ 1) allows growth of a single crystal thin film without defects and misfit dislocations. In addition, since the occurrence of stress due to rapid heating during the film forming process can be reduced, slip dislocation is unlikely to occur.

According to one embodiment of the method for forming a semiconductor thin film of the present invention, before a desired single crystal Si _1-Y Ge _Y film is grown,
A single crystal Si _1-X Ge _X buffer layer (Ge composition ratio X is X <0.1) is formed on the substrate, and the substrate holding temperature before and after film formation is set to about 10% during rapid heat treatment during film formation. 250
Since the temperature is set to ˜350 ° C., it is possible to suppress the slip caused by the stress on the base.

Therefore, according to the present invention, Si having a large diameter is used.
So-called high-quality Si with a uniform film thickness and film quality on the lower surface
A Ge-based semiconductor thin film can be formed.

[Brief description of drawings]

FIG. 1 is a process chart for explaining a method for forming a semiconductor thin film of an example.

FIG. 2 is an explanatory diagram schematically showing the overall structure of a film forming apparatus used for carrying out the present invention.

FIG. 3 is a diagram for explaining thin film forming conditions of Examples, and is a diagram showing gas supply conditions and substrate heating conditions.

FIG. 4 is an explanatory diagram for explaining a comparison between a conventional example and an example of the present invention.

[Explanation of symbols]

15: Silicon substrate 61: Natural oxide film 63: Si _1-X Ge _x single crystal film 65: Si _1-Y Ge _Y single crystal film 67: Si-Ge thin film

Claims (5)

[Claims] 1. A method of forming a Si—Ge (germanium) -based semiconductor thin film on a lower surface of silicon (Si) in the same reaction furnace, wherein a reactive gas atmosphere in the reaction furnace contains silicon containing I
A buffer layer of a single-crystal Si _1-X Ge _X thin film on the main surface of the underlayer in a mixed gas atmosphere of a group V hydrogen-based gas and a group IV hydrogen-based gas containing germanium, and while heat-treating the underlayer. And the relative gas concentration of the germanium-containing Group IV hydrogen-based gas with respect to the silicon-containing Group IV hydrogen-based gas in the mixed gas atmosphere in the reaction furnace, the buffer layer is formed. And forming a single crystal Si _1-Y Ge _Y thin film on the buffer layer while increasing the relative gas concentration at that time and performing heat treatment on the underlayer (where Ge composition ratio X, Y is 0 ≦ X ≦ 0.1,
The value satisfies 0.1 ≦ Y ≦ 1. ) A method for forming a semiconductor thin film characterized by the above. 2. The method for forming a semiconductor thin film according to claim 1, wherein the heat treatment of the base when forming the single crystal Si _1-X Ge _X thin film and the Si _1-Y Ge _Y thin film is performed by infrared heating. And, the substrate holding temperature before and after film formation is about 250 to 350.
A method for forming a semiconductor thin film, characterized in that the temperature is set to ℃ 3. The method for forming a semiconductor thin film according to claim 1, wherein the single crystal Si _1-x Ge _x thin film has a Ge composition ratio X of 0 ≦.
X ≦ 0.1 and the film thickness t is 0 <t ≦
A method of forming a semiconductor thin film, which comprises forming the film to have a value within a range of 50 nm. 4. The method for forming a semiconductor thin film according to claim 1, wherein the group IV hydrogen-based gas containing silicon is SiH ₄ , S.
i ₂ H ₆ , Si (CH ₃ ) H ₃ , Si ₃ H ₈ , Si (C
H ₃ ) ₂ H ₂ , Si (CH ₃ ) ₃ H, Si (C
One or more gases selected from the gas group consisting of H ₃ ) ₄ , Si ₂ (CH ₃ ) ₆ , Si (CH ₃ ) ₃ F and Si (CH ₃ ) ₂ F _2. And a method for forming a semiconductor thin film. 5. The method for forming a semiconductor thin film according to claim 1, wherein the group IV hydrogen-based gas containing germanium is Ge.
A method for forming a semiconductor thin film, which comprises using one or more gases selected from a gas group consisting of H ₄ , GeF ₄ , GeF ₂ , GeF and GeH ₃ F.