JPH0669195A - Method of forming insulating film - Google Patents

Abstract

PURPOSE:To reduce the defects of a film caused by the unstable coupling, etc., occurring during the formation of an insulating film by performing the heat treatment in reductive gas and the heat treatment in reactive gas so as to clean the base, and heat-treating it in single crystal film formation gas, and then, heat-treating it in insulating film formation gas. CONSTITUTION:A natural oxide film is reduced and removed by radiating the heat of a substrate 18 in reductive gas. Next, inorganic matter, etc., adhering to the substrate 18 is removed by the reactive gas being thermally activated by a heater 16. Next, Si single crystal 51 is formed on the surface of a substrate by heating the substrate 18 by the heater 16. Next, a silicon oxide film 53 as an insulating film is formed on the Si single crystal film 51 by supplying oxygen gas into a reactor 10. Hereby, the unstable coupling such as Si-Si coupling, Si-O coupling, and O-O coupling vanishes in the insulating film.

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 an insulating film, and more particularly to a method for forming an insulating film having an extremely thin film with high quality.

[0002]

2. Description of the Related Art Silicon integrated circuits formed by the latest technology, especially MOS (Metal Oxide Sem)
In an integrated circuit, an oxide film having an extremely thin film thickness is used as a gate insulating film. Especially 1.0μ
A submicron MOS device having a gate length of m or less uses an oxide film having a film thickness of, for example, 100 angstroms or less, and the gain is improved by reducing the film thickness.

The formation of the oxide film is described, for example, in the document: "VLSI.
Manufacturing Technology, Shiba Tokuyama, Tetsuichi Hashimoto, Nikkei BP,
P. 83-109 (1989) "as follows.

In the method disclosed in this document, first, a cleaned substrate is placed in a quartz tube heated to 800 to 1200 ° C. by an electric furnace. Then, an oxidizing gas for forming an oxide film is introduced into the quartz tube. As the oxidizing gas, for example, dry oxygen gas, a mixed gas of oxygen and hydrogen, or a gas in which hydrochloric acid is atomized and mixed with oxygen gas is used. In a quartz tube with an oxidizing gas introduced,
By leaving the substrate at a constant temperature for a certain period of time corresponding to the film thickness to be formed and continuously growing an oxide film,
An oxide film having a uniform thickness is formed on the substrate surface.

[0005]

However, in the above-described oxide film forming method, since the oxide film is continuously grown without a break, it is difficult to control the film thickness in a thin region of 100 angstroms or less, for example. Met. Therefore, when forming such a thin oxide film, in order to control the film thickness, the oxidation temperature is lowered to 800 ° C. or lower to reduce the oxidation rate (hereinafter, this may be referred to as a low temperature oxidation method). Alternatively, a method has been employed in which oxygen is diluted with nitrogen to reduce the oxidation rate (hereinafter, this may be referred to as a diluted oxidation method).

However, the low temperature oxidation method has a problem that the silicon (substrate) / silicon oxide film interface is roughened. On the other hand, in the case of the diluted oxidation method, nitrogen is
Since it segregates at the interface of the silicon oxide film, there is a problem that a new interface level is generated. Therefore, no improvement in the film quality itself such as the dielectric breakdown resistance of the thin oxide film could be expected even if any of the above methods was performed.

The oxide film obtained by these low temperature oxidation method and dilution oxidation method is generally not dense and is
An unstable bond state of atoms in the silicon oxide film interface or oxide film, for example, dangling bonds or unpaired bonds of silicon atoms,
Si-Si bond including weak bond, Si-O bond, OO
Since it has an amorphous structure in which many bonds or distorted Si-O-Si bonds are present, the interface state (Di
t) tended to be high. When the oxide film thus formed is used as a gate oxide film of a MOS field effect transistor, various problems are caused by the above phenomenon. For example, in a fine MOS field-effect transistor having a gate length of 1.0 μm or less, when hot electrons generated in the channel region penetrate into the oxide film, electrons are unpaired with such silicon atoms or distorted Si. There is a problem that it is trapped by the —O—Si bond and a new interface state is generated, which causes a change in threshold voltage and a decrease in transfer conductance in the MOS transistor.

Further, according to the conventional method for forming a thin oxide film, which has been conventionally performed, even if the surface of the silicon substrate on which the oxide film is formed is cleaned, the surface still has unevenness when viewed in atomic order. It will remain. Therefore, even if an oxide film is formed on this uneven surface, as shown schematically in FIG. 5A, a step in atomic order is formed in the silicon (substrate) / oxide film interface and in the oxide film. Due to (step)
Si-Si bond including dangling bond, Si-O bond, O-O
This results in an amorphous structure with many bonds. That is, the quality of the obtained oxide film is deteriorated.

Therefore, using the conventional oxide film forming method,
When a MOS structure is configured and these breakdown voltage tests are performed, new traps are generated in the oxide film due to breakage of bonds such as unpaired bonds of silicon atoms and distorted Si—O—Si bonds. It may cause dielectric breakdown. Therefore, MO
There is a problem that the electrical characteristics of the S structure deteriorate.

The present invention has been made in view of the above-mentioned conventional problems. Therefore, the object of the present invention is to reduce film defects caused by dangling bonds or the like that occur during the formation of an insulating film and to improve the film quality. An object of the present invention is to provide an insulating film forming method capable of forming a thin insulating film.

[0011]

In order to achieve this object, according to the present invention, in forming an insulating film on a silicon underlayer in the same reaction furnace, heat treatment in a reducing gas atmosphere is performed. And a step of performing a heat treatment in a reactive gas atmosphere to clean the base, and a step of subsequently performing a heat treatment in a gas atmosphere for forming a single crystal film to form a single crystal film of silicon on the base. And a step of forming a silicon oxide film as an insulating film by performing heat treatment on the single crystal film in a gas atmosphere for forming an insulating film, following the single crystal film forming step. And

In carrying out the present invention, it is preferable that the silicon oxide film has a cristobalite structure.

Further, in carrying out the present invention, preferably, the single crystal film forming gas is any one or two selected from the gas group of SiH ₄ , SiH ₂ Cl ₂ and Si (CH ₃ ) ₂ H _2. It is better to use mixed gas of more than one kind.

Further, in carrying out the present invention, it is preferable that the heating temperature is at least 1000 ° C. or higher in the heat treatment for forming the single crystal film.

Further, in carrying out the present invention, the heating temperature in the heat treatment for forming the insulating film is at least 1000 ° C.
The above is better.

Further, in carrying out the present invention, it is preferable that all heat treatments are performed by irradiation with infrared rays.

Here, the term “silicon underlayer” means not only a silicon substrate, but also an epitaxial layer formed on this silicon substrate, and not limited to these, and an element is formed on the substrate or the epitaxial layer. It widely means a base on which an insulating film should be formed, such as an intermediate.

[0018]

According to the insulating film forming method of the present invention described above,
The film forming surface of the silicon base is once cleaned, a silicon single crystal film is formed on the cleaned base surface, and subsequently,
A silicon oxide film is formed as an insulating film on this silicon single crystal film. Therefore, it becomes possible to grow the same silicon (Si) atoms as the underlying constituent atoms one atomic layer at a time, and the surface of the silicon single crystal film becomes flat on the atomic layer order and the impurity concentration distribution is extremely high. The epitaxial layer becomes steep. Therefore, since the silicon oxide film is formed on the flat surface of the silicon single crystal film, the oxygen atoms and the silicon atoms in the insulating film are regularly arranged and stably bonded, and the atoms in the insulating film are Stable bond with the atoms in the single crystal, resulting in a stable bond state of the atoms as a whole. As a result, the insulating film becomes a high quality film with no film defects.

[0019]

Embodiments of the invention of this application will be described below with reference to the drawings.

It should be noted that the drawings merely schematically show the dimensions, shapes, and positions of the constituent components so that the invention can be understood. Further, in the following description, specific materials and specific numerical conditions will be described, but these materials and conditions are merely preferable examples, and are not limited thereto.

First, before entering the description of the method of the present invention,
An apparatus for carrying out the present invention will be described. <Description of Embodiments of Structure of Insulating Film Forming Apparatus Suitable for Use in Carrying Out the Invention> FIG. 2 shows a main part of an insulating film forming apparatus (mainly a reactor and heating) for carrying out the method of the invention. FIG. 3 is a cross-sectional view schematically showing a configuration of a part). still,
FIG. 2 shows a state where the substrate is installed in the reaction furnace.

FIG. 3 is a diagram for explaining the embodiment of the present invention, and is a diagram schematically showing the overall structure of the insulating film forming apparatus.

As shown in FIG. 3, this insulating film forming apparatus has a reaction furnace 10 in which a substrate is installed, an exhaust means 12 for evacuating the reaction furnace 10, and a gas supply section 14.
And a heating unit 16 for performing heat treatment.
An example of the structure of this device will be described below.

As shown in FIG. 2, in this embodiment, the reaction furnace (chamber) 10 is, for example, a main body 10a and a lid member 10b.
And an elevating member 10c. As the material for forming the main body 10a and the elevating member 10c, for example, stainless steel may be used, and as the material for forming the lid member 10b and the support 20 described later, for example, quartz or vice versa may be used.

The main body 10a and the elevating member 10c are separably integrated to form a concave portion a. A supporting body 20 for mounting the substrate 18 is provided on the side of the concave portion of the elevating member 10c to provide the elevating member 10c. Support 20 by raising and lowering
The substrate 18 on which is placed is placed in the reaction furnace 10 or the reaction furnace 1
0 Allow it to be taken out. In the illustrated example, the lifting member 10
An elevating member 10c for mechanically elevating and lowering c is connected to the elevating device 22.

The lid member 10b is detachably attached to the main body 10a.
Attach to. An airtight holding member 24, for example, a Viton packing is provided between the main body 10a and the lid member 10b and the elevating member 10c. Therefore, when the inside of the reaction furnace 10 is evacuated, the airtight state is maintained via the airtight holding member 24. It is designed so that it can be formed.

Further, a temperature measuring means 26 for measuring the surface temperature of the substrate 18 such as an optical pyrometer is provided at a position near the substrate in the recess a.

Further, in this embodiment, the heating section 16 is provided with an infrared irradiating means of any suitable structure, for example, an infrared lamp 16a.
And a support member 16b for supporting the means 16a. The infrared lamp 16a is preferably a lamp that emits light in a wavelength range capable of efficiently heating the substrate 18, and may be any suitable lamp depending on the substrate material. In this embodiment, a tungsten halogen lamp or any other suitable lamp is used. Preferably, the plurality of infrared lamps 16a are arranged so that the inside of the reaction furnace 10 can be heated uniformly.

Usually, the infrared lamp 16a is used in the reaction furnace 10.
Place it outside. At this time, a part of the reaction furnace 10 is made of a material that transmits infrared rays, and the infrared rays are transmitted from outside the reaction furnace 10 into the reaction furnace 10. As described above, in this embodiment, since the lid member 10b is made of quartz, infrared rays can be transmitted.

The structure and position of the heating unit 16 may be any suitable structure and position where the heat treatment described later can be performed. For example, the heating unit 16 is composed of a heater, and this heater is provided in the reaction furnace 10. You can

Although the disposing position of the supporting member 16b is not limited to this, in the illustrated example, the supporting member 16b is closed between the supporting member 16b and the main body 10a so that the abutting portions of the lid member 10b and the main body 10a are confined. In addition, the airtight holding member 24 is provided between the support member 16b and the main body 10 so as to be detachably attached to the main body 10a. In this way, the support member 1
By providing 6b, the vacuum tightness in the reaction furnace 10 can be improved.

In FIG. 2, reference numeral 28 denotes a gas supply pipe provided between the reaction furnace 10 and the gas supply unit 14, and 30
Indicates an exhaust pipe provided between the reaction furnace 10 and the exhaust means 12.

Next, the vacuum exhaust system and the gas supply system of this embodiment will be described with reference to FIG. The vacuum exhaust system and the gas supply system are not limited to the examples described below.

First, the vacuum exhaust system will be described. In this embodiment, the exhaust means 12 is, for example, a turbo molecular pump 12a and a rotary pump 12b connected to this pump 12a.
And with. The exhaust means 12 is communicated with and connected to the reaction furnace 10 via an exhaust pipe 30 and a valve arranged as shown in the figure.

In FIG. 3, 32a to 32d are exhaust pipes 30.
A vacuum gauge (or pressure gauge) provided in communication with the vacuum gauges 32a and 32d, for example, 1 to 10 ^-3 (1
A baratron vacuum gauge (or a Pirani vacuum gauge) used for pressure measurement in the range of 0 to 3) Torr, and the vacuum gauges 32b and 32c are, for example, 10 ⁻⁴ (10 ⁻⁴ ) to 10 ⁻¹⁰ (10 Minus 10th) Tor
An ion gauge used for pressure measurement in the range of r. An automatic opening / closing valve 34 for protecting the vacuum gauge 32b is provided between the vacuum gauge 32b and the exhaust pipe 30 so that a pressure of 10 ^-3 Torr or more is not applied to the vacuum gauge 32b when the vacuum gauge 32b operates. Automatically controls the opening and closing of the valve 34.
Reference numerals 36a to 36f are automatic opening / closing valves provided between the exhaust means 12 and the reaction furnace 10.
By arbitrarily opening and closing each of ~ 36f,
By controlling the pressure in the reaction furnace 10 to any suitable pressure, the reaction furnace 1
A low vacuum exhaust state and a high vacuum exhaust state are formed in zero.

Further, 38 is a needle valve for pressure adjustment and 40 is a relief valve. The valve 40 is automatically opened when the pressure in the reaction furnace 10 exceeds atmospheric pressure, for example, 760 Torr. The gas supplied from the gas supply unit 14 into the reaction furnace 10 is exhausted.

Next, the gas supply system will be described. In this embodiment, the gas supply unit 14 comprises a reducing gas source 14a, a reactive gas source 14b, a single crystal film forming raw material gas source 14c, and an oxidizing gas source 14d. The gas supply unit 14 is connected to the reaction furnace 10 through a supply pipe 28 and a valve arranged as shown in the drawing so as to communicate with the reaction furnace 10. An inert gas source may be provided if necessary.

In FIG. 3, 42 is a gas supply system, 44 is a valve, 46a to 46d, 48a and 48b are automatic opening / closing valves, and 50a and 50b are automatic gas flow controllers for gases introduced from the gas supply unit 14 into the reactor gas. Is.

Valves 44, 48a, 48b, 46a-4
A desired gas can be supplied from the gas supply unit 14 to the reaction furnace 10 by opening / closing each of 6d arbitrarily and suitably. <Description of Embodiment of Insulating Film Forming Method of the Present Invention> Next, the insulating film forming method of the present invention will be described.

FIG. 1 is a diagram for explaining a heating cycle, which is used for explaining the present invention. The horizontal axis of the figure shows time and the vertical axis shows temperature.

Further, FIGS. 4A to 4D are process drawings for explaining one embodiment of the insulating film forming method of the present invention, and each of the drawings is a structure obtained in the main process steps. The cross section of FIG.

Further, FIGS. 5A and 5B are diagrams schematically showing the interface structure.

In the following description, please refer to FIG. 2 and FIG. 3 as appropriate.

In the present invention, after the silicon base is placed in the reaction furnace, the base is cleaned and then the insulating film is formed. This will be sequentially described below. [Cleaning] A method for cleaning the substrate before forming the insulating film has been already proposed by the applicants of the present application, but it is preferable to use this cleaning method also in the method of the present invention. Yes, I will explain this.

In the embodiment of the present invention, for example, a silicon substrate is prepared as a base, and the substrate 18 is pre-cleaned by using a chemical agent, pure water, etc. as in the conventional process.

First, the substrate 18 is set in the reaction furnace 10. The substrate 18 is fixed on the support 20 of the elevating member 10c.

After this pretreatment, the substrate surface is cleaned. In this cleaning process, heat treatment is sequentially performed in a reducing gas atmosphere to clean the substrate 18 in the reaction furnace 10.

The process of cleaning the substrate will be described below. (A) Removal of natural oxide film When cleaning the substrate, first the valves 44, 48b, 46b.
Is closed and the supply of the inert gas into the reaction furnace 10 in which the substrate 18 is installed is stopped.

Next, the inside of the reaction furnace 10 is evacuated to a high vacuum of, for example, 1 × 10 ⁻⁸ (10 ⁻⁸ ) Torr by the exhaust means 12 to clean the inside of the reaction furnace 10. The valves 38, 36a, 36e, 36 are used to perform this vacuum evacuation.
With valves f and 34 closed, valves 36b, 36c and 36d
Open the rotary pump 12b to open the reactor 10
Vacuum exhaust is performed while monitoring the internal pressure with the vacuum gauge 32a. The inside of the reaction furnace 10 is, for example, 1 × 10
^-3 (10-th power of 3) After the pressure becomes Torr,
The valves 36c and 36d are closed, the valves 36e and 34 are opened, and the pressure inside the reaction furnace 10 is evacuated to 1 × 10 ⁻⁶ (10 ⁻⁶ ) Torr while monitoring the pressure inside the reaction furnace 10 with a vacuum gauge 32b. .

After the inside of the reaction furnace 10 is evacuated to a high vacuum, a reducing gas such as hydrogen gas is introduced into the reaction furnace 10 (H ₂ (hydrogen) flow in FIG. 1). In introducing the reducing gas, the valves 36b, 36e, 34 are closed and the valves 38, 36a are closed in order to maintain the reduced pressure state in the reaction furnace 10 in the heat treatment in the reducing gas atmosphere to be performed next. With the valve open, keep the valves 44, 48a, 46
A is opened and a reducing gas such as hydrogen gas is supplied into the reaction furnace 10.

The reduced pressure in the reaction furnace 10 can be maintained by operating the valve 38 while introducing the reducing gas and adjusting the flow rate of the reducing gas and the automatic flow controller 50a. In this embodiment, the inside of the reaction furnace 10 is maintained in a low vacuum depressurized state of, for example, 100 to 10 ⁻² (10 ⁻² ) Torr.

Next, the natural oxide film 18a is formed by the heating unit 16.
A heat treatment for removing (see (A) of FIG. 4) is performed (heating in the H ₂ flow of FIG. 1). By this heat treatment, the substrate 18 is heated in a reducing gas atmosphere to reduce the natural oxide film 18a of the substrate 18 and remove the natural oxide film from the substrate 18 ((B) of FIG. 4). For example, the substrate 1 is heated by heating the substrate 18.
8 is irradiated with infrared rays. As described above, in this embodiment, the heat treatment is performed while maintaining the inside of the reaction furnace 10 in a reduced pressure state. As a result, the reaction product resulting from the reduction of the natural oxide film is exhausted to the outside of the reaction furnace 10, and as a result,
The degree of contamination of the substrate 18 and the reaction furnace 10 by the reaction product can be reduced.

In this heat treatment, while measuring the surface temperature of the substrate 18 by the temperature measuring means 26, for example, the surface temperature of the substrate 18 is set at an appropriate rate between 50 ° C./sec and 200 ° C./sec, preferably, Approximately 10 at 10 ° C / sec
When the temperature reaches 00 ° C., the heating of the substrate 18 is controlled so that the temperature of 1000 ° C. is maintained for about 10 to 30 seconds.

Next, the heating of the substrate 18 by the heating unit 16 is stopped, the valve 46a is closed to stop the supply of the reducing gas, and the surface temperature of the substrate 18 is kept at room temperature, for example, about 25 ° C. Wait for them to cool down. For this cooling, the substrate 18 may be naturally cooled or may be forcibly cooled. The forced cooling can be performed, for example, by closing the valve 48a and opening the valves 48b and 46d to introduce a large amount of inert gas into the reaction furnace 10.

Next, the valves 38 and 36a are closed and the valve 3
6b and 36e are opened and the inside of the reaction furnace 10 is set to, for example, 1 × 10 ^-8
The inside of the reaction furnace 10 is cleaned by evacuating to a high vacuum of (10 −8) Torr. (B) Cleaning of substrate surface Next, the valves 36b and 36e are closed to close the valves 38 and 36.
a is opened, and the reactive gas is, for example, 1% hydrochloric acid-99% by weight.
Hydrochloric acid is atomized at a ratio of hydrogen gas and a gas mixed with hydrogen gas is introduced (HCl flow in FIG. 1). In introducing the reactive gas, in order to maintain the reduced pressure state in the reaction furnace 10 in the heat treatment in the reactive gas atmosphere to be performed next,
In the same manner as the heat treatment in the reducing gas atmosphere, the inside of the reaction furnace 10 is, for example, 100 to 10 ^-2 (10 minus the square).
Maintain a low vacuum vacuum of Torr.

Next, a heating process is performed by the heating unit 16.
By this heat treatment, the thermally activated reactive gas chemically reacts with the substrate 18 itself and impurities to form a volatile reaction product, which etches the substrate 18 and thus adheres to the substrate 18. Impurities such as existing inorganic substances can be removed. The thermal activation of the reactive gas is performed, for example, by irradiating the reactive gas with infrared rays. Since the heat treatment is performed while the inside of the reaction furnace 10 is maintained under a reduced pressure, the volatile reaction product of the etching of the substrate 18 is exhausted to the outside of the reaction furnace 10, and as a result, the reaction product causes the substrate 18 and the reaction furnace 10 to be exhausted. The degree of contamination of the inside can be reduced.

If the substrate 18 is also heated by this heat treatment, the reactivity of the reactive gas with the substrate 18 and impurities can be improved.

For example, the surface temperature of the substrate 18 is about 1000.
The substrate 18 may be etched with the reactive gas for about 20 seconds while heating the substrate 18 so as to maintain the temperature at ℃.

Next, the heating process by the heating unit 16 is stopped, the valve 46b is closed to stop the supply of the reactive gas, and the substrate 18 is waited to cool to room temperature. This cooling may be natural cooling of the substrate 18 or forced cooling.

Next, the valves 38 and 36a are closed, the valves 36b and 36e are opened, and the inside of the reaction furnace 10 is, for example, 1 × 10 ^-8.
(10 to the 8th power) Evacuate to a high vacuum of Torr. [Formation of Si Single Crystal Film] Next, the valves 36b and 36e are closed to form a silicon (Si) single crystal film on the substrate 18 by performing heat treatment in a source gas atmosphere, and the valve 38,
36a, 48b, 46c are opened, and a source gas such as SiH
₂ Cl ₂ gas is supplied into the reaction furnace 10 (SiH _{2 in} FIG.
Cl ₂ flow). At this time, since the reaction product at the time of forming the Si single crystal film is exhausted to the outside of the reaction furnace 10, the inside of the reaction furnace 10 is maintained in a low vacuum reduced pressure state of, for example, 100 to 10 ⁻² (10 ⁻² ) Torr. .

Next, the substrate 18 is heated by the heat treatment by the heating unit 16 to form the Si single crystal film 51 on the substrate surface (FIG. 4C).

The heating of the substrate 18 is carried out, for example, at a temperature of 50.degree. C. while measuring the substrate surface temperature by the temperature measuring means 26.
In an appropriate ratio between the second to 200 DEG ° C. / sec, about preferably at a heating rate of about 100 ° C. / sec, a heating temperature T ₁ 100
Raise to 0 ° C., preferably about 100 for about 20 seconds
Hold at 0 ° C. In this case, it is preferable to raise the temperature at a constant rate because the growth rate of the Si single crystal film is kept constant and a high quality film is formed. The heating rate is set within the above range in order to form a film with good controllability and / or quality. Further, the heating temperature T _{1 is set} to about 1000 ° C. because S
This is because the temperature is suitable for forming the i single crystal film. The reason for setting the time for about 20 seconds is from the viewpoint of the controllability of the film thickness and / or the film quality. By heating the substrate under such conditions, a film thickness of several tens of angstroms
A Si single crystal film as thin as about 100 Å can be formed on the substrate. The thickness of the epitaxial film can be controlled by adjusting the temperature, the time and the flow rate of the raw material gas.

After the Si single crystal film 51 having a desired film thickness is formed, the heating of the substrate 18 is stopped. Next, the substrate 18 is cooled to room temperature, for example, 25 ° C. Next, the valves 38, 36a
Is closed, the valves 36b and 36e are opened, and the inside of the reaction furnace 10 is evacuated to a high vacuum of, for example, 1 × 10 ⁻⁸ (10 ⁻⁸ ) Torr.

In this way, the interface of the single crystal film to be formed is flat at the atomic level, and
It is necessary for the impurity concentration to change extremely sharply in order to prevent unbonding and weak bonding from occurring. For example,
Within the range of 10-20 angstroms, 1 x 10
^It is preferable that the impurity concentration be changed within the range of ¹⁶ (10 +16 power) ions / cm ³ (= cubic centimeter) to 1 × 10 ¹⁹ (10 +19 power) ions / cm ³ (= cubic centimeter). [Formation of Oxide Film] Next, a silicon oxide film is formed as an insulating film on the Si single crystal film 51. In this embodiment, a silicon dioxide (SiO ₂ ) film 53 is formed as an oxide film ((D) of FIG. 4).

The SiO ₂ film 53 is continuously formed by the method described below without exposing the reaction furnace 10 to the atmosphere after the formation of the Si single crystal film 51 described above.

The formation of a SiO ₂ film as the oxide film 53 will be described. In order to form a SiO ₂ oxide film on the substrate 18 by performing heat treatment in an oxidizing gas atmosphere, the valve 38,
36a, 48b, and 46d are opened, and an oxidizing gas such as oxygen (O ₂ ) gas is supplied into the reaction furnace 10 (O ₂ flow in FIG. 1). At this time, in order to exhaust the reaction product at the time of forming the oxide film of SiO _{2 to} the outside of the reaction furnace 10, for example, 100
-10 ⁻² (10 ⁻² ) Torr Low vacuum pressure is maintained.

Next, the substrate 18 is heated by the heat treatment by the heating unit 16 to form an SiO ₂ oxide film on the substrate surface.

The heating of the substrate 18 is carried out, for example, at 50 ° C./sec while measuring the substrate surface temperature by the temperature measuring means 26.
The heating temperature is raised to about 1000 ° C. at a suitable rate of 200 ° C./sec, preferably at a heating rate of about 100 ° C./sec, and maintained at about 1000 ° C. for about 30 seconds. In this case, it is preferable to perform the temperature raising rate at a constant rate, because the growth rate of the oxide film is kept constant and a high quality film is formed. Also, the heating temperature is about 1000 ℃
The reason is that the temperature is a preferable temperature required for forming the insulating film.

By heating the substrate under these conditions, a thin, high-quality S film having a film thickness of about 50 angstroms is obtained.
An oxide film of iO ₂ can be formed.

The above-mentioned film thickness control of the oxide film can be performed by, for example, adjusting the oxidation temperature, the oxidation time, and the flow rate of the oxidizing gas.

After the oxide film having a desired film thickness is formed, the heating of the substrate 18 is stopped. Next, the substrate 18 is placed at room temperature, for example, 2
Cool to 5 ° C.

FIG. 5B is a schematic diagram showing the interface structure between the SiO ₂ oxide film thus formed and the Si single crystal. As can be understood from FIG. 5B, the Si single crystal film grown on the Si film of the substrate is flat at the atomic level, and when the SiO ₂ film is formed on the Si single crystal film, the oxygen atoms and the silicon atoms are separated from each other. It becomes a regular array (β-cristobalite structure) and forms a crystalline oxide film.
With such an interface structure, the Si single crystal film and SiO ₂
An unstable bond state of atoms such as Si—Si bond including unbonded bond, Si—O bond, and O—O bond disappears with the film. Therefore, in the interface structure obtained by the present invention, dangling bonds or weak bonds, which are unstable bond states of atoms, are reduced, and as a result, the formed insulating film is free of film defects and has high defects. The quality of the film is improved, and the electrical characteristics of the electronic device formed using this insulating film can be improved.

The present invention is not limited to the above-described embodiments, but various changes or modifications as described below can be added.

In the above-mentioned embodiments, SiH ₂ Cl ₂ gas was used as the Si single crystal film forming gas, but instead, SiH ₂ Cl ₂ gas or Si (CH ₃ ) ₂ H ₂ gas or a mixture thereof is used. You may form a Si film using gas. Further, although oxygen (O ₂ ) gas is used as the oxidizing gas in the above-mentioned embodiments, a sufficient oxidizing effect can be similarly obtained by using dinitrogen monoxide (N ₂ O) gas instead of this oxygen gas. be able to.

Although the SiO ₂ layer has been described as an example of the insulating film, any insulating film can be used as the gate oxide film if the interface stability can be obtained and the transistor characteristics can be satisfied. A film other than the SiO ₂ layer may be used.

In the above-mentioned embodiment, each heat treatment is performed by the infrared lamp, but this heat treatment may be performed by an arc lamp, a laser beam, a heater, or the like.

In addition, the insulating film forming method of the present invention can be applied to the low temperature oxidation method to form the insulating film, or to the diluting oxidation method to form the insulating film even when the film quality of the insulating film is high. It will be apparent to those skilled in the art that improvements can be made.

Further, in the above-mentioned embodiment, the substrate as the base is cleaned by heating in the reducing gas atmosphere before forming the insulating film, but this process may be omitted if necessary. Of course good.

[0079]

As is apparent from the above description, according to the insulating film forming method of the invention of this application, the substrate is placed in the reaction furnace, and the reducing gas atmosphere and the reactive gas atmosphere are used. After heat treatment is performed to clean the substrate, a raw material gas for forming a single crystal film is introduced and heat treatment is performed to previously form an extremely flat thin Si single crystal film. Then, heat treatment is performed in a gas atmosphere such as an oxidizing gas for forming an insulating film to form a silicon oxide film as an insulating film on the substrate. Therefore, in the formed insulating film, a β-cristobalite structure in which oxygen atoms and silicon atoms are regularly arranged is formed, and a crystalline oxide film is formed. Therefore, in the insulating film, only stable bonds of Si—O bonds are formed, and unstable bonds such as Si—Si bonds, Si—O bonds, and O—O bonds are eliminated. Therefore, a high quality insulating film having no film defect can be obtained. Therefore, when an electronic device such as a MOS transistor is manufactured using the insulating film formed according to the present invention, the electrical characteristics of these electronic devices can be improved as compared with conventional ones.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of an insulating film forming method of the present invention.

FIG. 2 is a cross sectional view schematically showing a main part for carrying out an embodiment of an insulating film forming method of the present invention.

FIG. 3 is a diagram schematically showing an overall configuration of an apparatus for carrying out an embodiment of an insulating film forming method of the present invention.

FIG. 4 is a process chart for explaining an embodiment of the insulating film forming method of the present invention.

FIG. 5: S obtained according to the insulating film forming method of the present invention
The iO ₂ / Si interface structure is a view schematically showing.

[Explanation of symbols]

10: Reactor 10a: Main body 10b: Lid member 10c: Elevating member 12: Exhaust means 12a: Turbo molecular pump 12b: Rotary pump 14: Gas supply unit 14a: Reducing gas source 14b: Reactive gas source 14c: Single crystal film Source gas source for film formation 14d: Oxidizing gas source 16: Heating unit 16a: Infrared lamp 16b: Support member 18: Substrate 18a: Natural oxide film 20: Support member 22: Lifting device 24: Airtight holding member 26: Temperature measuring means 28: Gas supply pipe 30: Exhaust pipe 32a to 32d: Vacuum gauge 34, 36a to 36f, 38, 40, 44, 46a to 4
6d, 48a, 48b: valve 42: gas supply system 50a, 50b: gas flow controller 51: Si single crystal film 53: SiO ₂ film

Claims (6)

[Claims] 1. When forming an insulating film on a silicon substrate in the same reaction furnace, heat treatment in a reducing gas atmosphere and heat treatment in a reactive gas atmosphere are performed to clean the substrate. A step of subsequently performing a heat treatment in a gas atmosphere for forming a single crystal film to form a single crystal film of silicon on the base, and continuing the single crystal film forming step, And a step of performing a heat treatment in an insulating film forming gas atmosphere to form a silicon oxide film as the insulating film. 2. A method of forming an insulating film, wherein the structure of the silicon oxide film according to claim 1 is a cristobalite structure. 3. The insulating film forming method according to claim 1, wherein the single crystal film forming gas is SiH ₄ , SiH ₂ Cl ₂
And a method of forming an insulating film, which comprises using one kind of gas selected from the gas group of Si (CH ₃ ) ₂ H ₂ or a mixed gas of two or more kinds. 4. The insulating film forming method according to claim 1, wherein the heating temperature in the heat treatment for forming the single crystal film is at least 1000 ° C. or higher. 5. The insulating film forming method according to claim 1, wherein the heating temperature in the heat treatment for forming the insulating film is at least 1000 ° C. or higher. 6. The insulating film forming method according to claim 1, wherein the heat treatment is all performed by infrared irradiation.