JPH03154340A - Formation of insulating film - Google Patents

Abstract

PURPOSE:To form an insulating film that is superior in film quality by forming the insulating film which has specific film thickness at a base after performing heat treatment in an atmosphere of an oxidizing gas and after that, in a state that a certain heat treatment temperature is maintained, by performing heat treatment continuously in an atmosphere of an inactive gas. CONSTITUTION:An oxidizing gas, e.g. an oxygen gas is supplied in a reaction furnace 10 in order to form an insulating film having a film thickness of less than about 100Angstrom on a substrate 18 by performing heat treatment in an atmo sphere of the oxidizing gas and an oxide film is formed on the surface of the substrate after heating the substrate 18 by giving heat treatment to a heating part 16. Then, an inactive gas, e.g. an Ar gas is supplied in the reaction furnace 10 in a state that a certain heat treatment temperature in the case of forming the oxide film is maintained for the substrate 18 on which the oxide film is formed and heat treatment is carried out for hours desired. As a result, after insulating films are formed, the insulating films which are not bonded yet and have weak bonding are lessened by heat treatment in an atmosphere of the inactive gas. Each insulating film which has the film thickness of less than about 100Angstrom and is superior in film quality is thus formed.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for forming an insulating film.

(Conventional technology) Silicon integrated circuits formed using cutting-edge technology, especially M
OS (Metal Oxide Sem1conduc
(tor) In integrated circuits, an extremely thin oxide film is used as a gate insulating film. In particular, in submicron MOS devices having a gate length of 1.0 um or less, an oxide film having a film thickness of, for example, 100 Å or less is used, and by reducing the film thickness in this way, the gain is improved.

As an example of a conventional method for forming an oxide film, for example, see the literature:
There was one disclosed in rMO3LsI production technology, edited by Todoroki Tokuyama and Satoshi Hashimoto, published by Nikkei McGraw-Hill, P, 64 (+985) J.

In the method disclosed in this document, first, a cleaned substrate is placed in a quartz tube heated to 800 to 1200"C in an electric furnace. During its dredging, an oxidizing gas for forming an oxide film is released. The oxidizing gas used is, for example, dry oxygen gas, a mixed gas of oxygen and hydrogen, or a gas made by atomizing hydrochloric acid and mixing it with oxygen gas. By leaving the substrate in the tube for a certain period of time at a certain temperature, an oxide film of uniform thickness is formed on the surface of the substrate.

In addition, in method 1 using the electric furnace described above, the film thickness was 1
If you want to form a thin oxide film of about 00A or less with good controllability of film thickness, a method is to heat the quartz tube to a low temperature of 800°C or less (hereinafter sometimes referred to as low-temperature oxidation method).
Alternatively, a method has been used in which oxygen is diluted with nitrogen to reduce the oxidation rate (hereinafter sometimes referred to as dilution oxidation method).

In addition, as another method that can form a thin oxide film with a film thickness of about 100 A or less with good controllability, for example, the literature (Electronic Materials Seisakusho 100 Edition, Industrial Research Institute, p.

65, (1987)')
(Rapid Thermal Oxidation) technology has been known. According to today's To technology, a substrate is heated to a temperature of over 1000"C in a few seconds by energy from a suitable rapid heating source such as a tungsten-halogen lamp, an arc lamp, a laser beam, etc. An oxide film is formed.

(Problem to be Solved by the Invention) However, when an oxide film with a thickness of about 100A or less is formed using the above-mentioned low-temperature oxidation method 1, the silicon/silicon oxide film interface becomes rough, and when it is formed using the dilution oxidation method, the silicon/silicon oxide film interface becomes rough. Since nitrogen segregates at the silicon/silicon oxide film interface, there are problems such as the generation of new interface states in both cases.

In addition, the oxide film formed by low-temperature oxidation method or dilution oxidation method is not w1-dense, and the silicon/silicon oxide film interface has
For example, a dangling bond in a silicon atom or a distorted 5i-
Since there are many 0-8i bonds, there is a tendency for the interface state to become high in the first place.

Therefore, when such an oxide film is used as a gate electrode of an MO8 type field effect transistor, various problems arise due to the above-mentioned phenomena.For example, gate length 1.
In a micro MO8 field effect transistor with a thickness of 0 um or less, when hot electrons generated in the channel region enter this oxide film, the electrons are transferred to unpaired bonds or distorted 5i-0 bonds of silicon atoms in this oxide film. A problem arises in that it is trapped and generates a new interface state, which causes a fluctuation in the threshold voltage and a decrease in the transfer conductance in the MO8 type transistor.

On the other hand, the oxide film formed by RTO technology has better film quality than the oxide film formed by the above-mentioned low-temperature oxidation method or diluted oxidation method, since the oxidation temperature is higher and there is no need to include nitrogen, but silicon Unpaired bonds of atoms and distorted 5i
There were still effects such as -0 coupling, and improvements were desired.

The present invention was made in view of the above points, and therefore, an object of the present invention is to provide a method for forming an insulating film having a thickness of approximately 100λ or less and having excellent film quality. be.

(Means for Solving the Problems) In order to achieve this object, according to the insulating film forming method of the present invention, the base is placed in a reaction furnace and heat-treated in an oxidizing gas atmosphere. a step of forming an insulating film with a thickness of about 100λ or less, and a step of continuously heat-treating the base on which the insulating film has been formed in an inert gas atmosphere while maintaining the heat treatment temperature used for forming the insulating film. It is characterized by including.

Note that the base mentioned here includes, for example, a substrate such as a silicon substrate, a silicon substrate with a silicon substrate and a taxial silicon layer, and an intermediate material in which a semiconductor element or the like is built into these substrates. That's true.

Furthermore, the process of forming an oxide film with a thickness of about 100λ or less referred to here refers to a process using, for example, the already explained low-temperature oxidation method, dilution oxidation method, or RTO technology, etc.
This is a process that uses technology that allows easy control of film thickness in forming an oxide film with a thickness of approximately 0λ or less. Note that a film thickness of about 100λ means, for example, a fine MO with a gate length of 1.0um or less.
It should be understood that this refers to a film thickness that can be used for a gate oxide film of a type 3 field effect transistor, and is not limited to 100 mm.

In carrying out the present invention, it is preferable to carry out the heat treatment during the formation of the insulating film and to maintain the heat treatment temperature after forming the insulating film by infrared irradiation.

Further, in carrying out the present invention, it is preferable to sequentially perform heat treatment in a reducing gas atmosphere and heat treatment in a reactive gas atmosphere on the base before forming the insulating film to clean the base. . And each heat treatment during this cleaning,
Preferably, this is carried out by infrared irradiation.

(Function) According to the insulating film forming method of the present invention, after the insulating film is formed, the insulating film is continuously subjected to heat treatment in an inert gas atmosphere. Therefore, after the insulating film is formed, the insulating film has a structure containing many unbonded or weak 5i-8i bonds, 5i-0 bonds, and 〇-〇 bonds at the interface between the base and the oxide film and/or in the oxide film. However, unbonded and weak bonds can be reduced by heat treatment in an inert gas atmosphere. Therefore, as is clear from the experimental results described later, the electrical characteristics of the oxide film can be improved.

In addition, since the atmosphere for heat treatment after forming the insulating film is an inert gas atmosphere, the insulating film is annealed in a state in which growth is substantially stopped and unnecessary reactions do not occur. Ru. Since heat treatment is performed continuously in the same reactor after forming the insulating film, the insulating film is not contaminated.

Furthermore, if each heat treatment is performed by irradiation with infrared rays, rapid heating and rapid cooling becomes possible, which makes it easy to control the start and stop of the reaction. l! It also becomes easier to control the thickness of the membrane.

(Example) Hereinafter, an example of the insulating film forming method of the present invention will be described with reference to the drawings. Note that the drawings only schematically show the dimensions, shapes, and arrangement positions 1 of each component to the extent that these inventions can be understood. Therefore, the dimensions of each component,
The shape and weight capacity are not limited to the illustrated example.

Further, in the following description, specific materials and specific numerical conditions will be listed and explained, but these materials and conditions are merely preferred examples, and therefore, the invention is not limited to these materials and conditions. Please understand that there is no such thing.

First, we will start with an absolute material suitable for carrying out the insulating film forming method of the present invention. !
I will explain the configuration of the @formation mine.

The second figure is this lol! FIG. 2 is a cross-sectional view schematically showing the main parts of the lattice pattern forming apparatus (mainly the configuration of a reactor and a heating section). In addition, FIG. 2 shows a state in which, for example, a silicon substrate (hereinafter sometimes abbreviated as a substrate) with a base layer is placed in the reactor.

Also, Figure 3 shows w! FIG. 1 is a diagram schematically showing the overall configuration of a binding film forming apparatus.

As shown in FIG. 3, the lightning after forming the insulating film is connected to the reactor 10 in which the substrate is installed, the exhaust means 12 for evacuating the inside of the reactor 10, and the reactor 1°. The heating section 16 includes a gas supply section 14 for rapidly heating the substrate. The detailed structure of the apparatus of this embodiment will be explained below.

As shown in FIG. 2, in this embodiment, the reactor (chamber) 10 is composed of, for example, a main body 10a, an M member 10b, and an elevating member 10c. For example, stainless steel is used as the material for forming the main body 10a and the lifting member 10c, and quartz, for example, is used as the material for forming the lid member 10b and the support body 2Q, which will be described later.

The main body 10a and the elevating member 10c are integrally separable to form a recess a, and a support 20 for placing the substrate 18 on the recess a of the elevating member 10c is provided so that the elevating member 10c can be moved up and down. Substrate 1 with support 20 placed on it
8 into the reactor 10 or taken out from the reactor 10. In the illustrated example, a lifting member 10c is connected to a lifting device 22 for mechanically raising and lowering, for example.

Furthermore, an airtight retaining member 24, for example, a piton packing, is provided between the main body 10a, which attaches and detaches the lid member 10b to the main body 10a, the lid member 10b, and the elevating member 10c, so that the inside of the reactor 10 is evacuated. When this happens, an airtight state can be created via the airtight maintenance member 24.

Further, a humidity measuring means 26, such as an optical pyrometer, for measuring the surface temperature of the substrate 18 is provided in the concave portion a near the substrate.

Roughly speaking, in this embodiment, the heating section 161v is constituted by an infrared irradiation means of any suitable structure, for example, an infrared lamp 16a and a support member +6b for supporting this means 16a. The infrared lamp 16a may be a Kungesten-halogen lamp or any other suitable lamp. Preferably, a plurality of infrared lamps 16a are distributed so as to uniformly heat the interior of the reactor 10.

In this embodiment, an infrared lamp 16a is placed outside the reactor 10 in a position facing the lid member +ob.

By installing the infrared lamp 16a outside the reactor 10, the infrared lamp 16a can be isolated from the oxidizing gas atmosphere, the reaction gas atmosphere, etc., thereby extending the life of the lamp. Further, as described above, since the lid member 10b is made of quartz, infrared rays easily pass through the lid member 10b and reach the substrate 18.

The arrangement position M8 of the support member tab is not limited to one, but in the illustrated example, the support member +6b is set so that the abutting portions of the lid member 10b and the main body 10a are confined between the support member +6b and the main body 10a. The airtight member 24 is detachably attached to the main body 10a and is further provided between the support member +6b and the main body 10. By providing the support member +6b in this manner, the vacuum stability within the reactor 10 can be improved.

Note that in FIG.
0 and the exhaust pipe provided between the exhaust means 12.

Next, the vacuum evacuation system and gas supply system of this embodiment will be explained with reference to FIGS. Note that the vacuum evacuation system and gas supply system are not limited to the examples described below.

First, the vacuum evacuation system will be explained. In this embodiment, the exhaust means 12 includes, for example, a turbo molecular pump 12a and this pump 1.
2a and a connected rotary pump 12b. The exhaust means 12 is connected in communication with the reactor 10 via, for example, an exhaust pipe 30 and a valve arranged as shown.

In FIG. 3, 32a to 32d are vacuum gauges (or pressure gauges) provided in communication with the exhaust pipe 30.
a and 32d 1 For example, Baratron vacuum gauge (or Villany vacuum gauge) used for pressure measurement in the range of 1 to 1 O-3 Torr, and vacuum gauges 32b and 32c @For example 1
The ion gauge is used for pressure measurement in the range of 0-' to 10-'Torr. In the darkness between the vacuum gauge 32b and the exhaust pipe 30 is the vacuum gauge 32b! An automatic opening/closing valve 34 is provided for protection, and the opening/closing of the single valve 34 is automatically controlled so as not to apply a pressure of 10<-3 >Torr or more to the vacuum gauge 32b during operation of the vacuum gauge 32b. 36a-36
f is an automatic opening/closing valve provided between the exhaust means 12 and the reactor 10, and by opening and closing these valves 36a to 36f as desired, the pressure inside the reactor 10 is controlled to an arbitrary desired pressure and the reaction is started. A low vacuum evacuation state and a high vacuum evacuation state are created in the furnace 10.

Roughly, 38 is a needle valve for pressure adjustment, and 40 is a relief valve, and the valve 40 automatically opens when the pressure inside the reactor 10 exceeds atmospheric pressure, for example, when it exceeds 780 Torr. By opening the gas supply section 14, the gas supplied into the reactor 10 is exhausted.

Next, the gas supply section will be explained. In this embodiment, the gas supplies 14 include a reducing gas source 14a, a reactive gas source 14b,
It consists of an oxidizing gas source 14c and an inert gas source +4d. This gas supply section 14 is connected in communication with the reactor 10 via, for example, a supply pipe 28 and a valve arranged as shown in the figure.

In FIG. 3, 42 is a gas supply system, 44 is a valve, and 46
a, 46b and 48a, 48b are automatic opening/closing valves, 5
0a.

50b is an automatic gas flow controller for the gas introduced from the gas supply section 14 into the reactor gas.

Valve 44.48a, 48b, 46a, 46b
A desired gas can be supplied from the gas supply section 14 to the reactor 10 by opening and closing each of them as desired.

In this embodiment, since the heat treatment is performed by infrared irradiation, the heating section 16 is equipped with an infrared lamp 16a.
%. However, the configuration and arrangement position of the heating section 16 may be any suitable configuration and arrangement (i2 position may be used) that can perform the heat treatment described later.For example, the heating section 16 may be configured with a heater, and this heater may be It may be arranged within 10.

Next, an example using the insulating film forming method described using FIGS. 2 and 3 will be described. The film is a silicon oxide film.

FIG. 1 is a diagram for explaining a heating cycle used to explain the present invention. In FIG. 1, the horizontal axis plots time and the vertical axis plots temperature. Also, please refer to FIGS. 2 and 3 as appropriate in the following description.

In this embodiment, a silicon substrate is prepared as the substrate 18,
First, this substrate 18 is cleaned, and then an insulating film (silicon oxide film, hereinafter sometimes abbreviated as oxide film) is formed and a heat treatment is performed in an inert gas atmosphere after the film formation. , which will be explained in turn.

(2) Cleaning Cleaning of the substrate before forming an insulating film is performed as described below.

<Pre-treatment> First, as a pre-treatment, the silicon substrate 18 is first subjected to pre-oxidation cleaning using chemicals, pure water, etc., as is conventionally done.

Further, as a preliminary treatment, a valve 46d,
48b and 44 are opened from the inert gas source +4d to the reactor 1.
For example, argon (Ar) gas is introduced in advance as an inert gas into the 0.Reducing gas, reactive gas, and oxidizing gas are not introduced yet.

Next, a substrate is placed in the reactor 10 for one day. The substrate 18 is fixed on a support 20 of the elevating member 10c.

After these preliminary treatments, the surface of the substrate 18 is cleaned by sequentially heating it in a reducing gas atmosphere and then in a reactive gas atmosphere.
is cleaned in the reactor 10.

The cleaning process for this substrate will be explained below.

Removal of natural oxide film> When cleaning the substrate, first remove the valves 48b and 46d'.
iFr is closed to stop gas introduction from the inert gas source +4d.

Next, the inside of the reactor 10 is pumped by the exhaust means 12, for example, 1 x
The inside of the reactor 10 is cleaned by evacuation to a high vacuum of 10-' Torr. This evacuation is performed by valve 38.3.
6a, 36f, 34. Close valve 3.
8c and 36d are opened, the rotary pump 12b is activated, and the pressure inside the reactor 10 is evacuated while being monitored with the vacuum gauge 32a, and the pressure inside the reactor 10 is, for example, 1X70-'' Torr. This can be done by closing the valves 36c and 36d %, opening the valves 36e and 34, and evacuating the inside of the reactor 10 to lX10 to 'Torr while monitoring the pressure inside the reactor 10 with the vacuum gauge 32b.

After the reactor 10 is evacuated to a high vacuum as described above, the valves 36a, 36b, 36d, and 36e are then closed. Thereafter, the valves 44, 48a, and 46a are opened, and a reducing gas such as hydrogen is supplied from the reducing gas source 14a (H270- in FIG. 1). At this time, the valve 36f is opened by 34%.
While monitoring the pressure inside the reactor 10 with the vacuum gauge 32b, the inside of the reactor 10 was measured at a pressure of, for example, 100 to 1 (12T).

Maintain a low vacuum of rr.

Next, in order to perform a heat treatment to remove the natural oxide film of the substrate 18 by the heating section 16, the substrate 18 is heated in a reducing gas atmosphere using infrared rays 1 from the infrared lamp 16a of the heating section 16, and the substrate 18 is heated in a reducing gas atmosphere. By reducing the natural oxide film of 18 and removing this natural oxide film from the substrate 18, the reaction products from the reduction of the natural oxide film are removed from the outside of the reactor 10 by performing heat treatment while maintaining the inside of the reactor 10 in a reduced pressure state. As a result, the degree of contamination of the substrate 18 and the inside of the reactor 10 by reaction products can be reduced.

In this heat treatment, while measuring the surface temperature of the substrate 1B with the temperature measuring means 26, for example, the surface temperature of the substrate 18 is
The temperature is increased at an appropriate rate between 100° C./second and 200° C./second, preferably about 100° C./second, and once the temperature reaches about 1000° C., the temperature is maintained at 1000° C. for about 10 to 30 seconds. (Area engineering in Figure 1) Controls the heating of the substrate for one day.

Next, the heating of the substrate 18 by the heating unit 16 is stopped, the valve 46a is closed, the supply of reducing gas is stopped, and the substrate 18 is cooled until the surface temperature of the substrate 18 reaches room temperature, for example, 25°C. Wait, this cooling may be done by allowing the board 18 to cool naturally or by forcing it.
6a This can be done by opening the reactor 10 and introducing a large amount of inert gas into the reactor 10.

Next, valves 38 and 36at are closed and valves 36b and 3 are closed.
6e and inside the reactor 10, for example, 1 x 10-'T.
The inside of the reactor 10 is cleaned by evacuating to a high vacuum of o r r.

<Cleaning of the substrate surface> Next, close the valves 36b and 36e and close the IFr valve 38.
．． 36at is opened and the valves 48a and 46b are opened, and a reactive gas such as 1% hydrochloric acid to 99% hydrogen gas (by weight ratio) is sprayed into the reactor 1.
When introducing the reactive gas into the reactor 10 (HCρ flow in Figure 1), a natural The interior of the reactor 10 is maintained at a low vacuum of, for example, 100 to 100<-2 >Torr in the same manner as the heat treatment for removing the oxide film.

Next, heat treatment is performed by the heating unit 16, and a reactive gas thermally activated by this treatment removes impurities such as inorganic substances adhering to the substrate 18. In this embodiment, the thermal activation of the reactive gas is carried out by irradiating the reactive gas with infrared rays.Since the heat treatment is carried out while maintaining the inside of the reactor 10 in a reduced pressure state, volatilization due to etching of the substrate 18 is prevented. The reaction products are exhausted to the outside of the reactor 10, and as a result, the reaction products damage the substrate 18 and the reactor 1.
The degree of contamination within 0 can be reduced.

This cleaning of the substrate surface is carried out, for example, by heating the substrate 18 so as to maintain the surface temperature of the substrate 18 at approximately 1000° C. (region ■ in FIG. 1), and cleaning the substrate 18 with a reactive gas for approximately 20 seconds. Just do some etching.

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

Next, valve 38.36a! Closed, valves 36b, 36
e is opened and the inside of the reactor 10 is evacuated to a high vacuum of, for example, 1xlO-8 Torr.

■... Formation of oxide film Next, heat treatment is performed in an oxidizing gas atmosphere to form the substrate 1.
8 to form an insulating layer with a thickness of about 100λ or less,
Close the valves 36b and 36e, and close the valves 38° and 36a and 4.
8b and 46c are opened to supply an oxidizing gas such as oxygen gas into the reactor 10 (flow 02 in FIG. 1).

Although oxide film formation can be performed under atmospheric pressure, the reactive products at the time of oxide film formation are exhausted outside the reactor 10.
It is preferable to maintain the inside of the chamber at a low vacuum of, for example, 100 to 10<-2 >Torr. In this state, heating section 1
The substrate 18 is heated by the heat treatment according to No. 6 to form an oxide film on the surface of the substrate.

The substrate 18 is heated by the infrared radiation 16a of the heating section 16.
At this time, while measuring the surface temperature of the substrate 18 with the temperature measuring means 26, the temperature of the substrate 18 is preferably increased at an appropriate rate between, for example, 50"C/sec to 200"C/sec. At a speed of about 00℃/sec, about 20 seconds, 100
The temperature is maintained at 0°C (region III in Figure 1).
In this case, it is preferable to perform heating so that the rate of increase in temperature is constant, and this is in order to form a high-quality oxide film by keeping the growth rate of the oxide film constant. By heating the substrate under these conditions, an oxide film with a thickness of about 100 oxides can be formed. The thickness of the oxide film can be controlled, for example, by adjusting the oxidation temperature, oxidation time, and oxidation gas flow ffi.

After forming the oxide film with the desired thickness, the valve 46c is closed to stop the supply of the oxidizing gas. An oxide film is formed on the substrate 18 through the above steps.

Next, while maintaining the heat treatment temperature of 1000° C. for forming the oxide film on the substrate 18 on which the oxide film has been formed, the valves 48b and 46d are immediately opened, and an inert gas such as argon (
Ar) gas is supplied into the reactor 10 (Ar
Although the inside of the reactor 10 at this time is not limited to this, for example, 100 to 10
Maintain a low vacuum of -2 Torr.

The inside of the reactor 10 is made into an inert gas atmosphere, and the substrate temperature is set at 100℃.
After heating the substrate 18 while maintaining the temperature at 0"C for a desired time (region ■ in FIG. 1), the heating of the substrate 18 is stopped. At the same time or after the heating is stopped, the valve 46d
Close to stop inert gas supply.

Next, the substrate I8 is cooled to room temperature, for example, 25°C.

Once the substrate 18 has cooled down to room temperature, remove the substrate 18 from the reactor 10.
Take out.

FIG. 4 is a diagram showing an example of the evaluation results of the insulating film formed by the insulating film forming method of the above-mentioned example, and is a diagram showing an example of the evaluation results based on the interface level 2 determined by the capacitance measurement method of the formed insulating film. FIG.

Here, the interface state density is 0.7 from the valence band (Ev)
It is at the eV position. In addition, in Fig. 4, the horizontal axis represents the heat treatment time (
Bost annealing time: (seconds), and the vertical axis is the interface state degree N. It is. Roughly speaking, in FIG. 4, the solid line connects the average value of the interface state density at each level, and O at both ends of each level is the maximum or minimum value of the interface state density at that level. Further, in FIG. 4, the interface state density of absolute RM with a boss annealing time of 0 seconds corresponds to the data of the comparative example.

As can be understood from FIG. 4, the interface state density of the sample subjected to boss annealing according to the insulating film forming method of the present invention is improved compared to the comparative sample without boss annealing. Although a detailed analysis of this experimental data has not yet been conducted, in this experimental data, there are variations in the interface states and levels when the boss annealing time is short, and as the boss annealing time increases, the variation and the average value decrease. It can be seen that both are smaller.

Although the embodiment of the insulating film forming method of the present invention has been described above, the present invention is not limited to this embodiment, and various changes and modifications as described below can be made.

In the above embodiments, each heat treatment is performed using an infrared lamp, but this heat treatment may also be performed using an arc club, a laser beam, a heater, or the like.

Further, in the above embodiment, the insulating film is formed by so-called RT.
Although the oxidation process is carried out using O technology, it may also be carried out by a low temperature oxidation method or a diluted oxidation method.

In addition, in the example, before forming the insulating film, heat treatment is performed in a reducing gas atmosphere and a reactive gas atmosphere to clean the base, but this treatment may of course be omitted depending on the design. .

Further, in the above-described embodiments, a silicon oxide film is formed on a silicon substrate, but the method for forming an insulating film of the present invention can also be suitably applied to the formation of oxide films other than silicon.

(Effects of the Invention) As is clear from the above description, according to the method for forming an insulating film of the present invention, heat treatment is performed in an oxidizing gas atmosphere to form an insulating film under the board to a thickness of about 100 mm. After forming the insulating film, heat treatment is continuously performed in an inert gas atmosphere while maintaining the heat treatment temperature used for forming the insulating film. Therefore, unbonded bonds and weak bonds contained in the interface between the base and the insulating film and/or in the insulating film are reduced by heat treatment in an inert gas atmosphere, so that the electrical characteristics of the insulating film are improved.

Therefore, it is possible to form an insulating film having a thickness of about 100λ or less and having excellent film quality.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the insulating film forming method of the embodiment, FIG. 2 is a cross-sectional view showing the main parts of a snowmaking machine suitable for carrying out the insulating film forming method of the present invention, and FIG. FIG. 4 is a diagram showing the overall configuration of an apparatus suitable for carrying out the insulating film forming method of the present invention. FIG. 4 is a diagram for explaining the insulating film forming method of the embodiment. DESCRIPTION OF SYMBOLS 10...Reactor, 10b--Lid member, 12...Exhaust means, +2b...Rotary pump 14...Gas supply section, +4b--Reactive gas source, +4d...Inert Gas source, 10a - Main body 10c = Lifting member 12a... Coupo molecular pump 14a - Reducing gas source 14c... Oxidizing gas source 16... Heating section 16a... Infrared lamp, +6b... Supporting member 1
8...Substrate, 20-...Support body 22...
・Elevating device, 24-・Airtight maintenance member 26-・
-Temperature measuring means, 28-...Gas supply pipe 30-...
Exhaust pipe, 32a to 32d...vacuum gauge 3
4.36a ~36f, 38,40.44.46a ~
46d, 48a, 48b - Valve 42 - Gas supply system 50a, 50b... Gas flow controller.

Claims (4)

[Claims] (1) A step of placing a base in a reactor and performing heat treatment in an oxidizing gas atmosphere to form an insulating film with a thickness of about 100 Å or less on the base, and insulating the base on which the insulating film has been formed. A method for forming an insulating film, comprising the step of continuously performing heat treatment in an inert gas atmosphere while maintaining the heat treatment temperature during film formation. (2) The insulating film forming method according to claim 1, wherein the heat treatment during the insulating film formation and the maintenance of the heat treatment temperature after the insulating film formation are performed by infrared irradiation. (3) In the method for forming an insulating film according to claim 1 or 2, a heat treatment in a reducing gas atmosphere and a heat treatment in a reactive gas atmosphere are sequentially performed on the base before forming the insulating film. Characteristic insulating film formation method. (4) The insulating film forming method according to claim 3, wherein each of the heat treatments in a reducing gas atmosphere and a reactive gas atmosphere is performed by infrared irradiation.