JPH03244125A - Formation of insulating film - Google Patents

Abstract

PURPOSE:To enable formation of insulating films excellent in quality by forming the first insulating film from the first oxidizing gas containing no nitrogen and the overlying second insulating film from the second oxidizing gas containing nitrogen. CONSTITUTION:After a silicon substrate 18 is mounted on a supporter in a reactor furnace, this substrate 18 is cleaned and treated for deposition of an insulating film. That is, the first oxidizing gas containing no nitrogen is used as the insulating film deposition gas to deposit the first insulating film 61 on the substrate 18; then, the second oxidizing gas containing nitrogen is used to deposit the second insulating film 63 on the film 61. In other words, the substrate 18 is overlaid with a silicon oxide film as the film 61 and a silicon oxide nitride film as the film 63, and nitrogen atoms contained in the silicon oxide nitride film by several atom % diffuse uniformly through an insulating film constituted of the silicon oxide nitride film. Therefore, silicon atoms act on unpaired coupling means such as unpaired coupling of silicon atoms contained in these films or strained Si-O-Si coupling to constitute SiN coupling, thereby providing an insulating film excellent in quality.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for forming an insulating film, and particularly to a method for forming an insulating film that is thin and has excellent quality. .

(Conventional technology) Cutting edge technology (silicon integrated circuits formed from this, especially MOS (Metal Oxide Sem1cond)
In integrated circuits, an extremely thin oxide film is used as a gate insulating film. Especially 1. In a submicron MOS device having a gate length of Oum or less, an oxide film having a film thickness of, for example, 100 nm 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:
"rMO3LsI Production Technology," edited by Todoroki Tokuyama and Satoshi Hashimoto, Nikkei McGraw-Hill Publishing, P. 65 (1985).

In the method disclosed in this document, first, a cleaned substrate is placed in a quartz tube heated to 800-1200'C in an electric furnace. Thereafter, 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, a gas obtained by atomizing hydrochloric acid and mixing it with oxygen gas, etc. are used. By leaving the substrate in a quartz tube into which oxidizing gas is introduced at a constant temperature for a period of time commensurate with the thickness of the oxide film to be formed, an oxide film with a uniform thickness is formed on the surface of the substrate. .

(Problems to be Solved by the Invention) However, in the insulating film forming method disclosed in the above-mentioned literature, it is difficult to control the film thickness when forming a thin oxide film having a film thickness of, for example, 100 or less. Therefore, when forming a thin oxide film as described above using the conventional insulating film forming method, the heating temperature of the quartz tube is set to 800 degrees Celsius or less (hereinafter, this may be abbreviated as low-temperature oxidation method). Alternatively, it is necessary to use a method of diluting oxygen with nitrogen to reduce the oxidation rate (hereinafter, this may be abbreviated as a dilution oxidation method).

However, the low-temperature oxidation method has a problem in that the silicon (substrate)/silicon oxide film interface becomes rough. In addition, the dilute oxidation method has problems such as the fact that nitrogen segregates at the silicon/silicon oxide film interface, resulting in the generation of new interface states.

In addition, in both the low temperature oxidation method and the diluted oxidation method,
The resulting oxide film is not dense, and there are many unpaired bonds of silicon atoms or distorted Si-〇Si bonds, for example, at the silicon/silicon oxide film interface and in the oxide film. There was a tendency for the rank to be higher. Therefore, when such an oxide film is used as a gate insulating film of a GMO5 type O5 effect transistor, various problems arise due to the above-mentioned causes. For example, gate length 1
In the case of a micro MO8 field effect transistor with a size smaller than um, when hot electrons generated in the channel region enter the oxide film, the electrons are absorbed into the unpaired bonds of silicon atoms in the oxide film and the distorted Si-〇-. 31 bonds and generates a new interface level, which causes a fluctuation in the threshold voltage and a decrease in transfer conductance in the MO3 type transistor. Alternatively, when an MO3 structure is constructed using such an oxide film and a withstand voltage test is performed on the structure, dangling bonds and distortions of silicon atoms occur.
When bonds such as bonds are broken, new traps are generated in the oxide film, causing dielectric breakdown.

The present invention has been made in view of these points, and therefore, an object of the present invention is to provide a method that can form an insulating film with superior film quality compared to the conventional method.

(Means for Solving the Problems) In order to achieve this objective, according to the present invention, a heat treatment is performed on a substrate in an atmosphere of an absolutely R film forming gas in a reaction furnace, so that the substrate is completely In forming the R film, a first insulating film is formed using a nitrogen-free first oxidizing gas as the insulating film forming gas, and then the above-mentioned insulating film forming gas is replaced with a nitrogen-containing second oxidizing gas. Instead, the method is characterized in that it includes at least one step of forming a second insulating film on the first insulating film described above.

Note that the term "substrate" here refers to not only the substrate itself such as a silicon substrate, but also a substrate on which an epitaxial layer is formed, a substrate, or an epitaxial layer (
This broadly refers to the base material on which an insulating film is to be formed, such as an intermediate body in which a device is fabricated.

Further, in carrying out the present invention, it is preferable to heat the above-mentioned substrate in a reducing gas atmosphere before forming the insulating film.

Further, in carrying out the present invention, it is preferable that the heat treatment in the insulating film-forming gas atmosphere and the heat treatment in the reducing gas atmosphere are each performed by infrared irradiation.

(Function) The method for forming an insulating film of the present invention (according to which a first insulating film is first formed on a substrate using a first oxidizing gas that does not contain nitrogen, and then a second oxidizing gas that does not contain nitrogen is used). First using sexual gas
A second insulating film is formed on the insulating film. Therefore, although a nitrogen-containing oxidizing gas is used, since the first insulating film is already formed on the substrate when this gas is used, nitrogen segregates at the substrate/insulating film interface. Such a thing doesn't happen.

Further, when considering an example in which an insulating film is formed on a silicon substrate, according to the present invention, a silicon oxide film as a first insulating film and a silicon oxynitride film as a second insulating film are formed on the silicon substrate. are formed in this order. In this configuration, the silicon oxynitride film contains several atomic percent of nitrogen atoms. These nitrogen atoms then diffuse uniformly into the silicon oxynitride film and the silicon oxide film, causing unpaired bonds or distorted Sl-○-31 bonds of the silicon atoms contained in these films. It acts on dangling bonds, etc., to form SiN bonds and ON bonds, thereby contributing to the reduction of the dangling bonds.

In addition, according to the configuration in which the substrate is heat-treated in a reducing gas atmosphere before forming the insulating film, natural oxide films etc. on the substrate can be removed and the insulating film can be formed on the cleaned substrate ( This will happen.

Furthermore, when the heat treatment in a reducing gas atmosphere and the heat treatment in an insulating film forming gas atmosphere are each performed by irradiation with an infrared lamp, the substrate can be heated and cooled with good responsiveness.

(Example) Examples of the insulating film forming method of the present invention will be explained below with reference to the drawings.

Note that the drawings only schematically show the dimensions, shapes, and arrangement positions of each component to the extent that the present invention can be understood. Therefore, the dimensions, shapes, and distribution relationships of each component are not limited to the illustrated examples. Further, in the following explanation, specific materials and specific numerical conditions will be cited and explained, but these materials and conditions are merely preferred examples, and therefore, the present invention is not limited to these materials and conditions. .

First, prior to explaining the insulating film forming method of the present invention, an insulating film forming apparatus suitable for carrying out this method will be explained.

FIG. 3 is a sectional view schematically showing the main parts of this insulating film forming apparatus (mainly the structure of the reactor and heating section). Note that FIG. 3 shows a state in which the substrate is installed in the reactor.

Further, FIG. 4 is a diagram schematically showing the overall configuration of this insulating film forming apparatus.

As shown in FIG. 3 (in this embodiment, the reactor (chamber) 10 is composed of, for example, a main body 10a, a lid member +ob, and an elevating member 10c.A main body 10a and an elevating member 1
For example, the material for forming 0c is stainless steel, and the material for forming the lid member 10b and the support body 20, which will be described later, is as follows:
For example, use quartz.

Moreover, the main body 10a and the elevating member 10c of the above-mentioned reactor 10
are separably integrated to form a recess aU shape. Further, a support 20 for placing the substrate 18 is provided on the side of the recess a of the elevating member 10c, so that the elevating member 10c can be raised and lowered (
Thus, the substrate 18 on which the support 20 is placed can be put into the reactor 10 or taken out from the reactor 10. In the illustrated example, the elevating member 10c is connected to, for example, an elevating device 22 for mechanically elevating the elevating member 10c.

Further, the lid member 10b M is detachably attached to the main body 10a. An airtight maintenance member 24, for example, a piton packing, is provided between the main body 10a, the lid member +ob, and the lifting member 10c. Therefore, when the inside of the reactor 10 is evacuated, the airtight state is maintained through the airtightness maintenance member 24. Can be formed.

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

Further, in this embodiment, the heating section 16 is constituted by an infrared irradiation means of any suitable configuration, such as an infrared lamp 16a, and a support member +6b for supporting the infrared lamp 16a. The infrared lamp 16a may be a tungsten halogen lamp or any other suitable lamp. Preferably, a plurality of infrared lamps 16a are arranged so as to uniformly heat the interior of the reactor 10. usually,
The infrared lamp 16a is placed outside the reactor 10. At this time, the reactor 10 is configured to allow infrared rays to pass from outside the reactor 10 into the reactor 10. In this example,
As described above, since the lid member 10b is made of quartz, it is possible to transmit infrared rays.

In addition, the arrangement position of the support member 16b of the infrared lamp 16a is set as follows (although not limited to this, in the illustrated example, the support member +6b% is placed between the support member +6b and the main body 10a, and the cover member +ob and the main body 10a are placed between the support member +6b and the main body 10a). An airtight retaining member 24 is provided between the support member tab and the main body 10, which is removably attached to the main body 10a so as to confine the contact part. 10 can be improved in vacuum tightness.

In addition, in FIG. 3, the reference numeral 28 is a gas supply pipe provided between the reactor 10 and the gas supply section 14 (see FIG. 4), and 30 is an exhaust pipe provided between the reactor 10 and the exhaust means 12. Showing the tube.

Next, the evacuation system and gas supply system of this embodiment will be explained with reference to FIG. 4. Note that the evacuation system and gas supply system are not limited to the example described below.

I will now explain the vacuum exhaust system. In this embodiment, the exhaust means +2i, for example, the turbo molecular pump 12a and the pump 1
2a and a connected rotary pump +2b. 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. 4, 32a to 32d are vacuum gauges (or pressure gauges) provided in communication with the exhaust pipe 30.
a and 32d 8 are Baratron vacuum gauges (or Villany vacuum gauges) used for pressure measurement in the range of 1 to 1 O-3 TOrr, and vacuum gauges 32b and 32c are, for example, 10
An ion gauge used for pressure measurement in the range of -3-10-8 Torr. An automatic opening/closing valve 34 is provided between the vacuum gauge 32b and the exhaust pipe 30 to protect the vacuum gauge 32b.
The opening and closing of the valve 34 is automatically controlled so that a pressure of 10-3 TOrr or more is not applied to the vacuum gauge 32b during operation of the vacuum gauge 32b. 36a to 36f are automatic opening/closing valves provided between the exhaust means 12 and the reactor 10, and by opening and closing these valves 36a to 36f, the pressure inside the reactor 10 can be adjusted to any suitable pressure 1. This control creates a low vacuum evacuation state and a high vacuum evacuation state within the reactor 10.

Furthermore, 38 is a needle valve for pressure adjustment, and 40 is a relief valve. The valve 40 automatically opens when the pressure inside the reactor 10 exceeds atmospheric pressure, for example, 760 Torr. Supply section 14
The gas supplied into the reactor 10 from the reactor 10 is exhausted.

Next, the gas supply system will be explained. In this embodiment, the gas supply unit 14 includes a reducing gas source 14a, a first oxidizing gas source in this case an N20 gas source +4b, and a second oxidizing gas source in this case an 02 gas source 14c. It consists of 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. 4, 42 is a gas supply system, 44 is a valve, 46a to 46d, 48a, 48b are automatic opening/closing valves, and 50a, 50b is a gas flow l introduced into the reactor 10 from the gas supply section 14. Automatic gas flow controller to control.

A desired gas can be supplied from the gas supply unit 14 to the reactor 10 by opening and closing the valves 44, 48a, 48b, and 46a to 46b as desired.

・Multi-method Miro Next, an embodiment of the insulating film forming method of the present invention will be explained using an example in which a silicon substrate is used as the substrate and an insulating film is formed on this substrate. Here, FIGS. 1(A) to 1(F) are process diagrams for explaining the insulating film forming method of the example, and are cross-sectional views of the sample in the main steps of the process, taken in the thickness direction of the silicon substrate. It is a process diagram shown with a figure. Moreover, FIG. 2 is a diagram for explaining the heating cycle carried out during the constraining film forming step of the example. Note that FIG. 2 shows time on the horizontal axis and temperature on the vertical axis.

In the following description, please refer to FIGS. 3 and 4 as appropriate.

In this embodiment, after a silicon substrate 18 (hereinafter referred to as substrate 18) is installed on a support 20 in a reactor 10, the substrate 18 is cleaned and then an insulating film is formed. . Now, let me explain the difficulty of this cleaning.

<Cleaning> The substrate 18 can be cleaned by, for example, a method proposed by the applicant of this application, and this method is also used in this embodiment. I will explain in detail.

(1)-(2) Pre-treatment First, the substrate is pre-cleaned using chemicals, pure water, etc. as has been conventionally done.

Next, in order to prevent the formation of a natural oxide film on the substrate 18 in the reactor 10, an inert gas such as nitrogen gas or argon is introduced in advance into the reactor 10 (for example, as a purge gas). At this point, the reducing gas and oxidizing gas are not introduced yet.
It is sufficient to close the valves 48a, 46a to 46c 7Fr.

Next, one substrate 18 is installed in the reactor 10. Substrate 18
is fixed on the support body 20 of the elevating member 10c.

■-■ Removal of natural oxide film The silicon substrate 18 is placed in the reactor 10 in a state where consideration is given to preventing the formation of a natural oxide film as much as possible as described above. Even if it does, it is unavoidable (a natural oxide film is often formed on the surface).

FIG. 1(A) is a diagram showing this situation, and 18a in the figure
What is shown is a natural oxide film. Therefore, in this embodiment, the natural oxide film 18a is removed as described below.

First, the valves 44, 48b and 46d are closed to stop the supply of inert gas into the reactor 10.

Next, the inside of the reactor 10 is pumped by the exhaust means 12, e.g.
]○ Evacuate the reactor 1 to a vacuum level of -6 TOrr.
Clean the inside of 0. For this evacuation, the valves 38, 36a, 36f, 34 are closed, the valves 36b, 36c, 36d are opened, the rotary pump 12bu is operated, and the pressure inside the reactor 10 is monitored with the vacuum gauge 32a. (monitoring) while exhausting the inside of the reactor 10. Furthermore, the inside of the reactor 10 is, for example, 1×1O-3To.
After the pressure reaches rr, the valves 36c and 36d are closed, the valves 36e and 34u are opened, and the pressure inside the reactor 10 is monitored with the vacuum gauge 32b.
The inside of the reactor 10 is evacuated until the temperature is reached.

After the inside of the reactor 10 is evacuated to a high vacuum as described above, a reducing gas such as hydrogen gas is then introduced into the reactor 10 (region flow in FIG. 2). Introduction of this reducing gas 1
In this case, the valves 36b, 36e, and 34 are closed, and the valve 38.
6a is open, and in this state valves 44, 48a,
Open 46a% and introduce a reducing gas such as hydrogen gas into the reactor 1.
Supply within 0. The reduced pressure state in the reactor 10 at this time can be maintained by operating the valve 38 while introducing the reducing gas and adjusting the flow rate of the reducing gas with the automatic controller 50a. In this embodiment, the interior of the reactor 10 is maintained at a low vacuum of, for example, 100 to 1 O-2 Torr.

Next, heat treatment is performed using the heating unit 16 to remove the native oxide film (in the area shown in FIG. 2). By this heat treatment, the substrate 18 is heated in a reducing gas atmosphere and the substrate 18 is heated.
The natural oxide film is reduced and removed from the substrate 18 (FIG. 1 (8)). When removing the natural oxide film, impurities and the like attached to the surface of the silicon substrate 18 can also be removed. In this example, the heat treatment is performed while maintaining the inside of the reactor 10 in a reduced pressure state. As a result, reaction products resulting from the reduction of the natural oxide film are exhausted to the outside of the reactor 10,
As a result, the reaction products cause the substrate 18 and the reactor 10 to
The degree of internal contamination can be reduced.

Here, this heat treatment is carried out by the infrared lamp 1 of the heating section 16.
6a, and while measuring the surface temperature of the substrate 18 with the temperature measuring means 26, for example, the surface temperature of the substrate 18 is measured at a suitable rate between 50'C/sec and 200'C/sec, preferably about 100'C/sec. Rise at °C/s to approx. 10
When the temperature reaches 00°C, the heating of the substrate 18 is controlled so as to maintain the state at 1000°C for about 10 to 30 seconds.

Next, heating of the substrate 18 by the heating section 16 is stopped, the valve 46a is closed to stop the supply of reducing gas, and the substrate 18 is heated until the surface temperature of the substrate 18 reaches room temperature, for example, about 25°C. Wait for the board 18 to cool down.This cooling may be done by allowing the board 18 to cool naturally, or may be forced to cool down.Forced cooling, for example, the valve 4
8a @ Close, open the valves 48b and 46d, and introduce an inert gas into the reactor 10.

Next, valve 38.36a@close and valve 36b, 36
e@Open the reactor 10 and set the inside of the reactor 10 to, for example, 1×1O-6 Torr.
The inside of the reactor 10 is cleaned by evacuating to a high vacuum of r.

■<Film formation of insulating film> ■-■...Film formation of first insulating film Next, heat treatment is performed in a nitrogen-free first oxidizing gas atmosphere to form the first insulating film on the substrate 18. To form a film,
Valve 36b, 36e % closed, valve 38° 36a,
48b, 46c @open, and in this embodiment, oxygen gas is supplied into the reactor 10 as the first oxidizing gas (region t12rr:02 flow in FIG. 2). Although this first insulating film formation can be performed under atmospheric pressure, in order to exhaust the reactive products during the insulating film formation to the outside of the reactor 10, the interior of the reactor 10 is The substrate 18 is maintained in a reduced pressure state of vacuum. In this state, the substrate 18 is heated by heat treatment by the heating unit 16. Specifically, while measuring the surface temperature of the substrate 18 with the temperature measuring means 26, the temperature of the substrate 18 is measured, for example. at a suitable rate between 50°C/sec and 200'C/sec,
Preferably, the temperature should be raised at a rate of about 00°C/sec and then held at 1000'C for about 20 seconds (region ■ in Figure 2). In this case, the rate of temperature rise is constant. It is preferable to heat the substrate under such conditions in order to maintain a constant growth rate of the first insulating film and form a high-quality insulating film. Therefore, in this case, the silicon oxide film 61 can be formed with a thickness of about 50 mm as the first insulating film (FIG. 2(C)).

Note that the thickness of the first insulating film can be controlled by, for example, adjusting the oxidation temperature, oxidation time, and O2 gas flow Jl.

■-〇... Formation of second insulating film Next, the insulating film forming gas is replaced with a nitrogen-containing second oxidizing gas on the first insulating film 61 (this second insulating film). Forming a film, which in this example is done as described below.

First, the heating of the infrared lamp 16a @extinguishing board 18 is stopped. Next, valve 38.36au is closed, valve 36
b, 36e is opened and the inside of the reactor 10 is heated to, for example, 1×1O-
Evacuate to a high vacuum of 6 Torr.

Next (this, valve 36b, 36e % closed, valve 36a
3848a, 46b are opened to supply a second oxidizing gas, in this example - dinitrogen oxide (N20) gas, into the reactor 10 (region III in FIG. 2: N20 flow). At this time, it is preferable that the inside of the reactor 10 is maintained in a reduced pressure state. According to this, reactive products etc. generated in the subsequent heat treatment can be efficiently removed from the outside of the reactor 10. Also, the reduced pressure state inside the reactor 10 can be maintained by using N20 gas. This can be done by operating the valve 38 while introducing the N20 gas and adjusting the flow rate of the N20 gas with the automatic controller 50a.In this embodiment, the interior of the reactor 10 is maintained at a low vacuum of, for example, 100 to 1 O-2 Torr. .

Note that it is also possible to perform the first insulating film formation @ (changing the reactor atmosphere from the first oxidizing gas atmosphere to the second oxidizing gas atmosphere while continuing to heat the substrate. However, when forming a thin oxide film with a final film thickness of about 100 people, there is a high risk that the insulating film will grow during gas exchange and reach the final film thickness.
In this embodiment, gas exchange is performed while substrate heating is stopped.

Next, the infrared lamp 16a is turned on to heat the first insulating film-formed substrate 18 in an N20 gas atmosphere. Specifically, while measuring the surface temperature of the substrate 18 with the temperature measuring means 26, for example, the surface temperature of the substrate 18 is increased at a rate of, for example, 100°C/second, and when it reaches about 1000°C, the temperature is increased by about 10 to 30°C.
The heating of the substrate 18 is controlled so as to maintain the temperature at 1000° C. for 0 seconds (region 2 in FIG. 2). By heating the substrate 18 under such conditions, a silicon oxynitride film 63 with a film thickness of approximately 50 mm is formed as a second insulating film on the first insulating film 61 (S z 0XNv 0, where X and Y are each ,X
, Y2O. However, ×=Y=○ is not taken. ) can be formed (Fig. 1(D)). Note that the thickness of the second insulating film 63 can be controlled by, for example, adjusting the oxidation temperature, oxidation time, and flow rate of N20 gas.

After the formation of the second insulating film 63 with the desired thickness is completed, the next step (
The heating of the substrate 18 is then stopped.

At the same time or after the heating stops, the valve 46b
i Close to stop the supply of N20 gas.

Through the steps up to this point, an insulating film having a thickness of approximately 100 layers is formed on the silicon substrate 18 by laminating the silicon oxide film 61 and the silicon oxynitride film 63 in this order.

After this, if you want to obtain a roughly thicker insulating film, repeat the steps shown in region II and region (■) in FIG. 2 alternately to correspond to the film thickness ((E) and (F) in FIG. ).Second
Figure area ■~■).

After forming the insulating film with the desired thickness, the infrared lamp 16a
After that, in order to prevent the insulating film from growing more than necessary, the valve 46d is opened and the reactor 10 is turned off.
For example, nitrogen gas is introduced into the chamber.

Next, the substrate 18 is cooled to room temperature, for example, 25°C.

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

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 lamp, a laser beam, a heater, or the like.

Furthermore, it is clear that when the insulating film forming method of the present invention is applied to a low-temperature oxidation method, the film quality of the insulating film can be improved.

In addition, in the example, 02 gas was used as the nitrogen-free first oxidizing gas, and N was used as the nitrogen-containing second oxidizing gas.
It is clear that the first and second oxidizing gases may be other gases that provide the same effect.

Further, in the embodiment, the substrate is cleaned by heat treatment in a reducing gas atmosphere before forming the insulating film, but this treatment may of course be omitted depending on the design.

(Effects of the Invention) As is clear from the above description, the method for forming an insulating film of the present invention includes first forming a first insulating film on a substrate using a first oxidizing gas that does not contain nitrogen. Then, a second insulating film is formed on the first insulating layer using a second oxidizing gas containing nitrogen.

Therefore, even though nitrogen-containing oxidizing gas is used,
When using this gas, it is necessary to avoid the problem of nitrogen segregating on the substrate (this is because the first R film has already been formed) and the interface between the substrate and the insulating film, which was a problem with the diluted oxidation method. The thing is,
That doesn't happen with this invention. Furthermore, when considering an example of forming an insulating film on a silicon substrate, a silicon oxide film as a first insulating film and a silicon oxynitride film as a second R film are formed on the silicon substrate in this order. be done. The nitrogen atoms contained in the silicon oxynitride film at several atomic percent are uniformly diffused into the insulating film composed of the silicon oxynitride film and the silicon oxide film, and the silicon atoms contained in these films are Unpaired bond or distorted Si-○-3i
SiN bonds act on dangling bonds such as bonds, etc.
Constructs an N-coupling.

Therefore, dangling bonds and weak bonds are reduced, so that the dielectric breakdown characteristics of the insulating film can be improved, and an insulating film of excellent quality can be obtained.

Furthermore, according to a configuration in which the substrate is heat-treated in a reducing gas atmosphere before forming the insulating film, natural oxide films etc. on the substrate can be removed, and the insulating film can be formed on the cleaned substrate. Become.

Furthermore, when the heat treatment in the insulating film forming gas atmosphere is performed by irradiation with an infrared lamp, the substrate can be heated and cooled with good responsiveness. Therefore, even if the insulating film is formed under high-temperature conditions, the insulating film can be easily deformed or stopped, making it possible to form an insulating film with a thin film thickness and excellent quality.

[Brief explanation of drawings]

FIGS. 1(A) to (") are process diagrams showing the insulating film forming method of the example, FIG. 2 is a diagram showing a heat cycle carried out in the insulating film forming method of the example, and FIG. FIG. 4 is a detailed explanatory diagram of the present invention, and is a sectional view showing essential parts of an apparatus suitable for implementing the insulating film forming method. FIG. It is a diagram showing the overall structure 1512 of a suitable device. 0... Reactor, 1oa... Main body Ob...
- Lid member, IOc...Elevating member 2...Exhaust means, 12a...Turbo molecular pump 2b...
- Rotary pump 4...Gas supply unit, 14a...Reducing gas source 4b...N20 gas source, 14c...02 gas source 4
d... Inert gas source, 16... Heating section 6a...
Infrared lamp, +6b...Support member 8...Substrate,
2o...Support body 22...Elevating device,
24...Airtight maintenance member 26...Temperature measuring means, 28...Gas supply pipe 30...Exhaust pipe,
32a to 32d...vacuum gauges 34, 36a to 36
f, 38.40.44.46a -46d, 48a,
48b - Valve 42... Gas supply system 50a, 50b... Gas flow controller 18a...
・Natural oxide film 61...First insulating film (silicon oxide film) 63...
Second insulating film (SiOxNy). Gute

Claims (3)

[Claims] (1) When forming an insulating film on the substrate by heat-treating the substrate in an insulating film-forming gas atmosphere in a reaction furnace, the insulating film-forming gas is used as a nitrogen-free first oxidizing gas. forming a first insulating film, and then forming a second insulating film on the first insulating film by replacing the insulating film forming gas with a second oxidizing gas containing nitrogen. An insulating film forming method characterized by: (2) The method for forming an insulating film according to claim 1, wherein the substrate is subjected to heat treatment in a reducing gas atmosphere before forming the first insulating film. (3) The insulating film forming method according to claim 1 or 2, wherein the heat treatment is performed by infrared irradiation.