JPH03203236A - Insulation film forming method - Google Patents

Abstract

PURPOSE:To enable film detect due to an uncoupled bond etc., which is produced during formation of an insulation film to be reduced by changing environment within a reaction furnace to a reducing gas environment during formation of the insulation film and by allowing a substrate where the insulation film is being formed to be subjected to heat treatment. CONSTITUTION:An environment within a reaction furnace 10 is changed to a reducing gas environment during formation of an insulation film and a process for performing heat treatment of a substrate 18 while forming the insulation film is included at least once. Thus, heat treatment within the reducing gas environment is performed appropriately for the insulation film which is being formed, thereby enabling the insulation film part which grows to a state before heat treatment is performed within the reducing gas environment to be accurate, with defects removed, contaminants on the surface removed, and then an unpaired coupling of a silicon atom included at this insulation film part and a distorted Si-O-Si coupling are reduced.

Description

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

(Conventional technology) Silicon integrated circuits formed using cutting-edge technology, especially M
OS (Metal Oxide Sem1condu
ctor) In integrated circuits, an extremely thin oxide film is used as a gate insulating film. In particular, in a submicron MOS device having a gate length of 1.0 um or less, an oxide film having a film thickness of, for example, ]0λ 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:
rMO5LsI manufacturing technology, Todoroki Tokuyama, Satoshi Hashimoto
Author, Nikkei McGraw-Hill, Inc., p. 65 (+985)''.

In the method disclosed in this document, first, a cleaned substrate is placed in a quartz tube heated to 800-1200"Cl in an electric furnace. After that, an oxidizing gas for forming an oxide film is applied to the quartz tube. The oxidizing gas used is, for example, dry oxygen gas, a mixed gas of oxygen and hydrogen, or a gas obtained by atomizing hydrochloric acid and mixing it with oxygen gas. By leaving the substrate in the introduced quartz tube 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 method for forming an insulating film disclosed in the above-mentioned document, the film thickness is thin, for example, 100 Å or less. @
It was difficult to control the film thickness in the case of formation. Therefore, when forming a thin oxide film as described above using the conventional absolute Rs formation method, there is a method in which the heating temperature of the quartz tube is lower than 8800°C
Hereinafter, this may be abbreviated as a low-temperature oxidation method. ) or a method of diluting oxygen with nitrogen to reduce the oxidation rate (
Hereinafter, this may be abbreviated as the dilution oxidation method. ).

However, the low-temperature oxidation method has a problem in that the silicon (substrate)/silicon oxide film interface becomes rough. Further, in the diluted oxidation method, nitrogen segregates at the silicon/silicon oxide film interface, resulting in new interface states, and other problems.

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 at the silicon/silicon oxide film interface, which causes the interface state to be high in the first place. There was a tendency. Therefore, when such an oxide film is used as a gate insulating film of a MOS field effect transistor, various problems arise due to the above-mentioned causes. For example, in the case of a fine MOS field effect transistor with a gate length of 11 μm or less, when hot electrons generated in the channel region enter the oxide film, electrons are removed from the silicon atoms in the oxide film. It is trapped by the pair bond or the distorted Si-〇-3i bond and generates a new interface state, which causes a fluctuation in the threshold voltage and a decrease in the transfer conductance in the MO3 type transistor.

The present invention has been made in view of the above points, and therefore, an object of the present invention is to provide an absolute am forming method that can reduce film defects caused by dangling bonds etc. that occur during the formation of an insulating film. .

(Means for Solving the Problems) In order to achieve this objective, according to the present invention, a substrate is subjected to heat treatment in an oxidizing gas atmosphere in a reaction furnace to form an insulating film on the substrate. The method is characterized by including the step of changing the atmosphere in the reactor to a reducing gas atmosphere during the formation of the insulating film and heat-treating the substrate on which the insulating film is being formed at least once.

Note that the substrate referred to here includes not only the substrate itself such as a silicon substrate, but also a substrate on which an epitaxial layer is formed, and an intermediate in which an element is built into a substrate or epitaxial layer. etc., broadly refers to the base on which an insulating film is formed.

Further, in carrying out the present invention, it is preferable to sequentially perform heat treatment on the substrate in a reducing gas atmosphere and heat treatment in a reactive gas atmosphere to clean the substrate before forming the absolute R film. suitable.

Further, in carrying out the present invention, it is preferable to carry out the heat treatment in each of the oxidizing gas atmosphere, reducing gas atmosphere, and reactive gas atmosphere by infrared irradiation.

(Function) According to the insulating film forming method of the present invention, the step of changing the atmosphere in the reactor to a reducing gas atmosphere and heat-treating the substrate on which the insulating film is being formed is included at least once during the insulating film formation. Heat treatment in a reducing gas atmosphere is appropriately performed on the insulating film in the middle. As a result, the insulating film portion that had grown before the heat treatment in a reducing gas atmosphere becomes denser, defects are removed, contaminants on the surface are removed, and unpaired bonds of silicon atoms contained in this insulating film portion are removed. and distorted S
It is possible to reduce i-〇-8i coupling.

Furthermore, when the heat treatment in an oxidizing gas atmosphere is performed by irradiation with an infrared lamp, the substrate can be heated and cooled with good responsiveness.

(Example) Hereinafter, an example of the insulating film forming method of the present invention will be described with reference to the drawings.

The drawings depict each structure 11i to the extent that this invention can be understood.
, the dimensions, shape, and location of the precepts are shown schematically (not too large. Therefore, the dimensions, shapes, and arrangement relationships of each component are not limited to the illustrated example. Also, in the following description, Although specific materials and specific numerical conditions will be cited and explained, these materials and conditions are merely preferred examples, and therefore, the present invention is not limited to these materials and conditions.

2nd First, prior to explaining the insulating film forming method of the present invention, an insulating film forming apparatus suitable for use in carrying out this method will be explained.

FIG. 2 is a cross-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. 2 shows a state in which the substrate is installed in the reactor.

Further, FIG. 3 is a diagram schematically showing the overall configuration of this insulating film forming apparatus.

As shown in FIG. 2, in this embodiment, a reactor (chamber) 10 is composed of, for example, a main body 10a, a lid member 10b, and an elevating member 10c. Main body 10a and lifting member 10
For example, stainless steel is used as the forming material of c, and quartz, for example, is used as the forming material of the lid member 10b and the support body 20, which will be described later.

Moreover, the main body 10a and the elevating member 10c of the above-mentioned reactor 10
are separably integrated to form the recess a. Further, a support 20 for placing the substrate 18 is provided on the side of the recess a of the elevating member 10c, and the substrate 18 with the support 20 placed thereon is put into the reactor 10 or the reactor 10 is moved up and down by the elevating member 10c. Make it possible to take it outside. 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 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 10b, 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.

Furthermore, in this embodiment, the heating section 16 is constructed of an infrared ray 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, a part of the reactor 1o is configured to allow infrared rays to pass from the outside of the reactor 10 into the reactor 1o. In this embodiment, since the lid member 10b is made of quartz as described above, it is possible to transmit infrared rays.

Moreover, the arrangement position M of the support member +6b of the infrared lamp 16a
Although not limited to this, in the illustrated example, the support member +6b is configured such that the contact portion of the cover member +ob and the main body 10a is confined between the support member 161] and the main body 10a.
The support member +6 is detachably attached to the main body 10a.
An airtight member 24 is provided between b and the main body 10. By providing the support member +6b in this way, the reactor 10
It is possible to improve the vacuum tightness inside.

In addition, in FIG. 2, the reference numeral 28 is a gas supply pipe provided between the reactor 1o and the gas supply section 14, and 3o is the gas supply pipe provided between the reactor 1o and the gas supply section 14.
0 and an exhaust pipe provided between exhaust means 120.

Next, the vacuum evacuation system and gas supply system of this embodiment will be explained with reference to FIG. Note that the 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 +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. 3, 32a to 32d are vacuum gauges (or pressure gauges) provided in communication with the exhaust pipe 30.
a and 32d are, for example, Baratron vacuum gauges (or Villany vacuum gauges) used for pressure measurement in the range of 1 to 1 (13 Torr), and vacuum gauges 32b and 32c are, for example, 10
The ion gauge is used for pressure measurement in the range of -'' to 10-'' 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, and when the vacuum gauge 32b is operated, a pressure higher than 1 (I" Torr) is not applied to the vacuum gauge 32b. The opening and closing of the valves 34 are automatically controlled as shown in FIG. The pressure inside the reactor 10 is controlled to any suitable pressure to form a low vacuum evacuation state and a high vacuum evacuation state within the reactor 10.

38 is a needle valve for pressure adjustment, and 40 is a relief valve. The valve 4o automatically opens when the pressure inside the reactor 1o exceeds the atmospheric pressure, for example, 760 Tor rlfr. The gas supplied from the gas supply section 14 into 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 and a reactive gas source +4b.
, an oxidizing gas source 14c, and an inert gas source +4d. For example, as shown in the figure, this gas supply section 14 is connected to the reactor 10 through a supply pipe 28 and a valve provided therein.
Connect by communicating with.

Furthermore, in FIG. 3, 42 is a gas supply system, 44 is a valve, 46a to 46d and 48a, 48b are automatic opening/closing valves, and 50a, 50b are automatic valves that control the flow rate of gas introduced into the reactor 1o from the gas supply section 14. It is a gas flow controller.

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

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 a silicon oxide film is formed on this substrate. Here, FIG. 1 is a diagram for explaining a heating cycle for explaining the insulating film forming method of the present invention. Note that the diagram shows time on the horizontal axis and temperature on the vertical axis.

Also, please refer to FIGS. 2 and 3 as appropriate in the following description.

In this embodiment, after a silicon substrate 18 (hereinafter referred to as the substrate 18) is installed on a support 20 in a reactor 10, an insulating film is formed while cleaning the substrate 18. . This will be explained in detail below.

(2) Cleaning> The substrate 18 can be cleaned, for example, by 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) Pretreatment First, the substrate is precleaned using chemicals, pure water, etc., as is conventionally done.

Next, in order to prevent the formation of a natural oxide film on the substrate 18 in the reactor 1o, an inert gas such as nitrogen gas or argon is introduced in advance into the reactor 1o as a purge gas. I'll keep it. No reducing gas, reactive gas or oxidizing gas is introduced here yet. To supply gas in this way, valves 44, 48b and 46d @
Open, valve 48a.

46a to 46c may be closed.

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

Next, the substrate that has been pretreated as described above is sequentially subjected to heat treatment in a reducing gas atmosphere and heat treatment in a reactive gas atmosphere to clean the substrate. One concrete step is as follows.

■-■ Removal of natural oxide film 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, for example, by 1×
The reactor 1 was evacuated to a vacuum level of lO-8 Torr.
Clean the inside of 0. In addition, for this evacuation, the valves 38, 36a, 36f, 34 are closed, the valves 36b, 36c, 36d are opened %, the rotary pump 12b 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, lX1O-3
After reaching the pressure of Torr, the valves 36c and 36d are closed, the valves 36e and 341 are opened, and the pressure in the reactor 10 is monitored with the vacuum gauge 32b while
The reactor 10 is evacuated to rr.

After the reactor 10 is evacuated to a high vacuum as described above, a reducing gas such as hydrogen gas is introduced into the reactor 10 (region @I:H270- in FIG. 1). 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,
46al is opened and a reducing gas such as hydrogen gas is introduced into the reactor 1.
Supply within 0. At this time, the reduced pressure state in the reactor 10 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, the heating section 16 (thus performs heat treatment for removing the natural oxide film (in the area shown in FIG. 1). This heat treatment heats the substrate 18 in a reducing gas atmosphere,
The natural oxide film No. 8 is reduced and removed from the naturally oxidized 111M substrate 18. In this example, the heat treatment is performed while maintaining the inside of the reactor 10 in a reduced pressure state. Thereby, the reaction products resulting from the reduction of the natural oxide film are exhausted to the outside of the reactor 10, and as a result, the degree of contamination of the substrate 18 and the inside of the reactor 10 by the reaction products 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 0.00° C./sec. Rise at ℃/sec to about 1000
Once the temperature reaches 1000°C, the heating of the substrate 18 is controlled so as to maintain the temperature at 1000°C for approximately 10 to 30 seconds.

Next, the heating of the substrate 18 by the heating unit 16 is stopped, and the IFr valve 46a is closed to stop the supply of reducing gas, and the substrate 18 is cooled until the surface temperature of the substrate 18 reaches room temperature, for example, about 25°C. wait. This cooling may be done so that the substrate 18 is naturally cooled (by straining or forcedly cooled). For forced cooling, for example, the valves 48a and 48a are closed and the valves 48b and 46d are opened and an inert gas is pumped into the reactor. This can be done by introducing a large amount into 10 cells.

Next, valves 38 and 36at are closed and valves 36b and 3 are closed.
6e is opened and the inside of the reactor 10 is heated to, for example, 1x10-8 Torr.
The inside of the reactor 10 is cleaned by evacuating to a high vacuum of r.

■-■...Cleaning of the board surface (close valves 36b and 36e%, then close valve 38,
36aV opening, reactive gas e.g. 1% hydrochloric acid-9 by weight
Hydrochloric acid is atomized at a ratio of 9% hydrogen gas and mixed with hydrogen gas, and the gas is introduced into the reactor 10 (region ■ in FIG. 1: day Cβ flow). When introducing the reactive gas, the reaction furnace 1 is
In order to maintain the reduced pressure state within 0, the inside of the reactor 10 is heated to
Maintain a low vacuum of 100-2 TOrr.

Next, heat treatment is performed by the heating section 16. By this process, the thermally activated reactive gas chemically reacts with the substrate 18 itself and impurities and evaporates, so that impurities such as inorganic substances adhering to the substrate 18 can be removed. Thermal activation of the reactive gas is carried out in this embodiment by irradiating the reactive gas with infrared rays. In addition, since the heat treatment is performed while maintaining the inside of the reactor 10 in a reduced pressure state, the substrate 1
The volatile reaction products from the etching in step 8 are transferred to the reactor 10.
The substrate 18 is evacuated to the outside by reaction products.
And the degree of contamination inside the reactor 10 can be reduced.

This cleaning of the substrate surface can be done, for example, by etching the substrate 18 with a reactive gas for about 20 seconds while heating the substrate 18 so as to maintain the surface temperature of the substrate 18 at about 1000° C. (region ■ in FIG. 1). All you have to do is

Next, the heating section 16 (the heating process is stopped) and the valve 46b is closed to stop the supply of reactive gas and wait for the substrate 18 to cool down to room temperature.
8, natural cooling may be used, or forced cooling may be used.

Next, valve 38.36a! Closed, valves 36b, 36
e lFr open reactor 10, for example, 1x10-'To
Evacuate to high vacuum of rr.

(2) <Formation of oxide film> Next, in order to form an oxide film on the substrate 18 by performing heat treatment in an oxidizing gas atmosphere, the valve 36b is used.

36e lFr open, valves 38.36a, 48b,
46+J open oxidizing gas such as oxygen gas into the reactor 10
(area m in FIG. 1: 0270-). Although oxide film formation can be performed under atmospheric pressure, in order to exhaust the reactive products during oxide film formation to the outside of the reactor 10,
The interior is maintained at a low vacuum of, for example, 100 to 1 O-2 Torr. In this state, the substrate 18 is heated by heat treatment by the heating section 16 to form an oxide film on the surface of the substrate.

The substrate 18 is heated by the infrared lamp 16a of the heating section 16.
It is done by At this time, while measuring the surface temperature of the substrate 180 with the temperature measuring means 26, the temperature of the substrate 18 is increased at an appropriate rate of, for example, 50°C/sec to 200°C/sec, preferably at a heating rate of 100°C/sec. After raising the temperature for about 20 seconds, the temperature was maintained at 1000° C. (region ■ in FIG. 1). In this case, it is preferable to perform heating so that the rate of increase in temperature is constant, and this is because the growth rate of the oxide film is kept constant and oxide S of good quality is formed.

By heating the substrate under these conditions, the film thickness increases by 5.
An oxidation film of 1 m (hereinafter referred to as the first oxide film for convenience of explanation) having a temperature of 0λ can be formed. Note that the thickness of the first oxide film can be controlled, for example, by adjusting the oxidation temperature, oxidation time, and flow rate of the oxidizing gas.

Next, in this embodiment, during the formation of the insulating film, the atmosphere in the reactor is changed to a reducing gas atmosphere and the substrate on which the disconnected film is being formed is subjected to heat treatment in the following manner.

First, the infrared lamp 16a is turned off to stop heating the substrate 18. Next, valve 3 + 36a! Closed, valve 36
b, 368! For example, lXl0-
'Evacuate to high vacuum of Torr.

Next, close the valves 36b, 36c, 36d, and 36e,
Valves 36a and 38 are opened, and in this state valve 44.
48a and 46a are opened to supply a reducing gas, such as hydrogen gas, into the reactor 10 (area ■ in FIG. 1: 270-
). At this time, it is preferable to maintain the inside of the reactor 10 in a reduced pressure state. According to this, impurities and the like that are removed from the first oxide film by the reducing gas in the subsequent heat treatment can be efficiently removed to the outside of the reactor 10. Reactor 10
Maintaining the reduced pressure inside the tank can be achieved by operating the valve 38 while introducing the reducing gas and adjusting the flow rate of the reducing gas field using the automatic controller 50a. In this embodiment, the inside of the reactor 10 is, for example, 100 to 10-2 To
Maintain a low vacuum of r r.

Note that it is possible to change the reactor atmosphere from an oxidizing gas atmosphere to a reducing gas atmosphere after forming the first oxide film while continuing to heat the substrate, but the final film thickness may When forming an oxide film as thin as about 100λ, there is a high risk that the oxide film will grow during gas exchange and reach the final thickness. Therefore, in this embodiment, gas exchange is performed while substrate heating is stopped.

Next, the infrared lamp t6a is turned on and the first oxide film is heated in a reducing gas atmosphere (region ■ in Figure 1). , 1st
It is possible to remove impurities and defects from the oxide film. In this embodiment, this heating is performed as follows.

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 an appropriate rate of 50° C./sec to 200° C./sec, preferably about 00° C./sec, When it reaches about i ooo℃, press 10 for about 10 to 30 seconds.
The heating of the substrate 18 is controlled so as to maintain the temperature at 00°C.

Next, the heating of the substrate 18 by the heating unit 16 is stopped, and the valve 46 is closed to stop the supply of reducing gas, and the substrate 18 is cooled until the temperature of the substrate 18 reaches room temperature, for example, about 25° C. wait for. Note that this cooling may be performed by natural cooling or forced cooling.

Next, valve 38.36a @ closed valve 36b, 36e
Open the IE and check the inside of the reactor 10, for example, lXl0-'To
The inside of the reactor 10 is cleaned by evacuating the high vacuum of rr.

Next, the formation of the oxide film is started again. This formation can be performed in the same manner as the first oxide film formation procedure, and specifically, as follows.

Valve 36b, 36e 'Pa close, valve 38.36
a, 48b, and 46c are opened to supply oxygen gas into the reactor 10 (area V in FIG. 1: 02 flow). At this time, in order to exhaust the reactive products during oxide film formation to the outside of the reactor 10, the inside of the reactor 10 is
Maintain a low vacuum of o r r.

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

Here, the substrate 18 can be heated under the same conditions as when forming the first oxide film. That is, while measuring the surface temperature of the substrate 1 day with the temperature measuring means 26, the temperature of the substrate 18 is adjusted to 50° C., for example.
After increasing the temperature at an appropriate rate between 100°C/sec and 200°C/sec, preferably at a rate of 100°C/sec,
The temperature was maintained at 000°C (area ■ in Figure 1).

By heating the substrate under these conditions, the film thickness increases by 5.
Oxidation S of OA (hereinafter referred to as a second oxide film for convenience of explanation) can be formed. The thickness control of the second oxide film is as follows:
As in the case of the first oxide film, this can be done, for example, by adjusting the oxidation temperature, oxidation time, and flow rate of the oxidizing gas.

After the formation of the second oxide film with the desired thickness is completed, heating of the substrate 18 is then stopped.

At the same time or after the heating stops (this valve 46c
The valve 46d is closed to stop the supply of oxidizing gas and also to prevent the oxide film from growing more than necessary.
It is opened to replace the oxygen gas in the reactor 10 with inert gas.

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.

According to the procedure of the above-mentioned example, the desired film thickness can be achieved by a method that includes the step of changing the atmosphere in the reactor to a reducing gas atmosphere and heat-treating the substrate for oxide film formation once during the formation of the oxide film. An oxide film (approximately 100 in size in this example) is obtained.

Fig. 4(A) 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.

Specifically, a large number of samples having Si oxide with a film thickness of 10oλ were prepared according to the procedure of the example, and the electric field strength (
MV/cm) is shown to show the results of measuring the frequency (%) of occurrence of wire breakage when changing the MV/cm. In addition, Fig. 4 (B) shows a comparison in which the insulating film was formed continuously in an oxidizing gas atmosphere without changing the atmosphere in the reactor to a reducing gas atmosphere (this film thickness was 100 mm). It is a diagram showing the measurement results of electric field strength vs. total clamping breakdown occurrence frequency for the example sample.In addition, in both diagrams, the vertical axis indicates dielectric breakdown occurrence III.
The electric field strength is shown on the horizontal axis.

As is clear from comparing FIG. 4(A) and CB), it can be seen that the breakdown voltage is improved in the case of the example.

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. I can do it.

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, or even a heater.

Further, it is clear that the insulating film forming method of the present invention can improve the quality of the insulating film even when applied to 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. .

Furthermore, in the above embodiment, the atmosphere in the reactor was changed to a reducing gas atmosphere during the formation of the insulating film, and the substrate on which the insulating film was being formed was heat-treated only once, but this number of times was limited to this. Of course, it is okay to do it more than once.

Further, if necessary, heat treatment in a reducing gas atmosphere can be performed even after the formation of the insulating film is completed.

(Effects of the Invention) As is clear from the above description, according to the insulating film forming method of the present invention, the atmosphere in the reactor is changed to a reducing gas atmosphere during the insulating film formation, and the substrate on which the insulating film is being formed is heated. Since the step of heat treatment is included at least once, the insulating film that is being formed is appropriately heat treated in a reducing gas atmosphere. As a result, the insulating film portion that had grown before the heat treatment in the reducing gas atmosphere was densified, defects removed, and
It is possible to remove surface contaminants and further reduce unpaired bonds of silicon atoms and distorted Si--Si bonds contained in this insulating film portion. Therefore, the film quality of the insulating film can be improved, and an insulating film with excellent characteristics can be obtained.

Furthermore, when the heat treatment in an oxidizing gas atmosphere is performed by irradiation with an infrared lamp, the substrate can be heated and cooled with good responsiveness. Therefore, the growth and termination of the insulating film can be performed with good controllability. Therefore, not only can an insulating film with a desired thickness be obtained, but also the growth of the insulating film can be easily stopped when the atmosphere in the reactor is changed to a reducing gas atmosphere during the formation of the insulating film.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining an insulating film forming method according to an embodiment, and is a diagram showing a heating cycle, and FIG. 2 is a detailed explanatory diagram of the present invention, which is suitable for implementing the insulating film forming method. 3 is a detailed explanatory diagram of the present invention, and is a diagram showing the overall configuration of an apparatus suitable for implementing the insulating film forming method. B) is a diagram showing the evaluation results of the insulating films formed by the methods of Examples and Comparative Examples. 0... Reactor, IOa... Main body Ob...
- Lid member, IOc...Elevating member 2...Exhaust means, 12a...Turbo molecular pump 2b...
- Rotary pump 4... gas supply section, 14a - reducing gas source 4
b... Reactive gas source, 14c... Oxidizing gas source 4
d... Inert gas source, 16... Heating section 6a = infrared lamp, +6b... Supporting member 8... Substrate,
20... Support body 22... Lifting device,
24...Airtight maintenance member 26...Temperature measuring means,
28... Gas supply pipe 30... Exhaust pipe,
32a to 32d - Vacuum gauge 34.36a to 36
f, 38, 40, 44.46a ~ 46d, 48a, 4
8b--Valve 42...Gas supply system 50a, 50b...Gas flow rate controller.

Claims (5)

[Claims] (1) In a method of forming an insulating film on a substrate by performing heat treatment on the substrate in an oxidizing gas atmosphere in a reactor, the atmosphere in the reactor is changed to a reducing gas atmosphere during the formation of the insulating film. A method for forming an insulating film, the method comprising the step of heat-treating a substrate during the formation of the insulating film at least once. (2) The insulating film according to claim 1, wherein the substrate is sequentially subjected to heat treatment in a reducing gas atmosphere and heat treatment in a reactive gas atmosphere before forming the insulating film. Formation method. (3) The insulating film forming method according to claim 1, wherein the insulating film is an oxide film. (4) The insulating film forming method according to claim 1 or 2, wherein the reducing gas is hydrogen gas. (5) The insulating film forming method according to claim 1 or 2, wherein the heat treatment in each of the oxidizing gas atmosphere, reducing gas atmosphere, and reactive gas atmosphere is performed by infrared irradiation.