JPH0418728A - Insulating film formation process - Google Patents

Abstract

PURPOSE:To form the title high quality insulating film developing no film defect with the atoms contained in the insulating film to be formed changing from unstable to stable coupling state by a method wherein a silicon oxide film formed on an underneath silicon is heattreated in the atmosphere of the mixed gas comprising the gas containing the metallic element capable of changing the atoms contained in the silicon oxide film from unstable to stable coupling state as well as an oxidizing gas. CONSTITUTION:A natural oxide film 18a formed on the surface of silicon substrate 18 is heated in a reducing atmosphere to be reduced and then removed. Next, a silicon oxide film 51 is formed on the substrate 18 by heat treatment. Furthermore, Al is selected as a metallic element capable of changing the atoms contained in the silicon oxide film 51 from unstable to stable coupling state; Al(CH3) gas as an organic metallic gas containing said metallic element as well as O2 gas as oxidizing gas are led-in to be mixed with each other at the ratio of 1:1; and then the mixed gas is fed to a reaction furnace to be heat- treated to form an Al2O3 film 53 on the oxide film 51. Finally, an insulating film 55 comprising both films 51, 53 formed by said processes in one laminated body can be formed.

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 extremely thin insulating film with high quality.

(Conventional technology) Silicon integrated circuits formed using cutting-edge technology, especially M
OS (Metal Oxide Sem1conduc
(tor) In integrated circuits, a very thin oxide film is used as a gate insulating film. Especially 1. In a submicron MOS device having a gate length of less than Oum, 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.

The formation of the oxide film is carried out as follows, for example, as shown in the document: rMO3LsI Manufacturing Technology, edited by Tokuyama ^, Satoshi Hashimoto, Nikkei McGraw-Hill Publishing, P. 65-82 (+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. Thereafter, a preliminary oxidizing gas for forming an oxide film is introduced into the quartz tube. As the oxidizing gas, for example, dry oxygen gas or a mixed gas of oxygen and hydrogen,
Alternatively, use a gas containing atomized hydrochloric acid (strained and mixed with oxygen gas). As shown by the broken line curve shown in Pro. Release the board with M()
By growing the oxide film continuously, an oxide film with a uniform thickness is formed on the surface of the substrate.

(Problem to be solved by the invention) However, in the oxide film forming method described above, the oxide film is grown continuously without any break, so for example,
It was difficult to control the film thickness in the thin region below A.

Therefore, when forming such a thin oxide film, in order to control the film thickness, it is necessary to lower the oxidation temperature to below 800°C to reduce the oxidation rate (hereinafter, this may be referred to as the low-temperature oxidation method). ), or a method was used in which the oxidation rate was lowered by diluting the oxygen with crab meat (hereinafter, this may be referred to as the diluted oxidation method).

However, the low temperature oxidation method has a problem in that the silicon/silicon dioxide interface becomes rough.

On the other hand, in the case of the diluted oxidation method, nitrogen segregates at the silicon/silicon dioxide interface, resulting in problems such as the generation of new interfacial quasi-sulfur. Therefore, no matter which of the above-mentioned methods is carried out, it is not possible to expect an improvement in the film quality itself such as resistance to bond breakdown of a thin oxide film.

In addition, the oxide films obtained by these low-temperature oxidation methods and dilute oxidation methods are generally not dense, and there may be unstable bonding states of atoms at the silicon/silicon oxide film interface or in the oxide film, for example,
It has an amorphous structure in which there are many dangling bonds, unpaired bonds of silicon atoms, 5i-3i bonds including weak bonds, S]-〇 bonds, ○-O bonds, or distorted 5i-0-8i bonds. Therefore, there was a tendency for the interface level (Dit) to become high in the first place. When the oxide film formed in this manner is used as a gate oxide film of a MOS field effect transistor, various problems arise due to the above-mentioned phenomenon. For example, in a micro MOS field effect transistor with a gate length of 1.0 um or less, if hot electrons generated in the channel region enter the oxide film, the electrons will form bonds between silicon atoms or strained Sl This results in problems such as being trapped by the -○ bond and generating a new interface level, causing fluctuations in threshold voltage and reduction in transfer conductance in MO3 type transistors.

Additionally, in general, when stress is applied to the formed oxide film, the 5i-3i bonds and 〇-〇 bonds, which include dangling bonds and weak bonds, in the oxide film are broken, and holes are created in the insulating film 5102. Since a trap occurs, the C-7 curve moves largely in the negative voltage direction. Additionally, new interface levels (Di) are generated at the silicon oxide film interface due to stress. Therefore, we fabricated a MOS capacitor using the conventional oxide film formation method, and the C~
When the curve was measured, the C-7 curve was as shown in FIG. Before stress application (
Compared to the solid line curve), after the stress is applied (broken line curve), the voltage moves significantly toward the negative voltage side, and the slope of the curve becomes smaller. Therefore, there is a problem that the electrical characteristics of the MOS capacitor deteriorate.

This invention has been made in view of the above-mentioned conventional problems, and therefore, an object of the invention is to reduce film defects caused by dangling bonds generated during the formation of an insulating film.
An object of the present invention is to provide an insulating film forming method that can form a thin insulating film.

(Means for Solving the Problems) In order to achieve this object, according to the present invention, a silicon base is heat-treated in a gas atmosphere for forming an insulating film in a reaction furnace to form an insulating film on the base. In forming the first insulating film, the silicon base is heat-treated in a gas atmosphere of the first oxidizing gas to convert the first insulating film into a silicon oxide film and [
), and then in a mixed gas atmosphere of a gas containing a metal element and a second oxidizing gas, which changes the unstable bonding state of atoms in this silicon oxide film to a stable bonding state. The method is characterized in that it includes a step of forming a second insulating film containing the aforementioned metal element on the aforementioned silicon oxide film by heat treatment.

In carrying out the present invention, preferably, the gas containing the metal element is an organometallic gas containing the aluminum (Δβ) element.

Furthermore, in carrying out the present invention, preferably the organometallic gas is one type of gas selected from the gas group Aβ(CH3) 3 , A, Q(C4H9)3 and Δρ(CH3)2H. good.

In general, in carrying out the present invention, it is preferable to use a gas containing a metal element as an organic substance (Ta (OCH3)5) gas or (Ta(○C2H)) gas containing a tantalum (C2H) element.
! ) 5) Is it better to use gas?

Furthermore, in carrying out the present invention, the oxidizing gas is oxygen (O
2) Either gas or dinitrogen monoxide (N2O) gas may be used.

Further, in carrying out the present invention, the second oxidizing gas may be either oxygen (O2) gas or dinitrogen monoxide (N2O) gas.

Further, in carrying out the present invention, it is preferable to use a silicon base that has been cleaned by performing heat treatment on the base in a reducing gas atmosphere before forming the first insulating film. good.

Further, in carrying out the present invention, the heat treatment is preferably performed by infrared irradiation.

Note that the term "silicon base" as used herein refers to not only a silicon substrate, but also a silicon substrate on which an epitaxial layer is formed, and other intermediates in which elements are built into the substrate or epitaxial layer. , refers to a wide base on which an insulating film is to be formed.

(Function) According to the insulating film forming method of the present invention described above, atomic free atoms present in the silicon oxide film are formed on the silicon oxide film as the first insulating film formed on the silicon base. The second insulating film is formed by heat treatment in a mixed gas atmosphere of a gas containing a metal and an oxidizing gas that changes a stable bonding state to a stable bonding state. Therefore, the obtained second insulating film is a metal oxide film, and the degree of oxidation is sufficiently compensated by the oxidizing gas, and moreover, the fully bent atoms in this metal oxide film are bonded with silicon atoms and oxygen atoms. , resulting in a stable bonding state of atoms. As a result, the insulating film composed of the first and second insulating films becomes a high quality film free from film defects.

Furthermore, the formation method of the present invention (according to which the first insulating film and the second insulating film can be continuously formed in the same reactor) simplifies the insulating film forming process, and also increases the thickness of the film. control is also improved.

(Embodiments) Hereinafter, embodiments of the invention of this application will be described with reference to the drawings.

Note that the drawings only schematically illustrate the dimensions, shapes, and locations of each component to the extent that the invention can be understood.

Further, in the following description, 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 in any way.

First, before entering into a detailed description of the present invention, an apparatus for carrying out the present invention will be explained.

<Description of an embodiment of the structure of an insulating film forming apparatus suitable for use in carrying out the present invention> FIG. 2 shows the main parts (main and () 2 is a cross-sectional view schematically showing the configuration of a reactor and a heating section. FIG. 2 shows a state in which a substrate is installed in the reactor.

Moreover, FIG. 3 is a diagram provided for detailed explanation of this invention,
1 is a diagram schematically showing the overall configuration of an insulating film forming apparatus.

As shown in FIG. 3, this insulating film forming apparatus includes a reactor 10 in which a substrate is installed, an exhaust means 12 for evacuating the inside of the reactor 10, a gas supply section 14, and a heat treatment. A first heating section 16 is provided. below,
An example of the structure of this device will be described.

As shown in FIG. 2, in this embodiment, the 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
As the forming material of c, for example, stainless steel may be used, and as the forming material of the lid member 10b and the support body 2O, which will be described later, for example, quartz may be used, or the reverse combination may be used.

The main body 10a and the elevating member 10c are separably integrated to form a recessed portion a, and a support 2O for placing the substrate 18 is provided on the side of the recessed portion a of the elevating member 10c, so that the elevating member 10c can be moved up and down. Substrate with supporting body 2O+
8V so that it can be put into the reactor 10 or taken out from the reactor 10. In the illustrated example, an elevating member 10c for mechanically elevating and lowering the elevating member 10c is connected to an elevating device 22.

Further, the lid member 10b is detachably attached to the main body 10a. An airtight maintaining 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, air and the holding member 24 are used to maintain the airtight state. This allows for the formation of

A temperature measuring means 26, for example, an optical pyrometer, for measuring the surface temperature of the substrate 18 is provided in the vicinity of the substrate in the concave portion a.

Further, in this embodiment, the heating section 16 is configured with an infrared ray irradiation means of any suitable configuration, for example, an infrared lamp 16a and a support member +6b for supporting the negative means 16a. It would be better to use a lamp that emits light in a wavelength range that can efficiently heat 18.
It is composed of any suitable lamp depending on the substrate material. This embodiment uses a tungsten Herroken 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.

Typically, the infrared lamp 16a is placed outside the reactor 10. At this time, a part of the reactor 10 is made of a material that transmits infrared rays, and infrared rays are transmitted from outside the reactor 10 to the reactor 10.
Allow it to penetrate inside. As already explained,
In this embodiment, since the lid member 10b is made of quartz, it can transmit infrared rays.

The configuration and placement position of the heating unit 16 may be any suitable configuration and placement position that can perform the heat treatment described below. For example, the heating unit 16 may be configured with a heater, and this heater may be provided in the reaction furnace 10. It's okay to say "Yo" (Kol).

The arrangement position of the support member +6b may not be limited to this.In the illustrated example, the support member +6b is arranged so that the abutting portions of the M member +01) and the main body 10a are confined between the support member +6b and the main body 10a. In addition, an air retaining 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 way, it is possible to improve the vacuum recordability within the reactor 10.

In FIG. 2, the reference numeral 28 indicates the gas supply pipe between the reactor 10 and the gas supply section 14, and the reference numeral 30 indicates the gas supply pipe provided therein.
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 FIG. 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 boss 12a and the 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 Et and 32d @For example 1-10-3To r r
Baratron vacuum gauge (or Villany vacuum gauge) used for pressure measurement in the range of , and vacuum gauges 32b and 32c @
For example, the ion cage is used for pressure measurement in the range of 10-''-1O-8 Torr.The vacuum gauge 32b and the exhaust pipe 30
There is an automatic opening/closing valve 34 between the vacuum gauge 32b to protect the vacuum gauge 32b, and the valve 34 is automatically opened/closed so as not to apply a pressure of 10-3 Torr or more to the vacuum gauge 32b when the vacuum gauge 32b is operated. Control. Reference numerals 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 as desired, the pressure within the reactor group can be controlled to any desired pressure. Then, a low vacuum evacuation state and a high vacuum evacuation state are created in the reactor IO.

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 or the atmospheric pressure exceeds, for example, 760 Torr. Supply section 14
The gas supplied into the reactor 10 is then exhausted.

Next, the gas supply system (we will explain the difficulty. In this embodiment, the gas supply section 14 is a reducing gas source 14a, a reactive gas source 14b
, an oxidizing gas source 14c, and a purge gas source such as an inert gas source +4d. The gas supply section 14 is connected in communication with the reactor 10 via a supply pipe 28 and a valve arranged as shown in the figure, for example.

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

Valves 44.48a, 48b, 46a-46d
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.

<Description of Examples of the Insulating Film Forming Method of the Invention> Next, the insulating film forming method of the invention will be described.

FIGS. 1 (Δ) to (D) are process diagrams for explaining one embodiment of the insulating film forming method of the present invention, and each figure shows a cross-sectional view of the structure obtained in the main process steps. This is schematically shown.

Further, FIG. 4 is a diagram for explaining a heating cycle, which is provided for explaining the present invention. The horizontal axis of the figure plots time and the vertical axis plots temperature.

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

In this invention, after a silicon base is placed in a reactor, the base is cleaned and then an insulating film is formed. This will be explained in detail below.

(1) [Cleaning] Regarding the cleaning method of the substrate before forming this insulating film, the applicant of this application (therefore, whether it has already been proposed or not)
It is preferable to use this cleaning method in the method of the present invention, and this will be explained below.

In the embodiment of the present invention, a silicon substrate, for example, is prepared as a base, and the substrate is pre-cleaned for one day using chemicals, pure water, etc., as is conventionally done.

Next, in order to prevent a natural oxide film from being formed on the substrate 18 in the reactor 10, an inert gas for purging, such as nitrogen gas or argon gas, is introduced into the reactor 10 in advance. Reducing gases, reactive gases and oxidizing gases are not yet introduced. At this time, valves 44.48b and 46d%
open, and keep valves 48a, 46a-46c closed.

Next, the substrate 18 is placed inside the reactor 10 . The substrate 18 is fixed on the support 2O of the elevating member 10c. At this time, since the substrate 18 is once exposed to air, a natural oxide film 18a is formed on the surface of the substrate (FIG. 1 (Δ)).

Next, after these pretreatments, the substrate surface is cleaned. In this cleaning process, the substrate 18 is cleaned in the reactor 10 by performing heat treatment in a reducing gas atmosphere.

The cleaning process for this substrate will be explained below.

When cleaning the opening string a row shade wide board, please use the mass valves 44, 48b, 46d.
The reactor 10 is closed and the supply of inert gas to the inside of the reactor 10 in which the substrate 18 is installed is stopped.

Next, the inside of the reactor 10 is pumped by the exhaust means 12, e.g.
The inside of the reactor 10 is cleaned by evacuating to a high vacuum of 10-6 Torr. To perform this vacuum evacuation, valve 38.
36a, 36e, 36f, and 34 are closed, valves 36b, 36c, and 36d are opened to operate the rotary pump 12b, and the pressure inside the reactor 10 is measured by the vacuum gauge 32.
Perform vacuum evacuation while monitoring with a.

And inside the reactor 10, for example, 1 x 1O-3 Torr
The pressure becomes r.1. : Rear, valves 36c, 36d
@Close valve 36e, 34u open, vacuum gauge 32b
Monitor the pressure inside the reactor 10 with 1xlO-6
The inside of the reactor 10 is evacuated to Torr.

After evacuating the reactor 10 to a high vacuum, a reducing gas such as hydrogen gas is introduced into the reactor 10 (H2 in FIG. 4).
flow). When introducing the reducing gas, the valves 36b and 36e are used to maintain the reduced pressure state in the reactor 10 during the next heat treatment in the reducing gas atmosphere.
, 34u is closed to open the valve 38.36a, and in this state, the valves 44.48a and 46a are opened to supply reducing gas, such as hydrogen gas, into the reactor 10.

The reduced pressure state in the reactor 10 can be maintained by operating the valve 38 without introducing the reducing gas and by adjusting the flow rate of the reducing gas and the automatic flow rate controller 50a. In this embodiment, the interior of the reactor 10 is, for example, 100
Maintain a low vacuum of ~10-2 Torr.

Next, the heating unit 16 heats the natural oxide film 18a (FIG. 1(A)
))) (see H in Figure 4).
2 heating during flow). By this heat treatment, the substrate 18 is heated in a reducing gas atmosphere to reduce the natural oxide film 18a of the substrate 18 and remove the natural oxide film from the substrate 18 (FIG. 1(B)). The substrate 18 is heated, for example, by irradiating the substrate 18 with infrared rays. In addition, as already explained in 1,
In this embodiment, the heat treatment is performed while the inside of the reactor 10 is maintained in a reduced pressure state. As a result, the reaction products caused by 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 reaction products can be reduced.

In this heat treatment, 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
Rise to about 1000°C at a suitable rate of 100'C/sec to 200'C/sec, preferably about 100'C/sec.
When this happens, the heating of the substrate 18 is controlled so as to maintain the temperature at 000° C. for approximately 10 to 30 seconds.

Next, the heating of the substrate 18 by the heating unit 16 is stopped, and the supply of reducing gas is stopped by closing the valve 46a, and the surface temperature of the substrate 18 is reduced to room temperature, for example, about 25°C.
Wait for the substrate 18 to cool down until the temperature reaches C.

This cooling may be done by allowing the substrate 18 to cool naturally or by forcibly cooling it. Forced cooling can be performed, for example, by closing the valve 48a and opening the valves 48b and 46d to introduce a large amount of inert gas into the reactor 1o.

Next, valve 38.36a @close and valve 36b, 3
6e is opened and the inside of the reactor 10 is heated to, for example, lXl0-'Tor.
The inside of the reactor 10 is cleaned by evacuating to a high vacuum of r.

■ [Cleaning of the substrate surface] Next, close the valves 36b and 36e to clean the valve 38.3.
6a and add a reactive gas such as 1% hydrochloric acid-99 by weight.
% hydrogen gas and a mixture of hydrogen gas and atomized hydrochloric acid is introduced (HCβ flow in FIG. 4). When introducing the reactive gas, in order to maintain the reduced pressure state in the reactor 10 during the next heat treatment in the reactive gas atmosphere, the same procedure as in the heat treatment in the reducing gas atmosphere is carried out. ,
The interior of the reactor io is maintained at a low vacuum of, for example, 100 to 1 O-2 Torr.

Next, heat treatment is performed by the heating section 16. By this heat treatment, the thermally activated reactive gas
Since the substrate 18 is etched by chemically reacting with itself and impurities to form a volatile reaction product, impurities such as inorganic substances adhering to the substrate 18 can be removed. Thermal activation of the reactive gas is carried out, for example, by irradiating the reactive gas with infrared rays. Since the heat treatment is performed while maintaining the inside of the reactor 10 in a reduced pressure state, volatile reaction products from etching the substrate 18 are exhausted to the outside of the reactor 10, and as a result, the reaction products cause the substrate 18 and the reactor 10 to The degree of internal contamination can be reduced.

If the substrate 1B is also heated in this heat treatment, the reactivity between the reactive gas and the substrate 18 and impurities can be improved.

For example, the substrate 18 may be heated to maintain the surface temperature of the substrate 18 at about 1000° C., and then the substrate 18 may be etched with a reactive gas for about 20 seconds.

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

Then valve 38.36a lFr closes, valve 36b
, 36e is opened and the inside of the reactor 1o is heated with, for example, 1xlO-6T.

Evacuate to high vacuum of rr.

■ [Formation of silicon oxide film, which is the first insulating film.] Next, heat treatment is performed in an oxidizing gas atmosphere to form a silicon oxide film, which is the first insulating film, on the substrate 18 using the valve 36.
b, 36e closed, valves 38.36a, 48b
, 46c @open, and oxidizing gas, such as oxygen (O2) gas, is supplied into the reactor 10 (02 flow in FIG. 4). At this time, in order to exhaust the reaction products during the oxide film formation to the outside of the reactor 10, the interior of the reactor 10 is
Maintain a low vacuum of rr.

Next, the substrate 18 is heated by heat treatment by the heating unit 16 to form an oxide film 51 on the substrate surface (FIG. 1(C)).
).

The substrate 18 is heated, for example, at 50'C/sec to 2O0 while measuring the substrate surface temperature with the temperature measuring means 26.
heating temperature T, about 1000° C., preferably at a heating rate of about 100° C./sec.
preferably for about 20 seconds (tl in Figure 4).
(for the time shown in ), so as to maintain it at approximately 10006G. In this case, whether it is preferable to increase the temperature at a constant rate is the key to forming a high-quality film by keeping the growth rate of an insulating film such as an oxide film constant. The temperature increase rate is set within the above-mentioned range in order to control the film thickness and/or to form a film with good quality. Also, the heating temperature T
, % is set at about 1000° C. because this is the preferable minimum temperature required for forming an insulating film. In addition, the reason why tl is set to about 20 seconds is from the viewpoint of controllability of film thickness and good film quality. oxide film can be formed.

The thickness of the oxide film can be controlled, for example, by adjusting the oxidation temperature, oxidation time, and flow rate of the oxidizing gas.

After forming the oxide film 51 of a desired thickness, heating of the substrate 18 is then stopped.

At the same time or after the heating stops, the valve 45
Close c to stop the supply of oxidizing gas.

Next, the substrate 18 is cooled to room temperature, for example, 256C.

The oxide film obtained through such a process has unstable bonding states of silicon atoms and oxygen atoms in the silicon oxide film (including the silicon/oxide film interface), such as 5i-8i bonds containing dangling bonds, It has an amorphous structure with a large number of 5i-0 bonds, O-○ bonds, and other non-bonds.

■ [Deposition of second insulating film] Next, the first step in improving the electrical characteristics of the first insulating film 51 is to
A second insulating film is formed.

In this embodiment, an aluminum oxide (Aff2O3) film 53 is formed as the second insulating film (FIG. 1(D)).

This Aβ2O3 film 53 is similar to the silicon oxide film 51 described above.
After completion of the formation, the film is continuously formed by the method described below without exposing the reactor 10 to the atmosphere.

First, valve 38.36a k closed, valve 361),
36e is opened and the inside of the reactor 10 is 1×10-”T'or
After evacuation to a high vacuum of r, valves 36b and 36e are closed again, and valves 38.36a, 48b and 46d are opened. Then, aluminum (Aβ) is selected as the metal element that changes the unstable bonding state of atoms in the silicon oxide film 51 to a stable bonding state, and trimethylaluminum (Aβ) is selected as the organometallic gas containing this aluminum element.
ρ(CH3)) gas is introduced, and at the same time, valves +4d and 46c are opened to inject oxygen (CH3) as an oxidizing gas.
O2) gas 14c is introduced, and these are mixed at a ratio of 1.1,
Supplied into the reactor 10 (Aβ(CH3)2 in FIG.
H+02 flow). At this time, the reaction products are removed from the reactor 1o in the same manner as in the silicon oxide film 51 which is the first insulating film 51.
In order to exhaust the air to the outside, the inside of the reactor 10 is adjusted by the automatic flow rate controller 50a, and the inside of the reactor 10 is heated to, for example, 1×102 to 1×
Maintain a low vacuum of 10-2 Torr.

Next, a p2O3 film 53 is formed on the oxide film by heat treatment using the heating unit 16. The heat treatment is preferably performed under the same treatment process, temperature increase, heating temperature, and heating time conditions as those used for forming the first insulating film. As a result, about 50 Aβ2O3 films 53 are grown on the oxide film (FIG. 1(D)). When the Aρ2O3 film 53 has a desired thickness and a film length of 3, heating is then stopped. Along with this heating stop, the valve 4
6d and stop the supply of Al2(CH3)3 gas,
At the same time, the valve 46c is closed to stop the supply of oxygen (O2) gas.

Next, the valve 46d is opened to replace the gas with nitrogen (N2). By replacing with an inert gas, excessive growth of Vf (fl) can be stopped.

Finally, the film forming process is completed by cooling the substrate 1B to room temperature by forced cooling in a furnace.

Through these steps, a silicon oxide film, which is the first insulating film 51, and an aluminum oxide (Aρ2O3) film, which is the second insulating film, are mainly formed, and both films are used to cover the silicon substrate 18. One layered insulating film 55 is obtained on top.

A MOS capacitor was manufactured using the insulating film 55 obtained in this way, and the C-V before and after the constant voltage stress application test was
When the curve was examined, the results shown in FIG. 6(B) were obtained. This Fig. 6(B) is similar to the already explained Fig. 6(B).
As in case A), the horizontal axis represents the gate voltage (V) and the vertical axis represents the normalized capacitance (C/Cox)! The solid line curve shows the C-7 curve before stress application, and the broken line curve shows the C-7 curve after stress application.

As can be understood from this test result, the MOS capacitor C with the same laminated insulating film obtained in this example has the same stress as the MOS capacitor C manufactured by the conventional method and having a hollow insulating film. It can be seen that the amount of variation in the C-7 curve is small upon application. The reason for this is that AI2 atoms contained in the formed △ρ2O3 film 53 penetrate into the underlying silicon oxide film, and as a result, new 5i
It is thought that this is because stable bonding states of atoms such as -Af2 bond and 〇-Al bond are already generated. Therefore,
When such a metal oxide film is formed on a silicon oxide film to form a single insulating film with a stacked structure, the unstable bonding state of atoms in the underlying silicon oxide film (including the interface) Some dangling bonds or weak bonds are reduced, and as a result, the formed insulating film has no film defects, resulting in a high-quality film, which in turn improves the electrical performance of electronic devices formed using this insulating film. It is possible to improve the characteristics.

The present invention is not limited to the embodiments described above, and various changes and modifications as described below can be made.

In the above-mentioned embodiment, AI! Using (CH3)3, we can write 1, /l (
Instead of using CH3)3, Aρ(C4Hq)3
A similar effect can be achieved using gas or 8β(CH3)2H gas.

In addition, Aβ will be explained as this metal element.1. l:
It is also possible to use a metal element other than the aluminum (β) element, for example tantalum (Ta), in which case tantalum pentoxide (Ta2O5) is added to the silicon oxide layer.
) or layered as a metal oxide film. This Ta, Os film is generally formed by thermal chemical vapor deposition. Ta (ocH3) in raw materials and lno5. Ta (OC2N
5) Is it possible to use Ta-based organic substances such as s and oxygen (O2)? Since Ta-based organic substances are liquid at room temperature,
Ta (OCH
3) 5 gases or 1,tTa(○C2H3)5 gases may be introduced into the reactor.

In addition, in the above-mentioned embodiment, the oxidizing gas was "C oxygen (O
2) Although a gas was used, a sufficient oxidizing effect can be similarly obtained by using a nitrogen oxide (N2O) gas instead of this oxygen gas.

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

Further, the insulating film forming method of the present invention includes heat treatment using a mixed gas of a gas containing a metal element and an oxidizing gas that changes the unstable bonding state of atoms in the silicon oxide film to a stable bonding state. As long as the film is formed using low-temperature oxidation, it is natural that the quality of the insulating film can be improved even if the insulating film is formed using the low-temperature oxidation method or the diluted oxidation method. It is clear to the business operator.

Furthermore, in the above-described embodiments, the underlying substrate is cleaned by heating in a reducing gas atmosphere before forming the insulating film, or this treatment may of course be omitted if necessary.

(Effects of the Invention) As is clear from the above description, according to the method for forming an insulating film of the present invention, a silicon oxide film formed on a silicon base is coated with a silicon oxide film (silicon/' The metal is bonded by heat treatment in a mixed gas of an oxidizing gas and a gas containing a metal element that can change the unstable bonding state of atoms contained in the silicon oxide film (including the silicon oxide film interface) to a stable bonding state. An oxide film is formed, and an insulating film with a laminated structure of silicon oxide film and gold R oxide film is formed.In the formed insulating film, atoms that have survived unstable bonds or atoms of this metal element are formed. A high-quality insulating film with no film defects can be obtained by bonding with atoms in a stable bonding state (this changes). Therefore, when an electronic device such as a MOS transistor is manufactured using an insulating film formed according to the present invention, these The electrical characteristics of electronic devices can be improved more than before.

However, according to the forming method of the present invention, heating treatment in a gas atmosphere J,! After forming a wrinkled oxide film as the first insulating film, a metal oxide film as the second insulating film was subsequently deposited in a gas atmosphere without exposing the reactor to the atmosphere. Since the film is formed by heat treatment, the process of forming the insulating film is simplified, and the film thickness can be controlled with high precision by controlling the gas flow rate, heating time, and temperature rise and humidity.

[Brief explanation of drawings]

FIG. 1 is a process diagram for explaining an embodiment of the insulating film forming method of the present invention, and FIG. 2 schematically shows the main parts for carrying out an embodiment of the insulating film forming method of the present invention. 3 is a diagram schematically showing the overall configuration of an apparatus for carrying out an embodiment of the insulating film forming method of the present invention, and FIG. 4 is a diagram showing one embodiment of the insulating film forming method of the present invention. Figure 5 is an oxidation time-oxide film thickness characteristic curve diagram used to explain the present invention and the conventional insulating film forming method. and C-■ curve diagrams before and after stress application, which serve to explain the present invention. 0... Reactor, Ob... Lid member, 2... Exhaust means, 2b... Rotary 4... Gas supply section, 4b... Reactive gas source, 4d... Inert gas Source, 6a...Infrared lamp, 8...Substrate, 2O...Support, 24...Presence holding member, 28...Gas supply pipe, to 32a/32d...Vacuum gauge 34.36a -36f, 38. 48a, 48b - Valve pump 10a... Main body IOC... Lifting member 12a... Turbo molecular pump 4a... Reducing gas source 4G... Oxidizing gas source 6... Heating section 6b... Support Member 8a... Natural oxide film 22... Lifting device 26... Temperature measurement means 30... Exhaust pipe 40.44, 46a = 46d, 42... Gas supply system 50a, 50b... Gas flow rate Controller 51・
...Oxide film, 53...△f! 2O3 film 55
...Insulating film.

Claims (8)

[Claims] (1) When performing heat treatment on a silicon base in a gas atmosphere for forming an insulating film in a reaction furnace to form an insulating film on the base, the silicon base is heated in a gas atmosphere of the first oxidizing gas. forming a first insulating film as a silicon oxide film by heat-treating the silicon oxide film, and subsequently using a gas containing a metal element to change an unstable bonding state of atoms in the silicon oxide film to a stable bonding state. 2. A method for forming an insulating film, comprising the step of forming a second insulating film containing the metal element on the silicon oxide film by heat treatment in a mixed gas atmosphere with an oxidizing gas. . (2) A method for forming an insulating film, characterized in that the gas containing the metal element according to claim 1 is an organometallic gas containing an aluminum (Al) element. (3) Al(CH_3
)_3, Al(C_4H_9)_3 and Al(CH_
3) An insulating film forming method characterized by using one type of gas selected from the _2H gas group. (4) The gas containing the metal element according to claim 1 is an organometallic gas containing tantalum (Ta) element (Ta(OCH
_3)_5) Gas or (Ta(OC_2H_5)_5
) An insulating film forming method characterized by using gas. (5) The first oxidizing gas according to claim 1 is oxygen (O_2
) gas and dinitrogen monoxide (N_2O) gas. (6) The second oxidizing gas according to claim 2 is oxygen (O_
2) An insulating film forming method characterized by using either gas or dinitrogen monoxide (N_2O) gas. (7) The silicon base according to claim 1 is a base that has been cleaned by subjecting the base to heat treatment in a reducing gas atmosphere before forming the first insulating film. A method for forming an insulating film. (8) A method for forming an insulating film, characterized in that the heat treatment according to claim 1 or 7 is performed by infrared irradiation.