JPH01198033A - Formation of thin film - Google Patents

Abstract

PURPOSE:To improve film quality by supplying reaction product produced by raw gas or raw gas/excited reaction gas to a substrate surface, whereon the reaction product is liquefied, by irradiating the excited reaction gas, ion or light to make an oxide film and thereafter rising a substrate temperature, by irradiating the excited reaction gas, ion or light and by repeating these processes. CONSTITUTION:After the inside of a container 11 is exhausted and a substrate 12 is cooled to -40 deg.C, valves 21, 22 are opened, tetramethylsilane and oxygen are supplied, the pressure in the inside of the container 11 is set at 2Torr, microwave discharge is performed, and reaction product is liquefied on the substrate 12. Microwave discharge is stopped, valves 12, 22 are closed to stop gas supply and exhaust is conducted. A valve 23 is opened, oxygen gas is supplied into the container 11, discharge is started at a pressure of 2Torr and reaction product supplied onto the substrate 12 is oxidated. Then the valve 23 is closed, a heater 61 is made conductive and heated, the temperature of the substrate 12 is increased to 300 deg.C, a valve 62 is opened to introduce oxygen, and annealing is made under oxygen atmosphere. The above mentioned operations are repeated to deposit an oxide film which scarcely contains methyl group.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a thin film deposition method used in the manufacture of semiconductors such as VLSI devices, and particularly relates to a thin film deposition method for forming a thin film embedded in a groove. Regarding the forming method.

(Conventional technology) Thin film forming methods can be roughly divided into chemical vapor deposition (Chemistry)
Mical Vapor Deposition;
CVD) and physical vapor deposition (Physreal
It is classified as Vapor Depositon (PVD). The CVD method is a method of depositing a thin film on a substrate using chemical reactions on the substrate surface or in a gas phase, and is mainly used for forming insulating films such as silicon oxide films and silicon nitride films. The PVD method forms a thin film by colliding deposited particles generated in a gas phase with a substrate, and is mainly used for forming metal films.

On the other hand, in recent VLSI devices, thin film deposition technology in trenches with a high aspect ratio (depth 7 width) is becoming essential. However, the Braz vCVD method, which is one of the CVD methods (
For example, J. L. Vossen'& L. Kern;
Inlet 1m Process; Academic P
When an insulator 83 is deposited in a deep groove 82 formed in a Si substrate 81 as shown in FIG. As the deposition is large, it becomes increasingly difficult for the deposited species to enter the bottom of the groove, creating a cavity 84 and deteriorating the step coverage characteristics.

This step) 71 As a method to improve the ffl shape, P
A technique called bias sputtering method, which is one of the VD methods, is used (for example, T, Mogal.

Morlmoto & 0kabayashl: Ex
pending abstracts18L1+ con
l', 5olid 5tate Devices &
Materials.

Kobe, 1984. p43) OThis method is
While physically sputtering the substrate surface with ions,
For example, since a silicon oxide film is formed, deposition does not occur at the corners but only at the flat areas. Therefore, it is possible to fill the groove without creating cavities, but since the deposited species in the gas phase enter the groove obliquely, the aspect ratio>1
This makes it difficult to embed.

Furthermore, since a competitive reaction between removal of the deposited film by physical sputtering and deposition is used, the net deposition rate is low and productivity is extremely poor. However, irradiation in plasma cannot be avoided. Recently, the ECR bias sputtering method (for example, Il
,0jkava;SEMITECNOl,OGY SY
M, 1980 E3-1) has also been proposed, but although it alleviates the above problem, it does not provide a wooden solution.

In addition, for example, the thermal decomposition method of TE01 (for example, lt, D
, Rangt Y, Momose & Y, Nagak
ubo; IIEDM, TECII.

DIG, 1982. When a silicon oxide film is formed using 237), it exhibits excellent step coverage characteristics as shown in FIG. 8(b) due to large movement of deposited species on the surface.

However, if the oxide film 83 buried in the trench is cleaned using a diluted HF solution using this method,
), the removal rate of the oxide film 83 in the central portion 85 becomes abnormally fast, and the current situation is that buried planarization cannot be achieved. The reason for this is thought to be that distortions between the oxide films that have grown from both sides of the trench wall remain near the center.

As described above, even with the method of forming a thin film in a conformable manner, it was considered extremely difficult to fill the trench with a high aspect ratio.

To solve the above problem, tetramethylsilane (S
There is a method of depositing a silicon oxide film in a high aspect ratio trench by cooling the substrate below the boiling point of a reaction product of a gas and oxygen atoms excited by a microwave discharge. However, since the film deposited by this method is deposited at a low temperature of -40° C., it is a coarse film with a low density. This is due to the inherent problem of the liquid phase oxidation method, in which the oxidized and solidified atoms cannot freely move around because the substrate temperature is cooled below the boiling point of the reaction product. According to this method, a substance that liquefies on the substrate, namely tetramethoxysilane, which is a raw material gas, and oxygen are supplied with a reaction product by oxygen atoms excited by microwave discharge, and the oxygen excited by the microwave discharge of this liquid is supplied. Atomic oxidation is proceeding simultaneously, making it difficult to control the liquid supply rate and oxidation rate. Therefore, it is difficult to control or improve the film composition and film density.

Fig. 9(a) shows that the Si plate 8 was damaged due to the liquid being supplied too quickly.
In this example, the liquid that had accumulated at the bottom of the groove 1 was not sufficiently oxidized and remained liquid, resulting in the formation of a cavity 86. FIG. 9(b) shows an example in which a portion that was not sufficiently oxidized and remained liquid exists like a bubble, resulting in a cavity 87.

Figure 10 shows the relationship between the deposition rate and the deposition shape with respect to the total flow rate, but when the total flow rate is reduced to slow down the deposition rate, the gas phase reaction progresses, resulting in the formation of a layer as shown in Figure 8 (a) above. This results in a piled-up shape.

Conversely, if the total flow rate is increased to increase the deposition rate, the liquefaction reaction progresses and cavities are generated as shown in FIG.

(Problem to be Solved by the Invention) In the conventional method of filling the groove with an oxide film etc. using the liquid phase oxidation method, it is difficult to control the amount of liquid supplied and the oxidation rate. There is a problem in that it is difficult to control or improve the composition of the film and the density of the film.

The present invention has been made in consideration of the above circumstances, and its purpose is to be able to independently control the amount of liquid supplied and the oxidation rate in the liquid phase oxidation method, etc., and to form a thin film in the groove. It is an object of the present invention to provide a method for forming a thin film that can be embedded in the film and improve the film quality.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is that when a thin film is formed by a liquid phase oxidation method, a raw material gas that is liquefied on the surface of a substrate or a reactive gas that is excited with the raw material gas is generated. The amount of liquid supplied can be reduced by separating the time for supplying the reaction product and the time for turning the liquid liquefied on the substrate surface into a thin film using reaction gas, ions, or light, and repeating these steps to form a deposited film. and the ability to independently and freely control the oxidation rate of the liquid.

Reactive gas or ions are excited by the liquid liquefied on the surface of the substrate, and reactive gases or ions are excited by increasing the temperature of the substrate after forming an oxide film with light.

The purpose is to improve the film quality by performing a process of improving film quality using light and repeating this process to form a deposited film.

That is, the present invention provides a thin film forming method in which a substrate to be processed having grooves formed on its surface is accommodated in a reaction container, and a predetermined gas is supplied into the container to form a thin film in the grooves of the substrate to be processed. As the second thin film forming process, only the raw material gas or both the first reaction gas and the raw material gas excited in a region different from the container are supplied into the container, and the substrate to be processed is heated to the dew point of the raw material gas. or below or below the dew point of the reaction product of the raw material gas and the first reaction gas, and the raw material gas or the reaction product is liquefied and attached to the surface of the substrate to be treated, as a second thin film forming process. After completing the first thin film forming process, a second reaction gas excited in a region different from the container is supplied into the container.

Perform at least one of irradiating the substrate surface with light and irradiating the substrate surface with ions, generate a thin film from the liquid attached to the surface of the substrate to be treated, and perform these two thin film formation processes in a temporal manner. In this method, the grooves of the substrate to be processed are filled with a thin film by separating and repeating the process alternately.

The present invention provides a thin film forming method in which a substrate to be processed having grooves formed on its surface is accommodated in a reaction container, and a predetermined gas is supplied into the container to form a thin film in the grooves of the substrate to be processed. As the thin film forming process of 10th, a raw material gas alone or both a first reaction gas excited in a region separate from the container and a raw material gas are supplied into the container, and the substrate to be treated is exposed to the raw material gas. Cooling to below the dew point or below the dew point of the reaction product of the raw material gas and the first reaction gas, and liquefying and depositing the raw material gas or the reaction product on the surface of the substrate to be treated, a second thin film forming step. After the first thin film forming process is completed, a second reaction gas excited in a region different from the container is supplied into the container.

performing at least one of irradiating the substrate surface with light and irradiating the substrate surface with ions to generate a thin film from the liquid adhering to the surface of the substrate to be processed; and as a third thin film forming process, a second After completing the second thin film forming process, the substrate to be treated is heated to a temperature higher than the boiling point of the raw material gas or reaction product, and a second thin film is excited in a region different from the container.
supply the reaction gas. performing at least one of irradiating the substrate surface with light and irradiating the substrate surface with ions, temporally separating these three thin film formation processes, and sequentially repeating them to fill the grooves of the substrate to be processed with the thin film; This is how I did it.

(Function) According to the present invention, when depositing a thin film by a liquid phase oxidation method or the like, the amount of liquid supplied and the rate of oxidation can be freely and independently controlled. Therefore, the quality of the film buried in the groove can be easily controlled, and the film can be densified and sufficiently oxidized. That is, by applying a thin layer of liquid to the surface of the substrate to be processed in the first thin film forming process, and performing sufficient oxidation in the second thin film forming process, a high quality thin film can be formed without causing cavities. can be formed. By repeating this process, it is possible to form a thin film thick enough to fill the inside of the groove.

Reactive gas or ions are excited by the liquid liquefied on the surface of the substrate, and reactive gases or ions are excited by increasing the temperature of the substrate after forming an oxide film with light.

By performing the process of improving the film quality with light (third thin film formation process) and repeating these (first to third thin film formation processes) to form a deposited film, the film can be made denser and the film quality can be improved. You can go even further.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic diagram showing the procedure for carrying out the method according to claim 1 of the present invention. First, supplying only a raw material gas or both a first reaction gas and a raw material gas excited in a region different from the container into a reaction container containing a substrate to be processed,
The substrate to be processed is cooled to below the dew point of the source gas or below the dew point of the reaction product of the source gas and the first reaction gas. As a result, the raw material gas or the reaction product liquefies and adheres to the surface of the substrate to be processed (liquid supply). Although this liquid accumulates in the grooves of the substrate to be processed, the amount thereof is extremely small.

Next, after stopping the supply of the liquid, a second reaction gas excited in a region different from the container is supplied into the container. At least one of irradiating the surface of the substrate with light and irradiating the surface of the substrate with ions is performed to oxidize the liquid applied in the grooves of the substrate to be processed and form an oxide film (oxidation of the liquid). At this time, since the amount of liquid in the groove is extremely small, no cavities are generated, and the liquid is sufficiently oxidized to form a high-quality oxide film.

Furthermore, by repeating the supply of the liquid and the oxidation of the liquid, the inside of the groove of the substrate to be processed can be reliably filled with a laminated film of thin oxide films. Note that when forming a thin film, the present invention is not limited to forming an oxide film, but can be applied to forming a nitride film and other various films.

FIG. 2 is a schematic diagram showing a thin film forming apparatus for carrying out the method shown in FIG. 1. In the figure, 11 is a reaction vessel, and inside this vessel 11 is a Si substrate 1 as a substrate to be processed.
A sample stand 13 on which a specimen 2 is placed is accommodated. Sample stand 13
is cooled by a cooling mechanism (not shown), and the substrate 12 placed thereon is also cooled.

A raw material gas is supplied into the container 11 from a gas inlet 14 , and this gas is exhausted from a gas exhaust port 15 . did,
A reaction gas excited by a microwave discharge tube 16 is supplied into the container 11 through a gas inlet 17, and this gas is also exhausted through a gas exhaust port 15.

In the figure, 18 indicates a microwave power source, and 21, 22, and 23 each indicate a valve.

Next, a method for forming a thin film using the apparatus shown in FIG. 2 will be explained. Tetramethylsilane (TMS) as raw material gas
, oxygen atoms obtained by microwave-discharging oxygen were used as the first and second reaction gases. First, after sufficiently evacuating the inside of the container 11 and cooling the substrate 12 to -40°C, the valve 21.
2, TMS for 7 sec, oxygen for 168 sec
m flow, and the pressure inside the container 11 is set to 2 Torr. Then, microwave discharge was started for 30 seconds, and the reaction product was liquefied on the substrate 12 and supplied. Then, the microwave discharge was stopped, the valves 21 and 22 were closed, the gas supply was stopped, and the gas was evacuated.

Next, the valve 23 was opened to supply oxygen gas into the container 11, and discharge was started at a pressure of 2 Torr to oxidize the reaction product supplied onto the substrate 12 for 5 minutes.

Then, valves 21 and 22 with valve 23 closed were opened, TMS and oxygen were supplied, and the same operation was performed.

When this process was repeated 16 times to deposit an oxide film, the deposited film contained almost no methyl groups, and a complete silicon oxide film could be deposited. This reduces the effective deposition rate by 1 by repeating the procedure described above.
This is thought to be due to sufficient oxidation at a temperature of /11. However, the shape of the deposit at this time also completely filled in the grooves with a high aspect ratio. In this way, the liquid supply rate and oxidation rate can be controlled without changing the deposition shape,
By slowing down the deposition rate and sufficiently oxidizing, we were able to improve the film quality.

Figure 3 shows an apparatus for irradiating the substrate surface with light to decompose and oxidize the liquid adsorbed on the substrate through a photochemical reaction in the second thin film formation process, that is, the process of oxidizing the liquid adsorbed on the substrate. . The same parts as in Fig. 2 are given the same reference numerals, and detailed explanation thereof will be omitted.The difference between this apparatus and the apparatus in Fig. 2 is that instead of supplying the second reaction gas, the second reaction gas is supplied to the substrate surface. The reason is that a mechanism for irradiating light is provided.

That is, a light transmitting window 31 is provided in the clay wall of the container 11, and light 33 from a light source 32 is introduced into the container 11 through the window 31 and is irradiated onto the surface of the substrate 12. . ``The same raw material gases and the first and second reaction gases as shown above were used, and an ArF excimer laser (wavelength: 193 rv) was used as the irradiating light. The deposited film was formed in the same manner as described above. After cooling the substrate to -40°C, TMS and oxygen as the first reaction gas were introduced, microwave discharge was performed for 30 seconds, and then the introduction of TMS was stopped. Ar
F laser was irradiated for 5 minutes. When this was repeated 16 times for deposition, the deposited film contained almost no methyl groups and a hard silicon oxide film could be deposited.

This is considered to be because hexamethyldisiloxane, which is a reaction product of TMS and oxygen and liquefied on the substrate, has absorption near 193 na, so that the chemical reaction due to light progressed.

Figure 4 shows an apparatus for irradiating the substrate surface with ions and decomposing and oxidizing the liquid adsorbed on the substrate by photochemical reaction in the second thin film formation process, that is, the process of oxidizing the liquid adsorbed on the substrate. . The same parts as in Fig. 2 are given the same reference numerals, and detailed explanation thereof will be omitted.The difference between this apparatus and the apparatus in Fig. 2 is that instead of supplying the second reaction gas, the second reaction gas is supplied to the substrate surface. The reason is that a mechanism has been installed to irradiate the area with ions. That is, an ion source 41 is provided at the top of the container 11, and the gas introduced into the ion source 41 is ionized and introduced into the container 11. In addition, in the figure, 42 indicates an ion accelerating power source, and 43 indicates a valve.

TMS was used as the raw material gas, and oxygen atoms obtained by microwave-discharging oxygen were used as the first reaction gas. The ions used were those obtained by ionizing oxygen with an ion source and accelerating it with an acceleration voltage of 100V. The deposited film was formed in the same manner as described above. After cooling the substrate to -40°C, TMS and oxygen as the first reaction gas were introduced, microwave discharge was performed for 30 seconds, and then the introduction of TMS was stopped. Oxygen ions were irradiated for 5 minutes. After repeating this process 16 times and depositing,
The deposited film contains almost no methyl groups, is dense, and has a high etching rate with respect to BHF.

It was extremely slow (person/m1n). This is thought to be because the kinetic energy of the ions was given to the deposited species, which could not move around on the substrate due to the low substrate temperature, and became able to move around on the substrate.

Thus, according to the method of this embodiment, TMS is
and a liquid supply step of supplying activated oxygen gas;
By alternately carrying out the 1-stage oxidation of the liquid by supplying activated oxygen gas, the amount of liquid supplied and the oxidation time of the liquid can be independently and freely set. can be easily oxidized. Therefore, a high-quality oxide film can be buried in the grooves provided in the substrate, and furthermore, it is possible to prevent the formation of cavities and the like. Unlike other methods such as bias sputtering, this method stacks a thin oxide film from the bottom of the trench, so even trenches with a large aspect ratio can be reliably filled, making it possible to
It is extremely effective in producing I.

FIG. 5 is a schematic diagram showing the procedure for carrying out the method according to claim 2 of the present invention. In this method, the liquid supply step and the liquid oxidation step are similar to those shown in FIG. 1, and then a third reaction gas excited in a region different from the container is supplied into the container.

Perform at least one of irradiating the substrate surface with light and irradiating the substrate surface with ions, and further oxidize the oxide film oxidized by the liquid oxidation step, or oxidize the liquid remaining without being oxidized. do. This ensures that the liquid is oxidized and the film quality can be improved.

Furthermore, by repeating the above-mentioned liquid supply, liquid oxidation, and film quality improvement treatment, it is possible to reliably fill the grooves of the substrate to be treated with a laminated film of thin oxide films, and to improve the film quality of the oxide film. It can be done. Note that when forming a thin film, the present invention is not limited to forming an oxide film, but can be applied to forming a nitride film and other various films.

FIG. 6 is a schematic diagram showing a thin film forming apparatus for carrying out the method shown in FIG. 5. Note that the same parts as in FIG. 2 are given the same reference numerals, and detailed explanation thereof will be omitted. This apparatus differs from the apparatus shown in FIG. 2 in that the sample stage is provided with a heating mechanism for heating as well as a cooling mechanism. That is, a heater 61 is provided inside the sample stage 13, and the substrate 12 is heated by this heater 61. 62 supplies the third reaction gas.

This is a valve for stopping.

Next, a thin film forming method using the apparatus shown in FIG. 6 will be explained. TMS was used as the raw material gas, and oxygen atoms obtained by microwave-discharging oxygen were used as the first to third reaction gases. First, the inside of the container 11 is sufficiently evacuated and the substrate 12 is cooled to -40°C. Then, the valves 21 and 22 are opened and TMS is heated to 75°C.
CrA and oxygen were flowed at 168 sccal, and the pressure inside the container 11 was set to 2 Torr. Then, microwave discharge was started for 30 seconds, and the reaction product was liquefied on the substrate 12 and supplied. Then, the microwave discharge is stopped, and the valve 21
．． 22 was closed, gas supply was stopped, and exhaust was performed.

Next, the valve 23 was opened to supply oxygen gas into the container 11, and discharge was started at a pressure of 2 Torr to oxidize the reaction product supplied onto the substrate 12 for 5 minutes.

Next, the valve 23 was closed, and the heater 61 was heated to bring the temperature of the substrate 12 to 300°C. Further, the valve 62 was opened to introduce oxygen as a third reaction gas, and annealing was performed in an oxygen atmosphere for 5 minutes.

Next, the valve 62 was closed, the valves 21 and 22 were opened again, TMS and oxygen were supplied, and the same operation was performed. When this process was repeated 16 times to deposit an oxide film, the deposited film contained almost no methyl groups, and a complete silicon oxide film could be deposited. B of this film
The etching rate with respect to HF was 1000 people/sin, which was approximately the same as that of a film formed by thermal oxidation.

FIG. 7 is a schematic configuration diagram showing an apparatus that instantaneously performs annealing using a laser instead of the heater. In this device, a light introduction window 71 is provided in the clay wall of the container 11 so that light 73 from a laser light source 72 can be guided into the container 11. By using this apparatus, film quality modification treatment, which is the third thin film formation process, can be performed in a short time, making it possible to improve throughput.

Thus, the method of this embodiment not only provides the same effects as the method of the previous embodiment, but also has the advantage of further improving the quality of the oxide film buried in the trench.

Note that the present invention is not limited to the methods of each embodiment described above. For example, if a gas in which an oxygen atom is bonded to a silicon atom, such as tetraethoxysilane, hexamethyldisiloxane, trimethylsilanol, or tetramethoxysilane, is used as the raw material gas, the composition of the produced film will be closer to 5i02. Become. In this case, the raw material gas,
Since oxygen atoms are contained therein, it is possible to eliminate the need for supplying the first reaction gas.

Yes, 2nd. When a halogen gas such as chlorine is used in combination with oxygen as the third reactive gas, atoms bonded to silicon atoms such as methyl groups are reduced, and CH, CH, CI, etc. are formed and removed. The carbon concentration in the film decreases,
The composition of the produced film becomes closer to 5iOz. Similar effects can also be obtained by using only a halogen gas such as chlorine as the third reaction gas. Yes, 2nd. When an inert gas such as argon gas is mixed with oxygen and used as the third reaction gas, a metastable excited film in a high energy state is generated and the reaction proceeds, resulting in the formation of a dense and high quality film. Furthermore, similar effects can be obtained by using only an inert gas such as argon gas as the third reaction gas.

However, the present invention is not limited to the formation of oxide films, but can be applied to the formation of nitride films, polymer films, metal films, and other thin films. For example, in the case of forming a polymer film, P, M M
A film can be formed. In addition, in the case of forming a metal film, All (CH)) 3 is used as a raw material gas.
By using H2 or the like as a reactive gas, an AfI film can be formed. That is, the types of the source gas and the reaction gas can be changed as appropriate depending on the composition of the thin film to be formed. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to independently control the liquid supply amount and oxidation rate in a liquid phase oxidation method, etc., and even if the groove has a high aspect ratio, the groove It is possible to realize a method for forming a thin film that can satisfactorily embed a thin film within the film and improve the film quality.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the procedure for implementing the thin film forming force method according to claim 1 of the present invention, Figure 2 is a schematic diagram showing the procedure for implementing the method of forming a thin film according to claim 1 of the present invention, and Figure 4 is a schematic diagram showing the thin film used to implement the method of Figure 1. FIG. 5 is a schematic diagram showing the procedure for carrying out the thin film forming method according to claim 2 of the present invention, and FIGS. 6 and 7 are diagrams for carrying out the method of FIG. 5, respectively. FIGS. 8 and 9 are a schematic configuration diagram showing the thin film manufacturing apparatus used for this purpose, and FIGS.
The figure is a characteristic diagram □ showing the relationship between flow rate and deposition rate. 11... Reaction container, 12... Sl substrate, 13...
Sample stage, 14.17...Gas inlet, 15...Gas exhaust port, 16...Microwave discharge tube, 18...Microwave power supply, 21.22.23.43.62... Bulb, 32° 72... Light source, 41... Ion source, 61
···heater. Applicant's agent Patent attorney Takehiko Suzue

Claims (3)

[Claims] (1) A thin film forming method in which a substrate to be processed with grooves formed on its surface is housed in a reaction vessel, and a predetermined gas is supplied into the vessel to form a thin film in the grooves of the substrate to be processed. As a thin film forming process, only the raw material gas or both the first reaction gas and the raw material gas excited in a region different from the container are supplied into the container, and the substrate to be treated is heated to a temperature below the dew point of the raw material gas or below. The raw material gas or the reaction product is cooled to a temperature below the dew point of the reaction product of the raw material gas and the first reaction gas, and the raw material gas or the reaction product is liquefied and deposited on the surface of the substrate to be treated. After completing the first thin film forming process, supplying a second reaction gas excited in a region different from the container into the container, irradiating the substrate surface with light, and irradiating the substrate surface with ions. forming a thin film from the liquid adhering to the surface of the substrate to be processed, separating these two thin film forming processes in time, and repeating them alternately to form a thin film in the grooves of the substrate to be processed. A thin film forming method characterized by embedding. (2) A thin film forming method in which a substrate to be processed with grooves formed on its surface is housed in a reaction container, and a predetermined gas is supplied into the container to form a thin film in the grooves of the substrate to be processed. As a thin film forming process, only the raw material gas or both the first reaction gas and the raw material gas excited in a region different from the container are supplied into the container, and the substrate to be treated is heated to a temperature below the dew point of the raw material gas or below. The raw material gas or the reaction product is cooled to a temperature below the dew point of the reaction product of the raw material gas and the first reaction gas, and the raw material gas or the reaction product is liquefied and deposited on the surface of the substrate to be treated. After completing the first thin film forming process, supplying a second reaction gas excited in a region different from the container into the container, irradiating the substrate surface with light, and irradiating the substrate surface with ions. At least one of the following is performed to generate a thin film from the liquid attached to the surface of the substrate to be processed, and as a third thin film forming process, after completing the second thin film forming process, the substrate to be processed is used as a raw material. Heating the gas or reaction product above the boiling point, supplying a third reaction gas excited in a region different from the container into the container, irradiating the substrate surface with light, and irradiating the substrate surface with ions. A method for forming a thin film, comprising performing at least one of the following steps, temporally separating these three thin film forming processes, and sequentially repeating the steps to fill the groove portion of the substrate to be processed with the thin film. (3) Tetramethylsilane, tetraethoxysilane, hexamethyldisiloxane, trimethylsilanol, or tetramethoxysilane is used as the raw material gas, and the reaction gas is a gas containing oxygen, hydrogen, nitrogen, or a halogen gas such as chlorine or fluorine. The thin film forming method according to claim 1 or 2, characterized in that one or a mixture of these gases is used: or an inert gas such as argon.