JPH08100264A - Formation of thin film and device therefor - Google Patents

Abstract

PURPOSE: To form a film uniform in thickness and to facilitate maintenance with a simple structure. CONSTITUTION: A substrate 102 is arranged in a film forming chamber 101, a substrate heater 103 is furnished in the film forming chamber 101, and further an active species generating tube 104 is fitted. Gaseous silane is introduced into the active species generating tube 104 through a valve 107 and a mass flow controller 109, and gaseous chlorine is introduced into the tube 104 through a valve 108 and a mass flow controller 110. When a silicon oxide film is formed, gasseous oxygen is passed through an ozonizer 112 by a mass flow controller 113, mixed with ozone and introduced into the film forming chamber through a valve 111. The active species generating tube 104 consists of a high-temp. heating part 104a and a low-temp. heating part 104b, and a high-temp. heating part heater 105 and a low-temp. heating part heater 106 are arranged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for forming a thin film in a semiconductor device or the like.

[0002]

2. Description of the Related Art The chemical vapor deposition method has been most often used conventionally to form a thin film such as amorphous silicon, polysilicon, a silicon oxide film, a silicon nitride film or the like using a gas raw material. This is a method in which a source gas is directly introduced into the reaction chamber by heating with a heater from the outside of the quartz furnace which is the reaction chamber. That is, a thin film is deposited by supplying to the surface of the substrate the active species generated by the reaction of the gas raw material in the surface of the substrate at a high temperature, the inner wall of the reaction chamber, and the gas phase. As another method, there is a plasma chemical vapor deposition method in which an active species generated from a source gas by using plasma is supplied to the surface of a substrate to form a thin film.

[0003]

However, in the chemical vapor deposition method, which is the first method described above, the temperature of the substrate is increased during film formation because the temperature at which active species are generated is equal to the temperature of the substrate. Had to set. For this reason, there is a drawback that the applicable temperature range is limited, such as melting of aluminum when a film is formed on aluminum in the process of manufacturing a semiconductor device. Furthermore, since the reaction proceeds at a high temperature even in the gas phase or on the surface other than the substrate surface such as the inner wall of the reaction chamber, generation of particles not necessary for film formation easily occurs, which is a factor that deteriorates the yield in the production of fine semiconductor devices. It was

In the plasma chemical vapor deposition method, which is the second method described above, the structure of the apparatus is complicated because an electrode for generating plasma, a microwave generator, and the like are required, and the apparatus is complicated. However, it is expensive and difficult to maintain, and the presence of electrodes and the like in the film forming chamber is a cause of heavy metal contamination and particle generation. Further, since it is extremely difficult to generate plasma uniformly over a wide space region, it is difficult to uniformly form a film on a substrate having a large area required in recent semiconductor device manufacturing processes. There was a problem. Furthermore, in plasma, many decomposition reactions proceed at the same time to generate various active species. Therefore, it is difficult to extract only the active species necessary for film formation, and particles are generated in plasma, so that the yield at the time of manufacturing a semiconductor device is deteriorated.

Therefore, the present invention has been made in view of the above-mentioned problems or drawbacks of the related art, and an object of the present invention is to suppress the generation of particles while maintaining a surface having a step at a low substrate temperature. To provide a thin film forming method of forming a thin film uniformly over a wide area with good controllability, and a thin film forming apparatus having a simple structure and easy maintenance.

[0006]

In order to achieve this object, a method for forming a thin film according to the present invention is to generate an active reactive species by passing a part or all of a raw material gas through a part of a heated apparatus, and then, By passing a part of the apparatus heated to another temperature, the reactive species having too high reactivity are removed, and then the surface of the substrate to be deposited is irradiated to form a thin film. The method for forming a thin film according to the present invention is
The growth is performed under a reduced pressure of 0 ^-2 Torr or less. Further, the thin film forming apparatus according to the present invention is provided with an active species generating part for generating an active reactive species from a raw material gas, and a substrate on which an active reactive species is introduced from the active species generating part to form a film. A film forming chamber is provided, and a high temperature heating unit for generating active reactive species from a raw material gas and a low temperature heating unit for removing active species having too high reactivity are continuously provided in the active species generating unit. . Further, the thin film forming apparatus according to the present invention is provided with an etching gas supply mechanism for removing deposits adhering to the active species generating portion and the inner wall of the film forming chamber. Further, the thin film forming apparatus according to the present invention is provided with control means for independently controlling the heating temperature in the high temperature heating section and the low temperature heating section.

[0007]

According to the present invention, since the highly reactive active species react in the low temperature heating section, the reactivity of the active species supplied to the substrate is limited by changing the temperature of the low temperature heating section.
Only active species with reduced reactivity are supplied. Further, according to the present invention, by reducing the pressure inside the film forming chamber, the probability of collision between reactive species in the gas phase is reduced. Further, according to the present invention, a plasma generation source or the like is not required and an electrode or the like is not required in the film forming chamber, so that the etching gas can be introduced. Further, according to the present invention, the deposit adhered in the apparatus without contributing to the film formation by the introduction of the etching gas,
It becomes possible to remove it as a product having a high vapor pressure.
Further, according to the present invention, the optimum heating temperature for controlling the reaction of the active species can be selected by controlling the temperature of the high temperature heating section and the temperature of the low temperature heating section independently.

[0008]

1 is a block diagram of a thin film forming apparatus according to the present invention. In this embodiment, silane (SiH ₄ ) is used as a source gas.
And an example of a single-wafer growth apparatus using oxygen gas containing ozone (O ₃ ), in which only silane is used for forming amorphous silicon, and ozone (O ₃ ) is used for forming a silicon oxide film. Oxygen gas containing is added. In the figure, reference numeral 101
In the film forming chamber, a substrate 102 to be film-formed is shown.
A substrate heating heater 103 that controls the temperature by heating the substrate 102 from the rear side is provided. This film forming chamber 10
In No. 1, a turbo molecular pump (not shown) can be evacuated to an ultimate vacuum of 10 ⁹ Torr, and by evacuation to an ultrahigh vacuum, only the film formation reaction can be investigated without being affected by atmospheric components. Reference numeral 104 denotes an activated species generating tube, around which a high temperature heating unit heater 105 and a low temperature heating unit heater 1 are provided.
06 are arranged in succession, and are heated by the respective heaters, a high temperature heating unit 104a and a low temperature heating unit 10.
The temperature of 4b can be controlled independently.

Inside the active species generating tube 104, the inner wall is arranged in a zigzag shape so that the passing molecular species always collides with the inner wall. Reference numerals 107 and 109 are a valve and a mass flow controller for introducing silane gas into the activated species generating tube 104. Numerals 108 and 110 represent chlorine gas as an activated species generating tube 1
A valve and a mass flow controller introduced in 04. The active species obtained from the active species generation tube 104 is the film formation chamber 1
01 is supplied to the surface of the substrate 102. When the silicon oxide film is formed, the mass flow controller 113
Oxygen gas whose flow rate is controlled by the ozone generator 11
2 through 5 containing 5-50% ozone (O ₃ ), valve 11
1 is introduced into the film forming chamber 101.

In such a structure, when the degree of vacuum in the film forming chamber 101 is kept at 10 ^-2 Torr or less, the reaction in the gas phase is so small that it can be almost ignored, so that the generation of particles due to the gas phase reaction However, the film formation proceeds only by the surface reaction. This is because by reducing the pressure in the film forming chamber 101, the probability of collision between reactive species in the gas phase is reduced, and when the vacuum degree in the film forming chamber 101 is set to 10 ^-2 Torr or less, the active species are If the path of the active species from the supply nozzle to the occurrence of deposition is several tens cm or less, the reaction in the vapor phase in the middle can be almost ignored, and therefore, by reducing the pressure inside the film forming chamber 101. This is because it is possible to suppress the generation of particles generated from the reaction in the gas phase. In the reaction between the silicon surface and silane, the growth rate is limited by the desorption of hydrogen from the surface, so film formation does not proceed below the substrate temperature at which hydrogen is desorbed from the surface. By using active species generated by decomposition of silane molecules on a high temperature surface, it is possible to form a film even at a low temperature.

The effect of the activated species generating tube is that a substrate having a hole with a diameter of 1 μm and a depth of 2 μm is used to change the temperatures of the high temperature heating section heater 105 and the low temperature heating section heater 106 to form an amorphous silicon film. This was confirmed by examining the film forming rate and the coating property. That is, in a state where the high temperature heating unit heater 105 and the low temperature heating unit heater 106 are not heated, silane is set to a flow rate of 50 sccm by the mass flow controller 109 at a substrate temperature of 400 ° C.
When supplied for a minute, the degree of vacuum in the film forming chamber 101 during film formation was about 10 Torr, and the deposited film thickness of silicon was 1 nm or less, and almost no deposition was observed. Therefore, it was confirmed that the film formation did not proceed only by directly supplying the silane molecules.

Even under the same conditions, when the high temperature heating section heater 105 and the low temperature heating section heater 106 are both set at 900 ° C. to form a film, a flat surface portion at the center of the substrate is heated to 200.
Although amorphous silicon with a thickness of nm was deposited, the film thickness in the deep part of the hole was less than half that in the flat part. In addition, the thickness of the surface portion also varies depending on the distance from the activated species generating tube, and the difference between the thickest portion and the thinnest portion is about 60% of the thinnest portion. Therefore, it was confirmed that the active species are generated by the high-temperature active species generating tube and the film formation proceeds, but uniform coverage cannot be obtained because many reactive species having too high reactivity are present. This is because active species are generated by supplying the raw material gas to the high temperature heating unit. The active species generated at this time are
Contains many highly reactive substances. The highly reactive active species reacts immediately when they are supplied to the surface of the substrate, so that the deposition occurs only in the portion directly flying from the source of the active species. Therefore, when the substrate is directly irradiated with the active species generated in the high temperature heating unit, a large amount of deposition occurs at a position expected from the source of the active species on a substrate having a step on the surface or a substrate having a recessed surface, This is because the film cannot be formed uniformly.

Under the same conditions, when the high temperature heating part heater 105 and the low temperature heating part heater 106 are set to 600 ° C. to form a film, both the deep part of the hole and the flat surface part are formed on the entire surface of the substrate. On the other hand, 5 nm of amorphous silicon was deposited. Furthermore, under the same conditions, the high temperature heating unit heater 105 is set to 900 ° C. and the low temperature heating unit heater 106 is set to 55 ° C.
When film formation was performed at 0 ° C., the depth of the holes and the flat surface were 50% over the entire surface of the substrate.
nm of amorphous silicon was deposited. Therefore, a high deposition rate cannot be obtained only with the low temperature active species generation tube 104b because the generation of active species is small.
It was confirmed that a uniform coating property and a high film formation rate can be obtained by passing a large amount of active species by 04a and then passing the active species generation tube 104b at a low temperature. this is,
When the active species generated in the high temperature heating section are passed through the low temperature heating section, the highly reactive active species react in the low temperature heating section. By changing the temperature of the low temperature heating section, the reactivity of the active species supplied to the substrate can be limited. This is because by supplying only the active species whose reactivity is suppressed, the active species also enter into the recessed portion due to scattering, so that uniform film formation is possible.

Simultaneously with the film formation on the substrate, active species are supplied to the inner wall of the reactive species generating tube 104 and the inner wall of the film forming chamber 101, so that silicon is deposited. If the deposit becomes thick, problems such as clogging of the reactive species generation tube and generation of particles occur. In this example, chlorine gas was used as an etching gas to remove deposits. The high-temperature heating unit heater 105, the low-temperature heating unit heater 106, and the substrate heating unit heater 103 are set to 900 ° C., and the silane gas passes through chlorine gas (Cl ₂ ) whose flow rate is controlled to 0.5 sccm by the mass flow controller 109 during film formation. When introduced into the route, it was confirmed that the deposit was removed.

Even when the silicon oxide film was formed by adding oxygen gas containing ozone, the same result as the above-mentioned amorphous silicon film formation was obtained. It was confirmed that it is also an effective means for forming a thin film having a composition having atomic species. In this embodiment, the film formation of silicon and a silicon oxide film using silane as a source gas has been described, but it is also effective for other source gases that generate active species by thermal decomposition. Further, although oxygen containing ozone was used as the oxygen source of the oxide film, not only oxide film formation using other oxygen sources such as nitrogen dioxide (NO ₂ ), but also nitride film using ammonia (NH ₃ ). It is also effective for forming a thin film having other components such as film formation. Further, although chlorine gas is used as the etching gas in the present embodiment, it is possible to use a gas such as fluorine (F ₂ ) or hydrogen chloride (HCl) which reacts with the deposit to generate a product having a high vapor pressure. It is possible.

As described above, since only the thermal reaction is used for the generation and selection of the active species, a plasma generation source or the like is not required and the apparatus is simplified. In addition, it is extremely easy to keep the temperature constant and reproduce the same temperature by a method such as feeding back the output of the thermocouple.Therefore, by using only the thermal reaction, good controllability and reproducibility can be obtained. Can be easily realized. Further, since only the thermal reaction is used, no electrode or the like is required in the film forming chamber, so that not only metal contamination can be suppressed but also an etching gas can be introduced. Then, by introducing this etching gas, it is possible to remove deposits adhering to the inside of the device without contributing to film formation as products with a high vapor pressure, which are conventionally required parts in the device. It is possible to significantly reduce maintenance such as cleaning and washing.

FIG. 2 is a block diagram showing a second embodiment of the present invention. The second embodiment is an application of the first embodiment to a batch type for simultaneous growth of a plurality of sheets. 201
Is a film forming chamber in which a plurality of substrates 202 are arranged,
Reference numeral 3 is a substrate heater disposed outside the film forming chamber 201, and 204 is a high temperature heating unit 204a and a low temperature heating unit 204b.
The activated-species generating tubes, and 205 and 206 are a high temperature heating section heater and a low temperature heating section heater, respectively. 207 and 209 are silane gas activated species generation tubes 204
A valve and a mass flow controller to be introduced into. Two
Reference numerals 08 and 210 are a mass flow controller and a valve for introducing chlorine gas into the activated species generating pipe 204. When the silicon oxide film is formed, the oxygen gas whose flow rate is controlled by the mass flow controller 213 passes through the ozone generator 212 and contains 5 to 50% of ozone (O ₃ ) and is introduced into the film forming chamber 201 through the valve 211. .

In such a structure, the temperature of a substrate having a hole having a diameter of 1 μm and a depth of 2 μm on the surface is set to 400 ° C., and silane is supplied at 50 sc by a mass flow controller 209.
It was confirmed by examining the film forming rate and film forming property of the amorphous silicon when the temperature of the high temperature heating part heater 205 and the low temperature heating part heater 206 was changed by controlling the flow rate of cm and supplying for 30 minutes. That is, the degree of vacuum in the film forming chamber 201 during film formation is about 10 ⁻³ Torr. Almost no deposition was observed in a state where the high temperature heating part heater 205 and the low temperature heating part heater 206 were not heated. Therefore, in the conventional low pressure chemical vapor deposition method in which gas molecules are supplied as they are, it is understood that the film formation does not proceed at a low temperature when the pressure is so low that the vapor phase reaction can be ignored.

Next, when the film formation is carried out by setting both the high temperature heating part heater 205 and the low temperature heating part heater 206 to 900 ° C., most of the active species having high reactivity are deposited in the part close to the active species reaction tube. As a result, the film thickness of the substrate close to the active species generating tube and that of the substrate far from the active species generating tube were significantly different. High temperature heating unit heater 205 is set to 900 ° C.
Then, when the film was formed by setting the low-temperature heater 206 to 550 ° C., amorphous silicon of 50 nm was uniformly deposited on the inner surface of the hole and the flat surface portion of all the substrates. In addition, the inner wall of the film forming chamber 201 and the reactive species generation tube 20
The deposit adhered to the inner wall of the No. 4 inner wall of the high-temperature heating unit heater 205, the low-temperature heating unit heater 206, and the substrate heating heater 203 is 900 times as in the first embodiment.
It could be removed by setting the temperature to 0 ° C. and introducing chlorine gas of 0.5 sccm as an etching gas.

[0020]

As described above, according to the present invention, a part or all of the raw material gas is passed through a part of the heated apparatus to generate active reactive species, and then a part of the apparatus heated to another temperature is passed. By removing the reactive species that are too reactive, and then irradiating the surface of the substrate to be formed with a film to form a thin film. Since the reactivity of the species is limited and only the active species with suppressed reactivity is supplied,
A uniform film can be formed.

Further, according to the present invention, since the growth is carried out under a reduced pressure of 10 ^-2 Torr or less, the collision probability of the reactive species in the gas phase is reduced, and therefore, in the gas phase. It is possible to suppress the generation of particles generated from the reaction in.

Further, according to the present invention, the active species generating portion for generating the active reactive species from the source gas, and the substrate on which the active reactive species are introduced from this active species generating portion to form a film are arranged. By providing a film forming chamber, a high temperature heating unit for generating active reactive species from the raw material gas in the active species generating unit, and a low temperature heating unit for removing active species having too high reactivity are continuously provided, Since only a thermal reaction is used for generation and selection of active species, a plasma generation source or the like is not required and the apparatus is simplified. In addition, it is extremely easy to keep the temperature constant and reproduce the same temperature by a method such as feeding back the output of the thermocouple.Therefore, by using only the thermal reaction, good controllability and reproducibility can be obtained. Can be easily realized.

Further, according to the present invention, since an etching gas supply mechanism for removing deposits adhering to the active species generating portion and the inner wall of the film forming chamber is provided, it is possible to provide the inside of the apparatus without contributing to film formation. The attached deposit can be removed as a product having a high vapor pressure, and it is possible to greatly reduce the maintenance such as cleaning and cleaning of the internal parts of the apparatus, which has been conventionally required.

Further, according to the present invention, since the high temperature heating section and the low temperature heating section are provided with the control means for independently controlling the heating temperature, the optimum heating temperature for controlling the reaction of the active species can be selected.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a thin film forming apparatus according to the present invention.

FIG. 2 is a configuration diagram of a second embodiment of a thin film forming apparatus according to the present invention.

[Explanation of symbols]

101, 201 ... Film forming chamber, 102, 202 ... Substrate, 10
3, 203 ... Substrate heating heater, 104, 204 ... Activated species generating tube, 104a, 204a ... High temperature heating section, 104
b, 204b ... Low temperature heating unit, 105, 205 ... High temperature heating unit heater, 106, 206 ... Low temperature heating unit heater.

Claims (5)

[Claims] 1. A reactive species that is too reactive is generated by passing some or all of the source gas through a portion of the heated apparatus to generate active reactive species and then passing through a portion of the apparatus heated to another temperature. A method for forming a thin film, which comprises removing and then irradiating the surface of a substrate to be formed with a film to form a thin film. 2. The method for forming a thin film according to claim 1, wherein the growth is performed under a reduced pressure of 10 ⁻² Torr or less. 3. An active species generating part for generating an active reactive species from a raw material gas, and a film forming chamber in which a substrate on which an active reactive species is introduced from this active species generating part and a film is to be formed is disposed. A thin film forming apparatus, characterized in that a high temperature heating unit for generating active reactive species from a raw material gas and a low temperature heating unit for removing active species having too high reactivity are continuously provided in the active species generating unit. 4. The thin film forming apparatus according to claim 3,
A thin film forming apparatus comprising a mechanism for supplying an etching gas for removing deposits adhering to the active species generating portion and the inner wall of the film forming chamber. 5. The thin film forming apparatus according to claim 3,
A thin film forming apparatus characterized in that the high temperature heating section and the low temperature heating section are provided with control means for independently controlling the heating temperature.