JPH07307292A - Film formation method and low pressure cvd device used for film formation method - Google Patents

Abstract

PURPOSE:To improve uniformity between wafers/in wafer surfaces of film thick ness and impurity concentration even in a dilute doping region at the time of batch low pressure CVD. CONSTITUTION:A low pressure CVD device 100, in which an inner tube 9 is mounted into a silica tube 1, is used, the inside of the tube is supplied with a PH3/SiH4/N2 gases before film formation, and Si thin-films containing phosphorus (P) are deposited on the surfaces of the silica tube 1 and the inner tube 9 (pre-doping). The insides of the tubes are supplied with the SiH4/N2 gases, and polysilicon thin-films are grown on wafers W while phosphorus discharged from tube walls is taken into the films. Or the upper sections of the wafers W are fed uniformly with the dilute PH3 gas by using another decompression CVD device capable of forming gas flows in the tubes in parallel with the main surfaces of the wafers W, and impurity concentration is equalized without pre-doping. Accordingly, gate electrodes in low impurity concentration corresponding to a change into thin-films of gate insulating films can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film forming method mainly applied to the field of manufacturing semiconductor devices and a low pressure CVD apparatus used therefor. And a device for achieving the same.

[0002]

2. Description of the Related Art A low pressure CVD apparatus (LPCVD apparatus)
This is an apparatus for forming a thin film by causing the gas phase reaction to proceed by applying thermal energy to the gas phase under reduced pressure, and depositing the reaction product on the substrate (wafer). In the field of manufacturing semiconductor devices, a polysilicon thin film used as a gate electrode, an amorphous silicon thin film used as an active layer of a TFT (thin film transistor), a Si ₃ N ₄ thin film used as a selective oxidation mask or a capacitor insulating film,
SiO ₂ used as an interlayer insulating film or a sidewall
It is widely used as an apparatus for forming a material film such as a thin film.

FIG. 5 shows the configuration of a batch type vertical low pressure CVD apparatus which is widely used at present. In this apparatus 102, a wafer made of quartz is also placed in an upright quartz tube 1.
Using the boat 7, about 100 wafers W are set in a direction in which the main surfaces thereof are stacked horizontally, and the wafer boat 7
Is rotated by the motor built into the boat loader,
A film is formed while heating the quartz tube 1 with a heater 2 from the outside. In the apparatus shown in this figure, the quartz tube 1 is used as a gate
It is connected to the vacuum load lock chamber 3 via a partition wall 4 having a valve. Further, the raw material gas is supplied from the direction of arrow A into the quartz tube 1 through the gas supply tube 5 which is inserted through the partition wall 4. Exhaust in the quartz tube 1 is performed in the direction of arrow B through an exhaust tube 6 that opens at the top.

Such a vertical apparatus has the advantages of less entrainment of the atmosphere during wafer loading, less deflection of the columns 8 of the wafer boat 7 supporting a large number of wafers, a long soaking length, and excellent mass productivity. Although it has a large volume, the temperature, pressure, and pressure inside the deposition chamber (quartz tube)
A large amount of know-how is required for uniform control of the source gas concentration. In reality, it is difficult to control the pressure and the source gas concentration uniformly, so the temperature that is relatively easy to control is usually set as a control target, and this temperature is set for each predetermined region of the film forming chamber under the reaction-controlled condition. The method of changing to. That is, the reaction gas is supplied in a much larger amount than the consumption amount by the chemical reaction, and the film formation is performed under the condition that the change of the chemical reaction rate depends only on the temperature change.

[0005]

By the way, low pressure CVD
As the thin film formed by the method, there is a thin film doped with an impurity element during film formation, such as a polysilicon thin film for forming a gate electrode. This doping is performed by adding a doping gas, which is a supply source of an impurity element, to a film forming gas that supplies a constituent element of a thin film at a predetermined ratio. Hereinafter, a mixture of the doping gas and the film forming gas will be referred to as a source gas.

In recent years, with the miniaturization and high integration of semiconductor devices, it is required to precisely control this doping in a dilute region. For example, MOS
Since the gate oxide film of the transistor becomes an ultra-thin film of 10 nm or less after 64 MDRAM, in order to prevent the formation of the impurity level due to the impurity diffusion from the gate electrode and the occurrence of the charge trap, the doping concentration in the polysilicon thin film is reduced. Is required to be in the range of 0.01 wt%.

However, the reaction rate controlling condition for obtaining a desired doping concentration and the reaction rate controlling condition of the above film forming reaction do not always coincide with each other, and even if the film forming rate is at a certain temperature, the impurities are not controlled. The diffusion rate does not always follow this. However, in the field of semiconductor device manufacturing, the deposition rate, that is, the film thickness uniformity has generally been emphasized, so that the doping concentration in the diluted region within a batch (between wafers)
The uniformity was not always good.

Moreover, the deviation between the reaction rate-determining conditions becomes more remarkable as the desired doping concentration becomes lower, that is, the doping gas becomes leaner and the supply rate-limiting condition approaches. Therefore, for example, if the doping concentration of the gate electrode is further reduced in the future, there is a great possibility that the resistance value of the gate electrode varies between the wafers and eventually the characteristic of the MOS transistor changes.

Further, the non-uniformity of the doping concentration occurs not only between wafers but also within the wafer surface. This is as shown by an arrow G in the figure in the conventional batch type low pressure CVD apparatus as shown in FIG.
Most of the source gas (film forming gas + doping gas) forms a laminar flow along the tube wall of the quartz tube 1, and only the diffusion flow separated from the laminar flow enters the gap between the wafers W. Is due to. That is, most of the gas flow in the tube passes through the peripheral portion of the arranged wafers.

However, the concentration of the doping gas in the raw material gas is extremely low, and the doping rate gas is close to the condition where the rate-determining condition is satisfied. Therefore, the doping gas is almost consumed in the peripheral portion of the wafer W, and there is a problem that the doping concentration is lowered in the central portion of the wafer W.

Therefore, the present invention provides a film forming method capable of improving the wafer-to-wafer / wafer-plane uniformity of the film thickness and the impurity concentration even in a dilute doping region, and a low pressure CVD apparatus used for the film forming method. To aim.

[0012]

The present invention is proposed to achieve the above objects. That is, the film forming method of the present invention holds the substrate in the film forming chamber of the low pressure CVD apparatus, and when forming a thin film containing a desired impurity on the substrate, The impurities are preliminarily supported on the internal constituent members of the film forming chamber, and the film forming gas is supplied into the film forming chamber at the time of film forming and the impurities are released into the film forming atmosphere.

The type of the low pressure CVD apparatus is roughly classified into a batch type or a single-wafer type according to the number of substrates (wafers) to be processed at one time. Further, the batch type is divided into a vertical type and a horizontal type depending on the installation type of the film forming chamber. Be separated. The reduced pressure CVD apparatus of the present invention may be of any of these types.

The internal constituent member of the film forming chamber means any member that is in contact with the atmosphere inside the film forming chamber and can retain impurities on its surface under heating conditions. Usually, a film forming chamber made of quartz and a boat supporting the wafer are considered as typical examples of the internal constituent members. However, depending on the constituent materials, a gas supply system nozzle, a control / monitor system,
A member such as a jig can be an internal constituent member in the above meaning.

The loading of impurities on the internal components can be easily and uniformly carried out under a reaction rate-determining condition by supplying a large amount of doping gas into the reaction chamber.

Here, as a method of supporting the impurities on the internal constituent member, first, it is considered that the impurities are directly diffused into the surface layer portion of the internal constituent member. However, in this method, when it is attempted to diffuse phosphorus (P) into a film forming chamber made of quartz or an internal constituent member, for example, about 9
There are many problems that heating at a temperature as high as 00 ° C. is required, it is difficult to control the diffusion concentration, and the absolute amount of impurities may be insufficient. Therefore, as a highly practical method, a method of depositing a thin film containing a target impurity on the surface of the internal constituent member is preferable.

Alternatively, an active gas flow from a source gas supply system, which is a mixture of a film forming gas and a dopant gas in the film forming chamber, to an exhaust system is substantially parallel to the main surface of the substrate. The above object can also be achieved by forming the above. Here, if the low pressure CVD apparatus is a batch type vertical apparatus, since the wafer is accommodated in the film forming chamber with its main surface horizontal, the gas flow is formed substantially horizontal. Further, in the case of the batch type horizontal apparatus, since the wafer is accommodated in a state where the main surface is vertical, the gas flow is formed almost vertically.

The film forming method of the present invention may form any kind of thin film as long as it is a thin film containing impurities. In particular, in the future, it is desired to form a polysilicon thin film whose impurity concentration is desired to be reduced. It is suitable to be applied to.

On the other hand, the low pressure CVD apparatus of the present invention contains a substrate, a film forming chamber for forming a desired thin film on the substrate, a heating means for heating the film forming chamber, and A film forming gas supply unit for supplying a film forming gas into the film forming chamber, an exhaust unit for exhausting the film forming chamber, and an auxiliary wall member for increasing the surface area of the internal components of the film forming chamber. It is equipped with.

The film forming gas is a gas for supplying a desired constituent element of the thin film, and does not include a doping gas.
It is particularly preferable to use a film-forming chamber having a tubular shape and arranging a plurality of substrates (wafers) such that the main surface thereof is perpendicular to the axial direction of the film-forming chamber. This is a general configuration of a film forming chamber of a recent batch type apparatus.

Here, the auxiliary wall material does not hinder the installation of the wafers, keeps the distances as uniform as possible with respect to all the wafers in a single batch, and effectively increases the surface area. From the viewpoint of aiming, it may be provided as a plate-like member along the inner wall surface of the film forming chamber. Further, at this time, if the film forming gas is supplied between the film forming chamber and the auxiliary wall material, a CVD reaction occurs and is consumed while the gas flows therethrough, and the amount of gas reaching the wafer side decreases. . Therefore, it is advisable to open the film forming gas supply means to the inner wall surface side of the auxiliary wall material.

As the auxiliary wall material, one having a large number of fine through holes may be used in order to effectively increase the surface area of the internal constituent members. Practically, a mesh-shaped or punching sheet-shaped plate member can be used.

Alternatively, instead of disposing the auxiliary wall material, a source gas supply means and an exhaust means each having a nozzle opening in the film forming chamber are provided, and a pair is provided for each of these nozzles. It can also be achieved by forming a gas flow substantially parallel to the main surface of the substrate. Here again, it is particularly preferable to use the one in which the film forming chamber has a tubular shape and in which a plurality of substrates are arranged such that the main surface thereof is perpendicular to the axial direction of the film forming chamber.

Further, it is preferable that each of the nozzles extends along the axial direction of the tubular film forming chamber, and the openings thereof are composed of a large number of fine holes arranged regularly in the nozzles.

[0025]

In the film forming method of the present invention, the impurities that have been previously carried (hereinafter referred to as pre-doping) by the internal constituent members of the film forming chamber of the low pressure CVD apparatus before film formation are heated during film formation. Release under conditions. Therefore, it is not necessary to mix and supply the film forming gas and the doping gas, and the reaction rate controlling condition of the film forming reaction and the reaction rate controlling condition for obtaining a desired doping concentration can be independently controlled. Therefore, it becomes possible to perform dilute doping with high uniformity between wafers, while placing importance on film thickness uniformity.

The above-mentioned pre-doping can be carried out by using a conventionally known low pressure CVD apparatus, but if it is carried out by using the low pressure CVD apparatus of the present invention having an auxiliary wall material in the film forming chamber, Impurities can also be carried on the auxiliary wall material, and a large amount of impurities can be released from this during film formation.
Therefore, the doping concentration can be set without being restricted by the inner wall area of the film forming chamber. If this auxiliary wall material is constituted by a plate-shaped member and is provided along the inner wall surface of the film forming chamber of the batch type low pressure CVD apparatus, the auxiliary wall material is arranged so as to surround the wafer. Become. Therefore, it is possible to uniformly release the impurities toward the wafer during film formation.

On the other hand, in another film forming method of the present invention, the gas flow of the raw material gas is made substantially parallel to the surface of the wafer inside the film forming chamber.
Moreover, it is formed actively. Therefore, compared with the conventional method in which only the diffusion flow penetrates between the arranged wafers, the flow velocity of the gas on the wafer surface is remarkably high, and even if the rate-determining condition for the dopant gas is established, There is no concern that all of this will be consumed at the peripheral edge of the wafer. That is, it is possible to avoid the problem that the doping concentration is lowered in the central portion of the wafer.

At this time, if the low-pressure CVD apparatus of the present invention in which the nozzle of the source gas supply means and the nozzle of the exhaust means are paired and opened in the film forming chamber, the above gas flow can be easily formed. be able to. Also, the reduced pressure C of the present invention
When the VD apparatus is a batch type low pressure CVD apparatus that accommodates a plurality of wafers arranged in a line, each of these nozzles is extended along the axial direction of the film forming chamber, and its openings are regularly formed in the nozzles. By having a large number of arranged pores,
A gas flow substantially parallel to the main surface of any wafer can be formed with a uniform flow velocity.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings.

Example 1 In this example, a conventional batch type vertical decompression CVD apparatus was used, and a Si thin film containing phosphorus (P) was preliminarily doped on the inner wall surface of a quartz tube which was a film forming chamber. This is an example of forming a polysilicon thin film for forming a gate electrode of a MOS-FET by incorporating phosphorus into the film after forming the polysilicon thin film on the wafer after deposition.

The apparatus used in this example is the conventional batch type vertical decompression CVD apparatus 102 shown in FIG.
It is possible to set 120 wafers with a diameter of 8 inches at a time.

First, a dummy wafer W was set on the wafer boat 7, and pre-doping was performed under the following conditions as an example. SiH ₄ flow rate 500 SCCM N ₂ flow rate 2000 SCCM PH ₃ flow rate 0.5 SCCM doping temperature 550 ° C. pressure 50 Pa By this pre-doping, the inner wall surface of the quartz tube 1 and the surface of the wafer boat 7 are made to contain extremely small amounts of phosphorus. A thin Si thin film was formed.

Next, a single crystal Si substrate having a gate oxide film formed on its surface in advance is used as a wafer W for the process.
The thin film was set on the boat 7, and as an example, a polysilicon thin film having a film thickness of about 0.2 μm was formed under the following conditions. SiH ₄ flow rate 500 SCCM N ₂ flow rate 2000 SCCM Film formation temperature 550 ° C. Pressure 50 Pa Since this condition is a reaction rate-determining condition for the growth of the polysilicon thin film, the film thickness uniformity of the polysilicon thin film is within the wafer surface and between wafers. All were good. Moreover, the growth of this thin film depends on the S deposited on the inner wall surface of the quartz tube 1.
The process proceeded while incorporating the phosphorus released from the i thin film.

Next, the polysilicon thin film obtained as described above was evaluated by secondary ion mass spectrometry (SIMS). The primary ion used is Cs ⁺ . The analysis results are shown in FIG. This figure shows the depth (μm) from the wafer surface and the phosphorus concentration (number of atoms / c) based on the measured raw data.
m ³⁾ is a graph showing a result of calculating the relationship between the. From this, the phosphorus concentration is about 3 × 10 ¹⁸ atoms / cm ³ (about 0.
It is clear that a polysilicon thin film (01 wt%) is formed. This phosphorus concentration was uniform within the wafer surface.

As described above, according to this embodiment, it is possible to form a polysilicon thin film having a low doping concentration and excellent film thickness uniformity. Such a polysilicon thin film is a gate insulating film (SiO 2) having a film thickness of 10 nm or less.
It was extremely suitable as a gate electrode formation layer formed on _two films).

Example 2 In this example, a batch type vertical low pressure CVD apparatus having an inner tube as an auxiliary wall material for increasing the amount of phosphorus introduced during pre-doping was constructed. FIG. 1 shows a configuration example of a low pressure CVD apparatus 100 with an inner tube according to this embodiment. Reference numerals in FIG. 1 are partially common to those in FIG. 5 described above, and description of common members is omitted.

Depressurized CV with inner tube of this embodiment
The D device 100 also includes a cylindrical inner tube 9 along the inner wall surface of the cylindrical quartz tube 1. The inner tube 9 is composed of a quartz plate in which a large number of circular fine through holes are regularly arranged, and serves as a base material on which the phosphorus-containing Si thin film is deposited together with the inner wall surface of the quartz tube 1 during pre-doping.

The gas supply pipe 5 is opened inside the inner tube 9.

Example 3 In this example, the reduced pressure C with the inner tube of Example 2 was used.
Using the VD device 100, a polysilicon thin film having a phosphorus concentration higher by one digit than that of Example 1 was formed. First, a dummy wafer W was set on the wafer boat 7, and pre-doping was performed under the following conditions as an example.

SiH ₄ flow rate 500 SCCM N ₂ flow rate 2000 SCCM PH ₃ flow rate 10 SCCM doping temperature 550 ° C. pressure 50 Pa

By this pre-doping, a Si thin film containing a high concentration of phosphorus was formed on the inner wall surface of the quartz tube 1, the surface of the inner tube 9 and the surface of the wafer boat 7. Subsequently, when a polysilicon thin film was formed under the same conditions as in Example 1, a large amount of phosphorus was released into the atmosphere during the film formation. As a result, the phosphorus concentration is about 3 × 10 ¹⁹ atoms / c
A polysilicon thin film of m ³ (about 0.1 wt%) was deposited. This polysilicon thin film is a gate insulating film (S
It was suitable as a gate electrode forming layer on the iO ₂ film).

As described above, the present invention can be applied to the future dilute doping as described in the first embodiment, but can of course be accurately applied to the current concentration doping as in the present embodiment. it can.

Example 4 In this example, a batch type vertical decompression CVD apparatus was devised in which the shapes of the gas supply nozzle and the exhaust nozzle were devised in order to make the gas flow in the quartz tube 1 parallel to the wafer surface. Configured.
FIG. 3 shows a reduced pressure CVD apparatus 10 with an improved nozzle according to this embodiment.
1 in the longitudinal direction, and FIG. 4 shows a cross section taken along line XX in FIG. Reference numerals in these drawings are partly common to those in FIG. 5, and description of common members is omitted.

In the improved low pressure CVD apparatus 101 with a nozzle of the present embodiment, the gas supply pipe 10 which is opened in the partition wall 4 at the bottom of the quartz tube 1 is supplied with the gas which extends in the axial direction of the quartz tube 1. Nozzle 10a is connected, while quartz tube 1
At the tip of the exhaust pipe 11 opened at the top of the
An exhaust nozzle 11a extending in the axial direction of is connected.

The gas supply nozzle 10a and the exhaust nozzle 11a have a semicircular cross section as shown in FIG. 4, and a large number of pores 10b arranged regularly on the surface facing the wafer W, respectively. 11b is opened. Therefore, the source gas introduced into the gas supply pipe 10 from the direction of the arrow D is discharged from the pores 10b as shown by the arrow F, and the source gas passes between the three columns 8 of the wafer boat 7. And flow on the surface of the wafer W, and then the facing pores 1
1b, and exhausted from the exhaust pipe 11 in the direction of arrow E.

Example 5 In this example, the low pressure CVD apparatus 101 with the improved nozzle of Example 4 was used to form a polysilicon thin film having a phosphorus concentration similar to that of Example 3. That is, the wafer W was set on the wafer boat 7, and film formation was performed under the following conditions as an example.

SiH ₄ flow rate 500 SCCM N ₂ flow rate 2000 SCCM PH ₃ flow rate 0.01 SCCM film formation temperature 550 ° C. pressure 50 Pa wafer boat rotation speed 0.2 to 1.0 rpm In this example, the quartz tube 1 The gas flow inside the wafer W is formed parallel to the wafer W, and the wafer W is rotated to form a polysilicon thin film having extremely excellent uniformity in film thickness and doping concentration (about 0.1 wt%). I was able to.

The present invention has been described above based on the five embodiments, but the present invention is not limited to these embodiments. For example, in each of the above-described embodiments, a low pressure CVD apparatus with an inner tube and a film forming process for pre-doping using the same, a low pressure CVD apparatus with an improved nozzle, and a gas flow parallel to a wafer are formed using the same. Although the film forming process is described separately, these device configurations or processes can be combined. For example, pre-doping can be performed using a low pressure CVD apparatus equipped with an improved nozzle.

The present invention is also applicable to a low pressure CVD apparatus having no load lock chamber and a horizontal low pressure CVD apparatus. In addition, the types of impurities used, the doping conditions, the film forming conditions, and the types of thin films to be formed can be changed as appropriate.

[0050]

As is apparent from the above description, according to the film forming method of the present invention, it is possible to perform the thin doping while making the film thickness of the thin film uniform without necessarily modifying the conventional low pressure CVD apparatus. The concentration uniformity can also be improved. Therefore, it is possible to sufficiently meet the demand for precise film formation in the field of manufacturing semiconductor devices.

The low pressure CVD apparatus of the present invention can be constructed by modifying the conventional apparatus by a relatively simple modification.
Extremely excellent in space efficiency and economy. Therefore, the present invention greatly contributes to high integration, miniaturization, and high performance of semiconductor devices through advanced film formation control.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a configuration example of a low pressure CVD apparatus with an inner tube of the present invention.

FIG. 2 is a characteristic diagram showing a phosphorus concentration depth distribution in a polysilicon thin film formed by a film forming method of the present invention in which pre-doping is performed.

FIG. 3 is a schematic cross-sectional view showing a configuration example of a reduced pressure CVD apparatus with an improved nozzle of the present invention.

4 is a sectional view taken along line XX of FIG.

FIG. 5 is a schematic cross-sectional view showing a configuration example of a conventional batch type vertical low pressure CVD apparatus.

[Explanation of symbols]

 1 Quartz Pipe 2 Heater 3 Load Lock Chamber 5, 10 Gas Supply Pipe 6, 11 Exhaust Pipe 7 Wafer Boat 9 Inner Tube 10a Gas Supply Nozzle 10b (Gas Supply Nozzle 10a) Pore 11a Exhaust Nozzle 11b (Exhaust Nozzle 11a) ) Pore 12 Motor 100 Low pressure CVD apparatus with inner tube 101 Low pressure CVD apparatus with improved nozzle W Wafer

Claims (10)

[Claims] 1. A film forming method for holding a substrate in a film forming chamber of a low pressure CVD apparatus and forming a thin film containing a desired impurity on the substrate, the method comprising: 2. The film forming method, wherein the internal constituent member is loaded with the impurities in advance, and a film forming gas is supplied into the film forming chamber at the time of film forming, and the impurities are released into a film forming atmosphere. 2. The film forming method according to claim 1, wherein the impurities are supported on the internal constituent member by depositing a thin film containing the impurity on the surface of the internal constituent member. 3. A film forming method for holding a substrate in a film forming chamber of a low pressure CVD apparatus and forming a thin film containing a desired impurity on the substrate, wherein a film forming gas and a doping film are formed in the film forming chamber. A film forming method characterized in that an active gas flow from a supply system of a raw material gas mixed with a gas to an exhaust system is actively formed substantially parallel to the main surface of the substrate. 4. The film forming method according to claim 1, wherein the thin film is a polysilicon thin film. 5. A film forming chamber for accommodating a substrate and forming a desired thin film on the substrate, a heating means for heating the film forming chamber, and a film forming gas in the film forming chamber. A reduced pressure CVD apparatus comprising: a film forming gas supply unit that supplies the gas; a gas exhaust unit that exhausts the film forming chamber; and an auxiliary wall material that increases the surface area of internal components of the film forming chamber. 6. The film forming chamber has a tubular shape, and a plurality of the substrates are arranged in the film forming chamber with the main surface being perpendicular to the axial direction of the film forming chamber. The reduced pressure CVD apparatus described. 7. The auxiliary wall material is a plate-shaped member provided along the inner wall surface of the film forming chamber, and the film forming gas supply means is opened on the inner wall surface side of the auxiliary wall material. The reduced pressure C according to claim 5 or claim 6.
VD device. 8. A film forming chamber for accommodating a substrate and forming a desired thin film on the substrate, a heating means for heating the film forming chamber, and a film forming gas in the film forming chamber. A low pressure CVD apparatus comprising: a source gas supply unit configured to supply a source gas mixed with a doping gas; and an exhaust unit configured to exhaust the film forming chamber. A low pressure CVD apparatus in which the exhaust means and the nozzle both have openings in the film forming chamber, and these nozzles form a pair to form a gas flow substantially parallel to the main surface of the substrate. 9. The film forming chamber is formed of a tubular member capable of accommodating a plurality of substrates, and the main surface of each substrate can be held perpendicular to the axial direction of the film forming chamber. 8. The reduced pressure CVD apparatus according to 8. 10. The nozzle according to claim 8, wherein each of the nozzles extends along an axial direction of the film forming chamber, and an opening of the nozzle is formed by a large number of pores regularly arranged in the nozzle. 9. The low pressure CVD apparatus according to item 9.