JP2003197548A - Method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the corrosion of metallic parts provided in a throat section by avoiding the temperature rises of the parts even when high-temperature cleaning is performed. <P>SOLUTION: The reaction furnace of a semiconductor manufacturing device which performs a method of manufacturing semiconductor device is constituted of a vertical reaction pipe 9, a heater 1, and a metallic throat flange 6 which is provided below the heater 1 and supports the reaction pipe 9. The method of manufacturing semiconductor device includes a film forming step of respectively forming films on a plurality of wafers W in a state where the wafers W are held by a boat 4 in the reaction pipe 10, and a cleaning step of removing films deposited in the reaction pipe 10 by using a fluorine-based gas (NF<SB>3</SB>or ClF<SB>3</SB>). When the cleaning step is performed at a temperature of <600°C, the step is performed in a state where the boat 4 is attached to a throat cap 8. When the step is performed at a temperature of ≥600°C, the step is performed in a state where the boat 4 is removed from the cap 8. At this time, it is preferable to attach a throat-section reflecting heat insulating member 20 which reflects the radiation from the heater 1 to the top of the cap 8. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for removing a film deposited in a thermal CVD furnace by using a cleaning gas.

[0002]

2. Description of the Related Art When a CVD film is formed, a film as a reaction by-product is deposited in a reaction furnace. As the CVD film is continuously formed, the accumulated film thickness of the deposited film increases. Therefore, the quartz members such as the reaction tube, which is a component in the CVD furnace, are removed at regular intervals to remove the HF (hydrogen fluoride) solution,
Wet cleaning such as DIW is performed to remove the film. This cleaning method is troublesome because it is necessary to remove the quartz members that are the components inside the furnace.

On the other hand, there has been proposed a dry cleaning method capable of performing cleaning without removing the components inside the furnace. For example, JP-A-8-124
No. 870 (hereinafter referred to as a publicly known technique) discloses a fluorine-based N in a thermal CVD apparatus that batch-processes a plurality of substrates held in a boat in a vertical CVD furnace heated by a heater.
It is disclosed that the inside of the CVD furnace is cleaned using F ₃ (nitrogen trifluoride) gas. The temperature in the CVD furnace is 5
00-650 ° C, pressure 1,330-26,600 Pa
It is set to (10 to 200 Torr). The film deposited on the reaction tube or boat is cleaned by flowing NF ₃ gas or a gas containing NF ₃ gas into the reaction furnace while the boat is still inserted in the CVD furnace. Films deposited on reaction tubes and boats are silicon films, polysilicon films,
It is a CVD film such as a doped silicon film.

[0004]

In the above-mentioned known technique, the boat is not removed from the reaction furnace during cleaning, and an empty boat that does not hold the substrate remains inserted in the reactor heated by the heater. Is cleaning at. At this time, the furnace opening of the reaction furnace is closed by the furnace opening cap in which the boat is installed. Therefore, the boat is heated to a high temperature by heating the heater, and heat is transferred from the heated boat to the furnace opening and the furnace opening near the furnace opening.
No problem occurs in cleaning at a cleaning temperature of less than 600 ° C., but especially during high-temperature cleaning at 600 ° C. or higher, the metal parts forming the furnace opening are exposed to high temperatures.

A method of removing the film deposited in the CVD furnace with NF ₃ gas at a predetermined temperature and pressure is also disclosed (JP-A-7-78808). However, since the processing method is a single-wafer type and there is no boat or metal furnace opening that supports the reaction tube, the metal furnace opening is exposed to high temperatures unlike the vertical reactor described above. There is no problem with

An object of the present invention is to provide a vertical reactor in
It is an object of the present invention to provide a method of manufacturing a semiconductor device that solves the above-mentioned problems of the conventional technology and prevents the metal components of the furnace opening from being exposed to high temperatures even during high temperature cleaning.

[0007]

A first aspect of the present invention is directed to a vertical reaction tube, a heater for heating the reaction tube, and a metal furnace port flange provided below the heater to support the reaction tube. A vertical reaction furnace composed of, a boat holding a plurality of substrates is inserted into the reaction furnace, and the furnace opening of the reaction furnace is closed by a furnace opening cap in which the boat is installed. A method for manufacturing a semiconductor device, comprising: a film forming step of forming a film on a substrate; and a cleaning step of removing the film deposited in the reaction furnace in the film forming step using a fluorine-based gas, the method comprising: The cleaning step is a semiconductor device manufacturing method, wherein the cleaning step is performed with the boat removed from the furnace port cap.

According to the first aspect of the invention, since the cleaning step is performed with the boat removed from the furnace port cap, heat transfer from the boat to the furnace port is eliminated, unlike when the cleaning process is performed without removing the boat. You can Therefore, even during high-temperature cleaning, the metal parts at the furnace opening are not exposed to high temperatures.

A second aspect of the present invention is a reaction furnace comprising a vertical reaction tube, a heater for heating the reaction tube, and a metal furnace port flange provided below the heater to support the reaction tube. A film forming step of forming silicon nitride films on a plurality of substrates in the reaction furnace, and a silicon nitride film deposited in the reaction furnace in the film forming step, using a nitrogen fluoride gas or a nitrogen fluoride film. A method of manufacturing a semiconductor device, comprising: a cleaning step of removing using a gas containing a gas, wherein the cleaning step includes:
330 Pa (10 Torr) or more, 66,500 Pa (50
0 Torr) or less is a method for manufacturing a semiconductor device.

According to the second aspect of the invention, since the cleaning step for removing the silicon nitride film is performed under the above-mentioned temperature and pressure conditions, the silicon nitride film can be effectively cleaned without exposing the furnace port metal parts to high temperatures. .

Nitrogen fluoride has a high decomposition temperature, and if it is less than 500 ° C., etching cannot be performed. Further, if the temperature is raised, the temperature of the metal parts at the furnace mouth also rises and corrosion progresses. Therefore, the temperature during cleaning is preferably 500 ° C. or higher and 650 ° C. or lower.

If the pressure is less than 1,330 Pa, the etching rate becomes slow and a practical etching rate cannot be obtained. If the pressure is higher than 66,500 Pa, pressure control becomes difficult. Therefore, the pressure during cleaning is 1,330 Pa or more and 66,500 P.
It is preferably a or less.

In the first aspect of the invention, in the cleaning step, the boat on the furnace port cap is removed, and a furnace port reflection heat insulating material for reflecting radiant heat from the heater is installed on the furnace port cap instead of the boat. It is preferable that the inside of the furnace is cleaned while the furnace opening is closed by the furnace opening cap provided with this furnace opening reflection heat insulating material. According to this, heat transfer from the heater to the furnace opening through the boat can be eliminated, and the radiant heat from the heater is reflected by the furnace opening reflective heat insulating material, and the furnace opening receives the radiant heat and is heated. Therefore, even during high-temperature cleaning at 600 ° C. or higher, the temperature of the furnace port metal component can be maintained at a temperature at which corrosion does not occur.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 5 shows a schematic structure of a thermal CVD apparatus having a vertical reactor for carrying out the method for manufacturing a semiconductor device.

The vertical reaction furnace 10 comprises a vertical reaction tube 9, a resistance heater 1, and a furnace port flange 6.
A vertical reaction tube 9 is provided inside the resistance heater 1. The reaction tube 9 is composed of an outer tube 2 that maintains a vacuum and an inner tube 3 that forms a gas exhaust passage 11. Inside the outer tube 2 that maintains a vacuum, an inner tube 3 that constitutes a reaction chamber having an open upper end and that forms a gas exhaust passage 11 with the outer tube 2 is concentrically arranged. The outer tube 2 and the inner tube 3 are erected on a furnace port flange 6 that forms a furnace port provided below the heater 1, and an O-ring 19 seals between the outer tube 2 and the furnace port flange 6. The lower opening of the furnace port flange 6 constitutes the furnace port of the reaction furnace 10. This furnace opening is hermetically closed by a furnace opening cap 8 via an O-ring 13. The boat 4 is installed on the furnace port cap 8 via the boat cap 12, and the boat 4 is inserted into the inner tube 3. A large number of wafers W to be processed are held in the boat 4 in a horizontal posture in multiple stages.

A plurality of (two in the illustrated example) gas supply nozzles 7 are connected to a position below the inner tube 3 of the furnace port flange 6, and a cylindrical shape formed between the outer tube 2 and the inner tube 3. A gas exhaust port 5 is formed in the furnace port flange 6 so as to communicate with the lower end of the gas exhaust flow channel 11. The gas exhaust port 5 is connected to a vacuum pump (not shown).

The boat 4 is supported by a boat elevator (not shown) via a furnace port cap 8. The boat 4 is lowered by the boat elevator, the wafer W is loaded and held in the boat 4, and the wafer W is held by the boat elevator. The boat 4 supporting the is inserted into the inner tube 3. After the furnace opening cap 8 completely seals the furnace opening of the furnace opening flange 6, the inside of the reaction furnace 10 is exhausted.

Reactive gas GAS from gas supply nozzle 7
1 and GAS2 are discharged from the gas exhaust port 5 while being supplied into the reaction furnace 10 by controlling the flow rate through the mass flow controller MFC. The inside of the inner tube 3 is heated by the resistance heater 1 to a predetermined temperature necessary for film formation, and a film is formed on the surface of the wafer W. After film formation is completed, gas supply nozzle 7
Inert gas is introduced to replace the outer tube 2 and the inner tube 3 with inert gas to return to normal pressure, the boat 4 is lowered, and the wafer W after film formation is completed is discharged from the boat 4.

Next, the film forming process and the cleaning process in the process of manufacturing the semiconductor device by the above-mentioned vertical CVD apparatus will be described with reference to FIG. FIG. 1A shows the film formation. 1 (b) and 1 (c) show a cleaning operation,
(B) shows the case where the cleaning temperature is lower than 600 ° C., and (c) shows the case where the cleaning temperature is 600 ° C. or higher.

A. Film Forming Step (FIG. 1A) First, film forming will be described. A predetermined number of wafers W are loaded and held in the boat 4. After wafer loading, boat 4
Is loaded into the vertical reactor 10. After the boat is loaded, the temperature inside the reaction furnace 10 is set to a predetermined film forming temperature by the resistance heater 1. Moreover, the pressure in the reaction furnace 10 is made uniform by a vacuum pump (not shown). A film forming gas is introduced into the reaction furnace 10 to form a predetermined film on the wafer W by the thermal CVD method.

For example, when forming a Si ₃ N ₄ film, the film forming conditions are as follows.

Furnace temperature: 750 ± 50 ° C. Furnace pressure: 13.3 to 133 Pa (0.1 to 1 Torr) Film forming gas: SiH ₂ Cl ₂ + NH ₃ , Si ₂ Cl ₆ + NH ₃ ,
After forming a film of SiCl ₄ + NH _3, etc., the residual gas in the reaction furnace 10 is removed from the gas exhaust port, the boat 4 is unloaded, and the processed wafer W is recovered.

B. Cleaning process (Fig. 1 (b),
(C)) Next, cleaning in the furnace will be described. A fluorine-based gas is used as the cleaning gas. Since a fluorine-based gas is used, it is not necessary to desorb the quartz reaction tube or the like, which was necessary when performing liquid cleaning using HF / DIW or the like. The fluorine-based gas may be ClF ₃ , but if a gas containing NF ₃ gas or NF ₃ gas is used, C
Since the lF ₃ does not include the difference chlorine content, corrosion, pollution is not, is less quartz surface damage. NF ₃ is Cl
The decomposition temperature is higher than that of F _{3, and} a furnace temperature of 500 ° C. or higher is required.

When the temperature inside the furnace during cleaning is lower than 600 ° C., the inside of the reaction furnace 10 is cleaned together with the boat 4 without removing the boat 4 from the furnace port cap 8 (FIG. 1).
(B)). At this time, all the production wafers and the dummy wafers are removed from the boat 4. When the cleaning is performed at a temperature lower than 600 ° C., the temperature is not so high that the metal parts forming the furnace port 15 are corroded. Therefore, the boat 4 may be cleaned without removing the boat 4.

During high-temperature cleaning at 600 ° C. or higher, it is necessary to lower the temperature of the furnace opening 15 so as not to corrode the metal parts of the furnace opening to prevent corrosion of the metal parts of the furnace opening 15. There is. Therefore, in order to eliminate the heat transfer from the boat 4 heated to a high temperature by the heater 1 to the furnace port portion 15, the boat 4 is removed together with the boat cap 12 from the furnace port cap 8 for cleaning. Further, in order to eliminate heat radiation from the heater to the furnace striking portion in addition to the heat transfer from the boat 4 heated to a higher temperature to the furnace mouth portion 15, the boat 4 and the boat cap 12 are removed from the furnace mouth cap 8 and In place of the above, the furnace opening portion reflective heat insulating material 22 that reflects the radiant heat H from the heater 1 is installed on the furnace opening cap 8. The furnace opening 15 is closed by the furnace opening cap 8 provided with the furnace opening reflecting heat insulating material 22 to perform high temperature cleaning (FIG. 1C). By dismounting the boat 4 together with the boat cap 12 and installing the furnace opening reflection heat insulating member 22, the radiant heat from the heater 1 to the furnace opening 15 can be reflected, and the temperature of the metal parts of the furnace opening 15 can be changed to metal. It can be lowered to a temperature at which the parts do not corrode. The boat 4 and the boat cap 12 removed from the furnace port cap 8 are separately washed or replaced to prepare for the next film formation.

As shown in FIG. 2, the furnace-portion reflective heat insulating material 20 described above is, for example, a hollow cylinder having the same shape as the boat cap 12 that supports the boat 4 on the furnace-port cap 8. Quartz is used as the material of the hollow furnace port reflection heat insulating material 20. The inside of the hollow is held in a vacuum and is filled with a heat insulating material such as glass wool 22.

As shown in FIG. 6, the boat cap 12 forms a cylindrical space, a columnar heat insulating plate holder 12a is provided inside the boat cap 12, and the heat insulating plate holder 12a has a required number of sheets. A heat insulating plate (not shown) is held horizontally. The boat cap 12 communicates with the inside of the inner tube 3 through a hole (not shown) provided in the lower portion. The boat cap 12 also insulates the furnace opening 15. Since the boat cap 12 is configured in this way,
It can be used in place of the above-mentioned furnace port reflective heat insulating material 20. That is, it is possible to remove only the boat 14 and leave it without removing the boat cap for cleaning.

Next, the cleaning conditions using the above-mentioned NF ₃ gas will be described. The cleaning temperature is preferably 500 ° C. or higher and 650 ° C. or lower in consideration of the cumulative film thickness and the apparatus down time. The cleaning pressure is 1,33
An optimum process window is obtained by performing the process at 0 to 13,300 Pa (10 Torr to 100 Torr).

That is, nitrogen fluoride (NF ₃ ) has a high decomposition temperature, and if it is less than 500 ° C., etching cannot be performed. Further, if the temperature is raised, the temperature of the metal parts at the furnace mouth also rises and corrosion progresses. Especially when the temperature is higher than 650 ° C., the temperature of the metal part of the furnace mouth, for example, Hastelloy, becomes the critical temperature (20
The temperature will exceed 0 ° C and will corrode. Therefore, the temperature during cleaning is preferably 500 ° C. or higher and 650 ° C. or lower.

If the pressure is less than 1,330 Pa, the etching rate becomes slow and a practical etching rate cannot be obtained. Further, the selectivity of the members forming the reaction tube, for example, quartz and the silicon nitride film cannot be obtained, and not only the silicon nitride film deposited in the reaction furnace but also the reaction tube is scraped. If the pressure is higher than 66,500 Pa, pressure control becomes difficult. Therefore, the pressure during cleaning is preferably 1,330 Pa or more and 66,500 Pa or less.

(I) Necessity of lowering the furnace port temperature during cleaning At the time of high-temperature cleaning at 600 ° C. or higher, heat transfer from the boat heated to high temperature to the furnace port, and heat from the heater to the furnace port Due to the radiation, the metal parts at the furnace mouth also become hot and corrode. Therefore, the furnace temperature during cleaning is 600
When the temperature is higher than or equal to ℃, it is necessary to lower the temperature of the metal part at the furnace opening to a temperature at which the metal part does not corrode.

FIG. 6 shows the detailed structure of the lower part of the furnace of the vertical CVD apparatus described above. Among the members forming the furnace opening 15 near the furnace opening, the outer tube 2, the inner tube 3, the boat cap 12 and the like are made of quartz. The furnace port flange 6 that supports the outer tube 2 and the inner tube 3, the furnace port cap 8 that closes the furnace port of the furnace port flange 6, and the base 31 fixed to the boat rotation shaft 30 are made of metal such as SUS. In addition, a high Ni material is used for the portion where the temperature is high (200 ° C. or higher) to prevent corrosion. For example, a cap support 32 that supports a boat including the boat cap 12, a boat rotation shaft 30, a washer 33 that fixes the boat rotation shaft 30 and the cap support 32, a screw 34, a seal flange 35 that seals the inner tube 3, and a seal flange. Inner tube support 36 for supporting inner tube 3 on 35, seal flange 3
The screws 37 for fixing the inner tube support 36 to 5 are each made of a high Ni material such as Hastelloy. The metal parts forming the above-mentioned furnace opening 15 are referred to as furnace opening metal parts 30.

By the way, Hastelloy, Inconel, SU
The three materials of S were evaluated by NF ₃ cleaning. Cleaning conditions are: furnace temperature 585 ° C, N
F ₃ flow rate: 500 sccm, cleaning time 120 m
in. The results of Ni, Cr, F, and O components of each material by XPS (X-ray photoelectron spectroscopy) analysis are as follows. Hastelloy C22 Inconel SUS316L Ni: 50 atom% Ni: 15 atom% Cr: 30 atom% Cr: 10 atom% − F: 10 atom% F: 55 atom% O: 5 atom% O: 5 atom% Cleaning evaluation result by SEM Was OK with no corrosion, and other Inconel and SUS were NG with corrosion. The more Ni and Cr the better the corrosion resistance, Ni is 50 atom% or more, Cr is 30 atom%
It is understood that the above is desirable. F and O are taken into the metallic material by fluorination and oxidation, but F and O
The less O is better. Therefore, as described above, a metal part whose temperature is 200 ° C. or higher contains Ni at 50 atom% or higher and C
It is preferable to use Hastelloy, which is a high Ni material having r of 30 atom% or more.

(Ii) Grounds of pressure range during cleaning In the above embodiment, NF ₃ gas is used for removing the film, but this is based on a basic test using a monitor metal (SUS316L). In the basic test, a monitor metal was previously put on a boat and a furnace port cap to which a boat cap was attached, and cleaning was performed under the following conditions using ClF ₃ and NF ₃ gas. ClF ₃ NF ₃ temperature 595 ° C. 595 ° C. Pressure 70.49Pa (0.53Torr) 3,325Pa (25Torr) Gas flow rate NF _3: 500sccm ClF _3: 21 sheets 21 sheets the number of 1250sccm cleaning time 60 minutes 60 minutes insulating plates Incidentally, the heat insulating plate , Means a heat insulating plate held by the boat cap 12.

As a result, the corrosion of the sample metal is caused by ClF.
In the _{three-cleaning} was NG, but in the NF ₃ cleaning became OK. Therefore, it is understood that the NF ₃ gas is preferable as the cleaning gas at least at 595 ° C.

By the way, the NF ₃ gas reacts as follows by thermal decomposition to remove the Si-based film, for example, the Si ₃ N ₄ film. Si ₃ N ₄ (target film) + 4NF ₃ → 3SiF
₄ (G) + 4N _{2 In} this reaction formula, SiF ₄ (G) is in the gas phase and is discharged as a gas.

FIG. 3 shows the pressure dependence of etching during NF ₃ gas cleaning. In both cases, the furnace temperature is 585
The temperature and the NF ₃ flow rate are controlled to 500 sccm. In addition, the data is 133 Pa (1 Torr), 399 Pa (3
Torr), 798Pa (6Torr), 1330Pa (10To)
The value in (rr) was collected. The data ● TOP, ▲ CE
N and BTM mean the top, center and bottom of the wafer holding on the boat 4 shown in FIG. 5, respectively. Regarding the etching characteristics, the lower limit of the pressure inside the furnace becomes a problem, so data for 10 Torr or more is not collected. The upper limit of furnace pressure is rather limited by pressure control.

The reaction steps of NF _3, compared to NF ₃ was excited by ClF ₃ or plasma, low reaction rate, for example, S
In the case of i ₃ N ₄ , the etching rate and the selection ratio of SiN (nitride film) and SiO ₂ (quartz) are as shown in FIG.

FIG. 3A shows S with respect to furnace pressure (Torr).
Etching rate of i ₃ N ₄ film (angstrom / mi
n) is shown. FIG. 3B shows the etching rate (angstrom / min) of SiO ₂ with respect to the furnace pressure (Torr) during cleaning. FIG. 3 (c) shows the pressure in the furnace during cleaning and the etching selection ratio characteristics of SiN with respect to SiO ₂ (etching rate (SiN) / etching rate (SiO ₂ )).

As shown in FIG. 3, the pressure is 1,330 Pa.
If it is less than (10 Torr), the etching rate of the Si ₃ N ₄ film becomes slow and a practical etching rate cannot be obtained. Further, the selectivity of the reaction tube 9 with a member such as quartz cannot be obtained, and not only the SiN adhering to the inside of the reaction tube 9 but also the reaction tube 9 is scraped. Also, the pressure is 66,
If it exceeds 500 Pa (500 Torr), pressure control becomes difficult. Therefore, the pressure during cleaning is preferably 1,330 Pa or more and 66,500 Pa or less. Within this range, the selection ratio can be increased and the cleaning speed can be significantly improved. Also,
The SiO ₂ film can be removed by overetching.

The pressure control can be performed by either a fine control system using a valve element (variable orifice) or a control system using an orifice (fixed orifice). Pressure is
Both methods are controlled by generating pressure loss due to the orifice.

(Iii) Grounds for the temperature range during cleaning As described above, NF ₃ has a high decomposition temperature, and if it is less than 500 ° C., etching cannot be performed. Further, if the temperature is raised, the temperature of the furnace-portion metal part 30 also rises and corrosion progresses. In particular, if the temperature is higher than 650 ° C, the temperature of the metal component (Hastelloy) at the furnace opening exceeds its limit temperature (200 ° C) and corrodes. Therefore, the temperature during cleaning is 50
It is preferably 0 ° C or higher and 650 ° C or lower.

FIG. 4 shows the etching temperature dependence during cleaning. In both cases, the furnace pressure was 133 Pa (1
Torr) and NF ₃ flow rate is controlled to 500 sccm. Further, as the temperature data, values at 585, 600, and 620 ° C. that substantially cover the above temperature range were collected. The meanings of ● TOP, ▲ CEN, and ■ BTM of the data are the same as in the case of FIG. In the case of Si ₃ N ₄ , the etching rate,
Further, the selection ratio of SiN (nitride film) and SiO ₂ (quartz) is as shown in FIG.

FIG. 4 (a) shows Si with respect to furnace temperature (° C.).
Etching rate of ₃ N ₄ film (angstrom / min)
Indicates. Fig. 4 (b) shows SiO _{2 with} respect to the furnace temperature (° C).
Shows the etching rate (angstrom / min) of. FIG. 4C shows the temperature inside the furnace during cleaning and SiO ₂
The etching selectivity ratio characteristics of SiN with respect to (quartz or SiO ₂ film) (etching rate (SiN) / etching rate (SiO ₂ )) are shown.

These have a furnace pressure of 133 Pa (1 Torr).
When the cleaning temperature is 500 ° C. or higher and 650 ° C. or lower,
Both the etching rates of ₃ N ₄ and SiO ₂ are smaller by one digit. However, it can be seen that the etching selection ratio can be increased even when the pressure in the furnace is 133 Pa (1 Torr). Therefore, the furnace pressure is 1,330 Pa (10 Tor
r) or higher, a practical etching rate can be obtained for the Si ₃ N ₄ film even when the cleaning temperature is 500 ° C. or higher and 650 ° C. or lower, and the selectivity ratio between quartz and SiN is obtained. It can be inferred that the value can be larger.

As described above, according to the embodiment, since the gas cleaning of the fluorine-based gas is adopted, the thermal CV
There is no liquid cleaning of the in-furnace components of device D, which facilitates cleaning. In addition, since the cleaning step is performed with the boat removed from the furnace port cap, heat transfer from the boat to the furnace port can be eliminated, unlike when the boat is not removed. Therefore, even during high-temperature cleaning, the metal parts at the furnace opening are not exposed to high temperatures. As a result, the maintenance cycle can be reduced and COO (cost of ownership) can be expected to improve.

In particular, in the high temperature cleaning step, since the furnace opening portion reflective heat insulating material is installed on the furnace opening cap instead of the boat and the boat cap to perform cleaning, not only the heat transfer from the boat to the furnace opening portion but also the furnace opening portion is performed. Heat radiation from the heater to the parts can also be reduced. Therefore, it is possible to maintain the temperature of the furnace-portion metal parts at a temperature at which corrosion does not occur, not only when cleaning at temperatures lower than 600 ° C. but also when cleaning at temperatures above 600 ° C. As a result, as the fluorine-based gas, NF ₃ having a high decomposition temperature but less corrosion or pollution can be effectively used instead of ClF ₃ having a lower decomposition temperature.

The object to be cleaned according to the present invention is made of polysilicon such as polysilicon, phosphorus-doped polysilicon, boron-doped polysilicon, SiN, or the like.
It can be applied to all those formed by thermal CVD such as SiO ₂ .

[0049]

According to the present invention, since the boat is removed for cleaning, heat transfer to the furnace opening through the boat does not occur, and the metal parts constituting the furnace opening are exposed to high temperatures. Can be effectively prevented.

When the silicon nitride film is cleaned with nitrogen fluoride gas, the temperature is set to 500 to 650 ° C. and the pressure is set to 1,330 Pa to 66,500 Pa. Therefore, the silicon nitride film is effectively used. Can be removed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a cleaning method according to a cleaning temperature after film formation according to an embodiment, (a) is during film formation, (b) is below 600 ° C. during cleaning,
(C) shows high-temperature cleaning at 600 ° C. or higher.

FIG. 2 is a perspective view showing a configuration of a furnace mouth portion reflective heat insulating material according to the embodiment.

FIG. 3 is a characteristic diagram showing the relationship between the pressure in the furnace and the etching rate during cleaning, (a) is the etching rate of SiN, (b) is the etching rate of SiO ₂ , and (c) is S.
The etching selectivity ratio characteristics of SiN with respect to iO ₂ are shown respectively.

FIG. 4 is a characteristic diagram showing a relationship between an in-furnace temperature at the time of cleaning and an etching rate, (a) is an etching rate of SiN, (b) is an etching rate of SiO ₂ , and (c) is S.
The etching selectivity ratio characteristics of SiN with respect to iO ₂ are shown respectively.

FIG. 5 is a configuration diagram of a CVD furnace according to an embodiment.

FIG. 6 is a sectional view showing a flange structure (furnace opening) of the CVD furnace according to the embodiment.

[Explanation of symbols]

1 Resistance heating heater 4 boats 8 Furnace cap 9 reaction tubes 10 Reactor 15 Furnace mouth 20 Furnace mouth reflective insulation W wafer (substrate)

Claims (2)

[Claims] 1. A vertical reaction furnace comprising a vertical reaction tube, a heater for heating the inside of the reaction tube, and a metal furnace port flange provided below the heater to support the reaction tube. A film-forming method in which a boat holding a plurality of substrates is inserted into the reaction furnace, and a film is formed on the substrate in a state where the furnace opening of the reaction furnace is closed by a furnace opening cap in which the boat is installed. A method of manufacturing a semiconductor device, comprising: a step of removing a film deposited in the reaction furnace in the film forming step using a fluorine-based gas, wherein the cleaning step is performed from the furnace port cap. A method of manufacturing a semiconductor device, which is performed with a boat removed. 2. A reaction furnace comprising a vertical reaction tube, a heater for heating the inside of the reaction tube, and a metal furnace port flange provided below the heater for supporting the reaction tube, A film forming step of forming a silicon nitride film on a plurality of substrates in a reaction furnace, and a silicon nitride film deposited in the reaction furnace in the film forming step,
A method of manufacturing a semiconductor device, comprising: a cleaning step of removing using a nitrogen fluoride gas or a gas containing a nitrogen fluoride gas, wherein the cleaning step includes a temperature of 500 ° C. to 650 ° C. and a pressure of 1,330 Pa (10 Torr). ) Above, 66,50
A method for manufacturing a semiconductor device, which is performed at 0 Pa (500 Torr) or less.