JP4131677B2 - Semiconductor device manufacturing method and substrate processing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a semiconductor device in which a thin film is formed on the surface of a semiconductor substrate or the like by a chemical vapor deposition (CVD) method, and in particular, the film thickness formed on the substrate is a residual gas after fluorine gas cleaning. It is related with the method of suppressing that falls by this.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a semiconductor device manufacturing method adopts a cleaning process for removing a film attached to a reaction furnace in a film forming process (see, for example, Patent Document 1). In Patent Document 1, in a CVD apparatus capable of heating a plurality of substrates held by a boat in a CVD furnace, nitrogen trifluoride (hereinafter referred to as NF), which is a fluorine-based gas._ThreeA method for dry cleaning the inside of a CVD furnace using a gas is disclosed.
[0003]
The temperature in the CVD furnace is set to 500 ° C. to 650 ° C., and the pressure is set to 1,330 Pa to 26,600 Pa (10 to 200 Torr). With the boat inserted in the CVD furnace, NF is put in the reaction furnace._ThreeGas or NF_ThreeBy injecting a gas containing gas, the film attached to the reaction furnace or the boat is cleaned. The film adhering to the reaction furnace or the boat is a CVD film such as a silicon film, a polysilicon film, or a doped silicon film.
NF_ThreeIn addition to gas, chlorine trifluoride (hereinafter referred to as ClF)_ThreeGas) can also be used, but ClF_ThreeNF with little damage in the furnace because the gas is highly corrosive_ThreeGas is mainly used.
[0004]
[Patent Document 1]
JP-A-8-124870 (Detailed Description of the Invention, FIG. 1)
[0005]
[Problems to be solved by the invention]
However, while dry cleaning using a fluorine-based gas has an advantage of being maintenance-free, there is a problem that a film thickness reduction phenomenon occurs when a film is formed on a substrate in a film forming process after cleaning. . This has been a problem particularly when a film is formed using a thermochemical reaction such as a thermal CVD method.
[0006]
In view of the above circumstances, an object of the present invention is to provide a method of manufacturing a semiconductor device in which a film thickness reduction phenomenon does not occur during film formation in a film formation process after the cleaning process even if a cleaning process is incorporated.
[0007]
[Means for Solving the Problems]
According to a first aspect of the present invention, a film forming gas is supplied to a reaction furnace containing a substrate to form a thin film on the substrate by a thermochemical reaction, and the reaction furnace in a state where the substrate is not accommodated. Supplying a fluorine-based gas, a cleaning process for removing the thin film adhered in the reaction furnace in the film formation process by a thermochemical reaction, and in the reaction furnace in a state where the substrate is not accommodated after the cleaning process, NH in a state where the pressure in the furnace is higher than the pressure in the film forming process._ThreeAnd a purging step for purging by supplying a gas.
[0008]
According to the first invention, after the cleaning process using the fluorine-based gas, the NH 2 is kept in a state where the pressure in the furnace is higher than the pressure in the film forming process._ThreeIt has a purge process for supplying gas, and this NH is performed at this high pressure._ThreeSince the cleaning gas residue can be sufficiently decomposed and removed by purging, when the film is formed by a thermochemical reaction, a decrease in film thickness in the film forming process after the cleaning process can be suppressed. Note that all fluorine-containing gases include fluorine. For example, NF_ThreeGas or ClF_ThreeThere is.
[0009]
According to a second aspect of the present invention, in the first aspect of the present invention, the film forming gas is supplied in a state where the furnace pressure is lower than the furnace pressure in the purge process in the reaction furnace in a state where the substrate is not accommodated after the purge process. A semiconductor device manufacturing method comprising a coating step of forming a thin film in the reaction furnace by a thermochemical reaction.
[0010]
According to the second invention, after the purge process, the coating gas is supplied in a state where the pressure in the furnace is lower than the pressure in the purge process, and the coating process for forming the coating film in the reaction furnace is provided. In the film-forming process after cleaning, the film thickness can be further prevented from decreasing.
[0011]
According to a third invention, in the first or second invention, in the film forming step, SiH is used as a film forming gas.₂Cl₂And NH_ThreeA method of manufacturing a semiconductor device, wherein a silicon nitride film is formed on a substrate by a thermal CVD method using a gas containing
As in the third invention, NH is performed at a high pressure (higher pressure than the film forming step) after the cleaning step using a fluorine-based gas._ThreePurge is SiH₂Cl₂And NH_ThreeAnd a silicon nitride film (Si_ThreeN_FourThis is particularly effective when forming a film.
[0012]
According to a fourth aspect of the present invention, there is provided a reaction furnace for performing a process for forming a thin film on a substrate by a thermochemical reaction, a supply port for introducing a film forming gas into the reaction furnace, and an NF as a cleaning gas in the reaction furnace._ThreeSupply port for supplying fluorine gas such as gas, and NH as purge gas in the reactor_ThreeNF for cleaning by thermochemical reaction in a supply port for supplying gas, an exhaust port for exhausting the inside of the reaction furnace, and a reaction furnace in a state where no substrate is accommodated_ThreeFluorine-based gas such as gas is supplied, and then the furnace pressure is set higher than the pressure at the time of film formation and NH is purged in the reaction furnace in a state in which the substrate is not accommodated._ThreeAnd a control means for controlling to supply gas.
According to the fourth invention, NF is used for cleaning._ThreeFluorine-based gas such as gas is supplied, and then the furnace pressure is set higher than the pressure at the time of film formation and NH is purged._ThreeSince a thin film is formed on a substrate using a substrate processing apparatus having control means for controlling supply of gas, the semiconductor device manufacturing method of the first invention can be easily implemented.
[0013]
According to a fifth invention, in the fourth invention, the control means is NF for cleaning by a thermochemical reaction in a reaction furnace in a state in which the substrate is not accommodated._ThreeFluorine-based gas such as gas is supplied, and then the furnace pressure is set higher than the pressure at the time of film formation and NH is purged._Three, And thereafter, the furnace pressure is controlled to be lower than the pressure at the time of purging to supply a film forming gas for coating.
According to the fifth aspect of the invention, since the control means is further provided with a control function to supply the film forming gas for the coating after the purge, the semiconductor device manufacturing method of the second to fourth aspects of the invention can be easily performed. Can be implemented.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. FIG. 1 shows a schematic configuration diagram of a substrate processing apparatus according to an embodiment. The substrate processing apparatus is a vertical thermal CVD apparatus for carrying out a method of forming a thin film on a substrate as one step of a semiconductor device manufacturing process. The vertical thermal CVD apparatus includes a reaction furnace 1 that performs a process of forming a thin film on a wafer by a thermochemical reaction, and a vacuum prechamber (load lock chamber) disposed under the reaction furnace 1 via a furnace port gate valve 8. ) 13.
[0015]
The reaction furnace 1 includes a heater 14, a double reaction tube 2 that is heated by the heater 14, and a furnace port flange 6 that is connected to the bottom of the double reaction tube 2 and supports the double reaction tube 2. The A quartz outer tube 3 and an inner tube 5 constituting the double reaction tube 2 are provided inside the heater 14. The outer tube 3 has a headed cylinder shape with the head closed and the bottom open. The inner tube 5 has a cylindrical shape with its head and bottom open, and is disposed coaxially so as to constitute a furnace space 4 having an upper end opened inside the outer tube 3. The furnace space 4 includes not only the inner space of the outer tube 3 but also the cylindrical exhaust space 7 formed in the gap between the outer tube 3 and the inner tube 5 and the inner space of the furnace port flange 6. The outer tube 3 and the inner tube 5 are erected on the furnace port flange 6, and the outer tube 3 and the furnace port flange 6 are sealed by an O-ring 16. The inner tube 5 is placed on a support portion 5 a provided in the furnace port flange 6. The lower end opening of the furnace port flange 6 is airtightly closed by an openable / closable furnace port gate valve 8.
[0016]
The furnace port flange 6 constitutes a furnace port part of the reaction furnace 1 by being connected to the reaction tube 2 and is formed in a cylindrical shape with a metal such as stainless steel or hastelloy. A gas supply port 15 communicating with the inner tube 5 is provided at a position below the inner tube 5 of the furnace port flange 6. A gas exhaust port 17 communicating with the exhaust space 7 is provided at a position below the exhaust port space 7 of the furnace port flange 6. Therefore, the gas supply port 15 and the gas exhaust port 17 communicate with each other through the furnace space 4. A plurality of gas supply ports 15 are provided, and a plurality of gas types (film forming gas, NF_Three, NH_Three, N₂Gas) is supplied into the reaction tube 2, but in the illustrated example, only one is shown for convenience. The reaction tube 2, the heater 14 and the furnace port flange 6 described above are accommodated in the casing 24. Further, a heat insulating material 18 is provided between the outer tube 3 and the casing 24. Supplyed through the gas supply port 15 so that the furnace space 4 in the reaction tube 2 can be evacuated by the vacuum pump 19 through the gas exhaust port 17 with the furnace port gate valve 8 completely sealed at the lower end opening of the furnace port flange 6. The exhausted gas can be discharged.
[0017]
The vacuum prechamber 13 allows the boat 11 to be taken in and out of the reaction tube 2 while keeping the inside of the reaction tube 2 of the reaction furnace 1 in a vacuum or a predetermined reduced pressure state. For this purpose, the space 23 where the boat 11 exists can be evacuated by the vacuum pump 19 through the gas exhaust port 21 and the gas supplied through the gas supply port 25 can be discharged. In the vacuum preparatory chamber 13, a boat 11 erected on a furnace port seal cap 12 via a boat support 9 is disposed. In the boat 11, wafers 10 to be processed in the reaction furnace 1 are horizontally arranged in multiple stages. Loaded. When the boat elevator 40 is lifted, the boat 11 is lifted together with the furnace port seal cap 12 and the boat support 9, the furnace port gate valve 8 is opened and passes through the open furnace port, and the inner tube 5 Inserted (loaded) inside. When the boat 11 reaches a predetermined position, the lower end opening of the furnace port flange 6 serving as the furnace port part of the reactor 1 is covered with the furnace port seal cap 12, and the furnace is sealed by the O-ring 20 provided in the furnace port seal cap 12. The space 4 is sealed. Further, the boat 10 is unloaded by lowering the boat 11 with the boat elevator 40 and extracting it from the reactor 1. After unloading the wafer, the furnace space 4 is again sealed by closing the furnace gate valve 8 at the lower end opening of the furnace opening flange 6.
[0018]
The gas supply ports 15 and 25 are provided with valves 27 and 29 for opening and closing the gas supply ports 15 and 25 and adjusting the flow rate, respectively. Valves 31 and 33 for opening and closing 21 are provided.
[0019]
Further, as schematically shown in FIG. 2, the reaction furnace includes a control unit 22 that controls operation of each part constituting the reaction furnace. NF_ThreeCleaning process, NH_ThreeA purge process and a coating process are performed. Therefore, the control means 22 controls the boat elevator 40, the furnace gate valve 8 and the heater 14 to move the boat up and down and adjust the temperature in the reaction furnace. Further, the control means 22 controls the valve 31 and the vacuum pump to evacuate the reaction furnace 1 or controls the pressure in the reaction furnace 1 to a predetermined pressure described later. The gas supply port 15, here three NFs_ThreeGas supply port 15a, NH_ThreeGas supply port 15b, SiH₂Cl₂The valves 27a, 27b and 27c provided in the gas supply port 15c are controlled, and a film forming gas is used for film formation by a thermal CVD method using a thermochemical reaction while the wafer 10 is accommodated in the reaction furnace 1. Or supply. Further, NF is used for cleaning by the thermal CVD method without containing the wafer 10 in the reaction furnace 1._ThreeOr after that the furnace pressure is higher than the pressure at the time of film formation and NH for purging_ThreeAnd a function of supplying a film forming gas for coating by lowering the pressure in the furnace below the pressure at the time of purging.
[0020]
Next, the vertical reactor 1 forms Si on the substrate as one step of the semiconductor device manufacturing process._ThreeN_FourAn example of a method for forming a film will be described. As the process, mainly,
(1) A film forming process for supplying a film forming gas into the vertical reactor 1 to form a thin film on the wafer 10;
(2) NF in the reactor 1 in a state where the wafer 10 is not accommodated._ThreeA cleaning step of supplying a gas and removing a thin film adhering in the reaction furnace 1 in the film-forming step;
(3) In the reaction furnace 1 in a state where the wafer 10 is not accommodated after the cleaning process, the NH pressure is set to be higher than the furnace pressure in the film forming process._ThreeA purge process for supplying and purging gas;
(4) A thin film is formed in the reaction furnace 1 by supplying a deposition gas into the reaction furnace 1 in a state where the wafer 10 is not accommodated after the purge process in a state where the furnace pressure is lower than the furnace pressure in the purge process. Coating process
Is mentioned. Hereinafter, these steps will be described in order.
[0021]
(Film formation process)
The film forming process will be described with reference to FIG. In the film forming step, first, the furnace gate gate valve 8 (see FIG. 1) is opened by the control means 22 (see FIG. 2), and the boat elevator 40 is lifted to raise the boat 11 holding a large number of wafers 10. The wafer 10 is loaded into the reaction tube 2 of the reaction furnace 1.
[0022]
When the boat 11 reaches a predetermined processing position in the furnace, the furnace port seal cap 12 hermetically closes the furnace port portion of the reaction furnace 1, and the furnace space 4 is in a sealed state. Thereafter, the control means 22 controls the valve 31 and the vacuum pump 19 to suck the gas in the furnace space 4 so that the furnace space 4 is brought into a vacuum state or a predetermined reduced pressure state. Next, when the furnace space 4 is in a vacuum or in a predetermined reduced pressure state, the control means 22 controls the heater 14 to set the temperature of the furnace space 4 to a predetermined film formation temperature. The heating of the furnace space 4 by the heater 14 may be performed before the furnace space 4 is brought into a vacuum state or a predetermined reduced pressure state, or may be performed before the wafer 10 is loaded into the reaction furnace 1.
[0023]
When the wafer temperature reaches the film formation temperature and stabilizes, SiH is used as the film formation gas.₂Cl₂(Dichlorosilane: DCS) and NH_Three(Ammonia) is flowed into the furnace space 4 from the gas supply ports 15c and 15b under the control of the control means 22, and Si is deposited on the wafer 10 by the thermal CVD method._ThreeN_Four(Silicon nitride film) is formed. At this time, the film space is supplied from the gas supply ports 15 c and 15 b to the furnace space 4 and is exhausted from the gas exhaust port 17. In this case, the following reaction occurs, and Si_ThreeN_FourA film is formed.
10NH_Three+ 3SiH₂Cl₂→ Si_ThreeN_Four+ 6NH_FourCl + 6H₂
Of these, the reaction products are mainly NH._FourCl. NH_FourCl is cooled in a water trap (not shown), and is precipitated and removed from the exhaust gas.
[0024]
Si_ThreeN_FourThe film forming conditions for forming the film are as follows.
Furnace temperature: 750 ± 50 ° C
Furnace pressure: 13.3 to 133 Pa (0.1 to 1.0 Torr)
In addition, as a film forming gas, SiH₂Cl₂+ NH_ThreeInstead of BTBAS (Bicterary butylaminosilane) + NH_Three, Si₂Cl₆+ NH_ThreeOr SiCl_Four+ NH_ThreeMay be used.
[0025]
Next, after the film formation is completed, N 2 is introduced into the reaction furnace 1 from the gas supply port 15 under the control of the control means 22.₂The residual gas in the outer tube 3 is exhausted from the gas exhaust port 17 by exhausting from the gas exhaust port 17 by the vacuum pump 19 while supplying an inert gas such as.
Finally, the boat 11 holding the deposited wafer 10 is moved (unloaded) to the space 23 in the vacuum preliminary chamber 13 and the furnace gate valve 8 (see FIG. 1) is closed. After the wafer 10 is cooled to a predetermined temperature, the wafer 10 is recovered.
When such a film forming process is repeated for a predetermined batch, the film is deposited in the reaction furnace 1. The adhered film is removed in the next cleaning step.
[0026]
(Cleaning process)
The cleaning process will be described with reference to FIG. In the cleaning step, first, the furnace port gate valve 8 (see FIG. 1) is opened, and an unillustrated boat elevator is lifted to load an empty boat 11 that does not hold the wafer 10 into the reaction tube 2 of the reaction furnace 1. . When the boat 11 reaches a predetermined position in the reaction furnace 1, the furnace port seal cap 12 hermetically closes the furnace port portion of the reaction furnace 1, and the furnace space 4 is sealed. Thereafter, the control means 22 controls the valve 31 and the vacuum pump 19 to bring the furnace space 4 into a vacuum or a predetermined reduced pressure state. When the vacuum or the predetermined pressure is reached, the control means 22 controls the heater 14 to control the furnace space. The temperature of 4 is set to a predetermined cleaning temperature. The heating of the furnace space 4 by the heater 14 may be performed before the furnace space 4 is brought into a vacuum state or a predetermined reduced pressure state, or may be performed before the boat 11 is loaded into the reaction furnace 1. When the furnace space 4 reaches the cleaning temperature and stabilizes, the valve 27a is controlled by the control means 22 and the NF is supplied from the gas supply port 15a._ThreeGas flows into the furnace space 4. At this time, NF is introduced into the furnace space 4 from the gas supply port 15a._ThreeThe gas is exhausted from the gas exhaust port 17 while supplying gas.
[0027]
As the cleaning gas, NF, which is a fluorine-based gas, is used._ThreeGas or NF_ThreeA gas containing a gas is used. Since the fluorine-based gas is used, it is not necessary to desorb the quartz reaction tube, which is necessary when performing wet cleaning such as HF (hydrogen fluoride) solution or DIW (pure). Fluorine gas is ClF_ThreeBut NF_ThreeGas or NF_ThreeWhen a gas containing a gas is used, ClF_ThreeUnlike chlorine, since it does not contain chlorine, it is less corrosive and polluting, and less damage to the quartz surface. NF_ThreeIs ClF_ThreeThe decomposition temperature is higher than that, and a furnace temperature of 500 ° C. or higher is required.
[0028]
Next, NF_ThreeThe cleaning conditions when using gas will be described. The furnace temperature during cleaning is preferably 500 ° C. to 650 ° C. in view of the relationship between the accumulated film thickness and the apparatus down time. In addition, an optimum result is obtained by setting the pressure in the furnace during cleaning to about 1,330 Pa to 66,500 Pa (10 Torr to 500 Torr).
[0029]
That is, NF_ThreeHas a high decomposition temperature, and if it is less than 500 ° C., etching cannot be performed. If the furnace temperature is too high, the temperature of the metal part of the furnace port composed of the furnace port flange 6 and the like also rises and corrosion progresses. In particular, when the furnace temperature is higher than 650 ° C., the temperature of the metal part of the furnace opening, for example, Hastelloy, exceeds the limit temperature (200 ° C.) and corrodes. Therefore, the furnace temperature during cleaning is preferably 500 ° C. to 650 ° C.
On the other hand, if the pressure is less than 1,330 Pa, the etching rate becomes slow and a practical etching rate cannot be obtained. Conversely, if the pressure is greater than 66,500 Pa, pressure control becomes difficult. Therefore, the furnace pressure during cleaning is preferably 1,330 Pa to 66,500 Pa.
[0030]
By the way, NF_ThreeThe gas reacts as follows by thermal decomposition to form Si._ThreeN_FourRealize film removal.
Si_ThreeN_Four+ 4NF_Three→ 3SiF_Four+ 4N₂
In this reaction formula, SiF_FourIs discharged as gas.
[0031]
(Purge process)
Next, the purge process will be described. The purge process is performed continuously with the cleaning process after the cleaning process. That is, as shown in FIG. 4, the process is performed in a state where an empty boat 11 is accommodated in the reaction furnace 1 as in the cleaning process. In the purge process, first, the control means 22 sets the pressure in the furnace space 4 to a predetermined pressure higher than the pressure in the furnace in the film forming process, and sets the temperature of the furnace space 4 to a predetermined temperature. When the furnace space 4 reaches a predetermined temperature and pressure, the control means 22 controls the NH 4 into the furnace space 4 from the gas supply port 15b._ThreeGas is supplied, and the residual gas remaining in the furnace space 4 in the cleaning process in the reaction furnace 1 is decomposed and discharged from the gas exhaust port 17. At this time, NH as a purge gas is introduced into the furnace space 4 from the gas supply port 15b._ThreeThe gas is exhausted from the gas exhaust port 17 while supplying the gas. The predetermined pressure may be the same as, higher than, or lower than the pressure in the furnace in the cleaning process, but is preferably a high pressure from the viewpoint of the purge effect.
Where NH_ThreePurge conditions are preferably a temperature of 700 to 900 ° C., a pressure of 1,300 Pa to atmospheric pressure, a flow rate of 300 to 800 sccm, and a purge time of 30 to 60 min. If the temperature is below 700 ° C, NH_ThreeLow activity (NH_ThreeHowever, if the temperature is higher than 900 ° C., there is a problem in heat resistance. Therefore, the above-mentioned NH of 700 to 900 ° C._ThreeIs effective in a temperature range that is sufficiently activated and heat resistant. If the pressure is less than 1,300 Pa, NH_ThreeIf the activity is weak and the pressure is higher than atmospheric pressure, overpressure is applied. Therefore, the above-mentioned 1,300 Pa to atmospheric pressure, NH_ThreeIs effective in a high pressure treatment range in which is sufficiently activated and over-pressurized. If the flow rate is less than 300 sccm, NH_ThreeThe activity is weak, and if it is greater than 800 sccm, the flow rate is too fast. Therefore, a flow rate within the above range is effective. If the time is less than 30 min, NH_ThreeIf the activity is weak and longer than 60 min, the tact time is lost. Therefore, the time within the above range is effective.
[0032]
Thus, after the cleaning process, the purge gas (NH_Three) Is supplied to purge the inside of the reactor 1 so that the NF_ThreeEven if the residual fluorine level in the vertical reactor 1 after gas cleaning is high, NH_ThreeBy performing the purge at high pressure, the residual gas can be sufficiently decomposed and removed using only thermal energy (thermochemical reaction) without using energy such as plasma (plasma chemical reaction). Cleaning gas remaining in the furnace 1 (NF_Three) Can be reduced. Therefore, in the film-forming process after the cleaning process, Si caused by residual fluorine_ThreeN_FourIt is possible to prevent a decrease in film thickness during film formation. In particular, when the purge gas is supplied after the cleaning process in a state where the pressure in the furnace is higher than the pressure in the cleaning process, the cleaning gas (NF_Three) Can be further reduced, Si_ThreeN_FourIt is possible to more effectively prevent the film thickness from being reduced during film formation.
[0033]
(Coating process)
Next, the coating process will be described. The coating process is performed continuously with the purge process after the purge process. That is, as shown in FIG. 4, the process is performed in a state where an empty boat 11 is accommodated in the reaction furnace 1 as in the purge process. In the coating process, NF, which is a cleaning gas_ThreeIn order to further eliminate the influence of gas, the inner wall of the reaction tube 2 is coated. As the coating gas, the same gas as the deposition gas, that is, SiH₂Cl₂+ NH_ThreeIs used.
[0034]
In the coating process, first, the gas in the furnace space 4 is sucked by the vacuum pump 19 by the control means 22 to set the furnace space 4 to a predetermined pressure lower than the pressure in the furnace in the purge process, and the heater 14 is controlled. Thus, the temperature of the furnace space 4 is set to a predetermined coating temperature.
[0035]
When the furnace space 4 reaches the coating temperature and is stabilized, the control means 22 controls to supply SiH as a coating gas from the gas supply ports 15c and 15b.₂Cl₂, NH_ThreeIs introduced into the furnace space 4 and a coating film is formed in the reaction tube 2 by thermal CVD. At this time, the furnace space 4 is exhausted while supplying the coating gas from the gas supply ports 15c and 15b.
As coating conditions, a furnace temperature of 650 to 780 ° C., a furnace pressure of 30 to 100 Pa, a flow rate of 20 to 100 sccm, and a coating film thickness of 500 to 1,500 mm are preferable. If the thickness of the coating film is less than 500 mm, the effect of removing fluorine is weak. Therefore, a film thickness range that can sufficiently remove the above-described fluorine of 500 to 1500 mm and is not excessive is effective.
[0036]
Thus, after the purge process, the coating gas (SiH₂Cl₂+ NH_Three) And a coating process for forming a coating film in the reactor 1 is provided._ThreeEven if the residual fluorine level in the vertical reactor 1 after gas cleaning is high, NH_ThreeIn addition to performing the purging at a high pressure and further forming a coating film, the residual gas can be effectively removed, and the cleaning gas (NF) remaining in the vertical reactor 1 can be removed._Three) Can be further reduced. Therefore, in the film-forming process after cleaning, Si_ThreeN_FourFurther reduction of the film thickness can be prevented.
As a film type using dry cleaning, Si_ThreeN_FourIn addition to the film, there is a Poly-Si film. In the case of a Poly-Si film, a thick film called an empty deposit is generally formed after cleaning, but the effect of the cleaning gas can be confined by performing the empty deposit. But usually Si_ThreeN_FourSince such a thick film empty deposition is not performed on the film, a decrease in the film thickness particularly in the film formation after cleaning has been a problem. Therefore, the present invention capable of suppressing a decrease in film thickness is a Si film that does not perform thick film empty deposition as in the embodiment._ThreeN_FourThis is particularly effective when forming a film.
[0037]
<Example>
Hereinafter, N after the cleaning process₂When the purge process is performed and then the coating process is performed, and after the cleaning process, NH_ThreeSi formed in the film forming process before and after purging and then the coating process_ThreeN_FourThe difference in film thickness difference will be described. In addition, the film thickness of the coating layer in the coating process performed in common after the purge process was 979 mm.
FIG. 5 shows N after the cleaning process.₂It is a graph at the time of purging. That is, film formation →... (Repeat) → film formation → (film thickness measurement A) → NF_ThreeCleaning → N₂Purge → Si_ThreeN_FourThe film thickness measured before cleaning (film thickness measurement A) and the film thickness measured after cleaning (film thickness measurement B) in a series of film formation cycles of coating (979 cm) → film formation → (film thickness measurement B) Shows changes.
N₂The purge conditions were a temperature of 760 ° C., N₂The gas flow rate is 800 sccm, the pressure is 200 Pa, and the processing time is 60 minutes. Black circle marks, black triangle marks, and black square marks in the graph indicate the results of measuring the film thickness of the wafer 10 held at three locations on the boat 11, Top, Center, and Bottom, respectively. As can be seen from the figure, Si in the film formation after cleaning at any measurement location._ThreeN_FourThe film thickness of Si in the film formation before cleaning is_ThreeN_FourThe film thickness is reduced by 20 mm or more.
[0038]
FIG. 6 shows NH after the cleaning process._ThreeIt is a graph at the time of purging. That is, film formation →... (Repeat) → film formation → (film thickness measurement A) → NF_ThreeCleaning → NH_ThreePurge → Si_ThreeN_FourThe film thickness measured before cleaning (film thickness measurement A) and the film thickness measured after cleaning (film thickness measurement B) in a series of film formation cycles of coating (979 cm) → film formation → (film thickness measurement B) It shows a change.
NH_ThreeThe purge conditions are as follows: temperature 760 ° C., NH_ThreeThe gas flow rate is 800 sccm, the pressure is 200 Pa, and the processing time is 60 minutes. Black circle marks, black triangle marks, and black square marks in the graph mean data at three locations, Top, Center, and Bottom, as in FIG. As can be seen from the figure, Si in the film formation before cleaning at any measurement location._ThreeN_FourSi in the film formation after cleaning with respect to the film thickness of_ThreeN_FourThere is almost no decrease in film thickness.
[0039]
From these results, NF_ThreeNH after cleaning at a pressure higher than the deposition pressure_ThreeWhen purging, N₂Compared to purging, Si in film formation after cleaning_ThreeN_FourIt can be seen that the decrease in film thickness can be greatly suppressed. This is the remaining NF_ThreeActive NH_ThreeThis is because fluorine can be removed by decomposition.
[0040]
As described above, according to the embodiment, the pressure in the furnace is made higher than the pressure in the film forming step in the state where the wafer 10 is not accommodated in the outer tube 3 after the cleaning step, and the purge gas is used as the purge gas. NH_ThreeThe cleaning gas (NF) remaining in the outer tube 3 by supplying the gas_ThreeSi) formed in the film-forming process after the cleaning process._ThreeN_FourTherefore, the maintenance-free and stable film thickness and film quality can be achieved at the same time. As a result, high-quality film formation can be performed without reducing the yield of semiconductor devices.
[0041]
In the above embodiment, a method of performing a cleaning process, a purging process, and a coating process in a state where an empty boat 11 is inserted into the reaction furnace 1 and the reaction furnace 1 is covered with a furnace port seal cap 12. As described above, the cleaning process, the purging process, and the coating process may be performed without inserting the boat 11 into the reaction furnace 1, that is, with the reactor gate gate valve 8 covering the reaction furnace 1.
[0042]
In the above embodiment, the reaction tube has a double structure, but the present invention can also be applied to a reaction furnace having a single structure reaction tube. Although a batch type vertical reactor has been described, it can also be applied to a single wafer type. In addition, any semiconductor device manufacturing method can be used as long as it is a process of forming a film after performing a treatment using a fluorine-based gas. Si_ThreeN_FourAlthough the case where a film is formed has been described, the present invention can also be applied to the case where another film type is formed. Furthermore, the present invention can be applied to a manufacturing method using a thermochemical reaction other than thermal CVD.
[0043]
【The invention's effect】
As described above, according to the present invention, after the cleaning process using a fluorine-based gas, the pressure in the furnace is set higher than the pressure in the film-forming process so that the inside of the reaction furnace is NH._ThreeSince it has a purge step of purging with gas, a decrease in film thickness is suppressed in the film formation step after the cleaning step, and a semiconductor device having a stable film thickness can be obtained.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a vertical thermal CVD apparatus for carrying out a method of forming a thin film on a substrate as a process of manufacturing a semiconductor device according to an embodiment.
FIG. 2 is a schematic configuration diagram illustrating a control system of a substrate processing apparatus for carrying out a semiconductor device manufacturing method according to an embodiment.
FIG. 3 is an explanatory diagram illustrating a state during a film forming process according to the embodiment.
FIG. 4 is an explanatory diagram showing in common a state during a cleaning process, a purge process, and a coating process according to the embodiment.
FIG. 5 shows N after the conventional cleaning process.₂Si in the film-forming process after cleaning when purging is performed_ThreeN_FourIt is explanatory drawing which shows the change of the film thickness.
FIG. 6 shows NH after the cleaning process of the embodiment._ThreeSi in the film-forming process after cleaning when purging is performed_ThreeN_FourIt is explanatory drawing which shows the change of the film thickness.
[Explanation of symbols]
1 reactor
3 Outer tube (reaction tube)
5 Inner tube (reaction tube)
10 Wafer (substrate)
11 boats
14 Heater
15 Gas supply port
17 Gas exhaust port

Claims (2)

Silicon nitride is formed on the substrate by a thermochemical reaction by supplying a gas containing SiH ₂ Cl ₂ , BTBAS, Si ₂ Cl ₆ , SiCl ₄ , and NH ₃ as a film forming gas into a reaction furnace containing the substrate. A film forming step for forming a film;
A cleaning step of supplying a fluorine-based gas into the reaction furnace in a state where the substrate is not accommodated, and removing the silicon nitride film adhering to the reaction furnace in the film formation step by a thermochemical reaction;
Purging the reaction furnace by supplying NH ₃ gas into the reaction furnace in a state where the substrate is not accommodated after the cleaning process in a state where the furnace pressure is higher than the furnace pressure in the film forming process. A purging step to be performed;
After the purge step, the same gas as the film forming gas is supplied into the reaction furnace that does not contain the substrate, and a silicon nitride film having a thickness of 500 to 1500 mm is formed in the reaction furnace by a thermochemical reaction. A coating process to be formed;
A method for manufacturing a semiconductor device, comprising: A reactor for performing a process of forming a thin film on a substrate;
SiH in the reactor ₂ Cl ₂ , BTBAS, Si ₂ Cl ₆ Or SiCl ₄ A supply port for supplying a gas containing,
A supply port for supplying a fluorine-based gas into the reaction furnace;
NH in the reactor ₃ A supply port for supplying gas;
An exhaust port for exhausting the reaction furnace;
SiH is contained in the reactor containing the substrate. ₂ Cl ₂ , BTBAS, Si ₂ Cl ₆ Or SiCl ₄ And NH ₃ And forming a silicon nitride film on the substrate by a thermochemical reaction, and then supplying a fluorine-based gas into the reaction furnace in a state in which the substrate is not accommodated. Supplying and performing cleaning to remove the silicon nitride film adhering to the reactor by the film formation by thermochemical reaction, and thereafter, the furnace pressure is set in the reactor without containing the substrate. NH in a state higher than the pressure in the furnace in the film ₃ Purging the inside of the reaction furnace by supplying a gas, and then in the reaction furnace in a state in which the substrate is not accommodated, the film-forming gas in a state where the furnace pressure is lower than the furnace pressure in the purge A control means for supplying the same gas and controlling the coating to form a silicon nitride film in the reaction furnace having a film thickness of 500 to 1500 mm in the reaction furnace by a thermochemical reaction;
A substrate processing apparatus comprising:

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