JP2008283148A - Cleaning method for thin film forming apparatus, thin film forming method, and thin film forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film forming apparatus, a method for cleaning the thin film forming apparatus, and a thin film forming method, capable of removing fluorine having entered into materials in the inside of an apparatus. <P>SOLUTION: A film forming gas is supplied to the inside of a reaction tube 2 of a heat treatment device 1 to form a silicon nitride film on a semiconductor wafer, and a cleaning gas is supplied to the inside of the reaction tube 2 to remove a silicon nitride attached to the inside of the heat treatment device 1. Then, the temperature inside of the reaction tube 2 is increased to a predetermined temperature, and an exhausting gas is supplied into the inside of the reaction tube 2 having the increased temperature. In this way, the exhausting gas is activated to generate radicals. The generated radicals can remove the fluorine contained in a quartz of the reaction tube 2 from the quartz of the reaction tube 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cleaning method for a thin film forming apparatus, a thin film forming method, and a thin film forming apparatus.

  In a manufacturing process of a semiconductor device, it is widely performed to form a thin film on an object to be processed, for example, a semiconductor wafer, by a process such as CVD (Chemical Vapor Deposition). In such a thin film forming process, for example, a thin film is formed on a semiconductor wafer as follows.

  First, the inside of the reaction tube of the heat treatment apparatus is heated to a predetermined load temperature by a heater, and a wafer boat containing a plurality of semiconductor wafers is loaded. Next, the inside of the reaction tube is heated to a predetermined processing temperature by a heater, and the gas in the reaction tube is exhausted from the exhaust pipe to reduce the pressure in the reaction tube to a predetermined pressure. When the inside of the reaction tube is maintained at a predetermined temperature and pressure, a film forming gas is supplied from the processing gas introduction tube into the reaction tube. When the film-forming gas is supplied into the reaction tube, for example, the film-forming gas causes a thermal reaction, the reaction product generated by the thermal reaction is deposited on the surface of the semiconductor wafer, and a thin film is formed on the surface of the semiconductor wafer. Is formed.

  By the way, the reaction product generated by the thin film forming process is deposited (attached) not only on the surface of the semiconductor wafer but also inside the heat treatment apparatus such as the inner wall of the reaction tube and various jigs. If the thin film formation process is continued with such deposits attached in the heat treatment apparatus, stress is generated due to the difference in thermal expansion coefficient between the quartz constituting the reaction tube and the deposits. The kimono will break. As described above, the quartz and the cracked deposits become particles, which causes a decrease in productivity.

For this reason, a gas containing fluorine as a cleaning gas, for example, a mixed gas of hydrogen fluoride and fluorine, is supplied into a reaction tube heated to a predetermined temperature by a heater and adhered to a heat treatment apparatus such as an inner wall of the reaction tube. A cleaning method for a heat treatment apparatus that removes (removes dry) the reaction product has been proposed (for example, Patent Document 1).
JP-A-3-293726

  By the way, in such a cleaning method of the heat treatment apparatus, fluorine contained in the cleaning gas enters the apparatus, for example, quartz which is a material of the reaction tube, and is released from the quartz during the thin film forming process after the cleaning. There is a fear. When the released fluorine is mixed into the thin film, the yield of the manufactured semiconductor device is lowered.

The present invention has been made in view of the above problems, and has an object to provide a thin film forming apparatus, a thin film forming apparatus cleaning method, and a thin film forming method capable of removing fluorine that has entered the material inside the apparatus. To do.
Another object of the present invention is to provide a thin film forming apparatus, a cleaning method for the thin film forming apparatus, and a thin film forming method capable of suppressing the mixing of fluorine into the thin film.

In order to achieve the above object, a method for cleaning a thin film forming apparatus according to the first aspect of the present invention comprises:
A cleaning method of a thin film forming apparatus for forming a thin film on a target object by supplying a processing gas into a reaction chamber containing the target object,
A purge step of purging the reaction chamber by supplying an exhaust gas that can be activated into the reaction chamber;
In the purge step, the exhaust gas is activated to generate radicals, and fluorine contained in the material inside the apparatus is removed from the material by the generated radicals.

  It is preferable to further include a deposit removing step of supplying a cleaning gas capable of removing deposits attached to the inside of the apparatus by forming a thin film on the object to be processed into the reaction chamber to remove the deposits. In this case, the purge step is performed after the deposit is removed by the deposit removal step.

It is preferable to use a gas containing fluorine as the cleaning gas.
It is preferable to use a gas containing oxygen and hydrogen as the exhaust gas.
In the purge step, for example, the exhaust gas is supplied into the reaction chamber heated to a predetermined temperature and activated.
In the purge step, it is preferable to raise the temperature in the reaction chamber to 600 ° C. to 1050 ° C.
The material inside the device is preferably quartz.

The thin film forming method according to the second aspect of the present invention is:
A cleaning step of cleaning the thin film forming apparatus by the cleaning method of the thin film forming apparatus according to the first aspect of the present invention;
A film forming step of heating the reaction chamber containing the object to be processed to a predetermined temperature, supplying a processing gas into the heated reaction chamber, and forming a thin film on the object to be processed;
It is characterized by comprising.

A thin film forming apparatus according to a third aspect of the present invention is:
A thin film forming apparatus that forms a thin film on a target object by supplying a processing gas into a reaction chamber that houses the target object,
An exhaust gas supply means for supplying an activatable exhaust gas into the reaction chamber;
Activating means for activating the exhaust gas;
Fluorine removing means for controlling the activating means to activate the exhaust gas, generating radicals thereof, and removing fluorine contained in the material inside the apparatus from the materials by the generated radicals;
It is characterized by comprising.

Cleaning gas supply means for supplying a cleaning gas capable of removing deposits attached to the inside of the apparatus by forming a thin film on the object to be processed into the reaction chamber;
It is preferable that the apparatus further includes a deposit removing unit that controls the cleaning gas supply unit to remove deposits attached to the inside of the apparatus. In this case, the fluorine removing unit removes the fluorine from the material by controlling the activating unit after the deposits adhered to the inside of the apparatus are removed by the deposit removing unit.

The cleaning gas is, for example, a gas containing fluorine.
The exhaust gas is, for example, a gas containing oxygen and hydrogen.
The activation means is, for example, a heating means for raising the temperature in the reaction chamber to 600 ° C. to 1050 ° C.
The activation means is, for example, a plasma generation means, a photolysis means, or a catalyst activation means.

The program according to the fourth aspect of the present invention is:
A program for supplying a processing gas into a reaction chamber containing a target object to function as a thin film forming apparatus for forming a thin film on the target object,
Computer
An exhaust gas supply means for supplying an activatable exhaust gas into the reaction chamber;
Activating means for activating the exhaust gas;
A fluorine removing means for controlling the activating means to activate the exhaust gas to generate radicals thereof, and to remove fluorine contained in the material inside the apparatus from the materials by the generated radicals;
It is made to function as.

  According to the present invention, fluorine that has entered the material inside the apparatus can be removed.

  Hereinafter, the thin film forming apparatus, the thin film forming apparatus cleaning method, and the thin film forming method of the present invention will be described. In the present embodiment, the present invention will be described taking the case of the batch type vertical heat treatment apparatus 1 shown in FIG. 1 as an example of the thin film forming apparatus.

  As shown in FIG. 1, a heat treatment apparatus 1 as a thin film forming apparatus includes a reaction tube 2 that forms a reaction chamber.

  The reaction tube 2 is formed in, for example, a substantially cylindrical shape whose longitudinal direction is directed in the vertical direction. The reaction tube 2 is made of a material excellent in heat resistance and corrosion resistance, for example, quartz. At the upper end of the reaction tube 2 is provided a top portion 3 formed in a substantially conical shape so as to reduce in diameter toward the upper end side. An exhaust port 4 for exhausting the gas in the reaction tube 2 is provided at the center of the top 3, and an exhaust tube 5 is connected to the exhaust port 4 in an airtight manner. The exhaust pipe 5 is provided with a pressure adjusting mechanism such as a valve (not shown) and a vacuum pump 127 described later, and controls the inside of the reaction pipe 2 to a desired pressure (degree of vacuum).

  A lid 6 is disposed below the reaction tube 2. The lid 6 is made of a material excellent in heat resistance and corrosion resistance, for example, quartz. The lid 6 is configured to be movable up and down by a boat elevator 128 described later. When the lid 6 is raised by the boat elevator 128, the lower side (furnace port portion) of the reaction tube 2 is closed, and when the lid 6 is lowered by the boat elevator 128, the lower side (furnace port portion) of the reaction tube 2. Is opened.

  A heat insulating cylinder 7 is provided on the top of the lid 6. The heat retaining cylinder 7 includes a planar heater 8 made of a resistance heating element that prevents a temperature drop in the reaction tube 2 due to heat radiation from the furnace port portion of the reaction tube 2, and the heater 8 from a top surface of the lid 6 to a predetermined amount. It is mainly comprised from the cylindrical support body 9 supported to height.

  A rotary table 10 is provided above the heat insulating cylinder 7. The turntable 10 functions as a mounting table for rotatably mounting an object to be processed, for example, a wafer boat 11 that accommodates a semiconductor wafer W. Specifically, a rotary column 12 is provided at the lower part of the rotary table 10, and the rotary column 12 is connected to a rotary mechanism 13 that rotates through the central portion of the heater 8 and rotates the rotary table 10. The rotation mechanism 13 is mainly composed of a motor (not shown) and a rotation introduction portion 15 including a rotation shaft 14 that is penetrated and introduced in an airtight manner from the lower surface side to the upper surface side of the lid body 6. The rotary shaft 14 is connected to the rotary column 12 of the rotary table 10 and transmits the rotational force of the motor to the rotary table 10 via the rotary column 12. For this reason, when the rotating shaft 14 is rotated by the motor of the rotating mechanism 13, the rotating force of the rotating shaft 14 is transmitted to the rotating column 12 and the rotating table 10 rotates.

  The wafer boat 11 is configured to accommodate a plurality of semiconductor wafers W at a predetermined interval in the vertical direction. The wafer boat 11 is made of, for example, quartz. The wafer boat 11 is placed on the turntable 10. For this reason, when the turntable 10 is rotated, the wafer boat 11 is rotated, and the semiconductor wafer W accommodated in the wafer boat 11 is rotated by this rotation.

  Further, around the reaction tube 2, for example, a temperature raising heater 16 made of a resistance heating element is provided so as to surround the reaction tube 2. The inside of the reaction tube 2 is heated to a predetermined temperature by the temperature raising heater 16, and as a result, the semiconductor wafer W is heated to a predetermined temperature.

  A plurality of process gas introduction pipes 17 are connected to the side surface near the lower end of the reaction tube 2. The processing gas introduction pipe 17 is inserted into the side wall near the lower end of the reaction tube 2 and introduces the processing gas into the reaction tube 2.

  As the processing gas supplied into the reaction tube 2, a film forming gas for forming a thin film on the semiconductor wafer W and deposits (reaction products and the like) adhering to the inside of the heat treatment apparatus 1 are removed (cleaned). There is a cleaning gas for exhausting and an exhaust gas for removing (exhausting) the fluorine that has entered (diffused) into the material (quartz) inside the heat treatment apparatus 1 by cleaning out of the reaction tube 2.

As the film forming gas of the present invention, a gas capable of forming a thin film, and a gas capable of removing deposits adhering to the inside of the apparatus by forming the thin film with a cleaning gas is used. For example, when a silicon nitride film is formed on the semiconductor wafer W, dichlorosilane (DCS: SiH ₂ Cl ₂ ) and ammonia (NH ₃ ) or hexachlorodisilane (HCD: Si ₂ Cl ₆ ) are used as film forming gases. And ammonia (NH ₃ ) are used. In the present embodiment, dichlorosilane and ammonia are used as the film forming gas.

As the cleaning gas of the present invention, a gas capable of removing deposits adhering to the inside of the apparatus by forming a thin film is used. For example, when a silicon nitride film is formed on the semiconductor wafer W, the cleaning gas contains, for example, a gas containing fluorine (F ₂ ) and hydrogen fluoride (HF), or fluorine and hydrogen (H ₂ ). Gas is used. In the present embodiment, fluorine, hydrogen, and nitrogen (N ₂ ) as a dilution gas are used as the cleaning gas.

The exhaust gas of the present invention is an activatable gas that generates radicals when activated, and the generated radicals are used to convert materials inside the heat treatment apparatus 1 such as fluorine that has entered quartz. A gas that can be removed (exhaust) is used. In the present embodiment, oxygen (O ₂ ), hydrogen (H ₂ ), and nitrogen (N ₂ ) as a diluent gas are used as the exhaust gas.

  In FIG. 1, only one processing gas introduction pipe 17 is drawn, but in this embodiment, the processing gas introduction pipe 17 is inserted into the side surface near the lower end of the reaction pipe 2 for each type of gas. . These processing gas introduction pipes 17 are connected to a gas supply source corresponding to the type of the processing gas, and supply a desired amount of processing gas from the gas supply source into the reaction tube 2.

  Further, as shown in FIG. 1, a purge gas supply pipe 18 is inserted into a side surface near the lower end of the reaction tube 2. The purge gas supply pipe 18 is connected to a purge gas supply source (not shown), and supplies a desired amount of purge gas from the purge gas supply source, for example, nitrogen gas, into the reaction pipe 2.

  Moreover, the heat processing apparatus 1 is provided with the control part 100 which controls each part of an apparatus. FIG. 2 shows the configuration of the control unit 100. As shown in FIG. 2, the control unit 100 includes an operation panel 121, a temperature sensor (group) 122, a pressure gauge (group) 123, a heater controller 124, an MFC control unit 125, a valve control unit 126, a vacuum pump 127, a boat An elevator 128 or the like is connected.

  The operation panel 121 includes a display screen and operation buttons, transmits an operation instruction of the operator to the control unit 100, and displays various information from the control unit 100 on the display screen.

The temperature sensor (group) 122 measures the temperature of each part in the reaction tube 2, the exhaust pipe 5, the processing gas introduction pipe 17, etc., and notifies the control unit 100 of the measured values.
The pressure gauge (group) 123 measures the pressure of each part in the reaction tube 2, the exhaust pipe 5, the processing gas introduction pipe 17 and the like, and notifies the control unit 100 of the measured value.

  The heater controller 124 is for individually controlling the heater 8 and the heater 16 for raising temperature. In response to an instruction from the control unit 100, the heater controller 124 energizes them to heat them. Are measured individually and notified to the control unit 100.

  The MFC control unit 125 controls the MFC (not shown) provided in the processing gas introduction pipe 17 and the purge gas supply pipe 18 to control the flow rate of the gas flowing through these to the amount instructed by the control unit 100, The flow rate of the gas that actually flows is measured and notified to the control unit 100.

The valve control unit 126 controls the opening degree of the valve disposed in each pipe to a value instructed by the control unit 100.
The vacuum pump 127 is connected to the exhaust pipe 5 and exhausts the gas in the reaction pipe 2.

  The boat elevator 128 lifts the lid 6, loads the wafer boat 11 (semiconductor wafer W) placed on the rotary table 10 into the reaction tube 2, and rotates the lid 6 to lower the lid 6. The wafer boat 11 (semiconductor wafer W) placed on the table 10 is unloaded from the reaction tube 2.

  The control unit 100 includes a recipe storage unit 111, a ROM 112, a RAM 113, an I / O port 114, a CPU 115, and a bus 116 that interconnects them.

  The recipe storage unit 111 stores a setup recipe and a plurality of process recipes. At the beginning of manufacturing the heat treatment apparatus 1, only the recipe for setup is stored in the recipe storage unit 111. The setup recipe is executed when generating a thermal model or the like corresponding to each heat treatment apparatus. The process recipe is a recipe prepared for each heat treatment (process) actually performed by the user. For example, from loading of the semiconductor wafer W to the reaction tube 2 to unloading the processed semiconductor wafer W, The change in temperature of each part, the change in pressure in the reaction tube 2, the start and stop timing of the supply of the processing gas, the supply amount, etc. are defined.

The ROM 112 is a recording medium that includes an EEPROM, a flash memory, a hard disk, and the like, and stores an operation program of the CPU 115 and the like.
The RAM 113 functions as a work area for the CPU 115.
The I / O port 114 is connected to the operation panel 121, temperature sensor 122, pressure gauge 123, heater controller 124, MFC control unit 125, valve control unit 126, vacuum pump 127, boat elevator 128, etc. Control the output.

A CPU (Central Processing Unit) 115 constitutes the center of the control unit 100, executes a control program stored in the ROM 112, and stores recipes (for process) stored in the recipe storage unit 111 in accordance with instructions from the operation panel 121. The operation of the heat treatment apparatus 1 is controlled along the recipe. That is, the CPU 115 causes the temperature sensor 122, the pressure gauge 123, the MFC control unit 125, and the like to measure the temperature, pressure, flow rate, and the like of each part in the reaction tube 2, the processing gas introduction tube 17, and the exhaust pipe 5, Based on the measurement data, control signals and the like are output to the heater controller 124, the MFC control unit 125, the valve control unit 126, the vacuum pump 127, and the like, and the above-described units are controlled to follow the process recipe.
The bus 116 transmits information between the units.

  Next, the cleaning method and the thin film forming method of the thin film forming apparatus of the present invention will be described using the heat treatment apparatus 1 configured as described above. FIG. 3 shows a recipe for explaining the thin film forming method of the present embodiment.

In the present embodiment, DCS (SiH ₂ Cl ₂ ) and ammonia (NH ₃ ) are supplied into the reaction tube 2 to form a silicon nitride film having a predetermined thickness on the semiconductor wafer W, and the heat treatment apparatus 1 The present invention will be described by taking as an example the case of removing silicon nitride (adhered matter) adhering to the inside. In the following description, the operation of each part constituting the heat treatment apparatus 1 is controlled by the control unit 100 (CPU 115). Further, as described above, the controller 100 (CPU 115) is controlled by the heater controller 124 (heater 8 and the temperature raising heater 16) and the MFC controller 125 for the temperature, pressure, gas flow rate, etc. in the reaction tube 2 in each process. By controlling the valve control unit 126, the vacuum pump 127, etc., the conditions according to the recipe shown in FIG.

  First, the inside of the reaction tube 2 is set to a predetermined temperature, for example, 400 ° C. as shown in FIG. Further, as shown in FIG. 3C, a predetermined amount of nitrogen is supplied from the purge gas supply pipe 18 into the reaction tube 2, and the wafer boat 11 in which the semiconductor wafer W as the object to be processed is accommodated is covered with the lid body 6. Place on top. Then, the lid 6 is raised by the boat elevator 128, and the semiconductor wafer W (wafer boat 11) is loaded into the reaction tube 2 (loading step).

  Next, as shown in FIG. 3 (c), a predetermined amount of nitrogen is supplied from the purge gas supply pipe 18 into the reaction tube 2, and the reaction tube 2 is given a predetermined temperature, for example, as shown in FIG. 3 (a). Set to 760 ° C. Further, the gas in the reaction tube 2 is discharged, and the reaction tube 2 is depressurized to a predetermined pressure, for example, 26.5 Pa (0.2 Torr) as shown in FIG. And the inside of the reaction tube 2 is stabilized at this temperature and pressure (stabilization step).

  When the inside of the reaction tube 2 is stabilized at a predetermined pressure and temperature, the supply of nitrogen from the purge gas supply tube 18 is stopped. Subsequently, a film forming gas is introduced into the reaction tube 2 from the processing gas introduction tube 17. In this embodiment, as shown in FIG. 3 (d), ammonia is supplied at 1 slm, as shown in FIG. 3 (e), DCS is supplied at 0.1 slm, and as shown in FIG. 3 (c), Nitrogen is supplied at 0.25 slm. The film forming gas introduced into the reaction tube 2 is heated in the reaction tube 2 to form a silicon nitride film on the surface of the semiconductor wafer W (film forming step).

  When a silicon nitride film having a predetermined thickness is formed on the surface of the semiconductor wafer W, the introduction of the deposition gas from the processing gas introduction pipe 17 is stopped. Then, the gas in the reaction tube 2 is discharged, and as shown in FIG. 3C, a predetermined amount of nitrogen is supplied from the purge gas supply tube 18, and the gas in the reaction tube 2 is discharged to the exhaust tube 5. (Purge process). In addition, in order to discharge | emit the gas in the reaction tube 2 reliably, it is preferable to repeat discharge | emission of the gas in the reaction tube 2, and supply of nitrogen gas in multiple times.

  Subsequently, as shown in FIG. 3 (c), a predetermined amount of nitrogen is supplied into the reaction tube 2 from the purge gas supply pipe 18, and the pressure in the reaction tube 2 is kept constant as shown in FIG. 3 (b). Return to pressure. Further, the inside of the reaction tube 2 is set to a predetermined temperature, for example, 400 ° C. as shown in FIG. Then, the lid 6 is lowered by the boat elevator 128 to unload the semiconductor wafer W (wafer boat 11) from the reaction tube 2 (unload process). Thereby, the film forming process is completed.

  When the film forming process as described above is performed a plurality of times, for example, silicon nitride generated by the film forming process is deposited (attached) not only on the surface of the semiconductor wafer W but also on the inner wall of the reaction tube 2 and the like. For this reason, after performing the film forming process a predetermined number of times, a cleaning process (a cleaning method for a thin film forming apparatus of the present invention) is executed.

  First, the inside of the reaction tube 2 is set to a predetermined temperature, for example, 400 ° C. as shown in FIG. Further, as shown in FIG. 3C, a predetermined amount of nitrogen is supplied from the purge gas supply pipe 18 into the reaction pipe 2, and an empty wafer boat 11 in which no semiconductor wafer W is accommodated is placed on the lid 6. Put. Then, the lid 6 is raised by the boat elevator 128, and the semiconductor wafer W (wafer boat 11) is loaded into the reaction tube 2 (loading step).

  Next, as shown in FIG. 3 (c), a predetermined amount of nitrogen is supplied from the purge gas supply pipe 18 into the reaction tube 2, and the reaction tube 2 is given a predetermined temperature, for example, as shown in FIG. 3 (a). Set to 400 ° C. Further, the gas in the reaction tube 2 is discharged, and the reaction tube 2 is depressurized to a predetermined pressure, for example, 13300 Pa (100 Torr) as shown in FIG. And the inside of the reaction tube 2 is stabilized at this temperature and pressure (stabilization step).

When the inside of the reaction tube 2 is stabilized at a predetermined pressure and temperature, the supply of nitrogen from the purge gas supply tube 18 is stopped. Subsequently, a cleaning gas is introduced into the reaction tube 2 from the processing gas introduction tube 17. In the present embodiment, ₂ slm of fluorine (F ₂ ) is supplied as shown in FIG. 3 (f), ₂ slm of hydrogen (H ₂ ) is supplied as shown in FIG. 3 (g), and FIG. ), 8 slm of nitrogen as a dilution gas is supplied.

  The cleaning gas supplied into the reaction tube 2 is heated in the reaction tube 2 and the fluorine in the cleaning gas is activated. The activated fluorine comes into contact with deposits (silicon nitride) adhered to the inside of the heat treatment apparatus 1, and the silicon nitride is etched. Thereby, the deposit | attachment adhering to the inside of the heat processing apparatus 1 is removed (cleaning process).

  When the deposits adhering to the inside of the heat treatment apparatus 1 are removed, the supply of the cleaning gas from the processing gas introduction pipe 17 is stopped. Then, as shown in FIG. 3 (c), a predetermined amount of nitrogen is supplied from the purge gas supply pipe 18, the gas in the reaction pipe 2 is discharged, and the reaction pipe 2 is set to a predetermined pressure, for example, FIG. ), The pressure is reduced to 46.55 Pa (0.35 Torr). Further, the inside of the reaction tube 2 is set to a predetermined temperature, for example, 850 ° C. as shown in FIG. Then, the temperature and pressure operation of the reaction tube 2 is performed until the reaction tube 2 is stabilized at a predetermined pressure and temperature (stabilization step).

  Here, the temperature in the reaction tube 2 is preferably 400 ° C to 1050 ° C. This is because if the temperature is lower than 400 ° C., it may be difficult to release fluorine that has entered the quartz of the reaction tube 2 in the radical purge step described later. Further, when the temperature is higher than 1050 ° C., the softening point of quartz forming the reaction tube 2 is exceeded. The temperature in the reaction tube 2 is more preferably 600 ° C to 1050 ° C, and most preferably 800 ° C to 1050 ° C. This is because, within this range, the release of fluorine in the radical purge step is promoted.

  The pressure in the reaction tube 2 is preferably 931 Pa (7 Torr) or less. This is because if the pressure is higher than 931 Pa, it may be difficult to release fluorine in the radical purging process described later. The pressure in the reaction tube 2 is more preferably 532 Pa (4 Torr) or less, and most preferably 133 Pa (1 Torr) or less. This is because the release of fluorine in the radical purge step is promoted by reducing the pressure in the reaction tube 2 in this way.

When the inside of the reaction tube 2 is stabilized at a predetermined pressure and temperature, the supply of nitrogen from the purge gas supply tube 18 is stopped. Next, exhaust gas is introduced into the reaction tube 2 from the processing gas introduction tube 17. In this embodiment, oxygen (O ₂ ) is supplied at 1.7 slm as shown in FIG. 3 (h), and hydrogen (H ₂ ) is supplied at 1 slm as shown in FIG. 3 (g). As shown in (c), 0.05 slm of nitrogen (N ₂ ) is supplied. After a predetermined time has elapsed, the gas in the reaction tube 2 is discharged. Then, the supply of the exhaust gas and the discharge of the gas in the reaction tube 2 are repeated a plurality of times (radical purge process).

  When exhaust gas is supplied into the reaction tube 2, the exhaust gas is excited (activated) by heat in the reaction tube 2 to generate radicals (oxygen active species, hydroxyl active species, etc.). Due to the generated radicals, fluorine contained in the quartz of the reaction tube 2 is released (diffused) from the quartz of the reaction tube 2. Here, the fluorine contained in the quartz of the reaction tube 2 includes fluorine adsorbed on the surface during cleaning. For this reason, the fluorine contained in the material inside the apparatus, for example, quartz contained in the reaction tube 2 can be removed, and release of fluorine from the reaction tube 2 during the film forming process can be suppressed. As a result, the amount (concentration) of fluorine in the silicon nitride film formed by the subsequent film formation process can be reduced.

  When the radical purge step is completed, the supply of the exhaust gas from the processing gas introduction pipe 17 is stopped. Subsequently, as shown in FIG. 3 (c), a predetermined amount of nitrogen is supplied into the reaction tube 2 from the purge gas supply pipe 18, and the pressure in the reaction tube 2 is kept constant as shown in FIG. 3 (b). Return to pressure. Further, the inside of the reaction tube 2 is set to a predetermined temperature, for example, 400 ° C. as shown in FIG. And the inside of the reaction tube 2 is stabilized at this temperature and pressure (stabilization step).

  Next, the lid 6 is lowered by the boat elevator 128 to unload the wafer boat 11 from the reaction tube 2 (unload process). This completes the cleaning process. Then, by placing the wafer boat 11 containing the semiconductor wafers W on the lid 6, it becomes possible to perform a film forming process for forming a silicon nitride film on the semiconductor wafers W again.

  In this way, by performing a thin film forming method that performs a cleaning process (cleaning process and purge process) after a predetermined number of film formation processes, even if a silicon nitride film is formed on the semiconductor wafer W after the cleaning process, The fluorine concentration in the formed silicon nitride film can be suppressed.

  Next, in order to confirm the effect of the present embodiment, a cleaning process (cleaning process and purge process) is performed under the same conditions as in the above-described embodiment, and then a semiconductor wafer W is placed in the reaction tube 2 and formed. Film treatment was performed, and the fluorine concentration in the silicon nitride film formed on the semiconductor wafer W was measured (Example 1). In addition, as shown in FIG. 4, when the exhaust gas flow rate ratio and total flow rate are changed, the radical purging time (purge time) is changed, and the cleaning process and the film forming process are performed in the same manner. The fluorine concentration in the silicon nitride film formed on the wafer W was measured (Examples 2 and 3). For comparison, a case where a nitrogen purge using a general nitrogen gas is performed after performing a cleaning process under the same conditions as in the above embodiment is similarly formed on the semiconductor wafer W. The fluorine concentration in the silicon nitride film was measured (Comparative Example 1). These results are shown in FIG.

  As shown in FIG. 5, it was confirmed that the concentration of fluorine contained in the formed silicon nitride film was significantly reduced by performing radical purging as compared to when performing general nitrogen purging. For this reason, it was confirmed that the fluorine purged into the quartz of the reaction tube 2 and the like was removed by performing radical purge, and it was confirmed that the release of fluorine during the film forming process could be suppressed. Therefore, even if a silicon nitride film is formed on the semiconductor wafer W after the cleaning process, the concentration of fluorine in the formed silicon nitride film can be suppressed.

  As described above, according to the present embodiment, fluorine that has entered quartz in the reaction tube 2 or the like can be removed by performing radical purge. For this reason, the concentration of fluorine in the formed silicon nitride film can be suppressed.

  In addition, this invention is not restricted to said embodiment, A various deformation | transformation and application are possible. Hereinafter, other embodiments applicable to the present invention will be described.

  In the above embodiment, the present invention has been described by taking the case of using a mixed gas of oxygen, hydrogen, and nitrogen as the exhaust gas. However, for example, a mixed gas of oxygen and hydrogen may be used. The exhaust gas may be any gas that can be activated, can be activated to generate radicals, and can remove the material inside the heat treatment apparatus 1, for example, fluorine that has entered quartz, by the generated radicals. . Such an exhaust gas is preferably a gas containing oxygen and hydrogen.

  In the above embodiment, the present invention has been described by taking as an example the case where the exhaust gas is supplied into the heated reaction tube 2 and the exhaust gas is activated. For example, the processing gas introduction tube for introducing the exhaust gas is used. 17 may be provided with an activating means, and the exhaust gas activated by the activating means may be supplied into the reaction tube 2. In this case, the temperature in the reaction tube 2 in the radical purge step can be lowered. As the activation means, there are a plasma generation means, a photolysis means, a catalyst activation means and the like in addition to the heating means.

  In the above embodiment, the present invention has been described by taking the case of forming a silicon nitride film as an example. However, the thin film formed on the object to be processed is not limited to the silicon nitride film, and is, for example, a polysilicon film. May be. The deposition gas may be any gas that can remove deposits attached to the inner wall of the reaction tube 2 or the like by the cleaning gas and can form a thin film. For example, a silicon nitride film is formed. In this case, a mixed gas of hexachlorodisilane (HCD) and ammonia may be used.

  In the above embodiment, the present invention has been described by taking an example of the case where a mixed gas of fluorine, hydrogen, and nitrogen is used as the cleaning gas. However, the cleaning gas is a gas that can remove deposits attached by the film formation process. I just need it. Further, the cleaning gas may not contain nitrogen gas as a dilution gas. Since the present invention removes the material inside the heat treatment apparatus 1, such as fluorine that has entered quartz, it is preferable to use a gas containing fluorine as the cleaning gas. In this case, it is because the effect of this invention is exhibited most.

  In the above embodiment, the present invention has been described by taking as an example the case where the cleaning process and the purge process are performed after performing the film forming process a plurality of times, but the present invention is not limited thereto. The cleaning process and the purge process may be performed every time after the film formation process.

  In the above embodiment, the present invention has been described by taking the case where the purge process is performed after the cleaning process as an example. However, the purge process can be arbitrarily performed, for example, before the film formation process is performed. A purge process may be performed.

  In the above embodiment, the present invention has been described by taking as an example the case where the processing gas introduction pipe 17 is provided for each type of gas. For example, the film formation gas introduction pipe, the cleaning gas introduction pipe, and the chlorine purge gas You may provide the process gas introduction pipe | tube 17 for every kind of process gas so that it may be comprised from a supply pipe | tube. In addition, a large number of process gas introduction pipes 17 may be inserted into the side surface near the lower end of the reaction tube 2 so that the same type of gas is introduced from a plurality of tubes. In this case, the processing gas can be introduced into the reaction tube 2 more uniformly.

  In the above embodiment, the present invention has been described by taking the case of a batch type heat treatment apparatus having a single tube structure as the heat treatment apparatus. For example, a double tube structure in which the reaction tube 2 is composed of an inner tube and an outer tube. It is also possible to apply the present invention to the batch type vertical heat treatment apparatus. In addition, the present invention can be applied to a single wafer heat treatment apparatus.

  The control unit 100 according to the embodiment of the present invention can be realized using a normal computer system, not a dedicated system. For example, the control unit 100 that executes the above-described processing is configured by installing the program from a recording medium (such as a flexible disk or a CD-ROM) that stores the program for executing the above-described processing in a general-purpose computer. be able to.

  The means for supplying these programs is arbitrary. In addition to being able to be supplied via a predetermined recording medium as described above, for example, it may be supplied via a communication line, a communication network, a communication system, or the like. In this case, for example, the program may be posted on a bulletin board (BBS) of a communication network and provided by superimposing it on a carrier wave via the network. Then, the above-described processing can be executed by starting the program thus provided and executing it in the same manner as other application programs under the control of the OS.

It is a figure which shows the heat processing apparatus of embodiment of this invention. It is a figure which shows the structure of the control part of FIG. It is a figure which shows the recipe explaining the thin film formation method of embodiment of this invention. H _{2 /} O 2 in the exhaust gas in each example _is a table showing the total flow, the purge time. It is a graph which shows the density | concentration of the fluorine contained in the silicon nitride film in the Example shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heat processing apparatus 2 Reaction tube 3 Top part 4 Exhaust port 5 Exhaust pipe 6 Cover body 7 Heat insulation cylinder 8 Heater 9 Support body 10 Rotary table 11 Wafer boat 12 Rotation support | pillar 13 Rotation mechanism 14 Rotation shaft 15 Rotation introduction part 16 Heating heater 17 Process gas introduction pipe 18 Purge gas supply pipe 100 Control unit 111 Recipe storage unit 112 ROM
113 RAM
114 I / O port 115 CPU
116 Bus 121 Operation Panel 122 Temperature Sensor 123 Pressure Gauge 124 Heater Controller 125 MFC Control Unit 126 Valve Control Unit 127 Vacuum Pump 128 Boat Elevator W Semiconductor Wafer

Claims (15)

A cleaning method of a thin film forming apparatus for forming a thin film on a target object by supplying a processing gas into a reaction chamber containing the target object,
A purge step of purging the reaction chamber by supplying an exhaust gas that can be activated into the reaction chamber;
In the purge step, the exhaust gas is activated to generate radicals, and fluorine contained in the material inside the apparatus is removed from the material by the generated radicals. How to clean the device. A cleaning gas capable of removing deposits attached to the inside of the apparatus by forming a thin film on the object to be processed is supplied to the reaction chamber, and further includes a deposit removal step for removing the deposits.
The thin film forming apparatus cleaning method according to claim 1, wherein the purge step is performed after the deposit is removed by the deposit removing step.   The thin film forming apparatus cleaning method according to claim 2, wherein a gas containing fluorine is used as the cleaning gas.   The thin film forming apparatus cleaning method according to any one of claims 1 to 3, wherein a gas containing oxygen and hydrogen is used as the exhaust gas.   5. The cleaning of a thin film forming apparatus according to claim 1, wherein in the purge step, the exhaust gas is supplied into a reaction chamber heated to a predetermined temperature and activated. Method.   6. The thin film forming apparatus cleaning method according to claim 5, wherein, in the purge step, the temperature in the reaction chamber is raised to 600 to 1050.degree.   The thin film forming apparatus cleaning method according to claim 1, wherein the material inside the apparatus is quartz. A cleaning step of cleaning the thin film forming apparatus by the cleaning method of the thin film forming apparatus according to any one of claims 1 to 7,
A film forming step of heating the reaction chamber containing the object to be processed to a predetermined temperature, supplying a processing gas into the heated reaction chamber, and forming a thin film on the object to be processed;
A thin film forming method characterized by comprising: A thin film forming apparatus that forms a thin film on a target object by supplying a processing gas into a reaction chamber that houses the target object,
An exhaust gas supply means for supplying an activatable exhaust gas into the reaction chamber;
Activating means for activating the exhaust gas;
Fluorine removing means for controlling the activating means to activate the exhaust gas, generating radicals thereof, and removing fluorine contained in the material inside the apparatus from the materials by the generated radicals;
A thin film forming apparatus comprising: Cleaning gas supply means for supplying a cleaning gas capable of removing deposits attached to the inside of the apparatus by forming a thin film on the object to be processed into the reaction chamber;
A deposit removing means for controlling the cleaning gas supply means to remove deposits adhering to the inside of the apparatus;
10. The fluorine removing means controls the activating means to remove fluorine from the material after the deposit attached to the inside of the apparatus is removed by the deposit removing means. The thin film forming apparatus described in 1.   The thin film forming apparatus according to claim 10, wherein the cleaning gas is a gas containing fluorine.   The thin film forming apparatus according to claim 9, wherein the exhaust gas is a gas containing oxygen and hydrogen.   13. The thin film forming apparatus according to claim 9, wherein the activating unit is a heating unit configured to raise the temperature in the reaction chamber to 600 ° C. to 1050 ° C. 13.   13. The thin film forming apparatus according to claim 9, wherein the activating means is a plasma generating means, a photolysis means, or a catalyst activating means. A program for supplying a processing gas into a reaction chamber containing a target object to function as a thin film forming apparatus for forming a thin film on the target object,
Computer
An exhaust gas supply means for supplying an activatable exhaust gas into the reaction chamber;
Activating means for activating the exhaust gas;
A fluorine removing means for controlling the activating means to activate the exhaust gas to generate radicals thereof, and to remove fluorine contained in the material inside the apparatus from the materials by the generated radicals;
Program to function as.

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