PATENT ABSTRACT
A substrate processing unit comprises a processing vessel for receiving a substrate, a cleaning gas supply system for supplying cleaning gas to the processing vessel so as to clean the interior of the processing vessel, an exhauster for exhausting the processing vessel, an operating state detector for detecting the operating state of the exhauster, and an end point detector for detecting the end point of the cleaning on the basis of the detection result from the operating state detector.

PATENT DESCRIPTION
FIELD OF THE INVENTION 
     The present invention relates to a substrate processing unit, a method of detecting an end point of a cleaning of a substrate processing unit, and a method of detecting an end point of a substrate processing. 
     BACKGROUND OF THE INVENTION 
     There has been known a film forming apparatus for chemically forming a thin film on a semiconductor wafer (hereinafter, referred to as ‘wafer’ for simplicity). In such a film forming apparatus, the thin film is formed on the wafer by using a plasma or the like. 
     However, after forming the thin film on the wafer, there are found reaction by-products adhering on an inner wall of a chamber or the like. In case of forming the thin film on the wafer in the presence of the reaction by-products accumulated on the inner wall of the chamber or the like, the reaction by-products may then peel off therefrom to contaminate the wafer. Accordingly, there is a need to remove the reaction by-products adhered to the inner wall of the chamber or the like by regularly cleaning an interior of the chamber. 
     In cleaning the interior of the chamber, it is important to detect a proper end point of the cleaning in order to avoid an insufficient cleaning, a damage to the inner wall of the chamber or the like due to an excessive cleaning, and a waste of a cleaning gas. Currently, as for a method of detecting the end point of the cleaning, there is known a method of measuring a luminous intensity of a plasma by a spectrometer and then detecting the end point based on the luminous intensity. 
     Such a method, however, is problematic in that it requires a plasma to be generated to detect the end point of the cleaning, and consequently, is unusable if the cleaning is carried out without generating a plasma. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to provide a substrate processing unit and a method of detecting an end point of a substrate processing, which are capable of detecting an end point of a cleaning without the generation of a plasma. Further, it is another object of the present invention to provide a substrate processing unit and a method of detecting an end point of a substrate processing, which are capable of detecting an end point of a substrate processing without the generation of a plasma. 
     In accordance with one aspect of the invention, there is provided a substrate processing unit including: a processing vessel for accommodating a substrate; a cleaning gas supply system for supplying a cleaning gas into the processing vessel to be used in performing a cleaning of an interior of the processing vessel; an exhauster for exhausting the interior of the processing vessel; an operating state detector for detecting an operating state of the exhauster; and an end point detector for detecting an end point of the cleaning based on a detection result from the operating state detector. Since the substrate processing unit of the present invention includes the operating state detector and the end point detector, the end point of the cleaning can be detected without the generation of a plasma. 
     In accordance with another aspect of the invention, there is provided a substrate processing unit including: a processing vessel for accommodating a substrate; a process gas supply system for supplying a process gas into the processing vessel to be used in performing a processing on the substrate; an exhauster for exhausting an interior of the processing vessel; an operating state detector for detecting an operating state of the exhauster; and an end point detector for detecting an end point of the processing based on a detection result from the operating state detector. Since the substrate processing unit of the present invention includes the operating state detector and the end point detector, the end point of the substrate processing can be detected without the generation of a plasma. 
     The operating state detector may include a vibration detector for detecting a vibration of the exhauster. The vibration of the exhauster, which is detected by the vibration detector, may be the vibration itself or a sound wave. By including the vibration detector, it is possible to detect the end point of the cleaning or the substrate processing based on the vibration caused by the exhauster. 
     The vibration detector may include a sound wave detector for detecting the sound wave produced by the vibration of the exhauster. By including the sound wave detector, it is possible to detect the end point of the cleaning or the substrate processing based on the sound wave produced by the vibration of the exhauster. 
     The end point detector may detect the end point based on a change in the intensity of a vibration. The change in the intensity of the vibration includes a change in the intensity of the vibration at a predetermined frequency or a peak frequency. By detecting the end point based on the change in the intensity of the vibration, the end point of the cleaning or the substrate processing can be detected reliably. 
     The exhauster may include a rotatable body of revolution for exhaust, and the operating state detector may include a rotation detector for detecting a rotation of the body of revolution. The rotation of the body of revolution may be detected by the rotation detector in terms of the rotational frequency or rotational velocity of the body of revolution. By including the rotation detector, it is possible to detect the end point of the cleaning or that of the substrate processing based on the rotation of the body of revolution. 
     The exhauster may include a rotatable body of revolution for exhaust and a driving mechanism for rotating the body of revolution by a current supply, and the operating state detector may include a current detector for detecting a current supplied to the driving mechanism. By including the current detector, it is possible to detect the end point of the cleaning or that of the substrate processing based on the current supplied to the driving mechanism. 
     The exhauster may include a rotatable body of revolution for exhaust and a magnetic bearing for supporting the body of revolution by a current supply, and the operating state detector may include a current detector for detecting a current supplied to the magnetic bearing. By including the current detector, it is possible to detect the end point of the cleaning or that of the substrate processing based on the current supplied to the magnetic bearing. 
     In accordance with still another aspect of the invention, there is provided a method of detecting an end point of a cleaning of a substrate processing unit, the method including the steps of: an operating state detecting process for detecting an operating state of an exhauster wherein a cleaning gas is supplied into a processing vessel of the substrate processing unit to be used in cleaning an interior of the processing vessel and the interior of the processing vessel is exhausted by the exhauster; and an end point detecting process for detecting the end point of the cleaning based on the detected operating state of the exhauster. Since the method of detecting the end point of the cleaning of the substrate processing unit of the present invention includes the operating state detecting process and the end point detecting process, the end point of the cleaning can be detected without the generation of a plasma. 
     In accordance with a still further aspect of the invention, there is provided a method of detecting an end point of a substrate processing, the method including the steps of: an operating state detecting process for detecting an operating state of an exhauster wherein a process gas is supplied into a processing vessel which accommodates therein a substrate to be processed and an interior of the processing vessel is exhausted by the exhauster; and an end point detecting process for detecting the end point of the processing based on the detected operating state of the exhauster. Since the method of detecting the end point of the substrate processing of the present invention includes the operating state detecting process and the end point detecting process, the end point of the substrate processing can be detected without the generation of a plasma. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic diagram of a film forming apparatus in accordance with a first preferred embodiment; 
         FIG. 2  illustrates a schematic diagram of a turbo molecular pump in accordance with the first preferred embodiment and peripheral portions thereof; 
         FIG. 3  provides a flowchart depicting a film forming process performed in the film forming apparatus in accordance with the first preferred embodiment; 
         FIG. 4  describes a flowchart showing a cleaning process performed in the film forming apparatus in accordance with the first preferred embodiment; 
         FIGS. 5A and 5B  present a schematic cleaning process in accordance with the first preferred embodiment; 
         FIG. 6  represents a graph schematically illustrating an intensity of a sound wave produced in a case in accordance with the first preferred embodiment; 
         FIG. 7  offers a schematic diagram of the turbo molecular pump in accordance with a second preferred embodiment and the peripheral portions thereof; 
         FIG. 8  shows a flowchart describing a cleaning process performed by a film forming apparatus in accordance with the second preferred embodiment; 
         FIG. 9  illustrates a schematic cleaning process in accordance with the second preferred embodiment; 
         FIG. 10  depicts a schematic diagram of a turbo molecular pump in accordance with a third preferred embodiment and peripheral portions thereof; 
         FIG. 11  provides a flowchart describing a cleaning process performed by a film forming apparatus in accordance with the third preferred embodiment; 
         FIG. 12  presents a schematic cleaning process in accordance with the third preferred embodiment; 
         FIG. 13  is a graph schematically showing a rotational frequency of a rotor in accordance with the third preferred embodiment; 
         FIG. 14  depicts a schematic diagram of a turbo molecular pump in accordance with a fourth preferred embodiment and peripheral portions thereof; 
         FIG. 15  represents a flowchart describing a cleaning process performed by a film forming apparatus in accordance with the fourth preferred embodiment; 
         FIG. 16  illustrates a schematic cleaning process in accordance with the fourth preferred embodiment; 
         FIG. 17  depicts a graph schematically describing a current supplied to a motor in accordance with the fourth preferred embodiment; 
         FIG. 18  presents a schematic diagram of a turbo molecular pump in accordance with a fifth preferred embodiment and peripheral portions thereof; 
         FIG. 19  sets forth a flowchart describing a cleaning process performed by a film forming apparatus in accordance with the fifth preferred embodiment; 
         FIG. 20  shows a schematic cleaning process in accordance with the fifth preferred embodiment; and 
         FIG. 21  offers a graph schematically illustrating a current supplied to a thrust magnetic bearing in accordance with the fifth preferred embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Preferred Embodiment 
     Hereinafter, a first preferred embodiment of the present invention will be described.  FIG. 1  shows a schematic diagram of a film forming apparatus in accordance with this preferred embodiment, and  FIG. 2  illustrates a schematic diagram of a turbo molecular pump in accordance with this preferred embodiment and peripheral portions thereof. 
     As illustrated in  FIG. 1 , a film forming apparatus  1  has a chamber  2  made of, e.g., aluminum or stainless steel. Further, a surface treatment such as an alumite treatment or the like may be performed on the chamber  2 . 
     An opening  2 A is formed at a side portion of the chamber  2 , and a gate valve  3 , which is opened and closed for loading and unloading a wafer W into and from the chamber  2 , is attached near the opening  2 A. A heater  4  for heating the chamber  2  to a predetermined temperature winds around an exterior of the chamber  2 . 
     Provided in the chamber  2  is a susceptor  5  for mounting thereon the wafer W. The susceptor  5  is made of ceramic such as, e.g., AlN, Al 2 O 3  or the like. Provided in the susceptor  5  is a heater  6  for heating the susceptor  5  to a predetermined temperature. By heating the susceptor  5  with the heater  6  to the predetermined temperature, the wafer W mounted on the susceptor  5  is heated to a predetermined temperature. 
     Holes  5 A for raising and lowering the wafer W are formed at three portions of the susceptor  5  in a vertical direction. Provided under the holes  5 A are wafer elevating pins  7  that are insertable into the respective holes  5 A. The wafer elevating pins  7  are fixedly installed standing on a wafer supporting pin support  8 . 
     An air cylinder  9  is fixed to the wafer elevating pin support  8 . As a rod  9 A of the air cylinder  9  is contracted by an operation of the air cylinder  9 , the wafer supporting pins  7  are lowered, thereby making the wafer W be mounted on the susceptor  5 . And, as the rod  9 A is extended by an operation of the air cylinder  9 , the wafer elevating pins  7  are raised, thereby resulting in the wafer W being separated from the susceptor  5 . Provided in the chamber  2  is an expansible/contractible bellows  10  covering the rod  9 A. By covering the rod  9 A with the bellows  10 , an interior of the chamber  2  is airtightly maintained. 
     An opening is formed at an upper portion of the chamber  2 . Inserted into the opening is a shower head  11  for supplying a gas such as TiCl 4  or the like into the chamber  2 . The shower head  11  has a structure divided into a gas supply unit  11 A for supplying TiCl 4  and Ar and a gas supply unit  11 B for supplying NH 3  and ClF 3 . Formed at the gas supply units  11 A and  11 B are a plurality of gas supply openings for discharging gases such as TiCl 4  or the like. 
     Connected to the gas supply unit  11 A is a gas supply line  12  for supplying TiCl 4  and Ar to the gas supply unit  11 A, and a leading end of the gas supply line  12  is divided into two parts. Connected to the gas supply unit  11 B is a gas supply line  13  for supplying NH 3  and ClF 3  to the gas supply unit  11 B, and a leading end of the gas supply line  13  is divided into two parts. 
     A TiCl 4  supply source  21  accommodating therein TiCl 4  is connected to one end portion of the gas supply line  12 . Interposed at the gas supply line  12  are an openable and closable valve  22  for supplying TiCl 4  and a mass flow controller (MFC)  23  for controlling a flow rate of TiCl 4 . By opening the valve  22  when the mass flow controller  23  is adjusted, TiCl 4  of a predetermined flow rate is supplied from the TiCl 4  supply source  21  into the chamber  2 . 
     An Ar supply source  31  accommodating therein Ar is connected to the other end portion of the gas supply line  12 . Interposed at the gas supply line  12  are an openable and closable valve  32  for supplying Ar and a mass flow controller (MFC)  33  for controlling a flow rate of Ar. By opening the valve  32  when the mass flow controller  33  is adjusted, Ar is supplied at a predetermined flow rate from the Ar supply source  31  into the chamber  2 . 
     An NH 3  supply source  41  accommodating therein NH 3  is connected to one end portion of the gas supply line  13 . Interposed at the gas supply line  13  are an openable and closable valve  42  for supplying NH 3  and a mass flow controller (MFC)  43  for controlling a flow rate of NH 3 . By opening the valve  42  when the mass flow controller  43  is adjusted, NH 3  is supplied at a predetermined flow rate from the NH 3  supply source  41  into the chamber  2 . 
     Connected to the other end portion of the gas supply line  13  is a ClF 3  supply source  51  accommodating therein ClF 3  for removing TiN adhered to an inner wall of the chamber  2  or the like. Interposed at the gas supply line  13  are a valve  52  and a mass flow controller  53  for controlling a flow rate of ClF 3 . By opening the valve  52  when the mass flow controller  53  is adjusted, ClF 3  is supplied at a predetermined flow rate from the ClF 3  supply source  51  into the chamber  2 . 
     Connected to a bottom portion of the chamber  2  is a turbo molecular pump  63  for exhausting the interior of the chamber  2  via an auto pressure controller (APC)  61  for controlling an inner pressure of the chamber  2  and a gas exhaust line  62 . By operating the turbo molecular pump  63  in a state that a conductance is adjusted by the auto pressure controller  61 , the interior of the chamber  2  is maintained under a predetermined pressure. 
     As shown in  FIG. 2 , the turbo molecular pump  63  has a case  64 . Provided in the case  64  are a stator  65  and a rotor  66  that rotates relative to the stator  65 . The stator  65  has stator blades  65 A, and the rotor  66  has rotor blades  66 A and a rotation axis  66 B. A motor  67  is provided between the stator  65  and the rotation axis  66 B. By operating the motor  67 , the rotor  66  rotates relative to the stator  65 . 
     Provided near the rotation axis  66 B is a rotational frequency sensor  68  for measuring a rotational frequency of the rotor  66 . Electrically connected to the rotational frequency sensor  68  is a motor controller  69  for correcting a deviation of the rotational frequency of the rotor  66  by controlling the motor  67 , and thereby rotating the rotor  66  at a predetermined rotational frequency. The motor controller  69  corrects the deviation of the rotational frequency of the rotor  66  by controlling a current supplied to the motor  67  based on a measurement result of the rotational frequency sensor  68 , and thereby rotates the rotor  66  at the predetermined rotational frequency. 
     A radial magnetic bearing  70  and a thrust magnetic bearing  71  are provided between the stator  65  and the rotation axis  66 B. With currents supplied to the radial magnetic bearing  70  and the thrust magnetic bearing  71 , the rotor  66  is raised and then supported by the radial magnetic bearing  70  and the thrust magnetic bearing  71  without being in contact therewith. Further, a protection bearing  72  is provided between the stator  65  and the rotation axis  66 B. The protection bearing  72  supports the rotor  66  while currents are not supplied to the radial magnetic bearing  70  and the thrust magnetic bearing  71 . 
     Provided near the rotation axis  66 B is a radial position sensor  73  for detecting a position of the rotor  66  in a radial direction. Electrically connected to the radial position sensor  73  is a radial magnetic bearing controller  74  to correct a misalignment of the rotor  66  in the radial direction by controlling the radial magnetic bearing  70 , and thereby to position the rotor  66  at a predetermined location. The radial magnetic bearing controller  74  controls an attractive force of the radial magnetic bearing  70  by controlling the current supplied to the radial magnetic bearing  70  based on a detection result of the radial position sensor  73 , thereby correcting the misalignment of the rotor  66  in the radial direction to position the rotor  66  at the predetermined location. 
     Provided near the rotation axis  66 B is a thrust position sensor  75  for detecting a position of the rotor  66  in a thrust direction. Electrically connected to the thrust position sensor  75  is a thrust magnetic bearing controller  76  to correct a misalignment of the rotor  66  in the thrust direction by controlling the thrust magnetic bearing  71  to position the rotor  66  at a predetermined location. Same as in the radial magnetic bearing controller  74 , the thrust magnetic bearing controller  76  controls an attractive force of the thrust magnetic bearing  71  by controlling the current supplied to the thrust magnetic bearing  71  based on a detection result of the thrust position sensor  75 , thereby correcting the misalignment of the rotor  66  in the thrust direction to thereby position the rotor  66  at the predetermined location. 
     Provided near the case  64  is a microphone  81  for measuring an intensity of a sound wave generated from the case  64 . Electrically connected to the microphone  81  is an end point detector  84  for detecting an end point of a cleaning via an amplifier  82  for amplifying an output signal of the microphone  81  and a bandpass filter  83  for passing a signal in a specified frequency range from the signals amplified by the amplifier  82 . Electrically connected to the end point detector  84  is a system controller  85  for controlling the valve  52  and the like. 
     The end point detector  84  includes an A/D conversion interface  84 A, a CPU  84 B and the like. The A/D conversion interface  84 A converts an analog signal outputted from the bandpass filter  83  into a digital signal. The CPU  84 B detects the end point of the cleaning based on the output signal of the A/D conversion interface  84 A. 
     To be specific, the CPU  84 B reads intensity information on a sound wave based on the A/D conversion interface  84 A to thereby determine whether or not an intensity of the sound wave has declined. If it is determined that the intensity of the sound wave has not declined, intensity information on a next sound wave is read and then it is determined again whether or not the intensity thereof has declined. On the other hand, if it is determined that the intensity of the sound wave has declined, it is determined whether or not the intensity thereof is stable. If the intensity thereof is determined to be unstable, intensity information on a next sound wave is read and then it is determined again whether or not the intensity thereof is stable. On the other hand, in case the intensity of the sound wave is determined to be stable, a signal informing that the end point of the cleaning is detected is outputted to the system controller  85 . Based on such a signal, the system controller  85  controls the valve  52  to be closed or the like. 
     Hereinafter, a film forming process performed in the film forming apparatus  1  will be described with reference to  FIG. 3 .  FIG. 3  provides a flowchart depicting the film forming process performed in the film forming apparatus  1  in accordance with this preferred embodiment. 
     First of all, a rough pumping process is performed by operating a rough pumping pump (not shown). When the interior of the chamber  2  is depressurized to a certain extent, a main pumping process of the interior of the chamber  2  is performed by operating the turbo molecular pump  63 . And, a current flows in the heater  6  to heat the susceptor  5  (step  101 ). 
     After the inner pressure of the chamber  2  decreases to a predetermined pressure level and the susceptor  5  is heated to a predetermined temperature, the gate valve  3  is opened and a wafer W is loaded into the chamber  2  by extending a transfer arm (not illustrated) supporting the wafer W (step  102 ). 
     Next, the transfer arm is gradually contracted, and thus, the wafer W is mounted on the wafer elevating pins  7 . After the wafer W is mounted on the wafer elevating pins  7 , the wafer elevating pins  7  are lowered by an operation of the air cylinder  9 , thereby mounting the wafer W on the susceptor  5  (step  103 ). 
     After the wafer W is stabilized at a temperature of about 400° C., the valve  22  is opened to supply TiCl 4  at a flow rate of about 30 sccm into the chamber  2  (step  104 ) while maintaining the inner pressure of the chamber  2  at a level ranging from about 50 to 400 Pa. When the supplied TiCl 4  is in contact with the wafer W, TiCl 4  is adsorbed on a surface of the wafer W. 
     After a predetermined period of time, the valve  22  is closed to stop the supply of TiCl 4 , and TiCl 4  remaining in the chamber  2  is discharged therefrom (step  105 ). Further, while discharging, the pressure in the chamber  2  is maintained at about 1.33×10 −2  Pa. 
     After a predetermined period of time, the valve  42  is opened and NH 3  is supplied at a flow rate of about 100 sccm into the chamber  2  (step  106 ). If the supplied NH 3  is in contact with TiCl 4  adsorbed on the wafer W, TiCl 4  reacts with NH 3 , thereby forming a TiN film on the wafer W. 
     After a predetermined period of time, the valve  42  is closed to stop the supply of NH 3 , and NH 3  and the like remaining in the chamber  2  is discharged therefrom (step  107 ). Further, while discharging, the pressure in the chamber  2  is maintained at about 1.33×10 −2  Pa. 
     After a predetermined period of time, assuming that the processes of steps  104  to  107  are included in one cycle, the system controller  85  determines whether or not a treatment of about 200 cycles has been performed (step  108 ). If it is determined that the treatment of about 200 cycles has not been performed, the processes of steps  104  to  107  are performed again. 
     If it is determined that the treatment of about 200 cycles has been performed, the wafer elevating pins  7  are raised by an operation of the air cylinder  9 , thereby resulting in the wafer W being separated from the susceptor  5  (step  109 ). Further, if the treatment of about 200 cycles has been performed, a TiN film of about 10 nm is formed on the wafer W. 
     Thereafter, after the gate valve  3  is opened, the transfer arm (not shown) is extended to support the wafer W thereon. Finally, the transfer arm is gradually contracted to unload the wafer W from the chamber  2  (step  110 ). 
     Hereinafter, a cleaning process performed in the film forming apparatus  1  will be described with reference to  FIGS. 4 to 6 .  FIG. 4  describes a flowchart showing the cleaning process performed in the film forming apparatus  1  in accordance with this preferred embodiment.  FIGS. 5A and 5B  present a schematic cleaning process in accordance with this preferred embodiment.  FIG. 6  shows a graph schematically illustrating an intensity of a sound wave produced from the case  64  in accordance with this preferred embodiment. 
     First of all, a rough pumping process is performed by operating a rough pumping pump (not shown). When the interior of the chamber  2  is depressurized to a certain extent, a main pumping process of the interior of the chamber  2  is performed by operating the turbo molecular pump  63 . Further, currents flow in the heaters  4  and  6  to heat the chamber  2 , the susceptor  5  and the like (step  201 A). Moreover, while the turbo molecular pump  63  is operated, a rotational frequency of the rotor  66  is measured by the rotational frequency sensor  68 , and a deviation of the rotational frequency of the rotor  66  is corrected by the motor controller  69 . Furthermore, the radial position sensor  73  and the thrust position sensor  75  detect a position of the rotor  66  in a radial and a thrust direction, respectively, and the radial magnetic bearing controller  74  and the thrust magnetic bearing controller  76  correct misalignments of the rotor  66  in the radial and the thrust direction, respectively. 
     After the inner pressure of the chamber  2  is maintained at about 150 Pa and a temperature of the chamber  2  and that of the susceptor  5  are respectively stabilized at about 120° C. and 200° C., the valve  32  is opened to supply Ar at a flow rate of about 100 sccm into the chamber  2  (step  202 A). Here, Ar is supplied at a nearly constant flow rate while a cleaning is performed. 
     Then, the valve  52  is opened to supply ClF 3  at a flow rate of about 200 sccm into the chamber  2  as illustrated in  FIG. 5A  (step  203 A). Once ClF 3  begins to be supplied into the chamber  2 , the cleaning of the chamber  2  is started, and accordingly, TiN adhered to the chamber  2  or the like is removed. Specifically, if ClF 3  is supplied into the chamber  2 , ClF 3  reacts on TiN, resulting in a production of TiF 4 , NF 3 , and ClF. Since TiF 4 , NF 3 , and ClF thus produced are in a gas state, they are immediately discharged from the chamber  2  by the exhaust. Besides, ClF 3  is supplied at a nearly constant flow rate while the cleaning is performed. 
     Next, in a state where the cleaning is being carried out, an intensity of the sound wave produced from the case  64  is measured by the microphone  81 , as shown in  FIG. 5B  (step  204 A). Hereinafter, a generation principle of the sound wave produced from the case  64  will be described. If a gas such as TiF 4  or the like, which is discharged from the chamber  2 , collides with the rotor blade  66 A, the rotor blade  66 A vibrates to thereby produce a sound wave. Further, the sound wave makes the case  64  vibrate and the vibration produce a sound wave. 
     The information on the intensity of the sound wave, which is measured by the microphone  81 , is sent to the A/D conversion interface  84 A via the amplifier  82  and the bandpass filter  83 . The intensity information of the sound wave, which is sent to the A/D conversion interface  84 A, is read by the CPU  84 B to determine whether or not the intensity of the sound wave has declined (step  205 A). In case it is determined that the intensity thereof has not declined, intensity information of a next sound wave is read and it is determined again whether or not the intensity of the sound wave has declined. 
     If it is determined that the intensity of the sound wave has declined, it is determined whether or not the intensity thereof is stable (step  206 A). In case the intensity thereof is determined to be unstable, intensity information of a next sound wave is read and it is determined again whether or not the intensity thereof is stable. 
     As depicted in  FIG. 6 , in case the intensity of the sound wave is determined to be stable, a signal is outputted from the CPU  84 B to the system controller  85  to close the valve  52  and stop the supply of ClF 3  (step  207 A). Thereby, the cleaning is completed. As a final step, the valve  32  is closed, and the supply of Ar is stopped (step  208 A). 
     In this preferred embodiment, the intensity of the sound wave produced from the case  64  is measured, and then, the end point of the cleaning is detected based on a change in the intensity of the sound wave. Therefore, the end point of the cleaning can be detected without the generation of a plasma. In detail, the intensity of the sound wave produced from the case  64  changes depending on a type and an amount of a gas discharged from the chamber  2 . Specifically, as a molecular weight of the gas colliding with the rotor blade  66 A becomes smaller, the intensity of the sound wave declines; and as the amount of the gas colliding with the rotor blade  66 A becomes smaller, the intensity of the sound wave declines. Meanwhile, the amount of a produced gas such as TiF 4  or the like decreases as the cleaning progresses. Therefore, as the cleaning progresses, the intensity of the sound wave produced from the case  64  declines. Further, by the time the gas is rarely produced to be discharged, the intensity of the sound wave becomes stable. Accordingly, the end point of the cleaning can be detected based on the change in the intensity of the sound wave produced from the case  64 . As a result, without the generation of a plasma, it is possible to detect the end point of the cleaning. 
     Second Preferred Embodiment 
     Hereinafter, the second preferred embodiment of the present invention will be described. Further, when describing preferred embodiments hereinafter, any redundant repetition may be omitted. In this preferred embodiment, an example in which an end point of a cleaning is detected by measuring an intensity of a vibration of a case will be described.  FIG. 7  offers a schematic diagram of a turbo molecular pump in accordance with this preferred embodiment and peripheral portions thereof. 
     As shown in  FIG. 7 , fixed on the case  64  is a piezoelectric sensor  91  for measuring intensity of a vibration of the case  64 . The piezoelectric sensor  91  is electrically connected to the end point detector  84  via the amplifier  82  and the bandpass filter  83 . 
     Hereinafter, a cleaning process performed in the film forming apparatus  1  will be described with reference to  FIGS. 8 and 9 .  FIG. 8  shows a flowchart describing the cleaning process performed in the film forming apparatus  1  in accordance with this preferred embodiment, and  FIG. 9  illustrates a schematic cleaning process in accordance with this preferred embodiment. 
     First of all, a rough pumping process is performed on the interior of the chamber  2 , and then, a main pumping process is performed thereon. And, the chamber  2 , the susceptor  5  and the like are heated (step  201 B). 
     After the inner pressure of the chamber  2  is maintained under 150 Pa and a temperature of the chamber  2  and that of the susceptor  5  are respectively stabilized at about 120° C. and 200° C., Ar is supplied at a flow rate of about 100 sccm into the chamber  2  (step  202 B). 
     Next, ClF 3  is supplied at a flow rate of about 200 sccm into the chamber  2  (step  203 B). 
     Thereafter, in a state in which the cleaning is being performed, the intensity of a vibration of the case  64  is measured by the piezoelectric sensor  91 , as illustrated in  FIG. 9  (step  204 B). 
     The intensity information of the vibration, which is measured by the piezoelectric sensor  91 , is sent to the A/D conversion interface  84 A via the amplifier  82  and the bandpass filter  83 . The intensity information of the vibration, which is sent to the A/D conversion interface  84 A, is read by the CPU  84 B to thereby determine whether or not the intensity of the vibration has declined (step  205 B). In case it is determined that the intensity thereof has not declined, intensity information of a next vibration is read and it is determined again whether or not the intensity of the vibration has declined. 
     In case it is determined that the intensity thereof has declined, it is determined whether of not the intensity thereof is stable (step  206 B). If the intensity thereof is determined to be unstable, intensity information of a next vibration is read and it is determined again whether or not the intensity of the vibration is stable. 
     If the intensity thereof is determined to be stable, a signal is outputted from the CPU  84 B to the system controller  85  and the supply of ClF 3  is stopped (step  207 B) As a final step, the supply of Ar is stopped (step  208 B). 
     The Third Preferred Embodiment 
     Hereinafter, the third preferred embodiment of the present invention will be described. In this preferred embodiment, an example in which an end point of a cleaning is detected by measuring a rotational frequency of a rotor will be described.  FIG. 10  depicts a schematic diagram of a turbo molecular pump in accordance with this preferred embodiment and peripheral portions thereof. 
     As illustrated in  FIG. 10 , the rotational frequency sensor  68  is electrically connected to the end point detector  84 . Further, in this preferred embodiment, the motor controller  69  supplies a nearly constant current to the motor  67  regardless of a measurement result of the rotational frequency sensor  68 . 
     Hereinafter, a cleaning process performed in the film forming apparatus  1  will be described with reference to  FIGS. 11 to 13 .  FIG. 11  provides a flowchart describing the cleaning process performed in the film forming apparatus  1  in accordance with this preferred embodiment.  FIG. 12  presents a schematic cleaning process in accordance with this preferred embodiment.  FIG. 13  is a graph schematically showing a rotational frequency of the rotor  66  in accordance with this preferred embodiment. 
     First of all, a rough pumping process is performed on the interior of the chamber  2 , and then, a main pumping process is performed thereon. Further, the chamber  2 , the susceptor  5  and the like are heated (step  201 C). 
     After the inner pressure of the chamber  2  is maintained under 150 Pa and a temperature of the chamber  2  and that of the susceptor  5  are respectively stabilized at about 120° C. and 200° C., Ar is supplied at a flow rate of about 100 sccm into the chamber  2  (step  202 C). 
     Next, ClF 3  is supplied at a flow rate of about 200 sccm into the chamber  2  (step  203 C). 
     Thereafter, in a state in which the cleaning is being performed, the rotational frequency of the rotor  66  is measured by the rotational frequency sensor  68 , as illustrated in  FIG. 12  (step  204 C). 
     The information on the rotational frequency of the rotor  66 , which is measured by the rotational frequency sensor  68 , is sent to the A/D conversion interface  84 A. The information on the rotational frequency, which is sent to the A/D conversion interface  84 A, is read by the CPU  84 B to thereby determine whether or not the rotational frequency has increased (step  205 C). In case it is determined that the rotational frequency has not increased, next rotational frequency information is read and it is determined again whether or not the rotational frequency has increased. 
     In case it is determined that the rotational frequency has increased, it is determined whether or not the rotational frequency is stable (step  206 C). If the rotational frequency is determined to be unstable, next rotational frequency information is read and it is determined again whether or not the rotational frequency is stable. 
     As described in  FIG. 13 , if the rotational frequency is determined to be stable, a signal is outputted from the CPU  84 B to the system controller  85  and the supply of ClF 3  is stopped (step  207 C). As a final step, the supply of Ar is stopped (step  208 C). 
     In this preferred embodiment, the rotational frequency of the rotor  66  is measured, and then, an end point of the cleaning is detected based on a change in the rotational frequency. Therefore, the end point of the cleaning can be detected without the generation of plasma. In detail, the rotational frequency of the rotor  66  changes depending on a type and an amount of a gas discharged from the chamber  2 . Specifically, as a molecular weight of a gas colliding with the rotor blade  66 A becomes smaller, the rotational frequency increases; and as the amount of the gas colliding with the rotor blade  66 A becomes smaller, the rotational frequency increases. This is because a load applied to the rotor blade  66 A is reduced. Meanwhile, the production of a gas such as TiF 4  or the like decreases as the cleaning progresses. Therefore, as the cleaning progresses, the rotational frequency of the rotor  66  increases. Further, by the time the gas is rarely produced to be discharged, the rotational frequency of the rotor  66  becomes stable. Accordingly, the end point of the cleaning can be detected based on the change in the rotational frequency of the rotor  66 . As a result, without the generation of plasma, it is possible to detect the end point of the cleaning. 
     Fourth Preferred Embodiment 
     Hereinafter, the fourth preferred embodiment of the present invention will be described. In this preferred embodiment, an example in which an end point of a cleaning is detected by measuring a current supplied to a motor will be described.  FIG. 14  depicts a schematic diagram of a turbo molecular pump in accordance with this preferred embodiment and peripheral portions thereof. 
     As depicted in  FIG. 14 , provided between the motor  67  and the motor controller  69  is an ampere meter  101  electrically connected to the motor  67  and the motor controller  69 , for measuring a current supplied to the motor  67 . Further, the ampere meter  101  is electrically connected to the end point detector  84  also. 
     Hereinafter, a cleaning process performed in the film forming apparatus  1  will be described with reference to  FIGS. 15 to 17 .  FIG. 15  represents a flowchart describing the cleaning process performed in the film forming apparatus  1  in accordance with this preferred embodiment.  FIG. 16  illustrates a schematic cleaning process in accordance with this preferred embodiment.  FIG. 17  depicts a graph schematically describing a current supplied to the motor  67  in accordance with the fourth preferred embodiment. 
     First of all, a rough pumping process is performed on the interior of the chamber  2 , and then, a main pumping process is performed thereon. Further, the chamber  2 , the susceptor  5  and the like are heated (step  201 D). 
     After the inner pressure of the chamber  2  is maintained under 150 Pa and a temperature of the chamber  2  and that of the susceptor  5  are respectively stabilized at about 120° C. and 200° C., Ar is supplied at a flow rate of about 100 sccm into the chamber  2  (step  202 D). 
     Next, ClF 3  is supplied at a flow rate of about 200 sccm into the chamber  2  (step  203 D). 
     Thereafter, in a state in which the cleaning is being performed, the current supplied to the motor  67  is measured by the ampere meter  101 , as illustrated in  FIG. 16  (step  204 D). 
     Information on the current measured by the ampere meter  101  is sent to the A/D conversion interface  84 A. The current information sent to the A/D conversion interface  84 A is read by the CPU  84 B to thereby determine whether or not the current has declined (step  205 D). In case it is determined that the current has not declined, next current information is read and it is determined again whether or not the current has declined. 
     As described in  FIG. 17 , in case it is determined that the current has declined, it is determined whether or not the current is stable (step  206 D). If the current is determined to be unstable, next current information is read and it is determined again whether or not the current is stable. 
     If the current is determined to be stable, a signal is outputted from the CPU  84 B to the system controller  85  and the supply of ClF 3  is stopped (step  207 D). As a final step, the supply of Ar is stopped (step  208 D). 
     In this preferred embodiment, the current supplied to the motor  67  is measured, and then, an end point of the cleaning is detected based on a change in the current. Therefore, the end point of the cleaning can be detected without the generation of a plasma. In detail, the current supplied to the motor  67  changes depending on a type and an amount of a gas discharged from the chamber  2 . Specifically, as a molecular weight of a gas colliding with the rotor blade  66 A becomes smaller, the current declines; and as the amount of the gas colliding with the rotor blade  66 A becomes smaller, the current declines. This is because a load applied to the rotor blade  66 A is reduced. Meanwhile, the production of a gas such as TiF 4  or the like decreases as the cleaning progresses. Therefore, as the cleaning progresses, the current supplied to the motor  67  declines. Further, by the time the gas is rarely produced to be discharged, the current supplied to the motor  67  becomes stable. Accordingly, the end point of the cleaning can be detected based on the change in the current supplied to the motor  67 . As a result, without the generation of a plasma, it is possible to detect the end point of the cleaning. 
     Fifth Preferred Embodiment 
     Hereinafter, the fifth preferred embodiment of the present invention will be described. In this preferred embodiment, an example in which an end point of a cleaning is detected by measuring a current supplied to a thrust magnetic bearing will be described.  FIG. 18  presents a schematic diagram of a turbo molecular pump in accordance with this preferred embodiment and peripheral portions thereof. 
     As depicted in  FIG. 18 , provided between the thrust magnetic bearing  71  and the thrust magnetic bearing controller  76  is the ampere meter  111  electrically connected to the thrust magnetic bearing  71  and the thrust magnetic bearing controller  76 , for measuring a current supplied to the thrust magnetic bearing  71 . Further, the ampere meter  111  is electrically connected to the end point detector  84 . 
     Hereinafter, the cleaning process performed in the film forming apparatus  1  will be described with reference to  FIGS. 19 to 21 .  FIG. 19  sets forth a flowchart describing the cleaning process performed in the film forming apparatus  1  in accordance with this preferred embodiment.  FIG. 20  shows a schematic cleaning process in accordance with this preferred embodiment.  FIG. 21  offers a graph schematically illustrating the current supplied to the thrust magnetic bearing  71  in accordance with this preferred embodiment. 
     First of all, a rough pumping process is performed on the interior of the chamber  2 , and then, a main pumping process is performed thereon. Further, the chamber  2 , the susceptor  5  and the like are heated (step  201 E). 
     After the inner pressure of the chamber  2  is maintained under 150 Pa and a temperature of the chamber  2  and that of the susceptor  5  are respectively stabilized at about 120° C. and 200° C., Ar is supplied at a flow rate of about 100 sccm into the chamber  2  (step  202 E). 
     Next, ClF 3  is supplied at a flow rate of about 200 sccm into the chamber  2  (step  203 E). 
     Thereafter, in a state in which the cleaning is being performed, the current supplied to the thrust magnetic bearing  71  is measured by the ampere meter  111 , as illustrated in  FIG. 20  (step  204 E). 
     Information on the current measured by the ampere meter  111  is sent to the A/D conversion interface  84 A. The current information sent to the A/D conversion interface  84 A is read by the CPU  84 B to thereby determine whether or not the current has declined (step  205 E). In case it is determined that the current has not declined, next current information is read and it is determined again whether or not the current has declined. 
     In case it is determined that the current has declined, it is determined whether or not the current is stable (step  206 E). If the current is determined to be unstable, next current information is read and it is determined again whether or not the current is stable. 
     As illustrated in  FIG. 21 , if the current is determined to be stable, a signal is outputted from the CPU  84 B to the system controller  85  and the supply of ClF 3  is stopped (step  207 E). As a final step, the supply of Ar is stopped (step  208 E). 
     In this preferred embodiment, the current supplied to the thrust magnetic bearing  71  is measured, and then, an end point of the cleaning is detected based on a change in the current. Therefore, the end point of the cleaning can be detected without the generation of a plasma. In detail, the current supplied to the thrust magnetic bearing  71  changes depending on a type and an amount of a gas discharged from the chamber  2 . Specifically, as a molecular weight of a gas colliding with the rotor blade  66 A becomes smaller, the current declines; and as the amount of the gas colliding with the rotor blade  66 A becomes smaller, the current declines. This is because a load applied to the rotor blade  66 A is reduced. Meanwhile, the production of a gas such as TiF 4  or the like decreases as the cleaning progresses. Therefore, as the cleaning progresses, the current supplied to the thrust magnetic bearing  71  declines. Further, by the time the gas is rarely produced to be discharged, the current supplied to the thrust magnetic bearing  71  becomes stable. Accordingly, the end point of the cleaning can be detected based on the change in the current supplied to the thrust magnetic bearing  71 . As a result, without the generation of a plasma, it is possible to detect the end point of the cleaning. 
     Further, the present invention is not limited to the description of the aforementioned embodiments. Various changes and modifications can be made in a structure, a material, an arrangement of each member or the like without departing from the spirit and scope of the invention. Although the end point of the cleaning is detected by the end point detector  84  in accordance with the first to the fifth embodiments, it is possible to detect an end point of a treatment on a wafer W such as an etching or the like. In this case, instead of a cleaning gas, a process gas, e.g., an etching gas or the like, for processing the wafer W is supplied into the chamber  2 . And, other details are almost same as those in the method of detecting an end point of a cleaning, which have been described in the first to the fifth embodiments. 
     Although ClF 3  is excited by heat in accordance with the first to the fifth embodiments, it is possible to excite ClF 3  by a plasma, light or the like. Further, although TiCl 4  and NH 3  are supplied alternatively, they may be supplied simultaneously also. Furthermore, although a wafer W is used, a glass substrate can also be used instead. 
     In the fifth embodiment, the current supplied to the thrust magnetic bearing  71  is measured. However, it is possible to measure a current supplied to the radial magnetic bearing  70 . 
     While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims. 
     INDUSTRIAL APPLICABILITY 
     The substrate processing unit, method of detecting an end point of a cleaning of the substrate processing unit, and method of detecting an end point of a substrate processing in accordance with the present invention can be used in a semiconductor manufacturing industry.