Patent Publication Number: US-2009237496-A1

Title: Substrate for observation and observation system

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a substrate for observation and an observation system, and more particularly, to an observation substrate for observing a state of emission of plasma in a processing chamber. 
     2. Description of the Related Art 
     In a prior art substrate processing system that comprises a processing chamber in which a substrate, e.g., a semiconductor wafer is housed and processed using plasma, a plasma is generated from a processing gas in the processing chamber after the inside of the chamber is depressurized. In the substrate processing system of this type, an abnormality of plasma, e.g., an ununiform plasma distribution, sometimes occurs due to generation of abnormal discharge, consumption of component parts inside the processing chamber, adherence of deposits on component parts in the processing chamber, etc. Since abnormality of plasma greatly affects on results of processing on wafers, it is important to identify and remove the cause of abnormality of plasma. 
     After occurrence of abnormal discharge, a burnt mark which can be visually confirmed is left on a component part within the processing chamber. Consumption of component parts in the processing chamber and adherence of a large amount of deposit on component parts can also be easily visually confirmed. Conventionally, therefore, when an abnormality of plasma occurs, an operator stops the substrate processing system, detaches a lid of the processing chamber from the chamber, and visually confirms a state inside the processing chamber. 
     However, the pressure inside the processing chamber must be resumed to an atmospheric pressure in order to detach the lid from the processing chamber, and the lid must be attached to the chamber after completion of visual inspection. Since it takes a long time (e.g., two or three hours) to depressurize the inside of the processing chamber, the rate of operation of the substrate processing system is lowered. 
     Since, as describe above, a change occurs in plasma emission state in the processing chamber due to occurrence of abnormal discharge, etc., it is known to identify the cause of abnormality of plasma based on a result of observation of plasma emission state. 
     For the observation of plasma emission state in the processing chamber, a small-sized camera can be disposed within the processing chamber, but there is a fear that abnormal discharge begins at the camera. Also known is an observation wafer having an embedded thermocouple to measure the temperature inside the processing chamber (see, for example, “Wafer Surface Temperature Detection Wafer (MODEL TCW-800/MODEL TCW-1400)” on the web page of Hugle Electronics Inc., searched Mar. 3, 2008 on the Internet &lt;URL:http://www.hugle.co.jp/index.html&gt;). Thus, it may be possible to embed a camera into the observation wafer, instead of the thermocouple. In that case, however, lead wires for data readout required to connect the thermocouple with an external temperature measurement unit still remain in the resultant observation wafer having the embedded camera instead of the thermocouple, making it difficult for the observation wafer to be conveyed in the substrate processing system. 
     At present, therefore, observation of plasma emission state in the processing chamber is carried out externally through a window (e.g., view port) formed in the processing chamber, without the lid of the processing chamber being detached from the chamber. 
     However, an abnormal discharge, consumption of component parts in the processing chamber, and adhesion of large amount of deposit to component parts in the chamber take place locally. It is therefore necessary to observe an overall plasma emission distribution in the processing chamber in order to identify the cause of abnormal plasma. On the other hand, the window of the processing chamber is generally small in size and only permits the observation of plasma from lateral side, making it difficult to observe the overall plasma emission distribution. 
     SUMMARY OF THE INVENTION 
     The present invention provides a substrate for observation, i.e., an observation substrate and an observation system capable of observing an overall plasma emission distribution. 
     According to a first aspect of this invention, there is provided an observation substrate for observing a plasma emission state within a processing chamber, which comprises a plurality of image pickup units disposed on a surface of the observation substrate adapted to face an interior of the processing chamber, wherein the plurality of image pickup units each include a lens and an image pickup device, and the plurality of image pickup units include at least one memory for storing a picked-up image. 
     With the observation substrate of this invention, each of image pickup units disposed on a surface of the observation substrate facing the interior of the processing chamber includes a lens and an image pickup device, and it is therefore possible to observe an overall plasma emission distribution in a space facing the surface of the observation substrate. In addition, a picked-up image is stored into the memory of the image pickup devices and can be taken out therefrom after the observation substrate is transferred out from the processing chamber. Therefore, it is unnecessary to provide lead wires for data readout. Furthermore, since a plasma emission state can be observed only by transferring the observation substrate into the processing chamber, it is possible to eliminate the need of detaching a lid of the processing chamber from the chamber, whereby a reduction in the rate of operation of the substrate processing system can be prevented. 
     In the observation substrate of this invention, the plurality of image pickup units can be arranged in an array. 
     With this observation substrate, the image pickup units are arranged in an array, and it is therefore possible to fully observe the overall plasma emission distribution in a space facing the surface of the observation substrate. 
     The lens of each of at least part of the plurality of image pickup units can be slanted relative to the surface of the observation substrate. 
     With the above observation substrate, since at least part of the image pickup units each include a lens slanted relative to the surface of the observation substrate, it is possible to observe a plasma emission state in a space other than the space perpendicularly facing the surface of the observation substrate. 
     The memory of the plurality of image pickup units can be adapted to store a moving image. 
     With the above observation substrate, since the memory of the image pickup units stores a moving image, it is possible to observe a time-dependent change in plasma emission state. 
     The observation substrate can include at least one switch adapted to cause the plurality of image pickup units to start image pickup after elapse of a predetermined time period. 
     With the above observation substrate, since the observation substrate has the switch for causing the plurality of image pickup units to start image pickup after elapse of a predetermined time period, it is possible to observe a plasma emission state after elapse of the predetermined time period from when the observation substrate is transferred into the processing chamber. 
     The switch can be adapted to be turned on after being charged with a predetermined amount of charge. 
     With the above observation substrate, since the switch is turned on after it is charged with a predetermined amount of charge, it is possible to turn on the switch simply by transferring the observation substrate into the processing chamber and exposing the switch to plasma so that the switch is charged with the predetermined amount of charge by the plasma. It is therefore unnecessary to provide the switch with a timer or the like, making it possible to simplify the construction of the switch. 
     The observation substrate can further include spectrometers each disposed between the lens and the image pickup device of a corresponding one of the plurality of image pickup units. 
     With the observation substrate, since the image pickup units further include spectrometers interposed between the lenses and the image pickup devices of the image pickup units, incoming light from plasma can be spectrally analyzed to thereby make it possible to analyze plasma components to identify the cause of abnormal plasma in more detail. 
     The observation substrate can further include a plurality of laser oscillators disposed on the surface of the observation substrate. 
     With this observation substrate, the laser oscillators are disposed on the surface of the observation substrate, and irradiate laser beams toward the plasma. The image pickup units receive incoming light from the plasma due to the irradiation of laser beams and pick up an image of a plasma emission state. Thus, a clearer image can be picked up as compared to an image based on light spontaneously emitted from the plasma. 
     The lens of each of the plurality of image pickup units can include a protective film formed on its surface. 
     With this observation substrate, since the lens of each image pickup unit has its surface formed with a protective film, it is possible to prevent the lens from being consumed by plasma even when the observation of plasma emission state is repeated. 
     According to a second aspect of this invention, there is provided an observation system having an observation substrate for observing a plasma emission state within a processing chamber, and a container for housing the observation substrate, wherein the observation substrate includes a plurality of image pickup units disposed on a surface of the observation substrate adapted to face an interior of the processing chamber, the plurality of image pickup units each include a lens and an image pickup device, and the plurality of image pickup units include at least one memory for storing a picked-up image, and the container includes an image readout unit adapted to read out the image stored in the memory of the plurality of image pickup units, and a display unit adapted to display the image read out therefrom. 
     With the observation system of this invention, the image pickup units disposed on a surface of the observation substrate facing the interior of the processing chamber each include a lens and an image pickup device, and it is therefore possible to observe an overall plasma emission distribution in a space facing the surface of the observation substrate. In addition, a picked-up image is stored into the memory of the image pickup units and can be taken out therefrom after the observation substrate is transferred out from the processing chamber. Therefore, it is unnecessary to provide lead wires for data readout. Furthermore, since a plasma emission state can be observed only by transferring the observation substrate into the processing chamber, it is possible to eliminate the need of detaching a lid of the processing chamber from the chamber, whereby a reduction in the rate of operation of the substrate processing system can be prevented. Since the image read out from the memory of the image pickup units of the observation substrate is displayed by the display unit of the container, an overall plasma emission distribution can be confirmed immediately after the observation substrate is transferred out from the processing chamber, making it possible to rapidly identify the cause of abnormal plasma. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  is a plan view schematically showing the construction of a substrate processing system to which an inspection system according to one embodiment of this invention; 
         FIG. 2  is a section view schematically showing the construction of a process module in  FIG. 1 ; 
         FIG. 3A  is a plan view schematically showing the construction of an observation wafer as an observation substrate according to one embodiment of this invention, and  FIG. 3B  is a fragmentary enlarged section view showing a circumferential edge portion of the observation wafer; 
         FIG. 4  is a section view schematically showing the construction of an observation FOUP capable of housing the observation wafer in  FIG. 3 ; 
         FIG. 5A  is a fragmentary enlarged section view showing a first modification of the observation wafer in  FIG. 3 ,  FIG. 5B  is a view showing a second modification thereof, and  FIG. 5C  is a view showing a third modification thereof; 
         FIG. 6  is a fragmentary enlarged section view schematically showing the construction of an observation wafer as an observation substrate according to a second embodiment of this invention; and 
         FIG. 7  is a fragmentary enlarged section view schematically showing the construction of an observation wafer as an observation substrate according to a third embodiment of this invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     The present invention will now be described in detail below with reference to the drawings showing preferred embodiments thereof. 
       FIG. 1  schematically shows in plan view the construction of a substrate processing system to which an inspection system according to one embodiment of this invention is applied. 
     As shown in  FIG. 1 , the substrate processing system  10  includes a transfer module  11  having a hexagonal shape as viewed in plan, four process modules  12  to  15  radially arranged around the transfer module  11 , and a loader module  16  as a rectangular shaped common transfer chamber. 
     The process modules  12  to  15  are substrate processing apparatuses each for performing predetermined processing on a semiconductor device substrate (hereinafter referred to as wafer) W. For example, the process module  12  is an etching processing apparatus that performs etching processing on the wafer W using a plasma. 
     In the substrate processing system  10 , the pressures within the transfer module  11  and the process modules  12  to  15  are maintained at vacuum, whereas the pressure within the loader module  16  is maintained at atmospheric pressure. 
     The transfer module  11  has disposed therein a frog leg-type substrate transfer unit  17  that can bend/elongate and turn. The substrate transfer unit  17  includes an arm  18  able to horizontally expand and contract and rotatable, and a bifurcated transfer form  19  coupled to a tip end of the arm  18  and supporting a wafer W. The substrate transfer unit  17  transfers a wafer W between the process modules  12  to  15 . The transfer fork  19  has a plurality of protruding taper pads  20  adapted to be in contact with the periphery of the wafer W and stably support the wafer W. 
     The loader module  16  is connected to three FOUP mounting stages  22  each mounted with a FOUP (front opening unified pod)  21 , which is a container for housing, e.g., twenty-five wafers W, and is connected to an orienter  23  that pre-aligns the position of each wafer transferred out from the FOUP  21 . The loader module  16  includes a substrate transfer unit  26  disposed therein for transferring the wafer W to a desired position. 
       FIG. 2  schematically shows in section view the construction of the process modules  12  to  15  in  FIG. 1 . These modules  12  to  15  are the same in construction as one another, and the following is a description of the process module  12 . 
     As shown in  FIG. 2 , the process module  12  has a chamber  27  (processing chamber) for housing a wafer W having a diameter of, for example, 300 mm. In the chamber  27 , a cylindrical susceptor  28  is disposed on which the wafer W is placed. The chamber  27  is connected with an exhaust pipe  29  to which a TMP (turbo molecular pump) and a DP (dry pump), none of which are shown, are connected. These pumps vacuum and depressurize the inside of the chamber  27 . 
     A lower high-frequency power source  30  is connected to the susceptor  28  in the chamber  27  and supplies the susceptor  28  with predetermined high frequency electric power. On an upper portion of the susceptor  28 , there is disposed a table-like electrostatic chuck  32  incorporating an electrostatic electrode plate  31  to which a DC power source  33  is electrically connected. When a positive DC voltage is applied to the electrostatic electrode plate  31 , the wafer W is attracted and held on an upper surface of the electrostatic chuck  32  through a Coulomb force or a Johnsen-Rabek force. 
     On the electrostatic chuck  32 , an annular focus ring  34  is disposed such as to surround the wafer W attracted to and held on the chuck  32 . The focus ring  34  is made of a conductive member, e.g., silicon, and converges plasma in a processing space S defined between the susceptor  28  and a shower head  35 , described later, toward the surface of the wafer W to improve the efficiency of etching processing. 
     In a ceiling portion of the chamber  27 , the shower head  35  is disposed so as to face the susceptor  28 . An upper high-frequency power supply  36  is connected to the shower head  35  and supplies it with predetermined high-frequency power. The shower head  35  includes a disk-shaped ceiling electrode plate  38  formed with a number of gas holes  37 , and a cooling plate  39  that supports the ceiling electrode plate  38  hanging therefrom. The shower head  35  functions as a lid for the chamber  27  and can be detached from the chamber  27 . 
     A buffer chamber  41  is defined within the cooling plate  39  of the shower head  35 . A processing gas introduction pipe  42  is connected to the buffer chamber  41  to which a processing gas, e.g., a mixture gas containing a gas of CF system, is supplied from the gas introduction pipe  42 . The shower head  35  supplies the processing gas to the processing space S via the gas holes  37 . 
     In the process module  12 , the processing gas is supplied to the processing space S as described above, and high-frequency power is also applied to the processing space S by the susceptor  28  and the shower head  35 , whereby a plasma is generated from the processing gas. Using the plasma, etching processing is performed on the wafer. 
       FIG. 3A  schematically shows in plan view the construction of an observation wafer as an observation substrate of this embodiment, and  FIG. 3B  shows in enlarged section view a circumferential edge portion of the observation wafer. 
     As shown in  FIGS. 3A and 3B , the observation wafer  43  includes a disk-shaped base  44  made of silicon and having a diameter of, e.g., 300 mm, and a plurality of image pickup units  45  disposed on a surface  44   a  of the base  44  facing the processing space S. The image pickup units  45  are disposed in an array so as to cover the entirety of the surface  44   a  of the base  44 . 
     The image pickup units  45  each include a lens  46  made of, e.g., quartz and disposed to face the processing space S and an image pickup device (for example, a CMOS sensor or a CCD sensor)  47  interposed between the lens  46  and the surface  44   a  of the base  44 . The image pickup device  47  has a memory  47   a.  Each image pickup unit  45  picks up an image of a plasma emission state in a portion of the processing space S to which the image pickup unit  45  faces, and stores data of the picked-up image of emission state into the memory  47   a.  As described above, the image pickup units  45  cover the entirety of the surface  44   a  of the base  44 , and are therefore able to pick up an overall plasma emission distribution in the processing space S facing the observation wafer  43 . 
     Abnormality of plasma sometimes takes place after the elapse of a predetermined time period from when the plasma is generated in the processing space S. In this embodiment, therefore, the memories  47   a  of the image pickup devices  47  have a capacity large enough to be able to store a moving image, making it possible to observe a time-dependent change in plasma emission state and identify the cause of abnormality of plasma. It should be noted that at least one memory common to the image pickup devices  47  of the image pickup units  45  may be used, instead of using the memories  47   a  respectively provided in the image pickup devices of the image pickup units  45 . 
     On a rear surface  44   b  at a circumferential edge portion of the observation wafer  43 , there is disposed an output terminal  48  from which image data stored in the memories  47   a  of the image pickup devices  47  are read out to the outside. The image pickup devices  47  are connected to the output terminal  48  via wiring  49 . 
     In the observation wafer  43 , the image pickup devices  47  of the image pickup units  45  are bonded to the base  44 , and the lenses  46  are bonded to respective ones of the image pickup devices  47 . The observation wafer  43  has a thickness at a maximum of 2 mm in consideration of transferability of the observation wafer  43  in the substrate processing system  10 . The base  44  may not be made of silicon but made of quartz. 
       FIG. 4  schematically shows in section view the construction of an observation FOUP capable of housing a plurality of observation wafers  43  in  FIG. 3 . The observation FOUP has the same outer profile as that of the FOUP  21  for wafers W, and can be placed on each of the FOUP mounting stages  22 . 
     As shown in  FIG. 4 , the observation FOUP  50  (container) includes a housing body  51 , support members  52  projecting from a side wall of the body  51  so as to support circumferential edge portions of the observation wafers  43  within the body  51 , a computer  53  (image readout unit) that processes image data read out from the memories  47   a  of the image pickup units  45  of the observation wafer  43 , and a display  54  (display unit) that displays the processed image. 
     In the observation FOUP  50 , the support members  52  each have a readout terminal  55  disposed in contact of the output terminal  48  of the observation wafer  43  concerned, the computer  53  reads out data of the picked-up image of a plasma emission distribution from the memories  47   a  of the image pickup units  45  of each observation wafer  43  via the readout terminal  55 , and the display  54  displays an image of an overall plasma emission distribution. 
     In this embodiment, the observation wafers  43  and the observation FOUP  50  constitute an observation system. 
     With the observation wafer  43  as the observation substrate of this embodiment, the image pickup units  45  disposed on the surface  44   a  of the base  44  facing the processing space S each have the lens  46  and the image pickup device  47 , and these image pickup units  45  are disposed in an array to cover the entirety of the surface  44   a  of the base  44 , whereby an overall plasma emission distribution in the processing space S can be fully observed. Since the image pickup devices  47  store a picked-up image into memories, the picked-up image can be taken out after the observation wafer  43  is transferred out from the chamber  27 , and lead wires for data readout can be eliminated. Furthermore, since a plasma emission state can be observed only by transferring the observation wafer  43  into the chamber  27 , it is possible to eliminate the need of detaching the shower head  35  from the chamber  27 , whereby a reduction in the rate of operation of the substrate processing system  10  can be prevented. 
     With the observation FOUP  50  of the observation system of this embodiment, the display  54  displays an image read out from the memories  47   a  of the image pickup units  45  of the observation wafer  43 , the overall plasma emission distribution can be confirmed immediately after the observation wafer  43  is transferred out from the chamber  27 , making it possible to rapidly identify the cause of abnormality of plasma. 
     In the observation wafer  43 , the lenses  46  of the image pickup units  45  are disposed to face the processing space S. Alternatively, the lenses  46  and image pickup devices  47  of some of the image pickup units  45  may be slanted relative to the surface  44   a  of the base  44  (see,  FIG. 5A ) In that case, a plasma emission state in a space not perpendicularly facing the surface  44   a  of the base  44  can be observed. The observation wafer  43  can include image pickup units  45  provided on a side portion  44   c  of the base  44  (see,  FIG. 5B ). In that case, a plasma emission state in a broad range beyond the processing space S can be observed. 
     In the observation wafer  43 , the memories  47   a  have a capacity large enough to be able to store a moving image in order to observe an abnormality of plasma which can take place after elapse of a predetermined time period from when the plasma is generated in the processing space S. Instead of setting the memory capacity large enough to store a moving image, there may be provided at least one switch for causing the image pickup units  45  to start image pickup after elapse of a predetermined time period. In an example shown in  FIG. 5C , a plurality of switches  70  corresponding in number to the image pickup unit  45  are each disposed and electrically connected between the image pickup device  47  and the memory  47   a  of a corresponding image pickup unit  45 . When the switches  70  are turned ON, storage of an image picked up by the image pickup devices  47  into the memories  47   a  is started. Thus, an abnormality of plasma generated after the elapse of the predetermined time period can be observed. Preferably, the switches are each configured by a capacitor or the like such that it is turned ON after being charged with a predetermined amount of charge. In that case, it is possible to turn ON the switches simply by transferring the observation wafer  43  into the processing space S and exposing the switches of the observation wafer  43  to the plasma so as to be each charged with the predetermined amount of charge. It is therefore unnecessary to provide the switch with a timer or the like, making it possible to simplify the construction of the switch. In stead of the switches  70 , a switch having switch portions thereof respectively electrically connected between the image pickup devices  47  and the memories  47   a  of the image pickup units  45  is disposed at an arbitrary portion of the observation wafer  43 . 
     In each of the image pickup units  45 , a protective film may be formed on the surface  44   a  of the lens  46 . In that case, consumption of the lens  46  by plasma can be prevented, even if the observation of plasma emission state is repeated. 
     In the observation FOUP  50 , the computer  53  performs processing on image data read out from the memories of the image pickup units  45 . Alternatively, image data may be read out from the memories of the image pickup units  45  and then processed by a computer provided separately from the observation FOUP  50 . 
     Next, a description will be given of an observation substrate according to a second embodiment of this invention. 
     This embodiment is basically the same in construction and function as the first embodiment. In the following, a description of common constructions and functions is omitted, and only the different constructions and functions are described. 
       FIG. 6  schematically shows in fragmentary enlarged section view the construction of an observation wafer as an observation substrate of this embodiment. 
     As shown in  FIG. 6 , the observation wafer  56  includes a plurality of image pickup units  57  disposed on a surface  44   a  of abase  44  of the observation wafer  56  facing the processing space S. The image pickup units  57  are disposed in an array so as to cover the entirety of the surface  44   a  of the base  44 . Each image pickup unit  57  includes a lens  46  slanted relative to the surface  44   a  of the base  44 , an image pickup device  47  disposed on the surface  44   a  of the base  44 , and a prism  58  interposed between the lens  46  and the image pickup device  47 . 
     In each of the image pickup units  57 , incoming light from plasma in the processing space S passes through the lens  46  and is then spectrally dispersed by the prism  58 , and the spectrally dispersed incoming light reaches the image pickup device  47 . Data of an image of spectrally dispersed incoming light from the plasma is stored in the memories of the image pickup devices  47 . Subsequently, when the observation wafer  56  is housed in the observation FOUP  50 , the spectrally dispersed incoming light from the plasma is displayed on the display  54  of the observation FOUP  50 . Thus, spectral analysis on the incoming light from the plasma can be carried out with ease. 
     With the observation wafer  56  as an observation substrate of this embodiment, incoming light from plasma can be spectrally analyzed, making it possible to analyze plasma components and identify in detail the cause of abnormality of plasma. 
     Next, a description will be given of an observation substrate according to a third embodiment of this invention. 
     This embodiment is basically the same in construction and function as the first embodiment. In the following, a description of common constructions and functions is omitted, and only the different constructions and functions are described. 
       FIG. 7  schematically shows in fragmentary enlarged section view the construction of an observation wafer as an observation substrate of this embodiment. 
     As shown in  FIG. 7 , an observation wafer  59  includes a plurality of image pickup units  45  disposed on a surface  44   a  of a base  44  of the observation wafer  59  facing the processing space S, and a plurality of laser oscillators (e.g., semiconductor laser oscillators)  60  disposed on the surface  44   a  of the base  44  so as to be adjacent to respective ones of the image pickup units  45 . 
     Each of the laser oscillators  60  irradiates a laser beam toward that portion of plasma in the processing space S to which the laser oscillator  60  faces, and the plasma irradiated with laser beam emits light. Each image pickup unit  45  receives incoming light from that part of plasma to which the adjacent laser oscillator  60  faces. Since an amount of incoming light from plasma varies depending on an amount of laser beam irradiated to the plasma, the amount of incoming light from plasma received by each image pickup unit  45  can be increased by increasing an amount of laser beam. 
     With the observation wafer  59  as an observation substrate of this embodiment, an amount of incoming light from plasma can be adjusted by an amount of the laser beam irradiated on the plasma, and a clearer image can be picked up as compared to an image based on light spontaneously emitted from the plasma, whereby the cause of abnormality of plasma can be identified in more detail. 
     In the above described embodiments, the image pickup devices  47  of the image pickup units  45  ( 57 ) of the observation wafer  43  ( 56 ,  59 ) each have a memory or have at least one common memory. Alternatively, a wireless communication device able to communicate with an external unit may be provided in the observation wafer. In that case, data of picked-up image of plasma emission distribution can be transmitted to the external unit without the need of transferring the observation wafer out from the chamber  27 , making it possible to observe realtime the plasma emission distribution in the processing space S. Since high-frequency electric power is applied to the processing space S, the radio wave for communication with the external unit preferably has a frequency different from that of the high-frequency electric power, whereby reliable communication with the external unit can be ensured. 
     In the embodiments, the plasma emission distribution in the processing space S is observed by the observation wafer  43  ( 56 ,  59 ). Alternatively, a state in the chamber  27  may be observed by the observation wafer  43  ( 56 ,  59 ), without generating plasma in the chamber  27 . Further alternatively, a state in the transfer module  11  or in the loader module  16  may be observed. In that case, preferably, the observation wafer  43  ( 56 ,  59 ) is moved to a desired position by the substrate transfer unit  17  or  26 . 
     In the embodiments, a plasma emission distribution at the time of etching processing is observed. Alternatively, there may be observed a plasma emission distribution at other plasma processing, e.g., CVD processing. 
     In the embodiment, the substrate subjected to etching processing is a semiconductor wafer W, but the substrate to be etched is not limited thereto. For example, the substrate may be a glass substrate for LCD (liquid crystal display) or FPD (flat panel display).