Abstract:
According to an aspect of the present invention, a semiconductor manufacturing apparatus, including: a treatment chamber configured to house a substrate; an electrode which is disposed in said treatment chamber and on which the substrate is placed; a robot arm configured to convey the substrate to said electrode; and a sensor configured to detect a detection pattern of a focus ring which is disposed on an outer peripheral edge portion of said electrode, surrounds an peripheral edge of the substrate placed on said electrode and has the detection pattern, wherein clearance between the substrate and the focus ring is adjusted based on detection result of said sensor, is provided.

Description:
CROSS-REFERENCE TO THE INVENTION  
       [0001]     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2004-379446, filed on Dec. 28, 2004; the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates to a semiconductor manufacturing apparatus and a manufacturing method of a semiconductor device.  
         [0004]     2. Description of the Related Art  
         [0005]     A robot arm is conventionally used when a wafer is placed on a lower electrode of a plasma processor. More specifically, a wafer is taken out of the carrier in a load lock chamber by a robot arm, and the wafer is conveyed to an orienter, by which deviation in the two-dimensional direction of the wafer with respect to the robot arm is corrected, and the wafer is conveyed into a plasma processing apparatus or in this state and is placed onto the lower electrode.  
         [0006]     In the plasma processing apparatus, plasma treatment is performed for a wafer by generating plasma between an upper electrode and a lower electrode with the wafer placed on the lower electrode, and in order to effectively bring plasma into contact with the wafer, an annular focus ring is sometimes disposed on an outer peripheral edge portion of the lower electrode.  
         [0007]     However, when the wafer is placed on the lower electrode in accordance with the above described procedure in the case where the focus ring is disposed, an error of about 500 μm to 1000 μm occurs to clearance between the wafer and the focus ring. Therefore, in-plane dispersion of characteristics occurs, for example, etching shape at the side near the focus ring becomes thin due to difference in plasma distribution, in the edge of the wafer, when etching of the wafer is performed, for example.  
         [0008]     Here, an art of detecting a push pin provided at a stage by an optical sensor provided at a robot arm and placing a wafer on the stage is disclosed (for example, Japanese Patent Laid-open Application No. 2002-124556). However, even when the wafer is positioned with respect to the lower electrode by applying this art, the center of a focus ring and the center of the lower electrode are not aligned with each other in many cases, and therefore, it is difficult to make the clearance between the wafer and the focus ring constant.  
       SUMMARY OF THE INVENTION  
       [0009]     According to an aspect of the present invention, a semiconductor manufacturing apparatus, including: a treatment chamber configured to house a substrate; an electrode which is disposed in said treatment chamber and on which the substrate is placed; a robot arm configured to convey the substrate to said electrode; and a sensor configured to detect a detection pattern of a focus ring which is disposed on an outer peripheral edge portion of said electrode, surrounds an peripheral edge of the substrate placed on said electrode and has the detection pattern, wherein clearance between the substrate and the focus ring is adjusted based on detection result of said sensor, is provided.  
         [0010]     According to another aspect of the present invention, a manufacturing method of a semiconductor device, including: conveying a substrate by a robot arm into a treatment chamber in which an electrode is disposed and a focus ring having a detection pattern is disposed on an outer peripheral edge portion of the electrode, adjusting clearance between the substrate and the focus ring by detecting the detection pattern of the focus ring by a sensor provided at the robot arm and adjusting a position of the robot arm based on the detection result of the sensor, placing the substrate on the electrode while keeping the adjusted clearance, and performing plasma treatment for the substrate placed on the electrode, is provided.  
         [0011]     According to still another aspect of the present invention, a manufacturing method of a semiconductor device, including: conveying a substrate by a robot arm into a treatment chamber in which an electrode is disposed and a focus ring having a detection pattern is disposed on an outer peripheral edge portion of the electrode, placing the substrate on the electrode so that the substrate and the focus ring are partially overlay each other and an outer periphery of the substrate is along the detection pattern of the focus ring, estimating actual positional relationship between the substrate and the focus ring by detecting the detection pattern of the focus ring in the state in which the substrate is placed on the electrode, and performing plasma treatment for the substrate placed on the electrode, is provided. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a schematic diagrammatic view showing a semiconductor manufacturing apparatus according to a first embodiment.  
         [0013]      FIGS. 2A and 2B  are a side view including a schematic partial vertical sectional view and a plan view of an inside of an etching chamber according to first embodiment.  
         [0014]      FIG. 3  is a side view including a schematically shown partial vertical sectional view of the inside of the etching chamber according to the first embodiment;  
         [0015]      FIG. 4A  to  FIG. 4C  are views schematically showing an operational situation of the semiconductor manufacturing apparatus according to the first embodiment.  
         [0016]      FIG. 5A  to  FIG. 5C  are views schematically showing the operational situation of the semiconductor manufacturing apparatus according to the first embodiment.  
         [0017]      FIG. 6  is a side view including aschematic partial vertical sectional view of an inside of an etching chamber according to a second embodiment.  
         [0018]      FIG. 7A  and  FIG. 7B  are front views including a schematic partial vertical sectional view of an inside of an etching chamber according to a third embodiment.  
         [0019]      FIG. 8A  and  FIG. 8B  are a side view including a schematic partial vertical sectional view and a plan view of an inside of an etching chamber according to a fourth embodiment.  
         [0020]      FIG. 9  is a view schematically showing an operational situation of a semiconductor manufacturing apparatus according to the fourth embodiment.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
     FIRST EMBODIMENT  
       [0021]     Hereinafter, a first embodiment will be explained.  FIG. 1  is a schematic diagrammatic view of a semiconductor manufacturing apparatus according to this embodiment, and  FIGS. 2A and 2B  are a side view including a schematic partial vertical sectional view and a plan view of an inside of an etching chamber according to this embodiment.  FIG. 3  is a side view including a schematically shown partial vertical sectional view of the inside of the etching chamber according to this embodiment.  
         [0022]     As shown in  FIG. 1  to  FIG. 2B , a semiconductor manufacturing apparatus  1  includes a load lock chamber  2  in which a carrier (not shown) housing a plurality of wafers W (substrates) is disposed. A transfer chamber  3  is connected to the load lock chamber  2 , and an orienter  4  and an etching chamber  5  (treatment chamber) are connected to the transfer chamber  3 . The orienter  4  is for correcting a deviation in the two-dimensional direction of the wafer W with respect to a robot arm  6  which will be described later.  
         [0023]     The robot arm  6  which supports the wafer W and conveys the wafer W is disposed in the transfer chamber  3 . The robot arm  6  is configured to be able to come and go freely to and from the load lock chamber  2 , the orienter  4  and the etching chamber  5 .  
         [0024]     A disc-shaped lower electrode  7  (electrode) for placing the wafer W thereon is disposed in the etching chamber  5 . On the lower electrode  7 , an upper electrode (not shown) is disposed at a position opposed to the lower electrode  7 . In the state in which the wafer W is placed on the lower electrode  7 , etching gas is supplied into the etching chamber  5  and voltage is applied between the lower electrode  7  and the upper electrode, whereby plasma occurs and the wafer W is etched.  
         [0025]     A retractable push pin  8  for placing the wafer W on the lower electrode  7  and for separating the wafer W from the lower electrode  7  is disposed on the wafer placing surface of the lower electrode  7 . When the wafer W is to be placed on the lower electrode  7 , the wafer W is placed on the push pin  8  by the robot arm  6  with the push pin  8  projected from the lower electrode  7 , and thereafter, the push pin  8  is lowered, whereby the wafer W is placed on the lower electrode  7 . On separating the wafer W from the lower electrode  7 , the wafer W is lifted by raising the push pin  8  with the push pin  8  housed in the lower electrode  7 , and thereby, the wafer W is separated from the lower electrode  7 .  
         [0026]     A focus ring  9  is disposed on an outer peripheral edge portion of the lower electrode  7  to surround a peripheral edge of the wafer W placed on the lower electrode  7 . For example, an annular detection pattern  9 A is formed in the focus ring  9 .  
         [0027]     The detection pattern  9 A is formed inside the focus ring  9 . As shown in  FIG. 3 , the detection pattern  9 A may be formed on the surface of the focus ring  9 . The detection pattern  9 A is constituted of a material with a different reflection rate from that of a part  9 B (hereinafter, this part will be called “focus ring main body part”) of the focus ring  9  other than the detection pattern  9 A. In this embodiment, the case where the material constituting the detection pattern  9 A has a larger reflection rate than the material constituting the focus ring main body part  9 B will be explained. As an example in which the material constituting the detection pattern  9 A has a larger reflection rate than the material constituting the focus ring main body part  9 B, the case where the detection pattern is constituted of Al 2 O 3 , and the focus ring main body part  9 B is constituted of SiO 2  is cited, for example. It is possible to constitute the focus ring main body part  9 B of, for example, SiO 2 , Al 2 O 3 , C, Si and the like though it depends on the material quality of the film to be etched.  
         [0028]     The robot arm  6  is provided with an optical sensor  11  (sensor) which is a part of clearance adjusting mechanism  10 . The clearance adjusting mechanism  10  is for adjusting clearance between the wafer W and the focus ring  9 , and is constituted of a controller  12  electrically connected to the optical sensor  11  other than the optical sensor  11 , and the like.  
         [0029]     The optical sensor  11  is for detecting the detection pattern  9 A. More specifically, the optical sensor  11  is constituted of a projector, a light receiver and the like, and detects the detection pattern  9 A by irradiating the focus ring  9  with light by the projector, and detecting intensity of the reflected light reflected at the focus ring  9  by the light receiver. Here, in this embodiment, the material constituting the detection pattern  9 A has a larger reflection rate than the material constituting the focus ring main body part  9 B, and therefore, when the focus ring  9  is irradiated with light by the projector, the intensity of the light reflected at the detection pattern  9 A is larger than the intensity of the light reflected at the focus ring main body part  9 B.  
         [0030]     As the projector, the one that generates light which is mainly reflected at the detection pattern  9 A and transmits through the focus ring main body part  9 B is preferable, and for example, a lamp, LED, laser or the like can be used.  
         [0031]     The optical sensors  11  are provided at a plurality of spots of the robot arm  6 , for example, three spots. When the center of the wafer W and the center of the focus ring  9  are aligned with each other, the optical sensors  11  are disposed at positions where the intensities of the reflected light detected by the respective optical sensors  11  all become the maximum.  
         [0032]     A controller  12  is for controlling an operation of the robot arm  6  and the like based on the detection result of the optical sensor  11 . More specifically, the controller  12  is configured to detect the position where the intensity of the reflected light detected by the optical sensor  11  becomes the maximum and determine the center position of the focus ring  9 , then determine a deviation amount from the current position to the center position of the focus ring  9 , and move the robot arm  6  by the deviation amount toward the center position of the focus ring  9 .  
         [0033]     Hereinafter, an operation of the semiconductor manufacturing apparatus  1  will be explained.  FIGS. 4A  to  4 C and  FIGS. 5A  to  5 C are views schematically showing an operational situation of the semiconductor manufacturing apparatus  1  according to this embodiment.  
         [0034]     As shown in  FIG. 4A , the robot arm  6  enters the inside of the load lock chamber  2 , and takes the wafer W from the carrier. Subsequently, as shown in  FIG. 4B , the wafer W is placed on the orienter  4  via the transfer chamber  3 . When the wafer W is placed on the orienter  4 , the deviation in the two-dimensional direction of the wafer W is corrected, and the wafer W is placed on the robot arm  6  again.  
         [0035]     Thereafter, the wafer W is conveyed into the etching chamber  5  via the transfer chamber  3  as shown in  FIG. 4C . In the etching chamber  5 , the robot arm  6  moves a very small distance while light reflected at the focus ring  9  is detected by the optical sensor  11  as shown in  FIG. 5A . Subsequently, the positions where intensities of reflection light respectively become the maximum are detected by the controller  12 , and the center position of the focus ring  9  is determined. Next, a deviation amount from the current position to the center position of the focus ring  9  is determined by the controller  12 , and the robot arm  6  moves to the center of the focus ring  9  by the deviation amount. Thereby, the center of the wafer Wand the center of the focus ring  9  are aligned, so that the clearance between the wafer W and the focus ring  9  becomes constant.  
         [0036]     Thereafter, the robot arm  6  descends, and as shown in  FIG. 5B , the wafer W is placed on the push pin  8  projecting from the lower electrode  7 . When the wafer W is placed on the push pin  8 , the push pin  8  descends while maintaining the adjusted clearance between the wafer W and the focus ring  9 , and as shown in  FIG. 5C , the wafer W is placed on the lower electrode  7 . Subsequently, etching gas is supplied into the etching chamber  5  by an etching gas supply mechanism (not shown), and voltage is applied between the lower electrode  7  and the upper electrode, whereby plasma occurs and the wafer W is etched.  
         [0037]     In this embodiment, the detection pattern  9 A is detected by the optical sensor  11  provided at the robot arm  6 , and the position of the robot arm  6  is adjusted based on the detection result of the optical sensor  11 , whereby the center of the wafer W and the center of the focus ring  9  are aligned. Therefore, a variation of clearance between the wafer W and the focus ring  9  can be reduced, so that process stability can be enhanced.  
         [0038]     In this embodiment, the optical sensors  11  are provided at the three spots of the robot arm  6 , and therefore, the center of the focus ring  9  can be easily and accurately determined. The optical sensors  11  may be provided at three or more spots of the robot arm  6 .  
       SECOND EMBODIMENT  
       [0039]     Hereinafter, a second embodiment will be explained. In this embodiment, an example of using a metal detector as a sensor will be explained. In the same member and the like as the member explained in the first embodiment, the explanation will be omitted.  FIG. 6  is a side view including a schematic partial vertical sectional view of the inside of the etching chamber according to the second embodiment.  
         [0040]     In this embodiment, the detection pattern  9 A is constituted of the material with different magnetic permeability from that of the focus ring main body part  9 B. More specifically, the focus ring main body part  9 B is constituted of nonmetal when the detection pattern  9 A is constituted of metal, and when the detection pattern  9 A is constituted of nonmetal, the focus ring main body part  9 B is constituted of metal. In this embodiment, the case where the detection pattern  9 A is constituted of metal and the focus ring main body part  9 B is constituted of nonmetal will be explained.  
         [0041]     As shown in  FIG. 6 , the robot arm is provided with metal detectors  13  (sensors) which are part of the clearance adjusting mechanism  10 . The metal detector  13  is for detecting the detection pattern  9 A. More specifically, the metal detector  13  is constituted of a coil or the like, and detects the detection pattern  9 A by detecting change in impedance of the coil by an eddy current occurring to the surface of the detection pattern  9 A.  
         [0042]     The metal detectors  13  are provided at three spots of the robot arm  6 . The metal detectors  13  are disposed at the positions where all the impedances detected by the respective metal detectors  13  are the maximum when the center of the wafer W and the center of the focus ring  9  are aligned.  
         [0043]     The controller  12  is electrically connected to the metal detectors  13 , and is configured to detect the positions where the impedances detected by the metal detectors  13  become the maximum, determine the center position of the focus ring  9  and the deviation amount from the current position to the center position of the focus ring  9 , and move the robot arm  6  by the deviation amount toward the center position of the focus ring  9 .  
         [0044]     Hereinafter, an operation of the semiconductor manufacturing apparatus  1  will be explained. Here, the operation of the robot arm  6  until the wafer W is conveyed into the etching chamber  5 , the operation of the push pin  8  after the wafer W is placed on the push pin  8  and the like are the same as in the first embodiment, and therefore, the explanation will be omitted.  
         [0045]     In the etching chamber  5 , the robot arm  6  moves a very small distance while a change in impedance of the coil is detected by the metal detectors  13 . Subsequently, the positions where the impedances respectively become the maximum are detected by the controller  12 , andthecenterpositionof the focus ring  9  is determined. Next, the deviation amount from the current position to the center position of the focus ring  9  is determined by the controller  12 , and the robot arm  6  moves to the center position of the focus ring  9  by the deviation amount. Thereby, the center of the wafer W and the center of the focus ring  9  are aligned, and the clearance between the wafer W and the focus ring  9  becomes constant.  
         [0046]     In this embodiment, the detection pattern  9 A is detected by the metal detectors  13  provided at the robot arm  6 , and the position of the robot arm  6  is adjusted based on the detection result of the metal detectors  13 , and therefore, the same effect as the first embodiment can be obtained.  
         [0047]     In this embodiment, the case in which the detection pattern  9 A is constituted of metal and the focus ring main body part  9 B is constituted of nonmetal is explained, but the detection pattern  9 A may be constituted of nonmetal, and the focus ring main body part  9 B may be constituted of metal. In this case, the position where the impedance becomes the minimum is detected by the metal detector  13 , whereby the center of the focus ring  9  can be determined.  
       THIRD EMBODIMENT  
       [0048]     Hereinafter, a third embodiment will be explained. In this embodiment, an example in which recessed and projected portions are formed on the focus ring will be explained. In the same member and the like as the member explained in the first embodiment, the explanation will be omitted.  FIG. 7A  and  FIG. 7B  are front views including schematic partial vertical sectional views of the inside of the etching chamber according to the third embodiment.  
         [0049]     As shown in  FIG. 7A , a recessed portion is formed on the surface of the focus ring  9 , and the recessed portion becomes the detection pattern  9 A. The projector of the optical sensor  11  is configured to irradiate light of which light diameter is larger than the width of the detection pattern  9 A. When the focus ring  9  is irradiated with light by the projector, there exist the place where light is reflected at only the focus ring main body part  9 B, and the place where light is reflected at the detection pattern  9 A and the focus ring main body part  9 B. Since in the place where light is reflected at the detection pattern  9 A and the focus ring main body part  9 B, the light reflected at the detection pattern  9 A differs in phase from the light reflected at the focus ring main body part  9 B and the intensity of the reflected light becomes small due to interference, the intensity of the reflected light becomes smaller than the intensity of the reflected light which is detected at the place where the light is reflected at only the focus ring main body part  9 B.  
         [0050]     The controller  12  is configured to detect the position where the intensity of the reflected light detected by the optical sensor  11  becomes the minimum and determine the center position of the focus ring  9 , then determine the deviation amount from the current position to the center position of the focus ring  9  and move the robot arm  6  toward the center position of the focus ring  9  by the amount of deviation.  
         [0051]     Hereinafter, the operation of the semiconductor manufacturing apparatus  1  will be explained. Here, the operation of the robot arm  6  until the wafer W is conveyed into the etching chamber  5  and the operation of the push pin  8  and the like after the wafer W is placed on the push pin  8  are the same as those in the first embodiment, and therefore, the explanation will be omitted.  
         [0052]     In the etching chamber  5 , the robot arm  6  moves a very small distance while the light reflected at the focus ring  9  is being detected by the optical sensor  11 . Then, the positions where the intensities of the reflected light respectively become the minimum are detected by the controller  12 , and the center position of the focus ring  9  is determined. Next, the deviation amount from the current position to the center position of the focus ring  9  is determined by the controller  12 , and the robot arm  6  moves toward the center position of the focus ring  9  by the deviation amount. As a result, the center of the wafer W and the center of the focus ring  9  are aligned, and the clearance between the waferw and the focus ring  9  becomes constant.  
         [0053]     In this embodiment, the detection pattern  9 A of the recessed portion is formed on the focus ring  9  and the detection pattern  9 A is detected by the optical sensor  11  provided at the robot arm  6 , and the position of the robot arm  6  is adjusted based on the detection result of the optical sensor  11 . Therefore, the same effect as in the first embodiment can be obtained.  
         [0054]     In this embodiment, the case where the detection pattern  9 A is the recessed portion is explained, but as shown in  FIG. 7B , the projected portion may be formed on the surface of the focus ring  9  and this projected portion may be used as the detection pattern  9 A. In this case, the center position of the focus ring  9  can be determined by detecting the position where the intensity of the reflected light becomes minimum by the optical sensor  11 .  
       FOURTH EMBODIMENT  
       [0055]     Hereinafter, a fourth embodiment will be explained. In this embodiment, an example in which a deviation amount of the center position of the wafer and the center position of the focus ring is actually measured in the state in which the wafer is placed on the lower electrode so that the outer periphery of the wafer is along the detection pattern formed in the focus ring. The explanation will be omitted in the same members and the like as those explained in the first embodiment.  FIG. 8A  and  FIG. 8B  are a side view including a schematic partial vertical sectional view and a plan view of the inside of the etching treatment chamber according to this embodiment.  
         [0056]     As shown in  FIG. 8A  and  FIG. 8B , an outer peripheral edge portion of the lower electrode  7  becomes lower in height than in the other part of the lower electrode  7 , and on this outer peripheral edge portion, the focus ring  9  is disposed. A top surface of the inner peripheral edge portion of the focus ring  9  has substantially the same height as atop surface of the other part of the lower electrode so that the outer periphery of the wafer W partially overlays the inner peripheral edge portion of the focus ring  9  when the wafer W is placed on the lower electrode  7 , and a top surface of the other part of the focus ring  9  is not lower than a top surface of the wafer W.  
         [0057]     Disc-shaped detection patterns  9 A are disposed at, for example, three spots in the inner peripheral edge portion of the focus ring  9 . In this embodiment, the detection patterns  9 A are disposed in the focus ring  9 , but they may be disposed on the surface of the focus ring  9 . As in the first embodiment, the annular detection pattern  9 A may be formed in the focus ring  9  or on the surface thereof.  
         [0058]     The detection patterns  9 A are all formed into the equal sizes and the distances from the center position of the focus ring  9  to the detection patterns  9 A are all equal. In the state in which the center of the wafer W and the center of the focus ring  9  are aligned with each other, the detection pattern  9 A has a part of the detection pattern  9 A disposed at the position overlaying the wafer W. The detection pattern  9 A may be disposed at the position where the detection pattern  9 A and the wafer W circumscribe each other when the detection pattern  9 A is seen from directly above in the state in which the center of the wafer W and the center of the focus ring  9  are aligned with each other.  
         [0059]     The detection pattern  9 A is constituted of the same material as that in the first embodiment. When the metal detector  13  is used as the sensor for detecting the detection pattern  9 A, the detection pattern  9 A may be constituted of the same material as in the second embodiment. A recessed portion or a projected portion may be formed at the focus ring  9  as in the third embodiment, and this may be used as the detection pattern  9 A.  
         [0060]     The optical sensor  11  (first sensor) is controlled so as to detect the detection patterns  9 A in the state in which the wafer W is placed on the lower electrode  7  as well as detect the detection patterns  9 A before the wafer W is placed on the push pin  8  as in the first embodiment. In detection of the detection pattern  9 A in the state in which the wafer W is placed on the lower electrode  7 , intensity of light detected by the optical sensor  11  changes in accordance with the overlaying amount of the wafer W and the detection pattern  9 A. Namely, when the center of the wafer W and the center of the focus ring  9  are substantially aligned with each other, the overlaying amounts of the wafer W and the detection patterns  9 A at three spots are substantially equal to each other, and therefore, the intensities of light reflected at the detection patterns  9 A are substantially equal to each other. On the other hand, when the center of the wafer W and the center of the focus ring  9  are not aligned with each other, the overlaying amounts of the wafer W and the detection patterns  9 A at three spots are different from each other, and therefore, a variation occur to the intensities of light reflected at the detection patterns  9 A.  
         [0061]     In this embodiment, the optical sensor  11  may not be provided at the robot arm  6 . Detection of the detection patterns  9 A in the state before the wafer W is placed on the push pin  8  and detection of the detection patterns  9 A in the state in which the wafer W is placed on the lower electrode  7  may be performed by using separate sensors (second sensor).  
         [0062]     The controller  12  is configured to determine the deviation amount from the current position to the center position of the focus ring  9  based on the detection result from the optical sensor  11  as in the first embodiment and move the robot arm  6  toward the center position of the focus ring  9  by the deviation amount, before the wafer W is placed on the push pin  8 .  
         [0063]     The controller  12  is configured to measure the actual deviation amount of the actual center position of the wafer W and the center position of the focus ring  9  by the optical sensor  11 , then perform etching for the wafer W in this state when the actual measured deviation amount is smaller than a predetermined deviation amount stored in the controller  12 , and place the wafer W on the lower electrode  7  again when the actual measured deviation amount is larger than the predetermined deviation amount.  
         [0064]     Hereinafter, an operation of the semiconductor manufacturing apparatus  1  will be explained. Here, the operation and the like of the robot arm  6  and the push pin  8  until the wafer W is placed on the lower electrode  7  is the same as in the first embodiment, and therefore, the explanation will be omitted.  FIG. 9  is a view schematically showing the operational situation of the semiconductor manufacturing apparatus  1  according to this embodiment.  
         [0065]     The detection patterns  9 A are detected by the optical sensor  11  as shown in  FIG. 9  in the state in which the wafer W is placed on the lower electrode  7 , and based on the detection result of the optical sensor  11 , the actual deviation amount of the center position of the wafer W and the center position of the focus ring  9  is measured. Namely, the current center position of the wafer W is determined by comparing the intensities of light reflected at the detection patterns  9 A by the controller  12 , and the actual deviation amount is determined by the determined current center position of the wafer W and the center position of the focus ring  9 .  
         [0066]     When the actual deviation amount is smaller than a predetermined deviation amount, etching is performed for the wafer Win this state. On the other hand, when the measured actual deviation amount is larger than the predetermined deviation amount, the push pin  8  rises to separate the wafer W from the lower electrode  7 . Thereafter, the wafer W is supported by the robot arm  6 , and the robot arm  6  moves toward the center position of the focus ring  9  by the actual deviation amount. Thereafter, the wafer W is placed on the push pin  8  again, then the push pin  8  is lowered to place the wafer W on the lower electrode  7  again. Subsequently, the actual deviation amount of the center position of the wafer W and the center position of the focus ring  9  is measured again. These operations are repeatedly performed until the actual deviation amount becomes smaller than the predetermined deviation amount.  
         [0067]     In this embodiment, the actual deviation amount of the current center position of the wafer W and the center position of the focus ring  9  is measured in the state in which the wafer W is placed on the lower electrode  7 , and therefore, the deviation amount can be accurately grasped. Namely, even when the clearance between the wafer W and the focus ring  9  is adjusted before the wafer W is placed on the lower electrode  7 , there is the possibility of the position of the wafer W being deviated, for example, when the push pin  8  on which the wafer W is placed is lowered, or when the wafer W is placed on the push pin  8 . On the other hand, in this embodiment, the actual deviation amount of the current center position of the wafer W and the center position of the focus ring  9  is measured in the state in which the wafer W is placed on the lower electrode  7 , and therefore, the deviation amount can be accurately grasped when the center of the wafer W and the center of the focus ring  9  are deviated from each other.  
         [0068]     In this embodiment, actual positional relationship of the wafer W and the focus ring  9  is estimated in the state in which the wafer W is placed on the lower electrode  7 , and when the actual deviation amount of the current center position of the wafer W and the center position of the focusring  9  is larger than the predetermined deviation amount, the deviation is corrected based on the actual deviation amount. Therefore, the center of the wafer W and the center of the focus ring  9  can be reliably aligned, and the clearance between the wafer W and the focus ring  9  can be made constant.  
         [0069]     The present invention is not limited to the description of the above described embodiments, and the structure and material, disposition or the like of each component can be properly changed without departing from the spirit of the present invention. For example, the example in which the focus ring  9  is incorporated in the etching chamber  5  is explained in the first to fourth embodiments, but any apparatus using plasma such as, for example, an ashing apparatus and a plasma CVD apparatus can be applied.