Patent Publication Number: US-2006012796-A1

Title: Plasma treatment apparatus and light detection method of a plasma treatment

Description:
BACKGROUND OF THE INVENTION  
      1. Technical Field Relating to the Invention  
      The present invention relates to a plasma treatment apparatus and a light detection method of a plasma treatment apparatus.  
      2. Conventional Technology  
      Etching treatment by plasma is widely used for the production processes of semiconductor devices and LCD (Liquid Crystal Display) substrates. The treatment apparatus utilized for this plasma treatment, for example, is equipped with an upper electrode and a lower electrode disposed parallel to one another. While the treatment workpiece (e.g. a semiconductor wafer) is carried and held on the lower electrode, plasma is generated between the upper electrode and the lower electrode. The treatment workpiece is subjected to etching of a certain pattern by this plasma.  
      Scale of the holes and trenches formed by plasma treatment is currently being reduced. This requires real-time observation of the treatment apparatus operating state and more highly precise detection of the endpoint of etching.  
      Conventional detection of the endpoint of etching has widely utilized the high sensitivity spectroscopic analysis method due to its relative simplicity (see Japanese publication of unexamined patent application no. 2000-331985 (JP2000331985)). According to this spectroscopic analysis method, a specific active species is selected among active species such as ions, etc. (e.g. CO*, N*, etc.), radicals of reaction products, etc., of the gas used for etching or decomposition products thereof. The endpoint of etching is detected based on variation of the emission spectrum of the selected specific active species (emission intensity at each wavelength). For example, if a silicon oxide film is etched using a fluorocarbon type (CF 4 , etc.) etchant gas, the emission spectrum from the reaction product CO* (219 nm, 483.5 nm, etc.) is measured. Moreover, if a silicon nitride film is etched using a fluorocarbon-type etchant gas, the emission spectrum from the reaction product N* (674 nm, etc.) is measured. Then the etching endpoint is determined by comparison of emission intensity at the above mentioned type of specific wavelength, or the value of the first, second, etc. differential of such emission intensity, with a previously established value.  
      Moreover, according to this spectroscopic analysis method, plasma light during etching treatment is measured sequentially from the lateral direction. This measured emission spectrum of the plasma and data detected from other parts of the treatment apparatus (e.g., electrical power of the upper/lower electrode, temperature of the upper/lower electrode, internal wall temperature of the treatment apparatus, etc.) are used (e.g. by multi-variable analysis) to make possible real-time observation of operating state of the treatment apparatus.  
      However, the spectroscopic analysis method determines the endpoint of etching by variation of intensity of the plasma light generated when a layer (referred to hereinafter as the “underlying layer”) below the layer subject to treatment becomes exposed by etching. Thus there is concern that the underlying layer may be removed (so-called “over etching”), particularly when the etch rate is high.  
      For the case when etching treatment is not ended simultaneously with exposure of the underlying layer, or for the case when etching treatment is ended while leaving behind a certain thickness of the layer under treatment without exposure of the underlying layer, a method other than the spectroscopic analysis method is used. For example, a method that measures interference light (referred to hereinafter as the “interference light measurement method”) illuminates the layer under treatment of the treatment workpiece (layer subject to etching) with light and measures the. interference light generated by reflection from the layer subject to treatment (see Japanese publication of unexamined patent application no. Hei 3-283165 (JP3283615) and Japanese publication of unexamined patent application no. 2000-212773 (JP200021273)). If the interference light measurement method is adopted, it becomes possible even to detect directly the rate of etching of the layer under treatment during etching.  
      In order to detect the etching endpoint with higher precision, and to furthermore observe etching rate of the layer under treatment and operating state, etc. of the treatment apparatus in real time, it is desirable to use a treatment apparatus that incorporates several optical measurement methods as represented by the spectroscopic analysis method and the interference light measurement method.  
     SUMMARY OF THE INVENTION  
      Advantages to be Afforded by the Invention  
      However, when for example, detection of etching endpoint and etching rate of the layer under treatment are attempted using the spectroscopic analysis method and the interference light measurement method, it has been necessary to separately incorporate in the treatment apparatus optical system components for the spectroscopic analysis method and optical system components for the interference light measurement method. As a result, scale of the treatment apparatus increases, the space occupied by the treatment apparatus must be increased, and the cost of the treatment apparatus is increased.  
      The present invention was developed in consideration of the above mentioned considerations. The object of the present invention is to provide a novel and improved plasma treatment apparatus and light detection method for a plasma treatment apparatus, wherein the plasma treatment apparatus is capable of detecting multiple optical signals obtained from multiple measurement locations and is capable of analyzing conditions at each of the measurement locations using an apparatus of more simplified structure.  
      Means to Realize the Advantages  
      According to a first aspect of the present invention in order to realize the above mentioned advantages, a plasma treatment apparatus is provided for carrying out plasma treatment of a treatment workpiece in a treatment chamber, wherein the apparatus comprises the following: a first light path for transmission of interference light obtained by reflection at multiple faces of the treatment workpiece by light striking the treatment workpiece within the treatment chamber, a second light path for transmission of plasma light generated by plasma formed in the treatment chamber, a spectroscopic component for spectroscopically separating the interference light and the plasma light, and a photoelectric conversion component having a photoelectric conversion element region constructed as a two-dimensional array of multiple photoelectric conversion elements for conversion of incident light from the spectroscopic component into electrical charge and an electrical charge storage member for storage of electrical charge sent from the photoelectric conversion element region; wherein the photoelectric conversion element region of the photoelectric conversion component has at least the following: an interference light photoreception region for photoreception of the interference light spectroscopically separated at the spectroscopic component, and a plasma light photoreception region for photoreception of the plasma light spectroscopically separated at the spectroscopic component.  
      According to the plasma treatment apparatus having this structure, the photoelectric conversion element region having the interference light photoreception region and the plasma light photoreception region receives interference light and plasma light. Thus there is no need for preparation of separate respective photoelectric conversion components for interference light and for plasma light. This results in a size reduction of the plasma treatment apparatus.  
      Moreover, the above mentioned photoelectric conversion component has an electric charge storage member for storing electrical charge transmitted from the photoelectric conversion element region. The electric charge generated by those photoelectric conversion elements belonging to the interference light photoreception region is transmitted to the electric charge storage member through the plasma light photoreception region. Due to this structure, electric charge generated by photoelectric conversion elements belonging to the interference light photoreception region does not require securing a separate path for transmission to the electric charge storage member, and this results in a size reduction of the plasma treatment apparatus.  
      If considerable electric charge is sent at one time to the electric charge storage member, there is concern that the electric charge storage member would lapse into an overflow state. With respect to this point, according to the present invention, the electrical charge group obtained by photoelectric conversion of the plasma light undergoes time-wise division and is in sent to the electrical charge storage member (i.e., it is subdivided and sent in two successive steps). It is therefore possible to store all of the sent electrical charge without increasing capacity of the electrical charge storage member. The frequency of such transmission is preferably determined according to capacity of the electrical charge storage member.  
      The above mentioned photoelectric conversion element region preferably has a light-shielded region that overlaps neither the interference light photoreception region nor the plasma light photoreception region. By sending the photoelectric-converted electrical charge group to the light-shielded region from the interference light photoreception region and plasma light photoreception region, it becomes possible to continuously receive interference light in the interference light photoreception region, and it becomes possible to continuously receive plasma light in the plasma light photoreception region. Moreover, since external light does not strike the light-shielded region, it is possible to maintain electrical charge groups sent from the interference light photoreception region and the plasma light photoreception region in a stabilized state.  
      According to a second aspect of the present invention, in order to solve the above mentioned problems, a light detection method of a plasma treatment apparatus is provided, wherein the plasma treatment apparatus for carrying out plasma treatment of a treatment workpiece in a treatment chamber comprises the following: a first light path for transmission of interference light obtained by reflection at multiple faces of the treatment workpiece by light striking the treatment workpiece within the treatment chamber, a second light path for transmission of plasma light generated by plasma formed in the treatment chamber, a spectroscopic component for spectroscopically separating the interference light and the plasma light, and a photoelectric conversion component having a photoelectric conversion element region constructed as a two-dimensional array of multiple photoelectric conversion elements for conversion of incident light from the spectroscopic component into electrical charge; wherein the method has a step of receiving, at the interference light photoreception region established in the photoelectric conversion element region, the interference light having been spectroscopically separated by the spectroscopic component, and receiving, at the plasma light photoreception region established in the photoelectric conversion element region so as to not overlap the interference light photoreception region, the plasma light having been spectroscopically separated by the spectroscopic component.  
      According to this light detection method, it becomes possible to detect interference light and plasma light by a single photoelectric conversion component without provision of separate respective photoelectric conversion components for the interference light and the plasma light, and this results in a size reduction of the plasma treatment apparatus.  
      Furthermore, the electrical charge group obtained by photoelectric conversion of plasma light is sent to the electrical charge storage member from the plasma light photoreception region, and the electrical charge group obtained from the interference light is preferably sent to the electrical charge storage member through the plasma light photoreception region from the interference light photoreception region. The electrical charge group generated by photoelectric conversion elements belonging to the interference light photoreception region is sent to the electrical charge storage member without the need for securing a separate route, and this results in a size reduction of the photoelectric conversion component.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic cross-sectional diagram showing structure of the etching apparatus according to a working example of the present invention;  
       FIG. 2  is a block diagram showing structure of the light detection component provided for the etching apparatus according to the same working example;  
       FIG. 3  is a cross-sectional drawing showing structure of the spectroscopic component provided for the light detector component shown in  FIG. 2 ;  
       FIG. 4  is a tilted-perspective drawing showing structure of the spectroscopic component provided for the light detector component shown in  FIG. 2 ;  
       FIG. 5  is a block diagram showing structure of the photoelectric conversion component provided for the light detector component shown in  FIG. 2 ;  
       FIG. 6  is a block diagram showing operation (step S 01 ) of the photoelectric conversion component shown in  FIG. 5 ;  
       FIG. 7  is a block diagram showing operation (step S 02 ) of the photoelectric conversion component shown in  FIG. 5 ;  
       FIG. 8  is a block diagram showing operation (step S 03 ) of the photoelectric conversion component shown in  FIG. 5 ;  
       FIG. 9  is a block diagram showing operation (step S 04 ) of the photoelectric conversion component shown in  FIG. 5 ;  
       FIG. 10  is a block diagram showing operation (step S 05 ) of the photoelectric conversion component shown in  FIG. 5 ;  
       FIG. 11  is a block diagram showing operation (step S 06 ) of the photoelectric conversion component shown in  FIG. 5 ;  
       FIG. 12  is a block diagram showing operation (step S 07 ) of the photoelectric conversion component shown in  FIG. 5 ;  
       FIG. 13  is a block diagram showing operation (step S 08 ) of the photoelectric conversion component shown in  FIG. 5 ;  
       FIG. 14  is a block diagram showing operation (step S 09 ) of the photoelectric conversion component shown in  FIG. 5 ; and  
       FIG. 15  is a block diagram showing operation (step S 10 ) of the photoelectric conversion component shown in  FIG. 5 .  
                               Explanation of Items                                                    100   . . .   etching apparatus           102   . . .   treatment chamber           105   . . .   susceptor           111   . . .   electrostatic chuck           121   . . .   upper electrode           161   . . .   window           171   . . .   window           200   . . .   light detector component           210   . . .   light source           220   . . .   optical fiber           222   . . .   optical fiber           224   . . .   horizontal shift register           226   . . .   first light path           228   . . .   second light path           230   . . .   spectroscopic component           232   . . .   slit           234   . . .   grating           240   . . .   photoelectric conversion component           242   . . .   photoelectric conversion element part           242-1   . . .   interference light photoreception region           242-2   . . .   plasma light photoreception region           242-3   . . .   light-shielded region           244   . . .   horizontal shift register           250   . . .   calculation treatment component           L0   . . .   irradiating light           L1   . . .   interference light           L2   . . .   plasma light           L10   . . .   plasma light           L1g   . . .   interference light spectrum           L2g   . . .   plasma light spectrum           L1s   . . .   slit interference light           L2s   . . .   slit plasma light           P   . . .   plasma           S240   . . .   optical detection signal           W   . . .   wafer                        
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     WORKING EXAMPLES  
      Preferred embodiments of the plasma treatment apparatus and the plasma treatment apparatus light detection method according to the present invention are explained below while referring to the appended figures. Furthermore, within the present specification document and the figures, constituent elements having substantially the same mechanical structure are assigned the same identifying number, and redundant explanations are omitted.  
      Structure of an etching apparatus  100 , as a plasma treatment apparatus that is a working example of the present invention, is explained while referring to figures.  FIG. 1  is a cross-sectional schematic drawing showing structure of etching apparatus  100 . Etching apparatus  100  is constructed as a capacitively-coupled flat-plate etching apparatus having upper and lower parallel opposing electrodes for which one electrode contacts the power source used for plasma formation.  
      This etching apparatus  100  has a treatment chamber (chamber)  102  formed as a tubular shape from aluminum having undergone anodic oxidation treatment (alumite treatment). This treatment chamber  102  is grounded. A roughly cylindrical pillar-shaped susceptor support pedestal  104  is provided for carrying and holding a wafer W as the treatment workpiece via an insulating plate  103  of ceramic, etc. at the bottom of the interior of treatment chamber  102 . On this susceptor support pedestal  104  is provided a susceptor (referred to hereinafter as the lower electrode) forming the bottom electrode. This susceptor  105  is connected to a high pass filter (HPF)  106 .  
      Within susceptor support pedestal  104  is provided a temperature control medium chamber  107 . A temperature control medium is fed to temperature control medium chamber  107  via a feed line  108 , is circulated, and then is discharged from discharge line  109 . It becomes possible to control susceptor  105  at a desired temperature by circulation of the temperature control medium in this manner.  
      Susceptor  105  is formed as a circular plate having a central protuberance on the top. Thereon is disposed an electrostatic chuck  111  of roughly the same shape as that of wafer W. Electrostatic chuck  111  is constructed as an electrode  112  disposed between insulation material. Electrostatic chuck  111  draws-attaches wafer W by static electric force by application of a direct current voltage (e.g. 1.5 kV) from a direct current power source  113  connected to electrode  112 .  
      Then insulating plate  103 , susceptor support pedestal  104 , susceptor  105 , and also electrostatic chuck  111  form a gas flow route  114  for supply of a heat conduction medium (backside gas such as He and the like) to the backside face of wafer W which is the treatment workpiece. Furthermore, this heat conduction medium conducts heat between susceptor  105  and wafer W so as to maintain wafer W at a certain temperature.  
      At the upper perimeter edge part of susceptor  105 , a focus ring  115  of annular shape is disposed so as to surround the substrate W which is carried and held on electrostatic chuck  111 . This focus ring  115  is formed of an insulating or conductive material so as to improve uniformity of etching.  
      Moreover, the upper electrode  121  is disposed facing and parallel with this susceptor  105  above susceptor  105 . This upper electrode  121  is held in the interior of treatment chamber  102  by an insulator  122 . The upper electrode  121  comprises, on the surface facing susceptor  105 , an electrode plate  124  having a number of jet apertures  123 , and an electrode support body  125  for supporting this electrode  124 . The above mentioned electrode plate is constructed, for example, of quartz. The above mentioned electrode support body  125 , for example, is constructed from an electrically conductive material such as aluminum having undergone alumite surface treatment. Furthermore, the gap between susceptor  105  and upper electrode  121  is made to be adjustable.  
      A gas inlet port  126  is provided at the center of electrode support body  125  of upper electrode  121 . This gas inlet port  126  is connected to a gas supply line  127 . Furthermore, this gas supply line  127  is connected to a treatment gas supply apparatus  130  via a valve  128  and a mass flow controller  129 .  
      Etching gas for plasma etching is supplied from this treatment gas supply apparatus  130 . Furthermore, although  FIG. 1  shows only a single supply system for treatment gas (comprising the above mentioned treatment gas supply apparatus  130 , etc.), this can be constructed as a plurality of such treatment gas supply systems having respective independent flow control of gases such as C 4 F 6 , CF 4 , Ar, O 2 , and the like for feeding to the interior of treatment chamber  102 .  
      An exhaust gas line is connected to the bottom of treatment chamber  102 . This exhaust gas line  131  is connected to an exhaust gas device  135 . The exhaust gas device  135  is equipped with a vacuum pump, such as a turbo molecular pump, constructed so as to make possible pulling a vacuum down to a certain reduced pressure (e.g. less than or equal to 0.67 Pa) in the interior of treatment chamber  102 . Moreover, a gate valve  132  is provided at a side wall of treatment chamber  102 .  
      A first high frequency power supply  140  is connected to upper electrode  121 . A rectifier  141  is inserted in this power supply line. Moreover, a low pass filter (LPF)  142  is connected to this upper electrode  121 . This first high frequency power supply  140  has a frequency in the range of 50-150 MHz. By application of electrical power at this type of high frequency, it is possible to form a high density plasma of the desired disassociation state in the interior of treatment chamber  102 , and it becomes possible to perform more plasma treatment under still lower pressure conditions than was previously possible. The frequency of this first high frequency power supply  140  is preferably 50-80 MHz, and typically a frequency of 60 MHz is utilized, as shown in the figure, or a frequency in the vicinity of this frequency.  
      A second high frequency power supply  150  is connected to susceptor  105  as the lower electrode. A rectifier  151  is placed in this electrical supply line. The second high frequency power supply  150  has a frequency in the range of several hundred kHz to ten MHz or more. By application of a frequency in this range, it is possible to impart proper ion effects without damaging the wafer W which is the treatment workpiece. Typically a frequency of 13.56 or 2 MHz, etc. is adopted as shown in the figure for the frequency of the second high frequency power supply  150 .  
      The etching apparatus  100  of the present working example is equipped with a light detector component  220  for detection of multiple optical signals obtained from multiple parts under observation in the interior of treatment chamber  102 . The structure and function of this light detector component  200  is explained while referring to  FIG. 2 .  
      For the present working example, light detector component  200 , as shown in  FIG. 2 , is equipped with a light source  210 , a spectroscopic component  230 , a photoelectric conversion component  240 , and a calculation treatment component  250 . Due to such construction, it becomes possible to observe thickness or depth of a layer under observation formed on the wafer W (i.e. a layer subject to etching), and it becomes possible to observe the state of plasma P formed in treatment chamber  102 .  
      Irradiating light LO emanating from light source  210  passes through an optical fiber  220 , passes through window  161  provided at the upper part of treatment chamber  102 , and strikes the surface of wafer W in the interior of treatment chamber  102 . For example, a layer subject to etching (not shown in the figure) as the layer under observation is formed on wafer W. Irradiating light L 0  is reflected from an interface between the layer subject to etching and a mask layer (not shown in the figure) shielding the layer subject to etching. This light also reflects from the bottom surface of a hole formed by etching in the layer subject to etching. Interference light L 1  obtained by interference between these two reflected light beams passes through window  161 , passes through an optical fiber  222 , and is sent to spectroscopic component  230 . Intensity of the interference light L 1  varies in response to the depth of the hole (i.e. the degree of etching). Therefore it is possible to measure etching rate based on detection of the interference light L 1 .  
      When wafer W undergoes a certain treatment (e.g. when subjected to etching treatment), plasma P is formed between upper electrode  121  and wafer W in the interior of treatment chamber  102 . Plasma light L 2  generated by this plasma P passes through a window  171  provided at the side of treatment chamber  102 , passes through an optical fiber  224 , and is sent to spectroscopic component  230 .  
      However, plasma light L 10  generated by plasma P travels through widow  161  provided at the upper part of treatment chamber  102  and strikes optical fiber  222  which transmits interference light L 1 . That is to say, during the time interval when irradiating light L 0  is output from light source  210 , the interference light L 1  transmitted by optical fiber  222  includes plasma light L 10 . In contrast, during the time interval when irradiating light L 0  is not output from light source  210 , optical fiber  222  only transmits plasma light L 10 .  
      Furthermore, optical components (lenses, mirrors, and the like) may be disposed in the light path of irradiating light L 0 , interference light L 1  (plasma light L 10 ), and plasma light L 2 , and these components may be constructed such that each optical axis can be adjusted. Moreover, it is possible to construct each light path without utilizing optical fibers  220 ,  222 , and  224 .  
      Interference light L 1  together with plasma light L 2  are introduced to spectroscopic component  230 , and these light beams undergo spectroscopic separation. An interference light spectrum L 1   g,  obtained by spectroscopic separation of interference light L 1 , passes through a first light path  226  and strikes a photoreception face of photoelectric conversion component  240 . Plasma light spectrum L 2   g,  obtained by spectroscopic separation of plasma light L 2 , passes through a second light path  228  and strikes the photoreception face of photoelectric conversion component  240 .  
      Photoelectric conversion component  240  outputs an optical detection signal S 240  to calculation treatment component  250 . The calculation treatment component  250  carries out a certain calculation treatment utilizing this optical detection signal S 240 . Etching apparatus  100 , based on results of calculation treatment of calculation treatment component  250 , observes, for example, thickness of the layer subject to etching and condition of plasma P in real time. Thus it becomes possible, for example, to end etching treatment of the layer subject to etching prior to exposure of the underlying layer. Moreover, since it is possible to detect exposure of the underlying layer based on both change of thickness of the layer subject to etching and change of condition of plasma P, it becomes possible to complete etching simultaneously with exposure of the underlying layer without etching the underlying layer. Furthermore, since it is possible to understand operating state of etching apparatus  100  based on change of the condition of plasma P, automatically process control becomes possible by adjustment of the flow rate of treatment gas and the like.  
      Furthermore, although a halogen lamp (e.g. a xenon lamp) may be used as light source  210 , it is also permissible to use an LED lamp. Among such xenon lamps, use of a lamp suitable for turning ON/OFF over short time intervals is preferred (e.g. a xenon flash lamp having a major electrode and a trigger probe). An LED lamp is preferred as light source  210  due to capability for ON/OFF operation over short time intervals and longer run life and lower power consumption than a xenon lamp.  
      Structure of spectroscopic component  230  will be explained next while referring to  FIG. 3  and  FIG. 4 .  FIG. 3  is a top planar view of spectroscopic component  230 .  FIG. 4  is a tilted-perspective view of spectroscopic component  230 .  
      Spectroscopic component  230  comprises a slit  232  and a grating  234 . Interference light L 1  passes through optical fiber  222  and is introduced to spectroscopic component  230 . Plasma light L 2  passes through optical fiber  224  and is introduced to spectroscopic component  230 . These lights first pass through slit  232 . Interference light L 1  and plasma light L 2  are light beams which are emitted radially from optical fiber  222  and optical fiber  224 . This slit  232  is equipped with a slit hole used for interference light L 1  and a slit hole used for plasma light L 2 . Interference light L 1  is output as a slit interference light L 1   s,  and plasma light L 2  is output as a plasma light L 2   s.  This slit  232  adjusts the quantity of interference light L 1  and plasma light L 2  and also prevents crosstalk (mutual interference) between slit interference light L 1   s  and slit plasma light L 2   s.    
      Slit interference light L 1   s  and slit plasma light L 2   s,  having passed through slit  232  and having spread out, spread out perpendicularly to the slit direction of slit  232 , arrive respectively at grating  234 , and undergo spectroscopic separation there. The interference spectrum L 1   g  obtained by spectroscopic separation of slit interference light L 1   s  passes through a first light path  226  and is directed toward photoelectric conversion component  240 . The plasma spectrum L 2   g  obtained by spectroscopic separation of slit plasma light L 2   s  passes through a second light path  228  and is directed toward photoelectric conversion component  240 . The gap between first light path  226  and second light path  228  is adjusted so that crosstalk does not occur between interference light spectrum L 1   g  and plasma light spectrum L 2   g  at this time.  
      Furthermore, although a concave type grating is used as grating  234  for the present working example, a planar-type grating may be used. However, if a planar-type grating is used, an imaging element such as a concave mirror, lens and the like is also needed.  
      The photoelectric conversion component  240  positioned at the final stage of spectroscopic component  230  having this type of structure, as shown in  FIG. 5 , is equipped with a photoelectric conversion element part (photoelectric conversion element region)  242  for receiving light of interference light spectrum L 1   g  and plasma light spectrum L 2   g  (wherein this photoelectric conversion element part  242  stores electrical charge obtained from photoelectric conversion) and a horizontal shift register (electrical charge storage member)  244  for serial external output of the stored electrical charge.  
      Photoelectric conversion element part  242  is constructed as a two-dimensional array of multiple photoelectric conversion elements (not show in the figures). The photoelectric conversion element part  242  according to the present working example has  1024  photoelectric conversion elements (pixels) arrayed in the horizontal direction (X direction), and  256  photoelectric conversion elements (pixels) arrayed in the vertical direction (Y direction). A CCD (Charge-Coupled Device) or MOS (Metal-Oxide-Semiconductor) type photosensor can be used as the photoelectric conversion element.  
      The X direction of photoelectric conversion element part  242  corresponds to a wavelength range λ 1 -λ 2  of interference light spectrum L 1   g  and plasma light spectrum L 2   g.  That is to say, photoelectric conversion element part  242  has the ability to detect all spectrum components of interference light spectrum L 1   g  and plasma light spectrum L 2   g  divided into 1024 parts.  
      Moreover, disposed in sequence along the Y direction at the photoreception face of photoelectric conversion element part  242  are an interference light photoreception region  242 - 1 , a plasma light photoreception region  242 - 2 , and a light-shielded region  242 - 3 . For example, photoelectric conversion elements from the first line (row in the X direction) to line number  64  belong to interference light photoreception region  242 - 1 , photoelectric conversion elements from line number  65  to line number  128  belong to plasma light photoreception region  242 - 2 , and photoelectric conversion elements from line number  129  to line number  256  belong to shielded-light region  242 - 3 . Although it is possible to adjust the number of lines of photoelectric conversion elements belonging to each region, the line count of photoelectric conversion elements belonging to light-shielded region  242 - 3  is preferably the same or larger than the line count of photoelectric conversion elements belonging to interference light photoreception region  242 - 1  and the line count of photoelectric conversion elements belonging to plasma light photoreception region  242 - 2 .  
      Furthermore, by equipping photoelectric conversion element part  242  with another light reception region in addition to interference light photoreception region  242 - 1  and plasma light photoreception region  242 - 2 , it becomes possible to detect other light together with interference light L 1  and plasma light L 2 .  
      Interference light spectrum L 1   g  output from spectroscopic component  230  strikes interference light photoreception region  242 - 1  of photoelectric conversion element part  242  and is subject to photoelectric conversion there. Plasma light spectrum L 2   g  output from spectroscopic component  230  strikes plasma light photoreception region  242 - 2  of photoelectric conversion element part  242  and is subject to photoelectric conversion there. In contrast, the light reception face of light-shielded region  242 - 3  is shielded by a light shielding means (not shown in the figures). Interference light spectrum L 1   g,  plasma light spectrum L 2   g,  and of course other light do not strike light-shielded region  232 - 3 .  
      Multiple photoelectric conversion elements belonging to photoelectric conversion element part  242  function also as a vertical shift register for shifting electrical charge obtained by photoelectric conversion in the Y direction. Specifically, simultaneous with a vertical shift operation control signal (not shown in the figures), a line number n (1≦n≦255) photoelectric conversion element transfers electrical charge to a line number n+1 photoelectric conversion element. Then simultaneous with the vertical shift operation control signal, a final line number  256  photoelectric conversion element transfers electrical charge to a horizontal shift register  224 .  
      Horizontal shift register  244  does not simply store electrical charge from 1 line. It is possible for this register to add and store electrical charges of multiple lines for each column (Y direction column). Also horizontal shift register  244 , after storing electrical charge of 1 line or of multiple lines, simultaneous with a horizontal shift operation control signal (not shown in the figures), outputs the stored charge as a serial light detection signal S 240 . This light detection signal S 240  is given to calculation treatment component  250  in the above described manner, and this is used for a specific calculation (refer to  FIG. 2 ).  
      According to etching apparatus  100  of the present working example constructed as described above, due to equipping photoelectric conversion element part  242  with an interference light photoreception region  242 - 1  and plasma light photoreception region  242 - 2 , it becomes possible to detect interference light L 1  and plasma light L 2  by a single photoelectric conversion component  240 .  
      Furthermore, etching apparatus  100  is provided with the light path (optical fiber  222 , first light path  226 ) for transmission of interference light L 1  (slit interference light L 1   s,  interference light spectrum L 1   g ) and the independent light path (optical fiber  224 , second light path  228 ) for transmission of plasma light L 1  (slit plasma light L 2   s,  plasma light spectrum L 2   g ). Thus there is no crosstalk between interference light spectrum L 1   g  and plasma light spectrum L 2   g,  and these lights arrive at interference light photoreception region  242 - 1  and plasma light photoreception region  242 - 2  respectively. Photoelectric conversion component  240  therefore detects interference light spectrum L 1   g  and plasma light spectrum L 2   g  with high precision.  
      Detection of interference light L 1  and plasma light L 2  during this treatment and operation for plasma etching treatment will be explained next as operations of etching apparatus  100 . Furthermore, for the present working example, plasma etching treatment will be explained as an example of etching treatment of a silicon oxide layer (not shown in the figures) as a layer subject to treatment and formed on wafer W.  
      When wafer W undergoes plasma etching treatment, gate valve  132  is first opened, and wafer W is loaded into treatment chamber  102 . The wafer is placed on electrostatic chuck  111 . Thereafter gate value  132  is closed, and the interior of treatment chamber  102  is evacuated by exhaust gas device  135 . Then valve  128  is opened, treatment gas is fed from treatment gas supply apparatus  130 , and pressure of the interior of treatment chamber  102  becomes a certain pressure. Under these conditions, high frequency electrical power is supplied respectively from first high frequency power supply  140  and second high frequency power supply  150 , the treatment gas is made to form a plasma, and this acts on wafer W.  
      Before and after timing of the supply of high frequency electrical power, the direct current power supply  113  is applied to electrode  112  in the interior of electrostatic chuck  111 , and wafer W is electrostatically attached to electrostatic chuck  111 . Moreover, during etching treatment, a cooling medium (chiller) is fed to temperature control medium chamber  107  at a temperature set to a certain temperature value, susceptor  105  is cooled, heat conduction medium (e.g. a backside gas such as He and the like) at a certain pressure is fed to the backside of wafer W, and the surface of wafer W is controlled at a certain temperature.  
      When etching apparatus  100  starts plasma etching treatment of wafer W, light detector component  200  starts detection of interference light L 1  obtained from the silicon oxide layer that is the layer subject to treatment. The etched quantity (etching rate) of the silicon oxide layer is measured in this manner. Moreover, light detector component  200 , in parallel with this interference light L 1  detection operation, carries out detection of plasma light L 2  emitted by plasma P formed in the interior of treatment chamber  102  in order to carry out plasma etching of wafer W.  
      Step-wise operation of detection by light detector component  200  during operation of plasma etching treatment by etching apparatus  100  will be explained while referring to  FIG. 6 - FIG. 15 .  
      First, during step S 01  ( FIG. 6 ), while irradiating light L 0  from light source  210  is not emitted (in the state during which interference light L 1  is not generated), plasma light L 10  passes through window  161  disposed at the upper part of treatment chamber  102  and enters optical fiber  222 . Also plasma light L 2  passes through window  171  disposed at the side part of treatment chamber  102 , enters optical fiber  224 , and is observed.  
      Plasma light L 2  generated by plasma P formed in the interior of treatment chamber  102  passes through window  171  disposed at the wall part of treatment chamber  102 , passes through optical fiber  224 , and is transmitted to spectroscopic component  230 . Spectroscopic component  230  spectroscopically separates plasma light L 2  and forms the plasma light spectrum L 2   g  having a wavelength range of λ 1 -λ 2 . This plasma light spectrum L 2   g  strikes plasma light photoreception region  242 - 2  of photoelectric conversion element part  242  belonging to photoelectric conversion component  240 , and photoelectric conversion to electrical charge group C 2  occurs here.  
      However, as shown in  FIG. 2 , since interference light L 1  traverses plasma P formed in the interior of treatment chamber  102 , the interference light spectrum L 1   g  finally striking photoelectric conversion component  240  also includes a plasma light L 10  component. The plasma light L 10  component must be removed in order to more accurately measure interference light L 1 . In consideration of this point, plasma light L 10  is observed and measured during this step S 01 . This plasma light L 10  undergoes spectroscopic separation by spectroscopic component  230  and strikes interference light photoreception region  242 - 1  of photoelectric conversion element part  242  belonging to photoelectric conversion component  240 . Then this interference light photoreception region  242 - 1  carries out photoelectric conversion to electrical charge group C 10 .  
      Furthermore, since external light does not strike light-shielded region  242 - 3  of photoelectric conversion element part  242 , the photoelectric conversion elements comprising light-shielded region  242 - 3  do not carry out photoelectric conversion. Therefore a new electrical charge does not arise at light-shielded region  242 - 3 .  
      Then during step S 02  ( FIG. 7 ), electrical charge group C 10  generated by interference light photoreception region  242 - 1  and electrical charge group C 2  generated by plasma light photoreception region  242 - 2  are shifted collectively in the Y direction, and are temporarily stored at light-shielded region  242 - 3 . If electrical charge has been stored in light-shielded region  242 - 3  beforehand, this electrical charge is sent to horizontal shift register  244  and stored. Horizontal shift register  244  carries out the horizontal shift operation at the time of completion of electrical charge transfer from light-shielded region  242 - 3 , and the stored electrical charge is sent as a serial output as a light detection signal S 240 - 0  to calculation treatment component  250 . However, this light detection signal S 240 - 0  is based on electrical charge stored beforehand at light-shielded region  242 - 3  of photoelectric conversion element part  242  and is unrelated to plasma light L 10  and plasma light L 2 . Thus calculation treatment component  250  does not carry out calculation treatment based on this light detection signal S 240 - 0 .  
      Even after electrical charge group C 10  generated at interference light photoreception region  242 - 1  and electrical charge group C 2  generated at plasma light photoreception region  242 - 2  are sent to light-shielded region  242 - 3 , photoelectric conversion elements belonging to interference light photoreception region  242 - 1  and photoelectric conversion elements belonging to plasma light photoreception region  242 - 2  generate respective electrical charge groups. However, since these electrical charge groups are generated during transmission of the electrical charge group C 10  and electrical charge group C 2  that had been previously generated, there is concern that a noise component may be intermixed. Thus this is treated as an electrical charge group (referred to hereinafter as a “junk electrical charge group”) Cj that is not used for detection of interference light L 1  and plasma light L 2 .  
      Then during step S 03  ( FIG. 8 ), among electrical charge groups sent to light-shielded region  242 - 3  from interference light photoreception region  242 - 1  and plasma light photoreception region  242 - 2 , electrical charge group C 2  is first sent to horizontal shift register  244 . However, at this time when part of electrical charge C 2  is stored in horizontal shift register  244 , the shift operation in the Y direction is halted. If electrical charge group C 2  is stored in  64  line parts of the photoelectric conversion element,  48  line parts of electrical charge group C 2  equivalent to ¾ of 64 lines, for example, are sent from light-shielded region  242 - 3  to horizontal shift register  244 . The horizontal shift register  244  adds and stores electrical charge groups C 2  for 48 lines in each column (Y direction column).  
      Following transfer of the 48 line parts of electrical charge group C 2  to horizontal shift register  244 , the remaining  16  line parts of electrical charge group C 2 , electrical charge group C 10 , and junk electrical charge group Cj are shifted in order in the Y direction of photoelectric conversion element part  242 .  
      When transfer of  48  line parts of electrical charge group C 2  from light-shielded region  242 - 3  is completed, horizontal shift register  244  carries out the horizontal shift operation, and stored electrical charge undergoes serial output to calculation treatment component  250  as a light detection signal S 240 - 1 .  
      Then during step S 04  ( FIG. 9 ),  16  line parts of electrical charge group C 2  remaining in light-shielded region  242 - 3  are sent to horizontal shift register  244 . Horizontal shift register  244  adds and stores  16  line parts of electrical charge group C 2  for each column (Y direction column).  
      After sending of  16  line parts of electrical charge group C 2  to horizontal shift register  244 , electrical charge group C 10  and junk electrical charge group Cj are also shifted in order in the Y direction of photoelectric conversion element part  242 .  
      At the time when transfer of the  16  line parts of electrical charge group C 2  from light-shielded region  242 - 3  is completed, horizontal shift register  244  carries out the horizontal shift operation, and the stored electrical charge undergoes serial output as a light detection signal S 240 - 2  to calculation treatment component  250 .  
      Here the reason will be explained for two-stage transfer of electrical charge group C 2  to horizontal shift register  244  during step S 03  and step S 04 .  
      In the present working example, results of measurement of plasma light L 2  are used for detection of the endpoint of etching of the silicon oxide film layer (that is the layer subject to treatment) and are used for process observation. The  48  lines parts of electrical charge group C 2  transferred to horizontal shift register  244  during step S 03  are used for detection of the endpoint of etching treatment of the silicon oxide film layer. The 16 line parts of electrical charge group C 2  transferred to horizontal shift register  244  during step S 04  are used for process observation.  
      If light intensity of plasma light L 2  is high, the 64 line parts of electrical charge group C 2 , if sent at one time to horizontal shift register  244 , are highly likely to overflow by several register units. Since observation of the entire wavelength range of λ 1 -λ 2  of plasma light spectrum L 2   g  is necessary when carrying out process observation, it is necessary that the line count of electrical charge group C 2  transferred to horizontal shift register  244  is limited so as not to overflow any register units of horizontal shift register  244 . This limit is  16  lines for the present working example.  
      In contrast, for observation of the endpoint of etching, it is permissible to only pay attention to a specific wavelength λx contained in the total wavelength range λ 1 -λ 2  of plasma light spectrum L 2   g.  Thus it is permissible to adjust the line count of electrical charge group C 2  transferred to horizontal shift register  244  in a range such that register units do not overflow at the specific wavelength λx. This is selected as 48 lines for the present working example. In this manner, if line count used to observe etching endpoint is increased as much as possible and is increased to a value higher than the line count for process observation, measurement sensitivity at the specific wavelength λx in plasma light L 2  increases, and it becomes possible to detect the endpoint of etching with more precision.  
      Furthermore, during step S 05  ( FIG. 10 ), the electrical charge group C 10  transferred to light-shielded region  242 - 3  from interference light photoreception region  242 - 1  is sent to horizontal shift register  244 . Horizontal shift register  244  adds and stores electrical charge group C 10  for each column (Y direction column).  
      When electrical charge group C 10  has been transferred to horizontal shift register  244 , the junk electrical charge group Cj is also shifted in order in the Y direction of photoelectric conversion element part  242 .  
      At the time of completion of transfer of electrical charge group C 10  from light-shielded region  242 - 3 , the horizontal shift operation is carried out at horizontal shift register  244 , and stored electrical charge undergoes serial output as a light detection signal S 240 - 3  to calculation treatment component  250 .  
      Here during step S 06  ( FIG. 11 ), irradiating light L 0  from light source  210  is directed toward wafer W. Irradiating light L 0  emitted from light source  210  passes through optical fiber  220 , passes through widow  161  disposed at the upper part of treatment chamber  102 , and strikes the surface of wafer W in the interior of treatment chamber  102 . Irradiating light L 0 , in addition to reflecting from the interface between the silicon oxide film layer (layer subject to treatment) and the mask layer shielding the silicon oxide film layer, also reflects from the bottom surface of a hole formed by etching in the silicon oxide film layer. These two reflected light beams interfere to provide interference light L 1  which passes through window  161 , through optical fiber  222 , and is sent to spectroscopic component  230 . Interference light L 1  undergoes spectroscopic separation by spectroscopic component  230 , and as interference light spectrum L 1   g  strikes interference light photoreception region  242 - 1  of photoelectric conversion element part  242  belonging to photoelectric conversion component  240 . Furthermore, at this time, plasma light spectrum L 2   g  continuously strikes plasma light photoreception region  242 - 2 .  
      After junk electrical charge Cj is shifted to light-shielded region  242 - 3  from interference light photoreception region  242 - 1  and plasma light photoreception region  242 - 2 , the incident interference light spectrum L 1   g  undergoes photoelectric conversion at interference light photoreception region  242 - 1  and generates an electrical charge group C 11 . At plasma light photoreception region  242 - 2 , the incident plasma light spectrum L 2   g  undergoes photoelectric conversion and generates an electrical charge group C 2 .  
      Junk electrical charge group Cj is sent to horizontal shift register  244  from light-shielded region  242 - 3 . At the time of completion of transfer of junk electrical charge group Cj from light-shielded region  242 - 3 , horizontal shift register  244  undergoes a horizontal shift operation, and the stored electrical charge undergoes serial output as a light detection signal S 240 - 4  to calculation treatment component  250 .  
      Then during step S 07  ( FIG. 12 ), the electrical charge group C 11  generated in interference light photoreception region  242 - 1  and the electrical charge group C 2  generated in plasma light photoreception region  242 - 2  are shifted collectively in the Y direction and are stored temporarily in light-shielded region  242 - 3 . Moreover, junk electrical charge group Cj stored in light-shielded region  242 - 3  is transferred and stored in horizontal shift register  244 . At the time when transfer of junk electrical charge group Cj from light-shielded region  242 - 3  is completed, horizontal shift operation of horizontal shift register  244  is carried out, and the accumulated charge is output as a serial light detection signal S 240 - 5  to calculation treatment component  250 .  
      Even after electrical charge group C 11  generated at interference light photoreception region  242 - 1  and electrical charge group C 2  generated at plasma light photoreception region  242 - 2  are transferred to light-shielded region  242 - 3 , photoelectric conversion elements belonging to interference light photoreception region  242 - 1  and photoelectric conversion elements belonging to plasma light photoreception region  242 - 2  generate electrical charge groups. However, since these electrical charge groups are generated during transfer to the previously generated electrical charge group C 11  and electrical charge group C 2 , there is concern that a noise component may be intermixed. Thus these are treated as junk electrical charge groups Cj.  
      Thereafter during step S 08  ( FIG. 13 ), among electrical charge groups transferred to light-shielded region  242 - 3  from interference light photoreception region  242 - 1  and plasma light photoreception region  242 - 2 , electrical charge group C 2  is transferred to horizontal shift register  244 . Horizontal register  244  adds and stores electrical charge group C 2  for each column (Y direction column).  
      After transfer of electrical charge group C 2  to horizontal shift register  244 , electrical charge group C 11  and junk electrical charge group Cj are shifted in order in photoelectric conversion element part  242 .  
      At the time of completion of transfer of electrical charge group C 2  from light-shielded region  242 - 3 , the horizontal shift operation is carried out for horizontal shift register  244 , and stored electrical charge is output as a serial light detection signal S 240 - 6  to calculation treatment unit  250 .  
      Furthermore, previously during step S 03  and step S 04 , horizontal shift register  244  output light detection signals S 240 - 1  and S 240 - 2  based on electrical charge group C 2 . Thus calculation treatment component  250  during this step S 08  may ignore light detection signal S 240 - 6  output by horizontal sift register  244 .  
      Then during step S 09  ( FIG. 14 ), electrical charge group C 11  transferred to light-shielded region  242 - 3  from interference light photoreception region  242 - 1  is transferred to horizontal shift register  244 . Horizontal shift register  244  adds and stores electrical charge group C 11  for each column (Y direction column).  
      After transfer of electrical charge group C 11  to horizontal shift register  244 , junk electrical charge group Cj is also shifted in order in the Y direction in photoelectric conversion element part  242 .  
      At the time of completion of transfer of electrical charge group C 11  from light-shielded region  242 - 3 , the horizontal shift operation is carried out for horizontal shift register  244 , and stored electrical charge is output as a serial light detection signal S 240 - 7  to calculation treatment unit  250 .  
      Then just prior to step S 10  ( FIG. 15 ), output of irradiating light L 0  from light source  210  is halted. Then while irradiating light. L 0  is not output from light source  210  (state of non-generation of interference light L 1 ), plasma light L 10  passes through window  16  disposed at the upper part of treatment chamber  102 , enters optical fiber  222 , and is observed. This plasma light L 10  undergoes spectroscopic separation by spectroscopic component  230  and strikes interference light photoreception region  242 - 1  of photoelectric conversion element part  242  belonging to photoelectric conversion component  240 . Then this undergoes photoelectric conversion at interference light photoreception region  242 - 1  to electrical charge group C 10 .  
      However, plasma light spectrum L 2   g  continuously strikes plasma light photoreception region  242 - 2  and there undergoes photoelectric conversion to electrical charge group C 2 .  
      The above steps S 01 -S 10  are equivalent to a single cycle of observation of interference light L 1  and plasma light L 2 . By repetition of these steps S 01 -S 10  during etching treatment of the silicon oxide film, interference light L 1  and plasma light L 2  can be efficiently and precisely measured by photoelectric conversion component  240 .  
      Calculation treatment component  250 , based on light detection signal S 240  output from horizontal shift register  244  during each step, performs a certain calculation.  
      For example, calculation treatment component  250  calculates the difference between the light detection signal S 240 - 3  output from horizontal shift register  244  during step S 05  and the light detection signal S 240 - 7  output from horizontal shift register  244  during step S 09 . Based on this difference, the intensity change of interference light L 1  is obtained after removal of the effect of plasma P. This change of intensity of interference light L 1  makes possible observation of etching rate of the silicon oxide film and detection of the endpoint of etching.  
      Moreover, plasma light spectrum L 2   g  always strikes plasma light photoreception region  242 - 2 . Multiple photoelectric conversion elements belonging to plasma light photoreception region  242 - 2  continuously convert plasma light spectrum L 2   g  into electrical charge. However, electrical charge group C 10  generated at interference light photoreception region  242 - 1  passes through this plasma light photoreception region  242 - 2  during transfer to light-shielded region  242 - 3 . Thus electrical charge group C 10  during transfer becomes affected by electrical charge generated in plasma light photoreception region  242 - 2 . However, plasma light spectrum L 2   g  displays constant characteristics during plasma etching treatment. Etching of the silicon oxide film layer that is the layer subject to treatment proceeds, and major change starts at the point in time when the underlying layer is exposed. Thus as mentioned previously, by calculation of the difference between the light detection signal S 240 - 3  output from horizontal shift register  244  during step S 05  and the light detection signal S 240 - 7  output from horizontal shift register  244  during step S 09 , treatment component  250  removes the effect of plasma light spectrum L 2   g  that resulted during passage through plasma light photoreception region  242 - 2  of electrical charge group C 10  generated in interference light photoreception region  242 - 1 . This makes it possible to more accurately obtain of the quantity of electrical charge group C 10  as generated at interference light photoreception region  242 - 1 .  
      Moreover, by comparison of output of light detection signal S 240 - 1  by horizontal shift register  244  of step S 03  of a single measurement cycle and output of light detection signal S 240 - 1  by horizontal shift register  244  of step S 03  of the following measurement cycle, it is possible to understand the intensity of plasma light L 2  at the certain wavelength λx. It can be judged that the silicon oxide film layer (i.e. layer subject to treatment) is exposed when this intensity changes greatly.  
      By analysis of light detection signal S 240 - 2  output from horizontal shift register  244  during step S 04  in wavelength units, it is possible to observe the state of plasma P. Furthermore, it is permissible for this light detection signal S 240 - 2  to contain multiple data obtained at other measurement locations of etching apparatus  100  and for multivariate analysis to be carried out. Real-time observation of the operating state of etching apparatus  100  is realized by use of these analysis results.  
      As explained previously, by the etching apparatus  100  and by the light detection method used by etching apparatus  100  according to the present working example, photoelectric conversion element part  242  belonging to photoelectric conversion component  240  is provided with multiple photoreception regions (i.e. interference light photoreception region  242 - 1  and plasma light photoreception region  242 - 2 ). Then multiple detected lights (i.e. interference light L 1  and plasma light L 2 ) undergo photoreception respectively at interference light photoreception region  242 - 1  and plasma light photoreception region  242 - 2 . It thus becomes possible to measure and detect interference light L 1  and plasma light L 2  with efficiency and accuracy by a single photoelectric conversion component  240 . Moreover, it is possible to reduce the size of etching apparatus  100  that is capable of measuring light from multiple sources.  
      Although the plasma treatment apparatus and light detection method of a plasma treatment apparatus were explained while referring to the appended figures for a preferred embodiment of light detection, the present invention is not limited to these examples. One skilled in the art can clearly conceive of various types of modified examples or revised examples falling under the category of technical concepts mentioned in the scope of the patent claims, and it is naturally understood that these also belong to the technical scope of the present invention.  
      For example, although a working example of the present invention followed the case of measurement of interference light L 1  and plasma light L 2 , according to the present working example, it is also possible to detect and measure other light.  
      Moreover, the present invention can be also applied to cases of measurement and detection of  3  or more types of light. In this case, the photoelectric conversion element region is preferably divided according to the number of sources of light subject to detection.  
      It is also possible to simplify structure of the apparatus by omitted the light-shielding means for shielding the light-shielded region provided in the photoelectric conversion element region. By obtaining beforehand characteristics of the light striking this region, it becomes possible by subsequent calculation treatment to remove the effect of incident light on electrical charge transferred through the light-shielded region from the interference light photoreception region and the plasma light photoreception region.  
      Results of the Invention  
      According to the present invention as explained above in detail, interference light and plasma light reach the photoelectric conversion element region of the light detection component by passing separately through the respective first light path or second light path. The photoelectric conversion element region is provided with an interference light photoreception region and a plasma light photoreception region. Interference light strikes the interference light photoreception region, and plasma light strikes the plasma light photoreception region. It therefore becomes possible to detect multiple independent optical signals (interference light and plasma light) obtained from multiple locations subject to measurement, and it becomes possible to analyze conditions at each location subject to measurement.  
      Moreover, according to the present invention, a light-shielded region is provided in the photoelectric conversion element region. By transferring electrical charge groups that have been photoelectrically converted in the interference light photoreception region and the plasma light photoreception region to the light-shielded region, it becomes possible to continuously receive interference light in the interference light photoreception region, and it becomes possible to continuously receive plasma light in the plasma light photoreception region.