Patent Publication Number: US-2022229105-A1

Title: Inspection apparatus, control method, and storage medium

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-006267, filed on Jan. 19, 2021, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an inspection apparatus, a control method, and a non-transitory computer-readable storage medium storing a control program. 
     BACKGROUND 
     In general, inspection of the electrical characteristics of an electronic device (an inspection object) is performed using a predetermined inspection apparatus. Specifically, the inspection is performed by fixing a wafer on which an electronic device is arranged to a stage (a chuck) and supplying electric power from a tester to the electronic device via a probe or the like. 
     Here, the inspection apparatus performs a temperature control with respect to the electronic device using a temperature regulator arranged inside the stage at the time of inspection. In this case, for example, the inspection apparatus performs the temperature control using a temperature sensor which is positioned closest to the position of the electronic device to be inspected from a plurality of temperature sensors. 
     For example, in a case in which a plurality of electronic devices are arranged on the wafer, the temperature sensor positioned closest to the position of the electronic device refers to a temperature sensor having the shortest physical distance from a position specified by the average value (that is, an average vector) of coordinates indicating the positions of respective electronic devices. 
     However, in a case in which a plurality of electronic devices are arranged on the wafer in an uneven distribution, a temperature sensor positioned closest to any specific electronic device may not be a suitable temperature sensor for performing temperature control. 
     PRIOR ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: Japanese Laid-Open Patent Publication No. 2009-21311 
       
    
     SUMMARY 
     According to one embodiment of the present disclosure, there is provided an inspection apparatus includes: an acquisition part configured to acquire first coordinate information indicating a position of an inspection object on a stage and a plurality of pieces of second coordinate information indicating positions of a plurality of temperature sensors on the stage when performing an inspection of the inspection object; a calculation part configured to calculate a Mahalanobis distance between a position specified by an average vector of the first coordinate information and the positions of the plurality of temperature sensors; a selection part configured to select at least one temperature sensor including a temperature sensor having a smallest Mahalanobis distance, among the plurality of temperature sensors; and a controller configured to control a temperature of the inspection object using temperature data measured by the selected at least one temperature sensor. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the present disclosure, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the present disclosure. 
         FIG. 1  is a schematic cross-sectional view illustrating a configuration example of an inspection apparatus. 
         FIG. 2  is a view illustrating an example of a hardware configuration of a control device. 
         FIG. 3  is a view illustrating details of a configuration related to a temperature control function among respective configurations of the inspection apparatus. 
         FIGS. 4A to 4C  are views illustrating examples of positional relationships between electronic devices and temperature sensors at the time of inspection. 
         FIG. 5  is a view illustrating an example of a functional configuration of a temperature sensor selection part of the control device. 
         FIGS. 6A to 6C  are views illustrating specific examples of processing performed by the temperature sensor selection part. 
         FIG. 7  is a view illustrating details of processing performed by a Mahalanobis distance calculation part. 
         FIGS. 8A and 8B  are flowcharts illustrating a flow of inspection processing in the inspection apparatus. 
         FIG. 9  is a flowchart illustrating a flow of temperature sensor selection processing. 
         FIGS. 10A to 10C  are views illustrating other examples of positional relationships between electronic devices and temperature sensors at the time of inspection. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, each embodiment will be described with reference to the accompanying drawings. In addition, in the specification and drawings, constituent elements having substantially the same functional configurations will be denoted by the same reference numerals to omit redundant descriptions. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, systems, and components have not been described in detail so as not to unnecessarily obscure aspects of the various embodiments. 
     First Embodiment 
     &lt;Configuration Example of Inspection Apparatus&gt; 
     First, a configuration example of an inspection apparatus according to a first embodiment will be described.  FIG. 1  is a schematic cross-sectional view illustrating the configuration example of the inspection apparatus. As illustrated in  FIG. 1 , an inspection apparatus  100  includes a loader chamber  110 , an accommodation chamber  120 , a test head  130 , a tester  140 , and a display device  150 . 
     The loader chamber  110  includes a mechanism configured to take out a wafer W accommodated in a transfer container and transfer the same to the accommodation chamber  120 . In addition, the loader chamber  110  includes a mechanism configured to receive a wafer W for which inspection for the electrical characteristics of an electronic device has been completed and accommodate the same in the transfer container. 
     The accommodation chamber  120  includes a main chuck  121 , a probe card  122 , an alignment mechanism  123 , a temperature regulator control circuit  124 , and a control device  125 . 
     The main chuck  121  is an example of a stage, and is configured to fix the wafer W and move the wafer W in a horizontal direction and a vertical direction to adjust a relative position between the probe card  122  and the wafer W. As a result, the main chuck  121  may bring the electrodes of an electronic device arranged on the wafer W into contact with a probe group  122 A of the probe card  122 . 
     The probe card  122  is arranged above the main chuck  121  and electrically connected to the test head  130  via an interface  122 B. The probe group  122 A supplies electric power from the test head  130  to the electronic device via the interface  122 B by coming into contact with the electrodes of the electronic device arranged on the wafer W. In addition, the electronic device transmits a signal to the test head  130  via the interface  122 B in response to the electric power supplied thereto. 
     The alignment mechanism  123  acquires data for alignment adjustment between the probe group  122 A of the probe card  122  and the electrode pads of the electronic device on the wafer W fixed to the main chuck  121 . 
     Specifically, the alignment mechanism  123  includes an alignment bridge  123 A configured to move horizontally in a space between a rear surface in the accommodation chamber  120  and the probe center, and a first capturing device  123 B provided on the alignment bridge  123 A. 
     Of these, the first capturing device  123 B moves to a position between the probe card  122  and the main chuck  121  by advancing from the rear surface of the accommodation chamber  120  to the probe center via the alignment bridge  123 A. At the position, the first capturing device  123 B detects the positions of the electrodes of the electronic device arranged on the wafer W while the main chuck  121  moves in the horizontal direction. 
     The alignment mechanism  123  includes a second capturing device  123 C. The second capturing device  123 C detects a position of the probe group  122 A from below the probe card  122  while the main chuck  121  moves in the horizontal direction below the probe card  122  after the alignment bridge  123 A is retracted to the rear surface in the accommodation chamber  120 . 
     The temperature regulator control circuit  124  operates a temperature regulator (not illustrated) provided within the main chuck  121  in order to perform a high temperature inspection or a low temperature inspection on the electronic device of the wafer W. As a result, the electronic device of the wafer W fixed to the main chuck  121  is heated or cooled within an allowable range of a set target temperature. A plurality of temperature sensors (not illustrated) are provided within the main chuck  121 , and temperature data measured by any of the selected temperature sensors among the plurality of temperature sensors is used as temperature data of the electronic device arranged on the wafer W. 
     The control device  125  performs temperature control of the electronic device of the wafer W fixed to the main chuck  121 , movement control of the main chuck  121  in the horizontal and vertical directions, movement control of the alignment mechanism  123 , and the like. 
     The test head  130  is connected to the tester  140 . The tester  140  includes a test board that reproduces a portion of a circuit configuration of a motherboard on which an electronic device is arranged. The test board is connected to the control device  125  configured to determine a quality of the electronic device a signal from the electronic device. By replacing the test board in the tester  140 , it is possible to reproduce circuit configurations of a plurality of types of motherboards. 
     The display device  150  is configured to display various data including a set target temperature, image data captured by the first and second capturing devices  123 B and  123 C, and the like. 
     &lt;Hardware Configuration of Control Device&gt; 
     Next, a hardware configuration of the control device  125  will be described.  FIG. 2  is a view illustrating an example of the configuration of the control device  125 . 
     As illustrated in  FIG. 2 , the control device  125  includes a processor  201 , a memory  202 , an auxiliary storage device  203 , an interface (I/F) device  204 , a communication device  205 , and a drive device  206 . In addition, respective hardware components of the control device  125  are connected to each other via a bus  207 . 
     The processor  201  includes various arithmetic operation devices such as a central processing unit (CPU). The processor  201  reads various programs (e.g., a control program to be described later, or the like) onto the memory  202  and executes the programs. 
     The memory  202  includes a main storage device such as a read only memory (ROM), a random access memory (RAM), or the like. The processor  201  and the memory  202  constitute a so-called computer. When the processor  201  executes various programs read by the processor  201  on the memory  202 , the computer implements various functions. 
     The auxiliary storage device  203  stores various programs and various data used when various programs are executed by the processor  201 . 
     The I/F device  204  connects the temperature regulator control circuit  124 , which is an example of an external device, a plurality of temperature sensors (here, temperature sensors  220 _ 1  to  220 _ 4  are exemplified), a display device  150 , and the like, to the control device  125 . 
     The communication device  205  is a communication device for communicating with the tester  140 . 
     The drive device  206  is a device configured to set a recording medium  210 . Here, the “recording medium  210 ” includes a non-transitory computer-readable medium for optically, electrically, or magnetically recording information, such as a CD-ROM, a flexible disk, or a magneto-optical disk. In addition, the recording medium  210  may include, for example, a semiconductor memory that electrically records information, such as, a ROM or a flash memory. 
     In addition, the various programs to be installed in the auxiliary storage device  203  are installed, for example, by setting a distributed recording medium  210  into the drive device  206  and reading out, by the drive device  206 , the various programs recorded in the recording medium  210 . Alternatively, the various programs to be installed in the auxiliary storage device  203  may be installed by being downloaded from a network via the communication device  205 . 
     &lt;Configuration Related to Temperature Control Function&gt; 
     Next, among respective configuration of the inspection apparatus  100 , a configuration related to the temperature control function that controls the temperature of an electronic device at the time of inspection will be described.  FIG. 3  is a view illustrating a configuration related to the temperature control function among respective configurations of the inspection apparatus. 
     As illustrated in  FIG. 3 , the configuration related to the temperature control function in the inspection apparatus  100  includes:
         a temperature regulator  310  and the temperature sensors  220 _ 1  to  220 _ 4  which are installed in the main chuck  121 ;   the temperature regulator control circuit  124 ; and   the temperature sensor selection part  320  and a temperature controller  330 , which are implemented in the control device  125 .       

     A control program is installed in the control device  125 . When the program is executed, the control device  125  functions at least as the temperature sensor selection part  320  and the temperature controller  330 . 
     As illustrated in  FIG. 3 , when a target temperature is set in the temperature controller  330  and the temperature control is started, the temperature controller  330  calculates a control amount according to the set target temperature and transmits the control amount to the temperature regulator control circuit  124 . The temperature regulator control circuit  124  transmits an operation signal according to the control amount received from the temperature controller  330  to the temperature regulator  310  to operate the temperature regulator  310 . 
     When the temperature of the main chuck  121  changes due to the operation of the temperature regulator  310 , the temperature sensors  220 _ 1  to  220 _ 4  detect the temperature change and feedback temperature data to the temperature controller  330 . 
     The temperature controller  330  acquires temperature data from the temperature sensor selected in advance by the temperature sensor selection part  320  among the temperature data fed back from the temperature sensors  220 _ 1  to  220 _ 4 , and calculates a difference between the temperature data and the target temperature. In addition, the temperature controller  330  calculates a control amount according to the calculated difference (according to the difference, a differential value of the difference, and an integrated value of the difference), and transmits the same to the temperature regulator control circuit  124 . 
     In this way, the temperature controller  330  feeds back the temperature data and performs the temperature control of the electronic device through PID control. 
     The temperature sensor selection part  320  selects in advance a temperature sensor adapted for temperature control based on the “number and positions of electronic devices to be inspected” and the “positions of the temperature sensors  220 _ 1  to  220 _ 4 ”, and notify the temperature controller  330  of information relating to the selected temperature sensor. 
     Of these, the number and positions of the electronic devices to be inspected are acquired, for example, by receiving, by the control device  125 , device arrangement information in advance and reading, by the temperature sensor selection part  320 , the device arrangement information. Alternatively, when a capturing device configured to detect an electronic device is installed in the accommodation chamber  120 , the number and positions of electronic devices may be acquired based on an image captured by the capturing device (a device detection result). The positions of the temperature sensors  220 _ 1  to  220 _ 4  are acquired by reading, by the temperature sensor selection part  320 , sensor arrangement information previously held by the inspection apparatus  100 . 
     &lt;Positional Relationship Between Electronic Device to be Inspected and Temperature Sensor During Inspection&gt; 
     Next, the positional relationship between an electronic device to be inspected and a temperature sensor at the time of inspection will be described.  FIGS. 4A to 4D  are views illustrating examples of positional relationships between electronic devices and temperature sensors at the time of inspection, illustrating positional relationships between electronic devices arranged on a wafer W and temperature sensors, when viewed from above, in the state in which the wafer W is fixed to the main chuck  121  at the time of inspection. 
     Among these, the example of  FIG. 4A  illustrates a positional relationship between four temperature sensors  220 _ 1  to  220 _ 4  and one electronic device  401  to be inspected. In  FIG. 4A , the dotted lines represent a vertical average value and a horizontal average value of coordinates indicating the position of the electronic device  401 . Therefore, in  FIG. 4A , the intersection of the dotted lines is an average vector of the electronic device  401 . 
     The example of  FIG. 4B  illustrates a positional relationship between four temperature sensors  220 _ 1  to  220 _ 4  and four electronic devices  414  to be inspected. In  FIG. 4B , the dotted lines represent a vertical average value and a horizontal average value of coordinates indicating the positions of respective electronic devices  411  to  414 . Therefore, in  FIG. 4B , the intersection of the dotted lines is an average vector of the electronic devices  411  to  414 . 
     The example of  FIG. 4C  illustrates a positional relationship between four temperature sensors  220 _ 1  to  220 _ 4  and four electronic devices  421  to  424  to be inspected. In  FIG. 4C , the dotted lines represent a vertical average value and a horizontal average value of coordinates indicating the positions of respective electronic devices  421  to  424 . Therefore, in  FIG. 4C , the intersection of the dotted lines is an average vector of the electronic devices  421  to  424 . 
     As described above, since the number and positions (i.e., distribution) of electronic devices to be inspected vary, and the positional relationship with the temperature sensors  220 _ 1  to  220 _ 4  also changes depending on the number and positions (distribution) of the electronic devices to be inspected. 
     Therefore, for example, as in the example of  FIG. 4C , when four electronic devices  421  to  424  are arranged in a distribution biased from diagonally upper left to diagonally lower right, it cannot be said that the temperature sensor positioned closest to the average vector is always the appropriate temperature sensor for temperature control. 
     In the example of  FIG. 4C , the temperature sensor closest to the position specified by the average vector (the position of the intersection of the dotted lines) is the temperature sensor  220 _ 3 , but the temperature closest to the alternated long and short dash line directed from diagonally upper left to diagonally lower right is the temperature sensor  220 _ 1 . 
     Here, in order to perform appropriate temperature control for the electronic devices, it is necessary to use typical temperature data for the electronic devices to be inspected. Therefore, as described above, under the situation in which the positional relationships with the temperature sensors  220 _ 1  to  220 _ 4  change depending on the distribution of the electronic devices to be inspected, it is necessary to select the temperature sensor capable of measuring the typical temperature data according to the distribution. That is, in the example of  FIG. 4C , it is desirable to select the temperature sensor  220 _ 1  instead of the temperature sensor  220 _ 3  to perform temperature control. 
     For this reason, the control device  125  of the present embodiment is configured to select a temperature sensor according to the number and positions (distribution) of electronic devices to be inspected. 
     &lt;Functional Configuration of Temperature Sensor Selection Part&gt; 
     Next, among the functions implemented by executing the control program in the control device  125 , the functions of the temperature sensor selection part will be described.  FIG. 5  is a view illustrating an example of a functional configuration of the temperature sensor selection part of the control device. As illustrated in  FIG. 5 , the temperature sensor selection part  320  includes an electronic device position information acquisition part  501 , a temperature sensor position information acquisition part  502 , an average vector calculation part  503 , a Mahalanobis distance calculation part  504 , and a selection part  505 . 
     The electronic device position information acquisition part  501  is an example of an acquisition part, and is configured to acquire coordinates (first coordinate information) indicating the position of an electronic device to be inspected and notify the average vector calculation part  503  and the Mahalanobis distance calculation part  504  of the acquired coordinates. The electronic device position information acquisition part  501  is configured to acquire the coordinates of respective vertices of an electronic device to be inspected (coordinates of four points). 
     Specifically, when there is one electronic device to be inspected, the electronic device position information acquisition part  501  acquires the coordinates of four points. When there are four electronic devices to be inspected, the electronic device position information acquisition part  501  acquires the coordinates of 16 points. 
     The temperature sensor position information acquisition part  502  is an example of the acquisition part, and is configured to acquire coordinates indicating the position of a temperature sensor (second coordinate information) and notify the Mahalanobis distance calculation part  504  of the acquired coordinates. The temperature sensor position information acquisition part  502  is configured to acquire the coordinates of the center points of respective temperature sensors. 
     Specifically, when there are four temperature sensors, the temperature sensor position information acquisition part  502  acquires the coordinates of four points. 
     The average vector calculation part  503  is configured to calculate an average vector (an average value of respective coordinates) from the coordinates indicating the positions of the electronic devices to be inspected and notify the Mahalanobis distance calculation part  504  of the calculated average vector. For example, when there is one electronic device to be inspected, the average vector of the electronic device to be inspected is calculated based on the average value of the coordinates of respective vertices of the electronic device (the coordinates of four points). In addition, for example, when there are four electronic devices to be inspected, the average vector of the electronic device to be inspected is calculated based on the average value of the coordinates of respective vertices of the electronic devices (the coordinates of sixteen points). 
     The Mahalanobis distance calculation part  504  is an example of a calculation part, and is configured to calculate a Mahalanobis distance between the position specified by an average vector of an electronic device to be inspected and the position of each temperature sensor based on the following:
         the coordinates indicating the position of the electronic device to be inspected, notified from the electronic device position information acquisition part  501 ;   the average vector of the electronic device to be inspected notified from the average vector calculation part  503 ; and   the coordinates indicating the positions of temperature sensors, notified from the temperature sensor position information acquisition part  502 .       

     The Mahalanobis distance calculation part  504  is further configured to notify the selection part  505  of the calculated Mahalanobis distances from the positions of respective temperature sensors. 
     The selection part  505  selects a temperature sensor having the minimum Mahalanobis distance temperature among the Mahalanobis distances from the positions of respective temperature sensors, notified from the Mahalanobis distance calculation part  504 , and notifies the temperature controller  330  of the selected temperature sensor. 
     By calculating the Mahalanobis distances in this way, it is possible to select a temperature sensor according to the number and positions (distribution) of electronic devices to be inspected. As a result, the temperature controller  330  can perform temperature control of electronic devices to be inspected using an appropriate temperature sensor. 
     &lt;Specific Example of Processing Performed by Temperature Sensor Selection Part&gt; 
     Next, a specific example of processing performed by the temperature sensor selection part  320  will be described.  FIGS. 6A to 6C  are views illustrating specific examples of processing performed by the temperature sensor selection part, in which specific examples of processing in the case in which the temperature sensor selection part  320  selects one temperature with respect to each positional relationship between the electronic devices and the temperature sensors illustrated in  FIGS. 4A to 4C . 
     As illustrated in  FIG. 6A , the electronic device position information acquisition part  501  acquires coordinates indicating the position of an electronic device  401  (see four black circles). The average vector calculation part  503  calculates an average vector (see a mark X) from the coordinates indicating the position of the electronic device  401 . The Mahalanobis distance calculation part  504  calculates the Mahalanobis distances between the position specified by the average vector of the electronic device  401  and the positions of four respective temperature sensors  220 _ 1  to  220 _ 4 . In  FIG. 6A , the plurality of dotted concentric circles indicate positions at which the Mahalanobis distances are equal when viewed from the position specified by the average vector of the electronic device  401 . 
     According to the example of  FIG. 6A , the selection part  505  selects the temperature sensor  220 _ 3  having the smallest Mahalanobis distance from the position specified by the average vector of the electronic device  401 . As described above, according to the temperature sensor selection part  320 , an appropriate temperature sensor can be selected even when only one electronic device to be inspected is arranged. 
     As illustrated in  FIG. 6B , the electronic device position information acquisition part  501  acquires coordinates indicating the positions of electronic devices  411  to  414  (see sixteen black circles). The average vector calculation part  503  calculates an average vector (see a mark X) from the coordinates indicating the positions of the electronic devices  411  to  414 . The Mahalanobis distance calculation part  504  calculates the Mahalanobis distances between the position specified by the average vector of the electronic devices  411  to  414  and the positions of four respective temperature sensors  220 _ 1  to  220 _ 4 . In  FIG. 6B , the plurality of dotted concentric circles indicate positions at which the Mahalanobis distances are equal when viewed from the position specified by the average vector of the electronic devices  411  to  414 . 
     According to the example of  FIG. 6B , the selection part  505  selects the temperature sensor  220 _ 3  having the smallest Mahalanobis distance from the position specified by the average vector of the electronic devices  411  to  414 . As described above, according to the temperature sensor selection part  320 , an appropriate temperature sensor can be selected even when a plurality of electronic devices to be inspected are arranged in an even distribution. 
     As illustrated in  FIG. 6C , the electronic device position information acquisition part  501  acquires coordinates indicating the positions of electronic devices  421  to  424  (see sixteen black circles). The average vector calculation part  503  calculates an average vector (see a mark X) from the coordinates indicating the positions of the electronic devices  421  to  424 . The Mahalanobis distance calculation part  504  calculates the Mahalanobis distances between the position specified by the average vector of the electronic devices  421  to  424  and the positions of four respective temperature sensors  220 _ 1  to  220 _ 4 . In  FIG. 6C , the plurality of dotted concentric ellipses indicate positions at which the Mahalanobis distances are equal when viewed from the position specified by the average vector of the electronic devices  421  to  424 . 
     According to the example of  FIG. 6C , the selection part  505  selects the temperature sensor  220 _ 1  having the smallest Mahalanobis distance from the position specified by the average vector of the electronic devices  421  to  424 . As described above, according to the temperature sensor selection part  320 , an appropriate temperature sensor can be selected even when a plurality of electronic devices to be inspected are arranged in an uneven distribution. 
     &lt;Details of Processing by Mahalanobis Distance Calculation Part&gt; 
     Next, the details of processing performed by the Mahalanobis distance calculation part  504  when calculating the Mahalanobis distance between the position specified by the average vector of an electronic device and the position of each of the temperature sensors  220 _ 1  to  220 _ 4  will be described.  FIG. 7  is a view illustrating details of processing performed by the Mahalanobis distance calculation part. 
     As illustrated in  FIG. 7 , the Mahalanobis distance (dis(Tx, Ty)) from the temperature sensor  220 _ 1  is calculated based on, for example, Equation 1 below. 
     
       
         
           
             
               
                 
                   
                     
                       
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     In Equation 1 above, p n   x  represents an x-coordinate indicating the position of the n th  (here, n=1) temperature sensor  220 _ 1 , and p n   y  represents a y-coordinate indicating the position of the n th  (here, n=1) temperature sensor  220 _ 1 . Ave x  represents an x-coordinate of an average vector of an electronic device to be inspected, and Ave y  represents a y-coordinate of the average vector of the electronic device to be inspected. In addition, N represents the number of coordinates indicating the position of the electronic device to be inspected. For example, when the number of electronic devices to be inspected is one, N=4, and when the number is four, N=16. 
     Similarly, the Mahalanobis distance calculation part  504  calculates the Mahalanobis distances (dis(Tx, Ty)) for the temperature sensors  220 _ 2  to  220 _ 4  based on Equation 1 above. 
     &lt;Flow of Inspection Processing&gt; 
     Next, a flow of inspection processing in the inspection apparatus  100  will be described.  FIGS. 8A and 8B  are flowcharts illustrating a flow of inspection processing in the inspection apparatus. Of these,  FIG. 8A  illustrates a flow of inspection processing when the number and positions of electronic devices to be inspected are acquired by reading out device arrangement information. 
     In step S 801 , the inspection apparatus  100  reads device arrangement information of electronic devices to be inspected, and acquires the number and positions of the electronic devices to be inspected. 
     In step S 802 , the inspection apparatus  100  performs temperature sensor selection processing and selects a temperature sensor according to the number and positions of the electronic devices to be inspected. Details of the temperature sensor selection processing will be described later. 
     In step S 803 , the inspection apparatus  100  moves a wafer W on which electronic devices to be inspected are arranged to an inspection position. 
     In step S 804 , the inspection apparatus  100  performs temperature control of a main chuck using temperature data measured by the temperature sensor selected in step S 802 . 
     In step S 805 , the inspection apparatus  100  performs an inspection about the electrical characteristics of the electronic devices to be inspected. 
     In this way, when the number and positions of the electronic devices to be inspected are acquired by reading the device arrangement information, the temperature sensor selection processing may be executed before moving the wafer W on which the electronic devices to be inspected are arranged to the inspection position. 
     Meanwhile,  FIG. 8B  illustrates a flow of inspection processing when acquiring the number and positions of electronic devices to be inspected based on a device detection result. 
     In step S 811 , the inspection apparatus  100  moves the wafer W on which the electronic devices to be inspected are arranged to the inspection position. 
     In step S 812 , the inspection apparatus  100  acquires the number and positions of the electronic devices to be inspected based on the device detection result obtained by capturing the electronic devices to be inspected. 
     In step S 813 , the inspection apparatus  100  performs temperature sensor selection processing and selects a temperature sensor according to the number and positions of the electronic devices to be inspected. Details of the temperature sensor selection processing will be described later. 
     In step S 814 , the inspection apparatus  100  performs temperature control of a main chuck using temperature data measured by the temperature sensor selected in step S 813 . 
     In step S 815 , the inspection apparatus  100  performs an inspection about the electrical characteristics of the electronic devices to be inspected. 
     In this way, when the number and positions of the electronic devices to be inspected are acquired based on the device detection result, the temperature sensor selection processing may be executed after moving the wafer W on which the electronic devices to be inspected are arranged to the inspection position. This makes it possible to select an appropriate temperature sensor even when an inspection of electronic devices is performed for the number or positions different from those of the device arrangement information acquired in advance. 
     A case in which an inspection is performed for the number or positions different from those of the device placement information acquired in advance may include, for example, a case in which, after completion of a first round of inspection, a second round of inspection is performed except for the electronic devices determined to be good, or the like. 
     &lt;Flow of Temperature Sensor Selection Processing Performed by Temperature Sensor Selection Part&gt; 
     Next, a flow of temperature sensor selection processing shown in steps S 802  and S 813  of  FIGS. 8A and 8B  will be described.  FIG. 9  is a flowchart illustrating a flow of temperature sensor selection processing. 
     In step S 901 , the average vector calculation part  503  calculates an average vector from the number and positions of electronic devices to be inspected. 
     In step S 902 , the temperature sensor position information acquisition part  502  acquires the position of each temperature sensor. 
     In step S 903 , the Mahalanobis distance calculation part  504  calculates the Mahalanobis distance between the position specified by the average vector of the electronic device to be inspected and the position of each temperature sensor. 
     In step S 904 , the selection part  505  selects a temperature sensor having the smallest Mahalanobis distance from the position specified by the average vector of the electronic devices to be inspected. 
     SUMMARY 
     As is clear from the above description, the inspection apparatus  100  according to the first embodiment is configured to:
         acquire coordinates indicating the positions of the electronic devices in the main chuck and coordinates indicating the positions of the plurality of temperature sensors in the main chuck at the time of inspecting the electrical characteristics of the electronic devices;   calculate the average vector from the coordinates indicating the positions of the electronic devices in the main chuck and calculate the Mahalanobis distance between the position specified by the calculated average vector and the position of each of the plurality of temperature sensors;   select the temperature sensor having the smallest calculated Mahalanobis distance; and   perform the temperature control of the electronic devices using temperature data measured by the selected temperature sensor.       

     As described above, in the inspection apparatus according to the first embodiment, it is possible to select a temperature sensor according to a distribution of inspection objects by calculating the Mahalanobis distances from the position specified by the average vector of the inspection objects. 
     As a result, according to the first embodiment, when performing an inspection for inspection objects, it is possible to select an appropriate temperature sensor and perform temperature control. 
     Second Embodiment 
     In the first embodiment described above, the case illustrated in  FIGS. 4A to 4C  is exemplified as positional relationships between electronic devices to be inspected and temperature sensors. However, the positional relationships between electronic devices to be inspected and temperature sensors are not limited to the case illustrated in  FIGS. 4A to 4C .  FIGS. 10A to 10C  are views illustrating other examples of positional relationships between electronic devices and temperature sensors at the time of inspection. 
     Of these,  FIG. 10A  illustrates a case in which the number of electronic devices to be inspected is nine and respective electronic devices are arranged in a grid pattern.  FIG. 10B  illustrates a case in which the number of electronic devices to be inspected is four and respective electronic devices are arranged in a horizontal row. Furthermore,  FIG. 10C  illustrates a case in which the number of electronic devices to be inspected is three and respective electronic devices are arranged in a horizontal row in a state in which one electronic device is skipped. 
     Then, in any of the cases illustrated in  FIGS. 10A to 10C , an appropriate temperature sensor can be selected by executing the temperature sensor selection processing described in the first embodiment to select the temperature sensor. 
     Third Embodiment 
     In each of the above embodiments, the temperature sensor having the smallest Mahalanobis distance from the position specified by the average vector of the electronic devices is selected. However, the method of selecting a temperature sensor is not limited thereto. As an example, the method may be configured to select m high-ranked temperature sensors having relatively short Mahalanobis distances (where, m is an integer of 1 or more). 
     In this case, temperature data measured by each of the m temperature sensors may be weighted and summed according to the calculated Mahalanobis distance. 
     In each of the above-described embodiments, the case in which the coordinates of each vertex of an electronic device are used as the coordinates indicating the position of the electronic device has been described, but the coordinates indicating the position of the electronic device are limited to the coordinates of each vertex of the electronic device. For example, the coordinates may be coordinates of points distributed two-dimensionally on an electronic device, such as coordinates of a midpoint of each side of the electronic device. 
     It is possible to provide an inspection apparatus, a control method, and a non-transitory computer-readable storage medium storing a control program for selecting an appropriate temperature sensor and performing temperature control when performing an inspection of an inspection object. 
     The present disclosure is not limited to the configurations illustrated herein, such as combinations with other elements in the configurations exemplified in the above-described embodiments or the like. These points can be changed without departing from the gist of the present disclosure, and can be appropriately determined according to an application form thereof