Optical foreign matter inspection device and program

Abstract

Proposed is an optical foreign matter inspection device capable of achieving high accuracy of foreign matter position specification in a wider rotation speed range of a rotary stage.　This optical foreign matter inspection device comprises a first head and a second head for detecting a graduation on an annular scale provided on a rotary stage and outputting a signal. The rotation speed range of the rotary stage to which the first head is compatible with and the rotation speed range of the rotary stage to which the second head is compatible with partially overlap and are relatively different. A calculation control circuit included in the optical foreign matter inspection device sets a head to be used to either the first head or the second head on the basis of the rotation speed of the rotary stage, and determines the rotation angle of the rotary stage on the basis of a signal from the head that is used.

Description

Optical foreign matter inspection device and program

[0001] The present invention relates to an optical foreign matter inspection device and a program therefor.

[0002] An optical foreign particle inspection device is a device that detects foreign particles on a sample, such as a semiconductor wafer made of silicon or gallium arsenide. The optical foreign particle inspection device has a rotary stage and a translation stage that moves the rotary stage in a straight line in the radial direction. The optical foreign particle inspection device detects foreign particles on the sample by irradiating the sample with a laser beam while rotating and translating the rotary stage on which the sample is placed, and monitoring the intensity of the scattered light from the sample surface. The position of the foreign particle is generally identified by reading the scales of a rotary encoder attached to the rotary stage and a linear encoder attached to the translation stage. Patent Document 1 describes an optical foreign particle inspection device configured as described above.

[0003] International Publication No. 2019 / 039712

[0004] In recent years, optical foreign particle inspection systems have been required to achieve both high-sensitivity and high-throughput inspection. To meet this demand, it is necessary to expand the range of rotation speeds that can be supported by the rotary stage.

[0005] However, the rotational speed range of the rotary stage that allows the rotary encoder's scale to be read with high accuracy is determined by the specifications of each rotary encoder. The required rotational speed range is wider than the rotational speed range determined by the specifications. In other words, it is desirable for optical foreign substance inspection devices to achieve high foreign substance location accuracy over a wider rotational speed range of the rotary stage, but there is still room for improvement to achieve this.

[0006] An object of the present invention is to achieve high precision in identifying foreign particle positions over a wider range of rotational speeds of the rotary stage in an optical foreign particle inspection device.

[0007] One embodiment of the present invention is an optical foreign matter inspection device for detecting foreign matters on a surface of a sample, the optical foreign matter inspection device including: a rotary stage on which the sample is placed; a motor for rotating the rotary stage; a base to which the motor is fixed; an annular scale provided on the rotary stage; a first head and a second head that are installed on the base and detect graduations of the scale and output a signal; a laser light source that irradiates a laser beam toward the surface of the sample; an optical sensor that receives scattered light or reflected light of the laser beam from the surface of the sample and outputs a signal according to the intensity of the received light; and a calculation and control circuit that performs processing to identify the position of a foreign particle on the sample based on a signal from the optical sensor and a signal from the optical sensor, wherein the rotational speed range of the rotating stage that the first head can handle and the rotational speed range of the rotating stage that the second head can handle are relatively different so that they partially overlap, and the calculation and control circuit determines either the first head or the second head as the head to be used for identifying the rotation angle of the rotating stage based on the rotational speed of the rotating stage, and determines the rotation angle of the rotating stage based on the signal from the head to be used.

[0008] an optical sensor that receives scattered or reflected light of the laser light from the surface of the sample and outputs a signal according to the intensity of the received light; and a calculation and control circuit that controls the motor and identifies the position of a foreign particle on the sample based on a signal from the head and a signal from the optical sensor. The calculation and control circuit stores head rotation angle correction information, which has a characteristic that changes when an installed rotation angle of the head changes. The calculation and control circuit identifies the rotation angle of the rotary stage based on the signal from the head and corrects the identified rotation angle using the head rotation angle correction information.

[0009] One embodiment of the present invention relates to a measuring device comprising: a rotary stage on which a sample is placed; a motor for rotating the rotary stage; a base to which the motor is fixed; an annular scale provided on the rotary stage; first and second heads installed on the base for detecting graduations on the scale and outputting signals; a laser light source for irradiating a laser beam toward a surface of the sample; an optical sensor for receiving scattered light or reflected light of the laser beam from the surface of the sample and outputting a signal according to the intensity of the received light; and a calculation control circuit including a processor, wherein a rotation speed range of the rotary stage that the first head can handle and a rotation speed range of the rotary stage that the second head can handle are set. a rotation speed range of the rotating stage that is relatively different so as to overlap with a part of the rotation speed range of the rotating stage, the rotation speed range of the rotating stage being relatively different so as to overlap with a part of the rotation speed range of the rotating stage, the program being used in an optical foreign body inspection device, the program causing the processor to execute the following processes: a process of controlling the motor; a process of identifying the position of the foreign body on the sample based on a signal from the first head or the second head and a signal from the optical sensor; a process of determining either the first head or the second head as the head to be used for identifying the rotation angle of the rotating stage based on the rotation speed of the rotating stage; and a process of determining the rotation angle of the rotating stage based on the signal from the head to be used.

[0010] According to one embodiment of the present invention, in an optical foreign substance inspection device, high foreign substance position identification accuracy can be achieved over a wider range of rotation speeds of the rotary stage.

[0011] 1 is a diagram showing an example of the configuration of an optical foreign substance inspection device according to a first embodiment. FIG. 2 is a diagram showing an example of the hardware configuration of a semiconductor circuit device according to the first embodiment. FIG. 3 is a diagram showing a schematic view of a portion of the optical foreign substance inspection device according to the first embodiment that functions as a rotary encoder. FIG. 4 is a diagram showing the change over time in the rotation speed of a rotary stage during inspection and the range of rotation speeds that the head can handle during inspection in the first embodiment. FIG. 5 is a flowchart showing an example of the flow of processing in the optical foreign substance inspection device according to the first embodiment. FIG. 6 is a diagram showing an example of the configuration of an optical foreign substance inspection device according to a second embodiment. FIG. 7 is a diagram for explaining that the rotation angle at which foreign substances on a wafer are detected differs between an ideal rotary encoder and a real rotary encoder in the second embodiment. FIG. 8 is a diagram showing an example of the change in the rotation angle based on the pulse count number of the encoder relative to the true rotation angle in the second embodiment. FIG. 9 is a diagram showing the concept of encoder correction information and an example thereof. FIG. 10 is a flowchart showing an example of the flow of processing in an optical foreign substance inspection device 2 according to the second embodiment. FIG. 11 is a diagram showing an example of the configuration of an optical foreign substance inspection device according to a third embodiment. FIG. 12 is a flowchart showing an example of the flow of processing by a first method for generating encoder correction information in the optical foreign substance inspection device according to the third embodiment. FIG. 13 is a diagram for explaining in detail the first method for generating correction information according to the third embodiment. 13. A flowchart showing an example of the processing flow by a second generation method of encoder correction information in the optical foreign matter inspection device according to the fourth embodiment. A diagram for explaining a calculation method of angular velocity and angular acceleration in the fourth embodiment. A diagram for explaining the calculation flow of correction information in the fourth embodiment. A diagram showing an example of a graph obtained by plotting the rotation angle correction amount against the rotation angle based on the pulse count number of the encoder according to the fifth embodiment. A diagram for explaining a method of diagnosing the state of an encoder according to the sixth embodiment. A diagram showing an example of the configuration of a management system according to the seventh embodiment. An example of an image of a GUI displaying the monitoring results of multiple optical foreign matter inspection devices according to the seventh embodiment. A flowchart showing an example of the processing flow in the optical foreign matter inspection device according to the eighth embodiment.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, identical elements are generally designated by the same reference numerals, and repeated description will be omitted. When there are multiple identical or similar components, they may be described by using the same reference numerals with different subscripts. In the drawings, the depiction of each component may not represent its actual position, size, shape, scope, etc., in order to facilitate understanding of the invention, and the present invention is not necessarily limited to the position, size, shape, scope, etc., disclosed in the drawings. Expressions such as identification information, identifiers, IDs, names, and numbers for various data and information are interchangeable.

[0013] The functional blocks, circuits, computers, processing units, etc. that make up a device or system may be realized by electronic circuits combining electronic components, or they may be realized by a semiconductor device such as a processor or a computer including a processor executing a predetermined program.

[0014] A processor is composed of semiconductor devices such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or an MCU (Micro Controller Unit). A processor is composed of devices or circuits capable of performing predetermined calculations. The processing is not limited to software program processing, but can also be performed by dedicated circuits. Examples of the dedicated circuits that can be used include FPGAs (Field Programmable Gate Arrays) and ASICs (Application Specific Integrated Circuits).

[0015] The program may be pre-installed as data on the target computer, or may be distributed as data from a program source to the target computer and then installed. The program source may be a program distribution server on a communication network, or a non-transitory computer-readable storage medium. The program may be composed of multiple program modules. The computer system may be composed of multiple devices.

[0016] First Embodiment The first embodiment of the present invention relates to an optical foreign substance inspection device that expands the range of rotational speeds of a rotating stage that can be used to identify the rotational angle position of the rotating stage. The optical foreign substance inspection device according to the first embodiment is equipped with a first head that has a relatively high range of rotational speeds that can be read, and a second head that has a relatively low range of rotational speeds that can be read, as heads that read the graduations of an annular scale provided on the rotating stage. The optical foreign substance inspection device according to the first embodiment switches the head to be used based on the rotational speed of the rotating stage.

[0017] <Configuration of Optical Foreign Material Inspection Apparatus According to First Embodiment> Fig. 1 is a diagram showing an example of the configuration of an optical foreign material inspection apparatus according to the first embodiment. As shown in Fig. 1, the optical foreign material inspection apparatus 1 according to the first embodiment includes a laser light source 102, an optical sensor 105, a stage unit 113, and a calculation and control circuit 114. The stage unit 113 includes a rotating stage 107, a scale 108, a first head 109h, a second head 110h, a motor 111, and a base 112. The calculation and control circuit 114 further includes a stage control circuit 115, a computer 119, and an overall control circuit 139.

[0018] The rotary stage 107 has a roughly disk shape and is configured to be rotatable around the central axis of the rotary stage 107. A sample to be inspected is placed and held on the surface of the rotary stage 107. Here, the sample is assumed to be a wafer 106. The wafer 106 is, for example, a semiconductor wafer made of a material such as silicon or gallium arsenide.

[0019] The rotary stage 107 is connected to the rotation shaft of a motor 111, and rotates in a horizontal plane when the motor 111 is driven. The motor 111 is supported and fixed by a base 112. The base 112 has a mechanism that allows linear movement in the direction of the rotation radius of the rotary stage 107, and moves horizontally in a straight line when driven by a drive source (not shown). In other words, the rotary stage 107 is configured to perform rotational and translational motion.

[0020] The scale 108 is annular and is provided on the rear surface, i.e., bottom surface, of the rotary stage 107 so that the center of rotation of the rotary stage 107 and the geometric center of the scale 108 are in the same position except for mounting errors.

[0021] The first head 109h and the second head 110h are mounted on a base 112. The combination of the scale 108 and the first head 109h constitutes a first encoder 109. The combination of the scale 108 and the second head 110h constitutes a second encoder 110. In other words, the scale 108 is shared by the first encoder 109 and the second encoder 110.

[0022] The first encoder 109 outputs a read signal at the timing when the first head 109h detects and reads the graduations on the scale 108. Similarly, the second encoder 110 outputs a read signal at the timing when the second head 110h detects and reads the graduations on the scale 108. The read signal from the first head 109h, i.e., the first encoder 109, and the read signal from the second head 110h, i.e., the second encoder 110, are sent to the stage control circuit 115 almost in real time.

[0023] A laser light source 102 irradiates a wafer 106 on the surface of a rotating and translating rotary stage 107 with laser light 103. An optical sensor 105 receives scattered light 104 of the laser light 103 from the surface of the wafer 106 and outputs a light intensity signal 101 corresponding to the intensity of the received light.

[0024] In other words, the rotating stage 107 is rotated by the motor 111 while holding the wafer 106, and the base 112 moves in a translational motion, causing the wafer 106 to move relative to the irradiation point of the laser light 103, resulting in the laser light 103 scanning the entire wafer 106.

[0025] The intensity of the scattered light 104 received by the optical sensor 105 depends on the state of the surface of the wafer 106, for example, the presence of foreign matter, and the elevations, i.e., unevenness, of the surface. Therefore, by thoroughly scanning the surface of the wafer 106 with the laser light 103 and mapping the coordinates of the irradiation points of the laser light 103 in correspondence with the intensity of the scattered light 104 from those irradiation points, it becomes possible to determine the presence or absence of foreign matter or unevenness on the surface of the wafer 106, the positions of the foreign matter or unevenness, the size of the foreign matter or unevenness, etc. The coordinates of the irradiation point of the laser light 103 are specified by the rotation angle of the rotary stage 107 from an angular reference and the position in the translation direction of the rotary stage 107.

[0026] In the present application, foreign matter present on the surface of the wafer 106, and recesses, protrusions, and the like formed on the surface may be collectively referred to as "foreign matter."

[0027] The stage control circuit 115 includes a first encoder rotation angle calculation circuit 116 , a second encoder rotation angle calculation circuit 117 , and a motor rotation control circuit 118 .

[0028] The first encoder rotation angle calculation circuit 116 calculates the rotation angle of the rotary stage 107 based on a read signal of the graduations of the scale 108 from the first encoder 109, and outputs the calculated rotation angle as a first encoder rotation angle read value 120. The second encoder rotation angle calculation circuit 117 calculates the rotation angle of the rotary stage 107 based on a read signal of the graduations of the scale 108 from the second encoder 110, and outputs the calculated rotation angle as a second encoder rotation angle read value 122. The motor rotation control circuit 118 controls the power supplied to the motor 111 based on an input control signal or a set sequence, and as a result, controls the rotation speed, i.e., angular velocity, and rotation acceleration, i.e., angular acceleration, of the rotary stage 107.

[0029] The computer 119 includes a rotation angle read value selector 125 and an image generation circuit 136. The selector 125 is connected to the first encoder rotation angle calculation circuit 116 and the second encoder rotation angle calculation circuit 117. The selector 125 receives a control signal or a signal indicating the rotation speed of the rotation stage 107 from the stage control circuit 115. Based on the received signal, the selector 125 selects either the first encoder rotation angle read value 120 or the second encoder rotation angle read value 122 as the rotation angle read value of the rotation stage 107 appropriate for the current rotation angle of the rotation stage 107. The selector 125 outputs the selected rotation angle read value to the image generation circuit 136 as a selected rotation angle read value 124.

[0030] The image generation circuit 136 acquires the post-selection rotation angle read value 124, the base translation direction position information 121, and the light intensity signal 101. The image generation circuit 136 identifies the coordinates of the irradiation point of the laser beam 103 based on the post-selection rotation angle read value 124 and the base translation direction position information 121. The image generation circuit 136 also identifies the intensity of scattered light from the irradiation point of the laser beam 103 based on the light intensity signal 101. The image generation circuit 136 maps, for each coordinate of the irradiation point of the laser beam 103, the coordinates and the intensity of scattered light from the irradiation point at that coordinate, and generates an image representing the obtained map.

[0031] The stage control circuit 115 and the computer 119 are connected to an overall control circuit 139 , and a user 140 can control them via the overall control circuit 139 .

[0032] The calculation and control circuit 114 also includes a display (not shown), and is capable of displaying an image of the location of a foreign particle on the wafer 106, as well as various other GUIs (Graphical User Interfaces), on the screen of the display. By viewing the image displayed on the display, the user 140 can learn the state of the surface of the wafer 106, i.e., the presence or absence of a foreign particle, the location of the foreign particle, the size of the foreign particle, etc.

[0033] All or part of the calculation control circuit 114 is configured, for example, by a computer including a processor, a semiconductor circuit device such as a semiconductor IC chip, etc. Here, the hardware configuration of such a semiconductor circuit device will be described.

[0034] 2 is a diagram showing an example of the hardware configuration of a semiconductor circuit device according to the first embodiment. As shown in Fig. 2, a semiconductor circuit device 150 includes, for example, a processor 151, a memory 152, a storage 153, an interface 154, and a communication bus 155. The processor 151, the memory 152, the storage 153, and the interface 154 are each electrically connected to the communication bus 155 and are configured to be able to communicate with each other via the communication bus 155.

[0035] In the semiconductor circuit device 150, a program PG for executing various processes is stored in the storage 153 or the memory 152. The processor 151 reads out this program PG, expands it in the memory 152, and executes it to realize various functional blocks, circuits, etc. The calculation control circuit 114 may be realized by a single semiconductor circuit device or by multiple semiconductor circuit devices. The calculation control circuit 114 may be realized by a semiconductor device including a single processor or by a semiconductor device including multiple processors.

[0036] Next, the rotary encoder mounted on the optical foreign matter inspection device 1 will be described in more detail.

[0037] 3 is a diagram schematically showing a portion of the optical foreign matter inspection device 1 according to the first embodiment that functions as a rotary encoder. The portion that functions as a rotary encoder is a portion required to measure the rotational angle position of the motor 111.

[0038] Generally, a rotary encoder is composed of a combination of a scale and a head. The scale and head are fixed exclusively to either the rotating body or the base that supports the rotating body, respectively. The head can determine the rotation angle of the scale, i.e., the rotation angle of the rotating body, by reading the graduations on the scale.

[0039] A rotary encoder typically has a readable rotational speed range defined in its specifications. The readable rotational speed range refers to the range of rotational speeds of the scale at which the scale graduations can be read with a certain level of accuracy or higher. Here, it is assumed that the scale 108 is mounted on the rotating stage 107 and rotates integrally with the rotating stage 108. Therefore, the readable rotational speed range of the rotary encoder can also be said to be the rotational speed of the rotating stage 108 at which the reading accuracy of the scale graduations on the scale 108 is guaranteed to be a certain level or higher. In this application, the readable rotational speed range of the head, i.e., the encoder, is also referred to as the compatible rotational speed range or the compatible rotational speed range.

[0040] A plurality of rotary encoders are mounted on the optical foreign substance inspection device 1. The rotational speed ranges available for these rotary encoders are different, and the rotational speed ranges that are close to each other partially overlap. Here, it is assumed that the optical foreign substance inspection device 1 is mounted with two rotary encoders, a first encoder 109 and a second encoder 110.

[0041] In this embodiment, as described above, the scale 108 is fixed to the rotary stage 107, and the first head 109h and the second head 110h are fixed to the base 112. The scale 108 is annular and is disposed on the rear surface of the rotary stage 107. The rotation center of the rotary stage 107 and the geometric center of the scale 108 are located at the same position except for mounting errors. Furthermore, the first head 109h and the second head 110h are disposed apart by an appropriate inter-head installation angle difference 142, for example, 90°.

[0042] The first encoder 109 and the second encoder 110 share the scale 108, and the two heads, i.e., the first head 109h and the second head 110h, have different ranges of rotational speed that they can handle, but some ranges overlap. Here, the range of rotational speed that the first head 109h can handle is relatively high, and the range of rotational speed that the second head 110h can handle is relatively low.

[0043] In this embodiment, the scale 108 rotates in conjunction with the rotation of the rotary stage 107, and the scale 108 rotates relative to the first head 109h and the second head 110h, making it possible to measure the rotation angle of the rotary stage 107.

[0044] As an example, the rotary encoder according to this embodiment is assumed to be an incremental type. The first head 109h and the second head 110h detect and read the scale 108's equiangular graduations 145 and output pulse signals at the timing of their reading. These pulse signals are also referred to as encoder pulses. The stage control circuit 115 measures the rotation angle of the rotary stage 107 by integrating the pulse signals output from the first head 109h and the second head 110h. The scale 108 is provided with an angle reference 141 in addition to the graduations 145. The first head 109h and the second head 110h detect the angle reference 141 to detect that the scale 108 has completed one rotation. The stage control circuit 115 also measures the rotation speed of the rotary stage 107 based on the difference in detection time of the angle reference 141.

[0045] 4 is a diagram showing the time change in the rotation speed of the rotary stage during inspection and the range of rotation speeds that the head can handle in the first embodiment. Rotary encoders generally have a rotation speed range that is determined by their specifications, based on factors such as filter constants within the head. As shown in graphs F4a and F4b in FIG. 4, if the rotation speed during the inspection period falls within the range of rotation speeds that a single rotary encoder can handle, such as when the rotation speed of the rotary stage is constant during the inspection period, then it is sufficient to continue using only that rotary encoder during the inspection period.

[0046] For example, if the rotation speed of the rotating stage 107 falls within the range R1 of rotation speeds that can be handled by the high-speed encoder, or if the rotation speed of the rotating stage 107 falls within the range R2 of rotation speeds that can be handled by the low-speed encoder, there is no need to switch the encoder being used.

[0047] However, as shown in graph F4c in Figure 4, if the rotation speed of the rotating stage changes during the inspection period and exceeds the range of rotation speeds that can be handled by a single rotary encoder, continuing to use the same rotary encoder as when the inspection began will increase detection errors in the read signal from the encoder at rotation speeds outside the range of rotation speeds that can be handled, and the accuracy of identifying the rotation angle position will decrease.

[0048] For example, if the rotation speed of the rotating stage 107 gradually increases, the encoder used must be switched from a low-speed encoder to a high-speed encoder when the rotation angle enters a common rotation speed range R3, which is the overlapping portion of the compatible rotation speed ranges R1 and R2.

[0049] In this embodiment, as described above, the selector 125 selects either the first encoder rotation angle read value 120 or the second encoder rotation angle read value 122 as the rotation angle read value of the rotating stage 107 that is appropriate for the current rotation angle of the rotating stage 107, based on the control signal received from the stage control circuit 115 or the signal indicating the rotation speed of the rotating stage 107. Therefore, in this embodiment, it is possible to increase the usable rotation speed of the rotating stage 107 without reducing the accuracy of identifying the rotation angle position of the rotating stage 107.

[0050] 5 is a flowchart showing an example of a process flow in the optical foreign matter inspection device according to the first embodiment. This flowchart shows a method for expanding the range of rotational speeds that the rotation stage 107 can handle during inspection by the optical foreign matter inspection device 1.

[0051] The process flow in the optical foreign particle inspection device according to the first embodiment will now be described, assuming that the preparatory processes leading up to the start of inspection have already been performed. Specifically, the motor rotation control circuit 118 controls the motor 111 to rotate the rotary stage 107. The overall control circuit 139 controls the laser light source 102 to irradiate the wafer 106 with laser light 103. The optical sensor 105 receives scattered light 104 from the wafer 106 and outputs a light intensity signal 101 corresponding to the intensity of the received light. The stage control circuit 115 initially selects either the first encoder 109 or the second encoder 110 as the encoder to be used, based on the set rotation speed of the rotary stage 107 or its change over time.

[0052] As shown in FIG. 5 , in step S101, a process of detecting encoder pulses is performed. Specifically, the inspection is started by the overall control circuit 139 controlling each component. During the inspection, the stage control circuit 115 receives and detects pulse signals, which are read signals, from the first encoder 109 and the second encoder 110. The first encoder rotation angle calculation circuit 116 in the stage control circuit 115 calculates the rotation angle of the rotary stage 107 based on the pulse count of the first encoder 109 and outputs the calculated value to the selector 125. The second encoder rotation angle calculation circuit 117 in the stage control circuit 115 calculates the rotation angle of the rotary stage 107 based on the pulse count of the second encoder 110 and outputs the calculated value to the selector 125.

[0053] Under control of the stage control circuit 115, the selector 125 selectively outputs to the image generation circuit 136 either a rotation angle based on the pulse count number of the first encoder 109 or a rotation angle based on the pulse count number of the second encoder 110. When the first encoder 109 is set as the encoder to be used, the selector 125 outputs the rotation angle based on the pulse count number of the first encoder 109, and when the second encoder 110 is set as the encoder to be used, the selector 125 outputs the rotation angle based on the pulse count number of the second encoder 110. After the processing of step S101 is completed, the processing proceeds to step S102.

[0054] In step S102, a process is performed to determine whether or not the angle reference has been detected. That is, a process is performed to determine whether or not the rotary stage 107 or the scale 108 has rotated once. Specifically, the stage control circuit 115 determines whether or not the angle reference 141 has been detected based on a read signal from the encoder used or another encoder. Here, if it is determined that the angle reference 141 has been detected (S101: Yes), the process proceeds to step S103. On the other hand, if it is determined that the angle reference 141 has not been detected (S101: No), the process returns to step S101.

[0055] In step S103, a process is performed to determine whether the rotation speed falls within the common rotation speed range of the encoders. Specifically, the stage control circuit 115 measures the rotation speed of the rotary stage 107 based on a signal from the first encoder 109 or the second encoder 110. The stage control circuit 115 also determines whether the measured rotation speed falls within the common rotation speed range that can be supported by the first encoder 109 and the second encoder 110. Here, if it is determined that the measured rotation speed falls within the common rotation speed range (S103: Yes), the process proceeds to step S104. On the other hand, if it is determined that the measured rotation speed does not fall within the common rotation speed range (S103: No), the process returns to step S101.

[0056] In step S104, a process is performed to determine whether to switch the encoder to be used. That is, a process is performed to determine whether to switch the head to be used. Specifically, the stage control circuit 115 determines whether to switch the encoder to be used based on the set rotation speed of the rotary stage 107 or the change in the set rotation speed over time.

[0057] For example, if the rotation speed of the rotating stage 107 is in the process of increasing over time, that is, if the rotation speed is set to change from the lower rotation speed range that the second encoder 110 can accommodate to the higher rotation speed range that the first encoder 109 can accommodate, a decision is made to switch the encoder to be used from the second encoder 110 to the first encoder 109.

[0058] Also, for example, if the rotation speed of the rotating stage 107 is in the process of decreasing over time, that is, if the rotation speed is set to change from the high-speed rotation speed range that the first encoder 109 can handle to the low-speed rotation speed range that the second encoder 110 can handle, a decision is made to switch the encoder to be used from the first encoder 109 to the second encoder 110.

[0059] Also, for example, if the rotation speed is set to be constant, it is determined not to switch the encoder to be used.

[0060] If it is determined that the encoder should be switched (S104: Yes), the process proceeds to step S105. On the other hand, if it is determined that the encoder should not be switched (S104: No), the process returns to step S101.

[0061] In step S105, a process of switching the encoder is performed. Specifically, the stage control circuit 115 controls the selector 125 in the computer 119 to execute a process of switching the encoder to be used or its signal. For example, if the encoder to be used is the first encoder 109, it is switched to the second encoder 110. Also, if the encoder to be used is the second encoder 110, it is switched to the first encoder 109. Once the switching of the encoder to be used is completed, the process proceeds to step S106.

[0062] In step S106, a process is performed to determine whether or not to end the test. Specifically, whether or not to end the test is determined based on the set test sequence, the presence or absence of an error signal, etc. If it is determined that the test should be ended (S106: Yes), the process returns to step S101 and the process continues. On the other hand, if it is determined that the test should not be ended (S106: No), the process is ended.

[0063] As described above, according to the first embodiment, detection of encoder pulses is repeated until the rotary stage 107 makes one rotation, and the calculation of the rotation angle of the rotary stage 107 continues. The rotation speed of the rotary stage 107 is determined when the angle reference 141 of the scale 108 is detected. Based on the determined rotation speed, either the first head 109h or the second head 110h that is compatible with that rotation speed is selected as the head to be used to determine the rotation angle of the rotary stage 107. Furthermore, if the determined rotation speed falls within the common rotation speed range of the two rotary encoders, the rotary encoder to be used is switched if necessary. Furthermore, the rotation angle of the rotary stage 107 is calculated based on the signal from the head to be used. In this way, by monitoring the rotation speed of the rotary stage 107 and switching the rotary encoder signals within the common rotation speed range between the rotary encoders, the range of rotation speeds that the rotary stage 107 can support during the inspection can be expanded.

[0064] That is, according to the first embodiment, in the optical foreign substance inspection device, it is possible to achieve high foreign substance position identification accuracy over a wider range of rotation speeds of the rotary stage.

[0065] Second Embodiment A second embodiment of the present invention relates to an optical foreign substance inspection device that has a function for reading the rotational angle position of a rotation stage, and identifies the rotational angle with even higher accuracy while expanding the range of applicable rotational speeds. The optical foreign substance inspection device according to the second embodiment is based on, for example, the optical foreign substance inspection device according to the first embodiment, and further includes a function for correcting errors in the rotational angle based on a pulse signal read from a scale by an encoder. When a rotational angle based on a signal from a first encoder is used, the rotational angle is corrected using correction information for the first encoder. When a rotational angle based on a signal from a second encoder is used, the rotational angle is corrected using correction information for the second encoder.

[0066] It is assumed here that the above error occurs due to a deviation between the center of rotation of the scale and its geometric center, which is due to the molding accuracy or mounting accuracy of the scale. It is also assumed that the above error occurs due to a deviation between the rotation speed determined based on the time interval between the detection of the scale graduations by the first head or the second head, which is due to the scale graduations not being arranged at equal intervals.

[0067] Fig. 6 is a diagram showing an example of the configuration of an optical foreign substance inspection apparatus according to the second embodiment. As shown in Fig. 6, the optical foreign substance inspection apparatus 2 according to the second embodiment has a basic configuration similar to that of the optical foreign substance inspection apparatus 1 according to the first embodiment. The computer 119 in the optical foreign substance inspection apparatus 2 further includes a first encoder correction information storage circuit 128, a second encoder correction information storage circuit 129, an encoder correction information selector 132, and a rotation angle correction circuit 134.

[0068] The first encoder correction information storage circuit 128 stores first encoder correction information 128j, and the second encoder correction information storage circuit 129 stores second encoder correction information 129j. The first encoder correction information 128j is correction information used for correcting the rotation angle including an error output from the first encoder rotation angle calculation circuit 116 to approach the true rotation angle. The second encoder correction information 129j is correction information used for correcting the rotation angle including an error output from the second encoder rotation angle calculation circuit 117 to approach the true rotation angle.

[0069] The first encoder correction information 128j is also rotation angle correction information for the first head, and has a characteristic that changes with changes in the installation rotation angle of the first head 109h and the amount of eccentricity of the scale 108. Similarly, the second encoder correction information 129j is also rotation angle correction information for the second head, and has a characteristic that changes with changes in the installation rotation angle of the second head 110h and the amount of eccentricity of the scale 108.

[0070] The selector 132 switches the correction information used to correct the rotation angle between the first encoder correction information 128j and the second encoder correction information 129j, based on a control signal from the stage control circuit 115. When the rotation angle to be used is the rotation angle output from the first encoder rotation angle calculation circuit 116, the selector 132 outputs the first encoder correction information 128j to the rotation angle correction circuit 134. On the other hand, when the rotation angle to be used is the rotation angle output from the second encoder rotation angle calculation circuit 117, the selector 132 outputs the second encoder correction information 129j to the rotation angle correction circuit 134.

[0071] The rotation angle correction circuit 134 receives the rotation angle output from the selector 125 and the correction information output from the selector 132, corrects the input rotation angle using the input correction information, and outputs the corrected rotation angle 135 to the image generation circuit 136.

[0072] The image generation circuit 136 specifies the position of the irradiation point of the laser beam 103 based on the base translation direction position information 121 input from the stage control circuit 115 and the corrected rotation angle 135 of the rotation stage 107 input from the rotation angle correction circuit 134. The image generation circuit 136 also specifies the scattered light intensity of the laser beam 103 from the position of the irradiation point based on the light intensity signal 101 input from the optical sensor 105. The image generation circuit 136 then maps the specified position of the irradiation point of the laser beam 103 in association with the scattered light intensity of the laser beam 103 from the position of the irradiation point, and generates an image.

[0073] FIG. 7 is a diagram illustrating the difference in rotation angle at which a foreign particle on a wafer is detected between an ideal rotary encoder and a real rotary encoder in the second embodiment. As shown in FIG. 7 , a notch 106a is present on the wafer 106, which serves as a reference for the rotation angle position. As an example, as shown in the upper diagram F7a of FIG. 7 , assume that a foreign particle 106b is present at a rotation angle θd clockwise from the upper direction of the diagram when the notch 106a is positioned downward in the diagram, with the upper direction in the diagram being the rotation angle 0°. The lower diagram F7b of FIG. 7 illustrates the timing at which rotary encoder pulses are detected, with the horizontal axis representing the true rotation angle θ.

[0074] In an ideal encoder, encoder pulse signals are detected at equal intervals with respect to a linear change in the true rotation angle θ. Here, assume that the ideal encoder pulse signal corresponding to the rotation angle θd of the foreign object 106b is the 14th pulse signal from the state where the rotation angle θ = 0. In contrast, in actual rotary encoders, the first encoder 109 and the second encoder 110, the detection intervals of pulse signals relative to the rotation angle θ are not constant due to factors such as eccentricity of the scale and distortion of the scale 108. Therefore, the encoder pulse signal corresponding to the rotation angle θd at which the foreign object 106b is detected may deviate from the pulse count, i.e., the pulse number, of the ideal encoder. For example, the first encoder 109 may detect the 16th pulse, and the second encoder 110 may detect the 10th pulse.

[0075] A rotary encoder can only detect the divisions of the scale 108, not the actual rotation angle, and conversion from the pulse count counted corresponding to the divisions of the scale 108 to the rotation angle θ is normally performed on the assumption that the encoder is ideal. Therefore, unless this deviation is corrected, the detected rotation angle of the foreign object 106b when the first encoder 109 is used and when the second encoder 110 is used may differ, and further, the detected rotation angle may differ from the actual rotation angle θd of the foreign object 106b.

[0076] 8 is a diagram showing an example of changes in rotation angle α based on the encoder pulse count relative to the true rotation angle θ in the second embodiment. In the graph shown in Fig. 8, the horizontal axis represents the true rotation angle θ, and the vertical axis represents the rotation angle α based on the encoder pulse count. The rotation angle α based on the pulse count is obtained by integrating the number of pulse signals output from the encoder in response to detection of the scale graduations, and multiplying this integrated value by the angle corresponding to the interval between the graduations.

[0077] 8, the rotation angle read value α based on the pulse count of an ideal encoder is represented by a solid straight line. The rotation angle read value α based on the pulse count of the first encoder 109 is represented by a curved dashed line with short intervals. Furthermore, the rotation angle read value α based on the pulse count of the second encoder 110 is represented by a curved dashed line with long intervals. Note that the rotation angle read value α from an encoder is inherently discrete, but here it is shown continuously, assuming that the encoder resolution, i.e., the total number of pulses detected per rotation, is sufficiently large.

[0078] As shown in Figure 8, in an ideal encoder, the relationship between the true rotation angle θ and the rotation angle read value α from the encoder is represented by a straight line. However, in an actual encoder, due to variations in pulse intervals, the relationship between the true rotation angle θ and the rotation angle read value α from the encoder is represented by a curve that starts at 0° and ends at 360°, and the shape of the curve varies depending on the head installation position. If the difference between the line corresponding to the ideal encoder and the curve corresponding to the actual encoder in this graph is known in advance, the true rotation angle θ can be obtained by adding this difference to the rotation angle read value α from the actual encoder. That is, this difference can be stored as correction information in the calculator 119, and the true rotation angle θ can be calculated by correcting the rotation angle read value α from the encoder using the correction information.

[0079] FIG. 9 is a diagram showing the concept of and an example of encoder correction information in the second embodiment. Here, it is assumed that the encoder read pulse count corresponding to a rotation angle of 360° is 1000. In other words, it is assumed that the rotation angle resolution is 360° / 1000. Diagram F9a in the upper left of FIG. 9 shows a correction table that is an example of correction information for the first encoder 109, and diagram F9b in the upper right of FIG. 9 shows a correction table that is an example of correction information for the second encoder 110. These correction tables associate the encoder pulse count with the true rotation angle or the rotation angle correction amount for obtaining the true rotation angle.

[0080] 9 shows an example of a graph obtained by plotting the rotation angle correction amount against the encoder pulse count number on the horizontal axis and the rotation angle correction amount on the vertical axis. In this graph, an example of a graph curve corresponding to the first encoder 109 is represented by a dashed line with short intervals, and an example of a graph curve corresponding to the second encoder 110 is represented by a dashed line with long intervals.

[0081] From the above, for example, an engineer checks in advance the pulse count number, the true rotation angle corresponding to that pulse count number, the rotation angle correction amount, etc. for each pulse count number of the encoder for all encoders mounted in the optical foreign substance inspection device 2. Furthermore, a correction table that associates the pulse count number with the true rotation angle or the rotation angle correction amount for each pulse count number for each encoder is stored as correction information in the computer 119. Here, such correction tables are stored in the computer 119 as first encoder correction information 128j and second encoder correction information 129j.

[0082] Then, whenever the computer 119 detects a pulse from the encoder in use, it references the correction table for that encoder and corrects the rotation angle read value based on the encoder pulse count using the corresponding rotation angle correction amount. Alternatively, whenever the computer 119 detects a pulse from the encoder in use, it references the correction table for that encoder and directly identifies the true rotation angle corresponding to the encoder pulse count. This is essentially the same process as correcting the rotation angle read value to obtain the true rotation angle. By performing this process, the computer 119 can easily determine the true rotation angle.

[0083] 10 is a flowchart showing an example of the processing flow in the optical foreign matter inspection device 2 according to the second embodiment. This flowchart shows a method for determining the true rotation angle based on the pulse count number of the rotary encoder and a method for expanding the range of applicable rotation speeds.

[0084] The processing contents of steps S101, S102, S103, and S106 in the flowchart shown in Fig. 10 are substantially the same as the processing contents of the steps with the same reference numerals in the flowchart shown in Fig. 5. Therefore, detailed description of the processing of these steps will be omitted.

[0085] First, in step S101, a process of detecting encoder pulses is performed. Through this process, the rotation angle of the rotary stage 107 is derived based on the number of pulses counted from the encoder used.

[0086] Next, in step S107, the correction information is referenced using the pulse count number as a key, and a process is performed to determine the true rotation angle. Specifically, under control of the stage control circuit 115, the selector 132 outputs correction information corresponding to the encoder being used to the rotation angle correction circuit 134. For example, if the encoder being used is the first encoder 109, the selector 132 outputs first encoder correction information 128j to the rotation angle correction circuit 134. The rotation angle correction circuit 134 receives the rotation angle based on the pulse count number of the encoder being used from the selector 125, and receives the correction information corresponding to the encoder being used from the selector 132.

[0087] The rotation angle correction circuit 134 corrects the input rotation angle reading value using the rotation angle correction amount obtained by referring to the input correction information, and outputs a corrected rotation angle 135 representing the true rotation angle to the image generation circuit 136.

[0088] In this example, the first encoder rotation angle calculation circuit 116 or the second encoder rotation angle calculation circuit 117 in the stage control circuit 115 calculates the rotation angle based on the pulse count number of the encoder, and the calculated rotation angle is sent to the rotation angle correction circuit 134 via the selector 125.

[0089] On the other hand, as another example, the first encoder rotation angle calculation circuit 116 or the second encoder rotation angle calculation circuit 117 may send the encoder pulse count number itself to the rotation angle correction circuit 134 via the selector 125. In this case, the rotation angle correction circuit 134 refers to the correction information based on the input pulse count number, directly reads the corresponding true rotation angle, and outputs a corrected rotation angle 135 representing the true rotation angle to the image generation circuit 136.

[0090] The true rotation angle may be determined by either of the two methods described above, and this also applies to the other embodiments.

[0091] Next, in step S102, a process is performed to determine whether or not the angle reference 141 has been detected, i.e., whether or not the rotation stage 107 or the scale 108 has rotated once. If it is determined that the angle reference 141 has been detected (S101: Yes), the process proceeds to step S103. On the other hand, if it is determined that the angle reference 141 has not been detected (S101: No), the process returns to step S101.

[0092] In step S103, a process is performed to determine whether the rotation speed falls within the common rotation speed range of the encoder. If it is determined that the measured rotation speed falls within the common rotation speed range (S103: Yes), the process proceeds to step S108. On the other hand, if it is determined that the measured rotation speed does not fall within the common rotation speed range (S103: No), the process returns to step S101.

[0093] In step S108, a process is performed to determine whether to switch the encoder to be used, i.e., the head to be used and the correction table to be used. Specifically, the stage control circuit 115 determines whether to switch the head to be used and the correction information to be used based on the set rotation speed or the change in the set rotation speed over time.

[0094] For example, if the rotation speed is set to change from a lower rotation speed range that can be handled by the first encoder 109 to a higher rotation speed range that can be handled by the second encoder 110, a determination is made to switch the encoder to be used from the first encoder 109 to the second encoder 110. Also, if the set rotation speed is a constant speed, a determination is made not to switch the encoder to be used. If it is determined to switch the encoder to be used (S108: Yes), the processing proceeds to step S109. On the other hand, if it is determined not to switch the encoder to be used (S108: No), the processing returns to step S101.

[0095] In step S109, a process of switching the encoder to be used and the correction information to be used is performed. Specifically, the stage control circuit 115 controls the selector 125 and the selector 132 in the computer 119 to switch the signal of the encoder to be used and to switch the correction information to be used to the correction information corresponding to the switched encoder. For example, if the signal from the encoder to be used is the signal from the first encoder 109, the signal from the encoder to be used is switched to the signal from the second encoder 110, and the correction information to be used is switched from the first encoder correction information 128j to the second encoder correction information 129j. Furthermore, if the signal from the encoder to be used is the signal from the second encoder 110, the signal from the encoder to be used is switched to the signal from the first encoder 109. Once the switching of the signal from the encoder to be used and the correction information to be used is complete, the process proceeds to step S106.

[0096] In step S106, a process is performed to determine whether or not to end the test. Specifically, whether or not to end the test is determined based on the set test sequence, the presence or absence of an error signal, etc. If it is determined that the test should be ended (S106: Yes), the process returns to step S101 and the process continues. On the other hand, if it is determined that the test should not be ended (S106: No), the process is ended.

[0097] As described above, according to the second embodiment, the number of pulses counted at the timing when the encoder pulse is detected, i.e., the pulse number, is used as a key to refer to the correction table, which contains correction information, and read the necessary information, thereby making it possible to correct the rotation angle error caused by the encoder.

[0098] For example, assume that there is a misalignment between the rotation center of the scale 108 and the geometric center of the scale 108, and the installation rotation angle of the first head 109h and the installation rotation angle of the second head 110h are different from each other when the rotation center of the scale 108 is used as the rotation center of the rotation angle. In this case, it is possible to correct the error in the rotation angle read value that occurs due to this.

[0099] Furthermore, for example, it is assumed that the graduations on the scale 108 are not arranged at equal intervals, there is a discrepancy between the rotation speed determined based on the time interval at which the first head 109 h or the second head 110 h detects the graduations on the scale 108 and the actual rotation speed of the scale 108, and the installation rotation angle of the first head 109 h and the installation rotation angle of the second head 110 h are different from each other when the rotation center of the scale 108 is set as the rotation center of the rotation angle. In this case, it is possible to correct the error in the rotation angle read value that occurs due to this.

[0100] Furthermore, by switching the correction table to be used simultaneously with the signal from the encoder to be used when the angle reference is detected, it is possible to reduce the deviation in the foreign object detection position that accompanies switching the encoder to be used and expand the range of rotational speeds that the foreign object inspection device can handle. In other words, according to the second embodiment, it is possible to realize a foreign object inspection device that has high foreign object position identification accuracy over a wider range of rotational speeds of the turntable.

[0101] (Third Embodiment) A third embodiment of the present invention relates to an optical foreign substance inspection device with a function for reading the rotational angle position of a rotating stage, and generates correction information used to identify the rotation angle with high precision while expanding the range of applicable rotational speeds. The optical foreign substance inspection device according to the third embodiment is based on, for example, the optical foreign substance inspection device according to the second embodiment, and further includes a function for generating correction information by rotating the rotating stage under set conditions and recording the relative times at which encoder pulse signals are detected during this rotation.

[0102] Fig. 11 is a diagram showing an example of the configuration of an optical foreign substance inspection apparatus according to the third embodiment. As shown in Fig. 11, the optical foreign substance inspection apparatus 3 according to the third embodiment has a basic configuration similar to that of the optical foreign substance inspection apparatus 2 according to the second embodiment. The computer 119 in the optical foreign substance inspection apparatus 3 further includes a correction information generation circuit 126.

[0103] The correction information generation circuit 126 acquires information relating to the relationship between the rotation angle of the rotary stage 107 and the detection timing of the encoder pulse signal from the stage control circuit 115, and generates the encoder correction information described in the second embodiment based on the acquired information. A first method for generating encoder correction information will be described below.

[0104] 12 is a flowchart showing an example of the processing flow of a first method for generating encoder correction information in the optical foreign substance inspection device according to the third embodiment. Here, a method for generating encoder correction information for a single encoder will be described. Therefore, when generating both first encoder correction information 128j for the first encoder 109 and second encoder correction information 129j for the second encoder 110, it is necessary to execute the processing twice: once when the target encoder is set to the first encoder 109 and once when the target encoder is set to the second encoder 110.

[0105] 12 , first, in step S111, a process is performed to control the rotation speed of the rotation stage to a constant value. Specifically, the motor rotation control circuit 118 in the stage control circuit 115 controls the driving of the motor 111 in response to a control signal related to correction information generation from the overall control circuit 139 so that the rotation stage 107 rotates at a set constant rotation speed. However, strictly speaking, the actual rotation speed of the rotation stage 107 varies around the set rotation speed within the range of precision of the rotation speed control of the motor 111. Once the rotation of the rotation stage 107 has stabilized to a certain extent, the process proceeds to step S112.

[0106] In step S112, an estimate of the true rotation angle is calculated by multiplying the rotation speed by the elapsed time. Specifically, the correction information generation circuit 126 estimates the actual rotation angle by multiplying the set value of the rotation speed of the rotation stage 107 by the elapsed time for multiple points in time corresponding to one or more rotations of the rotation stage 107, and calculates an estimate of the true rotation angle corresponding to one rotation of the rotation stage 107. Then, the processing proceeds to step S113.

[0107] In step S113, the encoder pulse count is recorded at regular time intervals over one rotation of the rotary stage. Specifically, the correction information generation circuit 126 records the encoder pulse count at multiple times, i.e., at multiple points in time, at regular time intervals corresponding to at least one rotation of the rotary stage 107, based on information obtained from the stage control circuit 115. The regular time interval is, for example, a time that is sufficiently shorter than the time obtained by dividing the time required for the rotary stage 107 to rotate once by the number of divisions on the scale 108 for 360°. Once recording of the pulse count is complete, the process proceeds to step S114.

[0108] In step S114, a process is performed to determine whether or not to end recording. Specifically, the correction information generation circuit 126 determines whether or not to end the process of recording the pulse count number of the encoder. For example, if recording for a preset number of rotations has been completed, it is determined that recording should be ended. On the other hand, if recording for a preset number of rotations has not been completed, it is determined that recording should not be ended. The preset number of rotations is, for example, 10 to 100 rotations. If it is determined that recording should be ended (S114: Yes), the process proceeds to step S115. On the other hand, if it is determined that recording should not be ended (S114: No), the process returns to step S111.

[0109] In step S115, a process is performed to generate correction information for the encoder from the estimated value of the true rotation angle and the pulse count number for multiple rotations. Specifically, the correction information generation circuit 126 compares, for each time, the estimated value of the true rotation angle with the rotation angle obtained when the encoder is assumed to be ideal based on the pulse count number of the encoder, and obtains the difference between them.

[0110] The correction information generation circuit 126 further performs statistical processing such as averaging on the differences obtained at each time for multiple rotations of the rotary stage 107 to reduce variations in the differences caused by variations in the rotation speed, and calculates a correction amount for the rotation angle relative to the encoder pulse count. Alternatively, the correction information generation circuit 126 identifies the true rotation angle relative to the encoder pulse count. Through this processing, the correction information generation circuit 126 generates, as encoder correction information, the correspondence between the encoder pulse count and the correction amount for the rotation angle or the true rotation angle. Once the generation of the correction information is complete, the process of generating correction information ends.

[0111] In this manner, in this embodiment, the motor 111 is controlled so that the rotation speed of the rotating stage 107 is constant. As a result, the true rotation speed of the rotating stage 107 varies around the set rotation speed within the range of rotation speed control accuracy of the motor 111. Here, the product of the set rotation speed value and the elapsed time is used as an estimate of the true rotation angle, and this estimate is recorded along with the rotation angle based on the encoder pulse count for one rotation of the rotating stage 107. This recording is repeated over multiple rotations of the rotating stage 107, and statistical processing, such as averaging the difference between the estimate of the true rotation angle and the rotation angle based on the encoder pulse count, is performed over multiple rotations. This reduces the variation in the rotation speed of the rotating stage 107, and highly accurate correction information is generated.

[0112] Possible causes of rotational speed variations include random variations due to accidental external forces and periodic variations due to vibrations of the rotating body. However, unlike rotational angle errors caused by the encoder itself, these do not necessarily result in the same magnitude of error at the same rotational angle. For example, it is easy to imagine that temporally random variations can be attenuated by accumulating statistical data. Furthermore, because vibrations of the rotating body depend on the rotational speed of the rotating body, even at the same rotational angle, the rotational angle error detected at that rotational angle varies depending on the set rotational speed. Therefore, obtaining correction information using the method according to this embodiment is justified by continuing measurements for multiple rotations while changing the set rotational speed.

[0113] FIG. 13 is a diagram for explaining in detail the first method for generating correction information according to the third embodiment. Diagram F13a in the upper left of FIG. 13 plots the estimated true rotation angle over one rotation of the rotation stage 107 and the rotation angle based on the encoder pulse count over that one rotation against time. Tn is the time when the angle reference is detected for the nth time. The straight line is the estimated true rotation angle, calculated by multiplying the set rotation speed, i.e., the set angular velocity ω, by the elapsed time. In contrast, the rotation angle based on the encoder pulse count is a curved line that includes the error inherent in the encoder itself as well as the variation in the rotation speed. Diagram F13b in the upper right of FIG. 13 calculates the difference between the estimated true rotation angle and the rotation speed based on the encoder pulse count, and converts the horizontal axis to the rotation angle. When converting the horizontal axis from time to angle, the formula for calculating the estimated true rotation angle shown in Diagram F13a is used.

[0114] Figure F13b shows the calculation results for one rotation of the rotary stage 107, but as shown in Figure F13c, by calculating this over multiple rotations and performing statistical processing such as averaging, it is possible to reduce the variation in rotation speed and extract only the error inherent in the encoder itself. The error inherent in the encoder itself is, in other words, the correction information for the encoder. For example, if the speed variation is normally distributed, the variation in rotation speed can be reduced to 1 / √N by averaging the calculation results for N rotations.

[0115] As described above, the third embodiment provides a first generation method for generating the first encoder correction information 128j and the second encoder correction information 129j. The first generation method is a method for generating correction information for an encoder by comparing a rotation angle read value based on the pulse count number of the encoder with an estimate of the true rotation angle derived by theoretical calculation while the rotation speed of the rotary stage 107 is controlled to be constant. Furthermore, in the optical foreign substance inspection device 3, the correction information generation circuit 126 performs processing in accordance with this first generation method, and can automatically generate the first encoder correction information 128j and the second encoder correction information 129j.

[0116] In the third embodiment, the calculation control circuit 114 stores a table that associates the encoder pulse count with the rotation angle correction amount as correction information, identifies the rotation angle read value based on the pulse count obtained from the encoder being used, i.e., the head, and refers to this table to correct the rotation angle read value with the rotation angle correction amount to derive the true rotation angle.

[0117] However, the calculation control circuit 114 may store a table that directly associates the encoder pulse count with the true rotation angle as correction information, and directly derive the true rotation angle by referencing this table based on the obtained pulse count. In this case, the processes of obtaining a rotation angle read value from the pulse count and correcting the rotation angle read value using the rotation angle correction amount are essentially omitted, making it possible to quickly determine the true rotation angle. Note that this technique can be similarly applied to other embodiments.

[0118] (Fourth Embodiment) As with the third embodiment, the fourth embodiment of the present invention relates to an optical foreign substance inspection device that generates correction information used to identify the rotation angle with high precision while expanding the range of applicable rotation speeds in relation to the function of reading the rotation angle position of a rotation stage, however, the method of generating the correction information differs from the method described in the third embodiment.

[0119] That is, the optical foreign substance inspection device according to the fourth embodiment has a configuration similar to that of the optical foreign substance inspection device according to the third embodiment shown in FIG. 11, but the method of generating correction information in the correction information generation circuit 126 is different from that of the third embodiment.

[0120] Hereinafter, a second method for generating correction information in the correction information generating circuit 126 according to the fourth embodiment will be described.

[0121] In the third embodiment, the motor 111 controls the rotation speed of the rotary stage 107 to be constant, but if the control accuracy of the motor 111 is too low compared to the resolution of the target encoder, the variation in the rotation speed becomes relatively large, and even if statistical processing is performed, it may not be possible to reduce the variation with a realistic number of samples, making it impossible to calculate correction information. This problem is solved in the present embodiment.

[0122] 14 is a flowchart showing an example of the flow of processing by the second method for generating encoder correction information in the optical foreign substance inspection device according to the fourth embodiment. Note that, as in the third embodiment, a method for generating encoder correction information for a single encoder will be described here. Therefore, when generating both first encoder correction information 128j for the first encoder 109 and second encoder correction information 129j for the second encoder 110, it is necessary to execute processing twice: once when the target encoder is set to the first encoder 109 and once when the target encoder is set to the second encoder 110.

[0123] The processing contents of steps S113, S114, and S115 in the flowchart shown in Fig. 14 are substantially the same as the processing contents of the steps with the same reference numerals in the flowchart shown in Fig. 12. Therefore, detailed description of the processing of these steps will be omitted.

[0124] 14 , first, in step S116, a process for rotating the rotation stage 107 at high speed is performed. Specifically, the motor rotation control circuit 118 in the stage control circuit 115 controls the driving of the motor 111 in accordance with a control signal related to the generation of correction information from the overall control circuit 139 so as to accelerate the rotation of the rotation stage 107 until it reaches a set rotation speed. When the rotation speed reaches the set value, the process proceeds to step S117.

[0125] In step S117, the rotation drive is stopped and the rotation speed is naturally decelerated. Specifically, the motor rotation control circuit 118 stops the supply of power to the motor 111 and the rotation speed of the rotation stage 107 is naturally decelerated in accordance with a constant friction coefficient. The processing step proceeds to step S118.

[0126] In step S118, the angular velocity and angular acceleration are calculated from the detection time difference of the angle reference. Specifically, the correction information generation circuit 126 calculates the angular velocity and deceleration angular acceleration of the rotation of the rotation stage 107 at multiple times from the detection time difference when the angle reference 141 is repeatedly detected during a period in which the rotation speed of the rotation stage 107 naturally decelerates. Thereafter, the processing proceeds to step S119.

[0127] In step S119, a process is performed to calculate a predicted value of the true rotation angle from the angular velocity, angular acceleration, and elapsed time. Specifically, the correction information generation circuit 126 calculates a predicted value of the true rotation angle at each time based on the calculated angular velocity, angular acceleration, and elapsed time at multiple times. Thereafter, the process proceeds to step S113.

[0128] In step S113, the pulse count number of the encoder is recorded at regular time intervals over one rotation of the rotary stage, and the process proceeds to step S114.

[0129] In step S114, a process is performed to determine whether or not to end the recording. If it is determined that the recording should be ended (S114: Yes), the process proceeds to step S115. On the other hand, if it is determined that the recording should not be ended (S114: No), the process returns to step S118.

[0130] In step S115, a process is performed to generate correction information for the encoder from the estimated value of the true rotation angle and the number of pulse counts for multiple rotations. When the generation of the correction information is complete, the process of generating the correction information ends.

[0131] As described above, in this embodiment, the motor 111 is controlled to accelerate the rotational speed of the rotating stage 107 to a high speed and then naturally decelerate. Then, during this period of naturally decelerating rotational speed, the angular velocity and angular acceleration of deceleration are calculated from the detection time difference of the angle reference 141. An estimate of the true rotation angle is then calculated from the angular velocity, angular acceleration, and elapsed time. As in the third embodiment, the rotation angle is acquired based on the encoder pulse count, and the difference between the estimate of the true rotation angle and the rotation angle based on the pulse count is calculated. The difference at each time point over multiple rotations is statistically processed to generate encoder correction information. In this embodiment, all data required for generating correction information is acquired during the period of naturally decelerating rotation of the rotating stage 107, so the motor 111 does not control the rotational speed of the rotating stage 107. Therefore, the control accuracy of the motor 111 is not an issue in this second method of generating correction information.

[0132] FIG. 15 is a diagram illustrating a method for calculating angular velocity and angular acceleration in the fourth embodiment. Diagram F15a in the upper left portion of FIG. 15 shows the change over time in the rotational speed of the rotational stage 107. Here, it is assumed that the rotational stage 107 is accelerated to a high speed by the motor 111, then the speed control is stopped, and the stage exponentially decelerates naturally, assuming resistance proportional to the speed, such as air resistance. Generally, the rotational stage 107 carrying the wafer 106 is heavy, and if the rotational stage 107 rotates at a high speed, the rotational energy is high. Therefore, even if there is a disturbance, the effect on the change in angular acceleration is negligible, and it can be considered that the stage is moving at a constant angular acceleration within a short period of time.

[0133] Diagram F15b on the top right of Figure 15 is an enlarged view of a portion of the graph showing the time change in rotational speed over a period of six consecutive rotations, with the number of times the angular reference 141 is detected also shown as the number of rotations. Tn is the time when the angular reference is detected for the nth time. In the enlarged area, it can be seen that the time change in angular speed is almost linear, and that the speed is decelerating at a constant angular acceleration.

[0134] Because the angle reference 141 is detected once every 360° rotation of the rotation stage 107, an estimated value ω(Tn) of the angular velocity at the n-th detection time Tn of the angle reference can be calculated from the detection time difference of the angle reference 141, as shown in F15c on the lower left side of Fig. 15. Similarly, an estimated value a(Tn) of the angular acceleration at the detection time Tn can be calculated, as shown in F15d on the lower right side of Fig. 15. Because the estimated values ​​of the angular velocity and angular acceleration at the n-th detection time Tn of the angle reference can be calculated as described above, the time change θ(t) of the true rotation angle in the next rotation cycle can be predicted using the following equation (1).

[0135]

[0136] FIG. 16 is a diagram illustrating the flow of calculation of correction information in the fourth embodiment. Diagram F16a in the upper left of FIG. 16 plots the estimated true rotation angle calculated using Equation (1) above and the rotation angle based on the encoder pulse count for the period between the nth detection time Tn based on the angle and the next detection time Tn+1. Unlike the third embodiment, the estimated rotation angle is a quadratic curve. The rotation angle based on the encoder pulse count includes errors inherent in the encoder itself as well as variations in the rotation speed during natural deceleration. Diagram F16b in the upper right of FIG. 16 then calculates the difference between the two and plots it on the horizontal axis in degrees. Equation (1) above is used to convert the horizontal axis from time to degrees. As shown in diagram F16c in the lower left of FIG. 16, this process is repeated for multiple rotations, and statistical processing such as averaging is performed, as in the third embodiment, to generate correction information that cancels out the speed variations.

[0137] As described above, the fourth embodiment provides a second generation method for generating the first encoder correction information 128j and the second encoder correction information 129j. The second generation method generates the correction information for the encoder by comparing a rotation angle read value based on the encoder pulse count with an estimated value of the true rotation angle derived by theoretical calculation while the rotation speed of the rotary stage 107 is naturally decelerated due to a certain resistance or friction coefficient. Furthermore, in the optical foreign substance inspection device 3, the correction information generation circuit 126 performs processing in accordance with this first generation method, and can automatically generate the first encoder correction information 128j and the second encoder correction information 129j.

[0138] Fifth Embodiment Similar to the third embodiment, the fifth embodiment of the present invention relates to an optical foreign substance inspection device that generates correction information used to identify the rotation angle with high accuracy while expanding the range of applicable rotation speeds in relation to the function of reading the rotation angle position of a rotation stage. However, in the fifth embodiment, the method of generating the correction information differs from the methods described in the third and fourth embodiments.

[0139] That is, the optical foreign substance inspection device according to the fifth embodiment has a configuration similar to that of the optical foreign substance inspection device according to the third embodiment shown in FIG. 11, but the method of generating correction information in the correction information generation circuit is different from that of the third and fourth embodiments.

[0140] A third method for generating correction information in the correction information generation circuit 126 according to the fifth embodiment will now be described. In the third and fourth embodiments, generating correction information for a target encoder required the actual use of pulse signals from that target encoder. Therefore, if an optical foreign particle inspection device is equipped with n encoders, the correction information generation process must be executed n times. On the other hand, in the fifth embodiment, Example 5 describes a method for generating correction information for another encoder from the correction information of an arbitrary encoder.

[0141] FIG. 17 shows an example of a graph obtained by plotting the rotation angle correction amount against the rotation angle based on the pulse count of the encoder according to the fifth embodiment. Here, as in the optical foreign substance inspection devices according to the above embodiments, a first encoder 109 and a second encoder 110 are implemented, and these encoders are configured with multiple heads, i.e., a first head 109h and a second head 110h, having the same installation radius, and a single scale 108 shared by these heads. Also, assume that the rotation angle correction amount of the second encoder 110 configured by the second head 110h has already been calculated. In this case, the rotation angle correction amount of the first encoder 109 configured by the first head 109h can be calculated by phase-shifting, or cyclically shifting, the rotation angle correction amount of the second encoder 110 by the difference in installation angle between the first head 109h and the second head 110h, and adjusting the offset so that the starting point is zero. This is because the rotation angle correction amount is a periodic function with a period of 360°.

[0142] The fifth embodiment can be combined with the third or fourth embodiment. For example, consider a case where an optical foreign substance inspection device is equipped with a single scale and two or more heads with different compatible rotational speed ranges. First, the correction information generation circuit 126 applies the correction information generation method according to the third or fourth embodiment to encoder A, which is configured with head a, which has the highest compatible rotational speed range, to obtain correction information. Next, the correction information generation circuit 126 generates correction information for encoder B, which is configured with head b, by shifting the phase of the correction information for encoder A by the difference in installation angle between head a and another head b. Even when there are three or more heads, i.e., encoders, it is possible to obtain known correction information by shifting the phase of the information by the difference in installation angle between the heads.

[0143] As described above, the fifth embodiment provides a third generation method for generating second encoder correction information 129j from first encoder correction information 128j, or generating first encoder correction information 128j from second encoder correction information 129j. The third generation method utilizes the property that the rotation angle correction amount is a periodic function with a period of 360° to generate rotation angle correction information for one of the first head 109h and the second head 110h by shifting the phase of the rotation angle correction information for the other head by the installation angle difference between the first head 109h and the second head 110h. Furthermore, in the optical foreign substance inspection device 3, the correction information generation circuit 126 performs processing in accordance with this third generation method, and can automatically generate the first encoder correction information 128j or the second encoder correction information 129j.

[0144] Furthermore, according to the fifth embodiment, when a plurality of encoders are configured with a plurality of heads sharing a single scale, it is possible to determine the rotation angle correction amount for all of the other encoders configured with the other heads simply by determining the rotation angle correction amount for the encoder configured with one of the heads. Therefore, when a plurality of encoders are configured with a plurality of heads sharing a single scale, it is possible to determine the rotation angle correction amount, i.e., correction information, for all of the encoders efficiently and in a short time.

[0145] Sixth Embodiment An optical foreign substance inspection device can generate and store correction information regardless of the magnitude of the error of the encoder installed in the device, and can correct the rotation angle of the rotary stage 107 obtained by the encoder. However, if the error of the encoder itself is very large, it may be necessary to adjust or replace the encoder itself before correction can be made. In view of this situation, the sixth embodiment describes a method that enables encoder status diagnosis by periodically calculating and understanding the amount of rotation angle correction of the encoder even after the optical foreign substance inspection device has been delivered to a customer.

[0146] FIG. 18 is a diagram illustrating a method for diagnosing the condition of an encoder according to the sixth embodiment. Diagram F18a in the upper part of FIG. 18 is an example of a plot of the rotation angle correction amount of an encoder mounted on an optical foreign substance inspection device against the rotation angle based on the encoder pulse count. In diagram F18a, the solid line represents the graph curve of the rotation angle correction amount measured before shipment of the device, and the dashed line represents the graph curve of the rotation angle correction amount measured one month after delivery to the customer. It can be seen that the area CS or amplitude CA of the rotation angle correction amount is larger than that measured before shipment. In fact, with continued use of the optical foreign substance inspection device, the scale may shift in its mounting position due to centrifugal force or the like, increasing the amount of eccentricity compared to before shipment, and increasing the amount of encoder error that needs to be corrected.

[0147] Here, for example, by calculating the area CS or amplitude CA of the graph of the rotation angle correction amount, it is possible to index the correction strength of the encoder's rotation angle correction amount, i.e., the error level of the encoder's rotation angle. Then, by measuring the encoder correction information periodically before shipping the device or after delivery to the customer, and calculating and saving this index value, i.e., the area CS or amplitude CA, each time, it is possible to monitor changes in the encoder state over time.

[0148] Diagram F18b in the lower part of Figure 18 shows an example of the monitoring results of the area CS of the rotation angle correction information graph over a period of 13 months from the delivery of an optical foreign substance inspection device to a customer. First, the amount of rotation angle correction of the encoder is measured and saved before shipping the device. Then, after the device is delivered and installed at the customer's site, the amount of rotation angle correction is measured every month, and the encoder is corrected using that amount of rotation angle correction until the next measurement. Before shipping and immediately after installation, the area CS is at its lowest, meaning the encoder error is smallest, but it can be seen that the area increases over time.

[0149] Suppose that between the first and second month, an earthquake, for example, causes a malfunction that shifts the encoder's installation position. Then, in the graph of the rotation angle correction amount measured immediately after this, it is clear that the area CS has increased dramatically, exceeding the preset abnormality detection level. When an abnormality like this is detected, adjusting the encoder can reduce the error to the same level as before shipment. If there is no significant increase in error after that, but the error is gradually increasing, adjusting the encoder again during regular maintenance in the 12th month can also reduce the error to the same level as before shipment.

[0150] The optical foreign substance inspection device according to the sixth embodiment has a function that enables the setting of a correction information generation mode. The correction information generation mode is a mode in which the process of generating the rotation angle correction amount of the encoder as correction information is performed automatically or semi-automatically. The device also has a function that prompts the user to set this correction information generation mode periodically, for example, once a month, or that allows the mode to be set forcibly. Furthermore, the device also has a function that notifies the user of the encoder error level and whether the error level exceeds an abnormal level.

[0151] These functions are realized, for example, by configuring the overall control circuit 139 so that the overall control circuit 139 executes preset processing and automatically controls each circuit, etc. In order to configure the overall control circuit 139 in this way, for example, the program PG stored in the storage 153 and executed by the processor 151 may be designed so that the overall control circuit 139 executes the above-mentioned preset processing.

[0152] As described above, the sixth embodiment provides a method for diagnosing the status of an encoder mounted on an optical foreign substance inspection device. This encoder status diagnosis method periodically calculates the rotation angle correction amount of the encoder even after the optical foreign substance inspection device has been delivered to a customer, checks changes in that correction amount over time, and diagnoses the status of the encoder, such as whether it is in an abnormal state or is likely to become abnormal in the future. In the optical foreign substance inspection device 3, the correction information generation circuit 126 in the calculation and control circuit 114 periodically calculates the rotation angle correction amount of the encoder in accordance with this status diagnosis method, and the calculation and control circuit 114 outputs changes in that correction amount over time to the user, allowing the user to diagnose the status of the encoder in the optical foreign substance inspection device.

[0153] Seventh Embodiment The seventh embodiment is a management system in which a management device manages multiple optical foreign substance inspection devices. The management device monitors the status of the multiple optical foreign substance inspection devices and measures the differences between the devices. That is, the optical foreign substance inspection devices according to the seventh embodiment are configured to be connectable to the management device via a server.

[0154] Fig. 19 is a diagram showing an example of the configuration of a management system according to the seventh embodiment. The optical foreign substance inspection devices 3a to 3d shown in Fig. 19 have substantially the same configuration as the optical foreign substance inspection device according to the third embodiment. The optical foreign substance inspection devices 3a to 3d are connected to a management device 202 via a server 201, and each of the optical foreign substance inspection devices 3a to 3d and the management device 202 can communicate with each other. In this example, the number of devices connected to the server 201 is four, but the number of devices is not particularly limited.

[0155] As in the sixth embodiment, each of the optical foreign substance inspection devices 3a to 3d periodically measures correction information, then converts the correction information into an index and transmits the index value to the management device 202. The management device 202 monitors the index values ​​periodically transmitted from these four optical foreign substance inspection devices 3a to 3d. This allows the management device 202 to determine which devices tend to have large encoder errors and predict which devices are likely to require encoder adjustment next. Furthermore, these monitoring results can be displayed on a GUI (Graphical User Interface) so that the administrator can easily understand the results. Note that the term "administrator" here simply refers to the user who operates the management device 202.

[0156] FIG. 20 is an example of a GUI image displaying the monitoring results of multiple optical foreign substance inspection devices in the seventh embodiment. The management device 202 displays, for example, a GUI image 200 as shown in FIG. 20 on a display. In the GUI image 200, the layout of multiple devices connected to the management device 202 is displayed in the upper left. When the administrator selects one of the multiple devices on the GUI image 200, the periodic monitoring results of the encoder correction information of the selected device are displayed as shown in the upper right of the image 200. Furthermore, when the administrator selects any data of the monitoring results on the GUI image 200, the actual measurement results of the correction information, such as the rotation angle correction amount of the encoder, are displayed as shown in the lower left and lower right of the image 200. The management device 202 may output multiple pieces of rotation angle correction information received from the multiple connected optical foreign substance inspection devices in a comparable manner.

[0157] As described above, according to the seventh embodiment, by displaying the monitor results of multiple connected optical foreign matter inspection devices on the GUI image of the management device 202, the administrator can intuitively grasp the changes over time in the status of the encoders between multiple devices, predict deterioration of machine differences, speed up the identification of the cause when machine differences do worsen, and aim to reduce machine differences early by adjusting or replacing the encoders.

[0158] Eighth Embodiment An optical foreign substance inspection device according to an eighth embodiment is provided with a single encoder, and uses only this single encoder to correct the rotation angle based on the pulse count number of that encoder.

[0159] If the angular position can be determined using a single rotary encoder, such as when the rotation speed of the rotation stage 107 during inspection is constant, there is no need to switch encoders during inspection. However, even in this case, errors exist in the rotation angle read value based on the encoder pulse count, so in order to determine the accurate rotation angle position, it is necessary to correct the rotation angle based on the encoder pulse count. Therefore, in the eighth embodiment, a method for correcting the encoder rotation angle when using only a single encoder without switching encoders will be described.

[0160] FIG. 21 is a flowchart showing an example of the flow of processing in the optical foreign matter inspection apparatus according to the eighth embodiment.

[0161] In the eighth embodiment, similarly to the second embodiment, correction information for the encoder to be corrected, that is, a correction table, is stored in advance.

[0162] As shown in FIG. 21, first, in step S121, a process of detecting an encoder pulse is carried out.

[0163] Next, in step S122, at the timing when the encoder pulse is detected, the correction table is referenced using the pulse count, that is, the pulse number, as a key to read the true rotation angle.

[0164] Next, in step S123, a process is performed to determine whether or not to end the inspection. If it is determined that the inspection should be ended (S123: Yes), the inspection ends. On the other hand, if it is determined that the inspection should not be ended (S123: No), the process returns to step S121. That is, in this embodiment, since the encoder is not switched, if the determination that the inspection should be ended is met, the inspection ends as is.

[0165] As described above, the eighth embodiment provides a method for correcting a rotation angle read value based on an encoder pulse signal using stored rotation angle correction information when using only a single encoder without switching the encoder to be used. In the optical foreign substance inspection device, the calculation and control circuit 114 stores head rotation angle correction information, i.e., encoder correction information. The head rotation angle correction information has a characteristic that changes when the installed rotation angle of the head changes. The calculation and control circuit 114 identifies the rotation angle read value of the rotating stage 107 based on the signal from the head, and corrects the identified rotation angle read value using the head rotation angle correction information. As a result, even when using only a single encoder, the true rotation angle can be determined by correcting the rotation angle read value using the correction information.

[0166] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, the above-described configurations, functions, processing units, processing means, etc. may be implemented in hardware, in part or in whole, by designing, for example, an integrated circuit. Furthermore, the above-described configurations, functions, etc. may be implemented in software, by a processor interpreting and executing a program that realizes each function. Information such as programs, tables, and files that realize each function can be stored in memory, a recording device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD.

[0167] 1, 2, 3...optical foreign substance inspection device, 101...light intensity signal, 102...laser light source, 103...laser light, 104...scattered light, 105...optical sensor, 106...wafer, 107...rotary stage, 108...scale, 109...first encoder, 109h...first head, 110...second encoder, 110h...second head, 111...motor, 112...base, 113...stage unit, 114...calculation control circuit, 115...stage control circuit, 116...first encoder rotation angle calculation circuit, 117...second encoder rotation angle calculation circuit, 118...motor rotation control circuit, 119...computer, 120...first encoder circuit Rotation angle read value, 121...base translation direction position information, 122...second encoder rotation angle read value, 124...selected rotation angle read value, 125...selector, 126...correction information generation circuit, 128...first encoder correction information storage circuit, 128j...first encoder correction information, 129...second encoder correction information storage circuit, 129j...second encoder correction information, 132...selector, 134...rotation angle correction circuit, 135...corrected rotation angle, 136...image generation circuit, 139...overall control circuit, 140...user, 141...angle reference, 142...inter-head installation angle difference, 145...scale, 201...server, 202...management device

Claims

1. An optical foreign body inspection device for detecting foreign bodies on a surface of a sample, comprising: a rotating stage on which the sample is placed; a motor for rotating the rotating stage; a base to which the motor is fixed; a ring-shaped scale provided on the rotating stage; first and second heads mounted on the base for detecting the graduations of the scale and outputting a signal; a laser light source for irradiating a laser beam towards the surface of the sample; an optical sensor for receiving scattered light or reflected light of the laser beam from the surface of the sample and outputting a signal according to the intensity of the received light; and a calculation and control circuit for controlling the motor and for identifying the position of a foreign body on the sample based on a signal from the first head or the second head and a signal from the optical sensor, wherein a rotation speed range of the rotating stage that can be handled by the first head and a rotation speed range of the rotating stage that can be handled by the second head are relatively different so as to overlap partially, and the calculation and control circuit determines either the first head or the second head as the head to be used for identifying the rotation angle of the rotating stage based on the rotation speed of the rotating stage, determining a rotation angle of the rotation stage based on a signal from the head to be used.

2. An optical foreign body inspection device as described in claim 1, wherein the calculation control circuit stores rotation angle correction information for a first head and rotation angle correction information for a second head, the rotation angle correction information for the first head being information having a characteristic that changes when the installation rotation angle of the first head and the amount of eccentricity of the scale change, and the rotation angle correction information for the second head being information having a characteristic that changes when the installation rotation angle of the second head and the amount of eccentricity of the scale change, and when specifying the rotation angle of the rotating stage, the calculation control circuit corrects the rotation angle of the rotating stage using the rotation angle correction information for the first head when the head to be used is the first head, and using the rotation angle correction information for the second head when the head to be used is the second head.

3. An optical foreign body inspection device as described in claim 2, wherein there is a deviation between the center of rotation of the scale and the geometric center of the scale, and when the center of rotation of the scale is taken as the center of rotation of the rotation angle, the installation rotation angle of the first head and the installation rotation angle of the second head are different from each other.

4. An optical foreign body inspection device as described in claim 2, wherein there is a discrepancy between the rotation speed determined based on the time interval at which the first head or the second head detects the scale markings and the actual rotation speed of the scale, and when the center of rotation of the scale is taken as the center of rotation of the rotation angle, the installation rotation angle of the first head and the installation rotation angle of the second head are different from each other.

5. In the optical foreign body inspection device according to claim 1, the calculation control circuit controls the motor so that the rotation speed of the rotating stage becomes a set value; calculates an estimate representing a true rotation angle of the rotating stage for a plurality of time points corresponding to one or more rotations of the rotating stage based on a product of the set value of the rotation speed of the rotating stage and time; identifies a read value representing the rotation angle of the rotating stage for a plurality of time points corresponding to one or more rotations of the rotating stage based on a signal output by the first head after detecting the graduations of the scale; identifies a read value representing the rotation angle of the rotating stage for a plurality of time points corresponding to one or more rotations of the rotating stage based on a signal output by the second head after detecting the graduations of the scale; generates rotation angle correction information for a first head by comparing the calculated estimate values ​​of the rotation angles with the identified read values ​​of the rotation angles of the plurality of rotation angles by the first head; generates rotation angle correction information for a second head by comparing the calculated estimate values ​​of the rotation angles with the identified read values ​​of the rotation angles of the plurality of rotation angles by the second head. Optical foreign body inspection device.

6. In the optical foreign body inspection device according to claim 1, the calculation control circuit controls the motor so as to naturally decelerate the rotating stage after rotating it, calculates an estimate of the rotational speed and an estimate of the angular acceleration of the rotating stage for a plurality of time points corresponding to a plurality of rotations of the rotating stage based on the detection time difference based on the angle reference of the scale, calculates an estimate representing an actual rotational angle of the rotating stage for a plurality of time points corresponding to a plurality of rotations of the rotating stage based on the calculated estimate of the rotational speed and the estimated angular acceleration and elapsed time, specifies a read value representing the rotational angle of the rotating stage for a plurality of time points corresponding to a plurality of rotations of the rotating stage based on a signal from the first head, specifies a read value representing the rotational angle of the rotating stage for a plurality of time points corresponding to a plurality of rotations of the rotating stage based on a signal from the second head, and generates rotational angle correction information for the first head by comparing the calculated estimate of the rotational angle with the specified read values ​​of the rotational angles by the first head, the calculated estimated values ​​of the rotation angles are compared with the identified read values ​​of the rotation angles by the second head, to generate rotation angle correction information for the second head.

7. An optical foreign body inspection device as described in claim 1, wherein, when the center of rotation of the scale is set as the center of rotation of the rotation angle, the installation rotation angle of the first head and the installation rotation angle of the second head are different from each other, and the calculation control circuit generates rotation angle correction information for the other head by phase shifting rotation angle correction information for one of the first head and the second head by an installation angle difference between the first head and the second head.

8. An optical foreign body inspection device as described in claim 1, wherein the calculation control circuit executes predetermined processing to generate, at a period of time, rotation angle correction information for at least one of the first head and the second head, used for correction when identifying the rotation angle of the rotating stage based on a signal from the head, determines the change over time in correction intensity in the generated multiple pieces of rotation angle correction information, and outputs the determined change over time in correction intensity.

9. An optical foreign substance inspection device as described in claim 1, wherein the calculation control circuit executes predetermined processing to generate rotation angle correction information for at least one of the first head and the second head, which is used to correct when identifying the rotation angle of the rotating stage based on a signal from the head, and is connected to a management device via a server and transmits the generated rotation angle correction information to the management device, and the management device outputs multiple pieces of rotation angle correction information received from multiple connected optical foreign substance inspection devices in a comparable manner.

10. An optical foreign body inspection device as described in claim 1, wherein the calculation control circuit switches the head being used from one of the first head and the second head to the other when the rotational speed of the rotating stage is within a common rotational speed range that is an overlapping portion of the rotational speed range that the first head can handle and the rotational speed range that the second head can handle, and switches the head being used from the other of the first head and the second head to one when the rotational speed is in the process of decreasing over time.

11. An optical foreign body inspection device for detecting foreign bodies on a surface of a sample, comprising: a rotating stage on which the sample is placed; a motor for rotating the rotating stage; a base to which the motor is fixed; a stage unit including a ring-shaped scale provided on the rotating stage; a head provided on the base and detecting the graduations of the scale and outputting a signal; a laser light source for irradiating a laser light toward the surface of the sample; an optical sensor for receiving scattered light or reflected light of the laser light from the surface of the sample and outputting a signal according to the intensity of the received light; and a calculation and control circuit for performing a process of controlling the motor and a process of identifying a position of a foreign body on the sample based on a signal from the head and a signal from the optical sensor, wherein the calculation and control circuit stores head rotation angle correction information, the head rotation angle correction information having a characteristic that changes when an installed rotation angle of the head changes, and the calculation and control circuit identifies a rotation angle of the rotating stage based on the signal from the head, and corrects the identified rotation angle using the head rotation angle correction information.

12. A program for use in an optical foreign body inspection device comprising: a rotating stage on which a sample is placed; a motor for rotating the rotating stage; a base to which the motor is fixed; a ring-shaped scale provided on the rotating stage; first and second heads mounted on the base and configured to detect graduations on the scale and output a signal; a laser light source for irradiating a laser beam toward a surface of the sample; an optical sensor for receiving scattered or reflected light of the laser beam from the surface of the sample and outputting a signal according to the intensity of the received light; and a calculation and control circuit including a processor, wherein a rotation speed range of the rotating stage that can be accommodated by the first head and a rotation speed range of the rotating stage that can be accommodated by the second head are relatively different so as to overlap partially, the program comprising: a process for controlling the motor; a process for identifying a position of a foreign body on the sample based on a signal from the first head or the second head and a signal from the optical sensor; and a process for determining, based on the rotation speed of the rotating stage, either the first head or the second head as a head to be used for identifying a rotation angle of the rotating stage. A process for determining a rotation angle of the rotation stage based on a signal from the head to be used; and a program for executing the process.

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