JP2018096766A - Foreign matter inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection device using terahertz waves, with which it is possible to raise the accuracy of detecting foreign matter even when there is a flaw or a character on the surface of a measurement object.SOLUTION: Provided is a foreign matter inspection device for detecting foreign matter or a defect in an object 101, comprising: a control unit 104 for controlling the inspection device; an irradiation unit 1201 for generating light with which the object is irradiated; a first objective lens 1210 for condensing light emitted from the irradiation unit; a first light-receiving unit 1208 for detecting reflected light from the object surface; a second light-receiving unit 1214 for detecting transmitted light from the object; and a signal generation unit 105 for generating, from the reflected light detected by the first light-receiving unit, a relative positioning signal FE for determining the relative positions of the object surface and the first objective lens. The control unit controls the position of the first objective lens on the basis of the relative positioning signal, and detects foreign matter on the basis of the transmitted light detected by the second light-receiving unit.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a foreign object detection device.

An electromagnetic wave having a wavelength band of about 30 GHz to 10 THz is called a millimeter wave, a terahertz wave, or a microwave. This wavelength band is superior in permeability to substances such as cloth, paper, and plastic compared to electromagnetic waves in a high frequency band such as visible light. In addition, since it is a wavelength band that exhibits relatively strong properties of light compared to an electromagnetic wave in a low frequency band, the electromagnetic wave is easily controlled optically. Taking advantage of these features, millimeter waves and terahertz waves are applied to the inspection object, and the transmitted or reflected waves are observed to perform inspection of defects inside the inspection object and inspection for contamination by foreign objects. It is attracting attention as one method to implement by destruction.
When the inspection object is conveyed by a belt conveyor or the like, it is difficult to obtain high resolution because it is necessary to widen the beam waist in consideration of fluctuations in the focal length due to vibration or the like. Therefore, it is important to narrow the beam waist and narrow the focal point by adjusting the focal length so as to compensate the relationship between the object and the focal point.

WO2012 / 108306

Patent Document 1 discloses the position of an object to be measured when inspecting defects (bubbles) in a laminate such as a coating film for preventing metal corrosion by using a reflected wave of a terahertz wave or an epi layer of a semiconductor wafer. An inspection apparatus and an inspection method using a terahertz wave that can be easily combined are disclosed.
According to the above-mentioned patent document 1, “it is possible to detect whether or not the position and angle of the measurement object are in a predetermined state by providing a state detection unit (laser light source, lens, knife edge, and light receiving unit). Therefore, it is possible to easily align the measurement object and accurately determine the presence or absence of bubbles. "
According to Patent Document 1, it is described that autofocus is performed using reflected light to detect a foreign object. However, since the technique of Patent Document 1 detects a foreign object even when there are scratches or characters on the surface of the measurement object, there is a risk of erroneous detection.

  Therefore, an object of the present invention is to provide an inspection apparatus capable of increasing the detection accuracy of a foreign object even when there are scratches or characters on the surface of a measurement object.

The problem is a foreign matter inspection device for detecting foreign matter in an object, a control unit that controls the inspection device, an irradiation unit that generates light to irradiate the object,
A first objective lens for condensing the light emitted from the irradiation unit; a first actuator for driving the first objective lens; and a first detector for detecting reflected light from the object surface as a signal. A light receiving unit, a second light receiving unit that detects transmitted light from the object as a signal, and a surface position of the object and a position of the first objective lens from the signal detected by the first light receiving unit. A servo error signal generation unit that generates a relative positioning signal, and based on the relative positioning signal, the control unit controls the position of the first objective lens, and the signal detected by the second light receiving unit On the basis of the above, the control unit is solved by a foreign matter inspection apparatus characterized by detecting a foreign matter.

  According to the present invention, it is possible to detect the foreign matter of the measurement object on the entire surface, and to improve the reliability of the inspection apparatus.

1 is a configuration diagram illustrating a foreign substance inspection apparatus according to a first embodiment. Schematic diagram illustrating a method of generating a defocus signal according to the first embodiment (a) Relationship between positional deviation and beam shape (b) Beam shape when defocusing in a direction approaching the inspection object (c) Beam during just focus Shape and arithmetic circuit (d) Beam shape when defocusing away from inspection object (e) Relationship between focus direction position and defocus signal 1 is a configuration diagram of a servo signal generation circuit according to a first embodiment. FIG. 1 is a configuration diagram of a light receiving portion of a detector according to a first embodiment (a) A propagation diagram of incident waves and reflected waves (b) A configuration of a light receiving portion of the detector. (A) Flow chart (b) Side view of inspection object, (c) FOD waveform, (d) FE waveform, (e) Foreign object detection signal waveform, f) Foreign object detection flag (A) Flow chart (b) Side view of inspection object, (c) FOD waveform, (d) FE waveform, (e) Foreign object detection signal waveform, f) Foreign object detection flag, (g) Foreign object detection signal waveform by flag FIG. 1 is a configuration diagram of a light receiving unit of a detector according to a first embodiment (a) a propagation diagram of incident waves and reflected waves, and FIG. Configuration diagram of foreign matter inspection apparatus according to Embodiment 2 Configuration diagram of optical unit section and light receiving section of detector according to embodiment 2 (a) Propagation diagram of incident wave and reflected wave (b) Configuration of light receiving section of detector Configuration diagram of optical unit section according to embodiment 2 Configuration diagram of foreign matter inspection apparatus according to Embodiment 3 FIG. 6 is a diagram showing the relationship between the relay lens position and the condensing position according to the third embodiment. (A) Condensing position change when the incident wave is substantially focused. (B) Condensing position change when the incident wave is substantially divergent.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. Moreover, the structure demonstrated here shows an example of embodiment, and is not limited to this embodiment.

FIG. 1 is a block diagram showing a foreign substance inspection apparatus according to an embodiment of the present invention. In addition, the foreign material said here is not limited to a mere foreign material, and also includes defects such as voids.
The foreign object inspection apparatus is a light that has been irradiated with the light beam emitted from the light transmission unit 1201 while being moved in the direction of the arrow 1001 by a conveying device such as a belt conveyor, and transmitted through the inspection / measurement object 101. The presence or absence of foreign matter is detected from the beam intensity, and communication is performed with a host 200 such as a PC (Personal Computer) through an interface such as SATA (Serial Advanced Technology Attachment).
1 includes an optical unit unit 102, a signal processing unit 103, a servo error signal generation circuit 105, a signal processing circuit 106, and an actuator drive circuit 109. The inspection / measurement object 101 is, for example, a belt. It is moved in the direction of the arrow 1001 by a conveying device such as a conveyor. The frequency of the electromagnetic wave emitted by the light transmitting unit 1201 is, for example, a frequency that transmits through a non-hydrogen bonding substance, and is a frequency that is easily absorbed by the carbon component and the organic solvent component, for example, a terahertz wave of 0.1 THz to 3.0 THz. . The terahertz wave has a property of transmitting to some extent to semiconductors, ceramics, paper, etc., absorbing to water, and reflecting to metal.
The signal processing unit 103 is a circuit that performs various types of signal processing of the foreign matter inspection apparatus, and operates based on the potential Vref. The signal processing unit 103 includes a system control circuit 104, a focus control circuit 107, a switch 1216, an adder 1215, and a focus drive voltage generation circuit 108.

  The light amount control circuit 1218 of the optical unit unit 102 is controlled by the system control circuit 104 and outputs a voltage for driving the light transmission unit 1201. The light transmission unit 1201 emits a light beam having a frequency corresponding to the drive voltage. The emitted light beam becomes parallel light by the collimator lens 1202, a part of the light beam is reflected by the beam splitter 1203, and is condensed on the power monitor 1205 by the condenser lens 1204. The power monitor 1205 feeds back a current or voltage corresponding to the intensity of the light beam to the system control circuit 104. As a result, the intensity of the light beam focused on the inspection / measurement object 101 is maintained at a desired value such as 50 mW. On the other hand, the light beam transmitted through the beam splitter 1203 is reflected by the polarization beam splitter 1206. The reflected light beam becomes circularly polarized light by the quarter-wave plate 1209 and is condensed at a desired position on the inspection / measurement object 101 by the objective lens 1210. The position of the objective lens 1210 is controlled by the actuator 110 in accordance with the drive amount of the actuator drive circuit 109. The condensed beam reflected from the surface of the inspection / measurement object 101 is linearly polarized by the quarter-wave plate 1209, passes through the polarization beam splitter 1206, and the light beam collected by the cylindrical 1207 is detected by the detector 1208. This signal is output to the servo error signal generation circuit 105.

  Next, the intensity of the light beam transmitted through the inspection / measurement object 101 passes through the objective lens 1211 and the condenser lens 1213 and is detected by the detector 1214, and a signal corresponding thereto is output to the signal processing circuit 106. To do. The position of the objective lens 1211 is controlled by the actuator 111 according to the drive amount of the actuator drive circuit 109. Here, in order to maintain the relative positional relationship between the objective lens 1210 and the objective lens 1211 constituting the optical unit unit 102, control signals for the actuator 110 and the actuator 111 from the actuator drive circuit 109 are synchronized.

  The signal processing circuit 106 performs processing such as noise removal and amplification on the signal detected by the detector 1214, and outputs the signal detected by the detector 1214 to the system control circuit 104. For this signal, the system control circuit 104 sets a predetermined threshold value for the signal amplitude (for example, the amplitude change is 20% change when there is no foreign matter), and the presence or absence of the foreign matter is determined based on this threshold value. to decide. Alternatively, the presence / absence of a foreign substance is determined based on a waveform curve peculiar to a substance based on a fingerprint spectrum which is a characteristic of a terahertz wave. The result is output to the host 200.

  FIG. 2 shows an example in which the detector 1208 is composed of a four-part light receiving section. A method of generating a signal corresponding to a defocus amount (corresponding to FE output from the servo error signal generation circuit 105 in FIG. 1) from the light beam reflected on the surface of the inspection / measurement object 101 received by the detector 1208. FIG. FIG. 2A is a ray diagram showing a change in the beam shape 2201 collected by the cylindrical lens 1207 when the surface of the inspection / measurement object 101 is displaced in the focus direction. By passing the condensed lens reflected on the surface of the inspection / measurement object 101 through the cylindrical lens 1207, the light beam passing through the direction in which the cylindrical lens 1207 has a convergence effect is quickly condensed, and the direction in which there is no lens effect is obtained. Astigmatism is generated because the passing light beam is condensed slowly. FIGS. 2B to 2D are diagrams in which light is received by a detector 1208 having a four-divided light receiving surface using this aberration, and is collected according to the position in the focus direction as shown in FIG. The light beam shape changes. Assuming that the four-divided light receiving surface of the detector 1208 is A, B, C, and D clockwise from the upper left, the servo error signal generation circuit 105 calculates the signal (A + C) − (B + D). Here, the addition of (A + C) and (B + D) is performed by the addition computing units 2202 and 2204, and the difference between these is performed by the differential computing unit 2203. By this calculation, a signal (FE) corresponding to defocusing corresponding to the position in the focus direction is generated as shown in FIG. When (A + C)-(B + D)> 0, the focus is displaced to the + side in FIG. If (A + C)-(B + D) = 0, it is the just focus position. On the other hand, when (A + C)-(B + D) <0, it is displaced to the-side in FIG. In response to this FE, the focus control circuit 107 performs gain and phase compensation for the FE in response to a command signal from the system control circuit 104, and provides a drive signal for performing focus control on the surface of the inspection / measurement object 101. Output to the actuator drive circuit 109. Based on the signal applied from the actuator drive circuit 109, the objective lens 1210 and the objective lens 1211 are driven via the actuator 110 and the actuator 111. As a result, the foreign matter inspection apparatus shown in FIG. 1 adjusts the position in the defocus direction by feeding back the actuator 110 and the actuator 111 based on the FE corresponding to the defocus amount with respect to the surface of the inspection measurement object 101 described above. I do.

  FIG. 3 shows the configuration of the servo error signal generation circuit 105. The signal output from the detector 1208 is input to the focus error signal generation circuit 1051 and the total light amount signal generation circuit 1052. The focus error signal generation circuit 1051 generates FE to be used for focus control with respect to the surface of the inspection / measurement object 101, and the total light amount signal generation circuit 1052 outputs a SUM that is a total light amount signal. Here, each signal is output with reference to the potential Vref. Here, FE is divided by SUM to compensate for a decrease in the amount of light detected by the detector 1208 due to contamination on the surface of the inspection / measurement object 101 or the like, thereby performing auto gain control.

  FIG. 4 shows a case where a plurality of resonant tunneling diodes are used for the detector 1214. A resonant tunneling diode is a semiconductor device having directivity in the polarization direction of a light beam. As shown in FIG. 4A, the condensed beam reflected by the surface of the inspection / measurement object 101 becomes parallel light by the objective lens 1210, becomes linearly polarized light by the quarter wavelength plate 1209, and passes through the polarizing beam splitter 1206. To do. On the other hand, the intensity of the light beam transmitted through the inspection object 101 is detected by the detector 1214 through the objective lens 1211 and the condenser lens 1213 in the state of circular polarization. This detection signal is output to the signal processing circuit 106. When the detector 1214 detects a circularly polarized light beam incident on the resonant tunnel diode, for example, the resonant tunnel diode 502 and the resonant tunnel adjacent to the resonant tunnel diode 501 and the resonant tunnel diode 504 as shown in FIG. By arranging the polarization direction of the diode 503 to be changed by 90 degrees, it is possible to detect with a plurality of resonant tunneling diodes in a circular polarization state without making the quarter wave plate 1209 to be linearly polarized light.

  Next, focus control will be described using FIG. 1 so as to follow the surface of the inspection / measurement object 101. The system control circuit 104 sets the surface voltage of the inspection / measurement object 101 (that is, the voltage at which the focus error signal becomes 0) as the reference potential Vref. This reference potential is a potential serving as a control reference. The switch 1216 selects the output signal of the focus control circuit 107 or the reference potential Vref based on the FON output from the system control circuit 104 and outputs it to the actuator drive circuit 109 as FOD (focus drive signal). When a high level is input as FON, a is selected as the terminal of the switch 1216, and an output signal of the focus control circuit 107 is output to the actuator drive circuit 109. On the other hand, when the Low level is input as FON, the switch 1216 selects the terminal b and outputs the reference potential Vref.

  As a result, FON is a signal for instructing on / off of the focus control. The switch 1216 functions as a switch for switching focus control on and off. When FON is switched from Low to High, the focus control is turned on on the surface of the inspection / measurement object 101, and this operation is called a focus pull-in operation.

  The focus drive voltage generation circuit 108 outputs a predetermined voltage in response to a command signal from the system control circuit 104. For example, the focus drive voltage generation circuit 108 outputs a sweep voltage in the focus sweep operation. The output signal of the focus drive voltage generation circuit 108 and the output signal of the switch 1216 are added by the adder 1215 and output to the actuator drive circuit 109 as FOD. In order to perform a focus sweep operation for driving the actuator 110 and the actuator 111 in a direction approaching (or moving away from) the inspection / measurement object 101 according to the FOD, the sweep voltage of the focus drive voltage generation circuit 108 is added to the FOD to obtain the objective. The lens 1210 and the objective lens 1211 are driven in the focus direction. When the focus control is turned on and a focus pull-in operation is performed on the surface of the inspection / measurement object 101, the actuator drive circuit 109 drives the actuator 110 and the actuator 111 in accordance with the output signal of the focus control circuit 107, so that the light beam is emitted. Focus control is performed so as to follow the surface of the inspection / measurement object 101.

  FIG. 5A is a flowchart showing an outline of the operation of the foreign matter inspection apparatus of the present embodiment. FIG. 5B is a side view of an inspection / measurement object having scratches and foreign matters or defects on the surface, and FIGS. 5C to 5F are steps in the flowchart of FIG. It is the figure which showed the corresponding relationship with various signals. More specifically, FIG. 5C shows the FOD waveform, FIG. 5D shows the FE waveform, FIG. 5E shows the foreign object detection waveform detected by the detector 1214, and FIG. 5F shows the foreign object detection flag waveform. . First, in step 500, a foreign object detection flag indicating that a foreign object has been detected is initialized (OFF). In step S501, when the sweep voltage in the focus sweep operation is output from the focus drive voltage generation circuit 108 and added to the FOD, the FOD has a waveform as shown in FIG. 5C, and the objective lens 1210 passes through the actuator 110 and the actuator 111. Then, the objective lens 1211 moves in the direction approaching (or moving away from) the inspection / measurement object 101. At this time, the FOD starts to change from the reference potential Vref as shown in FIG. 5D according to the sweep voltage, and when approaching the surface of the inspection / measurement object 101, the FE once protrudes upward. It becomes a signal (FIG. 2 (e)). Next, in step S502, after FE becomes an upwardly convex signal, when FE crosses the reference potential Vref, focus control based on FE is turned on to start feedback control (S502 and FIG. 5D). 5 (c) S504). When the amount of change in FE (FE amplitude) from step S503Vref in FIG. 5A is set, a threshold value (for example, 60% of the maximum value of the FE amplitude) is set with respect to the absolute value of the FE amplitude. To do.

  Here, for example, when the absolute value of the amplitude of the FE changes by more than a threshold value due to the scratch on the surface of the inspection / measurement object shown in FIG. 5B (Y in the determination of S503), the FE. Therefore, when the absolute value of the FE amplitude changes more than the threshold value set in S503 in FIG. 5D, for example, the feedback control based on the FE is changed to the FE. The feed-forward control (switching from S505 in FIG. 5D to feed-forward control) that maintains a focus position that is not based is switched. As a result, even when the FE changes greatly, the positions of the actuator 110 and the actuator 111 are controlled by feedforward control that does not depend on the FE, so that the objective lens 1210 and the objective lens 1211 do not follow the change of the FE. As a result, a stable waveform of the foreign object detection signal of the inspection / measuring object as shown in FIG. Here, FIG. 5E describes the case where the positive voltage changes when there is a foreign substance. However, since there may be a case where the voltage changes to a negative voltage, the absolute amplitude of the foreign substance detection signal is detected in step S506. The value is compared with the threshold value. On the other hand, if the absolute value of the FE amplitude is less than the threshold value in step S503 (N in S503), feedback control based on FE is performed (feedback control in S504 of FIG. 5C). Next, a threshold value is set for the absolute value of the amplitude of the foreign object detection signal detected by the detector 1214 in step S506 (the amplitude of the foreign object detection signal is 30%).

  Here, when the foreign object detection signal changes by more than the threshold value (Y in S507), the foreign object is detected and the foreign object detection flag is changed to ON. On the other hand, if the foreign object detection signal is less than the threshold value (N in S506), the foreign object detection flag is changed to OFF because no foreign object is detected. Next, in step S509, it is determined whether or not the entire surface of the inspection / measurement object 101 is finished. If the determination in step S509 is Y, the inspection is ended. The full inspection end condition is determined by the host 200 based on a camera (not shown), the number of measured data points, and the like. On the other hand, if the determination in S509 is N, the process proceeds to step S503. For example, as shown in FIG. 5D, if the amplitude of the FE does not exceed the threshold value in step S503 (N in the determination of S503). , Feedback control based on FE is performed (switching to feedback control in S504 of FIG. 5D). Here, when the vertical axis of the waveforms of (c) to (f) in FIG. 5 is a positive voltage value, the foreign object detection waveform in FIG. 5 (e) changes to the positive side of the voltage. Alternatively, the waveform may change to the negative voltage side. In FIG. 5C, the threshold value of S503 is the same value for positive and negative voltages, but different threshold values may be set.

  As described above, the focus control method according to the present embodiment makes it possible to detect the foreign matter stably even with respect to the surface variation of the inspection / measurement object 101. In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, when the holding control start (S505) in FIG. 5 is not performed, a similar function can be realized by using a foreign object detection flag indicating that the FE amplitude has exceeded a threshold as shown in FIG. 6 as a mask. . For example, it can be realized as follows. In step S603 of FIG. 6A, a threshold value (for example, 60% of the maximum value of FE) is set for the absolute value of the FE amplitude. Here, when the amplitude of the FE changes more than the threshold value (Y in the determination of S603), as shown in the waveform of the foreign object detection signal in FIG. A change occurs in the signal waveform. For example, even if there is no foreign object in the inspection / measurement object, if the amplitude of the foreign object detection signal changes beyond the threshold set in S604, it is erroneously detected as a foreign object.

  As a countermeasure against this, when the absolute value of the FE amplitude changes to a threshold value or more in step S603, the foreign object detection flag is turned OFF (S606 in FIG. 6 (f)). On the other hand, if the absolute value of the FE amplitude is less than the threshold value in step 603 (N in S603), the threshold value is determined for the absolute value of the foreign object detection signal set in step S604. Here, when the amplitude of the foreign object detection signal changes by more than the threshold value (Y in S604), the foreign object detection flag is turned ON (S605 in FIG. 6 (f)). On the other hand, if the amplitude of the foreign object detection signal is less than the threshold value (N in S604), the foreign object detection flag is turned off (S606 in FIG. 6 (f)). The foreign object detection flag as shown in FIG. 6G is obtained by multiplying the foreign object detection flag (FIG. 6F) thus obtained by the foreign object detection signal (FIG. 6E) by the host 200. The waveform of the foreign object detection signal is obtained. This waveform is a signal obtained by masking all signals that are greater than or equal to the threshold value set in S603 and less than the threshold value set in S604 by the foreign object detection flag, as shown in FIG. 6B. Only internal defects can be detected.

  Further, for example, when a quarter wave plate 1212 is added to FIG. 1 as shown in FIG. 7 and the polarization direction of the light beam is not circularly polarized but linearly polarized as shown in FIG. It is also possible to arrange a unidirectional resonant tunneling diode so that linearly polarized light can be detected like the detector 1220. With respect to the problem that the spot diameter to the inspection / measurement object 101 cannot be maintained over the entire surface, the FE corresponding to the defocus amount from the light beam reflected from the surface of the inspection / measurement object 101 by the configuration described in the present embodiment, By performing focus control on the spot position focused on the inspection / measurement object 101 based on the surface of the inspection / measurement object 101, the spot diameter can be maintained with respect to the entire surface of the inspection / measurement object 101. Become.

  In the second embodiment, the incident wave to the detection measurement object 101 and the reflected wave from the surface pass through the same objective lens 1210 in the first embodiment, whereas the second embodiment passes through different objective lenses in the second embodiment ( Since the incident wave is the objective lens 1210 and the reflected wave is the objective lens 1611), it is not necessary to change the polarization state by the quarter wavelength plate 1212. As an effect in the implementation, the spot position focused on the inspection / measurement object 101 by the FE corresponding to the defocus amount from the light beam reflected from the surface of the inspection / measurement object 101 is placed on the surface of the inspection / measurement object 101. By performing the focus control based on this, the spot diameter can be maintained with respect to the entire surface of the inspection / measurement object 101.

  FIG. 8 is a block diagram showing an embodiment of the foreign matter inspection apparatus according to the present invention. The difference between FIG. 1 and FIG. 8 is the optical unit 602, and the configuration other than this point is the same, and therefore, the description overlapping with the contents described in the first embodiment is omitted.

  The light amount control circuit 1218 of the optical unit unit 602 is controlled by the system control circuit 104 and outputs a voltage for driving the light transmission unit 1201. The light transmission unit 1201 emits a light beam having a frequency corresponding to the driving voltage, and is converted into parallel light by the collimator lens 1202. The light beam that has passed through the beam splitter 1203 is reflected by the mirror 1606. The reflected light beam is condensed at a desired position on the inspection / measurement object 101 by the objective lens 1210. The positions of the objective lens 1210, the objective lens 1211, and the objective lens 1611 are controlled by the actuator 110, the actuator 111, and the actuator 612 in accordance with the drive amount of the actuator drive circuit 109. Here, in order to maintain the relative positional relationship between the objective lens 1210 and the objective lens 1211 and the objective lens 1611 constituting the optical unit unit 602, the control signals from the actuator drive circuit 109 to the actuator 110, the actuator 111, and the actuator 612 are synchronized. Signal.

  FIG. 9A is an enlarged view of a part of the optical unit 602 in FIG. As shown in FIG. 9A, the condensed beam reflected by the surface of the inspection / measurement object 101 becomes parallel light by the objective lens 1611, and the beam condensed by the cylindrical lens 1207 is detected by the detector 1208. The detection signal is output to the servo error signal generation circuit 105. The servo error signal generation circuit 105 generates FE from the signal detected by the detector 1208, and the focus control circuit 107 compensates the gain and phase with respect to the FE in response to the command signal from the system control circuit 104 in response to this FE. And a drive signal for performing focus control on the surface of the inspection / measurement object 101 is output to the actuator drive circuit 109. On the other hand, the light beam that has passed through the inspection / measurement object 101 passes through the objective lens 1211 and the condenser lens 1213, and the detector 1610 detects the intensity of the light beam, and outputs a signal corresponding thereto to the signal processing circuit 106. . The detector 1610 shown in FIG. 9B includes a plurality of resonant tunnel diodes in order to increase the resolution or increase the sensitivity when, for example, the detection size of a foreign substance or a defect is smaller than the wavelength of the light transmitter 1601. This is an example in which the intensity of the light beam is detected by configuring. In addition, in order to detect a change in polarization due to a foreign substance or a defect, the configuration of the detector 1214 of FIG. 4 can be applied to this embodiment to detect the vertical and horizontal polarization ratios.

  As described above, the focus control method according to the present embodiment makes it possible to detect the foreign matter stably even with respect to the surface variation of the inspection / measurement object 601. In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, as shown in FIG. 9, the foreign object inspection apparatus can be configured by deleting the actuator 612 of the objective lens 1611. In this case, since the focus control with respect to the surface variation of the inspection / measurement object 101 is within a range where the reflected light beam from the inspection / measurement object 101 can be received by the objective lens 1611, the range in which the focus control is possible compared to FIG. Although limited, the configuration is simplified as the number of actuators 612 is reduced.

  In the third embodiment, as shown in FIG. 11, a relay lens 900 that is not included in the first and second embodiments is added. This relay lens is driven via an actuator 901 by a command signal from the system control circuit 104. With this relay lens 900, the spot position focused on the inspection / measurement object 101 by the FE corresponding to the amount of defocus from the light beam reflected from the surface of the inspection / measurement object 101 is simply detected. In addition to performing the focus control based on the surface, the relay lens 900 can control the spot position in the focus direction that is focused on the inspection / measurement object 101.

  FIG. 11 is a block diagram showing one embodiment of the foreign matter inspection apparatus according to the present invention. The difference between FIG. 1 and FIG. 11 is that a relay lens 900 and an actuator 901 for controlling the convergence and divergence of the light beam emitted from the light transmission unit 1201 are added to the optical unit unit 2002. Since they are the same, the description overlapping with the contents described in the first embodiment is omitted.

  FIG. 11 shows an example in which the position where light is focused on a desired position of the inspection / measurement object 101 by the objective lens 1210 is controlled by the relay lens 900. FIG. 12A shows an example in which the spot position focused on the objective lens 1210 side of the inspection / measurement object 101 is changed, and FIG. 12B shows the spot focused on the objective lens 1211 side of the inspection / measurement object 101. It is an example which changes a position. For example, the light beam passing through the objective lens 1210 is condensed quickly by making the relay lens 900 substantially converge as shown in FIG. 12A, and the relay lens 900 is made substantially divergent as shown in FIG. Thus, the light beam passing through the objective lens 1210 is collected slowly. In this way, by controlling the convergence and divergence by the position of the relay lens 900, it is possible to change the position at which the light is focused on the objective lens 1210 side of the inspection measurement object 101. The feature of this embodiment is that the focus control is performed on the surface of the inspection / measurement object 101, and the position of the relay lens 900 is controlled via the actuator 901 by a command signal from the system control circuit 104. Thus, while controlling the focus with respect to the surface of the inspection / measurement object 101, a desired condensing position of the inspection / measurement object 101 with reference to the surface of the inspection / measurement object 101 (denoted as D0 to D4 in FIG. 12). It is possible to control the adjustment spot position so that the light is condensed. For example, when there is a foreign object on the inspection / measurement object 101, the position of the inspection / measurement object 101 at which the foreign object exists can be searched by driving the relay lens 900. As a result, if it is specified that there is a foreign substance at the position L4, the system control circuit 104 can determine where the foreign substance is mixed in the manufacturing process. As a result, it is possible to inspect the foreign object in the thickness direction of the inspection / measurement object 101 while following surface fluctuations that cannot be realized by simply changing the focal position by simple feedforward.

  The above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

DESCRIPTION OF SYMBOLS 101 ... Test object 102 ... Optical unit part 103 ... Signal processing part 104 ... System control circuit 105 ... Servo error signal generation circuit 106 ... Signal processing circuit 107 ... Focus control circuit 108 ... Focus drive voltage generation circuit 109 ... Actuator drive circuit DESCRIPTION OF SYMBOLS 110 ... Actuator 111 ... Actuator 1201 ... Light transmitter 1202 ... Collimator lens 1203 ... Beam splitter 1204 ... Condensing lens 1205 ... Power monitor 1206 ... Polarizing beam splitter 1207 ... Cylindrical lens 1208 ... Detector 1210 ... Objective lens 1211 ... Objective lens 1212 ... 1/4 wavelength plate 1213 ... Condensing lens 1214 ... Detector 1215 ... Adder 1216 ... Switch 2201 ... Beam shape 2202 due to astigmatism ... Addition computing unit 2203 ... Differential computing unit 204 ... adders 1051 ... focusing error signal generation circuit 1052 ... total light amount signal generating circuit

Claims (11)

A foreign matter inspection device for detecting foreign matter or defects in an object,
A control unit for controlling the inspection apparatus;
An irradiator that generates light to irradiate the object;
A first objective lens for condensing the light emitted from the irradiation unit;
A first light receiving portion for receiving reflected light from the object surface;
A second light receiving portion for receiving transmitted light from the object;
A signal generating unit that generates a relative positioning signal between the surface position of the object and the first objective lens position from the reflected light received by the first light receiving unit;
Based on the relative positioning signal, the control unit controls the position of the first objective lens,
The foreign matter inspection apparatus, wherein the control portion detects a foreign matter or a defect based on the transmitted light received by the second light receiving portion. The foreign matter inspection apparatus according to claim 1,
A first threshold is set for the relative positioning signal;
The foreign matter inspection apparatus, wherein the control unit compares an amplitude value of the relative positioning signal with the first threshold value. The foreign matter inspection apparatus according to claim 2,
The foreign matter inspection apparatus, wherein when the amplitude value of the relative positioning signal is smaller than the first threshold value, the controller controls to hold the position of the first objective lens. The foreign matter inspection apparatus according to claim 2,
A second threshold is set for a signal received and detected as transmitted light by the second light receiving unit,
The foreign matter inspection apparatus, wherein the control unit determines the presence or absence of foreign matter by comparing the amplitude value of the signal detected by the second light receiving unit with the second threshold value. The foreign matter inspection apparatus according to claim 1,
A relay lens that controls convergence and divergence of light emitted from the irradiation unit, and
The foreign matter inspection apparatus, wherein the control unit controls the position of the relay lens. The foreign matter inspection apparatus according to claim 2,
A first drive unit for driving the first objective lens;
A second objective lens that converts the transmitted light that has passed through the object into parallel light, and a second drive unit that drives the second objective lens;
A reference voltage generation unit that determines a reference voltage of the first drive unit and the second drive unit,
When the relative positioning signal is equal to or greater than the first threshold value, the control unit determines the position of the first objective lens and the position of the second objective lens based on the voltage generated by the reference voltage generation unit. A foreign matter inspection apparatus characterized by controlling The foreign matter inspection apparatus according to claim 1,
The second light receiving unit is composed of two or more sensors that receive transmitted light that has passed through the object,
The foreign matter inspection apparatus, wherein the sensors adjacent to each other in the second light receiving unit are arranged to have different light receiving polarization angles. The foreign matter inspection apparatus according to claim 7,
The foreign matter inspection apparatus, wherein the second light receiving unit receives the circularly polarized transmitted light. The inspection apparatus according to claim 6,
A third objective lens that collimates the reflected light from the object surface,
The foreign matter inspection apparatus, wherein the control unit controls the position of the third objective lens based on the relative positioning signal. A foreign matter inspection apparatus for detecting foreign matter or defects in an object,
A control unit for controlling the inspection apparatus;
An irradiator that generates light to irradiate the object;
A relay lens that controls the convergence and divergence of the light emitted from the irradiation unit;
A first quarter wave plate for changing the polarization of light controlled by the relay lens;
A first light receiving portion for detecting reflected light from the object surface;
A second light-receiving unit that detects transmitted light that has passed through the object, and includes a sensor having a single polarization direction;
A second quarter-wave plate for changing the polarization of the transmitted light,
The second light receiving unit is composed of two or more sensors that receive transmitted light that has passed through the object, and the adjacent sensors are arranged so that their polarization angles coincide with each other. apparatus. The foreign matter inspection apparatus according to claim 10,
The light polarization controlled by the relay lens is converted from linearly polarized light to circularly polarized light by the first quarter wave plate, and then irradiated to the object.
When the transmitted light passes through the second quarter-wave plate, the polarized light of the transmitted light is changed from circularly polarized light to linearly polarized light, and the second light receiving unit detects the transmitted light of the linearly polarized light. Foreign matter inspection equipment.

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