JP6783644B2 - Foreign matter inspection device - Google Patents

Description

The present invention relates to a foreign matter detecting device.

Electromagnetic waves in the wavelength band of about 30 GHz to 10 THz are called millimeter waves, terahertz waves, or inclusive microwaves. This wavelength band is superior in transparency to substances such as cloth, paper, and plastic as compared with electromagnetic waves in high frequency bands such as visible light. In addition, since it is a wavelength band that exhibits the properties of light relatively strongly as compared with electromagnetic waves in a low frequency band, it has a feature that electromagnetic waves can be easily controlled optically. Taking advantage of these characteristics, millimeter waves and terahertz waves are irradiated according to the inspection target, and by observing the transmitted wave or reflected wave, defect inspection inside the inspection target, foreign matter contamination inspection, etc. are non-contact non-contact. It is attracting attention as a method to be implemented 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 the fluctuation of the focal length due to vibration or the like. Therefore, it is important to narrow the beam waist and focus by adjusting the focal length so as to compensate for the relationship between the object and the focal point.

WO2012 / 108306

Patent Document 1 describes the position of an object to be measured when inspecting defects (bubbles) in a laminate such as a coating film or an epi layer of a semiconductor wafer for preventing metal corrosion by utilizing a reflected wave of a terahertz wave. An inspection device and an inspection method using a terahertz wave that can be easily adjusted are disclosed.
According to Patent Document 1, "By providing a state detection unit (laser light source, lens, knife edge, and light receiving unit), it is possible to detect whether or not the position and angle of the object to be measured are in a predetermined state. Therefore, the alignment of the object to be measured can be easily performed, and the presence or absence of air bubbles can be accurately determined. "
According to Patent Document 1, it is described that foreign matter is detected by performing autofocus using reflected light. However, the technique of Patent Document 1 detects foreign matter even if there are scratches or characters on the surface of the object to be measured, so that there is a risk of erroneous detection.

Therefore, an object of the present invention is to provide an inspection device capable of improving the detection accuracy of foreign matter even if there are scratches or letters on the surface of the object to be measured.

The above-mentioned problem is a foreign matter inspection device for detecting a foreign substance or a defect in an object, a control unit for controlling the inspection device, an irradiation unit for generating light to irradiate the object, and an irradiation unit emitting light from the irradiation unit. first for receiving a first objective lens for condensing light being the reflected light from the pre-Symbol object surface
The light receiving portion of the object, the second light receiving portion that receives the transmitted light from the object, and the surface position of the object and the position of the first objective lens from the reflected light received by the first light receiving unit. comprising a signal generating unit that generates a relative position signal, and based on the relative positioning signal, wherein the control unit controls the position of the first objective lens, and received by the second light receiving portion transmitting Based on the light , the control unit detects a foreign substance or a defect, and the second light receiving unit is composed of two or more sensors that receive the transmitted light transmitted through the object, and is composed of two or more sensors of the second light receiving unit. The problem is solved by a foreign matter inspection device characterized in that sensors adjacent to each other have different arrangements of light receiving and polarization angles .

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

Configuration diagram showing the foreign matter inspection device according to the first embodiment Schematic diagram showing a method of generating a defocus signal according to the first embodiment (a) Relationship between position shift and beam shape (b) Beam shape when focus shifts in a direction approaching an inspection object (c) Beam at just focus Shape and arithmetic circuit (d) Beam shape when the focus shifts in the direction away from the inspection object (e) Relationship between the position in the focus direction and the defocus signal Configuration diagram of the servo signal generation circuit according to the first embodiment Configuration diagram of the light receiving portion of the detector according to the first embodiment (a) Propagation diagram of incident wave and reflected wave (b) Configuration of the light receiving portion of the detector (A) Flow chart (b) Side view of the inspection object, (c) FOD waveform, (d) FE waveform, (e) Foreign matter detection signal waveform, (e) Foreign matter detection signal waveform, (a) Flow chart (b) Side view of the inspection object, (c) FOD waveform, (d) Foreign matter detection signal waveform, f) Foreign matter detection flag (A) Flow chart (b) Side view of the inspection object, (c) FOD waveform, (d) FE waveform, (e) Foreign matter detection signal waveform, (e) Foreign matter detection signal waveform, (a) Flow chart (b) Side view of the inspection object, (c) FOD waveform, (d) Foreign matter detection signal waveform, f) Foreign matter detection signal waveform by foreign matter detection flag and (g) flag Configuration diagram of the light receiving portion of the detector according to the first embodiment (a) Propagation diagram of incident wave and reflected wave (b) Configuration of the light receiving portion of the detector Configuration diagram of the foreign matter inspection device according to the second embodiment Configuration diagram of the optical unit unit and the light receiving unit of the detector according to the second embodiment (a) Propagation diagram of incident wave and reflected wave (b) Configuration of the light receiving unit of the detector Configuration diagram of the optical unit unit according to the second embodiment Configuration diagram of the foreign matter inspection device according to the third embodiment Relationship diagram of relay lens position and condensing position according to Example 3 (a) Condensing position change when incident wave is substantially focused (b) Condensing position change when incident wave is substantially divergent

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

FIG. 1 is a block configuration diagram showing an embodiment of a foreign matter inspection device according to the present invention. The foreign matter referred to here is not limited to a mere foreign matter, but also includes defects such as voids.
In the foreign matter inspection device, the inspection and measurement object 101 is moved in the direction of the arrow of 1001 by a conveyor device such as a belt conveyor, and the light beam emitted from the light transmitting unit 1201 is irradiated, and the light transmitted through the inspection and 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).
The foreign matter inspection device of FIG. 1 is composed of an optical 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, and the inspection measurement object 101 is, for example, a belt. It moves in the direction of the arrow 1001 by a transport device such as a conveyor. The frequency of the electromagnetic wave emitted by the light transmitting unit 1201 is, for example, a frequency that passes through a non-hydrogen bond substance and is easily absorbed by a carbon component and an organic solvent component, for example, a terahertz wave of 0.1 THz to 3.0 THz. .. Terahertz waves have the property of being transmitted to semiconductors, ceramics, paper, etc. to some extent, absorbed by water, and reflected by metals.
The signal processing unit 103 is a circuit that performs various signal processing of the foreign matter inspection device, and operates with reference to 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 transmitting unit 1201 emits a light beam having a frequency corresponding to the driving voltage. The emitted light beam becomes parallel light by the collimator lens 1202, a part of the light is reflected by the beam splitter 1203, and is condensed by the condenser lens 1204 on the power monitor 1205. The power monitor 1205 feeds back the current or voltage according 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 polarizing beam splitter 1206. The reflected light beam is circularly polarized by the 1/4 wave plate 1209, and is focused by the objective lens 1210 at a desired position of the inspection measurement object 101. The actuator 110 controls the position of the objective lens 1210 according to the driving amount of the actuator drive circuit 109. The focused beam reflected on the surface of the inspection and measurement object 101 is linearly polarized by the 1/4 wave plate 1209, passes through the polarizing beam splitter 1206, and the light beam focused by the cylindrical 1207 is detected by the detector 1208. Then, this signal is output to the servo error signal generation circuit 105.

Next, the light beam transmitted through the inspection and measurement object 101 passes through the objective lens 1211 and the condenser lens 1213, and the intensity of the light beam is detected by the detector 1214, and the corresponding signal is output to the signal processing circuit 106. To do. The actuator 111 controls the position of the objective lens 1211 according to the driving 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, the control signals from the actuator drive circuit 109 to the actuator 110 and the actuator 111 are synchronized signals.

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 changes by 20% when there is no foreign matter), and the presence or absence of foreign matter is determined based on this threshold value. to decide. Alternatively, the presence or absence of foreign matter is determined from the waveform curve peculiar to the substance based on the fingerprint spectrum, which is a characteristic of terahertz waves. This result is output to the host 200.

FIG. 2 shows an example in which the detector 1208 is composed of four divided light receiving units. Method of generating a signal corresponding to the amount of defocus (defocus) from the light beam reflected on the surface of the inspection measurement object 101 received by the detector 1208 (corresponding to the FE output by the servo error signal generation circuit 105 in FIG. 1). It is a schematic diagram which shows. FIG. 2A is a ray diagram showing a change in the beam shape 2201 focused by the cylindrical lens 1207 when the surface of the inspection measurement object 101 is displaced in the focus direction. By passing the focused beam reflected on the surface of the inspection and measurement object 101 through the cylindrical lens 1207, the light beam passing through the direction in which the cylindrical lens 1207 has the focusing effect is quickly focused and the direction in which the lens effect is not obtained is focused. Since the passing light beam is focused slowly, astigmatism occurs. FIGS. 2 (b) to 2 (d) are views in which light is received by the detector 1208 having a light receiving surface divided into four by utilizing this aberration, and are collected according to the position in the focus direction as shown in the figure. The shape of the light beam changes. Assuming that the light receiving surface of the detector 1208 divided into four 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 calculators 2202 and 2204, and the difference between them is performed by the differential calculator 2203. By this calculation, a signal (FE) corresponding to the defocus according to the position in the focus direction is generated as shown in FIG. 2 (e). When (A + C)-(B + D)> 0, the focus is displaced to the + side in FIG. 2 (a). If (A + C) − (B + D) = 0, the focus position is just right. On the contrary, when (A + C)-(B + D) <0, it indicates that the vehicle is displaced to the negative side of FIG. 2 (a) and is out of focus. In response to this FE, the focus control circuit 107 compensates the FE for gain and phase by a command signal from the system control circuit 104, and sends a drive signal for performing focus control on the surface of the inspection measurement object 101. Output to the actuator drive circuit 109. The objective lens 1210 and the objective lens 1211 are driven via the actuator 110 and the actuator 111 based on the signal applied from the actuator drive circuit 109. As a result, the foreign matter inspection device shown in FIG. 1 feeds back the actuator 110 and the actuator 111 based on the FE according to the defocus amount with respect to the surface of the inspection measurement object 101 described above, thereby adjusting the position in the defocus direction. 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 an FE to be used for focus control on the surface of the inspection measurement object 101, and the total light intensity signal generation circuit 1052 outputs a SUM signal which is a total light intensity signal. Here, it is assumed that each signal is output with reference to the potential Vref. Here, the auto gain control is performed by dividing the FE by the SUM in order to compensate for the decrease in the amount of light detected by the detector 1208 due to the dirt on the surface of the inspection measurement object 101.

FIG. 4 shows a case where a plurality of resonance tunnel diodes are used for the detector 1214. Resonant tunnel diodes are semiconductor devices that have directivity in the polarization direction of the light beam. As shown in FIG. 4A, the focused beam reflected on the surface of the inspection and measurement object 101 becomes parallel light by the objective lens 1210, linearly polarized by the 1/4 wave plate 1209, and passes through the polarization beam splitter 1206. To do. On the other hand, the light beam transmitted through the inspection and measurement object 101 passes through the objective lens 1211 and the condenser lens 1213 in a circularly polarized state, and the intensity of the light beam is detected by the detector 1214. This detection signal is output to the signal processing circuit 106. When the detector 1214 detects a circularly polarized light beam incident on the resonance tunnel diode, for example, as shown in FIG. 4B, the resonance tunnel diode 501, the resonance tunnel diode 502 adjacent to the resonance tunnel diode 504, and the resonance tunnel By arranging the diode 503 with the polarization direction changed by 90 degrees, it is possible to detect with a plurality of resonance tunnel diodes in a circularly polarized state without making the 1/4 wavelength plate 1209 linearly polarized.

Next, focus control will be described with reference to 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 control reference potential. The switch 1216 selects the output signal of the focus control circuit 107 or the reference potential Vref based on the FON output by the system control circuit 104, and outputs the FOD (focus drive signal) to the actuator drive circuit 109. When the High level is input as FON, a is selected as the terminal of the switch 1216, and the 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 becomes a signal instructing on / off of focus control. Further, the switch 1216 functions as a switch for switching the focus control on and off. When FON is switched from Low to High, focus control is turned on on the surface of the inspection measurement object 101, and this operation is called a focus pulling operation.

The focus drive voltage generation circuit 108 outputs a predetermined voltage in response to a command signal from the system control circuit 104. The focus drive voltage generation circuit 108 outputs, for example, the 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 a FOD. In order to operate the focus sweep that drives the actuator 110 and the actuator 111 in the direction of approaching (or moving away from) the inspection measurement object 101 according to the FOD, the objective is obtained by adding the sweep voltage of the focus drive voltage generation circuit 108 to the FOD. The lens 1210 and the objective lens 1211 are driven in the focus direction. When the focus control is turned on and the focus pulling 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 response to 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 operation of the foreign matter inspection device of this embodiment. 5 (b) is a side view of an inspection and measurement object having scratches and foreign matter or defects on the surface, and (c) to (f) are steps of the flowchart of (a) with time on the horizontal axis and voltage on the vertical axis. It is a figure which showed the correspondence relationship with various signals. More specifically, FIG. 5C is a waveform of FOD, FIG. 5D is a waveform of FE, FIG. 5E is a waveform of foreign matter detection detected by the detector 1214, and FIG. 5F is a waveform of a foreign matter detection flag. .. First, the foreign matter detection flag indicating that the foreign matter has been detected in step 500 is initialized (OFF). Next, 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. 5 (c), and the FOD has a waveform as shown in FIG. 5C, and the objective lens 1210 is passed through the actuator 110 and the actuator 111. And the objective lens 1211 moves in the direction of 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. 5 (d) according to the sweep voltage, and when the FE approaches the surface of the inspection measurement object 101, the FE is once convex upward. It becomes a signal (Fig. 2 (e)). Next, in step S502, after the FE becomes a convex signal upward, when the FE crosses the reference potential Vref, the focus control based on the FE is turned on and the feedback control is started (S502 and FIG. 5 (d)). 5 (c) S504). When the amount of change in FE from step S503Vref in FIG. 5A (the amplitude of FE) is used, a threshold value (for example, 60% of the maximum value of the amplitude of FE) is set with respect to the absolute value of the amplitude of FE. To do.

Here, when the absolute value of the amplitude of the FE changes by or more than the threshold value due to, for example, a scratch on the surface of the inspection measurement object shown in FIG. 5 (b) (Y in the determination of S503), the FE Since the amplitude of FE changes significantly and the focus control becomes unstable, for example, when the absolute value of the FE amplitude changes by or more than the threshold value set in S503 of FIG. 5 (d), the feedback control based on FE is changed to FE. It is switched to the feed forward control (switching from S505 in FIG. 5D to the feed forward control) that holds the non-based focus position. As a result, even if the FE changes significantly, the actuator 110 and the actuator 111 are positioned 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 in the FE. As a result, a stable waveform of the foreign matter detection signal of the inspection and measurement object as shown in FIG. 5 (e) can be obtained. Here, FIG. 5 (e) describes the case where the positive voltage changes when there is a foreign substance, but on the contrary, it may change to a negative voltage. Therefore, in step S506, the amplitude of the foreign substance detection signal is absolute. The value is compared to the threshold. On the other hand, when the absolute value of the amplitude of FE is less than the threshold value in step S503 (N in the determination of 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 matter detection signal detected by the detector 1214 in step S506 (the amplitude of the foreign matter detection signal is 30%).

Here, when the foreign matter detection signal changes by the threshold value or more (Y in the determination of S507), the foreign matter is detected and the foreign matter detection flag is changed to ON. On the other hand, if the foreign matter detection signal changes below the threshold value (N in the determination of S506), the foreign matter detection flag is changed to OFF because no foreign matter has been detected. Next, in step S509, the entire inspection completion determination of the inspection measurement object 101 is performed, and if the determination in S509 is Y, the inspection is terminated. The host 200 determines the conditions for completing the full-scale inspection 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, if the amplitude of the FE does not exceed the threshold value in step S503 as shown in FIG. 5 (d) (N in the determination in S503). , FE-based feedback control is performed (switched to feedback control in S504 of FIG. 5D). Here, when the vertical axis of the waveforms (c) to (f) in FIG. 5 is a positive voltage value, the waveform of foreign matter detection in FIG. 5 (e) changes to the positive side of the voltage, but the opposite is true. A waveform that changes to the negative voltage side may be used. Further, in FIG. 5C, the threshold value of S503 is the same value for the positive and negative voltage, but different threshold values may be set.

As described above, by the focus control method according to the present embodiment, it is possible to stably detect foreign matter even with respect to the surface fluctuation of the inspection measurement object 101. The present invention is not limited to the above-mentioned examples, and includes various modifications. For example, when the holding control start (S505) in FIG. 5 is not performed, the same function can be realized by masking the foreign matter detection flag indicating that the amplitude of the FE exceeds the threshold value as shown in FIG. .. 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 with respect to the absolute value of the amplitude of FE. Here, when the amplitude of the FE changes by the threshold value or more (Y in the determination of S603), as shown in the waveform of the foreign matter detection signal in FIG. 6 (e), the foreign matter is detected by a large change in the FE. Changes occur in the signal waveform. For example, even if there is no foreign matter in the object to be inspected and measured, if the amplitude of the foreign matter detection signal changes beyond the threshold value set in S604, it will be erroneously detected as a foreign matter.

As a countermeasure, when the absolute value of the FE amplitude changes beyond the threshold value in step S603, the foreign matter detection flag is turned off (S606 in FIG. 6F). On the other hand, if the absolute value of the amplitude of the FE is less than the threshold value in step 603 (N in the determination of S603), the threshold value is determined for the absolute value of the amplitude of the foreign matter detection signal set in step S604. Here, when the amplitude of the foreign matter detection signal changes by the threshold value or more (Y in the determination of S604), the foreign matter detection flag is turned ON (S605 in FIG. 6F). On the other hand, when the amplitude of the foreign matter detection signal is less than the threshold value (N in the determination of S604), the foreign matter detection flag is turned off (S606 in FIG. 6F). By multiplying the foreign matter detection flag (FIG. 6 (f)) and the foreign matter detection signal (FIG. 6 (e)) thus obtained by the host 200, the foreign matter detection flag as shown in FIG. 6 (g) is performed. The waveform of the foreign matter detection signal is obtained. This waveform is a signal that masks all signals above the threshold value set in S603 and below the threshold value set in S604 by the foreign matter detection flag, and is an inspection measurement object as shown in FIG. 6 (b). It is possible to detect only internal defects.

Further, for example, when the 1/4 wave plate 1212 is added to FIG. 1 as shown in FIG. 7 and the polarization direction of the light beam is changed to linearly polarized light instead of circularly polarized light as shown in FIG. 4, the detector 1214 It is also possible to arrange a unidirectional resonant tunneling diode so that linearly polarized light can be detected, such as the detector 1220. To solve the problem that the spot diameter on the inspection and measurement object 101 cannot be maintained on the entire surface, an FE corresponding to the amount of defocus from the light beam reflected from the surface of the inspection and measurement object 101 according to the configuration described in this embodiment is used. By performing focus control based on the surface of the inspection and measurement object 101 for the spot position focused on the inspection and measurement object 101, it is possible to maintain the spot diameter with respect to the entire surface of the inspection and measurement object 101. Become.

In the second embodiment, the incident wave on the detection and 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 a different objective lens (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 1/4 wave plate 1212. As an effect in the implementation, the spot position focused on the inspection measurement object 101 is placed on the surface of 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. By performing focus control based on this, it is possible to maintain the spot diameter with respect to the entire surface of the inspection measurement object 101.

FIG. 8 is a block configuration diagram showing an embodiment of a foreign matter inspection device according to the present invention. The difference between FIGS. 1 and 8 is the optical unit unit 602, and since the configurations other than this point are the same, the parts that overlap with the contents described in the first embodiment will be 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 transmitting unit 1201 emits a light beam having a frequency corresponding to the driving voltage, and the collimator lens 1202 produces parallel light. The light beam transmitted through the beam splitter 1203 is reflected by the mirror 1606. The reflected light beam is focused by the objective lens 1210 at a desired position of the inspection measurement object 101. The actuator 110, the actuator 111 and the actuator 612 control the positions of the objective lens 1210, the objective lens 1211 and the objective lens 1611 according to the driving amount of the actuator drive circuit 109. Here, in order to maintain the relative positional relationship between the objective lens 1210, 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 were synchronized. It is a signal.

FIG. 9A is an enlarged view of a part of the optical unit 602 of FIG. As shown in FIG. 9A, the focused beam reflected on the surface of the inspection and measurement object 101 becomes parallel light by the objective lens 1611, and the beam focused 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 an FE from the signal detected by the detector 1208, and the focus control circuit 107 compensates the FE for gain and phase by the command signal from the system control circuit 104 in response to the FE. Is performed, 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 transmitted through the inspection and measurement object 101 passes through the objective lens 1211 and the condenser lens 1213, detects the intensity of the light beam with the detector 1610, and outputs a signal corresponding to the light beam to the signal processing circuit 106. .. The detector 1610 shown in FIG. 9B uses a plurality of resonance tunnel diodes in order to increase the resolution or sensitivity, for example, when the detection size of foreign matter or defects is smaller than the wavelength of the light transmitting unit 1601. This is an example of detecting the intensity of the light beam by using it. Further, in order to detect a change in polarization due to a foreign substance or a defect, it is also possible to apply the configuration of the detector 1214 of FIG. 4 to this embodiment and detect the polarization ratio between the vertical and the horizontal.

As described above, by the focus control method according to the present embodiment, it is possible to stably detect foreign matter even with respect to the surface fluctuation of the inspection measurement object 601. The present invention is not limited to the above-mentioned examples, and includes various modifications. For example, as shown in FIG. 9, it is possible to configure the foreign matter inspection device by deleting the actuator 612 of the objective lens 1611. In this case, the focus control for the surface fluctuation of the inspection / measurement object 101 is the range in which the light beam reflected from the inspection / measurement object 101 can be received by the objective lens 1611. Therefore, the focus controllable range is larger than that in FIG. Although limited, the number of actuators 612 is reduced, which simplifies the configuration.

In the third embodiment, as shown in FIG. 11, a relay lens 900 which is not in the first and second embodiments is added. This relay lens is driven via the actuator 901 by a command signal from the system control circuit 104. The relay lens 900 thereby, with the FE corresponding to the amount of defocus from the light beam reflected from the surface of the inspection and measurement object 101, the spot position focused on the inspection and measurement object 101 is determined by the inspection and measurement object 101. Not only the focus control is performed based on the surface, but also the spot position in the focus direction condensing on the inspection measurement object 101 can be controlled by the relay lens 900.

FIG. 11 is a block configuration diagram showing an embodiment of an embodiment of a foreign matter inspection device according to the present invention. The difference between FIGS. 1 and 11 is that a relay lens 900 and an actuator 901 that control the convergence and divergence of the light beam emitted from the light transmitting unit 1201 are added to the optical unit unit 2002, and the configurations other than this point are Since they are the same, the parts that overlap with the contents described in the first embodiment will be omitted.

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

The above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the described configurations. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, the control lines and information lines indicate those that are considered necessary for explanation, and do not necessarily indicate all the control lines and information lines in the product. In practice, it can be considered that almost all configurations are interconnected.

101 ... Inspection and measurement object 102 ... Optical unit 103 ... Signal processing unit 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 110 ... Actuator 111 ... Actuator 1201 ... Optical transmitter 1202 ... Collimeter lens 1203 ... Beam splitter 1204 ... Condensing lens 1205 ... Power monitor 1206 ... Polarized 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 due to non-point aberration 2202 ... Addition calculator 2203 ... Differential calculator 2204 ... Addition calculator 1051 ... Focus error Signal generation circuit 1052 ... Total optical amount signal generation circuit

Claims (8)

A foreign matter inspection device that detects foreign matter or defects in an object.
A control unit that controls the inspection device and
An irradiation unit that generates light that irradiates the object,
A first objective lens that collects the light emitted from the irradiation unit, and
The first light receiving portion that receives the reflected light from the surface of the object, and
A second light receiving unit that receives the transmitted light from the object, and
A signal generation unit that generates a relative positioning signal between the surface position of the object and the position of the first objective lens from the reflected light received by the first light receiving unit is provided.
Based on the relative positioning signal, the control unit controls the position of the first objective lens.
Based on the transmitted light received by the second light receiving unit, the control unit detects a foreign substance or a defect, and then
The second light receiving unit is composed of two or more sensors that receive the transmitted light transmitted through the object.
The sensors adjacent to each other in the second light receiving unit are arranged so that the light receiving polarization angles are different from each other.
A foreign matter inspection device characterized by this. The foreign matter inspection device according to claim 1.
A first threshold value is set for the relative positioning signal,
The control unit is a foreign matter inspection device that compares the amplitude value of the relative positioning signal with the first threshold value. The foreign matter inspection device according to claim 2.
If the amplitude value of the relative positioning signal is above the first threshold, the control unit, the foreign matter inspection apparatus characterized by controlling so as to maintain the position of the first objective lens. The foreign matter inspection device according to claim 2.
A second threshold value is set for the signal received and detected as transmitted light by the second light receiving unit.
The control unit is a foreign matter inspection device, which 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 device according to claim 1.
A relay lens that controls the convergence and divergence of light emitted from the irradiation unit is provided.
The control unit is a foreign matter inspection device that controls the position of the relay lens. The foreign matter inspection device according to claim 2.
The first drive unit that drives the first objective lens and
A second objective lens that makes the transmitted light transmitted through the object parallel light, a second driving unit that drives the second objective lens, and a second driving unit.
A reference voltage generating unit that determines a reference voltage of the first driving unit and the second driving unit is provided.
When the relative positioning signal is smaller 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. braking Gyosu particle inspection apparatus according to claim Rukoto. The foreign matter inspection device according to claim 1 .
A foreign matter inspection device characterized in that the second light receiving unit receives the transmitted light of circularly polarized light. The inspection device according to claim 6.
A third objective lens that makes the reflected light from the surface of the object parallel light is provided.
A foreign matter inspection device, characterized in that the control unit controls the position of the third objective lens based on the relative positioning signal.

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