JP2018071970A - Inspection method for minute foreign substances and inspection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection method and an inspection apparatus capable of detecting foreign substances with high accuracy by stabilizing an irradiation laser power in an extended period.SOLUTION: A defect inspection apparatus 100 which inspects defects on a surface of a sample 1 by irradiating the surface of the sample 1 with a laser for a predetermined period, comprises: a laser light source 2 emitting a laser beam for irradiating the surface of the sample 1; a modulation unit 3 modulating the emitted laser beam; a control unit 12 controlling the voltage to be applied to the modulation unit 3; and a reflected light detection unit 9 detecting a scattered light reflected from the surface of the sample 1 to generate a detection signal. The control unit 12 controls the voltage applied to the modulation unit 3 to be switched based on the detection result of the reflected light detection unit 9.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a minute foreign matter inspection method and inspection apparatus.

  As a background art in this technical field, there is JP-T 2009-501902 (Patent Document 1). This publication also provides “Inspection systems, circuits and methods for enhancing defect detection by addressing saturation levels of amplifiers and analog and digital circuits as limiting factors in the measurement detection range of inspection systems. Inspection systems and circuits to enhance defect detection by reducing thermal damage to large particles by dynamically changing the incident laser beam power level delivered to the sample during the surface inspection scan, A method is provided "(see summary).

  Further, as means for driving the Pockels cell, for example, as described in Japanese Patent Application Laid-Open No. 2001-144357 (Patent Document 2), means for switching and applying a predetermined voltage to the Pockels cell. It is stated.

Special table 2009-501902 JP 2001-144357 A

  When the inspection device for minute foreign matters is operated for a long time, the characteristics of the crystal change due to the influence of the laser power passing through the Pockels cell. Due to this characteristic change, the rotation angle of the polarization plane of the laser passing through the Pockels cell changes, and there is a possibility that the laser power applied to the wafer, which is the sample, varies. For this reason, the intensity of scattered light from the foreign matter on the wafer changes, making it difficult to detect the foreign matter diameter with high accuracy. However, this point has not been considered in the prior art documents.

  Therefore, the present invention provides an inspection method and an inspection apparatus that can detect foreign matter with high accuracy.

  In order to solve the above problems, for example, the configuration described in the claims is adopted.

  The present application includes a plurality of means for solving the above-described problems. For example, a defect inspection apparatus for inspecting a defect on the sample surface by irradiating the sample surface with a laser for a predetermined time. A laser light source that emits a laser beam irradiated on the surface, a modulation unit that modulates the emitted laser beam, a control unit that controls a voltage applied to the modulation unit, and scattered light reflected from the sample surface are detected. And a reflected light detection unit that generates a detection signal, and the control unit controls the voltage applied to the modulation unit to be switched based on the detection result of the reflected light detection unit.

  According to the present invention, minute foreign matter can be detected with high accuracy.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is an example of the block diagram of the foreign material inspection apparatus which concerns on 1st embodiment. 2 is a configuration example of a driver circuit according to the first embodiment. It is an operation example of the driver circuit according to the first embodiment. It is an example of composition of a driver circuit concerning a 2nd embodiment. It is an example of composition of a driver circuit concerning a 3rd embodiment. It is an example of the block diagram of the foreign material inspection apparatus which concerns on 4th embodiment.

  Hereinafter, examples will be described with reference to the drawings.

  In this embodiment, an example of a foreign matter inspection apparatus that switches the laser power applied to a wafer under inspection and stabilizes the irradiation laser power for a long time will be described.

  FIG. 1 is an example of a configuration diagram of the foreign matter inspection apparatus of the present embodiment.

  The foreign substance inspection apparatus 100 includes a laser light source 2, an optical modulation element 3, a polarizing plate 4, a beam splitter 5, a mirror 6, lenses 7, 8, a sensor 9, a detection circuit 10, a data processing unit 11, a driver circuit 12, and optical power detection. Means 13 and stage 14 are provided.

  In the foreign matter inspection apparatus 100, the wafer 1 is placed on the stage 14, and the laser light output from the laser light source 2 is sent to the wafer 1 via the optical modulation element 3, polarizing plate 4, beam splitter 5, mirror 6, and lens 7. Irradiate up. At this time, in the foreign matter inspection apparatus 100, the wafer 1 is rotated by the stage 14 and is linearly operated by the translation stage (not shown), so that the laser light irradiated onto the wafer 1 is irradiated on the entire surface of the wafer 1. It becomes a spiral trajectory and the entire surface of the wafer 1 can be inspected. Scattered light from the foreign matter on the wafer 1 is detected through the lens 8, sensor 9, and detection circuit 10, and foreign matter determination is performed by the data processing unit 11 based on the detection result of the detection circuit 10.

  In the foreign matter inspection apparatus 100 according to the present embodiment, the driver circuit 12 switches the voltage applied to the optical modulation element 3 by switching control from the data processing unit 11. The data processing unit 11 predicts the presence / absence of a large-diameter foreign material based on the detection result in the previous circumference in which the wafer is spirally scanned, and controls voltage switching in the driver circuit 12. Specifically, when the data processing unit 11 predicts that there is a large-diameter foreign material, the laser power applied to the wafer 1 is reduced.

  The optical modulation element 3 controls the rotation of the polarization plane of the laser light passing therethrough and the laser power passing through the polarizing plate 4 by a predetermined voltage switched by the driver circuit 12. Specifically, when the data processing unit 11 predicts that there is a large-diameter foreign material, the driver circuit 12 outputs a predetermined voltage for reducing the laser power applied to the wafer 1 and there is no large-diameter foreign material. Is predicted, the driver circuit 12 outputs a predetermined voltage for increasing the laser power.

  In the data processing unit 11, the laser power applied to the wafer 1 via the beam splitter 5 is detected by the optical power detection unit 13, and the driver circuit 12 switches the optical modulation element 3 based on the detection result. Controls the voltage value output to. This is because the rotation angle of the plane of polarization of the laser light passing through the optical modulation element 3 is different even if the optical control element 3 applies the same control voltage from the driver circuit 12 depending on environmental conditions such as temperature. This is because the laser power applied to the wafer 1 varies. Since the detection accuracy of foreign matter on the wafer 1 deteriorates when the laser power fluctuates, the voltage to be switched by the driver circuit 12 is controlled so that a predetermined laser power is irradiated to the wafer 1 via the optical power detection means 13. Improve the detection accuracy of foreign matter.

  FIG. 2 is a configuration example of the driver circuit 12 in the foreign matter inspection apparatus 100.

  The driver circuit 12 includes an input circuit 51, high voltage generation circuits 52 and 53, level shift circuits 54 and 55, MOS drive circuits 56, 57, 58, and 59, PMOS transistors 60 and 62, and NMOS transistors 61 and 63.

  In the driver circuit 12, a switching signal (VIN) from the data processing unit 11 is input to the input circuit 51 triggered by the presence or absence of a large-diameter foreign matter detected via the sensor 9 and the detection circuit 10, and the input circuit 51 The PMOS transistors 60 and 62 and the NMOS transistors 61 and 63 are ON / OFF controlled through the level shift circuits 54 and 55 and the MOS drive circuits 56, 57, 58 and 59. Further, the high voltage generation circuits 52 and 53 generate voltages VH and VL based on the voltage control signals (VP and VN) from the data processing unit 11. Here, VP is a voltage control signal for generating the voltage VH by the high voltage generation circuit 52, and VN is a voltage control signal for generating VL by the high voltage generation circuit 53. Further, from the potential relationship applied to the PMOS transistors 60 and 62 and the NMOS transistors 61 and 63, a voltage that becomes a high potential is VH and a voltage that becomes a low potential is VL.

  FIG. 3 shows an operation example of the driver circuit 12. The switching signal VIN is a binary signal having a Low and High potential, and the respective states are represented as L and H. When VIN is L, the PMOS transistor 60 is turned on through the level shift circuit 54 and the MOS drive circuit 56 from the input circuit 51, the NMOS transistor 61 is turned off through the MOS drive circuit 57, and VOUTP has the same potential as VH. Become.

  At the same time, the PMOS transistor 62 is turned off via the level shift circuit 55 and the MOS drive circuit 58, the NMOS transistor 63 is turned on via the MOS drive circuit 59, and VOUTN has the same potential as VL. As a result, a potential difference of VH−VL is applied to the optical modulation element 3.

  On the other hand, when VIN is H, the PMOS transistor 60 is OFF, the NMOS transistor 61 is ON, VOUTP is the same potential as VL, the PMOS transistor 62 is ON, the NMOS transistor 63 is OFF, and VOUTN is the same as VH. A potential difference of VL−VH is applied to the optical modulation element 3 in terms of potential.

  Based on the voltage control signals (VP, VN) from the data processing unit 11, the high voltage generation circuits 52, 53 generate VH = V1, VL = V3, or VH = V2, VL = V4, respectively. A voltage of switching amplitude: | VH−VL | and offset voltage: (VH + VL) / 2 is applied to the modulation element 3.

  By adjusting the switching amplitude and the offset voltage applied to the optical modulation element 3 from the data processing unit 11 via the voltage control signals (VP, VN) based on the detection result of the optical power detection means 13, It is possible to correct the characteristic fluctuation and suppress the laser power fluctuation for a long time when the wafer 1 is irradiated.

  With the configuration of this embodiment, it is possible to accurately detect minute foreign matter by switching the laser power applied to the wafer under inspection and stabilizing the irradiation laser power for a long time. This effect is the same in the embodiments described below.

  FIG. 4 is a block diagram showing a second embodiment of the driver circuit according to the present invention. In addition, in order to avoid description becoming complicated, description about the component which attached | subjected the code | symbol same as Example 1 is abbreviate | omitted.

  The driver circuit 12 shown in FIG. 4 includes an input circuit 51, high voltage generation circuits 64 and 65, level shift circuits 54 and 55, MOS drive circuits 56, 57, 58, and 59, PMOS transistors 60 and 62, and NMOS transistors 61 and 63. Consists of. The high voltage generation circuit 64 generates a voltage based on the voltage control signal (VP) from the data processing unit 11 and is shifted using the VL generated by the high voltage generation circuit 65 as a reference voltage. The potential difference generated by the high voltage generation circuit 64 becomes the switching amplitude for the optical modulation element 3: | VH−VL |. In the present embodiment, the potential difference applied to the optical modulation element 3 is controlled only by the voltage control signal VP, and the offset voltage to the optical modulation element 3 is controlled only by the voltage control signal VN. Thereby, it becomes possible to change only one of a potential difference or an offset voltage, and the control method with respect to the optical modulation element 3 from the data processing part 11 becomes simple.

  FIG. 5 is a block diagram showing a third embodiment of the driver circuit according to the present invention. In addition, in order to avoid description becoming complicated, description about the component which attached | subjected the code | symbol same as Example 1 is abbreviate | omitted.

  The driver circuit 12 shown in FIG. 5 includes a plurality of driver circuits 12a and 12b. The configurations of the driver circuits 12a and 12b are the same as the components described in the first embodiment. The input circuit 51 of the driver circuit 12a receives control signals VIN and EN1 from the data processing unit 11, and the high voltage generation circuits 52a and 53b receive VP1 and VN1, respectively.

  In the driver circuit 12a, predetermined voltages VH1 and VL1 are generated by the high voltage generation circuits 52a and 53b, and whether or not the outputs of VOUTP1 and VOUTN1 are controlled by EN1. When output is enabled by EN1, VOUTP1 and VOUTN1 select and output VH1 and VL1 according to VIN1.

  Similarly, in the driver circuit 12b, according to the control signals VIN, ENn and VPn, VNn from the data processing unit 11, whether or not VOUTPn and VOUTNn are output and VHn and VLn are selectively output. VOUTP1 and VOUTPn from the driver circuits 12a and 12b are connected to one input of the optical modulation element 3, and VOUTN1 and VOUTNn are connected to the other input.

  The driver circuit 12 shown in FIG. 5 makes it possible for the driver circuit to select and apply an arbitrary voltage set in advance to the optical modulation element 3 under the control of the data processing unit 11. In general, the voltage applied to the optical modulation element 3 can be switched and controlled at a higher speed by switching the voltage using the MOS transistors 60a to 63b, rather than variably controlling the voltage using the high voltage generation circuits 52a, 53a, 52b, and 53b. Irradiation laser power control at multiple levels during the wafer inspection period is possible.

  FIG. 6 is a configuration diagram showing a fourth embodiment of the foreign matter inspection apparatus according to the present invention. Similarly to the above description, in order to avoid the description from becoming complicated, the description of the components having the same reference numerals as those in the first embodiment is omitted.

  In the foreign matter inspection apparatus 100 shown in FIG. 6, the data processing unit 11 predicts the presence or absence of a large-diameter foreign matter, and controls voltage switching in the driver circuit 12. The polarization plane of the laser light that passes through the optical modulation element 3 is rotationally controlled by the predetermined voltage switched by the driver circuit 12, and the laser power that passes through the polarizing plate 4 is controlled. In the data processing unit 11, the laser power applied to the wafer 1 through the beam splitter 5 is detected by the optical power detection means 13, and the laser power output to the laser light source 2 is controlled based on the detection result. To do.

  When the laser power is controlled by controlling the polarization plane of the laser beam by using only the optical modulation element 3 and the polarizing plate 4, the relationship between the rotation angle of the polarization plane and the laser power is not linear. For this reason, in order to obtain the desired laser power with high accuracy, depending on the polarization plane of the laser light, high-precision control of the voltage applied from the driver circuit 12 to the optical modulation element 3 is required, which increases the device cost. To do.

  On the other hand, by combining the laser light source 2 as shown in the present embodiment, it is not necessary to provide high-cost high-accuracy voltage generation / control means in the driver circuit 12, and the performance wafer 1 is irradiated. The laser power can be controlled with high accuracy.

  In the above description, a MOS transistor is used as the voltage switching means for the sake of explanation. However, other semiconductor switching elements, relays, etc. may be used. Switching control and power supply voltage as a connection source for these elements may be used. It goes without saying that the laser power to be irradiated to the wafer under inspection and the irradiation laser power stabilization for a long time can be realized by dynamically controlling.

  In the above description, the binary voltage VH and VL is switched for the purpose of explanation. However, as described in the third embodiment, a plurality of driver circuits are provided to switch a plurality of voltages. It goes without saying that irradiation laser power control at a plurality of levels can be realized.

  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 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. Also, addition / deletion of other configurations for a part of the configuration of each embodiment. It is possible to make a substitution. Specific modifications are as follows.

  As a first modification, a defect inspection apparatus for inspecting a defect on the sample surface by irradiating the sample surface with a laser for a predetermined time, a laser light source for emitting a laser beam irradiated on the sample surface, and the emitted light A modulation unit that modulates a laser beam, a control unit that controls a voltage applied to the modulation unit, and a reflected light detection unit that detects scattered light reflected from the sample surface and generates a detection signal, and There is a defect inspection apparatus in which the control unit controls to switch the voltage applied to the modulation unit based on the detection result of the reflected light detection unit.

  As a second modification, a defect inspection apparatus for inspecting a defect on the sample surface by irradiating the sample surface with a laser for a predetermined time, a laser light source for emitting a laser beam irradiated on the sample surface, and the emitted light A modulation unit that modulates a laser beam; a control unit that controls a voltage applied to the modulation unit; and a laser power detection unit that detects the laser power that is modulated and applied to the sample surface. Is a voltage applied to the modulation unit when the laser power of the first time and the laser power of the second time are different as a result of detection by the laser power detection unit at the first time and the second time. There is a defect inspection device that controls.

  The defect inspection apparatus according to Modification 1 as Modification 3 includes a laser power detection unit that detects the laser power that is modulated and applied to the sample surface, and the control unit includes a first time As a result of detection by the laser power detection unit at a second time, a defect inspection that controls a voltage applied to the modulation unit when the laser power at the first time differs from the laser power at the second time There is a device.

  As a fourth modification, the defect inspection apparatus according to the second or third modification, wherein the control unit generates a first voltage to be applied to the modulation unit based on a result detected by the laser power detection unit. A first voltage generation unit; a second voltage generation unit configured to generate a second voltage; and a voltage switching unit configured to switch the generated first voltage or the second voltage and apply the second voltage to the modulation unit. The defect inspection method is characterized in that the control unit variably controls the voltage generated by the first voltage generation unit and the second voltage generation unit.

  As a fifth modification, the defect inspection apparatus according to any one of the first to third modifications, wherein the control unit includes a first voltage generation unit and a second voltage generation unit. There is a defect inspection apparatus characterized in that a potential difference between one voltage generation unit and the second voltage generation unit is applied to the modulation means.

  As a sixth modification, there is a defect inspection apparatus according to any one of the first to third modifications, wherein the defect inspection apparatus includes a plurality of the control units.

  The defect inspection apparatus according to Modification 2 or 3 as Modification 7, wherein the control unit controls the laser power emitted from the laser light source based on the detection result of the laser power detection unit. There is a defect inspection device.

  A modification 8 is a defect inspection method for inspecting a defect on the sample surface by irradiating the sample surface with a laser for a predetermined time, a laser emission step for emitting a laser beam irradiated on the sample surface, and a voltage. A modulation step for applying and modulating the emitted laser beam, a control step for controlling a voltage applied in the modulation step, and a reflected light detection step for detecting scattered light reflected from the sample surface and generating a detection signal In the control step, there is a defect inspection method in which the voltage applied in the modulation step is controlled based on the detection result in the reflected light detection step.

  The modification 9 is the defect inspection method according to the modification 8, in which the laser power detection step of detecting the laser power that is modulated and applied to the sample surface, and the control step includes a first time and a first time A defect inspection method for controlling a voltage applied in the modulation step when the laser power in the first time and the laser power in the second time are different as a result of detection in the laser power detection step at a second time. is there.

  The modification 10 is the defect inspection method according to the modification 9, in which the control step generates a first voltage to be applied in the modulation step based on a result detected in the laser power detection step. A voltage generation step, a second voltage generation step of generating a second voltage, and a voltage switching step of switching the generated first voltage or the second voltage and applying in the modulation step, In the control step, there is a defect inspection method characterized in that the voltage generated in the first voltage generation step and the second voltage generation step is variably controlled.

  The modification 11 is the defect inspection method according to the modification 8 or 9, wherein the control unit includes a first voltage generation step and a second voltage generation step, and the first voltage generation step and the second voltage generation step. There is a defect inspection method characterized in that a potential difference from a voltage generation step is applied in the modulation step.

  As a modification 12, the defect inspection method according to the modification 9 is characterized in that, in the control step, the laser power emitted in the laser emission step is controlled based on the detection result in the laser power detection step. There is a defect inspection method.

  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 1 Wafer 2 Laser light source 3 Optical modulation element 4 Polarizing plate 5 Beam splitter 6 Mirror 7, 8 Lens 9 Sensor 10 Detection circuit 11 Data processing part 12 Driver circuit 13 Optical power detection means 14 Stage 51 Input circuit 52, 53 High voltage generation circuit 54 , 55 Level shift circuits 56, 57, 58, 59 MOS drive circuits 60, 62 PMOS transistors 61, 63 NMOS transistors 64, 65 High voltage generation circuit 100 Foreign matter inspection device

Claims (12)

A defect inspection apparatus for inspecting a defect on the sample surface by irradiating the sample surface with a laser for a predetermined time,
A laser light source for emitting a laser beam applied to the sample surface;
A modulator for modulating the emitted laser beam;
A control unit for controlling a voltage applied to the modulation unit;
A reflected light detector that detects scattered light reflected from the sample surface and generates a detection signal;
With
The said control part is a defect inspection apparatus which controls so that the voltage applied to the said modulation | alteration part may be switched based on the detection result in the said reflected light detection part. A defect inspection apparatus for inspecting a defect on the sample surface by irradiating the sample surface with a laser for a predetermined time,
A laser light source for emitting a laser beam applied to the sample surface;
A modulator for modulating the emitted laser beam;
A control unit for controlling a voltage applied to the modulation unit;
A laser power detector that detects the laser power that is modulated and applied to the sample surface;
With
When the laser power detection unit detects that the laser power at the first time and the laser power at the second time are different from each other as a result of detection by the laser power detection unit at the first time and the second time, A defect inspection device that controls the voltage to be applied. The defect inspection apparatus according to claim 1,
A laser power detector that detects the laser power that is modulated and applied to the sample surface;
With
When the laser power detection unit detects that the laser power at the first time and the laser power at the second time are different from each other as a result of detection by the laser power detection unit at the first time and the second time, A defect inspection device that controls the voltage to be applied. The defect inspection apparatus according to claim 2 or 3,
The controller is
Based on the result detected by the laser power detector, a first voltage generator that generates a first voltage to be applied to the modulator, a second voltage generator that generates a second voltage,
A voltage switching unit that switches the generated first voltage or second voltage to be applied to the modulation unit, and
The control unit variably controls a voltage generated by the first voltage generation unit and the second voltage generation unit;
A defect inspection apparatus characterized by that. A defect inspection apparatus according to any one of claims 1 to 3,
The control means includes a first voltage generation unit and a second voltage generation unit,
Applying a potential difference between the first voltage generation unit and the second voltage generation unit to the modulation unit;
A defect inspection apparatus characterized by that. A defect inspection apparatus according to any one of claims 1 to 3,
A defect inspection apparatus comprising a plurality of the control units. The defect inspection apparatus according to claim 2 or 3,
The said control part controls the laser power radiate | emitted from a laser light source based on the detection result in the said laser power detection part, The defect inspection apparatus characterized by the above-mentioned. A defect inspection method for inspecting a defect on the sample surface by irradiating the sample surface with a laser for a predetermined time,
A laser emission step of emitting a laser beam applied to the sample surface;
A modulation step of applying a voltage to modulate the emitted laser beam;
A control step for controlling the voltage applied in the modulation step;
A reflected light detection step of detecting scattered light reflected from the sample surface and generating a detection signal;
With
In the control step, a defect inspection method of controlling to switch a voltage applied in the modulation step based on a detection result in the reflected light detection step. The defect inspection method according to claim 8,
A laser power detection step of detecting the laser power that is modulated and applied to the sample surface;
In the control step, when the laser power detection step at the first time and the second time detect the laser power at the first time and the laser power at the second time are different, the modulation step A defect inspection method for controlling a voltage to be applied. The defect inspection method according to claim 9,
The control step includes
Based on the result detected in the laser power detection step, a first voltage generation step for generating a first voltage applied in the modulation step, a second voltage generation step for generating a second voltage,
A voltage switching step of switching the generated first voltage or second voltage and applying in the modulation step;
Have
In the control step, the voltage generated in the first voltage generation step and the second voltage generation step is variably controlled.
A defect inspection method characterized by that. The defect inspection method according to claim 8 or 9,
The control means includes a first voltage generation step and a second voltage generation step,
Applying a potential difference between the first voltage generation step and the second voltage generation step in the modulation step;
A defect inspection method characterized by that. The defect inspection method according to claim 9,
In the control step, the laser power emitted in the laser emission step is controlled based on the detection result in the laser power detection step.

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