JP2017142087A - Measurement device, measurement method, and computer program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep a sample from coming in contact with any special member in order to measure the refractive index of the sample.SOLUTION: A measurement device (100) comprises: acquisition means (1521) for acquiring, for each irradiation position, a first time (t) required for an electromagnetic wave (THz) radiated to the surface (10a) of a sample (10) to reach a prescribed position after being reflected at the surface and a second time (t) required for the electromagnetic wave to reach a prescribed position after being reflected at the reverse side of the sample; calculation means (1522) for calculating virtual data (A, B) pertaining to the sample for each of a plurality of irradiation positions on the basis of the first and second times and a virtual value (n) of the refractive index (n) of the sample; display means (181) for displaying the virtual data; and operation means (182) for accepting virtual value adjustment operation by a user.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a technical field of a measurement apparatus, a measurement method, and a computer program that measure a refractive index of a sample using, for example, a terahertz wave.

  As a measurement device for measuring the refractive index of a sample, a measurement device using a terahertz wave is known. For example, in Patent Document 1, a sample is irradiated with a terahertz wave through a transmission member that is in contact with the sample, and based on the time waveform of the terahertz wave reflected by the transmission member and the time waveform of the terahertz wave reflected by the sample. An information acquisition device for acquiring the refractive index of a sample is described. For example, Patent Document 2 discloses that a terahertz wave is irradiated on a specimen disposed between a reflecting member and a plate-like member through the plate-like member and reflected at the interface between the plate-like member and the specimen. An information acquisition device is described that acquires the refractive index of a specimen based on the time waveform of the wave and the time waveform of the terahertz wave reflected at the interface between the specimen and the reflecting member.

JP 2014-209094 A Japanese Patent Laying-Open No. 2015-83964

  In the information acquisition apparatuses described in Patent Documents 1 and 2, in order to measure the refractive index, a special member (specifically, a transmission member or a plate-like member) with respect to a sample (in other words, a specimen) And the reflective member) need to be in close contact with each other. However, for some reason, there is a possibility that a special member cannot be brought into close contact with the sample. In this case, the technical problem that the information acquisition apparatus described in patent documents 1 and 2 cannot measure the refractive index of a sample arises.

  Examples of problems to be solved by the present invention include the above. It is an object of the present invention to provide a measuring apparatus, a measuring method, and a computer program that do not require any special member to be brought into contact with the sample in order to measure the refractive index of the sample.

  The first example of the measuring device according to the present invention is the first time required for the electromagnetic wave applied to the surface of the sample to reach a predetermined position after being reflected by the surface, and after the electromagnetic wave is reflected from the back surface of the sample. Based on acquisition means for acquiring a second time required to reach a predetermined position for each of a plurality of different irradiation positions on the surface, the first and second times, and a virtual value of the refractive index of the sample, A calculation unit that calculates virtual data regarding the sample for each of a plurality of irradiation positions, a display unit that displays the virtual data, and an operation unit that receives an adjustment operation of the virtual value by a user.

  The first example of the measurement method of the present invention is the first time required for the electromagnetic wave irradiated on the surface of the sample to reach a predetermined position after being reflected on the surface, and after the electromagnetic wave is reflected on the back surface of the sample. Based on an acquisition step of acquiring a second time required to reach a predetermined position for each of a plurality of different irradiation positions on the surface, the first and second times, and a virtual value of the refractive index of the sample, A calculation step of calculating virtual data regarding the sample for each of a plurality of irradiation positions; a display step of displaying the virtual data; and an operation step of accepting an adjustment operation of the virtual value by a user.

  The first example of the computer program of the present invention causes a computer to execute the first example of the measurement method of the present invention described above.

FIG. 1 is a block diagram illustrating a configuration of the terahertz wave measuring apparatus according to the present embodiment. FIG. 2 is a flowchart illustrating an example of a flow of a first measurement operation for measuring a refractive index and a thickness performed by the terahertz wave measuring apparatus. FIG. 3 is a cross-sectional view of the sample showing the optical path of the terahertz wave irradiated to the sample and the optical path of the terahertz wave reflected by the sample. FIG. 4 is a graph showing a waveform signal of the terahertz wave detected by the terahertz wave detecting element. FIG. 5 is a cross-sectional view of the sample showing the optical path of the terahertz wave irradiated to the first position and the optical path of the terahertz wave irradiated to the second position. FIG. 6 is a flowchart illustrating an example of a flow of a second measurement operation for measuring the refractive index and the thickness performed by the terahertz wave measuring apparatus. FIG. 7 is a flowchart illustrating an example of a flow of a third measurement operation for measuring the refractive index and the thickness performed by the terahertz wave measuring apparatus. FIG. 8 is a cross-sectional view showing the relationship between the actual sample and the distance to the front surface and the distance to the back surface calculated when the refractive index is assumed to be a virtual value. FIG. 9 is a graph showing the distance to the front surface and the distance to the back surface. FIG. 9 is a graph showing the distance to the back surface calculated before the virtual value of the refractive index is adjusted and the distance to the back surface calculated after the virtual value of the refractive index is adjusted. FIG. 11 is a flowchart illustrating an example of a flow of a fourth measurement operation for measuring the refractive index and the thickness performed by the terahertz wave measuring apparatus. FIG. 12 is a graph showing the relationship between the distance to the front surface and the distance to the back surface. FIG. 13 is a flowchart illustrating an example of a flow of a fifth measurement operation for measuring the refractive index and the thickness performed by the terahertz wave measuring apparatus. FIG. 14 is a graph showing the relationship between the regression coefficient and the virtual value of the refractive index. FIG. 15 is a graph showing the relationship between the predetermined coefficient calculated from the regression coefficient and the virtual value of the refractive index.

  Hereinafter, embodiments of the measurement apparatus, the measurement method, and the computer program will be described.

(Embodiment of measuring device)
<1>
The measurement apparatus according to the present embodiment reaches the predetermined position after the first time required for the electromagnetic wave irradiated on the surface of the sample to reach a predetermined position after being reflected on the surface and the electromagnetic wave reflected on the back surface of the sample. The plurality of irradiation positions based on acquisition means for acquiring the second time required for each of the plurality of different irradiation positions on the surface, the first and second times, and a virtual value of the refractive index of the sample A calculation unit that calculates virtual data relating to each sample; a display unit that displays the virtual data; and an operation unit that receives an adjustment operation of the virtual value by a user.

  According to the measurement apparatus of the present embodiment, as will be described in detail later using specific mathematical formulas, a plurality of first times and a plurality of times corresponding to a plurality of irradiation positions without contacting any special member with the sample. The refractive index of the sample can be appropriately measured (that is, calculated) based on the virtual value of the refractive index of the sample during the second time. In particular, since the refractive index is measured based on virtual data (that is, virtual data indicating some characteristic of the sample) calculated under the assumption that the refractive index of the sample is a virtual value, the first and second Even when the accuracy of time is relatively deteriorated, the refractive index can be measured with a reasonably high accuracy. In addition, since the virtual data is presented to the user and the measuring device accepts the adjustment operation of the virtual value by the user, the refractive index is appropriately measured (calculated) while taking the user's judgment.

<2>
In another aspect of the measurement apparatus of the present embodiment, the virtual data includes virtual shape data related to a virtual shape of the sample for each of the plurality of irradiation positions when the refractive index is assumed to be the virtual value. Including.

  According to this aspect, the refractive index is appropriately measured based on the virtual shape data.

<3>
In another aspect of the measurement apparatus of the present embodiment, the virtual data includes virtual shape data related to a virtual shape of the back surface for each of the plurality of irradiation positions when the refractive index is assumed to be the virtual value. Including.

  According to this aspect, the refractive index is appropriately measured based on the virtual shape data.

<4>
In another aspect of the measurement apparatus of the present embodiment, the virtual data is a virtual distance from the predetermined position to the back surface for each of the plurality of irradiation positions when the refractive index is assumed to be the virtual value. The virtual shape data regarding the virtual shape of the back surface specified by is included.

  According to this aspect, the refractive index is appropriately measured based on the virtual shape data.

<5>
In another aspect of the measurement apparatus of the present embodiment, the calculation unit recalculates the virtual data based on the adjusted virtual value, triggered by the operation unit receiving the adjustment operation, The display means displays the virtual data calculated based on the adjusted virtual value.

  According to this aspect, the user can appropriately recognize the virtual data after performing the adjustment operation.

<6>
In another aspect of the measurement apparatus of the present embodiment, the display means further displays a smooth line connecting the discrete virtual data for each of the plurality of irradiation positions.

  According to this aspect, the user can appropriately recognize the virtual data.

<7>
In another aspect of the measurement apparatus of the present embodiment, the electromagnetic wave is a terahertz wave, an irradiation unit that irradiates the terahertz wave toward the surface, and a detection unit that detects the terahertz wave reflected by the sample. And the predetermined position is a position where the detection means is installed, and the first time, the terahertz wave reflected from the surface after the irradiation means irradiates the terahertz wave. The time required to reach the detection means, and the second time is required until the terahertz wave reflected from the back surface reaches the detection means after the irradiation means irradiates the terahertz wave. It's time.

  According to this aspect, the measuring apparatus can suitably measure the refractive index of the sample using the irradiation unit and the detection unit.

<8>
In another aspect of the measurement apparatus of the present embodiment, the thickness of the sample, which is a physical distance between the front surface and the back surface, differs for each irradiation position.

  According to this aspect, the measurement apparatus can suitably measure (that is, calculate) the refractive index of the sample by irradiating the terahertz waves to a plurality of irradiation positions having different sample thicknesses.

(Embodiment of measurement method)
<9>
In the measurement method of the present embodiment, the first time required for the electromagnetic wave irradiated on the surface of the sample to reach a predetermined position after being reflected on the surface and the predetermined position after the electromagnetic wave is reflected on the back surface of the sample. A plurality of irradiation positions based on an acquisition step of acquiring the second time required for each of the plurality of different irradiation positions on the surface, the first and second times, and a virtual value of the refractive index of the sample. A calculation step of calculating virtual data relating to each sample, a display step of displaying the virtual data, and an operation step of accepting an adjustment operation of the virtual value by a user.

  According to the measurement device of the present embodiment, it is possible to suitably enjoy the same effects as the effects that the measurement device of the present embodiment described above can enjoy.

  Incidentally, in response to various aspects adopted by the measurement apparatus of this embodiment, the measurement method of this embodiment may adopt various aspects.

(Embodiment of computer program)
<10>
The computer program of this embodiment causes a computer to execute the measurement method of this embodiment described above.

  According to the computer program of the present embodiment, it is possible to suitably enjoy the same effects as those received by the measurement apparatus of the present embodiment described above.

  Incidentally, in response to various aspects adopted by the measurement apparatus of the present embodiment, the computer program of the present embodiment may adopt various aspects. The computer program may be recorded on a computer-readable recording medium.

  The operation and other gains of the measurement apparatus, measurement method, and computer program of the present embodiment will be described in more detail in the following examples.

  As described above, the measurement apparatus according to the present embodiment includes an acquisition unit, a calculation unit, a display unit, and an operation unit. The measurement method of the present embodiment includes an acquisition process, a calculation process, a display process, and an operation process. The computer program of this embodiment causes a computer to execute the measurement method of this embodiment described above. Therefore, the refractive index of the sample is measured even when no special member is brought into contact with the sample.

  Hereinafter, embodiments of a measurement device, a measurement method, and a computer program will be described with reference to the drawings. In particular, in the following, examples of the measurement apparatus, the measurement method, and the computer program are applied to the terahertz wave measurement apparatus 100 that measures the refractive index n of the sample 10 by irradiating the sample 10 with the terahertz wave THz. Use this to explain. However, the embodiments of the measurement apparatus, the measurement method, and the computer program are applied to any measurement apparatus that measures the refractive index n (or other characteristics) of the sample 10 by irradiating the sample 10 with an arbitrary electromagnetic wave. May be.

(1) Configuration of Terahertz Wave Measuring Device 100 First, the configuration of the terahertz wave measuring device 100 of the present embodiment will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration of a terahertz wave measuring apparatus 100 according to the present embodiment.

  As shown in FIG. 1, the terahertz wave measuring apparatus 100 irradiates the sample 10 with the terahertz wave THz, and detects the terahertz wave THz reflected by the sample 10 (that is, the terahertz wave THz irradiated on the sample 10).

The terahertz wave THz is an electromagnetic wave including an electromagnetic wave component belonging to a frequency region (that is, a terahertz region) around 1 terahertz (1 THz = 10 ¹² Hz). The terahertz region is a frequency region that combines light straightness and electromagnetic wave transparency. The terahertz region is a frequency region in which various substances have unique absorption spectra. Therefore, the terahertz wave measuring apparatus 100 can measure the characteristics of the sample 10 by analyzing the terahertz wave THz irradiated on the sample 10. In the present embodiment, the terahertz wave measuring apparatus 100 can measure the refractive index n of the sample 10 which is an example of the characteristics of the sample 10 by analyzing the terahertz wave THz irradiated on the sample 10.

  Here, since the period of the terahertz wave THz is a period of the order of sub-picoseconds, it is technically difficult to directly detect the waveform of the terahertz wave THz. Therefore, the terahertz wave measuring apparatus 100 indirectly detects the waveform of the terahertz wave THz by employing a pump-probe method based on time delay scanning. Hereinafter, the terahertz wave measuring apparatus 100 that employs such a pump-probe method will be described more specifically.

  As shown in FIG. 1, the terahertz wave measuring apparatus 100 includes a pulse laser apparatus 101, a terahertz wave generating element 110 that is a specific example of “irradiating means”, a beam splitter 161, a reflecting mirror 162, and a reflecting mirror 163. A half mirror 164, an optical delay mechanism 120, a terahertz wave detecting element 130 which is a specific example of “detecting means”, a bias voltage generating unit 141, an IV (current-voltage) converting unit 142, A control unit 150, a stage 170, a display 181, and an input device 182 are provided.

  The pulse laser device 101 generates pulse laser light LB in the sub-picosecond order or femtosecond order having light intensity corresponding to the drive current input to the pulse laser device 101. The pulse laser beam LB generated by the pulse laser device 101 is incident on the beam splitter 161 via a light guide (not shown) (for example, an optical fiber).

  The beam splitter 161 branches the pulsed laser light LB into pump light LB1 and probe light LB2. The pump light LB1 is incident on the terahertz wave generation element 110 through a light guide path (not shown). On the other hand, the probe light LB2 enters the optical delay mechanism 120 via a light guide path and a reflecting mirror 162 (not shown). Thereafter, the probe light LB2 emitted from the optical delay mechanism 120 is incident on the terahertz wave detection element 130 via the reflecting mirror 163 and a light guide path (not shown).

  The terahertz wave generating element 110 emits a terahertz wave THz. Specifically, the terahertz wave generating element 110 includes a pair of electrode layers facing each other with a gap interposed therebetween. A bias voltage generated by the bias voltage generation unit 141 is applied to the gap via a pair of electrode layers. When the pump light LB1 is irradiated to the gap while an effective bias voltage (for example, a bias voltage other than 0 V) is applied to the gap, the pump light LB1 is also applied to the photoconductive layer formed below the gap. Is irradiated. In this case, carriers are generated in the photoconductive layer irradiated with the pump light LB1 by light excitation by the pump light LB1. As a result, the terahertz wave generating element 110 generates a pulse-shaped current signal in the order of subpicoseconds or in the order of femtoseconds corresponding to the generated carrier. The generated current signal flows through the pair of electrode layers. As a result, the terahertz wave generating element 110 emits the terahertz wave THz resulting from the pulsed current signal.

  The terahertz wave THz emitted from the terahertz wave generating element 110 is transmitted through the half mirror 164. As a result, the terahertz wave THz transmitted through the half mirror 164 is irradiated to the sample 10 (particularly, the surface 10a of the sample 10). The terahertz wave THz irradiated on the sample 10 is reflected by the sample 10 (particularly, by the front surface 10a and the back surface 10b of the sample). The terahertz wave THz reflected by the sample 10 is reflected by the half mirror 164. The terahertz wave THz reflected by the half mirror 164 enters the terahertz wave detection element 130.

  The terahertz wave detection element 130 detects the terahertz wave THz incident on the terahertz wave detection element 130. Specifically, the terahertz wave detection element 130 includes a pair of electrode layers facing each other with a gap interposed therebetween. When the probe light LB2 is irradiated to the gap, the probe light LB2 is also irradiated to the photoconductive layer formed below the gap. In this case, carriers are generated in the photoconductive layer irradiated with the probe light LB2 by light excitation by the probe light LB2. As a result, a current signal corresponding to the carrier flows through the pair of electrode layers included in the terahertz wave detection element 130. When the terahertz wave detection element 130 is irradiated with the terahertz wave THz while the probe light LB2 is irradiated on the gap, the signal intensity of the current signal flowing through the pair of electrode layers changes according to the light intensity of the terahertz wave THz. To do. A current signal whose signal intensity changes according to the light intensity of the terahertz wave THz is output to the IV conversion unit 142 via the pair of electrode layers.

  The optical delay mechanism 120 adjusts the difference (that is, the optical path length difference) between the optical path length of the pump light LB1 and the optical path length of the probe light LB2. Specifically, the optical delay mechanism 120 adjusts the optical path length difference by adjusting the optical path length of the probe light LB2. When the optical path length difference is adjusted, the timing at which the pump light LB1 is incident on the terahertz wave generation element 110 (or the timing at which the terahertz wave generation element 110 emits the terahertz wave THz) and the probe light LB2 are detected by the terahertz wave detection element 130. The time difference from the timing at which the light enters (or the timing at which the terahertz wave detecting element 130 detects the terahertz wave THz) is adjusted. The terahertz wave measuring apparatus 100 indirectly detects the waveform of the terahertz wave THz by adjusting the time difference. For example, when the optical path of the probe light LB2 is increased by 0.3 millimeters (however, the optical path length in the air) by the optical delay mechanism 120, the timing at which the probe light LB2 enters the terahertz wave detection element 130 is delayed by 1 picosecond. Become. In this case, the timing at which the terahertz wave detecting element 130 detects the terahertz wave THz is delayed by 1 picosecond. Considering that the terahertz wave THz having the same waveform repeatedly enters the terahertz wave detecting element 130 at intervals of about several tens of MHz, the timing at which the terahertz wave detecting element 130 detects the terahertz wave THz is gradually shifted. Thus, the terahertz wave detection element 130 can indirectly detect the waveform of the terahertz wave THz. That is, the lock-in detection unit 151 described later can detect the waveform of the terahertz wave THz based on the detection result of the terahertz wave detection element 130.

  The current signal output from the terahertz wave detection element 130 is converted into a voltage signal by the IV conversion unit 142.

  The control unit 150 performs a control operation for controlling the entire operation of the terahertz wave measuring apparatus 100. The control unit 150 includes a CPU (Central Processing Unit) and a memory. The memory stores a computer program for causing the control unit 150 to perform a control operation. When the computer program is executed by the CPU, a logical processing block for performing a control operation is formed inside the CPU. However, the computer program may not be recorded in the memory. In this case, the CPU may execute a computer program downloaded via a network.

  As an example of the control operation, the control unit 150 performs a measurement operation for measuring the characteristics of the sample 10 based on the detection result of the terahertz wave detection element 130 (that is, the voltage signal output from the IV conversion unit 142). In order to perform the measurement operation, the control unit 150 includes a lock-in detection unit 151 and a signal processing unit 152 as logical processing blocks formed in the CPU.

  The lock-in detection unit 151 performs synchronous detection on the voltage signal output from the IV conversion unit 142 using the bias voltage generated by the bias voltage generation unit 141 as a reference signal. As a result, the lock-in detection unit 151 detects a sample value of the terahertz wave THz. Thereafter, the same operation is repeated while appropriately adjusting the difference between the optical path length of the pump light LB1 and the optical path length of the probe light LB2 (that is, the optical path length difference). The waveform (time waveform) of the terahertz wave THz detected by the detection element 130 can be detected. The lock-in detection unit 151 outputs a waveform signal indicating the waveform of the terahertz wave THz detected by the terahertz wave detection element 130 to the signal processing unit 152. That is, the lock-in detection unit 151 removes a noise component having a frequency different from that of the reference signal from the voltage signal output from the IV conversion unit 142 (that is, the detection signal of the terahertz wave THz). That is, the lock-in detection unit 151 detects a waveform signal with relatively high sensitivity and relatively high accuracy by performing synchronous detection using the detection signal and the reference signal. When the terahertz wave measuring apparatus 100 does not use lock-in detection, a DC voltage may be applied to the terahertz wave generating element 110 as a bias voltage.

  As an example of the control operation, the signal processing unit 152 performs a measurement operation for measuring the characteristics of the sample 10 based on the waveform signal output from the lock-in detection unit 151. For example, the signal processing unit 152 acquires a frequency spectrum of the terahertz wave THz using terahertz time domain spectroscopy, and performs a measurement operation that measures the characteristics of the sample 10 based on the frequency spectrum.

  Particularly in the present embodiment, the signal processing unit 152 performs a measurement operation for measuring the refractive index n of the sample 10, which is a specific example of the characteristics of the sample 10, based on the waveform signal output from the lock-in detection unit 151. . Furthermore, the signal processing unit 152 is based on the waveform signal output from the lock-in detection unit 151, and the thickness d of the sample 10, which is a specific example of the characteristics of the sample 10 (that is, the terahertz wave THz relative to the sample 10 A measurement operation for measuring the thickness d) along the direction in which the light enters is performed. Here, the thickness d means “physical distance between the front surface 10a and the back surface 10b”. In order to perform the measurement operation, the signal processing unit 152 includes a detection time acquisition unit 1521, a refractive index calculation unit 1522, and a thickness calculation unit 1523 as logical processing blocks formed inside the CPU. Note that specific examples of operations of the detection time acquisition unit 1521, the refractive index calculation unit 1522, and the thickness calculation unit 1523 will be described in detail later and will not be described here.

  The stage 170 holds the sample 10. In the example shown in FIG. 1, the stage 170 holds the sample 10 so that the back surface 10b of the sample 10 faces the stage 170 side. The stage 170 is movable along a predetermined movement direction while holding the sample 10. When the stage 170 moves, the irradiation position on the sample 10 of the terahertz wave THz changes.

  The movement of the stage 170 is controlled by the control unit 150. Specifically, the control unit 150 includes an irradiation position changing unit 153 as a logical processing block formed inside the CPU. The irradiation position changing unit 153 controls the movement of the stage 170 so that the irradiation position of the terahertz wave THz is adjusted (for example, changed to a desired position).

  The irradiation position changing unit 153 moves the irradiation position of the terahertz wave THz by moving at least one of the terahertz wave generation element 110 and the terahertz wave detection element 130 in addition to or instead of moving the stage 170. May be adjusted.

The display 181 can display a desired image. Particularly in the embodiment, as described later, the display 181, under the control of the refractive index calculator 1522, a virtual relates to a sample 10 on the assumption that a virtual value n _v with the refractive index n of the sample 10 Display data.

  The input device 182 receives user operations. The input device 182 includes, for example, a keyboard, a mouse, a touch panel, operation buttons, an operation dial, and other arbitrary operation devices.

(2) Measurement Operation for Measuring Refractive Index n and Thickness d Performed by Terahertz Wave Measuring Device 100 Subsequently, referring to FIGS. 2 to 15, the refractive index n and the thickness d performed by the terahertz wave measuring device 100 are determined. A measurement operation to be measured will be described. In the present embodiment, the terahertz wave measuring apparatus 100 performs at least one of five types of measurement operations (first measurement operation to fifth measurement operation) as a measurement operation for measuring the refractive index n and the thickness d. . Hereinafter, the first measurement operation to the fifth measurement operation will be described in order.

(2-1) First Measurement Operation for Measuring Refractive Index n and Thickness d First, a first measurement operation for measuring refractive index n and thickness d performed by the terahertz wave measuring apparatus 100 with reference to FIG. explain. FIG. 2 is a flowchart illustrating an example of a flow of a first measurement operation for measuring the refractive index n and the thickness d performed by the terahertz wave measuring apparatus 100.

  2, the irradiation position changing unit 153 controls the stage 170 so that the irradiation position of the terahertz wave THz becomes the first position P # 1 (1) on the surface 10a of the sample 10 (step S101).

  Thereafter, the terahertz wave generating element 110 emits the terahertz wave THz toward the surface 10a of the sample 10 (step S102). That is, the terahertz wave generating element 110 irradiates the first position P # 1 (1) on the surface 10a of the sample 10 with the terahertz wave THz (step S102).

  The terahertz wave THz irradiated on the sample 10 a is reflected by the sample 10. Here, the reflection of the terahertz wave THz by the sample 10 will be described with reference to FIG. FIG. 3 is a cross-sectional view of the sample 10 showing the optical path of the terahertz wave THz irradiated on the sample 10 and the optical path of the terahertz wave THz reflected by the sample 10.

  As shown in FIG. 3, a part of the terahertz wave THz irradiated on the sample 10 is reflected by the surface 10 a of the sample 10. The terahertz wave THz reflected by the surface 10a propagates from the sample 10 to the terahertz wave detecting element 130.

  On the other hand, a part of the terahertz wave THz irradiated on the sample 10 passes through the inside of the sample 10 without being reflected by the surface 10a. Thereafter, the terahertz wave THz transmitted through the sample 10 reaches the back surface 10 b of the sample 10. As a result, a part of the terahertz wave THz transmitted through the sample 10 is reflected by the back surface 10 b of the sample 10. The terahertz wave THz reflected by the back surface 10b passes through the sample 10 again. Thereafter, the terahertz wave THz transmitted through the sample 10 reaches the surface 10 a of the sample 10. As a result, a part of the terahertz wave THz reflected by the back surface 10 b propagates from the sample 10 to the terahertz wave detecting element 130.

  In this embodiment, the front surface 10a and the back surface 10b are the two outer surfaces of the sample 10 facing each other along the propagation direction of the terahertz wave THz in the sample 10 (the horizontal direction in FIGS. 1 and 3). Means. In this case, the surface 10a corresponds to one outer surface close to the terahertz wave generating element 110 and the terahertz wave detecting element 130 among the two outer surfaces. On the other hand, the back surface 10b corresponds to the other outer surface far from the terahertz wave generating element 110 and the terahertz wave detecting element 130 out of the two outer surfaces.

  Further, in order to promote the reflection of the terahertz wave THz by the back surface 10b of the sample 10, a reflecting member may be disposed so as to be in contact with or in close contact with the back surface 10b of the sample 10.

  In FIG. 2 again, the terahertz wave THz reflected by the sample 10 is detected by the terahertz wave detecting element 130 (step S102). As a result, a waveform signal indicating the waveform of the terahertz wave THz detected by the terahertz wave detecting element 130 is input to the signal processing unit 152.

Thereafter, the detection time acquisition unit 1521 acquires the first detection time t _a1 and the second detection time t _b1 based on the waveform signal input to the signal processing unit 152 (step S103). That is, the terahertz wave measuring apparatus 100 acquires the first detection time t _a1 and the second detection time t _b1 based on the detection result of the terahertz wave THz irradiated to the first position P # 1 (1). Detection time acquisition unit 1521 outputs the terahertz wave THz first position P # 1 first detection time _{t a1} and the second detection time _{t b1} obtained when irradiated in (1), the refractive index calculation unit 1522 To do. The first detection time t _a1 and the second detection time t _b1 are specific examples of “first time” and “second time”, respectively.

Here, with reference to FIG. 4, the acquisition operation of the first detection time t _a1 and the second detection time t _b1 will be described. FIG. 4 is a graph showing a waveform signal of the terahertz wave THz detected by the terahertz wave detecting element 130.

  As shown in FIG. 4, the waveform signal includes a waveform signal corresponding to the terahertz wave THz reflected by the front surface 10a and a waveform signal corresponding to the terahertz wave THz reflected by the back surface 10b. The terahertz wave THz reflected by the back surface 10b reaches the terahertz wave detecting element 130 after passing through the inside of the sample 10, while the terahertz wave THz reflected by the front surface 10a does not pass through the inside of the sample 10 and does not pass through the terahertz wave THz. The wave detection element 130 is reached. For this reason, the terahertz wave THz reflected by the back surface 10b reaches the terahertz wave detecting element 130 later in time than the terahertz wave THz reflected by the front surface 10a. Therefore, also on the waveform signal, the waveform signal corresponding to the terahertz wave THz reflected by the back surface 10b is delayed in time from the waveform signal corresponding to the terahertz wave THz reflected by the front surface 10a.

The first detection time _ta1 is a time required for the terahertz wave THz reflected from the surface 10a of the sample 10 to reach the terahertz wave detection element 130 after the terahertz wave generation element 110 starts irradiation with the terahertz wave THz. is there. On the other hand, the second detection time _tb1 is from when the terahertz wave generation element 110 starts irradiation of the terahertz wave THz until the terahertz wave THz reflected by the back surface 10b of the sample 10 reaches the terahertz wave detection element 130. It takes time. The detection time acquisition unit 1521 can easily acquire (in other words, calculate or specify) the first detection time t _a1 and the second detection time t _b1 by analyzing the waveform signal.

In FIG. 2 again, after that, the terahertz wave measuring apparatus 100 performs the above-described operation (that is, the operation for obtaining the first detection time t _a2 and the second detection time t _b2 ) again after changing the irradiation position. Specifically, the irradiation position changing unit 153 determines that the irradiation position of the terahertz wave THz is the second position P # 1 (2) on the surface 10a of the sample 10 (however, the second position P # 1 (2) is The stage 170 is controlled so as to be different from the first position P # 1 (1) (step S111). As a result, the stage 170 moves by a predetermined movement amount along a predetermined movement direction.

  Here, the first position P # 1 (1) and the second position P # 1 (1) irradiated with the terahertz wave THz will be described with reference to FIG. FIG. 5 is a cross-sectional view of the sample 10 showing the optical path of the terahertz wave THz irradiated to the first position P # 1 (1) and the optical path of the terahertz wave THz irradiated to the second position P # 1 (2). .

  As shown in FIG. 5, in the first measurement operation, the first position P # 1 (1) and the second position P # 1 (2) are irradiated with the terahertz wave THz at the first position P # 1 (1). The distance L11 between the terahertz wave generating element 110 and the back surface 10b under the condition where the terahertz wave is generated, and the terahertz wave generating element 110 under the condition where the second position P # 1 (2) is irradiated with the terahertz wave THz. The first condition that the distance L21 to the back surface 10b is the same is satisfied. Further, the first position P # 1 (1) and the second position P # 1 (2) are the terahertz wave detection element 130 in a state where the first position P # 1 (1) is irradiated with the terahertz wave THz. L13 between the back surface 10b and the distance L23 between the terahertz wave detecting element 130 and the back surface 10b under the condition where the second position P # 1 (2) is irradiated with the terahertz wave THz. The second condition of being is satisfied. That is, the irradiation position changing unit 153 controls the stage 170 so as to satisfy the first and second conditions. In other words, the irradiation position changing unit 153 irradiates the terahertz wave THz to each of the first position P # 1 (1) and the second position P # 1 (2) that satisfy the first and second conditions. The stage 170 is controlled.

  In order to control the stage 170 so as to satisfy the first and second conditions, the irradiation position changing unit 153 controls the stage 170 so that the moving direction of the stage 170 is parallel to the back surface 10 b of the sample 10. In other words, in order to control the stage 170 so as to satisfy the first and second conditions, the irradiation position changing unit 153 moves the stage 170 so that the stage 170 moves along a direction parallel to the back surface 10 b of the sample 10. To control. As a result, even when the irradiation position of the terahertz wave THz is changed, the distance between the terahertz wave generating element 110 and the back surface 10b does not change. Similarly, even when the irradiation position of the terahertz wave THz is changed, the distance between the terahertz wave detecting element 130 and the back surface 10b does not change.

  Here, “the stage 170 moves along a direction parallel to the back surface 10b” means “the stage 170 in a state where the terahertz wave THz is applied to the first position P # 1 (1)”. And the stage 170 moves so that the stage 170 under the condition where the terahertz wave THz is irradiated to the second position P # 1 (1) is aligned along the direction parallel to the back surface 10b ". means. Such a state is realized by the stage 170 moving only along the first direction parallel to the back surface 10b. Alternatively, in such a state, even when the stage 170 moves along the first direction parallel to the back surface 10b and the second direction intersecting the back surface 10b, the amount of movement of the stage 170 along the second direction is small. As long as the total is zero (ie offset), it will be realized.

  In addition to or instead of moving the stage 170, the irradiation position changing unit 153 moves at least one of the terahertz wave generation element 110 and the terahertz wave detection element 130, whereby the irradiation position of the terahertz wave THz. As described above, may be adjusted. Even in this case, the irradiation position changing unit 153 moves at least one of the terahertz wave generation element 110 and the terahertz wave detection element 130 so as to satisfy the first and second conditions.

  In addition, as shown in FIG. 5, in the first operation example, the first position P # 1 (1) and the second position P # 1 (2) are the positions of the sample 10 at the first position P # 1 (1). The third condition is satisfied that the thickness d1 is different from the thickness d2 of the sample 10 at the second position P # 1 (2). That is, the irradiation position changing unit 153 controls the stage 170 so as to satisfy the third condition. In other words, the irradiation position changing unit 153 moves the stage 170 so that the terahertz wave THz is irradiated to each of the first position P # 1 (1) and the second position P # 1 (2) that satisfy the third condition. Control.

  In order to satisfy the third condition, it is preferable that the sample 10 satisfies the condition that the thickness d of the sample 10 varies. The variation in the thickness d may include a variation in the thickness d caused by unevenness (for example, a step or a curved surface) intentionally formed on the surface 10a of the sample 10. Alternatively, the variation in the thickness d may include a variation in the thickness d due to the roughness of the surface 10a of the sample 10 depending on the accuracy of the finishing process.

  In addition, when the back surface 10b of the sample 10 is a plane, the first position P # 1 (1) and the second position P # 1 (2) can easily satisfy the first and second conditions described above. For this reason, in the first measurement operation, the back surface 10b of the sample 10 is preferably a flat surface.

Thereafter, the terahertz wave generating element 110 irradiates the second position P # 1 (2) on the surface 10a of the sample 10 with the terahertz wave THz (step S112). Thereafter, the terahertz wave detecting element 130 detects the terahertz wave THz reflected by the sample 10 (step S112). As a result, a waveform signal indicating the waveform of the terahertz wave THz detected by the terahertz wave detecting element 130 is input to the signal processing unit 152. Thereafter, the detection time acquisition unit 1521 acquires the first detection time t _a2 and the second detection time t _b2 based on the waveform signal input to the signal processing unit 152 (step S113). That is, the terahertz wave measuring apparatus 100, based on the second position P # 1 (2) a detection result of the irradiated terahertz waves THz to, to obtain a first detection time _{t a2} and the second detection time _{t b2.} Detection time acquisition unit 1521 outputs the terahertz wave THz a second position P # 1 first detection time obtained when irradiated in (2) _{t a2} and the second detection time _{t b2,} the refractive index calculation unit 1522 To do. The first detection time t _a2 and the second detection time t _b2 are specific examples of “first time” and “second time”, respectively.

Thereafter, the refractive index calculator 1522 calculates the refractive index n of the sample 10 based on the first detection time t _a1 and the second detection time t _b1 , and the first detection time t _a2 and the second detection time t _b2. (Step S121). Specifically, the refractive index calculation unit 1522 calculates the refractive index n using Equation 1. Note that Δt _{1 in} Equation 1 corresponds to the time required for the terahertz wave THz to pass through the sample 10 when the first position P # 1 (1) is irradiated with the terahertz wave THz. That is, Δt _{1 in} Equation 1 indicates that when the first position P # 1 (2) is irradiated with the terahertz wave THz, the terahertz wave THz reaches the surface 10a again from the front surface 10a of the sample 10 through the back surface 10b. This corresponds to the time required for this. For this reason, Δt ₁ can be calculated from an equation: Δt ₁ = t _b1 −t _a1 . Δt _{2 in} Equation 1 corresponds to the time required for the terahertz wave THz to pass through the inside of the sample 10 when the second position P # 1 (2) is irradiated with the terahertz wave THz. That is, Δt _{2 in} Equation 1 indicates that when the second position P # 1 (2) is irradiated with the terahertz wave THz, the terahertz wave THz reaches the surface 10a again from the front surface 10a of the sample 10 through the back surface 10b. This corresponds to the time required for this. For this reason, Δt ₂ can be calculated from an equation: Δt ₂ = t _b2 −t _a2 .

その後、厚さ算出部１５２３は、第１検出時間ｔ_ａ１及び第２検出時間ｔ_ｂ１、第１検出時間ｔ_ａ２及び第２検出時間ｔ_ｂ２、並びに、ステップＳ１２１で算出した屈折率ｎに基づいて、試料１０の厚さｄを算出する（ステップＳ１２２）。第１計測動作では、上述したように第１位置Ｐ＃１（１）における試料１０の厚さｄ１と第２位置Ｐ＃１（２）における試料１０の厚さｄ２とが異なる。従って、厚さ算出部１５２３は、厚さｄ１及びｄ２の夫々を算出する。具体的には、厚さ算出部１５２３は、ｄ１＝（ｃ／ｎ）×Δｔ_１／２という数式を用いて、厚さｄ１を算出する。厚さ算出部１５２３は、ｄ２＝（ｃ／ｎ）×Δｔ_２／２という数式を用いて、厚さｄ２を算出する。

After that, the thickness calculation unit 1523 is based on the first detection time t _a1 and the second detection time t _b1 , the first detection time t _a2 and the second detection time t _b2 , and the refractive index n calculated in step S121. Then, the thickness d of the sample 10 is calculated (step S122). In the first measurement operation, as described above, the thickness d1 of the sample 10 at the first position P # 1 (1) is different from the thickness d2 of the sample 10 at the second position P # 1 (2). Therefore, the thickness calculation unit 1523 calculates each of the thicknesses d1 and d2. Specifically, the thickness calculation unit 1523 calculates the thickness d1 using a mathematical formula of d1 = (c / n) × Δt _1/2 . The thickness calculation unit 1523, using the formula that d2 = (c / n) × Δt 2/2, and calculates the thickness d2.

  As described above, the terahertz measurement apparatus 100 according to the present embodiment can suitably measure (that is, calculate) the refractive index n of the sample 10 by executing the first measurement operation. In particular, the terahertz measuring apparatus 100 according to the present embodiment irradiates a plurality of irradiation positions with different thicknesses d of the sample 10 with the terahertz wave THz, so that the refractive index n does not contact the sample 10 with any special member. Can be suitably measured. Furthermore, since the terahertz measuring apparatus 100 of the present embodiment can suitably measure the refractive index n, the thickness d of the sample 10 can also be favorably measured.

Here, as an example of a terahertz wave measuring apparatus of a comparative example that measures the thickness d of the sample 10 without measuring the refractive index n, the thickness d is measured by irradiating the single irradiation position with the terahertz wave THz. A terahertz wave measuring device is assumed. In this case, the terahertz wave measuring apparatus of the comparative example, to obtain a first detection time t _a and the second detection time t _b. Further, the terahertz wave measuring apparatus of the comparative example, using equation of thickness _{d = c × (t b -t} a) / 2, for measuring the thickness d of the sample 10. However, the speed c ′ of the terahertz wave THz inside the sample 10 varies according to the refractive index n. Therefore, the thickness d measured by the terahertz wave measuring apparatus of the comparative example, taken from the original thickness d = values greater than (c / n) × (t b -t a) / 2 samples 10 End up.

  For this reason, the terahertz wave measuring apparatus 100 of the comparative example needs to measure the refractive index n in order to measure the original thickness d. However, as described in Patent Documents 1 and 2, the measurement of the refractive index n is generally troublesome. However, the terahertz wave measuring apparatus 100 of the present embodiment has a great advantage that the refractive index n can be measured relatively easily.

(2-2) Second Measurement Operation for Measuring Refractive Index n and Thickness d Next, a second measurement operation for measuring refractive index n and thickness d performed by the terahertz wave measuring apparatus 100 with reference to FIG. Will be described. FIG. 6 is a flowchart showing an example of the flow of the second measurement operation for measuring the refractive index n and the thickness d performed by the terahertz wave measuring apparatus 100.

  In the first measurement operation described above, the stage 170 moves along a direction parallel to the back surface 10b of the sample 10. That is, even when the irradiation position of the terahertz wave THz is changed, the distance between the terahertz wave generating element 110 and the back surface 10b and the distance between the terahertz wave detecting element 130 and the back surface 10b do not change. However, depending on the movement conditions of the stage 170 and the state of the sample 10 (particularly, the state of the back surface 10b), the stage 170 may not be able to move along a direction parallel to the back surface 10b of the sample 10. That is, when the irradiation position of the terahertz wave THz is changed, at least one of the distance between the terahertz wave generation element 110 and the back surface 10b and the distance between the terahertz wave detection element 130 and the back surface 10b changes. In some cases.

  In this case, even if the terahertz wave measuring apparatus 100 performs the first measurement operation, it is difficult to measure the refractive index n. For this reason, when the stage 170 cannot move along the direction parallel to the back surface 10b of the sample 10, the terahertz wave measuring apparatus 100 measures the refractive index n by performing the second measurement operation. However, the second measurement operation is performed on the sample 10 whose back surface 10b is flat (in other words, the back surface 10b is not intentionally uneven).

Specifically, as illustrated in FIG. 6, the irradiation position changing unit 153 sets the stage 170 so that the irradiation position of the terahertz wave THz becomes the first position P # 2 (1) on the surface 10a of the sample 10. Is controlled (step S201). The terahertz wave generation element 110 irradiates the first position P # 2 (1) with the terahertz wave THz (step S202). Thereafter, the terahertz wave detection element 130 detects the terahertz wave THz reflected by the sample 10 (step S202). As a result, a waveform signal indicating the waveform of the terahertz wave THz detected by the terahertz wave detecting element 130 is input to the signal processing unit 152. Thereafter, the detection time acquisition unit 1521 acquires the first detection time t _a1 and the second detection time t _b1 based on the waveform signal input to the signal processing unit 152 (step S203). Note that the operations of step S201, step S202, and step S203 may be the same as the operations of step S101, step S102, and step S103 of the first measurement operation, respectively, unless otherwise specified.

  Thereafter, the irradiation position changing unit 153 uses the second position P # 2 (2) on the surface 10a of the sample 10 (however, the second position P # 2 (2) is different from the first position P # 2 (1)). The stage 170 is controlled so as to be different (step S211). As a result, the stage 170 moves along the predetermined movement direction by a predetermined first movement amount P1 in order to change the irradiation position from the first position P # 2 (1) to the second position P # 2 (2). Moving.

  However, the second measurement operation is an operation performed mainly when the stage 170 cannot move along the direction parallel to the back surface 10b of the sample 10. Therefore, when changing the irradiation position to the second position P # 2 (2), the irradiation position changing unit 153 does not have to control the stage 170 so as to satisfy the first and second conditions described above. Good.

Thereafter, the terahertz wave generating element 110 irradiates the second position P # 2 (2) with the terahertz wave THz (step S212). Thereafter, the terahertz wave detecting element 130 detects the terahertz wave THz reflected by the sample 10 (step S212). As a result, a waveform signal indicating the waveform of the terahertz wave THz detected by the terahertz wave detecting element 130 is input to the signal processing unit 152. Thereafter, the detection time acquisition unit 1521 acquires the first detection time t _a2 and the second detection time t _b2 based on the waveform signal input to the signal processing unit 152 (step S213). Note that the operations of step S211, step S212, and step S213 may be the same as the operations of step S101, step S102, and step S103 of the first measurement operation, respectively, unless otherwise specified.

  Thereafter, the irradiation position changing unit 153 moves the third position P # 2 (3) on the surface 10a of the sample 10 (however, the third position P # 2 (3) is the first position P # 2 (1) and the first position P # 2 (3)). The stage 170 is controlled so as to be different from the second position P # 2 (2) (step S221). As a result, the stage 170 moves along the predetermined movement direction by a predetermined second movement amount P2 in order to change the irradiation position from the second position P # 2 (2) to the third position P # 2 (3). Moving.

  Particularly in the second measurement operation, the irradiation position changing unit 153 determines that the moving direction of the stage 170 when the irradiation position is changed from the second position P # 2 (2) to the third position P # 2 (3) is the irradiation position. Is controlled to be the same as the moving direction of the stage 170 when the first position P # 2 (1) is changed to the second position P # 2 (2). That is, the irradiation position changing unit 153 changes the irradiation position from the first position P # 2 (1) to the third position P # 2 (3) via the second position P # 2 (2). The stage 170 is controlled so that the moving direction of the 170 is fixed.

  The second measurement operation is mainly performed when the stage 170 cannot move along a direction parallel to the back surface 10b of the sample 10. Therefore, when changing the irradiation position to the third position P # 2 (3), the irradiation position changing unit 153 does not have to control the stage 170 so as to satisfy the first and second conditions described above. Good.

Thereafter, the terahertz wave generation element 110 irradiates the third position P # 2 (3) with the terahertz wave THz (step S222). Thereafter, the terahertz wave detection element 130 detects the terahertz wave THz reflected by the sample 10 (step S222). As a result, a waveform signal indicating the waveform of the terahertz wave THz detected by the terahertz wave detecting element 130 is input to the signal processing unit 152. Thereafter, the detection time acquisition unit 1521 acquires the first detection time t _a3 and the second detection time t _b3 based on the waveform signal input to the signal processing unit 152 (step S223). Note that the operations of step S221, step S222, and step S223 may be the same as the operations of step S101, step S102, and step S103 of the first measurement operation, respectively, unless otherwise specified.

Thereafter, the refractive index calculation unit 1522 includes the first detection time t _a1 and the second detection time t _b1 , the first detection time t _a2 and the second detection time t _b2 , and the first detection time t _a3 and the second detection time. Based on _tb3 , the refractive index n of the sample 10 is calculated (step S231). Specifically, the refractive index calculation unit 1522 calculates the refractive index n using Equation 2. Note that Δt ₁ and Δt ₂ in Equation 2 have already been described when the first measurement operation is described. Δt _{3 in} Equation 2 corresponds to the time required for the terahertz wave THz to pass through the inside of the sample 10 when the third position P # 2 (3) is irradiated with the terahertz wave THz. That is, Δt _{3 in} Formula 2 indicates that when the third position P # 2 (3) is irradiated with the terahertz wave THz, the terahertz wave THz reaches the surface 10a again from the front surface 10a of the sample 10 through the back surface 10b. This corresponds to the time required for this. For this reason, Δt ₃ can be calculated from an equation: Δt ₃ = t _b3 −t _a3 .

その後、厚さ算出部１５２３は、試料１０の厚さｄ（つまり、厚さｄ１、ｄ２及びｄ３）を算出する（ステップＳ２３２）。具体的には、厚さ算出部１５２３は、ｄ１＝（ｃ／ｎ）×Δｔ_１／２という数式を用いて、厚さｄ１を算出する。厚さ算出部１５２３は、ｄ２＝（ｃ／ｎ）×Δｔ_２／２という数式を用いて、厚さｄ２を算出する。厚さ算出部１５２３は、ｄ３＝（ｃ／ｎ）×Δｔ_３／２という数式を用いて、厚さｄ３を算出する。

Thereafter, the thickness calculation unit 1523 calculates the thickness d of the sample 10 (that is, the thicknesses d1, d2, and d3) (step S232). Specifically, the thickness calculation unit 1523 calculates the thickness d1 using a mathematical formula of d1 = (c / n) × Δt _1/2 . The thickness calculation unit 1523, using the formula that d2 = (c / n) × Δt 2/2, and calculates the thickness d2. The thickness calculation unit 1523, using the formula that d3 = (c / n) × Δt 3/2, calculating the thickness d3.

  As described above, the terahertz measurement apparatus 100 according to the present embodiment can enjoy the same effects as those that can be enjoyed when the first measurement operation is performed by executing the second measurement operation. In particular, the terahertz wave measuring apparatus 100 includes a distance between the terahertz wave generating element 110 and the back surface 10b and a distance between the terahertz wave detecting element 130 and the back surface 10b by changing the irradiation position of the terahertz wave THz. Even when at least one of the above changes, the refractive index n of the sample 10 can be suitably measured (that is, calculated).

  Note that the movement amount P1 of the stage 170 and the irradiation position when the irradiation position is changed from the first position P # 2 (1) to the second position P # 2 (2) are changed from the second position P # 2 (2) to the second position P # 2 (2). When the movement amount P2 of the stage 170 when changing to the 3 position P # 2 (3) is the same, the above-described Expression 2 becomes Expression 3. Therefore, when the irradiation position changing unit 153 controls the stage 170 so that the movement amount P1 and the movement amount P2 are the same, the refractive index calculation unit 1522 uses Equation 3 instead of Equation 2. The refractive index n may be calculated.

（２−３）屈折率ｎ及び厚さｄを計測する第３計測動作
続いて、テラヘルツ波計測装置１００が行う屈折率ｎ及び厚さｄを計測する第３計測動作について説明する。上述した第１又は第２計測動作では、テラヘルツ波検出素子１３０が検出したテラヘルツ波ＴＨｚの波形を示す波形信号に誤差が含まれてしまうと、第１検出時間ｔ_ａ１からｔ_ａ３及び第２検出時間ｔ_ｂ１からｔ_ｂ３のうちの少なくとも一つの精度が大きく悪化する可能性がある。その結果、上述した第１又は第２計測動作では、波形信号に誤差が含まれてしまうと、算出された屈折率ｎ及び厚さｄの精度が大きく悪化する（つまり、真の値から大きく乖離する）可能性がある。そこで、テラヘルツ波計測装置１００は、第１及び第２計測動作に代えて、波形信号に誤差が含まれてしまう場合においても屈折率ｎ及び厚さｄを相応に高精度に計測可能な第３計測動作を行ってもよい。以下、図７を参照しながら、テラヘルツ波計測装置１００が行う屈折率ｎ及び厚さｄを計測する第３計測動作について説明する。図７は、テラヘルツ波計測装置１００が行う屈折率ｎ及び厚さｄを計測する第３計測動作の流れの一例を示すフローチャートである。

(2-3) Third Measurement Operation for Measuring Refractive Index n and Thickness d Next, a third measurement operation for measuring the refractive index n and the thickness d performed by the terahertz wave measuring apparatus 100 will be described. In the first or second measurement operation described above, if an error is included in the waveform signal indicating the waveform of the terahertz wave THz detected by the terahertz wave detection element 130, the first detection time t _a1 to t _a3 and the second detection time are detected. There is a possibility that the accuracy of at least one of the times t _b1 to t _b3 is greatly deteriorated. As a result, in the first or second measurement operation described above, if the waveform signal includes an error, the accuracy of the calculated refractive index n and thickness d is greatly deteriorated (that is, greatly deviated from the true value). there's a possibility that. Therefore, the terahertz wave measuring apparatus 100 is a third that can measure the refractive index n and the thickness d with high accuracy correspondingly even when an error is included in the waveform signal, instead of the first and second measurement operations. A measurement operation may be performed. Hereinafter, the third measurement operation for measuring the refractive index n and the thickness d performed by the terahertz wave measuring apparatus 100 will be described with reference to FIG. FIG. 7 is a flowchart showing an example of the flow of the third measurement operation for measuring the refractive index n and the thickness d performed by the terahertz wave measuring apparatus 100.

  The error included in the waveform signal is caused by at least one of noise superimposed on the terahertz wave THz itself, noise superimposed on the waveform signal processing process, and deterioration in detection accuracy of the terahertz wave detection element 130, for example. It is an error.

As shown in FIG. 7, the irradiation position changing unit 153 sets (that is, initializes) the variable i to 1 (step S301). The variable i is a variable for identifying the irradiation position where the terahertz wave THz is irradiated in the third measurement operation. Thereafter, the irradiation position changing unit 153 controls the stage 170 so that the irradiation position of the terahertz wave THz becomes the i-th position P # 3 (i) on the surface 10a of the sample 10 (step S302). The terahertz wave generating element 110 irradiates the i th position P # 3 (i) with the terahertz wave THz (step S303). Thereafter, the terahertz wave detecting element 130 detects the terahertz wave THz reflected by the sample 10 (step S303). Thereafter, the detection time acquisition unit 1521 acquires the first detection time t _ai and the second detection time t _bi based on the waveform signal input to the signal processing unit 152 (step S304). Note that the operations of step S302, step S303, and step S304 may be the same as the operations of step S101, step S102, and step S103 of the first measurement operation, respectively, unless otherwise specified.

Thereafter, the irradiation position changing unit 153 determines whether or not the variable i matches the threshold value THi (step S305). The threshold value THi is a constant indicating the total number of irradiation positions where the terahertz wave THz is to be irradiated in the third measurement operation. As a result of the determination in step S305, when it is determined that the variable i does not match the threshold value THi (step S305: No), the variable i is incremented by 1, and the operation from step S302 to step S304 is performed. Done again. That is, after the irradiation position of the terahertz wave THz is changed, the first detection time t _ai and the second detection time t _bi are acquired again. Therefore, in the third measurement operation, the terahertz wave THz is irradiated to each of the THi irradiation positions. As a result, the operation of obtaining the first detection time t _ai and the second detection time t _bi is performed THi times.

  In the third measurement operation, the irradiation position changing unit 153 does not have to control the stage 170 so as to satisfy the above-described first and second conditions when changing the irradiation position. In the third measurement operation, instead of the third condition described above, the irradiation position changing unit 153 does not have the same thickness d of the sample 10 at all the THi irradiation positions (that is, among the THi irradiation positions). The stage 170 is controlled so as to satisfy the fourth condition that the thickness d of the sample 10 is different at at least two irradiation positions.

On the other hand, as a result of the determination in step S305, when it is determined that the variable i matches the threshold value THi (step S305: Yes), the refractive index calculation unit 1522 indicates that the refractive index n of the sample 10 is the virtual value. It assumed to be n _v (step S311). Thereafter, the refractive index calculation unit 311 calculates virtual data regarding the sample 10 when the refractive index n is assumed to be a virtual value n _v (step S312).

Virtual data, the refractive index n the shape of the specimen 10 when it is assumed that a virtual value n _v (in particular, the shape of each of the THi pieces of irradiation position) preferably contains a virtual data related. In particular, the virtual data, the refractive index n includes a virtual data relating to the shape of the back surface 10b of the sample 10 on the assumption that a virtual value n _v (in particular, the shape of the back surface 10b in each of THi number of irradiation positions) Is particularly preferred. Therefore, in this embodiment, the refractive index calculation unit 1522, a distance B from the terahertz wave detecting element 130 to the back surface 10b in the case where the refractive index n is assumed to be virtual value n _v, THi pieces of irradiation each position To calculate. Specifically, the refractive index calculation unit 1522 calculates the distance B _i at the i-th position P # 3 (i) based on Expression 4. The distance B, the shape of the sample 10 when the refractive index n is assumed to be virtual value n _v (in particular, the shape of the back surface 10b) which is one specific example of a virtual data related. As a result, the refractive index calculation unit 1522, the distance _{B 1} at the first position P # 3 (1), the distance _B 2 at the second position P # 3 (2), ··· , and the THi position P # 3 A distance B _THi at (THi) is calculated.

加えて、屈折率算出部１５２２は、屈折率算出部１５２２は、屈折率ｎが仮想値ｎ_ｖであると仮定した場合におけるテラヘルツ波検出素子１３０から表面１０ａまでの距離Ａを、ＴＨｉ個の照射位置毎に算出する。具体的には、屈折率算出部１５２２は、数式５に基づいて、第ｉ位置Ｐ＃３（ｉ）における距離Ａ_ｉを算出する。距離Ａは、屈折率ｎが仮想値ｎ_ｖであると仮定した場合における試料１０の形状（特に、表面１０ａの形状）に関する仮想データの一具体例である。その結果、屈折率算出部１５２２は、第１位置Ｐ＃３（１）における距離Ａ_１、第２位置Ｐ＃３（２）における距離Ａ_２、・・・、及び、第ＴＨｉ位置Ｐ＃３（ＴＨｉ）における距離Ａ_ＴＨｉを算出する。

In addition, the refractive index calculation unit 1522 calculates the distance A from the terahertz wave detection element 130 to the surface 10a when the refractive index n is assumed to be a virtual value n _v by THi irradiations. Calculate for each position. Specifically, the refractive index calculation unit 1522 calculates the distance A _i at the i-th position P # 3 (i) based on Expression 5. The distance A is a specific example of a virtual data concerning the shape of the sample 10 when the refractive index n is assumed to be virtual value n _v (in particular, the shape of the surface 10a). As a result, the refractive index calculation unit 1522, the distance _{A 1} at the first position P # 3 (1), the distance _A 2 at the second position P # 3 (2), ··· , and the THi position P # 3 A distance A _THi at (THi) is calculated.

上述した数式４及び５は、各照射位置において、テラヘルツ波生成素子１１０と表面１０ａとの間の距離がテラヘルツ波検出素子１３０と表面１０ａとの間の距離と同一であり、且つ、テラヘルツ波生成素子１１０と裏面１０ｂとの間の距離（例えば、図５の距離Ｌ１１又はＬ２１）がテラヘルツ波検出素子１３０と裏面１０ｂとの間の距離（例えば、図５の距離Ｌ１３又はＬ２３）と同一である場合に用いることが好ましい数式である。この場合、屈折率ｎが仮想値ｎ_ｖであると仮定した場合におけるテラヘルツ波検出素子１３０から表面１０ａまでの距離Ａ_ｉは、屈折率ｎが仮想値ｎ_ｖであると仮定した場合におけるテラヘルツ波生成素子１１０から表面１０ａまでの距離（但し、第ｉ位置Ｐ＃３（ｉ）における距離）と同一である。同様に、屈折率ｎが仮想値ｎ_ｖであると仮定した場合におけるテラヘルツ波検出素子１３０から裏面１０ｂまでの距離Ｂ_ｉは、屈折率ｎが仮想値ｎ_ｖであると仮定した場合におけるテラヘルツ波生成素子１１０から裏面１０ｂまでの距離（但し、第ｉ位置Ｐ＃３（ｉ）における距離）と同一である。従って、以下では、説明の簡略化のために、各照射位置において、テラヘルツ波生成素子１１０と表面１０ａとの間の距離がテラヘルツ波検出素子１３０と表面１０ａとの間の距離と同一であるものとする。同様に、各照射位置において、テラヘルツ波生成素子１１０と裏面１０ｂとの間の距離がテラヘルツ波検出素子１３０と裏面１０ｂとの間の距離と同一であるものとする。

Equations 4 and 5 described above indicate that the distance between the terahertz wave generating element 110 and the surface 10a is the same as the distance between the terahertz wave detecting element 130 and the surface 10a at each irradiation position, and terahertz wave generation is performed. The distance between the element 110 and the back surface 10b (for example, the distance L11 or L21 in FIG. 5) is the same as the distance between the terahertz wave detecting element 130 and the back surface 10b (for example, the distance L13 or L23 in FIG. 5). This is a mathematical formula that is preferably used in some cases. In this case, the distance A _i from the terahertz wave detecting element 130 to the surface 10a in the case where the refractive index n is assumed to be virtual value n _v is the terahertz wave in the case where the refractive index n is assumed to be virtual value n _v It is the same as the distance from the generation element 110 to the surface 10a (however, the distance at the i-th position P # 3 (i)). Similarly, the distance B _i from the terahertz wave detecting element 130 to the back surface 10b in the case where the refractive index n is assumed to be virtual value n _v is the terahertz wave in the case where the refractive index n is assumed to be virtual value n _v It is the same as the distance from the generation element 110 to the back surface 10b (however, the distance at the i-th position P # 3 (i)). Therefore, in the following, for simplification of description, the distance between the terahertz wave generating element 110 and the surface 10a is the same as the distance between the terahertz wave detecting element 130 and the surface 10a at each irradiation position. And Similarly, at each irradiation position, the distance between the terahertz wave generating element 110 and the back surface 10b is the same as the distance between the terahertz wave detecting element 130 and the back surface 10b.

  However, the distance between the terahertz wave generating element 110 and the front surface 10a is not the same as the distance between the terahertz wave detecting element 130 and the front surface 10a, or the distance between the terahertz wave generating element 110 and the back surface 10b is a terahertz wave. Even when the distance between the detection element 130 and the back surface 10b is not the same, the refractive index calculation unit 1522 sets the distance A from the terahertz wave generation element 110 to the front surface 10a and the terahertz wave detection element 130. What is necessary is just to calculate at least one of the distances from the surface to the surface 10a. Similarly, the refractive index calculation unit 1522 may calculate at least one of the distance from the terahertz wave generation element 110 to the back surface 10b and the distance from the terahertz wave detection element 130 to the back surface 10b as the distance B.

Here, the distances A _i and B _i will be further described with reference to FIG. FIG. 8 is a cross-sectional view showing the relationship between the actual sample 10 and the distances A _i and B _i .

FIG. 8 shows distances A ₁ and B _{1 at} position # 3 (1) and distances A ₂ and B ₂ at position # 3 (2). As shown in FIG. 8, the distance A ₁ calculated when the refractive index n is assumed to be a virtual value n _v matches the actual distance A ₁ (that is, the true value of the distance A ₁ ). Similarly, the distance A ₂ calculated when the refractive index n is assumed to be a virtual value n _v coincides with the actual distance A ₂ (that is, the true value of the distance A ₂ ). This is because the distance A _i does not fluctuate depending on the virtual value n _v as shown in Equation 5 described above.

On the other hand, as shown in FIG. 8, the distance B ₁ calculated when the refractive index n is assumed to be a virtual value n _v is the actual distance B ₁ (that is, the true value of the distance B ₁ ). Often does not match. Similarly, the distance B ₂ calculated when the refractive index n is assumed to be a virtual value n _v often does not coincide with the actual distance B ₂ (that is, the true value of the distance B ₂ ). This is because the distance A _i varies depending on the virtual value n _v as shown in Equation 4 described above. Therefore, as long as the virtual value n _v does not match the true value of the refractive index n, the calculated distance B _i does not match the actual distance B _i. Conversely, if they match the virtual value n _v is the true value of the refractive index n, the calculated distance B _i is consistent with the actual distance B _i.

FIG. 8 shows the distance B _i calculated when the virtual value n _v is smaller than the true value (for example, 1). As shown in FIG. 8, when the virtual value n _v is smaller than the true value of the refractive index n, the shape of the back surface 10b defined by the calculated distance B _i (see the dotted line in FIG. 8) is the surface It is similar to the shape obtained by inverting the shape of 10a. In other words, the shape of the back surface 10b of the shape and surface 10a of the calculated distance B _i is defined, in the relation of inverse correlation. When the virtual value _nv is gradually increased in the state shown in FIG. 8, the shape of the back surface 10b defined by the calculated distance B _i gradually approaches the actual shape of the back surface 10b. As a result, when the virtual value n _v matches the true value of the refractive index n, the shape of the back surface 10b defined by the calculated distance B _i gradually becomes the actual back surface 10b regardless of the shape of the front surface 10a. Match the shape. Accordingly, the shape of the back surface 10b and the shape of the front surface 10a defined by the calculated distance B _i are uncorrelated. On the other hand, when the virtual value n _v is further increased in a state where the virtual value n _v matches the true value of the refractive index n, the shape of the back surface 10b defined by the calculated distance B _i gradually becomes actual. It deviates from the shape of the back surface 10b. If the virtual value n _v is larger than the true value of the refractive index n, the shape of the back surface 10b of the calculated distance B _i is defined are in a relationship of shape and similar surface 10a. In other words, the shapes of the surface 10a of the rear surface 10b of the calculated distance B _i is defined, in a positive correlation.

Then, it can be seen that the true value of the refractive index n can be specified based on the distance B _i calculated when the refractive index n is assumed to be a virtual value n _v . That is, the virtual value n _v that can realize a state in which the shape of the back surface 10b defined by the calculated distance B _i matches the actual shape of the back surface 10b corresponds to the true value of the refractive index n. In the third measurement operation, the terahertz wave measuring apparatus 100 determines (that is, calculates) the refractive index n using such a relationship between the distance B _i and the true value of the refractive index n. In particular, the terahertz wave measuring apparatus 100 presents the calculated distance B _i to the user (that is, substantially presents the user with the shape of the back surface 10b defined by the calculated distance B _i ). ), thereby determining whether the shape of the back surface 10b of the calculated distance B _i is defined is equal to the actual shape of the back surface 10b to the user. Further, the terahertz wave measuring apparatus 100 receives the adjustment operation of the virtual value n _v by the user, and when the adjustment operation is received, the terahertz wave measurement device 100 calculates when the refractive index n is assumed to be the adjusted virtual value n _v. The presented distance B _i is again presented to the user. As a result, the user determines a virtual value n _v that can realize a state in which the shape of the back surface 10b defined by the calculated distance B _i matches the actual shape of the back surface 10b as a true value of the refractive index n. be able to. Hereinafter, the operation of determining the true value of the refractive index n will be further described.

In FIG. 7 again, after calculating the distances A _i and B _i , the refractive index calculation unit 1522 controls the display 181 to display the calculated distances A _i and B _i (step S313). As a result, the display 181 displays the calculated distances A _i and B _i . Thereafter, the refractive index calculation unit 1522 determines whether or not the user is performing an adjustment operation of the virtual value n _v using the input device 182 (step S314).

As a result of the determination in step S314, when it is determined that the user is performing an adjustment operation (step S314: Yes), the refractive index calculation unit 1522 adjusts the virtual value n _v according to the user's adjustment operation. (Step S315). Thereafter, the refractive index calculation unit 1522 repeats the operations after step S312. That is, the refractive index calculation unit 1522 calculates the distances A _i and B _i when the refractive index n is assumed to be the adjusted virtual value n _v (step S312). However, since the distance A _i does not vary depending on the virtual value n _v , the refractive index calculation unit 1522 does not have to calculate the distance A _i . Further, the refractive index calculating unit 1522 controls the display 181 to display the calculated distances A _i and B _i (step S313). Further, the refractive index calculation unit 1522 determines whether or not the user is performing an adjustment operation (step S314).

Here, display examples of the distances A _i and B _i will be described with reference to FIGS. 9 and 10. As shown in FIG. 9, the display 181 displays a graph in which the horizontal axis indicates the irradiation position and the vertical axis indicates the distances A _i and B _i . If the distance A _i and B _i is considered to be a parameter calculated for each THi number of irradiation positions, distances A _i and each of B _i s will be discretely distributed along the horizontal axis. For this reason, the display 181 may further display a smooth line connecting the distances A _i distributed discretely. Similarly, display 181 may further display a smooth line connecting the distance B _i discretely distributed.

The distance A _i shown in FIG. 9 substantially indicates the shape of the surface 10 a defined by the distance A _i calculated when the refractive index n is assumed to be a virtual value n _v . However, as described above, the distance A _i calculated when the refractive index n is assumed to be a virtual value n _v coincides with the true value of the distance A _i . Accordingly, the distance A _i shown in FIG. 8 substantially indicates the actual shape of the surface 10a.

The distance B _i shown in FIG. 9 substantially indicates the shape of the back surface 10b defined by the distance B _i calculated when the refractive index n is assumed to be a virtual value n _v . 9, the calculated distance B _i is the shape of the back surface 10b that defines, shows an example of a relation of the shape and inverse correlation surface 10a. Therefore, the user recognizes that the virtual value n _v is smaller than the true value of the refractive index n. Therefore, the user performs the adjustment operation for increasing the virtual value n _v. Here, when the adjustment amount of the virtual value n _v by the user is appropriate (that is, when the adjusted virtual value n _v matches the true value of the refractive index n), the display 181 displays the display 181 in FIG. black as shown by a square mark, and displays the distance B _i defining the shape that matches the shape of the actual back surface 10b in. In this case, the user recognizes that the virtual value n _v matches the true value of the refractive index n. On the other hand, when the adjustment amount of the virtual value n _v by the user is excessive (that is, when the adjusted virtual value n _v is larger than the true value of the refractive index n), the display 181 is displayed. , as shown by the black circles mark in FIG. 10, the distance defining a does not match the shape of the actual back surface 10b shape (distance a _i shape in the relationship between the shape and the positive correlation between the surface 10a that defines) B _i Is displayed. In this case, the user recognizes that the virtual value n _v is larger than the true value of the refractive index n. Therefore, the user further performs the adjustment operation for reducing the virtual value n _v.

When the virtual value n _v is adjusted, the display 181 displays the refractive index n as a substitute for the distance B _i calculated when the refractive index n is assumed to be the virtual value n _v before adjustment. The distance B _i calculated when the virtual value n _v after the adjustment is assumed may be displayed. Alternatively, the display 181, in addition to the distance B _i calculated when the refractive index n is assumed to be virtual value n _v before adjustment, the refractive index n is assumed to be virtual value n _v after adjustment The distance B _i calculated in this case may be displayed.

Until the user recognizes that a distance B _i that defines a shape that matches (or is most similar or somewhat similar, the same applies below) with the actual shape of the back surface 10b is displayed, the virtual value n _v Repeat the adjustment operation. In addition, in order for a user to perform adjustment operation, the user needs to recognize the shape of the actual back surface 10b. However, the user does not have to strictly recognize the actual shape of the back surface 10b. That is, it is sufficient for the user to roughly recognize the actual shape of the back surface 10b. For example, it is sufficient for the user to roughly recognize whether or not the actual shape of the back surface 10b is substantially flat or inclined when viewed from the user.

In FIG. 7 again, when it is determined that the user is not performing the adjustment operation as a result of the determination in step S314 (step S314: No), the distance B _i displayed on the display 181 defines the back surface 10b. It is estimated that the user recognizes that the shape matches the actual shape of the back surface 10b. That is, the user is assumed that the virtual value n _v on which the distance B _i displayed on the display 181 is calculated coincides with the true value of the refractive index n (or closest or somewhat close, the same applies hereinafter). Is estimated to be recognized. Accordingly, in this case, the refractive index calculation unit 1522 determines the current virtual value n _v as the true value of the refractive index n (step S321).

Thereafter, the thickness calculation unit 1523 calculates the thickness d (that is, the thicknesses d1, d2, and d3) of the sample 10 (step S322). Specifically, the thickness calculation unit 1523 calculates the thickness di at the position P # 3 (i) using a mathematical formula of di = (c / n) × Δt _i / 2. Δt _i can be calculated from an equation: Δt _i = t _bi −t _ai .

As described above, the terahertz measurement apparatus 100 according to the present embodiment can enjoy the same effects as those that can be enjoyed when the first measurement operation is performed by performing the third measurement operation. In particular, the terahertz wave measuring apparatus 100 has a true value of the refractive index n based on virtual data (that is, distances A _i and B _i ) calculated when the refractive index n is assumed to be a virtual value n _v. Let the user determine a virtual value n _v that matches Therefore, the terahertz wave measuring apparatus 100 can measure the refractive index n and the thickness d with high accuracy even when an error is included in the waveform signal.

In addition, since the user determines the virtual value n _v , the terahertz wave measuring apparatus 10 can measure the refractive index n regardless of the shape of the back surface 10b. For example, the terahertz wave measuring apparatus 10 can measure the refractive index n even when the back surface 10b is a curved surface, the back surface 10b has a step, or the back surface 10b is inclined as viewed from the user.

(2-4) Fourth Measurement Operation for Measuring Refractive Index n and Thickness d Next, a fourth measurement operation for measuring the refractive index n and the thickness d performed by the terahertz wave measuring apparatus 100 will be described. Similarly to the third measurement operation, the fourth measurement operation is also refracted based on virtual data (that is, distances A _i and B _i ) calculated when the refractive index n is assumed to be a virtual value n _v. The rate n is calculated. However, the fourth measurement operation, operation by the user (i.e., adjustment operation of the virtual values n _v described above) without requiring to calculate the refractive index n. Hereinafter, the fourth measurement operation for measuring the refractive index n and the thickness d performed by the terahertz wave measuring apparatus 100 will be described with reference to FIG. FIG. 11 is a flowchart illustrating an example of the flow of the fourth measurement operation for measuring the refractive index n and the thickness d performed by the terahertz wave measuring apparatus 100.

As shown in FIG. 11, in the fourth measurement operation, similarly to the third measurement operation, the operations from step S301 to step S306 are performed. As a result, the terahertz wave THz is irradiated to THi irradiation positions. Further, the operation of acquiring the first detection time t _ai and the second detection time t _bi is performed THi times. However, in the fourth measurement operation, it is preferable that the first condition to the third condition are satisfied when the irradiation position is changed. Furthermore, in the fourth measurement operation, the back surface 10b of the sample 10 is preferably a flat surface.

Thereafter, the refractive index calculation unit 1522 sets (ie, initializes) the variable j to 1 (step S411). Variable j is a variable for identifying a virtual value n _v to set the fourth measuring operation. Thereafter, the refractive index calculation unit 1522 assumes that the refractive index n of the sample 10 is a virtual value n _vj (step S412). Thereafter, the refractive index calculation unit 311 calculates virtual data (that is, the above-described distances A _i and B _i ) related to the sample 10 when the refractive index n is assumed to be the virtual value n _vj (step S413).

Thereafter, the refractive index calculation unit 1522 determines whether or not the variable j matches the threshold value THj (step S414). The threshold value THj is a constant indicating the total number of virtual values n _{vj to} be used in the fourth measurement operation. As a result of the determination in step S414, when it is determined that the variable j does not match the threshold value THj (step S414: No), the variable j is incremented by 1, and the operation from step S412 to step S414 is performed. Done again. That is, the refractive index calculation unit 1522 assumes that the refractive index n of the sample 10 is a new virtual value n _vj different from the virtual value n _vj used so far (step S412). The refractive index calculation unit 311 calculates the distances A _i and B _i when the refractive index n is assumed to be a new virtual value n _vj (step S413). The refractive index calculation unit 1522 determines whether or not the variable j matches the threshold value THj (step S414). Therefore, in the fourth measurement operation, the operation for calculating the distances A _i and B _i is performed THj times.

On the other hand, as a result of the determination in step S414, when it is determined that the variable j matches the threshold value THj (step S414: Yes), the refractive index calculation unit 1522 calculates the distance A for each virtual value n _vj. A correlation coefficient ρ _j between _i and the distance B _i is calculated (step S421). Specifically, the refractive index calculator 1522 calculates the correlation coefficient ρ ₁ between the distance A _i and the distance B _i calculated when the refractive index n is assumed to be a virtual value n _v1 , the refractive index n. Is assumed to be the virtual value n _v2 , and the correlation coefficient ρ ₂ between the distance A _i and the distance B _i calculated when the refractive index n is assumed to be the virtual value n _vTHj. In this case, a correlation coefficient ρ _THj between the distance A _i and the distance B _i calculated is calculated. Note that the refractive index calculation unit 1522 calculates the correlation coefficient ρ _j using Equation 6, for example. A _{avg in} Equation 6 is an average value of distances A _i (that is, (A ₁ + A ₂ +... + A _THi ) / THi). B _{avg in} Equation 6 is an average value of distances B _i (that is, (B ₁ + B ₂ +... + B _THi ) / THi). However, the refractive index calculation unit 1522 may calculate the correlation coefficient ρ _j using a calculation method different from Equation 6.

その後、屈折率算出部１５２２は、相関係数ρ_ｊの絶対値が閾値ＴＨρ以下になる状態を実現可能な仮想値ｎ_ｖｊを、屈折率ｎの真の値として特定する（ステップＳ４２２）。

After that, the refractive index calculation unit 1522 identifies a virtual value n _vj that can realize a state where the absolute value of the correlation coefficient ρ _j is equal to or less than the threshold value THρ as a true value of the refractive index n (step S422).

As described above, when the virtual value n _vj is smaller than the true value, the shape of the back surface 10b and the shape of the front surface 10a defined by the calculated distance B _i (that is, the calculated distance A _i). And the shape of the surface 10a defined by is in an inverse correlation relationship. For this reason, as shown in FIG. 12, when the virtual value n _vj is smaller than the true value, the correlation coefficient ρ _j between the distance B _i and the distance A _i is a negative value ( For example, -1). Further, as described above, when the virtual value n _vj is larger than the true value, the shape of the back surface 10b and the shape of the front surface 10a defined by the calculated distance B _i have a positive correlation relationship. It is in. For this reason, as shown in FIG. 12, when the virtual value n _vj is larger than the true value, the correlation coefficient ρ _j between the distance B _i and the distance A _i is a positive value ( For example, +1). Further, as described above, when the virtual value n _vj matches the true value, the shape of the back surface 10b and the shape of the front surface 10a defined by the calculated distance B _i are uncorrelated. For this reason, as shown in FIG. 12, when the virtual value n _vj matches the true value, the correlation coefficient ρ _j between the distance B _i and the distance A _i becomes zero. Therefore, it is estimated that the virtual value n _vj that can realize the state in which the correlation coefficient ρ _j is zero matches the true value of the refractive index n. Alternatively, the virtual value n _vj that can realize a state in which the correlation coefficient ρ _j is a value close to zero is estimated to be a value close to the true value of the refractive index n. Therefore, the threshold THρ is preferably set to zero or an arbitrary value close to zero.

When there are a plurality of virtual values n _vj that can realize a state where the absolute value of the correlation coefficient ρ _j is equal to or less than the threshold value THρ, the refractive index calculation unit 1522 determines that the absolute value of the correlation coefficient ρ _j is the smallest The virtual value n _vj that becomes may be specified as the true value of the refractive index n. When there is no virtual value n _vj that can realize a state in which the absolute value of the correlation coefficient ρ _j is equal to or less than the threshold value THρ, the refractive index calculation unit 1522 has a virtual value that minimizes the absolute value of the correlation coefficient ρ _j. The value n _vj may be specified as the true value of the refractive index n. Alternatively, when there is no virtual value n _vj that can realize a state where the absolute value of the correlation coefficient ρ _j is equal to or less than the threshold value THρ, the refractive index calculation unit 1522 sets the virtual value n _vj and the correlation coefficient ρ _j to Based on this, a first approximation function for specifying an arbitrary correlation coefficient ρ from an arbitrary virtual value n _v may be specified. Thereafter, the refractive index calculation unit 1522 calculates a virtual value n _v that can realize a state in which the absolute value of the correlation coefficient ρ specified by the first approximate function is equal to or less than the threshold value THρ (or becomes zero or minimum). , May be specified as the true value of the refractive index n.

  Thereafter, the thickness calculator 1523 calculates the thickness d of the sample 10 in the same manner as the third measurement operation (step S322).

As described above, the terahertz measurement apparatus 100 according to the present embodiment can enjoy the same effects as those that can be enjoyed when the first measurement operation is performed by performing the fourth measurement operation. In particular, the terahertz wave measuring apparatus 100 specifies the refractive index n based on virtual data (that is, distances A _i and B _i ) calculated when the refractive index n is assumed to be a virtual value n _v . Therefore, the terahertz wave measuring apparatus 100 can measure the refractive index n and the thickness d with high accuracy even when an error is included in the waveform signal. Furthermore, the terahertz wave measuring apparatus 100 can specify the refractive index n without requiring user operation. Therefore, the burden on the user's operation is reduced.

(2-5) Fifth Measurement Operation for Measuring Refractive Index n and Thickness d Next, a fifth measurement operation for measuring the refractive index n and the thickness d performed by the terahertz wave measuring apparatus 100 will be described. The fifth measurement operation is different from the fourth measurement operation in that a regression coefficient k _j is used instead of the correlation coefficient ρ _j . Other operations of the fifth measurement operation may be the same as other operations of the fourth measurement operation. Hereinafter, the fifth measurement operation for measuring the refractive index n and the thickness d performed by the terahertz wave measuring apparatus 100 will be described with reference to FIG. FIG. 13 is a flowchart illustrating an example of a flow of a fifth measurement operation for measuring the refractive index n and the thickness d performed by the terahertz wave measuring apparatus 100.

As shown in FIG. 13, in the fifth measurement operation, similarly to the fourth measurement operation, the operations from step S301 to step S414 are performed. As a result, distances A _i and B _i corresponding to the virtual values n _vj are calculated. After that, when it is determined that the variable j matches the threshold value THj (step S414: Yes), the refractive index calculation unit 1522 determines the distance between the distance A _i and the distance B _i for each virtual value n _vj. The regression coefficient k _j is calculated (step S521). Specifically, the refractive index calculation unit 1522 calculates the regression coefficient k ₁ between the distance A _i and the distance B _i calculated when the refractive index n is a virtual value n _v1 and the refractive index n is When assuming that the regression coefficient k ₂ ,... And the refractive index n between the distance A _i and the distance B _i calculated when the virtual value n _v2 is assumed are the virtual value n _vTHj The regression coefficient k _THj between the distance A _i and the distance B _i calculated in (1 ₎ is calculated. The refractive index calculation unit 1522 calculates the regression coefficient k _j using Equation 7. However, the refractive index calculation unit 1522 may calculate the regression coefficient k _j using a calculation method different from Equation 7.

その後、屈折率算出部１５２２は、回帰係数ｋ_ｊの絶対値が閾値ＴＨｋ以下になる状態を実現可能な仮想値ｎ_ｖｊを、屈折率ｎの真の値として特定する（ステップＳ５２２）。

Thereafter, the refractive index calculation unit 1522 _specifies a virtual value n _vj that can realize a state where the absolute value of the regression coefficient k _j is equal to or less than the threshold value THk as a true value of the refractive index n (step S522).

Here, the regression coefficient k _j corresponds to the slope of a regression line that defines the relationship between the distance B _i and the distance A _i (that is, a regression line that can identify the distance B _i from the distance A _i ). Therefore, when the virtual value n _vj is smaller than the true value, the distance B _i and the distance A _i are negatively correlated (see FIG. 12), so the regression coefficient k _j is negative. Value. When the virtual value n _vj is larger than the true value, the distance B _i and the distance A _i have a positive correlation (see FIG. 12), so the regression coefficient k _j is a positive value. Become. When the virtual value n _vj matches the true value, the regression coefficient k _j is zero because the distance B _i and the distance A _i are uncorrelated (see FIG. 12). Therefore, it is estimated that the virtual value n _vj that can realize the state in which the regression coefficient k _j is zero matches the true value of the refractive index n. Alternatively, the virtual value n _vj that can realize the state where the regression coefficient k _j is close to zero is estimated to be close to the true value of the refractive index n. Therefore, the threshold THk is preferably set to zero or an arbitrary value close to zero.

When there are a plurality of virtual values n _vj that can realize a state where the absolute value of the regression coefficient k _j is equal to or less than the threshold value THρ, the refractive index calculating unit 1522 minimizes the absolute value of the regression coefficient k _j. The virtual value n _vj may be specified as the true value of the refractive index n. When there is no virtual value n _vj that can realize a state where the absolute value of the regression coefficient k _j is equal to or less than the threshold value THρ, the refractive index calculation unit 1522 causes the virtual value n that the absolute value of the regression coefficient k _j is minimum. _vj may be specified as the true value of the refractive index n. Alternatively, when there is no virtual value n _vj that can realize a state in which the absolute value of the regression coefficient k _j is equal to or less than the threshold value THk, the refractive index calculation unit 1522 uses the virtual value n _vj and the regression coefficient k _j. A second approximation function for specifying an arbitrary regression coefficient k from an arbitrary virtual value n _v may be specified. Thereafter, the refractive index calculation unit 1522 calculates a virtual value n _v that can realize a state in which the absolute value of the regression coefficient k specified by the second approximate function is equal to or less than the threshold value THk (or becomes zero or minimum), The true value of the refractive index n may be specified.

  Thereafter, the thickness calculation unit 1523 calculates the thickness d of the sample 10 as in the fourth measurement operation (step S322).

  As described above, the terahertz measurement apparatus 100 according to the present embodiment can enjoy the same effects as those that can be enjoyed when the fourth measurement operation is performed by performing the fifth measurement operation.

When there is no virtual value n _vj that can realize a state where the absolute value of the regression coefficient k _j is equal to or less than the threshold THk, the refractive index calculation unit 1522 uses the virtual value n _vj and the regression coefficient k _j. As described above, the second approximation function for specifying the arbitrary regression coefficient k from the arbitrary virtual value n _v may be specified. However, as shown in FIG. 14, the second approximate function may not be a linear function. In this case, there is a possibility that the approximation accuracy of the second approximate function is deteriorated as compared with the case where the second approximate function is a linear function. That is, the virtual value n _v that can realize a state where the absolute value of the regression coefficient k specified by the second approximation function is equal to or less than the threshold value THk (or zero or minimum) is a true value of the refractive index n. May be significantly different from Therefore, the refractive index calculation unit 1522 calculates the predetermined coefficient m _j based on the virtual value n _vj and the regression coefficient k _j instead of specifying the true value of the refractive index n based on the second approximate function. May be. The predetermined coefficient m _j can be specified from the mathematical formula m _j = 1 / (1−k _j ). Thereafter, the refractive index calculation unit 1522 may specify a third approximation function for specifying an arbitrary predetermined coefficient m from an arbitrary virtual value n _v based on the virtual value n _vj and the regression coefficient m _j . Thereafter, the refractive index calculation unit 1522 calculates a virtual value n _v that can realize a state in which the absolute value of the predetermined coefficient m specified by the third approximate function is equal to or less than the threshold value THm (or becomes 1 or becomes maximum), The true value of the refractive index n may be specified. As shown in FIG. 14, the third approximation function is a linear function due to the characteristics of the regression coefficient. In this case, compared with the case where the third approximate function is not a linear function, the possibility that the approximation accuracy of the third approximate function is deteriorated is small. In other words, the third approximate function becomes equal to or less than the threshold THm (or 1 to become or becomes maximum) state capable of realizing the virtual value n _v is smaller may deviate significantly from the true value of the refractive index n.

(2-6) Modified Examples of Fourth and Fifth Measurement Operations As described above, in the fourth and fifth measurement operations, the terahertz wave generation element 110 and the back surface 10b are changed even when the irradiation position is changed. The first condition that the distance between them is the same and the second condition that the distance between the terahertz wave detecting element 130 and the back surface 10b are the same even when the irradiation position is changed are satisfied. Is preferred. However, as mentioned in the description of the second measurement operation, the first and second conditions may not be satisfied depending on the state of the sample 10 or the like. Here, an example is assumed in which the back surface 10b is a flat surface and the stage 170 moves along the direction intersecting the back surface 10b. That is, an example in which the back surface 10b is inclined with respect to the moving direction of the stage 170 is assumed. In this example, the same amount of offset corresponding to the inclination amount of the back surface 10b is added to both the distances A _i and B _i described above. Therefore, even if the virtual value n _v matches the true value of the refractive index n, the distance B _i and the distance A _i are not correlated but have a positive correlation. For this reason, when the back surface 10b is inclined, the refractive index calculation unit 1522 does not use the distances A _i and B _i calculated from the first detection time t _ai and the second detection time t _bi as they are. It becomes difficult to accurately specify the true value of the rate n.

Therefore, when the back surface 10b is tilted, the refractive index calculation unit 1522 calculates the distances A _i and B _i (that is, after performing the operation of step S413 in FIGS. 11 and 13) and thereafter Perform the operation. First, the refractive index calculation unit 1522 specifies the coordinate position z of THi irradiation positions corresponding to the coordinate axes along the moving direction of the stage 170. That is, the refractive index calculation unit 1522, a coordinate position _z 2 of the coordinate position _{z 1} of the first position P # 3 (1), the second position P # 3 (2), · · ·, and the THi position P # The coordinate position z _THi of 3 (THi) is specified. Thereafter, the refractive index calculation unit 1522 calculates a correlation coefficient PA between the coordinate position z _i and the distance A _i using Expression 8. Furthermore, the refractive index calculation unit 1522 calculates the correlation coefficient PB between the coordinate position z _i and the distance B _i using Equation 9. Note that z _avg in Equation 8 and Equation 9 is an average value of coordinate positions z _i (that is, (z ₁ + z ₂ +... + Z _THi ) / THi).

その後、屈折率算出部１５２２は、回帰係数ＰＡ及び距離Ａ_ｉに基づいて、距離Ａ’_ｉを算出する。具体的には、屈折率算出部１５２２は、Ａ’_ｉ＝Ａ_ｉ−ＰＡ×ｚ_ｉと言う数式を用いて、距離Ａ’_ｉを算出する。更に、屈折率算出部１５２２は、回帰係数ＰＢ及び距離Ｂ_ｉに基づいて、距離Ｂ’_ｉを算出する。具体的には、屈折率算出部１５２２は、Ｂ’_ｉ＝Ｂ_ｉ−ＰＢ×ｚ_ｉと言う数式を用いて、距離Ｂ’_ｉを算出する。その後、屈折率算出部１５２２は、距離Ａ_ｉ及びＢ_ｉに代えて、距離Ａ’_ｉ及びＢ’_ｉを用いて、距離Ａ_ｉ及びＢ_ｉを算出した後に行うべき動作（つまり、図１１及び図１３のステップＳ４１３の動作を行った後に行うべき動作であり、ステップ５２１以降の動作）を行う。これにより、裏面１０ｂが傾いている場合であっても、屈折率算出部１５２２は、屈折率ｎの真の値を精度よく特定することができる。

Thereafter, the refractive index calculation unit 1522 calculates the distance A ′ _i based on the regression coefficient PA and the distance A _i . Specifically, the refractive index calculation unit 1522 calculates the distance A ′ _i using a mathematical expression of A ′ _i = A _i −PA × z _i . Further, the refractive index calculation unit 1522 calculates the distance B ′ _i based on the regression coefficient PB and the distance B _i . Specifically, the refractive index calculation unit 1522 calculates the distance B ′ _i using a mathematical expression B ′ _i = B _i −PB × z _i . Thereafter, the refractive index calculation unit 1522, instead of the distance _{A i} and _{B i,} with the distance A _'i and B' _i, the distance _{A i} and operation to be performed after calculating the _{B i} (i.e., 11 and The operation to be performed after performing the operation of step S413 in FIG. Thereby, even if the back surface 10b is inclined, the refractive index calculation unit 1522 can accurately identify the true value of the refractive index n.

  In the first measurement operation, the second measurement operation, the fourth measurement operation, or the fifth measurement operation, the display 181 and the input device 182 are not necessarily used. For this reason, the terahertz wave measurement device 100 that performs the first measurement operation, the second measurement operation, the fourth measurement operation, or the fifth measurement operation may not include at least one of the display 181 and the input device 182.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. A measurement method and a computer program are also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Sample 10a Front surface 10b Back surface 100 Terahertz wave measurement apparatus 101 Pulse laser apparatus 110 Terahertz wave generation element 120 Optical delay mechanism 130 Terahertz wave detection element 150 Control part 151 Lock-in detection part 152 Signal processing part 1521 Detection time acquisition part 1522 Refractive index calculation Unit 1523 thickness calculation unit 153 irradiation position changing unit 170 stage 181 display 182 input device LB1 pump light LB2 probe light THz terahertz wave

Claims (10)

A first time required for the electromagnetic wave applied to the surface of the sample to reach a predetermined position after being reflected on the surface and a second time required for the electromagnetic wave to reach the predetermined position after being reflected on the back surface of the sample, Obtaining means for obtaining each of a plurality of different irradiation positions on the surface;
Calculation means for calculating virtual data related to the sample for each of the plurality of irradiation positions based on the first and second times and a virtual value of a refractive index of the sample;
Display means for displaying the virtual data;
A measuring device comprising: an operation unit that receives an adjustment operation of the virtual value by a user. The measurement apparatus according to claim 1, wherein the virtual data includes virtual shape data related to a virtual shape of the sample for each of the plurality of irradiation positions when the refractive index is assumed to be the virtual value. The measurement apparatus according to claim 1, wherein the virtual data includes virtual shape data related to a virtual shape of the back surface for each of the plurality of irradiation positions when the refractive index is assumed to be the virtual value. The virtual data relates to a virtual shape of the back surface specified by a virtual distance from the predetermined position to the back surface for each of the plurality of irradiation positions when the refractive index is assumed to be the virtual value. The measuring device according to claim 1, comprising virtual shape data. The calculation means recalculates the virtual data based on the adjusted virtual value, triggered by the operation means accepting the adjustment operation,
The measuring device according to claim 1, wherein the display unit displays the virtual data calculated based on the adjusted virtual value. The measuring device according to any one of claims 1 to 5, wherein the display unit further displays a smooth line connecting the discrete virtual data for each of the plurality of irradiation positions. The electromagnetic wave is a terahertz wave,
Irradiating means for irradiating the terahertz wave toward the surface;
Detecting means for detecting the terahertz wave reflected by the sample; and
The predetermined position is a position where the detection means is installed,
The first time is a time required for the terahertz wave reflected from the surface to reach the detection unit after the irradiation unit irradiates the terahertz wave,
The second time is a time required for the terahertz wave reflected from the back surface to reach the detection means after the irradiation means irradiates the terahertz wave. The measuring device according to any one of the above. The measurement apparatus according to claim 1, wherein the thickness of the sample, which is a physical distance between the front surface and the back surface, differs for each of the plurality of irradiation positions. . A first time required for the electromagnetic wave applied to the surface of the sample to reach a predetermined position after being reflected on the surface and a second time required for the electromagnetic wave to reach the predetermined position after being reflected on the back surface of the sample, An acquisition step of acquiring for each of a plurality of different irradiation positions on the surface;
A calculation step of calculating virtual data related to the sample for each of the plurality of irradiation positions based on the first and second times and a virtual value of a refractive index of the sample;
A display step for displaying the virtual data;
An operation step of receiving an operation of adjusting the virtual value by a user.   A computer program for causing a computer to execute the measurement method according to claim 9.

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