Method and apparatus for temperature measurement

Abstract

An embodiment of the present invention discloses a temperature measuring device comprising: a measuring light source that incidents a measuring light on a target material at an angle of incidence smaller than the Brewster angle; a first detector that detects the intensity of reflected light reflected from the target material by the measuring light; and a processing unit that calculates a reflectance based on the intensity of the detected reflected light and calculates the temperature of the target material based on the calculated reflectance and reflectance-temperature correlation data, wherein the reflectance-temperature correlation data is determined using a temperature correction device comprising a correction light source that incidents a correction measuring light on a target material at an angle of incidence larger than the Brewster angle and a second detector that detects the intensity of the correction reflected light reflected from the target material by the correction measuring light.

Description

Technology Field

[0001] The present invention relates to a temperature measuring method and a temperature measuring device for measuring the surface temperature of a material. Background Technology

[0002] Since semiconductor manufacturing processes can take place at various temperatures, it is crucial to accurately measure the temperature of the substrate being processed at high speed and control the temperature.

[0003] A technique utilizing the change in reflectance of a substrate according to temperature is known as a technology for high-speed measurement of the temperature of a substrate to be processed. For example, Korean Published Patent No. 2024-0174766 discloses a technique for determining the surface temperature of a target material by irradiating the surface of the target material with measurement light, detecting the intensity of the reflected light from the target material, and calculating the reflectance. The intensity of the reflected light can be detected as voltage using a detector such as a photodiode.

[0004] This conventional temperature measurement technique measures temperature by utilizing the reflectance inversion phenomenon that occurs at the melting point of a target material by making the angle of incidence of the measurement light greater than the Brewster angle. That is, when the measurement light is incident at an angle greater than the Brewster angle, a reflectance inversion phenomenon occurs in which the reflectance decreases with increasing temperature but increases starting from the melting point; through this rapid change in reflectance, the melting point and the reflectance at the melting point can be accurately measured. Furthermore, using the melting point and the reflectance at the melting point measured in this way as reference points, the temperature at which an arbitrary reflectance is measured can be calculated.

[0005] On the other hand, this method has the problem that the angle of incidence of the measurement light is limited to a range greater than the Brewster angle. This limits the degrees of freedom, such as the location where the temperature measuring device is installed in the substrate processing device or the design of the optical system of the temperature measuring device.

[0006] In addition, as the angle of incidence of the measurement light increases, the depth of penetration of the measurement light in the direction perpendicular to the surface of the target material decreases; therefore, there is a problem in that the measured temperature is limited to the temperature of the surface region of the target material.

[0007] Therefore, a temperature measuring device and a temperature measuring method are required that can accurately measure the temperature of a target material at high speed using a measuring light incident at an angle smaller than the Brewster angle. The problem to be solved

[0008] The present invention aims to provide a temperature measuring method and a temperature measuring device capable of accurately measuring the temperature of a target material at high speed using a measuring light incident at an angle smaller than the Brewster angle. means of solving the problem

[0009] A temperature measuring device according to an embodiment of the present invention comprises: a measuring light source unit including a first measuring light source that incidents a first measuring light on the surface of a target material at an angle of incidence smaller than the Brewster angle, and a second measuring light source that incidents a second measuring light on the surface of a target material at an angle of incidence larger than the Brewster angle; and a light detector unit including a first light detector that detects a first reflected light reflected from the surface of a target material by the first measuring light source, and a second light detector that detects a second reflected light reflected from the surface of a target material by the second measuring light source; wherein the first light detector and the second light detector are balanced light detectors. Effects of the invention

[0010] According to an embodiment of the present invention, by calculating the correlation between the reflectance and temperature measured using a measurement light incident at an angle smaller than the Brewster angle based on the correlation between the reflectance and temperature measured using a measurement light incident at an angle greater than the Brewster angle, it is possible to accurately measure the temperature of a target material at high speed while using a measurement light incident at an angle smaller than the Brewster angle. Brief explanation of the drawing

[0011] FIG. 1 is a schematic diagram of a temperature measuring device according to an embodiment of the present invention. FIG. 2 is a block diagram of a processing unit according to an embodiment of the present invention. Figure 3 is an example of a graph of reflectance measured when using a measurement light larger than the Brewster angle. Figure 4 shows the results of measuring the reflectance while simultaneously operating the temperature measuring device and the temperature correction device. FIG. 5 is a flowchart of a temperature measurement method according to an embodiment of the present invention. FIG. 6 is an example in which the detector of a temperature measuring device according to an embodiment of the present invention is configured to include a balanced light detector. Specific details for implementing the invention

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. The present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0013] To clearly explain the present invention, parts unrelated to the explanation have been omitted, and the same reference numerals are used for identical or similar components throughout the specification.

[0014] In addition, in various embodiments, components having the same configuration are described using the same reference numerals only in the representative embodiment, and in other embodiments, only configurations different from the representative embodiment are described.

[0015] Throughout the specification, when a part is described as "including" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0016] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0018] FIG. 1 is a schematic diagram of a temperature measuring device according to an embodiment of the present invention.

[0019] Referring to FIG. 1, a temperature measuring device (10) according to an embodiment of the present invention may be configured to include a first light source (110), a first incident optical system (120), a first reflective optical system (130), a first detector (140), and a processing unit (400).

[0020] The first light source (110) provides a first incident light (L) on the surface of a target material (T) to be temperature measured. 11 It is a configuration for investigating ). In the present invention, the first light source (110) corresponds to a measurement light source, and the first incident light (L 11 ) corresponds to the measurement light. For example, the first light source (110) may be a laser light source and may be a CW (continuous-wave) laser light source that generates a continuous wave. The first incident light (L 11 The wavelength of ) may be a wavelength with high reflectivity to the target material (T) to improve the temperature matching of the measurement result. The target material (T) may be a silicon wafer, and a metal film, an insulating film, or a semiconductor film may be formed on the surface where the measurement light is incident.

[0021] The first incident optical system (120) is the first incident light (L 11It is a configuration for forming a light path of ). The first incident optical system (120) is configured so that light irradiated from the first light source (110) is incident at a measurement point on the surface of the target material (T) at a first angle of incidence (θ1). The first angle of incidence (θ1) is the Brewster angle (θ B It is determined by an angle smaller than ).

[0022] The first incident optical system (120) may include various optical elements such as a collimator and / or lenses for focusing the measurement light, a half-wave plate for generating an optical path difference of the measurement light, and a mirror for changing the optical path. Additionally, if only some polarizations of the measurement light are used as the measurement light, it may include a polarization splitter such as a polarization beam splitter or a Wollaston prism. The polarization splitter may cause only one of the p-polarized light and s-polarized light contained in the measurement light to be incident on the target material (T). For example, p-polarized light may be incident on the target material (T).

[0023] The first reflective optical system (130) is the first incident light (L 11 ) The first reflected light (L) reflected from the target material (T) 12 A configuration for forming an optical path of ), wherein a first reflected light (L) reflected from a target material (T) 12 ) can be directed toward the first detector (140). The first reflective optical system (130) reflects light (L 12 It may include various optical elements, such as collimators and / or lenses for focusing ), mirrors for changing the light path, etc. In the present invention, the first reflected light (L 12 ) corresponds to reflected light.

[0024] The first detector (140) is the first reflected light (L 12 A configuration for detecting the intensity of ) may be configured to include a photodiode. The first detector (140) is a first reflected light (L 12The intensity of ) can be detected and output as a voltage value. The first detector (140) may be configured to include a balanced light detector for noise removal, and this will be described later with reference to FIG. 6.

[0025] The processing unit (400) receives the first reflected light (L) output from the first detector (140). 12 The reflectance can be calculated based on the intensity of ), and the temperature of the target material (T) can be calculated from the calculated reflectance. To calculate the reflectance and temperature, the processing unit (400) uses the first incident light (L 11 You can refer to data such as the correlation between the intensity, reflectance, and temperature of ). The first incident light (L 11 The intensity of ) may be measured or predetermined and stored in a storage unit that can be read by the processing unit (400). Correlation data between reflectance and temperature may be predetermined and stored in a storage unit that can be read by the processing unit (400). The storage unit may be included inside the processing unit (400) or provided so that the processing unit (400) can access and read it via wired or wireless communication. The correlation data may be in the form of a correlation equation between reflectance and temperature or a lookup table that matches reflectance and temperature, but is not limited thereto.

[0026] FIG. 2 is a block diagram of a processing unit according to an embodiment of the present invention. Referring to FIG. 2, the processing unit (400) may be configured to include an input / output unit (410), a calculation unit (420), and a storage unit (430). The input / output unit (410) receives a first reflected light (L) from a first detector (140). 12 The intensity of ) is received. The input / output unit (410) can transmit the calculated temperature value to a separately provided display device for output. The calculation unit (420) receives the first reflected light (L) input to the input / output unit (410). 12 The reflectance can be calculated using the intensity of ), and the temperature can be calculated from the calculated reflectance. The calculation unit (420) uses the first reflected light (L 12 The intensity of ) is the first incident light (L11 Reflectance can be calculated by dividing by the intensity of ). The first incident light (L) used to calculate reflectance 11 The intensity of ) may be stored in the storage unit (430). The output unit (420) calculates the first incident light (L) stored in the storage unit (430). 11 The intensity of ) can be read and used to calculate the reflectance. Or the first incident light (L 11 The intensity of ) can be measured in real time and transmitted to the output unit (420) through the input / output unit (410). To this end, the temperature measuring device (10) has a first incident light (L 11 A separate detector may be additionally included to measure the intensity of ). The calculation unit (420) can calculate the temperature using the calculated reflectance and the correlation data between the reflectance and the temperature. For example, if the correlation data is a correlation equation between the reflectance and the temperature, the temperature can be calculated by substituting the calculated reflectance into the correlation equation. The correlation data between the reflectance and the temperature may be predetermined and stored in the storage unit (430). The calculation unit (420) can calculate the temperature using the correlation data stored in the storage unit (430) and the reflectance calculated in the previous step.

[0027] An embodiment of the present invention uses a temperature correction device (20) to determine correlation data between reflectance and temperature. The temperature correction device (20) will be described below with reference again to FIG. 1.

[0028] Referring to FIG. 1, the temperature correction device (20) may include a second light source (210), a second incident optical system (220), a second reflected optical system (230), a second detector (240), and a heating source (250).

[0029] The second light source (210) provides a second incident light (L) on the surface of the target material (T) to be temperature measured. 21 It is a configuration for investigating ). In the present invention, the second light source (210) corresponds to a correction light source, and the second incident light (L 21) corresponds to a correction measurement light. For example, the second light source (210) may be a laser light source and may be a CW (continuous-wave) laser light source that generates a continuous wave. The second light source (210) may use the same light source as the first light source (110).

[0030] The second incident optical system (220) is the second incident light (L 21 It is a configuration for forming an optical path of ). The second incident optical system (220) is configured so that light irradiated from the second light source (210) is incident at a measurement point on the surface of the target material (T) at a second angle of incidence (θ2). The second angle of incidence (θ2) is the Brewster angle (θ B It is determined by an angle larger than ).

[0031] The second incident optical system (220) may include various optical elements such as a collimator and / or lenses for focusing the correction measurement light, a half-wave plate for generating an optical path difference of the correction measurement light, and a mirror for changing the optical path. Additionally, if only some polarizations of the correction measurement light are used as the correction measurement light, it may include a polarization splitter such as a polarization beam splitter or a Wollaston prism. The polarization splitter may cause only one of the p-polarization and s-polarization included in the correction measurement light to be incident on the target material (T). For example, p-polarization may be incident on the target material (T).

[0032] The second reflective optical system (230) is the second incident light (L 21 ) the second reflected light (L) reflected from the target material (T) 22 A configuration for forming an optical path of ), wherein a second reflected light (L) reflected from a target material (T) 22 ) can be directed toward the second detector (240). The second reflective optical system (230) reflects light (L 22It may include various optical elements such as collimators and / or lenses for focusing light, and mirrors for changing the light path.

[0033] The second detector (240) is the second reflected light (L 22 A configuration for detecting the intensity of ) may be configured to include a photodiode. The second detector (240) is a second reflected light (L 22 The intensity of ) can be detected and output as a voltage value, and the output voltage value can be transmitted to the processing unit (400). The second detector (240) may be configured to include a balanced light detector for noise removal. The second detector (240) may use the same detector as the first detector (140).

[0034] The heating source (250) is configured to heat the target material (T). The heating source (250) can heat the target material (T) from room temperature to a temperature above the melting point of the target material (T). The heating source (250) may be a pulse beam light source having power capable of rapidly changing the surface temperature of the target material (T) to the melting point, but is not particularly limited as long as it is configured to heat the target material (T). When the temperature measuring device (10) is installed in a substrate processing device that performs a predetermined treatment on a substrate such as a silicon wafer, the heating source (250) may be a heating source provided to heat the substrate in the substrate processing device where the temperature measuring device (10) is installed. For example, when the substrate processing device is a rapid heat treatment device, the heating source (250) may be a heating light source for rapid heating of the substrate.

[0035] The temperature compensation device (20) is the Brewster angle (θ B It may correspond to a temperature measuring device that calculates temperature by measuring reflectance using an angle of incidence greater than ). FIG. 3 is an example of a reflectance graph according to temperature that can be measured by a temperature correction device (20). That is, the measurement light is a Brewster angle (θ BThis is an example of a reflectance graph when the incident light is applied above )

[0036] As shown in FIG. 3, the Brewster angle (θ B When using an angle of incidence greater than ), the reflectance continuously decreases as the temperature increases from room temperature, and then increases again starting from the melting point. Therefore, the reflectance at the point where the reflectance begins to increase again corresponds to the reflectance at the melting point. Since room temperature and the melting point of the target substance (T) are fixed values, the correlation between reflectance and temperature can be expressed as a linear relationship from the reflectance at room temperature and the reflectance at the melting point. The temperature between room temperature and the melting point can be easily calculated from the measured reflectance using this linear relationship.

[0037] Meanwhile, the phenomenon in which the decrease and increase in reflectance are reversed at the melting point as shown in Fig. 3 is the Brewster angle (θ B This phenomenon is observed only when the measurement light is incident at an angle greater than ). Therefore, the Brewster angle (θ B In the temperature measuring device (10) according to the embodiment of the present invention, which uses an incident angle smaller than ) as the measuring light, it is difficult to determine the reflectance at the melting point, so there is a limitation in that it is difficult to determine the correlation between the reflectance and the temperature.

[0038] According to an embodiment of the present invention, this problem can be solved by constructing correlation data between the reflectance measured by the temperature measuring device (10) and the temperature of the target material (T) based on the reflectance measured by the temperature correction device (20).

[0039] FIG. 4 shows the result of calculating the reflectance from the detection values ​​of the first detector (140) and the second detector (240) by simultaneously operating the temperature measuring device (10) and the temperature correction device (20). That is, while heating the target material (T) from room temperature with a heating source (250), the Brewster angle (θ B This is the result of displaying the reflectance measured by the temperature measuring device (10) using an angle of incidence (θ1) smaller than the Brewster angle and the temperature correction device (20) using an angle of incidence (θ2) larger than the Brewster angle, respectively, on the same time axis (temperature axis).

[0040] As illustrated exemplarily in FIG. 4, the reflectance calculated by the temperature correction device (20) continuously decreases as the temperature increases, and then begins to increase again starting from the melting point. From this, the reflectance at the melting point can be determined, and by using this, any temperature between room temperature and the melting point can be correlated one-to-one with the reflectance.

[0041] On the other hand, the reflectance calculated by the temperature measuring device (10) continuously increases as the temperature increases, and continues to increase even at the melting point without a reflectance inversion phenomenon. Therefore, the reflectance value at the melting point cannot be determined by using only the temperature measuring device (10). However, according to an embodiment of the present invention, by simultaneously operating the temperature measuring device (10) and the temperature correction device (20), the reflectance calculated by the temperature measuring device (10) and the reflectance calculated by the temperature correction device (20) can be correlated one-to-one. That is, the reflectance measured at the same time by the temperature measuring device (10) and the temperature correction device (20), respectively, can be estimated as the reflectance at the same temperature.

[0042] Referring to FIG. 4, the reflectance measured by the temperature measuring device (10) changes from R0 (reflectance at time t0) to R1 (reflectance at time t1) between room temperature and the melting point. Since the melting point of the target material (T) is a fixed value, correlation data between reflectance and temperature that can be referenced by the temperature measuring device (10) can be calculated. For example, a linear relationship equation can be calculated by assuming that the reflectance changes linearly with temperature. The correlation equation between reflectance and temperature calculated in this way can be stored in the storage unit (430) of the processing unit (400). In this case, the correlation data may be a correlation equation between reflectance and temperature.

[0043] Alternatively, instead of calculating a correlation equation between reflectance and temperature, reflectance and temperature can be matched one-to-one and stored in the form of a lookup table. In this case, the correlation data may be a lookup table that matches reflectance and temperature one-to-one.

[0044] FIG. 5 is a flowchart of a temperature measurement method according to an embodiment of the present invention. Referring to FIG. 5, a temperature measurement method according to an embodiment of the present invention includes a measurement light irradiation step (S10), a reflected light intensity detection step (S20), a reflectance calculation step (S30), and a temperature calculation step (S40).

[0045] The measurement light irradiation step (S10) is a step of irradiating measurement light onto the surface of a target material (T). The measurement light can be irradiated at an angle of incidence smaller than the Brewster angle. The measurement light irradiation step (S10) can be performed using a first light source (110) and a first incident optical system (120) of a temperature measuring device (10) according to an embodiment of the present invention. Referring to FIG. 1, the measurement light is a first incident light (L 11 It can be.

[0046] The reflected light intensity detection step (S20) is a step of detecting the intensity of reflected light reflected from the surface of a target material (T), and can be performed using the first detector (140) of the temperature measuring device (10) according to an embodiment of the present invention. Referring to FIG. 1, the reflected light is the first reflected light (L 12 It can be.

[0047] The reflectance calculation step (S30) is a step of calculating the reflectance from the detected reflected light intensity. The reflectance can be calculated by dividing the reflected light intensity by the incident light intensity. The incident light intensity can be a value that is predetermined and stored, or the incident light intensity measured in real time using a separate detector can be used.

[0048] The temperature calculation step (S40) is a step of calculating the temperature using the calculated reflectance and the previously stored correlation data between reflectance and temperature. The correlation data between reflectance and temperature may be stored in the form of a correlation equation or a lookup table. The correlation data between reflectance and temperature may be determined in advance using a temperature correction device (20).

[0049] According to the temperature measurement method of an embodiment of the present invention, by calculating the temperature from the reflectance measured using a measurement light incident at an angle smaller than the Brewster angle based on predetermined correlation data using a measurement light incident at an angle larger than the Brewster angle, the temperature can be accurately measured at high speed while using a measurement light incident at an angle smaller than the Brewster angle.

[0051] The first detector (140) and / or the second detector (240) according to an embodiment of the present invention may be configured to include a balanced light detector. FIG. 6 is an example in which the first detector (140) of the temperature measuring device (10) is configured to include a balanced light detector.

[0052] Referring to FIG. 6, the first incident optical system (120) is configured to include a beam splitter (121) and a mirror (122), and the first detector (140) is configured to include a balanced light detector (141) and a differential calculator (142). The beam splitter (121) separates light irradiated from the first light source (110), sending a portion of it to the target material (T) through the mirror (122), and transmitting the remaining portion to the first detector (140) without passing through the target material (T). The light incident on the target material (T) corresponds to the measurement light, and the separated light separated from the measurement light at the beam splitter (121) corresponds to the reference light. The measurement light and the reference light separated at the beam splitter (121) can be separated with the same intensity. The beam splitter may be a 5:5 beam splitter.

[0053] The measurement light incident on the target material (T) is reflected from the surface of the target material (T) and input into the first port of the balanced light detector (141), and the reference light separated by the beam splitter (121) is not incident on the target material (T) but is input into the second port of the balanced light detector (141). The balanced light detector (141) may include a plurality of photodiodes. The measurement light input into the first port of the balanced light detector (141) is transmitted to the first photodiode, and the reference light input into the second port can be transmitted to the second photodiode.

[0054] Graph A of Fig. 6 is the output voltage graph of the first photodiode, and graph B is the output voltage graph of the second photodiode.

[0055] As shown in graph A of FIG. 6, the measurement light input to the first port of the balanced light detector (141) has a voltage component (V) independent of the temperature of the target material (T) at the first photodiode. DC The voltage value that changes according to the temperature change of the ) and the target material (T) is output as a composite voltage value. In addition, since the reference light input to the second port of the balanced light detector (141) does not pass through the target material (T), the voltage component (V) at the second photodiodeDC It is output as a voltage value containing only ).

[0056] The differential operator (142) removes the output value of the second port from the output value of the first port of the balanced light detector (141) to remove noise components included in the measured light and outputs the result to the processing unit (400). Thus, noise caused by changes in the brightness of the measured light source (110) can be removed, and the temperature measurement resolution can be improved. Additionally, the differential operator (142) may be a differential amplifier. By using a differential amplifier, the output of the balanced light detector (141) is amplified, thereby reliably detecting even small changes in reflected light, and thus accurately measuring minute temperature changes.

[0057] In FIG. 6, an example is shown in which the first detector (140) includes a balanced light detector (141), but the second detector (240) of the temperature correction device (20) may also be configured to include a balanced light detector.

[0058] In addition, as shown in FIG. 6, by installing an ND filter (150) between the beam splitter (121) and the balanced light detector (141), the intensity of the light input to the first and second ports of the balanced light detector (141) can be made equal.

[0060] An embodiment of the present invention provides a method for measuring temperature using a measurement light having an angle of incidence smaller than the Brewster angle. Therefore, by utilizing the embodiment of the present invention, accurate temperature measurement is possible even under various angle of incidence conditions. Furthermore, by correcting reflectance data at an angle of incidence smaller than the Brewster angle based on the reflectance inversion phenomenon at an angle of incidence greater than the Brewster angle, the accuracy of temperature measurement can be significantly improved.

[0061] In addition, by using a balanced light detector to suppress relative intensity noise of the measurement light source, the noise problems that occurred in existing technologies can be resolved, and the accuracy of temperature measurement can be significantly improved.

[0062] The embodiments and drawings attached to this specification merely clearly illustrate a part of the technical concept included in the present invention, and it is obvious that variations and specific embodiments that can be easily deduced by a person skilled in the art within the scope of the technical concept included in the specification and drawings of the present invention are all included within the scope of the rights of the present invention.

[0063] Accordingly, the scope of the present invention should not be limited to the described embodiments, and all things equivalent to or having equivalent variations to the claims set forth below, as well as the claims set forth below, shall be considered to fall within the scope of the concept of the present invention. Explanation of the symbols

[0064] 10: Temperature measuring device 110: First light source 120: First incident optical system 130: First reflective optical system 140: 1st detector 141: Balanced light detector 142: Differential operator 150: ND filter

Claims

Claim 1 A temperature measuring device comprising: a measuring light source that incidents a measuring light on a target material at an angle of incidence smaller than the Brewster angle; a first detector that detects the intensity of reflected light reflected from the target material by the measuring light; and a processing unit that calculates a reflectance based on the intensity of the detected reflected light and calculates the temperature of the target material based on the calculated reflectance and reflectance-temperature correlation data; wherein the reflectance-temperature correlation data is determined using a temperature correction device comprising a correction light source that incidents a correction measuring light on a target material at an angle of incidence larger than the Brewster angle and a second detector that detects the intensity of the correction reflected light reflected from the target material by the correction measuring light. Claim 2 In claim 1, the reflectance-temperature correlation data is a temperature measuring device that calculates the data by simultaneously operating a temperature measuring device and a temperature correction device while heating the target material from room temperature to its melting point. Claim 3 In paragraph 2, the above-mentioned reflectance-temperature correlation data is a temperature measuring device calculated using the intensity of reflected light detected by the second detector at the melting point of the target material. Claim 4 A temperature measuring device according to paragraph 3, wherein the processing unit includes a storage unit, and the reflectance-temperature correlation data is stored in the storage unit in the form of a correlation equation or a lookup table. Claim 5 In claim 1, the temperature measuring device comprising a first detector or a second detector, wherein the first detector or the second detector comprises a balanced light detector. Claim 6 A temperature measurement method comprising: a measurement light irradiation step of irradiating a target material with a measurement light at an incident angle smaller than the Brewster angle; a reflected light intensity detection step of detecting the intensity of reflected light reflected from the target material; a reflectance calculation step of calculating a reflectance from the detected reflected light intensity; and a temperature calculation step of calculating the temperature of the target material based on the calculated reflectance and reflectance-temperature correlation data, wherein the reflectance-temperature correlation data is determined based on the result of detecting the intensity of the corrected reflected light reflected from the target material after irradiating a corrected measurement light on the target material at an incident angle larger than the Brewster angle. Claim 7 In claim 6, the temperature measurement method is calculated by irradiating a measurement light at an angle of incidence smaller than the Brewster angle while heating the target material from room temperature to its melting point, and simultaneously irradiating a correction measurement light at an angle of incidence larger than the Brewster angle. Claim 8 In claim 7, the above-mentioned reflectance-temperature correlation data is a temperature measurement method calculated using the intensity of the corrected reflected light detected at the melting point of the target material. Claim 9 In claim 8, the above-mentioned reflectance-temperature correlation data is a temperature measurement method in the form of a correlation equation or a lookup table. Claim 10 A temperature measurement method according to claim 6, wherein the measurement light is separated into a reference light before being incident on the target material, and noise included in the reflected light is removed by differential calculation of the reference light from the reflected light.

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