Optical measurement system, optical measurement method and measurement program

Abstract

To provide a technique for reducing errors due to temperature change and the like generated in a spectroscopic detector, etc.SOLUTION: An optical measurement system comprises: a light source; a spectroscopic detector; a reference sample configured to maintain its properties to temperature changes; a changeover mechanism changing over between a first optical path irradiating a sample as measuring object with light from the light source and guiding the light generated in the sample to the spectroscopic detector and a second optical path irradiating the reference sample with light from the light source and guiding the light generated in the reference sample to the spectroscopic detector; and a calculation part that calculates a measured value of the sample, by performing correction processing based on a change between a first detection result outputted by the spectroscopic detector by irradiating the reference sample with the light from the light source at a first clock time and a second detection result outputted by the spectroscopic detector by irradiating the reference sample with the light from the light source at a second clock time, from a third detection result outputted by the spectroscopic detector by irradiating the sample with the light from the light source at a third clock time temporally close to the second clock time.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an optical measurement system including a spectroscopic detector, an optical measurement method, and a measurement program. [Background technology]

[0002] Optical measurement systems are known that measure the film thickness and surface shape of a sample by irradiating the sample with light and observing the interference generated by the light with a spectroscopic detector. Such optical measurement systems are also called spectroscopic interference systems.

[0003] There are several factors that can reduce the accuracy of optical measurements, and therefore various methods have been proposed to improve the accuracy.

[0004] For example, Japanese Patent Application Laid-Open No. 2002-039955 (Patent Document 1) discloses an automatic optical measurement method that can estimate the reference light intensity during sample measurement without setting a reference reflecting object in the measurement light path, thereby improving measurement accuracy.

[0005] Furthermore, Japanese Patent Application Laid-Open Publication No. 2011-117777 (Patent Document 2) discloses a calibration device that can appropriately acquire the correspondence between the detection position and the wavelength even when the correspondence between the wavelength and the detection position changes due to changes over time or temperature changes. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-039955 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-117777 Summary of the Invention [Problem to be solved by the invention]

[0007] Spectroscopic detectors can produce errors in their detection results due to the influence of temperature changes. The optical automatic measurement method disclosed in the above-mentioned Patent Document 1 does not take into account the influence of temperature changes. Furthermore, the calibration device disclosed in the above-mentioned Patent Document 2 takes into account the influence of changes over time and temperature changes, but is intended for calibration using incident light that includes emission lines, and is not capable of correcting the influence of temperature changes that occur during measurement.

[0008] An object of the present invention is to provide a method for reducing errors caused by temperature changes that occur in a spectroscopic detector or the like in an optical measurement system that includes a spectroscopic detector. [Means for solving the problem]

[0009] An optical measurement system according to one aspect of the present invention includes a light source, a spectroscopic detector, a reference sample configured to maintain its characteristics against temperature changes, a switching mechanism that switches between a first optical path that irradiates the sample to be measured with light from the light source and guides light generated in the sample to the spectroscopic detector and a second optical path that irradiates the reference sample with light from the light source and guides light generated in the reference sample to the spectroscopic detector, and a calculation unit that calculates a measurement value of the sample from a third detection result that irradiates the sample with light from the light source and outputs it at a third time that is temporally close to the second time by performing a correction process based on changes between a first detection result that irradiates the reference sample with light from the light source and outputs it at a first time, and a second detection result that irradiates the reference sample with light from the light source and outputs it at a second time.

[0010] The correction process may be based on a change in the second detection result relative to the first detection result.

[0011] The calculation unit may include a means for calculating the film thickness based on the detection result output by the spectroscopic detector, and a means for calculating the measurement value of the sample by reflecting the rate of change of the second film thickness calculated from the second detection result relative to the first film thickness calculated from the first detection result in the third film thickness calculated from the third detection result.

[0012] The calculation unit may include means for associating wavelengths with detection results output by the spectroscopic detector by referring to wavelength calibration information, and means for correcting the wavelength calibration information based on a difference between a result of associating wavelengths with the first detection result and a result of associating wavelengths with the second detection result.

[0013] A heat insulating structure may be provided around the reference sample. The reference sample may be made of a material whose temperature dependency is substantially negligible.

[0014] The switching mechanism may include an optical switch provided on an optical path between the light source and the sample and reference sample.

[0015] The switching mechanism may include an optical shutter that selectively blocks light from either the optical path from the light source to the sample or the optical path from the light source to the reference sample.

[0016] According to another aspect of the present invention, an optical measurement method includes the steps of irradiating a reference sample with light from a light source at a first time and obtaining a first detection result output by a spectroscopic detector. The reference sample is configured to maintain its characteristics against temperature changes. The optical measurement method also includes the steps of irradiating the reference sample with light from the light source at a second time and obtaining a second detection result output by the spectroscopic detector, irradiating the sample with light from the light source at a third time close in time to the second time and obtaining a third detection result output by the spectroscopic detector, and calculating a measurement value of the sample from the third detection result by performing a correction process based on a change between the first detection result and the second detection result.

[0017] According to yet another aspect of the present invention, there is provided a measurement program for measuring a sample. The measurement program causes a computer to execute the steps of irradiating a reference sample with light from a light source at a first time and acquiring a first detection result output by a spectroscopic detector. The reference sample is configured to maintain its characteristics against temperature changes. The measurement program causes the computer to execute the steps of irradiating the reference sample with light from the light source at a second time and acquiring a second detection result output by the spectroscopic detector, irradiating the sample with light from the light source at a third time close in time to the second time and acquiring a third detection result output by the spectroscopic detector, and calculating a measurement value of the sample from the third detection result by performing a correction process based on a change between the first detection result and the second detection result. [Effects of the Invention]

[0018] According to an embodiment of the present invention, in an optical measurement system including a spectroscopic detector, errors caused by temperature changes occurring in the spectroscopic detector or the like can be reduced. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic diagram showing a configuration example of an optical measurement system according to an embodiment of the present invention; [Figure 2] 2 is a diagram for explaining the operation of the optical measurement system shown in FIG. 1 during measurement. FIG. [Figure 3] 10A and 10B are diagrams for explaining a correction process in the optical measurement system according to the present embodiment. [Figure 4] 1 is a schematic diagram showing a configuration example of an optical measurement system according to an embodiment of the present invention; [Figure 5] 1 is a schematic diagram showing a configuration example of an optical measurement system according to an embodiment of the present invention; [Figure 6] 1 is a schematic diagram showing a configuration example of an optical measurement system according to an embodiment of the present invention; [Figure 7] 1 is a schematic diagram showing a configuration example of an optical measurement system according to an embodiment of the present invention; [Figure 8]1 is a schematic diagram showing a configuration example of an optical measurement system according to an embodiment of the present invention; [Figure 9] FIG. 2 is a schematic diagram showing an example of the configuration of a processing device included in the optical measurement system according to the present embodiment. [Figure 10] FIG. 2 is a schematic diagram showing an example of a functional configuration for implementing a measurement process including a correction process in the optical measurement system according to the present embodiment. [Figure 11] 10 is a time chart showing an experimental example of a correction process in the optical measurement system according to the present embodiment. [Figure 12] 10 is a time chart showing an experimental example of a correction process in the optical measurement system according to the present embodiment. [Figure 13] 10 is a flowchart showing a processing procedure related to a measurement process including a correction process in the optical measurement system according to the present embodiment. [Figure 14] FIG. 10 is a schematic diagram showing an example of a functional configuration for implementing a measurement process including another correction process in the optical measurement system according to the present embodiment. [Figure 15] 10A and 10B are diagrams showing examples of interference waveforms used in correction processing in the optical measurement system according to the present embodiment. [Figure 16] 10A and 10B are diagrams showing examples of interference waveforms used in correction processing in the optical measurement system according to the present embodiment. [Figure 17] 10A and 10B are diagrams showing examples of interference waveforms used in correction processing in the optical measurement system according to the present embodiment. [Figure 18] 10A and 10B are diagrams showing examples of interference waveforms used in correction processing in the optical measurement system according to the present embodiment. [Figure 19] 10 is a flowchart showing a processing procedure related to a measurement process including another correction process in the optical measurement system according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their description will not be repeated.

[0021] As a typical example of an optical measurement system according to this embodiment, a spectroscopic interference film thickness measurement system will be mainly described. However, any optical system may be adopted as long as it has a configuration using a spectroscopic detector. In the following description, an optical system (reflected light observation system) that irradiates light on a sample to be measured (sample 50 described later) and observes the reflected light thereof will be exemplified, but it is naturally applicable to an optical system (transmitted light observation system) that irradiates light on a sample to be measured and observes the transmitted light thereof.

[0022] <A. Overview> FIG. 1 is a schematic diagram showing a configuration example of an optical measurement system 1A according to this embodiment. Referring to FIG. 1, the optical measurement system 1A includes a light source 10 that generates light for irradiating a sample 50, and a spectroscopic detector 20 that receives light (reflected light or transmitted light) generated by the sample 50.

[0023] The light source 10 includes a light emitting unit 12 that generates light having a predetermined wavelength range, a condenser lens 14, and an aperture 16. The wavelength range of the light generated by the light emitting unit 12 is arbitrarily determined according to the measurement range, the material of the sample 50, and the like. For example, a halogen lamp, a white LED, or the like may be adopted as the light emitting unit 12. Alternatively, an ASE (Amplified Spontaneous Emission) light source that generates measurement light including components in the near infrared region may be adopted as the light emitting unit 12. When an ASE light source is adopted, since the light source 10 is connected to an optical fiber via optical elements such as an isolator and a coupler, the condenser lens 14 and the aperture 16 can be omitted.

[0024] The spectroscopic detector 20 includes a diffraction grating 22 that diffracts incident light, a light receiving element 24 having multiple channels arranged in correspondence with the diffraction grating 22, and a slit 26 that narrows the light incident on the diffraction grating 22. The light receiving element 24 is configured as a line sensor or a two-dimensional sensor, and outputs the intensity for each wavelength as a detection result. In other words, the detection result indicates the light intensity at each position on the light receiving surface of the light receiving element 24. Note that a prism spectrometer may be used instead of the diffraction grating 22.

[0025] The light source 10 and the spectroscopic detector 20 are connected to one end of the coupler 30. More specifically, the light source 10 is connected to the coupler 30 via a connector 18 and an optical fiber 42. The spectroscopic detector 20 is connected to the coupler 30 via a connector 28 and an optical fiber 44.

[0026] The other end of the coupler 30 is connected to one end of an optical switch 32 via an optical fiber 46 .

[0027] The other end of the optical switch 32 is connected to a light projecting and receiving head 38 via an optical fiber 34 , and is also connected to a light projecting and receiving head 40 via an optical fiber 36 .

[0028] The optical switch 32 is provided on the optical path between the light source 10 and the sample 50 and reference sample 60. More specifically, the optical switch 32 optically connects the optical fiber 46 connected to one end thereof to either the optical fiber 34 or the optical fiber 36 connected to the other end thereof in accordance with a switching command from the processing device 200 or the like.

[0029] The optical elements constituting the optical measurement system according to this embodiment are not limited to those shown in the figure, and any optical elements that fulfill the intended function can be used. For example, a circulator or a beam splitter may be used instead of the coupler 30. The same applies to each of the embodiments described below.

[0030] FIG. 2 is a diagram for explaining the operation of the optical measurement system 1A shown in FIG. 1 during measurement. 2, in a measurement mode for measuring a sample 50, the optical fiber 46 and the optical fiber 34 are optically connected in the optical switch 32. As a result, light generated by the light source 10 enters the coupler 30 via the connector 18 and the optical fiber 42, and then passes through the optical fiber 46, the optical switch 32, and the optical fiber 34, before being irradiated onto the sample 50 from the light projecting and receiving head 38.

[0031] The reflected light generated by irradiating the sample 50 with light enters the light projecting / receiving head 38, passes through the optical fiber 34, the optical switch 32, and the optical fiber 46, and reaches the coupler 30. Furthermore, the reflected light from the sample 50 is guided by the coupler 30 to the optical fiber 44 and the connector 28, and enters the spectroscopic detector 20.

[0032] Finally, the detection results of the spectroscopic detector 20 are provided to the processing device 200. The processing device 200 calculates measurement values ​​such as the film thickness of the sample 50 based on the detection results from the spectroscopic detector 20.

[0033] In this specification, "film thickness" refers to the thickness of a specific layer contained in a given sample (or reference sample). However, if the sample (or reference sample) is composed of a uniform material such as a wafer, it is equivalent to a structure having only a single layer, and so the measured film thickness refers to the overall thickness of the sample (or reference sample). In other words, in this specification, "film thickness" does not only refer to the thickness of each layer contained in a sample having a layered structure, but can also refer to the thickness of the entire sample.

[0034] In the optical measurement system 1A shown in FIGS. 1 and 2, for example, temperature changes can affect the measurement system including the spectroscopic detector 20. In optical measurement systems that use spectroscopic interference, maintaining the accuracy of the measured optical distance is important. In other words, fluctuations in the measurement results of the optical distance can cause errors in the output measurements such as film thickness. The influence on the measured optical distance is typically greatest due to temperature changes in the installation environment of the measurement system including the spectroscopic detector 20.

[0035] Therefore, in the optical measurement system according to the present embodiment, in order to correct the influence of temperature changes occurring in the measurement system including the spectroscopic detector 20, a reference sample 60 (or a reference sample 60S described later) is used.

[0036] In the optical measurement system 1A shown in FIGS. 1 and 2, the reference sample 60 is positioned so that it is irradiated with light from the light projecting and receiving head 40. Furthermore, a heat insulating structure 62 is provided around the reference sample 60 to reduce the effects of temperature changes as much as possible. By providing the heat insulating structure 62, the effects of temperature changes on the reference sample 60 are reduced to a negligible level. In other words, even if the environmental temperature of the optical measurement system 1A changes, the reference sample 60 maintains its characteristics, such as film thickness, in its initial state (reference state). In this way, the reference sample 60 is configured to maintain its characteristics against temperature changes. The optical measurement system 1A uses the detection results for the reference sample 60 to perform correction processing to reduce the effects of temperature changes.

[0037] In the correction mode for measuring the reference sample 60, the optical fiber 46 and the optical fiber 36 are optically connected by the optical switch 32. As a result, the light generated by the light source 10 passes through the optical fiber 36 and the light projecting and receiving head 40, rather than the optical fiber 34 and the light projecting and receiving head 38. The light from the light source 10 is then irradiated onto the reference sample 60 from the light projecting and receiving head 40.

[0038] The reflected light generated by irradiating the reference sample 60 with light enters the light projecting / receiving head 40, passes through the optical fiber 36, the optical switch 32, and the optical fiber 46, and reaches the coupler 30. Furthermore, the reflected light from the light source 10 is guided by the coupler 30 to the optical fiber 44 and the connector 28, and enters the spectroscopic detector 20. The detection results obtained from the light from the reference sample 60 are provided to the processing device 200. The processing device 200 corrects the measured values ​​of the film thickness of the sample 50, etc., by performing a correction process based on the detection results for the reference sample 60.

[0039] As shown in Figure 2, the optical measurement system 1A has a switching mechanism that switches between an optical path (first optical path) in a measurement mode in which light from the light source 10 is irradiated onto a sample 50 to be measured and light generated in the sample 50 is guided to a spectroscopic detector 20, and an optical path (second optical path) in a correction mode in which light from the light source 10 is irradiated onto a reference sample 60 and light generated in the reference sample 60 is guided to the spectroscopic detector 20.

[0040] 3 is a diagram illustrating the correction process in the optical measurement system according to the present embodiment. Referring to FIG. 3, the optical measurement system measures reference sample 60 at reference time t0, which is set before the start of measurement (step S1: reference sample measurement). By measuring reference sample 60, a detection result 251 at reference time t0 can be obtained.

[0041] Thereafter, the optical measurement system measures the reference sample 60 at an arbitrary measurement time t1 (step S2: reference sample measurement), and measures the sample 50 at an arbitrary measurement time t1' (=t1±Δt) (step S3: sample measurement). By measuring the reference sample 60, a detection result 252 at the measurement time t1 can be obtained, and by measuring the sample 50, a detection result 253 at the measurement time t1' can be obtained. Note that between the measurement times t1 and t1' are assumed to be close in time.

[0042] As used herein, "temporally adjacent" means within a time range in which the difference in environmental temperature is negligible in any environment in which the temperature may change over time. That is, the detection results for the reference sample 60 and the detection results for the sample 50 obtained within a time range that is "temporally adjacent" can be considered to be detection results obtained at substantially the same environmental temperature. Therefore, by using the detection results for the reference sample 60, the influence of temperature changes contained in the detection results for the reference sample 60 (i.e., the influence of temperature changes contained in the detection results for the sample 50) can be corrected.

[0043] The optical measurement system reduces the influence of temperature changes from detection result 253 of sample 50 at measurement time t1' by performing correction processing 250 based on detection result 251 of reference sample 60 at reference time t0 and detection result 252 of reference sample 60 at measurement time t1, and then calculates measurement values ​​254 such as the film thickness of sample 50. Correction processing 250 is performed based on changes in detection result 252 at measurement time t1 using detection result 251 at reference time t0 as a reference.

[0044] In this way, the optical measurement system according to this embodiment performs correction processing 250 based on the change between detection result 251 (first detection result) output by spectroscopic detector 20 when light from light source 10 is irradiated onto reference sample 60 at reference time t0 (first time) and detection result 252 (second detection result) output by spectroscopic detector 20 when light from light source 10 is irradiated onto reference sample 60 at measurement time t1 (second time), thereby calculating measurement value 254 of sample 50 from detection result 253 (third detection result) output by spectroscopic detector 20 when light from light source 10 is irradiated onto sample 50 at measurement time t1' (third time), which is close in time to measurement time t1 (second time).

[0045] The optical measurement system according to this embodiment uses a reference sample 60 placed in an environment (e.g., a thermal insulating structure 62) where the effects of temperature changes are suppressed to a degree that they are negligible, and / or a reference sample 60S (described later) made of a material where the effects of temperature changes are negligible, to correct the detection results for the sample 50, thereby offsetting the effects of temperature changes on the measurement system including the spectroscopic detector 20 and improving the measurement accuracy of the sample 50.

[0046] The reference sample 60 may be placed inside or outside the measurement device.

[0047] FIG. 3 shows an example in which the reference sample 60 is measured at an arbitrary measurement time t1, and then the sample 50 is measured, but the order in which the sample 50 and the reference sample 60 are measured may be any as long as they are close in time.

[0048] Furthermore, the plurality of detection results 253 obtained by measuring the plurality of samples 50 may be corrected using the detection result 252 obtained by measuring the reference sample 60 at an arbitrary measurement time t1. For example, the reference sample 60 used for the correction process 250 may be measured every predetermined number of measurements or every predetermined measurement period.

[0049] Alternatively, the correction process 250 may be performed using the plurality of detection results 252 obtained by measuring the reference sample 60 a plurality of times.

[0050] When it is sufficient to correct the relative change in the measurement value due to the change in the ambient temperature, an arbitrary time point such as before the start of the measurement may be set as the reference time t0. On the other hand, when it is necessary to correct the absolute change in the measurement value due to the change in the ambient temperature, the spectroscopic detector 20 is maintained in the same environment as the environment in which the wavelength calibration was performed, and the detection result 251 (the first detection result) is obtained in a state where the spectroscopic detector 20 is stable. That is, the reference time t0 is set at an arbitrary time when the spectroscopic detector 20 is maintained in the same environment as the environment in which the wavelength calibration was performed and the spectroscopic detector 20 is in a stable state. As described above, the optical measurement system according to the present embodiment uses the detection result for the reference sample 60 (or the reference sample 60S) obtained in a state where the influence of the temperature change can be ignored to cancel out the influence of the temperature change on the measurement system including the spectroscopic detector 20 and improve the measurement accuracy of the sample 50. The details of the correction process 250 will be described later.

[0051] As described above, the optical measurement system according to the present embodiment uses the detection result for the reference sample 60 (or the reference sample 60S) obtained in a state where the influence of the temperature change can be ignored to cancel out the influence of the temperature change on the measurement system including the spectroscopic detector 20 and improve the measurement accuracy of the sample 50. The details of the correction process 250 will be described later.

[0052] <B. Configuration Example of Optical Measurement System> Next, in addition to the optical measurement system 一A shown in FIG. 1, some configuration examples of the optical measurement system according to the present embodiment will be described.

[0053] (b1: Optical Measurement System 1B) Fig. 4 is a schematic diagram showing an example of the configuration of an optical measurement system 1B according to this embodiment. Compared to optical measurement system 1A shown in Fig. 1, optical measurement system 1B shown in Fig. 4 has reference sample 60S instead of reference sample 60, and has removed heat insulating structure 62.

[0054] The reference sample 60S is configured to maintain its characteristics against temperature changes. More specifically, the reference sample 60S is made of a material that is resistant to the effects of temperature changes that may occur during measurement of the sample 50. That is, the reference sample 60S is made of a material whose temperature dependence is substantially negligible, and the temperature dependence of its characteristics is extremely small. Therefore, there is no need to provide a heat insulating structure 62 as shown in FIG. 1.

[0055] Even if the environmental temperature of the optical measurement system 1B changes, the reference sample 60S maintains its characteristics, such as film thickness, in its initial state (reference state).The optical measurement system 1B uses the detection results for the reference sample 60S to perform correction processing to reduce the effects of temperature changes.

[0056] Other configurations and processes of the optical measurement system 1B are similar to those of the optical measurement system 1A shown in FIG. 1, and therefore detailed description thereof will not be repeated.

[0057] (b2: Optical measurement system 1C) Fig. 5 is a schematic diagram showing an example of the configuration of an optical measurement system 1C according to the present embodiment. Compared to optical measurement system 1A shown in Fig. 1, optical measurement system 1C shown in Fig. 5 has a plurality of pairs of optical fibers 34 and light projecting and receiving heads 38. That is, to the other end of optical switch 32, a light projecting and receiving head 38-1 for irradiating light onto sample 50-1 is connected via optical fiber 34-1, and a light projecting and receiving head 38-2 for irradiating light onto sample 50-2 is connected via optical fiber 34-2.

[0058] The optical switch 32 is capable of optically connecting any one of the light emitting / receiving heads 38-1, 38-2 and the light emitting / receiving head 40 to the optical fiber 46.

[0059] Other configurations and processes of the optical measurement system 1C are similar to those of the optical measurement system 1A shown in FIG. 1, and therefore detailed description thereof will not be repeated.

[0060] (b3: Optical measurement system 1D) Fig. 6 is a schematic diagram showing an example of the configuration of an optical measurement system 1D according to this embodiment. The optical measurement system 1D shown in Fig. 6 has a plurality of components equivalent to the optical measurement system 1A shown in Fig. 1, and the plurality of optical measurement systems share a reference sample 60.

[0061] More specifically, the optical measurement system 1D includes an optical switch 33 to which multiple optical fibers 36 are connected. The optical switch 33 is also provided on the optical path between the light source 10 and the sample 50 and reference sample 60. More specifically, the optical switch 33 optically connects one of the multiple optical fibers 36 connected to one end to an optical fiber 37 in accordance with a switching command from the processing device 200 or the like. In other words, one optical fiber 36 selected from the multiple optical fibers 36 can measure the reference sample 60.

[0062] Other configurations and processes of the optical measurement system 1D are similar to those of the optical measurement system 1A shown in FIG. 1, and therefore detailed description thereof will not be repeated.

[0063] (b4: Modified examples of optical measurement systems 1A to 1D) The optical measurement system is not limited to the configurations shown in FIGS. 1 and 4 to 6 described above, and the following modified examples may also be employed.

[0064] 5 and 6 above show an example of a configuration using the reference sample 60 and the heat insulating structure 62, but a reference sample 60S as shown in FIG. 4 may also be used.

[0065] Although the above-mentioned FIG. 5 shows an example of a configuration including two light projecting and receiving heads 38 that irradiate light onto the sample 50, more light projecting and receiving heads 38 may be arranged.

[0066] 6 above shows an example of a configuration including two pairs of light sources 10 and spectroscopic detectors 20, but it is also possible to arrange more pairs of light sources 10 and spectroscopic detectors 20. Alternatively, instead of pairs of light sources 10 and spectroscopic detectors 20, it is also possible to arrange a plurality of light sources 10 alone or a plurality of spectroscopic detectors 20 alone.

[0067] In the configuration shown in FIG. 6, a plurality of light projecting and receiving heads 38 for irradiating light onto the sample 50 may be arranged, as in the optical measurement system 1C shown in FIG.

[0068] In either configuration, the configuration can be simplified and costs can be reduced by allowing a plurality of light sources 10 or spectroscopic detectors 20 to share the configuration for measuring the reference sample 60 or the reference sample 60S.

[0069] (b5: Optical measurement system 1E) 7 is a schematic diagram showing an example of the configuration of an optical measurement system 1E according to the present embodiment. The optical measurement system 1E shown in FIG.

[0070] The light source 10 is connected to one side of the measurement housing 80 via a connector 18, an optical fiber 42, and a connector 96. The spectroscopic detector 20 is connected to another side of the measurement housing 80 via a connector 28, an optical fiber 44, and a connector 98.

[0071] The measurement housing 80 includes a measurement chamber 80A and a reference sample chamber 80B. An aperture 92 is provided in the measurement chamber 80A of the measurement housing 80 to correspond to the opening of the connector 96, and an aperture 94 is provided to correspond to the opening of the connector 98. The measurement housing 80 also includes a beam splitter 82. The apertures 92 and 94 are each disposed at a position corresponding to the center of the beam splitter 82.

[0072] The condenser lens 86 and the condenser lens 90 are arranged in correspondence with the optical axis passing through the center of the beam splitter 82. The sample 50 is arranged in accordance with the focal position of the condenser lens 86, and the reference sample 60 is arranged in accordance with the focal position of the condenser lens 90. The reference sample 60 is , and is housed in the reference sample chamber 80B of the measurement housing 80.

[0073] The reference sample chamber 80B of the measurement housing 80 employs a heat insulating structure to reduce the influence of temperature changes as much as possible. That is, a heat insulating structure is provided around the reference sample 60.

[0074] An optical shutter 84 is provided on the optical path from the beam splitter 82 to the condenser lens 86 and the condenser lens 90. The optical shutter 84 selectively blocks either the optical path from the light source 10 to the sample 50 or the optical path from the light source 10 to the reference sample 60.

[0075] More specifically, the optical shutter 84 blocks either the optical path from the beam splitter 82 to the condenser lens 86 or the optical path from the beam splitter 82 to the condenser lens 90 in accordance with a switching command from the processing device 200 or the like. In other words, the optical shutter 84 guides the light from the light source 10, which is irradiated via the connector 96 and the aperture 92, to either the sample 50 or the reference sample 60.

[0076] In the measurement mode for measuring the sample 50, the optical shutter 84 is driven toward the condenser lens 90. As a result, the light generated by the light source 10 enters the measurement housing 80 via the connector 18, the optical fiber 42, and the connector 96, and is then reflected by the beam splitter 82 and directed to the condenser lens 86. The light from the light source 10 is then condensed by the condenser lens 86 and irradiated onto the sample 50.

[0077] The reflected light generated by irradiating the sample 50 with light is converted into convergent light by the condenser lens 86, and then passes through the beam splitter 82, aperture 94, connector 98, optical fiber 44, and connector 28, before entering the spectroscopic detector 20. The detection results obtained from the light from the sample 50 are provided to the processing device 200.

[0078] On the other hand, in the correction mode for measuring the reference sample 60, the optical shutter 84 is driven toward the condenser lens 86. As a result, the light generated by the light source 10 enters the measurement housing 80 via the connector 18, the optical fiber 42, and the connector 99, and then passes through the beam splitter 82 and is guided to the condenser lens 90. The light from the light source 10 is then condensed by the condenser lens 90 and irradiated onto the reference sample 60.

[0079] The reflected light generated by irradiating the reference sample 60 with light is converted into convergent light by the condenser lens 90, reflected by the beam splitter 82, and passes through the aperture 94, the connector 98, the optical fiber 44, and the connector 28 to enter the spectroscopic detector 20. The detection results obtained from the light from the reference sample 60 are provided to the processing device 200.

[0080] The processing device 200 corrects the measurement values ​​of the film thickness of the sample 50 and the like based on the detection results for the reference sample 60 through processing as described below.

[0081] (b6: Optical Measurement System 1F) Fig. 8 is a schematic diagram showing an example of the configuration of an optical measurement system 1F according to this embodiment. Compared to the optical measurement system 1E shown in Fig. 7, the optical measurement system 1F shown in Fig. 8 has reference sample 60S instead of reference sample 60, and is provided with a reference sample chamber 80C that does not have a thermal insulation structure, instead of reference sample chamber 80B that has a thermal insulation structure.

[0082] The reference sample 60S is made of a material that can ignore the influence of temperature changes that may occur during the measurement of the sample 50. That is, the temperature dependence of the reference sample 60S is extremely small. Therefore, there is no need to provide a reference sample chamber 80B by adopting a heat insulation structure as shown in FIG. 7. Even if the environmental temperature of the optical measurement system 1F changes, the reference sample 60S maintains its characteristics such as film thickness in the initial state (reference state).

[0083] Since other configurations and processes of the optical measurement system 1F are the same as those of the optical measurement system 1E shown in FIG. 7, detailed descriptions will not be repeated.

[0084] (b7: Modified examples of the optical measurement systems 1E and 1F) Not limited to the configurations of the optical measurement systems shown in FIGS. 7 and 8 above, the following modified examples may be adopted.

[0085] In the optical measurement systems shown in FIGS. 7 and 8 above, between the measurement housing 80 and the light source 10, and between the measurement housing 80 and the spectroscopic detector 20, they are connected via optical fibers respectively. However, one or both of the optical fibers may be omitted, and the measurement housing 80 and the light source 10 may be directly connected, or the measurement housing 80 and the spectroscopic detector 20 may be directly connected.

[0086] (b8: Modified examples regarding the heat insulation structure) As the heat insulation material used for the heat insulation structure, any material can be used. It may be appropriately designed considering the required heat insulation performance, weight, volume, cost, etc.

[0087] In addition to, or instead of, the heat insulation structures shown in FIGS. 2, 5, 6, and 7, etc., a temperature adjustment mechanism may be adopted. As the temperature adjustment mechanism, for example, any configuration such as a configuration using a Peltier element or a configuration using a heat pump can be adopted. |

[0088] <C. Configuration example of the processing device 200> 9 is a schematic diagram showing an example of the configuration of a processing device 200 included in the optical measurement system according to the present embodiment. Referring to FIG. 9, processing device 200 includes a processor 202, a main memory 204, an input unit 206, a display unit 208, a storage 210, a local communication interface 220, a host communication interface 222, and a media drive 224.

[0089] The processor 202 is typically a processing unit such as a central processing unit (CPU) or a graphics processing unit (GPU), and is stored in the storage 210. One or more programs are read into the main memory 204 and executed. The main memory 204 is a volatile memory such as a dynamic random access memory (DRAM) or a static random access memory (SRAM), and stores the write data required for the processor 202 to execute the programs. It functions as a working memory.

[0090] The input unit 206 includes a keyboard, a mouse, etc., and receives operations from the user. The display unit 208 outputs the results of program execution by the processor 202 to the user.

[0091] The storage 210 is made up of a nonvolatile memory such as a hard disk or flash memory, and stores various programs and data. More specifically, the storage 210 holds an operating system (OS) 212, a measurement program 214, detection results 216, and measurement results 218.

[0092] The operating system 212 provides an environment in which the processor 202 executes programs. The measurement program 214 is executed by the processor 202 to realize the optical measurement method according to the present embodiment. The detection result 216 includes data output from the spectroscopic detector 20. The measurement result 218 includes one or more measurement values ​​obtained by executing the measurement program 214.

[0093] The local communication interface 220 mediates data transmission between the processing device 200 and the spectroscopic detector 20 .

[0094] The host communication interface 222 mediates data transmission between the host device and the manufacturing device, etc. For example, the host communication interface 222 can accept user operations given to the host device, and can also output results of program execution by the processor 202 to the user via the host device.

[0095] The media drive 224 reads necessary data from a recording medium 226 (e.g., an optical disk) that stores programs to be executed by the processor 202, and stores the data in the storage 210. The measurement program 214 to be executed by the processing device 200 may be installed via the recording medium 226, or may be downloaded from a server device via the upper communication interface 222.

[0096] The measurement program 214 may execute processing by calling necessary modules in a predetermined sequence at a predetermined timing among the program modules provided as part of the operating system 212. In such a case, a measurement program 214 that does not include such modules is also included in the technical scope of the present invention. The measurement program 214 may be provided as part of another program.

[0097] All or part of the functions provided by the execution of a program by the processor 202 of the processing device 200 may be realized by a hardwired logic circuit (for example, an FPGA (field-programmable gate array), an ASIC (application specific integrated circuit), etc.).

[0098] Instead of the processing device 200 executing all the necessary processing, the processing may be shared among a plurality of processing devices, or part of the processing may be assigned to the spectroscopic detector 20. Further, computing resources (so-called cloud) on a network not shown may realize all or part of the necessary processing.

[0099] <D. Measurement Processing including Correction Processing: Correction of Measured Values> Next, an example of measurement processing including correction processing in the optical measurement system according to the present embodiment will be described. In the example of correction processing described below, the film thickness (measured value) of the sample 50 itself is corrected.

[0100] (d1: Functional Configuration) FIG. 10 is a schematic diagram showing an example of a functional configuration for realizing measurement processing including correction processing in the optical measurement system according to the present embodiment. Each module shown in FIG. 10 may typically be realized by the processor 202 of the processing device 200 executing a measurement program 214. Note that appropriate hardware for realizing the functional configuration shown in FIG. 10 is selected according to each era.

[0101] Referring to FIG. 10, the processing device 200 includes a preprocessing module 260, a film thickness calculation module 264, and a correction module 266 as a functional configuration related to measurement processing.

[0102] The preprocessing module 260 has a wavelength calibration table 262, associates wavelengths with the detection results from the spectroscopic detector 20, and outputs them as a spectrum (intensity for each wavelength).

[0103] The film thickness calculation module 264 calculates the film thickness based on the detection result output by the spectroscopic detector 20. More specifically, the film thickness calculation module 264 calculates the film thickness of the sample 50 based on the spectrum output from the preprocessing module 260. The film thickness of the sample 50 may be calculated using a power spectrum calculated by Fourier transforming the spectrum, or by fitting with a previously prepared model.

[0104] The correction module 266 performs a correction process to reduce the influence of temperature changes on the film thickness output from the film thickness calculation module 264. More specifically, the correction module 266 includes a correction coefficient calculation module 268 and a division unit 270.

[0105] The correction coefficient calculation module 268 calculates a correction coefficient K based on the film thickness ds0 (reference sample film thickness 256) obtained by measuring the reference sample 60 at the reference time t0 and the film thickness ds1 (reference sample film thickness 257) obtained by measuring the reference sample 60 at an arbitrary measurement time t1 that is close in time to the measurement time t1' at which the film thickness of the sample 50 was measured.

[0106] For example, the ratio of the film thickness ds1 (reference sample film thickness 257) of the reference sample 60 acquired at an arbitrary measurement time t1 to the film thickness ds0 (reference sample film thickness 256) of the reference sample 60 acquired at the reference time t0 can be calculated as the correction coefficient K. The rate of change of the reference sample film thickness 257 (film thickness ds1) relative to the reference sample film thickness 256 (film thickness ds0) can be used as the correction coefficient K. In other words, the correction coefficient K can be calculated as ds1 / ds0.

[0107] As described above, depending on whether a relative change or an absolute change in the measurement value needs to be corrected, the reference time t0 for acquiring the film thickness ds0 is set to any time, such as before the start of measurement, or to any time when the spectroscopic detector 20 is maintained in an environment similar to the environment in which the wavelength was calibrated and the spectroscopic detector 20 is in a stable state.

[0108] The division unit 270 calculates the corrected film thickness by dividing the film thickness output from the film thickness calculation module 264 by the correction coefficient K. That is, the film thickness d1 of the sample 50 acquired at the measurement time t1′ is corrected in accordance with the film thickness (corrected) d1a=d1 / K=d1 / (ds1 / ds0)=d1×(ds0 / ds1).

[0109] In this way, correction module 266 corrects the measurement value of sample 50 based on the change in the measurement value of reference sample 60. That is, correction module 266 calculates the measurement value of sample 50 (film thickness (corrected) d1a) by reflecting the change rate (correction coefficient K) of film thickness ds1 (second film thickness) calculated from detection result 252 of reference sample 60 acquired at measurement time t1 relative to film thickness ds0 (first film thickness) calculated from detection result 251 of reference sample 60 acquired at reference time t0 in film thickness d1 (third film thickness) calculated from detection result 253 of sample 50 acquired at measurement time t1'.

[0110] In response to the execution of the above-described correction process, the correction module 266 outputs a switching command to acquire the reference sample film thickness 257 (film thickness ds1). As described above, in response to the switching command, the light from the light source 10 is directed to the reference sample 60.

[0111] (d2: Experimental example) An experimental example of the correction process in the optical measurement system according to the present embodiment will be described.

[0112] 11 and 12 are time charts showing an experimental example of the correction process in the optical measurement system according to the present embodiment, which show an example of the results when the environmental temperature of the optical measurement system is changed by 5°C.

[0113] FIG. 11(A) shows the optical measurement system repeatedly measuring the same sample 50. 11(B) shows the change over time in the measured value (thickness of the reference sample) obtained by repeatedly measuring the same reference sample 60 with the optical measurement system.

[0114] 11(A) and 11(B), the environmental temperature changes significantly in the elapsed time interval of 8 to 11 hours, and accordingly, the measured values ​​of the same sample 50 and reference sample 60 change. More specifically, in the example of FIG. 11(A), a variation of more than 0.08 μm occurs.

[0115] Figure 12(A) shows the ratio (reference sample film thickness change rate: correction coefficient K) of the measurement value of the reference sample 60 (corresponding to film thickness ds1 in Figure 10) obtained after the measurement value of the reference sample 60 (corresponding to film thickness ds0 in Figure 10) obtained in the initial state (elapsed time 0 [hr]) to the reference value.

[0116] FIG. 12(B) shows the results of dividing the measurement value (sample film thickness) of sample 50 shown in FIG. 11(A) by the value of the reference sample film thickness change rate at the corresponding time shown in FIG. 12(A).

[0117] As shown in FIG. 11(A), changes in the environmental temperature cause errors in the measurement values ​​of the sample 50, but it can be seen that the errors that occur can be reduced by applying the correction process according to this embodiment.

[0118] (d3: Processing procedure) 13 is a flowchart showing the procedure of the measurement process including the correction process in the optical measurement system according to the present embodiment. Typically, each step shown in FIG. 13 may be realized by the processor 202 of the processing device 200 executing the measurement program 214.

[0119] 13, first, the processing device 200 outputs a switching command to select the reference sample 60 as the measurement target (step S100), calculates the film thickness based on the detection result for the reference sample 60 output from the spectroscopic detector 20, and stores it as film thickness ds0 (reference sample film thickness 256) (step S102). In this way, the processing device 200 performs a process of irradiating the reference sample 60 with light from the light source 10 and acquiring the detection result output from the spectroscopic detector 20. Note that the film thickness ds0 of the reference sample 60 may be set as the initial value of film thickness ds1.

[0120] Next, the processing device 200 determines whether the measurement conditions for the reference sample 60 are met (step S104). The measurement conditions for the reference sample 60 are conditions for determining whether or not it is necessary to measure the film thickness ds1 of the reference sample 60, and may be, for example, that a predetermined number of measurements have been performed since the previous measurement of the film thickness ds1, or that a predetermined period of time has elapsed since the previous measurement of the film thickness ds1.

[0121] If the measurement conditions for the reference sample 60 are met (YES in step S104), the processing device 200 outputs a switching command to select the reference sample 60 as the measurement target (step S106), calculates the film thickness based on the detection result for the reference sample 60 output from the spectroscopic detector 20, and updates it as a new film thickness ds1 (reference sample film thickness 257) (step S108). In this way, the processing device 200 performs a process of irradiating the reference sample 60 with light from the light source 10 and acquiring the detection result output by the spectroscopic detector 20.

[0122] On the other hand, if the measurement conditions for the reference sample 60 are not met (NO in step S104), the processes of steps S106 and S108 are skipped.

[0123] Next, the processing device 200 determines whether the measurement conditions for the sample 50 are met (step Sample 50 measurement condition can use conditions such as receiving a trigger from a transport mechanism (not shown) of sample 50. If the measurement condition of sample 50 is not satisfied (NO in step S110), the process of step S110 is repeated.

[0124] When the measurement condition of sample 50 is satisfied (YES in step S110), the processing device 200 outputs a switching command to select sample 50 as the measurement target (step S112), and calculates the film thickness based on the detection result of sample 50 output from the spectroscopic detector 20 (step S114). In this way, the processing device 200 executes a process of irradiating the light from the light source 10 to the sample 50 at a time close to the measurement time of the reference sample 60 and obtaining the detection result output by the spectroscopic detector 20.

[0125] Then, the processing device 200 calculates the correction coefficient K based on the pre-stored film thickness ds0 and the current film thickness d1 (step S116), and uses the calculated correction coefficient K to correct and output the calculated film thickness (step S118). In this way, the processing device 200 calculates the measured value of the sample 50 from the detection result obtained in step S114 by executing a correction process based on the change between the detection result obtained in step S102 and the detection result obtained in step S108. Hereinafter, the processes of step S104 and subsequent steps are repeated.

[0126] By the above processing procedure, measured values such as the film thickness of the sample 50 are sequentially calculated. Note that the processes of steps S100 and S102 may be executed at the factory shipment stage of the optical measurement system.

[0127] <E. Measurement process including correction process: Correction of wavelength calibration information> Next, another example of the measurement process including the correction process in the optical measurement system according to the present embodiment will be described. In the example of the correction process described below, the wavelength calibration information for calculating the spectrum of the sample 50 is corrected.

[0128] (e1: Functional configuration) Fig. 14 is a schematic diagram showing an example of the functional configuration for realizing measurement processing including another correction processing in the optical measurement system according to this embodiment. Typically, each module shown in Fig. 14 may be realized by processor 202 of processing device 200 executing measurement program 214. Note that the hardware realizing the functional configuration shown in Fig. 14 is selected appropriately according to the times.

[0129] Referring to FIG. 14, the processing device 200 includes a pre-processing module 260, a film thickness calculation module 264, and a wavelength calibration correction module 272 as functional components related to the measurement process.

[0130] The pre-processing module 260 has a wavelength calibration table 262 and a correction function 263. The correction function 263 is a function for correcting the characteristics of the wavelength calibration table 262, which is prepared in advance. In the following description, the wavelength calibration table 262 and the correction function 263 are also collectively referred to as "wavelength calibration information." In this way, the pre-processing module 260 refers to the wavelength calibration information, associates wavelengths with the detection results output by the spectroscopic detector 20, and outputs a spectrum.

[0131] The film thickness calculation module 264 is similar to the film thickness calculation module 264 shown in FIG. The wavelength calibration correction module 272 corrects the wavelength calibration information referred to by the pre-processing module 260 so as to reduce the influence of temperature changes. More specifically, the wavelength calibration correction module 272 calculates the reference interference waveform λs0 (reference sample spectrum 276) acquired by measuring the reference sample 60 at the reference time t0 and the reference interference waveform λs0 obtained by measuring the film thickness of the correction target at the reference time t0. At each measurement time t1, the correction function 263 is calculated or updated based on the reference interference waveform λs1 (reference sample spectrum 277) acquired by measuring the reference sample 60. Hereinafter, for convenience of explanation, the spectrum output by the preprocessing module 260 will also be referred to as an interference waveform or a reference interference waveform.

[0132] In order to correct the wavelength calibration information, it is necessary to acquire the reference interference waveform λs0 (reference sample spectrum 276) when the wavelength calibration table 262 is determined. Therefore, it is preferable that the reference time t0 is set to the time when the wavelength of the spectroscopic detector 20 is calibrated. In this case, it is necessary to measure the reference sample 60 together with the wavelength calibration of the spectroscopic detector 20.

[0133] Alternatively, the reference time t0 may be set to any point after wavelength calibration of the spectroscopic detector 20, when the spectroscopic detector 20 is maintained in an environment similar to that in which the wavelength calibration was performed and the spectroscopic detector 20 is in a stable state. The reference interference waveform λs0 (reference sample spectrum 276) obtained by measuring the reference sample 60 in such an environment can be considered to be substantially identical to that obtained during wavelength calibration.

[0134] In this way, the wavelength calibration correction module 272 corrects the wavelength calibration information (correction function 263 and / or wavelength calibration table 262) based on the difference between the reference interference waveform λs0 (reference sample spectrum 276) obtained by irradiating the reference sample 60 with light from the light source 10 at the reference time t0 (first time) and associating the wavelength with the detection result 251 (first detection result) output by the spectroscopic detector 20, and the reference interference waveform λs1 (reference sample spectrum 277) obtained by irradiating the reference sample 60 with light from the light source 10 at the measurement time t1 (second time) and associating the wavelength with the detection result 252 (second detection result) output by the spectroscopic detector 20.

[0135] In response to the execution of the above-described correction process, the wavelength calibration correction module 272 outputs a switching command to acquire the reference interference waveform λs1 (reference sample spectrum 277). As described above, in response to the switching command, the light from the light source 10 is directed to the reference sample 60.

[0136] In this manner, the wavelength calibration correction module 272 corrects the measurements of the sample 50 based on the variations in the detection results for the reference sample 60 .

[0137] The process by which the wavelength calibration correction module 272 corrects the wavelength calibration information will be described in more detail below.

[0138] 15 to 18 are diagrams showing examples of interference waveforms used in the correction process in the optical measurement system according to the present embodiment, and show the results of measuring the same sample 50 and reference sample 60.

[0139] 15(A) shows an example of a reference interference waveform λs0 (reference sample spectrum 276) obtained by measuring a reference sample 60 at a reference time t0. Also, FIG. 15(B) shows an example of an interference waveform λ0 obtained by measuring a sample 50 at a measurement time t0' that is temporally close to the reference time t0.

[0140] 16(A) shows an example of a reference interference waveform λs1 (reference sample spectrum 277) obtained by measuring a reference sample 60 at an arbitrary measurement time t1. Also, FIG. 16(B) shows an example of an interference waveform λ1 obtained by measuring a sample 50 at a measurement time t1' that is temporally close to the measurement time t1.

[0141] FIG. 17(A) shows a waveform obtained by superimposing the reference interference waveform λs0 shown in FIG. 15(A) and the reference interference waveform λs1 shown in FIG. 16(A), and FIG. 17(B) shows the interference waveform shown in FIG. 15(B). The waveform shown is a superposition of λ0 and the interference waveform λ1 shown in FIG. 16(B).

[0142] As shown in Figure 17(A), changes in the ambient temperature of the spectroscopic detector 20 can cause changes in the positional relationship between the diffraction grating 22 and the light receiving element 24, as well as in the diffraction grating 22 itself, which can result in a shift in the correspondence between the detection results of the spectroscopic detector 20 and the wavelength.

[0143] For example, the film thickness of the sample 50 calculated from the interference waveform λ0 shown in Fig. 15(B) is 100.000955 [μm], whereas the film thickness of the sample 50 calculated from the interference waveform λ1 shown in Fig. 16(B) is 101.276985 [μm]. In other words, the deviation of the interference waveforms causes an error of approximately 1.27 [μm].

[0144] The wavelength calibration correction module 272 corrects the wavelength calibration information (in essence, the correction function 263) so that the reference interference waveform λs0 acquired at the reference time t0 matches the reference interference waveform λs1 acquired at the measurement time t1.

[0145] As a method for correcting the wavelength calibration information, for example, the wavelength positions of multiple peaks appearing in the reference interference waveform λs0 and the wavelength positions of multiple peaks appearing in the reference interference waveform λs1 are extracted, and the coefficients of the polynomial approximation formula are determined so that the extracted wavelength positions match. The determined polynomial approximation formula is determined as the correction function 263 for correcting the wavelength calibration table 262.

[0146] As a calculation method for matching wavelength positions, the center of gravity of the wavelength positions of multiple peaks may be calculated. Furthermore, the peaks to be extracted may be a predetermined number of closely spaced peaks (e.g., three peaks), a predetermined number of discrete peaks, or all peaks may be extracted. Furthermore, any correction function may be used instead of a polynomial approximation formula.

[0147] Fig. 18(A) shows an interference waveform λ1a (a result of correcting the interference waveform λ1) for the sample 50, which is output using the wavelength calibration table 262 calculated from the reference interference waveform λs0 and the reference interference waveform λs1 shown in Fig. 17(A). Note that the film thickness of the sample 50 calculated from the interference waveform λ1a shown in Fig. 17(A) is 100.034616 [μm], which shows that the error has been greatly reduced.

[0148] Fig. 18(B) shows a waveform obtained by superimposing the interference waveform λ1a acquired at measurement time t1 shown in Fig. 18(A) and the interference waveform λ0 acquired at measurement time t0' shown in Fig. 15(B). Since these are results of measuring the same sample 50, ideally the same results would be shown regardless of the measurement time, but as shown in Fig. 18(B), it can be seen that the interference waveform λ1a and the interference waveform λ0 show almost the same waveform.

[0149] As described above, a change in the ambient temperature can cause a deviation in the correspondence between the detection results of the spectroscopic detector 20 and the wavelength, but it can be seen that the application of the correction process according to this embodiment can reduce the resulting error.

[0150] Although the above description shows an example of a process for correcting the correction function 263, rather than the wavelength calibration table 262 itself, the wavelength calibration table 262 itself may be updated by reflecting the correction function 263 in the wavelength calibration table 262.

[0151] (e2: Processing procedure) 19 is a flowchart showing a procedure for a measurement process including another correction process in the optical measurement system according to the present embodiment. Typically, each step shown in FIG. 19 may be realized by the processor 202 of the processing device 200 executing the measurement program 214.

[0152] 19, first, the processing device 200 outputs a switching command to select the reference sample 60 as the measurement target (step S200), and stores the spectrum calculated from the detection result for the reference sample 60 output from the spectroscopic detector 20 as the reference interference waveform λs0 (reference sample spectrum 276) (step S202). In this way, the processing device 200 performs a process of irradiating the reference sample 60 with light from the light source 10 and acquiring the detection result output from the spectroscopic detector 20.

[0153] The wavelength calibration table 262 is prepared in advance through a calibration process. The reference interference waveform λs0 of the reference sample 60 may be set as the initial value of the reference interference waveform λs1 (reference sample spectrum 277).

[0154] Next, the processing device 200 determines whether the measurement conditions for the reference sample 60 are met (step S204). The measurement conditions for the reference sample 60 are conditions for determining whether the correction function 263 needs to be updated, and may be, for example, that a predetermined number of measurements have been performed since the previous calculation of the correction function 263, or that a predetermined period of time has elapsed since the previous calculation of the correction function 263.

[0155] If the measurement conditions for the reference sample 60 are met (YES in step S204), the processing device 200 outputs a switching command to select the reference sample 60 as the measurement target (step S206), and stores the spectrum calculated from the detection results for the reference sample 60 output from the spectroscopic detector 20 as the reference interference waveform λs1 (reference sample spectrum 277) (step S208). In this way, the processing device 200 performs a process of irradiating the reference sample 60 with light from the light source 10 and acquiring the detection results output from the spectroscopic detector 20. Then, the processing device 200 updates the correction function 263 based on the reference interference waveform λs0 (reference sample spectrum 276) and the reference interference waveform λs1 (reference sample spectrum 277) (step S210).

[0156] On the other hand, if the measurement conditions for the reference sample 60 are not met (NO in step S204), the processes of steps S206 to S210 are skipped.

[0157] Next, the processing device 200 determines whether the measurement conditions for the sample 50 are met (step S212). The measurement conditions for the sample 50 can be, for example, a condition such as receiving a trigger from a transport mechanism for the sample 50 (not shown). If the measurement conditions for the sample 50 are not met (NO in step S212), the processing of step S212 is repeated.

[0158] When the measurement conditions for the sample 50 are met (YES in step S212), the processing device 200 outputs a switching command to select the sample 50 as the measurement target (step S214), and calculates and outputs the film thickness based on the detection results for the sample 50 output from the spectroscopic detector 20 (step S216). At this time, the wavelength calibration table 262 is corrected using the correction function 263, and then the interference waveform λ1 is calculated. In this way, the processing device 200 executes a process of irradiating the sample 50 with light from the light source 10 and acquiring the detection results output by the spectroscopic detector 20 at a time temporally close to the measurement time of the reference sample 60. Then, the processes from step S204 onwards are repeated.

[0159] Through the above-described processing procedure, measurement values ​​such as the film thickness of the sample 50 are sequentially calculated. As described above, the processing device 200 performs correction processing based on the change between the detection result acquired in step S202 and the detection result acquired in step S208, thereby calculating the measurement values ​​of the sample 50 from the detection result acquired in step S216.

[0160] The processes of steps S200 and S202 may be performed at the time of shipping the optical measurement system from the factory.

[0161] <F.まとめ> The optical measurement device according to this embodiment estimates and corrects the effect of temperature changes on a measurement system including spectroscopic detector 20, based on changes in the detection results for reference sample 60, which is configured to maintain its characteristics against temperature changes. This makes it possible to suppress the effect of temperature changes on measurement and reduce errors, even when measurements are performed over a relatively long period of time or when the device is placed in an environment where the environmental temperature changes relatively greatly.

[0162] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0163] 1A, 1B, 1C, 1D, 1E, 1F Optical measurement system, 10 Light source, 12 Light emitting unit, 14, 86, 90 Condenser lens, 16, 92, 94 Aperture, 18, 28, 96, 98, 99 Connector, 20 Spectroscopic detector, 22 Diffraction grating, 24 Light receiving element, 26 Slit, 30 Coupler, 32, 33 Optical switch, 34, 36, 37, 42, 44, 46 Optical fiber, 38, 40 Light emitting / receiving head, 50 Sample, 60, 60S Reference sample, 62 Heat insulating structure, 80 measurement housing, 80A measurement chamber, 80B, 80C reference sample chamber, 82 beam splitter, 84 optical shutter, 200 processing device, 202 processor, 204 Main memory, 206 input unit, 208 display unit, 210 storage, 212 operating system, 214 measurement program, 216, 251, 252, 253 detection results, 218 measurement results, 220 local communication interface, 222 upper communication interface, 224 media drive, 226 recording medium, 250 correction processing, 254 measurement values, 256, 257 reference sample film thickness, 260 preprocessing module, 262 wavelength calibration table, 263 correction function, 264 film thickness calculation module, 266 correction module, 268 correction coefficient calculation module, 270 division unit, 272 wavelength calibration correction module, 276, 277 reference sample spectrum, K correction coefficient.

Claims

1. A light source and a spectroscopic detector; a reference sample configured to maintain its properties over temperature; a switching mechanism that switches between a first optical path that irradiates the light from the light source onto a measurement target sample and guides light generated at the sample to the spectroscopic detector, and a second optical path that irradiates the light from the light source onto the reference sample and guides light generated at the reference sample to the spectroscopic detector; and a calculation unit that calculates a measurement value of the sample from a third detection result output by the spectroscopic detector when the sample is irradiated with light from the light source at a third time that is temporally close to the second time, by performing a correction process based on a change between a first detection result output by the spectroscopic detector when the reference sample is irradiated with light from the light source at a first time and a second detection result output by the spectroscopic detector when the reference sample is irradiated with light from the light source at a second time.

2. The optical measurement system of claim 1 , wherein the correction process is based on a change in the second detection result relative to the first detection result.

3. The calculation unit a means for calculating a film thickness based on the detection result output by the spectroscopic detector; 3. The optical measurement system according to claim 1, further comprising: means for calculating a measurement value of the sample by reflecting a rate of change of a second film thickness calculated from the second detection result relative to a first film thickness calculated from the first detection result in a third film thickness calculated from the third detection result.

4. The calculation unit a means for associating a wavelength with the detection result output by the spectroscopic detector by referring to wavelength calibration information; 3. The optical measurement system according to claim 1, further comprising: means for correcting the wavelength calibration information based on a difference between a result of associating a wavelength with the first detection result and a result of associating a wavelength with the second detection result.

5. 5. The optical measurement system according to claim 1, wherein a heat insulating structure is provided around the reference sample.

6. 5. The optical measurement system according to claim 1, wherein the reference sample is made of a material whose temperature dependency is substantially negligible.

7. 7. The optical measurement system according to claim 1, wherein the switching mechanism includes an optical switch provided on an optical path between the light source and the sample and the reference sample.

8. The optical measurement system according to any one of claims 1 to 6, wherein the switching mechanism includes an optical shutter that selectively blocks either the optical path from the light source to the sample or the optical path from the light source to the reference sample.

9. a step of irradiating a reference sample with light from a light source at a first time and acquiring a first detection result output by a spectroscopic detector, wherein the reference sample is configured to maintain its characteristics against temperature changes; At a second time, the reference sample is irradiated with light from the light source and the spectroscopic detector outputs an output. obtaining a second detection result; irradiating a sample with light from the light source at a third time point that is temporally close to the second time point, and acquiring a third detection result output by the spectroscopic detector; and calculating a measurement value of the sample from the third detection result by performing a correction process based on a change between the first detection result and the second detection result.

10. A measurement program for measuring a sample, the program being stored in a computer. a step of irradiating a reference sample with light from a light source and obtaining a first detection result output by a spectroscopic detector at a first time, the reference sample being configured to maintain its characteristics against temperature changes; At a second time, irradiating the reference sample with light from the light source and acquiring a second detection result output by the spectroscopic detector; irradiating the sample with light from the light source at a third time point that is temporally close to the second time point, and acquiring a third detection result output by the spectroscopic detector; and calculating a measurement value of the sample from the third detection result by performing a correction process based on a change between the first detection result and the second detection result.

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