Measuring device and measuring method

Abstract

To quickly measure the shape of the measurement surface of a sample. [Solution] The measuring device according to the present disclosure comprises: an illumination optical system that irradiates an object with illumination light; a detection optical system that causes a detector to detect reflected light from the object based on the illumination light; a position control unit that controls the height position, which is the relative height position between the object and the focusing position of the illumination optical system; an acquisition unit that acquires relational information showing the relationship between the height position and the detection intensity based on the detection results of the reflected light detector when illumination light is irradiated onto a prepared sample at a predetermined position on the prepared sample, which is the object, at multiple different height positions; and a measuring unit that uses the relational information to determine surface height information at multiple measurement positions based on the test detection results, which are the detection results of the reflected light detector when illumination light is irradiated onto multiple measurement positions on the test sample, with the height position of the test sample, which is the object, as a predetermined reference position.

Description

[[Technical Field]]

[0001] The present disclosure relates to a measuring apparatus and a measuring method. [[Background Art]]

[0002] Conventionally, various apparatuses for measuring the three-dimensional shape of an uneven measurement surface of a sample have been proposed (for example, Patent Document 1). [[Prior Art Literature]] [[Patent Literature]]

[0003] [[Patent Document 1]] Japanese Unexamined Patent Publication No. 2020-64127 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] In such a measuring apparatus, it is desired to shorten the measurement time while maintaining measurement accuracy.

[0005] The present invention has been made in view of the foregoing circumstances, and an object thereof is to provide a measuring apparatus and a measuring method capable of rapidly measuring the shape of a measurement surface of a sample. [[Means for Solving the Problem]]

[0006] The measuring device according to this disclosure comprises: an illumination optical system for irradiating an object with illumination light; a detection optical system for causing a detector to detect reflected light from the object based on the illumination light; a position control unit for controlling a height position which is the relative height position between the object and the focusing position of the illumination optical system; an acquisition unit for acquiring relational information showing the relationship between the height position and the detection intensity based on the detection results of the reflected light by the detector when the illumination light is irradiated onto the prepared sample, which is the object, at a predetermined position on the prepared sample, which is the object, at a plurality of different height positions; and a measuring unit for determining surface height information at a plurality of measurement positions based on the test detection results which are the detection results of the reflected light by the detector when the illumination light is irradiated onto a plurality of measurement positions of the test sample, which is the object, with the height position of the test sample being a predetermined reference position, using the relational information.

[0007] The measurement method according to this disclosure uses a measuring device having an illumination optical system that irradiates an object with illumination light and a detection optical system that causes a detector to detect the reflected light from the object based on the illumination light. The method controls the height position, which is the relative position in the height direction between the object and the focusing position of the illumination optical system. When the illumination light is irradiated onto the prepared sample, which is the object, at a predetermined position, at a plurality of different height positions, relational information showing the relationship between the height position and the detection intensity is obtained based on the detection result of the reflected light by the detector. Using the relational information, surface height information at a plurality of measurement positions is obtained based on the test detection results, which are the detection results of the reflected light by the detector, when the illumination light is irradiated onto a plurality of measurement positions of the test sample, with the height position of the test sample, which is the object, as a predetermined reference position. [Effects of the Invention]

[0008] According to this disclosure, the shape of the measurement surface of a sample can be measured rapidly. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram schematically shows the configuration of the measuring device according to Embodiment 1. [Figure 2] This diagram explains the "Z-scan" process during the preparation phase. [Figure 3] This diagram schematically shows the relationship between the detected intensity (luminance I) and height position (Z) of the reflected light L2, which is acquired during the preparation phase. [Figure 4] This diagram schematically illustrates the principle of measuring the surface irregularities of a test sample. [Figure 5] This diagram schematically illustrates the principle of measuring the surface irregularities of a test sample. [Figure 6] This diagram schematically illustrates how a test sample is scanned in two dimensions in the XY plane using illumination light. [Figure 7] Figure 6 schematically shows how the relative position of the detector to the test sample changes when two-dimensional scanning is performed. [Figure 8] This is an image of an example of a test sample. [Figure 9] Figure 8 shows a graph illustrating the unevenness of the measurement locations on the test sample, indicated by the dashed line. [Figure 10] This is an example of an image showing the height information of the measurement area of ​​a test sample in grayscale. [Figure 11] This is an example of a table showing multiple combinations of height and inclination information at the first measurement location. [Figure 12] This is another example of a table showing multiple combinations of height and inclination information at the first measurement location. [Figure 13] This is a flowchart illustrating the measurement method according to Embodiment 1. [Figure 14] This is a schematic diagram showing the change in focus in the measuring device according to Embodiment 2. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. Also, in each drawing, the same elements are denoted by the same reference numerals, and repeated descriptions are omitted as necessary. The following description shows preferred embodiments of the present disclosure, and the scope of the present disclosure is not limited to the following embodiments.

[0011] The embodiment relates to a measuring apparatus that measures the three-dimensional shape of an uneven measurement surface of an object. The measuring apparatus according to the embodiment includes an imaging optical system for imaging a sample, the imaging optical system including an illumination optical system that irradiates the object with illumination light, and a detection optical system that causes a detector to detect return light from the sample based on the illumination light. In the imaging optical system, light from the light-converging position of the illumination light is predominantly detected by the detector.

[0012] Embodiment 1 Fig. 1 is a diagram schematically showing the configuration of the measuring apparatus according to Embodiment 1. The measuring apparatus 100 mainly includes a light source 1, a beam splitter 2, an objective lens 3, a detector 4, and a lens 5 as main components. In the following description, the optical axis direction of the optical system is defined as the Z direction, and the direction perpendicular to the optical axis is defined as the XY direction.

[0013] The measuring apparatus 100 has sectional performance in the Z direction. The measuring apparatus 100 may be, for example, a confocal microscope having confocality along at least one dimension (the Z direction). Note that the measuring apparatus 100 is not limited to a confocal optical system, and may have another sectional optical system such as a multiphoton excitation microscope in which the amount of change in the Z direction is linked to the amount of change in luminance. Here, an example where the measuring apparatus 100 is a confocal microscope will be described.

[0014] The light source 1 emits illumination light L1 for irradiating the object T0. The light source 1 is, for example, a laser light source such as a laser diode. In FIG. 1, the optical path in the measurement apparatus 100 is indicated by arrow lines. The illumination light L1 passes through the beam splitter 2, the lens 5, and the objective lens 3, and irradiates the object T0. The light from the light source 1 may be emitted as the illumination light L1 via a slit or a pinhole.

[0015] The beam splitter 2 is, for example, a half mirror, and transmits part of incident light. The illumination light L1 transmitted through the beam splitter 2 enters the objective lens 3. The objective lens 3 condenses the incident illumination light L1 and irradiates the object T0. Thereby, the illumination light L1 from the light source 1 forms an image on the object T0. Assuming that the light source 1 is a point light source, a point-shaped spot is formed on the object T0. That is, the beam splitter 2, the lens 5, and the objective lens 3 can be referred to as an "illumination optical system".

[0016] Return light L2 from the object T0 based on the illumination light L1 passes through the objective lens 3 and the beam splitter 2, and enters the detector 4. The return light L2 that has entered the objective lens 3 from the object T0 propagates along the same optical path as the illumination light L1 up to the beam splitter 2. The beam splitter 2 reflects part of the incident return light L2 toward the detector 4. That is, the objective lens 3 and the beam splitter 2 can be referred to as a "detection optical system" that causes the detector 4 to detect the return light L2 from the object T0 based on the illumination light L1. In Embodiment 1, an imaging optical system including an illumination optical system that irradiates the object T0 with the illumination light L1 from the light source 1 and a detection optical system that guides the return light L2 from the object T0 to the detector 4 constitutes a confocal optical system.

[0017] The return light L2 may be reflected light generated when the object T0 is illuminated by the illumination light L1. Note that the return light L2 may be various light beams generated when the object T0 is illuminated by the illumination light L1, such as reflected light, transmitted light, scattered light, and fluorescent light.

[0018] Although not shown in the diagram, the object T0 is placed on a stage. The stage is a movable stage, such as a rotating stage or an XYZ stage. By driving the stage, the illumination position of the object T0 changes. The detector 4 detects the reflected light L2 from multiple measurement positions on the object T0, which are the irradiation positions of the illumination light L1. In other words, the stage can function as an example of a "scanning control unit" that moves the area on the object T0 that is imaged by the detector 4 relative to the object T0. The scanning control unit is not particularly limited in its form, as long as it can control the relative position of the object T0 and the area on the object T0 that is imaged by the detector 4. For example, the object T0 may be scanned in two dimensions by the illumination light using a galvanometer mirror or the like.

[0019] Furthermore, by driving the stage in the Z direction (optical axis direction), the distance between the objective lens 3 and the object T0 changes. This allows for adjustment of the focal position, and the object T0 can be moved to the focal position. The stage can function as an example of a "position control unit" that controls the height position, which is the relative height position between the object T0 and the focusing position of the illumination optical system. The object T0 may be held by a holding part realized by a clamping mechanism or a robot arm, in addition to the stage. In other words, the stage is an example of a holding part that holds the object T0.

[0020] The objective lens 3 is configured to be driveable along the direction (Z direction) of illumination light L1 directed onto the object T0, such that the focal point FP1 is aligned with the object T0. Let the focal length of the objective lens 3 be f1. The control unit that drives the objective lens 3 in the Z direction can function as another example of the "position control unit" that controls the height position as described above. The following description will explain an example of controlling the height position by changing the position of the objective lens 3.

[0021] The focal point FP2 of lens 5 coincides with the exit point of the illumination light L1 from light source 1. Let the focal length of lens 5 be f2. The focal point FP2 of the reflected light L2 from beam splitter 2 is at a position conjugate to the exit point of the illumination light L1 from light source 1.

[0022] The detector 4 is positioned at a location conjugate to the focusing position of the illumination light L1 directed at the object T0 by the objective lens 3. The detector 4 outputs a detection signal DET1 corresponding to the detection intensity (luminance) of the reflected light L2 from the object T0. Alternatively, a pinhole or slit may be placed at a position conjugate to the focusing position of the objective lens 3, and the detector 4 may detect the reflected light that has passed through the pinhole or slit.

[0023] The detector 4 may be a sensor having multiple pixels (photodetectors) arranged in one direction. For example, the detector 4 is a line sensor having 1024 pixels. In this case, the illumination light L1 is formed into a line shape through a slit (not shown). The pixels of the detector 4 are arranged along the direction corresponding to the illumination area of ​​the line-shaped illumination light L1. A CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) sensor can be used as the detector 4. Each pixel outputs a detection signal DET1 corresponding to the amount of light received. The detection signal DET1 is input to a processing device (not shown).

[0024] The processing unit comprises a processor, memory, and storage device (not shown in the diagram). The storage device stores a program that causes the computer to execute each process of the measurement method according to Embodiment 1. The processor loads the program from the storage device into memory and executes the program. In this way, the processor realizes each function such as the acquisition unit, measurement unit, and output unit. The operation of each function will be described in detail below.

[0025] Furthermore, each component of the processing unit may be implemented using dedicated hardware. Also, some or all of each component may be implemented using general-purpose or dedicated circuits, processors, etc., or combinations thereof. These may be comprised of a single chip or multiple chips connected via a bus. Some or all of each component may be implemented using a combination of the aforementioned circuits, etc., and a program. Additionally, a CPU (Central Processing Unit), GPU (Graphics Processing Unit), etc., may be used as the processor.

[0026] In the examples described above, the program includes a set of instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more of the functions described in the embodiments. The program may be stored on a non-temporary computer-readable medium or a physical storage medium. Examples, but not limited to, include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technologies, CD-ROM, digital versatile disc (DVD), Blu-ray® disc or other optical disc storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage devices. The program may be transmitted over a temporary computer-readable medium or a communication medium. Examples, but not limited to, include temporary computer-readable medium or a communication medium that includes electrically, optically, acoustically, or otherwise propagating signals.

[0027] The measuring device 100 can perform (1) a preparation stage and (2) a measurement stage. <Preparation Stage> In the preparation stage, a reference sample T1 is used as the object T0. The measuring device 100 irradiates the preparation sample T1 with illumination light L1 at a predetermined position on the reference sample T1, at multiple different height positions. The acquisition unit acquires relationship information showing the relationship between height position and detection intensity based on the detection result of the reflected light L2 by the detector 4 at this time (hereinafter referred to as the "preparation detection result"). The "height position" refers to the relative position in the height direction between a specific point on the object T0 (for example, the surface of the measurement position) and the focusing position (focus FP1) of the illumination optical system. Here, the height direction may refer to the optical axis direction of the objective lens 3, or it may refer to the normal direction of the main surface of the object T0.

[0028] Figure 2 illustrates the "Z-scan" during the preparation phase. "Z-scan" refers to continuously changing the height position, which is the relative height position between the reference sample T1 and the focusing position (focal point FP1) of the illumination optical system. As shown in Figure 2, the height position is changed by moving the objective lens 3 in the Z direction. For example, by moving the objective lens 3 away from the reference sample T1, the focal point FP1 moves upward from the reference sample T1. Conversely, by moving the objective lens 3 closer to the reference sample T1, the focal point FP1 moves downward from the reference sample T1. This allows for the acquisition of detection signals DET1 at multiple height positions.

[0029] Figure 3 schematically shows the relationship between the detection intensity (luminance I) of the reflected light L2 and the height position (Z) acquired during the preparation phase. In Figure 3, the horizontal axis represents the height position, and the direction in which the objective lens 3 moves away from the reference sample T1 (the direction in which the focal point FP1 moves away from the reference sample T1 in an upward direction) corresponds to the positive side of the horizontal axis. In Figure 3, the vertical axis represents the detection intensity (luminance I) of the reflected light L2. This relationship information showing the relationship between height position and detection intensity is also called the "IZ curve".

[0030] If we define the position of the objective lens 3 when the object T0 is at the focal point of the objective lens 3 as the focus Z position, then the "height position" can be said to represent the amount of defocus (μm) from the focus Z position. The greater the amount of defocus (greater than 0), the further the objective lens 3 is from the reference sample T1 (moving the objective lens 3 upwards). Conversely, the smaller the amount of defocus (greater than 0), the closer the objective lens 3 is to the reference sample T1 (moving the objective lens 3 downwards).

[0031] As shown in Figure 3, the relationship between height position and detection intensity is such that the detection intensity peaks when the "height position" is at a specific height. In the IZ curve shown in Figure 3, the detection intensity peaks when the defocus amount (μm) from the focus Z position is 0 (i.e., when the focal point FP1 is on the reference sample T1). It is known that the characteristics of the IZ curve depend on the wavelength of the illumination light L1 and the numerical aperture (NA) of the objective lens 3. The shorter the wavelength of the illumination light L1 and the higher the numerical aperture of the objective lens 3, the steeper the rise and fall of the IZ curve. The wavelength of the illumination light L1 and the numerical aperture of the objective lens 3 are appropriately selected to improve the sectioning performance in the Z direction.

[0032] Furthermore, it is preferable for the acquisition unit to acquire as relational information the portion of the relationship between height position and detection intensity that belongs to either the height side lower than or the height side higher than a specific height position. Specifically, the acquisition unit acquires as relational information the portion of the IZ curve that belongs to either the height side lower than or the height side higher than the height position where the detection intensity peaks.

[0033] In other words, the relationship information acquired in the acquisition unit may show a relationship in which the detection intensity decreases as the height position increases (i.e., as the objective lens 3 moves away from the reference sample T1). Such relationship information is the IZ curve in Figure 3 in the range where the amount of defocus is greater than the focus Z position (defocus amount > 0). Hereinafter, the IZ curve in the range of defocus amount > 0 will be referred to as the "right side of the IZ curve".

[0034] Alternatively, the relationship information acquired in the acquisition unit may show a relationship in which the detection intensity increases as the height position increases (i.e., as the objective lens 3 moves away from the reference sample T1). Such relationship information is the IZ curve in Figure 3 in the range where the amount of defocus is large on the negative side of the focus Z position (defocus amount < 0). Hereinafter, the IZ curve in the range of defocus amount < 0 will be referred to as the "left side of the IZ curve".

[0035] In this way, by using the range in which the IZ curve is monotonically increasing or decreasing as relational information, a one-to-one correspondence is established between the detected intensity and the height position. This allows for the identification of a single height information when the detected intensity (luminance) is acquired during the measurement stage. As an example, as shown in Figure 3, the range of 3 to 4 μm, indicated by the dashed line, within the IZ curve shown by the solid line for an objective lens 3 with a certain numerical aperture, can be used as the range of relational information.

[0036] The acquisition unit creates a correspondence table from the acquired relationship information in which the detected intensity (luminance) and the height information of the measurement position of the test sample T2 correspond one-to-one. The measurement unit uses this correspondence table to determine the height information of the measurement position of the test sample T2. In other words, in Embodiment 1, the height position of the objective lens 3 is converted into the height information of the measurement position based on the detected intensity of the measurement position of the test sample T2.

[0037] As described above, when the detector 4 has multiple pixels, the relationship information between height position and detection intensity differs for each pixel due to aberrations. For example, it is known that the IZ curve for pixels located near the center of the detector 4, among multiple pixels arranged in one direction, is sharper than the IZ curve for pixels located at both ends. Therefore, in this case, it is preferable to acquire multiple relationship information corresponding to each of the multiple pixels.

[0038] <Measurement stage> During the measurement phase, test sample T2 is used as the object T0. The reflectance of test sample T2 to illumination light L1 is approximately the same as that of preparation sample T1 to illumination light L1. For example, test sample T2 and preparation sample T1 may be the same object.

[0039] The measuring device 100 uses the above-described relationship information to irradiate multiple measurement positions on the test sample T2 with illumination light L1, using a predetermined height position Z0 as the reference position (referred to as the height position of the test sample T2) as the relative height position (referred to as the height position of the test sample T2) between the test sample T2 and the focusing position (focus FP1) of the illumination optical system. The measuring unit then determines the height information for each of the multiple measurement positions based on the detection result of the reflected light L2 by the detector 4 (hereinafter referred to as the "test detection result"). Specifically, the measuring unit refers to the above-described correspondence table and determines the corresponding height information from the "luminance" indicated by the detection result for each measurement position. By determining the height information for multiple measurement positions, the measuring device 100 can measure the unevenness of the measurement surface of the test sample T2.

[0040] Figures 4 and 5 schematically illustrate the principle by which the measurement unit refers to the correspondence table described above and measures the surface irregularities of the test sample T2 from the "luminance" indicated by the detection results at each measurement position.

[0041] Figure 4 shows an example of using the "right side of the IZ curve" as relational information (correspondence table). For ease of explanation, the "IZ curve" is rotated 90° clockwise and placed near the test sample T2 so that the position where the brightness of the "IZ curve" peaks (focus Z position) coincides with the reference position Z0.

[0042] Assume that when illumination light L1 is shone on multiple measurement positions of the test sample T2 by scanning in the Y-axis direction, the brightness of pixel p1 at a certain position is I1. Based on the related information, it can be seen that the surface position of the test sample T2 corresponding to pixel p1 is d1 units away from the reference position Z0. Thus, the measurement unit can measure that the surface position of the test sample T2 corresponding to pixel p1 is d1 units away (downward) from the objective lens 3 from the reference position Z0.

[0043] Furthermore, when illumination light L1 is shone on multiple measurement positions of the test sample T2 by scanning in the Y-axis direction, the brightness of a pixel at a certain position p2 is assumed to be I2 (I2 > I1). Based on the related information, it can be seen that the surface position of the test sample T2 corresponding to pixel p2 is d2 away from the reference position Z0. Thus, the measurement unit can measure that the surface position of the test sample T2 corresponding to pixel p2 is d2 away (downward) from the objective lens 3 from the reference position Z0.

[0044] Figure 5 shows an example of using the "left side of the IZ curve" as relational information (correspondence table). For ease of explanation, the "IZ curve" is rotated 90° clockwise and placed near the test sample T2 so that the position where the brightness of the "IZ curve" peaks (focus Z position) coincides with the reference position Z0.

[0045] Assume that when illumination light L1 is shone on multiple measurement positions of the test sample T2 by scanning in the Y-axis direction, the brightness of pixel p1 at a certain position is I1. Based on the related information, it can be seen that the surface position of the test sample T2 corresponding to pixel p1 is d1 units away from the reference position Z0. Thus, the measurement unit can measure that the surface position of the test sample T2 corresponding to pixel p1 is d1 units closer to (above) the objective lens 3 than the reference position Z0.

[0046] Furthermore, if the illumination light L1 is shone on multiple measurement positions of the test sample T2 by scanning in the Y-axis direction, and the brightness of a pixel at a certain position p2 is I2 (I2 > I1), then, based on the related information, the surface position of the test sample T2 corresponding to pixel p2 is d2 away from the reference position Z0. As a result, the measurement unit can measure that the surface position of the test sample T2 corresponding to pixel p2 is d2 closer to the objective lens (above) the reference position Z0.

[0047] As described above, when the detector 4 has a plurality of pixels, it is preferable that a plurality of pieces of relationship information respectively corresponding to the plurality of pixels are acquired. In FIGS. 4 and 5, it may be assumed that the plurality of pixels are arranged in the X-axis direction orthogonal to the Y-axis and the Z-axis (more accurately, regions on the test sample T2 imaged by the plurality of pixels are arranged in the X-axis direction). The relationship information may be acquired for each of the plurality of pixels. Even when measuring the height of the surface of the test sample T2 using different relationship information for each of the plurality of pixels, the height of the surface of the test sample T2 can be measured according to the principle described with reference to FIGS. 4 and 5 based on each pixel and each corresponding relationship information.

[0048] In both FIGS. 4 and 5, when I2>I1, the separation distance from the reference position Z satisfies d2<d1. However, according to FIG. 4, the higher the luminance of a pixel, the larger the surface height of the test sample T2 corresponding to that pixel (the closer it is to the objective lens). On the other hand, according to FIG. 5, the higher the luminance of a pixel, the smaller the surface height of the test sample T2 corresponding to that pixel (the farther it is from the objective lens). In consideration of such a characteristic, that is, how the magnitude of luminance appears as the magnitude of surface height, it is preferable to properly use "the right side of the I-Z curve" and "the left side of the I-Z curve". This proper use will be described later.

[0049] FIG. 6 is a diagram schematically showing how the test sample T2 is two-dimensionally scanned (2D scan) with illumination light L1 on the XY plane. FIG. 7 is a diagram schematically showing how the relative position, on the test sample T2, of the region on the test sample T2 imaged on the detector 4 changes when two-dimensional scanning is performed as shown in FIG. 6. In the examples shown in FIGS. 6 and 7, the test sample T2 is placed on a rotary stage. As described above, in the measurement step, the height position of the test sample T2 is set to a predetermined reference position Z0. Therefore, as shown in FIG. 6, two-dimensional scanning of the test sample T2 with the illumination light L1 is performed by rotating the stage in the circumferential direction without moving the objective lens 3 whose position has been adjusted such that the height position of the test sample T2 matches the predetermined reference position Z0.

[0050] The reflected light L2 from the test sample T2 is detected by a detector 4 having multiple pixels aligned in one direction. By rotating the stage in the circumferential direction, the test sample T2 moves in a direction (Y-axis direction) perpendicular to the direction in which the multiple pixels are aligned (X-axis direction) relative to the area imaged by the detector 4. Based on the above principle, the measurement unit can determine height information for each pixel based on the test detection result of each pixel, using the relationship information corresponding to each pixel. Thus, according to Embodiment 1, it is possible to measure the surface irregularities of the test sample T2 in a short time by simply performing a two-dimensional scan in the XY direction without performing a Z scan for multiple measurement positions.

[0051] Figure 8 shows an image of an example of test sample T2, captured by detector 4. The captured image is a two-dimensional confocal image in the XY direction. In Figure 8, the arrangement direction of the multiple pixels in detector 4 is assumed to be the X direction. Therefore, in the example shown in Figure 8, scanning is performed along the Y direction. In Figure 8, dark areas indicate the brightness of pixels with relatively low brightness, and bright areas indicate the brightness of pixels with relatively high brightness.

[0052] Figure 9 is a graph showing the unevenness of the measurement positions of the test sample T2, indicated by the dashed line in Figure 8. In Figure 9, the horizontal axis represents the length (μm) in the Y direction obtained by converting the pixel positions of the captured image on the dashed line in Figure 8 to the dimensions of the test sample T2, and the vertical axis represents the height (μm). In the measurement method of Embodiment 1, based on the principle described above, the brightness of the detection signal DET1 output from the detector 4 (brightness at the pixels on the dashed line in Figure 6) is converted to height using a correspondence table. This allows the height at each measurement position within the measurement area of ​​the test sample T2 to be determined.

[0053] In the examples in Figures 8 and 9, the "left side of the IZ curve" is used. That is, the objective lens 3 is positioned so that the reference position Z0 is inside the test sample T2. The brightness I1 of pixel p1 shown in Figure 8 is smaller than the brightness I2 of pixel p2. As can also be seen from Figure 5, the surface of test sample T2 at the position corresponding to pixel p1 is further away from the reference position Z0 than the surface of test sample T2 at the position corresponding to pixel p2 (d1>d2), and the height H1 of the surface of test sample T2 at the position corresponding to pixel p1 is higher (closer to the objective lens) than the height H2 of the surface of test sample T2 at the position corresponding to pixel p2. Specifically, the height H1 of the surface of test sample T2 at the position corresponding to pixel p1 is d1 higher than the reference position Z0, and the height H2 of the surface of test sample T2 at the position corresponding to pixel p2 is d2 (d1>d2) higher than the reference position Z0.

[0054] The output unit outputs an image that represents the height information at each measurement position of the test sample T2 in grayscale on an XY plane, for example, where the positions of multiple pixels of the detector 4 are the X coordinates and the positions in multiple scanning directions are the Y coordinates. Figure 10 is an example of an image showing the height information of the measurement area of ​​the test sample T2 in grayscale. By representing the irregularities of the measurement surface of the test sample T2 in grayscale in this way, the surface shape of the test sample T2 becomes easier to understand intuitively, making it possible to easily determine whether or not there is an abnormality.

[0055] Furthermore, the processing device may include a determination unit that determines whether the test detection result exceeds a predetermined threshold. For example, if the test detection result, i.e., the brightness of a certain pixel, exceeds the peak brightness of the IZ curve in Figure 3, the relationship between the detected intensity and the height information will no longer be one-to-one, and it will become impossible to determine the height information of the measurement position.

[0056] Therefore, in order to prevent the test detection results from exceeding the peak position, for example, the detection intensity (luminance) at the minimum defocus amount within the range used as relational information for the IZ curve can be set as a threshold. As an example, "2500", which is the detection intensity at the minimum defocus amount within the range used, can be set as the threshold, as shown in Figure 3.

[0057] If the determination unit determines that the test detection result (i.e., the brightness of any pixel) exceeds a predetermined threshold (positive determination), the measurement unit may stop calculating height information based on the test detection results after the positive determination as a measurement error. Furthermore, if the determination unit makes a positive determination, the position control unit may control the height position so that a height position different from the reference position at the time of the positive determination becomes the reference position.

[0058] As an example, if the relationship information indicates that the detection intensity increases as the height increases (left side of the IZ curve), the position control unit can control the relative height position between the test sample and the focusing position so that the reference position Z0 is set to a height lower than the reference position Z0 when a positive judgment was made (i.e., a position where the test sample T2 and the objective lens 3 are closer together). As another example, if the relationship information indicates that the detection intensity decreases as the height increases (right side of the IZ curve), the position control unit can control the relative height position between the test sample and the focusing position so that the reference position Z0 is set to a height higher than the reference position Z0 when a positive judgment was made (i.e., a position where the test sample T2 and the objective lens 3 are further apart). This prevents the test detection result from exceeding a predetermined threshold during subsequent surface shape measurements of the test sample T2, thereby suppressing the occurrence of measurement errors.

[0059] As mentioned above, it is preferable to use the "right side of the IZ curve" and the "left side of the IZ curve" by considering how the magnitude of brightness is reflected in the magnitude of surface height. Here, noting that it becomes difficult to obtain height information of the measurement position when the test detection result, that is, the brightness of a certain pixel, exceeds the peak brightness of the IZ curve in Figure 3, the relationship information acquired by the acquisition unit may be determined according to the surface shape of the test sample T2 being measured, as follows.

[0060] For example, if the test sample T2 has a measurement surface with a recess formed on a flat surface, using the "left side of the IZ curve" will cause the detection intensity to increase as the depth (amount of depression) of the recess increases, approaching or reaching the peak brightness. Therefore, when measuring the recess of the test sample T2, it is preferable for the measurement unit to determine the height information of the measurement position of the test sample T2 based on relational information (right side of the IZ curve) that shows the relationship that the detection intensity decreases as the height position increases. Furthermore, when using the right side of the IZ curve as relational information, it is preferable that the reference position Z0 is adjusted to be higher than the surface layer of the test sample T2.

[0061] On the other hand, if the right side of the IZ curve is used when the test sample T2 has a measurement surface with a convex portion formed on a flat surface, the detection intensity increases as the height (amount of elevation) of the convex portion increases, approaching or reaching the peak brightness. Therefore, when the measurement unit measures the convex portion of the test sample T2, it is preferable to determine the height information of the measurement position of the test sample T2 based on relational information (left side of the IZ curve) that shows the relationship that the detection intensity increases as the height position increases. Furthermore, when using the left side of the IZ curve as relational information, it is preferable that the reference position Z0 is adjusted to be further inside the test sample T2.

[0062] As described above, the measurement method of Embodiment 1 utilizes the fact that the detection intensity changes when the test sample T2 is out of focus from the state where it is in focus on the objective lens 3, in order to obtain height information of the measurement surface. However, it is known that the detection intensity changes not only due to the shift in focus, but also due to the tilt of the test sample T2. Normally, in a measurement device using a confocal optical system, almost all of the illumination light L1 irradiated onto the test sample T2 is detected by the detector 4 as reflected light L2. However, if the measurement surface of the test sample T2 is tilted, it is expected that a portion of the reflected light L2 will be directed outwards from the objective lens 3, resulting in a lower detection intensity.

[0063] Therefore, the measurement unit can identify one combination of height information and inclination information at a first measurement position from a plurality of combinations identified based on the test detection results, using the height information and inclination information of a second measurement position adjacent to the first measurement position. Note that "adjacent height information and inclination information" may refer to the height information and inclination information of a second measurement position that is geographically close to the first measurement position but is different from the first measurement position. For example, the measurement of the second measurement position is performed immediately before the measurement of the first measurement position when performing a two-dimensional scan. That is, the test detection result of the second measurement position is output immediately before the test detection result of the first measurement position.

[0064] Specifically, the measurement unit can first select a table that stores multiple combinations of height information and tilt information at the first measurement position, based on the test detection result (luminance) at the first measurement position. Figures 11 and 12 show tables that display multiple combinations of the defocus amount (height information) and the inclination of the test sample T2 (tilt information). Figure 11 shows multiple combinations of height information and tilt information at the first measurement position when the luminance at the first measurement position decreases by 1000 from the immediately preceding detection value (luminance at the second measurement position).

[0065] Figure 12 shows multiple combinations of height information and inclination information at the first measurement position when the brightness at the first measurement position decreases by 1500 from the immediately preceding detected value (brightness at the second measurement position). For example, if the difference in detection intensity between the first and second measurement positions is 1000, the measurement unit can select the table shown in Figure 11. Note that the tables shown in Figures 11 and 12 are just examples. The measurement device 100 may have two or more tables showing multiple combinations of height information and inclination information according to the difference in detection intensity between the first and second measurement positions.

[0066] The measurement unit can then identify one combination from among the multiple combinations included in the table in Figure 11, using the height information and inclination information of the second measurement position. The measurement device 100 assumes that the test sample T2, in which the measurement surface changes continuously, is the target of measurement. Therefore, the first measurement position and the second measurement position are smoothly connected. Accordingly, the measurement unit uses the height information and inclination information of the second measurement position to identify one combination from among the multiple combinations included in the table in Figure 11 that allows the second measurement position and the first measurement position to be smoothly connected.

[0067] In this way, the measurement unit can obtain height and inclination information for the first measurement position by connecting it to the adjacent second measurement position. In other words, the measurement unit can select the height and inclination information for the first measurement position that best matches the height and inclination information for the second measurement position. This makes it possible to estimate whether the change in detection intensity at the first measurement position is due to the inclination of the test sample T2 or to defocusing, and to measure the surface shape of the test sample T2 accordingly.

[0068] Figure 13 is a flowchart illustrating the measurement method according to Embodiment 1. In this measurement method, the measurement device 100 having the illumination optical system and the detection optical system described above is used. First, the measurement device 100 performs a Z scan of the reference sample T1 (step S10). Specifically, the measurement device 100 changes the height position, which is the relative height position between the reference sample T1 and the focusing position (focus FP1) at a predetermined position on the reference sample T1. Then, the measurement device 100 acquires relational information based on the detection results of the reflected light L2 by the detector 4 when the illumination light L1 is irradiated onto the reference sample T1 at multiple different height positions (step S11). As a result, the IZ curve shown in Figure 3 is obtained as relational information.

[0069] Next, the conditions of the test sample T2 are determined (step S12). As described above, if the test sample T2 has a concave portion, it is preferable to use the right side of the IZ curve as the relational information. Also, if the test sample T2 has a convex portion, it is preferable to use the left side of the IZ curve as the relational information. Therefore, in order to decide whether to obtain the "right side of the IZ curve" or the "left side of the IZ curve" as the relational information, a condition determination is performed to determine whether the surface of the test sample T2 has more concave or convex portions. Note that this step is optional and can be omitted. Then, it is decided whether to use the right side or the left side of the IZ curve as the relational information (step S13). Steps S10 to S13 show the processing of the measuring device 100 in the preparation stage.

[0070] Subsequently, the measuring device 100 proceeds to the testing phase. First, the measuring device 100 sets the height position of the test sample T2 as a predetermined height position, which is the reference position Z0, and irradiates the measurement positions of the test sample T2 with illumination light L1 (step S14). The measuring device 100 can irradiate multiple measurement positions of the test sample T2 with illumination light L1 by scanning the test sample T2 in two dimensions using illumination light L1. This allows the device to obtain test detection results when illumination light L1 is irradiated onto multiple measurement positions of the test sample T2.

[0071] Next, as an optional step, the measuring device 100 determines whether the test detection result exceeds a predetermined threshold (step S15). If it is clear that the test detection result does not exceed the predetermined threshold, step S15 may be omitted. If it is determined that the test detection result exceeds the threshold (affirmative determination) (step S15, YES), the measuring device 100 controls the height position so that a height position different from the reference position at the time of the affirmative determination becomes the reference position (step S16), and returns to step S15. On the other hand, if it is determined that the test detection result does not exceed the threshold (step S15, NO), the measuring device 100 can use the relationship information determined in step 13 to calculate surface height information at multiple measurement positions based on the test detection results when multiple measurement position illumination lights L1 are irradiated (step S17). Then, if necessary, the measuring device 100 can output information representing the height at each measurement position of the test sample T2 in grayscale (step S18).

[0072] Embodiment 2 A measuring device according to Embodiment 2 will now be described. The position control unit described in Embodiment 1 is not limited to the above example, as long as it can change the relative position in the height direction between the object T0 and the focusing position of the illumination optical system. In the measuring device according to Embodiment 2, the illumination optical system includes a tunable optical element, and the position control unit changes the relative position in the height direction between the object T0 and the focusing position (focus FP1) of the illumination optical system by driving the tunable optical element included in the illumination optical system.

[0073] The variable-focus optical element may consist of multiple mirrors, multiple lenses, or a single lens whose focal length is variable by changing its shape. The variable-focus optical element may also include an objective lens 3. The position control unit changes the focusing position (focus FP1) of the illumination optical system by changing the position of at least one of the multiple lenses or mirrors, or by changing the shape of the variable-focus lens.

[0074] Figure 14 is a schematic diagram showing the change in focal point FP1 in the measuring device according to Embodiment 2. The measuring device according to Embodiment 2 maintains a constant relative height position between the object T0 and the objective lens 3, and changes the position of the focal point FP1 of the objective lens 3. Based on the detection results of the reflected light detector when illumination light is irradiated onto the prepared sample T1 at multiple different height positions, the device acquires relationship information showing the relationship between height position and detection intensity.

[0075] Here, in Figure 14, the direction in which the focal point FP1 approaches the objective lens 3 corresponds to the positive side of the horizontal axis in the graph of Figure 3. That is, in the measuring device according to Embodiment 2, an increase in the "height position" (an increase in the relative height position between the object T0 and the focusing position (focal point FP1) of the illumination optical system) corresponds to bringing the focal point FP1 closer to the objective lens 3. Conversely, in the measuring device according to Embodiment 2, a decrease in the "height position" (a decrease in the relative height position between the object T0 and the focusing position (focal point FP1) of the illumination optical system) corresponds to moving the focal point FP1 further away from the objective lens 3.

[0076] The other components are the same as those of the measuring device according to Embodiment 1 and are included in the above description.

[0077] Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above. Various modifications to the structure and details of the present disclosure can be made as understandable to those skilled in the art within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0078] Each drawing is merely illustrative to illustrate one or more embodiments. Each drawing may be associated with one or more other embodiments rather than with only one specific embodiment. As those skilled in the art will understand, various features or steps described with reference to any one drawing can be combined with features or steps shown in one or more other drawings, for example, to create embodiments not explicitly shown or described. Not all features or steps shown in any one drawing to illustrate an exemplary embodiment are necessarily required, and some features or steps may be omitted. The order of steps shown in any of the drawings may be changed as appropriate. [Explanation of symbols]

[0079] 100 measuring devices 1 light source 2 Beam Splitter 3. Objective lens 4 detectors 5 lenses T0 Object T1 Reference Sample T2 Test Sample L1 illumination light L2 Reflected light DET1 detection signal FP1 focus FP2 focus

Claims

1. An illumination optical system that irradiates an object with illumination light, A detection optical system that causes a detector to detect reflected light from the object based on the illumination light, A position control unit controls the height position, which is the relative height position between the object and the light-gathering position of the illumination optical system. An acquisition unit acquires relational information showing the relationship between the height position and the detection intensity based on the detection results of the reflected light by the detector when the illumination light is irradiated onto the prepared sample, which is the object, at a predetermined position on the prepared sample, at a plurality of different height positions. A measuring unit that uses the aforementioned related information to determine surface height information at multiple measurement positions based on the test detection results, which are the detection results of the reflected light by the detector when the illumination light is irradiated onto multiple measurement positions of the test sample, with the height position of the test sample being the object being measured as a predetermined reference position, A measuring device equipped with the following features.

2. The relationship between the height position and the detection intensity is such that the detection intensity peaks when the height position of the prepared sample is at a specific height position. The acquisition unit acquires the portion of the relationship between the height position and the detection intensity that belongs to either the height side lower than or the height side higher than the specific height position as the relational information. The measuring device according to claim 1.

3. The relationship information indicates that the detection intensity increases as the height position increases, or that the detection intensity decreases as the height position increases. The measuring device according to claim 2.

4. The acquisition unit is, When measuring the recess of the test sample, relational information is obtained showing that the detection intensity decreases as the height position increases. When measuring the protrusions of the test sample, relational information is obtained that shows that the detection intensity increases as the height position increases. The measuring device according to claim 3.

5. The detector has a plurality of pixels, The acquisition unit acquires multiple relational pieces of information corresponding to each of the multiple pixels, The measurement unit obtains the surface height information using the relationship information corresponding to each pixel. The measuring device according to claim 1.

6. The detector has a plurality of pixels aligned in one direction, The system further includes a scanning control unit that moves the region on the test sample imaged by the detector relative to the test sample, such that the detector moves in a scanning direction perpendicular to the one direction relative to the test sample. The measuring device according to claim 5.

7. The measurement unit acquires the surface height information for each measurement position corresponding to the position of a plurality of pixels. The system further includes an output unit that outputs an image representing the surface height information of each measurement position in grayscale on a coordinate plane where the positions on the test sample corresponding to the positions of the plurality of pixels arranged in one direction are the first coordinates, and the positions on the test sample in the scanning direction are the second coordinates. The measuring device according to claim 6.

8. The system further includes a determination unit that determines whether the test detection result exceeds a predetermined threshold. The measuring device according to claim 1.

9. If the determination unit makes a positive determination, The measurement unit stops calculating height information based on the test detection results after the positive determination. The measuring device according to claim 8.

10. If the determination unit makes a positive determination, The position control unit controls the height position so that the reference position is a height position different from the reference position when a positive determination is made. The measuring device according to claim 8.

11. The position control unit, If the relationship information indicates that the detection intensity increases as the height position increases, the relative height position between the test sample and the focusing position is controlled so that the reference position is set to a height lower than the reference position at which a positive determination was made. Or, If the relationship information indicates that the detection intensity decreases as the height position increases, the relative height position between the test sample and the focusing position is controlled so that the reference position is set to a height higher than the reference position at which a positive determination was made. The measuring device according to claim 10.

12. The measuring unit identifies one combination of height information and inclination information at a first measurement position from a plurality of combinations identified based on the test detection results, using the height information and inclination information of a second measurement position adjacent to the first measurement position. The measuring device according to claim 1.

13. The reflectance of the illumination light of the test sample is substantially the same as the reflectance of the illumination light of the prepared sample. The measuring device according to claim 1.

14. The aforementioned test sample and the aforementioned preparation sample are the same. The measuring device according to claim 13.

15. A measuring device is used that has an illumination optical system for irradiating an object with illumination light, and a detection optical system for causing a detector to detect the reflected light from the object based on the illumination light. The height position, which is the relative position in the height direction between the object and the light-gathering position of the illumination optical system, is controlled. When the prepared sample, which is the object, is irradiated with illumination light at a predetermined position, at a plurality of different height positions, relationship information showing the relationship between the height position and the detection intensity is obtained based on the detection result of the reflected light by the detector. Using the aforementioned related information, surface height information at multiple measurement positions is determined based on the test detection results, which are the detection results of the reflected light by the detector when the illumination light is irradiated onto multiple measurement positions of the test sample, with the height position of the test sample being a predetermined reference position. Measurement method.

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