Sliding type white light interferometer

Abstract

A sliding white light interferometer is disclosed that acquires the shape of a sample at an improved speed by continuously capturing interference fringes through a scanning assembly tilted at a predetermined angle to the sample. The sliding white light interferometer comprises a light source, a stage, a mirror, a beam splitter, a stage moving assembly, a CCD image sensor, and an image analysis processor. The beam splitter modulates the path of the white light supplied to the sample so that it is at a predetermined angle to the sample. The stage moving assembly moves the stage in the x-axis direction in which the sample is scanned, while maintaining the predetermined angle of the white light path to the sample. The CCD image sensor generates multiple interference fringe images by continuously capturing interference fringes generated by the measurement light reflected from the surface of the sample and the reflected light reflected by the mirror while the stage is moved in the x-axis direction.

Description

Technical Field

[0001] The present invention relates to a sliding white light interferometer. More specifically, it relates to a sliding white light interferometer that acquires the shape of a sample by continuously capturing interference fringes through a scanning assembly inclined at a predetermined angle with respect to the sample.

Background Art

[0002] Recently, in the fields of nanoscience, semiconductors, nanophysics, nanochemistry, nanomaterials, nanooptics, surface science, medical imaging, biology, biophysics, medical physics, or medical optics, there has been an increasing demand to measure the three-dimensional shape information of samples having three-dimensional nanostructures or micrometer structures.

[0003] To measure such three-dimensional shape information of a sample, a white light interferometer (WHITE_LIGHT_INTERFEROMETRY) that utilizes the interference phenomenon of white light has been used.

[0004] A general white light interferometer uses a beam splitter that separates a white light source to generate paths respectively directed toward a sample and a mirror. After the white light irradiated on the sample and the mirror by the beam splitter is reflected, it is combined and transmitted to a CCD image sensor (CCD_image_sensor). The CCD image sensor captures an interference fringe image formed by the reflected light reflected from the sample and the mirror and combined. The image analysis processor generates the three-dimensional shape information of the sample by analyzing the interference fringe image captured by the CCD image sensor.

[0005] At this time, the sample is placed on the stage. The stage is moved along the path axis of the light source (generally the Z-axis) by a separate drive assembly, thereby generating a path difference between the sample side and the mirror side. The interference fringe images captured by the CCD image sensor form different interference fringe images due to the change in the path difference between the sample side and the mirror side. The image analysis processor generates three-dimensional shape information of the sample based on the interference fringes, which are the accumulation of these different interference fringe images.

[0006] On the other hand, conventional white light interferometers, as mentioned above, used a method called vertical scanning interferometry, which acquires interference fringes by changing the z-axis distance between the stage on which the sample is placed and the optical system, such as a beam splitter and a CCD image sensor. In vertical scanning interferometry, interference fringes of one frame are acquired by changing the z-axis distance between the stage and the optical system at a specific position on the sample. After the sample or optical system moves a certain distance along the x-axis, and then the interference fringes of another adjacent frame are acquired by changing the z-axis distance between the stage and the optical system, the sample is scanned by accumulating or stitching together the multiple interference fringes that have already been acquired.

[0007] However, in the aforementioned vertical scanning interferometry, interference fringes are acquired by changing the z-axis distance between the stage and the optical system at each specific position. Furthermore, after the sample or optical system moves along the x-axis, the interference fringes must be acquired by changing the z-axis distance between the stage and the optical system. Therefore, it has the problem that it takes a long time to scan the shape of the sample. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Korean Published Patent Publication No. 10-2014-0032665 [Overview of the project] [Problems that the invention aims to solve]

[0009] The objective of the present invention, in order to solve the above-mentioned problems, is to provide a sliding-type white light interferometer that acquires the shape of a sample at an even faster speed by continuously capturing interference fringes through a scanning assembly tilted at a predetermined angle relative to the sample. [Means for solving the problem]

[0010] To achieve the above-mentioned objectives, a sliding type white light interferometer according to one embodiment of the present invention comprises: a light source that provides white light; a stage on which a sample is placed; a mirror having a reflective surface; a beam splitter that divides the path of white light provided by the light source into the sample side and the mirror side; a stage moving assembly that moves the stage; a CCD image sensor (Charge_Coupled_Device_image_sensor) that receives measurement light reflected from the sample and reflected light reflected from the mirror from the beam splitter while the stage moving assembly moves the stage, and generates a plurality of interference fringe images by capturing the interference fringes generated by the measurement light and the reflected light; and an image analysis processor that generates white light interference fringes (WLI_Fringe) by accumulating the plurality of interference fringe images. The beam splitter modifies the path of the white light provided to the sample side so that it has a predetermined angle with respect to the sample side, so that the white light is irradiated onto the sample at a predetermined angle. The stage moving assembly moves the stage in the x-axis direction in which the sample is scanned, while the path of the white light maintains the predetermined angle with respect to the sample. The CCD image sensor generates multiple interference fringe images by continuously capturing interference fringes generated by the measurement light reflected from the surface of the sample and the reflected light reflected by the mirror while the stage is moved in the x-axis direction.

[0011] The stage moving assembly moves the stage in the x-axis direction, and also moves the stage in the z-axis direction toward the beam splitter, thereby changing the interference fringes during continuous imaging of the interference fringes.

[0012] When the image analysis processor accumulates a plurality of interference fringe images, it generates an accumulated white light interference fringe by aligning the plurality of interference fringe images at the same x position of each interference fringe image.

[0013] The stage moving assembly moves the stage in the x-axis direction, and when the stage moves in the z-axis direction and the -z-axis direction, it changes the interference fringes during continuous imaging of the interference fringes.

[0014] The stage moving assembly is characterized in that, when moving the stage in the z-axis direction, the stage is moved by a predetermined length, and the predetermined length is 60 to 80 nm.

[0015] A sliding white light interferometer further comprises multiple CCD image sensors that capture different frames of the sample. Each of the multiple CCD image sensors generates an interference fringe image based on the measurement light reflected from different specific surfaces of the sample.

[0016] To achieve the above-mentioned objectives, a sliding white light interferometer according to one embodiment of the present invention is a sliding white light interferometer (WLI) that acquires the shape of a sample by continuously photographing interference fringes generated by measurement light reflected from a sample and reflected light reflected from a mirror through a scanning assembly tilted at a predetermined angle with respect to the sample. The scanning assembly comprises a light source that provides white light, a mirror having a reflective surface, a beam splitter that divides the path of the white light provided by the light source into the sample side and the mirror side, and a CCD image sensor (Charge_Coupled_Device_image_sensor) that receives measurement light reflected from the sample and reflected light reflected from the mirror from the beam splitter and photographs the interference fringes generated by the measurement light and the reflected light. The white light interferometer further comprises an optical moving assembly for moving the scanning assembly, and an image analysis processor that generates a white light interference fringe (WLI_Fringe) by accumulating a plurality of interference fringes captured by the CCD image sensor while the optical moving assembly moves the scanning assembly. The beam splitter modulates the path of the white light supplied to the sample so that the path has a predetermined angle with respect to the sample, so that the white light is irradiated onto the sample at a predetermined angle. The optical moving assembly moves the scanning assembly in the x-axis direction in which the sample is scanned, while the path of the white light maintains the predetermined angle with respect to the sample. The CCD image sensor generates a plurality of interference fringe images by continuously capturing interference fringes generated by the measurement light reflected from the surface of the sample and the reflected light reflected by the mirror while the scanning assembly is moving in the x-axis direction.

[0017] The optical moving assembly moves the scanning assembly in the x-axis direction, and when the scanning assembly moves in the x-axis direction, it moves the scanning assembly in the z-axis direction toward the sample, thereby changing the interference fringes during continuous imaging of the interference fringes.

[0018] When the image analysis processor accumulates a plurality of interference fringe images, it generates an accumulated white light interference fringe by aligning the plurality of interference fringe images at the same x position of each interference fringe image.

[0019] The optical moving assembly changes the interference fringes during continuous imaging of the interference fringes by moving the scanning assembly back and forth in the z-axis direction and the -z-axis direction when the scanning assembly is moved in the x-axis direction.

[0020] The optical moving assembly moves the scanning assembly by a predetermined length when the scanning assembly is moved in the z-axis direction, and the predetermined length is 60 to 80 nm.

[0021] A sliding white light interferometer further comprises multiple CCD image sensors that capture different frames of the sample surface. Each of the multiple CCD image sensors generates an interference fringe image based on the measurement light reflected from different specific surfaces of the sample.

[0022] To achieve the above-mentioned objectives, a sliding white light interferometer according to one embodiment of the present invention is a sliding white light interferometer (WLI) that acquires the shape of a sample by continuously photographing interference fringes generated by measurement light reflected from a sample and reflected light reflected from a mirror through a scanning assembly tilted at a predetermined angle with respect to the sample. The scanning assembly comprises a light source that provides white light, a stage on which the sample is placed, a mirror having a reflective surface, a beam splitter that divides the path of the white light provided by the light source into the sample side and the mirror side, and a CCD image sensor (Charge_Coupled_Device_image_sensor) that receives measurement light reflected from the sample and reflected light reflected from the mirror from the beam splitter and photographs the interference fringes generated by the measurement light and the reflected light. The white light interferometer further includes a stage moving assembly that moves the stage in the x-axis direction from which the sample is scanned, an optical moving assembly that moves the scanning assembly in the z-axis direction toward the sample, and an image analysis processor that generates a white light interference fringe (WLI_Fringe) by accumulating a plurality of interference fringes captured by the CCD image sensor while the stage moving assembly moves the stage in the x-axis direction and the optical moving assembly moves the scanning assembly in the z-axis direction. The beam splitter modifies the path of the white light supplied to the sample so that the path has a predetermined angle with respect to the sample, so that the white light is irradiated onto the sample at a predetermined angle. The stage moving assembly moves the stage in the x-axis direction while the path of the white light maintains the predetermined angle with respect to the sample. The CCD image sensor generates a plurality of interference fringe images by continuously capturing interference fringes generated by the measurement light reflected from the surface of the sample and the reflected light reflected by the mirror while the stage is moved in the x-axis direction.

[0023] When the stage moving assembly moves the stage in the x-axis direction, the optical moving assembly moves the scanning assembly in the z-axis direction, thereby changing the interference fringes during continuous shooting of the interference fringes.

[0024] When the image analysis processor accumulates a plurality of the interference fringe images, the plurality of the interference fringe images are aligned at the same x position of each of the interference fringe images to generate a cumulative white light interference fringe.

[0025] When the stage moving assembly moves the stage in the x-axis direction, the optical moving assembly reciprocally moves the scanning assembly in the z-axis direction and the "-z" axis direction, thereby changing the interference fringes during continuous shooting of the interference fringes.

[0026] When the optical moving assembly moves the scanning assembly in the z-axis direction, the scanning assembly is moved by a predetermined length, and the predetermined length is 60 to 80 nm.

[0027] The sliding type white light interferometer includes a plurality of the CCD image sensors that photograph different frames of the sample surface. The plurality of the CCD image sensors each generate an interference fringe image based on the measurement light reflected from different specific surfaces of the sample.

Effect of the Invention

[0028] According to the sliding type white light interferometer of the present invention, by continuously photographing interference fringes through a scanning assembly inclined at a predetermined angle with respect to the sample, it is possible to obtain the shape of the sample at a further improved speed.

Brief Description of the Drawings

[0029] [Figure 1] It is a diagram showing an embodiment of a sliding type white light interferometer according to the present invention. [Figure 2]This figure shows another embodiment of the sliding type white light interferometer according to the present invention. [Figure 3] This figure shows a comparison between a conventional vertical scanning interferometry method and the sliding white light interferometry method according to the present invention. [Figure 4] This figure shows the actual scanning of a sample surface using both conventional vertical scanning interferometry and the sliding white light interferometry method according to the present invention. [Figure 5] This figure shows the scanning of the surface of a sample using the sliding type white light interferometry method according to the present invention, without the scanning assembly or the Z-axis movement of the sample. [Figure 6] This figure shows the scanning of the surface of a sample while moving the scanning assembly or the sample along the Z-axis using the sliding type white light interferometry method according to the present invention. [Figure 7] This figure shows the scanning of the surface of a sample along with further fine Z-axis movement of the scanning assembly or the sample itself, using the sliding type white light interferometry method according to the present invention. [Figure 8] This diagram provides a simplified comparison between conventional white light interferometer (WLI) measurements and conventional phase transition interferometer (PSI) measurements. [Figure 9] This figure shows a simplified diagram illustrating how the image analysis processor according to the present invention generates cumulative white light interference fringes. [Figure 10] This figure shows how the image analysis processor according to the present invention generates cumulative white light interference fringes by accumulating interference fringe images obtained by actually scanning the surface of a sample. [Modes for carrying out the invention]

[0030] Some embodiments of the present invention will be described in detail below with reference to illustrative drawings. It should be noted that when assigning reference numerals to the components in each figure, the same component will, to the greatest extent possible, have the same reference numeral when shown in other drawings.

[0031] Furthermore, in describing embodiments of the present invention, if it is determined that a specific description of a related known configuration or function would hinder the understanding of the embodiments of the present invention, such detailed description will be omitted.

[0032] Furthermore, when describing the components of the embodiments of the present invention, it is possible to use terms such as first, second, A, B, (a), (b), etc. Such terms are used solely to distinguish a component from other components, and the terms do not limit the essence, order, or sequence of the component in question.

[0033] In this specification, the singular form also includes the plural form unless otherwise specified. The terms “includes” and / or “encompass” as used in this specification do not preclude the presence or addition of one or more other components besides those mentioned.

[0034] The present invention will be described in more detail below with reference to the attached drawings. Figure 1 shows an embodiment of the sliding type white light interferometer 100 according to the present invention.

[0035] The "sliding type white light interferometer 100" according to the present invention (hereinafter referred to as "white light interferometer 100"), as shown in Figure 1, comprises a light source 10, a beam splitter 20, a mirror 30, a stage 40, a stage movement assembly 50, a CCD image sensor 60, and an image analysis processor 70. Centered around the beam splitter 20, the light source 10 side, the sample 41 side, the mirror 30 side, and the CCD image sensor 60 side may further include separate lenses (not shown) for focusing and path control of white light, measurement light, and reflected light, respectively.

[0036] The white light interferometer 100 according to the present invention measures the shape information of the sample 41, and more specifically the surface height of the sample 41, by continuously capturing interference fringes generated by the measurement light reflected from the sample 41 and the reflected light reflected from the mirror 30 through a scanning assembly 80 tilted at a predetermined angle relative to the sample 41. The scanning assembly 80 comprises a light source 10, a beam splitter 20, a mirror 30, and a CCD image sensor 60.

[0037] The light source 10 generates white light. The light source 10 may be a halogen lamp or a white LED that generates white light. The light source 10 provides white light to the beam splitter 20, which splits the white light provided by the light source 10 and provides it to the sample 41 and the mirror 30.

[0038] A sample 41 is placed on the upper surface of the stage 40. The sample 41 is the object to be measured for which surface information is to be measured. The sample 41 may be a nanostructure such as a semiconductor device. The stage moving assembly 50 moves the stage 40. The stage moving assembly 50 moves the stage 40 in the X-axis direction in which the sample 41 is scanned, while maintaining a predetermined angle between the path of white light supplied from the beam splitter 20 to the sample 41 and the sample 41.

[0039] Mirror 30 has a reflective surface on one side that faces the beam splitter 20. The beam splitter 20 divides the path of white light provided by the light source 10 into two paths: one for the sample 41 and the other for the mirror 30. The beam splitter 20 provides a portion of the white light provided by the light source 10 to the stage 40.

[0040] The beam splitter 20 provides the remaining white light from the light source 10 to the mirror 30. The white light that has been provided to the mirror 30 is reflected and transmitted back to the beam splitter 20. The beam splitter 20 changes the path of the reflected light so that the reflected light reflected by the mirror 30 is transmitted to the CCD image sensor 60.

[0041] The beam splitter 20 splits the white light into two streams: one for the sample 41 and the other for the reflective surface of the mirror 30. The measurement light reflected by the sample 41 and the reflected light reflected by the mirror 30 are transmitted to the CCD image sensor 60 by the beam splitter 20. The CCD image sensor 60 receives interference fringes generated by the change in the path difference between the measurement light reflected by the sample 41 and the reflected light reflected by the mirror 30.

[0042] The beam splitter 20 modifies the path of white light so that a portion of the white light supplied from the light source 10 is transmitted to both the stage 40 and the sample 41. The beam splitter 20 modifies the path of white light so that the path of white light supplied to the sample 41 has a predetermined angle with respect to the sample 41. The white light is irradiated onto the sample 41 at a predetermined angle. Therefore, the optical axis irradiating the sample 41 is tilted by a predetermined angle.

[0043] The beam splitter 20 can be tilted to maintain a predetermined angle with respect to the surface of the sample 41. The white light transmitted to the sample 41 is also reflected back to the beam splitter 20 as measurement light and transmitted through the beam splitter 20 to the CCD image sensor 60.

[0044] The CCD image sensor 60 (Charge_Coupled_Device_image_sensor) receives the measurement light reflected from the sample 41 and the reflected light reflected from the mirror 30 from the beam splitter 20. The CCD image sensor 60 receives the measurement light and reflected light from the beam splitter 20 while the stage moving assembly 50 moves the stage 40. The CCD image sensor 60 captures the interference fringes generated by the measurement light and reflected light. The CCD image sensor 60 generates multiple interference fringe images by continuously capturing the interference fringes while the stage moving assembly 50 moves the stage 40 in the X-axis direction.

[0045] The CCD image sensor 60 continuously captures interference fringes of pixels generated by measurement light and reflected light while the stage 40 is moving by the stage moving assembly 50. The CCD image sensor 60 generates multiple interference fringe images by continuously capturing interference fringes. Here, a pixel refers to a unit pixel contained in the XY plane of the interference fringe image.

[0046] The CCD image sensor 60 transmits multiple interference fringe images, captured in succession, to the image analysis processor 70. The image analysis processor 70 generates white light interference fringes (WLI_Fringe) by accumulating multiple interference fringe images received from the CCD image sensor 60. The image analysis processor 70 analyzes the generated white light interference fringes (WLI_Fringe) to measure the surface shape of the sample 41, and more precisely, the height of the sample 41. The white light interferometer 100 has the advantage of being able to measure the surface shape quickly without damaging the sample 41 because it measures the surface shape using light reflected from the sample 41.

[0047] In summary, in the white light interferometer 100 according to one embodiment of the present invention, the white light irradiated onto the sample 41 by an optical system tilted to have a predetermined angle with respect to the sample 41 is given a predetermined angle by the beam splitter 20. After the white light is irradiated onto the sample 41, the measurement light reflected after irradiation and the reflected light reflected from the reflective surface of the mirror 30 are transmitted to the CCD image sensor 60 by the beam splitter 20. The CCD image sensor 60 captures the interference fringes generated by the measurement light and the reflected light. When the white light is irradiated onto the sample 41, the stage 40 is moved by the stage moving assembly 50 in the X-axis direction in which the sample 41 is scanned or scanned. The CCD image sensor 60 generates multiple interference fringe images by continuously capturing the interference fringes generated by the surface of the sample 41 moving by the stage moving assembly 50.

[0048] Here, the stage movement assembly 50 can move the stage 40 in the X-axis direction and also move the stage 40 in the Z-axis direction so that it is either closer to or further away from the beam splitter 20. The stage movement assembly 50 moves the stage 40 in the Z-axis direction while maintaining a predetermined angle with respect to the path axis of the white light supplied from the beam splitter 20 to the stage 40. The stage movement assembly 50 can move the stage 40 in the Z-axis direction based on a fine z_step_size (for example, λ / 8, which is 68.75 nm). As the stage 40 moves in the Z-axis direction by the stage movement assembly 50, a minute path difference is generated between the measurement light and the reflected light transmitted to the CCD image sensor 60. This minute path difference causes changes in the interference fringes when continuous imaging of the interference fringes occurs.

[0049] Figure 2 shows another embodiment of the sliding-type white light interferometer 100 according to the present invention. Another embodiment of the sliding type white light interferometer 100 according to the present invention, referring to Figure 2, may further include an optical moving assembly 81 that moves the scanning assembly 80.

[0050] The optical moving assembly 81 can move the scanning assembly 80 in the X-axis direction in which the sample 41 is scanned or scanned, while white light is irradiated onto the sample 41 at a predetermined angle. The optical moving assembly 81 moves the scanning assembly 80 in the X-axis direction while maintaining the predetermined angle of the white light irradiated onto the sample 41. When the optical moving assembly 81 moves in the X-axis direction, the CCD image sensor 60 receives the measurement light reflected from the sample 41 and the reflected light reflected from the mirror 30 from the beam splitter 20, and generates multiple interference fringe images by continuously capturing the interference fringes generated by the received measurement light and reflected light.

[0051] Here, the optical moving assembly 81 can move the scanning assembly 80 in the X-axis direction and simultaneously move the scanning assembly 80 in the Z-axis direction toward the sample 41.

[0052] The optical moving assembly 81 moves the scanning assembly 80 in the Z-axis direction while maintaining a predetermined angle of the white light supplied from the beam splitter 20 to the stage 40. The optical moving assembly 81 can move the scanning assembly 80 in the Z-axis direction based on a fine z_step_size (for example, λ / 8, which is 68.75 nm). As the scanning assembly 80 moves in the Z-axis direction by the optical moving assembly 81, a minute path difference is generated between the measurement light and the reflected light transmitted to the CCD image sensor 60, and this minute path difference causes a change in the interference fringes when continuous imaging of interference fringes occurs.

[0053] In yet another embodiment of the sliding-type white light interferometer 100 according to the present invention, during continuous measurement of interference fringes by measurement light and reflected light, the stage 40 on which the sample 41 is placed is moved in the X-axis direction by the stage moving assembly 50, and along with the movement of the stage 40 in the X-axis direction, the optical moving assembly 81 can also move the scanning assembly 80 in the Z-axis direction. As described above, when the stage 40 is moved by the stage moving assembly 50 and the scanning assembly 80 is moved by the optical moving assembly 81, the predetermined angle between the white light and the sample 41 is maintained the same.

[0054] The scanning assembly 80 can be tilted at a predetermined angle relative to the sample by the optical moving assembly 81. Alternatively, the stage 40 can be tilted at a predetermined angle by the stage moving assembly 50. The optical moving assembly 81 provides z-axis movement of the scanning assembly 80. The stage moving assembly 50 provides x-axis movement of the stage 40. When the stage moving assembly 50 moves the stage 40 in the x-axis direction, the optical moving assembly 81 can also tilt only the lens positioned between the beam splitter 20 and the sample 41 at a predetermined angle.

[0055] The scanning assembly 80 may be tilted at a predetermined angle relative to the sample 41, or the stage 40 may be tilted at a predetermined angle relative to the scanning assembly 80. In this case, the direction in which the scanning assembly 80 or the stage 40 tilts may be in the x-axis direction, as shown in Figures 1 and 2, but is not limited to this; it may also tilt in the y-axis direction, or it may tilt on the xy-plane.

[0056] Figure 3 shows a conventional vertical scanning interferometry method and a sliding white light interferometry method according to the present invention. Specifically, Figure 3(a) shows a conventional vertical scanning interferometry method. Figure 3(b) shows the sliding white light interferometry method according to the present invention, in which the scanning assembly 80 is slid in the X-axis direction while tilted relative to the sample 41. Figure 3(c) shows the sliding white light interferometry method according to the present invention, in which the sample 41 is slid in the X-axis direction while the scanning assembly 80 is tilted relative to the sample 41.

[0057] Referring to Figure 3(a), in the conventional vertical scanning interferometry, the scanning assembly 80 is positioned in the first region and then moved along the Z-axis to capture interference fringes in the first region. The first region is then scanned by accumulating the interference fringes in the first region to generate an interference fringe image. After the scanning assembly 80 has completed scanning the first region, it moves along the X-axis to the second region and then along the Z-axis to scan the second region in the same manner as described above. In the conventional vertical scanning interferometry, the surface of the sample 41 is scanned by scanning multiple regions (for example, the first to fifth regions shown in Figure 3(a)) and then stitching together the images generated by each scan. Therefore, the conventional vertical scanning interferometry has the problem of requiring a long scanning time.

[0058] To quickly measure a wide area of ​​sample 41, rather than accumulating images taken at various positions and then stitching them together, as shown in Figures 3(b) and 3(c), the scanning assembly 80 is tilted at a predetermined angle between it and the sample 41, and the scanning assembly 80 slides across the area on the sample 41, or the interference fringes are continuously captured while the sample 41 slides. By accumulating or stitching the interference fringe images generated by this capture, the scanning time for the shape of the sample 41 can be shortened.

[0059] In summary, conventional white light interferometer (WLI) measurements use a review method, where the WLI_Lens60 white light interferometer must move to the measurement position, and then the sample 41 must be measured using Z_Scan. In other words, to measure the entire area of ​​the sample 41, after the WLI measurement at the measurement position, the XY_Stage40 must move to another measurement position for WLI measurement, and then the WLI measurement images from each WLI measurement must be stitched together using the Image_Stitching method. Therefore, it had the disadvantage of taking a long time to measure.

[0060] This invention aims to solve these shortcomings by having the white light interferometer WLI_Lens60 tilted while the XY_Stage40 moves in the scanning direction of the sample. Continuous measurement of the white light interferometer WLI is possible as the XY_Stage40 moves. Therefore, the measurement time of the white light interferometer WLI is shortened.

[0061] Figure 4 shows the results of actually scanning the surface of sample 41 using both the conventional vertical scanning interferometry method and the sliding white light interferometry method according to the present invention. In detail, Figure 4(a) shows the process of scanning the surface of sample 41 using conventional vertical scanning interferometry. Figure 4(b) shows the process of scanning the surface of sample 41 using the sliding white light interferometry method according to the present invention. During scanning in Figure 4, the white light interferometer WLI_Vision was captured while moving the scanning assembly 80 and stage 40 at 200 μm / s, respectively, during both Normal_White Light Interferometer WLI measurement and Sliding_White Light Interferometer WLI measurement (FOV_4500×3754 μm with ×2.5_White Light Interferometer WLI_Lens, overall image tilt_7 μm).

[0062] Comparing the frames in Figure 4(a) and Figure 4(b), it can be seen that scanning of the sample 41 using the sliding white light interferometry method of the present invention is even faster than scanning the sample 41 using the conventional vertical scanning interferometry method.

[0063] Figure 5 shows the scanning of the surface of sample 41 using the sliding white light interferometry method according to the present invention, without any Z-axis movement of the scanning assembly 80 or sample 41. Figure 6 shows the scanning of the surface of sample 41 using the sliding white light interferometry method according to the present invention, along with Z-axis movement of the scanning assembly 80 or sample 41. Figures 5(a) to (c) and Figures 6(a) to (c) are arranged in chronological order. Figure 7 shows the scanning of the surface of sample 41 using the sliding white light interferometry method according to the present invention, along with even finer Z-axis movement of the scanning assembly 80 or sample 41.

[0064] As shown in Figure 5, interference fringe images were generated by sliding the scanning assembly 80 or sample 41 in the X-axis direction while the scanning assembly 80 or sample 41 was tilted at a predetermined angle in the Y-axis direction. Referring to Figure 5, it can be seen that when interference fringe images are generated by sliding the scanning assembly 80 or sample 41 in the X-axis direction while the scanning assembly 80 or sample 41 is tilted at a predetermined angle in the Y-axis direction, the positions of the interference fringes in each frame were maintained to be similar. When the positions of the interference fringes are maintained to be similar, it is difficult to accurately measure the height of the surface of the sample 41 by the intensity of the interference fringes. When interference fringe images are generated by sliding the scanning assembly 80 or sample 41 in the X-axis direction while the scanning assembly 80 or sample 41 is tilted at a predetermined angle in the Y-axis direction, it is possible to indirectly measure defects on the surface of the sample 41 using visual inspection or other methods.

[0065] However, as shown in Figure 6, interference fringe images are generated by tilting the scanning assembly 80 or sample 41 at a predetermined angle in the Y-axis direction, sliding the scanning assembly 80 or sample 41 in the X-axis direction, and moving the scanning assembly 80 or sample 41 toward each other in the Z-axis direction. In this case, it can be seen that the interference fringes change with each frame. In Figure 6, the scanning assembly 80 or sample 41 was slid in the X-axis direction, and the scanning assembly 80 or sample 41 was also moved by 60 nm in the Z-direction for each frame. Therefore, in the white light interferometer 100 according to the present invention, by sliding the scanning assembly 80 or sample 41 in the X-axis direction and moving the scanning assembly 80 or sample 41 toward each other in the Z-axis direction, each interference fringe changes with each frame. The white light interference fringes generated by accumulating each frame can then be analyzed using the conventional phase transition interferometer (PSI) method. For example, it is possible to analyze the intensity at the same location on the sample 41 using methods such as PSI (Phase Shifting Interferometry) or WLPSI (White Light Phase Shifting Interferometry). The image analysis processor 70 may be pre-configured with known PSI, WLI, and WLPSI analysis algorithms.

[0066] Phase transition interferometry (PSI) uses a short-wavelength laser as the light source 10, scans in the Z-axis direction, and measures height by observing changes in the interference signal. PSI generally uses a piezoelectric drive to change the phase value, obtaining the intensity of 3 or 4 light pulses in one period to reconstruct the phase and measure the height. PSI can calculate the height of the sample 41 surface using the reconstructed phase. Using a wavelength in the visible light region as the light source 10 provides excellent height resolution. However, the reconstructed phase is obtained as a value between -π and π, which differs from the actual phase. PSI cannot determine the interference fringe order, so it can only measure the relative height difference between measurement data, resulting in phase ambiguity. While PSI has excellent height measurement resolution (sub-nm), it suffers from the disadvantage of being unable to measure steps greater than 1 / 4 of the wavelength of the light source 10 due to phase ambiguity. Therefore, the Phase Transition Interferometer (PSI) is either capable of measuring only smooth surfaces, or it is capable of measuring only the surface shape of sample 41 where the step difference is 1 / 4 or less.

[0067] The white light interferometer (WLI) is designed to overcome the shortcomings of the phase transition interferometer (PSI). The WLI uses a halogen lamp or white LED as the light source 10, which encompasses a wide range of wavelengths, rather than just short-wavelength lasers. Because white light encompasses a wide range of wavelengths, the interference signal obtained by the WLI can be expressed as the sum of the interference signals obtained by the aforementioned phase transition interferometer (PSI). Unlike short-wavelength interference signals, white light interference signals only appear within a short range of 2 μm. This means that reinforcement interference occurs at the point where the phase of all short-wavelength interference signals becomes "0". Therefore, the interference fringes are largest at the distance where the optical path difference (OPD) is "0", and the size of the interference fringes decreases as the optical path difference increases. Consequently, the WLI measures the surface shape by finding the peak of the visibility function calculated from the size of the interference fringes. While the white light interferometer (WLI), which utilizes the visibility function, offers an infinitely wide measurement range, it has the disadvantage of being inferior to the phase transition interferometer (PSI), with a measurement resolution of only a few tens of nanometers.

[0068] The White Light Phase Transition Interferometer (WLPSI) combines the Phase Transition Interferometer (PSI) and the White Light Interferometer (WLI). The WLPSI uses white light as the light source (10) and, by applying the analytical algorithm used in the PSI, offers excellent measurement capabilities, including sub-nm resolution, while having no limitations on the measurement range. Because the WLPSI utilizes white light with a short interference distance, it first determines the interference fringe order using a visibility function, and then reconstructs the phase using the PSI method. Subsequently, the surface shape of the sample (41) is measured by adding the interference fringe order to the reconstructed phase.

[0069] Referring to Figure 7, it is possible to confirm that the position of the interference fringes changes even when the scanning assembly 80 or the sample 41 is moved 10 nm in the Z-axis direction. In particular, it is possible to confirm that the white light interferometer WLI_Intensity above the text "0.13" in Figure 7 has changed.

[0070] The scanning assembly 80 or sample 41 according to the present invention can be moved toward each other in the Z-axis direction by the optical moving assembly 81 or the stage moving assembly 50, respectively. When the optical moving assembly 81 or the stage moving assembly 50 moves the scanning assembly 80 or sample 41 in the X-axis direction, it can reciprocate the scanning assembly 80 or sample 41 in the Z-axis direction or the "-z" axis direction. When the optical moving assembly 81 or the stage moving assembly 50 moves the scanning assembly 80 or sample 41 in the Z-axis direction, it can move it by a predetermined distance, in which case each predetermined movement distance (z_step) may be 60 to 80 nm, and preferably the predetermined movement distance may be λ / 8, which is 68.75 nm.

[0071] Figure 8 is a simplified diagram showing the conventional white light interferometer (WLI) measurement method and the conventional phase transition interferometer (PSI) measurement method. Referring to Figure 8, conventional white light interferometer (WLI) measurements have the advantage of being able to measure even samples 41 with high steps. However, conventional white light interferometer (WLI) measurements have the disadvantage of requiring a large number of image frames due to a narrow Z_Step_Size over a wide area.

[0072] In contrast, phase transition interferometry (PSI) measurements have the advantage of requiring only about 4 to 7 image frames, but they have the characteristic of being difficult to measure steps larger than 150 nm. This characteristic of being difficult to measure steps larger than 150 nm can be overcome by measuring while moving the Z_Step at intervals of 68.75 nm.

[0073] Figure 9 is a simplified diagram showing how the image analysis processor 70 according to the present invention generates cumulative white light interference fringes. Figure 10 is a diagram showing how the image analysis processor 70 according to the present invention generates cumulative white light interference fringes by accumulating interference fringe images actually scanned from the surface of the sample 41. More specifically, Figure 10(a) shows multiple white light interference fringes in a conventional white light interferometer 100. Figure 10(b) shows multiple white light interference fringes generated by the white light interferometer 100 according to the present invention. Figure 10(c) shows the accumulation of interference fringe images actually scanned from the surface of the sample 41 by the image analysis processor 70 according to the present invention.

[0074] The white light interferometer 100 according to the present invention is equipped with a movable stage 40 (Sliding Stage) for AFP measurement (absolute fringe phase measurement). The stage 40 according to the present invention is capable of maintaining a flatness level of 10 ppm while moving in the X-axis direction at a speed of 10 μm / s to several mm / s.

[0075] As described above, the white light interferometer 100 according to the present invention changes its interference fringes when the sample 41 or scanning assembly 80 moves in the X-axis direction and also moves in the Z-axis direction. It has been confirmed that by collecting data (pixels) corresponding to the same X_Position in accordance with the X-axis movement speed of the sample 41 or scanning assembly 80, it is possible to create fringes (interference fringes) similar to those of a typical white light interferometer (WLI).

[0076] Referring to Figures 9 and 10, the image analysis processor 70 according to the present invention generates accumulated white light interference fringes by aligning multiple interference fringe images at the same x-position for each interference fringe image when accumulating multiple interference fringe images.

[0077] The multiple white light interference fringes generated by the white light interferometer 100 according to the present invention change with each frame as the scanning assembly 80 or the sample 41 moves in the X-axis direction while the scanning assembly 80 is tilted at a predetermined angle, and as the scanning assembly 80 or the sample 41 moves in the Z-axis direction. The image also shows how the shape of the sample 41 moves in the X-axis direction.

[0078] The image analysis processor 70 according to the present invention generates cumulative white light interference fringes by aligning and accumulating the interference fringe images shown in Figure 10(b) based on the same x-position as shown in Figure 10(c). The image analysis processor 70 is made capable of obtaining the shape of the sample 41 by analyzing the aligned and accumulated cumulative white light interference fringes as shown in Figure 10(c).

[0079] The white light interferometer 100 according to the present invention can further shorten its measurement time by increasing the Pixel_Size to 10 μm, increasing the number of CCD image sensors 60, or increasing the Frame_Rate (frame rate) of the CCD image sensors 60.

[0080] For example, the white light interferometer 100 according to the present invention may include a plurality of scanning assemblies 80. Each of the plurality of scanning assemblies 80 may include a light source 10, a beam splitter 20, a mirror 30, and a CCD image sensor 60. Therefore, the white light interferometer 100 according to the present invention may include a plurality of CCD image sensors 60.

[0081] The plurality of CCD image sensors 60 according to the present invention may include a plurality of CCD image sensors 60 that capture different frames of the sample 41, as shown in Figure 3(c). Each of the plurality of CCD image sensors 60 generates an interference fringe image based on the measurement light reflected from each of the different specific surfaces of the sample 41. The plurality of CCD image sensors 60 are arranged to capture different frames, and the movement of the scanning assembly 80 or the sample 41 enables the generation of an interference fringe image based on the measurement light reflected from each of the different specific surfaces. Therefore, the white light interferometer 100 according to the present invention can further shorten its measurement time by increasing the number of CCD image sensors 60.

[0082] The white light interferometer 100 according to the present invention is capable of measuring the top surface flatness of the entire wafer area with a resolution of 3.65 μm.

[0083] The scope of protection of the present invention is not limited to the descriptions and expressions of the embodiments explicitly described above. Furthermore, it should be added once again that the scope of protection of the present invention is not limited by obvious modifications or substitutions in the art to which the present invention pertains.

Claims

1. A sliding-type white light interferometer, and a sliding-type white light interferometer is, A light source that provides white light, The stage on which the sample is placed, A mirror having a reflective surface, A beam splitter that divides the path of the white light provided by the light source into the sample side and the mirror side, A stage moving assembly for moving the aforementioned stage, A CCD image sensor (Charge_Coupled_Device_image_sensor) receives the measurement light reflected from the sample and the reflected light reflected from the mirror from the beam splitter while the stage moving assembly moves the stage, and captures the interference fringes generated by the measurement light and the reflected light to generate multiple interference fringe images, and An image analysis processor that generates white light interference fringes (WLI_Fringe) by accumulating multiple interference fringe images, It is equipped with, The beam splitter modifies the path of the white light supplied to the sample so that it has a predetermined angle with respect to the sample, thereby irradiating the sample with the white light at the predetermined angle. The stage moving assembly moves the stage in the x-axis direction in which the sample is scanned, while the path of the white light maintains the predetermined angle with respect to the sample. The CCD image sensor generates multiple interference fringe images by continuously capturing interference fringes generated by the measurement light reflected from the surface of the sample and the reflected light reflected by the mirror while the stage is moved in the x-axis direction. A sliding-type white light interferometer.

2. The stage moving assembly moves the stage in the x-axis direction, and also moves the stage in the z-axis direction toward the beam splitter, thereby changing the interference fringes during continuous imaging of the interference fringes. A sliding type white light interferometer according to claim 1.

3. The image analysis processor is characterized in that, when accumulating a plurality of interference fringe images, it generates accumulated white light interference fringes by aligning the plurality of interference fringe images at the same x position of each interference fringe image. A sliding type white light interferometer according to claim 2.

4. The stage movement assembly moves the stage in the x-axis direction, and when the stage is moved in the z-axis direction and the -z-axis direction, it changes the interference fringes during continuous imaging of the interference fringes. A sliding type white light interferometer according to claim 2.

5. The stage moving assembly is characterized in that, when moving the stage in the z-axis direction, the stage is moved by a predetermined length, and the predetermined length is 60 to 80 nm. A sliding type white light interferometer according to claim 2.

6. The sliding type white light interferometer further includes multiple CCD image sensors that capture different frames of the sample. Each of the multiple CCD image sensors generates the interference fringe image based on the measurement light reflected from different specific surfaces of the sample. A sliding type white light interferometer according to claim 1.

7. A sliding type white light interferometer (WLI) that acquires the shape of a sample by continuously photographing interference fringes generated by measurement light reflected from the sample and reflected light reflected from a mirror through a scanning assembly tilted at a predetermined angle with respect to the sample, The aforementioned scanning assembly is A light source that provides white light, A mirror having a reflective surface, A beam splitter that divides the path of the white light provided by the light source into the sample side and the mirror side, and A CCD image sensor (Charge_Coupled_Device_image_sensor) receives the measurement light reflected from the sample by the beam splitter and the reflected light reflected by the mirror, and captures interference fringes generated by the measurement light and the reflected light. It is equipped with, The aforementioned white light interferometer further, An optical moving assembly for moving the scanning assembly, and An image analysis processor generates white light interference fringes (WLI_Fringe) by accumulating multiple interference fringes captured by the CCD image sensor while the optical moving assembly moves the scanning assembly, It is equipped with, The beam splitter modifies the path of the white light supplied to the sample so that it has a predetermined angle with respect to the sample, thereby irradiating the sample with the white light at the predetermined angle. The optical moving assembly moves the scanning assembly in the x-axis direction in which the sample is scanned, while the path of the white light maintains the predetermined angle with respect to the sample. The CCD image sensor generates multiple interference fringe images by continuously capturing interference fringes generated by the measurement light reflected from the surface of the sample and the reflected light reflected by the mirror while the scanning assembly is moving in the x-axis direction. A sliding-type white light interferometer.

8. The optical moving assembly moves the scanning assembly in the x-axis direction, and when the scanning assembly is moved in the z-axis direction toward the sample, the optical moving assembly changes the interference fringes during continuous imaging of the interference fringes. A sliding type white light interferometer according to claim 7.

9. The image analysis processor is characterized in that, when accumulating a plurality of interference fringe images, it generates accumulated white light interference fringes by aligning the plurality of interference fringe images at the same x position of each interference fringe image. A sliding type white light interferometer according to claim 8.

10. The optical moving assembly changes the interference fringes during continuous imaging of the interference fringes by moving the scanning assembly back and forth in the z-axis direction and the -z-axis direction when the scanning assembly is moved in the x-axis direction. A sliding type white light interferometer according to claim 8.

11. The optical moving assembly moves the scanning assembly by a predetermined length when the scanning assembly is moved in the z-axis direction, and the predetermined length is 60 to 80 nm. A sliding type white light interferometer according to claim 8.

12. The sliding type white light interferometer further includes multiple CCD image sensors that capture different frames of the surface of the sample. Each of the multiple CCD image sensors generates the interference fringe image based on the measurement light reflected from different specific surfaces of the sample. A sliding type white light interferometer according to claim 7.

13. A sliding type white light interferometer (WLI) that acquires the shape of a sample by continuously photographing interference fringes generated by measurement light reflected from the sample and reflected light reflected from a mirror through a scanning assembly tilted at a predetermined angle with respect to the sample, The aforementioned scanning assembly is A light source that provides white light, A stage on which the aforementioned sample is placed, The mirror having a reflective surface, A beam splitter that divides the path of the white light provided by the light source into the sample side and the mirror side, and A CCD image sensor (Charge_Coupled_Device_image_sensor) receives the measurement light reflected from the sample by the beam splitter and the reflected light reflected by the mirror, and captures interference fringes generated by the measurement light and the reflected light. It is equipped with, The aforementioned white light interferometer further, A stage movement assembly that moves the stage in the x-axis direction in which the sample is scanned, An optical moving assembly for moving the scanning assembly in the z-axis direction toward the sample, and The image analysis processor generates a white light interference fringe (WLI_Fringe) by accumulating multiple interference fringes captured by the CCD image sensor while the stage moving assembly moves the stage in the x-axis direction and the optical moving assembly moves the scanning assembly in the z-axis direction. It is equipped with, The beam splitter modifies the path of the white light supplied to the sample so that it has a predetermined angle with respect to the sample, thereby irradiating the sample with the white light at the predetermined angle. The stage moving assembly moves the stage in the x-axis direction while the path of the white light maintains the predetermined angle with respect to the sample. The CCD image sensor generates multiple interference fringe images by continuously capturing interference fringes generated by the measurement light reflected from the surface of the sample and the reflected light reflected by the mirror while the stage is moved in the x-axis direction. A sliding-type white light interferometer.

14. The optical moving assembly changes the interference fringes during continuous imaging of the interference fringes by moving the scanning assembly in the z-axis direction when the stage moving assembly moves the stage in the x-axis direction. A sliding type white light interferometer according to claim 13.

15. The image analysis processor is characterized in that, when accumulating a plurality of interference fringe images, it generates accumulated white light interference fringes by aligning the plurality of interference fringe images at the same x position of each interference fringe image. A sliding type white light interferometer according to claim 14.

16. The optical moving assembly changes the interference fringes during continuous imaging of the interference fringes by reciprocating the scanning assembly in the z-axis direction and the -z-axis direction when the stage moving assembly moves the stage in the x-axis direction. A sliding type white light interferometer according to claim 14.

17. When the optical moving assembly moves the scanning assembly in the z-axis direction, it moves the scanning assembly by a predetermined length. The predetermined length is characterized by being 60 to 80 nm. A sliding type white light interferometer according to claim 14.

18. The sliding type white light interferometer further includes multiple CCD image sensors that capture different frames of the surface of the sample. Each of the multiple CCD image sensors generates the interference fringe image based on the measurement light reflected from different specific surfaces of the sample. A sliding type white light interferometer according to claim 13.

Images