Optical measurement system

Abstract

The present invention provides an optical measurement system, comprising an optical path conversion unit, an optical measurement module, and an optical imaging module. The optical measurement module comprises a first light source and a spectrometer, a first light beam emitted by the first light source passes through the optical path conversion unit and reaches the surface of a sample and is reflected thereby, and then passes through the optical path conversion unit and is received by the spectrometer, and a first optical path and a second optical path of the first light beam are respectively formed between the optical path conversion unit and the first light source and between the optical path conversion unit and the spectrometer; the optical imaging module comprises a second light source and an image acquisition element, a second light beam emitted by the second light source passes through the optical path conversion unit and reaches the surface of the sample and is reflected thereby, and then passes through the optical path conversion unit and is received by the image acquisition element, and a third optical path and a fourth optical path of the second light beam are respectively formed between the optical path conversion unit and the second light source and between the optical path conversion unit and the image acquisition element; and the first optical path partially coincides with the third optical path and / or the second optical path partially coincides with the fourth optical path. The system achieves a high system integration level, a simple optical path, high measurement efficiency, and a wide linear range of measurement.

Description

An optical measurement system Technical Field

[0001] The invention belongs to the technical field of optical measuring devices and relates to an optical measuring system. Background Art

[0002] Thin film technology is widely used in technical fields such as integrated circuit devices, photovoltaic devices, and electronic display devices. In practical applications, the thickness of the film has a significant impact on the performance of the film and the overall performance of the corresponding product. For example, for optical thin films, the film thickness directly affects the transmission, reflection, and absorption properties; for electrical thin films, the film thickness directly affects the conductivity, dielectric constant, and resistance. Therefore, the detection of film thickness is crucial. Taking the semiconductor field as an example, with the development of semiconductor integrated circuits, optical measurement systems are often required to monitor film thickness during the manufacturing process to ensure manufacturing process stability and product quality.

[0003] Currently, optical measurement systems used to measure film thickness include spectroscopic ellipsometers, spectroscopic interferometers, and spectroscopic reflectometers. Taking optical reflectometers as an example, their operating principle is that a light beam is incident vertically on a sample and reflected, and the thickness and optical parameters of the sample film are measured by analyzing the reflected light. These systems offer advantages such as non-destructive measurement, fast measurement speed, high accuracy, and low cost, making them widely used in semiconductor measurement systems. However, most existing semiconductor measurement equipment suffers from shortcomings such as low system integration, a narrow measurement linear range, and an inability to monitor the measurement process in real time, resulting in poor measurement stability, or high measurement accuracy but high cost and cumbersome operation, hindering their large-scale application in process stability testing in the semiconductor field or other technical fields.

[0004] Therefore, how to provide an optical measurement system to improve system integration and perform real-time monitoring of the measurement process to improve measurement efficiency and measurement stability has become an important technical problem that needs to be solved urgently by those skilled in the art.

[0005] It should be noted that the above introduction to the technical background is merely intended to provide a clear and complete description of the technical solutions of this application and facilitate understanding by those skilled in the art. Simply because these solutions are described in the background technology section of this application, it should not be assumed that the above technical solutions are well known to those skilled in the art.

[0006] Summary of the Invention

[0007] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide an optical measurement system for solving the problems of most semiconductor film thickness measurement equipment in the prior art, such as low system integration, inability to monitor the measurement process in real time, and poor measurement stability.

[0008] To achieve the above and other related objectives, the present invention provides an optical measurement system, comprising:

[0009] an optical path conversion unit, comprising a first beam splitter and a first objective lens, wherein the first objective lens focuses the incident light beam passing through the first beam splitter onto the sample surface and collimates the light beam reflected by the sample surface and outputs the collimated light beam;

[0010] An optical measurement module includes a first lighting unit and a measuring unit, wherein a first light beam emitted by a first light source of the first lighting unit enters the light path conversion unit along a first light path, reaches a sample surface, and is reflected. The reflected first light beam passes through the light path conversion unit and reaches a spectrometer of the measuring unit along a second light path;

[0011] An optical imaging module includes a second lighting unit and an imaging unit, wherein a second light beam emitted by a second light source of the second lighting unit enters the light path conversion unit along a third light path, reaches the sample surface, and is reflected. The reflected second light beam passes through the light path conversion unit and reaches the image acquisition element of the imaging unit along a fourth light path.

[0012] The first optical path partially overlaps with the third optical path, and / or the second optical path partially overlaps with the fourth optical path.

[0013] Optionally, the wavelength range of the light beam emitted by the first light source is 230nm-900nm, and the wavelength range of the light beam emitted by the second light source is 450nm-750nm.

[0014] Optionally, the first objective lens includes a concave reflector and a convex reflector, the concave reflector is coaxially arranged or off-axis with the convex reflector, when the first light beam enters the first objective lens, the concave surface of the concave reflector is opposite to the convex surface of the convex reflector, the focal length of the first objective lens is 10 mm, and the numerical aperture of the first objective lens is greater than or equal to 0.4.

[0015] Optionally, the first lighting unit further includes a first parabolic mirror, a second parabolic mirror, and a third parabolic mirror sequentially arranged between the first light source and the first beam splitter to adjust the propagation direction of the first light beam to be collimated and converge the collimated first light beam onto the sample surface through the first objective lens to form a measurement spot.

[0016] Optionally, the first lighting unit further includes a color wheel, which is located between the first parabolic mirror and the second parabolic mirror to control the light intensity of the first light beam. The color wheel includes multiple filters, and the transmittance of the filters includes at least one of 10%, 25% and 50%.

[0017] Optionally, the first lighting unit further includes an aperture diaphragm having an adjustable aperture, and the aperture diaphragm is located between the second parabolic mirror and the third parabolic mirror to adjust the size of the measurement light spot.

[0018] Optionally, the second lighting unit further includes a first collimator and a second beam splitter, and the second beam splitter is located between the first collimator and the first beam splitter on the propagation path of the second light beam, and the second beam splitter is also located between the third parabolic mirror and the first beam splitter on the propagation path of the first light beam.

[0019] Optionally, the measuring unit further includes a first tube lens, a first pinhole mirror and a first relay lens arranged in sequence, and the first light beam is reflected by the sample surface and then passes through the first tube lens, the hole on the first pinhole mirror and the first relay lens in sequence to reach the spectrometer.

[0020] Optionally, the first tube lens includes a first element, a second element and a third element that are separately arranged in sequence, wherein the material of the first element includes calcium fluoride, the material of the second element includes fused quartz, the material of the third element includes calcium fluoride, the focal length of the first tube lens includes 100 mm, and the numerical aperture of the first tube lens includes 0.04.

[0021] Optionally, the imaging unit further includes a second tube lens, a second pinhole lens and a second relay lens arranged in sequence. After the second light beam is reflected by the sample surface, it passes through the second tube lens, a side of the second pinhole lens facing the second tube lens and the second relay lens in sequence to reach the image acquisition element.

[0022] Optionally, the second tube lens and the first tube lens share the same tube lens, and / or the second pinhole mirror and the first pinhole mirror share the same pinhole mirror.

[0023] Optionally, the optical imaging module further includes a second objective lens, a reflector and a switching device, wherein the switching device is respectively connected to the first objective lens and the second objective lens to switch the objective lenses, and the magnification of the first objective lens is greater than the magnification of the second objective lens.

[0024] Optionally, the optical measurement system further includes an autofocus module, which includes a third lighting unit and a focusing unit. A third light beam emitted by a third light source of the third lighting unit enters the optical path conversion unit along a fifth optical path, reaches the sample surface and is reflected. The reflected third light beam passes through the optical path conversion unit and reaches the sensor of the focusing unit along a sixth optical path.

[0025] Optionally, the fifth optical path partially overlaps with the first optical path and / or the third optical path, and / or the sixth optical path partially overlaps with the second optical path and / or the fourth optical path.

[0026] Optionally, the third lighting unit is identical to the first lighting unit so that the first light path and the second light path completely overlap.

[0027] Optionally, the focusing unit includes a third beam splitter, a first cylindrical mirror and a second cylindrical mirror arranged in sequence, and the third beam splitter is located between the first beam splitter and the first cylindrical mirror on the propagation path of the third light beam, and the third beam splitter is located between the first beam splitter and the spectrometer on the propagation path of the first light beam.

[0028] As described above, the optical measurement system of the present invention includes an optical path conversion unit, an optical measurement module, and an optical imaging module. By designing the optical paths of the optical measurement module and the optical imaging module, the system integration can be effectively improved and the complexity of the optical path can be reduced. The operation is simple. By observing the measurement process in real time through the optical imaging module, the speed and efficiency of measuring the film thickness and other optical parameters on the sample can be improved. Furthermore, by adjusting the light source of the optical measurement module, and designing the objective lens and tube lens structure, wide-band measurement can be achieved without frequent switching of devices, thereby improving the measurement linear range. In addition, an additional autofocus module is added to adjust the foot position of the objective lens for rapid focusing, further improving measurement stability and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG1 is a schematic diagram showing the overall structure of the optical measurement system of the present invention.

[0030] FIG. 2 is a schematic diagram showing the overall structure of an optical measurement module in the optical measurement system of the present invention.

[0031] FIG3 is a schematic diagram showing the overall structure of the optical imaging module in the optical measurement system of the present invention.

[0032] FIG. 4 is a simplified structural diagram of the first objective lens in the optical measurement system of the present invention.

[0033] FIG5 is a simplified structural diagram of the first tube mirror in the optical measurement system of the present invention.

[0034] FIG. 6 is a schematic diagram showing a partial optical path of the first lighting unit in the optical measurement system of the present invention.

[0035] FIG. 7 is a schematic diagram showing an optical path of a measuring unit in the optical measuring system of the present invention.

[0036] FIG8 is a schematic diagram showing the optical path of the second illumination unit in the optical measurement system of the present invention.

[0037] FIG9 is a schematic diagram showing the optical path of the imaging unit in the optical measurement system of the present invention.

[0038] FIG10 is a schematic diagram showing the overall structure of the auto-focus module in the optical measurement system of the present invention.

[0039] DESCRIPTION OF REFERENCE NUMERALS 11 Optical path conversion unit 111 First beam splitter 112 First objective lens 1121 Concave reflector 1122 Convex reflector 20 Optical measurement module 21 First illumination unit 211 First light source 212 First parabolic mirror 213 Second parabolic mirror 214 Third parabolic mirror 215 Color wheel 216 Aperture diaphragm 22 Measurement unit 221 Spectrometer 222 First tube lens 2221 First element 2222 Second element 2223 Third element 223 First pinhole mirror 224 First relay lens 30 Optical imaging module 31 Second illumination unit 311 Second light source 312 First collimating lens 313 Second beam splitter 32 Imaging unit 321 Image acquisition element 322 Second tube lens 323 Second pinhole mirror 324 Second relay lens 325 Second objective lens 326 Reflector 40 Autofocus module 41Third lighting unit 411 Third light source 42 Focus unit 421 Sensor 422 Third beam splitter 423 First cylindrical mirror 424 Second cylindrical mirror S Sample DETAILED DESCRIPTION

[0040] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0041] Please refer to Figures 1 to 10. It should be noted that the figures provided in this embodiment are merely schematic illustrations of the basic concept of the present invention. Therefore, the figures only show components relevant to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be varied arbitrarily, and the component layout may also be more complex.

[0042] The present invention provides an optical measurement system. Please refer to Figure 1, which is a schematic diagram of the overall structure of the optical measurement system. The optical measurement system includes an optical path conversion unit 11, an optical measurement module 20, and an optical imaging module 30. Please refer to Figures 2 and 3 for an example illustration of the structure of the optical measurement system, wherein Figure 2 shows a schematic diagram of the overall structure of the optical measurement module, and Figure 3 shows a schematic diagram of the overall structure of the optical imaging module.

[0043] Specifically, as shown in Figures 1 to 3, the optical path conversion unit 11 includes a first beam splitter 111 and a first objective lens 112 arranged above the sample S. The first beam splitter 111 adjusts the light beam propagating parallel to the surface of the sample S (including the first light beam, the second light beam and the third light beam described below) from a parallel direction to a vertical direction. The first objective lens 112 focuses the incident light beam (referring to the part of the light beam reflected by the first beam splitter 111) passing through the first beam splitter 111 on the surface of the sample S and collimates the reflected light beam reflected by the surface of the sample S and outputs it.

[0044] Specifically, as shown in FIG2 , the optical measurement module 20 includes a first illumination unit 21 and a measurement unit 22. A first light beam (not shown in FIG2 ; the arrows connecting different components in FIG2 indicate the propagation direction and path of the first light beam) emitted by a first light source 211 of the first illumination unit 21 enters the optical path conversion unit 11 along a first optical path, reaches the surface of the sample S, and is reflected. After the reflection, the first light beam passes through the optical path conversion unit 11 and then reaches the spectrometer 221 of the measurement unit 22 along a second optical path. That is, along the propagation path of the first light beam, the optical path conversion unit 11 is located between the first illumination unit 21 and the measurement unit 22. The first illumination unit 21 includes the first light source 211, and the measurement unit 22 includes the spectrometer 221. The first light source 211 and the optical path conversion unit 11 constitute the first optical path, while the optical path conversion unit 11 and the spectrometer 221 constitute the second optical path.

[0045] Specifically, as shown in FIG3 , the optical imaging module 30 includes a second illumination unit 31 and an imaging unit 32. A second light beam (not shown in FIG3 ; the arrows connecting different components in FIG3 indicate the propagation direction and path of the second light beam) emitted by the second light source 311 of the second illumination unit 31 enters the optical path conversion unit 11 along a third optical path, reaches the surface of the sample S, and is reflected. The reflected second light beam then passes through the optical path conversion unit 11 and reaches the image capture element 321 of the imaging unit 32 along a fourth optical path. In the propagation path of the second light beam, the optical path conversion unit 11 is located between the second illumination unit 31 and the imaging unit 32. The second illumination unit 31 includes a second light source 311, and the imaging unit 32 includes an image capture element 321. The third optical path is formed between the second light source 311 and the optical path conversion unit 11, and the fourth optical path is formed between the optical path conversion unit 11 and the image capture element 321. The first optical path partially overlaps with the third optical path, and / or the second optical path partially overlaps with the fourth optical path.

[0046] In the optical measurement system of the present invention, the optical measurement module 20 is used to measure the film thickness at a specific position (i.e., a measurement calibration point) on the sample S, and the optical imaging module 30 is used to perform real-time observation at the measurement calibration point. When performing film thickness measurement and observation at the same measurement calibration point, the propagation path of the first light beam in the optical measurement module 20 and the propagation path of the second light beam in the optical imaging module 30 both need to pass through the optical path conversion unit 11 to achieve measurement or imaging. Therefore, the optical path conversion unit 11 is a functional unit shared by the optical measurement module 20 and the optical imaging module 30, and the optical paths of the first light beam and the second light beam in the optical path conversion unit 11 basically coincide. Furthermore, based on the actual functional differences between film thickness measurement and real-time observation, there are obvious differences between the light sources used to generate the measuring beam (the first beam) and the imaging beam (the second beam) and the equipment used to receive the measuring beam and the imaging beam. Generally speaking, on the incident path, the first optical path of the first light beam from the first light source 211 to the optical path conversion unit 11 and the third optical path of the second light beam from the second light source 311 to the optical path conversion unit 11 are separated from each other; similarly, on the reflected path, the second optical path of the first light beam from the optical path conversion unit 11 to the spectrometer 221 and the fourth optical path of the second light beam from the optical path conversion unit 11 to the image acquisition element 321 are separated from each other. However, observation and verification have found that such a configuration can make the parallel optical path in the optical measurement system too long. Under critical illumination conditions, it is easy for external field light to be unable to enter the objective lens, thereby limiting the illumination field range and affecting the measurement and imaging effects. Therefore, in the system of the present invention, by further designing and laying out the specific structures of the optical measurement module 20 and the optical imaging module 30 so that the propagation path of the first light beam and the propagation path of the second light beam, except for the optical path within the optical path conversion unit 11, overlap (i.e., a common optical path mode), the length of the parallel optical path can be reduced to a certain extent, making the optical path compact, while also reducing the number of components and the complexity of the optical path. More specifically, the common optical path mode can be achieved by partially overlapping the first and third optical paths, or partially overlapping the second and fourth optical paths, or partially overlapping the first and third optical paths and the second and fourth optical paths (as shown in FIG1 ). It should be noted that Figure 1 shows a schematic diagram of the system structure constructed using the third of the three common optical path implementation methods mentioned above. At this time, the overall optical path of the optical measurement system is more compact. In application, the first two methods can be selected based on actual conditions to construct a film thickness measurement system, which can also achieve different degrees of optical path compactness.

[0047] As an example, the sample S includes at least one of a semiconductor film layer (such as a photoresist layer, oxide layer, nitride layer, and metal layer), a solar cell thin film, and an optical coating (such as an anti-reflection film, an anti-reflection film, and an anti-reflection film). In other words, the optical measurement system can be applied to technical fields such as semiconductor manufacturing, photovoltaics, flexible electronic displays, and optical device manufacturing. In one embodiment, the optical measurement system is used to perform real-time measurement of film layers grown or coated on wafers.

[0048] As an example, the wavelength range of the light beam emitted by the first light source 211 is 230nm to 900nm. The first light source 211 includes a xenon lamp, a laser driven light source (LDLS) or other suitable light sources. The purpose of using the above light sources as the first light source 211 is that the wavelength band of the light beam emitted by the above light source is wider, covering the ultraviolet band, visible light band and infrared band. According to the Fresnel reflection law, the reflectivity is a function of the incident angle, light intensity, wavelength, film thickness, optical constants, etc. The wider the band of the light source used to emit the measuring light beam, the wider the linear range of the film thickness measurement. Therefore, when the band of the measuring light beam is wider, the measurement range of the film thickness is larger and the accuracy is higher. At the same time, it can avoid switching of multiple light sources in different bands for emitting the measuring light beam, thereby improving the measurement efficiency and being more suitable for practical applications.

[0049] As an example, as shown in Figure 2, the first lighting unit 21 also includes a first parabola 212, a second parabola 213 and a third parabola 214, which are sequentially arranged between the first light source 211 and the first beam splitter 111, so as to adjust the propagation direction of the first light beam to be collimated and enable the first objective lens 112 to converge the collimated first light beam on the surface of the sample S to form a measurement spot. In one embodiment, the first parabola 212 and the second parabola 213 are arranged relative to each other in the horizontal direction, and the second parabola 213 and the third parabola 214 are arranged relative to each other in the vertical direction. Of course, under the premise of ensuring that the first light beam is collimated and enters the optical path conversion unit 11, the specific positions of the above three parabolas can be reasonably designed based on actual working conditions without necessarily forcibly limiting them to the parallel or vertical arrangement as described above.

[0050] As an example, as shown in FIG2 , the first illumination unit 21 further includes a color wheel 215 located between the first parabolic mirror 212 and the second parabolic mirror 213 to control the intensity of the first light beam. The color wheel 215 includes multiple filters, each having a transmittance of at least one of 10%, 25%, and 50%. During use, filters with different transmittances are switched to adjust the measurement light intensity based on actual measurement needs. In one embodiment, the color wheel 215 includes three filters with transmittances of 10%, 25%, and 50%, respectively, which can meet measurement requirements in most situations. In other embodiments, the number of filters included in the color wheel 215 and the transmittance of each filter can be appropriately set based on actual measurement needs. Of course, the position of the color wheel 215 can also be adjusted based on actual needs while ensuring that the light intensity is controlled, and is not limited to the position shown in FIG2 .

[0051] As an example, as shown in FIG2 , the first illumination unit 21 further includes an aperture diaphragm 216 having an adjustable aperture. The aperture diaphragm 216 is positioned between the second parabolic mirror 213 and the third parabolic mirror 214 to adjust the size of the measurement spot. Because the aperture diaphragm 216 includes an adjustable aperture, the first light beam passes through the aperture in the aperture diaphragm 216 as it travels from the second parabolic mirror 213 to the third parabolic mirror 214. Adjusting the aperture allows for convenient adjustment of the size of the measurement spot formed on the surface of the sample S.

[0052] As an example, please refer to FIG4 , which shows a simplified schematic diagram of the structure of the first objective lens in the optical path conversion unit. The first objective lens 112 includes a concave reflector 1121 and a convex reflector 1122. The concave reflector 1121 and the convex reflector 1122 are coaxially or off-axis arranged. When the first light beam enters the first objective lens 112, the concave surface of the concave reflector 1121 is opposite the convex surface of the convex reflector 1122. The focal length of the first objective lens 112 is 10 mm, and the numerical aperture of the first objective lens 112 is greater than or equal to 0.4. The use of the above-mentioned two-reflecting objective lens structure can effectively avoid the influence of chromatic aberration during the measurement process. At the same time, the reflective surfaces (convex and concave surfaces) of the two-reflecting structure are coated with ultraviolet-reflecting aluminum film, which can ensure that a wide band of measurement light passes through to meet the requirements of wide-band measurement. The high numerical aperture structure can meet the requirements of high resolution to achieve high-definition image quality observation within the field of view. It should be noted that FIG4 illustrates a coaxial arrangement of the two reflectors to form a coaxial two-reflector first objective lens structure. In this case, the concave reflector 1121 is located between the first beam splitter 111 and the convex reflector 1122, and the central axes of the two coincide. In other embodiments, the two reflectors may also be arranged off-axis, wherein the convex reflector 1122 may be arranged at other positions in the optical measurement system and then driven by electrodes to move to the above-mentioned position to form an off-axis two-reflector objective lens. In addition, the above-mentioned structure of the first objective lens 112 is designed to meet the requirements of wide-band measurement. The actual morphology of the convex and concave surfaces of the convex reflector 1122 and the convex reflector 1122, the thickness of each reflector and other dimensional specifications, and the spacing between the two reflectors are reasonably adjusted based on actual needs when the focal length and numerical aperture of the first objective lens 112 are within the above-mentioned ranges, and are not limited here.

[0053] As an example, as shown in Figure 2, the measuring unit 22 also includes a first tube lens 222, a first pinhole mirror 223 and a first relay lens 224 arranged in sequence. After the first light beam is reflected by the surface of the sample S, it passes through the first tube lens 222, the hole on the first pinhole mirror 223 and the first relay lens 224 in sequence to reach the spectrometer 221, wherein the first tube lens 222 is used to focus the reflected first light beam so that the first light beam passes through the hole on the first pinhole mirror 223, the first pinhole mirror 223 is used to effectively filter stray light through its hole to reduce measurement errors, and the first relay lens 224 can adjust the optical path to meet the measurement requirements of the system.

[0054] As an example, see Figure 5, which shows a simplified schematic diagram of the structure of the first tube lens in the measurement unit. The first tube lens 222 comprises a first element 2221, a first element 2222, and a third element 2223, each of which is separately arranged. The material of the first element 2221 is calcium fluoride, the material of the first element 2222 is fused silica, and the material of the third element 2223 is calcium fluoride. The focal length of the first tube lens 222 is 100 mm, and the numerical aperture of the first tube lens 222 is 0.04. To meet the requirements of wideband measurement, after multiple verifications, the above structure and materials of the first tube lens 222 were designed in addition to the first objective lens 112. Due to the different material parameters such as the refractive index of fused silica and calcium fluoride, when the first tube lens 222 comprises these three elements, the materials of each element cannot be arbitrarily replaced to achieve wideband measurement. While meeting the requirements of wideband measurement, the specific parameters such as the shape, size, and spacing of these three elements can be adjusted based on the focal length, numerical aperture, and field of view, and based on lens optimization requirements.

[0055] For ease of understanding, please refer to Figures 2, 6, and 7 for an exemplary illustration of the propagation path of the measurement beam (the first beam) in the optical measurement module 20. Figure 6 shows a schematic diagram of a partial optical path of the first illumination unit (which can be considered a partial schematic diagram of the first optical path), and Figure 7 shows a schematic diagram of the optical path of the measurement unit (which can be considered a schematic diagram of the second optical path). Due to the operating characteristics of the light source and the actual structural requirements of the system, the first beam emitted by the first light source 211 cannot directly illuminate the surface of the sample S to measure the film thickness of the sample S. Therefore, additional optical elements need to be provided between the first light source 211 and the surface of the sample S to be measured to ensure that the first beam reaches the surface of the sample S smoothly. During this process, parameters such as the intensity and beam diameter of the first beam need to be adjusted to meet the measurement requirements. As shown in FIG2 , a first parabola 212, a color wheel 215, a second parabola 213, a pinhole diaphragm 216 and a third parabola 214 are sequentially arranged between the first light source 211 and the surface of the sample S, wherein the first parabola 212 is used to adjust the first light beam from divergent transmission to collimated transmission, and then adjust the light intensity through the filter on the color wheel 215 to meet the demand of measuring light intensity, and the collimated first light beam after the light intensity adjustment is converged by the second parabola 213 to pass through the small hole on the pinhole diaphragm 216 to adjust the size of the measurement spot formed by the subsequent arrival of the first light beam on the surface of the sample S, and the third parabola 214 collimates the converged first light beam adjusted by the pinhole diaphragm 216 again; as shown in FIG6 , the first light beam after the second collimation passes through the third parabola 214 in the optical path conversion unit 11. After being reflected by a beam splitter 111, it reaches the first objective lens 112 and is focused by the first objective lens 112 on the surface of the sample S to form a measuring light spot. As shown in FIG7 , the first light beam is reflected after being focused on the surface of the sample S. According to the Fresnel reflection law, when other parameters are known, the reflectivity is a function of the film thickness. Therefore, by collecting and analyzing the reflected first light beam, the specific information of the real-time film thickness of the sample S can be obtained. The first light beam reflected by the surface of the sample S is first collimated by the first objective lens 112 and then passes through the first beam splitter 111. It is then focused by the first tube lens 222 and passes through the hole on the first pinhole mirror 223. It is then focused again by the first relay lens 224 and then enters the spectrometer 221 through the optical fiber coupling connected to the spectrometer 221, completing the real-time collection and analysis of the film thickness information.

[0056] As an example, the wavelength range of the light beam emitted by the second light source 311 is 450nm~750nm. The second light beam emitted by the second light source 311 is used to observe and image the marking point of the sample S where the film thickness is to be measured. A light source in the visible light band can be used, which can save costs.

[0057] As an example, as shown in FIG3 , the second illumination unit 31 further includes a first collimator 312 and a second beam splitter 313. The second beam splitter 313 is located between the first collimator 312 and the first beam splitter 111 on the propagation path of the second light beam, and between the third parabolic mirror 214 and the first beam splitter 111 on the propagation path of the first light beam. This positioning of the second beam splitter 313 is equivalent to placing the second beam splitter 313 in the propagation path of the first light beam. Although this slightly reduces the energy of the first light beam on its way from the third parabolic mirror 214 to the first beam splitter 111, it does not affect the measurement or the measurement optical path. Instead, it allows the first and third optical paths to partially overlap, effectively increasing system integration.

[0058] As an example, as shown in Figure 3, the imaging unit 32 also includes a second tube lens 322, a second pinhole mirror 323 and a second relay lens 324 arranged in sequence. After the second light beam is reflected by the surface of the sample S, it passes through the second tube lens 322, the side of the second pinhole mirror 323 facing the second tube lens 322 and the second relay lens 324 in sequence to reach the image acquisition element 321.

[0059] Furthermore, the second tube lens 322 and the first tube lens 222 share the same tube lens, and / or the second pinhole lens 323 and the first pinhole lens 223 share the same pinhole lens. That is, in addition to increasing system integration by placing the second beam splitter 313 on the propagation path of the first optical path, the layout of optical components can also be used to partially overlap the second optical path with the fourth optical path, further increasing system integration while achieving multiple utilization of optical components and effectively reducing the number of optical components in the system, thereby meeting measurement requirements while simplifying the system structure and reducing costs.

[0060] As an example, as shown in Figure 3, the optical imaging module 30 also includes a second objective lens 325, a reflector 326 and a switching device (not shown in Figure 3), and the switching device is respectively connected to the first objective lens 112 and the second objective lens 325 to switch the objective lenses. The magnification of the first objective lens 112 is greater than the magnification of the second objective lens 325. In one embodiment, the magnification of the first objective lens 112 is 5-15 times, and the magnification of the second objective lens 325 is less than or equal to 2 times. Preferably, the magnification of the first objective lens 112 is 10 (i.e., the first objective lens 112 is a 10x objective lens), and the magnification of the second objective lens 325 is 1 (i.e., the magnification of the second objective lens 325 is a 1x objective lens). The first objective lens 112 in the optical imaging module 30 is used for real-time monitoring and high-magnification imaging of the measurement mark point. When the magnification is 10 times, it can basically meet the requirements of parameters such as imaging resolution and field of view. Therefore, it is set to about 10 times. The role of the second objective lens 325 is to achieve a larger observation field of view of the sample S surface. If the magnification is too high, the observation field of view may be insufficient, affecting measurement efficiency. Of course, the magnification of the first objective lens 112 and the second objective lens 325 can be selected based on actual needs and are not limited to the specific magnification values ​​mentioned above.

[0061] For ease of understanding, please refer to Figures 3, 8, and 9 for an example of the propagation path of the imaging light beam (i.e., the second light beam) in the optical imaging module, wherein Figure 8 shows a schematic diagram of the light path of the second lighting unit (which can be regarded as a partial schematic diagram of the third light path), and Figure 9 shows a schematic diagram of the light path of the imaging unit (which can be regarded as a schematic diagram of the fourth light path). Similar to the structure of the first lighting unit 21, the second light beam emitted by the second light source 311 cannot be directly irradiated on the surface of the sample S to achieve real-time observation of the marking points on the surface of the sample S. Therefore, it is necessary to set other optical elements between the second light source 311 and the surface to be measured of the sample S to enable the second light beam to reach the surface of the sample S smoothly, and in this process, it is necessary to adjust some parameters of the second light beam to meet the imaging requirements. As shown in FIG8 , a first collimator 312 and a second beam splitter 313 are sequentially disposed between the second light source 311 and the surface of the sample S. The first collimator 312 is used to collimate the second light beam emitted by the second light source 311. The second beam is then adjusted from vertical to horizontal via the second beam splitter 313. The collimated second light beam is then reflected by the first beam splitter 111 and focused onto the surface of the sample S via the first objective lens 112. As shown in FIG9 , after being focused on the surface of the sample S, the second light beam is reflected. After passing through the second tube lens 322, the reflected second light beam is reflected by the second pinhole lens 323 toward one side of the second tube lens 322 to adjust its direction of transmission. The reflected second light beam is then focused by the second relay lens 324, entering the image acquisition element 321 and forming an image. In one embodiment, the image acquisition element 321 is a camera, and the second light beam is formed onto the target surface of the camera after entering the camera.

[0062] As an example, please refer to Figure 1 and Figure 10. Figure 10 shows a schematic diagram of the overall structure of the autofocus module in the optical measurement system. The optical measurement system also includes an autofocus module 40, and the autofocus module 40 includes a third lighting unit 41 and a focusing unit 42. The third light beam emitted by the third light source 411 of the third lighting unit 41 (not marked in Figure 10, the arrows connecting different components in Figure 10 indicate the propagation direction and path of the third light beam) enters the optical path conversion unit 11 along the fifth optical path and reaches the surface of the sample S and is reflected. The reflected third light beam passes through the optical path conversion unit 11 and reaches the sensor 421 of the focusing unit 42 along the sixth optical path. Similarly, along the propagation path of the third light beam, the optical path conversion unit 11 is located between the third illumination unit 41 and the focusing unit 42. Furthermore, the third illumination unit 41 includes a third light source 411, and the focusing unit 42 includes a sensor 421. The third light source 411 and the optical path conversion unit 11 form the fifth optical path, while the optical path conversion unit 11 and the sensor 421 form the sixth optical path. Specifically, when the optical measurement system also includes an autofocus module 40, the optical path conversion unit 11 serves as a shared functional unit for the optical measurement module 20, the optical imaging module 30, and the autofocus module 40. Furthermore, the optical path of the third light beam in the optical path conversion unit 11 substantially overlaps with the optical paths of the other two light beams, thereby achieving the most accurate and rapid focusing effect.

[0063] As an example, the fifth optical path partially overlaps with the first optical path and / or the third optical path, and / or the sixth optical path partially overlaps with the second optical path and / or the fourth optical path. Similar to the partial overlap between the propagation paths of the first and second optical beams, by designing the propagation path of the third optical beam to partially overlap with the propagation path of the first and / or second optical beams, effects such as improved system integration can also be achieved.

[0064] Furthermore, as shown in FIG1 , the third lighting unit 41 is identical to the first lighting unit 21 so that the first optical path and the second optical path completely overlap (i.e., a same optical path mode). That is, the third lighting unit 41 has exactly the same components as the first lighting unit 21 (i.e., the first light source 211 and the fourth light source 411 share the same light source), and the layout of the components overlaps so that one functional module performs a dual function (implementing both illumination during measurement and illumination during focusing), thereby reducing the number of components while simplifying the system structure without sacrificing system functionality. Of course, depending on actual circumstances, the third lighting unit 41 can be completely separated from the first lighting unit 21 or partially separated like the second lighting unit 31. However, compared to the same optical path mode, a separate setup will occupy more system space and use more optical components, increasing system complexity and overall cost.

[0065] As an example, the sensor 421 includes a two-quadrant detector, a four-quadrant detector, or other suitable light detector. The sensor 421 is configured to receive information from the third light beam reflected from the surface of the sample S and analyze the information to adjust the focal position of the first objective lens 112, thereby achieving rapid focusing and improving measurement stability and accuracy. In one embodiment, the sensor 421 is a four-quadrant detector, which offers superior performance in position detection accuracy and focusing speed compared to other detectors.

[0066] As an example, as shown in Figure 10, the focusing unit 42 includes a third beam splitter 422, a first cylindrical mirror 423 and a second cylindrical mirror 424 arranged in sequence. On the propagation path of the third light beam, the third beam splitter 422 is located between the first beam splitter 111 and the first cylindrical mirror 423. On the propagation path of the first light beam, the third beam splitter 422 is located between the first beam splitter 111 and the spectrometer 221. When the third light beam is focused on the surface of the sample S through the first objective lens 112 and reflected, it is collimated by the first objective lens 112, and then the transmission direction is adjusted from vertical to horizontal through the third beam splitter 422. It is reflected and focused by the first cylindrical mirror 423 and the second cylindrical mirror 424 in sequence and then irradiated on the sensor 421 for collection. After analyzing the information data collected by the sensor 421, the focal plane position of the first objective lens 112 is adjusted to achieve fast focusing, thereby improving the focusing speed and enhancing the measurement efficiency. The role played by placing the third beam splitter 422 in the propagation path of the first light beam is similar to that played by placing the second beam splitter 313 in the propagation path of the first light beam, that is, the second light path and the sixth light path can be partially overlapped without affecting the measurement light path, thereby further increasing the system integration and reducing the complexity of the light path.

[0067] In summary, the optical measurement system of the present invention includes an optical path conversion unit, an optical measurement module, and an optical imaging module. The optical path design of the optical measurement module and the optical imaging module can effectively improve the system integration, reduce the number of optical components, and reduce the complexity of the optical path. It is easy to operate. The real-time observation of the measurement process by the optical imaging module can improve the speed and efficiency of measuring the film thickness and other optical parameters on the sample. Furthermore, by adjusting the light source of the optical measurement module and designing the objective lens and tube lens structure, wide-band measurement can be achieved without frequent switching of components, thereby improving the measurement linear range. In addition, an additional autofocus module is added to adjust the foot position of the objective lens for rapid focusing, further improving measurement stability and measurement efficiency. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has high industrial utilization value.

[0068] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. An optical measurement system, characterized in that: include: an optical path conversion unit, comprising a first beam splitter and a first objective lens, wherein the first objective lens focuses the incident light beam passing through the first beam splitter onto the sample surface and collimates the light beam reflected by the sample surface and outputs the collimated light beam; An optical measurement module includes a first lighting unit and a measuring unit, wherein a first light beam emitted by a first light source of the first lighting unit enters the light path conversion unit along a first light path, reaches a sample surface, and is reflected. The reflected first light beam passes through the light path conversion unit and reaches a spectrometer of the measuring unit along a second light path; An optical imaging module includes a second lighting unit and an imaging unit, wherein a second light beam emitted by a second light source of the second lighting unit enters the light path conversion unit along a third light path, reaches the sample surface, and is reflected. The reflected second light beam passes through the light path conversion unit and reaches the image acquisition element of the imaging unit along a fourth light path. The first optical path partially overlaps with the third optical path, and / or the second optical path partially overlaps with the fourth optical path.

2. The optical measurement system according to claim 1, wherein: The wavelength range of the light beam emitted by the first light source is 230nm-900nm, and the wavelength range of the light beam emitted by the second light source is 450nm-750nm.

3. The optical measurement system according to claim 1, wherein: The first objective lens includes a concave reflecting mirror and a convex reflecting mirror, and the concave reflecting mirror is coaxially arranged or off-axis arranged with the convex reflecting mirror. When the first light beam enters the first objective lens, the focal length of the concave surface of the concave reflecting mirror and the convex surface of the convex reflecting mirror relative to the first objective lens includes 10 mm, and the numerical aperture of the first objective lens is greater than or equal to 0.

4.

4. The optical measurement system according to claim 1, wherein: The first lighting unit also includes a first parabolic mirror, a second parabolic mirror, and a third parabolic mirror sequentially arranged between the first light source and the first beam splitter to adjust the propagation direction of the first light beam to be collimated and converge the collimated first light beam onto the sample surface through the first objective lens to form a measurement spot.

5. The optical measurement system according to claim 4, wherein: The first lighting unit also includes a color wheel, which is located between the first parabolic mirror and the second parabolic mirror to control the light intensity of the first light beam. The color wheel includes a plurality of filters, and the transmittance of the filters includes at least one of 10%, 25% and 50%.

6. The optical measurement system according to claim 4, wherein: The first lighting unit further includes an aperture stop having an adjustable aperture, and the aperture stop is located between the second parabolic mirror and the third parabolic mirror to adjust the size of the measurement light spot.

7. The optical measurement system according to claim 4, wherein: The second lighting unit also includes a first collimator and a second beam splitter. The second beam splitter is located between the first collimator and the first beam splitter on the propagation path of the second light beam. The second beam splitter is also located between the third parabolic mirror and the first beam splitter on the propagation path of the first light beam.

8. The optical measurement system according to claim 1, wherein: The measuring unit also includes a first tube lens, a first pinhole mirror and a first relay lens arranged in sequence. After the first light beam is reflected by the sample surface, it passes through the first tube lens, the hole on the first pinhole mirror and the first relay lens in sequence to reach the spectrometer.

9. The optical measurement system according to claim 8, wherein: The first tube lens includes a first element, a second element, and a third element that are separately arranged in sequence, wherein the material of the first element includes calcium fluoride, the material of the second element includes fused quartz, the material of the third element includes calcium fluoride, the focal length of the first tube lens includes 100 mm, and the numerical aperture of the first tube lens includes 0.

04.

10. The optical measurement system according to claim 8, wherein: The imaging unit also includes a second tube lens, a second pinhole lens and a second relay lens arranged in sequence. After the second light beam is reflected by the sample surface, it passes through the second tube lens, a side of the second pinhole lens facing the second tube lens and the second relay lens in sequence to reach the image acquisition element.

11. The optical measurement system according to claim 10, wherein: The second tube lens and the first tube lens share the same tube lens, and / or the second pinhole mirror and the first pinhole mirror share the same pinhole mirror.

12. The optical measurement system according to claim 10, wherein: The optical imaging module also includes a second objective lens, a reflector and a switching device. The switching device is connected to the first objective lens and the second objective lens respectively to switch the objective lenses. The magnification of the first objective lens is greater than that of the second objective lens.

13. The optical measurement system according to claim 1, wherein: The optical measurement system also includes an autofocus module, which includes a third lighting unit and a focusing unit. A third light beam emitted by a third light source of the third lighting unit enters the optical path conversion unit along a fifth optical path, reaches the sample surface, and is reflected. The reflected third light beam passes through the optical path conversion unit and reaches the sensor of the focusing unit along a sixth optical path.

14. The optical measurement system according to claim 13, wherein: The fifth optical path partially overlaps with the first optical path and / or the third optical path, and / or the sixth optical path partially overlaps with the second optical path and / or the fourth optical path.

15. The optical measurement system according to claim 13, wherein: The third lighting unit is identical to the first lighting unit so that the first light path and the second light path completely overlap.

16. The optical measurement system according to claim 13, wherein: The focusing unit includes a third beam splitter, a first cylindrical mirror and a second cylindrical mirror arranged in sequence. On the propagation path of the third light beam, the third beam splitter is located between the first beam splitter and the first cylindrical mirror. On the propagation path of the first light beam, the third beam splitter is located between the first beam splitter and the spectrometer.

Images