An online spectrophotometric difference detection system based on optical switch dual-path compensation

Abstract

This invention discloses an online spectrophotometric color difference detection system based on dual-optical-path compensation using an optical switch, comprising a main optical path, a reference optical path, a ring light source, an optical switch, a spectrometer, and a control unit. The ring light source illuminates the sample under test, the main optical path receives the reflected light from the sample, and the reference optical path receives the reference light emitted by the ring light source. The main and reference optical paths are respectively connected to two branch ports of the optical switch, and the common port of the optical switch is connected to the spectrometer. The control unit controls the two optical paths to be connected to the same spectrometer in a time-division manner. The ring light source illuminates the sample under test at an angle, and the main optical path receives the reflected light perpendicularly. This invention reduces the matching error of the dual-detection link, provides a reference for compensating for light source attenuation and system drift, and helps reduce specular reflection and stray light interference, thereby improving the stability of online color difference detection.

Description

Technical Field

[0001] This utility model belongs to the field of semiconductor optical detection technology, specifically relating to an online detection system for spectral color difference based on optical switch dual-optical-path compensation. Background Technology

[0002] Semiconductor wafers typically have oxide, nitride, polysilicon, or other dielectric thin films formed on their surfaces. Variations in film thickness and uniformity can cause changes in the reflectance spectrum and color of the wafer surface. Therefore, in semiconductor manufacturing, spectrophotometers are often used to collect the reflectance spectrum of the wafer surface and calculate color parameters and color differences based on the reflectance spectrum to determine film thickness uniformity, surface residues, and localized color spots.

[0003] Existing spectrophotometric color difference detection equipment mainly employs a single-beam detection structure or a fixed-beam dual-beam detection structure. Single-beam detection structures typically require periodic calibration using a standard white board. However, between two consecutive calibrations, factors such as light source attenuation, detector temperature drift, thermal deformation of optical components, and environmental changes can still cause spectral shifts, affecting the stability of continuous online detection. To mitigate these effects, frequent interruptions to the detection process are necessary for calibration, which is detrimental to improving production line efficiency.

[0004] Fixed-beam splitting dual-path detection structures typically utilize a beam splitter to separate the light source into sample light and reference light, which are then simultaneously acquired through two optical paths. Because the optical components, optical path lengths, and detectors used in the two optical paths are rarely perfectly identical, matching errors can easily arise after prolonged operation due to changes in the splitting ratio, component temperature drift, and differences in transmission losses. Simultaneously, the beam splitter reduces the light energy entering the sample detection path, easily weakening the detection signal. Furthermore, the wafer surface has strong specular reflection characteristics, and existing detection optical paths are also susceptible to interference from specular reflection light and ambient stray light, affecting the detection accuracy of minute color differences. Utility Model Content

[0005] To address the aforementioned issues, this invention provides an online spectrophotometric color difference detection system based on dual-optical-path compensation using an optical switch. This system enables time-division acquisition of the sample spectrum and the light source reference spectrum, sharing the same spectral detection unit, and is suitable for continuous online detection.

[0006] The technical solution provided by this utility model is as follows: An online spectrophotometric color difference detection system based on optical switch dual-optical-path compensation includes a ring light source, a main optical path, a reference optical path, an optical switch, a spectrometer, and a control unit; The ring light source is used to illuminate the sample to be tested located at the detection position. The light-incident end of the main optical path faces the detection area of ​​the sample to be tested and is used to receive the reflected light generated by the sample to be tested under the illumination of the ring light source. The light-incident end of the reference optical path faces the light-out area of ​​the ring light source and is used to receive the reference light emitted by the ring light source. The optical switch includes a first branch port, a second branch port, and a common port. The output end of the main optical path is optically connected to the first branch port, the output end of the reference optical path is optically connected to the second branch port, and the common port is optically connected to the input end of the spectrometer. The control unit is electrically connected to the optical switch and the spectrometer respectively, and is used to control the first branch port or the second branch port to selectively connect to the common port and receive the spectral data output by the spectrometer. A ring light source is arranged around the light-incident end of the main optical path. The light-out direction of the ring light source is tilted relative to the optical axis of the main optical path. The main optical path receives reflected light in a direction perpendicular to the surface of the sample to be tested.

[0007] In some implementations, the angle between the light emission direction of the ring light source and the optical axis of the main optical path is 45°, and the optical axis of the main optical path is perpendicular to the surface of the sample to be tested located at the detection position, so as to form a detection optical path with 45° illumination and 0° reception.

[0008] In some embodiments, the main optical path includes a second aperture, a second lens, a first aperture, and a first lens arranged sequentially along the propagation direction of the reflected light, wherein the first lens, the first aperture, the second lens, and the second aperture are coaxially arranged.

[0009] In some embodiments, the first aperture is disposed at the middle image plane position of the main optical path to define the receiving field of view of the main optical path; the second aperture is disposed on the side of the second lens facing the sample to be tested, and the aperture of the second aperture is adjustable to adjust the detection spot size on the surface of the sample to be tested.

[0010] In some embodiments, the ring light source includes multiple lamp panels arranged circumferentially along the main optical path, each lamp panel having multiple light-emitting elements, and the light emission direction of the multiple light-emitting elements all facing the detection area of ​​the sample to be tested.

[0011] In some embodiments, the light-incident end of the reference optical path is located inside the ring light source and faces the light-outceasing area of ​​the ring light source; the reference optical path is provided with an attenuator and a diffuser, the attenuator is used to reduce the light intensity of the reference light entering the reference optical path, and the diffuser is used to homogenize the reference light entering the reference optical path.

[0012] In some implementations, the output end of the main optical path is connected to the first branch port via a first optical fiber, the output end of the reference optical path is connected to the second branch port via a second optical fiber, and the common port is connected to the input end of the spectrometer via a third optical fiber.

[0013] In some embodiments, both the first and second optical fibers are multimode silica optical fibers, and the core diameter, numerical aperture, and operating wavelength are the same for both fibers; the core diameter of the first and second optical fibers is 200–600 μm, the numerical aperture is 0.22, and the operating wavelength covers 380–1100 nm.

[0014] In summary, the beneficial effects of this utility model are as follows: (1) This utility model enables the main optical path and the reference optical path to be connected to the same spectrometer in a time-division manner through an optical switch. The main optical path is used to collect the reflection spectrum of the sample to be tested, and the reference optical path is used to directly collect the reference spectrum of the ring light source. The two optical paths share the optical fiber and spectrometer after the optical switch, which can reduce the response differences and matching errors caused by using different detectors or different back-end optical paths, and provide stable reference data for correcting light source attenuation and system drift.

[0015] (2) The present invention adopts a detection structure with a ring light source tilted illumination and a main optical path vertical reception, so that the illumination light is tilted from the circumference of the sample to be tested to the detection area, and the main optical path collects reflected light along the normal direction of the surface of the sample to be tested, which helps to reduce the interference of specular reflection light on the wafer surface and environmental stray light, and improve the signal-to-noise ratio of thin film interference reflection spectrum acquisition and the stability of color difference detection. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the system structure of this utility model; Figure 2 This is a schematic diagram of the main optical path structure of this utility model; Figure 3 This is a schematic diagram of the ring light source and reference optical path structure.

[0017] The attached figures are labeled as follows: 1. Main optical path; 1-1. First lens; 1-2. First aperture; 1-3. Second lens; 1-4. Second aperture; 2. Reference optical path; 3. Ring light source; 3-1. Lamp board; 3-2. Light-emitting element; 4. Optical switch; 4-1. First branch port; 4-2. Second branch port; 4-3. Common port; 5. Spectrometer; 6. Sample to be tested; 7. Control unit. Detailed Implementation

[0018] To enhance understanding of this utility model, the present utility model will be further described in detail below with reference to the embodiments and accompanying drawings. These embodiments are only used to explain the present utility model and do not constitute a limitation on the scope of protection of the present utility model.

[0019] like Figures 1 to 3As shown, an online spectrophotometric color difference detection system based on dual-optical-path compensation using an optical switch includes a main optical path 1, a reference optical path 2, a ring light source 3, an optical switch 4, a spectrometer 5, and a control unit 7. The sample to be tested 6 is positioned at a predetermined detection location. The sample to be tested 6 is preferably a semiconductor wafer, such as a silicon-based wafer with an oxide layer, a nitride layer, a polycrystalline silicon layer, an atomic layer deposition film, or other dielectric films formed on its surface.

[0020] The ring light source 3 illuminates the detection area of ​​the sample 6, the main optical path 1 receives the reflected light from the sample 6 under the illumination of the ring light source 3, and the reference optical path 2 directly receives the reference light emitted by the ring light source 3. The main optical path 1 and the reference optical path 2 are respectively connected to two branch ports of the optical switch 4, and are connected to the same spectrometer 5 via the optical switch 4 in a time-division manner. Thus, the spectrometer 5 can separately acquire the reflection spectrum of the sample 6 and the reference spectrum of the ring light source 3, providing a hardware basis for online correction of light source brightness changes and spectral drift.

[0021] A ring light source 3 is arranged around the light-incident end of the main optical path 1 and around the optical axis of the main optical path 1. The light-emitting direction of the ring light source 3 is inclined relative to the optical axis of the main optical path 1, and the optical axis of the main optical path 1 extends in a direction perpendicular to the surface of the sample 6 to be tested.

[0022] In this embodiment, the angle between the light emission direction of the ring light source 3 and the optical axis of the main optical path 1 is 45°. The main optical path 1 receives the reflected light from the surface of the sample 6 under test in a 0° vertical receiving mode, thereby forming a detection optical path with 45° illumination and 0° reception. The ring light source 3 illuminates the detection area obliquely from the circumference of the sample 6 under test. The main optical path 1 mainly receives the reflected light propagating along the normal direction of the surface of the sample 6 under test, which can reduce the interference of specular reflection light and surrounding stray light on the detection results.

[0023] like Figure 3 As shown, the ring light source 3 includes multiple lamp plates 3-1 spaced circumferentially along the main optical path 1, and each lamp plate 3-1 is provided with multiple light-emitting elements 3-2. The multiple lamp plates 3-1 are evenly distributed along the circumference, and each lamp plate 3-1 is tilted towards the detection area of ​​the sample 6 to be tested, so that the light emitted by the multiple light-emitting elements 3-2 can cover the detection area of ​​the sample 6 to be tested.

[0024] The light-emitting element 3-2 can be an LED, with multiple LEDs of different wavelengths combined to form a broadband illumination source that meets the testing requirements. The ring light source 3 preferably forms a D65 standard illumination condition to facilitate color and color difference detection of the sample 6 to be tested.

[0025] In this embodiment, the ring light source 3 includes twelve lamp panels 3-1, and each lamp panel 3-1 is provided with six light-emitting elements 3-2. The specific number of lamp panels 3-1 and light-emitting elements 3-2 can be adjusted according to the size of the sample 6 to be tested, the size of the detection spot, the illumination intensity, and the illumination uniformity requirements, and is not limited to the above-mentioned number.

[0026] like Figure 2 As shown, the main optical path 1 includes, in sequence, a second aperture 1-4, a second lens 1-3, a first aperture 1-2, and a first lens 1-1 along the propagation direction of the reflected light from the sample 6 under test. The first lens 1-1, the first aperture 1-2, the second lens 1-3, and the second aperture 1-4 are coaxially arranged along the optical axis of the main optical path 1.

[0027] The reflected light generated on the surface of the sample 6 under test first passes through the second aperture 1-4, then sequentially through the second lens 1-3, the first aperture 1-2, and the first lens 1-1, and is output from the light-emitting end of the main optical path 1. The first lens 1-1 and the second lens 1-3 together constitute the optical acquisition system of the main optical path 1, which is used to collect the reflected light from the surface of the sample 6 under test and couple the collected reflected light into the optical fiber connected to the main optical path 1.

[0028] The first aperture 1-2 is positioned at the middle image plane of the main optical path 1 and serves as a field stop. The first aperture 1-2 is used to define the receiving field of view of the main optical path 1, so that the main optical path 1 mainly receives the reflected light within the predetermined detection area of ​​the sample 6 under test, and shields the reflected light and stray light outside the detection area, thereby reducing the measurement error caused by positional shift and vertical jitter of the sample 6 under test during transportation or testing.

[0029] The second aperture 1-4 is positioned on the side of the second lens 1-3 facing the sample 6 to be tested. The aperture of the second aperture 1-4 is adjustable. By adjusting the aperture of the second aperture 1-4, the detection area and detection spot size corresponding to the main optical path 1 can be changed to adapt to different sizes of the test area.

[0030] The main optical path 1 can be installed entirely within a metal lens barrel. The first lens 1-1, the first aperture 1-2, the second lens 1-3, and the second aperture 1-4 are all fixed within the metal lens barrel. The metal lens barrel can support and position the optical components within the main optical path 1, while also reducing the possibility of ambient light entering the main optical path 1 and improving the signal-to-noise ratio of the reflected spectrum.

[0031] The reference optical path 2 is located inside the ring light source 3, with its input end facing the output area of ​​the ring light source 3. The reference optical path 2 is used to directly receive the reference light emitted by the ring light source 3. This reference light does not pass through the surface of the sample 6 under test, and therefore can reflect the light intensity and spectral distribution of the ring light source 3 under its current operating state.

[0032] The light-incident end of the reference optical path 2 can be positioned towards the light-emitting surface of one of the lamp boards 3-1, or towards the mixed light-emitting area formed by multiple lamp boards 3-1. The reference optical path 2 and the ring light source 3 maintain a fixed relative position to reduce the fluctuation of reference light intensity caused by changes in the position of the reference optical path 2 during equipment operation.

[0033] The reference optical path 2 is equipped with an attenuator and a diffuser. The attenuator is used to reduce the intensity of the reference light entering the reference optical path 2, so that the intensity of the reference light is within a range that matches the intensity of the reflected light collected by the main optical path 1, and to prevent the spectrometer 5 from becoming too saturated due to excessively high reference light intensity.

[0034] The diffuser is used to scatter and homogenize the reference light entering the reference light path 2, reducing the influence of the light output direction of a single light-emitting element 3-2, local brightness differences, and installation deviation of the lamp board 3-1 on the reference spectrum acquisition results, so that the reference spectrum acquired by the reference light path 2 can more accurately reflect the overall spectral state of the ring light source 3.

[0035] The attenuator and diffuser can be arranged sequentially along the propagation direction of the reference light, or they can be integrated and installed at the light input end of the reference optical path 2. Depending on the light intensity of the ring light source 3 and the detection range of the spectrometer 5, attenuators with different transmittances can be replaced.

[0036] like Figure 1 As shown, optical switch 4 is a 1-to-2 optical switch, including a first branch port 4-1, a second branch port 4-2, and a common port 4-3. The output end of the main optical path 1 is connected to the first branch port 4-1 via a first optical fiber, the output end of the reference optical path 2 is connected to the second branch port 4-2 via a second optical fiber, and the common port 4-3 is connected to the input end of the spectrometer 5 via a third optical fiber.

[0037] The first and second optical fibers are preferably multimode silica fibers of the same specifications, so that the main optical path 1 and the reference optical path 2 have similar transmission loss characteristics in the optical fiber transmission stage. In this embodiment, the core diameter of the first and second optical fibers is 200-600 μm, the numerical aperture is 0.22, and the operating wavelength covers 380-1100 nm. The third optical fiber can also be a multimode silica fiber to transmit the optical signal output from the optical switch 4 to the spectrometer 5.

[0038] Under the control of the control unit 7, the optical switch 4 can selectively connect either the first branch port 4-1 or the second branch port 4-2 to the common port 4-3. When the first branch port 4-1 is connected to the common port 4-3, the main optical path 1 is connected to the spectrometer 5; when the second branch port 4-2 is connected to the common port 4-3, the reference optical path 2 is connected to the spectrometer 5.

[0039] Optical switch 4 activates only one branch port at a time, allowing the main optical path 1 and reference optical path 2 to be connected to the spectrometer 5 in a time-division multiplexing manner according to a predetermined timing sequence. Since the main optical path 1 and reference optical path 2 share the third optical fiber after optical switch 4 and the spectrometer 5, it can reduce the response differences and temperature drift differences caused by using different spectrometers or different back-end detection links.

[0040] The spectrometer 5 is used to receive the optical signal output by the optical switch 4 and convert the optical signal into corresponding spectral data. The spectrometer 5 can detect the visible light band, and can also be extended to the near-infrared band according to the thin film material of the sample 6 and the detection requirements.

[0041] The control unit 7 can be a host computer, an industrial computer, an embedded controller, or other devices with control and data processing functions. The control unit 7 is electrically connected to the optical switch 4 and the spectrometer 5, respectively, and is used to send switching signals to the optical switch 4 and receive spectral data output by the spectrometer 5.

[0042] When the system is working, the sample 6 to be tested is transported to the detection position corresponding to the ring light source 3 and the main optical path 1. The ring light source 3 is lit and emits illumination light to the detection area of ​​the sample 6. The thin film on the surface of the sample 6 is reflected by the illumination light.

[0043] During sample measurement, the control unit 7 controls the optical switch 4 to connect the first branch port 4-1 with the common port 4-3. The reflected light from the surface of the sample 6 is collected by the main optical path 1 and enters the spectrometer 5 through the first optical fiber, the first branch port 4-1, the common port 4-3, and the third optical fiber. The spectrometer 5 then collects the spectral data of the sample 6.

[0044] When it is necessary to acquire the reference spectrum of the ring light source 3, the control unit 7 controls the optical switch 4 to switch, so that the second branch port 4-2 is connected to the common port 4-3. The light emitted by the ring light source 3 directly enters the reference optical path 2, and after the light intensity is attenuated by the attenuator and homogenized by the diffuser, it enters the same spectrometer 5 through the second optical fiber, the second branch port 4-2, the common port 4-3 and the third optical fiber, and the spectrometer 5 acquires the reference spectral data.

[0045] After the reference spectrum acquisition is completed, the control unit 7 controls the optical switch 4 to reconnect the main optical path 1, restoring the system to the sample measurement state. The acquisition of the reference spectrum can be performed during the interval between the replacement of two adjacent samples 6, or it can be performed according to a preset time period to reduce the impact of the reference spectrum acquisition process on the online detection efficiency.

[0046] The control unit 7 corrects the light intensity variation and spectral drift of the ring light source 3 based on the sample spectral data and reference spectral data output by the spectrometer 5, and obtains the color parameters and color difference results of the sample 6 to be tested based on the corrected sample spectral data. The control unit 7 can convert the sample spectral data into tristimulus values, and further convert them into L*, a*, and b color parameters in the CIE Lab color space. By comparing the obtained color parameters with preset standard color parameters, the color difference of the sample 6 to be tested is obtained.

[0047] The reflected light from the sample 6 under test and the reference light from the ring light source 3 are collected by the main optical path 1 and the reference optical path 2 respectively. The two optical paths are connected to the same spectrometer 5 in a time-division manner by the optical switch 4. The current spectral state of the ring light source 3 can be periodically obtained without interrupting the online detection process of the sample 6 under test. This provides a structural basis for reducing the impact of light source attenuation, ambient temperature changes and detector link drift on the color difference detection results.

[0048] It should be noted that implementations not shown or described in the accompanying drawings or the main text of the specification are all forms known to those skilled in the art and are not described in detail. Furthermore, the definitions of the elements and methods described above are not limited to the various specific structures, shapes, or methods mentioned in the embodiments.

[0049] It should also be noted that this document may provide examples of parameters containing specific values, but these parameters need not be exactly equal to the corresponding values, but can approximate the corresponding values ​​within acceptable error tolerances or design constraints. Directional terms mentioned in the embodiments, such as "up," "down," "front," "back," "left," "right," "inner," and "outer," are only for reference to the directions in the accompanying drawings and are not intended to limit the scope of protection of this application.

[0050] The foregoing description illustrates and describes preferred embodiments of the present invention. As previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or related technical or knowledge. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A spectrophotometric color difference online detection system based on optical switch dual-optical-path compensation, characterized in that, It includes a ring light source (3), a main optical path (1), a reference optical path (2), an optical switch (4), a spectrometer (5), and a control unit (7); The ring light source (3) is used to illuminate the sample (6) to be tested located at the detection position. The light-incident end of the main optical path (1) faces the detection area of ​​the sample (6) to receive the reflected light generated by the sample (6) under the illumination of the ring light source (3). The light-incident end of the reference optical path (2) faces the light-out area of ​​the ring light source (3) to receive the reference light emitted by the ring light source (3). The optical switch (4) includes a first branch port (4-1), a second branch port (4-2), and a common port (4-3). The light-emitting end of the main optical path (1) is optically connected to the first branch port (4-1), the light-emitting end of the reference optical path (2) is optically connected to the second branch port (4-2), and the common port (4-3) is optically connected to the light-input end of the spectrometer (5). The control unit (7) is electrically connected to the optical switch (4) and the spectrometer (5) respectively, and is used to control the first branch port (4-1) or the second branch port (4-2) to selectively connect to the common port (4-3) and receive the spectral data output by the spectrometer (5); The ring light source (3) is arranged around the light-incident end of the main optical path (1). The light-out direction of the ring light source (3) is inclined relative to the optical axis of the main optical path (1). The main optical path (1) receives the reflected light in a direction perpendicular to the surface of the sample to be tested (6).

2. The online spectrophotometric color difference detection system based on optical switch dual-path compensation according to claim 1, characterized in that, The angle between the light emission direction of the ring light source (3) and the optical axis of the main optical path (1) is 45°. The optical axis of the main optical path (1) is perpendicular to the surface of the sample (6) to be tested located at the detection position, so as to form a detection optical path with 45° illumination and 0° reception.

3. The online spectrophotometric color difference detection system based on optical switch dual-path compensation according to claim 1, characterized in that, The main optical path (1) includes a second aperture (1-4), a second lens (1-3), a first aperture (1-2), and a first lens (1-1) arranged sequentially along the propagation direction of the reflected light. The first lens (1-1), the first aperture (1-2), the second lens (1-3), and the second aperture (1-4) are arranged coaxially.

4. The online spectrophotometric color difference detection system based on optical switch dual-optical-path compensation according to claim 3, characterized in that, The first aperture (1-2) is located at the middle image plane of the main optical path (1) to define the receiving field of view of the main optical path (1); the second aperture (1-4) is located on the side of the second lens (1-3) facing the sample to be tested (6), and the aperture of the second aperture (1-4) is adjustable to adjust the detection spot size on the surface of the sample to be tested (6).

5. The online spectrophotometric color difference detection system based on dual-optical-path compensation using an optical switch according to claim 1, characterized in that, The ring light source (3) includes multiple lamp plates (3-1) arranged circumferentially along the main light path (1). Each lamp plate (3-1) is provided with multiple light-emitting elements (3-2), and the light emission direction of the multiple light-emitting elements (3-2) is towards the detection area of ​​the sample to be tested (6).

6. The online spectrophotometric color difference detection system based on optical switch dual-path compensation according to claim 1, characterized in that, The light-incident end of the reference optical path (2) is located inside the ring light source (3) and faces the light-out area of ​​the ring light source (3); the reference optical path (2) is provided with an attenuator and a diffuser. The attenuator is used to reduce the light intensity of the reference light entering the reference optical path (2), and the diffuser is used to homogenize the reference light entering the reference optical path (2).

7. The online spectrophotometric color difference detection system based on optical switch dual-path compensation according to claim 1, characterized in that, The output end of the main optical path (1) is connected to the first branch port (4-1) through the first optical fiber, the output end of the reference optical path (2) is connected to the second branch port (4-2) through the second optical fiber, and the common port (4-3) is connected to the input end of the spectrometer (5) through the third optical fiber.

8. The online spectrophotometric color difference detection system based on optical switch dual-optical-path compensation according to claim 7, characterized in that, Both the first optical fiber and the second optical fiber are multimode silica optical fibers, and the core diameter, numerical aperture and operating wavelength are the same for the first optical fiber and the second optical fiber. The core diameter of the first optical fiber and the second optical fiber is 200-600 μm, the numerical aperture is 0.22, and the operating wavelength covers 380-1100 nm.

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