Film thickness measuring device

Abstract

The utility model relates to a film thickness measuring device, which comprises an objective table, a lens assembly, a signal light laser, a reference light laser, an optical fiber circulator and a detection assembly, and is characterized in that the objective table is provided with a bearing surface for placing a to-be-measured film sample, the lens assembly is arranged towards the bearing surface, and the signal light laser is used for emitting signal pulse light; the reference light laser is used for emitting reference pulse light with the repetition frequency different from that of the signal pulse light, the optical fiber circulator is provided with a first port, a second port and a third port which are sequentially arranged, the first port is communicated with the signal light laser, the second port is communicated with the lens assembly, and the third port is used for outputting echo pulse light from the second port; the detection assembly is provided with a first incident end communicated with the reference light laser and a second incident end communicated with the third port. The thin film thickness measuring device has the advantages of being high in precision, large in measuring range and capable of measuring multiple thin films at the same time, and can be applied to large-scale mass production projects.

Description

TECHNICAL FIELD

[0001] The utility model relates to thin film thickness measurement technical field, in particular to a thin film thickness measuring device. BACKGROUND

[0002] In the semiconductor manufacturing industry, the deviation of thin film thickness will affect the performance index of the product, and the measurement of thin film thickness is a key step in the development of the product. At present, there are the following schemes or devices for measuring thin film thickness: 1, ellipsometer; 2, monochrome confocal microscope; 3, color confocal; 4, infrared interferometer. However, the above methods or devices have certain limitations: the measurement speed of ellipsometer and monochrome confocal microscope is slow, and it is difficult to apply to large-scale production projects; color confocal scanning measurement speed is fast, but generally only single-layer thin film thickness can be measured, and it is difficult to measure multi-layer thin film thickness; infrared interferometer can only measure single-layer thin film thickness, and cannot measure thin films with close thickness at different positions, and cannot obtain the position information of the thin film. SUMMARY

[0003] Based on the existing thin film thickness measurement equipment, it is necessary to provide a thin film thickness measurement device considering the measurement accuracy, measurement range, measurement speed and the demand of measuring multi-layer thin film thickness at the same time.

[0004] A thin film thickness measurement device comprises:

[0005] A stage having a bearing surface for placing a thin film sample to be measured;

[0006] A lens assembly arranged towards the bearing surface;

[0007] A signal light laser for emitting signal pulse light;

[0008] A reference light laser for emitting reference pulse light with a different repetition frequency from the signal pulse light;

[0009] A fiber optic circulator having a first port, a second port and a third port arranged in sequence; the first port is connected to the signal light laser for receiving the signal pulse light emitted by the signal light laser; the second port is connected to the lens assembly for outputting the signal pulse light to the lens assembly to project onto the thin film sample to be measured, and receiving the echo pulse light reflected by the thin film sample to be measured; the third port is used for outputting the echo pulse light from the second port; and

[0010] A detection assembly having a first incident end connected to the reference light laser and a second incident end connected to the third port, the detection assembly being used for receiving the reference pulse light and the echo pulse light to measure the thickness of the thin film sample to be measured.

[0011] In this way, under the premise that the refractive index of the multilayer film of the to-be-measured film sample is known, the thickness of the multilayer film of the to-be-measured film sample is measured by using the double-optical-comb time-of-flight ranging principle, the measurement precision is greatly improved, the measurement range is expanded, and the measurement of the multilayer film can be realized at the same time, thereby facilitating the test project applied to large-scale production.

[0012] In one of the embodiments, the detection assembly comprises a data processor, a first photodetector and a second photodetector electrically connected to the data processor respectively, and a fiber coupler providing the first incident end and the second incident end;

[0013] The fiber coupler further has a first exit end connected to the first photodetector and a second exit end connected to the second photodetector.

[0014] In this way, the two photodetectors and the fiber coupler are combined into a balanced detector to measure the cross-correlation signal of the echo pulse light and the reference pulse light, and the sensitivity and anti-interference ability of the detection assembly are improved.

[0015] In one of the embodiments, the detection assembly comprises:

[0016] a data processor;

[0017] a third photodetector electrically connected to the data processor and having a receiving surface;

[0018] a sum-frequency component located at the receiving surface; and

[0019] an optical path folding assembly having a first incident surface facing the third port, a second incident surface facing the reference light laser, and an exit surface facing the sum-frequency component.

[0020] In this way, the number of photodetectors is reduced by introducing the sum-frequency component, the measurement error caused by the noise of the photodetector is reduced, the assembly is simplified, and the reliability of the entire film thickness measurement device is improved.

[0021] In one of the embodiments, the optical path folding assembly comprises:

[0022] a polarization beam splitter having a light splitting surface, the first incident surface being provided and the second incident surface and the exit surface being oppositely arranged on two sides of the incident surface, the light splitting surface being used to transmit first linearly polarized light toward the exit surface and reflect second linearly polarized light perpendicular to the polarization direction of the first linearly polarized light, and the exit surface being arranged toward the third photodetector;

[0023] a first half-wave plate located between the first incident surface and the reference light laser and used for converting the reference pulse light into the first linearly polarized light; and

[0024] a second half-wave plate located between the second incident surface and the fiber-optic circulator and used for converting the signal pulse light into the second linearly polarized light.

[0025] In this way, not only is the optical path folded and the volume of the detection assembly and even the film thickness measuring device reduced, but also the stray light in the polarization beam splitter is reduced as much as possible through selective absorption and transmission of the light by the light splitting surface, the first half-wave plate and the second half-wave plate.

[0026] In one of the embodiments, the detection assembly further comprises a filter located between the sum-frequency component and the third photodetector.

[0027] In this way, selective filtering of the light signal after sum-frequency mixing helps to improve the quality of the sum-frequency signal and reduce the processing pressure of the data processor.

[0028] In one of the embodiments, the object table comprises a fixed seat, a movable seat movably mounted on the fixed seat and providing the carrying surface, and a driving component drivingly connected to the movable seat.

[0029] In this way, the movable seat of the object table can be moved to move the film sample to be measured, so as to obtain the regional thickness distribution of the film sample to be measured.

[0030] In one of the embodiments, the film thickness measuring device further comprises a galvanometer mounted in the signal light laser.

[0031] In this way, the signal light laser also has a scanning function, which facilitates the acquisition of the regional film thickness information of the film sample to be measured, and the measurement speed is faster, and the film thickness measuring device can be applied to testing projects in large-scale production.

[0032] In one of the embodiments, the difference between the repetition frequency of the signal light laser and the repetition frequency of the reference light laser ranges from greater than or equal to 5 kHz to less than or equal to 100 kHz.

[0033] In this way, the requirement for the difference in repetition frequency can be met, and the working bandwidth of the existing photodetector will not be exceeded, which facilitates procurement and helps to reduce production costs.

[0034] In one of the embodiments, the working wavelength of the signal pulse light ranges from greater than or equal to 1000 nm to less than or equal to 1600 nm, and the working wavelength of the reference pulse light ranges from greater than or equal to 1000 nm to less than or equal to 1600 nm.

[0035] In this way, the light in the range is infrared light, and the low energy of the infrared light is beneficial to protect the photosensitive materials such as ultraviolet exposure etching resist, optical curing glue, and can also be adapted to measure the film thickness of the sample coated with a visible light band antireflection film.

[0036] In one of the embodiments, the measurement accuracy of the detection assembly is sub-micron.

[0037] In this way, the measurement accuracy of the measurement assembly is sub-micron. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 A schematic diagram of a film thickness measurement device in a first embodiment provided by the present application is shown in the figure.

[0039] Figure 2 A schematic diagram of a cross-correlation signal of the echo pulse light and the reference pulse light is shown in the figure.

[0040] Figure 3 A schematic diagram of a film thickness measurement device in a second embodiment provided by the present application is shown in the figure.

[0041] REFERENCE NUMERALS:

[0042] 10, stage; 20, lens assembly; 30, signal light laser; 40, reference light laser; 50, fiber optic circulator; 51, first port; 52, second port; 53, third port; 60, detection assembly; 61, first photodetector; 62, second photodetector; 63, third photodetector; 64, fiber coupler; 641, first incident end; 642, second incident end; 643, first exit end; 644, second exit end; 65, optical path folding assembly; 651, polarization beam splitter; 652, first half-wave plate; 653, second half-wave plate; 66, nonlinear crystal; 67, filter; 68, data processor; 70, film sample to be measured. DETAILED DESCRIPTION

[0043] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the drawings. In the following description, many specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the present application, therefore the present application is not limited to the specific embodiments disclosed below.

[0044] In the description of the utility model, it is understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like is the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the device or element indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the utility model.

[0045] In addition, the terms "first" and "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first" and "second" can explicitly or implicitly include at least one of the features. In the description of the utility model, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0046] In the utility model, unless otherwise specifically defined and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship of two elements, unless otherwise specifically limited. For ordinary skilled in the art, the specific meaning of the above terms in the utility model can be understood according to the specific circumstances.

[0047] In the utility model, unless otherwise specifically defined and limited, the first feature "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "above", "above" and "above" of the second feature can be that the first feature is directly above or obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" of the second feature can be that the first feature is directly below or obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0048] It is to be understood that when an element as a preamble is referred to as being "on" or "disposed on" another element, it can be directly on the other element or intervening elements can also be present. When an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements can also be present. As used herein the terms "vertical", "horizontal", "up", "down", "left", "right", and the like as well as the like are used for explanation only and not to limit the embodiments.

[0049] In the semiconductor manufacturing industry, the deviation of the thin film thickness will affect the performance index of the product, and the measurement of the thin film thickness is a key step in the development of the product. At present, there are the following schemes or devices for measuring the thin film thickness: 1, ellipsometer; 2, monochrome confocal microscope; 3, color confocal; 4, infrared interferometer. However, the above methods or devices have certain limitations: the measurement speed of the ellipsometer and the monochrome confocal microscope is slow, and it is difficult to quickly measure large-area products, and it is difficult to apply to large-scale production projects; the color confocal scanning measurement speed is fast, but generally only the thickness of a single layer of thin film can be measured, and it is difficult to measure the thickness of multiple layers of thin film; the infrared interferometer can generally only measure the thickness of a single layer of thin film, and cannot measure the thin film with close thickness at different positions, and cannot obtain the position information of the thin film.

[0050] Therefore, it is necessary to provide a thin film thickness measurement device with high measurement accuracy, high efficiency, large range and the ability to meet the demand of measuring the thickness of multiple layers of thin film at the same time.

[0051] Please refer to Figure 1 , Figure 1The utility model discloses a structure schematic drawing of the film thickness measuring device in first embodiment. The film thickness measuring device provided in the application includes object table 10, lens assembly 20, signal light laser 30, reference light laser 40, optical fiber ring 50 and detection assembly 60. Specifically, the object table 10 has a bearing surface for placing the film sample 70 to be measured, the lens assembly 20 is arranged towards the bearing surface, the signal light laser 30 is used for emitting signal pulse light, the reference light laser 40 is used for emitting reference pulse light with different repetition frequency from the signal pulse light, the optical fiber ring 50 has first port 51, second port 52 and third port 53 arranged in sequence, the first port 51 is communicated with the signal light laser 30 and is used for receiving the signal pulse light emitted by the signal light laser 30, the second port 52 is communicated with the lens assembly 20, on one hand, the second port 52 is used for outputting the signal pulse light to the lens assembly 20 to project to the film sample 70 to be measured, on the other hand, the second port 52 is also used for receiving echo pulse light reflected back through the film sample 70 to be measured, and the third port 53 is used for outputting the echo pulse light from the second port 52. The detection assembly 60 has first incidence end 641 communicated with the reference light laser 40 and second incidence end 642 communicated with the third port 53, and the detection assembly 60 is used for receiving the reference pulse light and the echo pulse light to measure the thickness of the film sample 70 to be measured.

[0052] The application is based on the principle of time-of-flight ranging, and the incident light is reflected at the film-air interface and the film-film interface. The arrival time of the reflection signal at the film-air interface is recorded as t0, and the arrival time of the reflection signal at the film-film interface is recorded as t1, t2, …, tn. The arrival time of the reflection signal at the film-air interface is recorded as t0, and the arrival time of the reflection signal at the film-film interface is recorded as t1, t2, …, tn. i Then the film thickness is given by the following formula:

[0053]

[0054] Wherein, c is the speed of light in vacuum, n i is the refractive index of the film.

[0055] The time-of-flight ranging based on double optical comb will have higher ranging accuracy, and the principle is as follows: due to the difference in repetition frequency, the sample reflection light pulse and the reference light pulse periodically overlap and misalign in the time domain, and an autocorrelation interference signal is generated in each measurement period (T=1 / Δf r ). Then the measurable time domain information period is amplified f r / Δf r . The film thickness formula based on double optical comb is:

[0056]

[0057] Wherein, (T i -T i-1) is the time delay of the cross-correlation interference signal. The refractive index of each layer of the thin film needs to be known in advance in order to accurately measure the thickness of each layer of the thin film.

[0058] The measurement range is given by the following formula:

[0059]

[0060] Based on the above-mentioned dual-optical comb time-of-flight ranging principle and the measuring device provided in the present application, when actually measuring the thickness of the thin film, as long as the thin film sample 70 to be measured is placed on the object table 10, the thickness of each layer of the thin film can be obtained according to the refractive index data of the multi-layer thin film. The device has at least the following advantages:

[0061] Firstly, the measurement accuracy of the device is relatively high. Since the device has a large measurable time domain information period, the identification of the optical signal by the same photoelectric detector is more accurate, thereby improving the measurement accuracy. Through actual measurement, the measurement accuracy of the device can reach the sub-micron level, which is comparable to the accuracy of the confocal microscope and the infrared interferometer;

[0062] Secondly, the measurement range of the device is relatively large. Taking the working bandwidth of the photoelectric detector as 200MHz for example, the measurement range of the device is 0.75m, reaching the meter level, which can cover the size of the thin film sample 70 to be measured of a larger size, and greatly improves the range compared to the existing ellipsometer, confocal microscope, white light interferometer, etc.

[0063] Thirdly, the single-point measurement time is in the order of milliseconds, which is significantly better than the ellipsometer and the confocal microscope, and is comparable to the color confocal microscope and the interferometer, and can be applied to testing projects in large-scale production.

[0064] Finally, the thickness information of all the thin films of the measured sample can be obtained by a single measurement of the device, without the need for model fitting correction, and the test data is intuitive and visible, which facilitates the observation of the operator.

[0065] Since the control of the accuracy of the device is mainly the repetition frequency difference of the signal light laser 30 and the reference light laser 40, and not dependent on the signal pulse light and the reference pulse light itself. Thus, in an embodiment provided in the present application, the thin film thickness measuring device uses infrared light with a larger wavelength, specifically, the wavelength of the infrared light ranges from 1000nm to 1600nm. Since the energy of the infrared light is relatively low, it is beneficial to protect the ultraviolet exposure resist, optical curing glue and other photosensitive materials, and at the same time, it can also be adapted to measure the thickness of the thin film in the sample coated with a visible light band antireflection film.

[0066] Optionally, in an embodiment provided by the present application, the difference between the repetition frequency of the signal light laser 30 and the repetition frequency of the reference light laser 40 ranges from 5 kHz to 100 kHz. This can meet the requirement of the difference between the repetition frequencies, and will not exceed the working bandwidth of the existing photoelectric detector, which is convenient for purchase and helps to reduce the production cost.

[0067] Optionally, in an embodiment provided by the present application, the measurement accuracy of the detection assembly 60 is sub-micron, which can meet the current accuracy requirement for film measurement, and also takes into account the measurement efficiency to meet the need for batch testing in large-scale production. Specifically, the measurement accuracy, i.e. the degree of deviation of the measurement result from the true value, for the film thickness measurement device involved in the present application, the sources of measurement uncertainty mainly include 1, the jitter σ (Δτ) of the measured pulse time; 2, the jitter σ (Δf) of the difference between the repetition frequencies of the signal light laser and the reference light laser. With the increase of the integration time, i.e. the increase of the sampling times, the measurement uncertainty caused by the jitter of the measured pulse time and the jitter of the difference between the repetition frequencies will decrease, and the measurement accuracy, the jitter of the pulse time and the jitter of the difference between the repetition frequencies satisfy the following formula:

[0068]

[0069] In the formula, c is the speed of light in vacuum, and n is the refractive index. Generally, the jitter of the measured pulse time is 100 ps, and the jitter of the difference between the repetition frequencies is 0.1 Hz. For example, taking the refractive index as 1.5, the difference between the repetition frequencies as 20 kHz, the repetition frequency as 100 MHz, the integration time Dwell Time as 1 ms, and Δτ as the photon flight time of 0.5 m interval, the measurement accuracy of the thickness can be calculated as 0.4 microns.

[0070] Optionally, in an embodiment provided by the present application, the object table 10 includes a fixed seat, a movable seat movably mounted on the fixed seat and providing a bearing surface, and a driving member drivingly connected to the movable seat. Thus, by moving the movable seat of the object table 10, the measured film sample 70 can be moved, so as to obtain the area thickness distribution of the measured film sample 70.

[0071] Optionally, in another embodiment provided by the present application, the film thickness measurement device includes a galvanometer mirror mounted in the signal light laser 30. Thus, the signal light laser also has a scanning function, which facilitates obtaining the area film thickness information of the measured film sample 70, and the measurement speed is faster, and the film thickness measurement device can be applied to testing items in large-scale production.

[0072] Optionally, in another embodiment provided by the present application, the lens assembly 20 preferably adopts a focusing lens group to reduce the diameter of the light spot projected onto the measured film sample 70, so as to improve the scanning resolution.

[0073] Please see Figure 1 and Figure 2 , Figure 2 This is a schematic diagram of the cross-correlation signal between the echo pulse light and the reference pulse light. Optionally, in the first embodiment, the detection component 60 of the thin film thickness measuring device includes a data processor 68, a first photodetector 61 and a second photodetector 62 electrically connected to the data processor 68, and an optical fiber coupler providing a first incident end 641 and a second incident end 642. The optical fiber coupler also has a first exit end 643 connected to the first photodetector 61 and a second exit end 644 connected to the second photodetector 62. In this way, the two photodetectors and the optical fiber coupler constitute a balanced detector, and measuring the cross-correlation signal between the echo pulse light and the reference pulse light is also beneficial to improving the sensitivity and anti-interference capability of the detection component 60. For example, the signal pulse light emitted by the signal laser 30 enters the fiber optic circulator 50 from the first port 51 and exits from the second port 52, reaching the lens assembly 20. After the signal pulse light projected by the lens assembly 20 reaches the thin film sample 70 under test, it is reflected and forms an echo pulse light. This echo pulse light passes through the lens assembly 20 again and enters the fiber optic circulator 50, then enters the fiber coupler from the third port 53 and the second incident end 642. The echo pulse light and the reference pulse light will superimpose and interfere in the fiber coupler, and enter the first photodetector 61 and the second photodetector 62 from the first exit end 643 and the second exit end 644, respectively. The two photodetectors convert the optical signal into an electrical signal and input it into the data processor 68. The measurement result obtained after digitization and filtering in the data processor 68 is as follows: Figure 2 As shown, Figure 2 The horizontal axis represents the time axis, and the vertical axis represents the interference amplitude of the cross-correlated signals. The distance between two identical peaks in the figure is one time-domain information period T = 1 / Δf. r The peak signal in each time-domain information period corresponds to a multilayer thin film.

[0074] Please see Figure 3 , Figure 3A schematic diagram of a thin film thickness measurement device according to a second embodiment of the present application is provided. In the thin film thickness measurement device, the detection assembly 60 comprises a data processor 68, a third photodetector 63 electrically connected to the data processor 68 and having a receiving surface, a sum-frequency component located on the receiving surface, and a light path folding assembly 65 having a first incident surface facing the third port 53, a second incident surface facing the reference light laser 40, and an exit surface facing the sum-frequency component. By introducing the sum-frequency component, the number of photodetectors is reduced, the assembly is simplified, the measurement error caused by the noise of the photodetectors is reduced, and the reliability of the entire thin film thickness measurement device is improved. Further, the light path folding assembly 65 comprises a polarization beam splitter 651 having a beam splitting surface, the first incident surface, and the second incident surface and the exit surface oppositely arranged on two sides of the first incident surface, the beam splitting surface being configured to transmit first linearly polarized light toward the exit surface and reflect second linearly polarized light perpendicular to the polarization direction of the first linearly polarized light, and the exit surface being arranged toward the third photodetector 63; a first half-wave plate 652 located between the first incident surface and the reference light laser 40 and configured to convert the reference pulse light into the first linearly polarized light; and a second half-wave plate 653 located between the second incident surface and the fiber loop 50 and configured to convert the signal pulse light into the second linearly polarized light. Specifically, the reference pulse light emitted by the reference light laser 40 will pass through the first half-wave plate 652 and the beam splitting surface of the polarization beam splitter 651 in sequence and reach the nonlinear crystal 66, and the echo pulse light emitted from the third port 53 will pass through the second half-wave plate 653 and reach the nonlinear crystal 66 after being reflected by the beam splitting surface of the polarization beam splitter 651. In this way, not only is the light path folded and the volume of the detection assembly 60 and the thin film thickness measurement device reduced, but also the stray light in the polarization beam splitter 651 is reduced as much as possible by selectively absorbing and transmitting the light by the beam splitting surface, the first half-wave plate 652, and the second half-wave plate 653. Optionally, in an embodiment of the present application, the first half-wave plate 652 and the second half-wave plate 653 are both half-wave plates. Further, the detection assembly 60 further comprises a filter 67 located between the sum-frequency component and the third photodetector 63, the filter 67 being a low-pass filter 67 with a passband cutoff wavelength of 1000 nm and configured to block the reference pulse light and the echo pulse light reflected by the sample. The measurement result processed by the detection assembly 60 is shown in FIG. 6. Figure 2

[0075] Optionally, in an embodiment of the present application, the sum-frequency component is a nonlinear crystal 66, which can be but is not limited to a PPKTP crystal and a barium borate crystal (BBO).

[0076] ​For example, in one embodiment provided by the present application, the repetition frequency of the signal light laser 30 is 100 MHz, the wavelength of the emitted signal pulse light is 1550 nm, the repetition frequency of the reference light laser 40 is 99.98 MHz, the wavelength of the emitted reference pulse light is 1550 nm, and thus the difference between the repetition frequencies is 20 kHz, and thus the time domain signal period is amplified by 5000 times. In the first embodiment, the working wavelength band of the first photoelectric detector 61 and the second photoelectric detector 62 is 1550 nm, and the working bandwidth is 200 MHz. In the second embodiment, the working wavelength band of the third photoelectric detector 63 is 1550 nm, the working bandwidth is 200 MHz, the wavelength of the sum frequency signal of the nonlinear crystal 66 is 775 nm, and the passband cutoff wavelength of the filter 67 is 1000 nm.

[0077] The technical features of the above embodiments can be combined in any manner. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described, but it should be understood that any combination of the technical features is within the scope of the present application as long as the combination does not result in a contradiction.

[0078] The above embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the present application. It should be noted that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A thin film thickness measuring device characterized by comprising: The film thickness measuring device comprises: a stage having a bearing surface for placing a film sample to be measured; a lens assembly arranged towards the bearing surface; a signal light laser for emitting signal pulse light; a reference light laser for emitting reference pulse light having a different repetition frequency than the signal pulse light; a fiber-optic circulator having a first port, a second port and a third port arranged in sequence; the first port is connected to the signal light laser for receiving the signal pulse light emitted by the signal light laser; the second port is connected to the lens assembly for outputting the signal pulse light to the lens assembly to project onto the film sample to be measured and receiving echo pulse light reflected by the film sample to be measured; and the third port is used for outputting the echo pulse light from the second port; a detection assembly having a first incident end connected to the reference light laser and a second incident end connected to the third port, the detection assembly being used for receiving the reference pulse light and the echo pulse light to measure the thickness of the film sample to be measured. The detection assembly comprises a data processor, a first photodetector and a second photodetector electrically connected to the data processor, and a fiber-optic coupler providing the first incident end and the second incident end; 2. The thin film thickness measurement device of claim 1, wherein the fiber-optic coupler further has a first exit end connected to the first photodetector and a second exit end connected to the second photodetector. The detection assembly comprises:

3. The thin film thickness measurement device of claim 1, wherein a data processor; a third photodetector electrically connected to the data processor and having a receiving surface; a summing element located at the receiving surface; and an optical path folding assembly having a first incident surface towards the third port, a second incident surface towards the reference light laser, and an exit surface towards the summing element. The optical path folding assembly comprises:

4. The thin film thickness measurement device of claim 3, wherein a polarization beam splitter having a splitting surface, the first incident surface and the second incident surface and the exit surface being arranged on two sides of the first incident surface in opposite directions, the splitting surface being used for transmitting first linearly polarized light towards the exit surface and reflecting second linearly polarized light perpendicular to the polarization direction of the first linearly polarized light, the exit surface being arranged towards the third photodetector; a first half-wave plate located between the first incident surface and the reference light laser and used for converting the reference pulse light into the first linearly polarized light; and a second half-wave plate located between the second incident surface and the fiber-optic circulator and used for converting the signal pulse light into the second linearly polarized light. The detection assembly further comprises a filter located between the summing element and the third photodetector.

5. The thin film thickness measurement device of claim 3, wherein The stage comprises a fixed seat, a movable seat movably mounted on the fixed seat and providing the bearing surface, and a driving element drivingly connected to the movable seat.

6. The thin film thickness measuring apparatus according to any one of claims 1 to 5, characterized by The film thickness measuring device further comprises a galvanometer mounted in the signal light laser.

7. The thin film thickness measuring apparatus according to any one of claims 1 to 5, characterized by The difference between the repetition frequency of the signal light laser and the repetition frequency of the reference light laser ranges from greater than or equal to 5 kHz to less than or equal to 100 kHz.

8. The thin film thickness measuring apparatus according to any one of claims 1 to 5, characterized by ​ 9. The thin film thickness measuring apparatus according to any one of claims 1 to 5, characterized by The operating wavelength range of the signal pulse light and the operating wavelength range of the reference pulse light are respectively equal to or greater than 1000 nm and equal to or less than 1600 nm, and equal to or greater than 1000 nm and equal to or less than 1600 nm.

10. The film thickness measuring device according to any one of claims 1 to 5, characterized by The measurement accuracy of the detection assembly is in the order of sub-microns.

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