A spectral measurement system and a spectroscopic thickness measurement system

Abstract

The present invention provides a spectral measurement system and a spectral thickness measurement system. The spectral measurement system includes a light source module, a dispersion element, a detector, a stage controller, and a stage; the light source module provides incident light, the incident light irradiates a first area on the sample to generate a first interference light, the first interference light is incident on the detector through the dispersion element to generate a first coherent spectrum; the stage controller controls the stage to move the sample so that the incident light irradiates a second area on the sample to generate a second interference light, the second area and the first area partially intersect, the second interference light is incident on the detector through the dispersion element to generate a second coherent spectrum; the first coherent spectrum is compensated based on the second coherent spectrum. The spectral thickness measurement system includes the spectral measurement system, and obtains the thickness of the first area based on the spectral database and the compensated first coherent spectrum. The present invention moves the position of the sample through the stage to compensate for the spectral information on the sample missed due to the spatial resolution limitation of the detector.

Description

Technical Field

[0001] The present invention relates to the field of optical measurement, and specifically, to a spectral measurement system and a spectral thickness measurement system. Background Art

[0002] A spectral measurement system can measure the spectrum of a sample. When the spectral measurement system is used to measure the thickness of a sample, it is called a spectral thickness measurement system. The spectral thickness measurement system can obtain the thickness related to the sample according to the spectrum, and this thickness can be the film thickness on the sample or the absolute thickness of the sample. There is already a wired light source spectral thickness measurement system as Figure 1 shown. This spectral thickness measurement system mainly includes a wired light source, a beam splitter, a displacement stage (not shown), a CCD camera, a dispersion element (such as a grating or a prism), and a spectral detector (such as a CCD array spectrometer). The measurement method is as follows:

[0003] 1. The wired light source irradiates the sample through the beam splitter and the objective lens, and forms a linear acquisition line spot on the surface of the sample. The sample is, for example, a wafer, which can be a wafer without a film layer or a wafer with a film layer. As Figure 2A shown, the incident light provided by the wired light source is, for example, broadband spectral incident light in the wavelength band of 193 - 1700 nm;

[0004] 2. The light reflected on the surface of the wafer and the light that enters the wafer and is then reflected by the interface form interference light, which returns to the beam splitter and then reaches the dispersion element through the reflection slit. The light reflected by the reflection slit is reflected by a plane mirror and reaches the CCD camera, and the CCD camera can observe the surface of the sample;

[0005] 3. The polychromatic light is decomposed into beams with different reflection angles according to wavelengths by the dispersion element, and reaches the spectral detector (such as a CCD array spectrometer) after being reflected by the plane mirror;

[0006] 4. The CCD array spectrometer collects the R(λ)-λ spectra of several sampling points on the acquisition line on the surface of the wafer, and receives the coherent spectra of the several sampling points at the composite wavelength under the spatial resolution of the CCD array spectrometer. As Figure 2B shown, where R is the reflectivity, λ is the wavelength, the spectral axis is the wavelength of the polychromatic light, the spatial axis is the spatial position of the sampling point, and the reflectivity R(λ) is positively correlated with the collected light intensity;

[0007] 5. When the spectral measurement system is used to measure the thickness of a sample, the spectrum detected by the CCD array spectrometer is fitted with a spectral database (theoretical spectrum or known spectrum) to obtain the material dispersion coefficients (n(λ), k(λ)), and then the thickness of the sample sampling point is obtained by looking up a table or model matching. This thickness can be the absolute thickness of a wafer without a film layer or the film thickness of a wafer with a film layer. Here, n is the refractive index of the medium, k is the extinction coefficient, the theoretical spectrum can be obtained through spectral modeling, and the known spectrum can be obtained by measuring the spectrum of a sample with a known thickness.

[0008] The spectral measurement system has high requirements for the spatial resolution of the detector. If spectral information at some positions in the illumination area of the sample surface by the light source is missed due to the limited spatial resolution of the detector, it will result in limited spatial resolution of both the measured spectrum and the sample thickness. Summary of the Invention

[0009] The present invention provides a spectral measurement system and a spectral thickness measurement system for solving the technical problems existing in the prior art.

[0010] According to a first aspect of the present invention, a spectral measurement system is provided, including a light source module, a dispersion element, a detector, a stage controller, and a stage for placing a sample. The light source module includes a line light source or a surface light source.

[0011] The light source module provides incident light. The incident light irradiates a first area on the sample and generates first interference light after being reflected by different interfaces. The first interference light is incident on the detector through the dispersion element to generate a first coherent spectrum.

[0012] The stage controller controls the stage to move the sample so that the incident light irradiates a second area on the sample and generates second interference light after being reflected by different interfaces. The second area and the first area partially intersect. The second interference light is incident on the detector through the dispersion element to generate a second coherent spectrum.

[0013] Based on the second coherent spectrum, the first coherent spectrum is compensated to obtain a compensated first coherent spectrum, so as to improve the spatial resolution of the detector.

[0014] The spectral measurement system provided by the present invention moves the position of the sample through the stage to compensate for the spectral information on the sample missed due to the limitation of the spatial resolution of the detector, and then measures the spectrum with high spatial resolution in the first area on the sample.

[0015] According to a second aspect of the present invention, a spectral thickness measurement system is provided, including the spectral measurement system. The spectral measurement system obtains the thickness of the first area based on a spectral database and the compensated first coherent spectrum.

[0016] A spectral thickness measurement system provided by the present invention moves the position of a sample through a displacement stage to compensate for spectral information on the sample that is missed due to the spatial resolution limitation of a detector, and then measures the thickness with high spatial resolution of a first region on the sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 FIG. is a schematic structural diagram of an existing spectral measurement system;

[0018] Figure 2A FIG. is a schematic diagram of signal acquisition of an existing spectral measurement system;

[0019] Figure 2B FIG. is a schematic diagram of a spectrum collected by an existing spectral measurement system;

[0020] Figure 3 FIG. is a schematic structural diagram of a spectral measurement system provided by an embodiment of the present invention;

[0021] Figure 4 FIG. is a schematic diagram of the moving and scanning mode of the displacement stage;

[0022] Figure 5A FIG. is a schematic diagram of a spectral measurement system including a reflective grating provided by an embodiment of the present invention;

[0023] Figure 5B FIG. is a schematic diagram of a spectral measurement system including a transmissive grating provided by an embodiment of the present invention;

[0024] Figure 6 FIG. is a schematic diagram of position comparison of pixel positions on the sample surface after the displacement stage moves;

[0025] Figure 7 FIG. is a schematic diagram of two adjacent light sources among multiple light sources;

[0026] Figure 8 FIG. is a schematic structural diagram of a spectral measurement system provided by an embodiment of the present invention;

[0027] Figure 9 FIG. is a schematic structural diagram of a spectral measurement system provided by an embodiment of the present invention;

[0028] Figure 10 FIG. is a schematic structural diagram of a spectral measurement system provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention. In addition, the technical features in each embodiment or individual embodiment provided by the present invention can be combined with each other arbitrarily to form a feasible technical solution. This combination is not restricted by the order of steps and / or the structural composition mode, but must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0030] Figure 3 A spectral measurement system provided by an embodiment of the present invention generally does not require adding optical elements to the existing spectral measurement system. Instead, the position of the sample is slightly moved by a displacement stage to compensate for the spatial resolution of the detector. Even when using a detector with low spatial resolution, high-spatial-resolution spectra can be obtained. However, a detector with high spatial resolution can also be used, and similarly, spectra with even higher spatial resolution can be obtained.

[0031] In this embodiment, a detector with high spatial resolution refers to a detector whose spatial resolution meets the spectral measurement resolution required by the spectral measurement system, that is, a detector with a spatial resolution less than or equal to the required value of the spectral measurement resolution is a detector with high spatial resolution. A detector with low spatial resolution refers to a detector whose spatial resolution does not meet the spectral measurement resolution required by the spectral measurement system, that is, a detector with a spatial resolution greater than the required value of the spectral measurement resolution is a detector with low spatial resolution. For example, if the required value of the spectral measurement resolution is 1 μm, then a detector with a spatial resolution less than or equal to this value is a detector with high spatial resolution, and a detector with a spatial resolution greater than this value is a detector with low spatial resolution.

[0032] In some embodiments, since using a detector with high spatial resolution will result in higher costs, a detector with low spatial resolution is used. For a detector with low spatial resolution, due to the low spatial resolution of the detector and the omission of spectral information, the spatial resolution of the measured sample thickness will be low, that is, because the sampling points of the detector on the sample are sparse, insufficient thickness information of points on the sample cannot be obtained. However, the spectral measurement system provided by the embodiments of the present invention can improve the spatial resolution of spectral measurement that can be achieved by the existing detector. Therefore, a spatial detector with low resolution can be used, which can save costs.

[0033] In some embodiments, such as Figure 3As shown, the spectral measurement system mainly includes a light source module, a dispersive element (such as a grating or a prism), a detector, a stage controller (not shown), and a stage (not shown) for placing a sample. The light source module includes a line light source or a surface light source.

[0034] Among them, the light source module provides incident light. The incident light irradiates a first region on the sample and generates first interference light after being reflected by different interfaces. The first interference light is incident on the detector through the dispersive element to generate a first coherent spectrum. The stage controller controls the stage to move the sample so that the incident light irradiates a second region (also called a compensation region) on the sample and generates second interference light after being reflected by different interfaces. The second region and the first region partially intersect. The second interference light is incident on the detector through the dispersive element to generate a second coherent spectrum. Based on the second coherent spectrum, the first coherent spectrum is compensated to obtain the compensated first coherent spectrum as the spectrum of the first region, so as to improve the spatial resolution of the detector and be able to improve the spatial resolution of the first coherent spectrum of the first region.

[0035] In some embodiments, referring to Figure 3 , Figure 3 the spectral measurement system in also includes a beam splitter. The light source module (such as including a line light source) irradiates the sample after passing through the beam splitter and an objective lens. The sample is, for example, a wafer, which can be a wafer without a film layer or a wafer with a film layer. The stage moves to the initial acquisition position, or the initial position of the stage is used as the initial acquisition position. The initial acquisition position is the position of the stage and has a corresponding relationship with the position on the sample. The initial acquisition position is set by the user. The stage controller controls the stage according to the initial acquisition position. The light source module irradiates the first region on the sample through the beam splitter. The light reflected on the sample surface and the light reflected after entering the sample form first interference light and return to the beam splitter and then reach the dispersive element. The first interference light is polychromatic light (light with a composite wavelength). The dispersive element decomposes the polychromatic light into beams with different reflection angles according to the wavelength, and after being reflected by a plane mirror, reaches the detector. The detector detects the first coherent spectrum of the first region on the sample. By moving the sample with the stage, based on the moved acquisition position, the detector detects the second coherent spectrum again, and compensates the first coherent spectrum based on the second coherent spectrum.

[0036] In one embodiment, the second coherent spectrum is used to compensate the spectrum in the first region that is missed by the first coherent spectrum, and the rest of the second coherent spectrum is discarded to obtain the compensated first coherent spectrum.

[0037] Exemplarily, compensating the first coherent spectrum based on the second coherent spectrum includes:

[0038] Traverse each pair of adjacent sampling points on the sample corresponding to the first coherent spectrum, and determine whether there is a compensation gap between the adjacent sampling points. The spectral measurement system responds to the existence of the compensation gap to search for the spectrum corresponding to the compensation gap in the second coherent spectrum according to the position of the compensation gap, and compensates the searched spectrum to the first coherent spectrum.

[0039] In some embodiments, each collected coherent spectrum can be referenced Figure 2B , and each coherent spectrum is a three-dimensional spectrum schematically represented by a reflectivity axis - wavelength axis - spatial axis. Among them, there are multiple discrete sampling points in the illumination area of the light source on the sample. As Figure 2B shown, these sampling points are distributed on the spatial axis, and the direction of the spatial axis is, for example, the x direction in this embodiment. Each sampling point corresponds to a schematic diagram of reflectivity and wavelength. Exemplarily, if there is a compensation gap between adjacent sampling points in the first coherent spectrum, then search for the sampling point with the same coordinates in the second coherent spectrum according to the coordinates of the compensation gap. If found, add the spectrum of this sampling point in the second coherent spectrum to the first coherent spectrum to achieve spectral compensation.

[0040] In one embodiment, determining whether there is a compensation gap between adjacent sampling points includes:

[0041] Obtain adjacent pixels on the detector corresponding to the adjacent sampling points, and determine whether there is a compensation gap between the adjacent sampling points according to the pixel interval d d between the adjacent pixels and the width w d of a single pixel. Among them, if the pixel interval d d is greater than the width w d of a single pixel, it is determined that there is a compensation gap between the adjacent sampling points, and the sizes of the pixels of the detector are the same.

[0042] Refer to Figure 6 , in another embodiment, determining whether there is a compensation gap between adjacent sampling points includes:

[0043] Obtain the magnification factor between the pixels of the detector and the sampling points on the sample. According to the width w d of a single pixel and the magnification factor, obtain the regional width w of a single sampling point corresponding to a single pixel on the sample. According to the pixel interval d d and the magnification factor, obtain the sampling interval d on the sample corresponding to the adjacent sampling points. Determine whether there is a compensation gap between the adjacent sampling points according to the comparison between the sampling interval d and the regional width w. Among them, if the sampling interval d is greater than the regional width w, it is determined that there is a compensation gap between the adjacent sampling points, and the sizes of the pixels of the detector are the same.

[0044] Among them, the magnification is obtained according to the pixel distribution of the detector and the distribution of the sampling points on the sample. Exemplarily, a sampling length L can be set on the sample w , which is a preset value, and the detection length L corresponding to the sampling length L on the detector is obtained w is obtained d , then the magnification is L w / L d . Thus, it can be known that the regional width w of a single sampling point on the sample = L w / L d *w d , and the sampling interval d = L w / L d *d d .

[0045] It can be understood that reference can be made to Figure 3 , and its spectral measurement mechanism is as follows:

[0046] 1. The line light source irradiates the sample after passing through the beam splitter and the objective lens;

[0047] 2. The light reflected on the surface of the sample and the light reflected after entering the sample form interference light, which returns to the beam splitter and then reaches the dispersion element through the reflection slit. The light reflected by the reflection slit is reflected by the plane mirror and reaches the CCD camera, and the CCD camera can observe the surface of the sample such as a wafer;

[0048] 3. The composite light is decomposed into beams with different reflection angles by the dispersion element and reaches the detector after being reflected by the plane mirror;

[0049] 4. The detector collects the R(λ)-λ spectra of each collection point on the irradiation line on the surface of the sample, and receives the coherent spectra of each point on the sample under the compound wavelength with the spatial resolution of the detector. For example, the first coherent spectrum of the first region is obtained, where R is the reflectivity and λ is the wavelength;

[0050] 5. After the displacement stage moves a small distance, steps 2 to 4 above are repeated for measurement to detect the coherent spectrum again through the detector. For example, the second coherent spectrum of the second region is obtained;

[0051] 6. The coherent spectra measured after the displacement stage is moved (such as the second coherent spectrum) are compensated for the coherent spectra measured before the displacement stage is moved (such as the first coherent spectrum) according to the position order on the sample to obtain the compensated spectrum.

[0052] In some embodiments, when the spectral measurement system is used to measure the thickness of a sample, i.e., when the spectral measurement system is a spectral thickness measurement system, the compensated spectrum is fitted with a spectral database to obtain the material dispersion coefficients (n(λ), k(λ)), and the thickness of the sample, such as the absolute thickness of the sample or the film thickness of the sample, is obtained by looking up a table or model matching. The thickness can be the absolute thickness of a wafer without a film layer or the film thickness of a wafer with a film layer. Here, n is the refractive index of the medium, k is the extinction coefficient, and the spectral database is a theoretical spectrum or a known spectrum. The theoretical spectrum can be obtained through spectral modeling, and the known spectrum can be obtained by measuring the spectrum of a sample with a known thickness.

[0053] Among them, as an embodiment, both the first region and the second region are less than or equal to the maximum irradiation region of the light source module. The spectral measurement system is configured to acquire a region of interest on the sample. The region of interest includes at least one first region. The stage controller obtains multiple sets of positions of the stage. Any set of the positions includes an acquisition position and a compensation position. A first coherent spectrum is obtained at the acquisition position. The spectral measurement system responds to the stage moving to the compensation position to obtain the second coherent spectrum based on the detector, and the spectrum of the region of interest is obtained according to each set of the first coherent spectrum and the second coherent spectrum.

[0054] In this embodiment, the maximum irradiation region is the maximum region that the light source module can cover on the sample. Taking a line light source as an example, the maximum irradiation region is a rectangular region. Since the line width of the line light source is usually much smaller than the line length, the rectangular region can also be referred to as a line segment, and the maximum irradiation region is the maximum measurement line length of the line light source.

[0055] In some embodiments, the region of interest includes a plurality of (i.e., at least two) first regions. Since the size of the first region is not limited, the region of interest can be divided into a plurality of first regions. For example, the region of interest is divided into two first regions with different sizes.

[0056] In some embodiments, both the acquisition position and the compensation position are positions of the stage and are set by the user. The stage controller controls the movement of the stage according to the acquisition position and the compensation position. The acquisition position is related to the scanning path of the stage set by the user. Specifically, the acquisition position corresponds to the first region of the sample. Since the spatial resolution of the detector is limited, the first region includes a plurality of discrete points on the scanning path, and these discrete points are sampling points. In one embodiment, the scanning path of the stage can be a curve scanning path or a straight scanning path, as Figure 4 shown, the scanning path is, for example, a serpentine scanning path, a spiral scanning path, or a straight scanning path.

[0057] In some embodiments, those skilled in the art know that, as Figure 3 andFigure 4 As shown, when the stage controller controls the stage to move along a serpentine scanning path, the spectral measurement system first completes a straight-line scan in the x direction, then the stage moves a certain distance in the y direction, and the spectral measurement system then completes another straight-line scan in the x direction, and so on; as Figure 4 shown, when the stage controller controls the stage to move along a straight-line scanning path, it first completes a straight-line scan in the x direction, then changes the position of the stage, and then completes another straight-line scan in the x direction, and so on.

[0058] In some embodiments, the stage controller controls the stage to move along a serpentine scanning path. The stage controller controls the stage to move in the x direction, and the spectral measurement system performs spectral measurement in the x direction to achieve spectral compensation for the detector (which is also applicable to the compensation for the beam interval in the following text), without the need to perform spectral measurement in the y direction.

[0059] Among them, each group of positions includes an acquisition position and a compensation position. The acquisition position corresponds to the first region of the sample, and the compensation position corresponds to the second region of the sample. The spectrum of the corresponding first region can be obtained according to a group of first coherent spectra and second coherent spectra.

[0060] Exemplarily, the region to be measured includes two first regions adjacent to each other in the x direction. The spectrum of one first region is obtained according to a group of first coherent spectra and second coherent spectra, the spectrum of the other first region is obtained according to another group of first coherent spectra and second coherent spectra, and the spectrum of the region to be measured is obtained according to the spectra of the two first regions.

[0061] In this embodiment, the description that A responds to B to execute C means that A immediately executes C or A executes C after a period of time after B is executed. Among them, A is the execution subject, B is an action, C is another action, and the word "execute" can be omitted.

[0062] Among them, the type of the detector is not limited as long as it can detect spectral information. For example, it is a spectral detector, specifically a matrix spectrometer or a linear spectrometer, etc. The beam shape of the light source module is not limited, and the light source module may include a line light source or a surface light source. The type of the objective lens is not limited, and both large FOV and small FOV are acceptable.

[0063] In some embodiments, the incident manner of the incident light provided by the light source module is not limited, including but not limited to normal incidence and oblique incidence. As Figure 3 shown, it schematically shows a spectral measurement system with normal incidence. As Figure 5A and Figure 5B shown, they respectively schematically show spectral measurement systems with oblique incidence. Among them, Figure 5A the grating in Figure 5B is a reflective grating, and the grating in

[0064] In one embodiment, with reference to Figure 5A and Figure 5B , the measurement method for the oblique incidence of the line light source is as follows: the line light source is obliquely incident and focused on the wafer through a cylindrical lens (not labeled) to generate interference light. The interference light is converged into a quasi-collimated beam by an objective lens (not labeled, such as a cylindrical lens), and then decomposed into monochromatic lights with different angles due to different wavelengths by a transmissive grating or a reflective grating, and then reflected by a plane mirror to reach the detector, forming a three-dimensional spectrum formed by the reflectivity axis - wavelength axis - spatial axis (position on the sample). In one embodiment, the illumination device includes a CCD camera and illumination (i.e., the illumination light source). The illumination beam is vertically incident on the wafer, and the CCD camera collects the surface image of the wafer, which can be used to check whether there are defects on the wafer surface or whether the line light source is in focus.

[0065] As an embodiment, the stage controller moves the stage based on a preset number of movements and movement step sizes to obtain one or more of the second regions, and the number of movements is the same as the number of the second regions.

[0066] In some embodiments, after obtaining the first coherent spectrum corresponding to the first region on the sample irradiated by the light source module through the detector, the stage controller controls the stage to move the sample position to obtain one or more second regions on the sample. Among them, each time the stage controller moves the stage, one second region is obtained, so that the number of movements is the same as the number of the second regions. For each second region, the detector detects the second coherent spectrum again; the second coherent spectra detected by the detector one or more times are compensated for the first coherent spectrum to obtain the compensated first coherent spectrum.

[0067] In one embodiment, when obtaining a plurality of different second regions that respectively partially intersect with the first region, the first coherent spectrum is compensated based on the plurality of second coherent spectra corresponding to the plurality of second regions, further improving the spatial resolution of the detector.

[0068] It can be understood that when detecting the spectral information on the sample, whether it is a detector with low spatial resolution or high spatial resolution, due to the limited spatial resolution of the detector, there is an interval between the two sampling points corresponding to the two pixels of the detector on the wafer, and there is often a situation of omission resulting in spectral information, which in turn affects the spatial resolution of the wafer spectral measurement. Therefore, the embodiment of the present invention compensates the measured spectrum by moving the stage to change the relative position between the light source module and the sample, so as to improve the spatial resolution of the detector.

[0069] Taking the light source module including a line light source as an example, Figure 6It shows the position on the wafer corresponding to the first spectral information acquisition by the detector, that is, a row of sampling points on the wafer. The row of sampling points is distributed along the x-direction to form a first region. After the displacement stage moves by Δx along the x-direction, it shows the position on the wafer corresponding to the detector's re-acquisition of spectral information, that is, another row of sampling points on the wafer. The other row of sampling points is distributed along the x-direction to form a second region. Among them, Figure 6 It shows the horizontal relative positions of the two rows of sampling points on the wafer before and after the displacement stage moves. It should be noted that for the convenience of viewing, the shape of the sampling points on the wafer corresponding to the detector's two measurements of pixels is simplified to a square, and the positions on the wafer corresponding to the detector's two measurements of pixels are vertically separated to only show the horizontal relative positions.

[0070] The moving mode of the displacement stage can be equidistant measurement, that is, the moving step length of the displacement stage (each time) is equal, or it can be non-equidistant measurement, that is, the moving step length of the displacement stage each time can be unequal. Exemplarily, when it is necessary to measure the spectra of all positions on the sample, equidistant measurement is usually adopted. When it is only necessary to focus on the spectra of a certain area on the sample, non-equidistant measurement is usually adopted.

[0071] In some embodiments, the number of movements is one or more. The displacement stage controller controls the displacement stage to move according to a linear scanning path or a serpentine scanning path. The moving step length is nΔx, and:

[0072]

[0073] Among them, w is the regional width of the sampling points on the sample corresponding to a single pixel of the detector, and n is a positive integer. The direction of the width is along the distribution direction of the sampling points on the sample corresponding to the pixels of the detector.

[0074] Exemplarily, the displacement stage controller controls the displacement stage to move according to a linear scanning path or a serpentine scanning path. And when equidistant measurement is performed, the optimal number of movements of the displacement stage is That is, take the integer part of, and it is recommended that the moving step length is The actual moving step length and number of movements are not restricted. d is the sampling interval between two sampling points on the sample corresponding to two adjacent pixels of the detector. In one embodiment, it is not recommended to set Δx < 1 / 2w, because at this time the detector is oversampled. Too many measurement times will consume unnecessary measurement time, while too few measurement times will not achieve the required spectral measurement accuracy.

[0075] Among them, as an embodiment, the light source module includes a light source controller and a plurality of light sources. The plurality of light sources are arranged in a first direction. There is a light beam interval between at least a pair of adjacent light sources adjacent in the first direction, so that there is a light beam interval area on the sample. The light source controller controls the on or off of each light source, and the displacement stage controller controls the displacement stage to move in the first direction along a linear scanning path or a serpentine scanning path, so as to obtain a third coherent spectrum for compensating the light beam interval area based on the detector and the currently working light source (similarly, the first area and a part of the third area on the sample corresponding to the third coherent spectrum intersect). The first coherent spectrum is compensated based on the second coherent spectrum and the third coherent spectrum to obtain the spectrum of the first area.

[0076] In this embodiment, the first direction is a straight line direction, and the term "arrangement" can be a row or a column. Exemplarily, a plurality of light sources form a row in the first direction. For example, Figure 7 and Figure 8 as shown, a plurality of light sources form a row in the x direction, that is, a row, and the first direction is the x direction; in addition, a plurality of light sources can also form a row in the z direction, that is, a column, and the first direction is the z direction. It should be noted that the above describes that a plurality of light sources are arranged in the first direction and is introduced by taking the formation of a row as an example, but it does not exclude the case where all light sources form multiple rows, because the number of a plurality of light sources in a row is less than or equal to the number of all light sources. For example, the number of all light sources is 8, 4 light sources form a row in the x direction, and 4 light sources form another row in the x direction.

[0077] It can be understood that for Figure 3 the spectral measurement system in Figure 7 , using a plurality of individually switchable light sources as the incident light source can increase the maximum irradiation area per time. Taking a line light source as an example, the maximum measurement line length per time can be increased, and the measurement efficiency can be further improved. For example, Figure 8 as shown.

[0078] In one embodiment, there is a physical interval between two adjacent light sources; in one embodiment, the outer casings of two adjacent light sources are in contact, that is, the possibility of two adjacent light sources being in contact is not excluded. This is because a light source usually has an outer casing. Even if there is a situation where the outer casings of two adjacent light sources are in contact, there is still a light beam interval between two adjacent light sources due to the wall thickness of the outer casing.

[0079] In Figure 7 andFigure 8 In this case, there is a beam interval between each line light source. Then, there will be an omission during a single detection process of the detector, and the beam interval area on the sample cannot be detected. The method of moving the displacement stage can be used to compensate for the spatial resolution of the detector while compensating for the spectrum corresponding to the beam interval. L is the total length of a single line light source, D is the beam interval between adjacent line light sources, and the square is the simplified shape of the sampling points on the wafer corresponding to the pixels of the detector.

[0080] Among them, when compensating for the spectrum corresponding to the beam interval of the line light source, the light source controller controls all light sources to work to obtain a first coherent spectrum based on the detector. The light source controller responds to the detector obtaining the first coherent spectrum to turn off some of the light sources. The displacement stage controller responds to the light source controller turning off some of the light sources to control the displacement stage to move and obtain the third coherent spectrum based on the detector.

[0081] See Figure 8 , this spectral measurement system includes a row of light sources that can be individually switched, a beam splitter, a dispersion element, a detector (for example, a CCD array spectrometer), and a displacement stage, and a sample is placed on the displacement stage.

[0082] In some embodiments, the displacement stage moves to the initial acquisition position, or the initial position of the displacement stage is used as the initial acquisition position. All the light sources in a row are turned on, and all the light sources irradiate the sample through the beam splitter. The light reflected from the surface of the sample and the light reflected after entering the sample form interference light and return to the beam splitter and then reach the dispersion element; the dispersion element decomposes the interference light into beams with different reflection angles according to the wavelength and reaches the detector after being reflected by the mirror. The detector detects the first coherent spectrum; some of the light sources among all the light sources are turned off, and through the movement of the displacement stage, based on the moved position, the detector detects the third coherent spectrum again to compensate for the spectrum of the beam interval area on the sample corresponding to the beam interval.

[0083] Among them, the light source controller responds to the detector obtaining the first coherent spectrum to turn off an edge light source among the multiple light sources. In one embodiment, the sizes of the light sources are the same. When the beam interval D is less than or equal to the length L of a single light source along the beam interval direction, the displacement stage moves once to obtain the third coherent spectrum. When the beam interval D is greater than the length L, the displacement stage moves multiple times to obtain the third coherent spectrum once after each movement.

[0084] It is understandable that the sample is moved by controlling the displacement stage and some of the light sources among all the light sources are turned off, so as to obtain a third correlation spectrum through the detector. By turning off one of the edge light sources among all the light sources, for example, turning off the first light source or the last light source arranged in sequence along the first direction, and determining the number of times the displacement stage moves according to the magnitude relationship between the beam interval D and the length L of a single light source along the beam interval direction. For example, each time the displacement stage moves, a third coherence spectrum is obtained.

[0085] On the basis of obtaining the third coherence spectrum, the light source controller responds to the detector obtaining the third coherence spectrum to select any one of the light sources to work, and the displacement stage controller responds to the light source controller selecting any one of the light sources to work to control the displacement stage to move and obtain the second coherence spectrum based on the detector.

[0086] It is understandable that the third coherence spectrum compensates for the spectrum of the beam interval region missing in the first coherence spectrum, and the second coherence spectrum also compensates for the first coherence spectrum. When the spectral measurement system is a spectral thickness measurement system, based on the first coherence spectrum and the spectral database compensated by the third coherence spectrum and the second coherence spectrum, the thickness of the sample in the first region is obtained.

[0087] Exemplarily, first, the displacement stage is moved to compensate for the beam interval between adjacent light sources, and then the displacement stage is moved to compensate for the spatial resolution of the detector.

[0088] The specific measurement process is as follows: First, all the line light sources in a row are turned on, and the detector detects the first coherence spectrum. At this time, the first coherence spectrum detected by the detector will have omissions because there is a beam interval between adjacent light sources. Therefore, then one of the light sources is turned off. The best way is to turn off the first light source or the last light source, and the displacement stage is moved. The moving direction of the displacement stage is the first direction (such as the x direction) and moves towards the direction of the turned-off light source. For example, Figure 8 for the two line light sources in , when the first light source on the left is turned off, the displacement stage moves to the left; when the second light source on the right is turned off, the displacement stage moves to the right, and the detector detects the third coherence spectrum again. Among them, the third coherence spectrum can compensate for the spectrum missing in the first coherence spectrum due to the beam interval.

[0089] The above movement of the displacement stage only compensates for the spectrum of the beam interval region corresponding to the beam interval, and the spatial resolution of the detector can be further compensated. In an embodiment, when the displacement stage is moved to compensate for the spatial resolution of the detector, only a single line light source is turned on, which can be any one of all the light sources. The step size and the number of times the displacement stage moves have been introduced in the foregoing embodiments, and the measurement mechanism when compensating for the spatial resolution of the detector has also been introduced, and will not be repeated here.

[0090] In one embodiment, the third coherent spectrum is used to compensate for the spectrum in the first region that is missed by the first coherent spectrum, and the remaining part of the third coherent spectrum is discarded to achieve spectrum compensation.

[0091] As analyzed above, when multiple light sources are set, there is a beam interval between at least a pair of adjacent light sources, resulting in a beam interval region on the sample.

[0092] Exemplarily, compensating the first coherent spectrum based on the third coherent spectrum includes:

[0093] The spectrum measurement system searches for the spectrum corresponding to the beam interval region in the third coherent spectrum according to the position of the beam interval region, and compensates the searched spectrum to the first coherent spectrum.

[0094] Among them, the spatial distribution and size of multiple light sources are known information. Based on this, the position of the beam interval between adjacent light sources can be obtained. Combining with the position conversion relationship between multiple light sources and the corresponding irradiation regions on the sample, the position of the beam interval region on the sample corresponding to the beam interval can be known.

[0095] In one embodiment, the detector makes three detections. The third coherent spectrum compensates for the spectrum missing due to the beam interval in the first coherent spectrum, and the second coherent spectrum compensates for the spectrum missing due to the limited spatial resolution of the first coherent spectrum. When the spectrum measurement system is a spectral thickness measurement system, the material dispersion coefficients (n(λ), k(λ)) are obtained by fitting according to the compensated first coherent spectrum and the spectrum database, and then the thickness of the sample is obtained by looking up a table or model matching.

[0096] Exemplarily, based on Figure 8 the spectrum measurement system, the description of the measurement method is as follows:

[0097] 1. The multi-probe line light source irradiates the sample after passing through the beam splitter and the objective lens;

[0098] 2. The light reflected from the surface of the sample and the light reflected after entering the sample form interference light, which returns to the beam splitter and then reaches the dispersion element through the reflection slit. The light reflected by the reflection slit is reflected by the plane mirror and reaches the CCD camera, and the CCD camera can observe the surface of the sample, such as a wafer;

[0099] 3. The dispersion element decomposes the composite wavelength light into light beams with different reflection angles, which are reflected by the plane mirror to the detector;

[0100] 4. The detector collects the R(λ)-λ spectra of each point on the measurement line, and receives the coherent spectra of each point on the measurement line at the composite wavelength under the spatial resolution of the detector, that is, the first coherent spectrum is obtained;

[0101] 5. Move the displacement stage by a distance and repeat steps 1-4 to complete the measurement for compensating the spectrum in the beam interval region, so as to obtain a third coherent spectrum.

[0102] 6. Use a single line light source. Move the displacement stage back to the measurement starting point in step 1 and move a distance △x along the direction of the line light source (i.e., the direction in which the spatial resolution needs to be compensated. If it is a surface light source, similarly move along the direction in which the resolution needs to be compensated), and then repeat steps 1-4 to obtain a second coherent spectrum for compensating the spatial resolution of the detector. n is a positive integer. Here, the purpose of moving the distance is to make the spot compensate the beam interval D. For example, first move a distance L. If moving a single distance L cannot compensate the beam interval D, then move the distance L again until it can be compensated;

[0103] 7. Use the second coherent spectrum and the third coherent spectrum to compensate the first coherent spectrum to obtain the compensated first coherent spectrum.

[0104] In some embodiments, when the spectral measurement system is used to measure the thickness of a sample, that is, when the spectral measurement system is a spectral thickness measurement system, fit the compensated first coherent spectrum with a spectral database to obtain the material dispersion coefficients (n(λ), k(λ)), and then look up a table or perform model matching to obtain the thickness of the sample.

[0105] It should be noted that in this embodiment, since the total length of multiple line light sources will be greater, optical components adapted to the multi-light sources, such as a longer beam splitter and dispersion elements, etc., need to be used. The above method of moving the displacement stage can compensate the spatial resolution of the detector while compensating the beam interval of the light source, and can measure a spectrum with high spatial resolution.

[0106] As an embodiment, the detector includes a spectral detector; or the detector includes a light intensity detector and the spectral measurement system further includes a wavelength controller and a wavelength modulator. The wavelength controller is configured to change the output wavelength of the wavelength modulator, and the light intensity detector detects the light intensity corresponding to different output wavelengths to form a spectrum with discrete wavelengths according to the output wavelength and the light intensity.

[0107] Among them, as Figure 9 and Figure 10 shows a spectral measurement system with a light intensity detector as the detector. If the detector is a light intensity detector, the spectral measurement system further includes a wavelength controller and a wavelength modulator, and the wavelength modulator is used to modulate the output wavelength. Its spectral measurement method is similar to the spectral measurement method when the detector is a spectral detector, and specifically includes:

[0108] The displacement stage controller controls the displacement stage to move to the initial acquisition position, or the initial position of the displacement stage is used as the initial acquisition position. The light source module irradiates the sample through the beam splitter. The light reflected from the sample surface and the light reflected after entering the sample form interference light, which returns to the beam splitter and then reaches the wavelength modulator. The output wavelength of the wavelength modulator is changed by the wavelength controller to output quasi-monochromatic light of different wavelengths (i.e., near-monochromatic light), which reaches the dispersion element to form monochromatic light of each wavelength and reaches the light intensity detector. The light intensity detector detects the first coherent spectrum. By moving the sample position with the displacement stage, based on the moved acquisition position, the detector detects the second coherent spectrum again. Among them, the second coherent spectrum compensates the first coherent spectrum to improve the spatial resolution of the light intensity detector. For other contents, please refer to the previous embodiments and will not be elaborated here.

[0109] It can be understood that reference can be made to Figure 9 , in Figure 3 the displacement stage movement mode, the light intensity detector can be used instead of the spectral detector to further reduce costs. The advantage is that specific discrete wavelengths can be used to simplify subsequent processing, that is, only the characteristic spectral lines are viewed, such as Figure 9 . The wavelength modulator includes but is not limited to a monochromator, a filter, a multi-filter, a spatial light modulator, etc. The position of the wavelength modulator is not limited and can be at any position between the light source module and the detector; the slit after the dispersion element is optional, and can be increased or decreased and the placement position can be adjusted according to the situation. Figure 9 the wavelength modulator in Figure 10 is located before the dispersion element,

[0110] Exemplarily, taking Figure 9 as an example, the description of its measurement method is as follows:

[0111] 1. The line light source irradiates the sample through the beam splitter and the objective lens;

[0112] 2. The formed interference light passes through the beam splitter and the reflection slit to reach the wavelength modulator and only passes through the line light at a certain wavelength;

[0113] 3. The line light generates monochromatic light after passing through the dispersion element. After passing through the slit, the wavelength is further filtered and reflected by the plane mirror and then reaches the light intensity detector;

[0114] 4. The detector collects the R(λ)-λ spectra of each point on the line and receives the coherent spectra of each point on the measurement line at the composite wavelength under the spatial resolution of the detector.

[0115] Among them, the multi-wavelength light only passes through approximately single-wavelength light after passing through the wavelength modulator. The wavelength range of this light is further narrowed after passing through the rotatable dispersion element and the slit to obtain single-wavelength light, that is, monochromatic light, which is reflected by the rotatable plane mirror to the detection surface of the light intensity detector, and the light intensity distribution at a single wavelength of the line light source carrying the information of the sample (such as a wafer) is obtained. At this time, the hardware and the position of the displacement stage remain unchanged, and by adjusting the wavelength that can pass through the wavelength modulator, another wavelength can reach the rotatable dispersion element and the slit and finally reach the detector to complete the measurement at this wavelength; after repeating the wavelength adjustment, the coherent spectrum of the composite wavelength at this measurement position can be obtained.

[0116] 5. After the displacement stage moves a small distance, repeat the above steps for measurement. Among them, the moving mode of the displacement stage is the same as that of the spectral detector when moving;

[0117] 6. According to the position order on the sample, after compensating the coherent spectrum (such as the second coherent spectrum) measured after the displacement stage moves with the spectrum (such as the first coherent spectrum) measured before the displacement stage moves, the compensated spectrum is obtained.

[0118] In some embodiments, when the spectral measurement system is used to measure the thickness of a sample, that is, when the spectral measurement system is a spectral thickness measurement system, the compensated spectrum is fitted with the spectral database to obtain the material dispersion coefficients (n(λ), k(λ)), and then the thickness of the sample is obtained by looking up a table or model matching.

[0119] Among them, the type of the detector is not limited, and it can detect the light intensity information of the light. When the detection surface of the detector is dot-shaped, the plane mirror is rotated along the length direction of the line light source so that each point on the line light source at this wavelength passes through the detector in turn, so that the dot-shaped detector can still obtain the light intensity information of any point on the line.

[0120] The spectral measurement system provided by the embodiments of the present invention has the following advantages:

[0121] (1) There is no need to add additional optical elements, and the spatial resolution of the detector is compensated by a small movement of the displacement stage;

[0122] (2) When multiple light sources form a row, the displacement stage is moved to compensate the beam interval area on the sample corresponding to the beam interval between the light sources;

[0123] (3) It is applicable not only to spectral detectors but also to light intensity detectors. When using a light intensity detector, a wavelength controller and a wavelength modulator need to be added, and optionally a slit can also be added.

[0124] An embodiment of the present invention further provides a spectroscopic thickness measurement system including a spectroscopic measurement system to obtain the thickness related to a sample based on the spectroscopic measurement of the sample. The thickness can be the film thickness on the sample or the absolute thickness of the sample. As described above, when the spectroscopic measurement system is used to measure the thickness of a sample, the spectroscopic measurement system is a spectroscopic thickness measurement system, and the thickness of the first region is obtained based on the spectroscopic database and the compensated first coherent spectrum. Among them, the spectroscopic database can be a theoretical spectrum or a known spectrum.

[0125] In this embodiment, the term "absolute thickness" is used to distinguish from the term "film thickness". For a sample without a film layer, the absolute thickness of the sample is the thickness of the sample; for a sample with a film layer, the sample includes a substrate and a film layer, and the absolute thickness of the sample can be the thickness of the substrate or the sum of the thicknesses of the substrate and the film layer. The spectroscopic thickness measurement system can measure the film thickness of the film layer and / or the thickness of the substrate.

[0126] Exemplarily, when the spectroscopic thickness measurement system is used to measure the film thickness of a sample, the spectroscopic thickness measurement system is, for example, Figure 3 the spectroscopic reflectance film thickness gauge shown in the figure. The light reflected from the upper surface of the film layer by the incident light and the light reflected from the lower surface of the film layer after the incident light enters the film layer form interference light.

[0127] Exemplarily, the spectroscopic thickness measurement system is used to measure the absolute thickness of a sample. Taking a wafer as an example, those skilled in the art know that a silicon wafer has good transparency to light in the wavelength range of about 1000 nm to about 6000 nm. Therefore, by selecting a light source with a suitable wavelength range, the absolute thickness of the silicon wafer can be measured. In one embodiment, the light source is a near-infrared light source with a wavelength range of 780 to 2526 nm; in one embodiment, the light source is a near-infrared light source with a wavelength range of 1000 to 1700 nm.

[0128] Exemplarily, when the spectroscopic thickness measurement system is used to measure the absolute thickness of a sample, the spectroscopic thickness measurement system is, for example, Figure 3 the spectroscopic reflectance absolute thickness gauge shown in the figure.

[0129] Taking a wafer without a film layer as an example, the light reflected from the upper surface of the wafer by the incident light and the light reflected from the lower surface of the wafer after the incident light enters the wafer form interference light. By processing the interference light, the absolute thickness of the wafer can be obtained.

[0130] Taking a wafer with a film layer as an example, the light reflected from the upper surface of the film layer by the incident light and the light reflected from the lower surface of the film layer after the incident light enters the film layer form interference, and the light reflected from the upper surface of the substrate by the incident light and the light reflected from the lower surface of the substrate after the incident light enters the substrate also form interference. The detector collects the interference light, and the film thickness of the film layer and the absolute thickness of the substrate can be obtained by processing the interference light. Among them, the wafer includes a substrate and a film layer located on the substrate.

[0131] Since the spectroscopic thickness measurement system includes the spectroscopic measurement system in the foregoing embodiment, when the spectroscopic measurement system obtains the spectrum with high spatial resolution of the first region on the sample, the spectroscopic thickness measurement system obtains the thickness with high spatial resolution of the first region on the sample.

[0132] It should be noted that in the above embodiments, the descriptions of the various embodiments have their own focuses. For the parts not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0133] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0134] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A spectral measurement system, characterized in that, It includes a light source module, a dispersion element, a detector, a stage controller, and a stage for placing a sample. The light source module includes a line light source or a surface light source; The light source module provides incident light. The incident light irradiates a first area on the sample, and after being reflected by different interfaces, first interference light is generated. The first interference light is incident on the detector through the dispersion element to generate a first coherent spectrum; The stage controller controls the stage to move the sample so that the incident light irradiates a second area on the sample, and after being reflected by different interfaces, second interference light is generated. The second area and the first area partially intersect. The second interference light is incident on the detector through the dispersion element to generate a second coherent spectrum; Based on the second coherent spectrum, the first coherent spectrum is compensated to obtain a compensated first coherent spectrum, so as to improve the spatial resolution of the detector.

2. The spectral measurement system according to claim 1, characterized in that, Both the first area and the second area are less than or equal to the maximum irradiation area of the light source module.

3. The spectral measurement system according to claim 1, wherein, The stage controller moves the stage based on a preset number of movements and movement steps to obtain one or more of the second areas, and the number of movements is the same as the number of the second areas.

4. The spectral measurement system according to claim 3, wherein The displacement stage controller controls the displacement stage to move along a linear scanning path or a serpentine scanning path, and the moving step size is n , and: ； Wherein, w is the width of the area on the sample corresponding to a single pixel of the detector, and n is a positive integer.

5. The spectral measurement system according to claim 1, characterized in that, The light source module includes a light source controller and multiple light sources. The multiple light sources are arranged along a first direction, and there is a light beam interval between at least a pair of adjacent light sources so that there is a light beam interval area on the sample. The light source controller controls the on or off of each light source. The stage controller controls the stage to move along the first direction according to a linear scanning path or a serpentine scanning path, so as to obtain a third coherent spectrum for compensating the light beam interval area based on the detector and the currently working light source. Based on the second coherent spectrum and the third coherent spectrum, the first coherent spectrum is compensated to obtain the spectrum of the first area.

6. The spectral measurement system according to claim 5, wherein The light source controller controls all the light sources to work to obtain a first coherent spectrum based on the detector. The light source controller responds to the detector obtaining the first coherent spectrum to turn off some of the light sources. The stage controller responds to the light source controller turning off some of the light sources to control the stage to move and obtain the third coherent spectrum based on the detector.

7. The spectral measurement system according to claim 6, wherein The light source controller responds to the detector obtaining the third coherent spectrum to select any one of the light sources to work. The stage controller responds to the light source controller selecting any one of the light sources to work to control the stage to move and obtain the second coherent spectrum based on the detector. The light source controller responds to the detector obtaining the first coherent spectrum to turn off one edge light source among the multiple light sources. The sizes of the light sources are the same. When the light beam interval D is less than or equal to the length L of a single light source along the light beam interval direction, the stage moves once to obtain the third coherent spectrum. When the light beam interval D is greater than the length L, the stage moves multiple times to obtain the third coherent spectrum once after each movement.

8. The spectral measurement system according to claim 5, characterized in that, Compensating the first coherent spectrum based on the third coherent spectrum includes: The spectral measurement system searches for the spectrum corresponding to the beam interval region in the third coherent spectrum according to the position of the beam interval region, and compensates the searched spectrum to the first coherent spectrum.

9. The spectral measurement system according to any one of claims 1-8, characterized in that, Compensating the first coherent spectrum based on the second coherent spectrum includes: Traversing each pair of adjacent sampling points on the sample corresponding to the first coherent spectrum, and determining whether there is a compensation gap between the adjacent sampling points. The spectral measurement system responds to the existence of the compensation gap to search for the spectrum corresponding to the compensation gap in the second coherent spectrum according to the position of the compensation gap, and compensates the searched spectrum to the first coherent spectrum.

10. The spectral measurement system according to claim 9, wherein Determining whether there is a compensation gap between the adjacent sampling points includes: Obtaining adjacent pixels on the detector corresponding to the adjacent sampling points, and determining whether there is a compensation gap between the adjacent sampling points according to the comparison between the pixel interval between the adjacent pixels and the width of a single pixel. Wherein, if the pixel interval is greater than the width of a single pixel, it is determined that there is a compensation gap between the adjacent sampling points, and the sizes of the pixels of the detector are the same; Alternatively, obtaining the magnification factor between the pixels of the detector and the sampling points on the sample, obtaining the regional width of a single sampling point corresponding to a single pixel on the sample according to the width of a single pixel and the magnification factor, obtaining the sampling interval on the sample corresponding to the adjacent sampling points according to the pixel interval and the magnification factor, and determining whether there is a compensation gap between the adjacent sampling points according to the comparison between the sampling interval and the regional width. Wherein, if the sampling interval is greater than the regional width, it is determined that there is a compensation gap between the adjacent sampling points, and the sizes of the pixels of the detector are the same.

11. A spectroscopic thickness measurement system, characterized in that, Including the spectral measurement system according to any one of claims 1-10, and the spectral measurement system obtains the thickness of the first region based on the spectral database and the compensated first coherent spectrum.

Images