A signal correction method, optical detection device and storage medium

Abstract

The application discloses a signal correction method, an optical detection device and a storage medium. The method comprises the following steps: acquiring a to-be-detected signal; performing first transformation on the to-be-detected signal to obtain a corresponding signal frequency phase relationship; performing phase compensation on the signal frequency phase relationship according to a preset frequency phase error relationship to obtain a compensated signal; performing second transformation on the compensated signal to obtain a corrected signal; the first transformation and the second transformation are inverse transformations of each other; wherein the frequency phase error relationship is configured as a deviation between a first frequency phase relationship of a reference signal and a second frequency phase relationship obtained by linear fitting. The scheme can perform phase compensation on the to-be-detected signal by using the preconfigured frequency phase error relationship, thereby correcting phase errors caused by optical parameter asymmetry in the detection device, improving the accuracy of the defocus amount detected by the optical detection device, and being beneficial to quickly and accurately focusing the sample.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of signal correction, and particularly relates to a signal correction method, an optical detection device, and a storage medium. BACKGROUND

[0002] When a wafer is detected using an optical detection device, it is necessary to ensure that the wafer is on the front focal plane of the objective lens, so it is necessary to detect the defocus amount between the wafer and the objective lens in real time during the detection process and dynamically adjust the relative distance between the two based on the defocus amount to ensure that the wafer is always on the front focal plane of the objective lens. This process can be referred to as focusing. The defocus amount can be understood as the offset of the position of the wafer relative to the front focal plane of the objective lens.

[0003] A linnik-type interferometer (hereinafter referred to as an interferometer) is a commonly used device for detecting the defocus amount between a wafer and an objective lens. Its working principle is to obtain the defocus amount between the wafer and the objective lens through the interference phenomenon of reflected light in two light paths (referred to as measurement light path and reference light path, respectively).

[0004] The problem with the current interferometer is that due to the influence of factors such as optical parameter asymmetry of the two light paths, the first interference signal measured by the interferometer is distorted. This distortion leads to inaccurate defocus amount detected by the interferometer, which in turn affects the adjustment of the relative distance, resulting in inaccurate focusing of the wafer. SUMMARY

[0005] To this end, the present application discloses the following technical solutions to improve the accuracy of the defocus amount of the sample and the objective lens detected by the optical detection device.

[0006] The first aspect of the present application provides a signal correction method, comprising:

[0007] obtaining a to-be-detected signal;

[0008] performing a first transformation on the to-be-detected signal to obtain a corresponding signal frequency phase relationship;

[0009] performing phase compensation on the signal frequency phase relationship according to a preset frequency phase error relationship to obtain a compensated signal;

[0010] performing a second transformation on the compensated signal to obtain a corrected signal; the first transformation and the second transformation are inverse transformations of each other;

[0011] wherein the frequency phase error relationship is configured as the deviation between the first frequency phase relationship of the reference signal and the second frequency phase relationship obtained by linear fitting.

[0012] Optionally, the phase compensation on the signal frequency phase relationship according to the preset frequency phase error relationship to obtain a compensated signal comprises:

[0013] obtaining the phase corresponding to each frequency point of the to-be-tested signal according to the signal frequency phase relationship;

[0014] obtaining the phase error corresponding to each frequency point according to the frequency phase error relationship;

[0015] adding the phase corresponding to each frequency point of the to-be-tested signal and the phase error corresponding to each frequency point to perform phase compensation, and obtaining the compensation signal of the to-be-tested signal.

[0016] Optionally, the configuration process of the frequency phase error relationship comprises:

[0017] obtaining a reference signal;

[0018] performing first transformation on the reference signal to obtain a first frequency phase relationship of the reference signal;

[0019] performing linear fitting on the first frequency phase relationship to obtain a second frequency phase relationship;

[0020] generating the frequency phase error relationship according to the deviation of each frequency point between the first frequency phase relationship and the second frequency phase relationship.

[0021] Optionally, the first transformation on the reference signal to obtain the first frequency phase relationship of the reference signal comprises:

[0022] performing Fourier transformation on the reference signal to obtain a frequency phase curve and a frequency amplitude curve of the reference signal;

[0023] determining the first frequency phase relationship of the reference signal according to the frequency phase curve and the frequency amplitude curve.

[0024] Optionally, the determination of the first frequency phase relationship of the reference signal according to the frequency phase curve and the frequency amplitude curve comprises:

[0025] identifying an amplitude peak value in the frequency amplitude curve;

[0026] determining a target frequency band in the frequency amplitude curve according to the amplitude peak value, the target frequency band comprising a frequency point corresponding to the amplitude peak value;

[0027] determining a curve segment in the frequency phase curve within the target frequency band as the first frequency phase relationship of the reference signal.

[0028] Optionally, the determination of the target frequency band in the frequency amplitude curve according to the amplitude peak value comprises:

[0029] determining a target amplitude value according to the amplitude peak value, the target amplitude value and the amplitude peak value having a preset proportional relationship;

[0030] determining a first frequency point and a second frequency point corresponding to the target amplitude value in the frequency-amplitude curve;

[0031] determining a target frequency band between the first frequency point and the second frequency point.

[0032] Optionally, the generating the frequency phase error relationship according to the deviation of each frequency point between the first frequency phase relationship and the second frequency phase relationship comprises:

[0033] for each frequency point of the first frequency phase relationship, calculating a difference value between a phase value of the frequency point and a corresponding phase value of the frequency point in the second frequency phase relationship to obtain a corresponding phase error of the frequency point;

[0034] statistically generating the frequency phase error relationship according to the phase errors corresponding to all frequency points in the first frequency phase relationship.

[0035] Optionally, the obtaining the to-be-tested signal comprises:

[0036] obtaining detection information of the to-be-tested sample by optical detection;

[0037] processing the detection information of the to-be-tested sample to obtain the to-be-tested signal; the to-be-tested signal is used to represent a fluctuation relationship between a signal amplitude and an off-focus amount of the to-be-tested sample relative to an optical focal plane.

[0038] Optionally, after the correction signal is obtained, the method further comprises:

[0039] identifying a wave peak of the correction signal;

[0040] determining the off-focus amount of the to-be-tested sample according to the wave peak of the correction signal;

[0041] adjusting a position of the to-be-tested sample according to the off-focus amount until the optical focal plane is reached.

[0042] The second aspect of the present application provides an optical detection device, comprising:

[0043] an illumination module, a detection table, a detection module and a processing module;

[0044] the illumination module is used to irradiate a to-be-tested sample placed on the detection table;

[0045] the detection module is used to obtain detection information of the to-be-tested sample;

[0046] The processing module is configured to perform the signal correction method according to any one of claims 1 to 9 based on the detection information of the test sample.

[0047] Optionally, the processing module comprises:

[0048] a obtaining unit configured to process the image of the test sample to obtain the to-be-tested signal;

[0049] a first transformation unit configured to perform first transformation on the to-be-tested signal to obtain a corresponding signal frequency phase relationship;

[0050] a compensation unit configured to perform phase compensation on the signal frequency phase relationship according to a preset frequency phase error relationship to obtain a compensated signal;

[0051] a second transformation unit configured to perform second transformation on the compensated signal to obtain a corrected signal; the first transformation and the second transformation are inverse transformations of each other;

[0052] The frequency phase error relationship is configured as a deviation between a first frequency phase relationship of a reference signal and a second frequency phase relationship obtained by linear fitting.

[0053] Optionally, the compensation unit performs phase compensation on the signal frequency phase relationship according to the preset frequency phase error relationship, and specifically includes:

[0054] obtaining a corresponding phase of the to-be-tested signal at each frequency point according to the signal frequency phase relationship;

[0055] obtaining a corresponding phase error of each frequency point according to the frequency phase error relationship;

[0056] adding the corresponding phase of the to-be-tested signal at each frequency point and the corresponding phase error of each frequency point to perform phase compensation to obtain a compensated signal of the to-be-tested signal.

[0057] Optionally, the processing module further comprises a configuration unit configured to:

[0058] obtain a reference signal;

[0059] perform first transformation on the reference signal to obtain a first frequency phase relationship of the reference signal;

[0060] perform linear fitting on the first frequency phase relationship to obtain a second frequency phase relationship;

[0061] generate the frequency phase error relationship according to a deviation of each frequency point between the first frequency phase relationship and the second frequency phase relationship.

[0062] Optionally, when the configuration unit performs first transformation on the reference signal to obtain the first frequency phase relationship of the reference signal, the configuration unit is specifically configured to:

[0063] performing Fourier transformation on the reference signal to obtain a frequency phase curve and a frequency amplitude curve of the reference signal;

[0064] determining the first frequency phase relationship of the reference signal according to the frequency phase curve and the frequency amplitude curve.

[0065] Optionally, the detection module comprises a reference objective lens, a measurement objective lens, a mirror, a beam splitter and a detection component.

[0066] The beam splitter is located on an optical path of the illumination beam generated by the illumination module, and is configured to split the illumination beam into a first beam and a second beam.

[0067] The measurement objective lens is located on an optical path of the first beam, and the first beam reaches the sample under test on the detection table after passing through the measurement objective lens and generates first signal light transmitted in the reverse direction.

[0068] The reference objective lens is located on an optical path of the second beam, and the second beam reaches the mirror after passing through the reference objective lens and generates second signal light transmitted in the reverse direction. The first signal light and the second signal light are configured to interfere with each other at the beam splitter and generate corresponding interference beams.

[0069] The detection component is located on an optical path of the interference beams, and is configured to acquire the detection beams and generate detection information of the sample under test.

[0070] The third aspect of the present application provides a computer storage medium for storing a computer program, and the computer program is executed to specifically implement the signal correction method provided in any one of the first aspect of the present application.

[0071] The present application has the following beneficial effects:

[0072] After obtaining the to-be-tested signal, the to-be-tested signal is phase compensated by using the pre-configured frequency phase error relationship, so as to correct the phase error caused by the optical parameter asymmetry in the detection device, improve the accuracy of the out-of-focus amount detected by the optical detection device, and facilitate fast and accurate focusing of the sample. BRIEF DESCRIPTION OF DRAWINGS

[0073] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below only illustrate some of the embodiments of the present application, and not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor should be within the scope of protection of the present application.

[0074] Figure 1 is a structural schematic diagram of an optical detection device provided by an embodiment of the present application;

[0075] Figure 2 is a flowchart of a method for configuring a frequency phase error relationship provided by an embodiment of the present application;

[0076] Figure 3 is a schematic diagram of an ideal white light interference signal and a measured white light interference signal provided by an embodiment of the present application;

[0077] Figure 4 is a schematic diagram of a frequency phase curve and a frequency amplitude curve of an ideal white light interference signal provided by an embodiment of the present application;

[0078] Figure 5 is a schematic diagram of a first frequency phase relationship and a second frequency phase relationship provided by an embodiment of the present application;

[0079] Figure 6 is a schematic diagram of a frequency phase error curve provided by an embodiment of the present application;

[0080] Figure 7 is a flowchart of a method for correcting a signal provided by an embodiment of the present application;

[0081] Figure 8 is a schematic diagram of a to-be-measured signal and a correction signal of a wafer without patterns provided by an embodiment of the present application;

[0082] Figure 9 is a schematic diagram of a to-be-measured signal and a correction signal of a wafer with patterns provided by an embodiment of the present application;

[0083] Figure 10 is a structural schematic diagram of an optical detection device provided by an embodiment of the present application. DETAILED DESCRIPTION

[0084] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, and not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor should be within the scope of protection of the present application.

[0085] The signal correction method provided by the embodiments of the present application can be applied to an optical detection device for adjusting the defocus amount of a sample relative to an objective lens according to a to-be-measured signal of the sample. For example, the method can be applied to a linnik type interferometer measurement system. Please refer to Figure 1 FIG. 1 is a structural schematic diagram of a linnik type interferometer measurement system.

[0086] The interferometer can include a light source 11, a beam splitter 12, a measurement objective lens 13, a reference objective lens 15, a mirror 16, and a detection component 17. Further, Figure 1 FIG. 1 also shows a to-be-detected sample 14 detected by the interferometer. The to-be-detected sample 14 can be a wafer, a chip, a mask, a glass screen, or the like.

[0087] The light source 11 can be a white light source with a wide spectrum characteristic. The generated illumination light is split into two beams by the beam splitter 12, and enters the measurement objective lens 13 in the measurement light path and the reference objective lens 15 in the reference light path, respectively. The light beam emitted by the measurement objective lens 13 returns to the beam splitter 12 via the to-be-detected sample 14. The light beam emitted by the reference objective lens 15 returns to the beam splitter 12 via the mirror 16. The two reflected light beams interfere with each other. The interference light beam is collected by the detection component 17 to obtain an interference image. Then, the detection component 17 processes the interference image to generate an interference signal of the sample.

[0088] Of course, the interferometer also includes an illumination lens group, an imaging lens group, a camera, and other optical components. These optical components are not shown in the simple structural schematic diagram of FIG. 1. Figure 1

[0089] The detection component can be a camera or a photoelectric sensor. It can be understood that the former generates an image, and the latter generates a photoelectric signal. Both the image and the photoelectric signal can be considered as detection information.

[0090] As introduced in the background section, Figure 1 In the device shown in the background section, the optical parameters of the two light paths are not symmetrical. Specifically, the optical parameters of the measurement objective lens 13 and the reference objective lens 15 are not completely equal. The optical parameters include, but are not limited to, objective lens chromatic aberration, transmittance, and the like.

[0091] Due to the asymmetry of the optical parameters, the zero-phase position of the objective lens will be offset after the interference of different wavelengths in the white light. Therefore, the finally measured wide-spectrum interference superposition signal (i.e., the interference signal of the sample) is often not an ideal white light interference signal, which leads to a certain deviation in the defocus amount determined according to the measured interference signal.

[0092] In order to at least solve the above problems, the embodiments of the present application provide a method for configuring a frequency phase error relationship. Please refer to Figure 2 ​For the flowchart of the method, the method can include the following steps.

[0093] S201, obtaining a reference signal by using a target optical detection device to be calibrated.

[0094] The execution subject of the method of the embodiment can be a processor with corresponding data processing capability, which can be a processor built in the target optical detection device, or a processor of other electronic device in communication connection with the target optical detection device.

[0095] The target optical detection device of the embodiment can be Figure 1 the interferometer shown in the figure, or other types of optical detection devices.

[0096] When the target optical detection device is the above-mentioned interferometer, the reference signal can be a first interference signal of the first sample detected by the interferometer; when the target optical detection device is other optical device, the reference signal can also be any one of a reflected light signal, a scattered light signal, and a diffracted light signal of the first sample.

[0097] Optionally, the implementation of step S201 can include:

[0098] Obtaining a target image of the first sample by using a detection component of the target optical detection device to be calibrated;

[0099] Processing the target image to obtain the reference signal of the first sample.

[0100] Taking the target optical detection device being the above-mentioned interferometer as an example, in step S201, the first sample can be installed in the interferometer first, then the light source 11 is started to form interference light of the first sample through the working principle of the aforementioned interferometer, then the formed interference light is photographed by using the detection component of the interferometer, the obtained image is the target image of the first sample, and then the target image is processed to obtain the first interference signal of the first sample.

[0101] The specific way of processing the target image to obtain the first interference signal can be referred to technical documents in related fields, and will not be described here.

[0102] According to different target optical detection devices to be detected, the first sample used can be different. For example, when the target optical detection device is an interferometer, the first sample can be a wafer without etched patterns, also known as a bare wafer, or the first sample can be a part of area on any wafer without etched patterns, in which case, the first interference signal detected by the target optical detection device can be a signal as shown in the figure. Figure 3

[0103] Figure 3 ​(1) represents an ideal first interference signal obtained when the interferometer detects a bare wafer, wherein the abscissa is the defocus amount (which can be expressed in microns), the ordinate is the signal amplitude (which can be expressed in voltage units), the defocus amount refers to the distance between the current position of the wafer and the front focal plane of the measurement objective, and the signal amplitude refers to the fluctuation intensity of the signal.

[0104] Ideally, the two optical paths of the interferometer are completely symmetrical, i.e., the optical parameters of the measurement objective and the reference objective are completely identical. As can be seen, under the ideal condition, the maximum value of the signal amplitude corresponds to the front focal plane.

[0105] Ideally, the two optical paths of the interferometer are completely symmetrical, i.e., the optical parameters of the measurement objective and the reference objective are completely identical. As can be seen, under the ideal condition, the maximum value of the signal amplitude corresponds to the front focal plane. Figure 3 As can be seen, under the actual condition, due to the asymmetry of the optical parameters of the measurement objective and the reference objective, the maximum value of the interference signal corresponds to a shifted position, i.e., the maximum value of the signal amplitude does not correspond to the front focal plane of the measurement objective, which leads to that the defocus amount detected according to the interference signal is not the real defocus amount, i.e., the so-called focus deviation.

[0106] S202, performing a first transformation on the reference signal to obtain a first frequency-phase relationship of the reference signal.

[0107] Optionally, the implementation of S202 can be:

[0108] performing Fourier transform (i.e., FFT transform) on the reference signal to obtain a frequency-phase curve and a frequency-amplitude curve of the reference signal; and determining the first frequency-phase relationship of the reference signal according to the frequency-phase curve and the frequency-amplitude curve.

[0109] The specific process of performing Fourier transform on the reference signal to obtain the frequency-phase curve and the frequency-amplitude curve can be referred to related technical documents, and will not be described herein.

[0110] Fourier transform is only one optional way to obtain the frequency-phase curve and the frequency-amplitude curve in this embodiment, and in other optional embodiments, the detection device can also obtain the above curves by processing the reference signal through other signal processing methods.

[0111] The advantage of obtaining the frequency-phase curve and the frequency-amplitude curve through Fourier transform is that, compared with other processing methods, Fourier transform is a relatively mature and simple signal processing method, and the above curves can be obtained through this method with high efficiency.

[0112] The advantage of obtaining the frequency-phase curve and the frequency-amplitude curve through Fourier transform is that, compared with other processing methods, Fourier transform is a relatively mature and simple signal processing method, and the above curves can be obtained through this method with high efficiency.

[0113] Exemplarily, in the scenario of detecting a bare wafer by an interferometer, according to the interference signal of the bare wafer, a frequency-phase curve and a frequency-amplitude curve as shown in the following figure can be obtained in an ideal case. Figure 4

[0114] In the above curves, the frequency can be in units of hertz, and the phase can be in units of radians.

[0115] In an ideal case, the zero phases of all the wave bands are completely aligned, and thus the signals of the reference light path and the measurement light path can be superimposed to obtain an ideal white light interference signal. At this time, the phases of all the frequency components of the interference signal are linearly distributed, in other words, the relationship between the phase and the frequency in the interference signal of the bare wafer in an ideal case is a linear relationship.

[0116] In contrast, in a real case, due to the problem of optical parameter asymmetry, the relationship between the phase and the frequency of the interference signal deviates from the linear relationship, and the embodiment can determine the phase error by using the degree of deviation of the relationship between the phase and the frequency from the linear relationship.

[0117] The manner of determining the first frequency-phase relationship of the reference signal according to the frequency-phase curve and the frequency-amplitude curve can include:

[0118] A1, identifying an amplitude peak value in the frequency-amplitude curve.

[0119] A2, determining a target frequency band in the frequency-amplitude curve according to the amplitude peak value, the target frequency band including a frequency point corresponding to the amplitude peak value.

[0120] A3, determining a curve segment in the frequency-amplitude curve located in the target frequency band as the first frequency-phase relationship of the reference signal.

[0121] In step A1, the processor can compare the amplitudes corresponding to each frequency point in the frequency-amplitude curve one by one, so as to screen out the maximum value, that is, the amplitude peak value,

[0122] In step A2, the processor can first determine a target amplitude value according to the amplitude peak value, the target amplitude value and the amplitude peak value having a preset proportional relationship.

[0123] The amplitude peak value is calculated to obtain the target amplitude value. An optional calculation manner is to multiply the amplitude peak value by a preset coefficient to obtain a result as the target amplitude value. The coefficient is a positive number less than 1, and its specific value can be set as needed without limitation.

[0124] Exemplarily, the coefficient is set to 0.2, and the amplitude peak value is 100, so that the determined target amplitude value can be 20.

[0125] ​Subsequently, the processor can determine the first frequency point and the second frequency point corresponding to the target amplitude value in the frequency-amplitude curve.

[0126] For example, the processor can determine the first frequency point P1 and the second frequency point P2 corresponding to the target amplitude value in the frequency-amplitude curve after obtaining the target amplitude value. Figure 4

[0127] Finally, the processor can determine the frequency band between the first frequency point and the second frequency point as the target frequency band.

[0128] In combination with the foregoing example, the processor can determine the frequency band between P1 and P2 as the target frequency band.

[0129] In step A3, the processor can cut out a segment of the curve in the frequency-phase curve within the target frequency band according to the target frequency band, and this segment of the curve is the first frequency-phase relationship of the reference signal.

[0130] It should be noted that the frequency-amplitude curve and the frequency-phase curve in steps A1 to A3 above are the curves of the reference signal of the first sample detected in the actual measurement, Figure 4 and the curves shown in the ideal case are only provided as examples for easy understanding.

[0131] The advantage of determining the first frequency-phase relationship of the reference signal in the above manner is that for those frequency bands far away from the amplitude peak, since the corresponding amplitude in the interference signal is low, even if there is a phase error in these frequency bands, it will not cause obvious interference to the detected defocus amount. By the above manner, these frequency bands far away from the amplitude peak can be ignored, thereby reducing the calculation amount when determining the phase error according to the first frequency-phase relationship in the subsequent step, achieving the effect of saving computing resources and improving efficiency without affecting the accuracy of the result.

[0132] S203, linearly fitting the first frequency-phase relationship to obtain a second frequency-phase relationship.

[0133] In step S203, the processor can linearly fit the first frequency-phase relationship by using any fitting algorithm in the related art to obtain a linear second frequency-phase relationship, and the specific fitting algorithm is not limited in the embodiment.

[0134] In the scenario of using an interferometer to detect a bare wafer, the obtained first frequency-phase relationship and the second frequency-phase relationship obtained after fitting can be as shown in Figure 5 .

[0135] S204, generating a frequency-phase error relationship according to the deviation of each frequency point between the first frequency-phase relationship and the second frequency-phase relationship. ​

[0136] Optionally, the implementation of step S204 can be:

[0137] For each frequency point of the first frequency-phase relationship, a difference between the phase value of the frequency point and the corresponding phase value of the frequency point in the second frequency-phase relationship is calculated to obtain a phase error of the frequency point.

[0138] The phase errors corresponding to all frequency points in the first frequency-phase relationship are counted to generate a frequency-phase error relationship.

[0139] In the above implementation, for each frequency point contained in the first frequency-phase relationship, the processor can determine the corresponding phase value of the frequency point in the first frequency-phase relationship, denoted as the first phase value of the frequency point, and determine the corresponding phase value of the frequency point in the second frequency-phase relationship, denoted as the second phase value of the frequency point, and then calculate the difference between the first phase value and the second phase value of the frequency point. The calculation result is the phase error of the frequency point.

[0140] For example, for the frequency point x1, the corresponding first phase value is denoted as Ph1, and the second phase value is denoted as Ph2. The phase error of the frequency point can be equal to Ph1-Ph2.

[0141] The advantage of determining the phase error of each frequency point one by one according to the above method is that more accurate phase errors of the target optical detection device at different frequency points can be obtained, so that more accurate corrected signals can be obtained when subsequent correction is performed according to the phase error.

[0142] The generated frequency-phase error relationship can be represented by a frequency-phase error curve. For example, the frequency-phase error relationship generated in step S204 can be represented by the frequency-phase error curve shown in FIG. 2, where the abscissa is the frequency in hertz, and the ordinate is the phase error value corresponding to each frequency point in radians. Figure 6

[0143] The beneficial effects of the present embodiment are:

[0144] Under ideal conditions, the frequency and phase of the target signal detected by the optical detection device such as an interferometer have a linear relationship. According to the present scheme, the phase error of the target optical detection device when detecting the target signal is determined according to the first frequency-phase relationship corresponding to the measured reference signal and the second frequency-phase relationship obtained by linear fitting of the first frequency-phase relationship. Then, the phase error is used to correct other target signals detected subsequently, thereby improving the accuracy of the out-of-focus amount detected by the optical detection device and facilitating fast and accurate focusing of the sample.

[0145] ​It should be noted that the frequency phase error relationship obtained here is a system error, and can be used to compensate for all subsequent measurement configurations of the to-be-measured signal. Of course, if the key parameters such as the illumination wavelength or the system numerical aperture (NA) of the optical detection device change, the corresponding frequency phase error relationship needs to be re-generated for compensation of the to-be-measured signal measured under the corresponding configuration.

[0146] After obtaining the frequency phase error relationship according to the above embodiment, the signal correction can be performed by the following method, please refer to Figure 7 A flowchart of a signal correction method provided for the embodiment, which can include the following steps.

[0147] S701, obtaining a to-be-measured signal.

[0148] When the detection component is a camera, the to-be-measured signal can be obtained by the following way: obtaining an image of the test sample by optical imaging; processing the image of the test sample to obtain the to-be-measured signal; the to-be-measured signal is used to represent the fluctuation relationship between the signal amplitude and the defocus amount of the test sample relative to the optical focal plane. In this case, the detection information of the test sample refers to the image of the test sample obtained by the camera.

[0149] When the detection component is a photoelectric sensor, the to-be-measured signal can be obtained by the following way: the reflected light of the test sample and the reflected light of the mirror interfere with each other to produce interference light, and the photoelectric sensor collects the interference light and converts the light intensity of the interference light into an electrical signal, and the converted electrical signal is the to-be-measured signal in S701. In this case, the detection information of the test sample can be the electrical signal (such as voltage signal) converted by the photoelectric sensor according to the light intensity of the interference light.

[0150] The test sample can be a wafer or other semiconductor products.

[0151] The test sample and the aforementioned first sample can be the same sample or different samples.

[0152] The image of the test sample refers to placing the test sample in the interferometer shown in Figure 1 and starting the light source of the interferometer, and the interference image obtained by the interferometer, which is generated by the mutual interference of the light beams reflected by the mirror and the test sample.

[0153] After obtaining the interference image, the to-be-measured signal can be obtained by the following way:

[0154] Scanning the light intensity of each pixel in the interference image along a certain direction through the center of the interference image, and according to the light intensity and position of each pixel, the to-be-measured signal corresponding to the interference image can be plotted.

[0155] Optionally, when obtaining the to-be-tested signal, scanning can be performed in multiple different directions, and the multiple signal waveforms obtained after scanning are accumulated and filtered, and the signal obtained after filtering is taken as the to-be-tested signal, so that the influence of noise in the scanning process can be reduced, and a more accurate to-be-tested signal can be obtained.

[0156] After obtaining the to-be-tested signal, the abscissa with the maximum signal amplitude in the to-be-tested signal can be taken as the focal plane, or the abscissa at 1 / 2 of the maximum signal amplitude in the to-be-tested signal can be taken as the focal plane, and the deviation between the focal plane and the midpoint of the to-be-tested signal waveform is determined as the defocus amount.

[0157] S702, performing first transformation on the to-be-tested signal to obtain a corresponding signal frequency phase relationship.

[0158] The first transformation can be Fourier transformation, and the obtained signal frequency phase relationship can be a frequency phase curve.

[0159] S703, performing phase compensation on the signal frequency phase relationship according to a preset frequency phase error relationship, to obtain a compensated signal.

[0160] The phase compensation can be performed in the following manner: obtaining the phase of the to-be-tested signal at each frequency point according to the signal frequency phase relationship; obtaining the phase error of each frequency point according to the frequency phase error relationship; and adding the phase of the to-be-tested signal at each frequency point to the phase error of each frequency point to perform phase compensation, to obtain the compensated signal of the to-be-tested signal.

[0161] For example, when the signal frequency phase relationship is a frequency phase curve, the frequency phase curve of the to-be-tested signal can be determined to be located at each frequency point in a target frequency band, then for each frequency point, the corresponding phase value of the frequency point in the frequency phase curve of the to-be-tested signal is determined, and the corresponding phase error of the frequency point in the frequency phase error relationship is determined, finally, the phase value of the frequency point is added to the phase error of the frequency point, and the result is the phase value of the frequency point after phase compensation, after phase compensation of all frequency points, the signal composed of the frequency points and the corresponding phase values after compensation is the compensated signal of the to-be-tested signal.

[0162] The advantage of the above-mentioned phase compensation method is that the actual phase error of each frequency point in the frequency phase curve of the test sample can also have a large deviation, and the above-mentioned method uses the specific phase error of each frequency point to correct the phase value of the frequency point, so that the corrected signal obtained finally is closer to the to-be-tested signal of the test sample under ideal conditions (i.e., the defocus amount is 0).

[0163] S704, performing second transformation on the compensated signal to obtain a corrected signal, and the first transformation and the second transformation are inverse transformations.

[0164] For example, when the first transform is a Fourier transform, the second transform can be an inverse Fourier transform.

[0165] The frequency phase error relationship is configured as a deviation between the first frequency phase relationship of the reference signal and the second frequency phase relationship obtained by linear fitting. The specific configuration method can be referred to Figure 2 Corresponding embodiments will not be described again.

[0166] The beneficial effects of the embodiment are that after obtaining the to-be-tested signal, the to-be-tested signal is phase compensated using the pre-configured frequency phase error relationship, thereby correcting the phase error caused by the optical parameter asymmetry in the detection device, improving the accuracy of the out-of-focus amount detected by the optical detection device, and facilitating the rapid and accurate focusing of the sample.

[0167] Optionally, after obtaining the corrected signal, the processor can adjust the position of the tested sample according to the corrected signal in the following manner.

[0168] (1) Identify the wave peak of the corrected signal.

[0169] (2) Determine the out-of-focus amount of the tested sample according to the wave peak of the corrected signal.

[0170] (3) Adjust the position of the tested sample according to the out-of-focus amount until the optical focal plane is reached.

[0171] The method of adjusting the position of the tested sample will be described below in combination with the to-be-tested signal and the corrected signal shown in Figure 8 and Figure 9 .

[0172] Please refer to Figure 8 , which is a schematic diagram of a to-be-tested signal and a corrected signal of a wafer without patterns (i.e., a bare wafer).

[0173] As can be seen, the surface of the bare wafer is smooth and free of photoetching grooves, so the original interference signal (i.e., the to-be-tested signal of Figure 8 ) has a relatively simple waveform shape. After the original interference signal is corrected by the method of the embodiment, the corrected signal shown in Figure 8 is obtained, and the waveform is restored to a left-right symmetric state at this time.

[0174] In the corrected signal, the processor can identify the maximum wave peak Q2 and further identify the corresponding value of the maximum wave peak on the horizontal coordinate, which is the out-of-focus amount of the tested sample. Then, the processor can use the out-of-focus amount to move the height of the tested sample, i.e., adjust the wafer to the front focal plane of the measurement objective lens.

[0175] Please refer to Figure 9 , which is a schematic diagram of a to-be-tested signal and a corrected signal of a wafer with patterns.

[0176] There are lithography marks on the wafer, such as overlay marks formed by upper and lower gratings, so that the to-be-detected signal has a relatively complex waveform shape, and the maximum peak corresponds to a position on the negative defocus amount. After correction processing on the to-be-detected signal, a correction signal as shown in the figure is obtained. Figure 9

[0177] It can be seen that the envelope profile (i.e., wave packet) of the correction signal is more obvious and the waveform is narrowed, and a new peak is more easily obtained from the wave packet. At this time, the processor can identify the maximum peak Q4 from the correction signal, and the position of the maximum peak corresponding to the positive defocus amount, and the height of the wafer is moved using the defocus amount, that is, the wafer is adjusted to the front focal plane of the measurement objective.

[0178] According to the method for correcting the optical detection device provided in the embodiments of the present application, the embodiments of the present application also provide an optical detection device. Please refer to Figure 10 , which is a structural schematic diagram of the device. The device can include:

[0179] an illumination module 1001, a detection table 1002, a detection module 1003, and a processing module 1004;

[0180] The illumination module is used to irradiate the detected sample placed on the detection table;

[0181] The imaging module is used to obtain detection information of the detected sample.

[0182] The processing module is used to execute the signal correction method provided in the foregoing embodiments according to the detection information of the detected sample, that is, to execute the following method:

[0183] obtain a to-be-detected signal;

[0184] perform first transformation on the to-be-detected signal to obtain a corresponding signal frequency phase relationship;

[0185] perform phase compensation on the signal frequency phase relationship according to a preset frequency phase error relationship to obtain a compensation signal;

[0186] perform second transformation on the compensation signal to obtain a correction signal; the first transformation and the second transformation are inverse transformations of each other;

[0187] The frequency phase error relationship is configured as a deviation between the first frequency phase relationship of the reference signal and the second frequency phase relationship obtained by linear fitting.

[0188] The detection module can include Figure 1 a reference objective 15, a measurement objective 13, a mirror 16, a beam splitter 12, and a detection component 17 as shown in the figure.

[0189] ​The beam splitter 12 is located in the light path of the illumination light beam generated by the illumination module (such as the light source 11), and is used to divide the illumination light beam into a first light beam and a second light beam.

[0190] The measurement objective 13 is located in the light path of the first light beam, and the first light beam passes through the measurement objective 13 to reach a test sample 14 on a detection stage (not shown in the figure) and generate a first signal light in a backward transmission; Figure 1 The reference objective 15 is located in the light path of the second light beam, and the second light beam passes through the reference objective 15 to reach the mirror 16 and generate a second signal light in a backward transmission; wherein the first signal light and the second signal light are used to interfere with each other at the beam splitter 12 and generate a corresponding interference light beam;

[0191] The detection component 17 is located in the light path of the interference light beam, and is used to obtain a detection light beam and generate detection information of the test sample.

[0192] The illumination module can be The light source 11 shown in the figure.

[0193] Figure 1 Optionally, the processing module includes a compensation unit, and the compensation unit is configured to: obtain the phase of the to-be-tested signal at each frequency point according to the signal frequency phase relationship; obtain the phase error of each frequency point according to the frequency phase error relationship; and add the phase of the to-be-tested signal at each frequency point and the phase error of each frequency point to perform phase compensation, to obtain the compensation signal of the to-be-tested signal.

[0194] Optionally, the processing module includes a configuration unit, and the configuration unit is configured to: obtain a reference signal; perform first transformation on the reference signal to obtain a first frequency phase relationship of the reference signal; perform linear fitting on the first frequency phase relationship to obtain a second frequency phase relationship; and generate a frequency phase error relationship according to the deviation of each frequency point between the first frequency phase relationship and the second frequency phase relationship.

[0195] Optionally, when the configuration unit performs first transformation on the reference signal to obtain the first frequency phase relationship of the reference signal, the configuration unit is specifically configured to: perform Fourier transformation on the reference signal to obtain a frequency phase curve and a frequency amplitude curve of the reference signal; and determine the first frequency phase relationship of the reference signal according to the frequency phase curve and the frequency amplitude curve.

[0196] Optionally, when the configuration unit determines the first frequency phase relationship of the reference signal according to the frequency phase curve and the frequency amplitude curve, the configuration unit is specifically configured to: identify an amplitude peak value in the frequency amplitude curve; determine a target frequency band in the frequency amplitude curve according to the amplitude peak value, the target frequency band including a frequency point corresponding to the amplitude peak value; and determine a curve segment in the target frequency band in the frequency phase curve as the first frequency phase relationship of the reference signal.

[0197] Optionally, when the configuration unit determines the first frequency phase relationship of the reference signal according to the frequency phase curve and the frequency amplitude curve, the configuration unit is specifically configured to: identify an amplitude peak value in the frequency amplitude curve; determine a target frequency band in the frequency amplitude curve according to the amplitude peak value, the target frequency band including a frequency point corresponding to the amplitude peak value; and determine a curve segment in the target frequency band in the frequency phase curve as the first frequency phase relationship of the reference signal.

[0198] Optionally, when the configuration unit determines the target frequency band in the frequency-amplitude curve according to the amplitude peak value, the configuration unit is specifically configured to: determine a target amplitude value according to the amplitude peak value, the target amplitude value and the amplitude peak value having a preset proportional relationship; determine a first frequency point and a second frequency point corresponding to the target amplitude value in the frequency-amplitude curve; and determine a frequency band between the first frequency point and the second frequency point as the target frequency band.

[0199] Optionally, when the configuration unit generates the frequency-phase error relationship according to the deviation of each frequency point between the first frequency-phase relationship and the second frequency-phase relationship, the configuration unit is specifically configured to: for each frequency point of the first frequency-phase relationship, calculate a difference value between a phase value of the frequency point and a corresponding phase value of the frequency point in the second frequency-phase relationship, to obtain a phase error corresponding to the frequency point; and statistically generate the frequency-phase error relationship by using the phase errors corresponding to all frequency points in the first frequency-phase relationship.

[0200] Optionally, the processing module includes an acquisition unit configured to acquire the to-be-tested signal, and the acquisition unit is specifically configured to: acquire an image of the test sample through optical imaging; and process the image of the test sample to obtain the to-be-tested signal; the to-be-tested signal is used to represent a fluctuation relationship between a horizontal coordinate corresponding to a signal amplitude and a defocus amount of the test sample relative to an optical focal plane.

[0201] Optionally, the processing module further includes an adjustment unit configured to perform the following steps after obtaining the corrected signal: identify a wave peak of the corrected signal; determine the defocus amount of the test sample according to the wave peak of the corrected signal; and adjust the position of the test sample according to the defocus amount until the optical focal plane is reached.

[0202] The optical detection device provided in the embodiments of the present application has the specific working principle and beneficial effects of the signal correction method provided in the embodiments of the present application, which will not be described again.

[0203] The embodiments of the present application further provide a computer storage medium for storing a computer program, and the computer program is executed to specifically implement the signal correction method provided in any of the embodiments of the present application.

[0204] It should be noted that each of the embodiments in the present specification adopts a progressive manner for description, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between the embodiments can be referred to each other.

[0205] For the convenience of description, the above system or device is described in various modules or units in terms of functions. Of course, the functions of each unit can be implemented in the same or multiple software and / or hardware in the implementation of the present application.

[0206] Those skilled in the art can clearly understand the application by the description of the above embodiments. The technical solutions of the application can be implemented by means of software and necessary universal hardware platforms. Based on such an understanding, the technical solutions of the application can be embodied in the form of a software product, which can be stored in a storage medium, such as a ROM / RAM, a magnetic disk, or an optical disk, and includes a number of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of the application.

[0207] Finally, it should be noted that the terms such as first, second, third, and fourth, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0208] The above description is only the preferred embodiments of the application, and it should be pointed out that those skilled in the art can make some improvements and refinements without departing from the principles of the application, and these improvements and refinements should also be regarded as the protection scope of the application.

Claims

1. A signal correction method characterized by, The method comprises: obtaining detection information of a test sample by optical detection; processing the detection information of the test sample to obtain a to-be-detected signal, the to-be-detected signal being used to represent a fluctuation relationship between a signal amplitude and an off-focus amount of the test sample relative to an optical focal plane; performing first transformation on the to-be-detected signal to obtain a corresponding signal frequency phase relationship; performing phase compensation on the signal frequency phase relationship according to a preset frequency phase error relationship to obtain a compensated signal; performing second transformation on the compensated signal to obtain a corrected signal, the first transformation and the second transformation being inverse transformations of each other; wherein the frequency phase error relationship is configured as a deviation between a first frequency phase relationship of a reference signal and a second frequency phase relationship obtained by linear fitting; wherein the configuration process of the frequency phase error relationship comprises: obtaining a reference signal, the reference signal being a signal obtained by detecting a first sample, the first sample comprising a bare wafer without etched patterns, or a portion of any wafer without etched patterns; performing first transformation on the reference signal to obtain the first frequency phase relationship of the reference signal; performing linear fitting on the first frequency phase relationship to obtain the second frequency phase relationship; generating the frequency phase error relationship according to deviations of each frequency point between the first frequency phase relationship and the second frequency phase relationship.

2. The method of claim 1, wherein, The performing phase compensation on the signal frequency phase relationship according to the preset frequency phase error relationship to obtain a compensated signal comprises: obtaining corresponding phases of the to-be-detected signal at each frequency point according to the signal frequency phase relationship; obtaining phase errors corresponding to each frequency point according to the frequency phase error relationship; adding the corresponding phases of the to-be-detected signal at each frequency point and the phase errors corresponding to each frequency point to perform phase compensation to obtain the compensated signal of the to-be-detected signal.

3. The method of claim 1, wherein, The performing first transformation on the reference signal to obtain the first frequency phase relationship of the reference signal comprises: performing Fourier transformation on the reference signal to obtain a frequency phase curve and a frequency amplitude curve of the reference signal; determining the first frequency phase relationship of the reference signal according to the frequency phase curve and the frequency amplitude curve.

4. The method of claim 3, wherein, The determining the first frequency phase relationship of the reference signal according to the frequency phase curve and the frequency amplitude curve comprises: identifying an amplitude peak value in the frequency amplitude curve; determining a target frequency band in the frequency amplitude curve according to the amplitude peak value, the target frequency band comprising a frequency point corresponding to the amplitude peak value; determining a curve segment in the frequency phase curve within the target frequency band as the first frequency phase relationship of the reference signal.

5. The method of claim 4, wherein, The determining a target frequency band in the frequency amplitude curve according to the amplitude peak value comprises: determining a target amplitude value according to the amplitude peak value, the target amplitude value and the amplitude peak value having a preset proportional relationship; determining a first frequency point and a second frequency point corresponding to the target amplitude value in the frequency amplitude curve; determining a frequency band between the first frequency point and the second frequency point as the target frequency band.

6. The method of claim 1, wherein, The generating the frequency phase error relationship according to the deviation of each frequency point between the first frequency phase relationship and the second frequency phase relationship comprises: For each frequency point of the first frequency phase relationship, calculating the difference between the phase value of the frequency point and the corresponding phase value of the frequency point in the second frequency phase relationship, to obtain the corresponding phase error of the frequency point; Statistically calculating the corresponding phase error of all frequency points in the first frequency phase relationship to generate the frequency phase error relationship.

7. The method of claim 6, wherein, After obtaining the correction signal, further comprising: Identifying the wave crest of the correction signal; Determining the defocus amount of the test sample according to the wave crest of the correction signal; Adjusting the position of the test sample according to the defocus amount until reaching the optical focal plane.

8. An optical detection device, characterized by Comprising: An illumination module, a detection table, a detection module and a processing module; The illumination module is used for irradiating a test sample placed on the detection table; The detection module is used for acquiring detection information of the test sample through optical detection; Processing the detection information of the test sample to obtain a to-be-measured signal; the to-be-measured signal is used for representing the fluctuation relationship between the signal amplitude and the defocus amount of the test sample relative to the optical focal plane; The processing module is used for executing the signal correction method according to any one of claims 1 to 7 according to the detection information of the test sample; The processing module further comprises a configuration unit configured to: Obtain a reference signal, the reference signal being a signal obtained by detecting a first sample, the first sample comprising a bare wafer without etched patterns, or a portion of any wafer without etched patterns; Perform first transformation on the reference signal to obtain a first frequency phase relationship of the reference signal; Perform linear fitting on the first frequency phase relationship to obtain a second frequency phase relationship; Generate the frequency phase error relationship according to the deviation of each frequency point between the first frequency phase relationship and the second frequency phase relationship.

9. The optical detection device of claim 8, wherein, The processing module comprises: An acquisition unit configured to process an image of the test sample to obtain the to-be-measured signal; A first transformation unit configured to perform first transformation on the to-be-measured signal to obtain a corresponding signal frequency phase relationship; A compensation unit configured to perform phase compensation on the signal frequency phase relationship according to a preset frequency phase error relationship to obtain a compensation signal; A second transformation unit configured to perform second transformation on the compensation signal to obtain a correction signal; the first transformation and the second transformation are inverse transformations of each other; The frequency phase error relationship is configured as the deviation between the first frequency phase relationship of the reference signal and the second frequency phase relationship obtained by linear fitting.

10. The apparatus of claim 9, wherein, The compensation unit performs phase compensation on the signal frequency phase relationship according to the preset frequency phase error relationship, specifically comprising: Obtaining the corresponding phase of the to-be-measured signal at each frequency point according to the signal frequency phase relationship; Obtaining the corresponding phase error of each frequency point according to the frequency phase error relationship; Adding the corresponding phase of the to-be-measured signal at each frequency point and the corresponding phase error of each frequency point to perform phase compensation to obtain the compensation signal of the to-be-measured signal.

11. The apparatus of claim 8, wherein, The configuration unit is configured to perform first transformation on the reference signal to obtain a first frequency phase relationship of the reference signal, and specifically configured to: perform Fourier transformation on the reference signal to obtain a frequency phase curve and a frequency amplitude curve of the reference signal; determine the first frequency phase relationship of the reference signal according to the frequency phase curve and the frequency amplitude curve.

12. The apparatus of claim 8, wherein, The detection module comprises a reference objective, a measurement objective, a mirror, a beam splitter and a detection component; The beam splitter is located on an optical path of an illumination beam generated by the illumination module, and is configured to divide the illumination beam into a first beam and a second beam; The measurement objective is located on an optical path of the first beam, and the first beam reaches a sample under test on the detection platform after passing through the measurement objective and generates a first signal light in reverse transmission; The reference objective is located on an optical path of the second beam, and the second beam reaches the mirror after passing through the reference objective and generates a second signal light in reverse transmission; the first signal light and the second signal light are configured to interfere with each other at the beam splitter and generate a corresponding interference beam; The detection component is located on an optical path of the interference beam, and is configured to obtain a detection beam and generate detection information of the sample under test.

13. A computer storage medium, characterized in that A computer program is stored, and the computer program is executed to specifically implement the signal correction method in any one of claims 1 to 7.

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