An angularly resolved snapshot overlay error measurement device and method

Abstract

The application belongs to the technical field of integrated circuit manufacturing optical online measurement, and discloses an angle-resolved snapshot overlay error measurement device and method. The device comprises: a probe light generation module for generating probe light; a spectrum modulation module for sequentially performing first polarization and first phase modulation on the probe light, and then irradiating the probe light on a to-be-measured overlay sample at different incident angles, and sequentially performing second phase modulation and second polarization on the reflected multi-beam light, so as to obtain polarization modulation light reflected by the to-be-measured overlay sample; an angle-resolved spectrum acquisition module for performing spectrum imaging on the polarization modulation light, so as to obtain the angle-resolved spectrum of the to-be-measured overlay sample; and an overlay error measurement module for obtaining the overlay error of the to-be-measured overlay sample at different incident angles based on the angle-resolved spectrum. The application can improve the measurement precision and stability of the overlay error, overcome the shortcoming of a large oblique incidence type structure spot, and still retain the advantages of simple and rapid measurement of a snapshot ellipsometer.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical on-line measurement of integrated circuit manufacturing, and more particularly relates to an angle-resolved snapshot overlay error measurement device and method. BACKGROUND

[0002] Semiconductor devices, such as memory devices and logic devices, are usually formed by layer-by-layer stacking of different structures using photolithography, etching, deposition and other processes. Overlay error is the registration error between a current layer (a pattern retained on a photoresist after exposure and development) and a reference layer (a pattern already present on a wafer) in x and y directions when a wafer is exposed. Ideally, the patterns of the current layer and the reference layer are in alignment, i.e., the overlay error is zero. However, in actual manufacturing processes, overlay error inevitably exists due to problems in processing technology and processing equipment. Fast measurement and accurate evaluation of overlay error are critical for optimization of lithography machine operating parameters and management of process yield.

[0003] Existing methods for measuring overlay error on a device structure (also referred to as product overlay error measurement) by measuring overlay marks have the problems of long measurement time and slow measurement speed. Moreover, since the exposure field or chip area is also the area where the lithography exposure pattern is located, the presence of overlay marks occupies valuable space positions, and therefore the overlay marks are usually required not to be too large, with a size of 10x10 μm 2 , which imposes certain restrictions on the size of the measurement spot. In the prior art, an overlay error measurement device and method are also disclosed, which adopts a conventional oblique incidence structure and has the disadvantages of a large measurement spot, easy vibration influence on oblique illumination, and low measurement precision and stability. SUMMARY

[0004] In view of the defects and improvement needs of the prior art, the present application provides an angle-resolved snapshot overlay error measurement device and method, which aims to provide a way of measuring product overlay error and improve the measurement precision and stability of overlay error.

[0005] To achieve the above-mentioned purpose, according to one aspect of the present application, an angle-resolved snapshot overlay error measurement device is provided, comprising:

[0006] a probe light generation module for generating probe light;

[0007] a spectrum modulation module, configured to sequentially perform first polarization and first phase modulation on the probe light, and irradiate the probe light on a to-be-measured overlay sample at different incident angles, and sequentially perform second phase modulation and second polarization on a plurality of beams of light reflected by the to-be-measured overlay sample, to obtain polarized modulation light reflected by the to-be-measured overlay sample;

[0008] an angle-resolved spectrum acquisition module, configured to perform spectrum imaging on the polarized modulation light, to obtain an angle-resolved spectrum of the to-be-measured overlay sample;

[0009] an overlay error measurement module, configured to obtain a linear combination of non-diagonal elements of a Mueller matrix of the to-be-measured overlay sample at different incident angles based on the angle-resolved spectrum, and further obtain an overlay error.

[0010] Further, the spectrum modulation module sequentially comprises, along an optical path, a polarizer, a first phase retarder, an optical stop, a first non-polarized beam splitter, a first lens, an objective lens, a second phase retarder and an analyzer.

[0011] The probe laser is converted into linearly polarized light after passing through the polarizer, and is subjected to first phase modulation by the first phase retarder; the laser beam passing through the optical stop changes the propagation direction of the light beam after passing through the first non-polarized beam splitter, and is focused on the back focal plane of the objective lens by the first lens.

[0012] The front focal plane of the objective lens coincides with the surface of the to-be-measured overlay sample, and a plurality of beams of light are formed by the objective lens to irradiate the to-be-measured overlay sample at different incident angles.

[0013] The plurality of beams of light reflected by the to-be-measured overlay sample passes through the objective lens, the first lens and the first non-polarized beam splitter again, is subjected to second phase modulation by the second phase retarder, and the polarized modulation light is obtained by the analyzer.

[0014] Further, the polarizer, the first phase retarder, the second phase retarder and the analyzer satisfy the following configurations:

[0015] The optical transmission axis azimuth angle of the polarizer is ±45°, the fast axis azimuth angle of the first phase retarder is 0°, the fast axis azimuth angle of the second phase retarder is ±45°, and the optical transmission axis azimuth angle of the analyzer is 0°.

[0016] Or the optical transmission axis azimuth angle of the polarizer is ±45°, the fast axis azimuth angle of the first phase retarder is 90°, the fast axis azimuth angle of the second phase retarder is ±45°, and the optical transmission axis azimuth angle of the analyzer is 90°.

[0017] or the pass axis azimuth angle of the polarizer is ±45°, the fast axis azimuth angle of the first phase retarder is 90°, the fast axis azimuth angle of the second phase retarder is 90°, and the pass axis azimuth angle of the polarizer is ±45°.

[0018] Further, the first phase retarder and the second phase retarder are both multistage wave plates made of birefringent crystals, and the thickness ratio is 1:1.

[0019] Further, the front focal plane of the first lens coincides with the back focal plane of the objective lens.

[0020] Further, the angularly resolved spectrum acquisition module comprises a second lens and an imaging spectrometer.

[0021] The second lens is used for converging the polarization-modulated light, and the imaging spectrometer is used for performing spectral imaging on the converged light to obtain the angularly resolved spectrum.

[0022] Further, the angularly resolved spectrum acquisition module further comprises a second non-polarization beam splitter, a third lens, and a face array camera.

[0023] The second non-polarization beam splitter is used for splitting the polarization-modulated light converged by the second lens, one of which is used for spectral imaging by the imaging spectrometer, and the other of which is used for imaging quality observation of the measured overlay sample by the face array camera after being converged again by the third lens, and the system parameters in the device are calibrated.

[0024] Further, in the overlay error measurement module, the Mueller matrix off-diagonal elements of the measured overlay sample at different incident angles are obtained by the following system model:

[0025] S out (λ, θ) = [M A R(α2)]·[R(-β2)M R (δ2)R(β2)]·M S (λ, θ)·[R(-β1)M R (δ1)R(β1)]·[R(-α1)M P ]·S in

[0026] In the formula, S out is the light beam corresponding to the Stokes vector after the spectral modulation module, M P , M Arespectively, are the Mueller matrices corresponding to the first polarization and the second polarization, R(*) represents the Mueller rotation matrix when the rotation angle is *, and a1, a2 are the azimuth angles of the pass axis when the first polarization and the second polarization are respectively, and b1, b2 are the azimuth angles of the fast axis when the first phase delay and the second phase delay are respectively, M R (δ1), M R (δ2) are the Mueller matrices corresponding to the first phase delay and the second phase delay respectively, M S (λ, θ) is the Mueller matrix corresponding to the measured overlay sample, S in is the Stokes vector corresponding to the light beam before the spectral modulation module, λ is the wavelength, and θ is the light beam incidence angle on the measured overlay sample;

[0027] wherein the Mueller matrix M S (λ, θ) corresponding to the measured overlay sample is:

[0028]

[0029] In the formula, m 11 (λ, θ), m 12 (λ, θ), …, m 44 (λ, θ) are Mueller matrix elements respectively.

[0030] Further, the probe light generation module sequentially includes a broadband light source, an optical fiber and a collimating lens along the light path direction.

[0031] According to another aspect of the present application, an angle-resolved snapshot overlay error measurement method is provided, comprising the following steps:

[0032] Step S1, the probe light is sequentially subjected to the first polarization and the first phase modulation, and then is irradiated on the measured overlay sample at different incidence angles, and the multiple beams of light reflected after passing through the measured overlay sample are sequentially subjected to the second phase modulation and the second polarization, to obtain the polarization modulation light reflected by the measured overlay sample;

[0033] Step S2, the polarization modulation light is subjected to spectral imaging, to obtain the angle-resolved spectrum of the measured overlay sample;

[0034] Step S3, based on the angle-resolved spectrum, the linear combination of the non-diagonal elements of the Mueller matrix of the measured overlay sample at different incidence angles is obtained, and then the overlay error is obtained.

[0035] Overall, the above technical solutions conceived by the present application can achieve the following beneficial effects:

[0036] (1) The measuring device of the present application, by sequentially performing first polarization and first phase modulation on the probe light, irradiating the measured overlay sample at different incident angles, and then performing second phase modulation and second polarization on the multiple light beams reflected by the measured overlay sample, an angularly resolved spectrum containing multi-dimensional information of the measured overlay sample is obtained, based on which the linear combination of the non-diagonal elements of the Mueller matrix of the overlay sample at multiple incident angles is obtained in a single measurement, and then the overlay error of the measured overlay sample is obtained, compared with the traditional snapshot overlay error measuring device which only solves parameters by using single-dimensional wavelength information, the present application can significantly improve the measurement accuracy and stability.

[0037] (2) Further, the specific optical path structure designed in the present application, the optical path design of the vertical objective imaging of the measured sample, the combination of the objective rear focal plane imaging technology and the snapshot polarization spectrum measurement technology, the clever use of the objective to obtain the angularly resolved spectrum of the measured sample at different incident angles, while improving the overlay error measurement accuracy and measurement stability, can also achieve the lateral resolution close to the optical limit of the optical microscope, which provides the possibility to reduce the size of the measurement spot, fundamentally avoids the phenomenon that the spot size of the ordinary oblique incidence optical measurement system is large and the oblique illumination is easily affected by vibration, meets the requirement that the overlay error measurement overlay mark size cannot be too large, and also retains the advantages of simple and fast measurement of the snapshot ellipsometer, which can be applied to real-time online measurement of the overlay error of the large-area module production integrated circuit elements on the production line.

[0038] (3) Further, under the ratio of the azimuth angle size to the thickness of the two phase retarders provided in the present application, the combination of the Mueller matrix elements sensitive to the overlay error of the sample can be directly obtained by the parameter extraction method, without the need to extract multiple channel coefficients for linear combination, which can reduce the calculation error, while effectively ensuring the sensitivity to the overlay error, and further improving the accuracy of the overlay error measurement.

[0039] (4) As a preferred, the front focal plane of the first lens coincides with the rear focal plane of the objective, which can realize uniform illumination of the light source on the measured overlay sample at the same incident angle, and further improve the accuracy of the overlay error measurement.

[0040] (5) As a preferred, the light source is a broadband light source, which can realize the measurement of the overlay error under a wide spectrum, to improve the sensitivity of the overlay error and solve the influence of process deviation on the accuracy of the overlay error measurement.

[0041] In summary, the device of the present application has simple and compact structure, and the spectral modulation elements have no movement requirement, which can effectively ensure the stability of the spectrum and the accuracy of the measurement. At the same time, it has certain expandability, and can be configured, adjusted and optimized in combination with different measurement objects. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 The structure schematic diagram of the overlay error measurement device provided by the present application is shown.

[0043] Figure 2 The schematic diagram of the overlay error measurement device provided by the embodiment of the present application is shown.

[0044] Figure 3 The schematic diagram of the back focal plane of the objective provided by the embodiment of the present application is shown.

[0045] In all the drawings, the same reference signs are used to indicate the same elements or structures, wherein:

[0046] 1 - light source, 2 - optical fiber, 3 - collimating lens, 4 - polarizer, 5 - first phase retarder, 6 - diaphragm, 7 - first non-polarizing beam splitter, 8 - first lens, 9 - objective, 10 - overlay sample to be measured, 11 - second phase retarder, 12 - analyzer, 13 - second lens, 14 - second non-polarizing beam splitter, 15 - imaging spectrometer, 16 - third lens, 17 - area array camera, 18 - data processing system. DETAILED DESCRIPTION

[0047] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as there is no conflict.

[0048] In the present application, the terms "first", "second", etc. (if any) in the present application and the drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence.

[0049] As shown in Figure 1 , Figure 2 The angular resolution snapshot overlay error measurement device of the present application mainly includes a probe light generation module, a spectrum modulation module, an angular resolution spectrum acquisition module and an overlay error measurement module.

[0050] The probe light generation module is used to generate probe laser;

[0051] The spectrum modulation module is used to irradiate the probe light on the overlay sample to be measured at different incident angles after the first polarization and the first phase modulation, and to obtain the polarization modulation light reflected by the overlay sample to be measured after the second phase modulation and the second polarization of the multiple light beams reflected after the overlay sample to be measured.

[0052] an angle-resolved spectrum acquisition module, configured to perform spectrum imaging on the polarization-modulated light reflected by the to-be-tested overlay sample to obtain an angle-resolved spectrum of the to-be-tested overlay sample;

[0053] an overlay error measurement module, configured to obtain a linear combination of non-diagonal elements of a Mueller matrix of the to-be-tested overlay sample at different incident angles based on the angle-resolved spectrum of the to-be-tested overlay sample, and further obtain an overlay error of the to-be-tested overlay sample.

[0054] Specifically, the probe light generation module sequentially includes, along an optical path direction, a light source 1, an optical fiber 2, and a collimating lens 3; as a preferred, the light source 1 is a broadband light source, which realizes the measurement of the overlay error under a wide spectrum to improve the sensitivity of the overlay error and solve the influence of process deviation on the measurement accuracy of the overlay error.

[0055] Specifically, the spectrum modulation module sequentially includes, along an optical path, a polarizer 4, a first phase retarder 5, an aperture 6, a first non-polarization beam splitter 7, a first lens 8, an objective lens 9, a second phase retarder 11, and an analyzer 12; the probe laser is converted into linearly polarized light after passing through the polarizer 4, and after being modulated in phase for the first time by the first phase retarder 5, the size of the light spot is controlled by the aperture 6, the laser beam emitted by the aperture 6 changes the propagation direction of the light beam after passing through the first non-polarization beam splitter 7, and then the light beam is focused on the back focal plane of the objective lens 9 by the first lens 8, the front focal plane of the objective lens 9 is coincided with the surface of the to-be-tested overlay sample 10, and under the action of the objective lens 9, multiple light beams are formed to irradiate on the to-be-tested overlay sample 10 at different incident angles, and after being reflected by the sample, the multiple light beams again pass through the objective lens 9, the first lens 8, and the first non-polarization beam splitter 7, and then are modulated in phase for the second time by the second phase retarder 11, and then pass through the analyzer 12 to obtain the polarization-modulated light reflected by the to-be-tested overlay sample.

[0056] In the spectrum modulation module, the first non-polarization beam splitter 7 is arranged between the first phase retarder 5 and the first lens 8, and also between the first lens 8 and the second phase retarder 11, which is used to realize the reflective propagation of the light beam in the spectrum polarization modulation light path, and at the same time realizes the transmission propagation of the light beam in the reflected light path.

[0057] As a preferred, the polarizer 4 and the analyzer 12 are both linear polarizers, and the analyzer 12 should have a sufficient extinction ratio, and as a preferred, the extinction ratio is less than 10 -4 .

[0058] The phase delay ratio of the first phase delayer 5 and the second phase delayer 11 is 1:1. Preferably, both the first phase delayer 5 and the second phase delayer 11 are multi-level waveplates made of birefringent crystals. Their phase delay is approximately linear with the wave number (i.e., the reciprocal of the wavelength). The two perform the first and second phase modulations on the linearly polarized light, so that the polarization state of the measurement beam changes periodically with the wave number. The thickness ratio of the first phase delayer 5 and the second phase delayer 11 is preferably 1:1. At this thickness ratio, it is easy to extract the linear combination of Mueller matrix elements that are sensitive to overlay errors.

[0059] Furthermore, the present invention provides specific designs for the transmission axis azimuth angle of the polarizer 4, the fast axis azimuth angle of the first phase delayer 5, the fast axis azimuth angle of the second phase delayer 11, and the transmission axis azimuth angle of the analyzer 12. The following configurations can be adopted: the azimuth angle of the transmission axis of the polarizer 4 is ±45°, the azimuth angle of the fast axis of the first phase delayer 5 is 0°, the azimuth angle of the fast axis of the second phase delayer 11 is ±45°, and the azimuth angle of the transmission axis of the analyzer 12 is 0°; or the azimuth angle of the transmission axis of the polarizer 4 is ±45°, the azimuth angle of the fast axis of the first phase delayer 5 is 90°, the azimuth angle of the fast axis of the second phase delayer 11 is ±45°, and the azimuth angle of the transmission axis of the analyzer 12 is 90°; or the azimuth angle of the transmission axis of the polarizer 4 is ±45°, the azimuth angle of the fast axis of the first phase delayer 5 is 90°, the azimuth angle of the fast axis of the second phase delayer 11 is 90°, and the azimuth angle of the transmission axis of the analyzer 12 is ±45°.

[0060] With the above configuration, the combination of Mueller matrix elements sensitive to sample overlay error can be obtained directly through parameter extraction methods, without the need for linear combination of multiple channel coefficients. This reduces calculation error to some extent and effectively ensures sensitivity to overlay error, thereby improving the accuracy of overlay error measurement.

[0061] Preferably, the front focal plane of the first lens 8 and the rear focal plane of the objective lens 9 coincide, so as to achieve uniform illumination of the light source on the sample to be tested at the same incident angle.

[0062] like Figure 3 As shown, the light beam emitted from objective lens 9 illuminates the overlay sample 10 under test at different incident angles θ. The relationship between the incident angle θ and the distance d from the axis of the focal point on the back focal plane of objective lens 9 is as follows:

[0063]

[0064] Wherein, the illumination incident angle θ is the angle between the beam emitted from the objective lens and the normal of the overlay sample to be measured, and f is the focal length of the objective lens 9. Figure 3 middle, I in I is the intensity of the incident light (i.e., the light beam incident on the overlay sample to be tested).out is the light intensity corresponding to the outgoing light (i.e. the light beam reflected by the overlay sample under test).

[0065] The light beams reflected by the overlay sample under test in a large angular range are collected by the objective 9 and returned into the optical path. The maximum illumination incidence angle θ max Depending on the numerical aperture of the objective 9, the specific relationship can be described as θ max = sin -1 (NA), NA being the numerical aperture value of the objective.

[0066] In particular, the angularly resolved spectrum acquisition module comprises a second lens 13 and an imaging spectrometer 15; the second lens 13 is used to converge the polarized modulation light reflected by the overlay sample under test; the imaging spectrometer 15 is used to perform spectral imaging on the converged modulation light to obtain the angularly resolved spectrum of the overlay sample under test.

[0067] As a preferred embodiment, the angularly resolved spectrum acquisition module further comprises a correction unit for calibrating the system parameters of the device and observing the imaging quality of the sample. In particular, the correction unit comprises a second non-polarized beam splitter 14, a third lens 16 and a face array camera 17, the third lens being arranged behind the second non-polarized beam splitter, and the face array camera being arranged behind the third lens.

[0068] The second non-polarized beam splitter 14 is used to split the polarized modulation light converged by the second lens 13, one of which is used for spectral imaging by the imaging spectrometer 15, and the other is converged again by the third lens 16 and then passes through the face array camera 17, so that the face array camera 17 can calibrate the azimuth angles of the polarizer, the first phase retarder, the objective, the second phase retarder and the analyzer, and observe the imaging quality of the sample and determine the focusing condition.

[0069] As a preferred embodiment, the focal plane of the third lens 16 coincides with the focal plane of the second lens 13, and forms a relay lens group with the second lens 13, so that the image on the back focal plane of the objective is imaged twice to the slit plane of the imaging spectrometer. The slit of the imaging spectrometer is arranged at the focal plane of the second lens, the imaging spectrometer disperses the linear light signal collected from the slit to obtain the angularly resolved spectrum, and then calculates the polarization parameters of the reflected light reaching the imaging spectrometer, and further obtains the combination of the Mueller matrix elements sensitive to the overlay error.

[0070] As a preferred embodiment, the focal plane of the second lens 13 coincides with the focal plane of the first lens 8, and forms a relay lens group with the first lens 8, and the lenses of the first lens and the objective 9 form a relay lens group, so that the image on the overlay sample under test is imaged to the pixel plane of the face array camera 17.

[0071] In this embodiment, the overlay error measurement module is the data processing system 18, which obtains the angularly resolved spectral signals of the overlay sample to be measured from the imaging spectrometer 15, and based on the signals, obtains the linear combination of the off-diagonal elements of the Mueller matrix of the overlay sample to be measured at different incident angles, and further obtains the overlay error of the overlay sample to be measured.

[0072] Wherein, the off-diagonal elements of the Mueller matrix of the overlay sample to be measured at different incident angles are obtained by using the following system model:

[0073] S out (λ, θ) = [M A R(α2)]·[R(-β2)M R (δ2)R(β2)]·M S (λ, θ)·[R(-β1)M R (δ1)R(β1)]·[R(-α1)M P ]·S in

[0074] Wherein, S out is the Stokes vector corresponding to the exit light (i.e. the light beam after the spectral modulation module), M A is the Mueller matrix corresponding to the second polarization, M P is the Mueller matrix corresponding to the first polarization, R(*) represents the Mueller rotation matrix when the rotation angle is *, α1 is the azimuth angle of the pass axis when the first polarization, α2 is the azimuth angle of the pass axis when the second polarization; β1 is the azimuth angle of the fast axis when the first phase delay, β2 is the azimuth angle of the fast axis when the second phase delay, M R (δ1) is the Mueller matrix corresponding to the first phase delay, M R (δ2) is the Mueller matrix corresponding to the second phase delay, M S (λ, θ) is the Mueller matrix corresponding to the overlay sample to be measured, S in is the Stokes vector corresponding to the incident light (i.e. the light beam before the spectral modulation module), λ is the wavelength, and θ is the incident angle of the light beam on the overlay sample to be measured.

[0075] Wherein, δ1 and δ2 are the phase delay angle when the first phase delay and the phase delay amount when the second phase delay, respectively, and δ i = 2πB i (σ)t i σ (i = 1, 2), here, B i (σ) and t i are the birefringence and thickness of the multi-stage wave plate, respectively, and σ is the wave number (i.e. the reciprocal of the wavelength λ).

[0076] The Mueller matrix M S (λ, θ) corresponding to the overlay sample to be measured is:

[0077]

[0078] wherein m 11 (λ,θ), m 12 (λ,θ), …, m 44 (λ,θ) are the Mueller matrix elements, respectively.

[0079] R(α) denotes a Mueller rotation matrix with a rotation angle of α:

[0080]

[0081] wherein α = α1, α2, β1, β2; and α1and α2are the azimuth angles of the pass axis at the first and second polarizations, respectively, and β1and β2are the azimuth angles of the fast axis at the first and second phase retardations, respectively.

[0082] In this embodiment, the azimuth angle of the pass axis at the first polarization is 45°, the azimuth angle of the fast axis at the first phase retardation is 90°, the azimuth angle of the fast axis at the second phase retardation is 90°, and the azimuth angle of the pass axis at the second polarization is 45°, i.e., α1= α2= 45°, β1= β2= 90°. If the devices used for the first and second phase retardations are both multi-order wave plates made of the same birefringent crystal material (i.e., B1(σ) = B2(σ), simply denoted as B(σ)), and the thicknesses of the two multi-order wave plates are equal (i.e., t1= t2, simply denoted as t), then the phase retardation amounts of the two phase retardations are δ1= δ2. For convenience, the phase retardation amounts of the first and second phase retardations are denoted as δ = 2πB(σ)tσ. Substituting the specific configuration information into the above system model, the first element of the Stokes vector S out corresponding to the outgoing light beam can be obtained, i.e., the light intensity I out corresponding to the outgoing light beam:

[0083]

[0084] Using Euler's formula, formula (6) can be transformed as:

[0085]

[0086] That is, the linear combination of the non-diagonal elements of the Mueller matrix of the measured overlay sample is obtained. As can be seen from the formula, the measured quantity (m 31 (λ,θ) + m 13 (λ,θ)) and (m 41 (λ,θ) - m 14 (λ,θ)) are modulated to f ±1The real and imaginary parts of the carrier frequency channel are ±B(σ)t.

[0087] Preferably, the overlay error of the overlay sample to be measured is obtained by an eDBO method or a machine learning method according to a combination of non-diagonal elements of the Mueller matrix.

[0088] The present application also provides an angularly resolved snapshot overlay error measurement method, comprising the following steps:

[0089] Step S1, the probe light is sequentially subjected to first polarization and first phase modulation, and then irradiated on the overlay sample to be measured at different incident angles, and the multi-beam light reflected by the overlay sample to be measured is sequentially subjected to second phase modulation and second polarization to obtain polarization modulation light reflected by the overlay sample to be measured;

[0090] Step S2, the polarization modulation light is subjected to spectral imaging to obtain an angularly resolved spectrum of the overlay sample to be measured;

[0091] Step S3, based on the angularly resolved spectrum, a linear combination of non-diagonal elements of the Mueller matrix of the overlay sample to be measured at different incident angles is obtained, and then the overlay error is obtained.

[0092] The angularly resolved snapshot overlay error measurement device described above is a specific implementation mode of the angularly resolved snapshot overlay error measurement method of the present application.

[0093] In summary, the angularly resolved overlay error measurement device designed by the present application combines objective rear focal plane imaging technology and snapshot polarization spectrum measurement technology, realizes angularly resolved measurement by using a high numerical aperture objective lens combined with a Kohler illumination mode, has the advantages of non-contact, high resolution, rapidity, non-destructive and accurate measurement, and the measurement speed only depends on the detection time of the detection system and the processing time of the data processing system, so it can be applied to real-time online measurement of overlay errors of large-area module production integrated circuit elements on a production line.

[0094] The measuring device and method of the present application can obtain the partial combination of the overlay sample Mueller matrix elements under multiple incident angles in a single measurement, and simultaneously realize the fast measurement of the partial Mueller matrix element combination under the two aspects of wide spectrum and multiple incident angles. Compared with the traditional snapshot overlay error measuring device which only solves the parameters through the wavelength single dimension information, the present application can significantly improve the measurement accuracy and stability. Meanwhile, the present application adopts the coaxial structure and the optical path structure design of the vertical objective imaging, has the opportunity to achieve the transverse resolution close to the optical limit of the optical microscope, provides the possibility for reducing the measurement spot size, fundamentally avoids the phenomenon that the spot size of the general oblique incidence optical measurement system is large and the oblique illumination is easily affected by the vibration, meets the requirement that the overlay mark size of the product overlay error measurement cannot be too large, and can be applied to the real-time online measurement of the overlay error of the large area module production integrated circuit element on the production line.

[0095] Those skilled in the art will easily understand that the above description is only the preferred embodiment of the present application, and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An angle-resolved snapshot overlay error measurement device, characterized by, The method comprises the following steps: a probe light generation module is used to generate probe light; a spectrum modulation module is used to sequentially perform first polarization and first phase modulation on the probe light, and then irradiate the probe light on a to-be-measured overlay sample at different incident angles, and sequentially perform second phase modulation and second polarization on the multiple beams of light reflected by the to-be-measured overlay sample, to obtain polarization modulation light reflected by the to-be-measured overlay sample; an angle-resolved spectrum acquisition module is used to perform spectrum imaging on the polarization modulation light, to obtain an angle-resolved spectrum of the to-be-measured overlay sample; an overlay error measurement module is used to obtain a linear combination of non-diagonal elements of a Mueller matrix of the to-be-measured overlay sample at different incident angles based on the angle-resolved spectrum, and then obtain an overlay error; the spectrum modulation module comprises, along an optical path, a polarizer (4), a first phase retarder (5), an optical stop (6), a first non-polarized beam splitter (7), a first lens (8), an objective lens (9), a second phase retarder (11), and an analyzer (12); the probe light is converted into linearly polarized light after passing through the polarizer (4), and is subjected to first phase modulation by the first phase retarder (5); the probe light beam that passes through the optical stop (6) changes the propagation direction of the light beam after passing through the first non-polarized beam splitter (7), and is focused on the back focal plane of the objective lens (9) by the first lens (8); the front focal plane of the objective lens (9) coincides with the surface of the to-be-measured overlay sample (10), and multiple beams of light are irradiated on the to-be-measured overlay sample (10) at different incident angles under the action of the objective lens (9); the multiple beams of light reflected by the to-be-measured overlay sample (10) pass through the objective lens (9), the first lens (8), and the first non-polarized beam splitter (7) again, are subjected to second phase modulation by the second phase retarder (11), and the polarization modulation light is obtained by the analyzer (12); the angle-resolved spectrum acquisition module comprises a second lens (13) and an imaging spectrometer (15); the second lens (13) is used to converge the polarization modulation light, and the imaging spectrometer (15) is used to perform spectrum imaging on the converged modulation light to obtain the angle-resolved spectrum.

2. The apparatus of claim 1, wherein, the polarizer (4), the first phase retarder (5), the second phase retarder (11), and the analyzer (12) satisfy the following configurations: the optical axis azimuth angle of the polarizer (4) is ± 45°, the fast axis azimuth angle of the first phase retarder (5) is 0°, the fast axis azimuth angle of the second phase retarder (11) is ± 45°, and the optical axis azimuth angle of the analyzer (12) is 0°; or the optical axis azimuth angle of the polarizer (4) is ± 45°, the fast axis azimuth angle of the first phase retarder (5) is 90°, the fast axis azimuth angle of the second phase retarder (11) is ± 45°, and the optical axis azimuth angle of the analyzer (12) is 90°. or the azimuth angle of the pass axis of the polarizer (4) is ± 45°, the azimuth angle of the fast axis of the first phase retarder (5) is 90°, the azimuth angle of the fast axis of the second phase retarder (11) is 90°, and the azimuth angle of the pass axis of the analyzer (12) is ± 45°.

3. The apparatus of claim 1, wherein, The first phase retarder (5) and the second phase retarder (11) are both multistage wave plates made of birefringent crystal, and the thickness ratio is 1:

1.

4. The apparatus of claim 1, wherein, The front focal plane of the first lens (8) coincides with the back focal plane of the objective lens (9).

5. The apparatus of claim 1, wherein, The angle-resolved spectrum acquisition module further comprises a second non-polarizing beam splitter (14), a third lens (16), and a face array camera (17). The second non-polarizing beam splitter (14) is used to split the polarization modulation light after converging by the second lens (13), one of which is used for spectral imaging by the imaging spectrometer (15), and the other is used for imaging quality observation of the measured overlay sample by the face array camera (17) after converging by the third lens (16), and the system parameters in the device are calibrated.

6. The apparatus of claim 1, wherein, In the overlay error measurement module, the Mueller matrix off-diagonal elements of the measured overlay sample at different incident angles are obtained by the following system model: In the formula, is the Stokes vector corresponding to the light beam passing through the spectral modulation module, , are the Mueller matrices corresponding to the first polarization and the second polarization, respectively, is the Mueller rotation matrix when the rotation angle is , , are the fast axis azimuth angles of the first phase retardation and the second phase retardation, respectively, , are the fast axis azimuth angles of the first phase retardation and the second phase retardation, respectively, , are the Mueller matrices corresponding to the first phase retardation and the second phase retardation, respectively, is the Mueller matrix corresponding to the overlay sample to be measured, is the Stokes vector corresponding to the light beam before the spectral modulation module, is the wavelength, is the light beam incidence angle irradiated on the overlay sample to be measured; Wherein, the Mueller matrix corresponding to the overlay sample to be measured is: wherein , , are the Mueller matrix elements, respectively.

7. The apparatus of claim 1, wherein, The probe light generation module sequentially comprises a broadband light source, an optical fiber (2), and a collimating lens (3) along the optical path direction.

8. An angle-resolved snapshot overlay error measurement method, characterized by, The device of any one of claims 1-7 is used for angle-resolved snapshot overlay error measurement, comprising the following steps: Step S1, the probe light is sequentially subjected to first polarization and first phase modulation, and then irradiated on the measured overlay sample at different incident angles, and the multiple beams reflected by the measured overlay sample are sequentially subjected to second phase modulation and second polarization, to obtain polarization modulation light reflected by the measured overlay sample; Step S2, the polarization modulation light is subjected to spectral imaging to obtain the angle-resolved spectrum of the measured overlay sample; Step S3, based on the angle-resolved spectrum, a linear combination of the Mueller matrix off-diagonal elements of the measured overlay sample at different incident angles is obtained, and then the overlay error is obtained.

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