Micro-nano structure detection method and device based on asymmetric interference

Abstract

The invention provides a micro-nano structure detection method and device based on asymmetric interference. The method comprises the steps that a light source generates a light beam for measurement; the front selection module prepares the light beam to a front selection polarization state; the dual-channel differential measurement module obtains wavefront differential information related to the micro-nano structure; the post-selection module is used for preparing the light beam to a post-selection polarization state and generating asymmetric interference; and according to the wavefront phase difference, inverting the size characteristic, the shape and the period consistency of the micro-nano structure. Diffracted wavefront phase distribution related to the micro-nano structure is reconstructed through the phase difference obtained through scanning, so that parameter information of the micro-nano structure is inverted, a light path is synchronously measured through the reflection channel and the diffraction channel, influences of posture changes of the micro-nano structure and the surface shape of a substrate are effectively avoided, and the method has the advantages of being high in precision and non-destructive.

Description

Technical Field

[0001] The present invention relates to the technical field of precision optical micro-nano structure measurement, and particularly relates to a method and device for detecting micro-nano structures based on asymmetric interference. Background Art

[0002] Micro-nano structure devices, such as metasurface structures, diffractive optical elements, computer-generated hologram structures, and photonic crystals, etc., play an important role in the fields of advanced manufacturing and scientific research. As a core device, high-precision micro-nano structures are widely used in high-end instrument and equipment such as spectrometers, grating scales, and biomedical detection devices. The quality and performance of micro-nano structures directly affect the accuracy and reliability of instrument and equipment. With the increasing accuracy requirements of high-end instrument and equipment, the accuracy requirements of micro-nano structures reach the sub-nanometer level. Therefore, the detection accuracy of micro-nano structure parameters also needs to be further improved.

[0003] Common methods for measuring micro-nano structure parameters include direct measurement methods using instruments such as atomic force microscopes, scanning electron microscopes, and transmission electron microscopes, as well as indirect measurement methods such as interference methods and diffraction methods. The direct measurement method is destructive, and the indirect measurement method has the problem of low accuracy. Therefore, the existing methods for measuring micro-nano structure parameters are difficult to meet the measurement requirements of high accuracy and non-destructiveness. To meet the measurement requirements of various high-precision micro-nano structure parameters, there is an urgent need for a detection means that can simultaneously meet high accuracy and non-destructiveness. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention proposes a method and device for detecting micro-nano structures based on asymmetric interference, and solves the technical problem that there is a lack of a detection means for micro-nano structure parameters that can simultaneously meet high accuracy and non-destructiveness in the existing technology.

[0005] The technical solution adopted by the present invention is as follows:

[0006] In the first aspect, a device for detecting micro-nano structures based on asymmetric interference is provided. The detection device is sequentially provided with a light source, a front selection module, a dual-channel synchronous differential measurement system, a rear selection module, and a displacement detector on the propagation optical path;

[0007] The light source is used to generate a continuous single-wavelength light beam for measurement;

[0008] The front selection module is used to prepare the continuous single-wavelength light beam into a front selection polarization state;

[0009] The dual-channel synchronous differential measurement module is used to direct the front selection polarization state light beam to the component to be measured and form reflected light and diffracted light; and inject the reflected light and diffracted light into the rear selection module;

[0010] The post-selection module is used to prepare the incident light beam into a post-selection polarization state and generate an asymmetric interference with a weak value amplification effect; it includes a first post-selection module for reflected light and a second post-selection module for diffracted light;

[0011] The displacement detector is used to collect the spot position offset and obtain the wavefront phase difference information of the reflected light and the diffracted light.

[0012] Furthermore, the dual-channel synchronous differential measurement module includes a beam splitting device, a shearing beam splitter, and a displacement stage for the measured object;

[0013] The beam splitting device is a non-polarizing beam splitter, and the light beam emitted by the light source does not change its propagation direction when passing through the beam splitting device for the first time; the beam splitting device is also used to inject the reflected light into the first post-selection module;

[0014] The shearing beam splitter is used to split the pre-selection polarization state light beam into two parallel orthogonally polarized light beams, and is also used to combine the two polarization components of the reflected light;

[0015] The displacement stage for the measured object is used to complete the point scanning detection of the diffraction wavefront phase difference at different positions of the measured object by moving the measured object.

[0016] Furthermore, on the propagation optical path, a beam collimator is provided between the light source and the pre-selection module, and the beam collimator is used to generate a Gaussian light beam.

[0017] Furthermore, on the propagation optical path, a second beam combiner is provided between the displacement stage for the measured object and the second post-selection module, and the second beam combiner is used to combine the two polarization components of the diffracted light.

[0018] Furthermore, it further includes a data processing system for inversely calculating the micro-nano structure parameter information from the wavefront phase difference information.

[0019] In a second aspect, a micro-nano structure detection method based on asymmetric interference is provided, which is implemented by using the micro-nano structure detection device based on asymmetric interference provided in the first aspect, and includes the following steps:

[0020] The light source emits a continuous single-wavelength light beam, which forms a polarized light beam after pre-selection;

[0021] The polarized light beam is sheared and split into two parallel orthogonally polarized light beams;

[0022] The orthogonally polarized light beams are incident on the measured micro-nano structure to form reflected light and diffracted light;

[0023] The reflected light and the diffracted light are respectively combined and then pass through post-selection, and then are respectively incident on the displacement detector, and the spot position offsets of the reflected light and the diffracted light are simultaneously obtained based on the displacement detector;

[0024] The displacement stage moves to complete the point-scanning detection of the wavefront phase difference of the device under test;

[0025] Based on the offset of the spot position, the wavefront phase difference between the reflected light and the diffracted light is obtained;

[0026] According to the wavefront phase difference, the parameter information of the micro-nano structure is inversely calculated.

[0027] Furthermore, a dual-channel synchronous differential measurement module is used to obtain the wavefront differential information related to the micro-nano structure, and the weak value amplification effect is utilized to achieve high-sensitivity phase difference measurement; according to the weak value amplification effect, the relationship between the spot position offset and the phase is as follows:

[0028]

[0029] In the above formula, represents the spot position offset, g is the asymmetry parameter (related to the small splitting of the polarization components in the asymmetric interference system), z is the waist position, is the phase difference, k is the wave vector, w0 is the waist radius, and w(z) is the spot radius at z; represents the linear approximation interval, represents the inverse linear approximation interval.

[0030] Furthermore, according to the phase difference inversion, the parameter information of the micro-nano structure includes:

[0031] Obtain the phase difference including the base surface shape and the attitude information of the device under test according to the beam position offset of the reflection channel;

[0032] Obtain the phase difference including the base surface shape, the attitude of the device under test, and the parameter information of the micro-nano structure according to the beam position offset of the diffraction channel;

[0033] Perform proportional conversion on the phase difference of the reflection channel and perform differential calculation with the phase difference of the diffraction channel to obtain the wavefront phase difference related only to the micro-nano structure parameters.

[0034] Using the reconstruction algorithm, the wavefront phase difference distribution obtained by scanning measurement is restored to the micro-nano structure parameters.

[0035] Furthermore, the parameter information of the micro-nano structure includes: size characteristics, shape, and periodic consistency.

[0036] From the above technical solutions, the beneficial technical effects of the present invention are as follows:

[0037] 1. By adopting the measurement method of this embodiment, the asymmetric interference is applied to the detection of micro-nano structure parameters. The reflection and diffraction double-pass synchronous channel measurement optical path is adopted, and the parameters of the micro-nano structure are inversed based on the phase difference, avoiding the influence of the attitude change of the micro-nano structure and the substrate surface shape, and having the advantages of high precision and non-destructiveness.

[0038] 2. Combined with the micro-nano structure parameter inversion algorithm based on phase difference, the measurement accuracy reaches the sub-nanometer level. This detection method has application prospects in the fields of semiconductor manufacturing, spectrometers, and quality control of metrological gratings. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0040] Figure 1 Schematic diagram of the asymmetric interference measurement system according to the embodiment of the present invention;

[0041] Figure 2 Schematic diagram of the beam splitting and beam combining principle according to the embodiment of the present invention;

[0042] Figure 3 Relationship diagram between the spot position offset and the phase according to the embodiment of the present invention;

[0043] Figure 4 Schematic diagram of the conversion process of physical quantities in the measurement according to the embodiment of the present invention;

[0044] Reference numerals:

[0045] 1 - Laser, 2 - Collimator, 3 - Front selection module, 4 - Non-polarizing beam splitter, 5 - PSD, 6 - PSD, 7 - Displacement stage of the component to be measured;

[0046] 11 - Shearing beam splitter, 21 - First post-selection module, 41 - λ / 4 wave plate, 42 - λ / 2 wave plate, 43 - Polarizer, 12 - Beam combiner, 22 - Second post-selection module, 31 - λ / 4 wave plate, 32 - λ / 2 wave plate, 33 - Polarizer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] The following will describe in detail the embodiments of the technical solutions of the present invention with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, so they are only examples and cannot be used to limit the protection scope of the present invention.

[0048] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application shall have the ordinary meanings understood by those skilled in the art to which the present invention pertains.

[0049] Embodiment

[0050] Asymmetric interference has a weak value amplification effect, which can effectively improve the phase measurement accuracy and realize the detection of tiny physical quantities. The asymmetric interference detection method demonstrates high-precision measurement capabilities in multiple aspects such as high-precision phase measurement and chiral molecule detection and has been verified in experiments, and is expected to play a role in the field of micro-nano structure detection.

[0051] This embodiment provides a micro-nano structure detection method based on asymmetric interference. This measurement method is realized based on a micro-nano structure detection device for asymmetric interference. The system structure of this device is as Figure 1 shown, a light source, a pre-selection module, a dual-channel synchronous differential measurement system, a post-selection module, and a displacement detector are sequentially provided on the propagation optical path;

[0052] The light source is used to generate a continuous single-wavelength light beam for measurement;

[0053] The pre-selection module is used to prepare the continuous single-wavelength light beam into a pre-selection polarization state;

[0054] The dual-channel synchronous differential measurement module is used to direct the pre-selection polarization state light beam to the component to be measured to form reflected light and diffracted light; and inject the reflected light and diffracted light into the post-selection module;

[0055] The post-selection module is used to prepare the incident light beam into a post-selection polarization state and generate asymmetric interference with a weak value amplification effect; it includes a first post-selection module for the reflected light and a second post-selection module for the diffracted light;

[0056] The displacement detector is used to collect the spot position offset and obtain the wavefront phase difference information of the reflected light and the diffracted light.

[0057] In a specific embodiment, a laser is selected as the light source. The single-wavelength light emitted by the laser 1 forms a Gaussian beam through an optical fiber and a collimator 2. The front selection module 3 (polarizer) prepares the beam system to the front selection polarization state. After the beam is split by the shearing beam splitter 11 into two parallel orthogonally polarized light beams, it then impinges on the device under test 7, forming a reflected beam and a diffracted beam. Among them, the reflected beam can use the shearing beam splitter 11 as a combiner after passing through the shearing beam splitter 11. After the reflected beam is combined by the combiner, it enters the first post-selection module 21 through the beam splitting device 4 (non-polarizing beam splitter), and uses a combination of a λ / 4 wave plate 41, a λ / 2 wave plate 42, and a Glan prism 43 to construct a post-selection of elliptical polarization. After the diffracted beam is combined by the second combiner 12, it enters the second post-selection module 22, and uses a combination of a λ / 4 wave plate 31, a λ / 2 wave plate 32, and a Glan prism 33 to construct a post-selection of elliptical polarization. The reflected light and the diffracted light respectively enter the displacement detector after passing through their respective post-selection modules. The displacement detector can use a position sensor (PSD) or a charge-coupled device image sensor (CCD). The displacement detector is used to collect the spot position offset, so as to obtain the phase difference related to the reflected and diffracted wavefronts. By moving the device under test with a displacement stage, point scanning detection of the wavefront phase difference at different positions of the device under test is realized. The data processing system inversely obtains the micro-nano structure parameter information from the scanned wavefront phase difference distribution.

[0058] The working process of the above asymmetric interference measurement system in a specific embodiment is as follows:

[0059] The light emitted by the laser is introduced into the measurement system through a single-mode optical fiber and becomes a Gaussian beam through the collimator. In a specific embodiment, the laser is a single-wavelength laser, such as a helium-neon laser. In this example, the light source wavelength is 632.8 nm.

[0060] As Figure 2 shown, the principle of shearing beam splitting is to split the Gaussian beam into two light beams with orthogonal polarization states in parallel; in a specific embodiment, the shearing beam splitter 11 is calcite with an inclined optical axis.

[0061] The front selection module 3 is used as a front selection to prepare the beam to the front selection state; in a specific embodiment, the front selection module 3 is a Glan-Taylor prism.

[0062] When the beam first passes through the 50 / 50 non-polarizing beam splitter 4, its propagation direction is not changed.

[0063] As Figure 1 shown, the reflected light is combined by the combiner and reflected by the non-polarizing beam splitter and then enters the first post-selection module. The diffracted light enters the second post-selection module through the second combiner 12. In a specific embodiment, the second combiner 12 is calcite.

[0064] The reflected light and diffracted light pass through a combination of a λ / 4 wave plate, a λ / 2 wave plate, and a Glan prism to perform post-selection of elliptical polarization; in a specific embodiment, the polarization post-selection is a Glan-Taylor prism.

[0065] Finally, two position sensors 5 and 6 are used to detect the centroid offset of the light spot, which is then converted into phase difference information. Then, based on the phase difference division, the phase distribution is reconstructed, and the micro-nano structure parameter information can be inversely obtained.

[0066] Combined with the weak value amplification theory of asymmetric interference, under specific optical parameters, the relationship between the light spot position offset and the phase difference is as follows:

[0067]

[0068] In the above formula, represents the light spot position offset, g is the beam translation distance, z is the beam waist distance, is the phase difference obtained by the shearing optical path, k is the wave vector, w0 is the beam waist radius, and w(z) is the light spot radius at z. represents the linear approximation interval, represents the anti-linear approximation interval.

[0069] The relationship between the light spot position offset and the phase is as Figure 3 shown. The polarization states of the pre-selection module and the post-selection module are nearly orthogonal, and the weak value amplification effect increases the position offset of the light spot, thereby realizing the measurement of the phase difference related to the micro-nano structure parameters.

[0070] In some examples, the test piece moves with the displacement stage to achieve point scanning detection of the phase difference of the diffracted wavefront of the test piece, and the micro-nano structure parameter information is inversely obtained from the scanned wavefront phase difference distribution.

[0071] The asymmetric interference measurement system provided in this embodiment constructs two channels, a reflection channel and a diffraction channel; the phase difference of the reflection channel is proportionally converted and differentially calculated with the phase difference of the diffraction channel to obtain a wavefront phase difference related only to the micro-nano structure parameters. Using a reconstruction algorithm, the wavefront phase difference distribution obtained by scanning measurement is restored to the micro-nano structure parameters.

[0072] According to the optical diffraction theory, when a light beam is incident on a micro-nano structure, the phase difference obtained by the reflection channel is related to the base surface shape and the attitude of the test piece, and the phase difference obtained by the diffraction channel is related to the base surface shape, the attitude of the test piece, and the micro-nano structure parameters. The parameter information of the micro-nano structure includes: size characteristics, shape, and periodic consistency. The following is an example:

[0073] For example, when measuring the grating period consistency, the spot position offsets of two channels are measured simultaneously and then converted into phase difference information. Then, based on the phase difference, the phase distribution is reconstructed, and the grating period consistency information can be inversely obtained. For example:

[0074] When the light beam is incident perpendicularly on the grating surface, the reflected light is the 0th-order diffraction of the grating, and the diffracted light is the 1st-order diffraction. The diffraction formula is:

[0075] sinθ1 + sinθ i = λ / D

[0076] where θ i is the incident angle. When θ i = 0, the diffraction equation can be written as sinθ1 = λ / D. λ is the wavelength of the light wave, and D is the grating period. Due to the influence of the attitude and surface slope, the normal angle offset δ0 = κ1 + κ2, where κ1 and κ2 are the attitude angle and surface slope respectively. The change in the reflected light angle is 2δ0, and the change in the diffracted angle is δ1. The change in the diffracted light angle after being affected by the grating attitude and surface slope is δ1 + δ0.

[0077] The phase difference φ0 measured by the reflection channel and the phase difference φ1 measured by the diffraction channel can be expressed as:

[0078]

[0079] where d is the beam lateral difference component of the differential measurement module. Then, the relationship between the period offset and the phase difference of the two channels is:

[0080]

[0081] According to this relationship, the period offset δ D can be calculated by measuring the phase difference of the reflection channel and the phase difference of the diffraction channel.

[0082] Combining the above measurement system, the grating period consistency detection method based on asymmetric interference in this embodiment has a measurement principle of using a dual-channel synchronous measurement module to obtain the phase difference information related to the grating period, and then inversely calculating the parameter information of the grating period consistency from the phase difference. This measurement system uses the weak value amplification effect constructed by asymmetric interference to achieve high-precision phase measurement, thereby realizing high-precision grating period consistency measurement. The physical conversion process of the measurement process is as Figure 4 shown.

[0083] By adopting the measurement method of this embodiment, applying asymmetric interference to the detection of grating period consistency, using a reflection and diffraction dual-channel synchronous measurement optical path, and inversely calculating the grating period consistency parameters based on phase difference, the influence of the attitude change of the micro-nano structure and the surface shape can be avoided, and it has the advantages of high precision and non-destruction.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the various embodiments of the present invention, and they should all be covered within the scope of the claims and the description of the present invention.

Claims

1. A micro-nano structure detection device based on asymmetric interference, characterized in that, The detection device is successively provided with a light source, a front selection module, a dual-channel synchronous differential measurement system, a rear selection module, and a displacement detector on the propagation optical path; The light source is used to generate a continuous single-wavelength light beam for measurement; The front selection module is used to prepare the continuous single-wavelength light beam into a front selection polarization state; The dual-channel synchronous differential measurement module is used to direct the front selection polarization state light beam to the workpiece to be measured and form reflected light and diffracted light; and to inject the reflected light and diffracted light into the rear selection module; The rear selection module is used to prepare the incident light beam into a rear selection polarization state and generate an asymmetric interference with a weak value amplification effect; it includes a first rear selection module for the reflected light and a second rear selection module for the diffracted light; The displacement detector is used to collect the spot position offset and obtain the wavefront phase difference information of the reflected light and diffracted light.

2. The micro-nano structure detection device based on asymmetric interference according to claim 1, wherein The dual-channel synchronous differential measurement module includes a beam splitting device, a shearing beam splitter, and a workpiece displacement stage; The beam splitting device is a non-polarizing beam splitter, and the light beam emitted by the light source does not change its propagation direction when passing through the beam splitting device for the first time; the beam splitting device is also used to inject the reflected light into the first rear selection module; The shearing beam splitter is used to split the front selection polarization state light beam into two parallel orthogonally polarized light beams, and is also used to combine the two polarization components of the reflected light; The workpiece displacement stage is used to complete the point scanning detection of the diffraction wavefront phase difference at different positions of the workpiece to be measured by moving the workpiece to be measured.

3. The micro-nano structure detection device based on asymmetric interference according to claim 1, characterized in that On the propagation optical path, a beam collimator is provided between the light source and the front selection module, and the beam collimator is used to generate a Gaussian beam.

4. The micro-nano structure detection device based on asymmetric interference according to claim 2, characterized in that On the propagation optical path, a second beam combiner is provided between the workpiece displacement stage and the second rear selection module, and the second beam combiner is used to combine the two polarization components of the diffracted light.

5. The micro-nano structure detection device based on asymmetric interference according to claim 1, characterized in that, It further includes a data processing system for inversely calculating the micro-nano structure parameter information from the wavefront phase difference information.

6. A detection method for micro-nano structures based on asymmetric interference, characterized in that, It is realized by using the micro-nano structure detection device based on asymmetric interference according to any one of claims 1-5, including the following steps: The light source emits a continuous single-wavelength light beam and forms a polarized light beam after front selection; The polarized light beam is split by the shearing beam splitter into two parallel orthogonally polarized light beams; The orthogonally polarized light beams are directed to the micro-nano structure to be measured to form reflected light and diffracted light; The reflected light and diffracted light are respectively combined and then pass through the rear selection, and then are respectively incident on the displacement detector, and the spot position offsets of the reflected light and diffracted light are simultaneously obtained based on the displacement detector; The displacement stage moves to complete the point scanning detection of the wavefront phase difference of the workpiece to be measured; Based on the spot position offset, the wavefront phase difference between the reflected light and diffracted light is obtained; The parameter information of the micro-nano structure is inversely calculated according to the wavefront phase difference.

7. The micro-nano structure detection method based on asymmetric interference according to claim 6, characterized in that The wavefront difference information related to the micro-nano structure is obtained by using the dual-channel synchronous differential measurement module, and the high-sensitivity phase difference measurement is realized by using the weak value amplification effect; according to the weak value amplification effect, the relationship between the spot position offset and the phase can be obtained as follows: In the above formula, represents the offset of the spot position, g is the asymmetry parameter (related to the slight splitting of the polarization components in the asymmetric interference system), z is the beam waist position, is the phase difference, k is the wave vector, w0 is the beam waist radius, and w(z) is the spot radius at z; represents the linear approximation interval, represents the anti-linear approximation interval.

8. The method for detecting micro-nano structures based on asymmetric interference according to claim 6, characterized in that Inversely calculating the parameter information of the micro-nano structure according to the phase difference, including: Obtaining the phase difference including the base surface shape and the workpiece attitude information according to the beam position offset of the reflection channel; Obtain the phase difference containing the information of the base surface shape and the attitude micro-nano structure parameters of the measured part according to the beam position offset of the diffraction channel; Perform proportional conversion on the phase difference of the reflection channel and perform differential calculation with the phase difference of the diffraction channel to obtain the wavefront phase difference related only to the micro-nano structure parameters. Use the reconstruction algorithm to restore the wavefront phase difference distribution obtained by scanning measurement into micro-nano structure parameters.

9. The method for detecting micro-nano structures based on asymmetric interference according to claim 6, wherein The parameter information of the micro-nano structure includes: size characteristics, shape, and periodic consistency.

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