CN116718603A - Diffraction imaging defect detection system and detection method thereof - Google Patents
Diffraction imaging defect detection system and detection method thereof Download PDFInfo
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Abstract
The application discloses a diffraction imaging defect detection system and a detection method thereof, which are based on large-angle dark field diffraction microscopic imaging and bright field microscopic imaging technologies, can simultaneously obtain bright field microscopic images and dark field diffraction microscopic images, rapidly acquire structural information of a large-area diffraction optical waveguide surface in multiple angles, and then complete automatic positioning of defects by matching with a corresponding image processing algorithm, judge defect types, are favorable for industrial application of diffraction optical waveguide defect detection, and improve detection efficiency. The application solves the problems that the traditional detection method for detecting the defects of the diffraction optical waveguide has strict requirements on environment, complex algorithm requirements and high cost, and is not suitable for large-scale industrialized popularization and application.
Description
Technical Field
The application relates to the technical field of optical detection, in particular to a diffraction imaging defect detection system and a detection method thereof.
Background
Augmented reality (Augmented Reality, AR) is a technology that superimposes virtual image information on a real environmental scene through a miniature imaging system and performs man-machine interaction using a camera, a sensor, and the like. In various technical routes of augmented reality, the scheme of the diffraction optical waveguide is considered to have the most market and commercial prospect, and the diffraction optical waveguide is taken as a core component of the scheme, and the main function of the scheme is to transmit image information projected by a micro projector into a user field of view, and to generate superposition with a real environment, and to synchronously enter human eyes, so that augmented reality is realized. Therefore, the structure distribution of the surface of the diffraction optical waveguide directly affects the imaging effect, and defects, especially periodic defects, of the grating structure of the surface of the diffraction optical waveguide cause imaging quality problems such as degradation of imaging definition and ghost images. However, at present, there is no simple and efficient detection system and detection method in the aspect of diffraction optical waveguide defect detection, and although atomic force microscope, scanning electron microscope and other microscopy technologies with extremely high spatial resolution are widely applied in the field of semiconductor defect detection, a large amount of detection time is required for applying the detection system and the detection method to large-area diffraction optical waveguide defect scanning, and the detection system and the detection method are not suitable for large-scale industrialized flow; other methods for detecting defects by using a laser scattering method, an interferometry method and the like have similar problems, and have the problems of severe environmental requirements, complex algorithm requirements, high cost and the like.
The information disclosed in this background section is only for enhancement of understanding of the general background of the application and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person of ordinary skill in the art.
Disclosure of Invention
In order to overcome the defects in the prior art, a diffraction imaging defect detection system and a detection method thereof are provided, so that the problems that the traditional detection method for detecting the defects of the diffraction optical waveguide is complex in steps, time-consuming, high in cost and not suitable for large-scale industrialized popularization and application are solved.
To achieve the above object, there is provided a diffraction imaging defect detection system including:
the electric sample table is arranged on the inner ring of the bearing table, the electric sample table can perform corresponding translational movement and rotary movement according to the shape and the size of the diffraction optical waveguide to be measured, and the electric rotary table is arranged on the outer ring of the bearing table and can rotate along the axial direction of the bearing table;
the first photoelectric detection equipment is used for respectively acquiring a bright field microscopic image and a dark field diffraction microscopic image of the diffraction optical waveguide to be detected and is aligned to the electric sample stage;
the dark field illumination module comprises a white light source for generating high-coherence light and a beam modulator aligned to the electric sample stage, wherein the white light source is connected to the beam modulator through an optical fiber so as to generate a dark field beam irradiated to the diffraction optical waveguide to be detected;
the first imaging light path comprises a microlens assembly used for collecting optical information of the surface of the diffraction optical waveguide to be detected and an imaging lens assembly used for imaging the optical information at the first photoelectric detection equipment;
the bright field illumination module comprises a beam splitter, a wide-spectrum light source aligned to the other exit port of the beam splitter and a 4f optical system for converging the wide-spectrum light source to form a bright field light beam, wherein the bright field light beam sequentially irradiates the diffraction optical waveguide to be detected through the beam splitter and the microlens assembly so as to enable the first photoelectric detection equipment to acquire the bright field microscopic image.
Further, the dark field illumination module further includes a polarization modulator mounted on the beam modulator.
Further, the first photoelectric detection device is a CCD or a CMOS.
Further, an electric telescopic rod is adjustably mounted on the electric rotary table of the bearing platform outer ring, and the beam modulator is rotatably mounted on the electric telescopic rod.
Further, the device also comprises a second imaging light path and a second photoelectric detection device which are rotatably arranged on the telescopic rod, wherein the second imaging light path comprises a microlens assembly and an imaging lens assembly which are aligned with the electric sample stage, the second photoelectric detection device is aligned with an emergent end of the microlens assembly, and the imaging lens assembly of the second imaging light path is arranged between the emergent end and the second photoelectric detection device.
Furthermore, the electric sample stage can preset a moving path in the detection process according to the shape and the size of the diffraction optical waveguide to be detected.
The application provides a detection method of a diffraction imaging defect detection system, which comprises the following steps:
a. mounting the diffraction optical waveguide to be measured on an electric sample stage;
b. opening a bright field illumination module, a broad spectrum light source of the bright field illumination module producing broad spectrum light that converges the broad spectrum light via a 4f optical system to form a bright field light beam;
c. the bright field light beam irradiates the diffraction optical waveguide to be measured through the first imaging light path to form a parallel light beam;
d. the first imaging light path images the optical information of the surface of the diffraction optical waveguide to be detected at the first photoelectric detection equipment, so that the first photoelectric detection equipment obtains a bright field microscopic image of the diffraction optical waveguide to be detected;
e. closing the bright field illumination module;
f. starting a dark field illumination module, wherein the white light source generates high-coherence light and inputs the high-coherence light into the light beam modulator through the optical fiber to generate a dark field light beam, and the dark field light beam irradiates on the first side of the diffraction optical waveguide to be detected at a preset incident angle;
g. the dark field light beam generates diffraction on a first side of the diffraction optical waveguide to be detected;
h. the microlens assembly of the first imaging light path collects optical information in a diffraction area generated on the surface of the diffraction optical waveguide to be detected and inputs the optical information into the imaging lens assembly;
i. the imaging lens assembly images the optical information at a first photoelectric detection device, so that the first photoelectric detection device obtains a dark field diffraction microscopic image of the diffraction optical waveguide to be detected;
j. b, adjusting the position of the diffraction optical waveguide to be detected through the electric sample table, and repeating the steps b-i to enable the first photoelectric detection equipment to continuously scan and acquire first image information of the diffraction optical waveguide to be detected;
k. rotating an electric rotating table to enable the dark field illumination module to be aligned to the second side, the third side and the fourth side of the diffraction optical waveguide to be detected, and repeating b-j to enable the first photoelectric detection equipment to continuously scan and acquire second image information, third image information and fourth image information of the diffraction optical waveguide to be detected;
and determining the defect position and the specific type of the diffraction optical waveguide to be detected based on the first image information, the second image information, the third image information and the fourth image information.
The diffraction imaging defect detection system has the advantages that based on the large-angle dark field diffraction microscopic imaging and bright field microscopic imaging technology, bright field microscopic images and dark field diffraction microscopic images can be obtained simultaneously, multi-angle rapid acquisition is carried out on structural information of a large-area diffraction optical waveguide, and then the corresponding image processing algorithm is matched to complete automatic positioning of defects, judge defect types, facilitate industrial application of diffraction optical waveguide defect detection and improve detection efficiency.
Drawings
Other features, objects and advantages of the present application will become more apparent upon reading of the detailed description of non-limiting embodiments, made with reference to the accompanying drawings in which:
fig. 1 is a schematic structural diagram of a diffraction imaging defect detection system according to an embodiment of the present application.
Fig. 2 is a layout diagram of a second photoelectric detection device according to an embodiment of the present application.
Fig. 3 is a schematic layout structure of a second photoelectric detection device and a dark field illumination module according to an embodiment of the application.
Fig. 4 is a schematic structural diagram of a transmissive bright field illumination module according to an embodiment of the application.
Fig. 5 is a schematic structural diagram of a platform according to an embodiment of the present application.
Fig. 6 is a diagram showing a detection effect of a diffraction optical waveguide to be detected according to a first embodiment of the present application.
Fig. 7 is a diagram showing a detection effect of a diffraction optical waveguide to be detected in case two according to an embodiment of the present application.
Detailed Description
The application is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the application and are not limiting of the application. It should be noted that, for convenience of description, only the portions related to the application are shown in the drawings.
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other. The application will be described in detail below with reference to the drawings in connection with embodiments.
Referring to fig. 1 to 5, the present application provides a diffraction imaging defect detection system, comprising: the system comprises a bearing platform 1, a first photoelectric detection device 2, a dark field illumination module 3, a first imaging light path 4 and a bright field illumination module 5.
Wherein, electric sample platform 11 is installed to cushion cap 1 inner circle. An electric rotating table 14 is arranged on the outer ring of the bearing platform 1.
The first photo detection device 2 is aligned to the motorized sample stage 1. The first photoelectric detection device 2 is used for respectively acquiring a bright field microscopic image and a dark field diffraction microscopic image of the diffraction optical waveguide to be detected. The first photo detection device 2 is a CCD or CMOS.
The dark field lighting module 3 comprises a white light source 31 and a beam modulator 32. The white light source 31 is used to generate highly coherent light. The white light source 31 is aligned with the motorized stage 11. The white light source 31 is connected to the beam modulator 32 through an optical fiber to generate a dark field beam that irradiates the diffraction optical waveguide to be measured.
The first imaging optical path 4 comprises a microlens assembly 41 for collecting optical information of the surface of the diffractive optical waveguide to be measured and an imaging lens assembly 43 for imaging the optical information at the first photodetection device 2.
The bright field illumination module 5 includes a broad spectrum light source 51 aligned with an exit port of the beam splitter 42 and a 4f optical system 52 for converging the broad spectrum light to form a bright field light beam. The bright field light beam is sequentially irradiated to the diffraction optical waveguide to be measured through the beam splitter 42 and the microlens assembly 41 to enable the first photoelectric detection device 2 to acquire a bright field microscopic image.
As a preferred embodiment, the dark field lighting module 3 further comprises a polarization modulator 33. The polarization modulator 33 is mounted on the beam modulator 32.
In this embodiment, an electric telescopic rod 13 is adjustably mounted on an electric turntable on the outer ring of the table 1, and a beam modulator 32 is rotatably mounted on the telescopic rod 13.
As a preferred embodiment, the diffraction imaging defect detection system of the present application further includes a second imaging optical path 6 and a second photodetection device 7 rotatably mounted to the telescopic link 13.
The second photodetector 7 is a CCD or CMOS.
The second imaging optical path 6 includes a microlens assembly 41 and an imaging lens assembly 43 aligned with the motorized sample stage 11. The second photodetector 7 is aligned with the exit end of the microlens assembly 41. The imaging lens assembly 43 of the second imaging light path 6 is arranged between the exit end and the second photo detection means 7.
In this embodiment, the second imaging beam path 6 and the second photodetector 7 are mounted on a support. One end of the supporting piece is hinged to the end part of the telescopic end of the telescopic rod. An electric hydraulic push rod for adjusting the angle of the supporting piece is hinged between the other end of the supporting piece and the fixed end of the telescopic rod.
The electric rotating table and the supporting member are respectively provided with an angle sensor to acquire the rotation angles of the electric telescopic rod and the electric rotating table and the inclination angles of the second imaging light path 6 and the second photoelectric detection device 7.
In order to acquire dark field and bright field microscopic images at the same time to further improve the detection efficiency, referring to fig. 2, the dark field illumination module is replaced by a dark field microscopic imaging light path, at this time, the bright field microscopic imaging light path is changed into a bright field microscopic imaging light path, and the bright field microscopic image and the dark field diffraction microscopic image can be obtained through two microscopic imaging light paths at the same time by illumination of the bright field light source. The dark field microscopic imaging light path can also regulate and control the azimuth angle and the pitch angle of the dark field microscopic imaging light path, so that multi-angle detection is realized. In addition, the wide-spectrum light source is replaced by a wide-spectrum light source with higher power and stronger coherence.
As a preferred embodiment, referring to fig. 4, the bright field illumination light path and the bright field microscopic imaging light path are separated, and a transmission type rather than reflection type illumination mode is adopted.
Referring to FIG. 3, the momentum conservation theorem k is followed //in +m·G＝k //out Diffraction formulas of the one-dimensional and two-dimensional gratings can be strictly deduced, and the diffraction formulas sin theta of the one-dimensional gratings are used in +sinθ out For obtaining higher-order diffraction information, a dark-field microscopic imaging optical path is arranged on the same side of the dark-field illumination module for obtaining higher-order diffraction information.
The diffraction imaging defect detection system provided by the application can simultaneously obtain the bright field microscopic image and the dark field diffraction microscopic image based on the large-angle dark field diffraction microscopic imaging and bright field microscopic imaging technology, rapidly acquire the structural information of the large-area diffraction optical waveguide surface in multiple angles, and then complete the automatic positioning of the defect by matching with a corresponding image processing algorithm, judge the defect type, thereby being beneficial to the industrialized application of diffraction optical waveguide defect detection and improving the detection efficiency.
The application provides a detection method of a diffraction imaging defect detection system, which comprises the following steps:
a. the diffraction optical waveguide to be measured is mounted on the motorized stage 11.
b. The bright field illumination module 5 is turned on, and the broad spectrum light source 51 of the bright field illumination module 5 generates broad spectrum light, and the broad spectrum light converges the broad spectrum light via the 4f optical system 52 to form a bright field light beam.
c. The bright field light beam passes through the first imaging light path 4 to form a parallel light beam to irradiate the diffraction optical waveguide to be measured.
d. The first imaging optical path 4 images the optical information of the surface of the diffraction optical waveguide to be measured at the first photoelectric detection device 2, so that the first photoelectric detection device 2 obtains a bright field microscopic image of the diffraction optical waveguide to be measured.
For the bright field microscopic imaging process, light generated by a bright field light source is converged by a lens group and then forms parallel light with uniform illuminance by a microscope group, so that the first photoelectric detection equipment can obtain sample surface information with uniform brightness.
e. The bright field illumination module 3 is turned off.
f. The dark field illumination module 3 is turned on, and the white light source generates high-coherence light and inputs the high-coherence light to the beam modulator 32 through the optical fiber to generate a dark field beam, and the dark field beam irradiates the first side of the diffraction optical waveguide to be measured at a preset angle θ.
g. The diffraction optical waveguide to be measured generates diffraction.
h. The microlens assembly 41 of the first imaging light path 4 collects optical information in the surface-generated diffraction region of the diffraction optical waveguide to be measured and inputs it into the imaging lens assembly 43.
i. The imaging lens assembly 43 images the optical information at the first photo-detection device 2 so that the first photo-detection device 2 acquires a dark field diffraction microscopic image of the diffraction optical waveguide to be measured.
For the dark field diffraction microscopic imaging process, the optical information (signal) of the diffraction optical waveguide structure in the corresponding area is collected by the microscope component and then emitted, and finally is focused by the imaging lens and then imaged at the first photoelectric detection equipment.
j. The position of the diffraction optical waveguide to be measured is adjusted by the electric sample stage 11, and the steps b to i are repeated to enable the first photoelectric detection device 2 to continuously acquire the first image information of the grating structure of the surface of the diffraction optical waveguide to be measured.
Specifically, the diffraction optical waveguide to be measured moves through a preset path of the electric sample stage, and further, the first image information of the grating structure of the surface of the diffraction optical waveguide to be measured is continuously acquired through the first photoelectric detection equipment 2.
By controlling the switching of the bright field light source and the dark field light source, the light source is switched on and off at an angle beta 1 A bright field microscopy image and a dark field diffraction microscopy image were obtained separately in that order. After which the sample stage is moved either transversely or longitudinally,and according to the serpentine motion mode, grating structure information of the whole diffraction optical waveguide sample surface is obtained, and then image analysis is carried out on the grating structure information, so that the detection process is completed.
k. The electric rotating table 14 is rotated, that is, the angle β is changed, so that the dark field illumination module 3 is aligned with the second side, the third side, and the fourth side of the diffraction optical waveguide to be measured, and b to j are repeated to make the second image information, the third image information, and the fourth image information of the grating structure of the surface of the diffraction optical waveguide to be measured.
And determining periodic defect positions on the surface of the diffraction optical waveguide to be measured based on the first image information, the second image information, the third image information and the fourth image information.
According to the optical reflection theorem, for random defects common to the surface of smooth optical elements (e.g., diffractive optical waveguides), due to their irregularities, when light is shone onto a surface containing defects, the local structure of the defects causes a portion of the incident light to be reflected at its respective surface, thereby deflecting this portion of the light from the reflection direction when it is defect-free, and being received in other directions. Thus, the topographical information of random defects is typically more readily manifested in scattered light that does not cover the reflected signal from the sample surface of the diffractive optical waveguide, meaning a higher signal-to-noise ratio. Based on this principle, dark field scatter imaging is widely used in random defect detection of optical elements. However, the size of random defects that can be detected by dark field scatter imaging is typically around hundred microns, and the choice of scatter angle and azimuth angle of the light source is critical.
According to the diffraction imaging defect detection system and the diffraction imaging defect detection method, a diffraction optical waveguide product with a hundred-nanometer period is focused according to a physical mechanism of grating diffraction, so that the purpose of detecting the surface structural defects of the diffraction optical waveguide, especially periodic defects, is achieved, and a set of large-angle dark field diffraction microscopic imaging scheme is provided.
In the present application, the periodic defect refers to another set of period generated by the diffraction optical waveguide product in the preset structural period in the processing process due to the processing error, and the set of periodic defect can have a great influence on the imaging effect of the final product.
Detection of grating structure defects by dark field diffraction provides higher contrast and more grating structure detail than bright field detection. Because, diffraction phenomena are the behavior of the fluctuating nature of light at the edges or apertures of an object (where the structures are typically on the order of wavelengths), when light waves interact with the edges of the structure, diffracted light is produced. These diffracted lights contain rich spatial frequency components, wherein higher order spatial frequencies correspond to the microscopic topography details of the structure, so that more grating topography information can be displayed by imaging the diffracted lights. While the direction of diffracted light is usually different from reflected light, diffraction imaging also usually means dark field imaging. Meanwhile, for grating diffraction, the physical mechanism comprises diffraction and interference modulation, so that the phenomenon of coherence enhancement can be observed under a specific angle (diffraction order), thereby generating extremely high contrast with dark field environment and presenting clear images. In addition to the above two points, conventional bright field microscopy typically requires a large refractive index difference between the grating structure surface and the substrate material, otherwise the contrast between the imaged grating structure surface and the background will be low, which is detrimental to observation and judgment.
The larger incident angle is reasonably designed according to a grating diffraction formula. With a one-dimensional grating diffraction formula sin theta in +sinθ out For example, =mλd, if an illumination source having a wavelength of 532nm is provided at an angle of incidence of 0 ° with a grating period of 550nm, the first order diffracted light is received at least at an angle of 75 °, at which diffraction imaging of the observed grating is most clear. Since the actual light source is a high-coherence wide-spectrum light source, and the wavelength band from ultraviolet to infrared is covered, for a grating of a specific period, there is a diffraction range in which diffraction information can be received, but when the period of the grating is very small (for example, 200 nm), most of the light in the wavelength band cannot be diffracted according to a diffraction formula, and the rest of the light in the wavelength band can be diffracted only at a large angle close to the horizontal.
Dark field scattering detection of random defects is quite different from the principle of dark field diffraction imaging of a diffraction optical waveguide grating, and for random defect detection, when the scattering angle is too large, the intensity of scattered light is usually gradually weakened to the noise level along with the increase of the scattering angle and is difficult to detect, so that for random defects on a smooth surface, large-angle scattered light detection is avoided. However, the large-angle scattering characteristic of the random defects brings convenience to the detection of the random defects of the diffraction optical waveguide. Because the grating diffracts, the grating structure surface appears as a bright area under a large angle, and the random defects appear as obvious low-brightness areas in the bright area, so that the periodic defects can be detected by diffraction imaging of the grating under a large angle, and the random defects can be detected at the same time.
In summary, based on the principle, in order to solve the problems of low detection speed, high environmental requirement and the like of the traditional other method for measuring the defects of the diffraction optical waveguide, the application provides a large-angle dark field diffraction microscopic imaging optical detection scheme taking dark field imaging as main bright field imaging as auxiliary.
In the detection system of the application, the dark field illumination module comprises a white light source capable of generating high-coherence light and a beam modulator which are connected with each other through a single-mode fiber. The white light source contains light in a wide spectrum from ultraviolet to infrared, and can meet the optimal diffraction wavelength of the angle at which the diffraction light of the diffraction optical waveguide with different periods is received.
The beam modulator is a beam control element for shaping an incident light source, so that the output light source has high collimation and uniform intensity distribution, and the diameter and energy density of an emergent beam can be adjusted according to defect detection requirements.
The beam adjuster may optionally be provided with a polarization modulator. A polarization modulator refers to a polarization adjusting element of a polarizer or a combination of a polarizer and a wave plate for producing an incident light beam of a particular polarization state.
The beam modulator is fixed on an electric rotary table capable of 360 DEG rotation around the electric sample table through a telescopic rod, so that dark field illumination light can be provided from various azimuth angles.
The beam modulator can also adjust the pitch angle, so that the imaging requirements of different large-angle diffracted lights are met.
The electric sample stage is integrated with the rotating motor and the stepping motor, so that the sample can be moved in multiple directions, and the position of the sample can be controlled more conveniently. The electric sample stage adopts a feedback regulating loop (such as an angle sensor, etc.), has extremely high repeated positioning precision, and can be controlled by a computer to record the moving position in real time.
The light and dark field microscopic imaging light path comprises a microscope group and an imaging lens.
Wherein the microscope group is a microscope objective or a lens group functionally equivalent to the objective for magnifying the detection area.
Wherein the imaging lens is used for imaging on the photodetector.
The bright field illumination module comprises an illumination light source and a bright field illumination light path.
The illumination light source is a wide-spectrum light source with a fixed position and is used for providing illumination.
The bright field illumination light path sequentially comprises two lenses and a beam splitter. The two lenses form a 4f system, after which the beam splitter is used to reflect the bright field illumination source without affecting the bright-dark field microscopic imaging light path.
In the diffraction imaging defect detection system, dark field microscopic imaging is used as a main part and bright field microscopic imaging is used as an auxiliary part, wherein the bright field microscopic imaging is used for rapidly positioning a sample surface and is convenient to focus. The bright field microscopic module directly images reflected light containing most of the information of the sample, so that the imaging definition is high. The structure and defect information of the sample can be more comprehensively restored by a subsequent image processing algorithm combining the bright field and the dark field.
In the diffraction imaging defect detection system, the light and dark field microscopic imaging shares a set of light paths, and bright field diffraction microscopic images and dark field diffraction microscopic images can be continuously obtained in a short time by controlling the light and dark field light source switch.
In the diffraction imaging defect detection system, for the same detection area of a sample, a dark field diffraction image with any azimuth angle can be obtained by rotating an electric rotating table at the fixed position of a dark field light source, however, in order to improve the detection efficiency, illumination detection is generally carried out by adopting four azimuth angles. The diffraction optical waveguide has obvious diffraction effect at certain azimuth angles due to the grating diffraction characteristic, so that the freedom of the azimuth angle of the light source is indispensable.
In the diffraction imaging defect detection system, no matter the diffraction imaging defect detection system is an electric rotating table or an electric sample table, a feedback regulating loop is introduced, so that the high-precision and high-stability position control can be realized, and meanwhile, the diffraction imaging defect detection system has good self-adaptability and robustness, and the accumulated error is avoided.
In the diffraction imaging defect detection system, in order to meet the imaging requirement of diffraction of the small-period grating, and meanwhile, in order to make random defect information more obvious, a large-angle pitch angle is adopted for illumination, different pitch angles can bring different diffraction imaging effects in a large-angle range, and the pitch angle can be adjusted according to a sample.
In the diffraction imaging defect detection system, the diffraction imaging effect of the grating can also generate different responses to different polarization states of incident light, so that a polarization modulator is introduced to regulate the polarization states of the incident light.
To further illustrate the detection effect of the diffraction imaging defect detection system of the present application, the following cases one and two are given.
Case one:
take as an example a two-dimensional defect diffraction grating sample of PMMA on silicon dioxide with a period of 700nm prepared in the laboratory. The grating was prepared by EBL etching according to a hexagonal lattice structure, while periodically missing a lattice point in the sample. The dark field diffraction microscopic image is acquired by using the main scheme, and polarization modulation is not performed in the process. The following is obtained under an objective lens having a pitch angle of a certain large angle, a certain azimuth angle, and a magnification of 100 times, and NA of 0.95, and subjected to simple image processing. Referring to fig. 6, the defect positions are very obvious, and the structural morphology of the sample and the defects can be very clearly observed.
Case two:
take as an example a two-dimensional defect diffraction grating sample of PMMA on silicon dioxide prepared in the laboratory with a period of a=500 nm. The grating was prepared by EBL etching according to a hexagonal lattice structure, while periodically shifting one lattice point in the sample. The dark field diffraction microscopic image is acquired by using the main scheme, and the polarization modulation is not performed in the process. The following is obtained under an objective lens having a pitch angle and an azimuth angle of a certain large angle and a magnification of 100 times and an NA of 0.95, and subjected to simple image processing. Referring to fig. 7, the defect position is quite clear, and the corresponding defect type and structure morphology can be further determined after the image is enlarged.
The first case and the second case adopt a laboratory self-made 500nm defect grating and a 700nm defect grating. The components include one EQ-99X LDLS laser driven white light source, one beam modulator, one electric displacement table, one objective lens with magnification of 100 and NA of 0.95, one pipeline lens, one photoelectric detection device, one bright field light source, two lenses and one beam splitter
During detection, the dark field light source is firstly turned on to fully preheat, so that the output power is ensured to be stable. In the process, the bright field light source is turned on, the focal length of the sample is adjusted, and the bright field light source is turned off after the adjustment is finished. After preheating, the diffraction optical waveguide is placed on the sample stage, the angle and the height of the beam modulator are adjusted to enable the incident beam to irradiate on the sample observation area, the diffraction intensity of the sample area is enabled to be maximum, and then the beam modulator is adjusted to reduce the beam diameter, improve the energy density and enable the image brightness to be further improved. And then controlling the electric rotating table, collecting dark field diffraction microscopic images on four azimuth angles, and selecting the image with the best dark field diffraction imaging effect after the collection is finished.
The above description is only illustrative of the preferred embodiments of the present application and of the principles of the technology employed. It will be appreciated by persons skilled in the art that the scope of the application referred to in the present application is not limited to the specific combinations of the technical features described above, but also covers other technical features formed by any combination of the technical features described above or their equivalents without departing from the inventive concept. Such as the above-mentioned features and the technical features disclosed in the present application (but not limited to) having similar functions are replaced with each other.
Claims (7)
1. A diffraction imaging defect detection system, comprising:
the electric sample table is arranged on the inner ring of the bearing table and can perform corresponding translational movement and rotary movement according to the shape and the size of the diffraction optical waveguide to be detected, the electric rotary table is arranged on the outer ring of the bearing table, and the electric rotary table can rotate along the axial direction of the bearing table;
the first photoelectric detection equipment is used for respectively acquiring a bright field microscopic image and a dark field diffraction microscopic image of the diffraction optical waveguide to be detected and is aligned to the electric sample stage;
the dark field illumination module comprises a white light source for generating high-coherence light and a beam modulator aligned to the electric sample stage, wherein the white light source is connected to the beam modulator through an optical fiber so as to generate a dark field beam irradiated to the diffraction optical waveguide to be detected;
a first imaging light path comprising a microlens assembly for collecting surface optical information of the diffraction optical waveguide to be measured and an imaging lens assembly for imaging the optical information at the first photodetection device;
the bright field illumination module comprises a beam splitter, a wide-spectrum light source aligned to an exit port of the beam splitter and a 4f optical system for converging the wide-spectrum light source to form a bright field light beam, wherein the bright field light beam sequentially irradiates the diffraction optical waveguide to be detected through the beam splitter and the microlens assembly so as to enable the first photoelectric detection equipment to acquire the bright field microscopic image.
2. The diffraction imaging defect detection system of claim 1, wherein the dark-field illumination module further comprises a polarization modulator mounted on the beam modulator.
3. The diffraction imaging defect detection system of claim 1, wherein the first photodetection device is a CCD or CMOS.
4. The diffraction imaging defect detection system of claim 1, wherein the motorized turntable of the table outer race is adjustably mounted with an motorized telescopic rod, and the beam modulator is rotatably mounted on the motorized telescopic rod.
5. The diffraction imaging defect detection system of claim 4, further comprising a second imaging optical path rotatably mounted to the telescoping rod, the second imaging optical path comprising a microlens assembly and an imaging lens assembly aligned with the motorized stage, the second imaging optical path comprising an imaging lens assembly aligned with an exit end disposed on the microlens assembly, the imaging lens assembly of the second imaging optical path disposed between the exit end and the second photodetection device.
6. The diffraction imaging defect detection system of claim 1, wherein the motorized stage presets a path of movement during detection according to a shape and size of the diffraction optical waveguide to be detected.
7. A method of detecting a diffraction imaging defect detection system according to any one of claims 1 to 6, comprising the steps of:
a. mounting the diffraction optical waveguide to be measured on an electric sample stage;
b. opening a bright field illumination module, a broad spectrum light source of the bright field illumination module producing broad spectrum light that converges the broad spectrum light via a 4f optical system to form a bright field light beam;
c. the bright field light beam irradiates the diffraction optical waveguide to be measured through the first imaging light path to form a parallel light beam;
d. the first imaging light path images the optical information of the surface of the diffraction optical waveguide to be detected at the first photoelectric detection equipment, so that the first photoelectric detection equipment obtains a bright field microscopic image of the diffraction optical waveguide to be detected;
e. closing the bright field illumination module;
f. starting a dark field illumination module, wherein the white light source generates high-coherence light and inputs the high-coherence light into the light beam modulator through the optical fiber to generate a dark field light beam, and the dark field light beam irradiates on the first side of the diffraction optical waveguide to be detected at a preset incident angle;
g. the dark field light beam generates diffraction on a first side of the diffraction optical waveguide to be detected;
h. the microlens assembly of the first imaging light path collects optical information in a diffraction area generated on the surface of the diffraction optical waveguide to be detected and inputs the optical information into the imaging lens assembly;
i. the imaging lens assembly images the optical information at a first photoelectric detection device, so that the first photoelectric detection device obtains a dark field diffraction microscopic image of the diffraction optical waveguide to be detected;
j. b, adjusting the position of the diffraction optical waveguide to be detected through the electric sample table, and repeating the steps b-i to enable the first photoelectric detection equipment to continuously scan and acquire first image information of the diffraction optical waveguide to be detected;
k. rotating an electric rotating table to enable the dark field illumination module to be aligned to the second side, the third side and the fourth side of the diffraction optical waveguide to be detected, and repeating b-j to enable the first photoelectric detection equipment to continuously scan and acquire second image information, third image information and fourth image information of the diffraction optical waveguide to be detected;
and determining the defect position and the specific type of the diffraction optical waveguide to be detected based on the first image information, the second image information, the third image information and the fourth image information.
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| CN117607165B (en) * | 2024-01-24 | 2024-03-26 | 上海鲲游科技有限公司 | Ghost image judging method of diffraction optical waveguide |
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