CN110987817A - Ellipsometer integrating dark field observation based on large-numerical-aperture objective lens and measurement method - Google Patents
Ellipsometer integrating dark field observation based on large-numerical-aperture objective lens and measurement method Download PDFInfo
- Publication number
- CN110987817A CN110987817A CN201911345061.0A CN201911345061A CN110987817A CN 110987817 A CN110987817 A CN 110987817A CN 201911345061 A CN201911345061 A CN 201911345061A CN 110987817 A CN110987817 A CN 110987817A
- Authority
- CN
- China
- Prior art keywords
- light
- lens
- sample
- dark field
- objective lens
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/21—Polarisation-affecting properties
- G01N21/211—Ellipsometry
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
Landscapes
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
- Length Measuring Devices By Optical Means (AREA)
Abstract
The invention belongs to the technical field related to optical measurement, and particularly discloses an ellipsometer integrating dark field observation based on a large-numerical-aperture objective lens and a measurement method. The ellipsometer comprises an objective lens, a tube lens, an illumination light path module and a bright field light path module, wherein the illumination light path module and the bright field light path module are symmetrically arranged about a central axis of the tube lens, the illumination light path module comprises a light source, a monochromator, an optical fiber, a polarizing arm and a first reflector, and the bright field light path module comprises a second reflector, a polarization analyzing arm and a bright field detector. The method comprises the steps of selecting polarized light with specified wavelength and characteristics, sequentially passing through an illumination light path module to realize oblique incidence conditions of polarization measurement, then introducing a reflector and a vertical objective light path, and passing through a bright field light path module and a dark field light path module to realize bright field and dark field observation and measurement at the same time. The invention can realize the full-field high-resolution, low-cost and nondestructive accurate measurement of the geometrical parameters of the nanostructure film such as the optical constant, the film thickness, the characteristic line width of the nanostructure, the line height, the side wall angle and the like.
Description
Technical Field
The invention belongs to the technical field related to optical measurement, and particularly relates to an ellipsometer integrating dark field observation based on a large-numerical-aperture objective lens and a measurement method.
Background
In the current common micro-nano measuring instruments, a Scanning Tunneling Microscope (STM) and an Atomic Force Microscope (AFM) both use an ultramicro probe to scan the surface of a sample; scanning Electron Microscopy (SEM) uses an electron beam to impact the sample, and the whole measurement process needs to be performed in a vacuum environment. Although these instruments have high measurement accuracy and resolution, the measurement process is time-consuming and destructive, and requires separate sample preparation, which is costly. In contrast, optical non-destructive inspection generally has the advantage of low cost, and methods like interferometry and ellipsometry are fast, non-contact, and non-destructive. However, the conventional interferometer and ellipsometer have limited lateral resolution and cannot adapt to smaller and smaller structure sizes, and therefore, the emerging imaging ellipsometer and the like have high lateral resolution and longitudinal resolution, and are a promising measuring tool.
Since the ellipsometry can measure the size and obtain the photoelectric characteristics of a sample, the imaging ellipsometry is widely used in many scientific research fields in addition to the semiconductor manufacturing field. In the research of two-dimensional materials, two types of methods, namely mechanical stripping and chemical growth, are mainly used in the preparation mode of the two-dimensional materials at present. In which the sample size obtained by Chemical Vapor Deposition (CVD) growth is limited, e.g. MoS2Typically an equilateral triangle with a side of a few tens of micrometers, the mechanically exfoliated material, such as graphene, also needs to be measured to determine its number of layers. The traditional ellipsometry obtains average information in the detection light spot region, and although a micro light spot system can be used to improve lateral resolution, the resolution is limited by factors such as lenses and light sources, and is difficult to be less than 50 μm. In order to further improve the resolution, the imaging ellipsometer is obtained by adding the imaging light path in the polarization light path, the transverse resolution can reach below 1 mu m, and the ellipsometer can be well competent for MoS2The thickness measurement and the study of the photoelectric properties of such two-dimensional materials have been carried out. The non-contact and rapid measurement characteristics are also suitable for measuring biological materials and liquid films, especially some fluid filmsAnd (5) observing dynamic processes of the membrane.
In the prior art, the ellipsometer structure light path comprises an inclined polarizing arm and an inclined polarization analyzing arm, and the ellipsometry parameter measurement with high resolution is realized by adding an imaging device on the polarization measurement light path. However, such an optical path is limited by the object-image relationship and the depth of field of the objective lens under oblique incidence conditions, and the clear field of view will be limited to a narrow band-shaped region during imaging, which limits the range of application of the device to some extent.
Therefore, there is a need in the art to provide an ellipsometer and a measurement method based on large-numerical-aperture objective lens integrated dark-field observation, which can integrate dark-field observation equipment and realize full-field high-resolution measurement of a sample in combination with ellipsometry.
Disclosure of Invention
Aiming at the defects or improvement requirements of the prior art, the invention provides an ellipsometer integrating dark field observation based on a large-numerical-aperture objective lens and a measurement method, wherein a polarization unit and an analysis unit which are independently arranged and a vertical objective lens type light path of a symmetrically distributed reflector structure are combined, natural light can be modulated to generate polarized light with different polarization states, a proper modulation and demodulation mode is selected according to a measurement target to obtain an ellipsometric parameter or all Mueller matrix elements of a sample, meanwhile, in the light transmission process, light rays emitted from a light source are firstly converted into parallel light through a collimating lens, the polarized light is modulated through the polarization unit, after being reflected by a reflector, light beam centroid light passes through a rear focal point of a lens, the light beam is projected onto a front focal plane of the converging lens, the objective lens and the tube lens are arranged in a conjugate mode, and in this way, the light beam is projected onto the sample at a larger incident angle after passing through the objective lens, the precision of polarization measurement is guaranteed, the vertical objective structure used by the light path can also collect high-order diffraction light and scattered light, a dark field imaging light path can be added above the reflector group, and observation of a fine structure is achieved. The invention adopts a two-reflector vertical objective lens type light path structure, compared with a vertical reflection type light path realized by a general beam splitter, the light path has higher light intensity utilization rate, and can integrate dark field observation equipment and realize full-field high-resolution measurement of a sample by combining ellipsometry. Meanwhile, the device can realize the full-field high-resolution, low-cost and nondestructive accurate measurement of the geometrical parameters of the nanostructure film, including the optical constants of the two-dimensional material and the nano processing structure, the film thickness, the characteristic line width of the nanostructure, the line height, the side wall angle and the like.
To achieve the above objects, according to one aspect of the present invention, there is provided an ellipsometer for integrating dark field observation based on a large numerical aperture objective lens, including an objective lens and a tube lens sequentially arranged perpendicularly above a sample, wherein,
an illumination light path module and a bright field light path module are arranged above the lens cone lens, and the illumination light path module and the bright field light path module are symmetrically arranged about a central connecting line of the lens cone lens and the objective lens;
the illumination light path module comprises a light source, a monochromator, an optical fiber, a polarizing arm and a first reflector, wherein the light source emitted by the light source is transmitted to the polarizing arm through the optical fiber after being screened by the monochromator, the polarizing arm is used for converting the light source transmitted by the optical fiber into incident polarized light with a known polarization state and reflecting the incident polarized light to the lens cone lens through the first reflector, the incident polarized light is focused by the lens cone lens and then irradiates a sample to the sample through the objective lens, the objective lens is used for increasing the incident angle of the focused incident polarized light irradiating the sample, and the incident polarized light enters the bright field light path module after being reflected by the sample;
the bright field light path module comprises a second reflecting mirror, an analyzing arm and a bright field detector, incident polarized light reflected by the sample is transmitted to the analyzing arm after being reflected by the second reflecting mirror, the analyzing arm is used for converting the incident polarized light reflected by the second reflecting mirror into reflected polarized light with a known polarization state, and the bright field detector is used for receiving the reflected polarized light and analyzing the reflected polarized light so as to measure the ellipsometry parameter, the thickness or the optical constant of the sample in the whole view field area.
As a further preferred feature, the ellipsometer further includes a dark field optical path module disposed above the illumination optical path module and the bright field optical path module, and having a central axis collinear with a central connecting line of the tube lens and the objective lens, wherein the first reflecting mirror and the second reflecting mirror are symmetrically disposed about a central axis of the dark field optical path module.
Preferably, the dark field optical path module includes a dark field relay lens and a dark field detector, the dark field relay lens is disposed below the dark field detector, after the incident polarized light is reflected by the sample, a part of the generated scattered light passes through the objective lens and the barrel lens in sequence, and is converted into scattered parallel light by the dark field relay lens, and then enters the dark field detector, and the dark field detector analyzes the characteristics of the scattered parallel light, so as to implement three-dimensional reconstruction of the surface characteristics of the sample and characterization of the polarization characteristics.
Preferably, the polarization arm includes a collimating lens and a polarization unit, the collimating lens is disposed on a side close to the emergent light of the optical fiber, and is configured to receive the light source emitted by the optical fiber and convert the scattered light source into parallel light; the polarizing unit is arranged between the collimating lens and the first reflector and is used for converting the parallel light into incident polarized light with a known polarization state;
the polarization detection arm comprises an image conversion lens group and a polarization detection unit, the image conversion lens group is arranged on one side close to the second reflecting mirror and used for converting incident polarized light reflected by the second reflecting mirror into parallel light after being focused, and the polarization detection unit is arranged between the bright field detector and the image conversion lens group and used for demodulating the polarized state of the parallel light generated by the image conversion lens group.
As a further preference, the polarizing unit comprises two polarizers and a compensator group; the analyzing unit comprises two polarizers and a compensator group.
More preferably, the relay lens group is composed of two conjugated first and second relay lenses;
and a second aperture diaphragm is arranged at the intermediate focus of the first steering lens and the second steering lens and is used for filtering part of scattered light.
Preferably, the ellipsometer further includes a first aperture stop disposed between the first reflector and the polarizing arm, and the first aperture stop is configured to filter a portion of scattered light of the incident polarized light processed by the polarizing arm.
Preferably, a first rotating table is arranged below the first reflecting mirror, a second rotating table is arranged below the second reflecting mirror, and the first rotating table is used for adjusting the inclination angle of the first reflecting mirror, so that the incident angle of the incident polarized light, which is reflected by the first reflecting mirror and is projected onto the surface of the sample through the objective lens, is the brewster angle of the sample; the second rotating stage is used for adjusting the inclination angle of the second mirror so that the second mirror and the first mirror are symmetrically arranged about the objective lens.
More preferably, the objective lens is an infinity light correction unstressed flat field apochromatic objective lens with a numerical aperture larger than 0.82 or an infinity light correction unstressed flat field apochromatic objective lens with a numerical aperture larger than 0.82; preferably, the objective lens is an infinity light correction unstressed flat field apochromatic objective lens with a numerical aperture of 0.95 or an infinity light correction unstressed flat field apochromatic objective lens with a numerical aperture of 0.95; the bright field detector and the dark field detector are CCD cameras or CMOS cameras.
According to another aspect of the present invention, there is provided a measurement method of an ellipsometer based on a large numerical aperture objective lens integrated dark field observation, comprising the steps of:
s1, turning on a light source, adjusting a monochromator to emit monochromatic light with a specified wavelength, adjusting the monochromatic light to a collimating lens and a polarizing arm to ensure the parallelism of the monochromatic light before entering the polarizing arm, generating incident polarized light with a known polarization state after passing through the polarizing arm, adjusting the inclination angles of a first reflector and a second reflector to ensure that the incident polarized light irradiates a sample at a preset incident angle after passing through a tube lens and an objective lens;
s2, placing the sample on a sample stage, and adjusting the distance between the sample and the objective lens to enable clear images to be seen in observation areas of a bright field detector and a dark field detector;
s3 the monochromatic light emitted by the light source through the monochromator is irradiated to the collimating lens through the optical fiber, the monochromatic light is converted into parallel light under the action of the collimating lens and then transmitted to the polarizing arm, the polarizing arm is used for converting the light source transmitted by the optical fiber into incident polarized light with a known polarization state, the incident polarized light is reflected to the lens cone lens through the first reflector, the incident polarized light is focused by the lens cone lens and then shines to a sample through the objective lens, the objective lens is used for increasing the incident angle of the incident polarized light after focusing and shines to the sample, the incident polarized light enters the bright field light path module through the reflection of the sample, the incident polarized light reflected by the sample is transmitted to the analyzer arm after being reflected by the second reflector, and the analyzer arm is used for converting the incident polarized light reflected by the second reflector into the reflected polarized light with a known polarization state, the bright field detector is used for receiving a light intensity signal corresponding to the reflected polarized light, and the dark field detector is used for receiving a light intensity signal of partial scattered light generated after the incident polarized light is reflected by the sample;
s4, changing the polarization states of the polarizing arm and the polarization analyzing arm, repeating the step S3, thereby obtaining light intensity signals corresponding to the different polarization state reflected polarized lights of the preset group, and analyzing the light intensity signals of the reflected polarized lights of the preset group, so as to realize measurement of ellipsometry parameters, thickness measurement parameters or optical constant measurement parameters of the sample in the whole view field region; the dark field detector receives light intensity signals of partial scattered light generated after the incident polarized light in different polarization states is reflected by the sample so as to realize the comparative observation and detection of the micro structure of the sample;
s5, changing the wavelength of monochromatic light emitted by the light source and the monochromator, repeating the steps S1-S4 to obtain the ellipsometry parameters, thickness measurement parameters or optical constant measurement parameters of the sample under different wavelengths of a preset group, and then calculating to obtain the ellipsometry parameters, thickness or optical constants of the sample; meanwhile, the dark field detector receives light intensity signals of partial scattered light generated after the incident polarized light under different wavelengths is reflected by the sample, and therefore three-dimensional reconstruction of surface characteristics of the sample and characterization of polarization characteristics are achieved.
Generally, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:
1. the invention combines the independent polarizing unit and the independent polarization detecting unit and the vertical objective lens type light path with the symmetrical distribution reflector structure, can modulate natural light to generate polarized light with different polarization states, selects a proper modulation and demodulation mode according to a measurement target to obtain an ellipsometry parameter of a sample or all Mueller matrix elements, simultaneously, in the light transmission process, firstly, light rays emitted from a light source are converted into parallel light through a collimating lens, the polarized light is obtained through modulation of the polarizing unit, after reflection of the reflector, the light beam passes through the back focal point of a tube lens, the light beam is converged on the front focal plane of the tube lens, and in the mode, the light beam is projected onto the sample at a larger incident angle after passing through the objective lens, thereby ensuring the precision of polarization measurement.
2. The invention adopts a two-reflector vertical objective lens type light path structure, compared with a vertical reflection type light path realized by a general beam splitter, the light path has higher light intensity utilization rate, and can integrate dark field observation equipment and realize full-field high-resolution measurement of a sample by combining ellipsometry.
3. The invention uses the vertical objective type light path, and the sample and the objective main plane are arranged in parallel, thereby fundamentally solving the problem of narrow clear view field in the light path with two obliquely arranged arms. By matching with an image rotating system with proper depth of field, full-field high-resolution ellipsometry can be realized.
4. The invention uses a symmetrical reflector to fold the incident light path to realize a vertical objective lens type light path with large-angle incidence close to the Brewster angle. Compared with the light path with the same function realized by using the beam splitter, the invention has higher light utilization rate and simultaneously can not generate ghost image interference in the imaging process.
5. The large numerical aperture objective lens used in the invention participates in bright field observation and dark field observation at the same time. The dark field observation can observe finer sample structures, and the application field of the invention can be further expanded. Under the light path structure, the objective lens simultaneously participates in illumination, bright field signal collection and dark field signal collection, so that the problem of mechanical structure interference of the objective lens when a dark field observation light path is added on the traditional ellipsometer is solved.
6. The invention uses a pair of conjugate image transfer lenses to project an intermediate image onto an area array detector. The light has a real focus between the two lenses, and the arrangement of the diaphragm at the position can effectively reduce the influence of stray light on measurement data, and has a remarkable effect when a sample with back reflection is measured.
In summary, the present invention provides a device capable of realizing full-field high-resolution polarization measurement and dark-field observation of a nanostructure film and a two-dimensional material, so as to realize rapid, efficient, non-contact and non-destructive measurement and calibration of characteristic parameters of a nanostructure film with non-uniform spatial distribution, such as a machined structure and a natural growth structure of the film, in view of the actual requirements of the measurement and characterization of the nanostructure film structure and the two-dimensional material at the present stage.
Drawings
Fig. 1 is a schematic structural diagram of an ellipsometer based on a large-numerical-aperture objective lens integrated dark-field observation according to an embodiment of the present invention;
FIG. 2 is a schematic view of the illumination path configuration referred to in FIG. 1;
FIG. 3 is a schematic diagram of the bright field imaging optical path structure referred to in FIG. 1;
FIG. 4 is a schematic diagram of the dark field imaging optical path structure referred to in FIG. 1;
FIG. 5 is a schematic diagram of the polarization measurement optical path structure referred to in FIG. 1;
FIG. 6 is a diagram of the mirror tilt arrangement of an ellipsometer based on the integrated dark field observation of a large numerical aperture objective according to an embodiment of the present invention;
FIG. 7 is a schematic view of the combined structure of different polarization units and analysis units for measuring ellipsometric parameters of a sample according to the present invention in FIG. 1, wherein (a) in FIG. 7 is a combination of different polarization units, and (b) in FIG. 7 is a combination of different analysis units;
fig. 8 is a schematic view of a combined structure of different polarization units and different polarization analyzing units for measuring an element of the full-muller matrix of the sample according to the present invention, shown in fig. 1, wherein (a) in fig. 8 represents a combination of the different polarization units, and (b) in fig. 8 represents a combination of the different polarization analyzing units.
The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein: 1-light source, 2-monochromator, 3-optical fiber, 4-polarizing arm, 5-collimating lens, 6-polarizing unit, 7-first aperture diaphragm, 8-first reflector, 9-cylindrical lens, 10-objective lens, 11-sample, 12-sample stage, 13-second reflector, 14-polarization detecting arm, 15-first steering lens, 16-second steering lens, 17-second aperture diaphragm, 18-polarization detecting unit, 19-bright field detector, 20-dark field relay, 21-dark field detector.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
As shown in fig. 1, 2, 3, 4 and 5, an ellipsometer and a measurement method for integrating dark field observation based on a large numerical aperture objective according to the present invention includes: the device comprises an objective lens 10 and a tube lens 9 which are sequentially arranged vertically above a sample 11, wherein an illumination light path module and a bright field light path module are further arranged above the tube lens 9, and the illumination light path module and the bright field light path module are symmetrically arranged about the central connecting line of the tube lens 9 and the objective lens 10; the illumination light path module comprises a light source 1, a monochromator 2, an optical fiber 3, a polarizing arm 4 and a first reflector 8, wherein the light source emitted by the light source 1 is screened by the monochromator 2 and then transmitted to the polarizing arm 4 through the optical fiber 3, the polarizing arm 4 is used for converting the light source transmitted by the optical fiber 3 into incident polarized light with a known polarization state and reflecting the incident polarized light to the tube lens 9 through the first reflector 8, the incident polarized light is focused by the tube lens 9 and then shined onto a sample 11 through the objective lens 10, the objective lens 10 is used for increasing the incident angle of the focused incident polarized light onto the sample 11, and the incident polarized light enters the bright field light path module through the reflection of the sample 11; the bright field optical path module comprises a second reflecting mirror 13, an analyzing arm 14 and a bright field detector 19, incident polarized light reflected by the sample 11 is transmitted to the analyzing arm 14 after being reflected by the second reflecting mirror 13, the analyzing arm 14 is used for converting the incident polarized light reflected by the second reflecting mirror 13 into reflected polarized light with a known polarization state, and the bright field detector 19 is used for receiving the reflected polarized light and analyzing the reflected polarized light so as to measure the ellipsometry parameter, the thickness or the optical constant of the sample 11 in the whole view field area.
The ellipsometer further comprises a dark field optical path module, wherein the dark field optical path module is arranged above the illumination optical path module and the bright field optical path module, the central axis of the dark field optical path module is collinear with the central connecting line of the tube lens 9 and the objective lens 10, and the first reflector 8 and the second reflector 13 are symmetrically arranged about the central axis of the dark field optical path module. The dark field optical path module comprises a dark field relay lens 20 and a dark field detector 21, the dark field relay lens 20 is arranged below the dark field detector 21, the incident polarized light is reflected by the sample 11, part of generated scattered light sequentially passes through the objective lens 10 and the tube lens 9, and is converted into scattered parallel light by the dark field relay lens 20 and enters the dark field detector 21, and the dark field detector 21 analyzes the characteristics of the scattered parallel light to realize the three-dimensional reconstruction and the characterization of the polarization characteristics of the surface characteristics of the sample 11.
The polarizing arm 4 comprises a collimating lens 5 and a polarizing unit 6, wherein the collimating lens 5 is arranged at one side close to the emergent light of the optical fiber 3 and is used for receiving the light source emitted by the optical fiber 3 and converting the scattered light source into parallel light; the polarizing unit 6 is arranged between the collimating lens 5 and the first reflecting mirror 8, and is used for converting the parallel light into incident polarized light with a known polarization state; the analyzer arm 14 includes an image transforming lens set and an analyzer unit 18, the image transforming lens set is disposed at one side close to the second reflecting mirror 13 and is used for transforming the incident polarized light reflected by the second reflecting mirror 13 into parallel light after being focused, and the analyzer unit 18 is disposed between the bright field detector 19 and the image transforming lens set and is used for demodulating the polarized state of the parallel light generated by the image transforming lens set.
The relay lens group is composed of two conjugated first steering lenses 15 and second steering lenses 16; a second aperture stop 17 is further disposed at the intermediate focal point of the first turning lens 15 and the second turning lens 16, and is used for filtering part of scattered light. The ellipsometer further comprises a first aperture diaphragm 7 arranged between the first reflector 8 and the polarizing arm 4, wherein the first aperture diaphragm 7 is used for filtering part of scattered light of the incident polarized light processed by the polarizing arm 4.
A first rotating table is arranged below the first reflector 8, a second rotating table is arranged below the second reflector 13, and the first rotating table is used for adjusting the inclination angle of the first reflector 8, so that the incident polarized light angle of the incident polarized light reflected by the first reflector 8 and projected onto the surface of the sample 11 through the objective lens 10 is the brewster angle of the sample 11; the second rotary stage is used to adjust the tilt angle of the second mirror 13 such that it is arranged symmetrically to the first mirror 8 with respect to the objective lens 10.
The objective lens 10 is an infinity light correction unstressed flat field apochromatic objective lens with a numerical aperture larger than 0.82 or an infinity light correction unstressed flat field apochromatic objective lens with a numerical aperture larger than 0.82; preferably, the objective lens 10 is an infinity light correction unstressed field apochromatic objective lens with a numerical aperture of 0.95 or an infinity light correction unstressed field apochromatic objective lens with a numerical aperture of 0.95; the bright field detector 19 and the dark field detector 21 are CCD cameras or CMOS cameras.
Specifically, the invention provides a vertical objective lens type optical path based on a symmetrical distribution reflector structure, wherein the optical path comprises a polarization unit and an analyzing unit which are independent. The polarizing unit is used as a lighting light path module part and can modulate natural light to generate polarized light with different polarization states, and the polarization detection unit is in front of the bright field detector and is responsible for demodulating the polarization state of sample reflected light. According to the measurement target, a proper modulation and demodulation mode is selected, the ellipsometer can obtain the ellipsometric parameters of the sample or all Mueller matrix elements, on the basis, the modeling analysis is carried out on the sample through the scattering measurement theory, and important information such as the film thickness, the dielectric constant, the characteristic structure parameters and the like of the sample can be obtained.
The device is based on a vertical objective lens type polarized illumination light path of a reflector, and components participating in the illumination light path comprise a collimating lens, a small aperture diaphragm, the reflector, a tube lens, a large numerical aperture infinity correction objective lens and the polarizing unit. Qualitatively describing the behavior of the light in the illumination path: the method comprises the steps that light rays emitted from a light source are converted into parallel light through a collimating lens, the parallel light is modulated through a polarizing unit to obtain incident polarized light, after the incident polarized light is reflected by a reflector, the centroid light of the incident polarized light beam passes through a back focal point of a tube lens, the incident polarized light is converged on a front focal plane of the tube lens, and an objective lens and the tube lens are arranged in a conjugate mode.
The device also comprises an analyzing light path which comprises an imaging device and an analyzing unit, wherein the imaging device comprises the objective lens and the tube lens, a second reflector, a first image transfer lens and a second image transfer lens. The second reflector is symmetrically distributed with the first reflector of the illumination light path. The incident polarized light reflected on the sample passes through the objective lens and the tube lens again and strikes the second reflecting mirror. The part of the light path is symmetrical to the polarized illumination light path, and the reflected light and the illumination light are completely symmetrical. The sample is imaged on the back focal plane of the lens barrel, and the image of the sample is projected on the detection surface of the bright field detector through the second reflecting mirror and the image transferring lens group. An analyzing unit is arranged in an imaging light path, so that the purpose of imaging ellipsometry measurement is realized. Meanwhile, the vertical objective structure used by the light path can also collect high-order diffraction light and scattered light, and a dark field imaging light path can be added above the reflector group, so that observation of a sample microstructure is realized.
The polarizing unit and the analyzing unit in the device comprise two linear polarizers and a series of compensators. The compensator type and the modulation mode are combined and adjusted differently according to different measurement targets, so that the target of polarization modulation measurement is realized. In the embodiment of the present invention, a modulation method of a rotating wave plate type is used. Specific examples of compensator schemes that can be selected when measuring the ellipsometric parameters of a sample are: the rotary modulation wave plate, the two liquid crystal phase-changeable devices and the like are respectively as follows along the light path polarization devices: polarizer, compensator, sample, analyzer (or polarizer, sample, compensator, analyzer); when measuring the full mueller matrix elements of a sample, the compensator schemes that can be selected are: two wave plates of rotation modulation, four liquid crystal variable phase shifters etc. are respectively: a polarizer, a first rotating wave plate (or two liquid crystal phase shifters), a sample, a second rotating wave plate (or two liquid crystal phase shifters), an analyzer, and so on. Specifically, in the case of the polarization unit and the polarization analyzing unit provided by the present invention as shown in fig. 7 and 8, the actually selected polarization device needs to be adjusted by an operator according to a specific measurement target. The measurement target of the ellipsometric parameters can be the ellipsometric parameter amplitude ratio angle Ψ and the phase difference angle Δ of the sample, and the sample full-muller matrix elements can also be selected. For isotropic samples, usually only the angle of the ellipsometric parameter is measured, but for anisotropic samples, the ellipsometric parameter does not well characterize the properties of the sample, and thus the measurement of the mueller matrix elements is also very important. The elements used by the polarizing unit and the polarization analyzing unit comprise linear polaroids, retarders and relevant retarder adjusting devices. The group of device combinations used by different targets is mainly focused on the choice of retarders. The linear polarizer is selected in principle as long as it maintains a good extinction ratio κ within the operating band, and common choices include a glan taylor prism, a glan thomson prism, a metal wire grid polarizer, and the like. The retarder can be selected from a wave plate, a liquid crystal variable phase device, a photoelastic modulator and the like, when the measurement target object is an ellipsometric parameter angle, a single wave plate combined with a polarization unit or an analysis unit, a double-liquid crystal variable phase device, a single photoelastic modulator or a double-photoelastic modulator and the like can be selected, and when the measurement target object is a full Mueller matrix element of a sample, two wave plates combined with a polarization unit and an analysis unit, a four-liquid crystal variable phase device, a four-photoelastic modulator and the like can be selected. The retardation adjusting devices corresponding to the combinations are different, wherein the wave plates are usually realized by using a motor to drive rotation modulation, for the two wave plates, the rotation speed ratios of the two wave plates are required to be controlled to be constant and synchronously rotated, the commonly selected rotation speed ratios comprise 5:1 and 5:3, the liquid crystal variable phase device uses voltage adjustment, different retardation amounts are provided under different voltages, and the photoelastic modulator can select a proper oscillation signal for adjustment and can also adopt a voltage adjustment mode. In particular, the installation of the polarizing unit and the polarization analyzing unit can be reversed in general, and the measuring function of the system is not influenced. The corresponding adjusting modes are adjusted through a matched computer, and the measuring requirement is realized.
The two symmetrically arranged reflector groups in the device realize light ray refraction and rotation, and realize off-axis of the focal position of the convergent light beam on the back focal plane of the objective lens. The inclination angle of the reflector is adjusted, so that the incident angle projected to the surface of the sample through the objective lens is the Brewster angle of the sample, and the accuracy of polarization measurement is ensured. The tilt angle of the mirror is adjusted using a rotary displacement stage. The distance between the reflector and each lens is calculated according to the focal length, and the two reflectors are symmetrically distributed along the optical axis of the objective lens. The intermediate gap can be used for carrying out dark field observation on the sample in the optical path of the objective lens on the basis of high-order diffraction light and scattered light on the surface of the sample. Specifically, the present invention is mainly characterized by a vertical objective optical path structure using a symmetric mirror structure. In the device, a light source selects a broad spectrum light source with wavelength selection equipment (such as a monochromator, a filter and the like), and the purpose of measuring the spectrum information of a sample is realized by variable wavelength scanning. The microscopic imaging light path mainly plays two roles in the whole light path: firstly, light rays after passing through a reflector are collected and pass through a lens system of a microscopic imaging system to generate a beam of parallel polarized light with a large angle (the incident angle is larger than the Brewster angle of a sample) to irradiate the sample; the second point collects the reflectance information on the sample for performingSubsequent polarization analysis and dark field observation. The reflectors are symmetrically arranged in the light path, and proper angles and intervals are set, so that two functions can be realized, wherein firstly, the light rays behind the polarizing unit have a proper light ray angle relative to the optical axis of the objective lens, and large-angle illumination is realized; and secondly, zero-order light and high-order light are separated, and synchronous observation of a light field and a dark field is realized. The light path of the invention achieves the purpose of light ray deviation by using the reflecting mirror, and directly avoids the problems. The tilt angle of the mirror is adjusted using a rotary displacement stage. Another benefit of using the mirror array is that the separation of the zero order light and the high order diffracted light of the system can be simultaneously adjusted, allowing the system to simultaneously integrate the dark field observation optical paths. The arrangement of mirrors and microscopic light paths required to achieve this goal is shown in fig. 6, using mirrors instead of beam splitters. To achieve the desired light path effect by using the reflector, the reflector needs to be set at a proper angle
From the reflection law and the lens relationship one can calculate:
under the angle relation, the chief ray of the reflected light beam of the plane mirror passes through the back focus of the tube lens, and the chief ray after passing through the tube lens is parallel to the optical axis and converged on the back focal plane of the objective lens. The converging beam, which is thus displaced with respect to the optical axis, passes parallel to the front focal point of the objective lens after passing the objective lens. It is thus readily apparent that the maximum angle of incidence that can be produced perpendicular to the objective path is equal to the maximum aperture angle of the objective. Therefore, the numerical aperture of the objective lens needed by applying the objective lens in the polarization light path is preferably larger than 0.9, and the numerical aperture of the objective lens used by the invention is 0.95, so that the requirements of measurement and imaging are met.
The objective lens and the tube lens in the device form a microscopic light path. The objective lens is an infinite flat field achromatic objective lens with large numerical aperture and can realize two functions of polarized light incidence at a Brewster angle and sample reflected light collection by matching with a tube lens and a reflector. The reflected light of the sample is imaged on the back focal plane of the lens barrel, and the size of the field of view can be controlled by the size of the illumination aperture diaphragm.
The image transfer lens group in the device comprises a group of conjugate lenses and is an afocal system. The first lens is conjugated with the tube lens under the reflection of the reflector, so that the bright field image formed by the objective system is transferred to the area array detector. Because light rays have a real focus between the lens groups, a small aperture diaphragm for blocking stray light can be arranged at the light focus, and the structure can ensure the measurement reliability when a sample with a back reflection phenomenon is measured. Specifically, due to the requirement of optical path observation, a relay lens group needs to be added in the optical path. The objective lens imaging optical path collects the reflected light on the sample and forms an intermediate image on the back focal plane of the tube lens. The light path structure of the invention is difficult to directly detect the light intensity distribution of the collected intermediate image by using the detector, and the object image information of the intermediate image surface needs to be transferred to the receiving surface of the area array detector by using the image transfer lens group. The basic structure of the relay lens for polarization measurement is an afocal system, and an analyzing unit can be added on the basis of the afocal system according to actual measurement needs. Afocal systems are implemented using a set of focal plane conjugate lenses, which have the advantage that there is a real focal point in the middle of the lens, at which a stop can be placed to filter stray light (mainly back-reflected). In the image conversion light path, the polarization state of the sample reflected light is modulated and demodulated by the polarization detection unit, and finally the measurement light intensity obtained by one independent ellipsometry can be seen from the light intensity measurement result corresponding to each pixel point on the detector. By carrying out independent ellipsometry parameter analysis on each pixel point on the image, the geometric parameter three-dimensional microscopic morphology and the optical constant three-dimensional microscopic morphology of the nano-structure film to be detected in a large area including the whole imaging field of view can be accurately reconstructed. Similar dark field information also requires a relay mirror configuration. The dark field relay lens can also realize imaging observation by using an afocal system, and compared with a bright field, the dark field relay lens does not need to be provided with an anti-stray diaphragm, mainly because the aperture angles of scattered light of all stages in the intermediate image are different and a uniform real focus position is not provided. In addition, a single lens can also be used for frequency domain observation of the dark field.
Dark field observation in the device of the invention is realized by using an objective lens, a tube lens and a relay lens. The focal planes of the three devices are conjugated. The 0-order reflected light collected by the objective lens enters an analyzing light path through a reflector, and the rest high-order diffracted light and scattered light are collected on the area array detector through a group of conjugate relay lens to realize dark field observation.
The light source in the device of the invention preferentially uses a plurality of monochromatic light sources with different wavelengths to realize the measurement of the ellipsometry. The light source can be realized by a combination of a broad spectrum white light source and a wavelength filter, and can also be measured by combining lasers with different wavelengths. It is noted that when a laser light source is used, a speckle dispersing device needs to be added behind the light source, so that laser shot noise is reduced.
The bright field detector and the dark field detector in the device of the invention can adopt CCD or CMOS cameras. During measurement, the light intensity acquired by each pixel point of the detector is independent, and ellipsometry analysis can be independently performed.
In the bright field optical path imaging process of the present invention, a specific imaging principle is shown in fig. 3. The objective lens and the tube lens form a microscopic imaging light path, the reflection angle of the reflected light on the surface of the sample is theta, the barycenter light is intersected with the optical axis of the objective lens, the light vertically gathers on the back focal plane of the objective lens after passing through the objective lens, the tube lens and the objective lens are placed in a conjugate mode, the image transfer imaging unit is composed of a group of conjugate image transfer lens groups, and the image formed by the microscopic imaging light path is transferred to the receiving surface of the camera after passing through the reflection device and the image transfer lens groups on the back focal plane of the tube lens. Note that in the arrangement of the microscopic light path, the intermediate image is inclined with respect to the optical axis of the light, and the relationship between the inclination angles θ' and θ satisfies the formula:
WDtanθ＝f1tanθ′
the focal length of the tube lens used in the device is far larger than the working distance of the objective lens with large numerical aperture, so the value of theta' is found to be very small by calculation. For the image transfer lens group, the whole intermediate image can be distributed in the depth of field range of the dark field relay lens group according to the depth of field formula, and the final imaging is ensured to have uniform high resolution in the full field of view range. The optical path between the first image transfer lens and the tube lens is equal to the sum of the focal lengths of the first image transfer lens and the tube lens, and the first image transfer lens and the second image transfer lens are conjugated. Under the action of the reflecting device, the intermediate image is equivalently distributed on the front focal plane of the dark field relay lens, and after passing through the image rotating lens group, the object image information is received by the camera in a light intensity signal mode, so that the measurement purpose is met.
The magnification of the imaging system is affected by the microscopic optical path and dark field relay imaging section. The magnification M of the system is:
wherein f is0,M0Respectively representing the focal length of the original factory standard tube lens matched with the objective lens and the calibration magnification of the objective lens, f3/f2The magnification of the relay lens group is as large as possible to ensure good resolution, so that it is preferable to select a lens that satisfies f3/f2Not less than 1. However, in order to ensure the space structure of the system to be compact, the focal length of the relay lens group is not too large, and can be selected according to specific measurement.
In order to meet the requirement of the incident angle of the polarized incidence, the device has definite requirement on the aperture angle of the objective lens. In the basic parameters of an objective lens, the numerical aperture is defined as the product of the object-side aperture angle and the refractive index. Since the brewster angle of most materials is about 55 °, the numerical aperture of the objective lens used in the present invention must be greater than 0.82 when the design is based on the minimum incidence angle θ of 55 °. In practice, the invention preferably uses an objective lens with a numerical aperture of 0.95, and the evaluation system resolution can be calculated using the rayleigh formula:
where the coefficient k is 0.61 when using incoherent light beams and λ is the wavelength of the light used in calibrating the resolution. The numerical aperture of the objective lens is large, so that the transverse resolution of the system can well meet the measurement requirement.
For complex surface micro-nano structures, the action of light and a sample can not satisfy the simple geometric optics theory any more, when the size of a fine structure on the sample is close to or less than the wavelength of light, the light can generate diffraction and scattering phenomena, and the scattering angle α of each level of diffracted light can be calculated by a grating formula:
d(sinθ+sinα)＝kλ
wherein most of the light intensity is concentrated in the zero-order reflected light (specular reflected light). Although the intensity of the higher order diffracted light is small, it contains much information about the fine structure of the sample surface. This part of the information tends to be buried in the white noise (zero-order reflected light) of the substrate in bright field detection and is difficult to observe. Dark field detection is a way to collect only high order light by separating the zero order reflected light. In the light path, the background signal of the detector is the dark current of the instrument, so that the high signal-to-noise ratio of the system collected signal to the high-order signal can be improved, and the high-resolution observation of the structure on the substrate can be realized. Dark field observation has a huge improvement in resolution over bright field. The limit resolution of the ordinary optical microscopic light path is about 200nm, and the resolution of dark field microscopic observation can be below 50 nm. In a conventional reflective imaging ellipsometry optical path with a vertical objective, a beam splitter is difficult to realize the separation of zero-order light, and meanwhile, the dark field observation is also difficult to be realized due to the huge light intensity loss of the beam splitter, so that the dark field observation is difficult to be realized while the polarization measurement is carried out. In the light path provided by the invention, the reflector can effectively separate zero-order light while ensuring the light intensity utilization rate, and can synchronously observe a bright and dark field with polarization modulation.
The dark field observation light path of the invention is shown in fig. 4, and light rays with large angle incidence simultaneously generate multi-order diffraction light on a sample. After passing through the microscopic light path, the light rays are imaged on the back focal plane of the lens barrel. This intermediate image contains both bright field information and dark field information. The high-order diffracted light does not pass through the subsequent reflector, passes through the gap between the two reflectors, is collected by the relay lens and is received by the camera, and dark field observation is realized.
The signal contrast of the detector can visually see the plane distribution condition of the sample. To better illustrate the measurement principle of the present invention, the propagation of the optical path is explained in detail in conjunction with the schematic diagram 1 of the apparatus and the optical path original device. The light source 1 uses a white light source with a broad spectrum, the emergent light directly enters monochromatic light generated by the wavelength selector 2, the light is guided into the polarizing arm 4 by using an optical fiber, and in order to ensure good light receiving efficiency, an optical fiber coupler is generally required to be arranged in front of a light inlet. The polarizing arm end comprises a collimating lens and a polarizing unit, a proper collimating lens 5 is selected according to the numerical aperture of the optical fiber to obtain incident light with good parallelism, the incident light passes through the polarizing unit 6, passes through the back focus of the tube lens 9 under the action of the first reflector 9, passes through the tube lens 9, is converged on the back focal plane of the objective lens, and irradiates a sample at a large angle under the action of the objective lens 10. The reflected light forms an intermediate image on the back focal plane of the tube lens 9 through the objective lens 10 and the tube lens 9. The subsequent detection light path can be divided into a bright field and a dark field, the second reflecting mirror 13 is used for separating zero-order reflected light in the bright field light path, the zero-order reflected light is received by the bright field detector after being refracted through the image transfer lens group and the polarization detection unit, stray light in the light path is filtered and removed through the small-hole diaphragm in the middle of the dark field relay lens, and the detection precision of the light path on a back reflection sample is improved. And the high-order light rays in the reflected light rays pass through a gap between the two reflectors and are projected onto a dark detector by the relay lens group, and dark field imaging is completed at the same time.
Specifically, the polarization measurement process of the device of the invention is summarized as the following steps:
s1, turning on the light source 1, adjusting the monochromator 2 to emit monochromatic light with a specified wavelength, adjusting the monochromatic light to the collimating lens 5 and the polarizing arm 4 to ensure the parallelism of the monochromatic light before entering the polarizing arm 4, generating incident polarized light with a known polarization state after passing through the polarizing arm 4, adjusting the inclination angles of the first reflector 8 and the second reflector 13 to ensure that the incident polarized light irradiates the sample 11 at a preset incident angle after passing through the tube lens 9 and the objective lens 10;
s2, placing the sample 11 on a sample stage, and adjusting the distance between the sample 11 and the objective lens 10 so that clear images can be seen in the observation regions of the bright field detector 19 and the dark field detector 21;
s3 monochromatic light emitted by the light source 1 through the monochromator 2 is irradiated to the collimating lens 5 through the optical fiber 3, the monochromatic light is converted into parallel light under the action of the collimating lens 5 and then is transmitted to the polarizing arm 4, the polarizing arm 4 is used for converting the light source transmitted by the optical fiber 3 into incident polarized light with a known polarization state, the incident polarized light is reflected to the tube lens 9 through the first reflector 8, the incident polarized light is focused by the tube lens 9 and then is irradiated to the sample 11 through the objective lens 10, the objective lens 10 is used for increasing the incident angle of the focused incident polarized light on the sample 11, the incident polarized light enters the bright field light path module through the reflection of the sample 11, the incident polarized light reflected by the sample 11 is transmitted to the analyzer arm 14 after being reflected by the second reflector 13, the analyzer arm 14 is used for converting the incident polarized light reflected by the second reflector 13 into the reflected polarized light with a known polarization state, the bright field detector 19 is used for receiving a light intensity signal corresponding to the reflected polarized light, and the dark field detector 21 is used for receiving a light intensity signal of part of scattered light generated after the incident polarized light is reflected by the sample 11;
s4 changing the polarization states of the polarizing arm 4 and the analyzing arm 14, and repeating step S3, thereby obtaining light intensity signals corresponding to the predetermined set of reflected polarized lights with different polarization states, and analyzing the light intensity signals of the predetermined set of reflected polarized lights, so as to measure ellipsometric parameters, thickness measurement parameters, or optical constant measurement parameters of the sample 11 in the entire view field region; the dark field detector 21 receives light intensity signals of partial scattered light generated after the incident polarized light in different polarization states is reflected by the sample 11, so as to realize comparative observation and detection of the micro structure of the sample;
s5, changing the wavelength of the monochromatic light emitted by the light source 1 and the monochromator 2, repeating the steps S1-S4 to obtain the ellipsometry parameters, thickness measurement parameters or optical constant measurement parameters of the sample 11 under different wavelengths of a preset group, and then calculating to obtain the ellipsometry parameters, thickness or optical constants of the sample 11; meanwhile, the dark field detector 21 receives light intensity signals of partial scattered light generated after the incident polarized light with different wavelengths is reflected by the sample 11, and accordingly three-dimensional reconstruction of surface features of the sample 11 and characterization of polarization characteristics are achieved.
Strong signal and thus enables the three-dimensional reconstruction of the surface features of the sample 11 and characterization of the polarization properties.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. An ellipsometer based on large numerical aperture objective lens integrated dark field observation is characterized by comprising an objective lens (10) and a tube lens (9) which are sequentially arranged above a sample (11) in a vertical mode,
an illumination light path module and a bright field light path module are further arranged above the tube lens (9), and the illumination light path module and the bright field light path module are symmetrically arranged about a central connecting line of the tube lens (9) and the objective lens (10);
the illumination light path module comprises a light source (1), a monochromator (2), an optical fiber (3), a polarizing arm (4) and a first reflector (8), the light source emitted by the light source (1) is screened by the monochromator (2) and then transmitted to the polarizing arm (4) through the optical fiber (3), the polarizing arm (4) is used for converting a light source transmitted by the optical fiber (3) into incident polarized light with a known polarization state, and reflects the incident polarized light to the tube lens (9) through the first reflecting mirror (8), the incident polarized light is focused by the tube lens (9) and then shines on a sample (11) through the objective lens (10), the objective lens (10) is used for increasing the incidence angle of the focused incident polarized light on the sample (11), and the incident polarized light enters the bright field light path module through the reflection of the sample (11);
the bright field light path module comprises a second reflecting mirror (13), an analyzing arm (14) and a bright field detector (19), incident polarized light reflected by the sample (11) is transmitted to the analyzing arm (14) after being reflected by the second reflecting mirror (13), the analyzing arm (14) is used for converting the incident polarized light reflected by the second reflecting mirror (13) into reflected polarized light with a known polarization state, and the bright field detector (19) is used for receiving the reflected polarized light and analyzing the reflected polarized light so as to realize measurement of ellipsometry parameters, thickness or optical constants of the sample (11) in the whole view field area.
2. The ellipsometer of claim 1, which integrates dark field observation based on large numerical aperture objective, further comprising a dark field optical path module, wherein the dark field optical path module is disposed above the illumination optical path module and the bright field optical path module, and the central axis of the dark field optical path module is collinear with the central line of the tube lens (9) and the objective lens (10), and the first reflector (8) and the second reflector (13) are symmetrically disposed about the central axis of the dark field optical path module.
3. The ellipsometer based on large numerical aperture objective lens integrated dark field observation of claim 2, wherein the dark field optical path module comprises a dark field relay lens (20) and a dark field detector (21), the dark field relay lens (20) is disposed below the dark field detector (21), after the incident polarized light is reflected by the sample (11), the generated partial scattered light passes through the objective lens (10) and the tube lens (9) in sequence, and then is collected by the dark field relay lens (20) to enter the dark field detector (21), and the dark field detector (21) performs fourier domain or spatial domain analysis on the characteristics of the scattered parallel light, so as to realize three-dimensional reconstruction of the surface characteristics of the sample (11) and characterization of the polarization characteristics.
4. The ellipsometer based on large numerical aperture objective lens integrated dark field observation of claim 1, wherein the polarizing arm (4) comprises a collimating lens (5) and a polarizing unit (6), the collimating lens (5) is disposed near one side of the emergent light from the optical fiber (3) for receiving the light from the optical fiber (3) and converting the scattered light into parallel light; the polarizing unit (6) is arranged between the collimating lens (5) and the first reflector (8) and is used for converting the parallel light into incident polarized light with a known polarization state;
the polarization detection arm (14) comprises an image conversion lens group and a polarization detection unit (18), the image conversion lens group is arranged on one side close to the second reflecting mirror (13) and used for converting incident polarized light reflected by the second reflecting mirror (13) into parallel light after being focused, and the polarization detection unit (18) is arranged between the bright field detector (19) and the image conversion lens group and used for demodulating the polarization state of the parallel light generated by the image conversion lens group.
5. An ellipsometer based on large numerical aperture objective integrated dark field observation according to claim 4, wherein said polarizing unit (6) comprises two polarizer and compensator sets; the analyzing unit (18) comprises two polarizers and a compensator group.
6. An ellipsometer based on large numerical aperture objective lens integrated dark field observation according to claim 4, characterized in that the relay lens group is composed of two conjugated first relay lens (15) and second relay lens (16);
and a second aperture diaphragm (17) is arranged at the intermediate focus of the first steering lens (15) and the second steering lens (16) and is used for filtering part of scattered light.
7. An ellipsometer based on large na objective integrated dark field observation according to any of claims 1-6, further comprising a first aperture stop (7) disposed between the first mirror (8) and the polarizing arm (4), wherein the first aperture stop (7) is used to filter part of the scattered light of the incident polarized light processed by the polarizing arm (4).
8. An ellipsometer based on large numerical aperture objective lens integrated dark field observation according to any one of claims 1-6, wherein a first rotating stage is disposed under the first reflector (8), a second rotating stage is disposed under the second reflector (13), and the first rotating stage is used to adjust the tilt angle of the first reflector (8) so that the incident polarized light reflected by the first reflector (8) is projected to the surface of the sample (11) through the objective lens (10) at the incident angle of the incident polarized light which is the Brewster angle of the sample (11); the second rotary stage is used to adjust the tilt angle of the second mirror (13) such that it is arranged symmetrically to the first mirror (8) with respect to the objective (10).
9. An ellipsometer based on large numerical aperture objective lens integrated dark field observation according to any of claims 1-6, wherein the objective lens (10) is an infinity light corrected unstressed field semi apochromatic objective lens with numerical aperture larger than 0.82 or an infinity light corrected unstressed field apochromatic objective lens with numerical aperture larger than 0.82; preferably, the objective lens (10) is an infinity light correction unstressed flat field apochromatic objective lens with a numerical aperture of 0.95 or an infinity light correction unstressed flat field apochromatic objective lens with a numerical aperture of 0.95; the bright field detector (19) and the dark field detector (21) are CCD cameras or CMOS cameras.
10. A method of ellipsometry based on large numerical aperture objective integrated dark field observation according to any of claims 1 to 9, comprising the following steps:
s1, turning on a light source (1), adjusting a monochromator (2) to emit monochromatic light with a specified wavelength, adjusting the monochromatic light to a collimating lens (5) and a polarizing arm (4), ensuring the parallelism of the monochromatic light before entering the polarizing arm (4), generating incident polarized light with a known polarization state after passing through the polarizing arm (4), adjusting the inclination angles of a first reflecting mirror (8) and a second reflecting mirror (13), and ensuring that the incident polarized light irradiates a sample (11) at a preset incident angle after passing through a tube lens (9) and an objective lens (10);
s2, adjusting the distance between the sample (11) and the objective lens (10) so that clear images can be seen in the observation areas of the bright field detector (19) and the dark field detector (21);
s3 the monochromatic light emitted by the light source (1) through the monochromator (2) is irradiated to the collimating lens (5) through the optical fiber (3), the monochromatic light is converted into parallel light under the action of the collimating lens (5) and then transmitted to the polarizing arm (4), the polarizing arm (4) is used for converting the light source transmitted by the optical fiber (3) into incident polarized light with a known polarization state, the incident polarized light is reflected to the tube lens (9) through the first reflector (8), the incident polarized light is focused by the tube lens (9) and then irradiated to the sample (11) through the objective lens (10), the objective lens (10) is used for increasing the incident angle of the incident polarized light irradiated to the sample (11), the incident polarized light enters the bright field light path module through the reflection of the sample (11), and the incident polarized light reflected by the sample (11) is transmitted to the polarization detecting arm (14) after being reflected by the second reflector (13), the analyzer arm (14) is used for converting incident polarized light reflected by the second reflecting mirror (13) into reflected polarized light with a known polarization state, the bright field detector (19) is used for receiving a light intensity signal corresponding to the reflected polarized light, and the dark field detector (21) is used for receiving a light intensity signal of partial scattered light generated after the incident polarized light is reflected by the sample (11);
s4, changing the polarization states of the polarizing arm (4) and the polarization analyzing arm (14), repeating the step S3, so as to obtain light intensity signals corresponding to the preset groups of reflected polarized light with different polarization states, and analyzing the light intensity signals of the preset groups of reflected polarized light, so as to realize measurement of ellipsometry parameters, thickness measurement parameters or optical constant measurement parameters of the sample (11) in the whole view field region; the dark field detector (21) receives light intensity signals of partial scattered light generated after the incident polarized light with different polarization states is reflected by the sample (11), so that the micro structure of the sample is observed and detected in a contrast mode;
s5, changing the wavelength of the monochromatic light emitted by the light source (1) and the monochromator (2), repeating the steps S1-S4 to obtain the ellipsometry parameters, the thickness measurement parameters or the optical constant measurement parameters of the sample (11) under different wavelengths of a preset group, and then calculating to obtain the ellipsometry parameters, the thickness or the optical constant of the sample (11); meanwhile, the dark field detector (21) receives light intensity signals of partial scattered light generated after the incident polarized light under different wavelengths is reflected by the sample (11), and therefore three-dimensional reconstruction of the surface characteristics of the sample (11) and characterization of polarization characteristics are achieved.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911345061.0A CN110987817B (en) | 2019-12-24 | 2019-12-24 | Ellipsometer integrating dark field observation based on large-numerical-aperture objective lens and measurement method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911345061.0A CN110987817B (en) | 2019-12-24 | 2019-12-24 | Ellipsometer integrating dark field observation based on large-numerical-aperture objective lens and measurement method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN110987817A true CN110987817A (en) | 2020-04-10 |
| CN110987817B CN110987817B (en) | 2021-01-19 |
Family
ID=70076212
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201911345061.0A Active CN110987817B (en) | 2019-12-24 | 2019-12-24 | Ellipsometer integrating dark field observation based on large-numerical-aperture objective lens and measurement method |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN110987817B (en) |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112577418A (en) * | 2020-11-26 | 2021-03-30 | 湖北爱默思智能检测装备有限公司 | Orthogonal polarization sorting optical acquisition device and application thereof |
| CN113358579A (en) * | 2021-05-21 | 2021-09-07 | 上海精测半导体技术有限公司 | Wide-spectrum ellipsometry optical system |
| CN113406842A (en) * | 2021-06-23 | 2021-09-17 | 湘潭大学 | Ultramicro stacked dark field photography system and method |
| CN113777049A (en) * | 2021-08-11 | 2021-12-10 | 华中科技大学 | Angle-resolved snapshot ellipsometer and measuring system and method thereof |
| CN114396888A (en) * | 2021-12-30 | 2022-04-26 | 北京无线电计量测试研究所 | Confocal microscopic device capable of realizing bright field and dark field imaging simultaneously |
| CN114577732A (en) * | 2022-02-18 | 2022-06-03 | 西北核技术研究所 | Mueller matrix ultrafast measurement device and method |
| CN114894712A (en) * | 2022-03-25 | 2022-08-12 | 业成科技（成都）有限公司 | Optical measurement equipment and correction method thereof |
| CN115289988A (en) * | 2022-08-22 | 2022-11-04 | 华中科技大学 | Method for measuring thickness and density nonuniformity of nano film material |
| TWI801224B (en) * | 2022-04-27 | 2023-05-01 | 財團法人工業技術研究院 | Microscopic observation method and microscopic observation device |
| CN116297337A (en) * | 2022-09-09 | 2023-06-23 | 山东大学 | Method for judging number of layers of two-dimensional material by using dark field optical imaging technology |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20130188184A1 (en) * | 2010-08-30 | 2013-07-25 | Atsushi Taniguchi | Defect inspecting apparatus and defect inspecting method |
| US9228943B2 (en) * | 2011-10-27 | 2016-01-05 | Kla-Tencor Corporation | Dynamically adjustable semiconductor metrology system |
| CN106595521A (en) * | 2016-12-12 | 2017-04-26 | 武汉颐光科技有限公司 | Vertical objective lens type Muller matrix imaging ellipsometer based on liquid crystal phase modulation |
| CN109540803A (en) * | 2019-01-04 | 2019-03-29 | 北京环境特性研究所 | A kind of ellipsometer device and the detection method based on the device |
-
2019
- 2019-12-24 CN CN201911345061.0A patent/CN110987817B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20130188184A1 (en) * | 2010-08-30 | 2013-07-25 | Atsushi Taniguchi | Defect inspecting apparatus and defect inspecting method |
| US9228943B2 (en) * | 2011-10-27 | 2016-01-05 | Kla-Tencor Corporation | Dynamically adjustable semiconductor metrology system |
| CN106595521A (en) * | 2016-12-12 | 2017-04-26 | 武汉颐光科技有限公司 | Vertical objective lens type Muller matrix imaging ellipsometer based on liquid crystal phase modulation |
| CN109540803A (en) * | 2019-01-04 | 2019-03-29 | 北京环境特性研究所 | A kind of ellipsometer device and the detection method based on the device |
Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112577418A (en) * | 2020-11-26 | 2021-03-30 | 湖北爱默思智能检测装备有限公司 | Orthogonal polarization sorting optical acquisition device and application thereof |
| CN113358579A (en) * | 2021-05-21 | 2021-09-07 | 上海精测半导体技术有限公司 | Wide-spectrum ellipsometry optical system |
| CN113406842A (en) * | 2021-06-23 | 2021-09-17 | 湘潭大学 | Ultramicro stacked dark field photography system and method |
| CN113777049B (en) * | 2021-08-11 | 2023-09-01 | 华中科技大学 | Angle-resolved snapshot ellipsometer and measuring system and method thereof |
| CN113777049A (en) * | 2021-08-11 | 2021-12-10 | 华中科技大学 | Angle-resolved snapshot ellipsometer and measuring system and method thereof |
| CN114396888A (en) * | 2021-12-30 | 2022-04-26 | 北京无线电计量测试研究所 | Confocal microscopic device capable of realizing bright field and dark field imaging simultaneously |
| CN114396888B (en) * | 2021-12-30 | 2023-11-14 | 北京无线电计量测试研究所 | Confocal microscopic device capable of simultaneously realizing bright field and dark field imaging |
| CN114577732A (en) * | 2022-02-18 | 2022-06-03 | 西北核技术研究所 | Mueller matrix ultrafast measurement device and method |
| CN114894712A (en) * | 2022-03-25 | 2022-08-12 | 业成科技（成都）有限公司 | Optical measurement equipment and correction method thereof |
| CN114894712B (en) * | 2022-03-25 | 2023-08-25 | 业成科技（成都）有限公司 | Optical measuring equipment and correction method thereof |
| TWI801224B (en) * | 2022-04-27 | 2023-05-01 | 財團法人工業技術研究院 | Microscopic observation method and microscopic observation device |
| CN115289988A (en) * | 2022-08-22 | 2022-11-04 | 华中科技大学 | Method for measuring thickness and density nonuniformity of nano film material |
| CN116297337A (en) * | 2022-09-09 | 2023-06-23 | 山东大学 | Method for judging number of layers of two-dimensional material by using dark field optical imaging technology |
| CN116297337B (en) * | 2022-09-09 | 2023-10-31 | 山东大学 | Method for judging number of layers of two-dimensional material by using dark field optical imaging technology |
Also Published As
| Publication number | Publication date |
|---|---|
| CN110987817B (en) | 2021-01-19 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN110987817B (en) | Ellipsometer integrating dark field observation based on large-numerical-aperture objective lens and measurement method | |
| CN106595521B (en) | vertical objective lens type Mueller matrix imaging ellipsometer based on liquid crystal phase modulation | |
| JP3697279B2 (en) | Thin film thickness measuring device | |
| CN108303020B (en) | Double-channel phase shift phase measurement microscope combining digital holography and differential interference | |
| TWI477758B (en) | Discrete polarization permutation angular scatterometer, optical subsystem of a scatterometer and scatterometry method | |
| RU2544876C1 (en) | Device to measure optical characteristics and method to measure optical characteristics | |
| US5764365A (en) | Two-dimensional beam deflector | |
| US7619746B2 (en) | Generating model signals for interferometry | |
| US6798511B1 (en) | Imaging ellipsometry | |
| CN106517086B (en) | A kind of large area high-resolution wide visual field on-line measurement device and its measurement method | |
| CN109975820B (en) | Linnik type interference microscope-based synchronous polarization phase shift focus detection system | |
| US8908180B2 (en) | Device and method for polarimetric measurement with microscopic resolution, polarimetry accessory for a microscope, ellipsomicroscope and ellipsometric contrast microscope | |
| CN113777049B (en) | Angle-resolved snapshot ellipsometer and measuring system and method thereof | |
| US7684039B2 (en) | Overlay metrology using the near infra-red spectral range | |
| JP2010530074A (en) | Single polarizer focus ellipsometer | |
| US10054423B2 (en) | Optical method and system for critical dimensions and thickness characterization | |
| WO2018102398A1 (en) | A scanning white-light interferometry system for characterization of patterned semiconductor features | |
| JP2000510951A (en) | Optical measurement | |
| TW202020400A (en) | Surface shape measurement device and surface shape measurement method | |
| Hillenbrand et al. | Parallelized chromatic confocal sensor systems | |
| CN107923735B (en) | Method and device for deducing the topography of an object surface | |
| KR100951110B1 (en) | Line Scan Type High Resolution Ellipsometer | |
| CN113777048B (en) | Coaxial ultrafast spectrum ellipsometer and measurement method | |
| KR102430925B1 (en) | Thickness and property measurement system of thin film using spatial light modulator | |
| WO2008151266A2 (en) | Interferometry for determining characteristics of an object surface, with spatially coherent illumination |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |