CN115164714A - Interference system - Google Patents
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- CN115164714A CN115164714A CN202210992776.0A CN202210992776A CN115164714A CN 115164714 A CN115164714 A CN 115164714A CN 202210992776 A CN202210992776 A CN 202210992776A CN 115164714 A CN115164714 A CN 115164714A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/02015—Interferometers characterised by the beam path configuration
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
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Abstract
The invention provides an interference system, wherein the interference system comprises: the device comprises a transmitting module, an interference lens group and a receiving screen; the transmitting module comprises a semi-transparent semi-reflecting mirror and is used for transmitting measuring beams with different angular frequencies to the interference mirror group; the interference lens group comprises a first surface and a second surface, wherein the first surface or the second surface is a super surface, and the super surface has phase distribution capable of reducing the distance between adjacent levels of fringes; the first surface is used for reflecting part of the measuring beam and transmitting the other part of the measuring beam; the second surface is used for reflecting the other part of the measuring beam; the half-mirror is used for transmitting the light beam emitted from the first surface to the receiving screen. By the interference system provided by the embodiment of the invention, any one of the two surfaces is a super surface, and the inherent phase distribution of the interference fringes originally formed in a far field can be changed more severely based on the phase distribution of the super surface, so that the distance between the adjacent fringes is smaller, and the interference fringes are finer.
Description
Technical Field
The invention relates to the technical field of equal inclination interference, in particular to an interference system.
Background
For interferometric measurements, the finer the interference fringes, the higher the accuracy of the interferometric scheme. The traditional equal inclination interference scheme has the limit of fringe fineness and cannot break through. At present, a special photon can be used, which is generated by a spontaneous parametric down-conversion process in a second-order nonlinear crystal, and the photon has a characteristic that the emission angle is related to the wavelength (or angular frequency), so that when a light source capable of emitting the photon is applied to a michelson system, the fineness of the generated interference fringes is improved by 27 times compared with the traditional interference scheme, but the fineness of the interference fringes of the scheme is still limited by the nonlinear crystal and cannot be improved again.
Disclosure of Invention
To solve the above problems, embodiments of the present invention provide an interference system.
An embodiment of the present invention provides an interference system, including: the device comprises a transmitting module, an interference lens group and a receiving screen; the emission module comprises a semi-transparent semi-reflecting mirror arranged on one side close to the interference mirror group, the emission module is used for emitting measuring beams with different angular frequencies to the interference mirror group, and the incidence positions of the measuring beams with different angular frequencies incident into the interference mirror group are different; the interference mirror group comprises a first surface and a second surface, the first surface or the second surface is a super surface, and the super surface has phase distribution capable of reducing the space between adjacent secondary fringes; the first surface is a surface capable of realizing transmission and reflection, and is used for reflecting part of the measuring beam to the half-mirror and transmitting the other part of the measuring beam to the second surface; the second surface is used for reflecting the other part of the measuring beam and transmitting the other part of the measuring beam to the half-transmitting and half-reflecting mirror through the first surface; the semi-transparent semi-reflecting mirror is used for emitting the light beam emitted by the first surface to the receiving screen; the receiving screen is used for receiving interference fringes formed by a plurality of fringes.
Optionally, the emission module further comprises a light source and a collimating lens; the light source is used for generating initial light beams with a plurality of emergent angles in one-to-one correspondence with angular frequencies; the collimating lens is arranged on the light emitting side of the light source, the distance between the collimating lens and the light emitting side is the focal length of the collimating lens, and the collimating lens is used for collimating the initial light beam to obtain a collimated light beam and emitting the collimated light beam to the semi-transparent and semi-reflective mirror; the half-transmitting and half-reflecting mirror is also used for emitting at least part of the collimated light beam to the first surface as a measuring light beam.
Optionally, a half-mirror is used for transmitting at least part of the collimated light beam to the first surface as a measuring beam and reflecting the light beam emitted from the first surface to the receiving screen; alternatively, the half-mirror is used for reflecting at least part of the collimated light beam to the first surface as a measuring light beam and transmitting the light beam emitted from the first surface to the receiving screen.
Optionally, the collimating lens comprises a lens for eliminating chromatic aberration.
Optionally, the collimating lens is a superlens.
Optionally, the exit angle of the primary beam satisfies:
wherein θ represents an exit angle of the primary beam; r represents the radial distance between the position of the initial light beam to the collimating lens and the center of the collimating lens; f denotes a focal length of the collimator lens.
Optionally, the first surface is parallel to said second surface.
Optionally, in the interferometric mirror array, a function between an incident position of the measuring beam on the super-surface and an angular frequency of the measuring beam at the incident position has the same monotonicity as a phase distribution of the super-surface along a radial direction.
Optionally, in the interferometric mirror array, a phase of the measuring beam incident on the incident position of the super-surface is positively correlated with an angular frequency of the measuring beam incident on the incident position.
Optionally, the phase distribution of the interferometric mirror group satisfies:
wherein, psi [ omega (r)]Representing the phase distribution of the interference mirror group; f [ omega (r)]Representing an inherent phase distribution resulting from an optical path difference resulting from a distance between the first surface and the second surface; l denotes the radius of the super-surface, and the phase distribution ψ [ omega (r) of the interference mirror group]A continuous function over the radius of the hypersurface.
In the above-mentioned scheme provided by the embodiment of the present invention, any one of the two surfaces of the interference lens group is made to be a super surface, and the inherent phase distribution of the interference fringes originally formed in the far field can be changed more severely based on the phase distribution of the super surface, so that the distance between adjacent fringes in the interference fringes received by the receiving screen is smaller, and the interference fringes are finer.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 shows a schematic diagram of an interferometric system provided by an embodiment of the invention;
FIG. 2 is a schematic diagram of another interferometric system provided by an embodiment of the invention;
FIG. 3 is a schematic diagram illustrating the behavior of a light source in an interferometric system provided by an embodiment of the invention;
FIG. 4 is a schematic diagram showing an interferometric system in which a half mirror transmits at least a portion of a collimated beam as a measuring beam toward a first surface and reflects the beam emitted from the first surface toward a receiving screen;
FIG. 5 is a schematic diagram illustrating the positions of a light source and a collimating lens in an interferometric system according to an embodiment of the invention;
FIG. 6 shows a schematic diagram of example 1 provided by an embodiment of the present invention;
FIG. 7 is a diagram showing an enlarged contrast of interference fringes in example 1 provided by the embodiment of the present invention;
FIG. 8 is a diagram showing the results of the positions of stripes and the orders in example 1 provided by the embodiment of the present invention;
FIG. 9 is a schematic diagram showing the detailed interference fringes finally generated in example 1 provided by the embodiment of the present invention;
fig. 10 shows a surface topography prediction map of a wafer to be measured in embodiment 1 according to an embodiment of the present invention;
fig. 11 is a schematic diagram illustrating a position of another wafer to be tested according to an embodiment of the invention.
Icon:
the optical system comprises a transmitting module 1, a 2-interference lens group, a 3-receiving screen, a 11-semi-transparent semi-reflecting mirror, a 12-light source, a 13-collimating lens, a 21-first surface and a 22-second surface.
Detailed Description
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood according to specific situations by those of ordinary skill in the art.
An embodiment of the present invention provides an interference system, as shown in fig. 1, the interference system includes: the device comprises a transmitting module 1, an interference lens group 2 and a receiving screen 3; the emission module 1 comprises a semi-transparent semi-reflecting mirror 11 arranged at one side close to the interference mirror group 2, the emission module 1 is used for emitting measuring beams with different angular frequencies to the interference mirror group 2, and the incidence positions of the measuring beams with different angular frequencies entering the interference mirror group 2 are different; the interference lens group 2 comprises a first surface 21 and a second surface 22, wherein the first surface 21 or the second surface 22 is a super surface, and the super surface has a phase distribution capable of reducing the space between the fringes of adjacent orders; the first surface 21 is a surface capable of transmission and reflection, and is used for reflecting part of the measuring beam to the half mirror 11 and transmitting the other part of the measuring beam to the second surface 22; the second surface 22 is used for reflecting the other part of the measuring beam and transmitting the first surface 21 to the half mirror 11; the half-mirror 11 is used for emitting the light beam emitted by the first surface 21 to the receiving screen 3; the receiving screen 3 is used for receiving interference fringes formed by a plurality of fringes.
As shown in fig. 1, in the interferometric system provided in the embodiment of the invention, the half mirror 11 is located at an end of the emission module 1 that finally emits the measuring beam, for example, the half mirror 11 can be disposed at an end of the emission module 1 closer to the interferometric mirror assembly 2, such as a right end of the emission module 1 in fig. 1, and the half mirror 11 is located at a left side of the interferometric mirror assembly 2. The measuring beams emitted by the emission module 1 are a plurality of beams for generating interference fringes, and the angular frequency corresponding to each measuring beam is different, and the incident position of each measuring beam incident on the interference lens 2 is also different. As shown in fig. 1, the measuring beams with different angular frequencies are represented by gray stripes with different shades in fig. 1, and it can be known from fig. 1 that the measuring beams with different angular frequencies respectively enter different positions of the interferometric mirror assembly 2, i.e. the incident position of the measuring beam with each angular frequency is different.
Wherein, the first surface 21 is located at one end of the interference lens group 2 closer to the emission module 1, and the second surface 22 is located at one end of the interference lens group 2 farther from the emission module 1; the first surface 21 may be transmissive or reflective to a light beam (e.g., a measuring light beam) incident thereon, for example, the measuring light beam incident on the first surface 21 may perform a dual function of being partially reflected (reflected back to the half mirror 11) and partially transmitted (transmitted to the second surface 22) on the first surface 21. In the case that the second surface 22 receives the measuring beam transmitted by the first surface 21 (the other measuring beam not reflected by the first surface 21), the second surface 22 can reflect the incident measuring beam back to the first surface 21, so that the reflected measuring beam is transmitted by the first surface 21 and transmitted to the half mirror 11.
As shown in fig. 1, the first surface 21 is disposed on the light emitting side of the transmitting module 1, such as the right side of the transmitting module 1, and the first surface 21 is used for receiving the measuring beams emitted by the transmitting module 1, reflecting part of the measuring beams back to the half mirror 11, and transmitting the other part of the measuring beams to the second surface 22; the second surface 22 is disposed at the right side of the first surface 21, and is configured to receive the measuring beam transmitted by the first surface 21 and reflect the incident measuring beam toward the half mirror 11 (transmitted through the first surface 21 and directed toward the half mirror 11).
Optionally, the first surface 21 is parallel to the second surface 22. For example, the two surfaces of the interferometer assembly 2 can be coaxially disposed with a certain distance therebetween, so that the incidence position of the measuring beam incident from the emission module 1 to the first surface 21 on the first surface 21 is the same as the incidence position of the measuring beam transmitted through the first surface 21 to the second surface 22 on the second surface 22. As shown in fig. 1, the first surface 21 and the second surface 22 are disposed parallel to each other and coaxially, and the distance between the two surfaces can be determined according to actual requirements.
In the embodiment of the present invention, the first surface 21 or the second surface 22 in the interferometric mirror group 2 is a super surface, for example, as shown in fig. 1, the second surface 22 is a super surface, or as shown in fig. 2, the first surface 21 is a super surface, and the embodiment of the present invention may be determined according to actual measurement requirements. Wherein the use of a meta-surface for either surface enables a beam incident on the meta-surface (e.g. a measuring beam emitted from the emission module 1 when the first surface 21 is a meta-surface; or a measuring beam emitted from the first surface 21 to the second surface 22 when the second surface 22 is a meta-surface) to be further modulated by a phase distribution possessed by the meta-surface, wherein the phase distribution is determined by the nanostructures possessed by the meta-surface, and the phase distribution is a phase distribution of the meta-surface in the radial direction, which can exacerbate a change in the intrinsic phase distribution, i.e. the phase distribution can exacerbate a change in the intrinsic phase distribution caused by an optical path difference generated by the distance between the first surface 21 and the second surface 22, so that a portion of the measuring beam reflected by the first surface 21 toward the half mirror 11 and a portion of the measuring beam reflected by the second surface 22 toward the first surface 21 and transmitted through the first surface 21 toward the half mirror 11, eventually form interference fringes (constituted by a plurality of interference fringes) in a far field (e.g. the receiving screen 3), which the interference fringes are formed with equal inclination, i.e. the adjacent fringes, the spacing between the adjacent fringes becomes smaller, also becomes higher as the spacing between the semi-fringes becomes larger.
In the embodiment of the present invention, any one of the two surfaces of the interference lens group 2 is a super surface, and the inherent phase distribution of the interference fringes originally formed in the far field can be changed more severely based on the phase distribution of the super surface, so that the distance between adjacent fringes in the interference fringes received by the receiving screen 3 is smaller, and the interference fringes are finer.
Optionally, as shown in fig. 1, the transmitting module 1 further includes: a light source 12 and a collimator lens 13; fig. 1 shows the right side of the light source 12 as its light exit side. The light source 12 is configured to generate initial light beams with multiple exit angles and multiple angular frequencies in one-to-one correspondence; the collimating lens 13 is arranged on the light emitting side of the light source 12, the distance between the collimating lens 13 and the light emitting side is the focal length of the collimating lens 13, and the collimating lens 13 is used for collimating the initial light beam to obtain a collimated light beam and emitting the collimated light beam to the half mirror 11; the half-mirror 11 is also used to direct at least part of the collimated beam towards the first surface 21 as a measuring beam.
In the embodiment of the present invention, the light source 12 can emit a plurality of initial light beams, each of the initial light beams corresponds to one angular frequency, and the exit angles of the initial light beams with different angular frequencies are different; for example, referring to FIG. 3, the primary beam emitted by the light source 12 is composed of a particular photon that can be generated by a spontaneous parametric down-conversion process in a second order nonlinear crystal, the photon having an emission angle (e.g., the emission angle θ of the primary beam emitted by the light source 12) and a wavelength (e.g., the wavelength λ of the primary beam, which can also be represented by an angular frequency ω, i.e., the angular frequency ω is represented by
) In relation to, in other words, in the case of using the photon as the light source 12, the exit angle θ of the primary light beam emitted by the light source 12 has a one-to-one correspondence relationship with the angular frequency ω of the primary light beam, which is ω as shown in fig. 3 1 At an exit angle theta (omega) 1 ) Emission at an angular frequency of ω 2 At an exit angle theta (omega) 2 ) Emission at an angular frequency of ω 3 At an exit angle theta (omega) 3 ) And ejecting, and so on.
In the embodiment of the present invention, the initial light beams with different angular frequencies emitted by the light source 12 to different exit angles can be emitted to the collimating lens 13 located on the light exit side of the light source 12, the distance between the collimating lens 13 and the light source 12 is the focal length of the collimating lens 13, for example, the initial light beams with different angular frequencies corresponding to different exit angles can be emitted into the collimating lens 13 at different incident angles and horizontally emitted in a direction parallel to the main optical axis of the collimating lens 13 by the modulation of the collimating lens 13, as shown in fig. 1, the initial light beams are modulated into the collimated light beams by the collimating lens 13 and horizontally emitted to the half mirror 11. Optionally, the collimator lens 13 includes a lens for eliminating chromatic aberration. Since the initial light beam propagates in the collimating lens 13 and generates chromatic aberration, a lens capable of eliminating chromatic aberration can be used as the collimating lens 13, so that the chromatic aberration originally generated by the initial light beam after passing through the collimating lens 13 can be corrected by the collimating lens 13. Furthermore, the collimating lens 13 adopted in the embodiment of the present invention is a superlens, which can further reduce the volume of the interference system, reduce the overall weight thereof, and reduce the cost.
Wherein, in the case that the half mirror 11 receives the collimated light beam, the half mirror 11 can emit the collimated light beam to the first surface 21, and since the half mirror 11 is an optical element that is formed by plating a half reflective film on optical glass, the light incident into the half mirror is transmitted and reflected, that is, the half mirror 11 is an optical element that can transmit a part of light and reflect another part of light; therefore, the incident collimated light beams can be reflected or transmitted, so that the interference system provided by the embodiment of the invention can set the positions of the emission module 1 (including the light source 12, the collimating lens 13 and the half-mirror 11) and the receiving screen 3 in a targeted manner according to actual needs; for example, the specific structure of the interferometric system may be specifically set by determining which way (reflected or transmitted) the emitted light is to be used as the measuring beam according to practical installation environment limitations. Alternatively, as shown in fig. 4, the half mirror 11 is used to transmit at least part of the collimated light beam as the measuring beam toward the first surface 21, and reflect the light beam emitted from the first surface 21 toward the receiving screen 3; alternatively, the half mirror 11 is used to reflect at least part of the collimated beam as a measuring beam towards the first surface 21 and transmit the beam emerging from the first surface 21 towards the receiving screen 3, which is not shown schematically in the present embodiment.
For example, as shown in fig. 4, fig. 4 provides an interferometric system that uses the light transmitted by the half mirror 11 (i.e., the partially collimated light beam emitted by the collimating lens 13 located above the half mirror 11 in fig. 4) as the measuring light beam, and emits the measuring light beam transmitted by the half mirror into the first surface 21 of the interferometric mirror group 2; also, the light incident on the half mirror 11 from the first surface 21 (i.e., a portion of the measuring beam reflected by the first surface 21 and another portion of the measuring beam reflected by the second surface 22) can be reflected by the half mirror 11 toward the receiving screen 3 (i.e., to the right of the half mirror 11 in fig. 4). Alternatively, the interference system uses the light reflected by the half mirror 11 (i.e. the partially collimated light beam emitted by the collimating lens 13) as the measuring light beam, and the measuring light beam reflected by the interference system is incident on the first surface 21 of the interference mirror group 2; also, the light incident on the half mirror 11 from the first surface 21 (i.e. part of the measuring beam reflected by the first surface 21 and another part of the measuring beam reflected by the second surface 22) can be transmitted by the half mirror 11 towards the receiving screen 3 (not shown for this configuration).
Alternatively, referring to fig. 5, the exit angle of the primary beam satisfies:
that is, the emergence angles corresponding to the initial light beams with different angular frequencies satisfy the formula; wherein θ represents the exit angle of the initial beam; r represents a radial distance from a position where the primary beam is emitted to the collimator lens 13 to the center of the collimator lens 13; f denotes the focal length of the collimator lens 13.
Based on FIG. 5 and the above formula
It can be known that, in the embodiment of the present invention, the light source 12 and the collimating lens 13 are coaxially disposed, and the distance between the two is the focal length f of the collimating lens 13; the exit angle θ of the primary light beams of different angular frequencies is related to the incident position (or the radial distance R between the incident position and the center of the collimator lens 13) of the primary light beams entering the collimator lens 13. In the embodiment of the present invention, under the condition that the light source 12, the collimating lens 13 and the interference lens group 2 of the interference system are coaxially arranged, the initial light beam enters the incident position of the collimating lens 13 (or the incident position of the initial light beam and the collimating lens group 2 are both coaxially arranged), the initial light beam enters the incident position of the collimating lens 13The radial distance R between the centers of the mirrors 13) is the same as the incidence position of the measuring beam on the set 2 of interferometer groups (comprising the first surface 21 and the second surface 22) (or the radial distance R between the incidence position of the measuring beam and the center of the corresponding surface of the set 2 of interferometer groups).
Alternatively, in the interferometric mirror array 2, the function between the incident position of the measuring beam onto the super-surface and the angular frequency of the measuring beam at the incident position has the same monotonicity as the phase distribution of the super-surface along the radial direction.
In the embodiment of the present invention, the light intensity distribution of the interference fringes finally reflected by the interference mirror group 2 and received on the receiving screen 3 satisfies
Where r represents a radial distance between an incident position of a measuring beam incident on the super-surface (the first surface 21 or the second surface 22) and a center of the super-surface, e.g., a radial distance of the nanostructure at the incident position of the measuring beam from the center of the super-surface; i (r) represents the light intensity corresponding to the fringes (received by the receiving screen 3) obtained by interference at a radial distance r (for example, at the nanostructure corresponding to the incident position of the measuring beam) from the center of the super-surface; ω (r) represents the function between the incident position of the measuring beam on the super-surface (at the nanostructure with radial distance r) and the angular frequency of the measuring beam at that incident position, f [ ω (r) ]]Represents the intrinsic phase distribution resulting from the optical path difference generated by the distance between the first surface 21 and the second surface 22, wherein the intrinsic phase distribution can be understood as a constant value if the radial distance r between the incident position and the center of the super-surface is determined;
indicating the phase distribution of the super surface (first surface 21 or second surface 22) in the radial direction, an embodiment of the present invention may make the second surface 22 a super surface. Specifically, f [ omega (r)]Can be that
L represents the distance between the first surface 21 and the second surface 22Separating; and c represents the speed of light. Further, the equation satisfied by the light intensity distribution of the interference fringes finally reflected by the interference mirror group 2 and received on the receiving screen 3 can be modified as follows:
based on the expression satisfied by the light intensity distribution, if the distance between adjacent fringes in the interference fringes is smaller and the interference fringes are denser, the inherent phase distribution can be made
Monotonicity and phase distribution of the super surface in the radial direction
If both are monotone increasing functions or both are monotone decreasing functions, a plurality of stripes finally received on the receiving screen 3 can become closer to each other, and the distance between adjacent stripes is smaller; while the monotonicity of the intrinsic phase distribution is determined by ω (r), and therefore the phase distribution of the hypersurface in the radial direction
Also required to be the same as the monotonicity of ω (r), i.e. both have the same monotonicity. In the embodiment of the invention, the phase corresponding to the position r is larger as the radial distance r is larger.
Embodiments of the present invention relate to
Is made to be uniform, i.e. the phase distribution of the super-surface in the radial direction is made to be uniform
Monotonicity and inherent phase distribution f [ omega (r) of (A)]And (4) the two phases are consistent. For example, ω (r) can be made to coincide with
Are all monotonically increasing functions, thereby enabling the phase distribution of the super-surface along the radial direction
With inherent phase distribution f [ omega (r)]Are all monotonically increasing functions; or, let ω (r) and
are all monotonically decreasing functions, thereby enabling the phase distribution of the super-surface along the radial direction
With inherent phase distribution f [ omega (r)]Are each a monotonically decreasing function.
The embodiment of the invention introduces the phase distribution of the super surface in the radial direction in the interference lens group 2
Ensure that
And inherent phase distribution
The coherence monotonicity is consistent, so that the interference fringes obtained by the interference system are finer, for example, the spacing between multiple fringes is smaller.
Alternatively, in the interferometric mirror array 2, the phase of the incident position of the measuring beam on the super-surface is positively correlated with the angular frequency of the measuring beam incident on the incident position.
In the embodiment of the invention, measuring beams with different angular frequencies respectively enter different positions (incidence positions) of the super surface, the different incidence positions correspond to different nano structures on the super surface, and the phase of the nano structure at the incidence position can modulate the measuring beam (measuring beam with a certain angular frequency) entering at the incidence position; in other words, different nanostructures on the super-surface modulate the measuring beam with different angular frequencies, respectively, e.g. at any radial distance r, the operating wavelength (or angular frequency) of the nanostructure is specific and unique. In the embodiment of the present invention, the angular frequency of the measuring beam incident on the nanostructure (at the incident position) is in a positive correlation with the phase of the nanostructure at the incident position, that is, the interference system satisfies: with the increase of the angular frequency of the measuring beam, the phase of the incident position (corresponding to the nano structure) of the measuring beam with the angular frequency on the super surface is also increased in positive correlation relationship, so as to ensure that the interference system has more severe phase distribution.
Optionally, the phase distribution of the interference mirror group 2 satisfies:
wherein psi [ omega (r)]Represents the phase distribution of the interference lens group 2; f [ omega (r)]Indicating the inherent phase distribution caused by the optical path difference generated by the distance between the first surface 21 and the second surface 22; l represents the radius of the super-surface and the phase distribution psi [ omega (r) of the interferometric mirror assembly 2]A continuous function over the radius of the super surface.
In the embodiment of the present invention, the phase distribution psi [ omega (r) of the interference lens group 2]The psi [ omega (r) is the overall phase distribution corresponding to when the interference fringes are finally formed]Is a natural phase distribution f [ omega (r)]And the phase distribution of the super surface of the interference lens group 2
And (3) the sum, namely the interference system satisfies the relation:
phase distribution psi [ omega (r) in interferometric systems]In [0,l]With continuity in range, the phase distribution ψ [ omega (r) of the interference system]The first derivative to r is greater than the natural phase profile f [ omega (r)]The first derivative of r, i.e. having a phase distribution of the super-surface along the radial direction
Phase division of an interferometric systemPsi [ omega (r)]The fineness of the interference fringes generated by the interference system is higher than that of the traditional interference system (such as the phase distribution without a super surface along the radial direction)
Interferometric system) of a phase distribution (e.g., a natural phase distribution f [ omega (r) ]]) The fineness of the generated interference fringes is determined by defining the final phase distribution (such as defining the phase distribution psi [ omega (r) of the interference system)]Continuously derivable functions over the super-surface area) a more evenly distributed interference fringe may be obtained.
Example 1:
referring to FIG. 6, FIG. 6 shows a schematic diagram of an interferometric system for wafer surface topography detection. The wafer to be tested is divided into two surfaces, in this embodiment 1, one surface is defined as a reference surface, and the other surface is defined as a surface to be tested; a first surface 21 is arranged on one side close to the reference surface, a second surface 22 is arranged on one side close to the surface to be measured, the first surface 21 and the second surface 22 form an interference lens group 2, and the wafer to be measured is arranged between the first surface 21 and the second surface 22; wherein, the material of the wafer to be measured is quartz glass, and the diameter is 300mm. In this embodiment 1, the second surface 22 close to the surface to be measured is provided with a nano structure to form a super surface, the nano structure is made of SiN and has a height of 400nm, and a nano-pillar structure is adopted and arranged in a concentric circle manner.
In this embodiment 1, the light source 12 uses a PPKTP (Periodically Poled KTP) crystal as a spontaneous parameter down-conversion crystal, a photon generated by the PPKTP crystal can generate an initial light beam, and a relationship between an emission angle of the initial light beam emitted from the light source 12 and an angular frequency thereof is as follows:
wherein b is a coefficient constant related to the refractive index of the crystal; Δ w is the variation of angular frequency; the distance L (distance between the first surface 21 and the second surface 22) was set to 200 μm, and the focal length of the collimator lens 13 was 20mm. Based on this, the phase distribution of the super surface (e.g. the second surface 22 close to the surface to be measured) can be designed as follows:
wherein a is a phase coefficient; i is any number greater than 1, and the value of i can be determined according to the characteristics of the light source 12 (such as the relationship between the exit angle and the angular frequency), so that the super-surface is ensured to be introduced on the basis of the operation of the light source 12, and the fineness of the stripes is greater than that of the case where the super-surface is not introduced. In this embodiment 1, the phase distribution of the final super-surface (e.g. the second surface 22 close to the surface to be measured) is:
wherein, a =0.54 pi, i =3, ω s0 Representing the angular frequency at the center point (e.g., at r = 0).
The enlarged schematic diagram of the interference fringes finally received by the receiving screen 3 in this embodiment 1 can be seen from the left side of fig. 7, and compared with the enlarged schematic diagram of the conventional interference system without the super-surface on the right side of fig. 7, the interference fringes finally generated in this embodiment 1 have higher fineness, the spacing between adjacent fringes is smaller, and the detection accuracy of the interference system is higher. Fig. 8 shows a schematic diagram of the results of the positions and the orders of the fringes of the interference system provided in this embodiment 1, and as can be seen from fig. 8, the order of the fringes corresponding to each position of the interference fringes finally generated in this embodiment 1 is greater than the order of the fringes corresponding to each position of the interference fringes finally generated in the conventional interference system without a super-surface, which can also prove that the fineness of the interference fringes finally generated by the interference system provided in this embodiment 1 is higher, and the detection effect is better. Referring to fig. 9 to 10, fig. 9 shows a schematic diagram of the detailed interference fringes finally generated in the embodiment 1, and fig. 10 shows a surface topography prediction map of the wafer to be tested; it can be seen that the interference fringes obtained by the interference system of this embodiment 1 are no longer standard equal inclination interference fringes, indicating that the surface heights of the wafer to be measured are different; and according to the interference fringes, the one-dimensional surface morphology of the wafer to be measured can be accurately measured.
It should be noted that: in the embodiment of the present invention, a nano structure may also be directly disposed on any surface of a wafer to be detected, so as to form a super surface (for example, a first surface 21 of the interference system shown in fig. 11, the surface corresponds to a reference surface of the wafer to be detected) capable of implementing transmission and reflection functions, and a reflective surface (for example, a second surface 22 of the interference system shown in fig. 11, the surface corresponds to a surface to be detected of the wafer to be detected) is formed on another surface of the wafer to be detected, and the interference system with this structure may also implement surface topography detection of the wafer to be detected.
The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of changes or substitutions within the technical scope of the present invention, and the present invention shall be covered by the claims. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (10)
1. An interferometry system, comprising: the device comprises a transmitting module (1), an interference lens group (2) and a receiving screen (3);
the emission module (1) comprises a semi-transparent semi-reflecting mirror (11) arranged at one side close to the interference mirror group (2), the emission module (1) is used for emitting measuring beams with different angular frequencies to the interference mirror group (2), and the incidence positions of the measuring beams with different angular frequencies to the interference mirror group (2) are different;
the interferometric mirror group (2) comprises a first surface (21) and a second surface (22), the first surface (21) or the second surface (22) being a super surface having a phase distribution capable of narrowing the spacing between fringes of adjacent orders; the first surface (21) is a surface capable of transmission and reflection, for reflecting a portion of the measuring beam towards the half mirror (11) and transmitting another portion of the measuring beam towards the second surface (22); the second surface (22) is used for reflecting the other part of the measuring beam and transmitting the measuring beam to the half mirror (11) through the first surface (21);
the half-transmitting and half-reflecting mirror (11) is used for transmitting the light beam emitted by the first surface (21) to the receiving screen (3); the receiving screen (3) is used for receiving interference fringes formed by a plurality of fringes.
2. The interferometry system of claim 1, wherein the emission module (1) further comprises a light source (12) and a collimating lens (13);
the light source (12) is used for generating initial light beams with a plurality of emergent angles in one-to-one correspondence with angular frequencies;
the collimating lens (13) is arranged on the light emitting side of the light source (12), the distance between the collimating lens (13) and the light emitting side is the focal length of the collimating lens (13), and the collimating lens (13) is used for collimating the initial light beam to obtain a collimated light beam and emitting the collimated light beam to the half-transmitting and half-reflecting mirror (11);
the half-mirror (11) is also used for directing at least part of the collimated light beam to the first surface (21) as a measuring beam.
3. An interferometry system according to claim 2, wherein said half-mirror (11) is adapted to transmit at least part of said collimated beam as a measuring beam towards said first surface (21) and to reflect the beam emerging from said first surface (21) towards said receiving screen (3); alternatively, the first and second electrodes may be,
the half-mirror (11) is used for reflecting at least part of the collimated light beam as a measuring light beam to the first surface (21) and transmitting the light beam emitted by the first surface (21) to the receiving screen (3).
4. An interferometry system according to claim 2, wherein said collimating lens (13) comprises a lens for eliminating chromatic aberration.
5. An interferometry system according to claim 2, wherein said collimating lens (13) is a superlens.
6. The interferometry system of claim 2, wherein the exit angle of the initial beam satisfies:
wherein θ represents an exit angle of the primary beam; r represents the radial distance between the position of the initial light beam to the collimating lens (13) and the center of the collimating lens (13); f denotes the focal length of the collimator lens (13).
7. Interferometry system according to claim 1, wherein said first surface (21) is parallel to said second surface (22).
8. The interferometry system according to claim 1, wherein in said interferometry assembly (2) the function between the position of incidence of said measuring beam on said super-surface and the angular frequency of said measuring beam at said position of incidence has the same monotonicity as the phase distribution of said super-surface along the radial direction.
9. Interferometry system according to claim 8, wherein in said interferometer group (2) the phase of incidence of said measuring beam on said super-surface at the position of incidence is positively correlated to the angular frequency of said measuring beam directed at said position of incidence.
10. The interferometry system according to claim 1, wherein said phase distribution of said set of interferometry lenses (2) is such that:
wherein ψ [ ω (r) ] represents a phase distribution of the interference mirror group (2); f [ ω (r) ] represents the intrinsic phase distribution resulting from the optical path difference resulting from the distance between said first surface (21) and said second surface (22); l represents the radius of the super surface, and the phase distribution ψ [ omega (r) ] of the interference mirror group (2) is a continuous function over the radius of the super surface.
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| CN202210992776.0A CN115164714A (en) | 2022-08-18 | 2022-08-18 | Interference system |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11927769B2 (en) | 2022-03-31 | 2024-03-12 | Metalenz, Inc. | Polarization sorting metasurface microlens array device |
| US11978752B2 (en) | 2019-07-26 | 2024-05-07 | Metalenz, Inc. | Aperture-metasurface and hybrid refractive-metasurface imaging systems |
| US11988844B2 (en) | 2017-08-31 | 2024-05-21 | Metalenz, Inc. | Transmissive metasurface lens integration |
-
2022
- 2022-08-18 CN CN202210992776.0A patent/CN115164714A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11988844B2 (en) | 2017-08-31 | 2024-05-21 | Metalenz, Inc. | Transmissive metasurface lens integration |
| US11978752B2 (en) | 2019-07-26 | 2024-05-07 | Metalenz, Inc. | Aperture-metasurface and hybrid refractive-metasurface imaging systems |
| US11927769B2 (en) | 2022-03-31 | 2024-03-12 | Metalenz, Inc. | Polarization sorting metasurface microlens array device |
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