An interference system

Abstract

The present invention provides an interference system, wherein the interference system includes: a transmitting module, an interference lens group and a receiving screen; the transmitting module includes a semi-transparent and semi-reflective mirror, which is used to transmit measurement beams of different angular frequencies to the interference lens group; the interference lens group includes a first surface and a second surface, the first surface or the second surface is a metasurface, and the phase distribution of the metasurface can reduce the spacing between adjacent order fringes; the first surface is used to reflect part of the measurement beam and transmit another part of the measurement beam; the second surface is used to reflect another part of the measurement beam; the semi-transparent and semi-reflective mirror is used to direct the beam emitted from the first surface to the receiving screen. Through the interference system provided by the embodiment of the present invention, any one of the two surfaces is a metasurface, and based on the phase distribution of the metasurface, the inherent phase distribution of the interference fringes originally formed in the far field can be changed more drastically, thereby making the spacing between adjacent fringes smaller and the interference fringes more refined.

Description

Technical Field

[0001] The present invention relates to the technical field of equal-inclination interference, and in particular to an interference system. Background Art

[0002] For interference measurement, the finer the interference fringes, the higher the accuracy of the interference measurement scheme. However, the traditional equal-inclination interference scheme has a limit to the fineness of the fringes, which cannot be broken. At present, a special photon can be used. This photon is generated by the spontaneous parametric down-conversion process in the second-order nonlinear crystal. This photon has a characteristic that its emission angle is related to the wavelength (or angular frequency). Therefore, the light source that can emit this photon is applied to the Michelson system. The fineness of the interference fringes generated is 27 times higher than that of the traditional interference scheme. However, the fineness of the interference fringes of this scheme is still limited by this nonlinear crystal and cannot be improved further. Summary of the invention

[0003] To solve the above problems, an object of an embodiment of the present invention is to provide an interference system.

[0004] An embodiment of the present invention provides an interference system, comprising: a transmitting module, an interferometer group and a receiving screen; the transmitting module comprises a semi-transparent and semi-reflective mirror arranged on one side close to the interferometer group, the transmitting module is used to transmit measurement light beams of different angular frequencies to the interferometer group, and the measurement light beams of different angular frequencies enter the interferometer group at different incident positions; the interferometer group comprises a first surface and a second surface, the first surface or the second surface is a metasurface, and the phase distribution of the metasurface can reduce the spacing between adjacent order fringes; the first surface is a surface capable of transmission and reflection, and is used to reflect part of the measurement light beam toward the semi-transparent and semi-reflective mirror, and transmit the other part of the measurement light beam toward the second surface; the second surface is used to reflect the other part of the measurement light beam and transmit it to the semi-transparent and semi-reflective mirror through the first surface; the semi-transparent and semi-reflective mirror is used to direct the light beam emitted by the first surface toward the receiving screen; the receiving screen is used to receive interference fringes formed by a plurality of the fringes.

[0005] Optionally, the emission module also includes a light source and a collimating lens; the light source is used to generate an initial light beam with an emission angle corresponding to an angular frequency one by one, and the emission angle is multiple; the collimating lens is arranged on the light emitting side of the light source, and the distance between the two is the focal length of the collimating lens, and the collimating lens is used to collimate the initial light beam to obtain a collimated light beam, and direct the collimated light beam to the semi-transparent and semi-reflective mirror; the semi-transparent and semi-reflective mirror is also used to direct at least part of the collimated light beam as a measuring light beam to the first surface.

[0006] Optionally, the semi-transparent and semi-reflective mirror is used to transmit at least part of the collimated light beam as a measuring light beam toward the first surface, and reflect the light beam emitted from the first surface toward the receiving screen; or, the semi-transparent and semi-reflective mirror is used to reflect at least part of the collimated light beam as a measuring light beam toward the first surface, and transmit the light beam emitted from the first surface toward the receiving screen.

[0007] Optionally, the collimating lens includes a lens for eliminating chromatic aberration.

[0008] Optionally, the collimating lens is a metalens.

[0009] Optionally, the exit angle of the initial light beam satisfies: Wherein, θ represents the emission angle of the initial light beam; R represents the radial distance between the position where the initial light beam is emitted toward the collimating lens and the center of the collimating lens; and f represents the focal length of the collimating lens.

[0010] Optionally, the first surface is parallel to the second surface.

[0011] Optionally, in the interferometer assembly, a function between an incident position at which the measuring light beam enters the metasurface and an angular frequency of the measuring light beam at the incident position has the same monotonicity as a phase distribution of the metasurface along a radial direction.

[0012] Optionally, in the interferometer assembly, the phase of the measuring light beam at the incident position where it enters the metasurface is positively correlated with the angular frequency of the measuring light beam incident on the incident position.

[0013] Optionally, the phase distribution of the interferometer group satisfies: Wherein, ψ[ω(r)] represents the phase distribution of the interferometer group; f[ω(r)] represents the inherent phase distribution caused by the optical path difference generated by the distance between the first surface and the second surface; l represents the radius of the metasurface, and the phase distribution ψ[ω(r)] of the interferometer group is a continuous function within the radius range of the metasurface.

[0014] In the solution provided in the above embodiment of the present invention, by making any one of the two surfaces of the interferometer group a metasurface, the inherent phase distribution of the interference fringes originally formed in the far field can be changed more dramatically based on the phase distribution of the metasurface, thereby making the spacing between adjacent fringes in the interference fringes received by the receiving screen smaller, and the interference fringes more refined.

[0015] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A schematic diagram of an interference system provided by an embodiment of the present invention is shown;

[0018] Figure 2 A schematic diagram showing another interference system provided by an embodiment of the present invention is shown;

[0019] Figure 3 A schematic diagram showing the principle of light source characteristics in the interference system provided by an embodiment of the present invention;

[0020] Figure 4 A schematic diagram showing an interference system provided by an embodiment of the present invention, in which a semi-transparent and semi-reflective mirror transmits at least a portion of a collimated light beam as a measuring light beam toward a first surface, and reflects the light beam emitted from the first surface toward a receiving screen;

[0021] Figure 5 A schematic diagram showing the positions of a light source and a collimating lens in an interference system provided by an embodiment of the present invention is shown;

[0022] Figure 6 A schematic diagram of Example 1 provided by an embodiment of the present invention is shown;

[0023] Figure 7 It shows an enlarged comparison schematic diagram of interference fringes in Example 1 provided by the embodiment of the present invention;

[0024] Figure 8 A schematic diagram of the stripe position and order results in Example 1 provided in an embodiment of the present invention is shown;

[0025] Fig. 9 A schematic diagram showing detailed interference fringes finally generated in Example 1 provided in an embodiment of the present invention is shown;

[0026] Fig.10 The figure shows the surface morphology prediction diagram of the wafer to be tested in the embodiment 1 provided by the embodiment of the present invention;

[0027] Fig.11 Another schematic diagram of the placement of wafers to be tested provided by an embodiment of the present invention is shown.

[0028] icon:

[0029] 1-transmitting module, 2-interference lens group, 3-receiving screen, 11-semi-transparent and semi-reflective mirror, 12-light source, 13-collimating lens, 21-first surface, 22-second surface. DETAILED DESCRIPTION

[0030] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0031] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0032] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] The embodiment of the present invention provides an interference system, see Figure 1As shown, the interference system includes: a transmitting module 1, an interferometer group 2 and a receiving screen 3; the transmitting module 1 includes a semi-transparent and semi-reflective mirror 11 arranged on a side close to the interferometer group 2, and the transmitting module 1 is used to transmit measurement light beams of different angular frequencies to the interferometer group 2, and the incident positions of the measurement light beams of different angular frequencies entering the interferometer group 2 are different; the interferometer group 2 includes a first surface 21 and a second surface 22, and the first surface 21 or the second surface 22 is a metasurface, and the phase distribution of the metasurface can reduce the spacing between adjacent order fringes; the first surface 21 is a surface capable of transmission and reflection, and is used to reflect part of the measurement light beam to the semi-transparent and semi-reflective mirror 11, and transmit the other part of the measurement light beam to the second surface 22; the second surface 22 is used to reflect the other part of the measurement light beam and transmit it to the semi-transparent and semi-reflective mirror 11 through the first surface 21; the semi-transparent and semi-reflective mirror 11 is used to direct the light beam emitted by the first surface 21 to the receiving screen 3; the receiving screen 3 is used to receive interference fringes composed of a plurality of fringes.

[0034] like Figure 1 As shown, in the interference system provided in the embodiment of the present invention, the semi-transparent and semi-reflective mirror 11 is located at the end of the transmitting module 1 that finally transmits the measuring light beam. For example, the semi-transparent and semi-reflective mirror 11 can be arranged at the end of the transmitting module 1 that is closer to the interference lens group 2, such as Figure 1 At the right end of the transmitting module 1, the semi-transparent and semi-reflective mirror 11 is located on the left side of the interferometer group 2. The measuring beams emitted by the transmitting module 1 are multiple beams used to generate interference fringes, and each measuring beam has a different angular frequency, and each measuring beam enters the interferometer group 2 at a different incident position. Figure 1 As shown, Figure 1 In the figure, the gray strips of different shades represent the measurement beams of different angular frequencies. Figure 1 It can be known that the measuring light beams with different angular frequencies are incident on different positions of the interferometer lens assembly 2 respectively, that is, the incident position of the measuring light beam with each angular frequency is different.

[0035] The first surface 21 is located at an end of the interferometer lens group 2 closer to the emission module 1, and the second surface 22 is located at an end of the interferometer lens group 2 farther from the emission module 1; and the first surface 21 can transmit or reflect the light beam (such as the measuring light beam) incident therein, for example, the measuring light beam incident on the first surface 21 can realize the dual functions of partial reflection (reflection back to the semi-transparent and semi-reflective mirror 11) and partial transmission (transmission to the second surface 22) at the first surface 21. When the second surface 22 receives the measuring light beam transmitted by the first surface 21 (the other part of the measuring light beam not reflected by the first surface 21), the second surface 22 can reflect the incident measuring light beam back to the first surface 21, so that the reflected measuring light beam is transmitted at the first surface 21 and transmitted to the semi-transparent and semi-reflective mirror 11.

[0036] like Figure 1 As shown, the first surface 21 is arranged on the light-emitting side of the emitting module 1, such as the right side of the emitting module 1. The first surface 21 is used to receive multiple measuring light beams emitted by the emitting module 1, and reflect part of the measuring light beams back to the semi-transparent and semi-reflective mirror 11, and transmit the other part of the measuring light beams to the second surface 22; the second surface 22 is arranged on the right side of the first surface 21, and is used to receive the measuring light beam transmitted by the first surface 21, and reflect the incident measuring light beam toward the semi-transparent and semi-reflective mirror 11 (transmitted through the first surface 21 and emitted toward the semi-transparent and semi-reflective mirror 11).

[0037] Optionally, the first surface 21 is parallel to the second surface 22. For example, the two surfaces in the interferometer assembly 2 can be coaxially arranged with a certain distance between them, so that the incident position of the measuring light beam emitted by the emission module 1 to the first surface 21 on the first surface 21 is the same as the incident position of the measuring light beam transmitted through the first surface 21 to the second surface 22 on the second surface 22. Figure 1 As shown, the first surface 21 and the second surface 22 are parallel to each other and coaxially arranged, and the distance between them can be determined according to actual needs.

[0038] In the embodiment of the present invention, the first surface 21 or the second surface 22 in the interference lens assembly 2 is a metasurface, for example, Figure 1 As shown, the second surface 22 is a super surface, which can also be Figure 2 As shown, the first surface 21 is a super surface, which can be determined according to actual measurement requirements in the embodiment of the present invention. Among them, the use of a metasurface on any surface can make the light beam incident on the metasurface (such as the measuring light beam emitted from the transmitting module 1 when the first surface 21 is a metasurface; or the measuring light beam emitted from the first surface 21 to the second surface 22 when the second surface 22 is a metasurface) can be further modulated by the phase distribution of the metasurface, wherein the phase distribution is determined by the nanostructure of the metasurface, and the phase distribution is the phase distribution of the metasurface along the radial direction, which can aggravate the change of the inherent phase distribution, that is, the phase distribution can aggravate the change of the inherent phase distribution caused by the optical path difference generated by the distance between the first surface 21 and the second surface 22, so that the part of the measuring light beam reflected by the first surface 21 to the semi-transparent and semi-reflective mirror 11 and the measuring light beam reflected by the second surface 22 to the first surface 21 and then transmitted to the semi-transparent and semi-reflective mirror 11 through the first surface 21 finally form interference fringes (composed of multiple fringes) obtained by equal-inclination interference in the far field (such as the receiving screen 3), and the spacing between adjacent fringes becomes smaller, that is, the fringes become denser, and the fineness of the interference fringes is also improved accordingly.

[0039] In the embodiment of the present invention, any one of the two surfaces of the interferometer group 2 is a metasurface. Based on the phase distribution of the metasurface, the inherent phase distribution of the interference fringes originally formed in the far field can be changed more dramatically, thereby making the spacing between adjacent fringes in the interference fringes received by the receiving screen 3 smaller, and the interference fringes are finer.

[0040] Alternatively, if Figure 1 As shown, the emission module 1 further includes: a light source 12 and a collimating lens 13; Figure 1 The right side of the light source 12 is shown as its light-emitting side. The light source 12 is used to generate an initial light beam with a one-to-one correspondence between an emission angle and an angular frequency, and the emission angles are multiple; the collimating lens 13 is arranged on the light-emitting side of the light source 12, and the distance between the two is the focal length of the collimating lens 13, and the collimating lens 13 is used to collimate the initial light beam to obtain a collimated light beam, and to direct the collimated light beam to the semi-transparent and semi-reflective mirror 11; the semi-transparent and semi-reflective mirror 11 is also used to direct at least part of the collimated light beam as a measurement light beam to the first surface 21.

[0041] In the embodiment of the present invention, the light source 12 can emit multiple initial light beams, each initial light beam corresponds to an angular frequency, and the initial light beams of different angular frequencies have different emission angles; for example, see Figure 3 As shown, the initial light beam emitted by the light source 12 is composed of a special photon, which can be generated by a spontaneous parametric down-conversion process in a second-order nonlinear crystal. The emission angle of the photon (such as the emission angle θ of the initial light beam emitted by the light source 12) and the wavelength (the wavelength λ of the initial light beam, which can also be expressed by an angular frequency ω, that is, ), in other words, when the photon is used as the light source 12, the emission angle θ of the initial light beam emitted by the light source 12 has a one-to-one correspondence with the angular frequency ω of the initial light beam, as shown in Figure 3 As shown, the initial light beam with an angular frequency of ω1 is emitted at an emission angle θ(ω1), the initial light beam with an angular frequency of ω2 is emitted at an emission angle θ(ω2), the initial light beam with an angular frequency of ω3 is emitted at an emission angle θ(ω3), and so on.

[0042] In the embodiment of the present invention, the initial light beams of different angular frequencies emitted by the light source 12 at different exit angles can be emitted to the collimating lens 13 located at the light exiting 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 of different angular frequencies corresponding to different exit angles can enter the collimating lens 13 at different incident angles, and can be modulated by the collimating lens 13 and emitted horizontally in a direction parallel to the main optical axis of the collimating lens 13, such as Figure 1As shown, the initial light beam is modulated into a collimated light beam through the collimating lens 13 and horizontally directed toward the semi-transparent and semi-reflective mirror 11. Optionally, the collimating lens 13 includes a lens for eliminating chromatic aberration. Among them, chromatic aberration will be generated when the initial light beam propagates in the collimating lens 13, so a lens capable of eliminating chromatic aberration can be used as the collimating lens 13, so that after the initial light beam passes through the collimating lens 13, the chromatic aberration originally generated can be corrected by the collimating lens 13. Furthermore, the collimating lens 13 used in the embodiment of the present invention is a super lens, which can further reduce the volume of the interference system, reduce its overall weight, and reduce costs.

[0043] Among them, when the semi-transparent and semi-reflective mirror 11 receives a collimated light beam, the semi-transparent and semi-reflective mirror 11 can direct the collimated light beam to the first surface 21. Since the semi-transparent and semi-reflective mirror 11 is an optical element with a semi-reflective film coated on optical glass, it can transmit and reflect the light incident therein, that is, the semi-transparent and semi-reflective mirror 11 is an optical element that can transmit part of the light and reflect another part of the light; therefore, the incident collimated light beam can be both reflected and transmitted. Therefore, the interference system provided in the embodiment of the present invention can set the positions of the transmitting module 1 (including the light source 12, the collimating lens 13 and the semi-transparent and semi-reflective mirror 11) and the receiving screen 3 according to actual needs; for example, according to the actual installation environment restrictions, it can be determined which method (reflection or transmission) of the emitted light should be used as the measurement beam, so as to set the specific structure of the interference system in a targeted manner. Optionally, see Figure 4 As shown, the semi-transparent and semi-reflective mirror 11 is used to transmit at least a part of the collimated light beam as a measuring light beam to the first surface 21, and reflect the light beam emitted from the first surface 21 to the receiving screen 3; or, the semi-transparent and semi-reflective mirror 11 is used to reflect at least a part of the collimated light beam as a measuring light beam to the first surface 21, and transmit the light beam emitted from the first surface 21 to the receiving screen 3. The schematic diagram of this situation is not shown in the embodiment of the present invention.

[0044] For example, Figure 4 As shown, Figure 4 The interference system provided is based on the light transmitted by the semi-transparent and semi-reflective mirror 11 (i.e. Figure 4 The part of the collimated light beam emitted by the collimating lens 13 located above the semi-transparent and semi-reflective mirror 11) is used as the measuring light beam, and the transmitted measuring light beam is injected into the first surface 21 of the interferometer lens group 2; and the light injected into the semi-transparent and semi-reflective mirror 11 by the first surface 21 (that is, the part of the measuring light beam reflected by the first surface 21 and the other part of the measuring light beam reflected by the second surface 22) can be reflected by the semi-transparent and semi-reflective mirror 11 toward the receiving screen 3 (such as Figure 4Alternatively, the interference system uses the light reflected by the semi-transparent and semi-reflective mirror 11 (i.e., part of the collimated light beam emitted by the collimating lens 13) as the measuring light beam, and injects the reflected measuring light beam into the first surface 21 of the interferometer group 2; and the light injected into the semi-transparent and semi-reflective mirror 11 by the first surface 21 (i.e., part of the measuring light beam reflected by the first surface 21, and another part of the measuring light beam reflected by the second surface 22) can be transmitted by the semi-transparent and semi-reflective mirror 11 to the receiving screen 3 (this structure is not shown in the drawings).

[0045] Alternatively, see Figure 5 As shown, the exit angle of the initial light beam satisfies: That is, the emission angles corresponding to the initial light beams of different angular frequencies satisfy the formula; wherein θ represents the emission angle of the initial light beam; R represents the radial distance between the position of the initial light beam emitted to the collimating lens 13 and the center of the collimating lens 13; and f represents the focal length of the collimating lens 13.

[0046] based on Figure 5 With 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 arranged, and the distance between the two is the focal length f of the collimating lens 13; the exit angle θ of the initial light beam of different angular frequencies is related to the incident position of the initial light beam entering the collimating lens 13 (or the radial distance R between the incident position and the center of the collimating lens 13). In the embodiment of the present invention, when the light source 12, the collimating lens 13, and the interferometer group 2 of the interference system are coaxially arranged, the incident position of the initial light beam entering the collimating lens 13 (or the radial distance R between the incident position of the initial light beam and the center of the collimating lens 13) is the same as the incident position of the measuring light beam entering the interferometer group 2 (including the first surface 21 and the second surface 22) (or the radial distance r between the incident position of the measuring light beam and the center of the corresponding surface of the interferometer group 2).

[0047] Optionally, in the interferometer assembly 2, a function between an incident position of the measuring light beam entering the metasurface and an angular frequency of the measuring light beam at the incident position has the same monotonicity as a phase distribution of the metasurface along a radial direction.

[0048] In the embodiment of the present invention, the light intensity distribution of the interference fringes finally reflected by the interference lens group 2 and received on the receiving screen 3 satisfies Wherein, r represents the radial distance between the incident position of the measuring light beam incident on the metasurface (the first surface 21 or the second surface 22) and the center of the metasurface, for example, the radial distance between the nanostructure at the incident position of the measuring light beam and the center of the metasurface; I(r) represents the light intensity corresponding to the fringes (the fringes received by the receiving screen 3) obtained by interference at a radial distance r from the center of the metasurface (such as at the nanostructure corresponding to the incident position of the measuring light beam); ω(r) represents the function between the incident position of the measuring light beam incident on the metasurface (at the nanostructure at a radial distance r) and the angular frequency of the measuring light beam at the incident position, and f[ω(r)] represents the inherent phase distribution caused by the optical path difference generated by the distance between the first surface 21 and the second surface 22, wherein the inherent phase distribution can be understood as a constant when the radial distance r between the incident position and the center of the metasurface is determined; represents the phase distribution of the metasurface (the first surface 21 or the second surface 22) along the radial direction. In the embodiment of the present invention, the second surface 22 can be a metasurface. Specifically, f[ω(r)] can be L represents the distance between the first surface 21 and the second surface 22; c represents the speed of light. Furthermore, the light intensity distribution of the interference fringes finally reflected by the interference lens group 2 and received on the receiving screen 3 satisfies the equation that can be rearranged and transformed into:

[0049] Based on the equation satisfied by the light intensity distribution, it can be seen that if the spacing between adjacent fringes in the interference fringes needs to be smaller and the interference fringes denser, the inherent phase distribution can be Monotonicity and phase distribution of the metasurface along the radial direction If the two are monotonically increasing functions or monotonically decreasing functions, the multiple fringes received on the receiving screen 3 can be made closer to each other and the spacing between adjacent fringes can be smaller. The monotonicity of the inherent phase distribution is determined by ω(r). Therefore, the phase distribution of the metasurface along the radial direction is The monotonicity of also needs to be the same as the monotonicity of ω(r), that is, the two have the same monotonicity. In the embodiment of the present invention, as the radial distance r increases, the corresponding phase at r increases.

[0050] In the embodiment of the present invention, ω(r) and The monotonicity of the metasurface can be consistent, that is, the phase distribution along the radial direction of The monotonicity of is consistent with the inherent phase distribution f[ω(r)]. For example, we can let ω(r) be are all monotonically increasing functions, which makes the phase distribution of the metasurface along the radial direction and the inherent phase distribution f[ω(r)] are both monotonically increasing functions; or, let ω(r) and are all monotonically decreasing functions, which makes the phase distribution of the metasurface along the radial direction It is a monotonically decreasing function of the inherent phase distribution f[ω(r)].

[0051] In the embodiment of the present invention, the phase distribution of the metasurface along the radial direction is introduced into the interferometer group 2. Guaranteed With the inherent phase distribution The interference system has consistent monotonicity, so that the interference fringes obtained by the interference system are finer, for example, the spacing between multiple fringes is smaller.

[0052] Optionally, in the interferometer assembly 2, the phase of the measuring light beam at the incident position where it enters the metasurface is positively correlated with the angular frequency of the measuring light beam incident on the incident position.

[0053] In the embodiment of the present invention, the measuring beams of different angular frequencies are respectively incident on different positions (incident positions) of the metasurface, and different incident positions correspond to different nanostructures on the metasurface, and the phase of the nanostructure at the incident position can modulate the measuring beam (the measuring beam with a certain angular frequency) incident at the incident position; in other words, different nanostructures on the metasurface modulate the measuring beams with different angular frequencies, for example, at any radial distance r, the working 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 positively correlated with the phase of the nanostructure at the incident position, that is, the interference system satisfies: as the angular frequency of the measuring beam increases, the phase of the measuring beam with the angular frequency incident on the metasurface at the incident position (corresponding to the nanostructure) also increases positively, so as to ensure that the interference system has a more drastic phase distribution.

[0054] Optionally, the phase distribution of the interferometer group 2 satisfies: Wherein, ψ[ω(r)] represents the phase distribution of the interferometer group 2; f[ω(r)] represents 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 metasurface, and the phase distribution ψ[ω(r)] of the interferometer group 2 is a continuous function within the radius range of the metasurface.

[0055] In the embodiment of the present invention, the phase distribution ψ[ω(r)] of the interferometer group 2 is the overall phase distribution corresponding to the final formation of interference fringes, and the ψ[ω(r)] is the phase distribution of the inherent phase distribution f[ω(r)] and the phase distribution of the metasurface in the interferometer group 2. The sum of , that is, the interference system satisfies the relationship: When the phase distribution ψ[ω(r)] of the interference system is continuous in the range [0, l], the first-order derivative of the phase distribution ψ[ω(r)] of the interference system with respect to r is greater than the first-order derivative of the inherent phase distribution f[ω(r)] with respect to r, that is, the phase distribution of the metasurface along the radial direction is The phase distribution ψ[ω(r)] of the interference system generates interference fringes with a finer resolution than that of the traditional interference system (e.g., a system without a metasurface with a radial phase distribution). The fineness of the interference fringes generated by the phase distribution of the interference system (such as the inherent phase distribution f[ω(r)]), the embodiment of the present invention can obtain more uniformly distributed interference fringes by limiting the final phase distribution (such as limiting the phase distribution ψ[ω(r)] of the interference system to be a continuous and differentiable function within the metasurface range).

[0056] Embodiment 1:

[0057] See also Figure 6 As shown, Figure 6 A schematic diagram of an interference system for wafer surface morphology detection is shown. The wafer to be tested is divided into two sides. This embodiment 1 defines one side as a reference surface and the other side as a surface to be tested. A first surface 21 is provided on the side close to the reference surface, and a second surface 22 is provided on the side close to the surface to be tested. The first surface 21 and the second surface 22 constitute an interference lens group 2, and the wafer to be tested is located between the first surface 21 and the second surface 22. The material of the wafer to be tested is quartz glass with a diameter of 300 mm. In this embodiment 1, a nanostructure is provided on the second surface 22 close to the surface to be tested to constitute a super surface. The material of the nanostructure is SiN, the height is 400 nm, and a nanocolumn structure is adopted, and the arrangement method is a concentric circle arrangement.

[0058] In this embodiment 1, the light source 12 uses a PPKTP (Periodically Poled KTP) crystal as a spontaneous parametric down-conversion crystal, and a photon generated by the PPKTP crystal can generate an initial light beam. The relationship between the emission angle of the initial light beam emitted from the light source 12 and its angular frequency is: Where b is a coefficient constant, which is related to the crystal refractive index; Δw is the change in angular frequency; the distance L (the distance between the first surface 21 and the second surface 22) is set to 200 μm, and the focal length of the collimating lens 13 is 20 mm. Based on this, the phase distribution of the metasurface (such as the second surface 22 close to the surface to be measured) can be designed as: Wherein, a is the 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 emission angle and the angular frequency), so as to ensure that the introduction of the metasurface on the basis of the operation of the light source 12 makes the fineness of the stripes greater than that without the introduction of the metasurface. In this embodiment 1, the phase distribution of the metasurface (such as the second surface 22 close to the surface to be measured) is finally obtained as: Among them, a=0.54π, i=3, ω s0 It represents the angular frequency at the center point (such as r=0).

[0059] The enlarged schematic diagram of the interference fringes finally received by the receiving screen 3 in this embodiment 1 can be seen in Figure 7 As shown on the left, compared to Figure 7 As for the enlarged schematic diagram of the traditional interference system without a metasurface on the right, the interference fringes finally generated by the present embodiment 1 are more precise, the spacing between adjacent fringes is smaller, and the detection accuracy of the interference system is higher. Figure 8 FIG. 1 shows a schematic diagram of the interferometric system provided in Example 1 for the fringe position and order results, wherein Figure 8 It can be seen that the fringe order corresponding to each position of the interference fringes finally generated by the present embodiment 1 is greater than the fringe order corresponding to each position of the interference fringes finally generated by the traditional interference system without a metasurface, which can also prove that the interference fringes finally generated by the interference system provided by the present embodiment 1 have higher precision and better detection effect. Figures 9 and 10 As shown, Fig. 9 FIG. 4 shows a schematic diagram of the detailed interference fringes finally generated in this embodiment 1, and FIG. Fig.10 A surface morphology prediction diagram of the wafer to be tested is shown; it can be seen that the interference fringes obtained by the interference system of this embodiment 1 are no longer standard equi-inclined interference fringes, indicating that the surface height of the wafer to be tested is uneven; and, based on the interference fringes, the one-dimensional surface morphology of the wafer to be tested can be accurately measured.

[0060] It should be noted that: in the embodiment of the present invention, nanostructures can also be directly arranged on any surface of the wafer to be tested to form a metasurface that can realize transmission and reflection functions (such as Fig.11 The first surface 21 of the interference system shown in the figure corresponds to the reference surface of the wafer to be tested, and forms a reflective surface (such as Fig.11 The second surface 22 of the interference system shown corresponds to the test surface of the wafer to be tested. The interference system with this structure can also realize the surface morphology detection of the wafer to be tested.

[0061] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technical solution that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. An interference system, characterized in that: include: A transmitting module (1), an interferometer lens group (2), a receiving screen (3), a light source (12) and a collimating lens (13); The transmitting module (1) comprises a semi-transparent and semi-reflective mirror (11) arranged on a side close to the interferometer group (2), and the transmitting module (1) is used to transmit measurement light beams of different angular frequencies to the interferometer group (2), and the measurement light beams of different angular frequencies enter the interferometer group (2) at different incident positions; The interferometer group (2) comprises a first surface (21) and a second surface (22); the first surface (21) or the second surface (22) is a metasurface; the metasurface has a phase distribution capable of reducing the spacing between adjacent order fringes; the first surface (21) is a surface capable of transmission and reflection, and is used to reflect part of the measurement light beam toward the semi-transparent and semi-reflective mirror (11), and transmit another part of the measurement light beam toward the second surface (22); the second surface (22) is used to reflect another part of the measurement light beam and transmit it through the first surface (21) toward the semi-transparent and semi-reflective mirror (11); The semi-transparent and semi-reflective mirror (11) is used to direct the light beam emitted from the first surface (21) toward the receiving screen (3); the receiving screen (3) is used to receive interference fringes formed by a plurality of the fringes; The light source (12) is used to generate an initial light beam with an emission angle corresponding to an angular frequency, and the emission angles are multiple; the collimating lens (13) is arranged on the light-emitting side of the light source (12); The exit angle of the initial light beam satisfies: ; in, represents the exit angle of the initial light beam; Indicates the radial distance between the position where the initial light beam is emitted toward the collimating lens (13) and the center of the collimating lens (13); represents the focal length of the collimating lens (13).

2. The interference system according to claim 1, characterized in that The distance between the light source (12) and the collimating lens (13) is the focal length of the collimating lens (13), and the collimating lens (13) is used to collimate the initial light beam to obtain a collimated light beam, and to direct the collimated light beam toward the semi-transparent and semi-reflective mirror (11); The semi-transparent and semi-reflective mirror (11) is also used to direct at least part of the collimated light beam as a measuring light beam toward the first surface (21).

3. The interference system according to claim 2, characterized in that The semi-transparent and semi-reflective mirror (11) is used to transmit at least part of the collimated light beam as a measuring light beam toward the first surface (21), and to reflect the light beam emitted from the first surface (21) toward the receiving screen (3); or, The semi-transparent and semi-reflective mirror (11) is used to reflect at least part of the collimated light beam as a measuring light beam toward the first surface (21), and to transmit the light beam emitted from the first surface (21) toward the receiving screen (3).

4. The interference system according to claim 2, characterized in that The collimating lens (13) comprises a lens for eliminating chromatic aberration.

5. The interference system according to claim 2, characterized in that: The collimating lens (13) is a super lens.

6. The interference system according to claim 1, characterized in that: The first surface (21) is parallel to the second surface (22).

7. The interference system according to claim 1, characterized in that: In the interferometer assembly (2), a function between an incident position of the measuring light beam entering the metasurface and an angular frequency of the measuring light beam at the incident position has the same monotonicity as a phase distribution of the metasurface in a radial direction.

8. The interference system according to claim 7, characterized in that In the interferometer assembly (2), the phase of the measuring light beam at the incident position of the metasurface is positively correlated with the angular frequency of the measuring light beam incident on the incident position.

9. The interference system according to claim 1, characterized in that: The phase distribution of the interferometer group (2) satisfies: ； in, represents the phase distribution of the interferometer group (2); Indicates an inherent phase distribution caused by an optical path difference generated by the distance between the first surface (21) and the second surface (22); l represents the radius of the metasurface, and the phase distribution of the interferometer group (2) It is a continuous function within the radius of the hypersurface.

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