Projection photoetching machine alignment sensing system based on vortex light spatial modulation

Abstract

The invention discloses a projection photoetching machine alignment sensing system based on vortex light spatial modulation. Wherein the reflector is located between the silicon wafer alignment mark and the first lens, reflects a light beam which is emitted by the alignment light source and is parallel to the silicon wafer alignment mark, and generates a first reflection light beam which vertically irradiates a first grating or a second grating of the silicon wafer alignment mark; after the first reflection light beam is diffracted by the silicon wafer alignment mark, generated positive first-level diffraction light and negative first-level diffraction light are upwards transmitted to the second lens through the first lens; the detector receives convergent light beams which vertically penetrate through a first vortex phase plate and a second vortex phase plate which are distributed on two sides of a central optical axis of the alignment sensing system in an xz plane; or receiving a convergent light beam which vertically penetrates through a third vortex phase plate and a fourth vortex phase plate which are distributed on the two sides of the central optical axis of the alignment sensing system in the yz plane. The system provided by the invention can realize the position detection of the alignment mark of the sub-nanometer and deep sub-nanometer precision photoetching machine.

Description

Technical Field

[0001] The present invention relates to the technical field of lithography machines, and particularly to a projection lithography machine alignment sensing system based on vortex light spatial modulation. Background Art

[0002] The lithography process is a key process in integrated circuit manufacturing. When a lithography machine works, the mask pattern carrying the integrated circuit layout information is transferred to the photoresist on the silicon wafer surface in an imaging manner through a projection objective lens. After dozens or even hundreds of lithography exposure processes, different mask patterns are precisely transferred layer by layer to the corresponding positions on the silicon wafer surface to form a complex three-dimensional structure of the integrated circuit.

[0003] A lithography machine requires high overlay accuracy. Overlay accuracy is the core performance index of a lithography machine and is used to evaluate the position error size of a new layer of pattern on the silicon wafer relative to the previous layer of pattern. Improving overlay accuracy is an important factor driving the continuous development of integrated circuit manufacturing technology. To achieve high overlay accuracy, before exposure, the silicon wafer and the mask are accurately aligned through an alignment system. First, the precise detection of the silicon wafer position needs to be achieved through an alignment sensing system. Therefore, the detection accuracy of the alignment sensing system largely determines the alignment accuracy of the lithography machine, and it can be said that it largely determines the level of overlay accuracy and is the key to realizing the core performance of the lithography machine.

[0004] For the lithography machines of the main manufacturers of lithography machines used in the manufacture of integrated circuits for advanced nodes, the overlay accuracy has been less than 2 nm, and the corresponding alignment accuracy has reached sub-nanometer and deep sub-nanometer, which requires very high detection accuracy for the corresponding alignment sensing system.

[0005] The alignment sensing systems SMASH and ORION in lithography machines used in the manufacture of integrated circuits for advanced nodes are based on the principle of phase grating alignment (PGA). The grating alignment marks diffract under the illumination of the light source, and the position of the silicon wafer alignment marks is calculated through the interference signal between the positive and negative diffraction orders, with very high alignment accuracy and process stability (see prior arts US6961116B2 and US10508906B2). Since this alignment sensing system is composed of a variety of optical elements such as a self-reference interferometer, the processing and alignment difficulty is relatively high. Summary of the Invention

[0006] In view of this, the present invention proposes a projection lithography machine alignment sensing system based on vortex light spatial modulation, with a simple system structure. By using a vortex phase plate to perform spatial modulation on the interference signal, high-precision detection of the position of the phase grating alignment marks can be achieved.

[0007] The present invention is implemented as follows.

[0008] A projection lithography alignment sensing system based on vortex light spatial modulation, wherein:

[0009] The mirror is located between the wafer alignment mark and the first lens, reflects the parallel beam emitted by the alignment light source and parallel to the wafer alignment mark, and generates a first reflected beam that perpendicularly irradiates the first grating or the second grating of the wafer alignment mark.

[0010] After the first reflected beam is diffracted by the wafer alignment mark, the generated positive first-order diffracted light and negative first-order diffracted light propagate upward through the first lens to the second lens, where the distance between the first lens and the second lens is the sum of the focal lengths of the first lens and the second lens; the wafer alignment mark is located at the object-side focal plane of the first lens.

[0011] The detector is located at the image-side focal plane of the second lens and receives the converging beam that perpendicularly passes through the first vortex phase plate and the second vortex phase plate located on both sides of the central optical axis of the alignment sensing system in the xz plane; or receives the converging beam that perpendicularly passes through the third vortex phase plate and the fourth vortex phase plate located on both sides of the central optical axis of the alignment sensing system in the yz plane.

[0012] The topological charge numbers of the first vortex phase plate and the third vortex phase plate are +l, and the topological charge numbers of the second vortex phase plate and the fourth vortex phase plate are -l; the x direction and the y direction are the horizontal direction and the vertical direction of the horizontal plane in the global coordinate system of the projection lithography respectively, and the z direction is the direction perpendicular to the xy plane determined by the x direction and the y direction.

[0013] Preferably, the wafer alignment mark is composed of a first grating and a second grating with a grating period of P; the first grating is used for detecting the position of the wafer alignment mark in the x direction, and the second grating is used for detecting the position of the wafer alignment mark in the y direction; the scribing direction of the first grating is along the y direction, and the scribing direction of the second grating is along the x direction.

[0014] Preferably, when detecting the position of the wafer alignment mark in the x direction, the emitted beam of the alignment light source is reflected by the mirror to generate a reflected beam, and the reflected beam perpendicularly irradiates the first grating for detecting the position of the wafer alignment mark in the x direction; the reflected beam diffracts on the first grating to generate positive first-order diffracted light and negative first-order diffracted light that propagate upward, converge after passing through the first lens and the second lens, wherein the positive first-order diffracted light perpendicularly passes through the first vortex phase plate, the negative first-order diffracted light perpendicularly passes through the second vortex phase plate, and the positive first-order diffracted light and the negative first-order diffracted light finally converge on the detection surface of the detector to form a first interference pattern; the position offset Δx of the wafer alignment mark is calculated according to the first rotation angle Δθ1 of the first interference pattern relative to the reference pattern.

[0015] Wherein, the reference pattern is the interference pattern detected on the detection surface of the detector when the position offset Δx of the wafer alignment mark is 0 and is obtained in advance.

[0016] Preferably, when detecting the y-direction position of the wafer alignment mark, the emitted light beam of the alignment light source is reflected by a mirror to generate a reflected light beam, and the reflected light beam is perpendicularly irradiated on the second grating for detecting the y-direction position of the wafer alignment mark; the reflected light beam diffracts on the second grating to generate positive first-order diffracted light and negative first-order diffracted light that propagate upward, and after passing through the first lens and the second lens, they converge. Among them, the positive first-order diffracted light perpendicularly passes through the third vortex phase plate, the negative first-order diffracted light perpendicularly passes through the fourth vortex phase plate, and the positive first-order diffracted light and the negative first-order diffracted light finally converge on the detection surface of the detector to form a second interference pattern; the position offset Δy of the wafer alignment mark is calculated according to the rotation angle Δθ2 of the second interference pattern relative to the reference pattern.

[0017] Preferably, the wafer alignment mark is a reflective phase grating.

[0018] A detection method for a projection lithography machine alignment sensing system based on vortex light spatial modulation, based on the projection lithography machine alignment sensing system based on vortex light spatial modulation as described above, the method includes:

[0019] Step S1: Determine the detection direction of the wafer alignment mark. After the emitted light beam of the alignment light source is reflected by a mirror, the reflected light beam is perpendicularly irradiated on the wafer alignment mark; the wafer alignment mark diffracts after being irradiated by the reflected light beam to generate positive first-order diffracted light and negative first-order diffracted light; after passing through the first lens and the second lens, the positive first-order diffracted light is perpendicularly irradiated on a vortex phase plate for detecting the position of the wafer alignment mark in this detection direction, and after passing through the first lens and the second lens, the negative first-order diffracted light is perpendicularly irradiated on another vortex phase plate for detecting the position of the wafer alignment mark in this detection direction; after the positive first-order diffracted light and the negative first-order diffracted light respectively pass through the corresponding vortex phase plates, they interfere on the detection surface of the detector to form an interference pattern; wherein, the detection direction is the x direction or the y direction.

[0020] Step S2: Obtain the interference pattern formed at the detector surface and calculate the rotation angle size between the interference pattern and the reference pattern.

[0021] Step S3: Calculate the position offset size of the wafer alignment mark based on the rotation angle between the interference pattern and the reference pattern.

[0022] Preferably, when the detection direction is the x direction, the position deviation Δx in the x direction is:

[0023]

[0024] wherein, P is the grating period of the wafer alignment mark, Δθ1 is the rotation angle size of the first interference pattern relative to the reference pattern, and l is the topological charge number.

[0025] Preferably, when the detection direction is the y - direction, the position deviation Δy in the y - direction is:

[0026]

[0027] where P is the grating period of the silicon wafer alignment mark, Δθ2 is the magnitude of the rotation angle of the second interference pattern relative to the reference pattern, and l is the topological charge number.

[0028] Beneficial effects:

[0029] (1) The alignment sensing system of the projection lithography machine based on the spatial modulation of vortex light according to the present invention can be used in a projection lithography machine and can realize the position detection of alignment marks of lithography machines with sub - nanometer and deep sub - nanometer precision.

[0030] (2) The silicon wafer position detection accuracy of the alignment sensing system of the projection lithography machine based on the spatial modulation of vortex light according to the present invention is high, and the optical path of the alignment sensing system of the present invention is simple, the number of optical elements is reduced, and the processing difficulty of the core optical elements and the debugging difficulty of the optical system are reduced.

[0031] (3) For the alignment sensing system of the projection lithography machine based on the spatial modulation of vortex light according to the present invention, the position offset of the silicon wafer alignment mark is calculated by detecting the rotation angle of the interference pattern of the vortex beam diffracted by the grating alignment mark and modulated by the vortex phase plate, and the information processing process is simple. Description of the drawings

[0032] Figure 1 It is a schematic optical path diagram of the alignment sensing system based on the spatial modulation of vortex light for detecting the x - direction position of a silicon wafer provided by the present invention;

[0033] Figure 2 It is a schematic optical path diagram of the alignment sensing system based on the spatial modulation of vortex light for detecting the y - direction position of a silicon wafer provided by the present invention;

[0034] Figure 3 It is a schematic diagram of the grating distribution on the silicon wafer alignment mark in the present invention;

[0035] Figure 4(A) is an interference pattern when the initial phase difference between two vortex beams with topological charge numbers equal to +3 and -3 is 0.

[0036] Figure 4(B) is a schematic diagram of an interference pattern when the initial phase difference between two vortex beams with topological charge numbers equal to +3 and -3 is π / 6.

[0037] Reference numerals:

[0038] 1. Alignment light source; 2. Reflecting mirror; 3. Wafer alignment mark; 4. First lens; 5. Second lens; 61. First vortex phase plate with topological charge of +l; 62. Second vortex phase plate with topological charge of -l; 63. Third vortex phase plate with topological charge of +l; 64. Fourth vortex phase plate with topological charge of -l; 7. Wafer to be aligned; 8. Detector; 31. First grating with period P; 32. Second grating with period P. Detailed implementation manner

[0039] The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

[0040] As Figure 1 and Figure 2 shown, the present invention proposes a projection lithography alignment sensing system based on vortex light spatial modulation, wherein:

[0041] The reflecting mirror 2 is located between the wafer alignment mark 3 and the first lens 4, and reflects the parallel beam emitted by the alignment light source 1 that is parallel to the wafer alignment mark 3, generating a first reflected beam that perpendicularly irradiates the first grating 31 or the second grating 32 of the wafer alignment mark 3.

[0042] After the first reflected beam is diffracted by the wafer alignment mark 3, the generated positive first-order diffracted light and negative first-order diffracted light propagate upward through the first lens 4 to the second lens 5, where the distance between the first lens 4 and the second lens 5 is the sum of the focal lengths of the first lens 4 and the second lens 5; the wafer alignment mark 3 is located at the object-side focal plane of the first lens 4.

[0043] The detector 8 is located at the image-side focal plane of the second lens 5 and receives the converging beam that perpendicularly passes through the first vortex phase plate 61 and the second vortex phase plate 62 distributed on both sides of the central optical axis of the alignment sensing system in the xz plane; or receives the converging beam that perpendicularly passes through the third vortex phase plate 63 and the fourth vortex phase plate 64 distributed on both sides of the central optical axis of the alignment sensing system in the yz plane.

[0044] The topological charges of the first vortex phase plate 61 and the third vortex phase plate 63 are +l, and the topological charges of the second vortex phase plate 62 and the fourth vortex phase plate 64 are -l; the x direction and the y direction are respectively the horizontal direction and the vertical direction of the horizontal plane in the global coordinate system of the projection lithography machine, and the z direction is the direction perpendicular to the xy plane determined by the x direction and the y direction.

[0045] In the present invention, the projection lithography alignment sensing system based on vortex light spatial modulation includes an alignment light source 1, a mirror 2, a wafer alignment mark 3, a first lens 4, a second lens 5, a first vortex phase plate 61, a second vortex phase plate 62, a third vortex phase plate 63, a fourth vortex phase plate 64 and a detector 8, which can realize the detection of the position of the wafer alignment mark 3. The parallel beam emitted by the alignment light source 1 and parallel to the wafer alignment mark 3 is reflected by the mirror 2. When a first reflected beam that perpendicularly irradiates the first grating 31 of the wafer alignment mark 3 is generated, the detector 8 receives the converging beam that perpendicularly passes through the first vortex phase plate 61 and the second vortex phase plate 62. The first vortex phase plate 61 and the second vortex phase plate 62 are distributed on both sides of the central optical axis of the alignment sensing system in the xz plane. When a first reflected beam that perpendicularly irradiates the second grating 32 of the wafer alignment mark 3 is generated, the detector 8 receives the converging beam that perpendicularly passes through the third vortex phase plate 63 and the fourth vortex phase plate 64. The third vortex phase plate 63 and the fourth vortex phase plate 64 are distributed on both sides of the central optical axis of the alignment sensing system in the yz plane.

[0046] As Figure 3 shown, the wafer alignment mark 3 is a reflective phase grating. The wafer alignment mark 3 is composed of a first grating 31 and a second grating 32 with a grating period of P. The first grating 31 is used for detecting the position of the wafer alignment mark 3 in the x direction, and the second grating 32 is used for detecting the position of the wafer alignment mark 3 in the y direction; the scribing direction of the first grating 31 is along the y direction, and the scribing direction of the second grating 32 is along the x direction.

[0047] In the present invention, when detecting the position of the wafer alignment mark 3 in the x direction, the emitted beam of the alignment light source 1 is reflected by the mirror 2 to generate a reflected beam, and the reflected beam perpendicularly irradiates the first grating 31 used for detecting the position of the wafer alignment mark 3 in the x direction; the reflected beam diffracts on the first grating 31, and the generated positive first-order diffracted light and negative first-order diffracted light propagate upward, converge after passing through the first lens 4 and the second lens 5, where the positive first-order diffracted light perpendicularly passes through the first vortex phase plate 61, and the negative first-order diffracted light perpendicularly passes through the second vortex phase plate 62. The positive first-order diffracted light and the negative first-order diffracted light finally converge on the detection surface of the detector 8 to form a first interference pattern; the position offset Δx of the wafer alignment mark 3 is calculated according to the first rotation angle Δθ1 of the first interference pattern relative to the reference pattern; the reference pattern is the interference pattern detected on the detection surface of the detector when the position offset Δx of the wafer alignment mark is 0 and is obtained in advance.

[0048] In the present invention, when detecting the y-direction position of the wafer alignment mark 3, the emitted light beam of the alignment light source 1 is reflected by the mirror 2 to generate a reflected light beam, and the reflected light beam perpendicularly irradiates on the second grating 32 for detecting the y-direction position of the wafer alignment mark 3; the reflected light beam diffracts on the second grating 32 to generate a positive first-order diffracted light and a negative first-order diffracted light that propagate upward, and are converged after passing through the first lens 4 and the second lens 5. Among them, the positive first-order diffracted light perpendicularly passes through the third vortex phase plate 63, and the negative first-order diffracted light perpendicularly passes through the fourth vortex phase plate 64. The positive first-order diffracted light and the negative first-order diffracted light are finally converged on the detection surface of the detector 8 to form a second interference pattern; the position offset Δy of the wafer alignment mark 3 is calculated according to the rotation angle Δθ2 of the second interference pattern relative to the reference pattern.

[0049] The present invention also provides a detection method for a projection lithography machine alignment sensing system based on vortex light spatial modulation. Based on the projection lithography machine alignment sensing system based on vortex light spatial modulation as described above, the method includes:

[0050] Step S1: Determine the detection direction of the wafer alignment mark 3. After the emitted light beam of the alignment light source 1 is reflected by the mirror 2, the reflected light beam perpendicularly irradiates on the wafer alignment mark 3; the wafer alignment mark 3 diffracts after being irradiated by the reflected light beam to generate a positive first-order diffracted light and a negative first-order diffracted light; after passing through the first lens 4 and the second lens 5, the positive first-order diffracted light perpendicularly irradiates on a vortex phase plate for detecting the position of the wafer alignment mark 3 in this detection direction, and after passing through the first lens 4 and the second lens 5, the negative first-order diffracted light perpendicularly irradiates on another vortex phase plate for detecting the position of the wafer alignment mark 3 in this detection direction; after the positive first-order diffracted light and the negative first-order diffracted light respectively pass through the corresponding vortex phase plates, they interfere on the detection surface of the detector 8 to form an interference pattern; wherein, the detection direction is the x direction or the y direction.

[0051] Step S2: Obtain the interference pattern formed at the detector surface 8, and calculate the rotation angle size of the interference pattern relative to the reference pattern.

[0052] Step S3: Calculate the position offset size of the wafer alignment mark 3 based on the rotation angle of the interference pattern relative to the reference pattern.

[0053] When the detection direction is the x direction, the position deviation Δx in the x direction is:

[0054]

[0055] wherein, P is the grating period of the wafer alignment mark 3, Δθ1 is the rotation angle size of the interference pattern relative to the reference pattern, and l is the topological charge number.

[0056] When the detection direction is the y direction, the position deviation Δy in the y direction is as follows:

[0057]

[0058] Where P is the grating period of the silicon wafer alignment mark 3, Δθ2 is the rotation angle size of the interference pattern relative to the reference pattern, and l is the topological charge number.

[0059] Taking the detection direction as the x direction as an example, the effectiveness of calculating the position deviation of the silicon wafer alignment mark in the present invention is deduced and explained.

[0060] The light beam a emitted from the alignment light source 1 is reflected by the mirror 2 and then vertically irradiates the first grating 31 on the silicon wafer alignment mark 3, and diffraction occurs. The positive first-order diffracted light and the negative first-order diffracted light propagate upward through the first lens 4 and the second lens 5, where and The complex amplitudes are respectively:

[0061]

[0062] Where A0 is the amplitude of the positive and negative first-order diffracted lights, is the initial phase of the light beam a, x w is the position of the silicon wafer alignment mark 3 in the x direction, and P is the grating period corresponding to the silicon wafer alignment mark 3.

[0063] The diffracted light After passing through the first vortex phase plate 61 with a topological charge number of +l, it is converted into a vortex beam with a topological charge number of +l The complex amplitude is:

[0064]

[0065] Where θ is the azimuth angle perpendicular to the light beam propagation plane. The diffracted light After passing through the second vortex phase plate 62 with a topological charge number of -l, it is converted into a vortex beam with a topological charge number of -l The complex amplitude is:

[0066]

[0067] On the detector 8, the vortex beams with topological charge numbers of +l and -l and Converge to interfere, and the resulting interference light intensity can be expressed as:

[0068]

[0069] Such as Figure 4(A)-Figure 4(B)The interference pattern when the topological charge number l = 3 is shown. The pattern generated by the interference of conjugate vortex light is petal-shaped and has central symmetry. Figure 4(A) shows the interference pattern when the silicon wafer alignment mark does not move, and Figure 4(B) shows the interference pattern when the silicon wafer alignment mark moves by P / 24. When the silicon wafer alignment mark 3 moves, the interference pattern rotates. The relationship between the rotation angle Δθ and the displacement Δx of the silicon wafer alignment mark 3 is as follows:

[0070]

[0071] The position offset Δx of the silicon wafer alignment mark 3 can be obtained by calculating the rotation angle of the interference pattern.

[0072]

[0073] When the rotation angle of the pattern is π / l, it coincides with the initial pattern, and at this time, it is impossible to distinguish the change of the interference pattern. Therefore, the system displacement measurement range x range = P / 2.

[0074] A specific embodiment of the detection direction provided by the present invention is in the x direction.

[0075] The laser LGK7665-18 is used as the alignment light source 1, and a beam with an emission wavelength of 632.8 nm illuminates the silicon wafer alignment mark 3. The grating period of the silicon wafer alignment mark 3 is 2 μm. The model of the first lens 4 is Thorlabs352110-B, and its focal length is 5.38 mm. The focal length of the second lens 5 is 61.06 mm. The topological charge numbers of the first vortex phase plate 61 and the second vortex phase plate 62 are +3 and -3 respectively. The detector 8 is a Hikvision MV-CU200-20GM, with a pixel size of 1.4 μm × 1.4 μm and a resolution of 5120 × 3840.

[0076] After the beam with an emission wavelength of 632.8 nm from the alignment light source 1 irradiates the silicon wafer alignment mark 3, the generated positive and negative first-order diffracted lights are modulated into vortex beams by the vortex phase plates after passing through the first lens 4 and the second lens 5 respectively, and interfere at the detector 8. The generated interference light intensity is expressed as:

[0077]

[0078] When the silicon wafer alignment mark 3 moves, the interference pattern rotates. The relationship between the rotation angle Δθ and the displacement Δx of the silicon wafer alignment mark 3 is as follows:

[0079]

[0080] The displacement Δx of the silicon wafer alignment mark 3 can be obtained by detecting the rotation angle of the interference pattern.

[0081]

[0082] The minimum rotation angle of the interference pattern detectable on the detector surface determines the detection accuracy of the position of the wafer alignment marks, that is, the detection resolution of the alignment sensing system. From the component parameters of the system, the minimum rotation angle Δθmin of the interference pattern detectable on the detector surface is 0.036°, so the position detection resolution of this system is 0.6 nm.

[0083] When the ratio of the focal length of the second lens 5 to the focal length of the first lens 4 in the alignment sensing system further increases, and the period of the wafer alignment marks and the pixel size of the detector used further decrease, the minimum displacement of the alignment marks detectable by the alignment sensing system can be further reduced. In addition, improving the processing accuracy of the grating alignment marks and the vortex phase plate, and improving the calculation method of the rotation angle of the interference pattern in the above step S2 can improve the detection accuracy of the position of the alignment marks.

[0084] The above specific embodiments only describe the design principle of the present invention. The shapes and names of the components in this description can be different and are not limited. Therefore, those skilled in the art of the present invention can modify or equivalently replace the technical solutions recorded in the foregoing embodiments; and these modifications and replacements do not depart from the spirit and technical solutions of the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A projection lithography alignment sensing system based on vortex light spatial modulation, characterized in that, Wherein: The mirror is located between the wafer alignment mark and the first lens, reflects the parallel light beam emitted by the alignment light source and parallel to the wafer alignment mark, and generates a first reflected light beam that vertically irradiates the first grating or the second grating of the wafer alignment mark; After the first reflected light beam is diffracted by the wafer alignment mark, the generated positive first-order diffracted light and negative first-order diffracted light propagate upward through the first lens to the second lens, where the distance between the first lens and the second lens is the sum of the focal lengths of the first lens and the second lens; the wafer alignment mark is located at the object-side focal plane of the first lens; The detector is located at the image-side focal plane of the second lens and receives the converging light beam that vertically passes through the first vortex phase plate and the second vortex phase plate distributed on both sides of the central optical axis of the alignment sensing system in the xz plane; or receives the converging light beam that vertically passes through the third vortex phase plate and the fourth vortex phase plate distributed on both sides of the central optical axis of the alignment sensing system in the yz plane; The topological charge numbers of the first vortex phase plate and the third vortex phase plate are +l, and the topological charge numbers of the second vortex phase plate and the fourth vortex phase plate are -l; the x direction and the y direction are respectively the horizontal direction and the vertical direction of the horizontal plane in the global coordinate system of the projection lithography machine, and the z direction is the direction perpendicular to the xy plane determined by the x direction and the y direction.

2. The system according to claim 1, wherein The wafer alignment mark is composed of a first grating and a second grating with a grating period of P; the first grating is used for position detection of the wafer alignment mark in the x direction, and the second grating is used for position detection of the wafer alignment mark in the y direction; the ruling direction of the first grating is along the y direction, and the ruling direction of the second grating is along the x direction.

3. The system according to claim 2, wherein When detecting the position of the wafer alignment mark in the x direction, the emitted light beam of the alignment light source is reflected by the mirror to generate a reflected light beam, and the reflected light beam vertically irradiates the first grating used for position detection of the wafer alignment mark in the x direction; the reflected light beam is diffracted on the first grating, and the generated positive first-order diffracted light and negative first-order diffracted light propagate upward, are converged after passing through the first lens and the second lens, wherein the positive first-order diffracted light vertically passes through the first vortex phase plate, the negative first-order diffracted light vertically passes through the second vortex phase plate, and the positive first-order diffracted light and the negative first-order diffracted light are finally converged on the detection surface of the detector to form a first interference pattern; the position offset Δx of the wafer alignment mark is calculated according to the first rotation angle Δθ1 of the first interference pattern relative to the reference pattern; wherein, the reference pattern is the interference pattern detected on the detection surface of the detector when the position offset Δx of the wafer alignment mark is 0 and is obtained in advance.

4. The system according to claim 2, wherein When detecting the y-direction position of the wafer alignment mark, the outgoing beam of the alignment light source is reflected by a mirror to generate a reflected beam, and the reflected beam vertically irradiates on the second grating for detecting the y-direction position of the wafer alignment mark; the reflected beam diffracts on the second grating to generate a positive first-order diffracted light and a negative first-order diffracted light that propagate upward, and are converged after passing through the first lens and the second lens. Among them, the positive first-order diffracted light vertically passes through the third vortex phase plate, and the negative first-order diffracted light vertically passes through the fourth vortex phase plate. The positive first-order diffracted light and the negative first-order diffracted light are finally converged on the detection surface of the detector to form a second interference pattern; the position offset Δy of the wafer alignment mark is calculated according to the rotation angle Δθ2 of the second interference pattern relative to the reference pattern.

5. The system according to any one of claims 1-4, characterized in that, The wafer alignment mark is a reflective phase grating.

6. A detection method for a projection lithography alignment sensing system based on vortex light spatial modulation, based on the projection lithography alignment sensing system based on vortex light spatial modulation according to any one of claims 1-5, characterized in that, The method includes: Step S1: Determine the detection direction of the wafer alignment mark. After the outgoing beam of the alignment light source is reflected by a mirror, the reflected beam vertically irradiates on the wafer alignment mark; the wafer alignment mark diffracts to generate a positive first-order diffracted light and a negative first-order diffracted light after being irradiated by the reflected beam; after passing through the first lens and the second lens, the positive first-order diffracted light vertically irradiates on a vortex phase plate for detecting the position of the wafer alignment mark in this detection direction, and after passing through the first lens and the second lens, the negative first-order diffracted light vertically irradiates on another vortex phase plate for detecting the position of the wafer alignment mark in this detection direction; after the positive first-order diffracted light and the negative first-order diffracted light respectively pass through the corresponding vortex phase plates, they interfere on the detection surface of the detector to form an interference pattern; wherein, the detection direction is the x direction or the y direction. Step S2: Obtain the interference pattern formed at the detector surface, and calculate the rotation angle size between the interference pattern and the reference pattern. Step S3: Calculate the position offset size of the wafer alignment mark based on the rotation angle between the interference pattern and the reference pattern.

7. The method according to claim 6, characterized in that, When the detection direction is the x direction, the position deviation Δx in the x direction is: where P is the grating period of the wafer alignment mark, Δθ1 is the rotation angle size between the interference pattern and the reference pattern, and l is the topological charge number.

8. The method according to claim 6, characterized in that When the detection direction is the y direction, the position deviation Δy in the y direction is: where P is the grating period of the wafer alignment mark, Δθ2 is the rotation angle size between the interference pattern and the reference pattern, and l is the topological charge number.

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