Alignment device and alignment method

Abstract

The application provides an alignment device and an alignment method. The alignment device is provided with a first polarization adjustment unit, which comprises a first wave plate and a second wave plate connected in sequence. Positive and negative orders of diffraction with the same diffraction order in diffracted light or scattered light pass through the first wave plate and the second wave plate respectively. The direction of the fast axis of the first wave plate and the direction of the fast axis of the second wave plate form a first included angle, so that the diffracted light or scattered light with any polarization state can form a first light beam with a first polarization direction and a second light beam with a second polarization direction after passing through the first polarization adjustment unit, and the alignment measurement is realized independently of the polarization state. Based on this, the application also provides an alignment device. The alignment device simultaneously processes the fifth light beam and the sixth light beam by using a second polarization adjustment unit, eliminates the phase difference of each detection signal, and reduces the risk of modulation depth reduction.

Description

Technical Field

[0001] The present invention relates to the technical field of photolithography machine manufacturing, and in particular to an alignment device and an alignment method. Background Art

[0002] In the field of integrated circuit manufacturing, a photolithography machine applies a mask pattern to a photosensitive film layer, such as a photoresist, on a silicon wafer (also known as a substrate) to create the desired circuit structure. To precisely control the position of each photolithography pass on the silicon wafer, photolithography alignment marks (usually alignment marks) are placed on the silicon wafer. One or more alignment devices are then used to measure the positions of the corresponding photolithography alignment marks on the silicon wafer, thereby determining the alignment position of the silicon wafer.

[0003] Currently, the commonly used alignment device is an alignment sensor based on a self-referencing interferometer. Alignment sensors based on self-referencing interferometers can complete alignment measurements for common marks, but in order to obtain coherent signals with high modulation depth and high precision, such alignment sensors usually require that the polarization state of the diffracted light or scattered light when entering the self-referencing interferometer is 45° linear polarization. However, with the continuous development of photolithography technology, measuring marks under various process conditions has become a new requirement. For example, the lines of the mark can be composed of subdivided lines in another direction. These subdivided lines can act as polarizers, so that the polarization state of the diffracted light or scattered light is no longer the same as the incident light. For example, under the condition that the incident light is linearly polarized, the polarization state of the diffracted light or scattered light may be linear polarization, elliptical polarization, or circular polarization. Under such conditions, the polarization state of the diffracted light or scattered light is not unique, so the requirement of 45° linear polarization cannot be achieved, resulting in deviations in the modulation depth and phase of the signal, causing the accuracy and repeatability of the alignment measurement to decrease.

[0004] Therefore, a new alignment device and alignment method are needed that can achieve polarization state independent of diffracted light or scattered light, and can ensure high alignment repeatability and improve product performance. Summary of the Invention

[0005] The object of the present invention is to provide an alignment device and an alignment method to solve the problem of how to improve the alignment repeatability accuracy.

[0006] In order to solve the above technical problems, the present invention provides an alignment device, comprising an illumination unit, a first polarization adjustment unit, a self-reference interferometer, a spectrometer unit, a first detection unit and a second detection unit; wherein,

[0007] The illumination unit is used to provide illumination; the illumination generates diffracted light or scattered light after passing through an alignment mark, and the diffracted light or scattered light enters the first polarization adjustment unit;

[0008] The first polarization adjustment unit includes a first wave plate and a second wave plate connected to each other, and the negative-order diffraction light and the positive-order diffraction light of the same diffraction order in the diffracted light or scattered light pass through the first wave plate and the second wave plate respectively; wherein the direction of the fast axis of the first wave plate and the direction of the fast axis of the second wave plate form a first angle, so that the diffracted light or scattered light forms a first light beam with a first polarization direction and a second light beam with a second polarization direction after passing through the first polarization adjustment unit; the first light beam and the second light beam enter the self-referencing interferometer; and after passing through the self-referencing interferometer, under the reflection action of the spectrometer, part of the light beam enters the first detection unit, and the remaining part of the light beam enters the second detection unit;

[0009] The first detection unit and the second detection unit respectively obtain the light intensity of the corresponding light beam.

[0010] Optionally, in the alignment device, the self-referencing interferometer is used to convert the first light beam into a third light beam having a second polarization direction, and to convert the second light beam into a fourth light beam having a first polarization direction, and the third light beam and the fourth light beam overlap to form an overlapping light beam; wherein, along a direction perpendicular to the junction of the first wave plate and the second wave plate, the overlapping light beam is divided into a fifth light beam and a sixth light beam; and, the partial light beam entering the first detection unit is the fifth light beam, and the remaining partial light beam entering the second detection unit is the sixth light beam.

[0011] Optionally, in the alignment device, the light splitting unit includes a first reflector and a second reflector; the first reflector is used to reflect the fifth light beam to the first detection unit; the second reflector is used to reflect the sixth light beam to the second detection unit;

[0012] The first detection unit and the second detection unit are used to obtain light intensities in the fifth light beam and the sixth light beam, respectively.

[0013] Optionally, in the alignment device, the first detection unit includes a first polarization beam splitter, a first detector and a second detector; wherein,

[0014] The first polarization beam splitter is used to split the fifth light beam into a seventh light beam having a first polarization direction and an eighth light beam having a second polarization direction;

[0015] The first detector is used to obtain the light intensity of the seventh light beam;

[0016] The second detector is used to obtain the light intensity of the eighth light beam.

[0017] Optionally, in the alignment device, the second detection unit includes a second polarization beam splitter, a third detector and a fourth detector; wherein,

[0018] The second polarization beam splitter is used to split the sixth light beam into a ninth light beam having a first polarization direction and a tenth light beam having a second polarization direction;

[0019] The third detector is used to obtain the light intensity of the ninth light beam;

[0020] The fourth detector is used to obtain the light intensity of the tenth light beam.

[0021] Optionally, in the alignment device, when the alignment mark is moved until the light intensities respectively acquired by the first detection unit and the second detection unit reach preset values, the position of the alignment mark is the alignment position.

[0022] Optionally, in the alignment device, both the first wave plate and the second wave plate are half wave plates, and the range of the first angle includes 45 degrees or 135 degrees.

[0023] Optionally, in the alignment device, the direction of the fast axis of the first wave plate coincides with the first polarization direction, and the direction of the fast axis of the second wave plate forms an angle of 45 degrees with the first polarization direction.

[0024] Optionally, in the alignment device, the first wave plate and the second wave plate are both quarter wave plates, and the first angle is 90 degrees.

[0025] Optionally, in the alignment device, the zero-order diffraction light in the diffracted light or scattered light passes through the interface between the first wave plate and the second wave plate.

[0026] Optionally, in the alignment device, the first polarization direction and the second polarization direction are perpendicular to each other.

[0027] Optionally, in the alignment device, the illumination unit includes a laser emitter.

[0028] Optionally, in the alignment device, the alignment device further includes an objective lens, the light is incident on the alignment mark through the objective lens, and diffracted light or scattered light is generated through the alignment mark, and the diffracted light or scattered light enters the first polarization adjustment unit through the objective lens.

[0029] Based on the same inventive concept, the present invention also provides an alignment method, comprising:

[0030] The lighting unit provides lighting;

[0031] The light irradiates the alignment mark to generate diffracted light or scattered light, and the diffracted light or scattered light passes through the first polarization adjustment unit to form a first light beam with a first polarization direction and a second light beam with a second polarization direction;

[0032] The first light beam and the second light beam are converted into a third light beam having a second polarization direction and a fourth light beam having a first polarization direction respectively by the self-referencing interferometer; the third light beam and the fourth light beam overlap to form a coincident light beam; wherein the coincident light beam is split into a fifth light beam and a sixth light beam along a direction perpendicular to the junction of the first wave plate and the second wave plate;

[0033] The fifth light beam and the sixth light beam are respectively reflected by the light splitting unit to the first detection unit and the second detection unit;

[0034] The first detection unit and the second detection unit respectively obtain the light intensity in the fifth light beam and the sixth light beam;

[0035] The workpiece stage is moved to drive the alignment mark to move. When the light intensities respectively acquired by the first detection unit and the second detection unit reach preset values, the position of the alignment mark is the alignment position.

[0036] Based on the same inventive concept, the present invention further provides an alignment device, comprising an illumination unit, a first polarization adjustment unit, a self-reference interferometer, a second polarization adjustment unit, and a third detection unit; wherein,

[0037] The illumination unit is used to provide illumination; the illumination generates diffracted light or scattered light after passing through an alignment mark, and the diffracted light or scattered light enters the first polarization adjustment unit;

[0038] The first polarization adjustment unit includes a first wave plate and a second wave plate connected to each other, and the negative-order diffraction light and the positive-order diffraction light of the same diffraction order in the diffracted light or scattered light pass through the first wave plate and the second wave plate respectively; wherein the direction of the fast axis of the first wave plate and the direction of the fast axis of the second wave plate form a first angle, so that the diffracted light or scattered light forms a first light beam with a first polarization direction and a second light beam with a second polarization direction after passing through the first polarization adjustment unit; the first light beam and the second light beam enter the self-referencing interferometer; and after passing through the self-referencing interferometer, enter the second polarization adjustment unit;

[0039] The second polarization adjustment unit includes a third wave plate and a fourth wave plate connected to each other, the fast axis of the third wave plate and the fast axis of the fourth wave plate form a second angle, and the direction of the connecting axis of the third wave plate and the fourth wave plate is perpendicular to the direction of the connecting axis of the first wave plate and the second wave plate; part of the light beam enters the third detection unit through the third wave plate, and the remaining part of the light beam enters the third detection unit through the fourth wave plate;

[0040] The third detection unit is used to obtain light intensity.

[0041] Optionally, in the alignment device, the self-referencing interferometer is used to convert the first light beam into a third light beam having a second polarization direction, and to convert the second light beam into a fourth light beam having a first polarization direction; and the third light beam and the fourth light beam overlap to form an overlapping light beam; wherein, along a direction perpendicular to the junction of the first wave plate and the second wave plate, the overlapping light beam is divided into a fifth light beam and a sixth light beam; and the fifth light beam enters the third detection unit through the third wave plate, and the sixth light beam enters the third detection unit through the fourth wave plate.

[0042] Optionally, in the alignment device, the third detection unit includes a first polarization beam splitter prism, a fifth detector and a sixth detector; wherein,

[0043] The first polarization beam splitter prism is used to split the fifth light beam and the sixth light beam incident through the second polarization adjustment unit into an eleventh light beam having a first polarization direction and a twelfth light beam having a second polarization direction;

[0044] The fifth detector is used to obtain the light intensity of the eleventh light beam;

[0045] The sixth detector is used to obtain the light intensity of the twelfth light beam.

[0046] Optionally, in the alignment device, when the alignment mark is moved until the light intensity obtained by the third detection unit reaches a preset value, the position of the alignment mark is the alignment position.

[0047] Optionally, in the alignment device, both the first wave plate and the second wave plate are half wave plates, and the range of the first angle includes 45 degrees or 135 degrees.

[0048] Optionally, in the alignment device, the direction of the fast axis of the first wave plate coincides with the first polarization direction, and the direction of the fast axis of the second wave plate forms an angle of 45 degrees with the first polarization direction.

[0049] Optionally, in the alignment device, the third wave plate and the fourth wave plate are both half wave plates, and the range of the second angle includes 45 degrees, 90 degrees or 135 degrees.

[0050] Optionally, in the alignment device, the angle between the fast axis of the third wave plate and the first polarization direction is 22.5 degrees or 67.5 degrees, and the angle between the fast axis of the fourth wave plate and the first polarization direction is -22.5 degrees or -67.5 degrees.

[0051] Optionally, in the alignment device, the first wave plate and the second wave plate are both quarter wave plates, and the first angle is 90 degrees.

[0052] Optionally, in the alignment device, the third wave plate and the fourth wave plate are both quarter wave plates, and the second angle is 90 degrees.

[0053] Optionally, in the alignment device, zero-order diffracted light or scattered light in the diffracted light or scattered light passes through the interface between the first wave plate and the second wave plate.

[0054] Optionally, in the alignment device, the first polarization direction and the second polarization direction are perpendicular to each other.

[0055] Optionally, in the alignment device, the illumination unit includes a laser emitter.

[0056] Optionally, in the alignment device, the alignment device further includes an objective lens, the light is incident on the alignment mark through the objective lens, and diffracted light or scattered light is generated through the alignment mark, and the diffracted light or scattered light enters the first polarization adjustment unit through the objective lens.

[0057] Based on the same inventive concept, the present invention also provides an alignment method, comprising:

[0058] The lighting unit provides lighting;

[0059] The light irradiates the alignment mark to generate diffracted light or scattered light, and the diffracted light or scattered light passes through the first polarization adjustment unit to form a first light beam with a first polarization direction and a second light beam with a second polarization direction;

[0060] The first light beam and the second light beam are converted into a third light beam having a second polarization direction and a fourth light beam having a first polarization direction respectively by the self-referencing interferometer; the third light beam and the fourth light beam overlap to form a coincident light beam; wherein the coincident light beam is split into a fifth light beam and a sixth light beam along a direction perpendicular to the junction of the first wave plate and the second wave plate;

[0061] The fifth light beam enters the third detection unit through the third wave plate in the second polarization adjustment unit, and the sixth light beam enters the third detection unit through the fourth wave plate;

[0062] The third detection unit acquires the light intensity in the fifth light beam and the sixth light beam;

[0063] The workpiece stage is moved to drive the alignment mark to move. When the light intensity acquired by the third detection unit reaches a preset value, the position of the alignment mark is the alignment position.

[0064] In summary, the present invention provides an alignment device and an alignment method. The alignment device includes an illumination unit, a first polarization adjustment unit, a self-reference interferometer, a spectrometer, a first detection unit, and a second detection unit. In addition, the first polarization adjustment unit includes a first wave plate and a second wave plate connected to each other, and the negative diffraction light and the positive diffraction light with the same diffraction order in the diffracted light or scattered light pass through the first wave plate and the second wave plate respectively. The direction of the fast axis of the first wave plate and the direction of the fast axis of the second wave plate form a first angle, so that regardless of whether the polarization state of the incident diffracted light or scattered light is linear polarization, (elliptical) circular polarization or non-polarization, it can form a first light beam with a first polarization direction and a second light beam with a second polarization direction after passing through the first polarization adjustment unit, and then enter the self-reference interferometer, thereby realizing alignment measurement of the mark diffraction independent of the polarization state.

[0065] Based on this, the present invention further provides an alignment device comprising an illumination unit, a first polarization adjustment unit, a self-referencing interferometer, a second polarization adjustment unit, and a third detection unit. Compared to the aforementioned alignment device, the beam splitting unit is removed, and the second polarization adjustment unit is used to simultaneously process the fifth and sixth light beams emitted by the self-referencing interferometer. This further eliminates the phase difference detected by the detectors in the aforementioned alignment device, reducing the risk of signal fluctuations canceling each other out and reducing the modulation depth.

[0066] Therefore, the alignment device provided by the present invention can not only expand the scope of application and is not limited by the polarization state of the incident diffracted light or scattered light, but also reduce the relative error between signals, improve the alignment repeatability, and also reduce the optical path complexity, noise and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a schematic structural diagram of an alignment device in the prior art;

[0068] Figure 2 Schematic diagram of the structure of a self-reference interferometer in the prior art;

[0069] Figure 3The light path diagram of P-polarized light and S-polarized light in the self-referenced interferometer in the prior art;

[0070] Figure 4 The structure diagram of the alignment device in Embodiment One of the present application;

[0071] Figure 5 The light path diagram of the diffracted light or scattered light into the first polarization adjustment unit in Embodiment One of the present application;

[0072] Figure 6 The light path diagram of the first light beam and the second light beam into the self-referenced interferometer in Embodiment One of the present application;

[0073] Figure 7 The structure diagram of the alignment device in Embodiment Two of the present application;

[0074] Figure 8 The light path diagram of the diffracted light or scattered light into the first polarization adjustment unit in Embodiment Two of the present application;

[0075] Figure 9 The structure diagram of the second polarization adjustment unit in Embodiment Two of the present application. DETAILED DESCRIPTION

[0076] In order to make the objects, advantages and features of the present application clearer, the following will further describe the present application in detail with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are very simplified and not drawn in proportion, and are only used to facilitate and clarify the purpose of assisting the description of the embodiments of the present application. In addition, the structures shown in the drawings are often a part of the actual structures. In particular, different proportions are sometimes used in the drawings to show different focuses. It should also be understood that, unless specifically described or indicated, the terms "first", "second", "third" and the like in the description are only used to distinguish the components, elements, steps and the like in the description, and are not used to represent the logical relationship or sequence relationship between the components, elements, steps and the like.

[0077] <Embodiment One>

[0078] In the existing alignment device, in order to ensure a high modulation depth (DOM) of the detection signal, the polarization state of the diffracted light or scattered light incident into the self-referenced interferometer needs to be set as 45-degree linear polarization. The modulation depth represents the proportion of the alternating current component in the signal, and is defined as:

[0079] DOM = (2Iac) / (Iac+Idc) (1.1)

[0080] Wherein, Iac is the alternating current; and Idc is the direct current.

[0081] Further, please refer to Figure 1 The light provided by the laser light source A is incident on the alignment mark M in the form of a plane wave through the objective lens Q. The alignment mark M can be a grating with a certain period. The light passing through the alignment mark M generates diffracted light or scattered light, which forms a parallel light beam after passing through the objective lens Q and then enters the wave plate 11. The wave plate 11 adjusts the polarization state of the diffracted light or scattered light to 45-degree linear polarization. For common mark diffraction, the polarization state of the diffracted beam can be determined according to the polarization state of the incident light, thereby determining the type and angle of the wave plate 11. For example, for 45-degree linearly polarized incident light, no wave plate is needed. For s-polarized or p-polarized incident light, a half-wave plate can be selected, and the angle between the fast axis of the half-wave plate and the s-direction can be 22.5 degrees or 67.5 degrees. For circularly polarized incident light, a quarter-wave plate can be selected, and the angle between the fast axis of the quarter-wave plate and the s-direction can be 0 degrees or 90 degrees.

[0082] Then, referring to Figure 1-3 The diffracted light or scattered light with a 45-degree linear polarization state enters the self-referencing interferometer 12. The self-referencing interferometer 12 functions to divide the incident diffracted light or scattered light into p-polarized light and s-polarized light, where the p-polarization direction and the s-polarization direction are perpendicular to each other. There are many optical devices that can achieve the self-referencing function, and a common device can be two specially processed prisms (the upper prism and the right prism) as shown in Figure 2 The contact surfaces of the two prisms are coated with a polarization beam splitting film, which can transmit p-polarized light and reflect s-polarized light, thereby dividing the incident 45-degree linearly polarized light into p-polarized light and s-polarized light with the same intensity and perpendicular polarization directions.

[0083] Further, the p-polarized light is reflected multiple times in the upper prism and returns to the polarization beam splitting surface, which is rotated 90 degrees counterclockwise (or clockwise) in space and polarization direction, and is reflected out of the self-referencing interferometer 12 through the polarization beam splitting surface in the self-referencing interferometer 12. The s-polarized light is reflected multiple times in the right prism and returns to the polarization beam splitting surface, which is rotated 90 degrees clockwise (or counterclockwise) in space and polarization direction, and is transmitted out of the self-referencing interferometer 12 through the polarization beam splitting surface in the self-referencing interferometer 12. The two light beams coincide and exit the self-referencing interferometer 12.

[0084] Among them, Figure 3The n shown in is the diffraction order, "+" represents positive diffracted light, and "-" represents negative diffracted light. Therefore, through the action of the self-referencing interferometer, the corresponding positive and negative orders in the emitted diffracted light or scattered light overlap with each other. Moreover, the polarization states of the corresponding overlapping positive and negative order diffracted lights are perpendicular to each other, and therefore need to pass through the polarization modulation element 13. The polarization modulation element 13 acts as a polarizer, which can be a half-wave plate, and the angle between its fast axis direction and the s polarization direction can be 22.5 degrees or 67.5 degrees. Its function is to make the overlapping diffraction orders coherent in the s and p polarizations, respectively, to form an interference signal.

[0085] Next, the interference signal is split into interference signals with s-polarization direction and interference signals with p-polarization direction by the polarization beam splitter 14. Detectors 151 and 152 respectively collect the interference signals directly at the pupil plane to obtain alignment position information.

[0086] Furthermore, before the diffracted light or scattered light enters the self-referencing interferometer 12, the electric field of the diffraction order +n can be expressed by the following equation:

[0087]

[0088] Where a is the amplitude of s polarization in the diffracted or scattered light; b is the amplitude of p polarization in the diffracted or scattered light; is the phase difference between p-polarization and s-polarization, which is 0 for linear polarization, a fixed value for elliptical (circular) polarization, and a random value for non-polarized state. It will be recorded as b′. n It is the electric field intensity of the +n / -n order of diffraction of the incident light projected on the mark. +n x-iθ n ) is the phase of the diffracted electric field.

[0089] The corresponding -nth order electric field strength is the same, and the phase subscript changes from +n to -n, and we can get:

[0090]

[0091] exist Figure 3 In the schematic diagram of the prism working principle on the right, the +n order of the upper coincident beam comes from the p-polarization of the +n diffraction, which is rotated 90 degrees counterclockwise. Its electric field is expressed as:

[0092]

[0093] Similarly, the -n order of the upper coincident beam originates from the s-polarization of the -n diffraction being rotated 90 degrees clockwise, and its electric field is expressed as:

[0094]

[0095] Therefore, the electric field of the upper side light beam is expressed as:

[0096]

[0097] When the polarization modulation element 13 is a half-wave plate, the angle between the fast axis direction and the s-polarization direction is 22.5°, and the matrix expression is:

[0098]

[0099] Therefore, the electric field of the upper side light beam after passing through the half-wave plate 13 is expressed as:

[0100]

[0101] After passing through the polarization beam splitter 14, the probe signal in the p-polarization branch is:

[0102]

[0103]

[0104] The process of analyzing the coherent signal of another diffraction spot and / or scattered spot is similar to formulas (1.1)-(1.8), and finally the following can be obtained:

[0105]

[0106] Therefore, the signal collected by the detector 151 is expressed as:

[0107]

[0108] The frequency, phase and modulation depth DOM of the signal can be analyzed by formula (1.11). When a / b = ±1, the AC and DC components of the signal have the same intensity, and the modulation depth reaches the maximum (i.e. 100%); when a = 0 or b = 0, the AC component of the signal is 0, and the modulation depth reaches the minimum value 0. Similarly, the form of the signal collected by another detector 152 can be deduced, and the analysis conclusion is the same as above. Therefore, the existing alignment device is limited to the polarization state of the diffraction light or scattered light from the reference interferometer being 45-degree linear polarization.

[0109] Therefore, to solve the above technical problems, the embodiment provides an alignment device, please refer to Figure 4-6 , comprising an illumination unit A, an objective lens Q, a first polarization adjustment unit 21, a self-reference interferometer 22, a light splitting unit 23, a first detection unit 24 and a second detection unit 25. Wherein,

[0110] The illumination unit A is used to provide illumination. Optionally, it is a laser emitter. After the illumination passes through the objective lens Q and is incident on an alignment mark M, diffracted light or scattered light is generated. The diffracted light or scattered light passes through the objective lens Q and enters the first polarization adjustment unit 21.

[0111] See also Figure 5-6 The first polarization adjustment unit 21 includes a first wave plate 211 and a second wave plate 212 connected to each other. This embodiment does not limit the splicing direction of the first wave plate 211 and the second wave plate 212, and can be any direction, but it must ensure that the positive-order diffracted light and the negative-order diffracted light of the same diffraction order in the diffracted light or scattered light pass through the first wave plate 211 and the second wave plate 212, respectively. For example, if the positive-order diffracted light passes through the first wave plate 211, the negative-order diffracted light passes through the second wave plate 212. However, the connecting axis between the first wave plate 211 and the second wave plate 212 only passes through the zeroth-order diffraction. In addition, the direction of the fast axis of the first wave plate 211 and the direction of the fast axis of the second wave plate 212 form a first angle, so that the diffracted light or scattered light is divided into a first light beam with a first polarization direction s (including a positive-order diffraction spot with an amplitude of b' and a negative-order diffraction spot with an amplitude of a) and a second light beam with a second polarization direction p (including a positive-order diffraction spot with an amplitude of a and a negative-order diffraction spot with an amplitude of b'). This can be expressed as: [first light beam s, b'(+n), a(-n)], [second light beam p, a(+n), b'(-n)]. The first polarization direction s and the second polarization direction p are perpendicular to each other, and the polarization intensities of the first light beam s and the second light beam p are the same.

[0112] Furthermore, the first wave plate 211 and the second wave plate 212 are connected in a direction perpendicular to the incident direction of the diffracted light or scattered light, and the splicing direction can be selected as follows: Figure 5 The direction of the middle dotted line shown. Furthermore, when both the first wave plate 211 and the second wave plate 212 are half-wave plates, the range of the first angle includes 45 degrees or 135 degrees. For example, the direction of the fast axis of the first wave plate 211 coincides with the first polarization direction s, and the direction of the fast axis of the second wave plate 212 forms an angle of 45 degrees with the first polarization direction s. Alternatively, when both the first wave plate 211 and the second wave plate 212 are quarter-wave plates, the first angle is 90 degrees.

[0113] The first light beam and the second light beam enter the self-reference interferometer 22. The self-reference interferometer 22 includes but is not limited to Figure 2The self-referencing interferometer shown is used to convert the first light beam into a third light beam having a second polarization direction p, and to convert the second light beam into a fourth light beam having a first polarization direction s. That is, under the action of the self-referencing interferometer 22, the propagation direction and polarization direction of the first light beam are both rotated 90 degrees counterclockwise (or clockwise) to form a third light beam. The propagation direction and polarization direction of the second light beam are both rotated 90 degrees counterclockwise (or clockwise) to form a fourth light beam. Figure 6 As shown, the third light beam has a second polarization direction p and includes a positive-order diffraction spot with an amplitude of b' and a negative-order diffraction spot with an amplitude of a, which can be recorded as: [third light beam p, a(-n), b'(+n)]. The fourth light beam has a first polarization direction s and includes a positive-order diffraction spot with an amplitude of a and a negative-order diffraction spot with an amplitude of b', which can be recorded as: [fourth light beam s, a(+n), b'(-n)].

[0114] When the third light beam and the fourth light beam overlap, a coincident light beam is formed. The coincident light beam has a first polarization direction s and a second polarization direction p, and includes a positive order diffraction light spot with an amplitude of a and a first polarization direction s, a negative order diffraction light spot with an amplitude of a and a second polarization direction p, a negative order diffraction light spot with an amplitude of b' and a positive order diffraction light spot with an amplitude of b' and a second polarization direction p. Figure 6 It can be seen that the positive-order diffraction spot with amplitude a and a first polarization direction s and the negative-order diffraction spot with amplitude a and a second polarization direction p overlap and are located in the upper half of the overlapping beam; the negative-order diffraction spot with amplitude b' and a first polarization direction s and the positive-order diffraction spot with amplitude b' and a second polarization direction p overlap and are located in the lower half of the overlapping beam. Therefore, the overlapping beam can be recorded as [coincident beam, a(-np, +ns), b'(-ns, +np)].

[0115] To this end, the coincident beam is divided into an upper half of the coincident beam and a lower half of the coincident beam along a direction perpendicular to the splicing direction of the first wave plate 211 and the second wave plate 212. The upper half of the coincident beam is recorded as the fifth beam with an amplitude of a, that is, [fifth beam, a(-np, +ns)]; the lower half of the coincident beam is recorded as the sixth beam with an amplitude of b', that is, [sixth beam, b'(-ns, +np)].

[0116] The light splitting unit 23 includes a first reflector 231 and a second reflector 232 . The first reflector 231 is used to reflect the fifth light beam to the first detection unit 24 . The second reflector 232 is used to reflect the sixth light beam to the second detection unit 25 .

[0117] The first detection unit 24 and the second detection unit 25 are used to obtain the light intensity of the fifth light beam and the sixth light beam respectively. Figure 4 As shown, the first detection unit 24 includes a first polarization beam splitter, a first detector 243, and a second detector 244. The first polarization beam splitter includes a fifth wave plate 241 and a second polarization beam splitter prism 242. When the first wave plate 211 and the second wave plate 212 are half-wave plates, the fifth wave plate 241 is a half-wave plate, and the angle between its fast axis and the s-polarization direction is 22.5 degrees. When the first wave plate 211 and the second wave plate 212 are quarter-wave plates, the fifth wave plate 241 is also a quarter-wave plate, and the angle between its fast axis and the s-polarization direction is 45 degrees. Therefore, after passing through the fifth wave plate 241 and then the second polarization beam splitter prism 242, the fifth light beam is split into two light beams: a seventh light beam having a first polarization direction s and an eighth light beam having a second polarization direction p. The seventh light beam is incident on the first detector 243, and the eighth light beam is incident on the second detector 244. The first detector 243 is used to obtain the light intensity of the seventh light beam; the second detector 244 is used to obtain the light intensity of the eighth light beam.

[0118] Furthermore, the second detection unit 25 includes a second polarization beam splitter, a third detector 253, and a fourth detector 254. The second polarization beam splitter includes a sixth wave plate 251 and a third polarization beam splitter prism 252. When the first wave plate 211 and the second wave plate 212 are half-wave plates, the sixth wave plate 251 is a half-wave plate, and the angle between its fast axis and the s-polarization direction is 22.5 degrees. When the first wave plate 211 and the second wave plate 212 are quarter-wave plates, the sixth wave plate 251 is also a quarter-wave plate, and the angle between its fast axis and the s-polarization direction is 45 degrees.

[0119] Therefore, after passing through the sixth wave plate 251, the sixth light beam is split into two light beams by the third polarization beam splitter prism 252: a ninth light beam having a first polarization direction s and a tenth light beam having a second polarization direction p. The ninth light beam is incident on the third detector 253, and the tenth light beam is incident on the fourth detector 254. The third detector 253 is used to obtain the intensity of the ninth light beam, and the fourth detector 254 is used to obtain the intensity of the tenth light beam.

[0120] Therefore, when the alignment mark M is moved until the light intensities respectively acquired by the first detection unit 24 and the second detection unit 25 reach preset values, the position of the alignment mark M is the alignment position.

[0121] In summary, the alignment device provided in this embodiment is provided with the first polarization adjustment unit 21 to achieve wavefront segmentation of the diffracted light or scattered light. This allows the incident diffracted light or scattered light to pass through the first polarization adjustment unit 21, regardless of whether the polarization state is linear polarization, (elliptical) circular polarization, or non-polarization, to form a first light beam having a first polarization direction s and a second light beam having a second polarization direction p. These light beams then enter the self-referencing interferometer 22, achieving alignment measurement of the mark diffraction independent of the polarization state. To further verify the technical effects of this embodiment, the first wave plate 211 and the second wave plate 212 in this embodiment are both half-wave plates, and the detection signal in this embodiment is calculated based on these.

[0122] The Jones matrices of the first wave plate 211 and the second wave plate 212 are respectively expressed as:

[0123]

[0124]

[0125] It is easy to derive that for any polarization state After the light passes through the first polarization adjustment unit 21, the polarization state of the light beam 21.1 is With the polarization state of the beam 21.2 perpendicular to each other (such as Figure 5 As shown). After the diffracted light or scattered light passes through the first polarization adjustment unit 21, the polarization state of the -n order is the 21.1 beam polarization state, and the polarization state of the +n order is the 21.2 beam polarization state perpendicular thereto.

[0126] Therefore, the analysis of this process is similar to that of formulas (1.3) to (1.11). The +n order of the upper half of the coincident beam (the fifth beam) comes from the p-polarization of the +n diffracted light being rotated 90° counterclockwise. Its electric field is expressed as:

[0127]

[0128] Similarly, the -n order of the upper half of the coincident beam comes from the -n diffracted light whose s polarization is rotated 90° clockwise. Its electric field is expressed as:

[0129]

[0130] Therefore, the electric field of the upper half of the coincident beam (fifth beam) is expressed as:

[0131]

[0132] Similarly, it can be deduced that the electric field of the lower half of the overlapping beam (the sixth beam) is expressed as:

[0133]

[0134] Since the fifth wave plate 241 and the sixth wave plate 251 are both half-wave plates, their Jones matrices are expressed as:

[0135]

[0136] The electric field of the fifth light beam after passing through the fifth wave plate 241 and the electric field of the sixth light beam after passing through the sixth wave plate 251 is:

[0137]

[0138]

[0139] Formula (1.16) shows that the upper half of the overlapping light beam (the fifth light beam) contains all the information of the s-polarization of the marked diffracted light or scattered light but does not contain p-polarization; conversely, the lower half of the overlapping light beam (the sixth light beam) contains all the information of the p-polarization of the marked diffracted light or scattered light but does not contain s-polarization.

[0140] Then, under the action of the second polarization beam splitter prism 242, the eighth light beam with the second polarization direction P enters the second detector 244, and the signal of the second detector 244 is:

[0141] I 244 =|E up_p | 2

[0142]

[0143] It can be seen that whether diffracted light or scattered light Regardless of the polarization state, the average energy of the detection signal is equal to the output energy in the p-polarization direction of the diffracted or scattered light, and the signal modulation depth is constant at 100%. Similarly, the detection signal of other detectors can be deduced as:

[0144]

[0145]

[0146]

[0147] At this point, the first detector 243, the second detector 244, the third detector 253, and the fourth detector 254 can all output signals, the modulation depth of the signal itself is high, and no additional phase difference (precision error) is introduced. Therefore, according to the above derivation, it can be seen that the alignment device provided in this embodiment is provided with the first polarization adjustment unit 21 to achieve wavefront segmentation of the diffracted light or scattered light, so that regardless of whether the polarization state of the incident diffracted light or scattered light is linear polarization, (elliptical) circular polarization, or non-polarization, it can form a first light beam with a first polarization direction s and a second light beam with a second polarization direction p after passing through the first polarization adjustment unit 21, and then enter the self-referencing interferometer 22, thereby achieving alignment measurement of the mark diffraction independent of the polarization state.

[0148] Similarly, when both the first wave plate 211 and the second wave plate 212 are quarter-wave plates, the Jones matrices of the first wave plate 211 and the second wave plate 212 are respectively expressed as:

[0149]

[0150]

[0151] It is easy to derive that for any polarization state After the light passes through the first polarization adjustment unit 21, the polarization state of the light beam 21.1 is:

[0152]

[0153] The polarization state of the beam 21.2 is:

[0154]

[0155] remember The polarization state of the light beam 21.1 can be expressed as The polarization state of the beam 21.2 is expressed as Obviously, the intensity of the s / p polarization state of 21.1 is the same as the intensity of the p / s polarization state of 21.2, and the phase difference is 90°.

[0156] The following analysis process is similar to formula (1.12)-formula (1.15). The electric field of the upper / lower half of the coincident beam (the fifth beam and the sixth beam) is expressed as:

[0157]

[0158]

[0159] The fifth wave plate 241 and the sixth wave plate 251 are both quarter wave plates, and their Jones matrices are expressed as:

[0160]

[0161] Then the electric field of the fifth light beam after passing through the fifth wave plate 241 and the electric field of the sixth light beam after passing through the sixth wave plate 251 is:

[0162]

[0163]

[0164] Then, under the action of the second polarization beam splitter prism 242, the eighth light beam with the second polarization direction P enters the second detector 244, and the signal of the second detector 244 is:

[0165]

[0166]

[0167] Similarly, the detection signals of other detectors can be deduced as follows:

[0168]

[0169]

[0170]

[0171] It can be seen that the alignment device provided in this embodiment is provided with the first polarization adjustment unit 21 to realize the wavefront splitting of the diffracted light or scattered light, so that no matter whether the polarization state of the incident diffracted light or scattered light is linear polarization, (elliptical) circular polarization or non-polarization, it can form a first light beam with a first polarization direction s and a second light beam with a second polarization direction p after passing through the first polarization adjustment unit 21, and then enter the self-reference interferometer 22, thereby realizing the alignment measurement of the mark diffraction independent of the polarization state.

[0172] Based on the same inventive concept, this embodiment further provides an alignment method, comprising:

[0173] Step 1: The illumination unit A provides illumination; the illumination passes through the alignment mark M to generate diffracted or scattered light. The diffracted or scattered light passes through the first polarization adjustment unit 21 to form a first beam with a first polarization direction s and a second beam with a second polarization direction p. The first and second beams are converted into a third beam with a second polarization direction p and a fourth beam with a first polarization direction s, respectively, by the self-referencing interferometer 22. The third and fourth beams overlap to form a superimposed beam, which passes through the self-referencing interferometer 22 and enters the spectrometer. The superimposed beam is split perpendicular to the joining direction of the first wave plate 211 and the second wave plate 212. The upper half of the superimposed beam forms the fifth beam, and the lower half forms the sixth beam. The fifth beam is reflected by the first reflector 231 in the spectrometer and enters the first detection unit 24. The sixth beam is reflected by the second reflector 232 in the spectrometer and enters the second detection unit 25. The first detection unit 24 and the second detection unit 25 respectively obtain the light intensities of the fifth and sixth beams.

[0174] Step 2: Move the workpiece stage to drive the alignment mark M to move. When the light intensities respectively acquired by the first detection unit 24 and the second detection unit 25 reach preset values, the position of the alignment mark M is the alignment position.

[0175] <Example 2>

[0176] According to formulas (1.17) to (1.20) in Example 1, the intensity of the interference signal detected by each detector is equivalent to the energy component of the initial diffracted light or scattered light in one polarization direction. Therefore, in some alignment measurement conditions, the user does not need to measure the energy of each polarization separately; instead, only a sufficiently strong alignment signal is sufficient. For example, the signal of the sum of formulas (1.17) and (1.20) or the signal of the sum of formulas (1.18) and (1.19) is sufficient.

[0177] Furthermore, as can be seen from equations (1.17) to (1.20), the phase difference between the signal fluctuations of first detector 243 and second detector 244 is pi. Directly using a single detector to detect the sum of the two beam signals risks signal fluctuations canceling each other out and reducing the modulation depth. Therefore, based on the same inventive concept, this embodiment provides an alignment device.

[0178] See also Figure 7-9The alignment device includes an illumination unit A, an objective lens Q, a first polarization adjustment unit 31, a self-referencing interferometer 32, a second polarization adjustment unit 33, and a third detection unit 34. Regarding the illumination unit A, the objective lens Q, the first polarization adjustment unit 31, and the self-referencing interferometer 32, please refer to the description of the illumination unit A, the objective lens Q, the first polarization adjustment unit 21, and the self-referencing interferometer 22 in Example 1, and will not be described in detail here.

[0179] In which, the second polarization adjustment unit 33 includes a third wave plate 331 and a fourth wave plate 332 connected to each other, the fast axis direction of the third wave plate 331 and the fast axis direction of the fourth wave plate 332 form a second angle, and the connecting axis direction of the third wave plate 331 and the fourth wave plate 332 is perpendicular to the connecting axis direction of the first wave plate 311 and the second wave plate 312 (for the first wave plate 311 and the second wave plate 312, please refer to the first wave plate 211 and the second wave plate 212 in Example 1).

[0180] Furthermore, when the first wave plate 311 and the second wave plate 312 are both half-wave plates, the third wave plate 331 and the fourth wave plate 332 are both half-wave plates, and the second angle range includes 45 degrees, 90 degrees, or 135 degrees. For example, the angle between the fast axis of the third wave plate 331 and the first polarization direction s is 22.5 degrees or 67.5 degrees, and the angle between the fast axis of the fourth wave plate 332 and the first polarization direction s is -22.5 degrees or -67.5 degrees. When the first wave plate 311 and the second wave plate 312 are both quarter-wave plates, the third wave plate 331 and the fourth wave plate 332 are both quarter-wave plates, and the second angle is 90 degrees. In addition, this embodiment does not limit the splicing direction of the first wave plate 311 and the second wave plate 312, nor does it limit the splicing direction of the third wave plate 331 and the fourth wave plate 332, but it is required that the first wave plate 311 and the second wave plate 312 are connected in a direction perpendicular to the incident direction of the diffracted light or scattered light; the third wave plate 331 and the fourth wave plate 332 are connected in a direction perpendicular to the incident direction of the overlapping light beam.

[0181] When the illumination provided by the illumination unit A is incident on the alignment mark M through the objective lens Q and generates diffracted light or scattered light, the diffracted light or scattered light enters the first polarization adjustment unit 31 through the objective lens Q. The polarization adjustment unit 31 divides the diffracted light or scattered light into a first light beam having a first polarization direction s and a second light beam having a second polarization direction p. The first polarization direction s is perpendicular to the second polarization direction p. The diffracted light or scattered light is then converted into a fourth light beam having a first polarization direction s and a third light beam having a second polarization direction p by the self-referencing interferometer 32. The third light beam coincides with the fourth light beam to form a coincident light beam. Furthermore, the coincident light beam is divided into a fifth light beam and a sixth light beam along a direction perpendicular to the splicing direction of the first wave plate 311 and the second wave plate 312. For a detailed description of the first light beam, the second light beam, the third light beam, the fourth light beam, the fifth light beam and the sixth light beam, please refer to Example 1, which will not be described in detail here.

[0182] The fifth and sixth light beams are incident on the second polarization adjustment unit 33. Furthermore, the fifth light beam passes through the third wave plate 331 and enters the third detection unit 34, while the sixth light beam passes through the fourth wave plate 332 and enters the third detection unit 34. The third detection unit 34 is configured to obtain the light intensities of the fifth and sixth light beams. When the alignment mark M is moved until the light intensity obtained by the third detection unit 34 reaches a preset value, the position of the alignment mark is considered the alignment position.

[0183] Furthermore, the third detection unit 34 includes a first polarization beam splitter prism 341, a fifth detector 342, and a sixth detector 343. The first polarization beam splitter prism 341 is configured to split the fifth and sixth light beams incident upon the second polarization adjustment unit 33 into an eleventh light beam having a first polarization direction s and a twelfth light beam having a second polarization direction p. The fifth detector 342 is configured to obtain the light intensity of the eleventh light beam. The sixth detector 343 is configured to obtain the light intensity of the twelfth light beam.

[0184] It can be seen that compared with Example 1, the alignment device provided in this embodiment eliminates the spectroscopic unit, and instead uses the third wave plate 331 and the fourth wave plate 332 in the second polarization adjustment unit 33 to respectively process the upper and lower overlapping positive and negative order light beams (the fifth light beam and the sixth light beam), further eliminating the phase difference detected by each detector in the alignment device provided in Example 1, and reducing the risk of signal fluctuations canceling each other and the modulation depth decreasing.

[0185] To further verify the technical effect of this embodiment, the first wave plate 311, the second wave plate 312, the third wave plate 331 and the fourth wave plate 332 in this embodiment are all half-wave plates, and the detection signal in this embodiment is calculated based on them.

[0186] Then the Jones matrices of the third wave plate 331 and the fourth wave plate 332 are respectively expressed as:

[0187]

[0188]

[0189] Before passing through the second polarization adjustment unit 33, the electric field of the upper / lower half of the overlapping light beams (the fifth light beam and the sixth light beam) is expressed by equations (1.14) / (1.15). The electric field after passing through the second polarization adjustment unit 33 is expressed as:

[0190]

[0191]

[0192] After the fifth light beam and the sixth light beam pass through the first polarization beam splitter prism 341, the detection signal of the twelfth light beam with p polarization obtained by the sixth detector 343 is:

[0193]

[0194] Since the detection signal formula (2.2) is the same as the sum of the signals in formulas (1.17) and (1.20), it can be deduced that the detection signal expression of detector 342 is the same as the sum of the signals in formulas (1.18) and (1.19).

[0195] Similarly, when the first wave plate 311, the second wave plate 312, the third wave plate 331, and the fourth wave plate 332 are all quarter-wave plates, the Jones matrices of the third wave plate 331 and the fourth wave plate 332 are respectively expressed as:

[0196]

[0197]

[0198] Before passing through the second polarization adjustment unit 33, the electric field of the upper / lower half of the overlapping light beams (the fifth light beam and the sixth light beam) is expressed by equations (1.23) / (1.24). The electric field after passing through the second polarization adjustment unit 33 is expressed as:

[0199]

[0200]

[0201] After the fifth light beam and the sixth light beam pass through the first polarization beam splitter prism 341, the detection signal of the twelfth light beam with p polarization obtained by the sixth detector 343 is:

[0202]

[0203] Since the detection signal formula (2.4) is the same as the sum of the signals in formulas (1.26) and (1.27), it can be deduced that the detection signal expression of detector 342 is the same as the sum of the signals in formulas (1.28) and (1.29).

[0204] Based on the same inventive concept, the present invention also provides an alignment method, comprising:

[0205] Step 1: The illumination unit A provides illumination; the illumination passes through the alignment mark M to generate diffracted or scattered light. The diffracted or scattered light passes through the first polarization adjustment unit 31 to form a first beam with a first polarization direction s and a second beam with a second polarization direction p. The first and second beams are converted into a third beam with a second polarization direction p and a fourth beam with a first polarization direction s, respectively, by the self-referencing interferometer 32. The third beam and the fourth beam overlap to form a superimposed beam. The superimposed beam is split perpendicular to the joining direction of the first wave plate 311 and the second wave plate 312. The upper half of the superimposed beam forms the fifth beam, and the lower half forms the sixth beam. The fifth beam passes through the third wave plate 331 in the second polarization adjustment unit 33 and enters the third detection unit 34. The sixth beam passes through the fourth wave plate 332 in the second polarization adjustment unit 33 and enters the third detection unit 34. The third detection unit 34 obtains the light intensities of the fifth and sixth beams.

[0206] Step 2: Move the workpiece stage to drive the alignment mark M to move. When the light intensity obtained by the third detection unit 34 reaches a preset value, the position of the alignment mark M is the alignment position.

[0207] In summary, both Embodiment 1 and Embodiment 2 provide an alignment device and an alignment method. The alignment device in Embodiment 1 includes an illumination unit A, a first polarization adjustment unit 21, a self-referencing interferometer 22, a spectrometer 23, a first detection unit 24, and a second detection unit 25. Furthermore, the first polarization adjustment unit 21 includes a first wave plate 211 and a second wave plate 212 connected to each other, and the positive diffracted light and the negative diffracted light of the same diffraction order in the diffracted light or scattered light pass through the first wave plate 211 and the second wave plate 212, respectively. The fast axis of the first wave plate 211 and the fast axis of the second wave plate 212 form a first angle, so that regardless of whether the polarization state of the incident diffracted light or scattered light is linear polarization, (elliptical) circular polarization, or non-polarization, it can form a first light beam with a first polarization direction s and a second light beam with a second polarization direction p after passing through the first polarization adjustment unit 21, and then enter the self-referencing interferometer 22, thereby achieving alignment measurement based on mark diffraction independent of the polarization state.

[0208] Based on this, the second embodiment further provides an alignment device. Compared to the alignment device in the first embodiment, the light splitting unit 23 is removed. Instead, the second polarization adjustment unit 33 is used to simultaneously process the fifth and sixth light beams emitted by the self-referencing interferometer 32. This further eliminates the phase difference detected by the detectors in the alignment device, reducing the risk of signal fluctuations canceling each other out and the modulation depth being reduced.

[0209] Therefore, the alignment device provided in Example 1 and Example 2 can not only expand the scope of application and is not limited by the polarization state of the incident diffracted light or scattered light, but also reduce the relative error between signals, improve the alignment repeatability, and also reduce the optical path complexity, noise and cost.

[0210] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other. In addition, the different parts between the various embodiments can also be used in combination with each other, and the present invention is not limited to this.

[0211] Furthermore, it should be recognized that although the present invention has been disclosed above with reference to preferred embodiments, the above embodiments are not intended to limit the present invention. Any person skilled in the art can utilize the above disclosed technical content to make many possible changes and modifications to the technical solution of the present invention, or modify it into equivalent embodiments with equivalent variations, without departing from the scope of the technical solution of the present invention. Therefore, any simple modifications, equivalent variations, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solution of the present invention, shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. An alignment device, characterized in that: It includes an illumination unit, a first polarization adjustment unit, a self-reference interferometer, a light splitting unit, a first detection unit and a second detection unit; wherein, The illumination unit is used to provide illumination; the illumination generates diffracted light or scattered light after passing through an alignment mark, and the diffracted light or scattered light enters the first polarization adjustment unit; The first polarization adjustment unit includes a first wave plate and a second wave plate connected to each other, and the negative-order diffraction light and the positive-order diffraction light of the same diffraction order in the diffracted light or scattered light pass through the first wave plate and the second wave plate respectively; wherein the direction of the fast axis of the first wave plate and the direction of the fast axis of the second wave plate form a first angle, so that the diffracted light or scattered light forms a first light beam with a first polarization direction and a second light beam with a second polarization direction after passing through the first polarization adjustment unit; the first light beam and the second light beam enter the self-referencing interferometer; and after passing through the self-referencing interferometer, under the reflection action of the spectrometer, part of the light beam enters the first detection unit, and the remaining part of the light beam enters the second detection unit; The first detection unit and the second detection unit respectively obtain the light intensity of the corresponding light beam.

2. The alignment device according to claim 1, characterized in that The self-referencing interferometer is used to convert the first light beam into a third light beam having a second polarization direction, and to convert the second light beam into a fourth light beam having a first polarization direction, and the third light beam and the fourth light beam overlap to form an overlapping light beam; wherein, along a direction perpendicular to the junction of the first wave plate and the second wave plate, the overlapping light beam is divided into a fifth light beam and a sixth light beam; and, the partial light beam entering the first detection unit is the fifth light beam, and the remaining partial light beam entering the second detection unit is the sixth light beam.

3. The alignment device according to claim 2, characterized in that The light splitting unit includes a first reflector and a second reflector; the first reflector is used to reflect the fifth light beam to the first detection unit; the second reflector is used to reflect the sixth light beam to the second detection unit; The first detection unit and the second detection unit are used to obtain light intensities in the fifth light beam and the sixth light beam, respectively.

4. The alignment device according to claim 3, characterized in that The first detection unit includes a first polarization beam splitter, a first detector and a second detector; wherein, The first polarization beam splitter is used to split the fifth light beam into a seventh light beam having a first polarization direction and an eighth light beam having a second polarization direction; The first detector is used to obtain the light intensity of the seventh light beam; The second detector is used to obtain the light intensity of the eighth light beam.

5. The alignment device according to claim 3, characterized in that The second detection unit includes a second polarization beam splitter, a third detector and a fourth detector; wherein, The second polarization beam splitter is used to split the sixth light beam into a ninth light beam having a first polarization direction and a tenth light beam having a second polarization direction; The third detector is used to obtain the light intensity of the ninth light beam; The fourth detector is used to obtain the light intensity of the tenth light beam.

6. The alignment device according to claim 1, wherein: When the alignment mark is moved until the light intensities respectively acquired by the first detection unit and the second detection unit reach preset values, the position of the alignment mark is the alignment position.

7. The alignment device according to claim 1, wherein: The first wave plate and the second wave plate are both half wave plates, and the first included angle ranges from 45 degrees to 135 degrees.

8. The alignment device according to claim 7, characterized in that The fast axis direction of the first wave plate coincides with the first polarization direction, and the fast axis direction of the second wave plate forms an angle of 45 degrees with the first polarization direction.

9. The alignment device according to claim 1, wherein: The first wave plate and the second wave plate are both quarter wave plates, and the first angle is 90 degrees.

10. The alignment device according to claim 1, wherein: The zero-order diffraction light in the diffracted light or scattered light passes through the interface between the first wave plate and the second wave plate.

11. The alignment device according to claim 1, wherein The first polarization direction and the second polarization direction are perpendicular to each other.

12. The alignment device according to claim 1, wherein The illumination unit includes a laser emitter.

13. The alignment device according to claim 1, wherein The alignment device further includes an objective lens, the light is incident on the alignment mark through the objective lens, and generates diffracted light or scattered light through the alignment mark, and the diffracted light or scattered light enters the first polarization adjustment unit through the objective lens.

14. An alignment method, characterized in that: Using the alignment device according to any one of claims 1 to 13, the alignment method comprises: The lighting unit provides lighting; The light irradiates the alignment mark to generate diffracted light or scattered light, and the diffracted light or scattered light passes through the first polarization adjustment unit to form a first light beam with a first polarization direction and a second light beam with a second polarization direction; The first light beam and the second light beam are converted into a third light beam having a second polarization direction and a fourth light beam having a first polarization direction respectively by the self-referencing interferometer; the third light beam and the fourth light beam overlap to form a coincident light beam; wherein the coincident light beam is split into a fifth light beam and a sixth light beam along a direction perpendicular to the junction of the first wave plate and the second wave plate; The fifth light beam and the sixth light beam are respectively reflected by the light splitting unit to the first detection unit and the second detection unit; The first detection unit and the second detection unit respectively obtain the light intensity in the fifth light beam and the sixth light beam; The workpiece stage is moved to drive the alignment mark to move. When the light intensities respectively acquired by the first detection unit and the second detection unit reach preset values, the position of the alignment mark is the alignment position.

15. An alignment device, characterized in that: It includes an illumination unit, a first polarization adjustment unit, a self-reference interferometer, a second polarization adjustment unit and a third detection unit; wherein, The illumination unit is used to provide illumination; the illumination generates diffracted light or scattered light after passing through an alignment mark, and the diffracted light or scattered light enters the first polarization adjustment unit; The first polarization adjustment unit includes a first wave plate and a second wave plate connected to each other, and the negative-order diffraction light and the positive-order diffraction light of the same diffraction order in the diffracted light or scattered light pass through the first wave plate and the second wave plate respectively; wherein the direction of the fast axis of the first wave plate and the direction of the fast axis of the second wave plate form a first angle, so that the diffracted light or scattered light forms a first light beam with a first polarization direction and a second light beam with a second polarization direction after passing through the first polarization adjustment unit; the first light beam and the second light beam enter the self-referencing interferometer; and after passing through the self-referencing interferometer, enter the second polarization adjustment unit; The second polarization adjustment unit includes a third wave plate and a fourth wave plate connected to each other, the fast axis of the third wave plate and the fast axis of the fourth wave plate form a second angle, and the direction of the connecting axis of the third wave plate and the fourth wave plate is perpendicular to the direction of the connecting axis of the first wave plate and the second wave plate; part of the light beam enters the third detection unit through the third wave plate, and the remaining part of the light beam enters the third detection unit through the fourth wave plate; The third detection unit is used to obtain light intensity.

16. The alignment device according to claim 15, characterized in that The self-referencing interferometer is used to convert the first light beam into a third light beam with a second polarization direction, and to convert the second light beam into a fourth light beam with a first polarization direction; and the third light beam and the fourth light beam overlap to form an overlapping light beam; wherein, along a direction perpendicular to the junction of the first wave plate and the second wave plate, the overlapping light beam is divided into a fifth light beam and a sixth light beam; and the fifth light beam enters the third detection unit through the third wave plate, and the sixth light beam enters the third detection unit through the fourth wave plate.

17. The alignment device according to claim 16, characterized in that The third detection unit includes a first polarization beam splitter prism, a fifth detector and a sixth detector; wherein, The first polarization beam splitter prism is used to split the fifth light beam and the sixth light beam incident through the second polarization adjustment unit into an eleventh light beam having a first polarization direction and a twelfth light beam having a second polarization direction; The fifth detector is used to obtain the light intensity of the eleventh light beam; The sixth detector is used to obtain the light intensity of the twelfth light beam.

18. The alignment device according to claim 15, characterized in that When the alignment mark is moved until the light intensity acquired by the third detection unit reaches a preset value, the position of the alignment mark is the alignment position.

19. The alignment device according to claim 15, characterized in that The first wave plate and the second wave plate are both half wave plates, and the first included angle ranges from 45 degrees to 135 degrees.

20. The alignment device according to claim 19, wherein The fast axis direction of the first wave plate coincides with the first polarization direction, and the fast axis direction of the second wave plate forms an angle of 45 degrees with the first polarization direction.

21. The alignment device according to claim 19, wherein The third wave plate and the fourth wave plate are both half wave plates, and the second angle ranges from 45 degrees, 90 degrees, or 135 degrees.

22. The alignment device according to claim 21, characterized in that The angle between the fast axis of the third wave plate and the first polarization direction is 22.5 degrees or 67.5 degrees, and the angle between the fast axis of the fourth wave plate and the first polarization direction is -22.5 degrees or -67.5 degrees.

23. The alignment device according to claim 15, wherein The first wave plate and the second wave plate are both quarter wave plates, and the first angle is 90 degrees.

24. The alignment device according to claim 23, characterized in that The third wave plate and the fourth wave plate are both quarter wave plates, and the second angle is 90 degrees.

25. The alignment device according to claim 15, wherein The zero-order diffracted light or scattered light in the diffracted light or scattered light passes through the interface between the first wave plate and the second wave plate.

26. The alignment device according to claim 15, wherein The first polarization direction and the second polarization direction are perpendicular to each other.

27. The alignment device according to claim 15, wherein The illumination unit includes a laser emitter.

28. The alignment device according to claim 15, wherein The alignment device further includes an objective lens, the light is incident on the alignment mark through the objective lens, and generates diffracted light or scattered light through the alignment mark, and the diffracted light or scattered light enters the first polarization adjustment unit through the objective lens.

29. An alignment method, characterized in that: Using the alignment device according to any one of claims 15 to 28, the alignment method comprises: The lighting unit provides lighting; The light irradiates the alignment mark to generate diffracted light or scattered light, and the diffracted light or scattered light passes through the first polarization adjustment unit to form a first light beam with a first polarization direction and a second light beam with a second polarization direction; The first light beam and the second light beam are converted into a third light beam having a second polarization direction and a fourth light beam having a first polarization direction respectively by the self-referencing interferometer; the third light beam and the fourth light beam overlap to form a coincident light beam; wherein the coincident light beam is split into a fifth light beam and a sixth light beam along a direction perpendicular to the junction of the first wave plate and the second wave plate; The fifth light beam enters the third detection unit through the third wave plate in the second polarization adjustment unit, and the sixth light beam enters the third detection unit through the fourth wave plate; The third detection unit acquires the light intensity in the fifth light beam and the sixth light beam; The workpiece stage is moved to drive the alignment mark to move. When the light intensity acquired by the third detection unit reaches a preset value, the position of the alignment mark is the alignment position.

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