Alignment device, photolithography machine and alignment method

Abstract

The present invention provides an alignment device, a photolithography machine and an alignment method. The first lens group divides the illumination into a first light beam and a second light beam, and the second lens group converts the second light beam into a third light beam. The first light beam and the third light beam are diffracted by a grating mark and generate diffracted light. The diffracted light of the first light beam enters a detection unit after passing through the second lens group and the first lens group, and the diffracted light of the third light beam enters the detection unit after passing through the first lens group. Then, it passes through a first wave plate to interfere in a first polarization direction and a second polarization direction respectively. Then, it is divided into a first polarized light and a second polarized light by a first polarization splitting prism, and the corresponding light energy is obtained by a first detector and a second detector respectively. When the grating mark is moved until the light energy reaches a preset value, the position of the grating mark is the alignment position. Therefore, the present invention obtains two diffracted lights respectively, and realizes interference between the two through the first wave plate, without using a self-reference interference prism, so as to reduce costs and improve alignment accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuit manufacturing, and particularly relates to an alignment device, a lithography machine, and an alignment method. Background Art

[0002] In the technical field of integrated circuit manufacturing, a lithography machine can apply a mask pattern onto a photosensitive film layer such as a photoresist on a silicon wafer (which can also be referred to as a substrate) to prepare a required circuit structure. In order to accurately control the position corresponding to each lithography on the silicon wafer, it is necessary to set lithography alignment marks (usually grating marks) on the silicon wafer, and determine the positions of the corresponding lithography alignment marks on the silicon wafer by setting one or more corresponding alignment devices, and then determine the alignment position of the silicon wafer.

[0003] Currently, the commonly used alignment device uses a self-reference interference prism to achieve the interference of diffracted light, and then determines the position of the grating mark on the silicon wafer. However, the alignment device based on the self-reference interference prism has some inevitable defects. For example, the self-reference interference prism uses prism components that require special optical design and manufacturing, with high processing specifications, difficult alignment and adjustment, and relatively high costs; and, the self-reference interference prism is usually relatively bulky, which will generate some negative effects such as low-bandwidth vibration modes, and ultimately affect the alignment accuracy.

[0004] Therefore, a new alignment device and alignment method are needed to avoid the disadvantages brought by using the self-reference interference prism, so as to reduce the alignment measurement cost and improve the alignment accuracy. Summary of the Invention

[0005] The purpose of the present invention is to provide an alignment device, a lithography machine, and an alignment method to solve at least one of the problems of high alignment measurement cost and low alignment accuracy.

[0006] To solve the above technical problems, the present invention provides an alignment device, which includes: a light illumination unit, a beam splitting unit, and a detection unit; wherein,

[0007] The light illumination unit is used to provide illumination;

[0008] The beam splitting unit includes a first mirror group and a second mirror group; the first mirror group is used to split the illumination into a first light beam with a first polarization direction and a second light beam with a second polarization direction, and the second mirror group is used to convert the second light beam into a third light beam with a first polarization direction; the first light beam and the third light beam are diffracted by a grating mark, and respectively generate diffracted light of the first light beam and diffracted light of the third light beam; wherein, the diffracted light of the first light beam enters the detection unit after passing through the second mirror group and the first mirror group in sequence, and the diffracted light of the third light beam enters the detection unit after passing through the first mirror group;

[0009] The detection unit includes a first wave plate, a first polarization beam splitter prism, a first detector, and a second detector; the diffracted light of the first light beam and the diffracted light of the third light beam change their polarization directions after passing through the first wave plate, so as to interfere in the first polarization direction and the second polarization direction respectively, and form interference light; the interference light enters the first polarization beam splitter prism and is split into first polarized light and second polarized light by the first polarization beam splitter prism; the first detector acquires the light energy of the first polarized light, and the second detector acquires the light energy of the second polarized light;

[0010] Wherein, when the grating mark is moved to a position where the light energies respectively acquired by the first detector and the second detector both reach a preset value, the position where the grating mark is located is the alignment position.

[0011] Optionally, in the alignment device, the first polarization direction and the second polarization direction are perpendicular to each other.

[0012] Optionally, in the alignment device, the diffracted light of the third light beam has a first polarization direction after passing through the first lens group; the diffracted light of the first light beam has a second polarization direction after passing through the second lens group and the first lens group in sequence.

[0013] Optionally, in the alignment device, the first polarized light has a first polarization direction, and the second polarized light has a second polarization direction.

[0014] Optionally, in the alignment device, the first lens group includes a second polarization beam splitter prism, and the second lens group includes a third polarization beam splitter prism, a second wave plate, and a first reflector;

[0015] The first light beam is reflected by the second polarization beam splitter prism to the grating mark;

[0016] After the second light beam passes through the second polarization beam splitter prism and enters the third polarization beam splitter prism, it is transmitted through the second wave plate and reflected by the first reflector in sequence, and then transmitted through the second wave plate and reflected by the third polarization beam splitter prism in sequence to form the third light beam, and the third polarization beam splitter prism reflects the third light beam to the grating mark;

[0017] The first light beam and the third light beam are diffracted by the grating mark and respectively generate the diffracted light of the first light beam and the diffracted light of the third light beam;

[0018] Among them, after the diffracted light of the first light beam is reflected by the third polarization beam splitter prism, it is successively transmitted through the second wave plate and reflected by the first mirror, and then transmitted through the second wave plate, changing the polarization direction to the second polarization direction, and then successively passing through the third polarization beam splitter prism and the second polarization beam splitter prism and propagating to the detection unit;

[0019] The diffracted light of the third light beam is reflected by the second polarization beam splitter prism to the detection unit.

[0020] Optionally, in the alignment device, the second wave plate is a quarter-wave plate.

[0021] Optionally, in the alignment device, the first mirror group includes a fourth polarization beam splitter prism, and the second mirror group includes a third wave plate, a second mirror, a third mirror, a fourth mirror, a fifth mirror, and a fifth polarization beam splitter prism;

[0022] The first light beam is reflected by the fourth polarization beam splitter prism to the grating mark;

[0023] The second light beam passes through the fourth polarization beam splitter prism and is transmitted through the third wave plate, and then is successively reflected by the second mirror, the third mirror, the fourth mirror, and the fifth mirror, and enters the fifth polarization beam splitter prism to form the third light beam, and the third light beam is reflected by the fifth polarization beam splitter prism to the grating mark;

[0024] The first light beam and the third light beam are diffracted by the grating mark and respectively generate the diffracted light of the first light beam and the diffracted light of the third light beam;

[0025] Among them, after the diffracted light of the first light beam is reflected by the fifth polarization beam splitter prism, it is first successively reflected by the fifth mirror, the fourth mirror, the third mirror, and the second mirror, and then transmitted through the third wave plate, changing the polarization direction to the second polarization direction, and then passing through the fourth polarization beam splitter prism and entering the detection unit;

[0026] The diffracted light of the third light beam is reflected by the fourth polarization beam splitter prism to the detection unit.

[0027] Optionally, in the alignment device, the third wave plate is a half-wave plate.

[0028] Optionally, in the alignment device, the first mirror group includes a sixth polarization beam splitter prism, a sixth mirror, a seventh mirror, an eighth mirror, and a ninth mirror; the second mirror group includes a fourth wave plate and a seventh polarization beam splitter prism;

[0029] The first light beam is first reflected by the sixth polarization beam splitter prism, and then reflected by the sixth mirror, the seventh mirror, the eighth mirror, and the ninth mirror in sequence to the grating mark;

[0030] After the second light beam passes through the sixth polarization beam splitter prism, it passes through the fourth wave plate and enters the seventh polarization beam splitter prism to form the third light beam, and the third light beam is reflected by the seventh polarization beam splitter prism to the grating mark;

[0031] The first light beam and the third light beam are diffracted by the grating mark, and the diffracted light of the first light beam and the diffracted light of the third light beam are respectively generated;

[0032] Among them, the diffracted light of the first light beam is first reflected by the seventh polarization beam splitter prism, then transmitted through the fourth wave plate, and the polarization direction is changed to the second polarization direction, and then passes through the sixth polarization beam splitter prism and enters the detection unit.

[0033] The diffracted light of the third light beam is first reflected by the ninth mirror, the eighth mirror, the seventh mirror, and the sixth mirror in sequence to the sixth polarization beam splitter prism, and then reflected by the sixth polarization beam splitter prism to the detection unit.

[0034] Optionally, in the alignment device, the fourth wave plate is a half-wave plate.

[0035] Optionally, in the alignment device, the first wave plate is a half-wave plate.

[0036] Optionally, in the alignment device, the light illumination unit includes a light emitter and a third mirror group; wherein, the light emitter is used to provide light illumination with at least one wavelength and at least one polarization direction; the third mirror group is used to change the propagation direction of the light illumination to obtain a preset propagation direction.

[0037] Optionally, in the alignment device, when the light emitter provides light illumination with multiple wavelengths, the light illumination unit further includes a beam combiner; the beam combiner is used to propagate the light illumination with multiple wavelengths to the beam splitting unit through the same optical fiber.

[0038] Optionally, in the alignment device, when the light emitter provides light illumination with multiple wavelengths, the detection unit further includes a first beam splitter and a second beam splitter; wherein, the first beam splitter is used to divide the first polarized light into first optical signals with multiple wavelengths; the second beam splitter is used to divide the second polarized light into second optical signals with multiple wavelengths.

[0039] Optionally, in the alignment device, the alignment device further includes a fifth wave plate, a sixth wave plate, and a seventh wave plate;

[0040] After the first light beam passes through the first lens group, it successively passes through the fifth wave plate and the sixth wave plate, and the polarization direction is changed to right-handed polarization and propagates to the grating mark;

[0041] The third light beam passes through the seventh wave plate, and the polarization direction is changed to left-handed polarization and propagates to the grating mark;

[0042] The first light beam and the third light beam respectively generate diffracted light of the first light beam and diffracted light of the third light beam through the grating mark;

[0043] The diffracted light of the third light beam successively passes through the sixth wave plate and the fifth wave plate, and the polarization direction is changed to the first polarization direction and enters the first lens group;

[0044] The diffracted light of the first light beam passes through the seventh wave plate, and the polarization direction is changed to the first polarization direction and enters the second lens group.

[0045] Optionally, in the alignment device, the fifth wave plate is a half-wave plate; both the sixth wave plate and the seventh wave plate are quarter-wave plates.

[0046] Optionally, in the alignment device, the alignment device further includes an objective lens; the objective lens is used to converge and transmit the first light beam, the third light beam, the diffracted light of the first light beam, and the diffracted light of the third light beam;

[0047] Wherein, the first light beam and the third light beam are transmitted to the grating mark through the objective lens; the diffracted light of the third light beam is transmitted to the first lens group through the objective lens; the diffracted light of the first light beam is transmitted to the second lens group through the objective lens.

[0048] Based on the same inventive concept, the present invention also provides a lithography machine, and the lithography machine includes the alignment device.

[0049] Based on the same inventive concept, the present invention also provides an alignment method, including:

[0050] The illumination unit provides illumination;

[0051] The illumination passes through the first lens group in the beam splitting unit, and the illumination is divided into a first light beam with a first polarization direction and a second light beam with a second polarization direction; the second lens group in the beam splitting unit converts the second light beam into a third light beam with a first polarization direction;

[0052] The first light beam and the third light beam are diffracted by a grating mark to respectively generate diffracted light of the first light beam and diffracted light of the third light beam. Among them, the diffracted light of the first light beam enters the detection unit after passing through the second lens group and the first lens group in sequence, and the diffracted light of the third light beam enters the detection unit after passing through the first lens group.

[0053] The diffracted light of the first light beam and the diffracted light of the third light beam change their polarization directions after passing through the first wave plate, so as to interfere respectively in the first polarization direction and the second polarization direction, and form interference light. The interference light enters the first polarization beam splitter prism and is split into first polarized light and second polarized light by the first polarization beam splitter prism.

[0054] The first detector acquires the light energy of the first polarized light, and the second detector acquires the light energy of the second polarized light.

[0055] The workpiece stage is moved to drive the grating mark to move. When the light energies respectively acquired by the first detector and the second detector both reach a preset value, the position where the grating mark is located is the alignment position.

[0056] In summary, the present invention provides a lithography machine, an alignment device and an alignment method. The alignment device includes: a light illumination unit, a light splitting unit and a detection unit. Among them, the first lens group in the light splitting unit is used to split the light illumination into a first light beam and a second light beam, and the second lens group is used to convert the second light beam into a third light beam. The first light beam and the third light beam are diffracted by a grating mark to respectively generate diffracted light of the first light beam and diffracted light of the third light beam. Among them, the diffracted light of the first light beam enters the detection unit after passing through the second lens group and the first lens group in sequence, and the diffracted light of the third light beam enters the detection unit after passing through the first lens group. The diffracted light of the first light beam and the diffracted light of the third light beam change their polarization directions after passing through the first wave plate, so as to interfere respectively in the first polarization direction and the second polarization direction, and form interference light. The interference light enters the first polarization beam splitter prism and is split into first polarized light and second polarized light by the first polarization beam splitter prism. The first detector acquires the light energy of the first polarized light, and the second detector acquires the light energy of the second polarized light. The grating mark is moved. When the light energies respectively acquired by the first detector and the second detector both reach a preset value, the position where the grating mark is located is the alignment position. Therefore, the present invention uses the light splitting unit to respectively acquire the diffracted light of the first light beam and the diffracted light of the third light beam, and then uses the first wave plate to realize the interference of the two in the first polarization direction and the second polarization direction respectively, without using a self-reference interference prism, thereby reducing costs and improving the alignment accuracy. Description of the Drawings

[0057] Figure 1 is a schematic structural diagram of an alignment device in Embodiment 1 of the present invention;

[0058] Figure 2 is a schematic structural diagram of an alignment device in Embodiment 2 of the present invention;

[0059] Figure 3 is a schematic optical path diagram of the second mirror group in Embodiment 2 of the present invention;

[0060] Figure 4 is a schematic structural diagram of an alignment device in Embodiment 3 of the present invention;

[0061] Figure 5 is a schematic optical path diagram in the beam splitting unit in Embodiment 3 of the present invention;

[0062] Figure 6 is a schematic structural diagram of an alignment device in Embodiment 3 of the present invention;

[0063] Among them, the reference numerals are:

[0064] 10 - illumination unit; 101 - light emitter; 102 - third mirror group; 103 - beam combiner;

[0065] 20 - beam splitting unit; 201 - first mirror group; 2011 - sixth reflector; 2012 - seventh reflector; 2013 - eighth reflector; 2014 - ninth reflector; 202 - second mirror group; 2021 - second wave plate; 2022 - first reflector; 2023 - third wave plate; 2024 - second reflector; 2025 - third reflector; 2026 - fourth reflector; 2027 - fifth reflector; 2028 - fourth wave plate;

[0066] 30 - detection unit; 301 - first wave plate; 302 - first detector; 303 - second detector; 304 - first beam splitter; 305 - second beam splitter;

[0067] 40 - objective lens; 50 - fifth wave plate; 60 - sixth wave plate; 70 - seventh wave plate;

[0068] PBS1 - first polarization beam splitter prism; PBS2 - second polarization beam splitter prism; PBS3 - third polarization beam splitter prism; PBS4 - fourth polarization beam splitter prism; PBS5 - fifth polarization beam splitter prism; PBS6 - sixth polarization beam splitter prism; PBS7 - seventh polarization beam splitter prism; M - grating mark. Detailed implementation manners

[0069] The following further elaborates on an alignment device, a lithography machine, and an alignment method proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise scales, only for conveniently and clearly assisting in explaining the purpose of the embodiments of the present invention. In addition, the structures shown in the accompanying drawings are often part of the actual structures. In particular, the focus of each accompanying drawing needs to be different, and sometimes different scales are used.

[0070] <Example 1>

[0071] To solve the above technical problems, this embodiment provides an alignment device, as Figure 1 shown, the alignment device includes: a light illumination unit 10, a beam splitting unit 20, and a detection unit 30.

[0072] The light illumination unit 10 is used to provide light illumination. The light illumination unit 10 includes a light emitter 101 and a third mirror group 102. The light emitter provides light illumination with at least one wavelength and at least one polarization direction, and the light illumination is linearly polarized light. Optionally, the third mirror group 102 is a plurality of reflectors, which are used to change the propagation direction of the light illumination. Figure 1 The number of the reflectors described therein is 2, but this embodiment does not limit the number of the reflectors. Among them, the light illumination propagates to the beam splitting unit 20 in a polarization direction of 45 degrees, so that the light energy ratio of the first light beam a and the second light beam b split by the beam splitting unit 20 is 1:1.

[0073] The beam splitting unit 20 includes a first mirror group 201 and a second mirror group 202. The first mirror group 201 is used to split the light illumination into a first light beam a with a first polarization direction and a second light beam b with a second polarization direction, and the second mirror group 202 is used to convert the second light beam b into a third light beam c with a first polarization direction. The first light beam a and the third light beam c are diffracted by a grating mark M and respectively generate diffracted light of the first light beam a and diffracted light of the third light beam c. The diffracted light of the first light beam a enters the detection unit 30 after passing through the second mirror group 202 and the first mirror group 201 in sequence, and the diffracted light of the third light beam c enters the detection unit 30 after passing through the first mirror group 201. Among them, the one polarization direction is perpendicular to the second polarization direction.

[0074] The detection unit 30 includes a first wave plate 301, a first polarization beam splitter prism PBS1, a first detector 302, and a second detector 303. The diffracted light of the first light beam a and the diffracted light of the third light beam c change the polarization direction to the +45-degree polarization direction and / or the -45-degree polarization direction after passing through the first wave plate 301, so as to interfere in the first polarization direction and the second polarization direction respectively, and form interference light. The interference light enters the first polarization beam splitter prism PBS1 and is split into a first polarized light and a second polarized light by the first polarization beam splitter prism PBS1. The first detector 301 acquires the light energy of the first polarized light, and the second detector 302 acquires the light energy of the second polarized light.

[0075] When the grating mark M is moved to a position where the light energies respectively acquired by the first detector 301 and the second detector 302 both reach a preset value, the position where the grating mark M is located is the alignment position.

[0076] Among them, the diffracted light of the third light beam c and the diffracted light of the first light beam a include diffracted lights of multiple corresponding orders, such as +1 / -1 order, -1 / +1 order, +2 / -2 order, or +3 / -3 order, etc. To more clearly show the optical path directions of the diffracted light of the third light beam c and the diffracted light of the first light beam a, only the +1 / -1 order diffracted light is marked in the illustrations of this embodiment to replace the corresponding diffracted light of the third light beam c and the diffracted light of the first light beam a.

[0077] Furthermore, this embodiment provides a splitting unit 20, as Figure 1 shown, the first lens group 201 includes a second polarization beam splitter prism PBS2, and the second lens group 202 includes a third polarization beam splitter prism PBS3, a second wave plate 2021, and a first mirror 2022.

[0078] The light passes through the second polarization beam splitter prism PBS2 and is split into a first light beam a with a first polarization direction and a second light beam b with a second polarization direction. Since the light with the first polarization direction is reflected by the polarization beam splitter prism and the light with the second polarization direction passes through the polarization beam splitter prism. Therefore, the first light beam a is reflected and propagated to the grating mark M, and the second light beam b passes through the second polarization beam splitter prism PBS2 and enters the second lens group 202. Therefore, the polarization directions of the first light beam a and the second light beam b are perpendicular to each other, and the propagation directions are also perpendicular to each other.

[0079] After the second light beam b passes through the second mirror group 202 as described above, it first passes through the third polarization beam splitter prism PBS3, and then successively passes through the transmission of the second wave plate 2021 and the reflection of the first mirror 2022. It passes through the second wave plate 2021 again. Since the second wave plate 2021 is a quarter-wave plate, after the second light beam b passes through the second wave plate 2021 twice, its polarization direction changes from the second polarization direction to the first polarization direction. Furthermore, it is reflected by the third polarization beam splitter prism PBS3 to form Figure 1 the third light beam c as shown. The third light beam c has the first polarization direction, is reflected by the third polarization beam splitter prism PBS3 to the objective lens 40, and propagates through the objective lens 40 to the grating mark M.

[0080] The first light beam a and the third light beam c are axisymmetric about the optical axis of the objective lens 40 and jointly propagate to the grating mark M to undergo diffraction, respectively generating the diffracted light of the third light beam c and the diffracted light of the first light beam a. Among them, the diffracted light of the third light beam c propagates along the reverse optical path of the first light beam a to the second polarization beam splitter prism PBS2. Since the diffracted light of the third light beam c has the first polarization direction, the diffracted light of the third light beam c is reflected by the second polarization beam splitter prism PBS2 to the detection unit 30. The diffracted light of the first light beam a propagates along the reverse optical path of the third light beam c to the third polarization beam splitter prism PBS3. Then, after the diffracted light of the first light beam a is reflected by the third polarization beam splitter prism PBS3, it successively passes through the transmission of the second wave plate 2021 and the reflection of the first mirror 2022, and then passes through the second wave plate 2021 again. Since the second wave plate 2021 is a quarter-wave plate, after passing through the second wave plate 2021 twice, the polarization direction of the diffracted light of the first light beam a changes from the first polarization direction to the second polarization direction. Therefore, the diffracted light of the first light beam a successively passes through the third polarization beam splitter prism PBS3 and the second polarization beam splitter prism PBS2 and enters the detection unit 30.

[0081] The diffracted light of the third light beam c with a first polarization direction and the diffracted light of the first light beam a with a second polarization direction jointly pass through the first wave plate 301. Since the first wave plate 301 is a half-wave plate, the polarization directions of the diffracted light of the third light beam c and the diffracted light of the first light beam a are both deflected by 45 degrees, being the +45-degree polarization direction and / or the -45-degree polarization direction, so that the diffracted light of the third light beam c and the diffracted light of the first light beam a can interfere respectively in the first polarization direction and the second polarization direction and generate interference light. The interference light propagates to the first polarization beam splitter PBS1 and is split into first polarized light and second polarized light by the first polarization beam splitter PBS1. Among them, the first polarized light has the first polarization direction, and the second polarized light has the second polarization direction. The first detector 302 acquires the light energy of the first polarized light, and the second detector 303 acquires the light energy of the second polarized light.

[0082] When the grating mark M is moved until the light energies respectively acquired by the first detector 302 and the second detector 303 both reach a preset value, the position where the grating mark M is located is the alignment position. Therefore, the alignment device provided in this embodiment can achieve high-precision alignment without using a self-reference interference prism and has a low cost.

[0083] Please continue to refer to Figure 1 , and take this as an example to specifically elaborate on the relationship between the light energy and the displacement of the grating mark M. Among them, the diffracted-order light field E of the grating mark M n is:

[0084]

[0085] Among them, n is the diffraction order, t is the period of the grating mark M, x is the displacement amount of the grating mark M, and here we first assume that the amplitude is 1. The following takes the +1-order diffracted light of the third light beam and the -1-order diffracted light of the first light beam as an example of coherence to calculate the signals detected by 302 and 303.

[0086] After the -1-order diffracted light of the first light beam passes through the objective lens 40, the third polarization beam splitter PBS3, the second wave plate 2021, the first mirror 2022, the second wave plate 2021, the third polarization beam splitter PBS3, the second polarization beam splitter PBS2, the first wave plate 301, and the first polarization beam splitter PBS1 in sequence:

[0087] The light energy E of the -1-order diffracted light of the first light beam in the first polarized light acquired by the first detector 302 (1,-1) :

[0088]

[0089] The optical energy E of the -1st order diffracted light of the first light beam in the second polarized light obtained by the second detector 303 (2,-1) :

[0090]

[0091] After the +1st order diffracted light of the third light beam passes through the objective lens 40, the second polarization beam splitter PBS2, the first wave plate 301 and the first polarization beam splitter PBS1 in sequence:

[0092] The optical energy E of the +1st order diffracted light of the third light beam in the first polarized light obtained by the first detector 302 (1,+1) :

[0093]

[0094] The optical energy E of the +1st order diffracted light of the third light beam in the second polarized light obtained by the second detector 303 (2,+1) :

[0095]

[0096] Wherein, J is the Jones matrix of each optical device, E in is the incident light field (1, 0), and the diffracted light field E of the -1st order diffracted light of the first light beam -1 is The diffracted light field E of the +1st order diffracted light of the third light beam +1 is In the formula, the subscripts 1 and 2 respectively represent that the corresponding light beams are the light in the first polarization direction and the second polarization direction. The subscripts -1 and +1 respectively represent the -1st order diffracted light of the first light beam and the +1st order diffracted light of the third light beam.

[0097] After the -1st order diffracted light of the first light beam and the +1st order diffracted light of the third light beam pass through the first wave plate 301, the polarization directions are changed to +45-degree polarization and / or -45-degree polarization, so as to interfere in the first polarization direction and the second polarization direction to generate interference light, and the interference light enters the first polarization beam splitter PBS1 to be divided into first polarized light and second polarized light. The first detector 302 and the second detector 303 respectively acquire the optical energies of the first polarized light and the second polarized light. Since the -1st order diffracted light of the first light beam passes through the reverse optical path of the third light beam c, and the +1st order diffracted light of the third light beam c passes through the reverse optical path of the first light beam a, the optical paths of the -1st order diffracted light of the first light beam a and the +1st order diffracted light of the third light beam c are the same. Then the light intensities finally detected by the first detector 302 and the second detector 303 are:

[0098]

[0099]

[0100] It can be seen that as the displacement x of the grating mark M changes, the light energy also changes accordingly. When reaching the peak, the light energy is at its maximum value, and the position corresponding to the displacement x of the grating mark M at this time is the required alignment position. Among them, the change in the displacement x of the grating mark M includes the displacement in the first direction and the displacement in the second direction, and the first direction and the second direction are perpendicular to each other.

[0101] Based on the same inventive concept, this embodiment further provides a lithography machine, and the lithography machine includes the alignment device.

[0102] Based on the same inventive concept, this embodiment further provides an alignment method, including:

[0103] The illumination unit 10 provides illumination.

[0104] The illumination passes through the first lens group 201 in the beam splitting unit 20, and the illumination is divided into a first light beam a with a first polarization direction and a second light beam b with a second polarization direction. The second lens group 202 in the beam splitting unit 20 converts the second light beam a into a third light beam c with a first polarization direction.

[0105] The first light beam a and the third light beam c are diffracted by the grating mark M, and diffracted light of the first light beam a and diffracted light of the third light beam c are respectively generated. The diffracted light of the first light beam a enters the detection unit 30 after passing through the second lens group 202 and the first lens group 201 in sequence, and the diffracted light of the third light beam c enters the detection unit 30 after passing through the first lens group 201.

[0106] The diffracted light of the first light beam a and the diffracted light of the third light beam c change their polarization directions to +45-degree polarization directions and / or -45-degree polarization directions after passing through the first wave plate 301, so as to interfere in the first polarization direction and the second polarization direction respectively, and form interference light. The interference light enters the first polarization beam splitter PBS1, and is divided into first polarized light and second polarized light by the first polarization beam splitter PBS1.

[0107] The first detector 302 acquires the light energy of the first polarized light, and the second detector 303 acquires the light energy of the second polarized light.

[0108] Move the workpiece stage to drive the grating mark M to move. When the light energies respectively acquired by the first detector 302 and the second detector 303 both reach a preset value, that is, when the light energy reaches the peak, the light energy is at the strongest value, and the position where the grating mark M is located is the alignment position. Among them, the displacement x of the grating mark M is respectively related to the light energy I 1 acquired by the first detector 302 2 and the light energy I

[0109]

[0110]

[0111] acquired by the second detector 303 as follows:

[0112] where x is the displacement of the grating mark, and t is the period of the grating mark.

[0113] Furthermore, the grating mark M can be set in multiple directions. When detecting the corresponding light energy, when the grating mark M in each direction reaches the peak value, the displacement of the workpiece stage at this time is the optimal value, and the corresponding position is the optimal alignment position.

[0114] <Example 2>

[0115] Please refer to Figure 2 , because the grating mark M can be set in multiple directions, so in order to be compatible with the diffracted light generated by the grating mark M in multiple directions, this embodiment provides an alignment device. Optionally, the direction of the grating mark M is the first direction X, the second direction Y or any direction in the plane where the first direction X and the second direction Y are located, where the first direction X and the second direction Y are perpendicular to each other.

[0116] The alignment device includes Figure 2 the splitting unit 20 shown in the figure. The remaining components of the alignment device can refer to the content described in Embodiment 1 and will not be elaborated here.

[0117] The beam splitting unit 20 includes a first lens group 201 and a second lens group 202. Among them, the first lens group 201 includes a fourth polarization beam splitting prism PBS4, and the second lens group includes a third wave plate 2023, a second mirror 2024, a third mirror 2025, a fourth mirror 2026, a fifth mirror 2027, and a fifth polarization beam splitting prism PBS5. The third wave plate 2023 is a half-wave plate.

[0118] Specifically, please refer to Figure 2 and 3 , the optical path of the light when it propagates through the beam splitting unit 20 to the grating mark M is as follows:

[0119] The light is split into a first light beam a and a second light beam b by the fourth polarization beam splitting prism PBS4. The first light beam a with the first polarization direction is reflected by the fourth polarization beam splitting prism PBS4 onto the grating mark M. After the second light beam b with the second polarization direction passes through the fourth polarization beam splitting prism PBS4, it is transmitted through the third wave plate 2023. Since the third wave plate is a half-wave plate, the polarization direction of the second light beam b changes from the second polarization direction to the first polarization direction. Then, the second light beam b is reflected by the second mirror 2024, the third mirror 2025, the fourth mirror 2026, and the fifth mirror 2027 in sequence, and is incident on the fifth polarization beam splitting prism PBS5. Among them, the angles between the second mirror 2024, the third mirror 2025, the fourth mirror 2026, and the fifth mirror 2027 and the first direction X are all 45 degrees. Since the polarization direction of the second light beam b incident on the fifth polarization beam splitting prism PBS5 is the first polarization direction, the second light beam b is reflected by the fifth polarization beam splitting prism PBS5 to form the third light beam c and propagates onto the grating mark M.

[0120] Furthermore, the diffracted light of the third light beam c and the diffracted light of the first light beam a propagate to the detection unit 30 along the reverse optical paths of the first light beam a and the third light beam c respectively, specifically as follows:

[0121] The first light beam a and the third light beam c act on the grating mark M to generate the diffracted light of the third light beam c and the diffracted light of the first light beam a. Among them, the diffracted light of the third light beam c propagates along the reverse optical path of the first light beam a. The diffracted light of the third light beam c with the first polarization direction is reflected by the fourth polarization beam splitting prism PBS4 to the detection unit 30. The diffracted light of the first light beam a propagates along the reverse optical path of the third light beam c. As Figure 3As shown, the diffracted light of the first light beam a with the first polarization direction is reflected by the fifth polarization beam splitter PBS5, and successively reflected by the fifth mirror 2027, the fourth mirror 2026, the third mirror 2025, and the second mirror 2024, and transmitted through the third wave plate 2023. Then, the polarization direction of the diffracted light of the first light beam a becomes the second polarization direction. Therefore, the diffracted light of the first light beam a passes through the fourth polarization beam splitter PBS4 and enters the detection unit 30.

[0122] Among them, Figure 2 only the -1st order diffracted light of the first light beam a distributed in the first direction X and the +1st order diffracted light of the third light beam c are marked; Figure 3 only the +1st / -1st order diffracted light of the first light beam a distributed in the second direction Y is marked, but during the alignment measurement process, it also includes the diffracted light of the third light beam c and the diffracted light of the first light beam a distributed in the direction of the plane formed by the first direction X and the second direction Y of the grating mark M.

[0123] Therefore, in this embodiment, by setting the third wave plate 2023, the second mirror 2024, the third mirror 2025, the fourth mirror 2026, and the fifth mirror 2027, the grating mark M in multiple directions is made compatible to include the diffracted light of the third light beam c and the diffracted light of the first light beam a distributed in multiple directions, improving the expandability of the alignment device. And because the alignment device can be compatible with the grating mark M in multiple directions, multiple grating marks M in different directions can be set during the alignment measurement process. When the workpiece stage is moved to drive the grating mark M to move, the diffracted light of the third light beam c and the diffracted light of the first light beam a generated by the multiple grating marks M, after interference, when the light energy reaches the peak, the light energy is the strongest value, and the alignment position obtained at this time is more accurate.

[0124] <Embodiment III>

[0125] In engineering implementation, it is difficult to obtain a beam that propagates completely parallel. Therefore, there is a part of the light incident on the beam splitting unit 20 at a certain angle. Thus, when the optical path of the light incident on the grating mark M is different, the spot sizes of the first light beam a and the third light beam c projected onto the silicon wafer are also inconsistent, which in turn leads to differences in the diffracted light energy, thereby affecting the detection of the light energy of the first polarized light and the second polarized light and reducing the alignment accuracy. Therefore, to obtain a more accurate alignment position, this embodiment provides an alignment device that can achieve adjustable optical path.

[0126] Specifically, please refer to Figure 4, the alignment device includes the beam splitting unit 20. For the remaining components, please refer to Embodiment 1. The beam splitting unit 20 includes a first mirror group 201 and a second mirror group 202. The first mirror group 201 includes a sixth polarization beam splitter prism PBS6, a sixth mirror 2011, a seventh mirror 2012, an eighth mirror 2013, and a ninth mirror 2014. The second mirror group 202 includes a fourth wave plate 2028 and the seventh polarization beam splitter prism PBS7. The fourth wave plate 2028 is a half-wave plate. Among them, the setting mode of the sixth polarization beam splitter prism PBS6 in this embodiment is symmetric about the Z-axis with the second polarization beam splitter prism PBS2 in Embodiment 1, and the setting mode of the seventh polarization beam splitter prism PBS7 is symmetric about the Z-axis with the third polarization beam splitter prism PBS3 in Embodiment 1.

[0127] Specifically, please refer to Figure 4 and Figure 5 , when the light propagates through the beam splitting unit 20 to the grating mark M, the optical path is as follows:

[0128] The light is split into a first light beam a and a second light beam b by the sixth polarization beam splitter prism PBS6. The first light beam a has a first polarization direction, so the first light beam a is reflected by the sixth polarization beam splitter prism PBS6 to the sixth mirror 2011, and successively reflected by the sixth mirror 2011, the seventh mirror 2012, the eighth mirror 2013, and the ninth mirror 2014 to the grating mark M. The second light beam b has a second polarization direction. After passing through the sixth polarization beam splitter prism PBS6, it passes through the fourth wave plate 2028 and then changes its polarization direction to the first polarization direction. Then it is reflected by the seventh polarization beam splitter prism PBS7 to form the third light beam c and propagates to the grating mark M.

[0129] The first light beam a and the third light beam c propagate through the objective lens 40 to the grating mark M and undergo diffraction, respectively generating the diffracted light of the first light beam a and the diffracted light of the third light beam c. The diffracted light of the first light beam a enters the detection unit 30 after passing through the second mirror group 202 and the first mirror group 201 in sequence, and the diffracted light of the third light beam c enters the detection unit 30 after passing through the first mirror group 201.

[0130] The diffracted light of the first light beam a and the diffracted light of the third light beam c change their polarization directions to the +45-degree polarization direction and / or the -45-degree polarization direction after passing through the first wave plate 301, respectively interfering in the first polarization direction and the second polarization direction to form interference light. The interference light enters the

[0131] Further, the diffracted light of the third light beam c and the diffracted light of the first light beam a respectively propagate to the detection unit 30 along the reverse optical paths of the first light beam a and the third light beam c, specifically as follows:

[0132] The diffracted light of the third light beam c is successively reflected by the ninth mirror 2014, the eighth mirror 2013, the seventh mirror 2012 and the sixth mirror 2011 to the sixth polarization beam splitter PBS6. Since the diffracted light of the third light beam c has a first polarization direction, it is reflected by the sixth polarization beam splitter PBS6 to the detection unit 30.

[0133] The diffracted light of the first light beam a has a first polarization direction, so it is reflected by the seventh polarization beam splitter PBS7 to the fourth wave plate 2028. After passing through the fourth wave plate 2028, the polarization direction is changed to a second polarization direction, and then it passes through the sixth polarization beam splitter PBS6 and propagates to the detection unit 30.

[0134] Further, the sixth mirror 2011 is optionally an isosceles right-angled triangular prism, and a reflective film is coated on the hypotenuse surface. The right-angled side length of the isosceles right-angled triangular prism is h. The sixth polarization beam splitter PBS6 and the seventh polarization beam splitter PBS7 are cubes with side length h. One surface of the right-angled side of the isosceles right-angled triangular prism is closely attached to one surface of the sixth polarization beam splitter PBS6 ( Figure 5 as shown). The sizes of the seventh mirror 2012, the eighth mirror 2013 and the ninth mirror 2014 are the same as the inclined surface of the isosceles right-angled triangular prism. The angles between the seventh mirror 2012, the eighth mirror 2013 and the ninth mirror 2014 and the first direction X are all 45 degrees. The first end of the seventh mirror 2012 is connected to an acute end of the sixth mirror 2011, and the included angle therebetween is 45 degrees. The eighth mirror 2013 and the ninth mirror 2014 are arranged in parallel, and the distance therebetween is h. The planes where the seventh mirror 2012 and the eighth mirror 2013 are located are perpendicular to each other. And the distance between the second end of the seventh mirror 2012 and the first end of the eighth mirror 2013 is h. In addition, the refractive indices of the sixth polarization beam splitter PBS6, the seventh polarization beam splitter PBS7 and the isosceles right-angled triangular prism are all n, then:

[0135] As Figure 5 shown, the optical path l from the light entering the sixth polarization beam splitter PBS6 to the light exiting from the ninth mirror 2014 is: s 1 = 2h * n + 4h;

[0136] The optical path of the light from entering the sixth polarization beam splitter PBS6 to exiting the seventh polarization beam splitter PBS7 to the same Z-axis position in the optical path 2 as in the optical path 1 is: s 2 = h*n + d + h*n + h = 2h*n + h + d;

[0137] where d is the distance between the sixth polarization beam splitter PBS6 and the seventh polarization beam splitter PBS7. Therefore, the difference between the optical path 1 and the optical path 2 is: s 2 -s 1 = d - 3h.

[0138] As can be seen from the above, to ensure that the optical path difference is zero, d = 3h can be achieved by adjustment. Therefore, the alignment device provided in this embodiment can adjust the optical path difference and improve the alignment accuracy.

[0139] In addition, please refer to Figure 6 , because the light can have multiple wavelengths and multiple polarization directions, in order to adapt to the light with multiple wavelengths and multiple polarization directions, the light unit 10 in this embodiment further includes a beam combiner 103. The beam combiner 103 is used to integrate the light with multiple wavelengths and propagate it through the same optical fiber. At the same time, the detection unit 30 further includes a first beam splitter 304 and the second beam splitter 305. Among them, the first beam splitter 304 is used to restore the first polarized light to a first optical signal with multiple wavelengths; the second beam splitter 305 is used to restore the second polarized light to a second optical signal with multiple wavelengths.

[0140] At the same time, in order to avoid the situation that the energy of the response of the grating mark M to the beam in the first polarization direction is low and the obtained optical signal is poor, the linearly polarized light needs to be converted into circularly polarized light. Therefore, a fifth wave plate 50, a sixth wave plate 60 and a seventh wave plate 70 are added between the beam splitting unit 20 and the objective lens 40. Among them, the fifth wave plate 50 is a half-wave plate, and the sixth wave plate 60 and the seventh wave plate 70 are both quarter-wave plates. When the first beam a passes through the fifth wave plate 50, the polarization direction of the first beam a changes from the first polarization direction to the second polarization direction. After continuing to pass through the sixth wave plate 60, the polarization direction of the first beam a with the second polarization direction becomes right-handed polarized and is incident on the grating mark M. The third beam c passes through the seventh wave plate 70, and its polarization direction changes from the first polarization direction to left-handed polarized and is incident on the grating mark M.

[0141] The first beam a with right-handed polarization and the third beam c with left-handed polarization are diffracted by the grating mark M and respectively generate the diffracted light of the first beam a and the diffracted light of the third beam c.

[0142] After the diffracted light of the third light beam c is transmitted through the sixth wave plate 60 and the fifth wave plate 50 in sequence, the polarization direction is changed to the first polarization direction and enters the first lens group 201. After the diffracted light of the first light beam a is transmitted through the seventh wave plate 70, the polarization direction is changed to the first polarization direction and enters the second lens group 202.

[0143] In addition, the beam combiner 103, the first beam splitter 304, the second beam splitter 305, the fifth wave plate 50, the sixth wave plate 60, and the seventh wave plate 70 provided in this embodiment are applicable to the illumination with multiple wavelengths and multiple polarization directions. Therefore, when the illumination has multiple wavelengths and multiple polarization directions, the above devices can be added to the alignment devices described in Embodiment 1 and Embodiment 2 to achieve compatibility with the illumination with multiple wavelengths and multiple polarization directions.

[0144] In summary, the alignment devices provided in each embodiment respectively obtain the diffracted light of the first light beam a and the diffracted light of the third light beam c by using the beam splitting unit 20, and then realize the interference of the two in the first polarization direction and the second polarization direction respectively through the first wave plate 301, without using a self-reference interference prism, thereby reducing the cost and improving the alignment accuracy.

[0145] It should be noted that the various embodiments in this specification are described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same and similar parts among the various embodiments can be referred to each other. In addition, the different parts among the various embodiments can also be combined and used, and the present invention does not limit this.

[0146] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention in any way. Any changes and modifications made by those of ordinary skill in the art of the present invention based on the above disclosure are within the protection scope of the claims.

Claims

1. An alignment device, characterized in that: The alignment device comprises: an illumination unit, a light splitting unit and a detection unit; wherein, The illumination unit is used to provide illumination; The light splitting unit comprises a first lens group and a second lens group; the first lens group is used to split the light into a first light beam with a first polarization direction and a second light beam with a second polarization direction, and the second lens group is used to convert the second light beam into a third light beam with the first polarization direction; the first light beam and the third light beam are diffracted by a grating mark, and diffracted light of the first light beam and diffracted light of the third light beam are generated respectively; wherein the diffracted light of the first light beam enters the detection unit after passing through the second lens group and the first lens group in sequence, and the diffracted light of the third light beam enters the detection unit after passing through the first lens group; The detection unit includes a first wave plate, a first polarization beam splitter prism, a first detector and a second detector; the diffracted light of the first light beam and the diffracted light of the third light beam change polarization directions after passing through the first wave plate, so as to interfere in the first polarization direction and the second polarization direction respectively and form interference light; the interference light enters the first polarization beam splitter prism and is divided into the first polarization light and the second polarization light by the first polarization beam splitter prism; the first detector obtains light energy of the first polarization light, and the second detector obtains light energy of the second polarization light; When the grating mark is moved until the light energies respectively acquired by the first detector and the second detector reach preset values, the position of the grating mark is the alignment position.

2. The alignment device according to claim 1, characterized in that The first polarization direction and the second polarization direction are perpendicular to each other.

3. The alignment device according to claim 1, characterized in that The diffracted light of the third light beam has a first polarization direction after passing through the first lens group; the diffracted light of the first light beam has a second polarization direction after passing through the second lens group and the first lens group in sequence.

4. The alignment device according to claim 1, characterized in that The first polarized light has a first polarization direction, and the second polarized light has a second polarization direction.

5. The alignment device according to claim 1, characterized in that The first mirror group includes a second polarization beam splitter prism, and the second mirror group includes a third polarization beam splitter prism, a second wave plate and a first reflector; The first light beam is reflected by the second polarization beam splitter prism to the grating mark; After the second light beam passes through the second polarization beam splitter prism and enters the third polarization beam splitter prism, it is sequentially transmitted through the second wave plate and reflected by the first reflector, and then sequentially transmitted through the second wave plate and reflected by the third polarization beam splitter prism to form the third light beam, and the third polarization beam splitter prism reflects the third light beam to the grating mark; The first light beam and the third light beam are diffracted by the grating mark, and diffracted light of the first light beam and diffracted light of the third light beam are generated respectively; Wherein, after being reflected by the third polarization beam splitter prism, the diffracted light of the first light beam is sequentially transmitted through the second wave plate and reflected by the first reflector, then transmitted through the second wave plate, the polarization direction is changed to the second polarization direction, and then sequentially transmitted through the third polarization beam splitter prism and the second polarization beam splitter prism to propagate to the detection unit; The diffracted light of the third light beam is reflected to the detection unit by the second polarization beam splitter prism.

6. The alignment device according to claim 5, characterized in that The second wave plate is a quarter wave plate.

7. The alignment device according to claim 1, characterized in that The first mirror group includes a fourth polarization beam splitter prism, and the second mirror group includes a third wave plate, a second reflector, a third reflector, a fourth reflector, a fifth reflector and a fifth polarization beam splitter prism; The first light beam is reflected by the fourth polarization beam splitter prism to the grating mark; After the second light beam passes through the fourth polarization beam splitter prism and the third wave plate, it is reflected by the second reflector, the third reflector, the fourth reflector and the fifth reflector in sequence, and enters the fifth polarization beam splitter prism to form the third light beam, and the third light beam is reflected by the fifth polarization beam splitter prism to the grating mark; The first light beam and the third light beam are diffracted by the grating mark, and diffracted light of the first light beam and diffracted light of the third light beam are generated respectively; Wherein, after the diffracted light of the first light beam is reflected by the fifth polarization beam splitter prism, it is first reflected by the fifth reflector, the fourth reflector, the third reflector and the second reflector in sequence, and then transmitted by the third wave plate, the polarization direction is changed to the second polarization direction, and then passes through the fourth polarization beam splitter prism to enter the detection unit; The diffracted light of the third light beam is reflected to the detection unit by the fourth polarization beam splitter prism.

8. The alignment device according to claim 7, characterized in that The third wave plate is a half wave plate.

9. The alignment device according to claim 1, characterized in that The first mirror group includes a sixth polarization beam splitter prism, a sixth reflector, a seventh reflector, an eighth reflector and a ninth reflector; the second mirror group includes a fourth wave plate and a seventh polarization beam splitter prism; The first light beam is firstly reflected by the sixth polarization beam splitter prism, and then sequentially reflected by the sixth reflector, the seventh reflector, the eighth reflector and the ninth reflector to the grating mark; After the second light beam passes through the sixth polarization beam splitter prism, it is transmitted through the fourth wave plate and enters the seventh polarization beam splitter prism to form the third light beam, and the third light beam is reflected by the seventh polarization beam splitter prism to the grating mark; The first light beam and the third light beam are diffracted by the grating mark, and diffracted light of the first light beam and diffracted light of the third light beam are generated respectively; The diffracted light of the first light beam is first reflected by the seventh polarization beam splitter prism, then transmitted by the fourth wave plate, and then changes its polarization direction to the second polarization direction, and then passes through the sixth polarization beam splitter prism to enter the detection unit; The diffracted light of the third light beam is first reflected by the ninth reflector, the eighth reflector, the seventh reflector and the sixth reflector in sequence to the sixth polarization beam splitter prism, and then reflected by the sixth polarization beam splitter prism to the detection unit.

10. The alignment device according to claim 9, characterized in that The fourth wave plate is a half wave plate.

11. The alignment device according to claim 1, characterized in that The first wave plate is a half wave plate.

12. The alignment device according to claim 1, characterized in that The illumination unit comprises a light emitter and a third lens group; wherein the light emitter is used to provide illumination having at least one wavelength and at least one polarization direction; and the third lens group is used to change the propagation direction of the illumination to obtain a preset propagation direction.

13. The alignment device according to claim 12, characterized in that When the light emitter provides illumination with multiple wavelengths, the illumination unit further comprises a beam combiner; the beam combiner is used to transmit the illumination with multiple wavelengths to the light splitting unit through the same optical fiber.

14. The alignment device according to claim 13, characterized in that When the light emitter provides light with multiple wavelengths, the detection unit also includes a first beam splitter and a second beam splitter; wherein the first beam splitter is used to split the first polarized light into a first light signal with multiple wavelengths; and the second beam splitter is used to split the second polarized light into a second light signal with multiple wavelengths.

15. The alignment device according to claim 1, characterized in that The alignment device also includes a fifth wave plate, a sixth wave plate and a seventh wave plate; After passing through the first mirror group, the first light beam is transmitted through the fifth wave plate and the sixth wave plate in sequence, the polarization direction is changed to right-handed polarization, and propagates to the grating mark; The third light beam is transmitted through the seventh wave plate, changes its polarization direction to left-hand polarization, and propagates to the grating mark; The first light beam and the third light beam respectively generate diffracted light of the first light beam and diffracted light of the third light beam through the grating mark; The diffracted light of the third light beam is transmitted through the sixth wave plate and the fifth wave plate in sequence, and then changes its polarization direction to the first polarization direction and enters the first mirror group; After being transmitted through the seventh wave plate, the diffracted light of the first light beam changes its polarization direction to the first polarization direction and enters the second mirror group.

16. The alignment device according to claim 15, characterized in that The fifth wave plate is a half wave plate; the sixth wave plate and the seventh wave plate are both quarter wave plates.

17. The alignment device according to claim 1, characterized in that The alignment device further includes an objective lens; the objective lens is used to converge and transmit the first light beam, the third light beam, the diffracted light of the first light beam and the diffracted light of the third light beam; The first light beam and the third light beam are transmitted to the grating mark through the objective lens; the diffracted light of the third light beam is transmitted to the first lens group through the objective lens; and the diffracted light of the first light beam is transmitted to the second lens group through the objective lens.

18. A photolithography machine, characterized in that: The lithography machine comprises an alignment device as claimed in any one of claims 1-17.

19. An alignment method, characterized in that: The alignment method is implemented using the lithography machine as claimed in claim 18, wherein the alignment method comprises: The illumination unit provides illumination; The light is divided into a first light beam having a first polarization direction and a second light beam having a second polarization direction by the first lens group in the light splitting unit; the second lens group in the light splitting unit converts the second light beam into a third light beam having the first polarization direction; The first light beam and the third light beam are diffracted by a grating mark, and diffracted light of the first light beam and diffracted light of the third light beam are generated respectively; wherein the diffracted light of the first light beam enters the detection unit after passing through the second lens group and the first lens group in sequence, and the diffracted light of the third light beam enters the detection unit after passing through the first lens group; The diffracted light of the first light beam and the diffracted light of the third light beam change their polarization directions after passing through the first wave plate, so as to interfere with each other in the first polarization direction and the second polarization direction respectively and form interference light, and the interference light enters the first polarization beam splitter prism and is split into the first polarization light and the second polarization light by the first polarization beam splitter prism; The first detector acquires light energy of the first polarized light, and the second detector acquires light energy of the second polarized light; The workpiece stage is moved to drive the grating mark to move. When the light energies respectively acquired by the first detector and the second detector reach preset values, the position of the grating mark is the alignment position.

Images