TWI733317B - Optical alignment device and photoetching system - Google Patents

Abstract

The invention provides an optical alignment device and a photolithography system, which can be compatible with narrow mark alignment scanning, can effectively increase the scanning signal energy of the mark, suppress the optical crosstalk between the mark and the mark, the mark and the photoetching line, and improve the alignment Quasi-precision. Further, the beam adjusting element in the imaging unit includes a plurality of sub-components respectively correspondingly arranged at the position of the light-passing area of the beam limiting element except for the ±1-order diffracted light beam passing through the diffraction grating, which can eliminate zero-order light. Interference with stray light, further increase the scanning signal energy of the mark, and improve the alignment accuracy.

Description

Optical alignment device and photoetching system

The present invention relates to the field of lithography technology, in particular to an optical alignment device and a lithography system.

In the semiconductor integrated circuit (IC) manufacturing process, the wafer usually needs to undergo multiple photolithography exposures to be completed. Except for the first photolithography, the other levels of photolithography must be aligned with the patterns left by the previous level exposure (ie precise positioning) before exposure, so as to ensure the correctness of the patterns between each layer. The relative position of the camera, that is, total overlay accuracy. Alignment is to determine the relative position relationship between them through the special marks on the mask plate (used to carry the mask pattern), silicon wafer, and workbench (used to carry the silicon wafer), so that the mask pattern can be accurately imaged on the silicon On-chip, realize the precision of engraving. Alignment can be divided into mask alignment and silicon wafer alignment. Mask alignment realizes the relative positional relationship between the mask plate and the worktable, and silicon wafer alignment realizes the relative positional relationship between the silicon wafer and the worktable. During the alignment and scanning process of the silicon wafer, the light beam irradiates the alignment marks on the silicon wafer to form a multi-level diffracted light beam that carries the marking information, and then receives the diffracted light beams of various levels through the imaging module and images them on the surface of the reference grating. Refer to the photodetector behind the grating to detect the light intensity signal, and combine the current position information of the workbench and the silicon chip to perform a series of digital signal processing to find the alignment position of the silicon chip. Since the alignment accuracy between the mask and the silicon wafer is a key factor that affects the uniform overlay accuracy of photolithography, many existing silicon wafer alignment technologies focus on improving the alignment accuracy. For example, the US Patent No. US7880880B2 The disclosed silicon wafer (off-axis) alignment system can use the secondary diffraction of two sets of gratings to perform coarse alignment and fine alignment of alignment marks, thereby improving alignment accuracy.

However, with the continuous improvement of the overlay accuracy and the continuous improvement of the photolithography process, the width of the alignment mark has become narrower and narrower, which affects the improvement of the alignment accuracy. As shown in Figure 1, a unidirectional grating type alignment mark (ie a narrow mark) 101 has a length L along the mark scanning direction (ie the length L of the alignment mark) and the diameter D of the illumination spot are quite large In the case of, the width W (that is, the width W of the alignment mark) along the scanning direction perpendicular to the mark is much smaller than the diameter D of the illumination spot, for example, W is 1/15, 1/8, etc. of D. When a narrow mark is used in a silicon wafer alignment system, light crosstalk is likely to occur between the narrow mark and other alignment marks or non-alignment marks, and between the narrow mark and the lithography line, which will cause the narrow mark to correspond The energy of the scanning signal is reduced, which affects the alignment accuracy.

An object of the present invention is to provide an optical alignment device, which can effectively suppress the optical crosstalk between the mark and the mark, the mark and the photoetching line, and improve the scanning signal energy corresponding to the alignment mark, thereby improving the alignment accuracy.

Another object of the present invention is to provide a lithography system, which can utilize the optical alignment device of the present invention to improve the overlay accuracy and lithography effect of the lithography system.

To achieve the above objective, the present invention provides an optical alignment device, which includes a light source lighting unit, an alignment mark unit, an imaging unit, and a reference mark unit arranged in sequence along the optical path, wherein the alignment mark unit includes at least one alignment mark, The reference mark unit includes at least one reference grating corresponding to the alignment mark, the light source lighting unit is used to emit an illumination beam and transmit it to the alignment mark, and the imaging unit is used to image the alignment mark on the reference grating; wherein the imaging unit includes an edge The beam limiting element for limiting the imaging range of the alignment mark and the beam adjusting element for adjusting the direction of the light beam output by the beam limiting element are arranged in the optical path in sequence. The ratio between the width and length of the alignment mark is not less than the aspect ratio of the alignment mark, and the effective beam adjustment area corresponding to the alignment mark in the beam adjustment element extends along the width direction and the length direction of the alignment mark. The ratio between the lengths of is not less than the aspect ratio of the alignment mark, and the width of the reference grating is not greater than the width of the alignment mark.

Preferably, the width of the alignment mark is 40 μm or less.

Preferably, the alignment mark is a diffraction grating.

Preferably, the light beam adjusting element is a diaphragm, and the diaphragm has a plurality of light-passing holes as light-passing regions.

Preferably, all the light-passing holes on the diaphragm are arranged in a one-dimensional structure along the length direction of the alignment mark, or all the light-passing holes on the diaphragm are arranged in a two-dimensional cross along the length and width directions of the alignment mark. structure.

Preferably, when all the light-passing holes on the diaphragm are arranged in a one-dimensional structure, the reference mark unit includes at least one reference grating whose length extends along the length direction of the alignment mark, and when the reference mark unit includes a plurality of reference gratings, all The reference gratings are arranged along the length of the alignment mark to form a one-dimensional structure; when all the apertures on the diaphragm are arranged in a two-dimensional cross structure, the reference mark unit includes a plurality of lengths extending along the length of the alignment mark The reference grating and a plurality of reference gratings whose lengths extend along the width direction of the alignment mark, and all the reference gratings in the reference mark unit are arranged in a two-dimensional cross structure along the length direction and the width direction of the alignment mark.

Preferably, the beam adjusting element includes a plurality of sub-components, and the effective beam adjusting regions of all the sub-components are respectively correspondingly arranged at the positions of the light-passing regions of the beam limiting element except for the ±1-level diffracted beam passing through the diffraction grating.

Preferably, the sub-component is a wedge block or a total reflection mirror or a half reflection mirror with an effective beam adjustment area.

Preferably, the lengths of the light-passing area and the effective beam adjustment area extending in the width direction of the alignment mark are both greater than the diameter of the diffracted beam spot in the width direction of the alignment mark at the first minimum.

Preferably, the length of the light-passing area and the effective beam adjustment area extending along the length direction of the alignment mark is the diameter of the diffracted beam spot in the length direction of the alignment mark at the first minimum.

Preferably, the light source illumination unit includes a light source for emitting an illumination beam and a mirror for reflecting the illumination beam to the alignment mark.

Preferably, the imaging unit further includes a first lens and a second lens, the first lens is arranged on the optical path between the beam limiting element and the alignment mark, and the second lens is arranged on the light path between the beam adjusting element and the reference mark unit. On the way.

Preferably, the optical alignment device further includes a signal detection and processing unit for detecting the optical signal output by the reference grating, and determining the position information of the alignment mark according to the optical signal.

Based on the same inventive concept, the present invention further provides a photolithography system, which includes a mask table for carrying a mask, a worktable for carrying a silicon wafer, and an optical alignment device according to the invention.

Preferably, the alignment mark of the optical alignment device is arranged on the mask plate or on the silicon wafer or on the workbench.

Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

The optical alignment device of the present invention can be compatible with narrow mark alignment scanning, can effectively increase the scanning signal energy of the mark, suppress the optical crosstalk between the mark and the mark, the mark and the photoetching line, and improve the alignment accuracy. Further, the beam adjustment element in the imaging unit includes a plurality of sub-components respectively correspondingly arranged at the position of the light-passing area of the beam limiting element except for the ±1 order diffracted light beam passing through the diffraction grating, which can eliminate zero-order light and The interference of stray light further increases the scanning signal energy of the mark and improves the alignment accuracy.

The photolithography system of the present invention adopts the optical alignment device of the present invention to realize mask alignment and/or silicon wafer alignment, so the alignment effect can be improved, and the overprinting accuracy and lithography effect of photolithography can be improved. .

In order to make the objectives and features of the present invention more obvious, the technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are in a very simplified form and all use imprecise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, in the terminology herein, "the length of the alignment mark" refers to the length of the alignment mark (ie diffraction grating) along the scanning direction (such as the Y direction in Figure 9A), and the "width of the alignment mark" Both refer to the length of the alignment mark (ie diffraction grating) extending in the direction orthogonal to the scanning direction (ie the non-scanning direction, such as the X direction in Figure 9A). "The width of the spot of the illumination beam" refers to The length of the spot formed by the illumination beam transmitted to the alignment mark extending along the width direction of the alignment mark. When the illumination spot is a round spot, the “width of the illumination spot” is the diameter of the round spot. In the case of a long elliptical spot extending in the length direction of the quasi-mark, the "width of the illumination spot" is the short axis of the long ellipse, and the "length of the light-passing area (light-passing hole)" refers to the light-passing area (light-passing hole) along the The length of the quasi mark extending in the width direction, "the width of the light-passing area (light-passing hole)" refers to the length of the light-passing area (light-passing hole) extending along the length of the alignment mark, "the length of the effective beam adjustment area" "All refer to the length of the effective beam adjustment area extending along the width direction of the alignment mark. "The width of the effective beam adjustment area" refers to the length of the effective beam adjustment area extending along the length of the alignment mark. "Refer to the length of the grating "Refers to the length of the reference grating extending in the length direction of the alignment mark image, and "the width of the reference grating" refers to the length of the reference grating extending in the width direction of the alignment mark image.

Example one

Please refer to Figure 2, an embodiment of the present invention provides an optical alignment device, including a light source lighting unit 1, an alignment mark unit 2, an imaging unit 3, a reference mark unit 4, and a signal detection and processing unit arranged in sequence along an optical path (Not shown). Wherein, the alignment mark unit 2 includes at least one narrow mark 20 for optical alignment, the reference mark unit 4 includes at least one reference grating (such as 41a, 41b in Figure 2) corresponding to the narrow mark 20, and the light source lighting unit 1 For emitting the illumination beam and transmitting it to the narrow mark 20, the imaging unit 3 is used for imaging the narrow mark 20 on each reference grating.

In this embodiment, the alignment mark unit 2 only includes a narrow mark 20 (shown as 101 in Figure 1), and the width of the narrow mark 20 (ie, the width W of 101 in Figure 1) is usually much smaller than the light source illumination The width of the illumination spot (ie, 100 in Figure 1) formed by the illumination beam irradiated by the unit 1 on the narrow mark 20, for example, the width of the narrow mark 20 is 40 μm or less, for example, 40 μm, 38 μm, or the like. When the illumination spot is a round spot, the width of the narrow mark 20 is 1/8, 1/15, etc. of the diameter of the round spot. In addition, in this embodiment, the narrow mark 20 is a one-dimensional diffraction grating as shown in FIG. 1. In other embodiments of the present invention, the alignment mark unit 2 may further include alignment marks in the form of other gratings. For example, as shown in FIG. 8, the alignment mark unit 2 may include narrow marks 20 side by side with a certain interval. And wide marks 21; for another example, each alignment mark contained in the alignment mark unit 2 is a diffraction grating, which can be arranged in a two-dimensional "cross" structure along the X direction and the Y direction. ”Word structure, “∟” structure, etc., and when the alignment mark unit 2 contains multiple diffraction gratings (ie multiple alignment marks), the grating period of these diffraction gratings may be exactly the same or not. Similarly, at this time, the arrangement of the clear area of the beam limiting element, the arrangement of the effective beam adjustment area of the beam adjustment element, and the arrangement of the reference grating all need to match the arrangement of these diffraction gratings, so that the corresponding order of diffraction can be achieved. The incident light beam passes through the light-passing area of the beam limiting element, and is focused and imaged on the corresponding reference grating. In addition, the overall shape of each diffraction grating (ie, each alignment mark) in the alignment mark unit is not limited to a rectangle formed by stripes of equal length, but may be an ellipse formed by stripes of not completely equal length. , Diamond and other structures. Wherein, when the alignment mark unit 2 includes a plurality of alignment marks including the narrow mark 20, the alignment marks other than the narrow mark 20 can be used to achieve rough alignment, and then the narrow mark 20 can be used to achieve fine alignment. In this way, the alignment position error caused by the asymmetric deformation of the single alignment mark can be reduced, thereby improving the alignment accuracy. In addition, it should be noted that the above alignment marks are all in the form of diffraction gratings, which can cause a uniform illumination beam to be diffracted after being irradiated on the alignment marks, and all levels of diffracted beams emitted after diffraction can carry For all the information about the alignment mark structure, the high-order diffracted beam can be scattered from the alignment mark in one or two dimensions at a large angle, and then the zero-order diffracted beam and non-diffracted impurities can be filtered out. After the astigmatism, collect the diffracted light beam with the diffracted light ±1 level or more and image it. The optical signal of the interference fringe after the alignment mark image passes through the reference grating (ie the alignment mark scanning signal) can be processed by the photodetector and the signal. Used to determine the center position of the alignment mark. However, the technical solution of the present invention is not limited to this. If the signal detection and processing unit is capable of permitting, the alignment mark may further include a form other than a diffraction grating, such as a transmission grating, as long as the illuminating beam is irradiated on the alignment The mark can generate a light beam carrying all the information about the alignment mark structure, and the light beam can be received by the imaging unit 3 to image the alignment mark on the reference grating.

The light source lighting unit 1 includes a light source (not shown) for generating and emitting an illuminating light beam and a mirror 10 for reflecting the illuminating light beam to the narrow mark 20. In this embodiment, the light source is a laser capable of generating a laser beam of a single wavelength (for example, 450 nm to 780 nm), and the reflector 10 can reflect the laser beam generated by the light source to irradiate it vertically to the alignment mark unit 2 The corresponding alignment marks can also be irradiated vertically on the narrow marks 20, while shielding the light reflected by each alignment mark, so as to improve the contrast of the subsequent interference fringe images formed at the reference grating, thereby improving the alignment Accuracy. In this embodiment, the mirror 10 can further reflect the zero-order diffracted beam of the narrow mark 20 to prevent it from reaching the beam limiting element 32. In other embodiments of the present invention, in order to meet the requirements of different alignment marks in the alignment mark unit 2 for illumination beams of different wavelengths, the light source may further be a composite laser device capable of generating laser beams of multiple wavelengths, At this time, the light source lighting unit 1 further includes a light source gating device (not shown) and a collimating light path device (not shown). The light source gating device is a switch that can control the light source to output laser beams of different wavelengths to emit In addition to the reflector 10, the collimating light path device for the illumination beam of the required wavelength may further include a beam splitter and/or a beam combiner for combining a plurality of laser beams into one. The illumination beam with high reflectivity of the quasi-mark irradiates the alignment mark to meet the requirements of various alignment marks, and to improve the contrast of the interference fringe image formed at the reference grating to achieve the purpose of enhancing the adaptability of the manufacturing process.

The imaging unit 3 includes a first lens 31, a beam limiting element 32, a beam adjusting element (shown as 33a and 33b in FIG. 2), and a second lens 34 arranged in order according to the optical path. Wherein, the first lens 31 is arranged on the optical path between the beam limiting element 32 and the narrow mark 20, and is used to collect the diffracted light of ±1 level or more generated by the narrow mark 20 in the alignment mark unit 2 and make it parallel to Its optical axis is emitted, as indicated by q(+1), q(-1), q(+2), q(-2) in Figure 2. At this time, the narrow mark 20 is set on the first lens 31 Focal plane. The cooperation of the first lens 31, the mirror 10 and the beam limiting element 32 can prevent the zero-order diffracted beam and stray light of the narrow mark 20 from reaching the signal detection and processing unit, thereby avoiding interference with the detection signal, especially the mirror 10 can The zero-order diffracted light beam of the narrow mark 20 emitted by the first lens 31 is directly reflected out to prevent the zero-order diffracted light beam of the narrow mark 20 from reaching the beam limiting element 32.

The beam limiting element 32 is used to limit the imaging range of the narrow mark 20, and the position, shape, and size of each light-passing area need to be matched with the beam emitted from the first lens 31. The beam limiting element 32 may be an aperture (hereinafter referred to as aperture 32) with a corresponding light-transmitting area (that is, 320 in Figure 3), where the aperture 32 may be the edge of the lens, a frame or a specially set belt Aperture screen. In this embodiment, the aperture 32 is a screen with a plurality of light-passing holes 320, and these light-passing holes 320 are respectively arranged corresponding to the diffracted light beams of ±1 level or more (including ±1 level) of the narrow mark 20, A diffracted light beam of ±1 level or more (including ±1 level) allowed to pass through the narrow mark 20, and because the narrow mark 20 is a diffraction grating, the diffracted light beams of each level are along the length direction of the narrow mark 20 (that is, the first In the figure, the direction L) is arranged on a straight line, so the apertures 320 corresponding to the diffracted beams of the narrow mark 20 of ±1 level or more of the narrow mark 20 are arranged on the same straight line along the length direction of the narrow mark 20 to form a one-dimensional structure. The cooperation of the mirror 10, the diaphragm 32 and the beam adjustment elements 33a, 33b can eliminate the interference of the zero-order diffracted light and other stray light of the narrow mark 20, and improve the scanning signal of the alignment mark detected by the signal detection and processing unit Energy (that is, the energy of the beam output by the reference grating), thereby improving the alignment accuracy. The shape of each light-passing hole 320 used to pass the diffracted light beams of ±1 level or more through the narrow mark 20 is a right-angled rectangle (as shown in FIG. 3) or a rounded rectangle, and the size of each light-passing hole 320 is the same. The length of the side length of the light-passing hole 320 extending along the width direction of the narrow mark 20 (that is, the W direction in Figure 1) (that is, the length of the light-passing hole corresponding to the diffracted light in the width direction of the narrow mark 20, that is, the length of the rectangle Side length) is the length L1, the length of the side length extending along the length direction of the narrow mark 20 (that is, the L direction in Figure 1) (that is, the length of the light hole corresponding to the diffracted light in the length direction of the narrow mark, which is rectangular The short side length) is L2. It should be noted that according to the needs of optical alignment, the diaphragm 32 can be a rotatable diaphragm, and its rotation can be driven by a motor, and the angle of the diaphragm 32 can be adjusted by the motor, so that the diffracted light beams of the corresponding order can be adjusted by the light beam. The elements 33a, 33b and the second lens 34 can then be imaged on the corresponding reference grating of the reference marking unit 4.

Please refer to Figure 2, Figure 4A and Figure 4B. The beam adjustment elements (ie 33a, 33b) are used to change the direction of the light emitted by the aperture 32 to further separate different ones in the plane where the reference mark unit 4 is located. beam. The beam adjustment elements 33a, 33b may include a plurality of sub-components, and the effective beam adjustment areas of all the sub-components are correspondingly set on the beam limiting element (that is, the aperture 32) except for passing through the diffraction grating (that is, the narrow mark 20) ±1 level An array structure is formed at the position of the light passing area (that is, the light passing hole 320) other than the diffracted beam. In this embodiment, the sub-component is a wedge block (as shown in Figure 4B) arranged on the light exit surface of the aperture 320 corresponding to the aperture 32, and the number of wedge blocks corresponds to the narrow mark 20 used for optical alignment. The number of diffracted light beams, these wedges can be fixedly arranged on the same board, and the area between adjacent wedges can pass light without changing the direction of light propagation. For example, when the ±1-level diffracted light q(+1), q(-1) and ±2-level diffracted light q(+2), q(-2) generated by the narrow mark 20 are used, the ±1-level diffracted light q(+2), q(-2) can be emitted at the aperture 32. A wedge-shaped block is set at the position of the second-order diffracted light q(+2) and q(-2) respectively, as shown by 33a and 33b in the second figure, so that the ±2-level diffracted light q(+2), q (-2) Deflection and converging on the reference grating 41a in the reference marking unit 4 through the second lens 34, the area between the wedge blocks 33a, 33b allows ±1 level diffracted light q(+1), q(-1) It passes along the original direction, and is converged on the reference grating 41b located on the optical axis of the imaging optical path in the reference marking unit 4 through the second lens 34. The wedge blocks 33a and 33b may have the same wedge angle, and the wedge angles are opposite to each other. Among them, because different light beams passing through the wedge block can be deflected at different angles, the images formed by the light beams reach the reference gratings at different positions in the plane where the reference marking unit 4 is located. These positions Xn are obtained by Xn = f2 * γn, where γn is the angle at which the sub-beam is deflected by the wedge, and f2 is the focal length of the second lens 34. Therefore, corresponding reference gratings can be installed at these positions, such as the second Shown in Figure 41a, 41b. Among them, please refer to Figures 4A and 4B, the length of the side length of each wedge block 33a (33b) extending in the width direction of the narrow mark 20 (ie, the W direction in Figure 1) (the diffracted light in the width direction of the narrow mark 20) The length of the corresponding effective beam restriction area) is the length L3, and the length of the side extending along the length direction of the narrow mark 20 (that is, the L direction in Figure 1) (the length of the effective beam restriction area corresponding to the diffracted light in the length direction of the narrow mark) Length) is the length L4.

It should be noted that in the technical solution of the present invention, the structure of the beam adjusting elements 33a, 33b is not only limited to the combination of wedges, but can be any other optical element that can change the propagation direction of the beam, for example, including A plurality of half mirrors (which can reflect and transmit) and/or total reflection mirrors arranged on the light exit surface of the diaphragm 32 and arranged according to the emitted light beam of the diaphragm 32, these half mirrors and/or total reflection mirrors are integrated in the same On the board, a mirror array structure is formed. Compared with the wedge block array structure, this mirror array structure can reduce the difficulty of system manufacturing and assembly adjustment, and eliminates the problem of inconsistent positive and negative order interference fringe images and poor magnification caused by the processing and manufacturing errors of the wedge block array.

The second lens 34 is arranged on the optical path between the beam adjustment elements 33a, 33b and the reference mark unit 4, and is used to converge the light beams output by the beam adjustment elements 33a, 33b onto the reference grating, and can further block the non-carrying alignment marks The stray light and diffracted light of the position information reach the reference grating. It should be noted that the above-mentioned first lens 31 and second lens 34 are not limited to only one lens, and may be a lens group structure in which a plurality of lenses are arranged along the optical path.

In this embodiment, since the diaphragm 32 shown in Figure 2 is selected, all the light-passing holes 320 on the diaphragm 32 for the diffracted light beams passing through the narrow mark 20 of ±1 level or more are along the length of the narrow mark 20. The directions are arranged in a straight line to form a one-dimensional structure. Therefore, the shape and arrangement of the reference grating used for receiving the image of the narrow mark 20 in the reference mark unit 4 need to be consistent with the shape and arrangement of the light-passing hole 320 of the diaphragm 32. The number of reference gratings is adapted to the number of narrow mark images formed by the second lens 34 to be detected. For example, when the alignment mark unit 2 has only one narrow mark 20, and only the second When the narrow mark image at one of the positions formed by the lens 34, the reference mark unit 4 may only include a reference grating whose length extends along the length of the narrow mark 20; when the alignment mark unit 2 has only one narrow mark 20, and When it is necessary to detect narrow mark images at a plurality of positions formed by the second lens 34, the reference mark unit 4 needs to include a number of reference gratings not less than the number of narrow mark images to be detected, and the length of each reference grating is along the narrow mark 20. Extend in the length direction, and are correspondingly set at the positions of the narrow mark images to be detected, as shown by 41a and 41b in Figure 2. When the narrow mark 20 is a diffraction grating, and all the apertures 320 of the aperture 32 for passing through the diffracted light beams of ±1 level or more of the narrow mark 20 are arranged on the same straight line along the length direction of the narrow mark 20. In the case of a one-dimensional structure, the reference gratings 41a and 41b in the reference mark unit 4 for receiving the image formed by the narrow mark 20 are also arranged on the same straight line along the length direction of the narrow mark 20, forming a one-dimensional structure. The reference gratings 41a and 41b can further process the mark images formed by the imaging unit 3 into corresponding interference fringe images. In addition, the grating period of each reference grating should be selected to be suitable for the diffracted beams it receives. The larger the number, the smaller the grating period of the reference grating. As a result, the smaller the alignment error can be achieved, and the higher the accuracy. Quasi-precision.

It should be noted that when the alignment mark unit 2 includes a narrow mark 20 and a plurality of other alignment marks, these other alignment marks are also diffraction gratings (that is, a diffraction grating is a diffraction grating used for optical alignment). When the alignment mark 20 is placed in the same direction as the narrow mark 20, and all the alignment marks in the alignment mark unit 2 are arranged on the same straight line along the length of the narrow mark 20, the aperture 32 is used to pass through the narrow mark. 20 and other diffracted light beams above ±1 level. All the through holes 320 are arranged in a straight line along the length direction of the narrow mark 20 to form a one-dimensional structure. The reference mark unit 4 is used to receive the narrow mark 20 and The reference gratings of the images formed by a plurality of other alignment marks are also arranged on the same straight line along the length direction of the narrow mark 20, and have a one-dimensional structure.

The signal detection and processing unit may include a photodetector (not shown) arranged behind each reference grating and a signal processor (not shown) connected to all the photodetectors. The photodetector is used to detect interference fringes passing through the reference grating. Energy (referring to the optical signal output by the grating). Preferably, the photodetector uses a photodiode; the signal processor can combine part of the movement information based on the optical signal detected by the photodetector (such as the movement stroke of the worktable, etc.) ) To calculate the position information and alignment position of the narrow mark.

Please refer to Figure 2, the optical alignment steps of the above-mentioned optical alignment system include: the illumination beam emitted by the light source is irradiated vertically on the narrow mark 20 through the reflector 10; the illumination beam is diffracted by the narrow mark 20 into a number of orders of diffraction (Figure 2 only shows 4 diffracted beams of ±1 and ±2 levels); these diffracted beams are collected by the first lens 31 and irradiated on the aperture 32, and the 0-level diffracted beams are The mirror 10 reflects out but does not reach the aperture 32; the aperture 320 corresponding to the diffracted beam position above ±1 level of the narrow mark 20 allows the diffracted light beams of these levels to pass through, and the light outside the aperture 320 The area of the stop 32 shields the zero-order diffracted light beam and the stray light of the non-diffraction order position of the narrow mark 20; the diffracted light beam passing through the corresponding level (such as ±2 level) of the stop 32 is adjusted by the beam adjustment elements 33a, 33b After that, it is imaged at the corresponding reference grating (shown as 41a in Figure 2) through the second lens, and the direction of the diffracted beam of the corresponding level (±1 level) that is not adjusted by the beam adjusting elements 33a and 33b is different. Will be adjusted, and the imaging position is at the reference grating (shown as 41b in Figure 2) on the optical axis of the imaging optical path; the reference grating will further process the received mark image into corresponding interference fringes. The photodetector detects the energy of the interference fringes passing through the reference grating (that is, the optical signal output by the reference grating). The signal processor connected to the photodetector can calculate the alignment mark based on the detected optical signal energy combined with part of the movement information Location information and alignment location, etc. In this process, the reference mark unit 4 can be moved by using a step scanning method, so that the imaging of the second lens 34 scans the reference grating, that is, the photodetector obtains the scanning signal energy of the alignment mark through the scanning method, and the signal processing The detector can calculate the position information and the alignment position of the alignment mark based on the detected scanning signal energy combined with part of the movement information.

Regarding the narrow mark 20, when it is used for optical alignment, the problem of optical crosstalk between the narrow mark and other adjacent alignment marks or non-alignment marks and between the narrow mark and adjacent lithographic lines often occurs. As a result, the energy of the scanning signal corresponding to the narrow mark is reduced, which in turn affects the alignment accuracy. In order to solve this problem, it is necessary to make the size design of the aperture 320 of the aperture 32 corresponding to the diffracted light beams of the narrow mark 20 and the effective beam adjustment area 330 of the beam adjustment elements 33a, 33b to match the dimensions of the narrow mark 20 levels. The size of the diffracted spot corresponding to the secondary diffracted beam in the frequency domain. For example, the design allows 85%, 90%, 95%, 99% of the energy of the diffracted beam to pass through the aperture 320 of the diaphragm 32 and the effective beam adjustment area 330 of the beam adjustment elements 33a, 33b, and the more energy passes High, the higher the intensity of the scanning signal of the alignment mark obtained by the signal detection and processing unit, and the optical crosstalk will be reduced accordingly.

Therefore, please refer to Fig. 3 and Fig. 4A to Fig. 4B, the aperture 320 of the aperture 32 for the diffracted light beam of ±1 level or more passing through the narrow mark 20 (hereinafter referred to as the aperture of the aperture 32) 320) length L1 and the effective beam adjustment area 330 of the beam adjustment elements 33a, 33b for adjusting the diffracted light beam of the narrow mark 20 at ±2 levels or more (hereinafter referred to as the effective beam adjustment area 330 of the beam adjustment elements 33a, 33b) The length L3 should match the size of the diffracted beam (that is, the diffracted spot) in the width direction of the narrow mark 20 (that is, the W direction in Figure 1). Among them, the intensity distribution of the diffracted beam in the frequency domain in the width direction of the narrow mark 20 (that is, the W direction in Figure 1) is approximately the case of single-slit diffraction, namely: I = (sin(πα) / (πα)) 2 , Α = W sin(θ) / λ, where W is the width of the narrow mark 20, λ is the light wavelength, and θ is the diffraction angle. The length L1 of the aperture 320 of the diaphragm 32 and the length L3 of the effective beam adjustment area 330 of the beam adjustment elements 33a and 33b should be: l = f1 * tan(θ), where f1 is the focal length of the first lens 31 , Θ is the angle of diffraction.

If the size of the length L1 and the length L3 is the diameter of the diffracted beam (ie diffracted spot) corresponding to -0.5>α>0.5, the energy of the diffracted beam transmitted by the diaphragm 32 and the beam adjustment elements 33a, 33b is approximately 78%. As shown in Figure 6, if the length L1 and the length L3 are equal to the diameter s1 of the first minimum of the diffracted spot in the width direction of the narrow mark 20, that is, s1 ≈ f1 * λ / W, -1>α>1, then The energy of the incident beam transmitted by the diaphragm 32 and the beam adjusting elements 33a, 33b is about 90%; if the length L1 and the length L3 are equal to the diameter s2 of the second minimum of the diffraction spot in the width direction of the narrow mark, that is- 2>α>2, then the energy of the diffracted beam transmitted by the diaphragm 32 and the beam adjustment elements 33a, 33b is about 95%; if the length L1 and the length L3 are equal to the third of the diffracted spot in the width direction of the narrow mark 20 The minimum diameter s3, that is -3>α>3, then the energy of the diffracted beam transmitted by the diaphragm 32 and the beam adjustment elements 33a, 33b is about 96%.

In order to further sharpen the edges of the narrow mark image formed by the second lens 34 in the width direction, the scanning signal energy obtained by the signal detection and processing unit is stronger and the crosstalk is smaller. The sidelobe light can also pass through the diaphragm 32 and the beam adjustment elements 33a, 33b. Therefore, preferably, the length L1 and the length L3 are greater than s1, such as s2 or s3, or between s1 and s2, or between s2 Between s3 and s3, even greater than s3.

Please refer to Figure 3 and Figures 4A to 4B, the length L2 of the aperture 320 of the diaphragm 32 and the length L4 of the effective beam adjustment area 330 of the beam adjustment elements 33a and 33b should also match the length direction of the narrow mark 20 ( That is, the size of the diffracted beam (ie, the diffracted spot) in the L direction in Figure 1. Among them, the diffraction intensity distribution in the frequency domain in the length direction of the narrow mark 20 is the case of multi-slit diffraction, namely: I = (sin(πα) / (πα))2 * (sin(Nπβ) / (sinπβ)) 2, α = a * sin(θ) / λ, β = b * sin(θ) / λ, a * b = L,

Where L is the length of the narrow mark 20, λ is the light wavelength, θ is the diffraction angle, a is the line width of the narrow mark 20, and b is the grating period of the narrow mark 20.

Please refer to FIG. 7, which shows the distribution of the diffraction spot in the frequency domain in the length direction of the narrow mark 20. The length L2 and the length L4 correspond to the length of s4 shown in Figure 7, s4 ≈ f * λ /L.

It can be obtained that the length L1 and the length L2 of the aperture 320 of the diaphragm 32 and the length L3 and the length L4 of the effective beam adjustment area 330 of the beam adjustment elements 33a and 33b are between the length L and the width W of the narrow mark 20 The relationship should satisfy: L1/L2≥L/W, L3/L4≥L/W. In other words, the light beam limiting element (i.e., the diaphragm 32) used to pass through the narrow mark 20 with a diffracted light beam of more than ±1 level (i.e., the light hole 320) along the width direction of the narrow mark 20 (i.e. The ratio L1/L2 between the length extending in the W direction in Figure 1) and the length direction (ie, the L direction in Figure 1) is not less than the aspect ratio L/W of the narrow mark 20, and the beam adjustment element (ie, the second 33a, 33b) in the figure is used to adjust the effective beam adjustment area of the diffracted beam above ±2 levels of the narrow mark 20 (i.e. 330 in Figure 4A) along the width direction of the narrow mark 20 (i.e., Figure 1 The ratio L3/L4 between the length extending in the W direction) and the length direction (ie, the L direction in Figure 1) is not less than the aspect ratio L/W of the narrow mark 20.

That is to say, the optical alignment system of this embodiment fully analyzes the energy distribution characteristics of the diffraction spot in the frequency domain of the narrow mark 20, and according to the size of the diffraction spot in the frequency domain in the width direction and the length direction of the narrow mark 20, The design and size characteristics of the aperture 320 of the aperture 32 corresponding to the diffracted light beam of the narrow mark 20 of ±1 level or more and the effective beam adjustment area 330 of the beam adjustment elements 33a and 33b are provided. For example, when the length L of the narrow mark 20 is 144 μm and the width W is 38 μm, the aspect ratio L/W of the narrow mark 20 is approximately 3.8, and the diaphragm 32 is used to pass the diffraction of the narrow mark 20 of ±1 level or more. The value of the side length ratio L1/L2 of the light beam 320 should be at least greater than 3.8, and the beam adjustment elements 33a, 33b are used to adjust the side length of the effective beam adjustment area 330 of the diffracted beam above ±2 of the narrow mark 20. The value of the ratio L3/L4 should also be at least greater than 3.8. Therefore, the problem of optical crosstalk can be eliminated, the scanning signal energy can be improved, and the alignment accuracy can be improved.

In order to better illustrate the effect brought by the design of the size of the aperture 320 of the aperture 32 and the effective beam adjustment area 330 of the beam adjustment elements 33a and 33b in this embodiment, FIGS. 8 to 10B show the effects of light The size of the aperture 320 of the stop 32 and the effective beam adjustment area 330 of the beam adjustment elements 33a, 33b do not match the size of the diffraction spot of the narrow mark 20 in the frequency domain and match the size of the diffraction spot of the narrow mark 20 in the frequency domain. Case. Specifically, Figure 8 shows a schematic structural diagram of an alignment mark unit 2 containing adjacent narrow marks 20 and wide marks 21; Figure 9A shows the case where L1/L2 and L3/L4 are equal to 1.34 , The imaging situation of the alignment mark unit 2 shown in Figure 8 after passing through the imaging unit 3; Figure 9B shows the energy distribution of a scanning signal along a non-scanning direction cross-section obtained in the imaging situation shown in Figure 9A Curve; Figure 10A shows the imaging situation of the alignment mark unit 2 shown in Figure 8 after passing the imaging unit 3 when L1/L2 and L3/L4 are equal to 4; Figure 10B shows Figure 10A The energy distribution curve of the scanning signal on the cross-section line along the non-scanning direction is obtained in the imaging situation shown. When the length L of the narrow mark 20 is 144 μm and the width W is 38 μm, the aspect ratio L/W of the narrow mark 20 is about 3.8, and when L1/L2 and L3/L4 are equal to 1.34, as shown in Figure 9A It can be seen from the imaging situation that the energy of the image 20a corresponding to the narrow mark 20 has dropped significantly, and part of the energy has entered the image 21a corresponding to the wide mark 21. It can be seen from Figure 9B that the energy distribution of the scanning signal is also There is no obvious demarcation, that is, when L1/L2 and L3/L4 are smaller than the aspect ratio of the narrow mark 20, the problem of optical crosstalk between the narrow mark 20 and the wide mark 21 may occur during the optical alignment process. When the wide mark 21 is replaced with the lithographic line 6 in Figure 11A, if the size of the aperture 320 of the diaphragm 32 and the effective beam adjustment area 330 of the beam adjustment elements 33a, 33b does not match the diffracted light spot of the narrow mark 20 In the size of the frequency domain, the problem of optical crosstalk between the narrow mark 20 and the adjacent lithographic line 6 may also occur. When the length L of the narrow mark 20 is 144 μm and the width W is 38 μm, when the aspect ratio L/W of the narrow mark 20 is about 3.8, when L1/L2 and L3/L4 are selected equal to 4, from Figure 10A It can be seen that the energy of the image 20b corresponding to the narrow mark 20 is not significantly reduced, and its definition is equivalent to that of the image 21b corresponding to the wide mark 21, and the boundary between the two images 20b and 21b is clearly divided. Figure 10B The scanning signal is also clearly demarcated, which means that when L1/L2 and L3/L4 are greater than the aspect ratio L/W of the narrow mark 20, the optical crosstalk between the narrow mark 20 and the wide mark 21 during the optical alignment process can be eliminated. problem. Similarly, when L1/L2 and L3/L4 are greater than the aspect ratio L/W of the narrow mark 20, the problem of optical crosstalk between the narrow mark 20 and the adjacent lithographic line 6 can also be eliminated.

In addition, in order to obtain the above-mentioned scanning signal, the narrow mark image formed by the second lens 34 and the reference grating receiving the narrow mark image are required to be able to generate relative movement. Therefore, please refer to Figure 5 for the width of the reference gratings 41a and 41b. The following relationship should be satisfied between W1 and the width W of the narrow mark 20: W1≤W. Please refer to Figure 11A, when W1≥W, the illuminating beam irradiates the lithography line 6 adjacent to the right side of the narrow mark 20 and/or the diffraction mark 5 adjacent to the left side of the narrow mark 20. The light beam will enter the reference grating 41a or 41b, which will result in the generation of scanning signals of the lithographic lines 6 and/or non-alignment marks 5. These scanning signals will cause signal interference and affect the alignment accuracy. When W1≤W, please refer to Figure 11B. Even if the illumination beam irradiates the lithography line 6 on the right side of the narrow mark 20 and/or the non-alignment mark 5 on the left side of the narrow mark 20, a diffracted beam is generated. The diffracted light beam will not enter the reference grating 41a or 41b, and therefore will not generate the scanning signal of the lithography line 6 or the non-alignment mark 5, thereby suppressing the narrow mark 20 and the adjacent lithography line 6 Optical crosstalk between the narrow mark 20 and other adjacent alignment marks and non-alignment marks 5.

To sum up, the optical alignment device of this embodiment is designed to match the aspect ratio of the alignment mark with the special size ratio design of the light-transmitting area of the beam limiting element, the effective beam adjustment area of the beam adjusting element, and the reference grating. It is compatible with the alignment scanning of narrow marks, and can effectively increase the scanning signal energy, inhibit the optical crosstalk between the mark and the mark, and the mark and the lithographic image, thereby improving the alignment accuracy. That is to say, it is required that the ratio between the length of the light passing area of the beam limiting element extending in the width direction and the length direction of the alignment mark is not less than the aspect ratio of the alignment mark, and the effective beam adjustment area of the beam adjustment element is respectively along the The ratio between the width direction of the alignment mark and the length extending in the length direction is not less than the aspect ratio of the alignment mark, and the width of the reference grating is not greater than the width of the alignment mark.

Example two

Please refer to Figure 12, another embodiment of the present invention provides an optical alignment device. Compared with the optical alignment device in the first embodiment shown in Figures 2 to 11B, the beam limiting element is used for Each light-passing area of the diffracted light beam above ±1 level passing through the narrow mark 20 (that is, the light-passing hole 320) is replaced by a rectangle with an oblong shape, wherein the length L1 of each light-passing area (that is, the light-passing hole 320) is long The length of the major axis of the ellipse, and the length L2 is the length of the minor axis of the oblong. This oblong light passing area can also achieve the same beneficial effects as the rectangular light passing area in the first embodiment.

In addition, since the other structures of the optical alignment device of this embodiment can be completely the same as the corresponding structures of the optical alignment device in the first embodiment shown in FIG. 2 to FIG. 11B, therefore, this embodiment compares these The structure will not be repeated.

The optical alignment device of this embodiment can effectively increase the energy of the scanning signal, and suppress the optical crosstalk between the mark and the mark, and the mark and the photoetching line.

It should be noted that the technical solution of the present invention does not limit the light-passing area of the diffracted light beam above ±1 level through the narrow mark 20 of the beam limiting element to be only rectangular or oblong, and may further have other shapes. For example, in other embodiments of the present invention, each light-passing area of the beam limiting element for diffracted light beams passing through the narrow mark 20 of ±1 level or more may be further diamond-shaped, wherein each light-passing area (that is, the light-passing area) The length L1 of the hole 320) is the length of the long diagonal of the rhombus, and the length L2 is the length of the short diagonal of the rhombus. Such a diamond-shaped light-transmitting area can also achieve the same beneficial effects as the rectangular light-transmitting area in the first embodiment.

Example three

Please refer to Figures 13 and 14, another embodiment of the present invention provides an optical alignment device. Compared with the optical alignment device in the first embodiment shown in Figures 2 to 11B, the alignment mark Unit 2 contains more than 4 narrow marks of diffraction grating type. These narrow marks are arranged in a two-dimensional cross structure along the X and Y directions of Figure 9A. At this time, in order to pass the ±1 level of these narrow marks The above diffracted light beams and the images formed by receiving these narrow marks, the arrangement of the clear regions of the diffracted light beams of ±1 level or more used in the beam limiting element to pass these narrow marks, and the reference grating in the reference mark unit 4 The arrangement needs to match the arrangement structure of all the narrow marks in the alignment mark unit 2. Specifically, the arrangement of each light-passing area (that is, the light-passing hole 320) of the beam limiting element is replaced by a one-dimensional cross structure. The arrangement of the reference grating in the reference mark unit 4 is replaced by a one-dimensional cross structure to meet the alignment requirements of a grating type alignment mark having a two-dimensional cross structure arrangement. That is, as shown in Fig. 13, when the beam limiting element is the diaphragm 32, all the light-passing holes 320 on the diaphragm 32 are arranged in two along the length direction and the width direction of a diffraction grating (ie, narrow mark). Dimensional cross structure. In this embodiment, the center of the cross structure has 4 small oblong light holes, these small light holes can be used to pass the corresponding narrow mark ±1 level diffracted light beam, other positions in the cross structure The light-passing hole is a large rectangular light-passing hole, which can be used for higher-order diffracted light beams passing through corresponding narrow marks. The beam limiting element 32 with the cross structure can not only meet the light transmission requirements of the corresponding diffracted beams of all narrow marks, but also help reduce the difficulty of manufacturing the beam limiting element 32. Since the reference grating in the reference mark unit 4 is used to receive the corresponding narrow mark image, its arrangement needs to be consistent with the arrangement of the light-passing holes 320 on the diaphragm 32. Please refer to Figure 14. The reference mark unit 4 includes a plurality of A reference grating whose length extends along the length of a narrow mark (that is, a certain diffraction grating) (that is, an image used to receive a narrow mark in one direction) and a plurality of reference gratings whose length extends along the width direction of the narrow mark ( That is, for receiving an image of a narrow mark in another direction), all the reference gratings 42 in the reference mark unit 4 are arranged in a two-dimensional cross structure along the length and width directions of the narrow mark. The reference grating 42 in the center of the cross structure of the reference mark unit 4 can be arranged in a staggered manner so as to be able to receive a narrow mark image at a corresponding position.

In addition, since the other structures of the optical alignment device of this embodiment can be completely the same as the corresponding structures of the optical alignment device in the first embodiment shown in FIGS. 2 to 11B, this embodiment has The structure will not be repeated.

The optical alignment device of this embodiment can meet the alignment requirements of more than four alignment marks arranged in a two-dimensional cross structure, and can effectively increase the scanning signal energy of the alignment marks, and suppress the alignment marks and adjacent marks. , The light crosstalk between the alignment mark and the adjacent lithography lines improves the alignment accuracy.

It should be noted that, in the technical solution of the present invention, the number of alignment marks in the alignment mark unit is not limited, and these alignment marks may all consist of narrow marks, or at least one narrow mark and at least one wide mark. The two-dimensional structure in which the plurality of alignment marks in the alignment mark unit are arranged is not limited to the cross structure, and can be other structures, such as "品" structure, "∟" structure, etc., at this time, in order to The diffracted light beam of ±1 level or more that can pass these alignment marks and the image formed by receiving these alignment marks, the beam limiting element is used to pass the alignment marks of the diffracted light beam of ±1 level or more. The arrangement of the regions and the arrangement of the reference gratings in the reference mark unit 4 need to match the arrangement structure of these alignment marks in the alignment mark unit 2. And in order to be compatible with the alignment scan of the narrow mark, and to effectively increase the scanning signal energy of the narrow mark, and to suppress the light crosstalk between the narrow mark and other marks, the narrow mark and the lithography line, further requirements: The L1/L2 of the pass area of the diffracted light beam passing through the narrow mark 20 ±1 level or more is not less than the narrow mark's aspect ratio L/W, and the beam adjustment elements 33a, 33b are used to adjust the narrow mark ±2 level or more The effective beam adjustment area L3/L4 of the diffracted beam is not less than the narrow mark's aspect ratio L/W, and the width of the reference grating is not less than the narrow mark's width W.

Example four

This embodiment provides a photolithography system, which includes a mask table for carrying a mask plate, a work table for carrying a silicon wafer, and the optical alignment device of the present invention. The alignment mark of the optical alignment device can be set on the mask or the workbench to realize the alignment of the mask, and can be further set on the silicon wafer or the workbench for the alignment of the silicon wafer.

The photolithography system of the present invention adopts the optical alignment device of the present invention to realize mask alignment and/or silicon wafer alignment, so the alignment effect can be improved, and the overprinting accuracy and lithography effect of photolithography can be improved. .

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. Those with ordinary knowledge in the field of the present invention can make various modifications and changes to the invention based on the content disclosed above without departing from the spirit and scope of the present invention. . In this way, if these modifications and changes of the present invention fall within the scope of the patent application of the present invention and the equivalent technology, the present invention is also intended to include these modifications and changes.

100: Illumination spot 101, 20: narrow mark 1: Light source lighting unit 10: Reflector 2: Alignment mark unit 21: wide mark 20a, 20b, 21a, 21b: image 3: imaging unit 31: The first lens 32: diaphragm (beam limiting element) 320: Clear hole 33a, 33b: beam adjustment element 330: Effective beam adjustment area 34: second lens 4: Reference mark unit 41a, 41b, 42: Reference grating 5: Non-alignment mark 6: Lithography lines q(+1), q(-1): first-order diffracted beam q(+2), q(-2): secondary diffracted beam L: Length of narrow mark 101 W: width of narrow mark 101 L1: The length of the light-passing hole corresponding to the diffracted light in the width direction of the narrow mark (the length of the light-passing area extending in the width direction of the alignment mark) L2: The length of the light hole corresponding to the diffracted beam in the length direction of the narrow mark (the length of the light passing area extending along the length of the alignment mark) L3: The length of the effective beam adjustment area of the beam adjustment element corresponding to the diffracted beam in the width direction of the narrow mark (the length of the effective beam adjustment area extending along the width direction of the alignment mark) L4: The length of the effective adjustment area of the beam adjustment element corresponding to the diffracted beam in the length direction of the narrow mark (the length of the effective beam adjustment area extending along the length of the alignment mark) W1: the width of the reference grating S: length of reference grating s1, s2, s3, s4: the diameter of the diffraction spot

Figure 1 is a schematic diagram of the relationship between a narrow mark and an illumination spot. Fig. 2 is a schematic structural diagram of an optical alignment device according to an embodiment of the present invention. Figure 3 is a schematic diagram of the diaphragm structure of an embodiment of the present invention. FIG. 4A is a schematic diagram of the size of a beam adjusting element according to an embodiment of the present invention. FIG. 4B is a schematic diagram of the structure of a beam adjusting element according to an embodiment of the present invention. FIG. 5 is a schematic diagram of the structure of a reference grating according to an embodiment of the present invention. Fig. 6 is a schematic diagram of the diameters s1, s2, and s3 of the first and second minima of the diffraction spot in the width direction of the narrow mark according to an embodiment of the present invention. FIG. 7 is a schematic diagram of the diameter s4 of the left and right first minima of the first-order diffraction spot in the length direction of the narrow mark according to an embodiment of the present invention. FIG. 8 is a structural diagram of an alignment mark unit including adjacent narrow marks and wide marks according to an embodiment of the present invention. Figure 9A is a schematic diagram of the imaging situation of the alignment mark unit shown in Figure 8 after passing through the imaging unit when L1/L2 and L3/L4 are equal to 1.34. Figure 9B is the energy distribution curve corresponding to the imaging situation shown in Figure 9A. Figure 10A is a schematic diagram of the imaging situation of the alignment mark unit shown in Figure 8 after passing through the imaging unit when L1/L2 and L3/L4 are equal to 4. Figure 10B is the energy distribution curve corresponding to the imaging situation shown in Figure 10A. FIG. 11A is a schematic diagram of scanning of a narrow mark and a reference grating when the width of the reference grating is greater than the width of the narrow mark in an embodiment of the present invention. FIG. 11B is a schematic diagram of scanning of a narrow mark and a reference grating when the width of the reference grating is less than or equal to the width of the narrow mark in another embodiment of the present invention. Fig. 12 is a schematic diagram of the structure of a diaphragm according to another embodiment of the present invention. Fig. 13 is a schematic diagram of the structure of a diaphragm according to another embodiment of the present invention. Fig. 14 is a schematic diagram of the structure of a reference grating matched with the diaphragm shown in Fig. 13.

1: Light source lighting unit

10: Reflector

2: Alignment mark unit

20: narrow mark

3: imaging unit

31: The first lens

32: diaphragm (beam limiting element)

320: Clear hole

33a, 33b: beam adjustment element

34: second lens

4: Reference mark unit

41a, 41b: Reference grating

q(+1), q(-1): first-order diffracted beam

q(+2), q(-2): secondary diffracted beam

Claims (15)

An optical alignment device includes a light source lighting unit, an alignment mark unit, an imaging unit, and a reference mark unit arranged in sequence along an optical path, wherein the alignment mark unit includes at least one alignment mark, and the reference mark The unit includes at least one reference grating corresponding to the alignment mark, the light source illuminating unit is used for emitting an illumination beam and transmitting it to the alignment mark, and the imaging unit is used for imaging the alignment mark on the reference grating; wherein The imaging unit includes a beam limiting element for limiting the imaging range of the alignment mark and a beam adjusting element for adjusting the direction of the light beam output by the beam limiting element, which are arranged in sequence along the optical path. The ratio between the length of a light passing area of the alignment mark that extends along the width direction and the length direction of the alignment mark is not less than the aspect ratio of the alignment mark, and one of the beam adjustment elements corresponds to the alignment mark. The ratio between the length of the effective beam adjustment area extending along the width direction and the length direction of the alignment mark is not less than the aspect ratio of the alignment mark, and the width of the reference grating is not greater than the width of the alignment mark. The optical alignment device as described in the first item of the scope of patent application, wherein the width of the alignment mark is 40 μm or less. According to the optical alignment device described in item 1 or item 2 of the scope of patent application, the alignment mark is a diffraction grating. According to the optical alignment device described in item 1 of the scope of patent application, the light beam limiting element is a diaphragm, and the diaphragm has a plurality of light-passing holes as the light-passing area. The optical alignment device described in item 4 of the scope of patent application, wherein all the light-passing holes on the diaphragm are arranged in a one-dimensional structure along the length direction of the alignment mark, or Moreover, all the light-passing holes on the diaphragm are arranged in a two-dimensional cross structure along the length direction and the width direction of the alignment mark. According to the optical alignment device described in item 5 of the scope of patent application, when all the light-passing holes on the diaphragm are arranged in a one-dimensional structure, the reference mark unit includes the length extending along the length direction of the alignment mark. At least one reference grating, and when the reference mark unit includes a plurality of reference gratings, all the reference gratings are arranged along the length direction of the alignment mark to form a one-dimensional structure; when all the light-passing holes on the diaphragm are arranged in two In the case of a three-dimensional cross structure, the reference mark unit includes the plurality of reference gratings whose length extends along the length direction of the alignment mark and the plurality of reference gratings whose length extends along the width direction of the alignment mark. In the reference mark unit All the reference gratings are arranged in a two-dimensional cross structure along the length direction and the width direction of the alignment mark. According to the optical alignment device described in item 3 of the scope of patent application, the beam adjustment element includes a plurality of sub-components, and an effective beam adjustment area of all the plurality of sub-components is correspondingly provided in the beam limiting element except for passing through the winding The position of the light-passing area other than the ±1st-order diffracted beam of the radiation grating. According to the optical alignment device described in item 7 of the scope of patent application, the plurality of sub-components are wedge blocks or total reflection mirrors or half mirrors having the effective beam adjustment area. The optical alignment device according to item 7 of the scope of patent application, wherein the length of the light-transmitting area and the effective beam adjustment area extending in the width direction of the alignment mark is greater than the diffraction in the width direction of the alignment mark The diameter of the beam spot at the first minimum. The optical alignment device described in item 9 of the scope of patent application, wherein the light-passing area The length of the domain and the effective beam adjustment area extending along the length direction of the alignment mark is the diameter of the diffracted beam spot in the length direction of the alignment mark at the first minimum. The optical alignment device according to the first item of the scope of patent application, wherein the light source illumination unit includes a light source for emitting the illumination beam and a mirror for reflecting the illumination beam to the alignment mark. The optical alignment device according to the first item of the scope of patent application, wherein the imaging unit further includes a first lens and a second lens, and the first lens is arranged between the beam limiting element and the alignment mark. On the road, the second lens is arranged on the optical path between the beam adjusting element and the reference mark unit. The optical alignment device as described in item 1 of the scope of patent application, wherein the optical alignment device further includes a signal detection and processing unit for detecting an optical signal output by the reference grating, and according to The optical signal determines the position information of the alignment mark. A photolithography system includes a mask table for carrying a mask, a worktable for carrying a silicon wafer, and the optical alignment according to any one of items 1 to 13 of the scope of patent application Device. The lithography system according to item 14 of the scope of patent application, wherein the alignment mark of the optical alignment device is arranged on the mask plate or the silicon wafer or the workbench.

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