Height measurement system and lithography apparatus thereof
By using gratings and filtering components to filter diffracted beams in lithography machines, the limitations of measurement accuracy and ghosting caused by defocusing in lithography machines have been solved, achieving higher measurement accuracy and imaging clarity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SHENZHEN WENDING CORE POLYMER TECH CO LTD
- Filing Date
- 2025-06-09
- Publication Date
- 2026-06-12
Smart Images
Figure CN224354710U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of lithography technology, and in particular to a height measurement system and its lithography equipment. Background Technology
[0002] During the operation of a lithography machine, there is always a high requirement for the accuracy of the wafer's height and surface shape. Therefore, a height measurement system is set up to detect the height and surface shape of the wafer. When the height measurement system is working, it can image the mark onto the wafer surface, and then use an imaging system to image it into a camera. When the wafer height changes, it will cause the position of the mark in the camera to change. Furthermore, through image recognition algorithms, the position of the mark in the camera can be identified, thereby deducing the height of the wafer.
[0003] However, conventional height measurement systems have two problems. First, due to space constraints, the size of optical lenses is limited, resulting in limited contrast of the measurement marks and affecting measurement accuracy. Second, when the object being measured rises, it can cause defocusing, leading to ghosting. Utility Model Content
[0004] Embodiments of this application provide a height measurement system and its lithography equipment, which can filter diffracted light that affects measurement accuracy, thereby improving measurement accuracy.
[0005] In a first aspect, embodiments of this application provide a height measurement system for detecting the wafer height and surface shape of a lithography machine, the height measurement system comprising:
[0006] A grating element is used to pass a light source to be tested, wherein the light source to be tested forms a diffracted beam with different diffraction orders distributed sequentially through the grating element;
[0007] An imaging component is disposed on one side of the grating that forms the diffraction beam. The imaging component is used to converge the diffraction beams of different diffraction orders to image the light source to be detected onto a specific position. The wafer is placed in the optical path within the imaging component.
[0008] A filtering component is disposed on the side of the imaging component near the grating or in the optical path within the imaging component; the filtering component is used to filter at least one diffraction order of diffracted light in the diffraction beam.
[0009] A sensor for receiving a diffracted beam filtered by the filtering assembly.
[0010] In some embodiments, the imaging component further includes:
[0011] A mirror assembly for reflecting the diffracted beam; the mirror assembly includes at least one mirror, and the filter assembly is disposed in the optical path of the diffracted beam after being reflected by the mirror.
[0012] In some embodiments, the mirror assembly includes a plurality of mirrors arranged sequentially, the plurality of mirrors being able to reflect the diffracted beam multiple times to converge the width of the diffracted beam.
[0013] In some embodiments, the reflector is one of a plane mirror, a concave mirror, and a convex mirror.
[0014] In some embodiments, the reflector assembly includes a first reflector, a second reflector, and a third reflector arranged sequentially; the diffracted beam is reflected by the first reflector to the second reflector, and then reflected by the second reflector to the third reflector;
[0015] Wherein, the first and third reflectors are concave mirrors, and the second reflector is a convex mirror, so that the light path reflected from the first reflector to the second reflector and the light path reflected from the second reflector to the third reflector at least partially overlap, and the filter assembly is disposed in the overlapping light path.
[0016] In some embodiments, the filtering component includes:
[0017] The mounting component has at least one through groove;
[0018] At least one aperture element is disposed within the slot, and at least one aperture element is disposed in a one-to-one correspondence with at least one slot. The at least one aperture element is parallel to each other. When the aperture element is placed in the optical path, it can filter a certain order of diffracted light in the diffracted beam.
[0019] The mounting component is movable relative to the reflector, and the direction of movement of the mounting component is tangent to the path of the optical path, so that a certain aperture component is placed in the optical path, thereby filtering diffracted light of different orders in the diffracted beam.
[0020] In some embodiments, the filtering component includes:
[0021] A first movable element is movable relative to the reflector, and the direction of movement of the first movable element is tangent to the path of the optical path; when the first movable element is placed in the optical path, it can block or reflect the diffracted light near the edge order in the diffracted beam.
[0022] The second movable member is movable relative to the reflector, and the direction of movement of the second movable member is tangent to the path of the optical path; when the second movable member is placed in the optical path, it can block or reflect the diffracted light near the central order in the diffracted beam.
[0023] A driving element, used to drive the first moving element and / or the second moving element to move;
[0024] The driving member moves by driving the first moving member and / or the second moving member so that the filtering component can filter at least one order of diffracted light in the diffracted beam.
[0025] In some embodiments, the filtering component includes:
[0026] A liquid crystal device, wherein the liquid crystal device is placed in the optical path;
[0027] An adjustment element is used to control the liquid crystal device to adjust the beam polarization state of the diffracted beam, thereby filtering at least one order of diffracted light in the diffracted beam.
[0028] In some embodiments, the filtering component includes:
[0029] A color-changing component, wherein the color-changing component comprises a plurality of color-changing layers arranged sequentially from the outside to the inside;
[0030] A control element that filters at least one order of diffracted light in the diffracted beam by controlling the colors of different color-changing layers.
[0031] Secondly, embodiments of this application provide a lithography machine, the lithography machine comprising:
[0032] A support platform, which can support wafers;
[0033] A height measurement system, wherein the height measurement system is any one of the height measurement systems described above.
[0034] The beneficial effects of this application are: this application diffracts the light beam through a grating device and achieves imaging through the cooperation of an imaging component and a sensing device. In particular, the filtering component filters out a certain order of diffracted light in the diffracted beam, thereby reducing defocus and ghosting phenomena and improving measurement accuracy. Attached Figure Description
[0035] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0036] Figure 1 This is a schematic diagram of a height measurement system according to an embodiment of this application;
[0037] Figure 2 This is a schematic diagram of a height measurement system according to another embodiment of this application;
[0038] Figure 3 This is a schematic diagram of a height measurement system according to yet another embodiment of this application;
[0039] Figure 4 This is a schematic diagram of the structure of a filtering component according to an embodiment of this application;
[0040] Figure 5 This is a schematic diagram of the filter component structure according to another embodiment of this application;
[0041] Figure 6 This is a schematic diagram of the structure of a filtering component according to another embodiment of this application;
[0042] Figure 7 This is a schematic diagram of the structure of a filtering component according to another embodiment of this application;
[0043] Figure 8 This is a schematic diagram of the structure of a filtering component according to another embodiment of this application.
[0044] Explanation of reference numerals in the attached drawings: 1000-Height measurement system; 10-Raster component; 20-Filter component; 30-Sensor; 30-Imaging component; 30-1-Reflector component; 40-Sensor; 50-Object to be measured; 300 Reflector; 301-First reflector; 302-Second reflector; 303-Third reflector; 304-Fourth reflector; 305-Fifth reflector; 306-Sixth reflector; 21-Mounting component; 211-Gate; 22-Aperture component; 23-First moving component; 24-Second moving component; 25-LCD component; 26-Adjusting component; 261-Polarizer; 262-Analyzer; 27-Color changing component; 271-Color changing layer; 28-Control component. Detailed Implementation
[0045] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.
[0046] Please refer to Figure 1One embodiment of this application provides a height measurement system for detecting the wafer height and surface shape of a lithography machine. The height measurement system 1000 includes:
[0047] The grating element 10 is used to pass through the light source to be tested, and the light source to be tested forms a diffracted beam with different diffraction orders distributed sequentially through the grating element 10 (please refer to the dashed lines in the various figures).
[0048] An imaging component 30 is disposed on one side of the grating 10 that forms the diffraction beam. The imaging component 30 is used to converge diffraction beams of different diffraction orders to image the light source to be detected onto a specific position. The wafer is placed in the optical path within the imaging component 30.
[0049] The filter assembly 20 is disposed on the side of the imaging assembly 30 near the grating member 10 or in the optical path within the imaging assembly 30; the filter assembly 20 is used to filter at least one order of diffracted light in the diffracted beam.
[0050] The sensor 40 is used to receive the diffracted beam filtered by the filter assembly 20.
[0051] In this embodiment, the grating 10 is used to diffract the incident light beam, forming a diffracted beam with different diffraction orders distributed sequentially. The beam at the center of the diffracted beam is the 0th order, the beam to the left of the 0th order is called the -n order, and the beam to the right of the 0th order is called the -n order. The diffracted beam facilitates filtering by the subsequent filtering component 20. In a conventional height measurement system 1000, when the measured object rises, it causes defocusing. Because the +n and -n order positions are located on either side of the 0th order, ghosting occurs.
[0052] In this embodiment, the imaging component 30 can converge different diffraction order sub-beams from the grating element 10 to image the light source to be tested in the grating element 10 to a specific position. In the imaging component 30, the optical path passes through the object under test 50. When the height of the object under test 50 changes, the imaging position changes. In this way, the height and surface shape of the object under test 50 can be detected. For example, when a height change occurs on a certain part of the surface of the object under test 50 (e.g., unevenness), the surface shape of that surface can be displayed accordingly during imaging. In one embodiment, the object under test 50 is a wafer.
[0053] In this embodiment, based on the reasons for ghosting caused by the diffracted beam, at least one order of diffracted light in the diffracted beam can be selectively filtered, thereby improving the accuracy of imaging and thus improving measurement precision. Please refer to... Figure 1The filter component 20 can be located on the side of the imaging component 30 near the grating component 10 to filter in the optical path of its diffraction beam, or it can be located in the optical path within the imaging component 30 to filter in the optical path of its diffraction beam. Of course, it can also be located in both of the above positions at the same time.
[0054] In this embodiment, the sensor 40 is used to receive the diffracted beam filtered by the filter assembly 20, thereby achieving accurate imaging of the final wafer height.
[0055] Please refer to Figure 2 and Figure 3 In one embodiment, the imaging component 30 includes:
[0056] The mirror assembly 30-1 is used to reflect the diffracted beam; the mirror assembly 30-1 includes at least one mirror 300, and the filter assembly 20 is disposed in the optical path of the diffracted beam after being reflected by the mirror 300.
[0057] In this embodiment, the mirror assembly 30-1 can reflect the diffracted beam to form an imaging system that can image the wafer in a camera. The mirror assembly 30-1 is provided with at least one mirror 300, which can reflect the diffracted beam at least once. At this time, the filter assembly 20 can be placed in the optical path of the diffracted beam after being reflected by the mirror 300, that is, placed on the side close to the mirror assembly 30-1, or placed among multiple mirrors 300.
[0058] In one embodiment, the imaging component 30 may also be an imaging method other than the mirror system, such as refraction, diffraction, etc. This application only describes the structure of reflection imaging by specific example, while other imaging methods can adopt the relevant structures in the prior art, which will not be elaborated here.
[0059] Please refer to Figure 2 and Figure 3 In one embodiment, the mirror assembly 30-1 includes a plurality of mirrors 300 arranged sequentially, which can reflect the diffracted beam multiple times to converge the width of the diffracted beam.
[0060] In this embodiment, multiple reflectors 300 are further provided, which can form a symmetrical imaging system to aid in camera imaging. Furthermore, by adjusting the shape of the reflectors 300 during multiple reflections of the diffracted beam, the width of the diffracted beam can be reduced. Since the diffracted beam formed after diffraction by the grating 10 is too divergent, its width may be excessively wide. The imaging optical lens, limited by space and its own size, results in insufficiently sharp image edges. Therefore, by providing multiple reflectors 300 that can reduce the width of the diffracted beam, when the filter assembly 20 is placed in the optical path of the reduced diffracted beam, the width of the diffracted beam can be reduced, resulting in a clearer image.
[0061] Please refer to Figure 2 and Figure 3 In one embodiment, the reflector 300 is one of a plane mirror, a concave mirror, and a convex mirror.
[0062] In this embodiment, the reflector 300 can be adjusted to the type of reflector 300 described above according to the actual imaging size requirements, and the concave and convex curvatures of the concave and convex mirrors can be further controlled to further precisely control the imaging accuracy.
[0063] Please refer to Figure 2 and Figure 3 In one embodiment, the reflector assembly 30-1 includes a first reflector 301, a second reflector 302 and a third reflector 303 arranged sequentially; the diffracted beam is reflected by the first reflector 301 to the second reflector 302, and then reflected by the second reflector 302 to the third reflector 303.
[0064] Among them, the first reflector 301 and the third reflector 303 are concave mirrors, and the second reflector 302 is a convex mirror, so that the light path reflected from the first reflector 301 to the second reflector 302 and the light path reflected from the second reflector 302 to the third reflector 303 at least partially overlap, and the filter component 20 is disposed in the overlapping light path.
[0065] In this embodiment, the specific shape and structure of at least a portion of the reflectors 300 in the reflector assembly 30-1, as well as the specific placement position of the filter assembly 20, are further defined to obtain the best filtering effect.
[0066] In this embodiment, a first reflecting mirror 301 is configured as a concave mirror, a second reflecting mirror 302 is configured as a convex mirror, and a third reflecting mirror 303 is configured as a concave mirror. The first reflecting mirror 301 and the third reflecting mirror 303 are symmetrically arranged with the center line of the second reflecting mirror 302 as the axis of symmetry. With this arrangement, the first reflecting mirror 301, the second reflecting mirror 302, and the third reflecting mirror 303 can form a curvature complementary design, making the overall space of the imaging system more compact. The converging effect of the concave mirror on the beam and the diverging effect of the convex mirror on the beam are combined to make the diffracted beam self-compensate the divergence angle in the three reflections. After the optical path is folded, a partially overlapping area is formed, which reduces the system volume and makes it more suitable for precision equipment with limited space.
[0067] In this embodiment, the filter component 20, through the above-described configuration, is placed in the overlapping optical path, simultaneously intercepting primary reflection residual stray light generated by diffraction at the edge of the first reflecting mirror 301 (concave mirror) and secondary reflection off-axis interference light scattered by the reflecting surface of the second reflecting mirror 302 (convex mirror). Furthermore, the symmetrical arrangement of the concave mirror (positive optical power) and the convex mirror (negative optical power) cancels out spherical aberration and field curvature, meeting the requirements of high-precision interferometric measurements. Additionally, the geometric constraints of the overlapping optical path passively collimate the defocused beam at the third concave mirror, extending the system's depth of focus and making it suitable for stable measurements under vibration environments.
[0068] In one embodiment, please refer to Figure 2 and Figure 3 The reflector assembly 30-1 includes a first reflector assembly, which comprises a fourth reflector 304, a first reflector 301, a second reflector 302, a third reflector 303, a fifth reflector 305, and a sixth reflector 306 arranged sequentially. The first reflector 301, the second reflector 302, and the third reflector 303 use the shape of the reflector 300 shown in the above embodiments, and the placement of the filter assembly 20 can be referred to the description in the above embodiments. Furthermore, the fourth reflector 304 and the fifth reflector 305 are plane mirrors.
[0069] Furthermore, in another embodiment, the reflector assembly 30-1 further includes a sixth reflector 306 and a second reflector assembly. The reflectors 300 of the second reflector assembly have the same composition and arrangement as those of the first reflector assembly, and the fifth reflector 300 is a plane mirror. The first and second reflector assemblies are symmetrically arranged about the centerline of the fifth reflector 300. Specifically, the diffracted beam reflected by the first reflector assembly can pass through the sixth reflector 306 and enter the second reflector assembly for further reflection. Similarly, the filter component 20 in this application can also be disposed in the second reflector assembly, which will not be elaborated further here.
[0070] Please refer to Figure 4In one embodiment, the filtering component 20 includes:
[0071] Mounting component 21, which has at least one through groove 211.
[0072] At least one aperture element 22 is disposed in the through slot 211, and at least one aperture element 22 is disposed in a one-to-one correspondence with at least one through slot 211. At least one aperture element 22 is parallel to each other. When the aperture element 22 is placed in the optical path, it can filter a certain order of diffracted light in the diffracted beam.
[0073] The mounting component 21 can move relative to the reflector 300. The direction of movement of the mounting component 21 is tangent to the path of the optical path, so that a certain aperture component 22 is placed in the optical path, thereby filtering diffracted light of different orders in the diffracted beam.
[0074] In this embodiment, the specific structure of the filter assembly 20 is further improved. The mounting member 21 is used to mount the aperture member 22, thereby driving at least one aperture member 22 to move. Furthermore, a through slot 211 is provided so that when the light beam is filtered by the aperture member 22, it can pass through the mounting member 21 and enter the next reflector 300. The aperture member 22 is used to filter light of a certain order. Specifically, the aperture member 22 can block light by using the geometry of its aperture diameter according to the different incident angles of different orders of light, thereby directly intercepting the light path of non-target orders.
[0075] In this embodiment, the moving direction of the mounting member 21 is tangent to the optical path, enabling the aperture member 22 to accurately filter. Specifically, only one aperture member 22 can be set to specifically intercept a certain order of light. In this case, when the mounting member 21 moves the aperture member 22 to place it in the optical path, the light beam passes through the aperture member 22 to filter out that order of light. When filtering is not required, or when it is necessary to turn off the filtering operation, the mounting member 21 moves the aperture member 22 away from the optical path so as not to affect the operation of the height measurement system 1000.
[0076] In this embodiment, multiple aperture elements 22 can be provided. In this case, different aperture elements 22 can filter different levels of light, that is, multiple levels are set, and different levels filter different levels of light. At this time, when the mounting member 21 moves the aperture element 22, different aperture elements 22 can be switched into the optical path, thereby switching the level and filtering different levels of light according to actual needs.
[0077] In one embodiment, three aperture stops 22 are provided, corresponding to three different settings. The aperture stop 22 corresponding to the first setting does not block light, meaning all orders of light in the beam pass through normally. This is suitable for situations where the measured object has minimal undulations and the grating mark contrast is sufficiently high. The aperture stop 22 corresponding to the second setting filters out positive or negative diffraction orders, thus avoiding ghosting. This filtering capability is suitable for situations requiring a large height measurement range. The aperture stop 22 corresponding to the third setting filters out negative and zero-order diffraction orders, thereby enhancing the grating edge contrast. The light intensity decreases, allowing for a longer camera exposure time. Specifically, the third setting filters out the zero-order diffraction order compared to the second setting, resulting in higher edge contrast and lower overall brightness. This is suitable for situations with poor contrast, a patterned measured object, sufficiently strong light source energy, or low measurement time requirements. In this embodiment, multiple aperture elements 22 are added to filter out diffracted light of different orders, which can adapt to different application scenarios for different levels.
[0078] Please refer to Figure 5 and Figure 6 In one embodiment, the filtering component 20 includes:
[0079] The first moving member 23 is movable relative to the reflector 300, and the moving direction of the first moving member 23 is tangent to the path of the optical path. When the first moving member 23 is placed in the optical path, it can block or reflect the diffracted light near the edge order in the diffracted beam.
[0080] The second moving member 24 is movable relative to the reflector 300, and the direction of movement of the second moving member 24 is tangent to the path of the optical path. When the second moving member 24 is placed in the optical path, it can block or reflect the diffracted light near the central order in the diffracted beam.
[0081] A driving element for driving the first moving element 23 and / or the second moving element 24 to move.
[0082] The driving member moves by driving the first moving member 23 and / or the second moving member 24 so that the filtering component 20 can filter at least one order of diffracted light in the diffracted beam.
[0083] In this embodiment, another improved structure for the filter component 20 is provided. Both the first moving member 23 and the second moving member 24 can directly block or reflect the light beam illuminating them. Based on this, the second moving member 24 is positioned corresponding to positive or negative diffracted light, and the first moving member 23 is positioned corresponding to zero-order diffracted light. It should be noted that in this embodiment, the number of moving members is not limited to two; multiple moving members can be set according to actual needs to correspond to more specific levels, thereby increasing the adjustable levels and filtering more specific levels. In this embodiment, the driving component can be a stepper motor.
[0084] The following explanation will focus on two moving parts, namely the first moving part 23 and the second moving part 24:
[0085] During operation, according to actual needs, the second moving part 24 is driven by the driving component to move closer to the optical path and be placed in the optical path, thereby blocking or reflecting the light of the positive or negative pole. Specifically, it is only necessary to block or reflect the light on the positive or negative pole side. This is because the positive and negative orders of the diffracted beam (such as +1 and -1 orders) are symmetrically distributed in space, but carry similar information. Therefore, by processing only the single-sided order, signal confusion caused by the superposition of symmetrical orders can be avoided, which significantly improves the accuracy and stability of the system.
[0086] During operation, the first moving part 23 can be moved closer to the optical path and placed in the optical path by the driving component according to actual needs, thereby blocking or reflecting zero-order light.
[0087] In one embodiment, to Figure 5 As shown, when the first moving part 23 and the second moving part 24 move up and down, they can be in the open (not blocking the light) and closed (blocking the light) states, respectively.
[0088] The switching logic between different speeds during operation is as follows:
[0089] 1. For the imaging system, when both the first moving element 23 and the second moving element 24 are positioned away from the optical path, i.e., when they are both fully open, the light beam can be completely received. This configuration is suitable for situations with low reflectivity and high requirements for the brightness of the marker imaging.
[0090] 2. When the imaging system has a high reflectivity and significant redundancy in light intensity, the first moving component 23 can be driven closer to the optical path and placed within it. In this case, the first moving component 23 is in the off state, while the second moving component 24 remains away from the optical path, i.e., in the on state. This filters out low-order diffracted light, significantly increasing the contrast of the marker edge relative to the background light. This setup achieves an effect equivalent to dark-field illumination. Using this method, the algorithm can identify higher contrast.
[0091] 3. When encountering significant wafer thickness variations leading to noticeable defocusing, ghosting can easily occur if both the first moving element 23 and the second moving element 24 are both away from the optical path and in the open state. Therefore, the second moving element 24 is driven to move closer to the optical path and thus into the optical path, i.e., the second moving element 24 is in the closed state, while the first moving element 23 remains away from the optical path, i.e., in the open state. This filters out negative order diffracted light, retaining only positive order light. This better adapts to situations with significant height variations.
[0092] Please refer to Figure 7 In one embodiment, the filtering component 20 includes:
[0093] Liquid crystal element 25 is placed in the optical path.
[0094] Adjustment element 26 is used to control liquid crystal element 25 to adjust the beam polarization state of the diffracted beam, thereby filtering at least one order of diffracted light in the diffracted beam.
[0095] In this embodiment, the same effect can be achieved by changing the spatial distribution of light intensity using liquid crystal, and the degree of freedom in filtering can be increased. Furthermore, the filter component 20 can also be replaced by a spatial light modulator (SLM).
[0096] In this embodiment, the liquid crystal element 25 and the adjustment element 26 are combined. The liquid crystal element 25 is controlled by the adjustment element 26, thereby adjusting the polarization state of the light beam. When the beam direction is adjusted to be perpendicular to the direction of the analyzer 262, it is equivalent to using an aperture to intercept the light beam. By changing the polarization distribution of the light beam in space, it means that diffracted light of different orders is filtered.
[0097] In one embodiment, the adjusting member 26 may be a polarization detection assembly. The polarization detection assembly includes a polarizer 261 and a polarizer 262, wherein the polarizer 261, the liquid crystal element 25, and the polarizer 262 are arranged coaxially in sequence.
[0098] In another embodiment, the adjustment element 26 may be an electro-optic modulator, which changes the refractive index of the liquid crystal by the applied electric field of the electro-optic modulator, thereby rapidly adjusting the polarization state of the light.
[0099] In this embodiment, the liquid crystal element 25 has two unique advantages compared to the aperture element 22:
[0100] 1. By adjusting the voltage, the polarization state of the beam can be continuously adjusted. This means that, unlike the adjustment of the aperture 22, which only has two states, on and off, for each diffraction order, this setting allows for dynamic and continuous adjustment of the proportion of beams at different diffraction orders. This increases the degree of freedom and adjustment range, allowing for a more precise search for the optimal configuration.
[0101] 2. For the filtering method using the aperture element 22, the aperture element 22 can only perform low-pass or high-pass filtering to a limited extent. During the screening process, different orders of diffracted light cannot be completely decoupled due to structural limitations. However, for liquid crystals, different orders of diffracted light can be controlled completely independently. For example, only odd-order diffracted light can be selected and retained, while even-order diffracted light can be removed. This also increases the degree of freedom in adjustment.
[0102] 3. Especially when there are structures on the wafer, the imaging system will also image the structures on the wafer into the camera, interfering with the detection marker signal. In this case, by selecting diffraction orders, it is equivalent to filtering the background noise, thereby more effectively reducing the impact of background noise.
[0103] Please refer to Figure 8 In one embodiment, the filtering component 20 includes:
[0104] The color-changing component 27 includes multiple color-changing layers 271 arranged sequentially from the outside to the inside.
[0105] The control element 28 filters at least one order of diffracted light in the diffracted beam by controlling the colors of different color-changing layers 271.
[0106] In this embodiment, the color-changing element 27 is provided with multiple color-changing layers 271 sequentially from the inside to the outside. Each color-changing layer 271 is filled with an electrochromic material. When an external voltage is applied, the electrochromic material undergoes an electrochemical oxidation-reduction reaction, which reversibly alters its optical properties (such as color, transparency, or reflectivity). This allows it to reflect or absorb light of a specific order in the beam, thereby filtering light of a certain order in the diffracted beam.
[0107] In this embodiment, the control unit 28 can independently control the voltage of the non-color-changing layer 271, thereby controlling the color change of the color-changing layer 271 to filter at least one order of diffracted light in the diffracted beam.
[0108] In another embodiment of this application, a lithography machine is provided, the lithography machine comprising:
[0109] The support platform can support the wafer.
[0110] The height measurement system 1000 is any one of the height measurement systems 1000 in the above embodiments.
[0111] In this embodiment, the support stage is used to support the wafer, which can be fixed and positioned by electrostatic clamping to prevent it from shifting. For the specific composition and control method of the height measurement system 1000, please refer to the description in the above embodiment.
[0112] In addition, the lithography machine equipment also includes an optical system, which comprises an illumination section and an objective lens section, capable of determining resolution and image quality. Furthermore, the lithography machine equipment also includes a motion control section, which includes structures such as a mask stage and a wafer stage, capable of supporting the wafer and mask to ensure overlay accuracy. In one embodiment, the structure of the lithography machine equipment can also utilize existing technology structures, which will not be elaborated upon here.
[0113] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.
Claims
1. A height measurement system for detecting wafer height and surface shape in a lithography machine, characterized in that, The height measurement system includes: A grating element is used to pass a light source to be tested, wherein the light source to be tested forms a diffracted beam with different diffraction orders distributed sequentially through the grating element; An imaging component is disposed on one side of the grating that forms the diffraction beam. The imaging component is used to converge the diffraction beams of different diffraction orders to image the light source to be detected onto a specific position. The wafer is placed in the optical path within the imaging component. A filtering component is disposed on the side of the imaging component near the grating or in the optical path within the imaging component; the filtering component is used to filter at least one diffraction order of diffracted light in the diffraction beam. A sensor for receiving a diffracted beam filtered by the filtering assembly.
2. The height measurement system according to claim 1, characterized in that, The imaging component includes: A mirror assembly for reflecting the diffracted beam; the mirror assembly includes at least one mirror, and the filter assembly is disposed in the optical path of the diffracted beam after being reflected by the mirror.
3. The height measurement system according to claim 2, characterized in that, The mirror assembly includes a plurality of mirrors arranged in sequence, which can reflect the diffracted beam multiple times to converge the width of the diffracted beam.
4. The height measurement system according to claim 3, characterized in that, The reflecting mirror is one of a plane mirror, a concave mirror, and a convex mirror.
5. The height measurement system according to claim 4, characterized in that, The reflector assembly includes a first reflector, a second reflector, and a third reflector arranged sequentially; the diffracted beam is reflected by the first reflector to the second reflector, and then reflected by the second reflector to the third reflector; Wherein, the first and third reflectors are concave mirrors, and the second reflector is a convex mirror, so that the light path reflected from the first reflector to the second reflector and the light path reflected from the second reflector to the third reflector at least partially overlap, and the filter assembly is disposed in the overlapping light path.
6. The height measurement system according to any one of claims 2-5, characterized in that, The filtering component includes: The mounting component has at least one through groove; At least one aperture element is disposed within the slot, and at least one aperture element is disposed in a one-to-one correspondence with at least one slot. The at least one aperture element is parallel to each other. When the aperture element is placed in the optical path, it can filter a certain order of diffracted light in the diffracted beam. The mounting component is movable relative to the reflector, and the direction of movement of the mounting component is tangent to the path of the optical path, so that a certain aperture component is placed in the optical path, thereby filtering diffracted light of different orders in the diffracted beam.
7. The height measurement system according to any one of claims 2-5, characterized in that, The filtering component includes: A first movable element is movable relative to the reflector, and the direction of movement of the first movable element is tangent to the path of the optical path; when the first movable element is placed in the optical path, it can block or reflect the diffracted light near the edge order in the diffracted beam. The second movable member is movable relative to the reflector, and the direction of movement of the second movable member is tangent to the path of the optical path; when the second movable member is placed in the optical path, it can block or reflect the diffracted light near the central order in the diffracted beam. A driving element, used to drive the first moving element and / or the second moving element to move; The driving member moves by driving the first moving member and / or the second moving member so that the filtering component can filter at least one order of diffracted light in the diffracted beam.
8. The height measurement system according to any one of claims 2-5, characterized in that, The filtering component includes: A liquid crystal device, wherein the liquid crystal device is placed in the optical path; An adjustment element is used to control the liquid crystal device to adjust the beam polarization state of the diffracted beam, thereby filtering at least one order of diffracted light in the diffracted beam.
9. The height measurement system according to any one of claims 2-5, characterized in that, The filtering component includes: A color-changing component, wherein the color-changing component comprises a plurality of color-changing layers arranged sequentially from the outside to the inside; A control element that filters at least one order of diffracted light in the diffracted beam by controlling the colors of different color-changing layers.
10. A lithography machine, characterized in that, The lithography equipment includes: A support platform, which can support wafers; A height measurement system, wherein the height measurement system is the height measurement system described in any one of claims 1-9.