A stepper photolithography machine, its working method and a pattern alignment device

Abstract

The application discloses a step-by-step photoetching machine, a photoetching pattern alignment device thereof and a working method. A plurality of three-dimensional marks are arranged on a wafer, which are used as coordinate presets for positioning the wafer surface; the three-dimensional marks are measured by using a needle-point sensing head sensing technology to obtain the sub-nanometer precision coordinates of the wafer surface; then the wafer workbench is moved; the new coordinates of the three-dimensional marks after the wafer workbench is moved are measured and compared with the same three-dimensional nanometer coordinates before the wafer workbench is moved to obtain the wafer area position coordinate error value. The coordinate error is compensated by moving the exposure beam generating device and the relative position of the wafer area by using the closed-loop control principle, and the relative coordinate position is re-accurately aligned. The application can be applied to the deep ultraviolet and extreme ultraviolet optical photoetching machine using a mask plate, and can also be applied to the sub-nanometer wafer area or the horizontal and vertical alignment splicing of the writing field of the electron beam / photon beam direct writing photoetching machine.

Description

Technical Field

[0001] The present invention relates to the technical field of photolithography, in particular to the technical field of overlay alignment and positioning of photolithography patterns. Background Art

[0002] Advances in microelectronics and optoelectronics have led to rapid growth in integrated circuit chips and integrated optical chips. These industries have become the foundation for core components and chips in modern computers, display screens, and even the entire information industry. Currently, the technology node of the modern chip industry has reached 5 nanometers or even smaller.

[0003] The manufacture of micro- and nano-devices like chips relies on lithography. Lithography encompasses conventional optical lithography, deep ultraviolet / extreme ultraviolet lithography, electron beam lithography, and ion beam lithography. These key lithography techniques enable the production of fine lithographic patterns and even the creation of a wide range of micro- and nano-device structures, such as integrated circuits and optoelectronic integrated chips.

[0004] Existing optical lithography systems, including deep ultraviolet (DUV) and extreme ultraviolet (EUV) lithography systems, are widely used in industrial chip manufacturing and MEMS manufacturing. As wafers become larger, 12-inch diameter wafers are now common, and the trend toward larger wafer sizes is ongoing. No system can expose the entire wafer at once. The typical approach is to expose individual die areas (DIE) sequentially. After exposure of one die area, the wafer is moved to the next die area using a wafer stage, where overlay alignment is performed before exposure. Alignment here means that the pattern being exposed must be vertically aligned with the existing pattern on the die area (i.e., overlay alignment) before exposure can proceed. The accuracy of alignment, or overlay accuracy, must be at least several times greater than the minimum dimension of the circuit pattern on the die area, currently around 5-10 nanometers. Multi-beam electron beam lithography systems used for mask production, such as the MBMW-101 series from Austrian high-tech company IMS, can be used for mask production at the 5-nanometer node, with overlay accuracy below 5 nanometers. ASML, a Dutch company specializing in extreme ultraviolet (EUV) lithography, manufactures its TWINSCAN 3400B and 4300C lithography systems for the 5nm technology node, achieving overlay accuracies of 2.5nm and 1.5nm, respectively. Chip structures will likely scale to 3nm in the future. Therefore, the overlay alignment accuracy of the lithography system used to expose the wafer area must be 1nm or less. Currently, no technology exists to achieve this high overlay accuracy requirement, necessitating the development of new technologies.

[0005] The difficulty in achieving the extremely high wafer stage positioning accuracy requirement stems from a characteristic of the photolithography process, which is also a significant drawback: a photosensitive layer is applied to the wafer before exposure. In photolithography, the lithographic pattern is transferred to the photosensitive layer through exposure, and then the lithographic pattern on the photosensitive layer is transferred to the wafer through an etching process. It is important to note that the photosensitive layer on the wafer covers the top surface. Because it is sensitive to light, the electron beam or photon beam cannot penetrate the photosensitive layer to observe the surface before exposure (i.e., exposure), and cannot penetrate the photosensitive layer to obtain the wafer pattern underneath. Therefore, the pattern to be exposed cannot be aligned with the pattern on the wafer below the photosensitive layer. In other words, the photolithography machine can only operate "blindly," moving the wafer stage and then exposing the beam "blindly." This leads to inaccurate wafer exposure positioning and large overlay errors. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a photolithography pattern alignment device, which is located in a photolithography machine body and includes:

[0007] A wafer workbench for carrying a wafer to be processed, the wafer comprising a plurality of wafer regions and an off-site region surrounding the wafer regions, a photosensitive layer disposed on a surface of the wafer, the photosensitive layer being provided with a three-dimensional mark, the three-dimensional mark having an area that is not on the same level as the upper surface of the photosensitive layer;

[0008] A nano-needle tip sensing device includes a needle tip sensing head, the needle tip sensing head is located above the photosensitive layer, and is used to move and scan within a scanning area and determine the coordinates of a three-dimensional mark within the scanning area;

[0009] an exposure beam generating device for providing an exposure beam required for exposing a wafer area and forming a projected exposure area on the photosensitive layer;

[0010] A displacement drive device is used to adjust the relative positions of the exposure beam generating device and the wafer workbench according to the three-dimensional mark coordinates measured by the needle tip sensor head, so that the projected exposure area is aligned with the wafer area to be exposed.

[0011] Optionally, the device also includes a computer control system, which is used to receive the three-dimensional mark coordinates measured by the nano-tip sensing device and compare them with the reference coordinates of the three-dimensional mark to obtain the difference between the two coordinates. The computer control system is used to transmit the difference to the displacement drive device and control the exposure beam generating device and / or the wafer workbench to move relative to each other to compensate for the difference.

[0012] Optionally, the reference coordinates are preset position coordinates of the three-dimensional mark. When the three-dimensional mark is located at the preset position, the wafer area to be exposed is aligned with the projection exposure area. The reference coordinates are pre-stored in the computer control system.

[0013] Optionally, the reference coordinates are the coordinates corresponding to the coordinates within the scanning area after the coordinates of the three-dimensional mark measured by the nano-tip sensing device before the exposure of the chip area are combined with the distance the wafer theoretically needs to move in order to align the next chip area to be exposed with the projection exposure area. The theoretical distances the wafer needs to move in the horizontal and vertical directions are pre-stored in the computer control system.

[0014] Optionally, the three-dimensional mark on the photosensitive layer includes a three-dimensional mark formed on the photosensitive layer corresponding to the underlying alignment mark arranged below the photosensitive layer and / or a three-dimensional stereoscopic pattern formed by radiation-induced modification of the photosensitive layer (IIRC) formed after the exposure beam is exposed on the surface of the photosensitive layer.

[0015] Optionally, the three-dimensional mark corresponding to the bottom layer alignment mark formed on the photosensitive layer is located in the wafer area or in an out-of-field area between adjacent wafer areas.

[0016] Optionally, the bottom layer alignment mark includes a mark produced on the surface of the wafer substrate before the wafer is exposed for the first time and / or a mark set under the photosensitive layer in a subsequent exposure process.

[0017] Optionally, the height of the three-dimensional mark is greater than the surface roughness of the photosensitive layer.

[0018] Optionally, the coordinates of the three-dimensional mark include the lateral position coordinates, longitudinal position coordinates and circumferential position coordinates of the wafer. The circumferential position coordinates of the three-dimensional mark refer to the coordinates of the three-dimensional mark in the circumferential direction, that is, the angular coordinates of the three-dimensional mark graphic in the circumferential direction.

[0019] Optionally, two or more three-dimensional marks are provided on the photosensitive layer.

[0020] Optionally, the three-dimensional mark has certain graphic features, and the graphic features include at least one point feature, and the point feature and the upper surface of the photosensitive layer are located in different horizontal planes.

[0021] Optionally, the graphic features further include ridge features connected to the dot features, and the ridge features and the upper surface of the photosensitive layer are not completely located in the same plane.

[0022] Optionally, the three-dimensional mark is a three-dimensional structure protruding from or recessed into the upper surface of the photosensitive layer.

[0023] Optionally, the three-dimensional structure is at least one of a conical structure, a polygonal prism structure, and a pyramidal structure.

[0024] Optionally, each wafer region corresponds to at least one three-dimensional marker, which is located in the wafer region or in an out-of-field region around the wafer region, and the reference coordinates of the three-dimensional marker are pre-stored in the computer control system.

[0025] Optionally, part of the wafer regions are not provided with corresponding three-dimensional markers, and the wafer regions are aligned with the projection exposure area according to the three-dimensional marker of the three-dimensional pattern in the wafer region of the previous completed exposure measured by the needle tip sensor head.

[0026] Optionally, the wafer regions not provided with corresponding three-dimensional markers are arranged at intervals with the wafer regions provided with corresponding three-dimensional markers.

[0027] Optionally, a positioning marker generating device is arranged on the exposure beam generating device, and the positioning marker generating device forms a three-dimensional positioning marker around the wafer region during exposure of the wafer region, and the needle tip sensor head positions and calibrates the position of the wafer region to be exposed according to the three-dimensional positioning marker.

[0028] Optionally, the height of the three-dimensional marker is less than or equal to 50 microns.

[0029] Optionally, the needle tip sensor head is one or a combination of active atomic force needle tip sensor head, laser reflection atomic force needle tip sensor head, tunnel electron probe sensor head, and nanoscale surface work function measurement sensor head.

[0030] Optionally, the needle tip sensor head measures the wafer surface structure in an atmospheric or vacuum environment, or measures the wafer surface structure by immersing the needle tip sensor head in a liquid in an immersion liquid environment.

[0031] Optionally, for immersion lithography, the three-dimensional marker is a three-dimensional marker in an immersion liquid environment, or the wafer region does not have a corresponding three-dimensional marker of an adjacent wafer region outside the exposure beam in an immersion liquid environment.

[0032] Optionally, the surface structure data of the three-dimensional marker measured by the needle tip sensor head is a mathematical convolution of the surface structure of the three-dimensional marker and the needle tip structure of the needle tip sensor head, and the needle tip structure is measured and calibrated before the needle tip sensor head measures the three-dimensional marker.

[0033] Optionally, the nanometer needle tip sensing device further comprises a micro-cantilever, one end of which is fixed and the other end of which is provided with the needle tip sensor head.

[0034] Optionally, the nano-tip sensing device includes one or more nano-tip sensing heads, and the nano-tip sensing heads are fixed on one side or both sides of the exposure beam generating device through the micro-cantilever.

[0035] Optionally, the exposure beam generating device includes a projection objective lens group arranged above the wafer, and the one or more needle tip sensor heads are fixed on one side or both sides of the projection objective lens group through micro cantilevers.

[0036] Optionally, the wafer workbench includes a moving part and a fixed part, and the needle tip sensor head is connected to the fixed part through the micro cantilever.

[0037] Optionally, the nano-tip sensor device includes two or more tip sensor heads, wherein one or more of the tip sensor heads are fixed on the fixed part of the wafer workbench, and one or more of the tip sensor heads are fixed on the side of the exposure beam generating device.

[0038] Optionally, the nano-tip sensing device includes two or more tip sensing heads, and several of the tip sensing heads are fixed to one side or both sides of the exposure beam generating device via a connecting piece, and the relative distance between the several tip sensing heads is fixed.

[0039] Optionally, the nano-tip sensing device includes three or more tip sensor heads, which are fixed to the fixed part of the wafer workbench and / or fixed to the exposure beam generating device through a connecting part. The tip sensor heads are located on different straight lines to determine whether the wafer is perpendicular to the exposure beam.

[0040] Optionally, each of the needle tip sensor heads tests the distance from the wafer surface or photosensitive layer surface corresponding to its position to the exposure beam generating device, determines whether the wafer and the exposure beam are perpendicular based on whether the measured distances are the same, and drives the wafer workbench through a computer control system to adjust until the wafer is perpendicular to the exposure beam.

[0041] Optionally, the nano-tip sensing device includes a plurality of needle tip sensing heads fixed by a connector, and the plurality of needle tip sensing heads are arranged in a row horizontally according to the distribution of the wafer area to form a horizontal needle tip sensing head array.

[0042] Optionally, at least one longitudinally distributed needle tip sensor head is provided at one end of the transverse needle tip sensor head array to form an L-shaped needle tip sensor head array.

[0043] Optionally, longitudinally distributed needle tip sensor heads are respectively provided at both ends of the transverse needle tip sensor head array to form a U-shaped needle tip sensor head array.

[0044] Optionally, the distance between two adjacent needle tip sensor heads is greater than or equal to the lateral width of a chip area.

[0045] Optionally, the displacement driving device includes a chip area switching driving device and a nano-displacement driving device.

[0046] Optionally, the wafer area switching drive device is connected to the moving part of the wafer workbench, and is used to drive the wafer areas to be exposed to be exposed under the projection exposure area in sequence.

[0047] Optionally, the moving part of the wafer workbench further includes a precision moving device, and the nano-displacement driving device is the precision moving device.

[0048] Optionally, the nano-displacement driving device is connected to the precision moving device of the exposure beam generating device and / or the wafer worktable, and is used to control the lateral and / or longitudinal and / or circumferential movement of the exposure beam generating device and / or the wafer worktable.

[0049] Optionally, the working principle of the nano-displacement driving device to drive the exposure beam generating device and / or the precision moving device to move is at least one of a piezoelectric principle, a voice coil driving principle or an electromagnetic driving principle.

[0050] Optionally, the exposure beam emitted by the exposure beam generating device is at least one of a light beam, an electron beam, an ion beam or an atomic beam.

[0051] Optionally, the exposure beam generating device is a light beam generating device, which includes a light source, a light gate, a beam deflector / reflector, a mask and a projection objective lens group, and the nano-displacement driving device is connected to at least one of the beam deflector / reflector, the mask and the projection objective lens group to adjust the position of the projection exposure area of ​​the light beam generating device.

[0052] Optionally, the at least one pinpoint sensor head is fixed on at least one side of the projection objective lens assembly.

[0053] Optionally, the light beam is a parallel light beam or a Gaussian light beam.

[0054] Optionally, the light beam shaping and focusing system may be composed of an optical lens or an optical reflector.

[0055] Optionally, the wafer includes a complete wafer, a partial wafer, or a non-wafer material requiring photolithography exposure processing.

[0056] Furthermore, the present invention also discloses a stepper lithography machine for repeatedly exposing multiple chip areas in a wafer, wherein the lithography pattern alignment device as described above is provided in the lithography machine.

[0057] Furthermore, the present invention also discloses a method for operating a stepper lithography machine, the method comprising:

[0058] A preparation step comprises providing at least one bottom layer alignment mark on a wafer and coating a photosensitive layer on the wafer to be processed, wherein the bottom layer alignment mark forms a corresponding three-dimensional mark on the photosensitive layer;

[0059] an alignment step, placing the wafer provided with the three-dimensional mark in the preparation step into the above-described lithography machine, disposing a projection objective lens group near the wafer in the lithography machine, the projection objective lens group corresponding to a projection exposure area on the wafer, driving the wafer worktable to place a first wafer area to be exposed under the projection objective lens group; using the needle tip sensor head to scan the photosensitive layer within a certain scanning area to obtain the position coordinates of the first three-dimensional mark, comparing the position coordinates of the first three-dimensional mark with the reference coordinates of the first three-dimensional mark to obtain the difference between the two position coordinates; and using the displacement drive device to adjust the relative position of the exposure beam generating device and the wafer worktable according to the difference between the two position coordinates, so that the projection exposure area is aligned with the first wafer area;

[0060] In the exposure step, the light beam generating device emits an exposure beam to the first chip area of ​​the wafer to achieve exposure of the first chip area.

[0061] Optionally, after completing the exposure of the first chip area, the second chip area is placed under the projection objective lens group, the needle tip sensor head scans the position coordinates of the first three-dimensional marker after movement and compares them with the reference coordinates of the first three-dimensional marker after movement to obtain the deviation of the two position coordinates, and the displacement drive device adjusts the relative positions of the exposure beam generating device and the wafer worktable according to the difference in the position coordinates, so that the projection exposure area is aligned with the second chip area, and the exposure of the second chip area is achieved.

[0062] Optionally, the reference coordinates of the first three-dimensional mark after movement are the position coordinates of the first three-dimensional mark when the first chip area is exposed, and are aligned with the projection exposure area to achieve the next chip area to be exposed, and the theoretical horizontal and vertical distances that the wafer needs to move are combined to form the corresponding coordinates in the scanning area.

[0063] Optionally, at least one of the pinpoint sensor heads is provided on both sides of the projection objective lens group, or a pinpoint sensor head is provided on one side of the projection objective lens group, and a scanning width of the pinpoint sensor head is greater than a width of a wafer area to be exposed.

[0064] Optionally, after completing the exposure of the first chip area, the second chip area is placed under the projection objective lens group, the needle tip sensor head scans the position coordinates of the second three-dimensional mark and compares them with the reference coordinates of the second three-dimensional mark to obtain the deviation of the two position coordinates, and the displacement drive device adjusts the relative position of the exposure beam generating device and the wafer workbench according to the difference in the position coordinates, so that the projection exposure area is aligned with the second chip area, and the exposure of the second chip area is realized, and the reference coordinates of the second three-dimensional mark are pre-stored in the computer control system.

[0065] Optionally, the first three-dimensional mark is arranged close to the first chip area, and / or the second three-dimensional mark is arranged close to the second chip area.

[0066] Optionally, after the exposure of the first chip area is completed, the second chip area is placed under the projection objective lens group, the needle tip sensor head scans the graphics and coordinates of the three-dimensional pattern formed on the photosensitive layer after the exposure of the first chip area and compares them with the preset graphics and coordinates of the three-dimensional pattern to obtain the difference between the positions of the two three-dimensional patterns, and the displacement drive device adjusts the relative positions of the exposure beam generating device and the wafer workbench according to the difference in the position coordinates, so that the projection exposure area is aligned with the second chip area, and the exposure of the second chip area is realized.

[0067] Optionally, the nano-tip sensing device is fixed on one side or both sides of the projection objective lens group, and is relatively fixed in position with respect to the projection objective lens group.

[0068] The lithography pattern alignment device of the present invention is suitable for lithography technologies such as deep ultraviolet and extreme ultraviolet lithography machines, such as ultraviolet stepper lithography machines. Its characteristic is that a light beam forms an exposure pattern through a mask, which is then irradiated onto a wafer coated with a photosensitive layer. Each time, one wafer area is aligned and exposed, another wafer area is aligned and exposed by moving the wafer worktable, and finally, all wafer areas on the wafer are exposed. Of course, the present invention is also applicable to lithography machines using electron beam or photon beam direct writing.

[0069] The present invention places three-dimensional markers on the wafer surface. A single measurement of the wafer fixes the coordinate relationship between these markers and each wafer region, allowing subsequent measurements of these markers to accurately locate the wafer region's coordinates. If the wafer is precisely temperature-controlled over a long period of time and does not deform due to thermal expansion or contraction, these coordinates can be accurately located down to the single-nanometer level.

[0070] The first measurement of the positions of these three-dimensional marks and the chip areas determines the relative deviation of the wafer with respect to the wafer table, specifically whether the wafer needs to be rotated when the wafer table moves to adjust the parallelism of the wafer table movement with the array of chip areas on the wafer.

[0071] Unlike electron beam lithography, which can observe and measure wafer surface patterns using scanning electron microscopes, photon beam lithography (deep ultraviolet and extreme ultraviolet lithography) cannot achieve nanometer-level resolution in wafer pattern measurement due to the wavelength of the exposure photons used. Therefore, photon beams cannot be used for alignment and positioning with dimensional accuracy of single nanometers or less. However, the technical solution of the present invention can achieve nanometer and sub-nanometer positioning accuracy in photon beam lithography.

[0072] The closer the 3D mark is to the wafer area being exposed, the higher the alignment accuracy for that wafer area. 3D marks can be placed between wafer areas or within wafer areas, a common practice for step-and-repeat lithography systems. If the 3D marks placed within the wafer area can be as small as a few nanometers to a few hundred nanometers, they will be very practical due to their minimal footprint. Even placing 3D marks within the wafer area will not affect wafer area yield.

[0073] The present invention adopts a measurement technology that can sense three-dimensional nanoscale structures, such as using a needle tip sensor head sensing technology to realize sub-nanometer three-dimensional morphology measurement technology (sub-nanometer atomic force three-dimensional morphology measurement technology), then the nanoscale three-dimensional mark can be measured by the needle tip sensor head sensing technology to play the role of nanoscale coordinates. The three-dimensional marks on the photosensitive layer and the wafer surface can be used as alignment marks. For example, by measuring the peak position or concave position of the three-dimensional mark, an accurate alignment coordinate can be determined. The concave-convex structure on the wafer surface generally causes the surface of the photosensitive layer covering it to follow and form a concave-convex structure, that is, the positioning can penetrate vertically, so that the surface covering the photosensitive layer can be measured due to its concave-convex structure and position. The needle tip sensor head sensing technology adopted by the present invention can enable optical measurement to achieve sub-nanometer measurement.

[0074] In addition to using the three-dimensional markings described above to position the wafer, the present invention can also locate wafer areas for exposure based on the characteristics of radiation-induced resist change (IIRC). Irradiation-induced resist change (IIRC) refers to changes in the chemical and / or physical properties of the photosensitive layer at the location of exposure by a photon beam, electron beam, or other particle beam. Chemical changes include chemical reactions on the surface of the photosensitive layer induced by the photon / electron beam, causing the irradiated portion of the photosensitive layer to change from an insoluble state to one that dissolves during development (positive resist), or from a dissolved state to one that becomes insoluble through exposure (negative resist). Photon / electron beam exposure can also cause physical changes in the photosensitive layer, including changes in minute geometric dimensions of the surface, such as swelling or shrinking at the subnanometer or nanometer scale to form a concave-convex structure. When the photon / electron beam exposure transfers the exposure pattern information to the photosensitive layer, changes in the concave-convex structure of the photosensitive layer occur. This deformation can be detected and sensed at the subnanometer scale using a needle-tip sensor head (a highly sensitive sensor head).

[0075] The advantages of the present invention are:

[0076] 1. Provide a new technology for lithography machines that can measure the actual position of wafer area patterns with sub-nanometer accuracy;

[0077] 2. Provide multiple methods and devices for correcting nanometer-level movement between the exposure photon beam / electron beam coordinate position relative to the wafer area / write field coordinate position;

[0078] 3. Provide an (extreme) ultraviolet optical lithography machine with ultra-high wafer area overlay alignment accuracy;

[0079] 4. Provide a method and device for combined lateral and longitudinal alignment stitching error correction and subsequent exposure of the chip area / write field in a photolithography machine based on a closed-loop control principle. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the description of the technical solution of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying any creative work, other implementation methods obtained based on the inventive concepts shown in these drawings all fall within the scope of protection of the present invention.

[0081] Figure 1 A schematic diagram of an alignment device for photolithographic patterns according to the present invention is shown.

[0082] Figure 2 A schematic structural diagram of a photolithography machine according to a specific embodiment is shown.

[0083] Figure 3 A schematic diagram showing the position of a three-dimensional mark on a wafer.

[0084] Figure 4A A schematic diagram of a surface protruding three-dimensional mark; Figure 4B A schematic diagram of a surface recessed three-dimensional mark; Figure 4C A schematic diagram of a surface concave-convex three-dimensional mark, Figure 4D A schematic diagram of a three-dimensional mark.

[0085] Figure 5A A schematic diagram of irradiation-induced expansion of a photosensitive layer; Figure 5B A schematic diagram of irradiation-induced contraction of a photosensitive layer.

[0086] Figure 6 A schematic diagram of a lithography machine structure according to another embodiment of the present application.

[0087] Figure 7 A schematic diagram of a lithography machine structure according to another embodiment of the present application.

[0088] Figure 8 A schematic diagram showing the correspondence between a plurality of needle tip sensing heads and wafer regions according to an embodiment of the present application.

[0089] Figure 9 A schematic diagram showing the correspondence between a needle tip sensing head and wafer regions according to another embodiment of the present application.

[0090] Figure 10 A schematic diagram showing the correspondence between a needle tip sensing head and wafer regions according to another embodiment of the present application. DETAILED DESCRIPTION

[0091] The inventive concept and technical solutions of the present application will be described in detail below with reference to the accompanying drawings.

[0092] In the field of step-and-repeat exposure lithography machines, after a wafer region is exposed, the wafer is moved to the next wafer region for overlay alignment by moving the wafer table, and then exposed. Currently, alignment of the lithography machine is mainly achieved by accurate positioning of the wafer table to align the wafer region on the wafer with the exposure area of the beam projection. This alignment can cause positioning errors caused by movement of the wafer table. Moreover, it cannot correct the alignment errors caused by beam deviation in time. The entire positioning process is an open-loop control state without coordinate measurement before positioning and without coordinate measurement after positioning. There is no real-time measurement of alignment errors and no feedback information using alignment errors. This error is generally several nanometers or even tens of nanometers.

[0093] The precision of the laser wafer stage can be obtained by high order processing of the light wavelength of the laser interference, and the precision can be several nanometers. The driving device of the wafer stage can be a piezoelectric driving mode or even a voice coil driving mode. The moving positioning precision can be sub-nanometer or even picometer. The problem is that the position measured by the laser interference is the distance of the optical path, and it is not necessarily the actual distance that the wafer stage needs to move. As long as there is a little temperature change around the wafer stage or the light beam, the change of air density and air pressure will cause the inconsistency between the optical path difference and the actual distance, so that the distance measured by the laser is not the actual distance that the wafer stage needs to move. Moreover, the multiple movements of the laser wafer stage will accumulate the error of each movement, thereby amplifying the error. The present inventors have found that it is very difficult to measure single-nanometer and sub-nanometer precision even if the most accurate laser interference correction mechanism is used, and even if the correction is successful, it is accidental.

[0094] In addition, it is found that some deep ultraviolet and extreme ultraviolet optical lithography machines have a laser interference positioning mechanism between the wafer and the exposure light beam, that is, a part of the lithography machine connected to the wafer side and the exposure light beam is formed, and the part is positioned by laser interference. This is a closed-loop control system. In the wafer area, a grating structure is arranged in the middle zone of the wafer area. Laser is emitted from the lithography machine part connected to the exposure light beam to the grating structure in the middle zone of the wafer area, and then returns to the lithography machine part connected to the exposure light beam, and forms interference with the emitted laser or double-grating interference with the grating on the side of the exposure light beam. The movement of the interference fringes corresponds to the relative movement between the wafer area and the exposure light beam. The positioning precision realized by this method is feasible in the order of 20 nanometers or even several nanometers. However, once it enters the nanometer or even sub-nanometer level positioning, the drift and jitter of the interference fringes will greatly affect the determination of the actual positioning.

[0095] Therefore, the present application discloses a technical scheme which can accurately position the wafer and align the wafer area to be exposed and the projection exposure area according to the positioning result. The technical scheme can find the positioning error of the wafer area, and then solve and eliminate the positioning error problem to realize sub-nanometer level alignment and overlay.

[0096] The embodiments of the present invention provide a device and method for sub-nanometer overlay alignment of an optical lithography machine, as well as application scenarios in lithography machine systems. The present invention uses the wafer worktable as a coarse positioning for overlay alignment of the chip area on the lithography machine wafer with the projection exposure area. The detailed overlay alignment is performed after measuring the positioning error and implementing error compensation. In the present invention, this subtle error compensation can be achieved by a sub-nanometer displacement drive device. The present invention solves the sub-nanometer displacement of the driving object and the alignment method to achieve a huge improvement in the sub-nanometer overlay alignment accuracy between the chip area on the wafer and the projection exposure area. The wafer includes a plurality of chip areas 120 and an out-of-field area 122 around the chip area. At least one bottom alignment mark is set on the wafer. A photosensitive layer 130 is set on the surface of the wafer. The bottom alignment mark forms a corresponding three-dimensional mark on the photosensitive layer. The three-dimensional mark has an area that is not on the same horizontal plane as the upper surface of the photosensitive layer. The three-dimensional mark described in the present invention includes a three-dimensional mark formed on the photosensitive layer by the bottom alignment mark pre-set on the wafer, and also includes a three-dimensional pattern three-dimensional mark formed on the photosensitive layer according to the characteristics of radiation-induced modification of the photosensitive layer.

[0097] Figure 1 A schematic diagram of a photolithography pattern alignment device according to the present invention is shown. The alignment device is located within a photolithography machine, which includes a wafer table 100 for supporting a wafer 110 to be processed. The photolithography machine according to the present invention is a stepper-type photolithography machine, which sequentially exposes different wafer regions by gradually moving the wafer table. A nanotip sensing device 90 is positioned above the wafer table. The nanotip sensing device includes at least one tip sensing head 91, which is located above the photosensitive layer. The tip sensing head moves within a scanning area to scan and determine the coordinates of three-dimensional marks within the area and / or three-dimensional patterns formed on the wafer area.

[0098] An exposure beam generating device 300 is arranged above the wafer, and the exposure beam generating device is used to provide the exposure beam required for exposing the wafer area, and the exposure beam forms a projected exposure area on the wafer; in addition, the alignment device of the present invention also includes a displacement drive device 400, which is used to adjust the relative position of the exposure beam generating device and the wafer workbench according to the three-dimensional mark coordinates measured by the nano-needle tip sensing device, so that the projected exposure area is aligned with the wafer area to be exposed.

[0099] Figure 1The illustrated lithography pattern alignment apparatus also includes a computer control system 200. The computer control system 200 is configured to receive the coordinates of the three-dimensional marker measured by the nanotip sensor and compare them with a reference coordinate to determine the displacement difference between the two coordinates in the lateral, longitudinal, or circumferential direction. The circumferential displacement difference between the two coordinates refers to the displacement difference of the three-dimensional marker in the circumferential direction. The computer control system is configured to transmit this displacement difference to the displacement drive 400, which causes the exposure beam generator and / or the wafer stage to move accordingly to reduce the error between two exposures of the same wafer region.

[0100] The reference coordinates described in the present invention are the coordinates of each three-dimensional mark in a certain scanning area pre-stored in the computer control system, or the coordinates of the three-dimensional mark measured by the nano-needle tip sensing device before exposing the wafer area and the theoretical horizontal and vertical distances to be moved in order to align the wafer area to be exposed next with the projection exposure area, and the corresponding coordinates in the scanning area after the combination. The theoretical horizontal and vertical distances to be moved are pre-stored in the computer control system. If the three-dimensional mark is a three-dimensional pattern on the surface of the photosensitive layer caused by radiation-induced denaturation of the photosensitive layer (IIRC), the reference coordinates of the three-dimensional mark are the graphics, coordinates and other parameters of the three-dimensional pattern of the exposed wafer area pre-stored in the computer control system in the scanning area.

[0101] The exposure beam emitted by the exposure beam generating device described in the present invention is at least one of a light beam, an electron beam, an ion beam or an atomic beam. The present invention is mainly introduced by taking an optical lithography machine as an example.

[0102] Figure 2 The following is a schematic diagram of a photolithography machine structure according to a specific embodiment, specifically a schematic diagram of a sub-nanometer step-and-repeat optical photolithography machine. The optical photolithography machine system mainly consists of the following parts:

[0103] The beam generating device includes a light source 10, an optical shutter 20, a beam shaping system 30, a beam deflector or reflector 40, a shaping lens assembly 50, a mask workpiece stage 60, and a projection lens assembly 70. The lithography machine computer control system 200 can control the optical shutter 20 and determine the exposure time of the light source.

[0104] The wafer worktable 100 is used to carry a wafer 110 to be processed. The wafer includes several wafer areas 120, and several three-dimensional markings are set on the wafer (described in detail later). The wafer worktable 100 includes a movable portion and a fixed portion, wherein the movable portion includes a wafer area switching drive device 105 and a precision moving device 106. The fixed portion 104 of the wafer area switching drive device is located below the wafer area switching drive device 105, and is used to carry the wafer area switching drive device 105 and drive the wafer to move in a step-by-step manner to expose different wafer areas in sequence below the light beam generating device. The computer control system 200 is connected to the wafer area switching drive device 105 that controls the precise movement of the wafer worktable, and is used to drive the wafer to move in a step-by-step manner to achieve exposure of all wafer areas. The wafer area switching drive device has a large displacement range, and the wafer area switching drive device has a movement distance of usually above the micron level. Currently, the movement of some more precise wafer area switching drive devices can be controlled to a positioning accuracy of 10 nanometers to 2.5 nanometers. Precision movement device 106 is located above fixture 107, which is positioned above wafer zone switching drive 105. Precision movement device 106 can fine-tune the wafer's position in the lateral, longitudinal, or circumferential directions at the subnanometer level. The precision movement device reduces the reliance of wafer positioning on the precision of the wafer stage's movement, allowing the use of a wafer stage with lower positioning accuracy. For example, a wafer stage with a positioning accuracy requirement of 1 nanometer can be replaced with one with a positioning accuracy of 1000 nanometers, significantly reducing wafer stage costs.

[0105] The nano-tip sensor device 90 includes a tip sensor head 91 and 92 and micro-cantilevers 91a and 92a connected to the tip sensor heads. The tip sensor heads are located above the photosensitive layer of the wafer and are used to scan and determine the coordinates of the three-dimensional mapping mark within a certain scanning area, and transmit the obtained signal to the computer control system 200 for comparison with the reference coordinates. The nano-tip sensor device can be fixed on a component close to the wafer but not affecting the positioning of the exposure beam. In this embodiment, the tip sensor heads 91 and 92 are fixed to the side of the lens of the projection objective lens group 70. The tip sensor head moves with the photon beam, and of course the tip sensor head also drifts with the photon beam. This has the advantage that the micro-cantilever of the tip sensor head can be made very short, thereby improving the resolution of the three-dimensional measurement of the tip sensor head surface.

[0106] exist Figure 2In the schematic diagram of the photolithography machine structure shown, pinpoint sensor heads 91 and 92, fixed to the beam projection objective lens assembly 70, are placed on either side of the beam projection objective lens assembly, one or a row on each side. This allows for measurement coverage of both sides of the projection exposure area of ​​the wafer region. In other words, each pinpoint sensor head or row corresponds to both sides of the projection exposure area of ​​the wafer region, enabling measurement of off-site three-dimensional marks between wafer regions on both sides of the wafer region. Each pinpoint sensor head or row is fixed to the beam projection objective lens assembly so that the distance between them is fixed. Therefore, their coordinates are also fixed. Placing pinpoint sensor heads on both sides of the wafer region significantly reduces the scanning range of each pinpoint sensor head. Specifically, each pinpoint sensor head only needs to scan the middle area of ​​its own wafer region, rather than scanning across the entire wafer region from the middle area between wafer regions on one side to the middle area between wafer regions on the other side. This significantly improves the linearity and positioning accuracy of the pinpoint sensor head scanning.

[0107] The displacement drive device 400 includes a wafer region switching drive device 105 for driving the stepwise switching of wafer regions, and a nano-displacement drive device 420. The nano-displacement drive device 420 is connected to the computer control system 200 and controls the light beam generator and / or the wafer worktable for fine-tuning based on the coordinates of the underlying alignment marks measured by the nano-tip sensor device 90, thereby achieving overlay alignment between the wafer region to be exposed and the exposure beam emitted by the light beam generator system, and completing the exposure. In this embodiment, the nano-displacement drive device 420 can selectively drive the movement of at least one of the reflective mirror 40, the shaping lens assembly 50, the mask 60, the projection objective lens assembly 70, or the wafer worktable 100 to achieve fine-tuning alignment between the projection exposure area and the wafer region to be exposed.

[0108] In this embodiment, a nano-displacement actuator 61 is mounted on the mask workpiece stage 60 to achieve lateral movement of the mask. Alternatively, a nano-displacement actuator 71 is mounted around the optical projection objective assembly 70 to drive the lateral movement of the lens. Alternatively, a nano-displacement actuator 41 is mounted to laterally move the photon / electron beam or deflection device 40. Any one of these nano-displacement actuators can be used to fine-tune the position of the projection exposure area. Optionally, more than one nano-displacement actuator may be installed on each of these components.

[0109] In order to achieve the placement of 3D marks on the wafer and thereby use the 3D marks on the wafer to align the wafer area to be exposed with the projected exposure area, it is necessary to place appropriate 3D marks on the wafer, as will be described in detail below.

[0110] Figure 3The figure is a schematic diagram of the position of pre-set three-dimensional marks on the wafer. Wafer 110 includes a wafer area 120 where a three-dimensional pattern is formed by exposure and an off-field area 122 arranged outside the wafer area. The three-dimensional mark can be set within the wafer area, and this three-dimensional mark is called an in-field three-dimensional mark 1201, or it can be set in the off-field area, and this three-dimensional mark is called an off-field three-dimensional mark 1221. The off-field three-dimensional mark can be set in the middle area between adjacent wafer areas or in the wafer edge area. The advantage of the off-field three-dimensional mark is that even if some destructive treatment is performed on these marks, it will not affect the wafer area yield. These marks can be used as alignment coordinate marks by photon beam / electron beam exposure, and can be repeatedly "observed" by the photon beam / electron beam, that is, exposed.

[0111] In-field 3D marks 1201 can include nanometer-scale 3D marks placed within the wafer region prior to the first processing step, or they can be 3D marks created by a photosensitive layer on the wafer surface after exposure to a light beam. In-field 3D marks 1201 can be as small as a few nanometers to a few hundred nanometers. Because they occupy a very small area, even marking within the wafer region does not affect wafer yield.

[0112] A single measurement of the wafer fixes the coordinate relationship between these 3D markers and each wafer region. Subsequent measurements of these 3D markers can accurately locate the wafer region's coordinates. Assuming the wafer maintains precise temperature control over a long period of time and does not deform due to thermal expansion or contraction, these coordinates can be accurately located to the single nanometer or sub-nanometer level.

[0113] The initial measurement of these 3D marks and the positions of the wafer regions determines the relative deviation of the wafer with respect to the wafer stage, specifically whether the wafer needs to be rotated during wafer stage movement to adjust the parallelism between the wafer stage and the array of wafer regions on the wafer. Computer control system 200 uses the external and internal 3D marks of the wafer regions to control every component of the lithography machine and, through pre-defined control methods, achieves sub-nanometer longitudinal overlay alignment and exposure of the wafer regions.

[0114] The closer the 3D mark is to the wafer area to be exposed, the higher the alignment accuracy for that wafer area. The 3D mark 1221 between wafer areas is set between the wafer areas. This 3D mark arrangement is suitable for step-and-repeat lithography machines. However, for non-mask-type direct-write photon beam / electron beam lithography machines, there are many situations where space between exposure fields is not practical. Gratings or Fresnel lenses are examples.

[0115] The present invention utilizes measurement technology that can sense three-dimensional nanoscale structures, such as the use of needle tip sensor head sensing technology to achieve sub-nanometer-level three-dimensional morphology measurement technology (sub-nanometer-level atomic force three-dimensional morphology measurement technology). The present invention sets a three-dimensional mark on the wafer, and the three-dimensional mark is measured by the needle tip sensor head sensing technology to achieve coordinate positioning. The three-dimensional marks on the photosensitive layer and the wafer surface can be used as alignment marks. For example, by measuring the peak position or concave position of the three-dimensional mark, a precise alignment coordinate can be determined. The concave-convex structure on the wafer surface generally causes the surface of the photosensitive layer covering it to follow and form a concave-convex structure, that is, the positioning can penetrate vertically, so that the surface covering the photosensitive layer can be measured due to its concave-convex structure.

[0116] The wafer described in the present invention includes several chip areas, at least one bottom layer alignment mark is set inside or around the chip area, a photosensitive layer is set on the wafer surface, the bottom layer alignment mark forms a corresponding three-dimensional mark on the photosensitive layer, and the three-dimensional mark has an area that is not on the same horizontal plane as the upper surface of the photosensitive layer.

[0117] Figure 4A 、 Figure 4B and Figure 4C Specific implementations of setting three-dimensional marks on wafers are respectively shown.

[0118] Figure 4A A schematic diagram of a convex 3D mark is shown. First, one or more underlying alignment mark projections 45a (HAMW) are deposited on the wafer through deposition or other methods. These are pre-deposited nanoscale underlying alignment marks. Then, a photosensitive layer is deposited above the wafer. Because the photosensitive layer has a certain degree of fluidity and is relatively soft, the underlying alignment mark projections 45a (HAMW) form a corresponding raised structure 46a (HAMR) on the upper surface of the photosensitive layer. This raised structure constitutes the 3D mark described herein. If the thickness of the photosensitive layer is between 10 and 100 nanometers, the surface of the photosensitive layer above the underlying alignment mark 45a (HAMW) on the wafer will also become a 3D mark. The height of this 3D mark can range from a few nanometers to tens of nanometers, typically less than 100 nanometers, accurately indicating its position as a 3D mark on the surface of the photosensitive layer. This position is vertically identical to the position of the underlying alignment mark on the wafer perpendicularly below. This method allows the precise determination of the lateral coordinates of the wafer pattern. Crucially, these lateral coordinates can be set within the wafer area (write field). The placement of these 3D markers determines alignment accuracy, making it independent of the wafer stage's movement accuracy. This allows the use of a wafer stage with lower positioning accuracy. For example, a wafer stage with a positioning accuracy of 1 nanometer can be replaced with one with a positioning accuracy of 1000 nanometers, significantly reducing wafer stage costs.

[0119] The three-dimensional mark described herein and the photosensitive layer have at least portions located on different horizontal planes. For example, in this embodiment, the three-dimensional mark 46a comprises a pointed protrusion protruding from the photosensitive layer. When a wafer with this three-dimensional mark is placed in a photolithography apparatus according to the present invention, the tip sensor head of a nanotip sensing device scans within a certain scanning area. Due to the extremely weak repulsive force between the atoms at the tip of the tip sensor head and the atoms on the wafer surface, the microcantilever will fluctuate perpendicular to the wafer surface, corresponding to the equipotential surface of the force between the tip sensor head and the atoms on the wafer surface. Optical detection or tunneling current detection can be used to measure the position change of the microcantilever at each scanning point, thereby obtaining information about the wafer surface topography. In the present invention, the three-dimensional mark has a pointed protrusion, and the distance from the tip sensor head to the tip sensor head is different from the distance from the top surface of the photosensitive layer to the tip sensor head, thereby enabling the tip sensor head to accurately locate the three-dimensional mark during scanning. To accurately identify the coordinates of the three-dimensional mark, the height of the three-dimensional mark provided by the present invention is greater than the surface roughness of the photosensitive layer, with an optional height of less than or equal to 50 microns.

[0120] Figure 4B The schematic diagram of the structure of the three-dimensional mark on the wafer surface is a recessed portion. Figure 4A The three-dimensional raised structure shown requires additional material on the wafer. In contrast, etching the wafer to form an inverse three-dimensional "protruding" structure 45b, or a recessed structure, has the advantage of not requiring additional material to be deposited on the wafer, but rather "digging" away existing wafer material, making it easier to manufacture than a three-dimensional raised structure. As described above, a corresponding recessed three-dimensional mark 46b is formed on the photosensitive layer. Because the tip-sensing atomic force microscope can measure the entire three-dimensional structure, even if the pit in the three-dimensional structure is only a few nanometers in size at its tip, the entire three-dimensional topographic information of the structure can improve positioning to the single-nanometer level.

[0121] Figure 4C This diagram illustrates a nanoscale, concave-convex, three-dimensional marking structure etched onto the wafer surface using etching technology. This method offers the advantage of obtaining a three-dimensional protrusion structure as a nanoscale, three-dimensional marking without depositing additional materials on the wafer. In this embodiment, the bottom-layer alignment mark 45c on the wafer includes one or more dot-like structures, and the corresponding three-dimensional mark 46c on the photosensitive layer also has one or more dot-like structures, enabling more precise positioning of the tip sensor.

[0122] In order to achieve accurate positioning of wafer coordinates with a three-dimensional mark, the three-dimensional mark described in the present invention may optionally have certain graphic features. In addition to at least one point feature 44, the graphic features also include an edge feature 43 connected to the point feature. The point feature and the edge feature are not completely located in the same plane as the upper surface of the photosensitive layer. Figure 4DA schematic diagram of a three-dimensional prism structure is shown. The prism structure increases the detectable area of ​​the three-dimensional mark and improves the positioning accuracy of the three-dimensional mark by adding a number of ridge features 43 located in different horizontal planes from the photosensitive layer.

[0123] In the above embodiments, protruding or recessed nanostructures, such as a micro-cone, a micro-pyramid, or a micro-tip sensor head, are pre-deposited on the wafer surface. These structures have diameters ranging from a few nanometers to tens of nanometers, typically less than 100 nanometers. These microstructures can be fabricated using plasma etching or electron beam induced deposition (EBID).

[0124] The present invention can set multiple three-dimensional marks on the wafer. One optional method is to set at least one three-dimensional mark corresponding to each wafer area. The three-dimensional mark can be an in-field three-dimensional mark set inside the wafer area, or an out-field three-dimensional mark set around the wafer area. The wafer area includes an out-field area between two laterally adjacent or two longitudinally adjacent wafer areas, or an out-field area corresponding to the edge of the wafer and the wafer area, etc. Optionally, the coordinates of the three-dimensional mark corresponding to each wafer area are fixed relative to its wafer area. The above description Figures 4A-4D The 3D mark shown here sets an absolute position on the wafer. Alternatively, wafer positioning can be performed using needle-tip sensor technology based on the specific shape of the photosensitive layer after exposure, leveraging the properties of the photosensitive layer. This relative positioning of the mark improves overlay accuracy across the wafer.

[0125] The bottom layer alignment marks mentioned above include marks made on the surface of the wafer before the first exposure of the wafer, and also include marks set under the photosensitive layer in the subsequent exposure process. Taking into account the possible loss of the three-dimensional marks during the graphic transfer process, resulting in the weakening of the point features and edge features of the three-dimensional marks, after a certain number of steps, the bottom layer alignment marks can be remade to improve the accuracy of the subsequent positioning of the three-dimensional marks on the surface of the photosensitive layer.

[0126] Figure 5AA schematic diagram of an irradiation-induced photosensitive layer modification (IIRC: Irradiation Induced ResistChange) pattern is shown. Irradiation-induced photosensitive layer modification refers to changes in the chemical and / or physical properties of the photosensitive layer at the location where the photon beam, electron beam, or other particle beam is irradiated and exposed. Chemical changes include chemical reactions on the surface of the photosensitive layer caused by the photon beam / electron beam, which causes the irradiated portion of the photosensitive layer to change from an insoluble state to a state that dissolves during development (positive resist), or the dissolved state becomes insoluble through exposure reaction (negative resist). Photon beam / electron beam exposure can also cause physical changes in the photosensitive layer, including changes in tiny geometric dimensions on the surface of the photosensitive layer. When the photon beam / electron beam exposure transfers the exposure pattern information to the photosensitive layer, changes in the concave-convex structure on the photosensitive layer are also produced. For example, the exposed area expands on the sub-nanometer or nanometer scale to form a protruding area 47a relative to the unexposed area 48a, see Figure 5A ; or the exposed area shrinks to form a concave structure, see Appendix Figure 5B , forming a recessed area 47b and an unexposed area 48b. The pinpoint sensor head can locate a specific wafer area by measuring the protruding area 47a and the recessed area 47b. This deformation can be detected and sensed at the sub-nanometer scale by the pinpoint sensor head (a highly sensitive sensor head).

[0127] To ensure the use Figure 5A and Figure 5B To achieve the accuracy of the IIRC marker positioning shown, several 3D markers, such as three or more, can be placed on the wafer edge. These markers can then determine the position of the entire wafer. A stylus sensor head can then measure and locate the wafer's absolute position. This can involve a combination of multiple stylus sensors, such as a linear array of multiple stylus sensors, to transmit the coordinates of the absolute 3D markers located at the wafer edge to the center of the wafer. A linear stylus sensor head array significantly expands the range of wafer measurements that can be performed accurately. In a one-dimensional linear stylus sensor array, the distance between the stylus sensors is fixed. The movement of the stylus sensors is achieved by uniformly moving the array using piezoelectric displacement or voice coil drive systems at both ends of the linear array. Therefore, the relative coordinate positions of the stylus sensors remain unchanged.

[0128] In addition to using the three-dimensional pattern of the three-dimensional mark generated by the exposure of the wafer area itself to align the exposure of the next wafer area, a positioning mark generating device (not shown in the figure) can also be set on the exposure beam generating device. The positioning mark generating device forms a three-dimensional positioning mark on the periphery of the wafer area while the wafer area is exposed. The needle tip sensor head calibrates the position of the wafer area to be exposed based on the three-dimensional positioning mark. For example, in an optical lithography system, one or more positioning mark generating devices can be set on the periphery of the normal pattern of the mask. When exposing a wafer area to be exposed, a three-dimensional positioning mark is exposed at the edge of the wafer area at the same time. The three-dimensional positioning mark can be optionally located between the two wafer areas to reduce the scanning area of ​​the needle tip sensor head and improve the efficiency of positioning. When exposing the next wafer area, the computer control system 200 uses the nano-displacement drive device to align the wafer area to be exposed with the projected exposure area based on the coordinates of the three-dimensional positioning mark corresponding to the previous wafer area scanned by the needle tip sensor head.

[0129] Figure 6 A schematic diagram of the structure of a lithography machine according to another embodiment of the present invention is shown. In this embodiment, a nano-tip sensing device is arranged on a wafer workbench 100. The wafer workbench 100 includes a moving part and a fixed part. The tip sensor heads 93 and 94 are connected to the fixed part through the micro-cantilevers 93a and 94a, respectively.

[0130] The alignment method of this embodiment first measures the three-dimensional marks set between wafer regions and / or measures the pattern structure and coordinate position of the wafer region before exposure. Then, during exposure, the wafer region switching drive device 105 drives the wafer stage 110 to move laterally, freeing up the projection exposure area for the next wafer region to be exposed. This movement also introduces write field motion error. The new coordinate values ​​of the three-dimensional marks outside the wafer region and / or on the surface of the wafer region after the wafer stage movement are measured by a needle tip sensor head. These values ​​can be compared with the coordinate values ​​of the original three-dimensional marks to determine the appropriate XY coordinates (and XY plane angles) of the wafer region motion error. This amount can be used to reposition the wafer stage or to move objects that affect the photon beam, such as a mask or projection lens assembly, by a few nanometers. In this embodiment, since the needle tip sensor head sensing technology is installed on the wafer stage, it can conveniently measure the three-dimensional marks in the wafer edge region. Since the distance between the three-dimensional marks in the wafer edge region is large, only a few three-dimensional marks are needed to determine the accurate position of the entire wafer.

[0131] A problem with this method and device is the large wafer stage, typically exceeding 200 mm. This results in a very long microcantilever connecting the tip sensor head to the base on which the tip sensor head is mounted. This very long microcantilever can reduce the resolution of the tip sensor head's three-dimensional surface measurement. Therefore, improvements can be made to this embodiment.

[0132] Figure 7 A schematic diagram of the structure of a lithography machine according to another embodiment of the present invention is shown. In this embodiment, the nano-tip sensing device is combined with Figure 2 and Figure 6 The advantage of fixed positions is that one set of pinpoint sensor heads 93 and 94 is fixed to the wafer worktable, while another set of pinpoint sensor heads 91 and 92 is fixed to one side of the photon beam, such as on either side of the projection objective lens. This allows for accurate measurement of the coordinates of off-site 3D markers corresponding to the wafer area to be exposed, and allows the exact position of the entire wafer to be determined using only a few 3D markers.

[0133] Figure 8 A schematic diagram showing the correspondence between multiple needle tip sensor heads and chip areas in an embodiment of the present invention is shown, and the coordinate position of each chip area is measured and determined by multiple needle tip sensor heads. In this embodiment, the multiple needle tip sensor heads 91, 92, ... 9n are fixedly connected by a connector 140, and are arranged in a row horizontally according to the distribution of the chip areas, forming a horizontal needle tip sensor head array. According to the above description, in the preparation step, at least one bottom layer alignment mark is set on the wafer to be processed, and the bottom layer alignment mark forms a corresponding three-dimensional mark on the photosensitive layer; when the wafer is exposed, the wafer with the three-dimensional mark in the preparation step is placed in the above-mentioned lithography machine, and a projection objective lens group 70 is set near the wafer in the lithography machine, and the projection objective lens group corresponds to a projection exposure area on the wafer, and the chip area switching drive device 105 of the wafer workbench is driven to place the first chip area to be exposed under the projection objective lens group; the needle tip sensor heads 91-9n are used to At least one scanning device scans the photosensitive layer within a certain scanning area to obtain the position coordinates of a first three-dimensional marker, such as three-dimensional marker 1221. The position coordinates of the first three-dimensional marker are compared with the reference coordinates of the first three-dimensional marker to obtain a difference between the two position coordinates. The displacement drive device adjusts the relative position of the exposure beam generator and the wafer worktable based on the difference between the two position coordinates, so that the projected exposure area is aligned with the first wafer area. The beam generator emits an exposure beam to the first wafer area of ​​the wafer to expose the first wafer area. The reference coordinates of the first three-dimensional marker are pre-stored in the computer control system. When the three-dimensional marker is located at the reference coordinates, the first wafer area is aligned with the projected exposure area.

[0134] After the first wafer area is exposed, the second wafer area is placed beneath the projection objective lens assembly. At this point, various alignment marks can be used to align the first wafer area with the projection exposure area. One method involves the tip sensor head scanning the position coordinates of the first three-dimensional marker after movement and comparing them with the reference coordinates of the first three-dimensional marker after movement to obtain a deviation between the two position coordinates. The reference coordinates of the first three-dimensional marker after movement are the coordinates of the first three-dimensional marker during exposure of the first wafer area, combined with the theoretical lateral and longitudinal distances required for the wafer to be moved to align the next wafer area to be exposed with the projection exposure area, and the corresponding coordinates within the scanning area. The theoretical lateral and longitudinal distances required for the wafer to be moved are predetermined and stored in a computer system based on parameters such as the size of the wafer area generated by exposure and the distance between adjacent wafer areas. The reference coordinates of a three-dimensional marker accurately positioned during exposure of the previous wafer area after movement by one or more steps can be accurately determined based on the number of wafer areas moved. When using the same three-dimensional mark for alignment, it is necessary to consider the number of needle tip sensor heads and the range of the scanning area. Since the same three-dimensional mark needs to be tracked and scanned, two needle tip sensor heads can be optionally set up to perform coordinate measurement of the three-dimensional mark before exposure of the chip area and the same three-dimensional mark after the wafer moves on both sides. Another optional method is to select a needle tip sensor head with a larger scanning range to achieve tracking scanning of the same three-dimensional mark.

[0135] Another alignment method involves placing the second wafer area below the projection objective lens assembly after exposure of the first wafer area is complete. The pinpoint sensor head scans the position coordinates of a second three-dimensional marker and compares them with the reference coordinates of the second three-dimensional marker to determine the deviation between the two coordinates. The displacement drive adjusts the relative positions of the exposure beam generator and the wafer worktable based on the difference in position coordinates, aligning the projection exposure area with the second wafer area and achieving exposure of the second wafer area. The reference coordinates of the second three-dimensional marker are pre-stored in the computer control system. To ensure accurate alignment, the first three-dimensional marker may optionally be positioned near the first wafer area, and the second three-dimensional marker may be positioned near the second wafer area.

[0136] The third alignment method is: after completing the exposure of the first chip area, the second chip area is placed under the projection objective lens group, the needle tip sensor head scans the graphics and coordinates of the three-dimensional pattern formed on the photosensitive layer after the first chip area is exposed, and compares the graphics and coordinates of the three-dimensional pattern with the reference graphics and coordinates pre-stored in the computer control system to obtain the difference between the positions of the two three-dimensional patterns, and the displacement drive device adjusts the relative positions of the exposure beam generating device and the wafer worktable according to the difference in the position coordinates, so that the projection exposure area is aligned with the second chip area, and the exposure of the second chip area is realized.

[0137] The three alignment methods described above can be selected based on whether a 3D mark generated by a bottom-layer alignment mark is set near the wafer area. Alternatively, two or more alignment methods can be selected to improve alignment accuracy. When aligning a specific wafer area, the coordinates of more than one 3D mark can be scanned simultaneously and their difference values ​​compared with the corresponding reference coordinates to improve alignment accuracy.

[0138] The third wafer area and subsequent wafer areas are sequentially exposed under the projection objective lens assembly, and exposure is achieved according to the alignment method described above.

[0139] Optionally, the nano-tip sensor device is fixed on one side or both sides of the projection objective lens group and is relatively fixed to the position between the projection objective lens group. When aligning with the same three-dimensional mark, it is necessary to consider the number of tip sensor heads and the range of the scanning area. Since it is necessary to track and scan the same three-dimensional mark, two tip sensor heads are optionally set up to measure the coordinates of the three-dimensional mark before the wafer area is exposed and the same three-dimensional mark after the wafer moves. Another optional method is to select a tip sensor head with a larger scanning range to achieve tracking scanning of the same three-dimensional mark. When two or more tip sensor heads are set, the distance between two adjacent tip sensor heads is equal to the sum of the lateral width of a wafer area and the width of the out-of-field area between the two wafer areas. Optionally, the distance between two adjacent tip sensor heads is a multiple of the sum of the above two distances. Such a design can ensure that when the wafer areas are exposed in sequence, the tip sensor head can scan within a smaller range to achieve precise positioning of the three-dimensional mark. Multiple tip sensors are fixed relative to each other via connectors, enabling the transfer of the coordinates of a 3D marker on the wafer to other wafer regions across the array of lateral tip sensors. The precise wafer coordinates measured by any tip sensor can be accurately transferred to the coordinates of other tips without error.

[0140] The spacing between the tip sensor heads can be greater than or equal to the size of the chip area plus the distance between chip areas, so that one tip sensor head measures the coordinate position of the three-dimensional mark at the edge of the wafer or near the edge of the wafer, another tip sensor head measures the three-dimensional mark in the middle area between chip areas, and another tip sensor head measures the middle area between chip areas of another chip area, and so on.

[0141] Specifically, the first pintip sensor head measures the position of the three-dimensional mark on the edge of the wafer, and the lateral pintip sensor head array transmits the absolute value of this position to the second pintip sensor head, which plays the role of determining the absolute coordinates of the position of the second pintip sensor head without setting a three-dimensional mark on the wafer. The coordinates of the first pintip sensor head can also be transmitted to the inner part of the wafer through the Nth pintip sensor head, and all the way to the last pintip sensor head. The last pintip sensor head can generally transmit the measurement to the three-dimensional mark on the edge of the other end of the wafer. The wafer area that the pintip sensor head cannot move to can be transferred to the exposure coordinate positioning of several wafer areas by the method of lateral write field splicing. Due to the limited number of transfers, the accumulation of excessive positioning coordinate errors is avoided, thereby forming a scene where all wafer areas on the wafer can be overlaid and positioned accurately for exposure.

[0142] Using an array of pinpoint sensors, nanometer-scale 3D marks on the wafer edge, or in the center of the wafer, are positioned relative to the light beam. To ensure the wafer is positioned relative to the light beam, at least three 3D marks are required. The more widely spaced the three 3D marks are on the wafer, the more accurately the wafer can be positioned. Figure 9 The multi-tip sensor head L-shaped array can use three-dimensional markers on the wafer edge with a large distance between them as the wafer's accurate coordinates for positioning.

[0143] Figure 9 A schematic diagram showing the correspondence between multiple needle tip sensor heads and wafer regions according to an embodiment of the present invention. In this embodiment, multiple needle tip sensor heads are connected to form an L-shaped array arrangement through a connector 150. Figure 8 The disclosed lateral tip sensor head array of the illustrated embodiment is supplemented with at least one tip sensor head 101 capable of measuring other rows of three-dimensional marks in the edge area. The L-shaped array can use three-dimensional marks at the edge of the wafer that are very far apart as accurate coordinates for wafer positioning.

[0144] The use of a needle tip sensor array to locate the relative position of nanometer-scale three-dimensional marks at both ends of the wafer edge and the light beam is one of the most accurate positioning methods. Figure 10 A schematic diagram showing the correspondence between multiple needle tip sensor heads and wafer regions according to an embodiment of the present invention. In this embodiment, multiple needle tip sensor heads are connected to form a U-shaped array through a connector 160. Figure 8The disclosed lateral tip sensor head array of the embodiment is increased with at least one tip sensor head 111 at each end of the array, which can measure the three-dimensional marks of the other rows in the edge area. Thus, the accurate coordinate position of the wafer relative to the exposure beam can be determined by the three or more nanoscale three-dimensional marks arranged at different distances on the edges of both ends of the wafer. The array can use the three-dimensional marks far apart from both ends of the wafer as the accurate coordinates of the wafer for positioning. The two arms of the U-shaped structure can be of different lengths. The linear array of tip sensor heads can be fixed on the beam projection objective group or on the wafer stage.

[0145] The tip sensor head can measure the wafer surface structure in an atmospheric or vacuum environment, or can measure the wafer surface structure by immersing the tip sensor head in a liquid in an immersion environment. For immersion lithography, the three-dimensional marks measured by the tip sensor head can be three-dimensional marks in the immersion environment, or can be three-dimensional marks corresponding to adjacent wafer regions outside the exposure beam in the wafer region without immersion environment.

[0146] The surface structure data of the three-dimensional marks detected by the tip sensor head is the mathematical convolution of the surface structure of the three-dimensional marks and the tip structure of the tip sensor head, so the shape of the tip sensor head can affect the surface structure data of the three-dimensional marks it detects. Therefore, the tip structure of the tip sensor head needs to be measured and calibrated before measuring the three-dimensional marks to improve the accuracy of the measurement.

[0147] The above-described cases mainly include adjusting the position of the wafer in the lateral, longitudinal or circumferential direction to achieve alignment with the projected exposure area. In some cases, the wafer may deviate from the perpendicularity of the exposure beam, for example, a wafer that should be set horizontally is tilted at an angle. In order to detect such cases, three or more tip sensor heads can be provided, and the three or more tip sensor heads are arranged on different straight lines. When the three or more tip sensor heads measure the three-dimensional marks in their respective scanning areas, the height difference of the identified three-dimensional marks can be used to determine whether the wafer region where the three-dimensional marks are located is tilted, causing the distance between the three-dimensional marks and the tip sensor head to change. The height difference is measured and the wafer stage is adjusted to the perpendicularity of the exposure beam by the computer control system.

[0148] The sub-nanometer high-precision lithography wafer area overlay alignment method realized by the alignment device of the present application includes the following preliminary preparation steps:

[0149] Preparation step 1: light beam positioning preparation. Fix the stylus sensor head at the side of the projection objective group of the light beam generator, so the relative position of the stylus sensor head to the light beam is fixed. In this way, the coordinate system of the stylus sensor head is the coordinate system of the light beam projection exposure area after a fixed translation. First, align the wafer coated with a photosensitive layer (it can be a wafer with test structures). Use a mask plate with enough fine structures as the calibration mask plate. Let the light beam pass through the mask plate to expose, the mask plate pattern is transferred to the photosensitive layer on the wafer surface and forms a wafer area pattern area on the photosensitive layer, and a three-dimensional pattern on the surface of the photosensitive layer is generated due to the irradiation-induced photosensitive layer change (IIRC). This three-dimensional pattern is the coordinate position of the light beam projection on the wafer surface. The three-dimensional marks outside the wafer area and the three-dimensional marks of the IIRC three-dimensional pattern inside the wafer area are measured by the stylus sensor head to determine the coordinate position of the light beam projection exposure area relative to the fixed coordinate position of the stylus sensor head.

[0150] The stylus sensor head moves together with the coordinate of the projection objective group (i.e. the light beam projection pattern). When measuring the position of the wafer area using the stylus sensor head, it is like the eye of the exposure beam, looking for the exact position of the wafer area.

[0151] Preparation step 2: wafer preparation. Before or after coating the wafer with a photosensitive layer, measure the three-dimensional mark coordinate positions of each wafer area using the stylus sensor head to determine the mutual positions of the three-dimensional marks outside each field.

[0152] Preparation step 3: find the coordinate positions of the projection exposure areas of each wafer area on the first wafer.

[0153] Method 1: Before the wafer is exposed by photolithography, there is no pattern on the wafer, so there is no alignment problem between the current projection exposure area and the pattern left on the wafer after the last exposure. It can be simply exposed to form the first wafer area pattern, then the wafer stage is moved to the next wafer area exposure pattern, until all the patterns on the wafer are exposed. By measuring the three-dimensional mark coordinates outside each wafer area and the three-dimensional mark coordinates inside the field obtained by measuring the IIRC of the photosensitive layer of the wafer area projection exposure area, the three-dimensional mark coordinates outside the wafer area field can be linked to the coordinate positions of the wafer area projection exposure area. In the future, only the three-dimensional mark coordinates outside the wafer area field need to be measured to determine the position of the projection exposure area.

[0154] Method 2: After the initial wafer exposure, the exposure pattern on the photosensitive layer is transferred to the wafer, for example, by plasma etching. The coordinates of the off-site 3D marker on the wafer are directly measured and recorded alongside the coordinates of the 3D marker on the wafer. This allows the projected exposure area position on the wafer to be calculated simply by measuring the off-site 3D marker coordinates. This measurement can be performed using a stylus sensor or other measuring instrument outside the lithography machine.

[0155] Preparation steps 1, 2, and 3 are one-time operations. After measuring the wafer once at the beginning, the coordinate positions of the wafer area can be determined using off-site 3D markers.

[0156] Wafer region coordinate reference points. Through the above preparatory steps, the wafer region coordinates are associated with the off-site 3D marker coordinates of each wafer region. Determining the off-site 3D marker coordinates can determine the wafer region position coordinates.

[0157] Preparation Step 4: If the measured wafer area arrays on the wafer have angular deviations from the wafer table, the angular error between the wafer and the wafer table in the horizontal two-dimensional movement direction, i.e., the circumferential direction, needs to be calibrated. After completing the above preparation steps, the wafer area overlay alignment step begins:

[0158] Alignment Step 1: The first wafer region overlay alignment process begins. Wafer 110 coated with a photosensitive layer 120 is placed on wafer table 100. A pinpoint sensor head, attached to beam projection objective lens assembly 70, measures the wafer region's off-site 3D mark. By using the coordinate relationship between the off-site 3D mark obtained in preparatory step 3 and the fixed coordinates of the wafer region's pattern area, it is possible to determine whether the beam is aligned with the wafer region's pattern area. This allows the coordinate deviation between the beam projection exposure area and the wafer region's pattern area to be determined, i.e., (ΔX1, ΔY1).

[0159] Alignment Step 2: Using a nano-displacement actuator 61 fixed to the mask, the coordinates (ΔX1, ΔY1) obtained in Alignment Step 1 are moved toward the mask to compensate for the error. This ensures that the projection exposure area is aligned with the pattern area on the wafer.

[0160] Alignment step 3: Expose the first wafer area within the projection exposure area.

[0161] Alignment Step 4: Activate the tip sensor head to measure the coordinates of the off-field 3D markers on the exposed wafer area and the position of the IIRC pattern 3D markers within the exposed area. This effectively remeasures the wafer area coordinates and the beam projection exposure area position, instantly calibrating the wafer area position and the beam projection exposure area position. This allows for correction of even minor drift in some lithography machine components over time.

[0162] Alignment step 5: Prepare the second wafer area for exposure. The mobile wafer worktable 100 drives the wafer 110 to move laterally, so that the first wafer area that has just been exposed moves out of the projection exposure area and becomes the wafer area with the three-dimensional pattern, making room for the second wafer area to enter the projection exposure area. The movement of the wafer worktable will cause wafer area positioning errors;

[0163] Alignment step 6: Activate the stylus sensor head to measure and identify the off-site 3D marker coordinates corresponding to the second wafer region, compare them with the off-site 3D marker coordinates associated with the first wafer region moved out of the projection exposure area and / or the on-site IIRC 3D marker coordinates, and determine the deviation (ΔX2, ΔY2) required to move the second wafer region.

[0164] Alignment step 7: Using the nano-displacement actuator 61 fixed to the mask, the mask is driven to move in a direction corresponding to the error compensation amount based on the coordinates (ΔX2, ΔY2) obtained in alignment step 6, so that the exposure area of ​​the light beam projection is aligned with the pattern area below the photosensitive layer of the wafer.

[0165] Alignment step 8: Expose the second wafer area within the projection exposure area.

[0166] Alignment step 9: activating the needle tip sensor head to measure the coordinates of the off-field 3D marker of the exposed wafer area and / or the position of the on-field IIRC 3D pattern 3D marker;

[0167] Alignment step 10: Pre-exposure preparation for the third wafer area. Wafer stage 100 moves wafer 110 laterally, moving the recently exposed second wafer area out of the projection exposure zone to become the wafer area with the three-dimensional pattern. This clears space for the third wafer area to enter the projection exposure zone. The movement of the wafer stage can introduce errors in wafer area positioning.

[0168] Alignment step 11: activating the stylus sensor head to measure and identify the coordinates of the off-field 3D marker associated with the third wafer region and the 3D marker of the in-field IIRC pattern of the second wafer region moved out of the projection exposure area, and comparing the coordinates of the off-field 3D marker and / or the in-field IIRC 3D marker associated with the first wafer region moved out of the projection exposure area to determine the deviation (ΔX3, ΔY3) required for the second wafer region to be moved.

[0169] Alignment step 12: Using the nano-displacement drive device 61 fixed to the mask, the mask is driven to move toward the wafer in a direction corresponding to the error compensation based on the coordinates (ΔX3, ΔY3) obtained in alignment step 11, so that the exposure area of ​​the light beam projection is aligned with the pattern position of the wafer area.

[0170] Alignment step 13: repeat the exposure, movement and overlay of the entire wafer area.

[0171] The three-dimensional marks used for alignment described in this embodiment can not only be selected from the field-out three-dimensional marks in the middle zone between the wafer area to be exposed and the adjacent wafer area, but also can be selected from the IIRC three-dimensional marks on the surface of the previous exposed wafer area (which has been coated with a photosensitive layer) as the coordinate reference system for the next wafer area exposure. Since IIRC does not require three-dimensional marks between wafer areas, the number of three-dimensional marks between wafer areas can be greatly reduced. However, using IIRC three-dimensional marks as the coordinate system of the previous exposed wafer area can cause the accumulation of errors caused by the measurement of each exposed wafer area by the stylus sensor head. Therefore, in general, the wafer area with corresponding three-dimensional marks and the wafer area without corresponding field-out three-dimensional marks are arranged alternately, and several IIRC patterns are used as reference points for alignment and positioning of the projection exposure area, thereby eliminating several field-out three-dimensional marks between wafer areas while ensuring that the total accumulated error is within an allowable range.

[0172] The present application Figures 8-10 In the embodiment shown, the linear array of multiple stylus sensor heads, together with the wafer area field-out three-dimensional marks and the wafer area field-in IIRC three-dimensional marks, can be combined to reduce the number of field-out three-dimensional marks. Specifically, the lateral stylus sensor head array directly binds the movement error of the first stylus sensor head to the position of the first stylus sensor head with other stylus sensor heads fixed on the linear array of stylus sensor heads, thereby eliminating the error accumulation that may be caused by the positioning of the wafer area without using the three-dimensional marks in the middle zone between adjacent wafer areas.

[0173] In another embodiment, nanoscale three-dimensional marks can be placed only on the edge of the wafer, and then multiple linear arrays of stylus sensor heads can be used to directly connect the coordinate positions inside the wafer to the wafer edge identified wafer area three-dimensional mark coordinate positions through the linear sensor head array, thereby eliminating the error accumulation caused by the exposure of the wafer area before and after the exposure of the wafer area.

[0174] Through the above description, the present application is mainly implemented by the following technical solutions to improve the overlay accuracy of the wafer during step-by-step exposure:

[0175] I. Sub-nanometer precision measurement of wafer area / written field actual coordinate position technology.

[0176] The system uses needle-tip sensor technology, including atomic force microscopy (AFM). AFM is a type of needle-tip sensor technology that can measure the three-dimensional surface topography and nanometer-scale distribution of surface work function of wafers with sub-nanometer precision.

[0177] 2. Sub-nanometer displacement driving technology of objects.

[0178] The first technology is piezoelectric ceramics, which enable sub-nanometer movement. Using the piezoelectric principle, sub-nanometer movement can be achieved. However, typical piezoelectric movement is nonlinear and exhibits hysteresis loops.

[0179] The second technology is electromagnetic drive. A voice coil motor (VCM) is a special form of direct-drive motor. It features a simple structure, small size, high speed, high acceleration, and fast response. Its positioning accuracy can reach 1 / 30 nanometer. Its operating principle is that a current-carrying coil (conductor) placed in a magnetic field generates a force proportional to the current applied to the coil. Voice coil motors manufactured based on this principle can move in a straight line or in a circular arc. Both technologies can be used in the present invention.

[0180] 3. Sub-nanometer displacement driving and positioning technology of objects.

[0181] With the above measurement and drive technologies, sub-nanometer positioning can be achieved. This positioning is to adjust the wafer chip area / write field relative to the photon beam / electron beam by nanometer-level positioning displacement to eliminate the relative coordinate offset caused by the movement of the wafer worktable or the photon beam / electron beam. This can provide a variety of methods and devices for correcting the position errors of the wafer chip area / write field relative to the photon beam / electron beam position, thereby achieving sub-nanometer-level lateral splicing and longitudinal overlay alignment of the wafer area / write field. Examples of the implementation of displacement drive and positioning of objects:

[0182] a. In photon / electron beam lithography machines, a wafer stage with sub-nanometer positioning can be used, or a smaller, more precise, picometer-level wafer stage can be added to the existing wafer stage for precise positioning. This allows for a smaller step size than the existing wafer stage. (The smaller wafer stage can move more slowly.)

[0183] b. In a photon beam / electron beam lithography machine using a mask, a drive device can be provided to drive the nanometer-level movement of the mask workpiece stage, and a drive device can be provided to drive the nanometer-level movement of the photon beam / electron beam projection objective lens group, which is sufficient to achieve the correction of the alignment error of the chip area / writing field.

[0184] c. In a photon beam / electron beam direct writing lithography machine, the photon beam / electron beam projection objective lens group can be driven to shift, so that the lens moves several to tens of nanometers, which is sufficient to correct its alignment positioning error relative to the writing field / wafer area.

[0185] d. In a lithography machine that directly writes with a photon beam or an electron beam or uses a mask, a driving device for the photon beam or electron beam itself or a deflection device can be set to achieve displacement and coordinate correction of the photon beam and electron beam.

[0186] 4. Provide a device and method for closed-loop control measurement and alignment of wafer areas and then exposure in a lithography machine.

[0187] The lithography alignment system disclosed in the present invention has the closed-loop control feature of measurement-movement-remeasurement for wafer area overlay alignment. The specific overlay alignment method of the wafer area of ​​the ultra-high precision lithography system is as follows:

[0188] Method 1: Using off-site 3D markers 1221 as reference points for wafer region alignment, such as the coordinate positions of 3D protruding (concave) marks between wafer regions or at the wafer edge, a needle-tip sensor head is used to measure the position of the wafer region pattern. (The coordinate positions of each wafer region pattern on the wafer and the 3D protruding (concave) marks on the wafer, as well as their relative coordinate positions, are predetermined and unaffected by wafer stage movement or beam offset.) The wafer stage 100 is then moved to move the exposed wafer region out of the projection exposure area. The new coordinates of the 3D protruding (concave) marks in the center of the wafer region or at the edge of the wafer are then measured. The resulting coordinate difference is then compared with the coordinates of the previously exposed wafer region in the projection exposure area to determine the coordinate offset difference for the next wafer region to be exposed. This coordinate difference can be used to drive the exposure beam generating device, such as the mask, to perform nanometer-level horizontal movement for compensation. It can also be set to drive the nanometer-level horizontal movement of the photon beam / electron beam projection objective lens group. It can also be set to drive the nanometer-level horizontal movement of the photon beam / electron beam itself or the deflection mirror. It can also be set to drive the wafer workbench or a piezoelectric wafer workbench with a smaller step size installed on the wafer workbench, which is sufficient to achieve the correction of the alignment error of the chip area / write field.

[0189] Method 2: A three-dimensional pattern formed by radiation-induced modification of the photosensitive layer (IIRC) after the first wafer area is exposed, such as Figure 5A and 5BAs the position coordinates for the next wafer area to be aligned. In this method, the wafer area to be exposed does not need to be provided with corresponding 3D markers, that is, no 3D markers are provided within or around the wafer area. When the needle tip sensor head scans within a certain scanning area, it determines the boundaries of the wafer area based on the three-dimensional pattern of 3D markers formed on the previously exposed wafer area, and then determines whether the next wafer area to be exposed requires nanometer-level displacement fine-tuning and the adjustment deviation.

[0190] Method 3: This method combines Method 1 and Method 2. Considering that the optimal implementation of Method 1 is to set a corresponding 3D mark for each wafer region, since there are many wafer regions on a wafer, a considerable number of bottom-layer alignment marks must be pre-fabricated on the wafer. Method 2, however, uses the 3D marks of the exposure pattern of the previous wafer region for positioning, which may result in cumulative errors. Therefore, this method combines Methods 1 and 2, spacing the wafer regions with corresponding 3D marks and those without. Specifically, the 3D marks corresponding to the wafer regions serve as absolute reference points to achieve exposure overlay alignment for the first wafer region. The radiation-induced modification of the photosensitive layer (IIRC) of the exposed wafer region is then used as the alignment coordinate for the lateral wafer regions. This alignment is then transferred to the alignment and exposure of the next wafer region. After exposing several wafer regions, the 3D marks corresponding to the wafer regions are obtained as absolute overlay alignment marks, and absolute exposure alignment is restarted for the next batch of wafer regions. This ensures overlay accuracy for all wafer regions while significantly reducing the number of bottom-layer alignment marks required on the wafer.

[0191] The present invention is applicable to deep ultraviolet and extreme ultraviolet optical lithography machines, and solves the technical problem that before exposure, a photon beam cannot be used to directly face a wafer coated with a photosensitive layer for alignment measurement, and the wafer area can only be positioned by moving the wafer worktable. The technical solution disclosed in the present invention does not produce cumulative errors. Therefore, it is avoided that the wafer worktable has to return to the origin every time and move to the specified position with the origin as the absolute reference point, which greatly improves the working speed. In addition, the present invention also solves the technical problem that even if the wafer worktable is accurately positioned, the photon beam will drift due to the drift of the projection objective lens group of the photon beam and the mask (due to various factors such as thermal expansion and contraction), resulting in the complication of the final alignment of the photon beam with the wafer.

[0192] All of the above approaches rely on closed-loop control of the relative position between the wafer and exposure beam to achieve wafer-area overlay alignment. This alignment mechanism is more precise than a precise wafer stage. Even if the wafer stage is temporarily positioned accurately, beam drift on the wafer is difficult to compensate for by the wafer stage or the laser interferometer used to align the wafer and beam.

[0193] While the application has been described in detail by reference to preferred embodiments thereof, it should be recognized that the description set forth herein is by way of example and that modifications of the procedures described can be employed without departing from the scope of the application. Accordingly, the scope of the application should be determined by the appended claims and equivalents thereof.

Claims

1. A photolithography pattern alignment device, the device being located in a photolithography machine body, characterized in that: The device comprises: A wafer workbench for carrying a wafer to be processed, the wafer comprising a plurality of wafer regions and an off-site region surrounding the wafer regions, a photosensitive layer disposed on a surface of the wafer, the photosensitive layer being provided with a three-dimensional mark, the three-dimensional mark having an area that is not on the same level as the upper surface of the photosensitive layer; A nano-needle tip sensing device includes a needle tip sensing head, the needle tip sensing head is located above the photosensitive layer, and is used to move and scan within a scanning area and determine the coordinates of a three-dimensional mark within the scanning area; an exposure beam generating device for providing an exposure photon beam required for exposing a wafer area and forming a projection exposure area on the photosensitive layer; A displacement drive device is used to adjust the relative positions of the exposure beam generating device and the wafer workbench according to the three-dimensional mark coordinates measured by the needle tip sensor head, so that the projected exposure area is aligned with the wafer area to be exposed.

2. The photolithography pattern alignment device according to claim 1, wherein: The device also includes a computer control system, which is used to receive the three-dimensional mark coordinates measured by the nano-needle tip sensing device and compare them with the reference coordinates of the three-dimensional mark to obtain the difference between the two coordinates. The computer control system is used to transmit the difference to the displacement drive device and control the exposure beam generating device and / or the wafer workbench to move relative to each other to compensate for the difference.

3. The photolithography pattern alignment device according to claim 2, wherein: The reference coordinates are preset position coordinates of the three-dimensional marker. When the three-dimensional marker is located at the preset position, the wafer area to be exposed is aligned with the projection exposure area. The reference coordinates are pre-stored in the computer control system.

4. The photolithography pattern alignment device according to claim 2, wherein: The reference coordinates are the coordinates corresponding to the coordinates within the scanning area after the coordinates of the three-dimensional mark measured by the nano-tip sensing device before the exposure of the wafer area are combined with the distance the wafer theoretically needs to move in order to align the wafer area to be exposed next with the projection exposure area. The theoretical distances the wafer needs to move in the horizontal and vertical directions are pre-stored in the computer control system.

5. The photolithography pattern alignment device according to claim 1, wherein: The three-dimensional mark on the photosensitive layer includes a three-dimensional mark formed on the photosensitive layer corresponding to the bottom alignment mark set below the photosensitive layer and / or a three-dimensional pattern formed by radiation-induced modification of the photosensitive layer (IIRC) formed after the exposure photon beam is exposed on the surface of the photosensitive layer.

6. The photolithography pattern alignment device according to claim 5, wherein: The three-dimensional mark corresponding to the bottom layer alignment mark formed on the photosensitive layer is located in the wafer area or in an out-of-field area between adjacent wafer areas.

7. The photolithography pattern alignment device according to any one of claims 5 or 6, wherein: The bottom layer alignment marks include marks made on the surface of the wafer substrate before the wafer is first exposed and / or marks set under the photosensitive layer in a subsequent exposure process.

8. The photolithography pattern alignment device according to claim 1, wherein: The height of the three-dimensional mark is greater than the surface roughness of the photosensitive layer.

9. The photolithography pattern alignment device according to claim 1, wherein: The coordinates of the three-dimensional mark include the lateral position coordinates, the longitudinal position coordinates and the circumferential position coordinates of the wafer.

10. The photolithography pattern alignment device according to claim 1, wherein: Two or more three-dimensional marks are arranged on the photosensitive layer.

11. The photolithography pattern alignment device according to claim 1, wherein: The three-dimensional mark has certain graphic features, and the graphic features include at least one point feature, and the point feature and the upper surface of the photosensitive layer are located in a different horizontal plane.

12. The photolithography pattern alignment device according to claim 11, wherein: The graphic features further include ridge features connected to the dot features, and the ridge features and the upper surface of the photosensitive layer are not completely located in the same plane.

13. The photolithography pattern alignment device according to claim 1, wherein: The three-dimensional mark is a three-dimensional structure protruding from or recessed into the upper surface of the photosensitive layer.

14. The photolithography pattern alignment device according to claim 13, wherein: The three-dimensional structure is at least one of a conical structure, a polygonal prism structure, and a pyramid structure.

15. The photolithography pattern alignment device according to claim 1, wherein: At least one three-dimensional marker is correspondingly provided for each wafer area. The three-dimensional marker is located within the wafer area or in an off-site area surrounding the wafer area. The reference coordinates of the three-dimensional marker are pre-stored in a computer control system.

16. The photolithography pattern alignment device according to claim 1, wherein: Some wafer areas are not provided with corresponding three-dimensional marks, and the wafer areas are aligned with the projected exposure area according to the three-dimensional marks of the three-dimensional pattern in the previous wafer area that has completed exposure measured by the needle tip sensor head.

17. The photolithography pattern alignment device according to claim 16, wherein: The wafer area where the corresponding three-dimensional mark is not set is spaced apart from the wafer area where the corresponding three-dimensional mark is set.

18. The photolithography pattern alignment device according to claim 1, wherein: A positioning mark generating device is provided on the exposure beam generating device. The positioning mark generating device forms a three-dimensional positioning mark on the periphery of the wafer area while the wafer area is exposed. The needle tip sensor head positions and calibrates the position of the wafer area to be exposed according to the three-dimensional positioning mark.

19. The photolithography pattern alignment device according to claim 1, wherein: The height of the three-dimensional mark is less than or equal to 50 microns.

20. The photolithography pattern alignment device according to claim 1, wherein: The needle tip sensor head is a combination of one or more of an active atomic force needle tip sensor head, a laser reflection atomic force needle tip sensor head, a tunnel electron probe sensor head or a nano-scale surface work function measurement sensor head.

21. The photolithography pattern alignment device according to claim 1, wherein: The needle tip sensor head measures the surface structure of the wafer in an atmospheric or vacuum environment, or immerses the needle tip sensor head in liquid in an immersion environment to measure the surface structure of the wafer.

22. The photolithography pattern alignment device according to claim 21, wherein: For immersion lithography, the three-dimensional mark is a three-dimensional mark in the immersion environment, or a three-dimensional mark where the wafer area is not corresponding to an adjacent wafer area in the immersion environment outside the exposure photon beam.

23. The photolithography pattern alignment device according to claim 1, wherein: The surface structure data of the three-dimensional mark measured by the needle tip sensor head is the mathematical convolution of the three-dimensional mark surface structure and the needle tip structure of the needle tip sensor head. The needle tip sensor head measures and calibrates the needle tip structure before measuring the three-dimensional mark.

24. The photolithography pattern alignment device according to claim 1, wherein: The nano-needle tip sensing device further comprises a micro-cantilever, one end of which is fixed and the other end of which is provided with the needle tip sensing head.

25. The photolithography pattern alignment device according to claim 24, wherein: The nano-needle tip sensing device includes one or more needle tip sensing heads, and the needle tip sensing heads are fixed on one side or both sides of the exposure beam generating device through the micro-cantilever.

26. The photolithography pattern alignment device according to claim 25, wherein: The exposure beam generating device comprises a projection objective lens group arranged above the wafer, and the one or more needle tip sensor heads are fixed on one side or both sides of the projection objective lens group via micro cantilevers.

27. The photolithography pattern alignment device according to claim 24, wherein: The wafer workbench comprises a moving part and a fixed part, and the needle tip sensor head is connected to the fixed part through the micro cantilever.

28. The photolithography pattern alignment device according to claim 27, wherein: The nano-tip sensor device includes two or more tip sensor heads, one or more of which are fixed on the fixed part of the wafer workbench, one or more of which are fixed on the side of the exposure beam generating device, and the relative distance between the plurality of tip sensor heads is fixed.

29. The photolithography pattern alignment device according to claim 1, wherein: The nano-tip sensor device includes two or more tip sensor heads. Several of the tip sensor heads are fixed on one side or both sides of the exposure beam generating device through a connecting piece. The distances between the several tip sensor heads are relatively fixed.

30. The photolithography pattern alignment device according to claim 1, wherein: The nano-needle tip sensing device includes three or more needle tip sensing heads, which are fixed to the fixed part of the wafer workbench and / or the exposure beam generating device through a connecting piece. The needle tip sensing heads are located on different straight lines to determine whether the wafer is perpendicular to the exposure photon beam.

31. The photolithography pattern alignment device according to claim 30, wherein: Each of the needle tip sensor heads tests the distance from the wafer surface or photosensitive layer surface corresponding to its position to the exposure beam generating device, and judges whether the wafer and the exposure photon beam are perpendicular based on whether the measured distances are the same, and drives the wafer workbench through the computer control system to adjust until the wafer is perpendicular to the exposure photon beam.

32. The photolithography pattern alignment device according to any one of claims 26 to 29, wherein: The nano-needle tip sensing device includes a plurality of needle tip sensing heads fixed by connecting members. The plurality of needle tip sensing heads are arranged in a row horizontally according to the distribution of the wafer area to form a horizontal needle tip sensing head array.

33. The photolithography pattern alignment device according to claim 32, wherein: At least one needle tip sensor head distributed longitudinally is provided at one end of the transverse needle tip sensor head array to form an L-shaped needle tip sensor head array.

34. The photolithography pattern alignment device according to claim 32, wherein: The two ends of the transverse needle tip sensor head array are respectively provided with longitudinally distributed needle tip sensor heads to form a U-shaped needle tip sensor head array.

35. The photolithography pattern alignment device according to claim 32, wherein: The distance between two adjacent needle tip sensor heads is greater than or equal to the lateral width of a chip area.

36. The photolithography pattern alignment device according to claim 1, wherein: The displacement driving device includes a chip area switching driving device and a nano-displacement driving device.

37. The photolithography pattern alignment device according to claim 36, wherein: The wafer area switching driving device is connected to the moving part of the wafer workbench and is used to drive the wafer areas to be exposed to be exposed below the projection exposure area in sequence.

38. The photolithography pattern alignment device according to claim 37, wherein: The moving part of the wafer workbench also includes a precision moving device, and the nano-displacement driving device is the precision moving device.

39. The photolithography pattern alignment device according to claim 38, wherein: The nano-displacement driving device is connected to the exposure beam generating device and / or the precision moving device of the wafer workbench, and is used to control the exposure beam generating device and / or the wafer workbench to move in the lateral and / or longitudinal and / or circumferential directions.

40. The photolithography pattern alignment device according to claim 38, wherein: The working principle of the nano-displacement driving device to drive the exposure beam generating device and / or the precision moving device to move is at least one of the piezoelectric principle, the voice coil driving principle or the electromagnetic driving principle.

41. The photolithography pattern alignment device according to claim 36, wherein: The exposure beam generating device is a light beam generating device, which includes a light source, a light gate, a beam deflector / reflector, a mask and a projection objective lens group. The nano-displacement driving device is connected to at least one of the beam deflector / reflector, the mask and the projection objective lens group to adjust the position of the projection exposure area of ​​the light beam generating device.

42. The photolithography pattern alignment device according to claim 41, wherein: The at least one needle tip sensor head is fixed on at least one side of the projection objective lens assembly.

43. The photolithography pattern alignment device according to claim 40, wherein: The exposure beam is a parallel beam or a Gaussian beam.

44. The photolithography pattern alignment device according to claim 41, wherein: The light beam shaping and focusing system may be composed of an optical lens or an optical reflector.

45. The photolithography pattern alignment device according to claim 1, wherein: The wafer includes a complete wafer, a partial wafer, or a non-wafer material that requires photolithography exposure processing.

46. ​​A stepper lithography machine for repeatedly exposing multiple chip areas within a wafer, characterized in that: The photolithography machine is provided with a photolithography pattern alignment device as described in any one of claims 1-45.

47. A method for operating a stepper lithography machine, characterized in that: The method comprises: A preparation step of providing at least one bottom layer alignment mark on a wafer and coating a photosensitive layer on the wafer to be processed, wherein the bottom layer alignment mark forms a corresponding three-dimensional mark on the photosensitive layer; an alignment step, placing the wafer provided with the three-dimensional mark in the preparation step into the lithography machine of claim 46, wherein a projection objective lens group is provided near the wafer in the lithography machine, the projection objective lens group corresponding to a projection exposure area on the wafer, driving the wafer worktable to place a first wafer area to be exposed under the projection objective lens group; using the needle tip sensor head to scan the photosensitive layer within a certain scanning area to obtain the position coordinates of the first three-dimensional mark, comparing the position coordinates of the first three-dimensional mark with the reference coordinates of the first three-dimensional mark to obtain the difference between the two position coordinates; and the displacement drive device adjusting the relative positions of the exposure beam generating device and the wafer worktable according to the difference between the two position coordinates, so that the projection exposure area is aligned with the first wafer area; In the exposure step, the light beam generating device emits an exposure photon beam to the first chip area of ​​the wafer to achieve exposure of the first chip area.

48. The method of claim 47, wherein: After the exposure of the first wafer area is completed, the second wafer area is placed under the projection objective lens group. The needle tip sensor head scans the position coordinates of the first three-dimensional marker after movement and compares them with the reference coordinates of the first three-dimensional marker after movement to obtain the deviation of the two position coordinates. The displacement drive device adjusts the relative position of the exposure beam generating device and the wafer worktable according to the difference in the position coordinates, so that the projection exposure area is aligned with the second wafer area, and the exposure of the second wafer area is achieved.

49. The method of claim 48, wherein: The reference coordinates of the first three-dimensional marker after movement are the position coordinates of the first three-dimensional marker when the first chip area is exposed, and are aligned with the projection exposure area to achieve the next chip area to be exposed. The theoretical horizontal and vertical distances that the wafer needs to move are combined to form the corresponding coordinates in the scanning area.

50. The method according to any one of claims 48 or 49, wherein: At least one pinpoint sensor head is respectively arranged on both sides of the projection objective lens group, or a pinpoint sensor head is arranged on one side of the projection objective lens group, and the scanning width of the pinpoint sensor head is greater than the width of a wafer area to be exposed.

51. The method of claim 47, wherein: After the exposure of the first wafer area is completed, the second wafer area is placed under the projection objective lens group. The needle tip sensor head scans the position coordinates of the second three-dimensional mark and compares them with the reference coordinates of the second three-dimensional mark to obtain the deviation of the two position coordinates. The displacement drive device adjusts the relative position of the exposure beam generating device and the wafer worktable according to the difference in the position coordinates, so that the projection exposure area is aligned with the second wafer area, and the exposure of the second wafer area is realized. The reference coordinates of the second three-dimensional mark are pre-stored in the computer control system.

52. The method of claim 51, wherein: The first three-dimensional mark is disposed close to the first wafer area, and / or the second three-dimensional mark is disposed close to the second wafer area.

53. The method of claim 47, wherein: After the exposure of the first chip area is completed, the second chip area is placed under the projection objective lens group. The needle tip sensor head scans the graphics and coordinates of the three-dimensional pattern formed on the photosensitive layer after the exposure of the first chip area and compares them with the preset graphics and coordinates of the three-dimensional pattern to obtain the difference between the positions of the two three-dimensional patterns. The displacement drive device adjusts the relative positions of the exposure beam generating device and the wafer workbench according to the difference in the position coordinates, so that the projection exposure area is aligned with the second chip area, and the exposure of the second chip area is realized.

54. The method according to any one of claims 47 to 53, wherein: The nano-needle tip sensor device is fixed on one side or both sides of the projection objective lens group, and is relatively fixed in position with respect to the projection objective lens group.

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