SUB-NANOSCALE HIGH-PRECISION LITHOGRAPHY WRITING FIELD STITCHING METHOD, LITHOGRAPHY SYSTEM, WAFER, AND ELECTRON BEAM DRIFT DETERMINATION METHOD

Abstract

The invention discloses a sub-nanoscale high-precision lithography writing field stitching method. A photosensitive resist layer is coated on the surface of the wafer to be exposed; after the surface of the photosensitive resist layer is exposed, the exposed pattern will generate a tiny concave-convex structure; the concave-convex structure patterns are identified with a nano contact sensor and can be used as in-situ alignment coordinate markers; by comparing the position coordinates of the writing field before and after exposure and wafer moving, the deviations of stitching can be calculated, and an high-precision lithography stitching of the wafer is performed in a negative feedback control mode, so that the disadvantages of the existing non-in-situ, far-from-writing field and the poor performance of stitching precision in blind type open-loop lithography technology due to the influence of mechanical motion precision of a wafer workbench and long-time drift of an electron beam are overcome.

Claims

1. A method for stitching lithography writing field, comprising: step 1: preparing a lithography system that comprises a chamber (31), a stage (37), an electron microscope comprising an electron beam column (32), an electron gun (372), a workbench (38), at least one nano contact sensor (39), and a numerical control driving device (371), wherein the stage (37), the electron beam column (32), the electron gun (372), the workbench (38), the at least one nano contact sensor (39) are disposed in the chamber (31), and the numerical control driving device (371) is disposed on the stage (37); coating a wafer (1) with a photosensitive resist layer (2); defining an area of the photosensitive resist layer (2) scanned with an electron beam as an exposure area; dividing the exposure area into a plurality of writing fields; in each writing field, establishing in-situ alignment coordinate marks (8, 10, 18, 43, 44) that are printed on the photosensitive resist layer after exposure to the electron beam; and denoting the plurality of writing fields as a first writing field (22-1), a second writing field (22-2), . . . , and Nth writing field (22-n), respectively; step 2: placing the wafer (1) on the workbench (38) so that the first writing field (22-1) of the wafer is within the exposure area (22); placing the electron beam column (32) perpendicular to the exposure area (22); and focusing the electron beam on the first writing field; step 3: exposing a part of the first writing field (22-1), so that the photosensitive resist layer (2) undergoes a chemical reaction that causes electron beam-induced changes and generates at least one or a group of concave-convex structures with specific shapes; using the specific shapes as feature shapes of the in-situ alignment coordinate marks; and establishing an in-situ aligned coordinate system by using a coordinate value of each feature point in the exposure area; step 4: measuring a surface shape of the concave-convex structure using the at least one nano contact sensor; identifying the in-situ alignment coordinate marks against the specific shapes; and determining coordinate values (C1L1; C1L2; C1L3; C1R1; C1R2; C1R3) of the in-situ alignment coordinate marks on the workbench; step 5: moving the wafer horizontally and/or longitudinally, so that the first writing field (22-1) is moved out of the exposure area to make room for a second writing field (22-2) to enter the exposure area; and denoting the first writing field (22-1) moved out of the exposure area as a moved first writing field (22-1′); step 6: starting the nano contact sensor (39) to recognize the alignment coordinate marks in the moved first writing field (22-1′); and determining location coordinates (C1L1′; C1L2′; C1L3′; C1R1′; C1R2′; C1R3′) of the first writing field on the workbench after the movement; step 7: using the data of the alignment coordinate marks in the moved first writing field (22-1′) after the movement as a reference of closed-loop feedback control; calculating an actual coordinate deviation before and after the movement of the writing field; and determining the coordinate correction value for the next entire exposure of the electron beam area: supposing that the coordinates of the second writing field (22-2′) adjacent to the moved first writing field (22-1′) that has been moved out of the exposure area are C1R1′, that is, the coordinates (XCiR1′, YC1R1′), this is also a new coordinate of the second writing field (22-2′) to be exposed, which needs to be seamlessly stitched to the moved first writing field (22-1′), namely:
(X.sub.C2L1′, Y.sub.C2L1′): X.sub.C2L1′=X.sub.C1R1′, Y.sub.C2L1′=Y.sub.C1R1′; the electron beam is facing the second writing field (22-2) located in the exposure area (22) before the error correction with the coordinates of C2L1, namely (X.sub.C2L1, Y.sub.C2L1); since this coordinate requires the stitch correction exposure of the coordinates of the second writing field (22-2) against the edge coordinates C1R1′ of the moved first writing field (22-1′) that has been moved by applying a deflection voltage to the electron beam, the corrected second writing field related coordinate is C2L1′, and the coordinate difference between C2L1′ and C2L1 is:
ΔX.sub.1=X.sub.C2L1′−X.sub.C2L1=X.sub.C1R1′−X.sub.C2L1;
ΔY.sub.1=Y.sub.C2L1′−Y.sub.C2L1=Y.sub.C1R1′−Y.sub.C2L1; given that the second writing field and its coordinates (X.sub.C2L1, Y.sub.C2L1) cannot be obtained because the workbench has not moved and has not been exposed, an overall electron beam drift between the first writing field and the second writing field in the exposure area is firstly ignored, so that the coordinates of the second writing field (22-2) in the exposure area before exposure and before correction are equal to the coordinates of the first writing field (22-1) in the exposure area during exposure: X.sub.C2L1=X.sub.C1L1, Y.sub.C2L1=Y.sub.C1L1, so that the coordinates are measured by the concave-convex structure formed by the exposure of the photosensitive resist layer before the workbench moves after exposing the first writing field, so as to obtain the coordinate difference of all the electron beam coordinates in the second writing field that needed to be compensated:
ΔX.sub.1=X.sub.C1R1′−X.sub.C1L1;
ΔY.sub.1=Y.sub.C1R1′−Y.sub.C1L1; step 8: adjusting the deflection voltage of the electron beam column (32) and correcting the exposure area according to the obtained coordinate difference (ΔX.sub.1, ΔY.sub.1) that needs to be compensated; correcting the stitching coordinates (C2L1; C2L2; C2L3; C2R1; C2R2; C2R3) of the second writing field (22-2) which subsequently enters the exposure area to the adjacent stitching coordinates of the moved first writing field, so that the second writing field (22-2′) are seamlessly stitched with the first writing field.

2. The method of claim 1, wherein the method further comprises: Step 9: moving the second writing field (22-2′) to the corrected exposure area; exposing a part of the wafer in the second writing field (22-2′) with the electron beam, so that the photosensitive resist layer is subjected to chemical reaction to expose the preset alignment coordinate marks characterized by the specific concave-convex structure in the writing field; Step 10: starting the nano contact sensor (39) to identify the preset alignment coordinate marks against the preset specific shapes; determining the position coordinates (C2L1′; C2L2′; C2L3′; C2R1′; C2R2′; C2R3′) of the corrected second writing field (22-2′) on the workbench; Step 11: moving the wafer horizontally and/or longitudinally, so that the second writing field (22-2) is moved out of the exposure area to make room for a third writing field to enter the exposure area; and denoting the second writing field (22-2) moved out of the exposure area as the second writing field (22-2′); wherein the position coordinates of the moved first writing field (22-1′) are changed from (C1Lx′, C1Rx′) to (C1Lx″, C1Rx″), and the position coordinates of the second writing field are changed from (C2Lx′, C2Rx′) to (C2Lx″, C2Rx″); Step 12: starting the nano contact sensor to recognize the alignment coordinate marks in the second writing field (22-2″) moved of the exposure area; and determining the position coordinates (C2L1″; C2L2″; C2L3″; C2R1″; C2R2″; C2R3″) of the second writing field (22-2″) on the surface of the workbench (38); Step 13: using the data of the alignment coordinate marks in the second writing field after the movement as a reference of closed-loop feedback control; calculating the deviation of the actual coordinates before and after the movement to determine a correction value ΔX.sub.2 and ΔY.sub.2 of the writing field in the next exposure: suppose that the coordinates of the third writing field that is adjacent to the moved second writing field that has moved out of the exposure area and is about to be exposed are C2R1″, that is, coordinates (X.sub.C2R1″, Y.sub.C2R1″); the coordinates are also the third writing field to be exposed, which is needed to be stitched to the corrected coordinates of the moved second writing field, namely:
(X.sub.C3L1″, Y.sub.C3L1″): X.sub.C3L1″=X.sub.C2R1″, Y.sub.C3L1″=Y.sub.C2R1″, the electron beam is now facing the third writing field located in the exposure area with the coordinates of C3L1, namely (X.sub.C3L1, Y.sub.C3L1); a coordinate difference between the coordinates and the moved second writing field, which is to be stitched and exposed as following, is this coordinate point to be stitched against the edge C2R1″ of the moved second writing field (22-2″) by adding a deflection voltage to the electron beam; the corrected related coordinate of the third writing field (22-3″) is C3L1″, and the coordinate difference between C3L1″ and C3L1′ is:
ΔX.sub.2=X.sub.C3L1″−X.sub.C3L1′=X.sub.C2R1″−X.sub.C3L1′;
ΔY.sub.2=Y.sub.C3L1″−Y.sub.C3L1′=Y.sub.C2R1″−Y.sub.C3L1′; the overall electron beam drift of the second writing field and the third writing field exposed by the electron beam in the exposure area is ignored, so that the coordinates of the third writing field before the correction of the exposure coordinate in the exposure area are equal to the second writing field coordinates during exposure: X.sub.C3L1′=X.sub.C2L1′, Y.sub.C3L1′=Y.sub.C2L1′, so that the coordinates can be measured by the concave-convex structure formed by the exposure on the surface of the photosensitive resist layer after the second writing field is exposed and before moving the workbench to obtain the coordinate difference to be compensated for the electron beam coordinate correction of all the writing field exposure points:
ΔX.sub.2=X.sub.C2R1″−X.sub.C2L1′;
ΔY.sub.2=Y.sub.C2R1″−Y.sub.C2L1′; Step 14: adjusting the deflection voltage of the electron beam column (32) according to the correction value; and correcting the exposure area so that the coordinates of all exposure points in the third writing field of the subsequent wafer are stitched seamlessly with the coordinates of the second writing field (22-2″); and Step 15: repeatedly completing the exposure, movement and stitching of the entire writing field area of the entire wafer.

3. The method of claim 1, wherein the electron beam is replaced by an ion beam, a photon beam, or an atomic beam.

4. The method of claim 1, wherein the nano-contact sensor is an atomic force tip sensor, a tunnel electron probe sensor, a nano-level surface work function measurement sensor, or a combination thereof.

5. The method of claim 1, wherein the wafer is an entire wafer, a part of a wafer, or non-wafer materials that require lithography writing field stitching processing.

6. The method of claim 1, wherein the in-situ alignment coordinate marks (8, 10, 18) are planar graphic marks; the planar graphic marks are provided with 1, 2, 3, 4, 5, 6 or more on a plane; and the planar graphic marks are formed by scanning the electron beam in a patterned fashion across a surface of the photosensitive resist layer to produce very small geometric structures.

7. The method of claim 1, wherein the in-situ alignment coordinate marks (43, 44) are three-dimensional marks; and the three-dimensional marks are pyramid-shaped or cone-shaped, and are provided with 1, 2, 3, 4, 5, 6 or more on a plane.

8. The method of claim 7, wherein at least one nano-contact sensor (39) is distributed around the exposure area; and the nano-contact sensor (39) comprises a lever type sensing contact arm (391); and the lever type sensing contact arm (391) comprises one or more needle point sensing contacts (392) arranged in a row.

9. The method of claim 1, wherein the electron beam is a Gaussian Beam or a Variable Shaped Beam.

10. A sub-nano-level high-precision writing field stitching lithography system, comprising a stationary chamber (31) and a stage (37) in the stationary chamber; an electron microscope, at least one nano-contact sensor (39), and a wafer workbench (38) are arranged on the stage (37); an electron beam column (32) is provided on the electron microscope; the wafer workbench (38) is provided with a numerical control driving device (371) for dragging a front, back and/or left, right and/or upward, downward movement of the wafer workbench and changing an angle of the wafer workbench.

11. The system of claim 10, wherein the lithography system further comprises a control computer (42), a pattern generator (46), and an electron beam control system (34); the control computer is connected to the pattern generator (46), the electron beam control system (34), and the numerical control driving device (371); the nano-contact sensor (39) is configured to send a collected in-situ alignment coordinate identification signal (40) and/or an electron beam drift signal on the measured wafer to the pattern generator (46) under the control of the control computer (42); the pattern generator (46) is configured to send the corrected electron beam scanning control signal after operation processing to the electron beam control system (34) under the control of the control computer (42); and the electron beam control system (34) is configured to control the shutter of the focusing system (32) on the electron beam column (32) and the deflection coil (35).

12. The system of claim 10, wherein the field stitching system further comprises a secondary electron imaging signal acquisition device (36) disposed on the electron beam column (32); the secondary electron imaging signal acquisition device (36) is configured to collect a secondary image scanned by the electron beam and feeds the secondary image back to the control computer (42) through the electron beam control system (34).

13. The system of claim 10, wherein the nano-contact sensor (39) is an atomic force tip sensor, a tunnel electron probe sensor, a nano-level surface work function measurement sensor, or a combination thereof

14. The system of claim 10, wherein the nano-contact sensor (39) is provided with a lever-type sensing contact arm (391), and the contact arm (391) is equipped with a needle tip sensing contact (392).

15. The system of claim 14, wherein one or more needle tip sensing contacts (392) are disposed on each contact arm (391).

16. The system of claim 14, wherein each contact arm (391) is provided with at least one row of needle tip sensing contacts, and each row is provided with more than one needle tip sensing contact (392).

17. The system of claim 10, wherein the field stitching system comprises two rows of the nano-contact sensor (39) arranged on both sides of the electron beam column (32), four contact sensors in each row; and the electron beam column (32) is directly facing the exposure area (22) of the wafer on the workbench (38).

18. A pre-processed wafer, being coated with a photosensitive resist layer to be exposed, where in-situ alignment coordinate marks (8, 10, 18, 43, 44) which have a specific concave and/or convex shape and used for a nano contact sensor (39) to recognize an in-situ coordinate are arranged inside a writing field area of the wafer and/or the photosensitive resist layer thereof after electron beam exposure.

19. The pre-processed wafer of claim 18, wherein the in-situ alignment coordinate marks (8, 10, 18) are planar graphic marks; and there are 1, 2, 3, 4, 5, 6 or more of the planar graphic marks on a plane.

20. The pre-processed wafer of claim 19, wherein the planar graphic marks are a pattern mark formed by a small geometric structure change on a surface of the photoresist layer induced by an electron beam.

21. The pre-processed wafer of claim 18, wherein the in-situ alignment coordinate marks (43, 44) are three-dimensional marks; and the three-dimensional marks are provided with 1, 2, 3, 4, 5, 6 or more on a plane.

22. The pre-processed wafer of claim 18, wherein the wafer comprises an entire complete wafer, a partial wafer, or a non-wafer material that requires a photolithography writing field stitching process.

23. A method for measuring electron beam drift, comprising: disposing a stage (37), an electron microscope lens column (32) and an electron gun (372) thereof, a wafer workbench (38) and a nano contact sensor (39) in a machine chamber (31) of a lithography system; equipping the wafer workbench (38) with a numerical control driving device (371) to control a movement of the wafer workbench; coating a photosensitive resist layer on a wafer, and emitting an electron beam (17) by the electron gun (372) to irradiate and expose the photosensitive resist layer at a focal point, whereby a small change in a concave-convex geometric shape induced by the electron beam forms on a surface of the photosensitive resist layer; measuring the small change and tracking the drift of the focus point over time, and recording the coordinate value and a drift amount of a drift track (30) of the electron beam over time.

24. The method of claim 23, further comprising: calculating exposure coordinate values and correction compensation differences generated by the drift of the electron beams over time in the initial and final interval time periods according to the recorded coordinate values and the drift amount of the drift track (30) of the electron beams over time, and obtaining correction coordinates of a next writing field exposure.

25. A vertical stitching method of sub-nano-level high-precision lithography writing field, comprising: presetting a three-dimensional alignment mark (43) with a protruding structure on a wafer to be lithographically processed, coating the three-dimensional alignment mark with a photosensitive resist layer (2) to generate a corresponding protruding structure of the three-dimensional alignment mark of the photosensitive resist layer at the position where the three-dimensional alignment mark is preset, moving a wafer with the three-dimensional alignment mark by the wafer workbench (38) to a writing field area that can be exposed by the electron beam (4), aligning the electron beam (4) at the position of the three-dimensional alignment mark (44) of the photosensitive resist layer and performing spot exposure, whereby an actual deviated three-dimensional mark (45) is generated outside the exposure point of the resist layer, measuring an actual coordinate value of the three-dimensional alignment mark (44) and the deviated three-dimensional mark (45) by the nano-contact sensor, calculating a correction value of the exposure area of the writing field, and controlling an electron gun to achieve vertical precise alignment and exposure, thus achieving vertical precise stitching.

Description

DESCRIPTION OF THE DRAWINGS

[0118] FIGS. 1A and 1B are schematic diagrams of electron beam lithography;

[0119] Among them: 1—wafer (substrate); 2—photosensitive resist layer; 3—pattern produced after electron beam exposure (take grating as an example); 4—electron beam emitted by electron gun in the electron beam column; 5—just exposed Position of the electron beam coordinates (CPJE); 6—No exposure but aiming at the coordinates of the electron beam to be exposed.

[0120] FIGS. 2A-2B are schematic diagrams of two principles of using electron beam-induced photoresist layer modification (EBIC) in the disclosure to expand or shrink on the sub-nanometer or nanometer scale to form a concave-convex structure.

[0121] Among them: 1—wafer (substrate); 2—photosensitive resist layer; 7—electron beam unexposed photosensitive resist layer; 8—electron beam exposed photosensitive resist layer EBIC (concave shrinkage); 10—electron The EBIC of the light-sensitive resist layer that has been exposed by the beam (produces convex expansion); 9, 11 are the height-direction concave contraction and convex expansion scales, usually on the order of sub-nanometer to several nanometers.

[0122] FIG. 3 is a schematic diagram of the locations of three types of alignment marks;

[0123] Among them: 1—wafer; 12—long-distance out-of-field mark (RA1); 13—in-field mark (IA); 14—out-of-field mark (RA2) located between writing fields; 15—writing field; 16—rotation Angle, x and Y are rectangular coordinate systems. The wafer moves in the XYZ direction or XY, YZ, XZ plane through the workbench.

[0124] The mark 12 far away from the writing field and the mark 14 between writing fields in the traditional technology are both outside the writing field: it is a long-distance alignment mark (RA mark), which can only allow the electron beam to radiate by moving the workbench away from the writing field.

[0125] The in-field mark is used in the disclosure. It is an in-field mark (IA mark), which can be radiated in the writing field without moving the wafer stage. If the in-field mark is placed exactly on or very close to the photoresist layer/wafer under the electron beam mark (CPJE, CPTE), it can be used as an in-situ alignment mark (ISA). If these two coordinates coincide, this in-situ alignment mark constitutes an overlapped alignment mark (OA mark).

[0126] FIG. 4 is a schematic diagram of the principle of another uneven structure of the disclosure;

[0127] Among them: 1—wafer; 2—photosensitive resist layer; 392—contact of nano-contact sensor 39; 18—photosensitive resist layer three-dimensional protrusion alignment mark (HAMR); 19—preset three-dimensional convexity on the wafer surface Out alignment mark (HAMW); 20—the height of the preset three-dimensional protruding mark on the surface of the wafer, located under the photosensitive resist layer 2; 21—the height of the three-dimensional protruding mark on the photosensitive resist layer 2, which is determined by the wafer 1. The three-dimensional protruding mark of the photosensitive resist layer caused by the transfer of the preset three-dimensional protruding mark on the surface can be detected by the contact 392 of the nano-contact sensor 39 for the uneven structure.

[0128] FIGS. 5A-5C are schematic diagrams of the process in which there is a huge stitching error between the writing fields of the previous writing field and the writing field of the next writing field in the prior art;

[0129] In FIG. 5A: 22—is the first writing field, the wafer in the writing field is at the exposure position; 23—is the grating (taking the grating as the exposure pattern as an example); 24—is the alignment mark far away from the writing field;

[0130] The figure shows the first writing field 22 that enters the exposure area and waits for electron beam exposure.

[0131] In FIG. 5B: 22′—is the first writing field moved out of the exposure area; 22—is the second writing field position moved into the exposure area subsequently; 27—is the actual moving direction of the workbench 38; 28—is the planned moving direction of the workbench 38;

[0132] In the figure, the workbench 38 moves to move the first writing field out of the range of the writing field irradiated by the electron beam, freeing up the electron beam exposure space for the next writing field, that is, the second writing field. The mechanical error of the moving of the workbench 38 will cause stitching errors.

[0133] In FIG. 5C: 29X is the horizontal (X direction) stitching error caused by the movement of the workbench 38, and 29Y is the vertical (Y direction) stitching error caused by the movement of the workbench 38.

[0134] FIG. 6A is a schematic diagram of the prior art when the wafer has not been moved out of the original position after being exposed in the first writing field 22 of the exposure area;

[0135] FIG. 6B is a schematic diagram of the wafer being placed in the first writing field 22 of the exposure area, the wafer is removed for other processing and then placed in the workbench exposure area for photolithography or for the second exposure. Due to the error caused by the movement of the stage, the new position 22′ of the first writing field is deviated. At this time, the writing field in the electron beam exposure area is the second writing field, that is, the original writing field position 22. The writing field 22′ does not coincide with the second writing field, resulting in a vertical alignment error.

[0136] FIGS. 7A-7B are schematic diagrams of describing and characterizing the electron beam by electron beam induced modification of the photosensitive layer 2 (EBIC);

[0137] In FIG. 7A: 1—wafer; 2—photosensitive resist layer; 17—electron beam; 29—exposure point of photosensitive resist layer 2 exposed electron beam focus point;

[0138] In FIG. 7B: 1—wafer; 2—photosensitive resist layer; 17—electron beam; 17′—the position of the electron beam drifted with time; 30—the exposed spot of the photosensitive resist layer 2 reveals the focus of the electron beam irradiation after the drift.

[0139] FIG. 8 is a schematic diagram of the composition of the sub-nano-level high-precision writing field stitching lithography machine system of the disclosure;

[0140] FIGS. 9A-9F are schematic diagrams of the stitching alignment method illustrated by the disclosure taking horizontal stitching as an example;

[0141] FIG. 9A shows the position coordinates of 6 in-situ alignment markers measured by the nano contact sensor after the wafer in the first writing field 22-1 has been exposed after exposure (for example): C1L1, C1L2, C1L3 and C1R1 C1R2, C1R3. Among them: C1 represents the first writing field, Lx represents the left coordinate of the writing field; Rx represents the right coordinate of the writing field.

[0142] FIG. 9B shows the position coordinates of the above-mentioned in-situ alignment coordinate mark after the movement is measured by the nano-contact sensor after the wafer in the first writing field 22-1 is exposed and moved out of the exposure area 22 to become the writing field 22-1′: C1L1′-L3′ and C1R1′-R3′, and the next writing field moved into the exposure area 22 is the second writing field (writing field 22-2); the electron beam scanning exposure area is still 22-1, which is the current writing field 22-2.

[0143] The wafer workbench moves, and then the second writing field cannot be exposed at this position due to stitching errors. Its coordinates are C2L1-L3 and C2R1-R3; after the workbench moves, the graphics related to the writing field 22-1′ are moved to the left of the second writing field that will be subjected to subsequent exposure, the corresponding coordinates measured by the nano contact sensor after moving are: C1L1′-L3′ and C1R1′-R3′;

[0144] FIG. 9C is calculated based on the comparison of the measured coordinate values of the first writing field 22-1 after exposure and moving out of the exposure area to become the writing field 22-1′ with the measured coordinate values of the first writing field 22-1 that have not moved out of the exposure area after exposure The error correction value negative feedback adjustment and correction of the writing field of the actual exposure area becomes the position schematic diagram of the corrected second writing field 22-2′;

[0145] The coordinates of the corrected second writing field 22-2′ are: C2L1′, C2L2′, C2L3′ and C2R1′, C2R2′, C2R3′, and: C2L1′ is the same as C1R1′, C2L2′ is the same as C1R2′, C2L3′ is the same as C1R3′, that is, the corrected second writing field 22-2′ and the writing field 22-1′ achieve precise stitching.

[0146] FIG. 9D: The workbench moves for the first time, and the second writing field is seamlessly stitched with the first writing field. At this time, the workbench moves a second time, freeing up a new exposure area space 22-3′. At this time, the coordinates of the first writing field become C1Lx″, C1Rx″ due to the second movement of the workbench, and the coordinates of the second writing field become C2Lx″, C2Rx″ due to the second movement of the workbench. The corresponding coordinates of 22-3′ are C3Lx′, C3Rx′. The electron beam exposure area still stays at the corrected second writing field 22-2′.

[0147] FIG. 9E: The electron beam obtains the coordinate deviation value of the exposure third writing field, and through the electron beam coordinate compensation, the exposure area is moved to be close to the second writing field 22-2″. Then the third writing field exposure is performed.

[0148] FIG. 9F: The third movement of the workbench. The first writing field 22-1″ moves to become 22-1″′, the second writing field 22-2″ moves to become 22-2″′, and the third writing field 22-3″ moves to become 22-3″′. Free up the exposure space 22-4″ (at the 22-3″ position).

[0149] FIGS. 10A and 10B are schematic diagrams of using two nano-contact sensors to measure in-situ coordinate marks to achieve stitching and alignment, so as to achieve faster measurement speed.

[0150] The contacts 392 of the two sets of nano-contact sensors 39 in FIG. 10a are placed on both sides of the writing field 22, which facilitates the wafer to move to the left or stitched to the right through the workbench. At this time, the writing field 22 has been exposed but has not moved out of the exposure area, the contacts 392 of the two sets of nano-contact sensors performs measurement to the in-situ align coordinate marks C1L1, C1L2, C1L3 and C1R1, C1R2, C1R3 preset on the writing field 22; each group of nano-contact sensors 39 contains three longitudinal contacts 392 for example.

[0151] FIG. 10B is a schematic diagram showing a process in which two sets of nano-tip sensors are moved to both sides of the writing field 22-1′, and in-situ alignment coordinate markers C1L1′, C1L2′, C1L3′, C1R1′, C1R2′ and C1R3′ on a wafer moved out of the exposure area after exposure and located at the position of the writing field 22-1′ are measured, so as to calculate an error correction value for a subsequently entered wafer of the writing field 22-2, and adjust exposure deflection parameters and a focus of an electron gun in a lens column of an electron microscope, so that the corrected stitching coordinates of the writing field 22-2′ are precisely matched with the writing field 22-1′.

[0152] FIG. 11 is a schematic diagram of a method for realizing vertical layer alignment and stitching by using preset three-dimensional protruding structures 43 on the wafer and the photosensitive resist layer and the three-dimensional structure 44 of the photosensitive resist layer as three-dimensional in-situ alignment coordinate marks, and schematic diagram of the method of aligning and stitching the vertical layer by measuring the offset exposure error using electron beam 4.

[0153] Firstly, pre-position the protruding structure of the wafer three-dimensional alignment mark 43 on the wafer to be processed by photolithography, and then coat the photo-sensitive resist layer on it, so that the three-dimensional alignment mark is also generated at the position where the three-dimensional alignment mark is preset. The three-dimensional alignment mark 44 of the photosensitive resist layer corresponding to the protruding structure.

[0154] Move the wafer with the three-dimensional alignment mark through the wafer stage 38 into the writing field area where the electron beam can be exposed, and align the electron beam to the three-dimensional alignment mark 44 (position 1) of the photosensitive resist layer for spot exposure. A three-dimensional mark 45 (position 2) that may be deviated is generated on the exposure point of the resist layer. Using the nano contact sensor to measure position 1 and position 2 can calculate the correction value of the exposure area of the writing field, thereby controlling the electron gun to achieve precise vertical alignment and exposure, thereby achieving precise stitching.

[0155] FIG. 12 is a schematic diagram of the rapid stitching and alignment of nano-contact sensors with multiple nano-contacts on each nano-contact sensor.

[0156] The sensing arm of the nano-contact sensor 39 is provided with 2 rows, each with 4 nano-contacts.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0157] Referring to FIGS. 1A-1B and 8, a sub-nano-level high-precision writing field stitching lithography machine system is constructed, which comprises a sealed, statically placed electron microscope chamber 31, a stage 37 in the chamber 31, an electron beam column 32, and at least one nano-contact sensor 39 and a wafer workbench 38; an electron beam column 32, an electron emission gun 372, a focusing system 33, a deflection coil 35, etc. are provided on the electron microscope. The wafer workbench 38 is provided with a numerical control driving device 371 for dragging it forward, backward, left, right and/or up and down, and angle changes.

[0158] The control computer 42 is connected to the electron beam column and the nano contact sensor 39 via an electron beam control system 34 and a pattern generator 46. The nano contact sensor 39 aligns the collected in-situ coordinate identification signals on the measured wafer 40 and/or the electron beam drift signal 40 is sent to the pattern generator 46 under the control of the control computer 42, and the pattern generator 46 sends the corrected electron beam scanning control signal after calculation and processing to the electron beam control under the control of the control computer 42 System 34. The electron beam control system 34 controls the shutter of the focusing system 33 on the electron beam column 32 and the deflection coil 35 that controls the deflection of the electron beam. In view of the fact that the structure and working principle of the electron microscope and the nano contact sensor are well known, the electron microscope and the nano contact sensor will not be described in more depth here.

[0159] The electron beam column 32 may further comprise a secondary electron image signal collecting device 36 for feeding back the collected secondary image scanned by the electron beam to the control computer 42 through the electron beam control system 34 for video display.

[0160] The nano-contact sensor 39 has sub-nano-level measurement accuracy, and can use any one or more of an atomic force tip sensor, a tunnel electron probe sensor, or a nano-level surface work function measurement sensor. The nano-contact sensor 39 is installed in the sample cavity of the electron beam lithography system, and can measure the three-dimensional surface topography with sub-nanometer accuracy and good spatial repeatability. The nano-contact sensor is located beside the electron beam column 32, near the focus point of the electron beam and above the surface of the photosensitive resist layer.

[0161] The nano contact sensor 39 is provided with a lever-type sensing contact arm 391, and the contact arm 391 is provided with a needle tip sensing contact 392, as shown in FIG. 8.

[0162] Each contact arm 391 is provided with at least one row of needle tip sensing contacts 392, and each row is provided with more than one needle tip sensing contacts 392.

[0163] Taking FIGS. 10A-10B as an example, there are two rows of needle tip sensing contacts 392, each row is provided with one needle tip sensing contact 392, and the two rows are arranged on both sides of the electron beam column 372.

[0164] FIG. 12 is an example, in which there are two rows of needle tip sensing contacts 392, and each row is provided with 4 needle tip sensing contacts 392.

[0165] The electron beam column 32 is facing the exposure area 22 of the wafer on the wafer stage 38.

[0166] At the beginning of the implementation of the method of the disclosure, the wafer needs to be pre-processed, that is, the photosensitive resist layer 2 to be exposed is coated on the wafer 1, and part of the writing field area of the wafer 1 and/or the photosensitive resist layer 2 is provided After electron beam exposure, it can reveal the in-situ alignment coordinate mark 8, the in-situ alignment coordinate mark 10, the in-situ alignment, which is composed of concave and/or convex and has a specific shape for the nano contact sensor 39 to recognize the in-situ coordinates. The coordinate mark 44 or the coordinate mark 45 is aligned in situ.

[0167] This in-situ alignment coordinate mark can be a graphic mark of a plane structure, and 1, 2, 3, 4, 5, 6 or more can be arranged on a plane, and of course there can be more. In this embodiment, it is preferable to use an electron beam to induce the surface of the photoresist layer to produce a small geometric structure change to form a graphic mark. It is also possible to use other well-known technologies to form a similar effect.

[0168] The in-situ alignment coordinate marks can also be made into three-dimensional marks, and 1, 2, 3, 4, 5, 6 or more can be arranged on a plane, of course, there can be more. The three-dimensional shape mark is preferably made into a pyramid-shaped or cone-shaped three-dimensional shape for easy electronic identification, and other shapes are also possible.

[0169] After constructing the above working environment, the sub-nano-level high-precision lithography writing field stitching method of the disclosure can be implemented, and the steps involved are as follows:

[0170] Step 1: In the chamber 31 of the lithography machine system, set the stage 37, the electron microscope and its electron beam column 32, the electron gun 372, the wafer moving stage 38 and at least one nano-contact sensor 39; wafer work The stage 38 is equipped with a numerical control driving device 371 that controls its movement; before the wafer is put into the lithography system, the entire wafer 1 is coated with a photosensitive resist layer 2, and the electron beam scanning range is the exposure area 22, the exposure area is divided into a plurality of writing fields, and each writing field on the photosensitive resist layer is provided with a specific in-situ alignment coordinate mark 8, which will reveal a predetermined shape after exposure in the exposure area, an in-situ alignment coordinate mark 10. Position alignment coordinate mark 18, in-situ alignment coordinate mark 43, in-situ alignment coordinate mark 44; the writing fields are the first writing field 22-1, the second writing field 22-2, . . . the nth writing field 22-n. For example, if there are 1000 writing fields, then n is 1000, and the wafers with 1000 writing fields need to be exposed and stitched.

[0171] Step 2: Place the wafer 1 coated with the photosensitive resist layer 2 on the workbench 38, and make the first writing field 22-1 of the wafer fall into the exposure area 22, so that the electron beam column 32 of the electron microscope is vertical for the exposure area 22, the electron beam is then focused on the writing field. The first writing field 22-1 refers to the first writing field, the second writing field 22-2 refers to the second writing field, and the third writing field refers to the third writing field. “′” of “22-1′” means that the workbench has moved once. “″” of “22-1″” means that the work stage has moved twice, that is, “22-1″” means the first writing field and the work stage has moved the first writing field twice, and so on.

[0172] Step 3: Expose a part of the wafer on the first writing field 22-1 in the exposure area 22, so that the photosensitive glue coated on the part of the wafer undergoes a chemical reaction after exposure to cause electron beam-induced changes to produce at least one or a group of concave-convex structures forming a pattern, the specific shape of the concave-convex structure is used as the feature shape of the preset in-situ alignment coordinate mark, and the coordinate value of the feature point in the exposure area is taken as the in-situ alignment coordinate.

[0173] Step 4: Enable the nano contact sensor (39) to measure the surface shape of the concave-convex structure first, then identify the above-mentioned alignment coordinate mark against the preset specific shape, and then determine and memorize its coordinate value on the work surface, for example: (C1L1; C1L2; C1L3; C1R1; C1R2; C1R3). In principle, more than one of these coordinate points can be selected in the writing field (the same below).

[0174] Step 5: Pre-exposure preparation for the second writing field. The moving stage 38 drives the wafer 1 to move laterally and/or longitudinally, so that the first writing field area 22-1 that has just been exposed moves out of the exposure area to become the writing field 22-1′, to make place for the second writing field 22-2 of the subsequent wafer to enter the exposure area.

[0175] Step 6: Start the nano contact sensor 39 to recognize the alignment coordinate mark in the first writing field 22-1′ moved out of the exposure area, and determine and memorize the first writing field position coordinate (C1L1′; C1L2′; C1L3′; C1R1′; C1R2′; C1R3′).

[0176] Step 7: Taking the data of the alignment coordinate mark in the first writing field 22-1′ after the movement as the basis for closed-loop feedback control, calculate the actual coordinate deviation before and after the writing field movement to determine the entire exposure area of the next electron beam coordinate correction value;

[0177] Suppose the first writing field 22-1′ that has moved out of the exposure area is adjacent to the second writing field 22-2′ to be exposed and the coordinates of the second writing field 22-2′ after error correction is C1R1′, that is, the coordinates X.sub.C1R1′, Y.sub.C1R1′, this is also about to be exposed The second writing field 22-2′ needs to be seamlessly stitched to the new coordinates of the moved first writing field 22-1′, namely:

(X.sub.C2L1′, Y.sub.C2L1′): X.sub.C2L1′=X.sub.C1R1′, Y.sub.C2L1′=Y.sub.C1R1′,

[0178] The electron beam is now facing the second writing field 22-2 in the exposure area 22. The coordinates of the second writing field 22-2 before the error correction is C2L1, that is, the coordinates (X.sub.C2L1, Y.sub.C2L1), because this coordinate point needs to be attached by applying a deflection voltage to the electron beam. Use the edge coordinates C1R1′ of the first writing field 22-1′ that have been moved to perform stitching correction exposure to the coordinates of the second writing field 22-2, so that the corrected second writing field related coordinate points are C2L1′, C2L1′ and The coordinate difference of C2L1 is:

ΔX.sub.1=X.sub.C2L1′−X.sub.C2L1=X.sub.C1R1′−X.sub.C2L1

ΔY.sub.1=Y.sub.C2L1′=Y.sub.C2L1′=Y.sub.C1R1′−Y.sub.C2L1

[0179] In view of the second writing field and its coordinates X.sub.C2L1, Y.sub.C2L1 is not available because the workbench has not moved and has not been exposed. First, the electron beam is exposed to the exposure area of the first writing field and the entire electron of the exposure area of the second writing field. The beam drift is ignored, so that the coordinates of the second writing field 22-2 in the exposure area before exposure and before the correction are equal to the coordinates of the first writing field 22-1 in the exposure area: X.sub.C2L1=X.sub.C1L1, Y.sub.C2L1=Y.sub.C1L1, and then The coordinates can be measured by the concave-convex structure formed by the surface of the photosensitive resist layer before the workbench moves after the exposure in the first writing field, so as to obtain the coordinate difference that needs to be compensated for all the electron beam coordinate points in the second writing field:

[0180] ΔX.sub.1=X.sub.C1R1′−X.sub.C1L1

[0181] ΔY.sub.1=Y.sub.C1R1′−Y.sub.C1L1.

[0182] Step 8: Adjust the deflection voltage of the electron beam column 32 according to the obtained coordinate difference (ΔX.sub.1, ΔY.sub.1) that needs to be compensated, and correct the electron beam exposure area to subsequently enter the second writing field 22-2 of the wafer in the exposure area The stitching coordinates (C2L1; C2L2; C2L3; C2R1; C2R2; C2R3;) are corrected to the adjacent stitching coordinates (C2L1′; C2L2′; C2L3′; C2R1′; C2R2′; C2R3′;), the stitched coordinates of the corrected second writing field 22-2′ are seamlessly connected to the moved first writing field.

[0183] Step 9: Perform electron beam exposure on the part of the wafer in the second writing field 22-2′ that is moved to the exposure area corrected by the electron beam exposure coordinates, so that the exposed part of the wafer is coated with photosensitive The glue chemically reacts to reveal the preset alignment coordinate mark in the writing field characterized by a specific concave-convex structure.

[0184] Step 10: Start the nano contact sensor 39 to identify the above-mentioned alignment coordinate mark against the preset specific shape, determine and memorize the position coordinates of the characteristic coordinate points in the corrected second writing field 22-2′ on the work surface (C2L1′; C2L2′; C2L3′; C2R1′; C2R2′; C2R3′).

[0185] Step 11: Perform pre-exposure preparations for the third writing field, move the workbench 38 again to drive the wafer 1 to move laterally and/or longitudinally, so that the previously moved first writing field 22-1′ and the corrected post-exposure The second writing field 22-2′ is moved so that the corrected second writing field that has just been exposed is moved out of the exposure area, and the position coordinates of the previously moved first writing field 22-1′ are generated by moving the workbench The first writing field 22-1′ which has been moved twice, the position coordinates are changed from (C1Lx′, C1Rx′) to (C1Lx″, C1Rx″), and the position of the second writing field moved out of the exposure area after correction The coordinates change from (C2Lx′, C2Rx′) to (C2Lx″, C2Rx″), and this second writing field becomes the second writing field after the movement (22-2″), which is the third writing field (22-3′) Move into the exposure area to make place.

[0186] Step 12: Start the nano contact sensor 39 again to recognize the alignment coordinate mark in the second writing field 22-2″ removed from the exposure area, and determine and memorize its position coordinates (C2L1″; C2L2; C2L3″; C2R1″; C2R2″; C2R3″) on the surface of the workbench 38.

[0187] Step 13: Taking the data of the alignment coordinate mark in the second writing field after the movement as the basis of closed-loop feedback control, the deviation of the actual coordinates before and after the movement is calculated to determine the correction value ΔX.sub.2 and ΔY.sub.2 of the writing field of the next exposure area of the electron beam:

[0188] Suppose that the coordinates of the third writing field that is adjacent to the moved second writing field that has moved out of the exposure area and is about to be exposed are C2R1″, that is, coordinates (X.sub.C2R1″, Y.sub.C2R1″). This is also the corrected coordinates of the third writing field to be exposed which is needed to be stitched to the moved second writing field, that is (X.sub.C3L1″, Y.sub.C3L1″): X.sub.C3L1″=X.sub.C2R1″, Y.sub.C3L1″=Y.sub.C2R1″;

[0189] Electron beam at this time is located in the exposure area of the third write field coordinates are C3L1, that is, the coordinates (X.sub.C3L1, Y.sub.C3L1), and the coordinate difference between it and the second writing field that has been moved to follow the stitching exposure is this coordinate point. By adding deflection voltage to the electron beam, the edge C2R1″ of the second writing field 22-2″ that has been moved is stitched and exposed, and the relevant coordinate points of the corrected third writing field 22-3″ are C3L1″, the coordinate difference of C3L1″ and C3L1′ is:

ΔX.sub.2=X.sub.C3L1″−X.sub.C3L1′=X.sub.C2R1″−X.sub.C3L1′

ΔY.sub.2=Y.sub.C3L1″−Y.sub.C3L1′=Y.sub.C2R1″−Y.sub.C3L1′;

[0190] The overall electron beam drift of the second writing field and the third writing field exposed by the electron beam in the exposure area is ignored, so that the coordinates of the third writing field before the correction of the exposure coordinate in the exposure area are equal to the second writing field coordinates during exposure: X.sub.C3L1′=X.sub.C2L1′, Y.sub.C3L1′=Y.sub.C2L1′, so that the coordinates can be measured by the concave-convex structure formed by the exposure on the surface of the photosensitive resist layer after the second writing field is exposed and before moving the workbench to obtain the coordinate difference to be compensated for the electron beam coordinate correction of all the writing field exposure points:

ΔX.sub.2=X.sub.C2R1″−X.sub.C2L1′;

ΔY.sub.2=Y.sub.C2R1″−Y.sub.C2L1′.

[0191] Step 14: Adjust the deflection voltage of the electron beam column 32 according to the obtained correction value, and correct the electron beam exposure area so that the coordinates of all the exposure points in the third writing field of the subsequent wafer are corrected to be the same as the moved second writing field The adjacent stitching coordinates are consistent and seamless.

[0192] Step 15: Repeatedly, complete the exposure, movement and stitching of the entire writing field area of the entire wafer.

[0193] In this embodiment:

[0194] The electron beam may also be any of ion beam, photon beam or atomic beam.

[0195] The nano-contact sensor 39 may be one or a combination of one or more of an atomic force tip sensor, a tunnel electron probe sensor, or a nano-level surface work function measurement sensor.

[0196] The in-situ alignment coordinate mark 8, the in-situ alignment coordinate mark 10, and the in-situ alignment coordinate mark 18 may be graphic marks of a plane structure, which are provided with 1, 2, 3, 4, 5 or 6 on a plane, you can also use more according to actual needs. The graphic mark of the plane structure mentioned here is in a broad sense, and especially it also comprises the graphic mark formed by the small geometric structure change induced by the electron beam on the surface of the photoresist layer.

[0197] In this embodiment, a graphic mark formed by a slight geometric structure change caused by the surface of the photoresist layer induced by an electron beam is used as a planar structure graphic mark.

[0198] The in-situ alignment coordinate mark 43, 44 may also be a three-dimensional shape mark. The specific shape is preferably a pyramid or cone shape. The mark may also be provided with 1, 2, 3, 4, 5, 6 or more on a plane.

[0199] In this embodiment, there are preferably 1-4 nano contact sensors 39 distributed around the exposure area.

[0200] The nano-contact sensor 39 is provided with a lever-type sensing contact arm 391, and the contact arm 391 is provided with one or more needle tip sensing contacts 392 arranged in rows.

[0201] The electron beam can be a Gaussian beam or a Variable Shaped Beam.

[0202] The measurement method of electron beam drift is shown in FIGS. 7A and 7B: it comprises the following steps. In the chamber 31 of the lithography system, the stage 37, the electron beam column 32 and its electron gun 372, and the wafer moving stage 38 and nano contact sensor 39 are first set up; the wafer stage 38 is equipped with a numerical control driving device 371 that controls its movement, and a photosensitive resist layer is coated on the wafer, and then an electron gun 372 is used to emit an electron beam 17 to irradiate the focused point to the photosensitive resist. The light-sensitive resist layer is exposed to light, and the surface of the photosensitive resist layer is exposed to a small change in the geometric shape of the concave-convex structure induced by the electron beam. The small change is measured and the focus drift is tracked over time, and then the electron beam over time is recorded, also the coordinate value and drift amount of the drift trajectory 30. And then according to the recorded coordinate value and drift amount of the drift trajectory 30 of the electron beam over time, the exposure coordinate value and the correction compensation difference value due to the drift of the electron beam over time between the start and end intervals are calculated to obtain the correction coordinate of the next writing field exposure.

[0203] As shown in FIG. 8, the nano-contact sensor 39 is provided with a lever-type sensing contact arm 391, and the contact arm 391 is provided with one or more needle tip sensing contacts 392 arranged in rows.

[0204] The vertical stitching method of sub-nano-level high-precision lithography writing field is shown in FIG. 11: firstly, a three-dimensional alignment mark 43 with a protruding structure is preset on the wafer to be lithographically processed, and then coated with the photosensitive resist layer 2 to generate a corresponding protruding structure of the photosensitive resist layer three-dimensional alignment mark 44 at the position where the three-dimensional alignment mark is preset, and then the wafer with the three-dimensional alignment mark 1 is moved by the wafer workbench 38 to the area of the writing field that can be exposed by the electron beam 4, align the electron beam 4 at the position of the three-dimensional alignment mark 44 of the photosensitive resist layer and perform spot exposure. The actual deviated three-dimensional mark 45 is generated outside the exposure point of the resist layer, and then the actual coordinate value of the three-dimensional alignment mark 44 and the deviated three-dimensional mark 45 is measured by the nano-contact sensor, and then calculated the correction value of the exposure area of the writing field, then control the electron gun to achieve vertical precise alignment and exposure, and achieve vertical precise stitching.

[0205] FIG. 12 is a schematic diagram of the nano-contact sensor with multiple nano-contacts 392 on each nano-contact sensor 39 being quickly stitched and aligned.