Sub-nanoscale high-precision lithography writing field stitching method, lithography system, wafer, and electron beam drift determination method

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:
• (XC2L1′, YC2L1′):
• XC2L1′=XC1R1′, YC2L1′=YC1R1′;
• 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 (XC2L1, YC2L1);
• 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:
• ΔX1=XC2L1′−XC2L1=XC1R1′−XC2L1;
• ΔY1=YC2L1′−YC2L1=YC1R1′−YC2L1;
• given that the second writing field and its coordinates (XC2L1, YC2L1) 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:
• XC2L1=XC1L1, YC2L1=YC1L1, 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:
• ΔX1=XC1R1′−XC1L1;
• ΔY1=YC1R1′−YC1L1;
• step 8:
• adjusting the deflection voltage of the electron beam column (32) and correcting the exposure area according to the obtained coordinate difference (ΔX1, ΔY1) 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.