Bidirectional calibration method for FIA sensor and reference unit of photoetching machine

Abstract

The invention provides a bidirectional calibration method for an FIA sensor and a reference unit of a photoetching machine, which comprises the following steps: moving the center of a workbench to be right below the projection center of an objective lens; calibrating the coaxial alignment optimal position of the reference unit based on the center coordinates of the center mark, the left side mark and the right side mark of the reference unit for the workbench and the center coordinates of the left side FIA sensor and the right side FIA sensor; the first FIA sensor is calibrated by imaging a second mark through the first FIA sensor; calibrating the reference unit according to a deviation value of the reference unit before and after movement measured by taking the first FIA sensor as a reference; and calibrating a second FIA sensor by imaging the first marker by the second FIA sensor. Thus, the center mark, the left side mark and the right side mark on the reference unit used for the workbench are aligned with the left side FIA sensor and the right side FIA sensor, and high-efficiency and high-precision bidirectional calibration is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photoetching machine, more particularly, to a bidirectional calibration method for FIA sensor and reference unit of photoetching machine. BACKGROUND

[0002] Photoetching machine is an important equipment in semiconductor manufacturing process, which is used to accurately transfer circuit pattern in mask (also known as photo mask) to silicon wafer or other substrates according to predetermined size and position through exposure process.

[0003] Reticle alignment (RA) system is responsible for aligning the pattern on the mask with the pattern already on the wafer in the photoetching machine, so as to ensure the accurate overlay between the patterns after exposure. The alignment step of the reticle alignment system is before the photoetching step, and thus the accuracy of this step directly affects the overlay accuracy.

[0004] In the photoetching step, the designed circuit pattern needs to be projected onto the wafer coated with photoresist by light. Therefore, in order to ensure that the pattern can be clearly and accurately overlaid, the wafer surface must be accurately located on the focal plane of the lens. However, due to the possible warping and unevenness of the wafer itself, and the slight change in position during high-speed scanning, the FIA (Focus Interferometer Assembly) sensor is needed for dynamic and real-time focus measurement and feedback control. Here, the FIA sensor can accurately measure and control the focal position of the wafer surface relative to the lens (projection objective) of the photoetching machine in real time. That is, in the photoetching process, the wafer stage, also referred to as worktable hereinafter, needs to be further aligned with the objective, and thus the FIA sensor and the reference unit for the worktable need to be calibrated.

[0005] Therefore, it is desirable to provide an improved calibration scheme for FIA sensor and reference unit of photoetching machine. SUMMARY

[0006] The embodiment of the present application provides a bidirectional calibration method for FIA sensor and reference unit of photoetching machine, which realizes high-efficiency and high-precision bidirectional calibration through the alignment of the center mark, left mark and right mark on the reference unit for the worktable with the left FIA sensor and the right FIA sensor.

[0007] According to an aspect of the present application, a bidirectional calibration method of an FIA sensor and a reference unit of a photolithography machine is provided, comprising: calibrating a coaxial alignment optimal position of a reference unit of a worktable by moving a center of a wafer stage to be directly below a projection center of an objective lens based on center coordinates of a center mark, a left mark and a right mark of the reference unit and center coordinates of a left FIA sensor and a right FIA sensor; correcting a position of a first FIA sensor by a pixel deviation of a second mark corresponding to the first FIA sensor imaged by a camera corresponding to the first FIA sensor to calibrate the first FIA sensor; calibrating a first rotation angle of the reference unit by moving the reference unit to a relative direction of the first FIA sensor based on a center coordinate difference value of the left mark and the right mark and measuring a deviation value before and after the movement based on the first FIA sensor; and correcting a position of a second FIA sensor by a pixel deviation of a first mark corresponding to the second FIA sensor imaged by a camera corresponding to the second FIA sensor after moving the reference unit to a corresponding direction of the first FIA sensor by the center coordinate difference value to calibrate the second FIA sensor.

[0008] In the bidirectional calibration method of the FIA sensor and the reference unit of the photolithography machine, the center coordinates of the center mark, the left mark and the right mark and the center coordinates of the left FIA sensor and the right FIA sensor are coordinates in a mechanical coordinate system with a point directly below the projection center of the objective lens as an origin and the objective lens vertically as a Z axis.

[0009] In the bidirectional calibration method of the FIA sensor and the reference unit of the photolithography machine, calibrating the coaxial alignment optimal position of the reference unit comprises: calculating a first deviation of the left FIA sensor from the left mark and a second deviation of the right FIA sensor from the right mark based on the center coordinates of the center mark, the left mark and the right mark and the center coordinates of the left FIA sensor and the right FIA sensor; calculating a sum of distances based on the first deviation and the second deviation; and obtaining the coaxial alignment optimal position of the reference unit by taking a partial derivative of the sum of distances with respect to the center coordinates of the center mark and setting the partial derivative to be equal to zero.

[0010] In the bidirectional calibration method for the FIA ​​sensor and reference unit of the aforementioned lithography machine, the center coordinates of the left FIA sensor are set as (cx1, cy1), the center coordinates of the right FIA sensor are set as (cx2, cy2), the center coordinates of the left mark are set as (mx1, my1), the center coordinates of the right mark are set as (mx2, my2), and the center mark coordinates of the reference unit are set as (fmx1, fmy1). Then: the first deviation is ldx1 = mx1 + fmx1 - cx1, ldy1 = my1 + fmy1 - cy1; the second deviation is rdx1 = mx2 + fmx1 - cx2, rdy1 = my2 + fmy1 - cy2; the sum of the distances is D = ldx1 2 +ldy1 2 +rdx1 2 +rdy1 2 The optimal coaxial alignment position of the reference unit is fmx1′=(cx1+cx2-mx1-mx2) / 2, fmy1′=(cy1+cy2-my1-my2) / 2.

[0011] In the bidirectional calibration method for the FIA ​​sensor and reference unit of the lithography machine described above, the method of correcting the position of the first FIA sensor to calibrate the first FIA sensor by using the pixel deviation obtained by the camera corresponding to the first FIA sensor to image the second mark corresponding to the first FIA sensor includes: obtaining the pixel deviation of the center of the second mark in the target coordinate system of the first FIA sensor by the camera corresponding to the first FIA sensor to image the second mark corresponding to the first FIA sensor; converting the pixel deviation into a coordinate deviation in the mechanical coordinate system through a pre-calibrated transformation coefficient; correcting the position parameters of the first FIA sensor by the coordinate deviation in response to the coordinate deviation being greater than the alignment error threshold; and repeating the above steps until the coordinate deviation is less than or equal to the alignment error threshold.

[0012] In the bidirectional calibration method of the FIA ​​sensor and reference unit of the above lithography machine, the pixel deviation is (Δu, Δv), the conversion coefficient is kx, ky, the coordinate deviation is dx1=kx·Δu, dy1=ky·Δv, and the correction of the position parameters of the first FIA sensor is offsetXR←offsetXR+dx1, offsetYR←offsetYR+dy1.

[0013] In the bidirectional calibration method of the FIA ​​sensor and reference unit of the above lithography machine, the deviation value before movement is (drx1, dry1), the deviation value after movement is (drx2, dry2), and the first rotation angle θ of the reference unit is θ=arctan[(drx2-drx1) / (dry2-dry1)].

[0014] In the bidirectional calibration method of the FIA sensor and the reference unit of the lithography machine, further comprising: moving the reference unit to a corresponding direction of the first FIA sensor based on a center coordinate difference value of the left mark and the right mark, and calibrating a second rotation angle of the reference unit by measuring a deviation value before and after the movement based on the second FIA sensor; in response to the second rotation angle of the reference unit being less than or equal to a predetermined threshold, determining that the calibration verification is successful; and in response to the second rotation angle of the reference unit being greater than the predetermined threshold, iterating the steps of calibrating the first FIA sensor, calibrating the reference unit, and calibrating the second FIA sensor until the second rotation angle is less than or equal to the predetermined threshold.

[0015] In the bidirectional calibration method of the FIA sensor and the reference unit of the lithography machine, for the deviation (dxLi, dyLi) of the right mark on the left FIA sensor relative to the target center of the left FIA sensor, and for the deviation (dxRi, dyRi) of the left mark on the right FIA sensor relative to the target center of the right FIA sensor, there are:

[0016] dxL = [dxL1, dxL2, …, dxLn];

[0017] dyL = [dyL1, dyL2, …, dyLn];

[0018] dxR = [dxR1, dxR2, …, dxRn];

[0019] dyR = [dyR1, dyR2, …, dyRn];

[0020] Then the left deviation matrix DL and the right deviation matrix DR are:

[0021]

[0022] In the bidirectional calibration method of the FIA sensor and the reference unit of the lithography machine, [dxLi, dyLi] = A[dxRi, dyRi] + B, A is a conversion matrix, and B is an offset vector, and then:

[0023]

[0024] The bidirectional calibration method of the FIA sensor and the reference unit of the lithography machine provided by the embodiments of the present application can realize efficient and high-precision bidirectional calibration through the alignment of the center mark, the left mark and the right mark on the reference unit for the workbench with the left FIA sensor and the right FIA sensor. BRIEF DESCRIPTION OF DRAWINGS

[0025] Various other advantages and benefits of the present application will become apparent to those of ordinary skill in the art, upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a better understanding of the preferred embodiments, and are not intended to be limiting of the present application. It should be readily understood that the drawings are not to scale, and are merely intended to depict the general structure of the application. It should be readily understood that the drawings are not to scale, and are merely intended to depict the general structure of the application.

[0026] Figure 1 FIG. 1 illustrates a schematic flow chart of a bidirectional calibration method of a FIA sensor and a reference unit of a lithography machine according to an embodiment of the present application.

[0027] Figure 2 FIG. 2 illustrates a schematic configuration diagram of a bidirectional calibration method of a FIA sensor and a reference unit of a lithography machine according to an embodiment of the present application.

[0028] Figure 3 FIG. 3 illustrates a schematic mechanical coordinate system diagram of a bidirectional calibration method of a FIA sensor and a reference unit of a lithography machine according to an embodiment of the present application. DETAILED DESCRIPTION

[0029] Hereinafter, example embodiments according to the present application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only a part but not all of the embodiments of the present application. It should be understood that the present application is not limited to the described embodiments.

[0030] Figure 1 FIG. 1 illustrates a schematic flow chart of a bidirectional calibration method of a FIA sensor and a reference unit of a lithography machine according to an embodiment of the present application.

[0031] As Figure 1 shown, the bidirectional calibration method of a FIA sensor and a reference unit of a lithography machine according to an embodiment of the present application comprises the following steps.

[0032] S110, by moving the center of the worktable directly below the objective lens projection center, calibrating the coaxial alignment best position of the reference unit based on the center coordinates of the center mark, left mark and right mark of the reference unit for the worktable, and the center coordinates of the left FIA sensor and the right FIA sensor. Here, as Figure 2As shown, in the bidirectional calibration method of the FIA sensor and the reference unit of the photolithography machine according to the embodiment of the present application, the system configuration for the bidirectional calibration of the FIA sensor and the reference unit includes an objective lens and two FIA sensors above the worktable, and the reference unit for the worktable includes a center mark, a left mark and a right mark, wherein the left FIA sensor and the right FIA sensor of the two FIA sensors perform reference unit alignment operation respectively for the right mark and the left mark. Figure 2 FIG. 1 illustrates a schematic configuration diagram of the bidirectional calibration method of the FIA sensor and the reference unit of the photolithography machine according to the embodiment of the present application.

[0033] Here, the center of the worktable is not the physical center of the worktable, but refers to the center of the position of the wafer supported on the upper surface of the worktable, specifically, a chuck for supporting and adsorbing the wafer is arranged on the worktable, that is, the chuck is arranged on the worktable, and the center of the chuck is the center of the worktable. Figure 3 The chuck is not shown because it is blocked by the wafer, and the center of the chuck is the center of the worktable. When the center of the worktable is moved directly below the objective lens and coincides with the origin of the mechanical coordinates, the center coordinates of the worktable measured by the interferometer at this time are (0, 0), and when the worktable moves in the horizontal direction (after the worktable is adjusted to the position, only moves in the horizontal direction, and does not move vertically, so only the horizontal coordinates are recorded), the interferometer always takes the measured center coordinates of the worktable in the mechanical coordinate system as the coordinates of the worktable, and the origin of the mechanical coordinate system is located at the position of the optical axis directly below the objective lens.

[0034] When the bidirectional calibration of the FIA sensor and the reference unit is performed, the mechanical coordinate system is set with the center of the objective lens projection as the origin, and the vertical objective lens as the Z axis, as shown in Figure 3 Figure 3 Only for the purpose of illustration, as shown in the figure, the cylindrical shape represents the objective lens, and the rectangle with a missing corner in the upper right corner represents the worktable, which is horizontally placed and located directly below the objective lens. The reference unit is fixed on one side of the objective table, and the wafer (silicon wafer) is supported on the worktable and moves with the horizontal movement of the worktable. Figure 3 ​Fig. 1 shows a schematic diagram of a mechanical coordinate system of a two-way calibration method of an FIA sensor and a reference unit of a lithography machine according to an embodiment of the present application. Thus, by controlling the movement of the worktable, the center mark of the reference unit can be moved directly below the center of the objective lens, so that the coordinate origin of the reference unit coincides with the coordinate origin of the mechanical coordinate system, and the coordinate position of the center of the worktable at this time is read by the interferometer, i.e. the coordinate position of the center point of the worktable in the mechanical coordinate system, for example (fmx1, fmy1), and the coordinates of the center of the left mark and the center of the right mark of the reference unit in the coordinate system are obtained, for example (x1, y1) and (x2, y1). Since the reference unit is fixed on the worktable, the position of the reference unit relative to the center of the worktable needs to be set in advance.

[0035] That is, when the center of the worktable is moved directly below the center point of the objective lens and coincides with the coordinate origin of the mechanical coordinate system, the coordinate position of the center point of the reference unit in the mechanical coordinate system at this time is marked as (fmx1, fmy1), and the coordinate of the center of the worktable at this time is read by the interferometer as (0, 0). According to the coordinate system conversion principle, when the center point of the reference unit is moved to the center of the objective lens, the center of the worktable needs to be moved to the position (-fmx1, -fmy1). At this time, the left mark of the reference unit should be imaged on the right FIA sensor according to the design, and the right mark should be imaged on the left FIA sensor. In fact, by moving the worktable in a Z-shaped manner (X step value and Y step value are moved by the minimum recognition accuracy, and the minimum value of (x1, x2) is taken as the limit range, and similarly the limit range of y is taken, and it is assumed that the step number is 3 according to the set range), the sampling values obtained by each step data are shown in the following table:

[0036]

[0037] Thus, the best position of the coaxial alignment of the reference unit can be calibrated according to the minimum value of the sum of the distances of the centers of the left and right FIA and the center of the mark, for example (fmx1', fmy1');

[0038] For example, the mechanical coordinates of the center of the left FIA are set as (cx1, cy1), the mechanical coordinates of the center of the right FIA are set as (cx2, cy2), the coordinates of the left mark are set as (mx1, my1), the coordinates of the right mark are set as (mx2, my2), and the coordinates of the center mark of the reference unit are set as (fmx1, fmy1).

[0039] First, the deviations are calculated, the deviation of the center of the left FIA and the left mark is ldx1 = mx1 + fmx1 - cx1, ldy1 = my1 + fmy1 - cy1, the deviation of the center of the right FIA and the right mark is rdx1 = mx2 + fmx1 - cx2, rdy1 = my2 + fmy1 - cy2.

[0040] Then, the sum of distances D is calculated as D = Idx1 2 + ldy1 2 + rdx1 2 + rdy1 2 .

[0041] Next, the sum of distances D is minimized, that is, in order to find (fmx1, fmy1) that minimizes the sum of distances D, the partial derivatives of D with respect to fmx1 and fmy1 are taken and set equal to zero.

[0042] Where the partial derivative with respect to fmx1 is taken and set to zero:

[0043]

[0044] 2(mx1 + fmx1 - cx1) + 2(mx2 + fmx1 - cx2) = 0

[0045] 2fmx1 + mx1 - cx1 + mx2 - cx2 = 0

[0046] 2fmx1 = cx1 + cx2 - mx1 - mx2

[0047] fmx1 = (cx1 + cx2 - mx1 - mx2) / 2

[0048] The partial derivative with respect to fmy1 is:

[0049]

[0050] 2(my1 + fmy1 - cy1) + 2(my2 + fmy1 - cy2) = 0

[0051] 2fmy1 + my1 - cy1 + my2 - cy2 = 0

[0052] 2fmy1 = cy1 + cy2 - my1 - my2

[0053] fmy1 = (cy1 + cy2 - my1 - my2) / 2

[0054] Thus, the optimal position of the coaxial alignment of the reference unit (fmx1', fmy1') that minimizes the sum of distances D can be determined as fmx1' = (cx1 + cx2 - mx1 - mx2) / 2, fmy1' = (cy1 + cy2 - my1 - my2) / 2.

[0055] Therefore, in the bidirectional calibration method of the FIA sensor and the reference unit of the photolithography machine according to the embodiment of the application, the center coordinates of the center mark, the left mark and the right mark and the center coordinates of the left FIA sensor and the right FIA sensor are coordinates in a mechanical coordinate system with the center of the objective lens projection as the origin and the vertical objective lens as the Z axis.

[0056] In the bidirectional calibration method of the FIA sensor and the reference unit of the photolithography machine, the step of calibrating the coaxial alignment optimal position of the reference unit comprises: calculating a first deviation of the left FIA sensor from the left mark and a second deviation of the right FIA sensor from the right mark based on the center coordinates of the center mark, the left mark and the right mark and the center coordinates of the left FIA sensor and the right FIA sensor; calculating a sum of distances based on the first deviation and the second deviation; and obtaining the coaxial alignment optimal position of the reference unit by taking the partial derivative of the sum of distances with respect to the center coordinates of the center mark and setting the partial derivative to zero.

[0057] In the bidirectional calibration method of the FIA sensor and the reference unit of the photolithography machine, the center coordinates of the left FIA sensor are set as (cx1, cy1), the center coordinates of the right FIA sensor are set as (cx2, cy2), the center coordinates of the left mark are set as (mx1, my1), the center coordinates of the right mark are set as (mx2, my2), the center mark coordinates of the reference unit are set as (fmx1, fmy1), the first deviation is set as ldx1 = mx1 + fmx1 - cx1, ldy1 = my1 + fmy1 - cy1, the second deviation is set as rdx1 = mx2 + fmx1 - cx2, rdy1 = my2 + fmy1 - cy2, the sum of distances is set as D = ldx1 2 + ldy1 2 + rdx1 2 + rdy1 2 , and the coaxial alignment optimal position of the reference unit is set as fmx1' = (cx1 + cx2 - mx1 - mx2) / 2, fmy1' = (cy1 + cy2 - my1 - my2) / 2.

[0058] Step S120, the pixel deviation of the second mark corresponding to the first FIA sensor imaged by the camera corresponding to the first FIA sensor is used to correct the position of the first FIA sensor to calibrate the first FIA sensor. That is, the above obtained coaxial alignment optimal position (fmx1', fmy1') of the reference unit is sent as an instruction to the wafer stage control motion, and then the reference unit is positioned. In theory, the center of the target of the first FIA sensor, for example, the right FIA sensor, should coincide with the center of the second mark on the opposite side, for example, the left mark, but due to mechanical errors, there may be residual deviation (dx1, dy1).

[0059] Therefore, the right camera corresponding to the first FIA sensor captures an image, and through image processing, the pixel deviation (Δu, Δv) of the center of the left mark in the target coordinate system of the right FIA sensor is obtained, and the mechanical coordinate deviation dx1=kx·Δu, dy1=ky·Δv is converted through the pixel-micron conversion coefficient kx, ky calibrated in advance. Then, it is judged whether the deviation is qualified, that is, if the process requires the alignment error threshold to be εx, εy (for example, ±0.1 μm). If |dx1|≤εx and |dy1|≤εy, it is considered that the calibration is successful, and the current interferometer reading is recorded as the mechanical coordinates (X0R, Y0R) of the right FIA sensor. Otherwise, the position parameters of the right FIA sensor are corrected, that is, (dx1, dy1) is used as a compensation amount to correct the position parameters of the right FIA sensor, offsetXR←offsetXR+dx1, offsetYR←offsetYR+dy1, and the image acquisition and correction steps are repeated until the threshold condition is met. In fact, it usually converges through 1-2 iterations, and the position information of the current wafer stage origin can be read from the interferometer of the wafer stage.

[0060] Therefore, in the bidirectional calibration method of the FIA sensor and the reference unit of the lithography machine according to the embodiment of the present application, the pixel deviation of the second mark corresponding to the first FIA sensor imaged by the camera corresponding to the first FIA sensor is used to correct the position of the first FIA sensor to calibrate the first FIA sensor, which includes: imaging the second mark corresponding to the first FIA sensor by the camera corresponding to the first FIA sensor to obtain the pixel deviation of the center of the second mark in the target coordinate system of the first FIA sensor; converting the pixel deviation into a coordinate deviation in the mechanical coordinate system through a conversion coefficient calibrated in advance; in response to the coordinate deviation being greater than an alignment error threshold, correcting the position parameters of the first FIA sensor through the coordinate deviation; and repeating the above steps until the coordinate deviation is less than or equal to the alignment error threshold.

[0061] And, in the bidirectional calibration method of the FIA sensor and the reference unit of the photolithography machine, the pixel deviation is (Δu, Δv), the conversion coefficient is kx, ky, the coordinate deviation is dx1=kx·Δu, dy1=ky·Δv, and the correction of the position parameter of the first FIA sensor is offsetXR←offsetXR+dx1, offsetYR←offsetYR+dy1.

[0062] In step S130, the first rotation angle of the reference unit is calibrated by moving the reference unit to the opposite direction of the first FIA sensor based on the center coordinate difference value of the left mark and the right mark, and measuring the deviation value before and after the movement of the reference unit based on the first FIA sensor. That is, first, the measurement point of the current position is measured and recorded based on the first FIA sensor, for example, the right FIA sensor, that is, the deviation value (drx1, dry1) of the center of the left mark from the center of the target of the right FIA sensor, then the reference unit is moved left by the distance value of |x2-x1| through the silicon wafer stage, and the deviation value (drx2, dry2) of the center of the right mark from the center of the target of the right FIA sensor is measured again through the right FIA sensor. Here, the deviation values before and after the movement are the deviation of the center of the mark measured by the FIA sensor from the center of the pixel coordinate system of the FIA sensor, specifically, the measurement value of the right FIA corresponding to the left mark before the movement, and the measurement value of the right FIA corresponding to the right mark after the movement

[0063] Then, according to the deviation values measured twice, the rotation angle θ of the reference unit can be obtained as θ=arctan[(drx2-drx1) / (dry2-dry1)], and thus the reference unit is calibrated based on the rotation angle θ of the reference unit.

[0064] Therefore, in the bidirectional calibration method of the FIA sensor and the reference unit of the photolithography machine according to the embodiment of the present application, the deviation value before the movement is (drx1, dry1), the deviation value after the movement is (drx2, dry2), and the first rotation angle θ of the reference unit is θ=arctan[(drx2-drx1) / (dry2-dry1)].

[0065] Step S140, after moving the reference unit to the corresponding direction of the first FIA sensor by the center coordinate difference value, the position of the second FIA sensor is corrected by the pixel deviation of the first mark of the reference unit imaged by the corresponding camera of the second FIA sensor to calibrate the second FIA sensor. That is, after the reference unit is translated by a distance of |x2-x1| to the corresponding direction of the first FIA sensor, for example, the right direction corresponding to the right FIA sensor, by the silicon wafer stage, the second FIA sensor, for example, the left FIA sensor, can monitor the image of the first mark of the reference unit, for example, the right mark, and the deviation value (dx2, dy2) is calculated by aligning the measurement image of the left FIA sensor. The position parameters of the left FIA sensor can be corrected according to the deviation value, and finally until dx2 and dy2 are within the error allowable range, thereby calibrating the left FIA sensor, and reading out the position information of the current silicon wafer stage origin from the interferometer.

[0066] Those skilled in the art can understand that the calibration process of the left FIA sensor is similar to that of the right FIA sensor, and therefore will not be described here. Also, although the first sensor is the right FIA sensor and the second sensor is the left FIA sensor in the above example, in the embodiments of the present application, the first sensor can also be the left FIA sensor and the second sensor can be the right FIA sensor.

[0067] In addition, in the bidirectional calibration method of the FIA sensor and the reference unit of the lithography machine according to the embodiments of the present application, the calibration verification of the reference unit can be further included, that is, after calibrating the second FIA sensor, the second FIA sensor is used as a reference to measure. Specifically, first, the deviation value (dlx1, dly1) of the center of the first mark corresponding to the second sensor, for example, the right mark corresponding to the left FIA sensor, from the target center of the left FIA sensor is recorded, then the silicon wafer stage is translated by a distance of |x2-x1| to the right, and the deviation value (drx2, dry2) of the center of the right mark from the target center of the left FIA sensor is measured and recorded by the left FIA sensor, and the rotation angle of the reference unit is calculated. If the rotation angle at this time is approximately 0, i.e. less than or equal to a predetermined threshold, the calibration verification is successful, and if the rotation angle is too large, the above steps S120 to S140 are repeated until the rotation angle is approximately 0 (or within a set tolerance range).

[0068] Therefore, in the bidirectional calibration method of the FIA sensor and the reference unit of the lithography machine according to the embodiment of the present application, further comprising: moving the reference unit to the corresponding direction of the first FIA sensor based on the center coordinate difference value of the left mark and the right mark, and calibrating the second rotation angle of the reference unit by measuring the deviation value before and after the movement based on the second FIA sensor; in response to the second rotation angle of the reference unit being less than or equal to a predetermined threshold, determining that the calibration verification is successful; and in response to the second rotation angle of the reference unit being greater than the predetermined threshold, iterating the above steps S120 to S140 until the second rotation angle is less than or equal to the predetermined threshold.

[0069] Specifically, let (dlx1, dly1) be the deviation of the right mark measured by the left FIA sensor at the current position, (drx2, dry2) be the deviation of the left mark measured by the left FIA sensor after moving right by |x2-x1|, Δx = |x2-x1| be the known mark spacing, and θ be the rotation angle of the reference unit around the Z axis (counterclockwise is positive).

[0070] Both measurements are completed in the coordinate system of the same sensor (the left FIA sensor), the theoretical displacement of the right mark relative to the left mark is Δx_theory = Δx*cosθ, Δy_theory = Δx*sinθ, and the measured displacement is Δx_meas = drx2-dlx1, Δy_meas = dry2-dly1. Let the measured displacement be equal to the theoretical displacement: {Δx*cosθ = Δx_meas, Δx*sinθ = Δy_meas, θ = arctan2(Δymeas, Δxmeas), that is, the rotation angle of the rigid body calculated from the displacement of the two measurements based on the geometric relationship of the rotation of the reference unit plane, that is, the rotation angle calculation of the reference unit, which calculates the rotation angle of the rigid body by measuring the displacement components of a point on the reference unit in two directions.

[0071] And, set the allowable rotation error εθ (such as ±0.05 mrad), if the absolute value of the angle θ |θ| ≤ εθ, then the verification is passed, otherwise if |θ| > εθ, then the iterative correction is still needed.

[0072] Specifically, in the iterative correction, θ is written as the compensation rotation amount of the reference unit to the motion rotation axis of the silicon wafer stage to adjust the reference unit, and the above steps of first FIA sensor calibration → reference unit calibration → second FIA sensor calibration → reference unit calibration verification are repeated until the allowable rotation error εθ is satisfied.

[0073] And, in the mapping relationship calibration between the two side FIA sensors and the reference unit, the right side marker and the left side marker can be measured by the left and right side FIA sensors respectively, and the deviation matrix of several feature points on the marker relative to the center of the sensor target is measured, that is, the left side marker has a deviation matrix on the right side FIA sensor, and the right side marker has a deviation matrix on the left side FIA sensor, and a mathematical model is constructed by the two deviation matrices to obtain the mapping relationship between the two side FIA sensors and the reference unit.

[0074] For example, several feature points on the right side marker are measured by using the left side FIA sensor, and the deviation (dxLi, dyLi) of each point relative to the center of the target of the left side FIA sensor is recorded, and several feature points on the left side marker are measured by using the right side FIA sensor, and the deviation (dxRi, dyRi) of each point relative to the center of the target of the right side FIA sensor is recorded.

[0075] For the measurement of the right side marker on the left side FIA sensor, a left deviation matrix is constructed, and for the measurement of the left side marker on the right side FIA sensor, a right deviation matrix is constructed:

[0076] dxL = [dxL1, dxL2, …, dxLn]

[0077] dyL = [dyL1, dyL2, …, dyLn]

[0078] dxR = [dxR1, dxR2, …, dxRn]

[0079] dyR = [dyR1, dyR2, …, dyRn]

[0080]

[0081] Then the mapping relationship is calculated, for example, using the least square method or other linear regression method to solve the linear relationship of the two deviation matrices. Assuming that the mapping relationship is: [dxLi, dyLi)] = A[dxRi, dyRi] + B, where A is a conversion matrix and B is an offset vector, then the conversion matrix and the offset vector are solved, for example, A and B are solved by the least square method:

[0082]

[0083] And the mapping relationship is verified, that is, each point in DR is mapped into the coordinate system of DL using the obtained A and B, the deviation of the mapped point from the actual measured point is checked to ensure that it is within the allowable error range.

[0084] In summary, the bidirectional calibration method of the FIA sensor and the reference unit of the photolithography machine according to the embodiment of the present application can realize the bidirectional calibration of the FIA sensor and the reference unit with high precision and high efficiency, in which the alignment precision can be improved to the sub-micron level, and the calibration efficiency can be improved by more than 30%.

[0085] The above describes the basic principles of the present application in combination with specific embodiments. However, it should be noted that the advantages, advantages, effects and the like mentioned in the present application are only examples and are not limiting, and these advantages, advantages, effects and the like cannot be considered as the must-have of each embodiment of the present application. In addition, the above specific details disclosed are only for the purpose of example and understanding, and are not limiting, and the above details do not limit the present application to the must-use specific details.

[0086] The block diagrams of the devices, apparatuses, equipment, systems involved in the present application are only illustrative examples and are not intended to require or imply the connection, arrangement, configuration shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, equipment, systems can be connected, arranged, configured in any manner. Words such as "include", "contain", "have" and the like are open-ended words, which mean "including but not limited to", and can be used interchangeably. The words "or" and "and" used herein mean the word "and / or", and can be used interchangeably unless the context clearly indicates otherwise. The word "such as" used herein means the phrase "such as but not limited to", and can be used interchangeably.

[0087] It should also be noted that in the devices, equipment and methods of the present application, each component or each step can be decomposed and / or recombined. These decompositions and / or recombinations should be considered as equivalent solutions of the present application.

[0088] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other aspects without departing from the scope of the present application. Thus, the present application is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0089] The above description has been given for the purpose of illustration and description. Furthermore, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, a person of skill in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. A method for bidirectional calibration of an FIA sensor and a fiducial unit of a lithography machine, comprising: calibrating a coaxial alignment optimal position of a fiducial unit based on center coordinates of a center mark, a left mark and a right mark of the fiducial unit for a worktable and center coordinates of a left FIA sensor and a right FIA sensor by moving a center of the worktable directly below a center of an objective lens projection; correcting a position of a first FIA sensor to calibrate the first FIA sensor by a pixel deviation of a second mark corresponding to the first FIA sensor imaged by a camera corresponding to the first FIA sensor; calibrating a first rotation angle of the fiducial unit by moving the fiducial unit to a relative direction of the first FIA sensor based on a center coordinate difference of the left mark and the right mark and measuring a deviation value before and after the movement with the first FIA sensor as a reference; and correcting a position of a second FIA sensor to calibrate the second FIA sensor by a pixel deviation of a first mark corresponding to the second FIA sensor imaged by a camera corresponding to the second FIA sensor after moving the fiducial unit to a corresponding direction of the first FIA sensor by the center coordinate difference. The center coordinates of the center mark, the left mark and the right mark and the center coordinates of the left FIA sensor and the right FIA sensor are coordinates in a mechanical coordinate system with the center of the objective lens projection directly below as an origin and a vertical objective lens as a Z axis.

2. The bidirectional calibration method of the FIA sensor and reference unit of a lithography machine according to claim 1, wherein, The calibration of the coaxial alignment optimal position of the fiducial unit comprises:

3. The bidirectional calibration method of the FIA sensor and reference unit of a lithography machine according to claim 2, wherein, calculating a first deviation of the left FIA sensor from the left mark and a second deviation of the right FIA sensor from the right mark based on the center coordinates of the center mark, the left mark and the right mark and the center coordinates of the left FIA sensor and the right FIA sensor; calculating a sum of distances based on the first deviation and the second deviation; and deriving a partial derivative of the sum of distances with respect to the center coordinates of the center mark and setting the partial derivative equal to zero to obtain the coaxial alignment optimal position of the fiducial unit. Setting the center coordinates of the left FIA sensor as (cx1, cy1), the center coordinates of the right FIA sensor as (cx2, cy2), the center coordinates of the left mark as (mx1, my1), the center coordinates of the right mark as (mx2, my2) and the center mark coordinates of the fiducial unit as (fmx1, fmy1), then:

4. The bidirectional calibration method of the FIA sensor and reference unit of a lithography machine according to claim 3, wherein, the first deviation is ldx1 = mx1 + fmx1 - cx1, ldy1 = my1 + fmy1 - cy1; the second deviation is rdx1 = mx2 + fmx1 - cx2, rdy1 = my2 + fmy1 - cy2; the coaxial alignment optimal position of the fiducial unit is fmx1' = (cx1 + cx2 - mx1 - mx2) / 2, fmy1' = (cy1 + cy2 - my1 - my2) / 2. The sum of the distances is D = Idx1 2 + ldy1 2 + rdx1 2 + rdy1 2 ; ​ 5. The bidirectional calibration method of the FIA sensor and reference unit of a lithography machine according to claim 1, wherein, correcting the position of the first FIA sensor by a pixel deviation obtained by imaging the second mark corresponding to the first FIA sensor by the camera corresponding to the first FIA sensor to calibrate the first FIA sensor comprises: imaging the second mark corresponding to the first FIA sensor by the camera corresponding to the first FIA sensor to obtain a pixel deviation of the center of the second mark in the target coordinate system of the first FIA sensor; converting the pixel deviation into a coordinate deviation in the mechanical coordinate system by a conversion coefficient calibrated in advance; correcting the position parameter of the first FIA sensor by the coordinate deviation in response to the coordinate deviation being greater than an alignment error threshold; and repeating the above steps until the coordinate deviation is less than or equal to the alignment error threshold.

6. The bidirectional calibration method of the FIA sensor and reference unit of a lithography machine according to claim 5, wherein, The pixel deviation is (Δu, Δv), the conversion coefficient is kx, ky, the coordinate deviation is dx1=kx·Δu, dy1=ky·Δv, and the correction of the position parameter of the first FIA sensor is offsetXR←offsetXR+dx1, offsetYR←offsetYR+dy1.

7. The bidirectional calibration method of the FIA sensor and reference unit of a lithography machine according to claim 1, wherein, The deviation value before movement is (drx1, dry1), the deviation value after movement is (drx2, dry2), and the first rotation angle θ of the reference unit is θ=arctan[(drx2-drx1) / (dry2-dry1)].

8. The bidirectional calibration method of the FIA sensor and the reference unit of the photolithography machine according to claim 1, further comprising: calibrating a second rotation angle of the reference unit by moving the reference unit to the corresponding direction of the first FIA sensor based on the center coordinate difference value of the left mark and the right mark, and measuring the deviation value before and after movement based on the second FIA sensor; determining that the calibration verification is successful in response to the second rotation angle of the reference unit being less than or equal to a predetermined threshold; and iterating the steps of calibrating the first FIA sensor, calibrating the reference unit, and calibrating the second FIA sensor until the second rotation angle is less than or equal to the predetermined threshold in response to the second rotation angle of the reference unit being greater than the predetermined threshold.

9. The bidirectional calibration method of the FIA sensor and reference unit of a lithography machine according to claim 8, wherein, For the deviation (dxLi, dyLi) of the right mark on the left FIA sensor relative to the target center of the left FIA sensor, and for the deviation (dxRi, dyRi) of the left mark on the right FIA sensor relative to the target center of the right FIA sensor, there are: dxL=[dxL1,dxL2,…,dxLn]; dyL=[dyL1,dyL2,…,dyLn]; dxR=[dxR1,dxR2,…,dxRn]; dyR=[dyR1,dyR2,…,dyRn]; then the left deviation matrix DL and the right deviation matrix DR are:

10. The bidirectional calibration method of the FIA sensor and reference unit of a lithography machine according to claim 9, wherein, [dxLi,dyLi]=A[dxRi,dyRi]+B, A is a conversion matrix, B is an offset vector, and then:

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