Two-way calibration method for fia sensor and reference unit of lithography machine

Abstract

Provided is a bidirectional calibration method for an FIA sensor and a reference unit of a photolithography machine, comprising: calibrating a coaxial alignment optimal position of a reference unit for a worktable 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 by moving a center of the worktable directly below a projection center of an objective lens; calibrating a first FIA sensor by imaging a second mark through the first FIA sensor; calibrating the reference unit by measuring a deviation value before and after movement of the reference unit with the first FIA sensor as a reference; and calibrating a second FIA sensor by imaging a first mark through the second FIA sensor. In this way, efficient and high-precision bidirectional calibration is achieved through alignment of the center mark, the left mark and the right mark on the reference unit for the worktable and the left FIA sensor and the right FIA sensor.

Description

Technical Field

[0001] This application relates to the field of lithography machine technology, and more specifically, to a two-way calibration method for the FIA ​​sensor and reference unit of a lithography machine. Background Technology

[0002] Photolithography machines are essential equipment in the semiconductor manufacturing process. Their function is to precisely transfer circuit patterns from a photomask (also known as a photomask) to a silicon wafer or other substrate according to predetermined dimensions and positions through an exposure process.

[0003] The Reticle Alignment (RA) system in a photolithography machine is responsible for aligning the pattern on the photomask with the existing pattern on the wafer to ensure accurate overlay after exposure. The alignment step of the photomask system occurs before the photolithography step, therefore the accuracy of this calibration directly affects the overlay precision.

[0004] In the photolithography process, the designed circuit pattern needs to be projected onto a wafer coated with photoresist using light. Therefore, to ensure the pattern is clearly and accurately etched, the wafer surface must be precisely positioned on the focal plane of the lens. Because the wafer itself may have warpage or unevenness, and its position may change slightly during high-speed scanning, a FIA (Focus Interferometer Assembly) sensor is required for dynamic, real-time focus measurement and feedback control. Here, the FIA ​​sensor can measure and control the focal position of the wafer surface relative to the lithography machine's lens (projection lens) in real time and with precision. In other words, during the photolithography process, the silicon wafer stage, hereinafter referred to as the stage, needs to be further aligned with the lens, thus requiring the calibration of the FIA ​​sensor and the reference unit for the stage.

[0005] Based on this, it is desirable to provide an improved calibration scheme for the FIA ​​sensor and reference unit of a lithography machine. Summary of the Invention

[0006] This application provides a bidirectional calibration method for the FIA ​​sensor and reference unit of a lithography machine. It achieves high-efficiency and high-precision bidirectional calibration by aligning the center mark, left mark and right mark on the reference unit used for the worktable with the left FIA sensor and the right FIA sensor.

[0007] According to one aspect of this application, a bidirectional calibration method for a lithography machine's FIA sensor and reference unit is provided, comprising: calibrating the optimal coaxial alignment position of the reference unit based on the center coordinates of a center mark, a left mark, and a right mark of the reference unit used for the stage, and the center coordinates of the left FIA sensor and the right FIA sensor, by moving the center of the silicon wafer stage directly below the projection center of the objective lens; calibrating the first FIA sensor by correcting the position of the first FIA sensor using pixel deviation obtained by imaging a second mark corresponding to the first FIA sensor with a camera corresponding to the first FIA sensor; calibrating the first FIA sensor by moving the reference unit in a direction relative to the first FIA sensor based on the difference in center coordinates of the left mark and the right mark, and calibrating the reference unit by measuring the deviation value before and after the movement with the first FIA sensor as a reference; and calibrating the second FIA sensor by correcting the position of the second FIA sensor using pixel deviation obtained by imaging a first mark corresponding to the second FIA sensor with a camera corresponding to the second FIA sensor after moving the reference unit in a direction corresponding to the first FIA sensor by the difference in center coordinates; and calibrating the second FIA sensor by correcting the position of the second FIA sensor using pixel deviation obtained by imaging a first mark corresponding to the second FIA sensor with a camera corresponding to the second FIA sensor.

[0008] In the bidirectional calibration method of the FIA ​​sensor and reference unit of the above-mentioned lithography machine, the center coordinates of the center mark, the left mark and the right mark, as well as the center coordinates of the left FIA sensor and the right FIA sensor, are coordinates in a mechanical coordinate system with the origin directly below the projection center of the objective lens and the Z-axis perpendicular to the objective lens.

[0009] In the bidirectional calibration method for the FIA ​​sensor and reference unit of the lithography machine described above, calibrating the optimal coaxial alignment position of the reference unit includes: calculating a first deviation between the left FIA sensor and the left mark and a second deviation between the right FIA sensor and the right mark based on the center coordinates of the center mark, the left mark, and the right mark, as well as the center coordinates of the left FIA sensor and the right FIA sensor; calculating the sum of distances based on the first deviation and the second deviation; and 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 to obtain the optimal coaxial alignment position of the reference unit.

[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] The bidirectional calibration method for the FIA ​​sensor and reference unit of the lithography machine described above further includes: calibrating the second rotation angle of the reference unit by moving the reference unit in the corresponding direction of the first FIA sensor based on the center coordinate difference between the left and right marks, and measuring the deviation value before and after the movement using the second FIA sensor as a reference; 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 above steps of calibrating the first FIA sensor, calibrating the reference unit, and calibrating the second FIA sensor in response to the second rotation angle of the reference unit being greater than the predetermined threshold, 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 reference unit of the above lithography machine, for the deviation (dxLi, dyLi) of the target center of the left FIA sensor marked on the right side relative to the left FIA sensor, and for the deviation (dxRi, dyRi) of the target center of the right FIA sensor marked on the left side relative to the right FIA sensor, we have:

[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 for the FIA ​​sensor and reference unit of the lithography machine described above, [dxLi,dyLi]=A[dxRi,dyRi]+B, where A is the transformation matrix and B is the offset vector, then:

[0023]

[0024] The bidirectional calibration method for the FIA ​​sensor and reference unit of the lithography machine provided in this application embodiment can achieve high-efficiency and high-precision bidirectional calibration by aligning the center mark, left mark and right mark on the reference unit used for the worktable with the left FIA sensor and the right FIA sensor. Attached Figure Description

[0025] Various other advantages and benefits of this application will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0026] Figure 1 The illustration shows a schematic flowchart of a bidirectional calibration method for a lithography machine's FIA sensor and reference unit according to an embodiment of this application.

[0027] Figure 2 The illustration shows a schematic configuration of a bidirectional calibration method for a lithography machine's FIA sensor and reference unit according to an embodiment of this application.

[0028] Figure 3 The figure illustrates a mechanical coordinate system schematic diagram of a two-way calibration method for a lithography machine's FIA sensor and reference unit according to an embodiment of this application. Detailed Implementation

[0029] Hereinafter, exemplary embodiments according to this application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments of this application. It should be understood that this application is not limited to the exemplary embodiments described herein.

[0030] Figure 1 The illustration shows a schematic flowchart of a bidirectional calibration method for a lithography machine's FIA sensor and reference unit according to an embodiment of this application.

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

[0032] S110, by moving the center of the stage directly below the center of the objective lens projection, the optimal coaxial alignment position of the reference unit is determined based on the center coordinates of the center mark, left mark, and right mark of the reference unit used for the stage, as well as 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 reference unit of the lithography machine according to the embodiments of this application, the system configuration for bidirectional calibration of the FIA ​​sensor and reference unit includes an objective lens above the stage and two FIA sensors, and the reference unit for the stage 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 operations for the right mark and the left mark, respectively. Figure 2 The illustration shows a schematic configuration of a bidirectional calibration method for a lithography machine's FIA sensor and reference unit according to an embodiment of this application.

[0033] Here, the center of the aforementioned worktable is not its physical center, but rather the center of the wafer support position on the upper surface of the worktable. Specifically, a chuck is provided on the worktable to support and hold the wafer in place. Figure 3 The central suction cup is located below the silicon wafer and is coaxial with it. The suction cup is not shown due to being obscured by the wafer; its axis is the center of the workpiece stage. When the center of the workpiece stage is moved directly below the objective lens and coincides with the origin of the mechanical coordinate system, the interferometer measures the center coordinates of the workpiece stage as (0, 0). When the workpiece stage moves horizontally (after calibration, it only moves horizontally and not vertically, so only its horizontal coordinates are recorded), the interferometer always uses the measured coordinates of the workpiece stage's center in the mechanical coordinate system as the workpiece stage's coordinates. The origin of the mechanical coordinate system is located on the optical axis directly below the objective lens.

[0034] When performing bidirectional calibration of the FIA ​​sensor and reference unit, the mechanical coordinate system is set with the origin directly below the projection center of the objective lens, and the Z-axis perpendicular to the objective lens, as follows: Figure 3 As shown ( Figure 3 For illustrative purposes only, the cylindrical shape in the figure represents the objective lens, the rectangle with a missing corner in the upper right corner represents the stage, the stage is placed horizontally and located directly below the objective lens, the reference unit is fixed to one side of the stage, and the wafer (silicon wafer) is supported on the workpiece stage and moves with the horizontal movement of the workpiece stage. Figure 3The illustration shows a schematic diagram of the mechanical coordinate system for a two-way calibration method of the FIA ​​sensor and reference unit of a lithography machine according to an embodiment of this application. By controlling the movement of the stage, the center mark of the reference unit can be moved directly below the center of the objective lens, aligning the origin of the reference unit's coordinates with the origin of the mechanical coordinate system. The coordinates of the center of the workpiece stage at this point are read using an interferometer; that is, the coordinates of the workpiece stage center point in the mechanical coordinate system, for example, (fmx1, fmy1). Furthermore, the coordinates of the center of the left and right marks 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 workpiece stage, the position of the reference unit relative to the center of the workpiece stage needs to be preset.

[0035] That is, when the center of the stage is moved directly below the center point of the objective lens projection and coincides with the origin of the mechanical coordinate system, the coordinates of the center point of the reference unit in the mechanical coordinate system are marked as (fmx1, fmy1), while the interferometer reads the coordinates of the center of the stage as (0,0). According to the principle of coordinate system transformation, when the center point of the reference unit moves to the center of the objective lens, the center of the stage needs to move to the position of (-fmx1, -fmy1). At this time, the left mark of the reference unit should be imaged on the right FIA sensor, and the right mark should be imaged on the left FIA sensor. In fact, by performing a zigzag movement of the stage (moving with the minimum recognition accuracy for both the X and Y steps, taking the minimum value of (x1, x2) as the limit, and similarly taking the limit for the y direction, assuming the number of steps is 3 according to the set range), the sampled values ​​obtained for each step are shown in the table below:

[0036]

[0037] In this way, the optimal coaxial alignment position of the reference element can be determined based on the minimum sum of the distances between the FIA ​​center on the left and right sides and the mark center, for example, (fmx1',fmy1').

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

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

[0040] Then, calculate the sum of distances D as D = ld x 1 2 +ldy1 2 +rdx1 2 +rdy1 2 .

[0041] Next, we need to minimize the sum of distances D. That is, to find the (fmx1,fmy1) that minimizes the sum of distances D, we need to take the partial derivatives of D with respect to fmx1 and fmy1 and set them to zero.

[0042] Here, 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] Therefore, the optimal coaxial alignment position (fmx1′, fmy1′) of the reference element 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 reference unit of the lithography machine according to the embodiments of this application, the center coordinates of the center mark, the left mark and the right mark, as well as the center coordinates of the left FIA sensor and the right FIA sensor, are coordinates in a mechanical coordinate system with the origin directly below the projection center of the objective lens and the Z-axis perpendicular to the objective lens.

[0056] Furthermore, in the bidirectional calibration method for the FIA ​​sensor and reference unit of the aforementioned lithography machine, calibrating the optimal coaxial alignment position of the reference unit includes: calculating a first deviation between the left FIA sensor and the left mark and a second deviation between the right FIA sensor and the right mark based on the center coordinates of the center mark, the left mark, and the right mark, as well as the center coordinates of the left FIA sensor and the right FIA sensor; calculating the sum of distances based on the first deviation and the second deviation; taking the 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 optimal coaxial alignment position of the reference unit.

[0057] Furthermore, 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). The first deviation is ldx1 = mx1 + fmx1 - cx1, ldy1 = my1 + fmy1 - cy1, and 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.

[0058] Step S120: The position of the first FIA sensor is corrected by the pixel deviation obtained from the imaging of the second mark corresponding to the first FIA sensor by the camera corresponding to the first FIA sensor, so as to calibrate the first FIA sensor. That is, the optimal coaxial alignment position (fmx1′, fmy1′) of the reference unit obtained above is sent as a command to the silicon wafer stage to control the movement. After the reference unit is in place, theoretically, the target center of the first FIA sensor, such as the right FIA sensor, should coincide with the center of the second mark on the opposite side, such as the left mark. However, due to mechanical errors, there may be residual deviations (dx1, dy1).

[0059] Therefore, the camera corresponding to the first FIA sensor, such as the right-side camera, acquires images and, through image processing, provides the pixel deviation (Δu, Δv) of the center of the left-side marker in the target coordinate system of the right-side FIA ​​sensor. This deviation is then converted into mechanical coordinate deviation using pre-calibrated pixel-micron coefficients kx and ky, i.e., dx1 = kx·Δu, dy1 = ky·Δv. Next, it is determined whether the deviation is acceptable, i.e., if the process requires an alignment error threshold of εx and εy (e.g., ±0.1 μm). If |dx1| ≤ εx and |dy1| ≤ εy, the calibration is considered successful, and the current interferometer reading is recorded as the mechanical coordinates (X0R, Y0R) of the right-side FIA ​​sensor. Otherwise, the position parameters of the right-side FIA ​​sensor are corrected, i.e., (dx1, dy1) is used as compensation to correct the position parameters of the right-side FIA ​​sensor, offsetXR ← offsetXR + dx1, offsetYR ← offsetYR + dy1, and the image acquisition and correction steps are repeated until the threshold condition is met. In practice, convergence is usually achieved in 1-2 iterations, and the position information of the origin of the silicon wafer stage can be read from the interferometer on the silicon wafer stage.

[0060] Therefore, in the bidirectional calibration method of the FIA ​​sensor and reference unit of the lithography machine according to the embodiments of this application, the correction of the position of the first FIA sensor to calibrate the first FIA sensor by the pixel deviation obtained by the camera corresponding to the first FIA sensor imaging 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 imaging the second mark corresponding to the first FIA sensor; converting the pixel deviation into a coordinate deviation in the mechanical coordinate system by a pre-calibrated conversion 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.

[0061] Furthermore, in the bidirectional calibration method of the FIA ​​sensor and reference unit of the above-mentioned 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.

[0062] Step S130 involves moving the reference unit relative to the first FIA sensor based on the center coordinate difference between the left and right marks, and calibrating the first rotation angle of the reference unit by measuring the deviation before and after the movement using the first FIA sensor as a reference. Specifically, the measurement point at the current position, i.e., the deviation value (drx1, dry1) between the center of the left mark and the target center of the right FIA sensor, is first measured and recorded using the first FIA sensor, for example, the right FIA sensor. Then, the reference unit is shifted to the left by a distance of |x2-x1| using the silicon wafer stage. The deviation value (drx2, dry2) between the center of the right mark and the target center of the right FIA sensor is measured again using the right FIA sensor. Here, the deviation value before and after the movement is the deviation between the mark center measured by the FIA ​​sensor and the pixel coordinate system center of the FIA ​​sensor. Specifically, before the movement, it is the measurement value of the right FIA sensor corresponding to the left mark, and after the movement, it is the measurement value of the right FIA sensor corresponding to the right mark.

[0063] Based on the deviation between the two measurements, the rotation angle θ of the reference element can be calculated as θ = arctan[(drx2-drx1) / (dry2-dry1)]. Thus, the reference element is calibrated based on the rotation angle θ of the reference element.

[0064] Therefore, in the bidirectional calibration method of the FIA ​​sensor and reference unit of the lithography machine according to the embodiments of this application, 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)].

[0065] Step S140: After moving the reference unit towards the corresponding direction of the first FIA sensor by the center coordinate difference, the position of the second FIA sensor is corrected by the pixel deviation obtained by imaging the first mark corresponding to the second FIA sensor using the camera corresponding to the second FIA sensor, thereby calibrating the second FIA sensor. That is, after translating the reference unit towards the corresponding direction of the first FIA sensor (e.g., to the right of the right FIA sensor) by a distance of |x2-x1| using the silicon wafer stage, the second FIA sensor (e.g., the left FIA sensor) can detect the first mark of the reference unit (e.g., the image of the right mark). By aligning the image with the left FIA sensor and measuring it, the deviation value (dx2, dy2) is calculated. The position parameters of the left FIA sensor can be corrected based on the deviation value until dx2 and dy2 are within the allowable error range. This calibrates the left FIA sensor, and the position information of the current silicon wafer stage origin is read from the interferometer.

[0066] Those skilled in the art will understand that the calibration process for the left-side FIA ​​sensor is similar to that for the right-side FIA ​​sensor, and therefore will not be repeated here. Furthermore, although the example above uses the first sensor as the right-side FIA ​​sensor and the second sensor as the left-side FIA ​​sensor, in this embodiment, the first sensor could also be the left-side FIA ​​sensor and the second sensor the right-side FIA ​​sensor.

[0067] Furthermore, in the bidirectional calibration method of the FIA ​​sensor and reference unit of the lithography machine according to the embodiments of this application, the calibration verification of the reference unit may be further included. That is, after calibrating the second FIA sensor, the second FIA sensor is used as a reference for measurement. Specifically, firstly, the first mark corresponding to the second sensor at the current position is recorded, for example, the deviation value (dlx1, dly1) of the center of the right mark corresponding to the left FIA sensor from the target center of the left FIA sensor. Then, the silicon wafer stage is shifted to the right by a distance of |x2-x1|. 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 to calculate the rotation angle of the reference unit. If the rotation angle is approximately 0, that is, less than or equal to a predetermined threshold, the calibration verification is successful. 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, the bidirectional calibration method for the FIA ​​sensor and reference unit of the lithography machine according to the embodiments of this application further includes: calibrating the second rotation angle of the reference unit by moving the reference unit in the corresponding direction of the first FIA sensor based on the center coordinate difference between the left mark and the right mark, and measuring the deviation value before and after the movement with the second FIA sensor as a reference; 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 above steps S120 to S140 in response to the second rotation angle of the reference unit being greater than the predetermined threshold 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 it moves to the 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 were performed in the same sensor (left FIA sensor) coordinate system. The theoretical displacement of the right marker relative to the left marker 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 equal to the theoretical displacement: {Δx*cosθ = Δx_meas, Δx*sinθ = Δy_meas, θ = arctan2(Δymeas, Δxmeas). This is derived from the geometric relationship of the plane rotation of the reference element, used to calculate the rigid body rotation angle based on the two measured displacements. It is used for the reference element rotation angle calculation, which inversely derives the rigid body rotation angle by measuring the displacement components of a point on the reference element in two directions.

[0071] Furthermore, an allowable rotation error εθ (e.g., ±0.05 mrad) is set. If the absolute value of angle θ, |θ| ≤ εθ, the verification passes; otherwise, if |θ| > εθ, iterative correction is still required.

[0072] Specifically, during iterative correction, θ is written as the compensation rotation amount of the reference unit into 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 met.

[0073] Furthermore, when calibrating the mapping relationship between the two FIA sensors and the reference unit, the right mark and the left mark can be measured by the left and right FIA sensors respectively, and the deviation matrix of several feature points on the mark relative to the center of the sensor target can be measured. That is, the left mark has a deviation matrix on the right FIA sensor, and the right mark has a deviation matrix on the left FIA sensor. A mathematical model is constructed from these two deviation matrices to find the mapping relationship between the two FIA sensors and the reference unit.

[0074] For example, use the left FIA sensor to measure several feature points on the right marker, and record the deviation (dxLi, dyLi) of each point relative to the target center of the left FIA sensor. Then use the right FIA sensor to measure several feature points on the left marker, and record the deviation (dxRi, dyRi) of each point relative to the target center of the right FIA sensor.

[0075] For measurements where the right-hand side is marked on the left-hand FIA sensor, construct the left-hand bias matrix; and for measurements where the left-hand side is marked on the right-hand FIA sensor, construct the right-hand bias matrix.

[0076] dxL = [dxL1, dxL2, ..., dxLn]

[0077] dyL = [dyL1, dyL2, ..., dyLn]

[0078] dxR = [dxR1, dxR2, ..., dxRn]

[0079] dyR=[dyR1,dyR2,…,dyRn]

[0080]

[0081] Then calculate the mapping relationship, for example, using the least squares method or other linear regression methods to solve for the linear relationship between the two deviation matrices. Assuming the mapping relationship is: [dxLi, dyLi)]=A[dxRi, dyRi]+B, where A is the transformation matrix and B is the offset vector, then solve for the transformation matrix and the offset vector, for example, by using the least squares method to solve for A and B:

[0082]

[0083] The mapping relationship is verified by using the obtained A and B to map each point in DR to the coordinate system of DL, and checking the deviation between the mapped points and the actual measured points to ensure that it is within the allowable error range.

[0084] In summary, the bidirectional calibration method for the FIA ​​sensor and reference unit of the lithography machine according to the embodiments of this application can achieve bidirectional calibration of the FIA ​​sensor and reference unit with high precision and high efficiency, wherein the alignment accuracy can be improved to the sub-micron level and the calibration efficiency can be improved by more than 30%.

[0085] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0086] The block diagrams of devices, apparatuses, devices, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0087] It should also be noted that in the apparatus, equipment, and methods of this application, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of this application.

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

[0089] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A bidirectional calibration method for the FIA ​​sensor and reference unit of a lithography machine, comprising: By moving the center of the stage directly below the center of the objective lens projection, the optimal coaxial alignment position of the reference unit is determined based on the center coordinates of the center mark, left mark, and right mark of the reference unit used for the stage, as well as the center coordinates of the left FIA sensor and the right FIA sensor. The position of the first FIA sensor is corrected by the pixel deviation obtained by the camera corresponding to the first FIA sensor imaging the second marker corresponding to the first FIA sensor to calibrate the first FIA sensor. The first rotation angle of the reference unit is calibrated by moving the reference unit in the relative direction of the first FIA sensor based on the difference in center coordinates between the left and right marks, and measuring the deviation value before and after the movement with the first FIA sensor as a reference. as well as After moving the reference unit to the corresponding direction of the first FIA sensor by the center coordinate difference, the position of the second FIA sensor is corrected by the pixel deviation obtained by the camera corresponding to the second FIA sensor imaging the first mark corresponding to the second FIA sensor to calibrate the second FIA sensor. The center coordinates of the center mark, the left mark, and the right mark, as well as the center coordinates of the left FIA sensor and the right FIA sensor, are coordinates in a mechanical coordinate system with the origin directly below the objective lens projection center and the Z-axis perpendicular to the objective lens. Calibrling the optimal coaxial alignment position of the reference unit includes: Based on the center coordinates of the center mark, the left mark, and the right mark, as well as the center coordinates of the left FIA sensor and the right FIA sensor, calculate the first deviation between the left FIA sensor and the left mark and the second deviation between the right FIA sensor and the right mark; The sum of distances is calculated based on the first deviation and the second deviation; and, Take the partial derivative of the sum of the distances with respect to the center coordinates of the center mark, and set the partial derivative to zero to obtain the optimal coaxial alignment position of the reference unit.

2. The bidirectional calibration method for the FIA ​​sensor and reference unit of a lithography machine as described in claim 1, wherein, Let the center coordinates of the left FIA sensor be (cx1, cy1), the center coordinates of the right FIA sensor be (cx2, cy2), the center coordinates of the left marker be (mx1, my1), the center coordinates of the right marker be (mx2, my2), and the center marker coordinates of the reference unit be (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 = ld x 1 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.

3. The bidirectional calibration method for the FIA ​​sensor and reference unit of a lithography machine as described in claim 1, wherein, Correcting the position of the first FIA sensor by using the pixel deviation obtained from imaging the second marker corresponding to the first FIA sensor by the camera corresponding to the first FIA sensor to calibrate the first FIA sensor includes: The camera corresponding to the first FIA sensor images the second marker corresponding to the first FIA sensor to obtain the pixel deviation of the center of the second marker in the target coordinate system of the first FIA sensor; The pixel deviation is converted into a coordinate deviation in the mechanical coordinate system using a pre-calibrated transformation coefficient; In response to the coordinate deviation exceeding an alignment error threshold, the position parameters of the first FIA sensor are corrected using the coordinate deviation; and, Repeat the above steps until the coordinate deviation is less than or equal to the alignment error threshold.

4. The bidirectional calibration method for the FIA ​​sensor and reference unit of a lithography machine as described in claim 3, 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 parameters of the first FIA sensor is offsetXR←offsetXR+dx1, offsetYR←offsetYR+dy1.

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

6. The bidirectional calibration method for the FIA ​​sensor and reference unit of a lithography machine as described in claim 1, further comprising: The second rotation angle of the reference unit is calibrated by moving the reference unit in the corresponding direction of the first FIA sensor based on the center coordinate difference between the left and right marks, and measuring the deviation value before and after the movement with the second FIA sensor as a reference. If the second rotation angle of the reference unit is less than or equal to a predetermined threshold, the calibration verification is determined to be successful. as well as, In response to the second rotation angle of the reference unit being greater than a predetermined threshold, the steps of calibrating the first FIA sensor, calibrating the reference unit, and calibrating the second FIA sensor are iterated until the second rotation angle is less than or equal to the predetermined threshold.

7. The bidirectional calibration method for the FIA ​​sensor and reference unit of a lithography machine as described in claim 6, wherein, For the deviations (dxLi, dyLi) of the target center relative to the left FIA sensor marked on the right side, and for the deviations (dxRi, dyRi) of the target center relative to the right FIA sensor marked on the left side, we have: dxL = [dxL1, dxL2, …, dxLn]; dyL = [dyL1, dyL2, …, dyLn]; dxR = [dxR1, dxR2, …, dxRn]; dyR = [dyR1, dyR2, …, dyRn]; Then the left deviation matrix DL And right deviation matrix DR for: 。 8. The bidirectional calibration method for the FIA ​​sensor and reference unit of a lithography machine as described in claim 7, wherein, [dxLi,dyLi]=A[dxRi, dyRi]+B, where A is the transformation matrix and B is the offset vector, then: 。

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