KR101948906B1 - Marker having focusing and tilt correction design and alignment method - Google Patents

Abstract

A method of aligning a marker having a focusing and tilt correction design, the marker comprising an alignment marker (20) and at least one pair of focusing markers, the center of the alignment marker (20) And the at least one pair of focusing markers among the plurality of focusing markers can achieve focusing and leveling of the alignment marker 20 by determining the optimal focal plane position of the at least one pair of focusing markers. Also, an alignment method applied to the markers is provided, thereby realizing high-precision focusing and leveling of alignment markers. The markers provided in the corresponding solutions eliminate the influence of the inclination on the markers as well as the focusing, thereby improving the measurement reproducibility.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to markers and aligning methods having a focusing and tilt correction design,

The present invention relates to markers and alignment methods having a focusing and tilt correction design, and more particularly to markers comprising alignment markers and at least one pair of focusing markers, and alignment methods therefor.

In the manufacture of integrated circuits, one complete chip typically has to undergo several photolithographic exposures before fabrication can be completed. In addition to photolithography of the first layer, photolithography of the remaining layers must precisely fix the geometry of the layer to the geometry (i.e., marker) left over from the previous layer exposure prior to exposure so that the correct relative position That is, alignment precision.

In the prior art, an alignment system based on the principle of optical imaging is one of the systems commonly used in lithographic apparatuses, such as the Nikon FIA system, Ultratec MVS, and the like. The marker format of the FIA is as shown in Fig. Ultratec MVS has a marker learning function, and the marker does not have a fixed format. In addition, US6344698 B2 and CN102103336 have designed a marker which has relatively little effect on each process considering the influence of the process on the markers.

In practice, besides the process affecting the measurement accuracy, a large number of factors affect the measurement accuracy.

First, distortion is a common aberration. In an optical imaging system, distortion can not neglect the influence on measurement reproducibility. Its effect mechanism is that the nonlinear coupling of the position uncertainty and distortion in the field of view of the measurement marker affects the measurement reproducibility. The FIA system repeatedly measures the marker by placing it at a fixed position, reducing the effect of distortion, but repeating consumes a large amount of time.

Next, as shown in FIG. 2, the decentering tilt effect of the marker also affects the measurement reproducibility, which causes an error D in the object tilt angle a. Since the focusing and leveling measurement surfaces are on the top surface of the photoresist and the alignment markers are sometimes located on the bottom surface of the photoresist, the thickness of the photoresist can be adjusted to some extent , The focusing and leveling system is insufficient to realize high precision focusing and leveling of alignment markers.

And, in an optical imaging system, although an auto focusing technique is already widely used for an alignment sensor, a sensor that implements inclination correction with automatic focusing has not yet been invented.

The present invention provides a marker and alignment method having a focusing and tilt correction design, wherein the marker includes an alignment marker and at least a pair of focusing markers to focus and eliminate tilting effects on the markers, It is aimed to reduce the influence on this marker.

To achieve the above object, in the present invention,

A focusing marker and at least one pair of focusing markers, wherein the center of the alignment marker is located on a connecting line of any pair of the focusing markers, wherein the at least one pair of focusing markers has its own optimal focal plane And a focusing and tilt correcting design for realizing the focusing and leveling of the alignment marker through determination of the position.

Additionally, the alignment markers may be cross-shaped or rice-shaped markers, horizontal linear markers or vertical linear markers.

In addition, the center of the alignment marker is positioned on the center point of any pair of the focusing marker connecting lines.

In addition, the line width of the alignment markers is greater than the dioxide particle size.

In addition, the line width of the alignment marker is greater than the double point spread function width.

Additionally, the focusing marker is a rectangular focusing marker or a lattice type focusing marker.

Additionally, the lattice-type focusing markers are horizontal lattice-type focusing markers or vertical lattice-type focusing markers.

In addition, the marker includes an alignment marker and a focusing marker, wherein the focusing marker includes a pair of the rectangular focusing markers, a pair of the horizontal grid type focusing markers, and a pair of the vertical grid type focusing markers.

The present invention further provides an alignment method, which is used in the marker, wherein the alignment method comprises the following steps.

(1) the center of the alignment marker is located on a connecting line of any pair of focusing markers, and each group of markers includes the alignment markers and at least one pair of the focusing markers, and n groups of focusing And forming the marker with an oblique calibration design;

(2) performing an initial alignment for the markers of each group using an alignment system;

(3) The workpiece table is moved in the vertical direction at a predetermined step distance, and the optimum focal plane position of the at least one pair of focusing markers {Pi , Qi}, where Pi and Qi are the optimal focal plane positions of a pair of focusing markers in the i-th group marker, respectively, and i = 1, 2, ... , n < / RTI >

(4) The optimal focal plane position {Pi, Qi} of each pair of focusing markers and the distance Dis (Pi, Qi) in the horizontal direction corresponding to each alignment marker, Acquiring an original value Mi of the position and an original value Ti of the inclination,

,

,

(5) The optimum focal plane position M and the tilt T of the workpiece are determined by an average value filtering or an intermediate value filtering method by the original value Mi of the optimal focal plane position of each alignment marker and the original value Ti of the tilt Establishing;

(6) moving the workpiece table in the vertical direction by the optimal focal plane position M of the workpiece and its tilt T to compensate for the vertical position of each alignment marker.

In addition, the focal plane determination criteria include a gradient magnitude method and a point spread function width method.

Additionally, the focusing marker is a rectangular focusing marker or a lattice type focusing marker.

In addition, the focal plane criterion of the grid-shaped focusing marker is the gradient magnitude of the marker image.

In addition, the focal plane determination criterion of the rectangular focusing marker is a width of a point spread function of the marker. Specifically, a gray distribution is obtained by extracting a gray value of a certain row or a certain row of the rectangular focusing markers, And the position of the focal plane is determined by the magnitude of the h value.

In addition, a method of acquiring the optimal focal plane position {Pi, Qi} of each pair of focusing markers is as follows:

(1) moving the workpiece table in a vertical direction at a predetermined step distance;

(2) taking an image at each vertical stepping position;

(3) extracting the focal plane determination reference value from the image;

(4) fitting curves to find the optimal focal plane position of each pair of focusing markers.

In addition, a method of acquiring the optimal focal plane position {Pi, Qi} of each pair of focusing markers is as follows:

(1) displaying the relationship between the focal plane determination reference value and the position of the workpiece table in the vertical direction;

(2) taking an image at the current position of the workpiece table in the vertical direction;

(3) extracting the focal plane determination reference value from the image;

(4) obtain a distance d away from the focal plane of the workpiece table on the current workpiece table vertical position by the relationship indicated and the extracted focal plane determination reference value;

(5) The work table is moved by d and -d on the basis of the current vertical position of the workpiece table, respectively, and images are taken to acquire the focal plane judgment reference values V1 and V2;

(6) comparing V1 and V2 to determine the optimal focal plane position of each pair of focusing markers.

In contrast to the prior art, the present invention provides a marker and alignment method with a focusing and tilt correction design to achieve high-precision focusing and leveling of alignment markers. Eliminates the effects of tilting on the markers while focusing on one side and improves measurement reproducibility; On the other hand, the mechanism of the influence of the distortion on the measurement reproducibility was analyzed, from which the limited condition of the alignment marker width was suggested, further improving the measurement reproducibility.

1 is a view showing an FIA marker;
FIG. 2 is a principle view of the defocusing effect; FIG.
3 is a view showing a marker of Embodiment 1 of the present invention.
4 is a diagram showing extraction of a gray value of a marker in embodiment 1 of the present invention;
5 illustrates extraction of a gray distribution of gray values of a marker in embodiment 1 of the present invention.
6 is a diagram showing a positional relationship between an alignment marker and a focusing marker in Embodiment 1 of the present invention.
Fig. 7 is a diagram showing calculation of vertical position types Mi and Ti of the respective alignment markers according to the obtained vertical position Pi and Qi of each focusing marker. Fig.
8 is a view showing a position where a workpiece (silicon wafer) position is calculated by the positions X, Y of a plurality of alignment markers;
Figure 9 also shows the principle of the influence of the distortion on the measurement reproducibility.
10 is a view showing a marker of Embodiment 2 of the present invention.
11 is a view showing a marker of Embodiment 3 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The advantages and features of the present invention will become more apparent from the following description and claims. It is to be understood that the drawings are in a very simplified form and are all in an inaccurate proportion, merely to assist in explaining the purpose of the embodiment of the present invention.

Example 1

As shown in Figure 3, the present embodiment provides a marker with a focusing and tilt correction design, which includes alignment markers 20 and at least one pair of focusing markers, Wherein the lattice-type focusing marker is a horizontal lattice-type focusing marker or a vertical lattice-type focusing marker, and the focusing marker comprises a pair of the rectangular focusing markers, a pair of the horizontal grid- A pair of the vertical grid type focusing markers, wherein the focusing markers include a rectangular focusing marker 10, a rectangular focusing marker 30, a horizontal grid type focusing marker 11, a horizontal grid type focusing marker 31, Type focusing marker 12 and a vertical grid type focusing marker 32. [ The rectangular focusing markers 10 and the rectangular focusing markers 30 are a pair of rectangular focusing markers and the horizontal grid type focusing markers 11 and the horizontal grid type focusing markers 31 are a pair of grid type focusing markers , And the vertical grid type focusing marker 12 and the vertical grid type focusing marker 32 are a pair of grid type focusing markers. The alignment marker 20 is a cross-shaped marker or an rice-shaped marker and is used for alignment. In Embodiment 1, the alignment marker 20 is a cross-shaped marker, the cross-shaped marker 20 includes a horizontal line and a vertical line, The line and the vertical line are perpendicular to each other and the center of the alignment marker 20 is positioned on the center point of any pair of the focusing marker connecting lines and any pair of the focusing markers are symmetrical to each other by the alignment marker , Determining that both focusing markers are relative to the height of the alignment system and combining the positional relationship of both focusing markers and center alignment markers to estimate the height and tilt of alignment markers 20, Thereby achieving high-precision focusing and leveling. The line width of the alignment markers 20 is larger than that of the alignment markers 20 and the focal plane is adjusted with respect to the plane on which the alignment markers 20 are positioned through at least one pair of focusing markers, Precision focusing and leveling of the surface on which the alignment markers 20 are located for the measurement of the alignment markers 20, i.e., through at least a pair of focusing markers. When the optimal focal plane of the focusing marker is determined, the focal plane criterion should be selected. There are two general focal plane criterion criteria, the gradient size method and the PSF (point spread function) width method, respectively.

In Embodiment 1, the focal plane criterion of the grid type focusing markers 11, 12, 31 and 32 is the gradient magnification method, that is, it convolutes and accumulates the image and the Sobel operator. The formula of the focal plane criterion is as follows.

Dx = Im age * SobelX

Dy = Im age * SobelY

Among them, Image is the original image, SobelX and SobelY are the lateral and longitudinal Sobel operators, Dx and Dy are the lateral and longitudinal edge detection images, respectively, and V is the gradient approximate value, to be.

In Embodiment 1, the focal plane determination criteria of the rectangular focusing markers 10 and 30 are based on the PSF width method, i.e., extracting any row or any number of rows of the rectangular markers, Similarly, the gray distribution as shown in FIG. 5 is obtained through accumulation (projection) of gray values, and the PSF width h, that is, the focal plane judgment reference value in FIG. 5 is obtained. Thereafter, by the size of the PSF width h value The focal plane position is determined.

The method for determining the optimal focal plane after selecting the focal plane criterion is the first method or the second method.

The first method includes the following steps.

(1) moving the workpiece table at a predetermined step distance;

(2) taking an image at each vertical stepping position of the workpiece table;

(3) extracting the focal plane determination reference value from the image;

(4) obtaining an optimal focal plane position by fitting the curve.

The second method comprises the following steps.

(1) displaying a relationship between the focal plane determination reference value and a workpiece table vertical direction position;

(2) photographing an image at a current vertical position of the workpiece table;

(3) extracting the focal plane determination reference value from the image;

(4) By combining the focal plane determination reference value extracted in the step (3) with the focal plane determination reference value displayed in the step (1) and the vertical position of the workpiece table, Obtaining a distance d away from the focal plane of the table;

(5) moving the workpiece table by d and -d based on the current position of the workpiece table in the vertical direction, respectively, and photographing an image to obtain focal plane judgment reference values V1 and V2;

(6) A step of determining an optimal focal plane position by comparing V1 and V2.

Among them, in the first step of the second method, the alignment system (including the lens) is usually fixed and can indicate the vertical distance of the marker to the lens in the vertical position of the workpiece table or marker , The term " position in the workpiece table vertical direction " in the step (1) can be replaced with " position in the vertical direction of the marker " It should be noted that the overall system described in this embodiment is based on the assumption that the silicon wafer lies horizontally and the lens is viewed from top to bottom so that the position in the vertical direction of the marker may be the position in the vertical direction of the alignment marker And may be a position in the vertical direction of the focusing markers, and the values thereof are the same.

In the fourth step of the second method, since the relationship between the " focal plane determination reference value " and the " workpiece table vertical position " (which indicates the vertical distance of the marker with respect to the lens) The distance from the marker to the lens at the time of photographing is not yet known. The image is photographed while keeping the workpiece table at the current vertical position, i.e., maintaining the distance between the marker and the lens, while calculating the " , The vertical distance from the workpiece stay to the lens on the current workpiece table vertical position can be calculated by substituting the again calculated focal plane judgment reference value into the displayed relation data, or if the object indicated in the step (1) Focal plane determination reference value " and " marker vertical position ", the lens from the marker on the current work table vertical position At the same time that the magazine calculated vertical distance it is possible to obtain a vertical distance d between the workpiece table or markers and the focal plane on the current workpiece table vertical position.

Since it is not possible to determine whether the workpiece table has deviated from the focal plane in the forward direction or the reverse direction after completing the step (4), the workpiece table is moved to the current position in the step (2) Based on the position of the workpiece table in the vertical direction, by d and -d in the vertical direction respectively, that is, by moving them in the vertical direction by d distance in the direction close to and farther from the lens respectively, thereby acquiring the corresponding focal plane judgment reference values V1 and V2 do.

In step (6) of the second method, it is determined which of the focal plane determination reference values V1 and V2 is more preferable, and when the current workpiece table is located at the vertical position of the workpiece table corresponding to the desired determination reference value, It can be determined that the marker is located at the optimum focal plane position.

6, when the alignment marker 20 is positioned between the pair of focusing markers, that is, when the center of the alignment marker 20 is positioned at the center of the center connection line of the pair of focusing markers The optimal focal plane position 2 of the alignment marker 20 is an average value of the optimal focal plane position 1 of one focusing marker and the optimal focal plane position 3 of the other focusing marker. Here, the optimal focal plane position of the alignment marker and the focusing marker can be displayed using a height value (i.e., a vertical direction coordinate value) relative to the alignment system of the marker center. In addition, the inclination of the alignment marker 20 can be obtained by the optimum focal plane position 1 of one focusing marker and the optimal focal plane position 3 of the other focusing marker.

The method of aligning the markers includes the following steps.

(1) placing a marker pre-formed workpiece having n groups of focusing and tilt correction designs on a workpiece table and then realizing the first stage of focusing and leveling through a focusing and leveling system (FLS);

Referring to FIG. 7, a marker having three groups of focusing and tilt correction designs was used, i.e., n = 3, and the three groups of markers were referred to as first marker group, second marker group, The third marker group is referred to as a third marker group. In each marker group, an alignment marker is located at the center of each pair of focusing markers.

(2) moving the workpiece table to introduce each group of markers into the alignment system field and aligning to complete the rudimentary measurement, thereby establishing a horizontal position parameter of the focusing marker in each group marker;

(3) Moving the workpiece table in the vertical direction at a predetermined step distance, and determining a focal plane determination criterion and an optimal focal plane determination method thereof, that is, a method for determining at least one pair Obtaining an optimal focal plane position {Pi, Qi} of the focusing marker,

Pi and Qi are the optimal focal plane positions of a pair of focusing markers in the i-th group marker, respectively, i = 1,2, ... , n < / RTI >

According to this embodiment, at this stage, the optimum focal plane positions P1, Q1 of the pair of focusing markers of the first marker group, the optimal focal plane positions P2, Q2 of the pair of focusing markers of the second marker group, Obtaining an optimal focal plane position P3, Q3 of a pair of focusing markers of the third marker group;

(4) Optimum focal plane position {Pi, Qi} of each pair of focusing markers, that is, a vertical focal plane position of the two focusing markers and a horizontal distance Dis (Pi, Obtaining an original value Mi of an optimal focal plane position of the corresponding alignment marker 20 and an original value Ti of the tilt by means of the correction value Qi,

,

,

The step can refer to FIG. 7, and by the optimum focal plane positions P1 and Q1, the optimal focal plane position M1 of the alignment marker in the first marker group and its slope T1 can be calculated, and the optimal focal plane position P2 and Q2 can calculate the optimal focal plane position M2 and its slope T2 of the alignment markers in the second marker group and calculate the best focal plane position M2 of the alignment marker in the third marker group by the optimal focal plane positions P3, The position M3 and its slope T3 can be calculated;

(5) Based on the original value Mi of the optimum focal plane position of each alignment marker 20 and the original value Ti of the tilt thereof, the image of the field of view surrounded by the plurality of alignment markers 20, Determining an optimal focal plane position M of the workpiece (silicon wafer) and its tilt T;

(6) By the optimum focal plane position M of the workpiece (silicon wafer) in the visual field and its inclination T, the workpiece table is moved in the vertical direction to compensate for the vertical position of the alignment marker requiring compensation among a plurality of alignment markers step;

(7) Calculate the horizontal position of the re-alignment marker 20, its horizontal position being xWZCS, yWZCS, and recording the position of the workpiece table at the time of measurement, the corresponding step may be referred to FIG. The position of the marker having the focusing and tilt correction design is obtained after the movement of the workpiece table in the step (6) (not showing the specific movement locus and positional change in the drawing) and the new horizontal position of each group marker, The horizontal positions X1 and Y1 of the first marker group, the horizontal positions X2 and Y2 of the second marker group, and the horizontal positions X3 and Y3 of the third marker group, respectively, as shown in FIG.

(8) Acquiring the position of the workpiece (silicon wafer) in the workpiece table.

Among them, step (1) is first stage focusing and leveling and is used for initial adjustment, and steps (3) to (8) are second stage focusing and leveling, realizing high precision focusing and leveling of alignment markers.

It should be pointed out that when there are a large number of pairs of focusing markers (e.g., m pairs) in each group of n groups, it is only possible to proceed to the calculation of the optimal focal plane position of a pair of focusing markers in each group marker If necessary, the set {Pij, Qij} can be obtained by calculating the optimal focal plane positions of two or more pairs of focusing markers in each group marker, where i = 1, 2, ... , n; j = 1, 2, ... , m. However, for example, when taking the average value of the optimal focal plane positions of two or more pairs of focusing markers in each group marker, it is possible to acquire the optimum focal plane positions Pi and Qi representing the group markers. Such a method is particularly suitable when the grid markers are used as focusing markers. As shown in FIG. 7, the grid markers are generally used to measure a grid (for example, a vertical grid and a horizontal grid) And then take an average. However, it is not necessary to measure the average value of several pairs for a direct type or other marker.

The design of the marker having the inclination correction was completed by the above description, and the alignment marker alignment method was provided, but the influence of the distortion on the alignment accuracy of the alignment marker was not considered.

As shown in FIG. 9, the alignment markers have a certain width, and the width in FIG. 9 is the LR segment length. The positions of the alignment markers on both sides are L and R, the center position is C, the actual imaging positions of the alignment markers are L 'and R', and the corresponding center position is CC. The display algorithm can establish an ideal imaging point relationship and a substantial imaging point position relationship, as shown by the arrows in Fig. Because of the non-linearity of the distortion, the CC point has deviated from the imaging point C 'corresponding to point C, so that the actual marker test position CC deviates from the actual position of the marker, but the reproducibility can still be secured if the deviation amount is fixed. However, as the field of view varies substantially, the amount of deviation also changes, affecting measurement reproducibility.

The calculation method of the influence on the alignment accuracy of the distortion includes the following steps.

(1) obtaining an offset curve O (t) for an ideal imaging point of the lens at each position in the field of view through optical software such as Zemax and CODE V;

(2) generating a window function by a width of a marker having a width T;

(3) dividing the window at the center into two adjacent subwindows, W (t) and W (t-T / 2), respectively, all of T / 2 in width;

(4) obtaining C (t) and D (t) by convolving the subwindow W (t) and W (t-T / 2) with O (t) respectively;

(5) taking E (t) = C (t) - D (t);

(6) Finding the maximum value Max and the minimum value Min in E (t).

On the image side, the effect on the accuracy of the distortion can be calculated as Err = Max-Min, and the corresponding object-side value is Err / magnification.

As can be seen from the above analysis, the smaller the width of the alignment marker 20, the smaller the influence on the accuracy of the distortion. However, since the disposition of the alignment markers 20 is greater than the discrete particle size of the image (size of the granules), the alignment markers 20 can be infinitely small none.

Then, the internal brightness value of the alignment marker 20 does not change, and does not include the alignment marker 20 position information. There is a feature that indicates the position of the alignment marker 20 only at the edge position of the alignment marker 20. In order to precisely position the rim of the alignment marker 20, four sampling points within the range covered by the rim (i.e., the PSF width) are required, so that the width of the alignment marker 20 must be greater than twice the PSF width, The width of the alignment marker 20 is fixed.

Example 2

Unlike Embodiment 1, in Embodiment 2, the center of the alignment marker may not always be located at the midpoint of the arbitrary pair of focusing marker connecting lines (as shown in FIG. 10), and the focusing marker 20 ' ) Comprises a pair of said rectangular focusing markers 10 'and 30', a pair of said horizontal grid-shaped focusing markers 11 'and 31' and a pair of said vertical grid-shaped focusing markers 12 'and 32' And the center of the alignment marker 20 'is not located at the midpoint of any pair of focusing marker connecting lines, and if only the distance of the two focusing markers is known, i.e., from the focusing marker to the alignment marker in FIG. 10 Knowing the distances W1W2 and W2W3, the optimal focal plane position of the alignment marker can be obtained by the distance from the known alignment marker to the two focusing markers. Compared to the first embodiment, the second embodiment provides the marker with a relatively small restriction, thereby satisfying the diversification requirement of the user.

In Embodiment 2, except for the above-mentioned content, the markers and the alignment method are all the same as Embodiment 1, and the detailed description thereof will be omitted here.

Example 3

Unlike Embodiment 1, in Embodiment 3, the alignment marker is a horizontal linear marker or a vertical linear marker, and is used for measuring the unidirectional position, as shown in FIG. The marker 20 " includes a pair of the rectangular focusing markers 10 " and 30 ", a pair of the horizontal grid type focusing markers 11 & &Quot; and 32 "), and the center of the alignment marker 20 " is not located at the midpoint of any pair of focusing marker connecting lines. Compared with the first embodiment, the third embodiment provides a marker for measuring the unidirectional position, satisfying the diversification requirement of the user.

In Embodiment 3, except for the above-mentioned content, the markers and the alignment method are all the same as those in Embodiment 1, and the detailed description thereof will be omitted here.

Example 4

Unlike Example 1, in Example 4, the alignment marker is an rice-rice-like marker. Compared to the first embodiment, the fourth embodiment provides an rice-rice marker (not shown) to satisfy the diversification requirement of the user.

In Embodiment 4, except for the above-mentioned content, the markers and the alignment method are all the same as Embodiment 1, and thus the detailed description thereof will be omitted.

In conclusion, the present invention discloses a marker and alignment method having a focusing and tilt correction design, and realizes highly accurate focusing and leveling of alignment markers. On the one hand, it eliminates tilting while focusing and improves measurement reproducibility; In another aspect, the mechanism of the influence of distortion on the measurement reproducibility was analyzed, from which the limiting condition for the width of the alignment marker was suggested, and further the measurement reproducibility was improved.

The above is merely a preferred embodiment of the present invention, and there is no limitation on the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims and their equivalents. And all of which fall within the scope of the present invention, which does not depart from the scope of the present invention.

a: object inclination angle; D: error; 10: Rectangular focusing markers; 30: Rectangular focusing marker; 11: Horizontal lattice focusing markers; 31: Horizontal lattice focusing markers; 12: Vertical grid type focusing marker; 32: Vertical grid type focusing marker; 20: alignment marker; h: PSF width; 1: optimal focal plane of one focusing marker; 2: optimal focal plane of the alignment marker; 3: Optimal focal plane of the other focusing marker.

Claims (15)

A marker having a focusing and tilt correction design, the marker comprising an alignment marker and at least one pair of focusing markers, the center of the alignment marker being located on a connecting line of any pair of the focusing markers, Wherein the at least one pair of focusing markers realizes focusing and leveling of the alignment markers by determining their optimal focal plane position. 2. The marker of claim 1, wherein the alignment marker is a cross-shaped marker, an in-rice marker, a horizontal linear marker, or a vertical linear marker. The marker according to claim 1, wherein the center of the alignment marker is located on the center of an arbitrary pair of the focusing marker connecting lines. 2. The marker of claim 1, wherein the line width of the alignment marker is greater than the dioxide particle size. 5. The marker of claim 4, wherein the line width of the alignment marker is greater than a doubled point spread function width. The marker of claim 1, wherein the focusing marker is a rectangular focusing marker or a grid-like focusing marker. 7. The marker of claim 6, wherein the grid-like focusing marker is a horizontal grid-type focusing marker or a vertical grid-type focusing marker. The apparatus of claim 1, wherein the focusing marker includes a pair of rectangular focusing markers, a pair of horizontal grid-type focusing markers, and a pair of vertical grid-type focusing markers. . An alignment method comprising the steps of:
(1) the center of the alignment marker is located on a connecting line of any pair of focusing markers, and each group of markers includes the alignment markers and at least one pair of the focusing markers, and n groups of focusing And forming the marker with an oblique calibration design;
(2) performing an initial alignment for the markers of each group using an alignment system;
(3) The workpiece table is moved in the vertical direction at a predetermined step distance, and the optimum focal plane position of the at least one pair of focusing markers {Pi , Qi}, where Pi and Qi are the optimal focal plane positions of a pair of focusing markers in the i-th group marker, respectively, and i = 1, 2, ... , n < / RTI >
(4) The optimal focal plane position {Pi, Qi} of each pair of focusing markers and the distance Dis (Pi, Qi) in the horizontal direction corresponding to each alignment marker, Acquiring an original value Mi of the position and an original value Ti of the inclination,

,

(5) The optimum focal plane position M and the tilt T of the workpiece are determined by an average value filtering or an intermediate value filtering method by the original value Mi of the optimal focal plane position of each alignment marker and the original value Ti of the tilt Establishing;
(6) moving the workpiece table in the vertical direction by the optimal focal plane position M of the workpiece and its tilt T to compensate for the vertical position of each alignment marker. 10. The method of claim 9, wherein the focal plane determination criteria include a gradient magnitude method and a point spread function width method. 11. The method of claim 10, wherein the focusing marker is a rectangular focusing marker or a lattice-type focusing marker. 12. The method of claim 11, wherein the focal plane criterion of the grid-like focusing marker is a gradient magnitude of the marker image. 12. The method of claim 11, wherein the focal plane criterion of the rectangular focusing marker is a point spread function width of the marker. The method according to claim 9, wherein as a method of obtaining an optimum focal plane position {Pi, Qi} of at least one pair of focusing markers in each group marker,
(1) moving the workpiece table in a vertical direction at a predetermined step distance;
(2) taking an image at each vertical stepping position;
(3) extracting the focal plane determination reference value from the image;
And (4) fitting the curve to obtain the optimal focal plane position of each pair of focusing markers. 10. The method according to claim 9, wherein obtaining an optimal focal plane position {Pi, Qi} of at least one pair of focusing markers in each group marker,
(1) displaying the relationship between the focal plane determination reference value and the position of the workpiece table in the vertical direction;
(2) taking an image at the current position of the workpiece table in the vertical direction;
(3) extracting the focal plane determination reference value from the image;
(4) obtaining a distance d away from the focal plane of the workpiece table on the current workpiece table vertical position by the relationship indicated and the extracted focal plane determination reference value;
(5) The work table is moved in the vertical direction by d and -d on the basis of the current position of the workpiece table in the vertical direction, respectively, so as to acquire focal plane judgment reference values V1 and V2 respectively;
(6) comparing V1 and V2 to determine an optimal focal plane position of each pair of focusing markers.

Images