CN109541898B - Method for calibrating positioning error of planar grating ruler - Google Patents
Method for calibrating positioning error of planar grating ruler Download PDFInfo
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- CN109541898B CN109541898B CN201710861965.3A CN201710861965A CN109541898B CN 109541898 B CN109541898 B CN 109541898B CN 201710861965 A CN201710861965 A CN 201710861965A CN 109541898 B CN109541898 B CN 109541898B
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F9/00—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically
- G03F9/70—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically for microlithography
- G03F9/7003—Alignment type or strategy, e.g. leveling, global alignment
- G03F9/7019—Calibration
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F9/00—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically
- G03F9/70—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically for microlithography
- G03F9/7073—Alignment marks and their environment
- G03F9/7076—Mark details, e.g. phase grating mark, temporary mark
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- General Physics & Mathematics (AREA)
- Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
- Length Measuring Devices By Optical Means (AREA)
Abstract
The invention relates to a method for calibrating the positioning error of a planar grating ruler, which comprises the following steps: s1: the workpiece table is not provided with a rotation inclination posture, and a large frame mark without rotation inclination on the mask is adopted to expose a first layer of overlay mark; s2: setting a certain rotary inclined posture on the workpiece table, and exposing a second layer of overlay marks by using small frame marks on the mask, wherein the small frame marks are consistent with the rotary inclined posture of the workpiece table; s3: measuring an overlay error between two layers of overlay marks; s4: and fitting an interferometer model according to the translation error of the two layers of overlay marks to compensate the influence of the rotation inclination on the translation error. The invention can eliminate the influence of system measurement errors on the calibration precision in the existing error calibration method, thereby improving the calibration precision.
Description
Technical Field
The invention relates to the field of photoetching equipment, in particular to a method for calibrating positioning errors of a planar grating ruler.
Background
In the current lithography equipment, mainly include the illumination system for exposure, objective lens group, support all movement and frame of the measuring mechanism, bear the weight of the work piece platform of the silicon chip, bear the weight of the mask platform of the mask, level to the position measuring transducer, vertical position measuring transducer divide system, silicon chip, mask transmission divide system, etc., wherein the most core positioning mechanism work piece platform divides the system, usually adopt the high-accuracy sensor as the positioning control sensor, and because the mechanical installation of the sensor can't have the error, the installation error can lead to the work piece platform six degrees of freedom not decoupling while moving. Chinese patent application No. CN200910047581.3 (published as 2009, 8/19) describes a method for abbe cosine error calibration of a workpiece stage controlled by an interferometer, which specifically includes: due to mechanical installation errors, installation errors exist in the grating ruler grids, and further translation errors in the direction X, Y are brought when the workpiece table is set to rotate Rz, incline Rx and Ry when the workpiece table actually moves. To correct these errors, the following method is used: first, exposing a first layer of overlay mark; then setting a plurality of rotary inclined postures on the workpiece table, and exposing a second layer of overlay marks; measuring the overlay error between the two layers of overlay marks; and finally, fitting an interferometer model according to the translation error of the two layers of overlay marks, and compensating the influence of the rotation inclination on the translation error. However, when the second layer of overlay mark is exposed, the workpiece table has a certain rotation inclined posture, especially a rotation posture, which has a large influence on the horizontal overlay error, and after the workpiece table is set to rotate when the second layer of overlay mark is exposed, the error can be directly fitted into the interferometer measurement model of the workpiece table, and the part of error cannot be calibrated by adopting the method, and the influence of the system measurement error in the method on the calibration precision cannot be eliminated.
Disclosure of Invention
The invention provides a method for calibrating a positioning error of a planar grating ruler, which aims to solve the technical problem.
In order to solve the technical problem, the invention provides a method for calibrating the positioning error of a planar grating ruler, which comprises the following steps:
s1: the workpiece table is not provided with a rotation inclination posture, and a large frame mark without rotation inclination on the mask is adopted to expose a first layer of overlay mark;
s2: setting a certain rotary inclined posture on the workpiece table, and exposing a second layer of overlay marks by using small frame marks on the mask, wherein the small frame marks are consistent with the rotary inclined posture of the workpiece table;
s3: measuring an overlay error between two layers of overlay marks;
s4: and fitting an interferometer model according to the translation error of the two layers of overlay marks to compensate the influence of the rotation inclination on the translation error.
Preferably, one large frame mark corresponds to one small frame mark, and a group of special marks is formed, and the center of the small frame mark in each group of special marks is offset in the Y-axis direction only relative to the center of the large frame mark.
Preferably, the center of the small box mark is offset (0mm, 2.56mm) with respect to the center of the large box mark.
Preferably, at least 7 groups of the special marks are arranged on each mask, and in each group of the special marks, the small frame marks are rotated by an angle deltaRzAre respectively set as RC_Range，
Wherein R isC_RangeIs the rotation stroke of the workpiece table.
Preferably, the distance between each group of the special marks in the X direction is at least 15 mm.
Compared with the prior art, the method for calibrating the positioning error of the planar grating ruler provided by the invention has the following advantages:
1. the invention can eliminate the influence of system measurement errors on the calibration precision in the existing error calibration method, thereby improving the calibration precision;
2. the method can be applied to a workpiece table positioning control system with higher precision, such as a workpiece table subsystem controlled by a planar grating ruler;
3. the invention can also be applied to integrated photoetching, the rubber coated silicon wafer is exposed, the rubber coated silicon wafer is read in an alignment machine after being developed, and the read data is returned to the photoetching machine for modeling calculation and then is used for compensating or monitoring the performance of the photoetching machine.
Drawings
FIG. 1 is a schematic diagram of a basic structure of a motion mechanism of a system of a lithographic apparatus;
FIG. 2 is a schematic view of a planar grating ruler of a workpiece stage;
FIGS. 3a and 3b are schematic views of an ideal grid of the workpiece table;
FIGS. 4a and 4b are schematic views of an actual grid of the workpiece table;
FIGS. 5a and 5b are schematic diagrams of overlay error calculation methods, respectively;
FIGS. 6a and 6b are schematic diagrams of test errors;
FIG. 7 is a schematic diagram of an overlay mark in the calibration method for positioning error of a planar grating ruler according to the present invention;
fig. 8a and 8b are schematic diagrams respectively illustrating that the method for calibrating the positioning error of the planar grating scale provided by the present invention is applied to alignment errors in other forms.
In the figure: 10-mask stage, 11-mask, 20-exposure objective lens group, 30-workpiece stage, 31-silicon chip, 41-displacement sensor, 42-material measurement sensor, 50-main frame and 60-plane grating ruler.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. It is to be noted that the drawings are in simplified form and are not to precise scale, which is provided for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
The lithography equipment system with the structure shown in fig. 1 mainly comprises a mask stage 10 for bearing a mask 11, an exposure objective lens group 20, a workpiece stage 30 for bearing a silicon wafer 31, a sensor subsystem (comprising a displacement sensor 41 and a material measurement sensor 42) for measuring the vertical surface shape and the horizontal position of the silicon wafer 31, and a main frame 50 for supporting all movement and measurement mechanisms, wherein the workpiece stage 30 and the mask stage 10 are both movement mechanisms controlled by a plane grating ruler 60.
The positioning subsystem structure of the workpiece platform plane grating ruler is shown in fig. 2, corresponds to one workpiece platform 30, and has four plane grating rulers 60 corresponding to displacement sensors 41 arranged at four corners of the workpiece platform 30, and measures and controls six-degree-of-freedom motion of the workpiece platform 30. For the stage 30, the grid of the planar grating scale 60 determines the movement grid of the stage 30. An ideal horizontal grating ruler grid is shown in fig. 3a and 3b, a zero coordinate system of the workpiece table 30 determined by the planar grating ruler 60 coincides with a position six-degree-of-freedom with a workpiece table coordinate system of 0, the workpiece table 30 rotates along an origin and tilts around a zero plane, and actually, due to a mechanical installation error, the grating ruler grid has an installation error, which is shown in fig. 4a and 4b, so that when the workpiece table 30 actually moves, X, Y horizontal translation errors are brought when the workpiece table 30 is set to rotate Rz, tilt Rx and Ry.
To correct these errors, the existing methods are:
1. the workpiece stage 30, without the rotational tilt attitude, exposes the first layer of overlay marks;
2. the workpiece stage 30 sets some rotation inclination postures to expose the second layer overlay mark;
3. measuring overlay error between the two layers of marks;
4. and fitting an interferometer model according to the translation error of the two layers of overlay marks, and compensating the influence of the rotation inclination on the translation error.
In step 3 of the method, when measuring the overlay error, the overlay error is read by using an overlay machine, the overlay error read by the overlay machine is dx and dy, as shown in fig. 5a, the calculation method is as follows:
dx＝(dx2-dx1)/2
dy＝(dy2-dy1) /2 (formula 1)
Wherein: dx (x)1、dx2、dy1、dy2Meaning is shown with reference to fig. 5 b;
for image-matched overlay machines, dx1、dx2、dy1、dy2In the measuring method, a small segment is respectively intercepted from four edges of an overlay mark to be used as a matching template, as shown in fig. 6a, the position matched with the corresponding template is used as a measuring point to measure an overlay error, in step 2, when the second layer of overlay mark is exposed, the workpiece table 30 has a certain rotation inclined posture, especially a rotation posture, and has a large influence on a horizontal overlay error, as shown in fig. 6b for example, after the workpiece table 30 is set to rotate during the exposure of the second layer of mark, dx and dy are increased, the error can be directly fitted into a measurement model of the interferometer of the workpiece table, the current existing practice data of the error is proved to be about 2.5nm, and the experimental method and the data are proved as follows:
1. exposing 11 fields on a 12-inch silicon wafer 31, wherein each field is exposed with 9 groups of different rotation inclination marks;
2. when the exposure of the second layer is selected, the workpiece stage 30 rotates to set the overlay marks formed when-200 urad, 0urad, 200 urad;
3. the overlay measurements of these three markers in each of the 11 fields were averaged as follows:
| Mark | Rz[urad] | dx[nm] | dy[nm] |
| 1 | -200 | 142.04 | -35.40 |
| 2 | 0 | 77.96 | -6.05 |
| 3 | 200 | 8.82 | 28.26 |
4. and (3) fitting and calculating the rotation center deviation, wherein x is-333 um, y is 159.2um, and removing the influence of the rotation center deviation on the alignment error in the alignment results of-200 urad and 200urad, wherein the converted alignment error result is as follows:
5. calculating the deviation between the translation deviation of the workpiece table 30 after the rotation center is removed from the rotation attitude exposure result and the translation deviation of the attitude-free exposure, wherein the absolute value of the x and y errors is about 2.5nm, and the errors brought to the measurement by the rotation of the overlay mark are as follows:
| deviation value from zero degree | -2.54nm | 2.48nm |
The experimental data shows that for an interferometer (positioning accuracy is 3nm) positioning system, the error is about 2-5nm and can be ignored, but for the planar grating ruler 60 (positioning accuracy is 0.5nm), the error needs to be eliminated, so the invention provides a method for calibrating the positioning error of the planar grating ruler, which comprises the following steps: taking Box in Box overlay as an example,
s1: the workpiece stage 30 is not provided with a rotation inclination posture, and a large frame mark without rotation inclination on the mask 11 is adopted to expose a first layer of overlay mark;
s2: setting a certain rotary inclined posture on the workpiece table 30, and exposing a second layer of overlay marks by using small frame marks on the mask 11, wherein the small frame marks are consistent with the rotary inclined posture of the workpiece table 30;
s3: measuring an overlay error between two layers of overlay marks;
s4: and fitting an interferometer model according to the translation error of the two layers of overlay marks to compensate the influence of the rotation inclination on the translation error.
Thus, when the positioning error of the workpiece table 30 is calibrated, the mask mark of the corresponding angle is selected for exposure when the workpiece table 30 is exposed at the set angle, so that the second layer of overlay mark does not rotate relative to the first layer of overlay mark, namely, the exposure mark is as shown in fig. 6a no matter the workpiece table 30 has a posture or no posture, and thus, when the overlay error is measured, no matter how the edge templates are matched, the measurement error caused by fig. 6b does not occur.
Preferably, referring to fig. 7 with emphasis, one large frame mark corresponds to one small frame mark, and a group of special marks is formed, and the center of the small frame mark in each group of special marks is offset from the center of the large frame mark only in the Y-axis direction, specifically, the center of the small frame mark is offset from the center of the large frame mark (0mm, 2.56 mm).
Preferably, at least 7 sets of the special marks are arranged on each of the masks 11, and in each set of the special marks, the small boxes are marked by rotation angles δRzAre respectively set as RC_Range，
Wherein R isC_RangeIs the rotational stroke of the workpiece table 30; the distance between each group of the special marks in the X direction is at least 15 mm.
Referring to fig. 7, the normal Box in Box overlay mark includes a first layer Box and a second layer Box which are square and do not have any posture, and the embodiment designs that two groups of marks are arranged at a certain distance in the positive and negative directions of the X direction, wherein each group of second layer Box (small Box mark) is designed to rotate positively and negatively by a certain angle δRzHere, it is necessary to ensure that the rotation posture set by the stage 30 is consistent with the rotation posture designated by the mark design in the exposure step of the calibration process, so as to ensure that there is no rotation between overlay marks exposed when the posture of the stage 30 is set for exposure.
Of course, the method for calibrating the positioning error of the planar grating ruler is not limited to Box-in-Box, and is also suitable for Bar-in-Bar and Frame-in-Frame marks, as shown in FIGS. 8a and 8 b.
In summary, the method for calibrating the positioning error of the planar grating ruler provided by the invention comprises the following steps: s1: the workpiece table is not provided with a rotation inclination posture, and a large frame mark without rotation inclination on the mask 11 is adopted to expose a first layer of overlay mark; s2: setting a certain rotary inclined posture on the workpiece table 30, and exposing a second layer of overlay marks by using small frame marks on the mask 11, wherein the small frame marks are consistent with the rotary inclined posture of the workpiece table 30; s3: measuring an overlay error between two layers of overlay marks; s4: and fitting an interferometer model according to the translation error of the two layers of overlay marks to compensate the influence of the rotation inclination on the translation error. The invention can eliminate the influence of system measurement errors on the calibration precision in the existing error calibration method, thereby improving the calibration precision.
It will be apparent to those skilled in the art that various changes and modifications may be made in the invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (5)
1. A method for calibrating the positioning error of a planar grating ruler is characterized by comprising the following steps:
s1: the workpiece table is not provided with a rotation inclination posture, and a large frame mark without rotation inclination on the mask is adopted to expose a first layer of overlay mark;
s2: setting a certain rotary inclined posture on the workpiece table, and exposing a second layer of overlay marks by using small frame marks on the mask, wherein the small frame marks are consistent with the rotary inclined posture of the workpiece table;
s3: measuring an overlay error between two layers of overlay marks;
s4: and fitting an interferometer model according to the translation error of the two layers of overlay marks to compensate the influence of the rotation inclination on the translation error.
2. The method according to claim 1, wherein a large frame mark corresponds to a small frame mark to form a group of special marks, and the center of the small frame mark in each group of special marks is shifted from the center of the large frame mark only in the Y-axis direction.
3. The method according to claim 2, wherein the offset of the center of the small frame mark relative to the center of the large frame mark is 0mm in the X-axis direction and 2.56mm in the Y-axis direction.
4. The method according to claim 2, wherein at least 7 sets of the special marks are provided on each of the masks, and each set is provided with at least 7 sets of the special marksAmong the special marks, the small frame marks the rotation angle deltaRzAre respectively set as RC_Range，
Wherein R isC_RangeIs the rotation stroke of the workpiece table.
5. The method according to claim 2, wherein the distance between each set of the special marks in the X direction is at least 15 mm.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6122036A (en) * | 1993-10-21 | 2000-09-19 | Nikon Corporation | Projection exposure apparatus and method |
| CN1945484A (en) * | 2005-09-13 | 2007-04-11 | 住友重机械工业株式会社 | Optical head action control device and method and carrying table device |
| CN101286013A (en) * | 2007-03-27 | 2008-10-15 | Asml荷兰有限公司 | Method of forming a substrate for use in calibrating a metrology tool, calibration substrate and metrology tool calibration method |
| CN102540783A (en) * | 2010-12-31 | 2012-07-04 | 上海微电子装备有限公司 | Automatic calibration device and method for abbe cosine error of interferometer |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7268360B2 (en) * | 2001-09-20 | 2007-09-11 | Litel Instruments | Method and apparatus for self-referenced dynamic step and scan intra-field scanning distortion |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6122036A (en) * | 1993-10-21 | 2000-09-19 | Nikon Corporation | Projection exposure apparatus and method |
| CN1945484A (en) * | 2005-09-13 | 2007-04-11 | 住友重机械工业株式会社 | Optical head action control device and method and carrying table device |
| CN101286013A (en) * | 2007-03-27 | 2008-10-15 | Asml荷兰有限公司 | Method of forming a substrate for use in calibrating a metrology tool, calibration substrate and metrology tool calibration method |
| CN102540783A (en) * | 2010-12-31 | 2012-07-04 | 上海微电子装备有限公司 | Automatic calibration device and method for abbe cosine error of interferometer |
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