JPH07105324B2 - Position correction method for laser mirror - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention corrects a measurement error based on a displacement generated when a high-precision moving stage (table) such as an electron beam drawing apparatus, a stepper, or a precision measuring machine is moved. Regarding the method.

[Prior art]

Conventionally, the high-precision moving stage device used in the above-mentioned electron beam drawing device, stepper, precision measuring instrument, etc., mounts and fixes an object to be processed, and moves in the X, Y, Z, θ axis direction (X, Y).
There is also only one in the axial direction) to accurately position. As shown in FIGS. 6 and 7, the structure of the moving stage device section for moving / positioning in the X / Y axis direction is shown in FIG. 6 and FIG.
An X stage 3 that is linearly reciprocally movable in the X axis direction is provided through the Y axis, and a Y that is reciprocally movable in the Y axis direction orthogonal to the X axis direction is provided on the X stage 3 via a guideway 4. A stage 5 is provided, and a workpiece fixing tool 6 such as a holder is provided on the upper surface of the Y stage 5. Then, with the object to be processed (not shown) placed and set on the fixture 6, the X stage 3 and the Y stage 5 are respectively guided by guide means 2, 4 by driving means (not shown).
By moving in a predetermined direction along the fixing tool 6
The object to be treated set in can be moved in both X-Y axis directions.

A laser mirror 7 having a plane L shape for position measurement in the X and Y axis directions is attached to the upper surface of the upper Y stage 5, and this laser mirror 7 and a laser interferometer (not shown) separately fixed to a surface plate or the like. The movement distance in the X and Y axis directions is calculated based on the amount of change in the laser value between and, and the position is measured by this to accurately grasp the position of the object to be processed.
The movement control of the stage 3 and the Y stage 5 is performed.

[Problems to be solved by the invention]

By the way, in such a conventional apparatus, as described above, the laser fixture 7 for position measurement is directly attached to the upper surface of the Y stage 5 together with the workpiece fixture 6, and the distance between the workpiece fixture 6 and the laser mirror 7 is increased. Does not change, the position is measured by calculating the moving distance from the amount of change in the laser value between the laser mirror 7 and a separately fixed laser interferometer. However, if the Y stage 5 is deformed into a convex shape or conversely a concave shape as shown in FIG. 8 when the Y stage 5 is moved, the distance between the workpiece fixture 6 and the laser mirror 7 is changed. However, the position measurement value has an error correspondingly, which causes a decrease in accuracy, which is not preferable as a highly accurate moving stage device.

That is, when moving the workpiece fixture 6 in the X and Y axis directions, the processing accuracy of the guideways 2, 4 of each stage, the processing accuracy of the guideway mounting surface of each stage 3, 5, and the stage movement. Due to a change in weight balance due to the above, a change in preload or the like occurs, and a deformation such as a distortion occurs in the Y stage 5. As a result, a tension or compression phenomenon occurs in the attachment surface (upper surface) of the workpiece fixture 6 and the laser mirror 7 of the Y stage 5, and expansion and contraction occur, so that the workpiece fixture 6 and the laser mirror 7 have a space between them. The distance fluctuates and causes an error in the position measurement value. Particularly in an electron beam drawing apparatus, the stage is usually made of a non-magnetic material and is therefore made of a material having low rigidity such as aluminum, so that it is likely to be deformed during movement.

Furthermore, the flatness of the laser mirror is extremely important,
The flatness is λ / 20 to λ / 10 (λ is the wavelength of the laser light,
-He is about 0.6 μm), but when the upper surface of the Y stage 5 to which the laser mirror is attached expands and contracts, the laser mirror is distorted and the flatness deteriorates, causing a measurement error. Becomes

These measurement errors are caused by, for example, in the electron beam drawing apparatus, when the line width of the pattern is in the region of 1 micron to submicron, the measurement accuracy of the absolute position of the stage (when the specific point is 0) is measured. Is required to be about 0.03 μm or less, which is no longer negligible in such a high-precision moving stage apparatus.

[Object of the Invention]

According to the present invention, fluctuations caused by the stage movement, which cannot be avoided even if the structure or machining accuracy is best, are actually measured and stored, and are input to the displacement amount input device to correct the displacement amount. It is an object of the present invention to provide a laser mirror position displacement correction method capable of highly accurately performing processing such as drawing, exposure, or precise measurement.

[Means for solving problems]

In order to achieve the above object, the present invention provides a relative relationship between a laser mirror generated at each point in the X and Y directions along with movement of a stage of a drawing device, a stepper, or a measuring machine, and an object to be processed or its fixture. The displacement amount is measured and stored in advance, and the relative displacement amount is corrected by the scanning position correction, the stage position correction, or the pattern correction of the processing device to process the object to be processed.

[Action]

According to the correction method described above, the table that can be moved through the guideway causes the upper surface of the stage to deform and expand due to an error in the processing accuracy of the guideway, the mounting surface, etc., and the relative distance between the laser mirror and the fixture to be processed. Even if a displacement occurs, it becomes possible to greatly improve the processing accuracy of the object to be processed by performing the processing operation in which the displacement is corrected.

〔Example〕

Hereinafter, an embodiment showing the details of the present invention will be described with reference to FIGS.
It will be described with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of an electron beam drawing apparatus and a control block. This apparatus is a so-called raster scan type electron beam drawing apparatus that scans an electron beam in a direction orthogonal to the stage while continuously moving the stage in one direction. A stage 12 having a workpiece 11 such as a mask mounted and mounted on a workpiece fixture is housed in the sample chamber 10.
The laser mirror 7 is attached to the upper surface of the laser. Sample chamber 10
An electron optical lens barrel 13 including an electron gun 14, a blanking deflector 15, a scanning deflector 16, various lenses, an aperture mask, and the like is provided above. Stage 12 is
In response to a command from the CPU 30, the stage drive circuit 36 causes the X direction (left and right of the paper) and the Y direction (front and back of the paper).
And the moving position of the stage 12 is measured by the laser measuring system 35. On the other hand, a blanking signal is applied to the blanking deflector 15 from the drawing control circuit 33 according to the pattern to be drawn, and a scanning signal is applied to the scanning deflector 16 by the scanning position control circuit 34. It has become a thing. Scan position correction circuit 37 or stage position correction circuit for correcting the amount of relative displacement between the laser mirror and the workpiece fixture generated by stage travel
Reference numeral 38 denotes a laser beam displacement measurement based on stage distortion 31 previously performed by a displacement measurement method or the like which will be described later, and inputs / stores the data in a displacement amount input 32, receives a necessary correction amount through the CPU 30, and scan position control circuit 34 Alternatively, the correction operation is instructed to the stage drive circuit 36.

FIG. 2 is a diagram showing a schematic configuration and its control block showing a case of a pattern dimension measuring and defect detecting apparatus. An object to be processed 11 such as a mask and a reticle is attached to an object to be processed fixture and placed on the stage 12, and a CPU 40 instructs a stage drive circuit 42 to move in the X direction (left and right direction on the paper) and Y.
Direction (front and back of the page). The moving position of the stage 12 is measured by a laser measuring system 41. A light beam is projected from a light source 20 for measurement or defect detection onto the pattern of the object to be processed 11, and the transmitted pattern is received by the line sensor 21 under the stage 12 as pattern information 44. The pattern information 44 is input in the displacement amount by performing “laser mirror displacement measurement by stage distortion” 31 in advance in the correction pattern circuit 45 by a displacement measurement method described later.
A correction pattern (element size, pitch size, total size, pattern orthogonality, etc.) that is corrected by the displacement data that has been input / stored in 32 and the displacement amount due to the travel of the stage 12 is obtained, and is sent to the pattern information comparison circuit 43. Sent. The position of the stage 12 is confirmed by the laser measuring system 41.
Next, the pattern information comparison circuit 43 receives the CAD data of the pattern design of the object to be processed 11 from the CPU 40, and corrects the pattern circuit.
Compensate the stage distortion sent from the 45 and compare and calculate it with the correction pattern, and output the result of the dimension measurement of the workpiece 11 and the presence / absence of the defect (content of defect, type, number, size, shape, etc.). Output to the device 46.

Further, FIG. 3 is a diagram showing a schematic configuration and a control block in the case of an exposure apparatus such as a stepper. The workpiece 11 such as a wafer is set on the workpiece fixture and placed on the stage 12,
In response to a command from U50, the stage drive circuit 52 moves in the X direction (left and right direction of the paper) and the Y direction (front and back direction of the paper). The moving position of the stage 12 is measured by a laser measuring system 52. The light irradiated on the reticle 26 by the exposure illumination system 25 is projected onto the object 11 to be processed such as a wafer through the reduction lens 27, and the pattern is transferred. Stage position correction circuit 53
Is "laser mirror displacement measurement due to stage distortion" 31 in advance by the displacement measurement method described later, and the displacement amount data is input / stored in the displacement amount input 32. A correction command is given to the stage drive circuit 52 via 53.

Next, an example of a displacement measuring method of the laser mirror position displacement by the traveling of the stage 12 will be described with reference to FIG. As shown in the figure, the non-contact sensor (eddy current type) 54 is attached to the workpiece fixture 6.
Displacement (measurement) of each point while moving the stage 12 in the X direction and the Y direction with a gap between the laser measuring surface and the laser measuring position on the laser mirror surface via the fixed base 55 and the arm 56 fixed on the upper side. Error). FIG. 5 is an example of a calculation of the displacement due to the stage traveling thus measured as a measurement error of the length measuring system at that position, and the pattern area (measurement area) 120 m in the X and Y directions.
Black dots on the grid coordinates of the displacement amount (measurement error amount, hereinafter referred to as the displacement amount) at each position when the stage travels m × 120 mm at a pitch of 20 mm. It is shown in. It is assumed that there is linear variation between each measurement. In this figure, when the Y stage 5 is moved from the M3 point toward the A point (without moving the X stage), the measuring system passes through the displacement curve Y1 to reach M4, and the X stage 3 (Y stage is moved). It shows that when moving from M3 to M2 (without moving 5), it reaches M2 through the displacement curve X1, and the amount of deviation of X1 and Y1 with respect to the grid coordinate axis is the laser mirror due to distortion during stage travel. And the amount of displacement of the workpiece fixture 6. As for the displacement amount curves X1, X2 ..., Y1, Y2 ..., the correction calculation becomes complicated in the actual processing work, so a method of simplifying this can be considered. That is, for example, the displacement amount curve of Y1 is simplified to a straight line Y1A (corrected coordinate axis) connecting the start point (M3) and the end point (M4) to the straight line or curve Y1B determined by the least squares method. Can be a displacement curve. In particular, for a workpiece having a mark position, the mark position (M1 to M4) is actually measured, and the displacement amount curve X1 in the X direction including the mark position and the displacement amount curve Y1 relative to the starting point of the displacement amount curve are set. A straight line or curve Y1B, X1B defined by the least-squares method of X1, Y1 with respect to the corrected coordinate axes Y1A, X1A connecting the end points.
The mark position M3 is shifted to the intersection point M3 ′ of (in the same manner for other mark positions), and the coordinate system inside the pattern is converted into a straight line or a curve determined by the least squares method by the above-mentioned method, and processed on the object to be processed. It was decided to apply.

〔The invention's effect〕

The accuracy of processing the object is improved by correcting the error of the length measurement system due to the stage traveling in the processing work such as pattern drawing, exposure, dimension measurement, or defect detection by placing it on the stage. To do.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is a diagram showing a schematic configuration and a control block in an electron beam drawing apparatus, and FIG. 2 is a schematic configuration and a control block in a dimension measuring / defect detecting apparatus. FIG. 3, FIG. 3 is a diagram showing a schematic configuration and a control block in an exposure apparatus such as steps, FIG. 4 is a diagram showing an embodiment of a displacement amount measuring method, and FIG. FIG. 6 is a diagram showing an example of calculation as a measurement error of the length measuring system in FIG. 6, FIGS. 6 and 7 are diagrams showing a conventional stage, and FIG. 8 is a model diagram of stage displacement. 3 ... X stage, 5 ... Y stage, 6 ... Processing object fixture, 7 ... Laser mirror, 11 ... Processing object, 12 ... Stage, 13 ... Electron optical lens barrel, 14 ... Electron gun, 15 ... Blanking deflector, 16 ... Scanning deflector, 20 ... Light source, 21 ... Line sensor, 25 ... Exposure illumination system, 26 ... Reticle, 27 ... Reduction lens, 30 , 40,50 …… CPU, 32 …… displacement input, 33 …… drawing control circuit, 34 …… scanning control circuit, 35,41,51 …… laser measurement system, 36,42,52 …… stage drive Circuit, 37 ... Scan position correction circuit, 38, 53 ... Stage position correction circuit, 43 ... Pattern information comparison circuit, 44 ... Pattern information, 45 ... Correction pattern circuit, 46 ... Output device, Y1, Y2 ...... Y direction displacement curve, 54 …… Non-contact sensor, 55 …… Fixed stand, 56 …… Arm, X1, X2 …… X direction displacement curve, Y1B, Y2B …… Y direction displacement curve is minimum Straight line or curve determined by the square method, X1B, X2B ... Straight line or curve determined by the least squares method of the displacement curve in the X direction, M1 to M4 ... Mark position (measurement), M1 'to M4' ... Mark position (Modify)

Claims (3)

[Claims] 1. A stage equipped with a stage movable in at least one axis direction and a position measuring laser mirror attached to the stage, and the object placed on the stage while measuring the position using the laser mirror. When processing the processed product,
The position displacement of the laser mirror to be processed caused by stage movement is measured and stored in advance, and the position correction data obtained by this is used to perform processing on the object while performing position correction corresponding to stage movement. A method for correcting a displacement of a laser mirror, which is characterized in that 2. A stage movable in XY directions, and a position measuring laser mirror attached to the stage, wherein a plurality of mark positions on an object to be processed placed on the stage are set by the laser mirror. When performing processing on the object to be processed while concurrently measuring, the positional displacement between the laser mirror and the object to be processed which is generated by the stage movement is measured and stored in advance,
Thus, the mark displacement is shifted (corrected) in the direction in which the displacement is corrected, and the object to be processed is processed. 3. A mark position shift (correction) is performed with respect to a corrected coordinate axis connecting a start point and an end point of a displacement curve including a mark position in a measurement region when the stage is moved in one direction in each of X and Y. 3. The position displacement correction method for a laser mirror according to claim 2, wherein the displacement curve is based on a coordinate system converted into a straight line or a curve defined by the least squares method.