JPH10161296A - Coordinate distorting correction method for laser reticle plotting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coordinate distortion correction method capable of obtaining a reticle without causing any distortion. SOLUTION: A positioned grid pattern is plotted on the reticle 11, and by measuring the coordinate of the plotted grid pattern by a size measuring device, a difference between with an ideal grid pattern is found, and coordinate distortion in an XY stage 10 is found. This coordinate distortion is stored beforehand in a correction table 31 as the specific coordinate distortion of its laser reticle plotting device. When a real pattern is plotted on the reticle 11, by plotting correcting a control amount based on the correction table 31 based on an XY instructed position of its pattern plotting, the rear pattern is plotted as the required pattern in real time. That is, even when the specific coordinate distortion exists on the XY stage 10, the high quality reticle without distortion is obtained without exchanging for another XY stage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting coordinate distortion in a laser reticle drawing apparatus.

[0002]

2. Description of the Related Art Semiconductor devices include individual components such as transistors and diodes, LSIs (large-scale integrated circuits),
There is an integrated circuit such as an LSI (ultra large scale integrated circuit). LS
In the manufacture of I and VLSI, a photolithography technique for exposing a semiconductor wafer by bringing a photomask into close contact with the semiconductor wafer is used. Lithography is a process of forming a resist film of a circuit pattern on the surface of a semiconductor wafer.
Lithography using ultraviolet light of 50 to 450 nm as an exposure medium is photolithography.

[0003] The photolithography technology can be classified into drawing exposure for manufacturing a photomask or a semiconductor wafer and transfer exposure for forming a mask pattern on a semiconductor wafer. Optical pattern generators (laser reticle writing equipment) that have been used in mask manufacturing technology are being replaced by electron beam writing equipment.
In the transfer process, photolithography, which is excellent in mass productivity, is the main technology.

In manufacturing a photomask required for photolithography, a reticle, which is an enlarged mask that is 4, 5 or 10 times the size of the photomask, is used, and a chromium layer, a resist layer, and the like are previously formed on a glass or quartz plate. It is formed by reducing exposure to a plate. The reticle also has a chromium layer, a resist layer, and the like formed on a glass or quartz plate like the photosensitive plate, so that a desired pattern is exposed or etched.

FIG. 6 is a conceptual diagram of a conventional laser reticle drawing apparatus.

[0006] The laser reticle drawing apparatus includes a laser light source 1.
The XY stage 3 is moved at a low speed in the X direction while the polygon mirror 2 scans the laser beam at a high speed in the Y direction. AO at the timing corresponding to the target pattern shape
The laser beam of the M (acousto-optical element) 4 is turned on and off by the ON / OFF signal. The laser beam scanned by the polygon mirror 2 is reduced by a reduction lens 5 such as an f-θ lens, and is drawn by forming a dot on the reticle 6 mounted on the XY stage 3 with a beam scanning width. It has become.

[0007]

The above-described conventional laser reticle drawing apparatuses are all mechanical distortions due to temperature change, humidity change, wear, etc., particularly the flatness, yaw, pitch and roll of the bar mirror of the XY stage. And so on. These distortions appear as they are in the drawing result as systematic errors inherent to the apparatus.

In order to reduce these errors, measures have been taken to improve the precision of machining, maintain a constant operating environment such as temperature and humidity, and periodically replace parts.

However, as the degree of integration of integrated circuits increases,
High positional accuracy is required, and the demand for distortion errors is inevitably increased. For example, when the distortion error is about 1 ppm (for example, an error of 0.15 μm with respect to a 150 mm square), it is a limit of hardware construction technology, and it is difficult to suppress distortion inherent to systematic devices. there were.

It is an object of the present invention to solve the above-mentioned problems and to provide a coordinate distortion correction method for a laser reticle drawing apparatus capable of obtaining a reticle without distortion.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a laser reticle drawing apparatus for drawing a desired pattern on a reticle mounted on an XY stage by using a laser beam. In the method of correcting distortion, a grid pattern whose position is determined in advance in the XY directions is drawn on a reticle by a laser reticle device, and the coordinate distortion of the drawn grid pattern is measured by a dimension measuring device. The coordinate distortion with respect to the grid pattern is stored in the correction table as coordinate distortion unique to the laser reticle drawing apparatus. When an actual pattern is drawn on the reticle, a control amount based on the XY command position of the pattern drawing is based on the correction table. The correction is performed for drawing.

In addition to the above configuration, the present invention assumes that an ideal grid set at equal pitches in the X and Y directions is drawn on a reticle having the largest drawing size, and the grid pattern is drawn. In addition, the amount of distortion at the position of each XY intersection of the measured grid pattern may be stored in the XY coordinate table, and the position between each XY intersection may be interpolated to form a correction table.

In addition to the above configuration, the present invention provides an
A correction table is stored in advance in a control computer for controlling the drawing position in the direction, and an XY position signal of the XY stage is input to the control computer, and a pattern to be drawn on the reticle is input to the control computer. The XY drawing position of the X deflection unit and the Y deflection unit may be corrected with reference to the correction table for the XY command position of the pattern.

According to the present invention, a grid pattern having a fixed position is drawn on a reticle, and the coordinates of the drawn grid pattern are measured by a dimension measuring device.
The difference from the coordinates of the ideal grid pattern is known, and the coordinate distortion of the XY stage is known. This coordinate distortion is stored in the correction table as coordinate distortion inherent to the laser reticle drawing apparatus. When an actual pattern is drawn on the reticle, the control amount is corrected based on the correction table based on the XY command position of the pattern drawing based on the correction table and drawn, so that the desired pattern can be drawn in real time. . That is, even if there is inherent coordinate distortion in the XY stage, a high-quality reticle without distortion can be obtained without replacing it with another XY stage.

The reticle having the largest drawing size has XY
The grid pattern is drawn assuming an ideal grid set at the same pitch in the direction. After the grid pattern is actually drawn with respect to the ideal grid, the amount of distortion at the position of each XY intersection of the measured grid pattern is represented by XY. By storing the coordinates in the coordinate table and interpolating the positions between the respective XY intersections to form a correction table, a pattern without distortion can be drawn on the reticle in real time.

A correction table is stored in advance in a control computer for controlling the drawing position of the laser beam in the XY directions, and the control computer receives the XY position signal of the XY stage and the pattern to be drawn on the reticle. XY of pattern corresponding to XY position of stage
By correcting the XY drawing positions of the X deflection unit and the Y deflection unit with reference to the correction table for the command position, a pattern without distortion can be drawn on the reticle in real time.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of a laser reticle drawing apparatus to which the coordinate distortion correcting method of the laser reticle drawing apparatus of the present invention is applied.

On the XY stage 10 shown in FIG. 1, an X servo motor system 12 for moving a reticle 11 mounted on a moving table 10a of the XY stage 10 in the X direction, and a reticle 11 in the Y direction. Servo motor system 13 is connected to each other.

The X servo motor system 12 includes an XY stage 1
Servo motor 1 for moving the moving table 0 in the X direction
4, a converter 15 for converting the rotation speed of the servomotor 14 into an electric signal, an amplifier 16 for amplifying the electric signal from the converter 15, a subtractor 17 connected to an output terminal of the amplifier 16, and an input terminal. Are connected to a subtractor 17 and an amplifier 18 is connected at the output end to the servomotor 14 to form a control loop that keeps the rotation speed of the servomotor 14 constant. The X servo motor system 12 is connected to a CPU 21 via an adder 19 and a D / A converter 20.

Like the X servo motor system 12, the Y servo motor system 13 includes a servo motor 22 for moving the movable stage of the XY stage 10 in the Y direction, and a servo motor 2
2, a converter 23 for converting the rotation speed into an electric signal, an amplifier 24 for amplifying the electric signal from the converter 23, a subtractor 25 connected to the output terminal of the amplifier 24, and an input terminal for the subtracter 25. The output terminal is connected to an amplifier 26 connected to the servomotor 22 to form a control loop that keeps the rotation speed of the servomotor 22 constant. The Y servo motor system 13 is connected to the CPU 21 via an adder 27 and a D / A converter 28.

On the XY stage 10, an X interferometer 57 and a Y interferometer 58 of the LMS 29 for measuring the position of the reticle 11 are provided.
Are connected, and a signal representing the position (coordinates) of the reticle 11 of the XY stage 10 is input to the CPU 21 via the pulse conversion circuits 59 and 60.

The CPU 21 has a correction table 31 and XY
X deflecting means 32 for correcting coordinates of the reticle 11 mounted on the stage 10 in the X direction, and an XY stage 1
The Y deflecting means 33 for correcting the reticle 11 mounted on the reticle 11 in the Y direction is connected.

The X deflecting means 32 is means for correcting a control amount based on the X command position of the pattern drawing based on the data stored in the correction table 31 before drawing the actual pattern on the reticle 11. And a deflecting mirror (see FIG. 2) 34 is used.

The Y deflecting means 33 is means for correcting a control amount based on the Y command position of the pattern drawing based on data stored in the correction table 31 before drawing an actual pattern on the reticle 11. A PMT (photoelectric tube) 36 for receiving light reflected from the polygon mirror 35 (see FIG. 2);
A D / A converter 39, which receives a signal from the CPU 21 and a Y correction value from the CPU 21, uses a delay timing generation circuit 37 for generating a switch trigger signal, and an AOM 38 for making a laser beam (not shown) into a pulse shape. Is connected to the CPU 21 via the.

Next, the relationship between the XY stage and the optical path of the laser reticle drawing apparatus will be described with reference to FIG. FIG. 2 is a block diagram for explaining the relationship between the XY stage and the optical path of the laser reticle drawing apparatus shown in FIG.

The laser reticle drawing apparatus is composed of a laser irradiation system, an XY stage system, and a control system in terms of hardware.

The laser irradiation system includes a pulse light source 40 and an optical path system 41. The pulse light source 40 includes a drawing light source laser 42, an AOM 38 for making the laser light La from the drawing light source laser 42 into a pulse, and a lens 43 for condensing the pulsed laser light Lp. . The AOM 38 has a function like a shutter that opens and closes the optical path of the laser light La by an ON / OFF signal sent from the data output timing control unit 45 of the control computer 44 via the AOM driver 46.

The optical path system 41 includes an X deflecting unit 32 using a deflecting mirror 34 disposed on the emission side of the pulse light source 40;
It comprises a polygon mirror 35 and a Y deflecting means 33 using an AOM 38.

The X deflecting means 32 uses the angle control voltage from the deflecting mirror control unit 47 of the control computer 44 to control the angle α.
Is changing. PMT3 of Y deflection means 33
6 detects the rotation cycle of the polygon mirror by detecting a part of the laser beam Lp reflected by the polygon mirror 35, and the polygon driver 48 controls the rotation cycle of the polygon mirror 35 to be constant by the electric signal from the PMT 36. In addition to the control, a polygon rotation timing signal is output to the data output timing control unit 45.

The XY stage system includes an XY stage 10 and
An X servo motor 49 for moving the moving table 10a of the XY stage 10 in the X direction, a Y servo motor 50 for moving the moving table 10a in the Y direction, an X motor driver 51 for driving the X servo motor 49, and a Y servo motor It is composed of a Y motor driver 52 for driving the moving table 50 and an LMS 29 for detecting the position of the moving table 10a.

The LMS 29 includes a laser light interferometer light source 53,
A half mirror 54 that splits the laser light Lb from the laser light interferometer light source 53 in two directions, XY, an X bar mirror 55 disposed along the X direction of the moving table 10a,
a laser beam Lb transmitted in the X direction by the Y bar mirror 56 and the half mirror 54 arranged along the Y direction of FIG.
X interferometer 57 for receiving reflected light obtained by irradiating X on X bar mirror 55, and receiving reflected light obtained by irradiating Y bar mirror 56 with laser light Lby reflected by Y mirror by half mirror 54 And a pulse conversion circuit 30 that converts signals from the X interferometer 57 and the Y interferometer 58 into pulse signals.

The pulse conversion circuit 30 includes an amplifier 59 for amplifying a signal from the X interferometer 57, an amplifier 60 for amplifying a signal from the Y interferometer 58, an X position counter 61,
And a position counter 62. X position counter 61
And the Y-position counter 62 is the moving table 1 from the LMS 29.
The signal representing the position of 0a is converted into a pulse and output to the X motor driver 51 and the Y motor driver 52.

The control computer 44 as a control system includes:
It comprises a data output timing control section 45, a deflection mirror control section 47, a CPU 21, an X motor driver 51, a Y motor driver 52, an operation control system bus 63, and a correction table 31 (see FIG. 1). I have.

Next, the XY correction of the laser reticle drawing apparatus will be described.

FIG. 3 is a block diagram for explaining the XY correction of the laser reticle drawing apparatus shown in FIG.

The control computer 44, the data output timing control unit 45, the X position counter 61, the Y position counter 62, and the deflection mirror control module 64 input and output data via the operation control system bus 63. It should be noted that the data output timing controller 45 shown in FIG. 3 does not include the polygon driver 48 shown in FIG.

When a signal representing the X command position is input to the control computer 44, the value obtained by subtracting the X counter value from the X command position is set as an error value (X POS ERROR), and the X correction table data from the correction table 31 is used. The value to which the error value is added is set as an X correction value, which is output to the deflection mirror control module 64 via the operation control system bus 63.

When the Y command position is input to the control computer 44, a value obtained by subtracting the Y counter value from the Y command position is set as an error value (Y POS ERROR), and the correction table 3
A value obtained by adding an error value to the Y correction table data from 1 is set as a Y correction value and output to the data output timing control unit 45 via the operation control system bus 63.

The deflection mirror control module 64 converts the X correction value from the control computer 44 into a D / A signal.
An A converter 65, an amplifier 66 for amplifying an output signal of the D / A converter 65, an adder 67 connected to an output terminal of the amplifier 66, and an amplifier 68 having an input terminal connected to the adder 67
And an amplifier 69 whose output terminal is connected to the adder 67.

Amplifier 6 of deflection mirror control module 64
The output terminal 8 is connected to the piezoelectric element 70. A deflecting mirror 34 that is rotatable about an axis 71 perpendicular to the plane of the drawing is attached to the expansion / contraction portion of the piezoelectric element 70, and the deflecting mirror 34 is expanded and contracted in accordance with the voltage of the deflecting mirror. Can be changed. The angle α of the deflecting mirror 34 is determined by a gap sensor (a sensor that detects an eddy current and a change in capacitance) 72.
, And the detected value is input to the amplifier 69. That is, the piezoelectric element 70, the gap sensor 7
2. A local loop is formed by the adder 67 and the amplifiers 68 and 69. Reference numeral 73 denotes a spring for holding the deflection mirror 34 at a neutral position.

The data output timing controller 45 controls the AOM 38 for driving the AOM 38 based on a pattern data sequence signal (a data sequence signal of a pattern to be drawn on a reticle).
An OM switching data output circuit 74 and a PMT 36 for receiving the laser beam Lp reflected by the polygon mirror 35
75 for amplifying the polygon facet signal from
A delay timing generating circuit 37 for generating a switching trigger signal in accordance with the polygon facet signal from the amplifier 75 and the Y correction value from the control computer 44, and a clock circuit 76 for supplying a clock signal to the delay timing generating circuit 37. It is configured. AOM driver 4
AOM38 is ON / O by ON / OFF signal from 6
FF operation is performed. That is, the delay timing generation circuit 3
7, AOM switching data output circuit 74, AOM driver 46, AOM 38, polygon mirror 35, PMT
36 and an amplifier 75 form a kind of control loop.

Next, a coordinate distortion correcting method of the laser reticle drawing apparatus shown in FIG. 1 will be described with reference to FIGS. FIG. 4A shows a pattern representing an ideal grid to be drawn on the reticle, FIG. 4B shows a cross pattern drawn on the reticle, and FIG. 4C shows a grid pattern actually drawn on the reticle. FIG. 9 is an explanatory diagram for explaining coordinate distortion. FIG. 5 is a partially enlarged view of FIG.

1) Preparation of Correction Table A reticle 11 is placed on the movable base 10a of the XY stage 10, and a reticle grid pattern of the maximum size that can be drawn by the laser reticle drawing apparatus (for example, an ideal grid pattern at 15 mm intervals, FIG. 4) (A)) Assuming a cross pattern at each intersection (for example, 4 μm in width, 20 μm in each of vertical and horizontal directions)
To draw. Since the beam diameter of the laser beam is only about 0.5 μm, for example, the deflecting mirror 3 of the X deflecting means 32
ON / O of AOM 38 of angle α and Y correction means 33 of No. 4
It is formed by scanning in both X and Y directions by slightly changing the interval between FF signals.

When a cross pattern is actually drawn on the reticle 11 at each intersection, the cross pattern is formed on an intersection of a distorted grid pattern shown by a solid line, for example, with respect to an ideal grid pattern shown by a broken line due to distortion inherent to the apparatus. (FIG. 4
(C)).

Next, the position of each cross pattern of the grid pattern that is actually drawn and measured is measured by a dimension measuring device (not shown), and the obtained distortion amount at each intersection is divided into both X and Y directions and tabulated.

In the example shown in FIG. 4A, since the grid pattern is a 9 × 9 grid, the number of intersections is 81 in total. As a result, 81 coordinate distortion data strings are obtained for each of X and Y. In the coordinate table composed of these data strings, X and Y do not necessarily have to be the same number (square), but an arbitrary grid form (m rows, m rows, etc.) according to the operation range of the XY stage 10 of the laser reticle drawing apparatus.
n columns).

The coordinates of each intersection in the coordinate table are further mathematically interpolated to create a coordinate distortion correction map having a pitch of, for example, 2 mm. The finer coordinate distortion correction table of the i-th row and the j-th column thus created is referred to as a correction table 31.

The correction table 31 obtained as described above
Is stored in the laser reticle drawing apparatus as a device parameter file of the laser reticle drawing apparatus, and is developed and used on a memory at the time of drawing.

2) Real-time correction using a correction table The laser reticle drawing apparatus described here uses laser light as a light source, and the laser light is
The XY stage 10 scans in the X direction while scanning on the Y stage 10 in the Y direction.

When the laser beam passes through the AOM 38 in the middle of the optical path, it is turned on / off by a signal applied to the AOM 38.
The laser beam is turned into a pulsed laser beam.

The scanning by the polygon mirror 35,
Scanning of XY stage 10 and ON / OFF of AOM 38
Of the XY stage 10 by controlling the timing of
A point (substantially circular) of the laser beam can be hit at an arbitrary position on the reticle 11 placed thereon. By performing such an operation over the entire surface of the reticle 11, a pattern is drawn by overlapping points.

The position of the XY stage 10 is LM in each axis direction.
By S29, it can be obtained with high accuracy.

The laser reticle drawing apparatus shown in FIG.
The following method is used to correct the difference between the XY stage position by the LMS 29 and the XY stage position obtained by the laser reticle drawing apparatus (hereinafter, referred to as “position error”).

First, in order to correct a position error in the X direction, a deflection mirror 34 arranged in the laser beam path is used. The deflection mirror 34 is driven by a signal obtained by D / A converting a position error. The light is deflected by the piezoelectric element 70.
This is performed by delicately deflecting the angle α of the deflecting mirror 34 by the method described above.

The position error in the Y direction is performed by adjusting the ON / OFF timing of the AOM 38.
If the ON / OFF timing of the AOM 38 is delayed, since the rotation of the polygon mirror 35 is advanced by that amount,
A light spot is hit at a position further advanced in the Y direction. FIG.
In the figure, the light spot is indicated by a black circle, but represents the above-mentioned cross pattern.

Here, for example, in FIG. 5, the coordinate position of the intersection point Qm, n of the ideal grid is (xmq, ynq),
If the coordinate position of the light point (black circle) Pm, n drawn on the reticle 11 is the (xmp, ynp) point, the amount of coordinate distortion is ΔXm, n, ΔYm, n.
Has coordinates (xmp, ynp) of light point P = (xmq−ΔX)
m, n, ynq-ΔYm, n). Hereinafter, the amount of coordinate distortion between the coordinate position of the intersection point of another ideal grid and the coordinate position of another light point is stored in the correction table.

When an actual pattern is drawn on the reticle 11, a new reticle is placed on the moving table 1 of the XY stage 10.
After being placed at 0a, a pattern without coordinate distortion can be drawn by drawing the control amount based on the XY command position of the pattern drawing with the data corrected based on the correction table 31.

In other words, the position of point R (referred to as a command position)
If a light spot is formed, the light spot is formed at the position of the point S if no correction is made. However, based on the data corrected at the time of forming the light point, a is set in the X direction and b is set in the Y direction. The position of the light spot is R (correction position) because the light spot is formed at the position of the control amount moved by the distance. In the following, a light spot is formed at a corrected position each time a light spot is formed, so that an accurate pattern without distortion is drawn on the reticle.

[0060]

In summary, according to the present invention, the following excellent effects are exhibited.

When an actual pattern is drawn on a reticle, the control amount based on the XY command position of the pattern drawing is corrected based on a correction table and drawn, so that a laser reticle drawing apparatus capable of obtaining a reticle without distortion can be obtained. Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a laser reticle drawing apparatus to which a coordinate distortion correction method for a laser reticle drawing apparatus according to the present invention is applied.

FIG. 2 is a block diagram for explaining a relationship between an XY stage and an optical path of the laser reticle drawing apparatus shown in FIG.

FIG. 3 is a block diagram for explaining XY correction of the laser reticle drawing apparatus shown in FIG.

4A is a pattern showing an ideal grid to be drawn on a reticle, FIG. 4B is a cross pattern drawn on a reticle, and FIG. 4C is a coordinate distortion of a grid pattern actually drawn on the reticle. FIG. 3 is an explanatory diagram for explaining the method.

FIG. 5 is a partially enlarged view of FIG. 4 (c).

FIG. 6 is a conceptual diagram of a conventional laser reticle drawing apparatus.

[Explanation of symbols]

 Reference Signs List 10 XY stage 11 Reticle 21 CPU 31 Correction table 32 X deflecting means 33 Y deflecting means

Claims (3)

[Claims] 1. A method for correcting a coordinate distortion in an XY direction of a laser reticle drawing apparatus that draws a desired pattern on a reticle mounted on an XY stage by using a laser beam. A basic pattern with a fixed position is drawn on a reticle, the coordinate distortion of the drawn basic pattern is measured by a dimension measuring device, and the coordinate distortion for an ideal basic pattern is determined from the measured values as a coordinate distortion inherent to a laser reticle drawing device. When storing in the correction table and drawing the actual pattern on the reticle,
A coordinate distortion correction method for a laser reticle drawing apparatus, wherein a control amount based on an XY command position of the pattern drawing is corrected based on the correction table to perform drawing. 2. A reticle having a maximum drawing size, assuming an ideal basic pattern set at an equal pitch in the X and Y directions, and drawing the basic pattern. The basic pattern is actually drawn with respect to the ideal basic pattern. 2. The coordinate distortion of the laser reticle drawing apparatus according to claim 1, wherein the measured amount of distortion at the position of each XY intersection of the basic pattern is stored in an XY coordinate table, and the position between each XY intersection is interpolated as a correction table. Correction method. 3. A control computer for controlling a drawing position of the laser beam in the XY directions is stored in advance, and an XY position signal of the XY stage and a pattern to be drawn on the reticle are input to the control computer. The XY command position of the pattern corresponding to the XY position of the XY stage is determined with reference to the correction table by using X deflection means and Y
3. The method according to claim 2, wherein the XY drawing position of the deflection unit is corrected.