JPH0715874B2 - Electron beam writer - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electron beam drawing apparatus.

BACKGROUND OF THE INVENTION Conventionally, when a reticle pattern is projected onto a semiconductor wafer surface using a reduction exposure apparatus, the configuration shown in FIG. 4 is adopted. In the figure, there is a light source 1, and the pattern of the reticle 2 irradiated by the light source 1 is 1/5 or 1/1 on a sample 4 surface made of a semiconductor wafer through a lens 3.
It is now scaled down to 0. The sample 4 is placed on a sample table 5, and the sample table 5 can be moved in the X and Y directions by a mechanism including a drive motor 6.

On the other hand, there is a laser light source 10, and the light of this laser light source 10 is a half mirror 13, a mirror 14, and a half mirror 13 '.
The light is projected onto the light receiver 11 via the mirror, and is reflected by the half mirror 13 and, after passing through the half mirror 13 ', is reflected by the mirror 12 on the sample table 5. . The light reflected by the mirror 12 is reflected by the half mirror 13 'and then projected onto the light receiver 11. The output from the light receiver 11 is adapted to measure the position of the sample table 5 with a precision of 0.01 μm by a laser interferometer 9. Then, based on this measured value and the data from the computer 8, the sample stage control system 7
The drive motor 6 is driven to set the sample table 5 at a predetermined position.

FIG. 5 is a diagram in which the pattern of the reticle 2 is reduced and transferred onto the surface of the sample 4 in this manner. Reference numeral 15 shows a reduced pattern. This figure shows a pattern in which the same pattern of the reticle 2 is juxtaposed on one sample surface and a plurality of patterns are transferred.

However, the lens 3 for reducing and transferring the pattern of the reticle 2 has a distortion that is unique and cannot be removed, and if the reticle pattern is a perfect square, the transfer pattern is shown by the dotted line in FIG. As shown, it becomes a pincushion shape. Such a distortion is 0.1 with ^{respect to} a pattern of 10 mm ^□ even with the current technology.
Non-linear distortion of about 0.2 μm occurs.

For this reason, in the process of manufacturing a semiconductor device, when exposure is performed using several reduction projection devices in order to save the labor of reticle conversion, the distortion of the lens of each reduction projection device is different, so that the sample 4 surface is reduced. There is a problem that it is difficult to overlay the patterns.

[Object of the Invention]

An object of the present invention is to provide an electron beam drawing apparatus for forming a pattern in which the pattern is distorted by the lens when the pattern is projected through the lens.

[Outline of Invention]

In order to achieve such an object, the present invention forms a pattern on a reticle projected onto a sample surface through an optical system lens, and therefore controls an accelerating electron beam to a desired shape and current density through the electron lens. Then, in the electron beam drawing apparatus for drawing a pattern consisting of a figure on the surface of the reticle coated with the electron beam photosensitizer, the correction coefficients a to i and a'of the distortion of the optical system lens.
Storage means having stored through i ', following is a approximate expression of the distortion of the optical lens (1) and (2) using the ^{equation, Δx = ax 3 + bx 2} y + cxy 2 + dy 3 + ex 2 + fxy + gy 2 + hx + iy ...... ( 1) Δy = a′x ³ + b′x ² y + c′xy ² + d′ y ³ + e′x ² + f′xy + g′y ² + h′x + i′y (2) The position where the pattern to be drawn (x , y), equations (1) and (2) have x, y and the distortion correction coefficient a
.About.i and a'.about.i ', and deviation amounts .DELTA.x, .DELTA.y from the position (x, y) determined corresponding to the distortion of the lens are obtained, and stored in advance based on the deviation amounts. A target position (x where x and Δy are added to the position data)
+ Δx, y + Δy) setting means and drawing for drawing the pattern on the reticle by moving the sample stage holding the reticle to the target position so that distortion of the lens does not occur when passing through the optical system lens Means and are provided.

With the above configuration, that is, since the approximate expressions (1) and (2) of the distortion of the optical lens are used, the correction coefficients a to
Since only a small number of measurement points are required to define i and a ′ to i ′, and further, the measurement for the correction is not required over the entire area, the deviation of the detection position and the detection error caused by the measurement at each measurement point. Is less. Then, in order to prevent distortion of the lens when passing through the optical system lens, the amount of deviation Δx, Δy is changed to the previously stored data based on the deviation amount (x
Since the sample table holding the reticle is moved as + Δx, y + Δy) to write the pattern on the reticle, a desired pattern can be accurately written on the reticle without being affected by the distortion of the lens.

Therefore, when the pattern is reduced and transferred to the sample surface by the reticle thus formed, the distortion of the lens is canceled and corrected, and the pattern having no distortion can be transferred to the sample surface.

Example of Invention

FIG. 1 is a block diagram showing an embodiment of an electron beam drawing apparatus according to the present invention. In the figure, the electron beam 17 emitted from the electron beam 16 is made to have a desired shape and current density by a diaphragm 18 and an electron lens 19. afterwards,
The light passes through the blanker 20, the diaphragm 18 ′ and the projection lens 19 and is irradiated onto the surface of the reticle 2 via the deflector 21.

On the other hand, the drawing data for drawing the reticle 2 is stored in a magnetic disk (not shown) and is sequentially sent to the deflection control system 24 via the computer 26. From the deflection control system 24, The deflection position signal is input to the deflector 21 and the blanker control signal is input to the blanker control system 23. The output signal from the blanker control system 23 is input to the blanker 20, which turns the electron beam 17 on and off.

A secondary electron detector 22 is arranged in the vicinity of the surface of the reticle 2 which is irradiated with the electron beam 17, and a signal output by detecting a mark on the reticle 2 from this is a mark position detection circuit.
It is output to the computer 26 via 25. Further, there is a laser oscillator 31, and the light of this laser oscillator 31 is reflected by the half mirror 32, the mirror 33, and the half mirror 3.
The light is projected onto the light receiver 30 via 2 ', and is reflected by the half mirror 32, so that the half mirror 3
After passing through 2 ', it is reflected by the mirror 33 on the stage 34. Further, the light reflected by the mirror 33 is projected on the light receiver 30 after being reflected by the half mirror 32 '. The output from the light receiver 30 is adapted to measure the position of the stage 34 by a laser interferometer length meter 28. Then, based on the measured value and the data from the computer 26, the stage drive system 27 drives the drive motor 29 to set the stage 34 at a predetermined position.

In the case of such a structure, it is difficult to deflect the electron beam 17 over the entire surface of the reticle 2 in consideration of the aberration or deflection distortion associated with the deflection of the electron beam 17. For this reason, a range of several mm is covered by the deflection of the electron beam by the deflector 21, and a region beyond that is moved by moving the stage 34 and performing deflection positioning with high accuracy to perform drawing on the entire surface of the reticle 2. is there.

Next, with respect to the positioning of the deflection position, the stage 34 is accurately measured by the laser interferometer 25, and the laser beam emitted from the laser oscillator 31 is reflected by the half mirrors 32, 3.
The reference light and the measurement light are separated by 2 ', and after being reflected by the mirror 33, the light and dark of the interference wave is pulsed by the light receiver 30. By counting this pulse, it is recognized as position information by the laser interferometer length measuring device 28, and is further read by the computer 26.

Further, regarding the control of the stage 34, the target position is given to the stage drive system 27 from the laser interferometer length measuring device 28, and the motor 29 is activated. When the stage 34 reaches the target position, the laser interferometer 28 stops the stage drive system 27. At this time, the computer 26 reads the stop error from the laser interferometer 28 and sends the deflection position correction data to the deflection control system 24. By doing so, beam deflection and stage movement can be executed step-and-repeat, and a desired pattern can be drawn on the reticle 2 with high accuracy.

The secondary electron detector 22 and the mark position detection circuit 25 detect the reference mark on the reticle 2 and use it to confirm the position of the electron beam 17.

Further, as shown in FIG. 2, the pattern drawn on the reticle 2 is drawn within the solid line 35a, but in the present embodiment, it is set as the pattern drawn within the dotted line 35b in the drawing. The pattern drawn in the dotted line 35b is set in consideration of the distortion in the lens of the reduction exposure device when the reduction transfer is performed on the sample of the semiconductor wafer using the reduction exposure device. When projected on the reticle 2, the pattern within the dotted line 35b on the reticle 2 is reduced by forming a straight line on the outer peripheral portion thereof. Therefore, when the reticle 2 is reduced to 1/5 to 1/10, the distortion amount is 0.1 to
Since it is 0.2 μm, the reticle 2 may be formed by correcting the distortion of 1 μm to 2 μm. In FIG. 2, the size of the pattern 35a of the reticle 2 is about 100 mm □, and the number of fields per side for executing drawing is determined by stepping the entire 100 mm by 3 mm □ along the broken line 35b and arranging the drawing fields. It is about 30, and the field connection is 0.07 μm even if the displacement at both ends is 2 μm.
Next, this is not a problem.

A method of correcting the position of the stage 34, that is, the array position of the field 36 will be described. Generally, the distortion of an optical lens can be expressed by a cubic expression.

^{ΔX = ax 3 + bx 2 y} + cxy 2 + dy 3 + ex 2 + fxy + gy 2 + hx + iy ...... (1) ΔY = a'x 3 + b'x 2 y + c'xy 2 + d'y 3 + e'x 2 + f'xy + g'y 2 + h ′ X + i′y (2) In the above equations (1) and (2), x and y are target positions, and ΔX and Δ
Y is the amount of deviation from the target position at that position. In this case, the coefficients a to i and a'to i'are the values obtained for each lens.

As for the means for drawing, as shown in FIG.
At 1, the correction coefficient is read from the external memory depending on the lens type. Next, in step 302, x and y are substituted into the above equations (1) and (2) from the drawing position (x, y) to obtain Δx and Δy. Further, the target position (x + Δx, y + Δy) is set in step 303, and the sample stage is moved in step 304 accordingly. Next, in step 305, the stop error is corrected and in step 3
Drawing is performed at 06, and the process returns to step 302 again to perform drawing, and when this drawing is completed over all fields, the process ends.

In this way, when projecting the pattern through the lens, the distortion caused by the lens is recognized in advance,
Since the pattern is formed while correcting the distortion, it is possible to form a normal pattern without the distortion of the pattern caused by the lens.

〔The invention's effect〕

According to the present invention, since the approximate equations (1) and (2) of the distortion of the optical lens are used, the correction coefficients a to i and a ′ thereof are previously set.
The number of measurement points required to determine .about.i 'is small, and the measurement for the correction is not required over the entire area, so that the detection position shift and the detection error caused by the measurement at each measurement point are small. . Then, based on the correction coefficients a to i and a'to i'of the distortion of the optical system lens,
The pattern is drawn on the reticle by changing the pre-stored data so that distortion of the lens does not occur when passing through the optical system lens, so that it is accurately affected without being affected by the distortion of the lens. A desired pattern can be drawn on the reticle.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an electron beam drawing apparatus according to the present invention, FIG. 2 is a view for explaining a method for forming a reticle by the electron beam drawing apparatus according to the present invention, and FIG. 3 is an electron according to the present invention. FIG. 4 is a diagram showing an operation flow of the line drawing apparatus, FIG. 4 is a diagram showing an example of a reduction exposure apparatus when exposing the reticle onto a semiconductor wafer, and FIG. 5 is a reduction exposure shown in FIG. FIG. 6 is an explanatory diagram for explaining a drawback of the above. 1 ... Light source, 2 ... Reticle, 3 ... Reduction lens, 4 ... Sample,
5,34 ... Stage, 6,29 ... Motor, 7,27 ... Stage control system, 8,26 ... Computer, 9,28 ... Laser measuring system, 10,31
… Laser light source, 11,30… Light receiver, 12, 14, 33… Mirror, 13,
32 ... Half mirror, 15 ... Reduction pattern, 16 ... Electron gun, 17
... Electron beam, 18 ... Aperture, 19 ... Electromagnetic lens, 20 ... Blanker, 21 ... Deflector, 22 ... Secondary electron detector, 23 ... Blanker control system, 24 ... Deflection control system, 25 ... Mark detector, 35 ... Reticle pattern, 36 ... Drawing field.

Claims (1)

[Claims] 1. In order to form a pattern on a reticle projected onto a sample surface through an optical system lens, an accelerating electron beam is controlled to a desired shape and current density through an electron lens, and an electron beam sensitizer is applied. In an electron beam drawing apparatus for drawing a pattern consisting of a figure based on data stored in advance on the surface of the reticle, correction coefficients a to i and a'to i'of distortion of the optical system lens are provided.
Using the storage means for storing the above and the following equations (1) and (2) which are approximate expressions of the distortion of the optical lens, Δx = ax ³ + bx ² y + cxy ² + dy ³ + ex ² + fxy + gy ² + hx + iy (1) Δy = A'x ³ + b'x ² y + c'xy ² + d'y ³ + e'x ² + f'xy + g'y ² + h'x + i'y (2) The position (x, y) of the pattern to be drawn For equations (1) and (2), x, y and the distortion correction coefficient a
.About.i and a'.about.i ', and displacement amounts .DELTA.x, .DELTA.y from the position (x, y) determined corresponding to the distortion of the lens are obtained, and stored in advance based on the displacement amounts. A means for setting a target position (x + Δx, y + Δy) obtained by adding the displacement amounts Δx, Δy to the position data, and a sample table for holding the reticle so as not to cause distortion of the lens when passing through the optical system lens An electron beam drawing apparatus comprising: a drawing unit that moves to the target position and draws the pattern on a reticle.