JPH047585B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary of the Invention] The present invention relates to an electron beam exposure apparatus, particularly a variable area type electron beam exposure apparatus, in which a refocus lens and a refocus coil provided for correcting a focus shift are corrected for installation errors. In order to further correct the lateral shift caused by the difference in the size of the electron beam, etc., an electron beam exposure apparatus is provided in which a different refocus flyback coefficient is given to each shot of a subfield.

[Industrial application field]

The present invention relates to an area-variable, for example, rectangular-variable electron beam exposure apparatus, and more particularly to an improvement of an electron beam exposure apparatus provided with a refocus lens.

[Conventional technology]

One method of electron beam exposure equipment is called the raster scan method, which scans the electron beam linearly at a constant speed and moves the stage in a direction perpendicular to the scanning direction to expose the pattern on the sample. has been proposed, but since it takes a long time for exposure, a variable area type electron beam exposure apparatus in which the size or shape and size of the cross section of the electron beam can be varied is often used. The principle of this configuration is as shown in FIG. The beam, which is irradiated with a mask, passes through this first passage hole, and is shaped into a rectangular shape is focused onto a second mask 9 by a second focusing lens 6 and a deflector 7. In order to deflect and focus the beam onto the second mask 9 in this manner, shot size data is given to the deflector 7 from an electronic computer. As a result, a rectangular beam of a desired size corresponding to the overlapping portion 10 of the first passage hole 3 and the second passage hole 8 is taken out from the passage hole 8 of the second mask 9, and a rectangular beam of a desired size is taken out from the passage hole 8 of the second mask 9. Sample 1 through the focusing lens 11 and deflector 12
The exposure pattern, beam 13, is projected in a reduced scale onto 4 and digitally scanned by a deflector 12 controlled by an electronic computer. In this electron beam exposure apparatus, the cross-sectional shape of the beam can be changed depending on the pattern to be exposed, and the exposure time can be greatly shortened. In this variable area type electron beam exposure device, the electron beam is exposed onto the wafer, and the third
As shown in Figure a, one chip, for example, 10 mm x 10 mm, is divided into a main field as shown by a plurality of W, X, YZ, etc., and this is further divided into subfields. That is, as shown in FIG. 3b, a rectangular electron beam is irradiated, and the cross-sectional shape of the beam is a,
The irradiation amount was changed according to changes in b, c, d, and e, or the beam irradiation amount was changed according to the length of the side of the beam cross section. As shown in Figure 4, when the shot size is varied, the shot current is plotted on the horizontal axis and the amount of blur is plotted on the vertical axis.As the variable area of the rectangular cross section increases, the amount of blur increases as shown by straight line 15. I was doing it. This is caused by the repulsion effect between electrons, resulting in an unclear pattern at the periphery of the pattern. In this way, blurring can be solved to some extent by reducing the beam current or increasing the beam acceleration voltage.

[Problem that the invention seeks to solve]

As another device for solving the blur caused by the above-mentioned variable area electron beam exposure system, the applicant previously proposed a method for correcting the focus blur by arranging a refocusing coil between the second mask and the sample. did. This configuration is constructed as shown in FIG. Now, in order to drive the rectangular pattern beam of the overlapping part 10 obtained by the second mask 9 shown in FIG. It is composed of a cass coil 19.
In addition to the refocus lens 20, a stepper coil 21, a dynamic focus coil 22, and a main deflector 2 are provided between the refocus lens 20 and the condenser lens 25.
3. A sub-deflector 24 is provided. The above refocus coil 19 carries a current of I=α+β lx・ly as shown by a, b, c, d, e... in Fig. 3b.
It was played every shot. In the above formula, α and β are constant values that are measured in advance to minimize blur, and lx and ly are the dimensions of the rectangular beam in the x and y axis directions, and lx and ly are variable for each shot. These data are given to the deflector 7 shown in FIG. 2 from an electronic computer. By arranging such a refocus coil 20, the straight line 15 shown in FIG. 4 becomes the straight line 16.
As shown in , it is possible to correct the blur to about 0.3μ with a variable area of 16μm ² (when using an electron beam of 50A/cm ² ). However, depending on the magnitude of the current flowing through the ref-focus coil 19, that is, when the rectangular area to be varied increases or decreases, due to the mechanical precision of the ref-focus coil, the difference between the center and four corners of the main field is approximately 0.2 μm at most. These misalignments that caused the differences had different drawbacks at all points within the main field.

[Means for solving problems]

The present invention has been made in view of the above drawbacks,
The purpose is to obtain an electron beam exposure apparatus that does not cause positional deviation even if the area of the variable rectangular beam changes from large area to small area for each shot in the field. In the variable rectangular electron beam exposure system, the same shot size data as that given to the refocus coil placed between the second mask having a rectangular passage hole and the main deflector is given to the sub-deflector, and the above is performed. This is accomplished by an electron beam exposure apparatus characterized in that the lateral deviation between the irradiation of a large-area rectangular beam and a small-area rectangular beam caused by installation errors of refocus coils is corrected for each subfield shot.

〔Example〕

An embodiment of the invention will be described below with reference to FIG. FIG. 1 is a system diagram showing the correction method of the present invention.

As described above, the present invention uses a sub-deflector 2 to deflect the lateral deviation that occurs within the main field.
The size data of lx and ly added to the above-mentioned ref-focus coil is added to the data added to 4. That is, in FIG. 1, 26 is a field correction memory, 27 is a pattern memory, and 28 is a field correction memory.
is an arithmetic circuit, 27X and 27Y are digital-to-analog converters for the X and Y axes, and 24X and 24Y are the fifth
This is a sub-deflector for the X and Y axes of the sub-deflector 24 shown in the figure, and main deflector data X, Y to be added to the XY axes of the main deflector 23 is taken out from the pattern memory 27 in the computer, and the sub-deflector 24X , 24Y are also stored in the pattern memory 27. Furthermore, the above-mentioned refocus coil 19
The shot size data lx, ly added to the sub-deflector data x, y and the shot size data lx, ly are given to the arithmetic circuit, and the shot size data lx, ly is A deflector 7 for deflecting the second mask in FIG. 2 is also provided. By accessing the field correction memory 26 using the memory data from the pattern memory 27 as an address set signal, the field correction memory 26 provides information on the X and Y axes for adjusting the voltage applied to the sub-deflector 23 within the main field. Constants gx and gy, constants rx and ry on the X and Y axes for adjusting the rotation angle based on the adjustment position deviation of the sub-deflector 23, and lateral deviation components caused by the above-mentioned installation error of the refocus coil 19, etc. , and the refocus coil 1
Constants hx and hy of the X and Y axes for correcting the amounts of spot size data lx and ly given to 9 are taken out and added to the arithmetic circuit 28. In the arithmetic circuit, field correction memory 26 and pattern memory 2
Based on the constants and data given in 7, the correction value of is calculated according to the following equation.

=gxX+rxY+hx・lx・ly...(1) =ryX+gyY+hy・lx・ly...(2) Obtained in this way by the arithmetic circuit 28,
The correction value is supplied to the digital-to-analog converter circuits 27X and 27Y for the
and Y-axis sub-deflectors 24X, 24Y for correction. That is, the same amount of corrected size data as added to the ref focus coil 19.
hxlxly and hylxly are sub-deflectors 24X, 24Y
is applied to correct the lateral deviation due to the mounting error of the refocus coil.

That is, the above configuration of the present invention has a memory corresponding to each position of the main field, and reading from the corresponding memory is performed every time the main field position changes depending on data applied to the main deflector. In general, the above constants gx, gy, rx,
ry, hx, and hy are written with the same value within the same subfield, but the shot size is lxly.
It is clear that the sub-deflector data and the sub-deflector data change sequentially within the sub-field.

〔Effect of the invention〕

Since the present invention is constructed as described above, the ref-focus coil not only suppresses the blur to 0.3μ or less, but also suppresses the lateral shift caused by the horizontal magnetic field caused by the eccentricity of the ref-focus coil with respect to the electron beam axis. By adding size data corresponding to the component to the sub-deflector, the electron beam is deflected back, making it possible to cancel the lateral shift that occurs when using a large-area beam and a small-area beam.

[Brief explanation of drawings]

Fig. 1 is a system diagram of the electron beam exposure apparatus of the present invention, Fig. 2 is a schematic diagram showing the optical system of a conventional variable area electron beam exposure apparatus, and Fig. 3a explains the exposure state within one chip. Chip plan view for 3rd
Figure b is a plan view showing the exposure state in the subfield of Figure 3 a, Figure 4 is a characteristic diagram showing the relationship between variable area and blur, and Figure 5 is a variable area electron beam with a conventional refocus coil. FIG. 2 is a schematic diagram showing a part of the optical system of the exposure apparatus. DESCRIPTION OF SYMBOLS 1... Beam source, 2... Electron beam, 3... First focusing lens, 4... First passing hole, 5... First mask, 6... Second focusing lens, 7, 12
...Deflector, 8...Second passage hole, 9...Second mask, 10...Overlapping portion, 11...Third
Focusing lens, 14...Sample, 17...Focusing lens, 18...Stop aperture, 19...Refocus coil, 20...Refocus lens, 2
3...Main deflector, 24...Sub deflector, 25...Focusing lens, 26...Field correction memory, 27...Pattern memory, 28...Arithmetic circuit, 27X, 27Y...Digital-analog conversion circuit.

Claims (1)

[Scope of Claims] 1. In a rectangular variable electron beam exposure apparatus, the same shot size data as the second mask having a rectangular passing hole and the refocus coil disposed between the main deflector is sub-imaged. An electron beam exposure apparatus characterized in that a deflector is provided to correct for each subfield shot a lateral shift during irradiation of a large area rectangular beam and a small area rectangular beam, which occurs due to installation errors of the refocus coil, etc. 2. The electron beam exposure apparatus according to claim 1, wherein the shot size data given to the sub-deflector is stored in a memory.