JPS62114221A - Charged beam lithography - Google Patents

Abstract

PURPOSE:To sufficiently apply charged beam lithography even if the area of a repetition pattern is large by providing an aperture for forming a repetition pattern and an aperture for varying a beam size in a mask, and selecting one of the apertures in response to the repetition pattern or a nonrepetition pattern, thereby improving a drawing throughput. CONSTITUTION:Apertures 21a, 21b of the first aperture mask 21 are rectangular so that the aperture 21b is smaller than the aperture 21a. An aperture 22a of the second aperture mask 22 is corresponds to a repetition pattern of a memory cell to be exposed. When the pattern of the memory cell to be exposed is, for example, the repetition of a shaped portion, the aperture 22a corresponds to both hatched portions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a charged beam lithography method, and particularly to a charged beam lithography method that achieves high throughput by selecting a plurality of apertures.

[Technical background of the invention and its problems]

Various electron beam lithography systems are used to form fine patterns on samples such as semiconductor wafers and mask substrates, but in recent years so-called variable-dimension beam lithography systems have been developed that change the beam size in order to improve the lithography speed. Electron beam lithography equipment has been developed. However, even with this type of apparatus, the throughput is extremely low when drawing ultra-high density patterns such as those for semiconductor memory devices.

Therefore, recently, an electron beam drawing apparatus called a character projection method has been developed. In this apparatus, a plurality of apertures with different patterns are formed in an aperture mask, and drawing is performed by selecting an aperture according to the figure to be drawn. Furthermore, it is possible to improve the writing throughput by several times compared to the variable size beam method.

However, this type of device has the following problems. That is, since many patterns are included in the same mask, it is necessary to largely deflect the beam when selecting a pattern, and depending on the pattern selection, the writing accuracy may be reduced. Furthermore, even if many patterns are inserted at the same time, there is a limit to the patterns that can be drawn, making it unsuitable for drawing LSIs and lacking in practicality.

In addition, since a character mask (a mask with multiple patterns of 7 perchas formed) is provided inside the lens,
When replacing the character mask, it was necessary to break the vacuum of the electron beam optical column and disassemble the lens, which required a large amount of space between surfaces.

Note that the above problem is not limited to electron beam lithography apparatuses, but also applies to ion beam lithography apparatuses that draw patterns on a sample using ion beams.

(Object of the Invention) The present invention has been made in consideration of the above circumstances, and its purpose is to be able to solve the problems of the conventional character projection method, and to solve the problems of the conventional character projection method. The object of the present invention is to provide a charged beam lithography method that can improve the lithography throughput and can be sufficiently applied even when the area of a repetitive pattern is large.

(Summary of the Invention) The gist of the present invention is to provide a mask with an aperture for forming a repetitive pattern and an aperture for varying beam dimensions, and to select one of the apertures depending on whether the pattern is a repetitive pattern or a non-repetitive pattern. . Furthermore, the beam current density is changed between when writing a repetitive pattern and when writing a non-repetitive pattern to prevent exposure blur caused by space charge effects.

Among VLSI devices, 90 [
% or more is a repeating pattern, and the remaining 10[%]
The peripheral circuit is made of a pattern different from that of the memory cell. Therefore, the memory cell portion is written using the character projection method, that is, the character mode, and the remaining portion is written using the variable dimension beam in the VSB mode. As a result, repetitive patterns can be drawn in a short time by selecting the pattern forming aperture.
Furthermore, as for non-repetitive patterns, by selecting a variable beam shaping aperture, it is possible to draw any desired pattern in the same manner as in the conventional variable beam method. moreover,
If a preliminary chamber for changing the character projection mask is provided on the side of the charged beam optical column,
It becomes possible to exchange masks in a short time.

In addition, when using a variable dimension beam, the beam area is 2[
μm] to 0.1 [μ77L], whereas in character projection, the beam area may exceed 5 [μ77L] depending on the size of the repeated pattern. Therefore, when the character mode is set, there is a risk that the focal condition of the lens will be significantly distorted due to the space charge effect, leading to a decrease in drawing accuracy. Therefore, by changing the excitation Iaffi flow of the lens in order to change the beam current density between the VSB mode and the character mode, it is possible to reduce the influence of space charges. However, changing this lens condition requires resetting the charged beam optical column, and if the resetting is performed many times, this time alone becomes long. Therefore, if you draw the entire repeating pattern or non-repetitive pattern and then draw the other pattern, you only need to switch the lens conditions once, and the drop in drawing speed due to this will be almost negligible. S? ! 4 I can do it.

The present invention focuses on such points, and focuses and deflects a charged beam emitted from a charged beam radiation source, and selectively irradiates the beam onto a sample to be exposed to produce a charged beam that draws a desired pattern on the sample. In the beam writing method, a pattern forming aperture corresponding to a repeating pattern, a variable beam forming aperture for forming a variable dimension beam,
An aperture selection deflection system is provided on the anti-recording charged beam radiation S side of these apertures and deflects the charged beam so that the charged beam is irradiated onto one of the apertures, and the repetitive pattern is formed on the pattern forming side. The non-repetitive pattern is drawn with a beam passing through the aperture, and the non-repetitive pattern is drawn with a beam passing through the beam shaping aperture, and after one of the repeating pattern and the non-repetitive pattern is completely drawn, the other pattern is drawn. This is the method.

〔Effect of the invention〕

According to the present invention, by selecting a pattern forming aperture for a repetitive pattern portion, it is possible to draw the pattern at a high throughput. Roughly speaking, any non-repetitive pattern can be drawn by selecting a variable beam shaping aperture. Therefore, patterns for LSI and the like can be easily drawn, and the overall drawing throughput can be improved.

Moreover, since switching between drawing of repetitive patterns and non-repetitive patterns is completed in one time, the F required for this switching is
RliI is so short that it can be ignored compared to the entire drawing time. Furthermore, by changing the excitation current of the lens system between the VSB mode and the character mode, beam blur due to the space charge effect can be minimized in each mode. Therefore, it is possible to draw both repetitive patterns and non-repetitive patterns with the same level of precision.

FIG. 2 is a schematic diagram showing an example of a memory cell pattern.

As is clear from this figure, even if a right triangle can be drawn with a variable dimension beam, it is necessary to perform at least 11 shots when the variable dimension beam is used. On the other hand, according to the present invention, since the memory cell portion can be written in one shot, writing can be completed in about 1/10 of the time, and non-repetitive patterns of peripheral circuits can also be written using a variable-dimension beam. u! If you use the i function, you can draw at a certain speed. Therefore, the overall writing time is 0.9 (memory cell part) + 0.1 (peripheral circuit) in the conventional simple variable dimension beam, whereas in the present invention the writing time is 0.09 (memory cell part) + 0.1 (peripheral circuit). 1 (peripheral circuit), the present invention/simple variable dimension beam #0.2, and the throughput is improved by about 5 times. Also, 20
Even when the pattern is a repeating unit, the space charge effect can be reduced by reducing the beam current density to about 1/2, and even if the actual exposure time is doubled, the memory cell area can be drawn in 1/10 of the time. In the end, the drawing time can be reduced to 115 minutes.

[Embodiments of the invention]

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic configuration diagram showing an electron beam lithography apparatus used in an embodiment of the method of the present invention. In the figure, 10 is a vacuum envelope constituting an electron optical lens barrel, and 11 is an electron gun housed within this envelope 10.

The electron beams emitted from the electron gun 11 are
Lens 12. ~, 16 and irradiates onto a target 17. Note that the semiconductor wafer or the like serving as the target 17 is generally placed on a sample stage that is movable in the X direction and the Y direction.

An aperture 2 is provided between the second and third lenses 13.14.
A seventh aperture mask 21 with 1a, 21b is arranged. Between the third and fourth lenses 14.15 is an aperture 22a.

A second aperture mask 22 with 22b is arranged. Here, each aperture 21a, 21b of the first aperture mask 21 has a rectangular shape, and the aperture 21b is smaller than the aperture 218. Furthermore, the apertures 22a of the second aperture mask 22 correspond to a repeating pattern of memory cells, etc. to be exposed. For example, if the pattern of the memory cell to be exposed is a repeated hatched area as shown in FIG. 2, the aperture 22a corresponds to both hatched areas in FIG. That is, the aperture 22a is a pattern forming aperture, and is formed in the second aperture mask 22 as shown in FIG. Further, the aperture 22k) of the second aperture mask 22 is for forming a variable-dimensional beam, and is formed in a rectangular shape on the same mask 22 as the pattern forming aperture t'22a, as shown in FIG. . Note that the second aperture mask 22 is arranged outside the lens 14, 15, etc., rather than inside it.

A deflection coil 23 is arranged at the beam crossover position between the first and second lenses 12.13, and the lens 13.1
A deflection coil 24 is arranged at the beam crossover position between the four beams. These deflection coils are an aperture selection deflection system that selects either the aperture 22a or 22b.

By deflecting the beam with the deflection coils 23 and 24, the optical overlap between the apertures 21a and 21b and the apertures t22a and 22b is varied as described later, and a beam having a predetermined shape made of this overlap portion is directed onto the target 17. It is assumed that the image is formed in

Note that the deflection coils 23 and 24 are controlled in conjunction with the objective lens 16 through the CPtJ 51 and the interface 52. That is, when the character mode is set, the beam area becomes large and underfocus occurs, so the focus condition is corrected by increasing the objective lens current.

Conversely, when changing to the VSB mode, the beam area is small and overfocus occurs, so correction is made by reducing the objective lens current.

Between the fourth and fifth lenses 15 and 16, a deflection plate 25 and a Y
A deflection plate 26 is arranged to deflect the light in the direction (left and right direction in the drawing). The beam having the predetermined shape is scanned over the target 17 by these deflection plates 25 and 26. Further, a mask preliminary chamber 28 is connected to the side wall of the envelope 10 at the location where the second aperture mask 22 is disposed via a gate valve 27 .

Preliminary+! A mask exchange mechanism 29 is provided inside the enclosure 10 , and by opening the gate valve 27 , the envelope 10 is replaced.
The mask 22 is exchanged between the mask spare room 28 and the mask spare room 28.

In the figure, reference numeral 31 denotes a beam size variable deflection plate for changing the optical overlapping area with, for example, the apertures 21a and 22b to change the size of the beam when forming the variable size beam. Also, 32, ~. 34 is a backscattered electron detector for monitoring whether the beam is normal or not; 35 is an astigmatism correction coil for correcting beam astigmatism and increasing beam resolution; 41. ~． Reference numeral 46 designates alignment coils for aligning the axes of the beams so that the beams pass through regular trajectories.

Here, the selection of the apertures 22a and 22b is performed as follows. That is, when exposing a repetitive pattern such as a memory cell, the shape of the aperture 21a is aligned with the pattern forming aperture 228 as shown by the solid line in FIG.
irradiate. In this case, a memory cell pattern, which is a pattern of apertures 22a, is exposed on the target 17. On the other hand, when exposing the peripheral circuit, the beam is deflected by the deflection coil 24 as shown by the broken line in the figure. In this case, the image of the aperture 21a will be irradiated onto the variable beam shaping aperture 22b. Therefore,
A variable dimension beam will be irradiated onto the target 17. Note that since the center of deflection by the deflection coil 24 is located at the crossover position of the beam, even if the beam is deflected by the deflection coil 24, the beam position will not shift on the target 17.

Furthermore, it is also possible to use the deflection coil 23 instead of the deflection coil 24 described above. That is, when exposing the peripheral area, as shown in FIG. 5, the beam is deflected by the Tachibana-oriented coil 23 as shown by the broken line in the figure, so that the image of the aperture 21b is irradiated onto the aperture 22b. As a result, the variable dimension beam is irradiated onto the target 17.In this case, since the aperture 21b is small when forming the variable dimension beam, it is possible to reduce the amount of beam cut by the aperture 22b. .

Next, a drawing method using the above device will be explained.

FIG. 6 is a schematic diagram for explaining the chip 62 of the semiconductor wafer 61 and the drawing procedure, and FIG. 7 is a schematic diagram showing an enlarged portion A surrounded by a broken line in FIG. First, as shown in FIG. 7, a mark 63 previously formed on a chip 62 of a wafer 61 is detected, the position is aligned, and drawing is started.

The wafer 61 is divided into narrow regions of 0, 5 to 2 [s+] indicated by 64, and these narrow regions are separated by continuously moving the sample stage.
65 is the moving direction of the sample stage during drawing. Further, in the figure, symbols ``■'' to ``■'' and ``■'' to ``■'' respectively indicate the movement order of the sample stage. The LSI chip is divided into a memory cell section 66 and a peripheral circuit section 67 or dicing lines 68 shown by diagonal lines.

First, while moving the sample stage in the order of ■ to ■, the peripheral circuit section 67 and the dicing line 68 are
Draw all. That is, the variable beam shaping aperture 22b is selected by the deflection coil 24, and the deflection plate 3
1, drawing is performed by controlling the optical shape of the apertures 21a and 22b. This drawing is continued until all non-repeating patterns on one wafer are completed.

Next, reduce the beam current density and move the sample stage to
While moving in the order of ', the entire memory cell section 66 is drawn using a beam based on the character projection method. That is, a pattern forming aperture 22a is selected by the deflection coil 24, and one memory cell portion 66 is exposed at once with a beam corresponding to the pattern of this aperture 22a. This drawing is also continued until all repeated patterns on one wafer are completed.

When the drawing of one wafer is completed, the next wafer is drawn. At this time, the electron optical lens barrel is in character mode, so in this case, after drawing the memory cell part 66, the peripheral circuit part 67 is drawn. Then, dicing lines 68 are drawn.

In addition, in character mode, drawing time is long, so
In order to compensate for the deviation caused by continuously moving the sample stage, the beam is made to track the movement of the sample stage. Furthermore, when there are multiple types of memory cell patterns, multiple masks 22 having respective patterns and rectangular patterns may be prepared and the masks may be exchanged between the envelope 11 and the mask spare seedling 28. In this case, the mask 22 can be replaced simply by opening the gate valve 27, so there is no need to break the vacuum in the envelope 10 (and there is no need to disassemble lenses etc.).
It can be easily implemented.

Thus, according to this embodiment, when drawing something with a repetitive pattern such as a memory cell, the pattern forming aperture 21a can be selected and the cell pattern can be exposed all at once, so that the drawing throughput can be greatly reduced. It can be improved. Furthermore, when drawing non-repetitive patterns such as peripheral circuits other than the memory cell section, by selecting the variable beam shaping aperture 21b and drawing with a variable dimension beam, any pattern can be drawn freely. can. In addition, since the lens excitation current is changed between VSB mode and character mode, it is possible to prevent the focus from shifting due to the influence of space charge caused by the difference in beam area. High-precision drawing can be performed even if Furthermore, switching between vSB mode and character mode can be performed once per wafer.
This switching does not increase the drawing time since it only takes a few times. Therefore, LSI pattern formation using the character projection method can be put to practical use, and its usefulness in semiconductor device manufacturing is tremendous.

In addition, since the mask can be replaced without disassembling the vacuum envelope 10, the repeating pattern is maf! Even if there are patterns, these patterns can be accommodated by replacing the mask. In addition, one mask 22 has 2 [
! aperture 22a.

22b, there is no need to excessively deflect the beam by selecting an aperture, and this will not cause a decrease in exposure accuracy.

FIG. 8 is a schematic diagram for explaining another embodiment method. In the case of a memory pattern, an II image of a memory cell may be arranged. In the case of the pattern shown in FIG. 8, patterns 81 and 83 can be formed by parallel movement.

However, 85. ~.

The hatched part of 88 does not overlap with the right side even if the left side is translated in parallel. Therefore, such a pattern is drawn in VSB mode. That is, pattern 81.8
3 and patterns 82 and 84 other than the hatched portions are drawn in character mode, and the hatched portions 85. ~． 88
All you have to do is draw it in VSB mode.

Note that the present invention is not limited to the embodiments described above. For example, the repeating pattern and the non-repetitive pattern may be drawn in any order. Further, the number of pattern forming apertures formed on the mask is 1.
The number is not limited to one, but may be more than one. Furthermore, it is not necessary to form the pattern forming aperture and the variable beam forming aperture on the same mask;
They may be formed on separate masks. In addition, the configuration of the optical system is not limited to that shown in Figure 1, and can be changed as appropriate depending on the specifications.In short, it includes an aperture for pattern forming, an aperture for variable beam forming, and a structure located closer to the electron gun than these apertures. Any aperture selection deflection system may be used as long as it has an aperture selection deflection system that deflects the beam so that the beam is irradiated onto any of the seven apertures. Furthermore, the deflection system for aperture selection is not limited to a deflection coil, but may also be a static N (I) direction plate.

Furthermore, the present invention is not limited to electron beam lithography apparatuses, but can also be applied to ion beam lithography apparatuses and ion beam implantation apparatuses that expose patterns using ion beams. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an electron beam lithography system used in an embodiment of the present invention, FIG. 2 is a schematic diagram showing a memory cell pattern, and FIG. 3 is a pattern-forming aperture and a variable beam-shaping aperture. A plan view showing the shape of the fourth
6 and 7 are schematic diagrams for explaining the principle of aperture selection using the aperture selection deflection coil, respectively, and FIGS. 6 and 7 are schematic diagrams for explaining the drawing process using the above device, FIG. 8 is a schematic diagram for explaining another embodiment. 10... Vacuum envelope, 11... Electron gun, 12. ~. 16...Lens, 17...Target, 21.22
...Aperture mask, 21a, 21b...Aperture, 22a...Aperture for pattern forming, 22k
)...Aperture for variable beam shaping, 23.24...
・Deflection coil for aperture selection, 25.26... Deflection plate for beam scanning, 31... Deflection plate for beam dimension variation,
32°~, 34... Backscattered electron detector, 35... Astigmatism correction coil, 41. ~． 46...Axis alignment coil, 5
1...CPtJ152...Interface, 61
... Semiconductor wafer, 62... Chip, 63... Mark, 66... Memory cell section, 67... Peripheral circuit section, 68... Dicing line. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 7 Figure 8

Claims (3)

[Claims] (1) In a charged beam drawing method in which a charged beam emitted from a charged beam radiation source is focused and deflected and selectively irradiated onto a sample to draw a desired pattern on the sample, it corresponds to a repetitive pattern. a pattern-forming aperture, a variable beam-forming aperture for forming a variable-dimensional beam, and a charged beam-forming aperture provided closer to the charged beam radiation source than these apertures so that either one of the apertures is irradiated with the charged beam. using an aperture selection deflection system that deflects the beam, a repetitive pattern is written with a beam passing through the pattern forming aperture, a non-repetitive pattern is drawn with a beam passing through the beam forming aperture, and A charged beam drawing method characterized in that after all of one of the above repeating pattern and non-repetitive pattern is written, the other pattern is written. (2) The charged beam drawing method according to claim 1, characterized in that the beam current density is changed between when writing the repetitive pattern and when writing the non-repetitive pattern. (3) A semiconductor memory pattern is formed on the sample, and a portion that can be considered as a repeating pattern is formed in the pattern forming aperture, excluding a portion of the non-repetitive pattern of the memory cell pattern that prevents it from being considered as a repeating pattern. 2. The charged beam drawing method according to claim 1, wherein drawing is performed with a beam passing through the charged beam.