JP2000068191A - Method of forming pattern by electron beam exposure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of forming a pattern by the electron beam exposure whereby the graphic deformation due to the proximity effect can be avoided, without needing the dimensional correction of an exposure graphic accompanying complicated simulation calculations. SOLUTION: A design graphic 11 is exposed on a resist-coated mask by the electron beam exposure. Between the design graphic 11 and auxiliary graphic 14 obtd. by applying the undersizing process of 0.1 μm to the design graphic 11, an XOR-treated second exposure graphic 15 is exposed. Thus only the exposure part near the end of the design graphic 11 is additionally exposed to correct the internal proximity effect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a resist pattern when forming an LSI pattern on a silicon wafer or a mask by electron beam exposure.

[0002]

2. Description of the Related Art Electron beam exposure is an exposure technique for directly drawing a circuit pattern on a mask and a silicon wafer by scanning a focused electron beam on a resist.
The main methods of such electron beam exposure include a raster scan type and a vector scan type. In the raster scan type, a spot-shaped electron beam is scanned on a resist in a fixed width and in a fixed direction like a cathode ray tube of a television. The pattern is formed on the resist by turning the beam on and off according to the pattern data. On the contrary,
The vector scan type is a drawing method in which a beam is two-dimensionally scanned only at a necessary portion on a resist to form a pattern.

[0003] This electron beam exposure technique can obtain a higher resolution than other exposure methods, but since it takes a long time to draw and the productivity is low, it is mainly used for masks of LSI and photolithography, which are thin and highly important. , Used in the manufacture of reticles.

When an electron beam is incident on a resist during electron beam exposure, forward scattering of the electron beam in the resist and back scattering of the substrate occur. For this reason, a phenomenon occurs in which the pattern after development is distorted from the design dimension, for example, the corners of the drawing pattern are rounded, and the size and shape of the figure are deteriorated due to the difference in pattern density. Such a phenomenon generally appears remarkably when the pattern interval is reduced, and is therefore called a “proximity effect”.

[0005] As one of the methods of preventing pattern distortion after drawing due to the proximity effect and drawing a pattern closer to the design figure on the resist, a complicated simulation calculation process considering the proximity effect at the time of exposure is performed on the design figure. A method is used in which the dimensions of the drawing pattern are corrected in advance from the calculation results to achieve the design dimensions.

[0006]

However, the simulation calculation processing for obtaining such an exposure pattern requires a great deal of time and complicated work. Further, the electron beam exposure is performed by dividing an exposure pattern into minimum exposure units (this is called a grid) corresponding to the beam diameter of the electron beam and irradiating the grid with an electron beam for a predetermined time. However, since the exposed figure is a complicatedly deformed design figure, it is necessary to set a small grid for exposing the exposed figure, and the time required for exposure must be long.

Further, the above-described proximity effect correction method can be used when the pattern of the design figure is simple and has a small number, but it is difficult to apply it to a complicated pattern of an LSI. Was.

Accordingly, an object of the present invention is to provide a direct drawing method of electron beam exposure which can prevent distortion of a figure due to a proximity effect without requiring dimensional correction of an exposed figure accompanied by complicated simulation calculations. I do.

[0009]

In order to solve the above-mentioned problems, the present invention provides a pattern by an electron beam exposure for forming an LSI pattern by scanning a spot-like electron beam on a resist material sensitive to the electron beam. The method is characterized in that an LSI pattern is formed by scanning an electron beam on a resist material and exposing two or more exposure figures on the resist in two or more exposure steps.

More specifically, the present invention relates to a pattern forming method by electron beam exposure for forming an LSI pattern by scanning a spot-like electron beam on a resist material sensitive to the electron beam, wherein (i) A) a first exposure pattern forming step of scanning the resist material with an electron beam to form a first exposure pattern on the resist material at a first exposure amount; and (ii) scanning the resist material with the electron beam. Forming a second exposure pattern on the resist material with a second exposure amount.

That is, according to the pattern forming method by electron beam exposure of the present invention, for example, a central portion having a small dimensional error due to a proximity effect in an LSI pattern to be formed is exposed as a first exposure pattern at a first exposure amount, The vicinity of the edge where dimensional errors due to the proximity effect and underexposure are likely to occur can be exposed as the second exposure pattern with the second exposure amount. For this reason, since the exposure amount at each position of the LSI pattern can be adjusted, the dimensional error of the LSI pattern due to the internal proximity effect can be prevented, so that a complicated exposure pattern based on the simulation calculation result is not required. An LSI pattern closer to the design figure can be formed on the resist.

When applying such a pattern forming method by electron beam exposure, the first exposure pattern is made to have the same shape as the LSI pattern to be formed on the resist, and the second exposure pattern is formed to the first exposure pattern. At least a part of the inside of the outline of the exposed figure may be bordered.

In the above-described pattern forming method using electron beam exposure, the first exposure pattern is formed in the same shape as an LSI pattern to be formed on the resist, and the second exposure pattern is formed in the second pattern.
The exposed figure may have a shape bordering at least a part of the outside of the outline of the first exposed figure.

In the above-described pattern forming method by electron beam exposure, the first exposure pattern is formed by reducing an LSI pattern to be formed on the resist by a predetermined size, and the second exposure pattern is formed by the first exposure pattern. At least a part of the outline of the exposed figure may be bordered by the predetermined dimension.

In the above-described pattern forming method using electron beam exposure, the first exposure pattern is formed in the same shape as an LSI pattern to be formed on the resist, and the second exposure pattern is formed at each corner of the LSI pattern. At least a part of the portion may be formed of a plurality of exposure figures. Further, the first exposure pattern has a shape obtained by reducing an LSI pattern to be formed on the resist by a predetermined size, and the second exposure pattern has at least a part outside each corner of the first exposure pattern. It may be composed of a plurality of exposure figures having a shape larger than a predetermined dimension. In this case, the second exposure pattern may be formed as a plurality of exposure patterns in which the corners of the LSI pattern are shaped such that the smaller the inner angles at the vertices of the corners, the greater the distance from the vertices. And the second exposure amount is the second exposure amount.
The pattern may be gradually changed so as to become larger as the inner angle of each corner of the LSI pattern to be formed by the exposure pattern becomes smaller.

Further, in the above-described pattern forming method using electron beam exposure, the minimum exposure unit corresponding to the size of the spot diameter of the electron beam scanned on the resist in the first step is the minimum exposure unit in the second exposure step. It may be set larger than the exposure unit.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. First Embodiment First, a pattern forming method by electron beam exposure of a raster scan system to which the present embodiment is applied will be described. FIG. 9 is a schematic diagram showing the concept of an electron beam exposure method using a raster method, and FIG. 10 is a schematic plan view showing a method for scanning an electron beam using a raster scan method. As shown in FIG. 9, a spot-shaped electron beam L is emitted from the optical system 91 of the electron beam exposure apparatus. This electron beam L is transmitted through the optical system 91.
Scanning is performed in the direction A in FIG. The exposure amount and spot diameter of the electron beam L can be arbitrarily set by the optical system 91 for each exposure step.

A substrate (IC substrate, reticle substrate, etc.) 92 on which a resist pattern is to be formed by the electron beam L is disposed below the optical system 91 in the drawing. Electron beam drawing resist that is sensitive to electron beam L (hereinafter simply referred to as “resist”)
93) is applied. Then, this substrate 92
The stage (not shown) fixes the laser beam L emitted from the optical system 91 on the entire surface of the substrate 92 in the direction A in FIG.
It can be moved in any direction.

The substrate 92 is moved in the direction B in FIG. 9 by a stage (not shown). Then, as shown in FIG. 10A, the electron beam L is scanned along the direction A in the range of the width 95. The electron beam L is turned on at a position where a pattern is to be formed on the substrate 92 (a position where exposure is to be performed by the electron beam L), and the electron beam L is turned off at a position where a pattern is not formed. Note that the arrow drawn on the resist 93 in FIG.
Each shows the scanning direction of the electron beam L. In this manner, a stage (not shown) moves in the B direction in synchronization with the scanning of the range of the width 95 of the substrate 92 from one end to the other end along the A direction while the electron beam L is turned on and off. Be moved. Then, as shown in FIG.
By irradiating the spot-shaped electron beam L only on the part where the pattern figure is to be formed, the resist pattern 9 is formed.
4 are formed. Such operations are repeated, and the entire substrate 92 is exposed.

Hereinafter, the pattern forming method according to the first embodiment of the present invention will be described. FIG. 1 is a diagram for explaining the pattern forming method according to the first embodiment. In this embodiment, the pattern of the design figure 11 shown in FIG. 1A is formed on the resist. The grid 12 drawn in a lattice shape in FIG. 1 has a design figure 1 corresponding to the spot diameter of the electron beam L.
1 is a dividing line divided into minimum exposure units, and an interval between the grids 12 (hereinafter, referred to as “grid size”) is set to 0.1 μm. And at the time of exposure,
An electron beam L is scanned on the resist 93, and FIG.
In FIG. 7, the pattern is formed by turning the beam on at the position of the square hatched by the design graphic 11 and turning off the beam in the other portions. The center 13 indicates the center of the design graphic 11.

FIG. 1B shows an auxiliary figure 14 for obtaining a second exposure figure used for exposure. This auxiliary figure 14
Is a design figure 1 shown in FIG.
1 is a figure obtained by performing an undersizing process of 0.1 μm. FIG. 1C shows a second exposure pattern 15 used for exposure. The second exposure graphic is obtained by performing XOR logic operation processing (hereinafter simply referred to as “XOR processing”) between the design graphic 11 and the auxiliary graphic 14. That is, each center 1 in FIGS.
Design figure 11 and design figure 14 so that the positions of 3
Are obtained by applying processing such that when one of the squares is filled, the part where one of the squares is filled is filled, and both the squares are filled or the part that is not filled is filled. The figure is the second exposure figure 15. By performing such processing, a second exposure graphic 15 having a shape bordering the inside of the outline of the design graphic 11 is obtained.

Hereinafter, the pattern forming method by electron beam exposure according to the present embodiment will be described. First, the designed figure 11 is exposed as a first exposure figure while scanning the electron beam L on the resist 93 using a raster scan type electron beam exposure apparatus. The exposure amount at this time is 4 μC / cm ²
(First exposure amount). Then, when the electron beam L scans over the resist 93, the electron beam L is applied only to the portion painted with the design figure 11 of the square surrounded by each grid 12 in FIG. Therefore, theoretically, only the irradiated portion is exposed, so that portion is exposed to the electron beam L, and a pattern having the same shape as the design figure 11 is formed on the mask.

However, as described above, since the proximity effect occurs due to the forward scattering of the irradiated electron beam L in the resist 93 and the back scattering from the substrate 92, as described above, the pattern formed on the resist 93 (hereinafter referred to as a pattern) is formed. , "Resist patterns") are distorted with respect to the exposed design figure 11. In particular, the vicinity of the end of the formed resist pattern is easily affected by the internal proximity effect due to the shortage of the accumulated charge. Therefore, insufficient exposure occurs at a portion of the formed resist pattern corresponding to the end portion of the design graphic 11, and a dimensional deviation from the design graphic 11 occurs.

Then, the second exposure pattern 15 is exposed on the resist 93 on which the design pattern 11 has been exposed.
The exposure amount at this time is 3 μC / cm ² (second exposure amount), which is smaller than the exposure amount when exposing the design figure 11. Then, only the end portion of the resist pattern where underexposure has occurred is exposed again, so that the shape of the resist pattern can be made closer to the design figure 11 than before.

As described above, in this embodiment, the design figure 1
In order to correct the effect of the internal proximity effect that the effective exposure amount in the vicinity of the end of the resist pattern generated when 1 is exposed is reduced, the second exposure pattern 15 is additionally exposed. For this reason, it is possible to eliminate insufficient exposure near the periphery of the figure 11. Therefore, at the time of electron beam exposure, it is not necessary to perform pattern exposure using an exposure pattern that is complicatedly deformed by a complicated simulation calculation, and a resist pattern having a desired shape can be easily obtained.

<Second Embodiment> In the first embodiment, the design figure 11 is exposed and then a second exposure figure 15 having a shape bordering the inside of the outline of the design figure 11 is additionally exposed. A resist pattern having a shape closer to that of FIG. 11 is obtained. On the other hand, the second embodiment is characterized in that a second exposure figure having a shape bordering the outside of the outline of the design figure is additionally exposed, and the other parts are the same as the first embodiment.

FIG. 2 is a view for explaining a pattern forming method according to a second embodiment of the present invention. FIG. 2 (a)
Similar to the first embodiment, a design figure 11 used for exposure is shown. FIG. 2B shows an auxiliary figure for obtaining a second exposure figure used for exposure. This auxiliary figure 24 has the center 1
3 shows an auxiliary figure 14 obtained by subjecting a design figure 11 to an oversizing process of 0.1 μm with the center being 3. FIG. 2C shows a second exposure pattern 25 used for exposure. The second exposure graphic 25 is a graphic obtained by performing an XOR process between the design graphic 11 and the auxiliary graphic 24, and has a shape bordering the outline of the design graphic 11.

Hereinafter, the pattern forming method by electron beam exposure according to the present embodiment will be described. First, the design figure 11 is exposed as a first exposure figure by scanning the electron beam L on the resist 93 using a raster scan type electron beam exposure apparatus. The exposure amount at this time is 4 μC
/ Cm ² (first exposure amount). Next, the second exposure pattern 25 is exposed on this resist pattern. The exposure amount at this time is set to 3 μC / cm ² (second exposure amount).

As in the first embodiment, at the stage where the design figure 11 is exposed, the design figure 11 is exposed due to the internal proximity effect.
In the vicinity of the peripheral portion, insufficient exposure occurs, so that a dimensional deviation occurs between the figure formed on the mask and the design figure.
Therefore, by exposing the second exposure pattern after exposing the design pattern 11, only the peripheral portion where the exposure amount is insufficient is exposed again. However, when the influence of the internal proximity effect is large at the end of the figure, the internal proximity correction may not be sufficiently performed even if this end is additionally exposed. In order to cope with such a case, in the present embodiment, the part exposed by the second exposure graphic 25 is shifted to the outside of the outline of the design graphic 11, and this is exposed, whereby the periphery of the graphic by the internal proximity effect is exposed. The dimensional deviation near the part is corrected. Therefore, even in the case described above, it is possible to easily obtain a finished resist pattern closer to the design figure 11 than before.

<Third Embodiment> FIG. 3 is a view for explaining a pattern forming method according to a third embodiment of the present invention. FIG. 3A shows the same design figure 1 as in each of the above embodiments.
FIG. FIG. 3B is a diagram illustrating a first exposure pattern 34 used for exposure, and is obtained by performing an undersizing process of 0.2 μm on the design pattern 11 centering on the center 13 of FIG. FIG. 3 (c)
FIG. 4 is a diagram showing a second exposure pattern 35 used for exposure. The second exposed figure 35 is composed of the design figure 11 and the first exposed figure 3
4 by performing an XOR process. That is, the second exposure pattern has a shape in which the outside of the outline of the first exposure pattern is bordered by a thickness of 0.2 μm.

At the time of exposure, first, the electron beam L is scanned on the resist 93 to thereby form the first exposed pattern 34.
Is exposed at an exposure amount of 4 μC / cm ² (first exposure amount). Next, a second exposure pattern 35 is exposed on the resist 93 at an exposure amount of 5 μC / cm ² (second exposure amount).

The magnitude of the influence of the internal proximity effect inside the design figure 11 differs between the center and the end of the figure. For this reason, if the entire design figure 11 is exposed with the same exposure amount, insufficient exposure occurs at the end of the figure. On the other hand, if the exposure amount is set such that the end is sufficiently exposed, the exposure amount at the center becomes excessive. In contrast, unnecessary portions are exposed. Therefore, in the present embodiment, the central portion of the design graphic 11 where the effect of the internal proximity effect is almost uniform is 4 μC / c.
exposing m ^2, and the different effects of internal proximity effect and the central portion, the peripheral portion of underexposure in the end when exposed under the same conditions as the central portion occurs at 5 [mu] C / cm ² greater than the exposure amount in the central portion Exposure. Therefore, the influence of the internal proximity effect can be suppressed as small as possible, and a resist pattern having a shape closer to the design figure 11 than in the past can be obtained.

<Fourth Embodiment> FIG. 4 is a view for explaining a pattern forming method according to a fourth embodiment of the present invention.
FIG. 4A shows a design graphic 11 similar to the above embodiments. FIG. 4B is a diagram showing a first exposure pattern 44 used for exposure. This first exposure pattern 44 is
In the design graphic 11 with the center 13 at the center 13 in FIG.
It is obtained by performing an undersizing process of 2 μm. In FIG. 4B, the grid size (minimum exposure unit) of the grid 46 for dividing the first exposure graphic 44 into the minimum unit at the time of electron beam exposure is 0.2.
It is set to μm.

FIG. 4C shows a second exposure pattern 45 used for exposure. The second exposure graphic 45 is obtained by performing an XOR process between the design graphic 11 and the design graphic 44. In FIG. 4C, the grid 4
The grid size of No. 7 is set to 0.1 μm.

At the time of exposure, first, the first exposure pattern 44 is exposed at an exposure of 4 μC / cm ² (first exposure) by scanning the resist 93 with an electron beam. Next, the second exposure pattern 45 is exposed to an exposure of 5 μC / cm ² ( ^second exposure pattern).
Exposure amount). Since the grid sizes for exposing the first exposure pattern 44 and the second exposure pattern 45 are different from each other, the spot diameter of the electron beam L when exposing each of the exposure patterns 44 and 45 is also different. Is set to

As described above, in the present embodiment, similarly to the third embodiment, the exposure amount is changed between the central portion and the peripheral portion of the design figure 11 where the influence of the internal proximity effect is different at the time of exposure. Therefore, since the influence of the internal proximity effect can be suppressed as much as possible, a finished mask figure having a shape closer to the shape of the design figure 11 can be obtained. Further, in the present embodiment, the grid size of the first exposure pattern 44 having a simple shape is set to be larger than the grid size of the first exposure pattern 34 of the third embodiment. Then, since the exposure area per beam spot irradiated on the mask when exposing the first exposure pattern 44 can be increased, the exposure time of the first exposure pattern can be shortened as compared with the third embodiment. Can be. That is, when performing mask exposure using a plurality of exposure figures, for example, the grid size of an exposure figure having a simple shape and a large area is set to be large, and the grid size of an exposure figure having a complicated shape is set to be small. By setting the grid size in accordance with the geometrical shape of each exposure pattern, a resist pattern having an accurate shape can be obtained in a short time, so that productivity can be improved.

<Fifth Embodiment> FIG. 5 is a view for explaining a pattern forming method according to a fifth embodiment of the present invention.
FIG. 5A is a diagram showing a design graphic 11 similar to the other embodiments. FIG. 5B shows an auxiliary graphic 54 for obtaining a second exposure graphic group used for exposure. The auxiliary graphic 54 is obtained by the same procedure as when the second exposure graphic 35 is obtained in the third embodiment. That is, the auxiliary graphic 54
Is obtained by performing an XOR process between the design figure 11 and a figure (not shown) obtained by subjecting the design figure 11 to an undersizing process of 0.2 μm.

FIG. 5C shows a second exposure pattern group 55 used for exposure. The exposed figure group 55 is composed of exposed figures 55a, 55b, 55c, and 55d obtained by cutting a range of a square having a side of 0.6 μm around the vertices 11a, 11b, 11c, and 11d from the auxiliary figure 54. Each side of each of the exposure figures 55a to 55d is formed along the grid.

At the time of exposure, first, the design pattern 11 is exposed at an exposure of 4 μC / cm ² (first exposure) as the first exposure pattern by scanning the electron beam L on the resist 93. Next, the second exposure pattern group 55 is
Exposure is performed at μC / cm ² (second exposure amount).

As described above, in the present embodiment, exposure is performed again only in the vicinity of the vertices 11a to 11d of the design graphic 11 where the decrease in the exposure amount due to the influence of the internal proximity effect is most remarkable. For this reason, the influence of the internal proximity effect can be more effectively corrected, and a resist pattern having a shape closer to the design figure 11 can be obtained than in the related art.

<Sixth Embodiment> FIG. 6 is a view for explaining a pattern forming method according to a sixth embodiment of the present invention. FIG. 6A shows a design figure 1 similar to that of the fifth embodiment.
1 is shown. FIG. 6B shows an auxiliary figure 64 for obtaining a second exposure figure group used for exposure. The auxiliary figure 64 includes a figure (not shown) obtained by performing an oversizing process of 0.1 μm on the design figure 11 and a design figure
It is obtained by performing an XOR process with a figure (not shown) subjected to an undersizing process of 1 μm.

FIG. 6C shows a second exposed figure group 65 used for exposure. The exposed figure group 65 includes the design figure 11
Exposure figures 65a, 65b, 65c, 65 obtained by cutting a range of a square having a side of 0.4 μm from the auxiliary figure 64 around a position corresponding to each of the vertices 11a to 11d.
d. Each side of these exposed figures 65a to 65d is formed along the grid.

At the time of exposure, first, the design pattern 11 is exposed at an exposure of 4 μC / cm ² (first exposure) as the first exposure pattern by scanning the electron beam L on the resist 93. Next, the second exposure figure group 65 is
Exposure is performed at μC / cm ² (second exposure amount).

If the influence of the internal proximity effect in the vicinity of the corner of the figure is very large, even if only the position corresponding to the vicinity of the corner is exposed again as in the fifth embodiment, the effect of the internal proximity effect will be sufficient. May not be corrected. In this case, if the additional exposure is performed using the second exposure graphic 65 obtained by oversizing the corners of the design graphic 11, insufficient exposure near the vertices 11a to 11d of the design graphic 11 can be compensated. . Therefore, since the influence of the internal proximity effect can be more effectively corrected, the design graphic 11
It is possible to obtain a finished mask figure having a shape close to.

<Seventh Embodiment> FIG. 7 is a view for explaining a pattern forming method according to a seventh embodiment of the present invention. Although each of the above-described embodiments has been described in connection with the case where the shapes of the corners that are easily affected by the internal proximity effect are the same, in the present embodiment, the angles formed by the corners of the figure to be exposed have various sizes. This is a pattern formation method applicable in certain cases. FIG. 7A shows a design figure 71 to be formed on a mask. In the design graphic 71, the inside angle of the vertex 71e is larger than 180 degrees, and the other vertices 71a, 71b, 71
c, 71d, and 71f have a concave hexagonal shape in which the internal angles are smaller than 180 degrees. The grid size of the grid 72 for dividing the design graphic 71 is 0.1 μm.

FIG. 7B shows an auxiliary graphic 74 for obtaining a second graphic group used for exposure. This auxiliary graphic 74 is
XOR processing is performed between a figure (not shown) in which the design figure 71 is oversized by 0.1 μm and a figure (not shown) in which the design figure 71 is undersized by 0.1 μm. (The figure drawn by the two-dot chain line in FIG. 7B indicates the design figure 71).

FIG. 7C shows a second figure group 7 used for exposure.
5 is shown. The second exposure graphic group 75 includes a plurality of second exposure patterns obtained by cutting the auxiliary graphic 74 into a circular shape having a radius of a predetermined length around each of the vertices 71a, 71b, 71c, 71d, and 71f of the design graphic 71. Figures 75a, 75
b, 75c, 75d, and 75f. At this time, the cutting radius of each of the second exposure figures 75a to 75f from the auxiliary figure 74 is set according to the size of the interior angle of each of the vertices 71a to 71f of the design figure 71. In the present embodiment, the maximum cutting radius at the corner of the design graphic 71 is 0.5 μm.
The cutting radius when the inner angle of each apex angle is θ (degree) is as follows: cutting radius (μm) = 0.5 × cos
(Θ / 2) (where 0 ≦ θ ≦ 180).
That is, as the inner angle at the apex angle is smaller, the cutout range from each corner of the auxiliary figure 74 in forming the second exposed figure is set to be larger, and the cutout range is reduced as the inner angle becomes larger. The second exposed figure is not formed at the vertex 71e where the inner angle is 180 degrees or more.

At the time of exposure, the design figure 7
After exposure at an exposure amount 4μC / cm ² to 1 as the first exposure figure (first exposure), exposing the second exposed pattern group 75 by exposure 3 .mu.C / cm ² (second exposure). As described above, at the time of exposure, the figure is exposed by the on / off of the electron beam L scanning on the resist 93. Therefore, at the boundary between the design graphic 71 and the second exposure graphic group 75 shown in FIGS.
Of the squares delimited by, the portion of the square where more than 50% of the area is filled by the figures 71 and 75 is turned on, and the portion of the square where less than 50% is filled In, the beam is turned off.

When the shape of the corner of the figure to be formed on the mask is not uniform, the smaller the inner angle of the corner, that is, the sharper the angle, the greater the effect of insufficient exposure due to the internal proximity effect. Therefore, in the present embodiment, the design graphic 71
When the second exposure pattern group 75 is additionally exposed after the exposure of
The shape of the second exposure graphic group 75 is set so that the corners of the design graphic 71 are exposed with a large number of small internal angles and a large internal angle with a small amount of exposure. As a result, it is possible to sufficiently correct a portion that is greatly affected by the internal proximity effect, and to prevent overexposure of a portion that does not need to be corrected. Can be formed efficiently.

<Eighth Embodiment> FIG. 8 is a view for explaining a pattern forming method according to an eighth embodiment of the present invention.
In the present embodiment, a design graphic 71 shown in the seventh embodiment is used.
This is a method that can be effectively applied when the influence of the internal proximity effect is significantly different between the center and the end of the figure when exposing the pattern.

FIG. 8A shows a first exposure figure 81 used for exposure. The first exposure graphic 81 is a design graphic 71 (FIG. 7).
(See FIG. 8 (a)) and a 0.1 μm undersizing process (see FIG. 8 (a)).
1 is indicated by a dotted line). The second exposed figure group 85 shown in FIG. 8B is a figure obtained by the same procedure as the second exposed figure group 75 of the seventh embodiment.

At the time of exposure, similarly to the seventh embodiment, first, the first exposed figure 81 is exposed at an exposure amount of 5 μC / cm ² (first exposure amount), and then the second exposed figure group 85 is exposed. Is exposed at an exposure of 3 μC / cm ² (second exposure).

When there is a large difference between the central portion and the peripheral portion of the figure to be exposed due to the internal proximity effect,
Since the amount of exposure is insufficient at the corners of the graphic and the amount of exposure at the center is excessive, the corners of the design graphic 71 are rounded and the straight line portions are fat. Therefore, in the present embodiment, the first exposure figure is set smaller than the design figure 71, and the shape of the second figure group is set so that the corners are sufficiently exposed when the second exposure figure group is exposed. Therefore, insufficient exposure at corners of the design graphic 71 can be prevented, and thickening of the graphic at unnecessary portions can be suppressed, so that a resist pattern having a shape closer to the design graphic than before can be formed.

<Modifications> In each of the above embodiments, an example has been described in which exposure is performed using a raster scan type electron beam exposure apparatus. However, the same applies to the case where a vector scan type electron beam exposure apparatus is used. The method of the present invention can be applied. Note that the vector scan type electron beam apparatus can arbitrarily change the intensity (exposure amount) of a beam emitted in the same exposure step. Therefore, the seventh,
When the eighth embodiment is applied to a vector scan type electron beam exposure method, the cut-out radius of the second exposure pattern group 75 is fixed regardless of the size of the inner angle at each vertex of the auxiliary pattern 74, and the second exposure pattern The exposure may be performed by changing the exposure amount when exposing the figures 75a to 75f according to the magnitude of the influence of the internal proximity effect.

The above embodiments can be combined and applied depending on the shape of the exposure pattern to be formed, the exposure conditions, and the degree of dimensional deviation from the design figure due to the internal proximity effect.

Further, in each of the above embodiments, the exposure by the electron beam was performed in two steps by changing the exposure amount. However, the exposure pattern was exposed in three or more exposure steps to expose the resist pattern. It may be formed.

[0057]

According to the present invention, it is possible to prevent a deviation from a design value of a figure after exposure due to a proximity effect without using an exposure figure complicatedly deformed by complicated simulation calculation or the like.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a pattern forming method by electron beam exposure according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a pattern forming method by electron beam exposure according to a second embodiment of the present invention.

FIG. 3 is an explanatory view of a pattern forming method by electron beam exposure according to a third embodiment of the present invention.

FIG. 4 is an explanatory view of a pattern forming method by electron beam exposure according to a fourth embodiment of the present invention.

FIG. 5 is an explanatory view of a pattern forming method by electron beam exposure according to a fifth embodiment of the present invention.

FIG. 6 is an explanatory diagram of a pattern forming method by electron beam exposure according to a sixth embodiment of the present invention.

FIG. 7 is an explanatory diagram of a pattern forming method by electron beam exposure according to a seventh embodiment of the present invention.

FIG. 8 is an explanatory diagram of a pattern forming method by electron beam exposure according to an eighth embodiment of the present invention.

FIG. 9 is a schematic view showing the concept of an electron beam exposure method using a raster scan method.

FIG. 10 is a diagram for explaining an electron beam exposure method using a raster scan method.

[Explanation of symbols]

 11, 71 Design figure 12, 46, 47, 72 Grid 13 Center 14, 24, 54, 64, 74 Auxiliary figure 15, 25, 35, 45 Second exposure figure 34, 44, 81 First exposure figure 55, 65, 75, 85 Second exposure pattern group 92 Substrate 93 Electron beam drawing resist L Electron beam

Claims (10)

[Claims] 1. A pattern forming method by electron beam exposure for forming an LSI pattern by scanning a spot-shaped electron beam on a resist material sensitive to an electron beam, wherein the electron beam is scanned on the resist material. A pattern forming method by electron beam exposure, wherein an LSI pattern is formed by exposing two or more exposure figures on the resist in two or more exposure steps. 2. A pattern forming method by electron beam exposure for forming an LSI pattern by scanning a spot-shaped electron beam on a resist material sensitive to an electron beam, wherein the electron beam is scanned on the resist material. A first exposure pattern forming step of forming a first exposure pattern on the resist material at a first exposure dose; and scanning the resist material with an electron beam to apply a second exposure pattern to the resist material at a second exposure dose. And a second exposure pattern forming step of forming a pattern by electron beam exposure. 3. The first exposure pattern has the same shape as an LSI pattern to be formed on the resist, and the second exposure pattern borders at least a part of the inside of the outline of the first exposure pattern. 3. A pattern forming method by electron beam exposure according to claim 2, wherein the pattern has a curved shape. 4. The first exposed figure has the same shape as an LSI pattern to be formed on the resist, and the second exposed figure borders at least a part of an outline of the first exposed figure. 3. A pattern forming method by electron beam exposure according to claim 2, wherein the pattern has a curved shape. 5. The first exposure pattern has a shape obtained by reducing an LSI pattern to be formed on the resist by a predetermined size, and the second exposure pattern has at least one outside an outline of the first exposure pattern. 3. The pattern forming method by electron beam exposure according to claim 2, wherein the portion has a shape bordered by the predetermined dimension. 6. The first exposure pattern has the same shape as an LSI pattern to be formed on the resist, and the second exposure pattern models at least a part of each corner of the LSI pattern. 3. The pattern forming method by electron beam exposure according to claim 2, comprising a plurality of exposure figures. 7. The first exposed figure has a shape obtained by reducing an LSI pattern to be formed on the resist by a predetermined size, and the second exposed figure is located outside each corner of the first exposed figure. 3. A pattern forming method by electron beam exposure according to claim 2, comprising a plurality of exposure figures having a shape in which at least a part of said pattern is larger than said predetermined dimension. 8. The second exposed figure comprises a plurality of exposed figures which model each corner of the LSI pattern such that the smaller the inner angle at the corner of the LSI pattern, the greater the distance from the corner is. 8. The pattern forming method according to claim 6, wherein the pattern is formed by electron beam exposure. 9. The method according to claim 6, wherein the second exposure amount is gradually changed so as to increase as the inner angle of each corner of the LSI pattern formed by the second exposure pattern decreases. Item 10. A pattern forming method by electron beam exposure according to any one of Items 8. 10. A minimum exposure unit according to a spot diameter of the electron beam scanned on the resist in the first step is set to be larger than a minimum exposure unit in the second exposure step. The pattern forming method by electron beam exposure according to claim 1.