JPH07211609A - System and method electron beam lithography - Google Patents

Abstract

PURPOSE:To realize shortening of exposing time and correction of proximity effect on the periphery of a pattern while preventing the resolution from lowering. CONSTITUTION:An electron beam 3 projected from an electron gun 1 passes through a first aperture to produce a rectangular beam. It is then directed toward a desired position of a second aperture 6 by a shaper/deflector 5 and the like. The second aperture 6 has openings representative of a plurality of exposing patterns. The electron beam passed through these openings is projected onto a sample 10 where a plurality of exposing patterns are formed. Only a part of patterns at the second aperture is employed for exposing the peripheral part of a pattern thus shortening the exposing time and correcting the proximity effect on the periphery of the pattern while preventing the resolution from lowering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam drawing apparatus and an electron beam drawing method, and more particularly to an electron beam drawing apparatus and an electron beam drawing method for performing electron beam lithography in an LSI manufacturing process.

[0002]

2. Description of the Related Art As a lithography technique using an electron beam, there are a variable rectangle drawing method and a collective drawing method. The variable rectangle drawing method is a method of drawing a rectangular pattern of arbitrary size on a sample by combining two apertures provided with rectangular holes. However, according to this method, when the same pattern is continuously drawn like a cell part of a memory LSI typified by a DRAM, a very large number of times of drawing is required and drawing time is long. Occurs.

On the other hand, the batch writing method is a method of simultaneously drawing a plurality of patterns on a sample using an aperture provided with a plurality of identical patterns. That is, this collective drawing method is a method of drawing a pattern by an electron beam formed by a first aperture and a second aperture opened in an arbitrary graphic shape, and has a periodicity compared to the conventional variable rectangle drawing method. It is possible to significantly reduce the drawing time in the pattern having the.

As an electron beam drawing apparatus using the conventional collective drawing method, one disclosed in Japanese Patent Laid-Open No. 3-174716 has been devised. This electron beam drawing device
This will be described with reference to FIG. The electron beam 2 emitted from the electron gun 1 is provided with a first aperture 3 having a rectangular opening.
To form a rectangle. Then, the electron beam is applied to the second aperture 6 by the shaping lens 4 and the shaping deflector 5. The second aperture 6 is provided with a shield (mesh or the like) having a resolution limit or less for so-called proximity effect correction. The electron beam shaped into an arbitrary shape by the second aperture 6 is further reduced and projected onto a desired position on the sample 10 by the reduction lens 7, the positioning deflector 8 and the objective lens 9. In this way, the batch writing method is a method of repeatedly drawing a plurality of exposure patterns formed on the second aperture 6 on a part of the LSI pattern. According to this method, a DRA having a particularly continuous pattern
The number of exposures can be greatly reduced in memory devices such as M,
It is possible to shorten the drawing time.

[0005]

However, the conventional electron beam drawing apparatus and electron beam drawing method have various problems as described below.

First, there has been a problem that the drawing time in the peripheral portion of the pattern becomes long. In the conventional batch writing method of simultaneously writing a plurality of patterns, the number of periodic repeating patterns to be written may not be an integral multiple of the number of patterns formed in the second aperture 6. For this reason, the batch drawing method cannot be used for the remaining pattern in the peripheral portion of the chip, and the variable rectangle drawing method can only be used. For this reason,
In this part, the drawing time was several tens of times longer than the batch drawing.

Secondly, there is a problem that it is difficult to perform appropriate proximity effect correction. When a repetitive pattern is drawn by the second aperture 6, the accumulated energy in the resist shows a distribution as shown in FIG. 4 in the central portion and the peripheral portion of the pattern due to the proximity effect caused by the forward scattering and the back scattering. The state of this distribution depends on the acceleration voltage of the electron beam, the pattern density, and the underlying material. In particular, when the accelerating voltage is relatively high such as 50 KV, the proximity effect gradually spreads over a wide range of about 10 to 20 μm, and the larger the area drawn at one time, the more remarkable the proximity effect appears. Also,
It is known that the accumulated energy in the resist is given by the product of the irradiation current density and the irradiation time. Since the current density is usually uniform in the beam, the irradiation time is changed for each pattern by the variable rectangle drawing method in the peripheral part of the pattern with relatively low accumulated energy in the conventional device, and the accumulated energy in the central part and peripheral part of the pattern It was drawn so that it would be almost equal. In this case, since the variable method is unavoidable, a large drawing time is required as compared with the batch drawing. Further, in the method of changing the irradiation time by operating the attribute information of the pattern data, it takes a long time to process the pattern data.

Therefore, in order to perform the proximity effect correction in the collective drawing method, in the drawing method according to the above-mentioned Japanese Patent Laid-Open No. 3-174716, a fine shield (not more than the limit resolution) in the second aperture opening ( Mesh etc.) is formed. Thereby, the proximity effect correction is performed by effectively reducing the radio wave density of the electron beam in the portion where the proximity effect is likely to occur. However, it is extremely difficult to form a fine mesh in the second aperture,
In addition, there have been problems such as insufficient mechanical strength.

Thirdly, in the above-mentioned conventional drawing method, when a pattern having a large opening area is drawn, the amount of transmitted electrons increases, so that beam blurring occurs due to the Coulomb effect and the space charge effect. That is, if a pattern with a large aperture ratio is used, many electrons will pass through the pattern and the electrons will repel each other. Therefore, there is a problem in that the beam is blurred and the resolution is deteriorated. To reduce this, it is effective to reduce the amount of transmitted electrons. A possible method to achieve this is to reduce the current density, but it is impossible to change the current density during writing. Is.

[0010]

An object of the present invention is to provide an electron beam drawing apparatus and an electron beam drawing method capable of shortening the drawing time when the number of repetitive drawing patterns is not an integral multiple of the number of patterns formed in the second aperture. To provide. A second object of the present invention is to provide an electron beam writing apparatus and an electron beam writing method capable of performing proximity effect correction without lowering the mechanical strength of the aperture. A third object of the present invention is to provide an electron beam writing apparatus and an electron beam writing method that do not cause beam blurring or the like by considering the Coulomb effect and space charge effect.

[0011]

The invention according to claim 1 is
An electron gun that emits an electron beam, a first aperture having a rectangular opening, a second aperture having a plurality of openings representing an exposure pattern, and an electron beam that has passed through the opening of the first aperture are deflected. The electron beam to the second
An electron beam drawing apparatus, comprising: a deflecting unit capable of selectively irradiating a part of the plurality of apertures of the aperture.

According to a second aspect of the invention, an electron beam emitted from an electron gun is applied to a rectangular opening formed in the first aperture, and the electron beam passing through the opening in the first aperture is deflected. A plurality of exposure patterns are simultaneously exposed on the sample by irradiating the whole of the plurality of openings formed on the second aperture with the use of, and projecting the electron beam passing through each of the openings of the second aperture onto the sample. And the electron beam that has passed through the opening of the first aperture is selectively irradiated to a part of the plurality of openings formed in the second aperture by using the deflecting means, and the electron beam of the second aperture is formed. A partial batch writing method for exposing a part of the exposure pattern of the second aperture to the sample by projecting the electron beam that has passed through some openings onto the sample. An electron beam writing method, wherein was e.

According to a third aspect of the present invention, an electron gun for emitting an electron beam, a first aperture having a rectangular opening, a second aperture having a plurality of openings representing an exposure pattern, and a first aperture The electron beam transmitted through both the first aperture and the third aperture, which is disposed between the aperture and the second aperture and in which the rectangular aperture is formed, and the apertures of both the first aperture and the third aperture are deflected, and the electrons are deflected. An electron beam writing apparatus, comprising: a deflecting unit capable of selectively irradiating a part of the plurality of openings of the second aperture with a beam.

According to a fourth aspect of the present invention, in the electron beam drawing apparatus according to the third aspect, the electron beam that has passed through the opening of the first aperture is deflected, and the electron beam is directed to a predetermined position of the opening of the third aperture. It is an electron beam drawing apparatus characterized by comprising a deflecting means for irradiating a part.

[0015]

In the invention of claim 1, the electron beam emitted from the electron gun is applied to the rectangular opening on the first aperture. The electron beam passing through this opening is
The light is deflected by the deflecting means, and a part of the plurality of openings on the second aperture is selectively irradiated. And the second
The electron beam transmitted through the aperture of the aperture is projected on the sample to form a predetermined exposure pattern. In this way, a part of the exposure pattern of the second aperture can be selectively exposed on the sample.

Further, in the central portion of the sample where the accumulated energy by the electron beam has a flat distribution, a repetitive pattern is drawn with a constant irradiation amount. On the other hand, in the peripheral portion of the sample, drawing is performed while changing the irradiation amount using a part of the exposure pattern of the second aperture so that the accumulated energy is reduced. This makes it possible to perform precise proximity effect correction. Therefore, according to the present invention, since it is not necessary to change the exposure time and the like in accordance with the pattern data, it is possible to perform the proximity effect correction without requiring complicated pattern data processing and the like. In addition, since it is not necessary to form a fine mesh or the like on the second aperture, it is possible to avoid the problem that the mechanical strength of the second aperture is lowered.

Furthermore, according to the present invention, the aperture ratio of the second aperture can be freely selected. Therefore, it is possible to prevent a problem such as beam blurring due to the repulsion of electrons caused by many electrons transmitting through a pattern having a large aperture ratio.

When forming a continuous pattern such as a DRAM, first, all the patterns of the second aperture are continuously drawn. If the number of patterns to be written on the chip is not an integral multiple of the number of patterns formed on the second aperture, partial batch writing is performed using a part of the patterns of the second aperture.
As a result, the drawing time in the peripheral portion of the pattern can be significantly shortened as compared with the case where variable rectangle drawing is performed. At the same time, since the irradiation amount of the electron beam in the peripheral portion is reduced, the proximity effect correction is performed.

In a second aspect of the invention, an electron beam emitted from an electron gun is applied to a rectangular opening formed in the first aperture, and the electron beam passing through the opening of the first aperture is deflected. Is used to irradiate the entire plurality of openings formed in the second aperture. And the second
By projecting the electron beam that has passed through the respective apertures of the aperture onto the sample, batch writing is performed in which a plurality of exposure patterns are simultaneously exposed on the sample. Further, the electron beam that has passed through the opening of the first aperture is selectively irradiated to a part of the plurality of openings formed in the second aperture by using the deflecting means, and a part of the opening of the second aperture is opened. The electron beam that has passed through the section is projected onto the sample. As a result, partial batch writing is performed in which a part of the exposure patterns formed on the second aperture is exposed on the sample. According to the present invention, similarly to the above-described invention of claim 1, the exposure time in the peripheral portion of the pattern is shortened, the proximity effect correction,
It is possible to realize resolution reduction prevention.

According to the third aspect of the invention, the third aperture is provided between the first aperture and the second aperture. Therefore, the position and shape of the electron beam with which the second aperture is irradiated can be arbitrarily changed depending on the degree of overlap between the first aperture and the third aperture. Therefore, according to the present invention, it is possible to shorten the exposure time in the peripheral portion of the pattern, correct the proximity effect, and prevent the resolution from decreasing.

According to another aspect of the invention, the deflection means deflects the electron beam that has passed through the opening of the first aperture and irradiates the electron beam onto a predetermined portion of the opening of the third aperture. . Thereby, the electron beam can be irradiated to a desired position of the second aperture.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram for explaining an electron beam drawing apparatus and an electron beam drawing method according to the first embodiment of the present invention. This electron beam drawing apparatus includes a first aperture 3 having a rectangular hole and a second aperture 6 having a plurality of patterns (exposure patterns) used in an LSI. The electron beam 2 emitted from the electron gun 1 is shaped into a rectangle by the first aperture 3, and is irradiated onto the opening of the second aperture 6 by the shaping lens 4 and the shaping deflector 5. The electron beam transmitted through the second aperture 6 is passed through the positioning deflector 8 and the objective lens 9 and the sample 10
Projected on. Although several types of patterns are formed in the second aperture 6, the shaping deflector 5 is used to irradiate a part of the pattern with the electron beam 2 instead of irradiating the entire pattern on the second aperture 6. To deflect.

Generally, in the electron beam writing method, a proximity effect occurs in which the accumulated energy is lower in the peripheral portion of the writing pattern than in the central portion. In particular, when the accelerating voltage is relatively high such as 50 KV, the proximity effect extends over a wide range of about 10 to 20 μm, and the proximity effect remarkably appears even in the collective writing region.
In order to correct this, a pattern is repeatedly drawn with a constant irradiation amount in a portion where the accumulated energy has a flat distribution. Then, a part of the pattern on the second aperture 6 is used so that the accumulated energy decreases toward the outside of the pattern, and drawing is performed while gradually changing the irradiation amount. This makes it possible to perform precise proximity effect correction.
As described above, this irradiation time differs depending on the acceleration voltage, the pattern density, and the underlying material.

The entire pattern on the second aperture 6 is first exposed, and then the three left patterns of the same pattern are selected to select an appropriate irradiation time so that the accumulated energy is almost equal to the central portion, and multiple exposure is performed. You can go. When performing the second irradiation, by irradiating two patterns on the second aperture 6 and one by one while controlling the irradiation time,
Accurate proximity effect correction can be executed at high speed without using the variable rectangle drawing method. In this multiple exposure, first the second
Even when a part of the pattern on the aperture 6 is irradiated and then the entire pattern is irradiated, the same effect can be obtained. In this way, when the influence of the proximity effect is significant in the pattern on the second aperture 6, the proximity effect can be corrected by drawing using a part of the pattern on the second aperture 6. it can.

Further, the Coulomb effect can be reduced by the above method. That is, the method for reducing the Coulomb effect is effective in reducing the absolute number of electrons passing through the second aperture 6, but the current density is changed for each pattern formed on the second aperture 6 and having a different aperture ratio. It is impossible to make them. Of course, the aperture ratio can be set in consideration of the Coulomb effect from the time of designing the second aperture 6, but in this case, the pattern area on the second aperture 6 becomes small and the writing time by batch writing is shortened. The effect decreases. Further, even when the aperture ratio is large, the current density may be lowered when writing is performed when the high-sensitivity resist is used. Therefore, it is desirable to increase the pattern area as much as possible. In other words, when the pattern area on the second aperture 6 is made as large as possible and the current density is increased and writing is performed when using a low-sensitivity resist or the like, in order to reduce the number of electrons passing through the second aperture 6, Only part of the pattern on the second aperture 6 is selectively illuminated. Thereby, the Coulomb effect can be reduced.

Further, the above-mentioned drawing method can improve the frequency of use of collective drawing and shorten the drawing time. That is, the pattern of the cell portion of the memory LSI such as DRAM has a periodicity, and the collective writing method using the aperture in which a part of the repeated pattern is opened is particularly effective for drastically shortening the drawing time for such a pattern. It is valid. When the batch drawing method is used, if the pattern to be drawn is not an integral multiple of the number of patterns formed in the second aperture 6, the remaining portion must be drawn by the variable rectangle drawing method. However, when the variable rectangle drawing method is used, the drawing time increases because the number of drawing times increases. So, if there are two remaining parts,
By exposing only two of the patterns on the second aperture 6, the drawing time can be shortened. Further, at this time, the proximity effect correction can be simultaneously performed as described above.

Next, referring to FIG. 2, the second embodiment of the present invention will be described.
An electron beam writing apparatus and an electron beam writing method according to an embodiment will be described. The electron beam drawing apparatus according to the present embodiment includes a third aperture between the first aperture 3 and the second aperture 6.
The electron beam drawing apparatus according to the first embodiment is different in that an aperture 11 and the like are provided. That is, the molded lens 4, the molded deflector 51, and the third aperture 11 are provided above the second aperture 6. In the electron beam writing apparatus configured as described above, the first
By appropriately changing the overlapping condition of the aperture 3 and the third aperture 11, it is possible to irradiate an arbitrary position on the second aperture 6 with an electron beam having an arbitrary shape.
This method is effective when the spacing between the plurality of patterns formed on the second aperture 6 is not sufficient to perform the beam deflection according to the first embodiment.

[0029]

As described above, according to the present invention, by selectively using a part of the plurality of exposure patterns formed in the second aperture, the drawing time in the peripheral portion of the pattern can be shortened. can do. Further, by reducing the irradiation amount of the electron beam in the peripheral portion of the pattern, it is possible to easily perform the proximity effect correction while using the collective writing method. Further, since the amount of electrons passing through the second aperture can be limited, it is possible to avoid a problem such as beam blurring caused by a large number of electrons repelling each other.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an electron beam drawing apparatus and an electron beam drawing method according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining an electron beam writing apparatus and an electron beam writing method according to a second embodiment of the present invention.

FIG. 3 is a diagram for explaining a conventional electron beam writing apparatus and electron beam writing method.

FIG. 4 is a diagram for explaining a proximity effect.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electron gun 2 Electron beam 3 1st aperture 4 Forming lens 5 Forming deflector (deflecting means) 6 2nd aperture 10 Sample 11 3rd aperture 51 Forming deflector (deflecting means) 52 Forming deflector (deflecting means)

Claims (4)

[Claims] 1. An electron gun for emitting an electron beam, a first aperture having a rectangular opening, a second aperture having a plurality of openings representing an exposure pattern, and a light passing through the opening of the first aperture. An electron beam drawing apparatus comprising: a deflecting unit capable of deflecting the electron beam and selectively irradiating the electron beam to a part of the plurality of openings of the second aperture. 2. An electron beam emitted from an electron gun is applied to a rectangular opening formed in the first aperture, and the electron beam passing through the opening of the first aperture is deflected by a second aperture. A batch drawing method in which a plurality of exposure patterns are simultaneously exposed to the sample by irradiating the whole of the plurality of openings formed on the sample and projecting the electron beam that has passed through the respective openings of the second aperture onto the sample. The electron beam that has passed through the opening of the first aperture is selectively irradiated to a part of the plurality of openings formed in the second aperture by using the deflecting means, and a part of the opening of the second aperture is exposed. And a partial batch writing method for exposing a part of an exposure pattern of the exposure pattern formed on the second aperture to the sample by projecting the passed electron beam onto the sample. Electron beam writing method that. 3. An electron gun which emits an electron beam, a first aperture having a rectangular opening, a second aperture having a plurality of openings representing an exposure pattern, a first aperture and a second aperture. An electron beam transmitted through both the first aperture and the third aperture having a rectangular aperture formed therein and the first aperture and the third aperture, and the second electron beam is deflected.
An electron beam drawing apparatus comprising: a deflecting unit capable of selectively irradiating a part of the plurality of apertures of the aperture. 4. The electron beam drawing apparatus according to claim 3, wherein the electron beam that has passed through the opening of the first aperture is deflected, and the electron beam is applied to a predetermined portion of the opening of the third aperture. An electron beam drawing apparatus comprising: