JP2000243335A - Aperture holding mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the current of an electron beam colliding with an aperture presser and to reduce the heat quantity in an aperture by boring a hole with the diameter smaller than the half-value width DFWHM of the current density distribution of the electron beam irradiated to the aperture on the aperture presser. SOLUTION: When the ratio between the diameter D0 of the hole 102a of an aperture presser 102 and the half-value width DFWHM becomes 1 or below, the aperture temperature is quickly decreased, because the current of the electron beam colliding with the aperture presser 102 is increased when the diameter D0 becomes the half-value width DFWHM or below, and the heat quantity in a first mold aperture 203 is decreased. Therefore, the diameter D0 is made smaller than the half-value width DFWHM to suppress the temperature rise of the first mold aperture 203, and the fusing of the aperture 203 by the high- acceleration voltage and large-current beam is prevented. The aperture 203 is made of molybdenum, and an aperture base 101, the aperture presser 102 and a ring 103 are made of titanium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an aperture holding mechanism mounted on an electron beam drawing apparatus or the like.

[0002]

2. Description of the Related Art FIG. 5 shows an example of a variable-shaped electron beam writing apparatus equipped with an aperture holding mechanism. In the figure, 201 is an electron gun, 202 is an irradiation lens, 20
3 is a first shaping aperture, 204 is a shaping deflector, 205
Is a molded lens, 206 is a second molded aperture, 207 is a reduction lens, 208 is an objective lens, 209 is a sample, 21
0 is an optical axis, 211 is an electron beam, 212 is a beam irradiation area on the first shaping aperture 203, and 213 is a beam irradiation area on the second shaping aperture 206.

In this electron beam drawing apparatus, an electron beam 211 emitted from an electron gun 201 passes through an irradiation lens 202 and is irradiated on a first shaping aperture 203. Beam irradiation area 2 on first shaping aperture 203
Numeral 12 is almost circular. First forming aperture 2
03, a rectangular hole 203a is formed. The electron beam 211 passing through the hole 203a is irradiated onto the second forming aperture 206. Second forming aperture 20
6 is provided with a rectangular hole 206a.
The sample 209 is irradiated with the electron beam 211 in the portion where the beam 06a and the beam irradiation area 213 overlap. By changing the position of the beam irradiation region 213 by the shaping deflector 204, the beam shape on the sample 209 can be changed.

FIG. 6 is a longitudinal sectional view of a holding mechanism of the first shaping aperture 203 in the variable shaping type electron beam writing apparatus. In the drawing, reference numeral 301 denotes an aperture base on which the first shaping aperture 203 is placed; 302, an aperture holder for holding the first shaping aperture 203 between the aperture base 301; and 303, a ring for fixing the aperture holder 302. Inner surface of aperture stand 301 and ring 303
Is threaded on the outer surface thereof, and a downward force is applied to the aperture holder 302 by screwing in the ring 303, so that the first
The shaping aperture 203 is fixed. In this case, the ring 303 uses the hollow portion 303 a as a passage for the electron beam, and the passage 303 a is used as an aperture holder 302.
The aperture holder 30 is connected to the hole 302a of the
Fix 2 The diameter D ₀ of the bore 302a of the aperture presser 302 is 3 mm, the thickness of the first shaping aperture 203 is 0.1 mm. The first shaping aperture 203 is made of molybdenum, the aperture base 301, the aperture holder 302, and the ring 303 are made of titanium.

[0005]

When the aperture holding mechanism shown in FIG. 6 is applied to a variable-shaped electron beam writing apparatus having a high acceleration voltage and a large current, the first shaped aperture 203 is required.
Since the energy of the electron beam applied to the first forming aperture 203 increases, the amount of heat generated in the first shaping aperture 203 increases, and the aperture temperature increases. For example, when the acceleration voltage of the electron beam is 100 kV and the current of the electron beam applied to the first shaping aperture 203 is 420 μA, the temperature of the first shaping aperture 203 rises to 2650 ° C. (calculated value) and the melting point of molybdenum (2610 ° C). For this reason, the conventional aperture holding mechanism has a problem that when the electron beam is irradiated with a large current at a high accelerating voltage, the aperture is melted. In addition,
Although the above-mentioned “2650 ° C.” is a calculated value, it has been experimentally confirmed that the aperture melts (higher than the melting point of molybdenum), which is consistent with this calculated value.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to suppress an increase in an aperture temperature under a beam condition of a high acceleration voltage and a large current, thereby dissolving the aperture. It is an object of the present invention to provide an aperture holding mechanism that can prevent the occurrence of an aperture.

[0007]

SUMMARY OF THE INVENTION In order to achieve such an object, the present invention provides a method for controlling the _full width at half maximum (D _FWHM) of the current density distribution of an electron beam applied to an aperture.
A hole with a diameter smaller than lf Maximum was opened in the aperture holder. According to the present invention, by _forming a hole having a diameter of half width _{DFWHM in} the aperture holder, the current of the electron beam colliding with the aperture holder increases, and the amount of heat generated in the aperture decreases.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments. Before describing the embodiments, the principle will be described first. In the present invention, the conventional aperture retaining mechanism shown in FIG. 6, focused on the diameter D ₀ of the bore 302a of the aperture retainer 302. That is, it was calculated how the temperature of the first forming aperture 203 changes when the diameter D ₀ is changed.

For this calculation, a heat calculation program using the finite element method was used. The acceleration voltage of the electron beam applied to the first shaping aperture 203 is 100 kV, and the current is 42 kV.
0 μA. The current density distribution on the first shaping aperture 203 is assumed to be a linear distribution as shown in FIG. 2, and the half width _DFWHM of this current density distribution is set to 1 mm. FIG. 3 shows the calculation result at this time. In this calculation, not only does the current density shown in FIG. 2 take into account the heat blocked by the aperture holder 302, but also the heat of the first forming aperture 203 and the heat of the aperture holder 302 are reduced by the aperture holder 302 and the ring 30.
3. The amount of escape through the aperture base 301 is also considered. When assuming a Gaussian distribution as the current density distribution,
A calculation result similar to that of FIG. 3 is obtained. Note that the actual current density distribution is an intermediate state between the linear distribution and the Gaussian distribution.

Referring to FIG. 3, D ₀ / D _FWHM is 1 (D ₀ =
1 mm, D _FWHM = 1 mm) or less, the aperture temperature sharply decreases. This is because D ₀ is D
_{When the FWHM} or less, the current of the electron beam colliding with the aperture holder 302 increases, and the amount of heat generated in the first shaping aperture 203 decreases. Focusing on this point, the present invention focuses on the diameter D of the hole 302a of the aperture holder 302.
_By setting ₀ to be smaller than the half width D _FWHM of the current density distribution on the first shaping aperture 203, the temperature rise of the first shaping aperture 203 is suppressed, and the second shaping under the beam condition of high acceleration voltage and high current is performed. (1) Dissolution of the forming aperture 203 is prevented. Similarly, the dissolution of the second forming aperture 206 is also prevented.

FIG. 1 is a longitudinal sectional view of an aperture holding mechanism showing an embodiment of the present invention. In the figure, 10
Reference numeral 1 denotes an aperture base on which the first shaping aperture 203 is placed, 102 denotes an aperture holder that sandwiches the first shaping aperture 203 between the aperture base 101, and 103 denotes a ring that fixes the aperture holder 102. Aperture stand 1
01 and the outer surface of the ring 103 are threaded.
2, a downward force is applied to fix the first forming aperture 203.

In this case, the ring 103 has its hollow portion 1
03a is a passage for the electron beam.
The aperture holder 102 is fixed with the aperture 3a communicating with the hole 102a of the aperture holder 102. Ring 10
3 through the passage 103a.
The communicating portion 103b with the hole 102a is formed as a mortar-shaped inclined surface (inclination angle θ = 45 °). The diameter D ₀ of the bore 102a of the aperture presser 102 is 0.5 mm, the thickness of the first shaping aperture 203 is 0.15 mm. The first forming aperture 203 is made of molybdenum and the aperture base 10.
1. The aperture holder 102 and the ring 103 are made of titanium.

In this embodiment, assuming a linear distribution as shown in FIG. 2 as a current density distribution on the first shaping aperture 203, when the half width D _FWHM is 1 mm, the maximum temperature of the first shaping aperture 203 is It will be 1046 ° C. Here, the acceleration voltage of the electron beam applied to the first shaping aperture 203 was 100 kV, the current was 420 μA, and the temperature was calculated by a heat calculation program using the finite element method.

In this calculation, not only does the current density shown in FIG. 2 take into account the heat blocked by the communication portion 103b of the ring 103, but also the heat of the first forming aperture 203 and the heat of the aperture holder 102 are reduced. Consideration is also given to the escape through the ring 102, the ring 103, and the aperture base 101. In addition, by increasing the contact area with the aperture holder 102 by forming the communicating portion 103b of the ring 103 as a mortar-shaped inclined surface, the amount of heat that escapes increases, and D ₀ / D
_{When FWHM} = 0.5 (D ₀ = 0.5 mm, D _FWHM = 1 mm), the aperture temperature is 1046 ° C. As described above, in the present embodiment, since the maximum temperature of the first forming aperture 203 is half or less of the melting point of molybdenum (2610 ° C.), there is no problem that the first forming aperture 203 is melted.

In the conventional holding mechanism, as shown in FIG. 3, when D ₀ / D _FWHM = 0.5, the aperture temperature is about 1400 ° C. On the other hand, in the present embodiment, the temperature is 1046 ° C., and it can be seen that the effect of increasing the contact surface with the aperture holder 102 by using the communicating portion 103b of the ring 103 as a mortar-shaped inclined surface is apparent.

In the present embodiment, the communicating portion 103b of the ring 103 is formed as a mortar-shaped inclined surface as follows.
For such reasons. In order to increase the contact area with the aperture holder 102, it is necessary to make the diameter of the lower portion of the passage 103 a of the ring 103 close to the diameter of the hole 102 a of the aperture holder 102. In order to increase the vacuum conductance of the ring 103, it is necessary to increase the diameter of the upper hole of the passage 103a of the ring 103.

The reason why the inclination angle す of the mortar-shaped inclined surface of the communication portion 103b is set to 45 ° is as shown in FIG.
This is to prevent reflected electrons generated from the electron beam 601 irradiating the communication portion 103b from reaching the first shaping aperture 203. That is, by setting the inclination angle の of the inclined surface to 45 °, the trajectories of the reflected electrons generated on the inclined surface of the communication portion 103b can be set to 602 and 603.

As described above, in the present embodiment,
Since the diameter D ₀ of the hole 102a of the aperture holder 102 is smaller than the half width D _FWHM of the current density distribution on the first forming aperture 203, the temperature of the first forming aperture 203 can be lower than the melting point of the aperture. This can prevent the aperture from melting under the conditions of a high acceleration voltage and a high current beam.

In the above description, the aperture table 10
1. Although the aperture holder 102 and the ring 103 are made of titanium, they may be made of a material other than titanium. For example, when these are formed of molybdenum, an acceleration voltage of 10
The maximum temperature of the first shaping aperture 203 under the conditions of 0 kV and a beam current of 420 μA is 678 ° C.

In the above description, the aperture holder 1
Although the 02 and the ring 103 are separate and independent parts, they may be integrally formed parts. In the above description, the holding mechanism for the first forming aperture 203 has been described. However, the same holding mechanism is used for the second forming aperture 206 so that the first forming aperture 2
03, the temperature rise of the second shaping aperture 206 can be suppressed.

In the above description, the aperture holding mechanism for the variable-shaped electron beam writing apparatus has been described as an example. However, other than the cell projection-type electron beam writing apparatus, the SCALPEL-type electron beam writing apparatus, and the variable-shaped electron beam writing apparatus. The present invention can also be applied to an aperture holding mechanism in the device (for example, an electron microscope).

[0022]

As is apparent from the above description, according to the present invention, a hole having a diameter smaller than the half width of the current density distribution of the electron beam applied to the aperture is formed in the aperture holder. The current of the colliding electron beam increases, and the calorific value in the aperture decreases, and the rise in the aperture temperature under high acceleration voltage and high current beam conditions can be suppressed, and the melting of the aperture can be prevented. Become like

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an aperture holding mechanism according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a current density distribution on a first shaping aperture.

FIG. 3 is a diagram showing a change in temperature (calculated value) of a first forming aperture when a diameter D ₀ of a hole of an aperture holder is changed in a conventional holding mechanism.

FIG. 4 is a diagram showing a trajectory of reflected electrons generated on an inclined surface of a communication portion of a ring in the holding mechanism shown in FIG. 1;

FIG. 5 is a configuration diagram illustrating an example of a variable-shaped electron beam writing apparatus equipped with an aperture holding mechanism.

FIG. 6 is a longitudinal sectional view of a holding mechanism of a first shaping aperture in the variable shaping type electron beam writing apparatus.

[Explanation of symbols]

101: aperture stand, 102: aperture holder, 1
02a: hole, 103: ring, 103a: hollow part (passage passage), 103b: communication part, 201: electron gun, 202:
Irradiation lens, 203 ... first forming aperture, 203a ...
Hole, 204: molded deflector, 205: molded lens, 206
... A second shaping aperture, 206 a, a hole, 207, a reduction lens, 208, an objective lens, 209, a sample, 210, an optical axis, 211, an electron beam, 212, a beam irradiation area on the first shaping aperture 203, 213, 2 Beam irradiation area on the shaping aperture 206.

Claims (3)

[Claims] 1. An aperture holding mechanism for holding an aperture for shaping an electron beam, comprising: an aperture base on which the aperture is placed; and an aperture holder sandwiching the aperture between the aperture base. An aperture holding mechanism, wherein a hole having a diameter smaller than a half width of a current density distribution of an electron beam applied to the aperture is formed in the aperture holder. 2. A ring according to claim 1, further comprising a ring for fixing said aperture holder in a state where said hollow part is a passage for said electron beam and said passage is communicated with a hole of said aperture holder. An aperture holding mechanism, characterized in that a communicating portion of the ring passage with the hole of the aperture holder is formed as a mortar-shaped inclined surface. 3. The aperture holding mechanism according to claim 1, wherein the aperture holder and the ring are formed integrally.