JP5806873B2 - Charged particle beam equipment - Google Patents

Description

The present invention relates to a charged particle beam apparatus, and more particularly to a charged particle beam apparatus that reduces current density unevenness caused by spherical aberration.

  The charged particle beam apparatus is an apparatus using a charged particle beam such as an electron beam. For example, an electron microscope and an electron beam drawing apparatus are typical charged particle beam apparatuses.

  FIG. 7 is a diagram showing a conventional example (optical system) of a variable shaped electron beam drawing apparatus that is currently generally used as a charged particle beam apparatus. In the figure, the path of the electron beam 1 is kept in a vacuum.

  First, as shown in FIG. 7, the electron beam 1 emitted from the light source 4 is irradiated onto the first molded aperture plate 3 through the irradiation lens 2. As the light source 4, a thermoelectron emission type electron gun having a LaB6 emitter is generally used. The image 5 of the light source 4 is tied under the first shaping aperture plate 3. Next, an image of the first molded aperture plate (or aperture) 3 is projected onto the second molded aperture plate 7 by the molded lens 6, and the image of the aperture of the first molded aperture plate 3 and the second A figure determined by the overlap (logical product) with the aperture of the molded aperture plate 7 is projected through a reduction lens 8 and an objective lens 9 onto a material 10 coated with a resist (photosensitive material).

  As a result, the resist is exposed. That is, the projected figure 11 is transferred to the material 10. Therefore, a desired pattern can be drawn on the material 10 by controlling the shape, size, and position of the projection figure 11. When the material 10 is developed after pattern drawing, the photosensitive part or the non-photosensitive part is dissolved depending on the resist mold, and a desired pattern appears on the material 10.

  A shaping deflector 12 is used to control the shape and dimensions of the projection figure 11. The electron beam 1 is deflected by the shaping deflector 12, and the image of the opening of the first shaping aperture plate 3 is moved with respect to the opening of the second shaping aperture plate 7. In order to control the position of the projection figure 11, the objective deflector 13 and the material stage 14 are used in combination. Since the deflectable region (deflection field) of the objective deflector 13 is limited, positioning with a large step is first performed by the material stage 14, and then positioning with a smaller step than the objective deflector 13 is performed. An electrostatic deflector is used as the shaping deflector 12 and the objective deflector 13 in order to increase the deflection speed.

  If the projected figure 11 is always projected onto the material 10, only a one-stroke figure can be drawn. Therefore, the drawing control of the electron beam 1 (blanking) is necessary for drawing a general figure. In the optical system of FIG. 7, this blocking control is performed by the blanker 15. More specifically, the blanker 15 is first actuated, the electron beam 1 is blocked by the blanking aperture plate 16, and then the shaping deflector 12 and the objective deflector 13 are actuated to determine the shape, size and position of the projection figure 11. After that, the blocking of the electronic beam 1 by the blanker 15 is released, and the projected figure 11 is projected onto the material 10. When the exposure is performed for a predetermined time, the electron beam 1 is interrupted again. This predetermined amount of exposure is usually called a “shot”.

In order to maintain and further improve the dimensional accuracy of the resist pattern obtained after development of the material 10, it is important to make the current density distribution on the first shaped aperture plate 3 as uniform as possible. Since the current density distribution on the first shaping aperture plate 3 is directly reflected on the current density distribution on the material 10, if the current density on the first shaping aperture plate 3 is uneven, Current density unevenness, that is, a partial excess or deficiency of the exposure amount, which appears as a dimensional error of the resist pattern.
In order to improve the current density uniformity on the first shaping aperture plate 3, the position of the image 5 may be separated from the position of the first shaping aperture plate 3 as shown in FIG. 7. Ideally, the image formation position of the image 5 should be at infinity. For this purpose, as shown in FIGS. 8 and 9, the image 4 ′ formed by the light source 4 or the first lens 17 provided separately is positioned on the object side focal plane of the irradiation lens 2. At this time, the electron beam 1 incident on the first shaping aperture plate 3 becomes a parallel beam.

  As described above, when the imaging position of the image 5 (not shown in FIGS. 8 and 9) is set to infinity, even if the current densities of the light source 4 and the image 5 are uneven, the unevenness is the first. It is no longer reflected in the current density distribution on the shaped aperture plate 3. This type of illumination is commonly referred to as Koehler illumination. However, in the optical system based on Koehler illumination, a field stop is usually inserted at a position optically conjugate with the position of the irradiated surface (the first shaping aperture plate 3 in FIGS. 8 and 9). 8 and 9 are not inserted into the optical system. Here, optically conjugate means that two surfaces are in a relationship between an object surface and an image surface. Further, as long as the current density uniformity on the first shaping aperture plate 3 is sufficiently good, the imaging position of the image 5 does not necessarily have to be infinitely far away.

However, simply separating the image 5 from the position of the first shaping aperture plate 3 in this way does not necessarily increase the current density uniformity on the first shaping aperture plate 3 sufficiently. This is because of the spherical aberration with respect to the irradiation lens 2 in FIG. 8 or the first lens 17 in FIG. The spherical aberration is an aberration that increases in proportion to the cube of the opening angle of the light beam. If the required beam current is large, the required opening angle increases, and as a result, the spherical aberration increases.
The reason why the current density uniformity is deteriorated by the spherical aberration is that the interval between the light rays changes due to the non-linearity of the spherical aberration. The current density increases as the distance between the light beams decreases, and decreases as the distance increases. This will be described with reference to FIG. However, for simplicity, it is assumed that there is no cause of current density irregularities other than spherical aberration.

FIG. 10 shows a light beam group in which the inclination u _{0 ′} with respect to the central axis (Z axis) in the light source 4 is an integer multiple of Δu _{0 ′} . As long as there is no spherical aberration, such a group of light rays is arranged concentrically at equal intervals around the central axis (solid line) regardless of before and after passing through the irradiation lens 2 as shown in FIG. And also in the 1st shaping | molding aperture plate 3, the space | interval between light rays becomes equal intervals. However, since spherical aberration actually exists, the ray group changes its orbit by the amount of spherical aberration (broken line).

  Because of the non-linearity of spherical aberration, the light rays that are on the outer side as viewed from the central axis show a larger orbital change nonlinearly. As a result, as can be seen from FIG. 10, the distance between the light beams in the first shaping aperture plate 3 is not equal, and becomes narrower with the distance from the central axis. That is, the current density in the first molded aperture plate 3 increases with the distance from the central axis.

When a field emission electron gun or a Schottky electron gun (also called a thermal field emission electron gun) is used as the light source 4, the opening angle u _{0 ′} increases and spherical aberration increases due to the large divergence of electrons. . These electron guns are useful electron guns used in electron microscopes and spot electron beam drawing apparatuses as electron guns with high luminance.

  When these electron guns are applied to a variable shaped electron beam drawing apparatus, a beam with a high current density can be obtained. If the current density on the material 10 is increased, the shot time is shortened and the drawing throughput is improved. Therefore, the improvement of the current density is an important issue in the development of the variable shaped electron beam drawing apparatus. At present, a variable shaped electron beam drawing apparatus using these electron guns has not been put into practical use, but if the current density unevenness caused by spherical aberration is reduced, its practical use can be promoted.

  Several techniques for reducing spherical aberration have been known so far. These methods are mainly aimed at reducing the diameter of the spot beam in an electron microscope or spot electron beam writing apparatus, that is, reducing the spherical aberration on the image plane. If applied to an illumination optical system and the spherical aberration coefficient is reduced, current density unevenness caused by spherical aberration can be reduced.

The spherical aberration on the image plane and the spherical aberration on the object plane are respectively expressed as dU _i = mCcu _{0 ′} 3 (1) using the spherical aberration coefficient.
dU ₀ = dU _i / m = Ccu _0'3 (2)
It is expressed. Here, m is the magnification, Cc is the object-side spherical aberration coefficient, and u _{0 ′} is the inclination of the light beam on the object surface. The spherical aberration on the object surface is a mapping of spherical aberration on the image surface onto the object surface. From equation (2), the spherical aberration coefficient Cc can be regarded as spherical aberration on the object surface when u _{0 ′} is 1. Therefore, the spherical aberration coefficient Cc is useful as an index indicating the performance of the lens regardless of the magnification m.
The maximum value of u _{0 ′} , that is, the opening angle in the equations (1) and (2) is determined from the following relationship.
u _0'max = (I / ΠJΩ) 1/2 (3)
Here, I is the required beam current, and JΩ is the angular current density on the object surface. The beam current I may be a product of the current density on the material 10 (see FIG. 7) and the area of the circumscribed circle of the projection figure 11. As can be seen from the equation (3), u _0′max does not depend on the magnification or the aberration coefficient of the irradiation lens 2 or the first lens 17 (see FIG. 9). In other words, as long as I and J _Omega is constant, in order to reduce the spherical aberration because u _0'Max is constant, it is necessary to reduce the spherical aberration coefficient Cc.

In order to make the spherical aberration coefficient Cc as small as possible, the first stage lens, that is, the irradiation lens 2 in FIG. 8 or the first lens 17 in FIG. 9 is placed as close to the light source 4 as possible, and the electron beam 1 is focused at an early stage. As shown in FIG. 11, the Z coordinate of the irradiation lens 2 (or the first lens 17) is changed from z ₁ to z ₂ , and the lens is moved closer to the light source 4 so that h (z This is because the height of the orbit (distance from the Z-axis) decreases from h (z ₁ ) to h (z ₂ ). Here, h (z) orbit, the object surface to position the plane of the light source 4, when the optical axis is Z-axis, the object plane _{Z = Z 0, h (z} 0) = 0, and h '(z ₀ ) = dh (z ₀ ) / dz = 1 (ie u _{0 ′} = 1).

Since the non-linear component of the lens field increases with the distance from the Z-axis, a small value of h (z ₁ ) or h (z ₂ ) corresponds to a ray passing through a small region of the non-linear component of the lens field. To do. Since the spherical aberration coefficient is derived from a non-linear component of the lens field, the spherical aberration coefficient Cc is reduced when the value of h (z ₁ ) or h (z ₂ ) is reduced.

  In order to make the first-stage lens as close to the light source 4 as possible, the first-stage lens may be simply an electrostatic lens. Since the electrostatic lens does not require a coil and can be composed of only electrodes, it can be easily placed in a vacuum without special consideration for the vacuum. Apart from this, a method of using a first-stage lens as a magnetic lens is also known (see, for example, Patent Document 1). In that case, the lens coil is placed in the atmosphere, and a lens magnetic field is locally applied near the light source via a nonmagnetic material. Also known is a method of providing a permanent magnet in a vacuum as a magnetic lens (see, for example, Patent Document 2).

Japanese Patent No. 4146103 (paragraphs 0022 to 0023, FIG. 1) US2007 / 0057617-A1 (paragraphs 0019 to 0020, FIG. 1) JP 2010-21462 A

  Although it is possible in principle to reduce the spherical aberration coefficient by the above-described method, the degree of improvement is actually limited by technical difficulties. First, when the first-stage lens is an electrostatic lens, it cannot be brought closer to the light source 4 side than the extraction electrode (provided immediately after the emitter in the field emission electron gun or the Schottky electron gun). When the first lens is a magnetic lens, it is difficult to apply a local magnetic field in the vicinity of the light source 4 while considering high vacuum and high voltage. Further, when the permanent magnet is provided in a vacuum, degassing from the permanent magnet becomes a problem.

  The present invention has been made in view of such problems, and an object of the present invention is to eliminate current density unevenness caused by spherical aberration by a method different from reducing the spherical aberration coefficient. This is to obtain a beam with high current density uniformity while using a field emission type electron gun or a Schottky type electron gun in the variable shaped electron beam drawing apparatus.

  In order to solve the above problem, the present invention has the following configuration.

  (1) According to the first aspect of the present invention, the charged particle source, the illumination lens group, the stop, the projection lens group, and the material surface are arranged in this order, and the charged particle beam emitted from the charged particle source is the illumination. In the charged particle beam apparatus in which a beam irradiated on the diaphragm through a lens group and further passed through the diaphragm in a state where an image of the diaphragm is formed on a material surface by a projection lens is irradiated on the material. The illumination lens group is arranged so that an image of the charged particle source is not formed on the diaphragm, and one lens of the illumination lens group is in a position optically conjugate with the position of the diaphragm. It is characterized by being arranged in.

  (2) The invention according to claim 2 is characterized in that the lens disposed at a position optically conjugate with the position of the stop is the lens closest to the charged particle source of the illumination lens group. To do.

(3) In the invention according to claim 3, the charged particle source, the illumination lens group, the stop, the projection lens group, and the material surface are arranged in this order, and the charged particle beam emitted from the charged particle source is the illumination lens group. In the charged particle beam apparatus, the beam is irradiated onto the material with the projection lens group irradiating the material with the projection lens group and the image passing through the diaphragm in a state where the image is formed on the material surface. The lens group is arranged so that the image of the charged particle source does not form an image on the stop, and the position and intensity of the illumination lens group are such that the surface on which the charged particle source is located is the object surface and the optical axis is Z An axis, and at a position z = z ₀ of the object surface, a point that intersects the optical axis on the object surface is a starting point,
h (z ₀ ) = 0 and h ′ (z ₀ ) = dh (z ₀ ) / dz = 1
When the spherical aberration trajectory representing the deviation from the paraxial trajectory h (z) becomes s (z),
In the position z = z _a of the diaphragm,
s (z _a ) = 0
It is set so that it may satisfy.

  (4) The invention according to claim 4 is characterized in that the image of the charged particle source is formed at the position of the object side focal plane of the lens closest to the stop side of the illumination lens group.

(5) The invention according to claim 5 is characterized in that the lens group closest to the charged particle source of the illumination lens group is an electrostatic lens.
(6) In the invention according to claim 6, the illumination lens group includes a first lens, a second lens, and a third lens in this order, and a blanker is provided between the second lens and the third lens. An image of the charged particle source is connected between the two lenses and the third lens, and a restriction stop is provided on the charged particle source side from the blanker and on the charged particle source side from the image of the charged particle source. And a leakage beam during blanking by the blanker is suppressed.
(7) In the invention according to claim 7, in the illumination lens group, these are arranged in the order of the first lens and the second lens, and a blanker is arranged between the first lens and the second lens, An image of the charged particle source is connected between the first lens and the second lens, a limiting aperture is provided on the charged particle source side from the blanker, and on the charged particle source side from the image of the charged particle source, It is characterized by suppressing a leakage beam during blanking by a blanker.
(8) The invention according to claim 8, wherein the stop comprises a plurality of stops having at least a first stop and a subsequent stop, and shields scattered electrons originating from the extraction electrode of the charged particle source. The
With respect to scattered electrons having energy that can form an exit pupil relating to the aperture of the extraction electrode of the charged particle source, it is arranged on the first stage aperture side from an optically conjugate position on the charged particle source side with respect to the first stage aperture. And
The aperture diameter of the limiting aperture, the exit pupil relating to the aperture of the extraction electrode of the charged particle source, the mapping of the aperture of the aperture other than the initial aperture of the initial aperture to the aperture of the initial aperture and the aperture of the initial aperture Determining an angle seen from the center of the circumscribed circle of the overlapping portion to be larger than an angle seen from the center of the circumscribed circle, the exit pupil relating to the aperture of the limiting aperture; and
The aperture diameter of the extraction electrode of the charged particle source is determined so that an exit pupil relating to the aperture of the extraction electrode of the charged particle source is larger than a circumscribed circle of the first stage aperture.
(9) In the invention according to claim 9, the charged particle of the first-stage aperture is positioned with respect to the electron having the minimum energy among the scattered electrons having the energy. The object side focal position of the lens located on the source side is used.

  The illumination optical system for the charged particle beam drawing apparatus of the present invention eliminates the height of the spherical aberration trajectory at the position of the first shaping aperture plate, that is, the distance from the Z axis, thereby eliminating the current density unevenness caused by the spherical aberration. Can be eliminated.

  In addition, the illumination optical system for a charged particle beam writing apparatus provided with a limiting diaphragm for shielding the bottom beam of the charged particle beam according to the present invention can suppress a leakage beam at the time of beam blanking and has spherical aberration. The resulting current density unevenness can be eliminated.

  In addition, the illumination optical system for a charged particle beam drawing apparatus provided with a limiting aperture for shielding scattered electrons according to the present invention can remove aberrations originating from scattered electrons from the electrodes of the light source, and is caused by spherical aberration. Uneven current density can be eliminated.

It is a figure which shows the structural example of the illumination optical system used as Example 1 of this invention. It is a figure which shows the h (z) and s (z) orbit in the structural example of FIG. It is a figure which shows the track | orbit of u (z, u0 _' ) in the structural example of FIG. It is a figure which shows the structural example of the illumination optical system used as Example 2 of this invention. It is a figure which shows the structural example of the illumination optical system used as Example 3 of this invention. FIG. 6 is a diagram illustrating h (z) and s (z) trajectories in the configuration example of FIG. 5. It is a figure which shows the prior art example of a variable shaping | molding electron beam drawing apparatus. It is a figure which shows the structural example of the optical system which illuminates the 1st shaping | molding aperture plate. It is a figure which shows the structural example of the optical system which illuminates the 1st shaping | molding aperture plate. It is a figure which shows a mode that the space | interval between light rays changes. The lens principal plane is a diagram showing a h (z) trajectory height h _{(z 1)} and h _{(z 2).} It is a figure which shows the mode of beam blanking. It is a figure which shows the current density distribution of the image 50 of the light source in the blanking aperture plate. It is a figure which shows the structural example of the illumination optical system used as Example 5 of this invention. It is a figure which shows the detailed structural example of a light source. FIG. 15 is a diagram illustrating h (z), k (z), and s (z) trajectories in the configuration example of FIG. 14. 15 is a graph showing h (z), k (z), and | h (z) / k (z) | with respect to z in the configuration example of FIG. 14. It is a figure which shows the structure of the 1st shaping | molding opening 3 board vicinity. It is a figure which shows a mode that a leak beam (beam originating in the light source skirt) is shielded. It is a figure which shows the structural example of the illumination optical system used as Example 6 of this invention. FIG. 21 is a diagram illustrating h (z), k (z), and s (z) trajectories in the configuration example of FIG. 20. It is a figure which shows the track | orbit of the scattered electron originating in an extraction electrode, and the imaginary light source 24. FIG. It is a figure which shows the structural example of the illumination optical system used as Example 8 of this invention. It is a figure explaining the shielding principle of a scattered electron. It is a figure explaining the position of an exit pupil. It is a figure explaining a mode that a scattered electron is not shielded. It is a graph which shows the right side S2 of the same type | formula as the left side S1 of (20) Formula. It is a figure which shows a mode that a scattered electron is shielded. It is a figure which shows the structural example of the illumination optical system used as Example 9 of this invention. It is a figure which shows the aperture diameter of the scattering-electron limiting aperture plate 30 in Example 10 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The configuration of the present invention is the same as that of FIG. 7 except for the configuration from the illumination optical system, that is, the light source 4 to the image 5 of the light source. Therefore, the same components as those in FIG. 7 are denoted by the same reference numerals.
[Example 1]
FIG. 1 shows an illumination optical system for a charged particle beam apparatus proposed in the present invention, that is, a light source 4 to a first shaped aperture plate 3. As shown in FIG. 1, the illumination optical system includes an illumination lens group including a light source 4, a first lens 17, a second lens 18, and an irradiation lens 2, a first molded aperture plate 3, and a blanker 15. Is done. The electron gun constituting the light source 4 is a Schottky electron gun.

The first lens 17 is an electrostatic lens, and the second lens 18 and the third lens 2 are magnetic lenses. The reason why the first lens 17 is an electrostatic lens is that it can be easily installed in a vacuum as described above. However, the first lens 17 may be a magnetic lens.
In order to explain the operation of the apparatus configured as described above, the following conditions are derived: the current density distribution in the first shaped aperture plate 3 is uniform, that is, the distance between the light beams is uniform. However, for simplicity, it is assumed that there is no cause of current density unevenness other than spherical aberration.

First, the ray trajectory in the first shaping aperture plate 3 is expressed by a mathematical formula. If the light ray inclination u _{0 ′} at the light source is used, the above-mentioned paraxial trajectory h (z), that is, the point intersecting the optical axis in the object plane, is set as the starting point, and the inclination with respect to the Z axis is 1 (h ′ (z ₀ ) = 1) And the above-mentioned spherical aberration trajectory s (z), that is, the aberration trajectory representing the deviation from the paraxial trajectory h (z),
u (z, u _{0 ′} ) = u _{0 ′} h (z) + u _{0 ′} 3s (z) (4)
It can be expressed. In the position z = z _a first shaping aperture plate 3, (4) expression
_{u (z a, u 0 '} ) = u 0' h (z a) + u 0 '3s (z a) (5)
It becomes.

FIG. 2 shows the h (z) orbit and s (z) orbit in the optical system of FIG. 1, and FIG. 3 shows the u (z, u _{0 ′} ) orbit of the equation (4). If the Z coordinate of the image plane (Z coordinate of the image 4 ′ or the image 5) is z _i and the magnification is m, s (z _i ) = mC _c .

Next, z = z _a spacing between light beams in _{Δu (z a, u 0 '} ) = u (z a, u 0' + Δu 0 ') -u (z a, u 0')
Dependency on u _{0 '} is examined. Therefore, the partial derivative of u (z _a , u _{0 ′} )

Lead. With this,

It can be expressed.

_{Δu (z a, u 0 '} ) that u _0' depends on, rather than at regular intervals the spacing between beam in z = z _a, corresponds to that there is a current density unevenness. Conversely, in order to reduce the current density unevenness in z = z _{a is, Δu (z a, u 0} ') is u _0' may be so as not to depend on. For this purpose, as can be seen from the equation (6), s (z _a ) may be reduced.

Therefore, if the spherical aberration trajectory s (z) is determined so that s (z _a ) = 0, the equation (5) becomes u (z _a , u _{0 ′} ) = u _{0 ′} h (z _a ) (7 )
(6) becomes Δu (z _a , u _{0 ′} ) = h (z _a ) Δu _{0 ′} (8)
It becomes. In _{this, Δu (z a, u 0} ') Since u _0' does not depend on the current density in the z = z _a is uniform. That is, the current density unevenness due to spherical aberration does not appear on the first shaped aperture plate 3. Further, the current density unevenness due to the spherical aberration does not appear on the surface optically conjugate with the first molded aperture plate 3, that is, on the second molded aperture plate 7 and the material 10 (see FIG. 7). .

In the image plane z = z _i (image 4 ′ or image 5), s (z _i ) = 0 is not satisfied, that is, C _c = s (z _i ) / m = 0 is not satisfied. in the position z = z _a a first shaping aperture plate 3, the conditions to be s (z _a) = 0 is present. In order to set s (z _a ) = 0, the position and strength of each lens are determined so that the main surface of the first lens and the first shaping aperture plate 3 are arranged at optically conjugate positions. Good. The optical system of FIG. 1 is configured as such.

Under such a configuration, it is assumed that the first lens 17 is sufficiently thin, and spherical aberration related to the lens is generated on the main surface of the lens, and is further generated by the second lens 18 and the third lens 2. Assuming that the spherical aberration is sufficiently small, as can be seen from FIG. 2, the spherical aberration trajectory s (z) increases from the position of the first lens, and then the second lens 18 and the third lens 2 is focused by, the s (z _a) = 0 at z = z _a.

  On the other hand, the paraxial trajectory h (z) intersects the Z axis between the second lens 18 and the third lens 2 as can be seen from FIG. The Z coordinate corresponds to the position of the image 4 'in FIG.

Actually, since the first lens 17 has a thickness and the spherical aberration caused by the second lens 18 and the third lens 2 is not zero, strictly speaking, s (z _a ) It is not 0. In order to make s (z _a ) = 0 strictly, the spherical aberration trajectory s (z) is obtained by numerical calculation, and a condition for s (z _a ) = 0 may be searched. That is, in order to find the optimum conditions of the position and intensity of the first lens 17, the second lens 18, and the irradiation lens 2, the paraxial orbital equation and the aberration orbital equation reflecting the electric field or magnetic field distribution of each lens are converged. It is sufficient to solve the condition repeatedly with s (z _a ) = 0.

However, in this case, in addition to s (z _a ) = 0, h (z _i ) = 0 and h (z _a ) = r _a / u _0′max may be _set as convergence conditions. Here, Z-coordinate of z _i is the image 5, r _a is the radius of the irradiated area required to illuminate the opening of the first shaping aperture plate 3, i.e., of the circumscribed circle of the projected figure 11 (see FIG. 7) The radius of the mapping (corresponding to a circle 25 shown in FIG. 18 described later) to the first shaping aperture plate 3 and h (z _i ) = 0 means that the image 5 is at the position of z = z _i . The fact that h (z _a ) = r _a / u _{0′max corresponds} to the fact that the necessary beam current passes through the first shaping aperture plate 3. These conditions are necessary for matching the illumination optical system of FIG. 1 with the optical system after the first shaping aperture plate 3.

  In order to obtain a solution satisfying these three convergence conditions, in the above calculation, three of the total six variables of the position and intensity of the first lens 17, the second lens 18, and the irradiation lens 2 are fixed. The remaining three are variable. For example, the position of the first lens 17 and the position and intensity of the irradiation lens 2 are fixed, and the voltage applied to the first lens 17 (electrostatic lens) and the position and intensity of the second lens 18 are variable. do it.

According to the present invention, the spherical aberration trajectory s (z) is, since the s (z _a) = 0 on the first shaping aperture plate, the current density unevenness of spherical aberration caused can be eliminated.
[Example 2]
The configuration of the second embodiment is basically the same as that of the first embodiment. The operation of the second embodiment is as follows.

In Example 2, as in Example 1, although the spherical aberration trajectory s (z) is s (z _a) = 0 at the position z = z _a first shaping aperture plate 3, FIG. 4 As shown, the position of the image 4 ′ is made to coincide with the object side focal plane position of the third lens 2. At this time, the beam incident on the first shaping aperture plate 3 is a parallel beam, and h ′ (z _a ) = 0.

In this way, since the imaging position of the light source image 5 is infinitely far, the influence of the current density unevenness of the light source 4 and the light source image 5 on the current density distribution on the first shaping aperture plate 3 is small. Become. In the calculation, of the three convergence conditions s (z _a ) = 0, h (z _i ) = 0 and h (z _a ) = r _a / u _0′max , h (z _i ) = It is sufficient to replace 0 with h ′ (z _a ) = 0.
[Example 3]
The configuration of the third embodiment is basically the same as that of the first and second embodiments, but in the third embodiment, the second lens 18 is omitted as shown in FIG. The operation is basically the same as that of the first and second embodiments. That is, as shown in FIG. 6, the spherical aberration trajectory s (z) is in the position z = z _a first shaping aperture plate 3, made to be s (z _a) = 0. However, it is necessary to increase the strength of the first lens 17 in order to compensate for the effect by omitting the second lens 18.
[Example 4]
The configuration of the fourth embodiment is basically the same as that of the first to third embodiments. In the fourth embodiment, an ion beam is used instead of the electron beam. The operation is the same as that of the first to third embodiments.
[Example 5]
The optical system proposed in this embodiment is the same as the illumination optical system for the charged particle beam apparatus proposed in Embodiment 1, but provided with a stop for suppressing a leakage beam during beam blanking. FIG. 7 shows the configuration of the illumination optical system.

  When a figure is drawn by a variable shaping electron beam drawing apparatus as shown in FIG. 7, first, the blanker 15 is operated to block the electron beam 1 (beam blanking), and then the shaping deflector 12, the material stage 14, and the objective. After operating the deflector 13 to determine the shape, size, and position of the projection figure 11, the blocking of the electron beam 1 by the blanker 15 is released, and the projection figure 11 is projected onto the material 10 and exposed for a predetermined time. Repeat a series of operations.

  At this time, at the time of the beam blanking, as shown in FIG. 12, the image 50 of the light source moves with respect to the blanking aperture plate 16, and the electron beam 1 is blocked by the aperture plate 16.

  At this time, if the electron beam 1 is not completely cut off, the electron beam 1 is irradiated onto the material 10, and the exposure amount to the resist becomes excessive, and as a result, the line width of the resist pattern increases. Alternatively, if the exposure amount becomes very large, a leak beam trace remains in the resist.

  This leakage beam originates from the bottom of the image 50 of the light source. The current density distribution of the image 50 of the light source reflects the crossover, that is, the current density distribution (for example, Gaussian distribution) of the light source 4, and generally, as shown by a solid line in FIG. On the optical axis), the current density is highest, and gradually decreases as the radius from the optical axis increases.

  At the time of the beam blanking, as shown in FIG. 13B, the light source image 50 moves from the opening of the blanking aperture plate 16, and the light source image 50 is blocked by the aperture plate 16. If the moving distance is not sufficient, the skirt of the image 50 of the light source covers the blanking opening 16 of the aperture plate 50, and the current component that has passed through the opening becomes a leakage beam.

  FIG. 14 is a schematic diagram illustrating a configuration of an illumination optical system for a charged particle beam apparatus that suppresses a leakage beam according to a fifth embodiment of the present invention. 14, the same symbols as those used in FIG. 1 indicate the same components.

  In FIG. 14, the difference from the irradiation optical system of the charged particle beam drawing apparatus of the first embodiment is that a leakage beam limiting aperture plate 19 that suppresses the leakage beam at the time of beam blanking is provided in front of the blanker 15 (on the light source 4 side). This is a point provided in the preceding stage (light source 4 side) from the light source image 4 ′.

  Here, the reason why the insertion position of the leakage beam limiting aperture plate 19 is set in front of the blanker 15 is to prevent the current density distribution on the first shaping aperture 3 from being changed due to beam blanking. If it is arranged at the latter stage, the position of the electron beam 1 with respect to the opening of the leaky beam limiting aperture plate 19 changes with beam blanking, and the current density distribution of the electron beam 1 passing through the aperture of the limiting aperture plate changes. The current density distribution on the first shaping aperture plate 3 may change. A change in current density on the first shaping aperture plate 3 causes a drawing error (see paragraphs 0010 to 0012 of Patent Document 3).

  The reason why the insertion position of the limiting aperture plate 19 is set to the front stage of the light source image 4 ′ is to reduce the current of the electron beam 1 before the light source image is formed, that is, before the beam diameter is reduced, This is to suppress an increase in electron energy dispersion (velocity dispersion) due to the Bercher effect (see paragraph 0023 of Patent Document 3).

  The opening of the limiting opening plate 19 is circular. Further, the height position of the deflection fulcrum 100 of the blanker 15 is matched with the height position of the first shaping aperture plate 3. The purpose is to prevent the current density distribution on the first shaped aperture plate from changing with beam blanking.

  The electron gun constituting the light source 4 is a Schottky type (thermal field emission type) and comprises a cathode electrode (hereinafter referred to as an emitter electrode) 20, an extraction electrode 23, and an anode electrode 22 as shown in FIG. The emitter electrode 20 is a ZrO / W emitter, and is an emitter that can obtain high brightness by lowering the apparent work function of W (tungsten) with ZrO (zirconium oxide).

  In the irradiation optical system for the charged particle beam drawing apparatus configured as described above, how to determine the insertion position and the aperture diameter of the leakage beam limiting aperture plate 19 will be described below.

First, FIG. 16 shows a paraxial trajectory h (z), a paraxial trajectory k (z), and a spherical aberration trajectory s (z) from the light source 4 of the illumination optical system for the charged particle beam apparatus to the image 5 of the light source. As described above, the paraxial trajectory h (z) is a paraxial trajectory in which h (z ₀ ) = 0 and dh (z ₀ ) / dz = 1, and the k (z) trajectory is k (z ₀ ). = 1 and k (z ₂ ) = 0. As described above, the s (z) trajectory is an aberration trajectory corresponding to a deviation from the h (z) trajectory. Here, z ₀ is the Z coordinate of the light source 4, and z ₂ is the Z coordinate of the first shaping aperture plate 3 (z _a in Examples 1 to 4).

  Actually, the paraxial trajectory h (z), the paraxial trajectory k (z) and the spherical aberration trajectory s (z) are strictly linear before and after the extraction electrode 23 and before and after the anode electrode 22. In FIG. 16, in order to make the operation of the first lens 17 easy to understand, these trajectories in the same region are linearly represented. The light source 4 is a virtual light source.

In the present illumination optical system, the conditions under which the skirt of the light source 4 is strongly restricted, that is, the conditions under which the apparent maximum diameter (effective diameter) a _{0max of the crossover} is reduced are the same as the conditions in the optical system described in Patent Document 3. If the insertion position of the leaky beam limiting aperture plate 19 is z ₁ , | h (z ₁ ) / k (z ₁ ) | becomes smaller (see paragraph 0070 of Patent Document 3). The axial trajectory k (z) is expressed as s (z) in Patent Document 3.) This is a formula for deriving the same condition, that is, (1) formula (see paragraph 0046), (7) formula (see paragraph 0055), (9) formula (see paragraph 0065) described in Patent Document 3, This is because the expression (10) (see paragraph 0067) has no restriction on the shape of the h (z) and k (z) trajectories. Therefore, in the following, the dependence of | h (z) / k (z)) | on Z will be seen.

Paraxial trajectory h (z), paraxial trajectory k (z), and | h (z) / k (z) | obtained by giving specific dimensions to this illumination optical system, and z is abscissa FIG. 17 shows a graph drawn for him. The range of Z in FIG. 17 is the range from the light source 4 to the first molded aperture plate 3 in FIG. 14, and the light source 4, the first lens 17, the second lens 18, the light source image 4 ′, and the irradiation lens. 2, Z coordinates representing the positions of the first shaped aperture plate 3 and the light source image 5 are 0.0, 5.0, 35.5, 69.0 (= z _i1 ), 140.0, respectively. 169.5 (= z ₂ ), 192.0 (unit: mm). However, the spherical aberration derived from the first lens 17 and the irradiation lens 2 was ignored, and the first lens 17 was disposed at a position optically conjugate with the first molded aperture plate 3.

In FIG. 17, | h (z) / k (z) | increases near the first lens 17 and the first molded aperture plate 3, and decreases near the light source 4 and the light source image 4 '. . This is a position optically conjugate with the position of the first shaping aperture plate 3, that is, the position of the first lens 17 if the spherical aberration derived from the second lens 18 and the irradiation lens 2 is ignored. | K (z ₁₁ ) | = 0, | k (z ₂ ) | = 0 at the position of the first shaping aperture plate 3, h (z ₀ ) = 0 at the position of the light source 4, image 4 ′ of the light source This is because h (z _il ) = 0 at the position. Here, z ₁₁ is the Z coordinate of the first lens 17, and z _i1 is the Z coordinate of the image 4 'of the light source.
That is, from the magnitude of | h (z) / k (z) |, in this optical system, a candidate for the insertion position of the leakage beam limiting aperture plate 19 can be a light source 4 or a light source image 4 ′. Nearby.
In order to confirm the generality of this, in the following, the derivative of | h (z) / k (z) | is obtained and its sign is determined. Therefore, the section from the light source 4 to the first shaping aperture plate 3 is divided into three sections, and the first section is divided from the light source 4 to the point where the k (z) trajectory intersects the Z axis, that is, from the light source 4. The section to the first lens 17, the second section, the section from the point where the k (z) trajectory intersects the Z axis to the light source image 4 ′, and the third section from the light source image 4 ′ It is set as a section to 1 shaping opening board 3. However, for convenience, points where h (z) = 0 or k (z) = 0 are not included in these sections.
As shown in FIG. 17, h (z)> 0 and k (z)> 0 in the first interval, h (z)> 0 and k (z) <0 in the second interval, In the interval, h (z) <0 and k (z) <0. Therefore,

Then, equation (9) can be used for the first and third sections.

And in the second leg

It becomes.
Then, if both sides of equations (10) and (11) are differentiated by z, the derivative of r (z)

Is obtained. Here, φ (z) represents an on-axis potential.
In the equations (12) and (13),

Is a paraxial invariant because the paraxial trajectories h (z) and k (z) are linearly independent of each other. That is, it does not depend on z. Using equation (14), equation (12) and equation (13) are respectively

It becomes.

From equations (15) and (16), r (z) increases monotonically in the first and third intervals and decreases monotonously in the second interval as z increases. This result is consistent with the trend shown in the graph of FIG. Therefore, in order to reduce r (z ₁ ) = | h (z ₁ ) / k (z ₁ ) |, the insertion position Z ₁ of the leakage beam limiting aperture plate 19 is set to Z in the first and third sections. It is better to approach the negative side and to the positive side of Z in the second interval. That is, the leakage beam limiting aperture plate 19 is preferably close to the light source 4 in the first section and close to the light source image 4 ′ in the second and third sections. However, the third section is excluded from the candidates for the section into which the leakage beam limiting aperture plate 19 is inserted, from the viewpoint of the Berch effect and the electrode length of the blanker 15. The electrode length of the blanker 15 will be described later.
Therefore, when the remaining two sections are compared, a spatial margin for inserting the leak beam limiting aperture plate 19 is larger in the second section than in the first section, and r (z ₁ ) = | h ( Since the range of Z in which z ₁ ) / k (z ₁ ) | becomes small is wide, the second section is suitable as the section into which the leak beam limiting aperture plate 19 is inserted. The range of Z in which | h (z ₁ ) / k (z ₁ ) | becomes smaller in the second section than in the first section is that the second section itself is larger than the first section itself. In addition to this, as shown in FIG. 17, | k (z ₁ ) | is larger in the second section than in the first section. That is, if | h (z ₁ ) | is the same, r (z ₁ ) = | h (z ₁ ) / k (z ₁ ) | becomes smaller as | k (z ₁ ) | is larger.

To summarize the results of the above examinations here, in this optical system, in order to increase the restriction on the skirt of the light source, the insertion position of the leakage beam restricting aperture plate 19 is set in front of the light source image 4 ′, and then the same. If the insertion position is close to the light source image 4 ′, that is, the distance from the light source image 4 ′ to the leakage beam limiting aperture plate 19 may be shortened. However, in order to determine the distance and further determine the insertion position of the leakage beam limiting aperture plate 19,
1) Restriction of beam current by leakage beam limiting aperture plate 19 2) Position of light source image 4 ′ 3) Position of light source image 5 and influence on current density on first shaped aperture plate 3 need to be considered There is.

First, 1) It is necessary to consider the beam current limitation by the limiting aperture plate because the leakage beam limiting aperture plate 19 is responsible for both the light source tail limitation and the beam current limitation. The beam current limitation by the leaky beam limiting aperture plate 19 becomes weaker as the distance becomes shorter, that is, as the limitation on the bottom of the light source becomes stronger. This is because a ₁ becomes larger with respect to a _{1 min} as a result of a _{1 min} becoming smaller with | h (z ₁ ) |. Here, a ₁ is the opening radius of the leakage beam limiting aperture plate 19, and a _{1 min} is the minimum value of a ₁ represented by equation (2) described in Patent Document 3 (see paragraph 0047).
Two numerical examples of a ₁ and a _{1 min} are shown below together with numerical examples of a 0 _max and D _{3 min} . Here, D _3min is the minimum value of the blanking deflection distance | d (z ₃ ) V | at the position z ₃ of the blanking aperture plate 16 shown in the equation (13 ′) described in Patent Document 3.
For those calculations, the paraxial trajectory h (z) and paraxial trajectory k (z) shown in FIG. 17 are used. However, the current passing through the circle 25 shown in FIG. 18 is 1 μA, and the emission current, that is, the current of the electron beam 1 before the leakage beam limiting aperture plate 19 is 100 μA.

Here, the circle 25 is a circumscribed circle of the opening 21. The opening 21 is an opening (logical product) generated by overlapping the mapping 7 ′ of the opening of the second molded aperture plate 7 onto the first molded aperture plate 3 and the aperture 3 ′ of the first molded aperture plate 3. It is.
As a first numerical example, let us consider a case where the position of the leakage beam limiting aperture plate 19 is 20 mm away from the position z _i1 = 69.0 mm of the light source image 4 ′ and z ₁ = 49.0 mm. In this case, | h (z ₁ ) / k (z ₂ ) | = 0.65 and | k (z ₁ ) | = 6.1.

At this time, if a ₂ = 30 μm, a ₃ = 30 μm, h (z ₃ ) = 0, and | k (z ₁ ) / k (z ₃ ) | = 1/3, Equation (7) described in Patent Document 3 From the paragraph 0055, a ₁ = 30 μm and a _1min = 20 μm. Here, a ₂ is the radius of the circle 25, and a ₃ is the opening radius of the blanking opening plate 16. By substituting these numerical values into equation (9) described in Patent Document 3 (see paragraph 0065) and equation (13 ′) described in Patent Document 3 (see paragraph 0087), a _0max = 8.1 μm, D _{3 min} = 177 μm.

The beam current passing through the leakage beam limiting aperture plate 19 is 2.3 μA when simply calculated from the area ratio (a _{1 min} / a ₁ ) ² . That is, 98% of the emission current is shielded by the leakage beam limiting aperture plate 19. In this example, it can be said that the limitation of the bottom of the light source and the limitation of the beam current are sufficient.

As a second numerical example, let us consider a case where the position of the leakage beam limiting aperture plate 19 is very close to the position z _il = 69.0 mm of the light source image 4 ′ and z ₁ = 67.8 mm. In this case, a ₁ = 11 μm, a _1min = 1.2 μm, a _0max = 2.0 μm, and D _3min = 67 μm. That is, the restriction on the skirt of the light source becomes stronger, and the necessary blanking deflection distance becomes smaller.

However, if the beam current passing through the leakage beam limiting aperture plate 19 is simply calculated from the area ratio (a _{1 min} / a ₁ ) ² , it becomes as large as 86 μA. This is about 40 times the beam current value in the first numerical example. At this time, the ratio of the emission current shielded by the leakage beam limiting aperture plate 19 is as small as 14%. In this case, the leakage beam limiting aperture plate 19 hardly plays a role of limiting the beam current.

  2) It is necessary to consider the position of the image 4 ′ of the light source because the blanker 15 is arranged at a stage subsequent to the leakage beam limiting aperture plate 19, and therefore the insertion position of the leaking beam limiting aperture plate 19 depends on the electrode length of the blanker 15. Is subject to restrictions. In other words, the position of the light source image 4 ′ indirectly determines the electrode length of the blanker 15. Therefore, even if the leakage beam limiting aperture plate 19 is in the second section, the electrode length is shortened depending on the position of the light source image 4 ′.

  In order to secure the blanking deflection distance, it is necessary to reduce the distance between the opposing electrodes of the blanker 15, which is a problem such as adhesion of contamination to the surface of the electrode and charging thereof. Is increased. That is, it is required to increase the electrode length of the blanker 15 while shortening the distance from the light source image 4 ′ to the leakage beam limiting aperture plate 19.

  In order to do so, the light source image 4 ′ may be moved to the light source 4 side together with the leakage beam limiting aperture plate 19. In other words, in the present optical system, the position of the light source image 4 ′ is preferably such that the distance from the second lens 18 to the light source image 4 ′ is shorter than the distance from the light source image 4 ′ to the irradiation lens 2.

  If this idea is pushed forward, the position of the light source image 4 ′ and the distance from the light source image 4 ′ to the leakage beam limiting aperture plate 19 are determined after the electrode length of the blanker 15 is determined. Is good. That is, the upper end of the blanker 15 is immediately after the second lens 18 or the lower end of the blanker 15 is immediately before the irradiation lens 2, and the electrode length of the blanker 15 is made as long as possible. The 19 positions may be determined. As a result, depending on the case, the insertion position of the leakage beam limiting aperture plate 19 can be in the second lens 18 or on the light source 4 side thereof.

  3) It is necessary to consider the influence on the position of the light source image 5 and the like, in order to change the position of the light source image 4 ′, optical parameters such as the intensity of the first lens 17 and the second lens 18 are set. When the change is made, the position of the image 5 of the light source is also changed in conjunction with the change. In other words, designing the present optical system is to determine the optical parameters so as to satisfy the respective conditions such as the position of the light source image 4 ′ and the position of the light source image 5.

  More specifically, in the present optical system, items to which conditions for determining optical parameters are added are: A) the position of the light source image 4 ′, B) the position of the light source image 5, and C) the blanking deflection fulcrum. Position, D) Position where the spherical aberration trajectory intersects the Z axis, and E) Five items of current density on the first shaped aperture plate 3. The conditions regarding these five items will be described below.

First, A) The condition relating to the position of the source image 4 'is that the position matches the optimum position from the viewpoint of the intensity of the light source tail restriction and the beam current restriction. If z _il is used for the position, the condition is | h (z _il ) | = 0. Next, the condition regarding the position of the image 5 of the source B) is that the same position coincides with the position of the image 5 of the light source in the optical system of FIG. _Assuming that position z _i2 , the condition is | h (z _i2 ) | = 0.

Next, a condition regarding C) the ranking deflection fulcrum position and D) a position where the spherical aberration trajectory intersects the Z axis is that these positions coincide with the position of the first shaping aperture plate 3. These conditions are | d (z ₂ ) | = 0 and | s (z ₂ ) | = 0, respectively. Here, d (z) represents a blanking deflection trajectory with respect to a unit blanking deflection voltage.

Next, the condition regarding the current density on the shaped aperture plate 3 of E) 1 is that the current density is the current density of the projected shape 11 and the projection of the projected shape 11 on the basis of the first shaped aperture plate 3. It is equal to the current density determined from the magnification.
Here, the target value of the current density on the first shaping aperture plate 3 is J ₂ , the current density of the projection figure 11 is J, and the projection magnification of the projection figure 11 based on the first shaping aperture plate 3 is m. In other words, there is a relationship of J ₂ = m ² J.

However, the condition regarding a current density in the first shaping aperture plate on 3, the current required to illuminate the interior of the circle 25 in FIG. 18 at a current density J ₂

The radius of the cross section a ₂ ′ = | h (z ₂ ) | α _{0 at} the position of the first shaping aperture plate 3 coincides with the radius of the circle 25, that is,

Is equivalent to That is, the condition regarding the current density on the first molded aperture plate 3 is expressed by the equations (17) and (18):

It can be expressed. Here, α ₀ is an electron emission angle (opening angle) in the light source 4 (virtual light source),
_JΩ is the angular current density of the light source 4. On the other hand, the optical parameters to be determined in this optical system are the brightness and angular current density of the electron gun, the position of the light source 4, the position and intensity of the first lens 17, the position and intensity of the second lens 18, and the irradiation lens 2. And the position of the blanker 15 and the deflection angle ratio (see paragraph 0010 of Patent Document 3), and the position of the first molded aperture plate 3. In order to satisfy the conditions regarding the above five items, five of these optical parameters may be made variable, and the degree of freedom of the present optical system may be set to five.

  Which five of the optical parameters are variable may be determined from physical constraints related to them. In this embodiment, among the optical parameters, a) the intensity of the first lens 17, b) the position of the second lens 18, c) the intensity of the second lens 18, d) the intensity of the irradiation lens 2, and e) Five of the deflection angle ratios of the blanker 15 are set as variable parameters, and the rest are set as fixed parameters. Specific numerical values of these fixed parameters are determined based on physical restrictions relating to them and target device specifications.

In order to determine the variable parameter so that the five conditions are satisfied, the magnetic field / electric field distribution on the Z axis is obtained, and then the five conditions are set as the convergence condition, and the paraxial trajectory h (z), In order to obtain the axial trajectory k (z), blanking deflection trajectory d (z), and spherical aberration trajectory s (z) trajectory, the paraxial trajectory equation and the aberration trajectory equation reflecting the variable / fixed parameters and the magnetic field / electric field distribution are used. Can be solved numerically by changing the value of the variable parameter until the solution converges. However, the paraxial trajectory h (z) and the paraxial trajectory k (z) shown in FIG. 17 of the above-described embodiment are obtained by approximating each lens with a thin lens and then calculating the lens formula l _o ⁻¹ + l _i ^{−. This} is simply obtained by using ¹ = f ⁻¹ . l _o is the distance from the object surface to the lens principal surface, l _i is the distance from the lens principal surface to the image surface, and f is the focal length. In FIG. 17, the spherical aberration derived from the second lens 18 and the irradiation lens 2 is ignored, and the first lens 17 is disposed at a position optically conjugate with the first shaping aperture plate 3. Orbital condition | s (z ₂ ) | = 0 was replaced by | k (z ₁₁ ) | = 0.

  Among the five variable parameters, a) the intensity of the first lens 17, c) the intensity of the second lens 18, and d) the intensity of the irradiation lens 2 design, construct, and adjust the optical system. However, even after starting the operation, it is easy to make it variable. That is, when operating the apparatus, these three parameters can be used as variable parameters. Here, the remaining two, ie, the position of the lens 18 and the deflection angle ratio of the blanker 15 are fixed parameters.

  By doing so, the degree of freedom during operation of the apparatus is 3, and for example, on the assumption that the change in the position of the light source image 4 'and the position of the blanking deflection fulcrum 100 is within an allowable range. , The current density on the first shaped aperture plate 3, and the position where the spherical aberration trajectory intersects the Z axis can be set independently. Alternatively, on the assumption that the change in the position of the light source image 4 ′ and the position where the spherical aberration trajectory intersects the Z axis are within an allowable range, the position of the light source image 5 and the current density on the first shaped aperture plate 3 , And the blanking deflection fulcrum position can be set independently. Supplementally, keeping the blanking deflection fulcrum position at the position of the first shaping aperture plate 3 corresponds to keeping the intensity of the irradiation lens 2 optimized with respect to the blanking deflection fulcrum position. That is, at this time, the intensity of the irradiation lens 2 is substantially a fixed parameter.

  As described above, with respect to the illumination optical system for the charged particle beam drawing apparatus according to the fifth embodiment of the present invention, the insertion position and the aperture diameter of the leakage beam limiting aperture plate 19 are determined together with the optical parameters.

  FIG. 19 shows how the leaked beam originating from the skirt of the light source is shielded in this optical system. In the figure, as indicated by the solid line, electrons emitted from the central portion of the light source 4 and directed to the inside of the circle 25 on the first molded aperture plate 3 pass through the aperture of the limiting aperture plate 19. As indicated by the broken line, electrons emitted from the skirt of the light source 4 and directed toward the inside of the circle 25 are largely bent by the first lens 17 and are placed on the limiting aperture plate 19, so that the blanking aperture plate is used during beam blanking. There is no leakage beam from 16.

As described above, in the illumination optical system for the charged particle beam apparatus for suppressing a leakage beam according to the present invention, the leakage beam limiting aperture plate 19 is disposed in front of the blanker 15 and in front of the light source image 4 ′. Thus, the position of the charged particle beam with respect to the leakage beam limiting aperture plate 19 is prevented from changing together with the beam blanking, and further, the beam blanking originating from the skirt of the light source 4 is suppressed while suppressing the Bercher effect in the image 4 ′ of the light source. Leakage beams during ranking can be suppressed.
[Example 6]
The sixth embodiment basically has the same configuration as that of the fifth embodiment, but in the sixth embodiment, the second lens 18 is omitted as shown in FIG. FIG. 21 shows a paraxial trajectory h (z), a paraxial trajectory k (z), and a spherical aberration trajectory s (z) from the light source 4 to the light source image 5 in the illumination optical system of FIG.
Although the operation and effect of the sixth embodiment are basically the same as those of the fifth embodiment, the optical parameters to be variable are different from those of the fifth embodiment because the second lens 18 is omitted.

  In this embodiment, at the time of designing and adjusting the apparatus, five parameters are set as variable parameters: the position of the light source 4, the intensity of the first lens 17, the position and intensity of the irradiation lens 2, and the deflection angle ratio of the blanker 15. The brightness and angular current density of the electron gun, the distance from the light source 4 to the first lens 17, the position of the blanker 15, and the position of the first shaping aperture plate 3 are set as fixed parameters.

During operation of the apparatus, among the five variable parameters, the three parameters of the position of the light source 4, the position of the irradiation lens 2, and the deflection angle ratio of the blanker 15 are fixed parameters, and the remaining two, that is, the first lens 17. And the intensity of the irradiation lens 2 are variable parameters. As a result, the degree of freedom during operation of the apparatus is 2, and for example, the change in the position of the light source image 4 ′, the blanking deflection fulcrum 100 position, and the position where the spherical aberration trajectory s (z) intersects the Z axis is within an allowable range. It is possible to set the position of the image 5 of the light source and the current density on the first shaped aperture plate 3 independently.
[Example 7]
The configuration of the seventh embodiment is basically the same as that of the fifth to sixth embodiments. In the seventh embodiment, an ion beam is used instead of the electron beam. The operation and effect are the same as those of the fifth and sixth embodiments.
[Example 8]
The optical system proposed in the eighth embodiment is obtained by providing a stop for shielding scattered electrons in the configuration of the illumination optical system for the charged particle beam apparatus proposed in the first embodiment.

  The electron gun constituting the light source 4 is a Schottky type (thermal field emission type) electron gun, and comprises an emitter electrode 20, an extraction electrode 23, and an anode electrode 22, as shown in FIG. The extraction electrode 23 is an electrode for increasing the electric field at the tip of the emitter electrode 20 and extracting more electrons from the emitter electrode 20. Since the potential in the extraction electrode 23 and the space thereafter is higher than the potential of the emitter electrode 20, the electron beam 1 emitted from the emitter electrode 20 collides with the edge of the opening of the extraction electrode 23.

  As a result, as shown in FIG. 22A, electrons are scattered at the edge of the opening of the extraction electrode 23. When this scattered electron trajectory is extended to the light source 4 side, as shown in FIG. 22B, an imaginary light source 24 having a larger spread is formed so as to overlap the light source 4 at the position of the light source. That is, the scattered electrons appear to come from the imaginary light source 24 when viewed from a point after the extraction electrode 23. Then, the light beam having the starting point in the imaginary light source 24 is positioned at the positions of the light source images 4 ′, 5 and 50, and further at the position of the light source image (not shown) connected in the objective lens 9. Construct an image of That is, the scattered electrons become beam components having a larger spread than the original image at the positions of the image images 4 ′ and 5 of these light sources.

  This beam component becomes a beam component with large aberration at the time of exposure, and the opening angle with respect to the objective lens 9 becomes large due to the image of the imaginary light source 24 connected to the position of the light source image 4 ′, and depends on the opening angle. Aberration (geometric aberration and chromatic aberration) increases. Further, the electrons scattered by the edge of the opening of the extraction electrode 23 show a large energy dispersion as a result of losing kinetic energy in the process of scattering, and the scattered electrons may cause chromatic aberration.

  FIG. 23 is a schematic diagram showing a configuration of an optical system proposed in this embodiment, that is, an illumination optical system for a charged particle beam apparatus that shields scattered electrons generated from an electrode of a light source. 23, the same symbols as those used in FIG. 1 indicate the same components.

  The optical system of FIG. 23 is different from the optical system of FIG. 1, that is, the irradiation optical system for the charged particle beam drawing apparatus of Example 1, in that the scattered electron limiting aperture plate 30 that shields scattered electrons originating from the extraction electrode 23 is used. It is a point with. The position is closer to the first molded aperture plate than the surface 31 that is optically conjugate with the first molded aperture plate 3 with respect to the scattered electrons.

  In the illumination optical system of FIG. 23, the first lens 17, the second lens 18, and the irradiation lens 2 are magnetic lenses, the opening of the blanking aperture plate 16 is circular, the center of the light source 4, and the emitter electrode 20 , The center of the opening of the extraction electrode 23 and the anode electrode 22, the center of the first lens 17, the irradiation lens 2, and the molded lens 6, the center of the opening of the blanking aperture plate 16, and the center of the circle 25 (see FIG. 18) , And the center of the mapping of the circle 25 onto the second shaping aperture plate 7 is on the Z axis.

  How to determine the insertion position and the aperture diameter of the scattered electron limiting aperture plate 30 in the irradiation optical system configured as Example 8 of the present invention will be described below.

In order to shield the scattered electrons from the extraction electrode 23, the scattered electrons may be prevented from passing through the circle 25 (FIG. 18) on the first shaped aperture plate 3. The condition for satisfying this requirement is that the light beam passing through the circle 25 starting from the edge of the extraction electrode 23 is shielded by the scattered electron limiting aperture plate 30.
In other words, as shown in FIG. 24 (a), the above-mentioned condition is that light rays passing through a circle 25 on the first shaping aperture plate 3 starting from the edge of the exit pupil 23 ′ relating to the opening of the extraction electrode 23 are This is to be blocked by the exit pupil 30 ′ related to the scattered electron limiting aperture plate 30.

  Here, the exit pupil is scientifically defined as an image of an aperture stop that is imaged by an optical system on the image side of the aperture stop.

The position of the exit pupil in the irradiation optical system for the charged particle beam drawing apparatus of the present invention is:
This depends on the positions of the extraction electrode 23 and the scattered electron limiting aperture 30, and the energy of the scattered electrons. In FIG. 25, the exit pupil 23 'is located closer to the light source 4 than the first shaping aperture plate 3, and the exit pupil 30' is located closer to the light source image 5 than the first shaping aperture plate 3. Therefore, the positions of these exit pupils can be on the light source 4 side or the light source image 5 side from the first shaping aperture plate 3.

  In FIG. 24A, from the geometric relationship between the circle 25 on the first shaping aperture plate 3 and the exit pupils 23 ′ and 30 ′, the condition is

It can be expressed. If both sides of equation (20) are multiplied by | l _e |

It becomes. Here, a _e ′ is the radius of the exit pupil 23 ′ related to the extraction electrode 23, a ₁ ′ is the radius of the exit pupil 30 ′ related to the scattered electron limiting aperture plate 30, and a ₂ is a circle 25 on the first shaping aperture plate 3. , L _e is the distance from the first shaping aperture plate 3 (from the circle 25) to the exit pupil 23 ′, and l ₁ is the distance from the first shaping aperture plate 3 to the exit pupil 30 ′. a _e 'and _{a 1'} is the magnification of the exit pupil 30 'relative to the opening of the scattered electrons limiting aperture plate 30 _{m 1,} if the magnification of the exit pupil 23' relative to the opening of the lead electrode 23 and _{m e,} respectively, a _e ′ = | m _e | a _e and a ₁ ′ = | m ₁ | a ₁ . a _e is the radius of the aperture of the extraction electrode 23, and a ₁ is the radius of the aperture of the scattered electron limiting aperture plate 30. The signs of l _e and l ₁ are positive if the exit pupils 23 ′ and 30 ′ are on the positive side (material side) of Z with respect to the first shaping aperture plate 3. In the following description, the expression (21) is mainly used instead of the expression (20) for convenience.

There are three necessary conditions for satisfying the equation (21). The first condition among them is l ₁ ≠ 0, that is, the Z coordinate of the exit pupil 30 ′ does not coincide with the Z coordinate of the first shaping aperture plate 3, and the second condition is θ _e > The _first condition is θ ₁ (see FIG. 24B), and the third condition is that a _e ′ ≧ a ₂ when l _e = 0. Θ _e = a _e ′ / | l _e | (> 0) is an angle at which the exit pupil 23 ′ is viewed from the center of the circle 25 of the first shaping aperture plate 3, and θ ₁ = a ₁ ′ / | l ₁ | (> 0) indicates the angle at which the exit pupil 30 ′ is viewed from the center of the circle 25. When the first condition is not satisfied, that is, when l ₁ = 0, the left side of Equation (21) is − | l _e | a ₂ (<0), but the right side is | l _e | a _{Since 1} ′ (> 0), equation (21) does not hold.

Further, when the second condition is not satisfied, that is, when θe ≦ θ1, | l ₁ | a _e ′ ≦ | l _e | a ₁ ′, and | l _e −l ₁ | a from both sides _If you subtract ₂ ,
_{| L 1 | a e'- |} l e -l 1 | a 2 ≦ | l e | a 1'- | l e -l 1 | a 2 <| l e | As can be seen from the _{a 1} ' ,
Also in this case, equation (21) does not hold.

When the third condition is not satisfied, that is, when a _e ′ <a ₂ when l _e = 0, the left side of the equation (21) is | l ₁ | a _e ′ − | l ₁ | A ₂ = | l ₁ | (a _e '-a ₂ ) (<0)
Similarly, since the right side of equation (21) is zero, equation (21) does not hold in this case as well.
However, since the quantities m _e , m ₁ , l _e , l ₁ , and a _e ′ = | m _e | a _e , a ₁ ′ = | m ₁ | a ₁ depend on the energy of electrons, Depending on the magnitude of energy dispersion and the dependence of the amount of electrons on the energy, the above three conditions may not be satisfied. In other words, the three conditions need to be satisfied regardless of the energy of electrons.
Next, energy dispersion of electrons in the irradiation optical system of the charged particle beam drawing apparatus of the present invention will be described. Hereinafter, the energy of electrons is expressed as a potential with respect to the emitter electrode 20, that is, as a voltage V to emitter. Therefore, the quantities m _e , m ₁ , l _e , l ₁ , a _e ′, a ₁ ′ are functions of the emitter voltage V. Assuming that the voltage applied to the extraction electrode 23, that is, the extraction voltage is V _e (> 0), the energy −V = V _e + ΔV of the electrons scattered by the extraction electrode 23 and having a velocity vector in the positive direction of Z is , 0 <V _e + ΔV ≦ V _e . That is,

The relationship holds. Note that ΔV represents a change in energy. Although scattering of electrons by the extraction electrode 23 is accompanied by generation of secondary electrons, the expression (22) is established even if the secondary electrons are included.

Here, ΔV ≦ 0 means that electrons lose energy in the scattering process. Since the extraction voltage is generally several kV, the size V _e of the width or energy dispersion in the range of ΔV, like large as several kV. Therefore, hereinafter, energy dispersion other than energy dispersion caused by scattering is ignored. Such energy dispersion is due to the energy dispersion possessed by the electrons at the time of emission from the emitter electrode 20 and the energy dispersion increased by the Berchet effect thereafter. This is because it is as small as several volts.
As described above, V _e can be several kV or more. Therefore, depending on the magnitude of V _a , the energy dispersion causes _a large chromatic aberration that cannot be ignored. Here, V _a is _a potential in the anode electrode 22 and the space thereafter. In particular, since the first lens 17 is between the extraction electrode 23 and the anode electrode 22, the axial potential at the position of the first lens 17 is in the range of V _e <V <V _a , and thus the energy dispersion is A very large chromatic aberration is produced with respect to the first lens 17.

Next, conditions for satisfying the above three conditions for electrons satisfying the equation (22) will be described. However, the radius a ₂ of the circle on the first shaping aperture plate 3, since an amount determined and a projection magnification and size of the projected figure 11, and fixed later.

In order to satisfy the first condition l ₁ ≠ 0, that is, in order to prevent the Z coordinate of the exit pupil 30 ′ from coinciding with the Z coordinate of the first shaping aperture plate 3, Equation (22) For the electrons to be filled, the position of the scattered electron limiting aperture plate 30 is optically conjugate with the first molded aperture plate 3 and is the surface 31 closest to the first molded aperture plate 3 (see FIG. 23). The position may be closer to the first shaping aperture plate 3 than the position of the reference). For this purpose, as the most severe condition, the condition that the position of the scattered electron limiting aperture plate 30 is closer to the first shaped aperture plate 3 side than the position of the surface 31 with respect to electrons satisfying ΔV = −V _e is satisfied. It only has to be done. If so, l ₁ > 0. This is because the position of the exit pupil 30 'moves in the positive direction of Z as ΔV increases.

In order to satisfy the second condition θ _e > θ ₁ , a ₁ ′ is made as small as possible for electrons satisfying the expression (22) within a range that does not affect the current density and the distribution of the projection figure 11. In addition, it is preferable to increase the radius ae of the opening of the extraction electrode 23 after increasing | l ₁ |. Here, in order to make a ₁ ′ as small as possible and | l ₁ | as large as possible, the radius of the aperture of the scattered electron limiting aperture plate 30 is as much as possible within the range that does not affect the current density and its distribution of the projected figure 11. a ₁ should be small and z ₁ should be as large as possible on the positive side of Z.

  According to Patent Document 3, the conditions under which the scattered electron limiting aperture plate 30 does not affect the current density of the projection figure 11 and its distribution are:

It is. Here, _{a 3} opening radius, _{z 3} of the blanking aperture plate 16 is the Z coordinate of the blanking aperture plate 16, h (z) and k (z) is the foregoing paraxial trajectory.

From equation (23), it can be seen that h (z ₁ ) should be reduced in order to reduce the opening radius a ₁ of the scattered electron limiting aperture plate 30. For this purpose, the position of the scattered electron limiting aperture plate 30 may be brought close to the position of the light source image 4 ′.

In order to satisfy the third condition, that is, the condition that a _e ′ ≧ a ₂ when l _e = 0, the position of the exit pupil 23 ′ among the electrons satisfying the expression (22) is set to the first shaping. Radius a _e ′ = | m _e | a of the exit pupil 23 ′ with respect to the energy having the energy matching the position of the aperture plate 3, that is, the electron having the energy that connects the image of the extraction electrode 23 onto the first shaped aperture plate 3. _e as is greater than the radius a ₂ of the circle 25, or by increasing the radius a _e of the opening of the lead electrode 23.

However, even if l _e ≠ 0, if l _e and l ₁ have different signs, when a _e ′ ≦ a ₂ , the edge of the exit pupil 23 ′ is used as the starting point as shown in FIG. A light beam that passes through the circle 25 on the one shaped aperture plate 3 and further passes through the exit pupil 30 ′ always exists regardless of the size of l ₁ or a ₁ . That is, some of the electrons scattered by the extraction electrode 23 are not shielded by the scattered electron limiting aperture plate 30 and pass through the circle 25. Since this must be avoided, it is preferable that a _e ′> a ₂ for all electrons satisfying the formula (22), not limited to electrons having energy with l _e = 0. That is, the third condition may be replaced with this.

In the irradiation optical system of the present invention shown in FIG. 23, when the signs of l _e and l 1 are different, as shown in FIGS. 24 to 26, l ₁ > 0 and l _e <0. Here, l ₁ > 0 is that the position of the exit pupil 30 ′ is on the first shaping aperture plate 3 side with respect to the surface 31 position with respect to the electrons satisfying ΔV = −V _e as described above. It is a result.

After the above three conditions of l ₁ ≠ 0, θ _e > θ ₁ , and a _e ′> a ₂ are satisfied by the above measures, finally, for the electrons satisfying the equation (22), the equation (21) Confirm that is true. This is because the three conditions are necessary conditions for the expression (21) to be satisfied, but the expression (21) may not be satisfied even if the three conditions are satisfied. For example, if a ₂ = 0, Equation (21) holds as long as the second condition θ _e > θ ₁ is satisfied, but if a 2 ≠ 0, the same condition is satisfied. However, equation (21) does not always hold.

Here, the size of the radius a2 of the circle 25 on the first shaping aperture plate 3 cannot be ignored when ΔV increases in the negative direction. If this is explained using the equation (20), when ΔV increases in the negative direction, both | l ₁ / l _e | and a _e ′ = | m _e | a _{e in the} equation (20). Because can be smaller. As a result, the first term | l ₁ / l _e | a _e ′ of the equation (20) becomes small, and the second term − | 1−l ₁ / l _e | a ₂ of the equation becomes relatively large.

In order to solve this problem, in order to make the first term | l ₁ / l _e | a _e ′ of Equation (20) as large as possible, l ₁ is made as large as possible in the positive direction, that is, the scattered electron limiting aperture plate 30 the position z ₁ after having as large as possible in the positive direction, it is preferable to increase the radius a _e of the opening of the lead electrode 23. Furthermore, when the position z ₁ of the scattered electron limiting aperture plate 30 is increased in the positive direction, the radius a of the aperture of the scattered electron limiting aperture plate 30 is within a range that does not affect the current density and the distribution of the projection figure 11. ₁ should be made small, that is, a ₁ should be made small according to the equation (23). By doing so, the right side a ₁ = | m ₁ | a ₁ of the equation (20) becomes small, and the equation (20) is more easily established. As a result, it is possible to more strongly suppress Berger effects in (20) to minimize the radius a _e of the opening of the lead electrode 23 to the extent that expression is established, the extraction electrode 23 or later.

However, in this embodiment, the scattered electrons limiting aperture plate 30 because there the front (light source side) than the blanker 15, a larger z ₁ in the positive direction, the electrode length of the blanker 15 is shortened. In other words, the upper limit of z ₁ is determined by the electrode length required for the blanker 15. In the present embodiment, the reason why the position of the scattered electron restricting aperture plate 30 is set in front of the blanker 15 is to prevent the condition that the expression (21) is satisfied from being broken by beam blanking.

Next, in order to apply the irradiation optical system for the charged particle beam apparatus of the present invention to an actual electron beam drawing apparatus, the above quantities m _e , m ₁ , l _e , l ₁ , θ _e , and θ ₁ are set to paraxial. A method of obtaining from the orbit will be described.

First, among the above amount _{of, m e, m 1, l} e, l 1 is a paraxial trajectory _t e in the optical system (z) paraxial trajectory _t 1 (z) paraxial trajectory _w e (z ), And a relational expression m _e = (dt _e (z ₂ ) / dz) l _e using the paraxial trajectory w ₁ (z),
m ₁ = (dt ₁ (z ₂ ) / dz) l ₁ ,
_{l e = -w e (z 2} ) / (dw e (z 2) / dz),
l ₁ = −w ₁ (z) / (dw ₁ (z ₂ ) / dz),
Can be obtained from

Then, θ _e and θ ₁ are | dt _e (z ₂ ) / dz | = | m _e / l _e |, | dt ₁ (z ₂ ) / dz | = | m ₁ / l ₁ from the geometric relationship. ｜
If we take advantage of

Can be obtained from

Here, t _e (z) is t _e (z _e ) = 1 at the position z = z _e of the extraction electrode 23 and t _e (z ₂ ) = 0 at the position z = z ₂ of the first shaping aperture plate 3. paraxial _{trajectory, t} 1 (z) is _t 1 _(z 1) = 1 and _t 1 _(z 2) = 0 and becomes paraxial _{trajectory, w} e (z) is _w e _(z e) = 0 and that the A paraxial orbit where dw _e (z _e ) / dz = 1, and w ₁ (z) is a paraxial orbit where w ₁ (z ₁ ) = 0 and dw ₁ (z ₁ ) / dz = 1.
As can be seen from the equations (24) and (25), θ _e and θ ₁ can be obtained by calculating dt _e (z ₂ ) / dz and dt ₁ (z ₂ ) / dz, respectively, without obtaining the magnifications me and m1. Can be obtained from _Here, since the expressed as _t 1 (z) _t 1 using _t e (z) is _{(z) = t e (z} ) / t e (z 1), dt 1 (z 2) / dz is dt _{1 (z 2) / dz =} | (dt e (z 2) / dz) / t e (z 1) | and it may be. That is, (25) of the theta ₁ is _{θ 1 = | (dt e (} z 2) / dz) / t e (z 1) | a 1 and expressed. With this relationship, condition θ _e> θ ₁ described _{above, | dt e (z 2)} / dz | a e> | (dt e (z 2) / dz) / t e (z 1) | a 1 That is, a _e > a ₁ / | t _e (z ₁ ) | can be replaced.

In order to obtain the four paraxial trajectories, the trajectory equation reflecting the axial potential V (z) and the axial magnetic field B (z) in the present optical system may be solved. At this time, in order to reflect ΔV in the trajectory equation, the on-axis potential V (z) may be replaced with V (z) + ΔV. However, since the orbital equation cannot be solved for electrons satisfying V (z) + ΔV = 0, immediately after being scattered by the extraction electrode 23, 0 ≦ V _e + ΔV <δV, that is, −V _e ≦ ΔV <−. ignore electrons filling the V _e + .DELTA.V, it may be carried out calculations for electrons filling the _{δV ≦ V e + ΔV ≦ V} e i.e. _{-V e + δV ≦ ΔV ≦ 0} . Here, a 0 ≦ δV << _{V e.}

Specific dimensions are given for this optical system, and the left side S1 = (l ₁ / l _e | a _e ′ − | 1−l ₁ / l _e | a ₂ of the equation (20) and the right side S2 = a _{1 of the} equation (20). The result obtained by calculating 'as a function of ΔV is shown in FIG. S1 and S2 in the figure are obtained according to the above procedure.

Here, the light source 4, the extraction electrode 23, the first lens 17, the anode electrode 22, the second lens 18, the scattered electron limiting aperture plate 30, the light source image 4 ′, the irradiation lens 2, and the first molded aperture plate 3. The Z coordinate of the image 5 of the light source is z = 0, 0.5, 2.0, 20.0, 52.5, 90, 108.6, 170.0, 200.0, and 220 (respectively). (Unit: mm), the aperture of the extraction electrode 23, the aperture of the scattering electron limiting aperture plate 30, and the radius of the circle 25 are a _e = 100, a ₁ = 20, and a ₂ = 14 (unit: μm), the extraction electrode The voltage applied to both the anode 23 and the anode electrode 20 (both with respect to the emitter voltage) is V _e = 8 and V _a = 50 (unit: kV). The intensity of the first lens 17, the light source image 4 ′, the light source image, and the irradiation lens 2 is such that the light source images 4 ′ and 5 are connected by the Z coordinate and the spherical aberration trajectory is the first shaped aperture plate 3. It is determined to be zero at the Z coordinate.

From the relationship between S1 and S2 shown in FIG. 27, it can be seen that since S1 is larger than S2, this optical system satisfies the expression (21) under the above conditions. The electrons scattered by the extraction electrode 23 do not pass through the circle 25 on the first shaping aperture plate 3. In FIG. 27, S1 becomes extremely large in the region near ΔV = −5 (unit: kV). The distance l _e from the first shaping aperture plate 3 to the exit pupil 23 ′ approaches zero in the region. It depends.

  FIG. 28 shows how scattered electrons from the extraction electrode 23 are shielded in the optical system of the present invention. The solid line in the figure indicates the trajectory of the electron beam emitted from the light source 4, and the broken line indicates the trajectory of the electrons scattered by the extraction electrode 23. As shown in the figure, the electrons emitted from the center of the light source 4 and directed to the circle 25 on the first shaping aperture plate 3 pass through the opening of the scattered electron limiting aperture plate 30, whereas at the extraction electrode 23. The scattered electrons are greatly bent by the first lens 17 and placed on the scattered electron limiting aperture plate 30. For this reason, aberrations derived from scattered electrons are removed.

As described above, in the illumination optical system for the charged particle beam apparatus according to the present invention, the scattered electron limiting aperture plate 30 is first molded from a position optically conjugate with the first molded aperture plate 3 with respect to the scattered electrons. It is arranged on the aperture plate side, the position and aperture diameter of the scattered electron limiting aperture plate 30 and the aperture diameter of the extraction electrode 23 are set to the scattered electrons, and the exit pupil 23 ′ relating to the aperture of the extraction electrode 23 is moved from the center of the circle 25. The angle of view is larger than the angle of viewing the exit pupil 30 ′ related to the aperture of the scattered electron limiting aperture plate 30 from the center of the circle 25, and the size of the exit pupil 23 ′ related to the aperture of the extraction electrode 23 is By determining to be larger than the size, it is possible to shield the scattered electrons from the extraction electrode 23 and remove the aberration derived from the scattered electrons.
[Example 9]
The configuration of the ninth embodiment is basically the same as that of the eighth embodiment. However, in the ninth embodiment, as shown in FIG. 29, the first lens 17 is changed from a magnetic lens to an electrostatic lens. The operation and effect are basically the same as those of the eighth embodiment. The first lens 17 functions as a deceleration type electrostatic lens.

  Also in the ninth embodiment, electrons scattered by the extraction electrode 23 and having a velocity vector in the positive direction of Z satisfy the equation (22). However, not all of the electrons pass through the first lens 17. Absent. In other words, the first lens 17 has a filter function with respect to the scattered electrons, and reduces the amount of scattered electrons passing through the first lens 17.

Here, the condition that the scattered electrons from the extraction electrode 23 do not pass through the first lens 17 (is reflected by the first lens 17) is that the minimum value of the on-axis potential derived from the first lens 17 is Assuming V _min , V = V _e + ΔV− (V _e −V _min ) = ΔV + V _min ≦ 0, that is, ΔV ≦ −V _min . On the other hand, the condition for the scattered electrons to pass through the first lens 17 is V = ΔV + V _min > 0, that is, ΔV> −V _min . From this equation and equation (22), for electrons passing through the first lens 17,

Holds. From this, in this embodiment, it is only necessary to confirm that Expression (21) is satisfied within the range represented by Expression (26). For that purpose, the method shown in Embodiment 8 may be used. However, in the decelerating type electrostatic lens, the off-axis potential (the potential at the radial position away from the Z-axis) is smaller than the on-axis potential, so the minimum value of the potential sensed by electrons passing through a certain off-axis trajectory is V _min. If ′ (> 0), 0 <V _min ′ <V _min , that is, a relationship of −V _min <−V _min ′ <0 is established. Accordingly, the condition −V _min ′ <ΔV ≦ 0 for the electrons to pass off the axis of the first lens 17 becomes stricter than the condition −V _min <ΔV ≦ 0. That is, with respect to the off-axis orbit, the width of ΔV of electrons passing through the first lens 17 becomes small. However, for the off-axis trajectory, if the condition for the electrons to pass through the lens 17 is −V _min <ΔV ≦ 0, the range in which the expression (21) is evaluated by V _min −V _min ′. since widens, correspondingly, the _{m e, m 1, l e} , l 1 is determined more strictly. That is, the scattered electron limiting aperture plate 30 shields scattered electrons passing through the on-axis trajectory with a margin.
[Example 10]
Example 10 basically has the same configuration as that of Example 8, but in Example 10, as shown in FIG. 29, the position of the scattered electron limiting aperture plate 30 is set to an irradiation lens for electrons satisfying ΔV = −V _e. The object side focal plane position of 2 is assumed. As described in the eighth embodiment, in the irradiation optical system for the charged particle beam apparatus of the present invention, even if the three conditions l ₁ ≠ 0, θ _e > θ ₁ , and a _e ′> a ₂ are satisfied. , [Delta] V is at large in the negative direction, depending the size of a ₂ (20) and equation (21) is not satisfied. The reason is that when ΔV is large in the negative direction as described above, a _e ′ and | l ₁ / l _e |

In order to alleviate this problem, in Example 8, it was considered to increase | l ₁ | and increase | l ₁ / l _e | so that the electrode of the blanker 15 does not become too short. In the present embodiment, this idea is developed, and it is considered to increase | l ₁ | so as to compensate when ΔV increases in the negative direction and a _e ′ decreases. In order to realize this, the position of the scattered electron limiting aperture plate 30 may be set to the object side focal plane position of the irradiation lens 2 with respect to electrons satisfying ΔV = −V _e . By doing so, the exit pupil 30 ′ can be set to infinity for electrons satisfying ΔV = −V _e , and at the same time, | l ₁ | = ∞.

In order to confirm this effect, dividing equation (20) by | l ₁ |

It becomes. In the equation (27), when | l ₁ | → ∞, the right side does not diverge and the left side
_{a e '/ | l e |} - | 1 / l 1 -1 / l e | a 2 → a e' / | l e | - | -1 / l e | a 2 = (a e '-a 2) / | A _e | That is, as the absolute value of 1 / l ₁ becomes smaller, the second term − | 1 / l ₁ −1 / l _e | a _{2 of} equation (27) becomes smaller, and equation (27) becomes easier to hold.

  However, in the irradiation optical system of the present invention, this means that the position of the scattered electron limiting aperture plate 30 is on the positive side of Z from the light source image 4 ′ (ΔV = 0). In this illumination optical system, since the image 5 of the light source is connected to the rear stage of the first shaping aperture plate 3 by the illumination lens 2, the image 4 ′ of the light source is obtained from the illumination lens 2 with respect to ΔV = 0. This is because it is on the negative side of Z from the position of the object side focal plane.

  Thus, when the position of the scattered electron limiting aperture plate 30 is on the positive side of Z from the position of the light source image 4 ′, the light source image 4 is reduced before the beam current of the electron beam 1 is reduced by the scattered electron limiting aperture plate 30. Since 'is connected, the current density at the position of the light source image 4' is increased. As a result, the Bercher effect is promoted at the position of the light source image 4 '. In order to prevent this, it is preferable to provide a limiting aperture plate different from the scattered electron limiting aperture plate 30 in front of the light source image 4 ′ to reduce the beam current.

  For example, if the leakage beam limiting aperture plate 19 shown in the fifth embodiment is arranged in front of the blanker 15 and in front of the light source image 4 ′ and the aperture diameter is made sufficiently small based on the equation (23), the leakage The scattered electron from the extraction electrode 23 can be shielded by the scattered electron limiting aperture plate 30 while reducing the beam current by the beam limiting aperture plate 19 and suppressing the leakage beam at the time of beam blanking.

At that time, if the aperture diameter of the scattered electron limiting aperture plate 30 is increased and the aperture diameter has a margin, even if the electron beam 1 is deflected by the blanker 15, the same beam, that is, the first shaped aperture plate originally. 3 can be prevented from being blocked by the scattered electron limiting aperture plate 30. For this purpose, if the blanking deflection distance at the position of the scattered electron restricting aperture plate 30 is D1, as shown in FIG. 30, the diameter of the aperture of the scattered electron restrictive aperture plate 30 having the allowance is d ₁ = 2a. _{1 +} D ₁ and then, Sonouede, the center of the scattered electrons limiting aperture plate 30 may be shifted only in the direction of the blanking deflection distance D1 / 2. At this time, the aperture radius of the scattered electron limiting aperture plate 30 in the equation (21) may be a ₁ + D ₁ . Here, a ₁ is the radius of the aperture of the scattered electron limiting aperture plate 30 that does not have a margin.

Thus, in the illumination optical system of the present invention, the position of the scattered electron limiting aperture plate 30 is set to the object side focal plane position of the irradiation lens 2 with respect to electrons satisfying ΔV = −V _e , so that ΔV is greatly increased in the negative direction. Thus, when the size a _e ′ of the exit pupil 23 ′ becomes smaller, the distance l ₁ from the first shaping aperture plate 5 to the exit pupil 30 ′ becomes larger so as to compensate for it, so that the amount (20) It becomes easy to satisfy | fill a formula and (21) Formula. That is, the opening diameter of the extraction voltage 23 is reduced by that amount, and the Bercher effect after the electrode is more strongly suppressed.
[Example 11]
Example 11 basically has the same configuration as that of Example 9, but in Example 11, as shown in FIG. 29, the position of the scattered electron limiting aperture plate 30 is set to an irradiation lens for electrons satisfying ΔV = −V _min. 2 is the position of the object-side focal plane.

The operation and effect of the eleventh embodiment are basically the same as those of the tenth embodiment, but in the eleventh embodiment, the electrons passing through the first lens 17 satisfy the equation (26).
[Example 12]
Example 12 basically has the same configuration as Example 8 to Example 11, but in Example 12, the opening shape of the second molded aperture plate 7 is not a simple rectangle, but a more complicated figure, Carry out character projection. The operation and effect of the twelfth embodiment are also the same as those of the eighth to eleventh embodiments.
[Example 13]
Embodiment 13 is basically the same as the configuration of Embodiments 8 to 12, but in Embodiment 13, an ion beam is used instead of an electron beam, and the operation and effect thereof are Embodiments 8 to 12. Is the same.

DESCRIPTION OF SYMBOLS 1 Electron beam 2 Irradiation lens 3 1st shaping | molding aperture plate 4 Light source 4 ', 5, 16, 50 Image of light source 6 Molding lens 7 2nd shaping aperture plate 8 Reduction lens 9 Objective lens 10 Material 11 Projection figure 12 Molding deflection Device 13 Objective deflector 14 Material stage 15 Blanker 16 Blanking aperture plate 17 First lens 18 Second lens 19 Leakage beam limiting aperture plate 20 Emitter electrode 22 Anode electrode 23 Extraction electrode 30 Scattered electron limiting aperture plate 23 ′ Extraction electrode Exit pupil 30 'exit pupil related to scattered electron limiting aperture plate

Claims (9)

These are arranged in the order of a charged particle source, an illumination lens group, a diaphragm, a projection lens group, and a material surface, and a charged particle beam emitted from the charged particle source is irradiated onto the diaphragm through the illumination lens group, Further, in the charged particle beam device in which the beam passing through the stop is irradiated onto the material in a state where the image of the stop is formed on the material surface by the projection lens, the illumination lens group includes the image of the charged particle source. A charged particle beam, wherein the charged particle beam is disposed so as not to form an image on the diaphragm, and one lens of the illumination lens group is disposed at a position optically conjugate with the position of the diaphragm. apparatus. The charged particle beam apparatus according to claim 1, wherein the lens disposed at a position optically conjugate with the position of the stop is a lens closest to the charged particle source of the illumination lens group. These are arranged in the order of a charged particle source, an illumination lens group, a diaphragm, a projection lens group, and a material surface, and a charged particle beam emitted from the charged particle source is irradiated onto the diaphragm through the illumination lens group, and In a charged particle beam apparatus in which a beam that has passed through a diaphragm is irradiated onto a material in a state where an image of the diaphragm is formed on a material surface by a projection lens group, the illumination lens group includes an image of the charged particle source. The illumination lens group is arranged so as not to form an image on the stop, and the position and intensity of the illumination lens group are determined by placing the charged particle source on the object surface,
The optical axis is the Z axis,
At the position z = z ₀ of the object surface,
Starting from the point of intersection with the optical axis on the object surface,
h (z ₀ ) = 0 and h ′ (z ₀ ) = dh (z ₀ ) / dz = 1
When the spherical aberration trajectory representing the deviation from the paraxial trajectory h (z) becomes s (z),
In the position z = z _a of the diaphragm,
s (z _a ) = 0
The charged particle beam device is set so as to satisfy The image of the charged particle source is formed at a focal position on the object side as viewed from a lens closest to the stop side of the illumination lens group. Charged particle beam device. 5. The charged particle beam device according to claim 1, wherein the lens group closest to the charged particle source of the illumination lens group is an electrostatic lens. 6. The illumination lens group first lens, second lens, they are arranged in order of the third lens, and blanker is disposed between the second lens and the third lens, before Symbol the two lenses 3 An image of the charged particle source is connected to the lens, a restriction aperture is provided on the charged particle source side from the blanker, and on the charged particle source side from the image of the charged particle source, and leakage at the time of blanking by the blanker charged particle beam device according to any one of claims 1 to 5, characterized in that to suppress the beam. In the illumination lens group, the first lens and the second lens are arranged in this order, and a blanker is arranged between the first lens and the second lens, and between the first lens and the second lens. The charged particle source image is connected to the charged particle source side with respect to the blanker, and a restriction aperture is provided on the charged particle source side with respect to the charged particle source image to suppress a leakage beam during blanking by the blanker. charged particle beam device according to any one of claims 1 to 5, characterized in that. The diaphragm comprises a plurality of diaphragms having at least a first stage diaphragm and a subsequent stage diaphragm, and a restriction diaphragm for shielding scattered electrons originating from the extraction electrode of the charged particle source,
With respect to scattered electrons having energy that can form an exit pupil relating to the aperture of the extraction electrode of the charged particle source, it is arranged on the first stage aperture side from an optically conjugate position on the charged particle source side with respect to the first stage aperture. And
The aperture diameter of the limiting aperture, the exit pupil relating to the aperture of the extraction electrode of the charged particle source, the mapping of the aperture of the aperture other than the initial aperture of the initial aperture to the aperture of the initial aperture and the aperture of the initial aperture Determining an angle seen from the center of the circumscribed circle of the overlapping portion to be larger than an angle seen from the center of the circumscribed circle, the exit pupil relating to the aperture of the limiting aperture; and
8. The aperture diameter of the extraction electrode of the charged particle source is determined so that an exit pupil relating to the aperture of the extraction electrode of the charged particle source is larger than a circumscribed circle of the first stage aperture. The charged particle beam apparatus of any one of Claims . The position of the limiting aperture for shielding the scattered electrons, among the scattered electrons having the energy to electrons with the lowest energy, the object-side focal position of the lens positioned in said charged particle source side of the first-stage diaphragm The charged particle beam apparatus according to claim 8, wherein:

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