JPS6161414A - Multicharged beam exposure device - Google Patents

Abstract

PURPOSE:To enable to irradiate electron beams of high current value on all electrostatic lenses even in case the accelerating voltage of the electron beams is high by a method wherein the title device is made in the specific structure and the electron gun, which meets the conditions of a Pierce gun from the configuration and position of the peripheral part of the central part of the anode and those of the beam control electrode, is used. CONSTITUTION:This multicharged beam exposing device consists of a cathode 201, which has the point formed in a roughly spherical form, an anode 202, which has the central part formed in the form of a roughly spherical surface having the nearly same center as that of the spherical surface of the point of the cathode 201 and has plural anode holes 204-208 provided in the central part, and a beam control electrode 203, which is provided between the cathode 201 and the anode 202. The electron gun, which meets the conditions of a Pierce gun from the configuration and position of the peripheral part A, B, C of the central part of the anode 202 and those of the beam control electrode 203, is provided. By this constitution, even in case the accelerating voltage of the electron beams is high, the angle, which is formed by the electron beams 610-614 and the central axis of the electron gun, can be arbitrarily set, the electron beams can be irradiated on all the electrostatic lenses 605 in a fly's eye lens 606, the area of a wafer, which can be exposed with the beam irradiation of one time, is augmented, and the number of times of shift of the stage can be lessened.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a multi-charged method for drawing fine patterns on a sample such as a wafer or a mask substrate using a plurality of charged beams in the manufacturing process of integrated circuit elements, etc. This invention relates to a beam exposure device.

[Background of the invention]

As an example of a multi-electron beam exposure system, 1.
ie, E. R., Asterberg, D. R., Con.
e.

J., J., Muray, N., Williams, an.
d L, Ga51orek: ”AMultiple
-Electron-flOaIllIExposur
e System for High-Throughp
ut, Dj, ract-Write Submicro
meterLithography”, IIEIEE
Trans, on Electron Devices,
The device described in Vol. ED-28, p. 1422 (1981) is shown in Fig. 1. 101 is an electron gun;
102 is an irradiation lens, 103 is a blanker, 104 is an object aperture, 105 and 106 are deflectors, 107 is an electrostatic lens, 108 is a fly's eye lens configured by arranging a large number of electrostatic lenses 107, 109
is a stage, 110 is a wafer mounted on the stage 109, 111 is an electron beam emitted from the electron gun 101 until it reaches the object aperture 104, and 112 is an electron beam that passes through the object aperture 104 and reaches the fly's eye lens 108. The electron beam represented by the electron beam 113 is the electron beam after passing through the fly's eye lens 108.

A crossover is created within the electron gun 101 by the electron beam emitted from the cathode. The electron beam 1ll spreads radially from the crossover in the electron gun 101 and passes through the illumination lens 102 to the object aperture 10.
It is focused on 4. That is, an image of the crossover within the electron gun 101 is formed on the object aperture 104 by the irradiation lens 102 . The electron beam 112 that has passed through the object aperture 104 spreads radially and almost uniformly illuminates the entire surface of the fly's eye lens 108. The diameter of the fly's eye lens 108 is approximately 10 an. Object aperture 10
4 to the fly's eye lens 108 is about 1 m. Each electrostatic lens 107 of the fly's eye lens 108
Through it, an image of object aperture 104 is projected onto wafer 110.

Since the distance from object aperture 104 to fly's eye lens 108 is fixed, the radius of the circular region in which electron beam 112 illuminates fly's eye lens 108 is limited by the aperture angle α0 of electron beam 112. In an aberration-free electron optical system, if the diameter of the crossover is d, the beam aperture angle at the crossover is α, and the potential of the crossover is V, d, α, and v' are conserved according to Lagrange-Helmholtz's law. . Therefore, in the optical system shown in FIG. 1, the diameter of the crossover in the electron gun 101 is do, the beam aperture angle at the crossover in the electron gun 101 is αc, and the potential of the crossover in the electron gun 101 is VC. , do the diameter of the crossover on the object aperture 104, and
The beam opening angle at the crossover on the aperture 104 is α. , d, where the crossover potential on the object aperture 104 is vo. ....・Vノ=do
・α.・The relationship V=C(1) holds true. Here, C
is a constant.

In this device, the electrostatic lens 107 that constitutes the fly's eye lens 108 is used as an aperture lens (a lens in which the space on the image side and the space on the object side have different potentials with the lens as a boundary).
is used. 1 kV to object aperture 104 and fly's eye lens 108, 9 to wafer 110.
kV is applied. Object aperture [0
4 is configured as a square with each side being 50-. The diameter of the crossover on object aperture 104 is 42
X50=71am.

Since the electron beam 112 illuminates the entire surface of the fly's eye lens 108, its aperture angle is α. is arctan(5
aa/1 m) = 50 mrad. Therefore, in equation 1 (1), v0 = 1kV, α. =50 mrad,
Substituting do=71urn and finding the value of constant C, we get
C==3500-・mrad・(kV)2.

Incidentally, when the energy of the electron beam incident on the sample is increased, the spread of electrons in the lateral direction due to electron scattering within the sample becomes smaller, which increases the resolution of the pattern, which is advantageous for drawing fine patterns. Consider a case where, for example, a voltage of 50 kV is applied to the wafer 110 in order to draw an ultra-fine pattern using the apparatus shown in FIG. In this device, the potential V of the object aperture 104 is determined by the imaging conditions of the aperture lens used for the fly's eye lens 108. needs to be maintained at 1/9 of the potential of the wafer 110. Therefore, if 50 kV is applied to the wafer 110, the potential v of the object aperture 104
0 is 5.6kV. At this time, the opening angle α of the electron beam 112. In equation (1), d o = 71 tm,
V o = 5, 6kV, C = 3500m ・m
rad ・(kV)), 21++
It becomes rad. From this, the radius of the circular area where the electron beam 112 irradiates the fly's eye lens 108 is 2. la
It becomes i. That is, the area of the region where the electron beam 112 irradiates the fly's eye lens 108 is approximately 1/6 of the area where the entire surface of the fly's eye lens 108 is irradiated with the beam. In this way, when a voltage of 50 kV is applied to the wafer 110 in order to draw an ultra-fine pattern using this device, the number of areas that can be simultaneously exposed by electron beam irradiation decreases to 176, and the number of times the stage moves increases six times. , there is a problem in that the wasted time associated with stage movement increases.

Furthermore, in this device, a three-electrode electron gun is used as the electron gun 101, and tungsten with a low work function is used as the cathode material.
The current value of the electron beam 113 after passing through 08 is 10n
It will only be a small value of A. Therefore, in an apparatus using this electron gun, the actual exposure time (the time required for the electron beam to irradiate and expose the resist) increases, and there is a problem in that it is difficult to significantly reduce this time.

[Purpose of the invention]

The purpose of the present invention is to solve these problems, and even when the beam acceleration voltage is high, it is possible to irradiate all the electrostatic lenses in the fly's eye lens with an electron beam with a high current value, thereby significantly improving the throughput. The object of the present invention is to provide a multi-charged beam exposure apparatus that can perform the following steps.

[Summary of the invention]

In order to achieve this object, the present invention provides a cathode having a substantially spherical tip, a central portion having a substantially spherical shape with a center substantially the same as the center of the spherical tip of the cathode, and a plurality of cathodes in the central portion. and an anode with holes.

Beam control type 1 provided between the cathode and the anode
The present invention is characterized in that it has an electron gun consisting of a pole, and the shape and position of the periphery of the central part of the anode and the beam control electrode satisfy the conditions of a piercing gun.

Next, an electron gun according to the present invention will be explained.

FIG. 2 is a sectional view for explaining the concept of the electron gun according to the present invention. 201 is a cathode, 202 is an anode, 203 is a beam control electrode, 204 to 208 are anode holes made in the anode 202, 209 is an electron beam emitted from the cathode 201, and 210 to 214 are electron beams after passing through the anode holes 204 to 208. is an electron beam. The dashed line oo' is the central axis of the electron gun. In the electron gun shown here, the cathode 201, the shape of the anode 202 excluding the anode elements 204 to 208, and the beam control @i 203 are rotationally symmetrical with respect to the central axis 00'.

In FIG. 2, the tip of the cathode 201 has a spherical shape. In the positive ji4i 202, the part indicated by CD is called the central part of the positive electrode.The central part of the positive electrode is a spherical surface having the same center as the spherical surface of the cathode tip.

Anode holes 204 to 208 are arranged in the center of the anode.

The situation is shown in Figure 3. FIG. 3 is a plan view of the anode 202 shown in FIG. 301 to 308 are anode holes 204
This is an anode hole similar to ~208. In fig.

The portion indicated by ABC of the anode 202 (hereinafter this portion will be referred to as the anode peripheral portion) and the beam control electrode 203 are designed to satisfy the conditions for a piercing gun, which will be described later.

Define shape and position. When the anode peripheral portion ABC and the beam control electrode 203 are arranged to satisfy the shape of the piercing gun, the electron beam 209 is emitted from the tip of the cathode 201.
The electron beam spreads radially, and the beam hardly goes outside the PC.The electron gun is used in a space charge limited state.

Here, a method for determining the shape and position of the anode peripheral portion ABC and the beam control electrode 203 will be explained for the case where the radius of the spherical surface of the cathode tip is Ro, the radius of the anode center is Ra, and the opening angle of the electron beam 209 is α. . In this method, J, R,
Pierce: “Theory and Desi+
;nof ELECTRON BEAMS”, D, V
AN, N0STRAND COMPANY.

The concept used in determining electrodes for piercing guns, published in INC. (1954), is used. Consider a modeled electron gun as shown in Section 4-.

401 is a cathode, and 402 is an anode. The cathode 401 and the anode/102 are concentric spheres, and the radius of the cathode 401 is Ro,
Let Ra be the radius of the anode 4()2. In this electron gun, electrons are uniformly emitted from the cathode 401 in all directions.

The potential distribution V (R) of this electron gun along the radial R direction in the space charge limited state is calculated. In FIG. 2, the potential distribution along PC is V (R), and the electric field component in the direction perpendicular to PC is O.

These conditions are the conditions for a piercing gun. The shape and position of the anode peripheral portion ABC and the beam control electrode 203 are determined so as to satisfy these conditions.

In the electron gun according to the present invention shown in FIG. 2, for example, the radius RO of the spherical surface at the tip of the cathode is 21 Tfi, the radius R6 of the anode center is 10 m, and the aperture angle α of the electron beam 209 is 45 Tfi.
''. According to the method described above, first, the fourth
In the figure, R6=2+m+, Ra=10 mm, and Ov is applied to the cathode 401 and 1V is applied to the anode 402.

Radial potential distribution V(R) in space charge limited state
was calculated. This result is shown by the solid line in FIG.
(R) does not depend on the voltage applied to the anode 402. Next, in FIG. By changing the angle Oa between BC and PC and the angle θ between HK and PC, the cathode 201
and OV to the beam control electrode 203, 1V to the anode 202
The potential distribution along the PC was determined by the finite element method when the voltage was applied.

As a result, when θ = 72.5° and ou = 61'', a potential distribution almost identical to the solid line, as shown by the dotted line in Figure 5, was obtained.At this time, the electric field in the direction perpendicular to the PC The component was 0. From the above, θ was 72.5"
, θ8 was set to 67″.

Each electron beam 21 after passing through the anode holes 204 to 208
Perveance P = I/V for 0-214
ar (where I: [current value of each of the child beams 210 to 214, va: acceleration voltage of the electron beams 210 to 214) is expressed by the following equation.

P = (8πt, / 9)・(2e/m)'(1-c
osO)/k" (2) where ε is the permittivity of vacuum, e is the amount of charge of electrons, m is the rest mass of electrons, and θ is the half-opening angle when looking into the anode hole from the cathode tip. It is a constant determined by the ratio of the radius Ro of the tip spherical surface and the radius R1 of the anode center.The values of ε., e, and m are known, and by substituting these into equation (2), P = 14.66X10-' X(1-cosO)/k”
(A/V') (3). Anode hole 204-2
The diameter of 08,301-304 is 0.025 nsm. At this time, 0 is 1.25 mrad.

R-/RO is 5, and the corresponding value of 2 is
B,I langmuir and K,B,Blog
ett: “Currents limited by
5pace charge between conc.
Phys, Rev.
24. p, 49. (1924), 1.1
It becomes 41. In equation (3), θ= 1, 25 mrad,
By substituting k''=1.141, the perveance P for each electron beam 210-214 is 1.0X
10A/V". For example, 5.6k is applied to the anode 202.
When V is applied, the current value of each electron beam 210 to 214 becomes a large value of 4.2 μA.

In the above description, an example of an electron gun of the present invention has been shown for one combination of the opening angle α of the electron beam, the radius R0 of the cathode tip, the radius R of the anode center, and the like. For other combinations, electron guns can be designed according to the method described above. Also, regarding the position and number of anode holes,
Various combinations are possible.

According to the electron gun of the present invention, by appropriately selecting the aperture angle α of the electron beam and the position of the anode hole, the angle formed between each electron beam after passing through the anode hole and the central axis of the electron gun can be set arbitrarily. Can be set to .

Also, the radius R0 of the spherical surface at the tip of the cathode, and the radius R at the center of the anode
, and the diameter of the anode hole, the perveance of the electron gun can be increased, and the current value of each of the plurality of electron beams emitted from the electron gun can be increased.

Here, the present invention has been explained in detail by taking as an example the case where the tip of the cathode and the center of the anode are completely spherical. ■If the shape of the tip of the cathode and the center of the anode deviates from a spherical surface, for example, an elliptical surface close to a spherical surface,
The inventor has confirmed that the same effect can be obtained even when the surface is a paraboloid or hyperboloid, or when the center of the spherical surface at the tip of the cathode and the center of the spherical surface at the center of the anode are misaligned.

〔Example〕

Next, an embodiment of a multi-electron beam exposure apparatus according to the present invention using an electron gun according to the present invention will be described. As an embodiment of the present invention, FIG. 6 shows a multi-electron beam exposure apparatus capable of simultaneously exposing a plurality of LSI patterns on a wafer using a plurality of electron beams. 601 is an electron gun according to the present invention, 602 is a blanker, 603 and 604 are deflectors, 605 is an electrostatic lens, 606 is a fly's eye lens configured by arranging a large number of electrostatic lenses 605, 607
is a stage, 608 is a wafer mounted on the stage 607, 609 is an object aperture, 610 to 614
is an electron beam emitted from the electron gun 601.

Electron beams 610 to 614 are radially emitted from an electron gun 601 and illuminate an electrostatic lens 605 on a fly's eye lens 606 through objects 1 to aperture 609. The diameter of the fly's eye lens 606 is approximately 10
cm. One object 1-aperture 609 for each of the electron beams 610-614, and one
electrostatic lenses 605 are made to correspond to each other. Images of the object aperture 609 are projected onto the wafer by the individual electrostatic lenses 605 on the fly's eye lens 606. In this embodiment, the electrostatic lenses 605 forming the fly's eye lens 606 Using an aperture lens, 5.6 kV is applied to the anode of the electron gun 601, the object aperture 609, and the fly's eye lens 606, and 50 kV is applied to the wafer 608.

Electron beams 610 to 61 are formed by deflectors 603 and 604.
4 is deflected and scanned in one direction. Adding a blanking signal to the blanker 602 based on the LSI pattern data,
The electron beams 610 to 614 are turned on and off in synchronization with the deflection signal. The stage 607 emits electron beams 610 to 6.
14 in a direction perpendicular to the deflection scanning direction.

In this way, on each LSI chip, an area of (deflection scanning width x chip - length of side) is drawn simultaneously. When the pattern drawing in this area is completed, the stage 607 is moved by the deflection scanning width in the same direction as the deflection scanning direction of the electron beams 610 to 614, and the pattern drawing in the next area is
Start F4. By repeating this operation, the wafer 6
An LSI pattern is drawn on the entire surface of 08.

Since this device uses the electron gun 601 of the present invention, even when the accelerating voltage of the electron beam I~ is high, the angle formed between the electron beams 610~614 and the central axis of the electron gun can be set arbitrarily, and the frying All the electrostatic lenses 605 in the eye lens 606 can be irradiated with the electron beam. Therefore, the area of the wafer that can be exposed by -times of beam irradiation increases, and the number of times the stage is moved can be reduced. In other words, it is possible to reduce wasted time during stage movement.

In addition, the current value of the electron beams 610 to 614 is 4.2 μA.
This is large, so the actual exposure time can be reduced.

As a result, throughput can be significantly improved.

As another embodiment of the present invention, a multi-electron beam exposure apparatus using a parallel irradiation optical system is shown in FIG.

In FIG. 7, 701 is an electron gun of the present invention, and 702 is a blanker.

703 is an irradiation lens, 704 is an object aperture, 705 and 706 are deflectors, and 707 is an electrostatic lens.

708 is a fly's eye lens constructed by arranging a large number of electrostatic lenses 707; 709 is a stage; 710 is a wafer mounted on the stage 709; and 711 to 715 are electron beams emitted from the electron gun 701.

Electron beam 711 radially emitted from the electron gun 701
~715 is turned into a parallel beam by the illumination lens 703 and illuminates the object aperture 04. Electron beam 711 exiting object aperture 04~
715 irradiates each electrostatic lens 707 on the fly's eye lens 708 as a parallel beam. object·
Images of the aperture 04 are projected onto the wafer 710 by the number of electron beams by each electrostatic lens 707 on the fly's eye lens.

The method of drawing the LS'L pattern is the same as that of the multi-electron beam exposure apparatus shown in FIG. Even with this device, the 6th
The same effects as the multi-electron beam exposure apparatus shown in the figure can be achieved.

〔Effect of the invention〕

As mentioned above, the cathode has a nearly spherical tip.

an anode having a central portion having a substantially spherical shape having a center approximately the same as the center of the spherical tip of the cathode, and a plurality of holes provided in the central portion; a peripheral portion of the central portion of the anode; and a beam control electrode. Since we used an electron gun arranged so that the peripheral part of the anode center and the shape and position of the beam control electrode met the requirements for a pierce gun, even when the accelerating voltage was high, the electron gun inside the fly's eye lens All electrostatic lenses can be irradiated with high current electron beams. As a result, the wasted time associated with stage movement and the actual exposure time can be reduced, and throughput can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a conventional electron beam exposure apparatus, FIG. 2 is a sectional view of an electron gun according to the present invention, FIG. 3 is a plan view of an anode constituting the electron gun of FIG. 2, and FIG. A schematic diagram of an electron gun composed of two concentric spheres; FIG. 5 is a diagram showing the potential distribution inside the electron gun in FIG. 4 and the potential distribution at the beam end of the electron gun in FIG. 2; FIG. FIG. 7 is a schematic diagram of a multi-electron beam exposure apparatus according to another embodiment of the present invention. FIG. 101...Electron gun 102...Irradiation lens 103...Blanker 104...Object aperture 105 and 1
06... Deflector 107... Electrostatic lens 108...
・Fly's eye lens 109...stage 110...wafer 11
1 to 113...Electron beam 201...Cathode 202...Anode 203
...Beam control electrode 204-208...Anode hole 2
09-214...Electron beam 301-308...Anode hole 401...Cathode 402...Anode 601
... Electron gun 602 ... Blankers 603 and 604 ... Deflector 605 ... Electrostatic lens 60
6... Fly's eye lens 607... Stage 608... Wafer 60
9...Object aperture 610-614...
・Electron beam 701...Electron gun 702...Blanker 7
03...Irradiation lens

Claims (1)

[Claims] a cathode whose tip has a substantially spherical shape; an anode whose central portion is substantially spherical with a center substantially the same as the center of the spherical tip of the cathode; and a plurality of holes in the center; It consists of a beam control electrode provided between the anode and the
A multi-charged beam exposure apparatus comprising an electron gun in which the shape and position of the periphery of the central part of the anode and the beam control electrode satisfy the conditions for a pierce gun.