JPS58103755A - Method of electron-beam exposure - Google Patents

Abstract

PURPOSE:To increase pattern-picturing accuracy, and enable minute elements to be worked, by using an exposure method in which the eddy current is prevented from developing in a magnetic field-deflecting coil, a lens coil and a lens coil frame. CONSTITUTION:A lens coil frame 23 made of an iron member is shielded by laying a member having a very low conductivity (sigma) and a high permeability (mu) on its inner wall. For instance, as an example of the method of shielding the frame 23 by use of ferrite, ferrite powder is mixed into an adhesive solution, and the mixture is applied to the surface before being hardened so as to form a ferrite film 24 as indicated in the figure. After that, fine litz wire having a small diameter of around 30mu is bundled and wound to form cores of a lens coil 22 and a deflecting coil 25. In addition, windings of the coils 22 and 25 themselves are formed by coiling in bundles small-diameter litz wire (L-10<-5>m), so that the time constant (gamma) of an eddy current can be suppressed to several mu seconds.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to an exposure method using an in-lens objective deflection system in an electron beam exposure apparatus.

(2) Background of the technology In recent years, it has not been easy to obtain a resolution of 1 micron or less using optical methods in fine element processing technology due to light diffraction, interference effects, etc.

For this reason, research and development of exposure methods using electron beams are being conducted.

Wafers used for VLSI are required to have high density, for example, 5
Million patterns/chip size requires a resolution of 0.1 to 0.2 microns, which requires improvements in the irradiation accuracy and performance of the electron beam optical system in electron beam exposure equipment.

(3) Prior art and problems When focusing and deflecting electrons at the same time, the superposition of the focusing magnetic field and the deflecting magnetic flux causes problems.

Goto, and A, Ono, “Eliminati
on third-order aberrat
ions in elec-tron-beam
scanning s)'Items, "Trans.

IECE japan, 54-B, P-73L 1
Since the axis of the focusing lens moves in accordance with the deflection, which is softened in 971, the deflection trajectory passes through the center of the lens, making it possible to perform irradiation with less aberration. Also harvesting sheep moe;
/11 It is possible to increase the ability of the child to have high school children's health. This type of lens, in which a lens magnetic field and a deflection magnetic field are superimposed on an objective lens, is often used in electron beam l1I single-source devices from the viewpoint of aberrations, and this type of lens is similar to the moving objective lens ( Eight'
Loving 0bjecNve T, ens). A Soshi beam positive system using this in-lens objective deflection system is shown in FIG. Figure 1: 1 electron gun, 2
3 is a condenser lens, 3 is a blanker for turning on/off the electron beam, 4 is a molded lens system, 5 is a reduction lens system, 6 is an electrostatic deflector, 7 is an in-lens objective deflection system, 8.9 is a rectangular shaped first ．． This is the second aperture.

The in-lens objective deflector 7 superimposes the lens magnetic field and the deflection magnetic field, and projects the electron beam onto the object in a predetermined number of turns at a predetermined position t. A second in-lens configuration for magnetic field deflection
As shown in the figure.

As shown in the figure, a lens convergence S field is generated by a coil 12 wound around the lens and a lens coil frame 13 made of an iron member. Further, the deflection coil 11 generates a magnetic field in the direction of the arrow (that is, the deflection magnetic field 14 and the lens magnetic field) 5 are superimposed.

However, eddy currents are generated by the deflection magnetic field in the lens coil frame 13, lens coil 12, and deflection coil 11, and the action of pulling back the electron beam causes pattern deviation to a predetermined writing position, resulting in poor pattern position accuracy and exposure time. It has a big impact. Conventional methods for suppressing eddy current include installing a small lζ correction coil near the deflection coil, or placing a shield ring around the deflection coil that does not disturb the lens magnetic field, as disclosed in U.S. Pat. No. 3,984,687. However, the effect was not sufficient.

(4J OBJECTS OF THE INVENTION The present invention ej) In view of the above points, it is an object of the present invention to provide an exposure method that suppresses the thin flow in the in-lens objective deflection system of an electron beam exposure device and performs high-precision exposure.

(5) Structure of the Invention The above object uses an electron beam 11 optical device having an in-lens objective deflection system that deflects an electron beam to a predetermined position on a sample, and 3- The lens coil frame of the in-lens objective deflection thread is made of ferrite. At the same time, the lens coil and the deflection coil are bundled with thin drawn wire and wound 101.
This can be carried out by suppressing eddy currents.

(6) Examples of the invention Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a diagram illustrating an in-lens structure for magnetic field deflection, which is an embodiment of the present invention.

A lens coil frame 23 made of an iron member is covered with a material having a very low conductivity (σ) and a high magnetic permeability (μ) on its inner surface. For example, as an example of a shielding method using ferrite, ferrite powder is mixed into an adhesive solution, applied to the surface, and cured to form a ferrite film 24 as shown in the figure. Furthermore, the lens coil 22 and the deflection coil 25 have 3
The wires are bundled and wound using wire drawn wire with a diameter of about 0 microns.

The time constant τ of the thin current is generally expressed by the following equation.

τ〈σμ. L" (σ2 conductivity, μ: magnetic permeability, L: dimension) The conductivity of ferrite 24 is σ~-, -1"T: #
4- The time constant τ of the thin current is several μ8ee, and the magnetic permeability μ
is extremely high, so the deflection magnetic field can be suppressed to a few μ8ee.

On the other hand, since the coil windings of the lens coil 22 and the deflection coil 25 are also wound by bundling small-diameter drawn wire L to 10 -5 m, the time constant τ of the thin current can be suppressed to several μsec. By using such a thin current suppressing means, it is possible to improve the pattern height and increase the light time.

(7) Effects of the Invention As explained in detail above, in the in-lens objective deflection system of an electron beam exposure apparatus, the magnetic field deflection coil of the present invention,
By using method ii to suppress eddy tS in the lens coil and frame, there is an excellent effect of improving pattern drawing accuracy and enabling finer element processing.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an electron beam fogging device using an in-lens objective deflection thread, Fig. 2 is a diagram explaining a conventional lens configuration for magnetic field deflection, and Fig. It is a diagram clarifying the lens structure. In the figure, 11 is a deflection coil, 12°22.25 is a coil, 13.23 is a lens coil frame, ]4 is a deflection magnetic field, 15 is a lens magnetic field,
24 indicates ferrite. 7- Figure 1 ~1,! ! 2 Figure No. 31 ¥] 299- 23 '22

Claims (1)

[Claims] An electron beam exposure apparatus is used that has an electron gun that emits a heavy particle beam, an electron lens system that focuses the electron beam, and an in-lens objective deflection thread that deflects the electron beam to a predetermined position on the sample. The lens coil frame of the objective deflection system is shielded with ferrite, etc., and a thin rod wire is bundled and wound around the lens coil and (M internal coil).
An electron beam 11-element method characterized by suppressing the thin current induced inside the lens by a deflecting magnetic field.