JPS6386235A - Focusing ion beam machining device - Google Patents

Abstract

PURPOSE:To aim at improvement in working efficiency, by giving a memory function for plural specified lens intensities in a focusing lens control part variable in the lens intensity, and selecting such one as the desired lens intensity during actual machining operations. CONSTITUTION:Ion beams emitted out of an ion source 201 are focused on a sample 206 by a focusing lens 202 and an objective lens 203. Hereat, three modes, namely, A, B and C modes are set by a combination of lens intensities of these focusing and objective lenses 202 and 203, and each lens voltage at that time is stored in a lens control part 208. And, at the time of machining operations, any one among these beam modes A, B and C is selected in switching the lens intensity electrically in order. With this constitution, a beam current and a beam diameter are easily alterable, thus working efficiency is improvable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a focused ion beam processing apparatus, and particularly to an ion beam processing apparatus capable of improving processing efficiency.

[Conventional technology]

Conventional focused ion beam processing equipment and processing methods are discussed in JP-A-60-5524.

An outline of the device is shown in Fig. 4. The ion optical column includes a liquid metal ion source 201, an extraction electrode 213, and an aperture 214.
, an electrostatic focusing lens 215, and a deflector 205. This provides a focused beam 215 that can be scanned as desired over a sample 206, eg a mask. Processing is performed by irradiating the desired position on the sample with an ion beam.
This is done by causing physical sputtering to remove unnecessary materials at the atomic level. Regarding the beam diameter, ion current, and ion current density in this ion optical system, please refer to Solid State Chikunoroshii May (1988).
3rd year) pages 97 to 103 (Solid 5ta
te Technology, May (1983
) pp 97-103).

In this case, the focused beam radius is given by ΔBD~Cα−(1). Here, C is the chromatic aberration coefficient of the lens, α is the beam opening angle, ΔE is the ion energy width, and E is the beam energy. However, the beam diameter is an area where chromatic aberration is dominantly influenced.

Also, the ion current of this beam! and ion current density are given by the following equations, respectively.

Here, (dJ/dΩ) is the ion emission angular current density of the ion source. From equations (1) to (3), when E is fixed, unless the operating conditions of the ion source are changed, ΔE and dl/dΩ
is constant, and the beam diameter and ion current I are determined by the opening angle α
You cannot change unless you change.

In the ion optical system of FIG. 2, when α=10 rad, it is 10.1 μm.

[Problem that the invention seeks to solve]

However, since the opening 213 is located in a vacuum chamber (not shown) and is at a high potential, it is not easy to change the opening angle α during the processing operation. However, in machining operations, it is required to make the beam radius and beam current I variable depending on the size of the machining area in order to improve machining efficiency.

The above-mentioned conventional technology did not take this point into consideration, and there was a problem in improving processing efficiency. An object of the present invention is to improve processing efficiency by making it possible to easily adjust the beam diameter and beam current I from outside the vacuum by changing the lens strength even during processing operations.

[Means for solving problems]

The above objective is achieved by providing the lens control unit of the electrostatic focusing lens with variable lens strength with a memory function for a plurality of predetermined lens strengths, and selecting the one with the desired lens strength during the finishing process. .

[Effect]

Therefore, the present invention is based on changing the lens strength.
This is a device that changes the beam aperture angle α to change the beam current I and beam radius. By placing its lens control unit outside the vacuum chamber, the beam diameter and beam current can be easily varied from outside the vacuum.

〔Example〕

The present invention will be explained below using examples.

[Example 1] FIG. 1 shows an embodiment of the present invention.

Ions emitted from the ion source 201 are collected by the focusing lens 20.
2 and an objective lens 203 onto a sample 206. The aperture 204 determines the beam diameter. In this embodiment, three modes, combination A, B, and C modes, are set by combining the focusing and objective lens strengths, and the respective lens voltages at that time are set by the lens control unit 20.
I memorized it to 8. Mode A is when the beam is nearly parallel between the focusing and objective lenses, B is when the focusing lens only focuses the beam onto the sample 206, and mode C is when the beam is focused at a specific location between the focusing and objective lenses. This is the case when you have .

The beam diameter of each of the focused beams A, B, and C that irradiates the sample 206 is determined by the aperture 204, but the effective beam opening angle (2α) on the ion source 201 side is as shown in FIG. 2α□, 2α8, and 2α0, respectively.
It is different from Since the beam current I on the sample is given by equation (2), 381 class beam currents are obtained in this example. Beam diameter is determined as a function of lens voltage, ion extraction voltage, ion acceleration voltage, and effective size of the ion source.

In a region where the focused ion beam diameter is several microns or less, axis misalignment of the ion optical system and asymmetry of the lens with respect to the optical axis cannot be ignored, and beam aligners are used to correct these.
and an astigmatism corrector (also not shown). The voltage applied to the beam aligner and stigmator is controlled by the beam aligner and stigmator controller (
(not shown), this control unit also has a memory function for the optimal voltage corresponding to the focused beam modes A%B and C, and by selecting the beam mode, these Corrections are made.

A deflector control (not shown) that provides the voltage applied to the deflector 205 also includes a focused beam, A,
There is a memory function for the correction amount to correct the irradiation position deviation on the samples 206 of B and C, and the position deviation is automatically corrected by selecting the beam mode.

In this example, the beam diameter and beam current in the beam modes A, B, and C from the gallium liquid metal ion source were [0,2ttrn, 0.4
nA ), (0,5 μm, 1 nA), and [2 μm
, 8 nA).

During processing work, this beam mode, A, B.

By electrically changing the lens strength and selecting one of C and C in sequence according to the processing specifications, the beam current and beam diameter can be easily changed and processing efficiency can be improved. Ta.

[Embodiment 2] Figure 2 shows an embodiment of the present invention. In the present invention, the electrostatic lens is a single-stage lens 209 consisting of four electrodes with round apertures, and a voltage is applied to each electrode. By controlling the voltage, the lens strength can be changed and the ion source 2
The emitted ions from 01 can be focused onto the sample 206. In this embodiment, as shown in FIG. 3, there are two beam modes, A and B, and the lens applied voltages corresponding to each are stored in the lens controller 208. As in Example 1, a stigma corrector (not shown)
Each control unit (not shown) that applies the voltage to the deflector 205 has a similar memory function, and the asymmetry of the beam shape and the beam irradiation position are corrected for each beam mode. There is. In this example, the mode obtained from the gallium liquid metal ion source, A
The beam diameter and beam current of the focused beams of and B are (0,2 μrn, 0.3 nA) and [0
, 4 μm, lnA). During machining work, by sequentially switching and selecting one of these beam modes, Ag and B, according to the machining specifications, the beam current and beam diameter can be electrically changed from outside the vacuum. We were able to improve machining efficiency.

[Example 3] FIG. 3 shows an embodiment of the present invention.

The electrostatic lens of this ion optical system has three stages, 210 to 212,
And the bottom is grooved. The beam modes A and B here are respectively two lenses, i.e. 210 and 212
, and 210 and 211 to create a focused beam. The beam between the lenses is operated by the lens 210 so that it becomes a nearly parallel beam, and switching between beam modes A and B is simple (by operating either lens 212 or 211). Since the lens is cut into small pieces, mode and folding changes can be easily controlled by the lens control unit 208.

In this embodiment, not operating the lens can be considered a special case where the lens strength is O.

In this embodiment, as in the first embodiment, the beam aligner 1 astigmatism corrector and the deflector 205 each have their own respective controls that apply voltages to them. @ part (not shown) 1
A memory function is provided for correcting beam shape and beam irradiation position deviation when switching between small beam modes.

The beam diameter and beam current of the focused beams of mode A and B obtained in this example are (0.2 μm
, 0.4 nA), and (0.6 μm, 3 nA)
It is.

During processing operations, among these beam modes A and B,
By electrically changing the lens strength and selecting one of them according to processing specifications, the beam diameter and beam current can be easily changed from outside the vacuum, improving processing efficiency.

In Examples 1 to 3, the aperture 204 is the objective lens 203.
It is placed immediately after, but the same effect can be obtained just before. In this case, the relationship between lens strength, beam diameter, and beam current becomes simple, which is convenient for practical beam control. On the other hand, when there are multiple apertures for determining the beam diameter, the relationship between the lens strength and the beam diameter and beam current becomes complicated, and the former is inferior to the former in terms of beam control simplicity.

Furthermore, the present invention can be applied not only to processing using a focused ion beam, but also to resist exposure using a focused ion beam, maskless ion implantation, and the like.

〔Effect of the invention〕

According to the present invention, any one of a plurality of combinations of beam diameter and beam current in a focused ion beam can be easily selected electrically from outside the vacuum, which is effective in improving the efficiency of beam processing.

[Brief explanation of the drawing]

1, 2, and 3 are schematic diagrams of a focused ion beam processing apparatus showing an embodiment of the present invention, and FIG. 4 is a schematic diagram of a conventional focused ion beam processing apparatus. Rod 1 Figure L 1

Claims (1)

[Claims] 1. In a focused ion beam processing device that focuses ions emitted from an ion source using an electrostatic lens to form a focused ion beam and processes a sample using the focused beam, a plurality of The invention is characterized by having a memory function for the lens strength corresponding to the combination of beam diameter and beam current of each of the focused ion beams, and configured so that one of the combinations can be electrically selected. Focused ion beam processing equipment.