JPS6264037A - Focused ion beam apparatus - Google Patents

Abstract

PURPOSE:To enable beam blanking without sacrifice of mass resolution by arranging beam blanking electrode respectively at the symmetric position on the beam axis with respect to the position of restriction board in the rear of a mass separator. CONSTITUTION:The ion beam emitted from liquid metal ion source 1 is focused through a focus lens 4 to form a cross-over image C1 of an ion source 1 onto a restriction board 10 in the rear of a Wien filter 8. Blanking electrodes 21, 22 are arranged at symmetrical positions on a beam axis respectively with respect to the position of a restriction board 10. Consequently, blanking deflection is substantially executed at the position of corss-over image C1 of beam of desired type of ion resulting in such beam blanking as will cause no disturbance of beam.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a focused ion beam apparatus suitable for implant exposure using a focused ion beam.

[Background of the invention]

The conventional focused ion beam device is disclosed in Japanese Patent Application Laid-open No. 6O-8905.
1. FIG. 1 shows an outline of this device.

The device includes an ion source 1 and a first focusing lens for focusing the ion beam emitted from the ion source 1 and forming a crossover image C1 of the ion source 1 at the center of a Wien filter 8 for mass separation. 4. Vienna filter 8
It consists of a second focusing lens 11 and a deflection electrode 13 for focusing the ion beam that has passed through the aperture plate 10 at a predetermined position b' of the material -L.

Now, control when the ion beam is shot onto the sample 12 is performed by a beam blanking electrode disposed on the beam path. That is, a pulse is applied to the blanking electrode from a pulse generator that generates a pulse signal having widths of peak and valley portions corresponding to the respective times based on the shot time and non-shot time signals from the control device 15. The shot time is controlled by supplying a signal. By the way, the pulse signal supplied to the blanking electrode generally has a slope in its rise and fall, and unless deflection for blanking is performed at the crossover point of the ion beam, the period of the rise and fall will be In this case, the beam oscillates on the sample, and the beam ends up hitting areas other than the predetermined areas.

In this conventional device, the beam blanking electrode 21.
．． 22 are arranged at symmetrical positions on the beam axis with respect to the center of the Wien filter 8, and deflection for beam blanking is substantially performed at the crossover image C1 position of the beam of the desired ion species. This ensures that the beam does not fluctuate on the sample 12 during the rising and falling periods of the pulse signals supplied to the blanking electrodes 21 and 22. However, from the viewpoint of increasing the mass resolution of the Wien filter 8, it is not a good idea to bring the crossover image C1 to the center of the Wien filter 8, but it should be brought above the aperture plate 10. In the latter case, there is a disadvantage that no substantial beam blanking is performed at the crossover image C1, and the beam oscillates on the sample 12 during blanking.

[Purpose of the invention]

An object of the present invention is to provide a focused ion beam device that enables beam blanking without lowering the mass resolution of a mass separator and without causing beam fluctuation at sample-1-.

[Summary of the invention]

Boo.

The present invention aims to achieve the following two objects by forming a crossover image of the ion source on a diaphragm plate after a Wien filter in a focused ion beam device, and with respect to the position of the diaphragm plate, the beam axis - 1-, is characterized in that deflection electrodes for beam blanking are provided at symmetrical positions.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. In the present invention, the ion beam emitted from the liquid metal ion source 1 is focused by the first focusing lens 4, and a crossover image C1 of the ion source 1 is formed on the aperture plate 10-1 after the Wien filter 8. do.

The blanking electrodes 21 and 22 are arranged at symmetrical positions with respect to the beam axis -1- with respect to the position of the aperture plate 10, and form a cross-over image C1 of the beam of desired ion species.
Since deflection for blanking is substantially performed at the position, there is an effect that the beam does not fluctuate on the sample 12 during blanking.

Next, mass resolution will be explained using FIG. 3.

The ion mass number of the desired beam reaching the aperture plate 10 is m
, the beam diameter at the aperture plate 10-A is d. On the other hand, if the distance between the respective beams 23 and 24 on the aperture plate 10 with mass numbers m-Δm and m is D, and the hole diameter or slit width of the aperture plate 10 is W, then the mass resolution R is given by the following formula. Desired. (However, W > d) From equation (1), R is higher when d is smaller, that is, when the crossover lik CI of the ion source 1 is focused on the aperture plate 10 than when it is focused on the center of the Wien filter 8. I know what will happen. However, from the viewpoint of reducing the chromatic aberration of the Wien filter, the latter is better than the former (for the reason, see JP-A-59-16065).

Next, another embodiment of the present invention will be described with reference to FIG. In this device, there are four electromagnets 25 to 28 between the first focusing lens 4 and the second focusing lens 11, and their magnetic fields have the same strength and size, but the direction of the magnetic field is the same as that of the first focusing lens. and the fourth electromagnet are the same, and the second and third ones are in opposite directions to the first one. Electromagnets 25 to 28 are aperture plate 10
The blanking electrodes 21 and 22 are also located at symmetrical positions on the beam axis.

The mass separator 8 in this device corresponds to the electromagnets 25 and 26. The electromagnets 27 and 28 are for canceling the chromatic aberration caused by the electromagnets 25 and 26. In this embodiment as well, the deflection for blanking is substantially over the crossover of the ion source 1 without reducing the mass resolution. It will be held at Statue C1.

This has the effect of not causing the beam to oscillate on the sample 2 during blanking.

In Examples 1 and 2, there are two stages of focusing lenses, but even if there are three or more stages, the beam blanking electrode is located at a symmetrical position on the beam axis with respect to the position of the aperture plate after the mass separator. A similar effect can be obtained if installed.

〔Effect of the invention〕

According to the present invention, the beam 11 of the desired ion species is shot at a predetermined position on the sample because the mass resolution of the mass separator is not reduced and the beam 11 does not move on the sample during blanking. There is an effect that it can be done.

4 and 4 are diagrams showing an embodiment of the focused ion beam device of the present invention. FIG. 3 is an explanatory diagram of the mass resolution at the aperture root of the focused ion beam device.

DESCRIPTION OF SYMBOLS 1... Ion source, 2... Power source for heating, 3... Extracting electrode, 4... First Kento lens, 5... Cathode, 6... Extracting power source, 7... Accelerating power source, 8... Mass separator, 9... Power source for mass separation, 10... Aperture plate, 11... Second focusing lens, 12... Sample, 13
... Deflector for position control, 14 ... Power supply for deflection, 15
...control device, 16.17...focusing lens power supply, 2
1.22...Blanking electrode, 23.24...Ion beam of mass number m and ■1-Δm, 25-28.
··electromagnet.

Claims (1)

[Claims] 1. An ion source, and a first ion source for focusing the ion beam extracted from the ion source and forming a crossover image of the ion source on the aperture plate after the mass separator for mass separation.
a second focusing lens for focusing the ion beam that has passed through the aperture plate onto the sample; and a second focusing lens for irradiating the ion beam focused on the sample onto a predetermined position on the sample. In an apparatus comprising deflection means,
A focused ion beam device in which beam blanking electrodes are arranged at symmetrical positions on the beam axis with respect to the aperture plate position.