JPH0332852B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides novel improvements in lenses for devices that use ion and electron beams, such as ion beam exposure devices and analyzers that use ion sources.

In an ion beam exposure device or a secondary ion mass spectrometer, a finely focused primary ion beam scans the surface of a sample to process the sample and analyze secondary signals obtained from the sample.

Electrostatic lenses are often used to focus ion beams, and this has the advantage that electrostatic lenses can focus ions with different mass numbers with the same voltage.

On the other hand, if the electron beam can be irradiated onto the sample from the same axis as the ion beam, there are many advantages. For example, the difference in physical characteristics between ions and electrons can be used to observe the surface shape with an electron beam, and microfabrication can be performed with an ion beam. Auger electron spectroscopy can be performed using an electron beam. In this case, since the processing and analysis area on the sample surface is minute, it is particularly important to be able to irradiate electrons and ions from the same axis. An electrostatic lens may be used to converge the electron beam, but if you try to converge the electron beam down to several tens of angstroms, the precision of lens machining becomes difficult. Therefore, magnetic lenses are usually used.

An object of the present invention is to provide extremely effective means for the above-mentioned device that shares ions and electrons.

The lens for converging charged particles is 1/a+, whether it is an electrostatic lens or a magnetic lens, the same as an optical lens.
The formula 1/b=1/f holds true. Here, a is the distance from the light source to the lens center, b is the distance from the lens center to the imaging point, and f is the focal length.

That is, in order to narrow down the aperture as narrowly as possible, it is better to shorten the distance from the center of the lens to the imaging point (sample position). However, if you want to install a detector for various information obtained from the sample in the chamber near the sample and bring it as close to the sample as possible to increase efficiency, a certain distance between the sample and the lower surface of the lens (referred to as working distance) is required. It's coming. Therefore, in order to maintain a certain operating distance and bring both the electrostatic lens and the magnetic lens close to the sample surface, it is necessary to combine them well.

A preferred embodiment of the charged particle lens according to the present invention will be described in detail below with reference to FIG.

In FIG. 1, a magnetic lens is constituted by a magnetic lens winding 1 and a magnetic circuit 2, in this case 4.
acts as a lens aperture. Further, 3 and 5 are the upper and lower electrodes of the electrostatic lens, which are normally at ground potential. Also 4
acts as an intermediate electrode and applies a high voltage. Also, the insulator 6 serves to float high voltage and bring voltage into the vacuum from the outside.

The lens diaphragm or intermediate electrode (4) in the figure has a hole diameter of 100μ to several hundred μ in the case of a magnetic lens, and 1 mm to several mm in the case of an electrostatic lens, so it is best suited depending on the purpose by making multiple holes and moving it from outside the vacuum. Allows selection of hole diameter. Further, if the three electrodes 3, 4, and 5 constituting the electrostatic lens are made of a non-magnetic material, such as tantalum or molybdenum, damage caused by ions can be reduced. When used as a magnetic lens, the intermediate electrode 4 is grounded or at a potential close to this.

[Brief explanation of drawings]

The drawing is a configuration diagram showing a charged particle lens according to the present invention. 1...Magnetic lens winding, 2...Magnetic circuit, 3...
...Upper electrode, 4...Middle electrode, 5...Lower electrode.

Claims (1)

[Claims] 1. A magnetic lens composed of a coil winding and a pair of magnetic poles, an aperture having a plurality of holes with different diameters provided between the pair of magnetic poles, and an electrostatic lens provided above and below the aperture. It consists of an electrode, a means for externally selecting a predetermined hole diameter of the aperture in a fixed position, and a means for applying a high voltage to the aperture, and an electrostatic lens is configured by applying a high voltage to the aperture. A charged particle lens characterized by: