JPH0547933B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a secondary ion mass spectrometer that is capable of analyzing a minute region with a diameter of several μm or less.

(b) Prior art Secondary ion mass spectrometers irradiate a sample surface with a primary ion beam of argon ions, etc., and mass analyze the secondary ions emitted from the sample surface. The analyzer requires a large dual-plasmatron ion source and a large electrostatic lens system as an ion gun in order to perform local analysis of several micrometers or less as mentioned above, making the equipment expensive. It became something.

Additionally, in the case of an electrically insulating sample, the sample is charged by the primary ions and the potential of the emitted secondary ions changes, causing the ions to be unable to pass through the energy selector that is part of the analysis system, or the ion source In many cases, this analysis method could not be applied because the potential difference between the material and the material became small.

(c) Purpose The present invention provides a secondary ion mass spectrometer that uses a simple microbeam ion gun with a beam diameter of several millimeters and is capable of analyzing minute regions of insulating samples. With the goal.

(d) Configuration The secondary ion mass spectrometer of the present invention is equipped with a microbeam electron gun that can obtain a beam diameter of 0.1 to 100 μm in addition to a microbeam ion gun, such as a BA type ion gun, that irradiates the sample surface. By irradiating an arbitrary point on the sample surface with the electron beam within the area irradiated by the primary ion beam emitted from the ion gun, only that part is charged by the primary ions. By neutralizing it, it is possible to distinguish low-energy secondary ions from that part from secondary ions from other parts, and select these low-energy secondary ions for mass spectrometry. It is characterized by

(E) Embodiment FIG. 1 shows an embodiment of the present invention. 1 is a microbeam ion gun that forms a beam of primary ions, F is a filament, G is a grid, and R is a repeller electrode. A gas such as argon is introduced into the repeller electrode R, and atoms of the gas are ionized by electrons accelerated between the filament F and the grid G. L constitutes an electrostatic lens system, which focuses the primary ion beam onto the sample 2. In the case of this ion gun, it is assumed that the ions are focused onto the sample. 3 is an electron optical system, f is a filament, w is a Wehnelt electrode,
1 and ¹ are electrostatic lens systems constituting a reduction projection system, which forms a minute image of the electron source on the surface of the sample 2, the diameter of which can be adjusted in the range of 0.1 to 100 μm. Furthermore, the electron beam can be swung in both the X and Y directions on the surface of the sample 2 using the scanning electrode. The optical axes of the ion gun 1 and the electron optical system 3 intersect on the surface of the sample 2, and as shown in FIG. It is designed to irradiate a minute area within the body. When the sample 2 is electrically insulating, when it is irradiated with positive primary ions, the irradiated area becomes positively charged, and the charged potential causes a change in the energy of the secondary ions. When the area irradiated by the primary ions is scanned with the electron beam E, the charge caused by the primary ions on the sample surface is neutralized in the area irradiated with the electron beam, and the secondary ions that can pass through the energy separator from that area are neutralized. Next ions will be released.

Returning to Figure 1, 4 is a spherical electric field type ion energy analyzer, which acts as an energy selector by applying a constant voltage between both electrodes, and detects low energy emitted from the surface of sample 2. Only secondary ions are allowed to pass through. Reference numeral 5 denotes a mass spectrometer, and although a quadrupole type mass spectrometer is used in this embodiment, a magnetic field type mass spectrometer may also be used. 6 is an ion detector, the output signal of which is amplified by an amplifier 7 and input to a recorder 8, which records a mass spectrum. Alternatively, the applied voltage of the mass spectrometer 5 is set so that only ions of one specific mass are detected, and the output of the amplifier 7 is inputted to the CRT 9 as a brightness signal.
The CRT 9 and the electron optical system 3 scan synchronously,
It is also possible to display the distribution pattern of a specific element on the sample surface.

(f) Effects According to the present invention, an ion gun with a simple structure, in other words, an ion gun that cannot narrow down the ion beam, is used, so the device cost is low, and the primary ion beam is relatively thick. Nevertheless, local analysis of insulating samples has become possible by using narrow electron beams, which are generally easily obtained.

[Brief explanation of the drawing]

FIG. 1 is a side view of an apparatus according to an embodiment of the present invention, and FIG.
The figure is a side view showing the relationship between the primary ion beam and the electron beam on the sample surface in the present invention. 1... Ion gun, 2... Sample, 3... Electron optical system, 4... Ion energy selector, 5... Mass spectrometer, 6... Ion detector.

Claims (1)

[Claims] 1. A macro beam ion gun that generates a primary ion beam that irradiates the sample surface, an electron optical system that irradiates an arbitrary micro region within the irradiation area of the sample surface with the primary ion beam, and an electron beam that irradiates the sample surface with the electron beam. A secondary ion system comprising an energy selection means for distinguishing low-energy secondary ions emitted from an irradiation region from secondary ions emitted from other regions, and a mass spectrometry means into which ions that have passed through the same means are incident. Mass spectrometer.