JPH0233848A - Secondary ion mass spectrometer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a secondary ion power purchase analyzer, and more particularly to a secondary ion mass spectrometer that can accurately analyze minute parts of a sample.

[Conventional technology]

For conventional secondary ion mass spectrometers, see Zahitachi.
Scientific Instrument News
27 (1984) pp. 2348-2354 (T
HE HITACHI SCTENTIFICINST
RUMENT NEWS 27 (1984) PP2
348-2354) L:, discussed in . Regarding the operation of conventional equipment.

This will be explained using FIG. The ions generated by the ion source are accelerated by tf! A high voltage is applied to the ion source 1 by 1g17, and the ions are extracted and accelerated by an electric field formed between the ion source 1 and the extraction electrode 2. After the path of the primary ion beam 15 accelerated in this way is refracted by, for example, 5 degrees by the ion beam refractor 6, the sample 10 is converge on the surface of Secondary ions 16 emitted from the sample 10 are subjected to mass separation by a mass separator 11 .

The above operations allow elemental analysis of the surface of the sample 10. In addition, by applying an appropriate scanning signal voltage to the deflection voltage pj49 from the deflection power supply 22, the next ion beam 1
5 can be scanned on the sample, and the signal of the secondary ions 16 detected by the mass separator 11 is used as a brightness modulation signal.
When applied to the CRT 13, a secondary ion image can also be obtained on the CRT screen. Furthermore, if the primary ion beam 14 is similarly scanned over the sample and the intensity of the mass-separated secondary ions is monitored at the same time, depth analysis can be performed by replacing the elapsed sputtering time with the depth from the surface of the sample 10. It can be done with high precision.

Here, the role of the ion beam refractor 6 will be explained.

When the accelerated primary ions collide with residual gas molecules in a vacuum, charge transfer occurs between the accelerated primary ions and the residual gas molecules. The ions lose their charge and become high-speed neutral particles 15 and continue flying. Without the ion beam refractor 6, the neutral particles 15 would travel straight, reach the sample 10 without being subjected to the focusing action of the electrostatic lens 8, and irradiate a larger area than the ion beam. When the sample 10 is irradiated with such neutral particles 15, the sample 10 is sputtered to emit secondary ions 16 in the same manner as in the case of ion irradiation. In such a case, (1) the accuracy of minute point analysis, line analysis, and surface analysis will be degraded; (2) Decrease the depth resolution of depth direction analysis. etc., which seriously affects measurement accuracy. To solve this problem, an ion beam refractor 6 is provided as shown in FIG. 2, and only the primary ion beam 14 is refracted and irradiated onto the sample, while the neutral particles 15 are not refracted. Go straight ahead to avoid irradiating the sample. This allows for highly accurate measurements. However, when an ion beam refractor is provided, the ion beam irradiating the sample cannot be made into a finer beam than when no ion beam refractor is provided.

[Problem to be solved by the invention]

The above-mentioned conventional technology does not take into account the deterioration of the convergence characteristics of the ion beam due to chromatic aberration occurring in the ion beam refractor. In other words, the ion beam extracted from the ion source generally has an energy spread of several tens of eV, and the degree of refraction by the ion beam refractor varies depending on the energy of the ions, so the ion beam spreads in the direction of refraction. Even if an attempt is made to condense the beam once expanded due to the chromatic aberration of the ion beam refractor, the ion beam cannot be condensed into a fine beam unless the ion beam refractor is used. Therefore, the ability to point-analyse the smallest part deteriorates, and there is a problem in that the resolution decreases in secondary ion image observation. However, as mentioned above, when an ion beam refractor is not used, there is a problem in that the neutral particles irradiate a larger area.

An object of the present invention is to provide a secondary ion mass spectrometer capable of obtaining high spatial resolution point analysis and high resolution secondary ion images without deteriorating the focusing characteristics of the ion beam even when the above-mentioned ion beam refractor is provided. The goal is to provide equipment.

[Means to solve the problem]

In order to achieve the above object, in the secondary ion mass spectrometer of the present invention, an ion beam converging lens is provided upstream of the ion beam refractor, and means for monitoring the beam convergence status is provided near the ion beam refractor. Ta.

[Operation] When the ion beam is focused on the effective refraction point of the ion beam refractor by the ion beam converging lens installed in the front stage of the ion beam refractor, chromatic aberration (refraction caused by the difference in energy of each ion making up the beam) It is possible to refract the beam under conditions where no difference in effect occurs. This will be explained using FIGS. 3 and 4. In FIGS. 3 and 4, reference numeral 6 denotes an ion beam refractor, which in this case consists of an electrostatic deflector consisting of two flat plates. FIG. 3 shows trajectories A, B, and C in which ions having different energies are refracted at different rates.

However, as shown in the figure, if the ion beam entering the refractor is aimed at the effective refraction fulcrum It appears to be launched from the effective refraction fulcrum X. Therefore, when the ion beam 14 is made incident so as to be converged on the effective refraction fulcrum X as shown in FIG. 4, all of the ion beams after being refracted appear to be emitted from the effective refraction fulcrum X. In other words, the refraction fulcrum becomes a new point source, and the beam spreading effect due to energy variation is canceled out. In order to set the ion beam to this chromatic aberration elimination condition, it is necessary to converge the ion beam to an effective refraction fulcrum, and the focal length of the ion beam converging lens is changed while monitoring the convergence status with a monitoring device.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
The device shown in the figure has the following components added to the conventional device shown in FIG. An electrostatic lens 3 is provided as an ion beam converging lens in the front stage of the ion beam refractor 6, its lens power source 18, deflection electrode 4, its deflection power source 19, an arbor 5 is provided at the entrance of the ion beam refractor 6, and a secondary electron is provided diagonally above the electrostatic lens 3. Detector 7 and CRT1,2. In this embodiment, the ion beam refractor 6 is composed of an electrostatic deflector 6 made up of two flat plates.

Next, the operation of this embodiment will be explained. After ions are extracted from the ion source 1 and accelerated in the same manner as in the conventional device, a scanning voltage signal is applied to the deflection electrode 4 from the deflection power source 19 to cause the primary ion beam 14 to scan. Here, if the secondary electrons emitted from the aperture 5 are detected by the secondary electron detector 7 and the signal is manually input to the CRT 12 as a brightness modulation signal, a secondary electron image of the aperture 5 can be obtained. While observing this secondary electron image, the primary ion beam 14 is focused onto the aperture 5 by applying a voltage of ga to the electrostatic lens 3 from the lens power source 8 . After that, the deflection power source 4 is turned off and scanning of the primary ion beam 14 is stopped. The primary ion beam 14 then passes through the hole of the aperture 5 and reaches the electrostatic deflector 6.

When the electrostatic deflector 6 is configured with a parallel plate as in this embodiment, the condition for canceling the chromatic aberration of the electrostatic deflector 6 is to focus the ion beam on the center point within the electrostatic deflector 6. . Therefore, the voltage applied to the electrostatic lens 3 is finely adjusted. This adjustment can be performed relatively easily because the distance between the center point of the electrostatic deflector 6 and the aperture 5 is short. Further, the 51 integer is calculated in advance from the relationship between the focal length of the electrostatic lens and the voltage. After this, the primary ion beam 1 is
4 on the sample and the subsequent analysis are the same as in the conventional apparatus.

According to this embodiment, the minimum primary ion beam diameter on the sample is approximately the same as the ion beam diameter obtained with an apparatus without an ion beam refractor 6, and approximately 1/2 of that obtained with an apparatus using an ion beam refractor. It was small. Therefore, there was no problem caused by high-speed neutral particles mentioned above, and it was possible to analyze minute parts with even higher spatial resolution. In addition, in this embodiment, an aperture aligned with the upper part of the ion beam refractor 6 was provided, and this secondary electron image was used to adjust the convergence conditions of the electrostatic lens 3. There was also the advantage that the optical axis of the ion beam entering 6 could be confirmed.

The ion beam can also be focused on the center point of the electrostatic deflector by providing a focus adjustment test sample at the center point and observing the secondary electron image on it in the same manner as in the above embodiment. was completed.

However, in this case, it is necessary to take out the sample outside the ion beam refractor while the ion beam refractor is in operation.
It was extremely complicated.

In this embodiment, a parallel plate electrostatic deflector is used as the ion beam refractor, but a general refractor such as a spherical electrostatic deflector or a magnetic field deflector may be used. Further, in this embodiment, the aperture is provided at the top of the ion beam refractor, but it may of course be provided at the bottom. Further, in this embodiment, an anno(-thia) secondary electron image is used, but a secondary ion image, an absorbed current image, and a transmitted ion image may also be observed.

〔Effect of the invention〕

According to the present invention, the sample is not irradiated with high-speed neutral particles generated near the ion source, the chromatic aberration of the ion beam refractor can be canceled, and the convergence characteristics of the primary ion beam do not deteriorate. , has the following effects.

(1) High spatial resolution point analysis and high resolution secondary ion images can be obtained.

(2) *Highly accurate analysis is possible in small point analysis, line analysis, and area analysis.

(3) In depth analysis, analysis with high depth resolution is possible.

The above effects are achieved by providing a mechanism that can monitor the convergence status of the ion beam within the ion beam refractor, improving the operability of the device, and improving the accuracy of canceling out the chromatic aberration of the ion beam refractor. Obtained.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention, FIG. 2 is an overall configuration diagram showing an example of a conventional device, and FIG. 3 is an illustration of ions with different energies entering the refractor. FIG. 4 is a diagram showing the ion beam trajectory when the ion beam is incident so as to be converged on the center point of the refractor. DESCRIPTION OF SYMBOLS 1... Ion source, 2... Extraction electrode, 3... Electrostatic lens, 4... Deflection electrode, 5... Aperture, 6
...Ion beam refractor, 7...Secondary electron detector,
8... Electrostatic lens, 9... Deflection electrode, 10... Sample, 11... Mass spectrometer, 12... CRT, 13...
...CRT, 14...Primary ion beam, 15...
Neutral particle, 16... Secondary ion, 17... Acceleration power source, 18... Lens power source, 19... Deflection power source, 20.
...Ion beam refractor power supply, 21Z 1. Distance 2. Flash

Claims (1)

[Claims] 1. An ion source that generates primary ions, a convergent lens system that focuses the generated primary ions into a fine ion beam, an ion beam deflection system that deflects the ion beam, a sample that is irradiated with the ion beam, and a sample that is irradiated with the ion beam. In a secondary ion mass spectrometer that consists of a mass spectrometer that performs mass analysis of emitted secondary ions, there is an ion beam refractor that refracts the ion beam between the ion source and the sample, and an ion beam refractor that refracts the ion beam between the ion source and the sample. A beam converging lens is provided, and the method includes means for monitoring the convergence status of the ion beam within the ion beam refractor in order to adjust the operating conditions of the convergent lens to cancel out chromatic aberration of the ion beam refractor. Secondary ion mass spectrometer. 2. In claim 1, the ion beam monitoring means includes an ion beam scanning deflector that is disposed upstream of the ion beam refractor and scans the ion beam two-dimensionally, and an ion beam refractor. It consists of a sample plate with holes provided on the top or bottom surface, and an observation means for observing an absorbed current image, transmitted ion image, or secondary particle image of the sample plate when the ion beam is scanned. A secondary ion mass spectrometer characterized by: