JPH0447423B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) When a sample surface is irradiated with an ion beam, the incident ions are scattered by the sample constituent atoms, or the sample constituent atoms are bounced off by the incident ions. By measuring the energy or mass of these scattered or recoil ions or neutral particles, elemental analysis and structural analysis of the sample surface are possible. The present invention relates to an ion scattering spectrometer which is an analysis device based on this principle.

(Prior Art) There are two types of ion scattering spectroscopy described above. One of them is ISS (lon scattering).
Spectroscopy is a method that captures the energy of incident ions that are scattered by colliding with sample atoms that are heavier than themselves, and measures the energy of the incident ions. Since the energy of the scattered incident ions is large (close to the energy before the incident), elements heavier than the incident ions can be detected and quantified based on the energy spectrum of the scattered ions. The other method is to detect elements that are lighter than the incident ions among the sample constituent elements and fly out from the sample surface when they are collided with the incident ions, and to measure the mass to discriminate between the elements. Detection
Analysis). In the case of ERDA, in addition to sample constituent atoms (rebound particles) flying out from the sample surface, there are also scattered components of incident ions, so normally the scattered components of incident ions are absorbed and removed by an absorber to determine the mass of the recoil particles. Analysis or energy analysis.

As mentioned above, the elements that can be analyzed by ISS and ERDA are divided into heavy and light elements based on the mass of the irradiated primary ions. On the other hand, in the past, ion scattering spectrometers were used only for the ISS or ERDA, which caused the inconvenience of not being able to analyze a wide mass range with a single device.

(Problems to be Solved by the Invention) The present invention aims to provide an ion scattering spectrometer that can perform both ISS and ERDE analysis simultaneously with one device. The problem here is that the scattering particles, which are the ions that are incident on the sample and are repelled by the sample's constituent atoms, and the recoil particles, which are the sample's constituent atoms that are bounced away from the sample by the incident ions, are emitted from the sample as a mixture. Therefore, the question is how to distinguish between these using a single device.

(Means for solving the problem) An ion source that irradiates the sample surface with a primary ion beam, and at the primary ion beam irradiation point on the sample surface,
A particle detection means is arranged in a direction that makes a small angle θ with the irradiation beam and detects the backscattered component of the primary ions from the sample surface, and a particle detection means that makes a large angle θ with the irradiation beam at the irradiation point of the primary ion beam on the sample surface. particle detection means for detecting emitted radiation particles recoiled by the primary ion beam from the sample surface; a chopper means for pulse-modulating the primary ion beam; and a pulse signal of the chopper means. An ion scattering spectrometer was constituted by a timer for starting a timer operation in synchronization, and a means for recording detection signals from each of the particle detection means in correspondence with the output of the timer.

(Function) When the sample surface is irradiated with a primary ion beam, the ions collide with the sample constituent atoms. When the collided sample constituent atoms are heavier than the primary ions, the primary ions are repelled. When this collision is close to a head-on collision, the primary ions are repelled in the opposite direction to the incident direction. These repelled particles are backscattered particles, and their energy increases as the sample constituent atoms that collide with them are heavier. Therefore, by analyzing the energy of the backscattered particles, it is possible to analyze sample constituent elements that are heavier than primary ions. I can do it. Particles that elastically collide with sample constituent atoms and are reflected, that is, scattering particles, are emitted from the sample in all directions, and the mass of the sample constituent atoms can be determined from the radiation angle and energy. Backscattered particles are particles close to , and these backscattered particles are detected almost purely in the direction forming a small angle θ with the primary irradiation ion beam in the figure. When the constituent atoms of the sample that are collided with the primary ions are lighter than the primary ions, they receive energy from the primary ions (the primary ions lose most of their own energy) and fly out from the sample surface. This is a recoil particle, and the recoil particle is recoil backward, that is, in a direction that makes a large angle (φ in the drawing) with the primary ion beam, so it is detected by a particle detection means placed in that direction, and the recoil particle ionizes the primary ion beam. Since the energy received from a recoil particle is related to the mass of the particle, elemental analysis and quantification of recoil particles can be performed by energy analysis.
Primary ion beam and large angle (see drawing)
In the direction of , the scattering particles have approximately the same energy as the primary irradiation ions, and the particles with different energy are recoil particles. In this way, the secondary radiation particles emitted from the sample are directed in the direction of detection.
They can be distinguished by making the angle nearly 180°. As a method of energy analysis, the primary ion beam is pulse-modulated, and a timing device synchronized with this modulation is used to collect secondary radiation particles (backscattered components, etc.) from the sample.
By measuring the time it takes for recoil particles to be detected, the energy of these particles can be analyzed regardless of whether or not they are charged.

(Example) The drawings show an example of the present invention. 1 is an ion source that forms a primary ion beam Iin for irradiating a sample.
2 is a sample, which is held on a table that can rotate around an axis perpendicular to the paper plane of the figure, and the primary ion beam on the sample surface.
It is now possible to change the slope relative to Iin. 3 is a microchannel plate for detecting scattered particles, which converts particles into electrons by hitting a honeycomb-shaped secondary electron emission surface, multiplies them, and collects the electrons with an anode 3a. Particles incident on the sensor are converted into electric current and detected. Using this detection means, both charged particles such as ions and neutral particles can be detected. Some of the primary ions scattered by the sample remain as ions, but many of them impart an electric charge to the sample and become neutralized when they collide with sample constituent atoms, so both charged particles and neutral particles can be detected. Detection methods are advantageous. The scattering particle detection means 3 is an ion beam irradiating the sample.
It is arranged to face the sample in a direction that makes a small angle θ with Iin, and is designed to detect backscattered components of primary ions incident on the sample. 4 is a microchannel plate for detecting recoil particles, and 4a is its anode, and this particle detection means is arranged so as to face the sample in a direction forming a large angle φ with the ion beam Iin irradiating the sample. An ion chopper 5 is arranged in front of the ion source 1. When a pulse signal is applied to the ion chopper 5, the ion beam can pass through the ion chopper 5 only while the pulse signal is applied. Numerals 6 and 7 are digital timekeeping devices which start their timekeeping operation at the fall of the pulse applied to the ion chopper 5. The clock outputs of the clock devices 6 and 7 are input to the CRTs 8 and 9 as X-axis coordinate signals. On the other hand, the output signals of the particle detection means 3 and 4 are applied to the CRT as a Y-axis signal.

When performing measurements using the ISS method, the irradiated primary ion beam Iin is modulated into pulses by the chopper 5 and is made incident on the sample 2. Particles scattered in the opposite direction to the incident ions, that is, backscattered incident ions and their neutralized particles enter the detection means 3 and are detected. If the pulse width of the pulse modulation of the irradiation ion beam Iin is small enough, the sample surface is the same as being instantaneously irradiated with ions, and the particles scattered on the sample surface are detected first, starting from those with the highest velocity. . Therefore, the X axis of the CRT8 is time, and the Y axis is
When the axis is displayed as the intensity of the particle detection signal, the speed distribution of the scattered particles is plotted on the CRT 8 because the timer 6 starts its timekeeping operation at the falling edge of the pulse applied to the chopper 5. The particles detected in this measurement are incident primary ions that collide head-on with sample constituent atoms and are repelled in the opposite direction to the ion incident direction. Capable of determining and quantifying sample constituent elements.

Next, when performing measurements using the ERDA method, the velocity distribution of recoil particles can be displayed on the CRT9 in the same way as in the case of the ISS. When an incident ion collides with an atom lighter than itself in the sample at an angle close to a head-on collision, the incident primary ion loses energy significantly and almost stops, and the collided atom gains the energy of the primary ion and becomes the incident primary ion. They are bounced off in roughly the same direction, but in this case, as the atoms leave the sample, they consume energy and lose speed. Therefore, in the velocity distribution drawn on the CRT9, the peak of the scattered component of the primary ion appears near the incident velocity of the primary ion, and the spectrum of the recoil sample atoms appears at a lower velocity than that.
Furthermore, at lower velocities, a spectrum of scattered components of primary ions that have lost most of their energy appears. The spectra of the recoil sample atoms can thus be identified.

In the above explanation, for convenience of explanation, it was written that they are performed separately, but since they are performed by irradiation with the same primary ion beam by two detection means placed in one device, they cannot be measured simultaneously. be.

In actual measurements, for example, helium ions are used as irradiation ions, the accelerating voltage is set to about several KV, the ISS method is used to detect and quantify elements heavier than Li, and the ERDA method is used to detect and quantify H.

(Effects of the Invention) According to the present invention, heavy elements can be determined by the ISS method and light elements can be determined by the ERDA method using one device. This type of device requires a vacuum, so when measuring all components of a single sample, it is extremely advantageous to be able to perform both the ISS method and the ERDA method with one device. In particular, since two types of measurements, ISS and ERDA, can be performed at the same time, the amount of analytical information that can be limited to the same amount of time is greater than in the past. As the conditions change, it becomes even more important to be able to perform both analytical methods with one instrument.

[Brief explanation of the drawing]

The drawing is a plan view of an apparatus according to an embodiment of the present invention.

Claims (1)

[Claims] 1. An ion source that irradiates the sample surface with a primary ion beam, and an ion source that is placed in a direction that makes a small angle θ with the irradiation beam at the primary ion beam irradiation point on the sample surface, and detects the backscattered components of the primary ions from the sample surface. a particle detection means arranged at the primary ion beam irradiation point on the sample surface in a direction forming a large angle with the irradiation beam, and detecting radiation particles recoil forward from the sample surface by the primary ion beam; a particle detection means, a chopper means for pulse-modulating the primary ion beam, and a timing means for starting a timing operation in synchronization with the pulse signal of the chopper;
An ion scattering spectrometer comprising means for recording detection signals from each of the particle detection means in correspondence with outputs from the timing means.