JPS5836818B2 - Sputter neutral particle mass spectrometer - Google Patents

Description

Detailed Description of the Invention The present invention irradiates the surface of a solid sample with an ion beam, ionizes spattered neutral particles emitted from the ion beam with rare gas plasma, and guides the ions to a mass spectrometer. Concerning a sputtering neutral particle mass spectrometer for obtaining information about composition.

When ions are irradiated onto the surface of a solid sample, the constituent elements of the sample are secondarily released from the surface in the form of atoms or molecules due to a sputtering phenomenon.

Of these sputtered particles, only 10-10-3% are ions and most are neutral particles.

SIMS (
S econda ryIonMass Spect
rmetry), and IMA (Ion Mi
Croprobe Analysis') This analysis method is applied and regarded as important in many fields as a highly sensitive surface analysis method.

However, there are disadvantages in that the sensitivity coefficient varies by a factor of 1 to 104 depending on the type of element, and this sensitivity coefficient is very sensitive to the surface condition of the analysis sample (presence or absence of active elements in the analysis area).

Therefore, a correction term is required for this sensitivity coefficient for quantitative analysis, but the secondary ion release mechanism itself is not yet fully understood, and depending on the type of sample, it may not always be satisfactory. At present, quantitative analysis accuracy has not been achieved.

On the other hand, a method has recently been proposed that focuses on sputtering neutral particles and performs surface analysis by ionizing them by some means and performing mass spectrometry.

This analysis method is SNMS (Sputtered Ne
utralMass Spectroscopy)
etc., and rare gas plasma is mainly used to ionize sputtering neutral particles.

In SNMS, the sensitivity coefficients between elements are in a much narrower range than in SIMS, making data analysis easier from the standpoint of quantitative analysis.

The inventors of the present application have already proposed this analysis method, and its feature is that it utilizes the superposition of microwaves and a DC magnetic field for plasma excitation.

FIG. 1 shows its configuration. In the same figure,
Microwaves generated by the magnetron 1 are introduced into the L-shaped waveguide 2 from the horizontal side thereof.

A coil 3 is provided on the outer periphery of the vertical portion of the waveguide 2 for applying a static magnetic field in the vertical direction within the waveguide 2 .

A rare gas controlled at low pressure is introduced into the waveguide 2, and the rare gas is discharged by a high-frequency electric field generated by microwaves and a static magnetic field perpendicular to this, generating plasma in a part of the waveguide 2. let

An ion beam 8 is extracted from this plasma below the vertical portion of the waveguide 2, and is irradiated onto the solid sample 4 through the aperture 5 to cause sputtering on the sample 4.

The sputtered particles pass through the aperture 5 and are taken into the plasma within the waveguide 2, where the sputtered neutral particles are ionized.

Thereafter, the ions are guided as an ion beam 9 from vertically above the waveguide 2 through an aperture 6 to a mass spectrometer 7.
Information about the composition of the solid sample is obtained.

In order to create high-temperature plasma in a high vacuum using this device, it goes without saying that the frequency of the high-frequency electric field and the magnetic field strength must satisfy the conditions for electron cyclotron resonance as the fundamental excitation mode.

This device can effectively ionize and analyze sputtered particles in solid samples, so it has features such as high quantitative analysis accuracy.

However, in the above device, in order to operate the mass spectrometer at ground potential, it is necessary to maintain the plasma potential at Vi to 3 KV, and this voltage is directly applied to the waveguide 2.

Therefore, since the magnetron is at the same potential as the waveguide,
It operates at high potential.

Of course, it goes without saying that the surface potential of the waveguide will also be the same.

As described above, equipment that has many high-voltage exposed parts is extremely dangerous, and countermeasures must be taken.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a sputtering neutral particle mass spectrometer that eliminates the problems of the conventional devices described above.

In order to achieve the above object, in the present invention, an insulating tube is provided coaxially within the waveguide for generating plasma, and plasma is generated within the waveguide. It is characterized in that a plasma potential is applied through the terminals.

By having such a device configuration, (1) plasma potential can be applied through the introduction terminal;
Magnetrons, waveguides, etc. can now be used at ground potential, which eliminates high-voltage exposed parts and allows for safer equipment design. Some of the constituent elements mix into the plasma as impurities, which increases the analytical detection limit value of the same elements. However, by using an insulator tube that does not contain metal elements, this drawback can be overcome, and the field of application can be expanded. .

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 2 shows a schematic configuration diagram of a spatter neutral particle mass spectrometer according to the present invention.

In the same figure, microwave oven magnetron 11 (Hitachi 2
Frequency 2.45GHz generated by M161,600W)
The microwave passes through the rectangular waveguide 15 and enters the cavity (
or a waveguide) 16.

A quartz glass tube 17 is provided inside the cavity portion 16 coaxially therewith.

On the outer periphery of the cavity portion 16, there is a maximum of 0.0 mm in the horizontal direction within the quartz glass tube 17. Coil 1 for applying IT static magnetic field
8 is installed.

A sample chamber 12 is placed at one end of the quartz glass tube 17, and a mass spectrometer 13 is placed at the other end.

Further, a plasma potential introducing terminal 19 is attached to the tube wall of the quartz glass tube 17, and a voltage of about 3 KV from a DC power source 20 is applied to the terminal 19.

Approximately 4 × 10
Ar gas having a partial pressure of Pa is introduced.

Then, the electric field caused by the microwave will
The Ar gas is applied in the direction perpendicular to the axis of the quartz glass tube 1, and this and the horizontal static magnetic field cause the Ar gas to discharge,
Plasma 14 is generated within 7.

The potential of the plasma 14 at this time is given by the introduction terminal 19 and is about 3 KV.

An ion beam is extracted from this plasma 14 and irradiated onto the surface of a solid sample placed in the sample chamber 12.

Sputtering occurs on the sample surface due to ion beam irradiation.

The spatter particles are drawn into the plasma 14, where the spatter neutral particles are ionized.

Thereafter, the ions are introduced into the mass spectrometer 13 through the quartz glass tube 17, where an analysis of the composition on the surface of the solid sample is performed.

In this apparatus, in order to create a high-temperature plasma 14 in a high vacuum, the following conditions near the electron cyclotron resonance are applied between the frequency f of the high-frequency electric field and the magnetic field strength B, and an excitation fundamental mode is set.

However, q/m is the specific charge of electrons.

In this case, the direction in which the ion beam is extracted is made to match the direction of the magnetic lines of force produced by the coil 18 to reduce the influence of the magnetic field.

In the above-mentioned apparatus, a microwave oven magnetron is used as the magnetron 11, but this is only used because it is easily available, and the present invention is not limited to this, and other magnetrons may be used.

Therefore, the frequency range may be arbitrary, as long as the above-mentioned electron cyclotron resonance conditions are satisfied as an excitation fundamental mode.

However, by using the microwave band, it is possible to create a compact device.

Of course, the waveguides 15 and 16 are not limited to rectangular waveguides, but may be other types.

Further, the quartz glass tube 17 may be made of any other material as long as it is electrically insulating.

Further, the mass spectrometer does not need to be special, and any well-known one may be used.

As mentioned above, by generating plasma in the insulator tube and applying a plasma potential through the potential introduction terminal, there are no exposed high voltage parts on the waveguide surface, including the magnetron and cavity, which makes it possible to design a safe device. Ta.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of a conventional sputter neutral particle mass spectrometer, and FIG. 2 is a schematic block diagram of a sputter neutral particle mass spectrometer according to the present invention. 11... Magnetron, 12... Sample chamber, 13... Mass spectrometer, 14... Plasma, 15... Waveguide, 16... Cavity part, 17... Quartz glass tube, 18...
... Coil, 19 ... Plasma potential introduction terminal, 20 ... DC power supply.

Claims (1)

[Scope of Claims] 1. A waveguide configured coaxially with and surrounding the insulator tube, a high-frequency electric field generating means provided at one end of the waveguide, and within the insulator tube. means for applying a static magnetic field perpendicular to the high-frequency electric field; a potential introduction terminal provided in the insulator tube and connected to a DC power source at one end; and a means for introducing a rare gas into the insulator tube; means for controlling the pressure to a predetermined pressure; an ion beam extracted from one of the insulator tubes from a gas plasma generated by the high frequency electric field and the static magnetic field in the insulator tube and irradiated onto the solid sample; means for introducing sputtered particles of the sample obtained by sputtering the sample into the insulator tube; and means for extracting ions in the plasma in the insulator tube from the other side of the insulator tube and guiding them to a mass spectrometer. A spatuta neutral particle mass spectrometer comprising: 2. The sputtered neutral particle mass spectrometer according to claim 1, wherein the insulator tube is a quartz glass tube.