JPS63193038A - Method and apparatus for analyzing solid element - Google Patents

Abstract

PURPOSE:To measure impurities of several ppm without requiring high vacuum, by irradiating a solid specimen with ions to generated secondary luminescence and detecting the timewise changes in the intensities of the spectrum pattern thereof and a specific spectrum. CONSTITUTION:For example, a turbo pump 12 of which the ultimate vacuum degree is 10<-6>-10<-7>Torr is provided to a vacuum chamber 10 equipped with a solid specimen M. Next, when the specimen M is irradiated with ion beam such as H<+> in energy of about 10-200KeV from an ion acclerator 22, secondary luminescence is emitted. Hereupon, a spectral path 34 and a luminous intensity detector 38 separate all of the spectra of the secondary luminescence emitted at a certain moment and detect the luminous intensities thereof to detect the contained in the specimen M. A specific spectrum is separated and, by detecting the quantity of light over a long time, the specimen M is sputtered in the depth direction of the specimen M almost in proportion to an irradiation time and, therefore, by detecting the timewise change in the intensity of the specific spec trum, the compositional components of the specimen in the depth direction thereof can be known.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and apparatus for analyzing elements in a solid, and in particular to analyzing elements in the depth direction of a thin film formed on a substrate.
The present invention also relates to a method and apparatus suitable for analyzing elements at the interface between a substrate and a thin film.

[Prior Art] Traditionally, secondary ion mass spectrometry (hereinafter referred to as SIMS) has been used for elemental analysis of solids, particularly for elemental analysis in the depth direction of fl films.
It is abbreviated as )It has been known.

This SIMS is usually used to irradiate a sample solid with primary ions of about 25 KeV from eV to directly perform mass spectrometry on secondary ions of sample atoms that are secondarily sputtered from the sample surface. This SIMS has a method in which the primary ion current density is high, the sputtering rate is high, and the surface is constantly changing due to etching, and a method in which the primary ion current density and sputtering rate are extremely reduced. There is a method in which spatter is suppressed as much as possible and analysis is performed in a state where destruction of the sample surface layer can be ignored.

The former analysis method is used for ultra-trace analysis and depth direction analysis of samples. On the other hand, the latter is used to detect molecular ions and their fragment ions in addition to elemental analysis, and to analyze molecular elements on the surface.

[Problems to be Solved] Incidentally, the former analysis method has the problem that the sample surface is destroyed by the etching phenomenon, and is not suitable for non-destructive analysis.

On the other hand, in the latter case, as mentioned above, the destruction of the sample surface is negligible, so non-destructive analysis is possible. However, since the sputtering speed is low, it is easily affected by residual gas in the sample chamber.
There is a problem in that a high degree of vacuum below rr is required.

In addition, in the latter case, since there were few secondary ions released from the sample surface, the amount of impurities in the sample could only be measured at about 1100 pp.

The present invention was made to solve the above problems, and
It is an object of the present invention to provide a solid state elemental analysis method and an apparatus therefor, which requires only a degree of vacuum of about 10 to 10 Torr, does not require an extremely high vacuum, and is capable of measuring impurities of several ppm.

[Means for solving the problem] The present invention irradiates energy from the outside to a sample solid placed as an object to be irradiated in a vacuum chamber, and detects photons emitted from the object with high sensitivity. The present invention relates to a method and apparatus for analyzing elements.

The method of the present invention aims to solve the problems in solid-state elemental analysis methods by irradiating a solid sample with ions having an energy of 1 OKeV or more to generate secondary luminescence, and then determining the spectral pattern and/or
Alternatively, a solid-state elemental analysis method is disclosed, which is characterized in that the elements of a solid are analyzed by detecting changes over time in the intensity of a specific spectrum of the luminescence.

In addition to ions, energy irradiated from the outside includes electrons, lasers, and the like, and detection photons include atomic spectra and the like.

Furthermore, to specifically disclose the method of the present invention, (1) to (
5), however, the method of the present invention is not limited to this.

(1) A sample solid placed as an irradiated object in a vacuum chamber is irradiated with ions, and ions are released from the irradiated object.
In a method of analyzing elements in a solid by secondary radiation, a sample solid is irradiated with ions having an energy of 10 KeV or more to generate secondary luminescence, and the spectral pattern of the luminescence and/or the intensity of a specific spectrum of the luminescence are A solid-state elemental analysis method that analyzes elements in solids by detecting changes over time.

(2) The above (1) using a thin film formed on a substrate as a sample solid
) solid state elemental analysis method described.

(3) The ions that irradiate the sample solid are H", He"
, Ar', the solid elemental analysis method according to (1) or (2) above.

(4) The degree of vacuum is 1O-6 Torr or less (1)
) or the solid-state elemental analysis method described in (2).

(5) The ions that irradiate the sample solid are H", He",
The method for solid elemental analysis according to (1) or (2) above, wherein the solid state is At' and the degree of vacuum is 10-' Torr or less.

The present invention also provides an apparatus for realizing a solid-state elemental analysis method, which includes: irradiation means for irradiating energy to a sample solid in a vacuum chamber; means for detecting a spectral pattern of photons emitted by the energy irradiation; /
The present invention also discloses a solid-state elemental analyzer equipped with a means for detecting a time change in the intensity of a specific spectrum of photons.

Furthermore, the device of the present invention is specifically disclosed as shown in (1) and (2), however, the device of the present invention is not limited to this.

(1) A sample solid placed as an irradiated object in a vacuum chamber is irradiated with ions, and ions are released from the irradiated object.
In an apparatus for analyzing elements in a solid by radiation, a sample solid in a vacuum chamber is exposed to l.

ion irradiation means for irradiating with ions having energy equal to or higher than KeV; means for detecting a spectral pattern of secondary luminescence emitted by the ion irradiation; and/or means for detecting temporal changes in the intensity of a specific spectrum of the luminescence. A solid-state elemental analyzer consisting of:

(2) The solid-state elemental spectrometer according to (1) above, further comprising a switch between the ion irradiation means and the vacuum chamber.

Although the present invention described above can select an appropriate solid as a sample, it is suitable for application to elemental analysis of a thin film formed on a substrate.

The energy irradiated to the sample solid includes ions, electrons,
There are lasers, etc., and in the case of ions, ions of atoms that do not cause a chemical reaction with the sample are selected, preferably H''',
He', Ar''. Note that ion, laser, etc. irradiation is suitable for internal analysis of solids.

Electron irradiation is suitable for analysis of fixed surfaces.

In addition, the vacuum degree of the vacuum chamber is 1G-6Tor.
r or less.

[Function] The present invention provides a sample solid in a vacuum chamber with 10Ke
By irradiating with energy equal to or higher than V, the kinetic energy is imparted to the sample solid, and electrons belonging to atoms forming the sample solid become excited. Light is emitted when these electrons transition to a lower energy state. That is, it emits secondary luminescence.

This secondary luminescence has a spectral pattern unique to each atom, so by detecting this pattern, it is possible to know the atoms contained in the sample. Furthermore, the content of each atom can be determined from the relative intensity ratio of a specific spectrum in the spectral pattern of each atom.

Furthermore, when the energy irradiation time is increased, the sample is sputtered in the depth direction of the sample solid almost in proportion to the irradiation time, atoms deep in the sample solid are excited, and secondary luminescence is generated from this position. radiated. Therefore, by emitting energy for a long time and detecting the time change in the intensity of a specific spectrum in the spectral pattern of each atom, it is possible to know the compositional elements in the depth direction of the sample solid.

By the way, in the conventional 5INS mentioned above, sputtering '
Only the atoms that are ejected by this method are subject to measurement.

Therefore, the remaining atoms that did not fly out are not included in the measurement, and if there are few sputtered atoms, the observed atoms will vary widely, resulting in low resolution.

On the other hand, in the present invention, since secondary luminescence is measured, it is necessary to measure not only atoms ejected by sputtering but also atoms remaining without ejecting as long as they emit luminescence. therefore,
Even if the sputtering rate is low, there will be no variation in observation.

High resolution of several pp.2, that is, high sensitivity detection can be achieved.

Note that, although detecting luminescence as photons facilitates high-sensitivity detection, it is also possible to implement the present invention by detecting and analyzing an atomic spectrum.

[Example] Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the solid-state elemental analyzer of the present invention.

The solid-state elemental analyzer of this embodiment has a vacuum chamber 10 that is equipped with a sample stage 14 for holding a sample M.
The device is configured to include an ion irradiation means for irradiating ions having an energy of V or more, a means for detecting a spectrum pattern of secondary luminescence, and a means for detecting a temporal change in the intensity of a specific spectrum of the luminescence.

The vacuum chamber IO has an ultimate vacuum level of 10-6 to 1
0-'Torr turbo pump 12 and the sample stage 14
A goniometer 1B is connected to adjust the orientation of the sample, and a cryostat 18 is provided to keep the sample at a low temperature. Further, this vacuum chamber 10 is provided with an ion introduction section 20 facing the front of the sample stage 14.

The cryostat 18 can set the temperature in the range of 10° to 300°. This cryostat 18 can be omitted, but by providing it, the vibration of electrons is reduced and there is no impurity movement.

An ion accelerator 22 is provided at the tip of the ion introduction section 20, and a switch 2B is provided at the intermediate portion.

The ion accelerator 22 emits ions such as H", He", Ar", etc. in a beam shape with an energy of 10 to 200 KeV, and irradiates the sample M through the ion introduction section 20.

As this ion accelerator 22, an ion implantation accelerator can also be used.

A controller 28 is connected to the ion accelerator 22 and the switch 26. The switch 26 is open to allow ions to pass during measurement, and is closed to prevent ions from passing when stopped.
Both are controlled synchronously. In addition, ion accelerator 2
2 is connected to a power source 24.

These function as ion irradiation means.

Further, as part of the ion irradiation means, an electron lens 30 is provided at the base end of the ion introduction section 20, and the ion beam is narrowed down and concentrated on a specific region of the sample M. Further, a slit 32 is arranged at a position immediately in front of the sample in the vacuum chamber 10 to prevent scattered ions and the like from being irradiated onto the sample.

Next, a spectroscope 34 and a light intensity detector 3B are provided as means for detecting the spectral pattern of secondary luminescence and means for detecting time changes in the intensity of a specific spectrum of the luminescence.

The spectrometer 34 includes, for example, a diffraction grating, and separates the spectrum of secondary luminescence emitted from the sample M into wavelengths. The light intensity detector 36 is composed of, for example, a 7-oto counter, a photomultiplier tube, an image intensifier, etc., and detects the light intensity of each wavelength divided into one wavelength.

The L distribution light device 34 and the light intensity detector 3B separate the entire spectrum of secondary luminescence emitted at a certain moment,
By detecting the light intensity of these spectra, it functions as a means for detecting the spectral pattern of secondary luminescence. On the other hand, these devices function as means for detecting temporal changes in the intensity of the specific spectrum of luminescence by separating specific spectra of secondary luminescence and detecting the light intensity of these spectra over a long period of time.

In addition, in this example, [(e-Cd laser emitter 3
It is equipped with 8. This method involves irradiating the sample M with laser light and detecting the resulting secondary luminescence to perform elemental analysis on the sample surface. Although quantitative analysis is not possible in this case, the constituent elements can be analyzed without damaging the sample surface at all. Since it can be analyzed, it can be used for confirmation or preliminary purposes.

Next, a method of the present invention using the apparatus configured as described above will be explained.

First, the sample M is placed on the sample stage 14, the vacuum chamber IO is sealed, and the turbo pump 12 is used to pump the chamber 1.
Create a vacuum inside 0. Then, the sample M is oriented in a predetermined direction using the goniometer 1B, and the sample M is cooled to a desired temperature using the cryostat 18.

The desired degree of vacuum inside the chamber 10 is 10-6 to 10-'T.
When it reaches orr, first, the He-Cd laser emitter 3
8, a laser beam is irradiated onto the sample M, and a spectral pattern is detected from the resulting secondary luminescence using a spectrometer 34 and a light intensity detector 36 to perform elemental analysis on the sample surface. It is possible to know in advance the spectral pattern that will be displayed.

However, this procedure may be omitted, or may be executed for confirmation after completing the procedure described later.

Next, the ion accelerator 22 is started, and H', He'
, Ar', etc. are ejected in a beam shape and irradiated onto the sample M through the ion introduction section 20. Then, at the same time as the switch 26 is opened by the controller 2B, ions are injected from the ion accelerator 22. In this example, Ar' ions are emitted with an energy of 20 KeV,
and emits with an ionic current of 5 gA.

The emitted ions pass through the switch 2B and enter the electron lens 3.
0, passes through the slit 32, and reaches the surface of the target sample M. Here, as mentioned above, the ions give energy to the sample atoms, and with this energy,
When the electrons belonging to the atoms are excited and transition to a lower energy state, secondary luminescence is generated.

A part of the luminescence emitted from the sample M enters the spectroscope 34.The spectrometer 34 spectrally spectra the incident luminescence in a preset wavelength range by rotating a diffraction grating or the like. and separate it into spectra. At the same time, the light intensity detector 3B detects the light intensity of the spectral output corresponding to the spectral output from the spectroscope 34. The light intensity is detected, for example, by measuring the amount of light.

The results are shown in Figure 2.The example shown in Figure 2 has a film thickness of 3.2
The sample was a Si:H compound in the end intestine. The horizontal axis shows wavelength (nm), and the vertical axis shows light intensity (arbitrary scale).

The figure shows, for example, 2882 typical spectral lines representing Si. Furthermore, a typical spectral line representing H appears at 85$3λ.

Next, Figure 3 shows the time change of a specific spectrum in secondary luminescence when ions are continuously irradiated for a long time. In the figure, the horizontal axis shows the ion irradiation time (minutes);
The vertical axis shows light intensity (arbitrary scale).

When the ion irradiation time is increased, the sample is sputtered in the depth direction of the sample M in approximately proportion to the irradiation time, atoms deep in the sample M are excited, and secondary luminescence is emitted from this position. Ru. Therefore, by emitting ions for a long time and detecting the time change in the intensity of a specific spectrum in the spectral pattern of each atom, it is possible to know the compositional elements in the depth direction of the sample solid.

The example in Figure 3 is 2882A (Si) and 8563A
These are the results of the above observations regarding (H) and 5890A (Na). Note that the sputtering rate at this time was 320 A/5 h.

As can be seen from the figure, Si and H have a certain irradiation time,
That is, each light intensity is maintained approximately constant until a certain sputtering depth is reached. On the other hand, Na is
It increases at a certain irradiation time period, that is, at a certain sputtering depth. The peak position of this increase is the sample M
This is the interface between the substrate and the S film.

From this, it can be seen that the thin film of sample M is
It can be seen that the elemental composition is almost constant. Also,
It can be seen that Na contamination from the substrate occurs near the interface.

In this way, by obtaining the observation data shown in FIGS. 2 and 3 above, various information about the composition of the sample can be obtained. Therefore, for example, if a calibration curve is created in FIG. 2, by combining it with FIG. 3, detailed compositional analysis at a certain depth of the sample becomes possible.

The above embodiment is equipped with a means for detecting the spectral pattern of secondary luminescence and a means for detecting the temporal change in the intensity of a specific spectrum of the luminescence. However, when performing only elemental analysis of the sample surface, only the former is provided. Furthermore, when performing composition analysis in the depth direction of the sample, only the latter is sufficient; however, in the present invention, it is preferable to have both.

, [Effects of the Invention] As explained above, the present invention provides
The degree of vacuum required is approximately r, and an extremely high vacuum is not required.Also, even if the sputtering rate is low, there will be no variation in observation, so it is effective to achieve a high resolution of several ppm.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of an apparatus for implementing the solid-state element analysis method of the present invention, and is also an embodiment of the solid-state element analyzer 21f of the present invention, and FIG. Graph showing the spectral output results of 3rd
The figure is a graph showing temporal changes in a specific spectrum in secondary luminescence when ions are continuously irradiated for a long time.

Claims (2)

[Claims] (1) A solid sample placed as an object to be irradiated in a vacuum chamber is irradiated with energy from the outside, and photons emitted from the object are detected with high sensitivity to perform elemental analysis of the solid. solid state elemental analysis method. (2) A means for externally irradiating a sample solid in a vacuum chamber with energy, a means for detecting a spectral pattern of photons emitted by this energy irradiation, and/or a means for detecting temporal changes in the intensity of a specific spectrum of the photons. A solid-state elemental analyzer characterized by comprising means for: