JPH0656367B2 - Solid surface condition analyzer - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an apparatus for analyzing the state of a solid surface, which is suitable for measuring the structure, bonding state, and motion state of a chemical species adsorbed on a solid surface.

[Background of the Invention]

Conventionally, methods such as photoelectron spectroscopy, Auger electron spectroscopy, and electron energy loss spectroscopy have been used for the state distribution on the solid surface. However, these methods can only measure the energy level and the width of the adsorbed species, and the bonding state between the adsorbed species and the surface, which is necessary for understanding the mechanism of the chemical reaction at the solid-gas phase interface. Moreover, it is difficult to obtain detailed knowledge about the state of motion on the surface.

In the field of semiconductor processing, which has been actively researched and developed in recent years, a chemical species is adsorbed on the surface of a solid sample so that a high resistance silicon thin film is formed on a low resistance silicon substrate by a CVD method. A technique of forming a thin film by reaction is widely used. In such a case, it is necessary to know the electronic state of the adsorbed chemical species (molecules or radicals containing silicon such as monosilane) on the solid sample (low resistance silicon substrate).

[Object of the Invention]

An object of the present invention is to provide an apparatus for analyzing the state of chemical species adsorbed on a solid surface, which is capable of compensating for the deficiencies of the existing surface measurement methods as described above, and which is capable of completely nondestructive measurement. To provide.

[Outline of Invention]

In order to achieve the above object, the present invention utilizes Raman scattering in which light in the X-ray region is used as excitation light.

Conventionally, Raman scattering has been used mainly for the activation of molecules and the measurement of lattice vibrations using visible light as an excitation light source. The principle of the present invention is that Raman scattering accompanied by electronic transitions of atoms and molecules can be observed by using X-rays with a shorter excitation light wavelength. According to the present invention, it is possible to analyze non-destructively a detailed change in electronic state due to adsorption of a chemical species on a solid surface.

Example of Invention

As shown in FIG. 1, Raman scattering is considered to be a phenomenon in which a process of absorbing light 1 having a certain wavelength and a process of emitting light 2 or 3 having another wavelength occur at the same time. Here, the substance is, for example, 4, 5, 6, 7 in the energy levels in the figure.
In, the state transits from the initial state 4 to the final state 6 or 7 via the intermediate state 5. Since the energy difference between the excitation light 1 and the scattered light 2 and 3 corresponds to the energy difference between the material energy levels 4 and 6 and 4 and 7, using this, for example, the energy levels 4 and 6 , Or even if no direct transition between 4 and 7 occurs, it is possible to determine the energy difference between those energy levels. When light in the visible region is used as the excitation light 1, it is possible to obtain knowledge about vibrations of molecules, rotational levels, lattice vibration levels of crystals, and the like.

When the wavelength of the excitation light 1 is shortened and set in the X-ray region, a similar phenomenon is observed between the electronic states of atoms and molecules.

FIG. 2 shows a device configuration in one embodiment of the present invention.
Excitation light 8 emitted from an excitation light supply unit A including an X-ray generation source and a spectroscopic system that selects X-rays having a predetermined wavelength is applied to a sample 10 held on a sample table 9. A part of the scattered light 11 from the surface of the sample 10 is taken out by the slit 12 and guided to the diffraction grating 14 via the slit 13. Here, the scattered light wavelength-dispersed is detected by a detector 15 such as a photographic plate, a diode array, or a scintillator to obtain a spectrum. Here, the entire optical paths of the excitation light 8 and the scattered light 11,
The sample 10 is stored in a vacuum container. Also,
The angles formed by the excitation light 8 and the scattered light 11 with the surface of the sample 10 can be changed independently of each other.

An example of the excitation light supply section A is shown in FIG. The excitation light 8 in FIG. 2 is converted into the orbital emission light (SOR) 17 in FIG.
Is obtained from The orbital radiation 17 generated by the acceleration of electrons in the magnet portion 16 which is a part of the electron storage ring is wavelength-selected by the diffraction grating 19 and the slit 20 to obtain the excitation light 8. The configuration of the wavelength selection spectroscopic system in FIG. 3 is made more complicated, and a spectroscopic system that does not change the imaging position of the dispersed light or the traveling direction of the excitation light 8 even if the wavelength of the excitation light 8 is changed You can also

FIG. 4 shows another embodiment of the excitation light supply section A. In the plasma X-ray source 18, the X-rays generated when the planar discharge is converged and pinched at the tip portion are wavelength-dispersed by the diffraction grating 19, and a part thereof is extracted as excitation light 8. Other X as a light source
It is also possible to use a radiation source.

In the above apparatus, if the glancing angle of the excitation light with respect to the sample surface is set to be smaller than the critical angle of the sample material, light does not enter the inside of the sample, so scattered light can be detected only on the surface.

FIG. 5 is a block diagram of another embodiment of the device according to the present invention. A predetermined wavelength component of the light dispersed by the excitation light diffraction grating 19 is extracted by the slit 20, and this is irradiated onto the sample 10 as the excitation light 8. The scattered light 11 is wavelength-dispersed by a diffraction grating 14 to obtain a spectrum detected by a detector 15 such as a photographic plate, a diode array, a scintillator.

Next, referring to FIGS. 6 and 7, in the present embodiment, the relationship between the dispersion direction z of the diffraction grating 19 for excitation light and the inclination of the sample 10 in FIG. 5 and the sample 10 of the excitation light 8 are shown. The relationship between the incident direction, the detection direction of the scattered light 11, and the imaging line 21 of the excitation light 8 on the surface of the sample 10 will be described.

FIG. 6 is a partial view of the sample portion of the present embodiment as seen from the dispersion direction of the excitation light diffraction grating 19 in FIG. 5, that is, the z-axis direction in FIG. The sample 10 is installed so that its surface is parallel to the z-axis and the excitation light 8 is incident on the sample surface at an angle nearly parallel to the sample surface. Detection is performed from the direction close to the incident direction and parallel to the sample surface.

FIG. 7 shows the sample portion of this embodiment in the y-axis direction in FIG. 5, that is, the dispersion direction z of the diffraction grating 19 for excitation light.
3 is a partial view as seen from a direction perpendicular to the traveling direction of the excitation light 8. FIG. In general, when light emitted from a point light source is dispersed by a diffraction grating, it forms an image in a line shape perpendicular to the direction of dispersion.

In FIG. 7, the width of the imaging line 21 of the excitation light 8 on the surface of the sample 10 in the z-axis direction is the incident angle of the excitation light 8 with respect to the sample surface if the sample surface is parallel to the z-axis. Changes,
It is kept almost constant. Therefore, in the case of the present embodiment in which the detection diffraction grating 14 in FIG. 5 is arranged in a direction close to the sample surface and in the direction in which it enters the plane formed by the imaging line 21 and the excitation light 8, or in the direction close thereto. The scattered light 11 from the image forming line 21 viewed from the detection diffraction grating 14 can be approximately regarded as a point light source. Under these conditions,
Even if the scattered light is directly guided to the detection diffraction grating 14 without passing through the pinhole or the like, the dispersed light forms an image similar to the light emitted from the point light source. Here, as the detection diffraction grating 14, the distance to the light source has almost no influence on the image forming position. For example, if a flat field type concave diffraction grating is used, the point light source is more than that in the case of using a normal diffraction grating. An image close to the light from can be obtained at the position of the detector 15.

In the method of the present embodiment as described above, both the incident angle of the excitation light 8 and the detection direction of the scattered light 11 are
Even if the excitation light 8 is set nearly parallel to the sample surface, it is not necessary to take measures against the excitation light 8 directly entering the detector 15 without passing through the sample 10. Moreover, scattered light 1
Since it is not necessary to convert this into a point light source with a pinhole or the like when performing the 1st spectroscopy, the scattered light 11 can be detected without loss. Therefore, high detection sensitivity can be obtained.

Generally, there is a relationship of ΔE = 1.25 × 10 ⁴ × (Δλ / λ) / λ among the energy resolution ΔE (eV) of the spectroscopic system, the wavelength resolution Δλ / λ, and the wavelength λ (Å) of light. Therefore, when the scattering of the excitation light of λ = 10 Å is observed using the spectroscopic system of Δλ / λ = 5 × 10 ⁻⁴ , it is 1 eV.
The scattered light can be measured with the following energy resolution. The transition energy is usually 0.5e in Raman scattering
In order to observe an electronic transition of V or more, excitation light 8
The wavelength must be in the X-ray region below 500Å. The wavelength resolution of the spectroscopic system is 10 in the above wavelength range.
Since the current value is ^-4 or less, the wavelength of the excitation light 8 needs to be 5 Å or more in order to obtain an energy resolution (1 eV) that is sufficient to observe changes in the electronic state due to adsorption.

As described above, in the apparatus according to the present invention, if the spectroscopic system having the above-described performance is used, the electron transition of the chemical species adsorbed on the surface can be absorbed by observing the spectrum of the scattered X-ray. The analysis can be performed with sufficient accuracy to detect the change in the electronic state caused by.

〔The invention's effect〕

Since the excited electronic state plays an important role in the movement of the adsorbed species on the surface and the surface chemical reaction, the dynamic properties of the surface, such as plasma CVD and photo CVD in the semiconductor process technology, are used. It is essential to fully understand the behavior in order to develop the technology using the.

According to the present invention, it is possible to obtain the knowledge about the level in which the transition that has undergone ordinary light absorption is prohibited due to the restriction of symmetry. Further, in the case of the photoelectron spectroscopy, only the information on the occupied state of the electron can be obtained, whereas the excited electronic state can be detected in the present invention.

Furthermore, the present invention has a new function as described above in the measurable information, and also detects scattered light having a slightly different energy from the excitation light without using particle beam irradiation of electrons, ion beams, etc. Since it is used as a means, it also has a feature that it is possible to capture the natural properties of the sample without adding significant disturbance to the sample. This feature can be particularly effectively used in the case where the same sample is continuously measured and a dynamic measurement for tracking the change is performed.

Next, an example of the result predicted by the device of the present invention is shown in FIG. FIG. 8 shows monosilane (SiH ₄ ) for growing a high resistance silicon thin film on a low resistance n-type silicon substrate.
It is a result of measuring the Raman scattering vector in the initial stage of the CVD process using. The energy of excitation light 1 is 1
keV (wavelength is 12Å).

FIG. 8 shows that monosilane (S
The spectrum of iH ₄ ) is also shown. The spectrum in vacuum shows a non-degenerate state peak (a1) in which electrons are localized in silicon and a triple degenerate state peak (t2) in which electrons are distributed throughout the molecule. The peak of a1 hardly changes even when monosilane (SiH ₄ ) is adsorbed on any of the silicon substrates having the plane orientations (100) and (111). This is because, as described above, the electrons are localized in silicon and are not affected by adsorption.

On the other hand, at the peak of t2, triple degeneracy is released by adsorption on a silicon substrate having a plane orientation (100), and split into one stabilized state and a double degenerate state that is almost the same as before adsorption. . Then, although triple degeneracy cannot be solved by adsorption of (111) onto a silicon substrate, two triple degenerate states having different stability appear due to the difference in adsorption direction.

As described above, according to the apparatus of the present invention, the change in the electronic state due to the difference in the adsorption condition can be analyzed in detail, so that it is predicted that the optimum film forming condition under each processing condition can be easily determined. To be done.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of Raman scattering, FIG. 2 is a basic configuration diagram of an apparatus according to an embodiment of the present invention, FIG. 3 is a diagram illustrating a part of the embodiment of the present invention, and FIG. FIG. 5 is a diagram for explaining a part of another embodiment of the present invention, FIG. 5 is a basic configuration diagram of an apparatus according to still another embodiment of the present invention, and FIGS. 6 and 7 are implementations in FIG. FIG. 8 is a diagram for explaining incident and scattered X-ray states in the example, and FIG. 8 is a diagram showing an example of a result predicted by the apparatus of the present invention. 1 ... Excitation light, 2,3 ... Raman scattered light, 4 ... Start state, 5 ... Intermediate state, 6,7 ... End state, A ... Excitation light supply unit, 8 ... Excitation light, 9 …… Sample stand, 10 …… Sample,
11 ... scattered light, 12,13 ... slit, 14 ... detection diffraction grating, 15 ... photodetector, 16 ... magnet, 17 ... orbital radiation, 18 ... plasma X-ray source, 1
9 ... Excitation diffraction grating, 20 ... Slit, 21 ... Imaging line.

Claims (9)

[Claims] 1. An X-ray source for generating X-rays, a spectroscopic means for selecting the X-rays having a predetermined wavelength in order to obtain an electronic state at a solid-vapor interface, and a chemical species adsorbed on the surface. A sample table on which the sample is placed, a means for irradiating the sample with the X-ray at a glancing angle smaller than the critical angle, a spectroscopic system for dispersing the wavelength of the X-ray dispersed from the surface of the sample, A solid surface condition analyzer comprising a detector for detecting dispersed X-rays. 2. A solid surface state analyzing apparatus according to claim 1, wherein the X-ray source, the spectroscopic means, the sample stage, the spectroscopic system, and the detector are provided. A solid surface condition analyzer characterized by being housed in a vacuum container. 3. The solid surface state analyzing apparatus according to claim 1, wherein an orbital radiation source is used as the X-ray source. 4. The solid state condition analyzer according to claim 1, wherein the X-ray source is plasma X
A solid surface condition analyzer characterized by using a radiation source. 5. The solid state condition analyzer according to claim 1, wherein the X-ray wavelength ranges from 5Å to 5Å.
A solid surface condition analyzer characterized by being in the range of 00Å. 6. The solid surface state analyzer according to claim 1, wherein the dispersed X-rays are detected with a small glancing angle with respect to the sample. Surface condition analyzer. 7. The solid surface state analyzing apparatus according to claim 1, wherein the sample is arranged in parallel with a dispersion direction of the dispersed X-rays. State analyzer. 8. A solid surface condition analyzer according to claim 1, wherein the detection of the dispersed X-rays is performed from a direction perpendicular to the dispersion direction of the dispersed X-rays. A solid surface condition analyzer characterized by the following. 9. The apparatus for analyzing the state of a solid surface according to claim 1, wherein the dispersed X-rays dispersed in the incident direction of the X-rays or in a direction close to the incident direction are detected. Characteristic solid state analyzer.