JP4607568B2 - Sample surface analyzer - Google Patents

Description

  The present invention irradiates a sample with a primary beam such as an electron beam, an ion beam, or an X-ray, detects an element existing near the surface of the sample by a secondary beam such as an X-ray generated from the sample, and analyzes a chemical state. The present invention relates to a sample surface analyzer such as a fluorescent X-ray analyzer and an X-ray microanalyzer.

  There is an X-ray analyzer as an apparatus for analyzing the composition, chemical state, etc. of the sample surface. Such an X-ray analyzer irradiates the sample surface with finely focused electrons, focuses the X-rays generated from the sample ultra-thin layer by irradiation with an X-ray focusing element, and disperses energy using a semiconductor detector. To a wavelength dispersive X-ray detector using a type X-ray detector or a proportional counter, where energy spectroscopy is performed, and the X-ray that has been dispersed is detected by the detector, and an energy spectrum of the detected X-ray is obtained. The spectrum is analyzed to analyze the composition, chemical state, etc. of the micro area (nano-order level) of the sample. That is, the amount of the predetermined element on the sample surface can be determined by calculating the amount of the predetermined element from the position of the peak appearing in the energy spectrum.

  If carbon particles or the like are present in the analysis chamber in which the sample is accommodated, when the electron beam hits the particle on the sample surface, the particle grows and good observation cannot be performed. For this reason, the analysis chamber needs to maintain an ultra-high vacuum.

  However, it has been difficult to analyze X-rays generated from a sample placed in an ultrahigh vacuum. That is, the inside of the energy dispersive X-ray detector cannot be made into an ultra-high vacuum and is a high vacuum whose degree of vacuum is lower than that of the ultra-high vacuum. A vacuum partition made of beryllium or the like is provided at the tip of the line detector. When a beryllium window is used as a vacuum barrier, X-ray absorption by the beryllium window is large, and low-energy X-rays (soft X-rays) generated from light elements such as boron and lithium in the sample must be detected. It was difficult.

  In the case of wavelength dispersive X-ray analyzers, polymer-based ultra-thin films are used as vacuum barriers, but analysis chamber baking is performed in order to obtain an ultra-high vacuum state by removing gases attached to the analysis chamber. Sometimes the polymer film is damaged by heat, and ultra high vacuum cannot be realized.

  As a conventional technique, there is an electron spectroscopic device that prevents gas from flowing into the analyzer even if the sample is irradiated with gas by the field-limiting aperture (for example, Patent Document 1).

JP2003-187738

  The problem to be solved by the present invention is that it is difficult to detect low energy X-rays when the vacuum system of the analyzer and the vacuum system of the analysis chamber are shut off using a partition wall.

According to the first aspect of the present invention, there is provided an analysis chamber for holding a sample in a vacuum, a primary beam irradiation means for irradiating the sample with a primary beam, and an X-ray generated from the sample by the irradiation of the primary beam. A spectroscopic means held in a vacuum for spectroscopic / detection of light, an X-ray condensing means composed of a polycapillary disposed on the axis of the condensing port of the spectroscopic means, and the X An aperture positioned at a focal point of X-rays from the sample collected by the line focusing means , wherein the spectroscopic means is provided with an X-ray spectrometer located on the axis The aperture of the aperture is circular or slit-shaped, thereby adjusting the beam shape of the X-ray bundle passing through the aperture and reaching the X-ray spectrometer, and the aperture serves as a differential exhaust aperture. Functioning, whereby a surface analysis apparatus characterized by holding the degree of vacuum in the analysis chamber at a high vacuum than the vacuum degree in the spectroscopic unit.

The invention according to claim 2 is the surface analysis apparatus according to claim 1, wherein the opening of the aperture has a circular shape set in a range of 0.5 mm to 1 mm in diameter .

The invention according to claim 3 is characterized in that the degree of vacuum in the spectroscopic means is on the order of 10 ⁻⁶ Pa and the degree of vacuum in the analysis chamber is on the order of 10 ⁻⁸ Pa . This is a surface analyzer.

The invention according to claim 4 is the surface analysis apparatus according to any one of claims 1 to 3, wherein the primary beam is an electron beam .

  According to the present invention, the vacuum system of the X-ray spectrometer and the vacuum system of the analysis chamber are shut off using an aperture, so that low energy X-rays can be detected. For this reason, the analysis of the light element in a sample is attained.

The configuration of the present invention will be described with reference to FIG. A sample 2 placed on the sample stage 3 is disposed in the analysis chamber 1, and the target portion of the sample 2 is moved to the observation point by the sample stage 3. The analysis chamber 1 is evacuated by a turbo molecular pump, a sputter ion pump, or the like (not shown) and an ultrahigh vacuum of 10 ⁻⁸ Pa or higher is maintained. For this reason, there are very few particles in the analysis chamber, and the sample surface is not contaminated with carbon particles or the like. An electron gun 4 is installed on the upper surface of the analysis chamber 1 to generate an electron beam 14 that irradiates the sample 2.

  An objective lens 5 composed of an electromagnetic lens is installed at the tip of the electron gun 4, and an electron beam 14 that is a primary beam generated by the electron gun 4 is focused on the sample 2. On the side of the analysis chamber 1 are a sample exchange chamber 12 that is an air lock chamber for introducing the sample 2 into the analysis chamber 1 and a means for transporting the sample to be measured introduced into the sample exchange chamber 12 to the analysis chamber 1. A sample transport bar 13 is installed.

An energy dispersive X-ray spectrometer chamber 6 is installed on the oblique upper surface of the analysis chamber 1, and is maintained at a high vacuum of 10 ^{−7 to} 10 ⁻⁶ Pa by a vacuum pump (not shown). An X-ray condensing element 7, an aperture 8, and an X-ray spectrometer 10 are arranged on the axis of the condensing port of the X-ray spectrometer chamber 6. The X-ray condensing element 7 composed of a polycapillary or the like focuses the X-ray 15 generated on the sample 2 in the vicinity of the aperture 8. The aperture 8 has a circular minute mouth or slit shape for sizing the X-ray 15 bundle collected by the X-ray focusing element 7 in accordance with the incident condition of the X-ray spectrometer 10. The aperture 8 adjusts the beam shape of the X-ray beam and functions as a differential exhaust aperture. The X-ray spectrometer 10 is installed in the X-ray spectrometer chamber 6, and energy spectrometers the X-ray 15 bundle formed by beam shaping by the aperture 8 and projects (images) it onto the X-ray detector 11. (Diffraction grating, etc.). An X-ray detector 11 is installed on the end face of the X-ray spectrometer chamber 6 and converts the intensity of X-rays into an electrical signal by utilizing the generation of electron-hole pairs proportional to the energy of the X-rays. To detect. The X-ray detector 11 is preferably a two-dimensional detector.

  The configuration of each unit in FIG. 1 has been described above. Next, the operation will be described. In FIG. 1, the degree of vacuum in the analysis chamber 1 is constantly monitored by a control device (not shown), and an ultrahigh vacuum is maintained by a vacuum pump (not shown). If the degree of vacuum is appropriate, the control device sends an electron beam irradiation signal for irradiating the sample 2 with the electron beam 14 to an electron beam source power source (not shown).

  The electron beam source power supply that has received the electron beam irradiation signal controls the electron beam source based on the electron beam irradiation signal. As a result, an electron beam 14 is generated from the electron gun 4 and the sample 2 is irradiated with the electron beam 14. The electron beam 14 is controlled to be appropriately focused on the sample 2 by the objective lens 5.

  On the other hand, as shown in FIG. 2, the X-ray 15 generated by irradiating the sample 2 with the electron beam 14 is focused on the position of the aperture 8 by the X-ray condensing element 7. At this time, since the opening of the aperture 8 is sized according to the input conditions such as the angle and size of the X-ray spectrometer 10, unnecessary X-rays 15 are blocked and the X-ray beam shape is adjusted. At this time, the aperture 8 may be exchanged according to the input conditions, or the aperture may be freely adjusted like a shutter. The X-ray 15 formed by the aperture 8 is subjected to energy spectroscopy by the X-ray spectrometer 10 and projected (imaged) on the X-ray detector 11. The imaged X-ray is converted into an electric signal by the X-ray detector 11. The detected electrical signal is developed into an energy spectrum by a computer (not shown). The energy spectrum is analyzed to analyze the composition, chemical state, and the like of the minute region (nano-order level) of the sample 2. That is, the amount of the predetermined element on the surface of the sample 2 can be determined by calculating the amount of the predetermined element from the position of the peak appearing in the energy spectrum.

At this time, the pressure of the analysis chamber 1 where the sample 2 is placed is maintained at P0, the pressure of the X-ray spectrometer chamber 6 maintained at the high vacuum is P1, and the exhaust speed of the exhaust pump of the analysis chamber 1 is exhausted. Is S and the exhaust conductance of the aperture 8 is C, the flow rate Q of the gas flowing from the high vacuum X-ray spectrometer chamber 6 into the ultrahigh vacuum analysis chamber 1 is expressed by the following equation.
Q = C * (P1-P0)
The pressure in the analysis chamber 1 when the X-ray spectrometer chamber 6 evacuated to the pressure P1 is connected is expressed by the following equation.
P = Q / S + P0
As a numerical ^{example, P0 = 5x10 -8 Pa, P1} = 5x10 -6 Pa, C = 2.8x10 -5 m 3 /s,S=0.1m 3 / s, the main component of the gas is exhausted water (molecular weight: 18 ). Under this condition, P = 5.0 × 10 ⁻⁸ Pa, and the analysis chamber 1 is kept in an ultrahigh vacuum. The opening of the aperture 8 that satisfies this exhaust conductance has a diameter of 0.5 mm, which is an optimum condition for the spectroscope 10 such as a diffraction grating that performs high-resolution X-ray spectroscopy.

Moreover, even when the diameter is set to 1 mm and the resolution of X-ray spectroscopy is lowered and the sensitivity is high, P = 5.1 × 10 ⁻⁸ Pa, and a sufficiently ultrahigh vacuum atmosphere can be maintained.

Even if a CCD element that cannot be baked at high temperature is used as the X-ray detector 11 from the above numerical calculation, the sample 2 is arranged if the X-ray spectrometer chamber 6 is evacuated to about P1 = 5 × 10 ⁻⁶ Pa without baking. The analysis chamber 1 can be maintained on the order of 10 ⁻⁸ Pa, and X-ray analysis under ultrahigh vacuum conditions is possible.

  Although the operation has been described above, since a vacuum partition such as a beryllium window is not used in the X-ray spectrometer chamber 6 according to the present invention, low energy X-rays generated from light elements such as boron and lithium in the sample 2 are used. The effect that (soft X-ray) can be detected is obtained. Since the aperture 8 functions as an operating exhaust means, the vacuum system of the analysis chamber 1 and the vacuum system of the X-ray spectrometer chamber 6 are shut off, the analysis chamber 1 is set to an ultrahigh vacuum, and the X-ray spectrometer 10 is set to a high vacuum. Can be held in. In other words, the X-ray condensing element captures and collects X-rays with a large capturing angle, thereby reducing the aperture opening and partitioning the region where there is a difference in atmospheric pressure. Can be transmitted at a rate. Many X-rays can be transmitted in proportion to the increase in the X-ray capture angle by the light collecting element.

  Further, since the light is condensed once at the opening by the light condensing element, it can be applied to both divergent light and parallel light.

  Furthermore, since the aperture opening is a thin aperture, particles and the like are difficult to adhere.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, the primary beam may be an ion beam or an X-ray instead of an electron beam.

1 is an overview of an apparatus according to the present invention. 4 is a detail of an aperture according to the present invention. It is an outline | summary of the apparatus by a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Analysis chamber 2 Sample 3 Sample stage 4 Electron gun 5 Objective lens 6 X-ray spectrometer chamber 7 X-ray condensing element 8 Aperture 9 Partition valve 10 X-ray spectrometer 11 X-ray detector 12 Sample exchange chamber 13 Sample conveyance rod 14 Electron beam 15 X-ray 16 Beryllium window

Claims (4)

An analysis chamber held in a vacuum containing the sample;
Primary beam irradiation means for irradiating the sample with a primary beam;
Spectroscopic means held in a vacuum for spectrally detecting and detecting X-rays generated from the sample by irradiation of the primary beam ,
X-ray condensing means comprising a polycapillary disposed on the axis of the condensing port of the spectroscopic means;
An aperture disposed on the axis and positioned at a focusing point of X-rays from the sample collected by the X-ray focusing means,
The spectroscopic means is provided with an X-ray spectrometer located on the axis,
The opening of the aperture is circular or slit-shaped, thereby adjusting the beam shape of the X-ray bundle passing through the aperture and reaching the X-ray spectrometer, and the aperture functions as a differential exhaust aperture,
Thus, the surface analysis apparatus is characterized in that the degree of vacuum in the analysis chamber is higher than the degree of vacuum in the spectroscopic means. The surface analysis apparatus according to claim 1, wherein the opening of the aperture has a circular shape set in a range of 0.5 mm to 1 mm in diameter . The surface analysis apparatus according to claim 1 or 2 , wherein the degree of vacuum in the spectroscopic means is on the order of 10 ^-6 Pa and the degree of vacuum in the analysis chamber is on the order of 10 ^-8 Pa . The surface analysis apparatus according to claim 1, wherein the primary beam is an electron beam .

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