JPH0980000A - X-ray evaluation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform X-ray evaluation with an improved S/N ratio without being affected by such noise as infrared rays other than X rays when a two-dimensional X-ray detector which is an assembly of a semiconductor position detection element and a micro channel plate and is sensitive to those other than X rays is used. SOLUTION: A filter 16 with spectral characteristics for shielding those other than X rays is provided at a window part for detecting a two-dimensional X-ray detector 13 consisting of the assembly of a semiconductor position detection element and a micro channel plate, thus preventing, for example, infrared rays, light, and electron beams which become noise sources other than X rays from entering the two-dimensional X-ray detector 13 using a filter 16 and enabling only target X rays to enter the two-dimensional X-ray detector 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X suitable for measurement and analysis of the surface structure of a substance, such as the atomic / electronic structure of the uppermost surface of a sample being deposited or formed in ultrahigh vacuum. The present invention relates to an X-ray evaluation apparatus that uses X-rays.

[0002]

2. Description of the Related Art In recent years, research and development of device materials having various functions have been actively conducted, and composition or structure analysis of material surfaces has become important.

As a method for evaluating the surface atomic / electronic structure of such a substance, there are many methods using an electron beam, an X-ray, a neutron beam, an ion beam or the like as a probe. For example, in the case of using an electron beam, a transmission microscope (T
EM) and a reflection microscope (REM) that analyzes the surface atomic structure and the like by using the detected amount as reflected electrons. As X-ray analysis, photoelectron spectroscopy (XPS = X-ray Photoelect) is used to analyze the band structure, density of states distribution, chemical bond state, etc., using the detected amount as electrons (energy spectrum).
ron Spectroscopy), an X-ray analysis method for analyzing the crystal structure or the local atomic structure (interatomic distance) using X-rays (diffraction, standing wave, absorption fine structure) and fluorescent X-rays (energy spectrum) as detection amounts, or Extended X-ray absorption fine structure method (EX
AFS = Extended X-ray Absorption Fine Struct
ure) etc.

Of these probes, electron beams other than X-rays, neutron beams, ion beams, etc. generally have the drawback of being easily absorbed and scattered in air. Therefore, in many cases other than these X-rays, the sample is placed in a vacuum for evaluation. In this respect, X-rays are promising because they are hardly absorbed or scattered even in air. However, even in the X-ray,
X-rays of several tens of liters or more, which are called soft X-rays, are easily absorbed and scattered in the air, and therefore a vacuum chamber is often used as used in the XPS method.

By the way, any of these probes (optical
Even in the case of (electrons), various researches and developments have been conducted on a method of making light or electrons incident on the surface of the sample to obtain information on the uppermost surface layer. For example, there is a total reflection X-ray fluorescence analysis method. Among these, surface analysis methods using X-rays, which are considered promising as described above, include surface fluorescence EXAFS method and total reflection X-ray measurement method. All of these are intended to evaluate the atomic / electronic structure of the sample surface, surface / interface roughness, density, film thickness, etc. by making X-rays incident on the sample surface at a grazing low incident angle. is there. In this case, conventionally, hard X-rays having a wavelength of several Å or less are mainly used.

The conventional X-ray detector used for the above evaluation is a large one such as PC (proportional counter), SC (scintillation counter), SSD (semiconductor detector), ion chamber, etc., and is one-dimensional. However, since it does not have a two-dimensional spatial resolution, there is a drawback that surface analysis is also impossible.

In consideration of such a conventional situation, the surface structure such as the light atom or electronic structure on the outermost surface of the sample, particularly the surface structure of the light atom during film formation, is measured and analyzed during film formation. It can be said that an evaluation method in which X-rays which are hardly absorbed and scattered by the particles, particularly soft X-rays, are used as a probe is preferable.

An example of such an X-ray evaluation apparatus is disclosed in, for example, Japanese Unexamined Patent Publication Nos. 6-160312 and 7-982.
No. 85, etc. In the X-ray evaluation apparatuses described in these publications, a sample held by a manipulator in a vacuum chamber is irradiated with X-rays, and X-rays transmitted through the sample or scattered by the sample are detected by a two-dimensional X-ray detector. Is detected by. This allows evaluation with a two-dimensional spatial resolution. Here, the two-dimensional X-ray detector is configured as an assembly of a semiconductor position detecting element (PSD) and a micro channel plate (MCP), and since it is small in size, there is no problem in disposing it in the vacuum chamber. Absent. Although not described in these publications, a heater for heating a sample is incorporated in a sample holder at the tip of a manipulator, and a sample, for example, a film laminated in two layers reacts at the interface while heating. There is also a proposal of observing the situation using X-rays as probe light.

[0009]

However, in such an X-ray evaluation apparatus, infrared rays are emitted from the heater when the sample is heated, and the infrared rays enter the two-dimensional X-ray detector. Further, the vacuum chamber has a glass observation window for confirming the state of the sample and the like, and light enters the two-dimensional X-ray detector from the outside through the observation window. Further, the vacuum chamber usually contains a gauge sphere of a vacuum gauge, and the electron beam and infrared rays emitted by the gauge sphere enter the two-dimensional X-ray detector.

The two-dimensional X-ray detector, which is an assembly of the semiconductor position detecting element and the microchannel plate described above, is sensitive to wavelengths other than X-rays. These infrared sources,
It also detects light and electron beams. If there is such noise, X-rays cannot be counted accurately and S / N
This hinders good X-ray evaluation.

As a countermeasure, around the two-dimensional X-ray detector,
It may be covered with aluminum foil or Be (beryllium) foil. However, the commercially available aluminum foil has a thickness of 25 to 50 μm even if it is thin,
It reduces the incident intensity of the rays. In addition, some Be foils have a thin thickness of 1 μm or less and have a good X-ray transmittance, but on the contrary, thin foils are difficult to handle and easily broken, and are originally expensive.

[0012]

According to a first aspect of the present invention, a sample disposed in a vacuum is irradiated with X-rays, and the X-rays transmitted through the sample or scattered by the sample are detected as semiconductor positions. In an X-ray evaluation apparatus for detecting by a two-dimensional X-ray detector composed of an assembly of an element and a micro channel plate, a filter having a spectral characteristic for blocking other than X-rays is provided in a detection window portion of the two-dimensional X-ray detector. Provided. Therefore, even if infrared rays, light, electron beams, etc., which are noise sources other than X-rays, enter the two-dimensional X-ray detector, they are blocked by the filter, and only the target X-rays enter the two-dimensional X-ray detector. , S / N with good X-ray evaluation becomes possible.

According to a second aspect of the present invention, in the X-ray evaluation apparatus according to the first aspect, the filter is replaceably provided with another filter having another spectral characteristic. Therefore, S / N
It is possible to perform not only good X-ray evaluation but also good S / N evaluation for the measurement target according to the spectral characteristics of the filter used by the two-dimensional X-ray detector having sensitivity to other than X-rays.

According to a third aspect of the invention, in the X-ray evaluation apparatus according to the first aspect, Al, Ti, Si, Mg, Mn.
Or the film thickness 50 which is easy to use light atom such as C as a component
A filter having a single layer structure or a laminated structure having a thickness of 00Å or less was used. Therefore, the X-rays to be measured have good transparency,
In addition to reducing the incident intensity of X-rays, the filter itself is easy to handle.

According to a fourth aspect of the invention, in the X-ray evaluation apparatus according to the first aspect, the sample holder for arranging the sample in a vacuum has a heater for heating the sample. Therefore, since the infrared rays emitted from the heater are not affected, the X-ray evaluation at the time of film formation heating by the heater can be performed in a good S / N state.

[0016]

An embodiment of the present invention will be described with reference to the drawings. First, a vacuum chamber 2 that communicates with the vacuum exhaust device 1 and has a high vacuum state inside is provided. The vacuum chamber 2 has an X-ray source 4 region partitioned by Be windows 3a and 3b and a spectroscopic region, which are connected in series.
A spectroscopic chamber 6 is built in the spectroscopic region together with a slit (which may be a pinhole depending on the purpose) 5. A channel-cut monochromator 7 acting as an X-ray spectroscope is built in the spectroscopic chamber 6. In the original vacuum chamber 2, a sample (silicon wafer) 8 to be measured is held downward (the surface to be evaluated is downward) by a sample holder (sample holder) 9a at the lower end of a rotatable manipulator 9. There is provided a total reflection mirror 10 for making X-rays, which are separated by the channel cut monochromator 7 and emitted through the Be window 3b, enter the surface of the sample 8 at a low incident angle.

Although not particularly shown, a heater capable of heating the held sample 8 from the back side (up to 1000 ° C.) is embedded in the sample holder 9a. Further, the manipulator 9 is provided so that the incident angle can be changed so that the incident angle of the X-ray on the surface of the sample 8 can be changed in a step of 0.002 °. In addition, a small ion chamber 12 for measuring the intensity of incident X-rays on the sample 8 is provided on the optical path between the total reflection mirror 10 and the sample 8.
Further, a two-dimensional X-ray detector 13 is arranged on the optical path on the exit side from the sample 8. In addition, in this embodiment, in order to enable analysis / evaluation during film formation, a K cell 14 which is a film forming apparatus is provided below the sample 8. Reference numeral 15 is the shutter.

Here, each part will be described. First, X
As the radiation source 4, it is preferable to use a rotor target mainly used in a laboratory, but a source called a plasma X-ray source or a laser X-ray source, or a sealed tube type may be used. However, considering simplicity and ease of use, W (tungsten), Mo (molybdenum), Ag
A rotor target using (silver), Al (aluminum) or the like and using white X-rays generated by irradiating an electron beam is preferable. In this embodiment, the rotor target is Cu.

The degree of vacuum in the vacuum chamber 2 is 10 to ⁶ Torr.
As described above, a high vacuum of 10 to ⁹ Torr or more is preferable, and an ultrahigh vacuum of 10 to ¹⁰ Torr or more is more preferable. On the other hand, the degree of vacuum in the spectroscopic chamber 6 is set to 10 ⁴ Torr or more.

The channel-cut monochromator 7 acting as an X-ray spectroscope is made by channel-cutting a single crystal. In order to disperse soft X-rays, EDDT, ADP, α- having a long lattice plane interval. Crystal, InSb, etc. are used.

Here, such an X-ray spectroscope using one or two flat plate monochromators cannot prevent the divergence of X-rays, and the X-rays with good parallelism cannot be obtained in the laboratory.
By the way, although SOR (synchronized light) provides parallelism and good spectrality, a single channel cut monochromator changes (or moves) the optical path. Therefore, in the present embodiment, the X-ray spectroscope is a monochromator that interlocks by arranging channel-cut crystals in (+, +) arrangement, which results in small X-ray divergence and good parallelism, and , Continuous spectroscopy is also possible and the energy resolution is good. Specifically, ADP (10
1) Crystals are arranged (+, +) so as to interlock with each other, and X-rays limited by the slits 5 are spectroscopically reflected four times by four spectroscopic crystals.

The total reflection mirror 10 totally reflects X-rays, is used for the purpose of cutting the secondary light from the channel cut monochromator 7, and it is desirable that the surface unevenness is 15 Å or less. The material is carbon, B
N, SiC or the like is used. In the present embodiment, for example, Pt / Si (a Pt thin film formed on a Si wafer) is used. Further, when the concave mirror shape is used, the separated X-rays can be condensed and the intensity of the incident X-rays can be improved. By the way, as a method of varying the X-ray incident angle on the sample 8, the total reflection mirror 10 side is provided rotatably around the rotation shaft 11 without moving the sample 8 by the manipulator 9. The incident angle may be changed by rotating 10.

The two-dimensional X-ray detector 13 is composed of an assembly of a PSD (semiconductor position detecting element) and a micro channel plate (MCP) and has a diameter of, for example, PIAS-TI manufactured by Hamamatsu Photonics KK. 70 m
It is a small one with a length of m and a length of about 50 mm. According to such a two-dimensional X-ray detector 13, since the detector itself is small, even if it is built in the vacuum chamber 2, the degree of vacuum does not rise, maintenance is inconvenient, the vacuum chamber 2
Does not have the inconvenience of becoming larger. Further, according to the two-dimensional X-ray detector 13, the evaluation having the two-dimensional spatial resolution can be performed as it is.

Furthermore, such a two-dimensional X-ray detector 13
Only the X-rays are transmitted to the entire surface of the detection window part of
A filter 16 having a spectral characteristic for blocking all infrared rays other than X-rays is provided. This filter 16 is an ultrathin film filter having a film thickness of 5000 Å or less, and is made of Al, T
A film body having a single-layer structure or a laminated structure containing light atoms such as i, Si, Mg, Mn, or C, which are easy to use as they are, is used. However, it is not limited to those components, but may be protected by a grid for supporting the membrane (such as a lattice thread), or may include a plastic membrane such as polyimide (thickness of 5000 Å or less in total). It may be. In the present embodiment, the thickness A of 1500 Å
A commercially available filter (specifically, TF114 manufactured by LUXEL CORPORATION) in which an I film and a polyimide film are laminated is used. This TF114 filter has an X-ray transmittance close to 100%, and blocks almost 100% of infrared rays from the heater, visible light entering from the viewing window of the vacuum chamber 2 and electron beams from the vacuum gauge sphere. It has characteristics. In addition, it is strong against heat and has good handling characteristics.

In such a structure, for example, Ti is 600 Å on the sample 8 which is a Si wafer by using the K cell 14.
X-ray from the X-ray source 4 is formed on the sample 8
It is incident on the surface at a low incident angle (2 degrees or less) that makes a smooth glance,
Consider a case where the reflection X-ray measurement is performed while changing the heating temperature for the sample 8 (20 to 800 ° C.) by the heater in the sample holder 9a.

The white X-rays emitted from the X-ray source 4 are limited by the slit 5 and then reflected by four crystals of the channel-cut monochromator 7 four times to be dispersed. In the present embodiment, the characteristic X-ray of CuKd is spectrally used. The dispersed X-rays are totally reflected by the total reflection mirror 10 so that the optical path is bent (secondary light is cut),
It is incident on the surface of the sample 8 at a low incident angle. At this time, the manipulator 9 can be rotated, and the incident angle on the sample 8 can be adjusted.

When the reflected X-ray is measured by the two-dimensional X-ray detector 13 while changing the heating temperature for the Ti / Si film of the sample 8,
At room temperature, vibrations corresponding to Ti of 600 Å can be observed in the reflected X-ray spectrum. However, this vibration became weak at 460 ° C and disappeared at 600 ° C. That is, 46
It was found that the interdiffusion between Ti and Si started at 0 ° C., and at 600 ° C., all the Ti layers were changed to TiSi layers. Since the film was formed in an ultra-vacuum, the measurement has almost no effect of oxidation by oxygen. Further, since the filter 16 is provided in the detection window portion of the two-dimensional X-ray detector 13 and blocks except for X-rays, it does not block the sight window of the vacuum chamber 2 or stop the vacuum gauge, and While the sample 8 was heated by the heater, the S / N was evaluated well.

The filter 16 for cutting off components other than X-rays is detachably attached to the detection window of the two-dimensional X-ray detector 13 and has a spectral characteristic different from that of the filter. It may be exchangeable. According to this, since the two-dimensional X-ray detector 13 has sensitivity to not only X-rays but also electron beams, for example, a filter having a spectral characteristic of transmitting only electron beams is attached to transmit the sample or It is also possible to analyze and evaluate the state of the electron beam scattered by the sample.

[0029]

According to the first aspect of the present invention, a two-dimensional X-ray detector including an assembly of a semiconductor position detecting element and a microchannel plate has a detection window portion having a spectral characteristic for cutting off other than X-rays. Since a filter is provided, it is possible to block infrared rays, light, electron beams, etc., which are noise sources other than X-rays, from entering the two-dimensional X-ray detector,
Since only the target X-ray can enter the two-dimensional X-ray detector, X-ray evaluation with good S / N can be performed.

According to the second aspect of the present invention, in the X-ray evaluation apparatus according to the first aspect, the filter is provided so as to be replaceable with another filter having another spectral characteristic.
It is possible to perform not only good X-ray evaluation but also good S / N evaluation for the measurement target according to the spectral characteristics of the filter used by the two-dimensional X-ray detector having sensitivity to other than X-rays.

According to the invention of claim 3, in the X-ray evaluation apparatus of claim 1, Al, Ti, Si, Mg,
Film thickness 50 that contains light atoms such as Mn or C that are easy to use
Since a filter having a single-layer structure or a laminated structure having a thickness of 00 Å or less is used, in obtaining the effect of the invention according to claim 1, the X-rays to be measured have good transmittance and the incident intensity of X-rays is reduced. In addition, there is an advantage that the filter itself is easy to handle.

According to the invention described in claim 4, in the X-ray evaluation apparatus according to claim 1, even if the sample holder for arranging the sample in a vacuum has a heater for heating the sample, the heater is Since it is not affected by the infrared rays emitted, X-ray evaluation during film formation heating by the heater can be performed in a good S / N state.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

[Explanation of symbols]

 8 sample 9a sample holder 13 two-dimensional X-ray detector 16 filter

Claims (4)

[Claims] 1. A two-dimensional structure comprising an assembly of a semiconductor position detecting element and a microchannel plate for irradiating a sample placed in a vacuum with X-rays, and transmitting X-rays scattered by the sample. An X-ray evaluation apparatus for detecting with an X-ray detector, characterized in that a filter having a spectral characteristic for blocking other than X-rays is provided in a detection window portion of the two-dimensional X-ray detector. 2. The filter is replaceably provided with another filter having another spectral characteristic.
The X-ray evaluation apparatus described. 3. The filter comprises Al, Ti, Si, Mg,
Film thickness 50 that contains light atoms such as Mn or C that are easy to use
The X-ray evaluation apparatus according to claim 1, wherein the X-ray evaluation apparatus has a single-layer structure or a laminated structure having a thickness of 00Å or less. 4. A sample holder for disposing a sample in a vacuum,
A heater for heating the sample is provided.
The X-ray evaluation apparatus described.