JPH02168149A - Measuring apparatus for x-ray standing wave using photoelectron - Google Patents

Abstract

PURPOSE:To enable measurement of an X-ray standing wave even in an ultra- high vacuum by using a rotary shaft having a microscopic rotary mechanism equipped with a differential exhaust mechanism and by rotating a sample precisely in the ultra-high vacuum. CONSTITUTION:An X-ray emitted from an X-ray source 16 is transmitted through an incident window 13 and led into a vacuum tank 10. The X-ray entering the vacuum tank 10 causes Bragg reflection due to a sample 12, and the intensity of photoelectrons radiated from the sample 12 on the occasion is measured by a detector 15. In order to confirm the occurrence of the Bragg reflection in the sample 12, the X-ray radiated from the sample 12 through an emission window 14 is measured by a scintillation counter 17. Since the sample 12 needs to be rotated with precision of 0.1 second or less in an X-ray standing wave method, a rotary shaft equipped with a differential exhaust mechanism is rotated in the vicinity of the Bragg reflection by a goniometer 11 for rotation having a microscopic rotation mechanism, and thereby measurement of an X-ray standing wave is executed. In this way, the X-ray standing wave can be measured even in an ultra-high vacuum.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention belongs to an X-ray diffraction device that uses X-rays and electrons to analyze the structure of the surface and interface of a solid material, and in particular, it belongs to It relates to a wave measuring device.

[Conventional technology]

Synchrotron synchrotron radiation (hereinafter referred to as synchrotron radiation) is emitted from a circular accelerator that accumulates charged particles accelerated to the speed of light.
A powerful light with a wide spectrum ranging from Xa to infrared radiation is emitted. This synchrotron radiation is white light with continuous wavelengths and is more than an order of magnitude more powerful than conventional light sources, and there is a growing movement to use this synchrotron radiation for structural analysis of solid materials using X-ray diffraction. . One such analysis method includes a method called the X-ray standing wave method that utilizes the interference effect in Bragg reflection of Xal. This method makes it possible to analyze the positions of atoms of interest on the surface/interface of conductive materials and the atomic-order structure of impurities. It is something to be used. At this time, the Xll111 standing wave method uses the Bragg
) to take advantage of the interference effect of the x gland in the reflection region,
To measure the effect of line standing waves, we usually use the Bragg (nr
agg) Fluorescence X in an angular range of several seconds or less, which is the width of reflection
It is necessary to capture changes in line strength. FIG. 5 shows an example of a conventional X-ray standing wave measuring device. 1 is an X-ray source, 2 is a slit for parallelizing the XJ, 3 is an asymmetrical monochromator, 4 is a slit that takes out only the necessary part of the parallelized Xall, 5 is a sample, and 6 is a firefly. A bull conductor detector for optical X-ray detection (hereinafter referred to as detector 6), 7 is a Bragg (srag)
g) Detector for reflection measurement (hereinafter referred to as detector 7), 8 is a detector for measuring incident X-ray intensity (hereinafter referred to as detector 8), 9 is a high-precision goniometer with a rotation accuracy of 0.1 seconds or less - (hereinafter referred to as high-precision goniometer 9). In the normal X-ray standing wave method, a necessary portion of XMA emitted from an X-ray source 1 is first taken out by a slit 2, and the X-rays emitted from the X-ray are incident on an asymmetric monochromator 3. The asymmetrical monochromator 3 has a crystal cut so that Bragg (nragg) reflection occurs when incident X-rays pass close to the crystal, and the same surface as the Bragg (CBrmgg) reflection surface of the normal sample is used. The role of this asymmetric monochromator 3 is to produce highly accurate parallelized X-rays with an angular spread of less than 1 second.The principle of this is described by Akimoto et al. , al :Ja
panaa*Journal j+f AppHs
d Ph1sica, Vol, 24. No,
12+pp, L917-920) et al. X parallelized by asymmetric monochromator 3
The line is cut with a slit 4 on the surface of the sample 5 to a size of about 21 m x 2 iut. Here, the reason for reducing the irradiation area of Xi on the surface of sample 5 is to reduce the influence of warpage and strain on the sample itself. It is detected by the detector 7. Here, the intensity of Xa incident on the sample 5 is monitored by a detector 8.

In order to measure information from the atom of interest using the
g) This is carried out by rotating the atom in the reflection region and measuring the intensity of the fluorescent X-edge of the atom of interest using the detector 6 at this time. By analyzing the distribution of fluorescent X-ray intensity obtained at this time, it becomes possible to analyze the structure of the target atom.

However, the conventional X-ray standing wave measuring device is based on the premise that the entire device is installed in the atmosphere and the measurement is performed in the atmosphere.

This is currently the 0000 required for this measurement in ultra-high vacuum.
This is due to the difficulty in installing a rotating shaft with an angular displacement of 1 second or less. For this reason, usually Xa
Elements that can be analyzed using the dosing technique are limited to relatively heavy elements whose fluorescent X-ray intensity can be measured in the atmosphere. In addition, it is possible to analyze only the structure of impurities in substances whose state does not change in the atmosphere and to measure the state of the interface between a relatively thick #film material and a substrate. For this reason, for example, if you want to know the structure of the interface between GaPJg grown on an Sl substrate and the substrate, the fluorescent X-rays of Qa can be measured with a conventional X-ray standing wave measuring device, but P is a light element. Therefore, the generation efficiency of fluorescent X-ray intensity is poor, and the problem arises that the fluorescent X-rays of KaP are largely absorbed by the atmosphere.

In addition, in the hand conductor process, there are many requests for structural analysis of relatively light elements such as fR, Sl, and nitrogen, rather than relatively heavy elements such as Qa and As, but in the conventional X-ray standing wave method, It is difficult to measure such elements because it is assumed that they will be measured.

For example, if we consider the process of producing St oxidized gold by blowing oxygen onto an Sl substrate, we can take a sample in such a state by
In order to analyze using the line standing wave method, fluorescence X due to absorption of Sl is required.
It is necessary to measure fluorescent X-rays and oxygen. However, in general, light elements have a low generation efficiency of fluorescent X-rays, and the generated fluorescent X-rays are quickly absorbed by the air, so it is difficult to measure them using the conventional X-ray wave method. Have difficulty.

Another example that occurs in an actual semiconductor process is when you want to know the structure of atoms grown in just one monoatomic layer on a substrate. Because of this change, it is difficult to analyze such a sample using the normal X-wave standing wave method even if the fluorescent X-rays are not absorbed by the atmosphere.

To deal with this, in the soft X-ray region, attempts have been made to measure standing waves of X-rays by changing the energy of incident X-rays without performing an angular sweep of the sample in an ultra-high vacuum. However, although this method is possible in the soft X-ray region where the Bragg reflection region is relatively wide, it is limited to samples with a wide lattice constant such as 5i (Ill) [ffi] where the reflection itself of the sample is Therefore, it would be difficult to apply it to samples with seven Sl (100) planes, which are often used in semiconductor processes. Due to the above-mentioned problems, it is difficult to apply the X-wave standing wave method using angle sweep to samples containing light elements or samples whose state can only be maintained in vacuum. An embarrassing problem arises.

Furthermore, the X-ray fixed wave method using fluorescent Xi has the following drawbacks. That is, since the mean free path of fluorescent XNA is relatively long, ranging from several hundred^ to several μm, only average information about the entire sample can be obtained.

For example, considering the fc case where GhAm is deposited on a Si substrate, the lattice constants of St and GaAm are about 4% different, so if 25 or more layers of GaAs are deposited, GaAa
The O structure is averaged, and information about the interface cannot be obtained. Also, even if there are only several layers of GaAs,
The information obtained in the Xa measurement is not the interface information itself, but only the average tin of the interface + the GaAm deposited on it. Furthermore, let us consider a case where, for example, the surface of a GaAs substrate is surface-treated with Ar-based footer ring. In this case, for example, if you want to know how many defects are occurring from the surface to the inside, the conventional method
The method of detecting can only obtain averaged information, and cannot obtain such information in the depth direction.

[Line layer that the invention attempts to solve]

The purpose of the present invention is to solve the problem that it is difficult to analyze the structure of a sample in the depth direction with conventional X-ray settled wave measurement equipment, and to solve the problem that it is difficult to analyze the structure of a sample in the depth direction using conventional X-ray settled wave measurement equipment. An object of the present invention is to provide a photoelectron-based X-ray standing wave measuring device that enables directional structural analysis.

[Means and actions to solve the green problem]

By using differential pumping, the present invention directly introduces a rotating shaft with an angular accuracy of 0.1 seconds or less, which is essential for the X-wave standing wave method, into a high vacuum or ultra-high vacuum, and also This is a photoelectron-based X-ray standing wave measurement device for vacuum use whose main feature is to measure generated electrons.

This method differs from conventional technology in that it is possible to measure X-ray settled waves even in high vacuum, cloudy conditions, or ultra-vacuum because the accuracy of the rotating shaft that provides rotational motion in ultra-high vacuum is significantly improved. ing. In the case of conventional technology, the angular accuracy in ultra-high vacuum is at most 0.1°, but the X-ray fixed wave method, which requires high angular accuracy, is used for measurement in ultra-high vacuum. Although it has rarely been applied in Tabata, by using the present invention, this becomes possible.

[Example 1] An example of the present invention will be described using FIGS. 1 and 2. Figure 1 shows the overall outline of the present invention, (al is a plan view, (b)
is a side view. 10 is a vacuum chamber, 11 is a rotating duometer, 12 is a sample, 13 is a 7-lunge with a Be window for entrance at the X-ray inlet (hereinafter referred to as the entrance window 13), and 14 is a Be window for exit at the X-ray exit port. Bragg (hereinafter referred to as exit window 14), 15 is an electron energy detector for photoelectron detection of the electron detector (hereinafter referred to as detector 15), J6 is an X-ray source, 17
is a Bragg detector that can detect X-rays in the atmosphere.
Bragg) is a scintillation counter for measuring reflected X-rays (hereinafter referred to as scintillation counter 17). X-rays emitted from the X-ray source 16 pass through the entrance window 13 and are guided into the vacuum chamber 10 . X incident on vacuum chamber lO
The beam causes Bragg reflection by the sample 12, and at this time the intensity of the photoelectrons emitted from the sample is measured by the detector 15. In addition, in sample 12, Bragg (
Bragg) To confirm that a reflex has occurred,
X-rays emitted from the sample 12 via the exit window 14 are measured by a radiation counter 17. In the X-ray standing wave method, it is necessary to rotate the sample 12 with an accuracy of 0.1 seconds or less, so the drive shaft is equipped with a Bragg
) Measure the X-ray standing wave by rotating it near the reflection.

Next, we will explain the drive shaft that enables highly accurate rotation in an ultra-high vacuum. FIG. 2 is a conceptual diagram of a cross section of the drive shaft.

18 is a vacuum chamber, 19 is a bellows, 20 is an outer wall of the vacuum chamber,
21, 22, and 23 are sealing materials made of 0 S/G or Teflon rings (hereinafter referred to as sealing material 21. sealing material 2).
2. (referred to as sealing material 23), 24. ze is a duct for differential exhaust, and 25.27 is an exhaust system for differential exhaust (hereinafter referred to as exhaust system 25).
28 is a rotation bearing for the drive shaft (hereinafter referred to as rotation bearing 28); 29 is a drive shaft for rotation of the rotation shaft (referred to as the exhaust system 27);
(hereinafter referred to as drive shaft 29), 30 is a coarse movement rotation stage, 3
1 is a high-precision fine-movement rotation stage (hereinafter referred to as fine-movement rotation stage 3) with a micro-rotation mechanism using a sign par or the like;
2 is a sample support stand on which a sample can be attached, and 33 is a sample. In this device, the drive shaft 29 is directly connected to the atmosphere side and the vacuum side. To achieve this, the present invention uses double differential pumping as follows. That is, the inside of the vacuum chamber 18 is maintained at an ultra-spring vacuum by the sealing material 21 and the sealing material No. 22, and the vacuum between the sealing materials 21 and 220 is maintained at lO~10-'T.
Hold in orr. Also, the sealing material 22 and the sealing material 2
3, the degree of vacuum between the sealing materials 22 and 23 is set to 10
It is possible to maintain the temperature at ~10'rorr and to make it outside the sealing material 23 @the entire atmosphere.

The sample 33 is rotated by a coarse rotation stage 30 and a fine rotation stage 31.

FIG. 3 shows an example of an X-ray standing wave using electronic measurement according to the present invention. A GaAm (ill) substrate surface treated by argon sputtering was used as a sample. A
rst! The conditions for the ivy are an applied dragon pressure of 1 kV.

Sputtering was performed for about 5 minutes at an ion current of 1 mA.

The measurements were carried out with the device set to 10-8 Torr.

(&) in Fig. 3 is the case where the measurement is performed focusing on Qa (D KLL Auger electrons. Also, (b) is the case where Ga
The results of measurements by LMM Auger electrons are shown. It can be seen that the changes in photoelectron intensity obtained are clearly different even though the samples are the same. It can be seen that the KLL Auger electron measurement results are in good agreement with the GaAm crystal calculation results, whereas the LMM calculation results are different. This is related to the escape depth of photoelectrons from the sample. In other words, when the energy of the electron excited by the incident X-ray is large, its mean free path also becomes long, giving average information from a deeper part of the sample, whereas when the energy of the excited electron is small, the mean free path becomes longer. This is due to the fact that information is only provided near the surface.

In this measurement, the energy of KLL Auger electrons in Ga is about 10 keV, and its mean free path is several hundreds of steps, giving information about the entire bulk crystal.

On the other hand, the energy of Su Auger electrons in Ga is about 1 keV
The mean free path is estimated to be about 20X. From this, it follows that (a) and (b) in FIG. 3 provide information from the surface to a depth of several hundred depths and approximately 20X, respectively.

Moreover, the solid line in FIG. 3 (&) is a calculated value when Ga is located on a crystal lattice arrangement within the crystal, and shows relatively good agreement with the experimental value. On the other hand, in Figure 3 (b), Ga is Ga
This is a calculated value when the As crystal is distributed almost randomly, and it almost agrees with the experimental value in (b). From this, in the sample used for this measurement, approximately 1
In the 5X region, the crystal lattice is almost destroyed by Ar spucking on the surface, whereas
It can be seen that the influence of the defect does not extend to the region below 00OX.

By using this apparatus in this way, it becomes possible to analyze the structure of the target atom in the depth direction of the sample using the X-ray standing wave method in a high vacuum or an ultra-high vacuum.

[Example 2] Next, the exhaust system of this device will be explained. Figure 4 shows the block of the main exhaust system. 34 is a vacuum chamber for setting a sample, 35 is a rough evacuation system (hereinafter referred to as rough evacuation system 35) that can exhaust air from the atmosphere, such as a target molecular pump, and 36 is for drawing the vacuum chamber 34 to a high vacuum. High vacuum vibration-free exhaust system (
37 is a rotating shaft for rotating the sample (hereinafter referred to as rotating shaft 37); 38 is a rotating shaft for rotating the sample;
39.40 is a sealing material (hereinafter referred to as sealing material 313.39) that isolates the vacuum chamber 34 from the atmosphere at the rotating shaft 37.
．． 40), 41 is a high vacuum vibrationless exhaust system (hereinafter referred to as vibrationless exhaust system 4) using an ion pump to evacuate the space closed by the sealing material 38 and 39 and maintain the vacuum in the vacuum chamber. ), 42 evacuates the space closed by the sealing material 39, 40, and evacuates the space closed by the vacuum chamber 34 and the sealing material 38.
．． ,? 9 is a non-vibration exhaust system (hereinafter referred to as vibration-free exhaust system 42) for maintaining the vacuum in the space surrounded by 43, a vacuum pulp (hereinafter referred to as vacuum (referred to as pulp 43), 44 is a sealing material 38
and a vacuum knob 44 (hereinafter referred to as vacuum pulp 44) that isolates the area surrounded by the sealing material 39 and the roughing system 35; Vacuum valve 4 that shuts off between the pull system 35
5 (hereinafter referred to as vacuum pulp 45). When evacuating and starting up this equipment from the atmosphere, follow the steps below.

■ Open vacuum valves 43, 44, and 45.

■ Roughing system 35, vacuum chamber 34, high vacuum vibrationless exhaust system 3
6. A non-vibration exhaust system 41 which is a differential exhaust system for the rotating shaft 37.
42 and the sealing material 3B, the space partitioned by 39° 40 is evacuated.

■ High vacuum vibration-free exhaust system 36, vibration-free exhaust system 41.42
When the degree of vacuum becomes 10-6 Torr or less, which is the level of vacuum that allows operation, the high vacuum vibrationless exhaust system 36 and the vibrationless exhaust system 41, 42 are operated differentially.

■ Continuing to close the vacuum valves 43, 44, and 45, and evacuate the vacuum chamber 34 with the high vacuum vibrationless exhaust system 36,
The space between the sealing materials 313 and 39° 40 of the rotating shaft 37 is evacuated only by vibrationless exhaust systems 41 and 42.

(2) Stop the rough evacuation system 35 and open the air from the rough evacuation system 35 to the vacuum valves 43, 44, and 45 to the atmosphere.

As described above, by combining a non-vibration high vacuum evacuation system and an evacuation system that generates vibrations that can be evacuated from the atmosphere, it is possible to realize a high vacuum and vibration-free vacuum chamber.

In this way, by using this device, it is possible to measure samples using the X-ray standing wave method in high vacuum or ultra-high vacuum. Structural analysis in this direction is possible using the X-ray standing wave method.

[Effects of the Invention] As explained above, according to the present invention, X-ray standing waves can be measured even in high vacuum or ultra-high vacuum by performing high-precision rotation in high vacuum or ultra-high vacuum. It has many advantages and is useful for analyzing the structure of superlattice thin films and the interface between epitaxially grown thin films and substrates.

[Brief explanation of the drawing]

FIG. 1 (,) is a schematic front view showing an embodiment of the present invention;
FIG. 1 (bl is a schematic side view showing one embodiment of the present invention,
FIG. 2 is a schematic sectional view showing an example of a rotating drive shaft according to the present invention, FIG. 3 is a characteristic diagram showing an example of an X-ray standing wave using electronic measurement according to the present invention, and FIG. 4 is a diagram showing an example of the present invention. FIG. 5 is an explanatory diagram showing an example of the configuration of an exhaust system related to the conventional X-ray standing wave measuring device. J... X-ray source, 2... Parallelizing slit, 3...
Asymmetric monochromator - 4... Slit, 5... Sample, 6... Semiconductor detector for fluorescence X-ray detection, 7... Bragg detector for reflection measurement, 8... Incident X Line intensity measurement detector, 9...high precision goniometer 10...vacuum chamber, Jl...rotating goniometer
12... Sample, 13... Flange with Ba window for incidence, 14... Flange with Be window for exit, 15... Electron energy detector for photoelectron detection, 16... X-ray source,
17... Bragg scintillation counter for measuring reflected X-rays 18... Vacuum chamber, 19.
...Hero! , 20... Outer wall of the vacuum chamber, 21...
- Seal material, 22... Seal material, 23... Seal material, 24... Duct for differential exhaust, 25... Exhaust system for differential exhaust, 26... Duct for differential exhaust, 22 ...Exhaust system for differential exhaust, 28...Rotation bearing of drive shaft, 29...
・Rotation drive shaft, 30...coarse rotation stage, 31・
...High-precision fine rotation stage, 32...sample support stand,
33... Sample, 34... Vacuum chamber, 35... Rough evacuation system, 36... High vacuum non-vibration exhaust system, 37... Rotating shaft, stt... Sealing material, 39...・Seal material, 4
0...Sealing material, 41...Vibration-free exhaust system, 42...
- Vibration-free exhaust system, 43... Vacuum pulp, 44... Vacuum pulp, 45... Vacuum pulp.

Claims (2)

[Claims] (1) A vacuum chamber, a rotating shaft equipped with a differential pumping mechanism consisting of two or more seals and an exhaust system, a minute rotating mechanism using a sine bar, etc., and a sample attached to the rotating shaft in ultra-high vacuum. an electron detector that can measure electrons emitted from the sample, an exhaust system that can exhaust from the atmosphere to ultra-high vacuum, and an X-ray system that can separate vacuum and atmosphere. In a device consisting of an inlet, an X-ray exit port, and a detector capable of detecting X-rays in the atmosphere, by connecting a minute rotation mechanism to a rotating shaft equipped with a differential pumping mechanism, it is possible to detect X-rays in an ultra-high vacuum. A photoelectron-based X-ray standing wave measurement device characterized by rotating a sample with high precision and measuring electrons emitted from the sample using an electron detector. (2) Consists of a rough evacuation system that can exhaust air from the atmosphere, such as a turbo molecular pump, and a vibration-free high vacuum evacuation system, such as an ion pump. 2. The photoelectron-based X-ray standing wave measuring device according to claim 1, characterized in that a high vacuum evacuation system is used.