JPH05346412A - Ion channeling analyzer - Google Patents

Abstract

PURPOSE:To obtain an ion channeling analyzer which can adjust crystal axis without suspending much time in the alignment of crystal axis and without causing irradiation damage or contamination on the surface of a sample. CONSTITUTION:Proton or helium ion from an ion source 1 is accelerated at 1-3MeV and impinges on a sample. A goniometer 6 having at least two axes is disposed in the center of a vacuum tank 5 communicated with the ion source 1. A sample 7 is loaded to the goniometer 6. A white X-ray source 11 and a semiconductor X-ray detector 14 are disposed at predetermined points of the vacuum tank 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion channeling analyzer, and more specifically, in the field of materials science including the field of semiconductor industry, a sample utilizing the channeling phenomenon of a high energy ion beam. The present invention relates to a technique for improving the function and structure of an apparatus for analyzing the crystal structure of.

[0002]

2. Description of the Related Art When a huge amount of information is processed by a computer, it is required to increase the storage capacity and the processing speed. For this purpose, high integration of IC
Development is progressing from SI to ULSI and from two-dimensional IC to three-dimensional IC. Along with this, individual devices and wirings are becoming extremely miniaturized and multilayered. Also, a region extremely shallow from the surface of the device is being used as an active layer.

In the development of such ICs and process studies, evaluation of crystal structure and crystallinity on the surface and under the surface is extremely important. To do so, Rutherford backscattering method (RB
S) and particle-excited X-ray method (PIXE) are effective analysis methods that utilize the channeling phenomenon. In addition, recently, three-dimensional analysis of the above method using a microbeam is being performed.

Under such a technical background, the conventional ion channeling analyzer is constructed as shown in FIG. Then, in a vacuum atmosphere in the vacuum chamber 16, a van der Graff (Van) of about several MeV is used.
A proton or helium ion beam 17 generated by an accelerator of de Graff type or the like is collimated to have a diameter of 1 mm or less and a divergence angle of 0.05 ° or less. The proton or helium ion beam 17 is applied to a sample 19 such as a single crystal on a goniometer 18 having at least two axes.

Ions backscattered from the sample or characteristic X-rays excited by the ions are mainly detected by the semiconductor detector 20. Then, after being amplified outside the vacuum chamber 16, the energy is analyzed by a multi-channel wave height analyzer (MCA) 22.

The method of aligning the crystal axes of the sample for the channeling measurement is as follows. That is,
As shown in FIG. 3A, an energy window is provided in atoms near the surface so that only scattered ions can be detected. Then, the intensity per unit incident ion is drawn as shown in FIG. 3B while scanning the rotation angle φ with the 1 tilt angle θ fixed.

The rotation angle φ at which the curve in FIG. 3 (b) is minimized (plane channeling) is drawn on polar coordinates as shown in FIG. 3 (c). In consideration of the symmetry of the crystal of the sample, the rotation angles φ that are the same-plane channeling condition are connected by a straight line, and the coordinates of the intersections of these straight lines give the channeling condition.

[0008]

The above-described conventional crystal alignment method has the following fundamental problems. That is, a large amount of time was spent on crystal axis alignment as compared with the time of actual channeling measurement. Further, since the ion beam is constantly irradiated during the crystal alignment work, irradiation damage or surface contamination due to the ion beam occurs. Therefore, there is a problem that the crystallinity of the sample or the composition distribution in the depth direction changes, which makes it difficult to perform an accurate channeling analysis.

[0009]

The present invention is directed to a vacuum chamber in which a sample for analysis is housed, an ion source provided outside the vacuum chamber for irradiating the sample in the vacuum chamber with ions, and a vacuum chamber of the vacuum chamber. An ion detector, which is provided inside and detects ions scattered by the sample, and an analyzer, which is provided outside the vacuum chamber and performs energy analysis of the ions detected by the ion detector, further include a vacuum chamber. An X-ray source provided on the outside of the vacuum chamber for irradiating the sample in the vacuum chamber with X-rays, and an X-ray detector provided on the outside of the vacuum chamber for detecting the X-rays diffracted by the sample. Ion channeling, in which a radiation source and an X-ray detector are provided so that a surface formed by connecting the X-ray source, the X-ray sample irradiation position, and the X-ray detector is parallel to the trajectory of the ion beam. It is an analyzer.

That is, the ion channeling analyzer of the present invention makes white X-rays incident on a sample and monitors the X-rays of a specific energy Bragg-reflected by the sample with an X-ray detector, thereby preliminarily performing ion channeling. The crystal axis direction of the sample can be matched with the direction of the ring analysis beam.

As the white X-ray target, a material having a high generation efficiency of continuous X-rays by bremsstrahlung is preferable, iron, copper and molybdenum are preferable, and tungsten is more preferable. The acceleration voltage E is λ = hc / E (h; Planck's constant, c; speed of light), and the short wavelength end λ (SWC;
Since the short wave cutoff is determined, it is set according to the sample to be measured.

However, in order to realize this function, it is necessary to align the X-ray source and the X-ray detector in advance by the following procedure. That is, first, a standard sample is used, and the sample is axially aligned by the ion beam so that the channeling conditions are satisfied. After that, the X-rays reflected by the Bragg on the surface corresponding to the crystal axis of the sample are X
The X-ray source and the X-ray detector are aligned and angled so as to be incident on the line detector.

[0013]

Once the above adjustment is made, the desired crystal axis can be aligned with the direction of the ion beam without using ions. Therefore, not only the axis alignment time, which has been a problem in the related art, can be shortened, but also the influence of measured values due to irradiation damage or surface contamination by the ion beam can be significantly reduced.

The apparatus according to the present invention is particularly effective when carrying out a channel analysis with a microbeam in which the beam current is small and the beam current density cannot be increased in order to avoid irradiation damage. In addition, an X-ray detector mounted on this apparatus can also detect X-rays excited by an ion beam. Furthermore, fluorescent X-ray analysis is also possible by using a powerful X-ray source. In addition, this device is advantageous because it is possible to perform axis alignment based on Bragg reflection from the substrate when evaluating the crystallinity of a film with poor crystallinity deposited on a single crystal substrate. is there.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to one embodiment shown in the drawings. The present invention is not limited to this.

FIG. 1 shows a schematic structure of an ion channeling device according to the present invention. In this figure, 1 is an ion source, which contains 1 to 3 protons or helium ions.
Accelerate with MeV to make the sample incident. Reference numeral 5 is a vacuum chamber connected to the ion source 1. A goniometer 6 having at least two axes is provided at the center of the vacuum chamber 5. A sample 7 is attached to the goniometer 6. Reference numeral 11 is a white X-ray source provided at a predetermined position of the vacuum chamber 5. 14
Is a semiconductor detector for X-ray detection.

The semiconductor detector 14 is provided in the vacuum chamber 5 on the side opposite to the X-ray source 11 with the sample 7 in between. That is, the semiconductor detector 14 is attached to the outside of the vacuum chamber 5 at a position deviated from the sample 7 toward the ion source 1 by an angle 2θ with respect to the X-ray incident direction. Further, the X-ray source 11 and the semiconductor detector 14 are provided such that the surface formed by connecting the X-ray source 11, the sample irradiation position and the semiconductor detector 14 is parallel to the ion beam.

Ion beam 2 generated from ion source 1
Is a parallel beam limited by the slits 3 and 4. Then, it is incident on the sample 7 in the vacuum chamber 5. The backscattered ion beam 2 is detected by a semiconductor detector 8 for ion detection, passes through an amplifier 9, and is subjected to channeling analysis by a multichannel wave height analyzer 10.

The X-ray generated by the X-ray source 11 is transmitted through the slit 1
It is incident on the sample 7 via 2. The X-ray scattered by the sample 7 enters the semiconductor detector 14 through the slit 13. The X-ray detected by the semiconductor detector 14 is the amplifier 15
After that, the energy is analyzed by the multi-channel wave height analyzer 10.

Here, the case of determining the condition of (111) axial channeling will be described by taking a Si (111) single crystal substrate as an example of the sample 7. Acceleration voltage 45k
Using an iron X-ray source operating at V and an emission current of 8 mA, the above angle 2θ was set to 30 °.
At this time, while monitoring the 7.64 keV X-rays that are Bragg-reflected by the (111) plane of Si and enter the detector,
The axis of Sample 7 was adjusted so that the peak was maximized. In that state, channeling measurement was performed using a 2.0 MeV helium ion beam. As a result, χmin
Was 3.6%, which was close to the theoretical value.

[0021]

As described above, according to the present invention, the axis alignment time can be shortened, and the influence of measured values due to irradiation damage due to the ion beam and surface contamination can be significantly reduced. Further, the ion channeling analyzer of the present invention is particularly effective when carrying out a microbeam channeling analysis in which the beam current is small and the beam current density cannot be increased in order to avoid irradiation damage. Further, the X-ray detection in the apparatus of the present invention can also detect the X-rays excited by the ion beam. In addition, fluorescent X-ray analysis is possible by using a powerful X-ray source. Moreover, the apparatus of the present invention can perform axis alignment based on Bragg reflection from the substrate when evaluating the crystallinity of a film having poor crystallinity deposited on a single crystal substrate. It is advantageous.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory diagram of an ion channeling analyzer according to an embodiment of the present invention.

FIG. 2 is a schematic configuration explanatory view of a conventional ion channeling analyzer.

FIG. 3 is an explanatory diagram illustrating a method of adjusting a crystal axis of a sample in a conventional ion channeling analyzer. (A)
Indicates the energy distribution of backscattered ions. (B) is a plot of the number of counts in the energy window shown in (a) against the rotation angle φ of the sample. (C) is a plot of the minimum value of (b) on polar coordinates.

[Explanation of symbols]

 1 ion source 2 ion beam 5 vacuum chamber 6 goniometer 7 sample 8 semiconductor detector (for ion detection) 9 amplifier 10 multi-channel wave height analyzer 11 X-ray source 14 semiconductor detector (for X-ray detection) 15 amplifier

Claims (1)

[Claims] 1. A vacuum chamber for storing a sample for analysis, an ion source provided outside the vacuum chamber for irradiating the sample in the vacuum chamber with ions, and a vacuum chamber provided inside the vacuum chamber and scattered by the sample. An ion detector for detecting the generated ions, and an analyzer provided outside the vacuum chamber for performing energy analysis of the ions detected by the ion detector, and further provided outside the vacuum chamber and provided in the vacuum chamber. An X-ray source for irradiating an internal sample with X-rays, and an X-ray detector provided outside the vacuum chamber and for detecting X-rays diffracted by the sample are provided. , An ion channeling analyzer provided such that a surface formed by connecting an X-ray source, a sample irradiation position of X-rays, and an X-ray detector is parallel to an orbit of an ion beam.