WO2007074696A1

WO2007074696A1 - Ion scattering spectroscopic analyzer

Info

Publication number: WO2007074696A1
Application number: PCT/JP2006/325410
Authority: WO
Inventors: Takane Kobayashi
Original assignee: Riken
Priority date: 2005-12-28
Filing date: 2006-12-20
Publication date: 2007-07-05
Also published as: JP2007178341A

Abstract

An ion spectroscopic analyzer that without frequent sample rotation and without the need of accurate sample surface matching, is capable of measuring the structure or strain of crystal material with high precision. Two-dimensional position sensitive/time analyzing detectors (14, 15) are disposed in the direction surrounding a scattering angle of 180° (observation angle 0°) and the direction surrounding a scattering angle of 135° (observation angle 45°).

Description

Specification

Ion scattering spectrometer

Technical field

The present invention relates to an ion scattering spectroscopic analyzer that examines “strain (structure)” of a crystalline material using ion scattering by a sample.

Background art

[0002] Conventionally, methods for investigating the "strain (structure)" of a crystalline material using ion scattering include medium energy single-coaxial direct collision ion scattering spectroscopy (ME-CAICISS), medium energy ion scattering, and so on. Spectroscopy (MEIS) is known. ME-CAICISS is a method for examining the crystal structure or strain by measuring the incident angle dependence of the scattering intensity by making an ion beam incident on the crystal material and rotating the crystal material. MEIS is a method for examining the crystal structure or strain by measuring the output angle dependence of scattering intensity using a one-dimensional position detector (electrostatic analyzer).

Non-Patent Document 1: Physical Review B 67, 035319 (2003)

Disclosure of the invention

Problems to be solved by the invention

[0003] ME-CAICISS requires a long time because it measures the incident angle dependence of the scattering intensity while rotating the crystal material, and a certain amount of incident beam for each angle of incident beam, crystal material, and angle to be measured. However, it is difficult to accurately measure or standardize the amount of incident light under different incident conditions. In the case of MEIS, the electrostatic analyzer is large because it has two electrodes opposite to each other, and it is impossible to make a hole for the incident beam to pass through the electrode, so the scattering angle is 180 ° (observation angle 0 °). The neighborhood cannot be measured. In addition, since it is a one-dimensional position, it is necessary to accurately align the crystal material. The “observation angle” in this specification is an angle with respect to the ion beam.

[0004] The present invention does not require frequent sample rotation and does not require accurate sample surface alignment, and ion scattering spectroscopy that can measure the structure or strain of a crystal material with high accuracy. An object is to provide an apparatus.

Means for solving the problem

[0005] In the present invention, a two-dimensional position sensitive 'time in the direction surrounding the scattering angle 180 ° (observation angle 0 °) (or near the observation angle 0 °) and the direction surrounding the scattering angle 135 ° (observation angle 45 °). Install an analytical detector. Scattering angle: 135 ° (Observation angle 0 °) (or near observation angle 0 °) The angle of the blocking cone detected by the detector placed in the direction surrounding the observation angle is the angle reference (angle 0 ° direction). The strain information (structure information) of the sample can be obtained by the deviation from the position of the blocking cone detected by the detector arranged in the direction surrounding the observation angle of 45 °.

That is, an ion scattering spectroscopic analyzer according to the present invention includes a sample holding unit that holds a sample, a pulsed ion beam source that irradiates a pulsed ion beam toward the sample, and ions scattered by the sample. A first two-dimensional position sensitive detector for detecting and a second two-dimensional position sensitive detector.The first two-dimensional position sensitive detector detects ions scattered in a direction surrounding an observation angle of 0 °. The second two-dimensional position sensitive detector is arranged between the pulsed ion beam source and the sample held by the sample holder so as to detect ions scattered in a direction surrounding an observation angle of 45 °. Arranged to be.

[0007] Here, the first two-dimensional position sensitive detector may have a structure having a hole through which an ion beam emitted from the pulse ion beam source passes in a central portion. The instrument is preferably a time-resolved detector because it can measure at high count rates. In addition, since the ion scattering apparatus of the present invention can be resolved in position, it can measure scattered or recoiled particles at a large solid angle as necessary.

The invention's effect

According to the present invention, the “strain (structure)” of a crystal material can be examined most sensitively and with high accuracy in ion scattering spectroscopic analysis.

Brief Description of Drawings

FIG. 1 is a schematic diagram showing how incident ions are scattered by crystal atoms.

FIG. 2 is an explanatory diagram showing minute displacements of atoms on an atomic row.

FIG. 3 is a schematic configuration diagram of an ion scattering spectroscopic analyzer according to the present invention. Explanation of symbols

[0010] 11 Pulsed ion beam source

12 samples

13 Goniometer

14 Two-dimensional position sensitive, time-analyzing detector measuring direction surrounding observation angle 0 ° 15 Two-dimensional position-sensitive, time-analyzing detector measuring direction surrounding observation angle 45 ° 16 Direction surrounding observation angle 45 ° 2D position sensitive 'time analysis type detector 17 measuring signal processing unit

18 Vacuum container

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing how incident ions are scattered by crystal atoms. When energy is aligned in the crystal material and parallel ion beams are incident, a conical shadow is formed behind the atoms that make up the crystal material, where the incident ions cannot enter. This shadow is called a shadow cone. And if another atom is in this shadow, it does not contribute to ion scattering. This is called the shadowing effect. On the other hand, when focusing on particles scattered by an atom, if another atom is present on the scattering trajectory, a conical shadow is created behind which the scattered ion cannot enter. This shadow is called a blocking cone. In the direction where the blocking cone is stretched, the scattered particles due to the first scattered atoms are not observed. This is called a blocking effect. In the case of a crystalline material, the arrangement of atoms (crystallographic axis) can be determined by examining the shadowing effect or blocking effect.

In ion scattering, the strain of a thin film grown on a substrate can be evaluated from the crystallographic axis direction of the thin film. When the atoms on the atomic column existing in the direction of the observation angle (Θ) are slightly displaced as shown in Fig. 2, the shift amount of the observation angle (ΔΘ) is given by the following equation (1).

[Number 1]

[0014] where a and c are the x and y components of the interatomic distance of the atomic sequence before the atoms are displaced, respectively, and Δa and Δc are the X and y components of the displacement of the atoms, respectively. is there.

[0015] As shown in Equation (1), if Equation (2) holds, that is, if the strain is not relaxed, the observation angle shift amount ΔΘ peaks at the observation angle Θ = 45 °. Show. In other words, thin film strain or strain relaxation can be most sensitively and accurately evaluated in the 45 ° direction.

[Equation 2]

^) _≠ 0…

AC)

[0016] Therefore, two units (or more) installed in the direction surrounding the observation angle 0 ° (scattering angle 180 °) (or near the observation angle 0 °) and in the direction surrounding the observation angle 45 ° (scattering angle 135 °). Two-dimensional position sensitive 'time analysis type detector, or the direction surrounding the observation angle 0 ° (scattering angle 180 °) (or near the observation angle 0 °) and the direction surrounding the observation angle 45 ° (scattering angle 135 °) are the same. By using one two-dimensional position sensitive and time analysis type detector that can be measured sometimes, it is possible to investigate the "strain (structure)" of the crystal material most sensitively and with high accuracy.

FIG. 3 is a schematic configuration diagram of an ion scattering spectrometer according to the present invention. This device consists of a pulsed ion beam source 11, a goniometer 13 holding the sample 12, a two-dimensional position sensitive 'time analysis type detector 14 measuring the direction surrounding the observation angle 0 °, and the direction surrounding the observation angle 45 °. It consists of two-dimensional position sensitive and time-analyzing detectors 15 and 16 to be measured, and a signal processing unit 17 for processing signals from the detectors. A nors ion beam source 11, a goometer 13, and two-dimensional position sensitive 'time analysis type detectors 14, 15, 16 are arranged in a vacuum vessel 18. The inside of the vacuum chamber is evacuated to a working vacuum of the detector (2 X 10 ^_4 Pa) or less.

The two-dimensional position sensitive 'time analysis type detector 15 has a fixed distance from the sample force, and the two-dimensional position sensitive' time analysis type detector 16 has a variable distance from the sample force. It is only necessary to have at least one that does not necessarily need to have both. By using two detectors 14, 15, the strain can be measured by absolute measurement, that is, the thin film alone on the substrate. Also, the relative measurement of strain with a single detector, i.e. how the thin film is against the substrate You can evaluate whether it is distorted!

[0019] From the pulsed ion beam source 11, a pulsed ion beam having a parallelism, for example, an energy source of lOOkeV (velocity 2.196 X 10 ⁸ cm / s) and a pulsed beam width of 2 ns Is extracted and made incident on the sample 12. Roughly adjust the orientation of the sample using the goometer 13. For example, if the sample is SiGe (001), the SiGe [00-l] axial force is applied to the detector 15 that measures the direction surrounding the scattering angle of 135 ° (observation angle of 45 °) with the pulsed ion beam incident. SiGe 011> Align the axis. As a result, a blocking cone of atoms aligned in the [00 1] axis direction is observed in the detector 14 measuring the direction surrounding the scattering angle 180 ° (observation angle 0 °) (or near the observation angle 0 °), and similarly scattered. A detector cone 15 measuring the direction surrounding the angle 135 ° is observed. Although it is not always necessary to pay attention to the [001] axis and the 011> axis, the SiGe sample has a diamond structure, so even if it is distorted, the SiGe [001] axis and the SiG e <011> axis are two axes. Since the angle formed by is around 45 °, it is a convenient angle relationship for examining strain.

[0020] A position sensitive and time analysis type MCP detector (RoentDek Hexl20 / o) with a center hole made by RoentDek was used as the detector 14 for measuring the direction surrounding the scattering angle of 180 °. In addition, a position sensitive and time analysis type MCP detector (RoentDek DLD120) manufactured by RoentDek was used as the detector 15 (and 16) for measuring the direction surrounding the scattering angle of 135 °. Hexl20 / o has an effective diameter of 120mm, a center hole in the center, and three delay lines spirally wound without contacting each other with a microchannel plate (MCP) at a 120 ° angle. (Delay line) It is constituted by an anode. The pulsed ion beam emitted from the pulsed ion beam source 11 passes through the center hole of the detector 14 and enters the sample 12. The DLD 120 has an effective diameter of 120 mm, and is composed of two delay line anodes wound spirally without making contact with the MCP at an angle of 90 °. Scattered (or recoiled) particles enter the MCP, secondary electrons are emitted from the MCP, and secondary electrons are multiplied in the MCP. The multiplied secondary electrons enter the delay anode and are directed to both ends of the delay line anode.

[0021] By measuring the time difference between the arrival of the signal at both ends of the delay line, the delay line is wound. The ion incident position in the direction is calculated. Also, the time of flight of the scattered (recoil) particles is calculated from the sum of the timing (start) signal that pulses the ion beam and the time that appears at both ends of the delay line. The flight time of this particle corresponds to the energy of the particle, and it is possible to know which element in the sample collided with the element and from which depth of the sample it was scattered (recoiled). Note that the start signal does not necessarily have to be a timing timing signal. For example, the measurement signal of the secondary electrons that come out of the sample force when ions enter the sample may be used as the start signal.

[0022] The Hexl20 / o used as the detector 14 achieves a position resolution of 0.2 mm or less, and it is assumed that the position resolution is 0.2 mm. Further, 0 0120 used as the detector 15 (16) achieves a position resolution of 0.1 mm or less, and it is assumed that the position resolution is 0.1 mm. Furthermore, it is assumed that the detector 14 and the detector 15 are installed 500 mm from the sample. In this case, the angular resolution of the position resolution capability is also calculated in the detector 14 is _{^{t an _1 (0. 2/500) =}} 0. The 023 °. Similarly, the angular resolution of detector 15 is tan — ¹ (0. 1/500) = 0.0115 °, and the total angular resolution of the two detectors 14 and 15 is based on statistical variations in the scattering intensity. Otherwise (0. 023 ² + 0. 0115 ² ) ^1/2 = 0.026 (.). When observing at an observation angle of 45 °, sin (2 X 45 °) = 1, so equation (3) is established from equation (1).

[Equation 3]

[0023] That is, the apparatus shown in Fig. 3 must naturally take into account the statistical dispersion of the scattering intensity, but if the statistical dispersion of the scattering intensity is not taken into account, a strain (structural change) of 0.1% can be obtained. I can catch it. Of course, if the distance between the detector and the sample is increased, the strain (structure) can be captured more accurately.

[0024] Since the effective diameter of both detector 14 (Hexl20 / o) and detector 15 (DLD120) is 120 mm, the output that can be detected by the detector when the distance between the detector and the sample is 500 mm. Both angles are in the range of tan ^{_ 1} (120Z500) 13. 4 ° (± 6.7 °), and the solid angle can be captured in the following formula for the blocking pattern in the range of 0.045sr.

[0025] (solid angle) = (area) / ^{^{(distance) 2 = π · 60 2/}} 500 2 = 0. 045sr Next, a measurement method when the sample is SiGe (Oil) will be described. In the case of the SiGe (011) sample, in contrast to the SiGe (001) sample, a detector that measures the direction surrounding the scattering angle of 135 ° with a nearly SiGe [0—1-1] axial force pulsed beam incident. Align the SiG e <001> axis with 15. As a result, a blocking cone of atoms aligned in the [011] axial direction is observed in the detector 14 measuring the direction surrounding the scattering angle of 180 °, and similarly to the detector 15 measuring the direction surrounding the scattering angle of 1 35 °. 001> Axial blocking cones aligned in the axial direction are observed. In this case as well, it is not always necessary to pay attention to the [011] axis and the 001> axis, but since the SiGe sample has a diamond structure, the SiGe [011] axis and the SiGe Since the angle between the two axes is around 45 °, it is a convenient angular relationship for examining strain.

Next, a measurement method when the sample is SiGe (111) will be described. In the case of the SiGe (111) sample, the beam is incident from the SiGe <00-1> (or SiGe 0-1-1>) axial direction. If the incident direction is SiGe 00-1>, the scattering angle is Strain can be measured by aligning the SiGe 011> axis to the detector 15 installed in the direction surrounding 135 °, and if the incident direction is SiGe 0-1-1>, the scattering angle is 135 °. Strain can be measured by aligning the SiGe 001> axis with the detector 15 installed in the surrounding direction.

[0027] Further, it is assumed that the detector 16 for measuring the direction surrounding the scattering angle of 135 ° is installed 300 mm from the sample. As a result, the measurable emission angle of this detector is in the range of tan ^_1 (120Z300) = 2.1.8 ° (± 10.9 °). With this detector, it is possible to evaluate the strain of SiGe <011>! /, By capturing the SiGe <001> axis. SiGe <011> or SiGe 001> is 54.74 ° or 35.26 ° from the Si [lll] axis when there is no strain. The pulsed ion beam is incident from the SiGe 1- 1-1 axis, and the SiG e <011> axis is! /, By the detector 16 measuring the direction surrounding the scattering angle of 135 ° with SiGe <001> Observe the blocking cone corresponding to the SiGe 011> or SiGe 001> axis. Their axes should be observed around the scattering angles of 144.74 ° and 125.26 °, respectively. In other words, the observation angle Θ is 35.26 ° and 54.7 4 °, respectively. Therefore, since sin2 Θ is sin2 Θ = 0.943 at both observation angles of 35.26 ° and 54.74 °, it is not the optimum condition, but it can capture the strain sufficiently. It is.

[0028] The angular resolution in which the position resolution capability is also calculated is as follows. The detector (Hexl20 / _O ) 14 is tan— ¹ (0.2 / 500) = 0.023 ° as before, and the detector (DLD120) 16 is tan- ¹ (0. 1/300) = 0.019 °, and the total angular resolution of the two detectors 14, 16 must naturally take into account the statistical dispersion of the scattering intensity. Without considering the statistical dispersion of scattering intensity, (0.023 ² + 0. 019 ² ) ^1/2 = 0.03 (.). When observed at an observation angle of Θ = 35.26 ° or 54.74 °, (sin2 0 = 0.9943), equation (4) is established from equation (1), and 0.1% It is possible to capture the strain (structural change).

Picture

—-—) = Αθ χ-^-$ ιη 2θ = 0.03 χ— χ 0.943 «0.001--(4)

{a c J 180 180

[0029] Regarding the distance between the detector and the sample, the measurable emission angle can be changed by placing the detector on a linear moving mechanism and adjusting the distance between the detector and the sample by the linear moving mechanism. In addition, as shown in Fig. 3, detectors are installed in two different scattering angles of 135 °, and on the one hand, the distance between the detector and the sample is increased to increase the angular resolution, depth resolution, and mass resolution. It is possible to measure a large solid angle by shortening the distance between the detector and the sample.

[0030] This measuring apparatus can analyze strain and structure even in other systems including a strained Si system.

Claims

The scope of the claims

[1] a sample holder for holding a sample;

A pulsed ion beam source that irradiates a sample with a pulsed ion beam; a first two-dimensional position sensitive detector that detects ions scattered by the sample; and a second two-dimensional position sensitive detector;

The first two-dimensional position sensitive detector is provided between the pulse ion beam source and the sample held by the sample holding unit so as to detect ions scattered in a direction surrounding an observation angle of 0 °. Arranged,

The second two-dimensional position sensitive detector is arranged so as to detect ions scattered in a direction surrounding an observation angle of 45 °, and an ion scattering spectroscopic analysis device characterized in that:

[2] The ion scattering spectrometer according to claim 1, wherein the first two-dimensional position sensitive detector has a hole through which an ion beam emitted from the Norse ion beam source passes in a central portion. An ion scattering spectroscopic analyzer characterized by that.

3. The ion scattering spectrometer according to claim 1 or 2, wherein the first and second two-dimensional position sensitive detectors are time-resolved detectors.