JP4660712B2 - X-ray microbeam generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray microbeam generator for generating an X-ray microbeam by using an asymmetric reflective crystal.
[0002]
[Prior art]
In recent years, when miniaturizing a semiconductor element, it is necessary to analyze a localized stress acting on a specific region of the semiconductor element (for example, a region directly under a gate electrode of a MOS transistor) with high accuracy. In order to perform such an analysis, it is considered optimal to perform X-ray diffraction using a highly parallel X-ray microbeam as a probe with radiant light having high directivity. Therefore, research for generating an X-ray microbeam having a small diameter (about several micrometers) and a small divergence angle (about 10 ⁻⁵ radians) in accordance with miniaturization of a semiconductor element is underway.
[0003]
[Problems to be solved by the invention]
As a technique for generating an X-ray microbeam, a technique using a curved multilayer mirror or a Fresnel zone plate is known. Although these techniques can reduce the beam diameter to some extent, a highly parallel beam with a sufficiently small divergence angle cannot be obtained. For this reason, it is practically impossible to use the X-ray microbeam generating apparatus obtained by the above technique in order to analyze the localized stress acting on the specific region of the semiconductor element with high accuracy. It is also conceivable to generate an X-ray microbeam having a small diameter and a small divergence angle by using an asymmetric reflection crystal having a surface that is not parallel to the crystal lattice plane. However, a specific configuration for this purpose is not yet known.
[0004]
Accordingly, an object of the present invention is to provide an X-ray microbeam generator capable of generating an X-ray microbeam having a sufficiently small diameter and a small divergence angle by using an asymmetric reflection crystal.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the X-ray microbeam generating apparatus according to claim 1 is an X-ray microbeam generating apparatus for generating an X-ray microbeam using an asymmetric reflective crystal having a surface not parallel to a crystal lattice plane. The first crystal support member and the second crystal support member are provided. The first crystal support member has a first asymmetric reflection crystal and a second asymmetric reflection crystal on which the diffracted X-rays incident on the first asymmetric reflection crystal are incident. It is possible to adjust the surface angles of the supported first and second asymmetric reflective crystals, respectively, while supporting both to be reduced in the first direction. The second crystal support member has a third asymmetric reflective crystal on which the diffracted X-rays from the second asymmetric reflective crystal are incident and a fourth diffracted X-ray from the third asymmetric reflective crystals is incident on the second crystal support member. the asymmetric reflective crystals, while supporting so that the beam width of the X-rays reflected by these are both reduced for the first direction and the vertical of the second direction, supported the third and fourth It is possible to adjust the surface angle of the asymmetric reflective crystal.
[0006]
According to the first aspect, since the first asymmetric reflective crystal and the second asymmetric reflective crystal are respectively supported by the first crystal support member so that the surface angle can be adjusted, the first and second asymmetric reflective crystals are connected to each other. It becomes possible to arrange them close enough. As a result, the beam reduced in the first direction by the first asymmetric reflection crystal is again reduced in the first direction by the second asymmetric reflection crystal before being expanded, so that the first direction An X-ray microbeam having a sufficiently small diameter and a small divergence angle (for example, in the horizontal direction) is generated. Similarly, since the third asymmetric reflective crystal and the fourth asymmetric reflective crystal are respectively supported by the second crystal support member so that the surface angle can be adjusted, the third and fourth asymmetric reflective crystals are sufficiently close to each other. Can be arranged. As a result, the beam that has been reduced in the second direction by the third asymmetric reflective crystal is again reduced in the second direction by the fourth asymmetric reflective crystal, so that the second direction. An X-ray microbeam having a sufficiently small diameter and a small divergence angle (for example, in the vertical direction) is generated. Thus, it is possible to generate an X-ray microbeam sufficiently small diameter and a small angle of divergence for any straight interlinks two directions.
[0007]
Further, in the X-ray microbeam generator according to claim 1 , the first crystal support member simultaneously adjusts the surface angle of the first and second asymmetric reflective crystals by rotating the first and second asymmetric reflective crystals about the same axis. And a second adjusting mechanism that adjusts the surface angle of only one of the first and second asymmetric reflective crystals, and the second crystal support member includes A third adjusting mechanism that simultaneously adjusts the surface angle of the third and fourth asymmetric reflective crystals by rotating them around the same axis; and only one of the third and fourth asymmetric reflective crystals. And a fourth adjusting mechanism for adjusting the surface angle .
[0008]
Large According to claim 1, since the two asymmetric reflective crystal is rotated around the respective same axis by the first or third adjustment mechanism, the relative positional relationship of the two asymmetric reflective crystal with respect to the incident X-ray It is possible to change with the degree of freedom. Therefore, when an X-ray microbeam is generated using X-ray diffraction using synchrotron radiation having a continuous energy value as a light source, the energy of incident X-rays near the surface depends on the measurement depth of the sample. It is possible to adapt to any Bragg diffraction condition by changing with a large degree of freedom. Further, since the second and fourth adjustment mechanisms adjust the surface angle of only one of the two asymmetric reflection crystals, the two asymmetric reflection crystals are rotated around the same axis by the first or third adjustment mechanism. This makes it possible to compensate for the angular deviation from the incident angle required to cause diffraction in the second and fourth asymmetric reflective crystals.
[0009]
In the X-ray microbeam generator according to claim 2 , the second adjustment mechanism and the fourth adjustment mechanism each have a solid actuator for adjusting a surface angle of the asymmetric reflection crystal. It is characterized by.
[0010]
According to claim 2, it is possible to adjust the surface angle of the asymmetric reflective crystals solid actuator, the second adjusting mechanism and the fourth adjusting mechanism can be made to have a simple configuration with a small size. As a result, the first and second asymmetric reflective crystals and the third and fourth asymmetric reflective crystals can be arranged sufficiently close to each other. As the solid actuator, for example, one having a piezo element, a magnetostrictive element or the like can be used.
[0011]
Further, in the X-ray microbeam generating apparatus according to claim 3 , the support axes of the first and second asymmetric reflective crystals and the support axes of the third and fourth asymmetric reflective crystals are orthogonal to each other. The first crystal support member and the second crystal support member are arranged.
[0012]
According to claim 3 , since both support shafts are orthogonal to each other, the first crystal support member and the second crystal support member hardly interfere with each other, and the tip positions of both support shafts Can be brought closer. As a result, the second asymmetric reflective crystal and the third asymmetric reflective crystal can be arranged sufficiently close to each other so that an X-ray microbeam having a smaller diameter and a smaller divergence angle can be generated. become.
[0013]
The X-ray microbeam generating apparatus of the present invention is not limited to the first to fourth asymmetric reflection crystals described above, and five or more asymmetric reflection crystals may be used. In that case, in addition to the first and second asymmetric reflective crystals (or the third and fourth asymmetric reflective crystals), the first crystal support member (or the second crystal support member) is further provided with another asymmetric reflective crystal. You may make it support, or you may make the crystal support member provided separately support the asymmetrical reflective crystal different from the 1st-4th asymmetrical reflective crystal. However, by using multiples of 2 pieces asymmetrical reflecting crystal to reduce the beam for each of the straight interlinks two directions, the the direction of the incident X-ray beam and the direction of the reflected X-ray beam it is easy to the same direction . On the other hand, considering that the intensity of diffracted X-rays decreases as the number of asymmetric reflection crystals used increases, the number of asymmetric reflection crystals for reducing the beam in each of two orthogonal directions is about four. Is realistic.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
First, the principle of X-ray asymmetric reflection according to the present invention will be described with reference to FIG. As shown in FIG. 1, the silicon single crystal 1 is an asymmetric crystal, and the surface 1a and the crystal lattice plane 1b are not parallel but form an angle α. Therefore, the incident X-ray beam 2 is not reflected so as to be symmetric with respect to an axis perpendicular to the surface 1a, but is reflected so as to be symmetric with respect to an axis perpendicular to the crystal lattice plane 1b. In other words, if the angle formed by the incident X-ray beam 2 and the crystal lattice plane 1b is θ _B , the angle formed by the diffracted X-ray beam 3 reflected by the crystal lattice plane 1b is also θ _B. On the other hand, the angle that the incident X-ray beam 2 makes with the surface 1a of the silicon single crystal 1 is θ _B + α, and the angle that the diffracted X-ray beam 3 makes with the surface 1a of the silicon single crystal 1 becomes θ _B −α.
[0015]
If the beam width of the incident X-ray beam 2 is L ₀ , the beam width L _h of the diffracted X-ray beam 3 is equal to b × L ₀ . Here, b is an asymmetric factor and is equal to sin (θ _B −α) / sin (θ _B + α). Since the asymmetry factor b is a value of 1 or less, the beam width L _h of the diffracted X-ray beam 3 is smaller than the beam width L ₀ of the incident X-ray beam 2. Further, with respect to the divergence angle, the diffracted X-ray beam 3 is larger than the incident X-ray beam 2. Since the divergence angle is about √b times the divergence angle of the diffracted X-rays from the symmetrical reflection crystal, it is avoided that the divergence angle becomes extremely large. In this way, it is possible to obtain a diffracted X-ray beam having a small diameter and a small divergence angle by reflecting X-rays using an asymmetric crystal.
[0016]
Next, a preferred embodiment of the present invention will be described with reference to the drawings.
[0017]
FIG. 2 is a schematic configuration diagram of an optical system of the X-ray analysis apparatus including the X-ray microbeam generation unit according to the present embodiment. As shown in FIG. 2, the synchrotron radiation light 11 given to the X-ray analysis apparatus 10 is incident on a spectroscope 12 having two symmetrical reflection crystals 12a and 12b, both of which are silicon single crystals. The X-ray beam 13 taken out from the spectroscope 12 is supplied to an X-ray microbeam generator 16 having four asymmetric reflection crystals 18a, 18b, 18c, and 18d, both of which are silicon single crystals, after passing through a slit 15. .
[0018]
Of the four asymmetric reflection crystals 18a to 18d, the asymmetric reflection crystals 18a and 18b are arranged so that the diameter and divergence angle of the incident X-ray beam 13 can be reduced in the horizontal direction based on the above-described principle. The asymmetric reflection crystals 18c and 18d are arranged so that the diameter and divergence angle of the incident X-ray beam 13 can be reduced in the vertical direction. Therefore, the X-ray beam 13 that has passed through the X-ray microbeam generation unit 16 becomes a microbeam having a reduced diameter and divergence angle in two horizontal and vertical directions.
[0019]
The X-ray beam 19 whose diameter and divergence angle are reduced by the X-ray microbeam generator 16 is incident on the sample 20 to be analyzed. The portion irradiated with the X-ray beam 19 on the surface of the sample 20 is photographed by two CCD cameras 21a and 21b. The X-ray beam 22 diffracted by the sample 20 enters the scintillation counter 24 through the analyzer 23.
[0020]
Next, the detailed structure of the X-ray microbeam generator 16 included in the X-ray analysis apparatus 10 depicted in FIG. 2 will be further described with reference to FIGS. FIG. 3 is a perspective view of a support mechanism for the asymmetric reflective crystal mounted on the X-ray analysis apparatus shown in FIG. FIG. 4 is a side view of the crystal holder included in the support mechanism for the asymmetric reflective crystal. FIG. 5 is a plan view of the crystal holder shown in FIG. FIG. 6 is an enlarged view of the vicinity of the tip of the piezoelectric element in the crystal holder shown in FIG. FIG. 7 is a schematic diagram of a main part of the support mechanism depicted in FIG.
[0021]
The X-ray microbeam generator 16 shown in FIG. 2 includes a support mechanism 30 for the asymmetric reflection crystal as shown in FIG. The support mechanism 30 includes a substantially L-shaped main body 31, a crystal holder 33 that is attached to a mounting portion 32 a provided on the inner side surface 31 a of the main body 31 so as to protrude in the horizontal direction, and a lower upper surface 31 b of the main body 31. It is comprised from the crystal holder 34 attached so that it might protrude upwards in the provided attachment part 32b.
[0022]
In the main body 31, levers (not shown) interlocked with the attachment portions 32a and 32b are provided so as to extend in the radial direction of the crystal holders 33 and 34, respectively. These levers are spring-biased in the circumferential direction of the crystal holders 33 and 34 in the vicinity of their outer ends, and on the side opposite to the springs, there is a micro head (the length in the direction of the rotation axis depends on the rotation angle). A changing member (not shown) is arranged. The amount of rotation of the microhead is controlled by a motor (not shown) coupled thereto through a plurality of gears. That is, it becomes possible to control the rotation position of the lever by changing the length of the micro head by motor control, and thereby the rotation angle of the attachment portions 32a and 32b is set to the minimum rotation angle unit of the motor and a plurality of rotation angles. The unit can be adjusted to a desired angle with a minute angle corresponding to the gear down ratio in the gear as a unit.
[0023]
As shown in FIGS. 4 and 5, the crystal holder 33 (hereinafter, the crystal holder 33 will be described. However, the crystal holder 34 is configured in substantially the same manner as the crystal holder 33, so the description of the crystal holder 34 is provided. Is omitted) is a substantially cylindrical base 41 fitted to the mounting portion 32a, a first support shaft 42 on the rotating shaft of the mounting portion 32a, and a side supported by the first support shaft 42. The second support shaft 43 is provided. Crystal stages 42a and 43a on which the asymmetric reflection crystals 18a and 18b are respectively installed are provided at the tops of the first support shaft 42 and the second support shaft 43, respectively. Near the center in the longitudinal direction of the second support shaft 43, a recess 43c having a depth to the center of the shaft is provided. In addition, the first support shaft 42 and the second support shaft 43 can be manually adjusted in angle by rotating the screw heads 42b and 43b with respect to the position of the crystal placed on the crystal stages 42a and 43a. As shown in FIG.
[0024]
As described above, since the attachment portion 32b can be rotated according to the rotation of the motor inside the main body 31, the first support shaft 42 rotates around the axis in accordance with the rotation of the attachment portion 32b. Further, the second support shaft 43 supported by the first support shaft 42 rotates around the first support shaft 42 in accordance with the rotation of the first support shaft 42. That is, the first support shaft 42 and the second support shaft 43 simultaneously rotate around the central axis of the first support shaft 42 as the mounting portion 32b rotates.
[0025]
In addition, the crystal holder 33 is displaced in a direction perpendicular to the central axis of the first support shaft 42 so as to penetrate the first support shaft 42 and have a tip abutting against the second support shaft 43 in the recess 43c. A piezo actuator 45 having a direction is supported. As shown in FIG. 6, the piezo actuator 45 has a hemispherical tip 45a, and the tip 45a is located at a second position 43e away from the axial center 43d of the second support shaft 43 by a distance d. It is in contact with the support shaft 43. Therefore, when an electric signal is applied to the piezo actuator 45 and its length changes, the second support shaft 43 rotates about the shaft center 43d, and the rotational displacement angle is proportional to the amount of change in the length of the piezo actuator 45. Will be.
[0026]
Thus, in this embodiment, since the two asymmetric reflection crystals 18a and 18b are supported by the single crystal holder 33 so that the surface angle can be adjusted, the two asymmetric reflection crystals 18a and 18b are sufficiently separated from each other. It is possible to arrange them close to each other. Accordingly, since the beam reduced in the horizontal direction by the asymmetric reflection crystal 18a is again reduced in the horizontal direction by the asymmetric reflection crystal 18b, the X-ray having a sufficiently small diameter and a small divergence angle in the horizontal direction. A microbeam is generated. Although the detailed description is omitted here, the crystal holder 34 generates an X-ray microbeam having a sufficiently small diameter and a small divergence angle in the vertical direction, like the crystal holder 33. For this reason, the X-ray microbeam generator 16 of the present embodiment can generate an X-ray microbeam having a sufficiently small diameter and a small divergence angle in both the horizontal and vertical directions.
[0027]
In the present embodiment, the crystal holder 33 attached to the main body 31 of the support mechanism 30 included in the X-ray microbeam generator 16 is supported by the first and second support shafts 42 and 43, respectively. A mechanism for simultaneously adjusting the surface angles of the asymmetrical reflection crystals 18a and 18b by rotating the two asymmetrical reflection crystals 18a and 18b around the first support shaft 42, and a piezo actuator 45 on the second support shaft 43. And a mechanism for adjusting the surface angle of only the asymmetric reflection crystal 18b installed.
[0028]
As a result, in the present embodiment, when the two asymmetric reflection crystals 18a and 18b are rotated around the first support shaft 42, the two asymmetric reflection crystals 18a and 18b with respect to the incident X-ray beam 13 are changed. It is possible to change the relative positional relationship with a large degree of freedom. Therefore, the determination is based on Bragg's diffraction formula (2 d sin θ _B = nλ: d = interplanar distance, θ _B = incident angle of the X-ray beam with respect to the lattice plane, n = arbitrary natural number, λ = wavelength of X-ray beam) Then, the energy of the incident X-ray beam 13 can be changed with a large degree of freedom according to the measurement depth of the sample 20 and the like.
[0029]
Further, in the present embodiment, by driving the piezo actuator 45, the surface angle of only the asymmetric reflection crystal 18b out of the two asymmetric reflection crystals 18a and 18b can be adjusted. Therefore, the two asymmetric reflection crystals 18a and 18b are adjusted. Can be compensated for the angle deviation from the incident angle of the X-ray beam 13 required to cause diffraction by the asymmetric reflection crystal 18b, which is caused by rotating around the first support shaft 42. ing.
[0030]
In the present embodiment, the surface angle of the asymmetric reflection crystal 18b is adjusted by a solid actuator such as the piezo actuator 45. Therefore, the angle can be adjusted with high accuracy of about 1/100 second, and the asymmetric reflection crystal The mechanism for adjusting the surface angle of 18b has a small and simple structure. Accordingly, the two asymmetric reflective crystals 18a and 18b can be arranged sufficiently close to each other. As the solid actuator, for example, an actuator having a magnetostrictive element in addition to the piezoelectric actuator 45 may be used.
[0031]
As shown in FIGS. 3 and 7, in the present embodiment, the two support shafts 42 and 43 of the crystal holder 33 and the two support shafts 42 and 43 of the crystal holder 34 are orthogonal to each other. The two crystal holders 33 and 34 do not interfere with each other at the base 41 and the mounting portions 32a and 32b, and the crystal stage 43a at the tip of the support shaft 43 of the crystal holder 33 and the tip of the support shaft 42 of the crystal holder 34 A certain crystal stage 42a can be brought close to. Thereby, since the asymmetric reflection crystal 18b of the crystal holder 33 and the asymmetric reflection crystal 18c of the crystal holder 34 can be arranged sufficiently close to each other, the X-ray microbeam generator 16 of the present embodiment An X-ray microbeam having a very small diameter (about 1.0 to 1.5 μm) and a small divergence angle (about 1 to 2 seconds) can be generated.
[0032]
The preferred embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and various design changes can be made as long as they are described in the claims. . For example, in the above-described embodiment, two asymmetric reflection crystals are used in the horizontal and vertical directions, but three or more asymmetric reflection crystals may be used in each direction. Further, as the asymmetric reflection crystal, not only a silicon single crystal but also other known ones can be used. The examples shown in FIGS. 3 to 6 are examples for embodying the present invention, and various mechanisms are conceivable as specific device configurations for supporting the asymmetric reflective crystal.
[0033]
【The invention's effect】
As described above, according to claim 1, using an asymmetric reflection crystal, it is possible to generate an X-ray microbeam sufficiently small diameter and a small angle of divergence for any straight interlinks two directions. As a result, for example, it is possible to analyze the local strain of a fine electronic device such as a compound semiconductor laser element with high accuracy, and to improve the manufacturing process of the electronic device based on the data of the strain analysis. It is expected that the product yield will be greatly improved by performing the above.
[0034]
Furthermore, according to the first aspect , since the relative positional relationship between the two asymmetric reflection crystals with respect to the incident X-ray can be changed with a large degree of freedom, the energy of the incident X-ray depends on the measurement depth of the sample. Can be changed with great flexibility. According to claim 2 , it is possible to arrange the first and second asymmetric reflective crystals and the third and fourth asymmetric reflective crystals sufficiently close to each other. According to claim 3 , it is possible to arrange the second asymmetric reflective crystal and the third asymmetric reflective crystal sufficiently close to each other, and to generate an X-ray microbeam having a smaller diameter and a smaller divergence angle. Will be able to.
[Brief description of the drawings]
FIG. 1 is a schematic diagram for explaining the principle of asymmetric reflection of X-rays according to the present invention. .
FIG. 2 is a schematic configuration diagram of an optical system of an X-ray analysis apparatus including an X-ray microbeam generation unit according to an embodiment of the present invention.
3 is a perspective view of a support mechanism for an asymmetric reflective crystal mounted on the X-ray analysis apparatus shown in FIG. 2. FIG.
FIG. 4 is a side view of a crystal holder included in a support mechanism for an asymmetric reflective crystal.
5 is a plan view of the crystal holder shown in FIG. 4. FIG.
6 is an enlarged view of the vicinity of the tip of the piezoelectric element in the crystal holder shown in FIG.
7 is a schematic view of a main part of the support mechanism depicted in FIG. 3. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Silicon single crystal 2 Incident X-ray beam 3 Diffracted X-ray beam 10 X-ray analyzer 11 Synchrotron radiation beam 12 Spectrometer 13 X-ray beam 15 Slit 16 X-ray microbeam generation part 18a-18d Asymmetric reflection crystal 20 Sample 24 Scintillation counter 30 Support mechanism 31 Main bodies 32a, 32b Attachment portions 33, 34 Crystal holder 41 Base portion 42 First support shaft 43 Second support shaft 45 Piezo actuator

Claims (3)

An X-ray microbeam generator for generating an X-ray microbeam using an asymmetric reflective crystal having a surface that is not parallel to a crystal lattice plane,
Both the beam width of the X-rays reflected by the first asymmetric reflection crystal and the second asymmetric reflection crystal on which the diffracted X-rays incident by the first asymmetric reflection crystal are incident are reduced in the first direction. A first crystal support member capable of adjusting the surface angles of the supported first and second asymmetric reflective crystals, respectively,
The third asymmetric reflective crystal on which the diffracted X-ray from the second asymmetric reflective crystal is incident and the fourth asymmetric reflective crystal on which the diffracted X-ray from the third asymmetric reflective crystal is incident are reflected by these. while supporting so that the beam width of the line are both reduced for the first direction and the vertical a second direction, the surface angle of the supported said third and fourth asymmetrical reflecting crystals by adjusting each A second crystal support member capable of
A first adjusting mechanism for simultaneously adjusting a surface angle of the first crystal support member by rotating the first and second asymmetric reflective crystals about the same axis; and the first and second A second adjustment mechanism that adjusts the surface angle of only one of the asymmetric reflective crystals,
A third adjusting mechanism for simultaneously adjusting a surface angle of the second crystal support member by rotating the third and fourth asymmetric reflective crystals about the same axis; and the third and fourth And a fourth adjustment mechanism for adjusting the surface angle of only one of the asymmetric reflection crystals . 2. The X-ray microbeam according to claim 1 , wherein each of the second adjustment mechanism and the fourth adjustment mechanism includes a solid actuator for adjusting a surface angle of the asymmetric reflection crystal. Generator. The first crystal support member and the second crystal support member so that the support axes of the first and second asymmetric reflection crystals and the support axes of the third and fourth asymmetric reflection crystals are orthogonal to each other. There X-ray micro beam generating apparatus according to claim 1 or 2, characterized in that it is arranged.

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