JP5255531B2 - Sample holder for charged particle beam equipment - Google Patents

Description

  The present invention relates to a sample holder for a charged particle beam apparatus, and more particularly to a sample holder for cross-sectional observation suitable for a charged particle beam apparatus having a side entry type sample stage.

  A scanning electron microscope scans an electron beam on a sample, detects secondary electrons or reflected electrons emitted from the sample, and obtains a scanning electron microscope image. The mounting method and mounting direction of the sample vary depending on the sample to be observed. Japanese Patent No. 3706285 describes a eucentric type sample stage for mounting a sample holder for a cross-sectional observation sample.

  In the semiconductor manufacturing industry, defect analysis and process analysis are performed by observing the edge of the cut wafer cross section. A sample holder for cross-sectional observation is used for this cross-sectional observation. A conventional sample holder for cross-sectional observation has a structure in which a cleaved wafer is mounted from the optical axis direction and the wafer is pressed from the horizontal direction in order to prevent the sample from dropping.

  Japanese Patent No. 2776858 describes means for mounting a wafer sample from the back side of the sample holder. In the example described in Japanese Patent No. 2776858, since the sample is pushed from the back surface, the observation surface of the sample is always constant even if the sample size varies. However, the sample holder described in Japanese Patent No. 2776858 is configured to observe a bulk sample. Therefore, it is not suitable for observing a wafer sample prepared for cross-sectional observation.

Patent No.3702685 Patent No. 2776858

  When observing a wafer sample prepared for cross-sectional observation, the observation position of the sample is an edge where the split cross-section and the surface on which the pattern is formed intersect. The cross-section observation sample is mounted on the cross-section observation sample holder so that the edge of the observation position faces the incident direction of the beam.

  In the side entry type sample stage, the sample can rotate around the eucentric axis. When observing the sample at an inclination, the sample holder is rotated around the eucentric axis. Thereby, the sample rotates about the eucentric axis. At this time, if the observation position of the sample is not on the eucentric axis, the observation position of the sample is displaced. For this reason, the field of view of the observation position escapes and the focus changes. This is a serious problem in an electron microscope capable of high-magnification observation.

  In cross-sectional observation of a wafer, a desired part is cut from a silicon wafer on which a pattern is formed, and an observation sample having a size of several mm × several mm is created. Since this cleaving operation is performed manually, the size and thickness of the sample are not constant. Therefore, it is difficult to arrange the observation position of the sample on the eucentric axis.

  An object of the present invention is to provide a sample holder for observing a cross section that is easy to mount a sample and can avoid the escape of the visual field even when the sample is tilted.

  The sample holder of the present invention includes a grip, a main body extending from the grip, and a sample mounting portion provided at an end of the main body. The sample mounting portion has a hole having an opening on the side opposite to the side irradiated with the charged particle beam. A part of this hole is constituted by a through-hole penetrating the main body. When the sample is inserted into the hole through this opening, the sample comes into contact with the bottom surface of the hole. Thereby, the edge which becomes the observation position of a sample is arrange | positioned on a eucentric axis | shaft, and it is comprised so that it may expose from a through-hole.

  According to the present invention, it is possible to provide a sample holder for observing a cross-section that is easy to mount the sample and can avoid the visual field escape even when the sample is inclined.

It is a figure which shows the whole structure of the example of the sample holder for cross-section observation by this invention. It is a disassembled perspective view of the example of the sample mounting part of the sample holder for cross-section observation by this invention. It is a figure which shows the example of the front structure of the sample mounting part of the sample holder for cross-section observation by this invention. It is a figure which shows the example of the plane structure of the sample mounting part of the sample holder for cross-section observation by this invention. It is a figure which shows the example of the side surface structure of the sample mounting part of the sample holder for cross-section observation by this invention. It is a figure explaining the observation position of a sample in the sample mounting part of the sample holder for cross-section observation. It is a figure explaining the method to mount | wear a sample in the example of the sample mounting part of the sample holder for cross-section observation by this invention. It is a figure which shows the other example of the plane structure of the sample mounting part of the sample holder for cross-section observation by this invention. It is a figure which shows the other example of the side surface structure of the sample mounting part of the sample holder for cross-section observation by this invention.

  An example of a sample holder for cross-sectional observation according to the present invention will be described with reference to FIG. The sample holder according to the present invention is used in a charged particle beam apparatus provided with a side entry type sample stage. The sample holder of this example includes a sample mounting portion 21, an O-ring 22 for interrupting vacuum, a guide pin 24 serving as a guide for mounting on a charged particle beam apparatus, and a grip 23 for carrying the sample holder. The sample mounting portion 21 is provided at the end of the rod-shaped main body 20.

  The case where the sample holder for cross-sectional observation according to the present invention is used in an electron microscope having an electron beam source, a lens mechanism for irradiating the sample with an electron beam, and a side entry type sample stage for holding the sample holder will be described below. . The present invention is not only an electron microscope having a side entry type sample stage, but also a charged particle source, a lens mechanism for irradiating a sample with a charged particle beam, and a charged particle beam apparatus having a side entry type sample stage for holding a sample holder It is also applicable to.

  FIG. 2 is an exploded perspective view showing an example of the sample mounting portion 21 of the sample holder for cross-sectional observation according to the present invention. The sample mounting portion 21 of the sample holder for cross-sectional observation according to the present invention is provided with a substantially square concave portion 12 on the beam incident side. The recess 12 has substantially the same dimensions as the visual field range, and its four corners are curved. A hole 13 is formed in the approximate center of the recess 12. The sample 15 and the partition plate 17 are inserted into the hole 13 from the side opposite to the side on which the beam is incident, and are fixed by screws 16.

  Here, the case of cross-sectional observation of a semiconductor wafer will be described. The sample 15 is a thin plate shape cut out from the semiconductor silicon wafer by hand. A sample having a size of several mm × several mm is created by cleaving a desired part from a silicon wafer. This cleaving work is performed manually. The observation position of the sample is an edge where the fractured surface and the surface on which the pattern is formed intersect.

  The partition plate 17 is used to prevent the screw 16 from coming into direct contact with the sample 15. That is, the tightening force of the screw 16 is applied to the sample 15 through the partition plate 17 over the entire surface. By using the partition plate 17, the tightening force of the screw 16 is prevented from being concentrated locally on a part of the sample 15. Thus, the use of the partition plate 17 prevents the sample 15 from cracking.

  The partition plate 17 is made of a nonmagnetic metal and has protrusions 17A and 17B and a leaf spring 17C. The first protrusion 17A is provided at the edge on the beam incident side and at the approximate center of the partition plate 17. The second protrusions 17B are provided on both sides from the center of the partition plate 17 on the edge opposite to the side on which the beam is incident. A leaf spring 17C is provided below the protrusion 17A. The functions of the projections 17A and 17B and the leaf spring 17C of the partition plate 17 will be described later.

  FIG. 3A shows an example of the front configuration of the sample mounting portion 21 of the sample holder for cross-sectional observation according to the present invention, and FIG. 3B shows an example of the planar configuration of the sample mounting portion 21 of the sample holder for cross-sectional observation according to the present invention. FIG. 3C shows an example of a side configuration of the sample mounting portion 21 of the sample holder for cross-sectional observation according to the present invention. These drawings show a state in which the sample 15 and the partition plate 17 are inserted into the sample mounting portion 21 of the sample holder.

  As shown in FIGS. 3A and 3B, the sample mounting portion 21 of the main body 20 of the sample holder has two flat surfaces 11A and 11B formed on the beam incident side, and a central flat surface 11C is formed between them. Is formed. Inclined surfaces 11D and 11E are formed at connecting portions of the central flat surface 11C and the flat surfaces 11A and 11B on both sides, respectively. A recess 12 is formed in the central flat surface 11C.

  As shown in FIG. 3A, the hole 13 has an opening on the side opposite to the side on which the beam of the sample holder is incident. The hole 13 extends in the depth direction, that is, toward the side on which the beam of the sample holder is incident. As shown in FIGS. 3A and 3B, the hole 13 is a through hole in the region of the central flat surface 11C, but is a through hole in the inclined surfaces 11D and 11E and the flat surfaces 11A and 11B on both sides. Not. That is, the inclined surfaces 11D and 11E and the flat surfaces 11A and 11B form the bottom of the hole 13.

  The bottom surface 13b of the hole 13 is flush with the central flat surface 11C. A plane passing through the central flat surface 11C is referred to as a reference plane 3 perpendicular to the optical axis. The bottom surface 13b of the hole 13 is on the reference plane 3 perpendicular to the optical axis. A plane passing through the central axis of the sample holder and the optical axis of the beam is referred to as a reference plane 4 in the optical axis direction. As shown in FIGS. 3B and 3C, one of the two parallel inner walls forming the hole 13 is on the reference plane 4 in the optical axis direction. A recess 13a is formed in the inner wall 13c.

  As shown in FIG. 3B, the hole 13 has an elongated rectangular cross section and extends along the central axis of the sample holder. The longitudinal dimension of the rectangular cross section of the hole 13 is longer than the planar dimension of the recess 12.

  A sample 15 and a partition plate 17 are inserted into the hole 13. As shown in FIG. 3C, the upper end of the sample 15 is in contact with the bottom surface 13 b of the hole 13, and the surface on which the pattern of the sample 15 is formed is in contact with the inner wall 13 c of the hole 13. As shown in FIG. 3C, the sample 15 is not in contact with the inner wall 13c of the hole 13 in the region where the recess 13a is formed. Thus, according to the present invention, the fractured surface of the sample 15 is arranged on the reference plane 3 perpendicular to the optical axis, and the surface on which the pattern of the sample 15 is formed is arranged on the reference plane 4 in the optical axis direction.

  The sample 15 and the partition plate 17 inserted into the hole 13 are exposed by the recess 12 in the region of the central flat surface 11C on the beam incident side, but the inclined surfaces 11D and 11E and the flat surface 11A are exposed. , 11B is not exposed.

  As shown in FIGS. 3B and 3C, the partition plate 17 is pressed against the sample 15 by the tightening force of the screw 16. As shown in FIG. 3C, the first protrusion 17A of the partition plate 17 is engaged with the bottom surface of the recess 12. However, the second protrusion 17B of the partition plate 17 is not in contact with the lower end of the sample 15.

  The rotation axis of the sample holder for cross-sectional observation is called eucentric axis 2. As shown in FIG. 3C, the eucentric axis 2 is an intersection line of the reference plane 3 perpendicular to the optical axis and the reference plane 4 in the optical axis direction. The observation position of the sample 15 is an edge where the fractured surface and the surface on which the pattern is formed intersect. The observation position of the sample 15 is the upper corner of the sample 15 in the example shown in FIG. 3C. The observation position of the sample 15 is exposed by the recess 12.

  When observing the sample at an inclination, the sample holder is rotated around the eucentric axis. In this example, the observation position of the sample 15 is arranged on the eucentric axis 2. As shown in FIG. 3B, the observation position of the sample 15 does not change even when the sample holder rotates around the eucentric axis 2. Even when the sample holder rotates about the eucentric axis 2, the observation position of the sample 15 does not change. Therefore, even if the sample holder rotates about the eucentric shaft 2, there is no need to change the focal position or the like.

  FIG. 4 shows a case where the observation position 51 of the sample 15 is not arranged on the eucentric axis 2. In this case, when the sample holder is rotated around the eucentric axis 2, the observation position 51 of the sample 15 changes. The observation position of the sample 15 moves from the position of the reference numeral 51 to the reference numeral 51 '. As a result, the field of view of the observation position escapes and the focus changes. This is a serious problem in an electron microscope capable of high-magnification observation.

  When the observation position 51 of the sample 15 is disposed on the optical axis 52 of the beam, when the sample holder is rotated around the eucentric axis 2, the amount of displacement of the observation position is reduced. However, unless the observation position 51 of the sample 15 is arranged on the eucentric axis 2, the observation position is displaced.

  On the other hand, in the present invention, as shown in FIG. 3C, the observation position of the sample 15 is arranged on the eucentric shaft 2. Therefore, when observing the sample at an inclination, the observation position of the sample 15 does not change even if the sample holder is rotated around the eucentric axis.

  A method for mounting the sample 15 on the sample mounting portion 21 of the sample holder for cross-sectional observation according to the present invention will be described with reference to FIG. As shown in the figure, the sample holder is rotated around the eucentric axis 2 and the side on which the beam is incident, that is, the flat surfaces 11A, 11B, and 11C are arranged on the lower side. On the upper side, the side opposite to the beam incident side, that is, the opening of the hole 13 is arranged. Therefore, the screw 16 is loosened. That is, the screw 16 is moved outward. Thereby, the leaf spring 17C of the partition wall plate 17 that has been compressed is extended. The partition plate 17 can be moved. A gap is formed along the partition plate 17. Sample 15 is inserted there. The sample is inserted so that the surface on which the pattern of the sample 15 is formed faces the inner wall 13c of the hole 13. Since the recess 13a is formed in the hole 13, when the sample 15 is inserted into the hole 13, the observation position does not come into contact with the hole 13 to be damaged.

  The insertion direction of the sample 15 is the same as the direction in which the inclination of the leaf spring 17C of the partition plate 17 increases. Therefore, the leaf spring 17C of the partition plate 17 does not prevent the sample 15 from being inserted. The sample 15 is inserted to the back of the hole 13 and comes into contact with the bottom of the hole 13. As described above, the bottom of the hole 13 is formed by the inclined surfaces 11D and 11E and the flat surfaces 11A and 11B. Thus, when the sample 15 is inserted until it contacts the bottom of the hole 13, the screw 16 is finally tightened. When the screw 16 is tightened, the sample 15 is pressed by the partition plate 17 against the inner wall of the hole 13 in which the recess 13a is formed. Thereby, the leaf spring 17C of the partition plate 17 is compressed. When the screw 16 is sufficiently tightened, the mounting of the sample 15 is completed. Therefore, the sample holder is rotated around the eucentric axis 2 and, as shown in FIG. 3C, the beam incident side, that is, the flat surfaces 11A, 11B, and 11C are arranged on the upper side.

  In the state shown in FIG. 3C, even if the screw 16 is loosened, the lower end of the sample 15 is in contact with the second protrusion 17B of the partition plate 17. Therefore, the sample 15 does not fall. Similarly, the first protrusion 17A of the partition plate 17 is engaged with the bottom of the recess 12. Therefore, the partition plate 17 does not fall.

  When removing the sample 15, the screw 16 is loosened. At this time, the compression force of the leaf spring 17C of the partition plate 17 pushes the sample 15 from the side. Therefore, the sample 15 moves with respect to the partition plate 17, and a gap is generated between the partition plate 17 and the sample 15. By inserting tweezers into this gap, the sample 15 can be easily removed.

  With reference to FIG. 6A and FIG. 6B, the structure of the other example of the sample mounting part of the sample holder for cross-section observation by this invention is demonstrated. When the sample holder for cross-sectional observation of this example is compared with the example shown in FIGS. 3A, 3B, and 3C, the sample fixing mechanism is different. The sample fixing mechanism of the sample holder for cross-sectional observation of this example is a lid 43 that can be pivoted around a fulcrum 42, an arcuate leaf spring 41 attached to the lid 43, and a lid 43 that can be engaged with the lid 43. A slider 44 and a push spring 45 for moving the slider 44 are provided.

  The end portions of the slider 44 and the lid 43 are formed with latches, and the lid 43 can be locked to the slider 44 only by pressing the lid 43. That is, the end of the lid 43 has a slope 43a. The end of the slider 44 has a slope 44a. The slope 43a of the lid 43 and the slope 44a of the slider 44 are disposed so as to face each other. The end of the slider 44 is pressed by the pressing spring 45 in a direction approaching the end of the lid 43. The lid 43 is pushed and pivoted around the fulcrum 42 to engage the end of the lid 43 with the end of the slider 44. The slope 43a at the end of the lid 43 is engaged with the slope 44a of the slider 44, and the slider 44 is pushed back. Accordingly, the slope 43a at the end of the lid 43 moves beyond the slope 44a at the end of the slider 44. The slider 44 returns to its original position and both are locked.

  Here, an example in which the latch mechanism at the end of the slider 44 and the lid 43 is used as the sample fixing mechanism has been described. However, various mechanisms other than screws and springs are conceivable as the sample fixing mechanism. According to the present invention, the sample fixing mechanism is not limited to these examples.

  In the above example, the wafer section has been described as the sample 15. However, the sample is not limited to a wafer section.

  According to the invention, it is possible to arrange the observation position of the sample for cross-sectional observation on the eucentric axis without using the sample mounting jig. Therefore, even if the sample is tilted during observation, visual field escape does not occur. Therefore, it is not necessary to search for the observation position again. Furthermore, there is no fluctuation of the focus position. This eliminates the need to change the focus condition.

  Therefore, according to the present invention, the time from the mounting of the wafer sample to the completion of the observation is reduced to about half, and the observation throughput is greatly improved. In addition, tweezers can be easily inserted when attaching and detaching the sample, and the workability of attaching and detaching the sample is improved.

  The example of the present invention has been described above, but the present invention is not limited to the above-described example, and various modifications can be easily made by those skilled in the art within the scope of the invention described in the claims. It will be understood.

1 ... Beam, 2 ... Eucentric axis, 3,4 ... Reference plane, 11A ... Flat surface, 11B ... Flat surface, 11C ... Flat surface in the center, 11D ... Inclined surface, 11E ... Inclined axis, 12 ... Recess, 13 ... Hole, 13a ... concave portion, 13b ... bottom surface, 13c ... inner wall, 15 ... sample, 15 '... sample, 16 ... screw, 17 ... partition plate, 17A ... projection, 17B ... projection, 17C ... leaf spring, 20 ... main body, 21 ... Sample mounting part, 22 ... O-ring, 23 ... Grip, 24 ... Guide pin, 41 ... Plate spring, 42 ... Support point, 43 ... Lid, 44 ... Slider, 45 ... Push spring, 51 ... Observation position, 51 '... Observation Position, 52 ... Optical axis

Claims (20)

In a sample holder having a grip, a main body extending from the grip, and a sample mounting portion provided at an end of the main body,
The sample mounting portion has a hole having an opening on a side opposite to the side irradiated with the charged particle beam, and a part of the hole is constituted by a through hole penetrating the main body, and a recess is formed in an inner wall of the hole Is formed,
Upon insertion of the sample into the hole through the opening, the sample in contact with the bottom surface of the hole, and is fixed so as to contact the inner wall of the recess is formed,
The edge serving as the observation position of the sample is arranged on the eucentric axis and is configured to be exposed from the opening of the through hole formed on the side irradiated with the charged particle beam. Sample holder. The sample holder according to claim 1, wherein
The sample holder has a fixing mechanism for fixing the sample inserted into the hole, and the sample is pressed against the inner wall of the hole by the fixing mechanism. The sample holder according to claim 2,
A sample holder, wherein a recess is formed in the inner wall of the hole on the side where the sample is pressed by the fixing mechanism. The sample holder according to claim 2,
The fixing mechanism includes a partition plate and a screw for holding the partition plate, and the sample is pressed against the inner wall of the hole by the partition plate. The sample holder according to claim 4, wherein
The said partition board has a 1st protrusion extended in the thickness direction of the sample inserted in the said hole, The sample holder characterized by the above-mentioned. The sample holder according to claim 4, wherein
The partition plate has a second protrusion extending on the opposite side to the thickness direction of the sample inserted into the hole, and the second protrusion is formed on the side irradiated with the charged particle beam. A sample holder configured to engage with an opening of a hole. The sample holder according to claim 4, wherein
The partition plate includes a leaf spring, and the sample is pressed against an inner wall of the hole by a compression force of the leaf spring. The sample holder according to claim 2,
The fixing mechanism includes a lid that can be pivoted around a fulcrum, a leaf spring attached to the lid, a slider that can be engaged with the lid, and a push spring for moving the slider. Characteristic sample holder. In a charged particle beam apparatus having a charged particle source, a lens mechanism that irradiates a sample with a charged particle beam, and a side entry type sample stage that holds a sample holder,
The sample holder has a grip, a main body extending from the grip, and a sample mounting portion provided at an end of the main body,
The sample mounting portion has a hole having an opening on a side opposite to the side irradiated with the charged particle beam, and a part of the hole is constituted by a through hole penetrating the main body, and a bottom surface of the hole is formed by Yusen. A first reference plane passing through the trick axis and perpendicular to the optical axis of the beam, the inner wall of the hole being positioned on a second reference plane passing through the eucentric axis and passing through the optical axis of the beam; When the sample is inserted into the hole through the opening, the sample comes into contact with the bottom surface of the hole, the edge serving as the observation position of the sample is disposed on the eucentric axis, and the side on which the charged particle beam is irradiated A charged particle beam device configured to be exposed from an opening of the through hole formed in the device. The charged particle beam apparatus according to claim 9, wherein
The charged particle beam apparatus according to claim 1, wherein the sample mounting unit has a fixing mechanism for fixing the sample inserted into the hole, and the sample is pressed against the inner wall of the hole by the fixing mechanism. The charged particle beam apparatus according to claim 10, wherein
A charged particle beam apparatus, wherein a recess is formed in an inner wall of the hole on a side to which a sample is pressed by the fixing mechanism. The charged particle beam apparatus according to claim 10, wherein
The fixed mechanism has a partition plate and a screw for holding the partition plate, and the sample is held by the partition plate so as to be pressed against the inner wall of the hole. The charged particle beam apparatus according to claim 12,
The charged particle beam apparatus according to claim 1, wherein the partition plate has a first protrusion extending in a thickness direction of the sample inserted into the hole. The charged particle beam apparatus according to claim 12,
The partition plate has a second protrusion extending on the opposite side to the thickness direction of the sample inserted into the hole, and the second protrusion is formed on the side irradiated with the charged particle beam. A charged particle beam device configured to engage with an opening of a hole. The charged particle beam apparatus according to claim 12,
The partition plate includes a leaf spring, and the sample is pressed against the inner wall of the hole by a compressive force of the leaf spring. The charged particle beam apparatus according to claim 10, wherein
The fixing mechanism includes a lid that can be pivoted around a fulcrum, a leaf spring attached to the lid, a slider that can be engaged with the lid, and a push spring for moving the slider. Characterized charged particle beam device. The charged particle beam apparatus according to claim 9, wherein
The sample mounting portion has a recess on the side irradiated with the charged particle beam, and the opening on the side irradiated with the charged particle beam among the openings on both sides of the through hole penetrating the main body is provided in the recess. A charged particle beam apparatus characterized by comprising: In a side entry type sample holder having a grip, a main body extending from the grip, and a sample mounting portion provided at an end of the main body,
A first reference plane passing through the eucentric axis and perpendicular to the optical axis of the beam; and a second reference plane passing through the eucentric axis and passing through the optical axis of the beam;
The sample mounting portion has a hole for storing the sample and a fixing mechanism for fixing the sample inserted in the hole,
The hole includes an opening for inserting a sample provided on the side opposite to the side irradiated with the charged particle beam, a bottom surface disposed along the first reference surface, and the second reference surface. An inner wall disposed along the top,
The fixing mechanism is configured to press the end surface of the sample inserted into the hole against the bottom surface of the hole, and press the surface of the sample inserted into the hole against the inner wall of the hole,
The side entry type sample holder is characterized in that an edge serving as an observation position of the sample is arranged on a eucentric shaft and exposed from an opening formed in a bottom surface of the hole. The side entry type sample holder according to claim 18,
The fixing mechanism has a partition plate and a screw for holding the partition plate, and the sample is held by the partition plate so as to contact the inner wall of the hole. The side entry type sample holder according to claim 19,
A side entry type sample holder, wherein a concave portion is formed in an inner wall of the hole on the side where the sample is pressed by the fixing mechanism.

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