JP2010146957A - Sample holder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shared sample holder by which a sample is machined from multi-directions without removing the sample, and which is used in a focused ion beam machining device and a transmission electron microscope. <P>SOLUTION: The sample holder at least includes: a sample holder body; a circular arc-shaped rotating table having a projection for rotating operation, a sample stand for mounting the sample and having a hole for fitting to the projection of the rotating table; a sample stand pressing means for pressing the sample stand mounted on the sample holder body from above the sample stand; and a fixing means for fixing the sample stand pressing means on the sample holder. The sample holder body includes a cutout part for FIB machining formed on a part of an incident side of an FIB, an electron beam passage hole for TEM observation, a circular arc-shaped groove along the passage hole formed so as to fit to the circular arc-shaped rotating table. The sample stand is fixed on the sample holder by the sample stand pressing means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a common sample holder used for a focused ion beam processing apparatus and a transmission electron microscope.

  As a method for manufacturing a thin film sample used for transmission electron microscope (hereinafter abbreviated as TEM) observation, a method using a focused ion beam processing apparatus (hereinafter abbreviated as FIB) is widely used. In particular, as described in Patent Documents 1 to 3, a method of extracting a small part of several μm to several tens of μm from a large sample and bonding the sample to a dedicated sample stage, and then thinning the extracted sample piece (Hereinafter referred to as a microsampling method) can be used as a thin film sample aiming at a portion to be observed, and is currently widely used.

  The sample processed by FIB is inserted into the TEM for observation with the TEM after the processing is completed. If different sample holders are used for FIB and TEM, it is necessary to transfer the sample from the FIB sample holder to the TEM sample holder, and the sample is very small and easily broken. There is a risk of damage. Therefore, it is desirable that the sample holder used when processing the sample with FIB and the sample holder used for observation with TEM are the same, and such a shared holder is widely used.

  Samples produced by FIB often have streaky surface irregularities parallel to the incident direction of the focused ion beam (see, for example, Patent Documents 1 and 2). Such streak-like surface irregularities are obstructive when observing the structure with a TEM, and are desirably reduced as much as possible. The most effective method for reducing streak-like surface irregularities is to process a sample from a certain direction and then from a direction orthogonal to the initial processing direction (see FIG. 1). Furthermore, the surface unevenness of the sample is further reduced by processing from multiple directions as well as the initial processing direction and the direction orthogonal thereto. When processing is performed only from one direction, the sample thickness is different between the sample portion close to the focused ion beam source and the sample portion far from the focused ion beam source. In order to reduce such a difference in thickness of the sample, it is preferable to process the sample from a certain direction and then process from the direction where the angle with the first processing direction is 180 ° (see FIG. 1). Therefore, in the sample processing in FIB, it is desirable that processing can be performed in as wide an angle range as possible.

  However, in the currently used FIB sample holder, in order to change the processing direction, the sample must be once removed from the sample holder, changed in angle, and reattached. The sample is often damaged.

  As an example of a method that enables processing from multiple directions without removing the sample, there is a FIB sample holder of Patent Document 2 and a sample retainer proposed in Patent Document 3. However, the sample holder proposed in Patent Document 2 is a FIB dedicated sample holder, not a TEM sample holder. In the actual sample preparation and observation process, after the FIB processing, the TEM observation, the FIB processing, and the TEM observation are often repeated many times. Each time, the sample is removed from the FIB sample holder and used for TEM. The FIB sample holder that requires the operation of transferring the sample to the sample holder is not preferable in terms of work efficiency, and has a high probability of damaging the sample due to a handling error when the sample is transferred.

  The sample retainer of Patent Document 3 is used by being attached to the tip of an FIB sample holder or a TEM sample holder. Therefore, when performing TEM observation after FIB processing, and when performing FIB processing again after TEM observation, It is also not preferable in terms of work efficiency. Furthermore, since the processing direction can be changed only in the range of 0 to 90 °, it is difficult to produce a sample having a uniform thickness.

JP 11-258129 A JP 2007-220344 A JP 2003-149103 A

  Therefore, the present invention provides a common sample holder for FIB and TEM that enables processing from multiple directions in an angle range of 0 to 180 ° without removing the sample when preparing a sample to be used for TEM observation by FIB. The purpose is to provide.

The gist of the present invention is as follows.
(1) A sample holder that can be used as a sample holder for a focused ion beam (FIB) processing apparatus and a transmission electron microscope (TEM), a sample holder main body, an arcuate turntable having a protrusion for rotating operation, A sample stage on which a sample is mounted and having a hole for fitting to a protrusion of the rotating table, and a sample stage pressing means for pressing the sample stage mounted on the sample holder body from above the sample stage And a fixing means for fixing the sample table pressing means to the sample holder so that the sample table can rotate in conjunction with the arcuate rotary table, and the side on which the FIB enters the sample holder main body A notch portion for FIB processing formed in a part of this, an electron beam passage hole for TEM observation, and an arcuate groove along the passage hole are formed so that the arcuate turntable can be fitted. A sample holder, characterized in that the sample table is fixed to the sample holder by a sample table pressing means.
(2) The sample holder according to (1), wherein the diameter of the protrusion is 0.1 to 1.0 mm and the height of the protrusion is 0.3 to 3 mm.

  By using the sample holder of the present invention, when a sample used for TEM observation is manufactured by FIB, a sample with less surface streaks and a uniform thickness can be efficiently manufactured. In addition, since there is no need to remove or transfer the sample, the work efficiency is high, and the sample holder body is disposed around the sample, so that the sample can be prevented from being damaged.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  FIG. 2 is a plan view showing an example of the tip portion of the sample holder of the present embodiment. The material may be brass or the like, similar to a normal FIB sample holder. As shown in FIG. 2, in this embodiment, the sample holder includes a sample holder main body 1, an arcuate rotating table 2, a sample table 16, and a pressing plate 20 as an example of the sample table pressing means of this embodiment. including. Similar to a normal FIB sample holder, a part of the incident side of the sample holder main body 1 is notched so that the focused ion beam can be incident on the sample. The angle 5 of the notch is preferably about 60 to 120 °. If it is too small (less than 60 °), the area of the sample that can be processed becomes too small. Conversely, if it is too large (over 120 °), the strength of the sample holder will be weak. Further, the sample presser fixing screw hole 9 is a hole for fixing a presser plate 20, which will be described later, to the sample stage with screws.

  In addition, an electron beam passage hole 10 is provided in the back of the notch so that an electron beam can pass during TEM observation. An arc-shaped groove 4 is carved into at least a part of the periphery of the electron beam passage hole 10 of the sample holder, and the arc-shaped turntable 2 is fitted into the groove. The arcuate turntable 2 can be moved along the groove 4. The arc-shaped turntable 2 is provided with a projection 3, and a substantially fan-shaped sample table 16 is fitted and fixed to the projection 3 (see FIG. 4).

  The size of the arc on the outer periphery of the groove 4 is determined by the size of the sample table 16. The sample stage 16 is difficult to handle if the radius is less than 1 mm. On the other hand, if the radius exceeds 3 mm, it is difficult to insert the sample holder into the sample chamber of a normal general-purpose TEM. Therefore, the size of the sample stage 16 is desirably a radius of 1 to 3 mm. Here, the radius means a radius of a circle including an arc as a part of the circumference. For example, the radius R in the substantially fan-shaped sample stage 16 is as shown in FIG. Since such a sample stage 16 is fitted, it is desirable that the size of the arc is also 1 to 3 mm in radius of the outer arc.

  The depth of the arc-shaped groove 4 is preferably about 0.1 to 2 mm, although it depends on the thickness of the sample holder body 1. If it is less than 0.1 mm, it is difficult to fit and fix the arcuate turntable 2, and if it is more than 2 mm, the thickness of the sample holder main body 1 becomes too thick, and the possibility of hindering TEM observation increases. Moreover, since it becomes difficult to place the arcuate turntable 2 when the arc-shaped groove 4 penetrates the sample holder main body 1, it is preferable that the arc-shaped groove 4 has a depth that does not penetrate the sample holder main body 1.

  The width 8 of the arcuate groove 4 is preferably about 0.1 to 2.0 mm. If it is less than 0.1 mm, handling is difficult, and there is a high possibility that it is difficult to fit and fix the arcuate turntable 2. If it exceeds 2.0 mm, the electron beam passage hole 10 at the time of TEM observation becomes small and the observation range becomes small, which is not preferable.

  The width of the sample holder portion 6 inside the arc-shaped groove 4 is preferably about 0.1 to 2.0 mm. If it is less than 0.1 mm, the strength of the sample holder becomes weak, which is not preferable. If it exceeds 2.0 mm, the electron beam passage hole 10 at the time of TEM observation becomes small and the observation range becomes small.

  FIG. 3 shows the shape of the arcuate turntable 2. The size of the apex angle 11 of the arcuate turntable 2 is desirably about 90 to 180 °. If it is less than 90 °, the area of the arcuate turntable 2 becomes small, and it is difficult to mount and fix the sample table. If it exceeds 180 °, the arcuate turntable 2 overlaps the path of the ion beam, so that the processing direction of the sample cannot be changed by 180 °.

  Since the thickness 15 of the arcuate turntable 2 is difficult to fix if it is too thick, it is preferably equal to or less than the depth of the groove 4 and may be 0.1 to 2 mm.

  The height 14 of the protrusion 3 attached to the arcuate turntable 2 is preferably 0.3 to 3 mm. If it is less than 0.3 mm, it is difficult to handle, and if it exceeds 3 mm, it is likely to be difficult to insert it into the TEM or FIB sample chamber.

  The diameter of the protrusion 3 is preferably 0.1 to 1.0 mm. If it is less than 0.1 mm, handling is likely to be difficult. If it exceeds 1.0 mm, the width of the arcuate turntable 2 may become too large, and the arcuate turntable 2 may not be fitted in the groove 4. However, the shape of the protrusion is not limited to a cylindrical shape, and may be any shape that can be easily handled, for example, a polygonal column such as a triangular column or a quadrangular column, an elliptical cross section, or other shapes. In this case, the size of the shape of the cross-section of the protrusion is within the shape of a circle having a diameter of 0.1 to 1.0 mm.

  FIG. 4 shows a state in which the sample stage 16 is mounted on the sample holder of the present embodiment. The sample 18 is mounted on the sample table 16 mounted on the sample holder at a position where the FIB irradiated from the notch and the electron beam at the time of TEM observation can be irradiated. FIG. 5 shows a state in which the presser plate 20 is mounted from above the sample stage 16 and the screw 21 is fitted and fixed to the sample presser fixing screw hole 19. The sample stage 16 may be a substantially semicircular or substantially fan-shaped metal plate that is usually used when processing with FIB. If necessary, a substantially semicircular or substantially fan-shaped part with a triangular portion may be used. The thickness of the sample stage 16 is desirably 0.01 to 0.2 mm. If the thickness is less than 0.01 mm, handling with tweezers or the like is difficult, and the strength of the sample holder is weakened, which may cause bending. When the thickness of the sample stage is more than 0.2 mm, it is difficult to firmly fix the sample stage to the sample holder of the present invention.

  In order to attach to the sample holder of this embodiment, the sample stage 16 needs to have a hole 17 into which the protrusion 3 is fitted. The diameter of the hole 17 is preferably about 0.15 to 1.1 mm, for example. In order to attach the sample table 16 to the sample holder of the present invention, the sample table is placed so that the hole 17 of the sample table is fitted into the protrusion 3 of the arcuate rotary table 2, and the pressing plate 20 is placed thereon, and the screw 21. Secure with. An arc-shaped hole 22 having the same curvature as the arc-shaped groove 4 of the sample holder is formed in the pressing plate 20 so that the protrusion 3 of the turntable does not get in the way when the pressing plate 20 is put on the sample.

  In order to rotate the sample stage 16, the screw 21 is once loosened, the protrusion 3 is grasped with tweezers or the like, and is rotated together with the arcuate turntable 2. In this method, it is not necessary to remove the sample holding plate 20, and the sample table 16 can be rotated while the sample table 16 is still mounted on the arcuate rotary table 2, so that almost no damage to the sample due to a handling mistake is eliminated. Can do.

Example 1
A steel having the chemical composition shown in Table 1 was prepared, cut into a width of 3 mm, a length of 5 mm, and a thickness of 1 mm, inserted into a FIB processing apparatus, and a part of the sample was obtained by microsampling using a tungsten needle. Extracted. The extracted sample is adhered to the tip of a tungsten needle. The extracted sample has a width of 5 μm, a length of 10 μm, and a height of 15 μm.

  Brass was processed to prepare a sample holder having a tip shown in FIG. 6, an arcuate turntable shown in FIG. 7, and a pressing plate shown in FIG. Furthermore, a hole was punched into a semicircular sample table made of Mo, and a sample table shown in FIG. 9 was produced. Fit the arc-shaped turntable into the groove of the sample holder, fit the hole of the sample table into the protrusion of the turntable, cover the sample table on the turntable, cover the pressing plate from above, and screw Fixed. In this way, the sample holder to which the sample stage was fixed was inserted into the FIB processing apparatus, and the previously extracted sample was placed on the sample stage and fixed by chemical vapor deposition of tungsten. FIG. 10 shows a state where the extracted sample is placed on the sample stage. The sample fixed on the sample stage was processed with a Ga ion beam from the direction shown in FIG. 10, and the sample thickness on the beam incident side was set to about 0.1 μm. At this time, the thickness of the sample on the side opposite to the beam incident side was about 0.3 μm (see FIG. 11). Next, loosen the sample holding screw, rotate the arcuate turntable 180 ° so that the Ga ion beam is incident from the opposite side of the sample, and fix the holding plate again with the screw. Was also processed to 0.1 μm (see FIG. 12). Next, the sample holding screw is loosened again, and the arcuate turntable is rotated 90 ° so that the Ga ion beam is incident from a direction perpendicular to the first processing direction, and the sample is further 0.01 μm with the Ga ion beam. Thinned about.

The sample produced by this method was observed with a TEM to examine the sample thickness and the presence or absence of streak irregularities on the sample surface. The TEM observation was performed with the sample holder on which the FIB processed sample was mounted mounted on the TEM as it was. The acceleration voltage used for the observation is 200 kV. The sample thickness was determined by the following equation from the elastic scattering intensity Ie and the inelastic scattering intensity In of electron beam energy loss spectroscopy (hereinafter referred to as EELS).
t = λ · ln {(Ie + In) / Ie}
Where t is the sample thickness and λ is the effective mean free path of the electron beam in the material. λ is R.I. F. Egerton, Electron Energy Loss Spectroscopic in the Electron Microscope Second Edition, calculated using the value (0.074 μm) described in Plenum Publishing Corporation (1996). The sample thickness was measured at four locations on the sample as shown in a, b, c, and d of FIG. The results are shown in Table 2.

  As a comparative example, Table 2 shows the result of TEM observation of a sample prepared by processing from one direction using a commercially available FIB sample holder. A schematic view of the sample holder used is shown in FIG. The semicircular sample stage shown in FIG. 15 was placed on the sample mounting portion 23, covered with a sample pressing plate 26, fixed with a spring 25, and subjected to FIB processing. The sample mounting portion 23 has a step 24.

  Next, using the sample holder of the present invention shown in FIGS. 6 to 8, the sample breakage probability due to a handling mistake when the sample was rotated together with the arcuate turntable was examined. In the investigation, 90 ° rotation was performed 50 times and 180 ° rotation was performed 50 times, and the probability was calculated. The results are shown in Table 3. When the sample holder of the present invention is used, there is no sample damage due to handling mistakes. On the other hand, when the commercially available FIB sample holder shown in FIG. 14 is used, in order to change the processing direction of the sample, the sample stage is once removed from the sample holder, the direction of the sample stage is changed, and the sample holder is mounted again. Become. In the sample holder shown in FIG. 14, the spring 25 and the sample pressing plate 26 are removed, the sample stage is removed from the sample holder, the direction of the sample stage is changed to an arbitrary direction, and the sample holder is mounted again. Thus, the sample breakage probability when the direction of the sample stage was changed by 90 ° and 180 ° was investigated. The results are shown in Table 3 as a comparative example. When the sample holder of the present invention was used, there was no sample damage due to handling mistakes, but when the sample stage was rotated with a commercially available FIB sample holder, the sample was broken with a probability of about 39%.

(Example 2)
Sample preparation similar to Example 1 was performed by changing the shape of the tip of the sample holder and the shape of the arcuate turntable in various ways. Using TEM, the sample thickness, the presence or absence of streaks on the sample surface, and the probability of sample breakage due to handling mistakes during sample stage rotation were investigated. The investigation on the establishment of sample breakage was carried out in exactly the same manner as in Example 1. The results are shown in Table 4. The uniformity of the sample thickness was judged by whether or not the difference in sample thickness between the thickest sample portion and the thinnest sample portion was 0.1 μm or less. Within the condition range of the present invention, the sample thickness was almost uniform, and there was no sample breakage due to streaky surface irregularities. In addition, when the sample holder to which the present invention is applied is used, the probability of sample breakage due to a handling mistake is very low. In particular, the height of the protrusion is 0.3 to 3.0 mm, and the diameter of the protrusion is 0.1. When it was in the range of -1.0 mm, there was no sample breakage.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

It is a figure which shows the processing direction (ion beam incident direction) at the time of the sample processing by FIB. It is a figure of an example which shows the shape of the sample holder of this invention. It is a figure of an example of the circular-arc-shaped turntable of the sample holder of this invention. It is a figure which shows the sample holder (state which mounted | wore the sample) of this invention. It is a figure which shows the sample holder (state which mounted | wore the sample and the press plate) of this invention. It is a figure which shows the shape of the sample holder of this invention used in Example 1. FIG. It is a figure which shows the shape of the circular turntable of the sample holder of this invention used in Example 1. FIG. It is a figure which shows the shape of the holding plate of the sample holder of this invention used in Example 1. FIG. 6 is a diagram showing the shape of a sample table used in a comparative example described in Example 1. FIG. 2 is a diagram illustrating a sample processing method using a Ga ion beam described in Example 1. FIG. 2 is a diagram illustrating a sample processing method using a Ga ion beam described in Example 1. FIG. 2 is a diagram illustrating a sample processing method using a Ga ion beam described in Example 1. FIG. It is a figure which shows the sample thickness measurement location as described in Example 1 and 2. FIG. It is a figure which shows the sample holder and holding plate of the comparative example of Example 1. FIG. 6 is a view showing a sample stage of a comparative example described in Example 1. FIG.

Explanation of symbols

0 Sample 1 Sample holder body 2 Arc-shaped turntable 3 Projection of arc-shaped turntable 4 Arc-shaped groove 5 Vertical angle of notch of sample holder 6 Sample holder portion inside arc-shaped groove 7 Arc radius 8 Arc-shaped groove 9 TEM observation electron beam passage hole 11 TEM observation electron beam passage hole 11 Apex angle of arcuate turntable 12 Radius of arcuate turntable 13 Width of arcuate turntable 14 Height of protrusion of arcuate turntable 15 Thickness of the arc-shaped rotary table 16 Sample table 17 Sample table hole 18 Sample 19 Sample presser fixing screw hole 20 Presser plate 21 Sample presser fixing screw 22 Presser plate hole 23 Sample mounting portion 24 Step 25 Presser plate fixing spring 26 Presser plate

Claims (2)

A sample holder that can be shared as a sample holder for a focused ion beam (FIB) processing apparatus and a transmission electron microscope (TEM),
A sample holder main body, an arcuate turntable having a protrusion for rotating operation, a sample stand for mounting a sample and having a hole for fitting into the protrusion of the turntable, and the sample holder main body A sample table pressing means for pressing the sample table mounted on the sample table from above, and the sample table pressing means fixed to the sample holder so that the sample table can rotate in conjunction with the arcuate rotating table. And at least fixing means,
The specimen holder main body has a notch for FIB processing formed in a part on the side where the FIB is incident, an electron beam passage hole for TEM observation, and an arc-shaped groove along the passage hole. A sample holder, which is formed so that an arcuate turntable can be fitted thereto, and the sample stage is fixed to the sample holder by a sample stage pressing means. The sample holder according to claim 1, wherein the diameter of the protrusion is 0.1 to 1.0 mm, and the height of the protrusion is 0.3 to 3 mm.

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