JP2010009774A - Sample stand and sample holder - Google Patents

Abstract

The present invention produces a sample with less so-called redeposition in which a sample stage material generated by sputtering an ion beam on a sample stage adheres to the sample surface when a sample used for TEM observation is produced by an ion milling method. A sample stage is provided.
A triangular or fan-shaped apex angle of 120 degrees or less, a tip portion having a thickness of 1 μm or more and 5 μm or less, having an inclined section as it goes away from the tip, and an inclination angle of the inclined section with respect to the vertical direction is 5 degrees or less. An ion milling sample stage characterized by having a hole for fixing to a TEM observation sample holder and an ion milling device sample holder.
[Selection] Figure 1

Description

  The present invention relates to a sample stage and a sample holder for producing a sample used for TEM observation by an ion milling method.

  As a method for producing a thin film sample used for transmission electron microscope (TEM) observation, a method using a focused ion beam processing apparatus 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 microsampling method) can be made into a thin film sample aiming at a portion to be observed, and is currently widely used.

  Here, in the sample manufactured by the focused ion beam processing apparatus, a damage layer having a thickness of 10 to 20 nm on one surface is generated on the sample surface due to damage by the focused ion beam. Because of this damaged layer, there is a problem that TEM observation with high resolution is difficult for a sample manufactured by the focused ion beam processing method. For this reason, ion milling with an Ar ion beam is often performed after the processing with the focused ion beam processing apparatus in order to remove the damaged layer on the sample surface.

  However, when ion milling with an Ar ion beam is performed, not only the sample but also the sample stage on which the sample piece is fixed by the microsampling method is sputtered by the Ar ion beam, and the sputtered sample stage material is reattached to the sample surface. So-called redeposition is a problem.

  In order to avoid redeposition, the sample stage should be as thin as possible. For example, as described in Patent Document 4, a sample stage has been proposed in which the cross-sectional shape of the sample stage is a trapezoid and the thickness of the tip is 2 to 5 μm or less. However, in the sample stage described in Patent Document 4, since the rate at which the thickness of the sample stage increases is as large as 45 degrees at the maximum, a great effect cannot be obtained for the purpose of preventing redeposition. Moreover, as described in Patent Documents 2 and 3, a semicircular shape is mainly used as the sample trapezoidal shape. However, in the semicircular sample stage, since the sample stage exists in the vicinity of the sample, the redeposition becomes remarkable. On the other hand, as described in Patent Document 5, a conical or pyramidal sample stage has been proposed, but in this case as well, the thickness of the sample stage near the sample is thick, so that redeposition is avoided. I can't.

Japanese Patent Laid-Open No. 11-108813 JP 2001-242051 A JP 2006-172958 A JP 2004-179038 A Japanese Patent Laid-Open No. 2004-199969 Materials Science and Engineering Vol. 40 No. 5 Page. 232-236 “The role of electron microscopes in the development of steel materials”

  Accordingly, an object of the present invention is to provide a sample stage for ion milling with less redeposition caused by sputtering of a sample stage by an ion beam when a sample used for TEM observation is produced by an ion milling method.

  The inventor makes the shape of the sample stage a triangle or a fan with an apex angle of 120 degrees or less, the thickness of the tip is 1 μm or more and 5 μm or less, and the thickness increases at a rate of 5 degrees or less as the distance from the tip is increased. It has been found that the redeposition is almost eliminated by adopting such a cross-sectional shape of the sample stage. Further, the inventors have found that by making a hole in a part of the sample stage, it becomes easy to fix to the sample holder for TEM observation and / or the sample holder for ion milling apparatus, and the present invention has been completed.

The main points are as follows.
(1) A sample stage made of a conductive material on which a sample used for TEM observation is mounted, having a plane on which the sample is mounted on a cross section of the sample stage tip, and the tip in the width direction of the sample stage The apex angle is 120 ° or less in a triangular shape or a fan shape, the tip portion has a thickness of 1 μm or more and 5 μm or less, and the thickness increases as the distance from the tip portion increases. A sample stage having a tilt angle with respect to the vertical direction of 5 degrees or less and having a hole for fixing to a sample holder for fixing the position of the sample stage.
(2) A sample stage made of a conductive material on which a sample used for TEM observation is mounted, having a flat surface on which the sample is mounted on a cross section of the sample stage tip, and the tip in the width direction of the sample stage The tip portion has a thickness of 1 μm or more and 5 μm or less, and has a sloped section that increases in thickness as it moves away from the tip portion, and the slope angle of the sloped section with respect to the vertical direction is 5 degrees or less. And a hole for fixing to the sample holder for fixing the position of the sample stage.
(3) A sample stage made of a conductive material on which a sample used for TEM observation is mounted,
The cross section of the sample stage tip has a flat surface for mounting the sample, spreads in the width direction of the sample stage from the tip in a triangle or fan shape with an apex angle of 120 degrees or less, and the thickness of the tip A sample stage having a thickness of 1 μm or more and 5 μm or less and having a constant thickness from the tip, and a hole for fixing to a sample holder for fixing the position of the sample stage.
(4) A sample stage made of a conductive material on which a sample used for TEM observation is mounted,
The front end of the sample stage has a flat surface for mounting the sample, the sample stage does not extend from the front end in the width direction, and the thickness of the front end is not less than 1 μm and not more than 5 μm. And a hole for fixing to a sample holder for fixing the position of the sample stage.
(5) The sample stage according to any one of (1) to (4), wherein a width of the flat portion for mounting the sample is 1 μm or more and less than 100 μm.
(6) A sample holder for fixing the sample stage according to any one of (1) to (5), wherein the sample holder has a protrusion that fits into a hole of the sample stage.
(7) The sample holder according to (6), wherein the sample holder is for TEM observation and / or for an ion milling device.

With the sample stage of the present invention, when a sample used for TEM observation is produced by the ion milling method, a sample with less so-called redeposition is produced, in which the sample stage material generated by sputtering the sample stage with an ion beam adheres to the sample surface. Therefore, observation with high resolution by TEM and detailed analysis are possible.
Further, by using the sample holder of the present invention, it is possible to easily attach the sample stage to the sample holder without damaging the sample, and the efficiency of sample preparation can be greatly improved.

  Exemplary embodiments of the present invention will be described below in detail 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. 1 is a plan view and a cross-sectional view showing an example of the sample stage of the present invention. The material may be conductive. For example, a metal material such as molybdenum, nickel, or copper can be used. However, in the case of a soft material, there is a risk of bending when it is thinned, so a hard material is preferable. For example, molybdenum is suitable.

  The sample stage 1 has a flat portion 4 at the tip for mounting the sample. A sample extracted by a microsampling method using a focused ion beam processing apparatus is mounted on the flat surface portion 4. The microsampling method is described in detail in Non-Patent Document 1. Briefly, the periphery of a portion to be observed of the sample is shaved with a Ga ion beam, a needle made of tungsten or the like is adhered to the portion to be observed, and the portion to be observed is lifted and extracted. The size of the extracted sample is often about 1 to 10 μm wide, 1 to 5 μm deep, and about 1 to 30 μm high. When preparing a sample for TEM observation, this extracted sample is placed on the sample stage 1 and bonded, and further processed to a thickness of about 0.1 μm in the focused ion beam apparatus, and a thin film sample for TEM observation is obtained. And Adhesion often uses chemical vapor deposition that occurs by irradiating a Ga ion beam while blowing a gas such as tungsten carbide (Non-patent Document 1).

  In the sample stage 1 as an example of the present invention, a sample extracted by the microsampling method is placed on and adhered to the flat surface portion 4 at the tip. In order to firmly bond and fix the sample, it is desirable that the width 5 of the flat portion 4 is larger than the width of the extracted sample. However, in order to avoid redeposition in ion milling after processing by the focused ion beam processing apparatus, it is desirable that the width 5 of the flat portion 4 of the sample stage 1 is smaller than the width of the sample. Therefore, it is most desirable that the width 5 of the flat portion 4 of the sample stage 1 is approximately the same as the width of the sample. Since the maximum width of the sample that can be extracted by the microsampling method is about 100 μm, the width 5 of the flat portion 4 of the sample stage 1 is preferably 1 to 100 μm.

  A smaller apex angle 3 at the tip of the sample stage 1 is desirable. If the angle exceeds 120 degrees, the redeposition becomes remarkable. The apex angle 3 may be 0 degrees. However, when the apex angle 3 is small, the sample table 1 may be bent when the sample is placed depending on the strength of the sample table 1. Therefore, when the apex angle 3 is small, it is desirable to reinforce the sample stage 1 in the vicinity of the attachment part of the sample stage 1 to the sample holder so that the sample stage 1 does not bend. An example of the reinforced sample stage 1 is shown in FIG. The shape of the reinforcement part 9 is not specifically limited. However, it is preferable that the reinforcing portion 9 is at least 30 μm away from the tip portion of the sample stage 1. If it is closer than 30 μm, it may cause redeposition.

  The thickness 6 of the tip of the sample stage 1 is preferably thin, but if it is less than 1 μm, it is difficult to fix the sample extracted by the microsampling method, and it is preferably 1 μm or more. Further, when the thickness exceeds 5 μm, the redeposition increases rapidly, so that the thickness is set to 5 μm or less. As the distance from the tip portion increases, the thickness of the sample stage 1 increases. That is, the sample stage 1 has an inclined cross section that increases in thickness as it moves away from the tip.

  As shown in the cross-sectional views of FIGS. 1 and 2, the rate of increase in thickness (inclination angle with respect to the vertical direction of the inclined cross section) 7 is set to 0 degree or more and 5 degrees or less. When a TEM sample suitable for high-resolution observation is produced, the ion milling beam incidence angle is often set to 5 degrees or less, and the cross-sectional shape of the sample stage 1 also increases in thickness at an inclination angle of 5 degrees or less. The shape is suitable. In the case of a shape in which the thickness increases at an inclination angle of more than 5 degrees, redeposition becomes severe when the beam incident angle of ion milling is 5 degrees or less. When the inclination angle is negative, that is, when the thickness decreases as the distance from the tip portion increases, the strength of the sample stage 1 becomes weak and the sample stage 1 may be bent. Therefore, the inclination angle is preferably 0 degrees or more. Further, even if the tilt angle is 0 degree or more, if the angle is small, there is a possibility that the sample table 1 bends depending on the material. Therefore, when the tilt angle is small, it is desirable to reinforce the sample stage 1 in the vicinity of the attachment part of the sample stage 1 to the sample holder so that the sample stage 1 is not bent. An example of the reinforced sample stage 1 is shown in FIGS. The shape of the reinforcement part 9 is not specifically limited. However, the thickness of the reinforcing portion 9 should not exceed the thickness of the sample table 1 when the inclination angle increases from the tip of the sample table 1 at a rate of 5 degrees. This is because it may cause redeposition.

  FIG. 5 shows the ion beam incident direction 11 and the cross-sectional shapes of the sample stage 1 and the sample 10 during ion milling. In consideration of mounting on a sample holder for TEM observation and / or a sample holder for an ion milling apparatus, the thickness 8 of the thickest part is desirably about 20 μm to 100 μm. If it is thicker than 100 μm, it may exceed the allowable thickness of the sample holder, and if it is less than 20 μm, it is difficult to handle with tweezers and the like, and the risk of damaging the sample increases. It is difficult to fix to a sample holder for an ion milling device.

  In the case of a conventional sample stage, a method is generally used in which a sample stage is placed on a TEM sample holder or a sample holder for an ion milling apparatus, a pressure plate is covered from above, and the pressure plate is fixed to the sample holder by screws or the like. However, if the thickness of the sample stage is thin, the sample stage cannot be firmly fixed by this method. It is possible to fix the sample stage to the sample holder with an adhesive, but in that case, it may cause sample contamination during TEM observation or ion milling, and the sample stage and the sample may be damaged when removing the sample stage. There is a high possibility that

  In the present invention, as shown in the plan view of FIG. 1, a hole 2 having a diameter of 0.2 mm to 0.5 mm is formed in the sample table 1. As shown in FIGS. 6 and 7, the tip portion 12 of the main body 15 of the TEM observation sample holder is provided with a protrusion 13 having a diameter of 0.18 mm to 0.48 mm, and the holding plate 16 has a diameter of 0.2 mm to 0. A hole 17 having a diameter of 5 mm is formed. The projection 13 of the TEM sample holder is mounted with the hole 2 of the sample table 1 aligned, the pressing plate 16 is covered from above, and the screw 19 is attached to the screw hole 14 and the pressing plate 16 of the upper end portion 12 of the TEM observation sample holder. The sample stage 1 is fixed to the TEM sample holder by being inserted into the screw hole 18 and screwed (FIGS. 8 and 9). The protrusions 13 of the TEM sample holder are 0.02 mm to 0. 0 mm in diameter than the holes 2 and 17 of the sample table 1 and the holding plate 16 so that they can be easily inserted into the holes 2 of the sample table 1 and the holes 17 of the holding plate 16. It is desirable to make it about 04 mm smaller. If the diameter of the protrusion 13 is smaller than the diameter of the holes 2 and 17 by 0.04 mm or more, the sample stage 1 may not be firmly fixed. If the difference in diameter is 0.02 mm or less, the operation of inserting the protrusion 13 into the holes 2 and 17 may be extremely difficult.

  If the hole 2 of the sample stage 1 is too small, it may be difficult to insert the protrusion 13 of the sample holder into the hole 2. However, if it is too large, the strength of the sample stage 1 is weakened and there is a risk of bending. As a result of studying a size that is relatively easy to handle while maintaining the strength of the sample stage 1, it is preferable to set the size as described above.

  A sample holder for ion milling for mounting the sample stage 1 is shown in FIGS. As in the case of the sample holder for TEM observation, a projection 20 for mounting the sample stage 1 is attached. The hole 2 of the sample stage 1 is fitted into the protrusion 20, and a pressing plate 23 is placed thereon, and the screw 24 is inserted into the screw hole 21 and fixed. The shape of the protrusion 20 is preferably 0.18 mmφ to 0.48 mmφ as in the case of the sample holder for TEM observation. The height of the protrusion 20 is desirably about the same as the sum of the thicknesses of the sample table 1 and the holding plate 23. If the height of the protrusion 20 is extremely lower than the sum of the thicknesses of the sample stage 1 and the holding plate 23, the sample stage 1 and the holding plate 23 cannot be fixed. However, if the height of the protrusion 20 is too high, it causes redeposition during ion milling.

  The thickness of the pressing plate 23 is desirably about 50 to 200 μm. If it is too thin, the strength of the holding plate will be weak and the sample stage 1 cannot be firmly fixed. If it is too thick, it will cause redeposition.

  A gear is provided around the sample turntable 22 so that it can be rotated in the ion milling apparatus.

Example 1
Steel having the chemical composition shown in Table 1 was prepared, a part of the sample was extracted by a microsampling method using a focused ion beam processing apparatus, and placed on a sample stage having the shape shown in FIG. The material used for the sample stage is molybdenum. In order to facilitate handling of the sample table with tweezers or the like, the bottom of the sample table has a shape with an arc-shaped ring.

  The size of the sample extracted by the microsampling method is 10 μm wide, 3 μm thick, and 20 μm high. The sample was fixed to the sample stage using a chemical vapor deposition method of tungsten. Furthermore, the thickness of the sample extracted by the focused ion beam apparatus was reduced to 100 nm. For micro-sampling and thinning, a Ga ion beam accelerated at an acceleration voltage of 30 kV was used. The sample stage on which the thinned sample was placed was placed on an ion milling sample holder having the shape shown in FIG. 14, fixed with screws, mounted on an ion milling apparatus, and ion milling was performed using an Ar ion beam. The ion milling was performed for 10 minutes while rotating the sample at an acceleration voltage of 300 V, a beam current of 4 μA, and an ion beam incident angle of 4 degrees. After the Ar ion milling, the sample stage was replaced with the TEM observation sample holder shown in FIG. 13, and the elemental analysis of the sample was performed in the TEM. Elemental analysis utilized an X-ray fluorescence analyzer attached to a TEM.

  As a comparative example, a sample was placed on a sample stage shown in FIG. 15 by a microsampling method and thinned with a focused ion beam processing apparatus, and then ion milling with an Ar ion beam was performed. FIG. 16 shows a state in which the sample stage is fixed to the ion milling sample holder used in the ion milling. The sample stage 27 was fixed with a commercially available resin wax. The conditions for microsampling, thinning with a focused ion beam processing apparatus, and ion milling with an Ar ion beam were the same as those described above. The material of the sample table 27 was also the same as the sample table (molybdenum). After completion of Ar ion milling, the sample stage 27 was replaced with a normal TEM observation sample holder, and elemental analysis of the sample 26 was performed in the TEM. FIG. 17 shows a state in which the sample stage 27 is attached to the TEM observation sample holder. The sample stage 27 was covered with a pressing plate and fixed with screws.

  The results are shown in Table 2. When a sample was prepared using the sample stage 27 of the comparative example, a molybdenum signal was detected by fluorescent X-ray analysis. This is presumably because the sample stage 27 was shaved during Ar ion milling and adhered to the surface of the sample 26. On the other hand, when the sample stage of the present invention was used, no molybdenum signal was detected in the fluorescent X-ray analysis, and there was no redeposition from the sample stage.

(Example 2)
Samples were prepared in the same manner as in Example 1 by changing the shape of the sample stage, and the presence or absence of redeposition was determined in the same manner as in Example 1. The results are shown in Table 3. Within the condition range of the present invention, no redeposition was detected. On the other hand, redeposition was detected in all of the comparative example in which the apex angle exceeded 120 degrees, the comparative example in which the thickness increase ratio exceeded 5 degrees, and the comparative example in which the thickness of the tip portion exceeded 5 μm.

(Example 3)
The sample stage of the present invention has a hole, and the sample stage can be easily fixed by fitting with the projection of the sample holder, and the sample breakage due to a handling mistake can be reduced. Using the sample stage of the present invention, the same sample preparation as in Example 1 was performed 100 times, and the probability of sample breakage due to a handling error was examined. The results are shown in Table 4. Table 4 also shows the results of using a sample table with no holes as a comparative example. Within the condition range of the present invention, the sample breakage due to the handling mistake is 10% or less, but the sample stage of the comparative example has a high probability of the sample breakage due to the handling mistake.

Example 4
The sample holder for ion milling of the present invention has a projection, and by fitting with the hole of the sample table, the sample table can be easily fixed, and the sample breakage due to a handling mistake can be reduced. In addition, sample contamination that becomes a problem when wax or adhesive is used to fix the sample stage can be avoided.
Using the sample stage of the present invention, the sample breakage probability due to sample contamination and handling errors was examined. The sample breakage probability was examined by performing the same sample preparation as in Example 1 100 times. Presence / absence of sample contamination was determined by performing fluorescent X-ray analysis in TEM and detecting whether carbon was detected. The case where no carbon was detected was marked with ◯, and the case where carbon was detected was marked with x. The results are shown in Table 5. Within the condition range of the present invention, there was no sample contamination, and the sample breakage due to a handling mistake was 10% or less. As a comparative example, a sample holder for ion milling without projections shown in FIG. 18 is covered with a pressing plate over the sample and fixed with screws, and a sample for ion milling without projections shown in FIG. When the sample was fixed to the holder with a resin wax, the probability of sample damage due to sample contamination and handling error was investigated. The results are also shown in Table 5.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

It is a figure which shows an example of a structure of the sample stand of this invention. It is a figure which shows an example of a structure of the sample stand of this invention in case an apex angle is 0 degree | times (with a reinforcement part). It is a figure which shows an example of a structure of the sample stand of this invention in case a thickness increase rate is 0 degree | times (with a reinforcement part). It is a figure which shows an example of a structure of the sample stand of this invention in case a thickness increase rate is 0 degree | times (with a reinforcement part). It is a figure which shows the cross-sectional shape of the ion beam incident direction at the time of ion milling, a sample stand, and a sample. It is a figure which shows an example of a structure of the sample holder for TEM observation of this invention. It is a figure which shows an example of a structure of the sample holder used for the sample holder for TEM observation of this invention. It is a figure which shows an example of the state which mounted the sample stand of this invention on the sample holder for TEM observation of this invention. It is a figure which shows an example of the state which mounted the sample stand of this invention on the sample holder for TEM observation of this invention, and was fixed with the pressing plate. It is a figure which shows an example of a structure of the sample holder for ion milling of this invention. It is a figure which shows an example of the state which mounted the sample stand of this invention, and was fixed with the pressing plate. It is a figure which shows the structure of the sample stand of this invention used in Examples 1-4. It is a figure which shows the shape of the sample holder for TEM observation used in Examples 1-4. It is a figure which shows the shape of the sample holder for ion milling of this invention used in Examples 1-4. FIG. 3 is a diagram showing the shape of a sample stage of a comparative example used in Example 1. 3 is a diagram showing a configuration of a sample holder for ion milling of a comparative example used in Example 1. FIG. 3 is a diagram showing a configuration of a sample holder for TEM observation of a comparative example used in Example 1. FIG. 6 is a view showing a configuration of a sample holder for ion milling of a comparative example used in Example 4. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sample stand 2 Hole 3 Vertical angle 4 Plane part 5 Plane part width 6 Tip part (plane part) thickness 7 Thickness increase rate 8 Maximum thickness 9 Reinforcement part 10 Sample 11 Ar ion beam incident direction 12 TEM observation Sample holder tip 13 Protrusion 14 Screw hole 15 Body of TEM observation sample holder 16 Holding plate 17 Hole 18 Screw hole 19 Screw 20 Projection 21 Screw hole 22 Sample turntable 23 Holding plate 24 Screw 25 Sample 26 Sample 27 Sample stand

Claims (7)

A sample stage made of a conductive material on which a sample used for TEM observation is mounted,
The cross section of the sample stage tip has a flat surface for mounting the sample, spreads in the width direction of the sample stage from the tip in a triangle or fan shape with an apex angle of 120 degrees or less, and the thickness of the tip Having an inclined cross section with a thickness of 1 μm or more and 5 μm or less and increasing in thickness as it moves away from the tip, the inclination angle of the inclined section with respect to the vertical direction being 5 degrees or less, and fixing the position of the sample stage A sample stage having a hole for fixing to the sample holder. A sample stage made of a conductive material on which a sample used for TEM observation is mounted,
The front end of the sample stage has a flat surface for mounting the sample, the sample stage does not extend from the front end in the width direction, and the thickness of the front end is not less than 1 μm and not more than 5 μm. An inclined cross-section that increases in thickness as it moves away from the part, has an inclination angle with respect to the vertical direction of the inclined cross-section of 5 degrees or less, and has a hole for fixing to the sample holder for fixing the position of the sample stage A sample stage characterized by that. A sample stage made of a conductive material on which a sample used for TEM observation is mounted,
The cross section of the sample stage tip has a flat surface for mounting the sample, spreads in the width direction of the sample stage from the tip in a triangle or fan shape with an apex angle of 120 degrees or less, and the thickness of the tip A sample stage having a thickness of 1 μm or more and 5 μm or less and having a constant thickness from the tip, and a hole for fixing to a sample holder for fixing the position of the sample stage. A sample stage made of a conductive material on which a sample used for TEM observation is mounted,
The front end of the sample stage has a flat surface for mounting the sample, the sample stage does not extend from the front end in the width direction, and the thickness of the front end is not less than 1 μm and not more than 5 μm. And a hole for fixing to a sample holder for fixing the position of the sample stage.   The sample stage according to any one of claims 1 to 4, wherein a width of the flat portion for mounting the sample is 1 µm or more and less than 100 µm. A sample holder for fixing the sample stage according to any one of claims 1 to 5,
A sample holder having a protrusion that fits into a hole of the sample table. The sample holder according to claim 6, wherein the sample holder is for TEM observation and / or for an ion milling device.

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