JP4597045B2 - Micro sample transfer apparatus and method - Google Patents

Description

  The present invention relates to a micro sample transfer apparatus and method for transferring a micro sample in a vacuum sample chamber.

  Along with the high integration and miniaturization of semiconductors, defects that cannot be determined by the image resolution of a scanning electron microscope (hereinafter abbreviated as SEM) as a means for analyzing malfunctions often cause defects. Instead, a transmission electron microscope and a scanning transmission electron microscope (hereinafter abbreviated as STEM) have become essential. However, it is not easy to prepare a sample for STEM observation, and there is a demand for a method for easily and reliably setting a target position in a short time.

  Recently, using a focused ion beam (hereinafter abbreviated as FIB) and a sharpened micro sample connection tool (hereinafter also referred to as a micro sample transport tool), a small piece of a few centimeters or a 300 mm diameter wafer is used as an original sample in a vacuum vessel. From there, a method of extracting a small sample of about 10 μm has been frequently used. Japanese Patent No. 2774884 (Patent Document 1) describes a method of separating a micro sample by using a micro sample connecting tool in which a part of the sample is FIB processed and sharpened. In addition, a method for mounting on an STEM sample stage to finish an observation sample is described in Japanese Patent No. 3547143 (Patent Document 2). Patent Document 2 discloses a method using a deposition film as a connection method between a fine sample piece and a fine sample connector, and a connection method using electrostatic adsorption without using a deposition film.

  In Patent Document 1, a fine sample connector having a sharp tip is arranged in the sample chamber of the focused ion beam apparatus, and after removing the periphery of the target position by FIB, the tip of the micro sample connector is brought into contact with the sample surface. , A FIB-assisted deposition film (hereinafter abbreviated as a deposition film) is formed so as to include the tip of the micro sample connector, and is connected to the sample to separate the micro sample including the target position from the substrate. Yes. Further, Patent Document 2 discloses that a STEM is completed by fixing a micro sample separated and extracted to a micro sample fixing base provided in a sample chamber and performing thinning processing so that STEM observation is easy. Further, in the connection method by electrostatic attraction described in Patent Document 2, the micro sample connector is connected to the micro sample in a point contact state.

  One of the great advantages of the STEM sample preparation method in Patent Documents 1 and 2 is that when a micro sample piece is extracted from the original sample and fixed to the STEM holder, the extracted micro sample does not change its orientation, If the sample fixing surface of the STEM holder is made parallel, a thin piece that can be easily observed by the STEM can be created without complicated operation of the micro sample connector. In other words, it is important that the posture of the extracted microsample does not collapse, and in order to realize this, the FIB that can be processed without stress, the deposition film of the microsample connector that does not deform, and the microsample Reliable connection is essential.

  Japanese Patent Laid-Open No. 2003-242921 (Patent Document 3) discloses a case where a peeling probe and an extraction probe are installed in an electron microscope that irradiates an electron beam such as an SEM and an observation surface of a sample is observed. In addition, a method and an apparatus are disclosed in which a voltage is applied to the separation probe and the extraction probe, and the micro object is taken out and dropped using the Coulomb attractive force and the Coulomb repulsive force acting on the micro object and the probe. ing.

Japanese Patent No. 2774884 Japanese Patent No. 3547143 JP 2003-242921 A

  As in Patent Documents 1 and 2, it has been found that a conventional device for connecting a sharpened micro sample connector to a micro sample has the following problems.

(1) The weakness of the mechanical strength of the micro sample connector The tip radius must be reduced to about 1 μm in order to achieve contact of the micro sample connector tip with the micro area. For this reason, the width of the minute sample connector near the tip must be reduced to about 2 μm. For this reason, mechanical rigidity is lowered, and even tungsten having high physical properties can be easily deformed if it is inadvertently brought into contact with the sample, and contact with or connection to the sample at the tip, which is the original purpose, becomes impossible. When the tip of the micro sample connector is deformed, the micro sample connector must be replaced, and a spare micro sample connector is necessary, and waste such as replacement work and apparatus stop time increases. It is disadvantageous to the user.

(2) Displacement of the posture of the micro sample to be transferred Even if the micro sample can be connected to the tip of the micro sample connector, the posture of the micro sample is disrupted due to the attractive force or repulsive force due to electrostatic force with the peripheral members such as the sample substrate. Changes. The collapse of the posture of the micro sample causes problems such as the vertical cross-section processing of the micro sample and the STEM thin piece processing of the vertical surface cannot be performed. More preferably, if the micro sample adheres to other than the tip of the micro sample connector, the micro sample cannot be separated from the micro sample connector, and STEM observation, which is the original purpose, cannot be performed. These causes are because the tip of the micro sample connector is thin, and the micro sample and the micro sample connector are in point contact at the tip, so the micro sample is easily affected by the attractive and repulsive forces of the surrounding electrostatic field, This is because the micro sample tilts around the point contact portion. For this reason, the posture cannot be maintained before and after the transfer of the minute sample. As a result, the desired location cannot be observed with the STEM, and the original observation cannot be realized.

(3) Shaping of the tip accompanying cutting and separation of the micro sample connector From the viewpoint of maintaining the posture of the micro sample at the tip of the micro sample connector and preventing the drop, the micro sample connector is connected to the micro sample with a FIB deposition film. The method is known and described in Patent Documents 1 and 2. In this case, there is an advantage that the connection strength becomes high and the posture of the connected micro sample does not collapse, but after the transfer to another location, the micro sample connecting tool and the micro sample must be separated. For this, either the method of cutting the micro sample connector, cutting a part of the micro sample, or removing the deposition film is used. In either method, the tip of the micro sample connector is connected. Unlike the previous shape, after separation of the micro sample connector and the micro sample, the tip of the micro sample connector must be shaped by FIB to return to the original shape or the micro sample connector must be replaced with a new one. The shaping of the micro sample connection tool takes time, but this shaping also increases the tip width of the micro sample connection tool by repeating about 10 times, and the shaping time becomes long, and finally it becomes unpractical. In such a situation, the micro sample connector itself must be replaced. Replacing the micro sample connector is not preferable from the viewpoint of working time and cost.

(4) Accuracy of the movement of the micro sample connector If the connection location between the micro sample connector and the micro sample is limited to a region having a diameter of about 1 μm, for example, the micro sample connector driving mechanism has a highly accurate mechanism system and control. Correction etc. are required and it becomes expensive.

  The following solutions can be considered for these problems, but they also have problems.

(1) In order to prevent deformation of the micro sample connector, it is easiest to increase the rigidity by increasing the diameter of the micro sample connector. However, if the diameter of the micro sample connector is increased, the radius of the tip cannot be reduced, and the micro sample connector cannot be connected to the specific micro area of the sample which is the original purpose.

(2) In order to withstand and hold the posture of the connected fine sample against the attractive force and repulsive force of the surrounding electrostatic field, it is necessary to strengthen the connection. Therefore, when the deposition film is used, the problem (3) occurs.

(3) As a connection between a sample and a micro sample connector without using a deposition film, Patent Document 2 discloses a reattachment film and electrostatic adsorption that occur during FIB irradiation. Since the connection by the redeposition film is accompanied by the separation by the FIB irradiation as in the case of the conventional deposition film, the shaping of the micro sample connector is inevitable. On the other hand, for connection by electrostatic adsorption, a method is known in which electrostatic adsorption is performed via an insulating film at one point on the tip of one sharp sample connector surface. This method has an advantage that the shape of the micro sample connector can be preserved at the time of separation because the deposition film is not fixed, and the micro sample connector is not required to be shaped. However, when a micro sample of about several μm cubic is extracted using this micro sample connection tool, the micro sample swings unstablely with the contact point with the micro sample connection tool as a fulcrum. In the worst case, the posture of the minute sample existing on the sample surface cannot be maintained, and a problem such as a tilted state occurs. This is because the micro sample in point contact with the micro sample connector is sensitively affected by the surrounding electrostatic field environment.

  When the posture of the micro sample collapses, in order to properly observe the inside of the micro sample with the STEM, the posture of the extracted sample must be adjusted to an appropriate orientation. In order to adjust the posture of the micro sample, a mechanism and a control system with an increased degree of freedom are provided on the micro sample connector driving side, or a mechanism and a control system with an increased degree of freedom of driving the sample carrier (micro sample fixing tool) are provided. Or a means of providing them both must be taken.

  Note that the micro object to be extracted in Patent Document 3 is to be discarded, and the collapse of the attitude of the micro object attached to the micro sample connector is not a problem. For measures for maintaining the micro object's attitude, Not suggested.

(4) Usually, the allowable area of the place to be contacted is about 2 μm square. In the conventional method of bringing a sharp micro sample connector into contact with this region, the micro sample connector driving mechanism is required to have a positional accuracy of 2 μm or less and a contact position resolution of about 0.2 μm.

  From such problems, there has been a demand for a micro sample connector, a micro sample extraction method, or a micro sample transport device that realizes these, which can be used repeatedly without deformation of the tip.

  An object of the present invention is to provide a micro sample transport device that can be used repeatedly many times without deformation of the tip of the micro sample transport tool even if the micro sample is separated. Another object of the present invention is to provide a method and apparatus for transferring a micro sample that does not require high-precision performance in a micro sample transfer tool drive mechanism.

  The micro sample transfer device of the present invention includes, as an example, a micro sample connector that contacts or contacts a micro sample in a vacuum sample chamber at a plurality of points, a drive mechanism that moves the micro sample connector in the vacuum sample chamber, A power source for applying a voltage to the micro sample connector. The micro sample connector that comes into surface contact with the micro sample is formed, for example, from a flat plate part connected to the micro sample and a base that supports the flat plate part, or a shape that has been processed to increase the area connected to the micro sample by a focused ion beam To.

  The micro sample connector and the micro sample are connected by micro fusion generated by a current flowing through the contact portion between the micro sample connector and the micro sample.

  According to the present invention, the tip of the micro sample connector that is in contact with the micro sample is not easily deformed, and can be transferred while maintaining the posture of the extracted micro sample. Is unnecessary and can be used repeatedly. Furthermore, the accuracy of driving the micro sample connector is lower than in the prior art.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an embodiment of a micro sample transfer device according to the present invention. The micro sample transfer apparatus 1 is composed of an ion beam irradiation system 4 for irradiating a sample 3 placed on a sample stage 2 with a focused ion beam, an electron beam irradiation system 5 for observing a sample, etc., and a conductive material. A micro sample connector (also referred to as a probe) 6 to be connected to or moved from the micro sample, a micro sample connector driving means 7 for moving the micro sample connector 6, secondary electrons from the sample 3 and the rear It has a detector 8 for detecting scattered electrons, and a gas supply means 9 for supplying a gas for forming a metal film on the sample surface or actively etching the sample. At the tip of the gas supply means 9, a nozzle 10 having a fine diameter of a gas outlet is provided.

  Also, the operation of the sample stage control unit 11 for operating the sample stage 2, the FIB control unit 12 for operating the focused ion beam irradiation system 4, the electron beam control system 13 for controlling the electron beam irradiation system, and the operation of the micro sample connector driving mechanism 7 A voltage is applied to the micro sample connector control unit 14 that controls the operation, the detector control system 15 that controls the operation of the detector 8, the gas supply control unit 16 that controls gas irradiation from the nozzle 10, and the micro sample connector 6. The power source 17, the flat stocker 18 provided with a spare flat plate so that it can be replaced when the flat plate at the tip of the micro sample connector 6 is damaged, the vacuum sample chamber 19 containing the sample stage 2, etc., and the various control units described above The calculation processing unit 20 that performs operation instructions and various data, and stores images, and the like, images of samples, micro samples, micro sample connectors, etc., and set values of various control units Displayed, and an image display unit 21 for setting.

  A typical micro sample connector 6 used in the micro sample transfer apparatus 1 according to the present embodiment has at least two contact portions with the sample, and a needle-like shape in which the tip of the conventional micro sample connector is sharpened. The shape is completely different from the one-point contact with the sample. Preferably, the shape in which the tip of the minute sample connector is located at the apex of the triangle is good.

  The micro sample connector used in this example will be described with reference to FIG. The tip of the micro sample connector is set to two points as shown in FIG. In FIG. 2, the tip of the micro sample connector 41 having a slightly thicker diameter is branched like 42 a and 42 b so that the tips 44 a and 44 b are in contact with the micro sample 43 almost simultaneously. At least one of the two tips is physically connected and plays a role of holding down the inclination of the posture of the micro sample at the remaining contact portion. As described above, in the conventional micro sample connection device connected at one point, it is electrostatically attracted at one point or a deposition film is formed at one point. Although the posture of the micro sample collapsed, in this shape, the posture does not collapse.

  The material of the micro sample connection tool was tungsten, and the tip was manufactured by electrolytic polishing of a thin wire. Such a shape can be processed into a bifurcated or trifurcated shape by scratching the cut surface of the tungsten fine wire in the direction of the fine wire axis. A bifurcated or trifurcated tip can also be produced by electroforming. Electroforming is preferred because of good shape controllability and reproducibility. It is important that a plurality of tip portions of the prepared micro sample connector are prepared so as to be in contact with the sample at the same time regardless of whether it is electrolytic polishing or electroforming. Note that if the micro sample connector is brought into contact with the original desired contact portion and at a position separated in the longitudinal direction of the micro sample at one point, the effect of maintaining the posture is greatly improved as compared with the conventional one point. Since there is still a possibility that the posture is broken around the line connecting the two, the tip of the micro sample connector is divided into three points located at the vertices of the triangle, and it is preferable that these contact the micro sample almost simultaneously.

  Microfusing by energization is used to connect either the bifurcated or trifurcated tip to the sample. A power source 17 is connected to the micro sample connector 6, a voltage of about +5 V is applied, and the sample is maintained at the ground potential. In this state, if the two points at the tip of the micro sample connector are brought into contact with the sample almost simultaneously, a current flows through one of the contacts slightly earlier, particularly because the contact area of the contact portion is small, the resistance is high, and the temperature becomes high. To wear. The tip of one micro sample connector has a small amount of current and mechanical contact becomes dominant, but it plays a role of holding down when the micro sample collapses around the connection part of the other micro sample connector Therefore, the collapse of the posture of the micro sample is greatly reduced. The micro-fusion by energization makes it unnecessary to form a deposition film that has been used in the past, and the advantage of shortening the time is born.

  As a conventional technique, a buzzer is installed between the power source connected to the micro sample connector to detect contact between the micro sample connector and the sample, and the tip of the micro sample connector contacts the conductive sample. There is a function to notify the operator of contact, such as a buzzer. Here, this power supply plays a different role, but in particular, in order to avoid excessive fusion and fusing between the micro sample connector and the sample, a circuit is formed so that an upper limit can be set for the energization current value and energization time. is doing.

  Another embodiment regarding the contact portion of the micro sample will be described. 3 and 4 show another embodiment of the micro sample connector in the micro sample transfer apparatus according to the present invention. Unlike the conventional sharpened shape and the above-mentioned branched shape, the tip of the micro sample connector has a flat shape that is in contact with the surface and has a shape that does not exist in the past. is there. FIG. 3A shows an example in which an oblique section 52 is processed into a cylindrical thin wire 51 to make a contact portion with the sample 53. FIG. 4A shows a minute flat plate 65 at the tip of a thick minute sample connector base 67. FIG. The shape is fixed, and the common point is that it can come into surface contact with the sample.

  First, an embodiment of a micro sample connector having an oblique section will be described with reference to FIGS. FIG. 3B shows a state in which the uniform thin wire 51 having a diameter of 3 μm is installed at an inclination of 45 ° with respect to the sample surface, and the uniform thin wire 51 is cut by the FIB 54 installed perpendicular to the sample surface. The uniform fine wire cut surface 52 has an elliptical cross section (minor axis: 3 μm, major axis is about 4.2 μm) as shown in FIG. After the cut surface is finished and flattened with a fine FIB, when the micro sample connector 51 ′ is rotated by 180 ° as shown in FIG. 3D, the cut surface 52 becomes parallel to the sample surface and the contact area is thin. It becomes wider than the orthogonal cross-sectional area.

  In order to create the minute sample connector 51 ′ of this shape, the uniform thin line is accurately tilted by 45 ° with respect to the sample surface, and there is no shaft shake in 180 ° rotation after forming the oblique section. If required and not satisfied, the cut surface will not come into surface contact with the sample surface. These problems can be solved by adding an inclination correction mechanism to the micro sample connector driving mechanism.

  Next, the configuration of the flat sample-attached micro sample connector and the principle of connection between the micro sample connector and the micro sample will be described with reference to FIG. Here, for easy understanding, the micro sample 61 and the sample substrate 63 separated in FIG. 4 are exaggerated. In FIG. 4A, the micro sample 61 is mechanically and electrically connected to the sample substrate 63 via the support portion 62. The micro sample connector 64 has a shape in which a flat plate 65 is fixed to the tip of the micro sample connector base 67 by a deposition film 66, and a voltage is applied to the entire micro sample connector 64 by an external power source 68. In this embodiment, the applied voltage is set to, for example, -5V. On the other hand, the sample substrate 63 is at ground potential. The micro sample connection tool 64 can be finely moved in at least three orthogonal directions by the drive mechanism 69, and can move to the connecting portion and the connected micro sample 61.

  The drive mechanism 69 is controlled to bring the micro sample connector 64 into contact with a desired region of the sample substrate 63. When the flat plate 65 of the probe 64 comes into contact with the micro sample 61, a current flows through the contact portion toward the flat plate 65 of the micro sample connector 64 that is -5V lower than the sample substrate 63 at the ground potential. Here, the flat plate 65 and the micro sample 61 seem to be in contact with each other at a glance, but microscopically, since the surface of the flat plate 65 and the micro sample 63 has micro unevenness, the convex portions of each other are in contact with each other. It becomes a point and a current path. This contact point is estimated to have a substantial contact area of about 10 nm square, and is very small. Therefore, even a small current is heated by resistance and fused. Even if the sample and the flat plate portion are silicon, they are easily fused. However, if the voltage of the power source 68 is set to be larger than 10V, the flowing current increases, and in the worst case, the flat plate 65 and the micro sample 61 are fused, so that the voltage setting is important. The applied voltage is preferably in the range of −0.5V to −10V or + 0.5V to + 10V.

  Next, when the support portion 62 is removed by FIB (not shown), the micro sample 61 and the sample substrate 63 are mechanically and electrically separated as shown in FIG. 4B, but the micro sample 61 and the flat plate 65 are separated. As a result, the micro sample 61 becomes the same as the potential of the micro sample connector. In addition, the posture of the micro sample 61 is also maintained. In other words, the tip of the micro sample connector is positively made flat and brought into surface contact with the target sample, so that the collapse of the posture of the micro sample piece 61 is suppressed and the post-separated posture is maintained.

  Since the micro sample handled here has a size of about 10 μm on a side, a contact area of the above level is sufficient for the joint portion by fusion, and the remaining area of the flat plate is micro in opposition to an external force trying to break the posture. It plays a role of suppressing the tilt of the sample. Therefore, the larger the size of the flat plate, the better. However, since the length of the sample piece to be handled is about 10 to 20 μm and the width is about 1 to 5 μm, it cannot be made meaninglessly, and the sample piece is about several μm square. It is preferable because the connection portion can be observed and there is no fear of forming an undesired current path by contacting the periphery. Also, if the absolute value of the potential of the micro sample connection tool is large, the flowing current increases, and there is a risk that the contact portion will be abnormally hot and the sample may be altered or the micro sample may be melted. For this reason, about -0.5V to -10V or +0.5 to + 10V is preferable.

  On the contrary, when separating the micro sample connector 64 from the micro sample 61, the micro sample 61 is fixed with a fixing force stronger than the micro fusion force between the current micro sample 61 and the flat plate 65. When 64 is moved away from the micro sample 61, the micro fusion force is lost and the both are easily separated. As in the prior art, shaping of the micro sample connector after separation is unnecessary, and the same micro sample connector can be used repeatedly. Here, a deposition film may be used for fixing the micro sample 61 to, for example, a micro sample fixing base (not shown). Since the adhesion force due to the deposition film is strong, and it is desired that the micro sample used for observation and analysis is fixed once, it is desired to be firmly fixed. Therefore, fixing with the deposition film is optimal.

  Further, the connection surface between the flat plate 65 and the sample piece 61 is not limited to the upper surface of the sample as described above. 4 (c) and 4 (d), a micro sample connector 64 is used in which a flat plate 65 is fixed upright at the tip of the micro sample connector base 67 and fixed so that the contact surface is vertical. Then, the micro sample piece 61 may be brought into contact with the side surface of the micro sample piece 61 so as to be connected by micro fusion.

  In this way, by using the micro sample connector having a flat plate at the tip, it is possible to transfer the extracted micro sample without breaking the posture. Moreover, the micro sample connection tool of the present embodiment using micro fusion by energization can be used repeatedly without wear.

  Further, if the allowable area of the place to be contacted is about 2 μm square, in the case of the conventional method in which a sharp micro sample connector is brought into contact with the micro sample, the micro sample connector driving mechanism has a positional accuracy of 2 μm or less and 0. A contact position resolution of about 0.2 μm is required. In contrast, if the micro sample connector has a contact surface larger than the contact area as in the present embodiment, the position accuracy and contact position resolution required for driving the micro sample connector are greatly reduced. For example, if a contact area of 3 μm square is used for a contact area of 2 μm square, a position accuracy of about 4 μm and a contact position resolution of about 0.4 μm are sufficient.

  Next, the manufacturing method of the above-mentioned flat sample connection tool with a flat plate will be described. The flat plate was produced by the following two methods. The first method is a method of picking up a flat micro sample using FIB processing and a sharpened conventional micro sample connector and replacing it with a micro sample connector base. The second method is a method in which a flat plate shape is prepared in advance by electroforming and prepared in a micro sample transfer device, and connected to a micro sample connector base when necessary.

First, the first method will be described in detail with reference to FIG.
(a): Holes 74 were formed in two rectangular shapes by FIB 72 on silicon plate 71, which is a raw material that is a flat plate at the tip of a micro sample connector. A portion 73 sandwiched between two rectangular holes is a portion that finally becomes a flat plate. The thickness is, for example, 0.5 to 1 μm.
(b): The sample is tilted, and grooves 74a, 74b, and 74c are formed around the region to be a flat plate, and processed into a shape that leaves the support portion 75.
(c): A sharpened conventional micro sample connector 76 is brought into contact with the processed thickness portion of the flat plate and connected by a deposition film 77. Thereafter, the support portion is cut by irradiating the support portion with FIB 72.
(d): In this way, a fine flat plate 73 having a substantially uniform thickness can be separated. The original sample can be completely separated by raising the micro sample connector as it is.
(e): In a state where the extracted flat plate 73 is in contact with the surface of the sample 71 having no interference portion around it, the deposition film 77 connecting the micro sample connector 76 and the flat plate 73 is removed by the FIB 72.
(f): The flat plate 73 separated from the micro sample connector 76 is placed while adjusting the micro sample connector so as to face the sample 71. At this time, since the flat plate 73 faces an arbitrary direction, the sample stage is rotated and adjusted so as to have a predetermined relationship with the minute sample connector base. Here, the flat plate 73 placed on the surface of the sample 71 may be further shaped by FIB. When completed, the flat size was 3 × 4 μm and the thickness was 1 μm.
(g): Finally, the micro sample connector base portion 76a slightly thicker than the micro sample connector 76 is brought into contact with the flat plate 73 whose orientation is adjusted. For example, the portion in contact with the flat plate 73 is 1 μm in diameter, and the diameter at a portion 3 μm away from the tip is increased to 3 μm to give rigidity. A deposition film 78 is attached to the contact portion, and the micro sample connector base 76a and the flat plate 73 are connected and fixed.
(h): In this way, the flat sample connecting tool 79 to which the flat plate 73 is fixed is completed, and when raised, the surface of the flat plate 73 is necessarily parallel to the surface of the sample 71.

  Such a series of operations is performed in a time zone when the sample of interest is not introduced into the sample chamber, and therefore, the deposition gas is not directly irradiated onto the sample surface.

  Next, the second method will be described. Here, a flat plate stocker 80 equipped with a plurality of flat plates that can be easily attached to the tip of the micro sample connector base is used. FIG. 6A shows a flat plate stocker 80, which is a thin metal plate 81 having a structure in which a flat plate can be easily removed by a plurality of opening patterns. The support portions 84a and 84b support the flat plate 82 by the arrangement of the opening patterns 83a and 83b. The thin metal plate 81 has a thickness of about 1 μm, and the opening pattern is arranged to be a flat plate 82 having a length of about 3 μm and a width of about 4 μm. The overall size is about 4 mm long and 2 mm wide and can be handled using tweezers. In FIG. 6, for the sake of convenience, the opening pattern, the support portion, and the flat plate are expressed with respect to the overall size for the sake of convenience. The back surface of the thin metal plate 81 has a reinforcing portion 85 having a thickness of about 10 μm as shown in FIG.

FIGS. 6C and 6D show a procedure for attaching a flat plate to the micro sample connector base. The minute sample connector base 85 is brought into contact with the flat plate 82, and a deposition film 86 is formed on the contact portion. Next, the support portions 84a and 84b are removed by sputtering with the FIB 87, whereby the flat plate 82 is separated from the metal thin plate 81, and the flat sample-attached micro sample connector 88 is completed as shown in FIG. Here, since the bottom surface of the flat plate 82 (contact surface with the micro sample) has the same inclination as the thin metal plate 81, the flat plate stocker 80 is placed horizontally with the sample surface to be extracted. 82 can make surface contact with the sample. In the micro sample transfer device 1 of FIG. 1, a flat plate stocker 18 is installed together with a sample (wafer) 3 on a wafer holder 2A.
Such a planar stocker 80 can be manufactured with high accuracy and at low cost by a semiconductor lithography technique and an electrochemical plating (electroforming) technique.

  A sample preparation procedure for STEM observation of a target portion from a wafer that is an original sample using the above-described micro sample transfer device will be described with reference to FIGS. 7, 8, and 9.

  7, 8, and 9 are FIB images (SIM images) a <b> 1 to a <b> 11, and perspective views from a different viewpoint from the FIB for easy understanding of the drawing. Figures (right column) b1 to b11 are also shown.

(Step 1): The rectangles 102 and 103 are processed by FIB with the region 100 to be left as an observation sample in the sample 101 interposed therebetween. For example, the rectangle 102 has a width of 20 μm, a length of 5 μm, a depth of 15 μm, and the rectangle 103 has a width of 20 μm, a length of 10 μm, and a depth of 10 μm. The thickness was 3 μm.
(Step 2): After the work in Step 1, the sample stage is tilted so that the side surface of the region 100 can be seen. Next, the thin rectangles 104a, 104b, and 104c are processed on the three surfaces of the fine sample piece to be extracted by FIB irradiation. By the thin rectangular processing, the remaining portion is processed into a shape that is supported only by the support portion 103 and is not in contact with other portions. In FIG. 2 (b2), the irradiation direction of the FIB 105 is shown for easy understanding.
(Step 3): When the inclination of the sample stage is returned and observed again with FIB, it can be seen that the region 100 is not in contact with the three surfaces by the rectangle 104. In the diagram (b3), the region 100 supported by the support portion 103 can be identified.
(Step 4): Here, the micro sample connector 107 is brought close to 100 in the region. The micro sample connector 107 is a tungsten thin wire with a base portion 108a having a metallic diameter of about 3 μm, and a nickel flat plate 108b is fixed to the tip. As will be described later, the flat plate 108b is fixed in advance by FIB deposition so as to be parallel to the surface of the sample 101.
(Step 5): The flat plate 108b of the micro sample connector 107 is brought close to the end of the region 100. When contact is made with the region, contact is confirmed by contact detection means installed in advance in the micro sample transfer device, and the movement of the micro sample connector stops. In this state, the micro sample connector is stopped and held. At this time, a current is applied between the micro sample connector 107 and the sample, and the flat plate 108 b of the micro sample connector 107 is micro fused to the region 100.
(Step 6): In order to cut the support portion 103 in the region 100, the FIB 105 is irradiated to the rectangular region 109. Since the substantial thickness (height) of the support 103 is about 3 μm, the FIB irradiation time is only about 1 minute.
(Step 7): The support portion 103 is removed by irradiating the rectangular region 109 with the FIB 105, and the region 100 is separated from the sample 101 to become a micro sample 110. At this time, the micro sample 110 is connected to the flat plate 108 b at the tip of the micro sample connector 107.
(Step 8): The micro sample connector 107 is moved away from the sample 101 (moved upward), the sample stage is moved, and the micro sample fixing base 111 is moved within the field of view. Although the description of the micro sample fixing base is omitted in the micro sample transfer device of FIG. 1, it is installed on the wafer holder 2A. The micro sample connector 107 is moved so that the micro sample piece 110 contacts the micro sample fixing base. In the case of an apparatus configuration having an electron beam irradiation system like the micro sample transfer apparatus of FIG. 1, it can be seen that the micro sample 110 approaches the micro sample fixing base 111, and the approach speed can be reduced when approaching. When the micro sample 110 comes into contact with the fixed base 111, the contact detector operates, and at the same time, the micro sample connector driving mechanism stops.
(Step 9): When a deposition film (not shown) is formed so as to straddle the micro sample 110 and the fixing table 111 in this state, the micro sample 110 is fixed to the fixing table 111.
(Step 10): Here, when the micro sample connector 107 is raised, the adhesion force by the deposition film is superior to the adhesive force by micro fusion of the micro sample connector 107 and the micro sample 110. The tool 107 is separated from the micro sample 110, and the micro sample 110 is self-supporting on the fixed base 111.
(Step 11): Thereafter, the micro sample 110 may be further processed into a shape suitable for various analysis techniques. For example, in the case of STEM or STEM, the sample is sliced to a thickness of about 100 nm.

  In this example, a flat plate is fixed to the tip of the micro sample connector, and the surface of this flat plate is in contact with and connected to the top surface of the micro sample to be extracted using a micro sample connector whose surface is parallel to the original sample surface. It was. The present invention is not limited to this, and the minute sample connector to be connected in contact with the sample may have a prismatic shape. This example will be described with reference to FIG.

  In FIG. 10, a prismatic tip micro sample connector 122 is formed at the tip of a micro sample connector base 121 connected to the micro sample connector driving mechanism 120 while being inclined downward. Since the prismatic micro sample connection tool is inclined downward with respect to the reference horizontal plane, the tip of the micro sample connection tool has a chamfered shape to facilitate surface contact with the sample. A dimension example of the prism portion is a square cross section with a side of 2 μm, a length of 10 μm, a tip chamfered at an angle corresponding to the inclination angle of the micro sample connector, and a substantial horizontal plane dimension is about 2 × 1 μm. Such a shape can be processed by FIB.

  With such a micro sample connector, as shown in FIGS. 10B, 10C, and 10D, the micro sample 123 to be extracted can be connected in surface contact with the upper surface or the side surface. When the micro sample connector is brought into contact with the upper surface of the sample, it is difficult to grasp the distance between the tip of the micro sample connector and the sample when the microscope as the observation means is viewed from directly above. In order to bring the sample into contact, skill and time are required. However, when the sample is brought into contact with the side surface of the sample as shown in FIGS. Is easy to grasp with a microscope from directly above, and can be safely and quickly contacted.

  In addition, the features of these micro sample connectors are that the tip of the micro sample connector has a unique shape rather than the conventional sharpened conical shape. Another feature is that only a part of the tip of the sample connector is recognized and easily identified. By adopting the tip of the micro sample connector with a shape that makes it easy to recognize the image, the tip of the micro sample connector is recognized by moving the micro sample connector to the target location on the sample. By controlling the micro sample connection tool so that the mark made in advance and the mark on the sample are in a predetermined positional relationship, the apparatus operator can perform the unattended automatic operation instead of controlling it.

  For example, it can be automatically performed by controlling the micro sample connector, stage control, and nozzle in the work flow as shown in FIG. That is, the flow of transferring the micro sample is started (S100). First, a power source having a predetermined voltage is connected to the micro sample connector. For example, a power supply of −5V was used (S110). Next, the micro sample connector is brought close to the target micro sample and brought into surface contact (S120). At this time, at least a part of the shape of the micro sample connector is registered as described above, and the tip of the micro sample connector can be easily moved to the target position by interlocking with the moving means of the micro sample connector. Can do. For shape registration, it is important to accurately recognize the shape of the tip itself or the mark on the tip, and in order to control this with high accuracy, it is necessary to create an artificial or geometric shape that is difficult to appear on the sample. It is important to.

  After confirming the contact, the micro sample connector is separated from the sample, and the micro sample is separated from the sample substrate. The micro sample is moved with the micro sample connected to the micro sample connector, and the micro sample is transferred (S130). The micro sample connector is moved so that the micro sample comes into contact with the member to which the micro sample is to be transferred in a desired posture (S140). After the micro sample comes into contact with the micro sample fixing tool, the sample is fixed by an adhesion means such as a deposition film, and the micro sample connecting tool is separated from the micro sample (S150). By such a procedure, the transfer of the micro sample is completed, and the series of flows is completed (S160).

The figure which shows the structural example of the micro sample transfer apparatus by this invention. The figure which shows the example of the micro sample connection tool by this invention. The figure which shows the example of the micro sample connection tool by this invention. The figure which shows the example of the micro sample connection tool by this invention. The figure explaining the manufacturing method of the flat micro sample connection tool by this invention. The figure explaining another manufacturing method of the flat micro sample connection tool by this invention. Explanatory drawing of the sample preparation method by this invention. Explanatory drawing of the sample preparation method by this invention. Explanatory drawing of the sample preparation method by this invention. Explanatory drawing of the contact of another example of the micro sample connection tool by this invention, and a sample, and the connection method. The flowchart which shows the sample transfer procedure by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Micro sample transfer apparatus, 2 ... Sample stage, 3 ... Sample, 4 ... Ion beam irradiation system, 6 ... Micro sample connector, 7 ... Micro sample connector drive mechanism, 17 ... Micro sample connector power supply, 18 ... Flat plate Stocker 41 ... Micro sample connector base, 42a, 42b ... Branch micro sample connector, 43 ... Micro sample, 44a, 44b ... Contact point, 45 ... Surface micro sample connector base, 46 ... Contact surface, 51 ... Uniform thin wire , 51 ′: surface micro sample connector, 52, contact surface, 53, sample surface, 54, focused ion beam, 61, micro sample, 63, sample substrate, 64, micro sample connector, 65, flat plate, 67, micro Sample connector base, 68 ... external power source, 69 ... drive mechanism, 120 ... micro sample connector drive mechanism, 121 ... micro sample connector base, 122 ... tip micro sample connector, 123 ... micro sample

Claims (23)

A vacuum sample chamber containing the sample;
A micro sample connector having a tip portion branched into a plurality, and the apexes of the tip portion being aligned on a plane;
A drive mechanism for moving the micro sample connector in the vacuum sample chamber;
A power source for applying a voltage to fuse between the micro sample connector and the sample;
I have a,
The micro sample connection device is characterized in that the sample is fused by at least one tip portion of the tip portions, and the sample is pressed by the remaining tip portion . 2. The micro sample transfer apparatus according to claim 1, wherein the tip portion is bifurcated or trifurcated. A vacuum sample chamber containing the sample;
A micro sample connector having a plane in surface contact with a portion of the micro sample to be separated from the sample;
A microscope capable of observing the minute sample;
A drive mechanism for moving the micro sample connector in the vacuum sample chamber;
A power source for applying a voltage to fuse between the micro sample connector and the micro sample;
I have a,
The micro sample connection device is characterized in that the sample is fused in a partial area of the plane and the sample is pressed in the remaining area . 4. The micro sample transfer device according to claim 3 , wherein the micro sample connector has a substantially cylindrical or substantially conical member, and a tip portion of the member is a flat surface in contact with the micro sample. A micro sample transfer device. 4. The micro sample transport device according to claim 3 , wherein the micro sample connector has a prism portion in surface contact with the micro sample. 4. The micro sample transport apparatus according to claim 3 , wherein the micro sample connector has a flat plate portion that is in surface contact with the micro sample, and a base portion that supports the flat plate portion. A sample stage on which the sample is placed;
A vacuum sample chamber containing the sample stage;
A micro sample connector for holding and transferring a micro sample separated from the sample;
A drive mechanism for moving the micro sample connector in the vacuum sample chamber;
A focused ion beam irradiation system for sample processing;
An electron beam irradiation system for sample observation;
A gas supply means for supplying a source gas for forming a deposition film;
And a conductive you apply a voltage source to fuse between the micro-sample connector and placed on the sample to the sample stage,
The micro-sample connecting device,
The tip has a plurality of branched ends, and the apexes of the tips are aligned on a plane , and the sample is fused with at least one of the tips, and the remaining tips are Hold down the sample, or
A flat surface that is in surface contact with a part of a micro sample separated from the sample, the sample is fused in a part of the plane, and the sample is pressed in the remaining area. A micro sample transfer device. 8. The micro sample transfer device according to claim 7, wherein the tip portion is bifurcated or bifurcated. 8. The micro sample transfer device according to claim 7 , wherein the micro sample connector has a substantially cylindrical or substantially conical member, and a tip portion of the member is a flat surface in contact with the micro sample. A micro sample transfer device. 8. The micro sample transport device according to claim 7 , wherein the micro sample connector has a prism portion that is in surface contact with the micro sample. 8. The micro sample transport device according to claim 7 , wherein the micro sample connector has a flat plate portion that is in surface contact with the micro sample, and a base portion that supports the flat plate portion. 12. The micro sample transfer device according to claim 11 , wherein the flat plate portion is prepared in advance in the vacuum sample chamber, and the flat sample portion and the base portion are fixed in the vacuum sample chamber to form the micro sample connector. A micro sample transfer device. 8. The micro sample transfer device according to claim 7 , wherein a contact portion of the micro sample connector with the micro sample is made of a conductive material or silicon. 8. The micro sample transfer device according to claim 7 , further comprising a micro sample installation tool for transferring the micro sample held and moved by the micro sample connection tool in the vacuum sample chamber. A flat surface of a micro sample connector is brought into surface contact with a sample accommodated in a vacuum sample chamber, and a voltage is applied between the sample and the micro sample connector to apply the sample in a part of the plane. Fusing and holding the sample in the micro sample connector by pressing the sample in the remaining area, moving the sample to a desired position by moving the micro sample connector holding the sample, A method of transferring a micro sample, wherein the sample is fixed at the desired position, and the micro sample connector is moved away from the sample to be separated from the sample. The micro sample transfer method according to claim 15 , wherein the micro sample connector is brought into surface contact with a side surface of the sample. 16. The micro sample transfer method according to claim 15 , wherein a contact member of the micro sample transfer tool that contacts the sample is prepared in the vacuum sample chamber, and the contact member is provided at a tip of the micro sample transfer tool in the vacuum sample chamber. A method for transferring a micro sample, wherein the sample is fixed. A surface of a micro sample connector is brought into surface contact with a micro sample to be separated from a sample accommodated in a vacuum sample chamber, and a voltage is applied between the sample and the micro sample connector to partially The sample is fused in the region, and the sample is held in the remaining region to hold the micro sample on the micro sample connector, the micro sample is separated from the sample, and the micro sample is held. A micro sample connector is driven to bring the micro sample into contact with a fixing table, the micro sample is fixed to the fixing table, and the micro sample connector is moved away from the micro sample to be separated from the micro sample. A method for transferring a micro sample, comprising: 19. The micro sample transfer method according to claim 18 , wherein the micro sample connector is brought into surface contact with a side surface of the micro sample. 19. The micro sample transfer method according to claim 18 , wherein a contact member of the micro sample transfer tool that comes into contact with the micro sample is prepared in the vacuum sample chamber, and the contact member is provided at the tip of the micro sample transfer tool in the vacuum sample chamber. A method of transferring a micro sample, characterized in that the sample is fixed to a surface. A sample accommodated in a vacuum sample chamber is processed with a focused ion beam and cut out from the sample in a state where the sample is connected to a support, and a surface of the micro sample connection tool is brought into surface contact with the micro sample. A voltage is applied between the micro sample connection tool and the sample is fused in a part of the plane, and the sample is held in the remaining area to hold the micro sample in the micro sample connection tool. The micro sample is separated from the sample by irradiating the support portion with a focused ion beam and cut, and the micro sample connector to which the micro sample is connected is moved so that the micro sample is fixed. A method of forming a beam-assisted deposition film in a contact region between the micro sample and the fixing table to fix the micro sample to the fixing table, and separating the micro sample connector from the micro sample. Micro sample transfer method moves and separating from the micro sample to. The micro sample transfer method according to claim 21 , wherein the micro sample connector is brought into surface contact with a side surface of the micro sample. 23. The micro sample transfer method according to claim 21 , wherein a contact member of the micro sample transfer tool that is in contact with the micro sample is prepared in the vacuum sample chamber, and the contact member is provided at the tip of the micro sample transfer tool in the vacuum sample chamber. A method of transferring a micro sample, characterized in that the sample is fixed to a surface.

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