JP2006120391A - Normally closed micro sample holder made with MEMS - Google Patents

Abstract

PROBLEM TO BE SOLVED: To operate a mechanism without requiring a high voltage, without damaging the sample when gripping the sample, and without losing or losing a fine sample due to human error In addition, the present invention provides a safe and quick method for handling TEM specimens, and also provides a structurally simple micro sample holder for realizing it.
A normally closed micro sample holder of the present invention is manufactured by a semiconductor silicon process technology, and has a tip member composed of two needle-like bodies 1a and 1b for holding a sample, The two needle-like bodies are always arranged close to each other or facing each other with a predetermined gap, and include electrostatic actuators 2a and 2b that drive the two needle-like bodies apart when a voltage is applied between the electrodes. When the voltage is applied, the interval between the two needle-like bodies is opened, and when the voltage is released, the interval is returned by the elastic force.
[Selection] Figure 1

Description

  The present invention is attached to an analysis apparatus such as a focused ion beam (FIB) apparatus, a scanning electron microscope (SEM), a transmission electron microscope (TEM), or a scanning probe microscope (SPM), and separates a minute sample. The present invention relates to a normally closed micro sample holder having a micro sample holding function during handling such as extraction and storage, and processing and observation of a micro sample.

  For processing a TEM sample, it is possible to cut out a part of a conductor wafer from a conductive wafer while observing it with a scanning electron microscope (SEM) or a scanning ion microscope (SIM), and to transfer it to a sample stage and fix it. This is done when cutting out defective defects. As a means for transferring such a finely extracted sample, there is one configured by using a single or a plurality of bimorph piezoelectric elements. For example, Patent Document 1 discloses a probe with good operability that can automatically correct a deviation DY in the circumferential direction around the fulcrum of the bimorph piezoelectric element 102 caused by the bending of the bimorph piezoelectric element and can be applied to fine operations. For the purpose of providing a moving device and a micro tweezers device, a strain gauge element 103 and a correction circuit 105, in which a bimorph piezoelectric element 102 is disposed in the expansion / contraction direction of the multilayer piezoelectric element 101 and attached to both surfaces of the bimorph piezoelectric element. And a correction amount is generated, and the movement trajectory of the probe tip is linearly displaced by expansion and contraction of the stacked piezoelectric element. Although this transfer means has been devised in terms of operability, since it uses a piezoelectric element for driving, it affects the vicinity of the sample by the optical system such as SEM or SIM drift, or causes electrical breakdown of the sample. It is necessary to apply a high voltage that causes this. In addition, it is necessary to adjust the position and shape of the tip to grasp the sample.

  In addition, Patent Document 2 aims to provide an apparatus and method for separating, extracting, and storing a micro sample piece reliably and stably without contaminating the micro sample piece and / or its surrounding area. The sample piece including the region to be observed is separated by ion beam sputtering, the sample is pushed in, held, pulled out and separated, and the tip is narrower than the root and the tip is cracked. In order to extract the sample piece from the sample substrate and place the sample piece by using a needle member made of a rod-like member that holds the sample piece by a force due to elastic deformation of a portion holding the sample piece obtained by the shape A technique is disclosed in which the sample piece is stored by separating the needle member and the sample piece after being moved onto the mounting table. This transfer means does not require the application of high pressure when gripping a micro sample. Further, the present invention does not require fixation between the probe and the sample piece by a method of depositing a component in gas called CVD (Chemical Vapor Deposition) at the beam irradiation position, and the working time is shortened as compared with that method. However, since the sample piece is gripped in the form of pressing tweezers sandwiched between the cracks, the operation of manipulating the manipulator while observing with a microscope requires considerable skill. Further, when releasing the sample piece, it is necessary to cut off the tip of the needle by FIB etching. Furthermore, the size and shape of the crack must be changed depending on the size and shape of the sample, and an excessive force may be applied when the sample piece is sandwiched to damage the sample piece.

Furthermore, in Patent Document 3, the sampling operation of the sample piece performed after the preparation of the sample piece by the focused ion beam can be accurately performed at low cost by a simple method in the atmosphere, and the high magnification observation of the TEM can be performed. In order to make it possible to perform additional processing of the sample piece, the surface of the sample substrate is irradiated with a focused ion beam to produce a fine sample piece, which is then transported under an optical microscope in the atmosphere. Under this optical microscope, using a micromanipulator that has a plurality of finger pieces and at least one of the finger pieces can perform a fine three-degree-of-freedom operation, the sample piece is extracted from the sample substrate and used for transmission electron microscope observation. A technique for fixing to a grid is disclosed. However, it is possible to operate the micromanipulator with the complicated mechanism presented here to move at least two arms and align the tips of the micromanipulator to perform operations such as gripping, transferring, and releasing fine sample pieces. It is not easy and requires considerable skill.
JP 2000-2630 A (2nd page, FIG. 1) JP 2002-333387 A (page 6, FIG. 3) JP 2003-65905 A (page 4, FIG. 1)

  The problem to be solved by the present invention is to provide a micro sample pick-up mechanism of an analyzer that overcomes the disadvantages of the above-described conventional mechanism, that is, when a sample is gripped without requiring a high voltage to drive the mechanism. Providing a safe and rapid handling method for TEM specimens that does not cause damage, and does not require the skill of operation to break or lose minute samples due to human error. Another object of the present invention is to provide a small sample holder that is structurally simple.

The normally closed micro sample holder of the present invention has a tip member composed of two needle-like bodies for holding a sample, and the two needle-like bodies are always arranged close to each other or with a predetermined gap therebetween. And an electrostatic actuator for driving the two needle-like bodies away from each other. When a driving force is applied, the interval between the two needle-like bodies is opened, and when the driving force is released, the structure has elasticity. The interval is restored by force.
The actuator was an electrostatic actuator.
The normally closed micro sample holder is manufactured by semiconductor silicon process technology. For this reason, the two positions of the tip portion made of the needle-like body of the sample holder are aligned when the sample is picked up and held.
The normally closed micro sample holder of the present invention forms the basic shape of the holder with a lithographic mask pattern, and performs fine adjustment of the size and shape of the structure including the electrostatic actuator portion and the tip shape by FIB processing. did.
In addition, the normally closed micro sample holder of the present invention includes one in which the tip portion composed of two needle-like bodies is connected at the stage of being manufactured by the semiconductor silicon process technology.

The method for adjusting the holding force of the normally closed micro sample holder of the present invention allows the holding force to be adjusted by changing the amount of the gap when the connected tip is cut and separated by FIB processing.
The method of using the normally closed micro sample holder of the present invention is used in TEM sample preparation as a micro sample cut out from a sample that is installed in an FIB apparatus and transferred onto a sample stage.
Another usage of the normally closed micro sample holder of the present invention is installed in an FIB apparatus, and is used for FIB processing by picking up and holding a micro sample.
Another usage of the normally closed micro sample holder of the present invention is installed in a TEM apparatus, and is used for TEM observation by picking up and holding a micro sample.

Since the normally closed micro sample holder of the present invention employs an electrostatic drive system, the applied voltage is lower than that of a conventional piezoelectric element drive and is less affected by damage to the sample. In addition, since the operation is a so-called normally closed sample holder in which the interval between the two needle-like bodies is opened when a voltage is applied between the electrodes, and the interval is returned by an elastic force when the voltage is released. It is only necessary to apply a voltage when holding the sample and releasing the sample. During the operation of separating, extracting and storing the minute sample piece, the sample piece is held by its own elastic force without applying electricity. Therefore, the holder grips the sample piece in a stable state and becomes an energy saving form.
Further, the normally closed micro sample holder of the present invention is manufactured by semiconductor silicon process technology, so that it can be manufactured in an arrangement in which the tip portions of two needle-shaped bodies are accurately opposed at a desired interval. Can produce a precise structure with a desired size precisely, and at the same time, many uniform products can be produced. Therefore, the micro sample holder which is a consumable can be stably supplied at low cost.
Furthermore, the normally closed type micro sample holder of the present invention is formed with a basic shape of the holder by a lithographic mask pattern and finely adjusted by FIB processing. Alternatively, the holding force of the holder can be adjusted.
In addition, the normally closed micro sample holder of the present invention has a variety of types depending on the micro sample to be handled, since the tip portion composed of two needle-like bodies is connected at the stage of being manufactured by the semiconductor silicon process technology. Can take a good response. That is, when cutting and separating the connected tip portions by FIB processing, the clamping force as a micro sample holder can be adjusted by changing the gap amount. This form and the adjustment method are not limited to electrostatic actuators but are also effective for thermal drive and piezoelectric drive types.

The normally closed micro sample holder of the present invention installed in the FIB apparatus has the effect of stably gripping the micro sample in a non-energized state. Therefore, the sample is picked up from the sample and picked up. In the preparation of a TEM sample to be fixed on a table, it can be suitably used as a pick-up / transfer means for separating, extracting and storing the small sample piece.
Further, the normally closed micro sample holder of the present invention installed in the FIB apparatus has an effect of stably holding the micro sample in a state where the actuator is not driven, so that the micro sample is fixed to the sample stage. The additional processing by the FIB of the minute sample can be executed in a state where the pickup is held without any trouble.
The normally closed micro sample holder of the present invention installed in the TEM apparatus has the effect of stably gripping the micro sample with the actuator not driven, so that the micro sample is not fixed to the sample stage. TEM observation of the minute sample can be executed while the pickup is held.
Further, the normally closed micro sample holder of the present invention installed in the FIB apparatus and TEM apparatus is equipped with the effect of stably holding the micro sample when the actuator is not driven. Can be continuously executed in the same chamber for additional processing by FIB and TEM observation of the minute sample in a state of picking up and holding without fixing to the sample stage, and the sample test can be performed with greatly reduced working time I can do it.

  In order to solve the above-described problems, the present invention employs a normally closed holder having an electrostatic actuator in a gripping portion of a pickup mechanism in an analysis / observation apparatus such as an FIB or SEM that requires handling of a minute sample. This is what I came up with. Since the electrostatic driving method is adopted, the voltage required for driving at the same level as that of the conventional piezoelectric element driving can be reduced by orders of magnitude, and the influence of damage to the sample is small. In addition, the normally closed holder has a so-called washing pinch shape, which requires force only when pinching and removing it, and is always held by its own spring force. It is the reverse action of the one opened by the spring force. The normally closed type fine sample holder of the present invention includes a pair of needle-like bodies for holding a sample as in the model shown in FIG. 1A, and an electrostatic actuator for driving the two needle-like bodies 1a and 1b away from each other. 2a and 2b. The electrostatic actuators 2a and 2b have comb-like electrodes that are intricately opposed to each other. With this structure, the driving force is simply increased as compared to the two plate electrodes. When a voltage is applied between the electrodes, the two needle-like bodies 1a and 1b are driven away from each other, and both intervals are opened so as to sandwich the sample. When the voltage application is released, the driving force of the electrostatic actuator disappears, and it tries to return to the original interval between the two needle-like bodies 1a and 1b. At that time, if there is a sample in the gap, it will be held, but the holding force is the difference between the interval between the two needle-like bodies 1a, 1b and the original interval when the sample is held. The amount of elastic deformation is a value corresponding to this. This normally closed sample holder only needs to apply a voltage when holding the sample and releasing the sample. Hold the sample piece. Since the sample gripping by its own elastic force is a static operation, the operation is constant and stable. However, since the clamping force is determined by the thickness of the sample to be gripped and the elastic coefficient and shape of the holder material, the two needle-like bodies when there is no power applied so that an appropriate clamping force acts in relation to the sample to be gripped. The shape of the holder, such as the distance between the tips, is an important design factor.

The normally closed micro sample holder of the present invention has one feature in that it is manufactured by a semiconductor silicon process technology. The present invention applies a micromachine manufacturing technology that handles recent nano-order samples, a technology called MEMS (Micro Electro Mechanical Systems), specifically, a semiconductor manufacturing technology manufactured by a lithographic technique. In this semiconductor silicon process technology, a two-dimensional pattern can be constructed in a laminated form to form a three-dimensional microstructure. Since the minute sample holder must hold and hold a minute sample piece, the tip portions of the holder are arranged at positions close to each other. Since the normally closed micro sample holder of the present invention is manufactured by semiconductor silicon process technology, it can be driven accurately by an electrostatic actuator in the substrate direction.
FIG. 1B is a model of a normally closed micro sample holder according to the present invention manufactured by semiconductor silicon process technology. The two needle-like bodies 1a and 1b are aligned at the center, and flat electrostatic actuators 2a and 2b are arranged on both sides so as to sandwich the two needle-like bodies 1a and 1b, and the electrostatic actuator 2a , 2b and the two needle-like bodies 1a, 1b are locally connected by a coupling member and formed in the same plane. In the electrostatic actuators 2a and 2b, the inner part connected to the needle-like bodies 1a and 1b by a coupling member is a movable part, and the outer part is a fixed part. Also, the base 1c opposite to the tip of the needle-like body 1a, 1b is connected, and when a voltage is applied to both electrodes of the electrostatic actuators 2a, 2b, the inner part is attracted to the outer part, and the force is It acts to widen the interval between the two needle-like bodies 1a and 1b via the coupling member. Then, the distal ends of the needle-like bodies 1a and 1b that are free ends are widened so that the sample can be sandwiched between them. It becomes a form which the front end side opened by being pulled. Subsequently, when voltage application to both electrodes of the electrostatic actuators 2a and 2b is stopped, the attractive force between the electrodes disappears, and the distance between the tips of the two needle-like bodies 1a and 1b is based on their own elastic force. Operates to return to 1d is formed of an insulator of SiO ₂ and is insulated from the two electrodes of the Si substrate, but is structurally connected and maintains the positional relationship between the tips 1a and 1b. The leaf spring structure shown in FIG. 1c is not limited to the shape shown in the figure, and a leaf spring may be formed in the same substrate as shown in FIG.

  This holder mechanism is attached to the tip of a manipulator in the observation apparatus or analysis apparatus. For example, as shown in FIG. 2, the manipulator is operated to move the minute sampling holder 3, and when the specific position of the semiconductor wafer is cut and processed, the operation of the manipulator is temporarily stopped (state A). When a voltage is supplied between the electrodes, the tip portions of the two needle-like bodies 1a and 1b are opened and the minute sample piece 5 is sandwiched. When the sample piece 5 is further moved and the supply of voltage is stopped in this state, the tip portions of the two needle-like bodies 1a and 1b return to their original intervals, and a minute sample can be held between them. . When the sample is clamped by the holder mechanism, the manipulator is operated to pick up the micro sample from the main body and transfer it to the position of the sample stage. Next, after the sample is positioned on the sample stage 4, the minute sample piece 5 is fixed by CVD using FIB. Therefore, when a voltage is supplied between the electrodes, the tip portions of the two needle-like bodies 1a and 1b are opened and placed on the fixed surface of the sample table 4 in an arbitrary posture by opening the fine sample piece 5 held between them. be able to. (State B) The thin sample piece fixed on the sample stage 4 is irradiated with FIB to perform thinning processing in order to obtain electron transmission in TEM observation. (State C)) A TEM sample is prepared by the above process.

  The normally closed micro sample holder of the present invention clamps a sample piece with the driving force of the electrostatic actuator released, and the clamping force is determined by the thickness of the sample to be gripped, the elastic coefficient and shape of the holder material. Therefore, the shape of the holder is an important element in design, such as the distance between the tip portions of the two needle-like bodies when there is no electric power, so that an appropriate clamping force acts in relation to the sample to be gripped. In the present invention, since this holder structure is manufactured by a semiconductor silicon process technology, the shape of the holder, such as the distance between the tip portions of two needle-like bodies, is designed in consideration of the elastic coefficient of silicon. Made to. The basic shape of the holder is formed by a mask pattern for lithography, and necessary fine adjustment can be performed by FIB etching. FIG. 3A shows the shape of the tip of the two needle-like bodies, but it is not necessary to have such a prismatic shape and can be designed as appropriate. FIG. 3B shows the two needle-like bodies 1a and 1b having different tip-to-tip distances and tip shapes, but the left side shows a closed state with no electrification, and the right side drives the electrostatic actuator. The open state is shown. If there is a micro sample to be gripped between the open needle-like body tips, the micro sample is clamped to return to the closed state when the voltage application is stopped. This clamping force varies depending on the amount of clearance in the closed state with no applied electricity. That is, the distance between the tip portions of the two needle-like bodies 1a and 1b when the sample is sandwiched differs depending on the thickness of the micro sample to be gripped, and the difference between the value and the clearance in the closed state without applying electricity Is the amount of elastic deformation. Since the clamping force has a value corresponding to this, in order to obtain an appropriate clamping force, it is important to adjust the amount of clearance in the closed state in accordance with the thickness of the minute sample to be handled.

  The merit of producing the normally closed micro sample holder of the present invention by the semiconductor silicon process technology is that not only precise work is possible, but also many of the same can be manufactured simultaneously. As shown in FIG. 3C, the tip member composed of two needle-like bodies is connected by a semiconductor silicon process technology, the interval amount according to the sample is adjusted, and the tip shape is also Similarly, by appropriately adjusting the FIB processing, the same parts can be supplied as holders with various clamping forces by simple processing, and the tip shape does not have to be changed at the MEMS process stage according to the sample. , Can reduce the cost.

  The FIB apparatus in which the normally closed micro sample holder 3 according to the present invention is attached to the micromanipulator 7 is shown in the center of FIG. Since the normally closed micro sample holder 3 according to the present invention is attached to the micro manipulator 7, the micro sample 5 cut out from the sample body is picked up for use in the TEM sample preparation as shown in FIG. Then, the sample can be transferred and fixed on the sample stage 4 to perform the thinning process. At the same time, the FIB processing of the tip shape shown in FIG. 3 can be processed or changed according to the sample. As an effective utilization method of the present embodiment, in the micro sample holding form shown on the right side of FIG. 4, the micro sample 5 can be reprocessed as it is without being fixed to the sample stage. As a conventional common sense, a micro sample picked up is fixed on a sample stage and then reprocessed. However, if it is the form of a present Example, it is not necessarily fixed to a sample stand, and it is possible to implement FIB processing as it is under a stable holding state. This saves the trouble of fixing to the sample stage by a method such as CVD using FIB, and can greatly increase the efficiency of work. Note that the micro sample 5 is thinned at a location where TEM observation is desired, so that the sample holder can be reused after observation by avoiding irradiation of the beam to the location gripped by the sample holder.

  FIG. 5 shows a TEM apparatus in which a normally closed micro sample holder according to the present invention is attached to a micromanipulator. The TEM device is in the upper center. By holding the sample stage 4 by the micromanipulator arranged in the TEM apparatus, it is possible to observe the TEM sample in a form in which the micro sample piece 5 created by the FIB apparatus is fixed to the sample stage 4 in the TEM apparatus. As a matter of course, according to the apparatus of the present embodiment, the minute sample piece 5 is held by the normally closed minute sample holder 3 as shown on the left side of the drawing without fixing the minute sample piece 5 to the sample table 4. TEM observation can be performed in the state of being performed. Since the normally closed micro sample holder 3 according to the present invention has a function of holding the micro sample piece 5 by its own elastic force without applying electricity, it replaces the conventional TEM sample fixed to the sample stage 4. The normally closed micro sample holder 3 according to the present invention can also serve as the role. Furthermore, it can be separated from the micromanipulator and managed as an individual TEM sample. By using this sample holder 3, the same process as before is performed until the sample is picked up after sample processing. However, since the sample does not need to be moved and re-fixed, the process up to the TEM observation is shortened. Shortening and risk of sample loss can be reduced.

  Next, FIG. 6 shows an embodiment in which the normally closed micro sample holder according to the present invention is mounted on the conventional TEM holder 8 as a mesh and used as a TEM sample. The minute sample holder 3 is installed at the distal end portion 9 of the TEM holder 8 and is inserted into the sample chamber 11 of the TEM 10 and observed. In this method, since the TEM sample processed by the FIB apparatus can be immediately fitted into the TEM holder 8 and observed, it has an advantage that necessary reworking that can be understood only by TEM observation can be efficiently performed. In this embodiment of the normally closed micro sample holder according to the present invention, as shown in FIG. 2, the sample is picked up from the main body sample 6 and held on the sample stage 4 in the form of holding the micro sample piece 5 in the non-energized state. It is possible to omit the fixing step, execute the thinning process by FIB directly in the state of being held by the micro sample holder 3, and perform the TEM observation as it is while holding the micro sample. Efficiently more efficient than conventional procedures for cutting out sample pieces with FIB equipment, picking them up and fixing them to the sample stage, thinning with FIB, transferring to TEM equipment 10, evacuating the chamber, and TEM observation Processing observation can be executed. When the normally closed micro sample holder is used as a mesh for a general-purpose TEM holder 8, the convenience can be improved without changing the conventional apparatus, and the time required for sample preparation can be greatly reduced.

It is a figure which shows the model of the normally closed type fine sample holder which concerns on this invention. It is a figure explaining the TEM sample preparation process by the FIB apparatus provided with the normally closed type fine sample holder which concerns on this invention. It is a figure explaining the front-end | tip part shape of the normally closed type fine sample holder which concerns on this invention, and its clamping force. It is explanatory drawing of FIB apparatus provided with the normally closed type fine sample holder which concerns on this invention. It is explanatory drawing of the TEM apparatus provided with the normally closed type fine sample holder which concerns on this invention. It is explanatory drawing in the case of using the sample holder which clamped the TEM sample corresponding to the conventional TEM sample holder. It is a figure which shows the conventional pick-up mechanism driven using a piezoelectric element.

Explanation of symbols

1a, 1b Needle-like body 1c Leaf spring structure
1d Insulation connecting material 2a, 2b Electrostatic actuator 3 Micro sample holder 4 Sample stand 5 Cut sample piece 6 Sample body 7 Micromanipulator 8 General-purpose TEM holder 9 TEM holder tip 10 TEM
11 TEM sample chamber

Claims (9)

  It has a tip member composed of two needle-like bodies for gripping the sample, and the two needle-like bodies are always arranged close to each other or facing each other with a predetermined gap, and the two needle-like bodies are separated from each other. A normally-closed type characterized in that an interval between the two needle-like bodies is opened when a driving force is applied, and the interval is returned by an elastic force of the structure when the driving force is released. Small sample holder.   The normally closed micro sample holder according to claim 1, wherein the actuator is an electrostatic actuator.   The normally closed type according to claim 2, wherein the basic shape of the holder is formed by a mask pattern for lithograph, the structure including the electrostatic actuator portion is finely adjusted by FIB processing, and the size and shape of the tip shape are finely adjusted. Small sample holder.   An actuator for driving the two needle-like bodies apart is provided. When a driving force is applied, the interval between the two needle-like bodies is opened, and when the driving force is released, the actuator is generated from an elastic structure included in the structure. An intermediate member of a normally closed micro sample holder whose interval is returned by an elastic force, and the tip of two needle-like bodies are connected at the stage of being produced by a semiconductor silicon process technology. Closed micro sample holder member.   A basic shape of a holder consisting of a tip member connected to the tip of two needle-like bodies for holding a sample and an actuator connected to the tip member is manufactured by a semiconductor silicon process technology using a mask pattern for lithography. When the member composed of the two needle-like bodies connected to the tip is cut and separated by FIB processing, the holding force is appropriately adjusted by changing the gap amount by cutting of the FIB etching processing. A manufacturing method of a normally closed micro sample holder characterized by the above.   A fine sample represented by a TEM sample cut out from a sample is installed in the FIB apparatus, and includes an actuator that drives the two needle-like bodies apart. When a driving force is applied, the two needle-like bodies A normally closed micro sample, which is picked up by a normally closed micro sample holder whose interval is opened and the interval is closed by an elastic force when the driving force is released, and is transferred onto a sample stage to produce a TEM sample. How to use the holder.   There is an actuator installed in the FIB device that drives the two needle-like bodies apart. When a driving force is applied, the interval between the two needle-like bodies opens, and when the driving force is released, an elastic force is applied. A method for using a normally closed micro sample holder, characterized in that a micro sample is picked up and held by a normally closed micro sample holder whose interval is returned, and FIB processing is performed with the sample held.   There is an actuator installed in the TEM device that drives the two needle-like bodies apart. When a driving force is applied, the interval between the two needle-like bodies opens, and when the driving force is released, an elastic force is applied. A method for using a normally closed type micro sample holder, characterized in that observation is performed by picking up and holding a micro sample whose observation site has been thinned by FIB processing with a normally closed type micro sample holder whose interval is returned.   An actuator that drives the two needle-like bodies away from each other. When a driving force is applied, the interval between the two needle-like bodies opens, and when the driving force is released, the interval is returned by an elastic force. An FIB device attached to a micromanipulator for moving the sample holder by the sample holder.

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