JP4319555B2 - Tweezers, manipulator system provided with tweezers, and manufacturing method of tweezers - Google Patents

Description

  The present invention relates to tweezers for holding a sample having a fine dimension necessary for observation with an electron microscope such as a transmission electron microscope (TEM), a manipulator system including the tweezers, and a method for manufacturing tweezers.

Conventionally, a sample for TEM observation produced by a focused ion beam (FIB) is taken out into the atmosphere, and then electrostatically adsorbed to, for example, a glass micropipette and attached to a sample holder for TEM. It was.
Also, as a method for picking up a sample from the FIB, in addition to the above-described method using a micropipette, for example, picking up by fixing the probe tip and the sample with a deposition film, or holding the sample with tweezers A probe moving device that can be used (for example, see Patent Document 1) is known. Furthermore, a micro tweezer having a force sensor for detecting a holding force when a sample is sandwiched is known (for example, see Patent Document 2).
JP 2000-2603 A (paragraph number 0024-0025, FIG. 4 etc.) JP-A-11-300662 (paragraph numbers 0013-0023, FIGS. 1-2)

However, since the tweezers used in the probe moving device described in Patent Document 1 cannot detect the clamping force (contact force) when clamping the sample, the sample or the tweezers themselves are too tightly clamped. There was a possibility of adversely affecting. In addition, by pinching strongly, the tips of the tweezers may cross each other and the sample may not be stably pinched. On the other hand, there was a case where the force to pinch was weak and it was not possible to pinch the sample. As described above, since the force of pinching of the tweezers cannot be detected, the person who operates the tweezers is limited to a skilled worker, or the sample preparation takes time due to trial and error in which the pinching operation is repeated many times. was there.
In addition, when an insulator is used as the material constituting the tweezers, there is a possibility that the image is distorted due to charge-up and that it is more difficult to hold the sample. Since the sample is charged with static electricity, it sticks to the tweezers, and it is difficult to release from the tweezers, or the sample and the tweezers may be adversely affected by the static electricity.

  On the other hand, the above-mentioned patent document 2 discloses a tweezers having a force sensor, and the force sensor can detect the holding force of the tweezers. No specific configuration such as how to integrally mold is shown, and it is difficult to actually realize microtweezers. In particular, when the sample is an electron microscope observation sample, the dimensions thereof are extremely small. Therefore, the tweezers corresponding to the sample are configured only by the disclosure information of the micro tweezers described in Patent Document 2. It is impossible.

  The present invention has been made in view of such circumstances, and an object of the present invention is to make it possible to easily and accurately detect a clamping force (clamping force) and to reduce the size of the tweezers. A manipulator system provided with the same and a manufacturing method of tweezers are provided.

The present invention provides the following means in order to solve the above problems.
The tweezers according to the present invention is a tweezers capable of holding a sample for observation with an electron microscope , and is adjacently arranged at a predetermined interval, has a holding surface for holding the sample at the tip of each facing side , and is long. sectional area perpendicular to the direction is formed between the small stress concentration portion is proximal and distal ends than the other part is a pair of bar-shaped clamping member made of a semiconductor material, the stress of at least one rod-like clamping member A piezoresistor that is arranged in a concentrating portion and detects a change in electrical characteristics of the pair of rod-shaped clamping members that have changed according to a gripping force when the sample is clamped, and the piezoresistor comprises: It is formed by adding impurities to the semiconductor material, and the base end side is branched into two so as to be U-shaped in plan view, and wirings are electrically connected to the branched portions, respectively. And

In the tweezers according to the present invention, when the sample is clamped between the clamping surfaces, the internal stress corresponding to the clamping force acts on each of the rod-like clamping members to cause distortion. At this time, since the rod-shaped holding member is made of a semiconductor material, the strain appears as a change in electrical characteristics according to the characteristics of the semiconductor material, for example, a change in resistance value. Since the piezoresistor incorporated in at least one of the rod-like holding members detects this change in electrical characteristics, the holding force of the pair of rod-like holding members can be detected easily and reliably. Accordingly, conventional or too strongly sandwich the sample, as, going sandwiches are no problems such as or not be nipped, it is possible to sandwich the sample reliably predetermined clamping force regardless of the operator. In particular, since the rod-shaped clamping member is made of a semiconductor material, it is not only easy to manufacture in a small size, but also has a built-in piezoresistor, so that distortion, that is, clamping force can be detected with high accuracy. can do.

Moreover, when the sample is clamped, the internal stress acting on the rod-shaped clamping member acts intensively on the stress concentration portion having a small cross-sectional area. Thereby, even if the sample is clamped with a very small clamping force, the piezoresistor can be detected as a large change in electrical characteristics. Therefore, it is possible to detect the clamping force of the rod-shaped clamping member with higher accuracy.

In addition, since the base end side of the piezoresistor is branched into two, and the wiring is electrically connected to each of the base end side, the wiring and the piezoresistor are formed in a U shape. Arranged. Thereby, a current path for a current flowing from one wiring to the other wiring through the piezoresistor is secured. In other words, since current can flow over the entire region from the proximal end side to the distal end side of the piezoresistor , electrical characteristics can be detected with high sensitivity when the sample is sandwiched, and further accuracy can be improved. it can.

The tweezers according to the present invention is characterized in that, in the tweezers according to the present invention, a conductive film capable of being electrically connected to the ground is formed on the clamping surface.
In the tweezers according to the present invention, even if the sample is charged with static electricity, the conductive film can be connected to the ground, so that static electricity can be released. Therefore, as in the prior art, the clamping surface and the sample can be prevented from sticking to each other due to static electricity, so that the sample can be easily clamped and released. Further, for example, even in the FIB, the charge-up is reduced by the conductive film and the distortion of the image is suppressed, so that the sample is easily sandwiched.

Further, the tweezers according to the present invention is the tweezers according to the present invention, wherein the pair of rod-shaped clamping members are formed so that the clamping surfaces are parallel to each other when the sample is clamped. It is a feature.
In the tweezers according to the present invention, when the sample is clamped, the clamping surfaces of each other are in a parallel state, so that the sample can be clamped by surface contact. Therefore, the contact area between the clamping surface and the sample increases, and the sample can be clamped more stably.

Further, the manipulator system according to the present invention is arranged at a proximal end side with respect to the tweezers of the present invention and the piezoresistor, and at least one of the rod-shaped clamping members is placed on the other side so that the clamping surfaces of each other are brought close to each other. A moving mechanism that can move to the rod-like holding member, a manipulator that holds the tweezers and can move to an arbitrary position, and the pair of rod-like holding members when the measured value of the piezoresistor reaches a predetermined value And a control unit that controls the moving mechanism so as to stop the approach.

In the manipulator system according to the present invention, after moving the tweezers to a desired position by the manipulator, the moving mechanism moves at least one of the rod-shaped clamping members to the other rod-shaped clamping member so that the clamping surfaces of each other are moved. The sample can be clamped by approaching. At this time, the moving mechanism, as well disposed proximal to the piezoresistor, since moving the rod-shaped clamping member in said position, piezoresistor, certainly the rod-shaped clamping member without being affected by the moving mechanism Can detect the strain acting on Therefore, the clamping force of the sample can be detected with high accuracy.
Further, the control unit stops the moving mechanism when the measured value of the piezoresistor reaches a predetermined value, that is, when the clamping force reaches a certain value, so that the sample is clamped with the optimum clamping force. be able to. Therefore, since an extra load is not applied to the sample and the tweezers, not only the sample is not scratched but also the reliability and durability of the tweezers can be improved.

The manipulator system according to the present invention is the manipulator system according to the present invention, wherein the tweezers include a piezoresistor that is the same as the piezoresistor, and is provided with a reference pin formed in a rod shape from a semiconductor material. The reference pin outputs a change in resistance value of the built-in piezoresistor that changes due to a temperature change around the pair of rod-shaped holding members as a reference value to the control unit, and the control unit A correction for removing a change in resistance value caused by a change in ambient temperature from the measured value is performed by subtracting the reference value from the measured value by the piezoresistor provided on the rod-shaped holding member. It is.
Oite the manipulator system according to the invention can be carried out because it corrects the resistance value variation due to ambient temperature changes a pair of rod-shaped clamping member, the measurement of the distortion of the more accurate the rod-shaped clamping member.

  The tweezers manufacturing method according to the present invention includes a tweezers according to the present invention, a silicon (Si) support substrate, and silicon dioxide (SiO 2) formed on the Si support substrate. ₂ ) And a Si active layer formed on the BOX layer, and an oxide film is formed on the Si active layer, and the oxide film is formed on the oxide film. A step of patterning the outer shape of the pair of rod-shaped holding members by photolithography, and after the step, selectively removing the Si active layer not masked by using the patterned oxide film as a mask, A pattern etching step for forming the pair of rod-shaped holding members, and after the step, the stress concentration of the pair of rod-shaped holding members formed so that the base end side branches into two and becomes U-shaped in plan view Forming a piezoresistor by adding impurities to the portion, and after the step, from the base end of the branched piezoresistor to the base end of the Si active layer Forming an insulating film and forming a contact hole in the insulating film to access a base end of the branched piezoresistor; and after the process, forming a base of the contact hole and the Si active layer on the insulating film Patterning a conductive layer between the ends and forming the wirings electrically connected to the base ends of the piezoresistors branched via contact holes, and after the step, And a removal step of selectively removing the BOX layer and the Si support substrate by etching so that the front end side of the rod-shaped holding member protrudes from the BOX layer and the Si support substrate.

  In the tweezer manufacturing method according to the present invention, the tweezers can be formed in a small size and with high accuracy by a semiconductor process. In addition, since the pair of rod-like holding members can be formed in the Si active layer having a preset thickness, a thin and highly accurate tweezers can be reliably formed. Further, by adding impurities by a thermal diffusion method or an ion implantation method, a piezoresistor can be easily formed using a semiconductor process.

According to the tweezers according to the present invention, the sample can be reliably clamped with a predetermined clamping force, and can be manufactured in a small size because it is formed of a semiconductor material. Moreover, since the piezoresistor is built in, the clamping force can be detected with high accuracy.
In addition, according to the manipulator system according to the present invention, the sample can be clamped with an optimal clamping force, and the reliability and durability of the tweezers can be improved as well as not scratching the sample.
Further, according to the tweezer manufacturing method of the present invention, the tweezers can be formed in a small size and with high accuracy by a semiconductor process.

A first embodiment of a tweezers and manipulator system according to the present invention will be described below with reference to FIGS.
The manipulator system 1 of the present embodiment is a transmission electron microscope (electron microscope) A and a sample 3 for observation by the transmission electron microscope A from a wafer-like sample substrate 2 as shown in FIGS. A sample preparation device B, a tweezers 4 that can hold the prepared sample 3, and a manipulator 5 that holds the tweezers 4 and can move to any position. It is provided in a chamber 6 that can be set in a vacuum state.

  The transmission electron microscope A is placed on a mesh 10 that is a holder for placing the sample 3, a moving mechanism 11 that moves the mesh 10 in the XY direction (horizontal direction) and the vertical direction (Z direction), and the mesh 10. An electron gun 12 that irradiates an electron beam (electron beam) in parallel with a focusing lens (not shown) toward the placed sample 3, various lenses (not shown) that observe and enlarge the electron beam that has passed through the sample 3, and observation of the electron beam An observation system (not shown) that performs the above and the like is provided. The moving mechanism 11 is controlled by the control unit 15.

  The sample preparation apparatus B includes a focused ion beam (FIB) irradiation optical system 20 for processing the sample 3 and observing an image, secondary electrons emitted from the sample 3 by the focused ion beam irradiation optical system 20, and 2 A secondary particle detector 21 for detecting secondary ions and the like, a deposition gas source 22 for supplying a raw material gas for forming a deposition film in the irradiation region of the FIB, and a stage 23 for fixing the sample substrate 2 on the upper surface are provided. Yes.

The focused ion beam irradiation optical system 20 can irradiate a FIB of about 1 μm by, for example, passing ions emitted from a liquid metal ion source through a beam limiting aperture, a focusing lens, and an objective lens (not shown). . The focused ion beam irradiation optical system 20 has a function of scanning the sample substrate 2 while deflecting the FIB irradiation angle by a deflector (not shown), and forming a concave portion by sputtering on the sample substrate 2, In addition to forming recesses, it is also possible to form protrusions by FIB assist deposition.
The secondary particle detector 21 has a function of displaying the detected secondary electrons, secondary ions, and the like on a display (not shown) so that the processing region of the sample 3 can be observed.
The stage 23 is mounted on the base 24 fixed on the bottom surface of the chamber 6 so as to be movable in the XY direction and the Z direction, and to be able to rotate around the XY axis and around the Z axis. It has been. The stage 23 is controlled by the control unit 15.
In addition to the stage 23, a holder 25 that accommodates the plurality of tweezers 4 is attached to the base 24. The position of the holder 25 is not limited to the base 24 and may be anywhere within the chamber 6.

As shown in FIG. 3, the tweezers 4 is formed of a semiconductor material, and includes a pair of pins (rod-like holding members) 31 and 32 having holding surfaces 31a and 32a for holding the sample 3 at the opposite ends. ing. In the present embodiment, each of the pair of pins 31 and 32 incorporates piezoresistors (strain sensors) 33 and 34 whose electrical characteristics change according to the characteristics of the semiconductor material. The piezoresistors 33 and 34 are obtained by adding impurities to a semiconductor material. A method of manufacturing the tweezers 4 including the piezoresistors 33 and 34 will be described in detail later.
The pair of pins 31 and 32 are both fixed on a Si support substrate 61 and a BOX layer 62, which will be described later, at a base end side, and spaced apart from each other by a predetermined distance so that the tips protrude from the Si support substrate 61 and the BOX layer 62. Adjacent to each other.

As shown in FIGS. 4 and 5, each pin 31, 32 has a stress concentration portion 35 having a cross-sectional area perpendicular to the length direction at a substantially intermediate position that is smaller than the other portions. That is, the lateral width H of the stress concentration portion 35 is formed to be smaller than the lateral width H1 of other portions (H <H1). The piezoresistors 33 and 34 are disposed in the stress concentration portion 35.
Each pin 31, 32 has a through hole 36 at a position where the base end side of the piezoresistors 33, 34 branches into two. As a result, the piezoresistors 33 and 34 are substantially U-shaped when viewed from above. A wiring 37 is electrically connected to the base end side branched into two of the piezoresistors 33 and 34 so as to sandwich the through hole 36, respectively.
Further, each of the pins 31 and 32 is formed with a conductive film 38 that can be electrically connected to the ground other than the upper surface. Thus, a conductive film 38 is formed on the surfaces facing each other, that is, on the surfaces of the clamping surfaces 31a and 32a.

As shown in FIG. 6, the tweezers 4 is mounted on the distal end side of a mounting substrate 40 such as an epoxy substrate in a state where the proximal end side is placed. The wiring 37 and the conductive film 38 are electrically connected to the electrode 42 made of copper or the like provided on the base end side of the mounting substrate 40 by the substrate wiring 41. The substrate wiring 41 is protected by a sealing resin 43. The tweezers 4 and the mounting substrate 40 constitute tweezers ASSY 45.
As shown in FIG. 7, the holder 25 includes a plurality of storage recesses 25 a that are larger than the lateral width of the tweezers 4 and smaller than the lateral width of the mounting substrate 40. That is, the tweezers ASSY 45 can be placed with the tweezers 4 inserted into the storage recess 25a. Further, when the tweezers ASSY 45 is placed, a claw portion (not shown) is fitted to the mounting substrate 40 so that the tweezers ASSY 45 can be held with a predetermined force.

As shown in FIG. 1, the manipulator 5 is fixed on a movable table 50 that can move in the XY direction and the Z direction, and includes an articulated arm 51 that can perform a three-dimensional operation. The operation of the movable table 50 is controlled by the control unit 15. Further, the manipulator 5 has a connector portion 52 that can be connected to the mounting board ASSY 45 at the tip of the articulated arm 51 as shown in FIG. The connector portion 52 includes a claw portion (not shown) that fits on the proximal end side of the mounting substrate 40 and holds the mounting substrate 40 with a predetermined force inside the distal end side. This claw portion serves as a contact point for the electrode 42 of the mounting substrate 40.
As a result, the manipulator 5 can move the mounting substrate ASSY 45 placed on the holder 25 in an electrically connected state by the connector portion 52 and then move it to an arbitrary position by the articulated arm 51. Yes. Further, when the tweezers ASSY 45 is placed in the storage recess 25 a, the claw portion of the storage recess 25 a holds the mounting substrate 40, so that the tweezers ASSY 45 can be separated from the connector portion 52.

Further, as shown in FIG. 2, the manipulator system 1 is arranged on the base end side with respect to the piezoresistors 33 and 34, and at least one pin 31 (32) is disposed so as to bring the holding surfaces 31a and 32a closer to each other. A pin manipulator (moving mechanism) 55 that can move toward the other pin 32 (31) is provided. In the present embodiment, the pin manipulator 55 moves both the pair of pins 31 and 32 together. The pin manipulator 55 may be provided at the tip of the manipulator 5, or may be provided separately on the base 34, for example.
The operations of the pin manipulator 55 and the manipulator 5 are controlled by the control unit 15. The measurement values measured by the piezoresistors 33 and 34 are sent to the control unit 15 via the manipulator 5.

As shown in FIG. 8, the control unit 15 includes a detection circuit 15a and a differential amplification unit 15b. When the measurement values sent from the piezoresistors 33 and 34 reach a predetermined value, the control unit 15 The pin manipulator 55 is feedback-controlled so as to stop the approach of the pair of pins 31 and 32. At this time, as shown in FIG. 6, the detection circuit 15a and the differential amplifying unit 15b are arranged in the vicinity of the pair of pins 31 and 32, and are formed of a semiconductor material and are the same as the reference sensors 33 and 34. The measurement value from the reference pin 56 with a built-in is input as a reference value (reference value).
Furthermore, the control unit 15 has a function of comprehensively controlling each component described above.

Here, the manufacturing method of the tweezers 4 will be described below.
The tweezers 4 according to the present embodiment includes a main body forming step of patterning the pair of pins 31 and 32 on the semiconductor substrate 60 by a photolithography technique, and impurities in a part of a region provided for the pair of pins 31 and 32 And forming the piezoresistors 33 and 34 by adding a sensor portion.
In the present embodiment, as shown in FIG. 9, the semiconductor substrate 60 includes a silicon (Si) support substrate (for example, a thickness of several hundred μm) 61 and silicon dioxide (on the Si support substrate 61). A description will be given as an SOI (Silicon On Insulater) substrate having a BOX layer 62 of SiO ₂ ) and a Si active layer (for example, 1 μm to 10 μm in thickness) 63 formed on the BOX layer 63.
The body forming step includes a pattern etching step of pattern-etching the Si active layer 63 to form the pair of pins 31 and 32, and a BOX layer 62 and the Si support substrate 61 after the pattern etching step. , And a removing step of removing the base body while leaving the base end side of the main body.
Each of these steps will be described in detail below.

First, as shown in FIG. 9, silicon oxide films (SiO ₂ ) 64 and 65 are formed by thermally oxidizing the front surface and the back surface of the semiconductor substrate 60.
Next, a photoresist film (not shown) serving as an etching mask is patterned on the silicon oxide film 64 on the surface in the shape of a pair of pins 31 and 32 shown in FIG. At this time, the stress concentration portion 35 and the through hole 36 are also patterned at the same time. Then, the silicon oxide film 64 is patterned in the shape of the pair of pins 31 and 32 by etching using the photoresist film as a mask. The resist may be positive or negative. Alternatively, the silicon oxide film 64 may be solution etched using a hydrofluoric acid solution (BHF) using the photoresist film as a mask.

  Subsequently, after removing the photoresist film used as a mask, reactive ion etching (RIE) and DRIE (Deep Reactive Ion Etching) are performed using the silicon oxide film 64 as a mask to form an unmasked Si. The active layer 63 is selectively removed. At this time, the reaction rate or the like is set so that RIE and DRIE stop at the BOX layer 62 below the Si active layer 63. Then, by removing the silicon oxide film 64 used as a mask, the Si active layer 63 is patterned into a pair of pins 31 and 32 as shown in FIG. This step is the pattern etching step.

Next, the sensor part forming step is performed. That is, on the Si active layer 63, a region where the piezoresistors 33 and 34 are formed, that is, a region including the stress concentration portion 35 and the base end side of which is branched into two by the through hole 36 is opened to form a photo (not shown). After forming the resist film, an impurity (dopant) is added (doping) from the opening by ion implantation to form the piezoresistors 33 and 34. In this embodiment, the N-type Si active layer 63 is doped with P ⁺ ions such as boron (B) and gallium (Ga) to form the piezoresistors 33 and 34. Note that the present invention is not limited to this case. When a P-type Si active layer 63 is used, n ⁺ ions such as phosphorus (P) and arsenic (As) are doped. That is, the piezoresistors 33 and 34 are formed so as to have different polarities with respect to the Si active layer 63. Then, by removing the photoresist film, the piezoresistors 33 and 34 are formed in the stress concentration portion 35 as shown in FIG. At this time, the base end portion of the through hole 36 protrudes from the base end portions of the piezoresistors 33 and 34 toward the base end side of the tweezers 4 (right side with respect to the paper surface). In particular, when the patterning of the through hole 36 is performed, the base end portion of the through hole 36 is located on the base end side of the tweezers 4 so that the positional relationship between the piezoresistors 33 and 34 and the through hole 36 is as described above. It is preferable to perform patterning so as to have a predetermined length in advance so as to approach each other.
The P-type Si active layer 63 may be doped with boron or gallium, or the N-type Si active layer 63 may be doped with phosphorus or arsenic (provided that the resistance value is lower than that of the original Si). .

After the sensor part process is completed, after impurity drive-in (diffusion) is performed, as shown in FIG. 12, the base end of the Si active layer 63 from the base end branched into two of the piezoresistors 33 and 34 An interlayer insulating film 66 such as silicon oxide (SiO ₂ ) or silicon nitride (SiN) is formed in the region up to the side. After the formation of the interlayer insulating film 66, a contact hole 67 is formed at the distal end of the interlayer insulating film 66 so that the base ends branched into two of the piezoresistors 33 and 34 can be respectively accessed.
After the contact hole 67 is formed, a conductive layer is patterned with a metal such as aluminum (Al) between each contact hole 67 on the interlayer insulating film 66 and the base end side of the Si active layer 63, as shown in FIG. As a result, the wiring 37 is formed.

Next, a photoresist film (not shown) is patterned on the silicon oxide film 65 on the back surface side of the silicon substrate 60, and the silicon oxide film 65 is patterned so as to remain on the base end side as shown in FIG. After the patterning, as shown in FIG. 15, a photoresist film 68 is applied so as to cover the BOX layer 62 and the Si active layer 63 to form a protective film. Then, using the patterned silicon oxide film 65 as a mask, the Si support substrate 61 is etched by anisotropic etching using an alkaline etchant such as potassium hydroxide (KOH) or tetramethylammonium hydroxide (TMAH) or by DRIE. Remove with the side left.
Thereafter, as shown in FIG. 16, the photoresist film 68 is removed, and the BOX layer 62 is similarly removed with BHF or the like leaving the base end side. This step is the removal step.

Finally, as shown in FIG. 17, aluminum (Al), titanium (Ti), chromium (in the region extending from the back and side surfaces of the pair of pins 31 and 32 to the back surface on the base end side by sputtering or vacuum deposition. The conductive film 38 is formed of a metal such as Cr). The conductive film 38 is not limited to a single layer, and may be, for example, two layers of Ti / Au (Ti is first formed as an adhesion layer and gold (Au) is formed thereon). In the case of two layers, Cr / Au, Ti / platinum (Pt), or Cr / Pt may be used.
Thereby, the tweezers 4 incorporating the piezoresistors 33 and 34 shown in FIG. 3 can be manufactured by semiconductor technology.

Next, a case where the sample 3 is produced from the sample substrate 2 by the manipulator system 1 configured as described above and then the sample 3 is sandwiched by the tweezers 4 will be described.
First, after the inside of the chamber 6 is evacuated by the vacuum pump P, the sample substrate 2 is positioned at the FIB irradiation position of the focused ion beam irradiation optical system 20 by the stage 23. After positioning, for example, a gas such as hexacarbonyl tungsten (W (CO) ₆ ) is blown onto the FIB irradiation region of the sample substrate 3 by the deposition gas source 22 to form a protective film, and then from the focused ion beam irradiation optical system 20. The sample substrate 2 is irradiated with FIB. At this time, the FIB irradiation angle is deflected, and the stage 23 is tilted about the XY axis and the Z axis, and the sample substrate 3 is cut as shown in FIGS. A sample 3 having dimensions of 1 μm, a height of 5 μm, and a width of 10 μm is prepared. At this time, the bottom surface of the sample 3 is also separated, and the sample 3 is standing by an electrostatic force acting between the sample substrate 2 and the sample 3 by FIB irradiation. The sample 3 is produced while viewing an observation image based on secondary electrons, secondary ions, etc. detected by the secondary particle detector 21.

After the preparation of the sample 3, the manipulator 5 is moved to a predetermined position by the moving base 50, and then the tweezers 4 at the tip is moved by the articulated arm 51, and as shown in FIG. The pins 31, 32 are positioned. Positioning of the tweezers 4 is performed while viewing an observation image by the secondary particle detector 21 described above. At this time, since the conductive film 38 is formed on the sandwiching surfaces 31 and 32a, the charge-up of the tweezers 4 is reduced, distortion of the observation image can be suppressed, and a good observation image can be obtained.
After the positioning of the pair of pins 31 and 32, as shown in FIG. 2, the base end sides of the pair of pins 31 and 32 are moved by the pin manipulator 55 so that the sandwiching surfaces 31 a and 32 a approach each other. That is, as shown in FIG. 20, the pair of 31 and 32 moves so that the distal end draws an arc with the base end side as the center. Then, as the clamping surfaces 31a and 32a further approach, the sample 3 is clamped as shown in FIG.

When the sample 3 is sandwiched, stress is applied to the inside of the pair of pins 31 and 32 to cause distortion. At this time, since the pair of pins 31 and 32 are formed of silicon which is a semiconductor material, a change in specific electrical characteristics, that is, a resistance value changes. Since the piezoresistors 33 and 34 detect this change in resistance value, it is possible to detect that the sample 3 has been clamped reliably. In particular, when the piezoresistors 33 and 34 are implanted with N-type ions and the Si active layer 63 is P-type, the current flowing through the contact hole 67 is less likely to leak outside the doped region. Since the piezoresistors 33 and 34 are electrodes different from the Si active layer 63 which is the substrate of the tweezers 31 and 32, the resistance of the entire tweezers 31 and 32 is lowered and the strain can be detected with high sensitivity.
Further, since the piezoresistors 33 and 34 are arranged in the stress concentration portion 35, distortion caused by a slight holding force can be detected as a large resistance change, and the pinching force can be detected with high accuracy. .
Further, since the piezoresistors 33 and 34 and the electric wire 37 are formed to be U-shaped with the through hole 36 interposed therebetween, a current path is secured in a region extending from the base end side to the tip end side. In addition, since the resistance value change can be detected reliably and with high accuracy, the clamping force can be detected with high accuracy.

Further, since the control unit 15 controls the pin manipulator 55 to stop when the measurement value measured by the piezoresistors 33 and 34 reaches a predetermined value, the sample 3 is clamped with an optimal clamping force. Can be done. Thereby, for example, the sample 3 can be clamped with an optimal clamping force according to the shape of the tweezers 4, the shape of the sample 3, the hardness, the material, and the like. Therefore, since no extra load is applied to the sample 3 and the tweezers 4, not only the sample 3 is scratched but also the reliability and durability of the tweezers 4 can be improved.
Further, since the reference value is input from the reference pin 56, the control unit 15 can cancel the influence of the electrical characteristics caused by the environmental conditions such as the temperature change around the pair of pins 31 and 32, and more accurately change the resistance value. Can be detected.

  After pinching the sample 3 with the tweezers 4, the tweezers 4 and the mesh 10 are relatively moved by the moving base 50, the articulated arm 51, and the moving mechanism 11, and the sample 3 is positioned on the mesh 10. Then, the pin manipulator 55 releases the approaching state of the pair of pins 31 and 32, and the sample 3 is placed on the mesh 10. At this time, since the conductive films 38 connected to the ground are formed on the sandwiching surfaces 31a and 32a, the sample 3 can be easily separated without being affected by static electricity. Thereafter, the sample 3 is irradiated with an electron beam by the electron gun 12 and the sample 3 is observed by the transmission observation microscope A. In particular, in the manipulator system 1 of the present embodiment, the sample 3 is not taken out from the chamber 6 set in a vacuum state, so that the sample 3 is lost or an oxide film or the like is formed on the surface of the sample 3. Can be prevented.

Further, the tweezers 4 pattern the pair of pins 31 and 32 on the Si active layer 63 by a photolithography technique in the main body forming process, so that the small and highly accurate tweezers 4 can be easily formed. In addition, the piezoresistors 33 and 34 can be easily formed using a semiconductor process by adding impurities by a thermal diffusion method or an ion implantation method in the sensor portion forming step. That is, the tweezers 4 can be formed in a small size and with high accuracy by a semiconductor process.
Further, since the BOX layer 62 and the Si support substrate 61 are removed in the removing process after the pattern etching process is performed in the main body forming process, the thin and highly accurate tweezers 4 can be reliably formed.

  When exchanging the tweezers 4, the tweezers ASSY 45 is removed from the connector portion 52 with the tweezers 4 inserted into the housing recess 25 a of the holder 25, and the other tweezers ASSY 45 placed on the holder 25 is again connected to the connector portion. 52 can be attached. By doing so, even if a trouble occurs in the tweezers 4, the tweezers 4 can be easily replaced in the chamber 6, and the tweezers 4 corresponding to the type of the sample 3 can be selected and used in a timely manner.

As described above, according to the tweezers 4 of the present invention, the sample 3 can be securely clamped with a predetermined clamping force, and can be manufactured in a small size because it is formed of a semiconductor material. Further, since the piezoresistors 33 and 34 are built in, the clamping force can be detected with high accuracy.
Further, according to the manipulator system 1 of the present invention, the sample can be clamped with an optimal clamping force, and the reliability and durability of the tweezers 4 can be improved as well as not scratching the sample 3. .

Next, a second embodiment of the tweezers according to the present invention will be described with reference to FIGS. Note that in the second embodiment, identical symbols are assigned to configurations identical to those in the first embodiment and descriptions thereof are omitted.
The difference between the second embodiment and the first embodiment is that in the first embodiment, the tweezers 4 detects the clamping force by detecting strain acting on the pair of pins 31 and 32 by the piezoresistors 33 and 34. On the other hand, the tweezers 70 of the second embodiment is to detect the clamping force by the electrostatic capacity.

  That is, the tweezers 70 of the present embodiment, as shown in FIGS. 22 and 23, are a pair of pins (rod-like holding members) 71 and 72 having holding surfaces 71a and 72a for holding the sample 3 at the opposite ends. Equipped with. Conductive portions 73 and 74 in which the pair of pins 71 and 72 are arranged to face each other in a state of being electrically independent of the sandwiching surfaces 71a and 72a on the proximal end sides of the sandwiching surfaces 71a and 72a, and the conductive portions 73 , 74 and a capacitance sensor 75 that measures the capacitance. 22 and 23 show only the pin 71 (72) on one side.

The pair of pins 71 and 72 are formed to branch into two from the proximal end portion toward the distal end, and the clamping surfaces 71a and 72a are arranged at the distal ends of the outer branch portions 76 and 77. . Further, the inner branch portions are the conductive portions 73 and 74.
Further, the tweezers 70 of the present embodiment is not limited to a semiconductor material, but is preferably an insulating material. For example, silicon, SiO ₂ , diamond or the like is adopted as a base material, and a conductive film 78 is formed on the surface with a metal such as Al, Au, Ti or the like by sputtering or vapor deposition. The conductive film 78 functions as a conductive film that can electrically connect the clamping surfaces 71a and 72a to the ground. Further, by forming the tweezers 71 and 72 from a semiconductor material, the conductive portions 73 and 74 can be formed by, for example, dry etching or the like.
The capacitance sensor 75 is formed at the tips of the conductive portions 73 and 74, and is formed by evaporating metal or the like, for example. Note that, by forming the tweezers 71 and 72 from a semiconductor material, it is possible to form the tweezers 71 and 72 by doping as in the first embodiment.

A case where the sample 3 is sandwiched by the tweezers 70 configured as described above will be described.
When the pair of pins 71 and 72 are brought closer to the pin manipulator 55, that is, when the conductive portions 73 and 74 are brought closer to each other, the capacitance sensor 75 changes the capacitance of the conductive portions 73 and 74 according to the distance between them. Measure. For example, since the capacitance increases as the pair of pins 71 and 72 approaches, it can be detected that the pair of pins 71 and 72 are still in a state before the sample 3 is sandwiched.
When the sample 3 is sandwiched, the pair of pins 71 and 72 stops approaching and the capacitance does not change. Therefore, the capacitance sensor 75 can easily and reliably detect that the pair of pins 71 and 72 have pinched the sample 3 by detecting that the change in capacitance has been eliminated.
Further, when the sample 3 is sandwiched, the conductive portions 73 and 74 that are the inner branch portions are branched separately from the outer branch portions 76 and 77 where the sandwich surfaces 71 and 72a are arranged. The conductive parts 73 and 74 are in an accessible state. That is, the capacitance can be measured even after the sample 3 is sandwiched. Therefore, by setting a predetermined capacitance in advance, the sample 3 can be clamped with a predetermined clamping force, and a clamping force corresponding to the sample 3 can be obtained.

  As described above, since the clamping force can be measured by measuring the capacitance according to the distance between the pair of pins 71 and 72, the sample is strongly clamped as in the first embodiment. There is no inconvenience such as excessive or unintentional clamping, and the sample can be securely clamped with a predetermined clamping force regardless of the operator. Further, by forming the pair of pins 71 and 72 from a semiconductor material, the pin can be made small.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, the manipulator system of the above-described nuclear embodiment is configured to include the transmission electron microscope in the chamber, but may be provided separately from the chamber. In this case, it may be configured so that the sample can be transferred onto a mesh provided outside the chamber after the sample is sandwiched with tweezers. The transmission electron microscope is not limited, and any electron microscope may be used.
Further, although the sample is sandwiched with tweezers and transferred to the mesh, for example, as shown in FIG. 24, the sample may be temporarily fixed to a sample stage for an electron microscope and reworked. In this case, with the sample sandwiched between tweezers placed on the sample stage, the deposition film is used to irradiate the FIB while allowing the deposition gas to flow out. Fix it.

In the first embodiment, the piezoresistors are built in both of the pair of pins. However, it may be built in either one of the pins.
Furthermore, the pin manipulator moves both of the pair of pins in the first embodiment and the second embodiment, but may be configured so that either one of the pins can be moved. Further, it is not necessary to be a manipulator, and for example, any moving mechanism using a ball screw or the like driven by a piezoelectric element or a micromotor may be used.

  Further, in both embodiments, as shown in FIG. 25, the shape of the sandwiching surface may be formed so as to be in a parallel state when the sample is sandwiched. By doing so, the contact area between the sample surface and the sample is increased, so that the sample can be more stably held, which is more preferable.

1 is a configuration diagram showing a first embodiment of a manipulator system according to the present invention. It is the figure which showed the positional relationship of the tweezers which concern on this invention, and the manipulator for pins. It is a top view which shows a 1st embodiment of tweezers used for a micro manipulator system concerning the present invention, and concerning the present invention. It is a top view which shows the pin of the tweezers shown in FIG. It is a side view of the pin shown in FIG. It is a top view which shows an example of the tweezers ASSY which mounted the tweezers on the mounting substrate. It is a side view which shows the state which took out tweezers ASSY from the holder with the manipulator. It is a figure which shows an example of the block diagram in the control part of the manipulator system shown in FIG. 1, (a) shows a detection circuit and a differential amplifier, (b) is the figure which showed the bridge circuit of the detection circuit. It is process drawing which showed the manufacturing method of the tweezers shown in FIG. 3, Comprising: It is the figure which showed the start board | substrate. FIGS. 10A and 10B are a process diagram illustrating a method of manufacturing the tweezers illustrated in FIG. 3, and are a side view and a top view illustrating a state in which a pair of pins are patterned on the Si active layer from the state illustrated in FIG. 9. FIGS. 11A and 11B are process diagrams illustrating a method of manufacturing the tweezers illustrated in FIG. 3, and are a side view and a top view illustrating a state in which a piezoresistor is manufactured from the state illustrated in FIG. 10. FIGS. 12A and 12B are a process diagram illustrating a method of manufacturing the tweezers illustrated in FIG. 3, and are a side view and a top view illustrating a state in which an interlayer insulating film is formed on the Si active layer from the state illustrated in FIG. 11. . FIGS. 13A and 13B are process diagrams illustrating a manufacturing method of the tweezers illustrated in FIG. 3, and are a side view and a top view illustrating a state in which a conductive film is patterned on the interlayer insulating film from the state illustrated in FIG. b). FIGS. 14A and 14B are a process diagram illustrating a method for manufacturing the tweezers illustrated in FIG. 3, and are a side view and a top view illustrating a state in which the silicon oxide film on the back surface of the silicon substrate is patterned from the state illustrated in FIG. . It is process drawing which showed the manufacturing method of the tweezers shown in FIG. 3, Comprising: It is the side view (a) and top view (b) which show the state which carried out the back etching of the Si support substrate from the state shown in FIG. FIGS. 16A to 16C are process diagrams illustrating a method for manufacturing the tweezers illustrated in FIG. 3, and are a side view and a top view illustrating a state in which the BOX layer is removed from the state illustrated in FIG. 15. FIG. 17 is a process diagram illustrating a method of manufacturing the tweezers illustrated in FIG. 3, and is a side view illustrating a state in which a conductive film is formed on the back and side surfaces of a pair of pins from the state illustrated in FIG. 16. It is a side view which shows the state just before pinching the sample produced from the sample board | substrate with tweezers. It is a side view of the sample shown in FIG. It is the upper side figure which showed the locus | trajectory of the front-end | tip when making a pair of tweezers move so that a clamping surface may approach by the manipulator for pins. It is a top view which shows the state which clamped the sample with a pair of tweezers. It is a figure which shows 2nd Embodiment of the tweezers which concern on this invention, Comprising: It is the top view which showed the pin of the one side. It is a side view of the pin shown in FIG. It is a perspective view which shows the state which fixed the sample to the sample stand. FIG. 6 is a top view showing another example of tweezers according to the present invention, in which the tweezers are parallel when the sample is nipped.

Explanation of symbols

A Transmission electron microscope (electron microscope)
DESCRIPTION OF SYMBOLS 1 Manipulator system 3 Sample 4, 70 Tweezers 5 Manipulator 15 Control part 31, 32, 71, 72 Pin (bar-shaped clamping member)
31a, 32a, 71a, 72a Nipping surface 33, 34 Piezoresistor (strain sensor)
35 Stress Concentration Part 36 Through-hole 37 Wiring 38, 78 Conductive Film 55 Pin Manipulator (Movement Mechanism)
56 Reference pin 60 Semiconductor substrate 61 Si support substrate 62 BOX layer 63 Si active layer 73, 74 Conductive part (inner branch part)
75 Capacitance sensor 76, 77 Outside branch

Claims (6)

Tweezers that can hold a sample for electron microscope observation,
Adjacent to each other at a predetermined interval, each of the opposing ends has a clamping surface for clamping the sample, and a stress concentrating portion whose cross-sectional area perpendicular to the length direction is smaller than that of the other portion is the proximal end and the distal end A pair of rod-shaped holding members made of a semiconductor material formed between
A piezoresistor that is disposed in the stress concentration portion of at least one of the rod-shaped clamping members and detects a change in electrical characteristics of the pair of rod-shaped clamping members that changes according to a gripping force when the sample is clamped ; With
The piezoresistor is formed by adding impurities to the semiconductor material, and the base end side is branched into two so as to be U-shaped in plan view, and wirings are electrically connected to the branched portions, respectively. Tweezers characterized by being . The tweezers according to claim 1 ,
The tweezers are characterized in that a conductive film that can be electrically connected to the ground is formed on the clamping surface. In the tweezers according to claim 1 or 2,
The tweezers, wherein the pair of rod-like holding members are formed so that the holding surfaces are parallel to each other when the sample is held . The tweezers according to any one of claims 1 to 3 ,
A movement mechanism that is arranged on the base end side with respect to the piezoresistor and is capable of moving at least one of the bar-shaped holding members to the other bar-shaped holding member so as to bring the holding surfaces of the two closer together;
A manipulator capable of holding the tweezers and moving to any position;
And a control unit that controls the moving mechanism to stop the approach of the pair of rod-shaped holding members when a measured value of the piezoresistor reaches a predetermined value. The manipulator system according to claim 4,
In the tweezers, the same piezoresistor as the piezoresistor is built in, and a reference pin formed in a rod shape by a semiconductor material is provided,
The reference pin outputs a change in the resistance value of the built-in piezoresistor as a reference value to the control unit, which changes due to a temperature change around the pair of rod-shaped holding members,
The control unit is configured to subtract the reference value from the measurement value obtained by the piezoresistors provided on the pair of rod-shaped sandwiching members, thereby removing a resistance value change caused by an ambient temperature change from the measurement value. manipulator system characterized by performing.   The tweezers according to claim 1, a silicon (Si) support substrate, and silicon dioxide (SiO 2) formed on the Si support substrate. ₂ ) And a Si active layer formed on the BOX layer, and a manufacturing method using the SOI substrate,
  Forming an oxide film on the Si active layer and patterning the outer shape of the pair of rod-shaped holding members by photolithography on the oxide film;
  After the step, a pattern etching step of forming the pair of rod-shaped holding members by selectively removing the Si active layer not masked by using the patterned oxide film as a mask, and
  After the step, the piezoresistor is formed by adding impurities to the stress concentration portions of the pair of rod-shaped holding members so that the base end side is branched into two and has a U shape in plan view. A sensor part forming process;
  After the step, an insulating film is formed between the base end of the branched piezoresistor and the base end of the Si active layer, and contact holes that respectively access the base end of the branched piezoresistor are formed in the insulating film. Forming, and
  After the step, a conductive layer is patterned on the insulating film between the contact hole and the base end of the Si active layer, and the base end of the piezoresistor branched through the contact hole is electrically connected to the base layer. Forming the interconnects connected electrically,
  And a removal step of selectively removing the BOX layer and the Si support substrate by etching so that the distal ends of the pair of rod-shaped holding members protrude from the BOX layer and the Si support substrate. A method for manufacturing tweezers.

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