JP2005349487A - Fine processing method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide fine processing of a type in which voltage is applied between working fluid and a workpiece using a combination of a scan type shear force microscope and a hollow probe. <P>SOLUTION: A micro-pipet probe 12, the tip of which is opened, is used as the probe of the scan type shear force microscope. The interior of the probe is filled with plating liquid 48. With the tip of the probe brought into contact with a desired position on the surface of the workpiece 18, voltage is applied between the plating liquid 48 and the workpiece support 16 only for predetermined time. Thus, the surface of the workpiece 18 is subjected to micro-plating processing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fine processing method and apparatus using a scanning shear force microscope.

The scanning probe microscope is a microscope that can detect various physical quantities acting between the tip and the sample surface using a fine probe and can image the surface distribution of the physical quantities with high resolution at a nanoscale. This scanning probe microscope is used not only for observation of the sample surface but also for nanoscale ultrafine surface processing. Such ultra-fine surface processing is described in the following Non-Patent Document 1, Non-Patent Document 2, and Patent Document 1.
Kakuya et al., “Nanoscale processing of polymer surface by SPM with micropipette probe”, Proceedings of the 2002 Annual Meeting of Precision Engineering, Japan Society for Precision Engineering, September 2002, p. 149 Iwata, “Development of nano-scale microfabrication methods using ultra-fine probes”, Preprints of the Ultra-precision Positioning Technical Committee, Japan Society for Precision Engineering, 2002, 2002-4 (2), p. 9-15 Japanese Patent Laid-Open No. 9-251979

  Non-Patent Document 1 described above employs a micropipette probe as a probe of a scanning shear force microscope. The micropipette is filled with a sample processing reagent solution (1,4-dioxane), the reagent is brought close to the polycarbonate substrate, and the substrate is processed by the vapor of the reagent. Since the micropipette probe does not contact the substrate and is processed only with the vapor of the reagent, the substrate can be processed with the same resolution as the aperture size (about 300 nm) of the micropipette probe.

  Non-Patent Document 2 mentioned above introduces some nanoscale microfabrication methods using a scanning probe microscope. Among them, there is a description of nano-processing (chemical vapor processing method) using chemical interaction, which is deeply related to the present invention. In this processing method, a micropipette probe is used as a probe for a scanning force mode scanning microscope. A chemical reagent solution is injected into the micropipette probe, and nanoscale processing is performed by a chemical reaction between the reagent solution and the surface of the workpiece. When a volatile polymer solvent reagent is used, if the micropipette probe is brought close to the nanometer range on the polymer surface, processing can be performed with the same precision as the pipette tip size by vapor of the solution (vaporizer action) even in a non-contact state Become. Then, by controlling the distance between the probe and the sample using a micropipette probe containing a reagent, both the observation mode and the processing mode can be selected continuously.

  On the other hand, Patent Document 1 described above uses an optical lever type atomic force microscope as a scanning probe microscope, and a micropipette is used as a probe of the atomic force microscope. Filling the inside of this micropipette with the processing liquid, bringing the micropipette close to the desired position of the workpiece and discharging the processing liquid allows etching or deposition on the surface of the workpiece. can do. As a description deeply related to the present invention, reference is also made to plating. That is, the gold plating solution can be activated by supplying a gold plating solution from the micropipette to the surface of the workpiece and passing an electric current between the aluminum layer of the micropipette and the workpiece. As the structure of the micropipette, one made from a silicon wafer or one made from a glass tube is disclosed.

  Non-Patent Document 1 and Non-Patent Document 2 described above can finely process the surface of a workpiece by combining a scanning shear force microscope and a micropipette probe. It does not disclose that a workpiece is processed by applying a voltage therebetween. On the other hand, Patent Document 1 combines an optical lever type atomic force microscope and a micropipette probe, and allows a fine plating process to be performed on the surface of the workpiece by passing an electric current between the micropipette probe and the workpiece. Suggests to do. However, this Patent Document 1 uses an optical lever type atomic force microscope, and in the observation mode, scanning is performed while the contact pressure between the probe and the workpiece is controlled to be constant. (1) Observation mode The machining liquid may adhere to the surface of the workpiece and machining may proceed at a location other than the machining position. (2) Therefore, it is difficult to select the observation mode in addition to the machining mode. (3) There are problems such as that the machining fluid tends to spread on the surface of the workpiece and that the machining size is difficult to control.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to apply a voltage between a machining fluid and a workpiece using a combination of a scanning shear force microscope and a hollow probe. It is an object of the present invention to provide a microfabrication method and apparatus capable of realizing the above microfabrication.

  The fine processing method of the present invention includes the following steps (a) to (d). (A) A step of preparing a scanning shear force microscope including a hollow probe having an open tip. (A) A step of filling the hollow probe with a processing liquid. (C) contacting the tip of the hollow probe with a desired position on the surface of the workpiece; (D) A step of applying a voltage between the machining liquid and the workpiece for a predetermined time to perform fine machining on the surface of the workpiece.

  A core wire made of a conductor can be provided inside the hollow probe. The core wire is in contact with the machining fluid, and a voltage can be applied between the machining fluid and the workpiece by applying a voltage between the core wire and the workpiece.

  As the processing liquid, a liquid containing metal ions can be used. By applying a voltage between the processing liquid and the workpiece, fine plating can be performed on the surface of the workpiece.

  It is also possible to observe the processing state of the surface of the workpiece using a scanning shear force microscope by scanning the hollow probe in a non-contact state on the surface of the workpiece subjected to micromachining. it can. That is, using the same hollow probe, an observation mode is possible in addition to the processing mode.

  The microfabrication apparatus of the present invention has the following configurations (a) to (d). (A) A scanning shear force microscope comprising a hollow probe having an open end, a sample stage, and a moving mechanism that moves the sample stage in a three-dimensional direction relative to the hollow probe. (A) A processing liquid filled in the hollow probe. (C) A conductive workpiece support that is fixed to the sample stage and supports the workpiece. (D) An electric circuit capable of applying a voltage between the machining fluid and the workpiece support. Note that the sample stage and the workpiece support may be integrally formed.

  The microfabrication method and apparatus of the present invention uses a scanning shear force microscope and a hollow probe to apply a voltage between the machining liquid inside the hollow probe and the work piece, thereby finely subtracting the surface of the work piece. Can be processed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram of a scanning shear force microscope for performing fine plating. FIG. 2 is a perspective view of the main part. In FIG. 1, the part illustrating the mechanical structure is a front view. Since the configuration of the scanning shear force microscope provided with the micropipette probe is disclosed in Non-Patent Document 1 and Non-Patent Document 2 described above, the configuration will be briefly described here. 1 and 2, a micropipette probe 12 is fixed on the central axis of a cylindrical probe support 10. This micropipette probe corresponds to the hollow probe in the present invention. An excitation piezoelectric element is incorporated in the probe support 10. The material of this piezoelectric element is PZT. Due to the vibration of the excitation piezoelectric element, the micropipette probe 12 vibrates in a direction perpendicular to the paper surface of FIG. The sample stage 14 can be moved within a predetermined moving distance in the XY direction (two-dimensional direction in a horizontal plane) and the Z direction (vertical direction) by a three-dimensional actuator driven by a piezoelectric element. A workpiece support 16 made of a conductor is fixed to the upper surface of the sample stage 14. A workpiece 18 can be placed on the upper surface of the workpiece support 16. The micropipette probe 12 vibrates in the horizontal direction by the exciting piezoelectric element, and the amplitude is detected by an amplitude detector. The amplitude detection device includes a laser diode 20, a condenser lens 22, and a two-divided photodiode 24. The laser diode 20 emits laser light having a wavelength of 670 nm, and this laser light 26 is condensed near the micropipette probe 12 by the condenser lens 22, and the laser light passing therethrough is condensed by the two-divided photodiode 24. The The output of the two-divided photodiode 24 depends on the vibration amplitude of the micropipette probe 12.

  Next, the control system of the scanning shear force microscope will be described. In FIG. 1, an oscillation output signal 29 is supplied from an oscillator 28 to the excitation piezoelectric element incorporated in the probe support 10, and the probe support 10 vibrates in the horizontal direction at a predetermined resonance frequency. The output signal of the two-divided photodiode 24 depends on the vibration amplitude of the micropipette probe 12. This output signal passes through the IV converter 30, the arithmetic circuit 32, and the lock-in amplifier 34, and the vibration of the micropipette probe 12. Converted to amplitude. The lock-in amplifier 34 receives the signal from the oscillator 28 as the reference signal 33, and noise is removed by the lock-in amplifier 34. The vibration amplitude 35 of the micropipette probe 12 output from the lock-in amplifier 34 is input to the control circuit 36. The control circuit 36 compares the vibration amplitude of the micropipette probe 12 with a predetermined reference value, and outputs a Z direction command signal 37 so that the vibration amplitude becomes equal to the reference value. That is, the Z direction command signal 37 is output so that the sample stage 14 is raised if the vibration amplitude is larger than the reference value, and conversely, if the vibration amplitude is smaller than the reference value, the sample stage 14 is lowered. To do. The Z direction drive signal is input to the Z direction drive circuit 40 of the PZT driver 38, and the Z direction drive signal 41 is output from the Z direction drive circuit 40 to the Z direction PZT actuator. As a result, the sample stage 14 moves up and down by a minute distance, and the vibration amplitude of the micropipette probe 12 is always kept constant. As will be described later, the vibration amplitude of the micropipette probe 12 depends on the distance between the tip of the probe and the surface of the workpiece 18. The distance from the surface of the workpiece 18 is kept constant.

  The personal computer 44 outputs an XY direction command signal 45 to the XY direction drive circuit 42 of the PZT driver 38. The XY direction drive circuit 42 accordingly outputs an XY direction drive signal 43 to the XY direction actuator, and the sample stage 14 moves in the XY direction. Thus, a desired position on the surface of the workpiece 18 can be opposed to the tip of the microprobe pipette 12. From the Z direction drive circuit 40, a Z direction command signal (this corresponds to the height signal of the surface of the workpiece) is input to the personal computer 44. Therefore, the personal computer 44 can acquire the value of the Z direction command signal corresponding to the XY direction command signal, that is, the height signal at each position on the surface of the workpiece, and based on this, the workpiece can be obtained. Surface height images can be created.

  FIG. 3 is an explanatory diagram showing the operating principle of the scanning shear force microscope. The upper state A is a state in which the distance d between the tip of the probe 54 and the surface of the sample 56 is sufficiently separated. At this time, the probe 54 vibrates at a predetermined resonance frequency, and its amplitude becomes the maximum value Wmax. In the upper B state, the tip of the probe 54 approaches the surface of the sample 56, and the vibration amplitude of the probe 54 is affected by the sample 56. That is, when the probe 54 that vibrates near the resonance frequency approaches the sample 56, the probe 54 receives a lateral force called shear force. The vibration amplitude at this time becomes smaller than the state of A. When the probe 54 further approaches the sample 56, the vibration amplitude is rapidly attenuated. When the tip of the probe 54 comes into contact with the surface of the sample 56 as shown at C in the upper stage, the vibration amplitude becomes zero. The lower graph shows the distance d between the tip of the probe 54 and the surface of the sample 56 on the horizontal axis, and the vibration amplitude of the probe 54 on the vertical axis. When the distance d is larger than d1, it corresponds to the upper state A, and the vibration amplitude of the probe is Wmax. As the distance d becomes smaller than d1, the vibration amplitude decreases, and this intermediate state corresponds to the upper B state. As the distance d becomes smaller and approaches zero, the vibration amplitude becomes zero. This corresponds to the upper C state. A region where the distance d is smaller than d1 is a control region, and this control region is defined as a region where the vibration amplitude changes according to the distance d. If a specific vibration amplitude value in this control region is a reference value Wref, the sample is scanned relative to the probe, and the distance d is controlled so that the vibration amplitude is always equal to the reference value Wref. A change in the height of the sample surface can be expressed by a change in the distance d. In this way, the surface shape of the sample can be acquired. In the embodiment of the present invention, the reference value Wref is set to 80% of Wmax.

  When the probe is gradually moved away from the state in contact with the sample, the vibration amplitude of the probe increases, but the rising curve 58 is different from the falling curve 60 when the distance is reduced. That is, it has hysteresis characteristics. The slope of the descending curve 60 indicates the sensitivity of distance control (height control).

  FIG. 4 is a plan sectional view showing a method for manufacturing a micropipette probe. The micropipette probe is manufactured by a micropipette enlarger. The stretching device includes a first chuck 62, a second chuck 64, and a heating device 66. The first chuck 62 holds one end of the glass tube 68 and applies a pulling force 70 in the left direction of the drawing. The second chuck 64 grasps the other end of the glass tube 68 and applies a pulling force 72 in the right direction of the drawing. The heating device 66 includes a heating coil 74 that surrounds the periphery of the glass tube 68, and a heating power source 76 that supplies power to the heating coil 74. When a tensile force is applied to the glass tube 68 by the two chucks 62 and 64, power is supplied from the heating power source 76 to the heating coil 74 to heat the center of the glass tube 68, and the center of the glass tube 68 is softened. As it grows, its diameter becomes smaller and finally it is separated at the center. This produces a micropipette probe with a tapered tip. By adjusting the strength of the tensile force applied to the two chucks 62 and 64 and the power supplied by the heating power source 76, the opening diameter of the tip of the micropipette probe to be completed can be changed. The higher the temperature, the smaller the opening diameter. In the examples, those having an opening diameter of about 200 nm were used.

  FIG. 5 is a plan view showing a schematic shape of the completed micropipette probe 12. A first taper portion 77 and a second taper portion 78 are formed near the tip of the probe 12.

  FIG. 6 is an explanatory view showing the structure of the micropipette probe and the electric circuit for plating. In FIG. 3, the part showing the mechanical structure is a front view. The vicinity 46 of the tip of the hollow micropipette probe 12 has a tapered shape, and the tip is open. The opening diameter is about 200 nm. The inside of the micropipette probe is filled with a plating solution 48. A conductive core wire 50 passes through the inside of the micropipette probe. A core wire 50 is drawn out from the upper end of the micropipette probe 12, and this core wire 50 is connected to one end of a DC power source 52. The other end of the DC power source 52 is connected to the workpiece support 16 made of a conductor and is grounded.

In this embodiment, a copper sulfate aqueous solution is used as the plating solution 48, and this plating solution 48 contains Cu ²⁺ ions. An n-type silicon substrate is used as the workpiece 18. When a voltage is applied between the plating solution 48 and the workpiece support 16, Cu (copper) is deposited on the surface of the workpiece 18. At that time, an electrochemical reaction as shown in the equation (1) in FIG. 11 occurs in the cathode (workpiece). Further, an electrochemical reaction as shown in the expression (2) in FIG. 11 occurs at the anode (core wire in the micropipette probe).

  The plating process is as follows. First, as shown in FIG. 6, the plating solution 48 is filled into the micropipette probe 12. In FIG. 1, an XY direction command signal 45 is output from the personal computer 44 to move the sample table 14 in the XY direction, and a desired point of the workpiece 18 (a point where plating is desired) is directly below the micropipette probe 12. Bring it to. Next, the control circuit 36 is set to the processing mode, and the Z direction command signal 37 is output until the workpiece 18 contacts the micropipette probe 12. When the vibration amplitude of the micropipette probe 12 becomes zero, it is determined that the probe 12 is in contact with the workpiece 18. When the micropipette probe 12 contacts the workpiece 18, the output voltage of the DC power source 52 is applied between the core wire 50 and the workpiece support 16 for a predetermined time in FIG. 6. As a result, a voltage is applied between the plating solution 48 and the workpiece 18, and a plating film 88 is formed on the surface of the workpiece 18.

  FIG. 7 is an example of an acquired image obtained by forming a 1-dot copper plating film on a silicon substrate by plating according to the present invention. The size of the rectangular image 82 is 1.8 μm × 1.8 μm, and a plating film 80 having a size of about 200 nm is formed in the center thereof. This image was obtained by performing plating processing and then switching to the observation mode and scanning the micropipette probe in a non-contact state on the silicon substrate. Only where the plating film is present is high, and the high portion is shown separately from other portions (for example, colored). The scanning conditions in the observation mode are as shown in FIG. The plating conditions are an applied voltage of 0.2 V and a voltage application time of 6 seconds.

  FIG. 8 is a graph showing a change in height along the line 79 in the image of FIG. The horizontal axis is the position along the line 79, and the vertical axis is the height of the silicon substrate surface. A high portion with a width of 207 μm is observed near the center, and this portion corresponds to a plating film.

  FIG. 9 is an example of an acquired image obtained by forming a 9-dot copper plating film on a silicon substrate by plating according to the present invention. The size of the rectangular image 84 is 8 μm × 8 μm, and nine plating films 86 are formed within the range. The scanning conditions in the observation mode are as shown in FIG. As for the plating conditions, the applied voltage is 6 V and the voltage application time is 6 seconds for all nine points.

  FIG. 10A is a graph showing the relationship between the applied voltage and the dot diameter of the plating film. The horizontal axis is the applied voltage of the plating circuit, and the vertical axis is the dot diameter of the formed plating film. The voltage application time is all 6 seconds. As the applied voltage increases, the dot diameter tends to increase. The dot diameter obtained is in the range of approximately 200-600 nm.

  FIG. 10B is a graph showing the relationship between the voltage application time and the dot diameter of the plating film. The horizontal axis represents the voltage application time of the plating circuit, and the vertical axis represents the dot diameter of the formed plating film. The applied voltage is all 8V. As the application time increases, the dot diameter tends to increase. The obtained dot diameter is in the range of approximately 300 to 1000 nm.

  In the above embodiment, an example of copper plating is shown as the plating process, but other metal plating is possible by changing the plating solution.

It is a block diagram of the scanning shear force microscope for performing fine plating processing. It is a perspective view of the principal part of the scanning shear force microscope shown in FIG. It is explanatory drawing which shows the operating principle of a scanning shear force microscope. It is plane sectional drawing which shows the manufacturing method of a micropipette probe. It is a top view which shows schematic shape of a micropipette probe. It is explanatory drawing which shows the structure of a micropipette probe, and the electric circuit for plating. The acquired image of one point processing and its conditions are shown. It is the graph which showed the height change along the line in the image of FIG. An acquired image of nine-point processing and its conditions are shown. It is a graph which shows the relationship between an applied voltage and the dot diameter of a plating film, and a graph which shows the relationship between a voltage application time and the dot diameter of a plating film. It is a reaction formula of an electrochemical reaction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Probe support body 12 Micropipette probe 14 Sample stage 16 Workpiece support body 18 Workpiece object 20 Laser diode 24 Two-division photodiode 28 Oscillator 30 IV converter 32 Arithmetic circuit 34 Lock-in amplifier 36 Control circuit 38 PZT driver 40 Z direction drive circuit 42 XY direction drive circuit 44 Personal computer 48 Plating solution 50 Core wire 52 DC power supply 88 Plating film

Claims (6)

A fine processing method comprising the following steps.
(A) A step of preparing a scanning shear force microscope including a hollow probe having an open tip.
(A) A step of filling the hollow probe with a processing liquid.
(C) contacting the tip of the hollow probe with a desired position on the surface of the workpiece;
(D) A step of applying a voltage between the machining liquid and the workpiece for a predetermined time to perform fine machining on the surface of the workpiece.   2. The microfabrication method according to claim 1, wherein a core wire made of a conductor is passed through the hollow probe, the core wire is in contact with the processing liquid, and a voltage is applied between the core wire and the workpiece. A voltage is applied between the machining fluid and the work piece by applying a micro-machining method.   3. The micromachining method according to claim 1, wherein the machining liquid is a liquid containing metal ions, and a voltage is applied between the machining liquid and the work piece so that a surface of the work piece is formed. A fine processing method characterized in that fine plating is applied to the surface.   4. The micromachining method according to claim 1, wherein the scanning is performed by scanning the hollow probe in a non-contact state with respect to a surface of the workpiece subjected to micromachining. 5. A fine processing method, wherein a processing state of a surface of the workpiece is observed using a type shear force microscope. A microfabrication device having the following configuration.
(A) A scanning shear force microscope comprising a hollow probe having an open end, a sample stage, and a moving mechanism that moves the sample stage in a three-dimensional direction relative to the hollow probe.
(A) A processing liquid filled in the hollow probe.
(C) A conductive workpiece support that is fixed to the sample stage and supports the workpiece.
(D) An electric circuit capable of applying a voltage between the machining fluid and the workpiece support.   6. The micromachining apparatus according to claim 5, wherein a core wire made of a conductor is disposed inside the hollow probe.

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