JPH05299014A - Manufacture of probe for probe scanning type microscope - Google Patents

Abstract

PURPOSE:To manufacture a probe for a probe scanning type microscope having the small tip radius of curvature and tip angle for measuring a steep uneven shape or the like with good accuracy. CONSTITUTION:Fine holes are formed on a silicon substrate 3 by performing electrolys is in an electrolyte 6 containing hydrofluoric acid with the silicon substrate 3 as a positive electrode and a conductive electrode as a negative electrode 2. Layer, an Si3N4 thin film is formed on the silicon substrate 3 including the fine holes by using the silicon substrate 3 as a mold. After that, a probe is formed on the Si3N4 thin film by removing the silicon substrate 3 by etching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a probe for a scanning probe microscope, and more particularly to a probe for stably and accurately measuring extremely small irregularities of 0.1 nm or less, and steep irregularities. The present invention relates to a method for manufacturing a probe for a needle scanning microscope.

[0002]

2. Description of the Related Art In recent years, an atomic force microscope (hereinafter referred to as AFM) and a scanning tunneling microscope (hereinafter referred to as STM) have been developed as an apparatus for observing a solid surface on an atomic scale. These microscopes are probe scanning microscopes (hereinafter SPM
It is called, and the various kinds of local physical quantities such as atomic force and electric conductivity are detected and imaged by scanning the sample surface with a probe having a sharp tip.
Therefore, the resolution of SPM depends on the radius of curvature of the tip and the tip angle of the probe, and researches for making them smaller are being actively conducted. The AFM has a probe at one end to detect minute force, and the length is 100 μm to 200 μm.
A certain degree of cantilever is required (see FIG. 2 (b)).
Conventionally, this probe is manufactured by using an etch pit created by anisotropically etching a part of the silicon crystal surface as a template. In STM, a probe with a sharp tip is created by electrolytically polishing platinum or tungsten wire.

[0003]

However, although it is possible to observe individual atoms arranged on an extremely smooth surface with conventional AFMs and STMs using a probe, sharp undulations on the scale of several nm to several tens of nm are possible. In the measurement of a certain surface shape, since the tip angle of the probe used is large, the tip cannot reach the bottom surface of the minute concave portion, and there is a problem that the measurement cannot be performed with high accuracy. Especially in the AFM, which can measure insulators and has a wide range of applications, the tip angle of the conventional probe is 30.
Since it is as large as ~ 70 degrees, there is a strong demand for the realization of a cantilever with a probe having a small tip radius of curvature and a small tip angle.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing a probe for a scanning probe microscope having a small tip curvature radius and tip angle.

[0005]

According to the present invention of claim 1, silicon is used as an anode and a conductive electrode is used as a cathode to form fine pores in silicon by electrolysis, and then silicon is used as a template. By forming a substance other than silicon on silicon containing at least fine pores, and then etching away the silicon in which the fine pores are formed,
A method for manufacturing a probe for a scanning microscope, which produces a protrusion of a formed substance.

According to the present invention of claim 3, the cathode is formed in a shape with a sharp tip, and the cathode is brought close to the silicon surface to perform electrolysis. It is a method of manufacturing a needle.

[0007]

According to the present invention, fine holes having a diameter of several to several tens nm and a depth of several μm or more are formed on the surface of silicon by electrolysis using silicon as an anode. Create a probe or a cantilever with a very small radius of curvature and tip angle.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing its embodiments.

First Embodiment FIG. 1 is a schematic view of a mold manufacturing apparatus for explaining a method for manufacturing a probe for a probe scanning microscope according to a first embodiment of the present invention. That is, the mold manufacturing apparatus is provided with the Teflon container 1 for performing electrolysis.
A cathode 2 made of, for example, a platinum electrode is arranged in the upper center of the center of the
The electrolyte 6 is replenished inside the Teflon container 1. The positive electrode of the DC power supply 4 is connected to the silicon substrate 3, and the negative electrode of the DC power supply 4 is electrically connected to the cathode 2 via the ammeter 5.

Micropores are formed on the surface of the silicon substrate 3 by the mold manufacturing apparatus configured as described above. That is,
As the electrolytic solution 6, a 1: 1 solution of 45% hydrofluoric acid and ethyl alcohol was used. The surface of the silicon substrate 3 is made of acid-resistant insulating resin 1 except for the area of 5 μm square where fine holes are created.
It is covered with 7. In this state, the DC power supply 4 supplies a current for 3 minutes while keeping the current at 25 nA. As a result, several to several tens of micropores could be formed in the area of 5 μm square.

Next, a probe is formed by using the silicon substrate 3 in which the fine holes are formed as described above as a mold. First, the acid resistant insulating resin 17 of the silicon substrate 3 was removed and washed with water, and then a Si ₃ N ₄ thin film with a thickness of 1 μm was deposited at a temperature of 400 ° C. or lower by a normal low pressure CVD method. afterwards,
As shown in FIG. 2A, the Si ₃ N ₄ thin film 7 was processed by using a photolithography process, and 9 parts of a cantilever was prepared. Further, the glass substrate 8 is used as a cantilever holding portion for S.
After adhering on the i ₃ N ₄ thin film 7 (see FIG. 2B), the silicon substrate 3 was removed by etching. By mechanically removing the other probe so as to leave one of the plurality of probes formed at the tip of the cantilever 9 as shown in FIG.
A cantilever 9 with a probe 10 as shown in (b) was completed.

Second Embodiment FIG. 3 shows a mold manufacturing apparatus for forming fine holes in the crystalline silicon of the second embodiment. A needle-shaped platinum electrode 11 serving as a cathode is arranged in the center of the Teflon container 1, and a P-type silicon substrate 3 serving as an anode is arranged in the lower center of the Teflon container 1. A DC power source 4 and an ammeter 5 are connected to the platinum electrode 11 and the silicon substrate 3. Electrically connected through. Further, as the electrolytic solution 6, a 1: 1 solution of 45% hydrofluoric acid and ethyl alcohol was used. The platinum electrode 11 is a mechanical position adjusting device 1 so that the position can be adjusted.
It is attached to 2. The platinum electrode 11 is processed by electrolytic polishing so that the radius of curvature of the tip becomes 100 nm or less, and as shown in FIG. 4, the side surface excluding the tip is covered with an acid resistant insulating resin 13. The distance between the tip of the platinum electrode 11 and the silicon substrate 3 was adjusted to 10 μm using the mechanical position adjusting device 12 while observing the microscope. In this state, the platinum electrode 11 is used as a cathode and the DC power source 4 is used.
As a result, by applying a current of 0.1 μA for 2 minutes, several tens of micropores with a depth of 10 μm could be formed in a region of about 20 μm in diameter. Using these fine holes as a mold, the cantilever 9 with a probe for AFM is used as in the first embodiment.
Could be created (see FIG. 2 (b)). Here, the radius of curvature of the tip of the platinum electrode 11 is preferably smaller than the distance between the platinum electrode 11 and the silicon surface.

In the above method, when an N type silicon substrate or a high resistance silicon substrate is used, 500
It was possible to make the material porous by applying an electric current while irradiating it with light from a tungsten lamp of W from a distance of about 15 cm.

Although platinum is used as the cathode of the conductive electrode in the above embodiment, the present invention is not limited to this.
Other conductive electrodes may be used as long as they are materials that are not affected by hydrofluoric acid, such as C and semiconductor diamond.

In the above embodiment, the electrolytic solution 4 is 4
A 1: 1 solution of 5% hydrofluoric acid and ethyl alcohol was used, but the hydrogen fluoride concentration may be 5% or more. Other electrolytic solutions may be used as long as porous silicon can be produced with good reproducibility.

Third Embodiment FIG. 5 shows a mold manufacturing apparatus for forming fine holes in the crystalline silicon of the third embodiment. A platinum electrode 11 serving as a cathode is arranged in the center of the Teflon container 1, and a P-type silicon substrate 3 serving as an anode is arranged below the platinum electrode 11, and a DC constant current power source 4 is provided on the platinum electrode 11 and the silicon substrate 3. It was electrically connected via an ammeter 5. Further, a feedback control circuit 18 was connected to the output of the ammeter 5, and the feedback control circuit 18 was connected to the three-dimensional fine movement device 14 and the computer 15 provided in the mechanical position adjusting device 12. The silicon substrate 3 used was one in which a cylindrical hole 16 having a diameter of 200 μm and a depth of 3 mm was mechanically and chemically processed on the surface of the platinum electrode 11 side. Also platinum electrode 1
No. 1 is processed by electrolytic polishing so that the radius of curvature of the tip becomes 50 nm or less, and as shown in FIG. 4, the side surface excluding the tip is covered with an acid resistant insulating resin 13. Here, the output signal from the ammeter 5 is the feedback control circuit 18
It is transmitted to the three-dimensional fine movement device 14 through the through-hole, and the distance between the platinum electrode 11 and the silicon substrate 3 can be controlled so that the current becomes constant. The three-dimensional fine movement device 14 is a combination of piezoelectric bodies in three orthogonal directions, and by using this, the platinum electrode 11 can be moved to an arbitrary place within the silicon substrate surface 3 according to an instruction from the computer 15. As the electrolytic solution 6, a 1: 1 solution of 20% hydrofluoric acid and ethyl alcohol was used.

A method of manufacturing fine holes using this apparatus will be described below.

First, the mechanical position adjusting device 1 is observed while observing the microscope so that the tip of the platinum electrode 11 is directly above the hole 16.
2 was used to adjust the position of the platinum electrode 11.

Next, a voltage of 1 V was applied by the DC power source 4 with the platinum electrode 11 as the cathode and the silicon substrate 3 as the anode. The current value at this time was about 50 pA. Using the three-dimensional fine movement device 14 and the mechanical position adjusting device 12, the platinum electrode 11 was gradually brought close to the silicon substrate 3 while monitoring the current value, and the approach was stopped when the current value became 1 nA. At this time, the current rapidly increases exponentially as the distance decreases, so most of the current is a tunnel current, and it is considered that the distance between the platinum electrode 11 and the silicon substrate 3 is about 1 nm. In this state, the platinum electrode 11 is fixed, and the applied voltage is maintained for 2 minutes, so that the platinum electrode 1
It was possible to form fine holes 19 having a diameter of 30 nm and a depth of 1 μm just below 1 (see FIG. 6A).

When performing electrolysis using the above-mentioned tunnel current, the radius of curvature of the tip of the platinum electrode 11 is preferably 0.1 μm or less (if it is larger than that, the tunnel current may become unstable and controllability may be increased. Can't make fine holes well).

After the silicon substrate 3 having the fine holes 19 thus formed is washed with water, the organometallic gas of tungsten, W (CO) _6, is used to form a low pressure CVD method at 400 ° C.
At the temperature below, as shown in FIG. 6 (a), the thickness is 50 μm.
Of the tungsten thin film 20 was deposited (if the temperature at this time is higher than 400 ° C., the fine pores may disappear,
Cannot create a probe with good reproducibility). After that, FIG.
As shown in (b) and (c), the silicon substrate 3 was removed by etching, and burrs were removed to complete a tungsten STM probe.

In the above embodiment, Si is used as a material to be deposited on the silicon substrate 3 having the fine holes 19 formed therein.
₃ N ₄ or tungsten was used, but not limited to this,
Of course, dielectrics such as SiO ₂ and TiO ₂ and metals such as Au and Pt can also be effectively used.

In the above embodiment, the case where the low pressure CVD is used as the thin film deposition method has been described, but the present invention is not limited to this, and plasma CVD, a plating method, a sputtering method or the like can be used. In particular, the CVD method makes it possible to produce a probe having an excellent shape in which the raw material gas wraps around most.

Further, in the above embodiment, crystalline silicon is used as the silicon for forming the fine holes, but the silicon is not limited to this, and other silicon such as amorphous may be used as long as the fine holes can be formed.

[0025]

As is clear from the above description, the present invention has an advantage that a probe for a scanning probe microscope having a small tip curvature radius and tip angle can be manufactured.

Further, by using the manufactured probe, there is an advantage that the resolution and accuracy of the probe scanning microscope can be improved.

[Brief description of drawings]

FIG. 1 is a schematic view of a mold manufacturing apparatus for explaining a method of manufacturing a probe for a scanning probe microscope according to a first embodiment of the present invention.

FIG. 2A and FIG. 2B are process diagrams showing a method for manufacturing a probe for a scanning probe microscope according to the first embodiment.

FIG. 3 is a schematic view of a mold manufacturing apparatus for explaining a method for manufacturing a probe for a scanning probe microscope according to a second embodiment of the present invention.

FIG. 4 is a partial enlarged view of a cathode in a mold manufacturing apparatus for a probe for a scanning probe microscope according to a second embodiment.

FIG. 5 is a schematic view of a mold manufacturing apparatus for explaining a method of manufacturing a probe for a scanning probe microscope according to a third embodiment of the present invention.

6A, FIG. 6B and FIG. 6C are process diagrams showing a method of manufacturing a probe for a probe scanning microscope according to a third embodiment.

[Explanation of symbols]

1 Teflon Container 2 Cathode 3 Silicon Substrate 4 DC Power Supply 5 Ammeter 6 Electrolyte 7 Si ₃ N ₄ Thin Film 8 Glass Substrate 9 Cantilever 10 Probe 11 Platinum Electrode 12 Mechanical Positioning Device 13, 17 Insulating Resin 14 3 Dimensional Fine Motion Device 15 computer 16 hole 18 feedback control circuit 19 fine hole 20 platinum thin film

Claims (9)

[Claims] 1. Silicon is used as an anode, and a conductive electrode is used as a cathode to form micropores in the silicon by electrolysis, and then the silicon is used as a template on the silicon containing at least the micropores. A probe for a scanning microscope, wherein a substance other than silicon is formed, and then the silicon in which the fine holes are formed is removed by etching to form a protrusion of the formed substance. Manufacturing method. 2. The method for manufacturing a probe for a probe scanning microscope according to claim 1, wherein silicon is covered with an insulating material except for a part of the cathode side. 3. The probe scanning microscope according to claim 1, wherein the cathode is formed to have a sharp tip, and the electrolysis is performed by bringing the cathode close to the silicon surface. Method of manufacturing probe. 4. The probe scanning microscope according to claim 3, wherein the distance between the silicon surface and the tip of the cathode is maintained at substantially 1 nm, and the electrolysis is performed by a current including a tunnel current. Manufacturing method for medical probe. 5. The method for manufacturing a probe for a scanning probe microscope according to claim 3, wherein the surface of the cathode other than the tip is covered with an insulating material. 6. The manufacturing of a probe for a scanning probe microscope according to claim 1, wherein the electrolysis is performed while irradiating the silicon surface with light having an energy larger than an energy gap of silicon. Method. 7. The method for manufacturing a probe for a scanning probe microscope according to claim 1, wherein the cathode is made of a metal containing platinum as a main component. 8. The method for manufacturing a probe for a probe scanning microscope according to claim 1, wherein silicon is crystalline. 9. The method for manufacturing a probe for a probe scanning microscope according to claim 1, wherein the electrolysis is performed in a solution containing hydrofluoric acid.