JPH07311206A - Manufacture of micro-probe - Google Patents

Abstract

PURPOSE:To form a probe by minimum processes by a method wherein a recessed substrate, is covered with a probe material layer, a mask pattern with a peripheral opening section is formed around a recessed section, the material layer in the opening section is removed, the residual section of the material layer except the recessed section is taken off mechanically, and the material layer in the recessed section is abutted and transferred onto another substrate as a probe. CONSTITUTION:An Si single crystal substrate 101 is etched by the mask of an Si3N4 film and a KOH solution, thus forming a hole section 201. A probe material layer 202 composed of Au is vacuum-deposited on the substrate 101, a mask 203 for etching is shaped through photolithography, and a peripheral opening section 102 is formed to the mask 203. The opening section 102 is removed by a mixed etchant of I and a KI aqueous solution, the mask 203 is taken away by an organic solvent, and a material-layer peripheral section 204 is peeled and detached mechanically from the peripheral section of the substrate 101. The substrate 101 is pushed against a transfer side substrate 205, overlaid with a probe transfer layer 206, and a probe seat section 104 is abutted against the substrate 205. Lastly, the substrate 101 is separated to form a probe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a scanning tunneling microscope or an information processing apparatus for applying high-density recording, reproduction, and erasing of information by applying the principle thereof, or an atomic force microscope for detecting a minute force. More specifically, the present invention relates to a method for manufacturing a microprobe that has a small tip curvature and exhibits excellent characteristics for the above-mentioned applications, and that can also be used for multiple probes with high mass productivity. .

[0002]

2. Description of the Related Art Recently, a scanning tunneling microscope (hereinafter referred to as "STM") has been developed which allows direct observation of the electronic structure of surface atoms of a conductor (G. Binnig et al. P.
hys. Rev. Lett. , 49, 57 (198
2)), it has become possible to measure with high resolution of real space images regardless of single crystal or amorphous. Such an STM utilizes that a tunnel current flows when a voltage is applied between a metal probe and a conductive substance to bring them closer to a distance of about 1 nm. Since this current is very sensitive to changes in the distance between the two and changes exponentially, observe the surface structure in real space with atomic resolution by scanning the probe so as to keep the tunnel current constant. You can The object of analysis using this STM is limited to the conductive material, but it is also being applied to the structural analysis of the insulating layer thinly formed on the surface of the conductive material. Further, since the above-mentioned devices and means use the method of detecting a minute current, they have an advantage that they can be observed with low power without damaging the medium. Also, since it can be operated in the atmosphere, S
A wide range of applications of TM are expected.

An ultra-high density recording / reproducing apparatus is one of the application examples of this STM, but in order to achieve a high recording density, the radius of curvature of the tip of the STM probe is required to be small. At the same time, from the viewpoint of improving the functions of the recording / reproducing system, in particular, from the viewpoint of speeding up, it has been proposed to drive a large number of probes at the same time (multi-probe). It is necessary to manufacture uniform probes.

Further, an atomic force microscope (hereinafter referred to as "AFM")
According to the above), the repulsive force and attractive force acting on the surface of the substance are detected, so that the uneven surface image of the sample surface can be measured regardless of the conductor or the insulator. For this atomic force microscope, a cantilever with a microprobe formed at its free end is used, and like the STM, it is required that the radius of curvature of the tip of the probe be small.

Conventionally, as a method of forming the above-mentioned microprobe, a microprobe formed by anisotropic or isotropic etching using single crystal silicon by using a semiconductor manufacturing process technology is known (special feature: Kaihei 3-135702). As shown in FIG. 6, the method for forming the microprobe is as follows.
First, a trench 603 is provided by anisotropic or isotropic etching using single crystal silicon (silicon) 601 coated with an etching mask 602, and this trench is used as a probe mold material. Then, silicon oxide, carbon, and After forming a cantilever layer 604 by coating with silicon nitride, silicon carbide, etc., and patterning into a cantilever shape, a cantilever portion 604 '.
The cantilever probe 605 made of the above-mentioned material is manufactured by removing the silicon underneath by etching.

However, the conventional method for forming a microprobe has the following problems. (A) Since the silicon substrate used as the mold material of the cantilever probe is removed by etching in a later step, there is a problem that the productivity is low and the manufacturing cost is high. (B) Although the tip of the cantilever probe is sharply formed, the probe is made of a material that is easily oxidized, such as silicon oxide or carbon. A coating of a conductive material is required. However, when an STM probe is formed by coating a conductive material on these probes, it is difficult to cover them, and it is difficult to obtain stable characteristics with an STM that handles a weak current such as a tunnel current. .

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and its object is to remove the substrate by etching in a subsequent process,
It is an object of the present invention to provide a method for manufacturing a probe in which productivity is improved, manufacturing cost is reduced, and multiple probes can be easily formed by forming the probe portion with a minimum etching process.

Another object of the present invention is to use a metal material as the material of the probe to obtain stable characteristics with good reproducibility as a microprobe and to form a sharp tip. A method for manufacturing a probe is provided. Further, even when the conductive material is coated according to the application after forming the probe portion, uniform coating is possible.

[0009]

The present invention which achieves the above object comprises a step of forming a concave portion on the surface of a first substrate, and a step of coating a probe material layer on the first substrate including the concave portion. ,
A step of forming a mask pattern having a peripheral opening on the first substrate around the recess, a step of removing the probe material layer of the peripheral opening formed around the recess, and a step other than the recess The step of mechanically removing the remaining portion of the probe material layer, the probe material layer provided in the recess on the first substrate is brought into contact with the second substrate, and the probe material layer is used as the probe portion. A method of manufacturing a microprobe for detecting a tunnel current or a micro force, comprising a step of transferring onto a second substrate. By forming the probe portion by transferring the probe material layer formed in the concave portion on the first substrate to the second substrate, the opening can be formed without etching the first substrate in a subsequent process. The microprobe can be formed extremely easily and accurately by etching only the part, which improves productivity and reduces the manufacturing cost, and the conventional silicon oxide, carbon, etc. can be used as the material for the SMT probe. It is possible to use a material other than the material that requires the coating of the conductive material, and it is possible to facilitate the multi-use of the probe. Here, it is preferable that the first substrate is a single crystal silicon substrate and a recess is formed on the substrate surface by crystal anisotropic etching, and before the probe material layer is coated on the first substrate. Is to cover the release layer of the probe material layer.

The present invention is also the method of manufacturing a microprobe described above, wherein the probe material layer is a single metal or an alloy. As described above, since the formation of the probe portion is performed not by etching the first substrate but by transferring it to the second substrate, it is possible to prevent deterioration and contamination of the material of the probe portion due to the etching liquid. As a result, stable characteristics with good reproducibility can be obtained as a microprobe, and the tip can be formed sharply, and excellent characteristics as a microprobe for AFM and STM can be realized. Here, preferably, the probe material layer has a multilayer structure composed of a single metal or alloy, and the transfer of the probe portion to the second substrate is
It can be achieved by pressure bonding between metal materials or by alloying between metal materials.

As described above, according to the present invention, it is possible to manufacture a probe having a small tip curvature and excellent characteristics for AFM and STM with excellent mass productivity.

[0012]

EXAMPLES The present invention will be described below with reference to examples shown in the drawings, but the present invention is not limited thereto.

(Embodiment 1) FIGS. 1 and 2 show a first embodiment of the present invention. FIG. 1 shows a step of forming a microprobe according to the present embodiment. FIG. 2 is a schematic cross-sectional view showing the steps of manufacturing in the order of g), and FIG. 2 is a schematic plan view of the circumferential opening of the etching mask portion used for forming the microprobe of this embodiment (corresponding to the step (c) in FIG. 1). Stage). In addition, FIG. 3 shows S using the microprobe obtained by the present invention.
FIG. 4 is an explanatory view showing a method of manufacturing a cantilever for TM, in which (a) and (b) are sequentially manufactured, and FIG. 4 is a block diagram of an STM device.

FIG. 1 is a diagram for explaining the steps of the method for forming a probe of the present embodiment. Step (a) is a silicon (100) single crystal substrate which is a probe forming substrate (first substrate) 101. The state in which the probe forming hole 201 is formed is shown in FIG. Process (a)
In forming the probe forming hole 201, a silicon nitride film (not shown) is used as a mask and an etching solution
The anisotropic etching method was performed using an aqueous potassium hydroxide solution heated to 00 ° C.

Step (b) shows a state in which the probe material layer 202 made of gold is formed to a thickness of 2 μm by the vacuum evaporation method. As the probe material, gold or an alloy of gold and silver, copper or the like is preferable because it has excellent releasability from the substrate, but in addition to such a metal, a metal such as platinum, iridium, palladium, rhodium, or ruthenium alone is used. Alternatively, those alloys can be preferably used. Further, the thickness of the probe material layer is usually 0.5 to 20 μm, preferably about 1 to 5 μm. If the probe material layer is too thin, the strength of the probe portion will be insufficient and it will be easily deformed. There is a problem that the size becomes large and the manufacturing time becomes long.

Step (c) shows a state in which a resist such as RU1100N (registered trademark, manufactured by Hitachi Chemical Co., Ltd.) is patterned as an etching mask 203 by using the photolithography method. The opening width of the mask peripheral opening 102 is 10 μm.
The workability and productivity are usually about 5 to 40 μm. Here, FIG. 2 is a plan view of a substrate for forming a fine probe in which a transfer probe is formed, and a circumferential opening of the etching mask 203 is provided around the probe 103 and the probe base 104. The state where 102 is provided is shown.

In this embodiment, the size of the probe portion 103 was 10 × 10 μm, the height was 8 μm, the radius of curvature of the tip portion was 0.01 μm, and the width of the probe base portion 104 was 5 μm.

In the step (d), the peripheral opening 102 is removed by etching with a mixed solution of iodine and an aqueous solution of potassium iodide, and then an etching mask 203 is formed with an organic solvent.
Shows a state in which is removed. In the present embodiment, the etching material 203 is removed first, and then the probe material peripheral portion 204 is mechanically removed. However, the order of the steps is reversed to etch the probe material peripheral portion 204 above it. Mask 20
It is also possible to remove the etching mask 203 on the probe portion 103 and the probe portion pedestal portion 104 mechanically after removing the etching mask 203 together with 3. The method of removing the probe material layer in the circumferential opening around the recess described above is not limited to the wet etching method using a solution that dissolves and removes the probe material layer, but also irradiation with ions excited in vacuum. It is possible to use a dry etching method using a gas such as an ion milling method for removing by ion removal or a reactive ion etching method for chemically removing activated ions, but since the removed portion is only an opening,
The former has the advantage that the consumption of the etching solution is small, and the latter has the advantage that the vacuum chamber and the like are less contaminated by the probe material.

Next, the peripheral portion 204 of the probe material layer is mechanically peeled and removed from the peripheral portion of the substrate 101 for forming a micro probe outside the probe forming region to obtain the state of step (e). At this time, since the peripheral portion of the probe material has a sufficient thickness as a film, it can be easily peeled from the peripheral portion by applying a mechanical tensile force using an adhesive such as tape. . Alternatively, the jig can be mechanically removed by pinching the end portion with a jig having a fixed sharp tip and moving the substrate side in parallel. In the invention, since the probe material layer other than the circumferential opening and the probe portion is mechanically separated from the first substrate, it can be easily regenerated as a probe material.

Next, as shown in step (f), the probe forming substrate 101 is pressed against the transfer side substrate 205 (second substrate) on which the probe transfer layer 206 is formed, and the probe pedestal portion 104 is attached. Contact the transfer substrate. Finally, the probe forming substrate 10
By pulling apart 1, a probe is formed as in step (g). As a means for transferring, the probe portion may be bonded to the substrate by pressure bonding between metal materials or may be formed by alloying between metal materials. For example, the former may be contacted and further heated, and the latter may be contacted and heated. In addition, it is possible to bond them by simultaneously applying pressure and heating. The probe transfer layer was formed by continuously depositing chromium as an undercoat layer to a thickness of 0.01 μm and gold to a thickness of 0.3 μm. Usually, the probe transfer layer is formed by coating chromium, nickel, titanium or the like with a thickness of about 0.005 to 0.05 μm to form an undercoat layer and then coating gold, aluminum or the like with a thickness of about 0.1 to 1 μm. Well, it may be appropriately designed according to the application of the probe.

FIGS. 3 and 4 are views for explaining an example in which the microprobe obtained in this embodiment is actually formed on a cantilever and used as a detection probe for STM, and FIG. 2 shows the case where a cantilever forming silicon substrate is used as the probe transfer side substrate of FIG. Figure 3 (a)
As shown in FIG.
In the state where the etching portion 302 is removed by etching and the thickness of the cantilever forming portion is reduced, the probe portion 103 and the probe pedestal portion 104 are transferred. Next, as shown in FIG. 3B, the peripheral portion of the cantilever is removed by etching from the back surface of the cantilever forming substrate 301 to remove the cantilever portion 303.
Was formed.

FIG. 4 shows an STM device to which this microprobe is applied. In FIG. 4, a tunnel current It flowing between the probe 405 and the sample 406 is detected, feedback is performed so that It becomes constant, and the Z direction of the XYZ drive piezo element is driven to detect the probe 405 and the sample 406. Keeps a constant distance from. Further, by driving the XY of the XYZ driving piezo element, the STM that is a two-dimensional image of the sample
The image can be observed. HOPG as a sample with this device
(Highly oriented pyrolytic graphite) Cleaved surface of substrate is bias current 1nA, scan area 0.01 × 0.01μm
As a result of observation, it was possible to obtain a good atomic image with good reproducibility.

(Embodiment 2) FIG. 5 shows a second embodiment of the method for manufacturing a micro-tip according to the present invention, which is a manufacturing step of another method for manufacturing a probe similar to that of the first embodiment. (Operations not specified are the same as in Example 1).

In step (a), a silicon oxide layer 502 is formed as a mask layer for etching on the surface of a single crystal (100) silicon substrate 501 by thermal oxidation to a thickness of 1 μm. Next, the silicon oxide layer in the etched portion is removed by photolithography and etching. Further, the probe forming hole 503 was formed by anisotropic etching using a potassium hydroxide aqueous solution. At this time, the hole 50
3 has a quadrangular pyramid shape having a sharp tip shape surrounded by the (111) crystal plane of silicon as in Example 1. In this embodiment, the depth to the tip is 7.1 μm. In the step (b), after the silicon oxide layer 502 is completely removed by a mixed aqueous solution of hydrofluoric acid and ammonium fluoride, silver is used as a peeling layer 504 by a vacuum film forming method to have a thickness of 0.05 μm (usually 0.01 to 0.1 μm). Formed). Process (c)
In addition, a platinum layer 505 was added as a probe material to 0.
3 μm (usually about 0.1 to 0.5 μm), nickel layer 5
06 to 5 μm (usually about 0.5 to 20 μm), gold layer 50
7 is continuously formed to have a thickness of 1 μm (usually about 0.1 to 5 μm) by using an electron beam evaporation method, and then gold of the opening 508 is formed by using photolithography and etching method as in the first embodiment. Layer 505, nickel layer 506, platinum layer 50
7 and the peeling layer 504 were sequentially removed. The gold layer 50
7 was etched by a mixed aqueous solution of potassium iodide and iodine, the nickel layer 506 was etched by a mixed aqueous solution of hydrochloric acid and ferric chloride, and the platinum layer 505 and the peeling layer 504 were etched by an ion milling method using argon plasma. . Next, the peripheral portion of the probe material layer was removed and the probe portion was transferred onto the transfer side substrate 509 by using the same method as in Example 1. In this embodiment, the transfer side substrate 50
9 as a bonding layer 510 with a nickel layer of 0.02 μm
(Normally about 0.005 to 0.05 μm) As an undercoat layer, aluminum was formed in a thickness of 0.3 μm (normally about 0.1 to 1 μm) by a vacuum deposition method. The joining was performed by holding the substrates together in a nitrogen atmosphere at 300 ° C. for 1 hour to form an alloy of gold and aluminum on the joined portion. Finally, the silver layer, which is the peeling layer 504, was removed using a nitric acid aqueous solution to form a microprobe portion.

When the microprobe portion of this embodiment was observed with an SEM (scanning electron microscope), it was confirmed that the probe had a sharp tip. At this time, the radius of curvature of the tip of the probe was 0.02 μm and the height was 14 μm.

Further, in this embodiment, the peeling layer 504 and the probe material layers 505 to 507 can be formed by using other metals and alloys. For example, the peeling layer 504 is a substrate such as gold. Which has excellent AFM and STM characteristics such as iridium, palladium and gold as the outermost layer 505 as the probe material layer, and aluminum, nickel and copper which are inexpensive as the intermediate layer 506. In addition, those that are easy to form, and examples of the innermost layer 507 include those that can be bonded to the transfer side, such as gold, aluminum, and indium. In the present embodiment, it is possible to use a material that is inexpensive and has a short forming time as the intermediate layer, and high mass productivity can be obtained.

[0027]

As described above, according to the present invention, it is possible to manufacture a probe having a small tip curvature and excellent characteristics for AFM and STM. At the same time, the amount of etching liquid consumed in the manufacturing process and the labor required for removing stains in the vacuum chamber and the like can be dramatically reduced, and high mass productivity can be obtained.

That is, the probe material layer formed in the recess on the first substrate is transferred to the second substrate to form the probe portion, so that the first substrate is removed by etching in a later step. Without the etching process of only the opening,
Since the micro probe portion can be formed extremely easily and accurately, the productivity can be improved, the manufacturing cost can be reduced, and the multi probe can be facilitated.

Further, as described above, since the probe portion is formed not by etching the first substrate but by transferring it to the second substrate, deterioration and contamination of the material of the probe portion due to the etching solution can be prevented. As a result, stable characteristics with good reproducibility can be obtained as a microprobe, and the tip can be formed sharply, and excellent characteristics as a microprobe for AFM and STM can be realized.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a step of forming a micro probe according to an embodiment of the present invention, showing steps of manufacturing in the order of (a) to (g).

FIG. 2 is a schematic plan view of a circumferential opening of an etching mask portion corresponding to step (c) of FIG.

[FIG. 3] ST using a microprobe obtained by the present invention
It is a manufacturing method of the cantilever for M, and is explanatory drawing which shows the process of manufacturing in order of (a) and (b).

[FIG. 4] ST using the microprobe obtained by the present invention
3 shows a block diagram of an M device.

FIG. 5 is a schematic cross-sectional view showing a step of forming a micro probe according to another embodiment of the present invention, showing steps of manufacturing in the order of (a) to (e).

FIG. 6 is a schematic explanatory view showing a manufacturing process of a conventional micro probe.

[Explanation of symbols]

 101 Micro Probe Formation Substrate 102 Mask Opening 103 Probe Section 104 Probe Base 201 201 Probe Formation Hole 202 Probe Material Layer 203 Etching Mask Section 204 Probe Material Layer Peripheral 205 Transfer Side Substrate 206 Probe Needle transfer layer 301 Cantilever forming silicon substrate 302 Etching portion 303 Cantilever portion 401 Bias applying power source 402 Tunnel current amplification circuit 403 XYZ driving driver 404 Cantilever 405 Probe 406 Sample 407 XYZ driving piezo element 501 Micro probe forming substrate 502 Silicon oxide layer 503 Probe forming hole 504 Release layer 505 Platinum layer 506 Nickel layer 507 Gold layer 508 Opening 509 Transfer side substrate 510 Probe transfer layer 601 Single crystal silicon 602 Etching mask 603 Trench 604 Can Chiller layer 604 'Cantilever part 605 Cantilever probe

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI technical display location // G01B 7/34 Z 21/30 Z (72) Inventor Yoshimasa Okamura 3 Shimomaruko Ota-ku, Tokyo Chome 30-2 Canon Inc. (72) Inventor Yasuhiro Shimada 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yu Nakayama 3-30-2 Shimomaruko, Ota-ku, Tokyo No. Canon Inc.

Claims (7)

[Claims] 1. A step of forming a concave portion on the surface of a first substrate, a step of coating a probe material layer on the first substrate including the concave portion, and a circumferential shape on the first substrate around the concave portion. A step of forming a mask pattern having an opening, a step of removing the probe material layer in the circumferential opening formed around the recess, and a step of mechanically removing the remaining probe material layer other than the recess And a step of bringing the probe material layer provided in the recess on the first substrate into contact with the second substrate and transferring the probe material layer as a probe portion onto the second substrate. 2. A method of manufacturing a microprobe for detecting a tunnel current or a microforce, comprising: 2. The method of manufacturing a microprobe according to claim 1, wherein the first substrate is a single crystal silicon substrate, and the concave portion is formed on the substrate surface by crystal anisotropic etching. 3. The method of manufacturing a microprobe according to claim 1, wherein the release layer of the probe material layer is coated before coating the probe material layer on the first substrate. 4. The method according to any one of claims 1 to 3,
A method for manufacturing a microprobe, wherein the probe material layer is a single metal or an alloy. 5. The method according to any one of claims 1 to 4,
A method for manufacturing a micro probe, wherein the probe material layer has a multi-layer structure made of a single metal or an alloy. 6. The method according to claim 4, wherein
A method for manufacturing a microprobe, wherein the transfer of the probe section to the second substrate is achieved by bonding the metal materials by pressure bonding. 7. The method according to any one of claims 4 to 5,
A method for manufacturing a microprobe, wherein the transfer of the probe section to the second substrate is achieved by a bond between metal materials by alloying.