CN201518226U - Composite cantilever beam needlepoint for micro-nano microtechnique - Google Patents

Abstract

The present utility model relates to a composite cantilever beam needlepoint for micro-nano microtechnique. The composite cantilever beam needlepoint comprising a base plate, cantilever beam and a needlepoint is characterized in that a layer of insulation dielectric layer is positioned on the base plate, the cantilever beam and the needlepoint, four varistors having an equal resistance value are distributed on the insulation dielectric layer, wherein, two varistors are positioned on the base plate, the other two varistors are positioned on the cantilever beam and are distributed in the direction parallel with the length direction of the cantilever beam, and the four varistors are connected into a wheatstone bridge through conducting wires. By adopting the utility model which pertains to the technical field of mechanical pick-up device, a composite cantilever beam needlepoint no longer uses laser positioning to measure tiny straining of a needlepoint of a microscope cantilever beam of a scanning detecting probe, but rather couples a varistor which is capable of measuring tiny straining and a cantilever beam needlepoint together to measure information of dynamics signals, electrostatic force, magnetic field distribution and the like, when the cantilever beam and a sample interact with each other.

Description

A composite cantilever tip for micro-nano microscopy

technical field

The utility model relates to a composite cantilever beam needle point for micro-nano microscopic technology, which belongs to the technical field of micro-mechanical sensors.

Background technique

With the development of nanotechnology, the requirements for testing methods of micro-nano signals (force, electricity, magnetism, light, etc.) are becoming stronger and stronger. The utility model and application of Scanning Electron Microscopy (SEM), Scanning Probe Microscopy (SPM), and Transmission Electron Microscopy (TEM) have greatly improved people's understanding and perception of the micro-nano world. ability. Scanning probe microscope is the collective name of atomic force microscope (Atomic Force Microscopy, AFM), electrostatic force microscope (Electrostatic Force Microscopy, EFM), magnetic force microscope (Magnetic Force Microscopy, MFM), etc. The structure and performance of its mechanical sensor will affect the instrument's Performance, measurement resolution and image quality have a dramatic impact. Generally, the probes of scanning probe microscopes are required to have low force elastic coefficient; high natural frequency, mechanical quality factors, etc., and also require the back to be flat and smooth to meet the requirements of laser displacement sensors, and must be accurate before each use. Only by adjusting the reflection angle and position of the laser through the back of the needle tip can the experiment be carried out. Although the laser displacement sensor can be positioned more accurately, it is precisely because of its existence that it is difficult to realize the coupling of the scanning probe fiber system with the transmission electron microscope system or scanning electron fiber system due to the complexity of the structure. , even if realized, the coupling of the two cannot maximize the advantages of the two due to the limitation of the structure.

In a series of articles published since 2002, the M.A.Haque research group mentioned that a nanomechanical sensor for transmission electron microscopy and scanning electron microscopy was fabricated using MEMS technology, and two mark positions were made on the sensor to measure the sample. The strain that occurs, and the mechanical signal applied to the sample is obtained, but as we all know, the field of view in the transmission electron microscope is small, and to monitor the changes in the positions of two marker points with a distance of several hundred μm, it must be done during the experiment. Continuously switch between high and low magnifications, so the opportunity to capture important structural change information may be lost during the process of magnification conversion, and it is impossible to truly monitor the structural changes of the sample in situ and at the same time obtain the occurrence of the sample. The strain and the stress signal applied to the sample.

The purpose of this utility model is to provide a positioning system without laser displacement, but use the resistance value of the piezoresistor on the back of the needle point to accurately and sensitively reflect the principle of the strain of the cantilever beam, and combine the needle point of the cantilever beam through an external circuit The piezoresistors on it form a Wheatstone bridge to accurately measure the strain of the composite cantilever beam tip when it is subjected to electrostatic force, magnetic force or other external forces. According to the Young’s modulus of the composite cantilever beam tip, the strain The magnitude of the stress can realize the sensing effect on the stress.

Utility model content

Aiming at the problems in the existing technology, the utility model aims to provide a composite cantilever beam tip which is suitable for scanning probe microscope and can be conveniently coupled in scanning electron microscope and transmission electron microscope to measure micro-strain by piezoresistor.

In order to achieve the above object, the utility model has the same base, cantilever beam and needle point as ordinary needle points, and there is a layer of insulating dielectric layer on the base, cantilever beam and needle point, and 4 equal resistances are distributed on the insulating dielectric layer. Two varistors are located on the base, and the other two are located on the cantilever beam, and are distributed parallel to the length direction of the cantilever beam. The 4 varistors are connected by wires to form a Wheatstone bridge.

Further, the substrate material of the composite cantilever tip is silicon, germanium, silicon carbide, silicon nitride, gallium nitride and the like. When used to measure the electrostatic force of the sample, a conductive layer such as gold, silver, platinum, copper, aluminum and other materials with good conductivity must be made on the surface of the needle tip; when used to measure the magnetic field distribution of the sample, a conductive layer can be made on the surface of the needle tip Layer ferromagnetic materials such as iron, cobalt, nickel. The size of the composite tip cantilever can be customized according to the needs of the experiment, and the shape can also be modified according to the needs of the experiment, and is not limited to the general shape of the probe used in the scanning probe microscope.

Further, the varistor is a material whose resistance changes significantly when the material is strained, such as: constantan, nickel-chromium alloy, nickel-chromium-aluminum alloy, platinum, platinum-aluminum alloy and other materials; the shape may not be fixed, but 4 The resistance values of the varistors must be the same.

Further, the electrodes and wires are made of gold, silver, platinum, copper, aluminum and other materials with good electrical conductivity.

Advantage of the utility model:

1. This utility model replaces the laser positioning system in the scanning probe microscope, which can more conveniently and accurately measure the tiny strain of the cantilever beam, and convert it into a mechanical signal and intuitively output it to the operator;

2. Since the utility model no longer uses the laser positioning system, it is convenient to couple the utility model with the scanning electron microscope and the transmission electron microscope sample to obtain the structural change information even at the atomic scale while testing the mechanical properties in situ Reveal the evolution process of material structure.

Description of drawings:

Figure 1 Cross-sectional view of composite cantilever beam needle point fabrication

Fig.2 Schematic diagram of the tip plane of the composite cantilever beam

Fig.3 Front view of composite cantilever beam tip

The drawing numbers are as follows:

1 substrate 2 cantilever beam 3 needle tip 4 base 5 insulating dielectric layer 6 varistor 7 wire 8 electrode I 9 electrode II 10 electrode III 11 electrode IV

Detailed ways:

A composite cantilever beam tip for micro-nano microscopy, comprising a base, a cantilever beam and a tip, characterized in that there is an insulating dielectric layer on the base, the cantilever beam and the tip, and 4 are distributed on the insulating dielectric layer Two piezoresistors with equal resistance, two piezoresistors are located on the base, and the other two piezoresistors are located on the cantilever beam and distributed parallel to the length direction of the cantilever beam, and the four piezoresistors are connected by wires into one Wheatstone bridge.

The composite cantilever beam needle point of the utility model is characterized in that it can be realized through the following process steps:

1. Prefabricate the cantilever beam 2, the needle point 3 and the base 4 on the substrate 1;

2. Prepare a layer of insulating dielectric layer 5 .

3. Prepare four piezoresistors 6 with equal resistance on the insulating dielectric layer 5 , two of which are located on the base 4 , and two are located on the cantilever beam 2 and distributed parallel to the length direction of the cantilever beam 2 .

4. Make wires 7 on the insulating dielectric layer 5 to connect the four varistors into a Wheatstone bridge.

Specific examples:

1. Use a silicon wafer with a diameter of 2 inches, an N-type (001) surface, and a thickness of 1 mm as the substrate. The front surface uses a mask and anisotropic wet etching to produce a needle tip with a height of 7 μm, a base with a length of 3 mm, and a width of 1 mm. 500 μm, 40 μm wide cantilever.

2. Fabricate a silicon dioxide insulating dielectric layer on the front and back of the silicon wafer with a thickness of 200nm.

3. The first photolithography on the insulating dielectric layer of silicon dioxide uses nickel-chromium alloy (Ni ₈₀ Cr ₂₀ ) to produce 4 varistors with a resistance value of 120Ω, 2 on the base and 2 on the cantilever on the beam and parallel to the length direction of the cantilever beam.

4. On the prepared piezoresistor, use gold for the second photolithography to make a wire with a thickness of 100nm and a width of 5μm and 4 electrodes I and electrode II with a thickness of 100nm, a length of 200μm, and a width of 200μm. Electrode III, electrode IV, connect 4 piezoresistors into a Wheatstone bridge.

5. The tip of the composite cantilever beam is finally formed by the back etching method, the final thickness of the cantilever beam is 2 μm, and the final thickness of the base is 400 μm.

6. Since multiple composite cantilever beam tips have been produced, it is necessary to split the silicon wafer into multiple composite cantilever beam tips through the split method.

7. Select a prepared composite cantilever beam tip and fix it on the sample stage of the scanning electron microscope. The cantilever beam and the needle tip are suspended in the air. Use wires to connect the electrode I, electrode II, electrode III, and electrode IV of the composite cantilever beam tip to the external mechanical test. Device connection, where electrode II and electrode III are used as voltage input terminals, connected to 3V DC, and electrode I and electrode IV are output terminals. Move the micromanipulator that has fixed the _SiO2 nanowires to a position close to the tip of the composite cantilever beam, and close the sample chamber.

8. After vacuuming, use the scanning electron microscope imaging system to observe the position of the micro-manipulator and the tip of the composite cantilever beam, and use the micro-manipulator rough adjustment device to move the micro-manipulator to the position of the tip of the composite cantilever beam so that the unfixed end of the _SiO2 nanowire can be just right. on top of the needle.

9. Fix the SiO ₂ nanowires on the needle tip by electron beam deposition, and move the micromanipulator to move the micromanipulator away from the needle tip, thereby applying force to the SiO ₂ nanowires to drive the bending of the cantilever beam. The strain and force of the cantilever beam will be Can be given by external mechanical testing equipment.

10. The stress-strain curve of SiO ₂ is obtained by combining the strain occurred in the sample.

Claims (1)

1. A composite cantilever beam needle point for micro-nano microscopic technology, comprising a base, a cantilever beam and a needle point, characterized in that, on the base, a cantilever beam and a needle point, there is an insulating dielectric layer, and on the insulating dielectric layer Distribute 4 varistors with equal resistance, two of which are located on the base, and the other two varistors are located on the cantilever beam and distributed parallel to the length direction of the cantilever beam, and the 4 varistors are connected by wires into a Wheatstone bridge.

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