Atomic force microscope and probe assembly therefor

Abstract

This invention discloses a probe assembly for an atomic force microscope, including a probe base with a probe hole and a scanning probe disposed in the probe hole. The scanning probe includes a cantilever beam, with a first end connected to the sidewall of the probe hole and a gap between the second end and the sidewall of the probe hole. A pressure sensor is disposed on the lower surface of the cantilever beam near the first end, and a piezoelectric ceramic layer and a probe tip are sequentially stacked and connected on the lower surface of the cantilever beam near the second end. The pressure sensor converts the deformation mechanical force of the cantilever beam into a corresponding electrical signal and outputs it to provide feedback on the interaction force between the probe tip and the sample under test. This invention uses a pressure sensor to convert the deformation mechanical force into an electrical signal to provide feedback for adjusting the height of the probe tip, avoiding the problem of mutual interference of feedback signals from levers in existing technologies when multiple probes are integrated into an array.

Description

Technical Field

[0001] This invention relates to the field of atomic force microscopy, and more specifically to an atomic force microscope and its probe assembly. Background Technology

[0002] Atomic force microscopy (AFM) is a novel probe microscopy technique developed from scanning tunneling microscopy. Its imaging principle utilizes the interatomic forces between the probe tip and the sample to scan and form images. Internationally, it has been widely used as a surface analysis instrument in various fields, including nanomaterials. With technological advancements, the applications of AFM are becoming increasingly broad, no longer limited to sample scanning, but also extending to areas such as atomic and molecular movement and micromachining.

[0003] As the application scope of atomic force microscopy (AFM) expands, the performance requirements for AFM are also increasing, especially for rapid, large-area scanning imaging of sample morphology and simultaneous scanning imaging of multiple localized points on the same sample. Traditional single-tip single-scan methods are no longer sufficient. Currently, when using AFM to scan the sample surface over a large area, scanning the sample surface morphology with a single probe tip is not only slow in scanning speed and imaging, but also requires sequentially raising the probe tip to determine the location of different localized points on the sample before making a single insertion. This is not only cumbersome but also inefficient.

[0004] Existing technologies include multi-probe arrays for sample scanning to improve efficiency. For example, Chinese patent application CN109799367A provides a laser-detected four-probe atomic force microscope (AFM). This AFM includes four probes, each equipped with a laser detection component to provide feedback on the deformation of the cantilever beam, thereby adjusting the height of the probe tip. This utilizes a traditional optical lever to provide feedback adjustment for the probe tip's contraction. However, this approach suffers from the following problems: using optical levers for feedback adjustment causes interference between multiple optical paths in the multi-probe array; and designing a complex optical path system to avoid interference limits the number of probes that can be integrated into the array. Summary of the Invention

[0005] In view of this, the present invention provides an atomic force microscope and its probe assembly to solve the problem of mutual interference of feedback signals when multiple probe assembly arrays are integrated.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A probe assembly for an atomic force microscope includes a probe base with a probe hole and a scanning probe disposed in the probe hole, the scanning probe including a cantilever beam; wherein...

[0008] The first end of the cantilever beam is connected to the side wall of the probe hole, and there is a gap between the second end and the side wall of the probe hole; a pressure sensor is provided on the lower surface of the cantilever beam near the first end, and a piezoelectric ceramic layer and a probe tip are sequentially stacked and connected on the lower surface of the cantilever beam near the second end;

[0009] The pressure sensor is used to convert the mechanical force of the cantilever beam deformation into a corresponding electrical signal and output it to provide feedback on the interaction force between the probe tip and the sample to be tested.

[0010] In a preferred embodiment, the pressure sensor is a piezoresistive flexible pressure sensor or a capacitive flexible pressure sensor.

[0011] In a preferred embodiment, the length of the cantilever beam is 100μm to 500μm, and the thickness of the cantilever beam is 500nm to 5μm.

[0012] In a preferred embodiment, the cantilever beam is an integrally formed structure with the probe base based on the etching of silicon wafer material.

[0013] In a preferred embodiment, the probe base is provided with an integrated circuit unit and a graphical electrical connection line. The integrated circuit unit is connected to the pressure sensor through the graphical electrical connection line. The integrated circuit unit is used to receive the electrical signal output by the pressure sensor and output the electrical signal to an external signal processing device.

[0014] In a preferred embodiment, the probe tip is selected from any one of contact mode probe tips, conductive probe tips, magnetic probe tips, high aspect ratio probe tips, and all-diamond probe tips.

[0015] In a preferred embodiment, the material of the piezoelectric ceramic layer is selected from any one of barium titanate, lead zirconate titanate, lead magnesium niobate, and polyvinylidene fluoride.

[0016] In a preferred embodiment, the probe base has a plurality of probe holes arranged in an array, and each probe hole is provided with a scanning probe that can be controlled independently.

[0017] In a preferred embodiment, the plurality of probe holes are arranged in an array of M rows × N columns on the probe base, and all scanning probes in the same row of probe holes have the same connection orientation; M and N are integers greater than 2.

[0018] Another aspect of the present invention is to provide an atomic force microscope, including the probe assembly described above.

[0019] The atomic force microscope and its probe assembly provided in this invention include a pressure sensor. This pressure sensor converts the mechanical force of the cantilever beam's deformation into an electrical signal, which is then used to adjust the height of the probe tip. Compared to traditional techniques that use optical levers for feedback adjustment, this invention avoids mutual interference in feedback adjustments when integrating multiple probes into an array for rapid, large-area scanning imaging of sample morphology, or when simultaneously scanning multiple points on the same sample. This significantly improves the speed and efficiency of scanning sample surface morphology. Attached Figure Description

[0020] Figure 1 This is a structural block diagram of the atomic force microscope provided in the embodiments of the present invention;

[0021] Figure 2 This is a top view of the probe assembly provided in an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the structure of a scanning probe in one embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of the scanning probe in another embodiment of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the drawings. The embodiments of the present invention shown in and described with reference to the drawings are merely exemplary, and the present invention is not limited to these embodiments.

[0025] It should also be noted that, in order to avoid obscuring the invention with unnecessary details, only the structures and / or processing steps closely related to the solution according to the invention are shown in the accompanying drawings, while other details that are not closely related to the invention are omitted.

[0026] This invention provides an atomic force microscope, such as... Figure 1As shown, the atomic force microscope includes a probe assembly 100, a data analysis system 200, a control system 300, and a feedback system 400 connected in sequence by electrical signals. The probe assembly 100 is used to test the sample and output the test parameters to the data analysis system 200. The data analysis system 200 collects and analyzes the test parameters received from the probe assembly 100 and feeds the analysis results back to the control system 300. Based on the analysis results, the control system 300 issues control commands to the feedback system 400, and the feedback system 400, based on the control commands, sends adjustment signals to the probe assembly 100 to adjust the test parameters of the probe assembly 100.

[0027] See Figure 2 and Figure 3 The probe assembly 100 in this embodiment of the invention includes a probe base 1 and a scanning probe 2 connected to the probe base 1. A probe hole 11 is formed on the probe base 1, and the scanning probe 2 is disposed in the probe hole 11.

[0028] In a preferred embodiment, the probe base 1 has a plurality of probe holes 11 arranged in an array, and each probe hole 11 is provided with an independently controllable scanning probe 2, thereby forming a scanning platform with a multi-probe array. More preferably, the plurality of probe holes 11 are arranged in an M-row × N-column array on the probe base 1, and all corresponding scanning probes 2 in the same row of probe holes 11 have the same connection orientation; M and N are both integers greater than or equal to 2.

[0029] As a specific example, such as Figure 1 As shown, the multiple probe holes 11 are arranged in a 2-row × 5-column array on the probe base 1, and a total of 10 scanning probes 2 are integrated.

[0030] In embodiments of the present invention, such as Figure 3 As shown, the scanning probe 2 includes a cantilever beam 21. A first end of the cantilever beam 21 is connected to the sidewall of the probe hole 11, and a second end opposite to the first end has a gap with the sidewall of the probe hole 11, meaning the second end of the cantilever beam 21 is suspended in the probe hole 11. A pressure sensor 22 is disposed on the lower surface of the cantilever beam 21 near the first end, and a piezoelectric ceramic layer 23 and a probe tip 24 are sequentially stacked and connected on the lower surface of the cantilever beam 21 near the second end.

[0031] The pressure sensor 22 converts the mechanical force of the cantilever beam 21 into a corresponding electrical signal and outputs it to provide feedback on the interaction force between the probe tip 24 and the sample under test. The piezoelectric ceramic layer 23 expands or compresses based on a control signal, causing a change in the height of the probe tip 24 relative to the sample surface, thus achieving tip extension and retraction. Figure 1 As shown, the electrical signal output by the pressure sensor 22 is sent to the data analysis system 200, and the control signal issued by the feedback system 400 is used to control the expansion or compression of the piezoelectric ceramic layer 23, thereby controlling the extension and retraction of the probe tip 24.

[0032] As a preferred solution, such as Figure 2 As shown, the probe base 1 is provided with an integrated circuit unit 3 and a patterned electrical connection line 4. The integrated circuit unit 3 is connected to the pressure sensor 22 through the patterned electrical connection line 4. The integrated circuit unit 3 is used to receive the electrical signal output by the pressure sensor 22 and output the electrical signal to an external signal processing device. In this embodiment of the invention, combined with... Figure 1 As shown, the integrated circuit unit 3 processes the electrical signal received from the pressure sensor 22 and outputs it to the data analysis system 200. Based on the interaction force between the probe tip 24 and the sample under test fed back by the electrical signal, the height information of the probe tip 24 relative to the surface of the sample under test is fed back.

[0033] Among them, such as Figure 2 As shown, the graphical electrical connection line 4 includes multiple independent connection lines that connect multiple scanning probes 2 to the integrated circuit unit 3 respectively. Further, the integrated circuit unit 3 outputs the electrical signals of the multiple scanning probes 2 to the data analysis system 200 respectively; in addition, the feedback system 400 is also connected to the multiple scanning probes 2 with separate electrical signals. That is, in the signal control loop, each scanning probe 2 has an independent feedback channel and adjustment channel, and the multiple scanning probes 2 can perform feedback adjustment independently of each other.

[0034] In this embodiment of the invention, the length of the cantilever beam 21 can be set to 100μm to 500μm, and the thickness can be set to 500nm to 5μm. The material of the cantilever beam 21 can be silicon or silicon nitride.

[0035] As a preferred option, such as Figure 4 As shown, the cantilever beam 21 in the scanning probe 2 is an integrally formed structure with the probe base 1 based on the etching of silicon wafer material. Figure 4The dotted line dividing the two indicates that they are integrally formed structures, which makes the connection between the cantilever beam 21 and the probe base 1 more robust, and the manufacturing process is simpler compared to the method of connecting the two separately.

[0036] In this embodiment of the invention, the pressure sensor 22 can be selected as a piezoresistive flexible pressure sensor or a capacitive flexible pressure sensor.

[0037] The working principle of the piezoresistive flexible mechanical sensor is as follows: When the sensor detects the force of the cantilever deformation, the composite material inside the sensor deforms due to the force, indirectly changing the distribution and contact state of the internal conductive filler, thereby causing a regular change in the resistance of the composite material. The formula for the resistance change is: ΔR / R=πσ; where ΔR is the resistance change value, R is the initial resistance value, π is the piezoresistive coefficient, and σ is the conductivity. The piezoresistive coefficient is the relative change in resistivity produced under unit stress. From this formula, the magnitude of the interaction force between the probe tip and the sample can be calculated.

[0038] Specifically, the capacitive flexible pressure sensor is an interdigital electrode capacitive flexible pressure sensor. Its working principle is as follows: When the cantilever arm undergoes slight deformation, the sensor receives an external force. Due to this force, the spacing between the interdigital electrodes in the capacitive pressure sensor changes, and its capacitance also changes systematically. At this time, the two plates of the interdigital electrodes are equivalent to a parallel-plate capacitor, and the formula for calculating its capacitance is: Where b is the electrode height, ω is the gap between the electrodes, n is the number of electrode fingers, and x = d / λ is the substrate thickness / wavelength. This formula shows that the capacitance changes linearly with the spacing, allowing for precise detection of the force and subsequent conversion of the interaction force between the probe tip and the sample.

[0039] In this embodiment of the invention, the material of the piezoelectric ceramic layer 23 is selected from any one of barium titanate, lead zirconate titanate (PZT), lead magnesium niobate (PMN), and polyvinylidene fluoride (PVDF). PVDF is preferred.

[0040] In this embodiment of the invention, the probe tip 24 is selected from any one of contact mode probe tips, conductive probe tips, magnetic probe tips, high aspect ratio probe tips, and all-diamond probe tips. Contact mode probe tips are preferred.

[0041] The atomic force microscope and its probe assembly provided in the above embodiment include the following process for detecting the sample to be tested:

[0042] (1) First, place the sample to be tested on the sample stage of the atomic force microscope, use the air pump to hold the sample, select the area to be scanned in the system control center, and select a large area on the sample surface or a small area with multiple different positioning points on the sample. Focus the sample surface clearly in the display system of the atomic force microscope, turn on the anti-vibration stage, and then insert the probe in probe contact mode.

[0043] (2) When the probe tip of the probe assembly contacts the surface of the sample to be tested, the cantilever beam undergoes slight deformation. At this time, the flexible pressure sensor is subjected to a force: When a piezoresistive flexible mechanical sensor is selected, its resistance value changes linearly. The magnitude of the interaction force between the probe tip and the sample surface can be detected by the law of change in resistance value; when an interdigital capacitive flexible mechanical sensor is selected, the distance between the interdigital electrode plates changes, and the capacitance changes linearly with the distance between the plates. The magnitude of the interaction force between the probe tip and the sample surface can be detected by the law of change in capacitance and the distance between the plates. The flexible pressure sensor transmits the detected electrical signal to the integrated circuit unit through a feedback loop, thereby the integrated circuit unit collects data corresponding to the magnitude of the interaction force between multiple probe tips and the sample surface.

[0044] (3) Data is transmitted to the data analysis system via the integrated circuit unit. The data is analyzed, and the parameters are adjusted by the control system. Then, through the feedback loop, the piezoelectric ceramic film of a specific probe in the scanning stage (probe assembly) is expanded or contracted to control the extension and retraction of the probe tip. This adjusts the magnitude of the interaction force between the probe tip and the sample, thereby enabling simultaneous large-scale scanning of the sample surface morphology and simultaneous scanning of different positioning points. This not only enables large-scale scanning of the sample in a short time, but also allows the control system to scan the morphology of different positioning points of the same sample at the same time, improving scanning efficiency.

[0045] In summary, the atomic force microscope and its probe assembly provided in this embodiment of the invention incorporate a pressure sensor within the probe assembly. This pressure sensor converts the mechanical force of the cantilever beam's deformation into an electrical signal to provide feedback and adjust the position of the probe tip. Compared to traditional techniques that use optical levers for feedback adjustment, this invention avoids mutual interference of feedback signals when integrating multiple probes into an array for rapid, large-area scanning imaging of sample morphology or simultaneous scanning imaging of multiple positioning points on the same sample. This significantly improves the speed and efficiency of scanning sample surface morphology.

[0046] It should be noted that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A probe assembly for an atomic force microscope, the probe assembly comprising: It includes a probe base with a probe hole and a scanning probe disposed in the probe hole, the scanning probe including a cantilever beam; wherein, The first end of the cantilever beam is connected to the side wall of the probe hole, and there is a gap between the second end and the side wall of the probe hole; an interdigitated electrode capacitive flexible pressure sensor is provided on the lower surface of the cantilever beam near the first end, and a piezoelectric ceramic layer and a probe tip are sequentially stacked and connected on the lower surface of the cantilever beam near the second end; The probe base is provided with an integrated circuit unit and a patterned electrical connection line. The integrated circuit unit is connected to the interdigital electrode capacitive flexible pressure sensor through the patterned electrical connection line. The integrated circuit unit is used to receive the electrical signal output by the interdigital electrode capacitive flexible pressure sensor and output the electrical signal to an external signal processing device. The probe base has a plurality of probe holes arranged in an array, and each probe hole is provided with an independently controllable scanning probe. In the signal control loop, each scanning probe has an independent feedback channel and an adjustment channel. The interdigitated electrode capacitive flexible pressure sensor is used to convert the deformation mechanical force of the cantilever beam into a corresponding electrical signal and output it to provide feedback on the interaction force between the probe tip and the sample to be tested.

2. The probe assembly of claim 1, wherein, The length of the cantilever beam is 100μm to 500μm, and the thickness of the cantilever beam is 500nm to 5μm.

3. The probe assembly of claim 1, wherein, The cantilever beam is an integrally formed structure with the probe base based on the etching of silicon wafer material.

4. The probe assembly of claim 1, wherein, The probe tip is selected from any one of the following: contact mode probe tip, conductive probe tip, magnetic probe tip, high aspect ratio probe tip, and all-diamond probe tip.

5. The probe assembly of claim 1, wherein, The material of the piezoelectric ceramic layer is selected from any one of barium titanate, lead zirconate titanate, lead magnesium niobate, and polyvinylidene fluoride.

6. The probe assembly of claim 1, wherein, The plurality of probe holes are arranged in an array of M rows × N columns on the probe base, and all scanning probes in the same row of probe holes are connected in the same direction; M and N are integers greater than 2.

7. An atomic force microscope characterized by Includes the probe assembly as described in any one of claims 1-6.

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