A method for purifying micro-area interface of non-thermal sensitive material based on AFM thermal probe scanning technology

Abstract

The application discloses a non-thermal sensitive material micro-area interface purification method based on an AFM thermal probe scanning technology, and aims to solve the technical problem of excessive contact resistance between a sensitive material and an electrode caused by organic polymer residues in the process of transferring the sensitive material and the electrode material and manufacturing a sensor. The application is based on the AFM thermal probe scanning technology, and according to the basic principle that the instantaneous heat released by the AFM thermal probe can remove the polymer, the application proposes a method for removing the organic polymer residues on the surface of the sensitive material by using the thermal probe scanning technology, improving the micro-area interface purification of the contact between the sensitive material and the electrode material, realizing the accurate removal of the organic polymer residues in the process of transferring the sensitive material, achieving the purpose of micro-area interface purification, and further improving the performance of the sensor.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sensor manufacturing, and particularly relates to a micro-area interface purification method for non-thermal sensitive material based on AFM thermal probe scanning technology. BACKGROUND

[0002] With the popularization of automation technology, sensors play an increasingly important role in production and life, and their application ranges cover many fields such as environmental monitoring, intelligent devices, medical diagnosis, and automatic driving. For example, the smart phones in our daily life contain a large number of sensors, among which the accelerometers and gyroscopes help the phones to realize screen automatic rotation and accurate motion detection; in the medical field, heart rate monitors and blood glucose sensors provide real-time health data to help doctors make accurate diagnoses. The research on sensor sensitive materials has been going on for a long time, because they can directly sense the physical quantity to be measured and are the core components of sensors. The signal output of the sensitive material needs the assistance of the conversion element and the conversion circuit, and the incomplete contact between the sensitive material and the electrode material will affect the performance of the sensor, which may cause the sensitivity of the sensor to decrease, the signal noise to be introduced, or the sensor to fail in part of the range. Therefore, how to ensure the purification of the contact interface between the sensitive material and the electrode in the core structure of the sensor has become a key problem in the manufacturing technology of the sensor, which needs to be solved through the improvement of the manufacturing process.

[0003] Two-dimensional materials are a hot spot in the field of sensor sensitive materials in recent years, and they have a wide application prospect due to their high sensitivity, low response time, and miniaturization. Two-dimensional materials are often manufactured by chemical vapor deposition (CVD) or physical vapor deposition (PVD) and left on the growth substrate. Most thin film type sensitive materials such as two-dimensional materials need to be transferred from the growth substrate to the sensor substrate during the sensor manufacturing process, and the mature method currently used is to use organic polymer support assistance. Therefore, when the organic polymer is removed later, there is often a problem of incomplete removal of the organic polymer, which causes the interface of the sensitive material to be impure. The residual organic polymer in the small area is difficult to remove and may form an insulating layer, which significantly increases the contact resistance between the sensor electrode and the sensitive material, thereby reducing the performance of the sensor. Since the residual is too small, existing physical and chemical methods are difficult to remove efficiently and with high quality, and too strong removal methods may damage the sensitive material. Therefore, the large amount of residual organic polymer on the surface of the sensitive material hinders the further application of the above-mentioned sensitive material in the sensor.

[0004] AFM thermal probe scanning is a technology that uses the heat release of the high-temperature tip of an atomic force microscope to realize the softening and decomposition removal of materials. Through reasonable parameter selection, accurate removal of materials can be realized. However, there is still a lack of a method for micro-area interface purification by AFM thermal probe scanning technology. SUMMARY

[0005] To solve the above technical problems, the present application provides a method for purifying the micro-area interface of non-thermal sensitive materials based on AFM thermal probe scanning technology.

[0006] To achieve the above purpose, the present application provides a method for purifying the micro-area interface of non-thermal sensitive materials based on AFM thermal probe scanning technology, comprising the following steps:

[0007] The sensitive material is transferred and fixed on the sensor substrate, the sensitive material is pretreated, the sensor substrate containing the pretreated sensitive material is placed on the object table of the AFM device, the laser light source of the AFM device is adjusted and focused, the thermal probe scanning control module is loaded on the AFM device, the probe on the AFM device clamp is replaced with a thermal probe, the working mode of the AFM device is set to contact mode, and the thermal probe parameters are determined based on the thermal decomposition point of organic polymer and the actual organic polymer removal effect data.

[0008] The AFM device is controlled by the thermal probe scanning control module to perform non-contact scanning on the surface of the sensitive material, and the residual distribution of the organic polymer is obtained; the surface of the sensitive material is scanned by the thermal probe based on the thermal probe parameters and the residual distribution of the organic polymer, and the clean sensitive material is obtained; the clean sensitive material is scanned by AFM surface morphology, and the organic polymer removal result is obtained; the thermal probe parameters are adjusted according to the organic polymer removal result until the organic polymer is completely removed.

[0009] The electrode is manufactured on the sensitive material subjected to and not subjected to the micro-area interface purification of the AFM thermal probe scanning by using the hard mask patterned evaporation method, the current-voltage information is obtained at the predetermined position by using the probe station and the precise current-voltage measuring device, the current-voltage information is compared, and the purification effect is obtained.

[0010] Preferably, the method for determining the probe parameters comprises:

[0011] Based on the thermal decomposition point of organic polymer and the actual organic polymer removal effect data, the tip temperature, scratching speed and vertical pressure data of the thermal probe are obtained.

[0012] Preferably, the method for scanning the surface of the sensitive material by the thermal probe based on the thermal probe parameters and the residual distribution of the organic polymer comprises:

[0013] Based on the thermal probe parameters, the surface of the sensitive material region with residual distribution of organic polymer is scanned by the AFM device, and the organic polymer on the surface of the sensitive material is removed by releasing instantaneous heat.

[0014] Preferably, the types of organic polymers include, but are not limited to, polymethyl methacrylate (PMMA), polycarbonate (PC), polypropylene carbonate (PPC), polyvinyl alcohol (PVA), polydimethylsiloxane (PDMS), polyvinyl chloride (PVC), volatile organic compounds (VOCs) and proteins.

[0015] Preferably, the method of transferring sensitive materials includes wet transfer, dry transfer and roll-to-roll transfer; when wet transfer is performed, PMMA is used as a temporary support layer for transfer, and after etching away the growth substrate, the sensitive material is transferred to the target substrate, and after drying, PMMA is removed by acetone. When dry transfer is performed, PDMS is used as a support layer, and the effective transfer of the sensitive material is realized by taking advantage of the difference in the binding force of the sensitive material with the growth substrate, PDMS and the target transfer substrate. When roll-to-roll transfer is performed, the sensitive material is tightly bonded with a polymer, and the transfer is completed with the aid of a roller.

[0016] Preferably, the types of sensor electrodes include, but are not limited to, chromium-gold electrodes, titanium-gold electrodes, silver electrodes, copper electrodes, nickel electrodes and conductive polymer electrodes.

[0017] Compared with the prior art, the present application has the following advantages and technical effects:

[0018] The present application realizes efficient and high-quality removal of residual organic matter on the surface of non-thermal sensitive materials, and realizes reduction of the contact resistance between the electrode and the sensitive material by several times, thereby providing a new technical route for the field of sensor sensitive material micro-area interface purification technology. BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of this application and its description are used to explain the application without imposing any undue limitation on the application. In the drawings:

[0020] Figure 1 The figure is a schematic diagram of the micro-area interface purification method based on the AFM thermal probe scanning technology of the embodiment of the present application;

[0021] Figure 2 The figure is a schematic diagram of the influence of scratching speed and vertical pressure on the removal of the film thickness during the process of removing the PMMA film by the AFM thermal probe of the embodiment of the present application;

[0022] Figure 3 The figure is an AFM characterization diagram of the sensitive material which is not treated by the micro-area interface purification method of the embodiment of the present application;

[0023] Figure 4 The figure is an AFM characterization diagram of the sensitive material which is treated by the micro-area interface purification method of the embodiment of the present application;

[0024] Figure 5 A schematic diagram of contact resistance measurement of a sensitive material and an electrode according to an embodiment of the present application;

[0025] Figure 6 A current-voltage data graph of contact resistance measurement of a sensitive material and an electrode before micro-interface purification according to an embodiment of the present application;

[0026] Figure 7 A current-voltage data graph of contact resistance measurement of a sensitive material and an electrode after micro-interface purification according to an embodiment of the present application. DETAILED DESCRIPTION

[0027] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0028] It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described herein can be executed in an order different from that shown herein.

[0029] Embodiment One

[0030] As shown in the drawings, the present embodiment provides a non-thermal sensitive material micro-interface purification method based on AFM thermal probe scanning technology, which is suitable for precise removal of thermal decomposition organic polymer residues on the surface of non-thermal sensitive materials, and includes the following steps: Figure 1 The sensitive material is transferred and fixed on the sensor substrate, the sensitive material is pretreated, the sensor substrate containing the pretreated sensitive material is placed on the object table of the AFM device, the laser light source of the AFM device is adjusted and focused, the thermal probe scanning control module is loaded on the AFM device, the probe on the AFM device clamp is replaced with a thermal probe, the working mode of the AFM device is set to contact mode, and the probe parameters are determined based on the thermal decomposition point of the organic polymer and the actual removal effect data of the organic polymer;

[0031] The AFM device is controlled by the thermal probe scanning control module to perform non-contact scanning on the surface of the sensitive material, and the residual distribution of the organic polymer is obtained; the surface of the sensitive material is scanned by the thermal probe based on the probe parameters and the residual distribution of the organic polymer, and the clean sensitive material is obtained; the clean sensitive material is scanned by AFM surface morphology, and the organic polymer removal result is obtained; the probe parameters are adjusted according to the organic polymer removal result until the organic polymer is completely removed;

[0032]

[0033] ​The electrode is manufactured on the sensitive material which is purified by the AFM thermal probe scanning or not by using the hard mask patterning assisted evaporation method. The current-voltage information is obtained by using the probe station and the precise current-voltage measurement device at the predetermined position. The purification effect is obtained by comparing the current-voltage information.

[0034] The specific operation steps are as follows:

[0035] (1) Determine the AFM thermal probe scanning parameters: the sensitive material is transferred to a flat and hard substrate, such as a Si / SiO2 substrate, and the organic layer is removed or not removed. Then the sensitive material and the substrate are placed on the stage of the AFM device, and they are adjusted to the appropriate position to facilitate the approach of the probe. The power supply of the AFM device and the computer control software are turned on, and the preparations such as laser light source adjustment and CCD focusing are performed. Then the thermal probe scanning control module is loaded on the AFM device, and the probe on the AFM clamp is replaced with a special thermal probe. After the above preparations are completed, the AFM working mode is set to contact mode, and the probe tip temperature, scratching speed and vertical pressure are determined according to the thermal decomposition point of the organic polymer and the removal effect of the organic polymer in the actual experiment.

[0036] (2) Accurate removal of organic polymer micro area residues: the sensor substrate with the transferred sensitive material is placed on the stage of the AFM device, and the preparations as described in step (1) are completed. The surface of the sensitive material is scanned in a non-contact mode to obtain the distribution of the organic polymer residues. Then the surface of the sensitive material is scanned by the thermal probe according to the previously obtained parameters to remove the targeted organic polymer residues. After the thermal probe purification, the surface morphology of the sensitive material is scanned by the AFM to confirm the removal effect of the organic polymer residues. In addition, the thermal probe scanning parameters can be adjusted according to the actual organic polymer residues.

[0037] (3) Interface purification effect verification: electrodes are manufactured on the sensitive materials which are purified by the AFM thermal probe scanning or not by using the hard mask patterning assisted evaporation method under the premise of avoiding the introduction of organic polymers again. Then the current-voltage information is obtained by using the probe station and the precise current-voltage measurement device at the predetermined position, and it can be confirmed that the interface contact resistance has changed.

[0038] The AFM thermal probe scanning technology of the embodiment can remove the polymer based on the principle of releasing instantaneous heat, and can selectively and efficiently remove the organic polymer residues with high quality, realize the micro area interface purification, reduce the contact resistance between the sensitive material and the electrode of the sensor, and improve the performance of the sensor.

[0039] Causes of organic residues in sensitive materials include, but are not limited to: organic polymer support layer residues that were not completely removed by soaking, organic polymer support layer residues that were not completely annealed and ablated, and adsorption of organic molecules caused by exposure of sensitive materials to air.

[0040] Organic residues include, but are not limited to: PMMA, PC, PPC, PVA, PDMS, PVC, VOCs, proteins and other organic polymers and thermally decomposable materials.

[0041] Methods for inducing the transfer of organic residues on the surface of sensitive materials include, but are not limited to, commonly used industrial and laboratory transfer methods such as wet transfer, dry transfer, and roll-to-roll transfer.

[0042] Sensors include sensor types that can measure a variety of physical quantities, such as sound, light, heat, force, and temperature.

[0043] Sensor-sensitive materials include, but are not limited to: two-dimensional materials, high-temperature resistant organic thin films, silicon and silicon dioxide thin films, and other semiconductor thin films.

[0044] Sensor electrode types include, but are not limited to: chromium gold electrodes, titanium gold electrodes, silver electrodes, copper electrodes, nickel electrodes, and conductive polymer electrodes.

[0045] This embodiment also includes a specific experiment to verify the above method. The experimental steps are as follows:

[0046] Specifically, the sensor's sensitive material is a G / h-BN / G heterojunction, which detects pressure changes through tunneling. It is fabricated on a Si / SiO2 substrate using polymethyl methacrylate (PMMA) as a support layer for assisted transfer. Even after dissolution with acetone, some organic polymer molecules remain on the graphene surface. The electrode surface material is gold, deposited onto the Si / SiO2 substrate by vapor deposition. The manufacturing sequence is: fabrication of the bottom electrode, transfer of the sensitive material, and fabrication of the top electrode. Before fabricating the top electrode, a micro-area interface purification method based on AFM thermal probe scanning technology is used to remove PMMA molecular residues, reduce interfacial contact resistance, and improve sensor performance.

[0047] To address this issue, the first step is to select the AFM thermal probe scanning parameters. The thermal decomposition temperature of PMMA is approximately 270℃, at which point PMMA rapidly softens and decomposes. Therefore, 300℃ was chosen as the probe tip temperature. Next, through experiments designing gradient-distributed scribing speeds and vertical pressure, the decomposition depth of PMMA under a single thermal probe scan at 300℃ was determined. Figure 2As shown in the figure, the surface of the sensitive material, after wet transfer and preliminary removal of the PMMA support layer with acetone, was first scanned using a non-contact mode to identify areas with high levels of contaminants requiring micro-area interface purification. To prevent damage to the heterojunction film material due to excessive thermal stress, operating parameters of 200°C thermal probe tip temperature, 100 μm / s scribing speed, and 100 nN vertical pressure were used. Areas with significant organic polymer residues were scanned multiple times until the material surface was clean. The AFM characterization images of the sensitive material treated with and without micro-area interface purification using AFM-based thermal probe scanning technology are shown in the figure. Figure 3 and Figure 4 As shown, it is evident that the number of polymer particles on the surface of the sensitive material after AFM thermal probe scanning is significantly less than that of traditional methods, demonstrating the effectiveness of its micro-area interface purification.

[0048] Due to graphene's excellent electrical conductivity and its relatively small theoretical contact barrier with gold, changes in the interface resistance between the sensitive material and the electrode can be observed quite significantly during the verification process. The selection of the contact resistance measurement points is as follows... Figure 5 As shown, the millivolt method was used to measure the contact resistance. Sensitive material locations close to the contact interface but not directly conductive were selected to minimize the influence of the surface resistivity of this sensitive material area on the interface contact resistance measurement. A comparison was made between sensitive materials treated without micro-area interface purification to remove PMMA and sensitive materials treated with a micro-area interface purification method based on AFM thermal probe scanning technology. Figure 5 The current and voltage data obtained from the selected measurement points are as follows: Figure 6 and Figure 7 As shown in the curve slope, the contact resistance after purification is an order of magnitude lower than that of traditional methods. In other words, the micro-area interface purification method based on AFM thermal probe scanning technology increases the current after purification to eight times or more at the same voltage. This demonstrates that the micro-area interface purification method significantly reduces the contact resistance between the sensitive material and the electrode, thus contributing to improved sensor performance.

[0049] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for purifying the interface of a non-thermal-sensitive material micro-region based on AFM thermal probe scanning technology, characterized in that, Includes the following steps: The sensitive material is transferred and fixed onto the sensor substrate. The sensitive material is pretreated. The sensor substrate containing the pretreated sensitive material is placed on the stage of the AFM device. The laser light source of the AFM device is adjusted and focused. The thermal probe scanning control module is installed on the AFM device. The probe on the AFM device fixture is replaced with a thermal probe. The working mode of the AFM device is set to contact mode. The thermal decomposition point of the organic polymer and the actual removal effect parameters of the organic polymer are determined through experiments. The probe parameters are determined. The method for determining probe parameters includes: Based on the thermal decomposition point of organic polymers and the actual removal effect data of organic polymers, the tip temperature, scribing speed and vertical pressure data of the thermal probe are obtained. The thermal probe scanning control module controls the AFM device to perform non-contact scanning on the surface of the sensitive material to obtain information on the residual distribution location and residual amount of organic polymer at each location. Based on the probe parameters and the residual distribution information of organic polymer, the surface of the sensitive material is scanned by the thermal probe to remove the residual organic polymer, resulting in a clean sensitive material. The surface of the clean sensitive material is then scanned by AFM to record the surface morphology and obtain the organic polymer removal result. The AFM probe parameters are adjusted based on the organic polymer removal result until the organic polymer is completely removed. Electrodes were fabricated on sensitive materials that had undergone and had not undergone AFM thermal probe scanning micro-area interface purification using a hard mask patterning-assisted vapor deposition method. Current and voltage information was acquired at predetermined locations using a probe station and a precision current and voltage measurement device. The current and voltage information was compared to obtain a comparison of the current density in the purified area and the unpurified area. The purification effect of AFM thermal probe scanning on the surface of the sensitive material was evaluated based on the comparison of the current density.

2. The method for purifying the interface of non-thermal materials in micro-regions based on AFM thermal probe scanning technology according to claim 1, characterized in that, The method for thermal probe scanning of the surface of a sensitive material based on the thermal probe parameters and the residual distribution of the organic polymer includes: Based on the thermal probe parameters, the surface of the sensitive material area with residual organic polymer distribution is scanned using an AFM device, and the organic polymer on the surface of the sensitive material is removed by releasing instantaneous heat.

3. The method for purifying the interface of non-thermal materials in micro-regions based on AFM thermal probe scanning technology according to claim 1, characterized in that, The types of organic polymers include: polymethyl methacrylate, polycarbonate, polypropylene carbonate, polyvinyl alcohol, polydimethylsiloxane, polyvinyl chloride, volatile organic compounds, and proteins.

4. The method for purifying the interface of non-thermal materials in micro-regions based on AFM thermal probe scanning technology according to claim 1, characterized in that, Methods for transferring sensitive materials include wet transfer, dry transfer, and roll-to-roll transfer; In wet transfer, the organic polymer PMMA is used as a temporary support layer for transfer. After etching away the growth substrate, the material is transferred to the target substrate. After drying, the PMMA is initially removed with acetone. In dry transfer, PDMS is used as a support layer. The difference in adhesion between the sensitive material and the growth substrate, PDMS and the target transfer substrate is utilized to effectively transfer the sensitive material. In roll-to-roll transfer, the sensitive material is tightly bonded with a polymer and a roller is used to assist in the transfer.

5. The method for purifying the interface of non-thermal materials in micro-regions based on AFM thermal probe scanning technology according to claim 1, characterized in that, The sensitive materials include two-dimensional materials, high-temperature resistant organic thin films, silicon and silicon dioxide thin films.

6. The method for purifying the interface of non-thermal materials in micro-regions based on AFM thermal probe scanning technology according to claim 1, characterized in that, Sensor electrode types include chromium-gold electrodes, titanium-gold electrodes, silver electrodes, copper electrodes, nickel electrodes, and conductive polymer electrodes.

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