Non-heat-sensitive material microcell interface purification method based on AFM thermal probe scanning technology

Abstract

The invention discloses a non-heat-sensitive material microcell interface purification method based on an AFM thermal probe scanning technology, and aims to solve the technical problem of overlarge contact resistance of a sensitive material and an electrode caused by organic polymer residues in the processes of transferring the sensitive material and an electrode material and manufacturing a sensor. On the basis of an AFM thermal probe scanning technology, according to the basic principle that polymers can be removed by instantaneous heat released by an AFM thermal probe, a method for removing organic polymer residues on the surface of a sensitive material by using the thermal probe scanning technology and improving the purification of a contact micro-area interface of the sensitive material and an electrode material is provided; the method realizes accurate removal of organic polymer residues in the sensitive material transfer process, achieves the purpose of micro-area interface purification, and further improves the performance of the sensor.

Description

Technical Field

[0001] The invention belongs to the technical field of sensor manufacturing, and in particular relates to a method for purifying a micro-region interface of a non-thermosensitive material based on an AFM thermal probe scanning technology. Background Art

[0002] With the popularization of automation technology, sensors are playing an increasingly important role in production and life, and their application scope covers many fields such as environmental monitoring, smart devices, medical diagnosis, and autonomous driving. For example, smartphones that we cannot do without in our daily lives contain a large number of sensors, among which accelerometers and gyroscopes help mobile phones achieve automatic screen 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. Research on sensor sensitive materials has been ongoing for a long time, because they can directly sense the measured physical quantity and are the core components of sensors. The signal output of sensitive materials requires the assistance of conversion elements and conversion circuits. The resistance caused by the incomplete contact between sensitive materials and electrode materials will affect the performance of the sensor, which may cause the sensitivity of the sensor to decrease, the introduction of signal noise, or the failure of the sensor in some ranges. Therefore, how to ensure the purity of the contact interface between sensitive materials and electrodes in the core structure of the sensor has become a key issue in sensor manufacturing technology, which needs to be solved through the improvement of manufacturing processes.

[0003] Two-dimensional materials have been a hot topic in the field of sensor sensitive materials in recent years. Their high sensitivity, low response time, miniaturization and other characteristics make them have broad application prospects. Two-dimensional materials are often manufactured by chemical vapor deposition (CVD) or physical vapor deposition (PVD) and remain on the growth substrate. Most thin-film sensitive materials such as two-dimensional materials need to be transferred from the growth substrate to the sensor substrate during the sensor manufacturing process. The most commonly used mature method is organic polymer support assistance. Therefore, when removing the organic polymer in the subsequent process, it is often difficult to completely remove it, resulting in impure interface of the sensitive material. The organic polymer residue in the tiny area that is difficult to remove 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. Because the residue is too small, it is difficult to remove it efficiently and with high quality by existing physical and chemical methods, and too strong removal methods may damage the sensitive material. Therefore, the large amount of organic polymer residue on the surface of the sensitive material hinders the further application of the above-mentioned sensitive materials in sensors.

[0004] AFM thermal probe scanning is a technology that uses the heat release of the high-temperature tip of an atomic force microscope to soften and decompose materials. By selecting reasonable parameters, it can achieve precise material removal. However, there is currently a lack of a method for purifying micro-area interfaces using AFM thermal probe scanning technology. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a method for purifying the micro-region interface of non-thermosensitive materials based on AFM thermal probe scanning technology to solve the problems existing in the above prior art.

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

[0007] Transferring and fixing the sensitive material to the sensor substrate, pre-treating the sensitive material, placing the sensor substrate containing the pre-treated sensitive material on the stage of the AFM device, adjusting the laser light source of the AFM device and focusing it, loading a thermal probe scanning control module on the AFM device, replacing the probe on the AFM device fixture with a thermal probe, setting the working mode of the AFM device to a contact mode, and determining the thermal probe parameters based on the thermal decomposition point of the organic polymer and the actual organic polymer removal effect data;

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

[0009] A hard mask patterning-assisted evaporation method is used to manufacture electrodes on sensitive materials that have and have not been purified by AFM thermal probe scanning micro-area interface. A probe station and a precision current and voltage measuring device are used to obtain current and voltage information at predetermined positions. The current and voltage information are compared to obtain a purification effect.

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

[0011] Based on the thermal decomposition point of the 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 of performing thermal probe scanning on the surface of a sensitive material 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 area where the organic polymer residue is distributed 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 the organic polymer 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; in wet transfer, organic polymer PMMA is used as a temporary support layer for transfer, and the growth substrate is etched away before transfer to the target substrate. After drying, PMMA is preliminarily removed by acetone. In dry transfer, PDMS is used as a support layer, and the difference in bonding strength between the sensitive material and the growth substrate, PDMS and the target transfer substrate is utilized to achieve effective transfer of the sensitive material. In roll-to-roll transfer, a polymer is used to tightly bond the sensitive material, and a roller is used to assist in the transfer.

[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 invention has the following advantages and technical effects:

[0018] The present invention achieves efficient and high-quality removal of residual organic matter on the surface of non-thermal sensitive materials, and reduces the contact resistance between electrodes and sensitive materials by several times, thereby providing a new technical route for the technical field of micro-region interface purification of sensor sensitive materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

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

[0021] Figure 2 This is a schematic diagram showing the effect of the scratching speed and vertical pressure on the thickness of the removed film during the process of removing a PMMA film by an AFM thermal probe according to an embodiment of the present invention;

[0022] Figure 3 This is an AFM characterization image of a sensitive material that is not processed using the micro-region interface purification method according to an embodiment of the present invention;

[0023] Figure 4 This is an AFM characterization image of a sensitive material using a micro-region interface purification method according to an embodiment of the present invention;

[0024] Figure 5 A schematic diagram of measuring the contact resistance between the sensitive material and the electrode according to an embodiment of the present invention;

[0025] Figure 6 This is a current-voltage data diagram of the contact resistance measurement between the sensitive material and the electrode before the micro-region interface is purified according to an embodiment of the present invention;

[0026] Figure 7 This is a current-voltage data diagram of the contact resistance measurement between the sensitive material and the electrode after the micro-region interface is purified in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. 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 flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0029] Embodiment 1

[0030] like Figure 1 As shown, this embodiment provides a method for purifying the micro-region interface of a non-thermally sensitive material based on AFM thermal probe scanning technology, which is suitable for accurately removing the thermally decomposed organic polymer residues on the surface of the non-thermally sensitive material, and includes the following steps:

[0031] Transferring and fixing the sensitive material to the sensor substrate, pre-treating the sensitive material, placing the sensor substrate containing the pre-treated sensitive material on the stage of the AFM device, adjusting the laser light source of the AFM device and focusing it, loading a thermal probe scanning control module on the AFM device, replacing the probe on the AFM device fixture with a thermal probe, setting the working mode of the AFM device to a contact mode, and determining the probe parameters based on the thermal decomposition point of the organic polymer and the actual removal effect data of the organic polymer;

[0032] The AFM device is controlled by the thermal probe scanning control module to perform non-contact scanning on the surface of the sensitive material to obtain the residual distribution of the organic polymer; the thermal probe scanning is performed on the surface of the sensitive material based on the probe parameters and the residual distribution of the organic polymer to obtain the clean sensitive material; the AFM surface morphology scanning is performed on the clean sensitive material to obtain the organic polymer removal result, and the probe parameters are feedback-adjusted according to the organic polymer removal result until the organic polymer is completely removed;

[0033] A hard mask patterning-assisted evaporation method is used to manufacture electrodes on sensitive materials that have and have not been purified by AFM thermal probe scanning micro-area interface. A probe station and a precision current and voltage measuring device are used to obtain current and voltage information at predetermined positions, and the current and voltage information are compared to obtain the purification effect.

[0034] The specific steps are:

[0035] (1) Determine the AFM thermal probe scanning parameters: Transfer the sensitive material to a flat and hard substrate, such as a Si / SiO2 substrate, and pre-remove or not remove the organic layer. Then place the sensitive material and substrate on the stage of the AFM device and adjust them to a suitable position to facilitate the approach of the probe. Turn on the power of the AFM device and the computer control software, and perform preparations such as laser light source adjustment and CCD focusing. Then load the thermal probe scanning control module on the AFM device and replace the probe on the AFM fixture with a dedicated thermal probe. After the above preparations are ready, set the AFM working mode to contact mode, and then determine the probe tip temperature, scratching speed, vertical pressure and other parameters based on the thermal decomposition point of the organic polymer and the removal effect of the organic polymer in the actual experiment.

[0036] (2) Precise removal of organic polymer micro-area residues: Place the sensor substrate to which the sensitive material has been transferred on the stage of the AFM device and complete the preparation work described in step (1). First, perform a non-contact scan on the surface of the sensitive material to obtain the distribution of the organic polymer residues. Then, based on the parameters obtained previously, perform a thermal probe scan on the surface of the sensitive material to perform targeted organic polymer residue removal. After the thermal probe is purified, perform an AFM surface morphology scan on the surface of the sensitive material to confirm the removal effect of the organic polymer residues. In addition, the thermal probe scanning parameters can be appropriately adjusted according to the actual organic polymer residue situation.

[0037] (3) Verification of interface purification effect: Using a hard mask patterning-assisted evaporation method, electrodes are manufactured on sensitive materials with and without AFM thermal probe scanning micro-area interface purification, while avoiding the reintroduction of organic polymers. Then, under the condition of determining the position, a probe station and a precision current and voltage measuring device are used to obtain current and voltage information, which can confirm that the interface contact resistance has changed.

[0038] The AFM thermal probe scanning technology of this embodiment is based on the principle that releasing instantaneous heat can remove polymers. It can perform high-efficiency, high-quality organic polymer residues with regional selectivity, achieve micro-region interface purification, and achieve the purpose of reducing the contact resistance between the sensor's sensitive material and the electrode, thereby improving the sensor performance.

[0039] The causes of organic residues in sensitive materials include, but are not limited to: residues of organic polymer support layers that have not been completely removed by immersion, residues of organic polymer support layers that have not been completely annealed and ablated, and adsorption of organic molecules caused by sensitive materials being exposed to air.

[0040] Types of organic residues, including but not limited to: PMMA, PC, PPC, PVA, PDMS, PVC, VOCs, proteins and other organic polymers and other thermal decomposition materials.

[0041] Transfer methods that induce 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, temperature, etc.

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

[0044] 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.

[0045] This embodiment also conducted a specific experiment to verify the above method, and the experimental steps are as follows:

[0046] Specifically, the sensitive material of the sensor is a G / h-BN / G heterojunction, and the pressure change is detected by the tunneling effect. It is prepared on a Si / SiO2 substrate by using an organic polymer polymethyl methacrylate (PMMA) as a support layer to assist in transfer. After being dissolved in acetone, some organic polymer molecules still remain on the graphene surface; the surface material of the electrode is gold, which is deposited on the Si / SiO2 substrate by evaporation. The manufacturing sequence is to prepare the bottom electrode, transfer the sensitive material, and prepare the top electrode. Before the top electrode preparation step, a micro-area interface purification method based on AFM thermal probe scanning technology is added to remove PMMA molecular residues, reduce interface contact resistance, and improve sensor performance.

[0047] To solve this problem, we first need to select the AFM thermal probe scanning parameters. The thermal decomposition temperature of PMMA is about 270°C. PMMA will soften and decompose rapidly around this temperature, so 300°C is selected as the probe tip temperature. Then, by designing the scratching speed and vertical pressure experiments with gradient distribution, we determined the PMMA decomposition processing depth under a single thermal probe scan at 300°C. Figure 2As shown. First, the surface of the sensitive material that has been wet transferred and the PMMA support layer has been preliminarily removed using acetone is scanned using non-contact mode to find areas with more pollutants that require micro-area interface purification. In order to ensure that the heterojunction thin film material is not damaged by excessive thermal stress, the working parameters of a thermal probe tip temperature of 200°C, a scratching speed of 100μm / s, and a vertical pressure of 100nN are used. Areas with a large amount of organic polymer residues are scanned multiple times until the material surface is clean. AFM characterization images of sensitive materials that are not treated with the micro-area interface purification method and those that are treated with the micro-area interface purification method based on AFM thermal probe scanning technology are shown in the figure below. Figure 3 and Figure 4 It is obvious that the polymer particles on the surface of the sensitive material after AFM thermal probe scanning are significantly less than those of the traditional method, which proves the effect of its micro-region interface purification.

[0048] Since graphene has good conductivity and a small theoretical contact barrier with gold, the change in the interface resistance between the sensitive material and the electrode can be observed significantly during the verification process. The measurement points of the contact resistance are selected as follows: Figure 5 As shown in the figure, the millivolt method is used to measure the contact resistance. The sensitive material position close to the contact interface but not directly connected is selected as much as possible to reduce the influence of the surface resistance of the sensitive material in this area on the interface contact resistance measurement. The sensitive material without using the micro-area interface purification method to remove PMMA and the sensitive material using the micro-area interface purification method based on AFM thermal probe scanning technology are compared. Figure 5 The current and voltage data obtained by point measurement are as follows: Figure 6 and Figure 7 As shown in the figure. According to the slope of the curve, the purified contact resistance is one order of magnitude lower than that of the traditional method. It can also be said that the micro-area interface purification method based on AFM thermal probe scanning technology increases the purified current to 8 times or more at the same voltage. This proves that the micro-area interface purification method significantly reduces the contact interface resistance between the sensitive material and the electrode, which helps to improve the performance of the sensor.

[0049] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for purifying the micro-area interface of non-thermosensitive materials based on AFM thermal probe scanning technology, characterized in that: The following steps are involved: Transfer and fix the sensitive material to the sensor substrate, pre-treat the sensitive material, place the sensor substrate containing the pre-treated sensitive material on the stage of the AFM device, adjust the laser light source of the AFM device and focus it, load the thermal probe scanning control module on the AFM device, replace the probe on the AFM device fixture with a thermal probe, set the working mode of the AFM device to the contact mode, determine the thermal decomposition point of the organic polymer and the actual removal effect parameters of the organic polymer through experiments, and determine the probe parameters; The AFM device is controlled by a thermal probe scanning control module to perform non-contact scanning on the surface of the sensitive material to obtain the residual distribution position of the organic polymer and the residual amount information at each position; based on the probe parameters and the residual distribution information of the organic polymer, the surface of the sensitive material is scanned by a thermal probe to remove the residual organic polymer and obtain a surface-cleaned sensitive material; the surface of the cleaned sensitive material is scanned by AFM to record the surface morphology and obtain the organic polymer removal result; the AFM probe parameters are feedback-adjusted according to the organic polymer removal result until the organic polymer is completely removed; A hard mask patterning-assisted evaporation method is used to manufacture electrodes on sensitive materials that have and have not been purified by AFM thermal probe scanning micro-area interface purification. A probe station and a precision current and voltage measuring device are used to obtain current and voltage information at predetermined positions. The current density comparison between the purified area and the non-purified area is obtained, and the purification effect of AFM thermal probe scanning on the surface of the sensitive material is evaluated based on the current density comparison.

2. The method for purifying the micro-region interface of non-thermosensitive materials based on AFM thermal probe scanning technology according to claim 1, characterized in that: The method for determining the thermal probe parameters comprises: Based on the thermal decomposition point of the 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.

3. The method for purifying the micro-region interface of non-thermosensitive materials based on AFM thermal probe scanning technology according to claim 1, characterized in that: The method for performing a thermal probe scan on the surface of a sensitive material based on the thermal probe parameters and the residual distribution of the organic polymer comprises: Based on the thermal probe parameters, the surface of the sensitive material area where the organic polymer residue is distributed is scanned by the AFM device, and the organic polymer on the surface of the sensitive material is removed by releasing instantaneous heat.

4. The method for purifying the micro-region interface of non-thermosensitive materials based on AFM thermal probe scanning technology according to claim 1, characterized in that: The types of organic polymers include, but are not limited to, polymethyl methacrylate, polycarbonate, polypropylene carbonate, polyvinyl alcohol, polydimethylsiloxane, polyvinyl chloride, volatile organic matter and protein.

5. The method for purifying the micro-region interface of non-thermally sensitive materials 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; During wet transfer, organic polymer PMMA is used as a temporary support layer for transfer. After etching off the growth substrate, the material is transferred to the target substrate. After drying, PMMA is preliminarily removed by acetone. During dry transfer, PDMS is used as a support layer, and the difference in bonding strength between the sensitive material and the growth substrate, and between PDMS and the target transfer substrate is utilized to effectively transfer the sensitive material. During roll-to-roll transfer, a polymer is used to tightly bond the sensitive material, and a roller is used to assist in the transfer.

6. The method for purifying the micro-region interface of non-thermally sensitive materials based on AFM thermal probe scanning technology according to claim 1, characterized in that: The sensitive materials include but are not limited to two-dimensional materials, high temperature resistant organic films, silicon and silicon dioxide films.

7. The method for purifying the micro-region interface of non-thermally sensitive materials based on AFM thermal probe scanning technology according to claim 1, characterized in that: 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.

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