Dual-transistor integrated piezoelectric capacitance dual-mode sensor and approach and contact signal identification method thereof
By integrating dual transistors and piezoelectric capacitors in piezoelectric transistor sensors, using the periodic on/off process of switching circuits to distinguish proximity and contact signals, the problem that the sensor cannot distinguish signals is solved, and a more accurate sensing effect is achieved.
Patent Information
- Application Number
- CN202411450075.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-17
- Publication Date
- 2025-03-04
AI Technical Summary
The two-in-one sensor of the piezoelectric transistor cannot effectively distinguish the proximity and contact sensing signals, limiting its application.
A dual-transistor integrated piezocapacitor dual-mode sensor is adopted. By integrating the piezocapacitor device with two field effect transistors to form a dual-extended gate transistor structure, the difference in the response rules of the source and drain current signal of the proximity sensing and contact sensing during the periodic opening/closing of the switching circuit can be used to distinguish the proximity sensing and contact sensing signals.
Effectively distinguishing proximity and contact signals improves the application potential of the sensor, can accurately judge the proximity and contact status of the target object, and quantify the proximity and contact process.
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Figure CN119555120A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of electronic information sensing, and in particular relates to a dual-transistor integrated piezoelectric capacitor dual-mode sensor and a method for identifying proximity and contact signals thereof. Background Art
[0002] Proximity sensing and contact sensing have broad application prospects in the fields of the Internet of Things, wearable devices, robots, etc. Taking the human-computer interaction environment as an example, based on proximity sensors, robots can detect and track the approach of the target object, so as to take possible countermeasures and avoid unnecessary collisions. In theory, any long-range interaction, such as magnetic field, static electricity, ultrasound, light, etc., can be applied to the design of proximity sensor devices. And contact sensing can quantify the force between the target object and the robot, which is convenient for the robot to perform various operations on the target object. Common contact sensing principles include piezoelectric, piezoresistive, capacitive, etc. In recent years, researchers have been committed to developing multi-mode sensor devices with multiple sensing functions in one, such as integrating proximity sensing and contact sensing functions into one device, which greatly simplifies the device processing technology and improves the device integration. In the early work of the inventor's team, piezoelectric devices were integrated with thin-film transistor devices to construct a piezoelectric transistor two-in-one sensor device. The proximity sensing function is realized by virtue of the transistor threshold voltage drift caused by the electrostatic induction between the charged target and the transistor; and the piezoelectric component can convert the contact signal into a voltage signal to induce the transistor threshold voltage drift to realize the force sensing function. For details, please refer to the research papers A Multi-Functional Flexible Ferroelectric Transistor Sensor for Electronic Skin, Advanced Materials Interfaces, 8 (2021) 2101166 and Ferroelectric Polarization Enhancement of Proximity Sensing Performance in Oxide Semiconductor Field-Effect Transistors, ACS Applied Electronic Materials, 2 (2020) 3443. However, in the piezoelectric transistor two-in-one sensor device, since the proximity sensing and contact sensing signals are both fed back by the transistor source-drain current, the proximity and contact sensing signals cannot be effectively distinguished. That is, although the two-in-one device can sense the approach and contact of charged objects, it cannot distinguish whether the detected signal is from the contact or approach process. This greatly limits the application of the piezoelectric transistor two-in-one sensor device.
[0003] Based on the above reasons, the present invention proposes a method for identifying proximity and contact signals of a dual-transistor integrated piezoelectric capacitor dual-mode sensor, specifically, a piezoelectric capacitor device with upper and lower electrodes is integrated with two field effect transistor devices to form a dual extended gate transistor structure, and the piezoelectric capacitor device serves as the sensing end of the proximity and contact signals. The top electrode of the piezoelectric capacitor device is electrically connected to a gate of the dual-gate transistor, and both are connected to the ground through a switching circuit. The difference in the response law of the proximity sensing and contact sensing source-drain current signals during the periodic on / off process of the switching circuit is used to achieve effective distinction between proximity sensing and contact sensing signals. Summary of the invention
[0004] The object of the present invention is to provide a dual-transistor integrated piezoelectric capacitor dual-mode sensor and a method for identifying proximity and contact signals thereof, so as to solve the problem of how to effectively distinguish proximity and contact signals in a piezoelectric transistor proximity / contact two-in-one sensor device.
[0005] The present invention first constructs a piezoelectric transistor proximity / contact dual-mode sensor device with a dual extended gate structure, specifically, two field effect transistors are combined with a piezoelectric capacitor, and the two electrodes of the piezoelectric capacitor are used as the sensing ends of the proximity and contact signals; then, the proximity and contact signals are identified during the operation of the proximity / contact dual-mode sensor; wherein:
[0006] The field effect transistor is composed of a gate, a source, a drain, a gate dielectric layer and a semiconductor;
[0007] The piezoelectric capacitor is composed of a top electrode, a piezoelectric body, and a bottom electrode, wherein the top electrode is relatively located at the top of the piezoelectric capacitor in space;
[0008] The top electrode and the bottom electrode of the piezoelectric capacitor are electrically connected to the gates of the two field effect transistors respectively. The sources of the two field effect transistors are grounded, and the drains are connected to a DC bias voltage. The source-drain current is measured and recorded by a current measuring device; see Figure 1 shown.
[0009] Further:
[0010] In the field effect transistor, the semiconductor is various silicon, oxide or organic and two-dimensional semiconductor materials, the gate dielectric is various organic or inorganic dielectric layer materials, and the source, drain and gate electrodes are various metals, conductive oxides or conductive polymer materials.
[0011] In the piezoelectric capacitor, the piezoelectric body is an inorganic crystal, ceramic, polymer or small molecule piezoelectric material exhibiting piezoelectric properties, and the piezoelectric electrode is a conductive metal, polymer or oxide material.
[0012] The dual-transistor integrated piezoelectric capacitor dual-mode sensor constructed by the present invention is used for the identification of proximity and contact signals. The target object is a charged object, an insulator with a surface potential, or a conductor with a voltage applied. Many common insulators in daily life and industrial production have surface potentials, such as polytetrafluoroethylene, rubber, plastic, etc. Even electrically neutral insulators can be charged by artificial means, such as friction charging, etc. Therefore, the target objects monitored here are universal and extensive.
[0013] The method for the piezoelectric transistor proximity / contact dual-mode sensor to identify proximity and contact signals provided by the present invention is divided into four stages, see Figure 2-4 ; Specifically:
[0014] In the first stage, there is no target effect, and the source and drain currents of the two transistors are both at the ground state current value;
[0015] In the second stage, the charged target approaches the sensor end from a distance;
[0016] Under the electrostatic action of the target object, charges of the same sign are induced on the top electrode and the bottom electrode of the piezoelectric capacitor, and charges of opposite signs to the top electrode and the bottom electrode are induced on the gates of the two field effect transistors connected to the top electrode and the bottom electrode respectively; the charges induced on the gates regulate the threshold voltage of the field effect transistor, strengthen or inhibit the formation of the conductive channel at the semiconductor / gate dielectric interface, resulting in a change in the source-drain current, thereby realizing the detection of the approaching target object;
[0017] As the distance between the target and the sensing end decreases, the source-drain current further deviates from the ground-state current; whether the induced charge on the gates of the two transistors strengthens or inhibits the formation of a conductive channel at the semiconductor / gate dielectric interface depends on the amount and polarity of the induced charge on the gates and the type of semiconductor; positive charges are induced on both gates, attracting majority carriers in the n-type semiconductor to form a channel at the semiconductor / gate dielectric interface, resulting in an increase in the source-drain current;
[0018] When the target object is approaching, the source-drain current values of the two transistors are detected by the current detection device at the same time. By comparing the source-drain current values of the two field effect transistors, it is observed that the source-drain currents of the two transistors have the same change trend in the second stage. It is thus determined that the target object is approaching the sensing end;
[0019] In the third stage, the target object contacts the sensing end and applies force;
[0020] As the piezoelectric body is acted upon by force, equal charges of opposite signs are induced on the top electrode and the bottom electrode, and the polarity of the induced charges on the top electrode and the bottom electrode depends on the polarization orientation of the piezoelectric body; charges of opposite signs to the top electrode and the bottom electrode are induced on the gate electrodes of the two transistors connected to the top electrode and the bottom electrode respectively; the induced charges on the gate electrode cause the transistor threshold voltage to drift, and promote or inhibit the formation of a conductive channel at the semiconductor / gate dielectric interface, thereby causing an increase or decrease in the source-drain current; channel enhancement or inhibition depends on the amount and polarity of the induced charges on the gate electrode and the type of semiconductor; the degree to which the source-drain current deviates from the ground-state current value is regulated by the magnitude of the force;
[0021] When the target object approaches, the source-drain current values of the two transistors are detected simultaneously by the current detection device. By comparing the source-drain current values of the two field effect transistors, it is observed that the source-drain currents of the two transistors have opposite change trends in the second stage. It is thus determined that the target object is in the process of contacting the sensing end;
[0022] In the fourth stage, the target object is far away from the sensing end, and its regulating effect on the source-drain current of the field effect transistor is negligible. At this time, the source-drain current returns to the ground state current value.
[0023] From the above, it can be seen that based on the criterion that the changing trends of the source-drain currents of the two field-effect transistors are the same or opposite, it can be determined whether the piezoelectric extended-gate transistor two-in-one sensor device is working in the proximity sensing or contact sensing state; at the same time, since the current changes with distance and force, it can be used to quantify the proximity sensing and contact sensing processes.
[0024] The surface potential of the target object that can be sensed by the present invention depends on the performance of the dual-gate transistor and the distance between the target object and the sensing end. The applicable absolute value of the surface potential is between 0V-10kV, which can be 0.1V-10kV; the distance between the target object and the sensing end that can be detected depends on the surface potential of the target object and the performance of the transistor. The applicable distance is between 0-1m, which can be 10μm-1m. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 It is a schematic diagram of the structure of the dual-transistor integrated piezoelectric capacitor dual-mode (proximity / contact) sensor of the present invention.
[0026] Figure 2 Schematic diagram of the change of source-drain current of two field effect transistors over time during the composite process of the target object approaching, contacting and moving away from the sensing end.
[0027] Figure 3 When an object with a positive surface potential approaches the sensing end, the induced charge on the top electrode, bottom electrode, and gates of the two transistors and the channel formation are shown.
[0028] Figure 4It shows the induced charge and channel formation on the top electrode, bottom electrode, and gates of the two transistors when an object comes into contact with the sensing end.
[0029] Figure 5 Typical current response curve of a dual-mode sensor device based on two oxide thin-film transistors and a piezoelectric polymer capacitor. DETAILED DESCRIPTION
[0030] The present invention is further described below by way of embodiments in conjunction with the accompanying drawings.
[0031] Example 1: Proximity / contact dual-mode sensor device based on two oxide thin film transistors and piezoelectric polymer P (VDF-TrFE) capacitors
[0032] Preparation and structure of oxide transistors: 1 mm thick polyethylene terephthalate (PET) was used as the substrate, and 50 nm thick aluminum (Al) was prepared as the gate by thermal evaporation process, followed by spin coating of 8 wt % P (VDF-TrFE-TFE) (vinylidene fluoride, trifluoroethylene, and chlorofluoroethylene) as the gate dielectric layer. After annealing at 130 ° C for 1 h, 100 nm post-doped zinc oxide (IZO) was prepared as the semiconductor layer by magnetron sputtering process, and then indium tin oxide (ITO) was deposited on the IZO as the source and drain electrodes by magnetron sputtering process and with the help of a mask.
[0033] Preparation and structure of piezoelectric capacitor: A 50nm thick aluminum electrode (electrode 2) was deposited on a clean glass slide by vacuum thermal evaporation, and then a 10μm thick P (VDF-TrFE) (copolymer of vinylidene fluoride and trifluoroethylene) was spin-coated on it as a piezoelectric body, and finally a 50nm thick aluminum electrode (electrode 1) was deposited on it by vacuum thermal evaporation. The polarization direction of the piezoelectric body is from the bottom electrode to the top electrode.
[0034] Circuit connection and attachment of piezoelectric capacitor integrated dual transistor Figure 1 Use 2902A precision source meter to apply 10V bias to the drain of the transistor and record the source-drain current value.
[0035] The target is biased at +300V and has an area of 4cm 2 The target gradually approaches the piezoelectric capacitor sensing end from a distance of 5 cm, and after contacting the sensing end, begins to apply pressure, then releases the pressure, and finally withdraws from the sensing end, repeating this process for several cycles. The changes in the source and drain current recorded during this process are shown in the attached figure. Figure 5As shown. It can be seen that the ground state current value of the transistor is about 0.2μA. During the proximity sensing process, the source-drain current of the two transistors increases with time (that is, as the distance between the target object and the sensing end decreases) and increases to 0.43μA. After the target object contacts the sensing end, the P(VDF-TrFE) is subjected to force to generate induced charges, causing the source-drain current value of the transistor corresponding to the top electrode to drop to 0.22μA, and the source-drain current value of the transistor corresponding to the bottom electrode to rise to 0.74μA. When in contact, the source-drain current change trends of the two transistors are opposite. After the target object moves away from the sensing end, the source-drain current returns to the ground state current value. By comparing the changes in the source-drain current of the transistors connected to the top and bottom electrodes, the approach process and the contact process can be effectively distinguished.
Claims
1. A dual-transistor integrated piezoelectric-capacitive dual-mode sensor, characterized in that: It is composed of two field effect transistors and a piezoelectric capacitor. The piezoelectric capacitor is used as the sensing end of the proximity and contact signals to identify the proximity and contact signals during the operation of the proximity / contact dual-mode sensor; wherein: The field effect transistor is composed of a gate, a source, a drain, a gate dielectric layer and a semiconductor; The piezoelectric capacitor is composed of a top electrode, a piezoelectric body, and a bottom electrode, wherein the top electrode is defined as the top electrode in the piezoelectric capacitor device; The top electrode and the bottom electrode of the piezoelectric capacitor are electrically connected to the gates of the two field effect transistors respectively. The sources of the two field effect transistors are grounded, the drains are connected to a direct current bias voltage, and the source-drain current is measured and recorded by a current measuring device.
2. The dual-transistor integrated piezoelectric-capacitive dual-mode sensor according to claim 1, characterized in that: In the field effect transistor, the semiconductor is silicon, oxide or organic and two-dimensional semiconductor material, the gate dielectric is an organic or inorganic dielectric layer material, and the source, drain and gate electrodes are various metals, conductive oxides or conductive polymer materials.
3. The dual-transistor integrated piezoelectric-capacitive dual-mode sensor according to claim 1, characterized in that: In the piezoelectric capacitor, the piezoelectric body is an inorganic crystal, ceramic, polymer or small molecule piezoelectric material exhibiting piezoelectric properties, and the piezoelectric electrode is a conductive metal, polymer or oxide material.
4. The method for identifying proximity and contact signals by a dual-transistor integrated piezoelectric capacitor dual-mode sensor as claimed in claim 1, characterized in that: The target object is identified as a charged object, specifically an insulator with a surface potential, or a conductor with a voltage applied. The identification process is divided into four stages, specifically: In the first stage, there is no target effect, and the source and drain currents of the two transistors are both at the ground state current value; In the second stage, the charged target approaches the sensor end from a distance; Under the electrostatic action of the target object, charges of the same sign are induced on the top electrode and the bottom electrode of the piezoelectric capacitor, and charges of opposite sign to the top electrode and the bottom electrode are induced on the gates of the two field effect transistors connected to the top electrode and the bottom electrode respectively; The charge induced on the gate regulates the threshold voltage of the field effect transistor, strengthens or inhibits the formation of a conductive channel at the semiconductor / gate dielectric interface, causing a change in the source-drain current, thereby realizing the detection of the approach of the target object; As the distance between the target and the sensing end decreases, the source-drain current further deviates from the ground-state current; whether the induced charge on the gate of the two transistors strengthens or inhibits the formation of a conductive channel on the semiconductor / gate dielectric interface depends on the amount and polarity of the induced charge on the gate and the type of semiconductor; Positive charges are induced on both gates, attracting majority carriers in the n-type semiconductor to form a channel at the semiconductor / gate dielectric interface, resulting in an increase in source-drain current; When the target object approaches, the source-drain current values of the two transistors are detected simultaneously by the current detection device. By comparing the source-drain current values of the two field effect transistors, it is observed that the source-drain currents of the two transistors have the same change trend in the second stage, thereby judging that the target object is in the process of approaching the sensing end; In the third stage, the target object contacts the sensing end and applies force; As the piezoelectric body is acted upon by force, equal charges of opposite signs are induced on the top electrode and the bottom electrode, and the polarity of the induced charges on the top electrode and the bottom electrode depends on the polarization orientation of the piezoelectric body; charges of opposite signs to the top electrode and the bottom electrode are induced on the gate electrodes of the two transistors connected to the top electrode and the bottom electrode respectively; The induced charge on the gate causes the transistor threshold voltage to drift and promotes or inhibits the formation of a conductive channel at the semiconductor / gate dielectric interface, thereby increasing or decreasing the source-drain current; Channel enhancement or suppression depends on the amount and polarity of the induced charge on the gate and the type of semiconductor; The degree to which the source-drain current deviates from the ground-state current value is regulated by the magnitude of the force; When the target object approaches, the source-drain current values of the two transistors are detected simultaneously by the current detection device. By comparing the source-drain current values of the two field effect transistors, it is observed that the source-drain currents of the two transistors have opposite change trends in the second stage; thus, it is judged that the target object is in the process of contacting the sensing end; In the fourth stage, the target is far away from the sensing end, and its regulation effect on the source-drain current of the field effect transistor is negligible. At this time, the source-drain current returns to the ground state current value; Based on the criterion that the changing trends of the source-drain currents of the two field effect transistors are the same or opposite, it is determined whether the piezoelectric extended gate transistor two-in-one sensor device is operating in a proximity sensing state or a contact sensing state; At the same time, the change of current with distance and force is used to quantify the proximity sensing and contact sensing processes.
5. The method according to claim 4, characterized in that The absolute value of the surface potential used is between 0V and 10kV; the distance between the target object and the sensing end that can be detected is 0-1m.