A transistor proximity sensor based on interdigital extended gate structure

Abstract

The application belongs to the technical field of instruments and meters, and particularly relates to a transistor proximity sensor based on an interdigital electrode extended gate structure. The proximity sensor is composed of a voltage source, an ammeter, a transistor, interdigital electrodes and the like. The voltage source is used for supplying power to the transistor drain and the far gate end of the interdigital electrodes, and the near gate end of the interdigital electrodes is electrically connected with the transistor gate via a conductive lead. The working mechanism of the proximity sensor of the application relies on the synergistic enhancement effect among the electrostatic induction between the target object and the interdigital electrodes, the regulation effect of the target object on the interdigital electrode capacitance and the modulation effect of the target object on the voltage division of the near gate end of the interdigital electrodes. When the charged target object or the uncharged target object approaches the extended gate end of the interdigital electrodes, the transistor source-drain current can be changed, so that the proximity sensing function is realized.

Description

Technical Field

[0001] This invention belongs to the field of instrumentation technology, specifically relating to a transistor proximity sensor based on an interdigitated electrode extended gate structure. Background Technology

[0002] Proximity sensing is a non-contact sensing method that detects the approach of a target object through long-range physical interaction before the object makes physical contact with the sensor. In human-computer interaction environments, proximity sensors can be used to prevent damage caused by physical collisions between robots and people or other surrounding environments. Common proximity sensing designs are based on mechanisms such as optics, ultrasound, capacitance, magnetic fields, and electrostatics. In recent years, transistor-based proximity sensing has been reported. These devices achieve proximity sensing based on the electrostatic interaction between a charged object and the transistor's channel and electrode layers. During operation, when a charged object approaches, the electrostatic interaction causes the accumulation or depletion of charge carriers at the transistor's semiconductor / gate dielectric interface, thereby changing the transistor's source and drain currents and enabling proximity sensing operation. The inventors have previously applied for several patents related to transistor proximity sensing based on electrostatic induction mechanisms, including non-contact real-time electrostatic detection methods (a non-contact real-time electrostatic monitoring method based on extended-gate transistors, application number CN202010153268.4), surface potential measurement methods (a surface potential measurement method based on an extended-gate transistor structure, application number CN201910733844.X), and multi-point proximity sensing network systems (a multi-point proximity sensing network system based on electrostatic induction mechanisms, application number 202111583143.6). However, due to the electrostatic induction mechanism, this type of sensor is only suitable for monitoring the approach / remote movement of charged objects and cannot monitor the approach of uncharged objects (i.e., objects with zero surface potential). This invention develops a transistor proximity sensor based on an interdigitated electrode extended-gate structure, which can monitor the approach of both charged and zero-potential objects. Summary of the Invention

[0003] The purpose of this invention is to provide a transistor proximity sensor based on an interdigitated electrode extended gate structure, which can monitor the approach process of charged and zero-potential targets.

[0004] The transistor proximity sensor based on the interdigitated electrode extended gate structure proposed in this invention has a typical structure as shown in the attached figure. Figure 1 As shown, it specifically includes: a first voltage source 1, an ammeter 2, a transistor 3, a second voltage source 5, and a finger electrode 5; wherein:

[0005] The source of transistor 3 is grounded; the drain of transistor 3, ammeter 2, and first voltage source 1 are connected in series; the gate of transistor 3 is electrically connected to one end of interdigital electrode 5, and this end of interdigital electrode electrically connected to the gate is named the near-gate end; the other end of interdigital electrode 5 is connected to second voltage source 4, and this end of interdigital electrode connected to second voltage source 4 is named the far-gate end; the target object 6 approaches / moves away from interdigital electrode 5, which can realize the detection of the approach process of charged target objects and zero potential target objects;

[0006] The first voltage source 1 and the second voltage source 4 are used to apply source-drain bias voltage and interdigital electrode far-gate bias voltage to transistor 3, respectively;

[0007] The ammeter is used to test the channel current of the transistor under source-drain bias.

[0008] The interdigitated electrode 5 is used to form a planar capacitor structure;

[0009] The far gate end of the interdigitated electrode is connected to the second voltage source 4, and the near gate end of the interdigitated electrode is electrically connected to the gate of the transistor 3.

[0010] The capacitance of the interdigitated electrode 5 is much smaller than that of the transistor gate dielectric.

[0011] In this invention, the transistor can be any three-terminal structure device with gate control function, including but not limited to silicon transistors, oxide transistors, organic transistors, transistors constructed from two-dimensional materials, etc.

[0012] In this invention, the transistor has a bottom-gate top-contact structure (e.g., Figure 1 It can also be a transistor structure of other types such as bottom gate bottom contact, top gate top contact, top gate bottom contact, etc., as long as the transistor gate is electrically connected to the interdigitated electrode.

[0013] In this invention, the interdigitated electrode refers to an electrode pair formed by interlocking the comb-tooth portions of two comb-shaped electrodes with the same structure, see [link to previous invention]. Figure 1 As shown. Depending on the application scenario, the spacing between interdigitated electrodes (i.e., the distance between adjacent comb-shaped electrodes) and the electrode width (i.e., the width of the comb-shaped electrode) range from 1 micrometer to 1 millimeter; the length of the comb-shaped electrode ranges from 10 micrometers to 10 centimeters, and the number of interdigitated electrode pairs is at least one pair. Depending on the dimensions and processing precision requirements of the interdigitated electrodes, the fabrication and processing of interdigitated electrodes can be based on photolithography, hard masking, electroplating, electroless plating, or other possible processing techniques.

[0014] In this invention, transistor 3 and interdigitated electrode 5 are connected by wires, with a distance between them ranging from 1 millimeter to 10 meters.

[0015] Furthermore, in the interdigitated electrodes, the spacing between adjacent comb teeth of the comb-shaped electrodes is equal, and the length of all comb teeth is equal.

[0016] The transistor proximity sensor of the present invention achieves proximity sensing function by synergistically enhancing the electrostatic induction between the target and the interdigital electrode, the regulation effect of the target on the capacitance of the interdigital electrode, and the modulation effect of the target on the voltage division near the gate end of the interdigital electrode.

[0017] Specifically:

[0018] When a target object approaches, it cuts the electric field lines at the outer edge of the interdigitated electrode, causing a decrease in the capacitance at the edge of the interdigitated electrode. The transistor proximity sensor based on the extended gate structure of the interdigitated electrode proposed in this invention can treat transistor 3 and voltage source 4 as a single integrated transistor. The voltage applied by voltage source 4 is considered the gate voltage of the integrated transistor, and the capacitance of the interdigitated electrode 5 and the gate dielectric capacitance of transistor 3 are connected in series to form the gate capacitance of the integrated transistor. Because the capacitance of the interdigitated electrode 5 is much smaller than the gate dielectric capacitance of transistor 3, the final gate capacitance of the integrated transistor is determined by the interdigitated electrode capacitance. The approach of the target object causes a decrease in the capacitance of the integrated transistor. As is known from the physics of transistor devices, the source-drain current of a transistor depends on the capacitance per unit area of ​​the transistor's gate dielectric. Therefore, this ultimately leads to a change in the source-drain current of the transistor.

[0019] When the target object approaches, the electrostatic interaction between the target object and the interdigitated electrodes causes the charge carriers at the transistor semiconductor / dielectric layer interface to tend to accumulate or be depleted, resulting in a change in the source current.

[0020] When the target object's surface potential is non-zero: When the target object approaches the extended gate interdigital electrode, electrostatic interaction occurs between the charged target object and the near-gate end of the interdigital electrode, leading to the accumulation / depletion of charge carriers at the transistor's semiconductor / dielectric layer. This alters the transistor's source-drain current, enabling proximity sensing. Whether the charge carriers at the transistor's semiconductor / dielectric layer interface tend to accumulate or deplete when a charged target object approaches the interdigital electrode depends on the target object's surface potential and the transistor's conductivity type. For example, a positively charged object approaching an n-type transistor tends to accumulate charge carriers at the semiconductor / dielectric layer interface, while a negatively charged object approaching a p-type transistor tends to deplete charge carriers at the interface.

[0021] When the target object has a zero surface potential but is not grounded, meaning that a net induced charge can be generated on the surface of the target object: when the target object approaches the extended gate interdigital electrode, the voltage applied to the far gate end of the interdigital electrode will induce polarization on the target object, causing the positive and negative charge centers in the target object to shift, ultimately resulting in electrostatic interaction between the target object and the near gate end of the interdigital electrode, thereby regulating the accumulation / depletion of charge carriers at the transistor semiconductor / dielectric layer and changing the source and drain current of the transistor.

[0022] When the target object has a zero surface potential and is grounded, meaning no net electrostatic charge can be generated on the target object (e.g., a grounded metal as the target object): the voltage at the far gate end of the interdigital electrode will not induce polarization on the target object, and there is no electrostatic interaction between the target object and the near gate end of the interdigital electrode. In this case, the electrostatic interaction mechanism is ineffective.

[0023] When a target object approaches the extended gate of the interdigitated electrode, the air layer between the target object and the near-gate end of the interdigitated electrode can be considered as an air layer capacitor. This air layer capacitor is connected in series with the interdigitated electrode capacitor via the near-gate end of the interdigitated electrode. The near-gate voltage (i.e., the gate voltage applied to the transistor) is determined by four factors: the surface potential of the charged object, the air layer capacitance, the far-gate bias voltage of the interdigitated electrode, and the interdigitated electrode capacitance. The approach of the target object increases the air layer capacitance. Simultaneously, the target object cuts the edge electric field lines of the interdigitated electrode capacitor, causing the interdigitated electrode capacitance to decrease. The interaction of these two factors alters the near-gate voltage (i.e., the transistor gate voltage), thereby changing the transistor's source-drain current and achieving the sensing function. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the device structure of the present invention.

[0025] Figure 2 The source-drain current response of a transistor when a grounded copper metal rod is brought close to the interdigitated electrode.

[0026] Figure 3 The source-drain current response of a transistor when a polytetrafluoroethylene rod with a surface potential of -500V is brought close to the interdigitated electrode.

[0027] The numbers in the diagram are: 1-first voltage source, 2-ammeter, 3-transistor, 4-second voltage source, 5-interdigital electrode, 6-target object; 7 is the approach stage, 8 is the stationary (distance unchanged) stage, 9 is the moving away stage; 10 is the approach stage, 11 is the stationary (distance unchanged) stage, 12 is the moving away stage. Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. The examples described herein are only a part of this invention, not all of it, and are used to explain this invention, but are not intended to limit this invention.

[0029] Example 1: A transistor proximity sensor based on an interdigitated electrode extended gate structure for monitoring the approach process of a grounded target.

[0030] The transistor used is a bottom-gate bottom-contact amorphous oxide transistor, in which the semiconductor layer is indium zinc oxide, the dielectric layer is 300nm thick SiO2, the gate electrode is n-type heavily doped silicon, the source and drain electrodes are conductive indium tin oxide thin films, and the channel length and width are 100um and 1mm, respectively.

[0031] The interdigitated electrodes used are copper interdigitated electrodes deposited by electroplating process, with a copper layer thickness of 12um, a finger length of 6.3mm, a line width of 100um, a line spacing of 100um, and 20 pairs of interdigitated fingers.

[0032] Conductive silver wires are connected between the interdigital electrode near the gate and the transistor gate using conductive silver paste. The silver wires are 0.3 mm in diameter and 10 cm in length.

[0033] The interdigitated electrode was biased at 5V to the far gate terminal, the transistor source was grounded, and the drain was connected to 1V. A grounded copper rod was used as the target object, gradually approached from a distance of 50mm to a distance of 1mm, paused briefly, then moved away from the interdigitated electrode back to a distance of 50mm, paused briefly again, and then approached again. The changes in the transistor source-drain current recorded during this process are shown in the attached figure. Figure 2 As shown, it is clear that the source-drain current of the transistor decreases when the grounded copper rod is close and increases when it is far away, thus achieving the proximity sensing function.

[0034] Example 2: A transistor proximity sensor based on an interdigitated electrode extended gate structure for monitoring the approach process of a charged target.

[0035] A transistor proximity sensor with an interdigitated electrode extended gate structure, constructed as described in Example 1, is used. The far gate end of the interdigitated electrode is biased at 5V, the transistor source is grounded, and the drain is connected to 1V. A charged target object, a copper rod biased at 200V, is gradually brought closer to the interdigitated electrode from a distance of 60mm until it is 2mm away. After a short pause, the copper rod is moved away from the interdigitated electrode back to a distance of 60mm, paused again, and then brought closer to the interdigitated electrode once more. This process is repeated. The changes in the transistor source and drain currents recorded during this process are shown in the attached figure. Figure 3 As shown, it is clear that when the 200V biased copper rod approaches, it causes the source-drain current of the transistor to increase, and when it moves away, it causes the source-drain current to decrease, thus achieving the proximity sensing function.

Claims

1. A transistor proximity sensor based on an interdigital extended gate structure, characterized in that, Specifically, it includes: First voltage source, ammeter, transistor, second voltage source, interdigitated electrodes; wherein: The source of the transistor is grounded; the drain of the transistor, the ammeter, and the first voltage source are connected in series; the gate of the transistor is electrically connected to one end of the interdigitated electrode, and this end of the interdigitated electrode connected to the gate is named the near-gate end; the other end of the interdigitated electrode is connected to the second voltage source, and this end of the interdigitated electrode connected to the second voltage source is named the far-gate end; the target object approaches / moves away from the interdigitated electrode, realizing the detection of the approach process of charged target objects and zero potential target objects; The first voltage source and the second voltage source are used to apply source-drain bias voltage and interdigital electrode far-gate bias voltage to the transistor, respectively; The ammeter is used to test the channel current of the transistor under source-drain bias. The interdigitated electrodes are used to form a planar capacitor structure; The far gate end of the interdigitated electrode is connected to the second voltage source, and the near gate end of the interdigitated electrode is electrically connected to the transistor gate. The interdigitated electrode capacitance is much smaller than the transistor gate dielectric capacitance. As the target approaches, the synergistic enhancement among the three factors—electrostatic induction between the target and the interdigital electrodes, the regulation effect of the target on the capacitance of the interdigital electrodes, and the modulation effect of the target on the voltage division near the gate of the interdigital electrodes—leads to a change in the source and drain current of the transistor, thereby achieving the proximity sensing function.

2. The transistor proximity sensor of claim 1, wherein, The interdigitated electrode refers to an electrode pair consisting of two comb-shaped electrodes with the same structure, whose comb teeth are interlocked. The spacing between the comb teeth of the interdigitated electrode and the width of the comb-shaped electrode are between 1 micrometer and 1 millimeter, the length of the comb-shaped electrode is between 10 micrometers and 10 centimeters, and the number of interdigitated electrode pairs is at least one pair.

3. The transistor proximity sensor of claim 1, wherein, The transistor and the interdigitated electrode are connected by wires, with a spacing between them ranging from 1 millimeter to 10 meters.

4. The transistor proximity sensor of claim 1, wherein, The transistor is a three-terminal structure device with gate control function, including silicon transistors, oxide transistors, or organic transistors.

5. The transistor proximity sensor of claim 1, wherein, The transistor has a bottom-gate-top contact structure, or a bottom-gate-bottom contact, top-gate-top contact, and top-gate-bottom contact structure.

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