Abstract:
An electronic skin is manufactured by disposing an oxide thin film transistor (TFT), a pressure sensor, and a temperature sensor on a flexible substrate. The pressure sensor and the temperature sensor are respectively located on two sides of the flexible substrate. The oxide TFT includes a first TFT and a second TFT. The pressure sensor is configured to drive the first TFT, and the temperature sensor is configured to drive the second TFT. The method for preparing the electronic skin is to form an oxide TFT, a pressure sensor, and a temperature sensor by means of etching and deposition on a flexible substrate whose double sides are covered with conductive materials. The electronic skin provided in the present invention may simultaneously measure pressure and temperatures, and has a simple structure, a low working voltage, small power consumption, high sensitivity, and small interference between sensor signals.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of PCT/CN2015/095549, filed on Nov. 25, 2015. The contents of PCT/CN2015/095549 are all hereby incorporated by reference. PCT/CN2015/095549 claims priority of Chinese application No. 201410770984.1, filed on Dec. 12, 2014. 
     
    
     BACKGROUND 
     Technical Field 
       [0002]    The present disclosure relates to an electronic skin and a manufacturing method therefor. 
       Related Arts 
       [0003]    An electronic skin is prepared by embedding various flexible thin film transistors (TFTs) and various sensors into a soft plastic thin film, and can satisfy large-area requirements of a human body because the electronic skin is soft and thin like a skin and is also an electronic device attached on a skin. The electronic skin not only can sense pressure and temperatures, but also can sense light, humidity, tension, ultrasonic waves, and the like, and can provide feedback in time to human body health data changes by means of real-time monitoring of human body health physiological indexes such as pulses, heartbeats, body temperatures, and muscle group vibrations, and even implement prophase prevention and diagnosis of diseases. Meanwhile, the electronic skin may further be equipped with a memory, and may also have the functions of wireless power supply and wireless data transmission, so that the electronic skin can be carried around, and perform continuous medical signal monitoring for a long time. Therefore, the technology opens a door leading to a micro mobile health monitor. It is necessary to provide a highly-sensitive and durable electronic skin with a simple structure. 
       SUMMARY 
       [0004]    To resolve the foregoing technical problems, the present disclosure provides an electronic skin and a manufacturing method therefor. The electronic skin may simultaneously measure pressure and temperatures, and has a simple structure, a low working voltage, small power consumption, high sensitivity, and small interference between sensor signals. 
         [0005]    To achieve the foregoing objectives, the present disclosure uses the following technical solutions: 
         [0006]    The present disclosure discloses an electronic skin, where an oxide TFT, a pressure sensor, and a temperature sensor are disposed on a flexible substrate, the pressure sensor and the temperature sensor are respectively located on two sides of the flexible substrate, the oxide TFT includes a first TFT and a second TFT, the pressure sensor is configured to drive the first TFT, and the temperature sensor is configured to drive the second TFT. 
         [0007]    Preferably, a material of the flexible substrate is polyimide having a thickness of 10 μm to 50 μm. 
         [0008]    Preferably, the first TFT and the second TFT use a same top gate structure, and each of the pressure sensor and the temperature sensor is provided with a corresponding storage capacitor. 
         [0009]    Preferably, each of the first TFT and the second TFT includes a drain, a source, a gate, an active layer, a first gate insulation layer, and a second gate insulation layer, and 
         [0010]    the drain and the source are located on a same layer, the active layer is located on the layer where the corresponding drain and source are located and partially overlaps with the corresponding drain and source, the first insulation layer covers the corresponding active layer, the second insulation layer covers the corresponding drain and source and the first insulation layer, and the gate is located on the corresponding second insulation layer; and the source of the first TFT is connected to the pressure sensor, and the source of the second TFT is connected to the temperature sensor through a through hole of the flexible substrate. 
         [0011]    Preferably, the drain, the source, and the gate of each of the first TFT and the second TFT use a metal electrode, a transparent conductive electrode, or a carbon nano-tube, the active layer of each of the first TFT and the second TFT uses a metal oxide semiconductor, the first insulation layer of each of the first TFT and the second TFT uses SiOx, and the second insulation layer of each of the first TFT and the second TFT uses SiNx. 
         [0012]    In addition, the present disclosure further discloses a method for preparing an electronic skin, where a first TFT, a second TFT, a pressure sensor, and a temperature sensor are formed, by means of etching and deposition, on a flexible substrate whose double sides are covered with conductive materials, and the pressure sensor and the temperature sensor are respectively formed on two sides of the flexible substrate. 
         [0013]    Preferably, the manufacturing method specifically comprises the following steps: 
         [0014]    S 1 : etching a pattern A on one side of the flexible substrate whose double sides are covered with conductive materials, where the pattern A includes a source and a drain of the first TFT and a source and a drain of the second thin film transistor; 
         [0015]    S 2 : etching a pattern B on the other side of the flexible substrate, where the pattern B includes an electrode of the temperature sensor; 
         [0016]    S 3 : drilling a hole at a corresponding position, connected to the pattern B, of the flexible substrate, and electroplating the drilling position, so that the pattern B is electrically connected to the pattern A; 
         [0017]    S 4 : forming a semiconductor layer on the pattern A, then depositing an insulation layer on the semiconductor layer, separately etching active layers of the first TFT and the second TFT on the semiconductor layer, separately etching first insulation layers of the first TFT and the second TFT on the insulation layer, and then depositing second insulation layers on the first insulation layers of the first TFT and the second TFT; and 
         [0018]    S 5 : forming a conductive layer on the second insulation layers, and etching gates of the first TFT and the second TFT and the pressure sensor. 
         [0019]    Preferably, step S 4  specifically includes: 
         [0020]    S 41 : forming a metal oxide semiconductor layer on the pattern A by using a magnetron sputtering method, and then forming an SiOx layer on the metal oxide semiconductor layer by using an ALD method; 
         [0021]    S 42 : respectively etching the first insulation layers of the first TFT and the second TFT on the SiOx layer by using a dry etching process, and respectively etching the active layers of the first TFT and the second TFT on the metal oxide semiconductor layer by using a wet etching process; and 
         [0022]    S 43 : forming the second insulation layers of the first TFT and the second TFT on the first insulation layers of the first TFT and the second TFT by using a plasma enhanced chemical vapor deposition method (PECVD), and forming, by using a dry etching method, through holes at corresponding positions where the second insulation layers are connected to the sources. 
         [0023]    Preferably, step S 5  specifically includes: 
         [0024]    S 51 : forming the conductive layer on the second insulation layers of the first TFT and the second TFT by using a magnetron sputtering method, and etching the gates of the first TFT and the second TFT and lower electrodes of the pressure sensor and the temperature sensor; 
         [0025]    S 52 : forming a passivation layer by using a PECVD method; and 
         [0026]    S 53 : etching a sensitive area of the pressure sensor by using a dry etching process, forming a sensitive layer of the pressure sensor by using a printing method or an ink jet printing method, and then forming an upper electrode of the pressure sensor on the sensitive layer. 
         [0027]    Preferably, a distance between the source and the drain of the first TFT is 2 μm to 20 μm and a distance between the source and the drain of the second TFT is 2 μm to 20 μm. 
         [0028]    Compared with the prior art, beneficial effects of the present disclosure are that: in the electronic skin provided in the present disclosure, the pressure sensor and the temperature sensor are disposed on two sides of the flexible substrate, so that pressure and temperatures may be simultaneously measured; the electronic skin is flexible, and has a simple structure, a low working voltage, small power consumption, high sensitivity, and small interference between sensor signals. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    The present disclosure will become more fully understood from the detailed description given herein below for illustration only, and thus are not limitative of the present disclosure, and wherein: 
           [0030]      FIG. 1  is a schematic sectional view of an electronic skin according to a preferable embodiment of the present disclosure; 
           [0031]      FIG. 2  is an equivalent circuit diagram of a sensor unit; 
           [0032]      FIG. 3  is a driving pulse diagram of the sensor unit; 
           [0033]      FIG. 4  is a schematic diagram  1  of manufacturing of an electronic skin according to a preferable embodiment of the present disclosure; 
           [0034]      FIG. 5  is a schematic diagram  2  of manufacturing of an electronic skin according to a preferable embodiment of the present disclosure; 
           [0035]      FIG. 6  is a top view in a manufacturing process of an electronic skin according to a preferable embodiment of the present disclosure; and 
           [0036]      FIG. 7  is a schematic diagram of a connection of a temperature sensor of an electronic skin according to a preferable embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]    The present disclosure is described in further detail below with reference to embodiments and the accompanying drawings. 
         [0038]      FIG. 1  is a schematic sectional view of an electronic skin according to a preferable embodiment of the present disclosure. The electronic skin includes a flexible substrate  50 . A first TFT, a second TFT, a pressure sensor, and a temperature sensor are disposed on the flexible substrate  50 . The pressure sensor and the temperature sensor are respectively located on two sides of the flexible substrate. The first TFT is configured to drive the pressure sensor, and the second TFT is configured to drive the temperature sensor. The first TFT includes a drain  11 , a source  12 , a gate  13 , an active layer  14 , a first insulation layer  15 , and a second insulation layer  16 . The second TFT includes a drain  21 , a source  22 , a gate  23 , an active layer  24 , a first insulation layer  25 , and a second insulation layer  26 . The drain  11 , the source  12 , the drain  21 , and the source  22  are located on a same layer. The active layer  14  is located on the layer where the drain  11  and the source  12  are located, and partially overlaps with the drain  11  and the source  12 . The active layer  24  is located on the layer where the drain  21  and the source  22  are located and partially overlaps with the drain  21  and the source  22 . The first insulation layer  15  covers the active layer  14 . The first insulation layer  25  covers the active layer  24 . The second insulation layer  16  covers the drain  11 , the source  12 , and the first insulation layer  15 . The second insulation layer  26  covers the drain  21 , the source  22 , and the first insulation layer  25 . The gate  13  is located on the second insulation layer  16 . The gate  23  is located on the second insulation layer  26 . The pressure sensor includes a lower electrode  31 , an upper electrode  32 , a pressure sensitive area  33 , and an electrode  34 . The lower electrode  31  of the pressure sensor is connected to the source  12  of the first TFT through a through hole  70 . The lower electrode  31 , the second insulation layer  16 , and the electrode  34  form a storage capacitor of the pressure sensor. Active areas of the pressure sensitive area  33  and the upper electrode  32  are limited by a passivation layer  60 . The temperature sensor includes a lower electrode  41 , an electrode  42 , a through hole  43 , and an electrode  44 . The electrode  42  of the temperature sensor is connected to the source  22  of the second TFT through a through hole  80  and the through hole  43 . The electrode  44 , the second insulation layer  26 , and the lower electrode  41  form a storage capacitor of the temperature sensor. Preferably, a material of the flexible substrate is polyimide having a thickness of 10 μm to 50 μm. The drain  11 , the source  12 , the gate  13 , the drain  21 , the source  22 , the gate  23 , the lower electrode  31 , the upper electrode  32 , the electrode  34 , the lower electrode  41 , the electrode  42 , the electrode  44 , and interconnected conductive layers may use a metal electrode, a transparent conductive electrode, conductive nano silver, a carbon nano-tube, and the like. The active layers  14  and  24  may use a metal oxide semiconductor, such as zinc tin oxide (ZTO) or indium gallium zinc oxide (IGZO). The first insulation layers  15  and  25  may use SiOx. The second insulation layers  16  and  26  may use SiNx. The pressure sensitive layer  33  may use a QTC material, a piezoelectric material, a piezoresistive material, or the like. The passivation layer  60  uses SiNx. 
         [0039]    A sensor unit of the electronic skin may read, by means of scanning and addressing, electrical signals generated by means of pressure and temperature changes. An equivalent circuit of the sensor unit is shown in  FIG. 2 , and a corresponding driving pulse is shown in  FIG. 3 . A row electrode  110  is connected to the gate of the first TFT T 1 ; a signal of a row driver  130  provides a scan pulse Vgate to the first TFT T 1  to select a row electrode; the source of the first TFT T 1  and the source of the second TFT T 2  are connected to a column electrode  120 . Equivalently, a pressure sensing unit may be a variable resistor R 1 . When there is a touch, the size of resistance is relevant to the size of pressure; when there is no touch, the resistance is great, and signals are stored in a capacitor C 1 . Equivalently, a temperature sensing unit is a variable resistor R 2  that changes with temperatures, and signals are stored in a capacitor C 2 . 
         [0040]    With reference to  FIG. 2  and  FIG. 3 , when Vgate is low, the first TFT T 1  and the second TFT T 2  are cut off, and the pressure sensor and the temperature sensor are both in a signal integration phase. When there is a touch action or when the temperature changes, resistance of the pressure sensing unit or the temperature sensing unit changes, and the corresponding storage capacitor discharges by using the corresponding sensing unit, and a voltage of a node A 1  or node A 2  changes; when Vgate is high, the first TFT T 1  and the second TFT T 2  are conducted, and the pressure sensor and the temperature sensor are both in a signal reading phase, and the column electrode  120  charges the capacitor C 1  and the capacitor C 2  respectively by using the first TFT T 1  and the second TFT T 2 , and charging signals are read by a column amplifier  140 . 
         [0041]    A method for manufacturing an electronic skin according to a preferable embodiment of the present disclosure includes the following steps. 
         [0042]    As shown in  FIG. 4 , a flexible substrate  50  whose double sides are covered with conductive materials is first selected. Preferably, the thickness of the flexible substrate is 10 μm to 50 μm. In this embodiment, a polyimide material whose double sides are covered with copper and thickness is 25 μm is selected. A pattern  100  is etched on copper on one side of the flexible substrate  50 , and the pattern  100  represents a source and a drain of a TFT, an electrode of a capacitor, a row electrode (data line), a column electrode (scanning line), interconnected conductive wires, and the like of. A pattern  200  is etched on copper on the other side of the flexible substrate  50 , and the pattern  200  represents an electrode and the like of a temperature sensor. 
         [0043]    As shown in  FIG. 5 , then the pattern  200  is protected by using an adhesive  300 . A hole is drilled at a corresponding position, connected to the pattern  200 , of the flexible substrate  50 . The aperture is preferably 10 μm to 50 μm. Then electroplating is performed to form a through hole  43 , and the adhesive  300  is removed. 
         [0044]      FIG. 6  is a top view of the flexible substrate  50  including a first TFT and a second TFT. It is seen from  FIG. 6  that copper on the flexible substrate  50  is etched to form: a source  12  and a drain  11  of the first TFT, a source  22  and a drain  21  of the second TFT, a row electrode (data line)  120  connected to both the drains  11  and  21 , an electrode  34  of a storage capacitor C 1  and an electrode  44  of a storage capacitor C 2 , and the through hole  43  formed by electroplating. The width of a channel between the source  12  and the drain  11  of the first TFT is 2 μm to 20 μm, and is preferably 10 μm, so as to satisfy the feature of flexibility of the electronic skin. 
         [0045]    With reference to  FIG. 1 ,  FIG. 5 , and  FIG. 6 , a semiconductor layer, such as ZTO and IGZO, is formed on the etched pattern  100  by using a magnetron sputtering method. Preferably, the thickness is 40 to 60 nm. An SiOx layer is deposited by using an ALD method. Preferably, the thickness is 20 nm. Then a first insulation layer  15  of the first TFT and a second insulation layer  25  of the second TFT are formed by using a dry etching process; and an active layer  14  of the first TFT and an active layer  24  of the second TFT are formed by using a wet etching process. An SiNx layer is deposited on the first insulation layer  15  of the first TFT and on the first insulation layer  25  of the second TFT by using a PECVD method. Preferably, the thickness is 80 nm to 200 nm, that is, a second insulation layer  16  of the first TFT and a second insulation layer  26  of the second TFT are simultaneously formed. A through hole  70  and a through hole  80  are formed by using a dry etching process. Then a conductive layer is formed by using a magnetron sputtering method. The formed conductive layer is etched to form: a gate  13  of the first TFT, a gate  23  of the second TFT, a column electrode (scanning line)  120  connected to the gates  13  and  23 , a lower electrode  31  of the pressure sensor, and a lower electrode  41  of the temperature sensor. The lower electrode  31  of the pressure sensor is connected to the source  12  of the first TFT through the through hole  70 . The lower electrode  31  of the pressure sensor and the electrode  34  form the storage capacitor C 1 . The lower electrode  41  of the temperature sensor is connected to the source  22  of the second TFT through the through hole  80 , and is also connected to the temperature sensor below the flexible substrate  50  through the through hole  43 . The lower electrode  41  of the temperature sensor and the electrode  44  form a storage capacitor C 2 . 
         [0046]    Finally, a passivation layer  60  is formed by using a PECVD method. A sensitive area of the pressure sensor is formed by using a dry etching method. A pressure sensitive layer  33  is formed by using a printing method and an ink jet printing method, and then an upper electrode  32  of the pressure sensor is formed by using a magnetron sputtering method. 
         [0047]    The temperature sensor may use a stacking method. However, flexibility of the manner is relatively poor. Therefore, a temperature sensor shown in  FIG. 7  is used in this preferable embodiment of the present disclosure. Electrodes  421  and  422  are both connection wires of the temperature sensor, that is, both correspond to the electrode  42  of the temperature sensor shown in  FIG. 1 . The electrode  421  is connected to the source of the second TFT. There may be multiple choices for the temperature sensor. A thermistor  45  is used in this preferable embodiment of the present disclosure, and the thermistor  45  is connected to the electrodes  421  and  422  within a plane. 
         [0048]    The electronic skin provided in the present disclosure is an electronic skin based on an oxide TFT. The electronic skin includes a flexible substrate, an oxide TFT, a pressure sensor, and a temperature sensor. The oxide TFT includes a first TFT and a second TFT. The first TFT and the second TFT use a same top gate structure, and are formed at a time in process. A source of the first TFT is connected to the pressure sensor; the first TFT becomes a signal reading mechanism of the pressure sensor; pressure signals are stored in a corresponding storage capacitor; a source of the second TFT is connected to the temperature sensor through a through hole on the flexible substrate; the second TFT becomes a signal reading mechanism of the temperature sensor, and temperature change signals are stored in a corresponding storage capacitor. In addition, the pressure sensor and the temperature sensor are located in a same TFT array, and the pressure change signals and the temperature change signals are read by using a row electrode (data line) by using a same scanning reading pulse. 
         [0049]    The electronic skin prepared by using the manufacturing method of the present disclosure implements the function of simultaneously measuring pressure and temperatures, may be used in detection of human pulses, heartbeats, intraocular pressure, muscular movement, and the like, and may also be used in detection of body temperatures or environmental temperatures. 
         [0050]    Although the present disclosure is described above in further detail with reference to specific preferable implementation manners, it should not be considered that the present disclosure is merely limited to the specific implementation manners. Several equivalent replacements or obvious variations with the same performance or purpose may be further made without departing from the spirit of the present disclosure by a person skilled in the art to which the present disclosure belongs shall fall within the protection scope of the present disclosure.