CN105628262A

CN105628262A - Thin film transistor pressure sensor based on organic elastomer gate insulating layer

Info

Publication number: CN105628262A
Application number: CN201510971268.4A
Authority: CN
Inventors: 姚若河; 蔡旻熹; 刘玉荣; 韦岗
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2015-12-20
Filing date: 2015-12-20
Publication date: 2016-06-01

Abstract

The invention discloses a thin film transistor pressure sensor based on an organic elastomer gate insulating layer. The pressure sensor has a top gate staggered structure. An organic elastomer which is deformed after being pressed and back to the original state after the pressure is removed serves as the gate insulating layer, and an inorganic semiconductor material with excellent electrical performance serves as an active layer. The pressure applied to the thin film transistor gate enables the actual thickness of the organic elastomer gate insulating layer to change, the capacitance of the gate insulating layer is thus influenced, drain current of the inorganic semiconductor thin film transistor is further changed, and through detection on the drain current, the size of the pressure applied to the gate can be reflected.

Description

Thin film transistor (TFT) pressure transducer based on organic elastomer gate insulation layer

Technical field

The present invention relates to MEMS pressure sensor field, be more particularly to a kind of gate insulation layer and elastically-deformable inorganic semiconductor thin film transistor (TFT) pressure transducer can occur.

Background technology

Traditional pressure type sensor mainly includes resistance-type, inductance type and condenser type three major types, mainly comprise the resistance of structure, inductance and electric capacity respectively through device to change under external pressure, the change of these three physical quantity is finally given the change of voltage by recycling measuring circuit through a series of process and conversion, thus reaching the purpose of detection external pressure change. This kind of sensor not only needs the measuring circuit of complexity, and the change of pressure easily causes bigger error via the conversion of multiple electrical quantities, is unfavorable for the raising of Pressure Sensor Precision. The OTFT sensor occurred in recent years uses organic semiconducting materials to do the active layer of device, but the carrier mobility of organic semiconducting materials is low, the thin film transistor (TFT) formed needs very big bias voltage when normal operation, cause that power consumption increases, and the major part organic semiconducting materials life-span is shorter, has a strong impact on the long-time stability of device electric property.

Summary of the invention

For overcoming disadvantages mentioned above, the present invention proposes a kind of inorganic semiconductor thin film transistor (TFT) pressure transducer being gate insulation layer with organic elastomer.

In order to realize foregoing invention purpose, the invention provides the technical scheme of complete set:

A kind of be gate insulation layer with organic elastomer body thin film inorganic semiconductor thin film transistor (TFT) pressure sensor structure, specifically include that top-gated staggered thin-film transistor structure; Organic elastomer gate insulation layer; The inorganic semiconductor active layer that electric property is excellent. Described top-gated staggered thin-film transistor structure, is different from traditional capacitance pressure transducer, by detecting thin film transistor (TFT) drain current but not the change of dielectric layer electric capacity, and directly reflection grid pressure situation; Source/drain electrode and top gate electrode are distributed in active layer not homonymy up and down, do not affect organic elastomer/inorganic semiconductor interface, are conducive to improving the stability of device.

Described top-gated staggered thin film transistor (TFT) is by its drain electrode output electric current I_DChange directly reflect grid pressure situation; First top-gated staggered structure particularly as follows: deposit source/drain electrode on substrate, deposit subsequently covers the inorganic semiconductor active layer of source/drain electrode, the source/drain contact making device is positioned at the lower surface of inorganic semiconductor active layer, and inorganic semiconductor active layer surface is carried out process obtain flat surfaces, then deposit organic elastomer gate insulation layer, finally deposit covers the top gate electrode thin layer in whole top device region, and so as to have smooth surface; The gate electrode of described top-gated staggered thin film transistor (TFT) is positioned at the top of whole device, source/drain electrode contacts with the lower surface of inorganic semiconductor active layer, and top gate electrode controls inorganic semiconductor active layer upper surface and forms conducting channel, namely source/drain contact and top gate electrode are positioned at the not homonymy up and down of inorganic semiconductor active layer.

Described organic elastomer material is for the gate insulation layer of thin film transistor (TFT), organic elastomer gate insulation layer adopts the organic elastomer material with superior isolation and high-k higher compared to having sensitivity with air for dielectric transistor sensor, the feature that performance is more stable. The active layer of described thin film transistor (TFT) is the inorganic semiconductor material that electric property is excellent, has compared to organic semiconductor thin film transistor sensor that sensitivity is higher, power consumption is lower, the better feature of long-time stability.

The top-gated staggered thin-film transistor structure that the present invention adopts, top grid insulating barrier can deform upon with extraneous stress, directly results in the change of device drain current. Gate electrode and source/drain electrode are positioned at semiconductor active layer not homonymy up and down, advantageously form good gate insulation layer/active layer interface, improve device stability;

Organic elastomer gate insulation layer, elastic deformation is there is after pressurized, pressure recovers rapidly after removing, for described inorganic semiconductor thin film transistor (TFT) top gate insulating barrier, can deform upon in a thickness direction with gate planar pressure, the gate insulation layer thickness making device produces change, and then affects the drain current of device.

The inorganic semiconductor active layer that electric property is excellent, its carrier mobility is relatively larger, stable chemical nature, and the active layer as thin film transistor (TFT) can obtain the electric property and long-time stability that are better than major part organic semiconductor thin film transistor.

Compared with prior art, the invention have the advantages that and technique effect:

The inorganic semiconductor pressure transducer being gate insulation layer with organic elastomer body thin film that the present invention proposes, the change of electric current can be exported either directly through device drain the pressure size of top device grid is detected, there is higher sensitivity within the scope of certain pressure. Compared to capacitance pressure transducer, the testing circuit of the pressure transducer that the present invention proposes is more simple; Compared with OTFT pressure transducer, during proper device operation, required bias voltage is little, low in energy consumption, and has higher long term device stability.

Accompanying drawing explanation

Fig. 1 is organic elastomer is the structural representation of inorganic semiconductor thin film transistor (TFT) pressure transducer of gate insulation layer.

Fig. 2 is organic elastomer is the fundamental diagram of inorganic semiconductor thin film transistor (TFT) pressure transducer of gate insulation layer.

Fig. 3 is that in example, organic elastomer is the drain electrode output electric current I of the inorganic semiconductor thin film transistor (TFT) pressure transducer of gate insulation layer_DRelation with gate stress P.

Detailed description of the invention

Below in conjunction with embodiment and accompanying drawing, the present invention is described in further detail, but embodiments of the present invention are not limited to this, is pointed out that, if having process or the raw material parameter of not detailed description especially below, it is all that those skilled in the art can refer to existing techniques in realizing or understanding.

With reference to Fig. 1, this example gives a kind of specific embodiment of the inorganic semiconductor thin film transistor (TFT) pressure transducer that organic elastomer is gate insulation layer, and its main material and construction features include: top-gated staggered thin film transistor (TFT); Polydimethylsiloxane (PDMS) organic elastomer is as gate insulation layer; Amorphous indium gallium zinc oxygen (a-IGZO) inorganic semiconductor is as active layer. Thin film transistor (TFT) (TFT) device overall length is 20 ��m, wide is 180 ��m, for top-gated staggered structure, " top-gated " refers to that the gate electrode of thin film transistor (TFT) of the present invention is positioned at the top of whole device, " stagger arrangement " refers to that source/drain electrode contacts with the lower surface of active layer, and top gate electrode controls active layer upper surface and forms conducting channel, namely source/drain contact and the grid at top are positioned at the not homonymy up and down of active layer. Wherein active layer channel length L=10 ��m, channel width W=180 ��m. Example device adopts glass substrate, on substrate, thickness is the Au/Ti source-drain electrode of the Au composition bilayer of Ti and the 20nm of 5nm, the length of source-drain electrode is 5 ��m, inorganic semiconductor amorphous indium gallium zinc oxygen (a-IGZO) that active layer above source-drain electrode uses thickness to be 30nm, magnetron sputtering method in the a-IGZO thin film deposited, each chemical constituent ratio is In:Ga:Zn=1:0.9:0.6. For the smooth interface obtained and between PDMS, dry etching is adopted to process the projection of the a-IGZO thin film directly over source-drain electrode, thus obtaining smooth upper surface, the original depth t of PDMS organic elastomer gate insulation layer thin film₀For 500nm, its preparation process is as follows: be mixed and stirred for uniformly for 10:1 by volume by polydimethylsiloxane (PDMS) performed polymer and firming agent (cross-linking agent with silicon hydrogen-based of catalyst made from platonic), it is poured on the a-IGZO active layer having passed through etching acquisition flat surfaces after vacuum outgas, namely obtaining PDMS elastomer gate insulation layer after its fully crosslinked solidification, its thickness is determined by the volume of the mixture poured into a mould. Tin indium oxide (ITO) electrode gate electrode as device covering whole top device that last top device adopts thickness to be 50nm.

The fundamental diagram of pressure transducer described in this example such as Fig. 2, wherein V_DFor 15V, V_GS=10V, for making device work in saturation region, R_DValue be 33k ��, the pressure acting perpendicularly to gate upper surface is 0N��1.008 �� 10^-3N, and with 7.2 �� 10^-5The interval of N is stepped up.

The drain electrode output electric current I of the a-IGZOTFT pressure transducer based on PDMS gate insulation layer that example obtains_DCurve such as Fig. 3 with gate stress change. Its test process is as follows: the uniformly applied applanation being perpendicular to this surface of upper surface at top device gate electrode, according to described present example, the area of device grids upper surface is 180 �� m 20 ��m, and the size P (MPa) of pressure added by grid represents the pressure (N/mm that its every square millimeter of surface is suffered²). The pressure that gate upper surface is applied is from 0N��1.008 �� 10^-3N (0MPa��0.28MPa) is with 7.2 �� 10^-5The interval of N (0.02MPa) is stepped up, the change of grid pressurized causes PDMS gate insulation layer thickness variation, showing as the change of the drain electrode output electric current of device in this instance graph 2, incrementally increase with gate stress, the saturated drain electrode output electric current of device is from 9.27 �� 10^-5A increases to 1.45 �� 10^-4A, then the drain electrode output electric current I of pressure transducer described in this example_D(A) being represented by the curve shown in this instance graph 3 with the variation relation of applanation P (MPa) added by grid, this slope of a curve can characterize the sensitivity of thin film transistor (TFT) pressure transducer. The sensitivity of definition pressure transducer is S=�� I_D/ �� P. Result according to Fig. 3 is visible, and when device grids is stressed less, the deformation that PDMS gate insulation layer occurs is smaller, I_DChange with P is substantially linear, namely the sensitivity of sensor is held essentially constant, the sensitivity extracting and obtaining under less pressure (< 0.1MPa) device from Fig. 3 is S=0.119mA/MPa, and when gate stress increase to make PDMS film thickness reduce to close to original depth 50% time (P��0.28MPa), sensitivity rises to and is about S=0.351mA/MPa.

Claims

1. based on the thin film transistor (TFT) pressure transducer of organic elastomer gate insulation layer, by directly detecting drain electrode output electric currentI _DSize variation obtain the size variation of grid pressure, it is characterised in that include top-gated staggered thin film transistor (TFT), organic elastomer gate insulation layer and inorganic semiconductor active layer.

2. the thin film transistor (TFT) pressure transducer based on organic elastomer gate insulation layer according to claim 1, it is characterised in that: described top-gated staggered thin film transistor (TFT) is by its drain electrode output electric currentI _DChange directly reflect grid pressure situation; First top-gated staggered structure particularly as follows: deposit source/drain electrode on substrate, deposit subsequently covers the inorganic semiconductor active layer of source/drain electrode, the source/drain contact making device is positioned at the lower surface of inorganic semiconductor active layer, and inorganic semiconductor active layer surface is carried out process obtain flat surfaces, then deposit organic elastomer gate insulation layer, finally deposit covers the top gate electrode thin layer in whole top device region, and so as to have smooth surface; The gate electrode of described top-gated staggered thin film transistor (TFT) is positioned at the top of whole device, source/drain electrode contacts with the lower surface of inorganic semiconductor active layer, and top gate electrode controls inorganic semiconductor active layer upper surface and forms conducting channel, namely source/drain contact and top gate electrode are positioned at the not homonymy up and down of inorganic semiconductor active layer.

3. the thin film transistor (TFT) pressure transducer based on organic elastomer gate insulation layer according to claim 1, it is characterised in that: described organic elastomer gate insulation layer adopts cured elastomer silicone.

4. the thin film transistor (TFT) pressure transducer based on organic elastomer gate insulation layer according to claim 1, it is characterised in that: the inorganic semiconductor active layer of described thin film transistor (TFT) is non-crystalline silicon, polysilicon or current existing metal-oxide semiconductor (MOS).