CN100514698C - Making method for organic thin film transistor - Google Patents

Abstract

The invention relates to a manufacturing method of an organic thin-film transistor, which is suitable for the fields of the display, the sensor, the radio frequency identification (RFID) of a label, etc. The organic thin-film transistor has the structure that a grid (102), a gate insulator layer (103), a source cathode (104), a drain (105), a surface modification layer (106) and an organic semiconductor layer are arranged on a basement (101) in sequence. The preparation of the organic semiconductor layer can be realized via the transformation of pentacene derivatives to pentacene crystal. Through the adoption of the method, the organic semiconductor material is spin-coated and printed in a large area via solution. The manufacture of the organic thin-film transistor in large scale integration with a flexible substrate is accomplished, and the manufacture cost of the integrated circuit with the organic thin-film transistor can be reduced. Simultaneously, the surface modification layer is formed in the source cathode and the drain via OTS solution. The high mobility of the organic thin-film transistor, low leakage current and circuit working voltage can be further guaranteed.

Description

The manufacture method of OTFT

Technical field

The present invention relates to a kind of manufacture method of OTFT.Be applicable to display, transducer, fields such as radio frequency identification (RFID) label.

Background technology

Flexible substrate, low cost, low temperature process, the chance that makes OTFT (OTFT) can be applied to large-area soft electronic product promotes greatly, simultaneously also can carry out the making of organic integration circuit, and preparation is on cheap plastic-substrates, form the printing-type circuit, the substituted for silicon chip, and can produce in batches by printing, make display, transducer, smart card, radio frequency identification (RFID) label introduce to the market on a large scale.

But at present in the manufacturing process of the large scale integrated circuit of these flexible substrate, repeatedly adopt the step (for example: PVD, CVD etc.) of lithography process and vacuum preparation process, be difficult to reduce the cost of device preparation, for convenient later commercial employing volume to volume (R2R) is produced on a large scale, begun the research of formulations prepared from solutions OTFT, more employing macromolecule organic prints and spin coating reduces cost of manufacture, but the mobility and the stability that are difficult to reach high are also relatively poor, cause device performance to be difficult to promote.And the pentacene of high mobility and polythiophene oligomer are difficult to be directly used in printing and spin coating and prepare transistor than indissoluble and instability.

Summary of the invention

Technical problem to be solved by this invention is to overcome existing technical bottleneck.

Technical scheme of the present invention:

A kind of manufacture method of OTFT, this method is in substrate, makes grid, gate insulation layer, self assembled monolayer, organic semiconductor layer, source electrode, drain electrode successively; Wherein:

1) on grid, plates the silicon dioxide of 250 nanometer thickness as gate insulation layer;

2) make self assembled monolayer

With 1) manufactured samples transfers in the alkylchlorosilane solution of 2wt%, soaks 4 hours, allow form the alkylchlorosilane self assembled monolayer on the gate insulation layer;

Or use the multi-functional high vacuum system of DEL, and adopt the thermal evaporation preparation, put into the OTS solution of several 2wt%, vapour deposition deposits 15 minutes on the good silicon dioxide of plating, formed self-assembled monolayer on the gate insulation layer.

3) on self assembled monolayer, make organic semiconductor layer

Make the filming process of organic semiconductor layer, adopt 6, the substituent pentacene derivative TIPS-pentacene[(bia of 13-(triisopropylsilylethynyl) pentacene)] its structural formula:

Be mixed with the toluene solution of 0.5wt%, in the time of 90 ℃, carried out spin coating 60 seconds with 2500rpm, pentacene derivative changes pentacene thin film into, obtains organic semiconductor layer.

Make the filming process of organic semiconductor layer or adopt 6, the substituent pentacene derivative TES thienyl of 13-pentacene, structural formula is

Be mixed with the toluene solution of 4wt%, be deposited on the slice, thin piece in 60 seconds with the 2000rpm spin coating after, then annealing 2 minutes in the air in the time of 90 ℃, the pentacene derivative precursor changes pentacene thin film into, obtains organic semiconductor layer.

Beneficial effect of the present invention:

The present invention adopts the formulations prepared from solutions OTFT, adopt benzene pentaphene and thiophene derivants to change into pentacene and polythiophene oligomer, and the gate insulation layer to OTFT has carried out surface treatment, form self assembled monolayer, under common experiment condition, guaranteed the mobility of OTFT and improved stability, device performance is further got a promotion.

Owing to form the alkylchlorosilane self assembled monolayer on the gate insulation layer, between gate insulation layer and organic semiconductor layer, form decorative layer, use this surface treatment, make surface free energy reduce (learning) by the test contact angle, reduce surface roughness, reduce the defective between organic semiconductor layer and the gate insulation layer, make organic molecule on insulating barrier, to arrange finely, further improve mobility, reduce operating voltage and leakage current.

Adopt benzene pentaphene and thiophene derivants as the organic semiconductor layer material, print and spin coating, form the oligomer polycrystal film that the total conjugated molecule connects by heat or photolysis mode again.Pentacene and thiophene derivants change into pentacene and polythiophene oligomer as precursor, have higher mobility than other macromolecule organic, have also solved the slightly solubility problem of pentacene and thiophene oligomers simultaneously.

Description of drawings

Fig. 1 is the section of structure of the OTFT of this method manufacturing;

Fig. 2 is the XRD figure spectrum of passing through the active layer material that precursor is transformed of the OTFT made of embodiment one;

Fig. 3 is the XRD figure spectrum of passing through the active layer material that precursor is transformed of the OTFT made of embodiment three.

Among the figure: substrate 101, grid 102, gate insulation layer 103, self assembled monolayer 104, organic semiconductor layer 105, source electrode 106, drain electrode 107.

Embodiment

The embodiment one of the manufacture method of OTFT:

Step 1 is cleaned with the good ito glass sheet of hcl corrosion, and sheet glass is as substrate 101, and ITO is as grid 102;

Step 2, the silicon dioxide of plating 250 nanometer thickness is as gate insulation layer 103 on ITO;

The SD400M-MULTISOURCE ORGANICMOLECULAR VAPOR inorganic filming equipment of DEPOSITION SYSTEM and the NG-3 type electron beam evaporation power supply that adopt Shenyang City four to reach the production of vacuum technique Applied Research Laboratory carry out the preparation of silica membrane; Plated film condition: system vacuum degree 9.8E-4Pa, fore vacuum degree 1.0EOPa, growth rate 1

/ S, the heavy film time is 45 minutes;

Step 3, the sample after handling through step 2, (molecular formula is C for octadecyl trichlorosilane Acros-14740, octadecyltrichlorosilane to transfer to the OTS solution of 2wt% ₁₈H ₃₇SiCl ₃, prepare with hexadecane) and the lining soaked 4 hours, formed self assembled monolayer 104 on gate insulation layer 103;

Step 4, with the sample after the processing of acetone rinsing process step 3, carry out the filming process of organic semiconductor layer 105, adopt 6, the substituent pentacene derivative TIPS-pentacene[(bia of 13-(triisopropylsilylethynyl) pentacene)] its structural formula:

Be mixed with the toluene solution of 0.5wt%, in the time of 90 ℃, with 2500rpm carry out spin coating after 60 seconds pentacene derivative change pentacene thin film into, obtain organic semiconductor layer 105.

Step 5 is made source electrode 106 and drain electrode 107; Materials used is a gold, and in the multi-functional high vacuum system of DEL, the chamber vacuum degree adopts mask plate less than 3E-3Pa, and thermal evaporation prepares the source electrode 106 and the drain electrode 107 of 50 nanometer thickness, and the breadth length ratio of its raceway groove is 100, obtains OTFT.

The structure of this OTFT is followed successively by: substrate 101, grid 102, gate insulation layer 103, self assembled monolayer 104, organic semiconductor layer 105, source electrode 106 and drain 107.

The thin film-forming method of organic semiconductor layer 105 also can adopt printing and inkjet printing preparation.

Embodiment two

Other step is identical with embodiment one, and difference is to form the mode difference of self assembled monolayer 104 on gate insulation layer 103; Use the multi-functional high vacuum system of DEL, adopt the thermal evaporation preparation, put into the OTS solution of several 2wt%, take out in advance and make the chamber vacuum degree less than 3E-3Pa, vapour deposition deposits 15 minutes on the good silicon dioxide of plating, formed self-assembled monolayer 104 on the gate insulation layer 103.

Embodiment three

Other step is identical with embodiment one, and difference is that the material of organic semiconductor layer 105 is different with generation type; Carry out the filming process of organic semiconductor layer, adopt 6, the substituent pentacene derivative TES thienyl of 13-pentacene, structural formula is

Be mixed with the toluene solution of 4wt%, be deposited on the slice, thin piece in 60 seconds with the 2000rpm spin coating after, then annealing 2 minutes in the air in the time of 90 ℃, the pentacene derivative precursor changes pentacene thin film into, obtains organic semiconductor layer 105.

I-V the characteristic curve that utilizes KEITHLEY 2410 source unit I-V test macros to carry out the OTFT device is measured, and draws at different grid voltage V _GSDown, source-drain current I _DSWith source-drain voltage V _DSI-V concern collection of illustrative plates, come the computation migration rate in the zone of saturation according to current equation again:

Promptly work as V _DSIncreasing (saturation region), and make drain current (I _DS) when reaching capacity

V _DS>(V _GS-V _TH)：

$I_{\mathrm{DS},\mathrm{sat}}=\frac{1}{2}\mathrm{\μ}{C}_i\frac{W}{L}{(V_{\mathrm{GS}}-V_{\mathrm{TH}})}^2$

${\left(I_{\mathrm{DS},\mathrm{sat}}\right)}^{\frac{1}{2}}={\left(\frac{1}{2}\mathrm{\μ}{C}_i\frac{W}{L}\right)}^{\frac{1}{2}}(V_{\mathrm{GS}}-V_{\mathrm{TH}})$

$\mathrm{\μ}=\frac{2L}{{\mathrm{WC}}_i}{\left(\frac{\∂\sqrt{I_D}}{\∂V_{\mathrm{GS}}}\right)}^2$

I wherein _DSBe drain current, μ is a carrier transport factor, and W, L are respectively width and the length in the transistor channel, and Ci is the capacitance of unit are insulating barrier, V _GSBe grid voltage, V _THBe threshold voltage (threshold voltage).Therefore can utilize (I _{DS, sat.}) ^1/2To V _GSThe characteristic transfer curve is drawn out in mapping, remakes linear regression, and the slope of the tropic is calculated carrier mobility (μ) thus, and tries to achieve V by the intercept of the tropic and X-axis _TH

By above calculating, at V _DS=-30V, under the situation that leakage-source electric current is full of, the mobility of each embodiment such as following table.

Table 1

The embodiment sequence number	Mobility (μ)
		Embodiment 1	1.21cm 2/Vs
Embodiment 2	1.09cm 2/Vs
		Embodiment 3	0.72cm 2/Vs

Fig. 2 is the XRD figure spectrum of passing through the organic semiconductor layer material that the pentacene precursor is transformed of the OTFT made of the embodiment of the invention one, the diffraction maximum of XRD figure spectrum is compared as can be known with the standard diagram diffraction maximum of pentacene, is crystal structure pentacene thin film preferably by the organic semiconductor layer material that is transformed by precursor.Ordinate is Intensity (CPS) intensity, abscissa deg. angle.

Fig. 3 is the XRD figure spectrum of passing through the organic semiconductor layer material that precursor is transformed of the OTFT made of the embodiment of the invention three, the diffraction maximum of XRD figure spectrum is compared as can be known with the standard diagram diffraction maximum of pentacene, the organic semiconductor layer material that is transformed by the pentacene precursor is a crystal structure pentacene thin film preferably, but the pentacene that transforms than the pentacene derivative of embodiment one is more weaker.

Claims (3)

1. the manufacture method of an OTFT, this method is in substrate, makes grid, gate insulation layer, organic semiconductor layer, source electrode, drain electrode successively; It is characterized in that:

1) makes gate insulation layer

The silicon dioxide of plating 250 nanometer thickness is as gate insulation layer on grid;

2) make self assembled monolayer

With 1) manufactured samples transfers in the OTS solution of 2wt%, soaks 4 hours, allow form the OTS self assembled monolayer on the gate insulation layer;

3) on self assembled monolayer, make organic semiconductor layer

Adopt 6, the substituent pentacene derivative TIPS-pertacene[(bia of 13-(triisopropylsilylethynyl) pentacene)] its structural formula:

Be mixed with the toluene solution of 0.5wt%, in the time of 90 ℃, carried out spin coating 60 seconds with 2500rpm, pentacene derivative changes pentacene thin film into, obtains organic semiconductor layer.

2. the manufacture method of a kind of OTFT according to claim 1 is characterized in that: on self assembled monolayer, makes organic semiconductor layer, adopts 6, and the substituent pentacene derivative TES thienyl of 13-pentacene, structural formula is

Be mixed with the toluene solution of 4wt%, be deposited on the slice, thin piece in 60 seconds with the 2000rpm spin coating after, then annealing 2 minutes in the air in the time of 90 ℃, pentacene derivative changes pentacene thin film into, obtains organic semiconductor layer.

3. the manufacture method of a kind of OTFT according to claim 1, it is characterized in that: make self assembled monolayer or use the multi-functional high vacuum system of DEL, the preparation of employing thermal evaporation, put into the OTS solution of several 2wt%, take out in advance and make the chamber vacuum degree less than 3E-3Pa, vapour deposition deposits 15 minutes on the good silicon dioxide of plating, formed self assembled monolayer on gate insulation layer.

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