CN101388342B

CN101388342B - Method for preparing inorganic thin-film transistor by complete solution treatment process

Info

Publication number: CN101388342B
Application number: CN2008102019651A
Authority: CN
Inventors: 魏斌; 李博; 孙三春; 张建华; 汪敏
Original assignee: University of Shanghai for Science and Technology
Current assignee: University of Shanghai for Science and Technology
Priority date: 2008-10-30
Filing date: 2008-10-30
Publication date: 2010-08-11
Anticipated expiration: 2028-10-30
Also published as: CN101388342A

Abstract

The invention relates to a process for preparing an inorganic film triode TFT by the all solution processing method, which adopts the all solution processing method to prepare the insulating layer TiO2 and the active layer ZnO of the triode, and specifically comprises the following steps: firstly preparing TiO2 and ZnO into solution with 0.05ml-0.1ml concentration through adopting the hydrothermal method and the sol-gel process, and coating the ZnO and TiO2 obtained in the first step on a substrate electrode through the spin-coating method, Czochralski method or the titration covering method to form a ZnO and TiO2 film which can form the micro-crystallization through the high-temperature annealing or the laser annealing technology. The invention can prepare the TiO2 film and the ZnO film with temperature lower than 500 DEG C, has relatively simple technology, is beneficial for reducing device cost and accelerating preparation speed, and is beneficial for the industrialization, can prepare on cheap materials such as glass and the like, and is compatible with elastic and plastic materials technology. TFT components with high dielectric constant insulating layer and super-high chargemobility active layer can be obtained, which have milliamp level heavy current density and current switch ratio as high as hundreds of thousand, and can drive low-voltage OLED.

Description

The method of preparing inorganic thin-film transistor by complete solution treatment process

Technical field

The present invention relates to the preparation method of a kind of inorganic thin-film transistors TFT, particularly a kind of complete solution treatment process prepares the method for inorganic thin-film transistors TFT.

Background technology

Thin-film transistor has obtained promotion and application very widely from the invention beginning sixties in last century, development speed beyond imagination soon.From the non-crystalline silicon tft to the multi-crystal TFT, to low temperature polycrystalline silicon TFT, technology is more and more ripe from high temperature polysilicon TFT, the object of application also from just drive LCD develop into both can drive LCD also can driving OLED even Electronic Paper.

TFT can be divided into amorphous silicon membrane, polysilicon membrane (poly-Si) and organic film TFT.Usually adopt TiO ₂Do insulating barrier wherein.Along with increasing transistor is installed by chip manufacturer on small silicon chip, semiconductor is made in the process of scaled down, and except dwindling of characteristic size channel length, gate oxide thickness also need be similar to pro rata attenuate to avoid short-channel effect.The equivalent gate oxide thickness EOT of 45nm technology node is 0.18nm; The EOT of 32nm technology node will further be reduced to 0.16nm, and this is equivalent to two SiO ₂The molecule bed thickness.Common used SiO ₂, on principle, can be thinned to two molecule bed thickness.But in fact, use this ultra-thin Si O ₂Make SiO ₂/ Si no longer is a best of breed, can cause the big and interface conditions variation of direct Tunneling electric current.Because SiO ₂Thin down, increase gradually, thereby cause electric current waste and the extra unnecessary heat that produces by the gate-dielectric leaky.And TiO ₂Have good insulation performance and very high dielectric constant, make with SiO ₂Under the identical condition of equivalence gate oxide thickness EOT, TiO ₂Thickness compare SiO ₂Thickness big, significantly reduce possible tunnel current like this.Use ZnO to do active layer, be based on its advantageous property.It is a kind of direct broad-band gap (band gap is 3.37eV under the normal temperature) transparent oxide semiconductor that belongs to, and has hexagonal wurtzite structure, C axle preferred orientation, has good piezoelectricity, photoelectricity, air-sensitive, character such as pressure-sensitive.ZnO.TFT can obtain higher electron mobility, can realize bigger drive current, response device speed faster, in limit of visible spectrum higher light transmission rate is arranged all, very little photosensitive degenerative.

Usually the processing method of insulating barrier and active layer can be divided into two kinds: (1) high-temperature technology refers to that temperature is higher than 900 ℃ in the whole course of processing.High-temperature technology can only be a substrate with the quartz of costliness, and the TFT performance is good, and high-temperature technology only is applicable to the display screen or the projection screen series of small-medium size.(2) low temperature process, temperature is lower than 600 ℃ in the whole course of processing.Adopt low temperature process can on the inexpensive glass substrate, make bigger display screen.Low temperature polycrystalline silicon (LTPS) TFT owing to its low-power consumption, light, slim, provide the big electric current and the system integration to be widely used in active (initiatively) drive to show among TFT-LCD and the AMOLED.

Summary of the invention

The object of the present invention is to provide a kind of complete solution treatment process to prepare the method for inorganic thin-film transistors TFT.

For achieving the above object, the present invention adopts following technical scheme:

A kind of complete solution treatment process prepares the method for inorganic thin-film transistors TFT, it is characterized in that this transistorized insulating barrier TiO ₂Adopt complete solution treatment process to prepare with active layer ZnO, concrete steps are as follows:

A) adopt hydrothermal method or sol-gal process respectively with TiO ₂Prepare certain density solution with ZnO;

B) with the ZnO and the TiO that obtain among the step a ₂Be coated on the underlayer electrode by spin-coating method, czochralski method or titration cladding process, form ZnO and TiO ₂Film.

Above-mentioned employing spin-coating method prepares TiO ₂During film, rotating speed is 2500-3500rpm, and the spin coating time is 90 seconds, thereby the film thickness that obtains is 100-120nm; When adopting spin-coating method to prepare ZnO film, rotating speed is 2000-2500rpm, and the spin coating time is 60 seconds, and the film thickness that obtains is 100-150nm.

During above-mentioned preparation ZnO film, adopt high annealing (400-600 ℃) or laser to carry out annealing in process, concrete technology is: Wavelength of Laser is 355nm or 532nm, uses the circular laser facula of the uniform diameter 0.25cm of Energy distribution, with 0.1-5J/cm ²Energy density, power is 75kW, the pulse irradiation depth reaches the ZnO film of 100-150nm, at N ₂In inert gas environment, and the temperature of adjustment substrate is at 25-250 ℃; Annealing time is 0.5-10 second.

The present invention can prepare TiO under less than 500 ℃ low temperature ₂Film and ZnO film, technology are simple relatively, help to reduce preparation cost, accelerate preparation speed, very help carrying out industrialization; And can on cheap materials such as glass, prepare, with elasticity, plastic material process compatible.Finally obtain the TFT device of the active layer of the insulating barrier of high-k and high charge mobility, it has a milliampere level high current density, and up to tens thousand of current on/off ratios, can drive low pressure OLED.

Description of drawings

Fig. 1 is TiO ₂Make the TFT of the bottom grating structure of insulating barrier

Fig. 2 is TiO ₂Make the TFT of the bottom grating structure of insulating barrier together with SiN

Fig. 3 is TiO ₂Make the TFT of the top gate structure of insulating barrier

Embodiment

Adopt hydrothermal method or Prepared by Sol Gel Method TiO ₂And ZnO film, and ZnO film is carried out laser annealing handle, last evaporation metal negative electrode, conducting channel forms in due course according to transistorized structure.

Embodiment one: with the preparation of ITO as the thin-film transistor of the bottom grating structure of grid (gate), referring to Fig. 1:

1.TiO ₂The preparation of solution: 1. measure 400ul hydrochloric acid and incorporate 200ml ethanol with liquid-transfering gun; 2. add the 55ml butyl titanate, and add the dissolving of 200ml ethanol; 3. continue to add 5ml acetylacetone,2,4-pentanedione and 11ml deionized water.Above-mentioned solution all is that the limit edged evenly stirs, and solvent adds fully, stirs promptly and finishes.Obtain concentration and be 0.33 TiO ₂Solution.

2.ZnO the preparation of solution: the Zn (CH that 1. takes by weighing 0.628g ₃COO) ₂.2H ₂O is dissolved in the ethanol of 250ml, with the extremely boiling of electrothermal furnace reflux.Treat the solution immigration conical flask that do not seethe with excitement after 30 minutes; 2. add a certain amount of LiOH.H ₂The O solid, vibration is 20 minutes in ultra sonic bath, makes colloid.Obtaining concentration is the ZnO solution of 0.05ml.

With ITO as grid (gate), adopt spin-coating method to make TiO thereon ₂As insulating barrier, ZnO prepares TiO as active layer ₂During film, rotating speed is 2500rpm, and the spin coating time is 90 seconds, thereby the film thickness that obtains is 110nm; When adopting spin-coating method to prepare ZnO film, rotating speed is 2500rpm, and the spin coating time is 60 seconds, and the film thickness that obtains is 150nm.

4. the metal (as Al, Mg/Ag etc.) that uses VPE method evaporation thickness 150nm then is as source electrode (source) and drain electrode (drain).Can obtain inorganic thin-film transistors.Can cover barred mask plate to form conducting channel in VPE method evaporation metal on device, channel width is from 5um～50um.

Embodiment two: with the preparation of ITO as the thin-film transistor of the bottom grating structure of grid (gate), referring to Fig. 2, concrete steps are:

1.TiO ₂The preparation of solution: 1. measure 400ul hydrochloric acid and incorporate 200ml ethanol with liquid-transfering gun; 2. add the 27.5ml butyl titanate, and add the dissolving of 200ml ethanol; 3. continue to add 5ml acetylacetone,2,4-pentanedione and 11ml deionized water.Above-mentioned solution all is that the limit edged evenly stirs, and solvent adds fully, stirs promptly and finishes.Obtain the TiO that concentration is 0.165mol/L ₂Solution.

2.ZnO the preparation of solution: the Zn (CH that 1. takes by weighing 0.319g ₃COO) ₂.2H ₂O is dissolved in the ethanol of 250ml, with the extremely boiling of electrothermal furnace reflux.After 30 minutes solution is cooled to room temperature and moves into conical flask; 2. simultaneously with a certain amount of LiOH.H ₂O adds in another conical flask, pours the ethanol of 100ml again into, and concussion is 30 minutes in ultra sonic bath; 3. with the LiOH.H that dissolves ₂O solution slowly adds chilled Zn (CH ₃COO) ₂.2H ₂In the O solution, vibration is 20 minutes in the ultra sonic bath, makes colloid.Obtaining concentration is the ZnO solution of 0.025mol/L.

3. leak (source-drain) with ITO as the source, adopt czochralski method to make the ZnO active layer earlier, concrete technology is: czochralski method is earlier oven temperature to be decided to be 80 ℃, the substrate taking-up that is immersed in after handling well in the ethanol is clipped with Small clamp, hang on the iron wire frame, putting into 80 ℃ of baking ovens warms substrate, taking-up is immersed it in ready colloid, take out rapidly, sop up the liquid of substrate lower limb with filter paper, put into baking oven and take out after dry 2 minutes, make 1 layer film, said process repeatedly just can make plural layers again.Re-use same method and make TiO ₂Insulating barrier.At TiO ₂Re-use PECVD deposition layer of sin layer on the insulating barrier, its thickness is 150nm.The metal electrode of last vacuum thermal evaporation thickness 150nm is as grid.Can cover barred mask plate to form conducting channel in VPE method evaporation metal on device, channel width is from 5um～50um.

Embodiment three: the preparation of top-grate structure thin film transistor, and referring to Fig. 3, concrete steps are:

1.TiO ₂The preparation of solution: 1. measure 400ul hydrochloric acid and incorporate 200ml ethanol with liquid-transfering gun; 2. add the 18.3ml butyl titanate, and add the dissolving of 200ml ethanol; 3. continue to add 5ml acetylacetone,2,4-pentanedione and 11ml deionized water.Above-mentioned solution all is that the limit edged evenly stirs, and solvent adds fully, stirs promptly and finishes.Obtain the TiO that concentration is 0.11mol/L ₂Solution.

2.ZnO the preparation of solution: the Zn (CH that 1. takes by weighing 0.511g ₃COO) ₂.2H ₂O is dissolved in the isopropyl alcohol of capacity.2. add and the equimolar monoethanolamine of zinc acetate, under the effect of catalyst glacial acetic acid, in 60 ℃ of water-baths, fully stir, make colloid.Obtaining concentration is the ZnO solution of 0.04mol/L.

3. do source electrode and drain electrode with ITO, metal is made grid.Its raceway groove can be formed by photoetching on the ITO substrate.Utilize on ITO superfine narrow slit arranged that (LiF of the mask plate evaporation 500nm of 5um～50um) uses lighttight metal A g (300nm) evaporation with hot water LiF to be washed off ultrasonic Treatment 30 minutes on substrate.Spin coating photoresist on metal A g mask at last uses 30 seconds of ultraviolet exposure, washes half an hour with strong acid is ultrasonic at last, forms the raceway groove that very thin space is arranged like this on ITO.On the ITO after the photoetching, adopt spin-coating method to make TiO ₂As insulating barrier, ZnO is as active layer.Preparation TiO ₂During film, initial speed is 600rpm, and the duration is 6 seconds, and final rotating speed is 3500rpm, and the spin coating time is 60 seconds, thereby is 220nm by the two-layer film thickness that obtains of this step spin coating; During the preparation ZnO film, initial speed is 500rpm, and the duration is 10 seconds, and final rotating speed is 2500rpm, and the spin coating time is 60 seconds, and the film thickness that obtains is 150nm.The metal electrode of last vacuum thermal evaporation 200nm has so just formed top-grate structure thin film transistor as negative electrode.

4.ZnO the laser annealing technique of active layer: adopt the laser radiation ZnO conducting channel of wavelength 532nm or 355nm, with the circular laser facula of the uniform diameter 0.25cm of Energy distribution, with 0.5-1.0J/cm ²Single pulse energy metric density, the repetition rate of 100Hz, near raceway groove, move horizontally in the 0.5mm scope, adjust annealing time at 0.5-10 between second.Whole laser annealing is at N ₂Deng what implement in the inert gas environment, and can in 25-250 ℃ of temperature range, adjust the temperature of substrate.

Claims

1. a complete solution treatment process prepares the method for inorganic thin-film transistors TFT, it is characterized in that this transistorized insulating barrier TiO ₂Adopt complete solution treatment process to prepare with active layer ZnO, concrete steps are as follows:

A. adopt hydrothermal method or sol-gal process respectively with TiO ₂Be prepared into solution with ZnO;

B. with the ZnO and the TiO that obtain among the step a ₂Be coated on the underlayer electrode by spin-coating method, czochralski method or titration cladding process, form ZnO and TiO ₂Film;

Adopt spin-coating method to prepare TiO ₂During film, rotating speed is 2500-3000rpm, and the spin coating time is 90 seconds, thereby the film thickness that obtains is 100-120nm; When adopting spin-coating method to prepare ZnO film, rotating speed is 2000-2500rpm, and the spin coating time is 60 seconds, and the film thickness that obtains is 100-150nm.

2. complete solution treatment process according to claim 1 prepares the method for inorganic thin-film transistors TFT, it is characterized in that adopting 400 ℃～600 ℃ high temperature or laser to carry out annealing in process to ZnO active layer film; The concrete technology of laser annealing is: Wavelength of Laser is 355nm or 532nm, uses the circular laser facula of the uniform diameter 0.25cm of Energy distribution, with 0.5～1.0J/cm ²The single pulse energy metric density, at N ₂In the atmosphere Deng inert gas environment, near the ZnO film the pulsed irradiation raceway groove in the 0.5mm scope, and the temperature of adjustment substrate is at 25-250 ℃; Annealing time is 0.5-10 second.