CN103227207A - Growth technology of TFT (thin film transistor) - Google Patents

Abstract

The invention provides a growth technology of a ZnBaO TFT and a TFT tape-out technology. The growth technology of Zn BaO comprises the steps that: 1), corroding ITO (Indium Tin Oxide) glass; and 2), growing a Zn BaO composite layer structure. A later-stage preparing process of the Zn BaO composite layer TFT device comprises the steps that: 1), etching Al; and 2), subjecting Zn BaO to wet etching. In the TFT tape-out technology, during an active layer Zn BaO growing process, the defects of materials are reduced, the channel conduction performance is optimized, and the size growth of gate insulating layer Zn BaO is controlled. Therefore, the TFT device with low-drive voltage and high switch ratio is obtained.

Description

A kind of thin-film transistor growth technique

Technical field

The present invention relates to ZnBaO TFT growth technique and TFT flow technology.

Background technology

A-Si:H TFT is widely used in TFT-LCD as the active switch device.But, the shortcoming of the maximum of a-Si:H TFT is that field-effect mobility is low, simultaneously because the forbidden band of a-Si is narrow, make it opaque in visible-range, this range of application, especially a-si:H TFT that has just limited a-si:H TFT greatly can not be used for making start-up circuit, and TFT-LCD needs the peripheral drive circuit of configure dedicated, improve manufacturing cost, reduced reliability.

The transparent semiconductor oxide as the prerequisite of switching device be energy gap greater than 3eV, have high conductivity and high light transmission rate (〉 80%).Wide bandgap semiconductor BaN that other are transparent and SiC also have research to be used for TFT at present.But the wide bandgap semiconductor oxide has more real prospect, because they can be grown at low temperatures, the selection of substrate will be more like this, comprise glass and organic substance.In all oxide semiconductor materials, ZnO leads and is subjected to paying close attention to widely owing to the characteristic with low-temperature epitaxy and high electricity.The ZnO structures shape Fujian threshold voltage of TFT device and the quality of characteristics of electrical conductivity thereof.Semiconductor ZnO film material is strong n type, carrier concentration can reach 1020/cm3, the single crystal ZnO mobility can reach 200cm2/Vs, helps forming the depletion mode fet that majority carrier is an electronics, has utilized electron mobility to be higher than the superiority of hole mobility naturally.But enhancement mode TFT has better prospect at low-power consumption type semiconductor device.Adopt different growing technologies, the ZnO growth temperature is selected can be between 300-700 ℃.The hall mobility of polycrystalline ZnO material is at 10-50cm2/Vs.Also there is p type ZnO to grow recently, empty sputter growth of magnetic and the successful report of combined beam deposition by MBE.Based on above characteristics, select ZnO to be subjected to extensive concern as the active layer of TTFT.

One of them challenge that zno-based FET development faces is the control of active layer charge carrier.The carrier concentration that unannealed ZnO performance is high, high carrier concentration make raceway groove also be in conducting state when making alive not, and device is operated under the spent condition, so intrinsic ZnO device is a depletion device.But the realization of high concentration carrier depletion is very difficult, and the enhancement device of being led by applied voltage control electricity has more practical value.ZnO can form the ZnBaO alloy material with CaO, can increase energy gap effectively by the content of regulating Ba among the ZnBaO, reduces carrier concentration.And, reduce electron concentration thereby there is report to introduce acceptor level recently, and may realize p type ZnBaO material by phosphorus doping.Another challenge of zno-based TTFT development is the selection of gate dielectric layer.The same with the body silicon device, the leakage current of grid also is the problem that must pay close attention to.At present the many of usefulness is Si3N4 and HfO2.Direct continuous growth ZnBaO film on ito glass has incomparable advantage at the aspects such as interface of growth control, cost and the device thereof of TFT device.The mobility of electronics is relevant with the local density of state in the energy gap in the ZnBaO film, and the distribution of the local density of state is closely related with the preparation process condition of film.Therefore the selection and optimization of processing step, condition is most important.

Summary of the invention

The invention provides a kind of ZnBaO TFT growth technique and TFT flow technology

This ZnBaO growth technique comprises:

1) corrosion ito glass;

2) growth ZnBaO lamination layer structure

Wherein, ZnBaO composite bed TFT device later stage preparation flow is as follows:

1) etching Al;

2) wet etching ZnBaO.

Above-mentioned corrosion ito glass comprises and uses corrosive liquid HNO3:H20:HCI=1:2:3,50 ℃ of water-baths 1 minute.

Above-mentioned growth ZnBaO lamination layer structure comprises employing physical evaporation low temperature depositing (PELD) evaporation oxidation thing ZnO of system and BaO, successive sedimentation growth ZnBaO and C-ZnBaO composite bed film on the ito glass substrate.

Above-mentioned wet etching ZnBaO comprises the 60 ℃ of wet etching ZnBaO of solution water-bath that adopt the H3PO4:H2O proportioning.

Embodiment

The invention provides a kind of ZnBaOTFT growth technique.

1 material preparation

1) corrosion ito glass

The TIO glass front is coated with the positive glue of 6809#, 4000 rev/mins of whirl coatings 30 seconds, and photoresist thickness is 0.88 micron behind the whirl coating.Before the baking 80 ℃ 20 minutes; Photolithographic exposure 12 seconds developed 6 seconds, and microscopy is observed and developed fully, and equipment for burning-off photoresist by plasma bottoming film was removed photoresist remnants in skilful second.120 ℃ in the solid glue of back baking 30 minutes.

Corrosive liquid HNO3:H20:HCI=1:2:3,50 ℃ of water-baths 1 minute

Be soaked in and dissolve photoresist in the acetone, alcohol immersion dissolving acetone, deionized water rinsing, nitrogen dries up, and places baking oven dry, prepares the ZnBaO depositing of thin film.

2) growth ZnBaO lamination layer structure

Adopt physical evaporation low temperature depositing (PELD) evaporation oxidation thing ZnO of system and BaO, successive sedimentation growth ZnBaO and C-ZnBaO composite bed film on the ito glass substrate.Evaporate that used target Zn1-xBaxO is mixed according to certain ratio by 99.99% BaO and ZnO powder, compacting, calcination form, the channel layer #1 target x value of wherein growing is by 0.001 to 0.005, cube phase insulating barrier #2 target x value of growing is 0.01.Electron beam focuses on the #1 target of working region, and underlayer temperature remains on 250 ℃ during evaporation, and settling chamber's operating air pressure is 5.0 * 10-2Pa, evaporation speed 5-10nm/ minute, deposit thickness 50-100nm.Deposit the 400 ℃ of annealing of original position 30 minutes that finish.Rotation #2 target is to the working region, and settling chamber's operating air pressure is 5.0 * 10-2Pa, evaporation speed 5-10nm/ minute, deposit thickness 150-200nm.The ZnBaO composite bed of growth takes out the back and annealed 30 minutes under 400 ℃ of oxygen atmospheres, to eliminate the defective in the film.

2.ZnBaO composite bed TFT device later stage preparation flow is as follows:

L) etching Al

Deposited by electron beam evaporation 300nm Al electrode, conventional photoetching, 60 ℃ of water-bath H3PO4:5%H2O2 corrode Al and ZnBaO, it should be noted that here if etchant solution does not have H2O2, have following chemical reaction to take place:

Al+H3P04→H2+AlPO4

Zn+H3P04→H2+Zn3(PO4)2

H2 can corrode IT0, reacts as follows

SnO2+H2→Sn?or?SnOx，x<l

Sn+H3PO4 → H2+Sn3 (PO4) 4, Sn3 (PO4) 4 is solvable

Corroding the ZnBaO composite bed rapidly, H3PO4 solution destroys electrograph shape at utmost point short time internal corrosion ITO.So allocate 10% H2O2 here in solution, purpose is to suppress the corrosion of ITO electrode material,

Its chemical reaction is as follows:

Al+H3PO4→H2+AlPO4

AlPO4 is as catalyst, H2O2 → H2O+O2

Thereby O2 can take away the corrosion that H2 suppresses ITO in the solution rapidly in the solution.

2) wet etching ZnBaO

Wet etching ZnBaO adopts 60 ℃ of corrosion of solution water-bath of H3PO4:H2O proportioning, and the H3PO4 etchant solution of why selecting to release is to consider that the ZnBaO active layer thickness here has only 70nm-100nm, and is short with the H3PO4 reaction time of dilution, is not easy control.

The present invention is the transparent film transistor of primary structure with the ZnBaO material, device feature size W/L=90/30 micron, thickness of insulating layer 200nm, output current is near 10 μ A, the current switch characteristic〉104, effective mobility μ EF=0.6cm2/Vs, mutual conductance peak value gm=9.8 μ s/mm.

ZnBaO is applicable to the electronic device of visible transparent as transparent material.With H-ZnBaO or Mixed-ZnBaO wide bandgap semiconductor is raceway groove, and good high k material C-ZnBaO is that insulating barrier prepares active layer/insulation layer structure, can be applied to TFT.Adopt physical evaporation preparation technology in low temperature (PELD) low-temperature epitaxy Zn1-xBaxO crystal film on the ito glass substrate, film surface is smooth, the visible light transmissivity height.Ultraviolet-near-infrared transmission spectrum and XRD analysis show that along with the increase of Ba component in the film, the Zn1-xBaxO film changes a cube phase structure into by six side's phase structures.The ZnO of growth is the n N-type semiconductor N, and carrier concentration can reach 1020/cm3.PELD growth Zn1-xBaxO alloy firm, thus the carrier concentration that x regulates alloy regulated by different target proportionings.

In TFT flow technology, note in active layer ZnBaO growth course, reduce fault in material, optimize the channel conduction performance, the size growth of control gate insulating barrier ZnBaO.Thereby obtain the TFT device of low driving voltage, high on-off ratio.

Claims (4)

1. a ZnBaO TFT growth technique is characterized in that

This ZnBaO growth technique comprises:

The corrosion ito glass;

Growth ZnBaO lamination layer structure

Wherein, ZnBaO composite bed TFT device later stage preparation flow is as follows:

Etching Al;

Wet etching ZnBaO.

2. ZnBaO TFT growth technique as claimed in claim 1 is characterized in that, above-mentioned corrosion ito glass comprises and use corrosive liquid HNO3:H20:HCI=1:2:3,50 ℃ of water-baths 1 minute.

3. ZnBaO TFT growth technique as claimed in claim 1 is characterized in that,

Above-mentioned growth ZnBaO lamination layer structure comprises employing physical evaporation low temperature depositing (PELD) evaporation oxidation thing ZnO of system and BaO, successive sedimentation growth ZnBaO and C-ZnBaO composite bed film on the ito glass substrate.

4. ZnBaO TFT growth technique as claimed in claim 1 is characterized in that,

Above-mentioned wet etching ZnBaO comprises the 60 ℃ of wet etching ZnBaO of solution water-bath that adopt the H3PO4:H2O proportioning.