CN103021872A - Thin film transistor growth process - Google Patents

Abstract

The invention provides an IGSZO TFT (thin film transistor) growth process and a TFT tape-out process. The IGSZO growth process includes the steps: 1) corroding ITO (indium tin oxide) glass; and 2) growing an IGSZO composite layer structure. An IGSZO composite layer TFT device post-preparation process includes the steps: 1) etching Al; and 2) wet etching IGSZO. In the TFT tape-out process, during growth of the IGSZO on an active layer, material defects are decreased, electric conductivity of a channel is optimized, size growth of the IGSZO on a gate insulating layer is controlled, and accordingly, a TFT device with low driving voltage and high switch ratio is obtained.

Description

A kind of thin-film transistor growth technique

Technical field

The present invention relates to IGSZO TFT growth technique and TFT flow technique.

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, so that it is opaque in visible-range, this range of application, especially a-si:H TFT that has just limited greatly a-si:H TFT 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%).The wide bandgap semiconductor SrN 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 widely and is paid close attention to 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-shaped, and carrier concentration can reach 10 ²⁰/ cm ³, the single crystal ZnO mobility can reach 200cm ²/ Vs is conducive to form the depletion mode fet that majority carrier is electronics, has naturally utilized electron mobility to be higher than the superiority of hole mobility.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 recently p-type ZnO to grow by MBE, magnetron sputtering growth and the successful report of combined beam deposition.Based on above characteristics, select ZnO to be subject 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 is so that raceway groove also is in conducting state when making alive not, and device is operated under the spent condition, so intrinsic ZnO device is 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 with Ga ₂O ₃, In ₂O ₃And SrO formation IGSZO alloy material, can effectively increase energy gap by the content of regulating Sr among the IGSZO, reduce carrier concentration.Another challenge of zno-based TFT development is the selection of gate dielectric layer.The same with the body silicon device, the leakage current of grid also is must problems of concern.At present the many of usefulness is Si ₃N ₄And HfO ₂Direct continuous growth IGSZO film on ito glass has unrivaled 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 IGSZO film, and the distribution of the local density of state is closely related with the thin film technology process conditions.Therefore the selection and optimization of processing step, condition is most important.

Summary of the invention

The invention provides a kind of IGSZO TFT growth technique and TFT flow technique

This IGSZO growth technique comprises:

1) corrosion ito glass;

2) growth IGSZO lamination layer structure

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

1) etching Al;

2) wet etching IGSZO.

Above-mentioned corrosion ito glass comprises use corrosive liquid HNO ₃: H ₂O:HCI=1:2:3,50 ℃ of water-baths 1 minute.

Above-mentioned growth IGSZO lamination layer structure comprises employing physical evaporation low temperature depositing (PELD) the evaporation oxidation thing ZnO of system and Ga ₂O ₃, In ₂O ₃And SrO, successive sedimentation growth IGSZO and C-IGSZO composite bed film on the ito glass substrate.

Above-mentioned wet etching IGSZO comprises employing H ₃PO ₄: H ₂60 ℃ of wet etching IGSZO of the solution water-bath of O proportioning.

Embodiment

The invention provides a kind of IGSZOTFT growth technique.

The preparation of 1 material

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.80 ℃ of front bakings 20 minutes; Photolithographic exposure 12 seconds developed 6 seconds, and microscopy is observed and developed fully, and it is remaining that equipment for burning-off photoresist by plasma bottoming film was removed photoresist in skilful second.120 ℃ in the solid glue of rear baking 30 minutes.

Corrosive liquid HNO ₃: H ₂O: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 deposition of IGSZO film.

2) growth IGSZO lamination layer structure

Adopt physical evaporation low temperature depositing (PELD) the evaporation oxidation thing ZnO of system, Ga ₂O ₃, In ₂O ₃And SrO, successive sedimentation growth IGSZO and C-IGSZO composite bed film on the ito glass substrate.Evaporate used target InGaZn _1-xSr _xO is by 99.99% ZnO, Ga ₂O ₃, In ₂O ₃And the SrO powder is mixed according to certain ratio, compacting, calcination form, and the channel layer #1 target x value of wherein growing is by 0.001 to 0.005, and growth of cubic phase insulating barrier #2 target x value is 0.01.Electron Beam Focusing is in the #1 of working region target, 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 400 ℃ of annealing of complete original position 30 minutes.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.After taking out, the IGSZO composite bed of growth under 400 ℃ of oxygen atmospheres, annealed 30 minutes, to eliminate the defective in the film.

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

1) etching Al

Deposited by electron beam evaporation 300nm Al electrode, conventional photoetching, 60 ℃ of water-bath H ₃PO ₄: 5%H ₂O ₂Corrosion Al and IGSZO it should be noted that here if etchant solution does not have H ₂O ₂, have following chemical reaction to occur:

Al+H ₃P0 ₄→H ₂+AlPO ₄

Zn+H ₃P0 ₄→H ₂+Zn ₃(PO ₄) ₂

H ₂Can corrode IT0, react as follows

SnO ₂+H ₂→Sn?or?SnO _x，x<1

Sn+H ₃PO ₄→ H ₂+ Sn ₃(PO ₄) ₄, Sn ₃(PO ₄) ₄Solvable

Corroding rapidly IGSZO composite bed, H ₃PO ₄Solution destroys electrograph shape at utmost point short time internal corrosion ITO.So in solution, allocate 10% H here into ₂O ₂, purpose is to suppress the corrosion of ITO electrode material,

Its chemical reaction is as follows:

Al+H ₃PO ₄→H ₂+AlPO ₄

AlPO ₄As catalyst, H ₂O ₂→ H ₂O+O ₂

O in the solution ₂Can take away rapidly H ₂Thereby the corrosion of ITO in the inhibition solution.

2) wet etching IGSZO

Wet etching IGSZO adopts H ₃PO ₄: H ₂Why 60 ℃ of corrosion of the solution water-bath of O proportioning select the H that releases ₃PO ₄Etchant solution is to consider that the IGSZO active layer thickness here only has 70nm-100nm, with the H of dilution ₃PO ₄Reaction time is short, is not easy control.

The transparent film transistor of the present invention take the IGSZO material as primary structure, device feature size W/L=90/30 micron, thickness of insulating layer 200nm, output current is near 10 μ A, current switch characteristic〉10 ⁴, effective mobility μ _EF=0.6cm ²/ Vs, mutual conductance peak value g _m=9.8 μ s/mm.

IGSZO is applicable to the electronic device of visible transparent as transparent material.Take H-IGSZO or Mixed-IGSZO wide bandgap semiconductor as raceway groove, good high κ material C-IGSZO 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 InGaZn on the ito glass substrate _1-xSr _xThe O crystal film, film surface is smooth, and visible light transmissivity is high.Ultraviolet-near-infrared transmission spectrum and XRD analysis show, along with the increase of Sr component in the film, InGaZn _1-xSr _xThe O film changes the Emission in Cubic structure into by six side's phase structures.The PELD InGaZn that grows _1-xSr _xThe O alloy firm, thus the carrier concentration that x regulates alloy regulated by different target proportionings.

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

Claims (4)

1. an IGSZO TFT growth technique is characterized in that

This IGSZO growth technique comprises:

The corrosion ito glass;

Growth IGSZO lamination layer structure

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

Etching Al;

Wet etching IGSZO.

2. IGSZO TFT growth technique as claimed in claim 1 is characterized in that, above-mentioned corrosion ito glass comprises and use corrosive liquid HNO3:H2O:HCI=1:2:3,50 ℃ of water-baths 1 minute.

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

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

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

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