CN103151378B - Utilize the thin film transistor (TFT) of thin film semiconductor material - Google Patents

Abstract

The present invention generally comprises the thin film transistor (TFT) (TFT) with semi-conducting material, described semi-conducting material comprise oxygen, nitrogen and one or more selected from the element in the group that is made up of zinc, stannum, gallium, cadmium and indium using as active channel.This semi-conducting material can be used in bottom gate TFT, top-gated TFT and other kinds of TFT.Pattern TFT by etching and can form raceway groove and metal electrode.Then, this semi-conducting material is used to limit source/drain as etch stop layer to perform dry etching.The carrier concentration of active layer, mobility and the interface with other layers of TFT are adjustable into predetermined value.Adjustment mode by changing the semiconductor film that nitrogenous gas is deposited with the flow proportional of oxygen-containing gas, annealing and/or Cement Composite Treated by Plasma, or can change aluminum doping content.

Description

Utilize the thin film transistor (TFT) of thin film semiconductor material

The application is filing date on August 1st, 2008, Application No. 200880106291.5, entrance state Family's day in stage is on March 9th, 2010, entitled " utilizing the thin film transistor (TFT) of thin film semiconductor material " The divisional application of application for a patent for invention.

Technical field

Embodiments of the invention relate generally to field-effect transistor (FET) and the thin film crystalline substance with semi-conducting material Body pipe (TFT), this semi-conducting material comprise oxygen, nitrogen and one or more selected from by zinc, gallium, cadmium, indium and Element in the group that stannum is constituted.

Background technology

It is usually used in the liquid-crystal active matrix display of computer and TV flat panel because tft array can be used on (LCD), therefore trend is interested in these devices at present.LCD is additionally provided with light emitting diode (LED) As backlight.It addition, Organic Light Emitting Diode (OLED) has been used for Active Matrix Display, and these OLED needs TFT to carry out the action of processing display.

The TFT made with non-crystalline silicon has become the critical component of flat display industry.Unfortunately non-crystalline silicon is originally Body has limitation, and such as mobility is low.Mobility required for OLED is at least more than ten times of non-crystalline silicon. The depositing temperature of non-crystalline silicon is high and causes Vth to drift about.Non-crystalline silicon needs high electric current, and high electric current may cause OLED is unstable.On the other hand, the mobility ratio non-crystalline silicon of polysilicon wants height.Polysilicon is crystallization, This can cause nonuniform deposition.Due to the multinomial restriction of non-crystalline silicon, the development causing OLED is difficult.

In recent years, having developed transparent TFT, in described transparent TFT, zinc oxide is used as active channel layer. Zinc oxide is a kind of compound semiconductor (compound semiconductor), and described compound semiconductor can be in On various substrate such as such as glass and plastics etc., crystalline material is generated under at a fairly low depositing temperature.Based on oxidation Can't degrade when the TFT of zinc is exposed to visible ray (degrade).Therefore, need unlike TFT based on silicon Want overcoat.Not having overcoat, TFT keeps transparent.Although the mobility of zinc oxide is higher than non-crystalline silicon, but The most not high enough.

Therefore, in this technical field, need to have transparent active channel and the high TFT of mobility.

Summary of the invention

The present invention generally comprises the thin film transistor (TFT) (TFT) with semi-conducting material, this semi-conducting material bag Oxygen-containing, nitrogen and one or more is selected from being made up of the element in group zinc, stannum, gallium, cadmium and indium, to make For active channel.This semi-conducting material can be used for bottom gate TFT, top-gated TFT and other kinds of TFT. TFT is patterned to form raceway groove and metal electrode by etching.Then, use semi-conducting material as Etch stop layer performs dry etching, to limit source/drain.The carrier concentration of active layer, move Shifting rate and the interface with other layers of TFT are adjustable into predetermined value.Adjustment mode can be to change nitrogenous gas The semiconductor film deposited with flow proportional, annealing and/or the Cement Composite Treated by Plasma of oxygen-containing gas, or change Aluminum doping content.

In one embodiment, open a kind of TFT.Transistor comprises semiconductor layer, and this semiconductor layer comprises Oxygen, nitrogen and one or more is selected from the group that is made up of the combination of zinc, indium, stannum, cadmium, gallium and above-mentioned element Element in group.In another embodiment, open a kind of TFT manufacture method.The method comprises deposition half Conductor layer on substrate, this semiconductor layer comprise oxygen, nitrogen and one or more selected from by zinc, indium, stannum, cadmium, Element in the group that the combination of gallium and above-mentioned element is constituted.

In another embodiment, open a kind of TFT manufacture method.The method comprises deposited semiconductor layer On substrate, this semiconductor layer comprises oxygen, nitrogen and one or more is selected from being filled up by s track and d track Element in element that element, f orbitals fill up and the group that the combination of above-mentioned element is constituted.The method is also Including deposition source-drain layer on this semiconductor layer, etch this source-drain layer and this quasiconductor for the first time Layer is to form active channel, and second time etches this source-drain layer to limit source electrode and drain electrode.

Accompanying drawing explanation

In order to understand the features described above of the present invention in more detail, the embodiment referring to partly be illustrated in accompanying drawing is come That reads the present invention is further discussed below content.It is noted that described figure only illustrates several representatives of the present invention Property embodiment, is not limited to the scope of the invention, and the present invention can comprise other Equivalent embodiments.

Fig. 1 is the sectional view of the PVD chamber according to one embodiment of the present of invention.

Fig. 2 A-2E is the XRD figure that thin film changes with oxygen flow, described XRD figure display formed zinc and The diffraction maximum of zinc oxide.

Fig. 3 A-3F is according to one embodiment of the present of invention, forms semiconductor film under different nitrogen flow rates XRD figure.

Fig. 4 A-4G illustrates the process sequence forming bottom gate TFT according to one embodiment of present invention.

Fig. 5 is the sectional view of the etch-stop TFT according to one embodiment of the present of invention.

Fig. 6 is the sectional view of top-gated TFT according to one embodiment of the present of invention.

Fig. 7 is the schematic diagram of the active array type LCD according to one embodiment of the present of invention.

Fig. 8 is the schematic diagram of the active array type OLED according to one embodiment of the present of invention.

The different active channel length of Fig. 9 A-9C display and the Vth of width.

Figure 10 A-10C is to compare the Vth having combined length with the active channel of width.

For helping understand, represent similar elements total in each figure with similar elements symbol as much as possible.Certain Element disclosed in one embodiment is when can be used in other embodiments, without specifically mentioned.

Detailed description of the invention

The present invention generally comprises the thin film transistor (TFT) (TFT) with semi-conducting material, this semi-conducting material bag Oxygen-containing, nitrogen and one or more selected from the element in the group being made up of zinc, stannum, gallium, cadmium and indium to make For active channel.This semi-conducting material can be used for bottom gate TFT, top-gated TFT and other kinds of TFT. Pattern TFT by etching and can form raceway groove and metal electrode.Then, this semi-conducting material is used to work as Dry etching is performed, to limit source/drain as etch stop layer.The carrier concentration of active layer, Mobility and the interface with other layers of TFT are adjustable into predetermined value.Adjustment mode can be to change nitrogenous gas The semiconductor film deposited with flow proportional, annealing and/or the Cement Composite Treated by Plasma of oxygen-containing gas, or change Become aluminum doping content.

The semiconductor film comprising nitrogen, oxygen and one or more element in zinc, indium, gallium, cadmium and stannum can Deposited by reactive sputtering and obtain.With reactive sputtering method and be performed in and process large-area substrates in literary composition Doing demonstration explanation in PVD chamber, the application material that PVD chamber such as takes from santa clara city is public The subsidiary of department (Applied Materials, Inc.): the 4300PVD room of AKT company of the U.S..But, The semiconductor film that method manufactures according to this is by membrane structure with depending on form, therefore it should be understood that reactive sputtering method ought be able to be answered Use other system structure, the system being designed to process large area circular substrate including those and other manufactures The system that business manufactures, scratches formula (roll-to-roll) processing platform including volume.It will be appreciated that, although the present invention be with Deposit as a example by PVD, but other include chemical gaseous phase deposition (CVD), ald (ALD) or rotation It is coated with the methods such as technique and also can be used to deposit the thin film of the present invention.

Fig. 1 is the sectional view of physical vapour deposition (PVD) (PVD) room 100 according to one embodiment of the invention.Utilize Vacuum pump 114 empties chamber 100.In chamber 100, substrate 102 is placed on target 104 opposite.Substrate Can be placed on the pedestal (susceptor) 106 in chamber 100.Actuator 112 can be raised according to arrow " A " And reduce pedestal 106.Pedestal 106 can rise and substrate 102 is lifted to processing position, and can fall and allow Substrate 102 is left chamber 100.When pedestal 106 is positioned at down position, lift pin 108 lifts base Plate 102 and higher than pedestal 106.During process, counterpoise grounding 110 is by pedestal 106 ground connection.Lift in time processing Pedestal 106 contributes to uniform deposition.

Target 104 may comprise one or more target 104.In one embodiment, target 104 comprises greatly The sputtering target material 104 of area.In another embodiment, target 104 comprises multiple target brick.At another In embodiment, target 104 comprises multiple target bar.In another embodiment, target 104 comprises one or more circle The rotary target of cylindricality.Target 104 can be bonded to backboard 116 by bonding layer (not shown).One or more magnetic Fulgurite 118 is located at after backboard 116.Magnetron 118 can be inswept in the way of linear movement or two dimensional path Backboard 116.Dark space shield (dark space shield) 120 and chamber guard shield 122 can protect chamber wall not Deposited.

Depositing whole substrate 102 to enable uniform sputter, anode 124 can be placed on target 104 and substrate 102 Between.In one embodiment, anode 124 is the bead blasting (bead blasted) of coating arc spraying aluminium Rustless steel.In one embodiment, one end of anode 124 is installed in chamber wall through bracket 130. Anode 124 provides the electric charge contrary with target 104 so that charged ion will be attracted by anode 124, rather than Attracted by the chamber wall being generally in earthing potential.By anode 124 is located at target 104 and substrate Between 102, can make plasma evenly and contribute to deposition.Peeling off for reducing, cooling fluid can flow through One or more anode 124.By lowering expansion and the amount of contraction of anode 124, material can be reduced from anode 124 Peel off.For room managed by less substrate and smaller part, chamber wall be enough to provide grounding path and make Gas ions is uniformly distributed, therefore is not required to use the anode 124 crossing over this process space.

For reactive sputtering, it is useful that reacting gas is supplied to chamber 100.One or more air inlet Pipe 126 also may span across the distance of the whole chamber 100 between target 104 and substrate 102.The least For substrate and less chamber, if the air intake installation of routine is distributed up to uniformly gas, then it is not required to make The air inlet pipe 126 in space is processed with leap.Air inlet pipe 126 is bootable from gas control plates (gas Panel) sputter gas of 132.One or more connector 128 is utilized to couple air inlet pipe 126 and anode 124. Connector 128 can be made up of Heat Conduction Material, it is allowed to cools down air inlet pipe 126 with conduction pattern.Additionally, connection Knot device 128 also can have electric conductivity, makes air inlet pipe 126 ground connection and as anode.

Reactive sputtering process comprises and is positioned in sputtering chamber by metal sputtering target and is positioned at substrate opposite.Metal Sputtering target material substantially comprises the unit in one or more group selecting free zinc, gallium, indium, stannum and cadmium to be constituted Element.In one embodiment, sputtering target material comprises one or more and has and fill up s track and fill up d track Element.Executing in example at another real, sputtering target material comprises one or more and has the element filling up f orbitals.? In another embodiment, sputtering target material comprises one or more bivalent element.In further embodiment, sputtering target Material comprises one or more trivalent element.In still further embodiment, sputtering target material comprises one or more tetravalence unit Element.

Sputtering target material also can comprise adulterant (dopant).The adulterant being suitable for includes aluminum (Al), stannum (Sn), gallium (Ga), calcium (Ca), silicon (Si), titanium (Ti), copper (Cu), germanium (Ge), indium (In), nickel (Ni), manganese (Mn), chromium (Cr), vanadium (V), magnesium (Mg), silicon nitride (Si_xN_y), aluminium oxide (Al_xO_y) and carborundum (SiC).Real one Executing in example, this adulterant comprises aluminum.In another embodiment, adulterant comprises stannum.On the other hand, substrate The compositions of plastics, paper, polymer, glass, rustless steel and above-mentioned substance can be comprised.If substrate is plastics, Then the execution temperature of reactive sputtering is below about 180 DEG C.The semiconductor film example that can deposit includes ZnO_xN_y:Al、ZnO_xN_y:Sn、SnO_xN_y:Al、InO_xN_y:Al、InO_xN_y:Sn、CdO_xN_y:Al、 CdO_xN_y:Sn、GaO_xN_y:Al、GaO_xN_y:Sn、ZnSnO_xN_y:Al、ZnInO_xN_y:Al、ZnInO_xN_y:Sn、 ZnCdO_xN_y:Al、ZnCdO_xN_y:Sn、ZnGaO_xN_y:Al、ZnGaO_xN_y:Sn、SnInO_xN_y:Al、 SnCdO_xN_y:Al、SnGaO_xN_y:Al、InCdO_xN_y:Al、InCdO_xN_y:Sn、InGaO_xN_y:Al、 InGaO_xN_y:Sn、CdGaO_xN_y:Al、CdGaO_xN_y:Sn、ZnSnInO_xN_y:Al、ZnSnCdO_xN_y:Al、 ZnSnGaO_xN_y:Al、ZnInCdO_xN_y:Al、ZnInCdO_xN_y:Sn、ZnInGaO_xN_y:Al、 ZnInGaO_xN_y:Sn、ZnCdGaO_xN_y:Al、ZnCdGaO_xN_y:Sn、SnInCdO_xN_y:Al、 SnInGaO_xN_y:Al、SnCdGaO_xN_y:Al、InCdGaO_xN_y:Al、InCdGaO_xN_y:Sn、 ZnSnInCdO_xN_y:Al、ZnSnInGaO_xN_y:Al、ZnInCdGaO_xN_y:Al、ZnInCdGaO_xN_y:Sn、 And SnInCdGaO_xN_y:Al。

During sputtering technology, can be supplied to argon, nitrogenous gas and oxygen-containing gas to chamber, spatter for reactivity Penetrate metal targets.During sputtering, such as diborane (B₂H₆), carbon dioxide (CO₂), carbon monoxide (CO), Methane (CH₄) and the additive such as compositions of above-mentioned substance also can be additionally provided to chamber.An embodiment In, nitrogenous gas comprises nitrogen (N₂).In another embodiment, nitrogenous gas comprises nitrous oxide (N₂O), ammonia (NH₃) or the compositions of above-mentioned substance.In one embodiment, oxygen-containing gas comprises oxygen (O₂).In another embodiment, oxygen-containing gas comprises N₂O.The nitrogen of nitrogenous gas and the oxygen of oxygen-containing gas With the metal reaction from sputtering target material, and on substrate formed comprise metal, oxygen, nitrogen and optional doping Semi-conducting material.In one embodiment, nitrogenous gas and oxygen-containing gas are gas with various.At another In embodiment, nitrogenous gas and oxygen-containing gas comprise same gas.

The thin film deposited is semiconductor film.The semiconductor film example that can deposit includes ZnO_xN_y、SnO_xN_y、 InO_xN_y、CdO_xN_y、GaO_xN_y、ZnSnO_xN_y、ZnInO_xN_y、ZnCdO_xN_y、ZnGaO_xN_y、 SnInO_xN_y、SnCdO_xN_y、SnGaO_xN_y、InCdO_xN_y、InGaO_xN_y、CdGaO_xN_y、 ZnSnInO_xN_y、ZnSnCdO_xN_y、ZnSnGaO_xN_y、ZnInCdO_xN_y、ZnInGaO_xN_y、 ZnCdGaO_xN_y、SnInCdO_xN_y、SnInGaO_xN_y、SnCdGaO_xN_y、InCdGaO_xN_y、 ZnSnInCdO_xN_y、ZnSnInGaO_xN_y、ZnInCdGaO_xN_yAnd SnInCdGaO_xN_y.Above-mentioned partly lead Body film each can adulterate adulterant.

Semiconductor film can comprise nitrogen oxides.In one embodiment, semiconductor film comprises metal oxynitride And metal nitride.In another embodiment, semiconductor film comprises metal oxynitride, metal nitride And metal-oxide.In yet another embodiment, semiconductor film comprises metal oxynitride and metal-oxide. In further embodiment, semiconductor film comprises metal nitride and metal-oxide.

The ratio regular meeting of nitrogenous gas and oxygen-containing gas affects the mobility of semiconductor film, carrier concentration and resistance Rate.When Table I shows sputtering stannum target in argon with nitrogen atmosphere, nitrogen flow rate is to mobility, resistivity Impact with carrier concentration.In general, Table I points out that nitrogen flow rate increases, and mobility improves therewith.

Argon remains unchanged with oxygen gas flow rate.In Table I, argon flow velocity is 60sccm, and oxygen gas flow rate is 5sccm. Substrate temperature is the highest, and mobility is the highest.Carrier concentration is little with associating of mobility.Deposition thin film is n Type semi-conducting material, described n-type semiconductor electronic carrier plays a major role, therefore shown carrier Concentration is negative value.

Table 1

Oxygen-containing gas also can affect the mobility of semiconductor film, carrier concentration and resistivity.Table II shows When sputtering stannum target in argon, nitrogen and oxygen atmosphere, oxygen gas flow rate is to mobility, resistivity and carrier The impact of concentration.Argon flow velocity remains unchanged.In Table II, argon flow velocity is 60sccm.In general, If Table II point out nitrogen and oxygen at high proportion, then mobility will be above the mobility of non-crystalline silicon.Additionally, nitrogen Gas is the highest with the ratio of oxygen, and carrier concentration is the lowest.When nitrogen flow rate is 200sccm, migrate take the lead in Oxygen gas flow rate to increase and improve, but when oxygen gas flow rate continues to increase, and mobility then will decline.One In individual embodiment, mobility when 150 DEG C between about 4 square centimeters/volt-second (cm²/ V-s) to about 10cm²Between/V-s.Mobility improves unrelated with carrier concentration.Therefore mobility raising is possibly due to carry Flow caused by sub less scattering.If without using nitrogen additive, then mobility is the lowest.In the case, along with Oxygen gas flow rate increases, and carrier concentration declines to a great extent.For stannum target, substrate temperature is the highest, mobility The highest.In one embodiment, pressure can be between about 5 millitorrs (mTorr) to about 20 millitorrs.

Table II

The amount of doping also can affect the mobility of deposition thin film.No matter so whether target has doping, mobility is still Substantially increase along with nitrogen flow and improve.Table III display doping is to mobility, carrier concentration and resistance The impact of rate.Adulterant represents by weight percentage.The argon flow velocity of each deposition thin film all as.Table III In, argon flow velocity is 120sccm.The carrier concentration using adulterant compares when not using adulterant low. Therefore, adulterant can be used to adjust carrier concentration.

Table III

The open oxygen gas flow rate impact on mobility, carrier concentration and the resistivity of semiconductor film of Table IV. Typically in the case of nitrogen flow is fixing, the migration of thin film takes the lead in increasing with oxygen flow and improving, but oxygen After gas velocity increases further, mobility will transfer to decline.The argon flow velocity of each deposition thin film all as. In Table IV, argon flow velocity is 120sccm.In one embodiment, when nitrogenous gas and oxygen-containing gas When ratio is less than about 10:1, the mobility of thin film reduces.When oxygen gas flow rate increases, mobility improves and carries Flow sub-concentration and increase unrelated.Use doping can reduce mobility and carrier concentration.Therefore doping can be used to adjust Whole carrier concentration and mobility.

Table IV

Table V display applies the power density shadow to mobility, carrier concentration and the resistivity of semiconductor film Ring.In general, power density is the most little on the impact of mobility, but power density is the biggest, and carrier is dense Degree and resistivity are the highest.In one embodiment, apply to sputtering target material power density between about 0.3 watt/ Square centimeter (W/cm²) to about 1.0W/cm²Between.

Table V

Table VI display uses N₂O carrys out the impact of deposited semiconductor film as oxygen-containing gas.N₂O is as oxygenous Physical ability is effectively improved the mobility of semiconductor film, and produces at a fairly low carrier concentration.

Table VI

Table VII lists utilize x-ray photoelectron spectroscopy instrument (XPS) chemical analysis to comprise stannum, oxygen and nitrogen half The result of electrically conductive film, and the display oxygen-containing gas impact on thin film.The depositional mode of thin film 1 is sputtering stannum Target 360 seconds, the direct current (DC) simultaneously applying 400W is biased in sputtering target material.Argon introduces process chamber Flow velocity is 60sccm, and it is 200sccm that nitrogen introduces flow velocity, and it is 5sccm that oxygen introduces flow velocity.Deposition temperature Degree is 250 DEG C.The carbon content of thin film 1 be 22.5 atomic percents (atomic%), nitrogen content be 19.4 former Sub-%, oxygen content are 29.4 atom %, Oil repellent is 0.7 atom %, Theil indices is 28.1 atom %.If Not all, then carbon is derived from external carbon mostly (i.e. from absorption on the sample surfaces of any contact air Carbon compound).The depositional mode of thin film 2, for sputtering stannum target 360 seconds, applies the DC of 400W simultaneously It is biased into sputtering target material.The argon flow velocity introducing process chamber is 60sccm, and it is 200 that nitrogen introduces flow velocity Sccm, it is 20sccm that oxygen introduces flow velocity.Depositing temperature is 250 DEG C.The carbon content of thin film 2 is 17.3 Atom %, nitrogen content are 4.5 atom %, oxygen content is 49.9 atom %, Oil repellent is 0.6 atom %, stannum Content is 27.7 atom %.If not all, then carbon is mostly derived from external carbon and (i.e. adsorbs in any contact big Carbon compound on the sample surfaces of gas).As shown in Table VII, along with oxygen gas flow rate is (with oxygen and nitrogen Ratio) increase, amount of nitrogen oxides increases, and stannum oxide content also increases.But nitridation Theil indices and nitrogen oxygen SiClx content reduces.In Table VII, R represents oxygen or nitrogen.

Table VII

Table VIII shows the result of the semiconductor film of several sputtering sedimentation.Semiconductor film comprises zinc, stannum, oxygen And nitrogen.It is heavy that semiconductor film is use Zn content 70 atom %, the sputtering target material of Theil indices 30 atom % sputters Amass and obtain.Depositing temperature is 250 DEG C, and the power of applying to sputtering target material is 400W.Sedimentation time is 360 Second, and argon flow velocity is 60sccm, oxygen gas flow rate is 20sccm.Data show, the migration of semiconductor film Rate increases with nitrogen flow rate (with the nitrogen ratio to oxygen) and improves.

Table VIII

Zinc, oxygen and nitrogen compound

For measuring the expectation oxygen gas flow rate being used for forming the semiconductor film containing zinc, oxygen and nitrogen, optional oxygen Amount so that the amount of oxygen is not enough to zinc complete oxidation is produced zinc oxide.If supplying too many oxygen-containing gas, then Meeting this thin film of over oxidation, so that the mobility of thin film is not high enough.The amount of oxidation of zinc can affect light transmittance.Example As, the zinc of complete oxidation has the light transmittance of greater than about 80%.A kind of measure expectation oxygen flow method be Use argon and oxygen and do not use nitrogen to implement reactive sputtering technique.Can enter by different oxygen gas flow rates Row experiment, and measure light transmittance at visible wavelengths.Desired oxygen flow is probably at thin film lucky Reach the amount before maximum transparency.Table ix is listed under different oxygen gas flow rate, the oxygen of reactive sputtering deposition Change the light transmittance of zinc.In one embodiment, maximum transmission rate is preferably 80%.In other embodiments, If counting glass to absorb or interference of light effect, then maximum transmission rate is not likely to be 80%.Experiment also can be taked Different DC target power, different substrate temperatures, even use different oxygen-containing gas, such as N₂O。

Table ix

Oxygen gas flow rate (sccm/m3)	Light transmittance (%)
		0	<5
50	<5
		100	<5
125	82
		150	85
200	90

The another kind of method measuring expectation oxygen flow at above-mentioned not the supply of nitrogen or supplies a small amount of nitrogen Under the conditions of implement reactive sputtering formed zinc oxide, then measure film resistor.Predetermined oxygen gas flow rate is for producing About 100 Ω/sq to 1.0 × 10⁷The film resistor of Ω/sq.

Another measures the method for expectation oxygen gas flow rate and measures for carrying out X-ray diffraction (XRD) membrane structure. Fig. 2 A to Fig. 2 E is the XRD figure that thin film changes with oxygen flow, and the display of described XRD figure forms zinc (Zn) Diffraction maximum with zinc oxide (ZnO).In Fig. 2 A to Fig. 2 E, the sedimentary condition of each thin film is: argon flow velocity 600sccm/m³, 1000W and different oxygen gas flow rate.

The XRD figure of the thin film that oxygen is formed is not supplied when Fig. 2 A is by sputtering.Described XRD figure produces number The zinc diffraction maximum of individual varying strength.Zinc (002) diffraction maximum occurs in 2 θ, and (i.e. incident X-rays is detected with diffractometer The angle of device) between about 35.5 to 37, intensity about 625 counts (count).Zinc (100) diffraction maximum goes out Between present about 38 to 40, intensity about 450 counts.Zinc (101) diffraction maximum occur in about 42.5 to 44 it Between, intensity about 1050 counts.Zinc (102) diffraction maximum occurs between about 53 to 55, and intensity about 325 is counted Number.Zinc (103) diffraction maximum occurs between about 69.5 to 70, and intensity about 300 counts.Zinc (110) diffraction maximum Occurring between about 70 to 71, intensity about 275 counts.Zinc (002): zinc (100): zinc (101): zinc (102): Zinc (103): the ratio of the diffraction maximum height of zinc (110) is about 2.27:1.64:3.82:1.182:1.091:1. The facies analysis of all diffraction maximums all uses joint committee (ICDD) PDF2 data base (2004 revision) Indicate.

As shown in Figure 2 B, oxygen supply flow velocity is 50sccm/m³Time, the strength reduction of zinc diffraction maximum.Zinc (002) diffraction maximum weakens into about 500 countings.Zinc (100) diffraction maximum weakens into about 375 countings.Zinc (101) spreads out Penetrate peak and weaken into about 750 countings.Zinc (102) diffraction maximum weakens into about 250 countings.Zinc (110) diffraction maximum subtracts Weak one-tenth about 225 counts, and zinc (103) diffraction maximum disappears.Zinc (002): zinc (100): zinc (101): zinc (102): The diffraction maximum aspect ratio of zinc (110) is about 2.22:1.67:3.33:1.11:1.

As shown in Figure 2 C, oxygen supply flow velocity is 100sccm/m³Time, all zn diffraction maximum disappears, except Zinc (101) diffraction maximum weakens into about 375 countings.As shown in Figure 2 D, oxygen supply flow velocity is 150sccm/m³ Time, zinc diffraction maximum is wholly absent, but zinc oxide (002) diffraction maximum occurs between about 33.5 to 35, intensity About 950 countings.As shown in Figure 2 E, oxygen supply flow velocity increases to 200sccm/m³Time, zinc oxide (002) Diffraction peak intensity brings up to about 1000 countings.

According to XRD data, oxygen supply amount should be less than about 150sccm/m³, because reaching 150sccm/m³Time There will be strong zinc oxide diffraction maximum.It should be understood that oxygen gas flow rate is directly proportional to chamber size.Therefore chamber size increases Greatly, oxygen gas flow rate increases therewith.Similarly, chamber size reduces, and oxygen gas flow rate reduces therewith.

For measuring expectation nitrogen flow rate, XRD membrane structure measurement can be carried out.According to Fig. 3 A to Fig. 3 F originally Invent an embodiment, under different nitrogen flow rates, form the XRD figure of semiconductor film.In Fig. 3 A to Fig. 3 F, The sedimentary condition of each thin film is: argon flow velocity 600sccm/m³, 2000W, oxygen gas flow rate 100sccm/m³ With different nitrogen flow rates.

The XRD figure of Fig. 3 A thin film by being deposited under without nitrogen.Figure shows several strong peak, including Between about 35 to about 37 and zinc oxide (101) and zinc (002) diffraction maximum, Jie of intensity about 575 counting Between about 38 to 40 and zinc (100) diffraction maximum of intensity about 380 counting, and between about 42.5 to 44 Between and intensity about 700 counting zinc (101) diffraction maximum.Less zinc oxide (002) diffraction maximum occurs in about Between 35.5 to 37, intensity about 390 counting zinc (102) diffraction maximum occurs between about 53 to 55, by force Degree about 275 counting zinc (103) diffraction maximums occur between about 69.5 to 70, intensity about 225 counting with And zinc (110) diffraction maximum occurs between about 70 to 71, intensity about 225 counts.Zinc oxide (101): zinc (002): zinc (100): zinc (101): zinc oxide (002): zinc (102): zinc (103): the diffraction maximum of zinc (110) Aspect ratio is about 2.55:2.55:1.24:3.11:1.73:1.22:1:1.

As shown in Figure 3 B, the nitrogen supply (NS) flow velocity during reactive sputtering is 300sccm/m³Time, zinc with Zinc oxide diffraction maximum by significantly weaken to no longer have zinc oxide a bit.As shown in Figure 3 C, nitrogen flow rate Increase to 500sccm/m³Time, all zn disappears with zinc oxide diffraction maximum, and thin film then has non crystalline structure.

As shown in Figure 3 D, nitrogen flow rate increases to 1000sccm/m³Time, two new diffraction maximums occur. First zinc nitride (Zn₃N₂) (222) diffraction maximum is between about 31 to 33, intensity about 2050 counts.The Two Zn₃N₂(411) diffraction maximum is between about 35 to 42, and intensity about 1850 counts.Zn₃N₂(222): Zn₃N₂(411) diffraction maximum aspect ratio is about 1.11:1.As shown in FIGURE 3 E, nitrogen flow rate increases to 1250 sccm/m³Time, Zn₃N₂(222) diffraction peak intensity is about 2500 countings, Zn₃N₂(411) diffraction peak intensity is About 2600 countings.Zn₃N₂(222): Zn₃N₂(411) diffraction maximum aspect ratio is about 0.96:1.Such as Fig. 3 F Shown in, nitrogen flow rate increases to 2500sccm/m³Time, Zn₃N₂(222) diffraction maximum and Zn₃N₂(411) diffraction Peak weakens into about 2350 and 2050 countings respectively, but produces new Zn between about 36 to 37.5₃N₂(400) Diffraction maximum, described Zn₃N₂(400) intensity of diffraction maximum about 1700 counting.Zn₃N₂(222): Zn₃N₂(411): Zn₃N₂(400) diffraction maximum aspect ratio is about 1.38:1.21:1.

According to XRD data, nitrogen supply (NS) amount should be greater than about 300sccm/m³, because at 300sccm/m³Time, Zinc oxide diffraction maximum can significantly weaken, so that thin film is substantially free of zinc oxide.It will be appreciated that, nitrogen flow rate It is directly proportional to chamber size.Therefore chamber size increases, nitrogen flow rate increases therewith.Similarly, chamber size Reducing, nitrogen flow rate reduces therewith.

Therefore, in conjunction with above-mentioned oxygen gas flow rate and nitrogen flow rate, can use nitrogen that the flow rate of oxygen is more than The condition of about 2:1 deposits the semiconductor film of novelty as herein described.In one embodiment, nitrogen It is 10:1 to 50:1 with the flow-rate ratio of oxygen.In another embodiment, nitrogen and the flow-rate ratio of oxygen For 20:1.

As above-mentioned, for manufacturing this semi-conducting material, the flow velocity of nitrogenous gas is much larger than the flow velocity of oxygen-containing gas. The mobility of the semi-conducting material deposited is higher than non-crystalline silicon.Table X is listed according to one embodiment of the invention, The relation that mobility changes with nitrogen flow rate.

Table X

For all nitrogen flow rates, under conditions of oxygen supply 0sccm, thin film obtained by deposition, described The mobility of thin film is less than 5cm²/V-s.At oxygen supply 25sccm/m³Under conditions of, with nitrogen flow rate For 1500sccm/m³Time deposited obtained by the mobility of thin film be about 8cm²/ V-s, nitrogen flow rate is 2500 sccm/m³Time deposited obtained by the mobility of thin film be about 15cm²/V-s.At oxygen supply 200 sccm/m³Under conditions of, nitrogen flow rate is 1500sccm/m³Time deposited obtained by the mobility of thin film be About 1cm²/ V-s, with nitrogen flow rate as 2500sccm/m³Time deposited obtained by thin film mobility be about 10cm²/V-s.At oxygen supply 250sccm/m³Under conditions of, nitrogen flow rate is 500sccm/m³Time institute The mobility of thin film obtained by deposition is about 5cm²/ V-s, nitrogen flow rate is 1500sccm/m³Time deposited Obtained by the mobility of thin film be about 2cm²/ V-s, nitrogen flow rate is 2500sccm/m³Time deposited and obtained The mobility of thin film be about 12cm²/V-s。

With oxygen gas flow rate as 50sccm/m³To 150sccm/m³For the thin film deposited, moving of this thin film Shifting rate is apparently higher than with oxygen gas flow rate as 25sccm/m³The thin film deposited, but less than with oxygen gas flow rate being 200sccm/m³Above deposited thin film.It addition, with oxygen gas flow rate as 50sccm/m³To 150sccm/m³ The mobility of the thin film deposited is far above the mobility of non-crystalline silicon.In most cases, nitrogen flow rate Between 1000sccm/m³To 2500sccm/m³Between time, the mobility of thin film be higher than 22cm²/V-s.Phase Compared with mobility about 1cm²The non-crystalline silicon of/V-s, the mobility of the semiconductor film containing zinc, oxygen and nitrogen is obvious Higher.Therefore, semiconductor film oxygen flow ratio formed with the nitrogen of about 10:1 to about 50:1, The mobility of the mobility ratio non-crystalline silicon of described semiconductor film wants big 20 times, and than the mobility of polysilicon Want big 2 times.It will be appreciated that, although table is listed multiple specific nitrogen and oxygen gas flow rate, but oxygen and nitrogen Gas velocity is relevant with chamber size, therefore can adjust according to different chamber size.

Table X I shows according to one embodiment of present invention, film resistor (sheet resistance), carrier The situation that concentration and resistivity change with nitrogen flow rate.The flow-rate ratio of nitrogen and oxygen between about 10:1 to about During 50:1, the film resistor of the semiconductor layer comprising zinc, oxygen and nitrogen is about 100 Ω/sq (or being expressed as Ω/) Between about 10000 Ω/sq.Along with nitrogen flow rate and oxygen gas flow rate increase, electron carrier density declines. Therefore, resistivity rises.

Table X I

Annealing also can be effectively improved the mobility of the semiconductor film containing zinc, oxygen and nitrogen.Table X II display basis One each embodiment of the present invention, after annealing, the situation that mobility changes with nitrogen flow rate.After annealing, move Shifting rate is more than 50cm²/V-s.In one embodiment, mobility rises above 90 because of annealing cm²/V-s.Can carry out making annealing treatment about 5 minutes in nitrogen atmosphere and at about 400 DEG C.

Table X II

Doping also can affect the mobility of the semiconductor film containing zinc, nitrogen and oxygen.Table X III and Table X IV Mobility when listing the zinc sputtering target material with different nitrogen and oxygen gas flow rate reactive sputtering adulterated al, thin film Resistance, carrier concentration and resistivity.Therefore, the doping of adjustable sputtering target material, to guarantee to reach pre- Fixed mobility, film resistor, carrier concentration and resistivity.

Table X III

Table X IV

Base-plate temp also can affect the mobility of semiconductor film.Table X V list with different nitrogen flow rates, At 30 DEG C, 50 DEG C and 95 DEG C sputter zinc sputtering target material time mobility, film resistor, carrier concentration and Resistivity.Can be seen that from Table X V, at a temperature of significantly lower than 400 DEG C, (include the temperature close to room temperature) Carry out reactive sputtering and can be effectively formed the mobility semiconductor film higher than non-crystalline silicon with polysilicon.Therefore, i.e. Making not make annealing treatment, the mobility of this semiconductor film remains above non-crystalline silicon.

Table X V

Although literary composition is enumerated the particular value of multiple power, it should be understood that the power applied to sputtering target material and target Area is directly proportional.Therefore between about 10W/cm²To about 100W/cm²Between performance number can be usually reached the phase The result hoped.Table X VI display nitrogen flow rate is 1500sccm/m³To 2500sccm/m³Between time, apply The impact on mobility, carrier concentration and resistivity of the DC power.Between about 1000W to 2000W Power formed thin film mobility apparently higher than non-crystalline silicon.

Table X VI

The ternary semiconductor with zinc, nitrogen and oxygen is comprised according to thin film obtained by above-mentioned techniques of deposition Material, such as ZnN_xO_y.In one embodiment, this ternary semiconductor material is dopant material, Such as ZnN_xO_y:Al.Compared to having high electron mobility and the zinc oxide of high electronic carrier density, The ternary semiconductor compound of room temperature deposition has high mobility and low electronic carrier density.An enforcement In example, the mobility of this ternary compound is higher than 30cm²/ V-cm, electronic carrier density is less than 1.0E+19 #/cc.If making annealing treatment this thin film with about 400 DEG C, then mobility then rises above 100 cm²/ V-cm, and electronic carrier density will be less than 1.0E+18#/cc, and will not change thin film crystal orientation and Composition.Even if thin film is amorphous compound or the crystalline compounds lacking orientation (poorly oriented), these are three years old Unit's compound still can reach high mobility and low electron density.

Compared to zinc oxide, it is possible to improve the optical band gap (band gap) of this ternary compound.Zinc oxide Band gap is generally 3.2 electron-volts (eV).Another aspect, comprises the ternary compound of zinc, nitrogen and oxygen Band gap is about from 3.1eV to about 1.2eV.Close by changing such as nitrogen and the flow proportional of oxygen, power The deposition parameters such as degree, pressure, annealing and depositing temperature, adjustable band gap.Owing to band gap is relatively low, this ternary Compound can be used for photoelectric device and other electronic devices.Under at a relatively high treatment temperature, such as 600 DEG C, Ternary compound thin film can be converted into p-type or n-type semiconductor.Annealing or Cement Composite Treated by Plasma can add With fine setting, therefore essentially without changing compound structure and chemical composition.It is finely adjusted the property that can make compound Matter meets the device performance requirements using this compound.

This ternary compound can be as the transparent semiconductor layer of TFT device, photoelectric device or solar panel In compound layer, or the compound layer in sensor device.Fig. 4 A to Fig. 4 G illustrates according to the present invention The processing step of the formation bottom gate TFT400 of one embodiment.TFT comprises substrate 402.An embodiment In, substrate 402 potentially includes glass.In another embodiment, substrate 402 comprises polymer.Again In one embodiment, substrate 402 comprises plastics.In a further embodiment, substrate 402 comprises metal.

Substrate is formed grid 404.Grid 404 comprises conductive layer, in order to current-carrying charged in controlling TFT The movement of son.Grid 404 can comprise metal, the such as compositions of aluminum, tungsten, chromium, tantalum or above-mentioned substance. Grid 404 can be formed with conventional deposition technique, and described deposition technique includes sputtering, photoetching and etching.Grid are situated between Matter layer 406 is deposited on grid 404.Gate dielectric layer 406 can comprise silicon dioxide, silicon oxynitride, nitridation Silicon or the compositions of above-mentioned substance.Gate dielectric layer 406 can be with existing techniques of deposition, described deposition skill Art includes plasma enhanced chemical vapor deposition (PECVD).

As shown in Figure 4 B, gate dielectric layer 406 forms active channel 408 (i.e. semiconductor layer).At one In embodiment, the annealed process of active channel 408.In another embodiment, active channel 408 Through Cement Composite Treated by Plasma.Annealing and/or Cement Composite Treated by Plasma can improve the mobility of active channel 408. Active channel 408 can comprise the ternary compound described above with zinc, oxygen and nitrogen.In one embodiment, This ternary compound adulterated al.As shown in Figure 4 C, after deposition active channel 408, source-drain layer is deposited 410 on active channel 408.In one embodiment, source-drain layer 410 comprises metal, such as aluminum, The compositions of tungsten, molybdenum, chromium, tantalum and above-mentioned substance.In order to limit active channel 408 and source electrode and drain electrode, Etchable source-drain layer 410 and active channel 408.

As shown in Figure 4 D, mask 412 is on source-drain layer 410.Mask 412 can have predetermined figure Case.Utilization includes depositing the routine techniques such as photoresist and developing pattern, mask 412 can be placed in source electrode-leakage On pole layer 410.

As shown in Figure 4 E, active channel 408 and source-drain layer 410 can be etched simultaneously.Fig. 4 F is figure The top view of 4E.As depicted in figs. 4 e and 4f, utilize etching to expose active channel 408.One In individual embodiment, can wet etching source-drain layer 410 and the active channel 408 of a part, and expose and have Source raceway groove 408.In another embodiment, can dry etching source-drain layer 410, then wet etching The active channel 408 of a part.In yet another embodiment, etchable source/drain layer 410, but do not lose Carve active channel 408.In one embodiment, can use containing selected from chlorine, oxygen, fluorine or above-mentioned substance The gas of the element of combination performs dry etching.

After exposing active channel 408, active channel 408 is used to carry out dry etching source electrode as etch stop layer -drain electrode layer 410, to limit source electrode and drain electrode.Fig. 4 G is the active channel 408 exposed and has limited The top view of source electrode 414 and drain electrode 416.Owing to plasma cannot effectively etch containing zinc, oxygen and nitrogen Ternary compound (some embodiment also containing aluminum), when therefore carrying out dry plasma etch, active channel The effect of 408 is treated as etch stop layer.

Fig. 5 is the sectional view of the etch-stop TFT500 according to one embodiment of the invention.Etch-stop TFT comprises substrate 502, grid 504 and gate dielectric layer 506.Etch-stop TFT500 is similar to above-mentioned figure The bottom gate TFT of 4A-4G, except etch stop layer 510 is disposed between source electrode 512 and drain electrode 514 On active channel 508.Substrate 502, grid 504, gate dielectric layer 506, active channel 508, source electrode 512 and the material of drain electrode 514 can material as shown in above-mentioned bottom gate TFT.Etch stop layer 510 can wrap Include containing the one or more dielectric material in silicon and oxygen and nitrogen.

Fig. 6 is the sectional view of top-gated TFT600 according to one embodiment of the invention.Top-gated TFT600 comprises Substrate 602, substrate 602 is provided with light shield layer 604.Dielectric layer 606 is deposited on light shield layer 604. Source electrode 608 and drain electrode 610 are deposited on dielectric layer 606.Active channel layer 612 is deposited on source electrode 608 With drain electrode 610 on.Gate dielectric layer 614 is deposited on active channel 612, and grid 616 is then deposited on grid and is situated between On matter layer 614.For substrate 602, grid 616, gate dielectric layer 614, active channel 612, source electrode 608 and the material of drain electrode 610 can material as shown in above-mentioned bottom gate TFT.Form top-gated TFT600 Time, available wet etching, or first dry etching carries out wet etching again to form raceway groove and electrode contact District.Then, active channel is used to carry out dry etching as etch stop layer, to limit contact area.

Fig. 7 is the schematic diagram of the active array type LCD700 according to one embodiment of the invention.Fig. 7 illustrates TFT substrate and filter substrate, and liquid crystal material is folded in described TFT substrate and described filter substrate Between.TFT controls electric current makes pixel electrode produce electric field, passes through with the direction and light controlling liquid crystal material The amount of color filter.TFT is arranged in the matrix of glass substrate.For controlling specific pixel, open suitably row, Then electric charge is transmitted in the direction toward correct row.It is all closedown owing to other intersected with this journey arrange, therefore only position Capacitor at specified pixel receives electric charge.Capacitor can store electric charge, updates circulation until next. If controlling to apply the voltage to crystal, then can turn on crystal and pass by some light.

The active array type LCD700 of Fig. 7 can be by TFT714 control.TFT714 can be turned on and off picture Element.LCD700 comprise bond pad (bonding pad) 706, pixel electrode 708, reservior capacitor 728, Polarizer 702, substrate 704, oriented layer 710, wadding 712, short circuit (short) 716, sealing gasket 718, Black matrix 720, color filter 724 and public electrode 726.

Fig. 8 is the schematic diagram of the active array type OLED800 according to one embodiment of the invention.Fig. 8 shows Go out TFT, described TFT and control to bestow the magnitude of current of the light emitting organic layers of OLED.Active array type OLED There is complete cathode layer, molecule organic layer and anode layer, but anode layer covers at the TFT forming matrix On array.Tft array is originally as circuit, and described circuit determines that opening which pixel produces image.Active The power consumption of matrix type OLED is fewer than passive matrix OLED, due to tft array needs Power is fewer than external circuit, therefore can be used for giant display.Active array type OLED also has the most more New speed, thus it is suitable for video.Active array type OLED can be used for computer screen, giant-screen electricity Depending on, electronic signal and electronic board.

OLED800 can be by TFT802 control, and TFT802 is used for being turned on and off pixel.OLED800 Comprise TFT802, anode 804, hole injection layer 806, ionosphere 808, cushion 810, transparent the moon Pole 812, luminescent layer 814 and encapsulated layer 816.

Fig. 9 A to Fig. 9 C shows the threshold voltage (Vth) of different active channel length (L) and width (W). Fig. 9 A shows active channel length 40 microns (μm) and the Vth of width 10 microns.Fig. 9 B shows active Channel length 80 microns and the Vth of width 10 microns.Fig. 9 C shows active channel length 80 microns and width Spend the Vth of 20 microns.Fig. 9 A to Fig. 9 C shows, this ternary compound active layer has high on-off ratio With high electric current.

Figure 10 A to Figure 10 C is to compare the Vth having common active channel length with width.This is active Channel length is 40 microns, and width is 10 microns.Figure 10 A is the Vth of non-crystalline silicon.Figure 10 B shows Ternary compound without annealing.Ternary compound after Figure 10 C display annealing.Figure 10 B The ternary compound TFT source-drain current when Vg=1 more than the non-crystalline silicon source electrode when 10V- Drain current.Therefore the thin film without annealing will 10 times than non-crystalline silicon.

In Figure 10 C, the thin film after annealing is more preferably.Compared to the thin film without annealing, annealed The thin film processed has higher saturation current.Source electrode-the leakage when Vd=0.1V of the thin film of annealed process Electrode current is close to the non-crystalline silicon tft electric current when Vd=10V.Therefore the thin film of annealed process compares non-crystalline silicon It is better 100 times.

Special with the interface of other layers by changing active layer carrier concentration, active layer mobility and active layer Property, the performance of the above-mentioned TFT of adjustable.By changing the nitrogenous gas flow velocity in deposition thin-film process, can Adjust TFT.As above-mentioned, the nitrogenous gas used in sputtering sedimentation active layer process and oxygen-containing gas ratio Mobility, carrier concentration and other factors can be affected.User can set carrier concentration, mobility or The predetermined value of other characteristics, adjusts the velocity ratio of nitrogen and oxygen, the most according to this to obtain desired thin film Matter.Even may also be responsive to be adjusted in in-site measurement value, immediately to control depositing operation.

Also TFT can be adjusted by changing aluminum doping.The doping of aluminum can predetermine, and use and have The suitably sputtering target material of composition is placed in process chamber.It addition, can after deposition or integrate other thin film Time, annealing and/or this active layer of Cement Composite Treated by Plasma are to adjust TFT.As above-mentioned, this is ternary for heat treatment Compound can improve the mobility of thin film.

Comprise oxygen, nitrogen and one or more is selected from by the element in the constituted group of zinc, stannum, gallium, indium and cadmium TFT, described TFT mobility is higher than TFT made by non-crystalline silicon.The mobility improving TFT can allow TFT can be applied not only to LCD, is also applied to follow-on display, OLED.

Although above with respect to embodiments of the invention, but can set without departing from the essential scope of the present invention Count other or the further embodiment of the multiple present invention, and protection scope of the present invention when regarding after attached right want Book is asked to be determined.

Claims (9)

1. a thin film transistor (TFT), described thin film transistor (TFT) comprises:

Semiconductor layer in thin film transistor (TFT), described semiconductor layer comprises:

Comprise the nitrogen oxides of oxygen, nitrogen, zinc, indium and gallium；Or

Comprise the nitrogen oxides of oxygen, nitrogen, zinc and stannum.

2. transistor as claimed in claim 1, wherein said transistor is top-gate thin-film transistors.

3. transistor as claimed in claim 1, described thin film transistor (TFT) also comprises:

Substrate；

Grid, described grid is arranged on the substrate；

Gate dielectric layer, described gate dielectric layer is arranged on described grid；

The described semiconductor layer being arranged on described gate dielectric layer；And

Source electrode and drain electrode, described source electrode and drain electrode be arranged on described semiconductor layer, and described source electrode and leakage Pole is separated by comes and limits active channel.

4. transistor as claimed in claim 3, described thin film transistor (TFT) also comprises etch stop layer, institute State etch stop layer to be arranged on the semiconductor layer in described active channel.

5. transistor as claimed in claim 1, the mobility of wherein said semiconductor layer is more than 50cm²/V-s。

6. transistor as claimed in claim 1, wherein said nitrogen oxides also comprises adulterant, described Adulterant is selected from by aluminum (Al), calcium (Ca), silicon (Si), titanium (Ti), copper (Cu), germanium (Ge), nickel (Ni), manganese (Mn), at least one in the group that chromium (Cr), vanadium (V) and magnesium (Mg) are constituted.

7. transistor as claimed in claim 6, wherein said nitrogen oxides comprises aluminium dopants.

8. transistor as claimed in claim 1, wherein said nitrogen oxides also comprises adulterant.

9. transistor as claimed in claim 8, wherein said adulterant comprises aluminum.